Process for producing polyesters containing at least one 1,4:3,6-dianhydrohexitol unit with reduced color and improved incorporation of said unit

Abstract

The present invention relates to a method for producing a polyester containing at least one 1,4:3,6-dianhydrohexitol unit, comprising the steps of: introducing into a reactor monomers including at least one monomer (A) that is a dicarboxylic acid or diester and at least one monomer (B) that is 1,4:3,6-dianhydrohexitol; introducing into the reactor a catalyst system including a catalyst containing elemental germanium and a catalyst containing elemental tin, or a catalyst containing elemental germanium and elemental tin, or a mixture of said catalysts; polymerizing the monomers to form a polyester; and recovering a polyester composition comprising the polyester and the catalyst system. The present invention also relates to a polyester composition containing a catalyst system including a catalyst containing elemental germanium and a catalyst containing elemental tin, or a catalyst containing elemental germanium and elemental tin, or a mixture of said two catalysts, and its use for reducing the color of polyester.

Description

[Technical Field]

[0001] The present invention relates to a method for producing polyesters containing at least one 1,4:3,6-dianhydrohexitol unit using a catalyst system to reduce the color of the polyester so formed and to increase the incorporation rate of the unit into the polyester. The present invention also relates to polyester compositions comprising the catalyst system. [Background technology]

[0002] The many advantages of plastics make them essential for the mass production of articles. In fact, their thermoplastic nature allows all kinds of articles to be manufactured from these plastics at high speeds.

[0003] Certain aromatic polyesters are thermoplastic, possessing thermal properties that allow them to be used directly in the production of materials. They contain units of aliphatic diols and aromatic dicarboxylic acids. Among these aromatic polyesters, mention may be made, for example, of polyethylene terephthalate (PET), a polyester containing units of ethylene glycol and terephthalic acid, used in the manufacture of containers, packaging, or textiles. PET can be a transparent polymer and is therefore useful for the manufacture of articles where optical properties are important. Where crystallinity and crystallite size are important, semi-crystalline polymers can also be opaque and white. Therefore, in all cases, it is necessary to minimize the coloration of PET as much as possible.

[0004] According to the present invention, the term "monomer unit" refers to a unit contained in a polyester obtained after polymerization of a monomer. As for the ethylene glycol and terephthalic acid units contained in PET, they can be obtained either by the esterification reaction of ethylene glycol and terephthalic acid, or by the transesterification reaction of ethylene glycol and terephthalic acid ester.

[0005] The development of polyesters from renewable biological resources is an urgent environmental and economic imperative in the face of the depletion and rising prices of fossil fuels such as petroleum. Therefore, one of the key current concerns in the polyester field is to provide naturally derived (bio-based) polyesters. This applies particularly to polyesters containing aliphatic diol and aromatic carboxylic acid units. Companies such as Danon and Coca-Cola now sell beverage bottles made from partially bio-based PET (PET) produced from bio-based ethylene glycol. The drawback of this PET is that it is only partially bio-based, since terephthalic acid is typically derived from fossil resources. However, recent developments in the synthesis of bio-based terephthalic acid and bio-based terephthalate esters have made it possible to produce completely bio-based PET. For example, International Publication No. WO 2013 / 034743(A1) describes such PET, among other things.

[0006] However, for certain applications or under certain operating conditions, these polyesters do not have all the necessary properties. Therefore, glycol-modified PET (PETg) has been developed. These are polyesters that generally contain cyclohexanedimethanol (CHDM) units in addition to ethylene glycol and terephthalic acid units. The introduction of this diol into PET makes it possible to tailor its properties to the intended application, for example, to improve its impact resistance or its optical properties, especially when PETg is amorphous.

[0007] Other modified polyesters have also been developed by incorporating 1,4:3,6-dianhydrohexitol units, particularly isosorbide (PEIT), into polyesters. These modified polyesters have higher glass transition temperatures than unmodified PET or PETg containing CHDM. Furthermore, 1,4:3,6-dianhydrohexitol has the advantage of being obtainable from renewable resources such as starch. These modified polyesters are particularly useful for the production of bottles, films, thick sheets, fibers, or articles where high optical properties are required.

[0008] On the other hand, a problem with these PEITs is that they generally have high color, usually higher than PETg or PET, even when the amount of isosorbide used in making the polyester is very low.

[0009] To solve this problem of high color, a method for preparing PEIT by melt polymerization has been described in U.S. Patent Application Publication No. 2006 / 0173154(A1). This method includes a first step of esterification and a second step of polycondensation, in which a primary antioxidant is used in the esterification step and a secondary antioxidant is used in the polycondensation step. In the examples, a catalyst system containing a germanium-based and a cobalt-based catalyst is used.

[0010] WO 2013 / 183873 and WO 2013 / 183874 describe methods for preparing polyesters, including esterifying monomers containing terephthalic acid, CHDM, isosorbide, and an additional diol compound in the presence of an esterification catalyst that is a zinc compound. This catalyst can improve the polymerization reaction rate and / or increase the viscosity of the polymer obtained by this method. In the methods exemplified in these two applications, a germanium-based catalyst is introduced during the polycondensation step.

[0011] The applicant has conducted research into polymerization catalysts for the preparation of polyesters containing 1,4:3,6-dianhydrohexitol units and has found that the polyesters obtained from these processes are not entirely satisfactory, particularly in terms of color. This color can be either very yellow, as when only a germanium-based polycondensation catalyst is used, or gray, when a catalyst system containing both a germanium and a cobalt catalyst is used. Therefore, there remains a need to find a new method for preparing polyesters containing 1,4:3,6-dianhydrohexitol units with improved color.

[0012] Another problem encountered in the production of polyesters containing 1,4:3,6-dianhydrohexitol units is the fact that the incorporation rate of these units is not always high, but a high incorporation rate of 1,4:3,6-dianhydrohexitol units is desirable to achieve sufficient thermal and mechanical performance for various applications, such as the packaging sector.

[0013] The low incorporation can be explained by the fact that the esterification reaction of isosorbide with terephthalic acid or the transesterification reaction with alkyl terephthalates involves secondary hydroxyls and is therefore slower than reactions involving primary alcohols such as ethylene glycol or 1,3-propanediol. This results in poor incorporation of isosorbide into the copolymer.

[0014] To improve the incorporation of isosorbide into polyesters, U.S. Patent No. 6,737,481 describes a method involving the synthesis of a linking unit. This linking unit consists of isosorbide and a dicarboxylic acid, such as isophthalic acid or phthalic acid. The linking unit is then subjected to a polycondensation process by mixing with a prepolymer. The prepolymer can be selected from poly(alkylene terephthalates), preferably poly(1,3-propylene terephthalate). After the polycondensation process, the preferred polymer is poly(ethylene-co-isosorbide isophthalate).

[0015] U.S. Patent No. 6,818,730 describes a method for producing polyesters containing isosorbide, which results in a high incorporation rate of isosorbide in the final polyester. The method describes melt-blending a first polyester incorporating isosorbide with a second polyester for a sufficient time to effect transesterification, thereby obtaining a copolymer. The first polyester consists essentially of isosorbide units and dicarboxylic acid units, while the second polyester consists essentially of dicarboxylic acid units and diol units other than isosorbide.

