JP-2026075308-A - Multilayer film for ultrasonic sealing and packaging

Abstract

[Problem] The present invention aims to solve the aforementioned problems of the conventional method and achieve the following objectives. Specifically, the present invention aims to provide a multilayer film for ultrasonic sealing that can be made into a single material, has sufficient rigidity, is capable of ultrasonic welding, and has a narrow seal width and uniform and stable ultrasonic sealing strength. [Solution] In the present invention, the above problem is solved by a multilayer film for ultrasonic sealing, which includes at least a surface layer and a sealing layer, wherein the surface layer contains 20% by mass or more of high-density polyethylene and the sealing layer contains an ethylene-vinyl acetate copolymer. Furthermore, the present invention provides a laminate containing at least the multilayer film and a package in which the multilayer film or laminate is sealed by ultrasound. [Selection Diagram] Figure 1

Inventors

• アウリア アウェルロース

Assignees

• ＤＩＣ株式会社

Dates

Publication Date

20260508

Application Date

20241022

Claims (9)

1. Including at least a surface layer and a sealing layer, A multilayer film for ultrasonic sealing, wherein the surface layer contains 20% by mass or more of high-density polyethylene, and the sealing layer contains an ethylene-vinyl acetate copolymer.
2. The ultrasonic sealing multilayer film according to claim 1, wherein the content of polyethylene-based resin in the resin component contained in the ultrasonic sealing multilayer film is 90% by mass or more.
3. The multilayer film for ultrasonic sealing according to claim 1, wherein the content of ethylene-vinyl acetate copolymer in the resin component contained in the sealing layer is 20% by mass or more.
4. The ultrasonic sealing multilayer film according to claim 1, wherein the ultrasonic sealing multilayer film further comprises an intermediate layer, and the intermediate layer comprises low-density polyethylene.
5. The multilayer film for ultrasonic sealing according to claim 1, wherein the thickness of the sealing layer is less than 10 μm.
6. A multilayer film for ultrasonic sealing according to claim 1, wherein the total thickness is 40 μm or less.
7. A laminate comprising at least one of the ultrasonic sealing multilayer films described in any one of claims 1 to 6.
8. A package body sealed by ultrasonic waves using a multilayer film for ultrasonic sealing according to any one of claims 1 to 6.
9. A package formed by sealing the laminate according to claim 7 using ultrasonic waves.

Description

This invention relates to a multilayer film for ultrasonic sealing and a packaging material. In packaging films for food products such as Western-style confectionery and snacks, the trend towards monomaterial (single-material) designs is progressing to promote recycling and reduce environmental impact. To accommodate monomaterial designs, multilayer films such as biaxially oriented polyethylene/unoriented polyethylene sealant are required, in contrast to conventional multilayer laminate configurations of different materials (e.g., multilayer films of stretched polyethylene terephthalate (OPT) and unoriented polypropylene (CPP)). However, conventional multilayer films made of biaxially oriented polyethylene/unoriented polyethylene sealant, which are designed for monomaterial construction, have a problem in that the heat resistance of the multilayer film surface decreases due to the difference in heat resistance between the materials, raising concerns about reduced packaging suitability. Furthermore, efforts to reduce environmental impact by creating thinner films are accelerating. On the other hand, multilayer films that can be ultrasonically sealed using ultrasound that can heat only the sealing surface are being investigated. To date, a laminated film has been disclosed that can be strongly welded by ultrasonic welding, comprising an outer layer made of uniaxially oriented polypropylene film, a barrier layer and a resin intermediate layer, and a sealant layer with a high Young's modulus, which may be made of linear low-density polyethylene (see, for example, Patent Document 1). However, in multilayer films that use polyethylene to accommodate monomaterialization, it has been difficult to obtain uniform and stable seal strength when ultrasonically sealed because the heat resistance of the materials differs. In addition, it is necessary to achieve rigidity of the film in order to obtain packaging suitability such as pillow packaging used for packaging of Western-style confectionery, snacks, etc. Moreover, the laminated film described in Patent Document 1 includes a polyethylene-based resin layer and a polypropylene-based resin layer and does not support monomaterialization. The inventors of the present invention proposed a multilayer film described in Patent Document 2 as a monomaterial polyethylene-based film with suitable rigidity that can be ultrasonically sealed. However, they conducted further studies to achieve thinner films and improved sealing strength. Japanese Patent Publication No. 2017-217902International Publication No. 2023/166995 Figure 1 is a schematic cross-sectional view showing an example of a multilayer film for ultrasonic sealing according to the present invention.Figure 2 is a schematic cross-sectional view showing another example of the multilayer film for ultrasonic sealing according to the present invention.Figure 3A is a schematic cross-sectional view (part 1) showing an example of an ultrasonic sealing apparatus used for ultrasonic welding of a multilayer film for ultrasonic sealing according to the present invention.Figure 3B is a schematic cross-sectional view (part 2) showing an example of an ultrasonic sealing apparatus used for ultrasonic welding of a multilayer film for ultrasonic sealing according to the present invention.Figure 3C is a schematic cross-sectional view (part 3) showing an example of an ultrasonic sealing apparatus used for ultrasonic welding of a multilayer film for ultrasonic sealing according to the present invention. (Multilayer film for ultrasonic sealing) The ultrasonic sealing multilayer film of the present invention is an ultrasonic sealing multilayer film having at least a surface layer and a sealing layer, and capable of being sealed by ultrasound. <Surface layer> The surface layer contains 20% by mass or more of high-density polyethylene. The surface layer may be a single layer or a plurality of layers. The surface layer may be a surface layer on which printing of the packaging film can be applied. The surface layer of the multilayer film for ultrasonic sealing according to the present invention is preferably a layer whose main resin component is a polyethylene-based resin, as it can be monomaterialized. However, other resins that can be co-extruded may be used in combination, as long as they do not impair the effects of the present invention. "The main resin component" specifically means that 70% or more by mass of the resin component used in the surface layer is polyethylene resin, preferably 80% or more by mass is polyethylene resin, and more preferably 90% or more by mass is polyethylene resin. --Polyethylene resin-- Examples of polyethylene resins that can be used include polyethylene elastomers such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), ethylene-vinyl acetate copolymer (EVA), and ethylene-α-olefin copolymer; ethylene copolymers such as e