Polythiol composition and preparation method thereof

Abstract

The present invention relates to a process for preparing a polythiol from a polyene, and also to a polythiol composition obtained from a cycloaliphatic polyene or an isocyanurate polyene. The process for preparing a polythiol comprises the steps of: a) reacting a polyene with a thiocarboxylic acid in the presence of oxygen (O2) and at least one organic solvent to obtain a reaction medium comprising a polythioacid ester and at least one solvent; b) carrying out a step of deprotecting the polythioacid ester obtained in step a) to obtain a polythiol; wherein the step a) and the step b) are carried out in one-pot synthesis.

Description

TECHNICAL FIELD

[0001] The present invention relates to a process for preparing a polythiol composition, and also to a polythiol composition obtainable by this process. BACKGROUND

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

[0003] Several synthetic routes for obtaining polythiols exist. In the most widely used process, mention can be made of the reaction between a polyol and a mercapto acid (described, for example, in application US2005153231). Although this reaction is easy and makes it possible to obtain different polythiol structures, the products obtained generally exhibit a low resistance to hydrolysis due to the significant presence of ester functions.

[0004] Alternatively, the direct addition of hydrogen sulfide onto a polyene by acid or photochemical catalysis makes it possible to obtain molecules free of hydrolysable functions. This addition is described in particular in application WO 12018757. However, with this process, a large number of sulfide-type compounds can be produced in common and, depending on the reactants used, problems of conversion can arise. Thus, the molecules obtained can comprise a number of unconverted double bonds, which creates problems of stability and reduces the total content of -SH functions. This is reflected in particular by the presence of a large number of monothiols and / or dithiols in the composition obtained, for example in the case of a triene-type starting reagent.

[0005] In fact, depending on the field of application targeted, it is important to control and / or reduce the formation of these by-products such as monothiols and / or dithiols. This is because their content has an influence on the degree of crosslinking of the materials subsequently prepared, in particular thermoset materials produced from resins and from hardeners of the polythiol type. It has thus been shown that the degree of crosslinking influences the physical and viscoelastic properties of the polymers, for example their density, their modulus, the limits of their range of elasticity or their glass transition temperature (Tg). The Tg is conventionally determined by DSC method for differential scanning calorimetry or by dynamic mechanical analysis (DM(T)A). These parameters are directly linked to the behaviour of the materials, for example the hardness, the elasticity, the flexibility or the tear strength.

[0006] In particular, it is sought to obtain polymers with a high glass transition temperature in order to obtain materials with a higher resistance to heat (that is to say, which retain their properties over a wider temperature range).

[0007] There is thus a need for a process for the industrial preparation of polythiols which makes it possible to control, indeed even maximize, the conversion of C=C double bonds into -SH functions. There is also a need for a process for the preparation of polythiols which makes it possible to control, indeed even reduce, the formation of by-products (such as monothiols and / or dithiols in the case of the preparation of tri thiols or sulfides).

[0008] One technical solution consists in converting the C=C double bonds into functions of the type -R'-C(O)-S-R" via polythioester intermediates, then deprotecting them in order to obtain the desired polythiol. However, these polythioester intermediates represent a major technical difficulty for industrial applications. They are generally very viscous, indeed even solid compounds. They are thus difficult to handle in order to participate in the deprotection phase. They thus raise many practical problems at an industrial level and are indeed almost never used.

[0009] Furthermore, these polythioesters are generally obtained by reaction of a polyene with a thio carboxylic acid, in particular a thioacetic acid. However, this reaction involves the use of a large excess of thio carboxylic acid which must be removed before the deprotection phase. Thus, in order to carry out the subsequent deprotection phase, an additional phase of evaporation of this excess thio carboxylic acid and / or purification of the polythioester is necessary.

[0010] There is thus a need for an improved process for the preparation of polythiols via polythioesters.

[0011] There is a need for polythiol compositions whose content of -SH functions is controlled, indeed even maximized. The term "content of -SH functions" is understood to mean the ratio of the weight of all -SH functions / total weight of the composition. SUMMARY

[0012] The object of the present invention is to provide an improved process for the preparation of polythiol compositions whose industrial implementation is simplified.

[0013] The object of the present invention is to provide an improved process for the preparation of polythiol compositions whose content of -SH functions is controlled, indeed even maximized.

[0014] Another object of the present invention is to provide improved polythiol compositions, in particular with a controlled, indeed even maximized, content of -SH functions.

[0015] In particular, the object of the present invention is to provide tri thiol compositions with a controlled, indeed even reduced, amount of dithiols.

[0016] One object of the present invention is to provide polythiol compositions for the preparation of polymers, preferably thermoset polymers.

[0017] The present invention responds, in whole or in part, to the above-mentioned objectives.

[0018] The inventors have surprisingly found that a "one-pot" process can be used to synthesize the polythiols. The term "one-pot process" is understood to mean in particular a process in which the synthesis intermediates, i.e. the polythioesters according to the invention, are not isolated from the reaction medium in order to carry out a subsequent deprotection stage. Such a one-pot process presents numerous advantages in the context of the industrial synthesis of polythiols.

[0019] In particular, the formation stage of the polythioester intermediates according to the invention (hereinafter stage a)) makes it possible to obtain very good conversion rates (in particular 90% to 100% polyene conversion), while avoiding the use of too large an excess of thio carboxylic acid. Indeed, a large excess of thio carboxylic acid is generally used in the processes of the prior art, which represents a loss for the process and generates a large amount of waste to be isolated and treated. Furthermore, such an excess is incompatible with a "one-pot" process, since it must be removed before the deprotection stage. The present invention makes it possible to avoid these drawbacks, which represent an economic advantage but also an environmental advantage.

[0020] Another advantage of the present invention is that the reaction medium comprising the polythioester intermediate obtained at the end of stage a) can be easily stirred and handled. It can in particular be in the form of a liquid or of a suspension, which is viscous or slightly viscous. Difficulties of operability at an industrial level are thus avoided.

[0021] The reaction medium comprising the polythioester intermediate is also compatible with the deprotection stage (hereinafter stage b)), which represents a simplification of the process.

[0022] Thus, stages a) and b) according to the invention, for example, are carried out as a "one-pot" reaction. The process is thus significantly improved, since the intermediate stages of removal of the excess thio carboxylic acid and / or purification of the polythioester intermediate, such as extraction, recrystallization and / or distillation, are thus avoided.

