FR2767328A1 - Method for making polyisocyanate composition - Google Patents

Abstract

Preparation of a (poly)isocyanate composition with reduced viscosity comprising dimeric isocyanate(s) with uretidine-dione unit from initial monomeric isocyanates. The initial reaction medium is heated, in the absence of a dimerization catalyst, to 50 deg C - 200 deg C for <= 24 hours. The preparation of a composition of polyfunctional isocyanates with reduced viscosity comprising isocyanate dimer(s), and / or trimer(s) with a uretidine-dione unit and other composition(s) with functional group derived from isocyanate group, from isocyanate monomers and another compound containing at least one group which can react with isocyanate comprises: (i) heating reaction mixture, in absence of dimerization catalyst, to at least 80 deg C, preferably at least 130 deg C, advantageously at least 170 deg C for advantageously less than 5 hours; (ii) reacting product from step (i) with compound containing at least one function different to isocyanate function, optionally in presence of a catalyst; (iii) eliminating isocyanate monomers from reaction product of step (ii); and (iv) isolating polyfunctional isocyanate composition.

Description

 The present invention relates to the preparation of polyfunctional polyisocyanates having reduced viscosity from aliphatic isocyanates.

 It is known to employ polyfunctional polyisocyanates for the preparation of polyurethanes, by polymerization and / or by polyaddition with polyhydroxy compounds with active hydrogen.

Among the nonaromatic polyisocyanates used for this purpose, mention may be made in particular of those obtained by polycondensation on themselves in the presence of a catalyst, of monomeric diisocyanates such as hexamethylene diisocyanate (HDI), tetramethylene diisocyanate (TMDI),
Isophorone diisocyanate (IPDI), norbornane diisocyanate (NBDI) and bis-cyanoxylmethane (H12MDI).

 It is generally preferred that the polyisocyanates comprise predominantly isocyanurate ring trimer obtained by trimerization of said starting isocyanates.

 During the polymerization in the presence of a catalyst of the starting diisocyanates, the reaction is generally stopped when a conversion rate of 20 to 40% is obtained, in order to prevent the amount of oligomers having more than three units. recurring derivatives of starting diisocyanates formed in the reaction medium is too important.

 The polycondensation products obtained therefore generally contain a majority amount of monomers and a minor amount of oligomers; the oligomeric fraction consisting mainly of triers and smaller amounts of tetramers, pentamers and heavy compounds, as well as digests in small amount.

 At the end of the reaction, the reaction mixture is distilled to remove the monomers which are both volatile and toxic organic compounds.

 When the starting isocyanate is a polymethylene diisocyanate, however, the oligomer mixture obtained at the end of the distillation step has the disadvantage of a relatively high viscosity, which is hardly compatible with the subsequent use of these compounds as hardeners. for polyurethane coatings.

 Thus, the oligomeric mixture obtained by polycondensation of HDI, after distillation of the monomer fraction, has a viscosity of about 1.2 to 2.4 Pa.s (1200 to 2400 cP) for a conversion ratio of 20. 40% of the starting monomers.

 One of the recommended solutions for lowering the viscosity of the oligomer mixture obtained is to add a quantity of low viscosity dimers (at most of the order of 800 mPa.s) until the desired viscosity is obtained. , generally of the order of 0.2 to 0.8 Pa.s.

 In general, in addition to decreasing the viscosity of the oligomeric mixture, the addition of dimers is also recommended in a number of cases.

 For example, the isophorone diisocyanate trimerization mixture of dimers of isophorone diisocyanate is added for their high temperature blocking function.

 The exogenous addition of dimers to the mixture obtained by trimerization of the starting diisocyanate has in all cases two disadvantages, the first being the yellow coloration of the dimeric compounds due to the relatively specific phosphine-based dimerization catalyst, the second being the need to implement two processes in two reactors, which increases the overall cost of the process.

 Other catalysts have been proposed to overcome the yellow coloration and the toxicity of phosphines, especially catalysts based on dimethylaminopyridine extremely toxic.

 Although the toxicity of dimethylaminopyridine can be reduced to a certain extent, by fixing on a solid support, the recommended solutions continue to require the implementation of two processes requiring two different reactors.

