Manufacturing method for polyester with lowered crystallization temperature

Abstract

The present invention relates to a process for producing polyesters, comprising the steps of: a) esterification of a monomer A of formula (1) and a monomer B of formula (2), or a mixture comprising a monomer A of formula (1), a monomer B of formula (2) and isophthalic acid, 1 is -(CH2) n -(wherein n is an integer from 2 to 4), -(CH-CHR 2 )-(where R 2 is selected from the group consisting of a linear or branched alkyl group containing 1 to 6 carbon atoms (C1-6) and a phenyl group), followed by b) a polycondensation step.

Description

[Technical field]

[0001] The present invention relates to a process for the production of polyesters, in particular thermoplastic polyesters, which are particularly suitable for bottle, packaging or coating applications, such as food container applications. More particularly, the present invention relates to a process for the production of polyesters from a mixture of at least two dihydroxyl aromatic diester monomers. Very advantageously, at least one of the two dihydroxyl aromatic diester monomers originates from a process for the recycling of polyesters, in particular from a process for the depolymerization of polyester feedstocks, such as polyester feedstocks comprising waste and / or post-consumer polyesters. [Background technology]

[0002] Chemical recycling of polyesters, particularly polyethylene terephthalate (PET), has been the subject of much research targeted at breaking down polyester recovered in waste form into monomers that can subsequently be used as feedstock for polymerization processes.

[0003] Processes for the polymerization of products resulting in particular from the depolymerization of polyesters, such as diol, diacid or diester monomers and / or oligomers, in order to obtain PET, have also been the subject of numerous investigations.

[0004] In particular, US Pat. No. 5,399,633 discloses a process for the production of high quality PET, which comprises the steps of continuously feeding ethylene glycol and terephthalic acid to an esterification medium containing bis(2-hydroxyethyl) terephthalate (BHET). US Pat. No. 5,499,633 provides a process which, for its part, comprises the esterification of a mixture of BHET and a mixture of aromatic polycarboxylic acids. US Pat. Nos. 5,499,633 and 5,499,645 each disclose a process for the preparation of flame-retardant dyed polyesters by esterification of bis(hydroxyalkyl) terephthalate monomers with a diacid mixture, followed by polycondensation, the diacid mixture comprising an aromatic dicarboxylic acid, preferably terephthalic acid, and a dyed aromatic dicarboxylic acid, each containing carboxyphosphinic acid and sulfonate groups, e.g., sulfoterephthalic acid. Patent document 5 discloses the preparation of polyester polyols by polycondensation of a diol composition comprising a dihydroxyalkyl terephthalate monomer, in particular BHET, and a short-chain C2-C9 diol, in particular ethylene glycol or diethylene glycol, with a dicarboxylic acid, for example phthalic acid. Finally, patent document 6 provides a method for the preparation of polyesters by polymerization in two reaction phases of a mixture comprising a first diol terephthalate monomer in a major amount in the mixture and a second monomer consisting of 2-(2-hydroxyethoxy)ethyl terephthalate (BHET-DEG) in a minor amount in the mixture, the first esterification phase being carried out at moderate temperature.

[0005] These documents provide for the polymerization of mixtures of BHET with diols and / or carboxylic compounds, but do not teach the preparation of polyesters by reaction of said BHET, bis(2-hydroxyethyl) terephthalate, with its meta isomer, i.e., bis(2-hydroxyethyl) isophthalate, nor how to adjust the proportion of meta-aromatic units during the esterification phase.

[0006] Similarly, US Pat. No. 5,399,663 discloses the preparation of polyesters, which comprises the depolymerization by glycolysis of PET flakes in a base of bis(2-hydroxyethyl) terephthalate (BHET) in the presence of ethylene glycol at atmospheric pressure. The intermediate product obtained at the end of the depolymerization stage is filtered through a sintered filter, retaining particles of at least 25 μm, before being introduced into a polymerization reactor to obtain polyesters. US Pat. No. 5,399,663 discloses a process for the preparation of glycol-modified polyethylene terephthalate (r-GPET), which comprises a stage of depolymerization of PET in the presence of a mixture of monoethylene glycol (MEG) and neopentyl glycol, followed directly by a stage of polymerization of the reaction effluent. US Pat. No. 5,399,663 describes, for its part, a process for the depolymerization of polyester feedstock by glycolysis in the presence of ethylene glycol, which contains in particular 0.1% to 10% by weight of a pigment. The bis(2-hydroxyethyl) terephthalate (BHET) monomer effluent obtained after specific separation and purification stages can be fed to a polymerization stage for the purpose of producing PET. US Patent No. 5,399,663 describes the production of purified BHET from PET, the resulting BHET can be used as starting material in processes for the production of plastics. US Patent No. 5,399,663 discloses the optional use of high purity bis(2-hydroxyethyl) terephthalate (BHET) as starting material for the production of high quality polyesters, the BHET being obtained by depolymerization of polyesters.