[0023] The polythiol compositions that can be obtained by the process according to the invention are novel and exhibit a controlled, indeed even maximized, -SH content. They are in particular characterized by a high weight ratio. For example, in the case of a starting triene, the said weight ratio is than 1.

[0024] These compositions are particularly suitable for the preparation of materials such as thermosetting plastics from resins. Thus, the present invention makes it possible to obtain materials with excellent properties. For example, it is possible to obtain polymers with a higher Tg, and thus with excellent heat resistance and / or excellent compression strength properties and / or a greater modulus and a greater range of elasticity.

[0025] The present application thus relates to a process for the preparation of a polythiol comprising the following stages:

[0026] a) reacting a polyene with a thiocarboxylic acid in the presence of oxygen (O2) and at least one organic solvent, thereby obtaining a reaction medium comprising a polythioester and said at least one organic solvent; and

[0027] b) carrying out a stage of deprotection of the polythioester obtained in stage a), thereby obtaining a polythiol;

[0028] wherein stages a) and b) are carried out in a one-pot synthesis.

[0029] The present application also relates to a polythiol composition A obtained from a cycloaliphatic polyene containing x C=C double bonds, said composition comprising:

[0030] - a polythiol corresponding to said cycloaliphatic polyene comprising x -SH functions; and

[0031] - a thiol corresponding to said cycloaliphatic polyene comprising (x-1) -SH functions; and

[0032] wherein the weight ratio is between 10.1 : 1 and 50 000 : 1, preferably between 10.1 : 1 and 20 000 : 1 ; and

[0033] x is an integer greater than or equal to 3.

[0034] The present application relates to a polythiol composition B obtained from an isocyanurate of general formula (I):

[0035] [Chem. 1]

[0036]

[0037] wherein R is a linear or branched hydrocarbon chain comprising at least one C=C double bond, which can optionally comprise one or more heteroatoms such as oxygen, nitrogen, sulfur and / or phosphorus, and which can optionally comprise one or more chemical groups;

[0038] said composition comprising:

[0039] - a polythiol corresponding to said isocyanurate comprising x -SH functions; and

[0040] - a thiol corresponding to said isocyanurate comprising (x-1) -SH functions;

[0041] wherein the weight ratio is between 2 : 1 and 50 000 : 1, preferably between 2 : 1 and 20 000 : 1 ; and

[0042] x is an integer greater than or equal to 3. DETAILED DESCRIPTION

[0043] The term "alkyl" is understood to mean, in particular, a saturated, linear, branched or cyclic hydrocarbon group comprising 1 to 10, preferably 1 to 4 carbon atoms.

[0044] The term "aryl" is understood to mean, in particular, a cyclic (monocyclic, bicyclic or tricyclic) aromatic hydrocarbon group comprising 6 to 10 carbon atoms, preferably a phenyl or naphthyl group, more preferably a phenyl group.

[0045] The term "aralkyl" is understood to mean, in particular, an alkyl group substituted with an aryl group, such as a benzyl group.

[0046] Polyene

[0047] The term "polyene" is understood to mean any organic compound comprising at least 3 C=C double bonds. The number of C=C double bonds comprised in said polyene is hereinafter referred to as "x", x being an integer greater than or equal to 3. Preferably, x is between 3 and 10, more preferably between 3 and 6, more preferably between 3 and 5.

[0048] Said polyene can be functionalized (i.e. comprising one or more chemical functions). Said polyene represents, in particular, a linear, branched, cyclic or branched cyclic hydrocarbon chain, which can optionally comprise one or more heteroatoms, such as halogen, silicon, oxygen, nitrogen, sulfur and / or phosphorus, and which can optionally comprise one or more chemical groups, such as selected from halogen, -OH, -C(O)-, amine, amide, ester, ether, urea, thioether, sulfoxide, sulfone, carbamate or thiocarbamate, preferably -OH or ether.

[0049] These chemical groups are, for example, selected from: -OH, -C(O)-, -NH2, -NHR8, -NR8R9, -C(O)NH2, -C(O)NHR8, -C(O)NR8R9, -C(O)OH, -C(O)OR8, -NH-C(O)-NH2, -NH-C(O)-NHR8, -NH-C(O)-NR8R9, -NR7-C(O)-NH2, -NR7-C(O)-NHR8, -NR7-C(O)-NR8R9, -NH-C(O)-OR8, -NR7-C(O)-OR8, -O-C(=S)-NH2, -O-C(=S)-NHR8, -O-C(=S)-NR8R9, -S-C(=O)-NH2, -S-C(=O)-NHR8, -S-C(=O)-NR8R9, -S(=O)R8or -S(=O)2R8, with R7, R8and R9being selected independently from one another an alkyl group as defined above.

[0050] The polyene can contain from 4 to 40 carbon atoms, for example from 4 to 30 carbon atoms, preferably from 4 to 20 carbon atoms, more preferably from 10 to 15 carbon atoms. It is in particular aliphatic (i.e. non-aromatic).

[0051] Preferably, the polyene is selected from:

[0052] Cycloaliphatic polyenes and polyenes of general formula (I) are defined hereinafter.

[0053] Cycloaliphatic polyenes

[0054] The term "cycloaliphatic polyene" is understood to mean a non-aromatic cyclic polyene. They can be cyclic and branched, as in the case of trivinylcyclohexane.

[0055] Preferably, they are not branched and thus their C=C double bonds are intraannular. In particular, they are formed from a hydrocarbon chain preferably comprising from 7 to 15 carbon atoms.

[0056] Preferably, the cycloaliphatic polyene is 1,5,9-cyclododecatriene (1,5,9-CDT or CDT hereinafter).

[0057] Particular mention can be made of its isomers of formula:

[0058]

[0059] Very particular preference is given to cis, trans, trans-1,5,9-cyclododecatriene of formula:

[0060]

[0061] Isocyanurate polyenes of the following general formula (I) :

[0062] [Chem. 1]

[0063]

[0064] in which R is a linear or branched hydrocarbon chain comprising at least one C=C double bond, which can optionally comprise one or more heteroatoms, for example oxygen, nitrogen, sulfur and / or phosphorus, and which can optionally comprise one or more chemical groups (in particular as described above).

