WO2019236026A2

WO2019236026A2 - Composite yarn, method and device for manufacturing same

Info

Publication number: WO2019236026A2
Application number: PCT/TR2019/000011
Authority: WO
Inventors: Mehmet AĞRIKLI; Servet BALCI; Hasan TEPE
Original assignee: Ağteks Örme Ve Teksti̇l Endüstri̇leri̇ Sanayi̇ Ve Li̇mi̇ted Şi̇rketi̇; Tepar Teksti̇l Sanayi̇ Ve Ti̇caret Anoni̇m Şi̇rketi̇
Priority date: 2018-02-14
Filing date: 2019-02-13
Publication date: 2019-12-12
Also published as: WO2019236026A3

Abstract

The present invention relates to a composite yam comprising a core with a first elastic fiber and a second inelastic fiber, and a sheath surrounding the core and comprising an inelastic staple fiber. The second inelastic fiber has a form not covered by the yam to be obtained upon a treatment of the composite yam. The invention also relates to a device for manufacturing such a yam.

Description

COMPOSITE YARN, METHOD AND DEVICE FOR MANUFACTURING SAME

TECHNICAL FIELD

BACKGROUND OF THE INVENTION AND PRIOR APPLICATIONS

Composite yams having an elastic fiber in the core are known from the art. For example, EP 2 145 034 discloses a denim fabric. Said denim fabric comprises a composite yam consisting of a core formed from an elastic performance filament and an inelastic control filament, and a sheath made of a staple fiber and surrounding the core.

EP 2 638 192 also discloses a composite stretch yam comprising a core formed from an elastic fiber and another inelastic fiber, and a staple fiber covering the core. It is disclosed that the elastic fiber and the inelastic fiber in the core are connected together by at a plurality of points, and the inelastic fiber has an elastic recovery of at least 93%.

US 4,470,250; US 4,998,403 also describe composite yams comprising an elastic fiber in the core.

Said known elastic core composite yams have some drawbacks in the manufacturing of a woven stretch fabric such as denim, where said yarns are used. For example, tension is applied on the warp and weft yams in weaving, and the elastic yams elongate to some extent with the effect of tension, but after the fabric is finally woven, the tension on the yams is removed, and thus the finished fabric contracts. Such contraction results in a substantial dimensional loss, especially in the width of the fabric, depending on the elastic rate of the yams that are used. As a result, the resulting fabric has a form contracted to a substantial extent. This means that a fabric is manufactured having a much less width than the fabric weaving width of the weaving machine, i.e. a significant loss in the weaving efficiency. On the other hand, such a fabric also has a relatively low comfortable stretch effect, when in use.

The methods of manufacturing elastic core composite yams are also known from the art. For example, composite yams may be manufactured by making various application amendments on the ring spinning machines. For example, EP 2 145 034 describes that an elastic yam and an inelastic yam are individually and directly supplied to an outlet of a draft unit on a ring spinning machine and spun by a staple fiber, in order to manufacture a dual core-spun yam.

In EP 2 638 192, an elastic yam and an inelastic textured yam are connected by intermingling, twisting etc. and then the two connected yams are loaded on a creel of a ring spinning machine in the form of a bobbin, and fed into an outlet of a draft unit in the form of a combined core, where it is spun by a staple fiber into a core-spun yam.

The elastic core composite yams that are manufactured using the known methods have a highly elastic final form. In fact, the inelastic yam and the elastic yam of the core are twisted together. This is illustrated in Figures 2 and 3 of EP 2 145 034. Accordingly, a subsequent use of the elastic core composite yams manufactured by the known methods causes the above-mentioned drawbacks, as it is the case in the manufacturing of a woven stretch fabric.

The inventive yams may also be converted into a fabric by means of knitting. By using the inventive yams in the knitted fabrics, the elasticity of the latter, which are already elastic, may be further increased. SUMMARY OF THE INVENTION

An object of the present invention is to provide a composite yam that is effective in the manufacturing of a textile material.

