Bis(2-hydroxyethyl) terephthalate solids exhibiting specific crystal morphology

Abstract

The present invention relates to a solid material based on BHET having a crystalline form with a specific X-ray diffraction pattern, a method for its preparation, a composition comprising said material, and the use of said composition for preparing polyesters.

Description

[Technical Field]

[0001] The present invention relates to a solid material composed mainly of bis(2-hydroxyethyl) terephthalate (BHET) and exhibiting a novel crystalline morphology. This crystalline morphology advantageously allows obtaining a solid material with a needle-like morphology, thus facilitating its drying. The present invention also relates to a composition comprising said solid material and the use of this composition to produce terephthalate polyesters, such as polyethylene terephthalate (PET). [Background technology]

[0002] Bis(2-hydroxyethyl) terephthalate (BHET) is a monomer for terephthalate polyesters, particularly polyethylene terephthalate (PET).

[0003] BHET can be obtained by direct esterification of terephthalic acid with ethylene glycol or by transesterification between dimethyl terephthalate and ethylene glycol, which traditionally correspond to the first reaction step in conventional PET production processes. BHET can also be obtained by depolymerization of polyesters, particularly polyethylene terephthalate (PET), in the presence of ethylene glycol. This is called chemical recycling of polyesters, particularly PET, because polyester waste, particularly PET waste, undergoes chemical treatment (depolymerization) to obtain monomer compounds that are then reused to regenerate polyesters, particularly PET, more particularly r-PET.

[0004] For example, Patent Document 1 describes a method for depolymerizing polyester feedstocks, particularly those containing 0.1% to 10% by weight of pigments, by glycolysis in the presence of ethylene glycol. The monomer effluent of bis(2-hydroxyethyl) terephthalate (BHET) obtained after specific separation and purification steps can be fed to a polymerization step for the purpose of producing PET. Patent Document 2 describes the production of refined BHET from PET, and the obtained BHET can be used as a starting material in processes for the production of plastics.

[0005] Although they disclose the polymerization of monomer products, in particular BHET, obtained from the depolymerization of PET by glycolysis, the cited documents, however, do not provide any information regarding the quality of the intermediates obtained from the depolymerization of PET, nor regarding the difficulties involved in the purification steps of BHET-based intermediates, in particular the washing and drying steps.

[0006] In fact, drying of BHET crystals is known to be problematic: for example, US Pat. No. 5,629,999 describes that the drying times for solid BHET are long, which affects the quality of the BHET, in particular by the appearance of color and the tendency of the crystals to agglomerate.

[0007] It is important to reduce the drying operation time in order to expedite drying and therefore reduce product deterioration. The residual moisture level of the cake as it leaves the filter is a good indicator of the ease of drying the cake, since drying becomes easier as the amount of water to be removed decreases.

[0008] Techniques known to those skilled in the art for reducing the water content of cakes of solid material include the use of centrifugal dryers for liquid / solid separation, which achieve residual moisture levels that are 2-3 times lower than with simple filtration, the residual moisture level corresponding to the balance between capillary and centrifugal forces (see Non-Patent Document 1).

[0009] Patent Document 4 indicates that the moisture level of the BHET crystal cake obtained from filtration is typically in the range of 20 to 50% by weight. The document then proposes granulating the BHET crystals to facilitate drying of the solid, relying on the porosity of the granules to facilitate mass and heat transfer.

[0010] Furthermore, it is known that a needle-type morphology for the crystals of a solid material makes it possible to obtain better performance qualities in terms of filterability than other morphologies, for example, plate-like morphologies (see Non-Patent Document 2).

[0011] Patent Document 5 confirms the effect of the needle-type morphology of BHET on the quality of BHET, in particular on the residual solvent content of the solid BHET obtained after crystallization and solid / liquid separation. However, this document does not provide any information on the crystalline form of the obtained BHET.

[0012] In a paper by Miyake (Non-Patent Document 3), four crystalline forms of BHET are disclosed: the alpha crystalline form and the beta, gamma, and delta forms; the alpha crystalline form appears to be the most stable. However, the paper does not provide any indication of their macroscopic morphology and their properties, in particular their filterability and / or ease of drying. According to a paper by Alvarez-Castillo (Non-Patent Document 4), the alpha crystalline form of BHET appears to be able to give BHET crystals a needle-like type morphology.

