Oxidation-stable dianhydrohexitol composition containing gallate ester

Abstract

The present invention relates to a method for improving the oxidative stability of compositions of products of internal dehydration of hydrogenated sugars, in particular isosorbide compositions, which method is based on the use of gallic acid esters. The present invention also relates to the compositions obtained according to this method and to their various uses.

Description

[Technical Field]

[0001] The present invention relates to a method for improving the oxidative stability of compositions of internal dehydration products of hydride sugars, particularly isosorbide compositions, and the method is based on the use of gallic acid esters. The present invention also relates to compositions obtained according to this method and various uses thereof. [Background technology]

[0002] The use of renewable biological resources has become a major ecological and economic necessity in the face of their depletion and rising prices of fossil fuels such as oil. The development of 1,4:3,6-dianehydrohexitol has been underway for several years.

[0003] Such products, also called isohexides, are obtained by the internal dehydration of C6 hydride sugars (hexitols) such as sorbitol, mannitol, and iditol. In this application, the term “dianhydrohexitol” encompasses isosorbide (1,4-3,6-dianhydro-sorbitol), isomannide (1,4-3,6-dianhydro-mannitol), isoidide (1,4-3,6-dianhydro-iditol), and mixtures thereof, as defined below.

[0004] [ka]

[0005] Today, isohexides, particularly isosorbide, have high potential for industrial development, and their use is envisioned for the preparation of the following: - Isosorbide 2-nitrate, 5-nitrate, or 2,5-dinitrate useful for the therapeutic treatment of diseases, especially cardiovascular diseases, alkylated, especially dimethylated isosorbide derivatives, particularly useful as solvents in the preparation of pharmaceutical or cosmetic compositions. - Isosorbide derivatives for use in fuel cleaning agent compositions, - Alkylated or alkenylated derivatives that can be used as plasticizers in polymers, adhesives, or inks. - Certain biphosphites that can be used as polymers or lubricant stabilizers. - Articles based on polymers and copolymers such as polyvinyl alcohol, polyurethane, polyester, and polycarbonate. - Biodegradable polycondensates, - Water-based lacquers or compositions for coating and / or coloring surfaces.

[0006] However, it is well known that when polyols such as hexitol are subjected to a dehydration process (e.g., sorbitol), they can be converted into a variety of co-products in addition to the desired dehydration product (e.g., isosorbide), such as the following: -Isomers of the desired product, for example, isosorbide isomers such as isomannide and isoidide, - A product that is less dehydrated than the desired product or its isomer, for example, sorbitan, mannitan, or iditan. - Derivatives resulting from the oxidation or more generally decomposition of the aforementioned products, these derivatives may include, for example, deoxymonoanhydrohexitol, monoanhydropentitol, monoanhydrotetriitol, anhydrohexose, hydroxymethylfurfural, or glycerol-type co-products when the desired product is isosorbide. - Derivatives obtained from polymerization of the above products, and / or strongly colored species with unclear properties.

[0007] Furthermore, there is an entire body of literature directed toward techniques aimed at obtaining compositions from the process that are improved in terms of purity or stability by changing the reaction conditions during the dehydration process, or by applying one or more purification treatments after the process, or even by combining these different means.

[0008] In this first category, we can cite Canadian Patent No. 1178288 (page 14, lines 3-8), which recommends carrying out the dehydration reaction under an inert gas atmosphere to avoid oxidation reactions, especially when relatively high temperatures and reaction times are anticipated. Similarly, U.S. Patent No. 4,861,513 describes carrying out a sorbitol dehydration reaction in the simultaneous presence of an inert gas (nitrogen) and a reducing agent (sodium hypophosphite) to prepare a mixture of certain polyols having a low content (10-26 wt% solids) of dianhydrosorbitol.

[0009] In the second category, one can refer to U.S. Patent No. 4,564,692, which describes the preliminary purification of an isosorbide or isomannide composition on an ion exchanger and / or activated carbon, followed by concentration by evaporation and crystallization in water after seeding of the desired isohexide crystals, but is not detailed in any respect. The inventors can also refer to International Publication No. 01 / 94352, which teaches purification by treatment with an ion exchange means followed by a decolorizing means.

[0010] Finally, in the third category, British Patent No. 613,444 describes obtaining an isosorbide composition by dehydration in a xylene medium in a water / xylene medium, followed by distillation, and then recrystallization in an alcohol / ether mixture. European Patent No. 0323994, on the other hand, envisions the use of specific dehydration catalysts (gaseous hydrogen halide and liquid hydrogen fluoride, respectively) in combination with a carboxylic acid as a co-catalyst, followed by distillation of the crude isosorbide or isomannide composition thus obtained.

