Flexible packaging materials and recycling methods

Abstract

To provide a packaging film that is easy to recycle, as a packaging film in which at least two base material layers made of different materials are laminated, .SOLUTION: In a packaging film, at least two base material layers 21, 22 made of different materials are laminated. The packaging film includes: two adjacent base material layers; and a solvent-soluble intervening layer 3 disposed between the two adjacent base material layers. The intervening layer 3 enables the two base material layers to be separated by immersion in a solvent.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a packaging film used for forming packaging materials such as pouch containers. [Background technology]

[0002] Conventionally, various products such as food, cosmetics, and medicines are distributed packaged in various packaging materials. Among the packaging materials, soft packaging materials such as pouch containers and pillow packaging bags are made of flexible packaging films. The packaging films that form soft packaging materials usually use laminates in which two or more base layers made of different materials are laminated. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2007-062786 A [Patent Document 2] JP 2003-084670 A Summary of the Invention [Problem to be solved by the invention]

[0004] The above-mentioned packaging film has a base layer made of different materials, so it is difficult to recycle it as a raw material unless it is separated into each base layer. Patent Document 1 (JP Patent Publication 2007-062786) discloses an easily peelable food packaging paper having a paper layer and a non-paper layer made of a resin film or a metal film attached to the paper layer by wax. The paper layer and the non-paper layer of this packaging paper can be separated by picking up either the paper layer or the non-paper layer and peeling it off from the other. However, the method of peeling and separating by hand requires a lot of time and labor for recycling. Patent Document 2 discloses a plastic label in which a display printing ink layer is formed on a base film via an alkaline aqueous solution soluble coating layer in order to peel the display printing ink layer from the base film. However, such Document 2 does not disclose the separation of two base layers made of different materials.

[0005] The object of the present disclosure is to provide a packaging film in which at least two base material layers made of different materials are laminated, the base material layers being easily separated, and which is easily recyclable, and a pouch container using this film. [Means for solving the problem]

[0006] The packaging film of the present disclosure is a packaging film in which at least two base layers made of different materials are laminated, and includes two adjacent base layers and a solvent-soluble intermediate layer disposed between the two adjacent base layers, the intermediate layer being a layer that allows the two base layers to be separated by immersion in a solvent. According to this packaging film, the two base layers can be easily separated by immersion in an appropriate solvent, and thus a packaging film that is easily recyclable can be provided.

[0007] In a preferred packaging film of the present disclosure, the intervening layer has at least one of water solubility and alkali solubility.

[0008] In a preferred packaging film of the present disclosure, the interposing layer comprises an acrylic acid copolymer-based resin.

[0009] In a preferred packaging film of the present disclosure, the intervening layer has an acid value of 40 mg-KOH / g or more and 150 mg-KOH / g or less.

[0010] A preferred packaging film of the present disclosure has a printed ink layer formed on at least one substrate layer.

[0011] In a preferred packaging film of the present disclosure, one of the two adjacent substrate layers is a resin layer, and the other substrate layer is a metal thin film layer or a resin layer.

[0012] The pouch container of the present disclosure is formed using any one of the packaging films described above. According to this pouch container, the two base material layers can be easily separated, making it possible to provide a pouch container that is easily recyclable. Effect of the Invention

[0013] The packaging film of the present disclosure can be easily separated into two base layers made of different materials by immersing it in an appropriate solvent. The packaging film of the present disclosure, which can be separated into different materials, and the pouch container using the same can be easily recycled. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a plan view in which a portion of the packaging film is omitted. [Diagram 2] FIG. 2 is a cross-sectional view showing an example of a first laminate structure of a packaging film. [Diagram 3] FIG. 3 is a cross-sectional view showing another example of the first laminate structure of the packaging film. [Figure 4] FIG. 4 is a cross-sectional view showing another example of the first laminate structure of the packaging film. [Diagram 5] FIG. 5 is a cross-sectional view showing another example of the first laminate structure of the packaging film. [Figure 6] FIG. 6 is a cross-sectional view showing another example of the second laminated structure of the packaging film. [Figure 7] FIG. 7 is a cross-sectional view showing another example of the second laminated structure of the packaging film. [Figure 8] FIG. 8 is a cross-sectional view showing another example of the second laminated structure of the packaging film. [Figure 9] FIG. 9 is a cross-sectional view showing another example of the second laminated structure of the packaging film. [Figure 10] FIG. 10 is a cross-sectional view showing another example of the third laminated structure of the packaging film. [Figure 11] FIG. 11 is a cross-sectional view showing another example of the third laminated structure of the packaging film. [Figure 12] FIG. 12 is a cross-sectional view showing another example of the third laminated structure of the packaging film. [Figure 13] FIG. 13 is a cross-sectional view showing another example of the third laminated structure of the packaging film. [Figure 14] FIG. 14 is a cross-sectional view of a packaging film having two substrate layers with a pre-adhesive layer disposed adjacent an interposer layer. [Figure 15] FIG. 15 is a cross-sectional view of a packaging film having three substrate layers with a pre-adhesive layer disposed adjacent an interposer layer. [Figure 16] FIG. 16 is a cross-sectional view of a packaging film having four substrate layers with a pre-adhesive layer disposed adjacent an interposer layer. [Figure 17] FIG. 17 is a perspective view showing an example of a pouch container formed using a packaging film. [Figure 18] FIG. 18 is a perspective view showing an example of a pillow packaging bag formed using a packaging film. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. In this specification, the term may be preceded by "first", "second", "third", etc., but this "first" etc. is added only to distinguish the term and does not have any special meaning such as order or superiority. In this specification, a numerical range represented by "lower limit value X to upper limit value Y" means a range from lower limit value X to upper limit value Y. When a plurality of numerical ranges are separately described, it is assumed that an arbitrary lower limit value and an arbitrary upper limit value can be selected to set "an arbitrary lower limit value to an arbitrary upper limit value". The dimensions, scale, and shape of the layers and members shown in each figure may differ from the actual ones. In addition, the surface of the packaging film is the upper surface of the packaging film shown in each figure, and the back surface of the packaging film is the lower surface of the packaging film shown in each figure. In addition, the surface of each layer is the upper surface of each layer shown in each figure, and the back surface of each layer is the lower surface of each layer shown in each figure.

[0016] <Overview of packaging film> The packaging film of the present disclosure is a packaging film in which at least two base layers made of different materials are laminated. Specifically, the packaging film of the present disclosure is a laminate including at least two adjacent base layers and an intervening layer disposed between the two base layers. The two base layers are made of different materials. The intervening layer is intervened between the two base layers adjacent in the thickness direction. The intervening layer is a layer that is solvent-soluble and allows the two base layers to be separated by immersion in a solvent. Solvent-soluble refers to the property of dissolving in a solvent.

[0017] In this way, the intervening layer is a layer that allows two adjacent base layers to be separated when the packaging film is immersed in an appropriate solvent. However, in a state not immersed in a solvent (a state not immersed in a solvent), the two adjacent base layers are not separated. In other words, in a state not immersed in a solvent, the packaging film is a laminate in which the adhesive state of each layer, such as the base layer and the intervening layer, is maintained to such an extent that they cannot be easily peeled off by human force. Note that adhesion refers to a state in which two layers are bonded by physical and / or chemical forces and are bonded in such a way that the layers cannot be easily peeled off by human force.

