COMPOUND COMPRISING AN EPOXIDE GROUP

Abstract

Disclosed is a compound of formula (I) below:

##STR00001##

in which: T is chosen from the group consisting of CN.sup.+—O.sup.−, CH═NOH and CHO; A represents a C.sub.6-C.sub.14 arenediyl ring optionally substituted with one or more identical or different, preferably saturated, linear or branched aliphatic hydrocarbon chains; represents a divalent C.sub.5-C.sub.12 hydrocarbon group optionally comprising one or more heteroatoms; and X.sub.1, X.sub.2 and X.sub.3, which may be identical or different, represent a hydrogen atom, a C.sub.1-C.sub.6 alkyl or a C.sub.6-C.sub.14 aryl. Also disclosed is a process for synthesizing compounds of formula (I), a modified polymer obtained by grafting the compound of formula (I) with T=CN.sup.+—O.sup.−, a composition based on the modified polymer and an additive, and to a composition based on at least one additive and at least one compound of formula (I) with T=CN.sup.+—O.sup.−.

Claims

1.-15. (canceled)

16. A compound of formula (I) ##STR00035## in which: T is selected from the group consisting of CN.sup.+—O.sup.−, CH═NOH and CHO; A represents a C.sub.6-C.sub.14 arenediyl ring optionally substituted with one or more identical or different linear or branched aliphatic hydrocarbon chains; E represents a C.sub.5-C.sub.12 divalent hydrocarbon group optionally comprising one or more heteroatoms; and X.sub.1, X.sub.2 and X.sub.3, which may be identical or different, represent a hydrogen atom, a C.sub.1-C.sub.6 alkyl or a C.sub.6-C.sub.14 aryl.

17. The compound of formula (I) according to claim 16, wherein T is CH═NOH.

18. The compound of formula (I) according to claim 16, wherein T is CHO.

19. The compound of formula (I) according to claim 16, wherein T is CN.sup.+—O.sup.−.

20. The compound of formula (I) according to claim 16, wherein E represents a divalent C.sub.5-C.sub.10 hydrocarbon group.

21. The compound of formula (I) according to claim 16, wherein E represents a C.sub.5-C.sub.10 alkanediyl.

22. The compound of formula (I) according to claim 16, wherein X.sub.1, X.sub.2 and X.sub.3, which may be identical or different, are chosen from the group consisting of a hydrogen atom, a methyl, an ethyl or a phenyl.

23. The compound of formula (I) according to claim 16, wherein X.sub.1, X.sub.2 and X.sub.3 represent a hydrogen atom.

24. The compound of formula (I) according to claim 16, wherein the compound of formula (I) is a compound of formulae (II) or (III) ##STR00036## in which a group chosen from R.sub.1 to R.sub.5 of formula (II) and a group chosen from R.sub.1 to R.sub.7 of formula (III) denote the group of formula (IV) below ##STR00037## in which symbol (*) represents an attachment to (II) or to (III), wherein the four groups of formula (II) chosen from R.sub.1 to R.sub.5 other than the one denoting the group of formula (IV) and the six groups of formula (III) chosen from R.sub.1 to R.sub.7 other than the one denoting the group of formula (IV), which may be identical or different, represent, independently of each other, a hydrogen atom or a linear or branched aliphatic hydrocarbon chain.

25. The compound of formula (I) according to claim 24, wherein the compound of formula (I) is a compound of formula (V) ##STR00038##

26. A modified polymer obtained by grafting at least one compound of formula (I) according to claim 16 onto at least one unsaturated carbon-carbon bond of a chain of an initial polymer.

27. A composition based on at least one additive and on a compound of formula (I) according to claim 16.

28. A composition based on at least one additive and on the modified polymer according to claim 26.

29. A process for preparing a compound of formula (Ia), the process comprising at least one reaction of a compound of formula (Ib) with an oxidizing agent in the presence of at least one organic solvent SL1 according to the reaction scheme ##STR00039## where: A represents a C.sub.6-C.sub.14 arenediyl ring optionally substituted with one or more identical or different linear or branched aliphatic hydrocarbon chains; E represents a C.sub.5-C.sub.12 divalent hydrocarbon group optionally comprising one or more heteroatoms; and X.sub.1, X.sub.2 and X.sub.3, which may be identical or different, represent a hydrogen atom, a C.sub.1-C.sub.6 alkyl or a C.sub.6-C.sub.14 aryl.

