JP3040694B2 - Composite multilayer film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention can be heat-sealed with a general-purpose polyolefin resin film, maintains transparency even when subjected to heat sterilization in hot water, and has heat resistance enough to secure an opening. The present invention relates to a composite multi-layer film for food packaging which has excellent sealing properties in a distribution process and can be easily peeled off when opened.

[0002]

2. Description of the Related Art In food packaging, there is complete sealing.
At the same time, packaging materials having characteristics that can be easily opened at the time of opening (hereinafter referred to as easy peelability) are widely used. Methods for obtaining easy peelability using a plastic packaging material are roughly classified into the following three methods. First
Is a method in which a layer to be heat-sealed with the sealing layer on the other side is thinned to some extent in advance, and this layer is peeled off from the sealing layer at the time of opening to open. Next, as a second method, a method is used in which the sealing layer is made of a mixture of different resins, and the sealing strength with the sealing layer on the other side is appropriately controlled. Finally, a third method is a method in which the materials to be sealed are made of different resins, pseudo-contacted by heat sealing, and opened at the interface when opening. However, the third method often did not provide sufficient sealing properties.

[0003] Recently, cooked foods that can be easily cooked at home have begun to spread widely due to changes in eating habits. These foods are sold after heat-sterilizing or cooking the vacuum-packed package in warm water. For these foods, the transparency of the film after the heat treatment is very important so that the display effect in a retail store and the content foods can be checked in advance by consumers. In addition, despite the fact that the packaging material has an easy opening property, if the opening is fused due to exposure to hot water, the easy peel function at the angle becomes meaningless. Therefore, heat resistance that does not cause the opening to fuse is also required. Further, in the case of food packaging, it is not sufficient to simply have an easy peel property, and if a fibrous seal layer remains on the peeled surface when opened (hereinafter referred to as a mustache phenomenon), It is not good because it reduces value. Furthermore, foods such as hamburgers and the like contain a large amount of fats and oils in the contents and sauces, and the fats and oils must not damage the seal layer and break the bag during transportation. In this sense, sufficient oil resistance is required for the seal layer material.

However, in each of the above-mentioned techniques, in the case of the first method, the thinned seal layer is eroded by the contents and various fats and oils accompanying the contents, delamination occurs, and the reliability of the seal is lacking. Also, the mating seal layer is often limited to a single resin, and lacks versatility. Next, also in the case of the second method, in many cases, if the blending of the mixed system is not good, the transparency is not good from the stage before the heat treatment, or the seal layer becomes cloudy due to moisture or oil during the hot water heat treatment. Had the disadvantage of doing so.

[0005]

SUMMARY OF THE INVENTION The present invention solves the problems of transparency, oil resistance and heat resistance, which are the problems of the easy-open seal layer in food packaging films used in conventional heat sterilization. At the same time, it was made as a result of various studies to solve the problem, and its purpose is to be able to select widely from the general-purpose polyolefin resin group as the mating material to be heat-sealed, and it is excellent even after heat sterilization treatment in warm water Another object of the present invention is to provide a composite multilayer film which provides a sealing layer having easy peelability and transparency and having a sealing property in a distribution process.

[0006]

According to the present invention, there is provided a sealing layer comprising 5 to 100 parts by weight of a crystalline polyamide resin having a melting point of 170 ° C. or higher, 10 to 160 parts by weight of a polypropylene resin, and 100 parts by weight of an ethylene ionomer resin. A composite multilayer film characterized by being a composition comprising 10 to 50 parts by weight of an ethylene-methacrylic acid copolymer resin, and preferably, a crystalline polyamide resin is nylon 6,
Nylon 66 and a copolymer thereof, wherein the ethylene ionomer resin has an α, β unsaturated carboxylic acid content of 6
~ 15 mol%, neutralization degree by transition metal cation is 20 ~
5. The composite multilayer film according to 4, which is a 100% ethylene ionomer resin, has a seal layer thickness of 2 to 100 μm, and is manufactured by a co-extrusion method.

[0007] As the ionomer used in the present invention, an ethylene ionomer resin in which a part of an ethylene-unsaturated carboxylic acid copolymer is neutralized by a metal cation can be used. As the constitution of the present ionomer, preferably, the acid content of the unsaturated carboxylic acid constituting the copolymer serving as the base of the ionomer is 6 to 15
Mol% range is well compatible with crystalline polyamide resin, good transition metal cation such as zinc, manganese, cobalt etc. as metal cation, and neutralization degree is 20% or more Is most preferable in terms of heat resistance.

