Compositions of polythiols and their preparation process from terpenes or terpene derivatives

Abstract

The present invention relates to a process for preparing a polythiol from a terpene or a terpene derivative, as well as polythiol compositions and novel polythiols. The process comprises the following steps: a terpene or a terpene derivative is reacted with a thiocarboxylic acid in the presence of oxygen (O2) and at least one organic solvent, so as to obtain a reaction medium comprising a polythioester and said at least one solvent; a deprotection step is carried out on the polythioester obtained in step a), so as to obtain a polythiol; wherein steps a) and b) are carried out in one-pot synthesis.

Description

Title of the invention: POLYTHIOL COMPOSITIONS AND THEIR PROCESS FOR PREPARATION FROM TERPENES OR TERPENIC DERIVATIVES

[0001] The present invention relates to a process for preparing polythiol compositions using terpenes or terpene derivatives as starting reagents, as well as the polythiol compositions that can be obtained by this process.

[0002] Polythiols are molecules of great industrial interest. They are used, for example, as crosslinking agents, particularly at low temperatures.

[0003] Several synthetic routes exist today for obtaining polythiols. Among the most widely used methods is the reaction between polyols and mercaptoacids (described, for example, in US patent application 2005153231). While this reaction is straightforward and allows access to a variety of polythiol structures, the products obtained generally exhibit low resistance to hydrolysis due to the significant presence of ester groups.

[0004] Alternatively, the direct addition of hydrogen sulfide to polyenes by acid or photochemical catalysis allows the production of molecules without hydrolyzable functional groups. This addition is described in particular in application WO 12018757. However, with this method, large quantities of sulfide-type compounds can be co-produced and, depending on the reagents used, conversion problems may arise. Thus, the molecules obtained may contain numerous unconverted double bonds, which generates stability problems and lowers the overall -SH functional group content. In the case of a triene-type starting reagent, for example, this results in the presence of significant amounts of mono- and / or dithiols in the resulting composition.

[0005] However, controlling and / or reducing the formation of these by-products, such as mono- and / or di-thiols, is important depending on the intended applications. Indeed, their content influences the degree of crosslinking of the materials subsequently prepared, particularly thermosetting materials produced from a polythiol-type resin and hardener. It has thus been demonstrated that the degree of crosslinking influences the physical and viscoelastic properties of polymers, such as their density, modulus, limits of elasticity, and glass transition temperature (Tv, or Tg). Tg is conventionally determined by the Differential Scanning Calorimetry (DSC) method or by dynamic mechanical analysis (DM(T)A).

[0006] These parameters are directly related to the behavior of materials such as the hardness, elasticity, flexibility, and tear resistance are all important factors. The aim is to obtain polymers with a high glass transition temperature, in order to produce materials with greater thermal resistance (i.e., materials that retain their characteristics over a wider temperature range).

[0007] There is therefore a need for an industrial polythiol preparation process that allows control, or even maximization, of the conversion of C=C double bonds into -SH functions. There is also a need for a polythiol preparation process that allows control, or even reduction, of the formation of by-products (for example, mono- and / or -dithiols in the case of trithiol preparation, or sulfides).

[0008] One technical solution involves using polythioester intermediates: the C=C double bonds are converted into R'-C(O)-SR type functions, which are then deprotected to obtain the desired polythiols. However, these polythioester intermediates present a significant technical challenge for industrial implementation. They are generally very viscous or even solid compounds. This makes them difficult to handle for the deprotection step. Consequently, they generate numerous practical problems at the industrial level and are therefore rarely used.

[0009] Furthermore, these polythioesters are conventionally obtained by reacting a polyene with a thiocarboxylic acid, in particular thioacetic acid. However, this reaction involves the use of a large excess of thiocarboxylic acid, which must be removed before the deprotection step. Thus, additional steps of evaporating this excess thiocarboxylic acid and / or purifying the polythioesters are necessary to carry out the subsequent deprotection step.

[0010] Finally, the reagents used in this type of process are generally petroleum-derived hydrocarbons. Given current environmental and climate challenges, processes using bio-based and / or renewable raw materials are being sought.

[0011] There is therefore a need for an improved process for preparing polythiols, via polythioesters.

[0012] There is also a need for an improved process for preparing polythiols from bio-based and / or renewable raw materials.

[0013] There is a need for polythiol compositions in which the proportion of -SH functions is controlled, or even maximized. The term "proportion of -SH functions" refers to the ratio of the mass of all -SH functions to the total mass of the composition.

[0014] There is also a need for polythiol compositions obtained from bio-based and / or renewable materials.

[0015] The present invention aims to provide an improved method for preparing polythiol compositions from terpenes or terpene derivatives, the industrial implementation of which is simplified.

[0016] The present invention aims to provide a method for preparing improved polythiol compositions from terpenes or terpene derivatives, by which the rate of -SH functions is controlled, or even maximized.

[0017] The present invention also aims to provide improved polythiol compositions, in particular with a controlled, or even maximized, -SH function ratio.

[0018] The present invention also aims to provide polythiol compositions derived from bio-based and / or renewable raw materials, namely terpenes and terpene derivatives.

[0019] The present invention aims to provide polythiol compositions useful for the preparation of polymers, preferably thermosetting polymers.

[0020] The present invention meets all or part of the above objectives.

