BHET Compositions and Uses of Such Compositions

Abstract

The present invention relates to a method for producing a cellulose ester polymer containing at least 90.0% by mass of bis(2-hydroxyethyl) terephthalate (BHET) based on the dry mass and having a pore volume of 0.20 to 1.0 cm. 3 / g. The porosity is greater than 25%, or even greater than 35%. The solid composition is made by crystallization, followed by granulation and fluidized bed drying. JPEG2022545677000008.jpg119170

Description

[Technical Field]

[0001] The present invention relates to compositions of bis-(β-hydroxyethyl) terephthalate and methods for preparing solid compositions of bis-(β-hydroxyethyl) terephthalate. [Background technology]

[0002] Bis-(β-hydroxyethyl) terephthalate (hereinafter also referred to as BHET and bis-(2-hydroxyethyl) terephthalate) is a monomeric compound used in the production of polyethylene terephthalate (PET). BHET can be produced by the transesterification of dimethyl terephthalate with ethylene glycol, the direct esterification of terephthalic acid with ethylene glycol, and the ethylene oxide process, which involves the direct reaction of terephthalic acid with ethylene oxide. Additional methods include the reaction of terephthalonitrile and water with ethylene glycol. However, given the significant volume of PET, there is considerable interest in recycling PET into BHET. This can be achieved by catalytic glycolysis.

[0003] Drying BHET is known to be problematic. As explained in U.S. Pat. No. 3,668,235, issued June 6, 1972, drying wet BHET under reduced pressure at relatively low temperatures, such as 40-60°C, results in inadequately long drying times and poor quality due to discoloration and other phenomena. However, attempting to dry solid BHET by heating to relatively high temperatures, such as 60-90°C, results in a sticky surface and a tendency for the BHET to agglomerate before drying is complete. Therefore, the patent proposes melting the solid BHET and evaporating the volatile solvent (which moistens the BHET) from the melt. To do this, the wet BHET is heated to temperatures between 90-180°C. This process obviously significantly increases the cost of producing BHET.

[0004] Therefore, it is not surprising that BHET is now being replaced by purified terephthalic acid as a monomer in the production of PET. However, BHET is also obtained as a monomer in the depolymerization of PET by glycolysis. In this situation, there is a need to produce BHET in a transportable, dry form with adequate product quality. As described in U.S. Pat. No. 7,030,264, BHET obtained by depolymerization of PET often contains many impurities that prevent its use in new polymerizations, and it is also referred to as "crude BHET." The patent also states that subjecting such crude BHET to evaporation or distillation can lead to condensation reactions, making it difficult to obtain high-quality BHET. Therefore, decationization and / or dianionization are required before evaporation or distillation at temperatures between 130 and 250°C and reduced pressure. Furthermore, multiple BHET crystallization and recrystallization steps are required using ethylene glycol as the primary solvent.

[0005] However, US 7,030,264 rather deals with a method for obtaining pure BHET with a purity of at least 98.0% by mass. The patent does not mention any drying method. Furthermore, even if the BHET obtained after the distillation and / or evaporation process is dry (this is not clear), the entire process is cumbersome and expensive, considering the desired recrystallization and required distillation and / or evaporation. In fact, as shown on the applicant's website (http: / / www.prt.ip / en.html), the distilled BHET is then polymerized into PET. PET granules, not dry BHET, constitute the final product. However, this immediate repolymerization has the disadvantage that it is more difficult to optimally adjust the polymerization process to produce expandable PET material in a stretch-blow molding process. PET is currently used in a variety of food applications, including 0.5- to 2-liter bottles of carbonated beverages, beer tanks with a capacity of 5 liters or more, and other packaging containers. It would be preferable to provide BHET in a solid form that can be transported from the depolymerization plant to the PET polymerization plant, where it can be used as a starting material, optionally in combination with additional components. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] US3,668,235 [Patent Document 2] US7030264 [Non-patent literature]

[0007] [Non-Patent Document 1] http: / / www.prt.ip / en.html Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, an object of the present invention is to provide an alternative solid form of high-quality BHET and a method for preparing the BHET.

Means for Solving the Problems

[0009] According to a first aspect, the present invention provides a solid composition comprising at least 90.0% by mass of bis(2-hydroxyethyl) terephthalate (BHET) based on the dry mass of the composition and having a pore volume in the range of 0.20 to 1.0 cm 3 / g.

[0010] According to a second aspect, the present invention provides a method for preparing a solid composition comprising at least 90.0% by mass of bis(2-hydroxyethyl) terephthalate (BHET) based on the dry mass of the composition and having a pore volume in the range of 0.20 to 1.0 cm 3 / g, the method comprising: (1) preparing a crystalline material comprising at least 90.0% by mass of BHET based on the dry mass of the solid composition; (2) granulating the crystalline material; and (3) fluidized-bed drying the granulated crystalline material.

[0011] According to a third aspect, the present invention relates to the use of the solid composition of the present invention in the polymerization of BHET to polyethylene terephthalate.

