FR3125684A1 - COMPOSITION OF OXIDATION-STABLE DINAHYDROHEXITOLS AND CONTAINING A GALLIC ACID ESTER - Google Patents

Abstract

The present invention relates to a method for improving the stability to oxidation of compositions of an internal dehydration product of a hydrogenated sugar, in particular an isosorbide composition, said method being based on the implementation of gallic acid esters. It also relates to the compositions thus obtained and to their various uses.

Description

COMPOSITION OF OXIDATION-STABLE DINAHYDROHEXITOLS AND CONTAINING A GALLIC ACID ESTER

The present invention relates to a method for improving the stability to oxidation of compositions of an internal dehydration product of a hydrogenated sugar, in particular an isosorbide composition, said method being based on the implementation of gallic acid esters. It also relates to the compositions thus obtained and to their various uses.

Developing our renewable biological resources has become a major ecological and economic imperative, in the face of the depletion and rising prices of fossil materials such as oil. It is in this context that the development of 1,4:3,6-dianhydrohexitols has been taking place for several years.

These products, also called isohexides, are obtained by internal dehydration of hydrogenated sugars in C6 (hexitols) such as sorbitol, mannitol and iditol. In the present application, the term “dianhydrohexitols” encompasses isosorbide (1,4-3,6-dianhydro-sorbitol), isomannide (1,4-3,6 dianhydro-mannitol), isoidide (1, 4 - 3,6- dianhydro-iditol) of the following formulas, as well as mixtures of these products:

Today, there is a strong potential for industrial development for isohexides, and in particular for isosorbide, the use of which is envisaged for the preparation:
- 2-nitrate, 5-nitrate or isosorbide 2.5 dinitrate, useful in the therapeutic treatment of diseases, in particular cardiac and/or vascular diseases; alkyl derivatives, in particular dimethyl derivatives, of isosorbide, useful in particular as solvents in the context of the preparation of pharmaceutical or cosmetological compositions;
- isosorbide derivatives intended for detergent compositions for fuels of alkylated or alkenyl derivatives which can be used as plasticizers for polymers, adhesives or inks;
- specific biphosphites which can be used as polymer stabilizers or lubricants;
- Articles based on polyvinyl alcohol, polyurethanes, or polymers and copolymers such as polyesters and polycarbonates;
- biodegradable polycondensates;
- aqueous lacquers or compositions with a covering and/or coloring action on surfaces.

However, it is well known that isohexides, when subjected to a dehydration step (for example sorbitol) are capable of being transformed, in addition to the desired dehydration product (for example isosorbide) into various co - products such as:
- isomers of said desired product, for example isosorbide isomers such as isomannide and isoidide,
- products less dehydrated than the desired product or its isomers, for example sorbitan, mannitan or iditan,
- derivatives resulting from the oxidation or more generally from the degradation of the aforementioned products, these derivatives possibly including, for example when the desired product is isosorbide, co-products of the deoxy monoanhydro hexitols, monoanhydro pentitols, monoanhydro tetritols type, anhydro hexoses, hydroxymethyl furfural, or glycerine:
- derivatives resulting from the polymerization of the aforementioned products, and/or strongly colored species, of a poorly defined nature.

Also, there is a whole section of the literature dedicated to technologies aimed at obtaining compositions resulting from said dehydration step, which are improved in terms of purity or stability and this, by varying the reaction conditions during said step, or by applying one or more purification treatment(s) after said step, or else by combining these various means.

In the first category, we can cite the patent CA 1 178 288 which recommends (page 14, lines 3-8) to carry out the dehydration reaction under an atmosphere of inert gas to avoid oxidation reactions, in particular when temperatures and relatively long reaction times are contemplated. US Patent 4,861,513 also falls within this line, by describing a dehydration reaction of sorbitol carried out in the simultaneous presence of inert gas (nitrogen) and a reducing agent (sodium hypophosphite) with a view to preparing mixtures of particular polyols, which have a low content (10 to 26% by dry weight) of dianhydrosorbitol.

In the second category, reference can be made to US Pat. No. 4,564,692, which mentions without any detail, the prepurification on ion exchangers and/or activated carbon of isosorbide or isomannide compositions then, after concentration by evaporation and seeding of crystals of the desired isohexide, crystallization of the latter in water. Patent application WO 01/94352 can also be indicated, which teaches purification by treatment with an ion exchange means, then a bleaching means.

