METHOD FOR PRODUCING AN ELASTIC YARN BY MEANS OF MELT EXTRUSION SPINNING

CROSS REFERENCE TO RELATED APPLICATIONS

[0001]This application is a National Stage of PCT Application No. PCT/FR2023/051107 filed on Jul. 18, 2023, which claims priority to French Patent Application Nos. 22/07328 filed on Jul. 18, 2022 and 22/14129 filed on Dec. 21, 2022, the contents each of which are incorporated herein by reference thereto.

TECHNICAL FIELD

[0002]The present disclosure relates to a method for manufacturing a recyclable elastic yarn, which can be used in particular for the manufacture of textiles and footwear.

BACKGROUND

[0003]Elastic textiles have been known for many years. For example, such textiles may be used in the sports field, to manufacture garments such as sports pantyhoses, socks, swimwear, but also shoes. The elasticity of these textiles is generally obtained by means of elastane yarns, which may be present for example in the textile in a content ranging from 2 to 50% of the total composition of yarns and/or fibers of the textile. Elastane is a segmented polyurethane in the form of a copolymer of a soft segment and of a hard segment. The elastane yarn has a high stretch level, or elongation: this yarn may for example be stretched to more than 600% of its original length before breaking up. The elastane yarn also has a high recovery capacity, or springback: thus, after having been stretched many times, this yarn recovers, when the stretching stress is relieved, a length very close to its original length, for example a length ranging from 90% to 100% of its original length.

[0004]Nonetheless, the production and the use of the elastane yarn has several drawbacks.

[0005]According to the Agency for the Environment and Energy Management (ADEME), the production of 1 kg of elastane yarn generates 1 kg of CO₂ equivalent (ADEME Base Impact V2.01). consequently, the elastane yarn production has a relatively high negative environmental impact.

[0006]Moreover, elastane being a thermosetting material, it degrades before being molten. Hence, elastane cannot be thermally recycled. A chemical recycling of elastane could be considered, but the necessary use of solvents in such a process generates an environmental impact that is excessively high for it to be reasonably implemented.

[0007]Consequently, to date in Europe, textiles containing elastane are generally incinerated or disposed of in landfills. The impact of these processes on the environment is negative. Thus, still according to the ADEME, 1 kg of incinerated textile emits 0.4 kg of CO₂ equivalent and 1 kg of buried textile emits 2.2 kg of equivalent CO₂ (ADEME Base Impact V2.01).

[0008]Thus, considering the current environmental concerns, there is still the need to have recyclable elastic textiles. In this respect, there is still the need to have recyclable elastic yarns, which would have elastic properties comparable, and even superior, to those of existing non-recyclable elastic yarns such as elastane yarns. These recyclable elastic yarns should also be able to be associated with non-elastic yarns, also recyclable, in order to produce fully recyclable elastic textiles, regardless of the proportion of elastic yarns within said textiles.

BRIEF SUMMARY

[0009]The present disclosure aims to address this need by providing a method for manufacturing a recyclable elastic yarn by the melt extrusion process.

[0017]In the present application, by yarn, it should be understood any fiber with an infinite length. In particular, the yarn may be in the form of single-strands or multi-strands.

[0018]In the present application, by glass-transition temperature, it should be understood the temperature below which a polymer is in the glassy state (solid) and above which said polymer has a rubbery state (plastic solid behavior).

[0019]The method according to the present disclosure allows obtaining an elastic yarn based on a recyclable copolymer, said elastic yarn having excellent elastic properties. In particular, the elastic yarn obtained by the method according to the present disclosure has an elongation, or elongation at break, higher than or equal to 106%, for example higher than or equal to 131%, for example higher than or equal to 164.5%, for example higher than or equal to 180%, for example higher than 200%, for example about 233.3%, measured according to the method described in Example 1 of the present document. Similarly, the elastic yarn obtained by the method according to the present disclosure has a springback which may range up to 96.6%, measured according to the method described in Example 1 of the present document. Moreover, the elastic yarn obtained by the method according to the present disclosure has a particularly low permanent deformation, for example in the range of 2.5%, measured according to the method described in Example 1 of the present document.

[0020]Another aspect of the present disclosure relates to an elastic yarn which can be obtained by the method according to the present disclosure, having an average elongation at break, measured according to the standard DIN ISO 13895, higher than or equal to about 106%, preferably higher than or equal to about 131%, preferably higher than or equal to 164.5%, preferably higher than or equal to 180%, for example about 233.3%, and/or having a springback, measured according to the standard DIN 53835-2, higher than or equal to about 86.5%, preferably higher than or equal to 91.8%, preferably higher than or equal to 94%, preferably higher than or equal to 96.3%, for example about 96.6%.

