| 摘要 |
PROBLEM TO BE SOLVED: To provide a synthetic resin cap which can keep high sealability even when an internal pressure of a container increases. SOLUTION: An internal surface of a top plate 2 of a cap body 4 including the top plate 2 and a cylinder 3 hanging from a periphery thereof is formed with an annular inner sealing protrusion 12 to be fitted into a container mouth 20 and an annular opening end sealing protrusion 13 which comes into contact with an opening end 20b of the container mouth 20. The protrusion 13 is provided to bending-deform in a radially expanding direction until it comes into contact with the cap body 4 by the container mouth 20.
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