JP2009018861A - Inflation film for double bag packaging and double packaging - Google Patents

Abstract

The present invention provides a double bag package excellent in transparency that allows a user to easily open a package by hand and does not break the bag even when the contents are filled or dropped during transportation. .
In an inflation film for a double bag package comprising an outer layer having an easy peel property, an intermediate layer comprising a polyamide resin, and an inner layer comprising a low density polyethylene resin, the outer layer having an easy peel property is provided. The first outer layer and the second outer layer adjacent to the first outer layer, and the first outer layer is made of any of linear low density polyethylene, low density polyethylene, or ethylene-vinyl acetate, and has a thickness of The layer is 1 μm or more and 7 μm or less, and the second outer layer is composed of a blend resin of 50% by mass to 95% by mass of polypropylene and 5% by mass to 50% by mass of ethylene-α-olefin copolymer. .
[Selection] Figure 1

Description

  The present invention relates to an inflation film for a double bag package, and a double bag package formed from the film. Specifically, for example, dry noodles, pasta, vegetables, coffee beans, castella, confectionery, pickles, rice, solid cheese, nuts and other solid foods, spices, seasonings, flour, granulated sugar, powdered coffee, kinako flour, powder TECHNICAL FIELD The present invention relates to an inflation film for a double bag package for forming a double package having an easy peel property (easy opening) that can be filled with a powdered food such as soap, and a double bag package formed by the film. .

  Conventionally, containers such as metal cans and glass bottles have been used as packaging containers for filling the above-described solid food and powdered food. However, recently, due to environmental problems, it has been required to reduce the volume of packaging containers and to make them easily disposable. In order to meet these requirements, packaging bodies made of plastic films have been used as these packaging containers.

  Plastic films are superior to metal cans and glass bottles in that they are lightweight and can reduce distribution costs and disposal costs. As a packaging container filled with solid food and powdered food, it is an absolute condition that the contents do not leak during storage and transportation. However, plastic film is thinner and less durable than containers such as metal cans and glass bottles, so pinholes can be generated or broken by vibrations, impacts, and friction during transportation. Had the essential problem of leaking.

  In order to solve such a problem, a double bag package in which two films are stacked is generally used as a package made of a plastic film (for example, Patent Documents 1 to 5).

According to such a double-layer double bag package, there is a certain degree of freedom between the two films even when an object to be stored is accommodated therein. Therefore, even if an impact is applied to the double bag package during transportation, the double bag package is supported in contact with the inner film that supports the object and the pallet or other package. It is possible to prevent the occurrence of pinholes and bag breakage by causing a certain amount of sliding between the outer film and the outer film and absorbing the impact.
JP 2003-305783 A JP 2003-335302 A JP 2003-26234 A JP 2002-234547 A JP 2007-15725 A

  However, when a laminated film having a stretched film is used as disclosed in Patent Document 1, the film is hard, so that it is difficult to squeeze the contents when the double package is opened, and the contents remain and work suitability deteriorates. There was a problem. Further, if the contents remain, there is a problem that a rotting odor due to the remaining contents is generated or bacteria are propagated until the contents are discarded.

  Moreover, as a resin material which comprises the inner layer of a double bag packaging body, for example, as disclosed in Patent Document 3, a relatively low density low density polyethylene (hereinafter sometimes referred to as “LDPE”). When the bag is used, it has an excellent aspect that heat sealing is easy at the time of bag making, while directly storing foods heated to 80 ° C. or more inside the double bag package. In this case, the inner layers are blocked, and there is a problem that the bag is easily broken by vibration, impact, and friction during transportation. In addition, there is a problem that it is difficult to control the pitch during continuous production because the film is stretched by the heat and weight of the contents to be filled.

  In order to solve the blocking problem, in Patent Document 5, LDPE is used as a resin material constituting the inner layer of the double bag package, and the Vicat softening point and density of the LDPE are set within a predetermined range. Even when foods heated to 80 ° C. or higher are directly stored in the double bag package, the inner layers are not easily blocked, have excellent pinhole resistance, and are hot filled with foods. A film that is difficult to stretch is described.

  It is preferable that the package has an easy peel property so that the contents can be easily taken out. However, the film described in Patent Document 5 forms a double bag package by perfect sealing, and it is necessary to open the package using a cutter or scissors in order to take out the contents from the package. was there. For this reason, there existed a problem that workability | operativity in the field | area which uses foodstuffs was bad. In addition, since opening is performed using a cutter or the like, there is a problem that the opened section becomes dust and the dust increases, and the section is mixed into the contents.

  Further, the double bag package filled with solid food and powdered food may be required to be transparent so that the contents can be visually recognized. For example, when a double bag package is filled with an oxygen scavenger or an inert gas and there is a dead space, it is necessary that the contents can be confirmed from the outside of the package through the dead space. Being able to visually confirm the contents gives a great sense of security to the user (consumer).

  Therefore, in order to solve these problems, the present invention allows the user to easily open the package by hand, and does not break the bag even when the contents are filled or dropped during transportation, and has excellent transparency. A double bag package is provided.

  The present invention will be described below.

