The present invention relates to a rubber composition which can be used in a mechanical member with a dynamic function, a process for preparing this composition, such a member and a use of a polymer with urethane functions. The invention applies in particular to mechanical members in particular chosen from anti-vibration mounts and elastic joints for motor vehicles or industrial devices, without limitation.

In a known manner, polyurethanes (PU) are obtained by reaction between isocyanate (NCO) and alcohol (OH) functional groups to obtain the urethane function (NHCOO).

Among the polyurethanes which are typically prepared by the reaction between a first precursor consisting of a polyisocyanate, a second precursor consisting of a long chain polyol and a polyol type chain extender, segmented polyurethanes are known which comprise flexible segments. formed by the second precursor and rigid segments formed by the first precursor and the chain extender, with phase separation between these flexible and rigid segments which are immiscible with each other.

Le document WO-A1 -2015/032681 concerne des mélanges de polyuréthanes thermoplastiques et de caoutchoucs notamment pour des rouleaux d’impression, et divulgue exclusivement dans ses exemples l’obtention in situ d’un polyuréthane-urée entremêlé à un caoutchouc nitrile (NBR) par réaction de ce dernier avec un unique prépolymère préalablement préparé qui incorpore conjointement deux précurseurs polyisocyanate et macroglycol et avec un allongeur de chaîne de type diamine.

A major drawback of the polyurethane-urea synthesized in this document lies in the use of a prepolymer of precursors, which limits the in situ synthesis of the polyurethane-urea to the use of a polar elastomer such as NBR, and in the that the dispersion obtained of the polyurethane-urea in the NBR generates insufficient mechanical and in particular dynamic properties for the NBR / polyurethane-urea mixtures tested, which do not incorporate any reinforcing filler.

Polyurethanes without isocyanate (“NIPU” for “non-isocyanate polyurethanes”) are also known which have been recently developed in order to overcome the problems of toxicity and stability of isocyanates and thus to anticipate more restrictive regulations. regarding their use. These "NIPUs" are typically prepared by reacting amino derivatives with cyclic carbonates, to obtain polyhydroxyurethanes (PHU) "according to the reaction scheme below:

Document US 9,416,227 B2 discloses the preparation without isocyanate of microparticles of such a polyhydroxyurethane.

Conventionally, the reinforcement of the elastomers within rubber compositions is carried out by adding fillers such as carbon black and / or silica, in order to improve the mechanical properties of the compositions thanks to the hydrodynamic effect and to the interactions between the elastomer and the fillers, on the one hand, and between the fillers themselves, on the other hand.

However, these charge-elastomer and charge-charge interactions generate an undesirable phenomenon which is usually referred to as the Payne effect and which results in non-linearity (ie amplitude stiffening) and stiffening, especially at low temperatures. crosslinked rubber compositions subjected to dynamic stresses. This stiffening results in dynamic properties which may prove to be unsatisfactory for the compositions due to the aforementioned interactions with the reinforcing fillers used, dynamic properties which usually can be evaluated by measuring, at two amplitudes of dynamic deformations, a ratio of conservation moduli G 'relating to the complex shear moduli G * of the compositions. As a reminder,

G ': real part of G * called the conservation or elastic modulus, G' characterizing the rigidity or the viscoelastic behavior of the composition (ie the energy conserved and totally restored); and

G ”: imaginary part of G * called the loss or dissipation modulus, G” characterizing the viscous behavior of the composition (ie the energy dissipated in the form of heat, it being specified that the ratio G ”/ G 'defines the factor of loss tan d).

This ratio typically corresponds to G ', measured by dynamic mechanical analysis (DMA) at a low amplitude of dynamic strain, compared to G' measured at a high amplitude of dynamic strain, with the two moduli G 'which are measured at the same frequency and at the same temperature (eg G '0.5% / G' 20%). In known manner, G '0.5% / G' 20% is usually between 1.80 and 2.00 for a rubber composition based on a polyisoprene (IR) and reinforced with 40 phr of a black of grade N330 carbon so that it can be used in dynamic applications (pce: parts by weight per 100 parts of elastomer (s)). Indeed, we know that in reinforced materials the viscoelastic behavior varies from low amplitudes of dynamic deformations,

During its recent research, the Applicant has sought intensively to minimize this Payne effect in crosslinked rubber compositions by reducing as much as possible the aforementioned ratio of storage moduli G ′ 0.5% / G ′ 20% so that it is as close to 1.00 as possible, so that the modulus of conservation G 'at a maximum strain of 20% is hardly less than that at almost zero strain of 0.5% without penalizing the static properties of compositions (in particular in terms of secant modulus and rigidity), so as to make these compositions particularly advantageous in dynamic applications.

An aim of the present invention is therefore to provide new rubber compositions which in particular remedy the aforementioned drawbacks by improving in particular the dynamic properties of the rubber compositions of the prior art while retaining their static properties.

This aim is achieved in that the Applicant has essentially just discovered, in a surprising manner, that if an elastomer is reacted by thermomechanical mixing with a reinforcing filler, precursors of a polymer containing urethane groups and a chain extender, then if the product of this reaction is crosslinked, then a fine and homogeneous dispersion in the elastomer of this polymer containing urethane groups which is segmented by being formed in situ in the elastomer matrix can be obtained under certain conditions detailed below. with, for the composition obtained, a minimized Payne effect and static properties retained,in comparison with a crosslinked rubber blend based on the same elastomer but devoid of polymer containing urethane groups and comprising instead the same reinforcing filler in an amount increased by the amount of said polymer in the composition.

In other words, a rubber composition according to the invention is based on at least one elastomer and comprises a reinforcing filler and a polymer containing urethane groups dispersed in said at least one elastomer, the composition comprising the product of a thermomechanical mixing reaction in situ of said at least one elastomer with said reinforcing filler, precursors of said polymer containing urethane groups and a chain extender.

According to the invention, the composition, which can be used in a mechanical member with a dynamic function, in particular chosen from among

anti-vibration mounts and elastic joints for motor vehicles or industrial devices, has a ratio G '0.5% / G' 20% of conservation moduli G 'relating to complex shear moduli G * satisfying at least one of the conditions following (i) to (v), G '0.5% and G' 20% being measured according to the ISO 4664 standard at respective dynamic deformation amplitudes of 0.5% and 20%, on double shear test specimens subjected to at shear strains of 0.02% to 50% at the same frequency of 5 Hz and at the same temperature T:

(i) G '0.5% / G' 20% £ 1.15 for T = 100 ° C,

(ii) G '0.5% / G' 20% £ 1.40 for T = 65 ° C,

(iii) G '0.5% / G' 20% £ 1.50 for T = 25 ° C,

(iv) G '0.5% / G' 20% £ 1.60 for T = 0 ° C,

(v) G '0.5% / G' 20% £ 2.50 for T = -30 ° C.

By “reinforcing filler” is meant here any filler dispersed by being very finely divided in the elastomeric matrix of the composition (ie in said at least one elastomer) and capable of reinforcing the composition in order to give it in particular secant moduli, resistance to sufficiently high fracture and rigidity, this filler possibly comprising at least one organic filler such as a sufficiently reinforcing carbon black for the application considered and / or at least one inorganic filler such as a sufficiently reinforcing silica for this application.

