JP2007062389A - Composite film and container for gas pack package - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composite film and a container suitable to gas pack package which are excellent in tough rigidity and an impact resistance at a low temperature. <P>SOLUTION: The composite film comprises a sealing layer, an intermittent layer and an outer layer, wherein a polyester type resin layer of 100-1,000 μm of thickness is constructed in the intermittent layer and a polyethylene type resin layer of 0.88-0.92 g/cm<SP>3</SP>of density and 20-150 μm of thickness is constructed in the outer layer. The container is manufactured by a deep-molding method of the composite film. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a composite film and container for gas pack packaging, and more specifically, as a bottom material (container body) that can withstand impacts during frozen storage and transportation in a gas pack package filled with an inert gas after storing food. The present invention relates to a composite film for gas pack packaging that can be suitably used and has excellent rigidity and a container obtained by deep drawing the composite film for gas pack packaging.

  A composite film formed by laminating various resin layers is used for the bottom material for gas pack packaging. As means for imparting rigidity to the bottom material, a polyvinyl chloride resin, a polyester resin, a polystyrene resin, or a polypropylene resin is used as the outermost layer resin. Among the above-exemplified resins, the polyvinyl chloride resin has an advantage that it has excellent rigidity and is difficult to crack because it has excellent low-temperature characteristics as a bottom material for cryopreservation.

  However, polyvinyl chloride resin tends to be avoided in the food packaging field due to environmental problems and the like. Therefore, how to use a resin other than polyvinyl chloride resin has become a problem.

  A composite film using a polypropylene resin is weaker than other resins, and in particular, those with improved cold resistance have no rigidity as a bottom material and have a problem in practicality. In addition, the composite film using polyester-based resin and polystyrene-based resin as the outermost layer has a low cold resistance strength, and particularly, when it is frozen, it is extremely susceptible to cracking and has a problem that it cannot withstand frozen storage and transportation. .

  Therefore, the present invention aims to provide a composite film for gas pack packaging that can solve the above-mentioned problems, has excellent rigidity and can withstand impacts at low temperatures, and a container comprising the composite film for gas pack packaging. It is said.

In order to achieve the above object, the composite film for gas pack packaging of the present invention is a composite film comprising a seal layer, an intermediate layer and an outermost layer, and the intermediate layer has a polyester resin layer or polystyrene having a thickness of 100 to 1000 μm. In addition, a polyethylene resin layer having a density of 0.88 to 0.92 g / cm ³ and a thickness of 20 to 150 μm is provided in the outermost layer.

  Here, the outermost polyethylene resin layer is more preferably composed of a linear low density polyethylene resin polymerized with a metallocene catalyst. Furthermore, an ethylene-vinyl acetate copolymer saponified resin layer and / or a polyamide resin layer can be arranged in the intermediate layer according to the required quality.

  Moreover, the container of this invention forms the bottom material by carrying out the deep drawing process of said composite film for gas pack packaging.

  Since the composite film for gas pack packaging of the present invention has excellent stiffness and can withstand impacts at low temperatures, it is highly useful as a bottom material for gas pack packaging and vacuum packaging. Therefore, the container formed using this composite film is most suitable for gas pack packaging and vacuum pack packaging of foods and various products, and can sufficiently withstand impacts during frozen storage and transportation.

  First, the composite film for gas pack packaging of this invention is demonstrated. The basic layer structure of the composite film for gas pack packaging of the present invention consists of a seal layer, an intermediate layer and an outermost layer, and conventionally a polyester-based resin layer or a polystyrene-based resin for imparting rigidity provided in the outermost layer. The resin layer is arranged in the intermediate layer, and a specific polyethylene resin layer is arranged in the outermost layer.

The polyethylene resin used for the outermost layer needs to use a resin having a density in the range of 0.88 to 0.92 g / cm ³ . A resin having a density of less than 0.88 g / cm ³ has a problem that the surface of the composite film becomes slippery and it is difficult to handle the container after it is formed into a bottom material. On the other hand, when the density exceeds 0.92 g / cm ³ , there is a problem that the elastic modulus at a low temperature becomes too high and is easily cracked.

