FR2815349A1 - New catalysts based on fluoride salts of trivalent metals useful in transcarbamation reactions carried out on masked isocyanate compounds to form aliphatic polyurethanes - Google Patents

Abstract

Acid salts of trivalent metals (I) used in transcarbamation reactions to convert low alcohol carbamates to polyurethanes, is new. Acid salts of trivalent metals of formula (I) used in transcarbamation reactions to convert low alcohol carbamates to polyurethanes, is new: MY3-q(Z)q (I) Z = anion of a superacid with a Hammet constant of 13 or more; M = a trivalent metal, preferably known for forming Lewis acids; Y = a monovalent anion; and q = 1-3. Independent claims are included for: (1) compositions containing the catalysts; and (2) the transcarbamation reactions in which they are used.

Description

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USE AS CATALYST FOR THE FORMATION OF TRIALENTAL METAL PERHALOGEN SULFONATE URETHANES, COMPOSITION CONTAINING THE SAME, AND PROCESS USING THE SAME
The subject of the present invention is novel transcarbamation catalysts. It relates more specifically to the use of new catalysts that are not based on tin.

 Because of their high reactivity and relative toxicity, isocyanates are often used in a derived form or in a masked form. This derivative form or this masked form has the disadvantage corresponding to its advantages, that is to say that it is not very reactive, so it requires the use of catalysts so that the reaction can take place at the same time. temperatures acceptable by the industry.

 The masked isocyanates can be used in all isocyanate applications, namely paints, varnishes and more generally coatings, adhesives and adhesives, as well as certain specialty polymers.

 The most commonly used catalysts are dialkoyl tin alkanoates, the best known of which is dibutyl tin dilaurate. However, for some applications, dibutyltin dilaurate has insufficient activity, so it is necessary to use it at very high concentrations.

 These (trans) carbamation catalysts make it possible to produce polyurethanes, in particular aliphatic polyurethanes.

 However, tin salts have a reputation for toxicity that impedes their use, so we seek for many applications to replace them with compounds that do not have these disadvantages.

 In addition, the industry is always on the lookout for compounds with catalytic activities superior to existing catalysts.

 The catalyst most used as a reference in the field of polyurethanes is dibutyltin dilaurate.

 One of the aims of the present invention is therefore to provide a carbamation catalyst which is at least as active as dibutyltin dilaurate, but which is not based on tin.

 Another object of the present invention is to provide a catalyst which can be used for the synthesis of polyurethanes, in particular of aliphatic nature.

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Another object of the present invention is to provide a catalyst of the above type which makes it possible to carry out the synthesis of polyurethane from masked polyisocyanates.

 Another object of the present invention is to provide a catalyst which makes it possible to perform a transcarbamation resulting in polyurethanes from light alkyl carbamates; the term alkyl corresponding to an alcohol whose boiling point under ordinary pressure is at most equal to 150OC (2 significant digits), advantageously at most 100OC (2 significant digits).

 Another object of the present invention is to provide a catalyst of the above type which can be used when the urethanes or polyurethanes serve as binder coating (varnishes or paints).

où : M représentant un métal trivalent, de préférence connu, pour former des acides de Lewis ; - Y est un anion ou une fonction anionique monovalente et ; - Rx est un radical dont le carbone porteur de la fonction sulfonique est perhalogéné, et - q est un entier choisi avantageusement entre 1 et 3, y compris les bornes. These and other objects which will become apparent are achieved by using as the catalyst compounds having the following general formula: MY [(Rx) -SO 2 -O-] q,

where: M represents a trivalent metal, preferably known, to form Lewis acids; Y is an anion or a monovalent anionic function and; Rx is a radical whose carbon bearing the sulphonic function is perhalogenated, and q is an integer advantageously chosen between 1 and 3, including the boundaries.

 M is thus the trivalent cation corresponding to an element of metallic nature.

 Very good results are obtained when q is equal to 3. The halogenated carbon is advantageously a perfluorinated carbon and more preferably a perfluoromethylene group, as will appear below. The other anion or other anions are organic or inorganic anions, preferably monoanions.

 These anions include sulfonates, monoalkyl sulphates (when they are stable in the medium), carboxylates, halides, halogenates (when the latter are not too oxidizing for the medium), phosphates, phosphonates and phosphinates, preferably rendered monovalent by partial esterification when necessary; pyrophosphates can be considered in the environments where they are stable.

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However, it is preferable that these anions other than the perhalogenated sulfonates are not chelating.

