Patent Application
20090285511
[Not Applicable]
[Not Applicable]
The invention relates to films, and in particular to films having easy cross-directional tear properties, as well as packages made from such films.
Certain techniques have been proposed to control the tear properties of films, such as those described in US Patent Application 20020068668, and U.S. Pat. Nos. 7,052,750, and 5,786,050.
An aspect of the present invention is a film having a sealant layer having a cyclic olefin copolymer. The film has a cross directional tear/machine directional tear ratio below 1.
Another aspect of the invention is a package made from a film as described in the preceding paragraph.
A still further aspect of the present invention is a method for producing a film as described in the second preceding paragraph.
The package 10 can also have one or more tear notches 16. For example the package can have a modified top-seal 12 having a notch 16 at one or both sides. The notch 16 can be in any one or more positions on the package, including any one or more seal areas. The notch 16 does not affect the seal integrity of the package, and is used as a starting point to tear open the package. In an embodiment, tear notches are located on one or both side seals.
Packages according to the present invention have a machine-direction and a cross-direction. As used herein the phrase “machine direction”, herein abbreviated “MD”, refers to a direction along the length of the film, or in the direction the film is formed or fabricated into packages. As used herein the phrase “cross-direction”, herein abbreviated “CD”, refers to a direction across the film, or perpendicular to the MD. In the embodiment according to
The package of
The packages according to the present invention can take any shape or design, including for example three-sided or four-sided side-seal pouches, pillow pouches, or stand-up pouches. The package can also be made resealable or reclosable, for example by the use of a ziplock closure or an adhesive coating.
The sealant layer A contains a cyclic olefin copolymer (COC). The phrase cyclic olefin copolymer or “COC” generally refers to a copolymer of norbornene and ethylene. Cyclic olefin copolymers are a class of polymers generally based on cyclic olefin monomers and ethene. There are several types of cyclic olefin copolymers based on different types of cyclic monomers and polymerization methods. Pure Appl. Cem. Vol. 77, No. 5, pp. 801-914, 2005 is incorporated herein by reference to provide a general description of cyclic olefin copolymers. A cyclic olefin copolymer also can be, for example, any of those described in U.S. Pat. No. 7,052,750, col. 1, lines 25-40; U.S. Pat. No. 6,921,563; U.S. Pat. No. 6,068,936; U.S. Pat. No. 5,912,070; U.S. Pat. No. 5,494,969; or U.S. Pat. No. 5,786,050.
The amount of the cyclic olefin copolymer contained within the sealant layer can vary according to the properties desired in the film, including for example the tear properties of the film. For example, the sealant layer according to the present invention can have from 5 to 95 weight percent of a cyclic olefin copolymer, optionally from 5 to 80 weight % of a cyclic olefin copolymer, optionally from 15 to 40 weight % of a cyclic olefin copolymer, optionally at least 10 weight % of a cyclic olefin copolymer, optionally at least 20 weight % of a cyclic olefin copolymer, optionally at least 30 weight % of a cyclic olefin copolymer, and optionally at least 40 weight % of a cyclic olefin copolymer.
The sealant layer according to the present invention can also include one or more additional polymers, such as for example an ethylene polymer or a propylene polymer. In addition to a cyclic olefin copolymer, the sealant layer can also have, for example, a plastomer or ionomer. Suitable polymers added to the sealant layer in addition to the cyclic olefin copolymer include but are not limited to linear low-density polyethylene, linear medium density polyethylene, low-density polyethylene, medium density polyethylene, ethylene vinyl acetate copolymer, ethylene methyl acrylate copolymer, ethylene methyl acrylic acid copolymer, or high density polyethylene.
As used herein, the term “polymer” refers to the product of a polymerization reaction, and is inclusive of homopolymers and copolymers. In general, the layers of a film can have a single polymer, or can have additional polymers together therewith, for example blended therewith.
As used herein, the phrase low density polyethylene (“LDPE”) refers to ethylene homopolymer having a density ranging from about 0.91 g/cm3 to about 0.925 g/cm3. LDPE is typically produced using conventional high pressure process.
As used herein, the phrase linear low density polyethylene (“LLDPE”) refers to ethylene alpha-olefin copolymers having a density ranging from about 0.915 g/cm3 to about 0.94 g/cm3. LLDPE can be manufactured using a conventional Ziegler Natta catalyst or a single site catalyst, such as metallocene.
As used herein, the phrase linear medium density polyethylene (“LMDPE”) refers to ethylene alpha-olefin copolymers having a density ranging from about 0.925 g/cm3 to about 0.94 g/cm3. LMDPE can be manufactured using conventional Ziegler Natta catalysts or single site catalysts, such as metallocene.
As used herein, the phrase high density polyethylene (“HDPE”) refers to ethylene alpha-olefin copolymers or ethylene homopolymer having a density of about 0.94 g/cm3 or greater. HDPE can be produced with several classes of catalysts, such as Ziegler-Natta catalysts and metallocene catalysts.
The amount of the sealant layer contained within the film may also vary according to the properties desired in the film. For example, the film according to the present invention can be a monolayer having 100 weight % of the sealant layer. Alternatively the film can be a multilayer film having the sealant layer and one or more additional layers in any arrangement and combination of weight percentages. For example, the film can have from 5 to 95 weight % of the sealant layer, optionally from 10 to 90 weight % of the sealant layer, optionally from 10 to 70 weight % of the sealant layer, or optionally from 15 to 40 weight % of the sealant layer in combination with one or more additional layers.
