Bis(2-hydroxyethyl)terephthalate solid having a particular crystal form

Abstract

The present invention relates to a solid material mainly composed of BHET having a crystal form with a particular X-ray diffraction diagram, a method for the preparation thereof, a composition comprising said material, and the use of said composition for preparing a polyester.

Description

[0001] SOLID BIS(2-HYDROXYETHYL) TEREPHTHALATE HAVING A FORM

[0002] PARTICULAR CRYSTALLINE

[0003] TECHNICAL FIELD

[0004] The invention relates to a solid material composed mainly of bis(2-hydroxyethyl) terephthalate (BHET), having a novel crystalline form. This crystalline form advantageously makes it possible to obtain a needle-like morphology of the solid material, thus facilitating its drying. The invention also relates to a composition comprising said solid material and the use of this composition for producing a polyester terephthalate, for example a polyethylene terephthalate (PET).

[0005] PRIOR ART

[0006] Bis(2-hydroxyethyl) terephthalate (BHET) is a monomer of polyester terephthalates and in particular polyethylene terephthalate (PET).

[0007] BHET can be obtained by direct esterification of terephthalic acid with ethylene glycol or transesterification between dimethyl terephthalate and ethylene glycol, methods typically corresponding to the first reaction step in conventional PET production processes. BHET can also be obtained by depolymerization of polyester, in particular polyethylene terephthalate (PET) in the presence of ethylene glycol. This is referred to as chemical recycling of polyester, in particular PET, since polyester waste, in particular PET, undergoes chemical treatment (depolymerization) to obtain a monomeric compound which is then reused to produce more polyester, in particular PET and more specifically r-PET.

[0008] For example, patent application FR 3053691 describes a process for depolymerizing a polyester filler comprising in particular from 0.1 to 10% by weight of pigments, by glycolysis in the presence of ethylene glycol. A bis-(2-hydroxyethyl) terephthalate (BHET) monomer effluent, obtained after specific separation and purification steps, can feed a polymerization step to produce PET. Patent JP3715812 describes the production of refined BHET from PET, the BHET obtained being able to be used as a raw material in a process for producing plastic products.

[0009] Although they disclose the polymerization of monomeric products, in particular BHET, resulting from the depolymerization of PET by glycolysis, the cited documents do not, however, provide any information on the quality of the intermediate products resulting from the depolymerization of PET, nor on the difficulty of the purification steps, in particular washing and drying of the BHET-based intermediates. However, the drying of BHET crystals is known to be problematic. For example, US patent 3,668,235 explains that the drying times of solid BHET are long, which impacts the quality of the BHET, in particular by the appearance of coloration and by a tendency for the crystals to agglomerate.

[0010] In order to facilitate drying and thus limit product degradation, it is important to reduce the drying operation time. The residual humidity of the cake at the filtration outlet is a good indicator of the ease of drying the cake since drying will be all the easier when the quantity of water to be removed is low.

[0011] A technique known to those skilled in the art for lowering the water content of a cake of solid material is the use of centrifugal spin dryers for liquid / solid separation, which achieve residual humidity levels 2 to 3 times lower than simple filtration, the residual humidity corresponding to the balance between capillary forces and centrifugal forces (cf. M. Robatel et al., Centrifugation: Generalities, Theories, Engineering Techniques, A5550 V1, 1989, 10-17).

[0012] Patent application WO 2021 / 032826 indicates that the humidity of the BHET crystal cake resulting from filtration is typically in the range of 20-50% by weight. This document then proposes granulation of the BHET crystals in order to facilitate the drying of the solid, relying on the porosity of the granules to promote mass and heat transfer.

[0013] Furthermore, it is known that a needle-like morphology for crystals of a solid material allows for superior performance to other morphologies, for example platelet morphology, in terms of filterability (cf. D. Bourcier et al., “Influence of particle size and shape properties on cake resistance and compressibility during pressure filtration”, Chemical Engineering Science, 2016, 144, 176-187).

[0014] Patent JP 5189266 confirms the effect of the needle-like morphology of BHET on the quality of BHET, and in particular on the residual solvent content of a solid BHET obtained after crystallization and solid / liquid separation. However, this document does not provide any information regarding the crystalline form of the obtained BHET.

