Method for increasing the elastic properties of a yarn

Abstract

The present invention relates to a method for increasing the elastic properties of a yarn obtained by a melt spinning process comprising a step 1°) in which the yarn undergoes relaxation at a temperature ranging from approximately 70°C to approximately 110°C.

Description

[0001] DESCRIPTION

[0002] TITLE: Method for increasing the elastic properties of a thread

[0003] The present invention relates to a method for increasing the elastic properties of a recyclable yarn, said yarn having an initial elasticity. The yarn obtained by the method according to the invention can be used in particular for the manufacture of textiles and footwear.

[0004] Elastic textiles have been known for many years. Such textiles can be used, for example, in the sports field, to make clothing such as sports tights, socks, swimsuits, but also shoes. The elasticity of these textiles is generally achieved by means of elastane threads, which can, for example, be present in the textile in a content ranging from 2 to 50% of the total composition of threads and / or fibers of the textile. Elastane is a segmented polyurethane in the form of a copolymer of a soft segment and a hard segment. Elastane thread has a high level of stretch, or elongation: this thread can, for example, be stretched to more than 600% of its original length before breaking.Elastane yarn also has a high recovery power, or elastic return: thus, after being stretched several times, this yarn returns, when the stretching stress is released, to a length very close to its original length, for example a length ranging from 90% to 100% of its original length.

[0005] However, there are several disadvantages to the production and use of spandex yarn.

[0006] According to ADEME (French Environment and Energy Management Agency), the production of 1 kg of elastane yarn generates 21 kg of CO2 equivalent (ADEME Base Impact V2.01). The production of elastane yarn therefore has a relatively high negative environmental impact.

[0007] Furthermore, since elastane is a thermosetting material, it degrades before being melted. Elastane cannot therefore be thermally recycled. Chemical recycling of elastane could be considered, but the necessary use of solvents in such a process generates too high an environmental impact for it to seem reasonable to implement it.

[0008] Therefore, to date in Europe, textiles containing elastane are generally incinerated or landfilled. The impact of these processes on the environment is damaging. Thus, still according to ADEME, 1 kg of incinerated textiles emits 0.4 kg of CO2 equivalent and 1 kg of buried textiles emits 2.2 kg of CO2 equivalent (ADEME Base Impact V2.01).

[0009] Thus, in view of current environmental considerations, there remains a need for recyclable elastic textiles. In this regard, there remains a need for recyclable elastic yarns, which would have elastic properties comparable to, or even superior to, those of existing non-recyclable elastic yarns such as elastane yarns. These recyclable elastic yarns should also be able to be combined with non-elastic yarns that are also recyclable, in order to produce fully recyclable elastic textiles, regardless of the proportion of elastic yarns within said textiles.

[0010] The present invention aims to address this need by providing a method for increasing the elastic properties of a recyclable yarn obtained by a melt extrusion process.

[0011] The present invention relates to a method for increasing the elastic properties of a yarn obtained by a melt spinning process comprising the following steps:

[0012] A) an extruder is fed with granules of a thermoplastic copolymer, the hardness of the copolymer measured according to standard 7619-1 ranging from 10 to 61 ShD, in order to obtain by extrusion a molten elastomer of said copolymer,

[0013] B) the molten elastomer obtained in step A) is spun within a spinneret of a spinning pack in order to obtain a thread of the copolymer,

[0014] C) the copolymer yarn obtained in step B) is subjected at the outlet of the die to cooling to a temperature ranging from approximately 10°C to approximately 40°C, preferably ranging from approximately 20°C to approximately 25°C,

[0015] D) the yarn from step C) is subjected to preliminary drawing at the temperature of step C),

[0016] E) the wire from step D) is subjected to hot drawing at a temperature ranging from approximately 40°C to approximately 125°C, preferably ranging from approximately 45°C to approximately 90°C,

[0017] F) the wire from step E) is subjected to cold drawing at a temperature ranging from approximately 10°C to approximately 40°C, preferably ranging from approximately 20°C to approximately 25°C,

[0018] G) optionally, the yarn from step F) is subjected to relaxation at a temperature ranging from approximately 10°C to approximately 40°C, preferably ranging from approximately 20°C to approximately 25°C,

[0019] H) optionally, the yarn from step F) or step G) is subjected to at least one post-stretching comprising hot stretching, for example at a temperature ranging from 30°C to 70°C, followed by cold relaxation, for example at a temperature ranging from 20°C to 25°C,

[0020] I) optionally, the yarn from one of steps F), G) or H) is wound on an initial storage winder, without drawing and without relaxation, said method being characterized in that it comprises a step 1°) in which the yarn obtained in any one of steps F) to I) is subjected to relaxation at a temperature ranging from approximately 40°C to approximately 110°C.

[0021] As will appear from the description and examples below, the method according to the invention makes it possible to improve the elastic properties of a wire manufactured according to at least steps A) to F) above. In particular, the method according to the invention makes it possible to increase the deformation at break of such a wire.

[0022] The method according to the invention also makes it possible to improve the extensibility (more elongation at break) of a textile comprising a yarn manufactured according to at least steps A) to F) above. The method according to the invention makes it possible in particular to improve the elastic modulus (i.e. the force) necessary to stretch or relax such a textile. The method according to the invention thus makes it possible to improve the level of elasticity of such a textile in all directions (warp direction, weft direction and diagonal direction for example for a knit). The method according to the invention also makes it possible to give such a textile more holding properties.

[0023] In one embodiment, the thermoplastic copolymer is a copolymer with polyamide blocks and polyether blocks, the polyamide blocks being chosen from PA 11, PA 12, PA 1010, PA 1014, their copolymer and their mixture, the polyether blocks being blocks derived from polytetramethylene glycol, the hardness of the copolymer measured according to standard 7619-1 being between 22 and 61 ShD, preferably between 22 and 55 ShD, more preferably between 22 and 40 ShD. Preferably, the polyamide blocks are chosen from PA 11, PA 12, their copolymer and their mixture. More preferably, the polyamide blocks are PA 11 blocks.

