Патент USA US3077016код для вставки
Feb. 12, 1963 s. M. lBRAHlM I 3,077,006 PRODUCTION OF STAPLE FIBERS Filed Oct. 30. 1961 INVENTOR SALIM M. IBRAHIM ATTORNEY , United States Patent“ 0 "ice senses Patented Feb. 12, l??? 31 . $377,696 PRGDUQ'HQN all? S'IAQLE ll'ii?ERr-‘S Salim M. Ibrahim, Wilmington, Deb, ass.‘ nor to E. i. du Pont de Nemours and Company, ‘Wilmington, Bela, a corporation of Delaware Filed 36, mm, No. lli???ii ii laims. (ill. iii-.48} tie or initial modulus, e.g., from 4 to 100 grams per denier ‘or greater. The invention will be more fully understood by refer ence to the accompanying drawing in which the ?g ore is ‘a side view of a schematic representation of ap paratus for converting the ?laments to staple ?bers. Referring now to the ?gure, reference letters A and A’ represent ?at sheets or tows of inelastic ?laments and reference letter B represents a flat sheet of con This invention relates to a method for preparing blends of staple ?bers from continuous elastic ?laments and 10 tinuous elastic ?laments. The inelastic ?laments A are passed over tension bars til, 12, id, ‘and to to a pair inelastic laments. More particularly, this invention re of input feed rolls 33 and at}. Simultaneously the lates to a method for converting continuous elastic ?la~ elastic ?laments E are passed over a tension bar 13, be ments and inelastic ?laments into staple fiber which may tween two pairs of feed rolls 2?-—22 and 26-23- and be processed into slivers of intermingled elastic and inelastic staple fibers which may be subsequently pro 15 forwarded in a stretched condition to the input feed rolls 38 and so. At the same time, inelastic ?laments A’ cessed into high quality stretchable yarns and stretchable are passed over tension bars 3th 3-2, 34- and 36 to the input fabrics by utilizing known processing equipment. feed rolls 33 and 4th in delivering the elastic ?laments ethods for preparing blended sliver from two or E to the input feed rolls 3t} and 4d, a predetermined more different kinds of inelastic continuous ?laments are well known. However, the application of these methods 20 amount of stretch is imparted to the ?laments by driv ing feed rolls 26—2% at a higher linear surface speed to ‘the preparation of blended sliver from continuous elastic ?laments and inelastic ?laments has not proved to be satisfactory. After cutting the elastic ?bers to staple than feed rolls 2t‘l—--22. This stretch is maintained by input feed rolls 38‘ and lit), at which point the sheets of inelastic ?laments A and A’ are combined into a com lengths, they tend to remain in tightly formed clumps that resist separation in the blending with inelastic staple 25 posite web with the sheet of elastic ?laments E. The composite web is forwarded by the input feed rolls 38 ?bers and cause such crinkling and wrinkling of the ?ber sheet ‘as to render it totally unprocessable. and so to fracturing rolls 42. and 44 where the con it is, therefore, an object of this invention to provide an improved method for preparing blends of staple ?bers from continuous elastic ?laments and inelastic ?laments. It is another object of this invention to provide a method for preparing blended sliver from continuous elastic ?lo tinuous ?laments are cut to staple ?ber length. The staple ?bers are picked up by pick-up rolls 45 and 43 and may ments and inelastic ?laments which permits the use of be forwarded directly to a suitable container 52 as cut ?ber ‘or processed to sliver form S by suit-able apparatus ‘Eli. As previously indicated, the stretching of elastic ?la inafter. The objects of this invention are achieved by a method ments B may be accomplished by driving feed rolls 2l?—2? at a higher linear surface speed than feed rolls Edi-22. Unless some appreciable stretch, e.g., at least about 2%, is imparted to the elastic ?laments, the cut bers tend to form tight clumps that resist distribution in the blend and cause such severe crinkling and wrinkling in the cut ?ber sheet as to make it totally unprocessable. Generally it is preferred that the elastic ?laments E be which comprises ?rst forming a plurality of separated stretched an amount from about 5% to about 15% conventional equipment for converting such ?laments into sliver form. A further object of this invention is to provide a method whereby continuous elastic ?laments ‘and inelastic ?laments are simultaneously cut to staple lengths whereby the elastic ?bers have a high degree of length uniformity. Other objects will be apparent here greater than their relaxed length; however, it has been flat sheets of continuous elastic ?laments and inelastic found that little advantage is gained in processability or ?laments. The