JPH06297655A - Co-extrusion composite film for gas pack wrapping - Google Patents

Abstract

(57) [Summary] [Object] To provide a coextrusion composite film which is excellent in hermeticity and unsealing ability and can be suitably used as a bottom material for gas pack packaging. [Structure] The outermost layer contains an ethylene-vinyl acetate copolymer as a main component and has a cohesive force of 500 to 1000 gf / 15.
Providing a seal peel layer with cohesive failure of mm width,
A coextrusion composite film for gas pack packaging, wherein the thickness of the seal / peel layer is in the range of 5 to 15 μm. [Effect] Since it has excellent sealing property after sealing and also has the ability to be easily opened, it can be suitably used as a gas pack package which is sealed with various lid materials and filled with an inert gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite film, and more particularly to a coextrusion composite film which is excellent in hermeticity and unsealing property and can be suitably used as a bottom material for gas pack packaging.

[0002]

2. Description of the Related Art As a gas pack package that can be stored for a long period of time, a composite film having a layered structure made of various resins is deep-drawn, and the deep-drawn bottom material is filled with contents such as sliced ham. The lid material is heat-sealed by enclosing an inert gas such as nitrogen gas. The resulting package does not easily leak the enclosed inert gas and requires extremely good sealing performance on the sealing surface to protect the contents during distribution and storage. However, there is no composite film having a so-called seal peel layer which satisfies both characteristics.

The composite film which is required to be easily opened is generally classified into an interfacial failure type and a cohesive failure type depending on the peeling state on the sealing surface, and differs depending on the resin used for the seal / peel layer. For example, as the interfacial destruction type, there is a combination of one side seal layer resin with ethylene-vinyl acetate copolymer and the other layer resin with an ionomer resin.
Examples thereof include a mixture of a vinyl acetate copolymer with another polyolefin resin such as polypropylene resin.

In the former interface destruction type, the seal temperature is easily affected, and the optimum temperature range during the sealing process is very narrow. Therefore, if the seal temperature is low, the seal becomes incomplete, and if the seal temperature is high, the seal is incomplete. It has the disadvantage that it is too strong to open. On the other hand, in the latter case, the optimum temperature range during sealing is wide, but "fluff", which causes thread-like residuals in the opening when opening, and "film residue", which causes incomplete opening, open There was a problem that it was difficult to use.

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems, and particularly in gas pack packaging for heat sealing such as frame sealing with a relatively narrow width, cohesion satisfying sealing property and easy opening property. The present invention succeeds in obtaining a coextrusion composite film having a breakage type seal / peel layer, and the gist thereof is that the outermost layer has an ethylene-vinyl acetate copolymer as a main component and a cohesive force of 500. -10
A seal peel layer having a cohesive failure property of 00 gf / 15 mm width is provided, and the thickness of the seal peel layer is 5 to 15
The coextrusion composite film for gas pack packaging is characterized in that it is in the range of μm.

The present invention will be described in detail below. The composite film of the present invention may be a multi-layered one composed of various resins, but the outermost layer has a seal
A peel layer is provided, and the cohesive force of this seal peel layer is 50
It must be in the range of 0 to 1000 gf / 15 mm width. The composite film is produced by a common coextrusion molding method. The cohesive strength of the seal / peel layer is 500 gf /
If the width is less than 15 mm, there is a problem that after sealing, the inert gas that has been opened and enclosed during handling during transportation may escape, and if it exceeds 1000 gf / 15 mm width, fluff or film residue that causes incomplete opening may occur. There is a problem that it is difficult to open it.

The cohesive force is measured by heat-sealing (sealing temperature = 130 ° C.) a composite film having an ethylene-vinyl acetate copolymer layer (EVA) as a seal layer on the outermost layer of the above-mentioned composite film, and then, Part pull speed 200
It is a numerical value obtained by measuring the peel strength in a stable peeled state when peeled at 180 ° in mm / min. The seal / peel layer contains EVA as a main component and can be combined with various resins as long as the cohesive force is satisfied. Especially, 100 parts by weight of EVA is added to polybutene-1 (PB-1). What added 15 to 45 weight part can be used conveniently. If it is less than 15 parts by weight, it is difficult to open at the time of opening, and if it exceeds 45 parts by weight, the sealing property is poor.

Here, the seal / peel layer is required to have cohesive failure which causes peeling due to cohesive failure at the time of opening. There is a problem that it is easily affected by and stable performance does not appear. The thickness of the seal layer is 5 to
It is necessary to set the thickness in the range of 15 μm, and if it is less than 5 μm, there is a problem that sealing performance is poor and film formation is difficult.
If the thickness exceeds 15 μm, there is a problem that fluffing or film residue occurs during opening and it is difficult to open. Hereinafter, the present invention will be specifically described with reference to Examples.

[0009]

[Example] The layer structure of the composite film was a 5-layer product having the following structure. [Ethylene-vinyl acetate copolymer saponified product / nylon 6-66 / adhesive resin / EVA / seal / peel layer] The mixing ratio and thickness of the resin used for the seal / peel layer are changed as shown in Table 1. A composite film for evaluation was obtained by coextrusion (the vinyl acetate content of EVA shown in Table 1 was 5% by weight). Using the obtained composite film, the cohesive force was measured and the unsealing property and the sealing property were evaluated by the methods described above, and the results are shown in Table 1.

Regarding the unsealing property, using the above-mentioned composite film, a bottom material was obtained by drawing to a diameter of 100 mm and a depth of 20 mm, and sliced ham was filled, and then an inert gas was sealed therein. A laminate obtained by dry laminating axially stretched polypropylene on the outer layer was used, frame sealing was performed at 130 ° C. with a heat sealer, and the lid material was peeled off with a finger to evaluate the peeled state. Those which could be easily peeled off and whose peeling surface was cohesively destroyed (O), those whose sealing strength was too strong and which were difficult to open (A), those which had fluff and film residue were (X). Regarding the hermeticity, 20 pieces were packed in a box using the above-mentioned sliced ham-filled package, and the state after the drop test (the bottom drop from the height of 1.8 m was performed 4 times) was evaluated. The good one (○) without peeling of the lid material and the one (×) in which peeling of the lid material was observed.

[0011]

[Table 1]

From Table 1, Sample 1 which is the composite film of the present invention
It can be seen that Nos. 4 to 4 are excellent in both openability and hermeticity.
On the other hand, Sample 5 having a low cohesive force is inferior in sealing performance, Sample 6 having an excessively high cohesive force is inferior in unsealing property, and fluff and film residue are generated also in Samples 7 and 8 in which the seal peel layer is too thick. It is found that the opening property is poor.

EFFECT OF THE INVENTION The coextrusion composite film of the present invention is excellent in hermeticity after sealing and has the ability to be easily opened. It can be suitably used for packaging.

Claims (2)

[Claims] 1. An outermost layer comprising an ethylene-vinyl acetate copolymer as a main component and having a cohesive force of 500 to 1000 gf /
A coextrusion composite film for gas pack packaging, characterized in that a seal peel layer having a cohesive failure property of 15 mm width is provided, and the thickness of the seal peel layer is in the range of 5 to 15 μm. 2. A seal / peel layer comprising 15 parts of polybutene-1 per 100 parts by weight of ethylene-vinyl acetate copolymer.
The coextrusion composite film for gas pack packaging according to claim 1, wherein the coextrusion composite film is added in an amount of ˜45 parts by weight.