Method for spinning an elastic yarn

Abstract

The present invention relates to a method for producing an elastic yarn (20) by means of melt extrusion spinning using a spinning machine (1) comprising an extruder (2) and a spinning pack (3) comprising at least one spinneret (19), the method comprising at least the following steps: a preliminary step of cold drawing the yarn (20) at the outlet of the spinneret (19), followed by a step of hot drawing the yarn (20) and subsequently a step of cold drawing the yarn (20). The invention also relates to a textile comprising such an elastic yarn and to a facility configured to carry out this method.

Description

[0001] DESCRIPTION

[0002] TITLE: Process for spinning an elastic thread

[0003] The present invention relates to a method for manufacturing a recyclable elastic thread, usable 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 manufacturing a recyclable elastic thread by the melt extrusion process.

[0011] The present invention relates to a method for manufacturing an elastic yarn by melt spinning using a spinning machine comprising 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 draw roller, said method comprising at least the following steps:

[0012] A) said extruder is fed with granules of a copolymer chosen from thermoplastic elastomers (TPE), thermoplastic polyurethane elastomers, thermoplastic polyolefin elastomers (POE), polyphthalamides (PPA), polyether-esteramide-based elastomers, 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, in order to obtain by extrusion a molten elastomer of said copolymer,

[0013] B) the molten elastomer obtained in step A) is spun within the die of said 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 45°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] In the present application, yarn means any fiber of infinite length. In particular, the yarn may be in the form of monofilaments or multifilaments.

[0019] 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 has a rubbery state (plastic solid behavior). The process according to the invention makes it possible to obtain an elastic thread based on a recyclable copolymer, said elastic thread having excellent elastic properties. In particular, the elastic thread obtained by the process according to the invention has an elongation, or elongation at break, greater than or equal to 105%, measured according to the method described in Example 3 of the present document. Furthermore, the elastic thread obtained by the process according to the invention has a particularly low permanent deformation, for example of the order of 9%, measured according to the method described in Example 4 of the present document.

[0020] Another aspect of the invention relates to an elastic thread capable of being obtained by the method according to the invention, having an average elongation at break, measured according to the BISFA 2015 standard, greater than or equal to approximately 105%.

[0021] Another aspect of the invention relates to a textile comprising at least one elastic thread capable of being obtained by the method according to the invention.

[0022] Another aspect of the invention relates to a method for recycling a textile comprising at least one elastic yarn according to the invention and at least one thermoplastic yarn, characterized in that it comprises the following steps:

[0023] - i) said textile is crushed in order to obtain small pieces of textile,

[0024] - ii) the small pieces of textile from step i) are then melted in an extruder in order to obtain granules of said mixture.

[0025] The recycling process may further comprise the following step iii):

[0026] - iii) a recycled yarn is spun by melt extrusion from the granules obtained in step ii), in particular according to the process according to the invention, to obtain an elastic yarn.

[0027] The granules from step ii) constitute raw materials for all applications, particularly textiles.

[0028] 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.

[0029] Another aspect of the invention relates to a garment comprising at least one elastic thread capable of being obtained by the method according to the invention.

[0030] Another aspect of the invention is an installation configured to implement the method according to the invention, said installation comprising:

[0031] - a spinning machine comprising an extruder, a spinning metering pump, a spinning pack comprising at least one spinneret,

[0032] - a cooling system located at the outlet of the die,

[0033] - at least one delivery roller placed at the outlet of the cooling system,

[0034] - at least one first stretching roller, arranged downstream of the delivery roller, - at least one second stretching roller, arranged downstream of the first stretching roller,

[0035] - a means of heating.

[0036] In one embodiment, the installation may comprise a winding roller downstream of the delivery roller in order to store the wire resulting from the preliminary cold drawing step. The wire resulting from this winding roller is then, in a second step, passed over the first drawing roller.

[0037] The method for manufacturing an elastic yarn 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, as will be described below. In particular, as will appear from the description below, according to the method of the invention, 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.

[0038] 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.

[0039] Thus, in a first step of the process according to the invention, an extruder is fed with granules of a copolymer chosen from thermoplastic elastomers (TPE), thermoplastic polyurethane elastomers, thermoplastic polyolefin elastomers (POE), polyphthalamides (PPA), 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. This step makes it possible to obtain by extrusion a molten elastomer of said copolymer.

[0040] Preferably, the hardness measured according to standard 7619-1 ranges from 10 to 45 ShD, more preferably from 10 to 35 ShD, and more preferably is about 22 ShD. Such hardness makes it possible to obtain a wire having good elastic properties.

[0041] 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.

[0042] The elastomers suitable for the process of the invention are copolymers composed of a succession of rigid polymer blocks, hereinafter called rigid blocks, and flexible polymer blocks, hereinafter called 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.

