Polyethylene furanoate spun yarn and its manufacturing method

Abstract

The present invention relates to a spun yarn comprising polyethylene 2,5-furandicarboxylate (PEF) filaments, which exhibits a breaking strength at least equal to 4 cN / dtex and a breaking energy at least equal to 40 cN / dtex, the breaking energy being defined as the product of the breaking strength (cN / dtex) and the breaking elongation (%), the breaking strength and breaking elongation being measured according to ASTM standard D885-03, and to a method for preparing the same.

Description

[Technical Field]

[0001] The present invention relates to the field of textile yarns and methods for their production.

[0002] prior art Polyesters have many applications in industrial and textile fields. Their versatility means that very large quantities of polyester are produced each year. Therefore, there is interest in synthesizing polyesters from monomers obtained from renewable resources, which exhibit technical characteristics that allow them to replace petroleum-based polyesters, such as polyethylene terephthalate (PET).

[0003] A great deal of research has been carried out to prepare polyesters from furandicarboxylate monomers, since they can be obtained from renewable resources, such as sugars, making it possible to envision a reduced environmental impact in the production of these polyesters. The synthesis of polyesters typically involves an esterification step and a polycondensation step, optionally followed by a crystallization step and a solid-state post-condensation step to adjust the polyester's properties, followed by a molding step, particularly a spinning step, if desired to obtain yarns. The structure of the resulting polyester, and therefore its characteristics, depend on how these various steps are carried out.

[0004] Among the various properties required, particularly for use in rubber articles (such as tires or conveyor belts), it is desirable for the yarn to be able to withstand high thermomechanical stresses and therefore to simultaneously exhibit high tensile mechanical strength and high elongation at break, high tensile stiffness and high heat resistance.

[0005] Document EP 3348679 describes, for example, that a combination of a draw ratio greater than 6 and a ratio of the take-up speed of the spun yarn to the exit speed of the filaments from the extrusion die (spinning draft) ranging from 700 to 2000 makes it possible to obtain PEF spun yarns with a high storage modulus (defined in a way known as the real part of the dynamic modulus or complex modulus, which describes the response of a material to dynamic stress) and a relatively high strength (greater than 3.0 cN / dtex).

[0006] Document WO2014 / 204313 teaches the production of PEF yarns that exhibit relatively high strength at the expense of elongation at break. These yarns are obtained by spinning PEF in a first stage at 90°C with a draw ratio of 2.5, followed by a second stage at 100°C or 150°C with a draw ratio of 1.8 (i.e., a total draw ratio of 4.5).

[0007] However, it is still desirable to obtain yarns that combine high breaking strength while maintaining high breaking elongation, where breaking elongation is expressed as breaking energy, which is defined as the product of breaking strength (cN / dtex) and breaking elongation (%), expressed in cN / dtex, which corresponds to [J] / [kg].

[0008] Detailed Description of the Invention The present invention relates to a spun yarn comprising polyethylene 2,5-furandicarboxylate (PEF) filaments, which exhibits a breaking strength at least equal to 4 cN / dtex and a breaking energy at least equal to 40 cN / dtex, the breaking energy being defined as the product of the breaking strength (cN / dtex) and the breaking elongation (%), the breaking strength and breaking elongation being measured according to ASTM standard D885-03.

[0009] definition The carbon-containing compounds referred to herein may be fossil-derived or bio-based. In the latter case, they may be derived, in part or entirely, from biomass or from renewable raw materials derived from biomass. Polymers, plasticizers, fillers, etc. are particularly relevant.

[0010] The yarn of the present invention The present invention relates to a spun yarn comprising polyethylene 2,5-furandicarboxylate (PEF) filaments, which exhibits a breaking strength at least equal to 4 cN / dtex and a breaking energy at least equal to 40 cN / dtex, the breaking energy being defined as the product of the breaking strength (cN / dtex) and the breaking elongation (%), the breaking strength and breaking elongation being measured according to ASTM standard D885-03.