 It is also preferable that the pKa of the acid associated with these anions is at most equal to about 10, preferably about 5, more preferably about 2.

 It is preferable that the associated acid is not more acidic than the hydrohalic acids.

 According to the present invention, the urethane formation reaction and in particular polyurethane can be a transcarbamation reaction. This term of transcarbamation must be taken lato sensu, that is to say that it also relates to the passage of a pseudocarbamate (reaction product of an isocyanate with a hydroxylated derivative not constituting an alcohol, for example chosen from oximes or hydroxyamides) urethane or polyurethane by condensation with an alcohol or more generally with a polyol known in the art.

 These catalysts are advantageously used in an amount of at least 0.5% and at most equal to 5% carbamate equivalent, preferably between 1% and 2%.

 The transcarbamation reaction depends on the alcohols and carbamates used. However, it is between 100 and 200oC, preferably between 120 and 180oC. The carbamates used are those resulting from the reaction of an isocyanate function with a hydroxyl function. Among the hydroxyl functions, mention should be made of the alcohol functional groups, especially those of volatile alcohols at the reaction temperature (boiling point at atmospheric pressure) and more particularly methanol.

 Among the other hydroxyl functions which may be mentioned as having a particular advantage, the phenol functions, the hydroxyl functional groups grafted on a nitrogen atom such as hydroxy-imides, oximes.

 The alcohols that substitute for these hydroxylated derivatives are advantageously polyols (especially di-and / or triols), advantageously primary.

 Molecular weights can vary over a wide range depending on the shape of the coating used. The molecular weights are relatively high, ranging up to about 20,000 when the catalysts according to the present invention are used in a powder paint, whereas for the more conventional applications, the polyols rarely exceed a molecular weight of about 3,000. .

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The molecular weights referred to herein are Mn-number average molecular weights and are defined by the gel permeation technique known to those skilled in the art. More specifically, the molecular weight is determined by gel permeation chromatography (GPC). The technique uses as gels, two gels of polystyrene (ultrastyragel * at 104 and 500 Ä), THF as solvent and sulfur as standard.

 The isocyanates giving rise to or corresponding to the preferred carbamates are at least partially aliphatic isocyanates, that is to say that the isocyanate function in question is connected by nitrogen to the backbone of the isocyanate molecule by a carbon atom of Sp3 hybridization.

composé désigné par le terme isophoronediisocyanate, ou IPDI), la partie du squelette reliant deux fonctions isocyanates comporte au moins un enchaînement polyméthylène (CH2) où représente un entier de 2 à 10, avantageusement de 4 à 8. Cette préférence joue sur les performances mécaniques. It is further desirable that in the structure of the monomeric isocyanate (s) (i.e., isocyanates, generally di-isocyanates, which are the precursors of the polyisocyanates used as the crosslinking agent, and the most commonly used are hexamethylenediisocyanate and

compound designated by the term isophorone diisocyanate, or IPDI), the part of the backbone connecting two isocyanate functional groups comprises at least one polymethylene (CH 2) chain where represents an integer of 2 to 10, advantageously from 4 to 8. This preference affects the mechanical performance .

 When there are several sequences, these can be similar or different. In addition, it is desirable that, in the monomer considered, these polymethylene linkages are free in rotation and therefore exocyclic, if there is a cycle. When using prepolymers, or oligomers, derived from more than one monomer, it is desirable that the condition relating to this sequence polymethylene is found in at least one of these monomers.

 Preferred polyisocyanates are those having at least one aliphatic isocyanate function. In other words, at least one masked isocyanate function according to the invention is linked to the backbone via a carbon of Sp3 type advantageously bearing a hydrogen atom, preferably two. It is desirable for said Sp3 type carbon to be carried by a Sp3-type carbon and advantageously provided with one, preferably two, hydrogen atoms, in order to prevent the isocyanate function in question from being in the neopentyl position.

 In other words, it is advisable to choose as monomer (which are usually carrying two isocyanate functions) at least

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un composé qui porte au moins une fonction isocyanate aliphatique qui ne soit ni secondaire ou tertiaire, ni néopentylique.

a compound which carries at least one aliphatic isocyanate function which is neither secondary nor tertiary nor neopentyl.

