METHOD FOR PRODUCING A DIENE ELASTOMER MODIFIED WITH A 1,3-DIPOLAR COMPOUND BY REACTIVE EXTRUSION

Description

[0001] The present invention relates to a method for modifying a diene elastomer by grafting a 1,3-dipolar compound.

[0002] The modification of a diene elastomer by a 1,3-dipolar compound is known. The modification occurs via a [3+2] cycloaddition reaction of the 1,3-dipolar compound onto the double bonds of the diene units of the elastomer. Very often, the 1,3-dipolar compound used is one that, in addition to the dipole, carries a chemical functional group, thus allowing the grafting of dangling chemical functions onto the elastomer. Such modified elastomers can be used in tire rubber compounds. These modification reactions can be carried out in solution or in bulk, for example, in an internal mixer, as described in documents WO 2012007442, WO 2015059271, and WO 2015177105.When the modified elastomer is intended for use in a rubber compound containing a reinforcing filler, and several tens or hundreds of kilograms of diene elastomer are modified in an internal mixer by thermomechanical mixing of the diene elastomer and the 1,3-dipolar compound, the modification reaction is followed by the addition and incorporation of the reinforcing filler, and possibly other ingredients of the compound. The mixture is then thermomechanically mixed in the internal mixer, and the resulting compound is collected. Upon collection, the compound is found to fall as a powder, making it very difficult to use in subsequent stages of preparing the rubber compound. Furthermore, the grafting yield is found to be fluctuating and can reach relatively low values.

[0003] The Applicants, continuing their efforts, have found a new mass process which makes it possible to obtain high and substantially constant grafting yields when large quantities of elastomer are modified.

[0004] The invention therefore relates to a process for preparing a diene elastomer modified by a 1,3-dipolar compound by a grafting reaction, characterized in that it comprises a step a) of reactive extrusion of a mixture of a diene elastomer and a 1,3-dipolar compound in a twin-screw extruder comprising a barrel, a set of two worm screws, a feeding zone, a mixing zone and a die, the extrusion temperature being greater than 100°C.

[0005] Another object of the invention is a process for preparing a rubber composition based on a diene elastomer modified by a 1,3-dipolar compound and a reinforcing filler, which comprises the following steps: a step a) of reactive extrusion of a mixture of a diene elastomer and a 1,3-dipolar compound in a twin-screw extruder comprising a barrel, a set of two worm screws, a feeding zone, a mixing zone and a die to form a modified diene elastomer, the extrusion temperature being greater than 100°C, a step of incorporating a reinforcing filler into the modified diene elastomer, by thermomechanical mixing in an internal mixer.

[0006] The invention also relates to a diene elastomer granule modified by a grafting reaction of a 1,3-dipolar compound that can be obtained by the process according to the invention in which step a) is followed by a granulation step of the modified diene elastomer.

[0007] Another object of the invention is the use of granules according to the invention in a rubber composition comprising a reinforcing filler. I. DETAILED DESCRIPTION OF THE INVENTION :

[0008] In this description, unless expressly stated otherwise, all percentages (%) given are percentages by mass. The abbreviation "pc" means parts by weight per hundred parts of elastomer (of the total elastomers if more than one elastomer is present).

[0009] Any range of values ​​designated by the expression "between a and b" represents the range of values ​​from more than a to less than b (i.e., bounds a and b excluded) while any range of values ​​designated by the expression "from a to b" means the range of values ​​from a to b (i.e., including the strict bounds a and b).

[0010] The expression "based on" composition is meant in this description as a composition comprising the mixture and / or the in situ reaction product of the different constituents used, some of these basic constituents (for example the elastomer, the filler or other additive classically used in a rubber composition intended for the manufacture of tires) being capable of, or intended to react with each other, at least in part, during the different manufacturing phases of the composition intended for the manufacture of tires.