[0018] The packaging film may have at least two adjacent substrate layers, and may have three or more substrate layers. When the packaging film has three or more substrate layers, the above-mentioned intervening layer is preferably provided between each two adjacent substrate layers. In addition, in the packaging film, at least one substrate layer selected from the multiple substrate layers (at least two substrate layers) may have a printing ink layer formed thereon, if necessary.

[0019] The printed ink layer is composed of a solidified ink film formed by directly printing a known ink onto a substrate layer or the like by a known printing method. The printed ink layer is firmly adhered to the surface of the other side on which it is formed. The printed ink layer may be colored or uncolored (colorless and transparent). A colored printed ink layer may be opaque or colored and transparent. In the substrate layer on which the printed ink layer is formed, the intervening layer may be disposed between the printed ink layer and the substrate layer, or may be disposed between the substrate layer on which the printed ink layer is formed and the substrate layer adjacent thereto.

[0020] In this specification, "transparent" means colorless transparent or colored transparent. "Transparent" refers to a state in which a number (12 point size) printed on white paper in black ink is placed 1 cm away from the back side of the layer to be measured, and the number can be identified from the front side through the layer to be measured. "Opaque" refers to a state in which a number placed on the back side under the same conditions as above cannot be seen from the front side (a state in which the number cannot be recognized).

[0021] An index of transparency (colorless transparent or colored transparent) can be expressed, for example, by total light transmittance. Transparency (colorless transparent or colored transparent) means, for example, a total light transmittance of 70% or more, preferably 80% or more, and more preferably 90% or more. However, the total light transmittance refers to a value measured by a measurement method conforming to JIS K 7361:1997 (Test method for total light transmittance of plastic transparent materials) for a transparent measurement object. In addition, when the substrate layer, intervening layer, or printing ink layer itself cannot be used as the measurement object, the measurement object is one in which they are provided on a support film having a total light transmittance of 90% or more as measured by the JIS standard.

[0022] The substrate layer, the intermediate layer, and the printing ink layer are all layered, but the substrate layer differs from the intermediate layer and the printing ink layer in that it can form a layer by itself. In other words, the substrate layer can maintain a layered structure by itself, whereas the intermediate layer and the printing ink layer form a layer while adhering to the substrate layer (they form a layer by being supported by the substrate layer), but are very fragile by themselves and will break with even a slight force, making it impossible to maintain a layered structure.

[0023] The packaging film is flexible. The packaging film may be transparent or opaque as a whole. The packaging film may have heat shrinkability, but preferably, a packaging film that does not have substantial heat shrinkability is used. Heat shrinkability refers to the property of shrinking when heated to a desired temperature (e.g., 70°C to 90°C).

[0024] The shape of the packaging film in plan view is a long strip shape as shown in FIG. 1. The long strip shape refers to a generally rectangular shape in plan view in which the length in the longitudinal direction is sufficiently longer than the length in the lateral direction, and for example, the length in the longitudinal direction is 3 times or more, preferably 5 times or more, of the length in the lateral direction. Specific dimensions of the long strip shape include, for example, a lateral length of 100 mm to 3000 mm and a longitudinal length of 2 m to 500 m. The long strip packaging film is usually wound into a roll shape for storage and transportation, and is cut into a desired shape when preparing a packaging material. However, the packaging film of the present disclosure is not limited to a long strip shape, and may be formed into a sheet shape in plan view (not shown). Examples of the sheet shape include a generally polygonal shape in plan view, such as a generally square shape, a generally triangular shape, or a generally hexagonal shape, and a generally circular shape in plan view.

[0025] <Example of laminated structure of packaging film> Next, several laminated structures of the packaging film of the present disclosure will be illustrated. Fig. 2 to Fig. 5 are cross-sectional views showing examples of a first laminated structure of the packaging film. In Fig. 2 to Fig. 5, the packaging film 1 has two laminated base layers (for convenience, referred to as a first base layer 21 and a second base layer 22). The first base layer 21 and the second base layer 22 are base layers made of different materials.

[0026] Specifically, the packaging film 1 in FIG. 2 is laminated in this order from the surface side (upper side in the figure) with a first base material layer 21, an intervening layer 3, and a second base material layer 22. The packaging film 1 in FIG. 3 is laminated in this order from the surface side with a first base material layer 21, a colored printed ink layer 41, an intervening layer 3, and a second base material layer 22. The packaging film 1 in FIG. 4 is laminated in this order from the surface side with a first base material layer 21, an intervening layer 3, a colored printed ink layer 41, and a second base material layer 22. The packaging film 1 in FIG. 5 is laminated in this order from the surface side with a colorless and transparent printed ink layer 42, a first base material layer 21, an intervening layer 3, and a second base material layer 22.

[0027] The packaging film 1 in which the colored printing ink layer 41 is formed between the first base layer 21 and the second base layer 22 may have, for example, the following configuration: (A) In order to make the color of the colored printed ink layer 41 visible from the front side of the packaging film 1, each layer arranged on the front side of the colored printed ink layer 41 (for example, the first base material layer 21 in FIG. 3 and the first base material layer 21 and the intermediate layer 3 in FIG. 4) is transparent, and each layer arranged on the back side of the colored printed ink layer 41 is transparent or opaque; (B) In order to enable the color of the colored printed ink layer 41 to be visible from the back side of the packaging film 1, each layer arranged on the back side of the colored printed ink layer 41 (for example, the second base material layer 22 and the intermediate layer 3 in Figure 3, and the second base material layer 22 in Figure 4) is transparent, and each layer arranged on the front side of the colored printed ink layer 41 is transparent or opaque.

[0028] The colored printed ink layer 41 is not limited to being formed between the first substrate layer 21 and the second substrate layer 22, but may be formed on the surface of the first substrate layer 21 (in this case, for example, even if the first substrate layer 21 etc. is opaque, the color can be seen from the surface side), or may be formed on the back surface of the second substrate layer 22 (in this case, even if the second substrate layer 22 etc. is opaque, the color can be seen from the back surface side). The colored printed ink layer 41 may be formed between substrate layers, and on the surface of the first substrate layer 21 or / and the back surface of the second substrate layer 22. The colorless and transparent printed ink layer 42 is not limited to being formed on the surface of the first substrate layer 21, but may be formed between the first substrate layer 21 and the second substrate layer 22, or / and the back surface of the second substrate layer 22.

[0029] 6 to 9 are cross-sectional views showing an example of the second laminated structure of the packaging film. In Fig. 6 to Fig. 9, the packaging film 1 has three laminated base materials layers (for convenience, referred to as a first base material layer 21, a second base material layer 22, and a third base material layer 23). In these packaging films 1, there are two pairs of adjacent base materials layers, and at least one pair of adjacent base materials layers is made of different materials, and preferably, the two pairs of adjacent base materials layers are made of different materials.

[0030] Specifically, the packaging film 1 in FIG. 6 is laminated in the following order from the surface side: a first base material layer 21, an intervening layer 3, a third base material layer 23, an intervening layer 3, and a second base material layer 22. In this example, the first base material layer 21 and the third base material layer 23 are adjacent to each other, and the third base material layer 23 and the second base material layer 22 are adjacent to each other. For example, the first base material layer 21, the second base material layer 22, and the third base material layer 23 are preferably made of different materials. The packaging film 1 in FIG. 7 is laminated in the following order from the surface side: a first base material layer 21, a colored printing ink layer 41, an intervening layer 3, a third base material layer 23, an intervening layer 3, and a second base material layer 22. The packaging film 1 in Fig. 8 has a first base material layer 21, an intervening layer 3, a colored printed ink layer 41, a third base material layer 23, an intervening layer 3, and a second base material layer 22 laminated in this order from the surface side. The packaging film 1 in Fig. 9 has a colorless and transparent printed ink layer 42, the first base material layer 21, an intervening layer 3, a third base material layer 23, an intervening layer 3, and a second base material layer 22 laminated in this order from the surface side.

