초록 ▼

An extrusion system for providing a foamed material in which a material such as a polymer material is supplied to an extruder for movement through a rotating screw member. The material is placed in a molten state and a foaming agent, such as a supercritical fluid, is introduced into the extruder at

An extrusion system for providing a foamed material in which a material such as a polymer material is supplied to an extruder for movement through a rotating screw member. The material is placed in a molten state and a foaming agent, such as a supercritical fluid, is introduced into the extruder at a selected pressure so that a two-phase mixture of the molten material and the foaming agent is formed. The foaming agent is then diffused into and dissolved in the molten material to form a single-phase solution which is forwarded from a solution formation to a nucleation device. A thermodynamic instability is induced through a rapid pressure drop, e.g., higher than 0.9 GPa/s in the nucleation device to nucleate microcells in the solution. A further shaping device, e.g., a die, can be used to produce a foamed material of a desired shape.

대표청구항 ▼

[ What is claimed is:] [1.] A method comprising:providing a material to be foamed;mixing a supercritical carbon dioxide foaming agent into said material to create a mixture;creating a homogeneous single-phase solution from the mixture having a uniform concentration of foaming agent distributed there

[ What is claimed is:] [1.] A method comprising:providing a material to be foamed;mixing a supercritical carbon dioxide foaming agent into said material to create a mixture;creating a homogeneous single-phase solution from the mixture having a uniform concentration of foaming agent distributed therein and maintaining said single-phase solution at a pressure of at least about 1530 psi;nucleating the homogeneous single-phase solution by passing the single-phase solution through a constriction creating a rapid pressure drop in the single-phase solution at a pressure drop rate of at least about 0.18 GPa/s (26,100 psi/s) due to friction, to create a nucleated stream;shaping the nucleated stream essentially immediately after nucleating the solution to create a shaped microcellular extrudate; andreleasing the shaped microcellular extrudate into ambient conditions essentially immediately after shaping.