As the polyamide used in the present invention, a crystalline polyamide resin having a melting point of 170 ° C. or more can be used. As such a polyamide,
Specifically, nylon 6, nylon 66, nylon 61
0, nylon 612, nylon 11, nylon 12, nylon 46, MXD6 nylon, and copolymers and mixtures thereof. In order to improve heat resistance efficiently,
A crystalline polyamide resin having a melting point of 200 ° C. or more is preferable, and nylon 6, nylon 66 and a copolymer thereof are particularly preferably used. The specific viscosity of the crystalline polyamide resin of the present invention in 98% sulfuric acid at 25 ° C. is 0.5.
To 10 are preferred. With respect to the compounding ratio of the crystalline polyamide resin in the present invention, the effect of improving the heat resistance is not so much recognized when the crystalline polyamide resin is less than 5 parts by weight with respect to 100 parts by weight of the ethylene-based ionomer resin. If the amount is too large, the original properties of the ionomer will be lost, and it will be difficult to seal with the ethylene sealant of the mating material. Therefore, 5 to 100 parts by weight, preferably 20 to 80 parts by weight
A proportion by weight is preferred.

The polypropylene resin used in the present invention includes a homopolymer of polypropylene and an ethylene / propylene copolymer. Homopolymers of propylene are slightly less transparent than copolymers, but have a greater effect of imparting easy peelability. When an ethylene / propylene copolymer is used as the polypropylene, the ethylene content is preferably low, and is preferably about 1 to 5% by weight. When the content of ethylene is large, the film to be sealed is relatively unaffected when the film to be sealed is an ionomer, but the easy peel property is impaired when the film is a polyethylene or ethylene-vinyl acetate copolymer.
MFR of polypropylene at 230 ° C is 0.1 to 1
It is preferable to be as low as about 0 g / 10 minutes. If the MFR of the polypropylene is increased, the transparency of the film is improved, but the whiskers at the time of peeling tend to occur, which is not practical. Although the blending ratio of the polypropylene resin in the present invention varies depending on the purpose of use, if the amount of the polypropylene resin is less than 10 parts by weight relative to 100 parts by weight of the ethylene ionomer resin, the effect of the easy-opening property is not so much recognized. If the amount is more than 10 parts by weight, the original properties of the ionomer will be lost, and it will be difficult to seal with the ethylene sealant of the mating material.
A ratio of 5 to 80 parts by weight is preferred.

In the present invention, the ethylene-methacrylic acid copolymer has the following two effects. First, it functions as a processing aid in a ternary mixed system of an ethylene ionomer, a crystalline polyamide and polypropylene. Its role is not a problem if the compounding ratio of crystalline polyamide or polypropylene is high, and if compounded in advance using a processing device such as a twin screw extruder or Banbury mixer, When a single screw is used to form a sheet suddenly, it is difficult to achieve good compatibility, and transparency may not be easily obtained. At this time, transparency can be remarkably improved by adding an ethylene-methacrylic acid copolymer. The reason for this is not always clear, but ethylene-
It is considered that the acid component of the methacrylic acid copolymer, together with that of the ionomer, greatly contributes to the improvement of the compatibility with the polyamide. Next, this is also effective when the ratio of the crystalline polyamide and polypropylene is high, but even when both components are added within the scope of the claims, the sealing strength is not sufficient depending on the application. There are cases. In such a case, the insufficient sealing strength can be compensated. The ethylene-methacrylic acid copolymer has an acid content of methacrylic acid of 3 to 15% by weight and 1%.
An ethylene-methacrylic acid copolymer having an MFR at 90 ° C. of 0.3 to 10 g / 10 min and a hardness (D scale) of 30 to 60 as measured according to JIS K-7215 can be used. As the compounding ratio of the ethylene-methacrylic acid copolymer in the present invention,
If the ethylene-methacrylic acid copolymer is less than 10 parts by weight with respect to 100 parts by weight of the ionomer, the above-mentioned effect is not so much recognized. Conversely, if it is more than 50 parts by weight, the easy-opening property is impaired. 50 parts by weight, preferably 1
A ratio of 5 to 40 parts by weight is preferred.

