0001] The invention relates to the preparation of polythiols, polythiols and more particularly to a preparation method of which the content of primary, secondary and tertiary thiols is controlled.

[0002] There are various methods of obtaining polythiols according to whether one desires to prepare polythiols primary, secondary or tertiary.

[0003] Among the polythiols preparation methods, including known preparing polythiols radical. This method mainly results in the production of primary polythiols, and more generally to the addition of -SH group on the sp carbon atoms 2 Least substituted and / or leading to the formation of the more stable radical. It is for instance disclosed in US application 2012/0035291, a method for preparing a polythiol composition comprising primary thiols, from a hydrocarbon compound having at least two double bonds, a phosphite compound and sulfide hydrogen.

[0004] It is also known preparing polythiols by acid catalysis; said catalysis to the formation of polythiols comprising predominantly secondary thiol and / or tertiary amines, more generally the addition of -SH group on the sp carbon atoms 2 more substituted and / or leading to the formation of the more stable carbocation. Thus, FR2844794 and FR2531426 applications describe a method by catalysis of a thiol acid, from an olefin and hydrogen sulphide.

[0005] However, all of these techniques do not allow obtaining polythiols with high thiol content and whose regioselectivity thiol groups is monitored.

[0006] There therefore remains a need for a method for obtaining polythiols whose primary thiol content, secondary and tertiary be controlled.

[0007] We have discovered that it was possible to achieve this through the process described in the following discussion.

[0008] According to a first aspect, the present invention relates to a polythiol of preparation process comprising at least the steps of:

a / preparing a reaction of sulfhydratation medium comprising contacting:

at least one polyene;

at least one radical initiator;

at least one acid catalyst;

at least one sulfhydryl group donor compound;

optionally, at least one solvent;

b / simultaneous driving sulfhydratation radical reaction said at least one polyene and the catalytic reaction sulfhydratation acid of said at least one polyene;

c / recovering a mixture comprising at least two polythiols.

[0009] The method of the invention allows obtaining a mixture comprising at least two polythiols, the at least two polythiols obtained being generally of the same molecular weight polythiols, but whose thiol functions are carried by carbon atoms different. Within the meaning of the present invention, the method allows obtaining a mixture of polythiols of positional isomers. Advantageously, and most preferably, the process of the invention leads to the formation of polythiols containing more double bonds, that is to say that all double polyene from the bonds are sulfhydratées with method according to the invention.

[0010] The term "polythiol" means a compound having at least two thiol functions (-SH).

[001 1] The term "controlled" is meant obtaining polythiols whose regioselectivity depending thiols is different from that which would be obtained by driving one sulfhydratation radical reaction or a catalytic reaction sulfhydratation acid alone.

[0012] Indeed, when the radical sulfhydratation reaction is carried out alone, it mainly obtained the less substituted polythiol, that is to say that the majority of thiol groups bind to the least substituted carbon atoms and / or from the formation of the most stable radicals.

[0013] With regard to the If acid catalytic hydration known reaction, when the latter is carried out alone, it mainly obtained the most substituted polythiol, that is to say that the majority of thiol functions are fixed on the carbon the more substituted carbon and / or from the formation of the most stable carbocations.

[0014] The method according to the invention, allowing the simultaneous unwinding of the two aforementioned reactions can control, that is to say to modify or even reverse this regioselectivity. Indeed, polythiols obtained after a single minority sulfhydratation radical reaction or after a catalytic reaction of one acid sulfhydratation become polythiols mainly obtained by the method according to the invention.

[0015] The term "polyene" means a compound in which the hydrocarbon chain comprises at least two unsaturations in the form of double bond (unsaturated "olefin"). The hydrocarbon chain may be linear or cyclic, saturated or unsaturated, may or may not comprise one or more heteroatoms, and may be interrupted or substituted by one or more aromatic groups. The polyene in the sense of the present invention has usually a molecular weight of from 40 g. mol "1 and 1500 g. mol " 1 , preferably between 40 g. mol "1 and 1000 g. mol " 1 , more preferably between 40 g. mol "1 and 500 g. mol " 1 inclusive.

[0016] According to one embodiment of the invention, the polyene compound is a hydrocarbon comprising from 2 to 20 double bonds, preferably from 2 to 16 double bonds, more preferably 2 to 10 double bonds, in particular 2 to 8 double bonds and typically from 2 to 4 double bonds inclusive.

[0017] According to an embodiment of the most preferred invention, the polyene is a hydrocarbon compound comprising two double bonds, preferably three double bonds, more particularly 4 double bonds.

[0018] Preferably, the double bonds of the polyene are not included in a ring. More preferably at least 2 double bonds of the polyene are not relocated to form an aromatic ring.

