A core spun yarn comprising short cellulosic staple fibers and polymeric fibers and process for its production

Abstract

A yarn consisting of a filament core and a staple sheath, the staple sheath of which is made of a mixture of primary and secondary fibers, or contains them in at least 95% by weight, where the primary fibers are natural cellulosic fibers and the secondary fibers are synthetic fibers; The filament core is characterized by having a weight ratio of 65 / 35 to 35 / 65 of the first fibers to 40 / 60 to 60 / 40, preferably around 50 / 50, and the elongation at break of the polyester filaments, as measured according to DIN ISO 2062, should be between 5% and 15%, preferably between 10% and 12%.

Description

Field of the invention

[0001] The present invention relates to the field of yarn production and to fabrics in general. In greater detail, the present invention relates to a yarn using short cellulosic, e.g. cotton, staple fibers typically obtained from recycling of yarns and fabrics, wherein the yarn is suitable for workwear garments and for medical garments.State of the art

[0002] Due to the costs and to the environmental impact of natural fiber production, methods have been developed to recycle natural fibers from textile waste, in order to re-use them. A prominent example is recycling cotton from waste textiles, in particular fabric and yarn waste, in order to obtain recycled cotton fibers.

[0003] Known recycling processes for fabrics and yarns generally include mechanically breaking down the textiles into loose fibers that can be used for spinning new yarns. In this process, machines are used that break down the fabric e.g. by means of rotating drums with metal pins. The mechanical strain on the fibers in the yarns causes the breakage of at least part of original fibres into shorter fibres.

[0004] A problem with recycled cotton fibers is that their content of short length fibers makes them unsuitable or badly suitable for yarn manufacturing, in particular in ring spinning machines, that is commonly used for denim production. Virgin cotton staple fibers have a greater amount of long fibers than recycled cotton fibers; e.g. the average length L(n) (considering all of the fibers of a yarn) of virgin cotton is usually greater than 20 mm, while recycled staple cotton fibers have an average length L(n) that is usually below 15 mm, usually between 6 and 15 mm, more commonly between 9 - 12 mm.

[0005] It is thus difficult to properly use the recycled (short) cotton fibers in yarn production by ring spinning.

[0006] Also, work-wear and medical garments are subject to frequent washing cycles, that usually involves temperatures and / or chemicals that are more aggressive than home washing cycles. Yarns made from recycled cotton usually are not able to withstand a high number of industrial washing cycles.

[0007] The short length of cotton fibers typically results in a yarn having a too low strength, resulting in a poor fabric, or may not even be workable into a yarn due to the breakages of the combined fibers occurring in the yarn manufacturing machines. For this reason, recycled cotton fibers have been mixed with virgin cotton fibers to impart to the final yarn acceptable mechanical properties and physical characteristics, such as the bulkiness and appearance, of yarns containing 100% virgin natural fiber, e.g. virgin cotton. The ratio of the amount of virgin cotton fibers (CO) to recycled cotton fibers (RCO) by weight in a yarn depends from the yarn production technique. Typically, open end yarns may comprise up to 100% recycled cotton, while in ring spun yarns RCO content does not exceed 40% (by weight) and generally the ratio (by weight) CO / RCO is in the range of 70 / 30 to 90 / 10.

[0008] It has also been proposed to reduce the amount of cotton in yarns with the use of polyester filaments and fibers in the yarn composition. In an embodiment polyester staple fibers are mixed with cotton fibers before being spun into a yarn; these yarns have the drawback that due to the presence of polyester they have a poor look, i.e. a non-cotton look.

[0009] US20150176160 discloses a fabric provided with core-spun yarns, having a draw textured yarn core and a cotton staple fiber sheath. JP S62 28426 A discloses a polyolefin resin composition. EP3701840A1 discloses a method for recycling short cotton fibers residues.

[0010] Core-spun yarns having a core including polyester filaments are also known; the use of recycled cotton in core-spun yarns is usually disadvantageous as, during production, the sheath of recycled cotton tends to break and to slip with respect to the core.

[0011] There is thus the need to solve the problems of the prior art and to provide a yarn in which cotton fibers are present in good quantity, all the cotton fibers are recycled fibers, the yarn is a ring spun yarn and has a good look and good to excellent mechanical characteristics, in particular the yarn is suitable for workwear and medical garments.Summary of the invention

[0012] An aim of the present invention is thus to provide a yarn in which all the cotton fibers are recycled, short length, cotton fibers and that has good to excellent mechanical properties and the look and aspect of a yarn obtained from virgin cotton fibers.