[0012] The present inventors have obtained a transportable, high-purity solid BHET composition suitable for polymerization into PET. The BHET composition of the present invention is characterized by a large pore volume and sufficient purity of at least 90.0% by weight, preferably at least 95.0% by weight, and more preferably at least 97.0% by weight. The BHET composition has been found to be less sticky, and the product is white. Furthermore, its use in polymerization is made possible by its high dissolution rate in either ethylene glycol or molten BHET, particularly compared to other BHET sources. The large pore volume is preferably obtained by granulation followed by fluidized-bed drying. The term "solid composition containing BHET" is used in the context of the present invention to refer to a solid composition consisting primarily, or even substantially, of BHET. However, this does not exclude the solid composition containing contaminants in addition to BHET. Typical contaminants include other terephthalate monomers, such as iso-BHET (ethylene isophthalate) and the BHET isomer known as hydroxyethyl terephthalate, as well as dimers of BHET.

[0013] Relatively large pore volumes were obtained in the experiments leading to the present invention when compared with commercially available BHET and comparative examples obtained with different drying techniques. Large pore volumes are highly advantageous for shortening the melting time of BHET into molten BHET and the dissolution time in solvents. The most preferred solvent for the polymerization of polyethylene terephthalate is ethylene glycol, although other solvents and / or polymerization reactions are not excluded. Despite the relatively large pore volume, the solid composition possessed sufficient strength to prevent the solid composition from disintegrating into powder, which is undesirable because it interferes with transportation.

[0014] Preferably, the solid composition is in the form of granules, the main size of which, as defined by sieving, is in the range of 0.1 to 10 mm, for example 0.5 to 8 mm, and further a part of which is in the range of 3 to 7 mm. It has been found that providing the solid composition in such granular form results in an excellent drying and flowability regime.

[0015] An advantage of this method is that it can increase the purity of the resulting BHET composition. Fluidized bed drying utilizes a carrier gas. Liquid droplets can be transported from the solid composition with the carrier gas. The liquid in the solid composition is or includes the mother liquor containing contaminants. Therefore, by transporting the liquid from the composition rather than simply evaporating it, the overall purity can be increased.

[0016] In one advantageous embodiment, the solid composition is dried in a fluidized bed dryer to a moisture content of at most 5% by weight (based on the total weight of the solid composition). Such a moisture level significantly reduces the risk of forming agglomerates that tend to prevent the free flow of the material. More preferably, the moisture content is at most 2% by weight, or even at most 1% by weight. Much lower moisture contents of less than 0.5% by weight, or even less than 0.3% by weight, have also been achieved. The moisture content before drying (after the crystallization step) is suitably in the range of 20-50% by weight, for example 30-40% by weight.

[0017] Preferably, the solid composition further contains reaction products other than BHET resulting from the depolymerization of PET, including dimers, trimers, mono-(β-hydroxyethyl) terephthalate, and bis-(β-hydroxyethoxyethyl) terephthalate. These reaction products are also referred to as other terephthalate compounds. The total content of terephthalate compounds, including BHET, is advantageously at least 98.0% by weight in the final product, preferably at least 99.0% by weight, more preferably at least 99.5% by weight, or even at least 99.7% by weight. Other contaminants in the final dried product include water, ethylene glycol, and inorganic elements such as sodium, iron, and chloride.

[0018] Typically, based on HPLC testing, the solid composition contains crystalline material, particularly only one single crystalline form. Therefore, the granulation and drying process is compatible with maintaining the crystalline form, but does not exclude the conversion of a portion of the BHET to amorphous material. Thus, the granulate can be considered polycrystalline in nature. The overall crystallinity of the solid composition is preferably at least 80% by weight, more preferably at least 90% by weight, or even at least 95% by weight, based on the dry weight of the composition. The advantage of the crystalline form is its mechanical strength, thereby reducing the risk of breakage and / or deformation during transportation. A further advantage of the crystalline form is its reduced sensitivity to moisture compared to amorphous (i.e., powdered) material. As a result, the risk of agglomeration during storage is lower than with amorphous material. The granules preferably have a size in the range of 1 to 10 mm. Granule size can be characterized by sieving. Such a size has been found to be practical to optimize drying time, dissolution time in ethylene glycol, dissolution time in molten BHET, and transportation characteristics. The granulation process typically involves a size reduction step, starting with a fairly lumpy agglomerated product. The granulation process may alternatively or additionally include an agglomeration step to combine fines and individual crystallites. Granulation can be accomplished, for example, by extrusion, pressing through a sieve, pelletizing, and / or nibblers. The latter method is considered particularly useful when starting with a cake of crystalline material, such as a filter cake. A nibbler is a tool based on a rotor with threaded strips and a screening plate. During use, the filter cake is continuously fed into the nibbler. The nibbler's inlet is adjusted to match the size of the filter cake. The nibbler's rotor may rotate at a speed ranging from 50 to 100 rpm, e.g., 80 rpm. The strips press the entire length of the filter cake against the screen. The shredded solids are collected in a tank or container.

