JP2022000388A - Inner bag for bag-in-box - Google Patents

Abstract

To provide an inner bag for a bag-in-box, having an excellent gas barrier property and reduced deterioration of the gas barrier property due to bending, and capable of preventing occurrence of pinholes due to friction with an outer box.SOLUTION: The present invention provides the inner bag for the bag-in-box that consists of an outer box made of paper as a base material and the inner bag being inside the outer box and capable of directly storing contents inside, in which the inner bag has a spout from which the contents can be taken out, the spout is fixed to the outer box, the inner bag is made up of a laminated body using a plastic film as a base material, and the laminated body is formed of a polyolefin-based resin film layer and a biaxially oriented polyamide-based resin film layer in order from the inside of the inner bag, and a biaxially oriented polypropylene-based resin film layer having a gas barrier layer made of an inorganic compound as an outermost layer.SELECTED DRAWING: Figure 2

Description

The present invention relates to an inner bag for a bag-in-box. The bag-in-box is a double container, the outside of which is a paper container, and the inside of which is a plastic film-based inner bag, which can be used as a liquid container, for example. ..

In recent lifestyles, in the distribution and sale of liquid products such as beverages, alcoholic beverages, and seasonings, many liquid containers using plastic films and products using liquid paper containers are produced, distributed, sold, and consumed. It has been delivered to the person.

For example, beverages such as juices, milk beverages, and liquors are often filled in a liquid container such as a bottle, a plastic bottle, or a liquid paper container by a liquid filling device at a manufacturer and sent out as a commercial product.

Among them, the bag-in-box is a double container in which an inner bag called a bag made of a plastic film is filled with a liquid and then spouted and stored in a paper box such as a cardboard box.

In the case of such a double container, since the outside is a paper container such as cardboard, it can be made into a rectangular parallelepiped or cube shape, so that it is possible to improve inventory efficiency and transportation efficiency in warehouses and the like. It is possible.

In addition, the outer paper container can enhance mechanical strength such as impact resistance and block the influence of the environment such as ultraviolet rays. In addition, the outer paper container can be easily decorated on the surface such as printing, and the outer paper box is more convenient to carry and easier to handle than the plastic container as it is.

In addition, since the inside is an inner bag made of a plastic film as a base material, it is suitable for storing liquids, and the required amount can be taken out each time by opening and closing the spout. Furthermore, when disposing of the used bag-in-box, it is easy to separate the paper container from the inner bag based on the plastic film, the volume can be reduced, and it is widely used as an environment-friendly liquid container. It has become acceptable.

In the case of such a bag-in-box that can store liquid, the spout attached to the inner bag can be taken out when necessary by protruding outward from the outer paper container and exposing it. , Can be done more conveniently.

However, although the inner bag is fixed to the outer box by the spout portion, the main body portion of the inner bag is subject to vibration such as transportation, and there is a possibility that friction may occur with the outer box. In addition, when the contents are contained, since the inner bag has a three-dimensional shape, it is inevitable that a bent portion is generated, and there is a possibility that friction with the outer box may occur locally. It causes pinholes in the inner bag.

The occurrence of pinholes in the inner bag causes serious defects as a packaging container, such as the possibility that the contents leak from the inner bag due to penetration, and the gas barrier layer is destroyed even if it does not penetrate, resulting in deterioration of gas barrier properties. May cause.

Patent Document 1 proposes a bag-in-box for liquids and a method of using the same, but the inner bag and the outer paper container are welded together, and in order to expose the spout to the outside, it is necessary to use the outside. Although the method of assembling both the top and bottom of the box at once and the friction between the outer box and the inner bag can be avoided, the manufacture and assembly of such a bag-in-box is not an easy process, and welding is performed. This caused the problem that it was not easy to separate after use.

Japanese Unexamined Patent Publication No. 58-203855

The present invention has been made in view of such a situation, and has a high gas barrier property, less deterioration of the gas barrier property due to bending, and can prevent the occurrence of pinholes due to friction with the outer box. The challenge is to provide an inner bag for the inbox.