[0015] Miyake's article (A. Miyake, “Polymorphism of Bis-p-hydroxyethyl Terephthalate”, Bulletin of the Chemical Society of Japan, 1957, 30(4), 361-363) discloses four crystalline forms of BHET: the alpha crystalline form, which appears to be the most stable, and the beta, gamma and delta forms. However, this article does not provide any information on their macroscopic morphology and properties, including filterability and / or ease of drying. According to Alvarez-Castillo's article (A. Alvarez-Castillo et al., “Studies on the crystallization of polyethylene terphthalate oligomer”, Journal of Materials Science Letters, 14, 1995, 139-141), it appears that the alpha crystalline form of BHET can give a needle-like morphology to BHET crystals.

[0016] The present invention aims at a high quality BHET and in particular at BHET crystals having the lowest possible residual solvent and / or moisture content. Thus, the inventors have surprisingly discovered a new crystalline form of BHET which inevitably leads to a needle morphology and therefore to improved filterability and drying properties of the BHET crystals.

[0017] SUMMARY OF THE INVENTION

[0018] The invention relates to a solid material composed mainly of BHET having a crystalline form presenting an X-ray diffraction diagram with the average values ​​of 20 and relative intensities l rei greater than or equal to 5%, following: Table 1 where FF = very strong; F = strong; m = medium; mf = medium weak; f = weak; ff = very weak. The relative intensity l reiis given in relation to a relative intensity scale where a value of 100 is assigned to the most intense line in the X-ray diffraction pattern: ff <15; 15 <f <30 ; 30 < mf <50 ; 50 < m < 65 ; 65 < F < 85 ; FF >85.

[0019] The advantage of the present invention lies in the fact that the particular crystalline form facilitates the filterability and drying of the BHET. Indeed, the solid material according to the invention has reduced residual humidity at the filtration outlet compared to other crystalline forms and is therefore easier to dry. Furthermore, the crystalline form of the solid BHET material according to the invention has a repeating structure which induces a needle-like morphology of the crystals which allows better filterability and improved washing of the crystals. Furthermore, another advantage of the present invention lies in the fact that the particular crystalline form of the BHET is stable, in particular thermally stable.

[0020] Another advantage of the present invention lies in the origin of the solid BHET material and the compositions comprising it, since it can both be obtained by direct synthesis of BHET from terephthalic acid or dimethylterephthalate and ethylene glycol but also come from and advantageously come from plastic recycling circuits, set up in recent years by national and international organizations to combat plastic pollution. Indeed, the solid BHET material of the present invention and the composition containing it can very advantageously be obtained following depolymerization processes by glycolysis of polyester such as PET, in the presence of diol, comprising purification steps, in particular a BHET crystallization step.The BHET resulting from these depolymerization processes is then called r-BHET and the PET prepared by polymerization from r-BHET is called r-PET (as opposed to PET or virgin resin resulting from the direct polymerization of terephthalic acid and fresh ethylene glycol). Thus, the present invention contributes to the fight against plastic pollution.

[0021] The present invention therefore also relates to the use of the composition comprising the solid BHET material for preparing a polyester, preferably a PET.

[0022] LIST OF FIGURES

[0023] Figure 1 represents an image of solid A of Example 1, observed by optical microscopy.

[0024] Figure 2 represents one of solid B of Example 1, observed by optical microscopy.

[0025] Figure 3 represents the DRX diagram obtained for solid A of Example 1.

[0026] Figure 4 represents an XRD diagram of solid B from Example 1.

[0027] Figure 5 represents an XRD diagram of solid G of Example 1.

[0028] Figure 6 represents an XRD diagram of solid D of Example 1.

[0029] DESCRIPTION OF EMBODIMENTS

[0030] According to the invention, the terms "bis(2-hydroxyethyl) terephthalate" and "BHET" designate the same compound and are interchangeable. Similarly, the terms "bis(2-hydroxyethyl) isophthalate" and "BHEI" designate the same compound and are interchangeable. The terms "2-(2-hydroxyethoxy) ethyl 2-hydroxyethyl terephthalate" and "BHET-deg" designate the same compound and are also interchangeable. According to the invention, the term "polyester" designates a thermoplastic polymer, advantageously saturated (as opposed to thermosetting polyesters) having as elementary repeating units diol diesters, and more particularly at least alkylene terephthalate units. The polymer chain may also comprise alkylene isophthalates and / or dialkyl terephthalate units. Thus, according to the invention, the term “polyester” is used to designate a poly(alkylene terephthalate) (or polyalkylene terephthalate, according to anglicized terminology).The polyester according to the invention may, for example, be poly(ethylene terephthalate) (or polyethylene terephthalate, PET), poly(butylene terephthalate) (or polybutylene terephthalate, PBT), poly(trimethylene terephthalate) (or polytrimethylene terephthalate, PTT). The polyester according to the invention may also comprise on its main polymer chain other units, such as vinyl or polyol units, depending on the final properties desired for the polymer and depending on the intended applications. According to the invention, the preferred polyester is polyethylene terephthalate or poly(ethylene terephthalate), also simply called PET.