[0013] The present invention targets high-quality BHET, in particular BHET crystals exhibiting the lowest possible water and / or residual solvent content. Therefore, the inventors have surprisingly discovered a new crystalline form of BHET, which inevitably results in a needle-like morphology and therefore improved filterability and drying properties of the BHET crystals. [Prior art documents]

Charter Documents

[0014] [Patent Document 1] Buddhist Patent Application Publication No. 3053691 [Patent Document 2] Patent No. 3715812 [Patent Document 3] U.S. Patent No. 3668235 [Patent Document 4] International Publication No. 2021 / 032826 [Patent Document 5] Patent No. 5189266

Non-licensed literature

[0015]

Non-patent document 1

Non-patent document 2

Non-patent document 3

Non-patent document 4

[0016] (Summary of the Invention) The subject of the present invention is the following average values ​​of 2θ and a relative intensity I of 5% or more: rel The solid material is composed mainly of BHET having a crystalline form exhibiting an X-ray diffraction pattern having the formula:

[0017] [Table 1A]

[0018] In the table, vs = very strong; s = strong; m = medium; mw = medium weak; w = weak; vw = very weak. Relative Strength I rel are given on a relative intensity scale in which a value of 100 is assigned to the most intense line of the X-ray diffractogram: vw<15; 15≦w<30; 30≦mw<50; 50≦m<65; 65≦s<85; vs≧85.

[0019] An advantage of the present invention resides in the fact that the particular crystalline morphology facilitates the filterability and drying of the BHET because the solid material according to the present invention exhibits reduced residual moisture levels upon filtration compared to other crystalline morphologies, and is therefore easier to dry. Furthermore, the crystalline morphology of the solid BHET material according to the present invention has a repeating structure, which induces a needle-like morphology of the crystals, thereby allowing for better filterability and improved washing of the crystals.

[0020] Furthermore, another advantage of the present invention resides in the fact that certain crystalline forms of BHET are stable, in particular thermally stable.

[0021] Another advantage of the present invention lies in the origin of the solid BHET material and compositions containing it. It can be obtained not only by direct synthesis of BHET from terephthalic acid or dimethyl terephthalate and ethylene glycol, but also advantageously originate from plastic recycling circuits recently established by national and international organizations to combat plastic pollution. This is because the solid BHET material of the present invention and compositions containing it can be obtained, highly advantageously, at the end of a process for depolymerization by glycolysis of polyesters, such as PET, in the presence of diols, which process includes a BHET purification step, particularly a crystallization step. BHET obtained from these depolymerization processes is called r-BHET, and PET prepared by polymerization from r-BHET is called r-PET (in contrast to virgin resin or PET obtained from the direct polymerization of fresh ethylene glycol and terephthalic acid). Therefore, the present invention contributes to the fight against plastic pollution.

[0022] The present invention therefore also relates to the use of a composition comprising a solid BHET material for preparing a polyester, preferably PET. DETAILED DESCRIPTION OF THE INVENTION

[0023] (List of drawings) FIG. 1 shows an image of Solid A of Example 1, as observed by optical microscopy.

[0024] FIG. 2 shows an image of Solid B of Example 1, as observed by optical microscopy.

[0025] FIG. 3 represents the XRD diagram obtained for solid A of Example 1.

[0026] FIG. 4 shows the XRD diagram of Solid B of Example 1.

[0027] FIG. 5 shows the XRD diagram of Solid C of Example 1.

[0028] FIG. 6 shows the XRD diagram of Solid D of Example 1.

[0029] (Description of the embodiment) According to the present invention, the terms "bis(2-hydroxyethyl) terephthalate" and "BHET" refer to the same compound and are interchangeable. Similarly, 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 "deg-BHET" refer to the same compound and are interchangeable.

[0030] According to the present invention, the term "polyester" refers to a preferably saturated thermoplastic polymer (as opposed to a thermosetting polyester) having, as a basic repeating unit, a diol diester, more particularly at least an alkylene terephthalate unit. The polymer chain may also contain alkylene isophthalate and / or dialkyl terephthalate units. Therefore, according to the present invention, the term "polyester" is used to refer to poly(alkylene terephthalate) (or polyalkylene terephthalate). Polyesters according to the present invention may be, for example, poly(ethylene terephthalate) (or polyethylene terephthalate; PET), poly(butylene terephthalate) (or polybutylene terephthalate; PBT), or poly(trimethylene terephthalate) (or polytrimethylene terephthalate; PTT). Polyesters according to the present invention may also contain other units, such as vinyl or polyol units, on their main polymer chain, depending on the final properties desired for the polymer and the targeted application. According to the present invention, the preferred polyester is polyethylene terephthalate or poly(ethylene terephthalate), also simply called PET.