[0016] A method for obtaining PEIT showing an improved incorporation rate of isosorbide of up to 30% is proposed in WO 2019 / 004679. According to the examples in the same document, when germanium dioxide GeO2 is used, the rate is about 10%.

[0017] Therefore, there remains a need to find new methods for producing polyesters containing 1,4:3,6-dianhydrohexitol units with improved color and incorporation of 1,4:3,6-dianhydrohexitol units. Summary of the Invention

[0018] The present invention improves the situation.

[0019] One object of the present invention is therefore a process for producing polyesters containing at least one 1,4:3,6-dianhydrohexitol unit, the process comprising at least - introducing into a reactor monomers comprising at least one monomer (A) which is a dicarboxylic acid or diester and at least one monomer (B) which is a 1,4:3,6-dianhydrohexitol unit, - introducing into the reactor a catalyst system comprising either a catalyst comprising elemental germanium and a catalyst comprising elemental tin, or a catalyst comprising elemental germanium and elemental tin, or a mixture of these catalysts; - polymerizing the monomers to form a polyester; recovering a polyester composition comprising a polyester and a catalyst system.

[0020] WO 2016 / 066956 already describes a catalyst system combining a germanium-based catalyst with an aluminum-based catalyst or a tin-based catalyst with an aluminum-based catalyst in the production of PEIT polyesters. This application compares the color of polyesters obtained from a germanium-based catalyst with polyesters obtained from a catalyst system containing a germanium and aluminum catalyst or a tin and aluminum catalyst. Even in cases where the color of the polyesters is reduced, they still exhibit a pale yellow color. Such catalyst systems do not appear to significantly affect the incorporation rate of 1,4:3,6-dianhydrohexitol units.

[0021] Surprisingly, as shown in the examples, polyesters recovered from the process according to the invention exhibit both less color and higher incorporation of 1,4:3,6-dianhydrohexitol units than polyesters obtained from similar processes using different catalyst systems.

[0022] WO 2018 / 101320 describes a catalyst system combining a germanium catalyst and a cobalt catalyst for the production of PEITg polyesters. However, the maximum incorporation rate of isosorbide in the polyester obtained from this catalyst system is only 14%.

[0023] According to a second aspect, - a polyester containing at least one 1,4:3,6-dianhydrohexitol unit, and The present invention proposes a polyester composition comprising a catalyst system comprising either a catalyst containing elemental germanium and a catalyst containing elemental tin, or a catalyst containing elemental germanium and elemental tin, or a mixture of these catalysts.

[0024] According to a third aspect, an article is disclosed comprising the polyester composition according to the second aspect.

[0025] According to a fourth aspect, the use of a catalyst system comprising a catalyst comprising elemental germanium and a catalyst comprising elemental tin, a catalyst comprising elemental germanium and elemental tin, or a mixture of these catalysts, is proposed for reducing the color of polyesters containing at least one 1,4:3,6-dianhydrohexitol unit. DETAILED DESCRIPTION OF THE INVENTION

[0026] The present invention relates to a method for producing polyesters containing at least one 1,4:3,6-dianhydrohexitol unit.

[0027] The method includes introducing monomers into a reactor, the monomers including at least one monomer (A) that is a dicarboxylic acid or diester and at least one monomer (B) that is a 1,4:3,6-dianhydrohexitol unit.

[0028] By dicarboxylic acid or diester is meant according to the invention dicarboxylic acids or diesters of carboxylic acids.

[0029] According to a preferred embodiment, monomer (A) is a dicarboxylic acid or a mixture of dicarboxylic acids. Some dicarboxylic acids, such as phthalic acid or maleic acid, may also be present in the form of their anhydrides.

[0030] The dicarboxylic acid may be an aromatic dicarboxylic acid, an aliphatic dicarboxylic acid, or a mixture of these dicarboxylic acids.

[0031] Preferably, the dicarboxylic acid is aromatic. It can be selected from terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, furandicarboxylic acid, and mixtures of these dicarboxylic acids. Preferably, the aromatic carboxylic acid is terephthalic acid. Monomer (A) can also be an aliphatic dicarboxylic acid or a mixture of such dicarboxylic acids. The aliphatic dicarboxylic acid can also be saturated or unsaturated.

[0032] The aliphatic dicarboxylic acid may be linear, branched, or cyclic. The linear saturated aliphatic dicarboxylic acid may be selected from succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and mixtures thereof. Preferably, the linear saturated aliphatic dicarboxylic acid is selected from succinic acid, adipic acid, and mixtures thereof, with succinic acid being the most preferred. The saturated cyclic aliphatic dicarboxylic acid may include 1,4-cyclohexanedicarboxylic acid.

[0033] Monomer (A) may also be an unsaturated aliphatic dicarboxylic acid such as fumaric acid or maleic acid or itaconic acid, or a mixture of these dicarboxylic acids.

[0034] When the monomer (A) is a diester (or a mixture of diesters), the diester is preferably a methyl and / or ethyl diester. The diester can be selected from the diesters of the aforementioned dicarboxylic acids. Preferably, the diester is an aromatic dicarboxylic acid diester, preferably a diester of terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, furandicarboxylic acid, or a mixture of these diesters, and most preferentially a diester of terephthalic acid.

[0035] According to the invention, mixtures of dicarboxylic acids and diesters can also be used as monomers (A).

[0036] Monomer (B) is a 1,4:3,6-dianhydrohexitol unit. As mentioned above, 1,4:3,6-dianhydrohexitol has the drawback of causing discoloration of polyesters when used as a monomer and conventional manufacturing methods are used for its production. This 1,4:3,6-dianhydrohexitol may be isosorbide, isomannide, isoidide, or a mixture thereof, preferably isosorbide. Isosorbide, isomannide, and isoidide can be obtained by dehydration of sorbitol, mannitol, and iditol, respectively. Isosorbide is sold by the applicant under the trade name POLYSORB® P.

[0037] Preferably, the monomers introduced into the reactor further comprise a diol (C) different from 1,4:3,6 dianhydrohexitol.

[0038] Diol (C) is aliphatic diols, in particular linear aliphatic diols (C1), cycloaliphatic diols (C2), branched aliphatic diols (C3), or - aromatic diols (C4), or a mixture of these diols.

[0039] The diol (C1) is advantageously chosen from ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol or mixtures of these diols, preferentially chosen from ethylene glycol, 1,4-butanediol and mixtures of these diols, very preferentially ethylene glycol.

[0040] The diol (C2) may be a cyclobutanediol, such as tetramethylcyclobutanediol, bis-hydroxymethyltricyclodecane, or cyclohexanedimethanol, in particular 1,4-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, or 1,3-cyclohexanedimethanol, or a mixture of these diols or isomers of these diols. In fact, these diols may be in either the cis or trans configuration. When various isomers of the same monomer exist, unless explicitly stated, any reference to this monomer may refer to one isomer or a mixture of isomers of this monomer.

