US3423809A - Process for forming differential shrinkage bulked yarn - Google Patents

Description

Patented Jan. 28, 1969 7 Claims ABSTRACT OF THE DISCLOSURE Improvements are disclosed in the production of composite yarn containing heat-shrinkable filaments, which develops bulk due to differential shrinkage of the filaments when heated. Filaments of synthetic linear condensation polymer are melt spun in conventional manner to form separate filament bundles, the bundles are separately drawn in a first jet supplied with superheated steam, the bundles are annealed under the same conditions on hot draw rolls, one bundle is further annealed in a second jet supplied with superheated steam, and the bundles are then combined in conventional manner to form a composite yarn. The filament bundles pass through separate passageways in the draw jet, so that they will receive the same heat treatment but entanglement of filaments will be avoided between the bundles. The yarn produced has highly uniform shrinkage characteristics when heat-bulked, thereby avoiding objectional streaks,-

or other non-uniformities, in fabric prepared from the yarn.

CROSS-REFERENCE TO RELATED APPLICATION This is a continuation-in-part of my application Ser. No. 623,406 filed Mar. 15, 1967, now abandoned.

BACKGROUND OF THE INVENTION This invention relates to an improved process for producing bulkable composite yarn, and more particularly to production of yarn which develops bulk due to differential shrinkage of filaments when the yarn is heated.

Processes for producing multifilarnent bulkable yarn, by preparing and combining filament bundles which have different heat-shrinkage characteristics, are disclosed in such prior art patents as Nott US. Patent No. 3,115,744 dated Dec. 31, 1963, Maerov et al. US. No. 3,199,281 dated Aug. 10, 1965, and Maerov et al. US. Patent No. 3,200,576 dated Aug. 17, 1965. When these yarns are heated to cause shrinkage, the filaments that shrink the most cause the lesser-shrinking filaments to take a nonlinear configuration that imparts bulk to the yarn. Generally speaking, the greater the differential shrinkage, the greater will be the bulk of the yarn.

In order to obtain highly uniform fabrics of these mixed-shrinkage yarns, it is important to have as little variation as possible in the shrinkage characteristics of each of the filament bundles combined in the yarn. As will be apparent, if the composite yarns used in a fabric develop different amounts of bulk, or if a single yarn will develop more bulk in one section of its length than it does in another section, the fabric will be non-uniform. When yarns which vary in shrinkage characteristics are present in a fabric and the fabric is heated to bulk the yarns by differential shrinkage, the fabric develops ob ectionable streaks.

SUMMARY OF THE INVENTION The invention is an improvement in the process of pro ducing mixed-shrinkage, bulkable yarns by melt-spinning a synthetic linear condensation polymer to form separate filament bundles, drawing and annealing the separate filament bundles under different conditions to provide differential shrinkage characteristics, and combining the filament bundles to form a composite yarn. The present improvement provides a composite yarn having highly uniform differential shrinkage. In the improved process, separate filament bundles are continuously melt spun from the polymer and drawn under identical conditions while passing through steam jets to localize the draw zone, one of the bundles of drawn filaments is annealed by passage through a second steam jet to provide an effective differential shrinkage of at least 1.5% between filament bundles, and the bundles are then combined to form a composite yarn.

BRIEF DESCRIPTION OF THE DRAWING FIGURE 1 is a schematic illustration of the process and apparatus for use in the invention.

FIGURE 2 is a sectional view of a steam jet device for use in the process, the cross-section being taken through the axis of a steam passageway and along the axis of a yarn passageway as indicated by the line 22 in FIGURE 3.

FIGURE 3 is a sectional view of the steam jet device taken along the line 3-3 in FIGURE 2.

FIGURE 4 is a sectional view of another steam jet device for use in the process, the cross-section being taken as in FIGURE 2.