The first aspect of the present invention is a double structure comprising an outer layer having an easy peel property, an intermediate layer made of a polyamide resin, and an inner layer made of a low density polyethylene resin (hereinafter sometimes referred to as “LDPE”). An inflation film for a bag package,
The outer layer having easy peel properties includes a first outer layer and a second outer layer adjacent to the first outer layer, and the first outer layer is a linear low-density polyethylene (hereinafter sometimes referred to as “LLDPE”). , Low density polyethylene, or ethylene-vinyl acetate, and a layer having a thickness of 1 μm or more and 7 μm or less, and the second outer layer is 50% by mass or more, where the mass of the entire second outer layer is 100% by mass An inflation film for a double package, comprising a blend resin of 95% by mass or less of polypropylene and 5% by mass or more and 50% by mass or less of an ethylene-α-olefin copolymer.

  The inflation film of the first aspect of the present invention has an outer layer comprising a predetermined first outer layer and a second outer layer. Thereby, a good easy peel property can be imparted to the double package manufactured using the inflation film of the present invention. The outer layer having the easy peel property (hereinafter sometimes referred to as “easy peel layer”) is a delamination type easy peel layer. For this reason, it is excellent in transparency and can provide transparency to the formed package.

  Moreover, the inflation film of 1st this invention is provided with the pinhole-proof property by providing the intermediate | middle layer which consists of a polyamide resin. Moreover, by providing the inner layer which consists of a low density polyethylene resin, the heat seal property at the time of package body preparation becomes favorable.

  In the first aspect of the present invention, the seal strength between the first outer layer and the second outer layer is preferably 0.98 N / 15 mm width or more and 19.6 N / 15 mm width or less. The package must have a sealing property to prevent leakage of the contents. Moreover, in this invention, the easy peel property is provided for workability | operativity improvement in use of a package body further. In the present invention, in the easy peel layer of the delamination type, the seal strength between the first outer layer and the second outer layer is set in the above range, thereby achieving a balance between the sealing property and the easy peel property in the double bag package. Yes.

  In the first aspect of the present invention, it is preferable that the first outer layer is disposed on the outermost layer and the second outer layer is disposed on the inner layer side. Since the first outer layer can be sealed at a lower temperature than the second outer layer, by arranging the first outer layer as the outermost layer, the first outer layers can be easily sealed when producing a double bag package. This is preferable because it is possible.

In the first invention, the low density polyethylene resin constituting the inner layer preferably has a Vicat softening point of 110 ° C. or more and 125 ° C. or less, and the density is more than 0.930 g / cm ³ and 0.940 g / cm ³ or less. It is preferable that Here, the “Vicat softening point” refers to the Vicat softening point measured by a method defined in JIS K7206 (1999) [Plastic-thermoplastic plastic—Vicat softening temperature (VST) test method]. By using such an inner layer made of a low-density polyethylene resin, an object to be accommodated at 80 ° C. to 100 ° C. in a state where a double bag package is formed with the inner layer inside while ensuring good heat sealability. It is possible to prevent blocking of the inner layers when hot filling is performed. And by preventing blocking, it can be set as the double bag packaging body which is hard to generate | occur | produce a pinhole and a bag breakage in the distribution | circulation stage of goods, such as the time of transportation and stock storage. Further, since food can be hot-filled, there is an advantage that it is not necessary to sterilize again after filling.

  In the first aspect of the present invention, the low-density polyethylene resin in the inner layer is preferably a linear low-density polyethylene resin. LLDPE is characterized by strong physical properties such as tensile strength, elongation, pinhole strength, and rigidity.

  In the first aspect of the present invention, the thickness of the intermediate layer is preferably 5 μm or more and 30 μm or less. By setting the thickness of the intermediate layer in such a range, it is possible to impart good pinhole resistance to the double bag package to be formed and also to impart good squeeze properties (easiness to squeeze out the contained material). .

  In the first aspect of the present invention, the inner layer preferably contains a slip agent and / or an antiblocking agent. Thereby, blocking of inner layers can be prevented more effectively.

  In the first aspect of the present invention, at least one adhesive resin layer may be provided between the intermediate layer and the outer layer and / or the inner layer. Thereby, the adhesive strength between each layer can be raised more.

  In the first aspect of the present invention, at least one ethylene-vinyl acetate copolymer saponified resin layer (hereinafter sometimes abbreviated as “EVOH layer”) is provided between the intermediate layer and the outer layer and / or inner layer. You may have. Thereby, a gas (oxygen) barrier property can be imparted to the inflation film.

  2nd this invention is the double bag package which has the easy peel property bag-made with the inflation film of 1st this invention. Since the double bag package of the present invention has good easy peel properties, it is not necessary to use a cutter or scissors to cut the package and can be easily opened by hand. Therefore, the problem that the piece produced when the package is cut is not mixed into the contents does not occur. Moreover, since it has a delamination-type easy peel layer, the transparency is good and the contents can be visually recognized through the package.

  The inflation film of the first aspect of the present invention has an outer layer comprising a predetermined first outer layer and a second outer layer. Thereby, a good easy peel property can be imparted to the double package manufactured using the inflation film of the present invention. The outer layer having the easy peel property is an easy peel layer of a delamination type. For this reason, it is excellent in transparency and can provide transparency to the formed package.

  Moreover, the inflation film of 1st this invention is provided with the pinhole-proof property by providing the intermediate | middle layer which consists of a polyamide resin. Moreover, by providing the inner layer which consists of a low density polyethylene resin, the heat seal property at the time of package body preparation becomes favorable.

  Hereinafter, the present invention will be described based on embodiments shown in the drawings.