Another object of the present invention is to provide a woven or knitted textile material with improved stretching properties.

The invention is a composite yam comprising a core with at least one elastic filament and at least one inelastic filament, and a sheath comprising a staple fiber surrounding the core, characterized in that the number of twists in the core is essentially zero and in that the at least one inelastic filament is a yam which is separable from the at least one elastic filament by means of a process and which is not covered in the final composite yam to be obtained after the said process.

In an embodiment of the invention, “a process” comprises passing through a liquid medium wherein temperature and/or pressure variables are controlled. In an embodiment of the invention,“a process” comprises passing through a gaseous medium wherein temperature and/or pressure variables are controlled Said gaseous medium may be a steam or hot air medium.

In the invention, the term“the number of twists in core” means the number of twisting of the filaments in the core at a certain length (twist meter). In other words, with the term“the number of twists in the core”, one should understand an individual number of twists on each filament yarn of the core.

Here, the term“essentially zero” may include“absolute zero” twist, or may include a few twists. In this case, the number of twists may preferably be no more than 10 twist/meter.

In the invention, the term“elastic filament”, as used herein, means a filament that may be stretched at least four times of its length in its unloaded condition until it breaks, when a load is applied thereon. In an embodiment of the invention,“the inelastic filament” is a polyvinyl alcohol (PYA) material. Such an inelastic filament may, at break, stretch at least one time of its length in its unloaded condition, when a load is applied thereon.

In another aspect, the invention relates to a method for manufacturing a composite yam, comprising the steps of: a. twisting at least one elastic filament and at least one inelastic filament to form a core,

b. untwisting of the twisted yam obtained in step a) in such a manner that the number of twists thereof is essentially zero,

c. surrounding the untwisted core by means of a sheath made of a staple yam, wherein the at least one inelastic filament is a yam which is separable from the at least one elastic filament by means of a process and which is not covered in the final composite yam to be obtained after the said process.

The composite yam of the invention may also be manufactured by a method comprising the steps of: a. providing at least one elastic filament and at least one inelastic filament to form a core without twisting,

b. inverse twisting of a staple yam sheath having a certain number of twists in a certain direction,

c. surrounding the said core by means of the said inverse twisted sheath, wherein the at least one inelastic filament is a yam which is separable from the at least one elastic filament by means of a process and which is not covered in the final composite yam to be obtained after the said process. Preferably, once the sheath is twisted inversely in step b), the net number of twists on the sheath is not zero and preferably, the number of twists on the sheath is 500-1000 twist/meter. In the above-mentioned methods, the at least one elastic filament and the at least one inelastic filament forming the core in step a) may also be connected at an earlier step. Said connection may, for example, be performed by intermingling or surrounding them by another filament. In such variant, if they are connected by intermingling, the number of intermingling points may, for example, be from 20 point/meter to 120 point/meter.

In another aspect, the invention relates to a fabric comprising a composite yam according to the invention. The fabric may especially be a denim fabric.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the embodiments of the invention along with the additional elements and the advantages thereof, the invention should be considered with reference to the drawings, in which:

Figure 1 shows a perspective view of a composite yam according to the invention.

Figure 2 shows an illustration of a device for twisting a staple yam and for winding the yam on a cylindrical bobbin.

Figure 3 shows an illustration of a device for manufacturing a composite yam according to the invention.

Figure 4 shows an illustration of a device for twisting a staple yam and for winding the yarn on a bobbin.

Figure 5 shows an illustration of a device for connecting the filaments in the core.

Figure 6 shows an illustration of a device for twisting the core in Figure 5 and for winding the yam on a bobbin.

Figure 7 shows an illustration of a ring twisting device for twisting the core and the staple yarn together. Figure 8 shows an illustration of a device for winding the composite yam in Figure 7 from a ring bobbin onto a yam bobbin. Figure 9 shows an illustration of an alternative device for manufacturing a composite yam according to the invention.

