CA1117286A - Bulkable filamentary yarn, a method and an apparatus for the preparation of the same - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A novel bulkable filamentary yarn having a flat yarn-like smooth appearance is disclosed, the bulkable filamentary yarn being composed essentially of bulkable portions and interlaced portions occurring alternately along the yarn length. Upon scouring, for example, the yarn develops its latent bulkiness similar to the fullness of silk and thus a silk-like appearance as well as a silk-like hand are provided in a fabric made from the yarn. The yarn itself can be obtained by heat-shrinking arc-like loops protruding from the yarn surface into a straightened state parallel to the yarn while the yarn is being tensioned along its length.

Description

BACKGROUND OF THE INVENTION
(1) Field of the Invention The present invention relates to a bulkable yarn for weaving or knitting into fabrics which are silk-like in general appearance, luster, hand liveliness and hue, and to a process and an apparatus for the preparation of the same.
The term "bulkable filamentary yarn", as used herein, comprehends a thermoplastic multi-filamentary yarn having mixed differential boil-off shrinkage portions at considerably short intervals along the yarn length, the portions being composed of filament.s differing in shr:inkage among the filaments as well as within each of the filaments, and deveiops its latent bulkiness to show silk-like hand and fullness when heat-relaxed. Although the word "fullness" means a bulky state in general it is characteristic of silk, and distinguished, for example, from the bulky state of crimped yarn.

(2) Description of the Prior Art As disclosed in British Patent No. 1,510,337 or Japanese Patent Publication No. ~7550/1972 and No. 18535/1976, it is well known to produce a textured yarn with crimps and length-difference induced among the constituent filaments by contacting a thermo-plastic filamentary yarn.instantaneously with a heated body (roll~
of the dry heat type under a tension below the thermal shrinkage stress of the yarn (more concretely under a substantially tension-. free state) wherein a part of the constituent filaments shrinksintermittently and, accordingly, another part of the same is puckered to form loops and slack protrusions.
Textured yarn so obtained bears on its surface a large .. .

- : . . . :
::
:: : . ..
. ~ . , . :
: ~.:

~L'7;~81~

number of loops and the like, and as a result, although the yarn presents a silk-like hand and tactility to some extent, many problems are left unsolved Erom the point of view of commercial production. These are as follows:
(i) Since the Eilamentary yarn undergoes an irregular thermal treatment in transverse and lengthwise directions, splashed pattern streaks arise on the surface of woven or knitted fabric made up of such yarn. This is due to an unstable heat-treating process because the filamentary yarn is subjected to contact heat-treatment in a state substantially free from tensioning which, in turn, prevents smooth running of the yarn over the heated body.
In order to avoid such streaks, one can imagine tllat the partial, predetermined filaments should undergo the heat-treatment selectively at a constant ratio. But, the limitation of "instan-taneous" with regard to treatment time makes it impossible, for example, to heat always one-half the filaments and actually makes a constant variance of the numbers of the filaments to be heated.
Further, the processing speed of the above method becomes limi-tative of its own accord.
(ii) As the result of partially shrinking the filamentary groups, loops and the like are formed on the surface of the yarn.
The existence of such protrusions adversely affects the handling and running properties of the yarn, and accordingly, the weaving or knitting efficiency (performance) especially. In addition, the surface appearance of fabrics obtained is spoiled and loses its commercial value.
For th:is reason, a process has also been proposed to re-heat the aforementioned loop yarn to diminish the loops in order to improve the handling and running properties. In this .

.,, ~. :

process, however, the difference in boil-off shrinkage between the more shrinkable portions and the less shrinkable portions origin-ally induced in the form of the loop yarn is easily reduced to a quite limited range.
Therefore, the hand and tactility originally possessed by the loop yarn can never be expected to develop again.
(iii) Since the textured (loop) yarn is composed oE
partially shrunken filaments under extremely lower tension, it possesses flow portions scattered therein. Due to the existence of these portions, the yarn is irregularly stretched during weaving or knitting operations so that tight spots inevitably arise and the fabrics obtained tend not to be restored to the original state after deformation.
(iv) Although the textured yarn possesses both more shrinkable components and less shrinkable components, these com-ponents exist in separate states (not commingled state), which are mainly attributable to the reason that the process itself adopts one-side instantaneous heating of the starting yarn. Accordingly, the loop or textured yarn obtained, when heat-relaxed, for example at the dyeing stage, only exhibits a puckered form as a whole and therefore, silk-like effects in the term of "moderate fullness"
as realized by the mixed differential shrinkage characteristics are ,,,,,,, lowered.
As mentioned above, conventional silk-like yarn of thermo-plastic material with differential shrinkage characteristics induced therein has always offered seriousproblems such as dyeing speck, lower restoring power deterioration of weaving efficiency, and even at present silk-like appearance inherently possessed by such

- 3 -.

,:, 1~l7%86 yarns has not been manifested sufficiently in fabrics.
SUM~RY OF THE INVENTION
The present invention, however, provides a novel bulkable filamentary yarn with improved handling and running properties for weaving and knitting into Eabrics which have not only a .silk-like appeal in hand, luster and liveliness, but are free from dyeing-speck and other problems.
The present invention also provides a method for the preparation of such yarns under stable operation.
The present invention further provides an apparatus for carrying out the above method efficiently and stably.
The present invention in another aspect provicles a more compact apparatus for carrying out the above mèthod, which enables one to employ a sequential draw-texturing process.
The present inventors have now shown that an extremely desirable latent-bulkiness character, as well as improved handling, can be imparted to a filamentary yarn of thermoplastic material when the yarn, having intermittently interlaced portions (points) and arc-like loops between each adjacent pair of interlaced portions, is subjected to heat-treatment to allow the loops only to shrink freely parallel to the major portion of the Eilaments.
The loop yarn as specified can preferably be obtained by sub-jecting it to an interlacing treatment under a cont~olled overfeed . . .
ratio.
Thus, according to the present invention there is provided ln more detail a novel bulkable filamentary yarn in which consti-tuent filaments of substantially straight form are assembled together, the yarn having interlaced portions of at least 20 per _ 4 :, :

~.

: ~

'~

.

meter along the yarn length wherein a filamentary group between each adjacent pair of interlaced portions exhibits mixed, differ-ential boil-off shrinkage characteristics both among the filaments and within each of the filaments, the K va~ue, as defined by the Eollowing formula, of the yarn being no more than 1.0 K =

wherein Ql is the length of an interlaced portion and Q2 is the length of a non-interlaced portion hereinbefore defined.

