US3927167A

US3927167A - Production of mixed shrinkage polyester yarn

Info

Publication number: US3927167A
Application number: US292300A
Authority: US
Inventors: Cecil E Reese
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1972-09-26
Filing date: 1972-09-26
Publication date: 1975-12-16
Anticipated expiration: 1992-12-16
Also published as: NL182579B; JPS578886B2; ES419060A1; IE38262L; IT1006091B; NL7313168A; CA1024320A; AR199920A1; FR2200389A1; IE38262B1; USB292300I5; NL182579C; DE2348451A1; DE2348451C2; LU68495A1; FR2200389B1; BE805338A; GB1434950A; BR7307498D0; JPS4975860A

Abstract

Mixed-shrinkage, continuous-filament, heat-bulkable yarn, composed of low and higher shrinking filaments of different polyester compositions, develops worsted-like bulk in fabric as a result of normal fabric-finishing operations. The yarn is prepared from two ethylene terephthalate polyesters, of different compositions and relative viscosities, by cospinning, drawing and heat-setting the filaments under identical, critically-controlled conditions.

Description

United States Patent [191 Reese Dec. 16, 1975 PRODUCTION OF MIXED SHRINKAGE [56] References Cited POLYESTER YARN UNITED STATES PATENTS [75] Inventor: Cecil E. Reese, Kinston, NC. 3,593,513 7/1971 Reese 57/140 Assigneez E. L Du Pont de mo s and 3,705,225 12/1972 Taylor 264/210 F Company wllmmgton Primary Examiner-Jay H. W00 [22] Filed: Sept. 26, 1972 21 Appl. No.2 292,300 [57] ABSTRACT Mixed-shrinkage, continuous-filament, heat-bulkable [44] g g i gg g ggfii g fg g gl gg g f yarn, composed of low and higher shrinking filaments B 3 300 Ty en of different polyester compositions, develops worstedlike bulk in fabric as a result of normal fabric-finishing operations. The yarn is prepared from two ethylene [52] Cl 264/210 57/140 g i terephthalate polyesters, of different compositions and [51] Int C12 D011) 5/12 relative viscosities, by cospinning, drawing and heat- [58] Fieid s 03 290 T setting the filaments under identical, criticall 264/210 controlled conditions.

4 Claims, N0 Drawings PRODUCTION OF MIXED SHRINKAGE POLYESTER YARN BACKGROUND OF THE INVENTION This invention relates to bulkable polyester textile yarns, and more particularly to mixed-shrinkage yarn composed of an intimate mixture of polyester filaments of more than one type.

Uncrimped polyester yarns of straight continuous filaments are undesirable-in most fabrics because they provide a non-bulky, slick hand. Various texturing methods have been devised for crimping the filaments to provide bulk. Bulk can also be produced by making the yarn of a mixture of filaments, some of which shrink more than others when heated. Such mixed-shrinkage yarns can be bulked by heating prior to weaving, but is it most advantageous to develop the bulk after weaving by heating during normal fabric finishing operations.

Mixed-shrinkage polyester yarns have been prepared by plying filaments produced under different conditions. Maerov et al. US. Pat. No. 3,200,576 discloses simultaneous melt-spinning of two plies, with one ply being annealed after drawing to provide from 2 percent to 20 percent difference in boil-off shrinkage relative to the other ply. Heating the mixed-shrinkage yarn causes the higher shrinking filaments to pull the other filaments into a bulky configuration, but the patent discloses that non-uniformity in bulkiness occurs to follow-the-leader looping of filaments and causes objectionable moire in fabric (undesirable patterning) unless the filaments are properly intermingled. Maerov et a1. teach jet interlacing the filaments to a split count of less than 12 inches (preferably 1 to 3 inches) to overcome this problem.

Reese US. Pat. No. 3,593,513 is concerned with improving the appearance of fabric when yarn filaments differ in color or luster, and discloses that formation of an objectionable moire due to heterogeneous yarn can be avoided if the filaments are spun simultaneously and brought together for intermingling prior to drawing. A uniform, pleasant heather was obtained in dyed fabric when filaments having different affinity for dye were cospun from different orifices of the same spinneret and thereafter processed in combination. A test for determining the degree of filament intermingling (DFI) is described. The patent teaches that the DFI should be between 80 percent and 100 percent for best results. The patent shows that this DFI was achieved when plies of as-spun filaments were combined into a yarn, intermingled during drawing, and then interlaced. The interlacing step was not needed when the filaments were cospun from the same spinneret and drawn as a composite yarn.

