JP6746885B2 - Packaging bag manufacturing method - Google Patents

Description

The present invention relates to a method of manufacturing a packaging bag.

A conventional laminated film forming a packaging bag for food or the like is disclosed in Patent Document 1. This laminated film is formed by laminating a base material layer and a sealing layer, and a sealing bag having an opening surface on one surface is formed by fixing a predetermined portion of the opposing sealing layers by a heat-bonded portion.

After the contents are stored in the packaging bag, the opening surface is fixed by the heat-bonding portion, and the packaging bag is hermetically sealed with the contents stored therein. When heat resistance or transparency of the packaging bag is required depending on the contents, biaxially oriented polypropylene is used as the base material layer and unoriented polypropylene is used as the seal layer.

The packaging bag is peeled off at the interface of the sealing layers facing each other at the heat-bonded portion by pulling the laminated films on the front and rear surfaces away from each other to be opened. Further, the packaging bag is opened by tearing the laminated films on the front and rear surfaces together.

JP, 08-217015, A

However, according to the conventional laminated film in which the base layer made of biaxially oriented polypropylene and the seal layer made of non-oriented polypropylene are laminated by extrusion lamination, the tear strength is so great that they cannot be easily torn. Further, even if the base material layer and the seal layer are adhered via the anchor coating agent, the adhesive strength between them is low. Therefore, when the front and rear surfaces of the packaging bag are pulled away from each other, the interface between the base material layer and the seal layer of the one laminated film of the heat-bonded portion is peeled off. As a result, the seal layer peeled off from the base material layer may be stretched by being pulled by the other laminated film, and the opening surface may not be formed. Therefore, since the packaging bag cannot be easily opened, there is a problem that the convenience of the packaging bag using the laminated film is low.

An object of the present invention is to provide a laminated film that can improve the convenience of a packaging bag and a method for manufacturing the laminated film. Another object of the present invention is to provide a packaging bag that can improve convenience.

In order to achieve the above object, the laminated film of the present invention is composed of a base layer made of biaxially oriented polypropylene and a biaxially oriented polypropylene having a lower melting point than that of the base layer and is directly laminated to the base layer. An intermediate layer and a seal layer made of unstretched polypropylene and directly laminated on the intermediate layer are provided.

Further, the invention is characterized in that, in the laminated film having the above-mentioned constitution, the melting point of the intermediate layer is lower than the melting point of the sealing layer.

Further, the present invention, in the laminated film having the above-mentioned constitution, an outer layer made of a biaxially oriented polypropylene having a melting point lower than that of the base material layer is laminated on a surface of the base material layer opposite to a surface on which the intermediate layer is formed. Characterize.

Further, the present invention is characterized in that, in the laminated film having the above-mentioned constitution, an ink for forming a pattern is arranged between the intermediate layer and the seal layer or on an outer surface opposite to the seal layer.

Further, the packaging bag of the present invention is characterized by being formed of each of the above-mentioned laminated films.

Further, the method for producing a laminated film of the present invention comprises a base layer made of biaxially oriented polypropylene and an intermediate layer made of biaxially oriented polypropylene having a lower melting point than the base layer and directly laminated on the base layer. A sealing layer made of unstretched polypropylene is laminated by extrusion lamination on the intermediate layer of the base film having

Further, the present invention is characterized in that, in the method for producing a laminated film having the above-mentioned constitution, a melting point of the intermediate layer is lower than a melting point of the sealing layer.

Further, the present invention, in the method for producing a laminated film having the above structure, the base film is laminated on the opposite surface of the base layer to the surface on which the intermediate layer is formed and has a lower melting point than the base layer. It is characterized by having an outer layer made of biaxially oriented polypropylene.

Further, the present invention is characterized in that, in the method for producing a laminated film having the above-mentioned constitution, the base film is formed by coextrusion.

According to the laminated film of the present invention, a base material layer made of biaxially oriented polypropylene, an intermediate layer made of biaxially oriented polypropylene having a melting point lower than that of the base material layer, and a seal layer made of non-oriented polypropylene were laminated in order. Therefore, the tear strength of the laminated film can be reduced and the adhesive strength between the layers can be increased. Thereby, the packaging bag using the laminated film can be easily opened, and the convenience of the packaging bag can be improved.