[0021] The present inventors have discovered, surprisingly, that it is possible to implement a "one-pot" (also called monotope) process for the synthesis of polythiols from terpenes or terpene derivatives. A "one-pot process" is understood to mean, in particular, a process in which the synthesis intermediates (i.e., the polythioesters such as those according to the invention) are not isolated from the reaction medium to carry out the subsequent deprotection step. In the context of the industrial synthesis of polythiols, such a one-pot process offers numerous advantages.

[0022] In particular, the polythioester intermediate formation step according to the invention (hereinafter referred to as step a)) makes it possible to obtain a very good conversion (in particular between 90% and 100% conversion of the terpene or terpene derivative) while avoiding the use of an excessive excess of thiocarboxylic acid. Indeed, a significant excess of thiocarboxylic acid is conventionally used in prior art processes, which represents a loss for the process and generates a large quantity of waste to be isolated and treated. Moreover, such an excess is not compatible with a "one-pot" process because it must be eliminated before the deprotection step. The present invention makes it possible to avoid these drawbacks, which represents an economic as well as an environmental advantage.

[0023] Another advantage of the present invention is that the reaction medium comprising the polythioester intermediates obtained at the end of step a) can be easily stirred and handled. In particular, it can be in the form of a liquid or a slightly viscous or viscous suspension. This avoids operational difficulties at an industrial level.

[0024] The reaction medium comprising the polythioester intermediates is also compatible with the deprotection step (hereinafter step b)), which represents a simplification of the process.

[0025] Thus, steps a) and b) according to the invention are carried out in a "one pot" process. The process is therefore significantly improved because the intermediate steps of removing excess thiocarboxylic acid and / or purifying poly-thioester intermediates, such as extraction, recrystallization and / or distillation, are thus avoided.

[0026] Furthermore, terpenes and their derivatives can prove particularly useful as starting polyenes leading to polythiols. Terpenes and their derivatives address many current environmental and climate challenges. They are generally bio-based, that is, derived from renewable organic matter (biomass) of plant or animal origin. They also exhibit a wide diversity of structures, allowing for a great versatility of applications.

[0027] The polythiol compositions that can be obtained by the process according to the invention are novel and have a controlled, or even maximized, -SH content. They are characterized in particular by a high mass ratio as defined below. (x-i)thiol(s) They are particularly well-suited to the preparation of materials such as thermosetting plastics from resins. Thus, the present invention makes it possible to obtain materials with superior properties. For example, polymers with a higher Tg value, and therefore greater heat resistance, can be obtained, and / or superior compressive strength properties, and / or a larger modulus and elastic range.

[0028] Thus, the present invention relates to a process for preparing a polythiol comprising the following steps: a. A terpene or a terpene derivative is reacted with a thiocarboxylic acid in the presence of oxygen (O2) and at least one organic solvent, so as to obtain a reaction medium comprising a polythioester and said at least one organic solvent; and b. a deprotection step is carried out on the polythioester obtained in step a), so as to obtain a polythiol;

[0029] in which step a) and step b) are carried out in one pot (or monotope) synthesis.

[0030] The present invention relates to a polythiol composition A obtained from a terpene or a terpene derivative having x C=C double bonds, said composition comprising: - the polythiol corresponding to the terpene or terpene derivative comprising x -SH functions; and - the thiol(s) corresponding to the terpene or terpene derivative comprising (x-1) -SH functions, with x being an integer greater than or equal to 3; and preferably in which the mass ratio is (xl)rfaW(s) between 1:1 and 50,000:1, preferably between 2:1 and 50,000:1.

[0031] The present invention also relates to a polythiol chosen from trithiol derived from dihydrofarnesene, heptathiol derived from isosqualene and tetrathiol derived from camphorene.

[0032] By "alkyl" is understood in particular a saturated hydrocarbon radical, linear, branched or cyclic, comprising from 1 to 10, preferably from 1 to 4, carbon atoms.

[0033] By "aryl" is meant in particular an aromatic cyclic hydrocarbon radical (monocyclic, bicyclic or tricyclic) comprising 6 to 10 carbon atoms, preferably a phenyl or a naphthyl, more preferably a phenyl.

[0034] By "aralkyl", we mean in particular an alkyl substituted by an aryl, for example benzyl. Terpenes

[0035] "Terpenes" include, in particular, linear, branched or cyclic hydrocarbon compounds consisting of repeating isoprene units (C5H8)n, n being an integer between 2 and 8, preferably between 2 and 6. In particular, said terpenes comprise at least three C=C double bonds. Preferably, said terpenes comprise 3, 4, 5 or 6 C=C double bonds.

[0036] Terpenes are often marketed in the form of compositions comprising different isomers, the proportions of which may vary (particularly depending on their production process). Such compositions are included within the scope of the present invention and can be used directly as a starting reagent.

[0037] Terpene families are classically categorized based on the value of n (with the corresponding number of carbon atoms), according to the table below:

[0038] [Tables] n-value: 2(C10) 3 (C15) 4 (C20) 5 (C25) 6 (C30) 8 (C40) Family: Monoterpenes, Sesquiterpenes, Diterpenes, Segerte^, Triterpenes, Tetraterpenes

[0039] In particular, the terpenes are selected from monoterpenes, triterpenes and sesquiterpenes. More specifically, the terpenes are selected from linear or branched terpenes.

[0040] Among the preferred terpenes, myrcene and famesene can be mentioned.

