JPH0675954B2 - Laminated film structure for packaging - Google Patents

Description

TECHNICAL FIELD 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 substance, a viscous substance, and a powder / granular substance, and in particular, The present invention proposes a film structure which can very easily open a packaging bag and, at the same time, enables high-speed sealing at a relatively low heat-sealing temperature in the automatic filling and bag-making of an object to be packaged.

[Conventional technology]

As a conventionally known laminated film structure for packaging, which includes 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 material, a viscous material, and a powder / granular material, for example, The base film layer is a biaxially stretched ethylene-vinyl alcohol copolymer resin film,
The intermediate layer is made of non-stretched low-density polyethylene, and the sealant layer mainly arranged for heat sealing is formed of non-stretched ethylene-vinyl acetate copolymer resin. Packaging of an object to be packaged by such a film structure is performed by, for example, an automatic filling bag-making machine, in which the sealant layers of the film structure, which are positioned to face each other, are shaded in FIG. This is performed by sealing the three-sided seal to form a packaging bag, and encapsulating the article to be packaged in a non-hatched portion of the packaging bag.

As shown in the figure, the I-notch c provided in the vertical seal portion b of the packaging bag a is used to take out the article to be packaged from the packaging bag formed by filling the film structure in this way. More preferably in a state in which the tearing of the bag is started and the tear of the bag caused thereby is advanced to a position at least passing the so-called bottle mouth portion e which functions as a part of the storage space d of the object to be packaged. This is performed by pressing the package storage space d so that the package is allowed to flow out from the opened bottle mouth portion e in a state where the crevice is advanced to a position where the package a completely crosses the bag a.

[Problems to be Solved by the Invention]

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 posture in FIG. 3 (a), when the end portion of the packaging bag is pulled toward the front side, even if the opening can be easily performed under a relatively small tear resistance, FIG. ), 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 becomes remarkably large, and it becomes very difficult to advance the tear beyond the bottle mouth portion e. There was a problem.

By the way, according to the tests conducted by the present inventor, as the base film layer, a film structure using a biaxially stretched ethylene-vinyl alcohol copolymer resin film having a thickness of 15 μm, and a biaxially stretched polyethylene terephthalate film having a thickness of 12 μm were used. In each of the film structure used and the film structure using a biaxially stretched nylon resin film with a thickness of 15 μm, the intermediate layer and the sealant layer were each made of unstretched low-density polyethylene with a thickness of 25 μm and unstretched with a thickness of 25 μm. The maximum force required to completely tear and cut a packaging bag when it is formed of ethylene-vinyl acetate copolymer resin is its cutting length, in other words, the bag width is 50 mm, and the molecular orientation direction of the base film layer is , About the direction of tearing
At 30 degrees, the results are shown in Table 1.

In addition, this does not impair the strength of the packaging bag,
In order to facilitate the initiation of tearing by fingers from any part of it, it is disclosed in, for example, Japanese Patent Laid-Open No. 61-142159 instead of the I notch or V notch in the heat seal portion of the bag. The same was true in the case where an easy-opening structure was provided, in which so-called many scratches without defects were provided at intervals in the length direction of the heat seal portion.

That is, in this type, 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 by improving the laminated structure of the film structure, and facilitates easy and smooth initiation of finger tearing from any position of the packaging bag. The maximum tearing force required to completely open the packaging bag is always small enough regardless of the tearing direction of the packaging bag. The present invention provides a laminated film structure for packaging which enables high-speed sealing and has no fear of unexpected breakage.

[Means for Solving the Problems]

The laminated film structure for packaging of the present invention is a film structure having a plurality of tearing-induced flaws located at intervals in the length direction on at least one side end portion, and particularly, the material of the stretched base film layer may be used. Regardless of which, the intermediate layer is formed by a non-stretched high-density polyethylene layer directly bonded to the base film layer, for example by extrusion, between the base film layer and the non-stretched sealant layer. Is.

