POLYETHYLENE FILM COMPOSITIONS, LAMINATES, AND METHODS FOR MAKING THE SAME

Abstract

Disclosed are transparent films having a core comprising at least 50 wt. % high-density polyethylene and, optionally, 50 wt. % or less of linear low-density polyethylene. Further, the transparent films may have a printable skin layer adjacent to a first side of the core, wherein the printable skin layer may comprise, consists essentially of or consists of linear low-density polyethylene or ethylene-propylene copolymer. Further, the transparent films may have a skin layer adjacent to a second side of the core, wherein the skin layer may comprise, consists essentially of or consists of linear low-density polyethylene or ethylene-propylene copolymer. Further still, the transparent films may be oriented in at least one direction and have a directional modulus of at least 1200 MPa. Such transparent films may be laminated to a laminating substrate, such as a biaxially oriented polyethylene single or multilayer film, to produce a laminated film with remarkable sealing and integrity.

Claims

1. A transparent film comprising: a core comprising at least 50 wt. % high-density polyethylene; a printable skin layer adjacent to a first side of the core; a skin layer adjacent to a second side of the core, wherein the transparent film is oriented in at least one direction, a directional modulus of at least 1200 MPa, and has a haze of 10% or less.

2. The transparent film of claim 1, wherein the printable skin layer consists essentially of linear low-density polyethylene or ethylene-propylene copolymer.

3. The transparent film of claim 1, wherein the skin layer consists essentially of linear low-density polyethylene or ethylene-propylene copolymer.

4. The transparent film of claim 1, further comprising 50 wt. % or less of linear low-density polyethylene.

5. The transparent film of claim 1, further comprising one or more additives.

6. The transparent film of claim 1, further comprising one or more tie layers.

7. The transparent film of claim 1, wherein the transparent film has a thickness of 20 m or less.

8. The transparent film of claim 1, wherein the transparent film has a dimensional stability of less than 10% after 7 minutes in an oven at 100 C.

9. The transparent film of claim 1, wherein the transparent film withstands directional stress of at least 70 MPa.

10. The transparent film of claim 1, wherein the transparent film withstands directional strain of at least 60 MPa.

11. The transparent film of claim 1, wherein the transparent film is coextruded.

12. The transparent film of claim 1, further comprising a laminating substrate, wherein the transparent film is laminated to the laminating substrate to produce a laminated film.

13. The transparent film of claim 12, wherein the laminating substrate is transparent.

14. The transparent film of claim 12, wherein the laminating substrate is a non-oriented film.

15. The transparent film of claim 12, wherein the laminating substrate is metallized.

16. The transparent film of claim 12, wherein the laminating substrate is coated.

17. The transparent film of claim 12, further comprising an adhesive between the transparent film and the laminating substrate.

18. The transparent film of claim 12, wherein the laminated film has a seal strength of at least 2000 g/inch at 130 C.

19. The transparent film of claim 12, wherein a 450-gram bag of the laminated film dropped from two meters remains intact.

20. The transparent film of claim 1, wherein the core layer comprises at least 75 wt. % high-density polyethylene.

Description

EXAMPLE EMBODIMENTS

[0053] The following are example, produced films in line with the foregoing disclosure:

Example 1

[0054]

TABLE-US-00001 skin LLDPE (e.g., Prime Polymer SP3022) + antiblock (e.g., silica) and slip (e.g., Erucamide) core HDPE (e.g., NOAV 19A or Exxon HTA108) printable LLDPE (e.g., Prime Polymer SP3022) + antiblock (e.g., layer silica)

Example 2

[0055]

TABLE-US-00002 skin EP copolymer (e.g., KS407) + antiblock (e.g., silica) and slip (e.g., Erucamide) core HDPE (e.g., NOAV 19A or Exxon HTA108) + 20% LLDPE (e.g., Prime Polymer SP3022) printable EP copolymer (e.g., KS407) + antiblock (e.g., silica) layer

[0056] In example 1, metallocene LLDPE was used, but other type(s) of LLDPE(s) may be used, whether formed under non-metallocene chemistry, e.g., employing lanthanides or actinides, or metallocene catalysis. Here, the Prime Polymer SP3022 had a density and melt index of 0.927 g/cm.sup.3 and 1.9, respectively. The core of example 1 comprises, consists essentially of, or consists of HDPE(s), wherein NOAV 19A and Exxon HTA108 have densities and melt indices of 0.962 g/cm.sup.3 and 0.72 and 0.961 g/cm.sup.3 and 0.70, respectively. In other example embodiments, the core may comprise, consist essentially of, or consist of PE(s) having a density 0.94 g/cm.sup.3.