[0031] According to the present invention, the terms "diol" and "glycol" are used interchangeably and correspond to compounds containing two hydroxyl -OH groups and preferably containing 2 to 12 carbon atoms, preferentially 2 to 4 carbon atoms. A suitable diol is ethylene glycol, also called monoethylene glycol or MEG.

[0032] A crystal is a solid in which atoms, ions, or molecules are arranged in three-dimensional space by periodically repeating structures. A crystalline form corresponds to the description of this repeating structure. A solid can exist in different crystalline forms: this is called polymorphism. In a crystallization process, the production of one form rather than another is determined by the choice of solvent and / or the way the crystallization process is carried out. Each form is generally characterized by X-ray diffraction (XRD). The group of peaks in the diffractogram obtained by XRD, in particular their position and preferably also their intensity, characterizes the crystalline form. In the case of BHET, four forms are known: alpha, beta, gamma, and delta forms (see Miyake, "Polymorphism of Bis-β-Hydroxyethyl Terephthalate", Bulletin of the Chemical Society of Japan, 1957, 30(4), 361-363).

[0033] According to the present invention, the expressions "of between A and B" and "between A and B" are synonymous and mean that both limits of the interval (A, B) are included in the range of values ​​stated. If this is not the case and if both limits are not included in the range stated, such information will be provided by the present invention.

[0034] Within the meaning of the present invention, various ranges of parameters for a given process, such as pressure ranges and temperature ranges, can be used alone or in combination, for example, in the context of the present invention, a range of preferred pressure values ​​can be combined with a range of more preferred temperature values.

[0035] Subsequently, specific embodiments of the present invention will be described, which can be carried out separately or in combination with each other, without any limitation to this, provided that the combination is technically feasible.

[0036] According to the present invention, the pressure is absolute and is given in MPa.

[0037] The present invention therefore relates to a solid material mainly composed of BHET, preferably a solid material containing BHET in a weight content of 50% or more, preferably 70% or more, preferentially 90% or more, very preferentially 95% or more, suitably 98% or more, indeed even 99% or more (percentages relative to the total weight of the dry matter, i.e. free from water or other solvents, such as those used during the process for the preparation of such solids, in particular during the crystallization stage, for example ethylene glycol or methanol or glycol ethers), the crystalline form of which exhibits an X-ray diffraction pattern (or XRD pattern) with the following average values ​​of 2θ and a relative intensity I of 5% or more: rel It has.

[0038] [Table 1B]

[0039] In the table, vs = very strong; s = strong; m = medium; mw = medium weak; w = weak; vw = very weak. Relative Strength I rel 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 diffractogram: vw<15; 15≦w<30; 30≦mw<50; 50≦m<65; 65≦s<85; vs≧85.

[0040] A solid material consisting primarily of a BHET according to the present invention may also be referred to as a BHET material or a solid BHET in the remainder of this description.

[0041] According to a particular embodiment of the present invention, a solid material consisting essentially of BHET having a crystalline form whose XRD pattern is presented in Table 1 exhibits a single crystalline form. In other words, it exhibits only a crystalline form that exhibits an X-ray diffraction pattern whose average values ​​of 2θ and relative intensities are given in Table 1. Preferably, a BHET material whose XRD pattern exhibits a single crystalline form presented in Table 1 does not exhibit an amorphous form.

[0042] According to another specific embodiment of the present invention, the solid material is composed primarily of BHET exhibiting a crystalline form exhibiting an X-ray diffraction pattern represented by the 2θ values ​​and relative intensity values ​​of 5% or more in Table 1, and another crystalline form of BHET, preferably selected from the alpha, beta, delta, or gamma forms, and combinations of at least two of these crystalline forms. The XRD patterns of the alpha, beta, delta, and gamma forms of BHET are shown in FIG. 1 and were determined by Miyake's group (A. Miyake, "Polymorphism of Bis-β-Hydroxyethyl Terephthalate," Bulletin of the Chemical Society of Japan, 1957, 30(4), 361-363). According to this specific embodiment of the present invention, the BHET material can also exhibit an amorphous form. Preferably, the BHET material of this specific embodiment does not include an amorphous form.

