US5866053A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for providing continuous processing of microcellular and supermicrocellular foamed materials
Assignee: Massachusetts Institute of Technology
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Filing: 1997-01-13
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Granted: 1999-02-02
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Expires: 2017-01-13
Abstract
Abstract An extrusion system for providing a foamed material in which a material such as a polymer material is supplied to an extruder for movement through a rotating screw member. The material is placed in a molten state and a foaming agent, such as a supercritical fluid, is introduced into the extruder at a selected pressure so that a two-phase mixture of the molten material and the foaming agent is formed. The foaming agent is then diffused into and dissolved in the molten material to form a single-phase solution which is forwarded from a solution formation to a nucleation device. A thermodynamic instability is induced through a rapid pressure drop, e.g., higher than 0.9 GPa/s in the nucleation device to nucleate microcells in the solution. A further shaping device, e.g., a die, can be used to produce a foamed material of a desired shape.
Inventors
- 👤 Chul B. Park
- 👤 Nam P. Suh
- 👤 Daniel F. Baldwin
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 04:42
CPC Classifications
B; B29; B29C; B29C44/00; B29C44/34; B29C44/36; B29C44/46; B29C44/461; B29C44/3469; B29C44/348
Claims Analysis
Total Claims: 29
Claim 1
Independent Claim
126 words
A method comprising: providing a material to be foamed; mixing a supercritical carbon dioxide foaming agent into said material to create a mixture; creating a homogeneous single-phase solution from the mixture having a uniform concentration of foaming agent distributed therein and maintaining said single-phase solution at a pressure of at least about 1530 psi; nucleating the homogeneous single-phase solution by passing the single-phase solution through a constriction creating a rapid pressure drop in the single-phase solution at a pressure drop rate of at least about 0.18 GPa/s (26,100 psi/s) due to friction, to create a nucleated stream; shaping the nucleated stream essentially immediately after nucleating the solution to create a shaped microcellular extrudate; and releasing the shaped microcellular extrudate into ambient conditions essentially immediately after shaping.
Claim 2
Independent Claim
126 words
A method comprising: providing a material to be foamed; mixing a supercritical carbon dioxide foaming agent into said material to create a mixture; creating a homogeneous single-phase solution from the mixture having a uniform concentration of foaming agent distributed therein and maintaining said single-phase solution at a pressure of at least about 1530 psi; nucleating the homogeneous single-phase solution by passing the single-phase solution through a constriction creating a rapid pressure drop in the single-phase solution at a pressure drop rate of at least about 0.18 GPa/s (26,100 psi/s) due to friction, to create a nucleated stream; shaping the nucleated stream essentially immediately after nucleating the solution to create a shaped microcellular extrudate; and releasing the shaped microcellular extrudate into ambient conditions essentially immediately after shaping.
Claim 3
Dependent Claim
18 words
The method of claim 1, further comprising mixing a metered amount of said foaming agent into said material.
Claim 4
Dependent Claim
24 words
The method of claim 2, comprising mixing a metered amount of said foaming agent into said material to be foamed while heating said material.
Claim 5
Dependent Claim
26 words
The method of claim 1 further comprising subjecting said single-phase solution to a decrease in temperature while subjecting said single-phase solution to a further pressure drop.
Claim 6
Dependent Claim
21 words
The method of claim 1 wherein said concentration of foaming agent in said single-phase solution is at least 1 wt %.
Claim 7
Dependent Claim
21 words
The method of claim 1 wherein said concentration of foaming agent in said single-phase solution is at least 5 wt %.
Claim 8
Dependent Claim
21 words
The method of claim 6 wherein said concentration of foaming agent in said single-phase solution is at least 10 wt %.
Claim 9
Dependent Claim
17 words
The method of claim 1 further comprising providing at least one nucleating agent in said single-phase solution.
Claim 10
Dependent Claim
16 words
The method of claim 1 comprising creating said single-phase solution in less than about 80 seconds.
Claim 11
Dependent Claim
26 words
The method of claim 1 further comprising subjecting said single-phase solution to an increase in temperature while subjecting said single-phase solution to a further pressure drop.