30. The process according to claim 29 further comprising a step of reacting a compound of formula (Ic) with an aqueous solution of hydroxylamine NH.sub.2OH according to the reaction scheme ##STR00040##

31. The process according to claim 30 further comprising a step of reacting a compound of formula (VII) with a compound of formula (VIII) in the presence of at least one base and at a temperature ranging from 20° C. to 150° C. according to the reaction scheme ##STR00041## where Z represents a nucleofugal group.

Description

EXAMPLES

[0195] The examples that follow make it possible to illustrate the invention; however, said invention shall not be limited to these examples alone.

1. Methods

1.1 Measurement of the Number-Average (Mn) and Weight-Average (Mw) Molar Masses and of the Polydispersity Index of the Elastomers

[0196] Size exclusion chromatography (SEC) is used. SEC makes it possible to separate macromolecules in solution according to their size through columns filled with a porous gel. The macromolecules are separated according to their hydrodynamic volume, the bulkiest being eluted first.

[0197] Without being an absolute method, SEC makes it possible to comprehend the distribution of the molar masses of an elastomer. The various number-average molar masses (Mn) and weight-average molar masses (Mw) may be determined from commercial standards and the polydispersity index (PDI=Mw/Mn) may be calculated via a “Moore” calibration.

Preparation of the Elastomer Test Sample

[0198] There is no specific treatment of the elastomer sample before analysis. The latter is simply dissolved, at a concentration of approximately 1 g/l, in chloroform or in the following mixture: tetrahydrofuran+1 vol % of diisopropylamine+1 vol % of triethylamine+1 vol % of distilled water (vol %=% by volume). The solution is then filtered through a filter with a porosity of 0.45 μm before injection.

SEC Analysis

[0199] The apparatus used is a Waters Alliance chromatograph. The elution solvent is the following mixture: tetrahydrofuran+1 vol % of diisopropylamine+1 vol % of triethylamine or chloroform, according to the solvent used for the dissolution of the elastomer. The flow rate is 0.7 ml/min, the temperature of the system is 35° C. and the analysis time is 90 min. A set of four Waters columns in series, having the commercial names Styragel HMW7, Styragel HMW6E and two Styragel HT6E, is used.

[0200] The volume of the solution of the elastomer sample injected is 100 μl. The detector is a Waters 2410 differential refractometer with a wavelength of 810 nm. The software for processing the chromatographic data is the Waters Empower system. The calculated average molar masses are relative to a calibration curve produced from PSS Ready Cal-Kit commercial polystyrene standards.

1.2. Characterizations of the Molecules

[0201] The structural analysis and also the determination of the molar purities of the synthesis molecules are performed by an NMR analysis. The spectra are acquired on a Brüker Avance 3 400 MHz spectrometer equipped with a “5 mm BBFO Z-grad broad band” probe. The quantitative .sup.1H NMR experiment uses a 30° single pulse sequence and a repetition time of 3 seconds between each of the 64 acquisitions. The samples are dissolved in a deuterated solvent, deuterated dimethyl sulfoxide (DMSO) unless otherwise indicated. The deuterated solvent is also used for the “lock” signal. For example, calibration is performed on the signal of the protons of the deuterated DMSO at 2.44 ppm relative to a TMS reference at 0 ppm. The .sup.1H NMR spectrum coupled with the 2D .sup.1H/.sup.13C HSQC and .sup.1H/.sup.13C HMBC experiments enable the structural determination of the molecules (cf. assignment tables). The molar quantifications are performed from the quantitative 1D .sup.1H NMR spectrum.

[0202] The analysis by mass spectrometry is performed by a direct-injection electrospray ionization method (DI/ESI). The analyses were performed on a Bruker HCT spectrometer (flow rate 600 μl/min, pressure of the nebulizer gas 10 psi, flow rate of the nebulizer gas 4 l/min).

