EP1358237A1

EP1358237A1 - (cyclo)condensation of isocyanate compounds

Info

Publication number: EP1358237A1
Application number: EP01989664A
Authority: EP
Inventors: Jean-Marie Bernard
Original assignee: Rhodia Chimie SAS
Current assignee: Vencorex France SAS
Priority date: 2000-12-29
Filing date: 2001-12-26
Publication date: 2003-11-05
Also published as: FR2818974A1; US6936677B2; US20040030085A1; WO2002053613A1; BR0116561A; FR2818974B1; US7524435B2; CN1492887A; US20050143575A1; CN1238393C

Abstract

The invention concerns the use of a compound comprising a nitrogenous heterocyclic group with five cyclic members including at least two nitrogen atoms, one of the nitrogen atoms bearing a hydrogen atom to promote the opening/closing reaction of uretidione cycles in the presence of a nucleophile compound provided that, when the nitrogenous heterocyclic group is imidazole, the opening/closing reaction is not the closing reaction of the uretidione cycle in the presence of a quaternary ammonium salt.

Description

(Cyclo) condensation of isocyanate compounds

The invention relates to a method for promoting the opening of uretidiones cycles or the closure of isocyanate compounds in uretidiones cycles.

The invention more particularly relates to the (cyclo) condensation of isocyanate compounds.

In the chemistry of polyisocyanates, in particular in the processes for the synthesis of trimer polyisocyanates having an isocyanurate ring, it is generally desirable, in particular for viscosity reasons, to obtain a reaction product having a certain content of compounds with a uretidione ring .

Generally, compounds with a uretidione ring also called dimers are obtained by dimerization of isocyanate compounds in the presence of a dimerization catalyst such as a trialkylphosphine, a tris- (N, N-dialkyl) phosphotriamide or an N, N , N ', N'-tetra-alkylguanidine.

In addition, WO 99/23128 describes a process for the catalytic trimerization of isocyanate using a catalyst based on a quaternary ammonium salt in which imidazole or one of its co-catalysts is used derivatives so as to increase the reactivity of isocyanates, in particular cycloaliphatic isocyanates and to control it effectively without it depending on the content of hydrolyzable chlorine contained in the starting isocyanate monomer.

The document also describes that the use of imidazole as a cocatalyst for a trimerization reaction in which the catalyst is a quaternary ammonium salt results in the formation of dimeric compounds with a uretidione cycle. The amount of imidazole or its derivatives is such that the imidazole / quaternary ammonium molar ratio is of the order of 14 or more.

It is also known that imidazole and other nitrogen-containing cyclic compounds having a five-membered nitrogen heterocyclic group comprising at least two nitrogen atoms add up on the isocyanate function at room temperature in accordance with the reaction scheme:

Temperature

R-NCO + HET-H - am - - ^H biante - R-NH-CO-HET (I) '

R being the residue of an isocyanate compound after removal of an isocyanate function and HET-H being a nitrogen heterocyclic compound as defined above, linked to the NCO group via the NH group of the heterocycle.

[0009] At high temperatures, of the order of 80 to 100 ° C., the nitrogen heterocycles as described above are released from the NCO function according to the reaction scheme:

R-NH-CO-HET ^{80 "100 ° C} ^ R-NCO + HET-H

The release temperature of nitrogenous heterocycles compounds is relatively low in comparison with other blocking agents of the NCO function. Therefore, imidazole and nitrogen heterocycles as defined above are considered to be "good leaving groups".

It is also known that when the HET-H / NCO ratio is small, the equilibrium of the reaction is shifted towards the formation of the protected form of the isocyanate (I).

The work carried out by the inventors has shown that in the presence of an anionic compound, especially from a strong base, that a cyclocondensation catalyst of an anionic nature, the reaction of an isocyanate with a heterocycle as defined above surprisingly favored the formation of a mono-uretidione compound also designated by "true dimer" derived polycondensation of two starting isocyanate molecules and comprising a single uretidione cycle. -.

The mechanism proposed by the inventors is based on the assumption that in the presence of isocyanate and an anionic compound, as defined above, the five-membered heterocyclic compound promotes the addition of the isocyanate function on the urea-HET compound (I) to give a biuret-HET compound or also designated by "pseudo-biuret" of formula (II):

Due to the nucleofuge characteristics of the HET group, this pseudo-biuret rapidly cyclodimerizes to "true dimer" with release of HET-H which reacts quickly on the isocyanate functions in excess in accordance with the reaction scheme:

Everything happens as if the base formed by the anionic group of the cyclocondensation catalyst accelerates the kinetics of cyclodimerization by promoting the stripping of a proton from the pseudo-biuret followed by a cyclization reaction of the atom of nucleophilic nitrogen thus born, on the carbonyl group of the urea function with release of the vicinal HET heterocyclic group.