[0031] According to the invention, the terms "diol" and "glycol" are used interchangeably and correspond to compounds comprising 2 hydroxyl groups -OH and preferably comprising between 2 and 12 carbon atoms, preferably between 2 and 4 carbon atoms. The preferred diol is ethylene glycol, also called mono-ethylene glycol or MEG.

[0032] Crystals are solids in which atoms, ions, or molecules are arranged in a three-dimensional space by repeating a structure periodically. The crystal form is a description of this repeating structure. A solid can exist in different crystal forms: this is called polymorphism. In a crystallization process, obtaining one form rather than another is guided by the choice of solvent and / or by the conduct of the crystallization process. Each form is generally characterized by X-ray diffractometry (XRD). The set of peaks in a diffractogram obtained by XRD, in particular their positions and preferably also their intensities, characterizes the crystal form. In the case of BHET, four crystal forms are known: alpha, beta, gamma, and delta forms (see A. Miyake, “Polymorphism of Bis- - hydroxyethyl Terephthalate,” Bulletin of the Chemical Society of Japan, 1957, 30(4), 361-363).

[0033] According to the present invention, the expressions "between ... and ..." and "between .... and ..." are equivalent and mean that the limit values ​​of the interval are included in the range of values ​​described. If this is not the case and the limit values ​​are not included in the range described, such precision will be provided by the present invention.

[0034] For the purposes of the present invention, the different parameter ranges for a given step such as pressure ranges and temperature ranges may be used alone or in combination. For example, for the purposes of the present invention, a range of preferred pressure values ​​may be combined with a range of more preferred temperature values.

[0035] In the following, particular embodiments of the invention may be described. They may be implemented separately or combined with each other, without limitation of combinations when technically feasible.

[0036] According to the invention, the pressures are absolute pressures and are given in MPa.

[0037] The invention thus relates to a solid material composed mainly of BHET, preferably comprising BHET at a weight content greater than or equal to 50%, preferably greater than or equal to 70%, preferentially greater than or equal to 90%, very preferentially greater than or equal to 95%, more preferably greater than or equal to 98%, or even greater than or equal to 99% (the percentages are relative to the total weight of the dry material, i.e. excluding moisture or other solvent, for example, used during the process for preparing such a solid and in particular during the crystallization step such as ethylene glycol or methanol or even a glycol ether), having a crystalline form exhibiting an X-ray diffraction pattern (or XRD pattern) with the average values ​​of 20 and relative intensities l rei greater than or equal to 5%, following: relative l reiis given in relation to a relative intensity scale where a value of 100 is assigned to the most intense line in the X-ray diffraction pattern: ff <15; 15 <f <30 ; 30 < mf <50 ; 50 < m < 65 ; 65 < F < 85 ; FF >85. The solid material composed mainly of BHET according to the invention may also be called BHET material or solid BHET, in the remainder of this description.

[0038] According to a particular embodiment of the invention, the solid material, which is composed mainly of BHET having the crystalline form whose DRX diagram is presented in Table 1, has a single crystalline form. In other words, it only has the crystalline form having the X-ray diffraction diagram whose average values ​​of 20 and relative intensities are given in Table 1. Preferably, the BHET material which has a single crystalline form, that whose DRX diagram is presented in Table 1, does not have an amorphous form.

[0039] According to another particular embodiment of the invention, the solid material is composed mainly of BHET which has the crystalline form having the X-ray Diffraction diagram represented by the values ​​of 20 and relative intensities, greater than or equal to 5%, of Table 1, and another crystalline form of BHET, preferably chosen from the alpha form, the beta form, the delta form, the gamma form of BHET and a combination of at least two of these crystalline forms. The DRX diagrams of the alpha, beta, delta, gamma forms of BHET are shown in Figure 1 and were determined by the Miyake team (A. Miyake, “Polymorphism of Bis-p-hydroxyethyl Terephthalate”, Bulletin of the Chemical Society of Japan, 1957, 30(4), 361-363). According to this particular embodiment of the invention, the BHET material can also have an amorphous form.Preferably, the BHET material of this particular embodiment does not comprise an amorphous form.

