Abstract: A polybutadiene rubber composition having an improved green strength is disclosed, which comprises a polybutadiene having a content of cis-1,4 bond of at least 70%, an average chain length of 1,4-bond of 110.about.450 and a molecular weight distribution represented by a ratio of weight-average molecular weight to number-average molecular weight of not less than 5.0.

Abstract: A rubber composition having excellent fracture properties and cut growth resistance is disclosed, which consists of 10-95 parts by weight of polybutadiene having a content of cis-1,4 bond of at least 70% and an average chain length of 1,4-sequence of 110-450 and 90-5 parts by weight of at least one diene rubber.

Abstract: A rubber composition suitable for use in tire tread is disclosed, which contains at least 20 parts by weight of a block copolymer per 100 parts by weight of total rubber content. This block copolymer comprises (A) a polymer segment obtained by starting from conjugated diolefin and monovinyl aromatic hydrocarbon and having a content of monovinyl aromatic hydrocarbon bond of not more than 10% by weight and (B) a copolymer segment obtained by copolymerization of conjugated diolefin and monovinyl aromatic hydrocarbon and having a content of monovinyl aromatic hydrocarbon bond of 15-50% by weight.

Abstract: A process for producing a conjugated diene polymer, characterized by polymerizing at least one conjugated diene with a catalyst consisting of (A) a reaction product of a Lewis base and a carboxylate of a rare earth element of the lanthanum series represented by Ln(R.sup.1 CO.sub.2).sub.3 wherein Ln is a rare earth element of the lanthanum series having an atomic number of 57 to 71 and R.sup.1 is a hydrocarbon substituent having 1 to 20 carbon atoms, (B) an organic aluminum compound represented by AlR.sup.2 R.sup.3 R.sup.4 wherein R.sup.2, R.sup.3 and R.sup.4, which may be identical or different, represent hydrogen atoms or hydrocarbon substituents having 1 to 8 carbon atoms, excluding the case where all of R.sup.2, R.sup.3 and R.sup.4 are hydrogen atoms at the same time, and (C) an (alkyl)aluminum halide represented by AlX.sub.n R.sup.5.sub.3-n wherein X is Cl, Br, F or I; R.sup.5 is a hydrocarbon substituent having 1 to 8 carbon atoms; and n has a value of 1, 1.

Abstract: A styrene-butadiene block copolymer having a Mooney viscosity (ML.sub.1+4, 100.degree. C.) of 10 to 150 comprising two specific random styrene-butadiene copolymer blocks different in bound styrene content and in vinyl content in the butadiene portion, and optionally polybutadiene blocks, wherein the total vinyl content in the whole bound butadiene is 30 to 70% and the total bound styrene content is 10 to 40% by weight. Said block copolymer is excellent in wet skid resistance and rolling resistance, well-balanced in fracture and wear characteristics and also satisfactory in processability and cold flow property.

Abstract: A rubber composition having improved cut growth resistance, processability and dimensional stability is disclosed, which comprises not less than 20 parts by weight of polyisoprene having a melting point of not less than 10.degree. C. and a content of cis-1,4 bond of not less than 88% and the balance of at least one diene rubber.

Abstract: High vinyl polybutadiene or styrene-butadiene copolymer obtained by polymerizing 1,3-butadiene alone or with styrene in a hydrocarbon solvent using an organolithium compound as an initiator and coupling the resulting polymer, characterized in that(1) the polybutadiene or styrene-butadiene copolymer comprises at least 20% by weight of a polymer having in its molecular chain a linkage between butadienyl and at least one metal selected from the group consisting of silicon, germanium, tin and lead,(2) the styrene content of said copolymer is 40% by weight or less, and(3) the polybutadiene or the butadiene portion of the styrene-butadiene copolymer has a vinyl content of 50 to 95%.Said polybutadiene or styrene-butadiene copolymer has low rolling resistance, high wet skid resistance, highly improved fracture property and, an excellent processability.