sheets ‘of elastic ?laments are tcnsioned to stretch the ?laments a predetermined amount beyond 45 cut length uniformity at stretch levels much above 15%. Some tension should also be applied to the inelastic their normal relaxed length. After the tensioning step, ?laments. This tension should, of course, be sufficient the elastic ?laments are combined in layered relationship to maintain a uniformly flat sheet. Tensions which with the inelastic ?laments to form a composite web stretch or deform the inelastic ?laments should generally in which the sheets of tensioned elastic ?laments lie between adjacent sheets of inelastic ?laments. ‘Without 50 be avoided. in practicing the present invention, particularly desir permitting the elastic ?laments to retract, the composite able results have been obtained by flexing the elastic ?la web is fed to fracturing means where the ?laments are merits E before formation of the composite web, e.g., as cut to staple length. Surprisingly, the elastic staple ?bers they pass between the two sets of feed rolls during the thus prepared are found to be of uniform length, and the tensioning step. Referring again to the ?gure, an os~ blend of elastic and inelastic ?bers exhibits excellent cillating roll 24 may be positioned between the two sets processability in the subsequent steps of converting the of feed rolls 243-22 and 26-213 to stretch the elastic ?bers to sliver and ultimately to yarn form. ?laments from about 2 to about 5 times, preferably about By the term “elastic ?laments and ?bers" it is meant 3.5 times, their relaxed length during the tension step. synthetic and natural ?laments and ?bers having a high Alternatively, the elastic ?laments may be flexed before brealdng elongation, e.g., 109% or more and preferably entering the stretching zone. One cycle of stretching and 5 00% to 800%, and a low elastic or initial modulus, e.g., relaxing is generally all this required; however, additional less than one gram per denier, preferably 0.08 gram per cycles may be used. It is, of course, necessary in all cases denier or lower, and exhibit a quick and substantially that the elastic ?laments be in the previously described complete recovery from stretching to an amount less than stretched condition of from about 2% to about 15% and their breaking elongation, e.g., have a tensile recovery sandwiched between layers of inelastic ?bers when fed to of about 90% or more and a stress decay of less than the fracturing rolls. about 20%. After fracturing the ?laments, the staple ?bers may, as By the term “inelastic ?laments and ?bers” it is meant previously indicated, he directed into a suitable receptacle those natural and synthetic ?bers which generally have 70 or preferably processed immediately into top, sliver, batts, . ya as, fabrics, and other textile forms using conventional a breaking elongation of less than about 100% and, as processing machinery. The fracturing step with the sub compared to the elastic ?bers, have a relatively high elas 3,077,006 sequent steps of aligning the ?bers to form a web and drafting the web and rolling the drafted staple ?bers into a helical roll or sliver are conveniently achieved using equipment described in U.S. 2,438,469, which is com monly known as the “Paci?c Converter.” The equipment described in U.S. 2,748,426, known as the “Turbo Stapler,” may also be used. Because of the signi?cant di?erence in break elongations of the elastic and inelastic ?bers in the composite web, less satisfactory results are achieved on systems which depend on breaking the ?bers 10 of hydrazine (35% in water) and diethylamine (5% in dimethylformamide) in the ratio of 37.5 parts of hydra zine to 1 part of diethylamine is added as a single stream at a rate of 0.465 pound per hour with strong agitation. The mixture passes to a reaction chamber held at a tem' tively long, '.e., from about 3.0 to 6.0 inches, although both longer and shorter lengths may be prepared by the perature of 20—40° C., the contents having residence time of about 2-3 minutes. The emerging polymer solution contains approximately 17.7% solids and has a viscosity of 700 poises at 30° C. To the polymer solution are added a slurry of titanium dioxide in dimethylformamide a solution of poly(N,N-diethyl-beta-aminoethyl methac rylate) in dimethylformamide and a solution of 4,4'-bu tylidenebis-(6-t-butyl-m - cresol) in dimethyl?ormamide, such that the ?nal mixture contains 5%, 5%, and 1%, respectively, of each additive based on the polyurethane. This solution is then extruded through a 960-l1ole spinneret (ori?ce diameter 0.0025 inch) into an aqueous‘ method described herein. bath containing 50% dirnethylformamide