[0013] Another aim of the invention is to provide a yarn reaching the above mentioned scope, that is easily woven in a fabric that can withstand repeated washings in hard conditions and that is suitable for work-wear garments and for medical fabrics and medical garments.

[0014] Another aim of the invention is to provide a core spun yarn containing short length cotton fibers that is elastic and stretchable.

[0015] Said aims are reached by means of the present invention according to one or more of the enclosed claims.

[0016] In particular, the present invention relates to a yarn and a relevant production method according to the enclosed independent claims, while preferred aspects are recited in the dependent claims.

[0017] The wording "blend of fibers" in the present description is used to identify a mixture of different fibers that is suitable to be used in a ring spinning process to provide the sheath of a core spun yarn. Single fibers in the sheath of the invention yarn can be identified and physically removed from the blend forming the sheath to be tested if required.

[0018] For the present invention, the term "virgin fiber" indicates cotton staple fibers deriving from cotton that has a high average length of the fibers e.g. because it has not been recycled from yarns and fabrics.

[0019] For the present invention the term "natural cellulosic fibers" indicates fibers obtained from plants. Preferred natural cellulosic fibers are fibers as obtained or as obtainable from the recycling process of fabrics and fibers coming from plants such as cotton, hemp, linen and so on. Typically, natural cellulosic fibers used in the invention are recycled fibers, having count similar to each other.

[0020] The term "recycled cotton fibers" in the following description indicates staple fibers of cotton deriving from the mechanical treatments, e.g. opening and sorting, of yarns and fabrics; a possible way to identify these fibers is by measuring their average fiber length. In embodiments, the fiber average length L(n), as measured with DIN 53805:1980-06, is in the range of 6 to 16 mm.

[0021] The term "synthetic fiber" indicates artificial fibers, in particular fibers made from polymers synthesized from chemical compounds - see definition in ASTM D123, option (1) of "manufactured fiber". Synthetic fibers are thus polymeric non-cellulosic fibers. Synthetic fibers are usually produced in filament (i.e. continuous) form. Synthetic staple fibers are commercially available and can be obtained by cutting the synthetic filaments. Preferred synthetic staple fibers are selected from polyester and polyamide, preferably they are polyester fibers.

[0022] In preferred embodiments the polyester for the staple fibers is selected from a semi-dull, dull or full-dull polyester; these polyester are known and commercially available, e.g. they contain TiO 2 to make the filament dull. In preferred embodiments the polyester filaments for the staple fibers are not texturized.

[0023] According to the invention the yarn is a core spun yarn having a core comprising or consisting of polyester filaments. The total linear density of the polyester filaments is in the range of 22.2 to 333.3 dtex (20 to 300 denier). The number of filaments is in the range of 6 to 288, while the total count for the final yarn is in the range of 1181 to 98.4 dtex (5 / 1 to 60 / 1 Ne).

[0024] In preferred embodiments, the ratio by weight of the polyester filaments to the total weight of the yarn is in the range of 30% to 70%, preferably 40% to 60%.

[0025] According to the invention, a yarn comprises a filament core and a staple fiber sheath. The staple fiber sheath is made of first and second fibers. The first fibers are natural cellulosic fibers, preferably cotton staple fibers having an average length in the range of 6 to 16 mm, even more preferably about 10 mm. These are the typical average lengths of recycled cotton fibers.

[0026] The second fibers are synthetic fibers, i.e. polymeric, non-cellulosic fibers. In preferred embodiments, the second fibers are made from polyester or polyamide.

[0027] The preferred average length for the second fibers is greater than average length of the first fibers, preferably the length is in the range between 25 mm and 40 mm, more preferably between 28 mm and 36 mm. High quality yarns have been achieved in particular with second fibers around 32 mm, such as in the range between 30 and 34 mm.

[0028] At least 95% of the fibers of the sheath are the above-mentioned first and second fibers, wherein the weight ratio of the first fiber to the second fibers is between 65 / 35 by weight to 35 / 65 by weight, preferably said ratio being in the range 40 / 60 by weight to 60 / 40 by weight.

[0029] In a preferred embodiment the first fibers are about 50% by weight of the blend and the second fibers are 50% by weight of the blend.

