Patent Description:
The yarns of the invention find application in particular in the production of casual, sport and comfort garments, including denim garments.

Yarns having a core including polymeric filaments are known in the art. <CIT> discloses a yarn having a core that includes at least one elastic performance filament, most preferably a spandex and/or a lastol filament, and an inelastic control filament formed of a textured polymer or copolymer of a polyamide, a polyester, a polyolefin and mixtures thereof. According to EP'<NUM>, the textured control filament is loosely wrapped around the elastic filament.

<CIT> in the name of the present applicant, discloses a stretch yarn having a composite stretchable core and a cotton fibre sheath. The stretchable core comprises first and second filaments that each have different elastic properties, the first filament is an elastomer and the second filament is a polyester based (co)polymer with limited elasticity; the second, polyester based (co)polymer fiber is in the range of <NUM>-<NUM>% (w/w) of the stretchable core.

<CIT> discloses core spun yarns with bi-component polyester filaments and an elastomeric fiber; to avoid grinning through of the elastic core, the polyester filaments include poly (trimethylene terephthalate) and either poly (ethylene terephthalate) or poly (tetramethylene terephthalate) and the elastomeric fiber is comprising spandex. The bi-component polyester filaments are drafted at a ratio of <NUM> to <NUM> and the elastomeric fiber is drafted at a ratio of <NUM> to <NUM> times the original length.

<CIT> discloses a core yarn having a textured monofilament core and a staple fiber sheath. The core has <NUM> to <NUM> dtex (<NUM> to <NUM> denier) and is twisted with the staple fibers.

<CIT> discloses a composite spun yarn having a sheath core structure with a core composed of a plied yarn comprising a polyester composite filament yarn and a polyurethane elastic yarn. <CIT> and <CIT> disclose core sheath yarns, which can have up to <NUM> wt% polymeric non-elastomeric material in the core.

A problem with known yarns, especially stretch yarns, having a composite elastic core is that the amount of the components of the core in the final yarn has to be kept low to avoid the core becoming visible, i.e. surfacing, through the sheath of fibers. This requirement results in the use of high amounts of staple fibers, particularly of cotton fibers, which is a cost. A related problem is that the high amount of fibers used in the sheath requires the use of a certain number of long fibers, which is expensive. Also, the use of highly twisted short fibers may result in the yarn to become "curly", i.e. provided with undulations; this would in turn provide an unsatisfactory appearance to the fabric obtained from the yarn.

Another problem with the yarns of the known art is that the use of cotton is not environmentally-friendly, as a high amount of water is needed during cotton growing, and also a high amount of water and energy is needed to dye cotton.

It is an aim of the present invention to solve the above mentioned problems and provide yarns and fabrics with a synthetic core having excellent appearance and also good or great elasticity.

A further aim is to provide a yarn having a synthetic core that is completely covered by the fibre sheath, preferably a sheath of cotton fibres, and a fabric and garment using said yarn, without the core surfacing through the fibres, especially during or after use of the fabric or garment.

A further aim is to provide a yarn that is environmentally-friendly and inexpensive to manufacture.

Another aim of the invention is to provide a yarn, and a fabric, having a soft hand and that is comfortable for the user.

These aims are obtained by means of the present invention as claimed in one or more of the enclosed claims.

In particular, the present invention relates to a yarn, and a method according to the independent claims. Preferred aspects are mentioned in the dependent claims.

According to the invention, the yarn has a synthetic core comprising a plurality of polymeric non-elastomeric fibres, said fibres being non-texturized and being present in an amount of at least <NUM>% by weight on the total weight of the yarn. Preferred embodiments are object of the dependent claims.

Further objects of the invention are a fabric, particularly a denim fabric, containing a yarn as above defined and a garment or an article containing said fabric.

The invention also relates to a method of producing a stretch yarn according to claim <NUM>, said method comprising the steps of: providing a core of polymeric non-elastomeric core fibers, which are non-texturized, providing a plurality of staple fibers, spinning together said core fibers and said staple fibers to cover said core with a sheath of fibers, wherein the amount of the said core fibers in the core is at least <NUM>% by weight of the total weight of the yarn.

In an embodiment, in the spun yarn, a portion of at least part of the fibers of the sheath are held by said core fibers.

The core fibers consists of non-elastomeric fibers. Elastomeric filaments are added to the core and combined with the non-elastomeric core fibers.

The above percentages of the core fibers thus refer only to the non-elastomeric fibers that are present in the core. In other words, the non-elastomeric fibers that are present in the core are at least <NUM>% by weight of the total weight of the yarn.

As a result, according to possible embodiments, the core comprises non elastomeric core fibers and further elastomeric filaments.

In other words, the "core fibers" consist of non-elastomeric fibers (typically continuous fibers).

Non elastomeric fibers may still have elastic properties.