Finally, in the third category, mention may be made of patent GB 613 444 which describes the production, by dehydration in a water/xylene medium, of an isosorbide composition then subjected to a distillation and then recrystallization treatment in an alcohol mixture. / ether. As for patent EP 0 323 994, it envisages the implementation of specific dehydration catalysts (respectively a gaseous hydrogen halide and liquid hydrogen fluoride) advantageously associated with carboxylic acids as co-catalysts, then the distillation of the crude compositions of isosorbide or isomannide thus obtained.

In opposition to this state of the art, the Applicant had made the double observation according to which the level of stability of a composition of isohexides was not correlated with its level of purity, but also that the implementation of a agent such as gaseous nitrogen or sodium borohydride as described in the prior art (at the latest at the time of the distillation step) did not make it possible to significantly improve this stability.

And it was while still continuing its work that the Applicant Company then found, surprisingly and unexpectedly, that only 1) particular stabilizing agents, in this case in non-gaseous form 2) implemented at a particular moment of the process preparation, in this case after the actual distillation step, made it possible to prepare isohexide compositions whose storage behavior, at least at ambient or moderate temperature, was improved.

This invention is the subject of patent EP 1 446 373, protecting a process for preparing a composition of internal dehydration product of a hydrogenated sugar, characterized in that it comprises:
a) a step of distilling a medium containing said internal dehydration product in order to obtain a distillate enriched in this product,
b) optionally, at least one subsequent stage of purification of the distillate thus obtained,
c) a subsequent step of bringing together the distillate obtained during step a), then optionally subjected to step b), with an agent capable of improving the stability of the product of internal dehydration mainly contained in the distillate, the said agent not being in gaseous form,
d) optionally, a subsequent step of shaping the resulting composition of internal dehydration product of a hydrogenated sugar.

This document relates a number of possibilities for the improvement agent implemented during step c), which can be chosen from:
- reducing agents, and in particular compounds based on boron or aluminum such as sodium borohydride (NaBH4) or lithium aluminum hydride (LÏAIH4);
- compounds based on phosphorus such as a phosphine or a phosphite;
- antioxidants, and in particular nitrogen-based compounds, in particular amines, aromatic or not, additionally containing or not containing at least one alcohol function, such as hydroxylamine, morpholine, and their derivatives;
- aromatic compounds, nitrogenous or not, containing or not containing at least one alcohol function, such as for example hydroquinone, phenol, tocopherols and their respective derivatives;
- antioxidant compounds based on phosphorus or sulfur such as phosphites, phosphonites, sulphites, salts of thiodipropionic acid esters and mixtures thereof;
- antacids;
- metal deactivating agents, such as complexing or chelating agents for metals of natural origin;
- products authorized as food additives, in particular those qualified as antioxidants, acidity correctors or sequestrants within the meaning of European regulations, such as ascorbic acid (vitamin C), erythorbic acid, lactic acid, citric acid, gallic acid, tocopherols, derivatives (in particular salts) of all of these products, BHT, butylhydroxyanisole (BHA) and any mixtures of these products.

The Applicant Company then demonstrated that by implementing such a process, particularly stable compositions were obtained. By stable composition within the meaning of document EP 1 446 373, is meant a composition which, stored in a non-inert atmosphere for a period of at least one month and at a temperature of 40° C., has both an acid content formic content of less than 0.0005% and an overall content of monoanhydrohexoses of less than 0.005%, these percentages being expressed by dry weight relative to the dry weight of said composition.

This stability is, for the compositions obtained by virtue of the aforementioned process, greater than 1 month and can reach at least 2 months, preferably at least 6 months and even more preferably at least one year. As an improving agent used during step c), document EP 1 446 373 exemplifies sodium borohydride, morpholine, BHT, vitamin C, sodium borate, sodium hydroxide, and disodium phosphate, the best results (stability of 6 months) being obtained for sodium borohydride and morpholine.

Working to improve this last process, the Applicant then succeeded in illustrating the influence of the nature of the agent introduced at step c) of the process, and that the particular choice of monoethanolamine, diethanolamine (DEA), triethanolamine (TEA) or mixtures thereof led to particularly advantageous results: the latter are in particular the subject of document EP 2 991 991. These results are supported by the monitoring of the pH over the time of compositions thus stabilized. By stable composition within the meaning of document EP 2 991 991, is meant a composition whose pH does not change significantly at 50° C. and this, for at least 1 month.

Continuing its research with a view to obtaining ever more stable compositions of internal dehydration product of a hydrogenated sugar, the Applicant came to the conclusion that oxidation was a preponderant phenomenon; in other words, the stability of said compositions is above all governed by their resistance to oxidation. In doing so, the Applicant has succeeded in identifying a particular class of chemical compounds, which are particularly effective in improving this stability to oxidation: esters of gallic acid, also called gallates.