[0043] 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.

[0044] 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.

[0045] A copolymer with polyether blocks and polyester blocks which can be used in the process according to the invention is a compound of the following formula (I):

[0046] [Chem 1] in which y=0.3x.

[0047] In this formula (I), the soft blocks are the polyether blocks which are themselves poly(tetramethylene ether) glycol blocks (hereinafter referred to as PTMEG) with a degree of polymerization DP of 27 ± 2 and a molecular weight of 1950 ± 150 g / mol, and the rigid blocks are based on polyester, which are themselves polybutylene terephthalate blocks (hereinafter referred to as PBT) with a molecular weight of approximately 875 ± 100 g / mol.

[0048] Thus, the structure of the copolymer of formula (I) can also be written as follows:

[0049] -(PBT)3-PTMEG27-(PBT)4-PTMEG27-(PBT)3-PTMEG27-

[0050] The copolymers that can be used in the process 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 thread obtained.

[0051] A copolymer that can be used in the process 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 copolymer with polyester blocks and polyether blocks 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.

[0052] To carry out the first step of the process according to the invention, the copolymer may be dried beforehand in order to reduce the moisture content of the copolymer to less than 200 ppm. The moisture content characterization tests may, for example, be carried out using the Karl-Fischer titration method.

[0053] The spinning machine comprises an extruder, for example a screw extruder, a spinning metering pump, and a spinning pack. The spinning pack typically comprises a die. The spinning pack may also typically contain a distribution plate, a metal filter, and filter sand. The extruder and the spinning pump are purged before being fed with copolymer. The spinning machine also comprises a cooling system, at least one delivery roller, for example a pair of delivery rollers, and 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.

[0054] In a first step, step A) of the process according to the invention, the flexible block and rigid block copolymer granules as described above are introduced into the extruder in which they are melted. At the outlet of the extruder, a molten elastomer of the copolymer is obtained. In a second step, step B) of the process according to the invention, the molten elastomer obtained in step A) is spun into the spinneret of the spinning pack in order 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.

[0055] According to a third step, step C) of the process according to the invention, 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] During the cooling stage, the wire solidifies.

[0060] According to a fourth step, step D) of the method according to the invention, 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.

[0061] In one embodiment, the yarn leaving the spinneret of the spinning pack of step B) at a spinning metering pump linear speed VP, the yarn is drawn in step D) by passing over a delivery roller having a delivery linear speed V1, V1 being chosen such that the rate D1 of the preliminary drawing 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 be about 12. Alternatively, the rate D1 may for example be about 24. Such a preliminary drawing rate makes it possible to give the yarn significant elasticity while retaining good tenacity, and therefore good mechanical properties.

[0062] In this 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.

[0063] In one embodiment, the wire obtained at the end of step D) can be stored on a winding roll before being subjected to step E).

[0064] According to a fifth step, step E) of the process according to the invention, 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 45°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.

[0065] 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.

[0066] In one embodiment, 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 = V2A / 1. The rate D2 may for example be approximately 1.28. Alternatively, rate D2 may for example be 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.

[0067] According to a sixth step, step F) of the process according to the invention, 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.

[0068] In one embodiment, the yarn is drawn in step F) by passing over a second draw roller having a linear draw speed V3, V3 being chosen such that the cold draw rate D3 is greater than or equal to 1, where D3 = V3 / V2. For example, the rate D3 may be approximately 2.83. Such a draw rate in this step makes it possible to obtain a yarn having very good elasticity.

[0069] The method may further comprise the following step G):

[0070] - 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.

[0071] The relaxation temperature can, for example, be strictly lower than the glass transition temperature of the rigid blocks of the copolymer.

[0072] 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.

[0073] In one embodiment, the wire may subsequently be subjected to further stretching, also called post-stretching, to improve its elastic recovery.

[0074] In one embodiment, the method according to the invention further comprises the following step H):

[0075] 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 40°C, followed by cold relaxation, for example at a temperature ranging from 20°C to 25°C.

[0076] 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 less than 1.3.

[0077] In one embodiment, the copolymer yarn may be subjected to multiple post-stretching operations. Subjecting the yarn to one or more post-stretching operations improves the elastic properties of the yarn.

[0078] The installation according to the invention can thus further comprise: at least one first post-stretching roller arranged downstream of the winding roller, at least one heating means arranged downstream of the first post-stretching roller, at least one second post-stretching roller arranged downstream of said heating means.

[0079] In one embodiment, the yarn is heat-set at the end of step F) or after post-stretching, or after relaxation, in particular according to steps G) and H) described above. Heat-setting allows the yarn to retain its elastic and mechanical properties over the long term, for example for one year. Heat-setting can, for example, be carried out at a temperature strictly higher than the glass transition temperature of the rigid blocks of the copolymer. For example, heat-setting is carried out at a temperature ranging from approximately 70°C to approximately 90°C, preferably approximately 80°C.