[0011] In contrast to this prior art, the applicant has made two distinct observations: not only does the level of stability of the isohexide composition not correlate with its level of purity, but the use of agents such as nitrogen gas or sodium borohydride (at the latest at the distillation stage), as described in the prior art, does not significantly improve this stability.

[0012] In the course of further research, the applicant surprisingly and unexpectedly found that only 1) a specific stabilizer (in this case, in a non-gaseous form) and 2) applied at a specific point in the preparation method (in this case, after the actual distillation step) enable the preparation of isohexide compositions having improved storage behavior at least at room temperature or a moderate temperature. [Overview of the project]

[0013] The present invention is the subject of European Patent No. 1446373, and is a method for preparing a composition containing at least an internal dehydration product of hydride sugar, a) A step of distilling a medium containing internal dehydration products to obtain a distillate in which these products are concentrated, b) Optionally, at least one subsequent step of purifying the distillate thus obtained, c) A subsequent step in which the distillate obtained during step a) and subsequently optionally subjected to step b) is brought into contact with an agent capable of improving the stability of the internal dehydration products mainly contained in the distillate, wherein the agent is not in gaseous form. d) A method comprising, optionally, a subsequent step of forming the resulting composition of internal dehydration products of hydrase sugars.

[0014] This document concerns several possibilities for the modifiers used in step c), which can be selected from the following: - Reducing agents, especially boron or aluminum-based compounds, such as sodium borohydride (NaBH4) or lithium aluminhydride (LiAlH4), - Phosphates or phosphorus-based compounds such as phosphine or phosphate, - Antioxidants, particularly nitrogen compounds, especially aromatic or non-aromatic amines containing or not containing at least one alcohol functional group, such as hydroxylamines, morpholine, and their derivatives. - An aromatic, nitrogen-containing or non-nitrogen-containing compound, which may or may not contain at least one alcohol functional group, such as hydroquinone, phenol, tocopherol and their respective derivatives, - Phosphites, phosphonates, sulfites, salts of esters of thiodipropionic acid and mixtures thereof, - Antacids, - Metal deactivators such as metal complexing or chelating agents of natural origin, - Products approved as food additives, particularly antioxidants, acidity correctors or sequestering agents within the meaning of European regulations, such as ascorbic acid (vitamin C), erythorbic acid, lactic acid, citric acid, gallic acid, tocopherol, derivatives of all these products (particularly salts), BHT, butylated hydroxyanisole (BHA) and any mixtures of these products.

[0015] Therefore, the Applicant has demonstrated that by implementing such a method, particularly stable compositions are joined. A stable composition in the meaning of European Patent No. 1446373 refers to a composition having both a formic acid content of less than 0.0005% and a total monoanhydrohexose content of less than 0.005%, which has been stored at a temperature of 40 °C for at least one month in a non-inert atmosphere, and these percentages are expressed by the dry weight relative to the dry weight of the composition.

[0016] This stability can reach more than one month, at least two months, preferably at least six months, and even more preferably at least one year for the compositions obtained using the method described above. As modifiers used during step C), European Patent No. 1446373 lists, by way of example, sodium borohydride, morpholine, BHT, vitamin C, sodium borate, sodium hydroxide and disodium phosphate, and the best results (six months of stability) have been obtained for sodium borohydride and morpholine.

[0017] By working on the improvement of the latter method, the Applicant has been able to show that the influence of the nature of the agent introduced in step c) of the method, and the specific choice of monoethanolamine, diethanolamine (DEA), triethanolamine (TEA) or mixtures thereof leads to particularly advantageous results (this matter forms in particular the subject matter of European Patent No. 2991991). These results are supported by the pH monitoring over time of the compositions thus stabilized. A stable composition in the meaning of European Patent No. 2991991 refers to a composition whose pH does not change significantly at 50 °C for at least one month.

[0018] Continuing the research to obtain more stable hydrogenated sugar internal dehydration product compositions, the Applicant has reached the conclusion that oxidation is the dominant phenomenon. In other words, the stability of the said compositions is governed, inter alia, by their resistance to oxidation. In that context, the Applicant has identified a specific class of chemical compounds that are particularly effective in improving the oxidation stability: gallic acid esters, also known as gallates.

[0019] It is also to the credit of the Applicant that they considered using their own mechanism, the so-called "PetroOxy" test, to demonstrate the effectiveness of these compounds. This test uses a device of the same name, commercially available from Anton Paar GmbH, which is commonly used to evaluate the oxidation resistance of distillate fuels. This experiment is based on the accelerated oxidation of a sample placed in a sealed chamber filled with oxygen up to a pre-fixed pressure and heated to a given temperature. Under these conditions, the oxidation of the sample is accelerated, and as a result, the pressure in the chamber decreases. The oxygen pressure difference is then measured inside the cell. The induction time is determined by the evaluation of the oxygen consumption rate over time.