The present invention also provides a method for the pre-paration of a bulkable filamentary yarn, which comprises heating an interlaced filamentary yarn of thermoplastic material having arc-like loops on the surface of the yarn, under controlled ten-sion so as not to remove the arc-like loops while maintaining the tension to a level of at least 0.02 g/denier, thereby subjecting the yarn as a whole to a heat-treatment while under tension, causing, concurrently, the loops to shrink freely in order to con-vert them into a straightened state.
The present inventlon, in another aspect, provides an apparatus which comprises (a) a feed roll and a withdrawal roll operating at a lesser peripheral speed than that of the feed roll, (b) a fluid interlace jet and a heater for thermal treatment located in sequence between the feed roll and the withdrawal roll ; and (c) a plurality of guides located between the jet and the heater, which deflect the yarn path while pressing the yarn laterally, whereby the yarn is relaxed in the fluid turbulent zone - : .. , 1~17Z~36 and strained in the heat treating zone.
According to yet another aspect of the invention there is provided a compact apparatus which comprises (a) a feed roll~ a heater and a stepped roll arranged in sequence on a substantially straight line wherein the larger diameter portion oE the stepped roll serves as a draw roll for an undrawn yarn coming from the feed roll via the heater, and also serves as a forwarding roll in turn for the drawn yarn in a direction opposite to the direction of the undrawn yarn, (b) a fluid interlace jet for receiving and fluid lQ treati,ng the drawn yarn and (c) yarn deflecting guides in combina-tion for introducing the fluid-treated yarn again at the entrance of the heater wherein the heat-relaxed yarn is withdrawn by the smaller diameter portion of the stepped roll.
BRIEF DESCRIPTION OF T~IE DRAWINGS
Figure 1 is a diagrammatic representation of apparatus for carrying out the process.
Figure 2 is an enlarged side view of an interlaced yarn having arc-like loops intermittently along the yarn length.
Figure 3 is a graph showing the relation between tension exerted in an interlaced yarn being heated and boil-off shrinkage of the heat-treated yarn.
Figure 4 is an enlarged side view of a bulkable filamentary yarn according to the present invention.
Figure 5 is a greatly enlarged side view of the yarn of Figure 4.
Figure 6 is an enlarged side view of a heat-treated "TASLAN" ~ yarn.
Figure 7 is an enlarged side view of a silk-like yarn .

:

.

7~86 . `~ .

obtained by heat-relaxing the yarn of Figure 4 (or 5).
Figure 8 is an enlarged side vlew of an intermittently bloomed yarn formed when the bulkable filamentary yarn of Figure

4 or 5 is allowed to float on water.
Figure 9 is a greatly enlarged side view of a full-hand (bulkable) portion occurring intermittently in the yarn of Figure 7.
Figure 10 is a greatly enlarged side view of an arc-like loop portion intermittently occurring in the yarn of Figure 2.
Figure 11 is a diagrammatic representation of another embodiment of apparatus according to the invention.
Figure 12 is a diagrammatic representation of a modifica-tion of the apparatus of Figure 11.
Figure 13 is a photographic representation (x 60) of the interlaced filamentary yarn with arc-like loops produced by the process of Example 10.
Figure 14 is a photographic representation (x 60) of the bulkable fiIamentary yarn produced by the process of Example 10.
Figure 15 is a photographic representation (x 60) of silk-like yarn produced by the process of Example 10.
Figure 16 is a photographic representation (x 40) of a cross section along the warp direction, after boil-off and heat- -setting, of the silk-like fabric produced by the process of Example 10.
Figure 17 is a photographic representation (x 40~ of a cross section along the warp direction of silk fabric.
Figure 18 is a photographic representation (x 40) of a cross section along the warp direction of a conventional flat .

721~6 yarn fabric.
DETAILED DESCRIPTION OF THE INVENTION
The description will begin with an explanation of an embodiment of the continuous process for manufacturing a bulkable filamentary yarn according to the invention with reference to Fig. 1.
This embodiment employs an undrawn or a partially drawn polyester yarn as the starting material to be treated. An undrawn yarn 1 unwound from a package 2 (in the form of a cheese) advances toward a feed roll 4 via a tension device 3, then passes around said feed roll 4 and a draw roll 5 sequentially. Between the feed roll 4 and the draw roll S, the feed yarn 1 is drawn at a predetermined- draw ratio. Drawn yarn 6 leaving the draw roll 5 is continuously introduced into a fluid-turbulency je-t 7 where it is converted into an intermittently interlaced yarn with arc-like loops. Then the yarn is forwarded, being deflected from its yarn path between and by guides 8, 8', 8" and passed through a buffer 9. The yarn 6 leaving the buffer 9 is further subjected to heat-treatment by heater 10 under a tension of at least 0.02 g/denier but which is not so great as to remove the loops by stretching.
-- On the heater the arc-like loops are allowed to shrink freely to become parallel to the major portion of the yarn. The heat-treated yarn is then passed around a withdrawal (delivery) roll 11 from which it is fed to a winding device 12.
The delivery roll 11 is adjusted to be driven at a peri-pheral speed less than that of the draw roll 5. Thus the drawn yarn 6 can be interlaced at a constant overfeed ratio to form arc-like loops thereupon. Although three series of guides 8, 8', ' : ' ~'' ' :

~L1728~ii .

8" are shown in lig. 1 this is not limiting to the invention, and, for example, two series of guides 8', 8" may be adopted instead. These guides are useEul in providing that the yarn ten-sion at the fluid treating æone is independent of that of the heat-treating zone, although the yarn is apparently in an overfed state between the draw roll 5 and the delivery roll 11. In other words, by the presence of the guides the yarn 6 is maintained at an overfed state in the fluid treating zone while under a tensioned state in the heat-treating zone. Further, these guides allow the yarn 6 to proceed while imparting contact pressure to the yarn 6 by deflecting it. The yarn 6 never stick~slips on the heater 10 and accordingly, a uniform heating of the yarn 6 is effected. Of course, an intermediate roll may be used instead of the guides if installation cost and ease of operation are ignored.
Additionally, the buffer shuts off the fluid vented from the jet 7 from the heater 10; otherwise the yarn 6 ~ay vibrate.
The above example, as will be understood, illustrates : the preparation of a novel bulkable filamentary yarn of the invention using an undrawn yarn as the starting material wherein the drawn yarn 6 may ordinarily have imparted to it a boil-off shrinkage of at most 15% and the yarn is further subjected to fluid and heat-treatment in sequence. In this regard, various modifi-cations may be made, for example, a drawing operation may be ; carried out separately and an undrawn yarn previously prepared may be fed by the draw roll 5 to the subsequent treatments or a previously prepared interlaced yarn with arc-like loops may be heat-treated in a single stage.
A mechanism for the formation of a novel bulkable fila-_ 9 :. ~ . ~:
~ ... - .