As a result, the core of the composite yarn may comprise filaments with elastic properties, that can be the the non-elastomeric filaments (i.e.continuous core fibers) that are part of the core fibers, as well as elastomeric filaments.

With the wording "filaments having elastic properties" it is meant elastomeric filaments such as the filaments in elastane or spandex, and elastic non-elastomeric filaments (e.g. T400 filaments). Suitable elastomeric filaments have an elongation at break higher than <NUM>%, preferably higher than <NUM>%, typically comprised between <NUM>% and <NUM>%. The amount of elastomeric filaments may be in the range of <NUM>% - <NUM>%, more preferably <NUM>% to <NUM>% of the total weight of the yarn. Filaments having elastic properties may be combined together. Preferred elastomeric filaments are elastane, polyurethane urea based fibers, lastol, Dow XLA. The filaments having elastic properties may be non-elastomeric filaments, preferably having elongation at break comprised between <NUM> - <NUM>%. Preferred fibers for elastic non-elastomeric filaments are T400 (co-polymer of Polyester, elastomultiester), PBT fibers, and other conjugate yarns such as PBT-PTT, PET-PTT and PET-PTMT. Total amount of filaments having elastic properties is <NUM> - <NUM>% of the weight of the composite yarn, preferably <NUM> - <NUM>%.

The above mentioned Elongation at break of non-elastomeric filaments may be measured with DIN ISO <NUM>, while elastomeric filaments may be tested with BISFA, test method for bare elastane yarns, Chapter <NUM>. Non elastomeric filaments have recovery of at least <NUM>%, preferably <NUM>%, most preferably at least <NUM>% or <NUM>% or higher of the fiber". Recovery is measured with DIN <NUM> part <NUM>, with <NUM>,<NUM> cN/tex force and <NUM>% elongation.

The elastomeric filaments suitable for use in the present invention are commercially available, e.g. under the trade mark Lycra, usually in the form of several filaments that have been extrude in a one-piece bundle of filaments attached together. In a preferred embodiment the elastomeric filaments are provided as a bundle of separated single filaments.

In brief, according to an aspect, a composite yarn comprises at least two single elastic filaments. With the definition according to which the elastic filaments are single, it is meant that they are not part of the same elastic bundle of continuously connected filaments. It is in fact known that for elastic textile elements, an amount of filaments may be bundled together to produce the desired thickness. It is e.g. known that a yarn of spandex is a bundle of filaments, as spandex yarns may be composed of a plurality smaller individual filament that adhere one another because of the natural stickiness of their surface. On the contrary, with single elastic filament is meant a monofilament yarn. According to a possible aspect, the single elastic filaments may be initially packaged in a bundle, loosely coupled one to the other, so as to be separated (and become "single filaments") during subsequent process steps for producing a yarn.

The core fibers are non-texturized filaments, that are typically flat, "flat" making reference to the non-texturized condition of the filament, and not to their section, that can be chosen as requested. In other words, the core of the yarn of the invention is free from texturized filaments.

With the wording "spinning" or "twisting" it is indicated a known process of combining a core with a sheath of staple fibers. The process typically includes positioning the core fibers on or adjacent to a sliver or bundle of sheath fibers and twist the core with the fibers. Suitable twisting methods include e.g. ring spinning. Thus, a core and a sheath in the present invention are spun together e.g. by ring spinning.

Exemplary materials for the core fibers are polyester polymers and copolymers, namely PET (polyethylene terephthalate), PBT (polybutylene terephthalate), PTT(Poly tri-methylene terephthalate) PTMT (poly tetra-methylene terephthalate) or copolymer of polyester PTT/PET, PTT/PBT, PTMT/PET. Other suitable polymers are polyamides, namely nylon: PA6 (polyamide), PA <NUM> or copolymers of nylon, and polyacrylic and polyacrylonitrile polymers. In an embodiment provided with further elastomeric filaments, the core fibers are in the range of <NUM>-<NUM>% by weight of the core. Preferred synthetic fibers for the core fibers are PP, PET, PA6, and PA6,<NUM>. The use of other synthetic materials for the core fibers, not explicitly mentioned in the above lists, is however not excluded.

Suitable staple fibers to be used for providing the sheath to the final yarn are known in the art and are e.g. cotton, rayon and its variation (Modal, Lyocell, Cupro, Viscose), linen, hemp, ramie, kapok, wool, silk, cashmere, etcetera.

The core fibers can be continuous fibers (i.e. filaments) and also staple fibers, e.g. obtained by cutting filaments. The staple fibers may be mixed with continuous filaments. Part of the core fibers are bundles of filaments known as FDY (Fully Drawn Yarns); known FDY are e.g. obtained by drawing the polymer filaments exiting from the spinneret of the machine for producing the filaments. Preferred polymers for the FDY fibers are the above mentioned (co)polyesters and nylons.