[0031] The packaging film 1 in which the colored printing ink layer 41 is formed between the first base material layer 21 and the third base material layer 23 may have a configuration such as (A) or (B) below: (A) In order to make the color of the colored printing ink layer 41 visible from the front side of the packaging film 1, each layer arranged on the front side of the colored printing ink layer 41 is transparent, and each layer arranged on the back side of the colored printing ink layer 41 is transparent or opaque; (B) In order to enable the color of the colored printed ink layer 41 to be visible from the back side of the packaging film 1, each layer arranged on the back side of the colored printed ink layer 41 is transparent, and each layer arranged on the front side of the colored printed ink layer 41 is transparent or opaque.

[0032] The colored printed ink layer 41 is not limited to being formed between the first substrate layer 21 and the third substrate layer 23, but may be formed between the third substrate layer 23 and the second substrate layer 22. In the packaging film 1 having three substrate layers, the colored printed ink layer 41 may be formed on the surface of the first substrate layer 21, or on the back surface of the second substrate layer 22, or between the substrate layers, and on the surface of the first substrate layer 21 and / or the back surface of the second substrate layer 22, as in the packaging film 1 having the above two substrate layers. In addition, the colorless and transparent printed ink layer 42 is not limited to being formed on the surface of the first substrate layer 21, but may be formed between the substrate layers or / and on the back surface of the second substrate layer 22.

[0033] 10 to 13 are cross-sectional views showing an example of a third laminated structure of a packaging film. In Figs. 10 to 13, the packaging film 1 has four laminated base materials layers (for convenience, referred to as a first base material layer 21, a second base material layer 22, a third base material layer 23, and a fourth base material layer 24). In the four laminated base material layers, there are three pairs of two adjacent base material layers, and at least one pair of adjacent base material layers is made of different materials, and preferably, the three pairs of adjacent base material layers are made of different materials.

[0034] Specifically, the packaging film 1 in Fig. 10 is laminated in the following order from the front surface side: a first base material layer 21, an intervening layer 3, a third base material layer 23, an intervening layer 3, a fourth base material layer 24, an intervening layer 3, and a second base material layer 22. In this example, the first base material layer 21 and the third base material layer 23 are two adjacent base material layers, the third base material layer 23 and the fourth base material layer 24 are two adjacent base material layers, and the fourth base material layer 24 and the second base material layer 22 are two adjacent base material layers. For example, it is preferable that the first base material layer 21, the second base material layer 22, the third base material layer 23, and the fourth base material layer 24 are all made of different materials. In the packaging film 1 of Fig. 11, the first base material layer 21, the colored printing ink layer 41, the intermediate layer 3, the third base material layer 23, the intermediate layer 3, the fourth base material layer 24, the intermediate layer 3, and the second base material layer 22 are laminated in this order from the surface side. In the packaging film 1 of Fig. 12, the first base material layer 21, the intermediate layer 3, the colored printing ink layer 41, the third base material layer 23, the intermediate layer 3, the fourth base material layer 24, the intermediate layer 3, and the second base material layer 22 are laminated in this order from the surface side. In the packaging film 1 of Fig. 13, the colorless and transparent printing ink layer 42, the first base material layer 21, the intermediate layer 3, the third base material layer 23, the intermediate layer 3, the fourth base material layer 24, the intermediate layer 3, and the second base material layer 22 are laminated in this order from the surface side.

[0035] The packaging film 1 in which the colored printing ink layer 41 is formed between the first base material layer 21 and the third base material layer 23 may have a configuration such as (A) or (B) below: (A) In order to make the color of the colored printing ink layer 41 visible from the front side of the packaging film 1, each layer arranged on the front side of the colored printing ink layer 41 is transparent, and each layer arranged on the back side of the colored printing ink layer 41 is transparent or opaque; (B) In order to enable the color of the colored printed ink layer 41 to be visible from the back side of the packaging film 1, each layer arranged on the back side of the colored printed ink layer 41 is transparent, and each layer arranged on the front side of the colored printed ink layer 41 is transparent or opaque.

[0036] The colored printed ink layer 41 is not limited to being formed between the first substrate layer 21 and the third substrate layer 23, but may be formed between the third substrate layer 23 and the fourth substrate layer 24, or / and between the fourth substrate layer 24 and the second substrate layer 22. In the packaging film 1 having four substrate layers, similar to the packaging film 1 having the above two substrate layers, the colored printed ink layer 41 may be formed on the surface of the first substrate layer 21, or on the back surface of the second substrate layer 22, or between the substrate layers, and on the surface of the first substrate layer 21 or / and the back surface of the second substrate layer 22. The colorless and transparent printed ink layer 42 is not limited to being formed on the surface of the first substrate layer 21, but may be formed between the substrate layers, or / and on the back surface of the second substrate layer 22.

[0037] Fig. 14 to Fig. 16 are cross-sectional views showing an example of a configuration in which a preliminary adhesive layer that complements an intermediate layer is provided between adjacent base material layers of a packaging film. Specifically, Fig. 14 is a cross-sectional view of a packaging film having two base material layers, in which a preliminary adhesive layer is provided in contact with the intermediate layer. Fig. 15 is a cross-sectional view of a packaging film having three base material layers, in which a preliminary adhesive layer is provided in contact with the intermediate layer. Fig. 16 is a cross-sectional view of a packaging film having four base material layers, in which a preliminary adhesive layer is provided in contact with the intermediate layer.

[0038] When the intervening layer does not or does not easily adhere to the base material layer or the printed ink layer formed on the base material layer, a preliminary adhesive layer 5 is provided between the intervening layer and the base material layer and / or between the intervening layer and the printed ink layer formed on the base material layer as necessary. In all of Figs. 14 to 16, the preliminary adhesive layer 5 is provided between the printed ink layer 41 formed on the first base material layer 21 and the intervening layer 3, but this is not limited to this and the preliminary adhesive layer 5 may be provided between any appropriate layers. Furthermore, the preliminary adhesive layer 5 is not limited to one layer and may be provided between several layers.

[0039] Although not particularly shown, the preliminary adhesive layer 5 may be disposed in the packaging film 1 having five or more laminated base material layers. As with the packaging film having five or more base material layers, it is sufficient that the packaging film has at least two base material layers in which two adjacent base material layers are made of different materials and an intervening layer is provided between the two base material layers, as described above.

[0040] <Intervening layer> The intermediate layer is solvent-soluble and disposed between adjacent substrate layers. For example, the intermediate layer is between two adjacent substrate layers, and is directly adhered to the back surface of one substrate layer and the front surface of the other substrate layer, thereby binding the two substrate layers. This embodiment is shown, for example, in FIG. 2, FIG. 5, FIG. 6, and FIG. 9. For example, the intermediate layer is between two adjacent substrate layers, and is directly adhered to the back surface (or front surface) of the printed ink layer of one substrate layer on which the printed ink layer is formed and the front surface (or back surface) of the other substrate layer, thereby binding the two substrate layers via the printed ink layer. This embodiment is shown, for example, in FIG. 3, FIG. 4, FIG. 7, and FIG. 8. For example, the intervening layer is between two adjacent base material layers and is directly adhered to the back (or front) of the printed ink layer of one base material layer on which a printed ink layer is formed and the front (or back) of the printed ink layer of the other base material layer on which a printed ink layer is formed, binding both base material layers via the one and the other printed ink layers.

