US2980492A

US2980492A - Process for preparing textile yarns

Info

Publication number: US2980492A
Application number: US738032A
Authority: US
Inventors: William H Jamieson; Cecil E Reese
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1958-05-27
Filing date: 1958-05-27
Publication date: 1961-04-18
Anticipated expiration: 1978-04-18

Description

April 18, 1961 w. H. JAMIESON El'AL 2,980,492

PROCESS FOR PREPARING TEXTILE YARNS Fiied May 27, 1958 INVENTORS WILLIAM- H. JAMIESON CECIL E. REESE ATTORNEY United States Patent 2,980,492 PROCESS FOR PREPARING TEXTILE YARNS William H. Iamieson, Newark, Del., and Cecil Reese, Kinston, N.C., assignors to E. I. du Pont deNemours and Company, Wilmington, DeL, a corporation of Delaware Filed May 27, 1958, Ser. No. 738,032

13 Claims. (CI. 18-54) This invention relates to a novel process for manufacturing composite yarns having the property of becoming permanently bulky when heated under controlled con- -ditions. More particularly, this invention relates to a been made to produce a bulky continuous filament yarn in order to combine the desirable aesthetic properties of staple yarns with the advantages of continuous filament yarn, such as strength and simplicity of processing. Thishas been accomplished in various ways by producing continuous filament yarns in which the various filaments 0on tained in a short segment of a yarn have different lengths when straightened out. 1 V

It has been found that, when continuous filament yarn is treated so that it becomes bulky and is then converted.

into fabric, some of the processing advantages of the originally smooth, dense continuous filament yarn are lost. This is due to the fact that in the bulky yarn the yarn bundle is not compact, so that the filaments are somewhat loose and have a tendency to snag as the yarns contact each other or contact various parts of the yarn processing equipment. This is particularly true during weaving or knitting. There is also a tendency for the bulky yarn to be pulled out into a smooth yarn bundle in response to tensions imposed by the yarn processing equipment, since in each segment of the yarn the longer filaments which provide the bulking effect remain free of tension while the shorter filaments support the load imposed on the yarn; For these reasons a continuous filament yarn has been desired which can be processed in its smooth, com-- pact form into fabric and subsequently treated to obtain a satisfactory amount of bulkin fabric form.; 1

' Composite continuous filament yarns comprised of filaments having different levels of shrinkagehave been'described in the prior-art. .Such yarns can be woven into fabrics and subjected to shririking toachieve bulking in fabric form owing to diflerential shortening of the lengths of the filaments inthe. ;yai'ns, especially whenthe construction of the fabric is loose enough to permitthe yarns to shrink under little orno restraint. Composite. convtinuous'filament yarns composed of filamentswhich-fm-ay f be caused to undergo spontaneous and irreversible extension in length in varying amounts may be used even more advantageously, since the ability of the filaments to ur1- dergo spontaneous extension in length is not influenced 2,980,492 Patented Apr. 18, 1 961 by fabric construction. Similarly, composite continuous filament yarns having good bulking properties are advantageously formed by combining spontaneously and irreversibly extensible .filaments with shrinkable filaments, or with filaments'which exhibit little or no change in length when they are heated or subjected to other processing conditions.

In the production of yarns capable of becoming bulky by differential change in length of the component strands upon heating or other appropriate treatment, it has been regarded as necessary in the past to ply together two different yarns, or otherwise associate together their filaments in some manner. Such a process has the disadvantage that numerous steps are required; i.e., the'yarns must be produced separately and selected according to their physical properties, following which the additional 7 object is to produce such a yarn directlyby extruding a usually employed. It is step of plying or otherwise associating the, yarns is required. g

It is, therefore, an object of this invention to provide a novel process for producing a composite yarn which has the property of becoming bulky when heated. Another molten polyester from a spinneret, and subsequently drawing the resulting yarn bundle, if desired. A further object is to provide such a process which is readily adaptable for the preparation of yarns which can be made to become bulky by differential shrinkability, difierential extensibility, or mixed shrinkability and extensibility.

The objects of this invention are accomplished by a process which comprises extruding a molten linear condensation polyester through a plurality of spinneret ori fices at unequal rates of flow to form solid filaments of at least two different sizes and forwarding the filaments so formed as a single filament-bundle, the-rates of poly: mer flow and the rate of forwarding being adjustedso that in the filament bundle the spun denier 'per filament of the filaments of smallest size is not more than about 8 and the ratio of the maximu'm'filament size to the minimum filament size is at least about. 1.25. The forwarding speed may be selected within a wide range, forwarding speeds in excess of about 300 yards per minute being generally desired that the extruded filaments be oriented to cause them to become tenacious. This may be done simply by winding the extruded filaments at very high rates of speed, e;g., at about 3000p about 5200 "yards per minute, as :described'by Hebeler in US. Patent 2,604,689. Alternatively, the ex truded filaments may be-wound up'in a yarn bundle and .then oriented by cold drawing the yarn up to about five;

times its original length in one ,or more separate steps, as disclosed by Whinfield and Dickson in U;S. Patent 2,465,3l9.-- Because the orientation of the yarn in the spinning step increases with spinning speed, the draw ratio required to reach a given levelof orientation in the yarn decreases as the spinning speed increases.

