PROCESS FOR PREPARING RANDOM BUTADIENE-ISOPRENE COPOLYMERS HAVING A HIGHT CONTENT OF CIS-1,4 UNITS

Abstract

Process for preparing a random butadiene-isoprene copolymer having a high content of cis-1,4 units comprising copolymerizing butadiene and isoprene, in the presence of at least one organic solvent, and a catalytic system prepared in situ comprising: (a.sub.1) at least one neodymium carboxylate soluble in said organic solvent, containing a variable amount of water, the H2O/Nd molar ratio being between 0.001/1 and 0.50/1; (a.sub.2) at least one aluminum alkyl compound; (a.sub.3) at least one aluminum alkyl compound containing at least one halogen atom. The random butadiene-isoprene copolymer having a high content of cis-1,4 units obtained from the abovementioned process may be advantageously used in a number of applications ranging from the modification of plastics [for example, obtainment of high impact polystyrene (HIPS)], to the production of tires, in particular the production of tire treads and/or of tire sidewalls.

Claims

1. A process for the preparation a random butadiene-isoprene copolymer having a high content of cis-1,4 units comprising copolymerizing butadiene and isoprene in the presence of at least one organic solvent and of a catalytic system prepared in situ comprising: (a.sub.1) at least one neodymium carboxylate which is soluble in said organic solvent, containing a variable amount of water, the H.sub.2O/Nd molar ratio being between 0.001/1 and 0.50/1; (a.sub.2) at least one aluminum alkyl compound; (a.sub.3) at least one aluminum alkyl compound containing at least one halogen atom.

2. The process for the preparation of a random butadiene-isoprene copolymer having a high content of cis-1,4 units according to claim 1, in which said butadiene and said isoprene are present in a total amount (i.e. butadiene amount+isoprene amount) between 5% by weight and 40% by weight with respect to the total weight of the organic solvent.

3. The process for the preparation of a random butadiene-isoprene copolymer having a high content of cis-1,4 units according to claim 1, in which said organic solvent is selected from: saturated aliphatic hydrocarbons such as butane, n-pentane, n-hexane, n-heptane, or mixtures thereof; saturated cycloaliphatic hydrocarbons such as cyclohexane, cyclopentane, or mixtures thereof; monoolefins such as 1-butene, 2-butene, or mixtures thereof; halogenated hydrocarbons such as methylene chloride, chloroform, carbon tetrachloride, trichlorethylene, perchlorethylene, 1,2-dichloroethane, chlorobenzene, bromobenzene, chlorotoluene, or mixtures thereof.

4. The process for the preparation of a random butadiene-isoprene copolymer having a high content of cis-1,4 units according to claim 1, in which said neodymium carboxylate (a.sub.1) is neodymium versatate [Nd (versatate).sub.3].

5. The process for the preparation of a random butadiene-isoprene copolymer having a high content of cis-1,4 units according to claim 1, in which said neodymium carboxylate is used in an amount of between 0.1 mmoles to 10 mmoles per 1000 g of monomers (butadiene+isoprene) being polymerized.

6. The process for the preparation of a random butadiene-isoprene copolymer having a high content of cis-1,4 units according to claim 1, in which said aluminum alkyl compound (a.sub.2) is selected from compounds having general formula (I) or (II):
Al(R.sup.1).sub.3  (I)
AlH(R.sup.1).sub.2  (II) in which R.sup.1 represents a linear or branched C.sub.1-C.sub.10 alkyl group.

7. The process for the preparation of a random butadiene-isoprene copolymer having a high content of cis-1,4 units according to claim 1, in which said alkyl aluminum compound containing at least one halogen atom (a.sub.3) is selected from compounds having general formula (III):
AlXnR.sup.2.sub.3-n  (III) in which R.sup.2 represents a linear or branched C.sub.1-C.sub.10 alkyl group, X represents a halogen atom such as chlorine, bromine, fluorine, iodine.

8. The process for the preparation of a random butadiene-isoprene copolymer having a high content of cis-1,4 units according to claim 1, in which the molar ratio between the aluminum alkyl compound (a.sub.2) and the neodymium carboxylate (a.sub.1) is between 1/1 and 30/1.

9. The process for the preparation of a random butadiene-isoprene copolymer having a high content of cis-1,4 units according to claim 1, in which the molar ratio between the halogen present in the aluminum alkyl compound containing at least one halogen atom (a.sub.3) and the neodymium carboxylate (a.sub.1) is between 2.5/1 and 5.5/1.

10. The process for the preparation of a random butadiene-isoprene copolymer having a high content of cis-1,4 units according to claim 1, in which the aluminum compound containing at least one halogen atom (a.sub.3) is used in such an amount that the ratio between the halogen present in said compound (a.sub.3) and the aluminum alkyl compound (a.sub.2) is between 0.4 and 5.

11. The process for the preparation of a random butadiene-isoprene copolymer having a high content of cis-1,4 units according to claim 1, in which said process is carried out: at a temperature of between 20° C. and 150° C. and/or at a pressure of between 1 bar and 10 bar.

12. The random butadiene-isoprene copolymer having a high content of cis-1,4 units having the following characteristics: cis-1,4-butadiene units content greater than or equal to 92%; cis-1,4-isoprene units content greater than or equal to 92%; isoprene randomization index (R.I.) calculated according to the following equation:
R.I.=[(BI+IB)/2]/total moles of bound isoprene in which BI and IB are the amounts of butadiene-isoprene and isoprene-butadiene dyad, respectively, present in the random butadiene-isoprene copolymer having a high content of cis-1,4 units, of between 0.5 and 1; a weight ratio (% by weight) between bound butadiene and bound isoprene of between 99:1 and 40:60; a single glass transition temperature value (Tg), an indicator of the actual randomization of both comonomers, of between −107° C. to −65° C.; a Mooney viscosity (ML1+4@100° C.) of between 30 and 70; a molecular weight distribution, indicated as a polydispersion index corresponding to the ratio between the weight average molecular weight (M.sub.w) and the number average molecular weight (M.sub.n) (i.e. the ratio M.sub.w/M.sub.n) of between 2.0 and 3.2.

13. A vulcanizable elastomer composition comprising at least one random butadiene-isoprene copolymer having a high content of cis-1,4 units obtained according to claim 1, at least one filler selected from silica, carbon black, or mixtures thereof, and at least one vulcanizing agent.