The present invention provides a process for preparing in a single reactor, a mixture of oligomers obtained by polymerization of aliphatic isocyanates, especially diisocyanates, having, after removal of the remaining monomer fraction, a reduced viscosity of the order of 0 , 2 to 0.8 Pa.s
The inventors of the present invention have developed a method for this purpose, which is achieved when a polyhydroxy compound of particular spatial structure and / or derivatives thereof, to substantially increase the proportion of dimers of the starting isocyanate from the reaction medium obtained at the end of the trimerization process and, after removal of the remaining monomers, to obtain a composition comprising essentially isocyanurate ring trimer obtained by trimerization of the starting isocyanates and a minor amount of dies formed from the starting isocyanates, and having a reduced viscosity in the desired range.

The catalyst used corresponds to the general formula I
R [-C- (CH 2 OH) 3] n (I) in which:
R is a mono- or n-valent hydrocarbon group having 1 to 30 carbon atoms whose hydrocarbon chain can be interrupted by one or more chalcogen atoms, advantageously light (O, S), and can carry 1 to 3 OH groups, R being advantageously a group chosen from a C 1 -C 4 alkyl group which may be interrupted by an oxygen or sulfur atom and / or optionally substituted with 1 to 3 OH groups, and a residue resulting from silylation reactions of pentaerythritol,
R being preferably a C 1 -C 4 alkyl group, optionally substituted with an OH group, in particular an ethyl or hydroxymethyl group, n is an integer ranging from 1 to 3, and / or products derived from this derivative by reaction with a compound carrying an aliphatic isocyanate function.

 By hydrocarbon group is meant a group comprising at least one carbon atom and a stable hydrogen atom, especially polymethylene groups such as hexamethylene and tetramethylene, cycloaliphatic, especially those derived from IPDI, NBDI and H12MDI or aliphatic groups substituted or interrupted by an arylene group such as -CH2-C6H4-CH2-.

 The term "aliphatic isocyanate" means all compounds whose open bonds (those linking the carbon atoms to an isocyanate or derivative function, in particular carbamate, biuret or allophanate) are carried by a carbon of sp3 configuration, including arylaliphatic or acyclic isocyanates. and / or may comprise one or more heterocycles. They preferably comprise less than 30 carbon atoms.

These products can in particular satisfy formulas II and / or III as follows:

- dans lesquelles un ou plusieurs de X1 X2 et X3 représente des groupes R'-(N=C=O)p dans lesquels R' identiques ou différents sont des groupes aliphatiques p valents, c'est-à-dire dont les liaisons ouvertes (celles liant les atomes de carbone à une fonction isocyanate ou dérivée, notamment carbamate, biuret ou allophanate) sont portées par un carbone de configuration sp3, y compris des groupes arylaliphatiques ou acycliques et/ou pouvant comporter des hétérocycles et/ou en particulier lorsque p = 0, des groupes carbamate, biuret et/ou isocyanurate, R' comportant de préférence de 3 à 30 atomes de carbone, et p est un nombre entier, variant suivant le degré de polymérisation du mélange réactionnel, en général compris entre 0 et 5, de préférence égal à 1, auquel cas R' est un groupe divalent tel que défini ci-dessus, les autres représentant, le cas échéant, un groupe de formule

in which one or more of X1 X2 and X3 represents R '- (N = C = O) p groups in which R' are identical or different and are aliphatic groups p valent, that is, whose bonds are open (those linking the carbon atoms to an isocyanate or derivative function, in particular carbamate, biuret or allophanate) are borne by a carbon of configuration sp3, including arylaliphatic or acyclic groups and / or which may comprise heterocycles and / or in particular when p = 0, carbamate, biuret and / or isocyanurate groups, R 'preferably having from 3 to 30 carbon atoms, and p is an integer, varying according to the degree of polymerization of the reaction mixture, generally between 0 and 5, preferably 1, in which case R 'is a divalent group as defined above, the others representing, where appropriate, a group of formula

R 'and p being as defined above,
R1 being R, with the OH groups optionally substituted by a group
CONX1H, X1 being as defined above. n is an integer from 1 to 3; and
- at least one of NX'1X "1, NX'2X" 2 and Nu ') ("3 represents the group

R 'being as defined above, the others representing a NX1H or NX1-silyl group with X1 as defined above, the silyl group optionally resulting from the destruction of the silazane type catalyst in particular as defined in EP 89297 and
R2 being R, with OH groups substituted where appropriate by a group

R 'being as defined above, and n is an integer from 1 to 3.