The sealing layer according to the present invention has a particle diameter of 0.1 to 2.0 μm for the purpose of preventing film blocking.
An inorganic filler selected from the group consisting of silicon oxide, magnesium silicate and aluminum silicate may be added in an amount of 0.1 to 5.0 parts by weight based on 100 parts by weight of the present thermoplastic resin composition. Since the required sealing strength varies depending on the type and form of the food to be packaged, it is necessary to adjust the sealing strength in consideration of the balance between the sealing property in the distribution process and the easy peel property at the time of opening. Within the range, the object can be achieved by adjusting the MFR and the composition ratio of each component.

As the composite multilayer film having an easy-peelable seal layer excellent in boil aptitude according to the present invention, the layer structure conventionally used for food packaging in the case of performing a heat treatment can be adopted. For example, the outermost layer (A)
As a polyolefin resin such as polyethylene or polypropylene, or a polyamide resin such as 6 nylon, 12 nylon, 66 nylon or a copolymer thereof, and a gas barrier layer such as an ethylene / vinyl alcohol copolymer or polyvinylidene chloride as an intermediate layer ( B), a polyamide resin resin as the pinhole resistance-imparting layer (C), and a sealing layer (D) according to the present invention may be laminated and provided with an adhesive resin layer (E) if necessary. . Specific layer configurations include, for example, A / E / C / E / D, A /
E / C / B / E / D, A / E / B / C / E / D, A / E
/ B / E / D, A / E / C / B / C / E / D, A / E /
B / C / B / E / D or 5 comprising an ethylene / vinyl alcohol copolymer layer (gas barrier property-imparting layer), an adhesive resin layer, a polyamide resin layer, an adhesive layer, and a seal layer according to the present invention from the outermost layer. A composite multilayer film in which polypropylene is dry-laminated for the purpose of preventing warpage or printing for the outer layer such as a layer co-extruded film or the like can be used for practical use.

[0013] The resin of the other sealing layer suitable for the composite multilayer film having the sealing layer of the present invention includes low density polyethylene, linear low density polyethylene, ethylene vinyl acetate copolymer, ethylene methacrylic acid copolymer, ethylene methacrylic. An acid methyl copolymer, an ethylene ionomer, an ethylene propylene copolymer and the like are used. Of course, the present seal layers may be sealed and used. Finally, as a method for producing a composite multilayer film having the present seal layer, it is preferable to use a co-extrusion method from the viewpoint of productivity and deep drawability due to the need for a complicated multilayer structure as described above. .

[0014]

EXAMPLE A composite multilayer film was prepared by a conventional method using a co-extruded 6-layer T-shaped die having a width of 600 mm. Each layer is composed of linear low density polyethylene (LLDPE) as the outermost layer.
30 μm, successively adhesive resin (AD layer) 15 μm,
Polyamide resin (6Ny) 15 μm, ethylene / vinyl alcohol copolymer (EVOH) 15 μm, adhesive resin (AD layer) 15 μm, and seal layer 60 according to the present invention
μm or 60 μm of a sealing layer not according to the present invention. The total thickness of the obtained film is 150 μm. The thermoplastic resin blended in the seal layer is as follows. As the ionomer, one having a methacrylic acid content of 9 mol% and a degree of neutralization with zinc ions of 50% (ION) is used. As the crystalline polyamide, nylon 6-66 having a specific viscosity of 2.0 (melting point by DSC method) is used. 195 ° C.), homopolymer as polypropylene, MFR at 230 ° C.
Using 2.5 g / 10 min (PP), ethylene-
As a methacrylic acid copolymer, an acid content of 9% by weight
MFR at 0 ° C of 8 g / 10 min (EMAA)
Was used.

The resin used for each layer other than the sealing layer is as follows.・ LLDPE: ULTEX 3520L, manufactured by Mitsui Petrochemical Industries, Ltd. ・ AD layer: Admar NF500, manufactured by Mitsui Petrochemical Industries, Ltd. ・ 6Ny: Ube nylon 1030B, manufactured by Ube Industries, Ltd. ・ EVOH: Eval EP, manufactured by Kuraray Co., Ltd. -E154B ・ AD layer: ADMER NF550 manufactured by Mitsui Petrochemical Industries, Ltd.

