JP2023117640A - Laminate and package - Google Patents

Abstract

The present invention provides a laminate in which a base film and a heat sealing layer can be easily separated to recover a monomaterial polyolefin resin, and a packaging body using this laminate as a packaging film. A laminate 10 is constructed by laminating a base film 11 and a heat sealing layer 13 with an easily peelable layer 12 interposed therebetween. Both the thermal adhesive layer 13 and the easily peelable layer 12 are made of polyolefin resin. The easily peelable layer 12 is made of a mixture of polyethylene resin and other polyolefin resin, and this polyethylene resin and other polyolefin resin are not compatible with each other. Since the easily peelable layer 12 easily undergoes cohesive failure, the base film 11 and the heat sealing layer 13 can be easily peeled and separated to recover the polyolefin resin. [Selection diagram] Figure 2

Description

TECHNICAL FIELD The present invention relates to a laminate having an easily peelable layer, and a laminate capable of separating a layer composed only of polyolefin resin from other layers by peeling the easily peelable layer. This laminate is used, for example, as a film for packaging, and after use, only the polyolefin resin can be recovered and recycled.

A film for packaging that constitutes a packaging bag or the like is generally constructed by laminating a heat-sealable layer on the inner surface of a base film. A polyolefin resin is usually used as the heat-sealable layer, but various films such as a polyester resin film are used as the base film. In some cases, a vapor-deposited film obtained by vapor deposition of metal or a multi-layered film containing metal foil in its layer structure is used as a base film for its light-shielding properties and gas-barrier properties.

By the way, from the viewpoint of SDGs and environmental protection, it is recommended to collect and recycle used materials. However, like the heat-sealable layer described above, a layer consisting only of polyolefin resin may contain different types of polyolefin resins, such as a mixture of polyethylene resin and polybutene resin. However, if it contains different resins such as polyolefin resin and polyester resin, it cannot be recycled. Of course, it is also impossible to regenerate polyolefin resins mixed with metals.

Therefore, in order to recover and recycle the packaging film, it is necessary to separate each material (mono-material) of a single type and recover and recycle each material (mono-material). For example, in order to recover and recycle a heat-sealable layer made of polyolefin resin, it is necessary to peel this heat-sealable layer from the base film.

Such a packaging film in which the heat-sealable layer can be peeled off from the base film is described in Patent Documents 1 and 2, for example. Patent document 1 uses a magnetic material for the adhesive layer that bonds the base film and the heat-sealable layer. Patent Document 2 uses a solvent-soluble adhesive layer. Considering that a consumer separates a mono-material heat-sealable layer from a used packaging bag, the packaging films described in Patent Documents 1 and 2 cannot be said to be realistic techniques.

Japanese Patent No. 4274684 WO2020/166685

Accordingly, the present invention provides a laminate from which the base film and the heat-sealable layer can be easily separated and the mono-material polyolefin resin can be recovered, and a package using this laminate as a packaging film. for the purpose.

That is, the invention according to claim 1 is a laminate configured by laminating a base film and a heat-sealable layer via an easily peelable layer,
Both the heat-sealable layer and the easy peeling layer are made of polyolefin resin,
The laminate is characterized in that the easily peelable layer is made of a mixture of a polyethylene resin and another polyolefin resin, and the polyethylene resin and the other polyolefin resin are incompatible with each other.

In addition, it is desirable that the easy peeling layer contains 70% by mass or more of polyethylene resin. Further, the other polyolefin resin can be composed of polybutene resin.

Further, the heat-sealable layer can be made of polyethylene resin.

Then, by using this laminate as a packaging film to package the contents, a package can be constructed. In this package, it is desirable that a trigger for separating the base film and the heat-sealable layer from the easily peelable layer is provided at the end of the packaging film.

In the present invention, the easily peelable layer is made of a mixture of polyethylene resin and other polyolefin resin, and the polyethylene resin and the other polyolefin resin are incompatible with each other. , separation is likely to occur at the interface between the polyethylene resin and the other polyolefin resin. Therefore, this easy peeling layer has a property of cohesive failure. Since the base film and the heat-fusible layer are laminated via the easily peelable layer, the base film and the heat-fusible layer can be separated by peeling due to cohesive failure of the easily peelable layer. . This peeling can be done by pinching the edge of the base film and the edge of the heat-sealable layer and tearing off, which is easy for the consumer.

In addition, the base film and the heat-sealable layer are peeled and separated in a state in which part of the easily peelable layer that has undergone cohesive failure adheres to the heat-sealable layer. Since they consist of, they can be reproduced as one.

FIG. 1 is a perspective view of a pillow packaging bag using the laminate of the invention as a packaging film according to an embodiment of the invention. FIG. 2 is an explanatory vertical cross-sectional view of the pillow packaging bag of FIG.