~7~

mentary yarn according to the invention will be explained with reference to Fig. 2 - Fig. 5.
In Fig. 2, 13 is a filamentary yarn composed of consti-tuent filaments 14 in which b is a looped-out portion (or loop portion) where some of the filaments form arc-like loops of various sizes and such portions occur between each adjacent pair of inter-laced portions designated by C. It is characteristic of this type of yarn that a major portion of the yarn is composed oE the filaments except those looping out on the surface thereoE, there- ;
fore, this major portion also serves as a tension bearing carrier.
For this reason, when this yarn is placed under a certain tens-ion ~ordinarily less than 1.1 g/denier with a provision of such tension so as not to remove the arc-like loops), stress (tension) is con-centrated in the major portion. In other words, the major portion bears all the stress and therefore the arc-like loops are never diminished by stretching. Accordingly, when the above yarn is heated under tension, the arc-like loops bearing no tension are allowed to shrink freely due to higher heat-treatment efficiency and the boil-off shrinkage of the loop portion is lowered to the full extent. On the other hand, the major portion is heated under tension and, therefore, less effect of thermal treatment is obtained compared with that of the loop portion. As the result .
of the differential treatment effect, the boil-off shrinkage difference between the loop portions and the major portion is further increased.
Fig. 3 shows the relation between tension and boil-off shrinkage in the above case, where Tl and T2 are tensions exerted in the loop portion and the major portion, respectively, while , , .

7;Z~

Sl and S2 are boil-off shrinkage induced by heat-treatment of the loop portion and the major portion, respectively. As w:ill be clear from the Figure, the lower tension during heat-treatment results in the higher heat-setting effect, as an amorphous phase of the fibre is relaxed and stabilized, which effects a consider-able lowering of the boil-off shrinkage. More concretely, the major portion heat-treated under the higher tension maintains substantially its original boil-off shrinkage S2 while the loop portion heat-treated substantially free from tension shows an extremely lowered boil-off shrinkage Sl. Thus between these por-tions occurring in the same yarn, the maximum shrinkage difference is obtained.
Fig. l, shows a heat-treated yarn as mentioned above. In appearance this yarn displays a smooth surface, and there is not a bit of difference between this and an ordinary flat yarn. When this yarn is, however, profiled in the order of single filament, it has, along the yarn length, the low shrinkage portion PQ (Fig.5) comprising shrunken loops and the high shrinkage portion Ph com-posed of substantially unshrunken filaments.
By the term "low shrinkage portion" is meant the portion composed of differentially shrinkable filaments in a randomly mixed state. Actually this portion is formed from shrunken loops which previously surrounded the major portion and shows the appear-ance of a flat yarn.
It is important to obtain such Elat or smooth surface of the low shrinkage portion of the yarn according to the invention.
For this purpose, individual filaments in the loop portions in Fig. 2 should form arc-like (half-arc state) loops or protrusions , : ,., , .. :
:. : . : . :
' ' '. .; " . ~ ~. , ' 1 .
.:
~: ;:. .;
, ~ :.: : : : :

7Z~6 .

so that smooth and eEficient shrinkage of the loops is possible.
In this regard, crunodal loops known to be inherent :in "TASLAN ~ "
to those skilled in the art, are substantially distinguished from the arc-like loops. The crunodal loops are formed ~y filament doubling back upon itself, crossing itself and then proceeding in substantially the original direction. This kind of loop, even if heat-shrunk, never shrinks in the straight form and results in small protuberances P on the surface of the yarn, as shown in Fig. 6. These protuberances P are not acceptable for the present invention because they not only form a kind of crimped portion but also display a hard and crisp hand when woven into a fabric.
The above protuberances may be avoided if the yarn is heated excessively. However filament distortion inevitably occurs and displays a glittering effect as frequently seen in fancy yarns.
This glittering is far removed from the mild luster possessed inherently by silk.
On the contrary, Fig. 7 shows the state after the bulkable yarn of Fig. 4 (or 5) is relaxed in 100C. water to develop its latent differential-shrinkage character wherein the major portion (core portion) occurring throughout the yarn length and the high shrinkage portion Ph (Fig. 5) occurring intermittently along the yarn length are differentially shrunken together to increase the interfilamentary space. Thus, the relaxed yarn has a heightened fullness, softness and suppleness very similar to natural sil~k.
According to the invention, the preparation of bulkable filamentary yarn of Fig. 4 (or 5) is quite important as mentioned before.
Insufficient heat-shrinkage of the arc-like loops, leaving .. :

:' , 7~:86 .: . .

still slack filaments on the surface oE the yarn produces a fancy fabric having enhanced contour surface which is quite differ-ent from that of silk fabrics. ~ccordingly, arc-like loops should be sufficiently heat-relaxed to present a straightened state parallel to the major portion of the yarn just as flat yarns. When a grey fabric made up of the above bulkable yarn is relaxed during a scouring process, for example, it presents a very smooth surface in addition to full tactility inherent to silk, and this effect can be obtained only when the mixed, differential shrinkage character of the yarn is developed to give full hand to the yarn.
Therefore, care must be taken not to leave crunodal loops as well as slack filaments on the bulkable filamentary yarn shown in ; Fig. 4 (or 5).
One more critical requirement is left for a bulkable filamentary;-yarn according to the invention. The yarn should have a K value of at most l.O expressed by the formula:

, K =
~ Q2 -~ wherein Ql is the length of an interlaced portion and Q2 is the length of a non-interlaced portion. This limitation is Eurther explained with reference to Fig. 8. The above bulkable yarn, when allowed to float on water exhibits an intermittently bloomed appearance as shown in Fig. 8 wherein Ql is the length of an interlaced portio~ which corresponds substantially to the high shrinkage portion Ph in Fig. 5, and Q2 is the length oE the bloomed portion which corresponds substantially to the low shrinkage portion PQ in Fig. 5, the latter especially being composed of differentially : ..... -~ . . , , :

' : , : .

