Polystyrene foam sheet useful for forming deep drawn articles, a process to produce those articles, and the deep drawn articles

Claim 1

A method of thermoforming deep drawn thermoplastic foam articles comprising, in sequence, the steps of: a. preheating a sheet of thermoplastic foam stock material which contains 1 to 15 wt % of a rubber component having a majority of particle sizes less than about 0.45 microns with the foamed sheet having a density of 0.04 to 0.16 g/cm 3 (21/2-10 lb/ft 3 ) and a thickness of 0.4 to 6.5 mm; b. clamping said preheated stock material in a fixed position between matched male and female mold members; and c. relatively moving said male and female mold members into final forming position to stretch said sheet into said cavity; d. applying a vacuum through both the male and female mold members to both sides of the foamed sheet, while performing step c), to help expand the sheet into conformity with substantially the entire cooperating surfaces of the mold members; and e. chilling the stock material to set a final shape.

Claim 2

A method of thermoforming deep drawn thermoplastic foam articles comprising, in sequence, the steps of: a. preheating a sheet of thermoplastic foam stock material which contains 1 to 15 wt % of a rubber component having a majority of particle sizes less than about 0.45 microns with the foamed sheet having a density of 0.04 to 0.16 g/cm 3 (21/2-10 lb/ft 3 ) and a thickness of 0.4 to 6.5 mm; b. clamping said preheated stock material in a fixed position between matched male and female mold members; and c. relatively moving said male and female mold members into final forming position to stretch said sheet into said cavity; d. applying a vacuum through both the male and female mold members to both sides of the foamed sheet, while performing step c), to help expand the sheet into conformity with substantially the entire cooperating surfaces of the mold members; and e. chilling the stock material to set a final shape.