[0011] The compounds mentioned in the description may be of fossil origin or bio-based. In the latter case, they may be partially or totally derived from biomass or obtained from renewable raw materials derived from biomass. This includes, in particular, polymers and 1,3-dipolar compounds.

[0012] By "dienic" elastomer (or indistinctly rubber) should be understood in a known way as one (or more) elastomer consisting at least in part (i.e., a homopolymer or a copolymer) of diene monomer units (monomers bearing two carbon-carbon double bonds, conjugated or not).

[0013] Having given these definitions, the term diene elastomer, which can be used in compositions according to the invention, is understood more specifically as: (a) - any homopolymer of a conjugated diene monomer, in particular any homopolymer obtained by polymerization of a conjugated diene monomer having from 4 to 12 carbon atoms; (b) - any copolymer obtained by copolymerization of one or more dienes conjugated to each other or with one or more aromatic vinyl compounds having from 8 to 20 carbon atoms; (c) - any ternary copolymer obtained by copolymerization of ethylene, of an α-olefin having 3 to 6 carbon atoms with an unconjugated diene monomer having from 6 to 12 carbon atoms, such as, for example, elastomers obtained from ethylene, propylene with an unconjugated diene monomer of the aforementioned type such as, in particular, hexadiene-1,4, ethylidene norbornene, dicyclopentadiene;(d) - any copolymer obtained by copolymerization of one or more dienes conjugated with ethylene, an acyclic aliphatic α-monoolefin having 3 to 18 carbon atoms or a mixture thereof such as those described in documents WO 2005028526, WO 2004035639 and WO 2007054224;

[0014] Preferably, the diene elastomer is chosen from the group consisting of polybutadienes, polyisoprenes, butadiene copolymers, isoprene copolymers, and mixtures thereof. Such copolymers are more preferably chosen from the group consisting of butadiene-styrene copolymers (SBR), isoprene-butadiene copolymers (BIR), isoprene-styrene copolymers (SIR), isoprene-butadiene-styrene copolymers (SBIR), and ethylene-butadiene copolymers. Most preferably, the diene elastomer is a polyisoprene comprising more than 90 mol% of 1,4-cis linkage. Synthetic polyisoprenes with such a microstructure are particularly suitable.

[0015] Diene elastomers preferably contain an antioxidant. The antioxidant can be any antioxidant, including any conventionally used to protect diene elastomers. Of course, the antioxidant can be a mixture of several antioxidants. Examples include antioxidants belonging to the phenol, amine, quinone, tocopherol, tocotrienol, and thiol families. As an example, suitable are derivatives of paraphenylenediamine, also commonly known as substituted para-phenylenediamines, such as N-1,3-dimethylbutyl-N'-phenyl-p-phenylenediamine (better known by the abbreviated term "6-PPD"), N-isopropyl-N'-phenyl-p-phenylenediamine (abbreviated "I-PPD"), phenyl-cyclohexyl-p-phenylenediamine, N,N'-di(1,4-dimethylpentyl)-p-phenylenediamine, N,N'-diaryl-p-phenylenediamine ("DTPD"), diaryl-p-phenylenediamine ("DAPD"), 2,4,6-tris-(N-1,4-dimethylpentyl-p-phenylenediamino)-1,3,5-Triazine, and mixtures of such diamines, quinoline derivatives ("TMQ") such as, for example, 1,2-dihydro-2,2,4-trimethylquinoline and 6-ethoxy-1,2-dihydro-2,2,4-trimethylquinoline, phenol derivatives, in particular those of cresol, such as 2,2'-methylenebis(6-tert-butyl-4-methylphenol) known as "AO2246", copolymers of dicyclopentadiene and paracresol, in particular the antioxidant "Struktol LA229" from Schill & Seilacher, derivatives of substituted diphenylamines or triphenylamines, as described, for example, in applications WO 2007 / 121936, WO 2008 / 055683 and WO2009 / 138460, in particular the 4,4'-bis(isopropylamino)-triphenylamine, 4,4'-bis(1,3-dimethylbutylamino)-triphenylamine, 4,4'-bis(1,4-dimethylpentylamino)-triphenylamine, 4,4',4"-tris(1,3-dimethylbutylamino)-triphenylamine, 4,4',4"-tris(1,4-dimethylpentylamino)-triphenylamine.