REFERENCE NUMBERS IN THE DRAWINGS

1 Elastic filament

2 Inelastic filament

3 Core

4 Sheath

5 First bobbin

6 Second bobbin

7 Third bobbin

8 Fourth bobbin

9 Motor

10 Main shaft

11 Disc

12 Tray

13 Yam guide

14 Roller

15 Belt

16 Stationary platform

17 Yam balloon

18 Composite yam

19 Elastic yam supply shaft

20 Yam traveller

21 Fifth bobbin

22 Sixth bobbin

23 Seventh bobbin

24 Yam supplying unit 25 Bobbin of a ring twisting machine

26 Ring

27 Brake mechanism

DETAILED DESCRIPTION OF THE INVENTION

An elastic core composite yam according to the invention comprises a core (3) and a sheath (4) surrounding same. As shown in Figure 1, the core (3) comprises an elastic filament (1) and an inelastic filament (2), and the filaments of the core (3) are essentially not twisted together, i.e. the net number of twists in the core is essentially zero. Here, said each“filament” may be a monofilament or a multifilament.

As an elastic filament, those made of synthetic rubber, elastomer or polyurethane polymers may be preferred. As disclosed in US 6,500,540, US 6,709,742, US 5,272,236, 5, 278,272, 5,322,728, 5,472,775, 5,645,542, 6,140,442 and 6,225,243, elastic or elastomeric polyolefins may be used as an elastic filament. The elastic filament may be commercially available, such as LYCRA^® from Invista and XLA™ from Dow Fiber Solutions. The elastic filament may have different denier values, for example LYCRA^® or XLA™ with a denier value of 20, 40, 70, 105 or 140 may be used. The elastic filament (1) may be provided with a twist before it is incorporated into the core of the composite yam according to the invention. In this case, the number of twists may, for example, be in the range of 10 twist/meter to 100 twist/meter. On the other hand, even if the net number of twists in the core of the composite yam is zero, the elastic filament (1) itself may still comprise a twist. The elastic filament may be formed from a single material, such as just synthetic rubber, elastomer or polyurethane, or a combination thereof.

The inelastic filament (2) is a soluble material in a liquid medium at a proper temperature and/or pressure. For example, it may be a polyvinyl alcohol (PVA) filament soluble in a liquid which is water. If a polyvinyl alcohol (PVA) filament is used, for example, a PVA filament which is soluble in water at an atmosphere pressure of 20°C to 95 °C may be used. The inelastic filament may have different denier values, for example Solvron^® filament of Nitivy Company with a denier value of 20, 40, 70, 105 or 140 may be used. The inelastic filament (2) may be provided with a twist before it is incorporated into the core of the composite yam according to the invention. In this case, the number of twists in the inelastic filament may, for example, be in the range of 10 twist/meter to 1000 twist/meter. On the other hand, even if the net number of twists in the core of the composite yam is zero, the inelastic filament (2) itself may still comprise a twist. If steam or hot air medium is used, but not a liquid medium, it may include a medium of 20°C to 95°C at atmosphere pressure.

The inelastic filament (2) may optionally be covered with a sizing agent, i.e. a natural sizing agent such as starch, or various adhesives that are easily soluble in hot water. Sizing or coating may be performed using a method known in the art. In the event of such coating, the inelastic filament (2) may have a denier value of 20, 40, 70, 105 or 140.

The sheath (4) preferably comprises spun cotton fiber. The staple fiber length thereof may be at various values, for example, typical cotton fibers may be used which have a length smaller than 2 cm or up to 4-5 cm. Prior to assuming its composite yam form, the sheath

(4) may have various twist values, for example the number of twists may be 500 twist/meter to 1000 twist/meter.

