JPH0760915A - Heat-shrinkable composite film - Google Patents

Abstract

PURPOSE:To provide a co-extrusion composite film excellent in opening properties and blocking resistance and good in glossiness, transparency and seal strength. CONSTITUTION:In a co-extrusion composite film containing a saponified ethylene/vinyl acetate copolymer layer and a polyamide resin layer as gas barrier layers, the innermost layer is composed of a heat-sealable layer formed from a compsn. prepared by compounding 0.3-3wt.% of a nonionic surfactant with an ethylene/ vinyl acetate copolymer. This composite film can be suitably used as a bag for the vacuum packaging of raw meat because it is excellent in opening properties and blocking resistance and good in glossiness, transparency and seal strength.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-shrinkable composite film which is excellent in opening property and blocking resistance, and has good gloss, transparency and sealing strength, and can be suitably used especially for vacuum packaging of raw meat and the like.

[0002]

2. Description of the Related Art Conventionally, as a film for vacuum-packing raw meat and the like, a composite film having various layer constitutions having a gas barrier layer has been used. A bag is formed from such a composite film and used, but from the viewpoint of workability, the opening is the property that the opening of the bag is easy to open, and the ability to take out the bag easily even if the bags are stacked for a long time. It is necessary to improve the blocking resistance. As a method for improving the above-mentioned openability and blocking resistance, it has been usual to add an inorganic filler such as silica or talc to the resin used for the innermost layer and / or the outermost layer of the composite film.

However, in the film to which the above-mentioned inorganic filler is added, it is necessary to increase the addition amount in order to improve the opening property and the blocking resistance, the gloss and the transparency are deteriorated, and the raw meat is vacuum-packed. However, there is a problem that the appearance of the package is inferior. Further, the one used for the innermost heat seal layer has a problem that the sealing strength is lowered.

[0004]

The present invention has solved the above-mentioned problems and has completed a heat-shrinkable composite film which is excellent in opening property and blocking resistance, and has good gloss, transparency and seal strength. In the heat-shrinkable composite film containing a saponified ethylene-vinyl acetate copolymer layer and a polyamide resin layer as a gas barrier layer, the innermost layer is a nonionic surfactant on the ethylene-vinyl acetate copolymer. A heat-shrinkable composite film comprising a heat-sealing layer containing 0.3 to 3% by weight of the agent.

As the heat-shrinkable composite film of the present invention, composite films having various layer constitutions can be used, but it is necessary to include a gas barrier layer in the layer constitution, and the gas barrier layer contains an ethylene-vinyl acetate copolymer solvent. Compound (hereinafter referred to as "EVO
H ") and a polyamide resin layer. EV
As OH, the ethylene content is 30 to 60 mol%,
Those having a saponification degree of 95% or more are preferable from the viewpoint of moldability and gas barrier property.

As the polyamide resin, nylon 6, nylon 66, nylon 6/66, nylon 6T /
6I and the like can be preferably used. The thickness of the gas barrier layer is 5 to 30 μm for the polyamide resin layer and 2 for the EVOH layer.
The range may be 10 μm. The gas barrier layer is usually arranged in the intermediate layer, and various resins can be used for the outermost layer and the innermost layer, but in the film of the present invention, the innermost layer is a heat seal layer, and the heat seal layer has ethylene. -Use a vinyl acetate copolymer (hereinafter referred to as "EVA"). The outermost layer has the same E as the heat seal layer
VA and other resins having rigidity can be preferably used, the outermost layer has a thickness of 5 to 20 μm, and the innermost layer has a thickness of 10 to 30 μm.
It may be about m.

If necessary, an adhesive resin layer may be provided between the outermost layer, the innermost layer and the gas barrier layer, and the adhesive resin may be at least one selected from unsaturated carboxylic acids or their derivatives. A modified polyolefin resin grafted with a monomer can be preferably used. The thickness of the adhesive resin layer may be in the range of 1 to 10 μm.

In the composite film of the present invention, it is necessary to blend the EVA of the heat seal layer with a nonionic surfactant in the range of 0.3 to 3% by weight. Ethylene oxide adduct,
Polyethylene glycol type nonionic surfactants such as alkylphenol ethylene oxide adducts and fatty acid ethylene oxide adducts and polyhydric alcohol type nonionic surfactants such as polyglycerin fatty acid esters, pentaerythritol fatty acid esters and sorbitol fatty acid esters are used. Of these, a combination of a polyglycerin fatty acid ester and an ethylene oxide adduct of a higher alcohol can be preferably used.