[0041] In addition, when it is difficult for the intermediate layer to directly adhere to the front or back surface of the substrate layer or the printed ink layer due to the relationship with the materials of the substrate layer or the printed ink layer, the above-mentioned preliminary adhesive layer is appropriately provided. As described above, the preliminary adhesive layer is provided between the intermediate layer and the substrate layer and / or between the intermediate layer and the printed ink layer. In this case, the preliminary adhesive layer and the intermediate layer work together to bind two adjacent substrate layers.

[0042] The solvent-soluble intervening layer has at least one property selected from, for example, water solubility, alkali solubility, organic solvent solubility, etc., and preferably has at least one of water solubility and alkali solubility. The solvent-soluble intervening layer contains a solvent-soluble polymer as a main component. The intervening layer may contain components other than the solvent-soluble polymer as a main component, and such components include known additives, residual solvents, etc.

[0043] In this specification, the main component of a layer refers to the component (weight ratio) that is the largest among the components contained in the layer. For example, the main component is contained in 50% by weight or more, preferably 70% by weight or more, and more preferably 90% by weight or more, when the entire layer is taken as 100% by weight.

[0044] Since the intervening layer contains a solvent-soluble polymer as a main component, when the packaging film is immersed in a solvent, the solvent-soluble polymer in the intervening layer dissolves into the solvent from between the substrate layers. As a result, the intervening layer gradually loses or loses its function of binding between layers or its function of binding between substrate layers in cooperation with the preliminary adhesive layer. Therefore, two substrates adjacent to each other with the intervening layer interposed therebetween can be easily separated.

[0045] The solvent-soluble polymer is a polymer that is soluble in a specific solvent. Examples of the solvent-soluble polymer include a water-soluble polymer, an alkali-soluble polymer, and an organic solvent-soluble polymer, and preferably, at least one of a water-soluble polymer and an alkali-soluble polymer is used. The intermediate layer mainly composed of a water-soluble polymer has water solubility, and the intermediate layer mainly composed of an alkali-soluble polymer has alkali solubility.

[0046] The water-soluble polymer is a polymer that is soluble in water or an aqueous solvent at normal temperature and pressure, and is, for example, a polymer with a solubility in water of 1 (g / 100g) or more at 23°C and 1 atm, preferably a polymer with a solubility of 5 (g / 100g) or more. In addition, the water-soluble polymer is preferably one that has improved solubility in water heated to an appropriate temperature. The heating temperature can be 50°C to 100°C.

[0047] The water-soluble polymer is not particularly limited, and examples thereof include synthetic resins and natural polymers. Examples of synthetic resins include polyvinyl alcohol-based resins such as polyvinyl alcohol and modified polyvinyl alcohol, polyvinyl acetate-based resins, cellulose-based resins, acrylic resins, polyacrylamide-based resins, polyethylene oxide-based resins, polyurethane-based resins, and amino-based resins. Examples of natural polymers include polysaccharides such as starch and polypeptides, glue, casein, and natural rubber. These may be used alone or in combination of two or more.

[0048] The aqueous solvent is a mixed solvent containing water and a hydrophilic solvent. The hydrophilic solvent is a solvent that can be dissolved uniformly in water. Examples of the hydrophilic solvent include alcohols such as methanol, glycols such as ethylene glycol, cellosolves such as methyl cellosolve, and esters such as ethyl acetate.

[0049] The alkali-soluble polymer is a polymer that is soluble in an alkaline aqueous solution at normal temperature and pressure, and is, for example, a polymer with a solubility of 1 (g / 100g) or more in an alkaline aqueous solution (aqueous sodium hydroxide solution with a concentration of 1.5% by weight) at 23°C and 1 atm, preferably a polymer with a solubility of 5 (g / 100g) or more. In addition, the alkali-soluble polymer is preferably one that has improved solubility in the alkaline aqueous solution heated to an appropriate temperature. The heating temperature can be 50°C to 100°C.

[0050] The alkali-soluble polymer is not particularly limited, and examples thereof include copolymers of one or more unsaturated carboxylic acids and one or more compounds having a polymerizable unsaturated group. Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, and itaconic acid. Examples of the compound having a polymerizable unsaturated group include alkyl acrylates such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate; alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, and butyl methacrylate; hydroxyl group-containing polymerizable unsaturated compounds such as hydroxyethyl acrylate and hydroxyethyl methacrylate; cyano group-containing polymerizable unsaturated compounds such as acrylonitrile and methacrylonitrile; amide group-containing polymerizable unsaturated compounds such as acrylamide, methacrylamide, N-alkoxyacrylamide, N-alkoxymethacrylamide, N-methylolacrylamide, and N-methylolacrylamide; styrene-based compounds such as styrene, vinyltoluene, α-methylstyrene, and divinylbenzene; olefins such as ethylene; allyl group-containing compounds such as diallyl phthalate, allyl glycidyl ether, and triallyl isocyanurate; vinyl esters such as vinyl acetate; and N-vinylpyrrolidone.

[0051] In particular, alkali-soluble polymers mainly composed of a styrene-maleic anhydride resin having an acid value of 50 to 300 (mg-KOH / g), a rosin-maleic acid resin having an acid value of 50 to 300 (mg-KOH / g), or an acrylic acid copolymer resin having an acid value of 50 to 300 (mg-KOH / g) are preferred.

[0052] As the styrene-maleic anhydride resin, a known styrene-maleic anhydride resin can be used. For example, suitable styrene-maleic anhydride resins include known styrene-maleic anhydride copolymers, which are copolymers of styrene and maleic anhydride, and modified products of the styrene-maleic anhydride copolymers (e.g., partially esterified products, etc.). In the styrene-maleic anhydride copolymer, in addition to styrene, styrene compounds such as α-methylstyrene can be used as the styrene.

[0053] The rosin-maleic acid resin may be any known rosin-maleic acid resin, such as an ester obtained by condensing an addition reaction product of rosin with maleic anhydride (e.g., an addition product of a tribasic acid) with a polyhydric alcohol (e.g., glycerin).

[0054] The acrylic acid copolymer resin is a resin having acrylic acid and / or methacrylic acid as a main repeating unit and further having a copolymerizable monomer copolymerizable with the acrylic acid and / or methacrylic acid. The acrylic acid copolymer resin preferably has a total ratio of acrylic acid and / or methacrylic acid and the copolymerizable monomer in the resin of 60 mol % or more.

[0055] Examples of the copolymerizable monomer include (meth)acrylic acid alkyl esters (preferably lower alkyl esters of (meth)acrylic acid) such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and t-butyl (meth)acrylate; hydroxyl group-containing (meth)acrylates such as hydroxyethyl (meth)acrylate; glycidyl group-containing (meth)acrylates such as glycidyl (meth)acrylate; and N,N'-dimethyl (meth)acrylamide. Examples of the copolymerizable monomer include (meth)acrylamides such as N,N'-diethyl(meth)acrylamide, (meth)acrylates containing an amino group such as dimethylaminoethyl(meth)acrylate, styrenes such as styrene, vinyl toluene, α-methylstyrene, vinyl esters such as vinyl acetate and vinyl propionate, vinyl halides such as vinyl chloride, vinyl ethers such as methyl vinyl ether, carboxyl group-containing vinyls such as itaconic acid and maleic anhydride [excluding (meth)acrylic acid], cyano group-containing vinyls such as acrylonitrile and methacrylonitrile, olefins and dienes such as ethylene and propylene, etc. The copolymerizable monomers can be used alone or in combination of two or more.