[0041] Myrcene:

[0042] Myrcene is a monoterpene. There are various isomers of myrcene, including ocimene and alloocimene. In particular, alpha-myrcene, the beta-myrcene, cis-alpha-ocimene, trans-alpha-ocimene, cis-beta-ocimene, trans-beta-ocimene, 4-cis-6-cis-alloocimene, 4-cis-6-trans-alloocimene, 4-trans-6-cis-alloocimene, and 4-trans-6-trans-alloocimene (see [Fig. 1]). Preferably, beta-myrcene, the natural form (CAS No. 123-35-3), with the following formula, is used:

[0043] [Chem.l] ÇHg CHg CH3

[0044] The famesene:

[0045] Famesene is a sesquiterpene. It exists in the form of two isomers: alpha-farnesene (CAS No. 502-61-4) and beta-farnesene (CAS No. 502-60-3) with the following formulas:

[0046] [Chem.2] ?'A-. a-famésène • xy>- X x.. •• ^-famesene

[0047] Cis-alpha-farnesene, trans-alpha-farnesene, cis-beta-farnesene and trans-beta-farnesene may be mentioned in particular. Beta-farnesene is preferred, and trans-beta-farnesene even more preferentially (CAS No. 18794-84-8).

[0048] Other terpenes that may be used include humulene (CAS 6753-98-6), elemene, germacrene, bisabolene, cembrene, casbene, zingiberene, camphorene and their isomers. In particular, the following isomers may be mentioned: alpha-elemene, beta-elemene, gamma-elemene, delta-elemene, germacrene A, germacrene B, germacrene C, germacrene D, germacrene E, alpha-bisabolene, beta-bisabolene and gamma-bisabolene.

[0049] Terpene derivatives:

[0050] The term “terpene derivatives” refers in particular to compounds whose structure is derived from that of terpenes. They may be produced by the chemical transformation of terpenes or may exist naturally. In particular, said terpene derivatives comprise at least three C=C double bonds, for example between 3 and 10 C=C double bonds.

[0051] The following terpene derivatives can be cited.

[0052] Hydrogenated terpene derivatives or hydrogenated terpenes:

[0053] In particular, the term "hydrogenated derivative of a terpene" means a compound with the molecular formula (C5nH8n+2z), where z is an integer at least equal to 1 and n is as defined above. Preferably, z is between 1 and 10, more preferably between 1 and 3.

[0054] Among hydrogenated derivatives, squalene and dihydrofarnesene are particularly preferred.

[0055] Squalene (CAS No.: 111-02-4) has the following formula:

[0056] It has the molecular formula C3oH5o.

[0057] Dihydrofarnesene has the molecular formula Ci5H26. It can exist in the form of different isomers depending on the double bond of the hydrogenated farnesene and the alpha or beta isomer of the farnesene chosen. Dihydro-beta-farnesene (and all its isomers) is preferred.

[0058] More specifically, the following isomers of dihydrofarnesene can be used according to the present invention:

[0059] [Chem.3]

[0060] [Chem.4]

[0062] When partial hydrogenation of farnesene (Ci5H24) is carried out, a composition comprising dihydrofarnesene and one or more other partially hydrogenated compound(s) selected from:

[0063] tetrahydrofamesene (Ci5H28) and hexahydrofarnesene (Ci5H30). Such a composition can be used as a starting reagent in the context of the present invention: the dihydrofarnesene it contains will give the corresponding trithiol according to the process of the invention. Preferably, such a composition comprises at least 70% by weight of dihydrofarnesene, preferably at least 80% by weight of dihydrofarnesene, relative to the total weight of the composition. Even more preferably, the composition comprises at least 85% by weight of dihydrofarnesene, relative to the total weight of unreacted farnesene, of all the partially hydrogenated compounds derived from farnesene and famesan present in the composition. In this type of composition, the beta isomer of farnesene is particularly preferred for obtaining dihydro-beta-famesene.

[0064] Thus, MYRALENE 10™ (CAS No. 1581740-29-5) is a particularly suitable example. This composition is obtained from the partial hydrogenation of beta-farnesene, and its preparation process is described in application WO 2016 / 064853. MYRALENE 10™ consists mainly of dihydro-beta-farnesene. Such a composition is perfectly suited as a starting reagent according to the present invention. Terpenoids:

[0065] The term "terpenoids" refers in particular to compounds whose structure is derived from terpenes and which may include one or more heteroatoms (in particular oxygen and / or nitrogen, preferably oxygen) and / or one or more chemical functional groups. For example, terpenoids may include at least one functional group selected from among alcohol, ketone, ether, ester, or aldehyde groups.

[0066] In particular, they can be of the crude formula (C5nH8n_2y), with n as defined above and y being an integer between 1 and 4.

[0067] Preferably, the terpenoid is chosen from the group consisting of:

[0068] cosmene, beta-carotene, lycopene, farnesol, retinol, retinal, vitamin A, nerolidol, isomyrcenol and ipsdienol.

[0069] Oligomers of terpenes and / or hydrogenated derivatives of terpenes and / or terpenoids:

[0070] The term “oligomer” refers in particular to an assembly of 2 to 10 terpenes and / or hydrogenated derivatives of terpenes and / or terpenoids as defined above, whether identical or different, preferably identical. Preferably, dimers and / or trimers of terpenes and / or terpenoids are used. More preferably, terpene dimers are used.

[0071] One can particularly cite the dimer of beta-farnesene, called isosqualene, with molecular formula C30H48, and the following formula (for example as described in US document 2011 / 0287988A1):

[0072] [Chem.6]

[0073] The following isomers of iso-squalene can also be used according to the present invention:

[0074] [Chem.7]

[0075] [Chem. 8] T5.and

[0076] [Chem.9]

[0077] Thus, the term "terpenes and terpene derivatives" is preferably understood to mean:

[0078] terpenes, hydrogenated terpene derivatives, terpenoids and oligomers of terpenes and / or hydrogenated terpene derivatives and / or terpenoids.

