JPH0848361A - Laminated film structure for packing - Google Patents

Abstract

PURPOSE:To easily tear a packing bag from an arbitrary position, completely open the bag with small tearing force and avoid accidental breakage by forming an intermediate layer of a man-stretched high density polyethylene layer and interposing an extrusion adhesive layer between the intermediate layer and a base film layer. CONSTITUTION:Non-stretched high density polyethylene 2 having a thickness of 20mum as an intermediate layer is laminated on a biaxially stretched ethylene- vinyl alcohol copolymer resin film having a thickness of 15mum as a base film layer via an extrusion adhesive layer comprising low density polyethylene 5. Non-stretched low density polyethylene 3 having a thickness of 20mum as a sealant layer is laminated further on the intermediate layer. This film structure is equipped on one of side ends with tearing guide cuts 4 comprising a plurality of cuts provided like perforations from a position a slightly distant from the side end inward along a widthwise direction of the film structure with predetermined intervals along a lengthwise direction of the film structure.

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 an object to be packaged such as a liquid material, a viscous material, a powder / granular material, etc. We propose a film structure that can be easily performed and, at the same time, enables high-speed sealing at a relatively low heat-sealing temperature in the automatic filling and bag making of a packaged object.

[0002]

2. Description of the Related Art A conventionally known laminated film for packaging, which comprises a base film layer, an intermediate layer and a sealant layer and is applied to package an object to be packaged such as a liquid substance, a viscous substance, powder or granules. As the structure, for example, a base film layer,
A biaxially stretched ethylene-vinyl alcohol copolymer resin film, an intermediate layer made of unstretched low-density polyethylene, and a sealant layer mainly arranged for heat sealing, which is also unstretched ethylene-vinyl. Some are made of acetate copolymer resin. The packaging of the object to be packaged by such a film structure is performed, for example, by an automatic filling bag-making machine, in which the film structure is folded in two at a central position in the width direction, and a sealant layer positioned facing each other is formed. 2 is hatched, a so-called three-sided seal is applied to form a packaging bag, and the packaging bag is sealed in a non-hatched portion of the packaging bag.

In order to take out the article to be packaged from the packaging bag formed by filling and forming the film structure in this way, the I notch c provided in the vertical sealing portion b of the packaging bag a More preferably, in a state in which the tearing of the packaging bag is started and the tearing of the bag caused thereby is advanced to at least a position that passes through the so-called bottle mouth portion e that functions as a part of the storage space d of the packaged object. Is performed by pressing the package storage space d so that the package is allowed to flow from the opened bottle mouth portion e in a state where the crevice is advanced to a position where the bag a is completely crossed. .

[0004]

However, the conventional packaging bag using the film structure has the following problems in opening the packaging bag. That is, as the base film layer, of the biaxially stretched ethylene-vinyl alcohol copolymer resin film, mainly due to the effect of molecular orientation, it becomes difficult to propagate the tear in a certain tearing direction. is there. For example, as shown in the tearing position in FIG. 3 (a), when pulling the end portion of the packaging bag toward the front side, even if the opening can be easily performed under a relatively small tear resistance, FIG. As shown in (), when the end portion of the packaging bag is pulled in the direction opposite to the direction shown above, the tear resistance of the bag is significantly increased, and it is extremely difficult to advance the tear beyond the bottle mouth portion e. There was a problem.

Incidentally, according to the tests conducted by the present inventor, 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. 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, the intermediate layer and the sealant layer are respectively made of unstretched low density polyethylene having a thickness of 25 μm and unstretched ethylene-vinyl acetate having a thickness of 25 μm. The maximum force required for completely tearing and cutting the packaging bag shown in FIG. 2 when formed from a polymer resin is
When the cut length, in other words, the bag width was set to 50 mm and the molecular orientation direction of the base film layer was set to approximately 30 degrees with respect to the direction of tearing, the results were as shown in Table 1.

