JPH07323508A - Soft multilayered film - Google Patents

Abstract

PURPOSE:To obtain a packaging material excellent in pinhole resistance and oxygen gas barrier properties by providing a nylon layer, a gas barrier layer, an adhesive layer, an ionomer layer and a layer of an ethylene/vinyl acetate copolyer with vinyl acetate content of a specific value or more. CONSTITUTION:Nylon generates no sudden softening even when a part of a film is strongly heated in the vacuum chamber part of a packaging machine for a skin pack at an initial stage and, since the film is relatively stretched as a whole, a perforation phenomenon is improved. Further, nylon has high mechanical strength and can reduce the thickness of the film to contribute to the enhancement of close adhesiveness. A multilayered film constituted of the outermost layer composed of nylon, a gas barrier layer, an adhesive layer, an ionomer layer and an ethylene/vinyl acetate copolymer layer with vinyl acetate content of 10wt.% or more is formed. The obtained soft multilayered film is excellent in oxygen gas barrier properties, sealability, flexibility and close adhesiveness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible and contents-containing vacuum packaging (hereinafter referred to as a skin pack) in which a film is heated on a hot platen and then adhered to the contents by air pressure while being heat-sealed. The present invention relates to a multi-layer film for food packaging having excellent adhesion.

[0002]

2. Description of the Related Art Deep-vacuum vacuum packaging is generally used for packaging processed animal products and processed marine products, and usually a film having an oxygen gas barrier property is used to enhance the preservation of the contents. An ethylene-vinyl alcohol copolymer (hereinafter referred to as EVOH) or a vinylidene chloride resin (hereinafter referred to as PVDC) is used for the oxygen gas barrier layer. Deep-draw vacuum packaging is suitable for those with a relatively smooth surface and uniform shape, but if the contents are not uniform in shape and surface or sliced ones are arranged side by side, a film Since the molding size is larger than the contents, the film formed during vacuum packaging remains as wrinkles on the surface of the package and remains unattractive, and pinholes easily occur in the wrinkles. It causes trouble. In addition, if the adhesion is poor after packaging, drip is accumulated between the film and the contents to deteriorate the appearance, and further deteriorate the quality. Therefore, irregularly shaped or sliced items arranged in a line are skin-packed, but it is preferred that the film used is flexible and easy to stretch, and because it is compatible with the packaging method, conventionally it is mainly soft chloride. A film having a constitution of vinyl (hereinafter referred to as PVC) / PVDC / ethylene-vinyl acetate copolymer (hereinafter referred to as EVA) is used. However, products related to processed livestock products and processed fishery products are generally distributed at a low temperature of 10 ° C. or lower, and in the above-mentioned multilayer film, pinholes may be generated in the distribution process, which may impair the storability of the contents. More recently, due to environmental issues, resins containing halogen (PVC, PVDC
Etc.) is not being used as a packaging material, and it is spreading rapidly from downstream. Under such circumstances, the flexible film was studied, but initially, considering the softening, the so-called hard resin other than EVOH of the oxygen gas barrier layer was examined in the direction of removing it from the layer structure. However, the packaging machine widely used by users for skin packs has a different mold structure of the vacuum chamber section from the general packaging machine, so a part of the film is heated strongly at the initial stage, and the film is heated closely to the heating plate in vacuum. When heated, only the part that was heated strongly was stretched and a perforation phenomenon was observed.

[0003]

DISCLOSURE OF THE INVENTION The present invention does not impair the flexibility and adhesiveness of the film and allows the user to use the conventional packaging machine as it is and has a pinhole resistance.
It is to provide a packaging material having an excellent oxygen gas barrier property.

