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

Abstract

The present disclosure relates to a method for manufacturing an elastic yarn by melt spinning by means of a spinning machine including an extruder and a spin pack comprising at least one die, the method comprising at least the following steps: a preliminary cold drawing of the yarn at the outlet of the die, followed by a hot drawing of the yarn then by a cold drawing of the yarn. The present disclosure also relates to a textile comprising such an elastic yarn and to a plant configured to implement this method.

Claims

1. A method for manufacturing an elastic yarn by melt spinning by means of a spinning machine comprising an extruder, a spinning metering pump, a spin pack comprising at least one die, a cooling system, at least one take-up roll and at least one drawer roll the method comprising at least the following steps: A) the 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, a 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, B) 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, C) the yarn of the copolymer with polyamide blocks and with polyether blocks obtained in step B) is subjected at an outlet of the die to cooling down to a temperature strictly lower than the glass-transition temperature of the polyamide blocks, for example to a temperature ranging from about 10 C. to about 49 C., ranging from about 10 C. to about 30 C., and ranging from about 20 C. to about 25 C., D) the yarn of the copolymer with polyamide blocks and with polyether blocks is subjected to a preliminary drawing at the temperature of step C), E) the yarn of the copolymer with polyamide blocks and with polyether blocks obtained upon completion of step D) is subjected to a hot drawing at a temperature strictly higher than the glass-transition temperature of the polyamide blocks, for example at a temperature ranging from about 45 C. to about 125 C., ranging from 45 C. to 120 C., ranging from about 50 C. to about 125 C., and ranging from about 90 C. to about 120 C., F) the yarn of the copolymer with polyamide blocks and with polyether blocks obtained upon completion of step E) is subjected to a cold drawing at a temperature ranging from about 10 C. to about 49 C., ranging from about 10 C. to about 30 C., and ranging from about 20 C. to about 25 C.

2. The method according to claim 1, wherein, the yarn coming out of the die of the spin pack in 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 preliminary drawing ratio D1 is greater than or equal to 2.53, where D1=V1/VP.

3. The method according to claim 1, wherein during step E), the yarn is drawn by passing over a first drawer roll having a drawer linear speed V2, V2 being selected such that the hot drawing ratio D2 is less than or equal to 8, where D2=V2/V1.

4. The method according to claim 1, wherein during step F), during step F), the yarn is drawn by passing over a second drawer roll having a drawer linear speed V3, V3 being selected such that the cold drawing ratio D3 is greater than or equal to 1, where D3=V3/V2.

5. The method according to claim 4, wherein the second drawer roll is a winding roll.

6. The method according to claim 1, wherein during step C), the yarn is cooled by water quenching.

7. The method according to claim 1, wherein during step C), the yarn is cooled by air quenching.

8. The method according to claim 1, wherein the yarn of the copolymer with polyamide blocks and with polyether blocks obtained upon completion of step F) is heat-set at a temperature strictly higher than the glass-transition temperature of the polyamide blocks, at a temperature ranging from about 70 C. to about 90 C., r at about 80 C.

9. The method according to claim 1, further comprising the following step G): G) the yarn of the copolymer with polyamide blocks and with polyether blocks obtained upon completion of step F) is subjected to a post-drawing at a temperature strictly lower than the glass-transition temperature of the polyamide blocks, for example at a temperature ranging from about 10 C. to about 30 C., or ranging from about 20 C. to about 25 C.

10. The method according to claim 9, wherein during step G), the yarn is 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 is greater than or equal to 1.65, where D4=V5/V4.

11. The method according to claim 9, wherein the method further comprises the following step H): H) the yarn of the copolymer with polyamide blocks and with polyether blocks obtained upon completion of step G) is subjected to a relaxation at a temperature strictly lower than the glass-transition temperature of the polyamide blocks, for example at a temperature ranging from about 10 C. to about 30 C., or ranging from about 20 C. to about 25 C.

