WO2024083724A1

WO2024083724A1 - Bis(2-hydroxyethyl)terephthalate solid having a particular crystal form

Info

Publication number: WO2024083724A1
Application number: PCT/EP2023/078640
Authority: WO
Inventors: Guillaume BLANCKE; David Chiche; Frederic Favre; Damien Leinekugel Le Cocq
Original assignee: IFP Energies Nouvelles; Jeplan, Inc.
Priority date: 2022-10-20
Filing date: 2023-10-16
Publication date: 2024-04-25
Also published as: FR3141175A1

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

SOLID BIS(2-HYDROXYETHYL) TEREPHTHALATE HAVING A FORM

SPECIAL CRYSTALLINE

TECHNICAL AREA

The invention relates to a solid material composed mainly of bis(2-hydroxyethyl) terephthalate (BHET), presenting a new crystalline form. This crystalline form makes it possible to advantageously obtain a needle 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 to produce a polyester terephthalate, for example a polyethylene terephthalate (PET).

PRIOR ART

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

BHET can be obtained by direct esterification of terephthalic acid with ethylene glycol or transesterification between dimethyl terephthalate and ethylene glycol, methods classically corresponding to the first reaction step of conventional PET production processes. BHET can also be obtained by depolymerization of polyester, in particular polyethylene terephthalate (PET) in the presence of ethylene glycol. We then speak of chemical recycling of polyester, in particular PET, since polyester waste, in particular PET, undergoes chemical treatment (depolymerization) to obtain a monomer compound which is then reused to produce polyester again, in particular of PET and more particularly of r-PET.

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. An effluent of bis-(2-hydroxyethyl) terephthalate (BHET) monomer, obtained after specific separation and purification steps, can feed a polymerization step with a view to producing PET. Patent JP3715812 describes obtaining refined BHET from PET, the BHET obtained being able to be used as raw material in a process for producing plastic products.

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, give any information on the quality of the intermediate products resulting from the depolymerization of PET, nor on the difficulty of purification steps, in particular washing and drying of BHET-based intermediates. However, drying BHET crystals is known to be problematic. For example, US patent 3,668,235 explains that drying times for solid BHET are long, which impacts the quality of the BHET, in particular through the appearance of coloring and a tendency for crystals to agglomerate.

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 constitutes 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.

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

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

Furthermore, it is known that a needle-type morphology for crystals of a solid material makes it possible to obtain superior performance to other morphologies, for example the 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).

Patent J P 5189266 confirms the effect of the needle-type 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 give any information as to the crystalline form of the BHET obtained.

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 crystalline form alpha, which appears to be the most stable, and the beta, gamma and delta forms. But this article gives no indication as to their macroscopic morphology and their properties, in particular filterability and/or ease of drying. According to the article by Alvarez-Castillo (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.

The present invention targets a high quality BHET and in particular 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.

SUMMARY OF THE INVENTION

The subject of the invention is a solid material composed mainly of BHET having a crystalline form presenting an X-ray Diffraction diagram with the following average values of 20 and relative intensities l _rei greater than or equal to 5%: Table 1

where FF = very strong; F = strong; m = medium; mf = medium low; f = low; 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 of the X-ray diffraction diagram: ff <15; 15 <f <30; 30 <mf <50; 50 < m <65; 65 < F <85; FF > 85.

The advantage of the present invention lies in the fact that the particular crystalline form facilitates the filterability and drying of 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 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 BHET is stable, in particular thermally stable.

Another interest of the present invention lies in the origin of the solid BHET material and the compositions which comprise it, since it can both be obtained by direct synthesis of BHET from terephthalic acid or dimethylterephthalate and from ethylene glycol but also come and advantageously come from plastic recycling circuits, set up in recent years by national and international organizations to fight against plastic pollution. Indeed, the solid BHET material of the present invention and the composition which contains it can very advantageously be obtained at the end of 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 d fresh ethylene glycol). Thus, the present invention contributes to the fight against plastic pollution.

The present invention therefore also relates to the use of the composition comprising the solid BHET material to prepare a polyester, preferably a PET.