By “product of an in situ thermomechanical mixing reaction” is meant here in the usual way the mixture produced by mechanical working of the aforementioned ingredients comprising at least one thermal step, during which not only said at least one elastomer is kneaded with said reinforcing filler, said precursors and said chain extender, but more preferably with other additives conventionally used in rubber compositions such as an activator complex (eg zinc oxide and stearic acid) and a plasticizer (eg a oil), with the exception of the crosslinking system (eg a vulcanization system comprising sulfur and accelerators) which is added to the uncrosslinked mixture obtained following this thermomechanical mixing with a view to obtaining the composition according to the invention ,which is finally crosslinked in a known manner, as explained below.

It will be noted that a crosslinked rubber composition according to the invention thus obtained forms entangled networks comprising a crosslinked elastomeric network incorporating rigid segments of said polymer containing urethane groups, and an organic reinforcing network comprising flexible segments of this polymer, which is advantageously dispersed in a fine and generally homogeneous manner in the elastomer, as explained below. The Applicant has discovered that this particular entanglement of respectively flexible and rigid segments formed by this polymer thus dispersed makes it possible to obtain the aforementioned conditions (i) to (v) which are particularly advantageous, at least one of which is verified for said ratio G ′ 0 , 5% / G '20%.

It will also be noted that these conditions (i) to (v) testify to a minimization (ie significant reduction) of the Payne effect over a wide temperature range going from -30 ° C to 100 ° C, compared to the Payne effect observed for a conventional crosslinked composition devoid of said polymer and comprising the same reinforcing filler but in an amount increased by the amount of said polymer in the composition (all the other ingredients being unchanged).

It will also be noted that in a rubber composition according to the invention, said polymer containing urethane groups also exercises a reinforcing function of the rubber composition, advantageously in addition to a given quantity of said reinforcing filler that this polymer can replace. in part, as demonstrated in the embodiments below which show static properties of secant modulus, tensile strength and hardness substantially retained.

Advantageously, the composition of the invention can verify at least condition (i), and more preferably conditions (ii), (iii), (iv) and (v), and said test pieces can be subjected to conditioning. prior mechanical 0 ± 4 mm, 50 mm / min for 8 cycles.

According to a preferred example of the invention, the composition comprises (phr: parts by weight per 100 parts of elastomer (s)) from 10 to 40 phr of a carbon black as reinforcing filler and from 10 to 50 phr of said polymer containing urethane groups, the composition preferably further satisfying the following condition (ia):

(ia) G '0.5% / G' 20% £ 1, 12 for T = 100 ° C.

Even more preferably, the composition of the invention comprises from 15 to 30 phr of said carbon black, for example of grade N330, and from 15 to 30 phr of said polymer containing urethane groups.

According to another aspect of the invention, said polymer containing urethane groups can be dispersed in said at least one elastomer in the form of nodules of greater transverse dimension (ie the diameter in the case of globally spherical nodules) average in number of between 1 nm and 5 mm, preferably between 50 nm and 2 mm and even more preferably between 100 nm and 1 mm.

It will be noted that this dispersion of said polymer in the continuous elastomeric matrix of the composition is thus advantageously fine and globally homogeneous, which contributes significantly to obtaining the aforementioned mechanical properties of the compositions of the invention including in particular their Payne effect. minimized by reducing said ratio G ′ 0.5% / G ′ 20%.

In general, the compositions of the invention can advantageously also have:

- at least one of the following secant moduli M100, M300 and M400 respectively at 100%, 300% and 400% deformation, measured in uni-axial tension according to standard ASTM D 412:

M100 ³ 1.5 MPa,

M300 ³ 5.5 MPa, and

M400 ³ 9.5 MPa;

and or

- a tensile strength R / r, measured in uniaxial traction according to standard ASTM D 412, of at least 26 MPa.

It will be noted that these static properties of the composition are advantageously close to those exhibited by a conventional crosslinked composition devoid of said polymer and comprising the same reinforcing filler, such as a carbon black for example of grade N330, but in an increased quantity of the amount of said polymer in the composition (all other ingredients being unchanged).

Advantageously, a composition according to the invention can exhibit a Shore A hardness, measured according to the ASTM D2240 standard, of at least 48 and preferably of between 50 and 55.

In general, for a composition according to the invention, said at least one elastomer can advantageously be a rubber chosen from diene elastomers or not, with the exception of silicone rubbers, and the composition comprises a crosslinking system, for example in sulfur which is capable of reacting with said product of said in situ thermomechanical mixing reaction to co-crosslink said at least one elastomer with said polymer containing urethane groups.

Preferably, said at least one elastomer is an apolar diene elastomer, being even more preferably chosen from natural rubber (NR), polyisoprenes (IR), polybutadienes (BR) and styrene-butadiene copolymers (SBR).

Unlike a polar diene elastomer such as nitrile rubber (NBR) tested in WO-A1 -2015/032681, it will be noted that the use of a specifically non-polar diene elastomer makes it possible to obtain an improved dispersion (both in fineness and in in homogeneity) of said polymer containing urethane groups in this non-polar elastomer, and consequently to improve the dynamic properties of the composition by minimizing said ratio G ′ 0.5% / G ′ 20% and thus the Payne effect observed for this composition .

Also generally for a composition according to the invention, said polymer containing urethane groups is advantageously segmented by:

- rigid segments which may be present in said polymer in a mass fraction of between 20% and 40%, preferably between 25% and 35%, and which comprise said chain extender and a first said precursor, and by

- flexible segments comprising a second said precursor which is a diene polymer with functionalized chain ends, preferably a functionalized polybutadiene,

said polymer containing urethane groups being co-crosslinked, via double bonds of said second precursor, with said at least one elastomer, forming a three-dimensional network connected by covalent bonds to said at least one elastomer.

It will be noted that this particular mass fraction of said rigid segments in said polymer is preferential, due to the fact that it contributes to minimizing said ratio G ′ 0.5% / G ′ 20% without penalizing the aforementioned static properties of the composition of the invention. .

It will also be noted that the chemical co-crosslinking according to the invention (eg co-vulcanization for crosslinking with sulfur) of the polymer containing urethane groups with said at least one elastomer is made possible by the double bonds present in said second precursor, and that 'it makes it possible to better reinforce the composition by the covalent bonds and to reduce the Payne effect therein, in comparison with a composition in which the polymer containing urethane groups would be bound to the elastomer only by bonds of weak Van der Waals type energy.

According to a preferred characteristic of the invention, said first precursor and second precursor form two separate reactants for said in situ thermomechanical mixing reaction with said at least one elastomer, said reinforcing filler and said chain extender, said precursors not forming a prepolymer. of precursors.

In other words and unlike the use of a prepolymer of precursors in the examples of WO-A1 -2015/032681 which limits the dispersion of polyurethane-urea in the NBR polar elastomer by penalizing the quality of this dispersion, the two precursors according to the invention are preferably added separately to the elastomer to implement the thermomechanical mixing.