[0080] 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 a first embodiment of an installation making it possible to implement the method according to the invention, [Fig. 2] is a diagram representing a second embodiment of an installation making it possible to implement the method according to the invention, [Fig. 3] is a diagram representing an installation making it possible to implement the post-stretching and relaxation steps,

[0081] [Fig. 4] is a graph showing the curve of tenacity (in g / den) as a function of elongation (in %) for the yarn of Example 1,

[0082] [Fig. 5] is a graph showing the curve of tenacity (in g / den) versus elongation (in %) for the yarn of Example 2,

[0083] [Fig. 6], [Fig. 7], [Fig. 8], [Fig. 9], [Fig. 10] and [Fig. 11] are graphs showing the curves of tensile force (in cN) as a function of elongation (in %) for Tests 1, 2, 3, 6, 7 and 8 of Example 3,

[0084] [Fig. 12] is a graph showing the hysteresis curve obtained for the wire of Example 1,

[0085] [Fig. 13] is a graph showing the hysteresis curve obtained for the wire of Test Example 3.

[0086] Referring to Figure 1, a first embodiment of an installation 100 is shown for implementing the method according to the invention. The installation 100 comprises a spinning machine 1 comprising an extruder 2 and a spinning pack 3. The installation 100 also comprises a tank 4 filled with water 5, a pair 6 of delivery rollers 6a, a first pair 7b of stretching rollers 7a, a second pair 7d of stretching rollers 7c and a winding roller 8. The installation 100 finally comprises an oven 9 located between the delivery rollers 6 and the stretching rollers 7a.

[0087] The steps of the method according to the invention will now be described with reference to Figure 1.

[0088] 10 granules of a polyester block and polyether block copolymer sold under the trade name “HERAFLEX E 2517 1000 NT” by the company Radici Group are available.

[0089] This elastomeric copolymer is a polyester block and polyether block copolymer of formula (I) above and has the following characteristics:

[0090] - a density of 1080 Kg / m 3 , measured according to ISO 1183,

[0091] - a hardness of 22 shore D, at 15 seconds, measured according to the ISO 7619-1 standard,

[0092] - a melting point of 175°C, measured according to ISO 11357-1 / -3,

[0093] - -a melt flow index of 12 g / 10 min, measured according to ISO 1133. Prior to their introduction into the extruder, the granules 10 are preferably dried in order to reduce the moisture content of the polymer to a level below 200 ppm. The moisture content characterization tests can, for example, be carried out using the Karl-Fischer titration method. For example, the granules 10 can be dried in an oven at 80°C overnight and under vacuum.

[0094] The granules 10 are then introduced into the extruder 2 by means of a feed hopper 11 at an inlet 2a of the extruder 2. The extruder 2 comprises a body 12 formed by a cylinder in which a worm screw (not shown) rotates. The extruder 2 comprises, within the body 12, heating zones 14, the temperature of these heating zones 14 increasing from the inlet 2a of the extruder 2 to an outlet 2b of the extruder 2. For example, the temperature of the heating zones 14 can vary from 185°C in the vicinity of the inlet 2a of the extruder to 195°C in the vicinity of the outlet 2b of the extruder 2. Within the extruder 2, the granules 10 are kneaded and melted. At the outlet 2b of the extruder 2, a molten elastomer is obtained, which is transported to the spinning pack 3 by means of a transport line formed of a thermally insulated metal pipe 16.The temperature within the transport line is close to that of the outlet temperature of extruder 2, for example 195°C.

[0095] The spinning pack 3 comprises a metering pump 17, a filter 18 and a die 19. The metering pump 17 controls the flow of the molten elastomer to the die 19. In the example shown, the metering pump 17 rotates at a linear speed of 3.68 m / min. The filter 18 is disposed between the metering pump 17 and the die 19 and serves to remove impurities potentially present in the molten elastomer. In the example shown, the filter 18 has a pressure of 40 bar.

[0096] After passing through the filter 18, the molten elastomer is injected into the die 19 at the temperature of the spinning pump 3 which is approximately 200°C. In the example shown, the size of the hole in the die 19 is 0.72 mm and the ratio of the length (L) of the die hole 19 to its diameter (D) is 1 / 2 (ratio L / D). At the outlet of the die 19, a wire 20 is thus established. The wire 20 leaves the die 19 at a linear speed VP corresponding to the linear speed of the metering pump 17. In the present example, since the die 19 has only one hole, the wire 20 is in the form of a monofilament.