[0007] Although they disclose the polymerization of products resulting from the depolymerization of PET by glycolysis, the cited documents give no information about the quality of the intermediate products resulting from the depolymerization of PET, in particular about the presence of para and meta isomers of the dihydroxyl aromatic diester monomers.

[0008] In a study by Non-Patent Document 1, the authors report that isophthalic acid (IPA) is a comonomer that influences the crystallization behavior of PET. It is introduced into PET in amounts up to 5 mol % and inhibits the crystallization behavior during injection molding and stretch blow molding, which makes it possible to obtain transparent and glossy bottles. Patent Document 12 confirms that traditional PET resins often contain comonomers, such as isophthalic acid (IPA), to provide an optical transparency acceptable for bottle packaging. The role of the comonomer is to disrupt the linearity of the PET chains and therefore reduce the tendency to crystallize. The reduction in crystallization makes it possible to improve the haze (e.g., a reduction in the haze value) and to improve the optical properties (e.g., an increase in luminosity and / or an increase in the transmission of visible light). Small amounts of IPA comonomer, for example 1% to 10% by weight, make it possible to significantly modify the properties of the polymer.

[0009] However, none of the prior art documents provides a simple method for the production of polyesters, showing formulations suitable for packaging applications, more particularly bottle-type applications, especially using starting materials that may result from recycling of plastics, especially polyesters. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] U.S. Pat. No. 4,001,187 [Patent Document 2] US Patent Application Publication No. 2019 / 0002632 [Patent Document 3] US Patent Application Publication No. 2019 / 0106567 [Patent Document 4] US Patent Application Publication No. 2020 / 031992 [Patent Document 5] US Patent Application Publication No. 2020 / 055982 [Patent Document 6] US Patent Application Publication No. 2018 / 0340041 [Patent Document 7] Mexican Patent Application Publication No. 2007 / 004429 [Patent Document 8] International Publication No. 2017 / 006217 [Patent Document 9] French Patent Application Publication No. 3053691 [Patent Document 10] Patent No. 3715812 [Patent Document 11] European Patent No. 1120394 [Patent Document 12] US Patent Application Publication No. 2020 / 079900 [Non-patent literature]

[0011] [Non-Patent Document 1] Scheirs J. and Long TE, "Modern Polyesters: Chemistry and Technology of Polyesters and Copolyesters", Chichester, John Wiley & Sons Ltd, 2003, p.750 (Wiley Series in Polymer Science) Summary of the Invention [Means for solving the problem]

[0012] (Summary of the invention) The subject of the present invention is also a process for the production of polyesters, comprising: a) a step of esterification of a mixture containing a monomer A of formula 1 and a monomer B of formula 2 or a mixture containing a monomer A of formula 1, a monomer B of formula 2 and isophthalic acid; obtaining an oligomeric intermediate; formula 1

[0013] [ka]

[0014] formula 2

[0015] [ka]

[0016] In the formula, R 1 is selected from the group consisting of: -(CH2) n - in which n is an integer from 2 to 4; -(CH2-CHR 2 )-; in the formula, R 2 is selected from linear or branched alkyl groups containing 1 to 6 carbon atoms (C1 to C6) and phenyl groups; b) The step of polycondensation of the oligomeric intermediate.

[0017] The advantage of the present invention is to provide a simple method for the production of polyesters that exhibit a content of meta units corresponding to a reduced crystallization behavior and a reduced melting point, and that are at least suitable for injection molding and / or injection blow molding processes, and therefore make them adaptable for packaging applications, more particularly for bottle-type applications. In particular, the content of meta units of the polyesters, preferably PET, obtained by using the process according to the invention is advantageously between 0.1 mol% and 10.0 mol%, preferably between 0.25 mol% and 7.0 mol%, preferentially between 0.5 mol% and 5.0 mol%, relative to all of the basic units of the polyester. Bottles can then be produced with the polyesters obtained according to the process of the present invention by known injection-stretch-blow molding processes, the bottles produced having a clear and transparent appearance.

