Abstract: A process for simply and inexpensively producing a conjugated diene polymer with a narrow molecular weight distribution and a high cis-bond content at a low cost is provided. The process comprises a polymerization step, wherein a conjugated diene polymer having a cis-1,4-bond content of 98.5 mass % or more and a ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) measured by gel permeation chromatography of 2.5 or less is obtained by carrying out a polymerization reaction in conjugated diene compounds using a catalyst composition containing a rare earth element-containing compound or a reaction product of the rare earth element-containing compound with a Lewis base, an aluminoxane and/or organoaluminum compound, and an iodine-containing compound.

Abstract: A rubber composition for tire sidewall which comprises a rubber component, which comprises polybutadiene rubber having a content of the cis-1,4-bond of 92% or greater and a content of the vinyl bond of 1.5% or smaller and natural rubber and/or at least one other diene-based synthetic rubber, and 10 to 70 parts by mass of carbon black having a specific surface area by nitrogen adsorption of 20 to 100 m2/g per 100 parts by mass of the rubber component and does not comprise a softener having an aniline point of 50° C. or lower and a tire using the rubber composition for sidewall. Excellent resistance to cut growth is obtained while sufficient workability is surely exhibited.

Abstract: A process for simply and inexpensively producing a conjugated diene polymer with a narrow molecular weight distribution and a high cis-bond content at a low cost is provided. The process comprises a polymerization step, wherein a conjugated diene polymer having a cis-1,4-bond content of 98.5 mass % or more and a ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) measured by gel permeation chromatography of 2.5 or less is obtained by carrying out a polymerization reaction in conjugated diene compounds using a catalyst composition containing a rare earth element-containing compound or a reaction product of the rare earth element-containing compound with a Lewis base, an aluminoxane and/or organoaluminum compound, and an iodine-containing compound.

Abstract: A process for simply and inexpensively producing a conjugated diene polymer with a narrow molecular weight distribution and a high cis-bond content at a low cost is provided. The process comprises a polymerization step, wherein a conjugated diene polymer having a cis-1,4-bond content of 98.5 mass % or more and a ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) measured by gel permeation chromatography of 2.5 or less is obtained by carrying out a polymerization reaction in conjugated diene compounds using a catalyst composition containing a rare earth element-containing compound or a reaction product of the rare earth element-containing compound with a Lewis base, an aluminoxane and/or organoaluminum compound, and an iodine-containing compound.

Abstract: This invention relates to a method for producing functionalized cis-1,4-polydienes having a combination of a high cis-1,4-linkage content and a high functionality, the resulting polymers and the vulcanized products containing the polymers. The functionalized cis-1,4-polydienes of the present invention are produced by a method comprising the steps of: (1) preparing a reactive polymer by polymerizing conjugated diene monomer with a lanthanide-based catalyst in the presence of less than 20% by weight of organic solvent based on the total weight of monomer, organic solvent, and resulting polymer, where the lanthanide-based catalyst is the combination of or reaction product of (a) a lanthanide compound, (b) an aluminoxane, (c) an organoaluminum compound other than an aluminoxane, and (d) a halogen-containing compound; and (2) contacting the reactive polymer with a functionalizing agent.

Abstract: The present invention provides a modified conjugated diene polymer that is prepared by polymerization of a conjugated diene compound using a catalyst containing a lanthanoid rare earth element compound in an organic solvent and then modifying the resulting polymer having an active organic metal site with a modifier, wherein the modification efficiency is not less than 15% and the cis-1,4 bond content in the conjugated diene moiety measured by Fourier transform infrared spectroscopy satisfies the relationship (I): cis-1,4 bond content?98.00(%)??(I), or the modification efficiency is not less than 75% and the cis-1,4 bond content in the conjugated diene moiety measured by Fourier transform infrared spectroscopy satisfies the relationship (II): 94.00(%)?cis-1,4 bond content<98.00(%)??(II).

Abstract: A process for producing a modified conjugated diene polymer includes subjecting an active terminal of a conjugated diene polymer having a vinyl content of less than 10% and a cis-1,4 bond content of 75% or more to a modification reaction with an alkoxysilane compound, and subjecting the alkoxysilane compound (residue) to a condensation reaction in an aqueous solution at a pH of 9 to 14 and a temperature of 85 to 180° C. in the presence of a condensation accelerator including a compound containing titanium. The modified conjugated diene polymer exhibits low heat build-up and increased reinforcing properties when used for a rubber composition, and exhibits excellent wear resistance, mechanical characteristics, and processability.

Abstract: A process for producing a modified conjugated diene polymer includes subjecting an active terminal of a conjugated diene polymer having a vinyl content of less than 10% and a cis-1,4 bond content of 75% or more to a modification reaction with an alkoxysilane compound, and subjecting the alkoxysilane compound (residue) to a condensation reaction in an aqueous solution at a pH of 9 to 14 and a temperature of 85 to 180° C. in the presence of a condensation accelerator including a compound containing titanium. The modified conjugated diene polymer exhibits low heat build-up and increased reinforcing properties when used for a rubber composition, and exhibits excellent wear resistance, mechanical characteristics, and processability.