In the case of heterocyclic groups comprising an NH group, the addition of the nitrogen heterocyclic group to the isocyanate function is carried out via this group, with subsequent release of a HET-H compound. In the case of substituted heterocyclic groups, the addition of the nitrogen heterocycle probably takes place by means of a function = N- of the nitrogen heterocyclic.

In other words in a reaction medium comprising isocyanate and uretidiones functions, the kinetics of addition of HET-H group on the isocyanate function is faster than the kinetics of addition of HET-H to the compound "true dimer".

On the other hand, the work of the inventors has shown that when the rate of NCO functions present in the reaction medium decreased and at a temperature of at least 40 ° C, the HET-H compound acted by opening the uretidione cycle and favored, in the presence of a monomeric isocyanate, the formation of a higher homologous cyclocondensation compound, in other words the cyclotimerization reaction.

It was also known that certain nucleophilic compounds Nu-H could promote the opening of uretidiones cycles to form the corresponding adducts according to the reaction scheme:

Thus, it is described in Houben-Weyl "Methoden der Organischen Chemie", 4. Auflage, Georg Thieme Verlag, (1983), pp 1110, that aliphatic amines open, at room temperature, the uretidione cycle. On the other hand, alcohols only open uretidiones cycles at high temperature, generally from 140-150 ° C.

Surprisingly, the present invention has made it possible to determine that the heterocyclic compounds defined above catalyzed the addition reaction of the nucleophilic compounds on the uretidione cycle. Thus, in the case in particular of alcohols, the reaction temperature for adding alcohol to the uretidione cycle is carried out at low temperature, generally around 80 to 100 ° C. instead of the high temperatures described below. - above.

This property can be taken advantage of in a particularly advantageous way for the opening of uretidiones rings originating from the condensation of isocyanate monomers, that is to say monomers in which the NCO function is carried by a carbon atom having steric hindrance, for example the dimers of IPD1, the opening of which is more difficult than for the true dimers formed by cyclodimerization of isocyanates. sparingly congested monomers, such as HDI.

The invention relates to the use of a compound comprising at least one heterocyclic nitrogen group having at least five atoms in the ring including at least two nitrogen atoms, to promote the closing reaction of uretidiones rings or of openings of uretidiones rings and their reaction with an isocyanate compound or a nucleophilic compound containing a mobile hydrogen atom, with the condition that, when the heterocyclic nitrogen group is imidazole, the opening / closing reaction is not not the closing reaction of isocyanate compounds in uretidiones cycles in the presence of a quaternary ammonium salt.

The nitrogen-containing cyclic compound advantageously has 5 links and is advantageously preferably chosen from imidazole, triazole, tetrazole and their derivatives comprising one or more substituents, in particular from 1 to 4 substituents depending on the nature of the cycle.

The substituents can, independently of one another, be chosen from the groups -R, -OR, -SR, -NRR ", -COR, -CONRR ', -NRCOR' and -NRCOOR ', R and R ', identical or different, being chosen from a hydrogen atom, a C ₁ -C ₄ alkyl, C ₃ -C ₈ cycloalkyl, C ₅ -C ₁ o aryl and a heterocycle comprising from 2 to 10 carbon atoms and from 1 to 4 identical or different heteroatoms chosen from O, S and N and the group -NR ", R" being a C ₁ -C ₄ alkyl or C ₃ -C cycloalkyl group ₈ , the alkyl, cycloalkyl, aryl or heteroaryl groups being optionally substituted by one or more groups chosen from OH, COOH, NH ₂ , SH, alkoxy or alkoxycarbonyl.

The heterocyclic nitrogen compound can also be an isocyanate masked by a masking agent meeting the definition of heterocyclic nitrogen compounds given above, in other words a precursor of a heterocyclic nitrogen compound as defined above.

Preference is given to compounds having an imidazole ring which is unsubstituted on the nitrogen atom or having an imidazole ring carrying an N-alkyl or N-aryl substituent having from 1 to 20 carbon atoms, preferably N- methyl.

According to a first embodiment of the invention, the nitrogenous heterocyclic compound is used to promote the closing reaction of a uretidione ring, starting from starting isocyanate monomers, these being in excess relative to the heterocyclic nitrogen compounds.

According to a second embodiment of the invention, the nitrogen heterocyclic compound is used to promote the opening reaction of a uretidione ring, in the presence of an anionic compound in particular derived from a strong base, said base being in particular a catalyst for cyclocondensation of isocyanates.

