Methods for controlling polymer chain scission

Patent metadata

Field	Value
Publication number	US-10471641-B2
Application number	US-201615545401-A
Country	US
Kind code	B2
Filing date	Jan 20, 2016
Priority date	Jan 21, 2015
Publication date	Nov 12, 2019
Grant date	Nov 12, 2019

Abstract

Methods for extrusion of polyolefins ( 110 ) that utilize melt temperature to control molecular weight and also reduce gels. Disclosed herein is an example method for controlling polymer chain scission in an extrusion system ( 100 ), comprising: melting a polyolefin resin ( 110 ) in extruder ( 102 ) at a first melt temperature to form a first melt ( 112 ); passing the first melt ( 112 ) through a screen pack ( 106 ); forming the first melt 112 ) into a first polyolefin product ( 116, 118 ); melting additional polyolefin resin ( 110 ) of the same grade in the extruder ( 102 ) at a second melt temperature to form a second melt ( 112 ), wherein the second melt temperature differs from the first melt temperature by 5° C. or more to control chain scission in the extruder ( 102 ); passing the second melt ( 112 ) through the screen pack ( 106 ); and forming the second melt ( 112 ) into a second polyolefin product ( 116, 118 ).

First claim

What is claimed is:

1. A method for controlling polymer chain scission in an extrusion system, comprising:
melting a polyolefin resin in extruder at a first melt temperature to form a first melt;
passing the first melt through a screen pack;
forming the first melt into a first polyolefin product;
melting additional polyolefin resin of the same grade in the extruder at a second melt temperature to form a second melt, wherein the second melt temperature differs from the first melt temperature by 5° C. or more to control chain scission in the extruder;
passing the second melt through the screen pack; and
forming the second melt into a second polyolefin product, wherein the screen pack comprises a plurality of screens arranged in series, wherein the screens comprise an inlet screen having a size from 20 mesh to 80 mesh, two or more intermediate screens having a size of 100 mesh or greater, and an outlet screen having a size from 20 mesh to 80 mesh, wherein a throughput channel in the screen pack has a cross sectional area of at least 344 cm 2 .

2. The method of claim 1 , wherein the two or more intermediate screens comprising a screen having a size from 20 mesh 80 mesh sandwiched between screens of 100 mesh or larger.

3. The method of claim 1 , wherein the two or more intermediate screens comprise at least one screen having a size from 200 mesh to 250 mesh.

4. The method of claim 1 , wherein the second melt temperature is greater than the first melt temperature such that the second polyolefin product has a molecular weight that is less than a molecular weight of the first polyolefin product.

5. The method of claim 1 , wherein the second melt temperature is less than the first melt temperature such that the second polyolefin product has a molecular weight that is greater than a molecular weight of the first polyolefin product.

6. The method of claim 1 , wherein the second melt temperature differs from the first melt temperature by 20° C. or more.

7. The method of claim 1 , wherein the extruder is a single screw extruder or a twin screw extruder.

8. The method of claim 1 , further comprising passing at least one of the first melt or the second melt through a pelletizer configured to form the first melt and/or the second melt into pellets.

9. The method of claim 1 , further comprising passing at least one of the first melt or the second melt through a die configured to form the first melt and/or the second melt into a polyolefin film.

10. The method of claim 1 , wherein the polyolefin resin comprises a polyolefin made from ethylene monomers or branched higher alpha-olefin monomers containing from 3 to 20 carbon atoms.

11. The method of claim 1 , wherein the polyolefin resin comprises a polyolefin having a density of from 0.910 g/cm 3 to 0.975 g/cm 3 .

12. The method of claim 1 , wherein the polyolefin resin comprises a polyolefin having a melt index ranging from 0.1 g/10 min to about 1000 g/10 min.

13. The method of claim 1 , wherein at least one of the first polyolefin product or second polyolefin product comprises pellets, pipe, sheet, or a film.

14. A method for controlling polymer chain scission in an extrusion system, comprising:
providing a polyolefin resin having a molecular weight;
selecting a melt temperature for an extruder to cause scission of the polyolefin with decrease in molecular weight;
melting the polyolefin resin in the extruder at the melt temperature to form a melt;
forming the melt into a polyolefin product; and
passing the melt through a screen pack comprises a plurality of screens arranged in series, wherein the screen comprise an inlet screen having a size from 20 mesh to 80 mesh, two or more intermediate screens having a size of 100 mesh or greater, and an outlet screen having a size from 20 mesh to 80 mesh, wherein a throughput channel in the screen pack has a cross sectional area of at least 344 cm 2 .

15. The method of claim 14 , wherein the extruder is a single screw extruder or a twin screw extruder.

16. The method of claim 14 , wherein the polyolefin resin comprises a polyolefin made from ethylene monomers or branched higher alpha-olefin monomers containing from 3 to 20 carbon atoms.

17. The method of claim 14 , wherein the polyolefin resin comprises a polyolefin having a density of from 0.910 g/cm 3 to 0.975 g/cm 3 .

18. The method of claim 14 , wherein the polyolefin product comprises pellets, pipe, sheet, or a film.

Assignees

• Univation Tech Llc

Inventors

• Abe Daudi A
• Locklear Brandon C

Classifications

• B29C2948/92209

  Temperature · CPC title

• B29C48/04

  Particle-shaped (making granules B29B9/00) · CPC title

• B29C48/254

  Sealing means · CPC title

• B29C2948/92542

  Energy, power, electric current or voltage · CPC title

• B29C2948/92047

  Energy, power, electric current or voltage · CPC title