[0006]

[Table 1]

[0007] This means 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, the heat sealing portion of the bag is
Instead of the I notch or the V notch, for example, Japanese Patent Laid-Open No. 61-14
The same was true in the case of providing an easy-opening structure in which so-called numerous scratches without defects were formed at intervals in the length direction of the heat-sealing portion as disclosed in Japanese Patent No. 2159. That is, in this type of bag, when opening the bag, tearing of the bag at an arbitrary scar position can be easily started, but the tear of the bag can be opened at a required opening position beyond the scratch forming portion. For example, in order to proceed to a position where the packaging bag is completely traversed, the problem as described above due to the acting direction of the external tearing force still remains.

The present invention advantageously solves the above problems of the prior art, particularly by improving the laminated structure of the film structure, and can prevent tearing by fingers from any position of the packaging bag. In addition to facilitating a smooth start, the maximum tearing force required to completely open the packaging bag can always be made sufficiently small, regardless of the tearing direction of the packaging bag. It is intended to provide a laminated film structure for packaging, which enables high-speed sealing under a low heat-sealing temperature and has no possibility of unexpected breakage.

[0009]

A laminated film structure for packaging of 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 thereof has a lengthwise direction. In a film structure having a plurality of tearing-induced flaws located at intervals, the intermediate layer is formed of a non-stretched high-density polyethylene layer, and the intermediate layer and the base film layer have a low density, for example. An extruded adhesive layer made of polyethylene or linear low-density polyethylene is interposed.

By the way, the tearing-induced flaws are one flaw formed by extending in a minus (-) shape in the width direction of the film structure, a plurality of perforations formed in the shape of a perforation, and intervals in the width direction. A plurality of small-hole-shaped flaws provided in advance, can be formed in an appropriate shape and number of flaws, such tear-induced flaws, the depth, the length in the width direction of the film structure, The distance 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. It should be noted that each tear-induced flaw is preferably formed with some separation from the side edge of the film structure in order to prevent accidental breakage thereof during handling of the film structure, but the breakage is sufficient. As long as it can be prevented, it can be opened every other piece or every plural pieces, at the side edge of the film structure.

This laminated film structure for packaging is provided with a conventional film structure by heat-sealing required portions including side end portions provided with tear-induced flaws with the sealant layers thereof facing each other. Similarly, the article to be packaged can be properly packaged.

On the other hand, the opening of the bag at the time of taking out the object to be packaged can be extremely easily started from an arbitrary position by the force of the finger under the action of the tearing-induced flaw existing in the heat-sealed portion. Then, the rip of the bag thus generated, the progression beyond the tear-induced flaw, in other words, the required opening is due to the existence of the unstretched high-density polyethylene layer itself, and further, the unstretched high-strength. Due to the presence of the density polyethylene layer, it is possible to effectively reduce the thickness of the unstretched sealant layer, which results in an increase in tear resistance, regardless of the molecular orientation of the film material forming the base film layer, i.e. its molecular orientation. This can also be done very easily regardless of the direction of action of the external tearing force without causing an increase in tear resistance of the sealant layer due to the direction.

This is because, for example, when the middle 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 used when opening the bag. Based on the fact that the base film layer and the sealant layer are adhered to the intermediate layer with sufficient strength based on the fact that they are extremely fragile, at the boundary of the rupture of the bag that has progressed along the tearing-induced flaw. 3) When the external force of tearing is applied in either direction indicated by the arrow in FIGS. 3 (a) and 3 (b), the intermediate layer will not reach the intermediate layer due to the small tear propagation resistance unique to the unstretched high-density polyethylene layer. The formation of shear cracks on the base film layer and the sealant layer prior to the formation of tears, and the tearing of those layers 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.