[0065] Preferably, R comprises a single C=C double bond and can optionally comprise one or more heteroatoms and in particular oxygen.

[0066] Preferably, R comprises from 2 to 15 carbon atoms, for example from 2 to 5 carbon atoms.

[0067] Very particular preference is given to the following two compounds:

[0068] [Chem. 2]

[0069] triallyl isocyanurate (hereinafter referred to as TAIC), and

[0070] [Chem. 3]

[0071] trimethallyl isocyanurate.

[0072] In particular, the polyene is selected from CDT and TAIC.

[0073] Trienes

[0074] Preferably, the polyene is a triene. The term "trienes" is understood to mean polyenes as defined above and comprising only 3 C=C double bonds (i.e. x = 3).

[0075] It is in particular selected from:

[0076] - linear, branched or cyclic aliphatic hydrocarbon trienes; and

[0077] - trienes of general formula (I) as defined above and wherein R comprises a single C=C double bond.

[0078] Among the trienes, one can in particular mention:

[0079] trivinylcyclohexane, trivinylbenzene, cycloheptatriene, dimethylheptatriene, octatriene, cyclooctatriene, cyclododecatriene (CDT), triallyl isocyanurate (TAIC), triallyl cyanurate, trimethallyl isocyanurate, pentaerythritol triallyl ether, pentaerythritol tetraallyl ether, trimethylolpropane triallyl ether and triallyl amine.

[0080] The preferred trienes according to the application are cyclododecatriene (CDT) and triallyl isocyanurate (TAIC).

[0081] Polythiols

[0082] According to the application, the term "polythiol" means a polythiol corresponding to the starting polyene as defined above.

[0083] The term "corresponding to the starting polyene" is understood to mean that the structure of the starting polyene and of the obtained polythiol are identical except that the C=C double bonds have been transformed into -SH functions (i.e. -CH-C(SH)-): for x C=C double bonds of the starting polyene, x -SH functions are obtained, wherein x is as defined above. The term "polythiol" also encompasses polythiols which are positional isomers of the double bonds of the starting polyene. The polythiol according to the application can also be referred to as (x)thiol.

[0084] Polythioester intermediates

[0085] The term "polythioester intermediate" or "polythioester" is to be understood as meaning a polythioester corresponding to the starting polyene. The term "corresponding to the starting polyene" is to be understood as meaning that the structure of the starting polyene and the polythioester obtained are identical, except that the C=C double bonds have been converted into -CH-C(S-C(O)-R1)- functions (R1 depending on the thio carboxylic acid used, preferably R1 is methyl): for x C=C double bonds, x thioester functions are obtained, with x as defined above. The term "polythioester" also includes polythioesters which are positional isomers of the double bonds of the starting polyene.

[0086] Process according to the application

[0087] Stage a)

[0088] During stage a), the polyene as defined above is reacted with a thio carboxylic acid in the presence of oxygen (O2) and of 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.

[0089] The reaction is as follows: R-CH=CH-R + R1-C(O)-SH -> R-CH2-CH(S-C(O)-R1)-R

[0090] Stage a) is carried out in the presence of oxygen (O2), which here acts as initiator of the reaction. Stage a) can thus be carried out in the presence of air, of lean air (mixture of oxygen and nitrogen N2) or of a mixture of oxygen and another inert gas. The oxygen can be introduced into the reaction medium by any technique. The oxygen can also be added or not added throughout the duration of stage a).

[0091] In particular, the oxygen is bubbled into the reaction medium, preferably in the form of lean air. For example, the lean air is passed through a frit or a diffuser immersed in the reaction medium. Alternatively, the oxygen can be bubbled into the reaction medium and the nitrogen can be introduced into the gas phase of the reactor, that is to say the headspace of the reactor.

[0092] The oxygen flow rate can be between 0.01 and 100 Sl / h, preferably between 0.05 and 10 Sl / h, more preferably between 0.05 and 5 Sl / h, in particular between 0.05 and 2 Sl / h (standard litres / h).

[0093] Stage a) is in particular carried out 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.

[0094] Step a) is also carried out in the presence of an organic solvent or mixture of organic solvents. A polar solvent or mixture of polar solvents is chosen very particularly. The solvent can be a polar protic or polar aprotic solvent. Among the solvents that can be used, mention can be made of alcohols, ethers (preferably cyclic ethers and glycol ethers, such as glycol dialkyl ethers), organic chlorinated solvents, carboxylic acids or mixtures thereof.

[0095] An alcohol is preferred, in particular an alcohol of general formula (IV) below:

[0096] R4-OH (IV)

[0097] in which R4 represents an alkyl group as defined above. Preferably, the alcohol is chosen from methanol, ethanol, isopropanol, n-propanol, n-butanol, butan-2-ol, isobutanol and tert-butanol, more preferably ethanol.

[0098] 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 known as glycol dimethyl ether), diethoxyethane, dibutoxyethane and mixtures thereof, more preferably ethanol.

[0099] The amount of solvent used is generally chosen according to the desired viscosity of the reaction medium. Complete or partial solubilization can be carried out by the person skilled in the art, depending on the target viscosity of the reaction medium. Preferably, 1 molar equivalent to 50 molar equivalents, more preferably 1 to 20 molar equivalents, of solvent are used relative to the polyene.

[0100] The solvent can be added completely or partially from the start of stage a). It can be added in one go, several times (semi-continuously) or gradually (continuously) during stage a) in a one-off manner.

[0101] The thiocarboxylic acid preferably has the following general formula (II):

[0102] R1-C(O)-SH (II)

[0103] in which:

[0104] R1 represents an alkyl group, an aryl group or an aralkyl group as defined above.

[0105] Preferably, R1 is chosen from methyl, ethyl and benzyl.

[0106] Thioacetic acid (hereinafter TAA) is very particularly preferred according to the application, in which R1 is methyl. For example, thioacetic acid is used, obtaining a polythiol acetate as a polythioester intermediate.

[0107] According to one embodiment, the thiocarboxylic acid can be generated in situ (cf. document US 3 270 063, Thompson Chemical Co., 1963: "Methods of Making Primary Mercaptans"): thioglycolic acid can be generated from acetic anhydride and hydrogen sulfide in the presence of a catalyst.