An exemplary process to obtain FDY yarns is as follows. The raw material, typically PET chips are dried, melted, filtered and then distributed to spinning manifolds. In more detail, to manufacture FDY yarns, PET chips are fed into a dryer where the moisture is reduced from <NUM>% to <NUM>%. After this, the chips are melted, filtered through a polymer filter and extruded through the spinnerets. The extruder is electrically heated, at a controlled temperature (typically using a microprocessor). The extruder screw speed is also controlled and monitored very precisely to ensure uniform quality. The extruded filaments are cooled by filtered air in a quench chamber with precise temperature control. Air having no turbulence is used to ensure uniformity. High quality anti-static lubricating oil is applied to avoid static charges in the yarn. The yarn is taken by heated rollers (godets) to maintain residual elongation. Air punching may be carried out at regular intervals by intermingling nozzles and the yarn is finally wound on an automatic winder. In the spinning process, a stretching effect can be obtained with a high degree of orientation filament winding and medium crystallinity.

In general, a flat, filament can be defined as a filament that has not been texturized; a flat filament used in the present invention undergoes a torsion during the spinning (or twisting) step and when removed from the yarn of the invention will no longer be completely flat. The filaments can be identified as a non-texturized filament because there is no false twist on them.

In an embodiment, the core fibers have a linear density of <NUM> dtex (<NUM> denier) or less, preferably <NUM> dtex (<NUM> denier) or less, more preferably the linear density is in the range of <NUM> to <NUM> dtex (<NUM> to <NUM> denier).

According to another aspect, the core fibers are continuous, i.e. they are core filaments, and the number of continuous core fibers (core filaments) in the core is at least <NUM>, preferably at least <NUM> filaments per yarn; this number does not include the elastomeric filaments present in the core.

In embodiments of the invention, the core fibers are continuous fibers, i.e. filaments, and the continuous core fibers and the elastomeric filaments are combined together by co-extrusion.

The elastomeric filaments are drafted, or elongated, before being combined with the continuous core fibers. In an embodiment, the draft ratio of the elastomeric filaments is in the range of <NUM> to <NUM>, more preferably <NUM> to <NUM>. Co-extrusion, also known as co-feeding, of bundles of filaments is obtained by forcing (feeding together) the two (or more) bundles of filaments (in a tensioned state) through a restriction where the fibers are compressed together to such a degree that they remain attached also after exiting the restriction. A suitable restriction is e.g. a "V"- shaped roll; the fibers are fed to the roll and are fed together and forced into the bottom of the "V" where they are compressed together and remain bound. The co-extruded filaments are preferably spun with the fibers of the sheath immediately after the co-extrusion step.

In embodiments of the invention, the amount of the core fibers (excluding the elastomeric fibers) is at least <NUM>% by weight of the total weight of the yarn, i.e. of the complete yarn including the sheath, and may be as high as <NUM>% of the weight of the complete yarn. Preferably, the amount of core fibers is at least <NUM> or <NUM>% by weight of the final yarn; preferably the amount of core fibers is in the range of <NUM>% to <NUM>% by weight of the final yarn, more preferably, the core is in the range of <NUM>% to <NUM>%, or <NUM>% to <NUM>%, of the weight of the yarn.

A first advantage of the claimed solution is that the yarn may have low twist multiple. According to exemplary embodiments, the twist level of the yarn may be dramatically reduced and twist multiples between <NUM> and <NUM>, preferably between <NUM> and <NUM> may be used. It is even more preferred that the twist multiple be between <NUM> and <NUM>, and even more preferable that the twist multiple be between <NUM> and <NUM>. This low level twist results in a very soft fabric with excellent light reflection that is brilliant in color. The twist multiple is obtained from the equation:<MAT>
where the value of twist per inch may be calculated with the equation<MAT>.

Further details on low-twist yarns and their method of production are available e.g. in <CIT>, in the name of the present applicant.

By using low twisting, it is possible to provide a coarser yarn, with respect to the prior art, i.e. a yarn that is bigger in dimension with respect to the prior art, as shown in the following comparative example.

Three yarns were prepared. Yarn A was a yarn according to the invention, while yarns B and C were <NUM>% ring spun cotton yarn according to the prior art. Data of the yarn is as follows.

As visible, yarn A according to the invention has a greater diameter than yarn B, i.e. a common <NUM>% cotton yarn having the same count of yarn A (i.e. <NUM>/<NUM> NE). The diameter of yarn A is similar to the one of yarn C, i.e. a common <NUM>% cotton yarn that is heavier than yarn A (<NUM>/<NUM> NE vs <NUM>/<NUM> NE).

Diameter of the yarns was measured with USTER TESTER <NUM>.