(Inflation film manufacturing method)
The schematic which shows the manufacturing process of the inflation film for double bag packaging bodies of this invention in FIG. 1 was shown. In the illustrated example, first, four or more types of resins are heated and melted to a predetermined temperature by an extruder, and the pressure is increased. Then, air is blown into the cylindrical mold 11, and the tubular film 10 composed of the outer layer (first outer layer and second outer layer), the intermediate layer, and the inner layer is discharged from the gap of the mold 11. The tube-shaped film 10 is folded into a flat film 10 ′ by folding means composed of rolls 12, 13, and then wound into a roll by a winder 14. In this way, the inflation film of the present invention is manufactured. The film wound up on the roll becomes the raw fabric 15 when the double bag package is produced.

  2A is a cross-sectional view of the tubular film 10 cut along the line IIA-IIA in FIG. 1, and FIG. 2B is a flat film cut along the line IIB-IIB in FIG. It is sectional drawing of 10 '. In any case, the films 10 and 10 ′ are provided with an inner layer 21, an intermediate layer 22, a second outer layer 23, and a first outer layer 24 in order from the cylindrical center side to the outer side, and a space 25 exists inside them. In the flat film 10 ′, the space 25 is crushed into an air layer 25. The illustrated form is a preferred form of the present invention in which the first outer layer 24 is disposed on the outermost layer and the second outer layer is disposed on the inner layer 21 side, but the inflation film of the present invention is not limited to such a form. In addition, a configuration in which the second outer layer 23 is disposed on the outermost layer and the first outer layer 24 is disposed on the inner layer 21 side is also included.

(Manufacturing method of double bag package)
3 and 4 show an example of a method for producing a double bag package. FIG. 3 is a diagram schematically showing a process of unwinding the raw fabric 15 and cutting it into a predetermined length. Each of the cut single leaves 30a, 30b, 30c... Is made into a double bag package through a folding and heat sealing process described below. In FIGS. 3 and 4, the four layers of the inner layer 21, the middle layer 22, the second outer layer 23, and the first outer layer 24 of the flat film 10 ′ are omitted.

  FIG. 4 is a diagram schematically showing a process of producing a double bag package from single leaves 30a and the like. First, the single leaf 30a is a single leaf 40a with a crease in which folds 41 to 44 are formed at positions indicated by alternate long and short dashed lines in FIG. First, the left and right ends of the creased single leaf 40a are folded by the folds 41 and 42 toward the center. The lower end portion is folded upward along the fold line 43. By these folding, the overlapping portion 45 on the left and right of the single leaf 40a and the overlapping portion 46 are folded and the lower end portion is heat-sealed. The intermediate product 40b shown in FIG. 4B is considered as a container having an opening 47 in the upper part. From this opening 47, the object to be accommodated is accommodated in the intermediate product 40b, the upper opening 47 is folded downward along the fold 44, and the overlapping portion 48 generated by the folding is heat-sealed, so that the double The bag package 40c is completed and is ready for stock and distribution.

  FIG. 5 is a cross-sectional view from the front side of the drawing in the depth direction along the line P-P in FIG. 4. The upper side of FIG. 5 corresponds to the front side of the page of FIG. 4, and the lower side of FIG. 5 corresponds to the back side of the page of FIG. As shown in FIG. 5, two films 30 and 30 are arranged above and below the object to be accommodated 50, and the inner layers 21 and 21 are arranged so as to face each other. That is, a total of four films (16 layers) exist along the penetration direction, thereby forming a double bag package 40c. Note that the thickness of the air layer 25 shown between the two inner layers 21 and 21 is exaggerated in the figure. The actual air layer 25 is a space that does not allow the two inner layers 21 to adhere to each other.

<Inflation film for double bag packaging>
The inflation film for double bag packaging of the present invention comprises an outer layer having an easy peel property, an intermediate layer made of a polyamide resin, and an inner layer made of a low density polyethylene resin. The outer layer comprises the first outer layer and And a second outer layer adjacent to the first outer layer. Here, the first outer layer, the second outer layer, the intermediate layer, and the inner layer correspond to the first outer layer 24, the second outer layer 23, the intermediate layer 22, and the inner layer 21 in the tubular film of FIG. Hereinafter, each layer will be described.

(Inner layer)
In the present invention, the inner layer is made of LDPE, and can be bonded by heat sealing when a double bag package is manufactured. Further, the LDPE constituting the inner layer preferably has a predetermined Vicat softening point and density. The lower limit of the Vicat softening point of LDPE is preferably 110 ° C or higher, more preferably 115 ° C or higher, still more preferably 120 ° C or higher, and the upper limit is preferably 125 ° C or lower, more preferably 124 ° C or lower. The density, the lower limit is preferably greater than 0.930 g / cm ^3, more preferably 0.935 g / cm ³ or more, still more preferably 0.937 g / cm ³ or more, and the upper limit is preferably 0.940 g / cm ³ or less.

  By using such LDPE, it is possible to prevent the inner layers from blocking during hot filling while ensuring good heat sealability. For example, it is possible to prevent the inner layers from blocking each other when an object to be stored at 80 ° C. or higher and 100 ° C. or lower is hot-filled in a state where a double bag is formed.

  Here, the blocking in the present invention means that the inner layers are fused. If the inner layers are fused, the degree of freedom of the two films, which is an advantage of the double bag, is hindered, and the impact cannot be absorbed and pinholes and bag breakage occur. .

In the case of LDPE having a Vicat softening point of 110 ° C. or higher, as the Vicat softening point increases, the density gradually increases. For example, in the case of LDPE having a Vicat softening point of 120 ° C. or higher, the density is close to 0.940 g / cm ^3. It is difficult to block each other, and the elongation of the film due to heat can be minimized.