Reese US. Pat. No. 3,444,681 discloses preparation of a mixed-shrinkage polyester yarn by a process in which two species of filaments having the same chemical composition and different relative viscosity (RV) are separately spun, the higher RV filaments are spinannealed, and the filaments are then combined for drawing and subsequent processing. The filaments may be composed of polyethylene terephthalate, where one species has an RV of 15 to 30 and the other species has an RV at least 8 units higher. Adequate filament intermingling can be achieved in the process, but the requirement for different spin-anneal conditions precludes cospinning the higher RV species for the same spinneret as the other species. Cospinning would be highly desiraable for economic reasons and because it provides better filament intermingling. Furthermore, it is frequently desirable to prepare mixed-shrinkage polyester yarns of filaments having different affinities for dyes in order to provide a uniform, attractive heather appearance in dyed fabric.

The filaments of a yarn must be drawn to at least the natural draw ratio, since less complete drawing results in undrawn segments which cause uneven dyeing and harsh tactility in fabric. For uniform drawing of a composite yarn, the filaments must have approximately the same natural draw ratio and also draw to nearly the same break elongation (no greater than 15 percent difference) in order to avoid broken filaments and segments which are weak or cause unevenly dyes filaments. US. Pat. No. 3,444,681 teaches that this is accomplished by critical adjustment of the spinannealing conditions. The yarn is also heat-treated at 135 to 165C. after drawing to provide a low boil-off shrinkage so that most of the bulk will develop at higher te mperatures when fabric is heat-set in normal finishing operations. Greater bulk is obtained by increasing the difference in molecular weight (which is indicated by RV) between the two species.

SUMMARY OF THE INVENTION The present invention provides an improvement in the process for producing mixed-shrinkage polyester yarn whereby the low-shrinkage and higher-shrinkage filaments are spun and processed under identical conditions. The invention further provides for cospinning the filaments from a single spinneret and thereafter processing the filaments as a single yarn so that a high degree of filament intermingling is achieved. Furthermore, the higher shrinkage filaments have a chemical composition which is different from that of the lowshrinkage filaments and can be varied to provide the same or different affinity for dyes. The invention provides an improved mixed-shrinkage yarn which imparts to fabrics produced therefrom a highly desirable worsted-like bulk and tactility. The yarn is free from undesirable loops after take-off from yarn packages and is suitable for weaving before bulking, followed by dev elopment of the bulk during normal fabric finishing op erations. The filament compositions can be varied to provide uniform dyeing or pleasant heather effects. A high degree of filament intermingling provides freedom from moire in fabric.

In the preferred process of the present invention, low-shrinkage filaments and higher-shrinkage filaments of different chemical composition are prepared sirn ultaneously under identical conditions by cospinning the different polyester compositions from separate orifices of the same spinneret, quenching the filaments and combining them into a yarn, drawing the yarn in to C. water to at least the natural draw ratio of the filaments, and heat-setting the yarn at a temperature within the range of about to C. to produce a yarn characterized by low-shrinkage filaments of polyester having a relative viscosity of about 14 to 19 and a density of at least 1.3800, aand higher-shrinkage filaments having a relative viscosity between 27 and 40, a density of less than 1.3840, a boil-off shrinkage greater than 7.5 percent, and a break elongation of within 15 percentage units of the low-shrinkage filaments. The yarn can also be drawn while passing through a steam jet instead of drawing in 85 to 100C. water. Super 3 heated steam at 200 to 270C. and 55 to 80 pounds per square inch gauge pressure is suitable for the steam jet. Steam drawn yarn can be heat-set at a temperature as low as l 10C. to provide the indicated properties.