The nature of R 'is indifferent, it does not intervene in the polymerization reaction. For practical reasons, however, R groups having from 3 to 30 carbon atoms are preferred.

Preferably, R 'is a group as defined above divalent with p equal to 1.

Mention may in particular be made of the divalent hexamethylene, tetramethylene, norbornylene, biscyclohexylenemethane groups, and the divalent radical derived from IPDI.

The catalyst according to the invention allows the preparation, with a high selectivity, of isocyanates digestible from isocyanate monomers, especially diisocyanates, the degree of conversion of the isocyanate functions being advantageously at least 5%, preferably at least 10%.

dans laquelle R' et p sont tels que définis précédemment, à partir d'isocyanates de départ de formule VIl R'-(N=C=O)p+, (Vll)
dans laquelle R' et p sont tels que définis ci-dessus, avec un taux de transformation de 5 % au moins, de préférence au moins 10 %, des fonctions isocyanates de départ en uréthinediones de formule générale VI.The subject of the invention is therefore the use of a compound of general formula I and / or II, and / or III as defined above for the preparation of digestive isocyanates of general formula VI:

in which R 'and p are as defined above, starting from isocyanates of formula VIl R' - (N = C = O) p +, (Vll)
in which R 'and p are as defined above, with a degree of conversion of at least 5%, preferably at least 10%, of the starting isocyanate functional groups of urethinediones of general formula VI.

 Advantageously, the invention uses a compound of general formula I and / or II and / or III for the preparation of compounds of general formula VI in which R 'is a group as defined previously divalent and p is equal to 1.

 The compounds of the general formula II and III can be and are generally obtained by reacting the compound of the general formula I with an isocyanate of the general formula VII.

Indeed, the inventors of the present invention have found that when a compound of general formula I as defined above was reacted with a compound of general formula VIII as defined above, it was generally formed a a certain proportion of compounds of general formula II and / or III as defined above, which in turn participate in the catalysis of the dimerization reaction of the starting diisocyanates
The compounds of general formula I and / or II, and / or III are used in an effective amount and preferably with an isocyanate functions / hydroxyl functions ratio greater than 4, preferably greater than 20.

 Advantageously, the polyamino compound of general formula I used is pentaerythritol or trimethylolpropane, and as the compound of general formula II and / or III, the corresponding carbamates and / or allophanates obtained by reaction of pentaerythritol or dimethylolpropane with a diisocyanate of general formula VII .

 No. 5,115,071 discloses the use of polyhydroxy compounds, especially trimethylolpropane for the preparation of prepolymers by polycondensation with aliphatic diisocyanates at a temperature of between 0 and 1200 ° C. However, this document does not mention the production of dimers. In addition, it indicates in particular that those skilled in the art will take the necessary precautions to ensure that the products obtained are free of parasitic products such as allophanates, oligomers and other products.

 On the contrary, the inventors of the present invention have found that, under the conditions of use of a polyhydroxy compound of general formula I as defined above, according to the present invention, for the production of dimers formed by condensation of two isocyanates initially, a certain amount of allophanate compounds was formed.

 The conditions of use of the polyhydroxyl compounds of general formula I as well as the carbamates of general formula II and the allophanates of general formula III of the invention comprise a temperature greater than 1100 C and preferably greater than 130 ° C., and at most 200 ° C., preferably at most 1800 ° C., and a reaction time of between 1 hour and 1 day, the reaction temperature being advantageously chosen so as to be greater than the dissolution temperature, if necessary; polyol of the general formula I or, where appropriate, compounds of the general formula II and III, the dissolution temperature being the temperature at which at least 1 g / l of reagent per isocyanate composition is dissolved.

 The compounds of general formula I, II or III may be added as such to the reaction medium comprising monomeric, similar or different isocyanates, preferably in the absence of solvents, or may be fixed (including adsorption) to a support, in particular a resin.

 In the case where a compound of formula I is added, the compounds of general formula II and / or III may form spontaneously after a sufficient reaction time.

 It is also possible to add to the reaction medium a compound of general formula II and / or a compound of general formula III.

