JPH07137216A - Easily openable film - Google Patents

Abstract

PURPOSE:To provide an easily openable film which has a stable heat-seal strength and easily openability, is superior in fragrance retention and oil- resistance, does not adsorb the component of a content, and is suitable as a lid of a molded container of polyester, etc. CONSTITUTION:On the surface of an aluminum foil 1 of a laminated article 3 of the aluminum foil l (thickness: 9mum) and a drawn polyethyleneterephthalate film 2 (thickness: 12mum), a maleic anhydride denaturated LLDPE (C1) and isophthalic acid component-containing polyehyleneterephthalate (A1) are laminated by co-extrusion to form the easily openable film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an easily openable film used as a lid material for a molding container made of a synthetic resin such as polyester, polycarbonate and polyvinyl chloride.

[0002]

2. Description of the Related Art Conventionally, foods, fragrances, etc. are stored in a vacuum molding container, an injection molding container or the like made of vinyl chloride, polypropylene, polystyrene or the like, and a thermoplastic resin film is used as a lid material around the opening of the container. Is heat-sealed. As the lid member, an easily openable (easily peelable) film that can be easily opened is used.

Recently, a polyester resin having high transparency and good appearance, excellent tasteless and odorless and aroma retaining property and easy to recycle has been attracting attention as the above-mentioned molding container, and an easily-openable film used therefor has been demanded. There is. For example, in the opening of the lid material or pouch for packaging, polyolefin resin,
Base resin made of the same kind of resin as the container body made of polyester resin or vinyl chloride resin, with a resin having low compatibility with base resin such as polypropylene, polyethylene, polyethylene wax, tackifying resin, etc. added. Those using a heat-sealable composition,
Those using an adhesive resin such as a vinyl chloride-vinyl acetate copolymer and an ethylene-vinyl acetate copolymer are used.

As described above, Japanese Patent Publication No. 3-507
In JP-A-06-2006, a lid member made of a blend of 20 to 80% by weight of a saturated polyester resin and 20 to 80% by weight of a polyethylene resin or the like having poor compatibility with the saturated polyester resin is described.

[0005]

SUMMARY OF THE INVENTION According to the above-mentioned publication, the polyolefin resin is inferior in aroma retention and oil resistance to the polyester resin, and components of the contents such as aroma are easily adsorbed. There is a risk that the advantages of will not be exhibited.

If only a polyester resin is used as the lid material, the heat sealing condition range is narrow and the easy-opening property cannot be obtained, so that the appearance after peeling from the container is poor and not practical.

The present invention solves the above-mentioned problems of the prior art, has stable heat-sealing strength and easy-opening property, is excellent in aroma retention and oil resistance, does not adsorb components of contents, and is formed of polyester or the like. An object is to provide an easily-openable film suitable as a lid material for a container.

[0008]

The easy-open film of the present invention is characterized in that a heat-sealing layer composed of a copolyester resin layer is laminated on one surface of a modified polyolefin resin layer.

The easy-open film of the present invention utilizes the low adhesive strength between the copolyester resin and the modified polyolefin resin. The modified polyolefin resin used in the present invention is generally called an adhesive resin, for example, maleic anhydride modified polyethylene,
Examples thereof include acrylic acid-modified polyethylene. By using a modified polyolefin resin as the adhesive resin, the resin and the copolyester resin are coextrusion-molded,
When laminated by extrusion lamination or the like, a peelable adhesive force can be obtained at the interface with the copolyester resin layer, which is the heat-sealing layer, when the heat-sealing portion is opened.

The copolymerized polyester resin layer comprises one or more glycol components and one or more dicarboxylic acid components, and the total of these two components is 3 or more, or such a copolymerized polyester resin. It is a mixture of several resins. A copolymerized polyester resin composed of one type of glycol component and one type of dicarboxylic acid component becomes crystalline and has poor heat sealability.

As the monomer constituting the above-mentioned copolymerized polyester resin, those conventionally used can be used. Examples of the dicarboxylic acid include terephthalic acid, isophthalic acid, adipic acid, succinic acid, maleic acid and sebacic acid. Among them, terephthalic acid or /
And isophthalic acid are common.