and 5-1 0% talc, by stretching rather than fracturing. Other apparatus such as the variable cutter attachment for the Paci?c Converter described in U.S. 2,599,148 may be utilized. Most advantageous results are obtained when the elastic ?ber component is cut to uniform lengths which are rela If it is desired to utilize in elastic ?laments of signi?cantly shorter lengths, it is within and maintained at about 95° C. The 6,000-denier tow the scope of the present invention to utilize, as the sheet 20 thus formed is removed at about 40-50 yards per minute of inelastic ?laments, natural or synthetic staple ?bers in and passed through a water bath maintained at 90° C. to sliver or web form. 95° C. until the ?laments contain less than 0.5% dirneth From a practical viewpoint, the commercially avail ylformamide. After application of a talc ?nish, the tow is able apparatus for converting continuous ?laments directly dried in a relaxed condition for three hours at 104° C. to sliver, i.e., the tow-to-top conversion systems widely 25 and then heated for 45 minutes at 140° C. The spandex used in the textile industry, are designed to operate on tow thus produced has an individual ?lament denier of 6 tow bundles of 1.5 to 2 million total denier. In addition, and total tow denier of approximately 6,000. the inelastic ?bers are commercially available in tows of (12) Preparation of Composite Tow from 200,000 to 500,000 total denier. Since it is a re quirement of the present invention that the elastic ?la 30 The spandex tow is used to prepare a composite tow rnents be sandwiched between the layers of inelastic ?bers, the inelastic ?bers will generally account for a minimum of one-half to one million denier or approximately one fourth to one-half the capacity of the conventional appa comprising about 10% by Weight of the spandex tow and about 90% by Weight of a commercially available inelastic acrylonitrile polymer ?ber tow. The inelastic tow has a ?lament denier of 3 and a total tow denier of ratus. Thus, from a practical standpoint, the elastic ?la~ 470,000. Referring to the apparatus illustrated in the ment content of the composite tow will have as its upper drawing, one end of the inelastic tow is spread out to limit approximately 50 %to 80% of the total ?ber weight. Preferably, the elastic ?laments will comprise from about form a wide sheet A and two ends of inelastic tow are spread similarly to form wide sheets and superposed in 3% to about 50% of the composite tow or web. It is to two layers to form sheet A’. Twenty-four ends of the be understood, however, that as little as about 1% of the 40 spandex tow are disposed over the same width to form total weight may be provided by the elastic ?laments. sheet E. The tension on the spandex tow E is so regulated The following examples, in which parts and percentages that the spandex ?laments are under a stretch of 5% to are by weight unless otherwise indicated, further illustrate 10% as they are sandwiched between the layers of inelastic the present invention. In the examples, the term “elon tow and enter between input rolls 38 and 40 which are, gation” when applied to yarns refers to the total yarn in this case, the input rolls of a Paci?c Converter de stretch attributable to the elastic ?ber component and is scribed in U.S. 2,438,469. the ratio of the extended length of the yarn to its original length expressed as percent of the original length. The (0) Preparation of Staple Fiber Staple ?ber samples are cut from the composite tow on the Paci?c Converter to lengths of 3", 4%", and 6". at selected points based on the extended length speci?ed. 50 No ?nish is applied to the composite tow during process ing. Staple length measurements are made on both the EYAMPLE I spandex and inelastic ?bers after cutting and the stand ,(a) Preparation 0]‘ Elastic Filaments ard deviation (3) and coe?icient of variation (CV) are calculated according to conventional statistical procedure. Into ‘a reverse centrifugal mixer maintained at 50° C. The results are set forth in Table 1, which follows. are fed a stream of polytetrarnethylene ether glycol at a term “power” is a measure of the resistance to stretch of the yarn expressed in grams per denier and is measured rate of 8 pounds per hour and a stream of liquid p,p’-meth ylenediphenyl diisocyanate at 2 pounds per hour. The polytetramethylene ether glycol has a molecular weight of about 2,000 and is thoroughly pre-dried by treatment with 60 a molecular sieve. The reagents are intimately mixed, and are discharged continuously into a jacketed pipeline maintained at about 96° C. and extending for 25 feet. The pipeline serves as a reactor in which the polyether glycol is “capped” wit-h 2 mols of the diisocyanate to yield an isocyanate-terminated polyether. The average time spent in the pipeline reactor is between 90 and 100 min utes. On emerging from the pipeline reactor, the iso cyan'ate-terminated polyether is cooled at once to below 45° C. The cooled isocyanate-terminated polyether is conducted at a rate of, 9.2 pounds per hour into a high shear mixer containing a rotating disc, and a stream of N,N-dimethylformarnide is added at 42.8 pounds per hour. The mixture (17.7% solids) is thoroughly agitated for 4 minutes and then passes to a chamber in which a mixture TABLE 1 Nominal cut length, inches Inelastic ?ber Avg. 2. 