[0016] Typically, the antioxidant concentration ranges from 1 to 20 parts per million (ppm). The presence of antioxidants in the diene elastomer helps to minimize, or even limit, macrostructural changes that could occur during its passage through the extruder. The maximum antioxidant concentration in the diene elastomer can be justified for economic reasons, namely minimizing the cost associated with the antioxidant itself.

[0017] Diene elastomer can be an extended elastomer. An extended elastomer is defined as one to which a plasticizer has been added, notably through conventional means, for example, in the finishing process of diene elastomer. Examples of plasticizers include the extending oils traditionally used in tire rubber compounds, such as naphthenic oils, paraffinic oils, DAE oils, and MES oils. Medium Extracted Solvates), TDAE oils ( Treated Distillate Aromatic Extracts ), RAE oils ( Residual Aromatic Extract oils ), TRAE oils ( Treated Residual Aromatic Extract ) and SRAE oils ( Safety Residual Aromatic Extract oils ), mineral oils.

[0018] The term 1,3-dipolar compound is understood according to the definition given by IUPAC. The dipole of the 1,3-dipolar compound may be a nitrile oxide, a nitrone, or a nitrile imine, preferably a nitrile oxide.

[0019] When the dipole of the 1,3-dipolar compound is a nitrile oxide, the compound preferably comprises a benzene ring substituted by the dipole. Even more preferably, the benzene ring is also ortho-substituted to the dipole. These preferred embodiments further optimize the grafting yield. Indeed, the presence of the benzene ring in the structure of the 1,3-dipolar compound, particularly when ortho-substituted, confers greater stability to the compound during storage before contact with the diene elastomer.

[0020] In addition to the dipole, the 1,3-dipolar compound may bear another chemical function. Examples of such chemical functions include groups that can associate by hydrogen bonds, such as those described in document WO 2012007441, particularly groups containing a 5-member diazotized and carbonyl heterocycle such as the 2-oxoimidazolidin-1-yl group; and groups that can interact with the surface of a reinforcing filler commonly used in tire rubber compositions, such as imidazole, ester, oxazoline, thiazoline, alkoxysilane, and allyletin groups, as described respectively in documents WO 2015059271, WO2015177105, and WO 2006045088.

[0021] The amount of 1,3-dipolar compound in the mixture of diene elastomer and 1,3-dipolar compound, expressed in moles per 100 moles of elastomer motifs, can vary to a wide extent, for example in a range of 0.01 to 50, preferably from 0.01 to 3. It is indexed to the grafting yield and the desired grafting rate on the diene elastomer which depends on the intended application of the modified diene elastomer.

[0022] The process according to the invention has as its essential characteristic a reactive extrusion step of the mixture of the diene elastomer and the 1,3-dipolar compound. This step is called step a). The extruder useful for the purposes of the invention is a twin-screw extruder. Conventionally, it comprises a barrel, a feeding zone, a mixing zone, a set of two worm screws, and a die.

[0023] The diene elastomer and the 1,3-dipolar compound are introduced into the extruder's feeding zone, typically via the hopper. While the diene elastomer is being fed into the extruder, the 1,3-dipolar compound is simultaneously introduced.

[0024] Alternatively, the diene elastomer and the 1,3-dipolar compound are introduced separately into the extruder. The diene elastomer is introduced into the extruder's feed zone, while the 1,3-dipolar compound is introduced downstream of the diene elastomer. Typically, the diene elastomer is fed into the extruder via the feed hopper that is conventionally fitted to an extruder. The 1,3-dipolar compound is preferably introduced into the extruder's mixing zone, conventionally downstream of the feed zone. This alternative is advantageous because it allows for a more homogeneous distribution of the 1,3-dipolar compound within the diene elastomer. Consequently, the grafting rate of the diene elastomer remains virtually constant at the die exit.