  The LDPE constituting the inner layer is preferably LLDPE, and the LLDPE is preferably a copolymer of ethylene and hexene-1 having 6 carbon atoms or octene-1 having 8 carbon atoms. LLDPE has higher physical properties such as tensile strength, elongation, anti-pinhole strength and rigidity than LDPE. Further, as the number of carbon atoms of the copolymer increases as described above, the physical property strength increases in proportion.

  The lower limit of the thickness of the inner layer is preferably 5 μm or more, more preferably 10 μm or more, further preferably 15 μm or more, and the upper limit is preferably 40 μm or less, more preferably 30 μm or less, and even more preferably 25 μm or less. Pinhole resistance and heat resistance can be maintained by setting the thickness of the inner layer to 5 μm or more. On the other hand, by setting the thickness of the inner layer to 40 μm or less, an appropriate squeeze property is imparted to the double bag package formed by the film, and the operation of squeezing the contents becomes good.

(Middle layer)
In the present invention, the intermediate layer is made of a polyamide resin. The type of polyamide resin is not particularly limited, but from the viewpoint of pinhole resistance, examples of the polyamide-based synthetic fiber-based resin include 6 nylon, 66 nylon, 69 nylon, 6-66 nylon, 12 nylon, 11 nylon, and 610. It is preferable to use a polymer such as nylon, 612 nylon, 6I-6T nylon, MXD6 nylon or the like, a copolymer containing two or more of these as polymerized units, and a mixture of these polymers. Among these, it is particularly preferable to use 6 nylon or 6-66 nylon because it is excellent in extrusion moldability and film forming stability in the inflation method, is inexpensive and can be stably obtained, and the like.

  The lower limit of the thickness of the intermediate layer is preferably 5 μm or more, more preferably 7 μm or more, further preferably 10 μm or more, and the upper limit is preferably 30 μm or less, more preferably 25 μm or less, and even more preferably 20 μm or less. By setting the lower limit of the thickness of the intermediate layer formed of the polyamide resin to 5 μm, good pinhole resistance can be obtained and the film is difficult to stretch. Moreover, moderate squeeze property can be provided to the double bag package formed with this film by making an upper limit into 30 micrometers.

(Outer layer (easy peel layer))
In this invention, an outer layer is a layer (easy peel layer) which has a delamination type easy peel property comprised including the 1st outer layer and the 2nd outer layer adjacent to this 1st outer layer.
The easy peel property of the delamination type of the present invention is manifested by delamination between the first outer layer and the second outer layer. Therefore, in the inflation film of the present invention, as long as the first outer layer and the second outer layer are adjacent to each other, the first outer layer may be located in the outermost layer, or the second outer layer is located in the outermost layer. Also good. However, since the first outer layer can be sealed at a lower temperature than the second outer layer, the first outer layer is preferably disposed as the outermost layer. In this case, the sealing process at the time of forming a double bag package becomes easy.

  The first outer layer is a layer made of any of linear low density polyethylene, low density polyethylene, or ethylene-vinyl acetate. Among these, when a linear low density polyethylene is used, when the first outer layer is the outermost layer, the sealing property is particularly good and the heat resistance immediately after sealing is good, which is preferable. The lower limit of the thickness of the first outer layer is preferably 1 μm or more, more preferably 2 μm or more, further preferably 3 μm or more, and the upper limit is preferably 7 μm or less, more preferably 6 μm or less, and even more preferably 5 μm or less. is there. If the thickness of the first outer layer is too thin, the first outer layer may be melted and dispersed during sealing. In addition, if the thickness of the first outer layer is too thick, there is a risk that when the seal portion is peeled off, the first outer layer is not cut at the end portion of the seal portion, and a film remaining phenomenon is caused in which the peeling proceeds to a place other than the seal portion. There is.

  The second outer layer is composed of 50% by mass to 95% by mass of polypropylene and 5% by mass to 50% by mass of an ethylene-α-olefin copolymer based on the mass of the entire second outer layer (100% by mass). The blend resin. The polypropylene constituting the second outer layer may be a random copolymer with ethylene. When a random copolymer with ethylene is used, the sealing property with the first outer layer can be improved, and the transparency of the resulting inflation film can be further improved.

  As the ethylene-α-olefin copolymer, those using propylene and butene-1 as the α-olefin are preferable, and those having a specific gravity of 0.85 or more and 0.90 or less are preferable. Use of a material having high crystallinity is not preferable because the sealing strength with the first outer layer becomes too small. Further, the content ratio of the α-olefin in the ethylene-α-olefin copolymer is preferably 3 mol% or more, more preferably 5 mol% or more when the polymerization unit of the entire copolymer is 100 mol%. The upper limit is preferably 25 mol% or less, more preferably 15 mol% or less. If the α olefin content is too high, the extrudability of the film will be poor, and if the α olefin content is too low, the sealing strength with the first outer layer will be low.

  When the second outer layer is the outermost layer, the thickness of the second outer layer is preferably 1 μm or more and 7 μm or less similarly to the thickness of the first outer layer. The reason is that if the thickness of the second outer layer is too thin, the second outer layer may melt and disperse during sealing. Further, if the thickness of the second outer layer is too thick, when the seal portion is peeled off, the second outer layer may not be cut at the end portion of the seal portion, and a film remaining phenomenon may occur in which peeling proceeds to a place other than the seal portion. There is.