 In the case of a mixture obtained from several (generally two) types of monomers, it is preferable that the one or those of the monomers which satisfy the above conditions and / or (advantageously "and") with the condition on the presence of The polymethylene (CH 2) chain is at least 1/3, advantageously 1/2, preferably 2/3, of the masked isocyanate functional groups. Thus, during the study according to the present invention, excellent results have been obtained with mixtures comprising 2/3 HMDT ("trimer" of Hexamethylene diisocyanate) with IPDI or IPDT ( "trimer" of IPDI), both being masked according to the invention (the nBDI, norbornane diisocyanate, and its trimer are similar).

 Of course, the case where all the isocyanates are aliphatic and even meet the above criteria is preferred.

 According to the present invention, the masked isocyanate, pure or mixed, is derived from a polyisocyanate, that is to say having at least two isocyanate functional groups, advantageously more than two (possible fractional values since it is generally acts as a mixture of oligomers more or less condensed), which itself is usually derived from a precondensation or a prepolymerization of unitary diisocyanate (sometimes described in the present description of "monomer").

 The average molecular weight of these prepolymers or precondensates is generally at most equal to 2,000 (a significant number), more usually at 1,000 (a significant number, preferably two).

 Thus, among the polyisocyanates used for the invention, mention may be made of those of the biuret type and those whose di-or trimerization reaction has led to four, five or six-membered rings. Among the six-membered rings, mention may be made of isocyanuric rings derived from a homo-or a heterotrimerization of various diisocyanates alone, with other isocyanate (s) [mono-, di-, or polyisocyanate (s) )] or with carbon dioxide (or carbon dioxide); in this case, one nitrogen of the isocyanuric ring is replaced by an oxygen. Oligomers with isocyanuric rings are preferred.

 Among the most interesting monomers, it should be mentioned on the one hand those which have a polymethylene sequence as defined above, exocyclic, obviously including non-cyclic. Among the monomers exhibiting a polymethylene linkage, mention may be made of tetramethylenediisocyanate optionally substituted by an alkyl group, advantageously of at most four carbon atoms, preferably from

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plus deux atomes de carbone ; le pentaméthylènediisocyanate éventuellement substitué par un groupe alcoyle, avantageusement d'au plus quatre atomes de carbone, de préférence d'au plus deux atomes de carbone et l'hexaméthylènediisocyanate. Comme monomères de nature cycloaliphatique qui sont de préférence utilisés en association avec des isocyanates ayant des enchaînements polyméthylènes exocycliques, ou non cycliques, on peut citer

les monomères et les composés issus des monomères suivants :

e Les composés correspondant à l'hydrogénation du ou des noyaux

aromatiques porteurs des fonctions isocyanates de monomères d'isocyanates aromatiques, et notamment du TOI (toluènediisocyanate) et des diisocyanates diphényles, le composé connu sous le sigle H12MDI et les divers B) C [b) s (isocyanatométhy ! cyc) ohexane)] ; et surtout

o lue norbornanediisocyanate souvent appelé par son sigle NBDI ; - l'isophoronediisocyanate ou IPDI ou 3-isocyanatométhyl-3, 5-triméthyl-

cyclohexylisocyanate.

plus two carbon atoms; pentamethylenediisocyanate optionally substituted by an alkyl group, advantageously of at most four carbon atoms, preferably of at most two carbon atoms and hexamethylene diisocyanate. As monomers of cycloaliphatic nature which are preferably used in combination with isocyanates having exocyclic or non-cyclic polymethylen linkages, mention may be made of

monomers and compounds derived from the following monomers:

e Compounds corresponding to the hydrogenation of the nuclei (s)

aromatic compounds carrying isocyanate functional groups of aromatic isocyanate monomers, and especially toluene diisocyanate (TOI) and diphenyl diisocyanates, the compound known by the acronym H12MDI and the various B) C (b) s (isocyanatomethylcyclohexane)]; and especially

o norbornanediisocyanate often called by its abbreviation NBDI; isophorone diisocyanate or IPDI or 3-isocyanatomethyl-3,5-trimethyl-

cyclohexyl.

It should be pointed out that the catalysts according to the present invention are also favorable when the urethane formation reaction comprises a reaction of passage from a urea function to a carbamate function. The urea function (> N-CO-N <) must be taken in the broad sense and is aimed above all at the compounds which constitute isocyanates masked by derivatives, or more exactly masking agents, carrying a hydrogen reactive with a nitrogen. These masked isocyanates lead to polyurethanes using alcohols and especially polyols.

 The concept of masking agent corresponds to that which has been the subject of books such as that of Petersen and that of Wicks.

 The present invention is particularly useful for masked isocyanates whose release temperature as defined in the octanol test (see infra) is relatively high, that is to say at least equal to 100oC, advantageously at 120oC, preferably at 130oC.