[0018] Another advantage of the present invention lies in the origin of the starting materials, in particular the dihydroxyl aromatic diester monomers, which can come from any known source, in particular from the networks for recycling of plastics set up in recent years by national and international organizations to combat plastic pollution. This is because at least one, or both, of the dihydroxyl aromatic diester monomers used to prepare the polyesters according to the present invention can result from a process for the depolymerization of polyesters, for example PET, in the presence of diols or methanol. The process according to the present invention can therefore contribute to the recycling of polyester materials and therefore to the fight against plastic pollution. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] (Description of the embodiment) According to the invention, the terms "diester monomer", "aromatic diester monomer" and "dihydroxyl aromatic diester monomer" denote monomer compounds which are compatible and can be condensed with each other to form the targeted polyester. More specifically, the diester monomers according to the invention are diester compounds derived from terephthalic acid or isophthalic acid and from a diol, preferably mono- or polyalkylene glycol, preferentially monoalkylene glycol, the term "derived" meaning in this case that the compound can result from the condensation of terephthalic acid or isophthalic acid with said diol. Thus, the diester monomers according to the invention comprise an aromatic ring doubly substituted in the para or meta position by an ester group which itself contains a hydroxyl group, respectively. Particular diester monomers according to the invention are in particular monomer A of formula 1, monomer B of formula 2 and monomer C of formula 3. formula 1

[0020] [ka]

[0021] formula 2

[0022] [ka]

[0023] formula 3

[0024] [ka]

[0025] During the ceremony: R 1 is selected from the group consisting of: -(CH2) n - in which n is an integer from 2 to 4, preferably equal to 2; -(CH2-CHR 2 )-; in the formula, R 2 is selected from linear or branched alkyl groups containing 1 to 6 carbon atoms (C1 to C6), preferably 1 to 3 carbon atoms (C1 to C3), preferably 2 carbon atoms (C2), and a phenyl group; R 3 is selected from the group consisting of: R 1 base -(CH2) n -(O-(CH2) n ) m - group; in which m and n are integers, m is from 1 to 4, preferably equal to 1 or 2, and n is from 2 to 4, preferably equal to 2; preferably -(CH2) n -(O-(CH2) n ) m The - group is a derivative of (i.e., derived from) diethylene glycol (i.e., -CH-CH-O-CH-CH-) or a derivative of (i.e., derived from) triethylene glycol (i.e., -CH-CH-(O-CH-CH)-); -(CH2-CH(CH3)2-CH2)- group, and -CH2-C6H 10 -CH2- group; in the formula, -C6H10 - is advantageously a disubstituted cyclohexyl, R 4 is selected from the group consisting of: -(CH2) n -(O-(CH2) n ) m - group; in which m and n are integers, m is from 1 to 4, preferably equal to 1 or 2, and n is from 2 to 4, preferably equal to 2; preferably -(CH2) n -(O-(CH2) n ) m The - group is a derivative of (i.e., derived from) diethylene glycol (i.e., -CH-CH-O-CH-CH-) or a derivative of (i.e., derived from) triethylene glycol (i.e., -CH-CH-(O-CH-CH)-); -(CH2-CH(CH3)2-CH2)- group, and -CH2-C6H 10 -CH2- group; in the formula, -C6H 10 - is advantageously a disubstituted cyclohexyl.

[0026] Highly preferably, monomer A is bis(2-hydroxyethyl) terephthalate (BHET) and monomer B is bis(2-hydroxyethyl) isophthalate (BHEI).

[0027] According to the present invention, the terms "terephthalic acid unit" and "para unit" are used interchangeably and refer to a unit of a polyester or monomer that contains an aromatic nucleus (hence the unit called an aromatic unit), which is substituted at the para position.

[0028] According to the present invention, the terms "isophthalate unit" and "meta unit" are used interchangeably and refer to a unit of a polyester or monomer that contains an aromatic nucleus (hence the term aromatic unit), which is substituted at the meta position.

