JPH10139065A - Deep-drawn gas pack package - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily identify a seal failure position by specifying the entire haze of a heat-sealed part of a composite film for constituting a lid material and a bottom material having a specific entire haze wherein either has a cohesive- failure type sealing layer. SOLUTION: In the deep-drawn gas pack package comprising a lid material and a bottom material made of a composite film, either of the composite films constituting the lid material and the bottom material has a cohesive-failure type sealing layer with the entire haze in a range of 10 to 20%, while the other composite film has the entire haze of 6% or less. By heat-sealing the composite films, the entire haze of a heat-sealed part of both should be in a range of 1 to 7%. If a failure in sealing should occur, transparency at the part might not be improved, while if peeling of the sealed part should occur during distribution, transparency at the part might drop. Blend of polyolefin containing resin may be selected as the sealing layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a deep drawn gas pack package having a cohesive failure type seal layer formed by blending two or more resins which are incompatible in a molten state. In particular, the present invention relates to an easily-openable deep-drawn gas pack package suitable for packaging fresh foods and processed foods.

[0002]

2. Description of the Related Art There are various forms of packaging of fresh foods and processed foods using a plastic film having a high gas barrier property. In recent years, it is necessary to maintain freshness and control microorganisms in response to the expiration date labeling. And gas pack packaging has become popular. That is, gas pack packaging is a packaging technology in which the air inside the package is degassed and filled with a gas such as carbon dioxide or nitrogen instead.By replacing the gas, the preservability of the contents is enhanced. I have.

[0003]

Further, in a deep-drawing gas pack package, a composite film is selected as a cover material and a bottom material constituting the gas pack package. A layer structure that satisfies openability has also been determined. For example, in a composite film having a total haze of 6% or less, the interlayer bonding strength between the seal layer and the adjacent base layer is made weaker than the seal strength (the bond strength at the interface of the heat-sealed seal layer). A delamination type layer configuration has been proposed.

Certainly, this allows not only the sealing performance to be maintained at the time of distribution of the package, but also the separation between the sealing layer and the adjacent base material layer at the time of taking out the packaged object. You can get something easy. However, a problem with this type of delamination type seal layer is that the peel strength tends to decrease at high temperatures, and the seal layer heated during heat sealing delaminates from the base material layer. It is in the point of raising. In addition, when defects such as defective sealing due to poor contact with the hot plate occur at the time of heat sealing, there is no means for confirming this.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that a cohesive failure type formed by blending two or more resins which are incompatible in a molten state is blended. By adopting the sealing layer of (1) and selecting an appropriate lid material and bottom material, the transparency of the heat-sealed portion of the deep-drawn gas pack package is clearly improved as compared to before heat sealing, and The total haze of the material and the lid material was adjusted to 1 to 7%. Therefore, if there is a defective seal, the transparency of that part is not improved, so that the defective position can be easily confirmed. Further, if peeling of the seal portion occurs at the time of distribution, the transparency of that portion is reduced, and this can be easily confirmed.

That is, according to the present invention, in a deep-drawn gas pack package comprising a lid and a bottom made of a composite film, one of the composite films constituting the lid and the bottom is made of a cohesive failure type seal. In the composite film having layers, the total haze is in the range of 10 to 20%, and the total haze of the other composite film is 6% or less. By heat sealing these, the total haze of both is 1%. ~ 7% in the deep drawn gas pack package characterized by the above-mentioned.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The deep drawn gas pack package of the present invention comprises a lid material and a bottom material for containing contents,
Further, both the lid member and the bottom member are composed of a composite film. Thus, the composite film constituting the lid material and the bottom material basically consists of a seal layer for providing a sealing property to the package and a base material layer for providing a gas barrier property and the like. As the material of the seal layer of the present invention,
There is no particular limitation, and it can be selected from conventional ones.
1-50 thickness in terms of cost and low-temperature heat sealing
A polyolefin resin of μm is used.

However, one of the sealing layers of the composite film used in the present invention must be of a cohesive failure type in order to impart easy-openability to the package. In general, when the sealed gas pack package is to be resealed at the sealed portion, the portion to be broken at the time of opening differs depending on the layer structure of the composite film. That is, occurring between the seal layer and the adjacent substrate layer,
It is roughly classified into three types: an interlayer delamination type, an interfacial delamination type that occurs at the interface between both seal layers, and a cohesive failure type that occurs in one of the seal layers. In the cohesive failure, the cohesive force (peel strength) of the material constituting the seal layer is determined by the interlaminar adhesive strength between the adjacent base material layer and the strength of the seal interface when heat-sealing with the other seal layer (seal strength). Occurs when weaker than any of the above.