[0025] In the extruder, the diene elastomer heats up under mechanical stress, particularly in the mixing zone. Additional heat, for example from a heat transfer fluid circulating in a double jacket of the extruder, may be necessary to further increase the extrusion temperature. The extrusion temperature is the setpoint temperature applied inside the extruder, specifically at the barrel. The extrusion temperature is above 100°C. Preferably, the extrusion temperature is between 110 and 140°C. Even more preferably, the extrusion temperature in the area extending from the mixing zone to the end of the screw assembly closest to the die is between 110 and 140°C. Such a temperature range provides the best compromise between grafting efficiency and productivity.Productivity is governed by the flow rate of the diene elastomer in the extruder, which is itself adjusted according to the residence time that one wishes to apply to the diene elastomer in the extruder from the mixing zone to the extruder die.

[0026] Residence times are typically short, at most 5 minutes, preferably less than 5 minutes. Residence times ranging from 30 seconds to 2 minutes can be sufficient to achieve both good grafting yield and precise control of the grafting rate, thus ensuring good reproducibility of the process. These process performance levels are achieved without compromising the properties of the diene elastomer, since the process does not involve cross-linking of the diene elastomer. The process according to the invention allows extrusion without applying any special atmospheric conditions inside the casing. Typically, extrusion takes place under ambient air. At the extruder outlet, after passing through the die, the modified diene elastomer is recovered. The modified diene elastomer is a diene elastomer in which the diene units have reacted by [3+2] cycloaddition reaction with the 1,3-dipolar compound.

[0027] Upon exiting the extruder, the modified diene elastomer is preferably cut into granules using a granulation step, a process well known to those skilled in the art. Any device known for cutting diene elastomers in synthetic rubber manufacturing processes can be used, such as a hammer or a granulator. It is positioned after the die. To prevent the granules from clumping, they can be dusted with talc and then, if necessary, placed in suitable packaging for transport, storage, or handling.

[0028] The granules that can be obtained according to the process according to the invention can be used as an elastomer in a rubber composition comprising a reinforcing filler.

[0029] The reinforcing filler can be any type of filler known for its ability to strengthen a rubber composition suitable for tire manufacturing. Examples include an organic filler such as carbon black, an inorganic reinforcing filler such as silica combined with a known coupling agent, or a mixture of both types of filler. Such a reinforcing filler typically consists of nanoparticles with an average size (by mass) of less than one micrometer, generally less than 500 nm, most often between 20 and 200 nm, and particularly and preferentially between 20 and 150 nm.

[0030] The process for preparing the rubber compound is characterized by the essential feature of comprising step a) defined according to any one of the embodiments of preparing the modified diene elastomer. It further comprises a step of incorporating the reinforcing filler into the modified diene elastomer, which is extruded, preferably in the form of granules, in an internal mixer. A granulation step of the modified diene elastomer may follow step a) and precede the step of incorporating the reinforcing filler.

[0031] The incorporation of the reinforcing filler into the modified and extruded diene elastomer can be carried out in a manner known to those skilled in the art and conventionally by performing high-temperature thermomechanical mixing (the so-called "non-productive" phase), up to a maximum temperature between 110°C and 200°C, preferably between 130°C and 185°C. During this "non-productive" phase, all the constituents necessary for the rubber compound, with the exception of the crosslinking system, can also be introduced into the internal mixer. The total mixing time in this non-productive phase is preferably between 2 and 10 minutes.After cooling the mixture thus obtained during the first non-productive phase, the low-temperature crosslinking system is then incorporated, generally in an external mixer such as a roller mixer; the whole is then mixed (productive phase) for a few minutes, for example between 5 and 15 min.

