The present invention provides a polybutadiene having improved workability and abrasion resistance. A polybutadiene according to the present invention has: (A) a Mooney viscosity (ML.sub.1+4,100 C.) being 43 or more; (B) a ratio (Tcp/ML.sub.1+4,100 C.) of 5 wt % toluene solution viscosity (Tcp) to Mooney viscosity (ML.sub.1+4,100 C.) being 0.9 to 2.3; (C) a stress relaxation time (T80) being 10.0 to 40.0 seconds, which is a time until a torque is attenuated by 80% when the torque at the end of ML.sub.1+4,100 C.measurement is 100%; and (D) a molecular weight distribution (Mw/Mn) being 2.50 to 4.00.

The present invention provides a rubber composition for a tire having improved workability and abrasion resistance. A rubber composition for a tire according to the present invention comprises: a polybutadiene which has: (A) a Mooney viscosity (ML.sub.1+4,100 C.) being 43 or more; (B) a ratio (Tcp/ML.sub.1+4,100 C.) of 5 wt % toluene solution viscosity (Tcp) to Mooney viscosity (ML.sub.1+4,100 C.) being 0.9 to 2.3; (C) a stress relaxation time (T80) being 10.0 to 40.0 seconds, which is a time until a torque is attenuated by 80% when the torque at the end of ML.sub.1+4,100 C. measurement is 100%; and (D) a molecular weight distribution (Mw/Mn) being 2.50 to 4.00; another rubber (ii); and a rubber reinforcing material (iii).

Process for the preparation of (co) polymers of conjugated dienes which comprises polymerizing at least one conjugated diene in the presence of a catalytic system comprising at least one bis-imine complex of cobalt having general formula (I) wherein: n is 0 or 1; Y represents a group CRR wherein R and R, equal to or different from each other, represent a hydrogen atom; or a linear or branched C.sub.1-C.sub.20, preferably C.sub.1-C.sub.15, alkyl group; or a divalent aromatic group optionally substituted; R.sub.1 and R.sub.2, equal to or different from each other, represent a hydrogen atom; or they are selected from a linear or branched Ci-C2o/preferably C.sub.1-C.sub.15, alkyl group optionally halogenated, cycloalkyl groups optionally substituted; or R.sub.1 and R.sub.2 can be optionally bound to each other to form, together with the other atoms to which they are bound, a cycle containing from 4 to 6 carbon atoms, saturated, unsaturated, or aromatic, optionally substituted with linear or branched C.sub.1-C.sub.20, preferably C.sub.1-C.sub.15, alkyl groups, said cycle optionally containing heteroatoms such as, for example, oxygen, sulfur, nitrogen, silicon, phosphorous, selenium; R.sub.3 and R.sub.4, equal to or different from each other, represent a hydrogen atom; or they are selected from a linear or branched Ci-C20, preferably C.sub.1-C.sub.15, alkyl groups optionally halogenated, cycloalkyl groups optionally substituted, aryl groups optionally substituted; or R2 and R4 can be optionally bound to each other to form, together with the other atoms to which they are bound, a cycle containing from 3 to 6 carbon atoms, saturated, unsaturated, or aromatic, optionally substituted with linear or branched Ci-C2o, preferably C1-C15 alkyl groups, said cycle optionally containing other heteroatoms such as, for example, oxygen, sulfur, nitrogen, silicon, phosphorous, selenium; or R.sub.1 and R.sub.3 can be optionally bound to each other to form, together with the other atoms to which they are bound, a cycle containing from 3 to 6 carbon atoms, saturated, unsaturated, or aromatic, optionally substituted with linear or branched C.sub.1-C.sub.20, preferably C.sub.1-C.sub.15, alkyl groups, said cycle optionally containing other heteroatoms such as, for example, oxygen, sulfur, nitrogen, silicon, phosphorous, selenium; X.sub.1 and X.sub.2, equal to or different from each other, represent a halogen atom such as, for example, chlorine, bromine, iodine; or they are selected from linear or branched C.sub.1-C.sub.20 preferably C.sub.1-C.sub.15, alkyl groups, OCOR.sub.5 groups or OR.sub.3 groups wherein R.sub.5 is selected from linear or branched C.sub.1-C.sub.20, preferably C.s

