US5180751A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Polypropylene foam sheets
Assignee: Fort James Corp
•
Filing: 1992-05-22
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Granted: 1993-01-19
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Expires: 2012-05-22
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 00:01
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: 11
Claim 1
Independent Claim
137 words
A process for producing 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 , 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 , comprising the steps of mixing pelletized polypropylene with a nucleating agent, plasticating the mixture, introducing a physical blowing agent into the substantially plasticated mixture to form a foaming mixture, mixing and cooling the foaming mixture, extruding the foaming mixture into a foamed extrudate, and forming the foamed extrudate into a continuous foam sheet.
Claim 2
Dependent Claim
137 words
A process for producing 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 , 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 , comprising the steps of mixing pelletized polypropylene with a nucleating agent, plasticating the mixture, introducing a physical blowing agent into the substantially plasticated mixture to form a foaming mixture, mixing and cooling the foaming mixture, extruding the foaming mixture into a foamed extrudate, and forming the foamed extrudate into a continuous foam sheet.
Claim 3
Dependent Claim
22 words
The process 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 4
Dependent Claim
30 words
The process of claim 1, wherein said sheet has a uniform cell structure with cells ranging from 5 to 18 mils and an open cell content of less than 40%.
Claim 5
Dependent Claim
14 words
The process of claim 1, wherein said sheet has a thickness of 0.020-0.200 inches.
Claim 6
Dependent Claim
21 words
The process of claim 1, wherein said sheet has a substantially non-cellular outer layer or skin on one or both sides.
Claim 7
Dependent Claim
28 words
The process of claim 1, wherein the physical blowing agent is selected from the group consisting of hydrocarbons, chlorinated hydrocarbons, chlorofluorocarbons, nitrogen, carbon dioxide and other inert gases.
Claim 8
Dependent Claim
17 words
The process of claim 6, wherein the physical blowing agent concentration is less than 25% by weight.
Claim 9
Dependent Claim
24 words
The process of claim 1, wherein said nucleating agent is selected from the group consisting of citric acid-sodium bicarbonare mixture, talc and titanium dioxide.
Claim 10
Dependent Claim
25 words
The process of claim 8, wherein said nucleating agent has a particle size of 0.3-5.0 microns and its concentration is less than 1% by weight.
Claim 11
Dependent Claim
22 words
The foam sheet of claim 5, wherein said sheet has a substantially non-cellular outer layer or skin on one or both sides.
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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) | 1996-01-19 | 1996-07-20 | 1997-01-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2000-01-19 | 2000-07-20 | 2001-01-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2004-01-19 | 2004-07-20 | 2005-01-19 | $7700.00 | Window Closed / Lapsed |