JP2728376B2 - Laminated film structure for packaging - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated film structure for packaging which is suitable for packaging objects to be packaged such as liquids, viscous materials, powders and granules, and more particularly to a method for opening a packaging bag. Another object of the present invention is to propose a film laminated structure which can be easily performed and enables high-speed sealing at a relatively low heat-sealing temperature in automatic filling and bag making of an article to be packaged.

[0002]

2. Description of the Related Art A conventionally known laminated film for packaging comprising a base film layer, an intermediate layer, and a sealant layer and applied for packaging objects such as liquids, viscous materials, powders and granules. As a structure, for example, a base film layer,
The biaxially stretched ethylene-vinyl alcohol copolymer resin film, the intermediate layer is made of unstretched low-density polyethylene, and the sealant layer disposed mainly for heat sealing is also made of unstretched ethylene-vinyl. Some are formed of acetate copolymer resins. Packaging of an object to be packaged by such a film structure is performed, for example, by an automatic filling and bag making machine, by folding the film structure in two at the center in the width direction and forming a sealant layer facing each other. The packaging bag is formed by applying a so-called three-sided seal as shown in FIG. 2 to form a packaging bag, and by enclosing an object to be packaged in a portion of the packaging bag which is not provided with a diagonal line.

[0003] As shown in the figure, an object to be packaged is taken out from a packaging bag formed by filling and making a film structure in this manner from an I-notch c provided in a vertical seal portion b of a packaging bag a. It is more preferable that the tearing of the packaging bag is started, and the resulting tear of the bag is advanced at least to a position past a so-called bottle opening portion e that functions as a part of the storage space d for the item to be packaged. Is performed by pushing the package storage space d in a state in which the rupture is advanced to a position completely traversing the bag a to cause the package to flow out of the opened bottle opening e. .

[0004]

However, a conventional packaging bag using a film structure has the following problems in opening the packaging bag. That is, as the base film layer, the biaxially stretched ethylene-vinyl alcohol copolymer resin film is mainly affected by the molecular orientation, so that the propagation of the tear becomes difficult in a certain tear direction. is there. For example, as shown in the tearing position in FIG. 3 (a), when the end portion of the packaging bag is pulled toward the near side, even if the opening can be easily performed with a relatively small tear resistance, it is possible to perform the opening in FIG. 3 (b). As shown in), when the end portion of the packaging bag is pulled in the direction opposite to the above direction, the tear resistance of the bag becomes extremely large, and it becomes extremely difficult to advance the tear beyond the bottle opening portion e. There was a problem.

[0005] Incidentally, according to tests conducted by the present inventors, a film structure using a biaxially stretched ethylene-vinyl alcohol copolymer resin film having a thickness of 15 µm as a base film layer, and a biaxially stretched polyethylene having a thickness of 12 µm as a base film layer. Film structure using terephthalate film and 15
In each of the film structures using the biaxially stretched nylon resin film having a thickness of μm, each of the intermediate layer and the sealant layer was made of a non-stretched low-density polyethylene having a thickness of 25 μm and a non-stretched ethylene-vinyl acetate having a thickness of 25 μm. The maximum force required for completely tearing and cutting the packaging bag in the form of a bag shown in FIG. 2 when formed from a polymer resin is:
When the cut length, in other words, the bag width was 50 mm, and the molecular orientation direction of the base film layer was approximately 30 degrees with respect to the direction of the tearing, the results were as shown in Table 1.

[0006]

[Table 1]

[0007] It should be noted that, in order to facilitate the initiation of tearing by a finger from any part of the packaging bag without impairing the strength of the packaging bag, a heat-sealing portion of the bag is provided.
In place of the I notch and the V notch, for example,
The same applies to the case where an easy-opening structure in which so-called many non-dropping scars are formed at intervals in the length direction of the heat-sealed portion as disclosed in Japanese Patent No. 2159 is provided. That is, in this type, when the bag is opened, tearing of the bag at an arbitrary scar position can be easily started, but the tear of the bag is required at the required opening position beyond the scar forming portion. For example, in order to advance the packaging bag completely to the position where the packaging bag completely crosses, the above-mentioned problem caused by the direction of the external force of tearing still remains.