Abstract: Styrene-butadiene random copolymers having an average vinyl content of at least 70%, a breadth of the distribution of vinyl contents of at least 20%, a Mooney viscosity (ML.sub.1+4, 100.degree. C.) of 10 to 150, and a styrene content of about 3 to 30% by weight. They are prepared by copolymerizing styrene and butadiene in a hydrocarbon solvent in the presence of an organolithium initiator and a Lewis base and, if necessary, an anionic surface active agent containing --SO.sub.3 M or --OSO.sub.3 M (wherein M is Na, K, Rb or Cs) under temperature-raising conditions. They are rubber materials having low rolling resistance and high wet skid resistance.

Abstract: A process for preparing polybutadiene having a 1,2-configuration content of 5-40% and a cis-1,4-configuration content of 60% or more, which comprises polymerizing 1,3-butadiene in the presence of a catalyst consisting of:(A) a cobalt compound,(B) at least one member selected from the group consisting of:(i) a trialkylaluminum,(ii) a reaction product of a trialkylaluminum and an alcohol or water,(iii) a mixture of a trialkylaluminum and a dialkylaluminum halide,(iv) a dialkylaluminum hydride, and(v) an organolithium compound, and(C) at least one compound selected from the group consisting of phenyl isothiocyanate and carbon disulfide, in a hydrocarbon or halogenated hydrocarbon solution of a high cis-1,4-polybutadiene obtained by polymerizing 1,3-butadiene with a catalyst consisting of:(D) at least one compound selected from the group consisting of the organocarboxylates of nickel and organic complex compounds of nickel,(E) at least one compound selected from the group consisting of boron trifluoride, boron tr

Abstract: In the preparation of 1,2-polybutadiene with a vinyl content of at least 70% by contacting 1,3-butadiene with a catalyst consisting of:(A) a cobalt compound,(B) an organic phosphine compound,(C) a trialkylaluminum compound, and(D) water in an amount of 0.1 to 1.2 moles per mole of said trialkylaluminum,in the presence of a molecular weight regulator,(E) an alkylaluminum halide compound is used as the molecular weight regulator in an amount of at least 0.01 mole per mole of the trialkylaluminum compound (C), whereby 1,2-polybutadiene with a regulated molecular weight can be produced without causing decreased polymerization activity and change of vinyl content and crystallinity of the produced polymer. The alkylaluminum halide compound (E) is preferably used in an amount of 0.05 to 1.0 mole per mole of the trialkylaluminum compound (C).

Abstract: A process for preparing crystalline 1,2-polybutadiene by contacting 1,3-butadiene with a catalyst consisting of (A) a cobalt compound, (B) an organoaluminum compound, (C) water in an amount of 0.25 to 1.5 mole per mol of said organoaluminum compound, and (D) an organic phosphorus compound in a halogenated hydrocarbon solvent to polymerize the butadiene, characterized in that as said organic phosphorus compound there is used a compound represented by the formula: ##STR1## wherein R.sup.1 is an alkyl or aryl group, and R.sup.2 and R.sup.3 represent independently hydrogen, or alkyl or aryl groups. This process can produce 1,2-polybutadiene having a degree of crystallization of 25 to 50% in a high yield at a temperature of from 0.degree. to 30.degree. C.

Abstract: A process for producing a chemically crosslinked polyethylene foam, which comprises heating a polyethylene composition consisting essentially of 97 to 50 % by weight of polyethylene, 3 to 50 % by weight of polybutadiene having a 1,2-addition unit content of at least 70 %, an intrinsic viscosity [.eta.] of at least 0.7 dl/g (as measured in toluene at 30.degree. C), at least one blowing agent and at least one crosslinking agent to foam and crosslink said polyethylene composition. The above process can be carried out with a smaller amount of crosslinking agents without expensive crosslinking equipment, and the foam obtained by this process has improved physical properties.

Abstract: Solvent-developed type photosensitive compositions containing as an essential ingredient at least one selected from the group of the cyclization product of butadiene polymer or copolymer and organic solvent, with or without at least one member selected from the group consisting of photosensitizer and photosensitive crosslinking agent, both soluble in an organic solvent.