Method for Forming a Thermoplastic Composition that Contains a Plasticized Starch Polymer
First Claim
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.
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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.
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Citations
21 Claims
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1. A method for forming a thermoplastic starch-based composition, the method comprising:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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- 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.
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18. A system for forming a thermoplastic starch-based composition, the system comprising:
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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.
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19. A method for forming a thermoplastic starch-based composition, the method comprising:
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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. - View Dependent Claims (20, 21)
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Specification