14. A vulcanized product obtained from vulcanization of the vulcanizable elastomer composition according to claim 13.

15. The process for the preparation of a random butadiene-isoprene copolymer having a high content of cis-1,4 units according to claim 2, in which said butadiene and said isoprene are present in a total amount (i.e. butadiene amount+isoprene amount) between 10% by weight and 25% by weight with respect to the total weight of the organic solvent.

16. The process for the preparation of a random butadiene-isoprene copolymer having a high content of cis-1,4 units according to claim 1, wherein said organic solvent is n-hexane.

17. The process for the preparation of a random butadiene-isoprene copolymer having a high content of cis-1,4 units according to claim 1, in which said neodymium carboxylate (a.sub.1) is neodymium versatate [Nd (versatate).sub.3], wherein the neodymium versatate [Nd (versatate).sub.3] has a free versatic acid/Nd molar ratio of less than 2, wherein the neodymium carboxylate is used in an amount of between 0.5 mmol and 5 mmol per 1000 g of monomers (butadiene+isoprene) being polymerized, wherein said aluminum alkyl compound (a.sub.2) is selected from compounds having general formula (I) or (II):
Al(R.sup.1).sub.3  (I)
AlH(R.sup.1).sub.2  (II) in which R.sup.1 represents a linear or branched C.sub.1-C.sub.10 alkyl group selected from the group consisting of triethyl aluminum (TEA), tri-isobutyl aluminum, diethyl aluminum hydride, di-isobutyl aluminum hydride (DIBAH), wherein said alkyl aluminum compound containing at least one halogen atom (a.sub.3) is selected from compounds having general formula (III):
AlXnR.sup.2.sub.3-n  (III) in which R.sup.2 is chlorine from diethyl aluminum chloride (DEAC) or ethyl aluminum sesquichloride (EASC), wherein n is 1 or 2, wherein the molar ratio between the aluminum alkyl compound (a.sub.2) and the neodymium carboxylate (a.sub.1) is between 1/1 and 10/1, wherein the molar ratio between the halogen present in the aluminum alkyl compound containing at least one halogen atom (a.sub.3) and the neodymium carboxylate (a.sub.1) is between 2.8/1 and 5.2/1, wherein the aluminum compound containing at least one halogen atom (a.sub.3) is used in such an amount that the ratio between the halogen present in said compound (a.sub.3) and the aluminum alkyl compound (a.sub.2) is between 0.5 and 2.0, in which said process is carried out: at a temperature of between 40° C. and 120° C.; and/or at a pressure of between 3 bar and 7 bar.

18. The process for the preparation of a random butadiene-isoprene copolymer having a high content of cis-1,4 units according to claim 1, in which said neodymium carboxylate (a.sub.1) is neodymium versatate [Nd (versatate).sub.3], wherein said aluminum alkyl compound (a.sub.2) is selected from compounds having general formula (I) or (II):
Al(R.sup.1).sub.3  (I)
AlH(R.sup.1).sub.2  (II) in which R.sup.1 is di-isobutyl aluminum hydride (DIBAH), in which said alkyl aluminum compound containing at least one halogen atom (a.sub.3) is selected from compounds having general formula (III):
AlXnR.sup.2.sub.3-n  (III) in which R.sup.2 is chlorine from diethyl aluminum chloride (DEAC), and wherein n is 1 or 2.

19. The random butadiene-isoprene copolymer having a high content of cis-1,4 units of claim 12 having the following characteristics: cis-1,4-butadiene units content between 95% and 99%; cis-1,4-isoprene units content between 95% and 99.95%; BI and IB are between 0.6 and 0.9; a weight ratio (% by weight) between bound butadiene and bound isoprene of between 90:10 and 45:55; Tg of between −105° C. and −85° C.; a Mooney viscosity between 35 and 65.

20. A vulcanized product obtained from vulcanization of the vulcanizable elastomer composition according to claim 12.

Description

EXAMPLES

[0072] The following characterization and analysis techniques were used.

[0073] .sup.13C-NMR Analysis—Study of Degree of Randomization, Determination of the Content of Cis-1.4 Units and of the Content of Bound Butadiene and Isoprene.

[0074] The signals relating to the butadiene and isoprene dyads (II; IB+BI; BB) can be attributed through .sup.13C-NMR analysis, as described, for example, in Lobach M. I. et al., “Polymer” (1977), Vol. 18, Issue 11, p. 1196-1198, in random butadiene-isoprene copolymers having a high content of cis-1,4 units according to the present invention with the possibility of defining the distribution of the co-monomers along the polymer chain and of obtaining the monomer composition, also considering the microstructure of said copolymers in terms of (cis/trans) 1,2- and 1,4-butadiene units and (cis/trans) 3,4- and 1,4-isoprene units.

[0075] The abovementioned .sup.13C-NMR analysis was carried out as follows.

[0076] Instrumentation [0077] BRUKER AVANCE-DPX-300 MHz spectrometer; [0078] Frequencies 300.13 (1H); 75.47 (13C); [0079] 10 mm .sup.1H/.sup.13C (Proton/Carbon) Dual “Probe” for high temperatures; [0080] “.sup.13C-Frequency”: 75 MHz.

[0081] Acquisition Parameters: [0082] Acquisition temperature: 79.85+99.85° C.; [0083] Number of points acquired (TD): 64; [0084] Size: 32; [0085] Line broadening (LB): 1.2 Hz; [0086] Spectral window (SW): 18000 Hz (240.0+0.0 ppm); [0087] PULPROG*: “zgig_bilev”; program based on INVGATE; [0088] CPDPRG2*: “waltz16_bilev”; decoupling program; (*) Acquisition programme with decoupling to eliminate the NOE (Nuclear Overhauser Enhancement) effect. [0089] Relaxation time (D1): 10 sec; [0090] Pulse angle: 90°; [0091] No of scans: 6600 (s/n=>750); [0092] Calculation of the s/n ratio:spectral amplitude from 200+10 ppm, automatic noise calculation between 60+50 ppm, calculation of the signal from the reference peak** of 27.9+27.3 ppm; (**) Peak assignment in the .sup.13C-NMR spectrum is based on TMS (Tetramethylsilane). [0093] Data acquisition/processing program: TOPSPIN.

