Multilayer film with reversible haze

Patent metadata

Field	Value
Publication number	US-11667104-B2
Application number	US-201716644795-A
Country	US
Kind code	B2
Filing date	Sep 5, 2017
Priority date	Sep 5, 2017
Publication date	Jun 6, 2023
Grant date	Jun 6, 2023

Abstract

The present disclosure provides a process. In an embodiment, the process includes elongating a multilayer film to a impart a haze value greater than 30% to the multilayer film. The multilayer film has at least two layers: (A) a core layer composed of an ethylene/α-olefin multi-block copolymer and (B) a first skin layer in contact with the core layer, the skin layer composed of an ethylene-based polymer. The process includes releasing the elongating force from the elongated multilayer film to form a hazed multilayer film having a haze value greater than 30%. The process includes stretching the hazed multilayer film to form a stretched multilayer film having a clarity value greater than 80%. The process includes relaxing the stretch force from the stretched multilayer film to form a relaxed multilayer film having a haze value greater than 30%.

First claim

The invention claimed is:

1. A process comprising:
elongating a multilayer film from at least 150% to less than or equal to 300% elongation to a impart a haze value greater than 30% to the multilayer film, the multilayer film having at least three layers
(A) a core layer consisting of an ethylene/α-olefin multi-block copolymer consisting of (i) ethylene and (ii) a C4-C8 α-olefin comonomer, and having a density from 0.865 g/cc to 0.880 g/cc,
(B) a first skin layer in direct contact with the core layer, the skin layer composed of an ethylene-based polymer,
(C) a second skin layer in direct contact with the core layer, the skin layer composed of an ethylene-based polymer, and multilayer film having a layer volume ratio of skin layer (C)-core layer (A)-to-skin layer (B) from 1:4:1 to 1:8:1;
releasing the elongating force from the elongated multilayer film to form a hazed multilayer film having a haze value greater than 30%, the haze measured in accordance with ASTM D1003;
stretching the hazed multilayer film to form a stretched multilayer film having a clarity value greater than 80%, the clarity measured in accordance with ASTM D 1746-15; and
relaxing the stretch force from the stretched multilayer film to form a relaxed multilayer film having a haze value greater than 30%,
wherein strain-stress behavior for the elongating, the releasing, the stretching and the relaxing is measured at 500 mm/min at a 25° C., in accordance with ASTM D5459.

2. The process of claim 1 wherein the elongating step comprises elongating the multilayer film from at least 150% elongation to less than 300% elongation.

3. The process of claim 1 wherein the elongation step imparts a haze value greater than 30% onto the hazed multilayer film.

4. The process of claim 1 wherein the elongating step activates hazing in the multilayer film.

5. The process of claim 1 comprising providing a multilayer film having (A) the core layer consisting of an ethylene/C 4 -C 8 α-olefin multi-block copolymer having density from 0.860 g/cc to 0.890 g/cc; (B) the first skin layer comprising a linear low density polyethylene having a density from 0.910 g/cc to 0.935 g/cc, and (c) the second skin layer comprising a linear low density polyethylene having a density from 0.910 g/cc to 0.935 g/cc, the density measured in accordance with ASTM D792.

6. A multilayer film comprising:
(A) a core layer consisting of an ethylene/α-olefin multi-block copolymer consisting of (i) ethylene and (ii) a C4-C8 α-olefin comonomer, and having a density from 0.865 g/cc to 0.880 g/cc;
(B) a first skin layer in direct contact with the core layer;
(C) a second skin layer in direct contact with the core layer;
the multilayer film is a mono-axially oriented hazed multilayer film and has a haze value greater the 30%, the hazed multilayer film has a layer volume ratio of skin layer (C)-core layer (A)-to-skin layer (B) from 1:4:1 to 1:8:1; and
the hazed multilayer film exhibits a clarity value greater than 80% when subjected to a stretching force from at least 150% elongation to less than or equal to 300% elongation, the hazed multilayer film further exhibiting a haze value greater than 30% when the stretching force is removed,
the haze measured in accordance with ASTM D1003 and the clarity measured in accordance with ASTM D 1746-15.

7. The multilayer film of claim 6 wherein the hazed multilayer film is a relaxed multilayer film when the stretching force is removed.

8. The multilayer film of claim 7 wherein the first skin layer directly contacts the core layer.

9. The multilayer film of claim 6 comprising a second skin layer (C), the first layer (B) in direct contact with a first surface of the core layer (A) and the second skin layer (C) in direct contact with a second surface of the core layer (A), the second skin layer composed of an ethylene-based polymer.

10. The multilayer film of claim 9 wherein the skin (B)-core (A)-skin layer (C) volume ratio is from 1:4:1 to 1:8:1.

11. A process comprising:
elongating a multilayer film from at least 150% to less than or equal to 300% elongation to a impart a haze value greater than 30% to the multilayer film, the multilayer film having a core layer (A) positioned between a first skin layer (B) and a second skin layer (C), the haze measured in accordance with ASTM D1003,
(A) the core layer consisting of an ethylene/α-olefin multi-block copolymer consisting of (i) ethylene and (ii) a C4-C8 α-olefin comonomer, and having a density from 0.860 g/cc to 0.887 g/cc, and optional additives,
(B) the first skin layer in contact with the core layer (A), the first skin layer consisting of a linear low density polyethylene having a density from 0.910 g/cc to 0.930 g/cc, and optional additives,
(C) the second skin layer in contact with the core layer, the second skin layer consisting of a linear low density polyethylene having a density from 0.910 g/cc to 0.930 g/cc, and optional additives;
and the multilayer film having a volume ratio of skin:core:skin layer from 1:4:1 to 1:8:1;
releasing the elongating force from the elongated multilayer film to form a hazed multilayer film having a haze value greater than 30%;
stretching the hazed multilayer film to form a stretched multilayer film having a clarity value greater than 80%, and a haze value less than 9%, the clarity measured in accordance with ASTM D 1746-15; and
relaxing the stretch force from the stretched multilayer film to form a relaxed multilayer film having a haze value greater than 30%,
wherein strain-stress behavior for the elongating, the releasing, the stretching and the relaxing is measured at 500 mm/min at a 25° C., in accordance with ASTM D5459.

12. The process of claim 11 wherein each skin layer is in direct contact with the core layer.

13. The process of claim 12 wherein the multilayer film consists of three layers.

14. The process of claim 13 wherein the linear low density polyethylene in the first skin layer is the same as the linear low density polyethylene in the second layer.

15. The process of claim 14 wherein the ethylene/α-olefin multi-block copolymer has a density from 0.860 g/cc to 0.870 g/cc.

Assignees

• Dow Global Technologies Llc

Inventors

• Chua Rou Hua
• Yee Wu Aik
• Low Bee Tin
• Subramanian Muthu Selva Annamalai
• Maehara Yutaka
• Wang Jian

Classifications

• B32B2307/412

  Transparent · CPC title

• B29C48/08

  flexible, e.g. films · CPC title

• B32B2307/514

  Oriented · CPC title

• B32B2307/732

  Dimensional properties · CPC title

• B32B2038/0068

  Changing crystal orientation · CPC title