The invention according to claim 1 is a means for solving the above problems.
In a bag-in-box consisting of an outer box made of paper as a base material and an inner bag inside the outer box that can directly store the contents inside.
The inner bag has a spout from which the contents can be taken out, and this spout is fixed to the outer box.
The inner bag is composed of a laminate made of a plastic film as a base material.
The laminate is characterized in that it is composed of a polyolefin-based resin layer, a stretched polyamide-based resin film layer, and a stretched polypropylene-based resin film layer having a gas barrier layer made of an inorganic compound on the outermost layer in this order from the inside of the inner bag. , Inner bag for bag-in-box.

Further, the invention according to claim 2 is based on the invention.
In the laminate, the thickness of the polyolefin-based resin film layer is in the range of 40 μm to 120 μm.
The stretched polyamide-based resin film layer is composed of a stretched polyamide film having a thickness of 15 μm to 25 μm.
The inner bag for a bag-in-box according to claim 1, wherein the stretched polypropylene-based resin film layer is composed of a stretched polypropylene film having a thickness of 20 μm to 40 μm.

Further, the invention according to claim 3 is based on the invention.
The stretched polypropylene-based resin film layer having the gas barrier layer made of the inorganic compound has a polyvinyl alcohol-based resin layer, a thin film layer made of a silicon or aluminum inorganic compound, and a polyvinyl alcohol-based resin layer as a gas barrier layer on the surface of the stretched polypropylene film. The inner bag for a bag-in-box according to claim 1 or 2, wherein the inner bag is sequentially laminated.

According to the present invention, there is provided an inner bag for a bag-in-box, which has a high gas barrier property, has little deterioration in gas barrier property due to bending, and can prevent the occurrence of pinholes due to friction with the outer box. It is possible.

The inner bag has a spout from which the contents can be taken out, and by fixing this spout to the outer box, it is possible to stably take out the contents of the inner bag, and the contents have been taken out. Later, with the separation of the spout portion as a trigger, there is an advantage that the outer box made of paper and the inner bag made of plastic material can be easily separated and separated.

The inner bag is made of a laminate made of a plastic film as a base material, and can store a liquid in the contents. Also, by providing the laminate with a sealant layer made of a thermoplastic resin, the inner bag is sealed. The inner bag can be easily made and sealed.

The laminate is composed of a polyolefin resin layer, a stretched polyamide resin film layer, and a stretched polypropylene resin film layer having a gas barrier layer made of an inorganic compound on the outermost layer in this order from the inside of the inner bag. The polyolefin-based resin layer on the interior side of the above can be used as a sealant layer to make a bag, and it is possible to store liquid contents. In addition, the polyolefin-based resin is a safe material even when it comes into direct contact with the contents such as a beverage as a liquid container.

Further, by having the stretched polyamide resin film layer as an intermediate film in the laminate, the inner bag is effective in improving the mechanical strength such as resistance to external force such as piercing.

Further, by arranging a stretched polypropylene-based resin film layer having a gas barrier layer made of an inorganic compound on the outermost layer, a high degree of gas barrier property can be provided. This gas barrier property protects the contents from deterioration of the external environment due to, for example, water vapor or oxygen, and also prevents the flavor and components of the contents from leaking to the outside, which is effective in improving the storage stability. ..

Further, since the stretched polypropylene-based resin film layer is arranged on the outermost layer of the inner bag, it is effective in improving the pinhole resistance against external forces such as vibration during transportation and friction with the outer box.

Further, in particular, according to the invention of claim 2, the thickness of the polyolefin-based resin layer of the laminate is 40 μm to 120 μm, so that sufficient sealing suitability as a sealant layer can be ensured.

Further, since the stretched polyamide resin film layer is a stretched polyamide film having a thickness of 15 μm to 25 μm, the inner bag can be provided with further toughness and flexibility with respect to mechanical strength and external force.

The outermost stretched polypropylene-based resin film layer is composed of a stretched polypropylene film having a thickness of 20 μm to 40 μm, so that the laminate constituting the inner bag does not lose its flexibility and toughness, and therefore is transported to and from the outer box. It is effective by avoiding the occurrence of pinholes due to friction such as time.