  As the polyethylene resin in the above density range, a normal linear low density polyethylene resin can be used, but a linear low density polyethylene resin polymerized using a metallocene catalyst has a narrow molecular weight distribution. Since it is more excellent in strength, it can be suitably used.

  The thickness of the polyethylene resin layer as the outermost layer needs to be in the range of 20 to 150 μm. When the thickness is less than 20 μm, the effect of preventing the occurrence of cracks at low temperature use is small, and when the thickness exceeds 150 μm, the deep drawability is deteriorated, which is not preferable.

  A polyester resin layer or a polystyrene resin layer is disposed on the intermediate layer of the composite film for gas pack packaging of the present invention. The polyester resin of the polyester resin layer is preferably a normal polyethylene terephthalate polymerized from terephthalic acid and ethylene glycol, or a copolymer polyester resin further containing isophthalic acid, neopentyl glycol, cyclohexane dimethanol or the like as a component. It can be used and may contain small amounts of additives such as PEN (polyethylene naphthalate).

  In particular, an amorphous polyester resin excellent in transparency and processability, for example, “Easter PETG” manufactured by Eastman Chemical Co., which is composed of terephthalic acid, ethylene glycol, and cyclohexanedimethanol can be suitably used.

  The polystyrene-based resin may be any one having polystyrene and a copolymer thereof as a main component, but HIPS (high impact polystyrene) in which a rubber component is dispersed or St-bd (styrene) which is a block copolymer with a diene component. It is more preferable to use a resin having improved low temperature impact strength such as (butadiene).

  Here, the thickness of the polyester resin layer or the polystyrene resin layer of the intermediate layer varies depending on the type of resin, the shape of the final bottom material, and the like, but is preferably in the range of 100 μm to 1000 μm. If it is less than 100 μm, the waist becomes too weak, so that it is difficult to use as a bottom material for gas packs, and if it exceeds 1000 μm, it tends to be difficult to perform deep drawing with a normal deep drawing packaging machine.

  The sealing layer is not particularly limited as long as the desired sealing property can be obtained. However, it is most preferable to use a linear low-density polyethylene having excellent low-temperature impact properties similar to the polyethylene resin disposed in the outermost layer. preferable. Further, by blending polybutene-1 with linear low density polyethylene, it is possible to impart cohesive failure type easy peel property (easy-opening property).

  When the composite film for gas pack packaging of the present invention is used as a bottom material for gas pack packaging of food, an ethylene-vinyl acetate copolymer saponified resin (hereinafter referred to as “EVOH”) layer having a low oxygen permeability. Is preferably disposed in the intermediate layer. Further, a polyamide resin layer may be provided for imparting strength. Especially when EVOH co-extruded film is used, even if EVOH and the sealing layer are bonded via an acid-modified polyethylene resin (adhesive resin), the interlayer strength is not strong. In the case of the pack product, it is difficult to obtain a good easy peel property by peeling between the layers at the time of opening.

  Therefore, by interposing a polyamide resin layer that has good adhesion to EVOH and that easily exhibits interlayer strength with the adhesive resin between the seal layer and the EVOH layer, the interlayer can be firmly bonded. .

  The type of the polyamide resin is not particularly limited, but 6-66 nylon has a low melting point, good co-extrusion with EVOH, interlayer strength with adhesive resin, and low temperature pinhole resistance It is preferable because of its good properties.

  The manufacturing method of the composite film for gas pack packaging of this invention is not specifically limited, It can manufacture by the manufacturing method of normal composite films, such as a co-extrusion method and a dry lamination method.

  FIGS. 1 to 4 show an example of a packaging container formed using the above-described composite film for gas pack packaging. First, the cross-sectional side view of FIG. 1 and the plan view of FIG. 2 show a first embodiment of the container of the present invention. It is formed of a material 11 and a lid material 14 which is attached to a lid material application surface 13 provided on the upper opening edge 12 of the bottom material 11 by heat fusion or the like.