The invention provides several further advantages over the prior art. A first advantage is that the yarn has a lower amount of cotton fibers than in a similar corresponding yarn according to the prior art. At the same time, the yarn of the invention has a very good appearance, substantially no surfacing of the core fibers, notwithstanding the higher amount of fibers used for the core. Additionally, it was found that it is possible to use a higher percentage of short fibers in the sheath than it is possible in the known art.

The amount of cotton used in the invention yarn is about <NUM>-<NUM>% less than the amount of cotton required in a corresponding yarn according to the prior art. The reduction in the quantity of cotton fibers results in a plurality of advantages the first being the environmental sustainability of the yarn production process.

According to an aspect, the sheath may be <NUM>% cotton. Other embodiments are possible where <NUM>% to <NUM>% of the sheath fibers are cotton fibers. The remaining part of the sheath may comprise other commercially available fibers. Cotton fibers may be regular cotton fibers, pre-consumer cotton fibers, or post-consumer cotton fibers. This results in saving water and in a greater sustainability of the yarn production.

Namely, the invention results in less sheath fiber (e.g. cotton) content, that results in saving water in cotton because less cotton is required, hence less water is used in cotton growing, in a reduced use of dyestuff for dyeing process (because there is a lower amount of cotton, or similar sheath fiber to be dyed), and also in a drying process that is shorter and/or at lower temperatures. This means lower cost for the process, compared with the process for drying a traditional yarn containing almost <NUM>-<NUM>% cotton.

As mentioned before, other fibers, different than cotton, can be used for the sheath. As an example, man made fibers (preferably cellulose-based) may be used, e.g. rayon and its variation (Modal, Lyocell, Cupro, Viscose). Natural fibers may be also used such as linen, hemp, rami, kapok.

According to a possible solution, animal fibers such as wool, silk, cashmere may be used as well.

Less energy is used in the drying process for a yarn according to the invention.

The invention also provides the following advantages in the production process.

In the ball warping step of the yarn production, the break ratio of the rope of the fabric can decrease by <NUM>-<NUM>% per <NUM><NUM> meters. Additionally, the amount of adhered pile is typically reduced by <NUM>-<NUM>%. The figure of broken end sent to the rope dye may decrease by <NUM>%.

In the rope dyeing step, the reduction in the amount of water to be used for dyeing the fabric can reach <NUM>-<NUM>% by volume. Similarly, since the water pick-up amount of the yarn is lower, the amount of chemicals and dye to be used is reduced by <NUM>-<NUM>% by weight, depending on the type of yarn.

The invention yarn has higher breaking strength, compared to a corresponding known yarn, having the same count, made from the same materials and having a higher percentage of cotton. For this reason, the rebeaming meter production can increase by <NUM>-<NUM>%. The <NUM><NUM> break ratio (i.e. the break ratio considered in the production of a million meter of yarns) can be reduced by <NUM>-<NUM>% as a result of the higher yarn strength. Yarn to yarn friction will also decrease, which will reduce <NUM>-<NUM>% of cotton-based breaks in reed region. Finally, the lost ends problem will be reduced because the yarn break decreases.

During sizing, yarn breakages that may occur in the sizing area due to yarn property can be reduced by <NUM>-<NUM>%. With the reduction of the number breakages, the number of missing tips to the weaving section can be reduced by <NUM>-<NUM>%. The amount of chemical used for the sizing step can also be reduced by <NUM>-<NUM>%. The steam consumption to be used for yarn drying can be reduced by <NUM>-<NUM>%. The fault score can decrease by <NUM>-<NUM>% due to the decrease in flying fibers.

In particular, according to a preferred aspect, the composite core yarn is provided with a hairiness, that provides a soft feeling and "hand" to a fabric obtained with this yarn.

A possible way to measure hairiness is disclosed in ASTM <NUM>. Hairiness index according to ASTM5647 of the composite yarn is preferably comprised between <NUM> and <NUM>, more preferably between <NUM> and <NUM>.

According to the invention, the tenacity of the composite yarn is comprised between <NUM> and 25cN/tex, preferably less than <NUM> cN/tex, more preferably less than <NUM> cN/tex. Tenacity is measured according to EN ISO <NUM>.

Elongation at break of the composite yarn is preferably comprised between <NUM>% to <NUM>%, more preferably for <NUM>% to <NUM>%, measured with EN ISO <NUM>.

Count of the composite yarn is preferably comprised between <NUM> to <NUM> dtex (Ne <NUM>/<NUM> to Ne <NUM>/<NUM>), more preferably between <NUM> to <NUM> dtex (Ne <NUM>/<NUM> to Ne <NUM>/<NUM>).

Total count of the core is preferably comprised between <NUM> dtex to <NUM> dtex (<NUM> den to <NUM> den), preferably from <NUM> dtex to <NUM> dtex (<NUM> den to <NUM> den).