[0097] As shown in Figure 1, once it has left the die 19, the wire 20 is passed through the reservoir 4 filled with water 5. The water 5 is at room temperature, in other words at a temperature ranging from approximately 20°C to approximately 25°C. The wire 20 is thus cooled by quenching with water.

[0098] Cooling the wire 20 allows it to solidify.

[0099] Once cooled, the wire 20 is made to pass over a delivery roller 6a. The delivery roller 6a has a linear speed V1, greater than the linear speed VP. Thus, the wire 20 is subjected, between the exit of the die 19 and the delivery roller 6a, to a preliminary stretching, the rate of which is equal to D1 = V1 / VP. This preliminary stretching takes place cold, and in particular at a temperature strictly lower than the glass transition temperature of the rigid blocks of the copolymer, for example at a temperature ranging from approximately 20°C to approximately 25°C. Such a preliminary cold stretching makes it possible to give the wire 20 a first elasticity.

[0100] In one embodiment, the linear speed V1 is 47 m / min. Thus, the cold preliminary drawing rate D1 is 47 / 3.68 = 12.

[0101] The wire 20 is then brought to pass through the furnace 9 and then, at the outlet of the furnace 9, to pass over a first pair 7b of drawing rollers 7a. In the example shown, the temperature to which the wire 20 is subjected inside the furnace 9 is approximately 75°C. In other embodiments not shown, the temperature of the furnace could range from 50°C to 120°C.

[0102] The stretching rollers 7a have a linear speed V2, greater than the linear speed V1. Thus, the wire 20 is subjected, between the delivery roller 6a and the stretching rollers 7a, to hot stretching, the rate of which is equal to D2 = V2 / V1. This hot stretching makes it possible to reduce the thickness of the wire 20, or even to give it a certain fineness.

[0103] In one embodiment, the linear speed V2 is 60 m / min. Thus, the hot drawing rate D2 is 60 / 47 = 1.28.

[0104] The wire 20 is then passed over a second pair 7d of stretching rollers 7c. In the example shown, the linear speed V3 of the stretching rollers 7d is 170 m / min. This linear speed is greater than the linear speed V2. Thus, the wire 20 is subjected, between the stretching rollers 7a and the stretching rollers 7d, to a stretching whose rate is equal to D3 = V3 / V2. This stretching takes place outside the furnace 9 at ambient temperature, i.e. at a temperature ranging from approximately 20°C to approximately 25°C. This second cold stretching makes it possible to give the wire 20 additional elasticity. In the example shown, the rate D3 of this second cold stretching is 170 / 60 = 2.83.

[0105] The wire 20 is then passed over a winding roller 8 on which it is stored. The winding roller 8 has a linear speed V4 slightly lower than the linear speed V3. For example, the ratio V4 / V3 is strictly less than 1. Thus, the wire 20 is subjected to a relaxation step. In one embodiment, the linear speed V4 is 165 m / min. Thus, the relaxation rate D4 is 165 / 170 = 0.97.

[0106] With reference to Figure 2, a second embodiment of an installation 200 is shown for implementing the method according to the invention. In this Figure 2, the references designating elements identical to those of Figure 1 have been retained.

[0107] The installation 200 comprises a spinning machine 1 comprising an extruder 2 and a spinning pack 3. The installation 200 also comprises a pair 26 of heatable delivery rollers 26a, a first drawing roller 27a, a second drawing roller 27b and a winding roller 8.

[0108] The extruder 2 comprises an inlet 2a and an outlet 2b, as well as a feed hopper 11. The extruder 2 comprises heating zones 14, the temperature of these heating zones 14 increasing from the inlet 2a of the extruder 2 towards an outlet 2b of the extruder 2.

[0109] The polyester block and polyether block copolymer is the same as that described for Figure 1, namely that sold under the trade name “HERAFLEX E 2517 1000 NT” by the company Radici Group.

[0110] Referring to Figure 2, the copolymer pellets 10 are prepared as described for Figure 1 and are introduced into the extruder 2 through the feed hopper 11.

[0111] Upon exiting extruder 2, the molten elastomer is transported to spinning pack 3 via a transport line 16.

[0112] The spinning pack 3 comprises a metering pump 17, a filter 18 and a spinneret 19. In the installation 200, the metering pump 17 rotates at a linear speed of 7.37 m / min. In the example shown, the size of the hole in the spinneret 19 is 0.72 mm and the ratio of the length (L) of the die hole 19 to its diameter (D) is 1 / 2 (ratio L / D). At the outlet of the spinneret 19, a yarn 21 is thus established. The yarn 21 leaves the spinneret 19 at a linear speed VP corresponding to the linear speed of the metering pump 17. In the present example, since the spinneret 19 has only one hole, the yarn 21 is in the form of a monofilament.