93 4. 56 5. 81 0 .36 .57 .45 S CV, percent 16.1 12. 2 7. 7 v ' pan d ex (elasm) ?ber Avg. 2.99 4. 50 5. 98 a- .270 .335 .418 C", percent 8.8 8.6 7.1 Surprisingly, as seen from Table 1, the cut length of the spandex ?ber is very close to the desired nominal length for which the Paci?c Converter was set, and the length distribution is unusually uniform. It is particular ly surprising that the spandex ?ber shows a greater accu racy of average cut length and a more uniform distribu tion of cut lengths than does the inelastic ?ber. ‘Cutting performance and subsequent processability to sliver on the Paci?c Converter are observed to be excels 0,077,000 55 lent, free of roll wrapping and tangling. The sliver ob tained is then spun into yarn using conventional equip ment and procedures for pin drafting, roving, and spinning. Samples of each of the three ?ber cut lengths are spun to 238% and the power is .073, .12 and .233 gram per denier at 60, 75 and 90% of the extended yarn length, respec tively. Processability and yarn properties are not a?ected adversely by the use of the low ?lament denier for the 20/1 cc. yarn with a twist of 13.4 2. inelastic ?ber. The power and 5 elongation values of the yarn, as previously de?ned, are 1" ' e ' f l Set form m Tabla 2’ Whlch ro‘lows‘ TABLE 2 EXAMPLE lV . . Four ends of the inelastic tow of Example I and 35 ends of the spandex tow of Example I are combined by the process of Example I and FlGURE l to form a com POWQY wrung/0611ier at indicated percent Yarn Spandex ?bers nominal cut length, of extended yarn elqngan ‘168 lengm 10 posits tow having a composition of 90% inelastic ?ber 1 1 0, __ ‘ i v . _. _ film 40/0 Slg??d?li ?lJBI'. 0116 part Of this Composite tow i101‘: is processed on the Paci?c Converter with a 31/2” variable percent 60% 75% . ,. .001 . 99% . .100 .10 _ . .,~ ,, table 4 below show that the ?ber length of the spandex 251 ?berris surprisingly close to the nominal cut lnegth in each instance and the yarn property data in Table 4 again 20 illustrate the desirable level of yarn properties attainable _ 1 , throueh the use of the The spandex tow and the inelastic t w or Example I are L m used to prepare a group of composite tows of different ?ber blend ratios, generally following the procedure indi- recess of this invention. P \ T T’*B“E 4‘ .T cated schematically in the FlGURE of the drawing. The . . . .a Yb 1 . When more 4- ” _ h . 34 ‘an . wicned between layers of the inelastic tow. ‘ _ b1 . in all cases, the ends of spandex tow under 5% to 10% stretch are sand. 1 v .. to produce the desired blend ratios. _ *‘Iommal cut'lengm number of ends 01’ the two tows are varied as necessary 25 . . H EXAppLE H . . cut and the remainder is processed Wlth a 6 straight out. _ Each portion is then further processed as in Example I 1” to a 20/1 cc. yarn with 13.4 t.p.i. Z twist. The data in e 6 “mg ‘7 t1 a . 1 “?m‘i’git?éfgvmge, inches _________________ __ 27 52 than one end of inelastic tow is used as either A or A’ in ¢(r;._\_/_.-__.‘-.‘-.t........... _- ;_ 1:8; .1851; the FIGURE, they are disposed as superimposed, wide 30 Smh§2¥§§$ég1gg5gggg1 ‘I35 63 sueets as in Example 1. Each composite tow sample is 'é»,\-,--;5;Eé;l-t----------- -- ‘i675; fig processed on the Paci?c Converter to a 41/2” variable cut, Yam pf-o‘gemgs}""""""""""""""""" " and subsequentlv processed as in Example I to a 20/1 cc. yarn with 13.4 t.p.1. Z twist. F1001 length distribution POWQPiHgFamS/denler mindicsledpercenl 60%" _ _ . ,,' . . ., _ F . L . . in the 1 Paci?c . Converter L . ,_.sliver is determined for each ‘ of extended yarn1engtl1— 35 -/ _ sample and is reported in lable 3. nisngahon, percent _____________________ __ ' .074 072 . . 