Elongation at break of the core is preferably comprised between <NUM>% and <NUM>%, preferably between <NUM>% to <NUM>%.

A yarn of the invention may have a combination of the above features.

The invention will be now further disclosed with reference to the following non-limiting figures, where:.

A composite yarn <NUM> has a core <NUM> and a sheath <NUM>, typically comprising staple fibers 3a. The core <NUM> comprises a plurality of core fibers <NUM>.

The core fibers <NUM> are preferably filaments (i.e. continuous endless fibers, e.g. as schematically shown in <FIG>). In other embodiments, the core fibers <NUM> may comprise also staple fibers, e.g. obtained by cutting filaments. According to an embodiment, the core fibers <NUM> may comprise both continuous filaments and a bundle of staple fibers.

The linear density of the core fibers <NUM> is preferably <NUM> dtex (<NUM> denier) or less, more preferably <NUM> dtex (<NUM> denier) or less, even more preferably <NUM> to <NUM> dtex (<NUM> to <NUM> denier). According to a possible embodiment, the denier of the core fibers <NUM> is comprised between <NUM> and <NUM> dtex (<NUM> and <NUM> denier).

Preferred materials for the core fibers <NUM> are polyester polymers and copolymers. Other suitable polymers are polyamides. Exemplary materials for the core fibers <NUM> are polyester polymers and copolymers, namely PET (poly ethylene terephthalate), PBT (poly butylene terephthalate), PTT(Poly tri-methylene terephthalate) PTMT (poly tetra-methylene terephthalate) or copolymer of polyester PTT/PET, PTT/PBT, PTMT/PET. Exemplary polyamides (namely nylon) are: PA6 (polyamide), PA <NUM> or copolymers of nylon, and polyacrylic and polyacrylonitrile polymers. The core fibers are non-elastomeric, i.e. they do not comprise an elastomeric yarn.

Suitable staple fibers 3a to be used for providing the sheath <NUM> to the composite yarn <NUM> are known in the art and are e.g. cotton, rayon and its commercially available variations (Modal, Cupro, Lyocell, Viscosa), linen, wool, hemp, ramie, kapok, silk, cashmere and etcetera.

The amount of the core fibers <NUM> is at least <NUM>% by weight of the total weight of the composite yarn <NUM>. In embodiments of the invention, the amount of the core fibers <NUM> may be as high as <NUM>% of the weight of the composite yarn <NUM>. Preferably, the amount of core fibers <NUM> is at least <NUM>% or <NUM>% by weight of the final composite yarn; preferably the amount of core fibers is in the range of <NUM>% to <NUM>% by weight of the final yarn, more preferably, the core is in the range of <NUM>% to <NUM>%, or <NUM>% to <NUM>%, of the weight of the yarn.

In the embodiment schematically shown in <FIG>, at least part of the core fibers may be provided as a bundle of fibers or as a core yarn <NUM>, e.g. a FDY yarn.

Other embodiments are possible, e.g. embodiments where the core <NUM> comprises more than one bundle of fibers and/or yarn <NUM>. Preferably, according to an aspect, the core <NUM> comprises at least <NUM>, more preferably at least <NUM>, even more preferably at least <NUM> continuous core fibers <NUM>. The number of continuous core fibers (i.e. the number of core filaments) is also preferably less than <NUM>.

The total count of the core is preferably comprised between, <NUM> and <NUM> dtex (<NUM> and <NUM> den), more preferably between <NUM> and <NUM> dtex (<NUM> and <NUM> den). Elongation at break of each core fiber <NUM> is preferably comprised between <NUM> and <NUM>%, elongation at break of the core yarn is preferably comprised between <NUM>% and <NUM>%, more preferably between <NUM>% and <NUM>%.

According to a possible embodiment not according to the invention, the core <NUM> (and thus the composite yarn <NUM>) is free from elastomeric fibers. In other words, the core <NUM> (and thus the composite yarn <NUM>) essentially consist of non-elastomeric fibers. Some of these fibers may be elastic.

According to a different embodiment, the core <NUM> comprises at least one elastomeric filament <NUM> (shown in dotted line), as schematically shown in <FIG>. According to possible embodiments, the core <NUM> of the composite yarn <NUM> comprises at least two single elastic filaments <NUM>, i.e. at least two different monofilament yarns.

As previously mentioned, the above discussed percentages ("at least <NUM>%", "at least <NUM>% or <NUM>%", "in the range of <NUM>% to <NUM>", etc.) of the core fibers <NUM> refer to the non-elastomeric fibers that are present in the core <NUM>. In other words, the non-elastomeric fibers of the core <NUM> (i.e. the core fibers <NUM>) are at least <NUM>% of the total weight of the composite yarn. Preferred ranges were previously discussed ("at least <NUM>% or <NUM>%", "in the range of <NUM>% to <NUM>", etc.).