[0004]

The present invention relates to a nylon layer (A), a gas barrier layer (B), an adhesive layer (C), an ionomer layer (D), and ethylene-acetic acid having a vinyl acetate content of 10% or more. A soft multilayer film containing at least a vinyl copolymer layer (E), wherein the layer structure is (A)-
(B)-(C)-(D)-(E) (A)-(C)-(B)-(C)-(D)-(E),
(B)-(A)-(C)-(D)-(E), (B)-
(C)-(A)-(C)-(D)-(E), or (A)
-(B)-(A)-(C)-(D)-(E) The above-mentioned soft multilayer film.

The nylon layer (A) used in the present invention is
6 nylon, 6-6 nylon, 6-10 nylon, 6-
12 nylon, 11 nylon, 12 nylon, and copolymers thereof, amorphous nylon, MXD6 nylon obtained by polycondensation of metaxylylenediamine and adipic acid, and blends thereof are used. Considering the adhesiveness of the skin pack, 6 nylon, 6 ・
66 nylon and 6/12 nylon are preferred. Nylon has excellent heat and cold resistance and mechanical strength, so it can add mechanical strength such as pinhole resistance to the packaging material. By incorporating it on the outside of the multilayer film, it is especially resistant to external impact. Can be given.

The gas barrier layer (B) is preferably EVOH having an ethylene content of 25 to 75 mol% and a saponification degree of 90% or more with respect to vinyl acetate in the copolymer. Further, in consideration of flexibility, the melting point ( DSC method) Young's modulus at 165 ° C or lower, 20 ° C, 130 kg under conditions of 65% RH
EVOH of / mm ² or less is more preferable. Adhesive layer (C)
Is polyethylene, polypropylene, copolymers of these copolymers and further different α-olefins, or ethylene-vinyl acetate copolymers such as acrylic acid, monobasic unsaturated fatty acids such as methacrylic acid, or maleic acid, An acid-modified olefin resin obtained by chemically binding an anhydride of a dibasic unsaturated fatty acid such as phthalic acid or itaconic acid, that is, maleic anhydride is used.

As the ionomer layer (D), an ethylene-methacrylic acid copolymer or a ternary copolymer with a third component other than ethylene and methacrylic acid, which is intermolecularly cross-linked with sodium ion or zinc ion, can be used. Considering flexibility, an ionomer based on a terpolymer of ethylene-methacrylic acid-ester monomers is preferable. Pinhole resistance to external impact is given by the nylon layer on the outside, but if part of the contents is hard, pinhole resistance to internal impact is necessary, and the nylon layer makes the film stiff and reduces adhesion. Therefore, an ionomer having flexibility and capable of imparting a certain degree of pinhole resistance is preferable. Furthermore, the EVA layer (E) is EVA having a vinyl acetate content of 10 wt% or more, and the vinyl acetate content is preferably 15 to 25 wt% in view of flexibility and processability. A coextrusion method, a dry laminating method and the like are used in the method for producing a flexible multilayer film of the present invention. However, in the dry laminating method, the use of an adhesive makes the film so stiff and hard that the flexibility should be considered. In this case, the coextrusion method is preferable.

The gas barrier layer is made of EVOH as described above.
When the melting point of the nylon layer is equal to or lower than that of EVOH, the mold structure of the vacuum chamber part is different from the general mold structure in the skin pack packaging machine currently widely used by users, and a part of the film is heated strongly at the initial stage. When a film is heated in close contact with a hot platen in vacuum, only a strongly heated part is stretched and the thickness becomes very thin, or a perforated phenomenon is observed in some cases. Therefore, the nylon layer used in the present invention is required to maintain mechanical strength so that the thickness does not become thin even if a part of the film is heated strongly.
It is preferable to use nylon having a melting point of 20 ° C. or higher than VOH. However, when the melting point is higher than 100 ° C., the film is not sufficiently softened even when heated by a hot platen, and the adhesiveness after packaging is significantly reduced. That is, the melting point (DSC method) Tn of the nylon layer (A) and the melting point (DSC method) Te of the ethylene-vinyl alcohol copolymer are 20 ° C. <Tn-Te <10.
It is preferable to satisfy the relational expression of 0 ° C. The nylon layer and the EVOH layer need to have a certain thickness from the viewpoint of pinhole resistance and gas barrier properties, but if they are too thick, the flexibility of the film is impaired and the adhesion is lost. Therefore, the total thickness of the nylon layer and the gas barrier layer is preferably 30% or less of the total thickness of the film.

