Method for Forming a Thermoplastic Composition that Contains a Plasticized Starch Polymer

• US 20130157031A1
• Filed: 12/20/2011
• Published: 06/20/2013
• Est. Priority Date: 12/20/2011
• Status: Active Grant

• Current Assignee: Kimberly-Clark Worldwide Incorporated (Kimberly-Clark Corporation)
• Original Assignee: Kimberly-Clark Worldwide Incorporated (Kimberly-Clark Corporation)
• Inventors: Wang, James H., Wideman, Gregory J., Lee, JaeHong
• Granted Patent: US 9,327,438 B2
• Time in Patent Office: Days
• US Class Current: 428/220
• CPC Class Codes: B29B 7/42 with screw or helix
• CPC Class Codes: B29B 7/46 with more than one shaft
• CPC Class Codes: B29B 7/726 Measuring properties of mixture, e.g. temperature or density B29B7/724 takes precedence
• CPC Class Codes: B29B 7/728 Measuring data of the driving system, e.g. torque, speed, power, vibration B29B7/724 takes precedence
• CPC Class Codes: B29B 7/90 Fillers or reinforcements , e.g. fibres
• CPC Class Codes: B29B 7/92 Wood chips or wood fibres
• CPC Class Codes: B29B 7/94 Liquid charges
• CPC Class Codes: B29B 9/02 by dividing preformed material
• CPC Class Codes: B29B 9/06 in the form of filamentary material, e.g. combined with extrusion
• CPC Class Codes: B29B 9/12 characterised by structure or composition
• CPC Class Codes: B29B 9/16 Auxiliary treatment of granules
• CPC Class Codes: B29C 2793/009 after shaping
• CPC Class Codes: B29C 2948/92704 Temperature
• CPC Class Codes: B29C 2948/92723 Content, e.g. percentage of humidity, volatiles, contaminants or degassing
• CPC Class Codes: B29C 2948/92923 Calibration, after-treatment or cooling zone
• CPC Class Codes: B29C 2948/92933 Conveying, transporting or storage of articles
• CPC Class Codes: B29C 2948/92942 Moulded article
• CPC Class Codes: B29C 48/0022 combined with cutting
• CPC Class Codes: B29C 48/022 characterised by the choice of material
• CPC Class Codes: B29C 48/04 Particle-shaped making granules B29B9/00
• CPC Class Codes: B29C 48/05 : Filamentary, e.g. strands
• CPC Class Codes: B29C 48/08 : flexible, e.g. films
• CPC Class Codes: B29C 48/345 : Extrusion nozzles comprising two or more adjacently arranged ports, for simultaneously extruding multiple strands, e.g. for pelletising
• CPC Class Codes: B29C 48/355 : Conveyors for extruded articles
• CPC Class Codes: B29C 48/91 : Heating, e.g. for cross linking
• CPC Class Codes: B29C 48/911 : Cooling
• CPC Class Codes: B29C 48/9135 : of flat articles, e.g. using specially adapted supporting means
• CPC Class Codes: B29C 48/914 : cooling drums
• CPC Class Codes: B29C 48/919 : using a bath, e.g. extruding into an open bath to coagulate or cool the material
• CPC Class Codes: B29K 2003/00 : Use of starch or derivatives as moulding material
• CPC Class Codes: B29K 2105/0038 : Plasticisers
• CPC Class Codes: B29K 2995/0056 : Biocompatible, e.g. biopolymers or bioelastomers
• CPC Class Codes: B29K 2995/006 : Bio-degradable, e.g. bioabsorbable, bioresorbable or bioerodible

Abstract

A method and system for melt processing a thermoplastic composition that contains a starch and plasticizer is provided. The composition is melt blended and extruded through a die to form an extrudate, which is thereafter cooled using a multi-stage system of the present invention that includes at least one water-cooling stage and at least one air-cooling stage. More particularly, the extrudate is initially contacted with water for a certain period time so that it becomes partially cooled and solidified on its surface. After the water-cooling stage(s), the extrudate is also subjected to at least one air-cooling stage in which a stream of air is placed into contact with the extrudate.

Claims

1. A method for forming a thermoplastic starch-based composition, the method comprising:

melt extruding a thermoplastic composition through a die to form an extrudate, wherein the thermoplastic composition comprises a starch polymer and plasticizer;

subjecting the extrudate to at least one water-cooling stage in which the extrudate is contacted with water for a first period of time; and

thereafter, subjecting the water-cooled extrudate to at least one air-cooling state in which the extrudate is contacted with air for a second period of time, wherein the air-cooled extrudate has a moisture content of from about 500 to about 20,000 parts per million.

2. The method of claim 1, wherein the first period of time is from about 1 to about 50 seconds.

3. The method of claim 1, wherein the temperature of the water is from about 10°

C. to about 60°

C.

4. The method of claim 1, wherein the substrate is immersed within a water cooling device during the water-cooling stage.

5. The method of claim 1, wherein the moisture content of the water-cooled extrudate is from about 2,000 to about 50,000 parts per million.

6. The method of claim 1, wherein the second period of time is from about 1 to about 50 seconds.

7. The method of claim 1, wherein the temperature of the stream of air is from about 0°

C. to about 40°

C.

8. The method of claim 1, wherein the stream of air is provided by an air knife.

9. The method of claim 1, wherein the moisture content of the air-cooled extrudate is from 1,000 to about 10,000 parts per million.

10. The method of claim 1, further comprising pelletizing the air-cooled extrudate.

11. The method of claim 1, wherein the starch polymer is a corn starch.

12. The method of claim 1, wherein the plasticizer is a polyhydric alcohol or a sugar alcohol.

13. The method of claim 1, wherein the weight ratio of starch polymers to plasticizers in the thermoplastic composition is from about 1 to about 10.

14. The method of claim 1, further comprising melt-extruding the air-cooled extrudate onto a surface to form a substrate.

15. A film formed according to the method of claim 1, wherein the film has a thickness of about 50 micrometers or less.

17. The film of claim 17, wherein the film exhibits a modulus of elasticity in the cross-machine direction of from about 80 to about 250 Megapascals.

16. The film of claim 17, wherein the film exhibits a percent strain at break of the film in the cross-machine direction of about 550% or more.

18. A system for forming a thermoplastic starch-based composition, the system comprising:

a supply of a starch polymer and a plasticizer;

an extruder and a die, wherein the starch polymer and plasticizer are capable of being melt blended within the extruder and through the die to form an extrudate;

at least one water-cooling stage located downstream from the extruder and die, the water-cooling stage comprising a water bath within which the extrudate is immersed upon exiting the die; and

at least one air-cooling stage located downstream from the water-cooling stage that is configured to supply a stream of air into contact with the extrudate upon exiting the water bath.

19. A method for forming a thermoplastic starch-based composition, the method comprising:

melt extruding a thermoplastic composition through a die to form an extrudate, wherein the thermoplastic composition comprises a starch polymer, plasticizer, biodegradable polymer, polyolefin, and a compatibilizer;

subjecting the extrudate to at least one water-cooling stage in which the extrudate is contacted with water for a first period of time; and

thereafter, subjecting the water-cooled extrudate to at least one air-cooling state in which the extrudate is contacted with air for a second period of time, wherein the air-cooled extrudate has a moisture content of from about 500 to about 20,000 parts per million.

20. The method of claim 19, wherein the polyolefin is a copolymer of an ethylene and an α

-olefin, and the biodegradable polymer is an aliphatic-aromatic copolyester.

21. The method of claim 20, wherein the compatibilizer has a polar component and a non-polar component, the non-polar component being provided by an olefin.