 The masking agents giving the best results are the masking agents having an NH function. Thus, advantageously, the masking agent, or at least one of them when there are more than one, is chosen from compounds having a function> NH, advantageously among the secondary amines, the rings five-membered aromatic nitrogen compounds, preferably having at least two nitrogens.

 However, those which are chosen from compounds bearing hydroxylated functional groups, advantageously chosen from saturated alcohols of

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point d'ébullition inférieur à 1500C (avantageusement à 100 C), les phénols, les oximes et l'hydroxyamide.

boiling point below 1500C (advantageously 100 C), phenols, oximes and hydroxyamide.

 According to the present invention, it is desirable that the metal corresponding to the cation M does not have a valence lower than 3.

 It is also advantageous for the metal to be a relatively heavy metal, i.e., said metal belongs to a period greater than the fourth period, advantageously to the fifth period. We can refer to the classification of periodicals that was the subject of the supplement to the bulletin of the Société Chimique de France No. 1, in January 1966.

 Among the metals giving the best results, it is appropriate to mention the lanthanides (lanthanide being taken here stricto sensu, that is to say it does not include lanthanum) and especially bismuth.

With regard to the sulphonates, it is desirable for Rx to be of the formula: ## STR5 ## where X, which are similar or different, represent a chlorine, a fluorine or a radical of formula CnF2n + 1, with n being at most equal to 5, preferably
2, with the proviso that at least one of the X is fluorine, fluorine advantageously carried by the carbon bonded to sulfur; p represents an integer at most equal to 2; GEA represents an electron-withdrawing group (that is to say sigma p greater than zero, advantageously 0.1, preferably 0.2), the possible functions of which are inert under the reaction conditions, advantageously fluorine or a perfluorinated residue of formula CnF2n + 1, with n being at most equal to 8, advantageously to 5, the total carbon number of Rf being advantageously between 1 and 15, preferably between 1 and 10.

 As indicated, it is preferred that the carbon carrying the sulphonate function is a perfluorinated carbon and in particular a carbon constituting a perfluoromethylene (-CF 2 -). For reasons of ease of industrial production, the first members of the Rf (perfluoroalkyl) groups are preferred and in particular the trifluoromethanesulfonic acid (triflic acid corresponding to triflate) and pentafluoroethanesutfonic acids give good results.

 The present invention also relates to masked isocyanate compositions, advantageously in the form of carbamates (late sensu, that is to say the functions corresponding to the sequence-N (R) -CO-O-

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où R est un radical hydrocarboné, en général alcoyle, voire aryle, ou plus fréquemment un hydrogène) et comportant en outre un catalyseur de formule générale (1) suivante : MY [ (Rx)-S02-0-] q. où : M représentant un métal trivalent, de préférence connu, pour former des acides de Lewis ; Y est un anion ou une fonction anionique monovalente et ; - Rx est un radical dont le carbone porteur de la fonction suffonique est perhalogéné, et q est un entier choisi avantageusement entre 1 et 3, y compris les bornes.

where R is a hydrocarbon radical, in general alkyl, or even aryl, or more frequently hydrogen) and further comprising a catalyst of the following general formula (1): MY [(Rx) -SO 2 -O-] q. where: M represents a trivalent metal, preferably known, to form Lewis acids; Y is a monovalent anion or anionic function and; Rx is a radical whose carbon bearing the suffonic function is perhalogenated, and q is an integer advantageously chosen between 1 and 3, including the boundaries.

où : M représentant un métal trivalent, de préférence connu pour former des acides de Lewis ; Y est un anion ou une fonction anionique monovalente et ; # Rx est un radical dont le carbone porteur de la fonction sulfonique est perhalogéné, et - q est un entier choisi avantageusement entre 1 et 3, y compris les bornes. The present invention also relates to a transcarbamation process in which the compounds of formula: MY3 [(Rx) -SO2-O-] q are used as transcarbamation catalyst.

where: M represents a trivalent metal, preferably known to form Lewis acids; Y is a monovalent anion or anionic function and; # Rx is a radical whose carbon carrying the sulphonic function is perhalogenous, and - q is an integer advantageously chosen between 1 and 3, including the boundaries.

 These catalysts make it possible to carry out the reaction at temperatures below 200 ° C., most often below 180 ° C.

 In general, to obtain sufficient kinetics, it is appropriate to place at a temperature at least equal to 100oC, preferably at a temperature at least equal to 120oC.