When the linear -condensation-polyester filamentsare spun and wound up together in a single yarn bundle in themanner described above, 'the yarn has the smooth anddense characteristics of-a typicalcontinuousifilament yarn; i.e.,- all ofthe filaments inia essentially freefrom loops or kinks The yarn may then fabrics areheated freefrom'tension, theyibeco'me merit yarns. Surprisingly, however, when these yarn s or given yarn segment i have substantiallythe same length and'the filaments are.

bulky and voluminous. The bulking effect results from the differential change in length response of the various filaments to the heat treatment. In yarns prepared by the process of the invention as described thus far, the diflerential response of the filaments to heat treatment is differential shrinkage; however, as described in detail below, the yarns are readily modified by preliminary heat treatment under controlled conditions so that the filaments exhibit differential spontaneous extension in length or mixed shrinkage and spontaneous extension.

In yarns made in accordance with the process of the invention, the difierence in length of the filaments in a given yarn segmentafter the final heat treatment amounts to at least about 5% of the length of the filaments prior to the final heat treatment. Yarns composed of filaments having less than about 5% length differential, such as may be prepared by various methods, approach the relatively low bulk characteristics-of standard continuous filament yarn. When very high bulk is desired, the process of the invention may be used to provide yarns having a length differential of 30% or even higher. The differ'ential response to heat treatment can be'observed in the yarn extruded and wound up in accordance with the process of the invention as described even in the absence of a drawing step. However, the effect may be frequently increased by the drawing step or by orienting the yarn by winding it at high speed in the extrusion step.

In one embodiment of the invention, the total shrinkage of yarn is reduced by a preliminary heat treatment. In this embodiment, a molten linear condensation polyester is formed into oriented solid filaments of at least two different sizes by extruding the molten polyester through a plurality of spinneret orifices into a fluid medium, e.g., air or an aqueous medium, and orienting the filaments so formed, the extruded filaments being wound in a single yarn bundle and the rates of polymer flow and the rate of winding being adjusted so that in the filament bundle the spun denier per filament of the filaments of smallest size is not more than about 8 and the ratio of the maximum'filament size to the minimum :filament'size is at least about 1.25, following which the bundle of oriented filaments is heated by passing it tures of- 150 C. and above.

through a zone maintained at a temperature of at least about 90 C. to": effect a shrinkage in the yarn not exceeding' the maximum shrinkage of the smallest denier filaments and passed. out of said zone and cooled before the yarnis fully crystallized. This is readily accomplished, since the rate at which the yarn relaxes orshrinks is much faster than-the rate:atwhichcrystallinity develops in the yarn. ,Of course, thetemperature and exposure timein the heatedzone should be such that the polymer does not melt or decompose. The orientation of the extruded filaments may be accomplished by winding them at high rates of speed, or in a separate drawing step, as previously described. Preferably, the yarn is maintained substantiallyamorphous or at only a low level of, crystal-' linityv throughout the orientation step and in the prelimmary. heating step Crystallinity is -minirnized in the orientation step byoperating at low temperatures, such as by drawing the yarn in the presence of Water, and by orienting the yarn to a moderate degree only. '-In addition, rapid cooling following the drawing stepwill tend to limit crystallization; In the preliminary heating step, cr'ystallinity is minimized bypassing the yarn through the heating zone as quickly as possible consistent with the processing advantages of the continuous filament yarn are thereby retained.

In a preferred embodiment of the process of the invention, a shrinkage of at least about 20% is effected in the yarn in the preliminary heat treatment described above, the crystallinity of the yarn preferably being maintained at a minimum level, as described. By effecting a sufficiently high shrinkage, a minimum of at least about 20% usually being required, at least some of the filaments comprising the yarn become spontaneously and irreversibly extensible, the spontaneous extension in length being achieved when the yarn is subjected to a final heat treatment at any desired stage in the processing of the yarn. Surprisingly, the difierentialrespon-se of the filaments in the yarn to heat treatment is retained, and a high degree of bulk may be achieved with these yarns containing spontaneously and irreversibly extensible filaments. Depending uponthe shrinkage level efiected in the preliminary heat treatment, some of the yarns may become spontaneously extensible while others remain shrinkable, or all of the filaments may become spontaneously extensible in varying amounts.

The final heat treatment used to cause the yarns to become bulky may be carried out at any'desired time. As mentioned previously, :it is generally preferred'to employ this treatment after thefyarns have been converted into fabric form, although if desired the treatment may be used at an earlier stage of processing. An aqueous bath at the boil is usually a satisfactory medium for bulking the yarns, although in some cases aqueous baths at temperatures as low as 70 C. may be used. Dry heat, such as hot air, may also be used, especially at tempera- The duration of the final heat treatment is sufiicient to allow-the yarn to become crystalline, in contrast to the brief duration'of the preliminary heat treatment (if any), in whichit is usually desired to minimize cryst-allinity. For any given heating ture, however, so that the heat treatment used to achieve the bulkingeffect need not be carried out Within a limited time after the yarns are prepared.-v It is only necessary to observethat the yarns are not subjected to temperatures in excess of about 70 C. during slashing or other yarn processing steps before the bulkiness in the yarns is desired. Moreover, once the yarns are bulked, they remain stable and do not return to their original form when cooled or dried, assuming of course that they are not subjected to tension high enough to stretch the shorter filaments in the yarn bundle. In some cases, if the yarn is heated at a temperaturein excess of the original heat treatment used to achieve bulking, however, the degree of bulk may actually increase to some extent. The heat treatment which is used to effect bulking inthe yarn can usually be carried out in water at. 70 C. tolOO" C. even ifa preliminary; heat treatment .is used in processing the obtainirigthedesired shrinkageat the giventempera'ture. I