DETAILED DESCRIPTION OF THE INVENTION Referring to FIGURE 1, two groups of filaments 4 and 4' from melt-spinning assembly 2 are separately converged at guides .6 and 6' to form filament bundles 7 and 7'. The filament bundles 7 and 7' pass across the face of finish roll 8 which applies an antistatic lubricating finish to the filaments. The finish may be either an aqueous or non-aqueous finish conventionally used for the purpose. The two bundles then pass around feed roll 10 and its associated separator roll 12. The bundles then pass thru separate passageways in draw jet 14, where the filaments are heated with impinging steam to localize drawing. The drawn filaments pass from the draw jet and around heated draw rolls 16 and 18. After leaving the draw rolls, the two bundles are led to guide pin 20 and are guided along separate paths. Yarn bundle 7 is directed to annealing jet 24, whereas yarn bundle 7' is diverted over guide pin 22 to pass around the anneal jet and to guide pin 28. Filament bundle 7 passes through anneal jet 24, where it is again heated with impinging steam, and then passes around guide pin 26 to guide pin 28, where it joins bundle 7' to form yarn 9. Yarn 9 is then passed to interlace jet 30 where the joined filaments are interlaced and passed to finish roll 32 where the yarns are treated with an aqueous emulsion of an antistatic lubricating composition. If desired, roll 32 may be positioned as indicated by the dotted line at A. Under some conditions, application of the finish at position A is preferred since wet yarns can be interlaced more effectively. The interlaced composite yarn is then led to a wind-up where it is wound on package 34 which is surface-driven by drive roll 36.

FIGURES 2 and 3 show a suitable steam jet device for use as the draw jet 14. For convenience in manufacture, this is made of four plates which are bolted together in use. Top plate 38 is grooved on the lower surface to provide yarn passageways 40. Eight of these passageways are shown in FIGURE 3, but any number can.

a second plate 44, so as to intercept the axis of the yarn passageway at a 30 angle as shown in FIGURE 2. A third plate 46 is hollowed-out to provide a common steam chamber 48 for supplying steam to the passageways under uniform conditions. A bottom plate 50 completes the assembly. The opening 52, which is suitably threaded for attaching a steam-supply line, conducts steam into the chamber 48.

FIGURE 4 shows a steam jet device which is suitable for use as the anneal jet 24. It is similar in construction to the jet device of FIGURES 2 and 3, but each yarn passageway 54 is longer so that the yarn will be exposed to the steam for a longer time. The length should be sufficient to provide an adequate amount of annealing under the conditions used. The hole 56, drilled perpendicular to the yarn passageway above the steam passageway 58, is for inserting a ceramic guide pin. This pin is notched to keep the filament bundle centered over the steam jetted from passageway 58. A ceramic guide should also be provided in the draw jet of FIGURES 2 and 3 but has not been indicated in order to avoid confusing the drawings.

Filaments are provided for use in this invention by melt spinning from spinneret orifices in conventional manner. The spinneret may be supplied with one or more metered streams from a meter pump so as to provide separate bundles of filaments. If the spinneret is supplied with one metered stream, it is preferred that each of the bundles come from separate spinnerets although the filaments from one metered stream can be divided to form separate bundles where such constitutes expedient practice.

After the separate bundles have been treated to provide differential shrinkage, the bundles are combined to form a composite yarn. It is preferred that the filaments of the separate bundles achieve some degree of intermingling rather than reside in a side-by-side relationship. Application of small amounts of twist to the combined bundles can be expected to give some improvement, but the results will not be optimum. Preferably, the filament bundles will be interlaced together to produce the composite yarn. By providing an interlaced composite yarn, it is believed that bulk develops equally along the yarn and does not become concentrated at separated points.

This invention involves the production of a composite yarn comprising thermally differentially-shrinkable components having a high degree of shrinkage uniformity. Because the shrinkage properties are thermally dependent, it is desirable, if not necessary, that the heat treatment be maintained as uniform as possible. Except for the necessary different treatment of the filament bundles while one is annealed to impart differential shrinkability, all of the filaments should be heat treated as if they were part of the same yarn bundle, even though they are processed as separate filament bundles. For instance, the separate filament bundles should be drawn in the same jet device, using the same steam supply, and partially annealed on hot rolls under the same conditions. This need for uniformity of treatment is, of course, concerned only with those treatments that affect the uniformity of differential shrinkage.

The differential shrinkability in the composite yarns of this invention is imparted by a differential annealing treatment of the drawn filaments. The term annealing refers to heating the filaments under tension at substantially constant length. By substantially constant length is meant that any change in the length of the filament will be less than 2% of the length of the filament prior to the heat treatment. No change in length is intended during the heat treatment, but due to small variations in roll speed or to applied tension, minor length changes may occur.

Annealing of polyester filaments reduces their shrinkage potential. The higher the annealing temperature that the filament reaches, the lower will be its shrinkage potential. When polyester filaments are insufiiciently heated under annealing conditions and subsequently found to shrink less than unheated filaments from the same conditions, but shrink more than filaments appropriately heated for minimum shrinkage under the same conditions, the filaments are said to be partially annealed. Polyester filaments may be annealed one or more times; the only requirement being that the heat treatment of a filament be severe enough to reduce the shrinkage potential relative to the filament when not so treated.

