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).

(Meth)acrylate-based reactive diluent compositions can be used for enabling styrene-free curing of unsaturated polyester resins. The reactive diluent compositions have a (meth)acrylic acid ester monomer and a compatibilizing agent including at least one (meth)acrylate moiety and at least one additional ethylenically unsaturated moiety.

A method for tailoring mechanical properties of a photopolymer includes providing an active monomer feedstock, adding a sulfur-free chain transfer agent (CTA) to the active monomer feedstock to form a mixture, and curing the mixture under predetermined conditions. The sulfur-free CTA includes a Cobalt(II) complex or a Cobalt(III) complex, the mechanical properties include glass transition temperature, crosslinking density, and/or conversion rate, and a concentration of the sulfur-free CTA is less than 30% of the mixture. The predetermined conditions include intensity, wavelength, and application time of energy from a light source, a cure temperature, and/or the concentration of the sulfur-free CTA in the mixture. The method may further include adding a diluent to the mixture to modify a viscosity of the active monomer feedstock. The diluent may include one of a reactive diluent and a non-reactive diluent, such as methyl methacrylate (MMA) and methacrylate (MA).

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.

A process for preparing a blend of cis-1,4-polybutadiene and syndiotactic 1,2 polybutadiene, the process comprising the steps of (i) polymerizing 1,3-butadiene in the presence of a lanthanide-based catalyst to form a polymerization mixture including cis-1,4-polybutadiene, and (ii) polymerizing 1,3-butadiene in the presence of a cobalt-based catalyst within the polymerization mixture including cis-1,4-polybutadiene to form syndiotactic 1,2-polybutadiene and thereby produce a blend of cis-1,4-polybutadiene and syndiotactic 1,2-polybutadiene.

A process for preparing a blend of cis-1,4-polybutadiene and syndiotactic 1,2 polybutadiene, the process comprising the steps of (i) polymerizing 1,3-butadiene in the presence of a lanthanide-based catalyst to form a polymerization mixture including cis-1,4-polybutadiene, and (ii) polymerizing 1,3-butadiene in the presence of a cobalt-based catalyst within the polymerization mixture including cis-1,4-polybutadiene to form syndiotactic 1,2-polybutadiene and thereby produce a blend of cis-1,4-polybutadiene and syndiotactic 1,2-polybutadiene.

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.

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.