[0020] The induction period is the initial stage of the oxidation process, during which the reaction is slow due to the low concentration of the reaction intermediate. After this period, the reaction becomes more rapid, leading to a sharp change in oxygen pressure. This determines the induction time, which corresponds to the duration of this initial induction period. For the use of the "PetroOxy" test and the interpretation of its results, please refer to the Examples chapter of this application.

[0021] Advantageously, this method made it possible to demonstrate that certain compounds in the prior art, which are said to be effective in terms of pH stability, do not affect the oxidation phenomenon. This is the case with disodium phosphate. This method also demonstrated the value of DEA and TEA as agents for improving oxidation resistance. However, this is particularly noteworthy by surprising the exclusion of previously known antioxidants that have a negative effect on isosorbide, and by identifying a class of compounds, gallic acid esters, that were particularly effective in terms of their antioxidant power against isosorbide. None of the compounds known to date, not even DEA and TEA, have achieved such antioxidant power against isosorbide.

[0022] In the prior art, no method used to prepare internal dehydration product compositions of hydride sugars has suggested that gallic acid esters conferring such resistance to oxidation of the composition have occurred. Similarly, there has been no system that would allow those skilled in the art to test a so-called "PetroOxy" device to identify compounds effective against oxidation in internal dehydration product compositions of hydride sugars. It is to the credit of the present applicant that such results have been achieved.

[0023] Therefore, the first subject of the present invention is a method for preparing an internal dehydration product composition of hydride sugars, a) A step of distilling a medium containing internal dehydration products to obtain a distillate in which these products are concentrated, b) Optionally, at least one subsequent step of purifying the distillate thus obtained, c) A subsequent step in which the distillate obtained during step a) and subsequently subjected to step b) is placed in the presence of at least one gallic acid ester, d) A method comprising the optional subsequent step of forming the resulting composition of internal dehydration products of hydride sugars.

[0024] Preferably, the gallate ester carried out in step c) is selected from alkyl esters, more preferably from ethyl gallate and propyl gallate and mixtures thereof. Even more preferably, the gallate ester carried out in step c) is propyl gallate.

[0025] In the first preferred variant, step c) also carries out the preparation of a phosphate compound, preferably disodium phosphate.

[0026] In a second preferred variant, step c) also carries out an amine, preferably an alkylamine, more preferably an amine selected from diethanolamine and triethanolamine, and very preferentially diethanolamine.

[0027] The method according to the present invention is advantageously characterized in that the gallic acid ester carried out in step c) is used in an amount of 0.0001 to 2%, preferably 0.001 to 2%, more preferably 0.002 to 1.5%, and even more preferably 0.002 to 0.1%, where these percentages are expressed as the dry weight of the gallic acid ester relative to the dry weight of the internal dehydration product of the hydride sugars mainly present in the distillate at that time, for example, the isosorbide present in the medium at that time.

[0028] In the first preferred variant described above, the phosphate compound used in step c) is advantageously used in a proportion of 0.0001 to 2%, preferably 0.001 to 2%, more preferably 0.002 to 1.5%, and even more preferably 0.002 to 0.1%, where these percentages are expressed by the dry weight of the phosphate compound relative to the dry weight of the internal dehydration product of the hydride sugars that are then predominantly present in the distillate, for example, the dry weight of the isosorbide present in the medium at that time.

[0029] In the second preferred variant described above, the amine used in step c) is advantageously used in a proportion of 0.0001 to 2%, preferably 0.001 to 2%, more preferably 0.002 to 1.5%, and even more preferably 0.002 to 0.1%, where these percentages are expressed by the dry weight of the amine relative to the dry weight of the internal dehydration product of the hydride sugars that are then predominantly present in the distillate, for example, the isosorbide present in the medium at that time.

[0030] In the context of the method according to the present invention, it should be noted that the medium subjected to step a) can have a wide variety of properties, including dryness, temperature, and / or purity of the desired dehydrated product. Thus, the purity of the medium subjected to step a) with respect to the desired product, e.g., isosorbide, can be 50-80%, or more than 80% (as a mass percentage relative to the total mass of the medium subjected to step a). According to a first variant, it may be an isosorbide composition consisting of a medium directly derived from an actual dehydration reaction, having, for example, a desired product purity (e.g., isosorbide) of about 50-80%. According to another possibility, the composition may already be obtained from one or more prior purification operations, particularly by distillation and / or crystallization, and having, for example, a desired product purity (e.g., isosorbide) of more than 80%.