[0040] According to the invention, the X-ray Diffraction (XRD) analysis, carried out on the BHET material, makes it possible to verify the presence of the crystalline form(s) of BHET. According to the invention, the solid BHET material has the X-ray Diffraction diagram including at least the lines listed in Table 1. Preferably, the X-ray Diffraction diagram does not contain any other lines of significant intensity (i.e. of intensity greater than or equal to 5% of the intensity of the most intense line in the XRD diagram) than those listed in Table 1. For those skilled in the art, the essential characteristic on an XRD diagram is the position of the peaks (values ​​of 2 theta), the relative intensities are often given for information purposes.

[0041] The X-ray diffraction pattern (or DRX pattern) is obtained by radiocrystallographic analysis using a diffractometer using the classical powder method with the Kai radiation of copper (X = 1.5406Â). The position of the diffraction peaks (or lines) is represented by the angle 20. An absolute error A(20), assigned to the measurement of 20, equal to ± 0.1° is commonly accepted. The relative intensity l rei assigned to each dhki value is measured from the height of the corresponding diffraction peak (or line). The X-ray diffraction pattern of the solid material comprising mainly BHET according to the invention comprises at least the lines given in Table 1.

[0042] Very advantageously, the solid material according to the invention is in the form of needles.

[0043] The present invention also relates to a composition comprising the BHET material according to the invention. Preferably, the composition comprising the BHET material according to the invention is in solid form or in liquid form (i.e. a composition macroscopically in liquid form, for example a suspension or a slurry being compositions in liquid form), and more particularly in solid form, in slurry form or in the form of a suspension of solid particles of the BHET material according to the invention suspended in a solvent. The composition comprising the BHET material according to the invention may therefore be in solid or liquid form (suspension or slurry) and further comprise a solvent, preferably chosen from an aqueous solvent, in particular water, an alcoholic solvent, for example methanol or a diol such as ethylene glycol, or a solvent composed of a glycol mono- or di-ether; preferably the solvent is water.

[0044] According to a particular embodiment of the invention, the composition comprising the BHET material according to the invention is a solid composition and further comprises a solvent, preferably at a content of less than or equal to 20% by weight, preferably less than or equal to 15% by weight, preferably less than or equal to 10.0% by weight and more particularly less than or equal to 5.0% by weight, or even less than or equal to 1.0% by weight.

[0045] According to another particular embodiment of the invention, the composition comprising the BHET material according to the invention is a composition in liquid form, more particularly a slurry or suspension type composition, which comprises a solvent and solid particles of the BHET material according to the invention, preferably between 1 and 75% by weight, preferentially between 5 and 45% by weight, preferably between 15 and 35% by weight of solid material according to the invention relative to the total weight of said composition.

[0046] Advantageously, the composition according to the invention is capable of being obtained by, preferably obtained by, a process for treating a polyester filler, preferably comprising PET, which comprises a step of depolymerization of the polyester filler, in particular of the PET which it contains, and preferably followed by at least one separation-purification step. The depolymerization step may implement depolymerization by glycolysis in the presence of ethylene glycol or by methanolysis in the presence of methanol. In the latter case, an additional step of transesterification in the presence of ethylene glycol is then necessary. Preferably, the depolymerization step implements depolymerization by glycolysis in the presence of ethylene glycol.The process for treating a polyester feedstock, preferably comprising PET, may for example comprise, as a step of purifying the effluent obtained by depolymerization of the polyester feedstock, in particular a step of crystallization of the BHET in water, in ethylene glycol, or in a glycol mono- or di-ether, preferably in water.

[0047] According to a particular embodiment of the invention, the composition according to the invention may further comprise bis(2-hydroxyethyl) isophthalate (BHEI), preferably in a molar amount such that the molar ratio (BHEI / [BHET + BHEI]) between the number of moles of BHEI relative to the number of moles of the BHET and BHEI combination present in the composition is less than or equal to 10.0 mol%, preferably less than or equal to 5.0 mol%, preferentially less than or equal to 1.0 mol% and preferably less than or equal to 0.5 mol%. In addition, if the composition comprises BHEI, the molar ratio (BHEI / [BHET + BHEI]) is greater than or equal to 0.001 mol%, preferably greater than or equal to 0.01 mol%, preferentially greater than or equal to 0.05 mol%.

