New estolides, their preparation process and their uses, particularly for the preparation of polyglycerol esters

Abstract

The present invention relates to an estolide having the general formula (I) as defined in this application. It also relates to a method for preparing an estolide of general formula (I). The invention further relates to the use of an estolide of general formula (I), in particular as a plasticizing agent, adhesive, lubricating agent, emollient, wetting agent, and / or emulsifying agent. In another aspect, the invention relates to the use of an estolide of general formula (I) with a polyol, said polyol preferably being a polyglycerol or sucrose, and even more preferably a polyglycerol, to obtain a polyol ester, and preferably a polyglycerol ester. The invention also relates to a polyglycerol ester of general formula (II) as defined in the application.The invention further relates to a process for preparing polyglycerol ester (II) by reacting an estolide of general formula (I) with a polyglycerol of general formula (III) as defined in the application. Finally, the invention also relates to the use of a polyglycerol ester of general formula (II), in particular as an emulsifying agent, pigment wetting agent, emollient and / or texturizing agent.

Description

Title of the invention: New estolides, their preparation process and their uses, in particular for the preparation of polyglycerol esters Technical field

[0001] The present invention relates to the field of chemistry. It relates in particular to new estolides and to a new process for preparing these estolides. The invention also relates to the use of these new estolides, in particular for the preparation of polyglycerol esters. The invention also relates to the new polyglycerol esters and their uses, in particular in the field of cosmetics. Prior art

[0002] Estolides are molecules resulting from the oligomerization of a fatty acid on the alkyl chain of another fatty acid. Different processes have been proposed in the literature to prepare estolides, such as for example the polycondensation of a hydroxy fatty acid on itself (eg ricinoleic acid) (Bastida-Rodriguez J., 2013), the polymerization of unsaturated fatty acids by a hydration and condensation reaction in an acidic medium (Cermak S. et al., 2013) and the opening of the ring in an epoxidized fatty acid (Salih, N. et al., 2011).

[0003] The fields of application of estolides are numerous. Thus in the food sector they are notably used as viscosity modifiers or as emulsifying agents. In the cosmetic field they can be used as a moisturizing agent, natural antioxidant, hair additive, texturizer etc. Estolides also find uses as plasticizers, biolubricants, paints etc. Estolides have also been used in reaction with polyglycerol to prepare polyglycerol esters, which also find numerous applications in the cosmetic and food industries. Bastida-Rodriguez J., 2013 describes the preparation of polyglycerol polyricinoleate from a ricinoleic acid estolide and polyglycerol. Polyglycerol polyricinoleate is used in the food and cosmetic industries as a texturizing agent and more specifically as an emulsifier. It is mainly used to stabilize water-in-oil emulsions. Ricinoleic acid is a hydroxy acid that therefore has both an alcohol and a carboxylic acid function, which gives it the unique ability to self-esterify. However, the problem with ricinoleic acid, which comes from castor oil, lies in its cultivation areas, which are mainly India and Brazil.Indeed, the cultivation of ricinoleic acid requires . Special conditions that make it difficult to cultivate in Europe. The supply of this raw material also generates carbon dioxide emissions linked to transport. Furthermore, the closure of borders due to the 2020 pandemic highlighted the risk of dependence on foreign raw materials obtained from castor oil.

[0004] One of the aims of the present invention is to find an alternative to castor oil and / or ricinoleic acid with the aim in particular of obtaining new estolides and new polyglycerol esters, which have properties at least equivalent to ricinoleic acid estolides or polyglycerol polyricinoleate.

[0005] After extensive research, the inventors discovered that oleic acid could represent a very interesting alternative to ricinoleic acid. Oleic acid can advantageously be obtained from oils grown in France, and particularly in Eure-et-Loir. Unlike ricinoleic acid, oleic acid is not a hydroxy acid. It is therefore not possible to obtain an estolide of this acid by direct polycondensation. The inventors therefore had to develop a strategy for synthesizing estolides that was simple, efficient, and inexpensive.

[0006] Estolides obtained from oleic acid have already been described in the literature, and are synthesized by successive hydration and condensation reactions under acidic conditions. Hydroxystearic acid estolides are thus obtained. However, the estolides obtained are colored and the reactions are slow (24 hours) and difficult to control. In addition, it is necessary to carry out additional purification steps of the estolide obtained (Cermark S. et al.). In the publication by Hoong SS et al. of 2019, a polyhydroxy estolide is obtained from oleic acid. The first step of this process consists of reacting oleic acid with hydrogen peroxide at a temperature of 80°C and for 24 hours. The peroleic acid thus formed will epoxidize another oleic acid. The epoxide thus obtained is attacked by the carboxylate, which causes it to open and the formation of a first dimer.The reaction continues until there are no more double bonds.

[0007] In the process of the invention, oleic acid is transformed into oleic acid epoxide using formic acid and hydrogen peroxide, said oleic acid epoxide is then isolated, which advantageously allows it to be transformed by autocatalysis into an oleic acid dimer comprising an epoxide function. The dimer thus formed is reacted with a fatty acid, such as for example oleic acid, but any fatty acid can be used, which advantageously allows the properties of the estolide of the invention to be modulated, which is not possible with an estolide derived from a single fatty acid.

[0008] To date and to the knowledge of the Inventors, there is no document of the art prior art that describes a process for preparing estolides as disclosed in the present application. Similarly, none of the prior art documents describe estolides as disclosed in the present application. Summary

[0009] According to a first aspect, the present invention relates to an estolide of general formula (I) as described in the detailed description below.

[0010] According to a second aspect, the invention relates to a process for preparing estolide of general formula (I).

[0011] According to a third aspect, there is provided the use of an estolide of general formula (I), in particular as a plasticizing agent, adhesive agent, lubricating agent, emollient agent, wetting agent and / or emulsifying agent.

[0012] According to another aspect, the invention relates to the use of an estolide of general formula (I) with a polyol, said polyol preferably being a polyglycerol or sucrose, and even more preferably a polyglycerol, to obtain a polyol ester, and preferably a polyglycerol ester.

[0013] According to yet another aspect, the invention relates to a polyglycerol ester of general formula (II) as described in the detailed description below.

