Importance

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Abstract

A cap for substantially gas-tight sealing engagement with a container wall having an opening therein circumscribed by a sealing surface has an end wall and a depending skirt with a portion for securing the cap to the container wall. The cap is preferably composed of about 94.5 to 99.89 weight percent low density polyethylene and may have a polybutylene copolymer present in an amount of about 0.01 to 5.0 weight percent. A mold release agent may be employed. A tab for manual engagement to rotate the cap between a container wall sealing surface engaging position and a storage position may be provided. The cap has a vent region provided by a weakened zone that is preferably located on or near the tab. The cap is adapted once in gas-tight sealing engagement with the sealing surface of the container wall to vent automatically in the weakened zone upon predetermined internal container pressure being attained and to subsequently reseal automatically. A container in combination with such a cap is also disclosed. A method of cap manufacture is disclosed.

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First Claim