[0113] The wire 21 is cooled by means of air quenching in the form of an air stream

[0114] 22, the air stream 22 having a temperature less than or equal to 25°C, for example a temperature of approximately 10°C. Preferably, the air stream 22 is applied to the wire 21 according to the arrows F shown in Figure 2 over a height of the wire 21 of several meters, for example over a height of 5 m.

[0115] In the example shown, the installation 200 comprises a device 23 configured to apply a sizing oil to the wire 21 and a guide 24 to guide the wire 21.

[0116] The wire 21 is then made to pass over a pair 26 of delivery rollers 26a. The rollers 26a have a linear speed V1, greater than the linear speed VP. Thus, the wire 21 is subjected, between the exit of the die 19 and the delivery rollers 26a, to a preliminary stretching, the rate of which is equal to D1 = V1 / VP. This preliminary stretching takes place cold, and in particular at a temperature strictly lower than the glass transition temperature of the rigid blocks of the copolymer, for example at a temperature ranging from approximately 20°C to approximately 25°C. Such a preliminary cold stretching makes it possible to give the wire 21 a first elasticity.

[0117] In the example shown, the speed V1 is 180 m / min. Thus, the preliminary stretching rate D1 is 180 / 7.37 = 24.

[0118] The delivery rollers 26a are heatable rollers and they have a temperature of 45°C. The wire 21 is then made to pass from the heated delivery rollers 26a to a first drawing roller 27a, which is maintained at ambient temperature, in other words between 20 and 25°C. The linear speed V2 of the roller 27a is 252 m / min. Thus, the wire 21 is subjected, between the delivery rollers 26a and the drawing rollers 27a, to hot drawing, the rate of which is equal to D2 = V2 / V1. This hot drawing makes it possible to reduce the thickness of the wire 21, or even to give it a certain fineness. The hot drawing rate is V2 / V1 = 252 / 180 = 1.4.

[0119] The wire 21 is then subjected to a second cold drawing consisting of a first partial cold drawing and a second partial cold drawing. The wire 21 is made to pass over a second drawing roller 27b, which is maintained at ambient temperature, in other words between 20 and 25°C. The linear speed V3p1 of the roller 27b is 315 m / min. This linear speed is greater than the linear speed V2. Thus, the wire 21 is subjected, between the drawing rollers 27a and the drawing rollers 27b, to the first partial cold drawing, the rate of which is equal to D3p1 = V3p1 / V2. This first partial cold drawing makes it possible to give the wire 21 additional elasticity. In the example shown, the rate D3p1 of this first partial cold drawing is 315 / 252 = 1.25.

[0120] The wire 21 is then passed over a winding roller 8 on which it is stored. The winding roller 8 has a linear speed V3p2 greater than the linear speed V3p1. Thus, the wire 21 is subjected to the second partial cold drawing. In one embodiment, the linear speed V3p2 is 570 m / min. Thus, the rate D3p2 of the second partial cold drawing is V3p2 / V3p1, 570 / 315 = 1.81. The overall rate D3 of the second cold drawing (composed of the first partial cold drawing and the second partial cold drawing) is thus 1.25 X 1.81 = 2.26.

[0121] Referring to Figure 3, there is shown a part of installation 300 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 Figures 1 and 2 for the wires (20, 21). The wire 28 subjected to the post-stretching and relaxation steps described in Figure 3 may be a wire 20 obtained according to the method described in Figure 1 or a wire 21 obtained according to the method described in Figure 2. The wire 28 is wound and stored on the winding roller 8.

[0122] The installation part 300 comprises a pair 30 of first post-stretching rollers 30a, an oven 31, a pair 32 of second post-stretching rollers 32a, a pair 33 of third post-stretching rollers 33a and a final winding roller 34.

[0123] The wire 28 is unwound from the winding roller 8 and is brought to pass over a first post-stretching roller 30a then into the oven 31, then over a second post-stretching roller 32a and over a third post-stretching roller 33a. The wire 28 is then brought to the final winding roller 34. The first post-stretching roller 30a has a linear speed V30, the second post-stretching roller 32a has a linear speed V32, the third post-stretching roller 33a has a linear speed V33 and the final winding roller 34 has a linear speed V34.

[0124] Post-stretching can include three steps:

[0125] Step 1: Hot stretching between post-stretching rolls 30a and 32a, Step 2: Cold stretching between post-stretching rolls 32a and 33a, Step 3: Relaxation between post-stretching roll 33a and final winding roll 34.

[0126] Depending on the values ​​of V30, V32 and V33, hot drawing can be high or low, and cold drawing can be high or low.