[0014] According to still another aspect, the invention relates to a process for preparing a polyglycerol ester of general formula (II), said polyglycerol ester (II) being obtained by reaction of an estolide of general formula (I) with a polyglycerol of general formula (III) as described in the detailed description below.

[0015] Finally, according to another aspect, the invention relates to the use of a polyglycerol ester of general formula (II), in particular as an emulsifying agent (in particular for water-in-oil emulsions), pigment wetting agent, emollient agent and / or texturizing agent. Brief description of the drawings

[0016] Other characteristics, details and advantages will appear on reading the detailed description below, and on analyzing the attached drawings, in which: Fig.l

[0017] [Fig.l] illustrates the synthesis scheme of an estolide of general formula (I) (represented by [Cheml] in the detailed description) from oleic acid. Fig. 2

[0018] [Fig.2] illustrates the synthesis scheme of a polyglycerol ester of general formula (II) (represented by [Chem7] in the detailed description) from an estolide of general formula (I). Fig. 3

[0019] [Fig.3] is an NMR spectrum of the epoxide compound of oleic acid (represented by [Chem5] in the detailed description) carried out with a 200 MHz DPX spectrometer from Bruker with deuterated chloroform as solvent. Fig. 4

[0020] [Fig.4] represents the superimposed infrared (IR) spectra of three estolides of general formula (I) more particularly represented by [Chem2], [Chem3] and [Chem4] in the detailed description. The top curve, in broken line, represents the spectrum of estolide [Chem3], the middle curve, in dotted line, that of estolide [Chem2] and the bottom curve, in solid line, that of estolide [Chem4]. Fig. 5

[0021] [Fig.5] the superimposed infrared spectra of three polyglycerol monoesters of general formula (II), represented by the numbers 11, 13 and 15. The solid line curve represents the spectrum of polyglycerol ester 15, the broken line curve that of polyglycerol ester 11 and the dotted line curve represents the spectrum of polyglycerol ester 13. Fig. 6

[0022] [Fig.6] represents the viscosity (Pa.s) as a function of the shear gradient (s1) of the three polyglycerol monoesters of general formula (II), represented by 11, 13 and 15. The top curve, with a broken line, represents the viscosity of 15, the one below, with a dotted line, the viscosity of 13, and the one just below, with a broken line and two dots, the viscosity of 11. The bottom curve, with a solid line, represents the viscosity of a reference product, polyglycerol polyricinoleate. Fig. 7

[0023] [Fig.7] represents the superimposed infrared spectra of three polyglycerol esters of general formula (II), namely more particularly monoester 11, diester 17 and triester 18. The broken line curve represents the spectrum of triester 18, the dotted line curve that of diester 17 and the solid line curve that of monoester 11. Fig. 8

[0024] [Fig.8] represents the viscosity (Pa.s) as a function of the shear gradient (s1) of the polyglycerol esters of general formula (II), namely more particularly the monoester 11, the diester 17 and the triester 18 but also of the estolide [Chem2] of general formula (I). The top curve, with a broken line, represents the viscosity of triester 18, the one below, with a dotted line, the viscosity of diester 17, the one a little below, with a broken line and a dot, the viscosity of monoester 11. The curve just a little above the bottom curve, with a broken line and two dots, represents the viscosity of estolide [Chem2]. The lower curve represents the viscosity of a reference product, polyglycerol polyricinoleate. Fig. 9

[0025] [Fig.9] shows photos of oleic sunflower oil samples comprising 5% monoester 11, diester 17 or triester 18. The samples represent respectively, from left to right: the sample comprising monoester 11, diester 17 and triester 18 for the 2 rightmost photos. Fig. 10

[0026] [Fig. 10] shows white background images of a mixture (50 / 50) of titanium dioxide and oleic sunflower oil alone (control) or comprising 1% of polyglycerol polyricinoleate (PRPG), monoester 11, diester 17 or triester 18. Fig. 11

[0027] [Fig. 11] represents the viscosity (Pa.s) as a function of the shear gradient (s1): - a mixture (50 / 50) of titanium dioxide and oleic sunflower oil alone (control) (top curve in broken line); - a mixture (50 / 50) of titanium dioxide and sunflower oil including 1% triester 18 (dotted curve just below); - a mixture (50 / 50) of titanium dioxide and sunflower oil comprising 1% of diester 17 (close-up broken line curve); - a mixture (50 / 50) of titanium dioxide and sunflower oil comprising 1% of monoester 11 (dashed line curve with two points); - a reference product, polyglycerol polyricinoleate (bottom curve in solid line). Detailed description

[0028] Estolides of formula (I)

[0029] The subject of the present invention is an estolide of the following general formula (I):

[0030] [Chem.l] O (I) in which: n is an integer ranging from 1 to 5, and preferably from 1 to 2, X represents a hydrocarbon radical originating from an unsaturated or saturated fatty acid, said radical X being a linear or branched hydrocarbon radical, having from 4 to 36 carbon atoms, saturated or unsaturated, unsubstituted or substituted by one or more hydroxy substituents (-OH), R represents, independently of one another, a hydrogen or a radical -CO-X with X as defined previously.

[0031] According to one embodiment of the invention, the radical X of the estolide of formula (I) comes from an unsaturated fatty acid chosen from the group comprising oleic, erucic, linoleic, eicosenoic, myristoleic, palmitoleic, γ-linolenic, arachidonic, α-linolenic and ricinoleic acid.

[0032] According to another embodiment of the invention, the radical X of the estolide of formula (I) comes from a saturated fatty acid chosen from the group comprising isostearic, stearic, palmitic, myristic, behenic, caprylic, pelargonic, capric, butyric, valeric, caproic, enanthic, undecyl, tridecyl, margaric, nonadecyl, arachidic (eicosanoic), lignoceric, pentacosanoic, cerotic, heptacosanoic, montanic, nonacosanoic, melissic and hen-triacontanoic acid.

[0033] According to an advantageous embodiment of the invention, the radical X of the estolide of formula (I) comes from a fatty acid chosen from the group comprising oleic, isostearic, stearic, palmitic, myristic, behenic, caprylic, pelargonic, capric, erucic and linoleic acid.