Further, according to the invention of claim 3, the stretched polypropylene resin film layer having a gas barrier layer made of an inorganic compound has a polyvinyl alcohol resin layer, silicon or aluminum inorganic as a gas barrier layer on the surface of the stretched polypropylene film. By sequentially laminating a thin film layer made of a compound and a polyvinyl alcohol-based resin layer, it is effective to obtain a laminated body having a high level of gas barrier property and less deterioration of gas barrier property due to bending. be.

FIG. 1 is a schematic perspective view (partially perspective view) for explaining the configuration of the entire bag-in-box according to the present invention. FIG. 2 is a schematic partial cross-sectional view for explaining an embodiment of a laminated body constituting an inner bag for a bag-in-box according to the present invention. FIG. 3 is a partial cross-sectional schematic diagram for explaining a gas barrier film layer made of an inorganic compound, among the embodiments of the laminate constituting the inner bag for a bag-in-box according to the present invention. FIG. 4 is a schematic partial cross-sectional view of a laminated body for explaining Example 1 of the inner bag for a bag-in-box according to the present invention. FIG. 5 is a schematic partial cross-sectional view of a laminated body for explaining Comparative Example 1 of the inner bag for a bag-in-box according to the present invention. FIG. 6 is a schematic partial cross-sectional view of a laminated body for explaining Comparative Example 2 of the inner bag for a bag-in-box according to the present invention. FIG. 7 is a schematic partial cross-sectional view of a laminated body for explaining Comparative Example 3 of the inner bag for a bag-in-box according to the present invention.

Hereinafter, a more detailed description of the present invention will be added with reference to the drawings. However, the present invention is not limited to the examples shown here. The present invention is specified by the claims.

FIG. 1 is a schematic perspective view (partially perspective view) for explaining the configuration of the entire bag-in-box according to the present invention.

The present invention relates to an inner bag for a bag-in-box. The bag-in-box (1) includes an outer box (10) made of paper as a base material and an inner bag (100) inside the outer box in which the contents can be directly stored inside.

In the bag-in-box (1), the inner bag (100) has a spout (22), and this spout is fixed to the outer box (10) by a fixing portion (23), and the contents from the spout (22). Can be taken out. In the example shown in FIG. 1, the spout (22) has a cap (21) at the tip and has a structure that can be sealed.

Generally, the spout (22) and the cap (21) are made of a plastic molded product of a separate member, and are excellent in repetitive opening and closing by screwing and sealing, and in particular, the spout (22) has an inner bag (100). It is possible to integrate by welding.

The outer box (10) is made of paper as a base material. For example, paper such as corrugated cardboard (micro flutes, colored balls, etc.), woodfree paper, and packing paper is punched out, bent, glued, or heat-sealed to form a box. It is assembled into a shape. If necessary, the surface of the outer box (10) may be varnish coated, PP laminated, embossed, decorative film laminated or the like.

Therefore, the bag-in-box (1) has advantages in terms of economy, the degree of freedom in appearance design, shape retention, good handling, stacking, etc. due to the fact that the outer box (10) is made of paper. On the other hand, since the inner bag (100) is made of a plastic film, it has advantages such as high performance as a liquid container such as water resistance and sealing property, gas barrier performance, etc., and has both advantages. It is a container.

FIG. 2 is a schematic partial cross-sectional view for explaining an embodiment of a laminated body constituting an inner bag for a bag-in-box according to the present invention.

The inner bag (100) is composed of a laminate (30) using a plastic film as a base material, and the laminate (30) is a polyolefin resin layer (30) which is a sealant layer in order from the inside of the inner bag (100). 33), a stretched polypropylene-based resin film layer (31) having a stretched polyamide-based resin film layer (32) as an intermediate film layer and a gas barrier layer (40) made of an inorganic compound as an outermost layer via an adhesive layer (35). It is composed of and.

In the example shown in FIG. 2, the gas barrier layer (40) made of an inorganic compound and the outermost stretched polypropylene-based resin film layer (31) are shown as a gas barrier film layer (50).

Further, if necessary, a printing layer (36) may be provided on the inner bag (100), and in this case, it may be provided between the gas barrier film layer (50) and the adhesive layer (34). can. By providing the printed layer (36) at this position, it is possible to provide the printed layer (36) without lowering the interlayer strength of the laminated body (30).