[0043] According to the present invention, X-ray diffraction (XRD) analysis performed on a BHET material makes it possible to confirm the presence of one or more crystalline forms of BHET. According to the present invention, the X-ray diffraction pattern of a solid BHET material contains at least the lines listed in Table 1. Preferably, the X-ray diffraction pattern does not contain any other lines of significant intensity (i.e., an intensity of 5% or more of the intensity of the most intense line in the XRD pattern) in addition to the lines listed in Table 1. For those skilled in the art, an essential feature on an XRD pattern is the position of the peaks (2θ values); relative intensities are often given for informational purposes.

[0044] X-ray diffraction patterns (or XRD patterns) are obtained by radiation crystallography with a diffractometer using conventional powder techniques with copper Kα1 (λ=1.5406 Å) radiation. The positions of the diffraction peaks (or lines) are expressed in terms of the angle 2θ. The absolute error Δ(2θ) assigned to the measured value of 2θ is equal to ±0.1 and is generally accepted. hkl The relative intensity I assigned to each value of rel are measured according to the height of the corresponding diffraction peaks (or lines). The X-ray diffraction diagram of a solid material containing predominantly BHET according to the invention will contain at least the lines given in Table 1.

[0045] Highly advantageously, the solid material according to the invention is in needle-like form.

[0046] The present invention also relates to a composition comprising a BHET material according to the present invention. Preferably, the composition comprising the BHET material according to the present invention is in solid or liquid form (i.e., a composition in macroscopically liquid form, e.g., a suspension or slurry, is a composition in liquid form), 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 present invention suspended in a solvent. The composition comprising the BHET material according to the present invention can therefore be in solid or liquid (suspension or slurry) form and further comprises a solvent, preferably selected from aqueous solvents, in particular water, alcoholic solvents, such as methanol, or diols, e.g., ethylene glycol, or solvents composed of glycol mono- or diethers; preferably, the solvent is water.

[0047] 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 in a content of less than or equal to 20% by weight, preferably less than or equal to 15% by weight, preferentially less than or equal to 10.0% by weight, more particularly less than or equal to 5.0% by weight, indeed even less than or equal to 1.0% by weight.

[0048] 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 composition of the slurry or suspension type, comprising a solvent and solid particles of the BHET material according to the invention, preferably in an amount of 1% to 75% by weight, preferentially 5% to 45% by weight, and suitably 15% to 35% by weight, by weight of the solid material according to the invention relative to the total weight of the composition.

[0049] Advantageously, the composition according to the invention can be obtained by, and preferably is obtained by, a process for treating a polyester feedstock, preferably containing PET, which process includes a step of depolymerizing the polyester feedstock, in particular the PET it contains, preferably followed by at least one separation-purification step. The depolymerization step can be depolymerization by glycolysis in the presence of ethylene glycol or by methanolysis in the presence of methanol. In the case of methanolysis, an additional step of transesterification in the presence of ethylene glycol is required. Preferably, the depolymerization step is depolymerization by glycolysis in the presence of ethylene glycol. The process for treating a polyester feedstock, preferably containing PET, can, for example, include a step of purification of the effluent obtained by depolymerization of the polyester feedstock, in particular a step of crystallization of BHET from water, ethylene glycol, or a glycol monoether or diether, preferably water.

[0050] According to a particular embodiment of the present 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 of the number of moles of BHEI to the total number of moles of BHET and BHEI present in the composition (BHEI / [BHET+BHEI]) is 10.0 mol% or less, preferably 5.0 mol% or less, preferentially 1.0 mol% or less, and suitably 0.5 mol% or less. Furthermore, if the composition contains BHEI, the molar ratio (BHEI / [BHET+BHEI]) is 0.001 mol% or more, preferably 0.01 mol% or more, and preferentially 0.05 mol% or more.

