초록 ▼

An extrusion die is described for extruding a polymer from a reactive precursor mixture without plugging of the die. The extrusion die includes a die inlet leading to at least one channel having dimensions which produce a wall shear stress value that exceeds the critical wall shear stress value for

An extrusion die is described for extruding a polymer from a reactive precursor mixture without plugging of the die. The extrusion die includes a die inlet leading to at least one channel having dimensions which produce a wall shear stress value that exceeds the critical wall shear stress value for the particular reactive precursor mixture to prevent occlusion of the die. The preferred configuration of the die channels is a tree-like structure to obtain a coating width which is greater than the dimensions of the individual channels. Other features of the invention include a method for determining the critical wall shear stress value and a method for extruding reactive precursor mixtures.

대표청구항 ▼

An extrusion die for the continuous extrusion of a premixed reactive precursor mixture having an increasing viscosity over time, comprising: (a) a die inlet for receiving the premixed reactive precursor mixture from a source of premixed reactive precursor mixture; (b) spreader means in flow communic

An extrusion die for the continuous extrusion of a premixed reactive precursor mixture having an increasing viscosity over time, comprising: (a) a die inlet for receiving the premixed reactive precursor mixture from a source of premixed reactive precursor mixture; (b) spreader means in flow communication with said die inlet for spreading the reactive precursor mixture through the die, said spreader means having at least one channel, said channel having dimensions which produce a wall shear stress value for the increasingly viscous reactive precursor mixture being extruded which exceeds the critical wall shear stress value for the reactive precursor mixture such that the viscosity of a substantial portion of the reactive precursor mixture does not increase to the gel point for the mixture within the die; substantially even flow rate of the reactive precursor mixture through the die is maintained; and occlusion of said channel is avoided; and (c) an outlet means connected in flow communication to said spreader means for extruding the reactive precursor mixture onto a substrate said outlet means having dimensions which will produce a wall shear stress value for the increasingly viscous reactive precursor mixture exceeding the critical wall shear stress value for the reactive precursor mixture such that the viscosity of a substantial portion of the reactive precursor mixture does not increase to the gel point for the mixture within the die; flow of the reactive precursor mixture through the die is maintained; and occlusion of said outlet means is avoided. A method for the continuous extrusion of a premixed reactive precusor mixture having an increasing viscosity over time, comprising: (a) selecting components for a premixed reactive precursor mixture; (b) mixing the components to form a premixed reactive precursor mixture; (c) introducing a flow of the premixed reactive precursor mixture into an inlet of an extrusion die, said extrusion die having at least one channel, the channel in flow communication with the inlet for conducting the flow of the premixed reactive precursor mixture through the die, said channel having dimensions which produce a wall shear stress value for the increasingly viscous reactive precursor mixture being extruded which exceeds the critical wall shear stress value for the premixed reactive precursor mixture; and (d) extruding the premixed reactive precursor mixture through an extrusion outlet means of the die, such that the viscosity of a substantial portion of the reactive precursor mixture does not increase to the gel point for the mixture within the die; the occlusion of the die is avoided; and flow of the reactive precursor mixture thereof the die is substantially maintained.