Foamed Polystyrene Packaging (Patent No: 895981)

Inventor: Allard, Charles A.

Location: Edmonton

Comments: b 1919 Edmonton; surgeon; Crosstown Motors, petrochemicals; set up CHQT, CITV; founded Oilers; in Edmonton Business Hall of Fame, d 1991; see City of Edmonton Archives clipping files

Description: 1. A process for manufacturing a packaging article with surfaces of selective hardness from polystyrene which comprises the steps of providing a perforated enclosing mold of a relatively good heat conducting material and with a portion of the mold lined with a relatively poor heat conducting material, the mold having a cavity of the desired shape of the article; charging the mold with finely divided polystyrene containing a volatile organic liquid blowing agent absorbed therein and homogeneously disbursed throughout the polystyrene said blowing agent having a boiling point lower than the softening point of the polystyrene, said charge of polystyrene when expanded being sufficient to fill said mold to a desired density of foamed polystyrene; heating said polystyrene to a first temperature above the boiling point of the boiling point of the blowing agent and above the softening point of the polystyrene and in a range from about 200°F. to about 350°F. to cause the polystyrene to expand and fill the mold to the desired density of foamed polystyrene and thereby form a packaging article of cohered expanded particles of polystyrene having the desired shapes and thereafter raising the temperature of the mold to a second temperature greater than said first temperature and in a range from 280°F. to 550°F. selectively to develop an essentially defoamed plastic skin adjacent said relatively good heat conducting material and a soft foamy structure adjacent said relatively poor heat conducting material

2. A process as defined in Claim 1 wherein all of the heating is effected by means of conduction through the mold.

3. A process as defined in Claim 2 wherein the heating is accomplished in an oven.

4. A process as defined in Claim 3 wherein the oven is provided with at least two zones of different temperatures and wherein the heating and subsequent raising of the temperature of the mold are achieved by moving the mold through said zones.