[0056] The intermediate layer preferably has an acid value of 40 to 150 (mg-KOH / g). For example, when the intermediate layer is mainly composed of an acrylic acid copolymer resin, and the acrylic acid copolymer resin is a mixed resin of two kinds of acrylic acid copolymer resins, the acid value of the intermediate layer is different from the acid value of each of the two kinds of acrylic acid copolymer resins. Also, when the intermediate layer contains a resin having an acid value other than the resin that is the main component, the acid value of the intermediate layer is different from the acid value of the resin that is the main component. The acid value of the intermediate layer varies depending on the acid value of each of the resins contained and the content ratio of each of them. The acid value of the intermediate layer can be confirmed, for example, by measuring the acid value of the resin composition that constitutes the intermediate layer.

[0057] In addition to the resin as the main component, the intermediate layer preferably further contains a vinyl chloride-vinyl acetate copolymer, which can improve the adhesion of the intermediate layer to other layers and enhance the design of the packaging film.

[0058] The content of the vinyl chloride-vinyl acetate copolymer in the intervening layer is preferably 1 to 10% by weight, more preferably 2 to 5% by weight, when the entire intervening layer is taken as 100% by weight. If the weight % is less than 1, the further improvement of the adhesion tends to be insufficient, and if it exceeds 10, the viscosity of the intervening layer tends to be too high, making handling difficult. The vinyl chloride-vinyl acetate copolymer preferably has an Mn (number average molecular weight) of 10,000 to 40,000, more preferably an Mn of 15,000 to 35,000. In this case, the improvement of the adhesion becomes significant.

[0059] The intervening layer of the present disclosure is preferably a layer formed from a resin composition having an acrylic acid copolymer resin as a main component and an apparent acid value of 40 to 150 (mg-KOH / g). It is preferable that the intervening layer further contains a vinyl chloride-vinyl acetate copolymer. In this case, the acrylic acid copolymer resin may be a mixed resin of two or more kinds of acrylic acid copolymer resins.

[0060] In addition, the alkali-soluble polymer described in Patent Document 2 (JP Patent Publication No. 2003-084670) may be used. As an intermediate layer containing an alkali-soluble polymer that can be used in the present disclosure, the alkali-soluble coating layer described in Patent Document 2 is described in this specification, and the description of Patent Document 2 is omitted in this specification due to space limitations. However, this specification is intended to incorporate at least the descriptions of

[0011] to

[0032] of Patent Document 2 as they are. The alkali-soluble coating layer described in Patent Document 2 is preferably used as an intermediate layer between the printing ink layer and the substrate layer of the present disclosure.

[0061] The thickness of the intermediate layer is not particularly limited and is, for example, 0.5 μm to 20 μm, and preferably 1 μm to 15 μm.

[0062] <Pre-adhesive layer> The preliminary adhesive layer is provided between the intermediate layer and the base layer, or / and between the intermediate layer and the printing ink layer, as necessary. The preliminary adhesive layer is not particularly limited as long as it can bond two layers between the layers between which it is interposed, and a known adhesive can be used. For example, the preliminary adhesive layer can be a so-called dry lamination adhesive such as a solvent volatilization type adhesive, a solventless adhesive, an anchor coating agent, or the like.

[0063] <Base material layer> Examples of the substrate layer include a resin layer, a metal thin film layer, a nonwoven fabric layer, and a paper layer. Examples of the resin layer include those containing a known resin as a main component. Examples of the resin include polyester-based resins such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and polylactic acid; polyolefin-based resins such as polyethylene and polypropylene; polyamide-based resins such as 6-nylon and 66-nylon; polystyrene-based resins such as polystyrene; polycarbonate-based resins; nitrile-based resins such as polyacrylonitrile; imide-based resins such as polyimide; vinyl chloride-based resins such as polyvinyl chloride and polyvinylidene chloride; and acrylate-based resins such as polymethyl methacrylate. The thickness of the resin layer is not particularly limited, and is, for example, 10 μm to 200 μm, and preferably 10 μm to 100 μm. The resin layer is usually a non-foamed layer, but may be foamed.

[0064] Examples of the metal thin film layer include aluminum foil and copper foil. The thickness of the metal thin film layer is not particularly limited and is, for example, 5 μm to 30 μm. Examples of the nonwoven fabric layer include nonwoven fabrics prepared in a sheet shape from fibers by a bonding method, a needle punching method, a spunbonding method, a meltblowing method, etc. Examples of the fibers include polyester fibers; polyolefin fibers such as polypropylene and polyethylene; rayon fibers; polyamide fibers such as nylon; and natural fibers. The basis weight of the nonwoven fabric is not particularly limited and is, for example, 10 to 100 g / m 2The paper layer may be plain paper, high-quality paper, or the like.

[0065] The polyvinylidene chloride resin layer and the metal thin film layer have gas barrier properties. By using a base layer having such gas barrier properties, the gas barrier properties can be imparted to the packaging film. In addition, the low-density polyethylene layer, the ethylene-propylene copolymer layer, the ethylene-olefin copolymer layer, and the like have sealant properties (thermal welding properties). By using a base layer having such sealant properties (for example, a base layer constituting the backmost surface of the laminate), the sealant properties can be imparted to the packaging film.

[0066] Furthermore, a polyester resin layer such as polyethylene terephthalate and a polyamide resin layer such as nylon have excellent heat resistance compared to their sealant properties. Therefore, by using a base layer having such heat resistance (for example, a base layer constituting the outermost surface of a laminate), heat resistance can be imparted to the packaging film. In addition, a foamed resin layer, a nonwoven fabric layer, etc. have heat insulating properties. By using a base layer having such heat insulating properties, heat insulating properties can be imparted to the packaging film.

[0067] As described above, the two adjacent base layers on which the intermediate layer is provided are made of different materials. Here, the two base layers made of different materials refer to those made of materials that are different from each other as main components, and the two base layers made of the same material refer to those made of the same material as a main component.

[0068] For example, examples of substrate layers made of different materials include combinations of a resin layer and a metal thin film layer (resin and metal are different materials), a resin layer and a paper layer (resin and pulp are different materials), and a metal thin film layer and a paper layer (metal and pulp are different materials).

[0069] In addition, in the resin layer, a resin layer mainly made of a different resin is in a relationship of a substrate layer made of a different material. Similarly, in the metal thin film layer, a metal thin film layer mainly made of a different metal is in a relationship of a substrate layer made of a different material, and in the nonwoven fabric layer, a nonwoven fabric layer mainly made of a different fiber is in a relationship of a substrate layer made of a different material.

[0070] For example, a resin layer mainly made of polyethylene terephthalate and a resin layer mainly made of polyethylene are two base layers made of different resins and different materials. A metal thin film layer (aluminum foil) mainly made of aluminum and a metal thin film layer (copper foil) mainly made of copper are two base layers made of different metals and different materials. A nonwoven fabric layer mainly made of rayon fiber and a nonwoven fabric layer mainly made of nylon are two base layers made of different fibers and different materials.

[0071] On the other hand, a resin layer mainly composed of polyethylene terephthalate and a nonwoven fabric mainly composed of polyethylene terephthalate fibers are two base material layers that have the same resin as the main component and are made of the same type of material.