[0011] PEF is a polyester containing ethylene 2,5-furandicarboxylate units and diethylene glycol units.

[0012] The spun yarn of the present invention preferably has a secant modulus at 3 cN / dtex of at least 13 GPa, preferably at least 15 GPa. Such a secant modulus enables the spun yarn of the present invention to exhibit very good tensile stiffness, making it useful for use as a reinforcing element for rubber articles, such as pneumatic or non-pneumatic tires or conveyor belts.

[0013] Preferentially, the spun yarn of the invention exhibits an elongation at break greater than 6%, preferably at least equal to 8%, which, together with the other characteristics of the yarn, allows the spun yarn of the invention to withstand the high mechanical stresses to which rubber articles, such as pneumatic or non-pneumatic tires or conveyor belts, may be subjected.

[0014] Preferentially, the PEF constituting the filaments of the inventive yarn exhibits a melting point at least equal to 215° C. Such a melting point allows the inventive yarn to respond to high thermal stresses, for example during the curing of rubber articles in which the yarn may be used as a reinforcing element.

[0015] Preferably, the spun yarn of the invention consists of PEF filaments. The term "consisting of" is understood to mean that the spun yarn of the invention preferentially does not contain filaments of any other chemistry than PEF filaments, and in particular does not contain PET (polyethylene terephthalate) filaments. This is because the thermomechanical properties of the spun yarn of the invention are sufficient to allow its use without the need to reinforce the yarn with filaments of another chemistry.

[0016] The present invention also relates to a textile article comprising at least one of the yarns of the present invention or prepared according to the method described below. The article may be a fabric that can be used to make reinforcing elements, for example, vehicle tires, or else clothing, inflatable articles, etc.

[0017] To make textile articles, the yarns of the invention, or yarns prepared according to the methods of the invention, can be twisted, embossed, reamed, weaved, knitted, braided, two-dimensionalized or three-dimensionalized, either alone or in combination with other yarns known to those skilled in the art, such as polyester, polyamide or aramid yarns, natural or regenerated fibers.

[0018] The present invention also relates to a reinforced product comprising the yarn of the present invention or the yarn prepared according to the method of the present invention, wherein said yarn is embedded in a polymeric matrix, in particular an elastomeric matrix.

[0019] Such a reinforced product may be any product reinforced by a textile article, and in particular may be a reinforced product chosen from transmission belts, conveyor belts, inflatable articles and tyres for wheels.

[0020] Synthesis of PEF used in the spun yarn of the present invention The PEF used in the spun yarn of the present invention has at least the following stages: · Esterification stage; · Polycondensation stage; · Crystallization stage; · Post-condensation stage in the solid state; The step of forming into granules It is synthesized by the method using

[0021] Esterification Stage The process for the synthesis of PEF used in the spun yarns of the present invention comprises a step of esterification of a composition comprising a dimethyl 2,5-furandicarboxylate compound, designated DMF, which also comprises ethylene glycol, designated EG, in the presence of a Lewis acid catalyst at an increasing temperature ranging from 150° C. to at least 185° C., with an EG / DMF molar ratio ranging from 3 to 1.3.

[0022] The esterification step allows the preparation of ethylene furan dicarboxylate oligomers from the reaction of ethylene glycol with a furan dicarboxylate compound. The operating conditions for this step have a decisive influence on the structure of the resulting polyester. The EG / DMF molar ratio in the composition fed to this step is preferentially between 2 and 1.5. A ratio below 1.3 significantly affects the degree of reaction, while a ratio above 3 results in an excessively high content of diethylene glycol (DEG) units in the polyester.

[0023] The esterification step is carried out for a period of time that is preferentially in the range of 1 to 5 hours, preferably in the range of 2 to 4 hours.