In an especially preferred embodiment of this invention, filaments of synthetic linear condensation polmer, melt spun in conventional manner from spinneret orifices, are provided as two bundles, the filament bundles are separately drawn in a first jet supplied with superheated steam, both bundles are annealed under the same conditions on hot draw rolls, one bundle is further annealed in a second jet supplied with super-heated steam, and the two bundles are combined and interlaced in a third jet to form a composite yarn. In drawing, the two filament bundles pass through separate passageways in the draw jet. Each passageway is a duplicate of the other, and they are supplied with steam from a common source, so that the filaments in both bundles will be impinged with steam of the same temperature and pressure. In order to localize the draw, the steam is impinged on the filaments in such a manner as to open up the bundle for equivalent heating of the individual filaments and, by providing sep arate passageways, filament entanglement between the two bundles is avoided. The steam is impinged onto the filament bundle at a high velocity, e.g., sonic velocity. The high velocity steam strips finish from the filaments and reapplication of finish becomes necessary at a later stage of the process. After being drawn, the filaments are subjected to additional heating as they pass along the length of the draw jet. This heating occurs under the draw tension and the filaments become partially annealed. On exiting from the draw jet the separate bundles pass to hot draw rolls where both bundles are heated under the same hot roll conditions to provide further annealing of the filaments. Preferably, the rolls are heated with hot air maintained at the desired temperature by electrical heating means. Since the filaments are relatively dry, are partially annealed and have been preheated in the draw jet, the heat requirement to reach a given condition is considerably less than would otherwise be the case. That is, the reduced heat load allows the filaments to approach the annealing temperature of the hot draw rolls in less time, and hence a longer interval remains for all of the filaments in the bundles to reach the same temperature. The shrinkage levels of filaments processed in this manner are surprisingly uniform. One of these bundles is then led to an annealing jet where it is further annealed at a higher temperature to provide a lower shrinkage level. The shrinkage levels of filaments in this lower shrinkage bundle become even more uniform as a result of the additional annealing. Although it is the differential between the shrinkage levels of the two components that produces the bulk in the composite yarn, it will be apparent that the more uniform the shrinkage level of each of the two components before they are combined, the more uniform will be the differential shrinkage in the yarn.

If desired, the annealing jet can be positioned between the draw jet and the hot draw rolls, and this arrangement constitutes a preferred embodiment for providing moderate degrees of bulk. In this embodiment, the need to keep the filament bundles separate on the draw rolls no longer exists, since the high shrinkage component and the low shrinkage component have both been produced prior to draw roll contact. Consequently, the filament bundles may be joined prior to the draw roll and thereby increase the effective annealing area. Due to the fact that the one yarn from two joined bundles requires only about half as much space on the draw roll as the two separate bundles, this positioning of the anneal jet permits one pair of hot draw rolls to accommodate twice as many bundles of filaments. It will be noted that, in this embodiment, the hot rolls can improve the uniformity of the high-shrinkage component, but the uniformity of the lowshrinkage component will remain unchanged. This embodiment suffers from the disadvantage that the further annealing to produce the low-shrinkage component must be carried out under the drawing tension. However, a satisfactory product is obtained and, for end uses where the degree of bulk provided is acceptable, this embodirnent provides a uniform yarn at a high rate of productivity.

In the practice of this invention, composite yarns having a high degree of shrinkage uniformity can be produced without resort to hot draw rolls. Suitable means may be used in conjunction with the draw and anneal jets to achieve the required degree of shrinkage uniformity. For example, steam from the jets may be introduced into a housing which will become filled with steam discharging from the jets, and thus provide a steam chamber for additional heat treatment of the yarn. This embodiment will have the further advantage of reducing the occurrence of steam condensate in the vicinity of the jets, since the housing may be connected to an exhaust system for removal of the discharged steam. This embodiment is preferred when the anneal jet is positioned before the draw rolls, but it can also be utilized when the jet used for annealing is located between the draw rolls and the interlace jet.

In the practice of this invention, filament bundles having zero twist are treated and passed to the interlace jet Where the two bundles are interlaced together to form a composite yarn. Twisted yarns, or yarns having twist substitutes are not susceptible to opening by the impinging steam jets and also lack the tendency to form ribbons on contact with hard surfaces, such as hot rolls, so these compact yarns are difficult to heat uniformly. For these reasons, interlacing of filaments should be deferred until both the high-shrinkage component and the low-shrinkage component have been produced.