Claim 12
Dependent Claim
25 words
The method of claim 1 comprising subjecting said single-phase solution to a pressure drop at a rate of at least about 0.9 GPa/s (130,500 psi/s).
Claim 13
Dependent Claim
25 words
The method of claim 1 comprising subjecting said single-phase solution to a pressure drop at a rate of at least about 6.9 GPa/s (1,000,500 psi/s).
Claim 14
Dependent Claim
16 words
The method of claim 1 wherein the single-phase solution is essentially free of auxiliary nucleating agent.
Claim 15
Dependent Claim
38 words
The method of claim 1 comprising creating said single-phase solution by allowing convective diffusion of molecules of said foaming agent in said material to be foamed, thereby substantially completely diffusing and dissolving said foaming agent in said material.
Claim 16
Dependent Claim
26 words
The method of claim 1 further comprising subjecting said single-phase solution to an increase in temperature while subjecting said single-phase solution to said rapid pressure drop.
Claim 17
Dependent Claim
21 words
The method as in claim 1, further comprising maintaining said single-phase solution at a pressure of at least about 2700 psi.
Claim 18
Dependent Claim
21 words
The method as in claim 1, further comprising maintaining said single-phase solution at a pressure of at least about 3200 psi.
Claim 19
Dependent Claim
21 words
The method as in claim 1, further comprising maintaining said single-phase solution at a pressure of at least about 4000 psi.
Claim 20
Dependent Claim
16 words
The method of claim 1, wherein the material to be foamed is a semicrystalline polymeric material.
Claim 21
Independent Claim
144 words
A method for forming foamed material comprising mixing together a supercritical carbon dioxide foaming agent and a material to be foamed, forming a single-phase solution of said foaming agent and said material to be foamed, maintaining said single-phase solution at a pressure greater than a solubility pressure of said foaming agent in said material to be foamed at a pressure of at least about 1530 psi, subjecting said single-phase solution to a pressure drop at a pressure drop rate of at least about 0.18 GPa/s (26,100 psi/s) to form sites of nucleation therein by passing said single-phase solution through a constriction causing friction in the solution, expanding said sites of nucleation to form cells, and causing said solution having cells therein to take the shape of a continuous extrusion of microcellular material having a cell density of at least 10 7 sites/cm 3 .
Claim 22
Independent Claim
144 words
A method for forming foamed material comprising mixing together a supercritical carbon dioxide foaming agent and a material to be foamed, forming a single-phase solution of said foaming agent and said material to be foamed, maintaining said single-phase solution at a pressure greater than a solubility pressure of said foaming agent in said material to be foamed at a pressure of at least about 1530 psi, subjecting said single-phase solution to a pressure drop at a pressure drop rate of at least about 0.18 GPa/s (26,100 psi/s) to form sites of nucleation therein by passing said single-phase solution through a constriction causing friction in the solution, expanding said sites of nucleation to form cells, and causing said solution having cells therein to take the shape of a continuous extrusion of microcellular material having a cell density of at least 10 7 sites/cm 3 .
Claim 23
Dependent Claim
19 words
A method as in claim 20 comprising maintaining said single-phase solution at a pressure of at least 4000 psi.
Claim 24
Dependent Claim
15 words
The method of claim 21 wherein said material to be foamed is an amorphous polymer.
Claim 25
Dependent Claim
15 words
The method of claim 22 wherein said material to be foamed is a semicrystalline polymer.
Claim 26
Dependent Claim
31 words
A method as in claim 20 comprising forming said single-phase solution in less than about 80 seconds by allowing convective diffusion of said foaming agent in said material to be foamed.
Claim 27
Dependent Claim
24 words
A method as in claim 20 comprising forming microcellular foamed material having a cell density of at least 10 8 cells per cubic centimeter.
Claim 28
Dependent Claim
24 words
A method as in claim 20 comprising forming microcellular foamed material having a cell density of at least 10 9 cells per cubic centimeter.
Claim 29
Dependent Claim
16 words
The method of claim 20, wherein the material to be foamed is a semicrystalline polymeric material.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2002-02-01 | 2002-08-03 | 2003-02-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2006-02-01 | 2006-08-03 | 2007-02-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2010-02-01 | 2010-08-03 | 2011-02-02 | $7700.00 | Window Closed / Lapsed |