  The lower limit of the sealing strength between the first outer layer and the second outer layer is preferably 0.98 N / 15 mm width or more, more preferably 7.84 N / 15 mm width or more, and the upper limit is preferably 19.6 N / 15 mm width or less, more preferably. Is 14.7 N / 15 mm width or less. Increasing the proportion of α-olefin in the second outer layer increases the sealing strength, and decreasing it decreases the sealing strength, so that the sealing strength between the first outer layer and the second outer layer can be adjusted.

  If the sealing strength is too low, the double bag package has insufficient bag resistance. On the other hand, if the sealing strength is too high, the unsealing property is deteriorated. The sealing strength between the first outer layer and the second outer layer is such that the outermost layers of the inflation film of the present invention are heat sealed (sealing temperature: 140 ° C.), and then the sealing portion is 180 ° C. at a pulling speed of 200 mm / min. The peel strength when peeled is measured.

  Although the manufacturing method of the double bag package using the inflation film of the present invention has been described with reference to FIG. 3 and FIG. 4, the formed package has both the vertical seal part and the horizontal seal part, and the seal part is all. Easy peel. Therefore, only the seal part 48 on the upper side of the drawing in FIG. 4C may be opened to take out the contents, or along with the seal part 48, the vertical seal part 45 may be opened to enlarge the opening. Also good. Further, all the seal portions 48, 45, 46 may be opened, and in this case, the original state 40a shown in FIG.

  The double bag package of the present invention is often used as a commercial package mainly containing a large amount of contents. As described above, when the package is made into the sheet shape 40a, a large amount of contents are placed on the sheet 40a, so that the workability at the time of subdividing work is improved.

(Slip agent)
A slip agent can be added to the inner layer or / and the outermost layer for the purpose of imparting slipperiness. The slip agent is not particularly limited as long as it can impart slipperiness, and examples thereof include hydrocarbon-based lubricants, fatty acid-based higher alcohol-based lubricants, amide-based lubricants, ester-based lubricants, and metal soap-based lubricants.

  Typical amide-based lubricants for polyethylene slip agents include stearic acid amide, oleic acid amide, and erucic acid amide. The addition amount of the amide-based lubricant is generally 0.1 parts by mass or more and 0.5 parts by mass or less with respect to 100 parts by mass of the resin constituting each layer, and this addition amount improves and prevents blocking between the inner layers. be able to. Examples of the metal soap-based lubricant include lead stearate, zinc stearate, calcium stearate, magnesium stearate and the like. The addition amount of the metal soap-based lubricant is 0.1 parts by mass or more, preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and 10 parts by mass with respect to 100 parts by mass of the resin constituting each layer. Hereinafter, it is preferably 5 parts by mass or less, more preferably 3 parts by mass or less.

(Anti-blocking agent)
An antiblocking agent can be added to the inner layer and / or the outermost layer for the purpose of imparting antiblocking properties. The anti-blocking agent is not particularly limited as long as it can impart anti-blocking properties, but examples of inorganic agents include talc and zeolite. Talc is a white powder rich in lubricity and oily, and its surface is lipophilic and hydrophobic. Zeolite is a hydrous aluminosilicate of alkali and alkaline earth metals and can prevent stickiness. The anti-blocking agent is considered to exhibit a function of preventing blocking by forming fine irregularities on the surface of the resin layer and suppressing adhesion between two adjacent layers. The addition amount of the anti-blocking agent is 0.1 parts by mass or more, preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and 10 parts by mass or less, relative to 100 parts by mass of the resin constituting each layer. Preferably it is 5 mass parts or less, More preferably, it is 3 mass parts or less.

  The addition of the above slip agent and anti-blocking agent prevents the inner layers from blocking each other in the inflation film, and can improve the slip between the outermost layer and the packaging machine in the production process of the double bag package. .

(Adhesive resin layer)
Further, at least one adhesive resin layer can be provided between the intermediate layer and the outer layer and / or the inner layer. The adhesive resin used in the adhesive resin layer is not particularly limited as long as the outer layer, the intermediate layer, and the inner layer can be bonded to a required strength, but a polyolefin resin modified with an unsaturated carboxylic acid or a derivative thereof is preferably used. Can be used. Examples of the unsaturated carboxylic acid and derivatives thereof include acrylic acid, methacrylic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid, citraconic acid and derivatives thereof. Examples of unsaturated carboxylic acid derivatives include esters and anhydrides of unsaturated carboxylic acids, such as methyl acrylate, methyl methacrylate, ethyl acrylate, propyl acrylate, butyl acrylate, butyl methacrylate, Examples include vinyl acetate, glycidyl acrylate, glycidyl methacrylate, acrylamide, methacrylamide, and sodium acrylate.

  As a commercially available adhesive resin, the Mitsui Chemicals make and brand name Admer are mentioned, for example, It can use suitably in this invention.

  The lower limit of the thickness of the adhesive resin layer is preferably 3 μm or more, more preferably 5 μm or more, and the upper limit is preferably 20 μm or less, more preferably 15 μm or less. If the thickness of the adhesive resin layer is too thin, sufficient interlayer adhesion cannot be obtained. On the other hand, when the thickness of the adhesive resin layer is too thick, raw material costs are increased, and the transparency is deteriorated.

(EVOH layer)
Between the intermediate layer and the outer layer and / or the inner layer, at least one EVOH layer can be provided for the purpose of providing an oxygen barrier property. The ethylene content of EVOH used in the EVOH layer is not particularly limited, but from the viewpoint of film formation stability, the lower limit is preferably 32 mol% or more, more preferably 38 mol% or more, and the upper limit is preferable. Is 47 mol% or less, more preferably 44 mol% or less. The saponification degree of EVOH is preferably 90% or more, more preferably 95 mol% or more. By maintaining the ethylene content of EVOH and the saponification degree within the above ranges, the coextrudability of the film of the present invention and the strength of the film can be improved.

