Granted Patent B2

US 12,491,678 · App. 17/770,822 · Granted Dec 9, 2025

Inventors: Norman Aubee (Okotoks, CA); Owen Lightbody (Calgary, CA); Maryam Fereydoon (Calgary, CA); Bronwyn Gillon (Calgary, CA); Patrick Lam (Calgary, CA); Shivendra Goyal (Calgary, CA)

Assignee: NOVA Chemicals (International) S.A.

B29C55/005B29C48/0018B29C55/143B29K2023/0641B29K2995/0053B29K2995/0063

Abstract

Claims (25)

1 . A biaxially oriented polyethylene film comprising at least 60 weight percent of a medium density polyethylene having:

1) A density of 0.94 to 0.95 grams per cubic centimeter;

2) a melt index, I 2 , as measured by ASTM D1238 at 190° C. using a 2.16 kg load of 0.2 to 5 grams/10 minutes; and

3) a molecular weight distribution, Mw/Mn, of 10 to 50;

wherein said biaxially oriented polyethylene film has at least three layers, and wherein at least one core layer of said biaxially oriented polyethylene film comprises said medium density polyethylene;

wherein said medium density polyethylene has an M z of 550,000 to 1,500,000; and

wherein said medium density polyethylene is made by the copolymerization of ethylene with butene in a solution polymerization process using a Zeigler Natta catalyst or is made by the copolymerization of ethylene with hexene in a gas phase process using a chromium catalyst.

2 . The film of claim 1 , characterized in that it is stretched in the machine direction to a degree of from about 3:1 to about 10:1.

3 . The film of claim 1 characterized in that it is stretched in the transverse direction to a degree of from about 3:1 to about 10:1.

4 . The film of claim 2 characterized in that it is stretched in the transverse direction to a degree of from about 3:1 to about 10:1.

5 . The film of claim 1 , characterized in that it is stretched in the machine direction to a degree of from about 3:1 to about 10:1.

6 . A process to prepare a biaxially oriented polyethylene film, the process comprising:

A) providing a base structure comprising at least 60 weight % of a medium density polyethylene having:

1) a density of 0.94 to 0.95 grams per cubic centimeter;

2) a melt index, I 2 , as measured by ASTM D1238 at 190° C. using a 2.16 kg load of 0.2 to 5 grams/10 minutes; and

3) a molecular weight distribution, Mw/Mn, of 10 to 50;

B) stretching said base structure to a degree of about 3:1 to about 10:1 in the machine direction; and

C stretching said base structure to a degree of about 3:1 to about 10:1 in the transverse direction,

wherein said base structure comprises at least three layers, and wherein at least one core layer of said base structure comprises said medium density polyethylene;

wherein said medium density polyethylene has an M z of 550,000 to 1,500,000; and

wherein said medium density polyethylene is made by the copolymerization of ethylene with butene in a solution polymerization process using a Zeigler Natta catalyst or is made by the copolymerization of ethylene with hexene in a gas phase process using a chromium catalyst.

7 . The process of claim 6 , wherein said MDPE has an Mn of from 11,000 to 15,000; an Mz of from 600,000 to 800,000 and an Mw/Mn of from 10 to 12.

8 . The process of claim 6 , wherein said MDPE is made in a solution polymerization process in the presence of a Ziegler Natta catalyst.

9 . The process of claim 6 , wherein at least one skin layer of said base structure comprises an ethylene-octene plastomer.

10 . The process of claim 9 , wherein both skin layers of said base structure comprise an ethylene-octene plastomer.

Assignments (1)

Continuity (3)

References Cited (119)