[0108] Preferably, in order to carry out stage a), the thiocarboxylic acid and the solvent(s) are first introduced into the reactor, then the oxygen is introduced, for example by bubbling with air. The polyene can subsequently be added to the reaction medium.

[0109] The temperature of stage a) can be between 5°C and 80°C, preferably between 5°C and 50°C, more particularly between 5°C and 25°C, for example between 5°C and 10°C. Stage a) is generally carried out at atmospheric pressure.

[0110] The molar ratio of the double bonds of the thiocarboxylic acid / polyene can be between 1 and 20, preferably between 1 and 10, for example between 1 and 5, more preferably between 1 and 3.

[0111] Stage a) makes it possible to form, starting from the polyene, a polythioester intermediate as defined above. Thus, the reaction medium obtained at the end of stage a) can comprise:

[0112] - a polythioester intermediate as defined above;

[0113] - a solvent or mixture of solvents as defined above;

[0114] - possible by-products, for example (x-1) polythioesters; and

[0115] - possible unreacted reactant(s).

[0116] The term "(x-1) polythioester" is understood to mean, in particular, a compound comprising x-1 thioester functions, with x as defined above. It is a compound that conserves C=C double bonds, i.e. unreacted C=C double bonds.

[0117] Thus, the reaction medium can comprise between 10% and 85% by weight of polythioester intermediate, relative to the entire reaction medium.

[0118] The reaction medium can comprise between 15% and 90% by weight of solvent(s), relative to the entire reaction medium.

[0119] Stage b)

[0120] Stage b) of deprotection of the polysulfoxide intermediate obtained in stage a) makes it possible to obtain a polysulfane. It can be carried out by any means known to the person skilled in the art. Since stages a) and b) are carried out in one-pot synthesis according to the application, it is understood that the reaction medium containing the polysulfoxide obtained at the end of stage a) is conserved to carry out the deprotection stage b). Thus, stages a) and b) are carried out in the presence of the same solvent (or mixture of solvents). More of said solvent (or said mixture of solvents) can be added during stage b). In particular, the process according to the application does not comprise, between stages a) and b), a stage of separation and / or extraction and / or washing of the (organic) phase containing the polysulfoxide. In particular, no intermediate stage of purification of the polysulfoxide is carried out. More particularly, no stage of recrystallization and / or distillation of the polysulfoxide is carried out.

[0121] Deprotection b) can be carried out by conventional methods: using a base or an acid, a catalyst of the Dy(OTf)3type (see Liang et al., Asian J. Org. Chem., 10.1002 / ajoc.201700481) or a compound of the quaternary ammonium cyanide salt type (see US 7 173 156).

[0122] Preferably, deprotection b) is a basic deprotection, preferably in the presence of an alcohol as defined above. It is generally carried out by adding a basic hydroxide, preferably NaOH or KOH. The addition can be carried out dropwise.

[0123] Deprotection stage b) can also be an acidic 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 solvent.

[0124] Sulfonic acids

[0125] The sulfonic acid is preferably an organic sulfonic acid, which is optionally anhydrous.

[0126] The sulfonic acid can have the following general formula (III):

[0127] R2-SO3H (III),

[0128] in which R2 represents:

[0129] - an alkyl group, preferably as defined above, optionally totally or partially substituted with one or more halogen atoms, identical or different, or

[0130] - an aryl group, preferably as defined above, optionally substituted with a saturated, linear or branched hydrocarbon chain comprising from 1 to 4 carbon atoms.

[0131] The halogen atom can be selected from fluorine, chlorine and bromine. In particular, the alkyl group can be perhalogenated, more particularly perfluorinated.

[0132] Preferably, the sulfonic acid is an alkylsulfonic acid, which is optionally anhydrous (in the above formula, R2 is an alkyl group).

[0133] Thus, the sulfonic acid (as well as their anhydrous forms) can be selected from:

[0134] Methanesulfonic acid, ethanesulfonic acid, n-propanesulfonic acid, isopropanesulfonic acid, n-butanesulfonic acid, isobutan- esulfonic acid, sec-butanesulfonic acid, tert-butan- esulfonic acid, trifluoromethanesulfonic acid, p-toluenesulfonic acid, benzenesulfonic acid and mixtures thereof in all proportions of two or more thereof.

[0135] According to a very particularly preferred embodiment, the sulfonic acid used in the context of the present application is methanesulfonic acid (MSA) or anhydrous methanesulfonic acid (AMSA).

[0136] The sulfonic acid can be supported or can not be supported. Preferably, it is not supported.

[0137] When it is supported, one can for example use a sulfonated resin of the styrene-divinylbenzene copolymer type, such as Amberlyst® 15 resin or Nafion®.

[0138] For example, for polythioesters, 0.1 - 10 equivalents of acid are used.

[0139] For example, for polythioesters, 3 - 60 equivalents (molar equivalents), preferably 3 - 20 equivalents of alcohol are used.

[0140] The deprotection stage b) can be carried out at a temperature of 10 °C to 100 °C, preferably 25 °C to 80 °C, more preferably 40 °C to 80 °C. It is generally carried out at atmospheric pressure.

[0141] Stages a) and b) can be carried out in the same reactor. For example, a batch reactor can be used.

[0142] Depending on the desired purity, a subsequent stage of conventional work-up and / or conventional purification can be carried out on the polythiol obtained at the end of stage b). For example, when the deprotection is carried out by addition of a base, the reaction medium can subsequently be acidified, and conversely, when the deprotection is carried out by addition of an acid, the reaction medium can be basified. The organic phase resulting therefrom and comprising the various thiols, in particular polythiol and (x-1)thiol, can subsequently be extracted and optionally concentrated.

[0143] Thus and in particular, the polythiol obtained can be in the form of a polythiol composition as mentioned hereinafter.

[0144] Composition according to the application

[0145] When polythiols are prepared from polyenes having x C=C double bonds, the conversion of these double bonds into -SH functions is generally not complete and can form by-products at each of the various stages, whatever the method used.

[0146] According to the application, the term "polythiol" thus means a polythiol corresponding to the starting polyene and comprising x -SH functions. For example, trimer captodiamine corresponds to cyclododecatriene. In this case, the conversion of the starting x C=C double bonds into -SH functions is complete.