A large number of cyclocondensation catalysts, in particular of cyclotrimerization, are anionic compounds within the meaning of the present invention.

The anionic compound may consist in particular of an alcoholate, hydroxide, fluoride, acetate, carbonate, hydrogen carbonate, carboxylate or a silazane salt of mineral or organic cations. Among the mineral cations, there may be mentioned alkali metals, alkaline earth metals, transition metals, as well as rare earths.

Among the organic salts, the "oniums" or the "iniums" are preferred. The oniums are chosen from the group of cations formed by the elements of columns Vb and Vlb (as defined in the table of the periodic classification of elements published in the supplement to the Bulletin of the Société Chimique de France in January 1966) with 4 (case of column Vb) or 3 (case of column Vlb) hydrocarbon chains.

Advantageously, the organic salt of the invention is in this case a phosphonium, sulfonium, ammonium, oxonium or diazonium.

The "iniums", group to which the pyridiniums belong, are derived from oniums by the replacement of two substituents by a double substituent

A first type of trimerization catalyst which is particularly suitable for the invention when it is combined with a cyclic nitrogen compound as described above, consists of the rare earth alcoholates. For the definition of rare earth elements, see the table on page B-208 of "Handbook of Chemistry and Physics", Editor Robert C. Weast, 67 ^th Ed.).

These include the following elements: scandium, yttrium, lanthanum as well as the lanthanides (cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, ytterbium and lutetium).

According to the invention, it is possible to add a compound comprising a rare earth alcoholate function or a mixture of compounds. The rare earth alcoholate function can consist of any function obtained by substitution of an alcoholic OH group with a rare earth metal.

Mention may in particular be made of propylates, in particular isopropylates, in particular isopropylate of the following rare earth elements: Y, Sm, Yb and The.

Also suitable are methylates, ethylates and butylates, as well as poly (alkylene glycol) alcoholates, of which preferably at least one of the alcohol functions at the chain end is substituted by an ether, ester function, etc.

A second type of trimerization catalysts consists of alkali, alkaline earth, tin, zinc, or other metals of carboxylic acids such as acetic, propionic, octanoic or benzoic acids.

A third type of catalyst is constituted by alkali, alkaline earth, tin, zinc, alcoholates or phenolates salts.

A fourth type of catalyst is formed by hydroxides, carbonates, hydrogen carbonates or carboxylates of quaternary ammoniums.

A fifth type of catalyst consists of silazane salts or silanolates of mineral or organic cations. These are in particular the compounds of formula (1) or (2):

in which the symbols:

• Ri, R ₂ , R ₃ , R ₄ , R 5 and R _{6, which are} identical or different, represent a monovalent group of saturated or unsaturated, aliphatic, cycloaliphatic, aryl, aralkyl or alkylaryl nature, optionally substituted by halogen atoms, CN groups, or ester, or • in formula (1) one of R _{1 (} R ₂ , R ₃ , R ₄ , R ₅ and R ₆ represents a motif of formula:

A being an alkylene group having from 1 to 30 atoms, advantageously from 2 to 20 carbon atoms, preferably (C ^ with n 'between 1 and 6, advantageously from 2 to 6, and R' ₁ to R ' ₅ identical or different representing a monovalent group of hydrocarbon, aliphatic, cycloaliphatic saturated or unsaturated, aryl, aralkyl or alkylaryl nature, optionally substituted by halogen atoms, CN groups, or ester, and n is an integer between 1 and 50, or

- two of Ri, R ₂ and R ₃ on the one hand and / or R ₄ , R ₅ and R ₆ on the other hand, together constitute a divalent hydrocarbon group, and / or

- At least one group chosen from Ri, R ₂ and R ₃ forms with at least one group from R ₄ , R ₅ and R ₆ a divalent hydrocarbon group.

Advantageously Ri to R ₆ and R'-i to R ' ₅ , identical or different represent:

an alkyl, alkenyl, haloalkyl or haloalkenyl group having from 1 to 20, preferably from 1 to 6 carbon atoms, and optionally comprising chlorine and / or fluorine atoms,

- a cycloalkyl, cycloalkenyl, halogenocycloalkyl or halogenocycloalkenyl group having from 3 to 30, preferably 3 to 10 carbon atoms and containing chlorine and / or fluorine atoms, - an aryl, alkylaryl or haloaryl group having from 6 to 30, preferably 6 to 10 carbon atoms and containing chlorine and / or fluorine atoms,

- a cyanoalkyl group having from 1 to 6 carbon atoms,

- or two groups from Ri, R ₂ and R ₃ or R ₃ , R and R5 together form a divalent radical comprising from 2 to 5 carbon atoms, - or two of Ri, R ₂ and R ₃ on the one hand and / or R ₄ , R ₅ and Rβ on the other hand, together constitute a divalent hydrocarbon group, or

at least one group chosen from Ri, R ₂ and R ₃ forms, with at least one group from R ₄ , R ₅ and Rβ, a divalent hydrocarbon group comprising from 2 to 5 carbon atoms.

