Process for producing high molecular weight polyester (copolymers)

Abstract

The present invention provides (a) adding a diphenyl oxalate ester to a starting polyester (co)polymer comprising at least alcohol end groups and units derived from 1,2-diol, wherein the phenyl groups of said diphenyl oxalate ester are substituted and the substituents are selected from one or more of C1-C6 o-alkoxy, m-alkoxy, and p-alkoxy, and C1-C6 o-alkyl, m-alkyl, and p-alkyl; (b) if the temperature has not already exceeded 220°C, increasing the temperature of the mixture resulting from step (a) to at least 220°C and reducing the pressure for a period of time sufficient to obtain a polyester (co)polymer product, wherein the amount of oxalate units remaining in the (co)polymer is less than the amount added in the form of diphenyl oxalate ester, and wherein either no oxalate units or 1 mole% or less of oxalate units relative to the total amount of monomer units are present, and the product has a higher molecular weight than the starting polyester (co)polymer. The present invention relates to a method for producing a (high molecular weight) polyester (co)polymer, comprising: The present invention is particularly useful for producing new and existing high molecular weight polyesters that do not require the addition of metal catalysts.

Description

[Technical Field]

[0001] The present invention relates to a process for producing high molecular weight polyester (co)polymers and to (metal catalyst-free) (co)polymers obtainable or obtained by said process. [Background technology]

[0002] One of the most important goals of a polymerization process is to obtain a polymer with a sufficiently high molecular weight for the desired application. This is important because the molecular weight of a polymer is related to the polymer's performance (e.g., strength, toughness, and durability). The use of a polymer with an insufficient molecular weight can cause the application to fail. Therefore, much research into polymerization methods and the conditions used in those methods is directed toward achieving the target (high) molecular weight.

[0003] Polyesterification is a reversible reaction with a relatively low equilibrium constant. Therefore, removal of condensation products has an impact on the molecular weight that can be achieved. Melt polymerization under reduced pressure is widely used to remove condensation products in polyesterification processes. However, the increase in polymer molecular weight during the process also increases the viscosity of the molten material, complicating removal of condensation products. This can ultimately become a limiting factor. Removal of condensation products can be improved by using, for example, higher temperatures, longer reaction times, catalysts, and improved reactor designs. However, under molten conditions, the limited mass transfer due to the high viscosity of the molten material, combined with longer residence times and potential chemical degradation, can limit the possibility of achieving high molecular weights. For example, to achieve the high molecular weights of polyethylene terephthalate (PET) needed for bottles (intrinsic viscosity (IV) of 0.73 to 0.85 dL / g) and industrial yarns (IV > 1.2 dL / g), an additional solid-state polymerization (SSP) step may be required. In SSP, polymer pellets are heated below the melting point under nitrogen flow or vacuum. The drawback of SSP is that due to the mobility of end groups and condensates in the solid state, the process is time and energy consuming and therefore a costly method.

[0004] When a less reactive diol such as isosorbide is introduced (e.g., to produce PEIT), it becomes even more difficult to obtain a sufficiently high molecular weight. The incorporation of isosorbide is interesting due to its additional benefits to thermomechanical stability and mechanical performance, opening up new possibilities for applications. Due to its secondary alcohol group, isosorbide has low reactivity, and melt polycondensation becomes significantly more difficult as the isosorbide content increases. Furthermore, when the isosorbide content exceeds about 15%, the amorphous polymer condenses with itself, resulting in a loss of polymer crystallinity, making the use of SSP impossible.

[0005] An alternative route to producing high molecular weight polymers is to use so-called chain extenders after melt polycondensation (see, for example, P. Raffa et al., Reactive & Functional Polymers 72 (2012) 50-60). Chain extenders are highly reactive molecules that react with remaining functional chain ends (alcohols and / or acids) and increase molecular weight. Typically, only small chain extenders are needed after melt polycondensation, since large chain lengths are already achieved. Due to the high reactivity of chain extenders, significantly shorter times and more stringent conditions are required to achieve high molecular weights. This can help reduce costs by reducing polymerization conditions (temperature, time, catalyst, reactor), or eliminate the need for SSPs. Ethylene carbonate, bis-oxazoline, pyromellitic dianhydride, organic phosphites, diisocyanates, diepoxides, carbonyl biscaprolactam, diphenyl carbonate, diphenyl terephthalate, bisketenimines, and bislactams have been used.

[0006] S. Takeo et al., Polymerization Kinetics and Technology 128 (1973) 183-207, describes a method of adding a small amount of an acid derivative to a poly(ethylene terephthalate) (PET) polycondensation reaction system at a specific stage.

[0007] However, the use of chain extenders does not come without drawbacks. Chain extenders are introduced into the polymer and become part of the polyester's molecular structure. Groups incorporated into the polymer backbone inevitably affect the material's properties. Furthermore, side reactions, such as crosslinking or chain scission, often occur, which also alter the polymer's physical properties. Furthermore, some chain extenders are significantly toxic, either by themselves or as polymer residues, thus precluding their use for food-grade applications. These drawbacks may be why chain extenders are now rarely used as a standard method in commercial polyester production. Additionally, the use of currently known chain extenders results in further changes to the resulting polymer's chemical structure with each recycling step, complicating the polymer's lifespan and limiting the number of recycling steps. [Prior art documents] [Non-patent literature]

[0008] [Non-Patent Document 1] P. Raffa et al., Reactive & Functional Polymers 72 (2012) 50-60 [Non-patent document 2] S. Takeo et al., Polymerization Kinetics and Technology 128 (1973) 183-207 [Non-patent document 3] Zoi Terzopoulou et al., Tuning the Properties of Furandicarboxylic Acid-Based Polyesters with Copolymerization: A Review, Polymers 2020, 12(6), 1209; https: / / doi.org / 10.3390 / polym12061209 Summary of the Invention [Problem to be solved by the invention]

[0009] Therefore, there is a need for an alternative and improved method for producing high molecular weight polyesters that does not require high energy consumption and / or does not suffer from one or more of the drawbacks of using commonly known chain extenders. [Means for solving the problem]

[0010] The present invention provides such an improved method for producing a (high molecular weight) polyester (co)polymer, comprising the steps of: (a) adding a diphenyl oxalate ester to a starting polyester (co)polymer comprising at least alcohol end groups and units derived from a 1,2-diol, wherein the phenyl groups of the diphenyl oxalate ester are substituted and the substituents are selected from one or more of C1-C6 o-, m-, and p-alkoxy, and C1-C6 o-, m-, and p-alkyl, and (b) if the temperature has not already exceeded 220°C, increasing the temperature of the mixture resulting from step (a) to at least 220°C and reducing the pressure for a period of time sufficient to obtain a polyester (co)polymer product, wherein the amount of oxalate units remaining in the (co)polymer is less than the amount added in the form of the diphenyl oxalate ester, and wherein either no oxalate units or 1 mole% or less oxalate units relative to the total amount of monomer units are present, and wherein the product has a higher molecular weight than the starting polyester (co)polymer.

[0011] In the method of the present invention, diphenyl oxalate esters are used under relatively mild conditions as "molecular weight extenders" instead of so-called "chain extenders" according to prior art methods. As discussed above, this addresses the drawbacks of commonly used chain extenders, which incorporate into the polymer chain, alter the physical properties of the polymer, and may leave toxic residues. Advantageously, the diphenyl oxalate esters used by the method of the present invention are essentially molecular weight extenders that are not incorporated into the polymer chain of the final product, and as a result, do not affect polymer properties (molecular weight and properties related only to molecular weight) and do not leave toxic residues in the final polymer product.

[0012] Furthermore, by using the molecular weight extender according to the invention, the process can completely avoid the use of (metal) catalysts, since low molecular weight polyester chains are formed via autocatalysis (without metal catalysts) and then linked using highly reactive diphenyl oxalate and removed from the polymer chains by heating.

[0013] The high reactivity of diphenyl oxalate esters, especially bis(2-methoxyphenyl) oxalate, offers flexibility in their use in polymerization processes. Because milder reaction conditions are required to reach sufficient molecular weight, they may be used as an alternative to SSP for crystalline polymers or open up new routes to producing polymers from less reactive and unstable monomers. For example, in the production of polymers containing isosorbide-derived units, achieving high molecular weight immediately after melt polycondensation is important because the polymer is amorphous (when the isosorbide content exceeds about 10 to 15 mole percent), and SSP is not possible. The methods of the present invention further enable more efficient recycling of certain polymers, since the number of recycles can be increased without changing the physical properties of the polymer produced at each recycle step.