The film can be a multilayer film having one or more additional layers. The additional layers can have one or more polymers, including for example an ethylene or a propylene polymer. Examples of suitable polymers include but are not limited to linear low-density polyethylene, linear medium density polyethylene, low-density polyethylene, medium density polyethylene, ethylene vinyl acetate copolymer, ethylene methyl acrylate copolymer, ethylene methyl acrylic acid copolymer, or high density polyethylene.
The film can have a sealant layer having a cyclic olefin copolymer and from 10-20 weight percent of an additional layer having a linear medium density polyethylene, high density polyethylene, or a polyolefin plastomer.
The film can have a sealant layer having a cyclic olefin copolymer and from 12-75 weight percent of an additional print receivable layer, having for example a linear medium density polyethylene or a high density polyethylene polymer.
The film can have a sealant layer having a cyclic olefin copolymer and from 10-15 weight percent of an additional layer having an ethylene vinyl alcohol copolymer or nylon.
The film can have a sealant layer having a cyclic olefin copolymer and from 4 to 12 weight percent of an additional tie layer having adhesive properties. In certain films, the tie layer can be for example a Bynel tie layer. Bynel is a trademark of E. I. du Pont de Nemours and Company for adhesive resins.
The present film can be laminated to other films or substrates, for example on the non-sealant side. For example, the film can be laminated to polyester, polypropylene, bi-axially oriented nylon, bi-axially oriented polypropylene, or polyethylene films. The present film can be laminated to a substrate with or without surface or reverse printing.
The film can be laminated to other films or substrates using adhesive lamination, extrusion lamination, thermal lamination, or other methods.
The present film can be an easy CD tear film having a CD Elmendorf tear below 90 (gf), optionally below 80 (go, optionally below 60 (go, optionally below 40, or optionally below 20. The film can have a CD Elmendorf tear/MD Elmendorf tear ratio below 1, optionally below 0.8, optionally below 0.6, optionally below 0.4, optionally below 0.2, or optionally below 0.1. The film can have a CD Elmendorf tear/MD Elmendorf tear ratio of from between 0.05 and 0.9, optionally from between 0.05 and 0.7, optionally from between 0.05 and 0.5, optionally from between 0.05 and 0.3, optionally from between 0.05 and 0.3, or optionally from between 0.05 and 0.1.
The film can have an MD ultimate tensile strength of from 3500 N/cm2 to 2000 N/cm2, and a CD ultimate tensile strength of from 3000 N/cm2 to 2000 N/cm2. The film can also have a CD ultimate tensile strength 1 MD ultimate tensile strength ratio of from 0.75 and 1.10.
The film can have an MD ultimate elongation of from 90% to 319%, and a CD ultimate elongation of from 5% to 410%. The film can also have a CD ultimate elongation %/MD ultimate elongation % ratio of from 0.05 to 3.5.
The film can have an MD secant modulus of from 100,000 N/cm2 to 60,000 N/cm2, and a CD secant modulus of from 105,000 N/cm2 to 60,000 N/cm2. The film can also have a CD secant modulus/MD secant modulus ratio of from 0.70 to 1.2.
Examples 1-6 are multilayer films having the 6 layer construction A/B/C/D/E/F illustrated in
Example 7 is a film containing 3 layers, represented by the construction A/B/C illustrated in
Each of the example films were tested for the following properties: MD and CD Elmendorf tear (gf); MD and CD ultimate tensile (PSI or N/cm2); MD and CD ultimate elongation (%); and MD and CD secant elongation (PSI or N/cm2). The test results for each film, examples 1-7, are shown in Table 8.
As is understood in the art, the Elmendorf tear (gf) of a film can be measured by ASTM D-1922. This test method determines the average force to propagate tearing through a specified length of film after the tear has been started, using an Elmendorf-type tearing tester. As is also understood in the art, the MD and CD ultimate tensile strength, ultimate elongation, or secant modulus of a film can be measured by ASTM D-882. This test method employs a constant rate of separation of the grips holding the ends of the test film. Extension may be measured in these test methods by grip separation, extension indicators, or displacement of gage marks.
The present invention is not limited to a MD/CD tear ratio as determined from Elmendorf tear testing. Any tear strength test method now or later developed can be used.
A sample film was prepared having the six layer construction shown in
Another sample film was prepared having the six layer construction shown in
Another sample film was prepared having the six layer construction shown in
Another sample film was prepared having the six layer construction shown in
Another sample film was prepared having the six layer construction shown in
Another sample film was prepared having the six layer construction shown in
Another sample film was prepared having the three layer construction shown in
Any of the films according to the present invention can be manufactured using any of those methods known in the art, including but not limited to those methods in which the film is blown or cast.
This patent application is a continuation of U.S. application Ser. No. 12/400,432, filed on Mar. 9, 2009, which patent application makes reference to, claims priority to and claims benefit from U.S. Provisional Patent Application Ser. No. 61/034,824, filed on Mar. 7, 2008 and which are incorporated hereby in their entireties.
| Number | Date | Country | |
|---|---|---|---|
| 61034824 | Mar 2008 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12400432 | Mar 2009 | US |
| Child | 12510406 | US |