The low-shrinkage, low RV filaments are prepared from polyester wherein 95 to 100 mole percent of the structural units are ethylene terephthalate and the remaining 5 to mole percent of the structural units are ethylene S-(alkali metal sulfo)isophthalate. A preferred copolyester has 98 mole percent ethylene terephthalate and 2 mole percent ethylene 5-.(sodium sulfo)isophthalate, abbreviated 2G-T/1S (98/2).

The higher-shrinkage, higher RV filaments are prepared from a polyester of different chemical composition wherein 85 to 95 mole percent of the structural units are ethylene terephthalate and the remainder are other ester units to retard crystallization of the copolyester relative to the homopolyester of ethylene terephthalate. Any of the structural units known to form useful copolyester filaments with ethylene terephthalate may be used for the purpose. This use of a crystallization retardant in proper amount makes possible cospinning and processing the low and higher shrinkage filaments under identical conditions to provide mixedshrinkage yarn having the desirable properties indicated herein.

To avoid confusion in the meaning of the terms polymer, polyester, copolymer, copolyester, terpolymer, terpolyester, etc., as used herein, it should be understood that polymer or polyester are generic to polymers wherein one, two or more different structural units are present, copolymer or copolyester mean that two or more are present, and terpolymer or terpolyester mean at least three. The relative viscosities are measured on filaments after spinning, drawing and heat-set ting at 130 to 160C. unless otherwise specified. The polymer before spinning must have a slightly higher relative viscosity to compensate for degradation which takes place during the melt-spinning operation.

The mixed-shrinkage yarn of the present invention is characterized by low-shrinkage and higher-shrinkage filaments have a degree of filament intermingling between 80 and 100 percent when measured as described in U.S. Pat. No. 3,593,513. The low-shrinkage filaments consist of polyester having a relative viscosity of 14 to 19, a density of at least 1.3800, and wherein 95 to 100 mole percent of the polymer structural units are ethylene terephthalate and the remaining 5 to 0 mole percent of structural units are ethylene 5-(alkali metal sulfo)isophthalate. The higher-shrinkage filaments consist of a different polyester having a relative viscosity greater than 27, a density of less than 1.3840, a boiloff shrinkage greater than 7.5 percent, a break elongation within 15 percentage units of the low-shrinkage filaments, and wherein 85 to 95 mole percent of the structural units are ethylene terephthalate and the remainder are crystallization retardant units forming a copolyester therewith. The yarn provides a differential filament length value (DFL) of 3.5 percent to percent when tested under simulated fabric finishing conditions as described subsequently.

One preferred embodiment of the invention is a mixed-shrinkage yarn wherein 25 to 75 percent of the filaments are low shrinkage filaments of 2G-T/1S polyester having an RV of about and a density of about 1.3834, and the other filaments are higher shrinkage filaments of a copolyester of ethylene terephthalate and ethylene isophthalate (2G-T/I) having an RV of 4 about 35 and a density of about 1.3660. This yarn provides excellent bulk when fabric containing it is subjected to normal finishing operations, dyes uniformly in disperse dye baths, and can be cross-dyed to provide desirable heather effects, since only the 2G-T/IS filaments are receptive to cationic dyes.

Another preferred embodiment is one in which the low-shrinkage filments are 2G-T/IS polyester having an RV of about 15 and a density of about 1.3834, and the higher-shrinkage filaments are 2G-T/6 copolyester (ethylene terephthalate and ethylene adipate structural units) having an RV of about 35 and a density of about 1.3668.

DETAILED DISCLOSURE The low-shrinkage 2G-T filaments may be prepared by any of a variety of procedures known in the art, such as by one of the methods taught by Whinfield and Dickson in U.S. Pat. No. 2,463,319. It will be apparent to those skilled in the art that the low-shrinkage component of the new yarns has an unusually low RV; i.e., from about 14 to 19. If 2G-T/IS is used for the lowshrinkage filaments, it may be prepared by one of the methods of Griffing and Remington described in U.S. Pat. No. 3,018,272. The mole ratio of S-(sodium sulfo)isophthalate units to terephthalate units is less than 5:95.

It was totally unexpected that 2G-T or 2G-T/IS could be spun and drawn at the same temperature and draw ratios to produce the same or nearly the same break elongations as a different ethylene terephthalate copolymer to produce a mixed-shrinkage yarn having not only such desirable differential filament length properties, but other aesthetic qualities sought after in commerce.