[0079] Thus, said terpene or terpene derivative may be chosen from the group consisting of:

[0080] myrcene, famesene, humulene, elemene, germacrene, bisabolene, cosmene, cembrene, casbene, zingiberene, beta-carotene, lycopene, camphorene, squalene, isosqualene, dihydro-farnesene, farnesol, retinol, retinal, vitamin A, nerolidol, iso-myrcenol and ipsdienol.

[0081] More preferably, the terpene or terpene derivative is chosen from the group consisting of: myrcene, famesene, squalene, isosqualene, humulene and dihydrofarnesene.

[0082] Such raw materials occur naturally in plants and marine species, or can be produced by fermentation, by genetically modified or non-genetically modified organisms, possibly using renewable carbon sources. They are also commercially available. For example, AMYRIS markets trans-beta-farnesene under the name BIOFENE®, and DRT markets myrcene. Polythiols

[0083] According to the invention, the polythiol corresponding to the starting terpene or terpene derivative as defined above is called "polythiol".

[0084] By "corresponding to the starting terpene or terpene derivative", it is meant that the structure of the starting terpene or terpene derivative and the resulting polythiol are identical, with the exception of the C=C double bonds which have been converted into -SH functions (i.e., -CH-C(SH)-): for x C=C double bonds of the starting terpene or terpene derivative, x -SH functions are obtained. The term "polythiol" also includes polythiols that are positional isomers of the double bonds.

[0085] The number of C=C double bonds contained in said terpene or terpene derivative is hereinafter referred to as "x", x being an integer, preferably greater than or equal to 3. Preferably, x is between 3 and 10, more preferably between 3 and 7. The polythiols according to the invention may also be called (x)thiols, with x as defined above. Polythioester intermediates

[0086] The term "intermediate polythioester" or "polythioester" refers to the polythioester corresponding to the starting terpene or terpene derivative. The term "corresponding to the starting terpene or terpene derivative" means that the structure of the starting terpene or terpene derivative and the resulting polythioester are identical, except that the C=C double bonds have been converted into -CH-C(O)-S-Ri functional groups (Ri depends on the thiocarboxylic acid used, preferably Ri is a methyl group): for x C=C double bonds, x thioester functional groups are obtained, with x as defined above. The term "polythioesters" also includes polythioesters that are positional isomers of the double bonds of the starting terpene or terpene derivative. METHOD ACCORDING TO THE INVENTION Step a)

[0087] In step a), a terpene or a terpene derivative as defined above is reacted with a thiocarboxylic acid in the presence of oxygen (O2) and at least one organic solvent, so as to obtain a reaction medium comprising a polythioester as defined above and said at least one organic solvent.

[0088] The reaction is as follows: R-CH=CH-R + RrC(O)-SH -> R-CH2-CH(SC(O)-Ri)-R

[0089] Step a) is carried out in the presence of oxygen (O2), which acts as a reaction initiator. Step a) can therefore be carried out in the presence of air, depleted air (a mixture of oxygen and nitrogen N2), or a mixture of oxygen and another inert gas. Oxygen can be introduced into the reaction medium by any technique. Oxygen can also be added during the entire duration of step a) or not.

[0090] In particular, oxygen is bubbled into the reaction medium, preferably in the form of depleted air. For example, depleted air is passed through a sintered diffuser or a diffuser that is immersed in the reaction medium. Alternatively, oxygen can be bubbled into the reaction medium and nitrogen introduced into the gas phase of the reactor (i.e., the reactor headspace).

[0091] The oxygen flow rate can be between 0.01 and 100 nL / h, preferably between 0.05 and 10 nL / h, preferably again between 0.05 and 5 nL / h, in particular between 0.05 and 2 nL / h (normo litres / h).

[0092] Step a) is carried out in particular in the absence of any other initiator of the reaction, and more preferably in the absence of AIBN (azobisisobutyronitrile) and / or in the absence of UV radiation.

[0093] Step a) is also carried out in the presence of an organic solvent or a mixture of organic solvents. A polar solvent, or a mixture of polar solvents, is particularly preferred. The solvent(s) may be protic or aprotic. Examples of solvents that may be used include: alcohols, ethers (preferably cyclic ethers and glycol ethers such as dialkyl glycol ethers), organochlorine solvents, carboxylic acids, or mixtures thereof.

[0094] Alcohols are preferred, in particular those of the following general formula (IV):

[0095] R4-OH (IV)

[0096] in which R4 represents an alkyl as defined above. Preferably, the alcohol is chosen from the group consisting of: methanol, ethanol, isopropanol, n-propanol, n-butanol, butan-2-ol, isobutanol, tert-butanol, preferably ethanol.

[0097] Preferably, the solvent is chosen from the group consisting of: tetrahydrofuran (THF), 2-methyltetrahydrofuran (Me-THF), dioxane, chloroform, acetic acid, methanol, ethanol, isopropanol, n-propanol, n-butanol, butan-2-ol, isobutanol, tert-butanol, dimethoxyethane (also called glyme), diethoxyethane, dibutoxyethane or mixtures thereof, more preferably ethanol.

[0098] The amount of solvent used is generally chosen according to the desired viscosity of the reaction medium. Total or partial solubilization can be achieved by a person skilled in the art, depending on the desired viscosity of the reaction medium. Preferred Typically, between 1 eq. and 50 eq. molar is used, preferably between 1 eq. and 20 eq. of solvent(s) relative to the terpene or terpene derivative.