[0072] In the packaging film 1 having two base material layers shown in Figures 2 to 5, for example, an arbitrary resin layer is used as the first base material layer 21, which is the base material layer on the front side, and a resin layer made of a different resin material is used as the second base material layer 22, which is the base material layer on the back side, and a solvent-soluble intermediate layer 3 is provided between them.

[0073] In the packaging film 1 having three substrate layers as shown in Figures 6 to 9, for example, any resin layer is used as the first substrate layer 21, which is the substrate layer on the front side, a resin layer made of a different resin material is used as the third substrate layer 23, which is the intermediate substrate layer, and a resin layer made of a different resin material is used as the second substrate layer 22, which is the substrate layer on the back side, and an intermediate layer 3 having solvent solubility is provided between the first substrate layer 21 and the third substrate layer 23, and between the third substrate layer 23 and the second substrate layer 22, respectively.

[0074] A metal thin film layer, a nonwoven fabric layer, or a paper layer may be used as the third base material layer 23. Furthermore, base material layers made of the same material may be used as the first base material layer 21 and the third base material layer 23, or base material layers made of the same material may be used as the third base material layer 23 and the second base material layer 22. In this way, in a packaging film 1 including two adjacent base material layers made of the same material, a solvent-soluble intermediate layer 3 may be provided between the two base material layers made of the same material, or such an intermediate layer may not be provided.

[0075] When the packaging film 1 having the three base material layers shown in Figs. 6 to 9 is used as a pouch film for forming a pouch container, it can be configured, for example, as follows. A first base material layer 21 having heat resistance, such as a polyester resin layer or a polyamide resin layer such as nylon; a third base layer 23 having gas barrier properties, such as a polyvinylidene chloride resin layer or a metal thin film layer; A second base material layer 22 having a sealant property, such as a low-density polyethylene layer or an ethylene-propylene copolymer layer.

[0076] In the packaging film 1 having four substrate layers as shown in Figures 10 to 13, for example, any resin layer is used as the first substrate layer 21, which is the substrate layer on the front side; a metal thin film layer is used as the third substrate layer 23, which is the intermediate substrate layer; any resin layer is used as the fourth substrate layer 24; and a resin layer made of a different resin material is used as the second substrate layer 22, which is the substrate layer on the back side; and intermediate layers 3 having solvent solubility are provided between the first substrate layer 21 and the third substrate layer 23, between the third substrate layer 23 and the fourth substrate layer 24, and between the fourth substrate layer 24 and the second substrate layer 22, respectively.

[0077] Also, a resin layer, a nonwoven fabric layer, or a paper layer may be used as the third base material layer 23, or a metal thin film layer, a nonwoven fabric layer, or a paper layer may be used as the fourth base material layer 24. Furthermore, base material layers made of the same material may be used as the first base material layer 21 and the third base material layer 23, or base material layers made of the same material may be used as the third base material layer 23 and the fourth base material layer 24, or base material layers made of the same material may be used as the fourth base material layer 24 and the second base material layer 22. In this way, in the packaging film 1 including two adjacent base material layers made of the same material, a solvent-soluble intermediate layer 3 may be provided between the two base material layers made of the same material, or such an intermediate layer may not be provided.

[0078] When the packaging film 1 having the four base material layers shown in Figs. 10 to 13 is used as a pouch film for forming a pouch container, it can be configured, for example, as follows. A first base material layer 21 having heat resistance, such as a polyester resin layer or a polyamide resin layer such as nylon; a third base layer 23 having gas barrier properties, such as a polyvinylidene chloride resin layer or a metal thin film layer; a fourth base material layer 24 having heat resistance, such as a polyester resin layer or a polyamide resin layer such as nylon; A second base material layer 22 having a sealant property, such as a low-density polyethylene layer or an ethylene-propylene copolymer layer.

[0079] <Wrapping film manufacturing method> The packaging film is obtained by laminating the respective base layers with an intervening layer interposed therebetween. For example, a solution of a solvent-soluble polymer dissolved in an appropriate solvent is applied to the joining surface of one or both of the two adjacent base layers to form an uncured intervening layer, and then the solvent is removed by drying or the like. As a result, the solvent-soluble intervening layer bonds the two adjacent base layers.

[0080] The method for applying the solution containing the solvent-soluble polymer is not particularly limited, and examples thereof include a conventionally known printing method, a coating method using an appropriate coater, etc. The concentration of the solution containing the solvent-soluble polymer is not particularly limited, and the concentration may be adjusted to have an appropriate viscosity according to the application method.

[0081] <Applications of packaging film> The packaging film of the present disclosure can be generally used as a known packaging material (including tack labels, etc.), and is used, for example, by processing it into a soft packaging material. The soft packaging material is a soft packaging material that wraps various items. The soft packaging material formed using the packaging film of the present disclosure is preferably one that wraps an item in a sealed state, and representative examples of such soft packaging materials include pouch containers and pillow packaging bags.

[0082] Fig. 17 is a perspective view showing an example of a pouch container formed using a packaging film. Fig. 18 is a perspective view showing an example of a pillow packaging bag formed using a packaging film. The packaging film forming the pouch container A1, the pillow packaging bag A2, etc. preferably uses a base material layer having a sealant property as the base material layer on the backmost surface (the surface facing the internal space of the container and the packaging bag).

[0083] The packaging film of the present disclosure has a solvent-soluble intermediate layer between two base layers made of different materials, which allows the two base layers to be separated by immersion in a solvent. By immersing such a packaging film in an appropriate solvent, the intermediate layer dissolves, allowing the base layers made of different materials to be easily separated.

[0084] For example, when a water-soluble intermediate layer is used in a packaging film, the packaging film is immersed in water or an aqueous solvent, whereby water penetrates into the intermediate layer from the end face of the intermediate layer, and the adhesive strength of the intermediate layer gradually decreases or disappears. This allows two base layers made of different materials to be easily separated. For example, when a packaging film is used in a packaging film, the packaging film is immersed in an aqueous alkali solution, whereby alkali penetrates into the intermediate layer from the end face of the intermediate layer, and the adhesive strength of the intermediate layer gradually decreases or disappears. This allows two base layers made of different materials to be easily separated. This allows the packaging film to be separated into each material, making it easy to recycle the packaging film.

[0085] In another aspect, the present disclosure provides a method for separating a packaging film having a solvent-soluble intermediate layer between two adjacent substrate layers made of different materials by immersing the film in an appropriate solvent. As is clear from the following examples, the intermediate layer can separate the two substrate layers at the latest 24 hours after immersion in the solvent.

[0086] The packaging film processed into the soft packaging material such as the above-mentioned pouch container can be immersed in an appropriate solvent while still in the form of the soft packaging material, so that the two adjacent base layers can be separated via the intervening layer. Preferably, the soft packaging material can be cut into small pieces as desired, so that the separation can be performed more quickly. The smaller the area of ​​the pieces, the shorter the time required for separation. The packaging film of the present disclosure is provided with an intervening layer that allows the two base layers to be separated without any particular load at the latest 24 hours after immersion in a solvent when cut into small pieces of, for example, 60 square centimeters.

[0087] The present disclosure will be described in further detail below with reference to examples and comparative examples. However, the present disclosure is not limited to the following examples.