[0024] According to the invention, the esterification step is carried out at an increasing temperature in the range of from 150°C to at least 185°C. The term "increasing in the range of from 150°C to at least 185°C" is understood to mean that the esterification step is carried out at a temperature comprised between the temperatures in the range of from 150°C to at least 185°C, and that the operating temperature increases during the esterification step. The use of an increasing temperature profile, especially in combination with other operating parameters, makes it possible to obtain polyesters that exhibit particularly high melting points. This is due to the very low content of DEG units and the very low amount of ester functions located at the chain ends.

[0025] In a preferred preparation, the temperature is continuously increased in the range of 150° C. to at least 185° C., according to a gradient of not more than +1° C. / min, preferably not more than +0.5° C. / min. Once the maximum temperature is reached, a stationary phase can be maintained until the degree of esterification exceeds 80%.

[0026] In another preferred preparation, the temperature is increased in the range of 150°C to at least 185°C, with stationary phases comprised between the range of 5°C and 15°C. Preferably, each stationary phase lasts independently from 15 minutes to 2 hours 30 minutes. Very preferentially, the esterification stage is carried out in at least three stationary temperature phases.

[0027] The maximum temperature at which the esterification step is carried out is preferentially comprised between 185° C. and 205° C., preferentially between 185° C. and 200° C., and very preferably between 190° C. and 200° C. Below 185° C., the reaction progress is significantly affected, reflected in an insufficient conversion of the ester chain ends and an insufficient final intrinsic viscosity, while above 205° C., the content of DEG units in the polyester increases significantly.

[0028] Preferably, the time between the end of the first stationary phase and the beginning of the last stationary phase, or between the maximum and minimum temperatures of the esterification stage when the temperature is continuously increased, is at least equal to 30 minutes, and preferentially at least 45 minutes, since it has been observed that a premature increase in temperature results in a higher content of DEG units.

[0029] Although other operating conditions of the present invention were also considered, the applicant observed that the application of these specific temperature conditions made it possible to significantly limit the formation of DEG units in the polyester while ensuring an excellent reaction rate.

[0030] For example, the esterification step can be carried out at 160° C. for 1 hour, then at 170° C. for 1 hour, and finally at 195° C. for 2 hours. In this case, the stationary phases are at 10° C. and 25° C., respectively, and the respective durations of the three stationary phases are 1 hour, 1 hour, and 2 hours.

[0031] The esterification step is preferentially carried out at moderate pressure, ranging from 0.8 to 2 bar. Preferably, said step is carried out under an inert atmosphere. Operating at moderate pressure, indeed even at slight excess pressure or underpressure, i.e. preferentially between 800 and 1700 mbar, makes it possible to carry out the esterification step in the liquid phase while discharging reaction products such as water.

[0032] The esterification step is carried out in the presence of a Lewis acid catalyst. Preferably, the Lewis acid catalyst is selected from hafnium acetylacetonate, zirconium acetylacetonate, titanium isopropoxide (TIS), and titanium tetrabutoxide (TTB). Preferably, the Lewis acid catalyst is titanium tetrabutoxide (TTB), which makes it possible to obtain a low content of DEG units and also a low degree of decarboxylation at the chain ends.

[0033] The esterification step is carried out with a catalyst content ranging from 100 to 1000 ppm, preferentially ranging from 150 to 500 ppm, very preferentially ranging from 200 to 450 ppm.

[0034] These operating conditions (temperature increase in the stated range with a steady state in the presence of a Lewis acid catalyst, in particular a catalyst such as titanium tetrabutoxide (TTB)) make it possible to significantly limit the formation of DEG units in the polymer while ensuring, at the end of the esterification of the resulting polyester prepolymer, a degree of esterification of more than 80% and an amount of ester functional groups located at the chain ends of less than 100 meq / kg, preferably less than 80 meq / kg. The degree of esterification is determined by dividing the weight of water resulting from the esterification step by the theoretical weight of water that would be produced if all the acid functional groups of the DMFC compound were reacted.