The core (3) may also comprise a filament dissoluble with steam or hot air, and another inelastic filament(s), except from a polyvinyl alcohol filament. They may, for example, be a polyamide, a polyester, a polyolefin, or a mixture thereof. Again, said additional inelastic filament may have a denier value of 20, 40, 70, 105 or 140.

The elastic core composite yam of the invention may be manufactured by a device as illustrated in Figure 3.

The device operates on the hollow spindle yam twisting machine principle, as known from the art. Here, the elastic filament (1) wound onto a first bobbin (5) and the inelastic filament (2) wound onto a second bobbin (6) are fed through a gap on the center of a fifth bobbin (21) without being twisted. A rotary elastic supply shaft (19) is arranged in contact with the external surface of the first bobbin (5) carrying the elastic filament (1). With the said shaft, the elastic yarn (1) is supplied at a tension of almost zero. The elastic supply shaft (19) may always be maintained in contact with the external surface of the first bobbin

(5) by means of a spring, although not shown in the drawings. Alternatively, the elastic supply shaft (19) may be arranged so as not to be in contact with the external surface of the first bobbin (5). In this case, the rotational speed of the shaft may be controlled by a motor using a method known from the art, in order to supply the elastic yam (1) at a tension of almost zero.

Said fifth bobbin (21) is the one on which a sheath filament having a certain number of twists in a specific direction is wound. The fifth bobbin (21) is rotated in the direction of an arrow by means of a driving means (not shown) and guides the sheath filament (4) thereon towards the core comprising the elastic filament (1) and the inelastic filament (2) that are not twisted together, and surrounds them. In fact, the tension of the elastic filament (1) and the inelastic filament (2) forming the core (3) is higher than that of the sheath filament (4). In order to achieve said difference in tension, a tensioning means known from the art such as a brake mechanism may be used, as shown in Figure 9. The composite yam (18), comprising an elastic filament (1) and an inelastic filament (2) in its core (3) as well as a sheath yam (4) on the outer thereof, is passed through a yam guide (13) fixed on the frame of the device, which is then wound onto a fourth bobbin (8) by means of a roller (14) rotated by a driving means as known from the art. The movement of the composite yam (18) obtained at the outlet of the yam guide (13) in the right and left direction so as to follow the grooves on the roller (14) is illustrated by two opposite arrows.

As shown in Figure 3, the sheath yam (4) received from the fifth bobbin (21) by rotating same is twisted while being passed through the yam guide (13). The direction of the twist (i.e. being a S or Z twist) depends on the rotational direction of the fifth bobbin (21). In this case, if it is desired to have a certain number of twists (or in a specific direction) on the sheath yam provided in the final composite yam (18), e.g. the composite yam wound onto the fourth bobbin (8), the sheath yam (4) on the fifth bobbin (21) may beforehand be twisted in a specific direction. Any yam twisting machines known from the art (for example, a Two-for-One machine) may be used for such purposes. An exemplary arrangement of this is shown in Figure 2.

The arrangement of Figure 2 mainly comprises a main shaft (10) rotatable by a driving force received from a motor (9) via a belt (15), a disc (1 1) positioned coaxially on the main shaft, and an annular tray (12) positioned at the upper section thereof, and a yam guide (13) positioned at an upper location.

Said device is essentially a simplified and modified version of the device disclosed in EP 2074247. As disclosed in EP 2074247, the yarns to be twisted are fed through a lower section of the main shaft and supplied from an edge of the tray onto a yam guide arranged on an upper section, to form a yam balloon; additionally, energy is transmitted on certain components located inside the yam balloon (the roller and yam supplier) by means of a magnetic coupling and in the direction of an axis of the main shaft, i.e. axially. Jn EP 2074247, the yams to be twisted are twisted once in the yam balloon and then twisted once again in the same direction after having been supplied downwards from the yam guide.

