JP2016112790A - Coextrusion multilayer film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a skin having excellent pinhole resistance, excellent content adhesion even for a complicated shape, and excellent heat sealability even if various types of resins are used for a sealing layer of a tray or a bottom material. Provision of coextruded multilayer film for packs. SOLUTION: An ionomer resin layer as an outer layer, a saponified ethylene-vinyl acetate copolymer layer as an intermediate layer, and an ethylene-vinyl acetate copolymer resin having a vinyl acetate content of 8 mol% or more and 20 mol% or less as an innermost layer or It is a coextruded multilayer film with a hot melt resin layer, the ionomer resin layer thickness ratio to the total film thickness is 40% to 70%, and the ethylene-vinyl acetate copolymer saponified layer thickness ratio is 10% or less. A co-extruded multilayer film for skin pack lidding, characterized by [Selection figure] None

Description

  The present invention relates to a coextruded multilayer film that can be suitably used mainly as a cover material for skin pack packaging of foods such as raw meat, prepared foods, processed meat products, and processed fishery products. The skin pack refers to a package in which a heated film is brought into close contact with the contents with compressed air and at the same time the bottom material (tray) and the film are heat-sealed and vacuum packaged.

  Conventionally, films made of polyvinyl chloride (PVC) / polyvinylidene chloride (PVDC) / ethylene-vinyl acetate copolymer (EVA) have been used as skin pack films for sliced ham, bacon, processed fishery products, etc. However, there is a problem that pinhole resistance is inferior when containing processed fishery products with sharp bones or under low temperatures such as special refrigeration, and the trend of dechlorination of packaging materials still continues .

In response to the above problem, a film having a structure in which a nylon (Ny) layer and an ethylene-vinyl alcohol copolymer (EVOH) layer are arranged on the outer layer side, and an ionomer (IO) layer and an EVA layer are arranged on the inner layer side is disclosed. (Patent Document 1, Patent Document 2).
However, when the Ny layer is arranged, although the film strength is increased and the pinhole resistance is excellent, on the other hand, the adhesiveness is lowered, and when the content shape is complicated or flexible, the content adhesiveness is reduced. There is an inferior problem. Further, when the EVOH layer is an outer layer, it is vulnerable to impacts and scratches, has insufficient pinhole resistance, and does not exhibit the gas barrier properties possessed by the EVOH resin.

  In addition, commercially available products having an IO / EVA configuration are often used, but they have a problem that the IO layer is thickened to increase the film strength and the cost is high. In addition, by using EVA with a vinyl acetate (VA) content of over 20 mol%, it is possible to form a film into a film so that it can be sealed on trays and bottom materials of various resin types (polyethylene, polypropylene, polystyrene, polyethylene terephthalate, etc.) There are disadvantages that are easily burnt by extrusion of the film, and the slipperiness of the film is very poor and the film is clogged by the packaging machine.

Japanese Patent No. 3085626 Patent No. 5034237

  The present invention is intended to solve the above-mentioned problems of the prior art, and the object of the present invention is excellent in pinhole resistance even from room temperature to under freezing, and content adhesion to complex shaped contents. An object of the present invention is to provide a coextruded multilayer film for a skin pack lid material, which has excellent heat sealability with respect to bottom materials of various materials, and film sliding of a packaging machine does not occur due to good film sliding. .

  An object of the present invention is that a coextruded multilayer film has an ionomer resin (IO) layer as an outer layer, an ethylene-vinyl acetate copolymer saponified product (EVOH) layer as an intermediate layer, and a vinyl acetate content of 8 mol% or more in an innermost layer. An ethylene-vinyl acetate copolymer resin (EVA) or hot melt resin (HM) layer of 20 mol% or less is disposed, and the ionomer resin (IO) layer thickness ratio with respect to the total film thickness is 40% or more and 70% or less, This is achieved when the ethylene-vinyl acetate copolymer saponified product (EVOH) layer thickness ratio is 10% or less.

  According to the co-extruded multilayer film for skin pack lid material of the present invention, the pinhole resistance is excellent even in a wide range of temperature conditions, and the content adhesion is excellent even for contents with complicated shapes. Even if the sealing layer is a resin other than polyethylene resin, a coextruded multilayer film for skin pack having good heat sealability can be provided.

<Outermost layer: ionomer resin layer>
An ionomer resin is disposed on the outermost layer of the film of the present invention in order to impart pinhole resistance and content adhesion.
Moreover, when an ionomer resin layer is also arranged inside the ethylene-vinyl acetate copolymer saponified product (EVOH) layer of the intermediate layer, the stretchability of the EVOH layer is improved and the content followability is improved.