The present invention is directed to a method of making a functionalized elastomer, comprising the steps of: forming a copolymer Y by copolymerizing a first monomer and a second monomer, wherein the first monomer is selected from the group consisting of 1,3-butadiene, isoprene, and styrene; the second monomer is selected from the group consisting of formula 1 or 2 ##STR00001##
wherein B is boron; O is oxygen; R.sup.1 and R.sup.2 are independently linear or branched alkyl groups containing 1 to 10 carbon atoms; R.sup.3 is hydrogen or a linear or branched alkyl group containing 1 to 10 carbon atoms; and R.sup.4 is a linear or branched alkane diyl group containing 1 to 20 carbon atoms, or a bridging aromatic group; and reacting the copolymer Y with a compound Z to form the functionalized elastomer, wherein Z is a compound of formula 3 ##STR00002##
where R.sup.5 is phenylene, a linear or branched alkane diyl group containing from 1 to 10 carbon atoms, or a combination of one or more phenylene groups and one or more linear or branched alkane diyl groups containing from 1 to 10 carbon atoms; and Q is hydrogen, bromine, or a functional group comprising at least one heteroatom selected from the group consisting of nitrogen, oxygen, phosphorus, silicon, and sulfur.

The present invention is directed to a method of making a functionalized elastomer, comprising the steps of: forming a copolymer Y by copolymerizing a first monomer and a second monomer, wherein the first monomer is selected from the group consisting of 1,3-butadiene, isoprene, and styrene; the second monomer is selected from the group consisting of formula 1 or 2 ##STR00001##
wherein B is boron; O is oxygen; R.sup.1 and R.sup.2 are independently linear or branched alkyl groups containing 1 to 10 carbon atoms; R.sup.3 is hydrogen or a linear or branched alkyl group containing 1 to 10 carbon atoms; and R.sup.4 is a linear or branched alkane diyl group containing 1 to 20 carbon atoms, or a bridging aromatic group; and reacting the copolymer Y with a compound Z to form the functionalized elastomer, wherein Z is a compound of formula 3 ##STR00002##
where R.sup.5 is phenylene, a linear or branched alkane diyl group containing from 1 to 10 carbon atoms, or a combination of one or more phenylene groups and one or more linear or branched alkane diyl groups containing from 1 to 10 carbon atoms; and Q is hydrogen, bromine, or a functional group comprising at least one heteroatom selected from the group consisting of nitrogen, oxygen, phosphorus, silicon, and sulfur.

The present invention provides a polybutadiene having improved workability and abrasion resistance. A polybutadiene according to the present invention has: (A) a Mooney viscosity (ML.sub.1+4,100 C.) being 43 or more; (B) a ratio (Tcp/ML.sub.1+4,100 C.) of 5 wt % toluene solution viscosity (Tcp) to Mooney viscosity (ML.sub.1+4,100 C.) being 0.9 to 2.3; (C) a stress relaxation time (T80) being 10.0 to 40.0 seconds, which is a time until a torque is attenuated by 80% when the torque at the end of ML.sub.1+4,100 C.measurement is 100%; and (D) a molecular weight distribution (Mw/Mn) being 2.50 to 4.00.

The present invention provides a polybutadiene having improved workability and abrasion resistance. A polybutadiene according to the present invention has: (A) a Mooney viscosity (ML.sub.1+4,100 C.) being 43 or more; (B) a ratio (Tcp/ML.sub.1+4,100 C.) of 5 wt % toluene solution viscosity (Tcp) to Mooney viscosity (ML.sub.1+4,100 C.) being 0.9 to 2.3; (C) a stress relaxation time (T80) being 10.0 to 40.0 seconds, which is a time until a torque is attenuated by 80% when the torque at the end of ML.sub.1+4,100 C.measurement is 100%; and (D) a molecular weight distribution (Mw/Mn) being 2.50 to 4.00.

Compositions may comprise symmetrical and asymmetrical pyridine-containing transition metal-complexes having appended group 13 Lewis acids positioned on the pyridine-containing ligands of the transition metal-complex such that the group 13 Lewis acid may be near the catalytic site, thereby allowing the appended group 13 Lewis acid to function more efficiently in promoting formation of a catalytically active species. Catalysts systems may comprise these symmetrical and asymmetrical pyridine-containing transition metal-complexes and methods of preparing polyolefins may use these catalyst systems.

Compositions may comprise symmetrical and asymmetrical pyridine-containing transition metal-complexes having appended group 13 Lewis acids positioned on the pyridine-containing ligands of the transition metal-complex such that the group 13 Lewis acid may be near the catalytic site, thereby allowing the appended group 13 Lewis acid to function more efficiently in promoting formation of a catalytically active species. Catalysts systems may comprise these symmetrical and asymmetrical pyridine-containing transition metal-complexes and methods of preparing polyolefins may use these catalyst systems.