The present invention relates to a copolymer including a monomer unit (a) derived from a conjugated diene having not more than 12 carbon atoms and a monomer unit (b) derived from farnesene; a process for producing the copolymer including at least the step of copolymerizing a conjugated diene having not more than 12 carbon atoms with farnesene; a rubber composition including (A) the copolymer, (B) a rubber component and (C) carbon black; a rubber composition including (A) the copolymer, (B) a rubber component and (D) silica; a rubber composition including (A) the copolymer, (B) a rubber component, (C) carbon black and (D) silica; and a tire using the rubber composition at least as a part thereof.

A rubber composition contains: a diene rubber; 1 to 25 parts by weight of aromatic modified terpene resin; 80 to 150 parts by weight of silica; 5 to 50 parts by weight of carbon black; an oil component; and 0.1 to 20 wt. % of the weight of the silica of alkyltriethoxysilane having an alkyl group having 3 to 20 carbons, the diene rubber containing 10 to 30 wt. % of natural rubber, 10 to 30 wt. % of solution polymerized styrene butadiene rubber having a styrene unit content of 30 to 40 wt. % and 80 to 40 wt. % of emulsion polymerized styrene butadiene rubber, and a ratio of a total amount of an oil-extending component in the solution polymerized styrene butadiene rubber and/or the emulsion polymerized styrene butadiene rubber, the aromatic modified terpene resin, and the oil component to a weight of the natural rubber being 3.0 to 4.0.

A rubber composition contains: a diene rubber; 1 to 25 parts by weight of aromatic modified terpene resin; 80 to 150 parts by weight of silica; 5 to 50 parts by weight of carbon black; an oil component; and 0.1 to 20 wt. % of the weight of the silica of alkyltriethoxysilane having an alkyl group having 3 to 20 carbons, the diene rubber containing 10 to 30 wt. % of natural rubber, 10 to 30 wt. % of solution polymerized styrene butadiene rubber having a styrene unit content of 30 to 40 wt. % and 80 to 40 wt. % of emulsion polymerized styrene butadiene rubber, and a ratio of a total amount of an oil-extending component in the solution polymerized styrene butadiene rubber and/or the emulsion polymerized styrene butadiene rubber, the aromatic modified terpene resin, and the oil component to a weight of the natural rubber being 3.0 to 4.0.

A benzoxazine resin, including a compound of the following Formula 1-1:

##STR00001##

where R.sup.1, R.sup.2, and R.sup.3 are as defined herein.

A benzoxazine resin, including a compound of the following Formula 1-1:

##STR00001##

where R.sup.1, R.sup.2, and R.sup.3 are as defined herein.

Provided is a sealant composition excellent in production efficiency (coating speed) and sealing characteristics, and a pneumatic tire using the sealant composition. The sealant composition contains 95 parts by mass to 150 parts by mass of a hydrocarbon resin, 20 parts by mass to 60 parts by mass of a liquid plasticizer, and 5 parts by mass to 30 parts by mass of a filler having a DBP absorption amount of 110 cm.sup.3/100 g or less, with respect to 100 parts by mass of a solid rubber component containing a diene rubber.

Provided is a sealant composition excellent in production efficiency (coating speed) and sealing characteristics, and a pneumatic tire using the sealant composition. The sealant composition contains 95 parts by mass to 150 parts by mass of a hydrocarbon resin, 20 parts by mass to 60 parts by mass of a liquid plasticizer, and 5 parts by mass to 30 parts by mass of a filler having a DBP absorption amount of 110 cm.sup.3/100 g or less, with respect to 100 parts by mass of a solid rubber component containing a diene rubber.

Provided is a sealant composition excellent in exothermic performance, rigidity, and sealing characteristics, and a pneumatic tire using the sealant composition. The sealant composition contains 95 parts by mass to 150 parts by mass of a hydrocarbon resin, 20 parts by mass to 60 parts by mass of a liquid plasticizer, and 0.1 parts by mass to 10 parts by mass of a cellulose nanofiber, with respect to 100 parts by mass of a solid rubber component containing a diene rubber.

Provided is a sealant composition excellent in exothermic performance, rigidity, and sealing characteristics, and a pneumatic tire using the sealant composition. The sealant composition contains 95 parts by mass to 150 parts by mass of a hydrocarbon resin, 20 parts by mass to 60 parts by mass of a liquid plasticizer, and 0.1 parts by mass to 10 parts by mass of a cellulose nanofiber, with respect to 100 parts by mass of a solid rubber component containing a diene rubber.

A tire composition is disclosed. The composition comprises a rubber component and based on 100 parts by weight (phr) of the rubber component, 50-200 phr of covered silica, with the covered silica comprising silica core and a first resin covering the silica core, wherein the first resin is not chemically bonded to the silica core. The silica core is covered with the first resin by mixing a slurry comprising silica core with a mixture containing the first resin as a solution, an aqueous dispersion; or a solution by dissolving the first resin in a solvent.