Octanol test "Release" temperature: This is the lowest temperature at which (or "unblocking") the masking agent of the masked isocyanate is displaced to 9/10 (rounded mathematically) by a primary monoalcohol (the primary alcohol is usually octanol).

Storage life: To ensure a good storage life, it is preferable to choose masked isocyanate functions whose octanol test shows a "release" at 80 C,

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avantageusement à 90oC, au plus égale à 90%.

advantageously at 90oC, at most equal to 90%.

Advancement of the reaction: It is considered that the reaction is complete if it is carried out more than 90%.

 The following nonlimiting examples illustrate the invention. These examples, in order to avoid any interaction problems, have substantially focused on monofunctional isocyanates. N-hexyl isocyanate was used.

EXAMPLE General Procedure: Choice of the Reaction Model The choice fell on the use of aliphatic isocyanates which are more expensive but which give access to polyurethanes having: - better resistance to U. V.; - a more stable color; - excellent hold in external use.

The action of primary alcohols gives carbamates which are very thermally stable with respect to aromatic isocyanates.

Methanol was chosen as the blocking agent for alkyl isocyanate.

Indeed, this alcohol has a low cost, a low molecular weight and a limited toxicity.

Such a blocking agent promotes a limitation of volatile organic compounds (C.O. V.) compared to other agents. This methodology fits well within the framework of the development of a cleaner chemistry, privileged axis of the contemporary research.

Reagents involved The alkyl isocyanate selected is hexyl isocyanate. Its blocking is carried out very simply by methanol under conventional heating for 4 hours.

réactif de départ au cours de la réaction de transcarbamatation.

n-hex-N=C=O + MeOH- n-hex-NH-CO-OMe

L'alcool primaire choisi pour réaliser la transcarbamatation est l'octan-1-ol. Son action sur l'isocyanate d'hexyle sous chauffage classique pendant 4 heures conduit à la formation du produit d'arrivée : le N-hexyloctyluréthane.

n-hex-N=C=O + n-OctOH-n-hex-NH-CO-0-n-Oct The reaction leads to the formation of N-hexylmethylurethane which will serve as the

starting reagent during the transcarbamation reaction.

n-hex-N = C = O + MeOH-n-hex-NH-CO-OMe

The primary alcohol chosen to carry out the transcarbamation is octan-1-ol. Its action on hexyl isocyanate under conventional heating for 4 hours leads to the formation of the product of arrival: N-hexyloctylurethane.

n-hex-N = C = O + n-OctOH-n-hex-NH-CO-O-n-Oct

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La caractérisation de ce produit par les techniques d'analyse classique a été nécessaire pour réaliser un suivi cinétique de la réaction de transcarbamatation par chromatographie en phase gazeuse (temps de rétention et coefficient de réponse).

The characterization of this product by conventional analysis techniques was necessary to perform a kinetic monitoring of the transcarbamation reaction by gas chromatography (retention time and response coefficient).

Cat. n-hex-NH-CO-OMe + OctOH- n-hex-NH-CO-Oct + MeOH

carba 1 carba 2 - Carba 1 : 3, 14 mmoles (500 mg) - OctOH : 1 éq. ou 10 éq. Kinetic study The studied transcarbamation reaction carried out in the absence of solvent and in the presence of 1 mol% of catalyst (to have a rapid reaction) is schematized below:

Cat. n-hex-NH-CO-OMe + OctOH-n-hex-NH-CO-Oct + MeOH

carba 1 carba 2 - Carba 1: 3, 14 mmol (500 mg) - OctOH: 1 eq. or 10 eq.

- Internal reference (hexadecane): 0, 5 eq.

- Cat. : 1 mol%

- 130 C Kinetic results of various catalysts tested

<Tb>
<tb> Catalyst <SEP> k <SEP> into <SEP> mol-1.L. <SEP> min-1 <SEP> Yield <SEP> (%)
<tb> Bu2Sn <SEP> (laurate) <SEP> 2 <SEP> 1,10.10-3 <SEP> 26
<tb> Reference
<tb> BiPh3 <SEP> comparative <SEP> 0 <SEP> 0
<tb> BiCl3 <SEP> comparative <SEP> 3.80. <SEP> 10-5 <SEP> 2
<tb> Bi <SEP> (OTf) <SEP> 3 <SEP> 5, <SEQ> 54. <SEP> 10-3 <SEP> 70
<tb> Yb <SEP> (OTf) 3 <SEP> 8,76.10-4 <SEP> 30
<tb> Sm <SEP> (OTfh <SEP> 2, <SEP> 0. <SEP> 10-3 <SEP> 45
<Tb>
Triphenylbismuth and bismuth chloride show almost no catalytic activity. As for the triflate of bismuth, it shows a remarkable efficiency with a speed constant of 4.54. 10-3 mol-1. L. min-1 and a final yield of 70%, a result quite comparable to dibromed distannoxane.