LIST OF FIGURES

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

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

Figure 3 represents the XRD diagram obtained for solid A of Example 1.

Figure 4 represents an XRD diagram of solid B of Example 1.

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

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

DESCRIPTION OF THE EMBODIMENTS

According to the invention, the terms “bis(2-hydroxyethyl) terephthalate” and “BHET” designate the same compound and are interchangeable. Likewise, the terms “bis(2-hydroxyethyl) isophthalate” and “BHEI” refer to the same compound and are interchangeable. The terms “2-(2-hydroxyethoxy)ethyl 2-hydroxyethyl terephthalate” and “BHET-deg” refer to 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 isophthalate 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 can, 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 other units on its main polymer chain, such as vinyl units or polyols, depending on the final properties desired for the polymer and depending on the targeted applications. According to the invention, the preferred polyester is polyethylene terephthalate or poly(ethylene terephthalate), also called simply PET.

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.

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

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.

In the sense of the present invention, the different parameter ranges for a given step such as pressure ranges and temperature ranges can be used. alone or in combination. For example, within the meaning of the present invention, a range of preferred pressure values can be combined with a range of more preferred temperature values.

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

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

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%, preferably greater than or equal to 90%, very preferably greater than or equal to equal to 95%, 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, that is to say excluding humidity or other solvent for example used during of 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 presenting an X-ray diffraction diagram (or XRD diagram ) with the following average values of 20 and relative intensities l _rei 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 of 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 can also be called BHET material or solid BHET, in the remainder of this description.

According to a particular embodiment of the invention, the solid material, which is mainly composed of BHET having the crystalline form whose XRD diagram is presented in Table 1, has a single crystalline form. In other words, it only presents the crystalline form presenting the X-ray diffraction pattern whose average values of 20 and relative intensities are given in Table 1. Preferably, the BHET material which presents a single crystalline form, the one whose XRD diagram is presented in Table 1, does not present an amorphous form.

According to another particular embodiment of the invention, the solid material is mainly composed of BHET which has the crystalline form presenting the X-ray Diffraction diagram represented by the values of 20 and relative intensities, greater than or equal to 5 %, from 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 XRD patterns of the alpha, beta, delta, gamma forms of BHET are shown in Figure 1 and were determined by Miyake's 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.

In accordance with the invention, the X-ray Diffraction (XRD) analysis carried out on the BHET material makes it possible to verify that the presence of the crystalline form(s) of BHET. According to the invention, the solid BHET material presents the X-ray Diffraction pattern including at least the lines listed in Table 1. Preferably, the X-ray Diffraction pattern does not contain 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.

The X-ray Diffraction pattern (or XRD pattern) is obtained by radiocrystallographic analysis using a diffractometer using the classic 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 value of dhki is measured according to 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.

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

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 (that is to say 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 can 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 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.

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 less than or equal to 20% by weight, preferably less than or equal to at 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.

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, preferably 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.

Advantageously, the composition according to the invention can be 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 it contains, and preferably followed by at least one separation-purification step. The depolymerization step can 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 filler, preferably comprising PET, can for example comprise, as a step of purifying the effluent obtained by depolymerization of the polyester filler, in particular a step of crystallizing BHET in water, in ethylene glycol, or in a glycol mono-or di-ether, preferably in water.

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 quantity such as the molar ratio (BHEI / [BHET + BHEI]) between the number of moles of BHEI relative to the number of moles of the BHET and BHEI assembly present in the composition is less than or equal to 10.0 mole%, preferably less than or equal to 5.0 mole%, preferably 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%, preferably preferably greater than or equal to 0 .05 mol%.

According to another particular embodiment of the invention, the composition based on BHET according to the invention may further comprise 2-(2-hydroxyethoxy) ethyl 2-hydroxyethyl terephthalate (BHET-deg), preferably in a quantity molar 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 all BHET and BHET-deg present in the composition is less or equal to 10.0 mol%, preferably less than or equal to 5.0 mol%, preferably 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 preferably greater than or equal to 0.10 mol%, preferably greater than or equal to 0.50 mol%.

One or the other or these two particular embodiments of the invention may possibly be found to be the case(s) of products obtained at the end of polyester filler treatment processes, which include a depolymerization step.