[0032] The final composition thus obtained is then calendered, for example in the form of a sheet or plate, particularly for characterization in the laboratory, or extruded in the form of a rubber profile usable, for example, as a semi-finished article for tires, such as a tire tread.

[0033] The aforementioned features of the present invention, as well as others, will be better understood upon reading the following description of examples of embodiments of the invention, given by way of illustration and not limitation. II. EXAMPLES OF THE IMPLEMENTATION OF THE INVENTION II.1-Examples not conforming to the invention:

[0034] The modified diene elastomers and the rubber compositions containing them are prepared according to a process not in accordance with the invention, but according to the following process described in the prior art, in this case document WO 2012007442.

[0035] Step 1: 150 kg of diene elastomer and a target quantity of 1,3-dipolar compound are introduced into an internal mixer with an initial vessel temperature of approximately 50°C. The mixture is then mixed by thermomechanical kneading for 2 minutes until a temperature of 120°C is reached.

[0036] Step 2:In the internal mixer containing the modified diene elastomer, the reinforcing filler (silica, 60 parts per cubic meter; carbon black N234, 3 parts per cubic meter) and the coupling agent (Si69, 6 parts per cubic meter) are introduced. After one to two minutes of mixing, the various other ingredients (antioxidant, 3 parts per cubic meter; paraffin, 1 part per cubic meter; stearic acid, 2.5 parts per cubic meter; ZnO, 3 parts per cubic meter) are added, with the exception of the vulcanizing system. A thermomechanical process (non-productive phase) is then carried out in a single step (total mixing time approximately 5 minutes) until a maximum "drop" temperature of 160°C is reached. The resulting rubber compound (composition NC1) is collected.

[0037] The 1,3-dipolar compound used is a compound whose dipole is a nitrile oxide, in this case 2,4,6-trimethyl-3-(2-(2-oxoimidazolidin-1-yl)ethoxy)benzonitroxide. The diene elastomer is an antioxidant polyisoprene, Nipol 2200 grade from Nippon Zeon.

[0038] The procedure described above is repeated to manufacture four other compositions, respectively NC2 to NC5. II.2-Examples according to the invention :

[0039] The modified diene elastomers C1 and C2 are prepared according to the process according to the invention.

[0040] Operating conditions: temperature 120°C, screw rotation speed 40 rpm, residence time 2 min.

[0041] The diene elastomer is fed into the extruder through the feed hopper as a strip at a rate of 1.7 kg / h. Simultaneously, the 1,3-dipolar compound is manually fed through the feed hopper as a powder to achieve an average flow rate of 0.5 g / min. The modified diene elastomer C1 is recovered at the die outlet. The procedure described above is repeated to manufacture another modified diene elastomer, C2. II.3-Results:

[0042] We define a target rate, an actual rate of 1,3-dipolar compound, a grafted rate, a grafting yield and a process efficiency.

[0043] The target rate is the quantity of 1,3-dipolar compound, expressed in moles per 100 moles of isoprene units, that has been weighed and introduced: in the internal mixer at stage 1 for NC1 to NC5, in the extruder via the feed hopper for C1 and C2;

[0044] The actual rate is the quantity, determined by nuclear magnetic resonance (NMR) analysis, of the 1,3-dipolar compound in both grafted and ungrafted forms on the diene elastomer at the end of stage 2 for NC1 to NC5, at the exit of the program for C1 and C2;

[0045] The grafted rate corresponds to the quantity, determined by NMR analysis, of 1,3-dipolar compound in the form grafted onto the diene elastomer at the end of step 2 for NC1 to NC5, at the exit of the line for C1 to C2. The grafting yield is the ratio between the amount of 1,3-dipolar compound grafted onto the diene elastomer and the actual rate; The process efficiency is the ratio between the amount of 1,3-dipolar compound grafted onto the diene elastomer and the target rate.

