Bi-directionally oriented multilayer film

Patent metadata

Field	Value
Publication number	US-2024239087-A1
Application number	US-202118014792-A
Country	US
Kind code	A1
Filing date	Jun 23, 2021
Priority date	Jul 8, 2020
Publication date	Jul 18, 2024
Grant date	—

Abstract

A multilayer film includes: an inner layer system having a first surface and a second surface; and a first skin layer and a second skin layer bound to the inner layer system at the first and second surfaces respectively. The inner layer system consists of a polymer formulation (A) containing: ≥60.0 and ≤90.0 wt % of a linear low-density polyethylene A; and ≥10.0 and ≤40.0 wt % of a high-density polyethylene having a density of ≥940 and ≤970 kg/m3; and at least one of the first or the second skin layer(s) is a sealing layer comprising a linear low-density polyethylene B comprising polymeric moieties derived from ethylene and 1-octene/1-hexene, having a density of ≥890 and ≤915 kg/m3.

First claim

1 . A multilayer film comprising:
an inner layer system comprising a first surface and a second surface; a first skin layer bound to the inner layer system at the first surface of the inner layer system; and a second skin layer bound to the inner layer system at the second surface of the inner layer system;
wherein
the inner layer system consists of a polymer formulation (A) comprising: ≥60.0 and ≤90.0 wt % of a first ethylene-based polymer being a linear low-density polyethylene A (LLDPE A); and ≥10.0 and ≤40.0 wt %, of a high-density polyethylene (HDPE) having a density of ≥940 and ≤970 kg/m 3 , as determined in accordance with ASTM D792 (2008); and
at least one or both of the first or the second skin layer(s) is a sealing layer comprising a second ethylene-based polymer being a linear low-density polyethylene B (LLDPE B) comprising polymeric moieties derived from ethylene and from 1-hexene or 1-octene, having a density of ≥890 and ≤915 kg/m 3 , as determined in accordance with ASTM D792 (2008);

wherein the multilayer film is a bi-directionally oriented film wherein the orientation in both directions is introduced in the solid state.

2 . The multilayer film according to claim 1 , wherein the linear low-density polyethylene A has:
a density of ≥918 and <940 kg/m 3 as determined in accordance with ASTM D792 (2008); a melt mass-flow rate of ≥0.5 and ≤5.0 g/10 min, as determined in accordance with ASTM D1238 (2013) at a temperature of 190° C. under a load of 2.16 kg; a fraction that is eluted in analytical temperature rising elution fractionation (a-TREF) at a temperature ≤30.0° C. of ≥3.0 wt %, with regard to the total weight of the LLDPE; and/or a fraction eluted in a-TREF at a temperature >94.0° C. of ≥20.0 wt %, with regard to the total weight of the LLDPE.

3 . The multilayer film according to claim 1 , wherein both the first and the second skin layers are sealing layers comprising the second ethylene-based polymer, or wherein the sealing layers consist of the second ethylene-based polymer.

4 . The multilayer film according to claim 1 , wherein, in the case that one of the first or the second skin layer is not a sealing layer, said skin layer comprises an LLDPE comprising polymeric moieties derived from ethylene and from 1-hexene or 1-octene, having a density of ≥918 and ≤940 kg/m 3 as determined in accordance with ASTM D792 (2008).

5 . The multilayer film according to claim 1 , wherein the second ethylene-based polymer has:
a melt mass-flow rate of ≥0.5 and ≤5.0 g/10 min, as determined in accordance with ASTM D1238 (2013) at a temperature of 190° C. under a load of 2.16 kg; a fraction that is eluted in analytical temperature rising elution fractionation (a-TREF) at a temperature ≤30.0° C. of ≤8.0 wt %, with regard to the total weight of the second ethylene-based polymer; a fraction eluted in a-TREF at a temperature of >30° C. and <94.0° C. of ≥90.0 wt %, with regard to the total weight of the second ethylene-based polymer; and/or a chemical composition distribution broadness (CCDB) of ≥5.0 and ≤25.0.