Steam temperature at the draw jet depends upon yarn denier, steam pressure, filament bundle speed and the draw ratio. In general, at a given draw ratio, an increase in bundle speed requires an increase in steam temperature. At draw ratios greater than 5.0 and at speeds in excess of 2500 y.p.m., steam temperatures of 200 to 375 C. give satisfactory results, and temperatures up to 450 C. have been used with no adverse effects. The same temperatures may be used at lower draw ratios but lower steam temperatures may be adequate to achieve uniform drawing performance. Similar considerations apply to steam temperature at the anneal jet.

The maximum operable temperature is related to the fibers stick temperature. When this temperature is reached, it is believed that individual filaments can break and stick to the body of the jet device, thereby causing a breakdown in the thread line. Steam temperatures above the polymer melting point may be used provided that they do not heat the yarn to the polymer stick point.

In the steam jet treatments of this invention, steam pressure must be sufiiciently high to insure fluid velocities of at least 500 feet/ sec. at the point of impingement but steam pressure, as such, is not critical. Supply pressure will normally range from 30-150 p.s.i.g.

The synthetic linear condensation polymer used in the practice of this invention is not critical. By synthetic linear condensation polyester is meant a fiber-forming composition comprising glycol dicarboxylate structural units as an integral part of the polymer chain. Preferably at least about 75% of the recurring structural units of the polyester are derived from a glycol containing 2 to 12 carbon atoms and a dicarboxylic acid selected from the group consisting of terephthalic acid, isophthalic acid, hexahydroterephthalic acid, sebacic acid, adipic acid and glutaric acid. Especially preferred polyesters are glycol terephthalates, including copolyesters thereof in which up to about of the structural units contain dicarboxylate units having dyeability-enhancing moieties such as, for example, 5-(sodium sulfo)-isophthalate units.

These polyesters may contain additives such as antistats, brighteners, fillers, rougheners, delusterants, viscosity boosters or depressants, and the like.

The polyesters may be shaped into multifilament yarns which will have a denier per filament of 0.5 to 5.0 or more after drawing. The total denier of the composite yarn may be from 15 to 220 and higher, but will preferably be between 20 and 150. The filaments may be of any suitable cross-section such as round, cruciform, Y- shaped, bi-lobal or tri-lobal, and the like.

The polyesters will preferably have a relative viscosity of about 10 to about 70. The term relative viscosity refers to the ratio of the viscosity of a 10% solution of polyethylene terephthalate in a mixture of 10 parts of phenol and 7 parts of 2,4,6-trichlorophenol (by Weight) to the viscosity of the phenol/trichlorophenol mixture, per se, measured in the same units at 25 C.

The measures of shrinkage used herein are S and 160 C. dry-heat shrinkage. S0112 shrinkage is measured on the high-shrinkage component and 160 C. dry-heat shrinkage is measured on the low-shrinkage component. Dry-heat shrinkage at 160 C. is the percent change in length of a sample of yarn when it is heated to 160 C. with dry heat in a free-to-shrink condition. $0.02 shrinkage is determined by the procedure described below.

One meter of the yarn bundle is measured with 0.02 gram per denier restraining load. The meter length of yarn bundle with restraining load is lowered at the rate of 1 meter in 15 seconds into a 1.25-meter depth of water maintained at 98:1" C. The yarn bundle with restraining load remains in the water bath for 40 seconds and then is withdrawn at the rate of 1 meter in 15 seconds. The length of the bundle is measured and percent $0.02 shrinkage is calculated as follows:

Original length-final length Original length S shrinkage rather than boil-off shrinkage is used because boil-off shrinkage is a free-to-shrink measurement and the high-shrinkage component of a composite yarn in fabric form is not free to shrink. It has been determined by separate measurement that the fabric construction will impose an average restraining force on yarns being shrunk in boil-off (about 98 C.) of about 0.02 gram per denier. The application of a small restraining force considerably alters the degree of shrinkage observed. For instance, a filament having a boil-off shrinkage of about 14% will have a 8 shrinkage of about 9.7%. Therefore, since it is the shrinkage differential occurring in the fabric that determines the bulk the fabric Will achieve, the S measurement provides a more meaningful value.