[0019] It is not excluded that a separate drying step may be carried out as a pre-treatment before fluidized bed drying, such as drying at atmospheric pressure in the range of 40-90°C.

[0020] Preferably, the pore volume of the dried granules is at least 0.30 cm 3 / g, more preferably at least 0.40 cm 3 / g, and also at least 0.50 cm 3 / g and the pore volume is 1.0 cm 3 / g, preferably at most 0.80 cm 3 / g, and even up to 0.70 cm 3 / g is considered advantageous. A relatively large pore volume is considered advantageous for shortening dissolution and melting times. A maximum pore volume is considered advantageous for ensuring sufficient stability of the granules and preventing them from collapsing into powders (which have less beneficial flow and transport properties). Herein, pore volume is measured by mercury porosimetry, as known to those skilled in the art and standardized by ASTM D 4404-10. Pore volume may vary depending on the processing steps carried out after crystallization, the average particle size, and even the composition of the granulate. Initial experiments have shown that pore volumes of 0.40-0.60 cm 3 Pore ​​volumes in the range of 0.15 to 0.5g / g have been achieved, with the porosity (%) being preferably at least 25%, more preferably at least 30%, or even at least 35%. Experimentally, porosities of more than 40%, such as between 40% and 50%, have been achieved.

[0021] Furthermore, the granules have a density of 0.33 to 0.56 g / cm 3 It is believed preferable to have a bulk density in the range of 0.40 to 0.55 g / cm. Bulk density is defined as the density of a material including both inter- and intra-particle pores, as well as the hollow spaces between individual granules. Bulk density is therefore a parameter describing the bulk material introduced into a mixing vessel prior to polymerization or another reaction. Bulk density is more preferably in the range of 0.40 to 0.55 g / cm. 3 The lower end of the range tends to depend largely on the presence of hollow spaces within the material. In one embodiment, with a fairly broad size distribution of granules, the bulk density is at least 0.45 g / cm 3 , and even at least 0.50 g / cm 3 is.

[0022] The solid composition of the present invention has been found to have a shorter dissolution time in heated ethylene glycol (particularly in the temperature range of 100-200°C, such as 120-195°C or 130-190°C) than other known or comparable solid compositions of BHET. This is believed to be highly beneficial on an industrial scale. Faster dissolution not only shortens production time but also significantly reduces the risk of retaining undissolved BHET material. If some BHET material does not dissolve, it can contaminate the resulting polymer (e.g., PET). Such contamination by solid particles can significantly affect the mechanical properties of the PET material during and after processing, such as blow molding. Furthermore, undissolved material can cause agglomerates to form within the reactor system. Such agglomerates can reduce or even block flow, for example, in heat exchangers.

[0023] The solid compositions of the present invention further have melting times in molten BHET that are shorter than or equal to other known or comparable solid compositions of BHET. When compared for samples of the same size, the melting times in molten BHET are significantly shorter than any other BHET compositions. This, again, is highly beneficial on an industrial scale for the same reasons as above. Furthermore, the reduction in melting time, or dissolution time in BHET, if applicable, or dissolution time in ethylene glycol, if applicable, is advantageous in providing customers with greater process flexibility.

[0024] Furthermore, in one embodiment, the solid composition has an angle of repose of less than 40 degrees, even less than 38 degrees. Herein, the angle of repose is measured according to the tilt method, which is specified in more detail below. The angle of repose is a parameter that represents the fluidity of a material. Fluidity is very important in industrial applications.

[0025] The BHET of the present invention is preferably obtained by depolymerizing terephthalate polymers, such as polyethylene terephthalate, polybutylene terephthalate, polypropylene terephthalate, polyethylene isoterephthalate, and polypentaerythrityl terephthalate, and copolymers of the above terephthalate polymers, such as copolymers of polyethylene oxide and polybutylene terephthalate. More preferably, the BHET of the present invention is obtained by depolymerizing polyethylene terephthalate. Alternatively, the BHET can be obtained by chemical reaction of a terephthalate source with an ethylene glycol source. Known sources of terephthalate include dimethyl terephthalate, terephthalic acid, and terephthalonitrile, as discussed in the background section. Known sources of ethylene glycol include ethylene glycol and ethylene oxide.

[0026] When BHET is obtained from depolymerization, it is preferred that the BHET be crystallized only after crystallizing the BHET dimer and removing it from the remaining mother liquor. This pretreatment step has been found to be advantageous in preventing contamination of the crystalline BHET with ionic contaminants such as ions of Na, K, Fe, Ca, etc. Furthermore, removal of the BHET dimer is advantageous in ensuring sufficient purity of the BHET without the need to use excessive amounts of ethylene glycol during depolymerization.

[0027] More preferably, the dimer of BHET is present in the solid composition in an amount of at most 3.0% by weight, more preferably at most 2.5% by weight, or even less than 2.0% by weight, for example 1.0-2.0% by weight, which level of impurity has been found not to adversely affect the purity with respect to cations that may be present in the mother liquor, such as iron ions.