[0009]

In the skin pack, adhesion to the contents is required, but if PVC or PVDC is not used, so-called hard resin other than EVOH, which is the gas barrier layer, is excluded from the layer structure in order to impart flexibility to the film. It was examined in the direction of doing. However, since the packaging machine widely used for skin packs has a different mold structure from that of a general packaging machine, the conventional flexible film cannot avoid the perforation phenomenon when the film is heated. In addition to EVOH, the film of the present invention uses nylon, which has a high softening temperature and mechanical strength to some extent, so that even when a part of the film is strongly heated in the initial stage in the vacuum chamber part of the packaging machine for skin packs, the film is sharply heated. Since the softening did not occur and the entire film was stretched relatively, the perforation phenomenon was greatly improved. Furthermore, nylon has high mechanical strength, which allows the film thickness to be made thinner than before, leading to improved adhesion. Also, by using nylon as the outermost layer resin, it is possible to sterilize the boil and it can be widely used for food packaging.

[0010]

EXAMPLE A multilayer film having the layer structure shown in Table 1 was prepared by a coextrusion method. The thickness of all the obtained films is 80 μm
Met. The resins and symbols used are as follows.・ Ny1: 6 nylon UBE nylon 1 made by Ube Industries
030B ・ Ny2: 6-12 Nylon UBE Nylon 7024B made by Ube Industries ・ EVOH1: Kuraray's Eval EP-S105 Young's modulus 120Kg / mm ²・ EVOH2: Kuraray's Eval EP-E105 Young's modulus 150Kg / mm ²・ Adhesive resin: Mitsui Petrochemical Industry Admer VF60
0 ・ ION1: Mitsui DuPont Polychemical made Himilan H1601 ・ ION2: Mitsui DuPont Polychemical made Himilan AM7908-2 ・ EVA1: Mitsui DuPont Polychemical made Everflex P2505C ・ EVA2: Mitsui DuPont Polychemical made Everflex P1403C ・ LLDPE: Sumitomo Chemical Industrial Sumikasen L F10
1-1 The obtained film was actually shifted with a packaging machine and packed with bacon, and the appearance and thickness were examined. For gas barrier property, the amount of oxygen permeation of the film was measured with OXTRAN of Mocon Co.
The results are shown in Table 2.

Table 1 Layer composition and thickness (μm) 1 2 3 4 5 6 Example 1 Ny1 (8) EVOH1 (8) contact (8) ION1 (8) EVA1 (48) − 2 Ny2 (8) EVOH2 (8) contact (8) ION1 (8) EVA2 (48) − 3 EVOH1 (8) contact (8) Ny1 (8) contact (8) ION1 (8) EVA1 (40) 4 Ny2 (6) EVOH2 (6) Ny2 (6) contact (8) ) ION2 (8) EVA2 (46) Comparative example 1 EVOH2 (8) contact (8) ION2 (8) EVA1 (56) − − 2 Ny1 (8) contact (8) ION2 (8) EVA1 (56) − − 3 Ny1 (8) EVOH2 (8) Ny1 (8) contact (8) LLLPE (48) − 4 Ny1 (15) EVOH1 (8) Ny2 (15) contact (8) ION2 (10) EVA1 (44) However contact is adhesive Resin.