Specific examples of the present invention will now be described with reference to the accompanying drawings. FIG. 1 is a perspective view of a pillow packaging bag A using the laminate of the invention as a packaging film according to an embodiment of the invention, and FIG. 2 is a longitudinal sectional view for explaining the same. Note that illustration of the contents is omitted in FIG.

As is well known, a pillow packaging bag A is formed by rolling a packaging film into a tubular shape, overlapping both ends of the packaging film in a palm-to-palm shape, and sealing to form a back seal line a, and after containing the contents, It is hermetically sealed by sealing both ends. In FIG. 1, symbols "b" and "c" indicate the seal lines at both ends, ie, the upper seal line b and the lower seal line c.

The packaging film that constitutes this pillow packaging bag A is composed of a laminate 10. As can be seen from FIG. It is configured by laminating through. The heat-sealable layer 13 constitutes the inner surface of the pillow packaging bag A, and the heat-sealable layers 13 are heat-sealed to form the back seal line a, the upper seal line b, and the lower seal line c. formed. The base film 11 constitutes the outer surface of the pillow packaging bag A. As shown in FIG. In the figure, d1 indicates a notch provided in the back seal line a, and d2 indicates a tear guide line following this notch d1.

The base film 11 may be any film, and may have a single-layer structure or a multi-layer structure, but if it contains a material different from the polyolefin resin, the gist of the present invention can be utilized.

Examples of the substrate film 11 having a single-layer structure include a polyester resin film and a polyamide resin film. A polyolefin resin film such as a polypropylene resin film may be used.

Examples of the base film 11 having a multilayer structure include a film obtained by bonding a polyamide resin film or an aluminum foil to a polyester resin film, or a vapor-deposited film obtained by vacuum-depositing a metal or an inorganic material. Of course, these may be laminated to form a multi-layer structure of three or more layers, or may be printed.

As described above, the heat-sealable layers 13 are heat-sealed to form the seal lines a, b, and c when the pillow packaging bag A is formed. A conventionally known sealant can be used for such a heat sealing layer 13 . It is generally a polyolefin resin. For example, polyethylene resins such as low-density polyethylene resin, medium-density polyethylene resin, and linear low-density polyethylene resin can be used. In addition, it is also possible to use polypropylene resin, but when the easy peeling layer 12 is mainly composed of polyethylene resin as described later, heat-sealable resin is used as the main component of the easy peeling layer 12 Layer 13 is also preferably made of polyethylene resin.

Next, the easily peelable layer 12 adheres the base film 11 and the heat-sealable layer 13 to prevent them from being carelessly peeled off. and the heat-sealable layer 13 are easily peeled off to separate the mono-material polyolefin resin. For this reason, the easily peelable layer 12 must be made of polyolefin resin, like the heat-sealable layer 13 .

In order to facilitate peeling between the base film 11 and the heat-sealable layer 13, the easily peelable layer 12 is made of a mixture of polyethylene resin and other polyolefin resin, and the polyethylene resin and the other polyolefin resin are mixed. must be incompatible with each other. The heat-sealable layer 13 composed of a mixture of resins that are incompatible with each other in this way has a sea as the main resin component and islands as the other resin component, and the sea is dotted with islands, so-called " adopts a sea-island structure. Then, it is easy to separate at the boundary between the sea and the island, that is, at the interface between the two resin components. Therefore, the easily peelable layer 12 has a property of cohesive failure. Since the substrate film 11 and the heat-fusible layer 13 are laminated via the easily peelable layer 12, the base film 11 and the heat-fusible layer 13 are separated by cohesive failure of the easily peelable layer 12. can be separated by This peeling can be done by pinching the edge of the base film 11 and the edge of the heat-sealable layer 13 and peeling them off, which is easy for the consumer.

In addition, the base film 11 and the heat sealing layer 13 are peeled and separated in a state in which a part of the easy peeling layer 12 that has undergone cohesive failure adheres to the heat sealing layer 13, but the heat sealing layer 13 and the easy peeling layer Since both 12 are made of polyolefin resin, they can be recycled as a unit.

A polyethylene resin can be used as the main component of the easy peeling layer 12, that is, the resin component that accounts for the majority of the mass of the easy peeling layer 12. As shown in FIG. Polybutene resin can be used as the polyolefin resin which is not compatible with the polyethylene resin.

By the way, the inventor conducted an experiment to confirm the lamination strength and peelability by changing the compounding ratio of the polyethylene resin and the polybutene resin.

