Patent ID: 7585439

Claim:
A process for making a shaped article of manufacture from a sheet or roll of a thermoplastic material, wherein the thermoplastic material consists essentially of a virgin thermoplastic material admixed with a previously foamed thermoplastic material, wherein the virgin material and the previously foamed thermoplastic material are of the same chemical composition, and wherein the previously foamed thermoplastic material is in an amount that ranges from about 5% to about 100% by weight of the thermoplastic material, the process comprising at least the following steps: (a) pressurizing the sheet or roll of the thermoplastic material with a plasticizing gas under a selected pressure and period of time sufficient to yield a reversibly plasticized thermoplastic material, the plasticized thermoplastic material being impregnated with the plasticizing gas; (b) depressurizing the plasticized thermoplastic material to thereby desorb some of the plasticizing gas from the plasticized thermoplastic material to thereby yield a partially desorbed plasticized thermoplastic material; (c) partially foaming the partially desorbed plasticized thermoplastic material to yield a plasticized and partially foamed thermoplastic material; and (d) thermoforming-foaming, while in a thermoforming mold, the plasticized and partially foamed thermoplastic material into the shaped article of manufacture, wherein the step of thermoforming-foaming occurs before the impregnated plasticizing gas concentration falls below about 0.5 percent by weight of the plasticized and partially foamed thermoplastic material, and wherein the plasticized and partially foamed thermoplastic material is additionally foamed by an amount ranging from 2% to 30%.