US2979883A

US2979883A - Composite yarn and process of producing bulked fabric therefrom

Info

Publication number: US2979883A
Application number: US677550A
Authority: US
Inventors: Joseph E Waltz
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1957-08-12
Filing date: 1957-08-12
Publication date: 1961-04-18
Anticipated expiration: 1978-04-18

Description

Aprxl 18, 1961 .1. E. WALTZ 2,979,883

COMPOSITE YARN AND PROCESS OF PRODUCING BULKED FABRIC THEREFROM Filed Aug. 12, 1957 I f I INVENTOR JOSEPH E. WALTZ BY M e, 14%

ATTORNEY COMPOSITE YARN AND PROCESS OF PRODUC- ING BULKED FABRIC THEREFROM Joseph E. Waltz, Wilmington, Del., assiguor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Filed Aug. 12, 1957, Ser. No. 677,550

13 Claims. (Cl. 57-140) This invention relatesto novel composite yarns and to fabrics prepared from such yarns. More particularly, it relates to composite yarns which can be caused to be- 'come permanently bulky by appropriate treatment at 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. This has been accomplished in various ways by producing continuous filament yarns in which the various filaments contained in a short segment of a yarn have different lengths when straightened out.

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. The reason for this is 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 various parts of the yarn processing equipment, particularly 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 supportthe load imposed on the yarn. For these reasons a continuous filament yarn has been desiredwhich can be processed in its smooth, compact form into fabric and subsequentlyv treated to obtain a satisfactory amount of bulk in fabric form.

Much attention. has been given to composite continuous filament yarns comprising filaments having different levels of shrinkage, with the object of obtaining bulking of the yarns in fabric form by differential shortening of the lengths of the filaments in the yarns. The results of this work have been somewhat disappointing and contrary to expectation. Although the individual yarns relax and become quite bulky in skein form, the amount of bulking which is obtained in fabric form is frequently quite small, especially when the intial fabric is of dense construction. The reason for this appears to be that the filaments which have a nominal high shrinkage usually also have a relatively low yield point, so that. they simply tend. to yield .0: flow internally rather than. shrink against. the-i constraint. afforded by the fabricv construction. For. thesametreasomit. isfound that yarns which. become bulky inskein form by differential shrink age. are largely pulled out straightagain. in response to.

the tensions applied during weaving and other yarn processing steps.

Even when bulking in fabric form by differential shrinkage is successful, it has been found that the process is usually accompanied by undesirable factors. The final dimensions of the fabrics are controlled by those filaments which have the greater shrinkage, and the high shrinkages required are regarded in the textile industry as wasteful of loom capacity. Owing to the uncertainty in the actual shrinkage which will be achieved, the attainment of a desired fabric density alsobecomesa matter of trial and error. Finally, the load-bearing members of the yarns in the fabric also tend to be the weaker. filaments in the fabric, as indicated above.

It is therefore an object of this invention to provide asmooth, composite yarn which can be caused to be,- come permanently bulky by treating the yarn in a simple manner. Another object of the invention is to provide such a smooth, composite yarn which can be woven -or knitted into fabric and subsequently treated to cause permanent bulking in the yarns comprising the fabric. A further object is to provide such a smooth, composite yarn which can be woven or knitted into fabric and subsequently caused to become. permanently bulky with no more than moderate changes in fabric dimensions. Other objects will become apparent from the following description and claims.

These objects have been realized by the present invention, which comprehends a composite yarn comprisinga plurality of strands of at least two species, said composite yarn being characterized in that at least a first species of strand in said yarn is spontaneously and irreversibly extensible and being further characterized in that said first species of strand is spontaneously and irreversibly extensible relative to the remainder of the strands in the yarn. The remainder of the strands in the composite yarn may be characterized by shrinkage, or they may be characterized by spontaneous and irreversible extensibility of asmaller magnitude than the strands of the first species. The composite yarn may be prepared by plying yarns together, one of the plies being spontaneously and irreversibly extensible and the other ply or plies being characterized by shrinkage or by spon taneous and irreversible extensibility of smaller magnitude than the first ply. The strands may also be associated together in other ways; for example, the strands may be assoicated together in a non-plied singles yarnin which some of the strands exhibit spontaneous andirreversible extensibility and the remainder of the strands are characterized by shrinkage or by spontaneous andirreversible extensibility of smaller magnitude than thefirst portion of strands.