Therefore, the cohesive failure type seal layer must satisfy the following conditions: (seal strength)> cohesive force (= peel strength) and (interlayer adhesive strength)> cohesive force (= peel strength). Each of these various strengths can be obtained by installing a test piece having a width of 15 mm in a tensile tester and measuring the peel strength at a tensile speed of 200 mm / min. It should be noted here that whether or not one composite film has a cohesive failure type seal layer is determined not only by the adjacent base layer of the same composite film but also by the seal layer of the composite film to be sealed. However, it depends on what kind of material is selected.

However, such a cohesive failure type seal layer is actually a blend of two or more resins which are incompatible in a molten state, preferably a blend of two or more polyolefin resins. This is realized by appropriately selecting from. As a blend of two or more olefin resins, specifically, a blend resin of an ethylene-vinyl acetate copolymer (vinyl acetate content of 3 to 15 mol%) and polybutene-1, ethylene-α Blend of olefin copolymer and polybutene-1, ethylene-α
It is preferable to select from a blend of an olefin copolymer and polypropylene.

In the present invention, further, of the composite film having the cohesive failure type seal layer, of the composite film constituting the lid material and the composite film constituting the bottom material, the entire haze including the base material layer is included. Is in the range of 10 to 20%, and the total haze of the other composite film is 6% or less. By heat sealing these, the total haze of the bottom material and the lid material is in the range of 1 to 7%. It is necessary to be in. By the way, in the present invention, as a substrate layer constituting a composite film on which a lid material or a bottom material is to be formed, various conventional synthetic resin substrate layers can be selected.
Specifically, A-PET resin as a transparent rigid material,
Examples thereof include a layer having a thickness of 10 to 500 μm made of PET resin or the like, and a layer having a thickness of 1 to 50 μm made of EVOH, K-coated nylon, nylon, glass-deposited plastic or the like as a transparent gas barrier material. others,
For example, an adhesive layer having a thickness of 1 to 30 μm used for the composite of these materials may be used. For example, it is preferable that the seal layer and the base material layer be firmly bonded by an adhesive layer.

In such a composite film including a base material layer, it is not so difficult to make the total haze including the seal layer and the adhesive layer 6% or less. Rather, as a composite film, the total haze before heat sealing is 10 to 20%, and after heat sealing, the total haze including the bottom material and the lid material is reduced to 1 to 7%.
Depending on the choice of the resin used for the seal layer as described above,
Achieved for the first time. That is, by selecting a blend of a polyolefin-based resin as the seal layer, the composite film including the base layer has a total thickness of 10 to 20% before heat sealing, and after the heat sealing, the bottom material and The total haze with the lid can be reduced to 1 to 7%.

The method for producing these composite films is not particularly limited. For example, each of these layers is separately formed by an appropriate technique, and a stretched film, if necessary, may be formed into a composite film by lamination or dry lamination, or may be formed into a composite film by application or co-extrusion. It may be something.

The deep-drawn gas pack package of the present invention is obtained by applying the deep-drawing technique to the composite film, shaping the lid material and the bottom material into desired shapes, storing the contents therein, It is commercialized by sealing. At the time of deep drawing, contact heating is performed by a hot plate from one side of the bottom material film, and when the entire film is given a sufficient amount of heat and softened, a molded product according to a mold is obtained by air pressure or vacuum forming. On the other hand, the contents to be contained include fresh food such as raw meat, ham,
Processed foods such as sausages, wieners, hamburgers,
Other examples include prepared foods and seafood paste products.

[0015]

EXAMPLES The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited by these examples. The terms and symbols used in the following examples and comparative examples have the following meanings. Terms and symbols Meaning LDPE Low density polyethylene (density 0.92, MFR = 1.5) EVA ethylene-vinyl acetate copolymer (vinyl acetate content 5 mol%, MFR = 2.3) PB-1 polybutene-1 ( LL ethylene-hexene-1 copolymer (density 0.92, MFR = 2.4) PP polypropylene (density 0.9, MFR = 4.0) EVOH ethylene-vinyl Alcohol copolymer (ethylene content 38 mol%, degree of saponification 99%, MFR = 3.5) KONy Vinylidene chloride coated biaxially oriented nylon film (Santonier SG, manufactured by Mitsubishi Chemical Corporation) Ny 6 nylon (intrinsic viscosity 4.5 dg) / L) AD Maleic anhydride-modified polyethylene resin (density 0.92, MFR = 1.5) Tuffmer ethylene-α-olefin copolymer Body (density 0.89, MFR = 3.0) PET biaxially stretched polyethylene terephthalate (manufactured by Diafoil Hoechst) A-PET polyethylene terephthalate (Iv = 0.67) / interlayer of co-extruded film // dry lamination ( Adhesive thickness 3-5μm) Underline Cohesive failure type seal layer

