JP2941596B2 - Flexible multilayer film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible content used in a vacuum packaging form (hereinafter referred to as "skin pack") in which a film is heated by a hot plate, and then the film is brought into close contact with the content by pressurized air and heat sealed. The present invention relates to a flexible multilayer film for food packaging having excellent adhesiveness to food.

[0002]

2. Description of the Related Art Deep-drawing vacuum packaging is generally used for packaging processed livestock products and processed marine products, and usually uses a film having an oxygen gas barrier property to enhance the preservability of the contents. For the oxygen gas barrier layer, an ethylene-vinyl alcohol copolymer (hereinafter referred to as EVOH) or a vinylidene chloride-based resin (hereinafter referred to as PVDC) is used. If the surface of the contents is relatively smooth and the shape is constant, deep drawing vacuum packaging is suitable.However, if the shape and the surface of the contents are not uniform or sliced, the film is shifted. Since the size of the molding is larger than the contents, the film formed when vacuum packaging is surplus, it becomes wrinkles on the surface of the package body and not only looks bad, but also the wrinkles tend to generate pinholes It causes trouble. If the adhesiveness after packaging is poor, drip accumulates between the film and the contents, which deteriorates the appearance and accelerates the quality deterioration. Therefore, irregular-shaped products and sliced products that are arranged in a shifted manner are skin-packed.However, flexible films that are easy to stretch are preferred, and because they are compatible with the packaging method, they are conventionally mainly soft-chlorinated. A film having a structure of vinyl (hereinafter, referred to as PVC) / PVDC / ethylene-vinyl acetate copolymer (hereinafter, referred to as EVA) is used. However, processed livestock products and products related to processed marine products are generally distributed at a low temperature of 10 ° C. or less. In the multilayer film, pinholes are generated in the distribution process, and the preservability of the contents may be impaired. More recently, resins containing halogens (PVC, PVDC
) Is rapidly spreading downstream. Under such circumstances, a flexible film was examined, but at the beginning, with consideration for softening, a so-called hard resin other than EVOH of the oxygen gas barrier layer was examined in a direction to remove it from the layer structure. However, the packaging machine widely used by users for skin packs differs from the general packaging machine in the mold structure of the vacuum chamber, so a part of the film is heated strongly in the initial stage, and the film is heated closely to the hot platen in vacuum. During the heating, only the strongly heated portion was stretched, and a perforation phenomenon was observed.

[0003]

DISCLOSURE OF THE INVENTION The present invention does not impair the flexibility and adhesion of the film, allows the user to use the packaging machine conventionally owned by the user as it is, and has the pinhole resistance.
It is to provide a packaging material having excellent oxygen gas barrier properties.

[0004]

According to the present invention, there is provided a nylon layer (A), a gas barrier layer (B), an adhesive layer (C), an ionomer layer (D), and an ethylene-acetic acid having a vinyl acetate content of 10% or more. In a soft multilayer film including at least a layer of a vinyl copolymer layer (E), a nylon layer (A)
Is 6 nylon, 6.66 nylon or 6.12 nylon, the gas barrier layer (B) is an ethylene-vinyl alcohol copolymer, and the total thickness of the nylon layer (A) and the gas barrier layer (B) is 30% of the thickness of the entire film
The following is a flexible multilayer film.

