| 摘要 |
PURPOSE:To prepare the titled composition having balanced rolling resistance of tire, wet grip property, abrasion resistance and crack resistance, by using a star copolymer of styrene and butadiene having specific styrene content and coupling efficiency and obtained by solution polymerization, as a component. CONSTITUTION:The objective composition is prepared by mixng a natural rubber or a synthetic diene rubber with a styrene-butadiene (SB) star copolymer having a styrene content X of 26-39 defined by the formulaIand a coupling efficiency of >=40% (the value defined by the formula II in the molecular weight distribution curve determined by gel-permeation chromatography). The amount of the SB copolymer is >=30%. The star SB copolymer is preferably the one having an S-content of <=20%, vinyl content of <=50% and a Mooney viscosity of 35- 120[ML1+4(100 deg.C)]. The coupling agent is SnCl4.
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