In the device in Figure 2, again a main shaft (10), a coaxial disc (11) thereon, and a coaxial tray (12) located on the latter, are arranged. At the top of the tray (12), a coaxial stationary platform (16) is arranged. When a motor (9) connected to the main shaft: (10) is rotated by means of a belt (15), said disc (11) and the tray (12) are also rotated. The sheath yam (4) wound onto a third bobbin (7) arranged on the stationary platform (16) is guided downwards through a gap at the center of the bobbin, is moved through the holes formed at the center of the stationary platform (16) and the rotary tray (12), and is output through a radial channel formed on the disc (11), as described in EP 2074247, which is then guided into the yam guide (13) in such a manner that it contacts to the periphery of the rotary tray (12) and form a yam balloon.

The said stationary platform (16) may be held in a fixed position by any methods known in the art. For this, an axial magnetic coupling may be used, as disclosed in EP 2074247, or a magnet may be arranged on the circumference of the stationary platform- (16), and the stationary platform (16) may be held in position through a magnetic force generated by an opposite-pole magnet attached to the frame in a radially spaced manner, such that the yam balloon may be passed therethrough.

As seen from Figure 2, the yam guide (13) is arranged at the upper section of the yam balloon (17), as described in EP 2074247. The sheath filament at the outlet of the yam guide (13) is wound onto a fifth bobbin (21) by a yam traveller (14) driven by a motor as known from the art. The movement of the twisted sheath yam at the outlet of the yarn guide (13) in the right and left direction so as to follow the yam traveller (20) is illustrated by two opposite arrows.

The rotational direction of the tray (12) as seen in Figure 2 is opposite to the that of the fifth bobbin in Figure 3. In this case, for example a twist (i.e. S twist) at a certain direction which is previously provided on the sheath yam by means of a device shown in Figure 2 is provided in a reverse direction and essentially at the same number (i.e. Z twist) in producing the composite yam, so that the number of twists in the sheath filament at the initial phase (i.e. when wound onto the third bobbin) would be same (or“essentially” same) when the composite yam is manufactured (i.e. when wound onto the fourth bobbin). When the sheath yam is a staple fiber such as cotton, it is desired that the number of twists thereon is especially 500-1000 twist/meter. In that case, the staple yam wound onto the third bobbin (7) and having 500-1000 twist/meter is twisted in the same direction, thereby increasing the number of twists up to 1000-2000 twist/meter. Then, when a composite yam is obtained by providing an opposite and essentially the same number of twist(s), as explained in Figure 3, the number of twists on the sheath yam and the direction thereof would be same with the third bobbin (7) (i.e. 500-1000 twist/meter).

The elastic core composite yam of the invention may be manufactured by_, a known ring twisting machine as shown in Figure 7.

The staple yam and the core forming the composite yarn to be obtained in the ring twisting device are fed to the device from two different bobbins. However, these yams wound onto two different bobbins must be subjected to a pre-treatment, as shown in Figures 4 to 6.

Figure 4 illustrates a device for twisting the sheath yam (4). This device has an identical structure to that shown in Figure 3 above. Here, the twisted sheath yam (4) is wound onto the fifth bobbin (21) by means of a roller (14), but not the yam traveller.

The sheath yam (4) which has been wound onto the third bobbin (7) initially has a certain number of twists and in a certain direction (for example, 500-1000 twist/meter in direction S). The sheath yam (4) is twisted in the same direction by means of the device in Figure 4 (for example, 1000-2000 twist/meter in direction S) and wound onto the fifth bobbin (21). The elastic filament (1) and the inelastic filament (2) are connected together without being twisted, by means of the device shown in Figure 5. To this end, the elastic filament (1) wound onto a first bobbin (5) and the inelastic filament (2) wound onto a second bobbin (6) are fed into a yam guide (13) without being twisted. Similar to the device described above in relation with Figure 2, the elastic yam (1) is fed at an almost zero tension via an elastic yam supply shaft (19). The filaments connected at the yam guide (13) are wound onto a sixth bobbin (22) by a roller (14),

The yam on the sixth bobbin (22) is then twisted by a device depicted in Figure 6. A twist on the core (3) of the yam output from the sixth bobbin (22), i.e. the composite yam to be obtained, is essentially same with the final twist of the staple yam shown in Figure 4. In order words, in compliance with the above exemplary numbers, for example if the staple yarn has 500-1000 twists in the direction S, the core wound onto the seventh bobbin (23) is essentially provided with 500-1000 twists per meter in the direction S.