Sample Preparation

[0094] For this purpose, approximately 250 mg of random butadiene-isoprene copolymer having a high content of cis-1,4 units to be analyzed, were dissolved in 2 ml of 1,1,2,2-tetrachloroethane-d2 (99.5% deuterated solvent—Aldrich), from which oxygen was previously removed by bubbling nitrogen at reduced pressure (about 15 minutes per 2 ml of 1,1,2,2-tetrachloroethane-d2) in a 10 mm calibrated glass NMR tube (˜12.5% w/v). The solution obtained was kept in a controlled temperature oven (80° C.-100° C.) with stirring for about 3-4 hours to eliminate the formation of concentration gradients, and in a flow of nitrogen to avoid degradation phenomena.

[0095] Spectral Assignment

[0096] Usually, for a copolymer obtained by the copolymerization of a monomer A and a monomer B, there are 4 (2.sup.2) dyads: AA, AB+BA and BB.

[0097] Actually, in the case of the random butadiene-isoprene copolymer having a high content of cis-1,4 units according to the present invention, the number of dyads will be higher because the isoprene unit is not symmetrical due to the presence of methyl, and consequently the two methyls (11 and 14) have a different chemical environment: the total list of actual dyads present in said random butadiene-isoprene copolymer having a high content of cis-1,4 units is shown in Table 1.

[0098] Table 2 instead shows the assignment of peaks in the .sup.13C-NMR spectrum of the random butadiene-isoprene copolymers having a high content of cis-1,4 units according to the present invention, used for quantitative analysis.

TABLE-US-00001 TABLE 1 (Dyads of a butadiene-isoprene copolymer) Isoprene dyads I1(i4) I1(b) I4(b) I4(i1) Butadiene dyads B(b) B(i1) B(i4) —

TABLE-US-00002 TABLE 2 (Assignment of peaks in the .sup.13C-NMR spectrum of random butadiene-isoprene copolymers having a high content of cis-1,4 units according to the present invention) Integration Signal Description* ranges (ppm) A Olefinic CH.sub.2, 1,2-butadiene units 116 + 113 B Aliphatic CH.sub.2, trans-1,4-butadiene units 32.74 + 32.64 1 I.sub.1(i.sub.4) dyad 32.64 + 32.38 2 I1(b) dyad 32.38 + 31.95 3 I4(b) dyad 28.68 + 28.08 4 B(i1) dyad 28.08 + 27.82 C, 5 B(b) dyad and aliphatic CH.sub.2, 27.82 + 27.10 1,2-butadiene units 6 I4(i1) dyad 26.90 + 26.42 7 B(i4) dyad 26.42 + 25.78 D CH.sub.3 cis-1,4-isoprene units 23.79 + 22.95 E CH.sub.3 3,4-isoprene units 19.53 + 19.15 F CH.sub.3 trans-1,4-isoprene units 16.5 + 16.0 *tetramethylsilane (TMS) reference and 1,1,2,2-tetracloroethane-d2 solvent (99.5% deuterated solvent).

[0099] Determination of Randomization Index (R.I.)

[0100] The Randomization Index (R.I.) was determined as follows.

[0101] Given the equivalence of the following dyads:

I1(i4)≡I4(i1);I1(b)≡I4(b);B(i1)≡B(i4)

there is a simplification for calculating the distribution of dyads, which may be summarized as follows:

II=I1(i4)/DEN with the I1(i4) integral of signal 1;

BI+IB=[I1(b)+I4(b)]/DEN with the I1(b) and I4(b) integrals respectively of signals 2 and 3;

BB=[B(b)×0.5]/DEN with the B(b) integral of signal 5;

in which: [0102] II and BB are the dyads formed by two identical monomer units (in this case isoprene and butadiene, respectively); [0103] BI and IB are the dyads formed by two different monomer units (in this case butadiene and isoprene, and isoprene and butadiene, respectively); [0104] DEN=[I1(i4)+I1(b)+I4(b)+B(b)*0.5].

[0105] In random butadiene-isoprene copolymers having a high content of cis-1,4 units according to the present invention there is a higher concentration of (IB+BI) dyads that can be used to evaluate the degree of randomization of the chain, while in block copolymers the percentage of (IB+BI) dyads decreases and there is an increase in the percentage of i and BB sequences, which dominate.

[0106] A Randomization index (R.I.) for the isoprene monomer is then defined according to the following equation:

R.I.=[(BI+IB)/2]/total moles of bound isoprene

BI and IB have the same meanings as reported above.

[0107] In the case of the random butadiene-isoprene copolymer having a high content of cis-1,4 units according to the present invention the Randomization Index, as reported above, is between 0.5 and 1.

[0108] Determination of Monomer Composition by Dyads

[0109] The monomer composition, in terms of total butadiene and isoprene units, in the random butadiene-isoprene copolymers having a high content of cis-1,4 units according to the present invention in question was obtained according to the following mathematical relationships:

[PIs] % mol=II+0.5*(IB+BI)

[PBu] % mol=BB+0.5*(IB+BI)

in which: PIs is polyisoprene; PBu is polybutadiene; II, BI, IB and BB, have the same meanings as above.

[0110] Taking into account the molecular weight of each monomer unit it is possible to obtain the composition in terms of % by weight.

[0111] Determination of the Isomer Configuration of Chain-Bound Monomers

[0112] Through the identification and integration of the characteristic signals of the (cis and trans) 1,4- and 1,2-butadiene units and of the (cis and trans) 1,4- and 3,4-isoprene units, it is possible to obtain the isomer ratios for both polybutadiene and polyisoprene according to the following equations.

[0113] Polybutadiene:

f.sub.P1,2-Bu=I.sub.A/(I.sub.A+I.sub.B+I.sub.C);

1,2-butadiene units=f.sub.P1,2-Bu*PBu.sub.tot;

f.sub.Pcis-1,4-Bu=I.sub.B/(I.sub.A+I.sub.B+I.sub.C);

cis-1,4-butadiene units=f.sub.Pcis-1,4-Bu*PBu.sub.tot;

f.sub.Ptrans-1,4-Bu=I.sub.C/(I.sub.A+I.sub.B+I.sub.C);

trans-1,4-butadiene units=f.sub.Ptrans-1,4-Bu*PBu.sub.tot;

in which: [0114] f.sub.PBui=molar fraction of the i-th isomer unit; [0115] I.sub.A=integral relating to the signal of the 1,2-butadiene units; [0116] I.sub.B=integral relating to the signal of the cis-1,4-butadiene units; [0117] I.sub.C=integral relating to the signal of the trans-1,4-butadiene units; [0118] PBu.sub.tot=total molar percentage calculated from the dyads.