[0041] The diol (C3) may be 2-methyl-1,3-propanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-2-butyl-1,3-propanediol, propylene glycol, neopentyl glycol, or a mixture of these diols.

[0042] The diol (C) is advantageously chosen from aliphatic diols, preferentially from ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,4-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol and mixtures of these diols, and most preferentially from ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol and mixtures of these diols, most preferably from ethylene glycol, 1,4-cyclohexanedimethanol and mixtures of these diols.

[0043] According to a first advantageous embodiment for introducing the diol (C) into the reactor, the monomer (A) is terephthalic acid, the monomer (B) is isosorbide and the monomer (C) is ethylene glycol.

[0044] According to a second advantageous embodiment for introducing the diol (C) into the reactor, the monomer (A) is terephthalic acid, the monomer (B) is isosorbide and the monomer (C) is a mixture of ethylene glycol and 1,4-cyclohexanedimethanol.

[0045] Advantageously, the molar percentage of monomer (A) relative to the total number of moles of monomers (A), (B) and, optionally, (C) ranges from 25 to 50%, preferably from 33 to 49% and most preferentially from 40 to 48%.

[0046] Preferably, when monomer (C) is introduced into the reactor, the molar percentage of (B) based on the total number of moles of monomers (B) and (C) ranges from 1 to 60%, preferably from 2 to 55%, and most preferentially from 5 to 50%.

[0047] Monomers (B) and (C) can be introduced into the reactor as aqueous solutions.

[0048] Monomers other than monomers (A), (B) and optionally (C), so-called "additional monomers", can also be added.

[0049] They may be hydroxy acid monomers having a hydroxy functional group and a carboxylic acid functional group. By way of example, the hydroxy acid may be glycolic acid, lactic acid, hydroxybutyric acid, hydroxycaproic acid, hydroxyvaleric acid, 7-hydroxyheptanoic acid, 8-hydroxyoctanoic acid, 9-hydroxynonanoic acid, hydroxymethylfurancarboxylic acid, hydroxybenzoic acid, or a mixture of these hydroxy acids. Additional monomers that may be used include dilactones such as glycolide or lactide.

[0050] Preferably, the amount of hydroxy acid monomer is less than 10 mol % based on the total amount of monomers. The monomers introduced into the reactor may be free of hydroxy acid monomers.

[0051] The additional monomers may also include chain extension monomers, which are generally introduced into the reactor before or during the formation of the polyester produced in the polymerization process, or before a second process, called a "post-polymerization process," which comprises reacting the polyester formed in the polymerization process with the chain extension monomer, which may in particular be a reactive extrusion process of the chain extension monomer with the polyester recovered after the polymerization process.

[0052] The term "chain extension monomer" refers to a monomer that contains two functional groups other than hydroxyl, carboxylic acid, and carboxylic acid ester functional groups and is capable of reacting with these same functional groups. The functional groups may be isocyanate, isocyanurate, lactam, lactone, carbonate, epoxy, oxazoline, and imide functional groups, and the functional groups can be the same or different. Chain extension monomers suitable for use in the present invention include: diisocyanates, preferably methylene diphenyl diisocyanate (MDI), isophorone diisocyanate (IPDI), dicyclohexylmethane diisocyanate (H12MDI), toluene diisocyanate (TDI), naphthalene diisocyanate (NDI), hexamethylene diisocyanate (HMDI) or lysine diisocyanate (LDI), aliphatic diisocyanates with a molar mass of 600 g / mol obtained from fatty acid dimers (DDI® 1410 diisocyanate), - dimers, trimers, and tetramers of diisocyanates, - "isocyanate-free" prepolymers obtained from the reaction of diols or amines with diisocyanates under conditions such that the prepolymer contains an isocyanate functional group at each of its ends without detectable free diisocyanates (α,ω-functional or telechelic polymers); dialkyl carbonates, in particular dialkyl carbonates of dianhydrohexitols, in particular isosorbide dialkyl carbonate, -dicarbamoylcaprolactam, preferably 1,1'-carbonyl-bis-caprolactam, dicarbamoylcaprolactone, - diepoxides, compounds containing epoxy and halide functional groups, preferably epichlorohydrin, heterocyclic compounds, preferably bis-oxazolines, bis-oxazolin-5-ones and bis-azalactones, methylene or ethylenic diester derivatives, preferably methyl or ethyl carbonate derivatives, Any mixture of at least two of the above products may be mentioned.

[0053] Preferably, the amount of chain extension monomer is less than 10 mol % based on the total amount of monomers introduced. The monomers introduced into the reactor may not include chain extension monomers.

[0054] The additional monomer may also be a polyfunctional monomer. A "polyfunctional monomer" is a monomer capable of reacting with hydroxy and / or carboxylic acid and / or carboxylic acid ester functional groups and having a functionality greater than 2. The polyfunctional monomer can be introduced into the reactor before the polymerization or post-polymerization steps described above (replacing the chain-extending monomer with the polyfunctional monomer), preferentially before the polymerization step. The reactive functional groups of these branching agents may be hydroxy, carboxylic acid, anhydride, isocyanate, isocyanurate, caprolactam, caprolactone, carbonate, epoxy, oxazoline, and imide functional groups, which may be the same or different, and are preferably carboxylic acid, hydroxy, epoxy, or isocyanate, and most preferably carboxylic acid or hydroxy. The functional groups of these branching agents may be 3 to 6, preferably 3 to 4. Branching agents that have traditionally been used include malic acid, citric acid or isocitric acid, tartaric acid, trimesic acid, tricarballylic acid, cyclopentanetetracarboxylic acid, trimellitic anhydride, pyromellitic anhydride or dianhydride, glycerol, pentaerythritol, dipentaerythritol, monoanhydrosorbitol, monoanhydromannitol, epoxy oils, dihydroxystearic acid, trimethylolpropane, ethers of these polyols such as, for example, glycerol propoxylate (available commercially as Voranol 450 from Dow Chemical), polymers containing pendant epoxy functional groups, triisocyanates, tetraisocyanates, and homopolymers of existing di-, tri-, and tetraisocyanates, respectively, polyanhydrides, and alkoxysilanes, preferably tetraethoxysilane.

[0055] Preferably, the amount of multifunctional monomer is less than 10 mol % based on the total amount of monomers. The monomers introduced into the reactor may not contain multifunctional monomers.

[0056] Advantageously, the molar amount of the additional monomer relative to the total amount of monomers introduced into the reactor is less than 20%, preferentially less than 10% or even less than 5%. The monomers introduced into the reactor may be free of additional monomers.

[0057] The method according to the present invention further comprises the step of introducing a catalyst system into the reactor, the catalyst system comprising: - a catalyst containing elemental germanium and a catalyst containing elemental tin, - or a catalyst comprising elemental germanium and elemental tin.