[0057] Turning to example 2, an EP copolymer was used in the film's skin and printable layers. The core comprises, consists essentially of, or consists of HDPE(s) in combination with 20% by weight of LLDPE(s). In other example embodiments, the HDPE(s) may constitute 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 98 percent by weight in combination with 50, 45, 40, 35, 30, 25, 20, 15, 10, 5, or 2 percent by weight of LLDPE(s). In such mixtures, the combinations of percent weights or HDPE(s) and LLDPE(s) may or may not add up to 100 as the core may or may not include other substances.

[0058] Examples 1 and 2 were oriented 4.5 times in the machine direction at 100 C. and 8-10 times in the transverse direction at 115 C. After stretching, both of these films were 20 m in thickness. In other embodiments, the films may be thinner or thicker.

[0059] Subsequent to biaxial orientation, mechanical properties of examples 1 and 2 were measured, wherein the results are stated in the following table:

TABLE-US-00003 TABLE 1 Modulus Stress at Break Strain at Break (MPa) (MPa) (%) Example 1 - MD 1427 106 263 Example 1 - TD 1571 117 60 Example 2 - MD 1245 74 196 Example 2 - TD 1436 97 83
Comparatively, if the foregoing biaxially oriented examples 1 and 2 contained LLDPE in the skin, core and printable layers instead of the LLDPE/HDPE/LLDPE composition of example 1 and the EP copolymer/(HDPE+20% LLDPE)/EP copolymer of example 2 (i.e., LLDPE reference), then the results would be:

TABLE-US-00004 TABLE 2 Modulus Stress at Break Strain at Break (MPa) (MPa) (%) LLDPE reference - MD 299 57 380 LLDPE reference - TD 500 74 186

[0060] Subsequent to biaxial orientation of examples 1 and 2 and placing in an over for 7 minutes, dimensional stabilities at the stated temperatures were measured, wherein the results are stated in the following table:

TABLE-US-00005 TABLE 3 100 C. 110 C. 120 C. LLDPE reference - MD 5.1 9.0 19.2 LLDPE reference - TD 6.5 13.3 34.5 Example 1 - MD .05 0.7 1.7 Example 1 - TD 0.0 0.0 0.4 Example 2 - MD 0.1 0.6 0.6 Example 2 - TD 0.1 0.3 0.5

[0061] Dimensional stability tests involve placing a film sample of known original dimensions into a temperature-controlled convection oven for a certain period of time and measuring the length of the sample after such conditioning. Results are reported as % change. Negative numbers indicate shrinkage, while positive numbers indicate expansion.

[0062] Haze (i.e., using ASTM D1003) of the LLDPE reference and examples 1 and 2 were measured to be 6%, 25%, and 7%, respectively.

[0063] The modulus data (i.e., using ASTM D790) shows that films having an HDPE core have mechanical properties that are stiffer and/or more conducive to printing than those with lower moduli. Furthermore, the HDPE film has good dimensional stability, which means that a laminate may seal at a broader temperature range before distorting the seal.

[0064] The LLDPE reference and the example 1 were laminated to a transparent substrate, a sealant BOPE film, and a metallized sealant BOPE film through adhesive lamination. Sealing strengths (i.e., using ASTM F2029 and F88) were measured on the laminated compositions/structures after using an Otto Brugger sealant equipment with a dwell time of 0.75 s and a jaw pressure of 41 N/cm.sup.2. These sealing strengths are reported in g/inch in the following table:

TABLE-US-00006 TABLE 4 80 C. 90 C. 100 C. 110 C. 120 C. 130 C. LLDPE 140 1560 1660 1040 2070 reference/ metallized BOPE film Example 190 1590 1460 1160 1320 2020 1/metallized BOPE film LLDPE 0 150 2120 2900 3020 reference/ transparent BOPE film Example 0 270 2540 3260 3730 2670 1/transparent BOPE film
The LLDPE reference/metallized BOPE and LLDPE reference/transparent BOPE film exhibited shrinking at 120 C. and melting at 130 C. Example 1/metallized BOPE film and example 1/transparent BOPE film exhibited melting at 140 C.