[0021]Thus, an aspect of the present disclosure relates to an elastic yarn which can be obtained by the method according to the present disclosure, having an average elongation at break, measured according to the standard DIN ISO 13895, of about 106%, and a springback, measured according to the standard DIN 53835-2, of about 86.5%.

[0022]An aspect of the present disclosure relates to an elastic yarn which can be obtained by the method according to the present disclosure, having an average elongation at break, measured according to the standard DIN ISO 13895, of about 131%, and a springback, measured according to the standard DIN 53835-2, of about 94%.

[0023]An aspect of the present disclosure relates to an elastic yarn which can be obtained by the method according to the present disclosure, having an average elongation at break, measured according to the standard DIN ISO 13895, of about 164.5%, and a springback, measured according to the standard DIN 53835-2, of about 91.8%.

[0024]An aspect of the present disclosure relates to an elastic yarn which can be obtained by the method according to the present disclosure, having an average elongation at break, measured according to the standard DIN ISO 13895, of about 180%, and a springback, measured according to the standard DIN 53835-2, of about 96.3%.

[0025]An aspect of the present disclosure relates to an elastic yarn which can be obtained by the method according to the present disclosure, having an average elongation at break, measured according to the standard DIN ISO 13895, of about 233.3%, and a springback, measured according to the standard DIN 53835-2, of about 96.6%.

[0026]Another aspect of the present disclosure relates to a textile comprising at least one elastic yarn which can be obtained by the method according to the present disclosure.

[0032]The granules derived from step ii) constitute raw materials for all applications and in particular textile applications.

[0033]In the present application, by “textile”, it should be understood 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 knitting, a woven fabric, a nonwoven fabric, a braid and combinations thereof.

[0034]Another aspect of the present disclosure relates to a garment comprising at least one elastic yarn which can be obtained by the method according to the present disclosure.

[0042]In the present application, by “upstream”, it should be understood the direction extending towards the “origin” or extrusion location of the yarn (spin pack) and by “downstream”, it should be understood the opposite direction, in other words the direction extending towards the storage location of the elastic yarn, once the yarn has undergone all of the desired drawing operations.

[0043]In one embodiment, the plant may comprise a winding roll downstream of the take-up roll in order to store the yarn derived from the preliminary cold drawing step. Afterwards, the yarn derived from this winding roll is in a second step brought to pass over the first drawer roll.

[0044]The method for manufacturing an elastic yarn according to the present disclosure is based on the melt spinning technique using the extrusion-spinning of a molten polymer within an extruder and then a spin pack. In this respect, the different steps of the method as described hereinbelow are carried out continuously.

[0045]Thus, in a first step of the method according to the present disclosure, an extruder is fed with granules of a copolymer with polyamide blocks and with polyether blocks, the polyamide blocks being selected amongst PA 11, PA 12, PA 1010, PA 1014, a copolymer thereof and a mixture thereof, the polyether blocks being blocks derived from polytetramethylene glycol, the hardness of the copolymer measured according to the standard 7619-1 being comprised between 22 and 61 ShD, in order to obtain, by extrusion, a molten elastomer of the copolymer with polyamide blocks and with polyether blocks.

[0046]The nomenclature used to define the polyamides is described in the standard ISO 1874-1:2011: “Plastics-Polyamide (PA) molding and extrusion materials-Part 1: Designation”, in particular in page 3 (Tables 1 and 2) and is known to those skilled in the art.

[0047]Moreover, it should be pointed out that each of the expressions “comprised between . . . and . . . ” and “from . . . to . . . ” used in the present description should be understood as including the mentioned bounds.

[0048]The term “polyamide” covers both homopolyamides and copolyamides.

[0049]The copolymer used in the method according to the present disclosure has a hardness measured according to the standard 7619-1 comprised between 22 and 61 ShD, preferably between 22 and 55 ShD, preferably between 22 and 40 ShD.

[0050]The polyamide blocks may be selected amongst PA 11, PA 12, a copolymer thereof and a mixture thereof. Preferably, the polyamide blocks are PA 11 blocks.

[0064]To proceed with the first step of the method according to the present disclosure, the copolymer may be dried beforehand in order to bring the moisture content of the copolymer below 200 ppm. For example, the tests for characterizing the moisture content may be performed using the Karl-Fischer titration method.

[0065]The spinning machine comprises an extruder, for example a screw extruder, a spinning metering pump and a spin pack. In general, the spin pack comprises a die. Conventionally, the spin pack may also contain a dispenser plate, a metallic filter, and a filtering sand. The extruder and the spinning pump are purged before feeding them with the copolymer. The spinning machine also comprises a cooling system, at least one take-up roll, for example a pair of take-up rolls, at least one drawer roll, for example a pair of drawer rolls. The drawer rolls may be heatable or not. Preferably, the spinning machine also comprises a winding roll to store the product yarn.

