Process for the preparation of functionalized and branched elastomeric copolymers and use thereof in vulcanizable elastomeric compositions
A process for the preparation of a functionalized and branched elastomeric copolymer comprising the following steps: (a) anionic copolymerization of at least one conjugated diene monomer and at least one vinyl arene, in the presence of at least one hydrocarbon solvent, of at least one lithium-based initiator, and of at least one polar modifier, obtaining a solution comprising an elastomeric copolymer; (b) reacting at least 10% by weight, preferably from 20% by weight to 100 % by weight, of the polymeric chains present in the elastomeric copolymer obtained in step (a) with at least one compound having at least one functional group selected from: epoxides, ketones, esters, aldehydes, obtaining a solution comprising a functionalized elastomeric copolymer; (c) adding a quantity of lithium-based initiator to the solution obtained in step (b), from 1 to 4 times, preferably from 1.5 to 3 times, the molar quantity of lithium-based initiator used in step (a) and a compound of bromine having general formula (I): R—Br (I) wherein R represents a linear or branched C 1 -C 30 , preferably C 2 -C 10 , alkyl group, a C 3 -C 30 , preferably C 4 -C 10 , cycloalkyl group, a C 6 -C 30 , preferably C 6 -C 12 , aryl group.
1. A process for the preparation of a functionalized and branched elastomeric copolymer comprising the following steps:
(a) anionic copolymerization of at least one conjugated diene monomer and at least one vinyl arene, in the presence of at least one hydrocarbon solvent, of at least one lithium-based initiator, and of at least one polar modifier, obtaining a solution comprising an elastomeric copolymer;
(b) reacting at least 10% by weight of the polymeric chains present in the elastomeric copolymer in step (a) with at least one compound having at least one functional group selected from: epoxides, ketones, esters, aldehydes, obtaining a solution comprising a functionalized elastomeric copolymer;
(c) adding a quantity of lithium-based initiator to the solution obtained in step (b), from 1 to 4 times the molar quantity of lithium-based initiator used in step (a) and a compound of bromine having general formula (I):
R—Br (I),
wherein R represents a linear or branched C1-C30 alkyl group, a C3-C30 cycloalkyl group, a C6-C30 aryl group,
wherein a functionalized and branched elastomeric copolymer is obtained in which the functionalization of the polymeric chains is of the terminal type.
2. The process according to claim 1 , wherein, in step (b), from 20% by weight to 100% by weight of the polymeric chains present in the elastomeric copolymer obtained in step (a) are reacted.
3. The process according to claim 1 , wherein said conjugated diene monomer is selected from: 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene (piperylene), 2-methyl-3-ethyl-1,36-butadiene, 1,3-octadiene, or mixtures thereof.
4. The process according to claim 1 , wherein said vinyl arene is selected from: styrene, α-methylstyrene, 1-vinyl-naphthalene, 2-vinyl-naphthalene, or their alkyl derivatives, or mixtures thereof.
5. The process according to claim 1 , wherein said anionic copolymerization is carried out in the presence of:
(a) 60% by weight-95% by weight with respect to the total weight of the conjugated diene monomer and vinyl arene, of at least one conjugated diene monomer; and
(b) 5% by weight-40% by weight with respect to the total weight of the conjugated diene monomer and vinyl arene, of at least one vinyl arene.
6. The process according to claim 1 , wherein said hydrocarbon solvent is an aliphatic or aromatic hydrocarbon solvent selected from n-pentane, n-hexane, n-heptane, cyclohexane, or mixtures thereof.
7. The process according to claim 1 , wherein said lithium-based initiator is selected from compounds having general formula (II):
R′(Li)n (II)
wherein R′ represents a linear or branched C1-C20 alkyl group, n is an integer ranging from 1 to 4.
8. The process according to claim 1 , wherein said lithium-based initiator of step a) is used in a quantity ranging from 0.005% by weight to 0.08% by weight with respect to the total weight of the conjugated diene monomer and vinyl arene.
9. The process according to claim 1 , wherein said polar modifier is selected from tetrahydrofuran (THF), tetrahydrofurfurylethyl ether (THFAethyl), or mixtures thereof; N,N,N′,N′-tetramethylethylenediamine (TMEDA), or mixtures thereof; or mixtures thereof.
10. The process according to claim 1 , wherein said polar modifier is used in a quantity ranging from 0.10 moles to 100 moles per mole of lithium-based initiator.
11. The process according to claim 1 , wherein said step (a) is carried out at a temperature ranging from 0° C. to 150° C.
12. The process according to claim 1 , wherein said step (a) is carried out for a time ranging from 5 minutes to 10 hours.
13. The process according to claim 1 , wherein said compound having at least one functional group is selected from epoxides.
14. The process according to claim 1 , wherein said step (b) is carried out at a temperature ranging from 0° C. to 150° C.
15. The process according to claim 1 , wherein said step (b) is carried out for a time ranging from 1 minute to 1 hour.
16. The process according to claim 1 , wherein said compound of bromine having general formula (I) is used in such a quantity that the molar ratio between said bromine compound having general formula (I) and total lithium-based initiator, the lithium-based initiator of step (a) and the lithium-based initiator of step (c), ranges from 0.6:1 to 1:1.
17. The process according to claim 1 , wherein said step (c) is carried out at a temperature ranging from 0° C. to 150° C.
18. The process according to claim 1 , wherein said step (c) is carried out for a time ranging from 1 minute to 1 hour.
19. A vulcanizable elastomeric composition comprising at least one functionalized and branched elastomeric copolymer obtained according to claim 1 , at least one filler selected from silica, carbon black, or mixtures thereof, and at least one vulcanizing agent.
20. A vulcanized end-product obtained from the vulcanization of the elastomeric composition according to claim 19 .