[0046] These quantities are determined by NMR analysis on diene elastomers or on NC1 to NC5 compositions. NMR analysis method:

[0047] 1D 1<H NMR experiments use a single pulse sequence with a 30° flip angle, the number of repetitions is 128 scans with a 5-second recycle time.

[0048] The two-dimensional 1<H / 13<C NMR experiments are HSQC (Heteronuclear Single Quantum Coherence) and HMBC (Heteronuclear Multiple-Bond Correlation) type sequences for 1<H / 13<C correlations at short (1<J) and long distance (3<J) respectively. The experiments are performed at 25 °C.

[0049] Two parts of the same sample are analyzed: one crude (directly from the end of the synthesis) and the other coagulated (devoid of any free molecules, in particular of ungrafted 1,3-dipolar compound).

[0050] Chemical shifts are calibrated with respect to the protonated impurity of CDCl3 δ(1<H) = 7.20 ppm, referenced on the TMS (δ(1<H) = 0.06 ppm).

[0051] Scheme 1 illustrates the motifs of the isoprene units modified by the grafting of the 1,3-dipolar compound, R representing the remainder of the polyisoprene chain.

[0052] The characteristic chemical shifts of the protons of the 1,3-dipolar compound grafted onto the polyisoprene chain (IR) are shown in Table 1.

[0053] Quantifications were performed from the integration of 1D 1<H NMR spectra using data acquisition software.

[0054] The massifs considered for quantification are: ✔ 1 proton of IR1-2 between 5.8 ppm and 5.6 ppm, ✔ 1 proton of IR1-4 between 5.4 and 4.7 ppm, ✔ 2 protons of IR3-4 between 4.7 and 4.5 ppm, ✔ 8 protons of the 1,3-dipolar compound (4 CH 2 ) between 3.9 and 3.3 ppm.

[0055] Using the integration of the 1D 1<H NMR spectrum of the raw portion of the sample The quantification of the total 1,3-dipolar compound motif in grafted and non-grafted form can be performed as a percentage of motifs as follows:

[0056] Using the integration of the 1D 1<H NMR spectrum of the coagulated part of the sample The quantification of the grafted 1,3-dipolar compound motif can be performed as a percentage of motifs as follows:

[0057] For analyses performed on compositions, sample preparation is carried out in rotors filled with the composition or elastomer to be analyzed and a deuterated solvent that allows swelling, generally deuterated chloroform (CDCl3). The quantities of sample used are adjusted to obtain spectra with sufficient sensitivity and resolution.

[0058] For analyses performed on modified elastomers, 25 mg of sample are solubilized in 1 mL of deuterated chloroform (CDCl3) for field-frequency locking.

[0059] The results are shown in Table 2.

[0060] For the examples not conforming to the invention, the actual yield is much lower than the target yield, clearly indicating a loss of 1,3-dipolar compound in the process. Furthermore, grafting yields vary considerably, ranging from 52% to 82%, demonstrating a lack of reproducibility in the process. It can also be noted that the process efficiency is low (at most 40%) if the grafting yield is calculated not based on the actual 1,3-dipolar compound yield, but on the target yield.

[0061] For the examples according to the invention, although the actual rate is lower than the target rate, the grafting yields are constant and at 100%, demonstrating control of the grafting reaction in the process according to the invention. Furthermore, a significantly improved process efficiency (of at least 50%) is also observed. These process performances are achieved without cross-linking of the diene elastomer.