[0030] The blend of the fiber sheath as well as the presence of one or more polyester filaments in the core provides for the claimed fibers and filament to be workable into a yarn that is, in turn, workable into a fabric that has excellent properties on the market. In particular, the resulting yarn can be ring spun, that is a process that was previously not possible to perform in yarn having a high percentage of short fibers, such as recycled cotton fibers.

[0031] The elongation at break of the polyester filaments of the filament core is between 5% and 15%, preferably between 5% and 12%, even more preferably between 10 and 12%, when tested with DIN ISO 2062.

[0032] The claimed elongation at break is the elongation of all the filaments of the core, tested together.

[0033] In particular, it has been found that if the elongation of the core is low (i.e. less than 15% measured by DIN ISO 2062 as above discussed), the yarn production and the weaving processes are easier and much more efficient. In particular, in these embodiments the elongation of the core is usually similar to the elongation of the sheath.

[0034] In fact, if the final yarn is tensioned, a high elongation (i.e. more than 15% or more than 20%) polyester core may cause slippage of the sheath from the core and cause a breakage in the staple fiber sheath while the core filaments do not break.

[0035] The use of low elongation polyester filament(s) in the core contributes in avoiding the above-mentioned problems; indeed when a yarn according to the invention breaks, there is no or very limited slippage of the sheath with respect to the core because the core filaments also are broken. The broken yarn can thus be spliced in a conventional way.

[0036] Low elongation polyester filaments are known in the art and are commercially available. They may be obtained in different ways. A possible solution may be to provide a draft during a texturing step of POY polyester filaments. Such a draft is preferably between 1.7 and 2.5, more preferably between 1.8 and 2.1.

[0037] The polyester filaments are in fact preferably textured and, as mentioned, draft can be applied during texturing process, usually by also heating the filaments during the drafting step in the texturing process.

[0038] According to an aspect, the amount of the polyester filaments of the core is between 30% and 70% of the weight of the yarn, more preferably between 40% and 60%. The above percentage relates to the total count of polyester filaments, i.e. to the total sum of the count of the filaments.

[0039] According to an aspect, the total count of the polyester filaments is between 55.5 and 333.3 dtex (50 and 300 den), preferably between 88.8 and 222.2 dtex (80 and 200 den), more preferably between 111.1 and 166.6 dtex (100 and 150 den).

[0040] As mentioned, the second fibers of the sheath have an average length that is greater than the average length of the first fibers. Generally, the average length of the second fibers is more than 200% than the average length of the first fibers, preferably more than 250% of the length of the first fibers. In other words, the ratio of average length of the second fibers to the average length of the first fibers is preferably greater than 2.0, preferably greater than 2.5.

[0041] The fiber length can be measured via suitable machines such as Uster Afis Pro 2 or TexTechno FCS-Fibro test, with methods know in the art such as, AFIS (advanced fiber information system) according to DIN 53805:1980-06, or ASTM D1447.

[0042] In order to detect the fiber nature and measure the fiber length of the first and second fibers in the sheath of a finished yarn, the sheath should be initially separated from the core and de-structured into a plurality of fibers. This can be done e.g. via un-twisting the yarn (i.e. applying a twist opposite to the one of the yarn, such as S-twisting a Z-twisted yarn). This can be done manually or by a twisting machine. Subsequently, the fiber length can be tested e.g. via DIN 53805 or ASTM D1447, via an USTER AFIS PRO 2 or a Textechno FCS-Fibrotest. In a histogram of the fibers the amount of short fibers can be detected; similarly synthetic staple fibers generally always have substantially a same length so that they can be seen in histograms.

[0043] It is also noted that, in the sheath, the first fibers can be separated from the second fibers via known chemical or biological methods. As an example, to isolate the natural cellulosic fibers, known methods can be used to dissolve the synthetic fibers, while leaving substantially intact the first fibers, in particular when the first fibers are cotton fibers and the second fibers are polyester or polyamide fibers.

[0044] Similarly, it is possible to isolate the synthetic fibers from the natural cellulosic fibers, e.g. via known enzymatic processes that degrade the cellulose, usually transforming it into glucose.

[0045] Fibers may be also manually separated to be tested.

[0046] Properties, such as the length, of the first fibers or the second fibers can thus be tested.

[0047] Preferably, in order to provide a better interaction between the first fibers and the second fibers of the sheath, the length of the second fibers is not too much greater than the length of the first fibers. A preferred ratio L(n) second / L(n) first between the average length L(n) of the second fibers versus the average length L(n) of the first fibers is between 1.5 and 3.8, more preferably between 2 and 3.5. The best results have been found to occur when the above discussed ratio is between 2.5 and 3.3.

