Synthetic resin container closure

A synthetic resin container closure for closing a container having a mouth-neck portion with an internal diameter D4, said container closure comprising:

• a circular top panel wall;
• a cylindrical skirt wall extending downwardly from the peripheral edge of the top panel wall and formed from a synthetic resin as a single unit with the top panel wall;
• an outer cylindrical sealing protrusion extending downwardly from the inner surface of the top panel wall;
• an inner cylindrical sealing protrusion extending downwardly from the inner surface of the top panel wall and having a maximum external diameter D3;
• and
• an annular sealing ridge located between the outer cylindrical sealing protrusion and the inner cylindrical sealing protrusion and projecting downwardly from the inner surface of the top panel wall, wherein:
• 0.25 mm≦(D3−D4)≦1.50 mm, so that when the container closure is mounted on the mouth-neck portion of the container, the inner peripheral surface of the outer cylindrical sealing protrusion is in close contact with the outer peripheral surface of the mouth-neck portion, the outer peripheral surface of the inner cylindrical sealing protrusion is in close contact with the inner peripheral surface of the mouth-neck portion, and the annular sealing ridge is in close contact with the top surface of the mouth-neck portion;
• the inner peripheral surface of the outer cylindrical sealing protrusion extends downwardly with an outward inclination at an angle θ6 with respect to the center axis of the container closure and then extends downwardly and radially outwardly in an arc form;
• the outer peripheral surface of the inner cylindrical sealing protrusion extends downwardly with an outward inclination at an angle θ1 with respect to the center axis of the container closure and then extends downwardly with an inward inclination at an angle θ2 with respect to the center axis;
• the inclination angle θ1 is 5° to 25° and the inclination angle θ2 is 5° to 30°;
• the inner peripheral surface of the inner cylindrical sealing protrusion extends downwardly with an outward inclination at an angle θ3 with respect to the center axis, and then extends substantially parallel with the center axis;
• the inclination angle θ3 of the inner peripheral surface of the inner cylindrical scaling protrusion is larger than the inclination angle θ1 of the outer peripheral surface of the inner cylindrical sealing protrusion at a position above the position having the maximum external diameter D3;
• and
• the thickness of the inner cylindrical sealing protrusion gradually decreases as the inner cylindrical sealing protrusion extends downwardly from the inner surface of the top panel wall.