JPH0212188B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laminate for easy-open sealed packaging and a method for producing the same.

There are two types of easy-open sealants: interfacial peeling type and cohesive failure type.

Generally speaking, when liquid contents are sealed and packaged and subjected to heat sterilization, the container is filled with the contents and sealed with as little air as possible to prevent the bag from breaking. . In other words, liquid sealing is performed through the contents. In this case, it is difficult to achieve an easy-to-open seal using an interfacial peeling type sealant because it is difficult to obtain stable seal strength. On the other hand, with a cohesive failure type sealant, since the adhesive interface is completely fused, easy-to-open sealed packaging can be performed without fear of bag breakage.

However, hermetic seals using cohesive failure sealants currently have the following problems.

That is, polypropylene-polyethylene blend polymers are currently known as materials for cohesive failure type sealants.

However, because polypropylene and polyethylene have poor compatibility, it is extremely difficult to form a polypropylene-polyethylene blend polymer into a film, and the surface of the formed film tends to be uneven, and in the worst case, the film may have holes. A film is formed.

When forming packaging materials for easy-open packaging, it is necessary to layer a sealant on a thermoplastic resin film or metal foil base material, but due to the poor surface condition of the sealant, there is a layer between the base material layer and the sealant layer. The strength becomes extremely unstable. This interlayer strength greatly affects the peel strength when opening the package. In extreme cases, delamination occurs between the base material layer and the sealant layer, resulting in a filmy state and the contents not being able to come out.

The present inventor has conducted research to develop a method that eliminates the above-mentioned drawbacks and maximizes the advantages of using a polypropylene-polyethylene blend polymer as a sealant material. α-olefin copolymer, high-density polyethylene,
Alternatively, by forming a multilayer film with a resin that is easy to form, such as low-density polyethylene, it is not only easy to form a polypropylene-polyethylene blend polymer film, but also the film is free from additives (slip agents, oxidation The present invention was completed based on this knowledge.

That is, the gist of the first invention is that at least the layer adjacent to the cohesive failure sealant layer is made of ethylene-α olefin copolymer, high-density polyethylene, or low-density polyethylene, and the supporting layer or layers are made of polypropylene-polyethylene. A laminated film on which a 10-100 μ thick cohesive failure sealant layer made of a blended polymer is laminated is placed on a base material made of thermoplastic resin, metal foil, paper, or a composite material thereof, with the support layer side facing the base material side. A second gist of the invention is a laminated material for easy-open sealed packaging, characterized in that the laminated material is laminated, and the gist of the second invention is that it is easy to form a film consisting of at least one layer of polypropylene-polyethylene blend polymer, and that the polypropylene-polyethylene blend polymer It is made from a polypropylene-polyethylene blend polymer by extruding it with ethylene-α olefin copolymer, high-density polyethylene, or low-density polyethylene, which is a resin with good heat fusion properties, and forming a film by a T-die method or an inflation method. A cohesive failure sealant layer with a thickness of 10 to 100 μ and supporting it, at least a layer adjacent to the cohesive failure sealant layer consisting of an ethylene-α olefin copolymer, high density polyethylene, or low density polyethylene, one or more layers. A process of obtaining a laminated film consisting of a support layer and laminating the laminated film to a base material made of thermoplastic resin film, metal foil, paper, or a composite material thereof with the side surface of the support layer facing the base material side. This is a method for producing an easily openable sealed packaging laminate, comprising the steps of:

Hereinafter, the present invention will be explained in detail with reference to the drawings.

First, a polypropylene-polyethylene blend polymer is extruded together with a resin that is easy to form into a film and has good thermal fusion properties with the polypropylene-polyethylene blend polymer, and a film is formed by a T-die method or an inflation method to obtain the film shown in Figure 1. A laminated film 3 consisting of a cohesive failure sealant layer 2 made of a polypropylene-polyethylene blend polymer and a support layer 1 supporting the sealant layer 2 is obtained.

Next, this laminated film 3 is processed as shown in the second figure.
By laminating the support layer side face to the base material 4, the easily openable sealed packaging laminate 5 of the present invention is obtained.

Therefore, in the present invention, ethylene-α olefin copolymer, high Density polyethylene and low density polyethylene are preferred.

Next, the thickness of the cohesive failure sealant layer made of polypropylene-polyethylene blend polymer is
A value of 10 to 100μ is appropriate; if it is less than 10μ, the peel strength after heat fusion is below practical strength, which is undesirable; if it is more than 100μ, not only will the cost increase, but the film formability will be extremely poor, which is undesirable. .

Next, in the present invention, along with a polypropylene-polyethylene blend polymer and a resin that is easy to form into a film and has good heat fusion properties with the polypropylene-polyethylene blend polymer, polypropylene, polyethylene, ethylene-
By extruding resins such as α-olefin copolymer, ethylene-vinyl acetate copolymer, saponified ethylene-vinyl acetate copolymer, ionomer resin, polyamide, and polyvinylidene chloride, the support layer is composed of two resin layers. Also good.

Next, in the present invention, polyethylene as a base material,
Thermoplastic resins such as polypropylene, polyester, polyamide, polycarbonate, polystyrene, and polyvinyl chloride, metal foils such as aluminum foil, paper, or composite materials thereof can be applied.