That is, since the gas barrier layer (40) made of the inorganic compound and the stretched polypropylene-based resin film layer (31) are transparent, the printed layer (36) is protected by these layers and is outside the inner bag (100). It becomes visible from.

Further, the print layer (36) may be provided over the entire surface of the inner bag (100), or may be provided partially. The print layer (36) may be provided not only as a decoration by a pattern or an information display, but also as a light-shielding layer by coloring the entire surface if necessary.

Here, the printing method of the printing layer (36) and the printing ink are not particularly limited, but among the known printing methods, printability, designability such as color tone, and adhesion to the object to be printed are not particularly limited. , It may be selected as appropriate if safety with respect to the contents is taken into consideration.

For example, it can be selected from known printing methods such as a gravure printing method, an offset printing method, a gravure offset printing method, a flexo printing method, a silk screen printing method, and an inkjet printing method. Above all, the gravure printing method can be preferably used in terms of productivity, printability, and high definition of the pattern.

In the process of diligently studying the present invention, the present invention is a subject of the laminated body (30) constituting the inner bag (100) for a bag-in-box according to the present invention, particularly when each layer has the following structure. Realization of an inner bag (100) for a bag-in-box that has a high gas barrier property, has little deterioration in gas barrier property due to bending, and can prevent the occurrence of pinholes due to friction with the outer box (10). We found that the offer was more effective.

That is, in the laminate (30) constituting the inner bag (100) for the bag-in-box, the thickness of the polyolefin-based resin layer (33) is in the range of 40 μm to 120 μm, and the stretched polypropylene-based resin film layer (32) is formed. It is effective that the stretched polypropylene-based resin film layer (31) is composed of a stretched polypropylene film having a thickness of 15 μm to 25 μm and is composed of a stretched polypropylene film having a thickness of 20 μm to 40 μm.

When each component is within these thickness ranges, the polyolefin resin layer (33)
) Is 40 μm to 120 μm, so that sufficient sealing suitability as a sealant layer can be ensured.

Further, since the stretched polyamide resin film layer (32) is a stretched polyamide film having a thickness of 15 μm to 25 μm, the inner bag can be provided with further toughness and flexibility with respect to mechanical strength and external force. ..

Further, the outermost stretched polypropylene resin film layer (31) is composed of a stretched polypropylene film having a thickness of 20 μm to 40 μm, so that the laminate constituting the inner bag does not lose its flexibility and toughness, and therefore. It is effective by avoiding the occurrence of pinholes due to friction during transportation with the outer box.

In particular, it is more preferable that the polyolefin-based resin layer (33), which is the sealant layer, has a thickness in the range of 60 μm to 120 μm, and the stretched polypropylene film has a thickness in the range of 20 μm to 30 μm. It was also found to be more preferable in solving the problems of the invention.

The sealant layer is formed by stacking two laminated bodies (30) so that the sealant layers face each other and adhering them to each other by, for example, heating, pressurizing and heat-sealing to form an inner bag (100). Enables.

Of the thermoplastic resins, polyolefin resins are generally used as the material of the sealant layer, and specifically, low-density polyethylene resin (LDPE), medium-density polyethylene resin (MDPE), and linear low-density polyethylene resin. (LLDPE), ethylene-vinyl acetate copolymer (EVA), ethylene-α-olefin copolymer, ethylene-methacrylic acid resin copolymer and other ethylene-based resins, polyethylene-polybutene blend resin, homopolypoly resin Polypropylene-based resins such as (PP), a propylene-ethylene random copolymer, a propylene-ethylene block copolymer, and a propylene-α-olefin copolymer can be used.

To form the sealant layer, a molten resin can be formed by using an extruder or the like to form a layer on the laminated body (30). Alternatively, it is also possible to form a sealant layer on the surface of the laminated body (30) by laminating a material that has been formed into a film state in advance by laminating.

FIG. 3 is a partial cross-sectional schematic diagram for explaining a gas barrier film layer made of an inorganic compound, among the embodiments of the laminate constituting the inner bag for a bag-in-box according to the present invention.

In the present invention, the stretched polypropylene-based resin film layer (31) having the gas barrier layer (40) made of an inorganic compound can be provided in the laminate (30) as the gas barrier film layer (50).

