Provided are a rubber composition for treads which achieves a balanced improvement in fuel economy, abrasion resistance, and wet grip performance while offering good processability, and a pneumatic tire formed from the rubber composition. The present invention relates to a rubber composition for treads containing: a polybutadiene; and a terpene resin having a glass transition temperature (Tg) of 40 C. to 90 C., the polybutadiene satisfying the following conditions (A), (B) and (C): (A) a ratio (Tcp/ML.sub.1+4, 100 C.) of 5% by mass toluene solution viscosity (Tcp) to Mooney viscosity (ML.sub.1+4, 100 C.) is 0.9 to 2.3; (B) a stress relaxation time (T80) is 10.0 to 40.0 seconds, which is a time required for torque to decay by 80%, where 100% represents torque at the end of a ML.sub.1+4, 100 C. measurement; and (C) a molecular weight distribution (Mw/Mn) is 2.50 to 4.00.

Provided are a rubber composition for treads which achieves a balanced improvement in fuel economy, abrasion resistance, and wet grip performance while offering good processability, and a pneumatic tire formed from the rubber composition. The present invention relates to a rubber composition for treads containing: a polybutadiene; and a terpene resin having a glass transition temperature (Tg) of 40 C. to 90 C., the polybutadiene satisfying the following conditions (A), (B) and (C): (A) a ratio (Tcp/ML.sub.1+4, 100 C.) of 5% by mass toluene solution viscosity (Tcp) to Mooney viscosity (ML.sub.1+4, 100 C.) is 0.9 to 2.3; (B) a stress relaxation time (T80) is 10.0 to 40.0 seconds, which is a time required for torque to decay by 80%, where 100% represents torque at the end of a ML.sub.1+4, 100 C. measurement; and (C) a molecular weight distribution (Mw/Mn) is 2.50 to 4.00.

A block copolymer and a method for preparing the same are disclosed. The method comprises the following steps: (A) mixing a compound of formula (I), a catalyst of formula (II), and a first solvent to obtain a first mixture; (B) adding a first monomer into the first mixture for reaction to obtain a second mixture; and (C) adding a second monomer into the second mixture for reaction to obtain a third mixture; wherein the compound of formula (I) and the catalyst of formula (II) are as defined in the specification.

Proposed are a complex catalyst containing an imine-based ligand for polymerizing a cyclic olefin-based monomer and a method of preparing a cyclic olefin-based polymer using the same. More particularly, proposed are a complex catalyst containing an imine-based ligand for polymerizing a cyclic olefin-based monomer, which can provide the complex catalyst containing the imine-base ligand having high activity in polymerizing the cyclic olefin-based monomer and can prepare a cyclic olefin-based polymer with high activity by polymerizing the cyclic olefin-based monomer in the presence of the complex catalyst containing the imine-based ligand, and a method of preparing a cyclic olefin-based polymer using the same.

The invention relates to polybutadiene, which contains the monomer units derived from 1,3-butadiene having a vinyl double bond in a proportion of 25 to 75 mole percent, having a trans-double bond in a proportion of 0 to 10 mole percent and a cis-double bond in a proportion of 25 to 75 mole percent, wherein the totality of the monomer units (A), (B) and (C) is supplemented to 100 mole percent, and which is characterized in that it has a number-average mole mass of 1,000 to 3,000 g/mole. The invention further relates to a method for producing polybutadienes, the use of the polybutadiene according to the invention and compositions containing polybutadiene according to the invention.

The invention relates to polybutadiene, which contains the monomer units derived from 1,3-butadiene having a vinyl double bond in a proportion of 25 to 75 mole percent, having a trans-double bond in a proportion of 0 to 10 mole percent and a cis-double bond in a proportion of 25 to 75 mole percent, wherein the totality of the monomer units (A), (B) and (C) is supplemented to 100 mole percent, and which is characterized in that it has a number-average mole mass of 1,000 to 3,000 g/mole. The invention further relates to a method for producing polybutadienes, the use of the polybutadiene according to the invention and compositions containing polybutadiene according to the invention.

A pneumatic tire having a tire component prepared by use of a rubber composition according to the present invention which comprises: a polybitadiene (i) which satisfies conditions of (A) a Mooney viscosity (ML.sub.1+4, 100 C.) of 43 to 70, (B) a ratio (Tcp/ML.sub.1+4, 100 C.) of 5% by mass toluene solution viscosity (Tcp) to Mooney viscosity (ML.sub.1+4, 100 C.) of 0.9 to 1.7, (C) a stress relaxation time (T80), being a time until a torque is attenuated by 80% assuming that the torque at the end of ML.sub.1+4, 100 C. measurement is 100%, of 10.0 to 40.0 seconds, (D) a molecular weight distribution (Mw/Mn) of 2.50 to 4.00, and (F) a proportion of cis-structure in microstructural analysis of not more than 98 mol %; another rubber (ii); and a rubber reinforcing material (iii), is excellent in processability and properties of tire.

A pneumatic tire having a tire component prepared by use of a rubber composition according to the present invention which comprises: a polybitadiene (i) which satisfies conditions of (A) a Mooney viscosity (ML.sub.1+4, 100 C.) of 43 to 70, (B) a ratio (Tcp/ML.sub.1+4, 100 C.) of 5% by mass toluene solution viscosity (Tcp) to Mooney viscosity (ML.sub.1+4, 100 C.) of 0.9 to 1.7, (C) a stress relaxation time (T80), being a time until a torque is attenuated by 80% assuming that the torque at the end of ML.sub.1+4, 100 C. measurement is 100%, of 10.0 to 40.0 seconds, (D) a molecular weight distribution (Mw/Mn) of 2.50 to 4.00, and (F) a proportion of cis-structure in microstructural analysis of not more than 98 mol %; another rubber (ii); and a rubber reinforcing material (iii), is excellent in processability and properties of tire.

Bimetallic catalytic compounds and compositions comprising permethylpentalene ligands, as well as their methods of preparation, are described. The catalytic compounds and compositions are promising catalysts in olefin (e.g. ethylene) polymerisation reactions.

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Bimetallic catalytic compounds and compositions comprising permethylpentalene ligands, as well as their methods of preparation, are described. The catalytic compounds and compositions are promising catalysts in olefin (e.g. ethylene) polymerisation reactions.

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