[0147] According to the application, the term "(x-1) thiol" means a thiol corresponding to the starting polyene and comprising (x-1) -SH functions. The term "corresponding to the starting polyene" is understood to mean that the structure of the starting polyene and of the (x-1) thiol obtained is identical, except for the x C=C double bonds which have been converted into (x-1) -SH functions. In this case, the conversion of C=C double bonds into -SH functions is not complete: -SH functions are missing. The C=C double bonds which have not been converted into -SH functions can in particular be:

[0148] - still in the form of C=C double bonds; or

[0149] - in the form of deprotected thioester functions.

[0150] There can thus be different structures of (x-1) thiols, but they are grouped under this generic name which characterizes the number of -SH functions thereof (unless otherwise specifically mentioned). Such (x-1) thiols which are positional isomers of the double bonds of the starting polyene are also included.

[0151] It is thus possible to obtain a polythiol composition resulting from a polyene having x C=C double bonds and comprising:

[0152] - a polythiol corresponding to said polyene comprising x -SH functions; and

[0153] - a thiol corresponding to said polyene comprising (x-1) -SH functions.

[0154] Such a composition can optionally comprise other by-products or impurities (for example monothiols). It can be characterized by a weight ratio. This is the weight ratio: [polythiol corresponding to said polyene comprising x -SH functions] / [thiol corresponding to said polyene comprising (x-1) -SH functions].

[0155] In particular, it is possible to obtain a trithiol composition from a triene, said composition comprising:

[0156] - a corresponding (respective) trithiol; and

[0157] - the corresponding dithiols.

[0158] For example, in the case of a polythiol formed from cis, trans, trans-1,5,9- cyclododecatriene as starting polyene, the following dithiol ester can be obtained as a by-product resulting from stage a):

[0159] [Chem. 4]

[0160]

[0161] During stage b), the deprotection can also be incomplete.

[0162] Thus, according to the process of the application, it is possible to form:

[0163] - (x-1) thiol from the (x-1) thioate formed in stage a); and / or

[0164] - (x-1) thiol from the polythioate which has not been completely deprotected.

[0165] In the case of CDT, it is thus possible to obtain the following dithiol at the end of stage b):

[0166] [Chem. 5]

[0167]

[0168] Composition A obtained from cycloaliphatic polyenes

[0169] The application relates to a polythiol composition A obtained from a cycloaliphatic polyene containing x C=C double bonds and as defined above, said composition comprising:

[0170] - a polythiol corresponding to said cycloaliphatic polyene comprising x -SH functions; and

[0171] - a thiol corresponding to said cycloaliphatic polyene comprising (x-1) -SH functions (also called (x-1) thiol as explained above),

[0172] wherein x is as defined above.

[0173] In particular, said composition A comprises at least 85% by weight, preferably at least 90% by weight, more preferably at least 95% by weight of said polythiol, relative to the total weight of the composition A.

[0174] In particular, said composition A comprises less than 9% by weight, preferably less than 5% by weight, more preferably less than 1 % by weight of said (x-1) thiol, relative to the total weight of said composition A.

[0175] Preferably, the composition A has a weight ratio of from 10.1 : 1 to 20 000: 1, preferably from 10.5: 1 to 20 000: 1, more preferably from 15: 1 to 20 000: 1, for example from 15: 1 to 20 000: 1.

[0176] Preferably, the composition A has a weight ratio of from 10.1 : 1 to 10 000: 1, preferably from 10.5: 1 to 10 000: 1, more preferably from 15: 1 to 1000: 1, for example from 15: 1 to 500: 1. Still more preferably, the composition A has a weight ratio of from 10.5: 1 to 1000: 1.

[0177] The preferred starting cycloaliphatic polyene is cyclododecatriene, preferably 1,5,9- cyclododecatriene, more preferably the cis, trans, trans-1,5,9-cyclododecatriene isomer.

[0178] In particular, the present application relates to a polysulfane composition A obtained from cyclododecatriene as defined above, said composition comprising:

[0179] - trismercaptocyclododecane;

[0180] - dimercyclo-dodecene; and

[0181] - S-[bis(sulfanyl)cyclododecyl]thioacetate.

[0182] Thus, the [trismercaptocyclododecane / (dimercyclo-dodecene + S- [bis(sulfanyl)cyclododecyl]thioacetate)] weight ratio is in particular as defined above.

[0183] Composition B obtained from isocyanurate polyenes

[0184] The present application also relates to a polysulfane composition B obtained from an isocyanurate having the following general formula (I) and as defined above:

[0185] [Chem. 1]

[0186]

[0187] wherein R is a linear or branched hydrocarbon chain comprising at least one C=C double bond, which can optionally comprise one or more heteroatoms such as oxygen, nitrogen, sulfur and / or phosphorus, and which can optionally comprise one or more chemical groups;

[0188] said composition comprising:

[0189] - a polysulfane corresponding to said isocyanurate comprising x -SH functions; and

[0190] - a thiol corresponding to said isocyanurate comprising (x-1) -SH functional groups, wherein x is as defined above.

[0191] In particular, the composition B comprises at least 70 wt%, preferably at least 80 wt%, more preferably at least 90 wt%, for example at least 95 wt% of said polythiol, relative to the total weight of the composition B.

[0192] In particular, the composition B comprises less than 30 wt%, preferably less than 20 wt%, more preferably less than 10 wt%, for example less than 5 wt%, indeed even less than 1 wt% of said (x-1) thiol, relative to the total weight of the composition B.

[0193] Preferably, the composition B has a weight ratio of: from 2:1 to 20 000:1, for example from 2.3:1 to 20 000:1, preferably from 4:1 to 20 000:1, more preferably from 9:1 to 20 000:1, for example from 19:1 to 20 000:1.

[0194] Preferably, the composition B has a weight ratio of: from 2:1 to 10 000:1, for example from 2.3:1 to 10 000:1, preferably from 4:1 to 10 000:1, more preferably from 9:1 to 1000:1, for example from 100:1 to 1000:1.

[0195] Still more preferably, the composition B has a weight ratio of: from 10:1 to 1000:1.

[0196] A preferred starting isocyanurate is triallyl isocyanurate.