[0051] According to another particular embodiment of the present invention, the BHET-based composition according to the invention may further comprise 2-(2-hydroxyethoxy)ethyl 2-hydroxyethyl terephthalate (deg-BHET), preferably in a molar amount such that the molar ratio of the number of moles of deg-BHET to the number of moles of BHET and deg-BHET combined (deg-BHET / [BHET+deg-BHET]) present in the composition is 10.0 mol% or less, preferably 5.0 mol% or less, and preferentially 1.0 mol% or less. Furthermore, if the composition contains deg-BHET, the molar ratio (deg-BHET / [BHET+deg-BHET]) is 0.001 mol% or more, preferably 0.05 mol% or more, preferentially 0.10 mol% or more, and suitably 0.50 mol% or more.

[0052] One or the other or these two particular embodiments of the present invention may be found to be the case in one or more cases for products obtained at the end of a process for the treatment of a polyester feedstock which includes a stage of depolymerization.

[0053] The present invention therefore relates to a process for the preparation of a composition according to the invention, comprising the following steps: - depolymerization of the polyester feedstock, preferably comprising PET, by depolymerization by glycolysis in the presence of ethylene glycol or by methanolysis in the presence of methanol, preferably by glycolysis in the presence of ethylene glycol; then - at least one purification step; preferably a step of crystallization from water, ethylene glycol or a glycol mono- or diether, preferably water.

[0054] Highly advantageously, the preparation process comprises or consists of the depolymerization process described in patent FR 3 053 691, the decolorization step of which comprises an adsorption step and can further comprise a step of purification by crystallization of BHET from water, ethylene glycol or glycol mono- or diethers, preferably water.

[0055] The BHET material according to the invention exhibits a particular crystalline form, the XRD diagram of which is shown in Table 1, which 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. Because these filtration and drying steps are facilitated, the solid according to the invention which is obtained at the end of such a step therefore advantageously contains a reduced content of residual solvent, and in particular a reduced content of water, which allows it to be used in the polymerization step without additional treatment which is costly in terms of energy.

[0056] Compositions comprising the BHET material according to the invention make it possible, highly advantageously, to obtain polyesters, preferably PET, and in particular r-PET, which, after polymerization, exhibit a bright, practically colorless coloration.

[0057] The present invention therefore also relates to the use of the composition according to the invention for preparing a polyester, preferably PET, optionally mixed with at least one dicarboxylic acid and / or at least one diol, the dicarboxylic acid preferably being chosen from terephthalic acid and isophthalic acid, the diol preferably being chosen from ethylene glycol, diethylene glycol, butylene glycol, cyclohexanedimethanol, neopentyl glycol or mixtures thereof, the preferred diol being ethylene glycol.

[0058] The present invention therefore also relates to a process for the production of polyesters, comprising or preferably consisting of the following steps: a) a stage of esterification of a feedstock comprising at least the composition according to the invention and optionally at least one dicarboxylic acid and / or at least one diol; the dicarboxylic acid is preferably selected from terephthalic acid and isophthalic acid, the diol is preferably selected from ethylene glycol, diethylene glycol, butylene glycol, cyclohexanedimethanol, neopentyl glycol or mixtures thereof, the preferred diol being ethylene glycol, then b) Polycondensation stage.

[0059] Advantageously, step a) is carried out at a temperature of 150 to 350° C., preferably 200 to 300° C., and suitably 250 to 285° C. Preferably, step a) is carried out at a pressure of 0.05 to 1.0 MPa, preferably 0.1 to 0.5 MPa. Highly advantageously, step a) is carried out with a residence time of 0.5 to 10.0 hours, preferably 1.0 to 6.0 hours, the residence time being defined herein as the ratio of the reaction volume of the reactor used in step a) to the volumetric flow rate of the liquid stream leaving said reactor.

[0060] 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).

[0061] The reaction carried out in step a) gives rise to a diol compound, which is advantageously separated during step a), for example by extraction, distillation and / or adsorption. Water may also be formed, which may itself advantageously be separated during step a).

[0062] Advantageously, the process for producing polyesters according to the invention comprises a polycondensation step b) at the end of step a), which can advantageously employ one or more, preferably one or two, polycondensation substeps, for example at least one, preferably one, liquid or melt phase polycondensation substep, optionally followed by at least one, preferably one, solid phase polycondensation substep.

