Patent ID: 7842225

Claim:
A method of preparing a molded article comprising: (a) providing a mold apparatus comprising, (i) a first mold portion having an interior mold surface, and a perimeter edge, said interior mold surface having a contour and a plurality of perforations, and (ii) at least one sheet retainer having an upper surface, at least a portion of the upper surface of said sheet retainer having a plurality of perforations, said sheet retainer having a longitudinal axis that is oriented along at least a portion of said perimeter edge, said sheet retainer being reversibly and controllably positionable along at least one of an x-axis, a y-axis and a z-axis relative to said perimeter edge, and said sheet retainer being rotatable around said longitudinal axis; (b) positioning said sheet retainer such that the upper surface of said sheet retainer is located above said perimeter edge; (c) forming, from at least one thermoplastic composition, a heated thermoplastic sheet having a temperature that allows said heated thermoplastic sheet to be thermoformable, said heated thermoplastic sheet having a first surface and a second surface; (d) contacting a first portion of said second surface of said heated thermoplastic sheet with at least a portion of the upper surface of said sheet retainer; (e) drawing reduced pressure through said plurality of perforations of said upper surface of said sheet retainer, thereby retaining said first portion of said second surface of said heated thermoplastic sheet on the upper surface of said sheet retainer; (f) contacting a second portion of the second surface of said heated thermoplastic sheet with at least a portion of the interior mold surface of said first mold portion; (g) (i) moving each sheet retainer independently at least one of towards said perimeter edge and away from said perimeter edge, in each case independently along at least one of said x-axis, said y-axis and said z-axis, and (ii) optionally rotating each sheet retainer, around said longitudinal axis of said sheet retainer, independently at least one of towards said perimeter edge and away from said perimeter edge; (h) drawing reduced pressure through said plurality of perforations of said interior mold surface of said first mold portion, such that said second portion of said second surface of said heated thermoplastic sheet substantially matches said contour of said interior mold surface of said first mold portion; (i) cooling said heated thermoplastic sheet thereby forming a shaped thermoplastic sheet that retains said contour of said interior mold surface of said first mold portion; and (j) removing said shaped thermoplastic sheet from said first mold portion, wherein said shaped thermoplastic sheet is said molded article.