Groups Ri to R ₆ and R'i to R'5 which are particularly preferred are chosen from methyl, ethyl, propyl, linear or branched where appropriate, vinyl and phenyl, which may optionally be chlorinated and / or fluorinated.

When the groups Ri to Rβ and R'1 to R ' ₅ are chlorinated and / or fluorinated, the number of halogen atoms varies from 1 to all of the valences available.

Mention may very particularly be made of the salts of the following silazane compounds:

• hexamethyldisilazane,

• diethyl-1, 3-tetramethyl-1, 1, 3,3-disilazane,

Divinyl-1, 3-tetramethyl-1, 1, 3,3-disilazane,

• hexa-ethyldisilazane, and • diphenyl-1, 3-tetramethyl-1,, 3,3-disilazane.

Mention may also be made of the following silanolates:

• trimethylsilanolate,

• triethylsilanolate, • ethyldimethylsilanolate,

• vinyldimethylsilanolate.

The salt of the compound of formulas (1) and (2) can be a mineral, monovalent or multivalent salt, or a mixture of these salts. The preferred mineral salts are those of K, Li, Na and Mg.

The salt of the compound of formulas (1) and (2) can also be an organic, monovalent or multivalent salt or a mixture of these salts. The salts preferred organics are stable "oniums" or "iniums".

In the case of multivalent cations, the salt according to the invention can comprise at least one ligand of formula (1) or (2) above and optionally one or more different ligands. Generally, it is preferred that all of the ligands are compounds of formula (1) or (2).

The number of ligands is a function of the valence of the mineral or organic cation, as well as the number of nitrogen atoms in the compound of formula (1).

When the nucleophilic compound or the solvent is an alcohol, the use of a catalyst of the silazane salt type is avoided.

One can also use as catalyst an anionic compound having a nitrogen group of the type described above. There may be mentioned histidine in its metallic carboxylate form which act both by its imidazole heterocycle to bind to the NCO function and COO function "of _the. Group amino acid to catalyze the cyclotrimerization of isocyanate monomers.

A cyclic nitrogen compound as defined above allows, when added to a polycondensation catalyst, in particular of (cyclo) trimerization of isocyanates, of anionic type in a molar cyclic nitrogen compound / anionic catalyst ratio included between 0.1 and 10, in particular between 0.2 and 5, preferably 0.3 and 2.5, to obtain a reaction product comprising true dimer polyisocyanates and true trimer polyisocyanates in a ratio of true dimer polyisocyanates / trimer polyisocyanates true greater than 0.5, in particular greater than 0.6, preferably greater than 0.75, or even greater than 1.

The invention also relates to a process for the preparation of a polyisocyanate composition comprising trimer polyisocyanates, in particular true trimer polyisocyanates and dimer polyisocyanates, in particular true dimer polyisocyanates, in which the polyisocyanate molar ratio true dimers / true trimer polyisocyanates is greater than 0.5, in particular greater than 0.6, preferably greater than ^" 0.75, or even greater than 1, in which polycondensation of isocyanate monomers is carried out, in the presence of a anionic type cyclotrimerization catalyst and of a nitrogen compound consisting of a five-membered heterocyclic compound, having at least two nitrogen atoms, the molar ratio of cyclic nitrogen compound / anionic catalyst being between 0.1 and 10, advantageously between 0.2 and 5, preferably between 0.3 and 2.5.

In the present invention, the term "true dimers" denotes the compounds obtained by condensation of two molecules of starting isocyanate monomers comprising a single uretidione ring.

The term "true trimers" denotes the compounds obtained by condensation of three starting isocyanate monomer molecules comprising a single isocyanurate ring.

The term “heavy compounds” denotes the compounds obtained by condensation of more than three monomeric isocyanate molecules, in particular “bis-trimers”, “bis-dimers”, tris-trimers and “dimers-trimers ".

Bis-trimers are polyisocyanate molecules comprising two isocyanurate rings, in which the connection between the two isocyanurate rings is ensured by a monomer unit, namely that two monomer units are engaged in each of the isocyanurate rings.

