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EP-4741163-A1 - SEALANT FILM FOR LAMINATE, LAMINATE, AND PACKAGING CONTAINER

EP4741163A1EP 4741163 A1EP4741163 A1EP 4741163A1EP-4741163-A1

Abstract

As a sealant film for laminates that is superior in heat resistance, low-temperature sealability, and impact resistance, there is provided a sealant film for use in a laminate in which the percentage of polypropylene is 80% by mass or more. The sealant film includes at least a first layer positioned at one surface of the laminate and a second layer in contact with the first layer. The first layer contains a first matrix resin component constituting 51% by mass or more and 90% by mass or less and at least one first dispersed component, and has a sea-island structure in which the first dispersed component is dispersed in the first matrix resin component. The second layer contains a second matrix resin component constituting 51% by mass or more and 85% by mass or less and at least one second dispersed component, and has a sea-island structure in which the second dispersed component is dispersed in the second matrix resin component. The first matrix resin component is a propylene-ethylene random copolymer, and the first dispersed component includes 5% by mass or more polyethylene. The second matrix resin component is block polypropylene, and the second dispersed component includes 5% by mass or more polyethylene.

Inventors

  • ISHIKAWA Shun
  • KONO SHINICHIRO
  • HASEGAWA TAKAYUKI
  • TAKUSHIMA KAZUHIRO

Assignees

  • Dai Nippon Printing Co., Ltd.

Dates

Publication Date
20260513
Application Date
20240823

Claims (20)

  1. A sealant film for a laminate, the sealant film being for use in a laminate in which a percentage of polypropylene relative to a total amount of resin materials is 80% by mass or more, and the sealant film comprising at least a first layer that, when the sealant film is used in the laminate, is positioned at one of two surfaces of the laminate and a second layer in contact with the first layer, wherein: the first layer contains a first matrix resin component constituting 51% by mass or more and 90% by mass or less relative to a total amount of the first layer and at least one first dispersed component, and has a sea-island structure in which the first dispersed component is dispersed in the first matrix resin component; the second layer contains a second matrix resin component constituting 51% by mass or more and 85% by mass or less relative to a total amount of the second layer and at least one second dispersed component, and has a sea-island structure in which the second dispersed component is dispersed in the second matrix resin component; the first matrix resin component is a propylene-ethylene random copolymer; the first dispersed component includes at least one type of polyethylene constituting at least 5% by mass or more relative to the total amount of the first layer; the second matrix resin component is block polypropylene; and the second dispersed component includes at least one type of polyethylene constituting at least 5% by mass or more relative to the total amount of the second layer.
  2. The sealant film for a laminate according to claim 1, wherein the block polypropylene contains at least a propylene homopolymer and a block elastomer and has a sea-island structure in which the block elastomer is dispersed in the propylene homopolymer.
  3. The sealant film for a laminate according to claim 2, wherein the block elastomer is an ethylene-propylene elastomer.
  4. The sealant film for a laminate according to claim 1, wherein a percentage of the second dispersed component to the total amount of the second layer is 15% by mass or more and 49% by mass or less.
  5. The sealant film for a laminate according to claim 4, wherein a percentage of the first dispersed component to the total amount of the first layer is 10% by mass or more and 49% by mass or less.
  6. The sealant film for a laminate according to claim 5, wherein the percentage of the first dispersed component to the total amount of the first layer is smaller than the percentage of the second dispersed component to the total amount of the second layer.
  7. The sealant film for a laminate according to claim 1, wherein the second dispersed component further includes a second elastomer.
  8. The sealant film for a laminate according to claim 7, wherein the second elastomer is a propylene-ethylene elastomer or an ethylene-α olefin elastomer.
  9. The sealant film for a laminate according to claim 7, wherein, in the second dispersed component, a ratio of an amount of the second elastomer to an amount of the polyethylene is 0.5 or more and less than 1.0.
  10. The sealant film for a laminate according to claim 1, wherein the first dispersed component further includes a first elastomer.
  11. The sealant film for a laminate according to claim 10, wherein, in the first dispersed component, a ratio of an amount of the first elastomer to an amount of the polyethylene is 0.5 or more and less than 1.0.
  12. The sealant film for a laminate according to claim 1, wherein a ratio of a thickness of the second layer to a thickness of the first layer is 3.0 or more.
  13. The sealant film for a laminate according to claim 12, wherein the second layer has a thickness of 50 µm or more.
  14. The sealant film for a laminate according to claim 1, wherein the polyethylene in the second dispersed component includes linear low-density polyethylene (LLDPE) or low-density polyethylene (LDPE).
  15. The sealant film for a laminate according to claim 1, wherein the polyethylene in the second dispersed component is linear low-density polyethylene (LLDPE).
  16. The sealant film for a laminate according to claim 2, the sealant film further comprising a third layer in contact with the second layer, wherein: the third layer contains a third matrix resin component constituting 51% by mass or more and 85% by mass or less relative to a total amount of the third layer and at least one third dispersed component, and has a sea-island structure in which the third dispersed component is dispersed in the third matrix resin component; and the third matrix resin component is the block polypropylene.
  17. The sealant film for a laminate according to claim 16, wherein the third dispersed component includes any one or both of polyethylene and a third elastomer.
  18. The sealant film for a laminate according to claim 1, wherein a thickness of the sealant film is 30 µm or more and 200 µm or less.
  19. A laminate for use in a packaging material, the laminate comprising at least a first base material and a sealant layer, wherein: the sealant layer is formed of the sealant film for a laminate according to any one of claims 1 to 18; and a percentage of polypropylene relative to a total amount of resin materials is 80% by mass or more.
  20. The laminate according to claim 19, further comprising a second base material between the first base material and the sealant layer.

