Provided are copolymers which provide improved overall performance in terms of fuel economy and wet grip performance, as well as rubber compositions and tires containing the copolymers. Included is a copolymer obtained by copolymerizing an aromatic vinyl compound, a conjugated diene compound, and a compound represented by the formula (1) below or by copolymerizing a conjugated diene compound and a compound represented by the formula (1) below, the copolymer having a weight average molecular weight of 1.0×10.sup.3 to 2.5×10.sup.6, ##STR00001##
wherein R.sup.1 and R.sup.2 may be the same or different and each represents a functional group containing at least two selected from the group consisting of carbon, hydrogen, and silicon, and R.sup.1 and R.sup.2 may be joined together to form a ring structure.

A composition for seeded polymerization includes: a seed copolymer which has a compound having dithioate, a mercaptan compound, a first aromatic vinyl monomer, and a first conjugated diene monomer, and has an average particle diameter of 10-30 nm; a second aromatic vinyl monomer; and a second conjugated diene monomer.

A rubber compound for a tire tread includes more than a 30% maximum difference in styrene content between a pair of functionalized diene elastomers. At least one of the diene elastomers contains a functional group that can interact with a precipitated silica that is also in the composition.

An object of the present invention is to provide a rubber composition for a tread which is good in the balance between its wet grip performance and its chipping resistance. The rubber composition for a tread comprises 1 to 20 parts by mass of an ethylene-propylene-styrene copolymer and 60 parts by mass or more of a filler comprising a silica based on 100 parts by mass of a rubber component comprising 20 to 50% by mass of a butadiene rubber and 30 to 80% by mass of a styrene butadiene rubber, wherein an elongation at break of the rubber composition is not less than 300% in the atmosphere of 180° C. according to JIS K 6251: 2017.

The invention relates to a copolymer of ethylene and of a 1,3-diene of formula CH.sub.2═CR—CH═CH.sub.2, which copolymer bears a silanol or alkoxysilane function, the symbol R representing a hydrocarbon chain having from 3 to 20 carbon atoms. Such a copolymer improves the compromise between the content of ethylene in the polymer, its crystallinity and the stiffness of a rubber composition containing it.

A motorcycle tyre (1) is described comprising an equatorial plane (X-X) and a tread band (8) comprising a radially inner portion (13) and a radially outer portion (11) respectively comprising a first and a second vulcanized elastomeric material obtained by vulcanizing respective elastomeric materials comprising 100 phr of at least one elastomeric diene polymer, from 30 to 130 phr of at least one reinforcing filler comprising an amount greater than 75% or, respectively, equal to or greater than 80% of a white filler. In the tyre (1) the ratio R1 between the dynamic elastic modulus (E′) and the tandelta measured at a frequency of 10 Hz and at 70° C. of the first vulcanized elastomeric material is comprised between 27 and 35, whereas the ratio R2 between the dynamic elastic modulus (E′) and the tandelta measured at a frequency of 10 Hz and at 70° C. of the second vulcanized elastomeric material is comprised between 15 and 30, the ratio R1/R2 being greater than or equal to 1.1.

The invention relates to a sulfur-crosslinkable rubber mixture and to a pneumatic vehicle tire comprising at least one rubber component made of the sulfur-vulcanized rubber mixture.

The rubber mixture contains 10-60 phr (parts by weight, based on 100 parts by weight of the total rubbers in the mixture) of at least one functionalized polybutadiene A,
wherein the functionalized polybutadiene A is functionalized at one chain end with an organosilyl group containing amino groups and/or ammonium groups,
and wherein the functionalized polybutadiene A is functionalized at the other chain end with an amino group, up to 90 phr of at least one further diene rubber and 30-350 phr of at least one filler.

Provided is a rubber composition having excellent low heat generating properties. The rubber composition of the present disclosure contains a rubber component, a filler containing silica, and a silane coupling agent, where the rubber component contains a conjugated diene-based polymer modified with a modifier containing a compound represented by the formula (1), and the silane coupling agent is a compound represented by the formula (2).

##STR00001##

Disclosed is a method of preparing a rubber composition comprising the steps of (a) blending in at least one preparatory mixing step at least one natural or synthetic rubbery polymer, a silica filler, a silica coupling agent, and at least one vulcanization accelerator; and (b) subsequently blending therewith in a final mixing step a sulfur curative, wherein the average glass transition temperature of the polymer(s) is −55° C. or less.

A polymer composition comprises (a) 50 to 100 phr of one or more branched thermoplastic elastomers each comprising an unsaturated elastomer block and at least three thermoplastic styrene blocks, the thermoplastic styrene blocks of each branched thermoplastic elastomer representing from 15% to 75%, preferably from 15% to 50%, by weight of the weight of each branched thermoplastic elastomer, and (b) 10 to 100 phr of one or more thermoplastic styrene polymers having a molecular mass of between 25,000 and 300,000 g/mol, preferably between 50,000 and 200,000 g/mol.