[0127] The elastic threads (20, 21, 28) obtained according to the method of the invention described above, in particular in Figures 1, 2 and 3, can be incorporated into a textile or into a garment, such as for example sports tights, swimsuits, etc. The threads obtained according to the method of the invention are entirely recyclable. Thus, the textiles or clothing incorporating these threads are also recyclable. For example, the threads obtained by the method according to the invention, the textiles or clothing incorporating them can be ground to obtain small pieces of textile.These small pieces of textile can be melted to form new granules of rigid block and soft block copolymers selected from thermoplastic elastomers (TPE), thermoplastic polyurethane elastomers, thermoplastic polyolefin elastomers (POE), polyphthalamides (PPA), polyether-esteramide-based elastomers, thermoplastic copolyester elastomers, copolyester (ether) elastomers. These granules can be reintroduced into an extruder of a spinning machine to form new yarns. This avoids landfilling and / or incineration of elastic yarns.

[0128] EXAMPLES

[0129] 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.

[0130] 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.

[0131] EXAMPLE 1

[0132] A wire 20 was produced according to the method described with reference to Figure 1 with the following data:

[0133] V1 = 47 m / min

[0134] - D1 = 12

[0135] Oven temperature 9: 75°C

[0136] V2 = 60 m / min

[0137] - D2 = 1.28

[0138] V3 = 170 m / min

[0139] - D3 = 2.83

[0140] V4 = 165 m / min

[0141] - D4 = 0.97. Figure 4 is a graph showing the curves of tenacity (in g / den) as a function of the elongation (in %) of the yarn thus obtained.

[0142] EXAMPLE 2

[0143] A wire 21 was produced according to the method described with reference to Figure 2 with the following data:

[0144] V1 = 180 m / min

[0145] - D1 = 24

[0146] Roller temperature 26a: 45°C

[0147] V2 = 252 m / min

[0148] - D2 = 1.4

[0149] V3p1 = 315 m / min

[0150] - D3p1 = 1.25

[0151] V3p2 = 570 m / min

[0152] - D3p2 = 1.81

[0153] - D3 = 2.26.

[0154] Figure 5 is a graph showing the curves of tenacity (in g / den) versus elongation (in %) of the resulting yarn.

[0155] Comparison between the curves in Figures 4 and 5

[0156] The curves in these figures show three distinct parts of the elastic behavior of the wire, part A, part B and part C. The part referenced A corresponds to the initial elastic part, the part referenced B corresponds to the rigid elastic (viscoelastic) part, and the part referenced C corresponds to the viscoplastic part.

[0157] Comparing Figures 4 and 5, it is noted that the water-quenched yarn 20 is relatively more elastic than the air-quenched yarn 21, relative to part A. However, both yarns are elastic. Part B is more evident for yarn 21 than for yarn 20: thus yarn 21 may be of interest for a yarn application in which support is required (such as for a bra), whereas yarn 20 may be of interest for an application such as leggings. EXAMPLE 3

[0158] The wire 20 obtained according to the method described in Figure 1 was stored on a winding roller 8.

[0159] Several post-stretching tests were then carried out on this wire 20 using the installation 300 described in Figure 3.

[0160] Referring to Figure 3, the following parameters were varied:

[0161] The linear speed V30 of the post-stretching rollers 30a,

[0162] The linear speed V32 of the post-stretching rollers 32a,

[0163] The linear speed V33 of the post-stretching rollers 33a,

[0164] The linear speed V34 of the winding roller 34,

[0165] The temperature T31 of the oven 31.

[0166] Furthermore, the stretching ratios between the different post-stretching rollers and the winding roller are defined as follows:

[0167] Stretch ratio E1 between rolls 30a and rolls 32a: E1 = V32 / V30, Stretch ratio E2 between rolls 32a and rolls 33a: E2 = V33 / V32, Stretch ratio E3 between rolls 33a and winding roll 34: E3 = V34 / V33,

[0168] Total stretch ratio ET between rolls 30a and winding roll 34: ET = V34 / V30.

[0169] The relaxation rate R3 between the rollers 33a and the winding roller 34 is also defined as follows: R3 = 1 / E3.

[0170] 10 tests were carried out by varying these parameters as shown in the following Table 1: [Table 1]

[0171] Table 1: Variations of parameters V30, T31, V32, E1, V33, E2, V34, E3, R3 and ET In this table, “RT” means ambient temperature, i.e. a temperature of approximately 20 to 25°C.

[0172] As a reminder, post-stretching can include the following three steps:

[0173] Step 1: Hot stretching between post-stretching rollers 30a and 32a, - Step 2: Cold stretching between post-stretching rollers 32a and 33a,

[0174] Step 3: A relaxation between the post-stretching roller 33a and the final winding roller 34.