[0066]According to a first step, step A) of the method according to the present disclosure, the granules of the copolymer with polyamide blocks and with polyether blocks as described hereinabove are introduced into the extruder within which they are molten. At the outlet of the extruder, a molten elastomer of the copolymer with polyamide blocks and with polyether blocks is obtained. According to a second step, step B) of the method according to the present disclosure, the molten elastomer obtained in step A) is spun within the die of the spin pack in order to obtain a yarn of the copolymer with polyamide blocks and with polyether blocks. The spinning metering pump controls the flow of the elastomer towards the die of the spin pack. The metallic filter and the filtering sand may be used to eliminate impurities. The elastomer is injected in to the die. At the outlet of the die, a yarn of the copolymer with polyamide blocks and with polyether blocs is established.

[0067]According to a third step, step C) of the method according to the present disclosure, the yarn of the copolymer with polyamide blocks and with polyether blocks is subjected at the outlet of the die to cooling down to a temperature strictly lower than the glass-transition temperature of said polyamide blocks, for example to a temperature ranging from about 10° C. to about 30° C., preferably ranging from about 20° C. to about 25° C.

[0068]Cooling of the yarn may be performed with air or by water quenching, depending on the thickness of the yarn and the efficiency of the cooling system. In the case of water quenching, the yarn may for example be brought to pass through a tank filled with water at a temperature of 20-25° C.

[0069]In the case of cooling with air, the yarn may be brought to pass through a cold air stream, for example brought to a temperature ranging from 10 to 25° C.

[0070]During the cooling step, the yarn solidifies.

[0071]According to a fourth step, step D) of the method according to the present disclosure, the yarn is subjected to a first drawing, or preliminary drawing, at the temperature of step C). This preliminary cold drawing allows conferring a first elasticity on the yarn.

[0072]In one embodiment, the yarn coming out of the die of the spin pack of step B) according to a spinning metering pump linear speed VP, the yarn is drawn in step D) by passing over a take-up roll having a take-up linear speed V1, V1 being selected such that the ratio D1 of the preliminary drawing is higher than or equal to 253, where D1=V1/VP. Such a preliminary drawing ratio allows conferring a significant elasticity on the yarn while preserving a good tenacity of the yarn, and therefore good mechanical properties.

[0073]In the present application, by “linear speed” of a pump or of a take-up, drawer or winding roll, it should be understood the linear speed of the external wall of the pump or of the roll in contact with the yarn during the movement of the latter.

[0074]In one embodiment, the yarn obtained upon completion of step D) may be stored on a winding roll before being subjected to step E).

[0075]According to a fifth step, step E) of the method according to the present disclosure, the yarn of the copolymer with polyamide blocks and with polyether blocks obtained upon completion of step D), whether it is stored on a winding roll or directly derived from the take-up roll, is subjected to a hot drawing. The temperature of the hot drawing is strictly higher than the glass-transition temperature of the polyamide blocks of the copolymer and may range from about 40° C. to about 125° C., preferably ranging from about 50° C. to about 125° C., preferably ranging from about 90° C. to about 120° C. The temperature of the hot drawing may depend on the linear speed of the yarn. For example, this temperature may be about 115° C. For this purpose, the yarn is brought to pass through or contact a heating means brought to the desired temperature. For example, the heating means may be an oven brought to the desired temperature. Alternatively or in combination, the heating means may comprise one or several drawer roll(s) brought to the desired temperature. For example, the hot drawing temperature may be 115° C. when the heating means is an oven located between two pairs of cold drawer rolls. In another example, the hot drawing temperature may be 45° C. when the heating means comprises hot drawing rolls (for example brought to 45° C.). The hot drawing allows reducing the thickness of the yarn, in other words increasing its fineness.

[0076]In one embodiment, the yarn is drawn in step E) by passing over a first drawer roll having a drawer linear speed V2, V2 being selected such that the hot drawing ratio D2 is lower than or equal to 8, where D2=V2/V1. When the heating means is an oven through which the yarn passes, the oven may thus be located between the take-up roll and the first drawer roll. Alternatively, the first drawer roll may be a heatable roll brought to the desired temperature. Such a hot drawing ratio allows conferring a significant fineness on the yarn while keeping an interesting elasticity.

[0077]According to a sixth step, step F) of the method according to the present disclosure, the yarn of the copolymer with polyamide blocks and with polyether blocks obtained upon completion of step E) is subjected to a cold drawing. The temperature of this cold drawing may range from about 20° C. to about 49° C., preferably from about 20° C. to about 25° C. This second cold drawing allows conferring an additional elasticity on the yarn.