Z~6 shrinkable filaments. The K value of at most 1.0 expressed by Ql/Q2 means that the bloomed portions governing mainly silk-like hand occupy at least 50% of the total length of the yarn. It is easily understood that the presenceoE interlaced portions is not significant to the development of silk-like hand although these are extremely useful for improving the handling and running of the yarn. For this reason, a K value of at most 1.0 becomes necessary to obtain such effect as if the interlaced portions do not exist.
On the contrary, when the major part of the yarn is occupied by the interlaced portions, one cannot expect silk-like effects due to decrease of the bloomed portions, Therefore, at most 130 interlaced portions per meter is an upper limit according to the invention.
Ordinarily, the number of interlaced portions per meter is expressed by counting the tight portions in a bulkable yarn of 100 cm length with the naked eye, as shown in Fig. 8.
With regard to Ql and Q2 from which the K value is determined, each is expressed as an average length calculated from the total number of interlaced portions or tight portions occurring in the bulkable yarn of 100 cm length, which is allowed to float on water as shown in Fig. 8. In detail, each length of the inter-laced portions, for example, is first measured and a total sum in . .
length is divided by the number of the interlaced portions to obtain Ql as the average length, and this step also applies to the calculation for Q2 In a preferred embodiment, a bulkable filamentary yarn accordîng to the present invention, has a boil-off shrinkage of no more than 13%, and exhibits, upon heat-relaxation at 195C., . , '~, "

ZB~:i dry heat atmosphere for a time of 5 minutes, the following features in bulky (full-hand) portions B as shown in Fig. 9 which have been bloomed portions b in Fig. 3.
(a) the maximum filament-amplitude is no more than 25 mm.
(b) the maximum length-difference of the filaments is no more than 15%, and (c) filaments having a length difference of 3% to 12%
occupy at least 15% of the total number of the constituent fila-ments.
Further explanation will be made of the above mentioned features with reference to Fig. 9, in addition to the limitation of boil-off shrinkage.
~ Boil-off shrinkage at 100C. water for 30 minutes]
The upper limit of 13% is determined from the point of view of maintaining soft hand of the bulk-developed yarn shown in Fig. 7. Although boil-off shrinkage of more than 13% will, of course, give a heightened interfilamentary spacing which is intended according to the invention, the bulk-developed yarn tends to present a rather harsh hand due to excessive shrinkage of the yarn.
CFeature (a)]
In Fig. 9, a full hand portion B is composed of various filaments fl~ f2~ f3..... f differing in their amplitude i.e., the degree of looping out. Of these filaments, filament fl has the largest size. The shortest line (distance) along the yarn axis is designated by QB For convenience, QB (mm) is defined as the "maximum filament-amplitude" according to the invention.

- , ., , :. , - : :. ~ .
. . ~

8~;

In the case when ~B exceeds 25 mm, the quality, especially silk-like appearance of the bulk-developed yarn, tends to be lowered and an unacceptable flash will appear in the fabric.
Accordingly, QB is understood to control an apparent si~e of the full-hand po-rtions.
~ Feature (b) ... M.L.D.F.~
This is defined by the formula:

M.L.D.F. = m B x 100 (%) B
where Qm is an actual length of the Eilament fl and QB is the same as hereinbefore defined.
In the case when the value of M.L.D.F. exceeds 15%, bulk-developed yarns tend to display slightly different hand and quality from those of silk.
[Feature (c)]
A factor important to full-hand portion B is inter-filament spacing which is governed by distribution of the filament length-difference. A preferred silk-like effect can be enhanced in the presence of filaments having filament length-difference of 3% to 12%, occupying at least 15% of the number of all the con-stituent filaments.
The filament length-difference in percent is determined in the same way as in explained about M.L.D.F..
The interfilament spacing formed by and in the presence of the filaments meeting the above two conditions is far less than that of so-called "bulky yarn" such as false-twist crimped yarns.
In this meaning, the term "full-hand portion" used according to : : ' , 7Z~6 the invention is distinct from the bulky state of crimped yarns.
For reference, a bulkable yarn according to the present invention usually displays a bulk of 14 cm3/g to 20 cm3/g when it is heat-relaxed for the development of latent bulk due to the differential shrinkage.
The above bulk is determined as follows:
A bulkable yarn is wound upon a wrap reel with a circumferential length of 1.125 m by rotating it 320 turns. A hand removed from the reel is folded in the center and a 6 g weight is suspended on an end of the folded hank. In this state, the hank is heated 195C. dry heat for 5 minutes, and then cooled to ambient tempera-ture. A volume (V) of a certain amount of hank having its own weight W(g) is measured from which the bulk (B.I.) is calculated in accordance with the formula:

3/ ) V
W

Referring to Fig. 1, various conditions Eor obtaining a bulkable filamentary yarn having the above mentioned specified properties are hereinafter described in detail. As a starting material, polyester, polyamide, polypropylene yarns etc., are employed and these yarns entering jet 7 generally have a total denier of 15 to 125, preferably 30 to 75, a monofilament denier of no more than 1.7 and a boil-off shrinkage of 5% to 15%. Also the cross-section of the filament may be round or non-round (prefer-ably trilobal).
As mentioned before the above filamentary yarn is first treated in the jet 7 where arc-like loops are imparted to the yarn , ' ' ' ~

~7;~8~;
.

intermittently along its length. For this purpose well-known interlace nozzles disclosed in United States Patent No. 2,985,995 are preferably used under a fluid pressure of 1 Kg/cm , G to

5 Kg/cm G at a yarn overfeed ratio of 1% to 15% (preferably 1.5%
to 6%) and yarn speed of at least 200 m/min. (preEerably 500 m/min.).
Thus interlaced yarn (Fig. 2) should have a number of interIaced portions of at least 20/meter (preferably 50) along the yarn length to obtain yarn coherency and also the yarn should be free from crunodal loops to the lesser extent, as explained before.
Next, the arc-like looped yarn is heated upon heater 10 in the form of a contact-type plate heater or a non-contact type pipe heater. In this step, it is necessary to shrink the arc-like loops only while a major part of the interlaced yarn is maintained under tension. Therefore the tension exerted on the yarn becomes critical. If the interlaced yarn is heated under a tension of less than the dry-heat shrinkage stress of the yarn, it shrinks freely as a whole, resulting in a lesser differential shrinkage in the heated yarn. To avoid such vital disadvantage, the yarn entering the heater 10 should be tensioned to a level of at least 0.02 gldenier. The upper limit of the tension is such as not to remove the arc-like loops by stretching.
The heater temperature and heating time must be adjusted to be enough for thorough shrinking of the loops~ and generally the former is selected from a range of 130C. to 250C. and the latter from a range of 0.01 sec. to 0.1 sec.
~ ddit:ionally, the size and number of loop portions b are fairly important. In Fig. 10, the maximum apparent length I. of the loop portion is preferably in the range of 1 mm to 25 mm and ~: . ... .