Bis-dimers are polyisocyanate molecules comprising two uretidion cycles, in which the connection between the two uretidion cycles is ensured by a monomer unit, namely that two monomer units are engaged in each of the uretidion cycles.

The tris-trimers are the higher counterparts of the bis-trimers comprising three cycles of isocyanurates. In the case where the monomers are diisocyanates, tris-trimers are obtained by polycondensation of seven monomer chains and comprise three isocyanurate rings, two consecutive isocyanurate rings being linked in pairs by a monomer unit.

The dimer-trimers are higher homologs of the above compounds comprising an isocyanurate function and a mono-uretidione function.

The method according to the invention can be used for the cyclocondensation of any type of isocyanates, or mixture of isocyanates as defined above whether they are aliphatic, cycloaliphatic or aromatic, including the prepolymers having terminal isocyanate groups , in particular those described in US 5,115,071, the content of which is incorporated by reference in the present application. It can thus be used for the trimerization of isocyanates in the presence of various diols, triols and other polyols whose molecular weights are in a wide range, including polyols and aminopolyols comprising polyether and polyester groups, used for the production of polyurethane resins and polyisocyanurates. Diisocyanates are however preferred.

The diisocyanates for which the invention is interesting are those whose nitrogen atom is linked to a sp ³ hybridization carbon, and more particularly the (cyclo) aliphatic diisocyanates. Mention may in particular be made of polymethylene diisocyanates, namely compounds having at least two isocyanate functions comprising a sequence (CH ₂ ) _π where π represents an integer from 2 to 10, advantageously from 4 to 8. When there are several sequences, these can be similar or different. In addition, it is desirable that at least one, preferably all of these sequences, are free to rotate and therefore exocyclic.

The preferred examples of polymethylene diisocyanates are TMDI (tetramethylene diisocyanate), HDI [hexamethylene diisocyanate,

OCN- (CH ₂ ) ₆ -NCO] and MPDI (2-methylpentane-diisocyanate) and 3,3,5- or 3,5,5-trimethylhexamethylene-diisocyanates. In the case of a mixture obtained from several (in general, two) types of monomers, it is preferable that the one or those of the monomers which meets the above conditions and in particular the condition on the presence of polymethylene sequences (CH ₂ ) _π , represents at least a third, advantageously a half, preferably two thirds of the masked isocyanate functions.

Isocyanate monomers which are particularly suitable are cycloaliphatic monomers, that is to say those in which the backbone comprises an aliphatic cycle.

These monomers are advantageously such that at least one, advantageously the two isocyanate functions, is distant from the nearest ring, at most one carbon and preferably is connected directly to it. In addition, these cycloaliphatic monomers advantageously have at least one, preferably two, isocyanate functions chosen from secondary, tertiary or neopentyl isocyanate functions.

The best results are obtained when the conformational freedom of the cycloaliphatic monomer is low. As monomers capable of giving good results, there may be mentioned by way of example, the following monomers:

• the compounds corresponding to the hydrogenation of the aromatic nucleus (s) carrying isocyanate functions of monomer of aromatic isocyanates and in particular of TDI (toluene diisocyanate) and of diisocyanato-biphenyls.

The following compounds are particularly preferred:

• the various BICs [bis (isocyanato-methylcyclohexane)]; and above all • norbomanediisocyanate often called by its acronym NBDI;

• isophoronediisocyanate or IPDI or 3-isocyanatomethyl-3,5,5-trimethylcyclohexylisocyanate; • H12 DI (1, 1-methylene-bis-4,4-isocyanatocyclohexane).

Arylenedialcylene diisocyanates such as OCN-CH ₂ -0-CH ₂ -NCO are also suitable for the process of the invention.

When the catalyst is a rare earth alcoholate, the cyclic nitrogen compound / rare earth alcoholate molar ratio advantageously varies between 0.1 and 10, preferably between 0.2 and 5.

The reaction temperature is the temperature usually used for catalytic trimerization and depends on the type of catalyst.

When the catalyst is a rare earth alcoholate, it is generally between 20 ° C, advantageously 50 ° C and 200 ° C, advantageously 150 ° C.

When the catalyst is a silazane salt, it is generally between 20 ° C., advantageously 40 ° C. and 200 ° C., advantageously 150 ° C.

It is generally preferred to add the catalyst and the nitrogenous cyclic compound to the reaction medium simultaneously in a solvent solution.

Mention may be made, as solvents, of substituted aromatic hydrocarbons such as SOLVESSO®, toluene, xylene or esters (n-butyl acetate) or ethers (propylene glycol methyl ether).