[0078]In one embodiment, the yarn is drawn in step F) by passing over a second drawer roll having a drawer linear speed V3, V3 being selected such that the cold drawing ratio D3 is higher than or equal to 1, where D3=V3/V2. Such a drawing ratio in this step allows obtaining a yarn having a very good elasticity.

[0079]In one embodiment, D1=5.07. In one embodiment, D1=5.07 and D2=4. In one embodiment, D1=5.07, D2=4 and D4=1. The obtained yarn has a very good elasticity while having a good fineness.

[0080]In one embodiment, the second drawer roll is a winding roll. Thus, the yarn is wound on this roll and can be stored.

[0081]In one embodiment, the stored yarn may be subsequently subjected to a new drawing, also called post-drawing, in order to improve its springback.

[0084]During step G), the yarn may be post-drawn by passing over a first post-drawer roll having a linear speed V4 and then over a second post-drawer roll having a linear speed V5, V4 and V5 being selected such that the post-drawing ratio D4 is higher than or equal to 1.65, where D4=V5/V4.

[0087]During step H), the yarn may be relaxed by passing over a winding roll having a linear speed V6 selected such that V6/V4 ranges from 1 to 1.50, preferably from 1 to 1.25, still preferably from 1.00 to 1.05.

[0091]In one embodiment, the yarn is heat-set upon completion of step F) or subsequently to a post-drawing, in particular according to the above-described step G), or subsequently to a relaxation, in particular according to the above-described step H). The heat-setting enables the yarn to preserve its elastic and mechanical properties on the long run, for example for one yarn. For example, the heat-setting may be performed at a temperature strictly higher than the glass-transition temperature of said polyamide blocks, for example at a temperature ranging from about 70° C. to about 90° C., preferably at about 80° C.

BRIEF DESCRIPTION OF THE DRAWINGS

[0092]Other features and advantages of the present disclosure will appear more clearly upon reading the following example and from the appended drawings wherein:

[0093]FIG. 1 is a diagram representing a first embodiment of a plant allowing implementing the method according to the present disclosure,

[0094]FIG. 2 is a graph showing the results of springback and permanent deformation tests for yarns made according to the method according to the present disclosure,

[0095]FIGS. 3A-3B and FIG. 3D are graphs showing the curves of the tensile force as a function of the elongation of the yarns of Example 1,

[0096]FIGS. 4A-4C and FIG. 4D are graphs showing the hysteresis curves obtained for the yarns of Example 1,

[0097]FIG. 5 is a diagram representing a second embodiment of a plant allowing implementing the method according to the present disclosure,

[0098]FIG. 6 is a graph showing the curve of the tensile force as a function of the elongation for the yarn of Example 2,

[0099]FIG. 7 is a graph showing the hysteresis curve obtained for the yarn of Example 2,

[0100]FIG. 8 is a diagram representing a plant allowing implementing the post-drawing and relaxation steps,

[0101]FIG. 9A and FIG. 9B are graphs showing the curves of the tensile force as a function of the elongation of the yarns of Example 3.

DETAILED DESCRIPTION

[0102]Referring to FIG. 1, a first embodiment of a plant 100 is shown allowing implementing the method according to the present disclosure. The plant 100 comprises a spinning machine 1 comprising an extruder 2 and a spin pack 3. The plant 100 also comprises a tank 4 filled with water 5, a pair 6 of take-up rolls 6a, a pair 7 of drawer rolls 7a and a winding roll 8. Finally, the plant 100 comprises an oven 9 located between the take-up rolls 6 and the drawer rolls 7a.

[0103]The steps of the method according to the present disclosure will now be described with reference to FIG. 1.

[0104]Granules 10 of a copolymer with polyamide blocks and with polyether blocks are provided 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.

[0110]Prior to introduction thereof into the extruder, the granules 10 are preferably dried in order to bring the moisture content of the polymer to a level lower than 200 ppm. For example, tests for characterizing the moisture content may be performed using the Karl-Fischer titration method. For example, the granules 10 may be dried in an oven at 80° C. for one night and under vacuum.

[0111]Afterwards, the granules 10 are introduced into the extruder 2 by means of a feed hopper 11 at the level of an inlet 2a of the extruder 2. The extruder 2 comprises a body 12 formed by a cylinder in which a worm screw (not represented) rotates. The extruder 2 comprises heating areas 14 within the body 12, the temperature of these heating areas 14 increasing from the inlet 2a of the extruder 2 towards an outlet 2b of the extruder 2. For example, the temperature of the heating areas 14 may vary from 195° C. in the vicinity of the inlet 2a of the extruder to 205° C. in the vicinity of the outlet 2b of the extruder 2. The granules 10 are blended and molten within the extruder 2. At the outlet 2b of the extruder 2, a molten elastomer is obtained, which is transferred up to the spin pack 3 by means of a transfer line formed by a heat-insulated metallic hose 16. The temperature within the transfer line is close to that of the outlet temperature of the extruder 2, namely for example 205° C.

