Methods for the synthesis of di(hydroxymethyl)tetrahydrofuran and its application in polyesters and polyurethanes

Abstract

The present invention relates to the synthesis of di(hydroxymethyl)tetrahydrofuran (DHMTHF) and the preparation of trans-enriched mixtures of DHMTHF. The invention further refers to polyester polyols which are obtained by reaction of cis / trans DHMTHF mixtures with a dicarboxylic acid. The invention further relates to polyurethanes and compositions containing a polyester polyol comprising DHMTHF, in particular to such polyurethane-containing (adhesive) compositions.

Description

[Technical Field]

[0001] This invention relates to the synthesis of bis(hydroxymethyl)tetrahydrofuran (DHMTHF) and the preparation of a trans-enriched mixture of DHMTHF. Further, this invention relates to polyester polyols obtained by reacting a mixture of cis / trans DHMTHF with a dicarboxylic acid. Further still, this invention relates to polyurethanes and compositions containing polyester polyols comprising DHMTHF, specifically to such polyurethane (adhesive) compositions. [Previous Technology]

[0002] The demand for novel polymers in the field of adhesives technology is constantly growing because adhesives need to meet the diverse requirements of a wide range of applications. Significant progress has been made in this regard over the past few decades through the development of novel synthetic polymers. However, these are primarily derived from fossil resources and are therefore characterized by low sustainability. In contrast, the use of renewable feedstocks can reduce the carbon footprint of the final product, while simultaneously providing novel chemical structures unavailable from traditional petroleum-based sources.

[0003] Among different types of adhesives, hot melt adhesives are characterized by a current growth rate 1.5 to 2 times higher than that of other types of adhesives. Typical components of reactive polyurethane hot melt adhesives are industrially produced through the reaction of polyisocyanates with polyether polyols or polyester polyols. It should be noted that there are increasing reports from industry and academia on bio-based polyester polyols, polyether polyols, and polyurethanes. However, research on the influence of different stereoisomers of bio-based polyols on the properties of derived polymers and materials is scarce.

[0004] The use of different diastereomers of bio-based diol di(hydroxymethyl)tetrahydrofuran (DHMTHF) in the synthesis of polyesters has been reported in this technology (Moore and Kelly, Macromolecules 1978, 11, 568-573). However, in the reported methods, the authors obtained these polymers by using chloroform (a non-benign solvent) and carboxylic acid chloride as comonomers in the presence of excess triethylamine. Furthermore, the polymerization process takes two weeks and the product consists only of low molecular weight materials. Finally, the cis and trans DHMTHF isomers were synthesized via a multi-step method, including reduction with sodium amalgam and stoichiometric reactions with toxic and explosive diazomethane and lithium aluminum hydride, respectively.

[0005] Recently, DHMTHF has been used to synthesize copolyesters with 1,4-cyclohexanediethanol and furan dicarboxylic acid (FDCA), and it has been revealed that increasing the content of cis-DHMTHF in the synthesized polymer can increase the hardness, storage modulus, and hydrophobicity of the latter (Jin et al., ACS Sustainable Chem. Eng. 2021, 9, 39, 13287-13302). It should be noted that even if the authors use only the cis isomer of DHMTHF, it can be assumed that the corresponding trans isomer will lead to different properties due to changes in the spatial shape and arrangement of the resulting polymer. Although cis / trans DHMTHF mixtures for FDCA polyesters have been revealed (WO 2017 / 091435 A1; WO 2017 / 091412 A1), economically feasible methods for synthesizing pure or trans-enriched DHMTHF remain unknown to date. In fact, in these disclosures, DHMTHF was obtained at 150 °C from the hydrogenation of L-glucanone (LGO) with only a moderate selectivity of 58% and a maximum trans content of 29% in the presence of a supported palladium catalyst (Figure 1). Furthermore, a series of homogeneous ruthenium precursors and combinations of ligands containing NHC or diphosphorus were reported for the hydrogenation of 5-HMF to DHMTHF, yielding a trans content as high as 44% despite a very poor yield of 17% (Cadu et al., Green Chem. 2018, 20, 3386-3393). In the latter case, the authors used a high catalyst loading, and both reported procedures resulted in problematic product mixtures for the separation of DHMTHF. Moreover, the use of both LGO and 5-HMF as high-purity, crystallization-initiating materials would certainly make DHMTHF prohibitively expensive as a polymer building block. The high cost of the latter is a result of the purification process required to remove impurities such as formic acid, acetylpropionic acid, and oligomers.

[0006] In this paper, it was found that a low-purity aqueous solution of 5-HMF obtained as a byproduct of hydrothermal carbonization of sugar or lignocellulose materials (Thoma et al., ChemSusChem 2020, 13, 3544-3564) can be used to synthesize DHMTHF and its corresponding polymers.

[0007] According to current research, the introduction of linear molecules containing ether bonds has a beneficial effect on the polarity, hydrophilicity, biodegradability, and biocompatibility of polyesters; however, these properties generally have a significant negative impact on strength and thermal properties. The inventors hypothesize that, from a molecular structure perspective, replacing linear monomers containing ether bonds with cyclic monomers could be a way to overcome this problem. Although several cyclic diols, such as 1,4-cyclohexanediol (CHDM), 2,2,4,4-tetramethyl-1,3-cyclobutanediol (CBDO), and isosorbide (IS), have been reported to improve the properties of synthetic polyesters, of these named cyclic diols, only isosorbide is currently available from biomass feedstocks.

[0008] Although DHMTHF is a promising novel bio-based monomer that allows for the synthesis of novel materials with attractive properties, scalable methods for synthesizing trans-enriched DHMTHF remain unknown to date. Trans-enriched DHMTHF certainly introduces differences in the properties of the resulting polymers compared to their corresponding cis-DHMTHF analogs. Furthermore, the use of DHMTHF as a primary diol in polyester polyols that simultaneously exhibit good tensile strength and high elongation in polyurethane adhesives is unknown. To benefit from the advantageous properties of polyester polyols derived from DHMTHF, it is therefore expected that they can also be used in other systems. [Summary of the Invention]

[0009] Therefore, the object of the present invention is to provide polyester polyols comprising bio-based monomers, which can be used in liquid systems under ambient temperature applications, such as polyurethane adhesives, specifically two-component polyurethane adhesives. Furthermore, the latter must meet the requirements of industrial applications, such as bonding materials with different coefficients of thermal expansion.

[0010] Surprisingly, the above objective was found to be achieved by developing a novel synthetic route to obtain DHMTHF with a high trans isomer content and further by using it to preferentially derive polyester polyols from biomass in the synthesis of a reaction mixture of cis / trans DHMTHF and dicarboxylic acid, which are available from the defined mixture.

Implementation Method

[0017] In the first state, therefore, the present invention relates to a method for producing di(hydroxymethyl)tetrahydrofuran (DHMTHF) from 5-hydroxymethylfurfural (5-HMF), the method comprising hydrogenating a solution of 5-HMF (such as an aqueous solution) in the presence of a non-homogeneous catalyst, wherein the 5-HMF is crude 5-HMF.

[0018] As used herein, "aqueous solution" means a solution in which water is the main solvent, i.e., water constitutes at least 50% by weight or volume of the total solvent used, for example at least 70%, at least 80% or at least 90% by weight or volume.

[0019] In various embodiments, the heterogeneous catalyst is a cis-hydrogenation mode catalyst, preferably selected from Raney nickel, Ru / C (ruthenium supported on carbon), Pd / Al (palladium supported on aluminum oxide), and Pd / C (palladium supported on carbon), with Raney nickel being more preferred. Other suitable catalysts include (but are not limited to) Pd / Si (palladium supported on silicon dioxide), Ru / Al (ruthenium supported on aluminum oxide), Raney cobalt, and Raney copper.

[0020] In various embodiments, the hydrogenation reaction is carried out in the presence of ethanol at a concentration of at least 1.3 mL of ethanol per 1 mmol 5-HMF, preferably 1.4 to 3.0 mL of ethanol per 1 mmol 5-HMF.

[0021] In various embodiments, the hydrogenation reaction is carried out at an H2 pressure of at least 10 or at least 20 bar, preferably at least 50 bar, more preferably 80 to 100 bar; and / or at a temperature of 80 to 120°C, preferably at about 100°C; and / or for a reaction time of at least 5 hours, preferably 5 to 60 hours.

