Abstract: Disclosed is a composition comprising a polyolefin polymer and a core-shell acrylic polymer comprising a high molecular weight processing aid and a carrier resin. The high molecular weight processing aid is present in an amount ranging from 30% to less than 100% by weight relative to the total weight of the high molecular weight processing aid and the carrier resin, and the carrier resin is present in an amount ranging from greater than 0% to 70% by weight relative to the total weight of the high molecular weight processing aid and the carrier resin. The composition is in the form of particles having an average particle size of at least 2 mm.

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.