  When the EVOH layer is provided, the lower limit of the thickness of the EVOH layer is preferably 3 μm or more, more preferably 5 μm or more, further preferably 8 μm or more, and the upper limit is preferably 20 μm or less, more preferably 18 μm or less, and even more preferably 15 μm. It is as follows. Sufficient oxygen barrier properties can be obtained by setting the lower limit of the thickness of the EVOH layer to 3 μm. Further, by setting the upper limit to 20 μm, the coextrudability of the film is not deteriorated and good film strength can be maintained.

<Layer structure of inflation film>
The layer structure of the inflation film of the present invention includes an outer layer having an easy peel property as the outermost layer (first outer layer and second outer layer), and an inner layer made of a low-density polyethylene resin as the innermost layer, and is made of a polyamide resin therebetween. As long as the intermediate layer is provided, the layer configuration of the other layers is not particularly limited.

For example, when represented by the first outer layer (A), the second outer layer (B), the intermediate layer (C), the EVOH layer (D), the inner layer (E), and the adhesive resin layer (F), for example, the following layers A configuration can be formed.
(1) A / B / F / C / F / E
(2) B / A / F / C / F / E
(3) A / B / F / D / C / F / E
(4) B / A / F / D / C / F / E
(5) A / B / F / C / D / F / E
(6) B / A / F / C / D / F / E

<Other additives>
In the present invention, an additive can be contained in any or all of the outermost layer, the intermediate layer, and the innermost layer as long as the effects of the present invention are not impaired. For example, when a pigment is added, there is a merit that it is easy to find out even if the freshness of the object to be accommodated due to the light shielding effect or a film piece is mixed into the object to be accommodated. In addition, the use of pigments having different colors also has the effect of allowing the type of the filling material to be identified by the color of the package. The pigment is preferably added to the outer layer side or the intermediate layer which does not come into contact with the contents. Further, by adding an antifogging agent to the outermost layer and / or the inner layer, the double bag package can be prevented from being fogged, and even if there is a head space, a double bag package having good transparency can be obtained. be able to.

<Preparation of sample film for evaluation>
As Examples 1 to 5 and Comparative Examples 1 to 9, coextruded blown films composed of 6 layers were produced. The total thickness of the film is 55 μm, 60 μm, or 100 μm depending on each example and comparative example.

Example 1
The layer structure of the inflation film is shown below. The inner layer is a layer on the axial center side of the cylindrical film, and the outer layer is a layer on the opposite side.
First layer (first outer layer): linear low density polyethylene resin (LLDPE) (4 μm)
Second layer (second outer layer) polypropylene + ethylene-α-olefin copolymer (20 μm)
Third layer (adhesive resin layer): carboxylic acid-modified ethylene-vinyl acetate copolymer (5 μm)
Fourth layer (intermediate layer): 6 nylon (11 μm)
Fifth layer (adhesive resin layer): carboxylic acid-modified ethylene-vinyl acetate copolymer (5 μm)
Sixth layer (inner layer): linear low-density polyethylene resin (LLDPE) (15 μm)
Total thickness 60μm

For the first outer layer, LLDPE (manufactured by Prime Polymer Co., Ltd., Motec) was used, and 0.3 parts by mass of a slip agent was added to 100 parts by mass of the LLDPE. As the second outer layer, a blend resin of 80% by mass of polypropylene (manufactured by Nippon Polypro Co., Ltd., Novatec) and 20% by mass of an ethylene-α-olefin copolymer (manufactured by Mitsui Chemicals, Tuffmer) was used. As the carboxylic acid-modified ethylene-vinyl acetate copolymer constituting the adhesive resin layer, Admer made by Mitsui Chemicals was used. As LLDPE constituting the inner layer, LLDPE having a density of 0.935 g / cm ³ and a Vicat softening point of 120 ° C. (manufactured by Prime Polymer Co., Ltd., Motec) is used, and the slip agent is 1.8 parts by mass with respect to 100 parts by mass of the resin. Then, 1.8 parts by mass of an antiblocking agent was added.

(Example 2)
Example 2 except that a blend resin of 60% by mass of polypropylene (manufactured by Nippon Polypro Co., Ltd., Novatec) and 40% by mass of an ethylene-α olefin copolymer (manufactured by Mitsui Chemicals, Tuffmer) is used as the second outer layer. An inflation film was produced in the same manner.

(Example 3)
An inflation film was produced in the same manner as in Example 1 except that low-density polyethylene (Novatec, manufactured by Nippon Polyethylene Co., Ltd.) was used as the first outer layer.

Example 4
An inflation film was produced in the same manner as in Example 1 except that ethylene-vinyl acetate (manufactured by Nippon Polyethylene Co., Ltd., Novatec) was used as the first outer layer.