When the catalyst is a rare earth alcoholate, it is generally preferred to add it at the same time as the nitrogenous cyclic compound, in particular imidazole or N-methylimidazole in solution in an ether alcohol, for example methoxyethanol.

>

The reaction is stopped at the rate of transformation of the desired NCO functions. This is generally between 5 and 100%, advantageously between 10 and 80%.

The invention also relates to the use of a nitrogen heterocyclic compound as defined above to promote the opening of a uretidione cycle and its reaction with a nucleophilic compound.

Advantageously, the nucleophilic compound is a compound having at least one function having a mobile hydrogen atom, reactive with the isocyanate function, such as phenol, amino alcohols, thiols, acids, amides, carbamates, ureas or releasing compounds. a mobile hydrogen function during the reaction, in other words the precursors of the compounds listed above.

The nucleophilic compound is advantageously chosen from amines, alcohols and thiols, preferably primary or secondary alcohols. It is also possible to use polyols, polyesters, polyethers, polyacrylics, polyurethanes, etc.

The invention is also particularly advantageous for compositions for polyurethane powder paints. The polyol compounds are in this case powder compounds. For the compositions for powder polyurethane paints, dimers of IPDI or HDI or their derivatives are used in particular, or compositions for powder paints comprising uretidiones functions resulting from the condensation of aliphatic or cycloaliphatic isocyanates.

The advantage of using a heterocyclic compound within the meaning of the invention makes it possible to lower the thermal threshold of the crosslinking which is generally between 80 and 150 ° C in the presence of the heterocyclic compound, whereas in absence of heterocyclic compound, the crosslinking temperatures are above 180 ° C., generally between 200 and 220 ° C. The compositions for powder paints are generally stable on storage at a temperature above 0 ° C, preferably above 20 ° C. We will therefore choose polyols whose glass transition temperature (Tg) is in line with the crosslinking temperature. The Tg is a function of the basic units of the polymer and therefore of the final structure of the polymer. It is generally between -20 ° C and 150 ° C, preferably between 0 and 100 ° C and advantageously between 20 and 80 ° C.

In the case of powdered polyurethane compositions, the heterocyclic compound can be incorporated at different stages of the manufacture of the powder paint, either at the stage of synthesis of the dimeric compound, either in the polyol, or at the time of manufacture of powder paint in combination with the various constituents of the paint, for example at the time of extrusion.

This will optimize the operating conditions for the preparation of this powder in such a way that there is not too great a reaction between the dimer and the compounds with mobile hydrogen.

To do this, we will especially optimize the extrusion conditions, namely the conditions for extruding the polyurethane powder paint, the extrusion temperature generally being around 100 ° C. with an extrusion time, less than 30 minutes.

The nucleophilic function / uretidione ratio is between 10 and 0.05, preferably between 5 and 0.1, advantageously between 3 and 0.25, this ratio being obtainable at any stage of the reaction. crosslinking. In the case where the ratio is small, dimer functions are preserved and can react subsequently with other subsequent nucleophilic functions. In the case where the ratio is higher, the nucleophilic functions are preserved and can react with other functions such as free isocyanate, masked isocyanate, anhydride or oxirane functions, etc.

In the case of powder paints, it is preferred that the heterocyclic compounds be solid, that is to say that they have a melting temperature above 25 ° C, preferably above 50 ° C. Preference is therefore given to preferably substituted heterocyclic compounds having an aliphatic chain the number of carbon atoms of which is between 1 and 10. One can also use heterocyclic compounds according to the invention in solution with polyols and uretidiones polyisocyanate compounds. In this case, the same solvent will be chosen as that used for the final formulations, preferably an ester, ether, substituted aromatic hydrocarbon, or optionally water for compositions of the water paint type.

It is not necessary for the nucleophilic compound participating in the opening of the uretidione cycle by the heterocyclic nitrogen compound to be an ionic compound. However, the presence of such a compound is not harmful to the opening reaction of the cycle and therefore the application of the final coating.

The following examples illustrate the invention. Unless otherwise indicated, the percentages are expressed by weight. The trimerization catalyst / imidazole ratios are molar ratios.

Example 1:

Polycondensation of IPDI in the presence of tris - (- 2-methoxy-ethylene glycolate) of lanthanum and imidazole

Preparation of the catalyst solution: First, the catalytic solution is prepared:

Is introduced into 100 mL of a 10% by weight solution of lanthanum tris- (2-methoxy-ethylene glycolate) in 2-methoxyethanol (density 1.01), 1.87 g (0.0275 moles) of imidazole. The lanthanum imidazole / tris- (2-methoxy-ethylene glycolate) molar ratio is equal to 1.