In addition, according to this film structure, the unstretched high-density polyethylene layer imparts sufficient rigidity to the packaging bag, in other words, rigidity, so that the intermediate layer is formed into the unstretched high-density polyethylene layer. By making it possible, the thickness of the sealant layer can be made the minimum necessary for heat sealing, and therefore, as described above, the tear resistance provided by the sealant layer can be further reduced. In addition, the amount of heat supplied to the sealant layer for heat sealing can be sufficiently reduced to significantly shorten the heat sealing time, and the heating temperature of the heat sealing roll or other heat sealing means can be lowered to reduce the heat loss in the intermediate layer. When unnecessary flow of a certain high-density polyethylene layer can be effectively prevented, and furthermore, the packaged item is a liquid substance, a viscous substance, etc. It is possible to prevent the generation of water vapor etc. from the object to be packaged in the case of foreign matter (biting) seal and eliminate the risk of seal failure due to the water vapor etc. remaining in the heat seal part. .

Further, here, since the unstretched high-density polyethylene layer as the intermediate layer can be formed by extrusion lamination, compared with the case where 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 very efficiently and at low cost without requiring any special laminating step and laminating equipment.

By the way, when the unstretched high-density polyethylene layer as the intermediate layer is directly extrusion-formed on the stretched base film layer, the adhesive strength between the base film layer and the intermediate layer can be increased so much. Because I can't
Here, by interposing an extrusion adhesive layer made of low-density polyethylene, linear low-density polyethylene, or the like between these two layers, the adhesive strength thereof is further enhanced.

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, the intermediate layer, and the intermediate layer are usually used. Since the layer and the base film layer can be firmly bonded together, the interposition of the above-mentioned extrusion adhesive layer is unnecessary, but in this case, due to the physical properties inherent to the high-density polyethylene that is the sealant layer,
It is inevitable to raise the heat seal temperature considerably,
Such a laminated structure is not included in the present invention because the above-described effects cannot be brought about by lowering the heat-sealing temperature, and the heat-sealing strength is inevitably lowered.

Further, as described above, when the formation position of each tearing-induced flaw is separated from the side end edge position of the film structure, as described above, the side end of the film structure during winding, rewinding, or the like. Unintentional breakage of the film structure due to stress concentration on the edges can be almost completely prevented.

Further, in the case where tearing-induced flaws are provided on the left and right side end portions of the film structure, when heat-sealing the flaws on both side end portions to correspond to each other, the force required to start opening is further increased. When the flaws on both end portions are staggered, the degree of freedom in selecting the opening start position can be further increased.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional perspective view showing an embodiment of the present invention, which shows a 15 μm-thick biaxially stretched ethylene-vinyl alcohol copolymer resin film 1 as a base film layer, for example, having a low density. An unstretched high-density polyethylene 2 having a thickness of 20 μm is laminated as an intermediate layer through an extrusion adhesive layer composed of polyethylene 5, and a non-stretched layer having a thickness of 20 μm, which is also a sealant layer, is laminated on the intermediate layer. A part of a film structure formed by further laminating low-density polyethylene 3 is shown. In this film structure, a tear-inducing defect 4 composed of a plurality of perforations formed in a widthwise inward direction of the film structure from a position slightly separated from the side edge is provided at one side end portion in the length of the film structure. It has a predetermined interval in the direction. Here, the depth of the tear guide flaw 4, the width direction length of the film structure, the interval of the tear guide flaw 4, and the like depend on the thickness of the film structure, the constituent material thereof, and the like, as described above. It can be selected appropriately.

In the production of such a film structure, the ethylene-vinyl alcohol copolymer resin film 1 and the low-density polyethylene 3 formed in advance in the form of a film are mixed with the low-density polyethylene extruded adhesive layer and the high-density polyethylene 2. Laminating through each of the extrusion laminate layers, or extrusion-coating the ethylene-vinyl alcohol copolymer resin film 1 with a low-density polyethylene extrusion adhesive layer, a high-density polyethylene 2 and a low-density polyethylene 3. Thus, it can be performed extremely efficiently and without requiring a special working apparatus such as a dry laminating apparatus and working man-hours.