this preliminary heat treatment, the yarn is still characterized by differential response of the filaments to'further heat treatment,- and' such, treatment accordingly causes it the "filaments in the yarn and this shrinkagelevel "is not Although the total shrinkage of the yarn is reduced'in I exceeded, the yarn bundle 'remzaas smooth and dense and 5':

yarn to reduce the shrinkage level of theyarn or to cause a some or all of the filaments therein ,to taneously extensible.-

The process of the present invention appears toclepend critically; upon the nature of" the polymer employed. In generaL; the process appears to; be operable only with linear condensation polyesters, especially when stable yarns are desired'which willgbulk up only when vgiven 'a specific treatment as described herein rathertha'nunstable yarns which may =bulk up.pr' ematurely. Ina preferred embodiment of theinve'nti'on, alinear terephthalate polyester is'employed. By linear terephthalate polyester. is

become spon- V meant linear polyesters iii-which at least about 75% of the recurring stuctural'units' are units of the formula neret.

filaments of each group, is controlled] The necessary wherein G represents -a divalent organic radical containing from 2 to 12 carbon atoms and attached to the adjacent oxygen atoms by saturated carbon atoms. I Thus, the radical G may be of the form CH A CH where m is 0 or 1 and A represents an alkylene radical, a cycloalky-lene radical, a bis-alkylene ether radical, or other suitable organic radical. The linear terephthalate polyesters may be prepared by reacting terephthalic acid or an ester-forming derivative thereof with a glycol, G(OH) where -G- is a radical as defined above, to form the bis-glycol ester of terephthalic acid, followed by polycondensation at elevated temperature and reduced pressure with elimination of excess glycol. Examples of suitable glycols include ethylene glycol, diethylene glycol, butylene glycol, decamethylene glycol, and trans-bis-1,4- (hydroxymethyl) cyclohexane. Mixtures of such glycols may suitably be used to form copolyesters, or small amounts, e.g. up to about 15 mol percent, of a higher glycol may be used, such as a polyethylene glycol. Similarly, copolyesters may be formed by replacing up to about 25 mol percent of the terephthalic acid or derivative thereof with another dicarboxylic acid or ester-forming derivative thereof, such as adipic acid, dimethyl sebacate, isophthalic acid, or sodium 3,5-dicarbomethoxybenzenesulfonate. Linear terephthalate polyesters and copolyesters are especially suitable for use in the present invention since they have high melting points and since the crystallinity and orientation of filaments formed from them may be readily control-led over a wide range.

If desired, the plurality of extruded filaments may be of a range of sizes, subject to the limitation that the denier of the filaments of smallest size is not more than about 8 spun denier per filament and the ratio of the maximum filament size to the minimum filament size is at least about 1.25. However, only two filament sizes need to be used. With respect to the critical limitations of the smallest size filaments and size ratio, it has been found that it is not possible to obtain a differential change in length of at least 5% throughout the range specified when the smallest filaments are larger than about 8 denier.

The filaments may also have a variety of cross-sections. In addition to usual round cross-section, shapes which may be used include cruciform, asterisk, Y, ribbon, zigzag, and keyhole cross-sections. Such cross-sections may be achieved by extruding the filament throughan orifice of appropriate shape formed by intersecting slots or holes, or by extruding a plurality of small filaments from a pattern of round or diamond-shaped holes spaced sufficicntly close together that the extruded filaments coalesce in the desired pattern. When more than one filament cross-section is employed in extruding filaments in accordance with the present invention, it is preferred that the larger denier filaments be of round cross-section or of more nearly, round cross-section than the smaller denier filaments; i.e., it is preferred that the cross-section of the larger denier filaments have a smaller ratio of permiter to diameter than the cross-section of the smaller-denier filaments. V i

This invention will be further illustrated by reference to the accompanying drawing in which: l-

Figure 1 is a schematic representation of suitable apparatus utilizing a divided pack spinneret; and

Figure 2 is a fragmentary cross-sectional view of a spinneret plate and metering plate of aisingle, pack spin- Referring to Fig. l, the base of a' portion of a spinneret assembly is represented by reference numeral 11. Wall 12 divides the spinneret into two separate cavities material 15 resting .on

screen assemblies

16 and 16.

forming two groups of filamentsil-S and19. By using different feed rates to the cavities, the relative size-of the 13 and 14 which are filled with a finely divided, inert Molten material,.meter,ed to

cavities

13 and 14 spin-QT ning pumps not shown, is extruded through; orifices 17,

rates of polymer How are readily calculated from the number of fialments desired of each size, the size or In carrying out the process of the present invention,

the filaments may also be extruded from-separate spinnerets arranged in side-by-side relationship, provided theyv are wound together at the same rate in a single yarn bundle in a manner similar to that shown in Fig. 1.