[0031] Advantageously, the distillation step a) is followed by step b) for purifying the obtained distillate. According to the first variant, step b) generally consists of a purification step in which the distillate, placed in solution, is treated with at least one purification means selected from a color-changing means and an ion-exchange means.

[0032] The color-changing means is understood to mean, in particular, granular or powdered activated carbon and adsorption resins. For example, granular activated carbon such as CECA DC 50 product, powdered activated carbon such as NORIT SX+ product, and / or resins such as DUOLITE XAD 761, MACRONET MN-600, or MACRONET MN-400 can be used alone or in combination. The ion exchange means is understood to mean, in particular, anionic, weak or strong resins, and cationic or strongly cationic resins. For example, strongly anionic resins such as AMBERLITE IRA 910 resin, or strongly cationic resins such as PUROLITE C 150 S resin can be used alone or in combination. The ion exchange means may advantageously include at least one anionic resin and at least one cationic resin. Preferably, this means consists of a mixed bed of an anionic resin and a cationic resin, or a mixed bed of a series of cationic resins followed by an anionic resin, or a mixed bed of a series of anionic resins and cationic resins.

[0033] Preferably, during step b) of the method according to the present invention, the distillate obtained during step a) is treated in any order with at least one activated carbon and at least one ionic or nonionic resin. Very advantageously, the distillate is first treated with activated carbon, then with at least one resin, and then again with activated carbon. According to another variation of the method according to the present invention, the applicant has found it particularly advantageous that the composition subjected to purification step b) already has certain characteristics with respect to the maximum content of certain impurities, such as formic acid and monoanhydrohexose type species. Furthermore, it has been found that such content can be ensured, in particular, by directly subjecting the distillate obtained during step a) to the purification step b).

[0034] Accordingly, the method according to the present invention may be characterized by the fact that the distillate subjected to step b) has a formic acid content of less than 0.002% and a monoanhydrohexose content of less than 0.02%, these percentages being expressed by the dry weight of the internal dehydration product of the hydride sugars mainly present in the distillate at that time, for example, the dry weight relative to the dry weight of isosorbide present in the distillate. The distillate may, in particular, have a formic acid content of less than 0.0005% and a monoanhydrohexose content of less than 0.005%.

[0035] Advantageously, purification step b) is carried out, and the gallic acid ester and optionally the first variant of the phosphoric acid compound or the second variant of the amine are carried out after step b), in particular by directly introducing the purified aqueous solution of the internal dehydration product obtained from step b), which generally has a temperature equal to at most 60°C.

[0036] After step c), as described above, the internal dehydration product composition of hydride sugar obtained according to the present invention can be molded in the subsequent step d). This step may consist of pelletizing or flakeging the crystallized or lumpy mass obtained from the composition obtained in step c), particularly by cooling by contact with a cold surface.

[0037] If desired, a grinding and / or sieving step may be performed after the molding step d), which is prior to any step of storing and / or bagging the composition thus obtained.

[0038] In another variant, the internal dehydration product composition of hydride sugar obtained according to the present invention can be stored as is, particularly in a liquid or paste state, after step c), without any further specific molding steps. The composition obtained from the method according to the present invention may also be subjected to a concentration step, particularly a vacuum evaporation step, at any point, which is carried out under the lowest possible conditions, particularly with respect to duration and temperature. This step then consists of concentrating the composition to a dry matter content of 50-90%, preferably 75-88%, while maintaining the composition in liquid form. It may also consist of concentrating the composition to obtain a final product in dry form.

[0039] Preferably, it is most advantageous to carry out the concentration step immediately after step c).

[0040] All steps of the above method, including step c) and / or any subsequent steps, particularly molding, storage, or packaging, which are characteristic of the present invention, may be carried out in an inert atmosphere as needed, whether essential or optional.

[0041] The expression "internal dehydration product of hydrinated sugars" particularly includes the internal dehydration products of C6 hydrinated sugars (hexitols) such as sorbitol, mannitol, and iditol, and therefore encompasses isosorbide (1,4-3,6-dianhydro-sorbitol), isomannide (1,4-3,6-dianhydro-mannitol), and isoidide (1,4-3,6-dianhydro-iditol). In a preferred modified form, the method according to the present invention is characterized in that the internal dehydration product of hydrinated sugars is isosorbide.

[0042] As a result, novel means are available to provide compositions of internal dehydration products of hydrides with improved oxidative stability, such as isosorbide compositions, which are required regardless of the intended use of the composition and its purity.

[0043] Therefore, another subject of the present invention relates to a composition containing at least one internal dehydration product of a hydrase, characterized in that it contains at least one gallic acid ester.

[0044] Preferably, the gallate ester is selected from alkyl esters, more preferably from ethyl gallate and propyl gallate, and is also preferably propyl gallate.