[0022] In these methods, the 5-HMF used is crude 5-HMF. This crude 5-HMF can be a side-stream product from a hydrothermal carbonization process of, for example, sugars or lignocellulose materials. Generally, the crude 5-HMF can have a purity of less than 95%, for example less than 94, less than 93, less than 92, less than 91, less than 90, less than 89, less than 88, or less than 87% (all by weight) relative to the total organic content. In various embodiments, the 5-HMF purity is in the range of 70 to 95%, such as 75 to 90%, for example 80 to 90%. As used herein, "purity" refers to the purity of the solid or organic solvent, i.e., the absence of any potentially present aqueous phase / water. The crude 5-HMF can be provided in the form of an aqueous solution containing, for example, 15 to 25% by weight of 5-HMF solids. The impurities contained in the crude 5-HMF may include those selected from the following: formic acid, acetylpropionic acid, oligomers of 5-HMF and combinations thereof, in an amount of at least 1%, at least 2%, at least 3%, at least 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20% by weight of the total weight of the organic matter in the crude 5-HMF, as required.

[0023] In various embodiments, these methods provide cis enrichment of DHMTHF, i.e., the content of the cis diastereomer is higher than the content of the trans diastereomer, preferably a molar ratio greater than 1, more preferably greater than 1.5, greater than 2, greater than 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20. In various embodiments, the cis to trans ratio is at least 80:20, preferably at least 85:15, more preferably at least 90:10, for example, about 92:8.

[0024] In another embodiment, the present invention relates to a method for enriching trans DHMTHF in a mixture of cis / trans DHMTHF, the method comprising reacting the mixture of cis / trans DHMTHF at high temperature in the presence of a metal catalyst suitable for a metal-catalyzed hydrogen-borrowing reaction, a base, and a suitable solvent.

[0025] As used herein, “high temperature” refers to a temperature above ambient temperature, i.e., 30°C or higher, such as at least 40, at least 50, at least 60 or at least 70°C.

[0026] In these methods, the mixture of cis / trans DHMTHF used as the starting material has a cis to trans ratio of at least 1, preferably at least 2, more preferably 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20, or 1 to 20, 2 to 20 or 3 to 20. In various embodiments, it may be DHMTHF obtainable according to the hydrogenation methods described herein.

[0027] Trans-enriched DHMTHF obtainable according to the methods described herein refers to a mixture of cis / trans DHMTHF, wherein the content of the trans diastereomer is at least 30 mol% relative to the total amount of cis and trans diastereomers, preferably at least 35 or at least 40 mol%. This is considered trans-enriched relative to a cis / trans mixture typically containing an excess of cis diastereomers used as a starting material. This enrichment generally means that the amount of trans diastereomers is increased by at least 5 mol%, preferably at least 10 mol%, preferably 20 mol% and greater relative to the starting material. For example, using a cis / trans DHMTHF mixture having a cis:trans ratio of 90:10, the enrichment method described herein can provide a trans-enriched mixture having a trans content of at least 30 mol% (i.e., the cis:trans ratio is 70:30 or lower, such as 60:40).

[0028] In various embodiments, the catalyst used for the hydrogen-borrowing reaction of metal catalysis is a metal complex catalyst, such as a ruthenium complex catalyst, a cobalt complex catalyst, a manganese complex catalyst or an iron complex catalyst.

[0029] In various embodiments, it is a ruthenium complex catalyst, preferably a ruthenium complex carrying a tridentate clamp-type ligand. This catalyst can be selected from (but is not limited to) carbonyl chlorohydro[bis(2-dicyclohexylphosphinoethyl)amine]ruthenium(II); carbonyl chlorohydro[bis(2-diisopropylphosphinoethyl)amine]ruthenium(II), carbonyl chlorohydro[bis(2-ditert-butylphosphinoethyl)amine]ruthenium(II), dichloro[rel-[N(S)]-N-[2-[(R)-phenylthio-κS]ethyl]-4-morpholinoethylamine-κNN4,κN4](triphenylphosphine)ruthenium(II), dichloro[rel-[N(R)]-N-[2-[(R)-(phenylmethyl)thio-κS]ethyl]-4-morpholinoethylamine-κNN4,κN4](triphenylphosphine)ruthenium(II). Ruthenium (II) is composed of the following compounds: dichloro[N-[2-(phenylthio-κS)ethyl]-[4-morpholinoethylamine-κNN1,κN1](tricyclohexylphosphine), dichloro[rel-[N(S)]-N-[2-[(R)-phenylthio-κS]ethyl]-[1-pyrrolididineethylamine-κNN1,κN1](triphenylphosphine), dichloro[N1,N1-dimethyl-N2-[2-(phenylthio-κS)ethyl]-1,2-ethylenediamine-κN1,κN2](tricyclohexylphosphine), and dichloro[N-[2-(diphenylphosphine-κP)ethyl]-2-(methylthio-κS)ethylamine-κN](triphenylphosphine). Dichloro[rel-[N(S)]-N-[2-(diphenylphosphino-κO)ethyl]-2-[(R)-methylthio-κS]ethylamine-κN](triphenylphosphine)ruthenium, carbonylhydrochloro[bis(2-(diphenylphosphinoethyl)amino]ruthenium(II), carbonylhydrochloro[6-(di-tert-butylphosphinomethyl)-2-(N,N-diethylaminomethyl)pyridine]ruthenium(II), carbonylhydrochloro-t-(triphenylphosphine)ruthenium(II), carbonyl(dihydro)t-(triphenylphosphine)ruthenium(II), carbonylhydro-[6-(di-tert-butylphosphinomethylene)-2-(N,N-diethylaminomethyl)-1,6-dihydropyridine]ruthenium(II), carbonylhydro-(tetrahydroborate)[bis(2-diphenylphosphinoethyl)amino]ruthenium(II) Cr(II) chlorocarbonyl hydrogenated [4,5-bis(diisopropylphosphinomethyl)acridinium], Cr(II) chlorohydro-triphenylphosphine, 1-hydroxytetraphenylcyclopentadienyl(tetraphenyl-2,4-cyclopentadien-1-one)-μ-hydroxytetracarbonyl diruthenium(II), dichloro(benzene)ruthenium(II) dimer, carbonyl(dihydro)triphenylphosphine (II), Cr(II) chlorohydro-triphenylphosphine, and [Ru(1,1,1-triphenylphosphine)ethane)TMM] (TMM = trimethylenemethane).

[0030] In various embodiments, the ruthenium catalyst is selected from: and, preferably Ru-2 and Ru-3, such as Ru-3.

[0031] Other suitable catalysts include (but are not limited to) [N2,N4-bis(diisopropylphosphino)-6-phenyl-1,3,5-triazine-2,4-diamine]-cobalt dichloride, [N2,N4-bis(diisopropylphosphino)-6-cyclopropylamino-1,3,5-triazine-2,4-diamine]-cobalt dichloride, [N2,N4-bis(diisopropylphosphino)-6-methyl-1,3,5-triazine-2,4-diamine]-manganese (dicarbonyl) bromide, [N2,N4-bis(diisopropylphosphino)-6-phenyl-1,3,5-triazine-2,4-diamine]-manganese dichloride; [N2,N4-bis(diisopropylphosphino)-6-cyclopropylamino-1,3,5-triazine-2,4-diamine]-manganese dichloride, [N2,N4-bis(diisopropylphosphino)-6-diethylamino-1,3,5-triazine-2,4-diamine]-manganese (dicarbonyl) bromide, and carbonyl hydrogen (tetrahydroborate)[bis(2-diphenylphosphinoethyl)amino]iron(II).

[0032] The catalyst can be used in amounts of 1 mol% or less, preferably about 0.5 mol% or less, such as about 0.5 mol%, 0.4 mol%, 0.3 mol%, 0.2 mol% or 0.1 mol%. It has been found that an amount of 0.1 mol% still provides good catalytic activity and may even be more advantageous than significantly higher concentrations (such as 1 mol% and greater).

[0033] In various embodiments, the reaction temperature is between 50 and 150°C, for example 80°C or higher, preferably 80 to 120°C.

[0034] In various embodiments, the base is a strong base. This strong base may be an alkoxide, specifically a metal alkoxide. Suitable bases include (but are not limited to) potassium terbutoxide, sodium terbutoxide, potassium terpentoxide, sodium terpentoxide, sodium methoxide, potassium methoxide, sodium ethoxide, and potassium ethoxide. In various embodiments, the base may be potassium terbutoxide (KOtBu) or potassium terpentoxide (KOtPen). The base may be used in any suitable amount, for example, at least 6, 7, 8, 9, or at least 10 moles. Lower amounts have been found to negatively impact the reaction, while higher concentrations do not provide additional benefits.

[0035] In various embodiments, the solvent is an organic solvent, preferably selected from (but not limited to) heptane, THF, 1,4-dioxane, toluene, cyclobutane, acetonitrile, 2-MeTHF, and mixtures thereof, such as toluene.