The present invention advantageously solves the above-mentioned problems of the prior art by improving the laminated structure of the film structure. The maximum tearing force required to completely open the packaging bag, regardless of the tearing direction of the packaging bag, can be reduced sufficiently, regardless of the tearing direction of the packaging bag. An object of the present invention is to provide a laminated film structure for packaging that enables high-speed sealing under a low heat sealing temperature and does not cause unexpected breakage.

[0009]

A laminated film structure for packaging according to the present invention comprises a stretched base film layer, a non-stretched intermediate layer, and a sealant layer, and at least one side end portion has a longitudinal direction. In the film structure having a plurality of tear-inducing flaws located at intervals, the intermediate layer is formed of a non-stretched high-density polyethylene layer, and between the intermediate layer and the base film layer, for example, a low-density It has an extruded adhesive layer made of polyethylene or linear low-density polyethylene.

The tear-inducing flaws include a single flaw provided extending in the width direction of the film structure in a minus (-) shape, a plurality of flaws provided in a perforated shape, and an interval in the width direction. Such as a plurality of small hole-like flaws provided in the, can be formed in a suitable shape and number of flaws, such tear induction flaws, depth, length in the width direction of the film structure, The interval in the length direction of the film structure and other dimensions can be selected according to the thickness of the film structure, the constituent material of the film structure, and the like. In addition, in order to prevent each tear induction flaw from being unexpectedly broken during the handling of the film structure, it is preferable to form the tears slightly apart from the side edge of the film structure. As far as it can be prevented, every other one or every other one can be opened at the side edge of the film structure.

This laminated film structure for packaging is heat-sealed to a required portion including a side end portion provided with a tear-inducing flaw in a state where the sealant layers thereof are opposed to each other, whereby a conventional film structure is obtained. Similarly, the article to be packaged can be properly packaged.

On the other hand, opening of the bag when taking out the packaged object can be started very easily from an arbitrary position with the force of a finger under the action of the tear induction flaw present in the heat-sealed portion. And the progression of the tear of the bag thus generated, which exceeds the tear-inducing flaws, in other words, the required opening depends on the existence of the unstretched high-density polyethylene layer itself, and furthermore, the unstretched height. Due to the presence of the density polyethylene layer, the thickness of the unstretched sealant layer, which increases the tear resistance, can be effectively reduced, so that regardless of the molecular orientation of the film material forming the base film layer, that is, its molecular orientation This can also be done very easily, regardless of the direction of action of the external tearing force, without increasing the tear resistance of the sealant layer due to the direction.

This is because, for example, when the intermediate layer of the bag is an unstretched high-density polyethylene layer and the sealant layer is an unstretched low-density polyethylene layer, the unstretched high-density polyethylene layer is opened when the bag is opened. On the condition that each of the base film layer and the sealant layer is adhered to the intermediate layer with sufficient strength, based on the property that it is extremely ruptured, the boundary of the bag rupture that has progressed along the tear induction flaws 3 (a) and 3 (b), even if an external force is applied in any of the directions indicated by arrows in FIG. Shear cracking precedes the occurrence of tearing in the base film layer and the sealant layer, and the tearing of both layers, which are strongly adhered to the intermediate layer, By generating so as to follow the the progress of cracking, the elongation of the sealant layer, is believed to be due to greatly reduced by the shearing cracks generated in the high density polyethylene layer.

[0014] In addition, according to this film structure, the unstretched high-density polyethylene layer imparts sufficient waist, in other words, rigidity, to the packaging bag. By forming the sealant layer, the thickness of the sealant layer can be minimized necessary for heat sealing, and therefore, as described above, the tear resistance provided by the sealant layer can be further reduced. In addition to this, the amount of heat supplied to the sealant layer for heat sealing can be reduced sufficiently to significantly reduce the heat sealing time, and the heating temperature of the heat sealing rolls and other heat sealing means can be lowered to reduce Unnecessary flow of a certain high-density polyethylene layer can be effectively prevented, and furthermore, when the object to be packaged is a liquid substance, viscous substance, etc. In the case of a foreign substance (biting) seal in the package, the generation of water vapor or the like from the packaged object can be prevented, and the possibility of occurrence of a sealing failure due to the water vapor or the like remaining in the heat sealing portion can be eliminated. .