Examples of the glycol component include ethylene glycol, propylene glycol, butylene glycol, 1,4-cyclohexanedimethanol, diethylene glycol and the like, and ethylene glycol or butylene glycol is generally used.

Further, when the acid-modified copolyester is used as the heat-sealing layer, the boundary between the heat-sealing portion and the non-sealing portion with the container is easily broken when opened.
That is, it is particularly preferable because it has good tearability. Further, in order to improve the tearability, it is preferable that the degree of polymerization of the copolyester is low enough not to hinder the film formation.

The thickness of the heat-sealing layer is selected according to the shape and rigidity of the container body and is not particularly limited. However, if it is excessively thick, it will not be destroyed at the boundary between the heat-sealing part and the non-sealing part when peeled from the container. If it is too thin, the heat seal strength tends to be insufficient. Therefore, the thickness of this layer is preferably 3 to 20 μm.

When an adhesive is used for the lamination of the adhesive resin layer and the heat seal layer, the adhesive strength becomes too strong and the heat seal cannot be peeled off. Therefore, it is preferable not to use the adhesive. Therefore, for laminating both layers, a coextrusion molding method in which both resins melted by different extruders are sent to one common die and laminated while being simultaneously extruded, is melted on one resin layer surface formed in advance into a film shape. It is preferable to use an extrusion laminating method in which the other resin is extruded and laminated, or a method in which one resin layer surface which has been formed into a film in advance is coated with the other resin dissolved in a solvent.

[0016] The adhesive strength between the adhesive resin layer and the heat seal layer is about 300 g / 15 mm or more, and
The lamination conditions may be set so that the weight is 2000 g / 15 mm or less. If necessary, additives such as an antiblocking agent, a stabilizer, an antiaging agent and a pigment may be added to the adhesive resin layer and the heat seal layer.

When it is used as a lid of a container, it can be made to have good transparency by using a laminated film having only the above adhesive resin layer and heat seal layer, but it is rarely used up to this point. In many cases, it is used by laminating another material such as a metal foil, a stretched polyethylene terephthalate film or a stretched nylon film on the other surface of the adhesive resin layer. Such other material may be adhered to the adhesive resin layer by using an adhesive, or the above method without using an adhesive may be adopted.

[0018]

The function of the easy-open film of the present invention is as shown in FIG.
The heat-sealing layer A is heat-sealed around the opening of the container 5 made of polyester resin or the like. The layer A exhibits aroma retention and oil resistance with respect to the contents, and does not adsorb the components of the contents such as the scent. When the lid is peeled off when opening, as shown in Fig. 3,
The heat-sealed portion 4 of the heat-sealing layer A is peeled off from the adhesive resin layer C and is broken at the boundary with the non-sealed portion, so that the heat-sealed portion 4 can be easily opened. The appearance of the container mouth after opening is not impaired.

[0019]

EXAMPLES Next, examples of the easy-open film of the present invention will be described. The following resins C ₁ and C are used as polyolefin resins.
₂ and C ₃ were used. C ₁ : Maleic anhydride modified LLDPE (melt index 6.8) C ₂ : LLDPE (melt index 7.2) ([Note] LLDPE: linear low density polyethylene) C ₃ : Polyethylene elastomer

The following resins A ₁ and A ₂ were used as the copolyester resin. A ₁ : Polyethylene terephthalate containing 15 mol% of isophthalic acid in all monomers (IV = 0.70) A ₂ : Polyethylene containing 10 mol% of isophthalic acid in all monomers and 5 mol% of diethylene glycol in all monomers Terephthalate (IV = 0.72) ([Note] IV is the intrinsic viscosity measured in orthochlorophenol)

(Embodiment 1) FIG. 1 is a cross-sectional view showing an embodiment of the easily-openable film of the present invention, in which the above resins C ₁ and A ₁ are combined in the thicknesses shown in Table 1 and separately prepared aluminum foil. 1 (thickness 9 μm) and stretched polyethylene terephthalate film 2 (thickness 12 μm) on the anchor coat surface of the aluminum foil 1 of the laminate 3 by co-extrusion of the above resins C ₁ and A ₁ using a feed block type T die. It is a laminate.