[0099] The solvent can be added from the beginning of step a) in whole or in part. It can be added at one point, in several stages (semi-continuous) or gradually (continuously), during step a).

[0100] The thiocarboxylic acid preferably has the following general formula (II):

[0101] RrC(O)-SH (II)

[0102] in which:

[0103] Ri represents an alkyl radical, an aryl radical or an aralkyl radical as defined above.

[0104] Preferably, Ri is chosen from methyl, ethyl and benzyl.

[0105] Thioacetic acid, for which Ri is a methyl group, is particularly preferred according to the invention. For example, with thioacetic acid, a polythioacetate is obtained as a polythioester intermediate.

[0106] According to one embodiment, thiocarboxylic acid can be generated in situ (cf. US document 3,270,063, THOMPSON CHEMICAL CO, 1963: “Methods of making primary mercaptans”): thioacetic acid can be produced from acetic anhydride and hydrogen sulfide, in the presence of a catalyst.

[0107] Preferably, to carry out step a), the thiocarboxylic acid and the solvent(s) are introduced into the reactor first, then oxygen is introduced, for example by bubbling air. The terpene or derivative can then be added to the reaction medium.

[0108] The temperature of step a) can be between 5 and 80°C, preferably between 5 and 50°C, more particularly between 5 and 25°C, for example between 5 and 10°C. Step a) is generally carried out at atmospheric pressure.

[0109] The thiocarboxylic acid / double bond molar ratio of the terpene or terpene derivative can be between 1 and 20, preferably between 1 and 10, for example between 1 and 5, preferably still between 1 and 3.

[0110] Step a) enables the formation of a polythioester intermediate as defined above from a terpene or a terpene derivative.

[0111] The reaction medium obtained at the end of step a) may thus comprise: - a polythioester intermediate as defined above; - the solvent or mixture of solvents as defined above; - possibly by-products such as (xl)polythioesters; and - possibly one or more reagents that did not react.

[0112] By "(x-l)polythioester" is meant in particular a compound comprising x-1 thioester functions, with x being as defined above. It is a compound having retained a C=C double bond (i.e. a C=C double bond that has not reacted).

[0113] The reaction medium may thus comprise between 10% and 85% by weight of polythioester intermediate, relative to the total reaction medium.

[0114] The reaction medium may comprise between 15% and 90% by weight of solvent(s), relative to the total reaction medium. Step b)

[0115] Step b) of deprotection of the polythioester intermediate obtained in step a) yields a polythiol. It can be carried out by any means known to those skilled in the art. Since steps a) and b) are performed in one-pot synthesis according to the invention, it is understood that the reaction medium comprising the polythioester obtained at the end of step a) is retained to carry out the deprotection step b). Thus, steps a) and b) are carried out in the presence of the same solvent (or mixture of solvents). It is possible to add said solvent (or mixture of solvents) during step b). In particular, the process according to the invention does not include any step of separation and / or extraction and / or washing of the (organic) phase comprising the polythioester between steps a) and b). In particular, no intermediate step of purification of the polythioester is carried out. More specifically, no recrystallization and / or distillation step of the polythioester is carried out.

[0116] Deprotection b) can be carried out by conventional methods: using a base or an acid, a Dy(OTf)3 type catalyst (cf. Liang et al., Asian J. Org. Chem. 10.1002 / ajoc.201700481) or a quaternary ammonium cyanide salt type compound (cf. US 7,173,156).

[0117] Preferably, deprotection b) is a basic deprotection, preferably in the presence of an alcohol as defined above. It is generally carried out by adding an alkali hydroxide, preferably NaOH or KOH. The addition can be made dropwise.

[0118] Step b) of deprotection can also be acid deprotection, preferably in the presence of an alcohol as defined above. It can be carried out with hydrochloric acid, methanesulfonic acid, or anhydrous methanesulfonic acid. When the deprotection is acidic, it is preferable to use an alcohol as defined above as the solvent.

[0119] Sulfonic acid

[0120] The sulfonic acid is preferably an organosulfonic acid, possibly anhydrous.

[0121] Sulfonic acid can have the following general formula (III):

[0122] R2-SO3H (III),

[0123] where R2 represents:

[0124] - an alkyl radical, preferably as defined above, optionally substituted, in whole or in part, by one or more identical or different halogen atoms, or

[0125] - an aryl radical, preferably as defined above, optionally substituted by a saturated hydrocarbon chain, linear or branched, comprising 1 to 4 carbon atoms.

[0126] The halogen atom may be chosen from fluorine, chlorine, and bromine. In particular, said alkyl may be perhalogenated, more particularly perfluorinated.

[0127] Preferably, the sulfonic acid is an alkane-sulfonic acid, possibly anhydrous (in the formula above, R2 is an alkyl).

[0128] Thus, sulfonic acids (as well as their anhydrous forms) can be chosen from:

[0129] methanesulfonic acid, ethanesulfonic acid, n-propanesulfonic acid, Ao-propanesulfonic acid, n-butanesulfonic acid, iso-butanesulfonic acid, sec-butanesulfonic acid, tert-butanesulfonic acid, trifluoromethanesulfonic acid, para-toluenesulfonic acid, benzenesulfonic acid and mixtures of two or more of them in any proportions.

[0130] According to a particularly preferred embodiment, the sulfonic acid used in the context of the present invention is methanesulfonic acid (MSA) or anhydrous methanesulfonic acid (ASA).