It is also to the Applicant's credit for having considered using an original device to demonstrate the effectiveness of these compounds: the so-called "PetroOxy" test. This test implements the eponymous apparatus marketed by Anton Paar GmbH, usually used to evaluate the resistance to oxidation of fuel distillates. The experiment is based on the accelerated oxidation of a sample: it is placed in an airtight chamber which fills with oxygen up to a previously fixed pressure and rises to a given temperature. These conditions lead to accelerated oxidation of the sample which results in the reduction of the pressure within the enclosure. A difference in oxygen pressure within the cell is then measured. The induction time is determined by evaluating the rate of oxygen consumption over time.

The induction period is the period at the beginning of the oxidation process during which the reactions are slow, due to a low concentration of reaction intermediates. Once this period has elapsed, the reactions are faster, which results in a sudden change in the oxygen pressure. The induction time is thus determined, which corresponds to the duration of this initial induction period. Refer to the exemplification part of this Application for the exploitation and interpretation of the results related to the implementation of the "PetroOxy" test.

Advantageously, this method has made it possible to demonstrate that certain compounds of the prior art, reputed to be effective with respect to stability at pH, had no effect on the phenomenon of oxidation: this is the case of disodium phosphate. It also made it possible to demonstrate the interest of DEA and TEA, as agents improving resistance to oxidation. But it has above all proved to be particularly discriminating, in particular by ruling out antioxidant agents known elsewhere but having a surprisingly negative effect on isosorbide, and by releasing a class of compounds that are particularly effective in terms of antioxidant power on the isosorbide: esters of gallic acid. No compound known until then had achieved such antioxidant power on isosorbide, not even DEA and TEA.

Nothing in the state of the art suggested that gallic acid esters, used in a method for preparing a composition of the product of internal dehydration of a hydrogenated sugar, would not lead to such resistance to oxidation of said compositions. In the same way, no element made it possible to induce the person skilled in the art to test the so-called "PetroOxy" device, to identify effective compounds with respect to oxidation, for compositions of internal dehydration product of a hydrogenated sugar. It is to the credit of the Applicant to have achieved such results.

Also, a first object of the present invention consists of a process for the preparation of a composition of the product of internal dehydration of a hydrogenated sugar, comprising:
a) a step of distilling a medium containing said internal dehydration product in order to obtain a distillate enriched in this product,
b) optionally, at least one subsequent stage of purification of the distillate thus obtained,
c) a subsequent step of bringing together the distillate obtained during step a), then optionally subjected to step b), with at least one gallic acid ester,
d) optionally, a subsequent step of shaping the resulting composition of internal dehydration product of a hydrogenated sugar.

Preferably, the gallic acid ester used in step c) is chosen from alkyl esters, more preferably from ethyl gallate and propyl gallate and their mixtures. Even more preferably, the gallic acid ester used in step c) is propyl gallate.

In a first preferred variant, step c) also uses a phosphate compound, preferably disodium phosphate.

In a second preferred variant, step c) also uses an amine, preferably chosen from alkylamines, more preferably from diethanolamine and triethanolamine, and which is very preferably diethanolamine.

The method according to the invention is advantageously characterized in that the gallic acid ester implemented in step c) is used at a rate of 0.0001 to 2%, preferentially from 0.001 to 2%, more preferentially from 0.002 to 1.5%, these percentages being expressed as dry weight of gallic acid ester relative to the dry weight of the product of internal dehydration of hydrogenated sugar then predominantly present in the distillate, for example isosorbide then present in this place.

In the first preferred variant above, the phosphate compound used in step c) is advantageously used at a rate of 0.0001 to 2%, preferentially from 0.001 to 2%, more preferentially from 0.002 to 1, 5%, these percentages being expressed as dry weight of said phosphate compound relative to the dry weight of the product of internal dehydration of hydrogenated sugar then predominantly present in the distillate, for example isosorbide then present in this medium.

In the second preferred variant above, the amine implemented in step c) is advantageously used at a rate of 0.0001 to 2%, preferentially from 0.001 to 2%, more preferentially from 0.002 to 1, 5%, these percentages being expressed as dry weight of said amine relative to the dry weight of the product of internal dehydration of hydrogenated sugar then predominantly present in the distillate, for example isosorbide then present in this medium.