[0175] Thus, the 10 trials in Table 1 above can be classified into 3 distinct approaches:

[0176] Approach 1: corresponding to Tests 1, 2 and 3: according to this approach, there is a first stage of high hot drawing (E1 between 1.5 and 2), then a second stage without cold drawing (E2 less than 1), then a third stage with low relaxation (R3 less than 1.3, temperature of 20-25°C); Approach 2: corresponding to Tests 4, 5, 6 and 7: according to this approach, there is a first stage of relatively low hot drawing (E1 close to 1), then a second stage of high cold drawing (E2 greater than 1.9), then a third stage with high relaxation (R3 greater than 1.9);

[0177] Approach 3: corresponding to Tests 8, 9 and 10: according to this approach, we have a first step without hot drawing (T31 is at room temperature), then a second step of high cold drawing (E2 greater than 1.3), then a third step with strong relaxation (R3 greater than 1.8).

[0178] The stability of the yarn manufacturing process was evaluated for each of the 10 tests above. It was evaluated whether the process was capable of spinning yarn (Stable Process) or whether the process was not capable of spinning yarn (Unstable Process). The results are summarized in Table 2 below:

[0179] [Table 2]

[0180] Table 2: Feasibility of the process

[0181] Thus, it appears that Trials 1, 2, 3, 6, 7 and 8 give the best results.

[0182] Figures 6, 7, 8, 9, 10 and 11 are graphs showing the tensile force versus elongation curves respectively for the yarns obtained with Tests 1, 2, 3, 6, 7 and 8.

[0183] It can be noted that these curves have a similar shape to the curves of Figures 4 and 5, with three distinct parts, a first part relating to the initial soft elastic behavior of the yarn, a second part relating to the rigid elastic behavior of the yarn, and a third part relating to the viscoplastic behavior of the yarn. The elastic properties of yarn 20 of Example 1 (which was not post-stretched) and the yarns of Tests 1, 2, 3, 6, 7 and 8 of this Example 3 (which were post-stretched) were compared. The results are summarized in the following Table 3: [Table 3]

[0184] Table 3: Elastic properties

[0185] Elongation is measured on Force-Elongation curves measured according to the BISFA 2015 standard.

[0186] It appears from Table 3 that Test 2 of this Example 3 gives the best result for the total elastic part (A + B) for the yarns which have been post-stretched.

[0187] Thus, the post-stretching that gives the best elasticity is a post-stretching according to Approach 1, in other words a high hot stretching followed by a low relaxation.

[0188] It can also be noted that the yarn from Example 1 and the yarn from Test 2 of this Example 3 have similar elasticity. However, they have different properties. Thus, the yarn from Example 1 may be suitable for applications requiring a support function, such as for bras, while the yarn from Test 2 may be suitable for the manufacture of leggings.

[0189] Of course, both yarns can be used to make any type of textile, regardless of the intended application, with the structure of the knitted fabric also playing a role in the elastic properties of the final textile.

[0190] EXAMPLE 4

[0191] The viscoelastic properties of the yarn of Example 1 and the yarn of Test 2 of Example 3 were evaluated as follows.

[0192] H5 hysteresis index

[0193] This index represents the performance of the elastic thread when using the elastic textile containing this elastic thread. It shows the ability of the elastic textile to maintain its shape when using this textile. The lower this index, the better the elastic textile is able to maintain its shape during use.

[0194] Hysteresis rate

[0195] This rate represents the ability of the elastic textile to maintain its original shape before being worn, otherwise before any use. The lower this rate, the more the elastic textile is able to maintain its shape before being worn.

[0196] Permanent deformation

[0197] It represents the permanent loss of elasticity of the wire after several successive stretches. The aim is to obtain the lowest possible permanent deformation.

[0198] The viscoelastic property parameters of elastic yarns are measured according to the BISFA 2015 standard.

[0199] Figures 12 and 13 show the graphs of the hysteresis curves obtained respectively for the wire of Example 1 and for the wire of Test 2 of Example 3. Table 4 below brings together the viscoelastic data for these two wires:

[0200] [Table 4]

[0201] Table 4: Viscoelastic properties

Claims

CLAIMS 1. Method for manufacturing an elastic yarn (20; 21) by melt spinning using a spinning machine (1) comprising an extruder (2), a spinning metering pump (17), a spinning pack (3) comprising at least one die (19), a cooling system (4, 5; 22), at least one delivery roller (6a) and at least one stretching roller (7a; 26a), said method comprising at least the following steps: A) said extruder (2) is fed with granules (10) of a copolymer chosen from thermoplastic elastomers (TPE), thermoplastic polyurethane elastomers, thermoplastic polyolefin elastomers (POE), polyphthalamides (PPA), polyether-esteramide-based elastomers, 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, in order to obtain by extrusion a molten elastomer of said copolymer, B) the molten elastomer obtained in step A) is spun within the die (19) of said spinning pack (3) in order to obtain a thread (20; 21) of said copolymer, C) the wire (20; 21) of the copolymer obtained in step B) is subjected at the outlet of the die (19) 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 wire (20; 21) from step C) is subjected to preliminary stretching at the temperature of step C), E) the wire (20; 21) from step D) is subjected to hot drawing at a temperature ranging from approximately 45°C to approximately 125°C, preferably ranging from approximately 45°C to approximately 90°C, F) the wire (20; 21) 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.

