JP3575774B2 - Easy-open composite film - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a composite film, and more particularly to an easily-openable composite film which has excellent heat sealing properties and can be easily peeled between layers when used, and can be suitably used as a bottom material and a lid material for gas pack packaging.
[0002]
[Prior art and its problems]
After deep drawing, it is packed with contents and inert gas and packed, as a composite film used for bottom material and lid material for so-called gas pack packaging, it has a gas barrier layer made of various gas barrier resins and Composite films having a heat seal layer made of various resins are used.
[0003]
Many of such composite films are of a 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.
[0004]
The present invention has found an easily openable composite film for gas pack packaging which can solve the above problems, and the gist of the invention is that the heat seal layer is made of an ionomer resin layer, and the ionomer is adjacent to the layer. A resin and a polyolefin resin layer that can be peeled off between layers are provided, and a saponified ethylene-vinyl acetate copolymer layer is provided in addition to the heat seal layer, and the melt flow rate of the ionomer resin layer is 1.0 to 10 g / 10 minutes. in the range of, in GasPak packaging easily openable composite film characterized in that said layer of thickness of 1 to 10 [mu] m.
[0005]
The ionomer resin used in the ionomer resin layer serving as the heat seal layer is a metal-neutralized product of an ethylene-α, β-unsaturated carboxylic acid copolymer, and the metal ions used include Na ions and Za ions. However, it is preferable because the interlayer adhesive strength is easily obtained.
[0006]
It is necessary to provide a polyolefin resin layer adjacent to the above-mentioned ionomer resin layer, and the polyolefin resin layer may be selected as appropriate. However, the low-density polyethylene and α-olefin have a linear low-density C4 to C8 carbon number. Ethylene-vinyl acetate copolymer having a content of polyethylene and vinyl acetate of 2 to 15% by weight is preferred because the interlayer adhesion strength with the ionomer resin layer can be easily adjusted.
[0007]
A saponified ethylene-vinyl acetate copolymer layer is provided in addition to the heat seal layer. The saponified ethylene-vinyl acetate copolymer has an ethylene content of 32 to 47 mol% and a saponification degree of 95% or more. Can be suitably used. Further, an adhesive resin layer, a polyamide resin layer, a polyester resin layer, or the like may be provided adjacent to the saponified ethylene-vinyl acetate copolymer layer, if necessary.
[0008]
Here, it is necessary to use the ionomer resin layer having a melt flow rate in the range of 1.0 to 10 g / 10 minutes. Here, the method of measuring the melt flow rate is a value measured in accordance with JIS K7210, and if it is less than 1.0 g / 10 minutes, there is a problem that the breaking strength of the film is too strong and it is difficult to break the film. If it exceeds, there is a problem that sufficient strength is difficult.
[0009]
Further, the thickness of the layer needs to be in the range of 1 to 10 μm. If the thickness is less than 1 μm, there is a problem that the ionomer resin layer is melted at the time of heat sealing and the seal portion is likely to be displaced. There is a problem.
[0010]
In the composite film of the present invention, the ionomer resin layer and the polyolefin resin layer need to be peelable, and the peel strength between the two is preferably 100 to 1500 gf / 15 mm. If the width is less than 100 gf / 15 mm, the seal strength is less than 100 gf / 15 mm. Is too low to easily break the bag, and if the width exceeds 1500 gf / 15 mm, the sealing strength is too strong to open easily.
[0011]
Hereinafter, the present invention will be described with reference to examples.