[0014] The present invention provides an advantageous method for producing existing and, in particular, new polyester (co)polymers while maintaining a high average molecular weight of the polyester final product. For example, the presently claimed method advantageously allows for the production of very high molecular weight polyethylene furanoate (PEF) of up to 200 kg / mol (Mw) without the addition of a metal catalyst. The elimination of the use of a metal catalyst can be advantageous from several perspectives. For example, the majority of current PET is produced using antimony (Sb) catalysts, but there are concerns about the depletion of Sb reserves. Furthermore, for medical applications, metal catalysts are often undesirable due to their toxicity.

[0015] Thus, in yet another aspect, the present invention relates to certain novel high molecular weight (co)polymers, and in particular to novel high molecular weight (co)polymers prepared without added catalysts.

[0016] The novel high molecular weight polyester (co)polymers produced according to the present invention can be advantageously used in a wide range of (industrial) applications such as fibers, injection (blow) molded parts and bottles, 3D printing, packaging materials, etc.

[0017] Additionally, the present invention provides compositions comprising one of any of the novel polyester (co)polymers plus one or more additives and / or one or more additional polymers.

[0018] Furthermore, the present invention provides an article comprising a polyester (co)polymer according to the present invention or a composition comprising a polyester (co)polymer and one or more additives and / or one or more additional (co)polymers. [Brief explanation of the drawings]

[0019] [Figure 1] Figure 1 shows the stepwise addition of DGO to a PEF sample after polycondensation (Example 2A). After each addition (1, 2, 3.5 mol%), the H NMR of the resulting polymer was taken. [Figure 2]Figure 2 shows an autoclave experiment with stepwise addition of DGO (PEIT) (Example 3). Experimental autoclave parameters: torque, temperature, and stirring speed. The experiment started after a short polycondensation of PEIT without catalyst. The molecular weight extender (DGO) was added stepwise (5 times). Each addition of DGO is marked. A sudden increase in torque is temporarily caused by the addition of DGO. [Figure 3] FIG. 3 shows the 1H-NMR of PEIT in TCE-d2 produced in the autoclave experiment of Example 3. [Figure 4] FIG. 4 shows the 1H-NMR of PEIT in TCE-d2 prepared in Example 4. [Figure 5] Figure 5 shows 3D designs printed using high-Mn PEIT: a small storage box with lid, a bench, and a flex clip. DETAILED DESCRIPTION OF THE INVENTION

[0020] The present invention relates to a process for the preparation of polyester (co)polymers, in particular for the preparation of high molecular weight polyester (co)polymers.

[0021] As used herein, "polyester" refers to a polymer containing multiple monomer units linked via ester functional groups in its backbone. Ester functional groups can be formed by the reaction of a hydroxyl group (-OH) with a carboxyl / carboxylic acid group (C(=O)OH). Typically, polyesters are synthetic polymers formed by the reaction of one or more difunctional carboxylic acids with one or more difunctional hydroxyl compounds. Polyesters can also contain units derived from monomers containing both hydroxyl and carboxylic acid groups, such as hydroxycarboxylic acids like lactic acid (LA) and glycolic acid (GA) and hydroxyalkanoates (HA). As used herein, "polyester copolymer" refers to a polyester in which three or more types of monomer units are added to the same polymer backbone. As used herein, the term "starting polyester (co)polymer" refers to the initial polyester (co)polymer used as a starting point and whose molecular weight is then increased.

[0022] By "monomer unit" herein is understood a unit contained in a polyester (co)polymer or oligomer, which is obtained after polymerization of the monomers, i.e., a "monomer unit" herein is a constitutional unit contributed to the structure of a polymer or oligomer by a single monomer or monomer compound, in this case in particular a repeating unit of a diol or diacid.

[0023] "Monomer" or "monomer compound" is understood herein as the smallest building block, such as a diol or diacid compound or a hydroxycarboxylic acid, that is used as a starting compound to be polymerized.

[0024] By "oligomer" or "oligomeric compound" is herein understood a molecular structure comprising, in total, an average number of monomer units of at least 2 and at most 50, preferably at least 25. Next to the monomer units derived from diols and diacids, the oligomer may also contain other monomer units such as monomer units derived from hydroxycarboxylic acids, in particular from α-hydroxycarboxylic acids such as glycolic acid, lactic acid, mandelic acid, 3-alkoxycarboxylic acids, etc.

[0025] The present invention relates to a method for producing high molecular weight polyester (co)polymers, comprising the step of using diphenyl oxalate esters as molecular weight extenders. The term "molecular weight extender" herein relates to chemicals used to increase the molecular weight of a polymer by assisting in chain extension of the polymer, thus forming a higher molecular weight polymer product without itself becoming part of the polymer product, i.e., being incorporated as a unit into the polymer chain.

[0026] In the prior art, diphenyl oxalate esters have been described as components of polyester products, forming polyester products containing oxalate units (see, for example, WO2018211132, WO2018211133, and WO2020106144). However, the use of (small amounts of) diphenyl oxalate esters as molecular weight extenders in polymerization processes, i.e., where the oxalate species are transiently present in intermediate polymer species and substantially absent in the final product, has not previously been described or proposed.

[0027] The method relates to the preparation of polyester (co)polymers, which includes adding a diphenyl oxalate ester as a molecular weight extender to a starting polyester (co)polymer containing at least alcohol end groups and units derived from 1,2-diol. The term "glycol-derived end group" as used herein refers to an end group in which two hydroxy groups (-OH) are attached to different carbon atoms, such as in monoethylene glycol, 1,2-propanediol, and 2,3-butanediol. A preferred glycol-derived end group is a monoethylene glycol-derived end group, i.e., a 2-hydroxyethyl end group.

[0028] Advantageously, in the current method, only a small amount of diphenyl oxalate ester is required to have a molecular weight increasing effect. Amounts of 0.2 mol%, preferably 0.4 mol%, of diphenyl oxalate ester may be suitable, particularly up to 10 mol%, preferably up to 5 mol%, and more preferably up to 2 mol%, with percentages relative to the total amount of monomers in the starting polyester (co)polymer. Ideally, the amount of diphenyl oxalate ester used is about half the amount of the total amount of diol present in the starting polyester (co)polymer. The diphenyl oxalate ester addition can be carried out in portions or all at once, depending on the circumstances and the desired product. A stoichiometric ratio of diphenyl oxalate ester to reactive end groups will result in very high molecular weights in a very short time. Therefore, ideally, and if necessary, the amount of diphenyl oxalate ester used in the method is approximately equal to the amount of glycol-derived end groups in the starting polyester (co)polymer.

[0029] The molecular weight extenders of the present invention are based on oxalate phenyl esters, where the phenyl group may be substituted, with the substituents being selected from one or more of C1-C6 o-, m-, and p-alkoxy and C1-C6 o-, m-, and p-alkyl. As used herein, o-, m-, and p- refer to ortho-, meta-, and para-substitution, respectively. Preferably, the phenyl group (in the oxalate ester) is mono-substituted, particularly with a mono-C1-C6 alkoxy substituent. In a particularly preferred embodiment, the phenyl group (in the oxalate ester) is substituted with a C1-C6 alkoxy substituent in the ortho (o-) position. Particularly preferred are diphenyl oxalate and bis(2-methoxyphenyl) oxalate (or diguaiacyl oxalate, DGO). Diphenyl oxalate esters are highly reactive with alcohol groups, to the extent that the process does not require additional catalysts. This reactivity is due to the excellent leaving group ability of the phenyl group combined with the oxalate structure, in which the carboxyl groups are directly bonded to each other. DGO has been found to be significantly more reactive than diphenyloxalate, and is therefore particularly preferred as a molecular weight extender in the process of the present invention. The high reactivity is thought to be related to the steric hindrance of the methoxy group attached to the phenyl ring. From an environmental point of view, DGO is a safer choice than, for example, diphenyloxalate, because the leaving group, guaiacol, is non-toxic (in contrast to phenol).

