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EP-4741162-A1 - GAS BARRIER FILM, MULTILAYER BODY, AND PACKAGING MATERIAL

EP4741162A1EP 4741162 A1EP4741162 A1EP 4741162A1EP-4741162-A1

Abstract

A gas barrier film includes a multilayer polyethylene film and a gas barrier layer, wherein the multilayer polyethylene film has a surface layer, an intermediate layer, and a back layer in this order, the surface layer is provided between the intermediate layer and the gas barrier layer, the surface layer is composed of a medium-density polyethylene resin or a high-density polyethylene resin having a density of 0.926 g/cm 3 or more, a complex modulus of the surface layer and the back layer is 1.45 GPa or more and less than 1.90 GPa, a complex modulus of the intermediate layer is 1.80 GPa or more and less than 2.50 GPa, a ratio of a thickness of the intermediate layer to a total thickness of the surface layer and the back layer is 0.5 or more, a temperature indicated by a maximum value of a melting peak of the multilayer polyethylene film is more than 129°C and less than 136°C, and the gas barrier layer has at least one of an inorganic oxide layer and a gas barrier coating layer.

Inventors

  • ISHII MEGUMI
  • TAKEI RYO
  • KAMEGAWA Yuki
  • KATO RYOJI
  • YAMADA MIKINORI

Assignees

  • Toppan Holdings Inc.

Dates

Publication Date
20260513
Application Date
20240719

Claims (15)

  1. A gas barrier film having a laminated structure comprising a multilayer polyethylene film and a gas barrier layer, wherein the multilayer polyethylene film has a surface layer, an intermediate layer, and a back layer in this order, the surface layer being provided between the intermediate layer and the gas barrier layer, the surface layer is composed of a medium-density polyethylene resin or a high-density polyethylene resin having a density of 0.926 g/cm 3 or more, a complex modulus of the surface layer and the back layer is 1.45 GPa or more and less than 1.90 GPa, a complex modulus of the intermediate layer is 1.80 GPa or more and less than 2.50 GPa, and the gas barrier layer has at least one of an inorganic oxide layer and a gas barrier coating layer.
  2. The gas barrier film according to claim 1, wherein a density of the multilayer polyethylene film is 0.940 g/cm 3 or more.
  3. The gas barrier film according to claim 1, wherein the gas barrier layer has the inorganic oxide layer, and the inorganic oxide layer comprises at least one of aluminum oxide and silicon oxide.
  4. The gas barrier film according to claim 1, wherein the gas barrier layer has the gas barrier coating layer, and the gas barrier coating layer comprises a water-soluble polymer and at least one selected from the group consisting of a metal alkoxide, a hydrolysate thereof, and a reaction product thereof.
  5. The gas barrier film according to claim 1, wherein the gas barrier layer has the gas barrier coating layer, and the gas barrier coating layer comprises at least one selected from the group consisting of a silane coupling agent, a hydrolysate thereof, and a reaction product thereof.
  6. The gas barrier film according to claim 1, wherein the gas barrier layer has the gas barrier coating layer, and the gas barrier coating layer comprises a polyvalent metal salt of carboxylic acid.
  7. The gas barrier film according to claim 1, wherein a ratio of a thickness of the intermediate layer to a total thickness of the surface layer and the back layer is 0.5 or more.
  8. The gas barrier film according to claim 1, wherein a thickness of the intermediate layer is 33% or more of a thickness of the multilayer polyethylene film.
  9. The gas barrier film according to claim 1, wherein a temperature indicated by a maximum value of a melting peak observed in differential scanning calorimetry of the multilayer polyethylene film is more than 129°C and less than 136°C.
  10. A multilayer body comprising: the gas barrier film according to any one of claims 1 to 9; an adhesive layer disposed on a surface of the gas barrier layer opposite the multilayer polyethylene film; and a sealant layer disposed via the adhesive layer, wherein an absolute value of a degree of molecular orientation of the multilayer polyethylene film is less than 1.07.
  11. The multilayer body according to claim 10, wherein a content of polyethylene resin in the multilayer body is 90 mass% or more based on a total amount of the multilayer body.
  12. The multilayer body according to claim 10, further comprising a gas barrier coating layer on a surface of the inorganic oxide layer on the sealant layer side.
  13. The multilayer body according to claim 10, wherein the adhesive layer comprises a gas barrier adhesive.
  14. The multilayer body according to claim 10, further comprising: a second adhesive layer disposed on a surface of the multilayer polyethylene film on the back layer side; and a base material disposed via the second adhesive layer.
  15. A packaging material comprising the multilayer body according to claim 10.

