Incrementally stretched films with tailored properties and methods for making the same

Patent metadata

Field	Value
Publication number	US-9790012-B2
Application number	US-201313837469-A
Country	US
Kind code	B2
Filing date	Mar 15, 2013
Priority date	Jul 19, 2010
Publication date	Oct 17, 2017
Grant date	Oct 17, 2017

Abstract

Methods of enhancing one or more physical properties of a thermoplastic film include incrementally stretching thermoplastic films in the machine direction and/or transverse direction. In one or more implementations, methods of incrementally stretching thermoplastic films include reducing the gauge of the films while maintaining or increasing a ratio of the machine direction to transverse direction resistance to tear. The methods can involve cold stretching the films and imparting rib patterns into the film. The linear ribs can have alternating thick and thin gauges.

First claim

We claim:

1. An incrementally-stretched thermoplastic film formed by incrementally stretching an initial thermoplastic film having a first ratio of machine-direction tear resistance to transverse-direction tear resistance between 0.3 and 1.6, comprising:
a thermoplastic material;
a ribbed pattern including thicker ribs and thinner stretched linear sections extending across the incrementally-stretched thermoplastic film;
a ratio of machine-direction tear resistance to transverse-direction tear resistance between 1.90 and 3.00 and that is between 1.5 and 4.9 times greater than the first ratio of machine-direction tear resistance to transverse-direction tear resistance of the initial thermoplastic film; and
a gauge by weight that is between 0.91 and 0.53 times a first gauge by weight of the initial thermoplastic film.

2. The incrementally-stretched film as recited in claim 1 , wherein the thicker ribs and thinner stretched linear sections further comprise a set of thicker ribs and thinner stretched linear sections extending across the incrementally-stretched thermoplastic film in a direction in which the incrementally-stretched thermoplastic film was extruded.

3. The incrementally-stretched film as recited in claim 2 , wherein the thicker ribs and thinner stretched linear sections further comprise a second set of thicker ribs and thinner stretched linear sections extending across the incrementally-stretched thermoplastic film in a direction perpendicular to the direction in which the incrementally-stretched thermoplastic film was extruded.

4. The incrementally-stretched film as recited in claim 1 , wherein the ratio of machine-direction tear resistance to transverse-direction tear resistance of the incrementally-stretched thermoplastic film is 1.5.

5. The incrementally-stretched film as recited in claim 4 , wherein the ratio of machine-direction tear resistance to transverse-direction tear resistance of the incrementally-stretched thermoplastic film is greater than 2.

6. The incrementally-stretched film as recited in claim 1 , wherein the gauge by weight of the incrementally-stretched thermoplastic film is between about 0.60 and about 0.91 times the first gauge by weight of the initial thermoplastic film.

7. The incrementally-stretched film as recited in claim 1 , wherein the thermoplastic material comprises linear low density polyethylene.

8. The incrementally-stretched film as recited in claim 7 , wherein the thermoplastic material further comprises low density polyethylene.

9. The incrementally-stretched film as recited in claim 1 , wherein the incrementally-stretched thermoplastic film is a blown film.

10. The incrementally-stretched film as recited in claim 1 , wherein the incrementally-stretched thermoplastic film is a cast film.

11. The film as recited in claim 1 , wherein the thicker ribs and thinner stretched linear sections comprise:
a first set of thicker ribs having a first width; and
a second set of thicker ribs having a second width;
wherein the second width is at least about two times the first width.

12. The incrementally-stretched thermoplastic film as recited in claim 1 , wherein:
the incrementally-stretched thermoplastic film comprises a transparent food wrap;
the incrementally-stretched thermoplastic film is a mono-layered film; and
the incrementally-stretched thermoplastic film is liquid impermeable.

13. The incrementally-stretched thermoplastic film as recited in claim 1 , wherein the incrementally-stretched thermoplastic film provides for easier dispensability from a roll than the initial thermoplastic film.

14. An incrementally-stretched thermoplastic film formed by incrementally stretching an initial thermoplastic film having a first ratio of machine-direction tear resistance to transverse-direction tear resistance between 0.3 and 1.6, comprising:
a first set of alternating thicker ribs and thinner stretched linear sections extending across the thermoplastic film in a first direction parallel to a direction in which the thermoplastic film was extruded;
a second set of alternating thicker ribs and thinner stretched linear sections extending across the thermoplastic film in a second direction transverse to the first direction;
a machine direction tear resistance that is greater than a machine direction tear resistance of the initial thermoplastic film; and
a transverse direction tear resistance that is less than a transverse direction tear resistance of the initial thermoplastic film;
wherein a ratio of the machine direction tear resistance to the transverse direction tear resistance between 1.90 and 3.00 and that is between 1.5 and 4.9 times greater than the first ratio of machine-direction tear resistance to transverse-direction tear resistance of the initial thermoplastic film;
wherein a gauge by weight that is between 0.91 and 0.53 times a first gauge by weight of the initial thermoplastic film.

15. The incrementally-stretched thermoplastic film as recited in claim 14 , wherein the ratio of the machine direction tear resistance to the transverse direction tear resistance is greater than about 2.

16. The incrementally-stretched thermoplastic film as recited in claim 15 , wherein the ratio of the machine direction tear resistance to the transverse direction tear resistance is greater than about 2.5.

17. The incrementally-stretched thermoplastic film as recited in claim 15 , wherein the gauge by weight of the incrementally-stretched thermoplastic film is 0.61 times the first gauge by weight of the initial thermoplastic film.

18. The incrementally-stretched thermoplastic film as recited in claim 14 , wherein the incrementally-stretched thermoplastic film is a blown film.

19. The incrementally-stretched thermoplastic film as recited in claim 14 , wherein the incrementally-stretched thermoplastic film is a cast film.

20. The incrementally-stretched thermoplastic film as recited in claim 14 , wherein:
the incrementally-stretched thermoplastic film comprises a transparent food wrap;
the incrementally-stretched thermoplastic film is a mono-layered film; and
the incrementally-stretched thermoplastic film is gas impermeable.

Assignees

• Glad Products Co

Inventors

• Bergman Carl L
• Wilcoxen Kyle R
• Borchardt Michael G
• Palmer Stacie A
• Dorsey Robert T
• Maxwell Jason R

Classifications

• B32B27/32

  comprising polyolefins {(comprising vinyl (co)polymers or acrylic (co)polymers B32B27/30)} · CPC title

• B32B2250/02

  2 layers · CPC title

• B32B2255/26

  Polymeric coating · CPC title

• B65D65/406 Primary

  with at least one layer provided with a relief other than corrugations · CPC title

• B65D83/0882 Primary

  and for cutting interconnected articles · CPC title