The present invention thus relates to a process for preparing a composition according to the invention 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.

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 the water, in ethylene glycol, or in a glycol mono-or di-ether, preferably in water.

The BHET material according to the invention which has the particular crystalline form whose XRD 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 stages of filtration and drying being facilitated, the solid according to the invention, obtained at the end of such stages, therefore advantageously comprises a residual level of solvent, in particular a reduced level of residual humidity, which allows it to be 'use in a polymerization step, without additional energy-intensive treatment.

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 clear or even colorless color.

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.

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 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 implemented 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 implemented in step a) on the volume flow rate of the liquid flow leaving said reactor.

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

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 form. The water then formed is also advantageously separated during step a).

Advantageously, the process for producing a polyester according to the invention comprises a polycondensation step b) at the end of step a). Step b) can advantageously implement one or more, preferably one or two, polycondensation substep(s), for example at least, preferably one, polycondensation substep in liquid or molten phase, optionally followed by at least one, preferably one, solid phase polycondensation substep.

Very advantageously, step b) of polycondensation implements at least one polymerization section, preferably one or two polymerization sections, advantageously carried out in the liquid or molten phase, said section(s) of polymerization being carried out at a temperature higher than the temperature at which step a) is carried out, preferably at a temperature between 190 and 400°C, preferably between 220 and 350°C, so as to 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 of 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 implemented in said polymerization section to the volume flow rate of the liquid flow, comprising the polyester produced, leaving said said polymerization section. reactor.

The polymerization reaction can optionally be continued in a polycondensation section located downstream of the polymerization section and carried out in the solid phase, preferably at a temperature (in particular a product temperature) 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 can preferably be operated under an inert atmosphere, for example under a flow of nitrogen at a pressure close to atmospheric pressure, or under vacuum (in particular at a pressure 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 can 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 which can be carried out 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.

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

Additives can be introduced in step b) of polycondensation. The additives optionally introduced in step b) can be for example: agents for inhibiting secondary etherification reactions, such as for example 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.

The following Figures and examples illustrate the invention without limiting its scope.

EXAMPLES

Example 1: Solids

Two solids, solid A and solid B, obtained following depolymerization processes by glycolysis of PET waste and purification by crystallization in water (gradual drop in temperature from 60°C to 20°C), are recovered after filtration. The solids A and B recovered comprise at least 98.5% by weight of BHET relative to their weight of dry solid. A fraction of solid B is then dried in an oven at 30°C for 15 hours to obtain 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. Photos of these observations are shown in Figures 1 and 2 for solids A and B respectively.

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

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

The XRD patterns of solids A, B, C and D are determined by radiocrystallographic analysis using a diffractometer using the classic 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 according to 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.

Table 2

where FF = very strong; F = strong; m = medium; mf = medium low; f = low; 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 of the X-ray diffraction diagram: ff <15; 15 <f <30;

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

The solid A corresponds to the form a.

Solids B, C and D correspond to the crystalline form according to the invention. According to the XRD diagrams, it appears that the crystalline form according to the invention is stable since the XRD diagrams of the 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.

Example 2: Centrifugal spinning of solids E (non-compliant) and F (in accordance with the invention)

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

The solid E has a platelet-like morphology and presents a crystallographic form a.

The solid F has a needle-type morphology and has a crystallographic shape in accordance with the invention.

Each of the solids E and F undergoes washing with water 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.

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.

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

Table 3

The results show that the solid F with a crystalline form according to the invention and having a needle type shape makes it possible to achieve a residual humidity (10%) significantly lower than that reached by the 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

1. Solid material composed mainly of BHET having a crystalline form presenting an X-ray Diffraction pattern 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 of 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 having the X-ray Diffraction pattern represented by the values of 29 and relative intensities in Table 1 and another crystalline form, preferably chosen from the alpha form, the form beta, the delta form, the gamma form of BHET and a combination of at least two of these crystal 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%, preferably greater than or equal to 98%, the percentages given in relation 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 even 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 purification and/or separation step, for example comprising a step of crystallization of 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, to prepare a polyester, preferably a PET.