1.3. Characterizations of the Compounds Grafted to the Diene Elastomers

[0203] The determination of the molar content of the compounds grafted to the diene elastomers is performed by an NMR analysis. The spectra are acquired on a Bruker 500 MHz spectrometer equipped with a “5 mm BBFO Z-grad CryoProbe” probe. The quantitative .sup.1H NMR experiment uses a simple 30° pulse sequence and a repetition time of 5 seconds between each acquisition. The samples are dissolved in deuterated chloroform (CDC.sub.13) for the purpose of obtaining a “lock” signal. 2D NMR experiments made it possible to confirm the nature of the grafted unit by means of the chemical shifts of the carbon atoms and protons.

1.4. Dynamic Properties of the Rubber Compositions:

[0204] The dynamic properties G* and tan(δ).sub.max are measured on a viscosity analyser (Metravib VA4000) according to Standard ASTM D5992-96. The response of a sample of vulcanized composition (cylindrical test specimen with a thickness of 4 mm and with a cross section of 400 mm.sup.2), subjected to a simple alternating sinusoidal shear stress, at a frequency of 10 Hz, at a temperature of 60° C., is recorded. A strain amplitude sweep is performed from 0.1% to 100% peak-to-peak (forward cycle) and then from 100% to 0.1% peak-to-peak (reverse cycle).

[0205] The results used are the complex dynamic shear modulus G* at 25% strain (G*.sub.25% return), the dynamic loss factor tan(δ) at 60° C. and the difference in modulus (ΔG*) between the values at 0.1% and 100% strain (Payne effect). For the return, the value of the complex dynamic shear modulus G* at 25% strain, denoted G*.sub.25% return at 60° C. and the maximum value of the dynamic loss factor tan(δ) observed, denoted tan(δ).sub.max at 60° C., are recorded.

[0206] The results are shown in base 100, the arbitrary value 100 being assigned to the control in order to calculate and compare subsequently tan(δ).sub.max at 60° C., G*.sub.25% return at 60° C. and ΔG* of the different samples tested.

[0207] For tan(δ).sub.max at 60° C., the value in base 100 for the test sample is calculated according to the operation: (tan(δ).sub.max at 60° C. value of the test sample/tan(δ).sub.max at 60° C. value of the control)×100. In this way, a result of less than 100 indicates a decrease in the hysteresis, which corresponds to an improvement in the rolling resistance performance.

[0208] For G*.sub.25% return at 60° C., the value in base 100 for the test sample is calculated according to the operation: (G*.sub.25% return at 60° C. value of the test sample/G*.sub.25% return at 60° C. value of the control)×100. In this way, a result of greater than 100 indicates an improvement in the complex dynamic shear modulus G*.sub.25% return at 60° C., which corroborates an improvement in the stiffness of the material.

[0209] For (ΔG*), the value in base 100 for the test sample is calculated according to the operation: (ΔG* value of the test sample/ΔG* value of the control)×100. In this way, a result of less than 100 indicates a decrease in the difference in modulus, i.e. an increase in the linearization of the rubber composition.

1.6. Tensile Test

[0210] These tensile tests make it possible to determine the elasticity stresses. Unless otherwise indicated, they are performed in accordance with the French standard NF T46-002 of September 1988. Processing the tensile test recordings also makes it possible to plot the curve of modulus as a function of the elongation. At first elongation, the nominal secant modulus, calculated with respect to the initial cross section of the test specimen, (or apparent stress, in MPa) is measured at 100% elongation, denoted MSA100, and at 300% elongation, denoted MSA300. All these tensile test measurements are performed under the standard temperature conditions (23±2° C.) according to Standard NF T 46-002.

[0211] The MSA300/MSA100 ratio is the reinforcement index. The value in base 100 for the test sample is calculated according to the operation: (MSA300/MSA100 value of the test sample/MSA300/MSA100 value of the control)×100. In this way, a result of greater than 100 indicates an improvement in the reinforcement index.

2. Synthesis of the Compounds

2.1. Synthesis of Compound A: 2-((9-Oxiran-2-Yl)Nonyl)Oxy)-1-Naphthonitrile Oxide

[0212] ##STR00029##

[0213] Compound A is synthesized according to the following reaction scheme:

##STR00030##

11-Bromo-1-undecene, 3-chloroperbenzoic acid, 2-hydroxy-1-naphthaldehyde, hydroxylamine and trimethylamine are commercial products. They may be obtained from Sigma-Aldrich.

