US5034171A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for extruding thermoplastic materials using low pressure inert gases as foaming agents
Assignee: Air Products and Chemicals Inc
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Filing: 1989-11-30
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Granted: 1991-07-23
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Expires: 2009-11-30
Abstract
Abstract A process for producing microcellular foamed articles wherein a low pressure compressible, inert gas such as nitrogen is used as a foaming agent. The process comprises introducing a thermoplastic material into an inlet of an extruder having a length to diameter ratio of at least 30:1, said extruder comprising a screw having at least one stage; heating the thermoplastic material in a melt zone to a temperature sufficient to melt or soften the thermoplastic material to form a melted thermoplastic material; injecting an insoluble compressible, inert gas into the melted thermoplastic material at a position approximately 1 to 2 screw diameters downstream of the melt zone; mixing the molten thermoplastic material and the inert, compressible gas to form a homogeneous dispersion of insoluble bubbles within the material; reducing the pressure of the molten thermoplastic material causing the homogeneously dispersed bubbles to expand within the melted thermoplastic material to form a foamed article and cooling the foamed article to a temperature below the melting or softening point of the foamed article.
Inventors
- 👤 Edward F. Kiczek
- 👤 Augustine I. Dalton, Jr.
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 23:19
CPC Classifications
B; B29; B29C; B29C44/00; B29C44/34; B29C44/3442; B29C44/3446; B29B; B29B7/00; B29B7/74; B29B7/7404; B29B7/7409; B29B7/7428; B29C44/36; B29C44/46; B29C44/50; B29C48/00; B29C48/25; B29C48/285; B29C48/29; B29C48/36; B29C48/50; B29C48/505; B29C48/53; B29C48/03; B29C48/295; B29K; B29K2105/00; B29K2105/0005
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
175 words
A process for producing a closed cell microcellular foamed article from a thermoplastic material comprising: a) introducing a thermoplastic material into an inlet of an extruder having a length to diameter ratio of at least 30:1, the extruder comprising a screw having at least one stage; b) heating the thermoplastic material in a melt zone to a temperature sufficient to melt or soften the thermoplastic material to form a melted thermoplastic material; c) injecting an insoluble compressible inert gas at a pressure ranging from 200 to 2,500 psi into the melted thermoplastic material at a position about 1 to 2 screw diameters downstream of the melt zone; d) mixing the molten thermoplastic material and the compressible, inert gas to form a homogeneous dispersion of insoluble bubbles within the material; e) reducing the pressure of the molten thermoplastic material causing the homogeneously dispersed bubbles to expand within the melted thermoplastic material to form a microcellular foamed article and f) cooling the foamed article to a temperature below the melting or softening point of the foamed article.
Claim 2
Dependent Claim
175 words
A process for producing a closed cell microcellular foamed article from a thermoplastic material comprising: a) introducing a thermoplastic material into an inlet of an extruder having a length to diameter ratio of at least 30:1, the extruder comprising a screw having at least one stage; b) heating the thermoplastic material in a melt zone to a temperature sufficient to melt or soften the thermoplastic material to form a melted thermoplastic material; c) injecting an insoluble compressible inert gas at a pressure ranging from 200 to 2,500 psi into the melted thermoplastic material at a position about 1 to 2 screw diameters downstream of the melt zone; d) mixing the molten thermoplastic material and the compressible, inert gas to form a homogeneous dispersion of insoluble bubbles within the material; e) reducing the pressure of the molten thermoplastic material causing the homogeneously dispersed bubbles to expand within the melted thermoplastic material to form a microcellular foamed article and f) cooling the foamed article to a temperature below the melting or softening point of the foamed article.
Claim 3
Dependent Claim
13 words
The process according to claim 1 wherein the extruder has a single stage.
Claim 4
Dependent Claim
12 words
The process according to claim 1 wherein the extruder has two stages.
Claim 5
Dependent Claim
32 words
The process according to claim 1 wherein the thermoplastic material is selected from the group consisting of polymers formed by polymerization of an olefin having from 2 to about 8 carbon atoms.
Claim 6
Dependent Claim
23 words
The process according to claim 4 wherein the olefin is selected from the group consisting of ethylene, propylene, 1-butene, 3-methyl-1-butene, 4-methyl-1-butene and 4-methyl-1-hexene.
