Polyethylene compositions with improved sealing performance and tear strength

Patent metadata

Field	Value
Publication number	US-11643530-B2
Application number	US-202117227490-A
Country	US
Kind code	B2
Filing date	Apr 12, 2021
Priority date	Apr 16, 2020
Publication date	May 9, 2023
Grant date	May 9, 2023

Abstract

Embodiments relate to polyolefin compositions containing one or more high-density polyethylenes (HDPEs) and linear low-density polyethylenes (LLDPEs) and methods for forming the same. The polyolefin composition contains about 40 wt % to about 60 wt % of HDPE and about 40 wt % to about 60 wt % of LLDPE, by weight of the polyolefin composition. The HDPE has a density of greater than 0.93 g/cm3 and a melt index of about 0.2 dg/min to about 10 dg/min. The LLDPE has a density of less than 0.915 g/cm3 and a melt index of about 0.2 dg/min to about 10 dg/min. The polyolefin composition has a density of about 0.91 g/cm3 or greater, a melt index of about 0.5 dg/min to about 6 dg/min, and a Tw1−Tw2 value of about −25° C. or less.

First claim

The invention claimed is:

1. A polyolefin composition, comprising:
a) about 40 wt % to about 60 wt %, by weight of the polyolefin composition, of a high-density polyethylene (HDPE) having a density of greater than 0.93 g/cm 3 and a melt index of about 0.2 dg/min to about 10 dg/min; and
b) about 40 wt % to about 60 wt %, by weight of the polyolefin composition, of a linear low-density polyethylene (LLDPE) having a density of less than 0.915 g/cm 3 and a melt index of about 0.2 dg/min to about 10 dg/min;

said polyolefin composition having a density of about 0.91 g/cm 3 or greater; a melt index of about 0.5 dg/min to about 6 dg/min; and a T w1 −T w2 value of about −25° C. or less.

2. The polyolefin composition of claim 1 , wherein the polyolefin composition has a T w1 −T w2 value of about −50° C. to about −35° C., and further has either or both of: (i) a M w1 /M w2 value of about 0.88 to about 1.08; and a density of about 0.915 g/cm 3 to about 0.935 g/cm 3 .

3. The polyolefin composition according to claim 1 , wherein the polyolefin composition comprises about 45 wt % to about 55 wt % of the HDPE and about 45 wt % to about 55 wt % of the LLDPE.

4. A film comprising the polyolefin composition according to claim 1 .

5. The film of claim 4 , wherein the film is a blown film, a cast film, a compression-molded film, a machine-direction oriented film, a biaxial oriented film, or any combination thereof.

6. The film of claim 4 , wherein the film comprises an additive at a concentration of about 0.001 wt % to about 2 wt %, based on the weight of the polyolefin composition.

7. The film according to claim 4 , wherein the film has one or more of the following properties:
(a) a 1% Secant average value of about 30,000 psi to about 44,000 psi;
(b) an Elmendorf Tear value in the machine direction of about 320 g/mil to about 500 g/mil;
(c) an Elmendorf Tear value in the transverse direction of about 475 g/mil to about 700 g/mil;
(d) a seal temperature at 5 N of about 80° C. to about 95° C.;
(e) a peel-break transition temperature of about 100° C. to about 120° C.;
(f) a hot tack temperature at 1 N of about 70° C. to about 95° C.;
(g) a hot tack window temperature at 5 N of about 40° C. to about 75° C.; and
(h) a maximum hot tack force of about 5 N to about 20 N.

8. The film according to claim 7 , having all of the properties (a)-(h).

9. The polyolefin composition according to claim 1 , wherein the HDPE has an Mw/Mn of about 1 to about 8.

10. The polyolefin composition according to claim 1 , wherein the LLDPE has an Mw/Mn of about 1 to about 8.

11. A polyolefin film comprising a polyolefin composition comprising:
a) about 40 wt % to about 60 wt %, by weight of the polyolefin composition, of a high-density polyethylene (HDPE) comprising a density of greater than 0.93 g/cm 3 ;
b) about 40 wt % to about 60 wt %, by weight of the polyolefin composition, of a linear low-density polyethylene (LLDPE) comprising a density of less than 0.915 g/cm 3 ;
c) an additive at a concentration of about 0.001 wt % to about 2 wt %;

wherein the polyolefin composition has a density of about 0.915 g/cm 3 to about 0.935 g/cm 3 ;
and a T w1 −T w2 value of about −60° C. to about −25° C.; and
wherein the film has
i) an Elmendorf Tear value in the machine direction of about 320 g/mil to about 500 g/mil;
ii) an Elmendorf Tear value in the transverse direction of about 475 g/mil to about 700 g/mil; and
iii) a seal temperature at 1 N of about 70° C. to about 85° C. or at 5 N of about 80° C. to about 95° C.

12. A method of forming an article comprising the polyolefin composition of claim 1 , comprising:
extruding or rolling the polyolefin composition to produce a film; and
cooling the film;

wherein the polyolefin composition comprises:
a) about 40 wt % to about 60 wt %, by weight of the polyolefin composition, of a high-density polyethylene (HDPE) comprising a density of greater than 0.93 g/cm 3 ;
b) about 40 wt % to about 60 wt %, by weight of the polyolefin composition, of a linear low-density polyethylene (LLDPE) comprising a density of less than 0.915 g/cm 3 ; and
c) an additive at a concentration of about 0.001 wt % to about 2 wt %;

wherein the polyolefin composition has a density of about 0.915 g/cm 3 to about 0.935 g/cm 3 ;
and a T w1 −T w2 value of about −60° C. to about −25° C.; and

wherein the film has
i) an Elmendorf Tear value in the machine direction of about 320 g/mil to about 500 g/mil;
ii) an Elmendorf Tear value in the transverse direction of about 475 g/mil to about 700 g/mil; and
iii) a seal temperature at 1 N of about 70° C. to about 85° C. or at 5 N of about 80° C. to about 95° C.

13. The method of claim 12 , wherein cooling the film comprises blowing air on at least a portion of the film.

Assignees

• Exxonmobil Chemical Patents Inc

Inventors

• Li Dongming
• Lue Ching-Tai
• Qian Qingyun
• Ge Ling
• Huang Gang

Classifications

• C08J2423/06

  Polyethene · CPC title

• C08J5/18 Primary

  Manufacture of films or sheets · CPC title

• C08L2207/062

  HDPE · CPC title

• C08L2207/066

  LDPE (radical process) · CPC title

• C08J2323/08

  Copolymers of ethene (C08J2323/16 takes precedence) · CPC title