[0112]The spin 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 towards the die 19. In the represented example, the metering pump 17 rotates at a linear speed of 7.5 m/min. The filter 18 is disposed between the metering pump 17 and the die 19 and is intended to eliminate the impurities potentially present in the molten elastomer. In the represented example, the filter 18 has a pressure of 40 bar.

[0113]After having passed through the filter 18, the molten elastomer is injected into the die 19 at the temperature of the spinning pump 3 which is about 210° C. In the represented example, the size of the hole of the die 19 is 0.73 mm and the ratio of the length (L) of the die hole 19 to its diameter (D) is 1/4 (L/D ratio). Thus, a yarn 20 is formed at the outlet of the die 19. The yarn 20 comes out of the die 19 at a linear speed VP corresponding to the linear speed of the metering pump 17. In the present example, the die 19 having only one hole, the yarn 20 is in the form of a monofilament yarn.

[0114]As shown in FIG. 1, upon coming out of the die 19, the yarn 20 is brought to pass through the tank 4 filled with water 5. The water is at room temperature, in other words at a temperature ranging from about 20° C. to about 25° C. Thus, the yarn 20 is cooled by water quenching.

[0115]Cooling the yarn 20 enables the latter to solidify.

[0116]Once cooled down, the yarn 20 is brought to pass over a take-up roll 6a. The take-up roll 20 is subjected, between the outlet f the die 19 and the take-up roll 6a, to a preliminary drawing, the ratio of which is equal to D1=V1/VP. This preliminary drawing takes place at cold temperature, and in particular at a temperature lower than the glass-transition temperature of the polyamide blocks of the copolymer, for example at a temperature ranging from about 20° C. to about 25° C. Such a cold preliminary drawing allows conferring a first elasticity on the yarn 20.

[0117]Afterwards, the yarn 20 is brought to pass through the oven 9 then, at the outlet of the oven 9, to pass over a drawer roll 7a. In the represented example, the temperature at which the yarn 20 is subjected inside the furnace 9 is about 115° C. In other non-represented embodiments, the temperature of the oven could range from 50° C. to 120° C.

[0118]The drawer roll 7a has a linear speed V2, higher than the linear speed V1. Thus, the yarn 20 is subjected, between the take-up roll 6a and the drawer roll 7a, to a hot drawing, the ratio of which is equal to D2=V2/V1. This hot drawing allows reducing the thickness of the yarn 20, or conferring some fineness thereon.

[0119]Afterwards, the yarn 20 is brought to pass over the winding roll 8. In the represented example, the linear speed V3 of the winding roll is 150 m/min. This linear speed is higher than the linear speed V2. Thus, the yarn 20 is subjected, between the drawer roll 7a and the winding roll 8, to a drawing the ratio of which is equal to D3=V3/V2. This drawing takes place outside the oven 9 at room temperature, namely at a temperature ranging from about 20° C. to about 25° C. This second cold drawing allows conferring an additional elasticity on the yarn 20.

[0120]In a non-represented embodiment, the winding roll 8 could be a drawer roll, the yarn continuing its course towards a subsequent winding roll.

[0121]Referring to FIG. 5, a second embodiment of a plant 200 allowing implementing the method according to the present disclosure is shown. In this FIG. 5, the references designating elements identical to those of FIG. 1 have been preserved.

[0122]The plant 200 comprises a spinning machine 1 comprising an extruder 2 and a spin pack 3. The plant 200 also comprises a pair 6 of take-up rolls 6a, two pairs 26 of heatable drawer rolls 26a, a pair 27 of relaxation rolls 27a and a winding roll 8. The extruder 2 comprises an inlet 2a and an outlet 2b, as well as a feed hopper 11. The extruder 2 comprises heating area 14, the temperature of these heating areas 14 increasing from the inlet 2a of the extruder 2 towards an outlet 2b of the extruder 2.

[0123]The copolymer with polyamide blocks and with polyether blocks is the same as that one described for FIG. 1, namely that one sold under the trade name “PEBAX RNEW 35R53 SP 01” by the company Arkema.

[0124]Referring to FIG. 5, the copolymer granules 10 are prepared as described for FIG. 1 and are introduced into the extruder 2 through the feed hopper 11.

[0125]At the outlet of the extruder 2, the molten elastomer is transferred up to the spin pack 3 via a transfer line 16.