The polymer to be used as the high-shrinkage filamentary member of the new yarn may be produced by known techniques for preparing the copolyester, bearing in mind that the relative viscosity should be greater than 27. Generally, it is made by charging into a distillation column the dimethyl esters of the appropriate acids, such as dimethylterephthalate and dimethylisophthalate in the required mole ratio. Approximately 2.2 moles of ethylene glycol or other suitable diol are added for each mole of diester. Manganese acetate and antimony oxide are added in catalytic amounts. The temperature is raised, methanol distills off, and the bisglycol of the ester is formed until the temperature of the still reaches about 240C., at which temperature substantially all the methanol hasevolved. The batch is then dropped into an autoclave equipped with a stirrer, the pressure is decreased, and the temperature is slowly increased to remove excess glycol and begin polymerization. The temperature is raised to 270C. When the desired RV is attained, the polymer is extruded as a ribbon over a cool moving surface and chopped into flake in a conventional manner.

A large number of ethylene terephthalate copolyesters are known to provide useful filaments and can be used for the present invention. The glycol and/or the acid can be varied, or caprolactone can also be used to provide structural units in the copolyester chain of the highershrinkage filaments. Illustrative of structural units which may be used as crystallization retardants in the polyester chain are from ethylene glycol and isophthalic acid,

II ll from 2,2-dimethyl-trimethylene glycol and terephthalic acid,

0 0 II II -ca cn -o-c-( c11 -c-ofrom ethylene glycol and dodecanedioc acid,

from ethylene glycol and hexahydroterephthalic acid, and others of the same class represented by the general formula 0 0 II II (A-O) -CB-C-O-' wherein A is a lower alkylene group, n is l, 2 or 3, and B is a divalent hydrocarbon group having up to carbon atoms in the polyester chain and is free from aliphatic unsaturation.

The new yarns contain from about 25 percent to about 75 percent of each type of filament. Preferably, they contain about 50 percent of low-shrinkage filaments and about 50 percent of high-shrinkage filaments. The yarns may be of any conventional denier and contain any number of filaments greater than 2. Preferably, the denier per filament of the filaments in the new yarns is substantially uniform and between i and 5. Yarn deniers are preferably at the commercial levels.

The break elongation of the constituent fibers of the new yarn must be within about 15 percent units of each other. If the break elongations of the filaments vary outside this range, problems such as broken filaments and undrawn segments. of yarn which cause dye nonui 6 niformities or weak spots along the filament length occur.

It is important that the relative viscosity of each group of filaments of the new yarns be within the specified ranges. If the RV of the high-shrinkage filamentary component of the new yarns is greater than about 40, it will be difficult to select a suitable common draw ratio. If the RV of the high-shrinkage filamentary component is less than the specified lower limit, its draw ratio will be too high and the DFL will be below the lower limit specified for a satisfactory product. If the RV of the low-shrinkage filamentary component is more than the specified upper limit, its shrinkage is too high and the DFL is unacceptably low. If the RV of the low-shrinkage filamentary component is less than about the specified lower limit, fabrics produced from the yarn are unacceptable because they are prone to abrasion damage which is caused by the ease of breaking of the lowshrinkage filamentary component.

The yarns of the present invention are, in general, produced by conventional melt-spinning techniques. Preferably, they are produced by cospinning both polymeric species through a single spinneret, one species extruding through some of the orifices of the spinneret and the other species through the other orifices. Methods for doing this are known in the art as disclosed, for example, in Reese US. Pat. No. 3,593,513. The new yarns may be spun and drawn as an integral yarn and thereafter heat-set and wound up onto a suitable package.

The fact that the new yarns may be produced by cospinning and codrawing presents an economic advantage because separate equipment is not required to process each filament species. Also, because the yarns may be cospun and codrawn, the filament species are well intermingled, producing a uniform visual appearance in fabrics made therefrom.

The new yarn has the advantage that the desirable bulk and tactile aesthetics can be developed in the normal sequence of finishing operations; namely, scour at the boil and fabric heat-setting under conventional conditions. No special treatments are required.

In order to produce the yarns of the present invention, these filaments must be heat-set in their manufacture to allow the low-shrinkage filaments to reach a density of at least 1.3800.