6 . The multilayer film according to claim 1 , wherein the high-density polyethylene has a melt mass-flow rate of ≥0.5 and ≤10.0 g/10 min, as determined in accordance with ASTM D1238 (2013) at a temperature of 190° C. under a load of 2.16 kg.

7 . The multilayer film according to claim 1 , wherein the second ethylene-based polymer comprises ≥5.0 and ≤20.0 wt % of moieties derived from 1-hexene or 1-octene, with regard to the total weight of the second ethylene-based polymer.

8 . The multilayer film according to claim 1 , wherein the second ethylene-based polymer comprises ≥80.0 and ≤95.0 wt % of moieties derived from ethylene, with regard to the total weight of the second ethylene-based polymer.

9 . The multilayer film according to claim 1 , wherein the high-density polyethylene is a homopolymer of ethylene.

10 . The multilayer film according to claim 1 , wherein the inner layer system consists of a single layer, or wherein the inner layer system consists of 3, 5 or 7 layers.

11 . The multilayer film according to claim 1 , wherein the inner layer system comprises ≤20.0 wt % of a cavitating agent.

12 . The multilayer film according to claim 1 , wherein the film has a thickness of ≥5 μm and ≤200 μm.

13 . A process for production of the multilayer film according to claim 1 , wherein the process involves the steps in this order of:
(a) manufacturing an unoriented multilayer film via cast extrusion, the unoriented film comprising
an inner layer system comprising a first surface and a second surface;
a first skin layer bound to the inner layer system at the first surface of the inner layer system; and a second skin layer bound to the inner layer system at the second surface of the inner layer system;
wherein
the inner layer system consists of a polymer formulation (A) comprising: ≥60.0 and ≤90.0 wt % of a first ethylene-based polymer being a linear low-density polyethylene A (LLDPE A); and ≥10.0 and ≤40.0 wt % of a high-density polyethylene (HDPE) having a density of ≥940 and ≤970 kg/m 3 , as determined in accordance with ASTM D792 (2008); and at least one or both of the first or the second skin layer(s) is a sealing layer comprising a second ethylene-based polymer being a linear low-density polyethylene B (LLDPE B) comprising polymeric moieties derived from ethylene and from 1-octene, having a density of ≥890 and ≤915 kg/m 3 , as determined in accordance with ASTM D792 (2008);
(b) subjecting the unoriented film to heat to bring the film to a temperature of >70° C. and <T pm of the first ethylene-based polymer, T pm being determined as peak melting temperature in accordance with ASTM D3418 (2008);
(c) stretching the heated cast film by:
 applying a stretching force in the machine direction (MD) to induce a drawing in the machine direction, and subsequently subjecting the obtained film to heat to bring the film to a temperature of between T pm −25° C. and T pm of the first ethylene-based polymer, under application of a stretching force in the transverse direction (TD) to induce a drawing in the transverse direction;
or
 simultaneously applying a stretching force in the MD and the TD to induce a drawing in the MD and the TD;

(d) maintaining the stretching forces and temperature to ensure drawing in TD is maintained to a level of >85% of the drawing in TD as applied; and
(e) cooling the stretched film to obtain a bi-directionally oriented film.

14 . The process according to claim 13 , wherein the degree of drawing in each of the MD and TD direction is at least 4.5, wherein the degree of drawing is the ratio between the dimension in the corresponding direction before and after the film is subjected to the orientation step in that particular direction.

15 . A package comprising the multilayer film according to claim 1 .

16 . The multilayer film according to claim 1 , wherein the sealing layer comprises ≥70.0 wt % of the second ethylene-based polymer.

17 . The multilayer film according to claim 1 , wherein the sealing layer consists of the second ethylene-based polymer.

Assignees

• Sabic Global Technologies Bv

Inventors

• Gerrits Niclasina Siberta Johanna Alberdina
• Scala Attilio

Classifications

• B32B2439/70

  Food packaging · CPC title

• B32B2323/046

  LDPE, i.e. low density polyethylene · CPC title

• B32B2323/043

  HDPE, i.e. high density polyethylene · CPC title

• B32B2307/518

  bi-axially · CPC title

• B32B2250/242

  All polymers belonging to those covered by group B32B27/32 · CPC title