0 202 274 it will be noted that the cut length distribution of the spandex ?bers is surprisingly good and again superior to EXAMPLE V that of the inelastic ?bers although not so markedly superior as we'e the straight out samples of Example I ‘10 Th?ty-?ve ends of the spa?deX low of Example 1 are shown in Table 1. It will further be noticed that this combmcd with four ends of a commercially available excellent cutting performance is achieved over the entire polyethylene terephthalate tow having a total tow denier range of blend levels represented in these samples. Data of 450,000 and an individual ?lament denier of 2.25. on the power and elongation of the yarns spun from the A, The composite tow formed by the process of Example I ' several composite tows are also given in Table 3. has a ?ber composition of 90% polyethylene terephthalate TABLE 3 _ _ . Cut length, inches Power in grams] Ccrnpositetow, denler 111 Spandex Sample m1 ons _ content, percent Inelastic ?ber Total Spandex Inelastic Aver- 0' age Spandex ?ber CV, Aver- percent age 0' CV, as 1. 401 .054 1.410 ______________________________________ _. 2.000 2.100 1.710 2.230 2.300 1.010 1. 010 2.010 .210 .300 .300 .400 .500 .400 .500 .000 1. 820 1.800 1.410 1.000 1.000 1.410 1. 410 1.410 .30 .33 .30 .27 .23 .20 .37 .20 s. 73 7.47 3.70 5.05 5.03 0.50 s. 70 0. 02 4.07 3.72 4. 09 3. 70 4.44 4.47 4.00 4.13 Yarn percent ofex- elonga tended yarnlength tiou, percent 60% 75% 90% 007 .141 .311 124 .073 .007 .000 .005 .003 .004 .002 .050 .122 .100 .102 .104 .000 .101 .000 .002 .240 .200 .100 .193 .173 .100 .175 .101 272 204 277 201 273 283 274 207 per cent 10.0 13.0 17.0 17.0 21.0 22.0 20.2 30.0 4.51 4.35 4. 47 4.59 4. 48 4.47 4.30 4. 27 denier at indicated .27 .10 .31 .23 .10 .22 .10 .13 0.03 4.30 7.03 0.00 4.00 5.01 4.02 4. 33 EXAMFLE III fiber and 10% spandex ?ber. The spandex ?bers under In this example, the inelastic tow of Example I is re- 05 5.40% stretch are sandwiched between layers or" the polyethylene terephthalate ?bers. The composite tow is placed by another inelastic tow of the same composition processed on the Paci?c Converter with excellent processe and total tow denier but having an individual ?lament bility and performance. denier of 2. Three ends of this tow are combined with in the same manner as in Example I, thirty-seven ends 35 ends of the spandex tow of Example I by the procedure outlined in Example I to form a composite tow compris 70 of the spandex tow of Example I are combined with three ends of the polyethylene terephthalate tow of the present ing 87% inelastic ?ber and 13% spandex ?ber. The example. The composite tow, comprising 86% poly composite tow is processed on the Pacific Converter with a 41/2" straight cut and is subsequently spun to a 42/2 cc. ethylene terephthalate ?ber and 14% spandex ?ber, is yarn with 22.8 t.p.i. Z. twist in the singles and 22.8 t.p.i. processed on the Paci?c Converter to 3%." variable cut. S twist in the ply. The elongation of the ply yarn is 75 Staple length measurements made on ?ber samples taken 3,077,006 7 5 from the Paci?c Converter sliver again show better cut length uniformity for the spandex ?ber than for the in Example I to form a composite tow comprising 90% inelastic ?ber and 10% spandex ?ber. The composite tow elastic ?ber as indicated in Table 5. is cut on the Paci?c Converter to 41/2" variable cut. The TABLE 5 Polyethylene terephthalate Spandex ?ber Cut length ?ber Average, inches _______________________ __ i1 CV, percent _____________________________ _. 3. 5 3. 2 .257 . 149 7.3 4. 7 spandex tow is given varying amounts of stretch as it is combined with the inelastic tow at the input rolls of the Paci?c Converter, as shown in Table 8. From the staple length data obtained on ?ber samples ‘from the Paci?c Converter slivers, it will be noted that the prin cipal effect of increasing the stretch is to decrease the staple length of the spandex ?bers. TABLE 8 EXAMPLE VI Six ends of the spandex tow of Example I are passed to a pair of driven rolls and thence to a second pair of Spandex ?ber length Percent stretch rolls driven at a linear surface speed 3.3 times that of the ?rst pair of rolls so that the spandex tow is stretched 3.3 times in passing between the two sets of rolls. _— Avg, a inches The 4. 5 4. 3 3. 9 3. 7 3. 5 3. l stretched tow is then wound on a spool motor-driven at a speed such that the tow is wound in a relaxed condition. Thirty-eight ends of this previously stretched and relaxed CV, Percent . 614 . 533 . 939 . 868 . 689 . 533 13.6 12. 4 24. l 23. 5 19. 7 17. 