The subject of the invention is also the use of a compound as defined above for the preparation of compounds with a function (s) of urethinedione (s) from monomers, in particular diisocyanates, as defined above, or from their derivatives obtained by polymerization or polycondensation in a reaction medium comprising, in addition to said compounds or derivatives, isocyanurate ring trimers of general formula Vlil:

R 'and p being as defined above, p being preferably 1.

 The synthesis of the trimer can be made in any manner known to those skilled in the art, but a particular mention must be made of the processes that use the alcohols, especially as co-catalysts (see in particular the techniques referred to in the application FR 2,613 363 and in the documents cited therein, in particular US Pat. No. 4,324,879). In this case, the compounds can then be used simultaneously with the trimerization catalyst. This way is however not very happy insofar as there is a risk that the dimer is destroyed by said catalyst. It is therefore preferred to add the catalyst according to the invention after destruction of said catalyst. In the case of the process described in particular in patent application EP 89 297, the compounds of formula I and / or II are advantageously used to destroy the catalyst. Thus, in this case, it is possible to use the alcohols and / or the carbamates which are derived therefrom as a catalyst destruction agent which then silylates part of the alcohol functional groups of the catalyst according to the invention and / or the carbamates which are derived therefrom.

 Thus, if it is desired to prepare isocyanate-functional trimers, in particular from monomeric diisocyanates, the trimerization reaction is stopped when the desired level of conversion of the monomeric diisocyanates, essentially of trimers, is obtained and the reaction medium is added to the reaction medium. as defined previously the compound (s) of general formula I and / or II and / or III of the invention.

 The inventors furthermore determined that when the trimerization catalyst used was a disilazane, for example hexamethyldisilazane, it was destroyed by the simple addition of a polyhydroxyl compound of the general formula I of the invention, in particular when this is pentaerythritol.

 Thus, after addition of the compounds of formula I and / or II and / or III of the invention, the reaction is carried out until the desired viscosity corresponding to a given level of dimer is obtained, or more generally until the desired desired dimer level.

 The reaction according to the present invention has a unique characteristic compared to other dimerization reactions, which is to present a very low production of trimers.

 Thus, for the preparation of HDI dimers, the reaction is conveniently carried out for a period of about 5 hours at a temperature of about 140 ° C, so that the dimer / trimer ratio is about 1/6 at 1/3.

 At the end of the reaction, there are found in the reaction medium, dimeric polyisocyanates of general formula VI, optionally trimers of general formula VIII, in particular when the dimerization is carried out from a reaction medium comprising trimeric polyisocyanates of general formula VII I, carbamates, especially carbamates of general formula II formed between the hydroxyl compounds of general formula I of the invention and the monomeric diisocyanates of general formula II and / or allophanates of general formula III, especially allophanates formed between said polyhydroxy compound of general formula I and the monomeric diisocyanates of general formula II.

The composition according to the invention preferably comprises compounds of formula II in which all the groups X1, X2 and X3 represent -R'-N = C = O with R 'identical or different, and / or compounds in which only one of X1, X2 and X3 represents the group of general formula
IV, the others being -R'-N = C = O, with R 'identical or different.

 Preferably, in the compounds of formula III, only one of the groups NX'1X "1, NX'2X" 2 and Nu'3) ("3 represents the group of formula V, the others representing the group NX1H, X1 being such as defined above.

 The subject of the invention is also a composition comprising at least one compound of general formula VI as defined above and at least one compound of general formula II as defined above and / or at least one compound of general formula III as defined above.

 The composition according to the invention also advantageously comprises a compound of formula VIII as defined above.

 These compositions are useful as hardeners for the preparation of polyurethanes, especially as coating agents, such as paints and varnishes.

They may include in addition to the components described below:
optionally one or more compound (s), mineral (s) or organic (s) having a function of pigmentation, charge, or a function to facilitate the application of the coating, such as for example a spreading agent , a matting agent, a "healing" agent, etc.

optionally, one or more catalysts,
- optionally one or more surfactants for improving the implementation of the formulation such as, for example, an agent having a surfactant property, an anti-foam agent, a solvent, an aqueous solution whose pH is optionally adjusted .

 The compositions and formulations can be solid, liquid, or be in the form of solutions, emulsions, or suspensions.

 The following examples are representative of the invention.