[0022] (Example 2) are the same easily openable film as in Example 1 except for using resin C _1, A ₂ instead of the resin C _1, A _1.

(Comparative Examples 1 to 3) Resins of the combinations shown in Table 1 were used in the same manner as in Examples 1 and 2, and the same laminated product 3 as above was used.
Is co-extruded and laminated (not shown).

Performance evaluation (1) Peel strength: The heat-sealing layer of each film of Examples and Comparative Examples was heat-sealed on the surface of an amorphous polyethylene terephthalate (APET) sheet having a thickness of 400 μm, and 15 mm between the heat-sealing layer and the APET sheet. The peel strength in the width was measured at 200 mm / min. The results are shown in Table 1.
Shown in.

(2) Evaluation as lid material 50 ml of mineral water containing 1% by weight of standard fragrance was placed in a vacuum forming container made of APET, and the films of Examples and Comparative Examples were heat-sealed and sealed at room temperature. Stored for 2 hours. (The vacuum forming container has a generally cylindrical shape with a diameter of 70 mm and a depth of 25 mm, a flange width of the mouth of 6 mm, and a sheet thickness before forming of 500 μm.)

Sealing state of the seal part: observing the presence or absence of water leakage Peeling feeling: Feeling when the lid material is peeled from the container by hand ○ It can be peeled while receiving an appropriate resistance feeling. △ There is little resistance because the adhesive strength by heat sealing is weak. × The adhesive strength by heat sealing is too strong to open. Appearance of peeled part: Observation of the state of the heat-sealed part after opening Sensory evaluation The changes in taste and odor of mineral water were examined. The degree of the change was expressed in five stages from “no change (a) to significant change (e)”. Adsorption of fragrance: It was examined whether or not the smell of fragrance remained on the lid material washed with water. The degree of the change was expressed in five stages from "no odor (no adsorption) (a) to significant change (e)". The results are shown in Table 1.

[0027]

[Table 1]

As is apparent from Table 1, the materials of Examples 1 and 2 have good heat-sealing properties with the container, but on the other hand, they have an appropriate peel strength and are easy to open, and the container after opening has a good appearance. . Further, since the copolyester resin layer is on the contents side, no odor is adsorbed on the lid material and the contents are not altered. On the other hand, Comparative Example 1 does not provide easy opening, and Comparative Example 2 has poor heat-sealing property with the container, which is unsuitable as a cover material because the quality of the contents and the absorption of aroma are remarkable. is there.
Further, in Comparative Example 3, alteration of the contents and adsorption of aroma are slightly strong, and the mouth of the container after opening is poor in appearance.

[0029]

EFFECTS OF THE INVENTION The easy-open film of the present invention has the above-mentioned constitution and has stable heat-sealing strength with a container and easy-opening property due to an appropriate peeling strength, and the appearance of the mouth of the container after opening is impaired. Never be In addition, since the copolyester resin layer is on the contents side, it exhibits aroma retention and oil resistance, does not adsorb odor to the lid material, and does not alter the contents, so it can be used as a lid material for molded containers such as polyester. It is suitable.

[0030]

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of the easily openable film of the present invention.

FIG. 2 is a sectional view showing a state in which the easy-open film of the present invention is heat-sealed in a container.

FIG. 3 is a cross-sectional view showing a state in which the heat seal part of FIG. 2 is peeled off.

[Explanation of symbols]

A, A ₁ : Heat seal layer C, C ₁ : Adhesive resin layer 1: Aluminum foil 2: Polyethylene terephthalate film 3: Laminated product 4: Heat seal part 5: Container

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location B65D 65/40 Z 77/20 L

Claims (1)

[Claims] 1. An easy-open film comprising a modified polyolefin resin layer and a heat-sealing layer comprising a copolyester resin layer laminated on one surface thereof.