Here, in forming the intermediate layer with an unstretched high-density polyethylene layer, an extrusion adhesive layer made of, for example, low-density polyethylene or linear low-density polyethylene is interposed between the intermediate layer and the base film layer. You can also

By the way, the tearing-induced flaws are one flaw formed by extending in a negative (-) shape in the width direction of the film structure, a plurality of perforations formed in a perforated shape, and provided at intervals in the width direction. It can be formed with an appropriate shape and number of flaws such as a plurality of small hole-shaped flaws, and the depth, the length in the width direction of the film assembly, and the film assembly of the tearing-induced flaws can be formed. The distance in the length direction of the film 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.

[Action]

This laminated film structure for packaging, in a state where the sealant layers thereof face each other, by heat-sealing required parts including side end parts provided with tear-induced defects,
Similar to the conventional film structure, it is possible to properly package the object to be packaged.

On the other hand, the start of opening the bag when taking out the items to be packed is
Under the action of the tearing-induced flaw existing in the heat-sealed portion, it can be carried out extremely easily by the force of the finger from any position. And, the crevice of the bag generated in this way,
Progressing beyond tear-induced flaws, in other words, the required opening, results in increased tear resistance due to the presence of the unstretched high-density polyethylene layer itself, and also due to the presence of the unstretched high-density polyethylene layer. The ability to effectively reduce the thickness of the unstretched sealant layer results in an increase in tear resistance of the sealant layer regardless of the molecular orientation direction of the film material forming the base film layer, that is, due to the molecular orientation direction. No matter which direction the action of the external tearing force is,
This too will be done quite easily.

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 extremely broken when the bag is opened. Based on the easy property, each of the base film layer and the sealant layer is adhered to the intermediate layer with sufficient strength, with the rupture of the bag progressing along the tearing-induced flaw as a boundary. Due to the small tear propagation resistance peculiar to the unstretched high-density polyethylene layer, which is the intermediate layer, no shearing force is applied to the intermediate layer regardless of the direction in which the external tearing force is applied in the directions shown by the arrows in FIGS. The initiation of cracking precedes the initiation of tearing into the base film layer and sealant layer, and the tearing of those layers strongly adhered to the intermediate layer By generating so as to follow 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 of the unstretched high-density polyethylene layer. This enables the thickness of the sealant layer to be the minimum required for heat sealing, and thus, as described above, the tear resistance provided by the sealant layer can be further reduced. 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 and other heat sealing means can be lowered to achieve high density of the intermediate layer. Unnecessary flow of the polyethylene layer can be effectively prevented, and further, when the material to be packaged is a liquid material, a viscous material, etc., it is contaminated. (Biting) per the seal, by preventing the occurrence of water vapor or the like from the objects to be packaged, the steam or the like can remove the risk of seal failure occurrence due to remaining heat-sealed portion.

Moreover, here, since the unstretched high-density polyethylene layer as the intermediate layer can be formed by extrusion lamination,
Compared with the case where a stretched high-density polyethylene film is laminated on the base film layer by dry lamination or the like, it requires extremely no special laminating step and laminating equipment, is extremely efficient, and is required at a low cost. A film assembly can be manufactured.

By the way, as described above, 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 is increased so much. Therefore, for example, when the weight of the packaged object is relatively large, the adhesive strength of the extruded adhesive layer made of low-density polyethylene, linear low-density polyethylene, etc. is interposed between the two layers to improve the adhesive strength. It is preferable to increase.

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 and the base are usually used. Since the film layer and the film layer can be firmly joined together sufficiently, the interposition of the above-mentioned extrusion adhesive layer is not necessary, but in this case, the heat seal temperature is considerably increased due to the physical properties inherent to the polyethylene sealant layer. Inevitably, it becomes impossible to bring about the above-mentioned effects due to the low heat-sealing temperature, and moreover, the heat-sealing strength is inevitably lowered. Therefore, such a laminated structure is included in the present invention. Not.

Further, as described above, when the formation position of each tearing-induced flaw is separated from the side edge position of the film structure to some extent, the side edge of the film structure to the side edge of the film structure is wound or rewound. Unexpected breakage of the film structure due to stress concentration can be almost completely prevented.