In the context of the process according to the invention, it should be specified that the medium subjected to step a) of distillation, can be of very varied nature, including in terms of dry matter, temperature and / or purity in the desired dehydration product. It may be, according to a first variant, an isosorbide composition consisting of the medium resulting directly from the dehydration reaction proper and having a purity of the desired product, for example of isosorbide, of the order of 50 at 80%. According to another possibility, said composition may, due in particular to the fact that it already results from one or more previous purification operations, in particular by distillation and/or crystallization, have a purity of the desired product, for example of isosorbide, greater than 80%.

Advantageously step a) of distillation is followed by a step b) of purification of the resulting distillate. According to a first variant, step b) consists of a purification step according to which the distillate, generally placed in solution, is treated with at least one purification means chosen from among decolorization means and ion exchange means.

By bleaching means is meant in particular activated carbon in granular or powder form and adsorption resins. By way of example, it is possible to use, alone or in combination, granular activated carbon such as the CECA DC 50 product, pulverulent activated carbon such as the NORIT SX+ product and/or a resin such as those called DUOLITE XAD 761, MACRONET MN- 600 or MACRONET MN-400. By means of ionic exchange, one understands in particular the anionic resins, weak or strong, and the cationic resins, weak or strong. By way of example, it is possible to use, alone or in combination, a strong anionic resin such as AMBERLITE IRA 910 resin or a strong cationic resin such as PUROLITE C 150 S resin. The ion exchange means can advantageously comprise at least one anionic resin and at least one cationic resin. Preferably, this means is composed of a mixed bed of anionic(s) and cationic(s) resins or of a succession of cationic(s) then anionic resin(s) or of a succession of anionic resin(s) (s) then cationic (s).

Preferably, during step b) of the process in accordance with the invention, the distillate obtained during step a) is treated in any order with at least one activated carbon and with at least one resin, ionic or non-ionic. Very advantageously, said distillate is treated first with an activated carbon then with at least one resin and then again with an activated carbon. According to another variant of the process according to the invention, the Applicant Company has found that it is particularly advantageous for the composition subjected to purification step b) to already have certain characteristics in terms of maximum content of particular impurities, for example formic acid and monoanhydrohexose species. It also found that such a content could in particular be guaranteed by directly subjecting the distillate obtained during step a) to said purification step b).

The process according to the invention can therefore be characterized in that the distillate subjected to said 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 weight dry relative to the dry weight of the product of internal dehydration of hydrogenated sugar then predominantly present in said distillate, for example to the dry weight of isosorbide present in said 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%.

Advantageously, stage b) of purification is implemented and the gallic acid ester is implemented after this stage b) and it is in particular introduced directly into the purified aqueous solution of product of internal dehydration resulting from step b), which generally has a temperature at most equal to 60°C.

After step c) and as indicated above, the composition of product of internal dehydration of a hydrogenated sugar obtained according to the invention can be shaped during a subsequent step d). This step can consist of an operation of tableting or flaking of the crystallized or massaged mass resulting from the cooling, in particular by contact on a cold surface, of the composition resulting from step c).

Step d) of shaping can, if desired, be followed by a step of grinding and/or sieving and this, before any step of storing and/or bagging the composition thus obtained.

According to another variant, the composition of product of internal dehydration of a hydrogenated sugar obtained according to the invention can, after step c), be stored as it is, in particular in the liquid or pasty state, without step specific for further shaping. The composition resulting from the process according to the invention may moreover have undergone, at any time, a concentration step, in particular an evaporation step under vacuum, said step being carried out under the mildest possible conditions, in particular in terms of time and temperature. This step then consists of concentrating said composition while maintaining it in liquid form, in particular at a dry matter content of between 50 and 90%, preferably between 75 and 88%. It may also consist in concentrating said composition so as to obtain a final product in dry form.

Preferably, it is most advantageous to carry out said concentration step directly after step c).

All the steps of the method according to the invention, mandatory or optional, which have just been described can also, if desired, be carried out under an inert atmosphere, including step c) characteristic of the present invention and / or any subsequent step, in particular shaping, storage or bagging.

The expression "internal dehydration product of a hydrogenated sugar" includes in particular the internal dehydration products of hydrogenated sugars at C6 (hexitols) such as sorbitol, mannitol and iditol and therefore encompasses isosorbide (1,4 - 3,6- dianhydro-sorbitol), isomannide (1,4 - 3,6 dianhydro-mannitol), isoidide (1,4 - 3,6- dianhydro-iditol). In a preferred variant, the process according to the invention is characterized in that the internal dehydration product of a hydrogenated sugar is isosorbide.

As a result of this, a new means is available which is capable of providing a composition of an internal dehydration product of a hydrogenated sugar, for example an isosorbide composition, whose oxidative stability is improved, such stability being required whatever the uses for which said composition is intended and whatever the purity of said composition.