[0029] According to the invention, the term "polyester" advantageously denotes a saturated thermoplastic polymer (as opposed to a thermosetting polymer) having as basic repeat units diol esters, more particularly at least alkylene terephthalate units, whose alkylene ester group is located in the para position on the aromatic nucleus, and alkylene isophthalate units, whose alkylene ester group is located in the meta position on the aromatic nucleus. Preferably, the alkylene terephthalate units predominate in the main polymer chain relative to the alkylene isophthalate units, which means that the alkylene terephthalate units represent at least 60 mol%, preferably at least 80 mol%, preferentially at least 90 mol%, suitably at least 95 mol% of the basic units present in the polymer chain relative to the alkylene phthalate units (i.e. relative to the combined alkylene terephthalate and alkylene isophthalate units). In a preferred manner, the alkylene isophthalate units are in the minority in the main polymer chain relative to the alkylene terephthalate units, and represent, relative to the alkylene phthalate units (i.e. relative to the combined alkylene terephthalate and alkylene isophthalate units), 0.1 mol% to 10.0 mol%, preferably 0.25 mol% to 7.0 mol%, preferentially 0.5 mol% to 5.0 mol% of the basic units present in the polymer chain. Therefore, according to the present invention, the term "polyester" is used to denote a polyalkylene terephthalate in whose chain the alkylene isophthalate units are found. The polyester according to the present invention can be, for example, polyethylene terephthalate PET, polybutylene terephthalate PBT or polytrimethylene terephthalate PTT, each of these polyesters also comprising alkylene isophthalate units, respectively ethylene isophthalate, butylene isophthalate or trimethylene isophthalate units. The polyesters according to the invention can also contain other units on their main polymer chain, for example vinyl or polyol units, depending on the final properties desired for the polymer and depending on the targeted application.According to the present invention, the preferred polyester is polyethylene terephthalate, also known simply as PET, whose predominant para base repeat units are of formula 4 and which contain, on the main polymer chain, at least one minority meta base unit of formula 5: formula 4

[0030] [ka]

[0031] formula 5

[0032] [ka]

[0033] According to the invention, the terms "diol" and "glycol" are used indistinguishably and correspond to compounds containing two hydroxyl OH groups and preferably containing from 2 to 12 carbon atoms, preferentially from 2 to 4 carbon atoms. A suitable diol is ethylene glycol, also called monoethylene glycol or MEG.

[0034] According to the invention, the expressions "of between A and B" and "between A and B" are equivalent and mean that both limits of the interval (A, B) are included within the stated range of values. If this were not the case and both limits were not included within the stated range, such information would be introduced by the invention.

[0035] Within the meaning of the present invention, various ranges of parameters for a given stage, such as pressure ranges and temperature ranges, may be used alone or in combination, for example, a preferred pressure value range may be combined with a more preferred temperature value range, within the meaning of the present invention.

[0036] In the remainder of the text, specific and / or preferred embodiments of the present invention will be described, which may be implemented separately or in combination together, without limitation of combinations where this is technically feasible.

[0037] According to the invention, the pressure is absolute and is given in MPa.

[0038] The present invention therefore relates to a process for the production of polyesters, comprising, and preferably consisting of: a) a stage of esterification of a mixture comprising a monomer A of formula 1 and a monomer B of formula 2 or a mixture comprising a monomer A of formula 1, a monomer B of formula 2 and isophthalic acid (IPA), preferably carried out with a molar ratio of aromatic units substituted in the meta position (meta / [meta+para]) between 0.1 mol % and 10.0 mol %, preferably between 0.25 mol % and 7.0 mol %, preferentially between 0.5 mol % and 5.0 mol %, relative to the combined aromatic units present in the mixture (in particular substituted in the meta and para positions), said molar ratio corresponding more particularly to the ratio of the number of moles of monomer B and of moles of isophthalic acid present in the mixture to the total number of moles of monomers present in the mixture and bearing an aromatic ring, and therefore in particular the total number of moles of monomer A, monomer B and isophthalic acid; obtaining an oligomeric intermediate; formula 1

[0039] [ka]

[0040] formula 2

[0041] [ka]

[0042] In the formula, R 1 is selected from the group consisting of: -(CH2) n-; in which n is an integer from 2 to 4, preferably equal to 2, such that R 1 is an ethylene group; -(CH2-CHR 2 )-; in the formula, R 2 is selected from linear or branched alkyl groups containing 1 to 6 carbon atoms (C1 to C6), preferably 1 to 3 carbon atoms (C1 to C3), preferably 2 carbon atoms (C2), and a phenyl group; b) The step of polycondensation of the oligomeric intermediate.