The easily openable sealed packaging laminate of the present invention can be used as a lid material or a material for sheet-formed containers.

As described in detail above, according to the easy-open laminate for sealed packaging and the method for producing the same of the present invention, a cohesive failure sealant layer made of a polypropylene-polyethylene blend polymer with a good surface condition is applied to the base material with sufficient interlayer strength. It can be laminated on top of polypropylene-polyethylene blend polymers, and it can be formed without additives such as slip agents and antioxidants, which are undesirable from a food hygiene perspective, so it exhibits stable peel strength. At the same time, the sealant layer does not peel off from the base material, and since the sealant layer does not contain any harmful additives, it is possible to produce an easily openable sealed packaging laminate that poses no problems in terms of food hygiene.

Next, the present invention will be specifically explained with reference to Examples.

Example 1 Ethylene-α-olefin copolymer (density 0.93, MI2) and polypropylene-polyethylene blend polymer (polypropylene; 50 wt%, random copolymer with ethylene content 3.5%, density 0.90, MI= 6.0, polyethylene; 50wt
%, density 0.96, MI=0.2). Thickness: 20μ ethylene-α olefin copolymer resin 20μ polypropylene-polyethylene blend polymer
The total is 40μ. Use this as a base material (PET12μ/Al40μ)
Using an isocyanate adhesive, the aluminum foil and the ethylene-α olefin copolymer resin layer are bonded together. Then, a lid material was formed.

When this was heat-sealed into a polypropylene container (sealing conditions of 200° C., 3 kg/cm ² , 1 sec), it exhibited a peel strength of 1500 g/15 mm width and good ease of opening. Further, even after retort treatment at 135°C for 30 minutes, the peel strength remained good without any change.

Example 2 High-density polyethylene (density 0.954, MI 0.9) and polypropylene-polyethylene blend polymer (polypropylene; 50 wt%,
Random copolymer with 3.5% ethylene content, density
0.90, MI6, polyethylene; 50wt%, density 0.96,
MI0.2) is formed into a multilayer film. The thickness is 20μ of high-density polyethylene and 20μ of polypropylene-polyethylene blend polymer, totaling 40μ. This is used as a base material (PET12μ/Al40μ) and an aluminum foil and a high-density polyethylene resin layer are attached using an isocyanate adhesive. Then, a lid body was formed. Heat seal this in a polypropylene container (200℃3
Kg/cm ² 1sec sealing condition), peel strength
It showed good ease of opening with a width of 1700g/15mm. or
Even after retort treatment at 135°C for 30 minutes, the peel strength remained good with no change.

Example 3 Low density polyethylene (density 0.924MI0.7) and polypropylene-polyethylene blend polymer (polypropylene; 50wt%,
Random copolymer with 3.5% ethylene content, density
0.90, MI=6.0 polyethylene; 50wt%, density 0.96,
MI=0.2) is deposited in multiple layers. The thickness is 20μ of low density polyethylene resin and 20μ of polypropylene-polyethylene blend polymer, totaling 40μ.

This is used as a base material (PET12μ/Al40μ) and an aluminum foil and a low density polyethylene resin layer are attached using an isocyanate adhesive. Then, a lid material was formed. When this was heat-sealed in a polypropylene container (sealing conditions of 3 kg/cm ² 1 sec at 200° C.), it exhibited good ease of opening with a peel strength of 1700 g/15 mm width.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a laminated film, and FIG. 2 is a cross-sectional view of a laminated material for easy-open sealed packaging. DESCRIPTION OF SYMBOLS 1... Support layer, 2... Cohesive failure sealant layer, 3... Laminated film, 4... Base material, 5... Laminated material for easy-open sealed packaging.

Claims (1)

[Scope of Claims] 1. At least the layer adjacent to the cohesive failure sealant layer is made of an ethylene-α olefin copolymer, high-density polyethylene, or low-density polyethylene, and one or more supporting layers include a polypropylene-polyethylene blend polymer. thickness consisting of
A laminated film with a cohesive failure sealant layer of 10 to 100 microns laminated to a base material made of thermoplastic resin film, metal foil, paper, or a composite material thereof, with the side surface of the support layer facing the base material side. A laminated material for easy-open sealed packaging characterized by: 2. Ethylene-α, which is a resin that is easy to form into a film consisting of at least one layer of polypropylene-polyethylene blend polymer and has good thermal fusion properties with polypropylene-polyethylene blend polymer.
Extruded with olefin copolymer, high-density polyethylene, or low-density polyethylene and formed into a film by T-die method or inflation method to form a cohesive failure sealant layer with a thickness of 10 to 100 μm made of polypropylene-polyethylene blend polymer and support it. , at least the layer adjacent to the cohesive failure sealant layer is an ethylene-α olefin copolymer,
A process of obtaining a laminated film consisting of one or more support layers made of high-density polyethylene or low-density polyethylene, and a process of obtaining a laminated film consisting of a support layer of one or more layers made of high-density polyethylene or low-density polyethylene; 1. A method for producing an easily openable sealed packaging laminated material, comprising the step of laminating the supporting layer side face to the base material side.