| 摘要 |
PROBLEM TO BE SOLVED: To provide a rubber composition containing a modified conjugated dienic polymer made by modifying a terminal-active polymer obtained by using a catalyst containing a lanthanum-based rare earth element-containing compound, having a high content of cis-1,4 bond and having a terminal modified ratio of a specific value or higher, and being excellent in low heat generation, fracture property and wear resistance; and to provide a tire made by using the rubber composition and having the above properties.SOLUTION: A polymer is made by modifying with a modifying agent, a polymer having an active organometal site obtained by using a catalyst containing a lanthanum-based rare earth element-containing compound and by polymerizing a conjugated dienic compound in an organic solvent, wherein the modifying agent is at least one selected from specific compounds; the modification rate is ≥15%; the cis-1,4-bond content of the conjugated diene moiety measured by a Fourier transform infrared spectrometry satisfies the following expression (I): (cis-1,4-bond content)≥98.00 (%)...(I); and the conjugated dienic polymer having a number-average molecular weight (Mn) of 100,000 to 500,000 is contained in a proportion of ≥10 mass% in the whole rubber component. |