Specifically, as the gas barrier layer (40), a polyvinyl alcohol-based resin layer (41), a thin film layer (42) made of an inorganic compound of silicon or aluminum, and a polyvinyl alcohol-based resin layer (43) are formed on the surface of the stretched polypropylene film. It can be sequentially laminated and configured.

For the polyvinyl alcohol-based resin layer (41) and the polyvinyl alcohol-based resin layer (43), for example, EVOH (ethylene-vinyl alcohol-based copolymer) can be used.

The polyvinyl alcohol-based resin layer (41) and the polyvinyl alcohol-based resin layer (43) can be formed by, for example, a coating method.

Further, with respect to the thin film layer (42) made of an inorganic compound of silicon or aluminum, it is possible to form a layer of an inorganic compound such as silicon oxide or aluminum oxide by using a vacuum vapor deposition method.

In this case, the polyvinyl alcohol-based resin layer (41) can be formed by coating on the stretched polypropylene-based resin film layer (31), and the thin film layer (42) made of an inorganic compound can be formed on the surface thereof.

The gas barrier film layer (50) thus constructed has high gas barrier performance and flexibility required as an inner bag (100) due to the thin film layer (42) made of an inorganic compound of silicon or aluminum.

That is, the thin film layer (42) made of an inorganic compound of silicon or aluminum is layered by sandwiching both sides with a polyvinyl alcohol-based resin layer (41) and a polyvinyl alcohol-based resin layer (43), whereby the inorganic compound is formed. It is possible to cover the brittleness of the thin film layer (42) made of the above material, and it is possible to realize a laminated body (30) having less deterioration in gas barrier property due to bending.

Regarding this gas barrier film layer (50) as well, in the process of diligently studying the present invention, each layer has the following structure in the laminate (30) constituting the inner bag (100) for the bag-in-box according to the present invention. Occasionally, it was found to be more effective in solving the problems of the present invention.

That is, the thickness of the polyvinyl alcohol-based resin layer (41) is preferably in the range of 0.05 to 0.5 μm, more preferably in the range of 0.1 to 0.2 μm. The thickness of the polyvinyl alcohol-based resin layer (43) is preferably 0.05 to 2 μm, more preferably 0.1 to 0.6 μm.

Further, the thickness of the thin film layer (42) made of an inorganic compound of silicon or aluminum is in the range of 5 to 80 nm, more preferably 10 to 50 nm, which has a high gas barrier property and a gas barrier property due to bending. It has been found that it is effective in providing the inner bag (100) for a bag-in-box, which has less decrease and can prevent the generation of pinholes due to friction with the outer box (10).

In this way, according to the present invention, for a bag-in-box, which has a high gas barrier property, is less likely to deteriorate the gas barrier property due to bending, and can prevent the occurrence of pinholes due to friction with the outer box. It is possible to realize and provide an inner bag.

Hereinafter, the present invention will be described in more detail with reference to Example 1 and Comparative Examples 1 to 3. However, the present invention is not limited to the examples shown here. The present invention is specified by the claims.

A laminated body of evaluation samples and a bag-in-box are prepared, and the following evaluations (1) to (3) are carried out.

(1) Planar gas barrier property Comparative evaluation of Example 1 and Comparative Example 1 was performed.
The evaluation method is as follows.
The measurement was performed by measuring the laminated body by the Mokon method.
The measurement conditions are as follows.
Moisture vapor transmission rate: 40 ° C 90% RH
Oxygen permeability: 20 ° C 65% RH
And said.

(2) Gas barrier deterioration resistance to bending The comparative evaluation of Example 1 and Comparative Example 2 was performed.
The evaluation method is as follows.
With the initial gas barrier performance of the smooth laminate as 100, after adding a linear bend,
The gas barrier performance of the laminate was measured and its deterioration rate was evaluated.

(3) Pinhole resistance when transport vibration is applied Comparative evaluation of Example 1 and Comparative Examples 1 to 3 was performed.
The evaluation method is as follows.
The evaluation sample assembled in the bag-in-box is filled with 1.8 liters of water as the contents, sealed, placed in a corrugated cardboard for transportation, sealed, and vibrated under random vibration conditions of JIS Z 0200 division level 1. Then, the number of evaluation samples with pinholes in the inner bag was confirmed.