2 tow are restretched to 5-10% stretch and then combined under this stretch with 3 ends of the inelastic tow of Ex ample III by the procedure of Example I to form a com It will be apparent to those skilled in the art that any posite tow comprising 86% inelastic ?ber and 14% span 25 of a great number of elastic and inelastic natural and synthetic ?bers, as well as ?ber blends, may be substi dex ?ber. The composite tow is processed on the Paci?c tuted for those speci?cally disclosed in the foregoing Converter with a 41/2" variable cut. The Paci?c Con examples. Among the many inelastic ?bers are those verter’s sliver is given 6 passes of pin drafting. Another prepared from the synthetic ?ber-forming materials such composite tow is prepared and processed in an identical manner except that the spandex ?ber is not stretched and relaxed before incorporation under 5-l0% stretch in the composite tow. Sliver from the ?nal pin drafting opera tion for each sample is examined for neps and unsepa rated clumps of ?bers. The results shown in Table 6 clearly show the improvement obtained by the stretching and relaxing pre-treatment of the spandex tow. as polyesters, e.g., polyethylene terephthalate; polyamides, e.g., polyhexamethylene adipamide, polyhexamethylene sebacamide, polycaproamide, and copolymers of various amides; acrylic polymers and copolymers, e.g., polyac rylonitrile, copolymers of acrylonitrile with vinyl chloride, vinylidene cyanide, vinyl pyridine, methyl acrylate; vinyl polymers, e.g., vinyl chloride/vinyl acetate copolymers; polymers and copolymers of tetra?uoroethylene, mono TABLE 6 chlorotri?uoroethylene, and hexa?uoropropylene; poly Neps/250 grains Unsepartaed ?bers 40 ethylene; cellulose derivatives, e.g., cellulose acetate, re generated cellulose, ethyl cellulose, cellulose triacetate; (clumps) per 250 grains sliver sliver Small Without stretching and relaxing ______ __ With stretching and relaxing _________ __ 100 60 Large 25 8 2 0 glass, or from any natural ?bers, such as cotton, wool, silk, jute, linen, or a blend of two or more inelastic ?bers. A particularly suitable class of elastic ?bers for use in this invention are the spandex ?bers. Among the seg 45 mented polyurethanes of the spandex type are those de scribed in several patents, among which are US. Patents 2,929,800, 2,929,801, 2,929,802, 2,929,804, 2,953,839, EXAMPLE VII 2,957,852, and Re. 24,689. As described in the aforemen One end of the inelastic tow of Example I is passed tioned patents, the segmented polyurethane elastomers through a Turbo Stapler as described in US. 2,748,426. 50 are comprised of amorphous segments derived from poly At the same time, three ends of the spandex tow of mers having a melting point below about 50° C. and a Example I are fed to the Turbo Stapler so that they by molecular weight above about’ 600, and contain from pass the heating and drawing zone and are folded into about 5% to 40% of crystalline segments derived from the inelastic tow at the rolls commonly known as the a polymer having a melting point above about 200° C. intermediate rolls. As they enter the intermediate rolls in the ?ber-forming molecular weight range. Most of and are combined with the inelastic tow, the spandex tows suchpolyurethanes, when in ?lament form, have elonga are under a stretch of about 50%, and still further stretch tion greater than 150%, tensile recovery of over 90%, and is applied as the combined tows pass to the breaker bars. a stress decay of less than 20% as ‘de?ned in U.S. Staple length measurements on ?bers taken from the 2,957,852. Turbo Stapler sliver show more uniform staple lengths Fibers of other types of condensation elastomers are for the spandex ?ber than for the inelastic ?ber, as shown also suitable. US. 2,670,267 describes N-alkyl-substi in Table 7. ~ tuted copolyamides which are highly elastic and have a TABLE 7 suitable low modulus. A copolyamide of this type, ob tained by reacting adipic acid with a mixture of hex Fiber length Inelastic ?ber Average, inches ............................. ._ Spandex er 6. 8 8. 0 0-. 1.05 . 757 CV, percent _________________________________ -_ 15. 4 9. 46 EXAMPLE VIII Three ends of the inelastic tow of Example I and ‘four ends of spandex t-ow identical to that of Example I ex cept having a total denier of 40,000 are combined as in 05 amethylenediamine, N - isobutylhexamethylenediamine, and N,N'-isobutylhexamethylenediamine, produces an elastomer which is particularly satisfactory for the pur poses of this invention. US. 2,623,033 describes linear 70 elastic copolyesters prepared by reacting glycols with a mixture of aromatic and acyclic dicarboxylic acids. Co polymers prepared from ethylene glycol, terephthalic acid, and sebacic acid have been found to be particularly use— ful. Another class of useful condensation elastomers is described in US. 2,430,860. The elastic polyamides of 3,077,006 3 10 this patent are produced by reacting polycarbonamides with formaldehyde. This last form shows good ai?nity for spandex ?bers but Elastic ?bers of textile denier from ?ber-forming addia tion polymers such as, for