Also, another object of the present invention relates to a composition containing at least one internal dehydration product of a hydrogenated sugar, characterized in that it contains at least one gallic acid ester.

Preferably, this gallic acid ester is chosen from alkyl esters, more preferably from ethyl gallate and propyl gallate and is still preferably propyl gallate

This composition is also characterized in that it contains from 0.0001 to 2%, preferably from 0.001 to 2%, more preferably from 0.002 to 1.5% of gallic acid ester, these percentages being expressed by dry weight of gallic acid ester based on the dry weight of the hydrogenated sugar internal dehydration product.

In a first variant, this composition is also characterized in that it also contains from 0.0001 to 2%, preferentially from 0.001 to 2%, more preferentially from 0.002 to 1.5% of a phosphate compound which is preferentially the disodium phosphate, these percentages being expressed as dry weight of phosphate compound relative to the dry weight of the product of internal dehydration of hydrogenated sugar

In a second variant, this composition is also characterized in that it also contains from 0.0001 to 2%, preferably from 0.001 to 2%, more preferably from 0.002 to 1.5% of an amine which is preferably diethanolamine or triethanolamine, very preferably diethanolamine, these percentages being expressed as dry weight of amine relative to the dry weight of the product of internal dehydration of hydrogenated sugar.

This composition in a preferred variant is characterized in that the product of internal dehydration of a sugar is isosorbide.

In a first variant where the composition is in liquid form, it is characterized in that it has a dry matter of between 50 and 90%, preferably between 75 and 88%.

In a second variant, said composition is in solid form (said composition therefore having a dry matter of 99 to 100.

Such compositions can in particular be used for the preparation of products or mixtures, polymeric or not, biodegradable or not, intended for the chemical, pharmaceutical, cosmetological or food industries.

Other characteristics, details and advantages will appear on reading the examples below, and the appended figure, in which:

Fig. 1

illustrates the determination of the induction time using an oxygen consumption curve obtained according to the PetroOxy test.

Examples

The following chemicals were used in the examples below:
Disodium phosphate (ref: S9763 At Sigma Aldrich)
Diethanolamine (ref: 398179, Sigma Aldrich)
Maltol (ref: W265624, Sigma Aldrich)
Trolox (ref: 238813, Sigma Aldrich)
Gallic acid (ref: 398225, Sigma Aldrich)
Ethyl gallate (ref: 48640, Sigma Aldrich)
Propyl gallate (ref: 48710, Sigma Aldrich).

Methodology associated with determining the effectiveness of an antioxidant additive according to the test Petro O xy

3g of purified isosorbide solution (50% DM) in distilled water with or without the addition of stabilizer are weighed precisely in a glass cup then placed in the hermetic enclosure of the measuring device (PetroOxy model 13 -3002 from Petrotest (now Anton Paar GmbH)). The air present in the cell is purged 3 times at room temperature with pure oxygen via a pressurized bottle (Alphagaz, purity >99.5%). The temperature and the working pressure of pure oxygen are then fixed at 100°C and 700 kPa (7 bars of oxygen). The pressure is monitored continuously during the experiment. The decrease in pressure in the enclosure of the test chamber is due to the consumption of oxygen during the oxidation reactions of the sample studied. The variation in relative pressure during the experiment makes it possible to determine the time after which the sample begins to degrade (known as the induction time, OIT) under the test conditions.

The induction time of the solution is determined as follows:

The relative oxygen consumption pressure is given by the relationship Pmax -Pt /Pmax (Pmax being the maximum pressure of the system over time (corresponding to the maximum pressure at the beginning of time, Pt is the pressure as a function of time when the oxygen is consumed).The induction time of the sample is given by the inflection point of the oxygen consumption curve: i.e. the intersection of the two linear domains (see ).

The longer the induction time, the greater the oxidation resistance of the sample. To precisely calculate this parameter, a calculation method by linear regression between the two line segments before and after the inflection point is carried out.

The effectiveness of an additive (Denoted E _i ), in terms of antioxidant power, is determined by the difference in induction time (t _i ) between an isosorbide solution with a stabilizer and a solution without stabilizer (isosorbide without additive, t _ref ), E _i =t _i -t _ref . An additive i having a positive efficiency E _i will have a beneficial effect while a negative efficiency E _i will show a deleterious effect. A synergy of a mixture of additives will result in an efficiency E _mixture greater than the sum of efficiencies E _i of the additives of the mixture taken independently and this, with the same concentrations of the additives used.

Reference example : preparation of an unstabilized isosorbide composition and study of its induction time .

