Patent US5116881A successfully refreshed from Google Patents.
US5116881A
Expired / Lapsed
US
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Polypropylene foam sheets
Assignee: Fort James Corp
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Filing: 1990-03-14
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Granted: 1992-05-26
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Expires: 2010-03-14
Abstract
Abstract A thermoformable, rigid or semi-rigid polypropylene foam sheet having a smooth surface and a uniform cell structure and a density of at least 2.5 lbs/ft 3 is prepared by extruding a mixture of a nucleating agent, a physical blowing agent and a polypropylene resin having a high melt strength and high melt elasticity.
Inventors
- 👤 John J. Park
- 👤 Leon Katz
- 👤 Norman G. Gaylord
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 06:44
CPC Classifications
C; C08; C08J; C08J9/00; C08J9/22; C08J9/228; C08J9/04; C08J9/12; C08J9/14; C08J9/141; B; B29; B29C; B29C48/00; B29C48/16; B32; B32B; B32B27/00; B32B27/06; B32B27/065; B32B27/30; B32B27/304; B32B27/32; B32B27/34; B32B5/00; B32B5/18; C08J5/00; C08J5/18; C08J9/0066; C08J9/143; C08L; C08L23/00; C08L23/02; C08L23/10; C08L23/12; B32B2266/00; B32B2266/02; B32B2266/0214; B32B2266/025; B32B2323/00; B32B2323/04; B32B2327/00; C08J2323/00; C08J2323/02; C08J2323/10; C08J2323/12; Y; Y10; Y10T; Y10T428/00; Y10T428/24; Y10T428/24942; Y10T428/2495; Y10T428/249921; Y10T428/249953; Y10T428/249981; Y10T428/249982; Y10T428/249987; Y10T428/249988; Y10T428/249989; Y10T428/249991; Y10T428/249992
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
83 words
A foam sheet of a polypropylene characterized by at least (a) either z-average molecular weight M z of at least 1.0×10 6 or a ratio of the z-average molecular weight M z to weight average molecular weight M w M z /M w of at least 3.0, and (b) either equilibrium compliance J eo of at least 12×10 -5 cm 2 /dyne or recoverable shear strain per unit stress Sr/S of at least 5×10 -5 cm 2 /dyne at 1 sec -1 .
Claim 2
Dependent Claim
83 words
A foam sheet of a polypropylene characterized by at least (a) either z-average molecular weight M z of at least 1.0×10 6 or a ratio of the z-average molecular weight M z to weight average molecular weight M w M z /M w of at least 3.0, and (b) either equilibrium compliance J eo of at least 12×10 -5 cm 2 /dyne or recoverable shear strain per unit stress Sr/S of at least 5×10 -5 cm 2 /dyne at 1 sec -1 .
Claim 3
Dependent Claim
20 words
A foam sheet of polypropylene having a biomodal molecular weight distribution, wherein the higher molecular weight fraction contains branched polymer.
Claim 4
Dependent Claim
20 words
A foam sheet of polypropylene having a biomodal molecular weight distribution, wherein the higher molecular weight fraction contains branched polymer.
Claim 5
Dependent Claim
23 words
The foam sheet of claim 1, wherein said sheet has a density of 2.5-25.0 lbs/ft 3 and a flexural modulus of 10,000-50,000 psi.
Claim 6
Dependent Claim
31 words
The foam sheet of claim 1, wherein said sheet has a uniform cellular structure with cells ranging from 5 to 18 mils and an open cell content of less than 40%.
Claim 7
Dependent Claim
15 words
The foam sheet of claim 1, wherein said sheet has a thickness of 0.020-0.200 inches.
References Cited (Backward Citations)
US3830900A
Cited
US3787543A
Cited
US3637458A
Cited
US3819784A
Cited
US3787443A
Cited
EP0001791A2
Cited
US4424293A
Cited
EP0071981A1
Cited
US4467052A
Cited
US4525257A
Cited
EP0122460A1
Cited
EP0178283A2
Cited
EP0178282A2
Cited
US4940736A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1995-05-26 | 1995-11-25 | 1996-05-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-05-26 | 1999-11-25 | 2000-05-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-05-26 | 2003-11-25 | 2004-05-26 | $7700.00 | Window Closed / Lapsed |