  The ionomer resin is obtained by crosslinking an ethylene-methacrylic acid copolymer with a metal ion such as zinc or sodium, and is not particularly limited, but a sodium ion neutralization type ionomer resin is preferably used.

  The lower limit of the ratio of the ionomer resin layer thickness to the film layer thickness is preferably 40% or more, and more preferably 50% or more. Further, the upper limit is preferably 70% or less, and more preferably 60% or less. By setting the lower limit to 40% or more, good pinhole resistance and content adhesion can be obtained, and by setting the upper limit to 70% or less, it is possible to ensure a heat seal layer thickness that enables appropriate heat sealing. Can do.

  In the case where the ionomer resin layer is disposed on both the outermost layer and the position inside the EVOH layer (two layers), the effect of the present invention can be obtained if the total thickness of the two layers is within the above ratio range. The thickness ratio configuration of the two layers is preferably 10:90 to 90:10 with respect to the total thickness of the two layers.

<Saponified ethylene-vinyl acetate copolymer layer>
In the intermediate layer, an ethylene-vinyl acetate copolymer saponified product (EVOH) layer is disposed for the purpose of imparting oxygen barrier properties. Although the ethylene content of EVOH used in the EVOH layer is not particularly limited, it is preferably 27 mol% or more and 47 mol% or less from the viewpoint of film formation stability, and is 32 mol% or more and 44 mol% or less. More preferably it is. Further, EVOH has a saponification degree of 90% or more, preferably 95 mol% or more. By maintaining the ethylene content of EVOH and the saponification degree within the above ranges, the coextrudability of the film of the present invention and the strength of the film can be improved.

  The thickness of the EVOH layer is not particularly limited, but the lower limit is 3% or more of the total thickness, and the upper limit is 10% or less of the total thickness. A sufficient oxygen barrier property can be obtained by setting the lower limit of the thickness of the EVOH layer to 3%, and good content adhesion can be maintained by setting the upper limit to 10%.

<Inner layer>
As the innermost layer, an ethylene-vinyl acetate copolymer resin (EVA) layer having a vinyl acetate content of 8 mol% or more and 20 mol% or less, or a hot melt resin (HM) for the purpose of imparting heat sealability and flexibility. Arrange the layers.
By setting the vinyl acetate content of the ethylene-vinyl acetate copolymer resin (EVA) to 8 mol% or more, good heat sealability and flexibility can be obtained. On the other hand, if it exceeds 20 mol%, the problem of productivity that it is easy to burn in a screw or a die during extrusion is large, and the film that has been formed is also not very slippery due to the adhesiveness of the resin, and blocking is not possible. This results in poor suitability for packaging machines.

  The type of hot melt resin (HM) used for the innermost layer is not limited as long as it is a heat sealable resin. For example, what used polyethylene (PE), polypropylene (PP), polystyrene (PS), polyester (PET, PBT) etc. as a base polymer is mentioned. Further, as the hot melt resin composition, a polyethylene resin base polymer containing a tackifier and a wax component can be suitably used.

  As the base polymer of the hot melt resin, low density polyethylene (LDPE), linear low density polyethylene (LLDPE), ethylene-vinyl acetate copolymer (EVA), ethylene-methyl methacrylate copolymer ( EMMA), ethylene-methyl acrylate copolymer (EMA), ethylene-acrylic acid copolymer (EAA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methacrylic acid copolymer (EMAA), ethylene- It is preferably composed of an ionomer of acrylic acid copolymer (EAA), an ionomer of ethylene-methacrylic acid copolymer (EMAA), and a resin composed of at least one selected from the group consisting of these ionomers. .

  The tackifier is not particularly limited as long as it can improve the hot tackiness and wettability of the base polymer, but rosin, modified rosin or ester compounds thereof, terpene resin, aliphatic petroleum resin, alicyclic group A petroleum petroleum resin, an aromatic petroleum resin, a styrene resin having the highest molecular weight, an isoprene resin, an alkylphenol resin, and the like can be suitably used.

  The content of the tackifier in the hot melt resin is preferably 5% or more, preferably 10% or more as the lower limit. The upper limit is 60% or less, preferably 50% or less. By setting the lower limit to 5% or more, good heat sealability can be obtained, and by setting the upper limit to 60% or less, the cohesive strength of the hot melt resin itself can be maintained, and as a result, good heat sealing is achieved. Strength can be obtained.

  As a wax component, it is not necessary to add it, but by adding it, film blocking can be prevented, and petroleum wax such as paraffin and microcrystalline wax, and synthetic wax such as low molecular weight polyethylene wax can be suitably used. However, you may mix | blend 2 or more types.