[0036] This method can be carried out under a nitrogen or argon atmosphere. It is advantageous if the reaction is not carried out under a hydrogen atmosphere.

[0037] In various embodiments, the reaction time is 2 to 48 hours, preferably about 4 to 24 hours.

[0038] In another embodiment, the present invention relates to an alternative method for enriching trans-DHMTHF in a mixture of cis / trans-DHMTHF, the method comprising (a) acetylating the mixture of cis and trans-DHMTHF at a high temperature, for example with acetic anhydride, as needed, to obtain a mixture of diacetic esters of cis and trans-DHMTHF; (b) crystallizing the diacetic esters of trans-DHMTHF in a solution of the mixture of diacetic esters of cis and trans-DHMTHF in a suitable solvent at a temperature that allows preferential crystallization of trans-DHMTHF, preferably between -5 and -20°C, and more preferably at about -15°C; (c) separating the crystalline diacetic esters of trans-DHMTHF; and (d) hydrolyzing the diacetic esters of trans-DHMTHF under alkaline conditions to obtain enriched trans-DHMTHF.

[0039] Step (a) may be followed by a step to remove acetic acid (if it is formed in step (a)).

[0040] In these methods, the cis / trans DHMTHF mixture used as the starting material has a cis to trans ratio of 3 or less, preferably 2.5 or less, more preferably 2 or less, most preferably 1.5 or less, but typically greater than 1. In various embodiments, it may be DHMTHF obtainable according to the hydrogenation methods described herein. In various other embodiments, the mixture used in these methods is produced by the catalytic trans enrichment methods described above.

[0041] The definition of trans enrichment DHMTHF provided above also applies to this method.

[0042] In various embodiments, the diacetyl ester residue remaining after the removal of acetic acid in step (b) is dissolved in a suitable solvent to allow for the crystallization / precipitation of the trans diastereomer. This solvent may be (but is not limited to) diethyl ether, THF, 2-MeTHF, 1,4-dioxane, methyl tributyl ether, cyclopentyl methyl ether, tripentyl ethyl ether, acetonitrile, and ethyl acetate. The enrichment of the trans diastereomer is based on the finding that the trans isomer crystallizes at higher temperatures than the cis diastereomer. In the method and solvent described herein, the temperature at which the trans diacetyl DHMTHF precipitates from solution is in the range of about -5 to about -20°C, preferably at about -15°C. It has been found that at lower temperatures, for example at about -30°C, both diastereomers precipitate from the solution. It should be understood that these temperature ranges may vary in other solvent systems and under different conditions. In various embodiments, a solvent system is used in which one of the two diastereomers crystallizes at a temperature at least 5°C higher than the temperature at which the other crystallizes. Preferably, it is at least 10°C higher. Generally, all temperatures used for crystallization can be below 5°C or below 0°C.

[0043] When “approximately” is used in relation to numerical values ​​in this article, it means ±10% of the reference value, or ±5% of the preferred value.

[0044] The separation of trans-enriched diacetyl DHMTHF can be carried out by centrifugation and decantation or filtration followed by drying. The crystalline precipitate can be washed multiple times with ether, for example, before drying to remove impurities. The drying can then be carried out under vacuum, i.e., under reduced pressure. The trans-enriched diacetyl DHMTHF thus obtained can have a cis:trans ratio of 30:70 or lower, preferably 20:80 or lower, for example, about 15:85.

[0045] Then, trans-enriched diacetyl DHMTHF can be produced by hydrolysis. For this reaction, the crystalline material can be dissolved in a suitable solvent (such as ethanol), and then a base (such as NaOH) can be added, for example in the form of an aqueous solution. Suitable reaction conditions are known to those skilled in the art and may require the slow addition of the base and thorough stirring over an extended time period, such as 48 hours. The resulting water can be removed under reduced pressure, and the residue filtered and precipitated with a suitable solvent (such as ethyl acetate). Then, all volatiles can be removed again under reduced pressure to obtain trans-enriched DHMTHF as a colorless liquid.

[0046] The trans enriched DHMTHF thus obtained can retain the previous cis / trans ratio and can have a cis:trans ratio of 30:70 or lower, preferably 20:80 or lower or even 10:90 and lower, such as about 15:85.

[0047] In these acetylation methods, the supernatant containing cis-enriched diacetylated DHMTHF remaining in step (d) can undergo a hydrolysis process similar to that for trans-enriched diacetylated DHMTHF to obtain cis-enriched DHMTHF, which may have a cis / trans ratio of 60:40 or higher, for example, 70:30 or higher. This cis-enriched DHMTHF can then undergo a hydrogen borrowing process to provide trans-enriched DHMTHF, which can then be subjected to the acetylation process again for further trans-enrichment. If this sequence of steps is repeated multiple times, near-stereoselective formation of trans-DHMTHF can be achieved. This method relates to the two trans-enrichment methods described herein.

[0048] The present invention also relates to the trans-enriched DHMTHF mixture thus obtained, specifically a cis / trans DHMTHF mixture having a molar ratio of cis to trans diastereomers of 70:30 or less, preferably 70:30 to 30:70, for example 60:40 to 40:60.

[0049] Another aspect of the invention relates to polyester polyols obtainable by reacting a diastereomeric mixture of cis / trans DHMTHF with a suitable diacid. The cis / trans DHMTHF mixture may be those obtainable by the methods described above. In various embodiments, the diastereomeric mixture of cis / trans DHMTHF has a cis to trans DHMTHF ratio of about 70:30 or less, for example, about 30:70 to about 70:30, preferably about 40:60 to about 60:40. Such mixtures are also referred to herein as trans-enriched cis / trans DHMTHF mixtures.

[0050] In various embodiments, the diacid is at least one dicarboxylic acid. The dicarboxylic acid may be aliphatic or aromatic and may contain 4 to 30 carbon atoms. If it is an aliphatic dicarboxylic acid, it may be saturated or unsaturated. In various embodiments, it is an aliphatic dicarboxylic acid, for example, an aliphatic dicarboxylic acid having a carbon chain of at least 2 carbon atoms, which may be saturated or unsaturated. In various embodiments, it may be a saturated aliphatic C4- to C24-dicarboxylic acid, such as 1,6-adipic acid, 1,7-heptanoic acid, 1,8-octanoic acid, 1,9-azelanoic acid, 1,10-sebacic acid, 1,11-undecanoic acid, 1,12-dodecanoic acid, 1,13-tetrazanoic acid, 1,14-tetradecanoic acid, 1,15-pentadecanoic acid, 1,16-hexadecanoic acid, 1,17-heptadecanoic acid, 1,18-octadecanoic acid, 1,19-nonadecanoic acid, 1,20-eicosanoic acid, 1,21-eicosanoic acid, 1,22-docosacanoic acid, 1,23-tricosacanoic acid, and 1,24-tetradecanoic acid, as well as anhydrides, halides (chlorides), and esters derived from such acids. In other embodiments, the acids used include (but are not limited to) succinic acid, adipic acid, sebacic acid, azelaic acid, isophthalic acid, phthalic acid, terephthalic acid, furan dicarboxylic acid, itaconic acid, and anhydrides, halides (chlorides), and esters derived from such acids. It should be understood that mixtures and salts of all the acids listed above and their derivatives (such as esters, halides, and acid anhydrides) may also be used.

[0051] The expression "carbon chain" used in conjunction with dicarboxylic acid refers to a straight carbon chain consisting of two separate carboxylic acid groups, wherein the chain is terminated at each end by a carboxylic acid group and the carbon atom of that carboxylic acid group is the starting point and the ending point, respectively, and is used to determine the number of carbon atoms in the carbon chain.

[0052] In various embodiments, the polymerization reaction is carried out using a two-stage melt condensation method, which includes a pre-condensation step at ambient pressure (i.e., about 1 bar) with a gradually increasing temperature from about 120 to about 220°C and a subsequent condensation step under reduced pressure, in the presence of a suitable catalyst, preferably a polycondensation catalyst, such as a metal alkoxide, more preferably a titanium alkoxide catalyst, or even more preferably titanium isopropoxide (IV).

[0053] Examples of suitable polycondensation metal catalysts include (but are not limited to) aluminum alkoxides, titanium alkoxides, magnesium alkoxides and zirconium alkoxides, tin compounds, and more specifically, organotin carboxylic acids such as dibutyltin dilaurate, dibutyltin diacetate, dibutyltin bis(2-ethylhexanoate) or other organotin compounds such as dibutyltin oxide, dibutyltin dimethylethanol, dibutyltin dibromide, dibutyltin dichloride, ditert-butyltin dichloride, dimethyltin dibromide, dimethyltin dichloride, diphenyltin dichloride or tin octoate, ferric acetate, ferric benzoate, ferric naphthenate; ferric acetopyruvate, manganese acetate, manganese naphthenate and manganese acetopyruvate.