[0045] This composition is also characterized by containing 0.0001-2%, preferably 0.001-2%, more preferably 0.002-1.5%, and even more preferably 0.002-0.1%, of gallic acid esters, where these percentages are expressed as the dry weight of the gallic acid esters relative to the dry weight of the internal dehydration product of the hydride sugar.

[0046] In the first variant, the composition is also characterized by containing a phosphate compound, preferably disodium phosphate. Preferably, according to this first variant, the composition contains 0.0001 to 2%, preferably 0.001 to 2%, more preferably 0.002 to 1.5%, and even more preferably 0.002 to 0.1% of the phosphate compound, where these percentages are expressed as the dry weight of the phosphate compound relative to the dry weight of the internal dehydration product of the hydride sugar.

[0047] In the second variant, the composition is also characterized by containing an amine, preferably diethanolamine or triethanolamine, very preferably diethanolamine. Preferably, according to this second variant, the composition contains 0.0001 to 2%, preferably 0.001 to 2%, more preferably 0.002 to 1.5%, and even more preferably 0.002 to 0.1% of the amine, where these percentages are expressed as the dry weight of the amine relative to the dry weight of the internal dehydration product of the hydride sugar.

[0048] In a preferred modified form, this composition is characterized in that the internal dehydration product of the sugar is isosorbide.

[0049] In the first variant, where the composition is in liquid form, the composition is characterized by having a dry matter content of 50-90%, preferably 75-88%.

[0050] In the second variant, the composition is in solid form (and therefore has a dry matter content of 99-100%).

[0051] Such compositions can be used, in particular, for the preparation of polymers or nonpolymers, biodegradable or non-biodegradable products or mixtures for the chemical, pharmaceutical, cosmetic, or food industries. [Brief explanation of the drawing]

[0052] Other features, details, and advantages will become apparent by reading the following examples and accompanying drawings. [Figure 1] This shows how induction time was determined using the oxygen consumption curve obtained from the PetroOxy test. [Examples]

[0053] The following chemicals were used in the following examples. Disodium phosphate (Reference number: Sigma Aldrich S9763) Diethanolamine (Reference number: 398179, Sigma Aldrich) Martol (Reference: W265624, Sigma Aldrich) Trolox (Reference number: 238813, Sigma Aldrich) Gallic acid (Reference number: 398225, Sigma Aldrich) Ethyl gallate (Reference number: 48640, Sigma Aldrich) Propyl gallate (Reference number: 48710, Sigma Aldrich)

[0054] Methodology related to determining the effectiveness of antioxidant additives using the PetroOxy test. 3 g of purified isosorbide distillate aqueous solution (50% DM) is accurately weighed into a glass dish with or without stabilizer, and then placed in a sealed chamber of a measuring device (PetroOxy model 13-3002, manufactured by Petrotest (now Anton Paar GmbH)). The air in the cell is purged three times at room temperature with pure oxygen via a pressurized cylinder (Alphagaz, purity: >99.5%). The pressure of the pure oxygen in the cell is increased to 700 kPa (7 bar of oxygen), and then the cell temperature is fixed at 100°C, allowing the oxygen pressure to fluctuate freely. The pressure is continuously monitored throughout the experiment. After the stabilization stage (pressure increase due to temperature increase), the decrease in pressure in the test chamber is due to the consumption of oxygen during the oxidation reaction of the sample under investigation. The relative pressure changes during the experiment allow for the determination of the time it takes for the sample to begin its decomposition under the test conditions (known as induction time, OIT).

[0055] The solution induction time is determined as follows:

[0056] The relative fluctuation of oxygen pressure within the enclosure, which indicates oxygen consumption, is given by the relation (Pt-Pmax) / Pmax, where Pmax is the maximum pressure of the system over time, corresponding to the maximum pressure during the stabilization phase, and Pt is the pressure as a function of time over which oxygen is consumed. The sample induction time is given by either the inflection point of the oxygen consumption curve; the intersection of two linear regions (see Figure 1).

[0057] The longer the induction time, the greater the oxidation resistance of the sample. To accurately calculate this parameter, a linear regression method is used between two line segments, one before and one after the inflection point.

[0058] Effectiveness of additives regarding antioxidant capacity (E i (as shown) are a solution of isosorbide containing a stabilizer and a solution without a stabilizer (isosorbide without additives, t ref Induction time (t) between ) i Determined by the difference between E i =t i -tref is. A positive effectiveness E i The additive i having has a beneficial effect, but a negative effectiveness E i exhibits harmful effects. The synergistic effect of the mixture of additives is the effectiveness E of the additives in the independently obtained mixture using the same concentration of additives i is greater than the sum of 混合物 resulting in.