Description

Technical Field The present disclosure relates to a gas barrier film, a multilayer body, and a packaging material. Background Art Packaging materials used for packaging foods, pharmaceuticals, and the like are required to have a property of preventing the entry of gases (water vapor, oxygen, etc.) that cause deterioration of the packaged goods (gas barrier property) in order to suppress alteration, spoilage, etc. of the packaged goods and maintain their functions and quality. In addition, since packaging materials are sometimes subjected to a heat sterilization treatment such as a boiling treatment, excellent heat resistance is required. Therefore, a multilayer body (gas barrier film) having a gas barrier property and heat resistance is used for these packaging materials. As a gas barrier film, one is known in which a gas barrier layer made of a material having a gas barrier property is provided on the surface of a resin substrate. As the gas barrier layer, a metal foil, a metal-deposited film, a coating film formed by a wet coating method, and the like are known. As the resin substrate, a polyolefin film such as a polyethylene film is known. For example, Patent Literature 1 describes an aluminum-deposited polyethylene film characterized by having an aluminum-deposited film on the surface of an unstretched polyethylene film with a thickness of less than 30 µm, which is made of linear low-density polyethylene produced by using a metallocene catalyst. In addition, it has been studied to improve the properties of a gas barrier film by making the resin substrate a multilayer body having a plurality of resin layers. For example, Patent Literature 2 describes a film that can suppress the occurrence of wrinkles, which includes a resin layer including a first surface and a second surface, and a vapor-deposited layer provided on the second surface of the resin layer, wherein the resin layer includes a first layer constituting the first surface, and at least one hard layer having a density higher than the density of the first layer and having a density of 0.934 g/cm3 or more, and the total thickness of the hard layer is 60% or more of the total thickness of the resin layer. Citation List Patent Literature Patent Literature 1: Japanese Unexamined Patent Publication No. 2001-179878Patent Literature 2: Japanese Unexamined Patent Publication No. 2018-24213 Summary of Invention Technical Problem However, in recent years, due to growing environmental awareness stemming from issues such as marine plastic waste, there has been a demand for further efficiency in the separate collection and recycling of plastic materials, and mono-materialization has also come to be required for packaging materials. However, in the course of studying the mono-materialization of gas barrier films, the present inventors found that depending on the type of polyethylene resin constituting each layer of the polyethylene film, wrinkles may occur on the surface of the polyethylene film, making it difficult to form a gas barrier layer, or it may be difficult to impart sufficient transparency and heat resistance. Therefore, an object of one aspect of the present disclosure is to provide a gas barrier film having excellent processing stability when providing a gas barrier layer, excellent transparency, and excellent heat resistance that can maintain the gas barrier property even after a heat sterilization treatment. Solution to Problem One aspect of the present disclosure includes the following [1] to [15]. [1] A gas barrier film having a laminated structure that includes a multilayer polyethylene film and a gas barrier layer, wherein the multilayer polyethylene film has a surface layer, an intermediate layer, and a back layer in this order, the surface layer is provided between the intermediate layer and the gas barrier layer,the surface layer is composed of a medium-density polyethylene resin or a high-density polyethylene resin having a density of 0.926 g/cm3 or more,a complex modulus of the surface layer and the back layer is 1.45 GPa or more and less than 1.90 GPa,a complex modulus of the intermediate layer is 1.80 GPa or more and less than 2.50 GPa, andthe gas barrier layer has at least one of an inorganic oxide layer and a gas barrier coating layer.[2] The gas barrier film according to [1], wherein a density of the multilayer polyethylene film is 0.940 g/cm3 or more.[3] The gas barrier film according to [1] or [2], wherein the gas barrier layer has the inorganic oxide layer, andthe inorganic oxide layer includes at least one of aluminum oxide and silicon oxide.[4] The gas barrier film according to any one of [1] to [3], wherein the gas barrier layer has the gas barrier coating layer, andthe gas barrier coating layer includes a water-soluble polymer and at least one selected from the group consisting of a metal alkoxide, a hydrolysate thereof, and a reaction product thereof.[5] The gas barrier film according to any one of [1] to [4], wherein the g