Further, according to the method for producing a laminated film of the present invention, an intermediate layer of a base film having a base layer made of biaxially oriented polypropylene and an intermediate layer made of biaxially oriented polypropylene having a melting point lower than that of the base layer. A sealing layer made of unstretched polypropylene was laminated on the top by extrusion lamination. Thereby, a laminated film having low tear strength and high adhesive strength between layers can be formed. Therefore, it is possible to easily realize a packaging bag that can improve convenience.

The perspective view seen from the back which shows the packaging bag of 1st Embodiment of this invention. Sectional drawing of the laminated film used with the packaging bag of 1st Embodiment of this invention. The perspective view seen from the back which shows the packaging bag of 2nd Embodiment of this invention. Sectional drawing of the laminated film used with the packaging bag of 2nd Embodiment of this invention.

<First Embodiment>
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a perspective view of the packaging bag 10 of the first embodiment as seen from the back side. The packaging bag 10 is fixed by the heat-bonding portion 10a by the heat-bonding portion 10a, which is formed by attaching the end portions 1a, 1b on both sides of the laminated film 1 to each other, and the lower end portion by the heat-bonding portion 10b. As a result, the storage space 8 is formed inside the packaging bag 10 having the opening surface 10e at the upper end. The packaging bag 10 is sealed by storing the contents (not shown) in the storage space 8 and thermally bonding the opening surface 10e.

FIG. 2 shows a sectional view of the laminated film 1. The laminated film 1 is formed by sequentially laminating the base material layer 3, the intermediate layer 4, and the seal layer 5. The base material layer 3 is made of biaxially oriented polypropylene. The intermediate layer 4 is made of biaxially oriented polypropylene having a melting point lower than that of the base material layer 3, and is directly laminated on the base material layer 3. The seal layer 5 is made of unstretched polypropylene and is laminated directly on the intermediate layer 4. The sealing layers 5 facing each other are fixed by thermal bonding to form thermal bonding parts 10a and 10b (see FIG. 1).

The laminated film 1 is formed by sequentially performing a coextrusion step, a stretching step, a corona treatment step, a printing step, and an extrusion laminating step. In the co-extrusion step, polypropylene having different melting points are co-extruded to form the base film 2 (see FIG. 2). As a result, the high melting point polypropylene layer serving as the base material layer 3 and the low melting point polypropylene layer serving as the intermediate layer 4 are directly laminated without using an anchor coating agent or the like.

In the stretching step, the base film 2 is biaxially stretched at high temperature. As a result, the base layer 3 and the intermediate layer 4 made of biaxially oriented polypropylene are formed. In the corona treatment step, the ink surface 4a of the intermediate layer 4 (the surface opposite to the base material layer 3) is subjected to corona treatment. In the printing process, ink 6 is placed on the ink surface 4a that has been subjected to corona treatment, and a pattern such as a character or a design is printed. The surface 3a of the base material layer 3 opposite to the intermediate layer 4 (outer surface of the laminated film 1) may be corona-treated and printed with the ink 6.

In the extrusion laminating step, the melted polypropylene is laminated on the intermediate layer 4 of the base film 2 by extrusion laminating. As a result, the intermediate layer 4 and the seal layer 5 made of unstretched polypropylene are directly laminated without using an anchor coating agent or the like. At this time, since the intermediate layer 4 has a lower melting point than the base material layer 3, the surface is easily melted, and the intermediate layer 4 is bonded to the seal layer 5 with high adhesive strength. It is more preferable to form the intermediate layer 4 to have a lower melting point than that of the seal layer 5 because the surface of the intermediate layer 4 is more easily melted.

In the packaging bag 10 having the above-described configuration, by gripping, for example, the upper portions of the back surface 10g and the front surface 10f of the packaging bag 10 and pulling them in directions away from each other, the heat-bonded portion at the upper end is peeled off and the packaging bag 10 is opened. .. The packaging bag 10 can also be opened by tearing the back surface 10g and the front surface 10f integrally from the left and right ends of the packaging bag 10.

Table 1 shows the results of measuring the heat seal strength and tear strength of the laminated film 1 of the present embodiment.