[0035] The content of DEG units in the polyester formed is less than 4 mol%, in fact less than 3 mol%, and preferably less than 2 mol%. Under the conditions of the present invention, particularly at increased temperatures, the addition of reagents that inhibit the formation of DEG units (e.g., ammonium compounds, particularly tetraalkylammonium compounds), as described in WO 2015 / 137805, did not provide any additional benefit. Therefore, the method of the present invention preferably does not include the addition of reagents that inhibit the formation of DEG units. By applying all the preferred conditions, the content of DEG units in the polyester obtained after the completion of the method of the present invention is below the detection limit by NMR-based measurements.

[0036] Polycondensation stage The process for synthesizing the PEF used in the spun yarn of the present invention comprises a polycondensation step in a molten medium, said polycondensation step being carried out at a temperature comprised between 220°C and 250°C and at a pressure less than 100 mbar.

[0037] After the end of the esterification stage, the pressure is gradually reduced over a period of between 60 and 120 minutes, preferentially between 80 and 100 minutes, until the operating pressure of the polycondensation stage is reached. When the pressure is less than 400 mbar, preferably less than 300 mbar, and very preferably less than 200 mbar, the temperature of the reaction medium is increased until the initial operating temperature of the polycondensation stage is reached. The increase in temperature to the initial operating temperature of the polycondensation stage is carried out over a period of between 15 and 45 minutes.

[0038] The use of low operating pressures, and in particular the use of decompression stages, allows the gradual venting of ethylene glycol (EG) present in the reaction system. Preferably, the polycondensation stage is carried out at increasing temperatures in the range of 220°C to 250°C. Preferentially, the temperature increases in the range of 225°C to 240°C, with stationary periods comprised between 2°C and 10°C. Preferably, each stationary period lasts independently from 15 minutes to 2 hours and 30 minutes. The applicant has observed that the application of an increasing temperature profile during the polycondensation stage allows the limitation of the formation of EG units in the polyester.

[0039] For example, the polycondensation step can be carried out at 230° C. for 1 hour and then at 240° C. for 1 hour. In this case, the stationary phase (i.e., the temperature difference between two successive operating temperatures) is 10° C., and the respective durations of the two stationary phases are 1 hour and 1 hour, respectively.

[0040] The use of increasing temperatures for the esterification and polycondensation steps is therefore advantageous, particularly in terms of controlling the structure of the resulting polyesters: they make it possible in particular to obtain polyesters containing amounts of decarboxylated chain ends below the detectable threshold.

[0041] The polycondensation step is preferentially carried out for a time ranging from 1 to 5 hours, preferably from 2 to 4 hours. This step is carried out under low pressure, preferentially below 100 mbar, very preferentially below 50 mbar. These specific conditions make it possible to maintain a very low content of DEG units in the polyester, in fact below the detection limit.

[0042] The polycondensation step is carried out using a catalyst content ranging from 100 to 1000 ppm, preferentially from 150 to 500 ppm, and very preferentially from 200 to 450 ppm. The catalyst is generally added to the reaction system during the esterification step. An additional addition of a catalyst, identical to or different from the catalyst used during the esterification step, can be carried out during the polycondensation step, if necessary.

[0043] The polyester obtained at the end of this stage, known as polycondensate, is then rapidly cooled by contacting with water and chopped into granules. This rapid contacting operation makes it possible to limit the agglomeration of the granules. The granulation step is carried out to form granules of substantially uniform size, which facilitates further processing.

[0044] The granules are then dried at a temperature ranging from 80°C to 100°C at sub-atmospheric pressure under an inert atmosphere, for example a nitrogen atmosphere.

[0045] The polyester obtained after the polycondensation step is substantially amorphous.