(Example 5)
An inflation film was produced in the same manner as in Example 1 except that the first layer and the second layer were changed to have the following layer structure.
First layer (second outer layer) polypropylene + ethylene-α-olefin copolymer (4 μm)
Second layer (first outer layer): linear low-density polyethylene resin (LLDPE) (4 μm)
Third layer (adhesive resin layer): carboxylic acid-modified ethylene-vinyl acetate copolymer (5 μm)
Fourth layer (intermediate layer): 6 nylon (27 μm)
Fifth layer (adhesive resin layer): carboxylic acid-modified ethylene-vinyl acetate copolymer (5 μm)
Sixth layer (inner layer): linear low-density polyethylene resin (LLDPE) (15 μm)
Total thickness 60μm

(Comparative Example 1)
An inflation film was produced in the same manner as in Example 1 except that the thickness of each layer was changed as follows.
First layer (first outer layer): 10 μm
Second layer (second outer layer): 18 μm
Third layer (adhesive resin layer): 4 μm
Fourth layer (intermediate layer): 6 μm
Fifth layer (adhesive resin layer): 4 μm
Sixth layer (inner layer): 13 μm
Total thickness 55μm

(Comparative Example 2)
An inflation film was produced in the same manner as in Example 1 except that only polypropylene (Novatec, manufactured by Nippon Polypro Co., Ltd.) was used as the second outer layer.

(Comparative Example 3)
As the first outer layer, a blend resin of 75% by mass of ethylene-vinyl acetate (manufactured by Nippon Polyethylene Co., Ltd., Novatec) and polypropylene (manufactured by Nippon Polypro Co., Ltd., Novatec) is used. An inflation film was produced in the same manner as in Example 1 except that 3 parts by mass was added and only ethylene-vinyl acetate (Novatec, manufactured by Nippon Polyethylene Co., Ltd.) was used as the second outer layer.

(Comparative Example 4)
As the first outer layer, a blend resin of 60% by mass of LLDPE (manufactured by Prime Polymer Co., Ltd., Moatech) and 40% by mass of polybutene (manufactured by Mitsui Chemicals, Toughmer BL) is used. An inflation film was produced in the same manner as in Example 1 except that 3 parts by mass of a slip agent was added and only polypropylene (Novatech, manufactured by Nippon Polypro Co., Ltd.) was used as the second outer layer.

(Reference Example 1)
As the LLDPE constituting the inner layer, LLDPE having a density of 0.937 g / cm ³ and a Vicat softening point of 102 ° C. (manufactured by Nippon Polyethylene Co., Ltd., Novatec) was used. An inflation film was produced in the same manner as in Example 1 except that 1.8 parts by mass of the blocking agent was added.

(Reference Example 2)
As the LLDPE constituting the inner layer, LLDPE having a density of 0.929 g / cm ³ and a Vicat softening point of 117 ° C. (Novatec, manufactured by Nippon Polyethylene Co., Ltd.) was used. An inflation film was produced in the same manner as in Example 1 except that 1.8 parts by mass of the blocking agent was added.

(Reference Example 3)
As LLDPE constituting the inner layer, LLDPE having a density of 0.910 g / cm ³ and a Vicat softening point of 85 ° C. (manufactured by Prime Polymer Co., Ltd., Motec) is used. An inflation film was produced in the same manner as in Example 1 except that 1.8 parts by mass of the blocking agent was added.

(Comparative Example 5)
Change the thickness of each layer as follows,
First layer (first outer layer): 4 μm
Second layer (second outer layer): 30 μm
Third layer (adhesive resin layer): 10 μm
Fourth layer (intermediate layer): 16 μm
Fifth layer (adhesive resin layer): 10 μm
Sixth layer (inner layer): 30 μm
Total thickness 100μm
An inflation film was produced in the same manner as in Example 1 except that the amount of the slip agent and antiblocking agent added to the inner layer was changed to 0.3 parts by mass with respect to 100 parts by mass of the resin. The produced inflation film was cut open and slit into a single film.

(Comparative Example 6)
Change the thickness of each layer as follows,
First layer (first outer layer): 4 μm
Second layer (second outer layer): 17 μm
Third layer (adhesive resin layer): 4 μm
Fourth layer (intermediate layer): 19 μm
Fifth layer (adhesive resin layer): 4 μm
Sixth layer (inner layer): 12 μm
Total thickness 60μm
An inflation film was produced in the same manner as in Example 1 except that the amount of the slip agent and antiblocking agent added to the inner layer was changed to 0.3 parts by mass with respect to 100 parts by mass of the resin. The produced inflation film was cut open and slit into a single film.

(Comparative Example 7)
Example 1 except that a blend resin of 40% by mass of polypropylene (manufactured by Nippon Polypro Co., Ltd., Novatec) and 60% by mass of an ethylene-α olefin copolymer (manufactured by Mitsui Chemicals, Tuffmer) is used as the second outer layer. An inflation film was produced in the same manner.