Thereafter, tile fifth bobbin (21) on which the sheath yam is wound and the seventh bobbin (23) on which the filament that will form the core of the composite yam are supplied to the creel of the ring twisting machine. A yam suppling unit (24) is provided at the outlet of each bobbin. The yam suppling units (24) may be units known from the art and controllable by a driving unit independent from each other. According to a preferred embodiment of the invention, the sheath yam (4) wound onto the fifth bobbin (21) is fed at a higher amount than the twisted core (3) wound onto the seventh bobbin (23) by no more than 3%, in order to have a relatively lower tension.

The core (3) and the sheath yam (4) from the yarn suppling units (24) are fed together to a yam guide (13). Here, the sheath yam (4) is wound around the core (3) due to its lower tension. The combined yams (3, 4) are wound onto a bobbin of the ring twisting machine (25) rotated through a ring (26) that is movable upwards and downwards, as shown in the drawings. The rotational direction of the bobbin of the ring twisting machine (25) is opposite to that of the third bobbin (7) in Figure 4 and of the sixth bobbin (22) in Figure 6. Thus, the sheath yam (4) and the core (3) twisted as depicted in Figures 4 and 6 are now twisted in a direction opposite to the previous one and essentially at the same number. Consequently, the number of twists in the core of the composite yam wound onto the bobbin of the ring twisting machine (25) is essentially zero; and the number of twists in the sheath yam is equal to that in the third bobbin (7) in Figure 4 (and in the same direction). For example, if there are 500-1000 twits per meter in direction S, it essentially returns said value.

The composite yam wound onto the bobbin of the ring twisting machine (25) as shown in Figure 8 is then wound onto a fourth bobbin (8) without being twisted. The device in Figure 8 is actually the one used in Figure 5 and disclosed above.

The elastic core composite yam of the invention may also be manufactured by an alternative device as depicted in Figure 9.

The device in Figure 9 is basically a simplified and modified version of the device described in EP 2074247, as mentioned above in the description of Figure 4 (and of Figure 2).

Also, in Figure 9, the elastic filament (1) wound onto a first bobbin (5) and the inelastic filament (2) wound onto a second bobbin (6) are fed through a hole made on the lower section of the main shaft (10) rotated by a motor (9), into an axial channel formed in the main shaft (10). The axial channel in the main shaft (10) is associated with a radial channel formed in the disc (11) as described in EP 2074247, and the yams are passed through the radial channel of the disc rotated with the main shaft (10) and guided through an edge of the rotatable tray (12) associated with the disc (11) so as to for a yarn balloon (17). As described above, the elastic yam (1) is fed at a tension of almost zero by means of an elastic yam supply shaft (19).

As seen from Figure 9, the yarn guide (13) is arranged at the upper section of the yam balloon (17) as described in EP 2074247. However, unlike to EP 2074247, since the yams twisted in the yam balloon (17) are supplied outwards through the yam guide (13), but not inwards, they are twisted in a direction opposite to that of the twist formed in the yam balloon (17). In other words, the core which is previously twisted in the yam balloon (17), i.e. the elastic filament (1) and the inelastic filament (2), are twisted in a direction opposite to the previous one, when being moved out from the yam guide (13), so that the net number of twists thereon is zero. The stationary platform (16) arranged at the top of the tray (12) may be realized by any methods known from the art, as mentioned above.