Polyisoprene:

[0119]
f.sub.P3,4-Is=I.sub.E/(I.sub.D+I.sub.E+I.sub.F);

3,4-isoprene units=f.sub.P3,4-Is*PIs.sub.tot;

f.sub.Pcis-1,4-Bu=I.sub.D/(I.sub.D+I.sub.E+I.sub.F);

cis-1,4-butadiene units=f.sub.Pcis 1,4-Is*PIS.sub.tot;

f.sub.Ptran-1,4-Is=I.sub.F/(I.sub.D+I.sub.E+I.sub.F);

trans-1,4-isoprene units=f.sub.Ptrans-1,4-Is*PIs.sub.tot;

in which: [0120] f.sub.PIs i=molar fraction of the i-th isomer unit; [0121] I.sub.D=integral relative to the signal of the cis-1,4-isoprene units; [0122] I.sub.E=integral relative to the signal of the 3,4-Isoprene units; [0123] I.sub.F=integral relative to the signal of the trans-1,4-isoprene units; [0124] PIs.sub.tot=total molar percentage calculated from the dyads.

[0125] Taking into account the molecular weight of each monomer unit it is possible to obtain each isomer composition in terms of % by weight.

[0126] Determination of Molecular Weight Distribution (MWD)

[0127] The molecular weight distribution (MWD) of the random butadiene-isoprene copolymers having a high content of cis-1,4 units according to the present invention, from which the polydispersion index corresponding to the ratio between the weight average molecular weight (M.sub.w) and the numerical average molecular weight (M.sub.n) is also obtained (i.e. the M.sub.w/M.sub.n ratio), was determined by gel permeation chromatography analysis (GPC), conveniently carried out according to standard method ISO 11344:2004, IDT (“Rubber, raw, synthetic—Determination of the molecular-mass distribution of solution polymers by gel permeation chromatography”), using polystyrene as standard and applying the universal calibration method.

[0128] Mooney Viscosity

[0129] Mooney viscosity (ML1+4@100° C.) was determined according to ASTM D1646. In particular, the viscosity of the random butadiene-isoprene copolymers having a high content of cis-1,4 units according to the present invention was measured at 100° C., with a wide rotor (L), preheating for 1 minute and measuring for 4 minutes.

[0130] Thermal Analysis (DSC): Determination of the Glass Transition Temperature (Tg)

[0131] Thermal analysis (DSC) (“Differential Scanning Calorimetry”) to determine the glass transition temperature (Tg) of the random butadiene-isoprene copolymers having a high content of cis-1,4 units according to the present invention, was carried out using a DSC Q1000 differential scanning calorimeter from TA Instruments.

[0132] The following thermal cycle was applied to the samples for this purpose (T=temperature; v=scanning speed): [0133] cooling of the sample from T=+25° C. to T=−130° C. at v=200° C./min; [0134] conditioning of the sample from T=−130° C.; [0135] subsequent heating from T=−130° C. to T=+100° C. at v=10° C./min (standard scan) (1st cycle); [0136] cooling of the sample from T=+100° C. to T=−130° C. at v=200° C./min; [0137] conditioning of the sample by T=−130° C.; [0138] subsequent heating from T=−130° C. to T=+100° C. at v=10° C./min (standard scan) (2nd cycle).

[0139] The glass transition temperature (Tg) was calculated on the 2nd cycle so as to reset any thermal history of the sample through the first standard scan (1st cycle).

Example 1 (Invention)

Preparation of Random Butadiene-Isoprene Copolymer (in a Batch Reactor)

[0140] 450 g of anhydrous hydrocarbon solvent comprising a mixture of hexanes (a mixture comprising 35% by weight with respect to the total weight of the mixture of n-hexane and 65% by weight with respect to the total weight of the mixture of a mixture comprising n-hexane isomers, aliphatic compounds and cycloaliphatic compounds from Cepsa) were loaded into a 1 litre reactor with stirrer and cooling system and heated to 60° C. Subsequently, 45 g of anhydrous 1,3-butadiene (from Versalis S.p.A.), 5 g of anhydrous isoprene (from Versalis S.p.A.) (% by weight butadiene:isoprene=90:10), 0.658 ml (0.625 mmol) of a 0.95 M solution of di-isobutyl aluminum hydride (DIBAH) (from Akzo Nobel) in n-hexane (from Aldrich) (molar ratio DIBAH/Nd=5), 0.665 ml (0.375 mmol) of a 0.564 M solution of diethyl aluminum chloride (DEAC) (Al/Cl molar ratio=1; from Albemarle) in n-hexane (from Albemarle) (molar ratio Cl/Nd=3) were added to said solvent, in that order, and the whole was kept, under stirring, at 60° C., for 25 minutes. Subsequently, 0.24 ml (0.125 mmol) of a 0.514 M solution of neodymium versatate [Nd(versatate).sub.3] [2.5 mmol Nd per 1000 g of monomers (1,3-butadiene+isoprene)] with a free molar acid/Nd ratio of 0.3 and a molar H.sub.2O/Nd ratio of 0.018 (from Rhodia) in n-hexane (from Aldrich), was added: the whole was kept, under stirring, for 90 minutes. After 90 minutes the reaction was considered complete and was interrupted. The polymer solution was extracted from the reactor and a phenolic antioxidant (Irganox® 1520 from Ciba, in an amount of 0.1% by weight with respect to the total weight of the copolymer obtained) was added. The polymer solution obtained was then fed to a vessel containing boiling water through the introduction of steam, and subjected to stirring: in this way the residual reaction solvent was eliminated, yielding a coagulum. Said coagulum was first pressed in a cold calender and then dried completely in a calender with rollers at 80° C. to obtain a random butadiene-isoprene copolymer.

[0141] The random butadiene-isoprene copolymer obtained underwent the characterizations mentioned above: the data obtained are shown in Table 3.