The spontaneous and irreversible extension in length of part of the strands in the composite yarn is conveniently achieved by heating strands whichhave been prepared in such a manner as to grow irreversibly when heated,

although the invention also comprehends composite yarns- The invention will be-better understood by reference.

to the drawings, in which-- Figure 1 is a side view, greatly enlarged, of a segment of a composite singles yarn of the present invention, before it has been caused tobiecome bulky,

,- Figure 2. isra. side view,,greatly' enlarged, of the seg-v ment of yarn of Figure 1 after it has been treated with a suitable agent to cause it to become bulky,

Figure 3 is a side view, greatly enlarged, of a segment of a composite plied yarn of the present invention, befiore it has been treated to cause it to become bulky, an

Figure 4 is a side view, greatly enlarged, of the segment of composite plied yarn of Figure 3 after it has been treated with a suitable agent to cause it to become bulky.

Referring to Figure 1, yarn segment 1 is a composite slngles yarn comprising spontaneously extensible filaments 5 and shrinkable filaments 6. Such a yarn may be prepared, for exampe, by spinning in a single yarn bundle polyethylene terephthalatefilaments of difierent denier and subsequently drawing and relaxing the yarn in a suitable manner as described more fully hereinafter. The composite yarn is smooth and compact prior, to heat treatment; after heat treatment, however, the yarn has the bulky and voluminous appearance depicted-in Figure 2. As illustrated in this figure, the length of yarn segment 1 has decreased slightly owing to a slight decrease in length of filaments 6, while filaments 5 have increased in length, so that the filaments 5 have become relatively much longer than the filaments 6.

In Figure 3, yarn segment 3 is a plied yarn comprising a plurality of spontaneously extensible filaments 7 plied with a plurality of shrinkable filaments 8. Such a yarn may be constructed, for example, by plying a shrinkable polyethylene terephthalate yarn with a spontaneously and irreversibly extensible polyethylene terephthalate yarn, which may be prepared by spinning, drawing, and relaxing polyethylene terephthalate filaments in a suitable manner as described more fully hereinafter. The plied yarn is smooth and dense prior to heat treatment; after heat treatment, however, the plied yarn has the bulky and voluminous appearance depicted-in Figure 4. As shown in the figure, the length of yarn segment- 3 has decreased slightly owing to a slight decrease-in length of filaments 8, while filaments 7 have increased in length, so that the ply 7 has increased greatly in length relative to ply 8.

In Figures 1 and 3, shrinkable filaments 6 and 8 may be replaced, respectively, by filaments which have a spontaneously extensibility of somewhat lesser magnitude than filaments 5 or 7 to form acomposite yarn having a similar capacity for becoming bulky.

If desired, the composite yarns of the present invention may be treated to cause them to become bulky before the yarns are formed into fabrics. It is usually preferred, however, to prepare a fabric from the composite yarn while the yarn is in its smooth, compact form and then to apply heat or other agents to cause the yarn to become bulky in the fabric. Surprisingly, the degree of bulkiness which may be achieved in the composite yarns in skein form is also fully achieved when the bulking treatment is delayed until the yarns have been processed into fabric, and there is no reduction in the degree of bulk in the yarn owing to any force of constraint imposed by the fabric construction. Nonuniformity arising from high fabric shrinkage, which is also regarded as wasteful of loom capacity, is easily avoided. In fact, it is preferred that any shrinkage in the composite yarn arising from the use of shrinkable strands in the yarn be not more than the maximum shrinkage level usually regarded as acceptable in commercial fabric preparation, i.e. not more than about 12% shrinkage. The composite yarns of the present invention include a wide variety of yarn products below this maximum shrinkage level. For example,a spontaneously I ae'zasesa 4 since changes in fabric dimensions. frequentlyoccur in a non-uniform way so that the regular fabric construction imparted during knitting or weaving is distorted. In another embodiment of the invention, each of the strands in the yarn is spontaneously and irreversibly extensible, although the degree of spontaneous extensibility differs. The dimensions of fabrics prepared from such yarns increase during the bulking treatment, resulting in an actual increase in loom productivity. In such fabrics the increase in bulk of the yarn during the bulking treatment more than compensates for the opening of the fabric construction caused by the spontaneous extension in length of each of the yarns. I