[0131] Said sulfonic acid may or may not be tolerated. Preferably, it is not tolerated.

[0132] When supported, for example, sulfonated resins of the co type can be used styrene-divinylbenzene polymer, for example Amberlyst® 15 resin, or Nafion®.

[0133] For example, between 0.1 and 10 eq. of acid are used for a polythioester.

[0134] For example, between 3 and 60 eq. are used, preferably between 3 and 20 eq. (equivalent molar) of alcohol for a polythioester.

[0135] Step b) of deprotection can be carried out at a temperature between 10 and 100°C, preferably between 25 and 80°C, and even more preferably between 40 and 80°C. It is generally carried out at atmospheric pressure.

[0136] Steps a) and b) can be carried out in the same reactor. For example, a batch reactor can be used.

[0137] Subsequent conventional recovery and / or purification steps of the polythiol recovered after step b) can be carried out, depending on the desired degree of purity. For example, when deprotection is achieved by adding a base, the reaction medium can then be acidified, and conversely: when deprotection is achieved by adding an acid, the reaction medium can be made alkaline.

[0138] The resulting organic phase comprising the various thiols (in particular the polythiol and the (xl)thiols) can then be extracted and possibly concentrated.

[0139] Thus and in particular, the polythiol obtained may be in the form of a polythiol composition as mentioned below.

[0140]

[0141]

[0142]

[0143]

[0144]

[0145]

[0146]

[0147]

[0148]

[0149]

[0150]

[0151] COMPOSITIONS ACCORDING TO THE INVENTION When preparing a polythiol from a terpene or a terpene derivative having x C=C double bonds, the conversion of these double bonds into -SH functions is generally not total and by-products may form at each of the different steps, regardless of the process used. According to the invention, the polythiol corresponding to the starting terpene or terpene derivative and comprising x -SH functions is therefore called a "polythiol". In this case, the conversion of the x starting C=C double bonds into -SH functions is total. According to the invention, a thiol corresponding to the starting terpene or terpene derivative and comprising (x-1) -SH functional groups is called "(xl)thiol". By "corresponding to the starting terpene or terpene derivative", it is understood that the structure of the starting terpene or terpene derivative and the resulting (xl)thiol are identical, except for the x C=C double bonds which have been converted into (x-1) -SH functional groups. In this case, the conversion of the C=C double bonds into -SH functional groups was not complete: one -SH functional group is missing. The C=C double bond not converted to a -SH function can, in particular: - always be in the form of a C=C double bond; or - in the form of a thioester function that has not been deprotected. Therefore, different structures of (xl)thiols can exist, but they are grouped here under this general name characterizing their number of -SH groups (unless otherwise specified). Positional isomers of the double bonds are also included. For example, in step a), (xl)thioesters can be formed. In this case, for x starting C=C double bonds, only (x-1) C=C double bonds react with the thiocarboxylic acid to form (x-1) thioester functions. Furthermore, during step b), it is also possible that the deprotection will not be total. Thus, it is possible to form according to the process according to the invention: - (xl)thiols from the (xl)thioesters formed in step a); and / or - (xl)thiols from polythioesters that are not completely degraded protected. Thus, a polythiol composition can be obtained from a terpene or a terpene derivative having x C=C double bonds, comprising: - the polythiol corresponding to the terpene or terpene derivative comprising x -SH functions; and - the thiol(s) corresponding to the terpene or terpene derivative comprising (x-1) -SH functions, with x as defined above.

[0152] Such a composition may optionally include other by-products or impurities (for example monothiols).

[0153] In particular, a trithiol composition can be obtained from a terpene or a terpene derivative having three C=C double bonds, said composition comprising: - the trithiol corresponding to said terpene; and - the dithiol(s) corresponding to said terpene.

[0154] In particular, a tetrathiol composition can be obtained from a terpene or a terpene derivative having four C=C double bonds, said composition comprising: - the tetrathiol corresponding to said terpene or terpene derivative; and - the corresponding trithiol(s) to the terpene or terpene derivative.

[0155] Thus, the present invention relates to a polythiol composition A obtained from a terpene or a terpene derivative having x C=C double bonds, said composition comprising: - the polythiol corresponding to the terpene or terpene derivative comprising x -SH functions; and - the corresponding thiol(s) of the terpene or terpene derivative comprising (x-1) -SH functions, with x as defined above.

[0156] In particular, said composition A comprises at least 50% by weight, preferably at least 60% by weight, for example at least 70% by weight, preferably still at least 80% by weight, more preferably at least 90% by weight, for example at least 95% by weight of said polythiol, relative to the total weight of composition A.

[0157] In particular, said composition A comprises less than 40% by weight, preferably less than 30% by weight, preferably still less than 25% by weight of said (xl)thiol(s), relative to the total weight of said composition A.

[0158] Preferably, the mass ratio polyMol ia composition A is between (x-iy / iMï) 1:1 and 20,000:1, for example between 1:1 and 10,000:1, preferably between 1:1 and 1,000:1, preferably again between 1:1 and 100:1, and more preferably between 1:1 and 10:1, for example between 2:1 and 10:1.

[0159] Said mass ratio is the mass ratio: [polythiol corresponding to said terpene or terpene derivative comprising x -SH functions] / [thiol(s) corresponding to said terpene or terpene derivative comprising (x-1) -SH functions].

