JP2020164195A - Laminate film for packaging and packaging bag - Google Patents

Abstract

To provide a laminate film for packaging in which a pinhole hardly occurs and which has an excellent tear opening property, not only in the case where a film is bent but also in the case where a corner part generated by the bending rubs with an inner surface of a cardboard box and the like.SOLUTION: A non-stretched polyamide film is made to be a center base material 13, and a three-layer structured co-extrusion film 11 is laminated on one surface, and a sealant layer 15 is laminated on the other surface. Then, a center layer 11b of a three-layer structured co-extrusion film 11 is constituted by polyamide resin, and layers 11a, 11c on both sides are constituted by medium-density polyethylene resin, and the co-extrusion film 11 and the center base material 13 are laminated via a molten extrusion resin layer 12.SELECTED DRAWING: Figure 1

Description

The present invention relates to a packaging bag and a laminated film for packaging used therein.

A packaging bag containing a large-capacity liquid content of about 5 to 20 liters is often sterilized with hydrogen peroxide and then filled and sealed with the sterilized content in advance to form a package. It should be noted that both the sterilization step and the filling and sealing step of the packaging bag are usually performed in a sterile atmosphere.

Then, the package body filled and sealed with the liquid contents in this way is stored and transported in a cardboard box or the like. However, when the packaging bag in which the liquid contents are sealed is stored in a cardboard box or the like and transported, the outer surface of the packaging bag and the inner surface of the cardboard box or the like rub against each other due to the vibration during the transportation.

Further, since the film constituting the packaging bag is bent by the vibration during transportation, pinholes are likely to occur due to this bending.

Patent Document 1 describes a technique of arranging a crosslinked polyethylene resin film on the outermost layer of a film constituting a packaging bag in order to prevent pinholes due to bending during transportation and rubbing against the inner surface of a cardboard box. ..

Japanese Unexamined Patent Publication No. 2003-192017

However, when a packaging bag containing liquid contents is stored in a cardboard box or the like and transported, the cause of pinholes in the packaging bag is simply that the film constituting the packaging bag is bent or rubs against the inner surface of the cardboard box. It's not just about doing things. Both of these, that is, the bending of the film and the rubbing against the inner surface of the cardboard box may interact with each other to generate pinholes.

That is, when the film is bent, the bent portion becomes sharp and becomes a corner portion, and when this corner portion rubs against the inner surface of a cardboard box or the like, a pinhole is generated at this corner portion.

Therefore, according to the present invention, not only when the film is bent, but also when the corners generated by the bending rub against the inner surface of a cardboard box or the like, pinholes are unlikely to occur, and at the same time, for packaging having excellent tear opening property. It is an object of the present invention to provide a laminated film.

That is, the invention according to claim 1 is composed of a non-stretched polyamide film as a central base material, a coextruded film having a three-layer structure laminated on one surface thereof, and a sealant layer laminated on the other surface. Laminated film for packaging
The central layer of the coextruded film having a three-layer structure is made of a polyamide resin, and the layers on both sides thereof are made of a medium-density polyethylene resin.
Moreover, the laminated film for packaging is characterized in that the co-extruded film and the central base material are laminated via a melt-extruded resin layer.

Next, the invention according to claim 2 is the laminated film for packaging according to claim 1, wherein the melt-extruded resin layer is made of a medium-density polyethylene resin.

Next, the invention according to claim 3 is the laminated film for packaging according to claim 1 or 2, wherein the melt-extruded resin layer has a thickness of 10 to 30 μm.

Next, in the invention according to claim 4, the sealant layer has a three-layer structure, the central layer thereof is made of a polyethylene resin having a density of 0.99 to 0.91 g / cm ³ , and both sides thereof. The laminated film for packaging according to any one of claims 1 to ³ , wherein the layer is made of a polyethylene resin having a density of 0.91 to 0.92 g / cm ³ .

Next, the invention according to claim 5 is a packaging bag packaging bag using the packaging laminated film according to any one of claims 1 to 4.

As can be seen from the examples described later, according to the laminated film for packaging of the present invention, pinholes are unlikely to occur even when the corners generated by bending are rubbed. In addition, it has excellent bending resistance and can suppress the occurrence of pinholes due to bending. Further, as can be seen from Examples described later, the laminated film for packaging of the present invention has a low tear strength and is excellent in tear opening property.

FIG. 1 is a cross-sectional explanatory view of a specific example of the laminated film for packaging of the present invention.

As shown in FIG. 1, the packaging laminated film 10 of the present invention has three layers of a coextruded film 11, a central base material 13, and a sealant layer 15 as essential components.