Spontaneously extensible strands which may be used to formthe composite yarns of the present invention may be prepared in various ways. For example, a cellulose acetate yarn may be heated to a temperature above the second order transition temperaureand below the decomposition temperature so that it shrinks without crystal-' lization to produce a yarn which elongates spontaneously and irreversibly when heated in 100 C. water. yarns are described more fully and claimed by M. H. Booth in his United States patent application No. 648,787 and now Patent No. 2,900,669, dated August 25, 1959.

In a preferred embodiment of the invention, a yarn containing strands of spontaneously and irreversibly extensible linear terephthalate polyesters is employed. By linear terephthalate polyesters is meant linear polyesters in which at least about 85% of the recurring structural units are units of the formula -o onnnoo o-Q-o 0- of (wherein n is equal to 2), can be readily prepared in the form of strands exhibiting spontaneous. and irreversible extensibility. For example, an oriented polyethylene terephthalate yarn, preferably one which is substantially amorphous, may be exposed to water or steam at 100% C. for an exposure time on the order of about 0.1 second to shrink the strand at least 20%, preferably 40% or more. In this way yarns exhibiting spontaneous and irreversible extensibility in 100 C. Water amounting to 15% or higher may be produced; in dry air at 200 C. 30% spontaneous and irreversible extensibility or even higher may be obtained with these yarns. Such yarns are described more fully and claimed by C. E. Reese and R. E. Kitson in their United States patent applications No. 648,797, filed March 27, 1957,

i and now abandoned and No. 718,114, filed February 28,

In one method of preparing the composite yarns of the present invention, a spontaneously and irreversibly extensible yarn is prepared first and subsequently plied or otherwise associated with a shrinkable yarn, or with a yarn having a ditierent degree of spontaneous and irreversible extensibility. In another method of preparing the composite yarns of the present invention, a composite singles yarn is produced directly. For example, polyethylene terephthalate filaments may be spun and wound up together at 1200 yards per minutes from a spinneret in such a way that a portion of the spun filaments have a spun denier of about 2 denier per filament and remainder of the filaments have a spun denier of about 5 denier per filament. Preferably, the higher denier filaments are of round cross-section and the lower denier filaments are of Y cross-section or other irregular crosssection, although this is not essential. The yarn is then oriented by drawing it about 2.5X in such a manner vthat the yarn remains substantially amorphous, after which it is caused to shrink approximately 50% by contacting it with hot air for an exposure time on the order Such of about 0.1 second. The, yarn so produced is, found.

per filament polyethylene terephthalate yarn spun and wound up as described by drawing it about 2.6X in such a manner that the yarn remains substantially amorphous, and then causing the yarn to shrink approximately 65% by contacting it with hot air for an exposure time of about 0.1 second.

For convenience, the strands which make up the composite yarn will frequently be composed of the same polymeric material, although in such cases there will be differences in the manner of preparing one portion of the strands as contrasted to the remainder of the strands. However, it is not essential that all of the strands in the composite yarn be composed of the same polymeric material. Spontaneously extensible strands of polyethylene terephthalate may be associated with the usual, commercially available, shrinkable strands of nylon, rayon, or polyacrylonitrile. Itis readily apparent that many other combinations are possible.

The following examples will serve to illustrate the invention, although they are not intended to be limitative.