[0034] According to a particularly advantageous embodiment of the invention, the radical X of the estolide of formula (I) comes from oleic acid and is represented by the semi-developed formula -(CH2)7-CH=CH-(CH2)7-CH3.

[0035] According to another embodiment of the invention, the radical X of the estolide of formula (I) comes from: - isostearic acid and is represented by the semi-developed formula -(CH2)7-CH 2-CH(CH3)-(CH2)7-CH3, or, - stearic acid and is represented by the semi-developed formula -(CH2)7-CH2 -CH2-(CH2)7-CH3.

[0036] According to a particularly advantageous embodiment of the invention, the integer n of the estolide of formula (I) is equal to 1.

[0037] According to a particularly advantageous embodiment of the invention, the estolide of general formula (I) is characterized in that n is an integer equal to 1, X represents the radical -(CH2)7-CH=CH-(CH2)7-CH3 and R represents hydrogen or the radical -CO-(CH2)7-CH=CH-(CH2)7-CH3, said estolide being represented more particularly by the formula

[0038] [Chem.2] O

[0039] According to another embodiment of the invention, the estolide of general formula (I) is characterized in that n is an integer equal to 1, X represents the radical -(CH2)7-CH2 -CH(CH3)-(CH2)7-CH3 originating from isostearic acid and R represents hydrogen or the radical -CO-(CH2)7-CH2-CH(CH3)-(CH2)7-CH3, said estolide being represented more particularly by the formula

[0040] [Chem.3]

[0041] According to yet another embodiment of the invention, the estolide of general formula (I) is characterized in that n is an integer equal to 1, X represents the radical -(CH2)7-CH2-CH2-(CH2)7-CH3 originating from stearic acid, R represents hydrogen or the radical -CO-(CH2)7-CH2-CH2-(CH2)7-CH3, said estolide being represented more particularly by the formula

[0042] [Chem.4]

[0043] The process for preparing estolides of formula (I)

[0044] Another object of the invention lies in the process for preparing an estolide of general formula (I) as defined above, said process being characterized in that it comprises: - the transformation of oleic acid, of semi-developed formula CH3-(CH2)7 -CH=CH-(CH2)7-COOH, into oleic acid epoxide of formula

[0045] [Chem.5] - the autocatalytic opening of oleic acid epoxide [Chem5] by reaction between the epoxide function of [Chem5] and the carboxylic acid function of another oleic acid epoxide molecule [Chem5] to obtain an oleic acid dimer comprising an epoxide function, called "dimer" in the present application, said dimer having the formula

[0046] [Chem.6] - the reaction between the dimer [Chem6] with a fatty acid of semi-developed formula X-COOH with X as defined above, in order to obtain the estolide of general formula (I) as defined above.

[0047] According to an advantageous embodiment, the process of the invention is more particularly characterized in that: - the step of transforming oleic acid into oleic acid epoxide of formula [Chem5] is carried out using formic acid and hydrogen peroxide at a temperature ranging from 15 to 25°C, for a period ranging from 2 to 4 hours, - oleic acid epoxide [Chem5] is purified by recrystallization.

[0048] According to another advantageous embodiment, the process of the invention is more particularly characterized in that the autocatalytic opening of the oleic acid epoxide [Chem5] is carried out at a temperature ranging from 140 to 210°C, preferably from 160 to 190°C, for a time ranging from 5 to 90 minutes (min), preferably from 8 to 25 min, which makes it possible to form the dimer [Chem6]. In order to determine whether a sufficient quantity of dimer [Chemô] is formed in the reaction medium, the half-life of the reaction is determined, which corresponds to the time after which at least 50% of the initial quantity of epoxide [Chem5] has been consumed. This half-life can, for example, be determined by NMR spectroscopy or by measuring the acid number and acidity according to the method described in international standard ISO 660, reference number ISO 660: 2020(F).

[0049] According to yet another advantageous embodiment, the process of the invention is more particularly characterized in that the mass ratio between the fatty acid X- COOH and oleic acid epoxide [Chem5] ranges from 1:0.5 to 1:4, and preferably from 1:1.25 to 1:2.5.

[0050] According to yet another advantageous embodiment, the process of the invention is more particularly characterized in that the reaction between the dimer [Chem6] and the fatty acid X-COOH is carried out at a temperature ranging from 140 to 210°C, preferably from 160 to 190°C, for a time ranging from 30 to 150 minutes, preferably from 40 to 90 minutes, which makes it possible to obtain the estolide of general formula (I). Under the above-mentioned conditions, it is possible to obtain a yield of estolide greater than or equal to 50%, preferably greater than 70%, and more preferably still greater than 90%.

[0051] The process of the invention of the estolides of formula (I) is particularly advantageous in particular because it generally allows working under low temperature conditions and for short reaction times. Thus, the first step of the process of the invention, which consists of obtaining oleic acid epoxide [Chem5] from oleic acid, is carried out at room temperature. In the second step, the opening of the epoxide [Chem5] is autocatalytic, which allows the dimer [Chem6] to be obtained from the oleic acid epoxide alone. The formation of the dimer [Chem6] is obtained within a maximum of 90 minutes for a temperature never exceeding 210°C. The third step of the process of the invention, which consists of reacting the [Chem6] dimer with the fatty acid X-COOH, is also carried out at temperatures never exceeding 210°C for a maximum period of 150 minutes. Indeed, the epoxide function of the [Chem6] dimer is very reactive, which allows in particular a rapid and efficient reaction with the fatty acid. The addition of a chosen fatty acid at this stage of the process also makes it possible to obtain a wide variety of estolides. Furthermore, the reactions involved in the process of the invention do not require a solvent. Indeed, once the epoxide [Chem5] is obtained, the only compound used is the fatty acid used in the third step of the process of the invention. Finally, the acid used as the starting compound for the process of the invention, namely oleic acid, is advantageously obtained from oils grown in France. According to an advantageous embodiment of the invention, the fatty acid reacted with the dimer [Chem6] is also oleic acid. For all these reasons, the process of the invention is ecological. It is simple to implement for a limited period of time. It therefore falls within the framework of the objectives of green chemistry.