That is, first, a low-density polyethylene resin (trade name: LC600A) manufactured by Japan Polyethylene Co., Ltd. is used as the main component of the easy peeling layer 12, and a polybutene resin (trade name: BL4000) manufactured by Mitsui Chemicals, Inc. is mixed with this. The resulting mixture was used as the mixture for the easy peeling layer 12 . Then, using this mixture, the base film 11 and the heat-sealable layer 13 were laminated by an extrusion lamination method to produce the laminate 10 . The base film 11 is a two-layer film of a polyester resin film (thickness 12 μm) and an aluminum foil (thickness 7 μm). Also, the thermal adhesive layer 13 is a polyethylene resin film having a thickness of 60 μm. The thermally peelable layer 12 is formed by laminating the base film 11, the easily peelable layer 12, and the heat-sealable layer 13 so that the heat-sealable layer 13 is positioned between the aluminum foil of the base film 11 and the heat-sealable layer 13. A laminated body 10 was obtained. The thickness of the easy peeling layer 12 is 10 μm.

Then, the laminate strength (N/15 mm) between the base film 11 and the heat-sealable layer 13 of this laminate 10 was measured.

In addition, a pillow packaging bag A was produced using this laminate 10, and its peelability was determined.

These results are shown in Table 1. The compounding ratio (mass ratio) of the polyethylene resin and the polybutene resin in the easy peeling layer 12 is shown in the table. In the table, "LDPE" indicates polyethylene resin, and "PB" indicates polybutene resin.

From this result, when the blending ratio of the polyethylene resin contained in the easy peeling layer 12 is less than 70% by mass, the laminate strength is extremely small and it is easy to peel off carelessly. It can be understood that it has strength and therefore can prevent inadvertent delamination.

On the other hand, when the blending ratio of the polyethylene resin contained in the easy peeling layer 12 is 90% by mass or more, the lamination strength is high, so it can be understood that peeling becomes difficult.

Therefore, it is desirable that the blending ratio of the polyethylene resin contained in the easy peeling layer 12 is 70% by mass or more and less than 90% by mass.

Next, as shown in FIGS. 1 and 2, the end of the back seal line a is provided with a tab piece x in which the base film 11 is not adhered to the heat-sealable layer 13 . The gripping piece x is a trigger for peeling and separating the base film 11 and the heat-sealing layer 13 . It can be separated from the adhesion layer 13 by peeling.

The tab piece x can be provided in a process of laminating the base film 11 and the heat-sealable layer 13 by an extrusion lamination method. That is, when two films are laminated by an extrusion lamination method, resin is extruded and laminated in the center of these two films, but the resin is usually not laminated on both sides. The two films described above are not adhered on both sides where the resin is not laminated. This non-adhesive portion is called an "ear" and will be cut off in the subsequent steps, but by leaving the ear uncut, the above-described tab x can be formed.

That is, the mixture constituting the easily peelable layer 12 is melted, and the melted product is applied on one of the base film 11 and the heat-sealable layer 13, and then the other is overlaid and pressure-bonded to be laminated and integrated. . At this time, the melt is applied only to the center of the base film 11 or the heat-sealable layer 13, and both sides thereof are left uncoated. This non-applied portion corresponds to the ear and can be used as the tab piece x.

As is clear from the above description, the package A can be separated by peeling the base film 11 from the heat-sealable layer 13 by pinching and pulling the tab x. The peeling principle is the cohesive peeling of the easy peeling layer 12. Therefore, part of the material constituting the easy peeling layer 12 adheres to the heat sealing layer 13, and is heat-fused with the base film. Although the adhesive layer is separated by peeling, since both the heat-sealable layer and the easily peelable layer are made of polyolefin resin, they can be regenerated as one.

The package A can be opened by tearing from the notch d1 along the tear guide line d2.

Although the pillow packaging bag has been described above as an example, it is obvious that the present invention is not limited to this, and that flat bags, gusset bags, standing pouches, and the like may also be used.

A: Pillow packaging bag 10: Packaging film 11: Base film 12: Easy-peeling layer 13: Heat sealing layer a: Back seal line b: Upper seal line c: Lower seal line x: Tab piece

Claims (6)

A laminate configured by laminating a base film and a heat-sealable layer with an easily peelable layer interposed therebetween,
Both the heat-sealable layer and the easy peeling layer are made of polyolefin resin,
A laminate, wherein the easily peelable layer is made of a mixture of a polyethylene resin and another polyolefin resin, and the polyethylene resin and the other polyolefin resin are incompatible with each other. 2. The laminate according to claim 1, wherein the easily peelable layer contains 70% by mass or more of polyethylene resin. 3. The laminate according to claim 1, wherein the other polyolefin resin comprises polybutene resin. 4. The laminate according to any one of claims 1 to 3, wherein the heat-sealable layer is made of polyethylene resin. A package comprising the laminate according to any one of claims 1 to 4 used as a packaging film to package contents. 6. The package according to claim 5, wherein an edge of the packaging film is provided with a trigger for separating the base film and the heat-sealable layer from the easily peelable layer.

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