[0043] The mixture of step a) may contain monomer B in a molar ratio of monomer B to the combined monomers A and B (monomer B / [monomer A+monomer B]) of 10 mol% or less, more particularly 0.01 mol% to 10.0 mol%, preferably 0.05 mol% to 7.00 mol%, and suitably 0.05 mol% to 5.00 mol%. If the amount of monomer B in the mixture of step a) is too small, in particular if the molar ratio of monomer B to the combined monomers A and B present in the mixture of step a) (monomer B / [monomer A+monomer B]) is less than 0.1 mol%, the mixture of step a) may contain, in addition to monomer A and monomer B, isophthalic acid to achieve a (meta / [meta+para]) molar ratio of 0.1 mol% to 10.0 mol%, preferably 0.25 mol% to 7.0 mol%, preferentially 0.5 mol% to 5.0 mol%. Likewise, if the molar ratio of monomer B to the combined monomers A and B present in the mixture of step a) (monomer B / [monomer A+monomer B]) is between 0.1 mol% and 10.0 mol%, preferably between 0.25 mol% and 7.0 mol%, preferentially between 0.5 mol% and 5.0 mol%, then the mixture of step a) can contain only monomers A and B or it can further contain isophthalic acid, adjusting the (meta / [meta+para]) molar ratio of the mixture to a precise value between 0.1 mol% and 10.0 mol%, preferably between 0.25 mol% and 7.0 mol%, preferentially between 0.5 mol% and 5.0 mol%.

[0044] According to a preferred embodiment of the present invention, monomer A is bis(2-hydroxyethyl) terephthalate (BHET), monomer B is bis(2-hydroxyethyl) isophthalate (BHEI), and R 1 The group is an ethylene -(CH2-CH2)- group. Preferably, BHEI is present in the mixture of step a) in a molar amount between 0.01 mol% and 10.00 mol%, preferentially between 0.05 mol% and 7.00 mol%, and preferably between 0.05 mol% and 5.00 mol%, relative to the molar amount of the combined monomers BHET and BHEI present in said mixture of step a). In this case, the polyester produced by the process according to the invention is a polyethylene terephthalate or PET, which is advantageously composed of ethylene terephthalate units (substitution of the aromatic nucleus in the para position) and contains ethylene isophthalate units (substitution of the aromatic nucleus in the meta position). Such a PET advantageously exhibits a lower crystallinity and melting point than those of a PET that does not contain ethylene isophthalate units. Therefore, PET containing ethylene isophthalate units in addition to ethylene terephthalate units is suitable for packaging applications, in particular for bottle applications, since it is suitable for injection blow molding processes and makes it possible to obtain clear, transparent bottles.

[0045] Very advantageously, at least one of the monomers A and B can be obtained by a process for the depolymerization, in particular in the presence of a diol, of a thermoplastic polyester, preferably obtained from a collection and sorting channel (i.e. obtained from a channel belonging to a system for the recycling of waste, in particular plastic waste). In particular, the mixture of step a) comprises BHET and BHEI, said mixture of at least the BHET, preferably BHET and BHEI, being obtained from a process for the treatment of polyesters, preferably PET, comprising the depolymerization of polyesters, preferably polyesters containing PET, in the presence of a diol, preferably ethylene glycol, or in the presence of methanol, preferably in the presence of a diol, in particular in the presence of ethylene glycol, said treatment process optionally comprising a purification step so as to obtain a purified BHET or a purified mixture of BHET and BHEI compatible with the polymerization step of the process according to the invention.

[0046] According to a particular embodiment of the invention, the mixture of step a) may further comprise a monomer C of formula 3: formula 3

[0047] [ka]

[0048] During the ceremony: R 3 is selected from the group consisting of: R 1 basis, -(CH2) n -(O-(CH2) n ) m -group

[0049] [ka]

[0050] In the formula, m and n are integers, m is from 1 to 4, preferably equal to 1 or 2, and n is from 2 to 4, preferably equal to 2; preferably -(CH2) n -(O-(CH2) n ) m The - group is a derivative of diethylene glycol (i.e., -CH-CH-O-CH-CH-) or a derivative of triethylene glycol (i.e., -CH-CH-(O-CH-CH)-); -(CH2-CH(CH3)2-CH2)- group