[0030] During the process of the present invention, it is hypothesized that oxalate ring products are formed from intermediate oxalate species and glycol-derived end groups or other suitable diol-derived units (present in the original starting polyester (co)polymer). Chain ends are attached to increase molecular weight, and the oxalate ring products are removed under high temperature and vacuum, further removing associated phenols released during the process. Furthermore, during the reaction, other suitable diol-derived units within the intermediate polymer product may react with the intermediate oxalate species (i.e., interchain reactions occur) to form oxalate ring products that are removed under high temperature and vacuum, with the effect of increasing molecular weight in the process. While the oxalate ring products and phenols are removed from the process, high molecular weight polymers are formed that are (substantially) free of oxalate-derived units in the polymer chain. Only trace, barely detectable, or undetectable amounts of oxalate-derived units remain in the product polymer chain.

[0031] For example, when DGO is used as a molecular weight extender, oxalate species are formed which (without being bound by theory) are likely part of the polymer chain and form a six-membered ring with units derived from the 1,2-diol. The resulting ethylene oxalate and guaiacol can be removed from the polymer under high temperature and low pressure, leaving a high molecular weight polymer free of any residue of the molecular weight extender.

[0032] Advantageously, no residues of the molecular weight extender units, or very few of them (less than 1 mol%), remain in the polymer chain. Therefore, the method does not change the mechanical and chemical properties of the polymer produced at the end of the method. This is a great advantage, especially when the polymer product is repeatedly subjected to recycling. As a result, the properties of the polymer product are not changed by the current method even after recycling. The absence of metal catalysts in the polymer, avoiding metal accumulation, is a further advantage in the recycling method. Preferably, the method of the present invention can avoid the use of catalysts.

[0033] A further advantage of the current process is that the cyclic oxalate species and aromatic alcohols can be suitably recycled. Advantageously, building blocks such as oxalate, ethylene glycol, and guaiacol can be reintroduced into the process again.

[0034] Current methods relate to the production of high molecular weight polyester (co)polymers, particularly those in which at least one of the 1,2-diol-derived units is derived from an aliphatic diol selected from monoethylene glycol, 1,2 propanediol, 1,2-butanediol, 2,3-butanediol and 1,2-cyclohexanediol.

[0035] The additional diol, other than the linear diol defined herein above, that can be used in the present process can be any suitable diol, primary or secondary, and can preferably be selected from cis- and / or trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol and 1,4,3,6-dianhydrohexitol, in particular isosorbide. Thus, the starting polyester (co)polymer can comprise units derived from an additional diol, preferably selected from cis- and / or trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol and 1,4,3,6-dianhydrohexitol, in particular isosorbide.

[0036] Suitably, the starting polyester (co)polymer may be any (co)polymer comprising alcohol end groups and units derived from 1,2-diol. Preferably, the starting polyester (co)polymer comprises units derived from dicarboxylic acids, wherein the dicarboxylic acid or any ester thereof is a (hetero)aromatic dicarboxylic acid or any ester thereof (preferably selected from terephthalic acid, terephthalic acid monoester, terephthalic acid diester, furandicarboxylic acid, furandicarboxylic acid monoester and furandicarboxylic acid diester) and a C2-C18 aliphatic dicarboxylic acid or any ester thereof, including but not limited to 1,4-cyclohexanedicarboxylic acid, diglycolic acid, and in particular the dicarboxylic acid of the formula HOOC(CH2). nThe dicarboxylic acid is selected from those which may be linear, cyclic or branched, such as a linear dicarboxylic acid of COOH (where n is an integer from 0 to 20).

[0037] In a preferred embodiment, the starting polyester (co)polymer contains dicarboxylic acid units derived from terephthalic acid and / or furandicarboxylic acid (especially 2,5-furandicarboxylic acid), units derived from monoethylene glycol, and optionally (depending on the desired properties of the final polyester (co)polymer product) units derived from isosorbide.

[0038] The method of the present invention is preferably carried out as follows: (i) providing or producing a starting polyester (copolymer), wherein the process for producing the polyester (copolymer) comprises an esterification / transesterification reaction and polycondensation; (ii) adding a diphenyl oxalate ester to the starting polyester (co)polymer; (iii) increasing the temperature of the mixture resulting from step (ii) to at least 220°C, or, if the temperature is already higher than 220°C, maintaining the temperature for a period of time; (iv) reducing the pressure, preferably to a maximum of 5 mbar, more preferably to 1 mbar or less, thereby removing the phenol (via the diphenyl oxalate ester) and producing the (co)polymer product; and (v) optionally repeating steps (ii) to (iv) one or more times using the (co)polymer having a higher molecular weight of the previous step (iv) as starting material until a final polyester (co)polymer product is produced having the desired high molecular weight characteristics, wherein there are no oxalate units or there are less than 1 mole% of oxalate units, the percentage being relative to the total amount of monomer units. Includes.

[0039] Preferably, step (i) comprises preparing a starting polyester (co)polymer by reacting, optionally in the presence of a catalyst, a dicarboxylic acid or an ester thereof with a diol and / or polyol and / or oligomer having a diol-derived end group (such as bis(2-hydroxyethyl) terephthalate (BHET) and other terephthalate oligomers (e.g., PET glycolysis products, see, e.g., T. Spychaj in "Handbook of thermoplastic polymers")), wherein the diol and / or polyol and / or oligomer having at least one diol-derived end group comprises a vicinal diol group. Preferably, the diol and / or polyol and / or oligomer having a diol-derived end group is selected from saturated C2-C12 aliphatic diol compounds and linear diols selected from BHET, preferably monoethylene glycol, 2,3-butanediol, and 1,2-cyclohexanediol, and comprises at least adjacent hydroxy groups (i.e., vicinal diol).

[0040] As mentioned above, the polymer in step (a) of the process can be easily prepared for this purpose in step (i), but, as described herein above, it can also advantageously be recycled polymeric material or a derivative thereof. Preferably, such polyester (co)polymers from recycled sources contain units derived from aliphatic 1,2-diols, the diols being selected from monoethylene glycol, 1,2-propanediol, 1,2-butanediol, 2,3-butanediol and 1,2-cyclohexanediol.

[0041] The temperature during step (iii) depends on the type of polyester (co)polymer being produced. Suitably, the temperature is high enough that the materials dissolve or are still molten after the addition of the diphenyl oxalate ester, and the mixture is properly stirred. For softer polyester (co)polymers with low melting points, the temperature may be, for example, at least 220°C, while for stronger polyester (co)polymers such as Pet or PEF, the temperature should preferably be at least 230°C.

[0042] As a further interesting aspect of the presently claimed method, the method has been scaled up to the kilogram-scale synthesis of isosorbide containing PET and PEF (co)polymers (PEIT and PEIF) with high molecular weight, demonstrating the possibility of using a molecular weight increasing agent, which in the scaled-up method can advantageously be added to the extruder at the end of the polycondensation (see step (ii)) or together with the (co)polymer to be extruded.

[0043] The molecular weight enhancement strategy of the present invention has been shown to be relatively easy to scale up. As an example, diphenyl oxalate ester DGO can be effectively synthesized from the transesterification of dimethyl oxalate with guaiacol. Advantageously, relatively small amounts of DGO are required to achieve the desired molecular weight enhancement effect. For example, for larger-scale production of PEF, only about 20 to 100 g of DGO per kg of PEF may be necessary. This strategy is not only economically attractive, but also easily adaptable to existing reactor equipment. The diphenyl oxalate ester can be fed to the reaction vessel, for example, via a catalyst addition funnel. Furthermore, the amount of diphenyl oxalate ester required can be reduced by increasing the polycondensation time or adding a catalyst.

[0044] Ton-scale polymer production can still result in the production of kilograms of guaiacol (when DGO is used) and ethylene oxalate rings as condensates. To make the process more economical, sustainable, and commercially attractive, the condensates should have a designated use. Guaiacol can be recycled and reused in the DGO synthesis process. Ethylene oxalate can also be reused in DGO synthesis, but it would be more effectively used directly as a monomer. Ethylene oxalate can be used to produce polyethylene oxalate, for example, by ring-opening polymerization, or it can be combined with other ring-opening monomers, such as lactide and glycosides, to produce PLA and PGA polymers with oxalate units.