[0052] The estolides of the invention of general formula (I) may also be called in the present application “estolides derived from epoxidized oleic acid and comprising a ending from a fatty acid”.

[0053] The process for preparing the estolides (I) of the invention as defined above is illustrated schematically in [Fig.l].

[0054] Uses of estolides of formula (I)

[0055] The invention also relates to the use of an estolide of general formula (I) as defined above or as obtained according to the process as described above, as plasticizing agent, adhesive agent, lubricating agent, emollient agent, wetting agent and / or emulsifying agent.

[0056] The invention also relates to the use of an estolide of general formula (I) as defined above or as obtained according to the process as described above, with a polyol, preferably a polyglycerol or sucrose, to obtain a polyol ester. According to an advantageous embodiment of the invention, the polyol is preferably a polyglycerol, which means that the polyol ester is a polyglycerol ester. Polyglycerol esters obtained from estolides of formula (I) are also part of the invention.

[0057] Polyglycerol esters of formula (II)

[0058] Another object of the invention lies in a polyglycerol ester characterized in that it has the following general formula (II):

[0059] [Chem.7] (II), in which: m is an integer ranging from 0 to 19, preferably from 1 to 15, and more preferably from 1 to 9, R' represents independently of each other a hydrogen or a radical of formula

[0060] [Chem. 8] in which X, n and R are as defined above, with the condition that at least one of the R' of formula (II) represents a radical [Chem8].

[0061] According to an advantageous embodiment, the polyglycerol esters (II) of the invention are those for which m is an integer ranging from 1 to 9, and one, two or three R' represent the radical [Chem8].

[0062] According to another advantageous embodiment of the invention, the radical R' of the polyglycerol ester (II) represents the radical of formula [Chem8] in which n is an integer equal to 1, X represents the radical CH3-(CH2)7-CH=CH-(CH2)7- and R represents hydrogen or the radical -CO-(CH2)7-CH=CH-(CH2)7-CH3, which means that the radical R' is more particularly represented by the formula

[0063] [Chem. 10] O OR O O OR O with R as defined above.

[0064] According to yet another advantageous embodiment, in the polyglycerol esters of formula (II), one, two or three R' represent the radical [Chem8] or [ChemlO], all the other R' representing hydrogen (H).

[0065] Examples of polyglycerol esters (II) include polyglycerol monoesters, which means that only one R' represents [Chem8] or [ChemlO], all other R' representing H. More specific examples of polyglycerol monoesters are: - compound 11 (called 11 in the application) corresponding to formula (II) in which m is an integer equal to 2, only one R' represents [ChemlO], the other R' representing H; - compound 13 (called 13) corresponding to formula (II) in which m is an integer equal to 3, only one R' represents [ChemlO], the other R' representing H; - compound 15 (called 15) corresponding to formula (II) in which m is an integer equal to 5, only one R' represents [ChemlO], the other R' representing H.

[0066] Still as examples of polyglycerol esters (II) we can cite polyglycerol diesters, which means that two of the R's represent [Chem8] or [ChemlO], the other R's representing H. A more specific example of a polyglycerol diester is compound 17 (designated 17) having formula (II) in which m is an integer equal to 2, two R's represent [ChemlO], the other R's representing H.

[0067] Finally, we can also cite as examples of polyglycerol esters (II) the following: polyglycerol triesters, meaning that three of the R's represent [Chem8] or [ChemlO], with the other R's representing H. A more particular example of a polyglycerol triester of the invention is compound 18 (referred to as 18) having formula (II) in which m is an integer equal to 2, three R's represent [ChemlO], the other R's representing H.

[0068] The process for preparing polyglycerol esters of formula (II) from estolides of formula (I)

[0069] The invention also relates to a process for preparing a polyglycerol ester of general formula (II) as defined above, characterized in that it comprises the reaction between an estolide of general formula (I) as defined above with a polyglycerol of general formula (III)

[0070] [Chem.9] (III), in which m is an integer ranging from 0 to 19, preferably from 1 to 15, and more preferably from 1 to 9, said reaction being carried out in the presence of a catalyst, in order to obtain said polyglycerol ester (II).

[0071] As an example of a catalyst, mention may be made of that chosen from the group comprising calcium hydroxide, potassium hydroxide, sodium hydroxide and magnesium hydroxide.

[0072] According to yet another advantageous embodiment, the process for preparing the polyglycerol ester of formula (II) as described above is characterized in that the mass ratio “estolide (I): polyglycerol (III)” varies from 0.5:1 to 30:1.

[0073] For information: - the polyglycerol monoester 11 as defined above is obtained by reaction between estolide [Chem2] and a polyglycerol which corresponds to the general formula (III) in which m is equal to 2, said polyglycerol being called PG 12; - the polyglycerol monoester 13 as defined above is obtained by reaction between estolide [Chem2] and a polyglycerol which corresponds to the general formula (III) in which m is equal to 3, said polyglycerol being called PG 14; - the polyglycerol monoester 15 as defined above is obtained by reaction between estolide [Chem2] and a polyglycerol of general formula (III) in which m is equal to 5, said polyglycerol being called PG 16.

[0074] More particularly, according to an advantageous embodiment of the invention, the process for preparing the polyglycerol monoester 11 is characterized in that the ratio mass ratio “estolide [Chem2]:PG 12” is 3.5:1.

[0075] According to another particular embodiment of the invention, the process for preparing polyglycerol monoester 13 is characterized in that the mass ratio “estolide [Chem2]: PG 14” is 2.8:1.

[0076] According to yet another particular embodiment, the process for preparing the polyglycerol monoester 15 is characterized in that the mass ratio “estolide [Chem2]: PG 16” is 1.9:1.

[0077] According to yet another particular embodiment, the process for preparing polyglycerol diester 17 is characterized in that the mass ratio “estolide [Chem2]: PG12” is 7.3:1.

[0078] Finally, according to yet another particular embodiment, the process for preparing the polyglycerol triester 18 is characterized in that the mass ratio “estolide [Chem2]: PG12” is 11.2:1.