The filaments may also be extruded from a single pack through a single spinneret plate containing orifices of different diameter to achive unequal rates of polymer flow and thereby form filaments of dilierent sizes due to the difierential pressure drop through the various orifices. However, when this method is used, some experi mentation may be necessary to achieve the desired range of filament sizes. i

As shown in Fig. 2, a metering plate 23 in contact with a spinneret plate 24, containing capillary holes 25 and 2.6 aligned with the spinneret orifices '27 may be used to deliver molten polymer to the spinneret orifices at unequal rates of fiow, the diameter of the capillaries in the meteringplate being varied to the extent sufficient toprovide thedesired rates of flow through the various orifices. I

The ex ression oriented filaments is used herein to denote filaments having a birefringence of .at least about 0.0 4. The birefringence,-or doublerefraction, of polymeric filaments is primarily dependent upon the orientation of the polymer molecules along the'axis of the filament and is a convenient measure of suchorientation.

Thebirefringence, which is also called the specific index 7 of birefringence, may be measured by the retardation technique described in Fibres From Synthetic Polymers by R. Hill (Elsevier Publishing Company, New York, 1953), pages 266-8, using a polarizing microscope with rotatable stage together with a cap analyzer and quartz wedge. The birefringence is calculated by dividing. the

measured retardation by the measured thickness of the structure, expressed in the same units as the retardation. The intrinsic viscosity of the polymer is used herein as a'measure .of the degree of polymerizationof the polymer and maybe defined as I limit as-C approaches!) wherein 1;,is the viscosity of a dilute solution of the polymer in a solyent divided by ,the viscosity of the solventper se'measu'red in the same unitsat the same temperature; and C is the concentration in grams of the polymerper ml. of solution. Fomal, which comprises 58.8 parts by weight of phenol and 41.2 parts by weight of trichlorophenol, is a convenient solvent for measuring theintrinsic viscosity of linear polyesters, and intrinsic iviscosity values reported herein are with reference to Fomal as a solvent.

The, expression spont aneous extensibility? s used hereinto denote extension in lengthunder zerotension,

that is, without external force being applied.

The following exam'pleswill serve to further illustrate the invention and are not intended to be construed as limitative, 1 1 j n V EXAMPLE 1; 1:

' Polyethylene terephthalate having "an intrinsic-lvisc'osity C.

from a divided pack through a spinneret having 27 round orifices, each 0.009 inch in diameter, 7 of the orifices being on one side of the pack and 20 of the orifices being on the other side of the pack. Molten polymer is metered at equal ratesseparately from each side of the divided pack to the spinneret. The yarn is wound up together as a single filament bundle at a speed of 1200 yards per minute and is found to have a denier as spun of 200. The yarn accordingly comprises 27 filaments of round cross-sections, 7 having a spun d.p.f. (denier per filament) of 14.2 and 20 having a spun d.-p.f. of 5.0. A sample of the spun yarn, when placed in a bath of 100 C. water for five minutes, shrinks and becomes quite bulky. By separating the filament bundle and measuring individual filaments before and after immersion in 100 C. water, it is found that the 14.2 d.p.f. filaments shrink only 40%, while the 5.0 d.p.f. filaments shrink 51%. The diiferential shrinkability accordingly amounts to 11%.

The yarn is passed from a supply package through a bath of water at 25 C. and over a sponge to leave a thin uniform film of water on the yarn, after which it is passed around a feed roll, around a draw pin 1.6 inches in diameter maintained at a temperature of 100 C., and then around a draw roll, finally being wound up on a suitable package. The speed at the draw roll is 454 yards per minute and the draw ratio is 3.113. A sample of the drawn yarn, when immersed in a bath of water at 100 C. for five minutes, is also found to become quite bulky. By separating the filament bundle and measuring individual filaments before and after immersion in 100 C. water, it is found that the larger denier fila ments shrink 43%, While the smaller denier filaments shrink only 33%, corresponding to a diiferential shrinkability of 7 In another experiment, the yarn is drawn as indicated above, except that the drawn yarn is passed continuously 'fromthe draw roll through a chamber containing steam maintained at 100 C., returned through the steam chamber on a second pass, and then wound up on a suitable package. The yarn path through the steam measures 12 inches on each pass. The yarn speed at the draw roll is 454 yards per minute as before; however, the rate of winding is only 318 yards per minute, corresponding to a 30% shrinkage of the yarn on passage through the steam chamber. The exposure time of the yarn to the steam is 0.125 second, based on the rate of withdrawal of the yarn from the chamber on the second pass. when drawn and heattreated in this manner, is again found to become quite bulkyv on immersion in 100 C. water for five minutes. By separating the filament bundle as before, it isfo-undthat the larger denier filaments shrink 13.9% and the smaller denier filaments only 2.6%, cor-.

.up speed being 270 yards per minute, corresponding to a shrinkage of 40.5% and an exposure time 0130.147 second. Immersion of the"drawn and heat-treated yarn in 100"C.'Water-for'five minutes results in 3.1% shrinkage in the larger denier filaments and 5.0% extension in length in the smaller denier filaments, a differential length change of,8.l% based'on the length of the yarn prior to immersion in water.

In a similar pair of jexperinients a draw ratio of 2.852

The yarn,

It is found that, upon immersionof the.

7 minute.