example, copolymer of buta diene/styrene, butadiene/acrylonitrile and butadiene/Z vinyl pyridine, polychlorobutadiene, copolymers of iso~ butylene with small proportions of butadiene, chlorosul fonated polyethylene, copolymers of monochlorotri?uoro ethylene with vinylidene fluoride, and the like, may be no af?nity for cotton. It has now been found that one-bath unions of cotton and spandex ?bers can be obtained by adjusting the alkalinity of the vat dye bath to a point where there is equilibrium between the sodium salt (basic leuco form) and the half acid. In this one-bath method, the vat dye is reduced in the usual manner with sodium hydrosul?te, but with only about half the usual amount. of alkali in employed. 10 the bath. The exact amount of alkali to be used will Both the elastic and inelastic ?laments may be supplied vary somewhat with the vat dye being used, and can be on packages of any convenient and available form. They readily determined by those skilled in this art. The alkalinity of vat dye baths for cotton is commonly equival~ may be in the form of individual ?laments, or of relatively small bundles of ?laments of low total denier, e.g., 200 cut to about 8 g. NaOH/liter. Optimum alkalinities for to 1,000, or as tows or" high total denier of the order of 15 union dyeing of cotton/ spandex blends with several repre 400,000. While the rawing shows a three-layered com sentative dyes are shown in the following table. Identi ?cation of the dyes is according to the Technical Manual posite tow structure, it is to be understood that other structures are within the scope of the invention provided of the American Association of Textile Chemists and that the elastic ?bers are sandwiched between at least Colorists, 1960 edition, page 308. The C1. references two layers of inelastic ?bers. The choice of alternate ar 20 are to the Colour Index, second edition, 1956. rangements will depend on the equipment to be used and TABLE 9 the form in which the starting yarns is supplied. The slivers made by the process of this invention can Optimum be used in the manufacture of yarns suitable for use in elastic or stretchy woven, knitted, and non-woven fabrics for use in universal ?tting apparel (socks, polo shirts, underwear, bathing suits, gloves, elastic cuffs, sweaters, waistbands, suits, coats, dresses, skirts, action sportswear, leotard-type outer wear, and ac essories such as tapes, webbings, and other woven, non-woven, or knit apparel fabrics), household products (form-?tting upholstery, slipcovers, sheets, carpets, mattress coverings, and narrow tapes and webbings for a Wide variety of uses), industrial products (transportation upholstery, woven and non woven felts, tapes and Webbings for varied applications), and medical products (surgical bandages, supports, elastic dressings, surgical stockings, and splint tapes). in addi Dyes for unions 0.1T. alkalinity for unions— g. NaOH/liter “Ponsol” .Tade Green __________ __ Vat Green 1, 59825.." 4. 0 “Ponsol” Golden Orange 2BG__ “Ponsol” Navy Blue llG_______ 3. 5 3. 5 “Ponsol” Brilliant Red B _____ __ 3. 5 At the optimum alkalinities of Table 9, the shades produced on the cotton and on the spandex ?ber are equivalent, that is, good unions are achieved. When the desired shade has been obtained, the leuco forms are then oxidized according to conventional practice for vat dyes, e.g., with sodium perborate. Union dyeing of cotton/spandex blends made by this modi?ed one-bath tion, low stretch, high recovery fabrics can be made suit procedure with the vat dyes listed in Table 9 and similar able for use in outer apparel (sweaters, knit jersey, and woven, knit, or non-woven suitings and dress goods), 40 dyes exhibit lightfastness in excess of 40 hours and good washfastness. household items (rugs, carpets and upholstery), and in The process of this invention makes possible the produc dustrial products (Woven, non-woven, and knit compres tion of new and useful elastic yarns making more efficient sion or impact-bearing structures). Illustrations of vari use of the elastic ?ber content than is obtained by the con ous speci?c products which may be prepared from the ventional cut staple ?ber route. The use of the composite ?ber blends and yarns made by the process of this inven tow eliminates the limitations on denier and length result~ tion are shoe laces, shoe liner fabric, shoe upper fabrics, ing from formation of neps and high ?ber breakage during house slippers, skin diving suits, snow suits, ski pants, carding. The use of longer staple ?ber lengths for the football pants, slacks, llannels, sport shirts, bulky knit elastic ?ber content reduces the number of free ?ber sweaters, blankets, swimming