2.1.1. Step a1: Preparation of 2-(9-Bromononyl)Oxirane

[0214] 10 g of 11-bromo-1-undecene (42.9 mmol) are dissolved in 200 ml of CH.sub.2Cl.sub.2. 11.84 g of 3-chloroperbenzoic acid (68.6 mmol or 1.4 eq, MCPBA) are then added in several portions over about 15 minutes and the reaction medium is stirred for 15 hours. The white precipitate is filtered off and washed with CH.sub.2Cl.sub.2 (2×20 ml). The filtrate is then stirred in the presence of aqueous NaHSO.sub.3 solution (40 g of NaHSO.sub.3 in 400 ml of distilled water) for 5 hours at room temperature (20° C.). The organic phase is recovered by decantation and is left to react with a solution of NaHCO.sub.3 (40 g) in water (400 ml) for 5 hours. After separation by decantation, the residual aqueous phase is extracted with CH.sub.2Cl.sub.2. The organic phases are combined, then dried with Na.sub.2SO.sub.4 and concentrated under reduced pressure (12 mbar; bath temperature=30° C.). A yellow oil is obtained (10.613 g, 42.90 mmol, 99% yield). The molar purity is >90% (.sup.1H NMR).

##STR00031##

TABLE-US-00001 TABLE 1 No. δ .sup.1H (ppm) δ .sup.13C (ppm) 1 2.39 and 2.68 47.0 2 2.84 52.3 3 1.49 32.5 4 1.38 25.9 5 1.25 28.7 to 29.4 6 7 8 9 1.36 28.1 10 1.79 32.8 11 3.34 33.9 Solvent CDCl.sub.3

2.1.2 Step a2: Synthesis of 2-((9-(Oxiran-2-Yl)Nonyl)Oxy)-1-Naphthaldehyde

[0215] A suspension of 2-hydroxy-l-naphthaldehyde (11.05 g; 64.2 mmol), 2-(9-bromononyl)oxirane (15.99 g; 64.2 mmol) and K.sub.2CO.sub.3 (8.87 g; 64.2 mmol) in 20 ml of N,N-dimethylformamide (DMF) is heated at 70° C. for 3 hours with stirring at 500 rpm (rpm =rotations per minute). The reaction medium is then poured into 250 ml of distilled water and then extracted with ethyl acetate (4×60 ml). The organic phases were combined and then evaporated under reduced pressure (bath temperature=40° C., 10 mbar) to obtain a brown oil (24.95 g). The product is then purified by column chromatography on silica gel, eluting with a 3/1 (v/v) mixture of petroleum ether/ethyl acetate.

[0216] The residual yellow oil is triturated with petroleum ether, allowing crystallization. The precipitate is filtered off and air-dried. A yellowish solid (14.545 g, 42.7 mmol, 67% yield) is obtained. The molar purity is greater than 97 mol %.

##STR00032##

TABLE-US-00002 TABLE 2 No. δ .sup.1H (ppm) δ .sup.13C (ppm) 1 10.87  192.1 2 — 116.9 3 — 131.6 4 9.22 125.0 5 7.55 129.8 6 7.35 124.7 7 7.70 128.2 8 — 128.5 9 7.97 137.4 10 7.21 113.7 11 — 163.7 12 4.17 69.7 13 1.82 29.4 14 1.46 25.9 15 from 1.24 to 1.35 29.4 16 17 18 19 1.40 20 1.46 32.5 21 2.84 52.3 22 2.40 and 2.68 47.1 Solvent: CDCl.sub.3

2.1.3 Step a3: Synthesis of 2-((9-(Oxiran-2-Yl)Nonyl)Oxy)-1-Naphthaldehyde Oxime

[0217] 1.521 g of hydroxylamine (23.02 mmol, i.e. 1.5 equivalents) are added, at room temperature 20° C., to a suspension of 2-((9-(oxiran-2-yl)nonyl)oxy)-1-naphthaldehyde (5.225 g, 15.35 mmol) in ethanol (50 ml). The reaction mixture is stirred for 3 hours; at the end of the reaction, a yellow solid precipitates. 30 ml of distilled water are then added and the medium is stirred for a further 10 minutes. The precipitate obtained is filtered off, washed with 2×5 ml of a distilled water/ethanol (1:1, v/v) mixture and then air-dried. A yellow solid (4.979 g, 14.01 mol, 91% yield) is obtained. The molar purity is 93% (NMR).