[0045] In a further aspect, the present invention relates to new (co)polymers obtainable or obtained by the presently claimed method. The method allows for the preparation of existing and new polyester (co)polymers of high molecular weight, not previously obtainable. In an embodiment of the present invention, the method comprises step (i) in which a starting polyester (co)polymer is produced using a catalyst, followed by steps (ii) to (v). Such a method combines the preferred features of the present invention with the features of existing methods for producing polyesters. In another preferred embodiment, no catalyst is used in the entire method, allowing for the production of metal catalyst-free polyester (co)polymers, which may be advantageous for certain uses requiring the absence of catalysts, such as medical uses of polyesters. Thus, in one embodiment, preferably the (new) polyester produced is a metal catalyst-free (i.e., less than 1 ppm metal is present) polyester (co)polymer, i.e., produced without the addition of a metal catalyst, and preferably has an Mn of 20 kDa or greater, and the polyester is - poly(ethylene furan-2,5-dicarboxylate), - poly(ethylene co-isosorbide furan-2,5-dicarboxylate), - poly(ethylene co-isosorbide co-cyclohexanedimethylene furan-2,5-dicarboxylate), - Poly(ethylene co-isosorbide terephthalate) with an isosorbide content of 15% or more - poly(ethylene co-isosorbide co-cyclohexanedimethylene terephthalate), - poly(ethylene furan-2,5-dicarboxylate co-terephthalate), - poly(ethylene co-isosorbide furan-2,5-dicarboxylate co-terephthalate), is selected from Mn is measured using gel permeation chromatography using poly(methyl methacrylate) standards as the reference material.

[0046] The weight average molecular weight (Mn) and number average molecular weight may be measured by gel permeation chromatography at 35°C using poly(methyl methacrylate) standards as the reference material for the calculation and hexafluoro-2-propanol as the eluent.

[0047] The polyester copolymers obtainable or obtained by the process of the present invention may be suitably combined with additives and / or other (co)polymers, and therefore the present invention further provides compositions comprising, in addition to the aforementioned polyester (co)polymer, one or more additives and / or one or more additional other (co)polymers.

[0048] Such compositions may contain, for example, nucleating agents as additives. These materials may be organic or inorganic in nature. Examples of nucleating agents are talc, potassium silicate, sodium benzoate, calcium titanate, boron nitride, zinc salts, porphyrins, chlorins, and phlorins.

[0049] The compositions according to the present invention may also contain nanometer (i.e., nanometer-sized particles) functionalized or non-functionalized fillers or fibers, organic or inorganic in nature, as additives. These may be silica, zeolites, glass fibers or beads, clay, mica, titanates, silicates, graphite, calcium carbonate, carbon nanotubes, wood fibers, carbon fibers, polymer fibers, proteins, cellulose fibers, lignocellulose fibers, and destructured granular starch. These fillers or fibers may improve hardness, rigidity, or permeability to water or gases. The compositions may contain from 0.1% to 75% by weight, for example, from 0.5% to 50% by weight, of fillers and / or fibers, based on the total weight of the composition. The compositions may be of the composite type, i.e., contain a large amount of these fillers and / or fibers.

[0050] The composition may also contain opacifiers, dyes and pigments as additives, which may be selected from cobalt acetate and HS-325 Sandoplast®, a compound containing an azo functional group and also known as Solvent Red 195, HS-510 Sandoplast® Blue 2B, Polysynthren® Blue R and Clariant® RSB Violet, which are anthraquinone-based.

[0051] The composition may also contain additives such as processing aids to reduce pressure in processing equipment. Release agents may also be used to reduce adhesion to equipment used to form the polyester, such as calendering molds or rollers. These agents may be selected from fatty acid esters and amides, metal salts, soaps, paraffins, or hydrocarbon waxes. Specific examples of these agents are zinc stearate, calcium stearate, aluminum stearate, stearamide, erucamide, behenamide, beeswax, or candelilla wax.

[0052] The composition may also include other additives, such as stabilizers, as described hereinabove.

[0053] In addition, the composition may comprise one or more additional polymers other than the one or more polyester (co)polymers according to the present invention, which may suitably be selected from the group consisting of polyamide, polystyrene, styrene copolymer, styrene / acrylonitrile copolymer, styrene / acrylonitrile / butadiene copolymer, polymethyl methacrylate, acrylic copolymer, poly(ether / imide), polyphenylene oxide such as poly(2,6-dimethylphenylene oxide), polyphenylene sulfide, poly(ester / carbonate), polycarbonate, polysulfone, polysulfone ether, polyether ketone and blends of these polymers.

[0054] The composition may also comprise, as additional polymers, polymers that make it possible to improve the impact properties of the polymer, in particular functionalized polyolefins such as functionalized polymers and copolymers of ethylene or propylene, core / shell copolymers or block copolymers.

[0055] The composition according to the invention may also contain naturally occurring polymers such as starch, cellulose, chitosan, alginic acid, gluten, pea protein, casein, collagen, gelatin, or other proteins, or lignin, as additional polymers, which may or may not be physically or chemically modified. Starch may be used in a degraded or plasticized form. In the latter case, the plasticizer may be water or a polyol, in particular glycerol, polyglycerol, isosorbide, sorbitan, sorbitol, mannitol, or urea. The method described in WO 2010 / 010282 A1 may be used to prepare this composition.

[0056] These compositions can be suitably produced by conventional methods for the conversion of thermoplastic resins. These conventional methods may include at least one step of melting or softening the polymers and at least one step of recovering the composition. Such blending can be carried out, for example, in an internal blade or rotor mixer, an external mixer, or a single-screw or coaxially rotating counter- or rotating twin-screw extruder (extruder). However, it is preferred to carry out the blending by this extrusion method, especially by using a coaxially rotating extruder. The blending of the components of the composition can be suitably carried out at a temperature ranging from 220 to 300°C, preferably under an inert atmosphere in the case of an extruder, and the various components of the composition can be suitably introduced using introduction hoppers arranged along the extruder.

[0057] The present invention also relates to articles comprising the polyester (co)polymer according to the invention or a composition comprising the polyester (co)polymer according to the invention and one or more additives and / or additional polymers. The polyester (co)polymer may be conveniently used in the manufacture of packaging materials such as films, fibers, injection-molded parts and containers. The use of polyester (co)polymers is particularly advantageous when the films, fibers, injection-molded parts or packaging materials require heat or cold resistance.

[0058] The article can also be, for example, a fiber used in the textile industry. These fibers can be corrugated or non-corrugated to form fabrics.

[0059] The article can also be a film or sheet. These films or sheets can be produced by calendering, cast film extrusion, or film blow extrusion techniques. These films can be used to make labels or insulators.

[0060] The article may be a container, particularly for hot-fill and recycling applications. The article may be manufactured using conventional conversion techniques from a polyester (co)polymer or a composition comprising a polyester (co)polymer and one or more additives and / or additional polymers. The article may also be a container for the transport of gases, liquids, and / or solids. The relevant container may be a baby bottle, a flask, a bottle, such as a carbonated or still water bottle, a juice bottle, a soda bottle, a carboy, an alcoholic beverage bottle, a medicine bottle, or a cosmetic bottle, a plate, such as a pre-made meal plate or a microwave plate, or a lid. These containers may be of any size.

[0061] The article may be suitably manufactured by, for example, extrusion blow molding, thermoforming, or injection blow molding.

[0062] Thus, and conveniently, the present invention comprises the use of one or more polyester (co)polymers according to the present invention, and preferably provides a method for producing an article, comprising the steps of: 1) providing a polyester (co)polymer obtainable or obtained by the method of the present invention, 2) dissolving said polyester (co)polymer and optionally one or more additives and / or one or more additional polymers, thereby producing a molten polymer, and 3) extrusion blow moulding, thermoforming or injection blow moulding the molten polymer into an article.

[0063] The article can also be manufactured by a method comprising the step of applying a layer of polyester in solution to a layer based on an organic polymer, metal or adhesive composition in the solid state, which can be carried out by pressing, overmolding, laminating, extrusion laminating, coating or extrusion coating.

[0064] Advantageously, the high molecular weight polyester (co)polymers produced by the method of the present invention can be used for 3D printing. If very high molecular weights are desired, the use of alternative types of reactors, such as extruders and compounders, which are known to use polymers produced with some types of chain extenders, could be a potential solution. For example, spinning disk reactors are well suited to processing high viscosity polymers.