  The layer thickness ratio of the innermost EVA layer or the hot melt resin (HM) layer is 5% or more with respect to the total film thickness, and good heat sealability is obtained. The film strength can be ensured by the balance with the thickness of the ionomer resin.

<Adhesive resin layer>
In the film of the present invention, at least one layer can be disposed between the outermost layer (ionomer layer) and the intermediate layer (EVOH layer), or between the innermost layer and the intermediate layer.

The adhesive resin used in the adhesive resin layer is not particularly limited as long as the outermost ionomer layer, the intermediate EVOH resin layer, and the innermost layer can be bonded with a required strength. A polyolefin resin modified with an unsaturated carboxylic acid or a derivative thereof is preferable.
Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid, citraconic acid and the like. In addition, an ester or anhydride of the unsaturated carboxylic acid can be used as an adhesive resin, and as derivatives, methyl acrylate, methyl methacrylate, ethyl acrylate, propyl acrylate, butyl acrylate, butyl methacrylate, vinyl acetate. , Glycidyl acrylate, glycidyl methacrylate, acrylamide, methacrylamide, sodium acrylate and the like can be used.

  Examples of commercially available adhesive resins include “Admer” manufactured by Mitsui Chemicals, Inc., and these can be suitably used. Among them, the LLDPE type or EVA type can be preferably used.

<Whole film>
The film of the present invention is composed of an ionomer resin (IO) layer as an outer layer, an ethylene-vinyl acetate copolymer saponified product (EVOH) layer as an intermediate layer, and a vinyl acetate content of 8 mol% or more and 20 mol% in an innermost layer. It is a coextruded multilayer film in which the following ethylene-vinyl acetate copolymer resin (EVA) or hot melt resin (HM) layer is arranged, and the ionomer resin (IO) layer thickness ratio with respect to the total film thickness is 40% or more and 70% or less As long as the ethylene-vinyl acetate copolymer saponified product (EVOH) layer thickness ratio is 10% or less, the layer structure of the other layers is not particularly limited.

  The film of the present invention is an inorganic particle such as silica, talc, kaolin, calcium carbonate, or the like for the purpose of improving and adjusting various properties such as molding processability and productivity within a range that does not significantly impair the effects of the present invention. Add additives such as pigments such as titanium and carbon black, flame retardants, weather resistance stabilizers, heat stabilizers, antistatic agents, melt viscosity improvers, crosslinking agents, lubricants, nucleating agents, plasticizers, anti-aging agents, etc. it can

  When represented by an ionomer layer (A), an EVOH layer (B), an ethylene-vinyl acetate copolymer resin layer (C), a hot melt resin layer (D), and an adhesive resin layer (E), for example, the following layer structure Can be formed.

(1) A / B / C
(2) A / B / D
(3) A / B / A / C
(4) A / B / A / D
(5) A / E / B / E / C
(6) A / E / B / E / D
(7) A / E / A / B / E / C
(8) A / E / A / B / E / D

  Among the above, the preferred layer structure is (5), (6), (7) or (8), more preferably (7) or (8).

  The film of the present invention can be produced using a known method. For example, an extrusion lamination method, a coextrusion inflation method, a coextrusion T die method, and the like can be used, and it is particularly preferable to use the coextrusion T die method from the viewpoint of layer thickness control.

Examples of the present invention will be described below, but the present invention is not limited thereto.
[Production of co-extruded multilayer film for skin pack cover]
A multilayer film having a layer structure described in each example was obtained by full-layer coextrusion and used for the production of a skin pack.

Example 1
IO (50 μm) / Adhesive resin (10 μm) / EVOH (10 μm) / Adhesive resin (10 μm) / EVA1 (20 μm)
IO: Mitsui DuPont High Chemical Na ion neutralization type Adhesive resin: Mitsui Chemicals Admer EVOH: Kuraray Eval Ethylene 44 mol type EVA1: Nippon Polyethylene Novatec EVA 15 mol% vinyl acetate type

(Example 2)
IO (30 μm) / Adhesive resin (10 μm) / EVOH (5 μm) / Adhesive resin (10 μm) / IO (30 μm) / EVA 2 (10 μm)
EVA2: Evaflex vinyl acetate 19 mol% type made by Mitsui DuPont Polychemical

(Example 3)
IO (60 μm) / Adhesive resin (10 μm) / EVOH (10 μm) / Adhesive resin (10 μm) / HM1 (10 μm)
HM1: Mersen M manufactured by Tosoh Corporation

Example 4
IO (30 μm) / Adhesive resin (10 μm) / EVOH (5 μm) / Adhesive resin (10 μm) / IO (30 μm) / HM2 (10 μm)
HM2: Hirodine made by Yasuhara Chemical