[0065] Bags were produced. Specifically, bags were produced on a vertical-form-fill-seal (VFFS) machine having transversal and longitudinal jaws at 130 C. All PE laminates used a lap seal, i.e., the outside web is sealed against the inside web to form the longitudinal seal. Hermeticity was excellent, i.e., there were no leaks when the bags were pushed by hand under water.

[0066] The bags were tested for drop resistance. Specifically, ten 450 g bags were dropped from a height of two meters. None of the bags in Table 4 opened, whereas had the bags would have opened if the outside web had been PET or BOPP instead of the LLDPE reference or examples 1 or 2.

[0067] In closing, it is noted that examples 1 or 2 in the laminate are stiffer than bags made with the LLDPE reference as the outside web. And as previously suggested, all-PE laminated bags can be recycled, whereas bags made with BOPP or PET as outside web and PE as sealant web would not be recyclable.

[0068] Although written in claim form, below are additional example embodiments in accordance with this disclosure: [0069] 1. A transparent film comprising:

[0070] a core comprising at least 50 wt. % high-density polyethylene;

[0071] a printable skin layer adjacent to a first side of the core;

[0072] a skin layer adjacent to a second side of the core,

[0073] wherein the transparent film is oriented in at least one direction, a directional modulus of at least 1200 MPa, and has a haze of 10% or less. [0074] 2. The transparent film of claim 1, wherein the printable skin layer consists essentially of linear low-density polyethylene or ethylene-propylene copolymer. [0075] 3. The transparent film of claim 1, wherein the skin layer consists essentially of linear low-density polyethylene or ethylene-propylene copolymer. [0076] 4. The transparent film of claim 1, further comprising 50 wt. % or less of linear low-density polyethylene. [0077] 5. The transparent film of claim 1, further comprising one or more additives. [0078] 6. The transparent film of claim 1, further comprising one or more tie layers. [0079] 7. The transparent film of claim 1, wherein the transparent film has a thickness of 20 m or less. [0080] 8. The transparent film of claim 1, wherein the transparent film has a dimensional stability of less than 10% after 7 minutes in an oven at 100 C. [0081] 9. The transparent film of claim 1, wherein the transparent film withstands directional stress of at least 70 MPa. [0082] 10. The transparent film of claim 1, wherein the transparent film withstands directional strain of at least 60 MPa. [0083] 11. The transparent film of claim 1, wherein the transparent film is coextruded. [0084] 12. The transparent film of claim 1, further comprising a laminating substrate, wherein the transparent film is laminated to the laminating substrate to produce a laminated film. [0085] 13. The transparent film of claim 12, wherein the laminating substrate is transparent. [0086] 14. The transparent film of claim 12, wherein the laminating substrate is a non-oriented film. [0087] 15. The transparent film of claim 12, wherein the laminating substrate is metallized. [0088] 16. The transparent film of claim 12, wherein the laminating substrate is coated. [0089] 17. The transparent film of claim 12, further comprising an adhesive between the transparent film and the laminating substrate. [0090] 18. The transparent film of claim 12, wherein the laminated film has a seal strength of at least 2000 g/inch at 130 C. [0091] 19. The transparent film of claim 12, wherein a 450-gram bag of the laminated film dropped from two meters remains intact. [0092] 20. The transparent film of claim 1, wherein the core layer comprises at least 75 wt. % high-density polyethylene.

[0093] While the foregoing is directed to example embodiments of the disclosed invention, other and further embodiments may be devised without departing from the basic scope thereof, wherein the scope of the disclosed compositions, systems and methods are determined by one or more claims.