[0048] The yarn according to one or more of the preceding aspects can be used to produce a fabric, in particular a woven fabric and a garment comprising such a woven fabric. It is in particular possible to produce a fabric wherein yarns according to the invention are used both in warp and weft direction.

[0049] It has been found that such a fabric, and in particular a garment made from such a fabric, can be made without using virgin (i.e. conventional) cotton, while having similar wearability properties (hand, softness, etc.) as well as optical properties (brightness, dyeability, etc.) with respect to a fabric made from conventional cotton yarns. Also, compared with fabrics made from conventional cotton yarns, the fabric according to the present invention shows similar mechanical properties, such as similar tensile strength, as well as better abrasion properties. Thus, a fabric made of yarns according to the invention can be effectively used in the production of apparels in the field of workwear and medical industry garments.

[0050] As above mentioned, the core may consist of a plurality of polyester filaments, in embodiments the core may comprise also one or more elastic filaments. Preferably elastolefin filaments are used as elastic filaments in order to withstand the heavy industrial washing cycles to which work apparels and medical apparels are subjected. Preferred elastolefin filaments are known and commercially available in the market as XLANCE.

[0051] The elastolefin filaments are usually in the range of 33.3 to 177.7 dtex (30 to 160 den), preferably in the range 44.4 to 155.5 dtex (40 to 140 den); said filaments are usually drafted at least 2.0 times, more preferably about 3.0 times before the sheath is applied, so that their count in the yarn would be smaller (with a 3.0 draft the dimensions would be between about 14.4 and 52.2 dtex (13 and 47 den)). In particular, in embodiments, the elastolefin filaments have a draft between 2.0 and 4.0, more preferably of at least 2.5, most preferably of about 3.0.

[0052] In other embodiments, the draft of the elastolefin filament(s) is greater than 4.0, preferably comprised between 4.0 and 6.0, more preferably comprised between 4.0 and 5.0.

[0053] The present invention also relates to a method for producing a yarn comprising the steps of: a) Selecting a filament core, comprising a plurality of polyester filaments, wherein the elongation at break of the polyester filaments of the filament core is in the range of 5% to 15%, preferably between 10% and 12%, when tested with DIN ISO 2062; b) Selecting first fibers that are natural cellulosic fibers; c) Selecting second fibers that are synthetic fibers; d) Providing a staple fiber sheath, comprising at least 95% by weight of a blend of said first fibers and said second fibers, wherein the weight ratio of said first fibers to said second fibers is in the range of 65 / 35 to 35 / 65, preferably said ratio being about 50 / 50; Combining said filament core and said staple fiber sheath, preferably via ring spinning so as to obtain a core-sheath yarn.

[0054] The present invention also relates to a method for producing a yarn comprising the steps of: a) Selecting a filament core, comprising a plurality of polyester filaments, wherein the elongation at break of the polyester filaments of the filament core, measured according to DIN ISO 2062, is in the range of 5% to 15%, more preferably between 10% and 12%; b) Selecting a staple fiber sheath wherein at least 95% of the sheath is made of first fibers and second fibers, said first fibers being natural cellulosic fibers, preferably having an average length between 6 and 16 mm, said second fibers being synthetic fibers, preferably having an average length greater than said first fiber and preferably between 25 and 40 mm.

[0055] As mentioned, recycled materials are preferably used, so that the first fibers of the sheath are recycled cotton fibers and / or the polyester filaments is made from recycled polyester.

[0056] According to a preferred aspect, dyeing is carried out in a single bath, wherein both the dyes for the cotton fibers and for the synthetic fibers are present.

[0057] The above discussed process provides for a good quality and uniform dyeing of the yarn, even if part of the sheath is made of polyester fibers.

[0058] According to a preferred aspect, the fabric is stabilized, usually during sanforizing, by passing along rolls that are curved, i.e. arched. As a result, the rolls will impart a different force (at least with different directions) to different parts of the fabric. In view of that, a twisting (torque) force is applied to the fabric, that prevents, or at least limits, movement of the yarns that tend (in particular in diagonal weaves, such as twill), to impart a shear force to the final fabric, thus causing a movement of one lateral end of the fabric with respect to the other in warp direction.Detailed description of the invention

[0059] Exemplary and non limiting embodiments will be now discussed.

