초록 ▼

A method and apparatus for preparing a substantially uniform thermoplastic foam extruded from an extruder, the molten thermoplastic resin having uniformly distributed therein a foaming agent. A cooling-mixer continuously receives the extruded mass of resin and foaming agent from the extruder and int

A method and apparatus for preparing a substantially uniform thermoplastic foam extruded from an extruder, the molten thermoplastic resin having uniformly distributed therein a foaming agent. A cooling-mixer continuously receives the extruded mass of resin and foaming agent from the extruder and intimately mixes and substantially cools the mass. A substantially adiabatic zigzag mixer is connected to the cooling-mixer and divides the mass into a plurality of separate streams which are at least partially separated and recombined. A die is connected to the zigzag mixer and extrudes the uniformly cooled mass into a lower pressure zone to produce a substantially uniform thermoplastic foam.

대표청구항 ▼

A method for preparing a thermoplastic foam board having a thickness greater than 10 mm by extruding molten thermoplastic resin having uniformly distributed therein a foaming agent for said resin, the method comprising the continuous steps of: (a) introducing an extruded mass of said molten thermopl

A method for preparing a thermoplastic foam board having a thickness greater than 10 mm by extruding molten thermoplastic resin having uniformly distributed therein a foaming agent for said resin, the method comprising the continuous steps of: (a) introducing an extruded mass of said molten thermoplastic resin from an extrusion zone into a cooling zone; (1) the cooling zone comprising an elongated barrel having a rotating member positioned axially therein in spaced relationship to the barrel so as to provide a passage for the extruded mass between an outer surface of the rotating member and an inner surface of the barrel, (2) the temperature of the cooling zone being controlled by fluid heat exchange, and (3) the extruded mass being under pressure in the extrusion zone and in the cooling zone; (b) passing the pressurized extruded mass through said passage while simultaneously: (1) intimately mixing the mass by means of projections extending radially from the outer surface of the rotating member into the passage and reaching a close proximity to the inner surface of the barrel and (2) substantially lowering the temperature of the mass, the cooled mass being maintained in its molten flowable state; (c) dividing the cooled mass into a plurality of separate, non-parallel streams in a zig-zag mixer under substantially adiabatic conditions; (d) separating and recombining at least a portion of said streams in said zig-zag mixer under substantially adiabatic conditions to form a combined homogeneous mass having a substantially uniform temperature; and (e) extruding the homogeneous mass into a lower pressure zone to form a substantially uniform thermoplastic foam.