[0054] The molecular weight of the components contained in the reaction mixture is determined according to standard procedures, such as by GPC or end-group titration (OH value determination).

[0055] In yet another embodiment, the present invention relates to polyester polyols (Ia) and (Ib) comprising monomer units of formula (Ia) and (Ib), wherein the molar ratio of (Ia) to (Ib) is 70:30 or less, preferably 70:30 to 30:70. In some embodiments, the monomer units of formula (Ia) and (Ib) constitute at least 5 molars of the total polyol units in the polyester polyol, at least 10, 15, 20, 25, 30, 35, 40, 45 or at least 50 molars or at least 60, 70, 80, 90 or at least 95 molars. In various embodiments, the ratio of the unit of formula (Ia) to the unit of formula (Ib) is about 30:70 to about 70:30, preferably about 40:60 to about 60:40. In various embodiments, the polyester polyol does not contain polyol units other than those of formulas (Ia) and (Ib), or such other polyols are present in an amount of 10 moles or less of all polyol units. In addition to these polyol-derived monomer units, the polyester polyol also contains diacid-derived monomer units connecting the polyol-derived units. These acid units may be derived from the diacids disclosed above. These polyester polyols may be produced according to the methods described herein.

[0056] It was further surprising to discover that some of the polyester polyols of the present invention are semi-crystalline and have low melting points, making them particularly suitable for temperature-sensitive applications. In one embodiment, the polyester polyols of the present invention have a (semi)crystalline form at ambient temperature and lower temperatures. As used in the present invention, ambient temperature refers to a temperature of 23 to 25°C at a pressure of 1000 to 1020 hPa.

[0057] Polyester polyols exhibiting a semi-crystalline morphology as described herein refer to polyester polyols in which the polymer chains are at least partially aligned. The morphology of such polyester polyols can be determined, for example, by DSC, where crystallinity is typically represented by melting and crystallization peaks defined in the spectrum. In contrast, amorphous materials are characterized by the lack of specified peaks in the DSC spectrum.

[0058] Various methods for producing (semi-)crystalline polyester polyols are known to those skilled in the art. However, these crystalline polyester polyols typically have melting or softening points much higher than room temperature. Surprisingly, it has been found that the melting point of the polyester polyols of the present invention can be adjusted by using an appropriate amount of trans-DHMTHF.

[0059] The melting point of the polyester polyol of the present invention can also be adjusted according to the requirements by selecting a suitable dicarboxylic acid.

[0060] In a particularly preferred embodiment, DHMTHF and the dicarboxylic acid derived from the polyester polyol of the present invention are further derived from renewable sources. Generally, such compounds obtained from renewable sources are referred to as "bio-based" compounds, as opposed to common gasoline-based compounds.

[0061] Some of the polyester polyols of the present invention are distinguished in particular by their (semi-)crystalline form, while simultaneously exhibiting low melting points. In contrast to crystalline polyester polyols that typically exhibit high melting points above 80°C according to current state-of-the-art technology, these polyester polyols are found to have melting points below 60°C in the low-temperature region, allowing for more flexible applications in many technical fields. In one embodiment, the polyester polyols of the present invention, measured by DSC at a heating rate of 10 K / min, have melting points ranging from -10 to 50°C, preferably from -5 to 30°C.

[0062] To adjust the properties of the polyester polyols of the present invention, in addition to the DHMTHF mixture and at least one dicarboxylic acid, other components may be included in the reaction mixture. Therefore, the reaction mixture may contain other diols. Examples of such polyols include monoethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol (including R-type, S-type and racemic forms), 1,4-butanediol, 1,4-pentanediol, 3-methylpentane-1,5-diol, neopentanediol (2,2-dimethyl-1,3-propanediol), 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, cyclohexanediol, 2-methylpropane-1,3-diol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, polypropylene glycol, dibutylene glycol, and polybutanediol.

[0063] However, these diols do not constitute more than 50 mol% of the total amount of the polyols used, preferably about 30 mol% or less, or 20 mol% or less, or 10 mol% or less.

[0064] The reactivity of the polyester polyol of the present invention can be adjusted as needed according to subsequent applications. In various embodiments, the polyester polyol of the present invention thus has a hydroxyl value (OH value) of 5 to 250 mg KOH / g, 5 to 150, 10 to 100 mg KOH / g, 20 to 50 mg KOH / g, or 25 to 34 mg KOH / g.

[0065] The hydroxyl value is a measure of the content of free hydroxyl groups in a chemical substance, usually expressed in milligrams of potassium hydroxide (KOH) equivalent to the hydroxyl content of one gram of the chemical substance. Analytical methods for determining the hydroxyl value traditionally involve acetylation of the free hydroxyl groups of the substance in a pyridine solvent with acetic anhydride. The hydroxyl value can be determined according to DIN 53240.

[0066] The hydroxyl value of the polyester polyol of the present invention can be adjusted, for example, by the ratio of diol to dicarboxylic acid in the reaction mixture. In a preferred embodiment, the molar ratio of at least one diol to at least one dicarboxylic acid in the reaction mixture is 1.5:1 to 1:1, preferably 1.2:1 to 1:1.

[0067] If the polyester polyol is -OH-terminated, the acid value is as high as 20 mg / g, preferably as high as 10, such as 0.5 to 10 or 1 to 3 mg / g.

[0068] In various embodiments, the polyester polyol may also be acid-terminated. In these embodiments, the acid value may be 5 to 250 and preferably 10 to 150 mg / g.

[0069] In a preferred embodiment, the polyester polyol of the present invention has an average molecular weight Mn of 1,000 to 25,000 g / mol, preferably 2,000 to 10,000 g / mol, as determined by GPC. The molecular weight of the polyester polyol of the present invention can be specifically determined by GPC using THF as the solvent.

[0070] In another embodiment, the present invention also relates to a method for producing a polyester polyol as described above, the method comprising reacting a diastereomeric mixture of cis / trans DHMTHF with a suitable diacid. All the embodiments disclosed above relating to this polyester polyol are also applicable to such methods.

[0071] Some of the polyester polyols of the present invention are particularly suitable for adhesive applications, specifically low-melting-point systems. The presence of such polyester polyols in the adhesive allows the advantageous properties of self-crystallizing polyester polyols to be utilized without melting the adhesive at high temperatures.

[0072] Another aspect of the invention is a composition, such as an adhesive or coating composition, comprising the DHMTHF mixture or polyester polyol according to the invention. In such compositions, the molar ratio of cis to trans DHMTHF as monomers or as monomer units in a polymer may be 70:30 or less, for example, 70:30 to 30:70 or 60:40 to 40:60. The invention also includes the use of the DHMTHF mixture and polyester polyol described herein in adhesive or coating compositions.

[0073] The polyester polyol of the present invention can be applied to many adhesive systems. Preferably, the adhesive system is a polyurethane adhesive, specifically a two-component polyurethane adhesive (2K system) or a one-component polyurethane adhesive (1K system). In various embodiments, the polyester polyol is therefore used in polyurethane adhesives and other PU applications (such as foams, thermoplastic PU (TPU), PU dispersions (PUD), and all other PU systems). It is further applicable to other applications in which polyester is used, such as reactive prepolymers for acrylic resins and as toughening agents in epoxy resins.

[0074] Therefore, in a particular instance, the present invention also relates to the use of mixtures of cis / trans DHMTHF derived polyester polyols according to the present invention as components of thermoplastic materials or adhesives and / or sealants. Although the polyester polyol mixtures according to the present invention can be used in thermoplastic plastics as deformable and extruded components or as melt components for physically bonded adhesives and / or sealants, the polymeric materials according to the present invention can be used in thermoplastic plastics as adhesives, preferably in hot melt adhesives, and in crosslinking reactive adhesives, because the polymeric materials according to the present invention allow for low application temperatures and high elasticity and mechanical stability of adhesive bonding.

[0075] In one embodiment, the present invention also relates to polyurethanes obtainable by reacting a polyester polyol, as described herein or obtainable by a method according to the present invention, with a polyisocyanate. The present invention also includes methods for synthesizing / producing such polyurethanes, such as reacting a polyester polyol, as described herein or obtainable by a method according to the present invention, with a polyisocyanate.

[0076] In addition to the polyester polyol of the present invention, other polyols may be used, specifically those that are used in the production of polyurethane according to standards. However, it is preferable that the total amount of the polyester polyol used in the present invention is at least 5 mol%, at least 10 mol%, at least 15 mol%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50 mol%, or at least 70 mol%, or at least 80%, 90%, or 95 mol%.