[0005] The nylon layer (A) used in the present invention comprises:
Considering the adhesiveness of the skin pack, 6 nylon,
It must be 6.66 nylon or 6.12 nylon. Nylon has excellent heat and cold resistance, and also has excellent mechanical strength, so it can impart mechanical strength such as pinhole resistance to packaging materials. 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 not less than 90% with respect to vinyl acetate in the copolymer. Method) 130 kg or less under the condition that the Young's modulus is 20 ° C. and 65% RH below 130 ° C.
EVOH of ² mm2 or less is more preferable. The adhesive layer (C) is made of polyethylene, polypropylene, a copolymer thereof or a copolymer with a different α-olefin, or an ethylene-vinyl acetate copolymer or the like, and a monobasic unsaturated fatty acid such as acrylic acid or methacrylic acid. Alternatively, an acid-modified olefin resin obtained by chemically bonding an anhydride of a dibasic unsaturated fatty acid such as maleic acid, phthalic acid or itaconic acid, ie, maleic anhydride, is used. As the ionomer layer (D), an ethylene-methacrylic acid copolymer or a ternary copolymer of ethylene and a third component other than methacrylic acid obtained by intermolecular crosslinking with sodium ions or zinc ions can be used. Considering this, an ionomer based on a terpolymer of an ethylene-methacrylic acid-ester monomer is preferable. Pinhole resistance to external impact depends on the nylon layer on the outside, but if part of the content is hard, pinhole resistance to internal impact is necessary. Therefore, an ionomer which is flexible and can impart a certain degree of pinhole resistance is preferable. Further, the EVA layer (E) has a vinyl acetate content of 10% or more.
VA, vinyl acetate content is 1 due to flexibility and processability
5-25% is preferred.

The method for producing the flexible multilayer film of the present invention employs a co-extrusion method, a dry lamination method and the like. In the dry lamination method, the film becomes rigid and hard when an adhesive is used. In consideration of the above, the coextrusion method is more preferable. As described above, the gas barrier layer is EVOH, and the melting point of the nylon layer is EV.
If it is equal to or lower than the OH, the mold structure of the vacuum chamber part is different from the general case in the skin pack packaging machine widely used by the users, and a part of the film is heated strongly at the initial stage, and the film is turned into a hot plate by vacuum. During the close contact heating, only the strongly heated portion is stretched and the thickness becomes extremely thin, or in some cases, a perforation phenomenon is observed. Therefore, the nylon layer used in the present invention is preferably made of nylon having a melting point of 20 ° C. or higher than EVOH because it is necessary to maintain mechanical strength so that the thickness does not become thin even when a part of the film is heated strongly. However, when the melting point is higher than 100 ° C., the film is not sufficiently softened even when heated on a hot platen, and the adhesion after packaging is greatly reduced. The nylon layer and the EVOH layer need to have a certain thickness from the viewpoints of pinhole resistance and gas barrier properties. However, 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 needs to be 30% or less of the total thickness of the film.

[0007]

The skin pack requires adhesion to the contents, but when PVC or PVDC is not used, so-called hard resins other than EVOH, which is a gas barrier layer, are excluded from the layer structure in order to impart flexibility to the film. Was considered in the direction to be. However, a packaging machine widely used in a skin pack differs from a general packaging machine in a mold structure of a vacuum chamber portion, so that a conventional flexible film cannot avoid a perforation phenomenon during film heating. The film of the present invention uses a nylon having a relatively high softening temperature and mechanical strength to some extent in addition to EVOH, so that even if a part of the film is strongly heated in the initial stage in the vacuum chamber portion of the skin pack packaging machine, it is abrupt. Since no softening occurred and the entire film was stretched relatively, the perforation phenomenon was greatly improved. Further, nylon has high mechanical strength, and can make the film thickness thinner than before, which leads to improvement in adhesion. In addition, by making the resin of the outermost layer nylon, boil sterilization becomes possible, and it can be widely used for food packaging.

[0008]

EXAMPLES A multilayer film having a layer constitution shown in Table 1 was produced by a co-extrusion method. The thickness of all 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 Nippon Sanyo UBE nylon 7024B ・ EVOH1: Kuraray EVAL EP-S105 Young's modulus 120 kg / mm ²・ EVOH2: Kuraray EVAL EP-E105 Young's modulus 150 kg / mm ²・ Adhesive resin: Mitsui ADMER VF60 manufactured by Petrochemical Industry
0 ・ ION1: Himilan H1601 made by Mitsui Dupont Polychemicals ・ ION2: Himilan AM7908-2 made by Mitsui Dupont Polychemicals ・ EVA1: Evaflex P2505C made by Mitsui Dupont Polychemicals ・ EVA2: Evaflex P1403C made by Mitsui Dupont Polychemicals ・ LLDPE: Sumitomo Chemical Industrial Sumikasen L F10
1-1 The obtained film was actually shifted by a packaging machine, bacon was packed, and the appearance and thickness were examined. The gas barrier property was determined by measuring the oxygen permeation amount of the film using OXTRAN manufactured by Mocon Corporation.
Table 2 shows the results.