[0012]
【Example】
(Example 1)
Layer structure:
Heat seal layer (first layer): ionomer (Na type, melt flow rate = 2.8), second layer: LDPE, third layer: carboxylic acid-modified LLDPE (AD), fourth layer: nylon 6-66, Fifth layer: EVOH (ethylene content: 44 mol%), sixth layer: carboxylic acid-modified PP (AD), seventh layer: nylon 6
[0013]
Thickness:
Ionoma / LDPE / AD / Nylon 6-66 / EVOH / AD / Nylon 6 (3 μm / 27 μm / 5 μm / 10 μm / 10 μm / 5 μm / 10 μm) The composite film having the above structure was formed by coextrusion molding. The obtained composite film was used as a lid, and heat-sealed at a flange portion of a vacuum-formed bottom material (layer constitution, ionomer (60 μm) / AD (10 μm) / nylon 6-66 (30 μm) / EVOH (20 μm)). Gas-packed.
[0014]
The transparency of the flange portion after sealing was good. Furthermore, when the package was opened from the seal portion, it could be easily opened, and the open portion was peeled off only at the flange portion, so that there was no problem in appearance.
[0015]
(Example 2)
Layer structure:
Heat seal layer (first layer): ionomer (Na type, melt flow rate = 1.2), second layer: ethylene-vinyl acetate copolymer (vinyl acetate content = 5% by weight), third layer: carvone Acid-modified LLDPE (AD), fourth layer: nylon 6-66, fifth layer: carboxylic acid-modified PP (AD), sixth layer: EVOH (ethylene content: 44 mol%).
[0016]
Thickness:
Ionomer / EVA / AD / Nylon 6-66 / AD / EVOH
(5 μm / 25 μm / 5 μm / 10 μm / 5 μm / 10 μm)
The composite film having the above structure was formed into a film by a co-extrusion molding method, and the sixth layer was dry-laminated to a polyester film (printed product having a thickness of 12 μm). Using the obtained composite film as a lid, heat sealing is performed on a flange portion of a vacuum-formed bottom material (layer structure, ionomer (60 μm) / AD (10 μm) / EVOH (20 μm) / AD (10 μm) / PP (200 μm)). And packed in a gas pack.
[0017]
As a result, as in Example 1, the transparency of the flange portion after sealing was good, and it was easy to open when opened from the seal portion, and the opened portion was peeled off only at the flange portion, and there was no problem in appearance. Was.
[0018]
(Comparative Example 1)
The gas pack was packaged in the same manner as in Example 1 except that the layer thickness configuration of the lid material was as follows.
Thickness:
Ionoma / LDPE / AD / Nylon 6-66 / EVOH / AD / Nylon 6 (15 μm / 15 μm / 5 μm / 10 μm / 10 μm / 5 μm / 10 μm)
As a result, the transparency of the flange portion was good, but when opened from the seal portion, the opened portion spread to areas other than the flange portion and was peeled off, which had a problem in appearance.
[0019]
(Comparative Example 2)
The gas pack was packaged in the same manner as in Example 1 except that the ionomer used in the heat seal layer (first layer) had a melt flow rate of 0.5.
As a result, although the transparency of the flange portion was good, when the film was opened from the seal portion, there was a problem that the breaking strength of the film was too strong to be easily broken.
(Comparative Example 3)
A lid material was produced from a composite film in the same manner as in Example 2 except that a cohesive failure type seal layer made of a blend of a polypropylene resin and an ethylene-vinyl acetate copolymer was used as a heat seal layer (first layer). When evaluated in the same manner as above, the openability of the flange portion after sealing was good, but the transparency was poor and there was a practical problem.
[0020]
【The invention's effect】
As described above, the composite film of the present invention has excellent heat sealing properties and can be easily peeled off at the time of use, and can be suitably used as a bottom material and a lid material for gas pack packaging.

Claims (1)

The heat seal layer is formed of an ionomer resin layer, and a polyolefin resin layer capable of being peeled off between the ionomer resin and the interlayer is provided adjacent to the layer, and a saponified ethylene-vinyl acetate copolymer layer is provided in addition to the heat seal layer. An easy-open composite film for gas pack packaging, wherein the ionomer resin layer has a melt flow rate in the range of 1.0 to 10 g / 10 minutes and a thickness of 1 to 10 μm.