This is preferably carried out by passing the yarn over draw rolls which are heated to a temperature within the range of about to C. and usually about 150C. When using certain polymers as the high-shrinkage component, such as poly(ethylene terephthalate/dodecanedioate) (90/ 10), draw roll temperatures as high as C. may be used without adversely affecting the differential filament length property. Yarn exposure to the heated rolls should be from about 1 to 0.001- second.

The invention will be further illustrated by the following examples of embodiments which are not intended'to be limitative.

DEFINITIONS Differential Filament Length (DFL). The yarn to be tested is wound on a reel the number of times required to achieve a loop denier of 3,000 using the formula:

n l500/D wherein n is the number of turns and D is the denier of the yarn. Obviously, the loop denier increases 2D for each n. The loop is removed from the reel and immersed in boiling water for minutes. The loop is then transferred to a second boiling aqueous bath which contains grams of Latyl Carrier A in 2 liters of water. Latyl Carrier A is the tradename for a dye assistant for improving the dye-ability of polyester fibers and which is sold commercially by E.l. du Pont de Nemours and Company. It is a mixture of about 0.2 percent sodium lauryl sulfate, about percent sodium sulfate, about 40 percent benzanilide, and about 40 percent dimethylterephthalate. After 1 hour, the loop is removed from the bath and then placed on a frame and tensioned slightly, just enough to straighten the shortest constituent loops. The frame bearing the loop is placed in an oven at 160C. dry heat. After seconds exposure, the loop is removed from the oven, removed from the frame and 150 gram weight is suspended from it and its length is measured (L The weight is removed and the loop is then stretched until the longest constituent loops are just straightened. In this condition, the high-shrinkage and low-shrinkage components of the loop are approximately of the same length. The length of the skein is then measured (L DFL is measured by the following formula:

It will be appreciated that in this measurement the yarn is treated much like it would be treated in a commercial fabric-manufacturing operation and DFL determines the suitability of a bulk yarn for a textile fabric. This method is used in Examples 1, II and Ill herein.

A short-cut method for approximating differential filament length is as follows:

The high-shrinkage component of the yarn to be tested is wound on a reel as shown above. The loop is removed from the reel, a 26.4 gm. weight is suspended therefrom, and its length measured (L The weight is removed and the loop is then suspended in boiling water, at 100C., for 1 hour. The loop is then removed from the water, the weight is again suspended therefrom, and its length measured (L The low-shrinkage component of the yarn to be testedis then treated in the same manner, its original length being recorded as L instead of L except that instead of being suspended in boiling water, the loop is suspended in an oven set at 160C. After 30-seconds exposure, the loop is removed from the oven, allowed to cool, the 26.4 gm. weight is again suspended therefrom, and the length of the loop is measured (L Approximate DFL is obtained by the following formula:

(Approximate) DFL(%) BOS DHS(%) wherein BOS(%) 100(L L )/L and DHS(%) G412 LH)/L02 Fabric bulk has been found to be a function of the shrinkage in boiling water of the high-shrinkage component minus the dry-heat shrinkage of the low-shrinkage component. Heretofore, this relationship was not clearly defined. It is evident that the method for approximating DFL may be used to show the suitability of various high-shrinkage and low-shrinkage components for the invention without having to combine them to a yarn. This method is used in Example IV of this specification. I

The new yarns have differential filament length values, measured according to either or both of the above methods, within the range of about 3.5 percent to 10 percent and preferably 6 to 8 percent. The improved 8 properties characteristic of this invention have not been obtained in fabrics produced from previous yarns having DFL values outside of this range.

Relative Viscosity (RV) of the polyester is a measure of its molecular weight. RV is the ratio of the viscosity of a solution of 2.15 grams of polymer dissolved at 140C. in 20 ml. of fomal to the viscosity of the fomal itself, both measured at 25C. in a capillary viscometer and expressed in the same units. Fomal is a mixture of 10 parts by weight of phenol and 7 parts by weight of 2,4,6-trichlorophenol.