EXAMPLE 1
In a thermostated reactor of 61, equipped with a half-moon type agitator, a condenser and addition ampoules, 4942.3 g of HDI and 100.1 g of pentaerythritol are introduced successively at room temperature. an inert atmosphere of nitrogen.

 The reaction medium is stirred and heated progressively to a temperature of 140 ° C. After 1H 50, the infrared analysis on a sample of the reaction mass indicates the presence of allophanate, carbamate and dimeric bands After 2H 35 at 140 ° C. the medium becomes translucent with the presence of insolubles. After 4 hours of reaction, the IR analysis on a reaction mass sample indicates the presence of allophanate bands, carbamates, and a strong band due to the dimer. After a reaction time of approximately 5 h at 140 ° C., the heating is stopped and the reaction medium is allowed to cool, the insolubles are filtered (the mass recovered is 3.7 g) and the solution thus filtered is distilled on a vacuum scraper film of 0.degree. , 5 to 1 mbar, at a temperature of 1600C and with a feed rate of between 1200 and 2300 ml per hour The product recovered (1340 ml) is a second time distilled under the same conditions except for the feed rate which is reduced (flow rate between 500 and 1200 ml per hour) The mass of product recovered is 819 g The title in NCO functions is 0.499 mol per 100 g of the mixture, the percentage of residual HDI monomer is 2% This mixture then undergoes a third distillation, thus recovering 742.7 g of polyisocyanate composition whose NCO function is 0.482 mol per 100 g of the mixture, ie a percentage by weight of 20.24%, the percentage of HDI monomer resid This is 0.16% and the viscosity of the final crude mixture is 11544 mPas at 25 ° C.

The composition of the mixture is determined after separation chromatography and infrared structural analysis on the eluted fractions.

<Tb>

Product <SEP> identified <SEP> in <SEP><SEP> composition <SEP> Quantity <SEP> measured <SEP> in <SEP>%
<tb><SEP> HDI <SEP> residual <SEP> 0.11 <SEP>
<tb><SEP> Digest <SEP> true <SEP> 20.2
<tb><SEP> Bis <SEP> dimer <SEP> true * <SEP> 0.65
<tb><SEP> Carbamate <SEP> true <SEP> dEDI ** <SEP> 33.2
<tb><SEP> Pentamers * <SEP> * <SEP> * <SEP> 18.3
<tb><SEP> Heavy **** <SEP> 27,54
<tb><SEP> biuret <SEP> lower <SEP> to <SEP> 0.5 <SEP>
<tb><SEP><SEP>SEP> detectable <SEP><SEP> functions <SEP>
<tb> * The true bis dimer is calculated on the specific bis-dimer trace.

Le Le massif de pentaméres correspond à un mélange de carbamate de dimère pentaérythritol et d'HDI (1), de masse moléculaire 976 et de fonctionnalité 4 et d'allophanate d'HDI et de pentaérythritol (2) de masse moléculaire de 976 et de fonctionnalité 5.

molécule 1

The true carbamate of HDI has a molecular weight of 808 and is represented by the following structure

The pentamer group corresponds to a mixture of pentaerythritol dimer carbamate and HDI (1), of molecular mass 976 and of functionality 4 and allophanate of HDI and pentaerythritol (2) with a molecular mass of 976 and functionality 5.

molecule 1

molecule 2
The heavy ones have carbamate, allophanate and dimer bands.

EXAMPLE 2
The same procedure as Example 1 is repeated.

 148.2 g of HDI and 3.042 g of pentaerythritol are worked with a temperature of the reaction medium of 1200 ° C.

 The infrared analysis carried out after 1 H 50 of reaction, indicates the presence of carbamate, allophanate and trimeric functions. The dimer function band is larger than the band corresponding to the carbamate / allophanate functions, indicating a large amount of dimer.

EXAMPLE 3
The same procedure as Example 1 is repeated.

 148.5 g of HDI and 3.068 g of pentaerythritol are worked with a temperature of the reaction medium of 1600 ° C.

 The infrared analysis carried out after 1 H 28 of reaction, indicates the presence of carbamate, allophanate and dimeric functions. This time, the bands corresponding to the carbamate / allophanate functions are of higher intensity than the bands of the dimer functions, which indicates that the amount of dimer formed is lower at high temperature.

EXAMPLE 4
The same procedure as Example 1 is repeated.

