| 摘要 |
PROBLEM TO BE SOLVED: To improve abrasion resistance by specifying values of the weight mixing ratio of thermoplastic resin, the mean bubble diameter and the bubble ratio in a specified range. SOLUTION: Thermoplastic resin having the melting point in the range of 80 to 160 deg. is mixed with foaming agent for performing vulcanizing and foaming, a rubber composition is vulcanized at the normal vulcanizing temperature (160 to 180 deg.), and the thermoplastic resin is softened at the vulcanizing temperature. Bubbles generated near it are taken into the softened resin from hard matrix rubber, as a result, bubbles covered with a sheath of a resin layer are formed. Since this resin has the hardness higher than rubber, it has the fracture limit higher than the matrix rubber, and therefore, generation of cracks taking bubbles as a core can be restrained. Moreover, in mixing of resin, resin of 1 to 40 pts.wt. is mixed to a rubber component of 100 pts.wt., the mean bubble diameter of a closed cell is set in the range of 20 to 500μm, and the bubble ratio is set in the range of 3 to 50%. |