It will be noted that this separate reaction of said at least one elastomer with the two separately added precursors contributes to improving the quality of the dispersion obtained from said polymer containing urethane groups in the elastomer matrix, both in fineness and in homogeneity.

Even more preferably, said chain extender has a molar mass of less than or equal to 700 g / mol and preferably less than 600 g / mol.

It will thus be noted that said chain extender is advantageously characterized by a short chain.

According to a first embodiment of the invention, said polymer containing urethane groups belongs to the family of polyurethanes (PU) obtained from an isocyanate compound, with the exclusion of polyurethane-urea such as those synthesized in the examples of WO -A1 -2015/032681.

In accordance with this first mode of the invention:

- said first precursor can be a polyisocyanate with a functionality greater than 2, preferably chosen from monomers or prepolymers based on 4,4'-methylene bis (phenyl isocyanate), isophorone diisocyanate, hexamethylene diisocyanate and Diphenylmethylene 4,4'-diisocyanate,

- said second precursor can be a functionalized diene polymer diol with a functionality greater than 2, preferably a non-hydrogenated hydroxytelechelic polybutadiene with a number-average molecular mass of between 1000 and 3000 g / mol and with a functionality equal to or greater than 2.2, and

- Said chain extender may be a polyol chosen from diols and triols which has a molar mass of less than or equal to 300 g / mol (short chain polyol), preferably chosen from cyclohexane dimethanol, isosorbide and glycerol.

According to a preferred example of this first embodiment of the invention:

- said at least one elastomer is advantageously an apolar diene elastomer preferably chosen from natural rubber (NR), polyisoprenes (IR), polybutadienes (BR) and styrene-butadiene copolymers (SBR),

- Said reinforcing filler comprises a carbon black, for example of grade N330, present in the composition in an amount of between 15 and 30 phr (phr: parts by weight per 100 parts of elastomer (s)),

- said polymer containing urethane groups is advantageously present in the composition in an amount of between 15 and 30 phr, and

the total amount of said carbon black and of said polymer containing urethane groups in the composition is advantageously between 35 and 55 phr.

In accordance with this preferred example of the first embodiment of the invention, the composition can advantageously verify the following condition (ia):

(ia) G '0.5% / G' 20% £ 1, 12 for T = 100 ° C.

According to a second embodiment of the invention, said polymer containing urethane groups belongs to the family of polyhydroxyurethanes obtained without isocyanate (NIPU).

In accordance with this second mode of the invention:

- Said first precursor can be a polyamine chosen from diamines and triamines, preferably chosen from 1, 3-cydohexanebis (methylamine), xylylenediamine, 2,2 '- (ethylenedioxy) bis (ethylamine) and tris (2-aminoethyl) annine,

- Said second precursor may be a diene polymer functionalized at chain ends, preferably a polybutadiene functionalized by two terminal carbonate rings with 5 or 6 members each, and

- Said chain extender can be a cyclic carbonate which has a molar mass of less than or equal to 500 g / mol (ie short chain), preferably chosen from cyclohexane bis carbonate, resorcinol bis carbonate, glycerol tri carbonate and phloroglucinol tri carbonate.

According to a preferred example of this second embodiment of the invention:

- said at least one elastomer is advantageously an apolar diene elastomer preferably chosen from natural rubber (NR), polyisoprenes (IR), polybutadienes (BR) and styrene-butadiene copolymers (SBR),

- Said reinforcing filler comprises a carbon black, for example of grade N330, present in the composition in an amount of between 15 and 30 phr (phr: parts by weight per 100 parts of elastomer (s)),

- said polymer containing urethane groups is present in the composition in an amount of between 15 and 30 phr, and

the total amount of said carbon black and of said polymer containing urethane groups in the composition is between 35 and 55 phr.

In accordance with this preferred example of the second embodiment of the invention, the composition can advantageously verify at least one and preferably all of the following conditions (ia) to (va):

(ia) G '0.5% / G' 20% £ 1, 12 for T = 100 ° C.

(ii-a) G '0.5% / G' 20% £ 1, 20 for T = 65 ° C,

(iii-a) G '0.5% / G' 20% £ 1.30 for T = 25 ° C,

(iv-a) G '0.5% / G' 20% £ 1.40 for T = 0 ° C,

(va) G '0.5% / G' 20% £ 1.50 for T = -30 ° C.

In accordance with this preferred example of said second embodiment, the composition furthermore satisfies even more advantageously at least one and preferably all of the following conditions (ib) to (vb):

(ib) G '0.5% / G' 20% £ 1.10 for T = 100 ° C.

(ii-b) G '0.5% / G' 20% £ 1, 15 for T = 65 ° C,

(iii-b) G '0.5% / G' 20% £ 1, 20 for T = 25 ° C,

(iv-b) G '0.5% / G' 20% £ 1.25 for T = 0 ° C,

(vb) G '0.5% / G' 20% £ 1.40 for T = -30 ° C.

A mechanical member with a dynamic function according to the invention is in particular chosen from anti-vibration mounts and elastic joints for motor vehicles or industrial devices, said member comprising at least one elastic part which consists of a rubber composition as defined. above and which is adapted to be subjected to dynamic stresses.

A process for the preparation according to the invention of a rubber composition as defined above comprises the following steps:

a) forming an uncrosslinked mixture comprising a dispersion, in said at least one elastomer, of said polymer containing urethane groups by said thermomechanical mixing reaction of said at least one elastomer with said reinforcing filler, said precursors and said chain extender, said reaction being preferably carried out in an internal mixer at a maximum temperature between 130 ° C and 180 ° C,

b) addition to the mixture of a crosslinking system with mechanical work of the crosslinkable mixture thus obtained, preferably carried out in an open mixer at a maximum temperature below 80 ° C, then

c) crosslinking of the crosslinkable mixture by vulcanization in a press at a temperature of between 130 ° C and 180 ° C, preferably by compression molding, said polymer containing urethane groups being chemically co-crosslinked with said at least one elastomer, forming with the latter has covalent bonds.

It will be noted that this chemical co-crosslinking makes it possible to reinforce the composition obtained satisfactorily while minimizing the Payne effect therein, and that this co-crosslinking is made possible by the double bonds that the said second precursor comprises and by the use of a functionality greater than 2 for each of the first and second precursors.

It will also be noted that the thermomechanical mixing of step a) can comprise at least one thermal step whose minimum temperatures to be reached and maximum temperatures not to be exceeded can be between 130 ° C and 180 ° C and preferably between 140 ° C. and 170 ° C. The appropriate duration of the mixing varies as a function of the operating conditions adopted by a person skilled in the art and in particular of the temperature chosen, of the nature and of the volume of the ingredients subjected to the thermomechanical work.

Preferably, said precursors form a first precursor and a second precursor which are added separately in step a) after said at least one elastomer, said polymer containing urethane groups being segmented by rigid segments comprising said chain extender and said first precursor. and by flexible segments comprising said second precursor.

It will be noted that the first introduction of said at least one elastomer (preferably an apolar diene elastomer) into the internal mixer makes it possible to sufficiently plasticize this elastomer and to facilitate the incorporation of the other ingredients added subsequently to the elastomer matrix.

