| 摘要 |
PROBLEM TO BE SOLVED: To provide a plastic cap which is excellent in combined capacities including openability, closability, preventiveness against micro leakage and hermetical sealing. SOLUTION: An one-piece plastic cap is such that is molded in an integral form comprising a top part, a skirt part having an internal thread at its inside and a seal-up part positioned at the inside of the top part for fitting to a mouth of a container, and the plastics used therefor is an environmental stress cracking resistive thermoplastic resin having a flexural elasticity (according to JIS K7203) extending in a range of 800 MPa to 1600 MPa, and the surface roughness for the seal-up part is set in a range of 1 to 5 μm (according to the maximum height Rmax based on JIS B0601). |