Example 2 (Invention)

Preparation of Random Butadiene-Isoprene Copolymer (in a Batch Reactor)

[0142] Example 2 was carried out in the same way as Example 1 with the only difference that 35 g of anhydrous 1,3-butadiene (from Versalis S.p.A.) and 15 g of anhydrous isoprene (from Versalis S.p.A.) (% by weight butadiene:isoprene=70:30) were used.

[0143] The random butadiene-isoprene copolymer obtained underwent the characterizations mentioned above: the data obtained are shown in Table 3.

Example 3 (Invention)

Preparation of Random Butadiene-Isoprene Copolymer (in a Batch Reactor)

[0144] Example 3 was carried out in the same way as Example 1 with the only difference that 25 g of anhydrous 1,3-butadiene (from Versalis S.p.A.) and 25 g of anhydrous isoprene (from Versalis S.p.A.) (% by weight butadiene:isoprene=50:50) were used.

[0145] The random butadiene-isoprene copolymer obtained underwent the characterizations mentioned above: the data obtained are shown in Table 3.

Example 4 (Invention)

Preparation of Random Butadiene-Isoprene Copolymer (in a Batch Reactor)

[0146] 450 g of anhydrous hydrocarbon solvent comprising a mixture of hexanes (a mixture comprising 35% by weight with respect to the total weight of the mixture of n-hexane and 65% by weight with respect to the total weight of the mixture of a mixture comprising n-hexane isomers, aliphatic compounds and cycloaliphatic compounds from Cepsa) were loaded into a 1 litre reactor with stirrer and cooling system and heated to 60° C. Subsequently, 35 g of anhydrous 1,3-butadiene (from Versalis S.p.A.), 15 g of anhydrous isoprene (from Versalis S.p.A.) (% by weight butadiene:isoprene=70:30), 0.658 ml (0.625 mmol) of a 0.12 M solution of di-isobutyl aluminum hydride (DIBAH) (from Akzo Nobel) in n-hexane (from Aldrich) (molar ratio DIBAH/Nd=5), 0.887 ml (0.5 mmol) of a 0.564 M solution of diethyl aluminum chloride (DEAC) (Al/Cl molar ratio=1; from Albemarle) in n-hexane (from Aldrich) (molar ratio Cl/Nd=4) were added to said solvent, in that order, and the whole was kept, under stirring, at 60° C., for 25 minutes. Subsequently, 0.24 ml (0.125 mmol) of a 0.514 M solution of neodymium versatate [Nd(versatate)3] [2.5 mmol Nd per 1000 g of monomers (1,3-butadiene+isoprene)] with a free molar acid/Nd ratio of 0.3 and a molar H.sub.2O/Nd ratio of 0.018 (from Rhodia) in n hexane (from Aldrich), was added: the whole was kept, under stirring, for 90 minutes. After 90 minutes the reaction was considered complete and was interrupted. The polymer solution was extracted from the reactor and a phenolic antioxidant (Irganox® 1520 from Ciba, in an amount of 0.1% by weight with respect to the total weight of the copolymer obtained) was added. The polymer solution obtained was then fed to a vessel containing boiling water through the introduction of steam, and subjected to stirring: in this way the residual reaction solvent was eliminated, yielding a coagulum. Said coagulum was first pressed in a cold calender and then dried completely in a calender with rollers at 80° C. to obtain a random butadiene-isoprene copolymer.

[0147] The random butadiene-isoprene copolymer obtained underwent the characterizations mentioned above: the data obtained are shown in Table 3.

Example 5 (Invention)

Preparation of Random Butadiene-Isoprene Copolymer (in a Batch Reactor)

[0148] Example 5 was carried out in the same way as Example 4 with the only difference that 1.11 ml (0.625 mmol) of a 0.564 M solution of diethyl aluminum chloride (DEAC) (Al/Cl molar ratio=1; from Albemarle) in n-hexane (from Aldrich) (molar ratio Cl/Nd=5) was used.

[0149] The random butadiene-isoprene copolymer obtained underwent the characterizations mentioned above: the data obtained are shown in Table 3.

Example 6 (Comparative)

Preparation of Random Butadlene-Isoprene Copolymer (in a Batch Reactor)

[0150] Example 6 was carried out in the same way as Example 4 with the only difference that 0.443 ml (0.25 mmol) of a 0.564 M solution of diethyl aluminum chloride (DEAC) (Al/Cl molar ratio=1; from Albemarle) in n-hexane (from Aldrich) (molar ratio Cl/Nd=2) was used.

[0151] The random butadiene-isoprene copolymer obtained underwent the characterizations mentioned above: the data obtained are shown in Table 3.

Example 7 (Comparative)

Preparation of Random Butadiene-Isoprene Copolymer (in a Batch Reactor)

[0152] Example 7 was carried out in the same way as Example 4 with the only difference that 1.33 ml (0.75 mmol) of a 0.564 M solution of diethyl aluminum chloride (DEAC) (Al/Cl molar ratio=1; from Albemarle) in n-hexane (from Aldrich) (molar ratio Cl/Nd=6) was used.

[0153] The random butadiene-isoprene copolymer obtained underwent the characterizations mentioned above: the data obtained are shown in Table 3.

Example 8 (Comparative)

Preparation of Random Butadiene-Isoprene Copolymer (in a Batch Reactor)

[0154] Example 8 was carried out in the same way as Example 4 with the only difference that 1.55 ml (0.875 mmol) of a 0.564 M solution of diethyl aluminum chloride (DEAC) (Al/Cl molar ratio=1; from Albemarle) in n-hexane (from Aldrich) (molar ratio Cl/Nd=7) was used.

[0155] The random butadiene-isoprene copolymer obtained underwent the characterizations mentioned above: the data obtained are shown in Table 3.