Even more preferably, the total mass fraction of said first precursor and of said chain extender in said polymer at

urethane groups formed in step a) is between 20% and 40%, preferably between 25% and 35%.

According to another aspect of the invention, a polymer containing urethane groups dispersed in a rubber composition based on at least one elastomer by an in situ reaction of thermomechanical mixing of said at least one elastomer with a reinforcing filler, precursors of said polymer and a chain extender, is used to reduce the Payne effect in the composition at a temperature T inclusive of between -30 ° C and 100 ° C, the Payne effect being quantified by said ratio G ′ 0.5% / G '20% of conservation moduli G' relating to the complex shear moduli G * of the composition,

in comparison with a rubber mixture based on said at least one elastomer, devoid of said polymer containing urethane groups and comprising said reinforcing filler in an amount in phr equal to the sum of phr, in the composition, of said reinforcing filler and of said polymer with urethane groups.

According to this use of the invention, the composition comprising (phr: parts by weight per 100 parts of elastomer (s)) from 10 to 40 phr of a carbon black as reinforcing filler and from 10 to 50 phr of said polymer containing urethane groups, can be advantageously used to reduce said ratio G ′ 0.5% / G ′ 20% by more than 40%, and optionally in addition to keep within 15% the Shore A hardness of the composition, in comparison of said rubber mixture devoid of said polymer containing urethane groups and comprising said carbon black in an amount in phr equal to the sum of the phr, in the composition, of said carbon black and of said polymer.

Other characteristics, advantages and details of the present invention will emerge on reading the following description of several exemplary embodiments of the invention, given by way of illustration and without limitation in relation to the accompanying drawings, among which:

For IQ first mode of the invention (PU):

FIG. 1 is a graph illustrating the secant moduli M100, M300, M400, the Shore A hardness and the ratio G '0.5% / G' 20% at 100 ° C of an unreinforced control rubber mixture, of a mixture of the prior art reinforced with 40 phr of carbon black, of a rubber mixture not in accordance with the invention which is not reinforced and comprises 40 phr of a PU without chain extender (ie without segments rigid, SR below) and of a rubber composition not in accordance with the invention which comprises 20 phr of carbon black and 20 phr of PU without SR,

Figure 2 is a graph illustrating the influence of adding a glycerol chain extender on M100, M300, M400, breaking strength R / r, Shore A and G '0.5% / G' 20 % at 100 ° C, for said mixture of the prior art reinforced with 40 phr of carbon black, another mixture of the prior art reinforced with 20 phr of carbon black, said composition not in accordance with the invention and a composition 11 according to the invention with 20 phr of carbon black and 20 phr of a PU comprising 30% by weight of SR,

FIG. 2a is a graph illustrating the influence of the functionality and the unsaturations of the second precursor on M100, M300, M400 and R / r, for a mixture of the prior art with 40 phr of carbon black, two non-compliant mixtures according to the invention with 20 phr of carbon black and 20 phr of a PU obtained from a first precursor according to the invention but from a second precursor not in accordance with the invention, and a composition 11 ′ according to the invention with 20 phr of carbon black and 20 phr of a PU obtained from the same first precursor but from a second precursor according to the invention,

FIG. 3 is a graph illustrating the influence, for the same polyisocyanate (Suprasec 2015) and polyol (polyBd R20 LM) precursors as for composition 11, of various chain extenders on M100, M300, M400, R / r, Shore A and G '0.5% / G' 20% at 100 ° C, for the mixture of the prior art reinforced with 40 phr of carbon black, the other mixture of the prior art reinforced with 20 phr of black of carbon and three compositions according to the invention I2, I3, 11 with 20 phr of carbon black and 20 phr of three PU comprising 30% by weight of SR and respectively obtained with CHDM, isosorbide and glycerol chain extenders (see formulas illustrated),

FIG. 4 is a graph illustrating, for the same CHDM chain extender and polyol precursor (polyBd R20 LM), the influence of various polyisocyanate precursors on M100, M300, M400, R / r, Shore A and G '0.5 % / G '20% at 100 ° C, for the mixture of the prior art reinforced with 40 phr of carbon black, the other mixture of the prior art reinforced with 20 phr of carbon black, composition I2 with the Suprasec 2015 polyisocyanate and three other compositions according to the invention I4, I5, I6 with 20 phr of carbon black and 20 phr of three other PUs comprising 30% by weight of SR but respectively obtained with polyisocyanates IPDI, HDI and 4, 4'-MDI (see illustrated formulas),

FIG. 5 is a graph illustrating the G ′ 0.5% / G ′ 20% ratios obtained at various temperatures ranging from -30 ° C to 100 ° C, for the mixture of the prior art reinforced with 40 phr of black of carbon and compositions 11, I2, I3, I4, I5 and I6,

FIGS. 6, 7, 8, 9, 10 are images under an atomic force microscope (“AFM”) in “tapping” mode respectively obtained for the compositions I2, I3, 11, I4, I5, with for each composition the image on the left as a topographic image and the image on the right as a phase image,

For the second mode of the invention (NIPU):

FIG. 11 is a graph illustrating the influence, for the same first polyamine precursor (1, 3-cyclohexanebis (methylamine), CHMA for short) and the same second polycyclocarbonate (polybutadiene terminated cyclocarbonate) precursor, of various extenders of cyclic carbonate chains (CC abbreviated below) on M100, M300, M400, R / r, Shore A and G '0.5% / G' 20% at 100 ° C, for the mixture of the prior art reinforced with 40 pce of carbon black, the other mixture of the prior art reinforced with 20 phr of carbon black, and four compositions according to the invention I7, I8, I9, l10 with 20 phr of carbon black and 20 phr of four NIPUs respectively obtained with the extenders cyclohexane bis CC, resorcinol bis CC, glycerol tri CC and phloroglucinol tri CC (see illustrated formulas),

FIG. 12 is a graph illustrating the influence, for the same phloroglucinol tri CC chain extender and the same second polycyclocarbonate (polybutadiene terminated cyclocarbonate) precursor, of various first polyamine precursors on M100, M300, M400, R / r, Shore A and G '0.5% / G' 20% at 100 ° C, for the mixture of the prior art reinforced with 40 phr of carbon black, the other mixture of the prior art reinforced with 20 phr of carbon black. carbon, composition l10 with the CHMA extender and three other compositions according to the invention l11, l12, l13 with 20 phr of carbon black and 20 phr of three NIPUs respectively obtained with the polyamines xylylenediamine, EDEA and TAEA (see formulas illustrated),

FIG. 13 is a graph illustrating the G ′ 0.5% / G ′ 20% ratios obtained at various temperatures ranging from -30 ° C to 100 ° C, for the mixture of the prior art reinforced with 40 phr of black of carbon and compositions I7, I8, I9, l10, l11, l12 and l13, and

FIGS. 14, 15, 16, 17, 18, 19 and 20 are atomic force microscope ("AFM") images in "tapping" mode respectively obtained for compositions I7, I8, I9, l10, l11, l12 and l13 with for each composition the left cliché as a topographic image and the right cliché as a phase image.