##STR00033##

TABLE-US-00003 TABLE 3 No. δ .sup.1H (ppm) δ .sup.13C (ppm) 1 8.84 148.1 2 — 113.9 3 — 131.7 4 8.80 125.8 5 7.47 127.8 6 7.32 124.0 7 7.72 128.3 8 — 129.1 9 7.79 132.0 10 7.19 114.0 11 — 156.6 12 4.08 69.8 13 1.79 29.4 14 1.47 26.0 15 1.28 29.2 to 29.4 16 17 18 19 1.38 26.0 20 1.47 32.4 21 2.86 52.4 22 2.42 and 2.69 47.1 Solvent: CDCl.sub.3

2.1.4 Step a4: Synthesis of 2-((9-(Oxiran-2-Yl)Nonyl)Oxy)-1-Naphthonitrile N-Oxide (Compound

[0218] 1.824 g of trimethylamine (18.03 mmol) and 2.037 g of N-chlorosuccinimide (15.25 mmol) are added in several portions over 10 to 12 minutes to a solution of 2-((9-(oxiran-2-yl)nonyl)oxy)-1-naphthaldehyde oxime (4.929 g; 13.87 mmol) in 100 ml CHCl.sub.3 cooled to a temperature of 0-2° C. The reaction mixture is stirred cold for 90 minutes. The organic phase is then washed with distilled water (3×50 ml), dried with Na.sub.2SO.sub.4 and concentrated under reduced pressure (bath temperature=25° C.; up to 2 mbar) to give 5.005 g of a yellow solid. The product is redissolved in a minimum volume of ethyl acetate to obtain a homogeneous solution; petroleum ether is then poured in until the first signs of cloudiness appear (not very clear either, it would be preferable to indicate the volume to be poured in). This solution is filtered on a column of silica gel (1=5 cm) while eluting with an ethyl acetate/petroleum ether (1:3, v/v) mixture. The permeate is evaporated under reduced pressure (bath temperature=25° C., down to 1 mbar). A yellow solid (4.593 g, 12.99 mol, 94% yield) with a melting point of 52-53° C. is obtained. The molar purity is 92% (.sup.1H NMR).

##STR00034##

TABLE-US-00004 TABLE 4 No. δ .sup.1H (ppm) δ .sup.13C (ppm) 1 — — 2 — 96.9 3 — 134.3  4 7.93 124.0  5 7.55 128.4 to 128.7 6 7.37 124.9  7 7.76 128.4 to 128.7 8 — 9 7.86 132.6  10 7.19 113.4  11 — 161.0  12 4.16 69.7 13 1.83 29.4 14 1.48 25.9 15 1.30 29.2 to 29.4 16 17 18 19 1.41 25.9 20 1.48 32.5 21 2.85 52.3 22 2.41 and 2.69 47.1 Solvent: CDCl.sub.3

2.2. Synthesis of 2-(Glycidyloxy)-1-Naphthonitrile Oxide

[0219] 2-(Glycidyloxy)-1-naphthonitrile oxide, compound B, is synthesized according to the 5 procedure described in patent application US 2012/0046418 A1.

3. Production of the Modified Diene Elastomers

[0220] 3.1 Rubber Modified with Compound A

[0221] 2-((9-(Oxiran-2-yl)nonyl)oxy)-1-naphthonitrile oxide (811 mg; 2.3 mmol, i.e. a mole fraction of 0.3 mol %), compound A obtained according to the process described above, with an NMR purity of 96 mol %, is incorporated into 50 g of natural rubber on an open mill (external mixer at 30° C.). The mixture is homogenized in 15 turnover passes. This mixing phase is followed by a heat treatment at 120° C. for 10 minutes under a press at a pressure of 10 bar.

[0222] Analysis by .sup.1H NMR made it possible to demonstrate a molar degree of grafting of 0.16 mol % with a molar grafting yield of 54%.