[0046] The polyester obtained after the polycondensation step has finished exhibits an intrinsic viscosity between 0.35 and 0.50 dL / g. This intrinsic viscosity is related to the molar mass of the polyester and is greater as the molar mass of the polyester increases. Preferably, the intrinsic viscosity of the polyester is between 0.4 and 0.50 dL / g.

[0047] Crystallization stage After shaping the polyester into granular form, a crystallization step is carried out at a temperature between the crystallization point and the melting point of the polyester, which step makes it possible to increase the crystallinity of the polyester.

[0048] To allow crystallization, the crystallization step is carried out at a temperature ranging from 150°C to 210°C for a time ranging from 15 minutes to 2 hours 30 minutes, and preferentially at a temperature ranging from 180°C to 200°C for a time ranging from 20 minutes to 1 hour 30 minutes.

[0049] Post-condensation steps in the solid state In order to increase the average molar mass of the resulting polyester and its melting point, a post-condensation step in the solid state is carried out after the crystallization step by heating the polyester to a temperature close to but below its melting point.

[0050] The solid-state post-condensation stage is therefore carried out for a time ranging from 24 to 72 hours at an increasing temperature ranging from 210° C. to 260° C., preferentially from 210° C. to 250° C., very preferentially from 210° C. to 235° C. Preferably, the temperature of the solid-state post-condensation stage is increased in a stationary phase ranging from 2° C. to 10° C.

[0051] By carrying out this step at increasing temperatures in the range of 210° C. to 260° C., preferentially in the range of 220° C. to 250° C., preferably by increasing this temperature in a stationary phase in the range of 2° C. to 10° C., preferentially 3° C. to 5° C., the increase in molar mass and melting point of the polyester obtained is maximized. Moreover, surprisingly, the melting zone (i.e., the temperature zone where melting is observed, visualized in a thermogram obtained by DSC, according to the method described hereinafter) is significantly reduced compared to polyesters obtained according to the methods of the prior art.

[0052] After the end of the post-condensation stage in the solid state, the intrinsic viscosity of the polyester increases and is preferably between 0.65 and 1.05 dl / g, preferentially between 0.65 and 0.90 dl / g.

[0053] The characteristics of the polyester synthesized according to the method described above make it particularly possible to spin it to obtain the yarn of the invention. In particular, its high molar mass, melting point, and intrinsic viscosity make it possible to obtain a yarn with particularly advantageous thermomechanical characteristics by spinning it under the specific conditions described below. The very high melting point of the resulting polyester makes it particularly possible for the yarn made from this polyester under the conditions of the invention to be incorporated into pneumatic tires and to withstand the harsh curing conditions imposed during the crosslinking operation of the tires.

[0054] The granules are subsequently used to form the spun yarn of the present invention by a melt-spinning process, said melt-spinning process comprising at least the following steps: Spinning the granules by melting / extrusion; drawing the spun yarn; Winding onto the take-up reel Includes.

[0055] Process for producing the spun yarn of the present invention The present invention also relates to a method for the production of a spun yarn made of PEF filaments, said method comprising at least the following steps: a. A spinning stage in which PEF granules are fed into an extruder where they are melted, extruded and passed through a die to give filaments which are then gathered together in the form of an undrawn spun yarn; b. drawing the undrawn spun yarn through at least two sets of drawing rolls wherein the ratio of the speed of the spun yarn at the first set of drawing rolls to the average speed of the filaments at the die exit is in the range of from 3 to 59, preferentially in the range of from 10 to 25.

[0056] Spinning the granules by melting / extrusion An extruder equipped with a feed hopper, a heated extrusion screw, a positive displacement pump, and a die (containing a large number of holes with diameters ranging from 250 to 800 μm, preferably from 300 to 500 μm) makes it possible to produce filaments with diameters ranging from 10 to 70 μm, preferentially from 30 to 70 μm, and preferably from 40 to 60 μm. The extruder is fed with polymer granules that have been pre-dried in-line at the inlet of the screw or in an oven to evacuate any residual moisture therefrom. The residual moisture would be detrimental to the quality of the filaments by causing polymer degradation, particularly chain hydrolysis, induced by heating during passage through the die.