In addition, since the non-stretched high-density polyethylene layer as the intermediate layer can be formed by extrusion lamination, the stretched high-density polyethylene film is laminated on the base film layer by dry lamination or the like. The required film structure can be manufactured extremely efficiently and at low cost without any special laminating step and laminating equipment.

When an unstretched high-density polyethylene layer as an intermediate layer is directly formed on a stretched base film layer by extrusion, it is necessary to increase the adhesive strength between the base film layer and the intermediate layer so much. I ca n’t
Here, the adhesive strength is further increased by interposing an extruded adhesive layer made of low-density polyethylene, linear low-density polyethylene, or the like between the two layers.

When the sealant layer is formed of a non-stretched high-density polyethylene layer and the intermediate layer is formed of, for example, a non-stretched low-density polyethylene layer, the sealant layer and the intermediate layer and the intermediate layer are usually used. Since the layer and the base film layer can be bonded together sufficiently firmly, the above-described interposition of the extrusion adhesive layer is unnecessary, but in this case, due to the physical properties inherent to the high-density polyethylene as the sealant layer,
It is inevitable to raise the heat sealing temperature considerably,
Such a laminated structure is not included in the present invention, since the above-described operation and effect due to the fact that the heat sealing temperature can be lowered cannot be obtained, and the heat sealing strength must be reduced.

Further, as described above, when the formation position of each tear induction flaw is somewhat separated from the side edge position of the film structure, when the film structure is wound up or rewound, the side end is removed. Accidental breakage of the film structure due to stress concentration on the edges can be almost completely prevented.

Further, in the case where the tear-inducing flaws are provided on the left and right side end portions of the film structure, when the flaws on both side end portions are located corresponding to each other at the time of heat sealing, the force required to start opening is increased. When the flaws on both side end portions are alternately located, the degree of freedom in selecting the opening start position can be further increased.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional perspective view showing one embodiment of the present invention, which shows a low-density biaxially stretched ethylene-vinyl alcohol copolymer resin film 1 having a thickness of 15 μm as a base film layer. A 20 μm-thick unstretched high-density polyethylene 2 as an intermediate layer is laminated via an extruded adhesive layer made of polyethylene 5, and a 20 μm-thick non-stretched as a sealant layer is laminated on the intermediate layer. A part of a film structure further laminated with low-density polyethylene 3 is shown. This film structure has a tear-inducing flaw 4 composed of a plurality of flaws provided in one side end portion at a position slightly distant from the side edge inward in the width direction of the film structure in the width direction of the film structure. It has a predetermined interval in the direction. Here, as described above, the depth of the tear-inducing flaw 4, its length in the width direction of the film structure, and the interval between the tear-inducing flaws 4 depend on the thickness of the film structure, its constituent material, and the like. It can be selected appropriately.

To manufacture such a film structure, an ethylene-vinyl alcohol copolymer resin film 1 and a low-density polyethylene 3 previously formed into a film are combined with a low-density polyethylene extruded adhesive layer and a high-density polyethylene 2. Laminating through each of the extruded laminate layers, or extrusion-coating the ethylene-vinyl alcohol copolymer resin film 1 with the low-density polyethylene extruded adhesive layer, the high-density polyethylene 2 and the low-density polyethylene 3 Accordingly, the operation can be performed extremely efficiently and without the need for a special working device such as a dry laminating device and man-hours.

[0022] Packaging of the packaged product with the film structure is performed by using a heat seal roll, a heat seal bar, or the like to fill the film structure with the low-density polyethylene 3 facing each other as a sealant layer. At the same time, heat sealing can be performed at a required position including the side end face portion provided with the tear guiding flaw 4.