3.2 Rubber Modified with Compound B

[0223] 2-(Glycidyloxy)-1-naphthonitrile oxide (564 mg, 2.34 mmol, i.e. a mole fraction of 0.3 mol %), with an NMR purity of 94 mol %, compound B, is incorporated into 50 g of natural rubber on an open mill (external mixer at 30° C.). The mixture is homogenized in 15 turnover passes. This mixing phase is followed by a heat treatment (10 minutes at 120° C.) under a press at a pressure of 10 bar.

[0224] Analysis by .sup.1H NMR made it possible to determine the molar degree of grafting of 0.16 mol % and the molar grafting yield of 54%.

3.3 Synthetic Polyisoprene Modified with Compound A

[0225] 2-((9-(Oxiran-2-yl)nonyl)oxy)-1-naphthonitrile oxide (811 mg; 2.3 mmol, i.e. a mole fraction of 0.3 mol %), compound A obtained according to the process described above, with an NMR purity of 96 mol %, is incorporated into 50 g of synthetic polyisoprene (containing 99.35% by weight of cis 1,4-isoprene units and 0.65% by weight of 3,4-isoprene units; Mn=375 000 g/mol and PDI=3.6 measured according to the method described above) on an open mill (external mixer at 30° C.). The mixture is homogenized in 15 turnover passes. This mixing phase is followed by a heat treatment at 120° C. for 10 minutes under a press at a pressure of 10 bar.

[0226] Analysis by .sup.1H NMR made it possible to demonstrate a molar degree of grafting of 0.22 mol % with a molar grafting yield of 74%.

3.4 Synthetic Polyisoprene Modified with Compound B

[0227] 2-(Glycidyloxy)-1-naphthonitrile oxide (564 mg; 2.34 mmol, i.e. a mole fraction of 0.3 mol %), with an NMR purity of 94 mol %, compound B, is incorporated into 50 g of synthetic polyisoprene (containing 99.35% by weight of cis 1,4-isoprene units and 0.65% by weight of 3,4-isoprene units; Mn=375 000 g/mol and PDI=3.6 measured according to the method described above) on an open mill (external mixer at 30° C.). The mixture is homogenized in 15 turnover passes. This mixing phase is followed by a heat treatment (10 minutes at 120° C.) under a press at a pressure of 10 bar.

[0228] Analysis by .sup.1H NMR made it possible to demonstrate a molar degree of grafting of 0.16 mol % with a molar grafting yield of 54%.

4. Ingredients Used in the Rubber Compositions

[0229] (1) Silica, Zeosil 1165MP, sold by Solvay;

[0230] (2) Bis[3-(triethoxysilyl)propyl] tetrasulfide (TESPT) silane, sold by Evonik under the reference Si69;

[0231] (3) Carbon black of N234 grade, sold by Cabot Corporation;

[0232] (4) N-(1,3-Dimethylbutyl)-N-phenyl-para-phenylenediamine, sold by Flexsys under the reference Santoflex 6-PPD;

[0233] (5) 2,2,4-Trimethyl-1,2-dihydroquinoline, sold by the company Flexsys;

[0234] (6) Zinc oxide (industrial grade), sold by the company Umicore;

[0235] (7) Stearin, Pristerene 4031, sold by the company Uniqema;

[0236] (8) N-Cyclohexyl-2-benzothiazolesulfenamide, sold by Flexsys under the reference Santocure CBS.

[0237] (9) natural rubber modified with compound B, obtained according to the process described in paragraph 3.1;

[0238] (10) natural rubber modified with compound A, obtained according to the process described in paragraph 3.2;

[0239] (11) synthetic polyisoprene modified with compound B, obtained according to the process described in paragraph 3.3;

[0240] (12) synthetic polyisoprene modified with compound A, obtained according to the process described in paragraph 3.4.

5. Test 1

[0241] The aim of this test is to show the improvement in the reinforcement of a rubber composition comprising natural rubber modified with the compound of the invention (composition C2) relative to a comparative composition (composition C1).

[0242] The contents of the various constituents of these compositions, expressed in phr, parts by weight per hundred parts by weight of elastomer, are presented in Table 5.

