Patent US4810457A successfully refreshed from Google Patents.
US4810457A
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US
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Method of blow molding on thermoforming a plastic hardskin/softcore multilayer sheet material
Assignee: RAMPART PACKAGING Inc A CORP OF
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Filing: 1987-09-28
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Granted: 1989-03-07
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Expires: 2007-09-28
Abstract
Abstract A process is disclosed for thermoforming a sheet or billet comprised of at least one outer layer of polypropylene and at least one adjacent layer of a random copolymer of propylene and ethylene and, optionally, a barrier layer. The sheet or billet is thermoformed into rigid articles which do not significantly distort under retort conditions by forming the sheet or billet at a temperature below the sticky point of the polypropylene layer and above the sheet distortion temperature.
Inventors
- 👤 R. James Kersting
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 04:00
CPC Classifications
B; B32; B32B; B32B27/00; B32B27/32; B29; B29C; B29C51/00; B29C51/14; B32B27/06; B32B27/08; B32B27/30; B32B27/306; B29K; B29K2023/00; B29K2023/10; B29K2023/12; B32B2307/00; B32B2307/50; B32B2307/544; B32B2323/00; B32B2323/04; B32B2323/10; B32B2329/00; B32B2439/00; B32B2439/70
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
116 words
A process for thermoforming a sheet or billet, comprised of at least one outer layer of polypropylene and at least one adjacent layer of a random copolymer of propylene and ethylene in which propylene is the major component, into rigid articles which do not significantly distort under retort conditions, which comprises forming the sheet or billet at a temperature at which the polypropylene layer is in the solid phase below its sticky point and the copolymer layer is in the melt phase, said temperature being above the highest temperature at which the copolymer layer will not be able to prevent stress relaxation in the polypropylene layer from causing significant distortion of the articles under retort conditions.
Claim 2
Dependent Claim
116 words
A process for thermoforming a sheet or billet, comprised of at least one outer layer of polypropylene and at least one adjacent layer of a random copolymer of propylene and ethylene in which propylene is the major component, into rigid articles which do not significantly distort under retort conditions, which comprises forming the sheet or billet at a temperature at which the polypropylene layer is in the solid phase below its sticky point and the copolymer layer is in the melt phase, said temperature being above the highest temperature at which the copolymer layer will not be able to prevent stress relaxation in the polypropylene layer from causing significant distortion of the articles under retort conditions.
Claim 3
Dependent Claim
23 words
The process of claim 1 wherein the thickness of the copolymer layer is at least four times the thickness of the polypropylene layer.
Claim 4
Dependent Claim
15 words
The process of claim 1 wherein a mineral filler is incorporated into the copolymer layer.
Claim 5
Dependent Claim
22 words
The process of claim 3 wherein the mineral filler is selected from the group consisting of mica, talc, clay and calcium carbonate.
Claim 6
Dependent Claim
18 words
The process of claim 1 wherein the sheet or billet also includes a layer of a barrier material.
Claim 7
Dependent Claim
15 words
The process of claim 5 wherein the barrier material is an ethylene vinyl alcohol copolymer.
Claim 8
Dependent Claim
106 words
A process for thermoforming a sheet or billet, comprised of at least one outer layer of polypropylene, at least one layer of a random copolymer of propylene and ethylene in which propylene is the major component and at least one layer of a barrier material, into rigid articles which do not significantly distort under retort conditions, which comprise forming the sheet or billet at a temperature below the sticky point of the polypropylene layer and above the highest temperature at which the copolymer layer will not be able to prevent stress relaxation in the polypropylene layer from causing significant distortion of the articles under retort conditions.
Claim 9
Dependent Claim
106 words
A process for thermoforming a sheet or billet, comprised of at least one outer layer of polypropylene, at least one layer of a random copolymer of propylene and ethylene in which propylene is the major component and at least one layer of a barrier material, into rigid articles which do not significantly distort under retort conditions, which comprise forming the sheet or billet at a temperature below the sticky point of the polypropylene layer and above the highest temperature at which the copolymer layer will not be able to prevent stress relaxation in the polypropylene layer from causing significant distortion of the articles under retort conditions.
Claim 10
Dependent Claim
23 words
The process of claim 7 wherein the thickness of the copolymer layer is at least four times the thickness of the polypropylene layer.
Claim 11
Dependent Claim
15 words
The process of claim 7 wherein a mineral filler is incorporated into the copolymer layer.
Claim 12
Dependent Claim
22 words
The process of claim 9 wherein the mineral filler is selected from the group consisting of mica, talc, clay and calcium carbonate.
Claim 13
Dependent Claim
15 words
The process of claim 7 wherein the barrier material is an ethylene vinyl alcohol copolymer.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-03-06 | 1992-09-05 | 1993-03-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-03-06 | 1996-09-05 | 1997-03-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-03-06 | 2000-09-05 | 2001-03-07 | $7700.00 | Window Closed / Lapsed |