[0077] Suitable other polyols include (but are not limited to) polyhydroxy ethers (substituted or unsubstituted polyalkylene ether diols or polyhydroxy polyalkylene ethers), polyhydroxy polyesters, ethylene oxide or propylene oxide adducts of polyols, monosubstituted esters of glycerol, and "polymer polyols" (i.e., grafted polyols containing a certain proportion of vinyl monomers, polymerized in situ) and mixtures thereof. Although such compounds are commercially available, methods for synthesizing such compounds are well known in the art. In various embodiments of the invention, such polyols are selected from other polyester polyols, polyether polyols, and combinations thereof.

[0078] Suitable polyether polyols include straight-chain and / or branched-chain polyethers having a plurality of ether bonds and at least two hydroxyl groups, and substantially free of functional groups other than hydroxyl groups. Examples of such polyether polyols may include polyoxyethylene polyols, such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polybutane glycol, and the like. Furthermore, homopolymers and copolymers of such polyoxyethylene polyols or mixtures thereof may also be used. Particularly preferred copolymers of such polyoxyethylene polyols may include at least one adduct of a compound selected from the group consisting of ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, 2-ethylhexanediol-1,3-glycerol, 1,2,6-hexanetriol, trimethylolpropane, trimethylolethane, tris(hydroxyphenyl)propane, triethanolamine, and triisopropanolamine, and at least one compound selected from the group consisting of ethylene oxide, propylene oxide, and butylene oxide. Although such compounds are commercially available, the methods for synthesizing such compounds are well known in the art. Non-limiting examples of commercially available polyols that can be used in the practice of this invention include polyethers, such as polyethertriols, such as those having a molecular weight of about 3,000 to 9,000, for example 4,000 to 8,000, such as about 6,000; OH-terminated polybutadienes, such as those having a molecular weight of about 2,000 to 4,000, for example 25,000 to 3,500, such as about 2,800; castor oil; and OH-terminated prepolymers available under the trade name Loctite UK 8201 HF (Henkel).

[0079] Suitable other polyester polyols are formed by the condensation of one or more polyols having about 2 to about 15 carbon atoms with one or more polycarboxylic acids having about 2 to about 14 carbon atoms. Examples of suitable polyols include ethylene glycol, propylene glycol (such as 1,2-propanediol and 1,3-propanediol), glycerol, neopentyl tertrol, trimethylolpropane, 1,4,6-octanetriol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,4-pentanediol, hexanediol, dodecanediol, octanediol, chloropentanediol, glyceryl monoallyl ether, glyceryl monoethyl ether, diethylene glycol, 2-ethylhexanediol, 1,4-cyclohexanediol, 1,2,6-hexanetriol, 1,3,5-hexanetriol, 1,3-bis(2-hydroxyethoxy)propane, and the like. Although these compounds are commercially available, the methods for synthesizing them are well known in the art. Commercially available semi-crystalline polyester polyols suitable for use in this invention include, for example, Dynacoll 7380 and 7360 (Creanova), Fomrez 66-32 (Crompton), and Rucoflex S-105-30 (Bayer).

[0080] Suitable hydroxyl polycarbonates can be obtained by reacting carbonate derivatives, such as diphenyl carbonate, dimethyl carbonate, or phosgene with diols. Suitable examples of such diols include ethylene glycol, 1,2- and 1,3-propanediol, 1,3- and 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, neopentyl glycol, 1,4-dimethylolcyclohexane, 2-methyl-1,3-propanediol, 2,2,4-trimethylpentanediol-1,3, dipropylene glycol, polypropylene glycol, dibutylene glycol, polybutanediol, bisphenol A, tetrabromobisphenol A, and lactone-modified diols. The diol component preferably contains 40 to 100% by weight of hexanediol, preferably 1,6-hexanediol and / or hexanediol derivatives. More preferably, the diol component includes examples showing ether or ester groups except for the terminal OH group. The hydroxyl polycarbonate should be generally linear. However, it may be slightly branched as needed by incorporating a polyfunctional component, specifically a low-molecular-weight polyol. Suitable examples include glycerol, trimethylolpropane, hexanetriol-1,2,6, butanetriol-1,2,4, trimethylolpropane, neopentyl tetrol, quinitol, mannitol and sorbitol, methyl glycosides, and 1,3,4,6-didehydrohexitol. Suitable polycarbonate polyols are (but are not limited to) those available under the trademarks Desmophen® C3200 (Bayer) and Kuraray® C2050 (poly-(3-methyl-1,5-pentanediol, 1,6-hexanediol) carbonate; Kuraray).

[0081] Polyurethanes can be produced using common polyisocyanates. Organic polyisocyanates suitable for practicing this invention include alkyl diisocyanates, cycloalkyl diisocyanates, aromatic diisocyanates, and aliphatic-aromatic diisocyanates. Specific examples of suitable isocyanate-containing compounds include (but are not limited to) ethyl diisocyanate, ethylene diisocyanate, propyl diisocyanate, butyl diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, cyclopentene-1,3-diisocyanate, cyclohexyl-1,4-diisocyanate, cyclohexyl-1,2-diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,2-diphenylpropane-4,4'-diisocyanate, xylene diisocyanate, 1,4-naphthalene diisocyanate, 1,5-naphthalene diisocyanate. Isocyanates, m-phenylene diisocyanate, terephthalene diisocyanate, diphenyl-4,4'-diisocyanate, azobenzene-4,4'-diisocyanate, diphenylazon-4,4'-diisocyanate, 2,4-toluene diisocyanate, dichlorohexamethylene diisocyanate, furanylene diisocyanate, 1-chlorobenzene-2,4-diisocyanate, 4,4,4''-triisocyanate triphenylmethane, 1,3,5-triisocyanate benzene, 2,4,6-triisocyanate toluene, 4,4'-dimethyldiphenylmethane-2,2',5,5-tetratetraisocyanate, and the like. Although these compounds are commercially available, the methods used to synthesize them are well known in the art. Preferred isocyanate-containing compounds are those that are (crystalline) solids at room temperature, including (but not limited to) polymers of methylene diphenyl diisocyanate (MDI) and toluene diisocyanate (TDI), such as dimers or trimers, specifically TDI dimers having urea or urea diketone bridges. In various embodiments, the polyisocyanate used is (but not limited to) 4,4'-, 2,2'-, or 2,4'-MDI.

[0082] Polyurethane can be obtained by using a polyisocyanate with a molar excess of NCO to OH ratio. In these embodiments, the obtained polyurethane may be an NCO-terminated polyurethane. For this purpose, the molar ratio of the total NCO groups of the polyisocyanate to the total hydroxyl groups of the polyol is greater than 1.00:1.00, for example 1.1:1, but may be in the range of up to, for example, 3:1 or 2:1. In some embodiments, the ratio of hydroxyl to NCO groups may be in any combination of an upper limit selected from less than 0.99:1, 0.975:1, 0.95:1, 0.9:1, 0.85:1, 0.8:1, 0.75:1 or 0.7:1 and a lower limit selected from 0.65:1, 0.7:1, 0.75:1, 0.8:1, 0.85:1, 0.9:1. In some embodiments, the ratio is in the range of 0.65 to 0.95:1. In a particular embodiment, the ratio is 0.7 to 0.9:1.

[0083] Alternatively, the NCO to hydroxyl ratio may be less than 1:1, for example, up to 1:3 or up to 1:2. In various embodiments, this ratio may be within any combination of an upper limit selected from less than 0.99:1, 0.975:1, 0.95:1, 0.9:1, 0.85:1, 0.8:1, 0.75:1, or 0.7:1 and a lower limit selected from 0.65:1, 0.7:1, 0.75:1, 0.8:1, 0.85:1, or 0.9:1. In some embodiments, the NCO to hydroxyl ratio may be in the range of 0.65 to 0.95:1. An excess of hydroxyl groups means that the PU obtained after curing is preferably hydroxyl-terminated.

[0084] The polyurethanes of this invention may be part of adhesive or coating compositions that also form part of this invention. These may additionally contain all additives known and conventional for such adhesives and coating compositions.

[0085] Such additives, which are inert to other components in the PU compositions of the present invention and in the conventional field of PU formulations to meet different properties and specific application requirements, may be included in the PU compositions as needed from 0% to about 40% by weight, for example up to about 20% by weight. These additives include, for example, diluents, plasticizers, fillers, driers, rheology modifiers, pigments, dyes, curing catalysts, and adhesion promoters, which may be incorporated into the adhesive formulation in small or larger quantities depending on the purpose.

[0086] In various embodiments, the composition is an adhesive composition, such as a reactive hot melt adhesive composition.