[0065] The present invention is further illustrated by the following non-limiting examples. [Example]

[0066] List of Abbreviations BHET = bis(2-hydroxyethyl) terephthalate DCM = dichloromethane DEG = diethylene glycol DGO = diguaiacyl oxalate FDCA = 2,5-furandicarboxylic acid ISO = isosorbide MEG = monoethylene glycol PDI = polydispersity index PEF = polyethylene furan-2,5-dicarboxylate PEFT = polyethylene furanoate co-terephthalate PEICF = polyethylene co-isosorbide co-cyclohexanedimethanol furan-2,5-dicarboxylate PEICT = polyethylene co-isosorbide co-cyclohexanedimethanol terephthalate PEIF = polyethylene co-isosorbide furan-2,5-dicarboxylate PEIFT = polyethylene co-isosorbide furan-2,5-dicarboxylate co-terephthalate PEIT = polyethylene co-isosorbide terephthalate PET = polyethylene terephthalate RPM = revolutions per minute SSP = solid state polymerization TEAOH = tetraethylammonium hydroxide THF = tetrahydrofuran TPA = terephthalic acid

[0067] Materials and Reagents Ethylene glycol (>99%), triethylamine (99%), titanium(IV) isopropoxide (97%), diphenyl terephthalate (98%), and diphenyl carbonate (99%) were supplied by Sigma Aldrich. Guaiacol (99%) was purchased from Carbosynth. Isosorbide (>99.5%) was supplied by Roquette. Dimethyl oxalate (>99%) and BHET (>85%) were purchased from TCI chemicals. Diguaiacyl oxalate was synthesized in-house (see Example 1). Tetrahydrofuran (99%), dichloromethane (99%), diethyl ether (99%), sodium bicarbonate (99.5%), sodium sulfate (99%; anhydrous), and sodium chloride (>99%) were supplied by VWR International. TCE-d2 (99.5%) and DMSO-d6 (99.8%) were ordered from ABCR chemicals. Titanium tetraphenoxide was prepared as described in WO2003080705.

[0068] evaluation NMR 1 H-NMR and 13 C-NMR spectra were recorded at appropriate frequencies on a Bruker AV 300 (1H, 300.10 MHz), Bruker DRX 300 (1H, 300.13 MHz), Bruker AMX 400 (1H, 400.13 MHz), Bruker DRX 500 (1H, 499.91 MHz) spectrometer and a Bruker Avance III HD 600 spectrometer. Chemical shifts were referenced to residual protons in the solvents indicated.

[0069] DSC Differential scanning calorimetry (DSC) calorimetry curves were obtained using a Mettler Toledo DSC 3 STAR e The data were acquired using a system. Approximately 5 mg of sample was weighed into a standard aluminum crucible (40 μl). The sample was then analyzed in three stages under nitrogen flow conditions of 50 mL / min. First, the sample was stabilized at 20 °C for 5 minutes, then analyzed from 20 °C to 250 °C at a rate of 10 °C / min. Next, the sample was cooled at a rate of 50 °C / min back to the starting temperature of 20 °C. Finally, the first step was repeated, and the data from this cycle was used for reporting.

[0070] GPC GPC measurements were performed at 35°C. PMMA standards were used as reference materials for calculations. HFIP was used as the eluent at 1 mL / min. Under these conditions, GPC measurements were performed on a Hitachi Chromaster 5450 using an Agilent HPLC system equipped with two PFG 7 micrometer (μm) Linear M (300 × 7.5 mm) columns. Molecular weight calculations were performed using Astra 6 software.

[0071] For PEIF: Molecular weight distributions were measured using size exclusion chromatography (SEC) on a Shimadzu LC-20AD system with two PLgel 5 μm MIXED-C columns (Polymer Laboratories) and a Shimadzu RID-10A refractive index detector, using polystyrene standards and dichloromethane as the mobile phase at a flow rate of 1 mL / min and a temperature of 35°C.

[0072] Filament manufacturing PEIT: Filaments were produced in a 3Devo Precision 350 filament maker using the following settings: heater 1 (240°C), 2 (225°C), 3 (220°C), 4 (210°C), screw speed (5 RPM), fan speed 5%, and filament diameter 2.85 mm.

[0073] PEIF: Filaments were produced in a 3Devo Precision 350 filament maker using the following settings: heater 1 (240°C), 2 (230°C), 3 (230°C), 4 (215°C), screw speed (5 RPM), fan speed 5%, and filament diameter 2.85 mm.

[0074] 3D printing The 3D models were printed using an Ultimaker 3 Extended. The hot plate was prepared by coating it with glue stick. The following settings were used for printing PEIT: hot plate (85°C), nozzle (230°C), infill rate (20 to 100%), print speed (60 mm / s), fan speed (20%), and layer height (0.2 mm).

[0075] Example 1 Diguaiacyl oxalate with dimethyl oxalate and guaiacol 1192 g of guaiacol (9.6 mol; 2.94 eq), 386 g of dimethyl oxalate (3.27 mol; 1 eq), and 2.9 g of titanium tetraphenoxide (5 mmol; 1.7 meq) were transferred to a 2 L steel kiloclave (Buchi). The reactor pressure was set to 3 bar with a N2 exhaust flow rate of 2 L / h. The heater oil temperature was set to 275 °C (internal 245 °C), and the stirring speed was set to 100 RPM when the reactor temperature reached 100 °C. The reaction was followed by removing and observing the product in the condensation flask. After 4 h of reaction time, the pressure was slowly reduced to 2 bar, and the reaction was continued for 2 h. The oil temperature was then set to 250 °C (internal 225 °C), and the pressure was slowly reduced to atmospheric pressure until guaiacol slowly distilled. When distillation had reduced to a minimum, the pressure was further reduced using a vacuum pump. The condensation flask was evacuated at 10 mbar pressure. The product was then distilled at full vacuum (<0.1 mbar) at an oil temperature of 260°C. The condensed product (300 g) was dissolved in THF (500 mL) and allowed to crystallize overnight. The resulting crystals were filtered and washed with 2 x 200 mL of diethyl ether. The crystals were dried under reduced pressure (1 mbar) at 60°C. The resulting product (225 g) was 1 Purity was analyzed by H-NMR and DSC and was usually above 99%.

[0076] Example 2 - Small-scale polycondensation of PEF with increasing molecular weight of DGO (directly 5 mole%) in the absence of a metal catalyst A 100 mL three-neck round-bottom flask was charged with 20.6 g of FDCA (132 mmol, 1 eq), 10.3 g of ethylene glycol (166 mmol, 1.25 eq), and 15 mg of ether inhibitor (35% aqueous TEAOH solution). The round-bottom flask was placed in an oil bath and equipped with a mechanical stirrer, a nitrogen inlet, and a Schlenk flask suitable for high vacuum. The polymerization was carried out in three steps: transesterification, polycondensation, and molecular weight increase.

[0077] For the transesterification step, the nitrogen flow was set at 50 mL / min, the stirring speed at 100 RPM, and the oil bath temperature at 220 °C. The set temperature was reached in approximately 30 minutes. The first transesterification step was judged complete after 2 hours when a clear melt was obtained. The transesterification reaction was allowed to continue for an additional 30 minutes before polycondensation was initiated.

[0078] For the polycondensation step, the temperature was set to 260°C and vacuum was applied (200 mbar). The pressure was slowly reduced to <1 mbar over 30 minutes. Full vacuum was maintained for 1 hour before the molecular weight increase began.

[0079] For the molecular weight build-up step, 2.0 g (6.6 mmol; 5 mole % relative to FDCA) of DGO was added to the melt under a nitrogen flow. The melt was stirred for 5 min and then slowly depressurized. Full vacuum (1 mbar) was achieved in 15 min and maintained for 10 min.

[0080] In the experiments, DGO (5 mol% relative to FDCA) was added directly after melt polycondensation. After the addition of DGO, the pressure was reduced very briefly (30 min), after which most of the condensate was removed for molecular weight buildup by SSP. Surprisingly, already only 30 min after the addition of DGO, a very high molecular weight was obtained: 42.2 / 127.3 kDa (Mn / Mw).

[0081] Note 1: This is close to the result obtained in a typical PEF polymerization using the catalyst after 24 hours of SSP at 200 °C (see "Comparative Example" below for a description of the method): 59.2 / 137.7 kDa (Mn / Mw).