In all these examples of mixtures and compositions thus illustrated, the same synthetic polyisoprene with IR name Nipol 2200, carbon black N330 as reinforcing filler and the ingredients identified in the tables below ( expressed in pc: parts by weight per 100 parts of IR).

For the first mode of the invention illustrated in FIGS. 1 to 10, the PUs were obtained in situ with the following first and second precursors for the compositions according to the invention 11, I2, I3:

The PUs of the compositions according to the invention 14, 15 and 16 were obtained with the same second precursor PoiyBd R20 LM but with the other first precursors IPDI, HDI and 4,4′-MDI of formulas illustrated in FIG. 4.

For the second mode of the invention illustrated in FIGS. 11 to 20, the NIPUs were obtained in situ with the following first and second precursors for the compositions according to the invention I7, I8, I9, I10:

- 1, 3-cyclohexanebis (methylamine) (cf. cyclohexane amine in the tables below or CHMA for short), and

- polybutadiene terminated cyclocarbonate (PolyBd-CC for short).

The NIPUs of compositions 11, 12, 13 were obtained with the same second precursor but with the other first precursors xylylenediamine, EDEA and TAEA of formulas illustrated in FIG. 12.

Regarding the process implemented for obtaining all of the compositions according to the invention 11 to 13, the following experimental protocol was followed.

The polyisoprene / polymer blends with urethane groups (PU or NIPU) were produced using a Haake internal mixer for the thermomechanical mixing step, then an open mixer with Polymix cylinders for incorporation into the mixture obtained. of the crosslinking system.

In the internal mixer, the elastomer was introduced first so that it could plasticize and to facilitate the incorporation of the other ingredients. The set temperature was then 55 ° C and the speed of the rotors 45 revolutions per minute. After 1.5 minutes of mixing, the activator complex consisting of stearic acid and ZnO (silox 3C), oil (Plaxolene 50) and carbon black N330 were added. One minute later, the first and second precursors were introduced into the internal mixer. These two precursors being liquid, the mechanical mixing torque dropped sharply when they were incorporated, and it was therefore necessary to wait for the formation of the PU or the NIPU so that this mechanical torque increases again. The material was then heated by increasing the speed of the rotors present within the Haake mixer,

The crosslinking system was then added to the Polymix open mixer, the temperature of the rolls having been set at 40 ° C. Then the vulcanization of the crosslinkable compositions obtained by compression molding was carried out in a hydraulic press at 150 ° C.

For the measurement of the static properties of the compositions including the secant moduli M100, M300, M400, the tensile strength R / r, (successively presented from left to right for each material on the attached graphs) and the Shore A hardness, we have performed uniaxial tensile tests according to ISO 37: at 23 ° C on an Instron 5565 dynamometer with a 10 kN load cell and with a traverse speed of 500 mm / min. The dumbbell specimens used were of type H2 (useful length = 25 mm, width = 4 mm, thickness = 2 mm).

For the measurement of the dynamic properties of the compositions and in particular of the said ratio G ′ 0.5% / G ′ 20% representative of the Payne effect of the various mixtures and rubber compositions, the procedure was carried out at different temperatures (-30, 0, 25 , 65 and 100 ° C) on a DMA + 1000 machine from Metravib. For this, double-shear ½ QC specimens were used which were subjected to a shear strain ranging from 0.02% to 50% at a frequency of 5 Hz. Mechanical conditioning was carried out (0 ± 4 mm , 50 mm / min, 8 cycles) beforehand. The standard IS04664 of 2005 (confirmed in 2011) was followed for the measurements of these conservation modules G '.

First mode of the invention (PU):

Table 1: Unreinforced control rubber mix

Table 2: Mixture of the prior art reinforced with 40 phr of carbon black

Table 3: Mixture of the prior art with 20 phr of carbon black

Table 4: Mixture of rubber not in accordance with the invention (unreinforced, with 40 phr of a PU obtained from PolyBd R20 LM and Suprasec

2015, without chain extender):

Table 5: Rubber composition not in accordance with the invention (with 20 phr of carbon black and 20 phr of PU obtained from PolyBd R20 LM and Suprasec 2015, without chain extender):

Table 6: Rubber composition I2 according to the invention (with 20 phr of carbon black and 20 phr of PU obtained from PolyBd R20 LM and Suprasec 2015, with CHDM chain extender):

Table 7: Rubber composition 16 according to the invention

(with 20 pce of carbon black and 20 pce of PU from PolyBd R20 LM and 4.4 'MDI, with CHDM chain extender):

Table 8: Rubber composition 14 according to the invention (with 20 phr of carbon black and 20 phr of PU obtained from PolyBd R20 LM and from IPDI, with CHDM chain extender):

Table 9: Rubber composition 15 according to the invention

(with 20 pce of carbon black and 20 pce of PU from PolyBd R20 LM and HDI, with CHDM chain extender):

Table 10: Rubber composition I3 according to the invention

(with 20 pce of carbon black and 20 pce of PU from PolyBd R20 LM and Suprasec 2015, with isosorbide chain extender):

Table 11: Rubber composition 11 according to the invention

(with 20 pce of carbon black and 20 pce of PU from PolyBd R20 LM and Suprasec 2015, with glycerol chain extender):

As can be seen in FIG. 1, the unreinforced mixture with 40 phr of PU synthesized in situ exhibits improved moduli in comparison with the unreinforced mixture without PU, without however reaching the level of the moduli of the mixture with 40 phr of carbon black. The Payne effect of this unreinforced mixture with 40 pce of PU is however very reduced compared to that of the mix with 40 pce of carbon black instead of PU. The non-conforming composition of the invention with a “mixed reinforcement” carbon black + PU synthesized in situ without SR makes it possible to obtain better static properties while having a Payne effect equivalent to that of the mixture not reinforced with 40 phr of PU. (cf. ratio G ′ 0.5% / G ′ 20% of 1.05 much less than that equal to 1.94 for the mixture with 40 phr of carbon black).

As visible in Figure 2, the addition of a chain extender makes it possible to further improve the static properties by the formation of rigid segments (SR) within the PU synthesized in situ, by increasing

in particular the moduli and the hardness of the compositions. With a mass rate of SR of 30%, composition 11 shows that the same level of hardness is reached as for the reference mixture (loaded with 40 phr of carbon black), with in addition a Payne effect greatly reduced compared to this reference mixture (cf. ratio G ′ 0.5% / G ′ 20% of 1.08).

As visible in FIG. 3, the choice of the structure of the chain extender chosen, and therefore of the nature of the rigid segments obtained in the elastomeric matrix, makes it possible to modulate the mechanical properties of the compositions 11, I2 and I3, for a same polyisocyanate (Suprasec 2015) and the same level of SR of 30%, while having hardnesses close or equivalent to that of said reference mixture as well as weak Payne effects (cf. the G '0.5% / G' ratios 20% at 100 ° C always less than 1, 12, or even less than or equal to 1, 10).