[0079] Thus, obtaining a monoester, a diester or a triester of polyglycerol depends on the mass ratio between the estolide and the polyglycerol.

[0080] The process for preparing the polyglycerol esters (II) of the invention as defined above is illustrated schematically in [Fig.2].

[0081] Uses of polyglycerol esters of formula (II)

[0082] Finally, another object of the invention lies in the use of a polyglycerol ester (II) as defined above or as obtained according to the process as defined above, as an emulsifying agent, in particular for water-in-oil emulsions, as a pigment wetting agent, as an emollient agent and / or as a texturizing agent. Examples

[0083] The following examples refer in particular to Figures 3 to 11 and describe the synthesis of estolides of formula (I), the synthesis of polyglycerol esters of formula (II), as well as their uses.

[0084] Example 1: synthesis of estolides of general formula (I) represented more particularly by the formulas [Chem2], [Chem3] and [Chem4].

[0085] The estolides synthesized in this example have the general formula (I) in which n is an integer equal to 1, R represents hydrogen or the radical -CO-X and X represents respectively: 1 / the radical -(CH2)7-CH=CH-(CH2)7-CH3 (namely the radical coming from oleic acid), which means that estolide is represented by the formula [Chem2] as defined above; 2 / the radical -(CH2)7-CH2-CH(CH3)-(CH2)7-CH3 (namely the radical originating from isostearic acid), which means that estolide is represented by the formula [Chem3] as defined above;

[0086] 3 / the radical -(CH2)7-CH2-CH2-(CH2)7-CH3 (namely the radical coming from the acid stearic), which means that estolide is represented by the formula [Chem4] as defined above.

[0087] Preparation of oleic acid epoxide [Chem51 The oleic acid used is supplied by the Rossow company. A quantity of 200 g of oleic acid is mixed with 192 mL of 35% hydrogen peroxide and 56 mL of formic acid, in a beaker immersed in a water bath. The medium is mechanically stirred at room temperature for at least 2 hours. The epoxidized oleic acid precipitates as a white solid. Ethyl acetate is added to dissolve the oleic acid epoxide and stop the reaction. The aqueous phase is separated and the organic phase is washed with brine. The organic phases are dried and concentrated to supersaturation. The resulting oleic acid epoxide [Chem5] is left to recrystallize overnight to obtain, after drying, 150 g of a white powder (i.e., 58% yield). The results obtained are illustrated in [Fig.3] (NMR spectrum of the epoxide [Chem5]).

[0088] Preparation of the rChem61 dimer followed by the rChem21 estolide The oleic acid epoxide [Chem5] (150 g) obtained in the previous step is placed in a flask provided with a nitrogen supply, an addition funnel containing 72 g of oleic acid and a thermometer. The system is placed under an inert atmosphere before starting heating. The oleic acid epoxide is then heated to a temperature of 180°C until the reaction medium comprises a quantity of dimer [Chem6] close to 100%, i.e. for a period of 11 minutes. A kinetic study of the reaction by NMR makes it possible to determine at what point a sufficient quantity of dimer is obtained. The oleic acid present in the addition funnel is then added to the reaction medium at the same temperature (180°C) for a period of 34 min. At the end of this period, all the epoxy rings are open. A quantity of 205 g of estolide [Chem2] is obtained (yield of 92%), which appears in the form of a viscous liquid of yellow color, which makes it easy to handle.

[0089] Preparation of estolides [Chem31 and [Chem4] Estolides [Chem3] and [Chem4] are prepared according to the same protocol as that described for estolide [Chem2], from 25g of epoxide [Chem5] with respective quantities of isosetaric acid and stearic acid of 11.2g each. Estolide [Chem3] appears as a yellow viscous liquid, and [Chem4] as a yellowish paste.

[0090] Infrared analysis of rChem21, rChem31 and rChem41 estolides The obtaining of estolides [Chem2], [Chem3] and [Chem4] is verified by in-analysis infrared (IR) using an Agilent Cary 360 KBr infrared spectrometer equipped with a diamond ATR, in the spectral range between 4000 - 650 cm1, resolution 4 cm 1 and 32 scans. The results obtained are presented in [Fig.4]. The infrared spectrum of the three compounds is identical except for the peak at 3010 cm 1 of [Chem2] corresponding to the double bonds of oleic acid. The peaks of the carbonyl bond of the ester and the carboxylic acid are present at 1735 and 1711 cm1.

[0091] Example 2: synthesis of polyglycerol monoesters 11, 13 and 15.

[0092] The polyglycerol esters synthesized in this example are monoesters of poly glycerol 11, 13 and 15 as defined previously. As already indicated they are synthesized respectively from estolide [Chem2] and polyglycerol PG12, PG14 and PG16.

[0093] Preparation of polyglycerol monoester 11 In a 100 ml three-necked flask are added 5.7 g of polyglycerol PG12, 20.2 g of estolide [Chem2] and 0.06 g of calcium hydroxide (catalyst). The three-necked flask is equipped with a temperature probe, a nitrogen supply and a Dean-Stark equipped with a condenser. The medium (which is inert) is stirred, and is heated at 250°C for approximately 40 min (i.e. until the medium becomes clear and the infrared (IR) spectrum no longer shows a peak at 1710 cm1 (characteristic of the carboxylic acid function) and only a peak around 1735 cm 1 (characteristic of the ester function) is observed. The catalyst is neutralized by adding 40.8 μl of phosphoric acid (85%) and heating is continued for a further 15 minutes, then the medium is left to cool. 21.9 g (a yield of 86%) of polyglycerol monoester 11 are obtained, which has the appearance of a viscous orange-yellow liquid (therefore easy to handle).

[0094] Preparation of polyglycerol monoester 13 In the three-necked flask as defined above are added 9.5 g of polyglycerol PG14, 26.5 g of estolide [Chem2] and 0.09 g of calcium hydroxide. The (inert) medium is stirred, heated at 250°C for approximately 60 min (until the medium becomes clear and the IR spectrum no longer shows a peak at 1710 cm 1 and only a peak around 1735 cm 1 is observed). The catalyst is neutralized by adding 55.8 μl of phosphoric acid (85%) and heating is continued for a further 15 minutes, then the medium is left to cool. 30.8 g (a yield of 87%) of polyglycerol monoester 13 are obtained, which has the appearance of a viscous orange-yellow liquid (therefore easy to handle).