pool covers, toupee bases, ends in the yarn bundle and is advantageous in improving belts, suspenders, garters, watch bands, ropes, elastic sew such yarn and fabric performancy characteristics as ing thread, shock cords, bookcover jackets, bookbinding cloth, synthetic paper, elastomer-coated fabrics, and super-dense felts, such as papermakers’ felts. The ?ber blends, yarns, fabrics, and other textile pro ducts prepared from the slivers made by this invention may be given the customary ?nishing treatments where necessary or desired, such as scouring, Washing, drying, pressing, dyeing, heat-treating, and softening. With particular reference to dyeing, good union dyeings fuzzing, pilling, hand, color change, and dyeability. As illustrated in the examples, the use of longer ?ber lengths results in more e?lcient use of the elastic ?ber component as re?ected in the values for yarn power. Improved recovery of yarns and fabrics is a direct consequence because of the increased power available to overcome friction caused by fabric or yarn geometry. it is particu larly surprising and unexpected that a ?ber of elastic of excellent lightfastness can be achieved on blends of 60 characteristics can be cut to uniform ?ber length when incorporated under tension in a composite tow. spandex ?bers with cotton in a one-bath procedure. Vat As many Widely di?erent embodiments of this inven dyes of the anthraquinone type are used under essentially tion may be made Without departing from the spirit and conventional vat dyeing conditions except that the alkalin~ scope thereof, it is to be understood that this invention is ity of the dye bath is reduced. not to be limited to the speci?c embodiments thereof ex 65 It is Well known to convert vat dyes by strong reducing cept as de?ned in the appended claims. agents, such as sodium hydrosul?te, to the sodium salt I claim: or basic leuco forms under conditions of relatively high 1. In the method of producing a blend of separate alkalinity, e.g., 8 g. NaOl-l/liter. Excellent fastness out lengths of elastic and inelastic ?bers the steps com properties result When cotton is dyed under these condi 70 prising forming a plurality of separated flat sheets of in tions. The spandex ?bers show very low a?lnity for the elastic ?laments and continuous elastic ?laments, ten~ basic leuco form of vat dyes. Under appropriate and well sioning said sheets of elastic ?laments to stretch said ?la~ known conditions, the dyes can be converted two further ments a predetermined amount beyond their normal re steps, ?rst to the half sodium salt or half acid form, and laxed length, combining said sheets of elastic and in second to the dihydroxy derivative or acid leuco form. 75 elastic ?laments in layered relationship to form a com 3,077,0oe ll amount beyond their normal relaxed length, combining posite web wherein said tensioned elastic ?laments lie be tween adjacent sheets of said inelastic ?laments, and thereafter feeding said composite web to fracturing means whereby said ?laments are cut to staple lengths. 2. The method of claim 1 wherein said elastic ?la 5 ?laments, and thereafter feeding said composite web to ments are stretched an amount from about 5% to about fracturing means whereby said ?laments are cut to staple said sheets of elastic and inelastic ?laments in layered relationship to form a composite web wherein said ten sioned elastic ?laments lie between said sheets of inelastic 15% greater than their relaxed length. lengths. 3. The method of claim 2 wherein said composite web 6. The method of claim 5 wherein said elastic ?la is comprised of from. about 3% to about 50% by Weight ments are extended an amount from about 5% to about of said elastic ?laments. 10 15% greater than their relaxed length. 4. The method of claim 2 wherein said elastic ?la 7. The method of claim 6 wherein said composite web ments are subjected to at least one cycle of stretching to is comprised of from about 3% to about 50% by weight from about two to ?ve times their original length and of said elastic ?laments. relaxing after being formed into a flat sheet. 8. The method of claim 6 wherein said elastic ?la 5. In a method of converting continuous elastic ?la 15 ments and inelastic ?laments into ‘a sliver of intermingled ments are subjected to at least one cycle of stretching to staple ?bers, the preliminary steps comprising forming a from about two to ?ve times their original length and relaxing after being formed into a flat sheet. plurality of separated ?at sheets of continuous elastic ?la ments and inelastic ?laments, tensioning said sheets of elastic ?laments to extend said ?laments a predetermined No references cited.