[0058] According to a first embodiment, with regard to the catalyst comprising elemental germanium, it may be selected from the following compounds: aliphatic carboxylates such as formate, acetate, propionate, butyrate, oxalate, acrylate, methacrylate, etc.; aromatic carboxylates such as benzoic acid; halogenated carboxylates such as trichloroacetate, trifluoroacetate, hydroxycarboxylates such as lactate, citrate, oxalate; inorganic salts such as carbonate, sulfate, nitrate, phosphate, phosphonate, phosphinate, hydrogensulfate, hydrogencarbonate, hydrogenphosphate, sulfite, thiosulfate, hydrochloride, hydrobromide, chloride, chlorate, bromide, bromate, etc.; organic sulfonates such as 1-propanesulfonate, 1-pentanesulfonate, naphthalenesulfonate, etc.; organic sulfates such as lauryl sulfate, etc.; alkoxides such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, etc.; acetylacetonate, oxide, mixed oxide with other metals, or hydroxide, and preferably selected from germanium dioxide.

[0059] Catalysts containing elemental tin include the following compounds: aliphatic carboxylates such as formate, acetate, propionate, butyrate, oxalate, acrylate, methacrylate, octanoate, etc.; aromatic carboxylates such as benzoate, halogenated carboxylates such as trichloroacetate, trifluoroacetate, hydroxycarboxylates such as lactate, citrate, oxalate, carbonate, sulfate, nitrate, phosphate, phosphonate, phosphinate, hydrogen sulfate, hydrogen carbonate, hydrogen phosphate, sulfite, thiosulfate, hydrochloride, hydrobromide. The metal oxide may be selected from inorganic salts such as chlorides, chlorates, bromides, bromates, etc.; organic sulfonates such as 1-propanesulfonate, 1-pentanesulfonate, naphthalenesulfonate, etc.; organic sulfates such as lauryl sulfate, etc.; mercaptides; alkoxides such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, etc.; acetylacetonates; oxides; mixed oxides containing other metals; or hydroxides, and preferably selected from tin(II) oxide, stannous oxide, tin(IV) oxide, or stannic oxide.

[0060] According to a second embodiment, the catalyst system comprises a catalyst comprising elemental germanium and elemental tin, for example a mixed oxide of germanium and tin.

[0061] According to a third embodiment, the catalyst system comprises a mixture of the catalysts described in the previous two embodiments.

[0062] The catalyst system may be selected so that the molar elemental ratio of Ge:Sn is in the range of 1:1 to 5:1, advantageously 1.5:1 to 5:1, advantageously 2:1 to 5:1, preferably 1:1 to 3:1, advantageously 1.5:1 to 3:1, advantageously 2:1 to 3:1, preferably 1:1 to 2.5:1, advantageously 1.5:1 to 2.5:1, advantageously 1.75:1 to 2.5:1. Very advantageously, the molar elemental ratio is about 2:1. This elemental ratio is determined so as to take into account only the metals contained in the catalyst system. According to the example shown below, when such a molar elemental ratio is about 2:1, the resulting resin is observed to be transparent, while when the molar elemental ratio is in the range of 2:1 to 5:1, the resulting resin has a slight yellow coloration.

[0063] According to the first and third embodiments, the catalyst may be present in an amount selected such that the molar elemental ratio Ge:Sn is one of those described above.

[0064] According to a second embodiment, a catalyst is selected which comprises elemental germanium and elemental tin in amounts such that the molar elemental ratio Ge:Sn is one of the above.

[0065] According to three embodiments, the amount of elemental germanium in the catalytic system varies between 50 and 300 ppm, preferentially between 180 and 220 ppm.

[0066] According to three embodiments, the amount of elemental tin in the catalytic system ranges from 10 to 200 ppm, preferentially from 50 to 150 ppm, and even more preferentially from 75 to 125 ppm.

[0067] For reasons of catalyst simplicity and availability, the use of a catalyst system comprising a catalyst containing elemental germanium and a catalyst containing elemental tin is preferred. Advantageously, the total mass of metals contained in the catalyst system introduced into the reactor, relative to the total mass of the polymer to be obtained, is in the range of 50 to 500 ppm.

[0068] The catalyst system can be introduced into the reactor before or during the polymerization step, preferentially before the polymerization step. It may also be introduced in different introduction stages, for example by introducing different catalysts at different times. Preferably, when the catalyst system comprises different catalysts, they are introduced into the reactor simultaneously, most preferentially before the polymerization step. The catalyst can be used in its pure form or in solution, in particular in an aqueous or alcoholic solution, preferably in the form of a solution in a monomer such as ethylene glycol, in which case the catalyst is diluted or dispersed.

[0069] By using a compound containing elemental cobalt in the reaction mixture, b * A polyester composition with improved color can be obtained.

[0070] Exemplary compounds containing elemental cobalt include the following compounds: aliphatic carboxylates such as formate, acetate, propionate, butyrate, oxalate, acrylate, methacrylate, etc.; aromatic carboxylates such as benzoate; halogenated carboxylates such as trichloroacetate and trifluoroacetate; hydroxycarboxylates such as lactate, citrate, oxalate; inorganic salts such as carbonate, sulfate, nitrate, phosphate, phosphonate, phosphinate, hydrogensulfate, bicarbonate, hydrogenphosphate, sulfite, thiosulfate, hydrochloride, hydrobromide, chloride, chlorate, bromide, bromate; organic sulfonates such as 1-propanesulfonate, 1-pentanesulfonate, naphthalenesulfonate; organic sulfates such as lauryl sulfate; alkoxides such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, etc.; acetylacetonate; oxide; mixed oxides with other metals; or hydroxide; and preferably cobalt acetate.

[0071] The process according to the invention also includes a step of polymerizing the monomers to form a polyester. Advantageously, this polymerization step is carried out by the melt method, by maintaining the reaction medium in a molten state in a reactor, in the absence of solvent. This polymerization step may be carried out by supplying heat. This polymerization step may also be carried out under vacuum.

[0072] Preferably, the step of polymerizing the monomers comprises: a first stage during which the reaction medium is stirred at a temperature ranging from 200 to 300°C, advantageously from 245 to 275°C, to form oligomers; - a second stage during which the formed oligomers are stirred under vacuum at a temperature in the range of 240-330°C, advantageously 255-275°C, to form the polyester.

[0073] The reaction medium can be agitated by any type of agitator conventionally used in polyester synthesis. The agitation speed can be kept constant during the polymerization process or can be decreased during the reaction as the viscosity of the polyester increases.

[0074] The first stage may be carried out at atmospheric pressure or under elevated pressure, generally in the range of 1.1 to 10 bar.

[0075] The oligomers formed in the first stage generally have a number average molar mass of less than 5000 g / mol, often less than 4000 g / mol. They generally have a viscosity index of less than 20 mL / g.

[0076] This first stage can be monitored by controlling the rate of distillate withdrawn from the reactor.

[0077] The second stage of the polymerization process is carried out under vacuum, preferably at a pressure of less than 10 mbar, more preferentially less than 1 mbar.