' the 'othrQside of the pack. Molten polymer ismetered;

' T pack to the spinneret. The yarn is wound upgtogether as is used and, when the drawn yarn is immersed in C.

waterforfive minutes, the larger denier filaments shrink 54% the isn'i'allerdenier filaments 36% correspondf 8. ing to a ditferential shrinkage of 18%. In one of the experiments, the yarn drawn at a ratio of 2.852 is passed continuously through a steam chamber in the manner described above, the windup speed being 270 yards per minute, corresponding .to a shrinkage of 40.5% and an exposure time of 0.147 second. Immersion of the drawn and heat-treated yarn in- 100 C. water for five minutes results in 2.0% extension in length in the larger denier filaments and 9.2% extension in length in the smaller denier filaments, a differential length change of 7.2%.

EXAMPLE II Polyethylene terephthalate having an intrinsic viscosity of 0.59 and containing 0.3% TiO is spun at 295 C. from a divided pack through a spinneret having 27 round orifices, each 0.009 inch indiameter, 7 of the orifices being on one side of the pack and 20 of the orifices being on the other side of the pack. Molten polymer is metered at equal rates separately from each side of the divided pack to the spinneret. The yarn is wound up together as a single filament bundle at a speed of 1200 yards per minute and is found to have a denier as spun of 138. The yarn accordingly comprises 27 filaments of round cross-section, 7 having a spun d.p.f. of 9.9 and 20 having a spun d.p.f. of 3.45. The yarn is passed from a supply package through a bath of water at 25 C. and over a sponge to leave a thin, uniform film of water on the yarn, after which it is passed around a feed roll, around a draw pin 1.6 inches in diameter maintained at a temperature of 92 C.,-and then around a draw roll, the draw ratio being 2.609 and the speed at the draw roll being 227 yards per The drawn yarn is passed continuously from the draw roll through. a chamber containing steam maintained at 100 C., the-coutact distance with the steam being 9 inches, and the yarn is then wound up on a suitable package. The rate of winding is only yards per minute, corresponding to a 40.5 shrinkage of the yarn on passage through thesteam chamber. The exposure time of the yarn to'the steam is 0.111 second, based on the rate of withdrawal of the yarn from the chamber. The resulting yarn has a tenacity of 1.7 grams per denier and a break elongation of When a sample of the yarn is immersed in water at 100 C. for five minutes, it is found to exhibit a spontaneous extension in length of 3.0%. By separating the filament bundle and measuring individual filaments before and after irmnersion in 100 C. water, it'is found that the larger denier filaments exhibit a'spontaneous extension in length of 3.3% and the smaller denier filaments exhibit a spontaneous extension in length of 8.3%, adifierential length change of 5.0% based on the length of the yarn prior to immersion in water. g v I Aquantity ofthe steam-relaxed yarn is woven into, a 135-sley, l'20-pick, 2x Zbasket weave fabric. Temperatures in 'exces's of 70 C. are avoided in slashing and otheryarn. processing steps. The woven fabric is smooth and has the characteristic slick hand of continuous filament synthetic yarns; however, after immersionin 100 C. water for five minutes the fabric develops a desirable soft hand with increased cover and opacity- EXAMPLE III Polyethylene terephthalate having an intrinsic viscosity of 0.57 and containing 0.3% 'TiO is spun at 295 C. from a divided pack through a spinneret having 11 round on"- fices, each 0. 006 inchin diameter, on one side'of the pack and 27 Y-shaped orifices, each wmprising three intersec'ting slots 0.003 inch wide and 0.025 'inch long, on

at equal'rates separately from each'side ofthe divided a single filament. bundle at a speed of 1200-yards per minute and isfound to have a denier as spun of 208. -The yarn accordingly comprises 11 filaments-of round crossse'c'tion having a spund p'ifi of about-9.5 and 27 filaments of Y-shaped cross-section having a spun d.p.f. of about 3.9 The yarn is passed from a supply package through is then passed from a feed roll through a hollow needle leading into a nozzle having a throat diameter of 0.062

inch and a 7 flared exit passage and thence to asuitable windup package. Air is maintained at 220 C. and p.s.i. pressure on the entrance side of the nozzle, so that a jet of hot air is caused to fiow through the nozzle in the same direction as the yarn is passed through the nozzle. The tip of the hollow needle from which the yarn is delivered is located within the throat of the nozzle and the efiective distance through which the yarn is heated is 1.35 inches. The yarn is passed into the nozzle at 302 yards per minute and wound up at 150 yards per minute, corresponding to a shrinkage of 49.6% and an exposure time of 0.015 second, based on the rate of withdrawal'of the yarn from the nozzle. The yarn prepared in this way is a composite yarn which becomes quite bulky after immersion in 100 C. water for five minutes. By separating the yarn bundle and measuring individual filaments before and after immersion in 100 C. water, it is found that the filaments which have a Y-shaped cross-section exhibit a 14% spontaneous and irreversible extension in length in the boiling water, while the round-shaped cross-section filaments exhibit a shrinkage of in the boiling water.