[0019] According to one embodiment of the invention, the polyene comprises one or more heteroatoms selected from the columns 15, 16 and 17 of the Periodic Table of the Elements, more particularly selected from sulfur, nitrogen, oxygen and phosphorus.

[0020] According to a preferred embodiment, the polyene is selected from terpenes and their derivatives, comprising at least two double bonds, such as for example isoprene, limonene, myrcene, phellandrene, terpinene, the ocimene, terpinolene, geraniol, citral, retinol, β-carotene, farnesene, the selinene, the cardinène, farnesol, humulene, linalool and nerolidol.

[0021] According to another preferred embodiment, the polyene is a compound having one or more heteroatoms, such as, for example triallyisocyanurate and its derivatives.

[0022] The radical initiator according to the invention may be any radical initiator known to those skilled in the art. The radical initiator can be selected from a thermal initiator, such as for example heating, such as photochemical e.g. radiation, especially ultraviolet radiation, and an organic compound or inorganic radical generator or the like, as well as combinations of two or more of them. In the case where said radical initiator is an organic or inorganic compound, it may be a peroxide such as, for example, hydrogen peroxide, sodium peroxide, potassium peroxide, hydroperoxides tert-alkyl peroxides, tert-alkyl, peresters of tertiary alkyl hydroperoxide, cumene hydroperoxide, or the radical initiator can also be azo-bis-iso-butyronitrile, 2,2-dimethoxy-1, 2-diphenylethan-1-one, said radical initiators can be used alone or in combination of two or more of between them. Use may also be alkyl phosphites or xanthene derivatives such as those described in the patent application FR2501679.

[0023] According to a preferred embodiment of the invention, the initiation of radicals is achieved by heating and / or light radiation, for example ultraviolet light.

[0024] According to another preferred embodiment of the invention, the radical initiator comprises 2,2-dimethoxy-1, 2-diphenylethan-1-one, for example sold under the trademark Irgacure® 651, optionally in mixture with other radical initiators as described, for example in US Pat 4,443,310 A and US 4233128 A.

[0025] Where necessary or desired, the reaction medium may be heated at temperatures between 25 ° C and 150 ° C, preferably between 25 ° C and 100 ° C, in particular between 25 ° C and 70 ° C.

[0026] When initiation comprises irradiation of the reaction medium, it can be done for example by direct or indirect photolysis, preferably directly, in a wavelength range extending from about 180 nm up 600 nm, preferably by ultraviolet radiation and, for example, wavelengths between 180 nm and 400 nm.

[0027] The acid catalyst is selected from any acid catalysts known to those skilled in the art for conducting catalyzed homogeneous or heterogeneous acid, and may for example be selected from Lewis acids, acidic resins such as sulfonated resins ( e.g., a styrene-divinylbenzene as described in application FR 2531426), and catalytic compositions comprising at least one metal salt wherein the metal is selected from metals belonging to groups 8, 9 and 10 of the periodic table elements (as described for example in patent application FR 2844794), taken alone or in combination of two or more of them.

[0028] According to one embodiment of the invention, the acid catalyst is a sulfonated resin of styrene-divinylbenzene copolymer, for example Amberlyst ® 15.

[0029] The compound sulfhydryl donor may be of any type known to those skilled in the art can generate a sulfhydryl group (-SH) in the reaction conditions, that is to say the addition of a group -SH and a hydrogen atom on the carbon sp 2polyene. Said compound sulfhydryl group donor may be selected from hydrogen sulfide, thiocarboxylic acids, for example thioacetic acid, and precursors of these compounds, alone or in combination of two or more of them. Among the precursors of the compounds sulfhydryl group donors include for example di- and poly-sulfides, dialkyl such as, for example, dimethyl disulfide (DMDS), diethyl disulfide (DEDS), dipropyl disulfide ( ELOS) disulfide, dibutyl (DBDS) and higher homologs, and also mixtures thereof in all proportions as found in the DSO (or "disulfide Oils" in English). [0030] According to a preferred embodiment, the method according to the invention is carried out in the

[0031] According to another preferred embodiment, the method according to the invention is conducted in the presence of solvent. The amount of solvent used may vary within wide limits and will be readily appreciated and adjusted by the skilled person depending on the reagents used, the reaction temperature and other reaction parameters.

[0032] When a solvent is used, it may be of any type well known to those skilled in the art and in particular a solvent selected from water and organic compounds and their mixtures in all proportions. The organic compounds can be used as solvent are typically selected from aliphatic hydrocarbon compounds, aromatic hydrocarbon compounds optionally comprising one or more heteroatoms selected from oxygen, sulfur, nitrogen, and halogens.

