초록 ▼

Melt fracture is reduced, without the necessity of polymer processing-aid additives specifically designed to alleviate exit region surface melt fracture phenomenon, by heating at least a portion of the die through which the polymer is extruded. The die exit region is maintained at a temperature abov

Melt fracture is reduced, without the necessity of polymer processing-aid additives specifically designed to alleviate exit region surface melt fracture phenomenon, by heating at least a portion of the die through which the polymer is extruded. The die exit region is maintained at a temperature above the bulk melt temperature of the polymer extruded through the die exit hole.

대표청구항 ▼

We claim: 1. A die plate comprising: (a) an upstream face; (b) a downstream face; (c) at least one passage having a first opening in said upstream face whereby molten resin at bulk temperature Tmelt may be received and a second exit opening in said downstream face whereby molten resin may be extrud

We claim: 1. A die plate comprising: (a) an upstream face; (b) a downstream face; (c) at least one passage having a first opening in said upstream face whereby molten resin at bulk temperature Tmelt may be received and a second exit opening in said downstream face whereby molten resin may be extruded; and (d) a heater at the exit opening in said downstream face and proximate with said at least one passage in said downstream face and capable of locally heating said molten resin to a temperature from about 245° C. to about 372° C., the local molten resin temperature being from 30-170° C. above bulk temperature Tmelt. 2. The die plate according to claim 1, wherein said at least one passage is generally cylindrical and having a substantially uniform diameter from said upstream face to said downstream face. 3. The die plate according to claim 1, wherein said heater is concentric with said at least one passage. 4. The die plate according to claim 1, wherein said at least one passage passes through a portion of said heater, such that said portion defines the wall of said passage proximate said downstream face. 5. The die plate according to claim 1, further comprising an insulation material concentric with said at least one passage proximate said downstream face and forming at least a portion of said downstream face at said second opening. 6. The die plate according to claim 1, further comprising an insulation material concentric with said at least one passage and contiguous with at least a portion of said heater, and contiguous with said at least one passage at said exit opening. 7. The die plate according to claim 1, wherein said die plate is a monolithic die plate. 8. The die plate according to claim 1, wherein said die plate comprises a first plate having said upstream face and a second plate having said downstream face and said heater, said first and second plates fluidically connected by said at least one passage. 9. The die plate according to claim 8, comprising a plurality of said at least one passage and wherein said first and second plates are fluidically connected by each of said at least one passage. 10. The die plate according to claim 1, comprising a plurality of said at least one passage. 11. The die plate according to claim 5, wherein said insulation material is selected from high temperature plastics, machineable ceramics, ceramics which may be deposited by spray coating techniques, and ceramics which may be deposited by vapor deposition techniques. 12. The die plate according to claim 6, wherein said insulation material is selected from high temperature plastics, machineable ceramics, ceramics which may be deposited by spray coating techniques, and ceramics which may be deposited by vapor deposition techniques. 13. An extrusion die assembly comprising a die plate for preparing pellets having at least one passage including an initial, upstream zone having an opening for receiving a polymer melt having a bulk temperature Tmelt, an intermediate zone for conveying said polymer melt, and a final, downstream zone terminating said extrusion die assembly at an exit opening whereby said polymer melt exits said extrusion die assembly, further comprising a heating means for said downstream zone at the exit opening whereby at least a portion of said polymer melt may be locally heated to a temperature from about 245° C. to about 372° C., the local molten resin temperature being from 30-170° C. above bulk temperature Tmelt. 14. The extrusion die assembly according to claim 13, the extrusion die further comprising a plurality of extrusion orifices forming a pattern, wherein said heating means comprises a heater concentric with the extrusion orifice pattern. 15. The extrusion die assembly according to claim 13, wherein said heating means is proximate said at least one passage. 16. The extrusion die assembly according to claim 13, wherein said downstream zone further comprises an insulation material concentric with said passage and contiguous with at least a portion of said heating means and said die assembly. 17. The extrusion die assembly according to claim 13, wherein said downstream zone further comprises an insulation material concentric with said passage and contiguous with at least a portion of said heating means, and contiguous with said passage at said exit opening. 18. The extrusion die assembly according to claim 13, wherein said passage is generally cylindrical and having a substantially uniform diameter from said opening for receiving a polymer melt to said exit opening. 19. The extrusion die assembly according to claim 13, wherein said die plate comprises a plurality of said at least one passage. 20. The extrusion die assembly according to claim 13, wherein said die plate is a monolithic die plate. 21. The extrusion die assembly according to claim 13, wherein said die plate comprises a first plate having an upstream face and comprising said upstream zone and a second plate having a downstream face and wherein said heating means, said first plate, and second plate are fluidically connected by said at least one passage. 