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

〔Example〕

 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 is a biaxially stretched ethylene-vinyl alcohol copolymer resin film 1 having a thickness of 15 μm as a base film layer and an intermediate layer as an intermediate layer. 20 μm thick unstretched high density polyethylene 2 and also as a sealant layer
A film structure obtained by sequentially laminating unstretched low-density polyethylene 3 having a thickness of μm is shown. This film structure is formed at one side end portion from the position slightly separated from the side edge to the inside in the width direction of the film structure. A tear-inducing flaw 4 having a plurality of flaws provided in a perforated shape is provided at predetermined intervals in the length direction of the film structure.

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.

The production of such a film structure is carried out by laminating the ethylene-vinyl alcohol copolymer resin film 1 and the low-density polyethylene 3 previously formed into a film shape by extrusion lamination of the high-density polyethylene 2 by extrusion, or The ethylene-vinyl alcohol copolymer resin film 1 is extruded and coated with the high-density polyethylene 2 and the low-density polyethylene 3 sequentially by using, for example, a tandem type extrusion laminating apparatus,
It can be carried out extremely efficiently and without requiring a special working apparatus and working man-hours such as a dry laminating apparatus.

The packaging of an object to be packaged by such a film structure is performed by using a heat-sealing roll, a heat-sealing bar or the like to form the low-density polyethylene 3 of the film structure facing each other,
Tear-induced flaws 4 in time with the filling of the packaged object
It can be performed by heat-sealing at a required position including the side end surface portion provided with.

On the other hand, when the film structure is formed into a bag similar to that described in the related art, the package bag is taken out from the tear guide flaw 4 located at the vertical seal portion of the heat seal portion. Tear through the bottle mouth portion, for example, over its entire width, and then the packaged object is
It can be carried out by extruding from the bottle mouth part, and at the time of taking out such a packaged object, according to the film structure of the present invention, the tearing direction is the direction shown in FIG. Regardless of the direction shown in (b),
Due to the action of the tearing-induced flaw 4, the opening can always be started sufficiently easily, and also due to the extremely fragile nature of the unstretched high-density polyethylene 2 as the intermediate layer, this also causes Regardless of the reason, as described above, the influence of the large tear resistance of the low density polyethylene 3 can be sufficiently reduced, and the packaging bag can be opened as expected with a remarkably small tear force.

Here, it goes without saying that the thickness of each constituent layer of the film structure can be appropriately increased or decreased as required.

By the way, the film structure of the present invention is not limited to the above-mentioned place, and includes a stretched base film layer,
It can also be formed from a biaxially stretched nylon film, polyethylene phthalate film, polypropylene film, polyvinyl alcohol film, or cellophane film, or a film in which vinylidene chloride coating is applied to each of these films, and also an unstretched sealant layer. Are ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene methyl acrylate,
It can also be formed of ethylene-methacrylic acid copolymer, ethylene-methyl methacrylate copolymer, polypropylene, linear low-density polyethylene, ionomer, or the like.

FIG. 1 (b) is a cross-sectional view showing another embodiment of the present invention. In particular, when the intermediate layer is formed of unstretched high density polyethylene 2, the unstretched high density polyethylene 2 and the base are formed. In order to sufficiently increase the adhesive strength with a film layer, for example, a biaxially stretched ethylene-vinyl alcohol copolymer resin film 1, an extruded adhesive layer made of, for example, low density polyethylene 5 is formed between them. The film structure also has the tearing-induced flaw 4 similar to that in the above-described embodiment.

According to this example, when the weight of the object to be packaged is large, even when the object to be packaged contains water or other liquid, the adhesiveness between the base film layer and the intermediate layer is very high, Heat seal strength can be exhibited. Here, 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 acetate. It can also be formed from a click acid copolymer or the like.

[Test Example 1] In the film structure illustrated in FIG. 1 (a), the base film layer is formed of a biaxially stretched ethylene-vinyl alcohol copolymer resin film having a thickness of 15 μm and a thickness of 12 μm. The maximum tearing force required for completely tearing the packaging bag was measured for each of the biaxially stretched polyethylene phthalate film and the biaxially stretched nylon film having a thickness of 15 μm. The results are shown in Table 2.