12. The method according to claim 11, wherein during step H), the yarn is relaxed by passing over a winding roll having a linear speed V6 selected such that V6/V4 ranges from 1 to 1.50, from 1 to 1.25, and from 1.00 to 1.05.

13. The method according to claim 2, wherein D1=5.07.

14. The method according to claim 3, wherein D2=4.

15. The method according to claim 4, wherein D3=1.

16. The method according to claim 1, wherein the hardness of the copolymer measured according to the standard 7619-1 is comprised between 22 and 55 ShD, or between 22 and 40 ShD.

17. The method according to claim 1, wherein the polyamide blocks are selected amongst PA 11, PA 12, a copolymer thereof and a mixture thereof.

18. The method according to claim 17, wherein the polyamide blocks are PA 11 blocks.

19. An elastic yarn obtained by the method according to claim 1, having a average elongation at break, measured according to the standard DIN ISO 13895, higher than or equal to at least one of the following; about 106%, about 131%, 164.5%, 180%, and about 233.3%, and/or having a springback, measured according to the standard DIN 53835-2, higher than or equal to at least one of the following: about 86.5%, 91.8%, 94%, 96.3%, and 96.6%.

20. A textile comprising at least one yarn obtained according to claim 1.

21. A garment comprising at least one yarn obtained according to claim 1.

22. A plant configured to implement the method according to claim 1, the plant comprising: a spinning machine comprising an extruder, a spinning metering pump, a spin pack comprising at least one die, a cooling system disposed at the outlet of the die, at least one take-up roll disposed at the outlet of the cooling system, at least one first drawer roll, disposed downstream of the take-up roll, at least one second drawer roll disposed downstream of the first drawer roll, a heating means disposed between the take-up roll and the first drawer roll.

23. The plant according to claim 22, wherein the second drawer roll is a winding roll.

24. The plant according to claim 23, further comprising: at least one first post-drawer roll disposed downstream of the winding roll, at least one second post-drawer roll disposed downstream of the first post-drawer roll.

25. A method for recycling a textile comprising at least one elastic yarn according to claim 19, and at least one thermoplastic yarn, preferably made of polyamide, wherein the method comprises the following steps: i) the textile is shredded in order to obtain particles, ii) the particles derived from step i) are molten afterwards within an extruder in order to obtain granules of the mixture.

26. The recycling-method according to claim 25, wherein the method it further comprises the following step iii): iii) a recycled yarn is spun by melt extrusion of the granules obtained in step ii).

Description

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.

[0105] This elastomer copolymer has the following characteristics: [0106] a density of 1,020 Kg/m.sup.3, measured according to the standard ISO 1183, [0107] a hardness of 25 shore D, at 15 seconds, measured according to the standard ISO 7619-1, [0108] a melting point of 135 C., measured according to the standard ISO 11357-1/-3, [0109] a polyamide PA 11 content, which is a bio-based polyamide, of 29%, measured according to the standard ASTM D6866.

[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:

[0140] Several tests have been carried out implementing the method described with reference to FIG. 1, wherein the following parameters have been varied: [0141] The linear speed V1 of the take-up roll 6a, [0142] The linear speed V2 of the take-up roll 7a, [0143] The drawing ratio D1, [0144] The drawing ratio D2, [0145] The drawing ratio D3.

[0146] The fixed parameters were the following ones: [0147] The linear speed VP was 7.4 m/min, [0148] The linear speed V3 was 150 m/min, [0149] The total drawing ratio TD, in other words TD=D1D2D3, was 20.3.

