JP2758200B2 - Multilayer packaging material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a multilayer packaging material having excellent heat sealing properties, light blocking properties, gas barrier properties, and fragrance retention properties.

More specifically, the present invention relates to a multilayer packaging material suitable for filling or packaging a food or the like containing an aroma component.

[Conventional technology and its problems] Aluminum foil is widely used as a multilayer packaging material such as a soft packaging material and a paper container because of its excellent light-shielding properties and gas barrier properties. As such a multilayer packaging material, a material provided with an olefin-based polymer layer having excellent heat sealing properties as a layer inscribed in an aluminum foil is often used in order to perform heat sealing in packaging. Olefin polymers are excellent in flexibility and have excellent features such as no pinholes even when bent, but they can easily absorb fragrance components and taste and smell depending on the type of package. Has the disadvantage of changing.

On the other hand, polyethylene terephthalate (hereinafter referred to as PET) is excellent in fragrance retention, but poor in heat sealability, and is unsuitable for use as the resin for the inner layer of the above-mentioned multilayer packaging material. Modified PET containing a considerable amount of a copolymer component such as isophthalic acid is superior to PET in heat sealability, but is inferior in flexibility, pinhole resistance, etc., and requires bending and the like. It was hard to say that it was suitable as an inner layer material for packaging containers. Furthermore, when such a modified PET is directly laminated on an aluminum foil, a solvent-type adhesive must be generally used, and there is a problem that productivity is poor.

[Problems to be Solved by the Invention] The present inventors make use of the light-shielding property, gas barrier property and heat-sealing property and fragrance retention property of the modified PET possessed by the aluminum foil, and modified PEL such as pinhole resistance. A new packaging material that has improved the disadvantages of the present invention has been studied. As a result, by interposing a specific ethylene copolymer between the aluminum foil and the modified PET, a packaging material having excellent interlayer adhesion and excellent packaging characteristics has been found.

Accordingly, an object of the present invention is to provide a novel packaging material having heat sealability suitable for packaging foods and beverages having an aroma component. Another object of the present invention is to provide a multilayer packaging material having excellent heat sealing properties, light shielding properties, gas barrier properties and fragrance retention. Another object of the present invention is to
It is an object of the present invention to provide a multilayer packaging material having good interlayer adhesion that can be easily produced by a coextrusion method.

[Means for Solving the Problems] The present invention provides: (A) a heat seal layer composed of a modified polyethylene terephthalate containing 5 to 20 mol% of a copolymer component; (B) a (meth) acrylic layer adjacent to the (A) layer; A flexible resin layer comprising an ethylene / (meth) acrylate / ((meth) acrylic acid copolymer having an acid ester content of 5 to 40% by weight and a (meth) acrylic acid content of 3 to 20% by weight; And (C) an aluminum foil layer adjacent to the (B) layer.

The modified PET used for the heat seal layer of the multilayer packaging material of the present invention contains, in addition to ethylene glycol units and terephthalic acid units, 5 to 20 mol%, preferably 5 to
It is copolymerized at a rate of 〜15 mol%. Examples of the copolymerization component include aromatic carboxylic acids such as isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid and p-oxybenzoic acid, and aliphatic or fatty acids such as adipic acid, sebacic acid and cyclohexanedicarboxylic acid. Cyclic carboxylic acid,
Examples thereof include diols such as propylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, diethylene glycol, and triethylene glycol. Among these copolymer components, isophthalic acid, 1,4
-Cyclohexanedimethanol, diethylene glycol and the like are particularly preferred. The modified PET preferably has an intrinsic viscosity of 0.60 to 1.4 dl / g, particularly preferably 0.7 to 1.0 dl / g.

When the amount of the copolymer component is less than 5 mol%, the heat sealability is poor, and a material having a high heat seal strength cannot be obtained for use as an inner layer material of a high-temperature filling paper container. On the other hand, when the amount of the copolymer component exceeds 20 mol%, the flexibility and elongation of the composition are not sufficient, and breakage or the like due to pinholes or bending tends to occur.

The multilayer packaging material of the present invention has a laminated structure in which a flexible resin layer is provided between a modified PET layer which is a heat seal layer and an aluminum foil layer. Thus, as the flexible resin, the (meth) acrylate content is 5 to 5.
40% by weight, preferably 7 to 30% by weight, and a content of (meth) acrylic acid of 3 to 20% by weight, preferably 5 to 10% by weight of ethylene / (meth) acrylic acid ester, (meth) acrylic acid copolymer Coalescing is used. Here, (meth) acrylic acid ester means acrylic acid ester or methacrylic acid ester, and (meth) acrylic acid means acrylic acid or methacrylic acid.