[0078] The polymerization reaction can be monitored by controlling the change in the amount of torque measured on the stirrer or by any other system capable of assessing the viscosity of the molten reaction medium.

[0079] Advantageously, a catalyst system comprising the aforementioned catalyst is introduced into the reactor before the first stage of the polymerization process.

[0080] Preferably, the process includes a reactor deoxidation step, advantageously carried out by placing the reactor in an atmosphere of an inert gas, such as nitrogen, prior to the monomer polymerization step, particularly the first stage of oligomerization. This deoxidation step is generally carried out at low temperatures, often below 100°C. This can be carried out, for example, by performing at least one series of vacuum steps, for example, to 100-700 mbar in the reactor, followed by a step of introducing an inert gas into the reactor at, for example, 1.2-2 bar. This vacuum-inert gas introduction cycle may be carried out, for example, three to five times. Preferably, this vacuum-nitrogen cycle is carried out at a temperature of 60-80°C to completely melt the reagents, particularly the monomer (B). This deoxidation step has the advantage of further improving the colorability of the polyester obtained at the end of the process.

[0081] It should be noted that when the reactor is placed under vacuum, especially during the second stage of oligomerization, small amounts of monomer may be drawn off from the reactor and thus lost. In particular, a small percentage of the more volatile monomers may be in excess. This loss of monomer may also result in a small loss of catalyst.

[0082] Furthermore, so-called "polymerization additives" may be introduced into the reactor prior to the polymerization step.

[0083] Among the polymerization additives, mention may be made of antioxidants, which can further reduce the color of the resulting polyester. The antioxidants can be primary and / or secondary antioxidants. The primary antioxidants can be sterically hindered phenols such as the compounds Hostanox® 03, Hostanox® 010, Hostanox® 016, Ultranox® 210, Ultranox® 276, Dovernox® 10, Dovernox® 76, Dovernox® 3114, Irganox® 1010, or Irganox® 1076, or phosphonic acids such as Irgamod® 195. The secondary antioxidants can be trivalent phosphorus compounds such as Ultranox® 626, Doverphos® S-9228, Hostanox® P-EPQ, or Irgafos® 168.

[0084] It is also possible to introduce as a polymerization additive at least one compound capable of limiting unwanted etherification reactions, such as sodium acetate, tetramethylammonium hydroxide, or tetraethylammonium hydroxide.

[0085] The process according to the present invention further comprises recovering the polyester composition comprising the polyester and the catalyst system. The composition can be recovered by removing it from the reactor in the form of a molten polymer rod. After cooling, the rod can be converted into granules using conventional granulation techniques.

[0086] The polyester obtained after the polycondensation step can be semi-crystalline or amorphous after cooling.

[0087] The process according to the invention may also include a solid state polycondensation (SSP) step after the step of recovering the polyester composition, which can be easily carried out by a person skilled in the art from semi-crystalline polyesters.

[0088] The present invention also relates to a polyester composition obtainable according to the process of the present invention, wherein the polyester contains at least one 1,4:3,6-dianhydrohexitol unit, and the composition further comprises either a catalyst comprising elemental germanium and a catalyst comprising elemental tin, or a catalyst comprising elemental germanium and elemental tin, or a mixture of these catalysts.

[0089] The catalyst system contained in the polyester composition is the same as that described above for the process according to the invention, and thus the metals contained in the catalyst system in the polyester composition according to the invention may have a molar element ratio Ge:Sn ranging from 1:1 to 5:1, advantageously from 1.5:1 to 3:1, and preferably from 1.75:1 to 2.5:1.

[0090] The catalyst content in the polyester composition is also close to the amount introduced into the reactor, but may be slightly less than the amount introduced into the reactor due to possible catalyst carryover losses as described above. However, these losses can be considered relatively small. The total mass of metals contained in the catalyst system of the polyester composition is typically in the range of 30 to 500 ppm, based on the total mass of the polyester.

[0091] The catalyst metal content in the polyester can be determined by elemental analysis.

[0092] According to the present invention, the term "monomer unit" refers to a unit contained in a polyester that can be obtained after polymerization of a monomer. For example, the ethylene glycol and terephthalic acid units contained in PET can be obtained by either the esterification reaction of ethylene glycol with terephthalic acid or the transesterification reaction of ethylene glycol with terephthalic acid ester.

[0093] The polyesters contained in the composition according to the invention may contain from 0.1 to 100% (100% if no monomer (C) is used in the process), advantageously from 1 to 60%, preferably from 2 to 550% and most preferentially from 5 to 50% of 1,4:3,6-dianhydrohexitol units, based on the total diol units (B) and optionally (C) of the polyester.

[0094] According to a first highly preferred embodiment, the polyester contained in the composition comprises, based on the sum of the monomer units, - 45-55% terephthalic acid units, - 1-25% isosorbide, - Contains 20-54% ethylene glycol.

[0095] According to a second highly preferred embodiment, the polyester contained in the composition comprises, based on the sum of the monomer units, - 45-55% terephthalic acid units, - 1 to 25% isosorbide units, - 1 to 53% ethylene glycol units, - Contains 1-53% of 1,4-cyclohexanedimethanol units.

[0096] The number of dicarboxylic acid units and the number of diol units are generally about the same, and the ratio of diol units to dicarboxylic acid units in the polyester can range from 1.15:1 to 0.85:1, often from 1.08:1 to 0.92:1.

[0097] The amount of different units in the polyester is 1 It can be determined by 1 H NMR.

[0098] Those skilled in the art can easily determine the analytical conditions for determining the amount of each unit in a polyester. For example, in the NMR spectrum of poly(ethylene-co-isosorbide terephthalate), the chemical shifts associated with ethylene glycol are 4.4 to 5.0 ppm, the chemical shifts associated with the terephthalate ring are 7.8 to 8.4 ppm, and the chemical shifts associated with isosorbide are 4.1 to 5.8 ppm. The amount of each unit in the polyester can be determined by integrating each signal.

[0099] Preferably, the polyester composition has a color value L of greater than 45, preferably greater than 55. * It has.

[0100] When a solid-state polycondensation process is carried out, the lightness L * may reach or exceed 65.

[0101] Preferably, the polyester composition has a b of -10 to 10, preferably -6 to 6. * This parameter determines the color blue (b * is negative) to yellow (b * The coloration up to (if sexual) can be quantified.

[0102] Parameter L * and b * can be determined using a spectrophotometer according to the CIE Lab model.

[0103] The polyester composition may have a relative viscosity greater than 35 mL / g, preferably greater than 50 mL / g. Viscosity index can be measured according to the method disclosed in the Examples section.

[0104] The number average molar mass of the polyester contained in the polyester composition according to the invention may range from 5000 to 50000 g / mol.

[0105] The molar mass of the polyester can be determined by conventional methods, such as by steric exclusion chromatography (SEC) in a 98:2 volumetric mixture of chloroform and 1,1,1,3,3,3-hexafluoro-2-propanol, and signal detection can then be performed by a differential refractometer calibrated with polymethyl methacrylate standards.

