Method for extruding a polystyrene foam with variations in mass concentration across the sheet and thermoforming the sheet
AssigneeMobil Oil Corporation
InventorVinod K. Luthra
Life of this patent
Estimating the term…
Abstract
A thermoplastic foamed resin extruding operation is described which uses an inner die lip machined to vary the width of the die annulus or opening so that varying thicknesses or mass concentrations or densities of preselected desired width will be formed in the extruded resin sheet obtained therefrom. The mass concentration variations in the extruded sheet are coordinated with a downstream thermoforming operation involving deep and shallow draw forming or different sheet fabrications such as folding, scoring, cutting, etc.
Claims3
In a method for the extrusion and subsequent thermoforming of polystyrene foam sheet material, the improvement which comprises, extruding polystyrene foam sheet material to produce an extrudate characterized by having varying mass concentrations in selected widths by the step of extruding polystyrene through an annular die orifice, said orifice having at least two adjacent sections around its periphery of varying gap size;
- subsequently subjecting the formed polystyrene sheet of varying thickness to thermoforming individual articles, said articles being characterized by having at least two sections, one of said sections being drawn to a greater extent than said other section, said article section being drawn to the relatively greater extent being formed from the thicker portion, having higher mass concentration, of said polystyrene foam sheet material.
Dependencies are inferred from the claim text.