Here, the cutting length of the packaging bag was 50 mm, and the intermediate layer and the sealant layer were each made of unstretched high density polyethylene of 25 μm thickness and unstretched ethylene of 25 μm thickness.
It was formed from a 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.

According to the table, in particular, by forming the intermediate layer of the film structure with an unstretched high-density polyethylene layer, the required tearing force is greatly reduced as compared with the conventional packaging bag shown in Table 1. It is clear that the required tearing force in the direction in which the conventional tearing was not possible can be reduced to the same extent as the required tearing force in the opposite direction.

Therefore, the opening of the packaging bag at the time of taking out the article to be packaged can be always easily performed with an extremely small force regardless of the tearing direction.

[Test Example 2] In the film structure illustrated in FIG. 1 (b), the base film layer is a biaxially stretched nylon film having a thickness of 15 μm, the intermediate layer is an unstretched high-density polyethylene having a thickness of 20 μm, When the sealant layer is formed of 20 μm thick unstretched ethylene-vinyl acetate copolymer and the extruded adhesive layer is formed of 10 μm thick low density polyethylene, the adhesive strength between layers, heat The seal strength and the maximum tearing force required to completely tear and cut the packaging bag are compared with those shown in FIG. 1 (a) and a laminated film structure similar to that shown in Tables 3 and 4. It became a street.

Here, in the film structure having the structure shown in FIG. 1 (a), the base film layer is a biaxially stretched nylon film having a thickness of 15 μm, and each of the intermediate layer and the sealant layer is a non-stretching film having a thickness of 25 μm. High density polyethylene and
It is formed of a non-stretched ethylene-vinyl acetate copolymer having a thickness of 25 μm.

As shown in Table 3, in the film structure shown in FIG. 1 (b), the action of the extruded adhesive layer can greatly improve the adhesive strength between the base film layer and the intermediate layer, and also improve the heat seal strength. It is also clear that the required 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.

〔The invention's effect〕

As described above, the packaging bag constituted by the film structure of the present invention starts the opening from any position thereof,
It can be performed very easily by the action of the tearing-induced flaw. Moreover, it is extremely easy to carry out the progress of the tear of the bag over the portion where the tearing-induced flaw is formed, that is, the required opening under the action of the unstretched high-density polyethylene, regardless of the direction of action of the tearing external force. it can.

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 the unstretched high-density polyethylene imparts sufficient rigidity to the film structure, and by extension, the packaging bag made of the film structure, the sealant layer is particularly required to have a minimum thickness. Further, 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 is prevented from unnecessary softening and flow, resulting in defective sealing, deterioration of the packaging bag function, and resin content to be packaged. It is possible to eliminate the risk of contamination, etc., and to prevent the evaporation of moisture contained in the packaged object during the sealing of foreign matter, and to prevent the occurrence of sealing defects due to the steam remaining in the heat seal section. The fear can be sufficiently removed.

By the way, when the unstretched high-density polyethylene layer as the intermediate layer is adhered to the base film layer through the extrusion adhesive layer, the adhesive strength between the intermediate layer and the base film layer is greatly improved, and the packaging bag Can be opened even easier.

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, it is needless to say that the film structure can be applied to various known bag forming modes such as a four-sided seal.

[Brief description of drawings]

1 (a) and 1 (b) are cross-sectional perspective views showing an embodiment of the present invention, FIG. 2 is a plan view illustrating a heat-sealing form of a package, and FIGS. 3 (a) and 3 (a), respectively. b) is a figure which respectively shows the action direction of the tearing external force of a packaging bag. 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 (2)

[Claims] 1. A film comprising a stretched base film layer, a non-stretched intermediate layer and a sealant layer, and at least one side end portion thereof having a plurality of tearing-induced flaws positioned at intervals in the lengthwise direction. In the structure, a laminated film structure for packaging, wherein the intermediate layer is formed by an unstretched high-density polyethylene layer directly bonded to a base film layer. 2. A film comprising a stretched base film layer, a non-stretched intermediate layer and a sealant layer, and at least one side end portion thereof having a plurality of tearing-induced flaws positioned at intervals in the lengthwise direction. 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.