[0082] Note 2: Typical PEF polymerization results after polycondensation using a polycondensation catalyst (i.e., before SSP): 28.6 / 63.0 kDa (Mn / Mw) and after polycondensation without a polycondensation catalyst (i.e., before SSP): 13.0 / 25.0 kDa (Mn / Mw).

[0083] Comparative Example: General procedure for typical conventional PEF synthesis A mixture of 2,5-furandicarboxylic acid (30 g, 1.92E-2 mol), catalyst Sb2O3 (10.5 mg, 3.60E-5 mol), inhibitor tetraethylammonium hydroxide (21 mg 35 wt% aq sol., 4.99E-5 mol), and MEG (14.30 g, 2.30E-2 mol) was stirred under a N2 atmosphere and heated to an oil temperature of 200°C. After 20 minutes, the oil temperature was increased to 220°C. The oil temperature was held at 220°C for 180 minutes, after which a 20-minute evacuation was applied, reducing the pressure from 1000 mbar to 1 mbar. Once the pressure reached 100 mbar, the oil temperature was increased to 260°C. Polycondensation (pressure below 1 mbar and T oil = 260°C) was carried out for 75 minutes, after which the vacuum was released with N2 and the molten resin was removed from the reactor.

[0084] General procedure for solid state polymerization: The resin obtained after melt polymerization was crushed and sieved, and the 0.6-2.0 mm sieve fraction was then dried / crystallized in an oven at 150 °C overnight. The resulting material was then solid-state polymerized under a nitrogen atmosphere at an oil temperature of 200 °C for 24 hours. After cooling to room temperature, the resulting resin was sieved, and the 1.4-2.0 mm sieve fraction was then subjected to further analysis.

[0085] Example 2A - Effectiveness of DGO as a (PEF) molecular weight extender in the absence of a metal catalyst To further investigate the effectiveness of using DGO as a molecular weight extender (i.e., without leaving impurities in the product), DGO was added in small increments to a polymer (PEF) with a relatively low molecular weight. After each addition, a full vacuum was applied for 30 minutes. A sample was then removed from the melt before the next addition. Each sample was 1 The resulting GPC molecular weight and ethylene glycol end groups are shown in Table 1 below.

[0086] [Table 1]

[0087] The NMR spectrum shows that DGO reacts effectively with the ethylene glycol end groups, reducing the amount of these end groups after each addition. This is confirmed by the GPC results, as the molecular weight increases after each addition. [For comparison: a typical melt polycondensate ion of PEF without a catalyst is found to have an Mn of 13 kDa. When a catalyst (Sb) is used, the Mn increases to 29 kDa. See "Comparative Example" above.]

[0088] Interestingly, significantly higher Mn values ​​could be obtained with DGO and without catalyst than with typical catalyzed melt polycondensation.

[0089] Comparative Examples 2 and 2A: The results of these examples show that the use of DGO could potentially obsolete SSP, saving time, equipment, energy consumption, and costs. The absence of a catalyst can result in reduced discoloration of PEF, an area that has been extensively studied and is often associated with catalytic systems.

[0090] The resulting polymer of Example 2 was further treated by SSP to increase its molecular weight by approximately 50%, to 64.6 / 199.9 kDa (Mn / Mw), exceeding the value typically obtained for PEF. This demonstrates the effectiveness of DGO as a molecular weight extender for PEF, especially considering that no catalyst was used.

[0091] Example 3 PEIT polymerization from BHET in the absence of metal catalysts BHET was analyzed for the presence of metals using standard procedures with inductively coupled plasma optical emission spectroscopy (ICP-OES) as the detection method. No metals (Ge, Zn, Pb, Co, Fe, Ti, and Sb) were detected above the detection limit (1 ppm).

[0092] 503.7 g of BHET (1.98 mol, 1 eq), 82.1 g of isosorbide (0.56 mol, 0.284 eq), and 33.2 g of TPA (0.199 mol, 0.1 eq) were charged to a 2 L steel kiloclave (Buchi). The oil temperature was set to 250 °C with a N2 exhaust flow rate of 2 L / h. The set temperature was reached in approximately 20 minutes (~230 °C internal). As soon as the internal temperature reached 200 °C, the stirring speed was set to 100 RPM (anchor stir bar). After 3 hours of transesterification, the nitrogen flow was heated, reduced pressure, and the oil temperature was set to 270 °C (250 °C internal). Full vacuum (<1 mbar) was reached in approximately 1 hour and maintained for 2 hours. After polycondensation the torque was increased from 500 to 570 Ncm and about 130 g of condensate was recovered from this stage.

[0093] The next day, 12.4 g (2.0 mole % relative to BHET + PTA) of DGO was added to the cooled copolymer. The oil temperature was then set to 270 °C with an N2 exhaust flow rate of 2 L / h. As soon as the internal temperature reached 200 °C, the stirring speed was set to 100 RPM. The nitrogen flow was applied for approximately 15 minutes, followed by a slow decompression. The torque was gradually increased to ~750 Ncm over approximately 30 minutes. Four additional portions of DGO were then added: 8, 8, 5, and 6.2 grams (hence, a total of 39.6 g, or 6 mole % DGO relative to BHET + PTA). After each addition, the reaction was stirred under nitrogen flow for 5 minutes, then decompressed for 30 minutes before the next addition. The final torque reached 1100 Ncm at 12 RPM (255 °C). See Figure 2. The polymer was extruded for approximately 1.5 hours at 3 bar N2 pressure. The extruded polymer was passed through a water bath and thinly chipped. The final yield was 350 g (70%) of golden-yellow polymer chips. The polymer had a high molecular weight of 24.8 / 55.1 kDa (Mn / Mw) and an isosorbide content of 16.1 mol%. The Tg was 93°C.

[0094] 1 See Figure 3 for H NMR.

[0095] Typical prior art polymerizations of PEIT with ~20% isosorbide and a good antimony catalyst system result in molecular weights of 8-9 / 24-29 kDa [Bersot, JC, et al., Macromol. Chem. Phys., 2011, 212, 19, 2114-2120]. In the experiments described here with DGO as the molecular weight extender, these molecular weights are easily exceeded without the need for a catalyst.

[0096] Example 4 Polymerization of PEIF from FDCA in the absence of metal catalysts (5 mol% DGO relative to FDCA) A 2 L steel kiloclav (Buchi) was charged with 702.0 g of FDCA (4.50 mol, 1 eq), 191.0 g of isosorbide (1.31 mol, 0.290 eq), 265.8 g of ethylene glycol (4.28 mol, 0.95 eq), and 0.5 mL of TEAOH (35% aqueous solution). The oil temperature was set to 230 °C under a 2 L / h N2 flow. The set temperature was reached in approximately 15 minutes (~215 °C internally). As soon as the internal temperature reached 175 °C, the stirring speed was set to 125 RPM (anchor bar). After 3.5 hours of transesterification, the nitrogen flow was turned on. At this stage, 188 g of condensate was collected. The pressure was reduced and the oil temperature was then set to 260-270°C (internal 243-255°C). Full vacuum (<1 mbar) was achieved in about 30 minutes and maintained for 2 hours. After polycondensation, the torque was increased from 500 to 550 Ncm.

[0097] The next day, 40 g (3.0 mol% relative to FDCA) of DGO was added to the cooled polymerized mixture. The oil temperature was set to 275 °C under a 4 L / h N2 flow. As soon as the internal temperature reached 200 °C, the stirring speed was set to 100 RPM. The nitrogen flow was continued for approximately 15 minutes, after which the pressure was slowly reduced. Three other portions of DGO, 15, 10, and 6 grams, were then added (hence, a total of 71 g, or 5.2 mol% DGO relative to FDCA, added). After each addition, the reaction was stirred under nitrogen flow for 5 minutes, and then the pressure was reduced for 30 minutes before the next addition. The final torque reached 1020 Ncm at 12 RPM. The polymer was extruded for approximately 1.5 hours under 3 bar N2 pressure. The extruded polymer was passed through a water bath and thinly chipped. The final yield was 650 g (78%) of dark polymer chips with a molecular weight of 28.0 / 66.9 kDa (Mn / Mw). The isosorbide content was 26.2 mol%, resulting in a high Tg of 109.9 °C.

[0098] 1 See Figure 4 for H NMR.