Claim 7
Dependent Claim
12 words
The process according to claim 1 wherein the thermoplastic material is polyethylene.
Claim 8
Dependent Claim
12 words
The process according to claim 1 wherein the thermoplastic material is polypropylene.
Claim 9
Dependent Claim
27 words
The process according to claim 1 wherein the insoluble compressible inert gas is selected from the group consisting of nitrogen, argon, xenon, krypton, helium and carbon dioxide.
Claim 10
Dependent Claim
14 words
The process according to claim 1 wherein the insoluble compressible inert gas is nitrogen.
Claim 11
Dependent Claim
182 words
A process for producing a closed cell microcellular foamed article from a thermoplastic material comprising: (a) introducing a thermoplastic material containing at least one nucleating agent into an inlet of an extruder having a length to diameter ratio of at least 30:1, the extruder comprising a screw having at least one stage; (b) heating the thermoplastic material in a melt zone to a temperature sufficient to melt or soften the thermoplastic material to from a melted thermoplastic material; (c) injecting an insoluble compressible inert gas at a pressure ranging from 200 to about 2,500 psig into the melted thermoplastic material at a position about 1 to 2 screw diameters downstream of the melt zone; (d) mixing the molten thermoplastic material and the compressible, inert gas to form a homogeneous dispersion of insoluble bubbles within the material; (e) reducing the pressure of the molten thermoplastic material causing the homogeneously dispersed bubbles to expand with the melted thermoplastic material to form a microcellular foamed article and (f) cooling the foamed article to a temperature below the melting or softening point of the foamed article.
Claim 12
Dependent Claim
182 words
A process for producing a closed cell microcellular foamed article from a thermoplastic material comprising: (a) introducing a thermoplastic material containing at least one nucleating agent into an inlet of an extruder having a length to diameter ratio of at least 30:1, the extruder comprising a screw having at least one stage; (b) heating the thermoplastic material in a melt zone to a temperature sufficient to melt or soften the thermoplastic material to from a melted thermoplastic material; (c) injecting an insoluble compressible inert gas at a pressure ranging from 200 to about 2,500 psig into the melted thermoplastic material at a position about 1 to 2 screw diameters downstream of the melt zone; (d) mixing the molten thermoplastic material and the compressible, inert gas to form a homogeneous dispersion of insoluble bubbles within the material; (e) reducing the pressure of the molten thermoplastic material causing the homogeneously dispersed bubbles to expand with the melted thermoplastic material to form a microcellular foamed article and (f) cooling the foamed article to a temperature below the melting or softening point of the foamed article.
Claim 13
Dependent Claim
32 words
The process according to claim 10 wherein the thermoplastic material is selected from the group consisting of polymers formed by polymerization of an olefin having from 2 to about 8 carbon atoms.
Claim 14
Dependent Claim
23 words
The process according to claim 11 wherein the olefin is selected from the group consisting of ethylene, propylene, 1-butene, 3-methyl-1-butene, 4-methyl-1-butene and 4-methyl-1-hexene.
Claim 15
Dependent Claim
12 words
The process according to claim 11 wherein the thermoplastic material is polyethylene.
Claim 16
Dependent Claim
12 words
The process according to claim 11 wherein the thermoplastic material is polypropylene.
Claim 17
Dependent Claim
32 words
The process according to claim 10 wherein the nucleating agent is selected from the group consisting of talc, wollastonite, attapulgus clay, kaolin clay, calcium carbonate, citric acid, polytetrafluoroethylene powder and zeolite powders.
Claim 18
Dependent Claim
14 words
The process according to claim 15 wherein the nucleating agent is zeolite 4A powder.
Claim 19
Dependent Claim
13 words
The process according to claim 10 wherein the nucleating agent is polytetrafluoroethylene powder.
Claim 20
Dependent Claim
27 words
The process according to claim 10 wherein the insoluble compressible inert gas is selected from the group consisting of nitrogen, argon, xenon, krypton, helium and carbon dioxide.
Claim 21
Dependent Claim
14 words
The process according to claim 10 wherein the insoluble compressible inert gas is nitrogen.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1994-07-22 | 1995-01-21 | 1995-07-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-07-22 | 1999-01-21 | 1999-07-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-07-22 | 2003-01-21 | 2003-07-23 | $7700.00 | Window Closed / Lapsed |