[0197] In particular, a polythiol composition B as defined above obtained from triallyl isocyanurate is obtained, said composition comprising:

[0198] - 1,3,5-tris(3-mercaptopropyl)-1,3,5-triazinane-2,4,6-trione and its isomers; and

[0199] - the corresponding dithiols (B1) and (B2) of the following formulae:

[0200] [Chem. 6]

[0201] and

[0202] [Chem. 7]

[0203]

[0204] Thus, the [(1,3,5-tris(3-mercapto propyl)-1,3,5-triazinane-2,4,6-trione) / (B1 +B2)] weight ratio is in particular as defined above.

[0205] The above composition is new and thus forms part of the present invention.

[0206] The present invention also relates to the polythiol composition obtainable by the process according to the present invention, obtained by the process according to the present invention or directly obtained by the process according to the present invention.

[0207] The present invention also relates to the polythiol obtained by the process according to the present invention or directly obtained by the process according to the present invention.

[0208] It is understood that the designation of a compound includes all possible positional isomers thereof, unless a specific isomer is mentioned.

[0209] It is understood that ranges given, for example "between X and X (X to X, X-X)", include the upper and lower limits.

[0210] The following examples are given by way of illustration and do not limit the present invention.

[0211] Example:

[0212] Example 1 : One-pot synthesis of polythiol composition from CDT under basic deprotection according to the present invention

[0213] Stage a):

[0214] 155 g (2.04 mol) of TAA (thioacetic acid) were introduced into a 1 liter jacketed reactor. The medium was placed under stirring at 5°C, then 28.4 g (0.62 mol) of ethanol were rapidly added. Air was bubbled into the reaction medium via a filter holder at a flow rate of about 0.4 Sl / h and nitrogen was passed into the headspace of the reactor at a flow rate of about 4 sl / h.

[0215] 100 g (0.62 mol) of 1,5,9-cyclododecatriene (CDT) were then added dropwise over about 1 h by means of a peristaltic pump. Once the addition was complete, 113.6 g (2.47 mol) of EtOH were added to the reaction medium.

[0216] The reaction medium was kept under stirring at 5°C overnight.

[0217] GC / FID analysis showed complete conversion of 1,5,9-cyclododecatriene.

[0218] The air supply was cut off.

[0219] Stage b) of basic deprotection:

[0220] Then 171 g of EtOH was added to the reaction medium. The reaction medium was then degassed with nitrogen for 1 hour, then brought to about 40°C, and 177 g of previously degassed 46% aqueous sodium hydroxide solution was added via a dropping funnel. The reaction medium was stirred under nitrogen at 40°C for 2 to 3 h.

[0221] Harvesting stage:

[0222] The reaction medium was then cooled to 20°C, then 200 g (2.03 mol) of 37% HCI was added dropwise to the medium via a peristaltic pump. The organic phase containing the mercaptans was removed. The aqueous phase was extracted with 105 g (1.24 mol) of dichloromethane.

[0223] The organic phases were then combined, washed 4 times with 14.8 g (0.82 mol) of water, then concentrated on a rotary evaporator.

[0224] GC / FID analysis showed complete conversion of the trithioacetate.

[0225] The composition obtained comprises:

[0226] - 0.36% of disulfide corresponding to CDT with 1 residual double bond,

[0227] - 0.47% of disulfide monothioacetate corresponding to CDT,

[0228] - 95.87% of trimer captan, and

[0229] - the remainder (100%) as impurities.

[0230] The weight ratio is 95.87:0.83, i.e. 116:1.

[0231] Example 2 : one-pot synthesis of a polythiol composition from CDT according to the application, deprotection with acid (AMSA and ethanol)

[0232] Stage a):

[0233] 155 g (2.04 mol) of TAA was introduced into a 1 -liter jacketed reactor. The medium was placed under stirring at 5°C, then 29 g (0.63 mol) of ethanol was added quickly. Air was bubbled into the reaction medium via a filter holder at a flow rate of about 0.4 Sl / h, and nitrogen was passed into the headspace of the reactor at a flow rate of about 4 Sl / h.

[0234] Subsequently, 100 g (0.62 mol) of 1,5,9-cyclododecatriene were added dropwise via a peristaltic pump over about 1 h. Once the addition was complete, 113.6 g (2.47 mol) of EtOH were added to the reaction medium.

[0235] The reaction medium was kept under stirring at 5°C for about overnight.

[0236] GC / FID analysis showed complete conversion of 1,5,9-cyclododecatriene.

[0237] The air supply was switched off.

[0238] Stage b) of acidic deprotection :

[0239] The temperature of the reaction medium was raised to 20°C and 85 g (1.85 mol) of EtOH were added to the reaction medium. 74 g of anhydrous methanesulfonic acid (0.77 mol) were added dropwise via a dropping funnel. The medium was stirred under reflux for 10 h under nitrogen.

[0240] Harvesting stage :

[0241] Subsequently, the reaction medium was cooled to 20°C and then 154 g (0.77 mol) of a previously degassed 20% NaOH solution were added dropwise to the medium via a peristaltic pump. The organic phase containing the mercaptans was withdrawn. The aqueous phase was extracted with 105 g (1.24 mol) of dichloromethane.

[0242] The organic phases were combined and then washed 4 times with 14.8 g (0.82 mol) of water and then concentrated on a rotary evaporator.

[0243] GC / FID analysis showed complete conversion of the trithioacetate.

[0244] The composition obtained comprises:

[0245] - 5.26% of a dithiol corresponding to CDT with 1 residual double bond,

[0246] - 0.58% of a dithiol monothioacetate corresponding to CDT,

[0247] - 90.60% of trismercaptocyclododecane, and

[0248] - the remainder (100%) as impurities.

[0249] The weight ratio is 90.60:5.84, i.e. 16:1.

[0250] Example 3 : synthesis of a polythiol composition from TAIC one-pot process according to the application with basic deprotection

[0251] Phase a) :

[0252] Into a 1 liter jacketed reactor, 101 g (1.33 mol) of TAA were introduced. The medium was left under stirring at 5°C, then 92 g (2.00 mol) of EtOH were rapidly added. Air was bubbled into the reaction medium via a filter holder at a flow rate of about 0.4 Sl / h, and nitrogen was passed into the headspace of the reactor at a flow rate of about 4 Sl / h.

[0253] Subsequently, 100 g (0.40 mol) of triallyl isocyanurate (TAIC) dissolved in 19 g (0.41 mol) of EtOH were added dropwise via a peristaltic pump over about 40 minutes. Once the addition was complete, 148 g (3.21 mol) of EtOH were gradually added to the reaction medium.