[0106] Preferably, the glass transition temperature of the polyester is above 80° C. The glass transition temperature of the polyester can be measured using conventional methods, in particular using differential scanning calorimetry (DSC) using a heating rate of 10 K / min. The experimental protocol is described in detail in the Examples section below.

[0107] Advantageously, the polyester has a glass transition temperature in the range of 80 to 190°C, preferably 100 to 170°C, more preferably 105 to 160°C.

[0108] The present invention also relates to a composition comprising a polyester according to the invention and at least one additive or at least one additional polymer or at least one mixture thereof.

[0109] The polyester composition according to the present invention may include any of the polymerization additives used in the present process. It may also include other additional additives and / or polymers that are typically added in a subsequent thermomechanical mixing step.

[0110] Thus, exemplary additives may include fillers or organic or inorganic fibers, whether nanometer-scale or not, functionalized or not. These may be silica, zeolite, glass beads or fibers, clay, mica, titanates, silicates, graphite, calcium carbonate, carbon nanotubes, wood fibers, carbon fibers, polymer fibers, proteins, cellulose fibers, lignocellulosic fibers, and undestructured granular starch. These fillers or fibers may improve hardness, stiffness, or permeability to water or gas. The composition may contain 0.1 to 75 wt. % of fillers and / or fibers, for example, 0.5 to 50 wt. % of fillers and / or fibers, based on the total weight of the composition. Additives useful in the compositions of the present invention may also include opacifiers, dyes, and pigments. They may be selected from cobalt acetate and the following compounds: HS-325 Sandoplast® RED BB (a compound with an azo functional group also known as Solvent Red 195), HS-510 Sandoplast® Blue 2B, which is an anthraquinone, Polysynthren® Blue R, and Clariant® RSB Violet.

[0111] The composition may also contain processing aids as additives to reduce pressure within the processing tool. Release agents may also be used to reduce adhesion of the polyester molding material to the mold or calender roll. These agents may be selected from esters and amides of fatty acids, metal salts, soaps, kerosene, or hydrocarbon waxes. Specific examples of these agents include zinc stearate, calcium stearate, aluminum stearate, stearamide, erucamide, behenamide, beeswax, or candelilla wax.

[0112] The compositions according to the invention may also contain other additives such as, for example, stabilizers, such as light stabilizers, UV stabilizers and heat stabilizers, flow agents, flame retardants, and antistatic agents.

[0113] The composition may further comprise an additional polymer different from the polyester according to the invention, which may be chosen from polyamides, polyesters other than the polyester according to the invention, polystyrene, styrene copolymers, styrene-acrylonitrile copolymers, styrene-acrylonitrile-butadiene copolymers, poly(methyl methacrylate), acrylic copolymers, poly(ether-imides), poly(phenylene oxides) such as poly(2,6-dimethylphenylene oxide), poly(phenylene sulfate), poly(ester-carbonates), polycarbonates, polysulfones, polysulfone ethers, polyether-ketones, and mixtures of these polymers.

[0114] The composition may further comprise additional polymers capable of improving the impact properties of the polymer, in particular functionalized polyolefins such as functionalized ethylene or propylene polymers, and copolymers, core-shell copolymers, or block copolymers.

[0115] The compositions according to the present invention may also contain naturally occurring polymers such as starch, cellulose, chitosan, alginate, gluten, pea protein, casein, collagen, gelatin, and other proteins, and lignin, which may or may not be physically or chemically modified. Starch can be used in a destructured or plasticized form. In the latter case, the plasticizer can be water or a polyol, including glycerol, polyglycerol, isosorbide, sorbitan, sorbitol, mannitol, or urea. The compositions can be prepared using the methods described in WO 2010 / 010282 A1.

[0116] The compositions according to the invention can be prepared by conventional thermoplastic processing methods. These conventional methods include at least one step of melt blending or softening the polymers and one step of recovering the composition. This can be done in an internal mixer equipped with a paddle or rotor, an external mixer, or a single-screw, co-rotating, or counter-rotating twin-screw extruder. However, it is preferred to carry out this mixing by extrusion using a co-rotating extruder.

[0117] Mixing of the components of the composition may be carried out under an inert atmosphere.

[0118] In the case of an extruder, the various components of the composition can be introduced by means of introduction hoppers located along the extruder.

[0119] The present invention also relates to articles comprising a polyester or composition according to the present invention.

[0120] The article may be of any type and may be obtained by using conventional processing techniques.

[0121] This may be, for example, a fiber or yarn useful in the textile or other industries. These fibers or yarns may be woven into fabrics or may be nonwoven.

[0122] The article according to the present invention may also be a film or sheet, which may be produced by calendering, cast film extrusion, and blown film extrusion.

[0123] The articles according to the present invention may also be containers for carrying gases, liquids, and / or solids. These may be baby bottles, water bottles, carbonated and non-carbonated water bottles, juice bottles, soda bottles, alcoholic beverage bottles, medical bottles, cosmetic bottles, prepared food trays, microwave trays, or even lids. These containers may be of any size. They may be manufactured by extrusion blow molding, thermoforming, or injection blow molding.

[0124] These articles may also be optical articles, i.e. articles requiring good optical properties, such as lenses, disks, transparent or translucent panels, optical fibers, LCD (liquid crystal display) screens or films for glass, etc. These optical articles have the advantage that they can be placed close to a light source, and therefore heat, while maintaining good dimensional stability and good light resistance.

[0125] The article may also be a multilayer article, in which at least one layer comprises a polymer or composition according to the invention. These articles can be produced by a process involving a coextrusion step in which the materials of the different layers are brought into contact in the molten state. Examples include tube coextrusion, profile coextrusion, and blow molding of bottles, vials, or tanks, generally referred to as hollow-body blow molding, film-blowing coextrusion, and cast coextrusion.

[0126] They can also be produced by a process that includes applying a layer of polyester in the molten state to a layer of organic polymer, metal, or adhesive composition in the solid state, which can be done by pressing, overmolding, laminating, extrusion laminating, coating, extrusion coating, or coating.

[0127] The present invention also relates to the use of the aforementioned catalyst system in a polymerization process for reducing the color of polyesters containing at least one 1,4:3,6-dianhydrohexitol unit.

[0128] It is clear that all of the above-mentioned embodiments relating to the method and polyester composition according to the invention are applicable to the use according to the invention.

[0129] The present invention will be illustrated by the following examples, which obviously should not be construed as limiting the invention.

[0130] method The polymers were characterized using the techniques described below.

[0131] The decrease in viscosity in solution is measured using an Ubbelohde capillary viscometer in orthochlorophenol at 35° C. after dissolving the polymer at 130° C. with stirring. For these measurements, the concentration of polymer introduced is 5 g / L.

[0132] The color of the polymer was measured on the pellet using a Konica Minolta CM-2300d spectrophotometer.

[0133] The thermal properties of the polyesters were measured by differential scanning calorimetry (DSC). First, the sample was heated in an open crucible under nitrogen atmosphere from 10 to 280°C (10°C / min), cooled to 10°C (10°C / min), and then heated again to 320°C under the same conditions as the first step. The glass transition temperature was taken at the midpoint of the second heat. Any melting points were determined from the endothermic peak (peak onset) of the first heat. Similarly, the enthalpy of fusion (area under the curve) was determined in the first heat.