[0126]The spin pack 3 comprises a metering pump 17, a filter 18 and a die 19. In the plant 200, the metering pump 17 rotates at a linear speed of 65.4 m/min. The die 19 comprises 17 holes: each hole has a size of 0.6 mm and the ratio of the length (L) of a die 19 hole to its diameter (D) is 1/4 (L/D ratio). Thus, the yarn 21 that comes out of the die 19 is in the form of a multifilament yarn. The yarn 21 comes out of the die 19 at a linear speed VP corresponding to the linear speed of the metering pump 17.

[0127]The yarn 21 is cooled down by means of air quenching in the form of an air stream 22, the air stream 22 having a temperature lower than or equal to 25° C., for example a temperature of about 10° C. Preferably, the air stream 22 is applied on the yarn 21 according to the arrows F represented in FIG. 5 over a height of the yarn 21 of several meters, for example over a height of 5 m.

[0128]The plant 200 comprises a device 23 configured to apply on the yarn 21 a greasing oil. The plant 200 also comprises a guide 24 adapted to combine the various strands of the yarn 21 derived from the holes of the die 19. Greasing the yarn 21 and the guide 24 allows holding together all of the filaments derived from the holes of the die 19 in order to form a multifilament yarn 21.

[0129]Afterwards, the yarn 21 is brought to pass over a take-up roll 6a, kept at room temperature, in other words at a temperature ranging from 20 to 25° C. The take-up roll 6a has a linear speed V1, higher than the linear speed VP. Thus, the yarn 21 is subjected, between the outlet of the die 19 and the take-up roll 6a, to a preliminary drawing, the ratio of which is equal to D1=V1/VP. This preliminary drawing takes place at cold temperature, and in particular at a temperature strictly lower than the glass-transition temperature of the polyamide blocks of the copolymer, for example at a temperature ranging from about 20° C. to about 25° C. Such a cold preliminary drawing allows conferring a first elasticity on the yarn 21.

[0130]Afterwards, the yarn 21 is brought to pass over a first pair 25 of rolls 25a, which are kept at room temperature, in other words between 2° and 25° C. The linear speed of the rolls 25a is identical to that of the take-up roll 6a.

[0131]Afterwards, the yarn 21 is brought to pass over two pairs 26 of heatable drawer rolls 26a. The rolls 26a have a temperature of 50° C. and a linear speed V2 equal to V1. Thus, the yarn 21 is subjected, between the take-up roll 6a and the drawer rolls 26a, to a hot drawing, the ratio of which is equal to D2=V2/V1. This hot drawing allows reducing the thickness of the yarn 21, or conferring some fineness thereon.

[0132]Afterwards, the yarn 21 is brought to pass over a second pair 28 of rolls 28a, which are kept at room temperature, in other words between 2° and 25° C. The linear speed V3 of the rolls 28a is higher than the linear speed V2. Thus, the yarn 21 is subjected, between the drawer rolls 26a and the roll 28a, to a drawing the ratio of which is equal to D3=V3/V2. This drawing takes place at room temperature, namely at a temperature ranging from about 20° C. to about 25° C. This second cold drawing allows conferring an additional elasticity on the yarn 21.

[0133]Afterwards, the yarn 21 is brought to pass over a pair 27 of relaxation rolls 27a. The rolls 27a are kept at room temperature, in other words between 2° and 25° C. and their linear speed is identical to that of the rolls 28a. Afterwards, the yarn 21 is brought to pass over the winding roll 8. The winding roll 8 is kept at room temperature, in other words between 20° C. and 25° C. Its linear speed may be slightly lower than V3.

[0134]Referring to FIG. 8, a plant portion 300 allowing implementing a post-drawing step and a relaxation step is shown, these steps being subsequent to the extrusion, preliminary drawing, hot drawing and cold drawing steps described in FIGS. 1 and 5 for the yarns (20, 21). The yarn 22 subjected to the post-drawing and relaxation steps described in FIG. 8 may be a monofilament yarn like the yarn 20 obtained according to the method described in FIG. 1 or a multifilament yarn like the yarn 21 obtained according to the method described in FIG. 5. The yarn 22 is wound and stored on the winding roll 8.

[0135]The installation portion 300 comprises a pair 30 of first post-drawer rolls 30a, a pair 31 of second post-drawer rolls 31a and a final winding roll 32. The installation portion 300 is kept at a temperature strictly lower than the glass-transition temperature of the polyamide blocks of the copolymer with polyamide blocks and with polyether blocks forming the yarn 22, for example at a temperature ranging from about 10° C. to about 30° C., preferably ranging from about 20° C. to about 25° C.

[0136]The yarn 22 is brought to pass over a first post-drawer roll 30a and then over a second post-drawer roll 31a. The first post-drawer roll 30a has a linear speed V4 and the second post-drawer roll 31a has a linear speed V5. The linear speed V5 is higher than the linear speed V4. Thus, the yarn 22 is subjected to a post-drawing whose ratio is equal to D4=V5/V4. Such a post-drawing allows conferring an additional elasticity on the yarn 22.