 This time it is used with an HDI / OH = 5 ratio. 148.6 g of HDI and 6.016 g of pentaerythritol are charged with a reaction medium temperature of between 137 and 143 ° C.

 Infrared analysis carried out after 2 hours of reaction, indicates the presence of carbamate, allophanate and dimeric functions. This time, the bands corresponding to the carbamate / allophanate functions are of higher intensity than the bands of the digest functions, which indicates that the amount of dimer formed is lower.

EXAMPLE 5
The same procedure as Example 1 is repeated.

 This time we work with a catalytic amount of pentaerythritol. 149.53 g of HDI and 1.523 g of pentaerythritol are charged. The reaction is carried out at a temperature of the reaction medium of approximately 15 ° C. for 7H30.

 The infrared analysis indicates the presence of bands corresponding to the carbamate / allophanate and dimeric functions.

EXAMPLE 6
The same procedure as Example 1 is repeated.

 This time is worked with trimethylolpropane. 151.01 g of HDI and 4.08 g of trimethylolpropane are charged. It is necessary to work at a higher reaction temperature to see the important formation of dimer. The temperature of the reaction medium is between 140 ° C. and 1 60 C.

 The infrared analysis indicates the presence of bands corresponding to the carbamate / allophanate and trimeric functions.

EXAMPLE 7 (comparative example)
In a 3 1 reactor equipped as in Example 1, 2101.5 g of HDI, 299.15 g of 4,4'-isopropylidene dicyclohexanol (RN CAS: 80-044) are successively introduced. The reaction mixture is heated for 1 hour at 80 ° C and 45 minutes at about 102 ° C. The product obtained is swirled twice at a temperature of 1600C and 0.5 mbar. The recovered product has an NCO function titre of 0.288, ie 12.1%, a residual monomeric HDI titre of 0.02%. The viscosity of the mixture could not be measured because the product is too viscous.

 Infrared analysis indicates that there are no dimeric functions in the product obtained.

 This example shows that the polyurethanes with isocyanate functions obtained according to a conventional method gives viscous polyisocyanate compositions.

EXAMPLES OF FORMULATIONS
EXAMPLE 8
A varnish formulation was made from the composition obtained in Example 1.

To do this, a mixture of two polyols by the company Jager was used. The dry extract (ES) is 90%, the title in hydroxyl functions (%
OH) is 3.97 (in mass on the dry mass).

 This mixture of polyols has been retained for its weak structuring properties and its ability to reduce the amount of solvent in the formulation, in order to reduce the level of volatile organic compounds (VOCs).

Two formulations were made: one with 0.05% catalyst (DBTL), and the other without catalyst.

<Tb>

Components <SEP> A <SEP> B
<tb><SEP> Jagotex <SEP> F262 / Jagapol <SEP> PE350 <SEP> (50/50 <SEP> in <SEP> Mass) <SEP> 44.06 <SEP> 43.99
<tb><SEP> EPE / 57 <SEP> 20.20 <SEP><SEP> 20.28 <SEP>
<tb><SEP> DBTL <SEP> (10% <SEP> in <SEP> buac / EEP <SEP> 8: 2) <SEP> 0 <SEP> 0.30
<tb><SEP> Solvent <SEP> (BuC / Solvesso <SEP> 100 <SEP> 6: 4) <SEP> 35.38 <SEP> 35.61
<Tb>
The viscosity adjustment was made at the FORD No. 4 cut, so that the composition was about 25 seconds before application.

 The applications were made using film pullers with a 200pm application bar (wet) on a glass plate.

The drying took place as follows:
* Plates A: 30 min drying at room temperature, then 3 hours at 100 ° C.

 * Plates B: 30 min drying at room temperature, then 1 hour at 100 ° C.

 The films obtained have a good tension (light orange peel) and have no surface defects elsewhere.

 The hardness of the film was measured 4 and 7 days after the application according to the standard NFT 30-016 (Pendulum of Persoz).

Results:

<tb> Plates <SEP> A <SEP> B
<tb><SEP> 59.9 <SEP> 59.9 <SEP>
<tb> VOC <SEP> 387 <SEP> 387 <SEP>
<tb> Pot-Life <SEP> 30h <SEP> lh20 <SEP>
<tb> Hardness <SEP> Persoz
<tb> To <SEP> + <SEP> 4d <SEP> (T <SEP> = <SEP> 21.5C, <SEP> Hr <SEP> = <SEP> 55%) <SEP> 159 <SEP> 190
<tb> To <SEP> + <SEP> 7d <SEP> (T <SEP> = <SEP> 21.2C, <SEP> Hr <SEP> = <SEP> 40%) <SEP> 170 <SEP> 188
<Tb>
It is noted that the VOC values are very low and are below the required regulatory values.