  The side wall 16 connected to the upper opening edge 12 from the bottom surface 15 of the bottom member 11 is formed in an inverted trapezoidal shape by an inclined surface that widens toward the upper opening edge 12. A large number of similar lateral ribs 17 are provided concentrically, and the vertical cross-sectional shape of each side wall 16 is formed in a staircase shape.

  The package formed in this manner is in a state in which air is enclosed inside in the state where the article is stored and the lid member 14 is attached to the lid-attachment surface 13 and sealed. Depending on the type, the inside is filled with nitrogen gas, so that the bottom material 11 is not crushed by the internal gas pressure, and the rigidity of the side wall 16 is improved by the large number of lateral ribs 17 so that the container is It becomes difficult to deform.

  Then, when a force is applied from the up and down direction after the lid member 14 is peeled off and the article is taken out, the side ribs 17 can be deformed into a bellows shape and the bottom material 11 can be flattened. Therefore, the volume of the bottom material 11 after use can be greatly reduced by crushing, and there is an advantage that the volume when discarded or recovered as garbage can be greatly reduced.

  Moreover, the cross-sectional side view of FIG. 3 and the plan view of FIG. 4 show a second embodiment of the container of the present invention, and the bottom in which the recessed portion for storage is formed by deep drawing the composite film for gas pack packaging. It is formed of a material 21 and a cover material 24 which is attached to a cover material attachment surface 23 provided on the upper opening edge 22 of the bottom material 21 by heat fusion or the like.

  The side wall 26 connected to the upper opening edge 22 from the bottom surface 25 of the bottom member 21 is connected to the upper opening edge 22 via a stepped portion 27 and a rising portion 28 protruding in the horizontal direction near the upper opening edge 22. . That is, the bottom member 21 is formed by a two-stage recess.

  In this way, by forming the step portion 27 in the vicinity of the upper opening edge 22, the step portion 27 can increase the strength of the upper opening edge 22, particularly the strength against the external force in the longitudinal direction of the opening edge. Can be made difficult to deform. In particular, since it is possible to suppress deformation when the lid member 24 is peeled off from the opening portion 24a by the easy peel, it is possible to prevent the stored items from popping out.

  Furthermore, by providing a large number of vertical ribs 29 at the rising portion 28 of the stepped portion 27, the strength of the stepped portion 27 can be further increased, so that the rigidity of the bottom member 21 can be further improved.

  The container as described above is particularly suitable for gas pack packaging of food, can sufficiently withstand impacts during frozen storage and transportation, and can be reduced in volume when discarded or collected after use. Further, deformation of the bottom material when the lid material is peeled can be suppressed. Further, in addition to food packaging containers, it is also useful as a vacuum pack container for plastic products, metal products, etc. that require pinhole resistance.

EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to the content of an Example.
The contents of the abbreviations in the following description are as follows. (The same abbreviation and number used the same resin)
Metallocene LL: Linear low density polyethylene resin polymerized by metallocene catalyst APET: Resin made from ordinary polyethylene terephthalate as a raw material in an amorphous state EVOH: Saponified resin of ethylene-vinyl acetate copolymer
Ny ... 6-66 nylon resin
AD ... acid-modified polyethylene resin St-bd ... styrene-butadiene copolymer
LL ... Linear low density polyethylene resin
VL ... Ultra low density polyethylene resin

Example 1
A composite film having the following layer structure was formed by a coextrusion method. Hereinafter, the parentheses represent the thickness of each layer, and the unit is μm.
APET1 / AD1 / EVOH1 / Ny / AD2 / metallocene LL1 (seal layer)
(400) (5) (10) (5) (5) (25)
APET1: “NOVAPEX GS600” manufactured by Mitsubishi Chemical Corporation AD1: “Admer SF715” manufactured by Mitsui Chemicals, Inc. EVOH1: “EVAL EP-E153” manufactured by Kuraray Co., Ltd. Ny: “Novamid 2030” manufactured by Mitsubishi Engineering Plastics Co., Ltd. AD2: “Admer NF548” Mitsui Chemicals Co., Ltd. Metallocene LL1: “Kernel KF370” Nihon Polychem Co., Ltd. Next, dry laminate a metallocene LL film with a thickness of 50 μm and a density of 0.907 g / cm ³ on the APET side. The outermost layer was bonded by the method to obtain the following composite film.
Metallocene LL2 (50) // APET1 (400) / AD1 (5) / EVOH1 (10) / Ny (5) / AD2 (5) / metallocene LL1 (25) (seal layer)
Metallocene LL2: “Kernel KF270” manufactured by Nippon Polychem Co., Ltd.