Break Elongation is measured according to the ASTM designation D-2256-69 (incorporating editorial edition of Section 2 and renumbering of subsequent sections as done in March 1971). It is defined as in Option 3.3 Elongation at Break of Section 3. The testing is performed on straight multifilament yarns which were conditioned by storing them at 65 percent relative humidity and 70F. (21 .1C.) for 24 hours prior to testing. An Instron Tensile Testing Machine is used. The test sample is 5 inches (12.7 cm.) long, no twist is added, the cross-head speed is 10 inches per minute (25.4 cm./min.), the rate of attenuation is 200 percent per minute, and the chart speed is 5' inches per minute (12.7 cm./min.).

EXAMPLE I This example shows the importance of controlling the relative viscosity (RV) or each filamentary component in the practice of the present invention.

A. RV of each component is in accordance with the teachings herein: v

2G-T/IS (92/2) flake as described in Griffing & Remington U.S. Pat. No. 3,018,272 of 16 RV and 2G- T/I (/10) flake of 40 RV are separately melted and cospun to a 70-denier/28-filament composite yarn by delivering equal volumes of each polymer melt to a spinneret containing orifices of uniform size arranged in concentric rings with an equal number of orifices in each .ring. The two polymer melts are prevented from mixing. The 2G-T/IS copolymer is spun through the outer ring and the other copolymer is spun through the inner ring.

Spinning temperature, measured at the spinneret,

is 300C. The filaments are air-quenched in normal fashion and drawn 4.5X by passing in contact with a draw pin situated between a feed roll and a set of two heated draw rolls. The draw pin is partially immersed in 95C. water. The filaments are wrapped 16 times around the two draw rolls, which are heated to C. The filaments are then given a coating of a standard finish and are passed to a suitable windup. Windup speed is about 2,700 yards per minute (2,469 meters/minute). Break elongation of each filament group of the composite yarn is about 23 percent. The yarn has a tenacity of 3.48 grams per denier. The 2G-T/IS filaments have arelative viscosity (RV) of 14.9 and a density of greater than 1.3830, while the ZG-T/l filaments have an RV of 38 and a density of less than 1.3830. The differential filament length is found to be 5.5 percent. The yarn forms no undesirable loops when removed from the package. Fabric woven from the yarn and finished in normal manner has a worstedlike hand.

B. RV of the low-shrinkage component is too high:

Part A of this example is repeated with the exception that the RV of the 2G-T/IS filaments is greater than 9 22, the break elongation difference in the two species of filaments is greater than percent units, and fabrics woven from this yarn lack bulk and have poor tactile aesthetics.

C. RV of the low-shrinkage filamentary component is too low:

Part A of this example is repeated with the exception that the RV of the 2G-T/lS flake is 13 and the RV of the 2G-T/l flake is 40, the draw ratio is 4.8x. The RV of the 2G-T/IS filaments is 13.4 and the RV of the 2G-T/l filaments is 34. The tenacity of the yarn is 3.19 grams per denier, and the break elongation of both species of filaments is 21.6 percent. The DFL of this yarn if 6.4 percent. A 7 oz. per yd. (237.4 gm./meter 2 X 2 twillherringbone greige fabric is maade from this yarn using 58 ends per inch (22.8 ends/cm.) for the warp and 56 picks per inch (22.0 picks/cm.) for the filling. After testing the fabric for the effects of abrasion by a standard test, the fabric is found to be unacceptable because it is damaged severely by abrasion. The damage is found to be caused by breaking of the lowshrinkage filamentary component.

D. RV of the high-shrinkage component is too low:

Part A of this example is repeated with the exception that the high-shrinkage component is poly(ethylene terephthalate/adipate) (92/ 8), abbreviated 2G-T/ 6, the RV of the 2G-T/ 6 flake is 27.5, and the RV of the 2G -T/1S flake is 16. The RV of the 2G- T/6 filaments is 25.4 and the RV of the 2G-T/IS filaments' is 15.4. The temperature of the draw rolls has to be reduced to 120C. in order to produce any differential length change whatever in the filame'ntsDFL of this yarn is found to be only 3.5 percent.

EXAMPLE 11 This example shows the criticality ofthe annealing temperature in the practice of this invention.

Part A of Example 1 is repeated with the exception that the draw roll temperature is 180C. instead of 140C. Broken filaments are numerous and the DFL of the resulting yarn is only 1 percent.