[0060] For easiness of discussion, in the following discussion, reference will be made to recycled cotton fibers as the first fibers of the sheath. However, unless specified, the following description applies to other natural cellulosic fibers as first fibers of the sheath. The second fibers will be referred as synthetic fibers.

[0061] In preferred embodiments, a yarn comprises a core provided with polyester filaments, and possibly also with elastolefin filaments; the sheath is made of staple fibers, comprising recycled cotton fibers and polyester fibers.

[0062] The core polyester filaments are usually within 30% to 70% of the total weight of the yarn, usually between 40 and 60% of the yarn. The total count of the polyester filaments is typically between 55.5 and 333.3 dtex (50 and 300 den), while the most preferred embodiments use a total amount of polyester that is between 111.1 and 166.6 dtex (100 and 150 den).

[0063] The elongation at break of the polyester filaments (i.e. of the polyester component of the core) is between 5 and 15%, more preferably between 8% and 12%, even more preferably between 10% and 12%. The test for elongation at break measurement is DIN ISO 2062.

[0064] As a comparison, a traditional polyester yarn, initially produced with the same method but without the claimed draft, will be heavier (i.e. as having a bigger count) and a greater elongation at break when tested with the same test, above 15%, usually in the range of about 17% - 25%.

[0065] Elastolefin filament(s), if present, is usually highly drafted (with a draft of more than 2.0, usually greater than 3.0, possibly between 4.0 and 6.0), and is present in low weight amount in the yarn, and is thus usually about 5 to 15% of the total weight of the yarn. It has been found that high draft (greater than 4.0) reduces the occurrence of breakings and thus provides for an easier working of the elastolefin into a yarn, and an easier weaving of the yarn comprising elastolefin filament(s) into a fabric.

[0066] According to an aspect, the core polyester filaments and the elastolefin filaments are combined together at least at a plurality of connecting points, in a known way, and preferably by means of intermingling, twisting or mechanical co-extrusion. As mentioned, the elastolefin filaments are preferably drafted before being combined with the core polyester filaments.

[0067] In preferred embodiments, the core polyester filaments and the elastolefin filament(s) are connected together in a continuous or substantially continuous way by "mechanical co-extrusion" of the filaments, preferably in a tensioned condition. During such co-extrusion, also known as co-feeding, two (or more) bundles of fibers (in a tensioned state) are forced (fed together) through a restriction where the fibers attach together to such a degree that they remain attached also after exiting the restriction.

[0068] The sheath is composed of staple fibers. At least 95% of the staple fibers of the sheath are a blend of recycled cotton fibers 35% to 65% by weight of the blend being made of the recycled cotton fibers, while the other fibers of the blend are synthetic fibers.

[0069] Preferred embodiments have about 50% of recycled cotton fibers and 50% of synthetic fibers. The remaining portion (up to 5%), if present, may be other staple fibers.

[0070] The average length of the recycled cotton fibers is between 6 and 16 mm.

[0071] Usually, more than 90% (in number) of the recycled cotton fibers are below 30 mm. Embodiments are possible where 50% of the fibers is below 15 mm.

[0072] The synthetic fibers are longer than the recycled cotton fibers, in order to provide strength to the sheath. However, as mentioned, it is preferred that they are not too much longer than the recycled cotton fibers, in order to promote coupling and blending of the fibers of the sheath.

[0073] The synthetic fibers have an average length greater than 25 mm, preferably greater than 30 mm, usually between 28 mm and 36 mm. In particular, it has been noted that too long synthetic fibers may lower the quality of the final yarn. In view of that, the most preferred embodiments use around 32 mm synthetic fibers, such as e.g. between 30 mm and 34 mm. Typically, synthetic staple fibers have uniform length, being produced via cutting of synthetic filaments.

[0074] The synthetic fibers are preferably chosen so that their average length is between 1.5 times and 3.8 times the average length of the recycled cotton fibers, preferably between 2 and 3.5 times, even more preferably between 2.5 and 3.3 times the average length of the recycled cotton fibers.

[0075] Preferred synthetic fibers are polyester and polyamide fibers more preferably polyester fibers.