[0051] [ka]

[0052] and -CH2-C6H 10 -CH2- group

[0053] [ka]

[0054] In the formula, -C6H 10 - is advantageously a disubstituted cyclohexyl, R 4 is selected from the group consisting of: -(CH2) n -(O-(CH2) n ) m - group; in which m and n are integers, m is 1 to 4, preferably equal to 1 or 2, n is 2 to 4, preferably equal to 2, and is suitably -(CH2) n -(O-(CH2) n ) m The - group is a derivative of diethylene glycol, for example -CH-CH-O-CH-CH-, or a derivative of triethylene glycol, for example -CH-CH-(O-CH-CH)-; -(CH2-CH(CH3)2-CH2)- group, and -CH2-C6H10 -CH2- group, in the formula -C6H 10 - is advantageously a disubstituted cyclohexyl.

[0055] Highly preferred is R 3 is R 1 group, in particular an ethylene -CH-CH- group, R 4 is a derivative of diethylene glycol, i.e., -CH2-CH2-O-CH2-CH2-.

[0056] In this particular embodiment, the mixture in step a) comprises monomer C, preferably in a molar ratio of monomer C relative to the combined monomers A and C present in the mixture of step a) (monomer C / [monomer A+monomer C]) between 0.05 mol % and 10.00 mol %, preferably between 0.10 mol % and 10.00 mol %, preferentially between 0.25 mol % and 7.00 mol %, suitably between 0.50 mol % and 5.00 mol %.

[0057] According to another particular embodiment, the mixture of step a) may further comprise at least one dicarboxylic acid other than isophthalic acid, such as terephthalic acid (PTA), or one of its dialkyl diesters, such as its dimethyl diester, for example dimethyl terephthalate, and / or at least one diol, preferably chosen from ethylene glycol, diethylene glycol, butylene glycol, cyclohexanedimethanol, neopentyl glycol, and mixtures thereof. Preferably, the mixture of step a) further comprises terephthalic acid (PTA), and optionally at least ethylene glycol.

[0058] In this embodiment, the amount of terephthalic acid (PTA) introduced into the mixture of step a) is such that the molar ratio (meta units / [meta units+para units]) of meta units, in particular contributed by monomer B and isophthalic acid (IPA), to the combined aromatic units, in particular contributed by monomer A, PTA, monomer B, IPA and optionally monomer C if monomer C is present in the mixture of step a), is preferably between 0.1 mol% and 10.0 mol%, preferentially between 0.25 mol% and 7.0 mol%, and preferably between 0.5 mol% and 5.0 mol%.

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

[0060] A polymerization catalyst, preferably one based on antimony, titanium, germanium, aluminium, 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 drawing off, distillation and / or adsorption. Water may also be formed, in particular when the mixture of step a) containing monomers A and B, and optionally C, further contains a dicarboxylic acid, for example isophthalic acid and / or terephthalic acid. The water formed then is itself advantageously separated during step a).

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

[0063] Very advantageously, the polycondensation stage b) is carried out in at least one polymerization section, preferably one or two polymerization sections, advantageously operated in the liquid or melt phase, said polymerization section or sections being carried out at a temperature higher than the temperature at which stage a) is carried out, preferably at a temperature between 190 and 400° C., preferentially between 220 and 350° C., suitably between 265 and 300° C., preferably at a pressure between 0.01 and 100.00 kPa, preferentially between 0.05 and 10.00 kPa, and preferably with a residence time between 0.1 and 5.0 hours, preferably between 0.5 and 4 hours, preferentially between 1.0 and 3.0 hours. According to the invention, the residence time in the polymerization section of stage b) is defined as the ratio of the reaction volume of the reactor in which said polymerization section is carried out to the volumetric flow rate of the liquid stream leaving said reactor comprising 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 (particularly product temperature) of 190 to 250° C., preferentially 200 to 230° C. Depending on whether the operation is carried out continuously or batchwise, 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 vacuum (particularly at a pressure of 0.01 to 100 kPa, or even 0.01 to 10 kPa). The residence time (defined as the time during which the product is subjected to 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, which can therefore be located between the polymerization section and the polycondensation section, and the formed polyester obtained at the end of the polymerization section is advantageously crystallized, said crystallization section being preferably operable at a temperature comprised between 110 and 210° C., for a residence time (defined as the time during which the product is subjected to crystallization conditions in said section) preferably comprised between 0.5 and 6 hours.