A third bobbin (7) is arranged on the upper surface of the stationary platform (16), on which the sheath (4) comprising a staple yam is wound. The sheath (4) is fed into the yam guide (13) along with the twisted core (3). Here, the tension of the core (3) is greater than that of the sheath yam (4). In order to achieve this, a tensioning means known from the art may be used. For example, in Figure 9, a brake mechanism (27) is provided on the lower section of the main shaft (10). The brake lever is actuated by the spring in the direction of an arrow, in order to apply tension on the elastic filament (1) and the inelastic filament (2). With the brake mechanism (27), the filaments (1, 2) may be tensioned simultaneously, or each filament may be individually tensioned using multiple brake mechanism. The tension of the core (3) may preferably be in the range of 50 to 200 cN. The tensioning means may be provided anywhere other than the lower section of the main shaft (10) in a manner to apply the desired tension. As a result, when the core (3) and the sheath (4) are fed into the yam guide (13), the sheath (4) is wound onto the core (3) and the composite yarn (18) is obtained.

It may not be necessary to have the third bobbin (7) on which the sheath (4) comprising the staple yam, on the stationary platform (16). Said third bobbin (7) may be fed into the yam guide (13) from elsewhere other than the yam balloon (17).

The composite yam at the outlet of the yam guide (13) is wound onto a fourth bobbin (8) by means of a roller (14) driven by a motor as known from the art. The movement of the composite yam (18) obtained at the outlet of the yam guide (13) in the right and left direction so as to follow the grooves on the roller (14) is illustrated by two opposite arrows.

After the elastic filament (1) and the inelastic filament (2) are twisted in the yam balloon (17), they are supplied outwards from the yam guide (13), but not inside, and accordingly, they are twisted in a direction opposite to the that achieved in the yam balloon (17), so that the net number of twists thereof is zero. The sheath yam (4) is not twisted while surrounding the core. A composite yam is thus obtained which has a core having a twist number of zero, and a sheath having the same number of twists as it has. In this embodiment, the elastic filament (1) and the inelastic filament (2) may be fed to the device as wound onto a single bobbin. In this case, the elastic filament (1) and the inelastic filament (2) are previously twisted together in order to form a twisted core. Then, the twisted core is twisted by the device in Figure 9 in the opposite direction, and the number of twists in the core is zero, and the sheath yam (4) is wound onto the core having essentially a twist number of zero, as mentioned above.

Claims

1. A composite yam comprising a core with at least one elastic filament and at least one inelastic filament, and a sheath comprising staple fibers surrounding the core, characterized in that the number of twists in the core is essentially zero and in that the at least one inelastic filament is a yam which is separable from the at least one elastic filament by means of a process and the inelastic filament being not existent in the final composite yam to be obtained after the said process.

2. A composite yam according to claim 1, characterized in that the at least one elastic filament comprises a synthetic rubber, elastomer or polyurethane filament.

3. A composite yam according to claim 1 , characterized in that the at least one inelastic filament comprises a polyvinyl alcohol (PVA) filament.

4. A composite yam according to claim 1, characterized in that said process comprises a step of passing through a liquid medium wherein temperature and/or pressure variables are controlled.

5. A composite yam according to claim 1 , characterized in that said process comprises a step of passing through a gaseous medium wherein temperature and/or pressure variables are controlled.

6. A composite yam according to claim 4 or 5, characterized in that the medium is at a temperature of 20°C to 95°C at atmosphere pressure.

7. A composite yarn according to claim 1 , characterized by comprising a sizing agent covering the at least one inelastic filament.

8. A composite yam according to claim 1 , characterized in that the at least one elastic filament and the at least one inelastic filament have a denier value of about 20 to about 140.

9. A composite yam according to claim 1 , characterized in that the core comprises an additional inelastic filament made from a polyamide, a polyester, a polyolefin or a mixture thereof.

10. A composite yam core comprising at least one elastic filament and at least one inelastic filament, characterized in that the number of twists in the core is essentially zero and in that the at least one inelastic filament is a yam which is separable from the at least one elastic filament by means of a process and the inelastic filament being not existent in the core to be obtained after the said process.