Experiment 1 in Table 1 is the laminated film 1 of this embodiment. In Comparative Example 1, the base film 2 is composed only of the base layer 3 of biaxially oriented polypropylene with the intermediate layer 4 omitted, and the sealing layer 5 is laminated on the base layer 3 by extrusion lamination. In Comparative Example 2, the base film 2 is composed only of the base layer 3 of biaxially oriented polypropylene in which the intermediate layer 4 is omitted, and the seal layer 5 is laminated on the base layer 3 via the anchor coating agent.

The thickness of the base film 2 of each test piece is 40 μm, the thickness of the intermediate layer 4 is about 2 μm, and the thickness of the seal layer 5 is 30 μm. The melting point of the base material layer 3 of each test piece is about 160° C., the melting point of the intermediate layer 4 is about 120° C., and the melting point of the seal layer 5 is about 140° C.

The heat seal strength (unit: N/15 mm) is measured according to JIS-Z-1707. At this time, the heat-bonding temperature is varied and a test is performed on a plurality of test pieces to which the opposing seal layers 5 of the laminated film 1 are heat-bonded. The tear strength (unit: N) is measured by the B method (Elmendorf tear method) of JIS-K-7128. The tear strength MD (Machine Direction) is the flow direction (winding direction), and the TD (Transverse Direction) is the direction perpendicular to the flow direction.

According to the same table, in Experiment 1, high heat sealing strength was obtained when the heat bonding temperature was 160° C. to 170° C., and peeling occurred at the interface of the opposing seal layers 5. At this time, in Comparative Example 1 and Comparative Example 2, peeling occurred at the interface between the intermediate layer 4 and the seal layer 5 of one of the laminated films 1, and the heat seal strength was lower than in Experiment 1.

Further, the tear strength of Experiment 1 was smaller than the tear strengths of Comparative Example 1 and Comparative Example 2 in MD and TD.

For this reason, when the back surface 10g and the front surface 10f of the packaging bag 10 of the present embodiment are pulled in a direction away from each other, the heat-bonded portion peels off at the interface of the opposing seal layers 5. Thereby, for example, the upper surface of the packaging bag 10 is opened and the packaging bag 10 can be reliably opened. Moreover, when the packaging bag 10 of this embodiment is torn, the tear strength of the laminated film 1 is small, so that it can be easily opened.

According to the present embodiment, the laminated film 1 forming the packaging bag 10 includes a base material layer 3 made of biaxially oriented polypropylene, an intermediate layer 4 made of biaxially oriented polypropylene having a melting point lower than that of the base material layer 3, and no stretching. A sealing layer 5 made of polypropylene is laminated in this order. Since the base material layer 3 and the intermediate layer 4 are made of biaxially oriented polypropylene, they can be integrally biaxially oriented in the stretching step. Therefore, the base material layer 3 and the intermediate layer 4 can be directly laminated by coextrusion in the coextrusion step, and the adhesive strength between them can be increased. Further, since the intermediate layer 4 has a lower melting point than the base material layer 3, the seal layer 5 can be directly laminated on the intermediate layer 4 in the extrusion laminating step to increase the adhesive strength between them.

Thereby, the tear strength of the laminated film 1 can be reduced and the adhesive strength between the layers can be increased. Therefore, the packaging bag 10 using the laminated film 1 can be easily opened, and the convenience of the packaging bag 10 can be improved.

When the melting point of the intermediate layer 4 is lower than the melting point of the seal layer 5, the adhesive strength between the layers of the laminated film 1 can be further increased. Therefore, the convenience of the packaging bag 10 can be further improved.

Ink 6 for forming a pattern is arranged between the intermediate layer 4 and the seal layer 5 (ink surface 4a) or on the outer surface (surface 3a) opposite to the seal layer 5. Therefore, it is possible to easily obtain the laminated film 1 in which the ink 6 is arranged on the base material film 2 in which the base material layer 3 and the intermediate layer 4 are integrated to print a pattern.

Further, since the corona treatment is performed on the surface on which the ink 6 is formed (ink surface 4a or surface 3a), the adhesive strength of the ink 6 can be improved.

Further, the base material film 2 in which the high melting point base material layer 3 and the low melting point intermediate layer 4 are directly laminated can be easily formed by coextrusion.