An isosorbide solution is prepared as follows:

1 kg of a 70% dry matter (DM) sorbitol solution marketed by the Applicant under the name NEOSORB 70/02 and 7 g of concentrated sulfuric acid are introduced into a jacketed stirred reactor. The mixture obtained is heated under vacuum (100 mbar) for 5 hours so as to eliminate the water contained in the reaction medium and that originating from the dehydration reaction of the sorbitol.

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

The lightly colored (light yellow) isosorbide distillate is then dissolved in isopropanol at a temperature of 60°C, so as to obtain a homogeneous solution at 75% DM. This solution is then cooled slowly, over 5 hours, to a temperature of 10°C. A recrystallized isosorbide primer is added at 40°C.

The crystals are then drained in a wringer and washed with isopropanol. After drying under vacuum, the crystals are redissolved in water to obtain a 50% DM aqueous solution.

This solution is then percolated on a column of granular activated carbon (CPG 12-40 at a relative rate of 0.5V/V/h (volume of product/volume of resin and per hour). The discolored isosorbide composition thus obtained is passed at a speed of 2 V/V/h successively over a column of strong cationic resin (PUROLITE C150 S then over a strong anionic resin AMBERLITE IRA910. This solution is then treated with powdered activated carbon (NORIT SX+) at 20° C for one hour The amount of charcoal used is 0.5% by weight relative to the dry weight of the solution.

After filtration of the activated carbon, the isosorbide solution is recovered and analyzed according to the methodology above.

The induction time of the isosorbide solution without additive is 5.0 h. This value will serve as a reference for determining the effectiveness of the additives.

Example outside the invention 1-1 : preparation of an isosorbide composition with additives with disodium phosphate at 50 ppm .

The synthesis process is identical to example 1 but in this case the additive used is disodium phosphate. 50 mg of disodium phosphate (50 ppm) are then added to 2 kg of purified isosorbide solution (50% DM). The solution is analyzed according to the methodology mentioned above.

The induction time obtained for a solution supplemented with disodium phosphate at 50 ppm is 5.0 h, i.e. an efficiency E of 0. The effect of this additive, at this dose, is nil on the antioxidant character of the isosorbide.

Example outside the invention 1-2: preparation of an isosorbide composition added with disodium phosphate at 100 ppm.

The synthesis process is identical to example 1 but in this case the additive used is disodium phosphate. 100 mg of disodium phosphate (100 ppm) are then added to 2 kg of purified isosorbide solution (50% DM). The solution is analyzed according to the methodology mentioned above.

The induction time obtained for a solution with disodium phosphate at 100 ppm is 5.0 h, i.e. an efficiency E of 0. The effect of this additive, at this dose, is nil on the antioxidant character of isosorbide .

Example outside the invention 1-3: preparation of an isosorbide composition with additives with disodium phosphate at 200 ppm.

The synthesis process is identical to example 1 but in this case the additive used is disodium phosphate. 200 mg of disodium phosphate (200 ppm) are then added to 2 kg of purified isosorbide solution (50% DM). The solution is analyzed according to the methodology mentioned above.

The induction time obtained for a solution with disodium phosphate at 200 ppm is 5.1 h, i.e. an efficiency E of 0.1. The effect of this additive on the antioxidant character of isosorbide is close to 0 at a dose of 200 ppm.

The comparison of counter-examples 1-1, 1-2 and 1-3 indicates that sodium phosphate, even at higher doses, does not seem to positively influence the antioxidant character of isosorbide.

Example outside the invention 2-1: preparation of an isosorbide composition with additives with diethanolamine at 50 ppm .

The synthesis process is identical to example 1 but in this case the additive used is diethanolamine at a dose of 50 mg of diethanolamine (50 ppm) are added to 2 kg of purified isosorbide solution (50% MS) . The solution is analyzed according to the methodology mentioned above.

The induction time obtained for a solution supplemented with diethanolamine at 50 ppm is 6.2 h, i.e. an efficiency E of 1.2.

Example outside the invention 2-2: preparation of an isosorbide composition with additives with diethanolamine at 100 ppm .

The synthesis process is identical to example 1 but in this case the additive used is diethanolamine at a dose of 100 mg of diethanolamine (100 ppm) are added to 2 kg of purified isosorbide solution (50% MS) . The solution is analyzed according to the methodology mentioned above.

The induction time obtained for a solution supplemented with diethanolamine at 100 ppm is 7.2 h, i.e. an efficiency E of 2.3.

Example outside the invention 2-3: preparation of an isosorbide composition with additives with diethanolamine at 200 ppm .