EXAMPLE 1 Polyethylene terephthlate having an intrinsic viscosity of 0.57 and containing 0.3% TiO is spun at 295 C. through a bath of water at 25 C. and over a sponge, in diameter, and the yarn is wound up at a speed of 1,200-

yards per minute. The yarn as spun is found to have a denier of 60. The yarn is passed from a supply package though 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 545 yards per minute and the draw ratio. is 2.385. The drawn yarn is then passed from a feed roll through a steam oven 12 inches. in length maintained at 100 C., the entrance and exit being /2 inch in diameter and steam at 100 C. being introduced along the bottom of the oven at a rate sufficient to keep the oven filled with steam. The yarn speed at the entrance to the oven is 282 yards per minute and at the exit of the oven is 150 yards per minute, corresponding to a shrinkage of 47% in the yarn as it passes through the oven and an exposure time of 0.133. second in the steam, calculated from the oven length and yarn exit speed. After leaving the oven the yarn is Wound up on a suitable package without twisting it. When the sample of the yarn is immersed in 100 C. water for five minutes, it is observed that the yarn undergoes spontaneous and irreversible extension in length of 17%.

The spontaneously extensible. yarn prepared as described above is plied with a twist of 2.5 turns per inch in the 2 direction with a commercial continuous filamentv polyethylene terephthalate weaving yarn. The commercial weaving yarn is anuntwisted, 40-denier, 27-filament, semi-dull (0.3% TiO polyethylene terephthalate yarn having a tenacity of 4.4 grams per denier, an elongation (amount of stretch before, breaking) of 25%, and a shrink.- age of 12% upon immersion in 100 C. water for five m nutes. A sample of the plied yarn, when immersed, in water at 100 C. for five, minutes, is observed to undergo ahigh degree of bulking. A large sampleof the unheated plied yarn, is woven into .a 1'20 -sley,'11,4-pick, 2 x 2 basket weave-fabric, Temperatures in excess of 70 C.v areavoided in slashing and other yarn processing steps. The resulting fabric is quite smooth and has the slick" hand usually associated with continuous filament synthetic fabrics. However, when the fabric is immersed in water at C. for five minutes, the yarn comprising the fabric becomes quite bulky, the hand of the fabrics becomes warm and soft, and the opacity and cover of the fabric increases materially. The following results illustrate power and a decreased value for visible light transmit-- tance.

Before Heat 7 Treatment After Heat Fabric Properties Treatment Specific Volume (ea/g.) Contact Covering Power, percent. Visible Light Transmittance, percent..

In the above tests, the specific volume is determined by dividing the volume of the fabric by its weight; the volume of. a fabric sample of known area being determined by multiplying the area by the thickness measured under a pressure of 3.4 p.s.i. in accordance with Method D7653 of the A.S.T.M. Standards on Textile Materials.

The visible light transmittance is determined by measuring the amount of light passing through the fabric from a source. of white light with the aid of a calibrated photocell. The contact covering power is determined by passing a beam of collimated light from a green filter perpendicularly to the fabric surface and measuring with a photovolt refiectometer (such as the Photovolt Corp. Model 610) the light reflected at a 45 angle from the fabric surface and comparing the reflectivity of the fabric surface with the reflectivity of a white background according to the following equation:

EXAMPLE 2 In a series of experiments, polyethylene terephthalate having an intrinsic viscosity of 0.57 and containing 0.3% TiO is spun at 295 C. through a spinneret having 27 orifices, each 0.009 inch in diameter, and the yarn is wound up at a speed of 1200 yds./min. The as-spun Contact covering power: X 100% deniers of the yarns obtained in the three experiments are shown in Table 1. The yarns are 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 545 yds ./min. and the draw ratios are listed in Table 1. The drawn yarn is then passed from the wind-up package over a feed roll through a steam oven 12 inches in length maintained at 100 C., the entrance and exit being. /2 inch in diameter and steam at,l00 C. being introduced along the bottom of the oven at a rate sufficient to keep the oven filled with steam. In each case the yarn speed.

at the exit of the oven is yds./min. and the calculated exposure time in the steam is 0.133 second. The yarn speed at the entrance to the oven, together with the cal.--- culated shrinkage, of the yarn as it passes through. the

oven, is listed in Table 1. After leaving. the oven the.