[0024] In another embodiment, the thermoplastic copolymer is selected from thermoplastic elastomers (TPE), thermoplastic polyurethane elastomers, thermoplastic polyolefin elastomers (POE), polyphthalamides (PPA), polyether-esteramide based elastomers, thermoplastic copolyester elastomers, copolyester (ether) elastomers and mixtures thereof, the hardness of the copolymer measured according to standard 7619-1 ranging from 10 to 57 ShD, preferably ranging from 10 to 45 ShD, preferably ranging from 10 to 35 ShD, more preferably is about 22 ShD. Preferably, the copolymer is chosen from copolymers comprising flexible blocks and rigid blocks, the flexible blocks being polyether blocks derived from polytetramethylene glycol (PTMEG), the rigid blocks being chosen from diisocyanate blocks and polyester blocks.Advantageously, the copolymer is chosen from copolymers whose flexible blocks are polyether blocks derived from polytetramethylene glycol and whose rigid blocks are polyester blocks. For example, the copolymer with polyether blocks and polyester blocks is the compound of formula (I) below:.

[0025] [Chem 1] in which y=0.3x.

[0026] In one embodiment, step 1°) of the method according to the invention is carried out at a temperature ranging from approximately 80°C to approximately 100°C, preferably ranging from approximately 90°C to approximately 100°C.

[0027] In one embodiment of the method according to the invention, the yarn obtained at the end of steps A) to F) and H) is treated with hot air at 70°C.

[0028] In one embodiment of the method according to the invention, the yarn obtained at the end of steps A) to F) and H) is treated with hot air at 100°C.

[0029] In one embodiment of the method according to the invention, during step 1°), the wire from step F) is made to pass over a first roller having a linear speed W1 then over a second roller having a linear speed W2, the linear speed W2 being strictly lower than the linear speed W1. In such an embodiment, the first roller may for example be heated to a temperature ranging from approximately 40°C to 125°C, preferably from 40°C to 90°C, preferably from 45°C to 70°C.

[0030] In another embodiment of the method according to the invention, step 1°) comprises the following steps:

[0031] 1 °)a1), the yarn from step F) is i) wound onto a perforated winding roller, the applied winding tension being chosen to allow the yarn to shrink when it is wound onto the winding roller, then

[0032] 1 °)a2) the winding roller on which the thread is wound is placed in a steam chamber or in a boiling water bath.

[0033] In another embodiment of the method according to the invention, during step 1°) the wire from step I) is unwound from the initial storage winder at a first linear speed W3, is made to pass through a heating medium, then is wound onto a final storage winder at a linear speed W4, the linear speed W4 being strictly lower than the linear speed W3.

[0034] In another embodiment of the method according to the invention, the yarn resulting from one of steps F) to I) being present within a textile, step 1) comprises the treatment of said textile at a temperature ranging from approximately 70°C to approximately 110°C. For example, said textile may be subjected to one or more of the following treatments:

[0035] Washing, Stripping,

[0036] Dyeing.

[0037] The method according to the invention is intended to be applied to a yarn obtained by a melt spinning process comprising steps A) to F) above, and optionally steps G) to I) above. These steps are for example carried out by means of a spinning machine comprising for example an extruder, a spinning metering pump, a spinning pack comprising at least one die, a cooling system, at least one delivery roller and at least one stretching roller.

[0038] In the present application, yarn means any fiber of infinite length. In particular, the yarn may be in the form of monofilaments or multifilaments.

[0039] In the present application, the term glass transition temperature means the temperature below which a polymer is in the glassy (solid) state and above which said polymer exhibits a rubbery state (plastic solid behavior).

[0040] In this application, the term "textile" means any material made from fibers or yarns. In particular, the textile may be an arrangement of fibers and / or yarns in the form of a knit, a woven, a non-woven, a braid and combinations thereof.

[0041] The process for manufacturing the yarn intended to be used in the method according to the invention is based on the melt spinning technique using the extrusion-spinning of a molten polymer within an extruder and then a spinning pack. Once extruded, the yarn undergoes a succession of drawings, which may be cold or hot. In particular, the extruded yarn undergoes at least one preliminary cold drawing, at least one hot drawing and at least one cold drawing subsequent to the hot drawing. Each of these drawings, namely the preliminary cold drawing, the hot drawing and the cold drawing subsequent to the hot drawing, may optionally consist of several partial drawings.

[0042] In the present application, "upstream" means the direction towards the place of "birth" or extrusion of the yarn (spinning pack) and "downstream" means the opposite direction, in other words the direction towards the place of storage of the elastic yarn, once the yarn has undergone all the desired stretching.

[0043] Thus, in a first step of the process, an extruder is fed with granules of a thermoplastic copolymer. This step makes it possible to obtain by extrusion a molten elastomer of said copolymer.

[0044] In one embodiment, the thermoplastic copolymer is a copolymer with polyamide blocks and polyether blocks, the polyamide blocks being chosen from PA 11, PA 12, PA 1010, PA 1014, their copolymer and their mixture, the polyether blocks being blocks derived from polytetramethylene glycol, the hardness of the copolymer measured according to standard 7619-1 being between 22 and 61 ShD, preferably between 22 and 55 ShD, more preferably between 22 and 40 ShD. Preferably, the polyamide blocks are chosen from PA 11, PA 12, their copolymer and their mixture. More preferably, the polyamide blocks are PA 11 blocks.

[0045] The nomenclature used to define polyamides is described in ISO 1874-1:2011 "Plastics - Polyamide (PA) materials for molding and extrusion - Part 1: Designation", particularly on page 3 (tables 1 and 2) and is well known to those skilled in the art.

[0046] It is further specified that the expressions "between. . . and. . ." and "from. . . to. . ." used in this description must be understood as including each of the limits mentioned.

[0047] The word "polyamide" covers both homopolyamides and copolyamides.

[0048] A copolymer that can be used to manufacture the thread intended to be used in the method according to the invention is the product sold under the trade name “PEBAX® RNEW 35R53 SP 01” by the company Arkema. This elastomeric copolymer has the following characteristics: a density of 1020 kg / m 3 , measured according to ISO 1183, a hardness of 25 shore D, at 15 seconds, measured according to ISO 7619-1, a melting point of 135°C, measured according to ISO 1 1357-1 / -3, a content of bio-sourced component, such as polyamide PA 11, of 29%, measured according to ASTM D6866.