In such a copolymer, 80% or less, preferably 60% or less of the (meth) acrylic acid component is sodium, magnesium,
It may be metal chlorided with calcium, zinc or the like. Here, as the (meth) acrylate, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, n-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, glycidyl acrylate, glycidyl methacrylate And the like.

If the content of the (meth) acrylate is less than the above range, not only the adhesion to the modified PET layer is not sufficient, but also the pinhole resistance of the laminate is not satisfactory. , Bending, etc.,
The modified PET layer is liable to be broken or generate pinholes. On the other hand, if the content is more than the above range, it is not preferable because the material becomes too flexible and the strength is insufficient, and the melting point is lowered and the heat resistance becomes extremely insufficient.

On the other hand, when the content of (meth) acrylic acid is less than the above range, the adhesive strength with the aluminum foil tends to be insufficient,
If the content is more than the above range, the rigidity becomes too large, the elongation becomes low, and pinholes are easily generated at the time of bending.

When the (meth) acrylic acid component is metal chlorided, if the degree of neutralization is too large, it will be difficult to adhere firmly to the aluminum foil by ordinary lamination, and the ethylene copolymer will be rigid. Because it becomes too much
The pinhole resistance of the laminate deteriorates, which is not preferable.

Such an ethylene copolymer preferably has a melt flow rate at 190 ° C. and a load of 2160 g of 0.05 to 100 g / 10 min, particularly 0.5 to 50 g / 10 min. This ethylene copolymer layer may also contain other ethylene polymers, tackifiers, various additives, and the like.

The multilayer packaging material of the present invention has such a three-dimensional structure as long as the modified PET layer is used as a heat sheet layer and a laminated structure of modified PET / ethylene copolymer / aluminum foil is used as an essential component.
Not only a layer structure, but also a multilayer structure of four or more layers in which one or more layers of various substrates are formed on the aluminum foil side. Examples of such a base material include paper, polyester, polyamide, polypropylene, and polyolefins such as various ethylene polymers. Although the thickness of each layer is arbitrary, it can be used, for example, with a thickness of 10 to 200 μm.

In order to produce the multilayer packaging material of the present invention, 1) a method in which an ethylene copolymer is first extrusion-coated on an aluminum foil substrate, and a modified polyethylene terephthalate is extrusion-coated thereon, 2) an ethylene-based copolymer And modified polyethylene terephthalate are co-extruded using a feed block, a multi-manifold die or a two-slot die, and coated on an aluminum foil substrate at one time. 3) Prepare a modified polyethylene terephthalate film first. A method of laminating an ethylene-based copolymer onto an aluminum foil while being melt-extruded (sandwich lamination). 4) Extrusion-coating the ethylene-based copolymer on an aluminum foil substrate, and then using an adhesive to apply Modified polyethylene terephthale For example, a method of laminating a heat film can be adopted.

A particularly suitable method is a method of laminating an ethylene copolymer on an aluminum foil, applying a surface treatment such as a corona treatment or a flame treatment, and then extrusion-coating the modified PET.
This method has good workability and is excellent as an industrial process, and further improves the interlayer adhesion between the ethylene copolymer layer and the modified PET layer.

[Examples] Example-1 Kraft paper (density 50 gr / m ² ) / low density polyethylene (M
FR3.6, thickness 20μm) / Aluminum foil (thickness 9μm)
A base material (C layer) in which three layers are laminated is prepared in advance, and a terpolymer (ethylene / isobutyl acrylate) composed of ethylene / isobutyl acrylate / methacrylic acid is formed as a B layer on the aluminum foil layer of the laminate. Acrylate /
Methacrylic acid = 80/10/10 wt%, MFR = 10)
The composition was applied by extrusion coating at 80 ° C. and a line take-up speed of 80 m / min. The thickness of the coating film was 20 μm. Next, after the applied terpolymer (hereinafter sometimes referred to as a terpolymer) layer is subjected to a corona discharge treatment, a modified polyethylene terephthalate (hereinafter referred to as a modified PET) is formed as an A layer on the terpolymer layer. , Isophthalic acid / terephthalic acid / ethylene glycol = 10/40/50 mol%, the same applies to the following).
Extrusion coating was performed at / min to obtain a multilayer packaging material. The thickness of the modified PET layer as the A layer was 20 μm.

The adhesive strength between the aluminum foil layer and the terpolymer layer and the adhesive between the terpolymer and the modified PET layer of this multilayer packaging material were evaluated. The results are shown in Table 1.

Next, the heat sealing property of this multilayer packaging material using the modified PET as a sealing layer was evaluated. Table 2 shows the results. This multilayer packaging material has practically sufficient heat sealing strength.