The co-extruded film 11 is a film having a three-layer structure formed by melt-co-extruding a two-kind three-layer resin. To prevent the occurrence of pinholes due to bending and the occurrence of pinholes due to the corners generated by bending rubbing against an outer box such as a cardboard box when transferring a package filled with liquid contents and sealed. The central layer 11b needs to be made of a polyamide resin.

Further, for the same reason, the layers 11a and 11c on both sides thereof need to be made of a medium density polyethylene resin having a density of 0.93 to 0.94 g / cm ³ . Since the layers 11a and 11c on both sides are made of medium-density polyethylene resin in this way, it is possible to prevent the occurrence of pinholes due to bending and pinholes due to the corners rubbing against an outer box such as a cardboard box. Moreover, the flexibility and strength required for a bag can be obtained.

Since the outer layer 11a of the coextruded film 11 is made of polyethylene resin in this way, even when the packaging laminated film 10 is sterilized with hydrogen peroxide, or the packaging laminated film 10 is used. This hydrogen peroxide can be tolerated even when the packaged packaging bag is sterilized with hydrogen peroxide.

Next, the central base material 13 needs to be made of an unstretched polyamide film.

When a stretched polyamide film is used as the central base material 13, the stretched polyamide film is inferior in flexibility. Therefore, as can be seen by comparing Comparative Example 1 and Comparative Example 2 described later, the corners must be increased in thickness. Pinholes are likely to occur when rubbed. On the other hand, if the thickness is large, the tear strength is high, and it becomes difficult to tear and open the packaging bag.

On the other hand, since the unstretched polyamide film has excellent flexibility, when the unstretched polyamide film is used as the central base material 13, pinholes are generated when the corners are rubbed even if the thickness is thin. hard. In addition, the tear strength is low, and the packaging bag can be easily torn and opened. The thickness of the unstretched polyamide film is preferably 10 μm or more. A thickness of 30 μm is sufficient.

The co-extruded film 11 and the central base material 13 need to be laminated via the melt-extruded resin layer 12. If the laminated film is laminated using an adhesive, as can be seen from Comparative Examples 3 and 4 described later, the obtained laminated film for packaging has low bending resistance and tends to cause pinholes due to bending. In addition, pinholes are likely to occur even when the corners are rubbed.

A low density polyethylene resin can be used as the melt extruded resin layer 12. That is, the low-density polyethylene resin is melted and extruded into a film from an extruder, and the co-extruded film 11 and the central base material 13 are overlapped and pressure-bonded on both sides of the melted low-density polyethylene resin film. The extruded film 11, the melt extruded resin layer 12, and the central base material 13 can be integrally laminated.

Next, the sealant layer 15 constitutes the inner surface of the packaging bag and needs to be heat-sealed with each other. Any polyolefin resin can be used as such a sealant layer 15, but a sealant film having a three-layer structure can be preferably used. The central layer 15b is made of a polyethylene resin having a density of 0.99 to 0.91 g / cm ³ . The layers 15a and 15c on both sides thereof are made of a polyethylene resin having a density of 0.91 to 0.92 g / cm ³ . Such a three-layer structure sealant film is commercially available from Idemitsu Unitech Co., Ltd. under the name of "Unicrest MB-200" or "Unicrest MB-201".

The sealant layer 15 and the central base material 13 can be laminated using the adhesive layer 14, but in order to prevent the solvent contained in the adhesive from migrating into the contents, a solvent-free adhesive is used. It is preferable to use it. For example, ADN369 manufactured by Toyo Ink Mfg. Co., Ltd.

It is desirable that the waist strength of the packaging laminated film 10 thus produced is 100 mN / 15 mm or less. This is because if the waist strength is too high, corners are likely to be formed due to bending, and pinholes are likely to be formed accordingly.

Next, the laminated film 10 for packaging can be made into a bag by using an aseptic filling and packaging system, and the liquid contents can be filled and sealed to form a package. That is, first, the laminated film 10 for packaging is immersed in a hydrogen peroxide solution in a sterile room, or the hydrogen peroxide solution is sprayed to sterilize the film, and then heat-dried to remove residual hydrogen peroxide. Next, the package can be manufactured by making a bag in the same sterile room, filling it with a pre-sterilized liquid content, and sealing it.

As the content, for example, milk is suitable. The form of the packaging bag is arbitrary, but it can be, for example, a pillow packaging bag having a back seal portion. The internal volume of the packaging bag or packaging may be about 5 to 20 liters. Then, as will be described repeatedly, this package in which the liquid contents are sealed can be stored or transported in a state of being housed in an outer box such as a cardboard box. Even in this case, pinholes are unlikely to occur in the packaging bag.