[0049] Another copolymer that can be used to manufacture the thread intended to be used in the method according to the invention is the product sold under the trade name “PEBAX® 7033 SP 01” by the company Arkema. This elastomeric copolymer has the following characteristics: a density of 1010 kg / m 3 , measured according to ISO 1183, a hardness of 61 shore D, at 15 seconds, measured according to ISO 7619-1, a melting point of 172°C, measured according to ISO 1 1357-1 / -3.

[0050] Another copolymer that can be used to manufacture the thread intended to be used in the method according to the invention is the product sold under the trade name “PEBAX® 2533 SA 01” by the company Arkema. This elastomeric copolymer has the following characteristics: a density of 1000 kg / m 3, measured according to ISO 1183, a hardness of 22 shore D, at 15 seconds, measured according to ISO 7619-1, a melting point of 134°C, measured according to ISO 1 1357-1 / -3. In another embodiment, the thermoplastic copolymer is selected from thermoplastic elastomers (TPE), thermoplastic polyurethane elastomers, thermoplastic polyolefin elastomers (POE), polyphthalamides (PPA), polyether-esteramide-based elastomers, thermoplastic copolyester elastomers, copolyester (ether) elastomers and mixtures thereof, the hardness of the copolymer measured according to standard 7619-1 ranging from 10 to 57 ShD, preferably ranging from 10 to 45 ShD, preferably ranging from 10 to 35 ShD, more preferably is about 22 ShD. Such hardness makes it possible to obtain a thread having good elastic properties.

[0051] Thermoplastic polyurethane (TPU) elastomers include the following types: (TPU-Polyester), (TPU-Polyether), (TPU-Polycarbonate), (TPU-Polycaprolactone) and (TPU-Ester / Ether). Thermoplastic copolyester elastomers include TPC-ET elastomers, TPC-ES elastomers and TPC elastomers.

[0052] Elastomers are copolymers composed of a succession of rigid polymer blocks, hereinafter referred to as rigid blocks, and flexible polymer blocks, hereinafter referred to as flexible blocks. The rigid blocks may, for example, be chosen from polyester blocks and diisocyanate blocks. The flexible blocks may, for example, be polyol blocks. The polyols may be based on polyester, polyether ester, polycarbonate, or polyether.

[0053] Thus, preferably, the copolymer is chosen from copolymers comprising flexible blocks and rigid blocks, the flexible blocks being polyether blocks derived from polytetramethylene glycol (PTMEG), the rigid blocks being chosen from diisocyanate blocks and polyester blocks.

[0054] More preferably, the copolymer is chosen from copolymers whose flexible blocks are polyether blocks derived from polytetramethylene glycol and whose rigid blocks are polyester blocks.

[0055] A polyether block and polyester block copolymer usable for the manufacture of a yarn intended to be used in the method according to the invention is a compound of the following formula (I):

[0056] [Chem 1] in which y=0.3x. In this formula (I), the soft blocks are the polyether blocks which are themselves poly(tetramethylene ether) glycol (hereinafter referred to as PTMEG) blocks with a degree of polymerization DP of 27 ± 2 and a molecular mass of 1950 ± 150 g / mol, and the rigid blocks are polyester-based, which are themselves polybutylene terephthalate (hereinafter referred to as PBT) blocks with a molecular mass of approximately 875 ± 100 g / mol.

[0057] Thus, the structure of the copolymer of formula (I) can also be written as follows:

[0058] -(PBT)3-PTMEG27-(PBT)4-PTMEG27-(PBT)3-PTMEG27-

[0059] The copolymers that can be used to manufacture the yarn intended to be used in the method according to the invention may have a melting point ranging, for example, from approximately 150°C to approximately 222°C. The melting point of the copolymer will be chosen according to the desired application for the elastic yarn obtained.

[0060] A copolymer that can be used to manufacture the yarn intended to be used in the method according to the invention is the product sold under the trade name “HERAFLEX E 2517 1000 NT” by the company Radici Group. This elastomeric copolymer is a polyester block and polyether block copolymer of formula (I) above and has the following characteristics: a density of 1080 kg / m 3 , measured according to ISO 1183, a hardness of 22 shore D, at 15 seconds, measured according to ISO 7619-1, a melting point of 175°C, measured according to ISO 11357-1 / -3, a melt flow index of 12 g / 10 min, measured according to ISO 1133.

[0061] To proceed to step A), the copolymer may be pre-dried to bring the moisture content of the copolymer below 200 ppm. Moisture content characterization tests may, for example, be carried out using the Karl-Fischer titration method.

[0062] The spinning machine may comprise an extruder, for example a screw extruder, a spinning metering pump and a spinning pack. The spinning pack generally comprises a die. The spinning pack may also conventionally contain a distribution plate, a metal filter, and filter sand. The extruder and the spinning pump are purged before being supplied with copolymer. The spinning machine also comprises a cooling system, at least one delivery roller, for example a pair of delivery rollers, at least one draw roller, for example a pair of draw rollers. The draw rollers may or may not be heatable. The spinning machine also preferably comprises a winding roller for storing the produced yarn. According to step A), the thermoplastic copolymer pellets, which are an elastomer, are introduced into the extruder where they are melted.At the outlet of the extruder, a molten elastomer of the copolymer is obtained. In a second step, step B), the molten elastomer obtained in step A) is spun into the spinneret of the spinning pack to obtain a copolymer yarn. The spinning metering pump controls the flow of the elastomer to the spinneret of the spinning pack. The metal filter and the filter sand can be used to remove impurities. The elastomer is injected into the spinneret. At the outlet of the spinneret, a copolymer yarn is established.

[0063] According to a third step, step C), the copolymer yarn is subjected at the outlet of the die to cooling to a temperature ranging from approximately 10°C to approximately 40°C, preferably ranging from approximately 20°C to approximately 25°C.

[0064] Preferably, when the copolymer is a copolymer with soft blocks and rigid blocks, the cooling of the copolymer takes place at a temperature strictly lower than the glass transition temperature of the rigid blocks.