Description

Cross-Reference to Related Applications The present application claims priority based on Patent Application No. 2023-139319, filed August 29, 2023, in Japan, the disclosure of which is hereby incorporated as part of the present description by reference in its entirety. Technical Field The present disclosure relates to a sealant film for laminates, a laminate, and a packaging container. Background Art In the related art, packaging containers have been composed of laminates in which a polyester film, superior in strength and heat resistance, or a nylon film, superior in impact resistance, for example, is used as a base material, and a polyolefin film, superior in heat sealability, is used as a sealant film. With the growing call for building a recycling-oriented society in recent years, however, there is a need for packaging containers having high recycling suitability. Nevertheless, known packaging containers, composed of different types of resin materials, are difficult to separate into the individual resin materials. To address this, researchers have been studying monomaterialization with polypropylene (e.g., PTL 1) from the perspective of monomaterialization for easier recycling. In PTL 1, a laminate for use in packaging materials, for example for packaging containers, is disclosed in which a stretched base material containing polypropylene is used as a base material instead of a polyester film or nylon film and is combined with a sealant film containing polypropylene. With this laminate, recycling suitability has been improved by virtue of the base material and the sealant film being both composed of polypropylene. Citation List Patent Literature PTL 1: Japanese Unexamined Patent Application Publication No. 2021-020391 Summary of Invention Technical Problem Meanwhile, when a laminate for use in packaging containers is made into a retort pouch or similar packaging container, the laminate is required to have heat resistance sufficient to withstand heat sterilization treatment. Since the laminate is made into the packaging container by heat sealing, furthermore, the laminate is required to have suitability for shaping into a bag, and the sealant film is required to have low-temperature sealability. Moreover, a laminate for use in a retort pouch or similar packaging container is required to have resistance to fall impact sufficient to withstand impact from a fall of the pouch (impact resistance). The reality, however, is that with laminates monomaterialized with polypropylene, the achievement of these characteristics requirements is not fully considered. One of the problems to be solved by the present disclosure is to provide a sealant film for laminates that is superior in heat resistance, low-temperature sealability, and impact resistance and is suitable for laminates monomaterialized with polypropylene. Solution to Problem A sealant film for a laminate according to the present disclosure is a sealant film for use in a laminate in which a percentage of polypropylene to a total amount of resin materials is 80% by mass or more, the sealant film including at least a first layer that, when the sealant film is used in the laminate, is positioned at one of two surfaces of the laminate and a second layer in contact with the first layer, wherein the first layer contains a first matrix resin component constituting 51% by mass or more and 90% by mass or less relative to a total amount of the first layer and at least one first dispersed component, and has a sea-island structure in which the first dispersed component is dispersed in the first matrix resin component, the second layer contains a second matrix resin component constituting 51% by mass or more and 85% by mass or less relative to a total amount of the second layer and at least one second dispersed component, and has a sea-island structure in which the second dispersed component is dispersed in the second matrix resin component, the first matrix resin component is a propylene-ethylene random copolymer, the first dispersed component includes at least one type of polyethylene constituting at least 5% by mass or more relative to the total amount of the first layer, the second matrix resin component is block polypropylene, and the second dispersed component includes at least one type of polyethylene constituting at least 5% by mass or more relative to the total amount of the second layer. Advantageous Effects of Invention According to the present disclosure, a sealant film for laminates that is superior in heat resistance, low-temperature sealability, and impact resistance and is suitable for laminates monomaterialized with polypropylene can be provided. Brief Description of Drawings [Fig. 1] Fig. 1 is a cross-sectional schematic view illustrating an embodiment of a sealant film for laminates.[Fig. 2] Fig. 2 is a cross-sectional schematic view illustrating an embodiment of a sealant film for laminates.[Fig. 3] Fig. 3 is a schematic cross-sectional view illustrat