Furthermore, perform a bending test with a gelbo flex tester, assuming the number of pinholes generated in the packaging material,
The pinhole resistance of this packaging material was evaluated. Table-Results
3 is shown. It can be seen that the pinhole resistance of the packaging material of the present invention hardly changes as compared with the laminate of Comparative Example-2 in which low density polyethylene is the innermost layer.

Further, in order to evaluate the fragrance retention of this packaging material, a 200 mm × 150 mm size bag was prepared using the denatured PET of the above laminate as the inner layer, and 200 ml of 100% fresh juice was filled therein and sealed by heat sealing. . This juice was left in a refrigerator for 2 weeks, and the change in the content of d-limonene contained therein was measured using a gas chromatograph. The results are shown in Table-4. Compared with the packaging material of Comparative Example-2 in which the inner layer is a low-density polyethylene, the amount of reduction of d-limonene is remarkably small.

Example 2 Same three-layer substrate (C layer) used in Example 1
Terpolymer of ethylene (E) / isobutyl acrylate (IBA) / methacrylic acid (MAA) (E / IBA / MAA = 77/15/8% by weight) , MFR = 8) and modified PET were coextruded and coated at a resin temperature of 285 ° C. and 295 ° C. using a feed block to obtain a laminate. Table 1 shows the adhesive strength between the aluminum foil layer and the terpolymer layer and between the terpolymer layer and the modified PET layer of the laminate.

Comparative Example-1 A binary copolymer of ethylene and methacrylic acid (ethylene / methacrylic acid = 90/10 weight) was formed as a layer B on an aluminum foil layer of the same three-layer substrate (layer C) as in Example-1. %, MFR = 7) was extrusion coated at 290 ° C. The film thickness is
It was 20 μm.

Further, a modified PET was extrusion-coated as a layer A on the binary copolymer (hereinafter sometimes referred to as a copolymer) of this laminate in exactly the same manner as in Example-1. The adhesive strength between the layers of the laminate was evaluated. The results are shown in Table 1 in comparison with Examples 1 and 2. The adhesive force between the binary copolymer and the modified PET is small, and there is a problem as a packaging material.

Comparative Example-2 As a C layer, low-density polyethylene (M
A laminate was prepared in the same manner as in Example 1, except that FR = 7 (hereinafter sometimes referred to as LDPE). The extrusion coating of LDPE was performed at a resin temperature of 290 ° C.

The pinhole resistance of this laminate was evaluated in the same manner as in Example-1. It can be seen that even if the innermost layer is modified PET, it is not much different from the case of LDPE.

Using this laminate, a fresh juice filling test was performed in exactly the same manner as in Example 1, and the change in d-limonene in the juice was measured using a gas chromatograph. The results are shown in Table-4. When the innermost layer is LDPE, the amount of reduction of d-limonene is extremely large.

Comparative Example-3 A 20 μm-thick modified PET film was prepared at a resin temperature of 260 ° C. using a cast molding machine. Next, an isocyanate-based adhesive was used for the kraft paper / LDPE / aluminum (base material C) used in Example 1, and this modified PET film was directly bonded to aluminum.

The pinhole resistance of this laminate was evaluated in the same manner as in Example-1. The results are shown in Table-3. This laminate having no terpolymer layer as an intermediate layer had large pinholes after bending.

[Effects of the Invention] According to the present invention, a modified PET having excellent heat sealing properties and fragrance retention properties is used as a heat sealing layer, and the pinhole resistance, which has been considered as a drawback of the modified PET, has a specific ethylene copolymer weight. Since the coalescence was significantly improved by being interposed between the aluminum foil, heat-sealing properties, light-shielding properties, gas barrier properties, as a packaging material with excellent fragrance retention, especially foods and beverages and cosmetics having an aroma component, It can be suitably used for packaging such as toothpaste.

Claims (2)

(57) [Claims] 1. A heat-sealing layer composed of (A) a modified polyethylene terephthalate containing 5 to 20 mol% of a copolymer component, (B) a layer adjacent to the (A) layer and having a (meth) acrylate content of 5 to 40%. Weight%, (meth) acrylic acid content is 3
A multilayer having a laminated structure of a flexible resin layer composed of an ethylene / (meth) acrylate / (meth) acrylic acid copolymer and an aluminum foil layer adjacent to the (C) and (B) layers in an amount of up to 20% by weight. Packaging material. 2. A flexible resin layer (B) made of ethylene / (meth) acrylate / ((meth) acrylic acid copolymer) is laminated on the aluminum foil layer (C), and the layer (B) is subjected to a surface treatment. The method for producing a multilayer packaging material according to claim 1, wherein the modified polyethylene terephthalate (A) is extrusion-coated thereon.