[0065] Wire cooling can be carried out by air or water quenching, depending on the thickness of each filament of the wire and the efficiency of the cooling system. In the case of water quenching, the wire may, for example, be passed through a tank filled with water at a temperature of 20-25°C.

[0066] In the case of air cooling, the wire may be passed through a current of cold air, for example brought to a temperature ranging from 10 to 25°C.

[0067] During the cooling stage, the wire solidifies.

[0068] According to a fourth step, step D), the wire is subjected to a first stretching, or preliminary stretching, at the temperature of step C). This preliminary cold stretching makes it possible to give the wire a first elasticity.

[0069] For example, the yarn leaving the spinneret of the spinning pack of step B) at a spinning metering pump linear speed VP, the yarn may be drawn in step D) by passing over a delivery roller having a delivery linear speed V1, V1 being chosen such that the preliminary drawing rate D1 is greater than or equal to 2, preferably greater than or equal to 8, for example greater than or equal to 12, where D1 = V1 / VP. The rate D1 may for example have a value greater than 100, for example 132. Such a preliminary drawing rate greater than or equal to 2 makes it possible to give the yarn significant elasticity while retaining good tenacity, and therefore good mechanical properties.

[0070] In the present application, the term "linear speed" of a pump or a roller, feeder, stretcher or winder, is understood to mean the linear speed of the outer wall of the pump or roller in contact with the wire during the movement of the latter. The wire obtained at the end of step D) can be stored on a winding roller before being subjected to step E).

[0071] According to a fifth step, step E), the copolymer yarn from step D), whether stored on a winding roll or directly from the delivery roll, is subjected to hot drawing at a temperature ranging from approximately 40°C to approximately 125°C, preferably ranging from approximately 45°C to approximately 90°C. Preferably, when the copolymer is a copolymer with flexible blocks and rigid blocks, the hot drawing is carried out at a temperature strictly higher than the glass transition temperature of the rigid blocks.

[0072] To carry out this hot drawing, the wire is brought through or into contact with a heating means heated to the desired temperature. For example, the heating means may be an oven heated to the desired temperature. Alternatively or in combination, the heating means may comprise one or more drawing rollers heated to the desired temperature. Hot drawing makes it possible to reduce the thickness of the wire, in other words to increase its fineness.

[0073] For example, the wire is drawn in step E) by passing over a first drawing roller having a linear drawing speed V2, V2 being chosen such that the rate D2 of the hot drawing is less than or equal to 2, where D2 = V2 / V1. The rate D2 may for example be approximately 1.28, or 1.05, or 1.10 or 1.4. When the heating means is an oven through which the wire passes, the oven may thus be located between the delivery roller and the first drawing roller. Alternatively, the first drawing roller may be a heatable roller brought to the desired temperature. Such a rate of hot drawing makes it possible to give the wire a significant fineness while retaining an interesting elasticity.

[0074] According to a sixth step, step F), the copolymer yarn from step E) is subjected to cold drawing. The temperature of this cold drawing can range from approximately 10°C to approximately 40°C, preferably from approximately 20°C to approximately 25°C. This second cold drawing makes it possible to give the yarn additional elasticity.

[0075] For example, the wire is drawn in step F) by passing over a second drawing roller having a linear drawing speed V3, V3 being chosen such that the cold drawing rate D3 is greater than or equal to 1, where D3 = V3 / V2. For example, the rate D3 may be 1.10 or 1.7 or about 2.83. Such a drawing rate at this step makes it possible to obtain a wire having very good elasticity.

[0076] The method of manufacturing the wire intended to be used in the method according to the invention may further comprise the following step G):

[0077] - G) the copolymer yarn resulting from step F) is subjected to relaxation at a temperature ranging from approximately 10°C to approximately 40°C, preferably ranging from approximately 20°C to approximately 25°C. The relaxation temperature may, for example, be strictly lower than the glass transition temperature of the rigid blocks of the copolymer.

[0078] In step G), the wire can be relaxed by passing over a winding roller having a linear speed V4 chosen such that V4 / V3 is strictly less than 1, preferably is approximately 0.97.

[0079] The wire can subsequently be subjected to further stretching, also called post-stretching, in order to improve its elastic return.

[0080] The method of manufacturing the wire intended to be used in the method according to the invention may further comprise the following step H):

[0081] H) the copolymer yarn, resulting from step F) or from step G) is subjected to at least one post-stretching comprising hot stretching, for example at a temperature ranging from 30°C to 70°C, followed by cold relaxation, for example at a temperature ranging from 20°C to 25°C.

[0082] Preferably, during post-stretching, the hot stretching has a stretching ratio E1 greater than 1.5 and the cold relaxation has a relaxation ratio R3 = V3 / V4 less than 1.3.

[0083] The copolymer yarn can be subjected to several post-stretching operations. Subjecting the yarn to one or more post-stretching operations improves the elastic properties of the yarn.

[0084] The method of manufacturing the wire intended to be used in the method according to the invention may further comprise the following step I):

[0085] I) the yarn from one of steps F), G) or H) is wound on a storage winder, without drawing and without relaxation.

[0086] The yarn manufactured according to the manufacturing method described above comprises at least 50%, preferably at least 80%, more preferably at least 90%, and in particular approximately 100% of thermoplastic copolymer by weight, relative to the weight of the yarn.

[0087] The method according to the invention comprises a step 1°) in which the yarn obtained in any one of steps F) to I) described above is subjected to relaxation at a temperature ranging from approximately 70°C to approximately 110°C.

[0088] During this relaxation step, the internal stresses stored within the wire during the manufacture of this wire as described above are eliminated. The elimination of these internal stresses causes shrinkage of the wire. The relaxation of the wire can be obtained either in-line during the continuous production of the wire by the extrusion process, or off-line, on the wire stored after production. Off-line, on a stored wire, the relaxation of the wire can be obtained by a simple heat treatment of the wire, in other words by bringing the wire to a temperature ranging from about 70°C to about 110°C using a heating means. On-line, the relaxation of the wire can be obtained by passing the wire over a heated roller: in such a case, the roller can be heated to a temperature ranging from about 40°C to 125°C, preferably from 40°C to 90°C, preferably from 45°C to 70°C.