On the other hand, the removal of the packaged object
When the film structure is formed into a bag in the same form as described in the prior art, for example, the packaging bag is transferred from the tear-inducing flaw 4 located at the longitudinally sealed portion of the heat-sealed portion to the entire width of the packaging bag through the bottle mouth portion. Tear over and then
The object to be packaged can be extruded from the bottle opening. When the object to be packaged is taken out according to the film structure of the present invention, the tearing direction is the direction shown in FIG. 3 (a). Irrespective of the direction shown in FIG. 3 (b), the opening of the unsealed high-density polyethylene 2 as an intermediate layer can always be easily started by the action of the tear-inducing flaws 4. Under the extremely fragile nature of the above, irrespective of the tear direction, as described above, the effect of the large tear resistance of the low-density polyethylene 3 is sufficiently reduced, and the packaging is performed with an extremely small tear force. The bag can be opened as expected. here,
Needless to say, the thickness of each constituent layer of the film structure can be appropriately increased or decreased as required.

The constituent materials of the film structure are not limited to those described above, and the stretched base film layer may be formed of a biaxially stretched nylon film, polyethylene phthalate film, polypropylene film, polyvinyl alcohol film, or cellophane film. , Or those films with vinylidene chloride coating, etc.
Further, a non-stretched sealant layer is formed of ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene methyl acrylate, ethylene-methacrylic acid copolymer, ethylene-methyl methacrylate. It can also be formed from a copolymer, polypropylene, linear low-density polyethylene, ionomer, or the like.

Moreover, in the film structure here,
The adhesive strength between the unstretched high-density polyethylene 2 and the base film layer, for example, the biaxially stretched ethylene-vinyl alcohol copolymer resin film 1 was disposed between them.
It is sufficiently increased based on the function of the extruded adhesive layer made of the low-density polyethylene 5, so that the packaging bag can be used when the weight of the packaged object is large, when the packaged object contains water or other liquid, or the like. Even under these conditions, extremely high heat seal strength can be exhibited under excellent adhesive strength between the base film layer and the intermediate layer. Incidentally, the extruded adhesive layer is made of a linear low-density polyethylene, an ethylene-acrylic acid copolymer, an ethylene-vinyl acetate copolymer, an ethylene-ethyl acrylate copolymer, an ethylene It can also be formed of a copolymer or the like.

[0026]

EXAMPLES Examples of the interlayer adhesive strength and the maximum tearing force of a packaging bag using the film structure when the material and thickness of each layer of the film structure are specified will be described below. Here, the comparative film structure
And with omitting the extruded adhesive layer made of low-density polyethylene 5 from the film structure illustrated in FIG. 1, a high-density polyethylene 2, and a stacked structure obtained by directly bonding the base film layer by extrusion lamination.

In the film structure of the comparative example, a base film layer formed of a biaxially stretched ethylene-vinyl alcohol copolymer resin film having a thickness of 15 μm was used.
FIG. 2 shows a film formed from a biaxially stretched polyethylene phthalate film having a thickness of μm and a film formed from a biaxially stretched nylon resin film having a thickness of 15 μm.
Table 2 shows the maximum tearing force required for completely tearing and cutting a packaging bag having the same bag-making form as that shown in Table 2 by holding the packaging bag in a chuck of a tensile tester and tearing it. It was as shown. Here, the molecular orientation direction of the base film layer is approximately 30
Degree. Here, the cutting length of the packaging bag was set to 50 mm, and each of the intermediate layer and the sealant layer was formed of a non-stretched high-density polyethylene having a thickness of 25 μm and a non-stretched ethylene-vinyl acetate copolymer having a thickness of 25 μm. .
By the way, the required tearing force of the bag at the portion where the tear-inducing flaws function to facilitate opening of the packaging bag by giving a trigger for opening the packaging bag is the maximum required for completely tearing and cutting the packaging bag. The value is much smaller than the tearing force.

[0028]

[Table 2]

According to Table 2, even when the film structure of the comparative example is used, particularly, the intermediate layer of the film structure is formed by a non-stretched high-density polyethylene layer. The maximum tearing force can be greatly reduced in comparison with the conventional packaging bag shown in (1), and the maximum tearing force in the direction in which tearing was not possible in the past is about the same as the maximum tearing force in the opposite direction. It is clear that it can be reduced to Therefore, according to the comparative example film, regarding opening of the packaging bag, regardless of the tear direction.
This can be easily performed with a small force.