[0076] In order to provide good mechanical properties to the final yarn so that it can be used to make fabrics for heavy duty applications such as workwear and medical wear, it is preferred to use high tenacity synthetic fibers. High tenacity synthetic fibers are fibers, preferably polyester staple fibers, having tenacity greater than 5.4 g / dtex (6 g / den), preferably greater than 6.3 g / dtex (7 g / den), more preferably greater than 7.2 g / dtex (8 g / den). High tenacity synthetic staple fibers can be obtained via cutting a high tenacity synthetic filament into multiple parts (i.e. fibers), the synthetic filament having tenacity greater than 5.4 g / dtex (6 g / den), preferably greater than 7.2 g / dtex (8 g / den). In addition to that, the tenacity is also usually equal to or lower than 9 g / dtex (10 g / den).

[0077] In order to test the tenacity of the synthetic fibers, they can be first isolated from the cotton fibers, e.g. via mechanical separation or via degradation (via enzymatic process), and subsequently tested with machine and methods known in the art.

[0078] The synthetic fibers and the recycled cotton fibers are mixed to form a blend that is at least 95% by weight of the fibers of the sheath; preferably the blend is 100% by weight of the sheath, i.e. the sheath consists of such a blend. As discussed, the ratio (in weight) between the synthetic fibers and the recycled cotton fibers is in the range between 35 / 65 and 65 / 35.

[0079] Apparatuses for yarn production are known in the art, and are here not discussed in detail.

[0080] The production method of the yarn according to the present invention comprises providing a core, by drawing polyester filaments, and possibly combining them with elastolefin filaments.

[0081] The core is then combined with the sheath, that is usually provided in form of one or more rovings of staple fiber.

[0082] Synthetic staple fibers can be obtained by cutting a continuous filament, e.g. a polyester or polyamide filament. As mentioned, in a preferred embodiment, the original filament has a tenacity greater than 5.4 g / dtex (6 g / den), preferably greater than 7.2 g / dtex (8 g / den). A suitable way of measuring tenacity is by applying ASTM D3822.

[0083] The obtained product is then spun into a yarn, preferably via ring spinning.

[0084] The obtained yarn can be used in a textile article and in particular, a plurality of yarns according to the invention can be used in a fabric for an article in the workwear of medical industry field. In particular they can be used as warp and / or weft yarns of the fabric.

[0085] According to a preferred aspect, dyeing is carried out in a single bath, wherein both the dyes for the natural cellulosic fibers and for the synthetic fibers are present. In particular, dyeing is preferably carried out in a single bath when the sheath comprises a blend of cotton and polyester fibers. In a preferred embodiment, a single bath comprises VAT dyes (e.g. indanthrene) and disperse dyes to dye at the same time the cotton staple fibers and the polyester staple fibers of the sheath of the yarn. The yarns can be dyed before or after being part (e.g. by weaving) of a fabric.

[0086] It is in particular an object of the invention to provide a fabric, wherein all the warp and weft yarns are yarns according to the invention. A preferred embodiment is provided with warp yarns without elastolefin filaments, and weft yarns with elastolefin filament(s). Embodiments of fabrics wherein no yarn is provided with elastolefin filaments, or wherein both warp and weft yarns are provided with elastolefin filaments are however within the scope of the invention.

[0087] As mentioned, a fabric obtained with the yarns according to the present invention is provided with improved abrasion performances with respect to fabrics made with standard cotton yarns and recycled cotton yarns.

[0088] Fiber composition and length can be tested according to the above discussed methods. They can be tested both before being woven, and after being woven, by removing them from a fabric, with similar results.

[0089] In the following, an example of a fabric produced with yarns according to the invention is discussed: Weave: 2 / 1 Z twill Weight: 195 g / m 2< Width: 140 cm Dye = VAT + disperse dye Fabric composition = recycled PES: 46% (w / w), PES (non recycled): 24% (w / w), recycled cotton: 24% (w / w), elastolefin: 6% (w / w) Warp count = 295.2 dtex (20 / 1 Ne) Warp core = 166.6 dtex (150 den) recycled polyester Warp sheath = 50% w / w recycled cotton and 50% w / w polyester Warp composition (w / w) = 56.4% recycled PES, 21.8% PES, 21.8% recycled cotton Weft Count = 328 dtex (18 / 1 Ne) Weft core = 111.1 dtex (100 den) recycled polyester + 155.5 dtex (140 den) elastolefin Weft Composition = 33.9% recycled PES, 23.5% PES, 23.5% recycled cotton, 19.1% elastolefin Weft sheath = 50% w / w recycled cotton and 50% w / w polyester