Claims (11)

R is a mono- or n-valent hydrocarbon group having 1 to 30 carbon atoms, the hydrocarbon chain can be interrupted by one or more chalcogen atoms and can carry 1 to 3 OH groups, and n is an integer ranging from from 1 to 3, and / or products derived therefrom by reaction with a compound carrying an aliphatic isocyanate function, for the preparation of digesting isocyanates from monomeric aliphatic isocyanates, with a conversion level of at least 5 %, preferably at least 10% of the starting isocyanate functions in urethinediones functions.  in which

 1. Use of a Compound of General Formula I  2. Use according to claim 1, characterized in that said products resulting from the reaction of the compound of general formula I with a compound carrying an isocyanate aliphatic function correspond to the following general formulas II and / or III:

 wherein one or more of X1, X2 and X3 represents a group R '(- N = C = O) p wherein R' is an aliphatic group p valent and p is an integer from 0 to 5, the others being , if applicable, a group of formula

At least one of NX'1X "1, NX'2X" 2 and NX'3X "3 represents the group CONX1H, X1 being as defined above, R1 is R, with OH groups substituted where appropriate by a group R 'and p being as defined above,

CONX1H or R2 being R, with OH groups substituted where appropriate by a group NX1H or NX1-silyl with X1 as previously defined, and R 'and p being as defined above, the others representing a group R 'and p being as defined above, with a conversion rate of advantageously 5%, preferably at least 10% of the isocyanate functions to compounds of formula VI.  R '- (N = C = O) pcl (Vll)  in which R 'and p are as defined in claim 1, starting from monomeric isocyanates of general formula VII:

R 'and p being as defined above, and n is an integer from 1 to 3, for the preparation of dimeric compounds of general formula VI:  3. Use according to claim 1 or claim 2, characterized in that R is a C 1 -C 4 alkyl group substituted with 1 to 3 OH groups.  4. Use according to claim 2, characterized in that the compound of general formula I is chosen from pentaerythritol and trimethylolpropane, and the compounds of general formula II and III are chosen where appropriate from the corresponding derivatives of pentaerythritol and trimethylolpropane as defined in claim 2.  5. Use according to claim 2, characterized in that the isocyanate of general formula VI is a diisocyanate chosen from hexamethylene diisocyanate, tetramethylene diisocyanate, norbornane di isocyanate, isophorone di isocyanate and bis-isocyanato-cyclohexylmethane .  6. Use according to claim 2, characterized in that the dimerization reaction of said monomeric isocyanates of general formula VII is carried out at a temperature of at least 110 and at most 200 ° C.  7. Use according to claim 2, characterized in that the preparation reaction of the compounds of general formula VI from the compounds of general formula VII is carried out in a reaction medium further comprising compounds of general formula Vlil:

 wherein R 'and p are as defined in claim 2.  8. Use according to claim 2, characterized in that the compound of general formula I, and / or II, and / or III is fixed on a support, in particular a resin.  9. Composition comprising at least one compound of general formula VI:

 in which R 'and p are as defined in claim 2, and at least one compound of general formula II:

 in which one or more of X1, X2 and X3 represents a group -R'-N = C = O as defined above and the others represent, where appropriate, a group

 wherein at least one of NX'1X "1, NX'2X" 2 and NX'3X't3 represents the group

CONX1H as defined above, and n being an integer of 1 and 3; and / or at least one compound of general formula lil: R 'and p being as defined above, and R1 is R, with the OH groups substituted where appropriate by a group  as defined above, and n is an integer from 1 to 3.

R2 being R, with the OH groups substituted by a CONX1H group or R 'and p being as defined above, the others representing a group NX1H with X1 as defined above, and  10. Composition according to claim 9, characterized in that it further comprises a compound of general formula VIII:

R 'and p being as defined in claim 2.  11. Use of a composition according to claim 9 or claim 10 for the preparation of a polyurethane coating.