In embodiments of the invention, continuous core fibers <NUM> and the elastomeric filament(s) <NUM> are connected together at a plurality of points by co-extrusion.

In view of the above, the core <NUM> may comprise different filaments having elastic properties. Filaments having elastic properties may be the elastic non-elastomeric core fibers <NUM>, and the elastomeric filaments <NUM>.

The total count of filaments having elastic properties is preferably comprised between <NUM> and <NUM> dtex ( <NUM> and <NUM> den), more preferably between <NUM> and <NUM> dtex (<NUM> and <NUM> den).

<FIG> schematically shows the "co-extrusion" or "co-feeding" method for a bundle of fibers or core yarn <NUM> (e.g. an FDY yarn) and an elastomeric filament <NUM>. The bundle of fibers or core yarn <NUM> and the elastomeric filament <NUM> are fed (preferably in a tensioned state) through a restriction <NUM> where they are pressed together and attach to each other to such a degree that they remain attached together also after exiting the restriction. In more detail, <FIG> shows a roll <NUM> having a "V"- shaped restriction <NUM>; the bundle of fibers or core yarn <NUM> and the elastomeric filament <NUM> are fed to the roll <NUM> and are forced into the bottom of the "V" restriction <NUM>, where they attach together, i.e. the bundle of fibers or core yarn <NUM> and the elastomeric filament <NUM> are connected together at least at a plurality of points, so that they exit the roll <NUM> as the substantially finished core <NUM>, that may be covered by the sheath <NUM>.

As previously discussed, a composite yarn <NUM> of the invention is typically soft. A possible factor that may help in providing a soft feeling may be the yarn hairiness.

A possible way to measure hairiness is disclosed in ASTM <NUM>. Hairiness index according to ASTM5647 of the composite yarn <NUM> is preferably comprised between <NUM> and <NUM>, more preferably between <NUM> and <NUM>. As known, the hairiness index H corresponds to the total length of protruding fibers within the measurement field of <NUM> length of the yarn.

According to the invention, the tenacity of the composite yarn <NUM> is comprised between <NUM> and 25cN/tex, preferably it is less than <NUM> cN/tex, more preferably less than <NUM> cN/tex. Tenacity is measured according to EN ISO <NUM>.

Elongation at break of the composite yarn <NUM> is preferably comprised between <NUM>% to <NUM>%, more preferably for <NUM>% to <NUM>%, measured with EN ISO <NUM>.

The count of the composite yarn <NUM> is preferably comprised between <NUM> dtex to <NUM> dtex (Ne <NUM>/<NUM> to Ne <NUM>/<NUM>), more preferably between <NUM> dtex to <NUM> dtex (Ne <NUM>/<NUM> to Ne <NUM>/<NUM>).

In preferred embodiments, the composite yarn <NUM> is obtained via ring spinning. In particular, preferred embodiments provide that the composite yarn <NUM> is obtained by a core <NUM> that is coupled to a single roving (typically cotton roving). This provides a better centering (i.e. less grin through) of the core <NUM>, and thus a softer and more appealing (in term of appearance) yarn. It is however possible to use two or more different rovings, as better discussed later.

<FIG> and <FIG> show an embodiment of a ring spinning apparatus for the production of an exemplary composite yarn <NUM>.

The core <NUM> is taken from bobbin <NUM> and is guided between two tension bars <NUM> that are used to give a low pre-tension to the yarn, just to align and straighten core yarn <NUM>. This is very useful when the core <NUM> is obtained by intermingling two different filaments. From pre-tension bars <NUM>, core <NUM> is fed to two driving rollers <NUM> on which a weight <NUM> is placed; core <NUM> is guided between the driving rollers and the weight <NUM> to avoid free movement of the core yarn with respect to the rollers <NUM>, however, other suitable means for imparting a controlled speed to the core yarn <NUM> may be used instead of the combination of rollers <NUM> and weight <NUM>, e.g. means such as draft rollers that are known in the art.

The advantage of the above disclosed arrangement is mainly in the fact that the same apparatus can be used also to prepare a standard elastane core yarn: in this case the elastane fiber is loaded in a package that is placed on the rollers <NUM> in the place of weight <NUM>.

From the first drafting arrangement <NUM>, <NUM>, core <NUM> (preferably a flat yarn, e.g. a bundle of filaments or a yarn <NUM>) is guided to a rolling guide <NUM> and from it to draft rollers <NUM>, that are the foremost couple of a plurality of drafting rollers for the cotton roving <NUM>, known per se in the art.

Cotton roving <NUM> is guided from spool <NUM> in front of pre-tension rollers <NUM>, tension rollers <NUM>, into a first guide <NUM> and a second guide <NUM>; as can be seen in <FIG>, guide <NUM> is staggered to the front of the apparatus with respect to second guide <NUM> in order to create a tension in the roving and keep the roving in a fixed position, avoiding that the roving moves freely.