Table 2 Adhesion Wrinkles Perforated gas barrier resistance Pinhole resistance Example 1 ○ ○ ○ ○ ○ 2 ○ ○ ○ ○ ○ 3 ○ ○ ○ ○ △ 4 ○ ○ ○ ○ ○ Comparative example 1 ○ × × ○ × 2 ○ △ × × ○ 3 × × ○ ○ △ 4 △ △ ○ ○ ○

Adhesion: ○ The shape of the content is maintained and adhered without a gap. △ The corner portion of the content is slightly deformed and there is a little gap. × The shape of the content is greatly deformed. Wrinkles: almost no wrinkles on the package △ Some wrinkles on the package × Many large wrinkles on the package Perforated: ○ Thickness inside the seal is 25 μm or more △ Thickness inside the seal Is less than 15 μm, but there is no perforation × perforation is seen inside the seal part Gas barrier property: ○ Oxygen permeation amount (23 ° C × 65% RH) is 10 cc / m ² · D or less △ Oxygen permeation amount (23 ℃ × 65% RH) is less than 20cc / m ² · D × Oxygen permeation rate (23 ° C × 65% RH) is more than 20cc / m ² · D Pinhole resistance: 20 packagings in a cardboard box Put it in a container and drop it on the concrete surface from the height of 1 m 10 times on each of the 3 sides of the cardboard box. ○ The number of bags is 0. △ The number of bags is 1 to 4 × The number of bags is 5 or more.

[0014]

The flexible multilayer film of the present invention is excellent in oxygen gas barrier property, sealing property, flexibility and adhesiveness and has a conventional P content.
With the exception of the VC / PVDC type film, it was possible to wrap without problems even with the method that was considered difficult to wrap. Furthermore, it is a packaging material for skin packs that does not use a halogen-based resin and can adapt to recent environmental problems.

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Claims (10)

[Claims] 1. A nylon layer (A), a gas barrier layer (B), an adhesive layer (C), an ionomer layer (D), and an ethylene-vinyl acetate copolymer layer (E) having a vinyl acetate content of 10% or more. A flexible multilayer film containing at least the layers of. 2. The flexible multilayer film according to claim 1, wherein the gas barrier layer (B) is an ethylene-vinyl alcohol copolymer. 3. The ethylene-vinyl alcohol copolymer has a melting point (DSC method) of 165 ° C. or lower and a Young's modulus of 20.
The soft multilayer film according to claim 2, which has a characteristic of 130 Kg / mm ² or less under conditions of ° C and 65% RH. 4. The nylon layer (A) comprises 6 nylon, 6 ·
The soft multilayer film according to claim 1, 2 or 3, which is nylon 66 or nylon 6.12. 5. The gas barrier layer (B) is an ethylene-vinyl alcohol copolymer, and the melting point (DS) of the nylon layer (A).
The soft multilayer film according to claim 1, 2, 3 or 4, wherein C method) Tn satisfies a relational expression of 20 ° C <Tn-Te <100 ° C with a melting point (DSC method) Te of an ethylene-vinyl alcohol copolymer. 6. A nylon layer (A) and a gas barrier layer (B)
The total thickness of the flexible multilayer film according to claim 1, which is 30% or less of the total thickness of the film. 7. An ethylene-vinyl acetate copolymer layer (E)
The vinyl acetate content of 15% to 25%.
The soft multilayer film according to 2, 3, 4, 5 or 6. 8. The ionomer layer (D) is an ionomer based on a terpolymer of ethylene-methacrylic acid-ester type monomers, 1.
The flexible multilayer film according to 5, 6, or 7. 9. The layer structure is (A)-(B)-(C)-
(D)-(E) (A)-(C)-(B)-(C)-(D)-(E),
(B)-(A)-(C)-(D)-(E), (B)-
(C)-(A)-(C)-(D)-(E), or (A)
-(B)-(A)-(C)-(D)-(E) The soft multilayer film according to claim 1, 2, 3, 4, 5, 6, 7 or 8. 10. The method according to claim 1, which is manufactured by a coextrusion method.
The soft multilayer film according to 2, 3, 4, 5, 6, 7, 8 or 9.