Regarding the compounding amount of the above-mentioned nonionic surfactant, if the content is less than 0.3% by weight in EVA, no improvement effect on the opening property and blocking resistance is observed, and if it exceeds 3% by weight, it is in the other layer. Since the interfacial adhesion strength with the is reduced, there is a problem that the sealing strength is reduced.

When a nonionic surfactant is used in combination with a polyglycerin fatty acid ester and an ethylene oxide adduct of a higher alcohol, the polyglycerin fatty acid ester is used in an amount of 55 to 95% by weight and the ethylene oxide adduct is in an amount of 5 to 45% by weight. It is preferably used in the range.

The method for producing the composite film of the present invention is generally a method of laminating by a coextrusion method and then stretching by an inflation method to form a film. The draw ratio is the longitudinal direction,
Stretching in the transverse direction is preferably 2.0 to 4.0 times, and the stretching temperature can be 70 ° C. to 140 ° C. For vacuum packaging of raw meats, the stretching conditions within this range are selected so that the heat shrinkage rate at 70 ° C is 20 in both the longitudinal and transverse directions.
% Or more is preferable.

Hereinafter, the present invention will be specifically described with reference to examples.

[0013]

[Example] The layer structure of the composite film was a 6-layer product having the following structure.

[EVA / adhesive resin / EVOH / nylon 6-66 / adhesive resin / heat seal layer] Thickness composition: 7 μm / 3 μm / 3 μm / 17 μm / 3 μm
/ 17μm The heat seal layer has EVA as the main component, and the surfactant used is polyglycerin fatty acid ester (hereinafter referred to as "PGE").
And a higher alcohol ethylene oxide adduct (hereinafter referred to as “EO adduct”) are used in combination,
The mixing ratio was changed according to the contents shown in Table 1, and the layers were laminated by the coextrusion method in the above layer constitution, and then the composite for evaluation was formed by molding under the conditions of a draw ratio of 2.7 × 2.4 in the machine direction × the transverse direction. It was a film. Using the obtained composite film, haze, gloss,
The openability, blocking resistance, and seal breakage were evaluated, and the results are shown in Table 1.

Here, the measuring method of "haze" is ASTM
According to D1003. Regarding "gloss", a bag was prepared from the above-mentioned composite film, 1 kg of raw meat chunks were vacuum-packaged, and the gloss of the film surface was evaluated. Those with excellent gloss (○) and those without gloss were (X)

Regarding "openness", when the opening is opened with a finger using the bag body, it can be easily opened (○), it is slightly difficult to open but there is no problem in practical use (△), It was difficult to use and was not practical (x).

Regarding the "blocking resistance", 100 bags described above are piled up, a weight of 10 kg is placed on the bag and stored for 1 month, and then the workability when inserting a chunk of raw meat into the bag is improved. evaluated. The bag was one in which the raw meat mass could be easily inserted without blocking (◯), there was some blocking but there was no problem in practical use (Δ), and there was severe blocking and there was no practical use (×).

As for "seal breakage", 1 kg of raw meat lumps are inserted using the above bag body, heat sealed at a sealing temperature of 80 ° C. for 3 seconds, and then the bag body is contracted by a vacuum packaging machine. In this case, 10 samples were prepared, and it was determined that no breakage was observed in the seal part of all the samples (◯) and even one seal part was broken (x).

[0019]

[Table 1] From Table 1 Examples 1 to 5 using the composite film of the present invention
For, it is understood that both properties are excellent. On the other hand, it can be seen that in Comparative Example 1 in which the amount of the surfactant added is too large, the seal portion is easily broken, and in contrast, in Comparative Example 2 in which the amount is too small, the blocking resistance is poor. Further, it can be seen that in Comparative Example 3 in which silica is added, the haze and gloss are inferior and the blocking resistance is inferior.

[0020]

As described above, the heat-shrinkable composite film of the present invention is excellent in opening property and blocking resistance, and is excellent in gloss, transparency and sealing strength, and is therefore a bag for vacuum packaging of raw meat and the like. Suitable for use on the body.

Claims (2)

[Claims] 1. A heat-shrinkable composite film comprising a saponified ethylene-vinyl acetate copolymer layer and a polyamide resin layer as a gas barrier layer, wherein the innermost layer contains an ethylene-vinyl acetate copolymer and a nonionic surfactant. A heat-shrinkable composite film comprising a heat-sealing layer formed by blending 3 to 3% by weight. 2. The heat-shrinkability according to claim 1, wherein the nonionic surfactant comprises polyglycerin fatty acid ester in an amount of 55 to 95% by weight and an ethylene oxide adduct of a higher alcohol in an amount of 5 to 45% by weight. Composite film.