[0028] In another aspect, the present invention relates to a method for preparing a solid composition comprising at least 60.0% by weight of bis(2-hydroxyethyl) terephthalate (BHET), the method comprising the steps of: (1) providing a crystalline material comprising at least 90.0% by weight of BHET, based on the dry weight of the solid composition; (2) granulating the crystalline material; and (3) fluid-bed drying the granulated crystalline material.

[0029] In a related aspect, the present invention relates to a solid composition containing at least 60.0% by weight of bis(2-hydroxyethyl) terephthalate (BHET), obtained by granulation of crystalline BHET and subsequent fluidized-bed drying. The BHET content after drying is preferably at least 70.0% by weight, more preferably at least 80% by weight, or even at least 90% by weight. Other compounds in the composition include other terephthalate compounds. These other compounds are suitably present in an amount such that the entire solid composition contains at least 90% by weight, more preferably at least 95% by weight, or even at least 98% by weight of terephthalate compounds. After fluidized-bed drying, the moisture content is typically at most 5% by weight, more preferably at most 2% by weight, or even at most 1% by weight.

[0030] Such solid compositions preferably have a pore volume and / or density as specified above, however, it is not excluded that the method may be extended or modified to obtain products with different, yet still advantageous, porosities.

[0031] In one embodiment, such a solid composition is obtained by mixing crystalline BHET with a crystalline dimer in a predetermined ratio. Mixing is preferably carried out before granulation and fluidized-bed drying. Alternatively or additionally, terephthalic acid and / or a terephthalate salt can be mixed into the solid composition. The predetermined ratio is more precisely defined in consideration of the subsequent polymerization of PET, ensuring fixation of a specific ratio and ensuring a suitable mixture of the different compounds in the melt or solution. Instead of mixing into a compound based solely on terephthalic acid and hydroxyethyl-terephthalic acid (or their anionic forms), a comonomer may be mixed into a solid composition based on, for example, hydroxybutyl-terephthalic acid.

[0032] In yet a further aspect, the present invention provides a composition comprising at least 90.0% by weight of bis(2-hydroxyethyl) terephthalate (BHET) based on the dry weight of the composition and having a bulk density of 0.33 to 0.56 g / cm 3 , preferably 0.40 to 0.55 g / cm 3 , and even 0.44 to 0.54 g / cm 3 The bulk density is determined as specified herein below in more detail.

[0033] The present invention further relates to the use of the solid composition of the present invention in the polymerization of BHET to polyethylene terephthalate (PET). It has been found that the BHET in this solid composition has the necessary purity for polymerization and suitable fluidity.

[0034] Preferably, the use involves dissolving the solid composition in ethylene glycol or melting the composition when immersed in a melt of BHET. These two options are common ways of creating an initial mixture of reagents. One advantage of using the solid composition is that it does not sink into the ethylene glycol or BHET but remains on the surface. This is believed to contribute to a faster dissolution rate and may also reduce the risk of some BHET remaining undissolved. More preferably, the solid composition has a melting time of less than 30 seconds at 140°C when immersed in molten BHET, and the solid composition is present as granules with a size limit of 5 mm in an amount of 5% by weight of the molten BHET, as determined by sieving. For clarity, it is noted that the presence of additional compounds (such as solvents, reagents, or additives) in the solvent (ethylene glycol) or molten BHET in which the solid composition dissolves or melts is not excluded. One typical additive is, for example, water, which may act as a catalyst in the polymerization or as a solvent for the catalyst. Furthermore, it is not excluded that the solid composition of the present invention may be used to prepare copolymers or polymers other than PET.

[0035] These and other aspects of the present invention will become more apparent with reference to the examples and figures. For clarity, it is acknowledged that any preferred embodiment described above applies to any and all claim categories and aspects, including solid compositions, methods for preparing said solid compositions, and uses thereof, even if not explicitly set forth to avoid repetition. [Brief explanation of the drawings]

[0036] [Figure 1] 1 is a graph of the intrusion and ejection volumes of a solid composition of the present invention and a larger granular fraction of the solid composition as a function of applied pressure during mercury intrusion porosimetry. [Figure 2] 2 is a graph of the pore size distribution derived from the intrusion curve shown in FIG. 1. DETAILED DESCRIPTION OF THE INVENTION

[0037] Measurement method Hereinafter, reference will be made to BHET for some solid compositions containing at least 90% by weight of BHET (hereinafter also referred to as BHET).

[0038] purity 25 mg of BHET was dissolved in 50 ml of 100% acetonitrile and measured using an HPLC "Agilent Technologies 1100 Series" equipped with an "XBridge C8 3.5 μm, 4.6 × 150 mm" column. The detector was DAD 242 nm.

[0039] The reported results (Table 1) are the average of the Duplo measurements.