[0099] Example 5 Polymerization of PEIF from FDCA in the absence of metal catalysts (9 mol% DGO relative to FDCA) A 100 mL three-neck round-bottom flask was charged with 19.757 g of FDCA flakes (127 mmol, 1 eq), 7.414 g of ethylene glycol (119 mmol, 1.25 eq), 6.884 g of isosorbide (47 mmol, 0.372 eq), and 17.8 mg of ether inhibitor (35% aqueous TEAOH solution). The round-bottom flask was placed in an oil bath and equipped with a mechanical stirrer, nitrogen inlet, and Schlenk flask suitable for high vacuum. The polymerization was carried out in three steps: transesterification, polycondensation, and chain extension.

[0100] For the transesterification step, the nitrogen flow was set at 50 mL / min, the stirring speed at 100 RPM, and the oil bath temperature at 220° C. The transesterification step had a total duration of 12 hours.

[0101] For the polycondensation step, the temperature was set to 260°C and a vacuum (200 mbar) was applied. The vacuum was slowly increased to <1 mbar over 30 minutes. Full vacuum was maintained for 1 hour before the start of the molecular weight build-up step.

[0102] For the molecular weight build-up step, a total of 3.4 g of DGO (9 mol% relative to FDCA) was added to the melt in five portions at 275 °C. After each addition, the melt was stirred for 5 min and then slowly depressurized. Full vacuum (1 mbar) was reached in 15 min and maintained for 10 min. The additions were carried out under a nitrogen atmosphere.

[0103] It was found that even when using the less reactive isosorbide, a high molecular weight was obtained: 25.1 / 63.9 kDa (Mn / Mw) without a catalyst or SSP.

[0104] A summary of the polymers produced using molecular weight extenders in Examples 2-5 is shown in Table 2 below.

[0105] [Table 2]

[0106] Example 6 Small-scale polymerization of PET using molecular weight growth of DGO in the absence of metal catalysts A 100 mL three-neck round-bottom flask was charged with 21.929 g of terephthalic acid (132 mmol, 1 eq.), 20.482 g of ethylene glycol (330 mmol, 2.5 eq.), and 15 mg of tetraethylammonium hydroxide (35% aqueous TEAOH solution, 0.1 mmol, 0.0008 eq.). The round-bottom flask was placed in an oil bath and equipped with a mechanical stirrer, a nitrogen inlet, and a Schlenk flask suitable for high vacuum. The polymerization was carried out in three steps: esterification, polycondensation, and molecular weight increase.

[0107] For the esterification step, the nitrogen flow was set to 50 mL / min, the stirring speed was set to 150 rpm, and the oil bath temperature was set to 225 °C. The set temperature was reached in approximately 40 minutes. The first esterification step was deemed complete after approximately 15 hours, when a clear melt was obtained. The esterification reaction continued for an additional hour before heating was stopped and the reactor was allowed to cool to room temperature. The next day, the oil bath temperature was set to 270 °C. Once reached, the reactor was depressurized (400 mbar) and the pressure was slowly reduced to <1 bar over 1 hour. The polymer melt was stirred at 100 rpm for 2 hours at <1 mbar. No significant change in melt viscosity was observed, indicating no polymer chain growth was occurring. The reactor was then purged with nitrogen, and sample (6i) was removed from the reaction melt. 0.8 g of DGO (2.6 mmol, 2 mol% relative to terephthalic acid) was added to the melt and stirred at 100 rpm for 5 minutes under a nitrogen atmosphere. The reactor was then depressurized to <1 mbar, and the reaction was stirred for 30 minutes, after which the reactor was purged with nitrogen. After removing the reaction melt sample (6ii), another 0.8 g of DGO (2.6 mmol, 2 mol% relative to terephthalic acid) was added to the reaction and stirred at 30 rpm for 5 minutes under nitrogen. Due to a significant increase in melt viscosity, the oil bath temperature was set to 300 °C. A vacuum of <1 mbar was applied to the reactor, and the reaction was stirred for an additional 30 minutes, after which the reactor was purged with nitrogen. After removing the final melt sample (6iii), 0.4 g of DGO (1.3 mmol, 1 mol% relative to terephthalic acid) was added to the reaction mixture. After stirring for 5 minutes under nitrogen, a vacuum of <1 mbar was applied and held for approximately 10 minutes. The reactor was purged with nitrogen, and the reaction product (6-product) was removed from the reactor.

[0108] [Table 3]

[0109] Example 7 Small-scale polymerization of PET using molecular weight growth of DGO in the presence of metal catalysts A 100 mL three-neck round-bottom flask was charged with 33.559 g of bis(2-hydroxyethyl) terephthalate (132 mmol, 1 eq.) and 0.22 g of 15 mg of titanium(IV) butoxide (0.07 mmol, 0.05 eq.). The round-bottom flask was placed in an oil bath and equipped with a mechanical stirrer, a nitrogen inlet, and a Schlenk flask suitable for high vacuum. The polymerization was carried out in three steps: transesterification, polycondensation, and molecular weight increase.

[0110] For the transesterification step, the nitrogen flow was set to 50 mL / min, the stirring speed was set to 100 RPM, and the oil bath temperature was set to 250 °C. The set temperature was reached in approximately 40 min, and the transesterification reaction was carried out for 2 h. The oil bath temperature was set to 270 °C, and the reactor was depressurized (400 mbar). The pressure was slowly reduced to <1 mbar over 1 h. After stirring the melt at <1 mbar for 20 min, the stirring speed was reduced to 30 rpm, and the oil bath temperature was increased to 300 °C. After 20 min, the oil bath temperature reached 300 °C, and the reactor was purged with nitrogen. A molten sample (7i) was removed from the reaction mixture, and 0.2 g of DGO (0.66 mmol, 0.5 mol% relative to BHET) was added. The reaction mixture was stirred under a nitrogen atmosphere for 5 min. A vacuum of <1 mbar was then applied, and the reaction mixture was stirred for 20 min. The reactor was purged with nitrogen and the polymer (7-product) was removed from the reactor.

[0111] [Table 4]

[0112] Example 8 Comparison of the reactivity of DPO and DGO for PEIF synthesis on a small scale (without metal catalyst) First, a batch of PEIF oligomer was prepared. FDCA (200.0 g, 1.3 mol, 1.0 eq.), ISO (60.3 g, 0.41 mol, 0.32 eq.), EG (73.0 g, 1.2 mol, 0.92 eq.), and a 35% w / w aqueous solution of TEA hydroxide (150 mg, 200 ppm) were charged into a 500 mL three-neck flask equipped with an overhead stirrer, a condenser, a N2 (50 mL / min) inlet, and a thermometer. The oil temperature was set to 230 °C and reached in approximately 15 minutes. Once the oil temperature reached 190 °C, the stirring speed was set to 125 RPM. After 3.5 hours of transesterification, a clear melt was obtained, and the N2 flow was heated. At this stage, 38.1 g of condensate was collected. The pressure was then reduced, and the oil temperature was set to 260 °C. Full vacuum (<1 mbar) was achieved in approximately 30 minutes and maintained for 2 hours. The torque after polycondensation increased from 3.8 to 4.4 Ncm. Colorless to slightly yellow PEIF oligomer was recovered on a plate covered with a Teflon sheet (227 g, 1.1 mol, 97% yield).

[0113] These PEIF oligomers were reacted with DPO or DGO enhancers. A 100 mL three-neck round-bottom flask was charged with 10 g of PEIF oligomer and 7 mol% enhancer relative to FDCA (DPO: 0.846 g or DGO: 1.036 g). The round-bottom flask was placed in an oil bath and equipped with a mechanical stirrer, nitrogen inlet, and Schlenk flask suitable for high vacuum. The nitrogen flow was set to 50 mL / min, and the oil bath temperature was set to 260 °C. Immediately after obtaining a melt, the stirring speed was set to 75 RPM. The set temperature was reached in approximately 25 min. After applying a vacuum (1 mbar) at the set temperature and maintaining it for one hour, the polymer was recovered (under nitrogen) and analyzed. 1 H-NMR analysis showed an isosorbide content of 25% (integrated ratio of FDCA signals, based on total diols).