<Example 1>
FIG. 4 is a schematic partial cross-sectional view of a laminated body for explaining Example 1 of the inner bag for a bag-in-box according to the present invention.

The laminated body (60) of Example 1 was prepared with the following layer structure according to the provisions of the present invention.
From the outer side of the inner bag (100)
Biaxially stretched polypropylene film (37) (thickness 20 μm) / gas barrier layer (40) made of inorganic compound / printing layer (36) / adhesive layer (34) / stretched polyamide film (38) (thickness 15 μm) / adhesion Agent layer (35) / polyethylene resin (39) (thickness 60 μm)
And said.

In the layer structure of Example 1, the portion of the gas barrier layer (40) made of the biaxially stretched polypropylene film (37) (thickness 20 μm) / inorganic compound is the structure of the gas barrier layer (50) shown in FIG. EVOH (ethylene-vinyl alcohol-based copolymer) was used for the polyvinyl alcohol-based resin layer (41) and the polyvinyl alcohol-based resin layer (43).

<Comparative Example 1>
FIG. 5 is a schematic partial cross-sectional view of a laminated body for explaining Comparative Example 1 of the inner bag for a bag-in-box according to the present invention.

The laminated body (61) of Comparative Example 1 was prepared with the following layer structure.
From the outer side of the inner bag (100)
Biaxially stretched polypropylene film (37) (thickness 20 μm) / printing layer (36) / adhesive layer (34) / stretched polyamide film (38) (thickness 15 μm) / gas barrier layer (44) /
Adhesive layer (35) / polyethylene resin (39) (thickness 60 μm)
And said.

At this time, the portion of the gas barrier layer (44) is provided on the stretched polyamide film (38) (thickness 15 μm) using polyvinylidene chloride (PVDC). This portion is different from Example 1 according to the present invention.

<Comparative Example 2>
FIG. 6 is a schematic partial cross-sectional view of a laminated body for explaining Comparative Example 2 of the inner bag for a bag-in-box according to the present invention.
The laminated body (62) of Comparative Example 2 was prepared with the following layer structure.
From the outer side of the inner bag (100)
Biaxially stretched polyethylene terephthalate film (29) (thickness 12 μm) / gas barrier layer (45) / printing layer (36) / adhesive layer (34) / stretched polyamide film (38) (thickness 15 μm) / adhesive layer ( 35) / Polyethylene resin (39) (thickness 60 μm)
And said.

It differs from Example 1 according to the present invention in that a biaxially stretched polyethylene terephthalate film (29) is used as the outermost film. Further, the gas barrier layer (45) is formed by sequentially providing an aluminum vapor deposition layer and a polyvinyl alcohol-based resin layer on a biaxially stretched polyethylene terephthalate film (29). This portion is different from that of the first embodiment and deviates from the scope specified by the present invention.

<Comparative Example 3>
FIG. 7 is a schematic partial cross-sectional view of a laminated body for explaining Comparative Example 3 of the inner bag for a bag-in-box according to the present invention.
The laminated body (63) of Comparative Example 3 was prepared with the following layer structure.
From the outer side of the inner bag (100)
Stretched polyamide film (38) (thickness 15 μm) / printed layer (36) / adhesive layer (34) / stretched polyamide film (38) (thickness 15 μm) / gas barrier layer (44) / adhesive layer (35) / Polyethylene resin (39) (thickness 60 μm)
And said.

It differs from Example 1 according to the present invention in that a stretched polyamide film (38) (thickness 15 μm) is used as the outermost film.
The portion of the gas barrier layer (44) is provided on a stretched polyamide film (38) (thickness 15 μm) using polyvinylidene chloride (PVDC). This part is also different from Example 1 according to the present invention.

Table 1 shows the evaluation results of the flat gas barrier property.

According to the results shown in Table 1, there is a large difference in gas barrier performance between Example 1 and Comparative Example 1 according to the present invention. It is considered that this is due to the difference in the composition of the gas barrier layer, and the gas barrier layer (40) made of the inorganic compound according to the present invention is more effective and higher than the gas barrier layer (44) using polyvinylidene chloride (PVDC). It shows that it is possible to achieve a level of gas barrier performance.