[0090] The above exemplary fabric was tested, providing the following results: Width (ISO 22198 - unwashed) = 140 cm Weight (BS EN 12127 - unwashed) = 195 g / m2 (min = -5%; max = +5%) Dimensional stability to washing (ISO 15797 -5x75°C) = warp: -1% (min: -3%, max 0%), weft: -0.5% (min: -3%, max: 0%) Stretch (ASTM D3107): weft: 15.2% Growth (ASTM D3107): weft: 2% Color Fastness to Crocking (BS EN ISO 105:X12) = dry rating: 4.5 Color Fastness to Drycleaning (BS EN ISO 105:D01) = Color change rating: 3.5 Color Fastness to perspiration (BS EN ISO 105:E04 - Acid) = Color change rating: 4.5, Cotton rating: 4.5, polyester rating: 4.5 Color Fastness to perspiration (BS EN ISO 105:E04 - Alcaline) = Color change rating: 4.5, Cotton rating: 4.5, polyester rating: 4.5 Color Fastness to washing (ISO 105 C06-E1S -95°C) = Color change rating: 4, Cotton rating: 3.5, polyester rating: 3 Pilling resistance (ISO 12945-2 -5000 Rev. - 5x75°C) = rating: 3.5 Tensile Strength (ISO 13934-1) = warp: 750N, weft: 350N Wrinkle recovery (AATC 124 - 3x75°C) = rating: 3.5

Claims

1. A yarn comprising a filament core including polyester filaments and a staple fiber sheath, said staple fiber sheath comprises at least 95% by weight, preferably consists of 100% by weight, of a blend of first fibers and second fibers, wherein said first fibers are natural cellulosic fibers and said second fibers are synthetic fibers, characterized in that: the weight ratio of said first fibers to said second fibers is in the range of 65 / 35 to 35 / 65, preferably said ratio being in the range 40 / 60 to 60 / 40, more preferably about 50 / 50; wherein the elongation at break of the polyester filaments of the filament core, measured according to DIN ISO 2062, is in the range of 5% to 15%, preferably between 10% and 12%.

2. The yarn of claim 1, wherein the average length of the natural cellulosic fibers is comprised between 6 and 16 mm.

3. The yarn of claim 1 or 2, wherein the average length of the synthetic fibers is between 25 and 40 mm.

4. The yarn of any preceding claim, wherein the first fibers are cotton fibers.

5. The yarn of any preceding claim, wherein the second fibers are polyester or polyamide fibers.

6. The yarn of any preceding claim, wherein the second fibers have tenacity higher than 5.4 g / dtex (6 g / den), preferably more than 6.3 g / dtex (7 g / den), more preferably greater than 7.2 g / dtex (8 g / den), said tenacity being measured according to ASTM D3822.

7. The yarn of any preceding claim, wherein the core comprises at least one elastolefin filament.

8. The yarn of claim 7, wherein the at least one elastolefin filament has a draft between 4.0 and 6.0.

9. A method for producing a yarn comprising the steps of: - selecting a filament core, comprising a plurality of polyester filaments, wherein the elongation at break of the polyester filaments of the filament core is in the range of 5% to 15%, preferably between 10% and 12%, when tested with DIN ISO 2062; - selecting first fibers that are natural cellulosic fibers; - selecting second fibers that are synthetic fibers; - providing a staple fiber sheath, comprising at least 95% by weight of a blend of said first fibers and said second fibers, wherein the weight ratio of said first fibers to said second fibers is in the range of 65 / 35 to 35 / 65, preferably in the range 40 / 60 to 60 / 40, more preferably about 50 / 50; - combining said filament core and said staple fiber sheath, preferably via ring spinning, so as to obtain a core-sheath yarn.

10. The method of claim 9, wherein the first fibers of the sheath are recycled cotton fibers.

11. The method of claim 9 or 10, wherein the polyester filaments of the core are made from recycled polyester.

12. The method of any claim 9 to 11, wherein the second fibers of the sheath are obtained via cutting of a filament into staple fibers, the filament having tenacity higher than 5.4 g / dtex (6 g / den), preferably higher than 6.3 g / dtex (7 g / den), more preferably higher than 7.2 g / dtex (8 g / den), said tenacity being measured according to ASTM D3822.

13. The method according to any claim 9 to 12 wherein the yarn is dyed in a bath where two different dyes are present.

14. The method according to claim 13, wherein the first fibers are cotton fibers, and wherein the second fibers are polyester fibers, and the yarn is dyed in a bath preferably comprising a VAT dye and a disperse dye.