Example 9 (Invention)

Preparation of Random Butadiene-Isoprene Copolymer (in a Batch Reactor)

[0156] 450 g of anhydrous hydrocarbon solvent comprising a mixture of hexanes (a mixture comprising 35% by weight with respect to the total weight of the mixture of n-hexane and 65% by weight with respect to the total weight of the mixture of a mixture comprising n-hexane isomers, aliphatic compounds and cycloaliphatic compounds from Cepsa) were loaded into a 1 litre reactor with stirrer and cooling system and heated to 60° C. Subsequently, 35 g of anhydrous 1,3-butadiene (from Versalis S.p.A.), 15 g of anhydrous isoprene (from Versalis S.p.A.) (% by weight butadiene:isoprene=90:10), 0.526 ml (0.5 mmol) of a 0.95 M solution of di isobutyl aluminum hydride (DIBAH) (from Akzo Nobel) in n-hexane (from Aldrich) (molar ratio DIBAH/Nd=4), 1.11 ml (0.625 mmol) of a 0.564 M solution of diethyl aluminum chloride (DEAC) (Al/Cl molar ratio=1; from Albemarle) in n-hexane (from Aldrich) (molar ratio Cl/Nd=5) were added to said solvent, in that order, and the whole was kept, under stirring, at 60°, for 25 minutes. Subsequently, 0.24 ml (0.125 mmol) of a 0.514 M solution of neodymium versatate [Nd(versatate)] [2.5 mmol Nd per 1000 g of monomers (1,3-butadiene+isoprene)] with a free molar acid/Nd ratio of 0.3 and a molar H.sub.2O/Nd ratio of 0.018 (from Rhodia) in n-hexane (from Aldrich), was added: the whole was kept, under stirring, for 90 minutes. After 90 minutes, the reaction was considered complete and was interrupted. The polymer solution was extracted from the reactor and a phenolic antioxidant (Irganox® 1520 from Ciba, in an amount of 0.1% by weight with respect to the total weight of the copolymer obtained) was added. The polymer solution obtained was then fed to a vessel containing boiling water through the introduction of steam, and subjected to stirring: in this way the residual reaction solvent was eliminated, yielding a coagulum. Said coagulum was first pressed in a cold calender and then dried completely in a calender with rollers at 80° C. to obtain a random butadiene-isoprene copolymer.

[0157] The random butadiene-isoprene copolymer obtained underwent the characterizations mentioned above: the data obtained are shown in Table 3.

Example 10 (Comparative)

Preparation of Random Butadiene-Isoprene Copolymer (in a Batch Reactor)

[0158] 450 g of anhydrous hydrocarbon solvent comprising a mixture of hexanes (a mixture comprising 35% by weight with respect to the total weight of the mixture of n-hexane and 65% by weight with respect to the total weight of the mixture of a mixture comprising n-hexane isomers, aliphatic compounds and cycloaliphatic compounds from Cepsa) were loaded into a 1 litre reactor with stirrer and cooling system and heated to 60° C. Subsequently 35 g of anhydrous 1,3-butadiene (from Versalis S.p.A.), 15 g of anhydrous isoprene (from Versalis S.p.A.) (% by weight butadiene:isoprene=90:10), 0.526 ml (0.5 mmol) of a 0.95 M solution of di isobutyl aluminum hydride (DIBAH) (from Akzo Nobel) in n-hexane (from Aldrich) (molar ratio DIBAH/Nd=4), 0.443 ml (0.25 mmol) of a 0.564 M solution of diethyl aluminum chloride (DEAC) (Al/Cl molar ratio=1; from Albemarle) in n-hexane (from Aldrich) (molar ratio Cl/Nd=2) were added to said solvent, in that order, and the whole was kept, under stirring, at 60° C., for 25 minutes. Subsequently, 0.24 ml (0.125 mmol) of a 0.514 M solution of neodymium versatate [Nd(versatate).sub.3] with a free versatic acid/Nd molar ratio of 0.3 and a molar H.sub.2O/Nd ratio of 0.018 (from Rhodia) in n-hexane (from Aldrich) [2.5 mmol Nd per 1000 g of monomers (1,3-butadiene+isoprene)], was added: the whole was kept, under stirring, for 90 minutes. After 90 minutes the reaction was considered complete and was interrupted. The polymer solution was extracted from the reactor and a phenolic antioxidant (Irganox® 1520 from Ciba, in an amount of 0.1% by weight with respect to the total weight of the copolymer obtained) was added. The polymer solution obtained was then fed to a vessel containing boiling water through the introduction of steam, and subjected to stirring: in this way the residual reaction solvent was eliminated, yielding a coagulum. Said coagulum was first pressed in a cold calender and then dried completely in a calender with rollers at 80° C. to obtain a random butadiene-isoprene copolymer.

[0159] The random butadiene-isoprene copolymer obtained underwent the characterizations mentioned above: the data obtained are shown in Table 3.

Example 11 (Invention)

Preparation of Random Butadiene-Isoprene Copolymer (Continuous)

[0160] Anhydrous 1,3-butadiene (from Versalis S.p.A.), anhydrous isoprene (from Versalis S.p.A.) and anhydrous hydrocarbon solvent comprising a mixture of hexanes (a mixture comprising 35% by weight with respect to the total weight of the mixture of n-hexane and 65% by weight with respect to the total weight of the mixture of a mixture comprising n-hexane isomers, aliphatic compounds and cycloaliphatic compounds from Cepsa) were fed to a plant comprising three reactors in series including a primary reactor of 100 I, a secondary reactor of 100 I and a tertiary reactor of 451 equipped with wall-scraping stirrers, distilled and further dried by passing through a bed of 3 A molecular sieves, in such ratios that the total concentration of the monomers was equal to 13% by weight with respect to the total weight of the mixture and the hourly amount of butadiene+isoprene was equal to 6 kg/hour with a butadiene:isoprene weight ratio of 90:10: the temperature of the monomer and solvent mixture obtained was set at a value not exceeding 22° C. and in any event such as to regulate (together with the amount of steam circulating in the jackets with which the reactors were provided) a synthesis temperature at the bottom of the primary reactor which was constant and centred on a value of 60° C. In the same feed line, a 0.0921 M solution of di-isobutyl aluminum hydride (DIBAH) (from Akzo Nobel) in n-hexane (from Aldrich) (DIBAH/Nd molar ratio=4), a 1 M solution of diethyl aluminum chloride (DEAC) (Al/Cl molar ratio=1; from Albemarle) in n-hexane (from Aldrich) (Cl/Nd molar ratio=4.3), while the 0.0248 M solution of neodymium versatate [Nd(versatate).sub.3]having a free versatic acid to Nd molar ratio of 0.3 and a molar H.sub.2O/Nd ratio of 0.014 (from Rhodia) in n-hexane (from Aldrich) [2.5 mmoles of Nd per 1000 g of monomers (1,3-butadiene+isoprene)] was separately fed directly into the primary reactor. After the addition of demineralized water and a phenolic antioxidant (Irganox® 1520 from Ciba, 0.1% by weight with respect to the total weight of the polymer solution), the polymer solution from the last polymerization reactor was transferred and stored in stirred blenders. Subsequently, the polymer solution was fed from said blenders to a stripper to remove residual reaction solvent and the random butadiene-isoprene copolymer discharged from the bottom of the stripper underwent a drying stage in an extruder. The random butadiene-isoprene copolymer obtained underwent the characterizations mentioned above: the data obtained are shown in Table 3.