[0087] Instance Method

[0088] Catalyst test for hydrogenation of 5-HMF aqueous solution. In typical screening of catalysts and reaction conditions, oven-dried 4 mL glass vials equipped with magnetic stir bars were used. A specific amount of heterogeneous catalyst was added to each vial to have a final metal content of 1.26 mg, corresponding to 1% by weight of the 5-HMF used. Subsequently, 560 µL (1 mmol) of crude 5-HMF aqueous solution (c = 1.79 mol / L) and 1 to 2 mL of ethanol were added to each vial. These vials were placed in aluminum inlets and sealed with PTFE / rubber diaphragms punctured by needles. Three vials were placed in the same aluminum inlet and then transferred to a 300 mL stainless steel autoclave from Parr. The autoclave was purified three times with 20 bar N2 and then twice with 10 bar H2. Finally, the autoclave was pressurized with 25 bar or 90 bar H2 and placed in a preheated aluminum block at 100°C. After the required time, place the reactor at room temperature and carefully reduce the pressure. Filter the reaction mixture through a diatomaceous earth liner, using ethanol as the solvent. Evaporate the solvent from the collected solution; add 1,4-dinitrobenzene as an internal standard and determine the conversion, yield, and cis / trans ratio by NMR spectroscopy.

[0089] Screening of catalysts and reaction conditions for hydrogen borrowing. In a typical reaction, a 10 mL pressure Schlenk tube (product number: F580810) equipped with a magnetic stir bar and dried in an oven from FengTecEx is used. Separate amounts of catalyst and base are loaded into the Schlenk tube under an argon atmosphere inside a glove box; the Schlenk tube is sealed with a Teflon screw cap and removed from the glove box. Subsequently, the desired solvent (4.0 mL or 2.0 mL) and 1.0 mmol (132 mg) of degassed cis-enriched DHMTHF (92% / 8% cis:trans) are added under a constant argon flow. The Schlenk tube is resealed with a Teflon screw cap and placed in a preheated oil bath at the desired temperature, where the mixture is stirred (500 rpm) for 24 hours. The reaction is then stopped and allowed to cool to room temperature. The mixture was filtered through a silica short pad under a constant argon flow using diethyl ether as the solvent. The solvent was then removed using a rotary evaporator, and the yield of DHMTHF was determined. Finally, aliquots of the product were analyzed by NMR spectroscopy to determine the cis / trans ratio.

[0090] Acetylation of cis / trans-DHMTHF. 20.0 g (151 mmol) of DHMTHF containing 44% of the trans isomer and acetic anhydride (34.0 mL, 360 mmol) were added to a round-bottom flask equipped with a reflux condenser. The mixture was heated to 140 °C with stirring, and after reaching this temperature, stirring was continued for 3 h. The mixture was then allowed to cool, and the formed acetic acid was removed under high vacuum at 70 °C. The resulting near-brown liquid system of the corresponding diacetate of DHMTHF was readily available for use in the following steps without any further purification. Yield: 32.3 g (99%).

[0091] Crystallization of trans-DHMTHF. 245.0 g of diacetylated-DHMTHF (61% cis / 39% trans) was transferred to a round-bottom flask and dissolved in 80 mL of anhydrous Et 2O. After the crude mixture was left at -15°C for more than 12 h, trans-enriched diacetylated-DHMTHF precipitated out of the solution as a white crystalline solid. The crystalline precipitate was filtered through a Buchner funnel fitted with filter paper (both pre-cooled in a refrigerator) and washed three times with cold Et 2O. Finally, the crystalline solid was dried under high vacuum. Yield: 63.0 g (66%), cis / trans ratio: 15% / 85%.

[0092] Hydrolysis of diacetylated-DHMTHF ester (Example of trans-enrichment of diacetylated-DHMTHF). A magnetic stir bar and 63.0 g of trans-enriched diacetylated-DHMTHF (291 mmol) were placed in a 1000 mL double-necked round-bottom flask equipped with a condenser. 40.0 mL of ethanol was added to predissolve the crystalline material. Subsequently, 600 mL of 4 M NaOH aqueous solution was added dropwise at 40 °C with stirring over 2 h. After complete addition, the mixture was stirred for another 48 h. The water was then removed using a rotary evaporator, and the resulting viscous suspension was filtered through silica using EtOAc as the precipitate. After removing the volatiles under reduced pressure, trans-enriched DHMTHF was obtained as a colorless liquid by vacuum distillation (0.3 mbar) at 130 °C. Yield: 27.6 g (72%), cis / trans ratio: 15% / 85%.

[0093] Synthesis of Polyester-Polyol. Dodecanoic acid and DHMTHF were charged into a 250 mL three-necked flask equipped with a mechanical stirrer, a Widmanstätten column, and a distillation bridge, attached to another 250 mL round-bottom flask for collecting water. The entire apparatus was purified with nitrogen for 1 h, and the mixture was then heated to 120 °C. The reaction was maintained at this temperature for 1 h, and then the temperature was further increased to 140 °C. The temperature was then continuously increased in increments of 20 °C up to 220 °C, and after each increase, it was maintained for at least 1 h. At 220 °C, a vacuum was applied, slowly decreasing from 850 mbar to 15 mbar. After 27 h at 220 °C and 15 mbar, the reaction mixture was cooled to 120 °C and the vacuum was released. Titanium isopropoxide (IV) was added as a catalyst, and the mixture was reheated to 220 °C and a vacuum (15 mbar) was applied. Finally, after another 7 h at 220°C under vacuum, the reaction mixture was cooled and the successful conversion was assessed by acid value titration using 0.1 M KOH aqueous solution and phenolphthalein as an indicator.

[0094] Formation of polyurethane membrane. 50 g of polyester (example: OH value 27) was charged into a 250 mL three-necked flask equipped with a mechanical stirrer and condenser. The polymer was heated to 80°C and maintained at this temperature under vacuum (<0.001 mbar) for 1.5 hours. Then, 2.2 equivalents of 4,4'-MDI (6.64 g) were added, and the mixture was stirred for 1 h under a nitrogen atmosphere. The obtained polymer was used to cast membranes with a thickness of 1 mm, and these membranes were stored under ambient conditions for one week.

[0095] Example 1: Hydrogenation of 5-HMF aqueous solution 56.0 mL (100 mmol) of 5-HMF aqueous solution (c = 1.79 mol / L) and 140.0 mL of ethanol were added to a 300 mL stainless steel autoclave (Parr) equipped with a PTFE horizontal stir bar (length: 38 mm). Subsequently, Raney nickel catalyst (2.5 g solid catalyst) in aqueous suspension form was added to the mixture. The autoclave was then closed, purified three times with 20 bar N₂, twice with 20 bar H₂, and finally pressurized with 90 bar H₂ and placed in an aluminum block preheated at 100 °C. The mixture was stirred at 650 rpm for 12 h, and then the autoclave was cooled to room temperature, repressurized with 90 bar H₂, and placed in the aluminum block at 100 °C for another 12 h. After a total of 24 h, the reactor was carefully depressurized at room temperature. The reaction mixture was filtered through a pleated filter, with the filter paper being continuously rinsed with ethanol with particular care. After evaporation of the solvent, a nearly brown liquid was obtained. Then, DHMTHF, a colorless viscous liquid, was collected by distillation at 130°C under vacuum (0.4 mbar) with a 92% yield (12.1 g) and a 92% cis content.

[0096] Table 1. Catalyst test for hydrogenation of aqueous 5-HMF. item catalyst Conversion rate 5-HMF a Y BHMF a Y DMF a Y DHMTHF a, b 1 Ra-Ni c 86% 7% 0% 78% (92% / 8%) 2 Ru / C >99% 2% 1% 96% (85% / 15%) 3 Pd / Al 92% 16% 0% 74% (88% / 12%) 4 Pd / C 99% 1% 1% 92% (80% / 20%) 5 Pt / C 80% 75% 4% <1% (nd) Reaction conditions: 0.56 mL (1.0 mmol) 5-HMF aqueous solution (c = 1.79 mol / L), 2.0 mL EtOH, 1 wt% (metal-based) heterocatalyst, 100 °C, 90 bar H₂, 5 h; a - determined by NMR using 1,4-dinitrobenzene as an internal standard (added after hydrogenation); b - in parentheses, report the ratio between the cis and trans isomers; c - 20 mg Ra-Ni slurry used in water. Conv. = conversion; Y = yield

[0097] Example 2: Cis-isomerization to trans-DHMTHF was performed using a hydrogen-based method. A PTFE horizontal stir bar and 23.8 g of cis-enriched DHMTHF-diol (180 mmol) were loaded into a 300 mL autoclave (Parr). The autoclave was then closed and a vacuum was applied for 30 min. Subsequently, 263.9 mg of Ru-3 (0.25 mol%), weighed from a vial inside a glove box, was added to the autoclave under a constant argon flow. Finally, 180.0 mL of toluene and 11.7 mL of KO tPen (10 mol%; 1.7 mol / L toluene solution) were added under argon. The autoclave was purified three times with 20 bar N₂ and placed inside a preheated aluminum block at 100 °C. The mixture was stirred (600 rpm) for 16 h within the aluminum block. The reaction mixture was then allowed to cool at room temperature and transferred to a round-bottom flask. Toluene was removed on a rotary evaporator and the final mixture was filtered through silica using diethyl ether as the solvent under a constant argon flow. The diethyl ether was then removed on the rotary evaporator and a viscous, colorless liquid DHMTHF cis / trans mixture was obtained by distillation under vacuum at 0.3 mbar and 130 °C in 94% yield (22.3 g).