(Example 2)
A composite film having the following layer structure was formed by a dry lamination method.
Metallocene LL3 // APET2 // Metalocene LL1 (seal layer)
(100) (400) (50)
Metallocene LL3: “Kernel KF260” manufactured by Nippon Polychem Co., Ltd. APET2: “Novaclear SG007” manufactured by Mitsubishi Chemical Co., Ltd. The density of the outermost metallocene LL3 was 0.903 g / cm ³ .

(Example 3)
A composite film having the following layer structure was formed by a coextrusion method.
EVOH1 / Ny / AD2 / metallocene LL1 (seal layer)
(10) (10) (5) (25)
Next, a St-bd film (thickness: 400 μm) and a metallocene LL film (thickness: 50 μm, density: 0.910 g / cm ³ ) were sequentially joined to the EVOH1 side by a dry laminating method to obtain the following composite film.
Metallocene LL4 (50) // St-bd (400) // EVOH1 (10) / Ny (10) / AD2 (5) / metallocene LL1 (25) (seal layer)
Metallocene LL4: “Affinity PL1845” manufactured by Dow Chemical Japan Co., Ltd. St-bd: “K Resin KK38” manufactured by Philips Oil Co., Ltd.

Example 4
A composite film having the following layer structure was obtained in the same manner as in Example 1 except that the thickness of the APET of the intermediate layer was different.
Metallocene LL2 (50) // APET1 (80) / AD1 (5) / EVOH1 (10) / Ny (5) / AD2 (5) / metallocene LL1 (25)

(Example 5)
A composite film having the following layer structure was obtained in the same manner as in Example 1 except that the thickness of the APET of the intermediate layer was different.
Metallocene LL2 (50) // APET1 (1200) / AD1 (5) / EVOH1 (10) / Ny (5) / AD2 (5) / metallocene LL1 (25) (seal layer)

(Comparative Example 1)
A composite film having the following layer structure was formed by a coextrusion method.
APET1 / AD1 / EVOH1 / Ny / AD2 / metallocene LL1 (seal layer)
(400) (5) (10) (5) (5) (25)

(Comparative Example 2)
A composite film having the following layer structure was formed by a coextrusion method.
EVOH1 / Ny / AD2 / metallocene LL1 (seal layer)
Next, a St-bd film (thickness: 400 μm) having a thickness of 400 μm was joined to the EVOH 1 side by a dry laminating method to obtain the following composite film.
St-bd // EVOH1 / Ny / AD2 / metallocene LL2
(400) (10) (10) (5) (25)

(Comparative Example 3)
The following composite film was obtained with the same contents as in Example 1 except that a metallocene LL film having a thickness of 200 μm was used for the outermost layer.
Metallocene LL2 (200) // APET1 (400) / AD1 (5) / EVOH1 (10) / Ny (5) / AD2 (5) / Metalocene LL1 (25) (seal layer)

(Comparative Example 4)
The following composite film was obtained with the same contents as in Example 1 except that a metallocene LL film having a thickness of 15 μm was used as the outermost layer.
Metallocene LL2 (15) // APET1 (400) / AD1 (5) / EVOH1 (10) / Ny (5) / AD2 (5) / metallocene LL1 (25) (seal layer)

(Comparative Example 5)
The following composite film was obtained in the same manner as in Example 1 except that an LL film having a density of 0.925 g / cm ³ was used for the outermost layer.
LL (50) // APET1 (400) / AD1 (5) / EVOH1 (10) / Ny (5) / AD2 (5) / metallocene LL1 (25) (seal layer)
LL: “Novatec LL UF420” manufactured by Nippon Polychem Co., Ltd.