[0137]Afterwards, the yarn 22 is brought to pass over the final winding roll 32. The final winding roll 32 has a linear speed V6. Preferably, this linear speed V6 is slightly higher than the linear speed V4. For example, the ratio V6/V4 ranges from about 1 to 1.50, preferably from 1 to 1.25, still preferably from 1.00 to 1.05. Thus, the yarn 22 is subjected to a relaxation step which does not alter the additional elasticity conferred by the passage of the yarn 22 over the post-drawer rolls (30a; 31a).

[0138]The elastic yarns (20, 21, 22) obtained according to the method of the present disclosure described hereinabove, in particular in FIGS. 1, 5 and 8, may be incorporated in a textile or in a garment, like for example sports pantyhoses, swimwear, etc., The yarns obtained according to the method of the present disclosure are fully recyclable. Thus, the textiles or garments incorporating these yarns are also recyclable. For example, the yarns obtained by the method according to the present disclosure, the textiles or garments incorporating them may be shredded to obtain particles. These particles may be molten to form new granules of copolymers with polyamide blocks or with polyether blocks. These granules may be introduced again in an extruder of a spinning machine to form new yarns. Thus, burying and/or incinerating the elastic yarns is avoided.

EXAMPLES

Example 1

[0139]Several yarns 20 have been obtained according to the method according to the present disclosure described hereinabove with reference to FIG. 1, while varying some parameters of the method.

a) Completed Tests:

[0150]Thus, the tests listed in Table 1 hereinbelow have been carried out:

b) Assessment of the Mechanical Properties:

[0155]All tests have been carried out under ambient conditions standardized by the standard DIN EN ISO 139 (the relative humidity (RH) being 65%+2%. The temperature being 20° C.±2° C.).

[0156][FIG. 3a], [FIG. 3b], [FIG. 3c] and [FIG. 3d] are graphs showing the curves of the tensile force as a function of the elongation respectively for the yarns of the Tests 1, 2, 3 and 4.

[0157]The results are reported in Table 2 hereinbelow:

[0158]These results show that the method according to the present disclosure allows making a yarn based on a recyclable copolymer with polyamide blocks and with polyether blocks having an average elongation at break higher than 200%, in particular 233.3%. Thus, the yarn of the Test 1 can be stretched over a length representing 233.3% of its initial length without breaking up. Thus, a yarn is obtained having a very good elasticity, which can be used in elastic textiles such as sports pantyhoses, swimwear, etc. . . .

[0159]Moreover, given its chemical nature based on polyamide and polyether, such an elastic yarn may be associated with other non-elastic yarns, based on polyamide (for example polyamide PA 6 or PA66) or polyester, to manufacture elastic textiles. The elastic textile thus obtained is fully recyclable. Thus, it is not necessary to incinerate or burry the elastic textiles thus obtained.

[0160]The results of the Table 2 hereinabove also show that at the same fineness, the higher the preliminary cold drawing ratio (D1), the more elastic the yarn will be: thus, the Test 1, for which the cold drawing ratio D1 is 5.07 has a particularly high (233.3%) average elongation at break, while the Test 3, wherein the preliminary cold drawing ratio is 2.53, has a lower (106%) average elongation at break.

[0161]Thus, the preliminary cold drawing ratio D1 is preferably higher than or equal to 2.53.

[0162]The results of Table 2 hereinabove also show that at the same fineness and at the same preliminary cold drawing ratio, the higher the cold drawing ratio (D3) after passage in the oven, the more elastic the yarn will be: thus, the Test 4, for which the cold drawing ratio (D3) after passage in the oven is 1.51, has a particularly high (180%) average elongation at break, while the Test 3, wherein the cold drawing ratio (D3) after passage in the oven is 1, has a lower (106%) average elongation at break.

[0163]Thus, the cold drawing ratio (D3) after passage in the oven is preferably higher than or equal to 8.

[0164]In any case, it is also noticed that the lower the hot drawing ratio (D2), the more elastic the yarn will be. Thus, the hot drawing ratio (D2) is preferably lower than or equal to 8.

c) Assessment of the Viscoelastic Properties:

[0168]All tests have been carried out under ambient conditions standardized by the standard DIN EN ISO 139 (the relative humidity (RH) being 65%+2%. The temperature being 20° C.±2° C.).

[0169][FIG. 4a], [FIG. 4b], [FIG. 4c] and [FIG. 4d] are graphs showing the hysteresis curves obtained respectively for the yarns of the Tests 1, 2, 3 and 4. Based on these curves, it is possible to calculate the springback and the permanent deformation of the yarns of the Tests 1-4.