A quantity of the air-jet relaxed composite yarn is woven into a 120.-sley, 114-pick, 2 x 2 basket weave fabric. Temperatures in excess of 70 C. are avoided in slashing and other yarn processing steps. The woven fabtic is smooth and has the characteristic slick hand of continuousfilament synthetic fabrics; however, after immersion in 100 C. water for five minutes, the fabric exhibits a warm and soft hand and shows a marked increase in cover and opacity.

EXAMPLE IV passed into the oven at 400ffeet perminute and wound up. at 180 feet. per minute, corresponding to a shrinkage of 55% and an exposure time of 0.333 second, based on the rate of withdrawal of the yarn from the oven.- The yarn prepared in this way is a composite yarn which becomes bulky after immersion in 100 C. water for five minutes. By separating the yarn bundle and measuring individual filaments before and after immersion in 100 C. water, it is foundthat the filaments which have a Y- shaped cross-section exhibita 12% spontaneous and irreversible extension in length in boiling water, while the round-shaped cross-section filaments exhibit a 3% extension in length.

A quantity of the steam-relaxed yarn is woveninto a 135,-sley, 120-pi'ck, 2 x 2 basket weave fabric. Temperatures in excess of 70 C. are avoided in slashing and other yarn processing steps. The woven fabric is smooth and has the characteristic slick hand of continuous filament synthetic yarns; however, after immersion in- 100 C. water for five minutes thefabric develops a warm 7 soft hand and shows a marked increase in cover and opacity Y 1 EXAMPLE v' I Polyethylene. terephthalate having an intrinsic viscosity eras is spun'at 298.C. through aspinneret ha ving 1 4 and averaging 17.4 d.p.f., and 3 filaments averaging 27.8 d.p.f. The yarn is drawn'3.4 over a 1.6 inch pin maintained at 101 C., the rate of winding in the drawing step being 227 yards per minute. The drawn yarn accordingly comprises 4 filaments averaging 1.2 d.p.f., 7 filaments averaging 5.1 d.p.f., and 3 filaments averaging 8.2 d.p.f. The yarn is found to have a tenacity and elongation at maximum strength of 3.6 grams per denier and 19.6%, re-

spectively. The yarn prepared in this way is a composite yarn which becomes bulky after immersion in C. water for five minutes. By separating the filament bundle and measuring individual filaments before and after immersion in 100 C. water, it is found that the drawn filaments averaging 8.2 d.p.f. shrink 15.0%, while the filaments averaging 1.2 d.p.f. shrink only 8.8%. The difierential shrinkability accordingly amounts to 6.2%.

The experiment is repeated, except that the yarn is wound at 800 yards per minute and the total spun denier is 262, the yarncomprising 4 filaments averaging 5.1 d.p.f., 7 filaments averaging 21.6 d.p.f., and 3 filaments averaging 30.2 d.p.f. The yarn is drawn as in the preceding experiment, using a draw ratio of 3.92. The drawn yarn accordingly comprises 4 filaments averaging 1.3 d.p.f., 7 filaments averaging 5.5 d.p.f., and 3 filaments averaging 7.7 d.p.f. The tenacity and elongation at maximum strength of the yarn are 4.0 grams per denier and 25.0%, respectively. The yarn prepared in this way is a composite yarn which becomes bulky after immersion in 100 C. water for five minutes. By separating the filament bundle and measuring individual filaments before and after immersion in 100 C. water, it is found that the drawn filaments averaging 7.7 d.p.f. shrink 15.6%, while thefilaments averaging 1.3 d.p.f. shrink only 9.8%. The differential shrinkability accordingly amounts to 5.8%.

7 EXAMPLE VI Polyethylene terephthalate having an intrinsic viscosity of 0.57 and containing 0.3% TiO is spun at 295 C. from a divided pack through a spinneret having 27 round orifices, each 0.009 inch in diameter, 7.of the orifices being on one side ofthe pack and the other 20 orifices beingon the other side of the pack. In a series of experiments, molten polymer is metered at various controlled rates separately from each side of the divided pack to th e spinneret to produce 7 large filaments and 20 small filamentsin each yarn, the filament sizes in each yarn being shown in Table I as'well as the denier. ratio of the larger to the smaller filaments. The "yarn is wound up together as a single filament bundle at a speed In each case, the spun yarn of 1200 yards per minute. is passed from a supply package through a bath of water at 25C. and over a sponge to leave a thin, uniform film of water on the yarn, after which it is passed around a feed roll, around a draw pin 1.6 inches in diameter maintained at a temperature of 100 C., and, then around a draw roll, finally being wound up on a suitable package. The speed at the draw roll is 100 yards per minute and the draw ratiois 3.0. The drawn yarn is then passed from a feed roll into a nozzle and exposed to a jetof hot air maintained at 220 C. in the manner described in Example III. The 'yarn is passed into the nozzle at 250 yards per minute and wound up atyards per minute, corresponding to a shrinkage of 40% and an Qchange.

1 Negative figures indicate extension in length.

EXAMPLE VII A polyethylene terephthalate/S (sodium sulfo) isophthalate (98/2) copolyester having an intrinsic viscosity of 0.52 is prepared by a condensation reaction between 2.1 mols of ethylene glycol and a mixture of 0.98 mol of dimethyl terephthalate and 0.02 mol of sodium 3,5- dicar'oomethoxybenzenesulfonate in the presence of manganous acetate and antimony trioxide as catalysts, 0.3% by Weight of TiO being added to the reactants to deluster the polymer. The copolyester is spun at 295 C. from a divided pack through a spinneret having 85 round orifices, each 0.009 inch in diameter, 17 of the orifices being on one side of the pack and 68 orifices being on the other side of the pack. The yarn is wound up together as a single filament bundle at a speed of 750 yards per minute and is found to have a denier as-spun of 400.