[0063] Highly advantageously, polycondensation stage b) employs at least one polymerization section, preferably one or two polymerization sections, advantageously operated in the liquid or melt phase, said polymerization section(s) being employed at a temperature higher than that at which stage a) is carried out, preferably between 190 and 400°C, preferentially between 220 and 350°C, and suitably between 265 and 300°C, preferably at a pressure of 0.01 and 100.00 kPa, preferentially between 0.05 and 10.00 kPa, and preferably with a residence time of 0.1 to 5.0 hours, preferably between 0.5 and 4 hours, and preferentially between 1.0 and 3.0 hours. The residence time in the polymerization section of stage b) is defined as the ratio of the reaction volume of the reactor employed in said polymerization section to the volumetric flow rate of the liquid stream leaving said reactor containing the polyester produced.

[0064] The polymerization reaction can optionally be continued in a polycondensation section, which is located downstream of the polymerization section and is operated in the solid phase, preferably at a temperature (especially the product temperature) of 190 to 250°C, preferentially 200 to 230°C, depending on whether the operation is carried out in continuous or batch mode. The polycondensation section can preferably be operated under an inert atmosphere, for example under a nitrogen stream, at a pressure close to atmospheric pressure or under reduced pressure (especially at a pressure of 0.01 to 100 kPa, in practice 0.01 to 10 kPa). The residence time (defined as the time during which the product is subjected to polycondensation conditions in the polycondensation section) is 5 to 20 hours, preferably 10 to 16 hours. The polycondensation section can advantageously be preceded by a crystallization section, therefore located between the polymerization section and the polycondensation section, and the polyester formed at the end of the polymerization section and obtained is advantageously crystallized, said crystallization section being preferably operable at a temperature of between 110 and 210°C and for a residence time (defined as the time during which the product is subjected to crystallization conditions in said section) of preferably between 0.5 and 6 hours.

[0065] Step b) is preferably carried out in the presence of a polymerization catalyst, in particular one based on antimony, titanium, germanium, aluminum, zinc acetate, calcium acetate and / or manganese acetate.

[0066] Additives can be introduced in the polycondensation step b). The additives optionally introduced in step b) can be, for example, agents for inhibiting etherification side reactions, such as amines (n-butylamine, diisopropylamine or triethylamine), sodium hydroxide or organic hydroxides or lithium carbonate, stabilizers, such as phosphites or phosphates, and polyamide-type compounds for reducing the amount of decomposition products, such as acetaldehyde.

[0067] The following figures and examples illustrate the present invention but do not limit its scope.

[0068] (Example) Example 1: Solid Two solids, Solid A and Solid B, are obtained at the end of the process for depolymerization by glycolysis of PET waste and purification by crystallization from water (gradually decreasing the temperature from 60°C to 20°C), and are recovered after filtration. The recovered solids A and B contain a minimum of 98.5 wt. % BHET based on their dry solid weight. A portion of Solid B is then dried in an oven at 30°C for 15 hours to obtain Solid C. A portion of Solid C is then placed at 60°C for 15 hours to obtain Solid D.

[0069] Solids A and B were observed by optical microscopy. Photographs of these observations are shown in Figures 1 and 2 for Solids A and B, respectively.

[0070] Solid A has a plate-type morphology (Figure 1).

[0071] Solid B has a needle-type morphology (Figure 2).

[0072] The XRD patterns of solids A, B, C and D are determined by radiation crystallography on a diffractometer using conventional powder methods with copper Kα1 (λ=1.5406 Å) radiation. The positions of the diffraction peaks (or lines) are expressed by the measured angle 2θ, with an absolute error Δ(2θ) equal to ±0.1°. The relative intensity I rel 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 are provided in Table 2 below.

[0073] [Table 2]

[0074] In the table, vs = very strong; s = strong; m = medium; mw = medium weak; w = weak; vw = very weak. Relative Strength I rel is given in relation to a relative intensity scale in which a value of 100 is assigned to the most intense line of the X-ray diffractogram: vw<15; 15≦w<30; 30≦mw<50; 50≦m<65; 65≦s<85; vs≧85.

[0075] Solid A corresponds to the α form.

[0076] Solids B, C and D correspond to crystalline forms according to the invention. From the XRD patterns, it appears that the crystalline forms according to the invention are stable, since the XRD patterns 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 unaltered or only slightly altered relative to that of solid B.