From guide <NUM>, cotton roving <NUM> is sent to draft rollers <NUM>. Draft rollers <NUM> are in common between core <NUM> and roving <NUM>.

According to the invention, core <NUM> is tensioned before being coupled with the cotton roving, the tensioning or stretching is obtained by means of the speed difference between rollers <NUM> and rollers <NUM>, i.e. the speed difference between rollers <NUM> and the last draft roller <NUM> create the draft ratio in composite core <NUM>.

The above draft ratio is calculated as the ratio of the speed of rollers <NUM> vs. the speed of rollers <NUM>, where the speed is the angular speed on the surface of the rollers.

It should be noticed that also pre-tensioning bars <NUM>, contribute to obtaining the required draft ratio. The additional pretension bars <NUM> are useful in increasing the draft ratio because they provide an alignment and slight tension of the core <NUM>, thus helping in the further stretch step. This results in the extreme accuracy with which the core <NUM> is kept in the center of the final yarn <NUM>.

Use of additional guide <NUM> and its staggered position with respect of guide <NUM> also allow to feed the cotton roving always at the same position and to prevent the moving of cotton roving during the long run production. The combination of a better control in keeping the position of cotton roving <NUM> and a high tension on core <NUM> makes it possible to keep core <NUM> always in the center of the yarn <NUM> and to perfectly cover the core with staple fibers <NUM>.

The two portions of final yarn <NUM> leaving draft rollers <NUM> are fed through guide <NUM> and spun together at spinning device <NUM>, known per se in the art and comprising in one embodiment ring, traveler and spindle.

Any spinning method to produce a yarn <NUM> having a core <NUM> centered in a sheath <NUM> is within the scope of the present invention. Such methods include e.g. covered yarn system (using machinery by JCBT, Menegato, OMM, RATTl, RPR, Jschikawa) or twisting machines (using machinery by Hamel, 2for1 by Volkman, SiroSpin by COGNETEX or Zinser).

The composite yarn produced can be used in production of elastic denim fabric and garments, especially as weft yarn. Machinery and methods of producing denim are well known in the art, as an example, Morrison Textile Machinery or Sulzer Machinery or modifications thereof maybe used to produce a denim fabric with great elasticity and excellent stretch recovery.

<FIG> and <FIG> show another possible apparatus <NUM> and method for the production of a composite yarn <NUM>.

In such an embodiment, the sheath <NUM> is made from two different rovings that, for part of their path, are treated separately, and subsequently combined to form the sheath. Similar methods are known in the art as "siro spinning". Further embodiments with a greater number of rovings are possible.

Core <NUM>, comprises polyester filaments <NUM> and elastane as elastomeric filament <NUM>. Polyester <NUM> comes from a bobbin <NUM>, and is passed through a tube <NUM>, where a first draft is applied. A further draft may be applied by rollers <NUM> at the exit of tube <NUM>.

Elastane <NUM> comes from bobbin <NUM>, and is guided to roller <NUM>, where it is combined with polyester <NUM> to form the core <NUM>. As an example, roller <NUM> may be of the kind shown in <FIG>.

The sheath <NUM> is provided by two cotton rovings 8a, 8b, that come from spools 206a, 206b. Rovings 8a, 8b are drafted separately (as better shown in <FIG>), e.g. by one or more draft rollers <NUM>. Core yarn <NUM> is guided to draft rollers <NUM>, where also cotton rovings 8a, 8b are fed.

The core yarns <NUM> and the cotton rovings 8a, 8b are then spun by a spinning device <NUM>. Preferably, before the spinning device <NUM>, the bundle of core yarn <NUM> and rovings 8a, 8b is passed through a further drafting and compacting device <NUM>, shown in an exemplary and preferred embodiment in the enlarged detail of <FIG>. In this embodiment, the drafting and compact device <NUM> comprises two compact rollers 209a, between which the bundle of yarns <NUM>, 8a, 8b (not shown for better clarity in the enlarged detail of <FIG>) is pressed. Each compact roller <NUM> drives an endless belt 209b. The belts 209b are facing one another, to define a passage 209c for the bundle of yarns <NUM>, 8a, 8b between the belts 209b. This kind of drafting and compacting device is known in the art as "double apron drafting system".

In general, the bundle of yarns <NUM>, 8a, 8b is guided and pressed by the drafting and compact device <NUM> (e.g. in the passage 209c by the belts 209b in the shown embodiment), providing an even pressing and drafting of all the components of the bundle of yarns <NUM>, 8a, 8b, i.e. polyester <NUM> and elastane <NUM> of the core yarn <NUM> and the rovings 8a, 8b that form the sheath <NUM>.