' asides-3 and irreversible extension in length when it is immersed in 100 C. water for minutes, the amount of extension being listed in the table.

Table I PREPARATION OF SPONTANEOUSLY EXTENSIBLE POLY- ETHYLENE TEREPHTHALATE YARNS -Each of the spontaneously extensible yarns prepared as described above is plied with a twist of 2.5 turns per inch in the 2 direction with commercial continuous filament nylon weaving yarn. The commercial weaving yarn is an untwisted -denier, 7-filament, semi-dull (0.3% TiO polyhexamethylene adipamide yarn having a tenacity of 5.0 grams/denier, a break elongation of 20%, and a shrinkage of 10% upon immersion in 100 C. water for 5 minutes. Samples of the plied yarns prepared from yarns A, B, and C, when immersed in water at 100 C. for 5 minutes, are observed to undergo low, moderate, and high degrees of bulking, respectively. A quantity of each of the unheated plied yarns is knit on a tricot machine as the front bar in a bar and bar construction with commercial, 30 filament, 10-denier nylon yarn in the opposite bar, using a Jersey stitch. The resulting fabrics are smooth and have the slick hand associated with fabrics made from filament yarns. However, when the fabrics are immersed in water at 100 C. for 5 minutes, the yarns comprising the fabrics become bulky and each of the fabrics exhibits a warm and soft hand. Among the three fabrics, the most marked increase in bulk and warmth of hand is exhibited by the fabric containing yarn C, the fabric containing yarn B ranking second.

EXAMPLE 3 as a single filament bundle at a speed of 1200 yards per minute and is found to have a denier as spun of 208. The yarn is passed from a supply package through a bath of water at 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 545 yards per minute and the draw ratio is 2.456. The drawn yarn 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 a suitablewind-up package. Air is maintained at 220 C. and 5 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 effective 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'y'arn 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 5 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 10% in the boiling water.

A quantity of the air-jet relaxed composite yarn is woven into a l20-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 fabric is smooth and has the characteristic slick hand of continuous filamentv synthetic fabrics; however, after immersion in C. water for five minutes, the fabric exhibits a warm and soft hand and shows a marked increase in cover and opacity.

EXAMPLE 4 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 orifices, each 0.006 inch in diameter, on one side of the pack and 27 Y-shaped orifices, each comprising three in tersecting slots 0.003 inch wide and 0.025 inch long, 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 yds./min. and is found to have a denier as spun of 208. The yarn is passed from a supply package to a bath of water at 25 C. and over a sponge to leave 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 of the draw roll is 580 ft./min. and the draw ratio is 2.9. The drawn yarn is then passed from a feed roll through a 12 inch steam oven maintained at 100 C. The yarn is passed into the oven at 400 ft./min. and wound up at 180 ft./min., 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 5 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 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 woven into a 135-sley, -pick, 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 5 minutes the fabric develops a warm and soft hand and shows a marked increase in cover and opacity.

EXAMPLE 5 A sample of cellulose acetate containing 2.4 acetyl groups per glucose unit is dry-spun by conventional methods from acetone to give a 75-denier, 24-filament yarn having a shrinkage of 2% after exposure to 100 C. water for 30 minutes. A quantity of this yarn is passed through a 2.5 foot tube 5 inches in diameter, maintained at 200 C. by means of a radiant heater extending its entire length. The yarn speed at the entrance to the tube is 338 yds./min. and at the exit of the tube is 270 yds./'

min., corresponding to a shrinkage of 20% in the yarn as it passes through the tube and an exposuretime of.'0.19i, second,'calculated from the tubelength and yarn exit" speed. When a sample of the yarn is immersed in 100 C. water for 30 minutes, it is observed that the yarn undergoes spontaneous and irreversible entension in length amounting to 14%.

