JP3483338B2 - Easy-open composite film - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite film,
In particular, the present invention relates to an easy-opening composite film which has excellent heat sealing properties, can be easily peeled off at the time of use, and can be suitably used for gas pack packaging. 2. Description of the Related Art A gas barrier made of various gas barrier resins is used as a composite film used for so-called gas pack packaging, in which the contents and an inert gas are filled and packed after deep drawing. A composite film having a layer and a heat seal layer made of various resins is used. [0003] Many of such composite films are of the type in which the heat seal layer is peeled off by cohesive failure in order to impart peelability upon opening. However, in the cohesive failure type, the heat seal layer is composed of a mixture of various resins. Depending on the resin used, transparency is likely to be inferior, and both properties of heat seal strength and easy peelability must be satisfied. There was a problem that was difficult. SUMMARY OF THE INVENTION The present invention has found an easy-opening composite film which can solve the above-mentioned problems. The gist of the present invention is that the heat seal layer is formed from the polyolefin resin layer 1. A saponified ethylene-vinyl acetate copolymer layer 3 is disposed adjacent to the layer via the modified polyolefin resin layer 2, and the total thickness of the layer 1 and the layer 2 is 1 to 3.
The easy-opening composite film is 10 μm and has a delamination strength between the layer 2 and the layer 3 of 100 to 800 gf / 15 mm width. In the composite film of the present invention, a layer structure consisting of a heat seal layer, a polyolefin resin layer 1, a modified polyolefin resin layer 2, and a saponified ethylene-vinyl acetate copolymer layer 3 is essential. And the layer 3 is delaminated. The polyolefin resin used in the polyolefin resin layer 1 serving as the heat seal layer may be appropriately selected depending on the resin to be sealed, such as low density polyethylene, linear low density polyethylene, polypropylene, ethylene-vinyl acetate copolymer and the like. Can be suitably used. Further, as the resin used for the modified polyolefin resin layer 2, a carboxylic acid or carboxylic anhydride modified resin can be used, and it is preferable to select the same resin as the main resin as the polyolefin resin used for the heat seal layer. . [0008] The total thickness of the polyolefin resin layer 1 and the modified polyolefin resin layer 2 must be in the range of 1 to 10 µm. If it exceeds, there is a problem that the peeled portion exceeds the seal portion and the appearance is deteriorated. Here, the modified polyolefin resin layer 2
Layer of saponified ethylene-vinyl acetate copolymer 3
The saponified ethylene-vinyl acetate copolymer has an ethylene content of 32 to 47 mol%,
Those having a saponification degree of 95% or more can be suitably used. Further, a polyamide resin layer, a polyester resin layer, or the like may be provided adjacent to the saponified ethylene-vinyl acetate copolymer layer 3 as necessary. In the composite film of the present invention, the peel strength between the modified polyolefin resin layer 2 and the saponified ethylene-vinyl acetate copolymer layer 3 is 100 to 800 gf / 15 mm.
When the width is less than 100 gf / 15 mm, the sealing strength is too low and the bag is easily broken, and the width is 800 gf / 15 mm.
If the width exceeds f / 15 mm, there is a problem that the seal strength is too strong and it is difficult to open the seal. Hereinafter, the present invention will be described with reference to examples. EXAMPLES Example 1 Linear low-density polyethylene (7 μm) as a heat seal layer 1, acid-modified linear low-density polyethylene (3 μm) as a layer 2, and ethylene-vinyl acetate copolymer as a layer 3 (Ethylene content 44 mol%, 20μ
m), and an amorphous polyethylene terephthalate film (300 μm) was formed on the layer 3 side.
m) was dry laminated. The delamination strength between layer 2 and layer 3 is 600 gf
/ 15 mm width. Using the obtained composite film, a rectangular container having a flange portion (7 mm width) having a length of 160 mm, a width of 120 mm and a depth of 30 mm is vacuum-formed, and then biaxially stretched polypropylene film (20 μm).
m) / a lid material composed of silica-deposited polyethylene terephthalate film (12 μm) / low-density polyethylene film (seal layer, 30 μm) was heat-sealed. The transparency of the flange portion after sealing was good. further,
When opened from the seal portion, it could be easily opened, and the opened portion was peeled off only at the flange portion, and there was no problem in appearance. Example 2 Ethylene-vinyl acetate copolymer (3 μm) as heat seal layer 1, acid-modified ethylene-vinyl acetate copolymer (2 μm) as layer 2, and saponified ethylene-vinyl acetate copolymer as layer 3 ( Ethylene content 38 mol%, 10 μm), Layer 4 composed of 6-66 nylon copolymer (5 μm), Layer 5 composed of acid-modified ethylene-vinyl acetate copolymer (10 μm), Layer 4 composed of 6 nylon (10 μm) Using a layer of co-extruded film,
Biaxially oriented polypropylene film (20 μm) on layer 6
Was dry-laminated. The delamination strength between layer 2 and layer 3 was 300 gf / 15 mm width. Using the obtained composite film, Example 1
The same evaluation was performed. The openability and transparency of the flange portion after sealing and the appearance of the open portion were all good. (Comparative Example 1) The thickness of the heat seal layer 1 is 1
A composite film was obtained in the same manner as in Example 1 except that the thickness of the layer 2 was 5 μm and the total thickness of the layer 1 and the layer 2 exceeded 10 μm. (600 gf / 15 mm width), and the same evaluation as in Example 1 was performed. Although the transparency and the opening property of the flange portion after the sealing were good, the opening portion was peeled off other than the flange portion, and there was a problem in appearance. Comparative Example 2 Linear low-density polyethylene (7 μm) as heat seal layer 1, acid-modified linear low-density polyethylene (3 μm) as layer 2, 6-66 nylon copolymer (10 μm) as layer 3, As the layer 4, a four-layer co-extruded film made of a saponified ethylene-vinyl acetate copolymer (ethylene content: 44 mol%, 10 μm) was used.
An amorphous polyethylene terephthalate film (300 μm) was dry-laminated on the layer 4 side. The delamination strength between Layer 2 and Layer 3 was 1,000 gf / 15 mm width. Using the obtained composite film, Example 1
The same evaluation was performed. Although the transparency of the flange portion after sealing was good, there was a problem that the unsealed portion was difficult to peel off and the film was broken. Comparative Example 3 As a heat seal layer 1, a cohesive failure type seal layer (30 μm) made of a blend of a polypropylene resin and an ethylene-vinyl acetate copolymer was used.
m), acid-modified linear low density polyethylene (10
μm), 6-66 nylon copolymer (10 μm)
m), layer 4 composed of saponified ethylene-vinyl acetate copolymer (ethylene content: 44 mol%, 10 μm)
A biaxially stretched polypropylene film (20 μm) was dry-laminated on the layer 4 side using the co-extruded film of the layer.
The same evaluation as in Example 1 was performed using the obtained composite film. Although the openability of the flange portion after sealing was good, the transparency was poor and there was a practical problem. As described above, the composite film of the present invention has excellent heat sealing properties and can be easily peeled off when used, and can be suitably used for gas pack packaging.

Claims (1)

(57) [Claim 1] The heat seal layer comprises a polyolefin resin layer (1), and an ethylene-vinyl acetate copolymer ken is provided adjacent to the heat seal layer via a modified polyolefin resin layer (2). And the total thickness of the layer (1) and the layer (2) is 1 to 10 μm, and the delamination strength between the layer (2) and the layer (3) is 100 to 800 gf / 15m
An easily openable composite film having a width of m.