(Comparative Example 6)
The following composite film was obtained with the same contents as in Example 1 except that a VL film having a density of 0.870 g / cm ³ was used for the outermost layer.
VL // APET1 (400) / AD1 (5) / EVOH1 (10) / Ny (5) / AD2 (5) / metallocene LL1 (25) (seal layer)
VL: “Affinity EG8100” manufactured by Dow Chemical Japan

Each composite film of Examples 1-5 and Comparative Examples 1-6 was evaluated by the following evaluation methods.
<Evaluation method>
Using each of the above composite films as the bottom material, the lid material is deep-drawn using a biaxially oriented polypropylene film (OPP) (30) // transparent vapor-deposited PET (12) // easy peel (50). A pack product of frozen hamburgers (130 g × 2 pieces) was produced using R530 manufactured by Multipack Inc. and evaluated.

Formability:
It was investigated whether or not molding was possible for a mold having a depth of 40 mm at the optimum temperature of each sheet by changing the molding temperature. ○ which can be molded according to the mold, △ which has a little poor followability to the mold but has no problem in practical use, △ which has poor followability to the mold and cannot be molded according to the mold × It was.

Waist:
The case where the corner of the packed product is difficult to deform and can be held by hand is indicated as ◯, and the case where the shape is deformed but has no practical problem is indicated as △.

Outer layer slip:
It was examined whether or not it was able to smoothly slide and fall on a stainless steel plate having an angle of about 25 degrees at the exit of the packaging machine.

Drop strength:
Put 12 packed items (2 stacks x 6 rows) in a cardboard case, leave it in a freezer at -20 ° C for more than 24 hours and then drop it on the concrete surface 10 times from a height of 50 cm. The number of occurrence was investigated. The case where 2 or less cracks occurred in 12 pieces was evaluated as ◯, and the case where 5 or more cracks occurred was evaluated as ×.
The results evaluated by the above evaluation method are shown in Table 1.

  From Table 1, it can be seen that Examples 1 to 6, which are composite films for gas pack packaging of the present invention, are all excellent in formability, waist, outer layer slip, and drop strength. On the other hand, Comparative Examples 1 and 2 in which the resin of the outermost layer is different and Comparative Example 4 in which the outermost layer is thin are inferior in drop strength, Comparative Example 3 in which the outermost layer is thick, and LL used for the outermost layer It turns out that the comparative example 5 whose density of is too large is inferior to a moldability. Moreover, it turns out that the comparative example 6 in which the density of resin used for an outermost layer is too small is inferior to outer layer sliding.

It is a cross-sectional side view which shows the 1st example of a package using the container of this invention. It is also a plan view. It is a cross-sectional side view which shows the 2nd example of a package using the container of this invention. It is also a plan view.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Bottom material, 12 ... Upper opening edge, 13 ... Lid covering surface, 14 ... Cover material, 15 ... Bottom surface, 16 ... Side wall, 17 ... Side rib, 21 ... Bottom material, 22 ... Upper opening edge, 23 ... Covering surface of cover material, 24: Cover material, 25: Bottom surface, 26: Side wall, 27: Stepped portion, 28: Standing portion, 29 ... Vertical rib

Claims (4)

In the composite film composed of the seal layer, the intermediate layer, and the outermost layer, a polyester resin layer or a polystyrene resin layer having a thickness in the range of 100 to 1000 μm is disposed on the intermediate layer, and the density is 0.88 to 0 on the outermost layer. A gas pack packaging composite film comprising a polyethylene resin layer having a thickness of .92 g / cm ³ and a thickness of 20 to 150 μm. 2. The gas pack packaging composite film according to claim 1, wherein the outermost polyethylene resin layer is made of a linear low density polyethylene resin polymerized by a metallocene catalyst. The composite film for gas pack packaging according to claim 1 or 2, wherein an ethylene-vinyl acetate copolymer saponified resin layer and / or a polyamide resin layer are arranged in the intermediate layer. A container formed by deep drawing the composite film for gas pack packaging according to any one of claims 1 to 3 to form a bottom material.

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