[0057] The polymer is melted, sheared and extruded by an extrusion screw at elevated temperature to a positive displacement pump, the throughput of which is selected and fed to a die. The extrusion temperature ranges from 240°C to 300°C, preferentially from 260°C to 290°C. The extrusion temperature is adjusted to a temperature above the melting point of the polymer, preferentially at least 20°C above the melting point of the polymer, and preferably at least 30°C above the melting point of the polymer, to ensure melting of the polymer.

[0058] The molten polymer reaches the die under pressure and at high temperature. After passing through a filter, the polymer is spun by forcing it through the holes in the die. The polymer flows by gravity through the holes to form filaments at a specific material flow rate based on the pump throughput.

[0059] The filaments, flowing out in several different streams in the molten state, are cooled by cross-current air streams to a temperature in the range of 10° C. to 30° C., preferably in the range of 15° C. to 25° C., for example to ambient temperature.

[0060] Drawing the spun yarn These filaments are subsequently brought together to form a multifilament spun yarn before being drawn and passed through a spraying or impregnation step with a sizing solution whose role is to reduce static buildup and to limit friction or rubbing between the filaments and on the spinning machine in order to facilitate subsequent processing steps of the multifilament.

[0061] Before drawing, the multifilament yarn is wound several times around a first set of rotating rolls at ambient temperature. The axes of the two cylinders are not perfectly parallel, and their surfaces are coated with a coating suitable for winding the yarn without degradation. They rotate in the same direction and at the same speed, and their temperature can be gradually adjusted. In practice, the yarn is wound around the two rolls for several revolutions. During part of its path, contact with the rolls changes its temperature, and in the case of this first set, the temperature decreases, but it is not drawn.

[0062] The yarn is passed from one set of rolls to the next set of rolls along the same trajectory with several windings around each set, up to the last set, and fed to a storage reel.

[0063] The spun yarn can also be stored on a storage reel as an intermediate step between two drawing stages, which is then referred to as two (or multiple) stage drawing.

[0064] Each set of rolls has a different temperature and a different speed than the previous set, which is selected according to the desired degree of drawing at each stage. It is the difference in rotational speed between two successive sets that causes a "cold" drawing of the filaments, as opposed to a "melt" drawing, during their gravity drop between the die exit and the first set of rolls. The speed between two successive sets of rolls can be slightly slowed to relax the spun yarn and thus limit its normal shrinkage, and the rotational speed increases throughout the forward direction of the spun yarn.

[0065] Preferably, each set of rolls, except for the first set, which is at ambient temperature, is regulated at a temperature ranging from 30°C to 180°C, preferably from 40°C to 150°C.

[0066] Preferably, each set of rolls, except the first set, is conditioned at a temperature above 100° C., preferably between 100° C. and 150° C. Such temperature conditioning makes it possible to obtain spun yarns with very good breaking elongation without degrading strength. Below these temperatures, spun yarns with very good strength can be obtained with lower breaking elongation.

[0067] Preferably, the step of drawing the spun yarn is carried out over 2 to 10 successive sets of rolls, preferably over 3 to 6 successive sets of rolls, and very preferentially over 4 to 6 successive sets of rolls.

[0068] Preferably, the draw ratio of the spun yarn in step b) is between 1.5 and 6, corresponding to the ratio of the speed of the last set of rolls to the speed of the first set of rolls.

[0069] At the exit of the last set of rolls, the yarn is spirally wound onto a take-up reel. [Brief explanation of the drawings]

[0070] [Figure 1] FIG. 1 shows a schematic representation of a possible sequence of the method of the present invention.

[0071] Through a feed hopper (A), PEF granules are fed into a heated extrusion screw (B), where they are melted and extruded into a positive displacement pump (C) and into a die (D) containing several holes. As they pass through these holes, the molten polymer forms filaments that flow out by gravity and are cooled by a cross-flow of air.

