EP-4735251-A1 - MULTILAYER FILM HAVING ENHANCED CREEP, TEAR, AND DART

EP4735251A1EP 4735251 A1EP4735251 A1EP 4735251A1EP-4735251-A1

Abstract

A multilayer film (100) may comprise a first skin layer (102), a second skin layer (104), and a core(106) positioned between the first skin layer (102) and the second skin layer (104). The first skin layer (102) and the second skin layer (104) may independently comprise linear low density polyethylene (LLDPE) resin. The core (106) may comprise a first core layer (108), a second core layer (110), and a third core layer (112). The first core layer (108) and the third core layer (112) may independently comprise high density polyethylene (HDPE), LLDPE, or a combination of these. The second core layer (110) may comprise an ethylene-based copolymer selected from the group consisting of ethylene/propylene copolymer, ethylene/butyl acrylate copolymer, ethylene/ethyl acrylate copolymer, ethylene/methyl acrylate copolymer, and ethylene/vinyl acetate copolymer. The thickness of the second core layer (110) may be less than 15 % of a thickness of the multilayer film (100). At least one of the core layers (108,110,112) may comprise HDPE.

Inventors

PARKINSON, SHAUN
COLOMBO, Veronica

Assignees

Dow Global Technologies LLC

Dates

Publication Date: 20260506
Application Date: 20240614

Claims (15)

1. A multilayer film comprising a first skin layer, a second skin layer, and a core positioned between the first skin layer and the second skin layer, wherein: the first skin layer and the second skin layer independently comprise linear low density polyethylene (LLDPE) resin; the core comprises a first core layer, a second core layer, and a third core layer; the first core layer and the third core layer independently comprise high density polyethylene (HDPE), linear low density polyethylene (LLDPE), or a combination of these; the second core layer comprises an ethylene-based copolymer selected from the group consisting of ethylene/propylene copolymer, ethylene/butyl acrylate copolymer, ethylene/ethyl acrylate copolymer, ethylene/methyl acrylate copolymer, and ethylene/vinyl acetate copolymer; the thickness of the second core layer is less than 15 % of the thickness of the multilayer fdm; and at least one of the core layers comprise high density polyethylene (HDPE).
2. The multilayer fdm of claim 1, wherein the second core layer is positioned between the first core layer and the third core layer.
3. The multilayer film of any preceding claim, wherein the second core layer further comprises calcium carbonate.
4. The multilayer film of any preceding claim, wherein the multilayer film comprises at least 30 wt. % of HDPE, on the basis of the total polymer weight of the multilayer film.
5. The multilayer film of any preceding claim, wherein the second core layer comprises an ethylene-based copolymer selected from the group consisting of ethylene/butyl acrylate copolymer, ethylene/ethyl acrylate copolymer, and ethylene/methyl acrylate copolymer.
6. The multilayer film of any preceding claim, wherein the first skin layer, the second skin layer, or both further comprise low-density polyethylene (LDPE).
7. The multilayer film of any preceding claim, wherein the core further comprises: a fourth core layer positioned between the first skin layer and the first core layer, and a fifth core layer positioned between the third core layer and the second skin layer.
8. The multilayer film of claim 7, wherein the fourth core layer and the fifth core layer each independently comprise HDPE, LLDPE, or combinations thereof.
9. The multilayer film of any preceding claim, wherein the second core layer has a thickness of less than or equal to 10 % of a thickness of the multilayer film.
10. The multilayer film of any preceding claim, wherein the multilayer film has a thickness of less than 180 pm.
11. The multilayer film of any preceding claim, wherein the multilayer film has a Dart Drop Impact Type A of at least 4.4 g/pm.
12. The multilayer film of any preceding claim, wherein the multilayer film has an Elmendorf Cross Direction Tear resistance of at least 16.6 gf/pm.
13. The multilayer film of any preceding claim, wherein the multilayer film has an Elmendorf Machine Direction Tear resistance of at least 8.8 gf/pm.
14. The multilayer film of any preceding claim, wherein the multilayer film has a high throughput creep of less than 50 %.
15. The multilayer film of any preceding claim, wherein: the second core layer is the central layer, the second core layer is positioned between the first core layer and the third core layer, the multilayer film has a density of from 0.929 g/cc to 0.942 g/cc, the first skin layer, the second skin layer, or both further comprise low-density polyethylene (EDPE), the second core layer has a thickness less than or equal to 10 % of a thickness of the multilayer film, the multilayer film has a thickness of less than or equal to 110 pm, the multilayer film has a Dart Drop Impact Type A of at least 4.4 g/pm, the multilayer film has an Elmendorf Cross Direction Tear resistance of at least 16.6 gf/pm, and the multilayer film has an Elmendorf Machine Direction Tear resistance of at least 8.8 gf/pm.