[0033] The solvent may thus be selected from hydrocarbons, ketones, alcohols, ethers, esters, sulfoxides (eg. Dimethylsulphoxide), sulfolanes, nitriles (eg. Acetonitrile), alone or in combination of two or more of 'between them.

[0034] According to one embodiment of the invention, the solvent is an aliphatic hydrocarbon compound wherein the hydrocarbon chain is linear or cyclic, branched or unbranched and contains 3 to 20 carbon atoms, preferably between 4 and 15 carbon atoms, in particular between 5 and 10 carbon atoms.

[0035] According to another embodiment of the invention, the solvent is an aromatic hydrocarbon compound having 6 to 30 carbon atoms, preferably 6 to 20 carbon atoms, in particular 6 to 10 carbon atoms. The aromatic hydrocarbon compound may for example be selected from benzene, toluene, xylene (ortho-xylene, para-xylene, meta-xylene), and ethylbenzene, alone or in combination of two or more of them.

[0036] According to one embodiment of the invention, the solvent is a ketone comprising from 2 to 20 carbon atoms, preferably 2 to 10 carbon atoms, in particular 2 to 6 carbon atoms. The ketone may thus be selected from acetone, ethyl methyl ketone, methyl isobutyl ketone, alone or in combination of two or more of them.

[0037] According to one embodiment of the invention, the solvent is an alcohol containing from 2 to 20 carbon atoms, preferably 2 to 10 carbon atoms. The alcohol is selected from methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, benzyl alcohol, phenol, cyclohexanol, alone or in combination of two or more of them.

[0038] According to one embodiment of the invention, the solvent is an ether containing 2 to 20 carbon atoms, preferably 2 to 10 carbon atoms. The ether may be cyclic or noncyclic and be selected from dimethyl ether, diethyl ether, methyl ethyl ether, monoethers, diethers glycol, furan, dihydrofuran, tetrahydrofuran, pyran, dihydropyran, tetrahydropyran, 1, 2-dioxane, 1, 3-dioxane, 1, 4-dioxane.

[0039] The contacting of the various components of the reaction medium can be effected by any technique known to the skilled person for example by simply mixing the reagents and starting reactants, optionally in the presence of solvent (s), the reaction medium can be homogeneous or heterogeneous. Alternatively, one can first solubilizing said at least one polyene in said at least one solvent and then adding said at least one sulfhydryl group donor compound, and implement said at least one radical initiator and said at least one acid catalyst.

[0040] The reaction is generally conducted at atmospheric pressure, but can also be conducted under vacuum, in vacuum or under pressure, said pressure may range from atmospheric pressure to 10 MPa (100 bar), preferably from atmospheric pressure to 5 MPa (50 bar), especially from atmospheric pressure to 2 MPa (20 bar).

[0041] The method of the invention can be carried at any temperature, preferably at a temperature between 25 ° C and 150 ° C, preferably between 25 ° C and 100 ° C, in particular between 25 ° C and 70 ° C, the temperature can be easily adjusted according to the nature of the reagents, solvents and types of catalysts used and the pressure applied to the reaction medium.

[0042] The reaction can be between a few minutes and a few hours, the duration depending on the operating conditions described above.

[0043] The process of the invention is characterized in that step bl of carrying out the reaction comprises both a catalytic sulfhydratation reaction of the acid and at least one polyene sulfhydratation radical reaction said at least one polyene , said catalytic reactions sulfhydratation acid and radical sulfhydratation being performed simultaneously.

[0044] The term "simultaneous" is meant that the catalytic reactions sulfhydratation acid and radical sulfhydratation are conducted simultaneously and / or alternately and / or sequentially without isolation of the reaction intermediates, up conversion, preferably up the total conversion of said at least one polyene polythiol.

[0045] As indicated above, the polyene comprises at least two unsaturations in the form of double bond so that these two reactions can take place simultaneously on the same polyene compound. Indeed, in the example where the polyene comprises two double bearer links of different substituents with respect to each other, one of them undergoes sulfhydratation radical reaction while the other undergoes reaction sulfhydratation catalytic acid.

[0046] When said at least one polyene comprises two double bearing identical substituents linkages (e.g. in the case of symmetrical polyenes), it is also possible to perform, by acting on the operating conditions, both reaction sulfhydratation radical and an acid catalytic reaction sulfhydratation, one on at least one olefinic unsaturation and the other on at least one other olefinically unsaturated.

[0047] The method of the invention can be carried out continuously or in batch. When the reaction takes place continuously, step b / comprises, advantageously but usually, one of the reaction medium recirculation step in a reaction loop.