(Example 1)
ZPB102 manufactured by Tamapoli Co., Ltd. was used as the coextruded film 11. This film is a co-extruded film having a three-layer structure in which a polyamide resin is used as the central layer 11b and the layers on both sides thereof are made of medium-density polyethylene resin, and the thickness thereof is 40 μm.

Further, Diamilon C manufactured by Mitsubishi Chemical Corporation was used as the central base material 13. This film is a non-stretched polyamide film having a thickness of 25 μm.

Then, the low-density polyethylene resin is melted and extruded into a film from an extruder, and the coextruded film 11 and the central base material 13 are placed on both sides of the melted low-density polyethylene resin film and pressure-bonded to coextrude the coextruded resin. The film 11, the melt-extruded resin layer 12, and the central base material 13 were integrally laminated. The thickness of the melt-extruded resin layer 12 is 15 μm.

Next, Unicrest MB-201c was used as the sealant layer 15. This film is a polyethylene-based sealant film having a three-layer structure, and its thickness is 50 μm.

Then, by laminating the sealant layer 15 on the surface of the central base material 13 using a solvent-free adhesive, the laminated film 10 for packaging of Example 1 was manufactured. As the solvent-free adhesive, ADN369 manufactured by Toyo Ink Mfg. Co., Ltd. was used.

(Example 2)
This example is an example in which a stretched polyamide film having a thickness of 20 μm is used as the central base material 13, and a polyethylene-based sealant film having a thickness of 60 μm is used as the sealant layer.

That is, Diamilon C manufactured by Mitsubishi Chemical Corporation with a thickness of 20 μm was used as the central base material 13, and Unicrest MB-201c having a polyethylene-based three-layer structure and a thickness of 60 μm was used as the sealant layer 15. .. The other points are the same as in the first embodiment.

(Comparative Example 1)
This example is an example in which a stretched polyamide film having a thickness of 25 μm is used as the central base material 13.

That is, as the central base material 13, Bonnir W manufactured by Kohjin Film and Chemicals Co., Ltd. having a thickness of 25 μm was used. The other points are the same as in the first embodiment.

(Comparative Example 2)
This example is an example in which a stretched polyamide film having a thickness of 15 μm is used as the central base material 13, and a polyethylene-based sealant film having a thickness of 60 μm is used as the sealant layer 15.

That is, Bonil W manufactured by Kohjin Film and Chemicals Co., Ltd. with a thickness of 15 μm is used as the central base material 13, and Unicrest MB having a polyethylene-based three-layer structure and a thickness of 60 μm is used as the sealant layer 15. -201c was used. The other points are the same as in the first embodiment.

(Comparative Example 3)
This example is an example in which the coextruded film 11 and the central base material 13 are laminated using a solvent-free adhesive.

In this example, ZPB102 manufactured by Tamapoli Co., Ltd. having a thickness of 40 μm was used as the coextruded film 11 as in Examples 1 and 2, but Mitsubishi Chemical having a thickness of 20 μm was used as the central substrate 13 as in Example 2. Diamilon C manufactured by Mitsubishi Corporation was used. As the sealant layer 15, Unicrest MB-201c having a thickness of 60 μm was used as in Example 2.

The coextruded film 11, the central base material 13, and the central base material 13 and the sealant layer 15 were all laminated using ADN369 manufactured by Toyo Ink Mfg. Co., Ltd.

(Comparative Example 4)
Similar to Comparative Example 3, this example is also an example in which the coextruded film 11 and the central base material 13 are laminated using a solvent-free adhesive. The difference from Comparative Example 1 lies in the thickness of the central base material 13.

That is, Diamilon C manufactured by Mitsubishi Chemical Corporation with a thickness of 15 μm was used as the central base material 13. The points other than that are the same as in Comparative Example 3.

(Evaluation)
The packaging laminated films of Examples 1 and 2 and Comparative Examples 1 to 4 were evaluated from 4 points.

That is, first, when a corner was generated by bending, it was evaluated whether or not a pinhole was generated by rubbing the corner against the cardboard (square pinhole test).

In this test, a tactile device (TL201Tt manufactured by Trinity Lab Co., Ltd.) was used as the test device.

Then, a sample of each packaging laminated film was exposed to an environment of 5 ° C. for 1 minute, folded in four to form corners, and then the corners were rubbed against a cardboard a specified number of times to see if pinholes were formed in the corners. I observed whether or not. The load when rubbing is 200 g, the speed is 100 mm / sec, and the reciprocating distance is 140 mm (70 mm one way). The specified number of round trips was 100 round trips and 300 round trips.

Then, the number of samples was set to 3 or 7, and the evaluation was made based on the number of samples in which pinholes were generated.

