PROBLEM TO BE SOLVED: To provide a plastic cap having a straw piercing port for which a straw port is easily formed by the piercing of a straw, and the insertion of the straw into a container can easily be performed by breaking a seal foil from the straw port.;SOLUTION: This plastic cap is used for a beverage container on the mouth port of which the seal foil 51 is provided, and of which the sealability is ensured by the seal foil. The plastic cap has a ceiling wall 1, and a cylindrical side wall 3 which is lowered from the peripheral edge of the ceiling wall. On the internal surface of the lower end of the cylindrical side wall, a protuberance 5 for engaging with the container mouth section is formed. At the same time, the straw piercing port 10 made of a thinner wall through which the straw can be pierced is formed on the ceiling wall. At an internal surface corner section from the ceiling wall to the cylindrical side wall, a plurality of raising ribs 11 which come into contact with the upper end surface of the container mouth section are provided in the circumferential direction with a proper interval.;COPYRIGHT: (C)2006,JPO&NCIPI
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