[0048] It has been found by the Applicant that the simultaneous conduct of sulfhydratation radical reaction and catalytic reaction sulfhydratation acid according to the process according to the invention can lead surprisingly to a complete conversion of said at least one polyene initially, conversion is usually not complete during the implementation of these separately reactions. By total conversion, is meant a conversion rate higher than 90%, more usually greater than 95%, typically greater than 99%, more specifically equal to 100% of the number of double bonds present in said at least one starting polyene.

[0049] The process of the invention also allows the preparation of high levels polythiols to thiol functions and a limited content or no double bond. For example, in the case where the starting polyene has 3 double bonds and in the case of a total conversion of said polyene, said polyene is converted to a mixture of polythiols, polythiol each having three functions sulfhydryl (-SH).

[0050] Combining the radical route and the acidic catalytically allows not only obtaining polythiols comprising primary thiols thiols and secondary and / or tertiary, but polythiols obtained are different from those which would have been obtained if the two reactions were performed separately. This control of the thiols content adjusts the responsiveness of the polythiol compound formed, particularly when using it.

[0051] Moreover, the method according to the invention allows to increase the reaction kinetics thus leading to minimize the formation of side reactions such as intramolecular reactions and limit the content of impurities such as sulfides.

[0052] Furthermore, it has been found that the regioselectivity of sulfhydratation reactions can be controlled by the operating conditions in the process of the present invention. Moreover, adjustment of operating conditions can also control the ratio of isomers formed polythiols.

[0053] The polythiols mixture obtained is isolated from the reaction medium by any method known to those skilled in the art, for example by evaporation or distillation of the solvent at atmospheric pressure or under reduced pressure. The polythiols mixture can be also purified by conventional methods well known to those skilled in the art and for instance selected from purification on ion exchange resins, activated carbon filtration, diatomaceous earths or zeolites, and the like.

[0054] The polythiols mixture obtained by the process according to the invention can be used as such or alternatively, polythiols said mixture can be isolated by any separation method well known to those skilled in the art such as for example distillation, crystallization, preparative chromatography and the like.

[0055] The present invention also relates to the mixture of at least two polythiols obtainable according to the method as described above. [0056] Thus, mixtures of polythiols obtainable by the method of the present invention can find many applications quite useful in many areas, for example and without limitation, as:

• cross-linking or vulcanization agent;

• reagent for preparing sulfur compounds such as thiourea urethanes, polysulfides and others;

• chain transfer agent;

• metal complexing agent;

• ore flotation agent;

• antioxidant;

• heat stabilizer;

• and others.

[0057] The present application also relates to the use polythiols obtained by the process according to the invention, such as crosslinking agents in the preparation of adhesives, glues, sealants, epoxy resin type coatings, acrylates, isocyanates and others.

[0058] The polythiols obtained by the process according to the invention can also be used as reagents in thiol-éniques reactions. Indeed, the presence of sulfhydryl groups with varying reactivity allows to adjust the kinetics of the reaction of addition of the thiol function of a diene moiety.

[0059] The polythiols obtained by the process according to the invention can also be used for the preparation of thio-urethanes. Indeed, by reacting polythiols with the thiol content is controlled are obtained thiourethane compounds of chemical structure and different performances from those which would have obtained from polythiols synthesized either by radical route or by acid catalytically classics.

[0060] The polythiols obtained by the process according to the invention can also be used as precursors for the synthesis of polysulphides. Indeed, by oxidation to sulfur, it is possible to obtain polysulfide compounds that may be used as additives for lubricants or for rubber. With polythiols obtained by the process according to the invention, due to the steric hindrance difference in sulfur bonds, polysulfides formed offer varying reactivities.

[0061] The polythiols obtained by the process according to the invention can act as agents for chain transfer during the synthesis of polymers from monomers such as, for example, vinyl monomers, conjugated diene monomers, the acrylic monomers, methacrylic monomers, and mixtures of two or more of them in any proportion. The difference in reactivity according to the type and the sulfhydryl group content allows for improved control of the polymerization reaction.

[0062] As another use, polythiols obtained by the process of the present invention can also be used as crosslinking agents for natural rubbers, artificial or synthetic complexing agents of metals, ore flotation agents, in as oxygen sensors, as corrosion inhibitors and the like.

[0063] The present invention is now illustrated by the following example, without providing a limitation to the invention whose scope is determined by the following claims.

example:

[0064] An embodiment of the inventive method is illustrated by this example in which implement is placed a photoinitiator and a radiation source in a photochemical reactor, said photochemical reactor comprising a recirculation loop on which is installed a tubular reactor. filters arranged upstream and downstream of the tubular reactor avoid driving the heterogeneous catalyst.