Next, the second evaluation item is waist strength. That is, a loop-shaped sample having a width of 15 mm and a length of 100 mm was prepared from each laminated film for packaging, and its waist strength was measured according to JIS K 7125. The measuring device is a Loop Stiffness Tester DA manufactured by Toyo Seiki Seisakusho Co., Ltd.

Next, the third evaluation item is bending resistance. That is, a sample of 200 mm × 290 mm was prepared from each laminated film for packaging, and bent in an environment of 5 ° C. with a twist of 440 degrees, a straight line of 3.5 inches and a straight line of 2.5 inches as one bending. The number of times was 1000 times, and the number of pinholes generated was counted. The test device is a Gelboflex tester manufactured by Tester Sangyo Co., Ltd.

The fourth endpoint is tear strength. This measurement was performed in accordance with JIS K 7128. The measuring device is Tensilon manufactured by A & D Co., Ltd. Then, each laminated film for packaging was torn by the trouser tearing method, and the tear strength in the flow direction (TD direction) was measured.

The results of these evaluation items are shown in Table 1.

(Discussion)
As a result, when the number of reciprocations is about 100, no square pinhole is generated in any of the laminated films for packaging. However, it can be seen that when the number of reciprocations is increased, a difference occurs between the laminated films for packaging. When the coextruded film 11 and the central base material 13 are laminated via the melt extruded resin layer (Examples 1 and 2 and Comparative Examples 1 and 2), most of the square pinholes are formed even if the number of reciprocations is 300. On the other hand, when the coextruded film 11 and the central base material 13 are laminated with a solvent-free adhesive (Comparative Examples 3 to 4), square pinholes are likely to occur after 300 round trips. Understandable. That is, the occurrence of square pinholes can be suppressed when the coextruded film 11 and the central base material 13 are laminated via the melt extruded resin layer.

Regarding the bending resistance, the case where the co-extruded film 11 and the central base material 13 are laminated via the melt-extruded resin layer (Examples 1 and 2) is the case where both are laminated with a solvent-free adhesive (comparison). It can be seen that the occurrence of pinholes is less than in Examples 3 to 4).

For the above reasons, when the co-extruded film 11 and the central base material 13 are laminated via the melt-extruded resin layer, both the generation of square pinholes and the generation of pinholes due to bending are suppressed. I understand what I can do.

On the other hand, when a stretched polyamide film is used as the central substrate 13 (Comparative Examples 1 and 2), if the thickness is thin (Comparative Example 2), square pinholes may occur. On the other hand, as the thickness increases (Comparative Example 1), the waist strength increases and the tear strength also increases, which may hinder the filling of the liquid content in the packaging bag and the tear opening. Therefore, it is difficult to use a stretched polyamide film as the central base material 13 to prevent square pinholes and to make it easy to tear and open.

On the other hand, when an unstretched polyamide film is used as the central base material 13 (Examples 1 and 2), the waist strength is low even when the thickness is thin, and therefore the flexibility required for the packaging bag. In addition, it can be easily attached to a filling machine in the content filling process. Moreover, since the tear strength is small, the tear opening is easy.

Therefore, when an unstretched polyamide film is used as the central base material 13 (Examples 1 and 2), it is possible to prevent square pinholes and facilitate tearing and opening.

10: Laminated film for packaging 11: Co-extruded film 11b: Center layer of co-extruded film 11a, 11c: Layers on both sides of co-extruded film 12: Molten extruded resin layer 13: Center substrate 14: Adhesive layer 15: Sealant layer 15b: Central layer of sealant layer 15a, 15c: Layers on both sides of sealant layer

Claims (5)

A packaging laminated film having a non-stretched polyamide film as a central base material, a coextruded film having a three-layer structure laminated on one surface thereof, and a sealant layer laminated on the other surface.
The central layer of the coextruded film having a three-layer structure is made of a polyamide resin, and the layers on both sides thereof are made of a medium-density polyethylene resin.
Further, a laminated film for packaging, wherein the co-extruded film and a central base material are laminated via a melt-extruded resin layer. The laminated film for packaging according to claim 1, wherein the melt-extruded resin layer is made of a medium-density polyethylene resin. The laminated film for packaging according to claim 1 or 2, wherein the melt-extruded resin layer has a thickness of 10 to 30 μm. The sealant layer has a three-layer structure, the central layer thereof is composed of a polyethylene resin having a density of 0.90 to 0.91 g / cm ³ , and the layers on both sides thereof have a density of 0.91 to 0.92 g / cm. ^The laminated film for packaging according to any one of claims 1 to 3, which is composed of the polyethylene resin of 3. A packaging bag using the packaging laminated film according to any one of claims 1 to 4.

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