[0040] Bulk density Bulk density (hereinafter also referred to as ρ) is the mass of a material in a container of a specific volume. The values ​​in the table are the average of Duplo measurements. The protocol includes:

[0041] 1. Tare a 1,000 ml graduated cylinder on a weighing scale. 2. Fill the cylinder with solid BHET and record the mass of the BHET. 3. Determine the volume of BHET added by reading from the graduated cylinder. 4.

number

[0042] A 1,000 ml graduated cylinder is used to avoid the influence of the cylinder walls, which reduces the precision of the method. However, the determination of the added volume sets a limit to the precision.

[0043] skeletal density Skeletal density is determined by gas pycnometry, which takes into account the reduction in particle density due to entrapped gas bubbles. The protocol is as follows:

[0044] Before the measurement, the samples are degassed for 16 hours in vacuum at 25°C. Measurements were carried out at 25°C using a Quantachrome Ultrapycnometer 1000 according to ISO 12154:2014. Due to the large particle size distribution, the 150 cm 3 A sample size of 100 was used.

[0045] Reported values ​​are the average of 10 consecutive dependent measurements on a single representative sample, with the maximum variation for these 10 consecutive measurements being less than 0.08%. Estimated imprecision is determined using the standard deviation of quality control material.

[0046] porosity Pore ​​volume was determined using a Hg porosimeter. Prior to mercury intrusion measurements, samples were degassed for 16 hours in a vacuum at 25°C. Subsequently, pressures ranging from 0.002 MPa to 220 MPa were applied, and intrusion and expulsion curves were recorded on a Micromeritics Autopore 9505 analyzer. This pressure was converted to pore diameter using the Washburn equation. A value of 140° was used for the contact angle. Measurements were performed according to ASTM D 4404-10. Due to the limited size of the cell used in mercury intrusion porosimetry, only particles smaller than 0.6 mm in size were tested to ensure fair comparisons between samples.

[0047] The porosity (%) is calculated based on these measurements.

[0048] Apparent density Apparent density is a calculated density based on mercury intrusion porosimetry.

[0049] angle of repose The angle of repose is defined as the angle from a horizontal plate to the free surface of the powder under gravity. The so-called tilting method is used for the measurement. This tilting method is known to generally result in higher values ​​than other methods such as the pouring method. A drum with a diameter of 153 mm and a height of 45 mm was used.

[0050] Approximately 200 ml of sample was placed in the drum. The drum rotation speed was set at 6.4 rpm. Three photographs were taken while the drum was rotating, and the angle of repose was determined optically from each photograph. The values ​​shown are averages.

[0051] Dissolution rate in ethylene glycol The dissolution of BHET is measured at two temperatures: T1 = 140° C. and T2 = 180° C. The protocol for the measurement method is as follows:

[0052] First, 95 g of ethylene glycol (EG) was heated to T1 or T2 in a 250 ml glass beaker closed with a watch glass or aluminum foil. A heating plate of type IKA C-MAG HS7 was used with a stirring speed set at 1.5, gradually increasing to a maximum of 6. A thermocouple was used to prevent the solution from overheating.

[0053] Once the EG reaches the specified temperature (T1 or T2), remove the watch glass or aluminum foil and add 5 g of solid BHET in one continuous motion. The temperature and stirring speed settings remain unchanged. The addition of BHET at room temperature causes a temperature drop, which the thermocouple will follow.

[0054] The dissolution time is then recorded. A video camera is used to record the introduction of BHET and its dissolution into EG. These recordings are analyzed in slow motion to visually determine when all solids have dissolved.

[0055] The values ​​in the table are the average of the Duplo measurements.

[0056] For the BHET according to the invention, the measurements were carried out on the BHET obtained after fluidized bed drying and on samples that had been subjected to a size reduction treatment and had reached a size of 5 mm as defined by sieving.

[0057] Melting rate to molten BHET The melting of BHET is measured at two temperatures: T1 = 140° C. and T2 = 180° C. The measurement method includes the following steps:

[0058] First, prepare the BHET melt. To do this, heat 47.5 g of BHET to T1 or T2 in a 250 ml Erlenmeyer flask submerged in a paraffin oil bath. This forms a melt. To ensure a uniform temperature of the melt, keep the Erlenmeyer flask with the BHET in the oil bath for at least 15 minutes. Stir both the melt and the oil at a stirring speed of 1.5 (up to 6 in stages) on a heating plate of type IKA C-MAG HS7. A thermocouple is used to maintain a constant temperature in the oil bath.

[0059] In the second step, solid BHET is added to the BHET melt. 2.5 g of solid BHET is added in one continuous motion. The temperature and stirring speed settings remain unchanged.

[0060] The melting time is then measured using a video camera. The introduction of the BHET and its melting are recorded. These recordings are analyzed in slow motion to visually determine when all the solids have dissolved.

[0061] For the BHET according to the invention, the measurements were made on the BHET obtained after fluidized bed drying and on samples that had been subjected to a size reduction treatment and had reached a size of 5 mm as defined by sieving.