As visible in FIG. 4, the choice of the structure of the polyisocyanate (for the same CHDM chain extender) also makes it possible to modulate the mechanical properties of the compositions I2, I4, I5 and I6. The Payne effect at 100 ° C remains weak for I2, I4, I5, I6 (cf. ratio G '0.5% / G' 20% less than or equal to 1, 12) and much lower than that of said reference mixture .

As visible in Figure 5 which shows the dynamic properties of compositions 11 to I6 measured at different temperatures (at -30 ° C, 0 ° C, 25 ° C, 65 ° C and 100 ° C), the Payne effect is considerably reduced for these compositions 11 to 16 compared to said reference mixture.

In conclusion, the aforementioned results demonstrate that the dynamic properties of the compositions according to this first embodiment of the invention are markedly improved compared to the prior art represented by said reference mixture (with 40 phr of carbon black and without PU), which advantageously makes it possible to use these compositions in dynamic applications and in a wide range of temperatures ranging from -30 ° C to 100 ° C.

FIGS. 6 to 10 show that the PUs thus obtained in situ are very finely dispersed in a relatively homogeneous manner in the polyisoprene in the form of nodules of greater transverse dimension, mean in number between 50 nm and 2 mm, or even between 100 nm and 1. mm. This dispersion contributes to obtaining the aforementioned mechanical properties of the compositions of the invention including in particular their minimized Payne effect.

In summary, the chemical reinforcement of the elastomeric matrix by networks of PU thus entangled makes it possible to maintain the mechanical properties (modulus and hardness) of compositions 11 to I6 with respect to said reference mixture, and by minimizing non-linearity (dynamic stiffening ) in relation to the latter.

We have also studied the influence of the functionality and ethylenic unsaturations of the second precursor on the mechanical properties obtained for the compositions, from the same given masterbatch, the formulation of which is that of the unreinforced control rubber blend detailed in table 1 above, by preparing:

A control rubber mixture of the prior art reinforced with 40 phr of N330 carbon black added to the masterbatch;

A composition 11 ′ according to the invention with, in addition to the masterbatch, 20 phr of carbon black N330 and 20 phr of a PU obtained from the first MDI precursor “Suprasec 2015”, of a hydroxytelechelic polybutadiene with the name “PolyBd-OH R45 HTLO ”as second precursor (Mn = 2800 g / mol, functionality = 2.5) and the aforementioned CHDM as chain extender;

A rubber mixture no.1 not in accordance with the invention with, in addition to the masterbatch, 20 phr of carbon black N330 and 20 phr of a PU obtained from the first MDI precursor “Suprasec 2015”, from CHDM as chain extender and hydroxytelechelic polybutadiene “Krasol LBH 2000” (Mn = 2100 g / mol and functionality equal to 1.9) as second precursor; and

A rubber mixture no.2 not in accordance with the invention with, in addition to the masterbatch, 20 phr of N330 carbon black and 20 phr of a PU obtained from the first MDI precursor “Suprasec 2015”, from CHDM as chain extender and hydrogenated hydroxytelechelic polybutadiene “Krasol HLBH-P 2000” (with Mn = 2100 g / mol and with a functionality equal to 1.9) as a second precursor.

The composition 11 ′ and the three aforementioned mixtures were prepared as indicated above with 1.6 equivalents of vulcanizing agents as a crosslinking system (see Table 1) and with a PU comprising 30% of rigid segments SR, as explained above for compositions 11 to I6. Table 12 below summarizes the formulations used from the masterbatch for 11 'and mixtures No. 1 and No. 2.

Table 12: Composition 11 ′ according to the invention and mixtures No. 1 and 2 (with 20 phr of carbon black and 20 phr of PU obtained from Suprasec 2015 and various polybutadienes-OH, with CHDM chain extender):

As can be seen in FIG. 2a, the second precursor Krasol LBH 2000 gives mixture no.1 significantly lower tensile moduli than those of composition 11 ′, of which the second polyol precursor (like the first precursor) has a functionality greater than 2. , while the molecular mass Mn of Krasol LBH 2000 is lower than that of PolyBd R45 HTLO. Despite shorter flexible segments, we have in fact obtained poorer mechanical properties for this mixture No. 1 in

which the PU formed is linear, which demonstrates the positive effect of the 2.5 functionality of the second polyol precursor which allows, via the double bonds of the latter, to chemically co-crosslink the PU formed with the elastomeric matrix of the composition 11 ′ by giving this PU a three-dimensional structure which better reinforces the composition.

It can also be seen in FIG. 2a that the second hydrogenated precursor Krasol HLBH-P 2000, devoid of double bonds, confers on mixture No. 2 mechanical properties which are even lower than those of mixture No. 1. Indeed, the absence of double bonds in this second precursor is opposed to the co-vulcanization of the PU with the polyisoprene (the PU formed in mixture No. 2 also being linear) and therefore does not generate any covalent bond between the PU and the elastomeric matrix of the mixture, which leads to less reinforcement of the latter.

The Payne effect obtained for the mixture of the prior art with 40 phr of N330 was measured at 100 ° C. as indicated above, for mixtures No. 1 and No. 2 and for composition 11 ′ (see table 13 below).

Table 13:

As shown in Table 13, the Payne effect is higher with mixtures # 1 and # 2 each incorporating a linear PU. It is in fact easier to break, during dynamic stress, the low-energy bonds between the chains of the linear PU of mixtures No. 1 and No. 2 than to break the three-dimensional network of the co-crosslinked PU of composition l1 '. .

The intrinsic properties of the second precursor (in particular its functionality and its double bonds) are therefore decisive for obtaining the intended mechanical properties of the composition.

Second mode of the invention (NIPU):

Table 14: Rubber composition I7 according to the invention

(with 20 pce of carbon black and 20 pce of NIPU from PolyBd-CC and 1, 3- cvclohexanebis (methylamine), with cvclohexane bis CC alonator):

Table 15: Rubber composition I8 according to the invention

(with 20 pce of carbon black and 20 pce of NIPU obtained from PolyBd-CC and 1, 3- cvclohexanebis (methylamine). with resorcinol bis CC alonator):

Table 16: Rubber composition I9 according to the invention

(with 20 pce of carbon black and 20 pce of NIPU from PolyBd-CC and 1, 3- cvclohexanebis (methylamine). with qlvcerol tri CC alonator):

Table 17: Rubber composition 110 according to the invention

(with 20 pce of carbon black and 20 pce of NIPU from PolyBd-CC and 1, 3- cvclohexanebis (methylamine). with phloroqlucinol tri CC alonator):

Table 18: Rubber composition 111 according to the invention (with 20 phr of carbon black and 20 phr of NIPU obtained from PolyBd-CC and xylylenediamine, with phloroqlucinol tri CCallonger):

Table 19: Rubber composition I12 according to the invention (with 20 phr of carbon black and 20 phr of NIPU obtained from PolyBd-CC and

EDEA, with tri CC phloroqlucinol allocator):

Table 20: Rubber composition 13 according to the invention

(with 20 pce of carbon black and 20 pce of NIPU from PolyBd-CC and

TAEA, with tri CC phloroglucinol allocator):

As visible in figure 11, the addition of a NIPU synthesized in situ also makes it possible to reinforce the elastomer matrix, as shown in particular by the moduli of the IR / NIPU mixtures which are greater than those of the mixture reinforced by only 20 phr of black. of carbon.