[0089] The heating means may be any device enabling the wire to be heated to a temperature ranging from approximately 70°C to approximately 110°C. The heating means may thus be chosen from an oven, a steam chamber, or a water bath heated to 100°C.

[0090] In the case where the wire is obtained at the end of step G), it will be understood that it undergoes several relaxations at different temperatures.

[0091] For example, the yarn obtained from steps A) to F) and H) is treated with hot air at 70°C. Such treatment increases the elasticity of the yarn from 52% to 100%, the elasticity being measured according to the method described in the Examples below.

[0092] Alternatively, the yarn obtained from steps A) to F) and H) is treated with hot air at 100°C. Such treatment increases the elasticity of the yarn from 52% to 200%, the elasticity being measured according to the method described in the Examples below.

[0093] In one embodiment of the method according to the invention, during step 1°), the wire from step F) is made to pass over a first roller having a linear speed W1 then over a second roller having a linear speed W2, the linear speed W2 being strictly lower than the linear speed W1. In such an embodiment, step 1°) of the method according to the invention is thus carried out directly on the wire production line, continuously. In particular, during its passage from the first roller to the second roller, the wire passes through a heating means as described above, for example an oven, or a steam bath or even a boiling water bath. Furthermore, the first and second rollers can be heated to a temperature ranging from approximately 40°C to 125°C, preferably from 40°C to 90°C, preferably from 45°C to 70°C.In such an embodiment, the relaxation of the wire is achieved both by the heat treatment and by the fact that the linear speed of the second roller is lower than that of the first roller, this difference in speed also participating in forcing the wire to shrink.

[0094] In another embodiment of the method according to the invention, step 1°) comprises the following steps:

[0095] 1 °)a1), the yarn from step F) is i) wound onto a perforated winding roller, the applied winding tension being chosen to allow the yarn to shrink when it is wound onto the winding roller, then

[0096] 1 °)a2) the winding roller on which the thread is wound is placed in a steam chamber or in a boiling water bath.

[0097] In such an embodiment, the perforations of the perforated winding roll allow the heat of the steam bath or boiling water bath to diffuse optimally onto the wound wire. The steam chamber can be configured to deliver the steam to the perforated winding roll directly, such as in the middle of the tube, or indirectly, for example by induction. In such an embodiment, the relaxation of the wire is achieved both by the heat treatment and by the mechanical action forcing the wire to shrink on the winding roll.

[0098] In another embodiment of the method according to the invention, during step 1°) the wire from step I) is unwound from the initial storage winder at a first linear speed W3, is made to pass through a heating medium, then is wound onto a final storage winder at a linear speed W4, the linear speed W4 being strictly lower than the linear speed W3.

[0099] In such an embodiment, the heating medium is obtained using a heating means as described above, for example an oven, or a steam bath or a boiling water bath. In such an embodiment, the relaxation of the wire is obtained both by the heat treatment and by the fact that the linear speed of the final storage winder is lower than that of the initial storage winder, this difference in speed also participating in forcing the wire to shrink.

[0100] In another embodiment of the method according to the invention, the yarn resulting from one of steps F) to I) being present within a textile, step 1) comprises the treatment of said textile at a temperature ranging from approximately 70°C to approximately 110°C. For example, said textile may be subjected to one or more of the following treatments:

[0101] Washing,

[0102] Stripping,

[0103] Dyeing.

[0104] For example, the textile can be washed at a temperature of about 90°C-100°C for at least 1 hour. Such treatment increases the elastic properties of the textile.

[0105] Other characteristics and advantages of the present invention will appear even more clearly on reading the following example and the appended drawings in which: [Fig. 1] is a diagram representing an installation for manufacturing a wire intended to be used in the method according to the invention,

[0106] [Fig. 2] is a diagram showing an installation for applying post-drawing to the wire produced with the installation of Figure 1,

[0107] [Fig. 3] is a graph showing the curves of the tensile force (in cN) as a function of the elongation (in %) for a yarn not treated by the method according to the invention and for two yarns treated with the method according to the invention, [Fig. 4] is a diagram showing the knitting weave of a textile intended to be used in the method according to the invention,

[0108] [Fig. 5] is a graph showing the curve of the tensile force (in N) as a function of the tensile deformation (or displacement) (in %) in the direction of the warp for a knitted fabric not treated according to the method according to the invention,

[0109] [Fig. 6] is a graph showing the curve of the tensile force (in N) as a function of the tensile strain (or displacement) (in %) in the warp direction for a knitted fabric treated according to the method according to the invention,

[0110] [Fig. 7] is a graph showing the curve of the tensile force (in N) as a function of the tensile strain (or displacement) (in %) in the weft direction for a knitted fabric not treated according to the method according to the invention,

[0111] [Fig. 8] is a graph showing the curve of the tensile force (in N) as a function of the tensile strain (or displacement) (in %) in the weft direction for a knitted fabric treated according to the method according to the invention,

[0112] [Fig. 9] is a graph showing the curve of the tensile force (in N) as a function of the tensile strain (or displacement) (in %) in the diagonal direction for a knitted fabric not treated according to the method according to the invention, [Fig. 10] is a graph showing the curve of the tensile force (in N) as a function of the tensile strain (or displacement) (in %) in the diagonal direction for a knitted fabric treated according to the method according to the invention,

[0113] [Fig. 11] is a graph showing the hysteresis curve in the warp direction for a knitted fabric not treated according to the method according to the invention,

[0114] [Fig. 12] is a graph showing the hysteresis curve in the weft direction for a knitted fabric not treated according to the method according to the invention,

[0115] [Fig. 13] is a graph showing the hysteresis curve in the warp direction for a knitted fabric treated according to the method according to the invention,

[0116] [Fig. 14] is a graph showing the hysteresis curve in the weft direction for a knitted fabric treated according to the method according to the invention,

[0117] [Fig. 15] is a bar chart showing the force at different loading and unloading elongations, in the warp direction, for a knitted fabric not treated by the method according to the invention and for a knitted fabric treated by the method according to the invention,

[0118] [Fig. 16] is a bar chart showing the force at different loading and unloading elongations, in the weft direction, for a knitted fabric not treated by the method according to the invention and for a knitted fabric treated by the method according to the invention. Referring to Figure 1, an installation 100 for manufacturing a yarn for use in the method according to the invention is shown.