[0048] According to another particular embodiment of the invention, the BHET-based composition according to the invention may further comprise 2-(2-hydroxyethoxy) ethyl 2-hydroxyethyl terephthalate (BHET-deg), preferably in a molar amount such that the molar ratio (BHET-deg / [BHET + BHET-deg]) between the number of moles of BHET-deg relative to the number of moles of the BHET and BHET-deg combination present in the composition is less than or equal to 10.0 mol%, preferably less than or equal to 5.0 mol%, preferentially less than or equal to 1.0 mol%. In addition, if the composition comprises BHET-deg, the molar ratio (BHET-deg / [BHET + BHET-deg]) is greater than or equal to 0.001 mol%, preferably greater than or equal to 0.05 mol%, preferably greater than or equal to 0.10 mol%, more preferably greater than or equal to 0.50 mol%.

[0049] Either or both of these particular embodiments of the invention may possibly be the case(s) of products obtained at the end of processes for treating polyester fillers, which include a depolymerization step.

[0050] The present invention thus relates to a process for preparing a composition according to the invention comprising:

[0051] - a step of depolymerization of a polyester filler, preferably comprising PET, implementing a depolymerization by glycolysis in the presence of ethylene glycol or by methanolysis in the presence of methanol, preferably a depolymerization by glycolysis in the presence of ethylene glycol; then - at least one purification step, preferably comprising a crystallization step in water, in ethylene glycol, or in a glycol mono- or di-ether, preferably in water.

[0052] Very advantageously, the preparation process comprises, consists of, the depolymerization process described in patent FR 3053691, the decolorization step of which comprises an adsorption step and may further comprise a purification step by crystallization of the BHET in water, in ethylene glycol, or in a mono- or di-ether of glycol, preferably in water.

[0053] The BHET material according to the invention which has the particular crystalline form whose DRX diagram is shown in Table 1, advantageously allows the filtration and drying of the composition according to the invention which contains it and which is obtained at the end of such a preparation process. These filtration and drying steps being facilitated, the solid according to the invention, obtained at the end of such steps, therefore advantageously comprises a reduced residual solvent level, in particular a reduced residual moisture level, which allows it to be used in a polymerization step, without additional energy-intensive treatment.

[0054] The composition which comprises the BHET material according to the invention very advantageously makes it possible to obtain, after polymerization, a polyester, preferably a PET, and in particular an r-PET having a light or even colorless coloring.

[0055] Thus the invention also relates to the use of the composition according to the invention, optionally mixed with at least one dicarboxylic acid, preferably chosen from terephthalic acid and isophthalic acid, and / or at least one diol, preferably chosen from ethylene glycol, diethylene glycol, butylene glycol, cyclohexane dimethanol, neopentyl glycol or mixtures thereof, the preferred diol being ethylene glycol, to prepare a polyester, preferably a PET.

[0056] The invention therefore also relates to a process for producing a polyester, comprising, preferably consisting of: a) a step of esterification of a filler comprising at least the composition according to the invention, and optionally at least one dicarboxylic acid, preferably chosen from terephthalic acid and isophthalic acid, and / or at least one diol, preferably chosen from ethylene glycol, diethylene glycol, butylene glycol, cyclohexane dimethanol, neopentyl glycol or mixtures thereof, the preferred diol being ethylene glycol; then b) a polycondensation step. Advantageously, step a) is carried out at a temperature of between 150 and 350°C, preferably between 200 and 300°C, preferably between 250 and 285°C. Preferably, step a) is carried out at a pressure between 0.05 and 1.0 MPa, preferably between 0.1 and 0.5 MPa.Very advantageously, step a) is carried out with a residence time between 0.5 and 10.0 hours, preferably between 1.0 and 6.0 hours, the residence time being defined here as the ratio of the reaction volume of a reactor carried out in step a) to the volume flow rate of the liquid stream leaving said reactor.

[0057] A polymerization catalyst, preferably based on antimony, titanium, germanium, aluminum, zinc acetate, calcium acetate and / or manganese acetate, may optionally be introduced in step a).

[0058] The reaction carried out in step a) generates a diol compound which is advantageously separated during step a), for example by withdrawal, distillation and / or adsorption. Water may also be formed. The water then formed is also advantageously separated during step a).

