US4981631A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for making lightweight polyester articles
Assignee: Shell USA Inc
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Filing: 1989-03-31
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Granted: 1991-01-01
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Expires: 2009-03-31
Abstract
Abstract This invention relates to a process for making a lightweight article which involves the steps of: (1) feeding a thermoplastic resin composition into an extruder, wherein the thermoplastic resin composition contains (a) from about 94 to about 99 weight percent polyethylene terephthalate, and (b) from about 1 to about 6 weight percent of at least one polyolefin; (2) mixing an inert gas into the thermoplastic resin composition in the extruder while the thermoplastic resin composition is in the molten state; (3) extruding the thermoplastic resin composition containing the inert gas through a sheet forming die to produce a substantially amorphous cellular sheet which contains a sufficient amount of inert gas cells to provide the cellular sheet with a density which is within the range of about 0.4 to about 1.25; and (4) thermoforming the cellular sheet in a heated mold to produce the lightweight article. Dual-ovenable trays and other types of food containers can be made utilizing the process of this invention. It is advantageous to utilize the process of this invention in making such articles because they are lightweight and can be made utilizing less polymeric materials.
Inventors
- 👤 Tak M. Cheung
- 👤 Charles L. Davis
- 👤 Jack E. Prince
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 12:23
CPC Classifications
C; C08; C08J; C08J9/00; C08J9/0061; B; B29; B29B; B29B11/00; B29B11/06; B29B11/10; B29C; B29C44/00; B29C44/02; B29C44/08; B29C44/34; B29C44/3442; B29C44/3446; B29C51/00; B29C51/002; B29C2949/00; B29C2949/07; B29C2949/0861; B29C2949/0862; B29C35/00; B29C35/02; B29C51/26; B29C51/42; B29C51/428; B29K; B29K2067/00; C08J2367/00; C08J2367/02; C08J2423/00; Y; Y10; Y10S; Y10S264/00; Y10S264/90; Y10S264/901
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
90 words
A process for making a lightweight thin walled article which comprises: thermoforming a substantially amorphous cellular sheet which is comprised of (a) from about 94 to about 99 weight percent polyethylene terephthalate, (b) from about 1 to about 6 weight percent of at least one polyolefin, (c) a sufficient amount of inert gas cells which are made by injecting inert gas to provide the cellular sheet with a density which is within the range of about 0.4 to about 1.25, (d) optionally, a heat stabilizer and (e) optionally, a colorant.
Claim 2
Dependent Claim
90 words
A process for making a lightweight thin walled article which comprises: thermoforming a substantially amorphous cellular sheet which is comprised of (a) from about 94 to about 99 weight percent polyethylene terephthalate, (b) from about 1 to about 6 weight percent of at least one polyolefin, (c) a sufficient amount of inert gas cells which are made by injecting inert gas to provide the cellular sheet with a density which is within the range of about 0.4 to about 1.25, (d) optionally, a heat stabilizer and (e) optionally, a colorant.
Claim 3
Dependent Claim
133 words
A process for making an amorphous cellular sheet which can be thermoformed into lightweight thin walled articles which comprises: (1) feeding a thermoplastic resin composition into an extruder; wherein the thermoplastic resin composition is comprised of (a) from about 94 to about 99 weight percent polyethylene terephthalate, and (b) from about 1 to about 6 weight percent of at least one polyolefin: (2) mixing an inert gas into the thermoplastic resin composition while the thermoplastic resin composition is in the molten state: and (3) extruding the thermoplastic resin composition containing the inert gas through a sheet forming die to produce a substantially amorphous cellular sheet which contains a sufficient amount of inert gas cells to provide the cellular sheet with a density which is within the range of about 0.4 to about 1.25.
Claim 4
Dependent Claim
133 words
A process for making an amorphous cellular sheet which can be thermoformed into lightweight thin walled articles which comprises: (1) feeding a thermoplastic resin composition into an extruder; wherein the thermoplastic resin composition is comprised of (a) from about 94 to about 99 weight percent polyethylene terephthalate, and (b) from about 1 to about 6 weight percent of at least one polyolefin: (2) mixing an inert gas into the thermoplastic resin composition while the thermoplastic resin composition is in the molten state: and (3) extruding the thermoplastic resin composition containing the inert gas through a sheet forming die to produce a substantially amorphous cellular sheet which contains a sufficient amount of inert gas cells to provide the cellular sheet with a density which is within the range of about 0.4 to about 1.25.