[0119] The installation 100 comprises a spinning machine 1 comprising an extruder

[0120] 2 and a spinning pack 3. The installation 200 also includes a pair of delivery rollers 4, a pair of draw rollers 5, and an initial storage winder 6.

[0121] Extruder 2 includes an inlet 2a and an outlet 2b, as well as a feed hopper 7.

[0122] The steps of the yarn manufacturing process will now be described with reference to Figure 1.

[0123] Step A)

[0124] Pellets of a thermoplastic copolymer are provided. The pellets are fed into the extruder 2 by means of a feed hopper 7 at an inlet 2a of the extruder 2. Within the extruder 2, the pellets are kneaded and melted. At the outlet 2b of the extruder 2, a molten elastomer is obtained, which is transported to the spinning pack

[0125] 3 by means of a transport line formed of a thermally insulated metal pipe 8.

[0126] Step B)

[0127] Spinning Pack 3 includes a metering pump, a filter, and a die 9. The metering pump controls the flow of molten elastomer to the die 9.

[0128] After passing through the filter, the molten elastomer is injected into the die 9. The die 9 has a multitude of holes. At the outlet of the die 9, two threads 10 are thus established, each thread 10 comprising several filaments. The two threads 10 join into a single thread 11 at a unit 12 configured to guide the two threads 10 into a single thread 11 and to apply a sizing oil to the thread 11.

[0129] Step C)

[0130] The wire 11 may be cooled to a temperature ranging from about 10°C to about 40°C, preferably from about 20°C to about 25°C, for example by air quenching.

[0131] Step D)

[0132] Once cooled, the wire 11 is passed over the delivery roller 4 and undergoes preliminary drawing at a temperature ranging from approximately 10°C to approximately 40°C, preferably ranging from approximately 20°C to approximately 25°C.

[0133] Step E)

[0134] The wire is then passed over the stretching roller 5 and undergoes hot stretching at a temperature ranging from approximately 40°C to approximately 125°C, preferably ranging from approximately

[0135] 45°C to about 90°C.

[0136] Step F) The wire 11 leaves the stretching roller 5 and undergoes cold drawing at a temperature ranging from about 10°C to about 40°C, preferably ranging from about 20°C to about 25°C.

[0137] Step I)

[0138] The yarn 11 is finally wound onto the initial winding roller 6. A 12-filament yarn with a count of 60 dtex is obtained.

[0139] Referring to Figure 2, an installation 200 is shown for implementing a post-stretching step and a relaxation step, these steps being subsequent to the extrusion, preliminary stretching, hot stretching and cold stretching steps described in Figure 1. The wire 11 is wound and stored on the initial storage winder 6.

[0140] The post-stretching and relaxation steps described in this Figure 2 therefore correspond to the optional step H) described in the description above.

[0141] The installation 200 comprises a pair of first heatable post-stretching rollers 12, a pair of second post-stretching rollers 13, a pair of third post-stretching rollers 14, a fourth post-stretching roller 15 and a final winding roller 16.

[0142] The yarn 11 is unwound from the initial storage winder 6 and is brought to pass over a first post-stretching roller 12, then over a second post-stretching roller 13, then over a third post-stretching roller 14 and over a fourth post-stretching roller 15. The yarn 11 is then brought to the final storage winder 16.

[0143] The temperatures and linear speeds of the post-stretching rollers are collected in Table 1 below:

[0144] [Table 1]

[0145] Table 1: Post-stretching parameters Thus, when passing over roller 12, wire 11 undergoes hot post-stretching. Then when passing over rollers 13 to 15, it undergoes relaxation.

[0146] The final post-stretch count is 50 + / - 3 dtex.

[0147] EXAMPLES

[0148] In all the examples below, the mechanical properties are measured according to the BISFA 2015 standard. The tests are carried out on a mechanical test bench with a constant elongation rate, using Tensolab software. The wire samples are placed between two jaws under compressed air, separated by 5 cm from each other. The upper jaw moves at a speed of 500 mm / min.

[0149] In all the examples below, the viscoelastic properties are measured as follows: the tests are carried out on a mechanical test bench used with Tensolab software, according to the BISFA Bare Elastic Yarn 2015 standard and with 100% extension. The yarn samples are placed between two clamps under compressed air, separated by 10 cm from each other. Five measurements are taken. The average of the five measurements can be calculated for a more accurate result.

[0150] EXAMPLE 1

[0151] A yarn is produced in accordance with the process described in Figures 1 and 2 using a polyamide block and polyether block copolymer sold under the trade name "PEBAX RNEW 35R53 SP 01" by the company Arkema. The polyamide blocks of this copolymer are PA 11 blocks, the polyether blocks being blocks derived from polytetramethylene glycol.

[0152] This elastomeric copolymer has the following characteristics:

[0153] - a density of 1020 Kg / m3, measured according to ISO 1183 standard,

[0154] - a hardness of 25 shore D, at 15 seconds, measured according to the ISO 7619-1 standard,

[0155] - a melting point of 135°C, measured according to ISO 11357-1 / -3,

[0156] - a polyamide PA 11 content, which is a bio-sourced polyamide, of 29%, measured according to the ASTM D6866 standard.

[0157] The yarn produced was therefore manufactured by carrying out steps A) to F), then step H) as described in the description above. A 12-filament yarn with a count of 60 dtex was obtained. This yarn is hereinafter referred to as “Yarn 1”. To evaluate the mechanical properties of Yarn 1, this yarn was subjected to various heat treatments as follows:

[0158] Yarn 1 without heat treatment, called “Unbleached Yarn”: five samples of this yarn were tested,

[0159] Wire 1 subjected to treatment in accordance with the method according to the invention, more precisely subjected to heat treatment with hot air at 70°C: five samples of this wire were tested,

[0160] Wire 1 subjected to treatment in accordance with the method according to the invention, more precisely subjected to heat treatment with hot air at 100°C: five samples of this wire were tested.

