US-12623443-B2 - Packaging bag and packaging multilayer film to be used for producing the packaging bag

Abstract

In a packaging bag ( 10 ) including multilayer films for packaging ( 5 ) including a heat-sealable resin layer ( 3 ) on a surface and formed by bonding two of the heat-sealable resin layers ( 3 ) of the multilayer films for packaging ( 5 ), oriented crystals are present in a seal portion ( 7 ) formed by bonding the heat-sealable resin layers ( 3 ).

Inventors

• Kenya MAJIMA
• Seishi Yoshikawa
• Koki SHIBATA
• Atsushi Ebata

Assignees

• TOYO SEIKAN GROUP HOLDINGS, LTD.

Dates

Publication Date

20260512

Application Date

20210910

Priority Date

20200911

Claims (11)

1. 1 . A packaging bag, comprising multilayer films for packaging including a heat-sealable resin layer on a surface, the packaging bag being formed by bonding two of the heat-sealable resin layers of the multilayer films for packaging, wherein oriented crystals are present in a seal portion formed by bonding the heat-sealable resin layers, wherein the heat-sealable resin layer is a non-stretched molded body containing an impact polypropylene component, and has a loss tangent (tan δ) of more than 0.0594 at 5° C. and a storage elastic modulus (E′) of more than 1 MPa at 110° C. in a test measurement of dynamic viscoelasticity.
2. 2 . The packaging bag according to claim 1 , wherein the multilayer films for packaging include a stretched film for reinforcing strength for allowing the oriented crystals to be present in the seal portion.
3. 3 . The packaging bag according to claim 2 , wherein the stretched film for reinforcing strength contains an olefin resin and a reinforcing resin having a melting point higher than a melting point of the olefin resin.
4. 4 . The packaging bag according to claim 3 , wherein the stretched film for reinforcing strength is formed of a blended material of the olefin resin and the reinforcing resin.
5. 5 . The packaging bag according to claim 3 , wherein the stretched film for reinforcing strength is a laminate of a layer of the olefin resin and a layer of the reinforcing resin.
6. 6 . The packaging bag according to claim 3 , wherein the reinforcing resin is polyamide, polyester, or an ethylene-vinyl alcohol copolymer.
7. 7 . The packaging bag according to claim 2 , wherein the multilayer film for packaging includes a substrate film for improving recyclability in addition to the stretched film for reinforcing strength.
8. 8 . The packaging bag according to claim 7 , wherein 80 mass % or more of the olefin resin is contained.
9. 9 . The packaging bag according to claim 1 , wherein the non-stretched molded body contains an impact polypropylene component (A) in which an ethylene-propylene copolymer is dispersed in polypropylene and linear low-density polyethylene (B).
10. 10 . The packaging bag according to claim 9 , wherein the non-stretched molded body contains 8 mass % or more of a xylene-soluble fraction percentage derived from the ethylene-propylene copolymer.
11. 11 . The packaging bag according to claim 9 , wherein the non-stretched molded body contains 20 mass % or less of the linear low-density polyethylene (B).

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is a National Stage of International Application No. PCT/JP2021/033241 filed Sep. 10, 2021, claiming priority based on Japanese Patent Application No. 2020-153226 filed Sep. 11, 2020. TECHNICAL FIELD The present invention relates to a packaging bag and further relates to a multilayer film for packaging to be used for producing the packaging bag. BACKGROUND ART Cast polypropylene (CPP) films (also referred to as non-stretched polypropylene films or cast PP films) consisting of polypropylene and having heat sealability have excellent heat resistance and are used for producing pouches for containing various types of food. In recent years, more heat resistance and impact resistance are required for retort sterilization (heat steam sterilization), and impact polypropylene (hereinafter, may be referred to as impact PP) has been used for producing CPP films. The impact PP, which is also referred to as block PP, an impact copolymer, or high-impact polypropylene, includes a rubber component, such as an ethylene-propylene copolymer (EPR) or a styrene-butadiene copolymer (SBR), dispersed in a matrix of homo-polypropylene or random polypropylene. Such a rubber component remarkably improves impact resistance strength. A known retort pouch uses a multilayer film having a layer structure of biaxially oriented PET, biaxially oriented nylon, Al, and CPP, and the pouch has high impact resistance and hardly breaks when the pouch filled with contents is dropped from a high place. However, the pouch has a multilayer configuration of different materials and thus has poor recyclability. Then, in response to recent recycling, a polypropylene monomaterial pouch is awaited. Unfortunately, such a mono-material pouch does not use biaxially oriented PET or biaxially oriented nylon, thus is suitable for recyclability, but has low impact resistance. For example, Patent Documents 1 and 2 propose a propylene-based resin composition in which a linear low-density polyethylene (LLDPE) is blended with a propylene impact copolymer (corresponding to impact PP) and disclose that such a resin composition can be used to obtain a film for heat sealing having various excellent properties. Patent Documents 1 and 2 improves physical properties of a film for heat sealing made of impact PP by blending a linear low-density polyethylene with impact PP, but a packaging bag obtained by using such a heat-sealable resin layer still has unsatisfactory bag drop strength. CITATION LIST Patent Literature Patent Document 1: JP 4844091 BPatent Document 2: WO 2017/038349 SUMMARY OF INVENTION Technical Problem In response to the above problems, an object of the present invention is to provide a packaging bag having a remarkably improved bag drop strength and a multilayer film for packaging for obtaining the packaging bag. Another object of the present invention is to provide a packaging bag having an enhanced bag drop strength without the recyclability impaired and a multilayer film for packaging for obtaining the packaging bag. Solution to Problem The present inventors have found that when using a multilayer film for packaging including a heat-sealable resin layer on a surface and laminating the multilayer films to face the heat-sealable resin layers each other to produce a packaging bag, the bag drop strength is improved without the recyclability impaired when oriented crystals are present in a seal portion (that is, a bonded portion of the multilayer films). According to the present invention, provided is a packaging bag including multilayer films for packaging including a heat-sealable resin layer on a surface and formed by bonding two of the heat-sealable resin layers of the multilayer films. In the packaging bag, oriented crystals are present in a seal portion formed by bonding the heat-sealable resin layers. The packaging bag according to the present invention preferably applies the following aspects. (1) The multilayer film for packaging includes a stretched film for reinforcing strength for allowing the oriented crystals to be present in the seal portion.(2) The stretched film for reinforcing strength contains an olefin resin and a reinforcing resin having a melting point higher than a melting point of the olefin resin.(3) The stretched film for reinforcing strength is formed of a blended material of the olefin resin and the reinforcing resin.(4) The stretched film for reinforcing strength is a laminate of a layer of the olefin resin and a layer of the reinforcing resin.(5) The reinforcing resin is polyamide, polyester, or an ethylene-vinyl alcohol copolymer.(6) The multilayer film for packaging includes a substrate film for improving recyclability in addition to the stretched film for reinforcing strength.(7) An amount of 80 mass % or more of the olefin resin is contained.(8) The heat-sealable resin layer is a non-stretched molded body containing an impact polypropylene component and has a loss tangent