[0062] The use of granules according to the invention in a rubber composition improves the efficiency and reproducibility of the manufacturing process for diene elastomer-based rubber compositions with a 1,3-dipolar compound, due to the absence of fluctuation in the diene elastomer grafting rate during the elastomer modification process. Since the grafting rate is constant, the changes in the properties of the rubber compositions resulting from the elastomer modification are more controlled and therefore more reproducible. Table 1 δ 1< H (ppm) Pattern 6,81 Chapter No. 5 3,39 Chapter 2, No. 4 3,65 Chapter 2, No. 3 3,51 Chapter 2, No. 2 3,78 Chapter 2, No. 1 Table 2 NC1 NC2 NC3 NC4 NC5 C1 C2 Target rate (% mol) 0.30 0.30 0.30 0.30 0.30 0.40 0.40 Actual rate introduced (%mol) 0.17 0.14 0.16 0.15 0.08 0.20 0.22 Grafting yield (%) 59 82 52 67 75 100 100 Process efficiency (%) 33 40 30 33 40 50 55

Claims

1. Process for the preparation of a diene elastomer modified by a 1,3-dipolar compound by a grafting reaction, characterized in that it comprises a stage a) of reactive extrusion of a mixture of a diene elastomer and of a 1,3-dipolar compound in a twin-screw extruder comprising a barrel, a set of two endless screws, a feed zone, a compounding zone and a die, the extrusion temperature being greater than 100°C.

2. Process according to Claim 1, in which the diene elastomer and the 1,3-dipolar compound are introduced simultaneously into the feed zone of the extruder.

3. Process according to Claim 1, in which the diene elastomer and the 1,3-dipolar compound are introduced separately into the extruder, the introduction of the diene elastomer being carried out in the feed zone of the extruder, the introduction of the 1,3-dipolar compound being carried out downstream of the introduction of the diene elastomer.

4. Process according to Claim 1 or 3, in which the 1,3-dipolar compound is introduced into the compounding zone of the extruder.

5. Process according to any one of Claims 1 to 4, in which the extrusion temperature is between 110 and 140°C.

6. Process according to any one of Claims 1 to 5, in which the extrusion temperature in the zone ranging from the compounding zone up to the end of the set of the two screws closest to the die is between 110 and 140°C.

7. Process according to any one of Claims 1 to 6, in which the dipole of the 1,3-dipolar compound is a nitrile oxide.

8. Process according to Claim 7, in which the 1,3-dipolar compound comprises a benzene ring substituted by the nitrile oxide dipole, the benzene ring being preferably substituted in the position ortho to the dipole.

9. Process according to any one of Claims 1 to 8, in which the 1,3-dipolar compound contains a group containing a 5-membered dinitrogenous and carbonylated heterocycle, preferably the 2-oxoimidazolidin-1-yl group.

10. Process according to any one of Claims 1 to 9, in which the diene elastomer is selected from the group consisting of polybutadienes, polyisoprenes, butadiene copolymers, isoprene copolymers and their mixtures, preferably is a polyisoprene comprising more than 90 mol% of cis-1,4 bonding, preferably a synthetic polyisoprene.

11. Process according to any one of Claims 1 to 10, in which the diene elastomer contains an antioxidant.

12. Process according to any one of Claims 1 to 11, in which stage a) is followed by a stage of granulation of the modified diene elastomer at the outlet of the extruder.

13. Process for the preparation of a rubber composition based on a diene elastomer modified by a 1,3-dipolar compound by a grafting reaction and on a reinforcing filler which comprises the following stages: - a stage a) of reactive extrusion of a mixture of a diene elastomer and of a 1,3-dipolar compound in a twin-screw extruder comprising a barrel, a set of two endless screws, a feed zone, a compounding zone and a die in order to form a modified diene elastomer, the extrusion temperature being greater than 100°C, - a stage of incorporation of a reinforcing filler in the modified diene elastomer by thermomechanical kneading in an internal mixer, preferably a stage of granulation of the modified diene elastomer follows stage a) and precedes the stage of incorporation of the reinforcing filler.

14. Granule of diene elastomer modified by a reaction of grafting a 1,3-dipolar compound capable of being obtained by the process defined according to Claim 12.

15. Use of granules according to Claim 14 in a rubber composition comprising a reinforcing filler.