[0062] The values ​​in the table are the average of the Duplo measurements. [Example]

[0063] Example 1 Preparation of BHET according to the present invention A mixture of polyethylene terephthalate (PET) flakes, ethylene glycol (EG), and catalyst was used in this range of relative ratios. In a laboratory-scale example, 1 g of dried catalyst composite was combined with 5 g of PET and 50 g of EG in a 100 mL flask. The catalyst composite was prepared by starting with magnetite nanoparticles (5 nm size), trisilanol propyl (C3H7Si(OR)3, where R is ethyl), and (bim)FeCl4 or (bim)Cl. Here, bim stands for butylimidazolium. The catalyst composite was prepared by reacting (bim)FeCl4 or (bim)Cl with trisilanol propyl. The resulting functionalized propyltrisilanol was contacted with nanoparticles to form aggregates as specified in WO2017111602 (incorporated herein by reference). However, the use of alternative catalysts is not excluded. The catalyst composite dispersion was homogenized by hand shaking for 5 minutes. 41 g of EG was added to 10 g of the catalyst composite dispersion, and the mixture was briefly mixed by hand to homogenize the dispersion. 5 g of PET flakes were then added, and the round-bottom flask was placed in a heating device. PET flakes were prepared from commercially available colored PET bottles, such as blue and red bottles. Heating was initiated, and the reaction mixture reached a reaction temperature of 170–200°C within 20 minutes.

[0064] The depolymerization was repeated in a 1,000-liter vessel. The decomposition reaction was carried out at temperatures ranging from 180 to 210 °C. The catalyst complex concentration was approximately 0.5% by weight, but this was not critical. After a predetermined reaction time, e.g., 60 to 180 minutes, the reaction mixture was cooled. Water was added, and the mixture was passed through a centrifuge for separation. This process resulted in a first hydrophilic solution and a second phase. The hydrophilic solution contained a mixture of water and the solvent ethylene glycol. The second phase was in the form of a slurry containing the majority of the solid material. At least 95% of the flow entering the centrifuge became the hydrophilic solution. Typically, this was greater than 98% and even greater than 99%. The hydrophilic solution was passed through a membrane filter, where the solid material was removed onto an adsorbent, i.e., activated carbon.

[0065] The hydrophilic solution was transferred to a dimer crystallization stage, which in this example was a mixing vessel equipped with temperature control means for bringing and maintaining the crystallization solution at a predetermined temperature, e.g., 57-64°C, e.g., 60°C, in the range of 50-70°C. The exact temperature will vary depending on the dimer concentration, the water to ethylene glycol ratio, and the desired residence time. After sufficient crystallization, the resulting combination of first mother liquor and dimer crystals was transferred to a separator, e.g., a filtration unit.

[0066] Downstream, BHET is crystallized and recovered in a further separator. The crystals were obtained with a purity of more than 90% by mass, based on the dry mass. In the example used, the crystallization of BHET occurred at a lower temperature compared to the crystallization of the dimer. The BHET crystals were then washed with water to remove any adsorbed mother liquor.

[0067] The material has a moisture content of 28 to 40% by mass and is in the form of a cake.

[0068] To confirm the purity, laboratory-scale tests were carried out. BHET crystalline material was obtained starting from 520 g of a hydrophilic solution containing 35.4 g (6.8 wt%) of BHET, 3.6 g of dimer (10.8 wt% based on BHET), and 50 ppm of Fe. The wet BHET was washed and then dried in a laboratory-scale drying apparatus. The total dimer content of the dried BHET was 1.5 wt%, and the Fe content was 20 ppm.

[0069] Example 2 500 g of the crystallized and washed material was then subjected to size reduction and drying. Size reduction was performed by pressing through a 5 mm (opening) sieve. The resulting material (granules) was then dried in a fluidized bed dryer using air as the carrier gas. The temperature of the carrier gas was 90°C. The flow rate was initially 0.9-1.2 kg / (m 2 ·s), but typically reached 0.8 kg / (m after 10 minutes. 2The moisture content decreased to 1.5% by weight and 0.1% by weight depending on the drying time. The material was white in color. No contamination was observed.

[0070] Example 3 The crystalline BHET material obtained in Example 1 in the form of a cake with a moisture content of 36% by weight was treated with a nibbler to reduce the size and obtain granules. The obtained granules were then subjected to fluidized bed drying. A white material without visible contamination was obtained. This material was further evaluated.

[0071] (Comparative Example 1) The crystallized BHET obtained in Example 1 after the washing step was dried by vacuum drying.

[0072] (Comparative Example 2) BHET was obtained from Sigma-Aldrich (product number 465151) and delivered in a poly bottle, with a purity of at least 94.5% by mass (GC) according to the supplier's specifications.