Reaction

20 g of isophorone diisocyanate (IPDI), ie 0.09 moles or 0.18 moles of NCO, are added at ambient temperature, under a nitrogen stream, to a 50 ml three-necked reactor. The catalytic solution (1 g, or 2.75 10 ^"4 moles of imidazole and 2.75 10 ^"4 moles of lanthanum tris- (2-methoxyethylene glycolate)) is added to the reaction medium. The amounts of lanthanum alcoholate and imidazole are respectively 100 mg and 19 mg, ie a ratio metal / NCO of 1.5 10 ^"3 . The temperature of the reaction medium is brought to 60 ° C. and the reaction left under stirring for 5 hours then is blocked by adding paratoluene sulfonic acid (200 mg). The IPDI transformation rate is 54.7%.

The analysis of the reaction medium before elimination of the monomeric IPDI is presented in the table below:

The presence of allophanate and dimer functions is noted under massive I of the bis trimers and heavy.

Example 2:

Polycondensation of IPDI in the presence of yttrium tris (2-methoxy-ethylene glycolate) and imidazole

The procedure is as in Example 1, replacing the lanthanum alcoholate with that of yttrium.

20 g of isophorone diisocyanate (IPDl), ie 0.09 moles, or 0.18 moles of NCO, are added at ambient temperature, under a nitrogen stream, to a 50 ml three-necked reactor. The catalytic solution is added to the reaction medium. The amounts of yttrium alcoholate and imidazole are respectively equal to 150 mg and 32 mg, ie a metal / NCO ratio of 2.6 × 10 ⁻³ . The temperature of the reaction medium is brought to 60 ° C. and the reaction left with stirring for 5 hours then is blocked by the addition of para-toluene sulfonic acid (200 mg) The IPDI transformation rate is 41%.

The presence of allophanate and dimer functions is noted under the masses of bis trimers and heavy.

Example 3:

Polycondensation of IPDI in the presence of tris (isopropylate) of yttrium and imidazole

20 g of isophorone diisocyanate (IPDl), ie 0.09 moles, or 0.18 moles of NCO, are added at ambient temperature, under a nitrogen stream, to a 50 ml three-necked reactor. 200 mg of yttrium tris (isopropylate) (7.5 × 10 ⁻⁴ moles) and 51 mg of imidazole are added, ie a metal / NCO ratio of 4 × 10 ⁻³ . The temperature of the reaction medium is brought to 60 ° C. and the reaction left under stirring for 5 hours then is blocked by adding para-toluene sulfonic acid. (150 mg). The NCO titer is 0.552 and the transformation rate of the IPDI is 77.3%.

Example 4:

Polycondensation of IPDI in the presence of neodymium tris (isopropylate)

The procedure is as in Example 3, replacing the alcoholate of Yttrium with that of neodymium.

20 g of isophorone diisocyanate (IPDl), ie 0.09 moles, or 0.18 moles of NCO, are added at ambient temperature, under a nitrogen stream, to a 50 ml three-necked reactor. 1% by weight relative to the reaction medium is added. to the IPDI of neoόyme tris (isopropylate), ie 200 mg (ie 6.2 × 10 ⁻⁴ mol or a metal / NCO ratio of 3.5 × 10 ⁻³ ) and 42 mg of imidazole. The temperature of the reaction medium is brought to 60 ° C. and the reaction left under stirring for 5 hours. The reaction is stopped by adding 200 mg of para-toluene, sulfonic acid. Analysis of the reaction medium before ^distillation of the IPDI monomer by chromatography gives the following composition:

We note the presence of allophanate functions under the mass of bis trimers and heavy.

Example 5:

20 g of isophorone diisocyanate (IPDl), ie 0.09 moles, or 0.18 moles of NCO, are added at ambient temperature, under a nitrogen stream, to a 50 ml three-necked reactor. 200 mg of yttrium tris (isopropylate) (7.5 × 10 ⁻⁴ moles) and 51 mg of imidazole are added, ie a metal / NCO ratio of 4 × 10 ⁻³ . The temperature of the reaction medium is brought to 60 ° C. and the reaction left under stirring for 5 hours then is blocked by addition of para-toluene sulfonic acid (150 mg). The NCO titer is 0.552 and the transformation rate of the IPDI is 77.3%. The analysis of the reaction medium before elimination of the monomeric IPDI is presented in the table below:

Example 6:

Polycondensation of IPDI in the presence of tris (isopropylate) of yttrium and N-methylimidazole

20 g of isophorone diisocyanate (IPDl), ie 0.09 moles, or 0.18 moles of NCO, are added at ambient temperature, under a nitrogen stream, to a 50 ml three-neck reactor. 200 mg of yttrium tris (isopropylate) (7.5 × 10 ⁻⁴ moles) and 51 mg of N-methylimidazole are added, ie a metal / NCO ratio of 4 × 10 ⁻³ . The temperature of the reaction medium is brought to 60 ° C. and the reaction left under stirring for 5 hours then is blocked by addition of para-toluene sulfonic acid (150 mg). There is the presence of dimer and trimer bands.