As before, the core <NUM> is drafted and guided in order to be centered with respect to the sheath <NUM> in the final yarn <NUM>.

In other embodiments, the drafting and compacting device <NUM> may be omitted.

In addition, a possible embodiment provides that one of the two rovings 8a, 8b is omitted (or in any case not used), to carry out a single roving ring spinning of the composite yarn <NUM>.

As an example, <FIG> shows an embodiment of a ring spinning apparatus, provided with a single source <NUM> for roving <NUM>, and without a compacting device <NUM>.

The other elements are similar to the ones of <FIG> and <FIG> and are shown with the same numeral references.

According to a possible embodiment, a brake element <NUM>, schematically shown in <FIG>, can be placed upstream the drafting means for the core <NUM>, e.g. the brake element <NUM> can be placed within the tube <NUM>. The brake element <NUM> is an element that is contacted by the core <NUM> (e.g. the core <NUM> goes around the brake element <NUM>, contacting its lateral surface), so that a force is applied to the core <NUM>, by friction of the core <NUM> against the braking element <NUM>, to adjust the speed of the core <NUM>. The brake element <NUM> (or a portion of the brake element <NUM>) can have a substantially cylindrical or prismatic shape, so that the core may slide against the lateral surface of the brake element <NUM>.

The composite yarn <NUM> is typically used to produce a fabric <NUM>. Such a fabric <NUM> may be used to produce an article <NUM>, that is preferably a garment. As an example, in <FIG>, the composite yarns <NUM> are used in a woven denim fabric <NUM>, that is in turn used to produce a pair of trousers.

Different treatments can be carried out on the final fabric <NUM>. In one embodiment, the fabric <NUM> can be embossed to obtain a three-dimensional design.

A chemical treatment can be applied to the fabric to dissolve (part of) the cellulose fibers to obtain a design or pattern on the fabric <NUM>. This technique is known in the art as "burnout" or "devoré".

Particular effects on the final fabric <NUM> can be obtained by using different colours between the core fibers and the sheath fibers.

The invention will now be further disclosed with reference to the following examples.

The yarns were prepared by ring spinning a bundle of the PES continuous filaments with a sliver of cotton fibers. The core is a <NUM> dtex (<NUM> denier) bundle formed by <NUM> filaments; each filament is a <NUM> dtex (<NUM> denier) filament. No grin through of the core fibers through the fiber sheath was detected.

Two fabrics, X1 and X2, were prepared using yarns according to the invention and a comparison yarn, Xcomp, was prepared using yarns according to the prior art. The composition of the sample weft yarns is recited in Table <NUM> under the Yarn Composition column. The composition of the warp yarns is the same as the composition of the weft yarns except that no elastane is present and the cotton amount is increased by the previously present elastane amount. The PES core in the yarns of X1 and X2 is a <NUM> dtex (<NUM> denier) bundle formed by <NUM> filaments, each filament is a <NUM> dtex (<NUM> denier) filament. The warp and weft yarns were used to prepare a finished woven fabric having the following features:
Weft density : <NUM>,<NUM> thread/cm; Warp Density: <NUM> thread/cm Fabric trials were carried out to evaluate fabric tear and tensile strength. The test results are summarized in the following table; from the results, it is apparent that the fabric performance has increased by <NUM> % or more.

In example <NUM> three samples of fabrics X1, X2 and Xcomp, prepared for example <NUM> were tested for their behaviour in the washing step.

The results are summarized in the following Table <NUM>.

It can be appreciated that the decrease in the drying time with respect to Xcomp, is about <NUM>% for sample X1 and more than <NUM>% for sample X2; this surprising reduction in the drying time of the fabric is reflected in a reduction of the energy used for the drying step and results in an important saving of drying costs.

Claim 1:
A yarn (<NUM>) having a core (<NUM>) and a sheath (<NUM>), preferably comprising staple fibers, said core comprising a plurality of polymeric non-elastomeric core fibers (<NUM>), wherein the amount of the polymeric non-elastomeric core fibers (<NUM>) is at least <NUM>% by weight of the total weight of the yarn (<NUM>), wherein said core (<NUM>) and said sheath (<NUM>) are spun together, wherein said polymeric non-elastomeric core fibers (<NUM>) are non-texturized fibers, wherein at least part of the polymeric non-elastomeric core fibers is provided as a fully drawn yarn (FDY) (<NUM>), wherein said yarn (<NUM>) having the core and the sheath has tenacity comprised between <NUM> and <NUM> cN/tex measured according to EN ISO <NUM>, wherein said core further includes elastomeric filaments (<NUM>), and wherein the FDY yarn (<NUM>) and the elastomeric filaments (<NUM>) are combined together in a manner as obtainable by feeding them through a restriction (<NUM>) where they are pressed together and attach to each other to such a degree that they remain attached together after exiting the restriction.