[0073] Form and purity assessment The shape, particle size distribution, and purity of the material were evaluated. The results are shown in Table 1. The material of the present invention is granular, with individual particles of various sizes, characterized by irregular shapes and non-smooth surfaces. In one test, a small particle size distribution was selected from the material. The purity of this particle size fraction was found not to deviate from the overall purity. Purity is measured herein based on HPLC. The material of Comparative Example 1 was stony and had a fairly smooth surface. Purity measurements showed greater variability. The material of Comparative Example 2 was in the form of flakes. The purity was found to be higher than the minimum purity specified by the supplier.

[0074] [Table 1]

[0075] The broad size distribution of the examples according to the invention was further determined based on particle sieving as 99% less than 6.3 mm and 70% less than 2.4 mm. In further experiments using laser diffraction, a venturi pressure of 0 bar was used to measure the volumetric particle size distribution shown in Table 2. The data here is the average of two separate measurements.

[0076] [Table 2]

[0077] It is observed that the value obtained by laser diffraction measurement does not include any particles present that are larger than 3.5 mm in size. This result is estimated to be applicable to the 70% sieved through a 2.36 mm sieve. It can therefore be concluded that the granulate according to the invention, at least in one preferred embodiment, has an average diameter in the range of 1.2 to 1.6 mm when measured by laser diffraction (excluding particles larger than 3.5 mm). Said average diameter is defined as the volume-weighted average diameter (Σn i D i 4 ) / (Σn i D i 3 )) Preferably, the average diameter is in the range of 1.3 to 1.5 mm. The average diameter is in the range of 1.1 to 1.5 mm, preferably 1.2 to 1.4 mm. The distribution width is in the range of 1.3 to 1.5.

[0078] Density and porosity tests The density and porosity measurements were carried out as described above. The results are shown in Table 3. A separate test was carried out on the material of the present invention using relatively large granules. The large granule fraction corresponds to fractions 1-3 shown in Table 1. The overall fraction contains smaller granules. In other words, the large granule fraction is a part of the overall fraction. The sample containing the large granules corresponds more closely to the particle size contained in the comparative sample.

[0079] [Table 3]

[0080] Skeletal density is 1.301-1.371g / cm 3 The maximum absolute error in the measurement is approximately 0.005 g / cm 3 Therefore, although the differences are small, the skeletal densities of all the samples are significantly different. These density differences may be caused by impurities and / or inaccessible voids within the material.

[0081] The bulk density is significantly lower than the skeletal density. This is a result of the presence of both intra- and inter-particle pores. A further contribution to the bulk density comes from the hollow spaces between the samples when filling the beaker. Considering that the comparative example particles are larger, the contribution of the hollow spaces is more significant for the comparative example. Nevertheless, it is clear from Table 1 that the bulk density of the inventive samples is lower than that of the comparative example. This is due to the increased porosity.

[0082] It is immediately apparent that the pore volume of the inventive sample is significantly larger than that of the comparative sample. The pore volume of the large granular fraction is smaller. The inventors have realized that selective variation of the pore volume can be obtained by designing the processing steps after crystallization (size reduction and fluidized bed drying). Mercury intrusion and desorption curves of the inventive sample are shown in Figure 1, where the intrusion volume (cm 3The pore size (µm / g) is shown as a function of applied pressure (MPa). The expulsion curve is indicated by open dots (starting at 0.1 MPa), and the intrusion curve is indicated by large dots. The upper curve is for a normal sample, while the lower curve is for a sample obtained from larger granules. The curves show the initial intrusion from a low pressure of approximately 0.002 MPa to approximately 0.05 MPa. This initial intrusion must be due to particle rearrangement and filling of interparticle voids. It is easy to see that this step is much lower for the larger granule fraction. The intrusion curves show a very similar second intrusion step, ranging from approximately 0.1 to 10 MPa. This contribution is likely due to intraparticle voids. A significant plateau is reached above a pressure of 10 MPa. This observation indicates that all porosity, at least 6 nm in size, has been adequately characterized. A pore size of 6 nm is the lower limit of the mercury intrusion porosimetry technique.

[0083] Quantitative information on the total pore volume and the derived porosity is summarized in Table 3. Since compaction occurs, the results at different pressures are used to exclude compaction in the calculations.

[0084] The apparent density obtained can be correlated with the skeletal density. Only small differences are obtained, with a maximum relative deviation of 5%.

[0085] The pore size distribution was derived from the intrusion curve. The results are shown in Figure 2. Two major contributions are evident. First, there is an interparticle contribution in the range of 50-700 μm, with a mode around 415 μm. This can be attributed to the filling of interparticle pores. The second contribution is in the range of approximately 0.3-10 μm, with a mode of 4 μm. This contribution can be attributed to the filling of intraparticle pores.

[0086] The pressure curve of the comparative example is significantly lower, with a maximum of about 0.04 cm 3 / g, but the larger granular fraction is 0.4 cm 3 / g. In the derived pore size distribution, the intraparticle contribution in the range of 0.03–10 μm is almost completely absent.

