| 摘要 |
PROBLEM TO BE SOLVED: To improve mainly durability by using simplified cord of 2+5 structure as a belt for passenger car tires. SOLUTION: A double layer belt on a carcass 2 is made of steel cord of layer twist structure in which a sheath is formed by twisting five strands of steel filaments around a core filament 1 which is made of two strands of steel filaments. The steel cord before making the tire is cut into 10 cm in length, then plating on each filament surface is removed by ammonium persulfate solution. After a semi-circumferential portion of each filament is covered with lacquer in a longitudinal direction, etching is performed in nitric acid solution. If bending of the filament to the etched side is considered to be negative and bending in the lacquer covered side is considered to be positive, the bending amount at which the filament is in a maximum bent state is +10 mm or less by the average of all filaments constituting the steel cord.
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