Table 2 shows the evaluation results of the gas barrier deterioration resistance to bending.

According to the results shown in Table 2, it can be seen that the degree of deterioration of the gas barrier property before and after bending of Example 1 according to the present invention is smaller than that of Comparative Example 2. This indicates that Example 1 has high gas barrier performance and flexibility because the gas barrier layer contains a thin film layer (42) made of an inorganic compound of silicon or aluminum as compared with Comparative Example 2.

That is, the gas barrier layer (40) made of an inorganic compound of silicon or aluminum is formed by sandwiching both sides with a polyvinyl alcohol-based resin layer to cover the brittleness of the inorganic compound of the gas barrier layer made of an inorganic compound. It is demonstrated that the laminated body (60) of Example 1 can be realized with little deterioration of gas barrier property due to bending.

Table 3 shows the evaluation results of pinhole resistance when transport vibration is applied.

According to the results shown in Table 3, in the pinhole resistance when transport vibration is applied, in Example 1 according to the present invention, the biaxially stretched polypropylene film (37) is arranged on the outermost layer, and the gas barrier layer is Although it deviates from the range specified in the present invention, no pinholes are observed in the vibration test in both Comparative Example 1 in which the biaxially stretched polypropylene film (37) is arranged on the outermost layer of the laminated body. From this, it is considered that the biaxially stretched polypropylene film (37) is effective.

As described above, the inner bag (100) for a bag-in-box according to the present invention has a high gas barrier property, the gas barrier property is less deteriorated due to bending, and the occurrence of pinholes due to friction with the outer box is prevented. It was possible to verify that the inner bag (100) for a bag-in-box can be used.

1 ... Bag-in-box 10 ... Outer box 21 ... Cap 22 ... Spout 23 ... Fixed part 29 ... Biaxially stretched polyethylene terephthalate film 30 ... Laminated body 31 ... Stretched Polyethylene resin film layer 32 ... Stretched Polyethylene resin film layer 33 ... Polyethylene resin layer 34 ... Adhesive layer 35 ... Adhesive layer 36 ... Printing layer 37 ... Biaxial stretching Polypropylene film 38 ... Stretched polyamide film 39 ... Polyethylene resin 40 ... Gas barrier layer 41 made of inorganic compound ... Polyvinyl alcohol-based resin layer 42 ... Thin film layer 43 made of inorganic compound ... Polyvinyl alcohol Resin layer 45 ... Gas barrier layer 50 ... Gas barrier film layer 60 ... Laminated body 61 of Example 1 ... Laminated body 62 of Comparative Example 1 ... Laminated body 64 of Comparative Example 2 ... Laminated body 100 of Comparative Example 3 ... Inner bag

Claims (3)

In a bag-in-box consisting of an outer box made of paper as a base material and an inner bag inside the outer box that can directly store the contents inside.
The inner bag has a spout from which the contents can be taken out, and this spout is fixed to the outer box.
The inner bag is composed of a laminate made of a plastic film as a base material.
The laminate is characterized in that it is composed of a polyolefin-based resin layer, a stretched polyamide-based resin film layer, and a stretched polypropylene-based resin film layer having a gas barrier layer made of an inorganic compound on the outermost layer in this order from the inside of the inner bag. , Inner bag for bag-in-box. In the laminate, the thickness of the polyolefin-based resin film layer is in the range of 40 μm to 120 μm.
The stretched polyamide-based resin film layer is composed of a stretched polyamide film having a thickness of 15 μm to 25 μm.
The inner bag for a bag-in-box according to claim 1, wherein the stretched polypropylene-based resin film layer is composed of a stretched polypropylene film having a thickness of 20 μm to 40 μm. The stretched polypropylene-based resin film layer having the gas barrier layer made of the inorganic compound has a polyvinyl alcohol-based resin layer, a thin film layer made of a silicon or aluminum inorganic compound, and a polyvinyl alcohol-based resin layer as a gas barrier layer on the surface of the stretched polypropylene film. The inner bag for a bag-in-box according to claim 1 or 2, wherein the inner bag is sequentially laminated.

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