[0095] Preparation of polyglycerol monoester 15 In the tricol as defined above are added 14.8 g of polyglycerol PG16, 28.2 g of estolide [Chem2] and 0.12 g of calcium hydroxide. The (inert) medium is stirred, heated to 250°C for approximately 75 min (until the medium becomes clear and the IR spectrum no longer shows a peak at 1710 cm 1 and only a peak around 1735 cm 1 is observed). The catalyst is neutralized by adding 76.2 μl of phosphoric acid (85%) and heating is continued for a further 15 minutes, then the medium is left to cool. 23.47 g (i.e. a yield of 55%) of polyglycerol monoester 15 are obtained, which has the appearance of a very viscous yellow gel.

[0096] Infrared analysis As indicated, the monitoring of each of the 3 esterification reactions leading to polyglycerol esters 11, 13 and 15 is carried out by infrared analysis using the infrared spectrometer as defined previously. The results of the obtained IR spectra are presented in [Fig.5]. The disappearance of the characteristic peak of the carboxylic acid at 1710 cm1 of estolide [Chem2] is well verified. The characteristic peak of OH is also observed at 3400 cm1. Since a larger amount of polyglycerol PG 16 was used to obtain polyglycerol monoester 15, the intensity of the OH peak is much higher with said monoester 15.

[0097] Measurement of the viscosity of polyglycerol esters IL 13 and 15 The viscosities of the polyglycerol esters were measured using the rheometer as defined previously. The results obtained are shown in [Fig.6]. Polyglycerol ester 15 obtained from polyglycerol PG 16 (which has a high molar mass), has the highest viscosity, namely 141 Pa.s, for a shear rate of 1 s1. This result is expected given the intensity of the alcohol peak on the IR spectrum. All polyglycerol esters are more viscous than the reference product, namely polyglycerol polyricinoleate. However, apart from polyglycerol ester 15, the other two polyglycerol esters 11 and 13 are still fluid. Polyglycerol esters 11 and 13 have a viscosity of 49.5 Pa.s and 57.9 Pa.s, respectively, at a shear rate of 1 s1. Both viscosities remain almost invariant with increasing gradient, characterizing them as Newtonian fluids. This aspect of viscosity is particularly interesting for the ease of handling of said polyglycerol esters and for their envisaged applications.

[0098] Example 3: Synthesis of polyglycerol diester 17 and polyglycerol triester 18

[0099] The polyglycerol esters of formula (II) synthesized in this example are more par- particularly polyglycerol diester 17 and polyglycerol triester 18. As with monoester 11, diester 17 and triester 18 are obtained by reaction of estolide [Chem2] with polyglycerol PG12. As already indicated, obtaining a monoester versus a diester or triester of polyglycerol depends on the mass ratio between estolide and polyglycerol.

[0100] Preparation of polyglycerol diester 17 In the three-necked flask as defined in Example 2 are added 4.14 g of polyglycerol PG12, 30.4 g of estolide [Chem2] and 0.09 g of calcium hydroxide. The (inert) medium is stirred, heated to 250°C for approximately 60 min (until the medium becomes clear and the IR spectrum no longer shows a peak at 1710 cm1 and only a peak around 1735 cm1 is observed). The catalyst is neutralized by adding 33.1 μl of phosphoric acid (85%) and heating is continued for a further 15 minutes, then the medium is left to cool. We obtain 30.8 g (a yield of 91%) of the polyglycerol diester 17 which has the appearance of a viscous yellow liquid (therefore easy to handle).

[0101] Preparation of polyglycerol triester 18 In the three-necked flask as defined in Example 2 are added 3.3 g of polyglycerol PG12, 36.2 g of estolide [Chem2] and 0.06 g of calcium hydroxide. The (inert) medium is stirred, heated to 250°C for approximately 120 min (until the medium becomes clear and the infrared spectrum no longer shows a peak at 1710 cm 1 and only a peak around 1735 cm1 is observed). The catalyst is neutralized by adding 38.5 μl of phosphoric acid (85%) and heating is continued for a further 15 minutes, then the medium is left to cool. 31.4 g (a yield of 79%) of polyglycerol triester 18 are obtained, which has the appearance of a very viscous yellow gel.

[0102] Infrared analysis Infrared analysis of polyglycerol esters 11, 17 and 18 was performed using the IR spectrometer as defined previously. The results of the obtained IR spectra are presented in [Fig.7]. The infrared is consistent with the synthesis conditions. The carboxylic acid peak of estolide [Chem2] disappeared in all cases to give rise to the ester peak at 1737 cm1. The alcohol peak is more intense in the monoesterified product 11 because fewer of these functions have been transformed into esters compared to 17 or 18.

[0103] Viscosity measurement The viscosities of polyglycerol esters 11, 17 and 18 were measured using the rheometer as defined previously. The results obtained are shown in [Fig.8]. Triester 18 is very viscous: it has a viscosity of 1083 Pa.s for a shear rate of 1 s 1 versus a viscosity of 63.5 Pa.s for diester 17 and a viscosity of 49.5 Pa.s for monoester 11 for the same shear rate.

[0104] Example 4: Use of polyglycerol esters 11, 17 and 18

[0105] Compatibility of polyglycerol esters with vegetable oils The compatibility of polyglycerol esters 11, 17 and 18 is studied with an oleic sunflower oil which contains 80% oleic acid. A respective quantity of 1.25 g of each of said monoester 11, diester 17 and triester 18 is dissolved hot (70°C) in 23.75 g of oleic sunflower oil, which represents 5% of each polyglycerol ester in the oleic sunflower oil. Given the origin of polyglycerol esters (obtained from oleic acid) it is expected that polyglycerol esters will be compatible with this oil. The results obtained are illustrated in [Fig.9]. It can be deduced from this figure that monoester 11 is not compatible with oleic sunflower oil, because the sample becomes cloudy after dilution. This cloudiness persists even when the sample is heated. Diester 17 is well compatible with oleic sunflower oil. It produces a transparent oil even when cold after dissolution. Triester 18 does not dissolve completely, even when heated. The temperature rose to 100°C without variation. Pieces of triester are observed at the bottom of the pillbox. This experiment demonstrates the need to find the right balance between viscosity, compatibility, and malleability. Taking these different parameters into account, it appears that diester 17 is the best emulsifying agent.