[0059] Advantageously, the process for producing a polyester according to the invention comprises a step b) of polycondensation at the end of step a). Step b) may advantageously implement one or more, preferably one or two, sub-steps of polycondensation, for example at least, preferably one, sub-step of polycondensation in liquid or molten phase, optionally followed by at least one, preferably one, sub-step of polycondensation in solid phase.

[0060] Very advantageously, the polycondensation step b) implements at least one polymerization section, preferably one or two polymerization sections, advantageously operated in the liquid or molten phase, said polymerization section(s) being implemented at a temperature higher than the temperature at which step a) is implemented, preferably at a temperature between 190 and 400°C, preferably between 220 and 350°C, preferably between 265 and 300°C, preferably at a pressure between 0.01 and 100.00 kPa, preferably between 0.05 and 10.00 kPa, and preferably with a residence time between 0.1 and 5.0 hours, preferably between 0.5 and 4 hours, preferably between 1.0 and 3.0 hours.The residence time in the polymerization section of step b) is defined as the ratio of the reaction volume of a reactor used in said polymerization section to the volume flow rate of the liquid stream, comprising the polyester produced, leaving said reactor.

[0061] The polymerization reaction may optionally be continued in a polycondensation section located downstream of the polymerization section and operated in solid phase, preferably at a temperature (in particular a product temperature) of between 190 and 250°C, preferably between 200 and 230°C. Depending on whether this operation is carried out in continuous mode or in batch mode. The polycondensation section may preferably be operated under an inert atmosphere, for example under a nitrogen flow at a pressure close to atmospheric pressure, or under vacuum (in particular at a pressure of between 0.01 and 100 kPa, or even between 0.01 and 10 kPa). The residence time (defined as the time during which the product is subjected to the polycondensation conditions in said polycondensation section) is between 5 and 20 hours, preferably between 10 and 16 hours.Said polycondensation section may advantageously be preceded by a crystallization section, thus located between the polymerization section and the polycondensation section, in which the polyester formed, obtained at the end of the polymerization section, is advantageously crystallized, said crystallization section being able to be operated at a temperature preferably between 110 and 210°C, and for a residence time (defined as the time during which the product is subjected to the crystallization conditions in said section) preferably between 0.5 and 6 hours.

[0062] Step b) is preferably carried out in the presence of a polymerization catalyst, in particular based on antimony, titanium, germanium, aluminum, zinc acetate, calcium acetate and / or manganese acetate.

[0063] Additives may be introduced in polycondensation step b). The additives possibly introduced in step b) may be, for example: agents for inhibiting secondary etherification reactions, such as amines (n-butylamine, diisopropylamine or triethylamine), sodium hydroxide or organic hydroxides or lithium carbonate, stabilizing agents such as phosphites or phosphates, and polyamide-type compounds to reduce the amount of degradation product such as acetaldehyde.

[0064] The following figures and examples illustrate the invention without limiting its scope.

[0065] EXAMPLES

[0066] Example 1: Solids

[0067] Two solids, solid A and solid B, obtained after depolymerization processes by glycolysis of PET waste and purification by crystallization in water (gradual decrease of temperature from 60°C to 20°C), are recovered after filtration. The recovered solids A and B comprise at least 98.5% by weight of BHET relative to their dry solid weight. A fraction of solid B is then dried in an oven at 30°C for 15 hours to obtain a solid C. A fraction of solid C is then placed at 60°C for 15 hours, to obtain solid D. Solids A and B were observed by optical microscopy. The photos of these observations are shown in Figures 1 and 2 respectively for solids A and B.

[0068] Solid A has a platelet-like morphology (Figure 1).

[0069] Solid B has a needle-like morphology (Figure 2).

[0070] The XRD patterns of solids A, B, C and D are determined by X-ray crystallographic analysis using a diffractometer using the classical powder method with Ka1 radiation from copper (X = 1.5406 Å). The position of the diffraction peaks (or lines) is represented by the angle 20 measured with an absolute error A(20) equal to ± 0.1°. The relative intensity Irel is measured from the height of the corresponding diffraction peak (or line). The XRD patterns of solids A, B, C and D are shown in Figures 3, 4, 5 and 6 respectively, and presented in Table 2 below.