[0134] For the illustrative examples set forth below, the following reagents were used:

[0135] monomer

[0136] Monomer (A): Terephthalic acid (purity 99+%), manufactured by Accros

[0137] Monomer (B): Isosorbide (purity >99.5%) Polysorb® P manufactured by Roquette Freres

[0138] Monomer (C): Ethylene glycol (purity >99.8%), Sigma-Aldrich

[0139] catalyst

[0140] Germanium dioxide (>99.99%), Sigma-Aldrich

[0141] Aluminum triethoxide (>97%), Sigma-Aldrich

[0142] Dimethyltin oxide CAS number: 2273-45-2, manufactured by Sigma-Aldrich

[0143] Dibutyltin oxide CAS number: 818-08-6

[0144] Molybdenum trioxide (>99.5%), Sigma-Aldrich

[0145] Cobalt acetate tetrahydrate (99.999%), Sigma-Aldrich

[0146] Polymerization Additives

[0147] Irganox® 195, BASF SE: antioxidant

[0148] Irganox 1010, BASF SE: antioxidant

[0149] HostanoxPEPQ, manufactured by Clariant: antioxidant

[0150] ADK REP-8: Antioxidant

[0151] Phosphoric acid (99.999+%), Sigma-Aldrich: antioxidant

[0152] Sodium acetate trihydrate (purity >99.0%): Etherification reaction limiting polymerization additive

[0153] Tetraethylammonium hydroxide 80% aqueous solution, Sigma-Aldrich: Etherification reaction limiting polymerization additive [Example]

[0154] Preparation of polyester

[0155] Example 1

[0156] To a 2 L reactor are added 3.481 moles of ethylene glycol and 1.958 moles of isosorbide, 695 g (4.183 moles) of terephthalic acid, 0.28 g of tetraethylammonium hydroxide (80% aqueous solution), 0.36 g of Irganox 1010, 0.36 g of ADK PEP-8, 0.073 g of cobalt acetate as a pigment, 65 mg of dimethyltin oxide (i.e., 50 ppm) as a catalytic agent, and 22 mg of germanium dioxide GeO2 (i.e., 200 ppm) as a catalytic agent.

[0157] To extract residual oxygen from the isosorbide crystals, four vacuum-nitrogen cycles are performed at 60-80°C. The reaction mixture is then heated to 250°C (4°C / min) under 2.5 bar pressure with constant stirring (150 rpm). The degree of esterification is calculated based on the amount of distillate collected.

[0158] The pressure was then reduced to 0.7 mbar over 90 minutes, and the temperature was increased to 265°C. These low-pressure conditions were maintained for 150 minutes, and the change in polymer viscosity was measured from the torque applied to the agitator. Finally, the PEIT polymer rod was poured through the bottom valve of the reactor, cooled in a thermoregulated water bath, and cut into approximately 500g pellets. Using this method, contact of the heated polymer with oxygen was avoided, reducing discoloration and thermooxidative degradation.

[0159] The properties of the resulting poly(ethylene-co-isosorbide) terephthalate resin are shown in Table 1 below.

[0160] Example 2

[0161] To a 2 L reactor are added 1.956 moles of ethylene glycol and 1.956 moles of isosorbide, 500 g (3.010 moles) of terephthalic acid, 0.28 g of tetraethylammonium hydroxide (80% aqueous solution), 0.36 g of Irganox 1010, 0.36 g of ADK PEP-8, 0.073 g of cobalt acetate as a pigment, 98 mg of dimethyltin oxide (i.e., 100 ppm) as a catalytic agent, and 416 mg of germanium dioxide GeO2 (i.e., 200 ppm) as a catalytic agent.

[0162] Using the same synthesis conditions, poly(ethylene-co-isosorbide) terephthalate resin was obtained, the properties of which are shown in Table 1 below.

[0163] Example 3

[0164] To a 2 L reactor, add 5.439 moles of ethylene glycol and isosorbide, 3.010 moles of terephthalic acid, 0.28 g of tetraethylammonium hydroxide (80% aqueous solution), 0.36 g of Irganox 1010, 0.36 g of ADK PEP-8, 0.073 g of cobalt acetate as a pigment, 98 mg of tin(II) oxide, also known as stannous oxide, as a catalytic agent (i.e., 100 ppm), and 416 mg of germanium oxide, GeO2, as a catalytic agent (i.e., 200 ppm).

[0165] The resulting resin has an isosorbide incorporation rate of 31.8 mol% based on the total amount of diols. The curing time (condensation) is 198 minutes. The viscosity index is 41 mL / g. The glass transition temperature, Tg, is 113°C. The final color of the polymer is pale yellow and has the following properties: L * =61.4, a * =0.1 and b * = 5.4.

[0166] Example 4

[0167] To a 30 L reactor are added 4826 g (77,751 mol) of ethylene glycol and 6818 g (28,873 mol) of isosorbide, 15,900 g (95.707 mol) of terephthalic acid, 6.41 g of tetraethylammonium hydroxide (80% aqueous solution), 8.23 ​​g of Irganox 1010, 8.23 ​​g of ADK PEP-8, 0.073 g of cobalt acetate as a pigment, 2.97 g of dimethyltin oxide (i.e., 100 ppm) as a catalytic agent, and 6.13 g of germanium dioxide GeO2 (i.e., 200 ppm) as a catalytic agent.

[0168] Using the same synthesis conditions, poly(ethylene-co-isosorbide) terephthalate resin was obtained.

[0169] Furthermore, the satisfactory results shown by these resins obtained in a 30 L reactor indicate that the process can be successfully scaled up.

[0170] Comparative Example 5

[0171] To a 2 L reactor are added 3.481 moles of ethylene glycol and 1.958 moles of isosorbide, 695 g (4.183 moles) of terephthalic acid, 0.28 g of tetraethylammonium hydroxide (80% aqueous solution), 0.36 g of Irganox 1010, 0.36 g of ADK PEP-8, 0.073 g of cobalt acetate as pigment, and 416 mg of germanium dioxide GeO2 (i.e., 300 ppm) as catalytic agent.

[0172] Using the same synthesis conditions, poly(ethylene-co-isosorbide) terephthalate resin was obtained, the properties of which are shown in Table 1 below.

[0173] Comparative Example 6

[0174] To a 7 L reactor, 893 g (14.386 mol) of ethylene glycol and 701 g (2.968 mol) of isosorbide, 2656 g (15.987 mol) of terephthalic acid, 0.1825 g of sodium acetate tetrahydrate, 0.7070 g of Irgamod 195 and 1.2020 g of dibutyltin oxide (i.e., 200 ppm) as a catalytic agent are added.

[0175] Using the same synthesis conditions, poly(ethylene-co-isosorbide) terephthalate resin was obtained, the properties of which are shown in Table 1 below.