TABLE-US-00005 TABLE 5 C1 C2 Diene elastomer modified with compound B (9) 100 — Diene elastomer modified with compound A (10) — 100 Reinforcing filler (1) 55 55 Coupling agent (2) 5.5 5.5 Carbon black (3) 3 3 Antioxidant (4) 1.5 1.5 TMQ (5) 1 1 Paraffin 1 1 ZnO (6) 2.7 2.7 Stearic acid (7) 2.5 2.5 CBS (8) 1.8 1.8 Sulfur 1.5 1.5

[0243] Compositions C1 and C2 comprise the same number of moles of grafted compound A or B, namely 0.3 mol %.

[0244] Compositions C1 and C2 are prepared in the following manner: the natural rubber modified with compound A or with compound B is introduced into an 85 cm.sup.3 Polylab internal mixer, filled to 70%, the initial vessel temperature of which is approximately 110° C.

[0245] Next, for each of the compositions, the reinforcing filler(s), the agent for coupling the filler with the diene elastomer and then, after kneading for one to two minutes, the various other ingredients, with the exception of the vulcanization system, are introduced. Thermomechanical work (non-productive phase) is then performed in one step, lasting a total of about 5 to 6 minutes, until a maximum drop temperature of 160° C. is reached.

[0246] The mixture thus obtained is recovered and cooled and the vulcanization system (sulfur and the sulfenamide-type accelerator) is then added on an external mixer (homofinisher) at 23° C., the whole being mixed (productive phase) for approximately 5 to 12 minutes.

[0247] The compositions thus obtained are subsequently calendered either in the form of slabs (thickness of 2 to 3 mm) or of thin sheets of rubber for measurement of their physical or mechanical properties.

[0248] The rubber properties of these compositions are measured after baking at 150° C. for 60 minutes. The results obtained are given in Table 6.

TABLE-US-00006 TABLE 6 Compositions C1 C2 MA300/MA100 100 108 ΔG* 100 88 Tan(δ).sub.max at 60° C. 100 88 G*.sub.25% return at 60° C. 100 104

[0249] The rubber composition C2 of the invention shows, relative to the comparative composition C1, a significant improvement in the hysteresis properties while also showing an increase in the linearization (ΔG*) and an improvement in the reinforcement index (MA300/M100). Surprisingly, this significant improvement in hysteresis is not achieved at the expense of the 25 baked stiffness properties. On the contrary, the baked stiffness properties are even improved relative to the comparative composition.

5. Test 2

[0250] The aim of this test is to show the improvement in the reinforcement of a rubber composition comprising a synthetic polyisoprene modified with the compound of the invention (composition C4) relative to a comparative composition (composition C3).

[0251] The contents of the various constituents of these compositions, expressed in phr, part by weight per hundred parts by weight of elastomer, are presented in Table 7.

TABLE-US-00007 TABLE 7 C3 C4 Diene elastomer modified with compound B (11) 100 — Diene elastomer modified with compound A (12) — 100 Reinforcing filler (1) 55 55 Coupling agent (2) 5.5 5.5 Carbon black (3) 3 3 Antioxidant (4) 1.5 1.5 TMQ (5) 1 1 Paraffin 1 1 ZnO (6) 2.7 2.7 Stearic acid (7) 2.5 2.5 CBS (8) 1.8 1.8 Sulfur 1.5 1.5

[0252] Compositions C3 and C4 comprise the same number of moles of grafted compound A or B, namely 0.3 mol %.

[0253] Compositions C3 and C4 are prepared according to the process described above for compositions C1 and C2.

[0254] The rubber properties of these compositions are measured after curing at 150° C. for 60 minutes. The results obtained are given in Table 8.

TABLE-US-00008 TABLE 8 Compositions C3 C4 MA300/MA100 100 110 ΔG* 100 83 Tan(δ).sub.max at 60° C. 100 82 G*.sub.25% return at 60° C. 100 105

[0255] The rubber composition C4 of the invention shows, relative to the comparative composition C3, a significant improvement in the hysteresis properties while also showing an increase in the linearization (ΔG*) and an improvement in the reinforcement index (MA300/M100). Surprisingly, this significant improvement in hysteresis is not achieved at the expense of the baked stiffness properties. On the contrary, the baked stiffness properties are even improved relative to the comparative composition.