The yarns prepared in the practice of this invention may be treated to develop the bulk either before or after the yarn has been converted into a fabric. Because the unbulked yarn can usually be processed more readily than the bulked yarn, bulk development will preferably be carried out on fabric. In the course of finishing fabric from the polyester yarns of this invention, the fabric is conventionally given a scour in an aqueous bath maintained at or near the boil in order to remove dirt, oils, sizes, and the like. Fabric bulk is developed in the scouring step, due to the high degree of shrinkage of one component relative to the other, and the S shrinkage level for the highshrinkage component becomes a determinant value. In a subsequent step, the fabric is heat-set by passage through an oven maintained at a high temperature. Preferably, these fabrics are heat-set at 160 C. During the heatsetting step, it is the dry-heat shrinkage characteristic of the low-shrinkage component that most effects fabric bulk. The low-shrinkage component of the yarns of this invention may have a dry-heat shrinkage value at 160 C. within the range of about 3% to 10%. However, when 100=percent S 2 a component having an $0.02 shrinkage of about 10% is shrunk in water at about 98 C. it will undergo no further shrinkage when subjected to dry-heat at 160 C. Thus it is seen that the differential shrinkage which is effective to produce actual bulk in the final fabric is measured by the difference between the 80,02 shrinkage value of the high shrinkage component and the dry-heat shrinkage at 160 C. of the low-shrinkage component. This effective shrinkage differential should be at least 1.5%. Preferably, the S shrinkage of the high-shrinkage component minus the dry-heat shrinkage at 160 C. of the low shrinkage component is about 3% to 6%.

Example I A copolyester is prepared in a standard manner from ethylene glycol and a mixture having 98 molecular proportions of the dimethyl ester of terphthalic acid and 2 molecular proportions of the dimethyl ester of the sodium salt of 5-sulfoisophthalic acid. The copolyester has a relative viscosity of 19.5 and contains 0.45%, by weight, of titanium dioxide. This is spun into filaments from a 50-hole spinneret and the extruded filaments are radially quenched by 21 C. air. The filaments are then divided into two groups of 25 filaments and converged to form two separate bundles. The two bundles contact a finish roll, for application of an aqueous-based antistatic lubricating composition, and pass around a feed roll and its associated separator roll in 2.5 wraps. The two bundles then pass through separate passageways in a draw jet wherein steam is impinged on the bundles at an angle of The supply steam has a temperature of 250 C. and a pressure of 60 p.s.i. (4.2 kg. per sq. cm.) gage. Each bundle is drawn in the jet to a denier of at a draw ratio of 2.68. The hot, essentially dry and partially annealed bundles then pass, at a speed of 2750 yards (2508 meters) per minute, to a pair of heated draw rolls. The draw rolls are heated to a temperature of 103 C. and the bundles traverse the rolls in 7.5 wraps to anneal the filaments. One bundle of annealed filaments is then passed through an annealing jet for additional annealing. The anealing jet is supplied with steam having a temperature of 270 C. and a pressure of 100 p.s.i. (7.0 kg. per sq. cm.) gage which is impinged onto the filament bundle at an angle of 30. The other bundle is forwarded, joins the additionally annealed bundle and the joined bundles are passed through an interlace jet. The interlace jet is supplied with air at a pressure of 65 p.s.i. (4.5 kg. per sq. cm.) gage and interlaces the filaments into a composite 70 denier yarn. The composite yarn is then passed across the face of a second finish roll where an aqueous-based antistatic lubricating composition is applied to the yarn. The yarn is then wound into packages at a speed of about 2750 yards (2508 meters) per minute. The high-shrinkage component has an 80,02 shrinkage value of 10.2%, and the low-shrinkage component has a dry-heat shrinkage at 160 C. of 6.4%. Using an averaging procedure, a coefficient of variation from 72 samples of high-shrinkage component is found to be 1.4%.

The coefficient of variation is determined on the highshrinkage component, since this is the controlling factor in obtaining uniform differential shrinkage in the composite yarn. The shrinkage of the other component is both lower and more uniform, as a result of the additional annealing treatment. For determining the coefficient of variation, the annealing jet is by-passed temporarily to give only high-shrinkage component. Using the procedure described above, packages containing 24 bundles, in 4 sets, of the high-shrinkage component are obtained. Three samples are taken from each bundle, the S shrinkage value for each sample is determined by the procedure described previously and the average of the three values determined. The coefiicient of variation (C.V.) for each set is calculated from the formula where S is the square root of the expression wherein i is the average of the 80,02 shrinkage values.

