Incrementally-stretched thermoplastic films and bags with increased haze

Patent metadata

Field	Value
Publication number	US-9108390-B2
Application number	US-201113289829-A
Country	US
Kind code	B2
Filing date	Nov 4, 2011
Priority date	Nov 4, 2011
Publication date	Aug 18, 2015
Grant date	Aug 18, 2015

Abstract

Methods of increasing the haze of a thermoplastic film include incrementally stretching thermoplastic films in the machine direction. In one or more implementations, methods of incrementally stretching thermoplastic films include reducing the gauge of the films without reducing the films' haze. 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. Incrementally stretched thermoplastic films can have a haze that is approximately equal to or greater than the haze of the film prior to stretching.

First claim

I claim:

1. An incrementally-stretched film formed by stretching a thermoplastic film with a first haze, comprising:
a thermoplastic material; and
a ribbed pattern including thicker and thinner linear ribs extending across the incrementally-stretched thermoplastic film; and
a haze that is greater than the first haze of the thermoplastic film;
wherein the haze is between 32.1 and 52.2 percent.

2. The incrementally-stretched film as recited in claim 1 , wherein the haze is between about 1.05 and about 1.5 times the first haze of the thermoplastic film.

3. The incrementally-stretched film as recited in claim 2 , wherein the haze is between about 1.05 and 1.30 times the first haze of the thermoplastic film.

4. The incrementally-stretched film as recited in claim 2 , further comprising a gauge by weight that is approximately equal to or less than a first gauge by weight of the thermoplastic film.

5. The incrementally-stretched film as recited in claim 4 , wherein the gauge by weight is between approximately 0.97 and 0.50 times the first gauge by weight of the thermoplastic film.

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

7. The incrementally-stretched film as recited in claim 6 , further comprising a second set of the thicker and thinner linear ribs extending across the incrementally-stretched thermoplastic film in the direction in which the incrementally-stretched thermoplastic film was extruded.

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

9. The incrementally-stretched film as recited in claim 1 , wherein:
the haze of the incrementally-stretched film is between 112% and 130% of the first haze of the thermoplastic film; and
the gauge by weight of the incrementally-stretched film is between about 0.70 and about 0.95 times the first gauge by weight of the thermoplastic film.

10. The incrementally-stretched film as recited in claim 1 , wherein the thermoplastic material comprises one or more of polyethylene or polypropylene.

11. The incrementally-stretched film as recited in claim 10 , wherein the thermoplastic material comprises linear low density polyethylene.

12. The incrementally-stretched as recited in claim 1 , wherein the incrementally-stretched film is devoid of voiding agents.

13. The incrementally-stretched as recited in claim 1 , further comprising a light transmission that is less than a first light transmission of the thermoplastic film.

14. The incrementally-stretched as recited in claim 1 , wherein the thermoplastic film is pigmented.

15. A thermoplastic bag, comprising:
a first sidewall including an incrementally-stretched film formed by stretching a thermoplastic film having a first haze;
a second sidewall, the first and second sidewalls being joined together along a first side edge, an opposing second side edge, and along a bottom edge, wherein at least a portion of the respective top edges of the first and second sidewalls define an opening of the thermoplastic bag; and
a first set of alternating thicker and thinner linear ribs in first and second sidewalls;
wherein the first sidewall has a haze between 32.1 percent and 52.2 percent, and wherein the haze that is greater than the first haze of the thermoplastic film.

16. The thermoplastic bag as recited in claim 15 , wherein the first set of alternating thicker and thinner linear ribs extend from the bottom edge toward the top edges of the thermoplastic bag.

17. The thermoplastic bag as recited in claim 16 , further comprising a second set of alternating thicker and thinner linear ribs in one or more of the first or second sidewalls, the second set of alternating thicker and thinner linear ribs extending from the first side edge toward the second side edge.

18. The thermoplastic bag as recited in claim 15 , wherein the first side wall comprises a gauge by weight that is between about 0.50 and about 0.95 times a first gauge by weight of the thermoplastic film.

19. The thermoplastic bag as recited in claim 15 , wherein the haze is between about 1.05 and about 1.5 times the first haze of the thermoplastic film.

20. An incrementally-stretched film formed by stretching a thermoplastic film with a first haze, comprising:
a thermoplastic material;
a ribbed pattern including thicker ribs that alternate with thinner linear stretched regions, the ribbed pattern extending across the incrementally-stretched thermoplastic film; and
a haze between 32.1 percent and 52.2 percent, wherein the haze is greater than the first haze of the thermoplastic film.

21. The incrementally-stretched film as recited in claim 20 , wherein the haze is between about 1.05 and about 1.3 times the first haze of the thermoplastic film.

22. The incrementally-stretched film as recited in claim 21 , further comprising a gauge by weight that is approximately equal to or less than a first gauge by weight of the thermoplastic film.

23. The incrementally-stretched film as recited in claim 22 , wherein the gauge by weight is between approximately 0.97 and 0.50 times the first gauge by weight of the thermoplastic film.

24. The incrementally-stretched film as recited in claim 20 , wherein the thicker ribs and the thinner linear stretched regions comprise a first set of thicker ribs and the thinner linear stretched regions extending across the incrementally-stretched thermoplastic film in a direction transverse to a direction in which the incrementally-stretched thermoplastic film was extruded.

25. The incrementally-stretched film as recited in claim 24 , further comprising a second set of the thicker ribs and thinner linear stretched regions extending across the incrementally-stretched thermoplastic film in the direction in which the incrementally-stretched thermoplastic film was extruded.

26. The incrementally-stretched film as recited in claim 20 , wherein the thermoplastic film comprises a hexene gas phase LLDPE that is devoid of pigments and voiding agents.

Assignees

• Borchardt Michael G
• Glad Products Co

Inventors

• Borchardt Michael G

Classifications

• B32B27/08 Primary

  of synthetic resin · CPC title

• Y10T156/1007

  Running or continuous length work · CPC title

• Y10T428/2457

  Parallel ribs and/or grooves · CPC title

• B32B2439/06

  Bags, sacks, sachets · CPC title

• B32B3/30

  characterised by a layer formed with recesses or projections, e.g. {hollows, grooves, protuberances, ribs (apertured layer B32B3/266; layer with cavities or internal voids B32B3/26)} · CPC title