<Second Embodiment>
FIG. 3 shows a perspective view of the packaging bag 10 according to the second embodiment as viewed from the back side. For convenience of description, the same parts as those in the first embodiment shown in FIGS. 1 and 2 described above are designated by the same reference numerals. The present embodiment is different from the first embodiment in that an outer layer 7 is provided and the form of the packaging bag 10 is different. Other parts are the same as those in the first embodiment.

The packaging bag 10 has the end portions 1a, 1b on both sides of the laminated film 1 fixed by a heat-bonding portion 10c which is overlapped with the envelope and is fixed by a heat-bonding portion 10b. The packaging bag 10 is sealed by accommodating the contents (not shown) in the accommodating space 8 and thermally adhering the opening surface 10e at the upper end.

FIG. 4 shows a sectional view of the laminated film 1. The laminated film 1 is formed by sequentially laminating the outer layer 7, the base material layer 3, the intermediate layer 4, and the seal layer 5. The base material layer 3, the intermediate layer 4, and the seal layer 5 are configured similarly to the first embodiment. The outer layer 7 is made of biaxially oriented polypropylene having a melting point lower than that of the base material layer 3, and is directly laminated on the surface of the base material layer 3 opposite to the surface on which the intermediate layer 4 is formed.

The outer layer 7 is formed by a coextrusion process. In the co-extrusion step, polypropylene having different melting points is co-extruded to form the base film 2 (see FIG. 4). As a result, a low-melting point polypropylene layer serving as the outer layer 7, a high-melting point polypropylene layer serving as the base material layer 3, and a low-melting point polypropylene layer serving as the intermediate layer 4 are directly laminated without an anchor coating agent or the like. It

Further, the base material film 2 is biaxially stretched in the stretching step to form the outer layer 7, the base material layer 3 and the intermediate layer 4 made of biaxially oriented polypropylene.

According to this embodiment, the same effect as that of the first embodiment can be obtained. An outer layer 7 made of biaxially oriented polypropylene having a melting point lower than that of the base material layer 3 was laminated on the surface of the base material layer 3 opposite to the surface on which the intermediate layer 4 was formed. Thereby, the outer layer 7 and the sealing layer 5 can be fixed to each other by the heat-bonding portion 10c to form the envelope-attached packaging bag 10.

The packaging film 10 of the first embodiment may be formed by the laminated film 1 having the outer layer 7 of the present embodiment.

Further, the laminated film 1 used in the first and second embodiments may form a three-sided or four-sided sealed packaging bag 10.

According to the present invention, it can be used for a packaging bag for packaging foods and the like.

DESCRIPTION OF SYMBOLS 1 Laminated film 2 Base film 3 Base layer 4 Intermediate layer 4a Ink surface 5 Seal layer 6 Ink 7 Outer layer 8 Storage space 10 Packaging bags 10a, 10b, 10c Heat-bonded part 10e Opening surface 10f Front surface 10g Rear surface

Claims (3)

In a method of manufacturing a packaging bag formed by a laminated film in which a base material layer, an intermediate layer and a seal layer are laminated,
A coextrusion step of forming a base material film by laminating polypropylene forming the base material layer and polypropylene forming the intermediate layer by coextrusion,
A stretching step of biaxially stretching the base film,
An extrusion laminating step of forming a laminated film by extrusion laminating polypropylene forming the sealing layer on the intermediate layer of the base film.
A heat-bonding step of forming the packaging bag by heat-bonding the opposing sealing layers of the laminated film;
And the melting point of the intermediate layer (the lowest melting point in the case of a resin mixture) is higher than the melting point of the base material layer (the lowest melting point in the case of a resin mixture) and the melting point of the seal layer (the highest melting point in the case of a resin mixture). Low, the heat-bonding temperature of the heat-bonding step is 160°C to 170°C. The laminated film has an outer layer on the surface opposite to the surface of the substrate layer on which the intermediate layer is formed, and in the coextrusion step, polypropylene is laminated by coextrusion to form the outer layer, and the melting point of the outer layer ( The method for producing a packaging bag according to claim 1, wherein the melting point of the resin mixture is lower than the melting point of the base material layer (the minimum melting point of the resin mixture) . The packaging bag according to claim 1 or 2, further comprising a printing step in which an ink for forming a pattern is arranged between the intermediate layer and the seal layer or on an outer surface opposite to the seal layer. Manufacturing method.

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