[0065] Step b) is preferably carried out in the presence of a polymerization catalyst, in particular based on antimony, titanium, germanium, aluminium, 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 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 to reduce the amount of decomposition products, such as acetaldehyde.

[0067] The process according to the invention thus makes it possible to obtain polyesters, advantageously with a content of meta units: 0.1 mol % to 10.0 mol %, preferably 0.25 mol % to 7.0 mol %, preferentially 0.5 mol % to 5.0 mol %, based on the combined basic units of the polyester obtained, which allows the polyester obtained to exhibit a reduced crystallinity and melting point while retaining satisfactory mechanical properties or at least mechanical properties suitable for injection moulding and / or injection blow moulding processes, and thus suitable for packaging applications, more particularly for bottle-type applications. In particular, the process according to the invention can be integrated into the channel for recycling plastic waste, since it is advantageously possible to prepare targeted polyesters in a simple manner using the monomers resulting from the depolymerisation of polyesters.

[0068] The following examples illustrate the invention without, however, limiting its scope.

[0069] (Example) (Example 1: In accordance with the present invention) A mixture of BHET and BHEI, BHEI / [BHET+BHEI]=2.2±0.1 mol%, is subjected to an esterification step a), which is carried out at 275° C. under 0.15 MPa in the presence of 250 ppm Sb2O3 catalyst for 99 min.

[0070] The reaction medium is subsequently subjected to a first polycondensation stage at a temperature of 285° C. and a pressure of 0.1 kPa for 105 minutes.

[0071] The polyester obtained at the end of this first polycondensation stage exhibits a ratio of meta units to combined aromatic units of 2.2±0.1 mol %.

[0072] Subsequently, after a preliminary crystallization step at 125°C (i.e. at the temperature of the granules) for 2 hours, the polyester obtained at the end of the first polycondensation step is subjected to a solid-phase polycondensation step at 200°C and atmospheric pressure under a nitrogen flow.

[0073] The proportion of meta units in the polyester obtained at the end of the second polycondensation step is 2.2±0.1 mol %, relative to the combined aromatic units, which is perfectly suitable for packaging applications, especially bottle-type applications.

[0074] (Example 2: Not in accordance with the present invention) A mixture of BHET and BHEI, BHEI / [BHET+BHEI]=0.2 mol%, is subjected to the esterification step a) at 275° C. under 0.15 MPa in the presence of 250 ppm of Sb2O3 catalyst for 75 minutes.

[0075] The reaction medium is subsequently subjected to a first polycondensation stage at a temperature of 285° C. and a pressure of 0.1 kPa for 120 minutes.

[0076] The polyester obtained at the end of this first polycondensation stage exhibits a ratio of meta units to combined aromatic units of 0.2 mol %.

[0077] Subsequently, after a preliminary crystallization step at 125°C (i.e. at the temperature of the granules) for 2 hours, the polyester obtained at the end of the first polycondensation step is subjected to a solid-phase polycondensation step at 205°C and atmospheric pressure under a nitrogen flow.

[0078] The proportion of meta units in the polyester obtained at the end of the second polycondensation stage is 0.2 mol %, relative to the combined aromatic units, which is a low proportion and not very suitable for packaging applications, especially bottle-type applications.

[0079] (Example 3: In accordance with the present invention) A mixture of BHET and BHEI, BHEI / [BHET+BHEI]=0.2 mol%, is subjected to an esterification step a), which is carried out at 275° C., under 0.15 MPa, for 86 minutes, in the presence of 250 ppm Sb2O3 catalyst, such that (BHEI+IPA) / (BHEI+IPA+BHET)=2.3 mol%.

[0080] The reaction medium is subsequently subjected to a first polycondensation stage at a temperature of 285° C. and a pressure of 0.1 kPa for 73 minutes.

[0081] The polyester obtained at the end of this first polycondensation stage exhibits a proportion of meta units, relative to the combined aromatic units, of 2.3 mol %.

[0082] Subsequently, after a preliminary crystallization step at 125°C (i.e. at the temperature of the granules) for 2 hours, the polyester obtained at the end of the first polycondensation step is subjected to a solid-phase polycondensation step at 205°C and atmospheric pressure under a nitrogen flow.