[0160] In a particularly preferred manner, said composition A is obtained from a terpene or a terpene derivative selected from myrcene, farnesene, squalene, isosqualene, humulene and dihydrofarnesene. POLYTHIOLS ACCORDING TO THE INVENTION

[0161] The present invention also relates to trithiol derived from dihydrofamesene, heptathiol derived from isosqualene and tetrathiol derived from camphorene (i.e., trithiol corresponding to dihydrofamesene, heptathiol corresponding to isosqualene and tetrathiol corresponding to camphorene).

[0162] Preferably, said trithiol is the trithiol of dihydro-beta-farnesene. The trithiol of dihydro-famesene may in particular be in the form of one of its following positional isomers:

[0163] [Chem. 10] r ... r _ I ch-y y J SH SH Pl>

[0164] [Chem. 11]

[0165] [Chem. 12] CH-, SH Pa, and

[0166] [Chem. 13]

[0167] Said dihydrofamesene trithiol can be obtained from a starting composition comprising at least 70% by weight of dihydrofamesene, preferably at least 80% by weight of dihydrofamesene, relative to the total weight of the composition. Preferably, said composition comprises at least 85% by weight of dihydrofamesene, relative to the total weight of farnesene, of all the partially hydrogenated compounds resulting from the hydrogenation of farnesene and farnesane present in said composition.

[0168] More specifically, said composition is a trithiol composition of dihydro-beta-farnesene obtained from MYRALENE 10™.

[0169] Isosqualene heptathiol may in particular be in the form of one of its following positional isomers:

[0170] [Chem. 14] P?, and

[0173] [Chem. 17]

[0174] The present invention also relates to polythiols derived from beta-carotene, lycopene, farnesol, retinol, retinal, vitamin A, nerolidol, isomyrcenol and ipsdienol.

[0175] These compounds are novel and form part of the present invention.

[0176] The present invention also relates to the compositions as defined above that can be obtained, obtained, or directly obtained by the process according to the invention. Likewise, it relates to the polythiols as defined above that can be obtained, obtained, or directly obtained by the process according to the invention. Description of the figures

[0177] [Fig-1]: Myrcene isomers

[0178] It is understood that, unless a specific isomer is mentioned, the name of a The compound includes all of its possible positional isomers.

[0179] The following examples are given for illustrative purposes only and are not limiting to the present invention. EXAMPLES:

[0180] Example 1: Trithiol of dihydro-beta-farnesene obtained from MYRALENE 10™, process according to the invention

[0181] Step a):

[0182] In a 250 mL double-jacketed reactor, 48.7 g (0.64 moles) of ATA are introduced. The medium is stirred at 5°C. Air is bubbled into the reaction medium via a sintered sinter at a flow rate of approximately 0.4 Nl / h and nitrogen is passed through the reactor head at a flow rate of approximately 4 Nl / h.

[0183] 40g (0.19 moles) of MYRALENE 10™ are then added drop by drop via a peristaltic pump for approximately 27 min. Once the addition is complete, 35.7g (0.77 moles) of EtOH are added to the reaction medium.

[0184] The reaction medium is kept under stirring at 5°C overnight.

[0185] A GC / FID analysis shows complete conversion of Myralene 10.

[0186] The air supply is cut off.

[0187] Basic deprotection step b:

[0188] 26.8 g (0.58 moles) of EtOH are then added to the reaction medium. The medium The reaction mixture is then degassed with nitrogen for 1 hour and cooled to approximately 10°C. 103 g (0.64 moles) of a previously degassed 25% sodium hydroxide solution is added over 38 minutes via a dropping funnel. The reaction mixture is stirred under nitrogen at 10°C overnight and then at 25°C for 6 hours.

[0189] A GC / FID analysis shows complete conversion of trithioacetate.

[0190] Recovery step:

[0191] The reaction medium is then cooled to 20°C, and 117 g (0.64 mol) of 20% HCl (previously degassed with nitrogen) is added dropwise via a peristaltic pump to the reaction medium. The trithiol phase is withdrawn. The aqueous phase is extracted three times with 16.5 g (0.19 mol) of dichloromethane.

[0192] The organic phases are collected, then washed four times with 7g (0.39 moles) of water and then concentrated in the rotary evaporator.

[0193] A composition comprising 82.29% by weight of the trithiol of dihydro-beta-farnesene and 9.71% by weight of the dithiol of dihydro-beta-farnesene is obtained (relative to the total weight of the composition).

[0194] The mass ratio p^yMol is 82.29 :9.71, i.e. 8.5 :1 (x~i)thiol(s)

[0195] Example 2: Myrcene trithiol, process according to the invention

[0196] Step a):

[0197] In a 250 mL double-jacketed reactor, 64.5 g (0.85 mol) of ATA are introduced. The mixture is stirred at 5°C, and then 5.9 g (0.13 mol) of EtOH are rapidly added. Air is bubbled into the reaction mixture via a sintered sinter at a rate of approximately 0.4 Nl / h, and nitrogen is introduced into the reactor head at a rate of approximately 4 Nl / h.

[0198] 35g (0.26 moles) of Myrcene are then added dropwise via a pump ristaltic for approximately 22 min. Once the addition is complete, 23.7g (0.51 moles) of EtOH are added to the reaction medium.

[0199] The reaction medium is kept under stirring at 5°C overnight.

[0200] A GC / FID analysis shows complete conversion of Myrcene.

[0201] The air supply is cut off.

[0202] Basic deprotection step b:

[0203] 82.9 g (1.80 moles) of EtOH are then added to the reaction medium. The medium The reaction mixture is then degassed with nitrogen for 1 hour and heated to approximately 30°C. 73.7 g (0.85 moles) of a previously degassed 46% sodium hydroxide solution is added via a dropping funnel. The reaction mixture is stirred under nitrogen at 40°C for 21 hours.