[0254] The reaction medium was left under stirring at 5°C for about 6 h.

[0255] GC / FID or HPLC / UV analysis showed complete conversion of triallyl isocyanurate.

[0256] The air supply was cut off.

[0257] Stage b) of basic deprotection :

[0258] The reaction medium was then degassed with nitrogen for 1 hour, then 115.1 g of previously degassed 46% sodium hydroxide aqueous solution were added dropwise via a dropping funnel. The reaction medium was left under stirring at 25°C under nitrogen for 5 h, then cooled to 10°C for about 17 h.

[0259] Harvesting stage :

[0260] The reaction medium was then cooled to 20°C, then 483 g (1.32 mol) of 10% HCI solution were added dropwise to the medium via a peristaltic pump. The organic phase containing the mercaptans was withdrawn. The aqueous phase was extracted three times with 68 g (0.80 mol) of dichloromethane.

[0261] The organic phases were combined, then washed twice with 14.4 g (0.80 mol) of water, then concentrated on a rotary evaporator.

[0262] GC / FID analysis showed complete conversion of the trithioacetate.

[0263] A polythiol composition comprising 95% by weight of trithiols corresponding to TAIC and about 0.2% by weight of dithiols corresponding to TAIC, relative to the total weight of the composition, was obtained.

[0264] Weight ratio of 95:0.2, i.e. 475:1.

[0265] Example 4: Synthesis of the polythiol composition from CDT one-pot according to the application, deprotection with acid (HCI and methanol)

[0266] Stage a) :

[0267] 155 g (2.04 mol) of TAA were introduced into a 3 liter jacketed reactor. The medium was left under stirring at 5°C, then 19.8 g (0.62 mol) of MeOH were rapidly added. Air was bubbled into the reaction medium via a frit at a flow rate of about 0.4 Sl / h and nitrogen was passed into the headspace of the reactor at a flow rate of about 4 Sl / h.

[0268] 100 g (0.62 mol) of 1,5,9-cyclododecatriene were then added dropwise via a peristaltic pump over about 1 h. Once the addition was complete, 78.9 g (2.46 mol) of MeOH were added to the reaction medium.

[0269] The reaction medium was left under stirring at 5°C overnight.

[0270] GC / FID analysis showed complete conversion of 1,5,9-cyclododecatriene.

[0271] The air supply was cut off.

[0272] Stage b) of acidic deprotection :

[0273] The reaction medium was brought to 20°C and 1119 g (34.93 mol) of MeOH were added to the reaction medium. The medium was heated to 40°C, 576.9 g (5.85 mol) of 37% HCI were added dropwise via a peristaltic pump, then the medium was heated under reflux under nitrogen for 48 hours.

[0274] Harvesting stage :

[0275] The reaction medium was then cooled to 20°C, the organic phase comprising the mercaptans was withdrawn, then 105 g (1.24 mol) of dichloromethane were added to the aqueous phase.

[0276] The organic phases were combined, then washed four times with 74 g (4.11 mol) of water, then concentrated on a rotary evaporator.

[0277] GC / FID analysis showed complete conversion of the trithioacetate. A polythiol composition comprising 96.28% of trismercaptocyclododecane and 0.25% of a dithiol corresponding to CDT was obtained.

[0278] The weight ratio is 96.28:0.25, i.e. 385:1.

[0279] Example 5 : One-pot synthesis of a polythiol composition from CDT according to the application, deprotection with acid (HCI and ethanol)

[0280] Phase a) :

[0281] 774.0 g (10.17 mol) of TAA were introduced into a 3-l jacketed reactor. The medium was left to stir at 5°C, then 142.0 g (3.08 mol) of ethanol were added quickly. Air was bubbled into the reaction medium via a filter holder at a flow rate of about 0.4 Sl / h and nitrogen was passed into the headspace of the reactor at a flow rate of about 4 Sl / h.

[0282] 500 g (3.08 mol) of 1,5,9-cyclododecatriene were then added dropwise over about 4 hours 30 via a peristaltic pump. Once the addition was complete, 851.7 g (18.49 mol) of ethanol were added to the reaction medium.

[0283] The reaction medium was left to stir at 5°C for about overnight.

[0284] GC / FID analysis showed complete conversion of the 1,5,9-cyclododecatriene.

[0285] The air supply was cut off.

[0286] Stage b) of acidic deprotection :

[0287] The reaction medium temperature was raised to 20°C and 1478.6 g (30.81 mol) of 96% EtOH were added to the reaction medium. The medium was heated to 40°C and 910.9 g (9.24 mol) of 37% HCI were added dropwise via a peristaltic pump, then the medium was heated under reflux for 22 h under nitrogen.

[0288] Harvesting stage :

[0289] The reaction medium was then cooled to 30°C and the organic phase comprising the mercaptans was removed, then 261.7 g (3.08 mol) of dichloromethane were added thereto.

[0290] The organic phase obtained was then washed four times with 110.9 g (6.16 mol) of water, then concentrated on a rotary evaporator.

[0291] GC / FID analysis showed complete conversion of the trithioacetate. A polythiol composition comprising 94.84% of trismercaptocyclododecane and 5.17% of a dithiol corresponding to CDT was obtained.

[0292] The weight ratio is 94.84:5.17, i.e. 18.34:1.

[0293] Example 6: Synthesis of the polythiol composition from TAIC one-pot process according to the application, deprotection with acid (HCI and ethanol)

[0294] Stage a) :

[0295] 302.3 g (3.97 mol) of TAA were introduced into a 3 liter jacketed reactor. The medium was left under stirring at 5°C, then 166.3 g (3.61 mol) of ethanol were rapidly added. Air was bubbled into the reaction medium via a frit at a flow rate of about 0.4 Sl / h and nitrogen was passed into the headspace of the reactor at a flow rate of about 4 Sl / h.

[0296] Subsequently, a solution of 300 g (1.20 mol) of triallyl isocyanurate in 27.7 g (0.60 mol) of ethanol was added dropwise via a peristaltic pump in about 1 hour 15. Once the addition was complete, 221.8 g (4.81 mol) of ethanol were gradually added to the reaction medium.

[0297] The reaction medium was left under stirring at 5°C for about 6 hours.