Claim 5
Dependent Claim
140 words
A process for making a lightweight article which comprises: (1) feeding a thermoplastic resin composition into an extruder, wherein the thermoplastic resin composition is comprised of (a) from about 94 to about 99 weight percent polyethylene terephthalate, and (b) from about 1 to about 6 weight percent of at least one polyolefin; (2) mixing an inert gas into the thermoplastic resin composition in the extruder while the thermoplastic resin composition is in the molten state: (3) extruding the thermoplastic resin composition containing the inert gas through a sheet forming die to produce a substantially amorphous cellular sheet which contains a sufficient amount of inert gas cells to provide the cellular sheet with a density which is within the range of about 0.4 to about 1.25: and (4) thermoforming the cellular sheet in a heated mold to produce the lightweight article.
Claim 6
Dependent Claim
140 words
A process for making a lightweight article which comprises: (1) feeding a thermoplastic resin composition into an extruder, wherein the thermoplastic resin composition is comprised of (a) from about 94 to about 99 weight percent polyethylene terephthalate, and (b) from about 1 to about 6 weight percent of at least one polyolefin; (2) mixing an inert gas into the thermoplastic resin composition in the extruder while the thermoplastic resin composition is in the molten state: (3) extruding the thermoplastic resin composition containing the inert gas through a sheet forming die to produce a substantially amorphous cellular sheet which contains a sufficient amount of inert gas cells to provide the cellular sheet with a density which is within the range of about 0.4 to about 1.25: and (4) thermoforming the cellular sheet in a heated mold to produce the lightweight article.
Claim 7
Dependent Claim
21 words
A process as specified in claim 1 wherein the substantially amorphous cellular sheet contains an effective amount of a heat stabilizer.
Claim 8
Dependent Claim
23 words
A process as specified in claim 2 wherein the thermoplastic resin composition is further comprised of an effective amount of a heat stabilizer.
Claim 9
Dependent Claim
23 words
A process as specified in claim 3 wherein said thermoplastic resin composition is further comprised of an effective amount of a heat stabilizer.
Claim 10
Dependent Claim
20 words
A process as specified in claim 4 wherein the polyethylene terephthalate has an intrinsic viscosity of at least 0.7 dl/g.
Claim 11
Dependent Claim
20 words
A process as specified in claim 5 wherein the polyethylene terephthalate has an intrinsic viscosity of at least 0.7 dl/g.
Claim 12
Dependent Claim
20 words
A process as specified in claim 6 wherein the polyethylene terephthalate has an intrinsic viscosity of at least 0.7 dl/g.
Claim 13
Dependent Claim
36 words
A process as specified in claim 7 wherein a sufficient amount of inert gas cells are present to provide the cellular sheet with a density which is within the range of about 0.7 to about 1.15.
Claim 14
Dependent Claim
25 words
A process as specified in claim 8 wherein the cellular sheet has a density which is within the range of about 0.7 to about 1.15.
Claim 15
Dependent Claim
25 words
A process as specified in claim 9 wherein the cellular sheet has a density which is within the range of about 0.7 to about 1.15.
Claim 16
Dependent Claim
15 words
A process as specified in claim 10 wherein the polyolefin is linear low density polyethylene.
Claim 17
Dependent Claim
15 words
A process as specified in claim 11 wherein the polyolefin is linear low density polyethylene.
Claim 18
Dependent Claim
15 words
A process as specified in claim 12 wherein the polyolefin is linear low density polyethylene.
Claim 19
Dependent Claim
41 words
A process as specified in claim 1 wherein the thermoforming is carried out in a heated mold for a time which is sufficient to achieve a crystallinity in said article which is within the range of about 5% to about 45%.
Claim 20
Dependent Claim
14 words
A process as specified in claim 10 wherein the polyolefin in a polyethylene ionomer.
Claim 21
Dependent Claim
14 words
A process as specified in claim 11 wherein the polyolefin is a polyethylene ionomer.
Claim 22
Dependent Claim
14 words
A process as specified in claim 12 wherein the polyolefin is a polyethylene ionomer.
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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) | 1993-12-31 | 1994-07-02 | 1995-01-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-12-31 | 1998-07-02 | 1999-01-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-12-31 | 2002-07-02 | 2003-01-01 | $7700.00 | Window Closed / Lapsed |