[0088] [Example 1] A water-soluble polymer (Nichigo G Polymer, product name: "Nichigo G Polymer") aqueous solution (polymer concentration: 10% by weight) was applied to the back surface of a 12 μm-thick biaxially stretched polyethylene terephthalate film (manufactured by Toyobo Co., Ltd. under the trade name "E5100") by gravure printing to a thickness of about 3 μm to form a first intervening layer. Then, an aluminum foil (manufactured by Toyo Aluminum Co., Ltd. under the trade name "General Foil") having a thickness of 7 μm was laminated and bonded to the first intervening layer. Furthermore, the water-soluble polymer aqueous solution was applied to the back surface of the aluminum foil under the gravure printing to a thickness of about 3 μm to form a second intervening layer. Then, a low-density polyethylene film (manufactured by Toyobo Co., Ltd. under the trade name "L4102") having a thickness of 80 μm was laminated and bonded to the second intervening layer to produce a laminate. Then, the entire laminate was dried with hot air at about 80°C. This resulted in the production of a packaging film having a laminated structure, from the surface side, of polyethylene terephthalate resin layer / water-soluble first intermediate layer approximately 3 μm thick / aluminum thin film layer / water-soluble second intermediate layer approximately 3 μm thick / polyethylene resin layer.

[0089] The packaging film of Example 1 was cut into strips 15 mm wide to obtain test pieces, and the 180° peel strength of the test pieces was measured. As a result, the 180° peel strength of the test pieces was 4.0 N / 15 mm, and the test pieces were bonded with sufficient strength. The peel strength was measured at a peel speed of 200 mm / min using a tensile tester (manufactured by Shimadzu Corporation under the trade name "Autograph"). In the above measurement, the peel strength when the polyethylene terephthalate resin layer was peeled from the laminate and the peel strength when the polyethylene resin layer was peeled from the laminate were measured, but since both showed the above values, one value was recorded. The same applies below.

[0090] Next, the packaging film of Example 1 was cut into pieces measuring 60 mm x 100 mm in length x width to prepare several identical sample pieces, which were then immersed in tap water at room temperature and left at room temperature (23° C.). After immersion, one sample piece was taken out every 20 minutes to check the peelability between the layers.

[0091] As a result, after 6 hours, the aluminum thin film layer and the polyethylene resin layer were peeled off without any resistance, and after 24 hours, the polyethylene terephthalate resin layer and the aluminum thin film layer were peeled off without any resistance.

[0092] [Example 2] 15 parts by weight of styrene-maleic anhydride resin (acid value: 270 mg-KOH / g) (product name "SMA17352P" manufactured by Kawahara Oil Chemical Co., Ltd.), 4 parts by weight of acrylic resin (acid value: 4 mg-KOH / g, glass transition temperature: 47°C) (product name "UH2011" manufactured by Toa Gosei Co., Ltd.), and 1 part by weight of cellulose derivative (product name "CAB-381-0.5" manufactured by Eastman Chemical Japan Co., Ltd.) were dissolved in a mixed solvent of 50 parts by weight of ethyl acetate and 30 parts by weight of isopropyl alcohol to obtain a uniform resin liquid (coating agent). Of the coating agents, the styrene-maleic anhydride resin is an alkali-soluble polymer. The apparent acid value of this coating agent is 203 mg-KOH / g.

[0093] This coating agent was applied to the back of a 15 μm-thick nylon film (manufactured by Unitika Co., Ltd. under the trade name "EMBLEM ON") in a solid manner using a gravure printing method to a thickness of about 1 μm, and then dried with hot air at about 80° C. to form an intervening layer. Next, white ink (manufactured by Toyo Ink Co., Ltd. under the trade name "Rio Alpha S") was printed in a solid manner to a thickness of about 1 μm on the back of this intervening layer using a gravure printing method. Thereafter, a dry laminating adhesive (manufactured by DIC Graphics Co., Ltd. under the trade name "LX500") was applied in a solid manner to a thickness of about 3 μm on the back of the printed ink layer using a gravure printing method, and the solvent component was volatilized to dry the adhesive so that it could be adhered, and a 70 μm-thick polyethylene film (manufactured by Tamapoly Co., Ltd. under the trade name "SE620") was laminated and bonded. As a result, a packaging film was produced in the following order from the front side: nylon resin layer / approximately 1 μm-thick alkali-soluble intervening layer / printed ink layer / adhesive layer / polyethylene resin layer.

[0094] When the peel strength of the packaging film of Example 2 was measured in the same manner as in Example 1, the 180° peel strength was 4.0 N / 15 mm, indicating that the film was adhered with sufficient strength.

[0095] Next, the packaging film of Example 2 was cut to a size of 60 mm x 100 mm to prepare one sample piece. This sample piece was immersed in a 1.5% by weight aqueous solution of sodium hydroxide at 85°C and continued to be stirred simply while maintaining the temperature, and the state of peeling between the nylon layer and the polyethylene layer was observed every 20 minutes.

[0096] As a result, 24 hours after the start of immersion, the nylon layer and the polyethylene layer were separated.

[0097] [Example 3] An acrylic acid copolymer resin having an acid value of 63 (mg-KOH / g) was prepared by mixing an acrylic acid copolymer resin (acid value: 50 mg-KOH / g) (manufactured by Mitsubishi Rayon Co., Ltd. under the trade name "Dianal LR-1941") and an acrylic acid copolymer resin (acid value: 85 mg-KOH / g) (manufactured by BASF under the trade name "JONCRYL JDX3000").

[0098] Next, 33 parts by weight of the acrylic acid copolymer resin (acid value: 63 mg-KOH / g) and 3 parts by weight of a cellulose derivative (product name "RS-1sec" manufactured by Corea CNC, solid content 70 parts by weight) were dissolved in a mixed solvent of 44 parts by weight of ethyl acetate and 20 parts by weight of isopropyl alcohol to obtain a uniform resin liquid (coating agent). Of the coating agents, the acrylic acid copolymer resin is an alkali-soluble polymer. The apparent acid value of this coating agent is 57 mg-KOH / g.

[0099] A packaging film was produced in the same manner as in Example 1, except that the coating agent prepared as above was used instead of the water-soluble polymer of Example 1, and a 15 μm-thick nylon film (trade name "EMBLEM ON" manufactured by Unitika Ltd.) was used instead of the aluminum foil. The produced packaging film has a laminated structure of, from the surface side, a polyethylene terephthalate resin layer / an alkali-soluble first intermediate layer having a thickness of about 2 μm / a nylon resin layer having a thickness of about 15 μm / an alkali-soluble second intermediate layer having a thickness of about 2 μm / a polyethylene resin layer.

[0100] When the peel strength of the packaging film of Example 3 was measured in the same manner as in Example 1, the 180° peel strength was 4.0 N / 15 mm, indicating that the film was adhered with sufficient strength.

[0101] Next, the packaging film of Example 3 was cut to a size of 60 mm x 100 mm to prepare several identical sample pieces. These sample pieces were then immersed in a 1.5% by weight aqueous solution of sodium hydroxide at 85°C, and while maintaining that temperature, simple stirring was continued. Every 20 minutes, one sample piece was removed and the peelability between each layer was confirmed.

[0102] As a result, the nylon resin layer and the polyethylene resin layer peeled off without any resistance 20 minutes after the start of immersion.Similarly, the polyethylene terephthalate resin layer and the nylon resin layer peeled off without any resistance 20 minutes after the start of immersion.

[0103] [Example 4] A packaging film was produced in the same manner as in Example 3, except that 1 part by weight of vinyl chloride-vinyl acetate copolymer (trade name "Solvine TA5R" manufactured by Nissin Chemical Industry Co., Ltd.) was added to the coating agent of Example 3, and the amount of isopropyl alcohol was changed to 19 parts by weight. The apparent acid value of this coating agent was 56 mg-KOH / g.