Abstract: A rubber composition comprises 10 to 70 parts by mass of carbon black having 20 to 100 m2/g of the specific surface area by nitrogen adsorption per 100 parts by mass of a rubber component comprising 20 to 80 parts by mass of a modified polybutadiene rubber and 80 to 20 parts by mass of natural rubber and/or at least one other diene-based synthetic rubber, wherein the modified polybutadiene is obtained by polymerizing 1,3-butadiene in an organic solvent using a compound having a rare earth element of the lanthanoid series, followed by modifying the obtained polybutadiene, and has a content of the cis-1,4-bond of 92% or greater, a content of vinyl bond of 1.5% or smaller and a fraction of the modified chain end of 20% or greater; and a tire using the rubber composition for a sidewall. The rubber composition exhibits excellent low heat buildup property and resistance to fracture.

Abstract: This invention is concerned with a butadiene-based polymer having a high cis-1,4 bond content, a low vinyl bond content and a molecular weight distribution of a specified range, and more particularly a butadiene-based polymer having a 1,3-butadiene monomer unit, characterized in that a cis-1,4 bond content and a vinyl bond content in the 1,3-butadiene monomer unit as measured by a Fourier transform infrared spectroscopy (FT-IR) is not less than 98.0% and not more than 0.3%, respectively, and a ratio (Mw/Mn) of weight average molecular weight (Mw) to number average molecular weight (Mn) is 1.6-3.5.

Abstract: The present invention provides a modified conjugated diene polymer that is prepared by polymerization of a conjugated diene compound using a catalyst containing a lanthanoid rare earth element compound in an organic solvent and then modifying the resulting polymer having an active organic metal site with a modifier, wherein the modification efficiency is not less than 15% and the cis-1,4 bond content in the conjugated diene moiety measured by Fourier transform infrared spectroscopy satisfies the relationship (I): cis-1,4 bond content?98.00(%)??(I), or the modification efficiency is not less than 75% and the cis-1,4 bond content in the conjugated diene moiety measured by Fourier transform infrared spectroscopy satisfies the relationship (II): 94.00(%)?cis-1,4 bond content<98.00(%)??(II).

Abstract: A process for simply and inexpensively producing a conjugated diene polymer with a narrow molecular weight distribution and a high cis-bond content at a low cost is provided. The process comprises a polymerization step, wherein a conjugated diene polymer having a cis-1,4-bond content of 98.5 mass % or more and a ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) measured by gel permeation chromatography of 2.5 or less is obtained by carrying out a polymerization reaction in conjugated diene compounds using a catalyst composition containing a rare earth element-containing compound or a reaction product of the rare earth element-containing compound with a Lewis base, an aluminoxane and/or organoaluminum compound, and an iodine-containing compound.

Abstract: A rubber composition for tire sidewall which comprises a rubber component, which comprises polybutadiene rubber having a content of the cis-1,4-bond of 92% or greater and a content of the vinyl bond of 1.5% or smaller and natural rubber and/or at least one other diene-based synthetic rubber, and 10 to 70 parts by mass of carbon black having a specific surface area by nitrogen adsorption of 20 to 100 m2/g per 100 parts by mass of the rubber component and does not comprise a softener having an aniline point of 50° C. or lower and a tire using the rubber composition for sidewall. Excellent resistance to cut growth is obtained while sufficient workability is surely exhibited.

Abstract: This invention relates to a method for producing functionalized cis-1,4-polydienes having a combination of a high cis-1,4-linkage content and a high functionality, the resulting polymers and the vulcanized products containing the polymers. The functionalized cis-1,4-polydienes of the present invention are produced by a method comprising the steps of: (1) preparing a reactive polymer by polymerizing conjugated diene monomer with a lanthanide-based catalyst in the presence of less than 20% by weight of organic solvent based on the total weight of monomer, organic solvent, and resulting polymer, where the lanthanide-based catalyst is the combination of or reaction product of (a) a lanthanide compound, (b) an aluminoxane, (c) an organoaluminum compound other than an aluminoxane, and (d) a halogen-containing compound; and (2) contacting the reactive polymer with a functionalizing agent.

Abstract: This invention is concerned with a butadiene-based polymer having a high cis-1,4 bond content, a low vinyl bond content and a molecular weight distribution of a specified range, and more particularly a butadiene-based polymer having a 1,3-butadiene monomer unit, characterized in that a cis-1,4 bond content and a vinyl bond content in the 1,3-butadiene monomer unit as measured by a Fourier transform infrared spectroscopy (FT-IR) is not less than 98.0% and not more than 0.3%, respectively, and a ratio (Mw/Mn) of weight average molecular weight (Mw) to number average molecular weight (Mn) is 1.6-3.5.