[0072] These filaments are gathered into a spun yarn and wound several times around a first set of rolls at ambient temperature (E1). Because the speed of the filaments at the die exit is slower than the speed of the spun yarn at the first set of rolls, the spun yarn is therefore subjected to a first drawing.

[0073] The yarn is passed from one set of rolls to the next (E1, E2, E3, E4) along the same trajectory with several windings around each set, up to the last set (E5), where it is fed to a storage reel (F).

[0074] The diagram presented in this application includes, but is not limited to, a total of five sets of rolls. This is a "single-stage" drawing diagram because the yarn is drawn from the die exit to the storage reel without intermediate storage on the reel. Intermediate storage can be envisioned after the first set of rolls or between subsequent sets of rolls.

[0075] Measurement method Secant Coefficient The secant modulus is determined from a strength / elongation curve obtained in a tensile test carried out in accordance with ASTM standard D885-3 by measuring the slope of a line passing through the origin and the point on the curve corresponding to a strength of 3 cN / dtex.

[0076] The strength 3 cN / dtex is converted to force by multiplying the strength by the count of the spun yarn tested:

number

number

number

number

[0077] Manufacturing of PEF granules In the transesterification step, a composition comprising dimethyl furan dicarboxylate (DMF) and ethylene glycol (EG) is fed in an EG / DMF molar ratio equal to 1.7, which is combined with 400 ppm of titanium tetrabutoxide (TTB) catalyst.

[0078] The transesterification step is carried out at 1.5 bar, with a temperature gradient of +0.2°C / min, varying from 160°C to 194°C over 3 hours, and once the maximum temperature is reached, maintaining it there.

[0079] At the end of this stage, a prepolymer is obtained in which the presence of DEG units is not detectable, the degree of transesterification being 82%.

[0080] The pressure of the reaction medium is first reduced to 200 mbar over 20 minutes while maintaining the temperature at 194° C. Once the pressure reaches 200 mbar, the temperature is increased to 230° C. over 30 minutes while continuing to reduce the pressure. Finally, 40 minutes after reaching 230° C., i.e., when P<1.3 mbar, the polycondensation stage begins, during which the temperature is maintained at 230° C. for 1 hour, then increased to 240° C. and maintained for 1 hour.

[0081] After the polycondensation stage is over, the polycondensate is rapidly cooled by contacting it with water and cut into granules.

[0082] The granules obtained are subsequently dried at 100° C. for 5 hours before they are subjected to a crystallization step in which they are raised to a temperature of 190° C. over 1 hour 30 minutes.

[0083] After the crystallization is complete, a post-condensation step in the solid state is carried out, in which the granules are brought to a temperature of 217° C. over 6 hours under a nitrogen stream and then to a temperature of 227° C. over 34 hours.

[0084] The polyester obtained at the end of this stage has the following characteristics: ·Intrinsic viscosity (IV): 0.71dl / g Crystallinity: 52% Melting point: 234.5℃ Shows.

[0085] The melting point, measured by applying a temperature gradient of 20 K / min, as recommended in ISO standard 11357-3 of March 2018, is 242.5 °C.

[0086] Spinning of PEF granules The granules are spun according to the method described below.

[0087] The granules are fed into a screw extruder and the temperature is gradually increased. A positive displacement pump feeds the molten polymer into a die containing four circular openings, the die temperature being T 紡糸 is equal to.

[0088] The four filaments are gathered into a spun yarn, which is drawn through a series of five sets of rolls and then spirally wound onto a take-up reel at a speed equal to the take-up speed.

[0089] The applied draw ratios are shown in Table 1, where the draw ratio corresponds to the ratio of the speed of the last set of rolls to the speed of the first set of rolls, as well as other parameters of the spinning process.