,The yarn accordingly comprises 85 filaments of round cross-section, 17 having a spun d.p.f. of 11.8 and 68 filaments of round cross-section having a spun d.p.f. of 2.94. The yarn is then passed from a supply package through a bath of water at 25 C. and over a sponge to leave a thin, uniform film of water on the yarn, after which it is passed around a feed roll, around a draw pin 1.6 inches in diameter maintained at a temperature of 100 C., and then around a draw roll, finally being wound up on a suitable package. The speed at the draw roll is 333 yards per minute and the draw ratio is 3.57. The drawn yarn is then passed from a feed roll into a nozzle and exposed to a jet of'hot air maintained at 220 C. in the manner described in Example III. The yarn is passed into. the nozzle at 250 yards per minute and wound up at 137.5 yards per minute, corresponding to a shrinkage of 45% andan exposure time of 0.0164second. The product is a smooth, continuous filament yarn; however, whenit is placed in a bath of water at 100 C. for

' and after immersion in-l 0 C. water, it is found that the larger denier filaments shrink 16%, While the-smaller denier filaments exhibit a spontaneous and irreversible extension in length amounting to 8%. This corresponds to a differential length change of 24%, based 'on the length of the yarn before treatment with 100 C; water.

In a rclated experiment, yarn is spun and drawn as described above,'except1that"a spinning speed of 1350 yards per minute is used. As in the first experiment described in this example, the yarn isfed into the air jet at 250 yards per minute and wound up at 137.5 yards per minute, corresponding to a shrinkage of 45% and an exposure time of 0.0164 second. By separating the filament bundle and measuring individual filaments before and after immersion in 100 C. water, it is found that the larger denier filaments shrink 4% and the smaller denier filaments exhibit a spontaneous and irreversible extension in length of 12%, corresponding to a differential length change of 16%.

As indicated in the foregoing discussion, the filaments are extruded and are forwarded as a filament bundle by a common forwarding means. In forwarding the filament bundle it will be apparent that many different means may be utilized. In addition to winding the filaments on a common package, they may be forwarded, e.g. by an air jet, to a container without winding and thereafter withdrawn for further processing.

Many advantages over the prior art accrue from the present invention. Oneadvantage resides in the simplicity of the present process. The yarns are handled as a continuous filament bundle, thus substantially reducing the tendency toward snagging in various processing operations. The necessity for plying different filaments together to produce bulky yarns is eliminated as well as the numerous steps required in preparing and selecting filaments having different physical characteristics. One of the primary advantages resides in the fact that bulking may be produced after the yarn has been woven or knitted into a fabric, e.g., as the fabric is passed through a hot dye bath. This eliminates the tendency of the bulky yarn to be pulled out into a smooth yarn bundle when subjected to tension during the knitting and weaving processes.

Throughout the specification and claims, any reference to parts, proportions and percentages refers to parts, proportions and percentages by weight unless otherwise specified.

It will be apparent that many widely different embodiments of this invention may be made without departing from the spirit and scope thereof, and therefore it is not intended to be limited except as indicated in the appended claims.

We claim:

1. A process for preparing textile yarn having the property of becoming bulky when heated to a temperature from about 70 C. to about 220 C. which comprises forming a filament bundle consisting of at least two species of continuous essentially straight-filaments of equal length by extruding a molten linear condensation polyester through a plurality of orifices at unequal rates of flow and forwarding said filaments as a continuous about 5200 yards per minute.

filament'bundle, the rate of flow through said orifices and the rate of forwarding being adjusted so that the first of said species has a denier of not greater than about 8 and anotherof said species has adenier at least 125 times the denier of said first species, maintaining a both of said species as separate essentially. straight continuous filamentary structures throughout said forwardmg step. i

2. The process of claim 1 a linear terephthalate polyester.

3. The process of claim lwherein said filaments are oriented by withdrawing them from said'orifices and windwherein said polyester is ing them in" continuous filament form onto .a common package at is rate from about 3000 yards permin'ute to 4. A process for preparing textile yarnhaving the property of becoming bulky when heatedtoa temperature from about 70 C.'to about 220 C. which comprises forming a filam cnt bundle consisting of at 'least two spe cies of continuous essentially straight filaments" of equal length by extruding a molten linear condensation polyester through a plurality. of orifices at unequal rates of flow, forwarding said filaments as a continuous filament bundl'fthe rate of flew throughisaid orific'es and'therate of forwarding being adjusted so that the first of said species has a denier of not greater than about 8 and another of said species has a denier of at least about 1.25 times the denier of said first species, and orienting said filaments by drawing them up to about five times their original length, maintaining both of said species as separate essentially straight continuous filamentary structures throughout said forwarding and orienting steps.

