A technique of improving the hydrogenation reaction of diene-based polymers, present in aqueous suspension, by in-situ synthesizing the catalyst in the presence of a specific aliphatic alcohol is disclosed. The process allows the selective hydrogenation of the carbon-carbon double bonds in the diene-based polymers with a high degree of hydrogenation and short reactions times. The improved process eliminates the complicated catalyst synthesis operations so far necessary.

A technique of improving the hydrogenation reaction of diene-based polymers, present in aqueous suspension, by in-situ synthesizing the catalyst in the presence of a specific aliphatic alcohol is disclosed. The process allows the selective hydrogenation of the carbon-carbon double bonds in the diene-based polymers with a high degree of hydrogenation and short reactions times. The improved process eliminates the complicated catalyst synthesis operations so far necessary.

A rubber composition contains: (A) a polymer having a carbon-carbon unsaturated bond and exhibiting a value α of 0.6 or more as obtained by the following formula (i):
α=(p+(0.5×r))/(p+q+(0.5×r)+s)  (i)
wherein p, q, r, and s are the proportions by mole of structural units represented by the following formulae (1), (2), (3), and (4), respectively in the polymer: ##STR00001## and (B) modified silica.

Provided is a pneumatic tire having well-improved fuel economy, rubber tensile strength, and abrasion resistance while maintaining adequate productivity. The present invention relates to a pneumatic tire formed from a rubber composition, the rubber composition containing a hydrogenated copolymer and a sulfur donor, the hydrogenated copolymer containing a structural unit derived from an aromatic vinyl compound and a structural unit derived from a conjugated diene compound and having a degree of hydrogenation of the conjugated diene portion of 75 mol % or more, the hydrogenated copolymer being present in an amount of 75% by mass or more based on 100% by mass of a rubber component in the rubber composition, the sulfur donor being present in an amount of 0.2 to 8 parts by mass per 100 parts by mass of the rubber component.

Provided is a pneumatic tire having well-improved fuel economy, rubber tensile strength, and abrasion resistance while maintaining adequate productivity. The present invention relates to a pneumatic tire formed from a rubber composition, the rubber composition containing a hydrogenated copolymer and a sulfur donor, the hydrogenated copolymer containing a structural unit derived from an aromatic vinyl compound and a structural unit derived from a conjugated diene compound and having a degree of hydrogenation of the conjugated diene portion of 75 mol % or more, the hydrogenated copolymer being present in an amount of 75% by mass or more based on 100% by mass of a rubber component in the rubber composition, the sulfur donor being present in an amount of 0.2 to 8 parts by mass per 100 parts by mass of the rubber component.

A method for producing a polymer has: a polymerization step of polymerizing at least a conjugated diene monomer in a hydrocarbon solvent using an organolithium compound as a polymerization initiator, and obtaining a polymer; and, following steps (1) to (4), successively performing after the polymerization step: (1) a step of mixing an acid and water of 20 to 300 parts by mass into the solution containing the polymer of 100 parts by mass, (2) a step of adjusting an amount of the water to 10 parts by mass or less based on 100 parts by mass of the solution containing the polymer, (3) a step of adding a carbon oxide gas and/or a compound to be decarboxylated to the solution containing the polymer, and (4) a step of removing a solvent from the solution containing the polymer until a concentration of the polymer reaches 95 mass % or more.

The present invention provides a pneumatic tire having well-improved rubber tensile strength and abrasion resistance. The present invention relates to a pneumatic tire formed from a rubber composition, the rubber composition containing: a hydrogenated copolymer obtained by copolymerization of an aromatic vinyl compound and a conjugated diene compound, the hydrogenated copolymer having a degree of hydrogenation of the conjugated diene units of 75 mol % or more; a fine particle silica having a CTAB specific surface area of 160 m.sup.2/g or more and a BET specific surface area of 170 m.sup.2/g or more; and carbon black, the rubber composition containing, per 100% by mass of the rubber component, 75% by mass or more of the hydrogenated copolymer, the rubber composition containing, relative to 100 parts by mass of the rubber component, 3 parts by mass or more of the carbon black.

The present invention relates to a catalyst system containing a metathesis catalyst containing at least one N-heterocyclic carbene ligand and at least one phenolic compound and to a process for performing the metathesis on nitrile rubbers for reducing their molecular weight using a metathesis catalyst containing at least one N-heterocyclic carbene ligand (NHC ligand) and at least one phenolic compound.

The present invention relates to a catalyst system containing a metathesis catalyst containing at least one N-heterocyclic carbene ligand and at least one phenolic compound and to a process for performing the metathesis on nitrile rubbers for reducing their molecular weight using a metathesis catalyst containing at least one N-heterocyclic carbene ligand (NHC ligand) and at least one phenolic compound.

Provided is a method for producing a hydrocarbon resin hydride, comprising: hydrogenating a hydrocarbon resin by bringing the hydrocarbon resin into contact with hydrogen in the presence of an antioxidative compound and a hydrogenation catalyst, the antioxidative compound being at least one selected from the group consisting of hindered phenolic antioxidants and antioxidants having a 2,2,6,6-tetraalkyl-4-piperidyl group.