A coefficient of variation from the 72 samples is then obtained by determining the average of the four sets.

For comparison, a yarn similar to that of Example I is produced in a manner similar to that described in Example II of Maerov et al. US. Patent No. 3,200,576, dated Aug. 17, 1965. The copolyester of Example I is spun from a 50-hole spinneret. The extruded filaments are cross-flow quenched by 21 C. air, divided into two groups of 25 filaments and converged to form two separate bundles. The two bundles contact a finish roll, for application of an aqueous-based antistatic lubricatin composition, and pass around a feed roll and its associated separator roll in three wraps. The bundles then pass to a draw bath and are drawn in the manner disclosed in the above-mentioned Maerov et a1. patent. The draw bath comprises an aqueous-based antistatic lubricating composition and is maintained at a temperature of C. The bundles are each drawn to a denier of 35 at a draw ratio of 2.71 and pass, at a speed of 2750 yards (2508 meters) per minute, to a pair of draw rolls heated to C. The two bundles are annealed by passing around the rolls in 10.5 wraps. One bundle of the annealed filaments is then passed through an annealing jet for additional annealing. The annealing jet is supplied with steam having a temperature of 270 C. and a pressure of 75 p.s.i. (5.3 kg. per sq. cm.) gage which is impinged onto the filament bundle at an angle of 30 C. The other bundle is forwarded, joins the additionally annealed bundle and the combined bundles are passed through an interlace jet. The interlace jet is supplied with air at a pressure of 65 p.s.i. (4.5 kg. per sq. cm.) gage and interlaces the 50 filaments into a composite 70-denier yarn. The composite yarn is then passed across the face of a second finish roll where an aqueous-based antistatic lubricating composition is applied to the yarn. The yarn is then wound into packages at a speed of about 2750 yards (2508 meters) per minute. The high-shrinkage component has an S shrinkage value of 10.0%, and the low-shrinkage component has a dry-heat shrinkage at 160 C. of 6.3%. The coefiicient of variation from samples of high shrinkage component is 3.8%, determined as above on 10 sets of packages. The physical properties of the two composite yarns are judged to be equivalent.

Based on a statistical study, it has been found that a CV. less than 1.9% will result in a streak-free fabric and a CV. greater than 3.2% will result in a fabric having objectionable streaks. Thus, it is seen that the process of this invention produces yarns having an improved level of shrinkage uniformity.

Since many different embodiments of the invention may be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited by the specific illustrations except to the extent defined in the following claims.

I claim:

1. In the process of producing mixed-shrinkage, bulkable yarn by melt-spinning a synthetic linear condensation polymer to form separate filament bundles, drawing and annealing the separate filament bundles under different conditions to provide differential shrinkage characteristics, and combining the filament bundles to form a composite yarn; the improvement for providing highly uniform differential shrinkage which comprises continuously melt spinning separate filament bundles and drawing the separate filament bundles under identical conditions during passage through steam jets to localize the draw zone, annealing one of the bundles of drawn filaments by passage through a second steam jet to provide an effective differential shrinkage of at least 1.5% between filament bundles, and then combining the bundles to form a composite yarn.

2. The process defined in claim 1 wherein the filament bundle passed through the second steam jet is annealed to provide a dry-heat shrinkage value at 160 C. within the range of about 3 to 10%, and the other filament bundle treatment provides an 8 shrinkage value which is 3 to 6% higher than said dry-heat shrinkage value.

3. The process defined in claim 1 wherein the separate filament bundles are drawn in jets of steam supplied from a common source at 30 to 150 pounds per square inch gage pressure and 200 to 375 C.

4. The process defined in claim 3 wherein the drawn filament bundles are partially annealed on hot draw rolls under the same conditions and then one of the bundles is further annealed in a second steam jet at a higher temperature than for the hot roll annealing treatment.

5. The process defined in claim 3 wherein the drawn bundle passing through the second steam jet is annealed under drawing tension.

6. The process defined in claim 3 wherein the drawn filament bundles are heat-treated in a steam chamber supplied with exaust steam from the steam jets.

7. The process defined in claim 1 wherein the filaments are of glycol terephthalate polyester, are drawn to have 0.5 to 5.0 denier per filament, and the filaments are interlaced to form a composite yarn of 20 to 150 total denier.

References Cited JOHN PETRAKES, Primary Examiner.

US. Cl. X.R.

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