| 摘要 |
PURPOSE: To provide the subject pneumatic radial tire that is light in weight and has excellent resistance to heat and to show good driving stability by using steel cords as belt cords and a sheath-core conjugated yarn comprising the polyester core component and the polyamide sheath component as carcass cords. CONSTITUTION: A sheath-core type conjugated fiber comprising polyester core component that mainly comprises ethylene terephthalate units as the main component with an intrinsic viscosity [η] of >=0.80 and the polyamide sheath component with the relative viscosityηr of >=2.8 in sulfuric acid where the proportion of the polyester core component is 30-90 wt.%, the peak temperature of the polyester core component according to the DSC of >=249 deg.C are twisted in the Z and S directions to give the tire cord having the twist coefficient K of 1,900-2,500, the strength of >=5.5 g/d, the intermediate elongation of 4-7%, the dry heat shrinkage of <=7% at 177 deg.C. The result tire cords are used as a carcass cord and the steel cords are used as a belt cord to produce the objective pneumatic radial tires.
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