Example 12 (Invention)

Preparation of Random Butadiene-Isoprene Copolymer (Continuous)

[0161] Anhydrous 1,3-butadiene (from Versalis S.p.A.), anhydrous isoprene (from Versalis S.p.A.) and anhydrous hydrocarbon solvent comprising a mixture of hexanes (a mixture comprising 35% by weight of with respect to the total weight of the mixture of n-hexane and 65% by weight with respect to the total weight of the mixture of a mixture comprising n-hexane isomers, aliphatic compounds and cycloaliphatic compounds from Cepsa) were fed to a plant comprising three reactors in series including a primary reactor of 100 I, a secondary reactor of 100 I and a tertiary reactor of 45 I equipped with wall-scraping stirrers, distilled and further dried by passing through a bed of 3 A molecular sieves, in such ratios that the total concentration of the monomers was equal to 13% by weight with respect to the total weight of the mixture and the hourly amount of butadiene+isoprene was equal to 6 kg/hour with a butadiene:isoprene weight ratio of 70:30: the temperature of the monomer and solvent mixture obtained was set at a value not exceeding 22° C. and in any event such as to regulate (together with the amount of steam circulating in the jackets with which the reactors were provided) a synthesis temperature at the bottom of the primary reactor, which was constant and centred on a value of 60° C. In the same feed line a 0.0921 M solution of di-isobutyl aluminum hydride (DIBAH) (from Akzo Nobel) in n-hexane (from Aldrich) (DIBAH/Nd molar ratio=4), a 0.119 M solution of diethyl aluminum chloride (DEAC) (Al/Cl molar ratio=1; from Albemarle) in n-hexane (from Aldrich) (Cl/Nd molar ratio=4.3), while the 0.0248 M solution of neodymium versatate [Nd(versatate).sub.3] having a free versatic acid to Nd molar ratio of 0.3 and a molar H.sub.2O/Nd ratio of 0.014 (from Rhodia) in n-hexane (from Aldrich) [2.5 mmoles of Nd per 1000 g of monomers (1,3-butadiene+isoprene)] was separately fed directly into the primary reactor. After the addition of demineralized water and a phenolic antioxidant (Irganox® 1520 from Ciba, 0.1% by weight with respect to the total weight of the polymer solution), the polymer solution from the last polymerization reactor was transferred and stored in stirred blenders. Subsequently, the polymer solution was fed from said blenders to a stripper to remove residual reaction solvent and the random butadiene-isoprene copolymer discharged from the bottom of the stripper underwent a drying stage in an extruder.

[0162] The random butadiene-isoprene copolymer obtained underwent the characterizations mentioned above: the data obtained are shown in Table 3.

Example 13 (Invention)

Preparation of Butadiene-Isoprene Copolymer (Continuous)

[0163] Anhydrous 1,3-butadiene (from Versalis S.p.A.), anhydrous isoprene (from Versalis S.p.A.) and anhydrous hydrocarbon solvent comprising a mixture of hexanes (a mixture comprising 35% by weight with respect to the total weight of the mixture of n-hexane and 65% by weight with respect to the total weight of the mixture of a mixture comprising n-hexane isomers, aliphatic compounds and cycloaliphatic compounds from Cepsa) were fed to a plant comprising three reactors in series including a primary reactor of 100 I, a secondary reactor of 100 I and a tertiary reactor of 45 equipped with wall-scraping stirrers, distilled and further dried by passing through a bed of 3 A molecular sieves, in such ratios that the total concentration of the monomers was equal to 13% by weight with respect to the total weight of the mixture and the hourly amount of butadiene+isoprene was equal to 6 kg/hour with a butadiene:isoprene weight ratio of 50:50: the temperature of the monomer and solvent mixture obtained was set at a value not exceeding 22° C. and in any event such as to regulate (together with the amount of steam circulating in the jackets with which the reactors were provided) a synthesis temperature at the bottom of the primary reactor, which was constant and centred on a value of 60° C. In the same feed line, a 0.0921 M solution of di-isobutyl aluminum hydride (DIBAH) (from Akzo Nobel) in n-hexane (from Aldrich) (DIBAH/Nd molar ratio=4), a 0.119 M solution of diethyl aluminum chloride (DEAC) (Al/Cl molar ratio=1; from Albemarle) in n-hexane (from Aldrich) (Cl/Nd molar ratio=4.3), while the 0.0248 M solution of neodymium versatate [Nd(versatate)] having a free versatic acid to Nd molar ratio of 0.3 and a molar H.sub.2O/Nd ratio of 0.014 (from Rhodia) in n-hexane (from Aldrich) [2.5 mmoles of Nd per 1000 g of monomers (1,3-butadiene+isoprene)] was separately fed directly into the primary reactor. The polymer solution from the last polymerization reactor, after the addition of demineralized water and a phenolic antioxidant (Irganox® 1520 from Ciba, 0.1% by weight with respect to the total weight of the polymer solution), was transferred and stored in stirred blenders. Subsequently, the polymer solution was fed from said blenders to a stripper to remove residual reaction solvent and the random butadiene-isoprene copolymer discharged from the bottom of the stripper underwent a drying stage in an extruder.

[0164] The random butadiene-isoprene copolymer obtained underwent the characterizations mentioned above: the data obtained are shown in Table 3.