The spontaneously extensible yarn prepared as described above is plied with a twist of 2.5 turns/inch in the 2 direction with a quantity of the original sample of 75-denier, 24-filament, cellulose acetate yarn exhibiting a shrinkage of 2% upon immersion in 100 C. water for 30 minutes. A sample of the plied yarn, when immersed in water at 100 C. for 30 minutes, is observed to undergo bulking. A large sample of the unheated piled yarn is woven into a 120-sley, 114-pick, 2 x 2 basket weave fabric. Exposure of the yarn to hot water is avoided in slashing and other yarn processing steps. The resulting fabric is smooth and has a relatively slick hand; however, after it is immersed in water at 100 C. for 30 minutes, the yarn comprising the fabric becomes bulky, and the hand of the fabric becomes warm and soft.

The present invention offers many advantages over the prior art. One of theprimary advantages is that it permits the use of continuous filament yarns which have excellent strength and simplicity of processing to produce yarns which can be made into fabrics having a high covering power and soft hand. Usually when continuous filament yarns are treated to increase their bulk some of the processing advantages of the original smooth dense continuous filaments are lost. In the present case, however, the bulking may be produced after the yarn has been woven or knitted. This eliminates the tendency of the bulky yarn to be pulled out into a smooth yarn bundle when knitted or subjected to similar processing tensions. A still further advantage is that a high degree of bulk can be achieved in the fabric without the use of highly shrinkable yarns. Heretofore, high shrinkages required considerable waste in loom capacity and in addition due to the uncertainty of the actual shrinkage to be attained, a given amount of shrinkage was necessarily arrived at by trial and error.

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. 7

I claim:

1. A composite yarn comprising a plurality of strands of at least two different species, at least one species of strand in said yarn having the property of being spontaneously and irreversibly extensible and being extensible relative to a second species of strand in said yarn.

2. The yarn of claim 1 in which the said second species of strand in said yarn is characterized by being shrinkable.

10 3. The yarn of claim 1 in which each of the strands in said yarn is spontaneously and irreversibly extensible.

4. The yarn of claim 1 in which the strands are twisted into a plurality of plies.

5. The yarn of claim 4 in which one of the plies is spontaneously and irreversibly extensible and another of the said plies is shrinkable.

6. The yarn of claim 1 in which the strands are continuous filaments associated as a non-plied singlesyarn.

7. The yarn of claim 1 in which at least one species of strand is spontaneously and irreversibly extensible when heat is applied.

8. The yarn of claim 7 in which. the heat extends some of the strands in the yarn and shrinks the remainder.

9. The process of producing bulked fabric which comprises weaving a yarn made up of a plurality of strands, at least one of which has the property of being spontaneously and irreversibly extensible, and being more extensible than at least one other strand in the yarn into a fabric and subsequently heating it.

10. The process of preparing a bulked fabric which comprises knitting a yarn made up of a plurality of strands, at least one of which has the property of being spontaneously and irreversibly extensible, and being more extensible than at least one other strand in the yarn into a fabric and subsequently heating the knitted fabric.

11. The process of claim 9 in which the fabric contains a shrinkable component of the yarn which is capable of shrinking up to 12%.

12. Theyarn of claim 1 in which at least one species of strand is a polyethylene terephthalate strand.

13. The yarn of claim 1 in which at least one species of strand is a cellulose acetate strand.

References Cited in the file of this patent UNITED STATES PATENTS 2,058,422. Dickie et a1 Oct. 27, 1936 2,212,909 Fonda June 28, 1938 2,171,626 Dreyfus et al. Sept. 5, 1939 2,174,878 Hardy Oct. 3, 1939 2,369,395 Heymann Feb. 13, 1945 2,413,123 Underwood Dec. 24, 1946 2,439,815 Sisson Apr. 20, 1948 2,701,406 Bloch Feb. 8, 1955 2,717,511 Rossak Sept. 13, 1955 2,810,281 Appleton et a1 Oct. 22, 1957 2,866,255 Keen Dec. 30, 1958 2,925,642 Pfeffer Feb. 23, 1960 FOREIGN PATENTS 497,689 Great Britain Dec. 23, 1938