[0059] Reference Example: Preparation of an Unstabilized Isosorbide Composition and Study of Its Induction Time. An isosorbide solution is prepared as follows.

[0060] 1 kg of a 70% dry matter (DM) sorbitol solution (commercially available as NEOSORB 70 / 02 by the applicant) and 7 g of concentrated sulfuric acid are introduced into a reactor with a stirring jacket. The resulting mixture is heated under vacuum (100 mbar) for 5 hours to remove the water contained in the reaction medium and the water from the sorbitol dehydration reaction.

[0061] Next, the crude reaction product is cooled to 100 °C and then neutralized with 11.4 g of a 50% sodium hydroxide solution. The isosorbide composition is distilled under vacuum (pressure less than 50 mbar).

[0062] Next, the slightly colored (light yellow) isosorbide distillate is dissolved in isopropanol at a temperature of 60 °C to obtain a homogeneous solution having 75% DM. Then, this solution is slowly cooled to a temperature of 10 °C over 5 hours in this case. Recrystallized isosorbide primer is added at 40 °C.

[0063] Next, the crystals are squeezed with a squeezer and washed with isopropanol. After drying under vacuum, the crystals are dissolved in water to obtain an aqueous solution having 50% DM.

[0064] Next, this solution is filtered over a granular activated carbon (GC12-40) column at a relative rate of 0.5 V / V / h (volume of product / volume of resin per hour). The resulting discolored isosorbide composition is then passed continuously through a strongly cationic resin (PUROLITE C150 S) column and then a strongly anionic resin (AMBERLITE IRA910) column at a rate of 2 V / V / h. Next, this solution is treated with powdered activated carbon (NORIT SX+) at 20°C for 1 hour. The amount of carbon used, y, is 0.5% by weight relative to the dry weight of the solution.

[0065] After filtration through activated carbon, the isosorbide solution is recovered and analyzed according to the method described above.

[0066] The induction time for an isosorbide solution without additives is 5.0 hours. This value is used as a criterion for determining the effectiveness of the additives.

[0067] Non-inventive example 1-1: Preparation of an isosorbide composition with 50 ppm of disodium phosphate added. The synthesis method is the same as in Example 1, but in this case, the additive used is disodium phosphate. Next, 50 mg of disodium phosphate (50 ppm) is added to 2 kg of purified isosorbide solution (50% DM). This solution is analyzed using the methodology described above.

[0068] For a solution to which disodium phosphate was added at 50 ppm, the induction time obtained was 5.0 hours, or the efficacy E was 0. The effect of this additive on the antioxidant properties of isosorbide at this dose is 0.

[0069] Non-inventive example 1-2: Preparation of an isosorbide composition with 100 ppm of disodium phosphate added. The synthesis method is the same as in Example 1, but in this case, the additive used is disodium phosphate. Next, 100 mg of disodium phosphate (100 ppm) is added to 2 kg of purified isosorbide solution (50% DM). This solution is analyzed using the methodology described above.

[0070] For a solution containing 100 ppm disodium phosphate, the induction time obtained is 5 hours, or the efficacy E is 0. The effect of this additive on the antioxidant properties of isosorbide at this dose is 0.

[0071] Non-inventive example 1-3: Preparation of an isosorbide composition with 200 ppm of disodium phosphate added. The synthesis method is the same as in Example 1, but in this case, the additive used is disodium phosphate. Next, 200 mg of disodium phosphate (200 ppm) is added to 2 kg of purified isosorbide solution (50% DM). This solution is analyzed using the methodology described above.

[0072] For a solution containing 200 ppm disodium phosphate, the induction time obtained was 5.1 hours, or the efficacy E was 0.1. The effect of this additive on the antioxidant properties of isosorbide is close to zero at a dose of 200 ppm.

[0073] Comparisons of Comparative Examples 1-1, 1-2, and 1-3 suggest that sodium phosphate does not appear to have a positive effect on the antioxidant properties of isosorbide, even at higher doses.

[0074] Non-inventive example 2-1: Preparation of an isosorbide composition with 50 ppm of diethanolamine added. The synthesis method is the same as in Example 1, but in this case, the additive used is diethanolamine. A dose of 50 mg of diethanolamine (50 ppm) is added to 2 kg of purified isosorbide solution (50% DM). This solution is analyzed using the methodology described above.

[0075] The induction time obtained for the solution to which diethanolamine was added at 50 ppm was 6.2 hours, and the efficacy E was 1.2.

[0076] Non-inventive example 2-2: Preparation of an isosorbide composition with 100 ppm of diethanolamine added. The synthesis method is the same as in Example 1, but in this case, the additive used is diethanolamine. 100 mg of diethanolamine (100 ppm) is added to 2 kg of purified isosorbide solution (50% DM). This solution is analyzed using the methodology described above.