[0083] The proportion of meta units in the polyester obtained at the end of the second polycondensation step is 2.3 mol %, relative to the combined aromatic units, which is perfectly suitable for packaging applications.

Claims

1. 1. A process for the production of polyester, comprising the steps of: a) a step of esterification of a mixture containing a monomer A of formula 1 and a monomer B of formula 2 or a mixture containing a monomer A of formula 1, a monomer B of formula 2 and isophthalic acid; obtaining an oligomeric intermediate; Formula 1 【Chemistry 1】 Formula 2 【Chemistry 2】 In the formula, R １ is selected from the group consisting of: - (CH ２ ) ｎ -; wherein n is an integer from 2 to 4. - (CH ２ -CHR ２ )-; in the formula, R ２ is a group consisting of 1 to 6 carbon atoms (C １ ~C ６ and a phenyl group, b) Polycondensation of the oligomeric intermediate.

2. 2. The process according to claim 1, wherein the mixture of step a) comprises monomer A and monomer B or monomer A, monomer B and isophthalic acid in a molar ratio of meta units to the combined aromatic units present in the mixture (meta / (meta+para)): from 0.1 mol % to 10.0 mol %, preferably from 0.25 mol % to 7.0 mol %, preferentially from 0.5 mol % to 5.0 mol %.

3. R １ The method of claim 1 or 2, wherein is an ethylene group.

4. 10. The method of claim 1, wherein the mixture of step a) comprises a monomer C of formula 3: Formula 3 【Transformation 3】 During the ceremony: R ３ is selected from the group consisting of: R １ base, - (CH ２ ) ｎ -(O-(CH ２ ) ｎ ) ｍ - group; in which m and n are integers, m is from 1 to 4 and is preferably equal to 1 or 2, and n is from 2 to 4 and is preferably equal to 2, - (CH ２ -CH(CH ３ ) ２ -CH ２ )-groups, and -CH ２ -C ６ H １０ -CH ２ - group, R ４ is selected from the group consisting of: - (CH ２ ) ｎ -(O-(CH ２ ) ｎ ) ｍ - group; in which m and n are integers, m is from 1 to 4 and is preferably equal to 1 or 2, and n is from 2 to 4 and is preferably equal to 2, - (CH ２ -CH(CH ３ ) ２ -CH ２ )-groups, and -CH ２ -C ６ H １０ -CH ２ - group.

5. 5. The method according to claim 4, wherein the mixture of step a) comprises a monomer C, which is present in a molar ratio of monomer C relative to the combined monomers A and C present in the mixture of step a) of from 0.05 mol % to 10.00 mol %, preferably from 0.10 mol % to 10.00 mol %, preferentially from 0.25 mol % to 7.00 mol %, and suitably from 0.50 mol % to 5.00 mol %.

6. 2. The process according to claim 1, wherein the mixture of step a) comprises a dicarboxylic acid other than isophthalic acid, such as terephthalic acid or one of its dialkyl diesters, such as its dimethyl diester, e.g., dimethyl terephthalate, and / or at least one diol, which diol is preferably selected from ethylene glycol, diethylene glycol, butylene glycol, cyclohexanedimethanol, neopentyl glycol or mixtures thereof, the preferred diol being ethylene glycol.

7. 2. The method according to claim 1, wherein step a) is carried out at a temperature of from 150 to 350°C, preferably from 200 to 300°C, suitably from 250 to 285°C.

8. 2. The method according to claim 1, wherein the pressure at which step a) is carried out is between 0.05 and 1.0 MPa, preferably between 0.1 and 0.5 MPa.

9. 2. The method of claim 1, wherein step b) comprises one or more polycondensation substeps, such as at least one liquid-phase or melt-phase polycondensation substep, optionally followed by at least one solid-phase polycondensation substep.

10. 2. The process according to claim 1, wherein step b) is carried out in at least one polymerization section, operating in the liquid or melt phase at a temperature higher than the temperature at which step a) is carried out, preferably at a temperature of from 190 to 400°C, preferentially from 220 to 350°C, suitably from 265 to 300°C, and preferably at a pressure of from 0.01 to 100.00 kPa, preferably from 0.05 to 10.00 kPa.

11. 2. The process according to claim 1, wherein step b) is carried out in the presence of a polymerization catalyst, which is preferably based on antimony, titanium, germanium, aluminum, zinc acetate, calcium acetate and / or manganese acetate.

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