:. . ~ . .,;
, ' ~

.

the maximum apparent height H is preferably in the range of 0.5 mm ~` to 3.5 mm when measured under a tension of 0.05 g/denier. As to the number of such portions, preferably at least 3 of them occur per 1 cm oE the interlaced yarn. Further it is preferable that at least 20% of the total number of constituent filaments take part in the formation of the loops. Of these conditions, the maximum apparent length L is the most important factor. For example, a loop with L value less than 1 mm is easily converted into the crimped state similar to false-twist crimped yarn which is quite different in appearance from the fullness of full hand of silk.
Thus heat-treated yarn (Fig. 4 or 5) having almost the same appearance as that of ordinary flat yarns is finally for-warded to a winding device.
As a winding device, a ring twister is shown in Fig. 2, but it is not intended to be limiting and other types of take-up means such as a cheese winder may be used.
In Fig. 11 is shown a compact apparatus for carrying out the process of the invention, which is a modified form based upon a drawing machine as disclosed in llnited States Patent No.
3,539,680. In the apparatus, an undrawn yarn 1 unwound from a package 2 is pre-tensioned between a pair of pre-tensioning rolls - 155 15' and a feed roll 4, then forwarded through a non-contact type heater to a stepped roll 17 upon the larger diameter portion 18 of which the forwarded yarn is passed around. This larger diameter portion operates at a higher peripheral speed (usually 1.5 - 4 times) than that of the feed roll 4 whereby the yarn 1 is drawn between the feed roll 4 and the stepped roll 17 and concur-~ rently heat-set by the heater 16 to adjust its boil-off shrinkage .~ ~, - 19 -`: ` ~ ` ' ` :.

iL1~728~

to a level of no more than 15%. The drawn yarn 6 is then for-warded toward jet 7 in a direction opposite to the direction of the undrawn yarn 1. The yarn 6 is deflected via guide 8 at a right angle, and while moving to guide 8' it is subjected to a fluid treatment by jet 7 to give an interlaced yarn with arc-like loops. Although the jet 7 is located between guides 8 and 8' in this Fig., it may be placed before guide 8. This interlaced yarn changes its path toward the heater 16 and is introducedagain into the same heater where the interlaced yarn is heated~ to shrink the loops parallel to the major portion. The yarn leaving the heater 16 is passed around the smaller diameter portion 19 of the stepped roll 17 from which it is fed to take-up means 12.
As will be easily understood from the above, the features of this apparatus reside in that three kinds oE different yarn-treatments can be carried out by using substnatially two rolls, namely, the feed roll 4 and the stepped roll 17. In the apparatus, a state of yarn overfeed can be reali7ed between the larger dia-meter portion 18 and the smaller diameter portion 19 both con-stituting parts of the same roll i.e., the stepped roll 17. As mentioned before, since an overfeed ratio of 1% to 15% is employed, the larger diameter portion 18 may have a diameter of 1.01 times to 1.15 times the lower dia~eter portion 19. Actually, substantial overfeed of the drawn yarn 6 is maintained between the portion 19 and the guide 8' for deflecting yarn path, for the same reason described in the case of Fig. 1. At the same time, the interlaced yarn is maintained under tension between the guide 8' and the por-tion 19 while the yarn is running through the heater 16 again.
The apparatus shown in Fig. 12 is essentially the same as - -. ~:

7;~6 , in Fig. 1], except that the hea~er 16 is used for heating an inter-laced yarn only. This apparatus is useful when a boil-oEf shrink-age of no more than 15% is attained without heating a drawn yarn.
As an advantage oE the apparatus using a non-contact type heater which uses a heated atmosphere therein, it is emphasized that all of the loops occurring randomly around the yarn are equally and uniformly shrunk. This effect is rather difficul. to obtain by a contact-type plate heater.
The advantages of a bulkable filamentary yarn provided by the invention are summari~ed below.
(i) Splash pattern streaks are prevented when the yarn is woven into a fabric since the bulkable filamentary yarn has undergone a regular heat-shrinking treatment along a transverse section and also the yarn length.
(ii) The handling and running is highly improved compared with convention textured yarns intended as silky material, since the bulkable filamentary yarn has not only almost the same appear-ance and smoothness as that of flat yarn but interlaced portions along the yarn length.
(iii) In spite of the flat yarn appearance, the bulkable - filamentary yarn comprises filaments substantially not shrunk throughout the yarn length, and the filaments which constitute a major portion bear all the stress exerted in the bulkable yarn.
Thus the problem of tight spots (ends or wefts) is completely overcome.
On this point, the conventional texture yarn mentioned above comprises shrunken filaments as a major (core) component by which non-shrunken filaments loop out on the yarn surface.
, ' ' .

(iv) In an intermediate yarn (an interlaced yarn with arc-like loops) randomly selected filaments due to whirling action of the turbulent fluid, loop out on the yarn surface to form arc-like loops of different loop sizes. When such loops different in size are shrunk, mixed, differential shrinkage characteristics are imparted to the bulkable filamentary yarn.
A mode of developing the latent silky characteristics of the above bulkable yarn is taken in various form. For example, such yarn may be heat-relaxed while being forwarded in hot water or heat-relaxed in the form of hank while immersed in hot water.
Further, a grey fabric made up of the yarns may be heat-relaxed during the scouring and finishing stage. When the fabric consti-tuent yarn is polyester, then the fabric is preferably subjected to reduction in weight treatment by an alkallne solution, to enhance interfilamentary spacing.
Generally speaking, it is preferable to weave or knit the bulkable yarn into fabrics and then to subject the fabrics to a heat-relaxing treatment in hot water to develop the latent silky characteristics of the yarn. In this case, interlaced portions of the yarn become loose by frictional contact, for example, with dents; harness and healds, and the said loosened interlaced portions contribute to increasein bulk.
The bulkable filamentary yarn may be used as the warp and/or weft when woven into fabric.
In a preferred embodiment, the yarn is used both as the warp component and the weft component wherein the warp is twisted to no more than 300 turns/meter while the weft is twisted to more than 300 turns/meter preferably more than 1000 turns/meter. In , : .