The example is repeated with the exception that the draw roll temperature is 170C. The DFL of this yarn is only 2.4 percent.

The example is repeated with the exception that the draw roll temperature is 155C. The resulting yarn has a DFL of 6.4 percent and forms no undesirable loops when removed from the package. Fabrics woven from the yarn hag; worsted-like hands. They have unusual and highly desirable bulk and texture, and fabrics woven therefrom have the aesthetics of worsted fabrics.

The example is repeated with the exception that the draw roll temperature is only C. The density of the 2G-T/1S filaments is less than 1.3800, and the fabrics woven therefrom have poor tactile aesthetics.

EXAMPLE III Part A of Example I is repeated, using 2G-T/6 (95/5) of 40 RV (flake) as the high-shrinkage component and 2G-T/lS (98/2) of 16 RV (flake) as the low-shrinkage member. Draw ratio is 4.6X instead of 4.3 and thedraw roll temperature is 134C. instead of C. The RV of the 2 G-T/6 filaments is 33.1 and the RV of the 2G-T/lS filaments is 15.6. Density of the 2G-T/6 filaments is less than 1.3830. Density of the 2G-T/IS filaments is greater than 1.3830. The DFL of this composite yarn is 7.1 percent, the tenacity is 4.65 grams per denier, and the break elongation is 23 percent. Both components of the yarn have approximately equal break elongations. The yarn is of high quality. No loops occur when the yarn is withdrawn from the package. When the yarn is woven to a fabric, the fabric has excellent bulk even after heat-setting, and has a worstedlike hand.

EXAMPLE IV This example shows the production of various copolymers and their suitability in the practice of the invention.

A series of polyesters, having 90 mole percent recurring structural unitsrepresented by the formula:

. 0 o r A 11 II rollers. The draw rolls rotate at a peripheral speed of about 2,5 50 yardsper minute (2,332 meters/min), are heated to 140C. and the yarns wrap around them as in the previous examples. The draw ratios and deniers after drawing are indicated in the Table.

70ml: of diatom. :sructunl Unit Elorgation It RV Density Ben-0!! Ink Tenacity of or Shrinks for-n1. of Addition]. av Extrusion mm xv !Ieruitj nan-or? lmetunl mm: of. l'caplrlck react-t1 of o 9 g f= 1-s 29o 3.11:1 11 2a .4 30 1.3381 19 I o o II N I II I -cx ca 0-c@-c-o 1:2.0 .a9o 7o 25 14.7 36 1.3600 in Bearing the foregoing teachings in mind, these data indicate that each of the above copolyesters is suitable for cospinning with either 2G-T or 2G-T/IS of an RV within the prescribed range, codrawing and heat-setting as specified to produce a mixed-shrinkage yarn of the present invention having a DFL within the range of about 3.8 to 10 percent.

The present invention provides a new process for producing an all-polyester mixed-shrinkage yarn having excellent bulk and worsted-like aesthetics which involves treating the extruded filaments as a single threadline from extrusion to windup. There is no necessity to split the process and thus costly equipment is avoided.

Fabrics prepared from yarns of the present invention 7 have unusual bulk and texture and possess the aesthetics of worsted fabrics. These qualities coupled with the inherent advantages of all-polyester fabrics, including moth and mildew resistance, make such fabrics highly desirable in todays market.

Fabrics produced from the new yarns may be made into slacks, coats, jackets, dresses, suits, and the like. Interesting dyeing effects can be obtained with fabrics made from the yarn of the present invention which comprises a mixture of 2G-T/IS fiber with another copolymer fiber such as 2-G-T/l. The 2G-T/I fiber dyes easily with disperse dyes, but does not take up cationic dyes, whereas, the ZG-T/IS fiber takes up both disperse and cationic dyes.

