Pelletization gas guide

Patent metadata

Field	Value
Publication number	US-11207799-B2
Application number	US-201715633227-A
Country	US
Kind code	B2
Filing date	Jun 26, 2017
Priority date	Jun 26, 2017
Publication date	Dec 28, 2021
Grant date	Dec 28, 2021

Abstract

Polymer pellets are formed using laminar gas flow within a downstream gas conduit, as may be implemented consistent with one or more embodiments herein. A gas channel directs gas to an outlet of a polymer extrusion mandrel via which a polymer melt is extruded. A downstream gas conduit extends away from the outlet of the polymer extrusion mandrel, and provides laminar gas flow along the polymer melt extending from the extrusion mandrel, and within the downstream gas conduit. Using this approach, laminar flow can be maintained along an initial portion of the polymer melt, and used to control the subsequent formation of pellets therefrom.

First claim

What is claimed is:

1. An apparatus comprising:
a polymer extruder configured and arranged to extrude polymer material through an extrusion nozzle; and
a gas nozzle coupled to the polymer extruder and having a gas channel, a downstream gas conduit and a gas outlet, the gas outlet being offset from the extrusion nozzle, the downstream gas conduit having a cylindrical inner sidewall extending away from an outlet of the extrusion nozzle to the gas outlet, the downstream gas conduit and extrusion nozzle being adjustable relative to one another for setting a length of a portion of the cylindrical inner sidewall that extends away from the extrusion nozzle,
wherein the gas nozzle is configured and arranged with the polymer extruder to provide laminar gas flow within the downstream gas conduit along a polymer melt extending from the extrusion nozzle.

2. The apparatus of claim 1 , wherein the cylindrical inner sidewall extends along the downstream gas conduit in parallel with a direction via which the polymer extruder extrudes the polymer material, and is responsive to gas presented by the gas channel to direct the gas from the gas channel in a direction that is parallel to the flow of the polymer melt extending from the extrusion nozzle.

3. The apparatus of claim 2 , wherein the gas nozzle is configured and arranged with the polymer extruder and with a length of the cylindrical inner sidewall to cause a non-uniform thickness along the polymer melt extending away from the extrusion nozzle and within the downstream gas conduit, by using the laminar flow within the downstream gas conduit to apply a drag force to the polymer melt.

4. The apparatus of claim 3 , wherein the downstream gas conduit extends from the outlet of the extrusion nozzle to the gas outlet and is configured and arranged to mitigate the formation of an open jet along the polymer melt within the downstream gas conduit and before the polymer melt exits the gas outlet.

5. The apparatus of claim 4 , wherein the gas nozzle is configured and arranged with the polymer extruder to fracture the polymer melt along a portion of the non-uniform thickness that is thinner than another portion of the polymer melt, by facilitating turbulent gas flow along a portion of the polymer melt extending out of the downstream gas conduit and away from the gas outlet.

6. The apparatus of claim 1 , wherein the downstream gas conduit is configured and arranged with a length extending from the outlet of the extrusion nozzle that is sufficient to maintain laminar flow along the polymer melt extending within the downstream gas conduit and to cause periodic necking along the polymer melt within the downstream gas conduit.

7. The apparatus of claim 1 , wherein the gas nozzle is configured and arranged with the polymer extruder to form discrete droplets from the polymer melt, by:
necking the polymer melt within the downstream gas conduit by using the laminar flow along the polymer melt to apply drag force to the polymer melt, and
fracturing the polymer melt along necked portions thereof that have been extruded beyond the gas nozzle outlet.

8. The apparatus of claim 7 , wherein the downstream gas conduit is configured and arranged with a length, extending from the outlet of the extrusion nozzle to the gas outlet, that is sufficient to cause periodic necking along the polymer melt within the downstream gas conduit by introducing Rayleigh disturbances along the polymer melt extending within the downstream gas conduit.