[0161] Figure 3 shows the tensile force (in cN) versus elongation (in %) curves for the three tests above. In this Figure 3:

[0162] The left curve corresponds to the ecru thread,

[0163] The middle curve corresponds to Wire 1 treated at 70°C,

[0164] The curve on the right corresponds to Wire 1 treated at 100°C.

[0165] The grayed-out part at the bottom left indicates the elastic zones of the curves.

[0166] The results are collected in Table 2 below.

[0167] [Table 2]

[0168] Table 2: Mechanical properties of Wire 1

[0169] These results show that the strain at break of Yarn 1 increases after the heat treatment applied in accordance with the method according to the invention. Furthermore, the strain at break increases with the increase in the value of the applied temperature. Thus, the same trend is observed for the elastic deformation (the gray area in Figure 3) with an increase in elasticity of 100% for Yarn 1 treated at 70°C and of 200% for Yarn 1 treated at 100°C, compared to the initial untreated raw Yarn whose elasticity is 52%.

[0170] EXAMPLE 2

[0171] From the untreated Yarn 1 of Example 1, a Yarn 2 is produced by coupling Yarn 1 with a 78 dtex, 23-filament, textured polyamide PA66 yarn. The Yarn 2 thus produced is suitable for use in knitting a textile.

[0172] We thus make a knit with Yarn 2 according to the jersey knitting weave shown in Figure 4. In Figure 4, the arrow referenced A indicates the direction of the warp, the arrow referenced B indicates the direction of the weft and the arrow referenced C indicates the diagonal direction.

[0173] The finished knitting is then subjected to the following treatment:

[0174] Machine wash at 98°C for 2 hours 40 minutes, tumble dry at 60°C for 2 hours 30 minutes.

[0175] The mechanical and elastic properties of the initial untreated knit, hereinafter called Knit 0, and of the knit treated according to the method according to the invention (washed and dried as described above), hereinafter called Knit 1, are tested according to the following methods:

[0176] Determination of the maximum force and elongation of a knitted fabric: the principle of this test is to stretch a specimen at a constant speed until it breaks. To do this, the textile is subjected to a temperature of (20 + / - 2) °C and a relative humidity of (65 + / - 4) %, for 24 hours. Then, five specimens with a length of 300 mm and a width of 50 mm are cut in the warp direction and five other specimens in the weft direction. Each specimen is fixed between the two clamps of a dynamometer. The upper clamp moves upwards until the sample is broken. The force-elongation curve is recorded.

[0177] Monitoring the elastic properties of elastic textiles: the principle of this test is to stretch the component at a defined load during three loading-unloading cycles. To do this, the textile is subjected to a temperature of (20 + / - 2) °C and a relative humidity of (65 + / - 4) %, for 2 hours. Then, three specimens with a length of 150 mm and a width of 50 mm are cut in the warp direction and three other specimens in the weft direction. Each specimen is fixed between the two clamps of a dynamometer (the lower clamp is fixed and the upper clamp is movable). The initial distance between the clamps is 100 mm. Then three loading and unloading cycles are carried out while recording the force-elongation curves. For each cycle, the upper clamp rises until the force reaches a value of 15 N (this is the loading phase), then it descends to the initial length of the specimen (this is the unloading phase).After three cycles (loading - unloading), the force - elongation curve is plotted, which describes the stretch properties of the elastic textile.

[0178] Mechanical properties

[0179] Figures 5 and 7 are graphs showing the curve of tensile force (in N) as a function of tensile strain (or displacement) (in %) in the warp direction, respectively in the weft direction, for Tricot 0.

[0180] Figures 6 and 8 are graphs showing the curve of tensile force (in N) as a function of tensile strain (or displacement) (in %) in the warp direction, respectively in the weft direction, for Knit 1.

[0181] Figure 9 is a graph showing the curve of tensile force (in N) versus tensile strain (or displacement) (in %) in the diagonal direction for Knit 0.

[0182] Figure 10 is a graph showing the curve of tensile force (in N) versus tensile strain (or displacement) (in %) in the diagonal direction for Knit 1.

[0183] The results are collected in the following Table 3:

[0184] [Table 3]

[0185] Table 3: Mechanical properties of Knit 0 and Knit 1

[0186] These results show that the strain at break of Knit 1 treated by the method according to the invention is much better than the strain at break of Knit 0 which has not been treated by the method according to the invention. Thus, the strain at break increases for Knit 1 by 32% in the warp direction, by 26% in the weft direction and by 38% in the diagonal direction, compared to that of Knit 0. Elastic properties

[0187] Figure 11, respectively Figure 12, are graphs showing the hysteresis curve in the warp direction, respectively in the weft direction, for Knit 0. Figure 13, respectively Figure 14, are graphs showing the hysteresis curve in the warp direction, respectively in the weft direction, for Knit 1.

[0188] These curves allow bar diagrams to be drawn showing the evolution of the elasticity properties of Tricot and Tricot 1. Thus: Figure 15 is a bar diagram showing the force at different load and unload elongations, in the warp direction, for Tricot 0 and for Tricot 1, Figure 16 is a bar diagram showing the force at different load and unload elongations, in the weft direction, for Tricot 0 and for Tricot 1.

[0189] In these diagrams:

[0190] The expression "at 30% def. (load)" for example means that we are at an elongation (stretching) of 30% on the load curve (upper curve) of the hysteresis curve of Figures 11 to 14,

[0191] The expression "at 40% def. (discharge)" for example means that we are at an elongation (stretching) of 40% of the discharge curve (lower curve) of the hysteresis curve of Figures 11 to 14,

[0192] For each stretch position shown, the left stick corresponds to Knit 0 and the right stick corresponds to Knit 1.

[0193] These diagrams show that there is an increase in force for Knit 1 compared to Knit 0, at any percentage of elongation, for loading and for unloading.

[0194] For example, referring to the diagram in Figure 15, if we consider 30% elongation under load, we can see that the force required to extend the knit to 30% of its original length increases from 1.9 N for Knit 0 to 2.8 N for Knit 1. This means that Knit 1 develops more holding properties than Knit 0 at a given elasticity.

[0195] The same trend can also be observed for the direction of unloading. The force required to relax the knit by 30% of its original length increases from 0.4 N for Knit 0 to 0.9 N for Knit 1. This means that Knit 1 develops more holding properties than Knit 0 at a given elasticity.