I claim:

1. In the production of continuous-filament textile yarns, wherein polyester filaments are melt-spun from spinneret orifices, quenched, combined into a yarn,

drawn to at least the natural draw ratio and heat-set, the improvement for preparing mixed-shrinkage, heatbulkable yarn, wherein the improved process comprises forming filaments having a relative viscosity of 14 to 19 by melt-spinning a polyester, wherein 95 to 100 mole percent of the repeating structural units are ethylene terephthalate and 5 to 0 mole percent of the structural units are ethylene S-(alkali metal sulfo)- isophthalate, simultaneously forming filaments having a relative viscosity between 27 and 40 by melt-spinning under the same conditions a different type of polyester of ethylene terephthalate which includes other ester units to retard crystallization of the polyester, from to mole percent of the polyester structural units being ethylene terephthalate, quenching the 14 .to 19' and 27 to 40 relative viscosity filaments under the same conditions and combining them into a yarn, then drawing the yarn about 4X and heat-setting the yarn at a.

temperature within the range of 130 to 160C. to produce 14 to 19 relative viscosity filaments having a density of at least 1.3800, and 27 to 40 relative viscosity filaments having a density of less than 1,3840, a boil-off shrinkage greater than 7.5 percent and a break elongation within 15 percentage units of the 14 to 19 relative viscosity filaments.

2. A process as defined in claim 1, wherein the filaments are cospun from separate orifices 'of the same spinneret.

3. A process as defined in claim 1, wherein the yarn is drawn in 85 to C. water. g

4. A process as defined in claim 3, wherein the yarn is heat-set for l to 0.001-second on draw rolls heated to a temperature within the range of to C.

Claims

1. IN THE PRODUCTION OF CONTINOUS-FILAMENT TEXTILE YARNS, WHEREIN POLYESTER FILAMENTS ARE MELT-SPUN FROM SPINNERET ORIFICES, QUENCHES, COMBINED INTO A YARN, DRAWN TO AT LEAST THE NATURAL DRAW RATIO AND HEAT-SET, THE IMPROVEMENT FOR PREPARING MIXED-SHRINKAGE, HEAT-BULKABLE YARN, WHEREIN THE IMPROVED PROCESS COMPRISES FORMING FILAMENTS HAVING A RELATIVE VISCOSITY OF 14 TO 19 BY MELT-SPINNING A POLYESTER, WHEREIN 95 RO 100 MOLE PERCENT OF THE REPEATING STRUCTURAL UNITS ARE ETHYLENE TEREPHTHALATE AND 5 TO 0 MOLE PERCENT OF THE STRUCTURAL UNITS ARE ETHYLENE 5-(ALKALI METAL SULFO)-ISOPHTHALATE, SIMULTANEOUSLY FORMING FILAMENTS HAVING A RELATIVE VISCOSITY BETWEEN 27 AND 40 BY MELT-SPINNING UNDER THE SAME CONDITIONS A DIFFERENT TYPE OF POLYESTER OF ETHYLENE TEREPHTHALATE WHICH INCLUDES OTHER ESTER UNITS TO RETARD CRYSTALLIZATION OF THE POLYESTER, FROM 85 TO 95 MOLE PERCENT OF THE POLYESTER STRUCTURAL UNITS BEING ETHYLENE TEREPHTHALATE, QUENCHING THE 14 TO 19 AND 27 TO 40 RELATIVE VISCOSITY FILAMENTS UNDER THE SAME CONDITIONS AND COMBINING THEM INTO A YARN, THEN DRAWING THE YARN ABOUT 4X AND HEAT-SETTING THE YARN AT A TEMPERATURE WITHIN THE RANGE OF 130* TO 160*C. TO PRODUCE 14 TO 19 RELATIVE VISCOSITY FILAMENTS HAVING A DENSITY OF AT LEAST 1.3800, AND 27 TO 40 RELATIVE VISCOSITY FILAMENTS HAVING A DENSITY OF LESS THAN 1,3840 A BOIL-OFF SHRINKAGE GREATER THAN 7.5 PERCENT AND A BREAK ELONGATION WITHIN 15 UNITS OF THE 14 AND 19 RELATIVE VISCOSITY FILAMENTS.

2. A process as defined in claim 1, wherein the filaments are cospun from separate orifices of the same spiNneret.

3. A process as defined in claim 1, wherein the yarn is drawn in 85* to 100*C. water.

4. A process as defined in claim 3, wherein the yarn is heat-set for 1 to 0.001-second on draw rolls heated to a temperature within the range of 130* to 160*C.