초록 ▼

The invention discloses an improved die assembly for the extrusion of thermoplastic resin cellulosic fiber composite profiles meant to minimize and substantially prevent the occurrence of melt fracture on the surface of the extruded composite profiles. Comprising the die assembly are a balanced flow

The invention discloses an improved die assembly for the extrusion of thermoplastic resin cellulosic fiber composite profiles meant to minimize and substantially prevent the occurrence of melt fracture on the surface of the extruded composite profiles. Comprising the die assembly are a balanced flow passage having a heated compression zone, a heated transition zone, a heated converging die zone, a die land, which corresponds to at least a portion of the downstream end of the flow passage and is cooled to temperature below the melting point temperature of the thermoplastic resin. The invention also discloses a production process for composite profiles which includes the steps of providing resin and fiber, producing a composite compound, processing the compound through an extrusion system, extruding the compound through the die assembly to form the desired profile, cooling the profile and cutting it to length. Also disclosed are products produced by the production process.

대표청구항 ▼

What is claimed as the invention is: 1. An extrusion die assembly for the continuous production of a composite profile comprising composite compound comprising thermoplastic resin and cellulosic fiber and having a desired cross-section and an exterior surface, wherein the die assembly has an axis o

What is claimed as the invention is: 1. An extrusion die assembly for the continuous production of a composite profile comprising composite compound comprising thermoplastic resin and cellulosic fiber and having a desired cross-section and an exterior surface, wherein the die assembly has an axis oriented from an upstream end to a downstream end, said die assembly comprising: a. a flow passage which results in a generally balanced flow of the composite compound from an upstream die assembly inlet to a downstream die assembly outlet, wherein the die assembly inlet and outlet are displaced along said axis; b. a compression zone of the flow passage having an inlet and an outlet, wherein the compression zone corresponds to at least a portion of the upstream end of the flow passage and the compression zone inlet corresponds to the die assembly inlet; c. a transition zone of the flow passage having an inlet and an outlet, wherein the transition zone inlet corresponds to the compression zone outlet; d. a converging die zone of the flow passage having an inlet and an outlet, wherein the converging die zone inlet corresponds to the transition zone outlet and the converging die zone outlet generally corresponds to the cross-section of the composite profile; e. a die land having an inlet and an outlet, wherein the die land corresponds to at least a portion of the downstream end of the flow passage, the die land inlet corresponds to the converging die zone outlet, the die land outlet corresponds to the outlet of the die assembly and the cross-section of die land outlet corresponds to the cross-section of the composite profile; f. a compression section, a transition section, a converging die section and a die land section of the die assembly, wherein the compression, transition, converging die and die land sections comprise sections of the die assembly obtained by passing a series of parallel planes perpendicular to said axis through the die assembly at the inlets and outlets of the compression, transition and converging die zones and the die land, respectively, wherein the die land section forms the exterior surface of the composite profile; g. cooling means positioned in the die land section to maintain the temperature of the die land section at a temperature below the melting point temperature of the thermoplastic resin; and h. heating means to maintain the temperature of the compression, transition and converging die sections at a temperature above the melting point temperature of the thermoplastic resin. 2. The die assembly of claim 1 further including a thermal break between the converging die section and the die land section adapted to minimize heat transfer between the heated converging die section and the cooled die land section. 3. The die assembly of claim 1, wherein the cooling means consists of cooling lines provided in the die land section which circulate a cooling fluid adapted to maintain the temperature of the die land section below the melting point temperature of the thermoplastic resin. 4. The die assembly of claim 1, wherein the die assembly is constructed with at least two rigidly connected die assembly sections that are displaced along said axis. 5. The die assembly of claim 4, wherein the compression section and the transition section comprise one die assembly section. 6. The die assembly of claim 4, wherein the converging die section and die land section comprise one die assembly section. 7. The extrusion die assembly of claim 1, wherein the composite profile is hollow and has at least one longitudinal hollow channel with an interior surface and the die assembly further comprises a mandrel adapted to form said longitudinal hollow channels, wherein: a. the mandrel, having an upstream portion and a downstream portion, is positioned within the flow passage forming an annular flow passage oriented along said die assembly axis, wherein the annular flow passage has an upstream end and a downstream end; b. the mandrel is held in position by at least one mandrel support, wherein each mandrel support is generally perpendicular to the mandrel and to said axis, intersects the annular flow passage and is rigidly connected to the upstream portion of the mandrel; and c. the downstream portion of the mandrel is comprised of at least one core with an exterior surface and is positioned within the die land section, wherein the exterior surface of each core forms the interior surface of one of said hollow channels and is equipped with core cooling means positioned in the core to maintain the temperature of the cores below the melting point temperature of the thermoplastic resin. 8. The die assembly of claim 7, wherein the cross-section of the annular flow passage at the converging die zone outlet and the cross-section of the annular flow passage along the full length of the die land corresponds to the cross-section of the hollow composite profile. 9. The die assembly of claim 7, wherein the cooling means consists of cooling lines provided in the die land section which circulate a cooling fluid adapted to maintain the temperature of the die land section below the melting point temperature of the thermoplastic resin. 10. The die assembly of claim 7, wherein said core cooling means comprises: a. at least one hollow channel in each of the cores, wherein each of said hollow channels is parallel to said die assembly axis and open at the downstream end of the core; b. at least one hollow channel generally perpendicular to the said die assembly axis positioned within a mandrel support, wherein each of the hollow channels in the cores is connected to at least one of the perpendicular hollow channels; and c. at least one tube inserted through the perpendicular hollow channels and the connecting hollow channels, wherein each tube is used to spray a cooling fluid into the each of the hollow channels in each of the cores. 11. The die assembly of claim 10, wherein the cooling means consists of cooling lines provided in the die land section which circulate a cooling fluid adapted to maintain the temperature of the die land section below the melting point temperature of the thermoplastic resin.