Multilayer thermoplastic film with improved puncture resistance performance

A method of forming a heat-shrinkable, biaxially stretched, multilayer thermoplastic film suitable for use in fabricating bags for packaging food articles, the method comprising:

• forming a first extruded bubble with a polyethylene based plastomer having a density of 0.890 g/cm3 to 0.910 g/cm3 as determined in accordance with ASTM D-792 and a melt index (MI) as measured by ASTM D-1238, Condition 190° C./2.16 kg, from 0.20 g/10 minutes to 1.5 g/10 minutes, wherein the polyethylene based plastomer has:
• a logM25% of an upper 25% of a GPC quadrant having a value of 5.1 to 5.7;
• an intermediate molecular weight distribution (Mw/Mn) of 2.5 to 3 and a Mz/Mw value of 2 to 2.5;
• a Comonomer Distribution Constant value from 60 to 400 and a single SCBD peak between 40-85° C. with a mass fraction of less than 3% above 85° C. as determined by CEF;
• and
• a ZSVR value from 1.0 to 5.5;
• collapsing the first extruded bubble to form a first multilayer structure;
• passing the first multilayer structure through a first water bath having a temperature of 5° C. to 50° C. to cool the first multilayer structure, wherein the first multilayer structure has a residence time of 0.5 to 50 seconds in the water of the first water bath;
• passing the first multilayer structure through a second water bath having a temperature of 80° C. to 100° C. to warm the first multilayer structure coming from the first water bath, wherein the first multilayer structure has a residence time of 5 to 50 seconds in the water of the second water bath;
• heating the first multilayer structure to a temperature of 60° C. to 120° C.;
• forming a second extruded bubble with the first multilayer structure heated to the temperature of 60° C. to 120° C., wherein the first multilayer structure has a blow-up ratio from 2:1 to 10:1 in forming the second extruded bubble;
• and
• collapsing the second extruded bubble to form the heat-shrinkable, biaxially stretched, multilayer thermoplastic film.