[0077] For a solution to which diethanolamine was added at 100 ppm, the induction time obtained was 7.2 hours, or the efficacy E was 2.3.

[0078] Non-inventive example 2-3: Preparation of an isosorbide composition with 200 ppm of diethanolamine added. The synthesis method is the same as in Example 1, but in this case, the additive used is diethanolamine. 200 mg of diethanolamine (200 ppm) is added to 2 kg of purified isosorbide solution (50% DM). This solution is analyzed using the methodology described above.

[0079] For a solution containing 200 ppm diethanolamine, the induction time obtained is 7.3 hours, or the efficacy E is 2.3.

[0080] A comparison of Examples 2-1, 2-2, and 2-3 outside the present invention shows that a plateau is rapidly reached with the use of diethanolamine, which indicates a threshold effect on the antioxidant effect of diethanolamine.

[0081] Non-inventive example 3: Preparation of an isosorbide composition with maltol added at 100 ppm. The synthesis method is the same as in Example 1, but in this case, the additive used is maltol. Next, 100 mg of maltol is added to 2 kg of purified isosorbide solution (100 ppm). This solution is analyzed using the methodology described above.

[0082] For a solution containing 100 ppm maltol, the induction time obtained is 3.9 hours, or the efficacy E is -1.1.

[0083] Maltol's antioxidant properties are detrimental to isosorbide.

[0084] Non-inventive example 4: Preparation of an isosorbide composition with 100 ppm of Trolox (6-hydroxy-2,5,7,8-tetramethylchrom-2-carboxylic acid) added. The synthesis method is the same as in Example 1, but in this case, Trolox is used as the additive. Next, 100 mg of Trolox is added to 2 kg of purified isosorbide solution (100 ppm). This solution is analyzed using the methodology described above.

[0085] For a solution containing 100 ppm Trolox, the induction time obtained was 2.9 hours, or the efficacy E was -2.1 hours.

[0086] Trolox is known for these antioxidant properties, but it negatively affects the antioxidant properties of isosorbide.

[0087] Non-inventive example 5: Preparation of an isosorbide composition with 100 ppm gallic acid added. The synthesis method is the same as in Example 1, but in this case, gallic acid is used as the additive. Next, 100 mg of gallic acid is added to 2 kg of purified isosorbide solution (100 ppm). This solution is analyzed using the methodology described above.

[0088] For a solution containing 100 ppm gallic acid, the induction time obtained was 3.4 hours, or the efficacy E was -1.6 hours.

[0089] Gallic acid has a structure similar to ethyl / propyl gallate, but it negatively affects the antioxidant properties of isosorbide.

[0090] Example 1 according to the present invention: Preparation of an isosorbide composition to which ethyl gallate is added at 50 ppm. The synthesis method is the same as in Example 0, but in this case, 50 mg of ethyl gallate is added to 2 kg of isosorbide solution after filtration through activated carbon (dosage 50 ppm). The medium is stirred for 30 minutes to completely dissolve and ensure the homogeneity of the solution. This solution is analyzed using the methodology cited above.

[0091] For a solution containing 50 ppm ethyl gallate, the induction time obtained is 7.3 hours, or the efficacy E is 2.3.

[0092] Example 2-1 according to the present invention: Preparation of an isosorbide composition with propyl gallate added at 50 ppm. The synthesis method is the same as in Example 1, but in this case, the additive used is propyl gallate. Next, 50 mg of propyl gallate is added to 2 kg of purified isosorbide solution (50 ppm dose). This solution is analyzed using the methodology described above.

[0093] For a solution containing 50 ppm propyl gallate, the induction time obtained is 7.5 hours, or the efficacy E is 2.5.

[0094] Example 2-2 of the present invention: Preparation of an isosorbide composition with propyl gallate added at 100 ppm. The synthesis method is the same as in Example 1, but in this case, the additive used is propyl gallate. Next, 100 mg of propyl gallate is added to 2 kg of purified isosorbide solution (100 ppm dose). This solution is analyzed using the methodology described above.

[0095] For a solution containing 100 ppm propyl gallate, the induction time obtained is 8.8 hours, or the efficacy E is 3.8.

[0096] Examples 2-3 of the present invention: Preparation of an isosorbide composition with propyl gallate added at 200 ppm. The synthesis method is the same as in Example 1, but in this case, propyl gallate is used as the stabilizer. Next, 200 mg of propyl gallate is added to 2 kg of purified isosorbide solution (200 ppm dose). This solution is analyzed using the methodology described above.

[0097] For a solution containing 200 ppm propyl gallate, the induction time obtained is 11.6 hours, or the efficacy E is 6.6.