[0196] The same trend is observed at 40%, 70% and 100% elongations.

[0197] It is clear from the results of this Example that the method according to the invention makes it possible to improve the extensibility (more elongation at break) of a textile comprising a yarn manufactured according to steps A) to F) described in the description above. These results also show that the method according to the invention makes it possible to improve the elastic modulus (i.e. the force) necessary to stretch or relax a textile comprising a yarn manufactured according to steps A) to F) described in the description above.

[0198] The method according to the invention makes it possible to improve the level of elasticity of a textile comprising a yarn manufactured according to steps A) to F) described in the description above in all directions (warp direction, weft direction and diagonal direction for example for a knit). The method according to the invention also makes it possible to give such a textile more holding properties.

Claims

CLAIMS 1. Method for increasing the elastic properties of a yarn obtained by a melt spinning process comprising the following steps: A) an extruder is fed with granules of a thermoplastic copolymer, the hardness of the copolymer measured according to standard 7619-1 ranging from 10 to 61 ShD, in order to obtain by extrusion a molten elastomer of said copolymer, B) the molten elastomer obtained in step A) is spun within a spinneret of a spinning pack in order to obtain a thread of the copolymer, C) the copolymer yarn obtained in step B) is subjected at the outlet of the die to cooling to a temperature ranging from approximately 10°C to approximately 40°C, preferably ranging from approximately 20°C to approximately 25°C, D) the yarn from step C) is subjected to preliminary drawing at the temperature of step C), E) the wire from step D) is subjected to hot drawing at a temperature ranging from approximately 40°C to approximately 125°C, preferably ranging from approximately 45°C to approximately 90°C, F) the wire from step E) is subjected to cold drawing at a temperature ranging from approximately 10°C to approximately 40°C, preferably ranging from approximately 20°C to approximately 25°C, G) optionally, the yarn from step F) is subjected to relaxation at a temperature ranging from approximately 10°C to approximately 40°C, preferably ranging from approximately 20°C to approximately 25°C, H) optionally, the yarn from step F) or step G) is subjected to at least one post-stretching comprising hot stretching, for example at a temperature ranging from 30°C to 70°C, followed by cold relaxation, for example at a temperature ranging from 20°C to 25°C, I) optionally, the yarn from one of steps F), G) or H) is wound on an initial storage winder, without drawing and without relaxation, said method being characterized in that it comprises a step 1°) in which the yarn obtained in any one of steps F) to I) is subjected to relaxation at a temperature ranging from approximately 40°C to approximately 110°C.

2. Method according to claim 1, characterized in that the thermoplastic copolymer is a copolymer with polyamide blocks and polyether blocks, the polyamide blocks being chosen from PA 11, PA 12, PA 1010, PA 1014, their copolymer and their mixture, the polyether blocks being blocks derived from polytetramethylene glycol, the hardness of the copolymer measured according to standard 7619-1 being between 22 and 61 ShD, preferably between 22 and 55 ShD, more preferably between 22 and 40 ShD.

3. Method according to claim 2, characterized in that the polyamide blocks are chosen from PA 11, PA 12, their copolymer and their mixture.

4. Method according to claim 3, characterized in that the polyamide blocks are PA 11 blocks.

5. Method according to claim 1, characterized in that the thermoplastic copolymer is chosen from thermoplastic elastomers (TPE), thermoplastic polyurethane elastomers, thermoplastic polyolefin elastomers (POE), polyphthalamides (PPA), elastomers based on polyether-esteramide, thermoplastic copolyester elastomers, copolyester (ether) elastomers and their mixtures, the hardness of the copolymer measured according to standard 7619-1 ranging from 10 to 57 ShD, preferably ranging from 10 to 45 ShD, preferably ranging from 10 to 35 ShD, more preferably is approximately 22 ShD.

6. Method according to claim 5, characterized in that the copolymer is chosen from copolymers comprising flexible blocks and rigid blocks, the flexible blocks being polyether blocks derived from polytetramethylene glycol (PTMEG), the rigid blocks being chosen from diisocyanate blocks and polyester blocks.

7. Method according to claim 6, characterized in that the copolymer is chosen from copolymers whose flexible blocks are polyether blocks derived from polytetramethylene glycol and whose rigid blocks are polyester blocks.

8. Method according to claim 7, characterized in that the copolymer with polyether blocks and polyester blocks is the compound of formula (I) below: [Chem 1] in which y=0.3x.

9. Method according to any one of claims 1 to 8, characterized in that step 1°) is carried out at a temperature ranging from approximately 80°C to approximately 100°C, preferably ranging from approximately 90°C to approximately 100°C.

10. Method according to any one of claims 1 to 9, characterized in that the yarn obtained at the end of steps A) to F) and H) is treated with hot air at 70°C.

11. Method according to any one of claims 1 to 9, characterized in that the yarn obtained at the end of steps A) to F) and H) is treated with hot air at 100°C.

12. Method according to any one of claims 1 to 9, characterized in that during step 1°), the wire from step F) is made to pass over a first roller having a linear speed W1 then over a second roller having a linear speed W2, the linear speed W2 being strictly lower than the linear speed W1.

13. Method according to any one of claims 1 to 9, characterized in that step 1°) comprises the following steps: 1°)a1), the yarn from step F) is i) wound onto a perforated winding roller, the winding tension applied being chosen to allow the yarn to shrink when it is wound onto the winding roller, then 1°)a2) the winding roller on which the thread is wound is placed in a steam chamber or in a boiling water bath.

14. Method according to any one of claims 1 to 9, characterized in that during step 1) the wire from step I) is unwound from the initial storage winder at a first linear speed W3, is made to pass through a heating medium, then is wound onto a final storage winder at a linear speed W4, the linear speed W4 being strictly lower than the linear speed W3.

15. Method according to any one of claims 1 to 9, characterized in that the yarn resulting from one of steps F) to I) being present within a textile, step 1) comprises the treatment of said textile at a temperature ranging from approximately 70°C to approximately 110°C.

16. Method according to claim 15, characterized in that said textile is subjected to one or more of the following treatments: Washing, Stripping, Dyeing.

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