[0176] Comparative Example 7

[0177] To a 7 L reactor, 893 g (14.386 mol) of ethylene glycol and 701 g (2.968 mol) of isosorbide, 2656 g (15.987 mol) of terephthalic acid, 0.1825 g of sodium acetate tetrahydrate, 0.7070 g of Irgamod 195, 0.9820 g of germanium dioxide GeO2 (i.e., 300 ppm) as a catalytic agent, and 3.0445 g of aluminum triethoxide (i.e., 150 ppm) as a catalytic agent are added.

[0178] Using the same synthesis conditions, poly(ethylene-co-isosorbide) terephthalate resin was obtained, the properties of which are shown in Table 1 below.

[0179] Table 1 summarizes the production testing and viscosity and color results of poly(ethylene-co-isosorbide) terephthalate.

[0180] [Table 1]

[0181] Coloring

[0182] The examples show that the use of a Ge / Sn catalyst mixture significantly reduces the color of the final polymer, which is notable in comparison of tests CEx5 and CEx6, which were performed in the presence of either Ge or Sn alone, with tests Ex1-Ex3, which were performed in the presence of a Ge / Sn catalyst mixture.

[0183] It is further noteworthy that the polymers according to inventive examples Ex1 and Ex3 have an incorporation rate of isosorbide relative to the diol of 30 mol %, whereas the polymers according to comparative examples CEx5 and CEx6 only have a 20 mol % incorporation rate.

[0184] Example 2 is also notable in that it has a molar incorporation of isosorbide approaching 40%, is colorless, and gives a polymer with a higher viscosity index than Comparative Example CEx4.

[0185] Comparative Example CEx4, in which the catalyst system contains only germanium, also gives a polymer with a low color, but its viscosity index is much lower than in Examples Ex1 and Ex3 according to the invention. However, polymers with viscosity indices as low as those obtained in Comparative Example CEx4 cannot be processed.

[0186] Example Ex3 according to the invention is therefore notable for its combination of good physical properties (viscosity index) and good color (pale yellow).

[0187] The CEx6 test corresponds to Example 4 of WO 2016 / 066956. It shows that when germanium is used in combination with a metal other than tin, in this case aluminum, it is not possible to obtain a colorless polymer in any case, but a lightly colored polymer.

[0188] Incorporation of isosorbide units into the final polymer compared to diols

[0189] In conclusion, under comparable preparation conditions, the resins according to the invention have reduced coloration, even transparent coloration and much higher molar incorporation of isosorbide than polymers obtained in the presence of other known catalyst systems presented in the context of the present disclosure, while retaining good deformability.

[0190] Catalytic activity

[0191] [Figure 1] [Brief explanation of the drawings]

[0192] [Figure 1] 1 shows a graph illustrating the variation of driving torque as a function of polycondensation time during PEIT synthesis in the presence of different catalyst systems.

[0193] This graph clearly shows the improvement in catalytic activity due to the addition of tin, as opposed to germanium alone. As mentioned above, the polymerization reaction is monitored by controlling the change in the magnitude of the torque measured on the stirrer. In other words, the catalytic activity is shown in the graph by the increase in engine torque according to the polycondensation time.

[0194] In fact, in the presence of germanium alone, the torque value does not increase even after more than 200 minutes, indicating no increase in viscosity and therefore no polymer formation.

[0195] Addition of tin to the catalyst system at a Ge / Sn molar ratio equal to 4 results in an exponential increase in torque observed after about 150 minutes. When the Ge / Sn molar ratio is decreased, such an exponential increase in torque is observed after about 125 minutes.

Claims

1. 1. A method for producing a polyester containing at least one 1,4:3,6-dianhydrohexitol unit, comprising: - introducing into a reactor monomers comprising at least one monomer (A) which is a dicarboxylic acid or diester and at least one monomer (B) which is a 1,4:3,6-dianhydrohexitol unit; - introducing a compound containing elemental cobalt into said reactor, - introducing into said reactor a catalyst system comprising either a catalyst comprising elemental germanium and a catalyst comprising elemental tin, or a catalyst comprising elemental germanium and elemental tin, or a mixture of these catalysts; - polymerizing said monomers to form said polyester; - recovering a polyester composition comprising said polyester and said catalyst system.

2. 2. The method according to claim 1, wherein the monomer (A) is an aromatic monomer selected from the group consisting of terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, furandicarboxylic acid, mixtures of these dibasic acids, dibasic esters of these dibasic acids, and mixtures of these diesters.

3. 3. The process according to claim 2, wherein the monomer (A) is terephthalic acid or a terephthalic acid diester.

4. 4. The process according to claim 1, wherein the monomer further comprises at least one diol (C) selected from ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,4-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, and mixtures of these diols.

5. The polymerization step a first stage during which the reaction medium is stirred at a temperature ranging from 200 to 300°C to form oligomers; - a second stage during which the formed oligomers are stirred under vacuum at a temperature in the range of 240-330°C to form the polyester.

6. Process according to any one of claims 1 to 5, characterized in that the catalyst system is introduced into the reactor before the polymerization step.

7. The process according to any one of claims 1 to 6, wherein the catalyst system is selected to have a molar elemental ratio of Ge:Sn in the range of 1:1 to 5:

1.

8. The method of claim 1, wherein the compound containing elemental cobalt is cobalt acetate.

9. 9. The process according to claim 1, wherein the total mass of metals contained in the catalyst system relative to the total mass of the polymer obtained is in the range of 50 to 500 ppm.

10. The method according to claim 1, wherein a reactor deoxidation step is carried out before the monomer polymerization step by placing the reactor under an inert gas atmosphere.

11. 11. The process according to claim 1, wherein the molar percentage of monomer (A) relative to the total number of moles of monomers (A), (B) and, optionally, (C) is in the range of 25 to 50%.

12. 12. The method according to any one of claims 1 to 11, characterized in that the 1,4:3,6-dianhydrohexitol unit is isosorbide.

13. 1. A polyester composition comprising: polyesters containing at least one 1,4:3,6-dianhydrohexitol unit, - Compounds containing the element cobalt, and - Polyester compositions comprising a catalyst system comprising either a catalyst comprising elemental germanium and a catalyst comprising elemental tin, or a catalyst comprising elemental germanium and elemental tin, or a mixture of these catalysts.

14. Lightness above 45L ＊ 14. The polyester composition of claim 13, wherein

15. -10 to 10 b ＊ 15. The polyester composition according to claim 13 or 14, characterized in that it has a color.

16. The polyester composition according to any one of claims 13 to 15, characterized in that it has a reduced viscosity of more than 35 mL / g.

17. An article comprising the polyester composition of any one of claims 13 to 16.

18. Poly(ethylene glycol) containing at least one 1,4:3,6-dianhydrohexitol unit The present invention relates to the use of a catalyst system comprising a catalyst containing elemental germanium and a catalyst containing elemental tin, a catalyst containing elemental germanium and elemental tin, or a mixture of these catalysts, and a compound containing elemental cobalt, to reduce the coloration of a polyester.

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