11. A composite yam core according to claim 10, characterized in that the at least one elastic filament comprises a synthetic rubber, elastomer or polyurethane filament.

12. A composite yam core according to claim 10, characterized in that the at least one inelastic filament comprises a polyvinyl alcohol (PVA) filament.

13. A method for manufacturing a composite yam comprising a core and a sheath, characterized by the steps of: a. inverse twisting a twisted core comprising at least one elastic filament and at least one inelastic filament, such that the number of twists is essentially zero, b. surrounding the core having a twist number of essentially zero by a sheath comprising a staple fiber, wherein the at least one inelastic filament is a yam which is separable from the at least one elastic filament by means of a process and the inelastic filament being not existent in the final composite yam to be obtained after the said process.

14. A method for manufacturing a composite yam comprising a core and a sheath, characterized by the steps of: a. twisting at least one elastic filament and at least one inelastic filament to form a core, b. twisting the twisted core obtained in step a) in the opposite direction, such that the number of twists is essentially zero,

c. surrounding the untwisted core by a sheath comprising a staple fiber, wherein the at least one inelastic filament is a yam which is separable from the at least one elastic filament by means of a process and the inelastic filament being not existent in the final composite yam to be obtained after the said process.

15. A method for manufacturing a composite yam comprising a core and a sheath, characterized by the steps of: a. providing, without twisting, at least one elastic filament and at least one inelastic filament to form a core,

b. twisting the sheath having a certain number of twists in a certain direction and comprising a staple fiber, in an opposite direction,

c. surrounding the said core by the inversely twisted sheath, wherein the at least one inelastic filament is a yam which is separable from the at least one elastic filament by means of a process and the inelastic filament being not existent in the final composite yam to be obtained after the said process.

16. A method for manufacturing a composite yam comprising a core and a sheath, characterized by the steps of: a. inverse twisting a twisted core comprising at least one elastic filament and at least one inelastic filament, such that the number of twists is essentially zero, b. twisting the sheath having a certain number of twists and in the same direction with the core and comprising a staple fiber, in an opposite direction, c. surrounding the core having essentially a twist number of zero by the inverse twisted sheath. wherein the at least one inelastic filament is a yam which is separable from the at least one elastic filament by means of a process and the inelastic filament being not existent in the final composite yam to be obtained after the said process.

17. A method according to any one of claims 13 to 16, characterized in that the at least one elastic filament comprises a synthetic rubber, elastomer or polyurethane filament.

18. A method according to any one of claims 13 to 16, characterized in that the at least one inelastic filament comprises a polyvinyl alcohol (PVA) filament.

19. A method according to any one of claims 13 to 16, characterized in that said process comprises a step of passing through a liquid medium wherein temperature and/or pressure variables are controlled.

20. A method according to claim 19, characterized in that the liquid medium is at a temperature of 20°C to 95°C at atmosphere pressure.

21. A method according to any one of claims 13 to 16, characterized by comprising a sizing agent covering the at least one inelastic filament.

22. A method according to any one of claims 13 to 16, characterized in that the at least one elastic filament and the at least one inelastic filament have a denier value of about 20 to about 140.

23. A method according to any one of claims 13 to 16, characterized in that the core comprises an additional inelastic filament made from a polyamide, a polyester, a polyolefin or a mixture thereof.

24. A method according to any one of claims 13 to 16, characterized in that the tension of the core is higher than that of the sheath before it is surrounded by the sheath comprising a staple fiber.

25. A method according to claim 24, characterized in that the core has a tension of 50 to 200 cN.

26. A fabric comprising a composite yam according to claim 1.

27. A fabric according to claim 26, characterized in that it is a denim fabric.

28. A composite yam according to claim 1 , characterized in that the number of twists in the core is in the range of zero to 10 twists/meter.

29. A composite yam according to claim 1, characterized in that it is used in weaving or knitting.