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

TABLE-US-00001 TABLE 1 variations of the parameters V1, V2, D1, D2 and D3 V1 V2 Test (m/min) D1 (m/min) D2 D3 Test 1 37.5 5.07 150 4 1 Test 2 25 3.37 150 6 1 Test 3 18.75 2.53 150 8 1 Test 4 19 2.57 99 5.21 1.51

b) Assessment of the Mechanical Properties:

[0151] For each Test 1-4, the following mechanical properties of the yarn obtained after winding on the winding roll 8 have been measured: [0152] the average fineness of the yarn: the fineness of the yarn is expressed in denier. It is representative of the size (diameter) of the yarn. The fineness has been measured in accordance with the method described in the standard DIN EN ISO 13392; [0153] the average tenacity of the yarn: the tenacity is expressed in cN/tex. It is representative of the tensile strength of the yarn. It has been measured in accordance with the method described in the standard DIN EN ISO 13895; [0154] the average elongation at break: the average elongation at break is expressed in percents (%). It is representative of the elasticity of the yarn. The higher the average elongation at break of the yarn, the more elastic the yarn will be. The average elongation at break has been measured in accordance with the method described in the standard DIN ISO 13895.

[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:

TABLE-US-00002 TABLE 2 mechanical properties Average Average Standard Average Standard fineness tenacity deviation elongation deviation Test (denier) (cN/tex) (cN/tex) at break (%) (%) Test 1 108 15.2 0.74 233.3 16.6 Test 2 108 20.2 0.42 164.5 22.6 Test 3 105 25.6 2.3 106 16.1 Test 4 108 22.9 1.95 180 27.5

[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:

[0165] For each Test 1-4, the following viscoelastic properties of the yarn obtained after winding on the winding roll 8 have been measured: [0166] The springback: the springback is expressed in percents (%). It is representative of the recovery capacity of the elastic yarn when the stresses applied to deform it are suppressed. The highest possible springback is to be obtained. The springback has been measured in accordance with the method described in the standard DIN 53835-2; [0167] The permanent deformation: the permanent or irreversible deformation is expressed in percents (%). It is representative of the permanent loss of elasticity of the yarn after several successive stretches. The lowest possible permanent deformation is to be obtained. The permanent deformation has been measured in accordance with the method described in the standard DIN 53835-2.

[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.

[0173] The values of the parameters were as follows: [0174] The linear speed VP was 65.4 m/min [0175] The linear speed V1 of the take-up roll 6a was 1,333 m/min [0176] The linear speed V2 of the drawer rolls 26a heated at 50 C. was 1,333 m/min [0177] The linear speed V3 of the roll 28a at room temperature was 2,000 m/min [0178] The linear speed of the winding roll is 1,950 m/min [0179] The drawing ratio D1 was: D1=VP/V1=20.4 [0180] The drawing ratio D2 was: D2=V2/V1=1 [0181] The drawing ratio D3 was: D3=V3/V2=1.5

[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:

TABLE-US-00003 TABLE 3 mechanical properties Average Standard Average Standard tenacity deviation elongation deviation Test (cN/tex) (cN/tex) at break (%) (%) Yarn 21 1.85 0.06 131 13

[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:

TABLE-US-00004 TABLE 4 viscoelastic properties Permanent Springback Test deformation (%) (%) Yarn 21 6 94

[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

[0190] A multifilament yarn 21 obtained according to the method described in FIG. 5 has been subjected to a post-drawing step and then a relaxation step as described in FIG. 8, with the following parameters: [0191] Initial average fineness of the multifilament yarn in denier, on the winding roll 8: 202 [0192] Linear speed V4 of the first post-drawer roll 30a: 103 m/min [0193] Linear speed V5 of the second post-drawer roll 31a: 107 m/min [0194] post-drawing ratio D4: D4=V5/V4=1.65 [0195] Linear speed V6 of the final winding roll 32:107 m/min [0196] relaxation ratio D5: D5=V6/V5=0.63

[0197] Hence, the overall post-drawing ratio over the two steps was: D4D5=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.

[0202] In these curves: [0203] the portion referenced A corresponds to the elastic initial portion, [0204] the portion referenced B corresponds to the rigid portion, [0205] the portion referenced C corresponds to the viscoelastic portion.

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

TABLE-US-00005 TABLE 5 On the winding On the winding Yarn 21 roll 8 roll 32 Average elongation 40 60 at break (%) of the portion A Average elongation 60 100 at break (%) of the portion B Average elongation 200 190 at break (%) of the portion C

[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.