[0170]The results are represented in the graph shown in FIG. 2.

[0171]It arises from this graph that the method according to the present disclosure allows making a yarn, for example a monofilament yarn, based on a recyclable copolymer with polyamide blocks and with polyether blocks having remarkable viscoelastic properties. Thus, the Test 1 has a springback of 96.6% and a permanent deformation of only 2.5%. Thus, the method according to the present disclosure allows making recyclable elastic yarns having elastic properties comparable to existing elastic yarns which are not recyclable.

Example 2

[0172]A yarn 21 has been obtained according to the method according to the present disclosure described in FIG. 5.

[0182]The yarn 21 has a linear density of 193 dtex (174 D) with 34 strands.

[0183]The mechanical properties of the yarn 21 have been measured according to the methods described in Example 1.

[0184][FIG. 6] is a graph showing the curve of the tensile force as a function of the elongation for the yarn 21.

[0185]The results are reported in Table 3 hereinafter:

[0186]The viscoelastic properties of the yarn 21 have been measured according to the methods described in Example 1.

[0187][FIG. 7] is a graph showing the hysteresis curve obtained for the yarn 21.

[0188]The results are reported in Table 4 hereinafter:

[0189]It arises from this example that the method according to the present disclosure allows making a yarn, for example a multifilament yarn, based on a recyclable copolymer with polyamide blocks and with polyether blocks having remarkable viscoelastic properties. Thus, the method according to the present disclosure allows making recyclable elastic yarns having elastic properties comparable to existing elastic yarns which are not recyclable.

Example 3

[0197]Hence, the overall post-drawing ratio over the two steps was: D4×D5=1.04.

[0198]The final average fineness of the yarn after the post-drawing and relaxation steps, on the final winding roll 32, was, in denier: 194.

[0199][FIG. 9a] is a graph showing the curve of the tensile force as a function of the elongation for the multifilament yarn 21 after the post-drawing and relaxation steps.

[0200][FIG. 9b] is a graph showing the curve of the tensile force as a function of the elongation for the multifilament yarn 21 after the post-drawing and relaxation steps.

[0201]The standards used to carry out these tests are the same as those of the previous examples.

[0206]The results are reported in Table 5 hereinafter:

[0207]These results show that the yarn has higher elastic properties after having undergone a post-drawing and a relaxation.

Example 4

[0208]A textile comprising elastic yarns (20, 21, 22) according to the present disclosure obtained according to the methods described in FIGS. 1, 5 and 8 and of the yarns made of a polyamide 6 (PA 6) has been recycled as described hereinafter.)

[0209]1° Preparation of the particles and of the mixtures of the particles:

[0210]The elastic yarns and the yarns made of polyamide 6 have been shredded in order to obtain particles.

[0214]The three following mixtures have been made:

[0224]These mixtures have been extruded using a six-side screw extruder. The used extrusion parameters are reported in Table 6 hereinbelow:

2°) Characterization

[0238]The measurement has been made after the first cycle for the Particles 1 and for the Particles 2.

[0239]The measurement has been made after the second cycle for the Granules 1, Granules 2 and Granules 3. The glass-transition temperature is determined from the second cycle. The melting point is determined from the first cycle. The crystallization temperature is determined from the first cooling cycle.

[0240]The results are reported in Table 7 hereinafter:

[0241]These results show that the Granules 1, Granules 2 and Granules 3 are homogeneous mixtures.

b°) Thermal Gravimetric Analysis

[0246]The results are reported in Table 8 hereinafter:

[0251]These results confirm that the conditions for spinning of the extruded mixtures Granules 1, Granules 2 and Granules 3 are combined.

c°) Measurement of the Viscosity Index

[0252]This test allows checking whether the viscosity of each extruded mixture Granules 1, Granules 2 and Granules 3 is suitable for melt spinning or not. The test has been carried out using sulfuric acid H2SO4 (0.5%).

[0253]The results are reported in Table 9 hereinafter:

[0254]These results confirm that the extruded mixtures Granules 1, Granules 2 and Granules 3 have a good viscosity, suitable for melt spinning.

3°) Manufacture of a Recycled Yarn from the Extruded Mixture Granules 2

[0255]The mixture Granules 2 has been dried at 65° C. under vacuum for one night.

[0256]A spinning machine is prepared comprising an extruder, a spinning metering pump and a spin pack comprising a die. The extruder is purged and then the spin pack is inserted.

[0257]The extruder is fed with Granules 2 and the extrusion is launched.

[0258]It has been possible to notice that it were possible to obtain a stable extrusion then a stable spinning. Thus, it has been possible to spin a recycled multi-stranded yarn having a fineness of about 480 dtex.

[0259]The recycled multi-stranded yarn thus obtained may be used to manufacture new textiles.