[0090] [Table 1]

[0091] The characterizations performed on the resulting spun yarn are shown in Table 2. These characterizations are performed starting from a spun yarn sample unwound from the take-up reel.

[0092] [Table 2]

[0093] The spun yarns shown in Table 3 were produced according to the same method as those in Table 1. The temperature of the sets of draw rolls was varied. "Amb." means that the first set of rolls was at ambient temperature, i.e., about 25°C.

[0094] [Table 3]

[0095] The properties of these spun yarns, determined from samples collected on the take-up reel, are shown in Table 4.

[0096] [Table 4]

[0097] By using temperatures above 100°C, it is possible to improve the elongation at break without significantly affecting the strength of the spun yarn.

Claims

1. A spun yarn comprising polyethylene 2,5-furandicarboxylate (PEF) filaments, the spun yarn exhibiting a breaking strength at least equal to 4 cN / dtex and an energy to break at least equal to 40 cN / dtex, the energy to break being defined as the product of the breaking strength (cN / dtex) and the elongation to break (%), the breaking strength and the elongation to break being measured according to ASTM standard D885-03.

2. 2. The spun yarn according to claim 1, which exhibits a secant modulus at 3 cN / dtex of at least 13 GPa, preferably at least 15 GPa.

3. 3. The spun yarn according to claim 1 or 2, which exhibits an elongation at break greater than 6%, preferably at least equal to 8%.

4. 4. The spun yarn according to claim 1, wherein the PEF constituting the PEF filaments of the spun yarn exhibits a melting point at least equal to 215°C.

5. 5. The spun yarn according to claim 1, which consists of PEF filaments.

6. 6. A method for producing spun yarn according to claim 5, said method comprising at least the following steps: a. A spinning stage in which PEF granules are fed into an extruder where they are melted, extruded and passed through a die to give filaments which are then gathered together in the form of an undrawn spun yarn; b. Drawing the undrawn spun yarn through at least two sets of drawing rolls. wherein the ratio of the speed of the spun yarn at the first set of draw rolls to the average speed of the filaments at the die exit is in the range of 10 to 25.

7. 7. A process according to claim 6, wherein the extrusion temperature in step a) ranges from 240°C to 300°C, preferentially from 260°C to 290°C.

8. 8. A method according to claim 6 or 7, wherein each set of drawing rolls, except for the first set, is adjusted to a temperature higher than 100°C, preferably between 100°C and 150°C.

9. 9. The method according to any one of claims 6 to 8, wherein the draw ratio of the spun yarn in step b) is between 1.5 and 6.

10. 10. A method according to any one of claims 6 to 9, wherein the step of drawing the spun yarn is carried out over 2 to 10 successive sets of rolls, preferably over 3 to 6 successive sets of rolls, very preferentially over 4 to 6 successive sets of rolls.

11. PEF granules, an esterification step of a composition comprising a dimethyl 2,5-furandicarboxylate compound, designated DMF, said composition also comprising ethylene glycol, designated EG, said esterification step being carried out in the presence of a Lewis acid catalyst at a temperature increasing between the range of 150°C and at least 185°C, with an EG / DMF molar ratio ranging from 3 to 1.3; a polycondensation step in a molten medium, carried out at increasing temperatures ranging from 220°C to 250°C and at a pressure of less than 100 mbar, to obtain a polyester; The method according to any one of claims 6 to 10, wherein the method is obtained by a process comprising the steps of:

12. 12. A textile article comprising at least one spun yarn according to any one of claims 1 to 5 or a spun yarn prepared by the method according to any one of claims 6 to 11.

13. 12. A reinforced product comprising the spun yarn according to any one of claims 1 to 5 or the spun yarn prepared according to any one of claims 6 to 11, wherein the spun yarn is embedded in a polymer matrix.

14. 14. The reinforced product of claim 13, selected from a transmission belt, a conveyor belt, an inflatable article, and a tire for a wheel.

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