Example 14 (Comparative)

Preparation of Butadiene-Isoprene Copolymer (Continuous)

[0165] Anhydrous 1,3-butadiene (from Versalis S.p.A.), anhydrous isoprene (from Versalis S.p.A.) and anhydrous hydrocarbon solvent comprising a mixture of hexanes (a mixture comprising 35% by weight with respect to the total weight of the mixture of n-hexane and 65% by weight with respect to the total weight of the mixture of a mixture comprising n-hexane isomers, aliphatic compounds and cycloaliphatic compounds from Cepsa) were fed to a plant comprising three reactors in series including a primary reactor of 100 I, a secondary reactor of 100 I and a tertiary reactor of 451 equipped with wall-scraping stirrers, distilled and further dried by passing through a bed of 3 A molecular sieves, in such ratios that the total concentration of the monomers was equal to 13% by weight with respect to the total weight of the mixture and the hourly amount of butadiene+isoprene was equal to 6 kg/hour with a butadiene:isoprene weight ratio of 70:30: the temperature of the monomer and solvent mixture obtained was set at a value not exceeding 22° C. and in any event such as to regulate (together with the amount of steam circulating in the jackets with which the reactors were provided) a synthesis temperature at the bottom of the primary reactor, which was constant and centred on a value of 60° C. In the same feed line, a 0.0921 M solution of di-isobutyl aluminum hydride (DIBAH) (from Akzo Nobel) in n-hexane (from Aldrich) (DIBAH/Nd molar ratio=4), a 0.119 M solution of diethyl aluminum chloride (DEAC) (Al/Cl molar ratio=1; from Albemarle) in n-hexane (from Aldrich) (Cl/Nd molar ratio=4.3), while the 0.0248 M solution of neodymium versatate [Nd(versatate)] having a free versatic acid to Nd molar ratio of 0.3 and a molar H.sub.2O/Nd ratio of 0.014 (from Rhodia) in n-hexane (from Aldrich) [2.5 mmoles of Nd per 1000 g of monomers (1,3-butadiene+isoprene)] was separately fed directly into the primary reactor. After the addition of demineralized water and a phenolic antioxidant (Irganox& 1520 from Ciba, 0.1% by weight with respect to the total weight of the polymer solution), the polymer solution from the last polymerization reactor was transferred and stored in stirred blenders. Subsequently, the polymer solution was fed from said blenders to a stripper to remove residual reaction solvent and the random butadiene-isoprene copolymer discharged from the bottom of the stripper underwent a drying stage in an extruder.

[0166] The random butadiene-isoprene copolymer obtained underwent the characterizations mentioned above: the data obtained are shown in Table 3.

TABLE-US-00003 TABLE 3 Mooney cis Bound Bound Viscosity BI + cis-1,4- 1, Nd/ DIBAH/ Cl/ butadiene isoprene Bound Bound (ML1 + .sup.(5) IB.sup.(6) BB.sup.(7) R.I..sup.(8) butadiene isoprene monomers.sup.(1) Nd.sup.(2) Cl/Nd.sup.(3) DIBAH.sup.(4) (% by (% by butadiene butadiene M.sub.n M.sub.w M.sub.w/ 4 @ 100° (% (% (% (mol/ T.sub.g.sup.(9) (% by (% by EXAMPLE (mmol/Kg) (mol/mol) (mol/mol) (mol/mol) weight) weight) (% mol) (% mol) (kdalton) (kdalton) M.sub.n C.) mol) mol) mol) mol) (° C.) weight) weight)  1 2.5 5 3 0.6 90.1 9.9 92.0 8.0 126 369 2.9 43 0.5 13.6 85.9 0.85 −104.3 98.6 99.9 (invention)  2 2.5 5 3 0.6 70.2 29.8 74.8 25.2 147 390 2.7 44 6.4 36.0 57.6 0.71 −96.8 98.8 98.9 (invention)  3 2.5 5 3 0.6 50.1 49.9 55.8 44.2 157 466 3.0 47 19.3 49.8 30.9 0.56 −87.9 97.0 98.8 (invention)  4 2.5 5 4 0.8 69.9 30.1 74.5 25.5 135 375 2.8 42 6.4 36.5 57.1 0.72 −96.5 98.8 98.9 (invention)  5 2.5 5 5 1 69.9 30.1 74.5 25.5 139 365 2.6 41 6.3 36.4 57.3 0.71 −96.4 98.7 98.8 (invention)  6 2.5 5 2 0.4 70.0 30.0 74.6 25.4 117 396 3.4 47 6.3 36.7 57.0 0.72 −96.5 98.5 98.5 (comparative)  7 2.5 5 6 1.2 70.1 29.9 74.7 25.3 101 360 3.6 39 6.4 36.0 57.6 0.71 −96.9 98.8 98.9 (comparative)  8 2.5 5 7 1.4 70.2 29.8 74.8 25.2 94 363 3.9 40 6.5 36.1 57.4 0.72 −96.8 98.5 98.6 (comparative)  9 2.5 4 5 1.25 70.1 29.9 74.7 25.3 147 410 2.8 47 6.4 36.5 57.1 0.72 −96.8 98.8 99.0 (invention) 10 2.5 4 2 0.5 70.2 29.8 74.8 25.2 127 450 3.5 46 6.3 36.1 57.6 0.72 −96.7 98.4 98 (comparative) 11 2.5 4 4.3 1.075 89.9 10.1 91.8 8.2 135 355 2.6 43 0.6 14.0 85.4 0.85 −103.9 98.9 98 (invention) 12 2.5 4 4.3 1.075 70.1 29.9 74.7 25.3 143 385 2.7 42 6.3 36.6 57.1 0.72 −96.6 98.7 98 (invention) 13 2.5 4 4.3 1.075 50.1 48.9 55.8 44.2 152 450 3.0 44 19.0 50.0 31.0 0.57 −87.8 98.7 98 (invention) 14 2.5 4 6 1.5 69.9 30.1 64.5 25.5 108 365 3.4 41 6.5 35.0 58.5 0.69 −96.4 98.4 98 (comparative) .sup.(1)amount of neodymium versatate [Nd(versatate).sub.3] per 1000 g of monomers (butadiene + isoprene); .sup.(2)molar ratio between di-isobutyl aluminum hydride (DIBAH) and neodymium versatate [Nd(versatate).sub.3]; .sup.(3)molar ratio between chlorine (Cl) present in diethyl aluminum chloride (DEAC) and neodymium versatate [Nd(versatate).sub.3]; .sup.(4)molar ratio between chlorine (Cl) present in diethyl aluminum chloride (DEAC) and di-isobutyl aluminum hydride (DIBAH)); .sup.(5)isoprene dyads; .sup.(6)sum of butadiene-isoprene dyads and isoprene-butadiene dyads; .sup.(7)butadiene dyads; .sup.(8)randomization index; .sup.(9)glass transition temperature. indicates data missing or illegible when filed