[0204] A GC / FID analysis shows complete conversion of trithioacetate.

[0205] Recovery stage:

[0206] The reaction medium is then cooled to 20°C, and 154.6 g (0.85 mol) of 20% HCl (previously degassed with nitrogen) is added dropwise via a peristaltic pump to the reaction medium. The trithiol phase is withdrawn. The aqueous phase is extracted three times with 21.8 g (0.26 mol) of dichloromethane.

[0207] The organic phases are collected, then washed four times with 9.2g (0.51 moles) of water and then concentrated in the rotary evaporator.

[0208] A composition comprising 50.56% by weight of myrcene trithiol and 23.6% by weight of myrcene dithiol is obtained (relative to the total weight of the composition).

[0209] The mass ratio p^yth^ is 50.56 :23.6, or 2.1 :1 (x- ï)thiol{i:)

[0210] Example 3: Tetrathiol obtained from farnesene, process according to the invention

[0211] Step a):

[0212] In a double-jacketed IL reactor, 163.9 g (2.15 moles) of ATA are introduced. The mixture is stirred at 5°C, and then 23.0 g (0.50 moles) of EtOH are rapidly added. Air is bubbled into the reaction mixture via a sintered nozzle at a rate of approximately 0.4 Nl / h, and nitrogen is passed through the reactor head at a rate of approximately 4 Nl / h.

[0213] 100g (0.49 moles) of farnesene, marketed under the brand name BIOFENE®, are then added drop by drop via a peristaltic pump for about 47 min. Once the addition is complete, 90.1g (1.96 moles) of EtOH are added to the reaction medium.

[0214] The reaction medium is kept under stirring at 5°C overnight.

[0215] A GC / FID analysis shows complete conversion of famesene and its intermediates reactive.

[0216] The air supply is cut off.

[0217] Basic deprotection step b:

[0218] The reaction mixture is then degassed with nitrogen for 1 h and cooled to approximately 10°C. 187.2 g (2.15 moles) of a previously degassed 46% sodium hydroxide solution is added over 35 min via a dropping funnel. The reaction mixture is stirred under nitrogen at 25°C for 19 h.

[0219] A GC / FID analysis shows complete conversion of tetrathioacetate.

[0220] Recovery stage:

[0221] The reaction medium is then cooled to 20°C, and 294.4 g (1.61 moles) of 20% HCl (previously degassed with nitrogen) are added dropwise via a peristaltic pump to the reaction medium. The trithiol phase is withdrawn. The aqueous phase is extracted three times with 41.6 g (0.49 moles) of dichloromethane.

[0222] The organic phases are collected, then washed four times with 17.6g (0.98 moles) of water and then concentrated in the rotary evaporator.

[0223] A composition comprising 61.24% by weight of famesene tetrathiol and 25.77% by weight of famesene trithiol is obtained (relative to the total weight of the composition).

[0224] The mass ratio poh'thM is 61.24 : 25.77 or 2.4 :1

Claims

Demands

1. A process for preparing a polythiol comprising the following steps: a) reacting a terpene or a terpene derivative with a thiocarboxylic acid in the presence of oxygen (O2) and at least one organic solvent, so as to obtain a reaction medium comprising a polythioester and said at least one solvent; and b) carrying out a basic or acid deprotection step of the polythioester obtained in step a), so as to obtain a polythiol in which steps a) and b) are carried out in one pot synthesis.

2. A preparation method according to claim 1, wherein step b) of basic deprotection is carried out by adding an alkali hydroxide.

3. A method according to claim 1, wherein step b) of acid deprotection is carried out in the presence of an alcohol.

4. A preparation method according to any one of the preceding claims, wherein said organic solvent is selected from the group consisting of: alcohols, ethers, organochlorine solvents, carboxylic acids or mixtures thereof.

5. A preparation method according to any one of the preceding claims, wherein the organic solvent is selected from alcohols, of the following general formula (IV): R4-OH (IV) in which R4 represents a saturated hydrocarbon radical, linear, branched or cyclic, comprising from 1 to 10, preferably from 1 to 4, carbon atoms.

6. A preparation method according to any one of the preceding claims, wherein the thiocarboxylic acid is thioacetic acid.

7. A preparation method according to any one of the preceding claims, wherein said terpene or terpene derivative is selected from the group consisting of myrcene, famesene, squalene, isosqualene, humulene and dihydrofamesene.

8. Composition A of polythiol obtained from a terpene or a terpene derivative having x C=C double bonds, said composition comprising: - the polythiol corresponding to said terpene or to said terpene derivative comprising x -SH functions; and - the thiol(s) corresponding to said terpene or to said terpene derivative comprising (x-1) -SH functions; with x being an integer greater than or equal to 3; and in which the mass ratio is between 1:1 and 50 (a- ! tfhioKs) 000:1, preferably between 2:1 and 50,000:

1.

9. Composition A of polythiol according to claim 8, wherein said terpene or terpene derivative is selected from the group consisting of myrcene, famesene, squalene, isosqualene, humulene and dihydrofamesene.

10.

11. Polythiol chosen from trithiol derived from dihydrofamesene, heptathiol derived from isosqualene and tetrathiol derived from camphorene. Polythiol according to claim 10, having one of the following formulas: [Chem 10] [Chem 11] [Chem 12] [Chem 15] [Chem 17]