Abstract: A process for modifying a polymer of a conjugated diene, which comprises reacting a polymer of a conjugated diene containing at least one metal selected from alkali metals and alkaline earth metals with a compound having a linkage of the following formula ##STR1## wherein X represents an oxygen or sulfur atom, in the molecule.

Abstract: A rubber composition for tire treads, comprising [I] 10 to 70% by weight of a polybutadiene rubber having bonded to a carbon atom of the rubber molecular chain at least 0.1 mole, per mole of the rubber molecular chain, of an atomic grouping represented by the following formula ##STR1## wherein X represents O or S, R.sub.1 and R.sub.2 are identical or different and each represents an amino group or an alkyl-substituted amino group, R.sub.3 and R.sub.4 are identical or different and each represents a substituent other than the above-mentioned, m, p and q each represent O or an integer of at least 1, n represents an integer of at least 1, m+p=0-5, and n+q=1-5,and [II] 90 to 30% by weight of at least one rubber selected from the group consisting of styrene-butadiene copolymer rubber having a bound stryene content of not more than 50% by weight and polyisoprene rubber.

Abstract: A rubber composition for tire treads, comprising [I] 10 to 90% by weight of a styrene-butadiene copolymer rubber containing not more than 40% by weight of bound styrene and having bonded to a carbon atom of the rubber molecular chain at least 0.1 mole, per mole of the rubber molecular chain, of an atomic grouping represented by the following formula ##STR1## wherein: X represents O or S,R.sub.1 and R.sub.2 are identical or different and each represents an amino group or an alkyl-substituted amino group,R.sub.3 and R.sub.4 are identical or different and each represents a substituent other than the above-mentioned,m, p and q each represent O or an integer of at least 1,n represents an integer of at least 1, m+p=0-5, and n+q=1-5,and [II] 90 to 10% by weight of at least one rubber selected from the group consisting of styrene-butadiene copolymer rubber having a bound styrene content of not more than 40% by weight and polyisoprene rubber.

Abstract: A rubber material having an excellent grip on ice comprising a mixture of an ordinary rubber and a powdered polymer, said powdered polymer having a maximum of tan .delta. at a temperature in the range of -5.degree. C. to +35.degree. C. when the tan .delta. is measured by a nonresonance, forced vibration apparatus at a frequency of 110 hertz and a heating rate of 2.degree. C./minute.

Abstract: A rubber composition comprising as main components (1) at least one rubber having a glass transition temperature of from -45.degree. C. to 0.degree. C. and selected from the group consisting of an isoprene-butadiene copolymer rubber and polyisoprene rubber and (2) at least one rubber selected from the group consisting of natural rubber and cis-1,4-polyisoprene rubber having a cis-1,4-linkage content of at least 90 mole %, said composition having a value, defined by the following formula, of at least 10,[(R-53)+(S-100)]wherein R is a rebound (%) measured at 51.degree. C. by a Dunlop Tripso meter for a vulcanized product of said rubber composition, and S, as defined in the specification, is a wet skid resistance index on a road surface defined by ASTM E-303-74 which is determined at 19.degree. C. by a portable skid tester for a vulcanized product of said rubber composition.

Abstract: A process for preparing a tire tread rubber composition having improved rolling resistance and wet skid resistance comprising [I] 100 parts by weight of a rubber material composed of 25 to 75% by weight of substantially amorphous polybutadiene having a 1,2-bond unit content of 65 to 90 mole % and a Mooney viscosity (ML.sub.1+4, 100.degree. C.) of 20 to 100 and 75 to 25% by weight of natural rubber and/or cis-1,4-polyisoprene, and [II] 40 to 70 parts by weight of carbon black, said process comprising (1) mechanically compounding 40 to 60 parts by weight of the rubber material [I] with 40 to 70 parts by weight of carbon black [II], and then (2) adding to the resulting mixture the rubber material [I] in an amount sufficient to adjust the amount of the carbon black [II] to 40 to 70 parts by weight per 100 parts by weight of the rubber material [I] and mechanically compounding them.

Abstract: A solderless type heat exchanger having an upper and lower tanks, header plates closing the opposing opened ends of respective tanks, a plurality of tubes extending through the head plates to provide a communication between the upper and lower tanks, and a plurality of plate fins attached to the outside of the tubes, the tubes being joined to the header plates and plate fins solely by pressure contact therebetween provided through expansion of the tubes. The header plate is provided with a collared portion around each bore for receiving the corresponding tube and an annular groove is formed around the periphery of each collared portion. The annular groove provides a resiliency which ensures the rigid and stable joint between the tubes and the header plate achieved solely by the pressure contact through the expansion of the tube.

Abstract: A rubber composition for the tread of tire having reduced rolling resistance and increased wet skid resistance with the mechanical properties unimpaired, said rubber composition comprising 20 to 80% by weight of (I) essentially amorphous polybutadiene having a 1,2-bond units content of at least 70% and a Mooney viscosity (ML.sub.1+4, 100.degree. C.) of 10 to 100; 10 to 75% by weight of (II) polybutadiene rubber having a 1,2-bond units content of 20% or less and a Mooney viscosity (ML.sub.1+4, 100.degree. C.) of 20 to 130; and 3 to 35% by weight of (III) at least one rubber selected from styrene/butadiene copolymer rubber having a bound styrene content of 15 to 25% by weight, natural rubber, and polyisoprene rubber having a cis-1,4-bond units content of at least 90%.

Abstract: A blended rubber composition comprising(a) 70 to 95% by weight of at least one diene rubber, and(b) 30 to 5% by weight of a polymer or copolymer obtained by polymerizing at least one norbornene compound expressed by the general formula ##STR1## wherein R and R', independently from each other, represent a hydrogen atom, an alkyl group with 1 to 4 carbon atoms, and alkoxy group with 1 to 4 carbon atoms or the group --OCOCH.sub.3.

Abstract: A rubber composition for tire treads includes (Ia) an oil-extended rubber having a Mooney viscosity (ML.sub.1+4, 100.degree. C) of 20 to 70 which is prepared by adding 20 to 80 parts of a hydrocarbon oil to 100 parts by weight of a rubber terpolymer which is composed of 2 to 13% by weight of combined styrene, 15 to 70% by weight of combined 1,3-butadiene and 17 to 83% by weight of combined 1,3-pentadiene with the dienes having a total 1,4-bond content of at least 65 mole%, (II) vulcanization additives, and (III) 30 to 110 parts by weight, per 100 parts by weight of the oil-extended rubber (Ia), of a carbon black for rubber having an average particle diameter of not more than 60 m.mu. the rubbery copolymer has a glass transistion temperature of -70.degree. to -20.degree. C., and is produced by emulsion-polymerization at 0.degree. to 30.degree. C.