[0298] GC / FID or HPLC / UV analysis showed complete conversion of triallyl isocyanurate.

[0299] The air supply was cut off.

[0300] Stage b) of acidic deprotection :

[0301] The reaction medium temperature was raised to 20°C and 462.1 g (9.63 mol) of 96% EtOH were added to the reaction medium. The medium was heated to 40°C and 355.8 g (3.61 mol) of 37% HCI were added dropwise via a peristaltic pump. The medium was then heated under reflux under nitrogen for 28 h.

[0302] Harvesting stage :

[0303] The reaction medium was then cooled to 30°C and the organic phase comprising the thiols was removed, then 102.2 g (1.20 mol) of dichloromethane were added thereto.

[0304] The organic phase obtained was then washed four times with 43 g (2.41 mol) of water, then concentrated on a rotary evaporator.

[0305] HPLC / UV analysis showed complete conversion of the trithioacetate.

[0306] A polythiol composition comprising 95.16% by weight of tri-thiols corresponding to TAIC and about 0.2% by weight of di-thiols corresponding to TAIC was obtained, relative to the total weight of the composition.

[0307] The weight ratio was 95.16:0.2, i.e. 476:1.

[0308] Example 7 : Application tests

[0309] Two polythiol compositions derived from triallyl isocyanurate (TAIC) were prepared for application tests. The mass ratio of tri-thiols / di-thiols and the -SH percentage of these compositions are given in the table below:

[0310]

[0311] Polythiol composition P1 is the polythiol composition obtained according to example 6.

[0312] Polythiol composition P2 was prepared using the same protocol as described in example 6, but using AIBN (azobisisobutyronitrile) as initiator instead of oxygen and heating at 65°C during step a).

[0313] Polythiol compositions P1 and P2 were used as hardeners for an epoxy resin (Araldite® LY 556, from Huntsman) with a tertiary amine (DABCO® 33-LV, from Sigma-Aldrich) as catalyst. Curing was performed at room temperature (i.e. 25°C) using a stoichiometric amount of thiol functional groups relative to the epoxy functional groups. The amounts used are summarized in the table below:

[0314]

[0315] Mixtures were prepared in aluminum cups: Araldite® LY 556, polythiol and amine were weighed by weight, respectively. The whole was mixed rapidly with a spatula. The compositions started to harden within a few minutes and were left at room temperature for 7 days. Rods from each hardened composition were taken and placed on a rectangular torsion assembly fixed on an ARES Rheometer (Rheometer Scientific) to perform dynamic mechanical analysis (DMA). The samples were submitted to a sinusoidal deformation at a frequency of 1 Hz over a temperature range varying from -50°C to 110°C. The glass transition temperature (Tg) was determined at the maximum of the mechanical loss factor (tan delta). This value as well as the value of the elastic modulus at the plateau were recorded and are summarized in the table below:

[0316]

[0317] Thus, the use of the polythiol composition P1 according to the application in an epoxy resin allows to obtain a greater degree of crosslinking and a denser network. The resins thus obtained are notably characterized by a higher Tg and a higher plateau modulus.

Claims

1. Process for the preparation of a polythiol comprising the following stages: a) reacting a polyene with a thiocarboxylic acid in the presence of oxygen (O2) and at least one organic solvent, thereby obtaining a reaction medium comprising a polythioester and said at least one organic solvent; and b) carrying out a stage of deprotection of the polythioester obtained in stage a), thereby obtaining a polythiol; wherein stages a) and b) are carried out in a one-pot synthesis.

2. Preparation process according to claim 1, wherein the stage of deprotection b) is a basic deprotection, preferably carried out by adding a basic hydroxide.

3. Preparation process according to claim 1, wherein the stage of deprotection b) is an acidic deprotection, preferably in the presence of an alcohol.

4. Preparation process according to any one of the preceding claims, wherein at the end of stage a), the reaction medium comprises from 15% to 90% by weight of solvent, relative to the total amount of the reaction medium.

5. Preparation process according to any one of the preceding claims, wherein the organic solvent is chosen from: alcohols, ethers, organic chlorinated solvents, carboxylic acids and mixtures thereof.

6. Preparation process according to any one of the preceding claims, wherein the organic solvent is chosen from alcohols of the following general formula (IV): R4-OH (IV) wherein R4 represents a saturated, linear, branched or cyclic hydrocarbon group comprising from 1 to 10, preferably from 1 to 4 carbon atoms.

7. Preparation process according to any one of the preceding claims, wherein the thiocarboxylic acid is thioacetic acid.

8. Preparation process according to any one of the preceding claims, wherein the polyene is a triene.

9. Preparation process according to any one of the preceding claims, wherein the polyene is chosen from cyclic aliphatic polyenes and isocyanurate polyenes of the following general formula (I):

10. Polythiol composition A obtained from a cyclic aliphatic polyene containing x C=C double bonds, said composition comprising: wherein R is a linear or branched hydrocarbon chain comprising at least one C=C double bond, which can optionally comprise one or more heteroatoms, such as oxygen, nitrogen, sulfur and / or phosphorus, and which can optionally comprise one or more chemical groups. - a polythiol corresponding to said cyclic aliphatic polyene comprising x -SH functions; and - a thiol corresponding to said cyclic aliphatic polyene comprising (x-1) -SH functions; and x is an integer greater than or equal to 3. wherein the weight ratio is 10.1 : 1 to 50 000: 1; 11. Polythiol composition A according to claim 10, wherein the cyclic aliphatic polyene is cyclododecatriene, preferably the cis, trans, trans-1,5,9-cyclododecatriene isomer thereof.

12. Polythiol composition B obtained from an isocyanurate of the following general formula (I): said composition comprising: wherein R is a linear or branched hydrocarbon chain comprising at least one C=C double bond, which can optionally comprise one or more heteroatoms, such as oxygen, nitrogen, sulfur and / or phosphor, and which can optionally comprise one or more chemical groups; - a polythiol corresponding to said isocyanurate comprising x -SH functions; and - a thiol corresponding to said isocyanurate comprising (x-1) -SH functions; x is an integer greater than or equal to 3. wherein the weight ratio is from 2: 1 to 50 000: 1 ; and 13. Polythiol composition B according to claim 12, wherein the isocyanurate is triallyl isocyanurate. ​

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