Claims (17)

 1. Use as a catalyst for the urethane formation of compounds of the following general formula (1): MY3 [(Rx) -SO2-O-] q, where: M represents a trivalent metal, preferably known to form Lewis acids; Y is a monovalent anion or anionic function and; Rx is a radical in which the carbon bearing the sulphonic function is perhalogenated, and q is an integer advantageously chosen between 1 and 3, including the terminals. 2. Use according to claim 1, characterized in that the urethane formation reaction is a transcarbamation reaction. 3. Use according to claim 1, characterized in that the urethane formation reaction comprises a passage reaction of a urea function (> N-CO-N <) to a carbamate function (> N-CO-O). -). 4. Use according to claims 1 to 3, characterized in that the precursor of the urethane function is a masked isocyanate function. 5. Use according to claim 4, characterized in that the masking agent, or at least one of them when there is more than one, is chosen from the hydroxy-functional compounds advantageously chosen from saturated alcohols with a boiling point below 150 ° C. (advantageously at 100 ° C.), phenols, oximes and hydroxyamide. 6. Use according to claims 4 and 5, characterized in that the masking agent, or at least one of them when there is more than one, is chosen from compounds having a function. > NH, advantageously among secondary amines, nitrogenous rings <Desc / Clms Page number 12>  five-membered aromatic compounds, preferably having at least two nitrogens. 7. Use according to claims 1 to 6, characterized in that said metal is a metal having no valence less than 3.

8. Use according to claims 1 to 7, characterized in that said metal belongs to a period greater than the fourth, preferably to the fifth period. 9. Use according to claims 1 to 8, characterized in that said metal is a lanthanide or bismuth. 10. Use according to claims 1 to 9, characterized in that Rx is of formula: GEA- (CX2) p- where: the X, similar or different, represent a chlorine, a fluorine or a radical of formula CnF2n + 1 with n being at most 5, preferably 2, with the proviso that at least one of X is fluorine, fluorine advantageously carried by the carbon bonded to sulfur; p represents an integer at most equal to 2; GEA represents an electron-withdrawing group (that is to say sigma p greater than zero, advantageously 0.1, preferably 0.2), the possible functions of which are inert under the reaction conditions, advantageously fluorine or a perfluorinated residue of formula CnF2n + 1 with n being at most equal to 8, advantageously to 5. the total carbon number of Rf advantageously being between 1 and 15, preferably between 1 and 10. 11. Composition characterized in that it comprises at least one carbamate that can be obtained by the action of a hydroxyl compound on a preferably aliphatic isocyanate, and at least one of the compounds corresponding to the following general formula (1) : MY [(Rx) -S02-0-] q, where: M represents a trivalent metal, preferably known to form Lewis acids; <Desc / Clms Page number 13>  Y is an anion or a monovalent anionic function and; Rx is a radical whose carbon bearing the sulphonic function is perhalogenated, and q is an integer advantageously chosen between 1 and 3, including the boundaries.

12. Composition according to claim 11, characterized in that it further comprises an alcohol or a polyalcohol advantageously primary. 13. Composition according to claims 11 and 12, characterized in that said hydroxyl compound is chosen from volatile alcohols at a temperature at most equal to 150 C and from hydroxyl masking agents. 14. Composition according to claims 11 to 13, characterized in that the said hydroxylated compound is methanol. 15. Composition according to claims 11 to 14, characterized in that the said hydroxylated compound is chosen from masking agents, advantageously from phenols and oximes. Transcarbamation process, characterized in that the compounds according to the following general formula (1) are used as transcarbamation catalyst: MY3Y [(Rx) -SO2-O-] q,

 or : M represents a trivalent metal, preferably known to form Lewis acids; Y is a monovalent anion or anionic function and; Rx is a radical in which the carbon bearing the sulphonic function is perhalogenated, and q is an integer advantageously chosen between 1 and 3, including the boundaries. 17. The method of claim 16, characterized in that the transcarbamatation reaction is conducted at a temperature between 100 and 200oC, preferably between 120 and 180oC.