11~L7~816 another embodiment, the yarn of the invention is preferably used as the warp component in the preparation of "de Chine" fabrics.
In this case, the warp is twisted to at most 800 turns/meter while the weft of ordinary flat yarns or crimped yarns, preferably false-twist crimped yarns, is twisted to at least 600 turns/meter.
These fabrics in the form of grey fabrics leaving the loom show only an appearance of fabrics made up of flat yarns, and to obtain silk-like and/or "de Chine" fabric, the grey fabric is, as mentioned before, heat-relaxed in hot water, for example, at scouring, dyeing. As dyeing machines, a winch type or circular type is preferably used. Upon heat-relaxing, these fabrics have imparted thereto silky appeal or mixed appeal of silky hand and "de Chine" hand according to the combination of yarns for the weft and the warp.
For further improvement in drapeability of these silky fabrics, they may be treated in an alkaline solutiDn for reduction in weight of the fabrics whereby contact pressure between the warp and weft is diminished enabling the warp to slip easily over or ~ below the weft. As alkaline substances, sodium hydroxide, potas-`~ 20 sium hydroxide and sodium carbonate are used, in combination - with accelerating agents such as lauryl dimethyl ben~yl ammonium ~ chloride or cetyl dimethyl ben~yl ammonium chloride.
The above treatnlent is carried out generally by dipping the fabrics in an aqueous solution containing alkaline substances.
The solution may be heated before or after the dipping operation.
Generally the aqueous solution contains 20 g - 400 g of alkaline substance per litre while a treating time is selected from a range of 30 minutes to ~0 minutes. The final reduction ratio of the -~
~0 , ~ .

, :: :. :. .
:

~72~36i , fabrics is important and at least 10%, preferably 15% to 30% of reduction is recommended.
According to ehe invention, a bulkable yarn can be realized from a single end yarn oE uniform shrinkability to which mixed differential shrinkage characteristics are imparted.
In the history of the textile industry, silk has been regarded as a royal fiber due to its luxurious luster and hand unmatched by other fibers. Although an extensive and continuing search has been made for a synthetic fiber with all of the desirable properties of silk, no one has obtained a satisfactory result from all the aspects of silk.
A woven fabric from a bulkable yarn of the present invention exhibits an appearance as well as hand indistinguishable from silk, although the yarn is composed of synthetic material.
In this meaning, it can be said that the present invention enables~
a synthetic fiber to achieve a novel commercial acceptability.
The following examples will serve to illustrate the invention, although they are not intended to be limiting to the scope thereof.
Example 1 Using an apparatus as shown in Fig. 1, bulkable fila-. . .
mentary yarns were obtained-under the conditions given in Table-I, and thereafter, the yarns were woven into fabric having the appearance of a palace crepe under the weaving conditions in ~ Table-II. Further, the fabric obtained was dyed with DIANIX
- YELLOW-GR-E (C.I. DISPERSE YELLOW 60) as a dyestuff. The result of evaluation of the dyed fabric is shown in Table-III.

. . .

:

7Z~3~
. .

_BLE-I
(Conditions for preparing bulkable filamentary yarns) (1) Undrawn yarn 1 Polyethylene terephthalate filaments with trilobal cross section, 143 de/36 fil.
(2) Peripheral speed 170 m/min.
of feed roll 4 (3) Peripheral speed of 500 m/min.
draw roll 5 (4) Draw ratio 2,933 (5) Boil-off shrinkage 6.7%
of drawn yarn 6

(6) Peripheral speed of 465 m/min.
delivery roll 11

(7) Fluid jet 7 Same type as shown in Fig. 3 of United States Patent No.
2,985,995, pressure....l Kg/cm G

(8) Overfeed ratio 7%

(9) Heater 10 Plate heater Temperature 200C
- 20 Length 36 cm -- (10) Yarn tension 0.06 g/denier (measured before en-trance to heater 10) (11) ~ppearance of H (Fig. 10) = 0.7 mm - interlaced yarn (average value) ~ L (Fig. 10) = 6 mm : (average value) Interlace portion....62/m ; - 25 -, .

., . . , :

~1~72~

(12) Winding device Ring twister Spindle r.p.m. 7,000 Tension ........... 0~16 g/de.
(13) Wound up yarn Ql (Fig- 8) = 3 mm Q2 (Fig. 8) = 5 mm K value = 0.6 1st yield point of 1.5 g/de.
Boil-ofE shrinkage...5.7%
Appearance...Flat yarn like (14) Processability 0.6% per l,OOO spindles (yarn breakage) TABLE-II
(Weaving a d Finishing Conditions) (1) Yarn Warp 300 turns/meter(S) Weft 2,000 turns/meter(S, Z) S and Z twisted yarn placed in alternate arrangement (2) End spacing 29.6/cm (3) Weft spacing 39.6/cm (4) Relaxing oE 95C. x 10 min. by a continuous ; grey fabric scouring machine (5) Pre-set 180C. x 45 sec.
(6) Alkaline treatment Aqueous solution containing 35 g. of NaOH/Q
Reduction ratio 20.7%
(7) Dyeing machine LINI-ACE ~ (NIPPON DYEING
MACHINE COMPANY),130C x 45 min.
.
~ .
~ - 26 -.

:;, .. :.,. :, : :: : :

~7Z1~6 :

(8) Final set 160C. x 45 sec.
: (9) Final spacing End 67.5/cm Weft 40.0/cm TABLE-III
(Evaluation) (1) Dyeing speck None (streak) (2) Hand tactility Silk-like fullness softness after relaxed (3) Drapeability ~uite similar to silk (4) Luster, hue Very good (5) Creep test 1.2%
Evaluation of the fabric and Creep test are made according to functional test by trained observers and JIS 1080-1967, respectively. ~dditionally, creep test represents a ratio (%) of residual deformation - after removal of stress to original length of fabric.
The above data shows that a silk-like fabric free from dyeing specks can be obtained by employment of the yarn of the invention since said yarn has a comparatively higher first (lst) yield point and a unitary coherency as a whole serving to improve weaving efficiency.
` Comparative Example 1 - In an apparatus as in Fig. 1, a jet 7, guides 8, 8', 8", ; buffer 9 and heater lO were taken out, and a roll of 4.0 cm diameter and heated to 180C. was placed for instantaneous heat-treatment of drawn yarn 6, in which the yarn was maintained under a tension of : .

L7Z~36 0.001 g/de before the heated roll. Other conditions were the same as in Example 1. The results are shown in Table-IV.