[0098] Table 2. Catalyst screening for isomerization cis enrichment of DHMTHF. item catalyst Y DHMTHF a cis contentb trans content b 1 Ru-1 90% 74% 26% 2 Ru-2 87% 56% 44% 3 Ru-3 89% 70% 30% 4 Ru-4 93% 87% 13% 5 Ru-5 91% 57% 43% 6 Ru-6 91% 75% 25% 7 Ru-7 85% 67% 33% 8 Ru-8 95% 57% 43% 9 Ru-9 93% 76% twenty four% Reaction conditions: 1 mmol cis enrichment of DHMTHF, 4 mL toluene, 140 °C, 24 h; a - separation yield; b - cis / trans ratio as determined by NMR spectroscopy.

[0099] Table 3. Optimization of reaction conditions for isomerization of cis-enrichment of DHMTHF. Item Catalyst (mole %) Alkali (mol%) T [℃] Ya DHMTHF cis content b trans content b 1 Ru-2 (0.5) KOtBu (10) 100 91% 55% 45% 2 Ru-3 (1.0) KOtBu (10) 100 90% 56% 44% 3 Ru-3 (1.0) KO t Bu (10) 60 93% 92% 8% 4 Ru-3 (1.0) KO t Bu (10) room temperature 95% 92% 8% 5 Ru-3 (1.0) KO t Bu (5) 100 93% 88% 12% 6 Ru-3 (1.0) KO t Bu (20) 100 88% 56% 44% 7 Ru-3 (1.0) - 100 92% 92% 8% 8 - KO t Bu (10) 100 84% 92% 8% 9 c Ru-3 (1.0) KO t Bu (10) 100 88% 76% twenty four% 10 Ru-3 (1.0) KO t Pen (10) 100 94% 55% 45% 11 Ru-3 (0.25) KO t Pen (10) 100 90% 55% 45% 12 Ru-3 (0.1) KO t Pen (10) 100 92% 57% 43% Reaction conditions: 1 mmol cis enrichment of DHMTHF, 2 mL solvent, 24 h; a - separation yield; b - cis / trans ratio determined by NMR spectroscopy; c - the reaction was carried out at 3 bar H 2 in a 4 mL vial with a needle-punctured PTFE / rubber diaphragm inside a 300 mL autoclave.

[0100] Example 3: Effect of DHMTHF diastereomeric derivatives on the properties of polyesters and polyurethanes. To examine the effect of incorporating two diastereomeric derivatives of DHMTHF into the polymer of an adhesive, novel and potentially 100% bio-based polyester polyols were synthesized using a combination of previously prepared diastereomeric mixtures (92:8, 57:43, 15:85) and dodecanoic acid (DDA). The polyester was thus prepared according to a two-stage melt condensation method, wherein (I) pre-condensation was performed under ambient pressure while the temperature was gradually increased from 120°C to 220°C, and (II) condensation was performed under vacuum in the presence of a catalytic amount of titanium isopropoxide (IV). The synthesized polyester had a measured hydroxyl number within the desired range (OH-N = 25 to 34 mg g⁻¹) and formed only a small amount of byproducts. Therefore, DHMTHF has been successfully used as a monomer in industrially superior melt condensation methods to produce polyester polyols with low acid values ​​(AN = 1 to 3 mg g⁻¹), high viscosity at room temperature, and honey-like viscosity at 80°C (see Table 4).

[0101] To investigate the effect of two different diastereomers on the thermal behavior of the derived polymers, differential scanning calorimetry (DSC) was performed (Figure 4). Interestingly, independent of the diastereomer mixtures used, all synthesized polyester polyols showed semi-crystalline properties indicated by the presence of at least two melting points. It should be noted that the integral area result of the latter is proportional to the molar fractions of cis and trans DHMTHF in the diol mixture. Specifically, the polyester polyol obtained from cis-enriched DHMTHF showed a dominant crystalline region with a peak temperature of 1 °C, which may be related to the cis isomer, and two small melting peaks concentrated at 11 °C and 21 °C, which are equivalent to the results of the crystalline phases with mixed and trans enrichment contents, respectively (Figure 4, bottom curve). Therefore, in the polymer based on trans-enriched DHMTHF, the dominant crystalline phase was found to be the one with a melting peak at 21 °C (Figure 4, top curve).

[0102] It is noteworthy that polymers derived from the 57:43 cis / trans DHMTHF mixture also exhibit two different melting points (Figure 4, intermediate curve). Interestingly, the higher the excess of trans DHMTHF used in the synthetic polyester, the higher the degree of crystallinity of the latter. It should be noted that the crystallization temperatures (Tc) of all three polyester polyols are almost identical, with only one peak observed in each case (data not shown).

[0103] To prepare a moisture-curing polyurethane prepolymer using synthesized polyester polyols, 4,4'-diphenylmethane diisocyanate (4,4'-MDI) was reacted in a slight excess with these polyester polyols to produce an isocyanate-terminated polymer, which was then cured in a climate chamber (23°C, 50% relative humidity) to provide a poly(urethane-urea) polymer (PU). Thermogravimetric analysis of the latter revealed good thermal stability in all cases, with a mass loss of 5% at approximately 300°C (see Figure 5).

[0104] Furthermore, the mechanical properties of the polymer were studied through stress-strain testing. As summarized in Table 5, PU films derived from cis / trans DHMTHF polyester polyols exhibited good tensile strength and significantly high elongation. This combination of properties is highly desirable for many applications, such as bonding materials with different coefficients of thermal expansion, or bonding windows and other components in automotive interiors. Although lower than those derived from cis / trans DHMTHF polyester polyols, PU derived from cis and trans-enriched DHMTHF polyester polyols also showed acceptable values ​​for both tensile strength and elongation at break. Therefore, it can be concluded that the balanced ratio of cis / trans DHMTHF to polyester polyol improves mechanical properties.

[0105] Table 4. Results of DHMTHF polycondensation using 1,12-dodecanoic acid. item Cis / Reverse OH-N a [mg / g] AN a [mg / g] M n (Calculated value) b [g / mol] M n (OH-N) a [g / mol] M n (GPC) [g / mol] Đ c η [Pas] d T m [℃] T c [℃] 1 92 / 8 27 3 3741 4156 5022 3.1 122 (4.2) 1 / 11 / 21 -14 2 57 / 43 34 1 3741 3301 4175 2.7 68 (2.4) 2 / 14 -15 3 15 / 85 25 1 3741 4489 6574 2.3 nd e (5.4) 5 / 21 -13 a - determined by titration with KOH aq (0.1 mol / L); OH-N is similar to DIN 53240-1; b - target molecular weight; c - measured by GPC; d - viscosity at 23°C, with the value in parentheses indicating viscosity at 80°C; e - the polyester polyol is a solid at room temperature.

[0106] Table 5. Thermal and mechanical properties of the corresponding PU films. a item Cis / Reverse b ε break [%] F break [Nmm -2 ] T deg (5%) c [℃] T m d [℃] T g d [℃] 1 92 / 8 630 2.0 299 -9 / -1.5 -33 2 57 / 43 1055 12.2 300 -12 -32 3 15 / 85 497 3.0 307 -10 / 5 -33 a - Main chain of DIN 53504-SF3A from 4,4'-MDI chain-stretched film; ε break: elongation at break; F break: stress at break; b - diastereomeric DHMTHF ratio used to synthesize the corresponding polyester polyol; c - measured by TGA; d - determined by DSC.