[0065] The reactor also has a heating system for heating to the desired temperature. A cooling system located after the tubular reactor to the recirculation loop allows for cooling or heating the photochemical reactor liquid feed. A pump arranged on this recirculation loop is used to vary the liquid flow rate.

[0066] are introduced 100 g (0.73 mol) of β-myrcene (from DRT) dissolved in 1000 g of tetrahydrofuran (Aldrich) and 0.25 g of Irgacure ® 651 (Ciba Specialty Chemicals). Are introduced 5 g of Amberlyst cation exchange resin ® 15 (Aldrich) was dried in the tubular reactor.

[0067] Under recirculation (20 Lh "1 ), the reaction medium is then subjected to bubbling with nitrogen to remove traces of residual oxygen. To the reaction mixture are then added 30 molar equivalents of hydrogen sulfide ( . h S) the tubular reactor is then brought to the desired temperature (100 ° C) once this temperature is reached, the lamp is then lit the reaction medium is subjected to UV radiation (wavelength:.. 355-365 nm, power: 8 Watt) for 6 hours at a temperature of 100 ° C and a constant pressure of 1 to 5 MPa, adjusted by addition of hydrogen sulfide.

[0068] The conversion control is done by analyzing the samples by high performance liquid chromatography (or pressure).

[0069] After 6 hours, the conversion of the starting polyene reached 100%. The lamp is switched off and the heating of the tubular reactor is stopped. Excess hydrogen sulfide is then purged to a thermal oxidiser by decompression of the medium, followed by a stripping with nitrogen. The mixture is then evaporated in vacuo to remove solvent and then distilled to remove any impurities, e.g., sulfide type.

[0070] The distilled mixture thus obtained has a purity greater than 98% expressed as weight of trithiols formed. The distilled mixture is characterized by NMR and found to be composed of the following chemical structures polythiols:

CLAIMS

1. A method of polythiols preparation comprising at least the steps of: a / preparing a reaction of sulfhydratation medium comprising contacting:

at least one polyene;

at least one radical initiator;

at least one acid catalyst;

at least one sulfhydryl group donor compound;

optionally, at least one solvent;

b / simultaneous driving sulfhydratation radical reaction said at least one polyene and the catalytic reaction sulfhydratation acid of said at least one polyene;

c / recovering a mixture comprising at least two polythiols.

2. The method of claim 1, wherein said at least one polyene is a compound having the hydrocarbon chain comprises at least two unsaturations in the form of double bond, said chain being linear or cyclic, saturated or unsaturated, and optionally include a or more heteroatoms selected from the columns 15, 16 and 17 of the periodic Table of the elements, more particularly selected from sulfur, nitrogen, oxygen, and phosphorus, and which may be interrupted or substituted by one or more groups aromatics.

3. A method according to any preceding claim, wherein said at least one polyene compound is a hydrocarbon comprising from 2 to 20 double bonds, preferably from 2 to 16 double bonds, in particular from 2 to 10 double bonds, all particularly from 2 to 8 double bonds, and more particularly from 2 to 4 double bonds inclusive.

4. A method according to any preceding claim, wherein said at least one polyene is selected from triallyisocyanurate and its derivatives, terpenes and their derivatives, comprising at least two double bonds.

5. A method according to any preceding claim, wherein said at least one radical initiator is selected from a thermal initiator, photochemical and an organic or inorganic compound generator of radicals, alone or in combination of two or more of between them.

6. The method of claim 5, wherein said at least one radical initiator is selected from peroxides, hydroperoxides, azo-bis-iso-butyronitrile, 2,2-dimethoxy-1, 2-diphenylethan-1 -one, alkyl phosphites and xanthene derivatives, taken alone or in combination of two or more of them.

7. A method according to any preceding claim, wherein said at least one acid catalyst is selected from Lewis acids, sulfonated and catalytic acid resins compositions comprising at least one metal salt, alone or in combination of two or more of them.

8. A method according to any preceding claim, wherein said at least one sulfhydryl group donor compound is selected among hydrogen sulfide, thiocarboxylic acids and their precursors, alone or in combination of two or more of them.

9. A method according to any preceding claim conducted in the absence of solvent.

10. A mixture of at least two polythiols obtained by the process according to any one of claims 1 to 9.

January 1. Use of the mixture according to claim 10 or obtained by the process of any one of claims 1 to 9, as cross-linking or vulcanization agent, reagent for the preparation of sulfur-containing compounds such as thio-urethanes, polysulfides and other, chain transfer agent, metal complexing agent, ore flotation agent, antioxidant, thermal stabilizer.