<Evaluation method>
Each sample film for evaluation produced in the above Examples and Comparative Examples was evaluated by the following test.
(1) Transparency Films obtained in Examples and Comparative Examples were measured with a spectrophotometer, and the obtained haze was 8% or less as “◯”, and more than 8% as “x”. evaluated.
(2) Peeling appearance Using the obtained inflation film, it was subjected to a vertical pillow packaging machine ONP-X (manufactured by ORIHIRO) to produce a double bag packaging. When the seal part of this double bag package was opened by hand, the seal part was evaluated as “◯” when the seal part did not remain in a film shape, and “×” when the seal part remained 3 mm or more in the film shape. .
(3) Seal strength The seal portion was cut into a strip shape having a width of 15 mm, and the stress was measured when the seal portion was pulled with a tensile tester at a pulling rate of 200 mm / min.
(4) Heat resistance Evaluation was made as “◯” when the seal portion did not peel immediately after sealing, and “×” when peel occurred.
(5) Gerboflex test
Using each of the obtained films, a gelboflex test (measurement of the number of pinholes generated when bent at 23 ° C. × 40% RH 500 times) was performed to evaluate pinhole resistance. Comparative Examples 5 and 6 were evaluated for a flat film that was slit. The number of pinholes generated at this time was evaluated as “◎” when the number was 0 to less than 5, and “◯” when 5 or more and less than 10, and “x” when 10 or more.
(6) Hot filling test Each of the obtained inflation films is applied to a vertical pillow packaging machine ONP-X (manufactured by Orihiro) to make a double bag, and the bag is filled with 10 kg of hot water at 90 ° C. It was confirmed whether they were blocking each other. The inner layer was evaluated as “◎” when the inner layers were not blocked, “◯” when partially blocked, and “X” when the majority was blocked.
(7) Modulus measurement When each of the obtained films was pulled using a precision universal material testing machine (manufactured by Intesco) at a constant speed (5 mm / min), and the strain reached 5% The stress of was measured. In this case, the stress value of 4.0N or more was evaluated as “◎”, the stress value of 3.5N or more and less than 4.0N was evaluated as “◯”, and the stress value of 3.5N or less was evaluated as “X”.

<Evaluation results>
Table 1 summarizes the results.

  In Examples 1 to 5, transparency, peel appearance, seal strength, and heat resistance were all good. Moreover, since it was tube film shape (two sheets piled up), the number of pinhole generation was few. Moreover, since high-density LLDPE was disposed as the resin constituting the inner layer, it did not block even when hot-filled. Further, since the PA layer had a thickness of 11 μm, it was excellent in pinhole resistance and difficult to stretch. Among these, Examples 3 and 4 showed results that were slightly inferior to those of the other examples in terms of modulus measurement because the resins constituting the first outer layer were LD and EVA, respectively.

  On the other hand, Comparative Example 1 in which the thickness of the first outer layer is thick has a poor peel appearance, and Comparative Example 2 in which the second outer layer is made of PP alone is inferior in easy peel strength. It can also be seen that Comparative Example 3 in which the first outer layer is a cohesive failure type easy peel layer has poor transparency of the seal portion, and Comparative Example 4 in which the B layer is a single PP layer has poor heat resistance.

  In each of Reference Examples 1 and 2, LLDPE having a low Vicat softening point or a low density was used as the resin constituting the inner layer, so the modulus measurement results were inferior (easily stretched). In Reference Example 3, LLDPE having a low density and a low Vicat softening point was used as the resin constituting the inner layer, so that the inner layers blocked each other and the results were inferior in terms of elongation. Since Comparative Examples 5 and 6 were single films, the pinhole resistance was inferior and there was a risk of causing bag breakage during transportation. In Comparative Example 7, the content of the ethylene-α olefin in the second outer layer was large, the seal strength was too high, and the peel appearance was inferior.

  While the present invention has been described in connection with embodiments that are presently the most practical and preferred, the present invention is not limited to the embodiments disclosed herein. Rather, it can be changed as appropriate without departing from the spirit or idea of the invention that can be read from the claims and the entire specification, and is produced using an inflation film for double bag packaging and such a film with such a change. Double bag packages should also be understood as being within the scope of the present invention.

It is a figure which shows roughly the manufacturing process of the inflation film used for producing a double bag packaging body. 2A is a cross-sectional view of the tubular film taken along the line IIA-IIA in FIG. 1, and FIG. 2B is a cross-sectional view of the flat film taken along the line IIB-IIB in FIG. It is a figure which shows roughly the process of unwinding an original fabric and cutting it to predetermined length. It is a figure which shows roughly the process of producing a double bag packaging body from a single leaf. It is sectional drawing represented to the back direction from the paper surface front side along the PP line of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Tube-shaped film 10 'Flat film 11 Cylindrical metal mold 12, 13 Roll 14 Winder 15 Original fabric 21 Inner layer 22 Intermediate layer 23 Second outer layer 24 First outer layer 25 Space (air layer)
30a, 30b, 30c Single leaf 40a Single leaf (with crease)
40b Intermediate product 40c Double bag package 41, 42, 43, 44 Fold 45, 46, 48 Overlapping portion 47 Opening 50 Contained matter

Claims (5)

An inflation film for a double bag package comprising an outer layer having easy peel properties, an intermediate layer made of polyamide resin, and an inner layer made of low-density polyethylene resin,
The outer layer having the easy peel property includes a first outer layer and a second outer layer adjacent to the first outer layer,
The first outer layer is made of either linear low density polyethylene, low density polyethylene, or ethylene-vinyl acetate, and has a thickness of 1 μm or more and 7 μm or less,
The second outer layer is a blend of 50% by mass to 95% by mass of polypropylene and 5% by mass to 50% by mass of an ethylene-α-olefin copolymer, with the total mass of the second outer layer being 100% by mass. Inflation film for double packaging made of resin. The inflation film for a double package according to claim 1, wherein the sealing strength between the first outer layer and the second outer layer is 0.98 N / 15 mm width or more and 19.6 N / 15 mm width or less. The inflation film for a double package according to claim 1 or 2, wherein the first outer layer is disposed on the outermost layer, and the second outer layer is disposed on the inner layer side. The low-density polyethylene resin constituting the inner layer has a Vicat softening point of 110 ° C or more and 125 ° C or less, and a density of more than 0.930 g / cm ³ and 0.940 g / cm ³ or less. An inflation film for a double bag package according to any one of the above. The double bag package which has the easy peel property bag-made with the inflation film in any one of Claims 1-4.

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