[0098] Examples 1, 2-1, 2-2, and 2-3 demonstrate that ethyl gallate and, in particular, propyl gallate have a very significant effect on the antioxidant properties of isosorbide.

[0099] Example 3 according to the present invention: Preparation of an isosorbide composition stabilized with propyl gallate (100 ppm) to which disodium phosphate (50 ppm) has been added. The synthesis method is the same as in Example 1, but in this case, 100 mg of propyl gallate (100 ppm) and 50 mg of disodium phosphate (50 ppm) are added to 2 kg of purified isosorbide solution.

[0100] The induction time of the solution stabilized by this mixture is 11.6 hours, or the efficacy E is 6.6. This value is greater than the sum of the efficacy of sodium phosphate at 50 ppm (0) and the efficacy of propyl gallate at 100 ppm (3.8). This is the case of a synergistic effect between the two additives tested regarding the antioxidant properties of isosorbide.

[0101] Example 4 according to the present invention: Preparation of an isosorbide composition containing propyl gallate (100 ppm) and diethanolamine (50 ppm). The synthesis method is the same as in Example 1, but in this case, 100 mg of propyl gallate (100 ppm) and 50 mg of diethanolamine (50 ppm) are added to 2 kg of purified isosorbide solution.

[0102] The induction time of the solution stabilized by this mixture is 13.8 hours, or the efficacy E is 8.8. This value is greater than the combined efficacy of diethanolamine at 50 ppm (1.2) and propyl gallate at 100 ppm (3.8). While not bound by any theory, this appears to indicate a strong synergistic effect in this composition.

Claims

1. A method for preparing an internal dehydration product composition of hydride sugar, a) A step of distilling the medium containing the internal dehydration product to obtain a distillate in which the product is concentrated, b) at least one subsequent step of optionally purifying the distillate thus obtained, c) A subsequent step in which the distillate obtained during step a) and subsequently subjected to step b) is placed in the presence of at least one gallic acid ester, d) optionally a subsequent step of forming the resulting composition of internal dehydration products of hydride sugars, A method wherein the gallic acid ester used in step c) is selected from ethyl gallate, propyl gallate, and mixtures thereof.

2. The method according to claim 1, characterized in that the gallic acid ester used in step c) is propyl gallate.

3. The method according to claim 1 or 2, further characterized in that step c) also uses a phosphoric acid compound.

4. The method according to claim 1 or 2, further characterized in that step c) also uses an amine.

5. The method according to claim 1 or 2, characterized in that the gallic acid ester used in step c) is used in an amount of 0.0001 to 2%, and these percentages are expressed as the dry weight of the gallic acid ester relative to the dry weight of the internal dehydration product of the hydride sugar mainly present in the distillate at that time.

6. The phosphoric acid compound used in step c) is used in an amount of 0.0001 to 2%, and these percentages are characterized by being expressed as the dry weight of the phosphoric acid compound relative to the dry weight of the internal dehydration product of the hydride sugar that is mainly present in the distillate at that time. The method according to claim 3.

7. The method according to claim 4, characterized in that the amine used in step c) is used in an amount of 0.0001 to 2%, and these percentages are expressed as the dry weight of the amine relative to the dry weight of the internal dehydration product of the hydride sugar that is mainly present in the distillate at that time.

8. The method according to claim 1 or 2, characterized in that the internal dehydration product of the hydride sugar is isosorbide.

9. A composition containing at least one internal dehydration product of a hydride sugar, characterized by containing at least one gallic acid ester, A composition in which the gallic acid ester is selected from ethyl gallate and propyl gallate.

10. The composition according to claim 9, characterized in that the gallic acid ester is propyl gallate.

11. The composition according to claim 9 or 10, characterized in that it contains 0.0001 to 2% gallic acid ester, and these percentages are expressed by the dry weight of the gallic acid ester relative to the dry weight of the internal dehydration product of the hydride sugar.

12. The composition according to claim 9 or 10, characterized in that it also contains 0.0001 to 2% of a phosphate compound, the percentages of which are expressed by the dry weight of the phosphate compound relative to the dry weight of the internal dehydration product of the hydrase sugar.

13. The composition according to claim 9 or 10, characterized in that it also contains 0.0001 to 2% of amines, the percentages of which are expressed by the dry weight of the amines relative to the dry weight of the internal dehydration product of the hydrase sugar.

14. The composition according to claim 9 or 10, characterized in that the internal dehydration product of the hydride sugar is isosorbide.

15. Use of the composition according to claim 9 or 10 for the preparation of polymers or nonpolymers, biodegradable or non-biodegradable products or mixtures for the chemical, pharmaceutical, cosmetic, or food industries.

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