22. The extrusion die assembly according to claim 21, comprising a plurality of said at least one passage and wherein said first and second plates are fluidically connected by each of said at least one passage. 23. The extrusion die assembly according to claim 16, wherein said insulation material is selected from high temperature plastics, machineable ceramics, ceramics which may be deposited by spray coating techniques, and ceramics which may be deposited by vapor deposition techniques. 24. The extrusion die assembly according to claim 17, wherein said insulation material is selected from high temperature plastics, machineable ceramics, ceramics which may be deposited by spray coating techniques, and ceramics which may be deposited by vapor deposition techniques. 25. An extrusion die assembly comprising an extrusion die for preparing pellets having a plurality of extrusion orifices and a monolithic heater for retrofitting a resin shaping apparatus having at least one extrusion die orifice, said heater having a first face to engage said at least one extrusion die orifice of said resin shaping apparatus and a second face opposite said first face, one or more passages between said first and second faces and substantially mating said at least one extrusion die orifice, wherein said orifice and said one or more passages are fluidically connected, and wherein a molten material at Tmelt passing out of said at least one extrusion die orifice is locally heated to a temperature from about 245° C. to about 372° C., the local molten material temperature being from 30-170° C. above Tmelt by passing through said one or more passages of said monolithic heater, said heater comprising a plurality of said one or more passages, wherein said plurality of extrusion orifices are fluidically engaged with said plurality of said one or more passages in said monolithic heater. 26. A die plate comprising: (a) an upstream face; (b) a downstream face; (c) at least one passage having a first opening in said upstream face whereby molten resin at bulk temperature Tmelt may be received and a second exit opening in said downstream face whereby molten resin may be extruded; and (d) an electrical heating element proximate said downstream face and proximate with said at least one passage and at the exit opening in said downstream face, wherein said electrical heating element is capable of locally heating said molten resin by direct contact of said molten resin with said electrical heating element. 27. The die plate according to claim 26, wherein said at least one passage passes through a portion of said heater, such that said portion defines the wall of said passage proximate said downstream face. 28. The die plate according to claim 26, wherein said die plate is a monolithic die plate. 29. The die plate according to claim 26, wherein said die plate comprises a first plate having said upstream face and a second plate having said downstream face and said heater, said first and second plates fluidically connected by said at least one passage. 30. The die plate according to claim 26, wherein said die plate comprises a material selected from brass, stainless steel, and nickel steel. 31. An extrusion die assembly comprising a die plate for preparing pellets having at least one passage including an initial, upstream zone having an opening for receiving a polymer melt having a bulk temperature Tmelt, an intermediate zone for conveying said polymer melt, and a final, downstream zone terminating said extrusion die assembly at an exit opening whereby said polymer melt exits said extrusion die assembly, further comprising an electrical heating means at the exit opening for said downstream zone whereby at least a portion of said polymer melt would be locally heated by direct contact of said polymer melt with said electrical heating means. 32. The extrusion die assembly according to claim 31, wherein said heating means is proximate said at least one passage. 33. The extrusion die assembly according to claim 31, wherein said die plate is a monolithic die plate. 34. The extrusion die assembly according to claim 31, wherein said die plate comprises a first plate having an upstream face and comprising said upstream zone and a second plate having a downstream face and wherein said heating means, said first plate, and second plate are fluidically connected by said at least one passage. 35. The extrusion die assembly according to claim 31, wherein said die plate comprises a material selected from brass, stainless steel, and nickel steel. 36. The extrusion die of claims 1 or 13 wherein said die plate comprises a material selected from brass, stainless steel, and nickel steel. 37. The extrusion die of claim 1, further comprising an insulation material contiguous with said heater and said die plate and concentric with said heater about said at least one passage proximate said downstream face. 38. The extrusion die of claims 26 or 31 wherein said insulation material is selected from high temperature plastics, machineable ceramics, ceramics which may be deposited by spray coating techniques, and ceramics which may be deposited by vapor deposition techniques. 39. The extrusion die of claim 31, wherein said downstream zone further comprises an insulation material concentric with said passage and contiguous with at least a portion of said heating means and said die assembly. 40. The extrusion die of claim 13, further comprising an insulation material contiguous with said heating means and said die plate and concentric with said heater about said at least one passage proximate said downstream face. 41. The extrusion die of claim 26, further comprising an insulation material contiguous with said heating element and said die plate and concentric with said heater about said at least one passage proximate said downstream face.