The packaging of an object to be packaged with such a film structure is performed by filling the object to be packaged with the low-density polyethylene 3 as a sealant layer of the film structure, which are opposed to each other, by a heat seal roll, a heat seal bar or the like. It can be performed by adjusting the timing and heat-sealing at a required position including the side end surface portion provided with the tear guide flaw 4.

On the other hand, the removal of the packaged object is
When the film structure is formed into a bag similar to that described in the prior art, for example, the packaging bag is passed from the tear guide flaw 4 located in the vertical seal portion of the heat seal portion to the bottle mouth portion and then, for example, the entire width thereof. Torn across, then
It can be carried out by extruding the object to be packaged from the bottle mouth portion, and at the time of taking out the object to be packaged, according to the film structure of the present invention, the tearing direction is the direction shown in FIG. 3 (a). Despite the direction shown in FIG. 3 (b), the tear-inducing flaw 4 can always start the opening sufficiently easily, and the unstretched high-density polyethylene 2 as the intermediate layer can be used. Under the extremely fragile nature of the wrapping, which is also irrespective of the tearing direction, as described above, the influence of the large tear resistance of the low density polyethylene 3 is sufficiently reduced, and the wrapping is performed with a remarkably small tearing force. The bag can be opened as intended. here,
It goes without saying that the thickness of each constituent layer of the film structure can be appropriately increased or decreased as required.

The constituent material of the film structure is not limited to the above-mentioned one, but a stretched base film layer is biaxially stretched nylon film, polyethylene phthalate film, polypropylene film, polyvinyl alcohol film, or cellophane film. , Or each of those films with a vinylidene chloride coating, etc.
Further, a non-stretched sealant layer, 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, is arranged between them.
It is sufficiently increased based on the action of the extruded adhesive layer made of the low-density polyethylene 5, and therefore, the packaging bag is used when the weight of the packaged object is large, the packaged object contains water or other liquid, and the like. However, extremely high heat-sealing strength can be exhibited under the excellent adhesive strength between the base film layer and the intermediate layer. By the way, the extruded adhesive layer is replaced by low-density polyethylene 5 and is replaced by linear low-density polyethylene, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene click acid. It can also be formed of a copolymer or the like.

[0026]

[Examples] Examples regarding the interlaminar 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, in the comparative film structure, the extruded adhesive layer made of low-density polyethylene 5 is omitted from the film structure illustrated in FIG. 1, and the high-density polyethylene 2 is directly adhered to the base film layer by extrusion lamination. With the structure.

In the comparative film structure, the base film layer is formed of a biaxially stretched ethylene-vinyl alcohol copolymer resin film having a thickness of 15 μm, 12
Fig. 2 for each of those formed of a biaxially stretched polyethylene phthalate film having a thickness of µm and those formed of a biaxially stretched nylon resin film having a thickness of 15 µm
The maximum tearing force required to completely tear and cut the packaging bag having the same bag-making form as that shown in Fig. 2 was measured by sandwiching the packaging bag in the chuck of the tensile tester and tearing it. It became as shown. Here, the molecular orientation direction of the base film layer is about 30 with respect to the direction in which tearing progresses.
I took it. Here, the cutting length of the packaging bag was 50 mm, and each of the intermediate layer and the sealant layer was formed of 25 μm-thick unstretched high-density polyethylene and 25 μm-thick unstretched ethylene-vinyl acetate copolymer. .
By the way, the required tearing force of the bag at the part where the tearing-induced flaw is formed, which gives a trigger for opening the packaging bag and facilitates the opening of the opening, is the maximum required to completely tear and cut the packaging bag. It is much smaller than the tearing force.

[0028]

[Table 2]

According to the results shown in Table 2, even when the comparative film structure is used, in particular, by forming the intermediate layer of the film structure with an unstretched high-density polyethylene layer, Compared with the conventional packaging bag shown in Fig. 3, the maximum tearing force can be greatly reduced, and the maximum tearing force in the direction that was previously impossible to tear is about the same as the maximum tearing force in the opposite direction. It is clear that it can be reduced to Therefore, even with the comparative example film, regarding opening of the packaging bag, regardless of the tearing direction,
It can be easily performed with a small force.