5. The process of claim 4 wherein said polyester is a linear terephthalate polyester.

6. A process for preparing textile yarn having the property of becoming bulky when heated to a temperature from about 70 C. to about 220 C. which com prises forming a filament bundle consisting of at least two species of continuous essentially straight filaments of equal length by extruding a molten linear condensation polyester through a plurality of orifices at unequal rates of flow, forwarding said filaments as a continuous filament bundle, the rate of flow through said orifices and the rate of forwarding being adjusted so that the first of said species has a denier of not greater than about 8 and another of said species has a denier of at least about 1.25 times the denier of said first species, orienting said filaments by drawing them up to about five times their original length, maintaining both of said species as separate essentially straight continuous filamentary structures throughout said forwarding, orienting and shrinking steps and thereafter shrinking said oriented filaments an amount less than the maximum shrinkage of said first species by passing them through a zone maintained at a temperature of at least 90 C.

7. The process of claim 6 wherein said filament bundle consists of essentially amorphous filaments and said essentially amorphous structure is maintained throughout the orienting and shrinking steps.

8. The process of claim 7 wherein said shrinkage is at least about 20% 9. The process of claim 8 wherein said polyester is a linear terephthalate polyester.

10. A process for preparing textile yarn having the property of becoming bulky when heated to a temperature from about 70 C. to about 220 C. which comprises forming a filament bundle consisting of at least two species of continuous essentially straight filaments of equal length having an essentially amorphous structure by extruding a molten linear condensation polyester through a plurality of orifices at unequal rates of flow whereby the first of said species has a denier of not more than about 8 and another of said species has a denier of at least about 1.25 times the denier of said first species,

' and the cross-section of the second of said species has a smaller ratio of perimeter to diameter than the crosssection of said first species, thereafter collecting said filament bundle while maintaining both of said species as 14 separate essentially straight continuous filamentary structures.

11. The process for preparing bulky yarn which comprises extruding a molten linear condensation polyester through a plurality of orifices at unequal rates of flow to form a filament bundle consisting of at least two species of continuous essentially straight filaments of equal length, the first of said species having a denier of not more than about 8 and the second of said species having a denier of at least 1.25 times the denier of said first species, thereafter collecting said filament bundle while maintaining both of said species as separate essentially straight continuous filamentary structures, and thereafter heating said filaments while essentially free, from tension to a temperature from about C. to about 220 C. whereby the differential change in length of said two species is at least 5%.

12. The process for preparing bulky yarns which comprises extruding a molten linear condensation polyester through a plurality of orifices at unequal rates of flow to form a filament bundle consisting of at least two species of continuous essentially amorphous filaments of equal length, the first of said species having a denier of not more than about 8 and the second of said species having a denier of at least 1.25 times the denier of said first species, orienting said filaments by drawing them up to about five times their original length and shrinking said oriented filaments an amount less than the maximum shrinkage of said first species by passing them through a zone maintained at a temperature of at least C. while maintaining said essentially amorphous structure, maintaining both of said species as separate essentially straight continuous filamentary structures throughout said extruding, orienting, and shrinking steps, and thereafter heating said filament bundle while essentially free from tension to a temperature from about 70 C. to about 220 C. whereby the differential change in length of said two species is at least 5%.

13. The process of claim 12 wherein said oriented filaments are shrunk at least about 20% References Cited in the file of this patent UNITED STATES PATENTS Great Britain Apr. 2,

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,980,492 April 18, 1961 Wil'ilgiam H. Jamieson et a1;

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

. Column 5, line 42 after "to" insert the column 6, line 2, for fialments"- read filaments column 13, lines 26 to 29, strike out H maintaining both of said species as separate essentially straight continuous filamentary structures throughout said forwarding, orienting and shrinking steps"; same column 13 line 32, after "90 C." insert maintaining both of said species as separate essentially straight continuous filamentary structures 6 throughout said forwarding, orienting and shrinking steps.

Signed and sealed this 2nd day of January 1962.

(SEAL) Attest:

ERNEST w. SWIDER DAVID L. LADD A'it testing Officer Commissioner of Patents

Claims

1. A PROCESS FOR PREPARING TEXTILE YARN HAVING THE PROPERTY OF BECOMING BULKY WHEN HEATED TO A TEMPERATURE FROM ABOUT 70*C. TO ABOUT 220*C. WHICH COMPRISES FORMING A FILAMENT BUNDLE CONSISTING OF AT LEAST TWO SPECIES OF CONTINUOUS ESSENTIALLY STRAIGHT FILAMENTS OF EQUAL LENGTH BY EXTRUDING A MOLTEN LINEAR CONDENSATION POLYESTER THROUGH A PLURALITY OF ORIFICES AT UNEQUAL RATES OF FLOW AND FORWARDING SAID FILAMENTS AS A CONTINUOUS FILAMENT BUDNEL, THE RATE OF FLOW THROUGH SAID ORIFICES AND THE RATE OF FORWARDING BEING ADJUSTED SO THT THE FIRST OF SAID SPECIES HAS A DENIER OF NOT GREATER THAN ABOUT 8 AND ANOTHER OF SAID SPECIES HAS A DENIER AT LEAST 1.25 TIMES THE DENIER OF SAID FIRST SPECIES, MAINTAINING BOTH OF SAID SPECIES AS SEPARATE ESSENTIALLY STRAIGHT CONTINUOUS FILAMENTARY STRUCTURES THROUGHOUT SAID FORWARDING STEP.