[0104] When the peel strength of the packaging film of Example 4 was measured in the same manner as in Example 1, the 180° peel strength was 4.5 N / 15 mm, indicating that the film was adhered with sufficient strength.

[0105] Next, the packaging film of Example 4 was cut to a size of 60 mm x 100 mm to prepare several identical sample pieces. These sample pieces were then immersed in a 1.5% by weight aqueous solution of sodium hydroxide at 85°C, and while maintaining that temperature, simple stirring was continued. Every 20 minutes, one sample piece was removed and the peelability between each layer was confirmed.

[0106] As a result, the nylon resin layer and the polyethylene resin layer peeled off without any resistance 20 minutes after the start of immersion. Similarly, the polyethylene terephthalate resin layer and the nylon resin layer peeled off without any resistance 20 minutes after the start of immersion. Furthermore, when the packaging film was visually observed before immersion, it was found that the laminate structure was highly uniform and had excellent design.

[0107] [Example 5] A packaging film was produced in the same manner as in Example 2, using the coating agent prepared in Example 3. The produced packaging film had a laminated structure of, from the surface side, a nylon resin layer / an alkali-soluble intermediate layer having a thickness of about 1 μm / a printing ink layer / an adhesive layer / a polyethylene resin layer.

[0108] When the peel strength of the packaging film of Example 5 was measured in the same manner as in Example 1, the 180° peel strength was 4.0 N / 15 mm, indicating that the film was adhered with sufficient strength.

[0109] Next, the packaging film of Example 5 was cut to a size of 60 mm x 100 mm to prepare one sample piece. This sample piece was immersed in a 1.5% by weight aqueous solution of sodium hydroxide at 85°C, and while maintaining the temperature, simple stirring was continued, and the state of peeling between the nylon layer and the polyethylene layer was observed every 20 minutes.

[0110] As a result, the nylon layer and the polyethylene layer were separated 20 minutes after the start of immersion.

[0111] [Example 6] Using the coating agent prepared in Example 4, a packaging film was produced in the same manner as in Example 2. The produced packaging film had a laminated structure of, from the surface side, a nylon resin layer / an alkali-soluble intermediate layer having a thickness of about 1 μm / a printing ink layer / an adhesive layer / a polyethylene resin layer.

[0112] When the peel strength of the packaging film of Example 6 was measured in the same manner as in Example 1, the 180° peel strength was 4.5 N / 15 mm, indicating that the film was adhered with sufficient strength.

[0113] Next, the packaging film of Example 6 was cut to a size of 60 mm x 100 mm to prepare one sample piece. This sample piece was immersed in a 1.5% by weight aqueous solution of sodium hydroxide at 85°C, and while maintaining the temperature, simple stirring was continued, and the state of peeling between the nylon layer and the polyethylene layer was observed every 20 minutes.

[0114] As a result, the nylon layer and the polyethylene layer were separated 20 minutes after the start of immersion. Furthermore, visual inspection of the packaging film before immersion revealed that the laminated structure was highly uniform and had excellent design properties.

[0115] [Comparative Example] A packaging film was prepared in the same manner as in Example 2, except that no coating agent was applied (no alkali-soluble intervening layer was formed), with the nylon resin layer / printed ink layer / adhesive layer / polyethylene resin layer in that order from the surface side.

[0116] The packaging film of the comparative example was also measured for peel strength in the same manner as in Example 1, and found to have a 180° peel strength of 4.0 N / 15 mm, indicating sufficient adhesion strength. The packaging film of the comparative example was also immersed in a 1.5 wt % sodium hydroxide aqueous solution at 85°C in the same manner as in Example 2, and the state of peeling between the layers was observed. As a result, no separation of the nylon layer and the polyethylene layer was observed even after 24 hours. [Explanation of symbols]

[0117] 1 Packaging film 21,22,23,24 Base material layer 3 Intervening layer 41,42 Printing ink layer

Claims

1. A flexible packaging material for sealingly packaging an article, The packaging film is made of a laminate including a first base material layer, an intermediate layer, a printing ink layer, and a second base material layer made of a different material from the first base material layer, laminated in this order; The intermediate layer is a layer that enables two base layers made of different materials to be separated by immersion in a solvent, the second base layer is a resin layer having a sealant property on the back surface of the packaging film, the resin layer having a sealant property is a low-density polyethylene layer or an ethylene-propylene copolymer layer, The first base layer is an outermost surface of the packaging film and is made of a polyester-based resin layer or a polyamide-based resin layer, the intermediate layer is alkali-soluble and contains a first acrylic acid copolymer resin and a second acrylic acid copolymer resin; The soft packaging material, wherein the apparent acid value of the intermediate layer is 40 mg-KOH / g or more and 150 mg-KOH / g or less.

2. A third base material layer made of a material different from both the first base material layer and the second base material layer is further provided between the printing ink layer and the second base material layer, the third base layer is a layer having a gas barrier property, Further comprising a second intermediate layer between the second base layer and the third base layer; the second intermediate layer is a layer that enables two base layers made of different materials to be separated by immersion in a solvent; the second intermediate layer is alkali-soluble and contains the first acrylic acid copolymer resin and the second acrylic acid copolymer resin, 2. The flexible packaging material according to claim 1, wherein the apparent acid value of the second intermediate layer is 40 mg-KOH / g or more and 150 mg-KOH / g or less.

3. A flexible packaging material for sealingly packaging an article, A packaging film is provided which is a laminate in which a first base material layer, a printing ink layer, an intervening layer, and a second base material layer made of a different material from the first base material layer are laminated in this order, The intermediate layer is a layer that enables two base layers made of different materials to be separated by immersion in a solvent, the second base layer is a resin layer having a sealant property on the back surface of the packaging film, the resin layer having a sealant property is a low-density polyethylene layer or an ethylene-propylene copolymer layer, The first base layer is an outermost surface of the packaging film and is made of a polyester-based resin layer or a polyamide-based resin layer, the intermediate layer is alkali-soluble and contains a first acrylic acid copolymer resin and a second acrylic acid copolymer resin; The soft packaging material, wherein the apparent acid value of the intermediate layer is 40 mg-KOH / g or more and 150 mg-KOH / g or less.

4. a third base material layer between the intermediate layer and the second base material layer, the third base material layer being made of a material different from both the first base material layer and the second base material layer; the third base layer is a layer having a gas barrier property, Further comprising a second intermediate layer between the second base layer and the third base layer; the second intermediate layer is a layer that enables two base layers made of different materials to be separated by immersion in a solvent; the second intermediate layer is alkali-soluble and contains the first acrylic acid copolymer resin and the second acrylic acid copolymer resin, 4. The flexible packaging material according to claim 3, wherein the apparent acid value of the second intermediate layer is 40 mg-KOH / g or more and 150 mg-KOH / g or less.

5. A method for recycling the flexible packaging material according to claim 1 or 2, comprising the steps of: A recycling method comprising the step of treating the packaging film with an alkali to separate the first base material layer and the second base material layer and to separate the printing ink layer from the first base material layer.

6. A method for recycling the flexible packaging material according to claim 3 or 4, comprising the steps of: A recycling method comprising the step of treating the packaging film with an alkali to separate the first base material layer and the second base material layer and to separate the printing ink layer from the second base material layer.

Images