[0114] The resulting polymer was further enriched using the same procedure. 4 g of the polymer mixture was removed and reacted with an additional 2 mol% of the enhancing agent (DPO: 0.0957 g or DGO: 0.1219 g) for 40 min at 260 °C (1 mbar). After that, the vacuum was replaced with a nitrogen atmosphere, and a sample was removed and analyzed under a nitrogen flow (50 mL / min). Following this, 1 mol% of the enhancing agent (DPO: 0.0497 g or DGO: 0.0637 g) was finally added to the melt. After the addition, the melt was stirred for 5 min and then decompressed. The polymerization was continued for 45 min at 260 °C (1 mbar), after which the polymer was collected and analyzed. The results are shown in the table below. As the enhancing agent addition progressed, the DGO enhancing agent exhibited significantly higher molecular weights than the DPO enhancing agent.

[0115] [Table 5]

[0116] NMR analysis PEIT polyester of Example 3 (Figure 3) 1 In the H-NMR, all signals were assigned to the molecular structure of PEIT and corresponded well to the spectra reported in the literature. Only additional signals from the guaiacyl end groups were observed, which likely indicates that a small excess of DGO was added.

[0117] No signal indicative of oxalate in the polymer chain was observed. If present, the signal of ethylene glycol oxalate ester would be observed in the spectrum at 4.64-4.57 ppm, slightly lower than the signal of terephthalate ester.

[0118] Additionally, the presence of oxalate in the polymer chain will decrease the ratio of TPA to diols, but normalizing the integrals of the diols (EG, DEG, ISO) and TPA gives a ratio of 1 between them.

[0119] Also, there was no sign of an ethylene oxalate ring, which would have given a sharp singlet at 4.62 ppm.

[0120] PEIF polyester of Example 4 1 The same results were obtained for H-NMR (Figure 4): as with PEIT, all signals were identifiable, and no signals indicating the presence of oxalate units were observed. This indicates that under the conditions used, oxalate easily leaves the polymer after chain extension.

[0121] 3D printing using metal-free PEIT and PEIF It was found that PEIT with a Mw of approximately 50 kDa exhibited excellent ductility and could be used, for example, for 3D printing. 350 g of PEIT and 650 g of PEIF polymer, produced in Examples 3 and 4, respectively, were further processed into filaments for 3D printing. This was done using a filament maker (3Devo precision filament). Both PEIT and PEIF successfully processed filaments with a diameter of 2.85 mm into several hundred grams. However, after processing the PEIF in the filament maker, the molecular weight decreased to 18.4 / 44.0 kDa (Mn / Mw), 65% of the original value. Unfortunately, this made the filament too brittle for printing. On the other hand, PEIT filament was strong and printable. Therefore, several types of designs were produced. The filament was used in an Ultimaker extended 3D printer to produce several designs from Thingiverse (a website dedicated to sharing user-created digital design files). First, a familiar platform was printed, which printed very cleanly, except for the string. Next, a replacement for the mechanical clamp was printed and functioned directly after removal from the build plate. Next, a small storage box with a twist-off lid was printed, see Figure 5.

[0122] Overall, these prints show that the polymer, filament, and print settings were all properly adjusted.

[0123] The introduction of isosorbide into PET or PEF is of interest for 3D printing because it increases the Tg while decreasing the required printing temperature. Furthermore, an isosorbide content greater than 15% renders the material amorphous, improving printability and aesthetics. For PEIT with 16% isosorbide, the required printing temperature is 230°C, with a Tg of 93°C. This is similar to that typically used for PETG, albeit with a higher Tg. These higher temperatures allow isosorbide-containing polymers to be used in more thermally demanding applications. Prints may be dishwasher safe or can be held in boiling water. The polyesters PEIF and PEIT are excellent recyclable materials, with PEIF being fully biobased. To our knowledge, there are currently no biobased polymers available for 3D printing that offer a combination of excellent thermal and mechanical properties.

Claims

1. (a) adding a diphenyl oxalate ester to a starting polyester (co)polymer comprising at least alcohol end groups and units derived from 1,2-diol, wherein the phenyl groups of said diphenyl oxalate ester are substituted and the substituents are selected from one or more of C1-C6 o-alkoxy, m-alkoxy, and p-alkoxy, and C1-C6 o-alkyl, m-alkyl, and p-alkyl; (b) if the temperature has not already exceeded 220°C, increasing the temperature of the mixture resulting from step (a) to at least 220°C and reducing the pressure for a period of time sufficient to obtain a polyester (co)polymer product, wherein the amount of oxalate units remaining in the (co)polymer is less than the amount added in the form of said diphenyl oxalate ester, and wherein either no oxalate units or 1 mole% or less of oxalate units relative to the total amount of monomer units are present, and the product has a higher molecular weight than the starting polyester (co)polymer.

1. A method for producing a (high molecular weight) polyester (co)polymer, comprising:

2. 2. The method of claim 1, comprising adding said diphenyl oxalate ester to said starting polyester (co)polymer in an amount of 0.2 to 10 mole %, said percentage being relative to the total amount of monomers in said starting polyester (co)polymer.

3. 3. The method of claim 1 or 2, wherein the diphenyl oxalate ester is a diphenyl oxalate substituted with C1-C6 o-alkoxy substituents, preferably bis(2-methoxyphenyl) oxalate.

4. 4. The method according to claim 1, wherein at least one of the units derived from a 1,2-diol is derived from an aliphatic diol selected from monoethylene glycol, 1,2-propanediol, 1,2-butanediol, 2,3-butanediol, and 1,2-cyclohexanediol.

5. 5. The method according to claim 4, wherein the starting polyester (co)polymer comprises monomer units derived from additional diols, preferably diols selected from cis- and / or trans-2,2,4,4-tetramethyl-1,3-cyclobutanediol and 1,4,3,6-dianhydrohexitol, in particular isosorbide.

6. 6. The method according to any one of claims 1 to 5, wherein the starting polyester (co)polymer comprises units derived from dicarboxylic acids, the dicarboxylic acids or any esters thereof being selected from (hetero)aromatic dicarboxylic acids or any esters thereof and C2-C18 aliphatic dicarboxylic acids or any esters thereof, which may be linear, cyclic or branched.

7. (i) providing or producing said starting polyester (co)polymer, wherein the process for producing said polyester (co)polymer comprises esterification / transesterification and polycondensation; (ii) adding said diphenyl oxalate ester to said starting polyester (co)polymer; (iii) increasing the temperature of the mixture resulting from step (ii) to at least 220°C, or, if said temperature is already higher than 220°C, maintaining said temperature for a period of time; (iv) reducing the pressure, preferably to a maximum of 5 mbar, more preferably to 1 mbar or less, thereby producing a (co)polymer product; and (v) optionally repeating steps (ii) through (iv) one or more times using the (co)polymer having a high molecular weight from the previous step (iv) as starting material until a final polyester (co)polymer product is produced having the desired high molecular weight characteristics, wherein either no oxalate units or less than 1 mole % oxalate are present, said percentage being relative to the total amount of monomer units.

7. The method of claim 1, comprising:

8. 8. The method of claim 7, wherein step (i) comprises preparing the starting polyester (co)polymer by reacting, optionally in the presence of a catalyst, a dicarboxylic acid or an ester thereof with a diol and / or polyol and / or oligomer having a diol-derived end group, wherein at least one of the diol and / or polyol and / or oligomer having a diol-derived end group comprises a vicinal diol group.

9. 9. The method according to claim 7 or 8, wherein said polyester (co)polymer is a recycled polyester material or is derived from a recycled polyester material.

10. 10. A polyester (co)polymer obtained or obtained from any one of claims 1 to 9, free from metal catalysts and preferably having a Mn of 20 kDa or more, - poly(ethylene co-isosorbide furan-2,5-dicarboxylate), - poly(ethylene co-isosorbide co-cyclohexanedimethylene furan-2,5-dicarboxylate), - Poly(ethylene co-isosorbide terephthalate) with an isosorbide content of 15% or more - poly(ethylene co-isosorbide co-cyclohexanedimethylene terephthalate), - poly(ethylene furan-2,5-dicarboxylate co-terephthalate), - poly(ethylene co-isosorbide furan-2,5-dicarboxylate co-terephthalate), is selected from The Mn is measured using gel permeation chromatography using poly(methyl methacrylate) standards as the reference material, polyester (co)polymer.

11. A composition comprising, in addition to the polyester (co)polymer of claim 10, one or more additives and / or one or more additional other (co)polymers.

12. 12. An article comprising a composition comprising the polyester (co)polymer of claim 10 or the polyester (co)polymer of claim 11 and one or more additives and / or additional polymers.

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