[0106] Use as a wetting agent for pigments Polyglycerol esters 11, 17 and 18 are studied for their properties as pigment wetting agents. A pigment mixture comprising a 50 / 50 mass ratio of titanium dioxide (TiO2) and oleic sunflower oil (as defined in the paragraph above) is previously prepared. An amount of 0.5 g of each of said monoester 11, diester 17 and triester 18 is added respectively in 50 g of the mixture beforehand. This means that each mixture of titanium dioxide (TiO2) and oleic sunflower oil comprises 1% of ester. The results obtained are shown in Figures 10 and 11. The control sample is the mixture of titanium dioxide (TiO2) and oleic sunflower oil (without polyglycerol ester0. The control mixture has a high viscosity of 310 Pa.s for a shear rate of 1s 1 (see [Fig. 11]). The control mixture appears as a paste that is difficult to stir (see [Fig. 10]). The addition of 1% of the inventive polyglycerol ester immediately changes the appearance of each blend. Polyglycerol polyricinoleate (reference) liquefies the paste, making it liquid but not homogeneous. Polyglycerol esters 11 and 17 liquefy the titanium dioxide / oleic sunflower oil mixture homogeneously. Diester 17 has the best performance as a pigment wetting agent. Triester 18 homogenizes the mixture and makes it easy to spread, but the triester does not dissolve completely.

[0107] Use as an emulsifier for water-in-oil (W / O) emulsions Table 1 below exemplifies three emulsions prepared using diester 17 and describes their respective viscosities. Viscosities were measured using a Brookfiled DV-1 Prime, needles and speeds (in rpm) are specified in Table 1, measurements were carried out at room temperature. Protocol for preparing the emulsions in Table 1 Phase A and phase B are prepared separately by mixing the ingredients in two beakers at room temperature. Phase A (internal phase) is introduced dropwise into phase B under vigorous stirring using a deflocculator.

[0108] [Tableauxl] Emulsion 1 Emulsion 2 Emulsion 3 Phase A Dehydrated water 73.5 48.5 23.5 Magnesium sulfate 0.7 0.7 0.7 Phenoxyethanol, Ethylene glycol 0.8 0.8 0.8 Phase B Caprylic / capric glyceride 20 45 70 Polyglycerol ester 17 (diester) 5 5 5 Total (mass percentage) 100 100.0 100.0 Appearance Smooth and glossy emulsion Smooth and glossy emulsion Smooth and glossy emulsion Viscosity (cP) (Needle 07, Speed ​​10 rpm) 23*0, 1 min 138000 Viscosity (cP) (Needle 04, Speed ​​100 rpm) 23°C, 1 min 332 Viscosity (cP) (Needle 02, Speed ​​100 rpm) 23*0, 1 min 125

[0109] It can be deduced from Table 1 that polyglycerol ester 17 makes it possible to produce water-in-oil emulsions with variable viscosities which depend on the quantity of water used in the internal phase A. Polyglycerol ester 17 allows the formation of emulsions with high (emulsion 1) to low (emulsion 3) internal phases (phase A). In fact, the higher the amount of water present in the internal phase A, the higher the viscosity. Polyglycerol ester 17 thus advantageously allows for the production of emulsions with different textures since the viscosity can be adjusted. This possibility of adapting the viscosity is extremely interesting. In addition, polyglycerol ester 17, which is liquid at room temperature, allows the production of water-in-oil emulsions at room temperature, without heating, which also saves time and energy.

[0110] CONCLUSION

[0111] The polyglycerol esters of the invention are extremely interesting surfactants for the production of emulsions (water-in-oil or oil-in-water) in the field of cosmetics. Furthermore, they are also interesting for the wetting of pigments in the industrial field of painting. In general, the polyglycerol esters of the invention are interesting in any field of industry where there is a need to mix a powder with an oily material. This disclosure is not limited to the examples described above, only as an example, but it encompasses all the variations that a person skilled in the art may envisage within the framework of the protection sought. List of cited documents Non-patent literature

[0112] For all useful purposes, the following non-patent elements are cited: - nplcitl : Bastida-Rodrîguez, J. The Food Additive Polyglycérol Polyricinoleate (E-476): Structure, Applications, and Production Methods. ISRN Chemical Engineering 2013, 124767(2013); - nplcit2 : Cermak, S. et al. Synthesis and physical properties of new estolide esters. Industrial Crops and Products 46, 386-391 (2013) ; - nplcit3 : Salih, N., Salimon, J. & Yousif, E. Synthesis of oleic acid based esters as potential basestock for biolubricant production. Env. Sri 35, 115-123 (2011) ; - nplcit4 : Hoong Seng Soi, Arniza, M., Nek Mat Din, N. S. M., Armylisas, A. H. & Yeong, S. Synthesis and physicochemical properties of novel lauric acid capped estolide esters and amides made from oleic acid and their évaluations for biolubricant basestock. Industrial Crops and Products 140, 111653 (2019).

Claims

Claims

1. Estolide characterized in that it has the following general formula (I) [Chem.l] 0 AXO OR 0 or n (I), in which: n is an integer ranging from 1 to 5, and preferably from 1 to 2, X represents a radical originating from a saturated or unsaturated fatty acid, said radical X being a hydrocarbon radical, linear or branched, having from 4 to 36 carbon atoms, saturated or unsaturated, unsubstituted or substituted by one or more hydroxy substituents (-OH), R represents, independently of one another, a hydrogen or a radical -CO-X with X as defined above.

2. Estolide according to claim 1, characterized in that the radical X comes from an unsaturated fatty acid chosen from the group comprising oleic, erucic, linoleic, eicosenoic, myristoleic, palmitoleic, y-linolenic, arachidonic, a-linolenic and ricinoleic acid.