9. The apparatus of claim 7 , wherein fracturing the polymer melt includes fracturing the polymer melt to form the discrete droplet having a volume that is at least half of the volume of the polymer melt that extends from the nozzle when the polymer melt is fractured.

10. The apparatus of claim 1 , wherein the downstream gas conduit extends in a direction that is parallel with a direction via which the polymer melt is extruded, and has a diameter relative to the polymer melt and to gas flow provided via the gas channel to apply pressure to the polymer melt that is sufficient to generate Rayleigh disturbances in the polymer melt.

11. The apparatus of claim 1 , wherein the cylindrical inner sidewall and the extrusion nozzle have fixed diameters, and wherein an orifice defined by the cylindrical inner sidewall and an exterior of the extrusion nozzle is constant for a range of adjustment of the length of the portion of the cylindrical inner sidewall that extends away from the extrusion nozzle, with the cylindrical inner sidewall extending in parallel with a direction via which polymer melt is extruded, the length of the portion of the cylindrical inner sidewall being sufficient to direct a laminar flow of gas from the gas channel in a direction that is parallel to the flow of the polymer.

12. A method comprising:
providing a polymer extruder having an extrusion nozzle to extrude polymer material through an extrusion nozzle; and
coupling a gas nozzle having a gas channel, a downstream gas conduit and a gas outlet to the extrusion nozzle, the gas outlet being offset from the extrusion nozzle, the downstream gas conduit having a cylindrical inner sidewall extending away from an outlet of the extrusion nozzle to the gas outlet;
setting a length of a portion of the cylindrical inner sidewall that extends away from the extrusion nozzle by adjusting the downstream gas conduit and extrusion nozzle relative to one another; and
using the gas nozzle, including the channel and downstream gas conduit, with the polymer extruder to provide laminar gas flow within the downstream gas conduit and along polymer melt extending from the extrusion nozzle.

13. The method of claim 12 , further including extruding the polymer material through the extrusion nozzle as a polymer melt, wherein the gas nozzle includes a sidewall extending along the downstream gas conduit in parallel with a direction via which the polymer extruder extrudes the polymer melt, further including using the sidewall to direct a laminar flow of gas from the gas channel in a direction that is parallel to the flow of the polymer melt extending from the extrusion nozzle.

14. The method of claim 13 , wherein using the sidewall to direct the laminar flow includes using the laminar flow of gas to generate a non-uniform thickness in the polymer melt extending away from the extrusion nozzle and within the downstream gas conduit, by applying a drag force to the polymer melt within the downstream gas conduit.

15. The method of claim 13 , wherein using the sidewall to direct the laminar flow of gas includes mitigating the formation of an open jet along the polymer melt within the downstream gas conduit.

16. The method of claim 12 , further including:
using the laminar flow to generate a non-uniform thickness in a polymer melt extruded through the extrusion nozzle, within the downstream gas conduit, and
fracturing the polymer melt along a relatively thin portion of the non-uniform thickness extending beyond the downstream gas conduit.

17. The method of claim 12 , wherein coupling the gas nozzle includes controlling the size and aspect ratio of pellets formed from a polymer melt extruded through the extrusion nozzle by providing the downstream gas conduit with a conduit width and a length extending away from the outlet of the extrusion nozzle that is sufficient to maintain laminar flow along the polymer melt extending within the downstream gas conduit and to cause periodic necking along the polymer melt within the downstream gas conduit.

18. The method of claim 12 , further including forming discr

Assignees

• Wisconsin Alumni Res Found

Inventors

• Schäfer Christian
• Osswald Tim Andreas

Classifications

• B29B7/582

  for discharging, e.g. doors · CPC title

• B30B7/00

  Presses characterised by a particular arrangement of the pressing members · CPC title

• B29B9/06

  in the form of filamentary material, e.g. combined with extrusion · CPC title

• B29B7/823

  Temperature control · CPC title

• B29B9/10 Primary

  by moulding the material, i.e. treating it in the molten state · CPC title