[0077] Example 2: Centrifugal spin of solids E (not in accordance with the invention) and F (in accordance with the invention) Solids E and F were obtained by crystallization of a solution of BHET in water by gradually lowering the temperature from 60° C. to 20° C. over 4 and 6 hours, respectively, and recovered after filtration, and contain a minimum of 98.5% by weight of BHET based on their dry solid weight. They were observed under an optical microscope, and their XRD patterns were determined in the same manner as detailed in Example 1.

[0078] Solid E has a tabular type morphology and exhibits the α crystallographic form.

[0079] Solid F has a needle-type morphology and exhibits the crystallographic form according to the invention.

[0080] Each of solids E and F undergoes a water wash to make each mixture a suspension of 20 wt% solids in 80 wt% water, followed by solid-liquid separation by centrifugal spin at 20°C.

[0081] The residual water content of each solid after washing is determined by the weight loss of the solid after drying in an oven under reduced pressure at 40° C. for 15 hours.

[0082] The results obtained for the two solids E and F are presented in Table 3.

[0083] [Table 3]

[0084] The results show that solid F, which has a crystalline morphology according to the invention and exhibits a needle-type morphology, makes it possible to achieve a residual moisture content (10%) that is significantly lower than that achieved with solid E, which has a crystalline morphology of α and exhibits a plate-type morphology. Solid F is therefore much easier to dry than solid F, since less water has to be removed. [Brief explanation of the drawings]

[0085] [Figure 1] 1 shows an image of Solid A of Example 1, as observed by optical microscopy. [Figure 2] 1 depicts an image of Solid B of Example 1, as observed by optical microscopy. [Figure 3] 1 shows the XRD diagram obtained for Solid A of Example 1. [Figure 4] 1 shows an XRD diagram of Solid B of Example 1. [Figure 5] 1 shows an XRD diagram of Solid C of Example 1. [Figure 6] 1 shows an XRD diagram of Solid D of Example 1.

Claims

1. The average value of 2θ below and the relative intensity I above 5% ｒｅｌ A solid material composed mainly of BHET having a crystalline form exhibiting an X-ray diffraction pattern having the formula: 【Table 1】 In the table, vs = very strong; s = strong; m = medium; mw = medium weak; w = weak; vw = very weak, and the relative strength I ｒｅｌ is given relative to a relative intensity scale in which a value of 100 is assigned to the most intense line of the X-ray diffractogram: vw<15; 15≦w<30; 30≦mw<50; 50≦m<65; 65≦s<85; vs≧85.

2. 10. The material of claim 1, exhibiting a single crystalline form.

3. 2. The material according to claim 1, having a crystalline form exhibiting an X-ray diffraction pattern represented by the 2θ values ​​and relative intensities in Table 1 and another crystalline form of BHET, wherein the other crystalline form of BHET is preferably selected from the alpha, beta, delta or gamma form of BHET and a combination of at least two of these crystalline forms.

4. 4. The material according to any one of claims 1 to 3, comprising BHET in said crystalline form in a weight content of at least 90%, preferably at least 95%, and suitably at least 98%, the percentages being given relative to the total weight of the dry material.

5. The material according to any one of claims 1 to 4, in the form of needles.

6. A solid or liquid composition comprising a material according to any one of claims 1 to 3.

7. 7. The composition according to claim 6, further comprising a solvent, which is preferably an aqueous solvent, an alcoholic solvent, such as methanol, or a mono- or diether of a diol or glycol, the preferred solvent being water.

8. 8. A solid composition according to claim 6 or 7, further comprising a solvent, preferably in a weight content of not more than 20% by weight, preferably not more than 15% by weight.

9. 9. A composition according to any one of claims 6 to 8, obtainable by a process for the treatment of a polyester feedstock, preferably comprising PET, said process comprising a step of depolymerisation by glycolysis in the presence of ethylene glycol, preferably followed by at least one purification and / or separation step, said step comprising, for example, a step of crystallisation of BHET, in particular from water.

10. A method for the preparation of a composition according to any one of claims 6 to 9, comprising the steps of: a stage of depolymerization of the polyester feedstock, preferably containing PET, employing depolymerization by glycolysis in the presence of ethylene glycol or by methanolysis in the presence of methanol, preferably by glycolysis in the presence of ethylene glycol; then at least one purification step; preferably including a step of crystallization from water, ethylene glycol or a glycol mono- or diether, preferably water;

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

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