In addition, the choice of the structure of the chain extender (with a first polyamine precursor 1, 3-cyclohexanebis (methylamine)) makes it possible to modulate the mechanical properties of compositions I7 to I10 in order to obtain hardnesses close to that of said reference mixture (with 40 pce of carbon black and without NIPU).

The Payne effect at 100 ° C of each of the compositions I7 to I10 is very weak (see said ratio less than or equal to 1.05), whatever chain extender is used.

As can be seen in figure 12, the choice of the polyamine used

(for the same phloroglucinol tri CC chain extender) also impacts the mechanical properties of compositions l10 to l13 and allows their

impart variable hardness (48 to 52 Shore A). In all cases, the Payne effect at 100 ° C. is always greatly reduced in comparison with said reference mixture (see said ratio less than or equal to 1.09, or even 1.06).

As visible in Figure 13 which shows the dynamic properties of compositions I7 to I13 measured at different temperatures (at -30 ° C, 0 ° C, 25 ° C, 65 ° C and 100 ° C), the Payne effect is considerably reduced for these compositions I7 to I3 compared to said reference mixture.

In conclusion, the aforementioned results demonstrate that the dynamic properties of the compositions according to this second embodiment of the invention are markedly improved compared to the prior art represented by said reference mixture (with 40 phr of carbon black and without NIPU), which advantageously makes it possible to use these compositions in dynamic applications and in a wide range of temperatures ranging from -30 ° C to 100 ° C.

FIGS. 14 to 20 show that the NIPUs thus obtained in situ are very finely dispersed in a relatively homogeneous manner in the polyisoprene in the form of nodules of larger mean transverse dimension in number between 50 nm and 2 mm, or even between 100 nm and 1 mm. This dispersion contributes to obtaining the aforementioned mechanical properties of the compositions of the invention including in particular their minimized Payne effect.

In summary, the chemical reinforcement of the elastomeric matrix by networks of NIPUs thus entangled makes it possible to maintain the mechanical properties (moduli and hardness) of the compositions I7 to I13 with respect to said reference mixture, and by minimizing the non-linearity (dynamic stiffening ) in relation to the latter.

CLAIMS

1) Rubber composition which can be used in a mechanical member with a dynamic function, in particular chosen from anti-vibration mounts and elastic joints for motor vehicles or industrial devices, the composition being based on at least one elastomer and comprising:

- a reinforcing filler, and

- a polymer containing urethane groups dispersed in said at least one elastomer,

the composition comprising the product of an in situ reaction of thermomechanical mixing of said at least one elastomer with said reinforcing filler, precursors of said polymer containing urethane groups and a chain extender,

in which the composition exhibits a ratio G ′ 0.5% / G ′ 20% of storage moduli G ′ relating to the complex shear moduli G * satisfying at least one of the following conditions (i) to (v), G '0.5% and G' 20% being measured according to the ISO 4664 standard at respective dynamic deformation amplitudes of 0.5% and 20%, on double shear specimens subjected to shear deformations of 0.02% at 50% at the same frequency of 5 Hz and at the same temperature T:

(i) G '0.5% / G' 20% £ 1.15 for T = 100 ° C,

(ii) G '0.5% / G' 20% £ 1.40 for T = 65 ° C,

(iii) G '0.5% / G' 20% £ 1.50 for T = 25 ° C,

(iv) G '0.5% / G' 20% £ 1.60 for T = 0 ° C,

(v) G '0.5% / G' 20% £ 2.50 for T = -30 ° C.

2) A rubber composition according to claim 1, wherein the composition satisfies at least condition (i), and further preferably conditions (ii), (iii), (iv) and (v), and wherein said specimens are subjected to prior mechanical conditioning of 0 ± 4 mm, 50 mm / min for 8 cycles.

3) A rubber composition according to claim 1 or 2, wherein the composition comprises (phr: parts by weight per 100 parts of elastomer (s)) from 10 to 40 phr of a carbon black as reinforcing filler and from 10 to 50 phr of said polymer containing urethane groups, the composition preferably also satisfying the following condition (ia):

(ia) G '0.5% / G' 20% £ 1, 12 for T = 100 ° C.

4) A rubber composition according to claim 3, wherein the composition comprises from 15 to 30 phr of said carbon black, for example of grade N330, and from 15 to 30 phr of said polymer containing urethane groups.

5) Rubber composition according to one of the preceding claims, wherein said polymer containing urethane groups is dispersed in said at least one elastomer in the form of nodules of larger mean transverse dimension in number between 1 nm and 5 mm, preferably between 50 nm and 2 mm.

6) Rubber composition according to one of the preceding claims, in which the composition has:

- at least one of the following secant moduli M100, M300 and M400 respectively at 100%, 300% and 400% deformation, measured in uni-axial tension according to standard ASTM D 412:

M100 ³ 1.5 MPa,

M300 ³ 5.5 MPa, and

M400 ³ 9.5 MPa;

and or

- a tensile strength R / r, measured in uniaxial traction according to standard ASTM D 412, of at least 26 MPa.

7) Rubber composition according to one of the preceding claims, in which the composition has a Shore A hardness, measured according to the ASTM D2240 standard, of at least 48 and preferably between 50 and 55.

8) Rubber composition according to one of the preceding claims, in which said at least one elastomer is a rubber chosen from diene elastomers or not, with the exception of silicone rubbers, the composition comprising a crosslinking system, for example with sulfur which is capable of reacting with said product of said in situ thermomechanical mixing reaction to co-crosslink said at least one elastomer with said polymer containing urethane groups.

9) A rubber composition according to claim 8, wherein said at least one elastomer is an apolar diene elastomer, preferably being chosen from natural rubber (NR), polyisoprenes (IR), polybutadienes (BR) and styrene copolymers -butadiene (SBR).

10) Rubber composition according to one of the preceding claims, wherein said polymer containing urethane groups is segmented by:

- rigid segments which are present in said polymer in a mass fraction of between 20% and 40%, preferably between 25% and 35%, and which comprise said chain extender and a first said precursor, and by

- flexible segments comprising a second said precursor which is a diene polymer with functionalized chain ends, preferably a functionalized polybutadiene,

said polymer containing urethane groups being co-crosslinked, via double bonds of said second precursor, with said at least one elastomer, forming a three-dimensional network connected by covalent bonds to said at least one elastomer.

11) A rubber composition according to claim 10, wherein said first precursor and second precursor form two separate reactants for said in situ thermomechanical mixing reaction with said at least one elastomer, said reinforcing filler and said chain extender, said precursors not forming not a precursor prepolymer.

12) A rubber composition according to claim 10 or 11, wherein said chain extender has a molar mass of less than or equal to 700 g / mol and preferably less than 600 g / mol.

13) Rubber composition according to one of claims 10 to 12, wherein said polymer containing urethane groups belongs to the family of polyurethanes obtained from an isocyanate compound, excluding polyurethane-urea.