2. Method according to claim 1, characterized in that, said yarn (20; 21) leaving the spinneret (19) spinning pack (3) of step B) according to a linear speed of the spinning metering pump VP, the yarn (20; 21) is drawn in step D) by passing over a delivery roller (6a; 26a) having a linear delivery speed V1, V1 being chosen such that the rate D1 of the preliminary drawing 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.

3. Method according to claim 1 or 2, characterized in that during step E), the wire (20; 21) is stretched by passing over a first stretching roller (7a; 26a) having a speed linear stretcher V2, V2 being chosen such that the rate D2 of the hot stretching is less than or equal to 2, where D2 = V2 / V1.

4. Method according to any one of claims 1 to 3, characterized in that during step F), the wire (20; 21) is drawn by passing it over a second drawing roller (8) 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.

5. Method according to any one of the preceding claims, characterized in that during step C), the wire (20) is cooled by quenching with water (5).

6. Method according to any one of claims 1 to 5, characterized in that during step C), the wire (21) is cooled by air.

7. Method according to any one of the preceding claims, characterized in that the thread (20) of the copolymer resulting from step F) is heat-set at a temperature ranging from approximately 70°C to approximately 90°C, preferably approximately 80°C.

8. Method according to any one of the preceding claims, characterized in that it further comprises the following step G): G) the thread (20) of the copolymer 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.

9. Method according to claim 8, characterized in that during step G), said wire (20) is relaxed by passing over a winding roller (8) having a linear speed V4 chosen such that V4 / V3 is strictly less than 1, preferably is approximately 0.

97.

10. Method according to any one of the preceding claims, characterized in that it further comprises the following step H): 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 40°C, followed by cold relaxation, for example at a temperature ranging from 20°C to 25°C.

11. Method according to claim 10, characterized in that during post-stretching, the hot stretching has a stretching rate E1 greater than 1.5 and the cold relaxation has a relaxation rate R3 less than 1.

3.

12. Method according to any one of the preceding claims, characterized in that the hardness of the copolymer measured according to standard 7619-1 ranges from 10 to 45 ShD, more preferably ranges from 10 to 35 ShD, more preferably is approximately 22 ShD.

13. Method according to any one of the preceding claims, 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.

14. Method according to the preceding claim, 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.

15. Method according to claim 14, characterized in that the copolymer with polyether blocks and polyester blocks is the compound of the following formula (I): [Chem 2] in which y=0.3x.

16. Elastic thread (20; 21) capable of being obtained by the method according to any one of claims 1 to 15, having an average elongation at break, measured according to the BISFA 2015 standard, greater than or equal to approximately 105%.

17. Textile comprising at least one yarn (20; 21) obtainable according to any one of claims 1 to 15 or a yarn according to claim 16.

18. Garment comprising at least one thread (20; 21) capable of being obtained according to any one of claims 1 to 15 or a thread according to claim 16.

19. Installation (100; 200) configured to implement the method according to any one of claims 1 to 15, said installation comprising: - a spinning machine (1) comprising an extruder (2), a spinning metering pump (17), a spinning pack (3) comprising at least one die (19), - a cooling system (4, 5; 22) arranged at the outlet of the die (19), - at least one delivery roller (6a, 26a) arranged at the outlet of the cooling system (4, 5; 22), - at least one first stretching roller (7a, 27a), arranged downstream of the delivery roller (6a, 26a), - at least one second stretching roller (7c, 27b), arranged downstream of the first stretching roller (7a, 27a), - a heating means (9, 26a).

20. Method for recycling a textile comprising at least one elastic thread (20; 21; 22) according to claim 16 or obtainable according to any one of the claims 1 to 15, and at least one thermoplastic yarn, characterized in that it comprises the following steps: i) said textile is ground in order to obtain small pieces of textile, ii) the small pieces of textile resulting from step i) are then melted in an extruder in order to obtain granules of said mixture.

21. Recycling method according to the preceding claim, characterized in that it further comprises the following step iii): iii) a recycled yarn is spun by melt extrusion from the granules obtained in step ii), in particular according to the method according to any one of claims 1 to 15, to obtain an elastic yarn.

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