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JP-7855912-B2 - Sealant films, packaging materials and packaging bodies

JP7855912B2JP 7855912 B2JP7855912 B2JP 7855912B2JP-7855912-B2

Inventors

  • ▲濱▼田 大輔
  • 大木 智子

Assignees

  • ＴＯＰＰＡＮホールディングス株式会社

Dates

Publication Date
20260511
Application Date
20220428

Claims (11)

  1. It contains a propylene homopolymer (A), a propylene-ethylene random copolymer (B), and a propylene-ethylene-α-olefin copolymer elastomer (C), The ethylene content of the propylene-ethylene random copolymer (B) is 6% by mass or less. A first heat-seal layer comprising a propylene-ethylene-α-olefin copolymer elastomer (C) having a content of 5.0 to 14.5 parts by mass relative to 100 parts by mass of the total amount of the propylene homopolymer (A) and the propylene-ethylene random copolymer (B) , A sealant film comprising a second layer containing a propylene-ethylene block copolymer (D) and an ethylene-propylene copolymer elastomer (E) .
  2. The sealant film according to claim 1, wherein the mass ratio of the content of the propylene homopolymer (A) to the content of the propylene-ethylene random copolymer (B) is 0.10 to 0.95.
  3. The first layer mentioned above, The aforementioned second layer, The sealant film according to claim 1 , comprising, in this order, a third layer containing a propylene homopolymer (A) and a propylene-ethylene random copolymer (B).
  4. The sealant film according to claim 1 , wherein the second layer contains 90 to 50% by mass of the propylene-ethylene block copolymer (D) and 10 to 50% by mass of the ethylene-propylene copolymer elastomer (E).
  5. The sealant film according to claim 3 , wherein the second layer contains 90 to 50% by mass of the propylene-ethylene block copolymer (D) and 10 to 50% by mass of the ethylene-propylene copolymer elastomer (E).
  6. The sealant film according to claim 1 , wherein the thickness of the second layer is 20 μm or more.
  7. The sealant film according to claim 3 , wherein the thickness of the second layer is 20 μm or more.
  8. A packaging material comprising a sealant film according to any one of claims 1 to 7 and a resin film having a metal oxide vapor deposition layer.
  9. A packaging material comprising a sealant film according to any one of claims 1 to 7 and a biaxially oriented polypropylene film.
  10. A package made from the packaging material described in claim 8 .
  11. A package made from the packaging material described in claim 9 .

Description

This invention relates to sealant films, packaging materials, and packaging bodies. More specifically, this invention relates to a sealant film made of polypropylene, which exhibits excellent heat resistance and low-temperature sealing properties, and is suitable for use as a packaging material even in harsh treatments such as boiling water treatment and retort treatment, as well as to packaging materials and packaging bags obtained using this sealant film. Polypropylene-based unoriented films are sometimes used as sealant films in various packaging materials, such as food packaging, due to their excellent rigidity, heat resistance, and low cost. Patent Document 1 proposes a polypropylene film comprising a crystalline propylene polymer with a melting point of 120 to 165°C, an ethylene-α-olefin copolymer, and a copolymer of ethylene and at least one selected from α-olefins, cyclic olefins, or cyclic polyenes having 3 to 20 carbon atoms. Patent Document 2 proposes a polypropylene-based film characterized by being composed of a crystalline propylene-α-olefin random copolymer and an ethylene-α-olefin random copolymer. Patent Document 3 proposes a polypropylene composite film composed of three layers, characterized in that the intermediate layer is made of a propylene-ethylene block copolymer and both surface layers are made of a propylene-based random copolymer. Japanese Patent Publication No. 2003-119298Japanese Patent Publication No. 2004-359711Japanese Patent Publication No. 2017-132186 Figure 1 is a cross-sectional view of a sealant film according to one embodiment of the present invention.Figure 2 is a cross-sectional view of a sealant film according to one embodiment of the present invention.Figure 3 is a cross-sectional view of a sealant film according to one embodiment of the present invention.Figure 4 is a cross-sectional view of a packaging material according to one embodiment of the present invention.Figure 5 is a cross-sectional view of a packaging material according to one embodiment of the present invention.Figure 6 is a cross-sectional view of a packaging material according to one embodiment of the present invention. <Sealant Film 100> Figure 1 is a cross-sectional view of a sealant film 100 according to one embodiment of the present invention. The sealant film 100 comprises a first layer 10 containing a propylene homopolymer (A), a propylene-ethylene random copolymer (B), and a propylene-ethylene-α-olefin copolymer elastomer (C). (Propylene homopolymer (A)) The propylene homopolymer (A) can be obtained by homopolymerizing propylene using, for example, a Ziegler-Natta type catalyst, a metallocene catalyst, or a half-metallocene catalyst. The inclusion of the propylene homopolymer (A) in the sealant film provides excellent heat resistance to the first layer. This makes it less likely for fusion to occur on the inner surface of the packaging bag after, for example, high-pressure heat treatment at 135°C. As the propylene homopolymer (A), a material can be used that has a melting onset temperature of 150°C or higher and a melting point of 155°C or higher, as measured by differential scanning calorimetry (JIS K 7121). By having both the melting onset temperature and melting point within this range, the first layer can be given superior heat resistance. As a result, for example, after pressurized heat treatment at high retort conditions of 135°C, fusion is less likely to occur on the inner surface of the packaging bag. The conditions for differential scanning calorimetry are as follows. [Differential scanning calorimetry conditions] When the temperature is increased from 25°C to 230°C at a rate of 10°C/min, the point at which the straight line extending the baseline on the low-temperature side of the DSC curve toward the high-temperature side intersects with a tangent line drawn so as to be tangent to the curve on the low-temperature side of the melting peak and have the maximum slope is defined as the melting onset temperature, and the temperature at the peak of the melting peak is defined as the melting point. As the propylene homopolymer (A), one with a melt flow rate (MFR: ISO 1133) (temperature 230°C, load 2.16 kg) in the range of 2.0 to 7.0 g/10 min can be used. A melt flow rate above the lower limit reduces the extruder load during molding, making it easier to maintain excellent productivity without a decrease in processing speed. Furthermore, a melt flow rate below the upper limit tends to result in the first layer having excellent impact resistance. (Propylene-ethylene random copolymer (B)) Propylene-ethylene random copolymer (B) can be obtained by copolymerizing ethylene as a comonomer in a main monomer consisting of propylene, for example, using a Ziegler-Natta type catalyst, a metallocene catalyst, or a half-metallocene catalyst. The inclusion of propylene-ethylene random copolymer (B) in the first layer makes it easier to obtain excellent low-temperature sealing properties while maintainin