On the other hand, in the example film structure having the laminated structure illustrated in FIG.
20 mm thick biaxially stretched nylon resin film and intermediate layer
An unstretched high-density polyethylene with a thickness of μm, a sealant layer was formed with an unstretched ethylene-vinyl acetate copolymer with a thickness of 20 μm, and an extrusion adhesive layer was formed with a low-density polyethylene with a thickness of 10 μm. In this case, the adhesive strength between layers, the heat-sealing strength, and the maximum tearing force required for completely tearing the packaging bag were compared with those of the comparative film structure, and the results were as shown in Tables 3 and 4.
In the comparative film structure, the base film layer was a 15 μm thick biaxially stretched nylon resin film, and the intermediate layer and the sealant layer were each a 25 μm thick unstretched high density polyethylene and 25 μm thick. Of unstretched ethylene-vinyl acetate copolymer.

[0031]

[Table 3]

[0032]

[Table 4]

As shown in Table 3, in the example film structure, the adhesive strength between the base film layer and the intermediate layer can be greatly improved by the action of the extrusion adhesive layer, and also the heat seal strength can be sufficiently improved. It is obvious that the maximum tearing force can be suppressed to a sufficiently small value in spite of the presence of the extrusion 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 any position can be started very easily by the action of the tearing-induced flaw. In addition, it is possible to easily perform the progress of the tear of the bag over the portion where the tear-induced flaw is formed, that is, the required opening under the action of the unstretched high-density polyethylene, regardless of the action direction of the tear external force. . Further, since 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 equipment such as a dry laminating equipment and the number of man-hours required for using the equipment. Without it, the required film structure can be manufactured very efficiently and cheaply.

Further, according to the film structure of the present invention,
Since unstretched high-density polyethylene imparts sufficient rigidity to the film structure, and thus to the packaging bag made of it, in particular, the sealant layer has a necessary minimum thickness,
The tear resistance of the packaging bag can be further reduced, the bag-making speed can be increased, and the heating temperature of the heat-sealing means can be lowered to provide excellent heat-sealing strength. Then, as a result of the decrease in the heat-sealing temperature, the unstretched high-density polyethylene as the intermediate layer prevents unnecessary softening flow, and the occurrence of a sealing defect,
It is possible to eliminate the risk of deterioration of the packaging bag function, mixing of resin content into the packaged object, etc., and also to prevent evaporation of moisture contained in the packaged object during sealing of foreign matters, so that steam, etc.
It is possible to sufficiently eliminate the risk of defective sealing due to the residual heat-sealed portion. by the way,
Here, the unstretched high-density polyethylene layer as the intermediate layer is adhered to the base film layer via the extruded adhesive layer, thereby significantly improving the adhesive strength between the intermediate layer and the base film layer, and The opening can be further facilitated and the heat seal strength can be further enhanced.

Although the case where the film structure of the present invention is sealed by three sides to form a bag has been described above as an example, the film structure can be applied to various known bag forming modes such as a four-sided seal. is there.

[Brief description of drawings]

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

FIG. 2 is a plan view illustrating a heat-sealed form of a package.

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

[Explanation of symbols]

1 Biaxially Stretched Ethylene-Vinyl Alcohol Copolymer Resin Film 2 Unstretched High Density Polyethylene 3 Unstretched Low Density Polyethylene 4 Tear Induced Defect 5 Low Density Polyethylene

Claims (1)

[Claims] 1. A film comprising a stretched base film layer, a non-stretched intermediate layer and a sealant layer, and a film having a plurality of tear-inducing flaws located at intervals in the lengthwise direction on at least one side end portion. In the structure, a laminated film structure for packaging, in which 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.