Description

MULTILAYER FILM HAVING ENHANCED CREEP, TEAR, AND DART CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims the benefit of Spanish Patent Application No. P202330544 filed June 28, 2023, the contents of which are incorporated in their entirety herein. TECHNICAL FIELD [0002] Embodiments described herein generally relate to multilayer films and, more specifically, to multilayer films used for heavy duty shipping sacks (HDSS). BACKGROUND [0003] In the interest of improving sustainability and reducing cost, it is desirable to reduce the thickness of the films used to make heavy-duty shipping sacks ("HDSS "). Reducing thickness reduces the amount of material employed and therefore the total emissions. However, this reduction in thickness (also called “downgauging”) must be accomplished without sacrificing impact resistance, tear resistance, and creep resistance. It becomes progressively more difficult to meet these specifications as the film is downgauged, especially below 100 pm. [0004] With regard to creep, it is well known that creep is inversely proportional to the cube of the thickness when thickness is near 100 pm. Creep can be improved by adding more HDPE and increasing the overall film stiffness. However, this worsens other mechanical properties, such as impact resistance. BRIEF SUMMARY [0005] Accordingly, thinner films which can still meet impact resistance, tear resistance, and creep resistance are desired. Embodiments of the present disclosure meet this need by providing a multilayer film comprising a core layer which comprises ethylene-acrylate copolymer, ethylenepropylene copolymer, or combinations thereof. Further embodiments of the present disclosure meet this need by providing a core layer which comprises ethylene-acrylate copolymer, ethylenepropylene copolymer, or combinations thereof and which is relatively thin, such as less than 20 % of the thickness of the multilayer film. [0006] According to one embodiment of the present disclosure, a multilayer film may comprise a first skin layer, a second skin layer, and a core positioned between the first skin layer and the second skin layer. The first skin layer and the second skin layer may independently comprise linear low density polyethylene (LLDPE) resin. The core may comprise a first core layer, a second core layer, and a third core layer. The first core layer and the third core layer may independently comprise high density polyethylene (HDPE), linear low density polyethylene (LLDPE) or a combination of these. The second core layer may comprise an ethylene-based copolymer selected from the group consisting of ethylene/propylene copolymer, ethylene/butyl acrylate copolymer, ethylene/ethyl acrylate copolymer, ethylene/methyl acrylate copolymer, and ethylene/vinyl acetate copolymer. The thickness of the second core layer may be less than 15 % of a thickness of the multilayer film. At least one of the core layers may comprise HDPE. [0007] Additional features and advantages will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments described herein, including the detailed description which follows and the claims. [0008] It is to be understood that both the foregoing general description and the following detailed description describe various embodiments and are intended to provide an overview or framework for understanding the nature and character of the claimed subject matter. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS [0009] To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the figure number in which that element is first introduced. Where two embodiments include the same component, like numerals will be used to describe like components (e.g. first layer 204 in FIG. 2 will correspond to first layer 104 in FIG. 1). [0010] FIG. 1 illustrates a side view of one embodiment of the present multilayer film. [0011] FIG. 2 illustrates a side view of one embodiment of the present multilayer film. DETAILED DESCRIPTION [0012] Specific embodiments of the present application will now be described. The disclosure may be embodied in different forms and should not be construed as limited to the embodiments set forth in this disclosure. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the subject matter to those skilled in the art. [0013] As discussed above, thinner films which can still meet impact resistance, tear resistance, and creep resistance for use in HDSS are desired. Embodiments of the present disclosure meet this need by providing a multilayer fdm comprising a second core layer which comprises ethylene-based copolymer selected from the group consisting of ethylene/propylene copolymer, ethylene/butyl acrylate copolymer, ethylene/ethy