- : . ~ : , ~728 - .

r---- ~ ~
A~-, S~

__ ___._ ._.___. .. _____ _ _,____. ._... _. _ _.. .

O ~ ~0 ~ O ~ ~ ~ ~ ~1 ~ ~ ~ ~i o o o _ _ -- -- 5 j~ 5 ¢ _._ _._.. .__ ~ _~ ___ . __ _ o ~ l Ix ~, ~x ~ 8 o _ ~ ~ '``i ~ 5 ~ ~ ~ * .
,~ __._ -~ u,~~~' ._ . . .__._ _._ _ _ _ . :.

~ ~J ~ n ~
... _ ..~ .. ... ._ . ._~ _ ~

~ - 29 -:

2~36 The above table shows that:
(i) Weaving efficiency is in inverse proportion to good hand, tactility realized by loop and slack filament which is, in turn, formed due to partial puckering of a yarn.
(ii) Textured yarn with fewer loops contributes to an improvement in weaving efficiency, but deterioration in fabric hand. Also yarn processability is bad.
For the purpose of improving the handling and running of the above yarn, it was heat-treated on a plate heater 4 cm long and heated to 210C. at 60 m/min. whereby loops and slack filaments on the yarn were shrunk in parallel to the yarn body. Although this yarn had a flat yarn-like appearance and showed good weaving efficiency when woven into a fabric, a relaxed fabric in subse-quent scouring process lacked silk-like fullness in addition to scroop and poor body.
Comparative Example 2 Example 1 was carried out except that the jet was similar to TASLAN ~ ~et in Fig. 8 of United States Patent No. 2,783,609, and drawn yarn 6 was introduced thereinto under an overfeed ratio of 15% and a fluid pressure of 5 Kg/cm G.
The fluid treated yarn had crunodal loops and slack ;~ filaments in a ratio of 2:3~ When the TASLAN ~ yarn was treated ` on the heater 10, for the shrinkage of loops, it had protuberances in the form of non-shrunken crunodal loops in a frequency of lO/cm and showed harsh hand.
Examples 2 - 9 and Comparative Examples 3 - 7 In Example 1, both pressure and overfeed ratio with ` respect to jet 7 were varied to obtain various interlaced yarns ..
! - 30 '''' :~
:: ,~ . :

1~L7~16 different from each other in the number of interlaced portion.
The relation between degree of interlacing and K value, and fabric hand is shown in Table-V.

TABLE-V

Run ¦ Pressure ¦ Over~eed Interlace K Value No. Portion Fabric hand (K~/cm3) ¦ (%) (Number/m) ( l/Q2) 3.,~ o ¦ n O O Flat yarn-like _ _ .
4~n . 3 n 6 o.or~ - do -5~ 0~ S 1 lL~ 0~ 12 ~ do -2 1 1 21 0 r2 0 Silk-like .
Eullness~ very _ _ _ _ 3 2 1 32 0 37 - do -. 4 3 1 51 0.52 - do -4 ¦ 2 66 0.64 - clo -6 3 j 3 ~0 0.72 1- clo -_ , .
7 5 3 90 O. 85 ~ do -.. _ _ _ .
8 L~ 5 100 0.96 - do -9 5 G 1300 ~ 9 8 ~ do -6:: 5 1 10 140 1.15 Similar to a Eals~-twist cr.imped yarn , I
7 t j 5 13 ¦ 1501~ 22 1- do -l l ; ~arlc [*] means compara-tive examples - 31 _ ;

:- .

, ; '`, '~ '' ' ' ~ '' ' .

~7~8~

As will be clear from the Table, a bulkable yarn of the invention must meet two requirements for obtaining silk-like effects, namely interlaced portions of at least 20/m and a K
value of at most 1Ø
Example 10 ~ sing the apparatus of Fig. 11, bulkable filamentary yarns were obtained under the conditions of Table-VI and thereafter the yarns were woven into a fabric of an appearance of a palace crepe under the weaving conditions given in Table-II in Example l.
Further, the fabric obtained was dyed with DIANIX YELLOW GR-E
(C.I. DISPERSE YELLOW 60~ as dyestuff. The results of evaluation of the dyed fabric are shown in Table-VII.
T~BLE-VI
(Conditions for Preparing Bulkable Filamentary Yarns) (1) ~ndrawn yarn 1 Polyethylene terephthalate filaments with trilobal cross section, 143 de/36 fil.
; (2) Peripheral speed 271 m/min.
of feed roll 4 -20 (3) Peripheral speed of 800 m/min.
- larger diameter portion 18 of stepped roll 17 (4) Draw ratio 2.95 ` (5) Boil-off shrinkage 10%
of drawn yarn 6 `

.;

~` :

` - 32 -. ~

. - - : :
; - . ~::
.

7Z8~

(6) Peripheral speed 784 rn/min.
of smaller dia-me-ter portion ~8 of stepped roll 17 - 5 (7) Jet 7 I:xample 1 Pressure...l.S Kg/cm2 G
(8) Yarn overfeed 2 ratio ~9) Heater 16 Slit-heater of non-contact type hea-ted to 200C. therein.
Lengt!l...30 cm, tlO) Yarn tension 0.11 g/de between guide 8' and entrance o~
hea-ter 16 (11) Winding device Ring twister 12 Spindle r.p.m. .... 10~000 Winding tension ... Ø4 g/de (12) Appearance of H (Fig. 10) = 1.1 mm an in-terlaced (~verage value) yarn (Fig. 13) . L (~ig. 10) = 13 mm ~; . (Average value) Number of an interlace portion ....62/m (13) Yarn breakage 0.2Q
, during -tex-turing : ~.
.

- . ~ . - . , , .. .. ., , - : .

.. , : ~ .

(14) Wound up yarn Shown in Fig. 14 l (Fig. 8) = 5 mm Q2 (Fig- 8) = 11 mm Flat yarn appearance 1st yield point...2.6 g/de Boil-off shrinkage...8.0%
TABLE-VII
(1) Weaving Good efficiency (2) Fabric, Dyeing Speck None Hand, Tactility Very soft Highly full as silk - Drapeability Good Luster, hue Excellent Creep test 0.2%
It is recognized that the fabric obtained in this example shows more silk-like appeal compared with those obtained in Examples 1 - 9. In Fig. 15 is shown one oE the ends taken apart from the above fabric. Also shown in Fig. 16 is a cross-section oE the fabric along the warp direction. When compared with that of silk . .
` fabric in Fig. 17, there is no diEference between them.
On the contrary, a cross-section of a fabric made up of Elat yarns only is shown in Fig. 18, from which one can easily understand that ~`` it has a compact, flat section quite diEferent from that of Fig. 16 or Fig. 17.
Example 11 Using the apparatus shown in Fig. 12 under the texturing conditions oE Table-VIII, bulkable yarns were obtained and woven ~` into fabric having the appearance of palace crepe and this was ~` ~ :

,~

.