[Example 1] A composite film constituting a lid material is a PET film, EVOH, Ny, AD and L
DPE was prepared by dry laminating a coextruded film composited in this order. At the time of dry lamination, the EVOH layer of the co-extruded film on the side opposite to the LDPE layer constituting the seal layer of the composite film was laminated so as to be in contact with the PET film via an adhesive. The thickness of each layer was as follows. PET 15 μm EVOH 5 μm Ny 10 μm AD 10 μm LDPE 30 μm

The composite film constituting the bottom material is made of A-PE
A T-film and a co-extruded film in which a blend of EVOH, Ny, AD and a polyolefin-based resin (a mixture of EVA and PB-1 in a weight ratio of 60:40) are combined in this order are dried. It was prepared by lamination. At the time of dry lamination, the EVOH layer of the co-extruded film on the side opposite to the polyolefin resin blend layer constituting the cohesive failure type seal layer of the composite film comes into contact with the A-PET film via an adhesive. Layered. The thickness of each layer was as follows. A-PET 300 μm EVOH 15 μm Ny 15 μm AD 10 μm Resin blend 10 μm

The lid material and the bottom material made of the above-mentioned composite film are deep-drawn and shaped, and the sealing layer provided on the lid material and the cohesive failure type sealing layer provided on the bottom material are overlapped with each other. Sealing was performed to obtain a gas pack package.
In addition, all the haze of the said cover material and the bottom material composite film before heat sealing was measured by the measuring method of the haze value of JISK6714. The total haze of the heat-sealed portion of the package after heat-sealing was measured in the same manner. These results are as shown in the column before sealing and the column of the sealing portion in Table 1, respectively.

[Examples 2 to 6] In Example 1, Table 1
As shown in Table 2, the packages of Examples 2 and 3 were obtained in exactly the same manner as in Example 1, except that the composition of the cohesive failure type seal layer was changed. In Examples 1 to 3, Table 1
As shown in, the sealing layer provided on the lid member and the various cohesive failure type sealing layers provided on the bottom member were replaced, and the thickness of each layer was slightly changed. And the package bodies of Examples 4 to 6 were obtained. Also in these examples, the total haze was measured in the same manner as in Example 1, and the results are shown in Table 1.

[Comparative Example 1] The composite film constituting the lid material was a PET film, a KONy film, a PP blend (a mixture of PP and tougher in a weight ratio of 60:40) and LDPE. Extruded film and
It was prepared by dry lamination in this order. At the time of dry lamination, the PP blend layer of the co-extruded film on the side opposite to the LDPE layer constituting the easy peel layer of the composite film was overlapped with the KONy film via an adhesive. The thickness of each layer was as follows. PET 15 μm KONy 16 μm Blend 30 μm LDPE 3 μm

The composite film constituting the bottom material is A-PE
T film, EVOH, Ny, AD and LDPE
And a co-extruded film composited in this order were prepared by dry lamination. When dry laminating,
The EVOH layer of the co-extruded film on the side opposite to the LDPE layer constituting the sealing layer of the composite film was overlapped with the A-PET film via an adhesive. Also,
The thickness of each layer was as follows. A-PET 300 μm EVOH 15 μm Ny 15 μm AD 10 μm LDPE 10 μm

In this comparative example, since the same resin was used for both seal layers, breakage occurs between the LDPE layer and the PP blend layer in the lid material at the time of resealing after sealing.
It turns out that it corresponds to a delamination type seal layer. Also in this comparative example, the total haze was measured as in Example 1, and the results are shown in Table 1.

[0023]

[Table 1]

From Table 1, it can be seen that, in Examples 1 to 6, which are the composite films of the present invention, either the lid material or the bottom material has a high haze of 10 to 20% before sealing, but after sealing, It can be seen that the total haze was 5% or less, and the transparency was improved. On the other hand, since the comparative example does not have the cohesive failure type seal layer, it can be seen that the haze hardly changes before and after sealing.

[0025]

According to the present invention, since a cohesive failure type seal layer formed of a blend of two or more polyolefin resins is provided, the seal strength is changed by changing the composition or the mixing ratio. Can be adjusted, and the haze can be as high as 10 to 20%. On the other hand, if the heat sealing with the sealing layer is performed appropriately, the sealing portion becomes transparent to a total haze of about 1 to 7%.
Therefore, it is possible to detect a defective seal by the change in the transparency.

Claims (2)

[Claims] 1. A deep drawn gas pack package comprising a lid and a bottom made of a composite film, wherein one of the composite films constituting the lid and the bottom has a cohesive failure type seal layer. In the film, the total haze is in the range of 10 to 20%, and the total haze of the other composite film is 6% or less. By heat sealing these, the total haze of both is 1 to 7%. A deep drawn gas pack package characterized by being within the range. 2. The deep drawing gas pack according to claim 1, wherein the resin used for the cohesive failure type seal layer is a blend of two or more resins which are incompatible in a molten state. Packaging.