(Comparative Example 1)
EVOH (20 μm) / Adhesive resin (5 μm) / IO (10 μm) / EVA1 (40 μm)

(Comparative Example 2)
IO (50 μm) / Adhesive resin (10 μm) / EVOH (10 μm) / Adhesive resin (10 μm) / EVA3 (20 μm)
EVA3: Evaflex made by Mitsui DuPont Polychemicals Vinyl acetate 25 mol%

(Comparative Example 3)
IO (30 μm) / Adhesive resin (10 μm) / EVOH (5 μm) / Adhesive resin (10 μm) / IO (30 μm) / LLDPE (10 μm)
LLDPE: Nippon Polyethylene Novatec LL density 0.920

(Comparative Example 4)
PA (8 μm) / EVOH (8 μm) / Adhesive resin (8 μm) / IO (8 μm) / EVA4 (48 μm)
PA: UBE Nylon 6-12 Copolymer Nylon made by Ube Industries EVA4: Everflex Acetic acid 14 mol% made by Mitsui DuPont Polychemical

[Production of skin pack]
In a skin pack packaging machine (QID300 manufactured by ISHIDA), 300g chicken thighs are heated using the coextruded film of each example and the following two types of layered forming trays (length 190mm x width 150mm x depth 50mm). Skin pack packaging was performed at a temperature of 120 ° C. The tray 1 was sealed on the polyethylene resin (PE) layer surface.

Tray 1: A laminate of co-extruded film of PE (10 μm) / adhesive resin (5 μm) / EVOH (5 μm) / adhesive resin (5 μm) / PE (15 μm) on a foamed polystyrene resin sheet (PSP).
Tray 2: Co-extruded sheet of polypropylene (220 μm) / adhesive resin (20 μm) / EVOH (20 μm) / adhesive resin (20 μm) / polypropylene (220 μm).

[Evaluation method]
The following evaluation was performed and the results are shown in Table 1.

<Applicability for packaging machines>
When the produced multilayer film was sent to a packaging machine, the case where no film clogging occurred in the packaging machine was indicated as “◯”, and the case where the packaging machine clogged occurred was indicated as “x”.

<Content adhesion>
The produced skin pack was observed, closely adhered to the contents, and those with little wrinkles and crushed contents were marked with ◯, and those with wrinkles or crushed contents were marked with x.

<Sealability>
Store the prepared skin pack in a refrigerator at 5 ° C. for 24 hours. If the drip exuded from the raw chicken thigh does not erode the seal part of the skin pack and the seal adhesion is not impaired, there is erosion. Was marked with x.

<Frozen pinhole resistance>
The prepared skin pack is frozen at -30 ° C for 24 hours, then packed in two rows and five rows in a corrugated cardboard box, dropped from the height of 50cm onto the concrete surface five times, and a pinhole is generated in the skin pack cover film. Those that did not did were marked with ◯, and those that had pinholes were marked with ×.

From Table 1, Examples 1-4 were favorable with any evaluation.
On the other hand, in Comparative Examples 1 and 4, the contents were crushed during packaging and the appearance was poor. Further, Comparative Example 1 was insufficient in pinhole resistance.
In Comparative Example 2, the slip of the film inner layer was poor, and the film was clogged with the packaging machine. In Comparative Example 3, the sealing performance was poor, and the seal portion was eroded by drip.

  The film of the present invention is low in cost, excellent in pinhole resistance, excellent in content adhesion even for complicated contents, has good heat sealability, and has good film slipping. This can provide a suitable skin pack lid material that does not cause film clogging, and can greatly contribute to food safety and hygiene, cost control, and efficiency in food processing, packaging, storage, and sales.

Claims (3)

  The outer layer is an ionomer resin (IO) layer, the intermediate layer is an ethylene-vinyl acetate copolymer saponified product (EVOH) layer, and the innermost layer is an ethylene-vinyl acetate copolymer having a vinyl acetate content of 8 mol% to 20 mol%. A coextruded multilayer film having a resin (EVA) or hot melt resin (HM) layer, the ratio of the ionomer resin (IO) layer thickness to the total film thickness being 40% or more and 70% or less, and ethylene-vinyl acetate copolymer A coextruded multilayer film for skin pack lid material, wherein the combined saponified product (EVOH) layer thickness ratio is 10% or less.   The coextruded multilayer film for skin pack lidding according to claim 1, wherein an ionomer resin (IO) layer is disposed between the intermediate layer and the innermost layer. The coextruded multilayer film for skin pack lid according to claim 1 or 2, wherein the total film thickness is 40 µm or more and 150 µm or less.