The obtained composite multilayer film is subjected to 20 mm deep drawing and pressure forming, filled with a hamburger as a content, and a lid having a total thickness of 80 μm comprising three layers of polypropylene, vinylidene-coated polyester and a linear low-density polyethylene as a sealing layer from the outer layer. Vacuum sealing was performed with the material. At this time, a place corresponding to the opening was created without intentionally sealing one corner of the package. Further, this package was heat-treated in boiling water for 30 minutes. The samples thus obtained were examined for transparency, heat resistance, oil resistance and sealability. In addition, these characteristics, such as transparency, were investigated by the method described below. (A) Transparency: For the molded film that was taken out of the sample and washed with a neutral detergent for kitchen and lukewarm water,
Haze was measured. (B) Heat resistance: It was examined whether or not an unsealed portion intentionally created at a corner of the sample was fused by heat sterilization. (C) Oil resistance: 20 samples each were placed in a cardboard case, and dropped on concrete six times from a height of 1 m on each of six sides of the cardboard case.
The cardboard case was opened and the number of broken bags was checked. (D) Seal strength: Using an autograph, the test piece width was 15 mm and the peeling speed was 200 mm / min.

Table 1 summarizes the contents and results of the experiment.
Examples 1 to 5 in the table are those in which the quaternary thermoplastic resin composition according to the present invention is used as a sealing layer, and are excellent in transparency, heat resistance, oil resistance and easy peelability, and have a very good balance. It shows that it is taken. In Comparative Examples 1 and 2, since the amount of polyamide added was small, sufficient heat resistance was not obtained. In Comparative Examples 2 and 3, since the amount of added polypropylene was small, the sealing strength was too high and opening was difficult. In Comparative Example 4, since the amount of the added polypropylene was too large, the sealing strength was weak and the bag was broken. In Comparative Example 5, since the added amount of the polyamide was too large, the transparency was poor and the sealing strength was not sufficient.

Table 1 Examples Comparative Examples 1 2 3 4 5 5 1 2 3 4 5 5 parts (parts by weight) Ionomer 100 100 100 100 100 100 100 100 100 100 Nylon 6-66 10 10 50 80 80 3 3 25 50 150 PP 10 55 35 15 140 35 5 5 200 35 EMAA 15 25 15 25 40 20 15 15 25 15 Evaluation item 1 Transparency ○ ○ ○ ○ ○ ○ ○ ○ ○ × 2 Heat resistance ○ ○ ○ ○ ○ × × ○ ○ ○ 3 Oil resistance ○ ○ ○ ○ ○ ○ ○ ○ × × 4 Sealability ○ ○ ○ ○ ○ ○ × × × ×

Evaluation criteria Transparency: The haze value after boiling was less than 10%. × The haze value after boiling is 10% or more. Heat resistance: ○ No fusing at the opening. X: The opening is fused. Oil resistance: ○ The number of broken bags is 0 to 2. × The number of broken bags is 3 or more. Sealing performance: ○ seal strength is 100g ^f / 15mm more than 500g ^f /
It is less than 15 mm. × Seal strength is less than 100 ^gf / 15 mm or 500 ^gf / 15 mm or more.

[0020]

The use of the composite multilayer film having the sealing layer according to the present invention makes it possible to perform heat sterilization treatment after vacuum packaging without impairing the easy peelability and transparency, and the conventional defect of heat resistance. And oil resistance,
It can be suitably used not only for fixed-size ones, but also for applications where deep-drawing or vacuum-packing amorphous and massive contents is carried out with bags.

Claims (5)

(57) [Claims] 1. A sealing layer comprising: 5 to 100 parts by weight of a crystalline polyamide resin having a melting point of 170 ° C. or higher, based on 100 parts by weight of an ethylene ionomer resin;
A composite multilayer film comprising a composition comprising 0 to 160 parts by weight and 10 to 50 parts by weight of an ethylene-methacrylic acid copolymer resin. 2. The method according to claim 1, wherein the crystalline polyamide resin is nylon 6,
The composite multilayer film according to claim 1, which is nylon 66 or a copolymer thereof. 3. An ethylene ionomer resin comprising α, β
3. The composite multilayer film according to claim 1, which is an ethylene ionomer resin having an unsaturated carboxylic acid content of 6 to 15 mol% and a degree of neutralization with a transition metal cation of 20 to 100%. 4. The composite multilayer film according to claim 1, wherein the thickness of the sealing layer is 2 to 100 μm. 5. The method of claim 1, wherein the composition is manufactured by a co-extrusion method.
5. The composite multilayer film according to 2, 3 or 4.