| 摘要 |
PROBLEM TO BE SOLVED: To provide the tank body of a septic tank easy to mold, enabling the simplification of a septic tank assembling process, especially, a partition plate attaching process and capable of being extremely enhanced in the watertightness between treatment tanks partitioned by a partition plate. SOLUTION: The tank body of a septic tank comprises a polynorbornene resin obtained by the reaction injection molding of a reaction raw soln. containing a norbornene monomer and corrugated projected parts 2a, 2b substantially extending along the peripheral direction of the tank body are formed to the inside of the tank body so as to be almost symmetric left and right with respect to the center line in the longitudinal direction of the tank body and the inner peripheral radii R1, R5 of curvature of the crossing parts 222a, 222b of the standard inner wall surface 142b of the tank main body and the side surfaces 22a, 22b of the corrugated projected parts are 1 mm or less.
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