Multilayer Films And Methods Of Making The Same

A multilayer film, comprising an MDO substrate and a sealant, wherein the MDO substrate comprises a substrate outer layer, a substrate inner layer, and a substrate core layer between the substrate outer layer and the substrate inner layer, wherein:

• (a) the substrate core layer comprises a first polyethylene, a second polyethylene, and a fourth polyethylene, wherein the first polyethylene has (i) a density of about 0.900 to about 0.925 g/cm3, (ii) a melt index (MI), I2.16, of from about 0.1 to about 10.0 g/10 min, (iii) a melt index ratio (MIR), I21.6/I2.16, of from about 15 to about 45, (iv) a weight average molecular weight (Mw) of from about 20,000 to about 200,000;
• (v) a molecular weight distribution (MWD) of from about 2.0 to about 5.0;
• and (vi) a z-average molecular weight (Mz) to weight average molecular weight (Mw) (Mz/Mw) ratio of from about 1.7 to about 3.5;
• wherein the second polyethylene has a higher density than the first polyethylene;
• the second polyethylene having a density of about 0.940 to about 0.945 g/cm3, an MI, I2.16, of about 0.1 to about 15 g/10 min, an MWD of about 2.5 to about 5.5, and an MIR, I21.6/I2.16, of about 25 to about 100;
• wherein the fourth polyethylene has a density of at least about 0.940 g/cm3, the fourth polyethylene different from the second polyethylene;
• wherein the weight amount ratio between the first polyethylene and the second polyethylene in the substrate core layer is about 2:3 to about 4:5;
• and
• (b) each of the substrate outer layer and the substrate inner layer comprises about 100 wt % of the second polyethylene, based on total weight of polymer in the layer;
• wherein the thickness ratio between the substrate outer layer, the substrate core layer, and the substrate inner layer is about 1:4:1;
• wherein the sealant comprises a sealant outer layer, a sealant inner layer, and a sealant core layer between the sealant outer layer and the sealant inner layer, each comprising polyethylene, wherein the sealant inner layer has a density lower than that of the sealant outer layer;
• wherein the thickness ratio between the sealant outer layer, the sealant core layer, and the sealant inner layer is 1:2:1;
• wherein the substrate inner layer is attached to the sealant outer layer and the thickness ratio between the substrate and the sealant is about 1:5 to about 1:6;
• wherein the multilayer film has at least one of the following properties:
• (i) an average tensile at break of at least about 36 MPa;
• (ii) an average 1% Secant Modulus of at least about 620 MPa;
• and (iii) a non-breakage rate of about 100%.

A method for making a multilayer film comprising an MDO substrate and a sealant, comprising the steps of:

• (a) preparing a substrate outer layer, a substrate inner layer, and a substrate core layer between the substrate outer layer and the substrate inner layer, wherein the substrate core layer comprises a first polyethylene and a second polyethylene, and at least one of the substrate outer layer and the substrate inner layer comprises a third polyethylene;
• (b) preparing an MDO substrate comprising the layers in step (a);
• and
• (c) forming a film comprising the substrate in step (b);
• wherein the first polyethylene has (i) a density of about 0.900 to about 0.925 g/cm3, (ii) a melt index (MI), I2.16, of from about 0.1 to about 10.0 g/10 min, (iii) a melt index ratio (MIR), I21.6/I2.16, of from about 15 to about 45, (iv) a weight average molecular weight (Mw) of from about 20,000 to about 200,000;
• (v) a molecular weight distribution (MWD) of from about 2.0 to about 5.0;
• and (vi) a z-average molecular weight (Mz) to weight average molecular weight (Mw) (Mz/Mw) ratio of from about 1.7 to about 3.5;
• the second polyethylene has a higher density than the first polyethylene;
• and the third polyethylene has a density of about 0.910 to about 0.945 g/cm3, an MI, I2.16, of about 0.1 to about 15 g/10 min, an MWD of about 2.5 to about 5.5, and an MIR, I21.6/I2.16, of about 25 to about 100;
• wherein the multilayer film has at least one of the following properties:
• (i) an average tensile at break of at least about 36 MPa;
• (ii) an average 1% Secant Modulus of at least about 620 MPa;
• and (iii) a non-breakage rate of about 100%.