[0071] Table 2 where FF = very strong; F = strong; m = medium; mf = medium weak; f = weak; ff = very weak. The relative intensity l rei is given in relation to a relative intensity scale where a value of 100 is assigned to the most intense line in the X-ray diffraction pattern: ff <15; 15 <f <30 ;

[0072] 30 < mf <50 ; 50 < m < 65 ; 65 < F < 85 ; FF > 85.

[0073] Solid A corresponds to the form a.

[0074] Solids B, C and D correspond to the crystalline form in accordance with the invention. According to the DRX diagrams, it appears that the crystalline form according to the invention is stable since the DRX diagrams of solids C (drying of the solid at 30°C for 15 hours) and D (drying of the solid at 30°C for 15 hours then at 60°C for 15 hours) are not or only slightly modified compared to that of solid B.

[0075] Example 2: Centrifugal spinning of solids E (non-compliant) and F (compliant with the invention)

[0076] Solids E and F, obtained by crystallization of BHET solutions in water by progressively lowering the temperature from 60°C to 20°C for 4 hours and 6 hours respectively, and recovered after filtration, comprise at least 98.5% by weight of BHET relative to their dry solid weight. They are observed under an optical microscope and their DRX diagram is determined, according to the same method as that detailed in Example 1.

[0077] Solid E has a platelet-like morphology and exhibits a crystallographic form a.

[0078] Solid F has a needle-like morphology and has a crystallographic shape in accordance with the invention.

[0079] Each of the solids E and F undergoes a water wash such that each mixture is a suspension of 20% by weight of solid in 80% by weight of water, then a solid-liquid separation by centrifugal spinning at 20°C.

[0080] The residual water content of each solid after washing is determined by the mass loss of the solids after drying in an oven at 40°C under vacuum for 15 hours.

[0081] Table 3 presents the results obtained for the two solids E and F.

[0082] Table 3

[0083] The results show that solid F with a crystalline form according to the invention and having a needle-like shape makes it possible to achieve a residual humidity (10%) significantly lower than that achieved by solid E having a crystalline form a and having a platelet-like shape. Solid F will therefore be much easier to dry compared to solid F because there is less water to remove.

Claims

CLAIMS 1. Solid material composed mainly of BHET having a crystalline form presenting an X-ray Diffraction diagram with the following average values ​​of 29 and relative intensities læi greater than or equal to 5%: relative l rei is given in relation to a relative intensity scale where a value of 100 is assigned to the most intense line in the X-ray diffraction pattern: ff <15; 15 <f <30 ; 30 < mf <50 ; 50 < m < 65 ; 65 < F < 85 ; FF >85.

2. Material according to claim 1, having a single crystalline form.

3. Material according to claim 1, having the crystalline form exhibiting the X-ray Diffraction pattern represented by the values ​​of 29 and relative intensities of Table 1 and another crystalline form, preferably chosen from the alpha form, the beta form, the delta form, the gamma form of BHET and a combination of at least two of these crystalline forms.

4. Material according to one of the preceding claims comprising BHET having said crystalline form, at a weight content greater than or equal to 90%, preferably greater than or equal to 95%, more preferably greater than or equal to 98%, the percentages being given relative to the total weight of the dry material.

5. Material according to one of the preceding claims, in the form of needles.

6. Solid or liquid composition comprising the material according to one of the preceding claims.

7. Composition according to claim 6, further comprising a solvent, preferably an aqueous solvent, an alcoholic solvent, for example methanol, or a diol, or a glycol mono- or di-ether, the preferred solvent being water.

8. Solid composition according to claim 6 or 7, further comprising a solvent, and preferably at a weight content less than or equal to 20% by weight, preferably less than or equal to 15% by weight.

9. Composition according to one of claims 6 to 8 capable of being obtained by a process for treating a polyester filler, preferably comprising PET, which comprises a step of depolymerization by glycolysis in the presence of ethylene glycol, and preferably followed by at least one step of purification and / or separation, for example comprising a step of crystallization of the BHET, in particular in water.

10. Process for preparing a composition according to one of claims 6 to 9, comprising: - a step of depolymerization of a polyester filler, preferably comprising PET, implementing depolymerization by glycolysis in the presence of ethylene glycol or by methanolysis in the presence of methanol, preferably depolymerization by glycolysis in the presence of ethylene glycol; then - at least one purification step, preferably comprising a crystallization step in water, in ethylene glycol, or in a glycol mono- or di-ether, preferably in water.

11. Use of the composition according to one of claims 6 to 9, for preparing a polyester, preferably a PET.

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