US4976898A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for making puncture resistant, heat-shrinkable films containing very low density polyethylene
Assignee: Curwood Inc
•
Filing: 1989-07-25
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Granted: 1990-12-11
•
Expires: 2009-07-25
Abstract
Abstract Method of manufacturing a heat shrinkable biaxially oriented thermoplastic film by extruding a primary tube including very low density polyethylene (VLDPE), heating the primary tube and biaxially stretching the heated primary tube using a double bubble method to form a tube which is heat shrinkable from about 30% to about 50% in at least one of the transverse and machine directions.
Inventors
- 👤 Stanley Lustig
- 👤 Nancy M. Mack
- 👤 Jeffrey M. Schuetz
- 👤 Stephen J. Vicik
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 00:46
CPC Classifications
B; B32; B32B; B32B27/00; B32B27/06; B32B27/08
Claims Analysis
Total Claims: 25
Claim 1
Independent Claim
113 words
A method of manufacturing a heat-shrinkable, puncture resistant, biaxially stretched, thermoplastic film comprising the steps of extruding a primary tube comprising a very low density polyethylene which is a linear copolymer of ethylene and higher alpha olefin containing from 3 to 8 carbon atoms, having a density below about 0.91 g/cm 3 and a 1% secant modulus below about 140,000 kPa; heating the very low density polyethylene primary tube; biaxially stretching the heated primary tube using a double bubble method under conditions wherein the biaxially stretched tube is heat shrinkable from about 30% to about 50% at a temperature of about 90° C. in at least one of the transverse and machine directions.
Claim 2
Independent Claim
113 words
A method of manufacturing a heat-shrinkable, puncture resistant, biaxially stretched, thermoplastic film comprising the steps of extruding a primary tube comprising a very low density polyethylene which is a linear copolymer of ethylene and higher alpha olefin containing from 3 to 8 carbon atoms, having a density below about 0.91 g/cm 3 and a 1% secant modulus below about 140,000 kPa; heating the very low density polyethylene primary tube; biaxially stretching the heated primary tube using a double bubble method under conditions wherein the biaxially stretched tube is heat shrinkable from about 30% to about 50% at a temperature of about 90° C. in at least one of the transverse and machine directions.
Claim 3
Dependent Claim
31 words
A method according to claim 1 wherein said biaxially stretched tube is heat shrinkable from about 30% to about 50% at a temperature of about 90° C. in the transverse direction.
Claim 4
Dependent Claim
31 words
A method according to claim 1 wherein said biaxially stretched tube is heat shrinkable from about 30% to about 50% at a temperature of about 90° C. in the machine direction.
Claim 5
Dependent Claim
34 words
A method according to claim 1 wherein said biaxially stretched tube is heat shrinkable from about 30% to about 50% at a temperature of about 90° C. in both the transverse and machine directions.
Claim 6
Dependent Claim
13 words
A method according to claim 1 wherein the film comprises a monolayer film.
Claim 7
Dependent Claim
13 words
A method according to claim 1 wherein the film comprises a multilayer film.
Claim 8
Dependent Claim
15 words
A method according to claim 6 wherein the primary multilayer film is prepared by coextrusion.
Claim 9
Dependent Claim
29 words
A method according to claim 6 wherein at least one layer of said multilayer film comprises a blend of said very low density polyethylene and an ethylene-vinyl acetate copolymer.
Claim 10
Dependent Claim
46 words
A method according to claim 6 wherein the multilayer film comprises a first outer layer of an ethylene-vinyl acetate copolymer, a core layer comprising a barrier film, and a second outer layer comprising a blend of said very low density polyethylene and an ethylene-vinyl acetate copolymer.
Claim 11
Dependent Claim
24 words
A method according to claim 6 wherein said film is irradiated to a dosage level of between about 1 megarad and about 5 megarads.
Claim 12
Dependent Claim
23 words
A method according to claim 1 wherein the polyethylene copolymer has a standard load melt index of up to about 25.0 g/10 minutes.
Claim 13
Dependent Claim
23 words
A method according to claim 1 wherein the polyethylene copolymer has a high load melt index of up to about 1000 g/10 minutes.
Claim 14
Dependent Claim
22 words
A method according to claim 6 wherein the multilayer film has a thickness of from about 1.75 mils to about 3.0 mils.
Claim 15
Dependent Claim
20 words
A method according to claim 6 wherein at least one layer of said multilayer film comprises an oxygen barrier layer.
Claim 16
Dependent Claim
15 words
A method according to claim 14 wherein said oxygen barrier layer is a core layer.
Claim 17
Dependent Claim
35 words
A method according to claim 14 wherein said oxygen barrier layer comprises a copolymer of vinylidene chloride and at least one comonomer selected from the group of comprising vinyl chloride, acrylonitrile and an acrylate ester.
Claim 18
Dependent Claim
33 words
A method according to claim 14 wherein said oxygen barrier layer comprises a copolymer of vinylidene chloride and an acrylate ester wherein vinylidene chloride constitute at least 65 weight percent of the copolymer.
Claim 19
Dependent Claim
33 words
A method according to claim 14 wherein said oxygen barrier layer comprises a copolymer of vinylidene chloride and a vinyl chloride wherein at least 65 weight percent of the copolymer comprises vinylidene chloride.
Claim 20
Dependent Claim
20 words
A method according to claim 14 wherein said oxygen barrier layer comprises a copolymer of vinylidene chloride and methyl methacrylate.
Claim 21
Dependent Claim
23 words
A method according to claim 16 wherein said oxygen barrier layer copolymer comprises between about 70 and 95 weight percent of vinylidene chloride.
Claim 22
Dependent Claim
15 words
A method according to claim 14 wherein said oxygen barrier layer comprises ethylene-vinyl alcohol copolymer.
Claim 23
Dependent Claim
19 words
A method according to claim 14 wherein said oxygen barrier layer comprises a copolymer of vinylidene chloride and acrylonitrile.
Claim 24
Dependent Claim
26 words
A method according to claim 14 wherein said oxygen barrier is a copolymer having at least 65 weight percent of said copolymer derived from vinylidene chloride.
Claim 25
Dependent Claim
22 words
A method according to claim 23 wherein from 70 to about 95 weight percent of said copolymer is derived from vinylidene chloride.
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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) | 1993-12-10 | 1994-06-11 | 1994-12-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-12-10 | 1998-06-11 | 1998-12-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-12-10 | 2002-06-11 | 2002-12-11 | $7700.00 | Window Closed / Lapsed |