[0087] Evaluation of flow, melting and dissolution behavior The behavior of the material when melted in molten BHET and dissolved in ethylene glycol was tested. This behavior is important for the intended repolymerization of the material. The results are shown in Table 4. Furthermore, the angle of repose is shown. This parameter indicates the flow behavior. The results are shown in Table 4. The tests were carried out in duplo. The sample of the invention was measured twice more. For the second experiment, size reduction was carried out. Furthermore, the tests were carried out at two different temperatures.

[0088] [Table 4]

[0089] The results in Table 4 show that Comparative Example 1 has the worst melting and dissolution. This material contains the same crystallized BHET as the present invention, but is then processed differently, resulting in low porosity rather than high porosity. The melting and dissolution times of the unsize-reduced material of the present invention are comparable to those of Comparative Example 2. However, it should be understood that this comparison cannot be considered appropriate, as the volume per particle of Samples 3-1 and 3-2 of the present invention is greater than that of the comparative example. When further size-reduced to achieve comparable volumes, the melting and dissolution times of the material of the present invention are significantly shorter.

[0090] [Table 5]

[0091] Table 5 shows the angles of repose, where the 95% confidence intervals are calculated using Student's t-test (students' t-method) for three observations. Based on the confidence intervals, Comparative Example 2 is significantly different from that of the present invention. Comparative Example 1 is quite different. However, due to the higher standard deviation, a statistically significant difference cannot be stated. The material of the present invention has the smallest angle and is therefore the most fluid.

[0092] These results are consistent with the observations regarding morphology. The material of Comparative Example 2 is in the form of flakes. This morphology can be expected to have the poorest flow properties. Another important factor is the particle size distribution. A narrow particle size distribution improves flow properties. The material of Comparative Example 1 has the broadest particle size distribution of all the samples. Therefore, it is not surprising that its flow behavior is poor.

Claims

1. Contains at least 90.0% by weight of bis(2-hydroxyethyl) terephthalate (BHET) based on dry weight and has a pore volume of 0.20 to 1.0 cm 3 / g, wherein at least 80% by weight of the BHET is present in crystalline form.

2. Bulk density: 0.33 to 0.56 g / cm 3 2. The solid composition of claim 1, wherein the solid content is in the range of

3. 3. The solid composition according to claim 1, wherein the water content is at most 5.0% by weight.

4. 4. The solid composition according to claim 1, comprising at least 95.0% by weight of BHET, based on dry weight.

5. 5. The solid composition according to claim 1, further comprising a dimer of bis(2-hydroxyethyl) terephthalate.

6. 6. A solid composition according to any one of claims 1 to 5, wherein the BHET is in the form of granules.

7. 7. A solid composition according to claims 1 to 6, obtained by granulation of crystalline BHET and subsequent fluidized bed drying.

8. 8. A solid composition according to claim 6 or 7, wherein the granulate has a size in the range of 0.1 to 10 mm as defined by sieving.

9. A solid composition described in any one of claims 1 to 8, which when immersed in molten BHET in an amount of 5% by mass of the molten BHET as granules with an upper size limit of 5 mm as defined by sieving, has a melting time of less than 30 seconds at 140°C.

10. 10. The solid composition of claim 1, wherein the BHET is obtained from the depolymerization of polyethylene terephthalate.

11. Contains at least 90.0% by mass of bis(2-hydroxyethyl) terephthalate (BHET) and has a pore volume of 0.20 to 1.0 cm 3 / g, wherein at least 80% by weight of the BHET is present in crystalline form, - providing a crystalline material comprising at least 90.0% by weight of BHET on a dry weight basis; - granulating the crystalline material; fluidized bed drying the granulated crystalline material; A method comprising:

12. 12. The method of claim 11, wherein the step of providing a crystalline material comprises crystallizing the BHET and washing the crystallized BHET with a volatile medium.

13. providing a crystalline material comprising at least 90.0 wt. % BHET; - preparing a solution of at least BHET and a dimer of BHET in a mixture of water and ethylene glycol; - selectively crystallizing the dimer of BHET and separating said dimer of BHET from the remaining mother liquor, and thereafter - crystallizing BHET from said mother liquor.

13. The method of claim 11 or 12, comprising:

14. 14. The method of claim 13, wherein the selective crystallization of the BHET dimer reduces the concentration of the BHET dimer in the mother liquor to a maximum of 3.0% by weight relative to BHET in the mother liquor.

15. 15. The method of any one of claims 11 to 14, wherein the granulating step comprises breaking up the cake of crystalline material by means of a nibbler.

16. 11. Use of the solid composition according to any one of claims 1 to 10 in the polymerization of BHET to polyethylene terephthalate.

17. 17. The use of claim 16, comprising dissolving the solid composition in ethylene glycol or melting the solid composition when immersed in a melt of BHET.

18. 18. The use according to claim 17, wherein the solid composition has a melting time of less than 30 seconds at 140°C when immersed in molten BHET in an amount of 5% by weight of the molten BHET as granules with an upper size limit of 5 mm as defined by sieving.

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