[0211] The following designations are used: [0212] Particles 1: the particles of yarns made of polyamide 6, [0213] Particles 2: the particles of elastic yarns.

[0214] The three following mixtures have been made:

[0215] Mixture 1: this mixture comprised, in mass with respect to the mass of the mixture: [0216] 90% of Particles 1, and [0217] 10% of Particles 2.

[0218] Mixture 2: this mixture comprised, in mass with respect to the mass of the mixture: [0219] 80% of Particles 1, and [0220] 20% of Particles 2.

[0221] Mixture 3: this mixture comprised, in mass with respect to the mass of the mixture: [0222] 70% of Particles 1, and [0223] 30% of Particles 2.

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

TABLE-US-00006 TABLE 6 Parameter Mixture 1 Mixture 2 Mixture 3 Pressure of the extruder (bar) 8.5 8.5 13 Temperature Area 1 235 235 235 of the Area 2 240 240 240 extruder ( C.) Area 3 245 245 245 Area 4 245 245 245 Area 5 245 245 245 Area 6 250 250 250 Speed of the metering unit of 15 15 15 the feeder (rpm) Speed of the screw of the 50 50 50 extruder (rpm)

[0225] At the extruder outlet, the molten mixtures are subjected to granulation. The following designations are used: [0226] Granules 1: the granules derived from the extrusion of the Mixture 1 [0227] Granules 2: the granules derived from the extrusion of the Mixture 2 [0228] Granules 3: the granules derived from the extrusion of the Mixture 3

2) Characterization

[0229] The Particles 1, the Particles 2, and the Granules 1, Granules 2 and Granules 3 have been characterized using the following tests: [0230] Differential Scanning calorimetry DSC [0231] Thermal Gravimetric Analysis TGA [0232] Measurement of the viscosity index
a) Differential Scanning calorimetry DSC

[0233] This test allows checking whether the granulate will form one phase or two phases. The test has been carried out according to the following procedure: [0234] First DSC cycle: from 70 C. to +350 C. or less if the thermal degradation starts before, no hold time, [0235] Second DSC cycle: from +350 C. to 70 C., no hold time, [0236] Third DSC cycle: from 70 C. to +350 C. or less if the thermal degradation starts before, [0237] Final cooling

[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:

TABLE-US-00007 TABLE 7 Parti- Parti- Gran- Gran- Gran- cles 1 cles 2 ules 1 ules 2 ules 3 Glass- 54.98 53.6 53.3 52.0 transition temperature ( C.) Melting 222.65 128.7 221.7 221.3 221.0 point (%) Crystallization 182.9 92.1 186.7 184.4 185.9 temperature (%) Crystallization 69.4 15.2 58.9 57.1 49.4 enthalpy H.sub.Recrist (J/g)

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

b) Thermal Gravimetric Analysis

[0242] This test allows verifying the start of the thermal degradation for each particle/granule. The test has been carried out according to the following program: [0243] Nitrogen condition [0244] Heating up to 600 C. [0245] Heating rate always at 10 C./min

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

TABLE-US-00008 TABLE 8 Parti- Parti- Gran- Gran- Gran- cles 1 cles 2 ules 1 ules 2 ules 3 Thermal 417.02 393.37 409.52 404.97 397.25 degradation start temperature ( C.) Mass 98.73 99.06 98.56 94.74 98.91 loss (%) Residues (%) 1.27 0.94 1.44 5.26 1.09

[0247] These results show that the Particles 1, the Particles 2 and the extruded mixtures Granules 1, Granules 2 and Granules 3 start thermally degrading at temperatures higher than their respective spinning temperatures. Indeed: [0248] Spinning temperature for the Particles 1:260 C. [0249] Spinning temperature for the Particles 2:220 C. [0250] Spinning temperature for the Granules 1, Granules 2 and Granules 3:250 C.

[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:

TABLE-US-00009 TABLE 9 Parti- Parti- Gran- Gran- Gran- cles 1 cles 2 ules 1 ules 2 ules 3 Viscosity 119 5 107 95 81 index (mg/L)

[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.