Patent ID: 8101102

Claim:
A method for improving the resistance of fumigant sorption in a produce container in a fumigation process, the steps comprising: making a produce container by pre-expanding expandable polymer particles comprising expandable polymer particles having a density ranging from about 40.0 pounds per cubic foot to about 32.0 pounds per cubic foot to form pre-expanded particles with a core bulk density ranging from about 12.5 pounds per cubic foot to 2.0 pounds per cubic foot and an outer skin with a density ranging from about 40.0 to about 32.0 pounds per cubic foot and a thickness ranging from about 0.10 to about 2.0 microns; and forming said produce container from said pre-expanded particles by injecting the pre-expanded particles into a mold having the shape of a produce container and heating the closed mold to further expand and fuse the pre-expanded particles to form said produce container; wherein the residual fumigant level of the produce container is not more than 5 ppm based on the weight of the produce container after the produce container has been introduced to a fumigant in a sealed chamber such that the concentration of the fumigant in the chamber is at least 48 ounces/1000 ft 3 for an initial 30 minutes and at least 38 ounces/1000 ft 3 for a subsequent 90 minutes and aeration air is subsequently exchanged for the fumigant in the chamber.