[0107] In summary, the synthesis of different cis / trans DHMTHF mixtures from aqueous 5-HMF was demonstrated on a multi-gram scale. Specifically, Raney nickel was shown to be active not only in the case of pure 5-HMF as a starting material, but also in the presence of a considerable amount of impurities, for the direct hydrogenation of 5-HMF to cis-enriched DHMTHF. Furthermore, cis DHMTHF was tested for the first time in a hydrogenation reaction, allowing for a significant increase in the trans isomer content while maintaining a high separation yield. Notably, commercially available Ru-trioxides were found to efficiently catalyze the isomerization of cis and trans DHMTHF under alkaline conditions at 100°C. Interestingly, the acetylation of this cis / trans mixture allowed for the separation of the trans isomer via crystallization, for example, in diethyl ether at -15°C. Additionally, the residual liquid containing cis-enriched DHMTHF diacetate was shown to undergo another isomerization / crystallization sequence after hydrolysis, qualifying the latter as a candidate for the synthesis of trans DHMTHF. Finally, the novel polyester polyols were synthesized from different mixtures of DHMTHF and diacids, and preferably from renewable sources. DSC analysis revealed that the higher the amount of trans-DHMTHF, the higher the crystallinity of the resulting polymer. [Simplified Explanation of the Diagram]

[0011] Figure 1 shows the synthesis of DHMTHF according to prior art and the present invention.

[0012] Figure 2 shows a metal-catalyzed hydrogen borrowing reaction for enriching trans DHMTHF in a mixture of cis / trans DHMTHF.

[0013] Figure 3 shows catalysts Ru-1 to Ru-9 in Example 2.

[0014] Figure 4 shows the DSC spectra of polyester polyols derived from different diastereomers in Example 3.

[0015] Figure 5 shows the thermogravimetric analysis of the poly(urethane-urea) polymer derived from the polyester polyol in Example 3.

[0016] Figure 6 shows the DSC spectrum of the poly(urethane-urea) polymer derived from the polyester polyol in Example 3.

Claims

1. A polyester polyol, (A) obtainable by reacting a diastereomeric mixture of cis / trans DHMTHF with a suitable diacid, wherein the diastereomeric mixture of cis / trans DHMTHF has a cis to trans DHMTHF ratio of about 70:30 or less; or (B) comprising monomer units of formulas (Ia) and (Ib), wherein the molar ratio of (Ia) to (Ib) is 70:30 or less, preferably 70:30 to 30:70, wherein the monomer units of formulas (Ia) and (Ib) preferably constitute at least 5 molars of the total polyol units in the polyester polyol, preferably at least 20 molars, more preferably at least 50 molars.

2. A method for producing polyester polyols, the method comprising reacting a diastereomeric mixture of cis / trans DHMTHF with a suitable diacid.

3. The polyester polyol of claim 1 or the method of claim 2, wherein (a) the diacid dicarboxylic acid is preferably an aromatic or aliphatic dicarboxylic acid having 4 to 30 carbon atoms; (b) the diastereomeric mixture of cis / trans DHMTHF has a cis to trans DHMTHF ratio of about 30:70 to 70:30, preferably about 40:60 to about 60:40; (c) the reaction is carried out using a two-stage melt condensation method comprising a pre-condensation step at ambient pressure with gradually increasing temperature from about 120 to about 220°C and a subsequent condensation step under reduced pressure; and / or (d) the polyester polyol has a hydroxyl number of 10 to 150 mg KOH / g.

4. A polyurethane that can be obtained by reacting a polyester polyol, which is obtained by the method of claim 1 or 3 or as claimed in claim 2, with a polyisocyanate.

5. A method for producing polyurethane, comprising reacting a polyester polyol, as claimed in claim 1 or 3 or as claimed in claim 2, with a polyisocyanate.

6. The polyurethane of claim 4 or the method of claim 5, wherein (a) the polyisocyanate is used in molar excess with respect to the NCO to OH ratio; and / or (b) the polyisocyanate is a diisocyanate, 4,4'-MDI as required.

7. A method for producing di(hydroxymethyl)tetrahydrofuran (DHMTHF) from 5-hydroxymethylfurfural (5-HMF), the method comprising hydrogenating a solution of 5-HMF in the presence of a non-homogeneous catalyst, wherein the 5-HMF is crude 5-HMF.

8. The method of claim 7, wherein the 5-HMF is (a) 5-HMF that can be obtained as a side-stream product in a hydrothermal carbonization process of sugars and / or lignocellulosic materials as needed; and / or (b) 5-HMF having a purity of less than 95%.

9. The method of claim 7 or 8, wherein the heterogeneous catalyst is a cis-hydrogenation mode catalyst, preferably selected from Raney nickel, Ru / C (ruthenium supported on carbon), Pd / Al (palladium supported on aluminum oxide), Pd / C (palladium supported on carbon), Pd / Si (palladium supported on silicon dioxide), Ru / Al (ruthenium supported on aluminum oxide), Raney cobalt, Raney copper, and more preferably Raney nickel.

10. The method of any one of claims 7 to 9, wherein the hydrogenation reaction is carried out under the following conditions: (a) in the presence of ethanol at a concentration of at least 1.3 mL of ethanol per 1 mmol of 5-HMF, preferably 1.4 to 3.0 mL of ethanol per 1 mmol of 5-HMF; (b) at an H₂ pressure of at least 10 or at least 20 bar, preferably at least 50 bar, more preferably 80 to 100 bar; (c) at a temperature of 80 to 120°C, preferably at about 100°C; and / or (d) for a reaction time of at least 5 hours, preferably 5 to 60 hours.

11. A method for enriching trans-DHMTHF in a mixture of cis / trans-DHMTHF, the method comprising (A) reacting the mixture of cis / trans-DHMTHF at high temperature in the presence of a metal catalyst suitable for a metal-catalyzed hydrogenation reaction, a base, and a suitable solvent; or (B) (i) acetylating the mixture of cis and trans-DHMTHF with acetic anhydride, if necessary, at high temperature, to obtain a mixture of diacetates of cis and trans-DHMTHF; (ii) crystallizing the diacetates of trans-DHMTHF from a solution of the mixture of diacetates of cis and trans-DHMTHF in a suitable solvent at a temperature allowing for preferential crystallization of trans-DHMTHF; (iii) separating the crystalline diacetates of trans-DHMTHF; and (iv) hydrolyzing the diacetates of trans-DHMTHF under alkaline conditions to obtain enriched trans-DHMTHF.

12. The method of claim 11, wherein in (A), (a) the mixture of cis / trans DHMTHF has a cis to trans ratio of at least 1, preferably at least 2, more preferably 3 to 20; (b) the catalyst is a ruthenium, cobalt, manganese or iron complex catalyst, preferably a ruthenium complex carrying a tridentate pincer ligand, more preferably a ruthenium complex selected from Ru-2, Ru-3, Ru-5 and Ru-8; (c) the reaction temperature is 80°C or higher, preferably 80 to 120°C; (d) the base is a strong base, preferably selected from metal alkoxides, more preferably selected from potassium butoxide, sodium butoxide, potassium pentanoxide, sodium pentanoxide, sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide; (e) the solvent is selected from the group consisting of: heptane, THF, 1,4-dioxane, toluene, cyclobutane, acetonitrile, 2-MeTHF, and mixtures thereof; (f) The reaction time is 2 to 48 hours, preferably about 4 to 24 hours; (g) the base is used in an amount of at least 7 mol%, preferably at least 10 mol%; (h) the catalyst is used in an amount of 1 mol% or less, preferably about 0.5 mol% or less; (i) the reaction is not carried out under a hydrogen atmosphere; (j) the trans-enriched product contains at least 10 mol% more trans-diastereomer than the cis / trans DHMTHF mixture used as the starting material, preferably at least 20 mol more.

13. The method of claim 11, wherein in (B), (1) the mixture of cis / trans DHMTHF has a cis to trans ratio of 3 or less, preferably 2.5 or less, more preferably 2 or less, most preferably 1.5 or less; and / or (2) the cis DHMTHF enrichment solution remaining after step (iv) is hydrolyzed under alkaline conditions and first subjected to the method of claim 11(A), and the resulting mixture of cis and trans DHMTHF is subjected again to the method of claim 11(B), wherein this sequence of steps is repeated as needed to achieve near stereoselective formation of trans DHMTHF.

14. A composition comprising (a) a diastereomeric mixture of cis / trans DHMTHF obtained as in any of the methods of claims 7 to 13; (b) a diastereomeric mixture of cis / trans DHMTHF in a molar ratio of cis to trans diastereomerics of 70:30 or less, preferably 70:30 to 30:70; (c) a polyester polyol as in claim 1 or 3 or obtainable as in claim 2; or (d) a polyurethane as in claim 4 or obtainable as in claim 5.

15. The composition of claim 14, wherein the composition is an adhesive composition.

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