On the other hand, in the example film structure having the laminated structure illustrated in FIG.
A biaxially stretched nylon resin film with a thickness of
The unstretched high-density polyethylene having a thickness of μm, the sealant layer was formed of a 20 μm-thick unstretched ethylene-vinyl acetate copolymer, and the extruded adhesive layer was formed of a low-density polyethylene having a thickness of 10 μm. In this case, the adhesive strength between the layers, the heat seal strength, and the maximum tearing force required for completely tearing and cutting the packaging bag were compared with those of the film structure of the comparative example.
Here, the film structure of the comparative example is such that the base film layer is a 15 μm-thick biaxially stretched nylon resin film, and each of the intermediate layer and the sealant layer is a 25 μm-thick non-stretched high-density polyethylene and a 25 μm-thick Of non-stretched ethylene-vinyl acetate copolymers.

[0031]

[Table 3]

[0032]

[Table 4]

According to Table 3, in the film structure of the example, the adhesive strength between the base film layer and the intermediate layer can be greatly improved by the action of the extruded adhesive layer, and the heat seal strength can also be sufficiently improved. It is evident that the maximum tearing force can be kept sufficiently low despite the presence of the extruded adhesive layer, as shown in Table 4.

[0034]

As described above, in the packaging bag constituted by the film structure of the present invention, the opening of the packaging bag from an arbitrary position can be extremely easily performed by the action of the tear-inducing flaw. Moreover, the progression of the tear of the bag beyond the part where the tear-inducing flaw is formed, that is, the required opening can be easily performed under the action of the non-stretched high-density polyethylene regardless of the action direction of the external tear force. . Further, since both the extruded adhesive layer and the unstretched high-density polyethylene layer of this film structure can be laminated or coated by an extrusion laminating device or the like, other special devices such as a dry laminating device and the device The required film structure can be manufactured extremely efficiently and at low cost without the number of man-hours required for the use of.

Further, according to the film structure of the present invention,
Since unstretched high-density polyethylene gives the film structure, and ultimately the packaging bag made of it, a sufficient waist, the sealant layer is made to the minimum necessary thickness,
In addition to further reducing the tear resistance of the packaging bag, it is possible to increase the bag-making speed and to lower the heating temperature of the heat sealing means, thereby providing excellent heat sealing strength. And, as a result of this decrease in the heat sealing temperature, the unstretched high-density polyethylene as an intermediate layer prevents unnecessary softening flow, and the occurrence of sealing failure,
It is possible to eliminate the danger of deterioration of the function of the packaging bag and the incorporation of resin components into the packaged items, and also to prevent evaporation of moisture contained in the packaged items at the time of sealing the contaminants, so that steam etc.
It is possible to sufficiently remove the possibility of occurrence of sealing failure due to remaining in the heat seal portion. by the way,
Here, an unstretched high-density polyethylene layer as an intermediate layer is adhered to a base film layer via an extruded adhesive layer to greatly improve the adhesive strength between the intermediate layer and the base film layer. The opening can be further facilitated, and the heat sealing strength can be further increased.

The case where the film structure of the present invention is sealed by three sides to form a bag has been described as an example. However, the film structure can of course be applied to four side seals and other known bag making methods. is there.

[Brief description of the drawings]

FIG. 1 is a sectional perspective view showing one embodiment of the present invention.

FIG. 2 is a plan view illustrating a heat-sealing mode of the package.

FIG. 3 is a view showing an action direction of an external tearing force of the packaging bag.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Biaxially stretched ethylene-vinyl alcohol copolymer resin film 2 Unstretched high-density polyethylene 3 Unstretched low-density polyethylene 4 Tear-induced flaw 5 Low-density polyethylene

Claims (1)

(57) [Claims] 1. A film comprising a stretched base film layer, a non-stretched intermediate layer and a sealant layer, and having a plurality of tear-inducing flaws located at least in one side end portion at intervals in the length direction. A laminated film structure for packaging, wherein the intermediate layer is formed of a non-stretched high-density polyethylene layer , and an extrusion adhesive layer is interposed between the intermediate layer and the base film layer.