The synthesis process is identical to example 1 but in this case the additive used is diethanolamine at a dose of 200 mg of diethanolamine (200 ppm) are added to 2 kg of purified isosorbide solution (50% MS) . The solution is analyzed according to the methodology mentioned above.

The induction time obtained for a solution with diethanolamine at 200 ppm is 7.3 h, i.e. an efficiency E of 2.3.

Comparison of non-inventive examples 2-1, 2-2 and 2-3 indicate that a plateau is reached quickly by the use of diethanolamine, which shows a threshold effect on the antioxidant effect of diethanolamine.

Example outside the invention 3: preparation of an isosorbide composition added with maltol at 100 ppm .

The synthesis process is identical to example 1 but in this case the additive used is maltol. 100 mg of maltol are then added to 2 kg of purified isosorbide solution (100 ppm). The solution is analyzed according to the methodology mentioned above.

The induction time obtained for a solution with maltol at 100 ppm is 3.9 h, i.e. an efficiency E of -1.1 h.

The antioxidant power of maltol is deleterious to isosorbide.

Example outside the invention 4: preparation of a composition of isosorbide added with Trolox ( 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid) at 100 ppm.

The synthesis process is identical to example 1 but in this case the additive used is Trolox. 100mg of Trolox are then added to 2 kg of purified isosorbide solution (100 ppm). The solution is analyzed according to the methodology mentioned above.

The induction time obtained for a solution with 100 ppm Trolox is 2.9 h, i.e. an efficiency E of -2.1 h.

Trolox, although known for its antioxidant properties, has a negative effect on the antioxidant character of isosorbide.

Example outside the invention 5: preparation of an isosorbide composition with additives of gallic acid at 100 ppm .

The synthesis process is identical to example 1 but in this case the additive used is gallic acid. 100 mg of gallic acid are then added to 2 kg of purified isosorbide solution (100 ppm). The solution is analyzed according to the methodology mentioned above.

The induction time obtained for a solution with gallic acid at 100 ppm is 3.4 h, i.e. an efficiency E of -1.6 h.

Gallic acid, although similar in structure to ethyl/propyl gallate, has a negative effect on the antioxidant character of isosorbide.

Example 1 according to the invention: preparation of a composition of isosorbide additive with ethyl gallate at 50 ppm .

The synthesis process is identical to example 0 but in this case 50 mg of ethyl gallate are added to 2 kg of the isosorbide solution after filtration of the activated carbon (dose 50 ppm). The medium is stirred for 30 min to allow complete dissolution and guarantee the homogeneity of the solution. The solution is analyzed according to the methodology mentioned above.

The induction time obtained for a solution with 50 ppm ethyl gallate is 7.3 h, i.e. an efficiency E of 2.3.

Example 2-1 according to the invention: preparation of an isosorbide composition with additives with propyl gallate at 50 ppm .

The synthesis process is identical to example 1 but in this case the additive used is propyl gallate. 50 mg of propyl gallate are then added to 2 kg of purified isosorbide solution (dose 50 ppm). The solution is analyzed according to the methodology mentioned above.

The induction time obtained for a solution with 50 ppm propyl gallate is 7.5 h, i.e. an efficiency E of 2.5.

Example 2-2 according to the invention: preparation of an isosorbide composition with additives with propyl gallate at 100 ppm .

The synthesis process is identical to example 1 but in this case the additive used is propyl gallate. 100 mg of propyl gallate are then added to 2 kg of purified isosorbide solution (dose 100 ppm). The solution is analyzed according to the methodology mentioned above.

The induction time obtained for a solution with 100 ppm propyl gallate is 8.8 h, i.e. an efficiency E of 3.8.

Example 2-3 according to the invention: preparation of an isosorbide composition with additives with propyl gallate at 200 ppm .

The synthesis process is identical to example 1 but in this case the stabilizer used is propyl gallate. 200 mg of propyl gallate are then added to 2 kg of purified isosorbide solution (dose 200 ppm). The solution is analyzed according to the methodology mentioned above.

The induction time obtained for a solution with 200 ppm propyl gallate is 11.6 h, i.e. an efficiency E of 6.6.

Examples 1, 2-1, 2-2 and 2-3 indicate a very marked effectiveness of ethyl gallate and especially propyl gallate on the antioxidant character of isosorbide.

Example 3 according to the invention: preparation of a composition of isosorbide stabilized with propyl gallate (100 ppm) with addition of disodium phosphate (50 ppm) .

The synthesis process is identical to 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 a solution of purified isosorbide.