COMPARATIVE EXAMPLE 1

The procedure is as for Example 1, except that a methoxybutanol solution containing 5% by weight of lanthanum tris- (2-methoxy-ethylene glycolate) is added.

COMPARATIVE EXAMPLE 2

The procedure is as for Example 2, except that a methoxyethylethylate solution containing 5% yttrium tris- (2-methoxy-ethylene glycolate) is added.

COMPARATIVE EXAMPLE 3

The procedure is as for Example 3, except that a solution containing 200 mg of yttrium tris (isopropylate) is added.

COMPARATIVE EXAMPLE 4 (CM1 129902)

The procedure is as for Example 4, except that a solution containing 200 mg of neodymium tris (isopropylate) is added. The results are reported in the table below: BOARD

Claims

1. Use of a compound comprising at least one heterocyclic nitrogen group having at least five links including at least two nitrogen atoms, to promote the reaction of closing of uretidiones cycles or opening of uretidiones cycles and their reaction with a compound nucleophile comprising a mobile hydrogen atom with the condition that, when the nitrogenous heterocyclic group is imidazole, the opening / closing reaction is not the closing reaction of isocyanate compounds in uretidionic rings in the presence of a salt of quaternary ammonium.

2. Use according to claim 1, characterized in that the nitrogen heterocyclic compound is put. implemented to promote the cyclodimerization of isocyanate compounds in the presence of an anionic compound, the isocyanate compounds being in excess relative to the heterocyclic nitrogen compounds, provided that the cyclodimerization is not carried out in the presence of quaternary ammonium, when the nitrogen heterocyclic compound is imidazole.

3. Use according to claim 1, characterized in that the heterocyclic nitrogen compound is used to promote the opening reaction of a uretidiones cycle in the presence of a nucleophilic compound.

4. Use according to claim 3, characterized in that the nucleophilic compound is the reaction product of a base on an isocyanate group.

5. Use according to claim 3, characterized in that the nucleophilic compound is a compound having a function having a mobile hydrogen atom, reactive with the isocyanate function.

6. Use according to claim 4, characterized in that said nucleophilic compound is chosen from amines, alcohols and thiols.

7 Use according to claim 1, - characterized in that said cyclic nitrogen compound is chosen from imidazole, triazole, tetrazole and their derivatives comprising one or more substituents.

8. Use according to claim 7, characterized in that the five-membered nitrogen heterocyclic compound is imidazole or one of its derivatives comprising one or more substituents.

9. Process for the preparation of a polyisocyanate composition comprising trimer polyisocyanates, in particular true trimer polyisocyanates and dimer polyisocyanates, in particular true dimer polyisocyanates, in which the molar ratio of true dimer polyisocyanates / true trimer polyisocyanates is greater than 0.5, in particular greater than 0.6, preferably greater than 0.75, in which polycondensation of isocyanate monomers is carried out, in the presence of a cyclotimerization catalyst of the anionic type and of a nitrogen compound consisting of a five-membered heterocyclic, having at least two nitrogen atoms, in a cyclic nitrogen compound / anionic catalyst molar ratio of between 0.1 and 10, advantageously between 0.2 and 8.

10. Use according to claim 9, characterized in that the (cyclo) trimerization catalyst is chosen from the group consisting of alcoholates, hydroxides, fluorides, acetates, carbonates, hydrogen carbonates, carboxylates, and silazane salts of alkali metals, alkali - earthy, transitional, rare earth and onium or inium cations.

11. Method according to claim 10, characterized in that the (cyclo) trimerization catalyst is a rare earth alcoholate.

12. Use according to claim 8, characterized in that the (cyclo) trimerization catalyst is a hydroxide, hydrogencarbonate or quaternary ammonium carboxylate.

13. Use according to claim 8, characterized in that the (cyclo) trimerization catalyst is a silazane salt of alkali metals, alkaline earth metals, transition, rare earths and cations of onium or inium type.

14. Compound of formula (II):

R being the residue of an isocyanate compound after removal of a w isocyanate function and HET being a nitrogen heterocyclic compound as defined in claim 1, linked to the NCO group via a nitrogen atom of the heterocyclic.