[0009]

[0010] Note Adhesion: ○ The shape of the contents is maintained and adheres without gaps. △ The corners of the contents are slightly deformed and there are slight gaps. × The shape of the contents is greatly deformed. Wrinkles: ○ Wrinkles are hardly seen on the package △ Wrinkles are slightly seen on the package × Many large wrinkles are found on the package Perforated: ○ The thickness of the inside of the seal is 25 μm or more △ The thickness of the inside of the seal Is less than 15 μm but no perforation × perforation is seen inside the seal part Gas barrier property: oxygen permeation (23 ° C x 65% RH) ○ 10 cc / m ² · D or less △ 20 cc / m ² · D or less × 20cc / m ² · D or more Pinhole resistance: Put 20 packages in a cardboard box and place 1
Drop 10 times on each of the three sides of the cardboard box on the concrete surface from the height of m. ○ There are 0 broken bags △ 1 to 4 broken bags × 5 or more broken bags

[0011]

The flexible multilayer film of the present invention has excellent oxygen gas barrier properties, sealing properties, flexibility and adhesion, and has the same properties as conventional P films.
Packaging other than VC / PVDC film was possible without any problem even in a system that was considered difficult to package. Furthermore, it is a packaging material for skin packs that does not use a halogen-based resin and can be adapted to recent environmental problems.

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B32B 1/00-35/00

Claims (11)

(57) [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. In a flexible multilayer film containing at least a layer of
6 nylon or 6.12 nylon, the gas barrier layer (B) is an ethylene-vinyl alcohol copolymer, and the total thickness of the nylon layer (A) and the gas barrier layer (B) is 30% of the total thickness of the film. A soft multilayer film characterized by the following. 2. The gas barrier layer (B) has a melting point (DSC).
Act) Young's modulus at 130 ° C. or less 20 ° C., of 130 kg / mm ² or less under the conditions of RH 65% ethylene - soft multilayer film according to claim 1 wherein the vinyl alcohol copolymer. 3. The melting point (DSC method) T of the nylon layer (A)
n is the melting point of the ethylene-vinyl alcohol copolymer (DS
C) The flexible multilayer film according to claim 1 or 2, which satisfies the following relational expression with Te. 20 ° C <Tn-Te <100 ° C 4. An ethylene-vinyl acetate copolymer layer (E)
The vinyl acetate content of the styrene is 15% to 25%.
4. The flexible multilayer film according to 3. 5. The flexible multilayer film according to claim 1, wherein the ionomer layer (D) is an ionomer based on a terpolymer of an ethylene-methacrylic acid-ester monomer. 6. The layer structure is (A)-(B)-(C)-
The flexible multilayer film according to any one of claims 1 to 5, wherein (D) to (E). 7. The layer structure is (A)-(C)-(B)-
The flexible multilayer film according to any one of claims 1 to 6, wherein (C)-(D)-(E). 8. The layer structure is (B)-(A)-(C)-
The flexible multilayer film according to any one of claims 1 to 7, which is (D) to (E). 9. The layer structure is (B)-(C)-(A)-
The flexible multilayer film according to any one of claims 1 to 8, wherein (C)-(D)-(E). 10. The layer configuration is (A)-(B)-(A)-
The flexible multilayer film according to any one of claims 1 to 9, which is (C)-(D)-(E). 11. The method according to claim 1, which is produced by a co-extrusion method.
0. The soft multilayer film according to 0.