The induction time of the solution stabilized by this mixture is 11.6 h, i.e. an efficiency of E of 6.6. This value is greater than the sum of the effectiveness of sodium phosphate at 50 ppm (0) and that of propyl gallate at 100 ppm (3.8). We are in the case of a synergy between the 2 additives tested, on the antioxidant character of isosorbide.

Example 4 according to the invention: preparation of an isosorbide composition with propyl gallate (100 ppm) and diethanolamine (50 ppm) .

The synthesis process is identical to 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 a purified isosorbide solution.

The induction time of the solution stabilized by this mixture is 13.8 h, i.e. an efficiency of E of 8.8. This value is greater than the sum of the effectiveness of diethanolamine at 50 ppm (1.2) and that of propyl gallate at 100 ppm (3.8). Without being bound by any theory, this seems to indicate a strong synergistic effect in this composition.

Claims (15)

A process for preparing a hydrogenated sugar internal dehydration product composition, comprising:
a) a step of distilling a medium containing said internal dehydration product in order to obtain a distillate enriched in this product,
b) optionally, at least one subsequent stage of purification of the distillate thus obtained,
c) a subsequent step of bringing together the distillate obtained during step a), then optionally subjected to step b), with at least one gallic acid ester,
d) optionally, a subsequent step of shaping the resulting composition of internal dehydration product of a hydrogenated sugar. Process according to Claim 1, characterized in that the gallic acid ester used in stage c) is chosen from ethyl gallate and propyl gallate and their mixtures and is most preferred is propyl gallate. Process according to one of Claims 1 to 2, characterized in that stage c) also uses a phosphate compound, preferably disodium phosphate. Process according to one of Claims 1 to 2, characterized in that stage c) also uses an amine, preferably chosen from diethanolamine and triethanolamine, and which is very preferably diethanolamine. Process according to one of Claims 1 to 4, characterized in that the gallic acid ester used in step c) is used at a rate of 0.0001 to 2%, preferably from 0.001 to 2 %, more preferably from 0.002 to 1.5%, these percentages being expressed as dry weight of gallic acid ester relative to the dry weight of the product of internal dehydration of hydrogenated sugar then mainly present in the distillate. Process according to one of Claims 1 to 3 and 5, characterized in that the phosphate compound used in step c) is used at a rate of 0.0001 to 2%, preferably 0.001 to 2%, more preferably from 0.002 to 1.5%, these percentages being expressed as dry weight of said phosphate compound relative to the dry weight of the product of internal dehydration of hydrogenated sugar then predominantly present in the distillate. Process according to one of Claims 1 to 2, 4 and 5, characterized in that the amine used in step c) is used at a rate of 0.0001 to 2%, preferably from 0.001 to 2 %, more preferably from 0.002 to 1.5%, these percentages being expressed as dry weight of said amine relative to the dry weight of the product of internal dehydration of hydrogenated sugar then predominantly present in the distillate. Process according to one of Claims 1 to 7, characterized in that the product of internal dehydration of a hydrogenated sugar is isosorbide. Composition containing at least one internal dehydration product of a hydrogenated sugar, characterized in that it contains at least one gallic acid ester. Composition according to Claim 9, characterized in that the gallic acid ester is chosen from ethyl gallate and propyl gallate and is preferably propyl gallate. Composition according to one of Claims 9 or 10, characterized in that it contains from 0.0001 to 2%, preferably from 0.001 to 2%, more preferably from 0.002 to 1.5% of gallic acid ester, these percentages being expressed as dry weight of gallic acid ester relative to the dry weight of the product of internal dehydration of hydrogenated sugar. Composition according to one of Claims 9 to 11, characterized in that it also contains from 0.0001 to 2%, preferentially from 0.001 to 2%, more preferentially from 0.002 to 1.5% of a phosphate compound which is preferentially the disodium phosphate, these percentages being expressed as dry weight of phosphate compound relative to the dry weight of the product of internal dehydration of hydrogenated sugar. Composition according to one of Claims 9 to 11, characterized in that it also contains from 0.0001 to 2%, preferentially from 0.001 to 2%, more preferentially from 0.002 to 1.5% of an amine which is preferentially diethanolamine or triethanolamine, very preferably diethanolamine, these percentages being expressed as dry weight of amine relative to the dry weight of the product of internal dehydration of hydrogenated sugar. Composition according to one of Claims 9 to 13, characterized in that the product of internal dehydration of a sugar is isosorbide. Use of a composition according to one of Claims 9 to 14 for the preparation of products or mixtures, polymeric or not, biodegradable or not, intended for the chemical, pharmaceutical, cosmetological or food industries.