3. Estolide according to claim 1, characterized in that the radical X comes from a saturated fatty acid chosen from the group comprising isostearic, stearic, palmitic, myristic, behenic, caprylic, pelargonic, capric, butyric, valeric, caproic, enanthic, un-decyl, tridecyl, margaric, nonadecyl, arachidic (eicosanoic), lignoceric, pentacosanoic, cerotic, heptaco-sanoic, montanic, nonacosanoic, melissic and hentriacon-tanoic acid.

4. Estolide according to any one of claims 1 to 3, characterized in that the radical X comes from a fatty acid chosen from the group comprising oleic, isostearic, stearic, palmitic, myristic, behenic, caprylic, pelargonic, capric, erucic and linoleic acid.

5. Estolide according to any one of claims 1, 2 and 4, characterized in that the radical X comes from oleic acid and is represented by the semi-developed formula -(CH2)7-CH=CH-(CH2)7-CH3.

6.

7. Estolide according to any one of claims 1 to 5, characterized in that in formula (I) n is an integer equal to 1. Estolide according to any one of claims 1 to 2 and 4 to 6, characterized in that n is an integer equal to 1, X represents the radical -(CH2) 7-CH=CH-(CH2)7-CH3 and R represents hydrogen or the radical -CO-(CH2)7-CH=CH-(CH2)7-CH3, said estolide being represented more particularly by the formula [Chem. 2]

8. Process for the preparation of an estolide as defined in any one of claims 1 to 7, characterized in that it comprises: - the transformation of oleic acid, of semi-developed formula CH3 -(CH2)7-CH=CH-(CH2)7-COOH, into oleic acid epoxide of formula [Chem. 5] - the autocatalytic opening of oleic acid epoxide [Chem5] by reaction between the epoxide function of [Chem5] and the carboxylic acid function of another oleic acid epoxide molecule [Chem5] to obtain an oleic acid dimer comprising an epoxide function, said dimer having the formula [Chem. 6] - the reaction between the dimer [Chemô] with a fatty acid of semi-developed formula X-COOH with X as defined in any one of claims 1 to 5, in order to obtain the estolide as defined in any one of claims 1 to 7.

9. Preparation process according to claim 8, characterized in that: - the step of transforming oleic acid into oleic acid epoxide of formula [Chem5] is carried out from formic acid and hydrogen peroxide at a temperature ranging from 15 to 25°C, for a period ranging from 2 to 4 hours, - the oleic acid epoxide [Chem5] is purified by recrystallization.

10. Preparation process according to claim 8 or 9, characterized in that the autocatalytic opening of the oleic acid epoxide [Chem5] is carried out at a temperature ranging from 140 to 210°C, preferably from 160 to 190°C, for a time ranging from 5 to 90 minutes (min), preferably from 8 to 25 min, which makes it possible to form the dimer [Chem6].

11. Preparation process according to any one of claims 8 to 10, characterized in that the mass ratio between the fatty acid X-COOH and the oleic acid epoxide [Chem5] varies from 1:0.5 to 1:4, and preferably from 1:1.25 to 1:2.

5.

12. Preparation process according to any one of claims 8 to 11, characterized in that the reaction between the dimer [Chem6] and the fatty acid X-COOH is carried out at a temperature ranging from 140 to 210°C, preferably from 160 to 190°C, for a time ranging from 30 to 150 minutes, preferably from 40 to 90 min, which makes it possible to obtain the estolide of general formula (I).

13. Use of an estolide as defined in any one of claims 1 to 7 or as obtained according to the process of any one of claims 8 to 12, as a plasticizing agent, adhesive agent, lubricating agent, emollient agent, wetting agent and / or emulsifying agent.

14. Use of an estolide as defined in any one of claims 1 to 7 or as obtained according to the process of any one of claims 8 to 12 with a polyol, preferably a polyglycerol or sucrose, to obtain a polyol ester.

15. Use according to claim 14 wherein the polyol is a polyglycerol, meaning that the polyol ester is a polyglycerol ester.

16. Polyglycerol ester characterized in that it has the following general formula (II) [Chem. 7] / 4^ R' oyoyo XO [ 0 r\ r\ (II), in which: m is an integer ranging from 0 to 19, preferably from 1 to 15, and more preferably from 1 to 9, R' represents independently of one another a hydrogen or a radical of formula [Chem. 8] ​​o X^O OR 0 OR n in which X, R and n are as defined in any one of claims 1 to 7, with the condition that at least one of the R' of formula (II) represents a radical [Chem8].

17. Polyglycerol ester according to claim 16, characterized in that in formula (II) the integer n of the radical [Chem8] is equal to 1, X represents the radical CH3-(CH2)7-CH=CH-(CH2)7- and R represents hydrogen or the radical -CO-(CH2)7-CH=CH-(CH2)7-CH3, which means that the radical R' is represented by the formula [Chem. 10] 0 OR 0 7 7 O OR 0 R being as defined above.

18. Polyglycerol ester according to claim 16 or 17, characterized in that in formula (II), one, two or three R' represents(s) the radical [Chem8] or [ChemlO].

19. Process for the preparation of a polyglycerol ester of general formula (II) as defined in any one of claims 16 to 18, characterized in that it comprises the reaction between an estolide of general formula (I) as defined in any one of claims 1 to 7 with a polyglycerol of general formula (III), [Chem.9] (HD, in which m is an integer ranging from 0 to 19, preferably from 1 to 15, and more preferably from 1 to 9, said reaction being carried out in the presence of a catalyst, in order to obtain said polyglycerol ester (II).

20. A process for preparing a polyglycerol ester according to claim 19, characterized in that the catalyst is chosen from the group comprising calcium hydroxide, potassium hydroxide, sodium hydroxide and magnesium hydroxide.

21. Process for the preparation of a polyglycerol ester according to claim 19 or 20, characterized in that the mass ratio “estolide (I): polyglycerol (III)” varies from 0.5:1 to 30:

1.

22. Use of a polyglycerol ester as defined in any one of claims 16 to 18 or as obtained according to the process of any one of claims 19 to 21, as an emulsifying agent, pigment wetting agent, emollient agent and / or texturizing agent.

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