~1~7~

dyed as in Example 1. Evaluation of the finished fabric is shown in Table-IX.
TABLE-VIII
(Conditions for Preparing Bulkable Filamentary Yarns) (1) Undrawn yarn 1 Polyethylene terephthalate filaments with trilobal cross section, 143 de/36 fil.
(2) Peripheral speed of 271 m/min.
; feed roll 4 (3) Peripheral speed oE 800 m/min.
larger diameter portion 18 oE
stepped roll 17 (4) Draw ratio 2.95 (5) Boil-off shrinkage 15%
oE drawn yarn 6 (6) Peripheral speed of 784 m/min.
smaller diameter portion 18 of ~ . _ stepped roll 17 ; (7) Jet 7 Example 1 Pressure...2.0 Kg/cm G

; (8) Yarn overfeed ratio 2%

(9) Heater 16 Slit-heater of non-contact type heated to 180C. therein Length...30 cm , 3~

:
- . . - ,: :, 728~i (lO) ~'arn tension 0.07 g/de between gulde 8' and entrance of heater 16 (11) Winding device 12 Ring twister Spindle r.p.m....10,000 Winding tension..Ø4 g/de (12) Appearance of H (Fig. 10~ = 0.9 mm (Average value) interlaced yarn L (Fig. 10) = 11 mm (Average value) Number oE an interlace portion ...60/m (13) Yarn breakage 0.2%/1,000 spindles during texturing (14) Wound up yarn Flat yarn appearance l (Fig- 8) = 5 mm Q (Fig 8) = 9 mm 1st yield point...2.6 g/de .
Boil-off shrinkage... 11%
When the above yarn was heat-relaxed at 195C., dry heat for 5 minutes in the form of hank, it developed its latent bulk in its bulkable portion as follows:
(i) Q in Fig. 9.............. 13 mm B
(ii) M.L.D.F. defined before.. l3.5%
(iii) Bulk..................... 17.5 cm /g (iv) Number of filaments having 3 - 12% of .-- length difference.. ll (about 30 in percentage of all the number of constituent filaments).
: .

., .

... .. . .. . .

: .

-- TA~LE-IX
(1) Weaving efficiency Good (2) Fabric, Dyeing speck None Hand, Tactility Very soft, HighIy full (silk-like) Drapeability Good ~silk-like) Luster, hue Excellent Creep test 0.3%
It is recognized that the fabric obtained in this example shows the same level of silk-like appeal as obtained in Example 10.
Example 12 Example 11 was carried out in the same manner except that polyester Elat yarn (50 de/24 fil.) twisted to 2,000 turns/
meter was used as the weft wherein S twist and Z twist were placed alternately and relaxing of the grey fabric was carried out by use of a rotary washer at 95C. for 25 minutes.
The finished fabric was quite similar to silk in fullness as well as softness and also free from any dyeing speck.
i Example 13 Example 11 was carried out in the same manner except that a false-twist crimped polyester yarn (50 de/24 fil.) was used as the weft wherein S twist-set crimped yarn and Z twist-set crimped yarn in the false twist crimping machine were placed alternately and relaxing was carried out by use of a rotary washer at 95C. for 25 minutes.
When producing the crimped yarn, a flat yarn was first pre-twisted to 800 turns/meter using a ring twister, then pre-twisted yarn was false-twisted in a direction the same as the ~, ., ., , ' :
~:

direction of the pre-twist.
For comparison, a conventional "de Chine 1I was prepared by replacing the bulkable filamentary yarns in the above with flat yarns of the same denier and the same twist.
The above two samples were evaluated by trained observers who concluded that the fabric according to the invention was superior in fullness, drapeability and softness as compared to the conventional fabric.

.

. . ~ :.. .: ~

; . ~ : .:
... .~: :

Claims (9)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A bulkable filamentary yarn in which constituent fila-ments of substantially straight form are assembled with each other, said yarn having interlaced portions of at least 20 per meter along the yarn length wherein a filamentary group between`
each adjacent pair of interlaced portions exhibits mixed, differ-ential boil-off shrinkage characteristics both among the filaments and within each of the filaments, and a K value, as defined by the following formula, of the yarn being no more than 1.0 wherein ?1 is the length of an interlaced portion and ?2 is the length of a non-interlaced portion.

2. A bulkable filamentary yarn according to claim 1 in which the yarn is composed essentially of polyethylene terephtha-late.

3. A bulkable filamentary yarn according to claim 1 in which the yarn has interlaced portions of at most 130 per meter of yarn length.

4. A bulkable filamentary yarn according to claim 1 in which the yarn has a total denier of no more than 75, and single filament (monofilament) denier no more than 1.7.

5. A bulkable filamentary yarn according to claim 1, in which the yarn has a boil-off shrinkage of no more than 13% and exhibits, upon heat-relaxing at 195°C., dry heat for a time of 5 minutes, full-hand portions meeting the following requirements:
(a) the maximum filament-amplitude is no more than 25 mm (b) the maximum length-difference of the filaments is no more than 15%, and (c) filaments having the length-difference of 3% to 12%
occupies at least 15% of the total number of the constituent filaments.

6. A bulky filamentary yarn according to claim 5 in which the yarn, after heat relaxation? exhibits a bulk of 14 cm3/g to 20 cm3/g

7. A method for the preparation of a bulkable filamentary yarn, which comprises heating an interlaced filamentary yarn of thermo-plastic material having arc-like loops on the surface of the yarn under a controlled tension so as not to remove said arc-like loops while maintaining said tension at a level of at least 0.02 g/denier thereby subjecting the yarn as a whole to a heat-treatment under tension while causing, concurrently, said loops to shrink freely in order to convert them into a straightened state.

8. A method for the preparation of a bulkable filamentary yarn according to claim 7 in which arc-like loops are obtained by subjecting a filamentary yarn to a turbulent fluid treatment.

9. A method for the preparation of a bulkable filamentary yarn according to claim 8 in which arc-like loops exist between each adjacent pair of interlaced portions.