14) A rubber composition according to claim 13, wherein:

- Said first precursor is a polyisocyanate with a functionality greater than 2, preferably chosen from monomers or prepolymers based on 4,4'-methylene bis (phenyl isocyanate), isophorone diisocyanate, hexamethylene diisocyanate and 4 , Diphenylmethylene 4'-diisocyanate,

- said second precursor is a functionalized diene polymer diol with a functionality greater than 2, preferably a non-hydrogenated hydroxytelechelic polybutadiene of molecular mass

number average between 1000 and 3000 g / mol and with functionality equal to or greater than 2.2, and

- Said chain extender is a polyol chosen from diols and triols which has a molar mass of less than or equal to 300 g / mol, preferably chosen from cyclohexane dimethanol, isosorbide and glycerol.

15) A rubber composition according to claim 13 or 14, wherein:

- said at least one elastomer is an apolar diene elastomer preferably chosen from natural rubber (NR), polyisoprenes (IR), polybutadienes (BR) and styrene-butadiene copolymers (SBR),

- Said reinforcing filler comprises a carbon black, for example of grade N330, present in the composition in an amount of between 15 and 30 phr (phr: parts by weight per 100 parts of elastomer (s)),

- said polymer containing urethane groups is present in the composition in an amount of between 15 and 30 phr, and

the total amount of said carbon black and of said polymer containing urethane groups in the composition is between 35 and 55 phr.

16) A rubber composition according to claim 15, wherein the composition satisfies the following condition (ia):

(ia) G '0.5% / G' 20% £ 1, 12 for T = 100 ° C.

17) Rubber composition according to one of claims 10 to 12, wherein said polymer containing urethane groups belongs to the family of polyhydroxyurethanes obtained without isocyanate.

18) A rubber composition according to claim 17, wherein:

- said first precursor is a polyamine chosen from diamines and triamines, preferably chosen from 1, 3-cyclohexanebis (methylamine), xylylenediamine, 2,2 '- (ethylenedioxy) bis (ethylamine) and tris ( 2-aminoethyl) amine,

- Said second precursor is a diene polymer functionalized at chain ends, preferably a polybutadiene functionalized by two terminal carbonate rings with 5 or 6 members each, and

- Said chain extender is a cyclic carbonate which has a molar mass of less than or equal to 500 g / mol, preferably chosen from cyclohexane bis carbonate, resorcinol bis carbonate, glycerol tri carbonate and phloroglucinol tri carbonate.

19) A rubber composition according to claim 17 or 18, wherein:

- said at least one elastomer is an apolar diene elastomer preferably chosen from natural rubber (NR), polyisoprenes (IR), polybutadienes (BR) and styrene-butadiene copolymers (SBR),

- Said reinforcing filler comprises a carbon black, for example of grade N330, present in the composition in an amount of between 15 and 30 phr (phr: parts by weight per 100 parts of elastomer (s)),

- said polymer containing urethane groups is present in the composition in an amount of between 15 and 30 phr, and

the total amount of said carbon black and of said polymer containing urethane groups in the composition is between 35 and 55 phr.

20) A rubber composition according to claim 19, wherein the composition satisfies at least one and preferably all of the following conditions (ia) to (va):

(ia) G '0.5% / G' 20% £ 1, 12 for T = 100 ° C.

(ii-a) G '0.5% / G' 20% £ 1, 20 for T = 65 ° C,

(iii-a) G '0.5% / G' 20% £ 1.30 for T = 25 ° C,

(iv-a) G '0.5% / G' 20% £ 1.40 for T = 0 ° C,

(va) G '0.5% / G' 20% £ 1.50 for T = -30 ° C.

21) A rubber composition according to claim 20, wherein the composition further satisfies at least one and preferably all of the following conditions (ib) to (vb):

(ib) G '0.5% / G' 20% £ 1.10 for T = 100 ° C.

(ii-b) G '0.5% / G' 20% £ 1, 15 for T = 65 ° C,

(iii-b) G '0.5% / G' 20% £ 1, 20 for T = 25 ° C,

(iv-b) G '0.5% / G' 20% £ 1.25 for T = 0 ° C,

(vb) G '0.5% / G' 20% £ 1.40 for T = -30 ° C.

22) Mechanical member with dynamic function in particular chosen from anti-vibration mounts and elastic joints for motor vehicles or industrial devices, said member comprising at least one elastic part which consists of a rubber composition and which is adapted to be subjected to dynamic stresses, in which said composition is as defined in one of the preceding claims.

23) Process for preparing a rubber composition according to one of claims 1 to 21, wherein the process comprises the following steps:

a) forming an uncrosslinked mixture comprising a dispersion, in said at least one elastomer, of said polymer containing urethane groups by said thermomechanical mixing reaction of said at least one elastomer with said reinforcing filler, said precursors and said chain extender, said reaction being preferably carried out in an internal mixer at a maximum temperature of between 130 ° C and 180 ° C,

b) addition to the mixture of a crosslinking system with mechanical work of the crosslinkable mixture thus obtained, preferably carried out in an open mixer at a maximum temperature below 80 ° C, then

c) crosslinking of the crosslinkable mixture by vulcanization in a press at a temperature of between 130 ° C and 180 ° C, preferably by compression molding, said polymer containing urethane groups being chemically co-crosslinked with said at least one elastomer, forming with the latter has covalent bonds.

24) The method of claim 23, wherein said precursors form a first precursor and a second precursor which are added separately in step a) after said at least one elastomer, said polymer containing urethane groups being segmented by rigid segments comprising said said elastomer. chain extender and said first precursor and by flexible segments comprising said second precursor.

25) The method of claim 24, wherein the total mass fraction of said first precursor and said chain extender in said polymer containing urethane groups formed in step a) is between 20% and 40%, preferably between 25% and 35%.

26) Use of a polymer containing urethane groups dispersed in a rubber composition according to one of claims 1 to 21, the rubber composition being based on at least one elastomer by an in situ thermomechanical mixing reaction of said at least one elastomer with a reinforcing filler, precursors of said polymer and a chain extender,

to reduce the Payne effect in the composition at a temperature T inclusive of between -30 ° C and 100 ° C, the Payne effect being quantified by said ratio G ′ 0.5% / G ′ 20% of storage moduli G 'relating to the complex shear moduli G of the composition,

in comparison with a rubber mixture based on said at least one elastomer, devoid of said polymer containing urethane groups and comprising said reinforcing filler in an amount in phr equal to the sum of phr, in the composition, of said reinforcing filler and of said polymer with urethane groups.

27) Use of a polymer containing urethane groups according to claim 26, the composition comprising (phr: parts by weight per 100 parts of elastomer (s)) from 10 to 40 phr of a carbon black as reinforcing filler and from 10 to 50 phr of said polymer containing urethane groups,

to reduce said ratio G ′ 0.5% / G ′ 20% by more than 40%, and optionally furthermore to keep the Shore A hardness of the composition to within 15%,

in comparison with said rubber mixture devoid of said polymer containing urethane groups and comprising said carbon black in an amount in phr equal to the sum of the phr, in the composition, of said carbon black and of said polymer containing urethane groups.