JP2023183633A - Multilayer body, method for producing the same, and packaging bag - Google Patents

Abstract

To provide a multilayer body with improved dimensional stability of printed patterns and lamination strength.SOLUTION: A multilayer body has a structure where a base material layer, a print layer, a first adhesive layer, an intermediate layer, a second adhesive layer, and a sealant layer are stacked in this order; the base material layer, the intermediate layer and the sealant layer are each composed of an unstretched polyethylene film; the first adhesive layer is formed using a solvent-free adhesive; and the ratio of polyethylene in the multilayer body is 90 mass% or more.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a laminate, a method for manufacturing the same, and a packaging bag. More specifically, the present disclosure relates to a laminate with excellent material recyclability and low environmental impact, a method for manufacturing the same, and a packaging bag.

Packaging bags are made of various materials, depending on the nature of the contents to be packaged, the amount of contents, post-treatment to prevent deterioration of the contents, the form in which the packaging bags are transported, the method of opening the packaging bags, the method of disposal, etc. are used in combination.

For example, in packaging bags for flexible packages that use laminated films, biaxially stretched films such as polypropylene and polyester are used to obtain the mechanical strength of the packaging bags, and polyethylene and polyester are used to seal the contents as packaging bags. It is used in combination with polypropylene, ethylene vinyl acetate copolymer, etc. as the heat seal material. Additionally, in order to suppress the deterioration of the contents, aluminum foil or ethylene vinyl alcohol copolymer is laminated.

The above-mentioned laminates using various functionally separated materials are designed with emphasis on suitability in each process, from packaging the contents to transportation, storage, and opening. However, as awareness of environmental issues has increased in recent years, emphasis has been placed on functions such as resource saving and recyclability of various products, and similar functions are now being required for the laminates used in packaging bags. There is. Generally, packaging materials are considered to be highly recyclable if their main resin content is 90% by mass or more, but many conventional packaging materials contain multiple resin materials and, in some cases, paper and metal materials. Currently, it is not recycled because it does not meet this standard.

Therefore, Patent Document 1 describes that in a laminate including a base material, an adhesive layer, and a heat seal layer, the base material and the heat seal layer are made of polyethylene. By configuring the base material and the heat-sealing layer from the same material, it becomes easier to meet the above-mentioned recyclability criteria. Moreover, Patent Document 1 proposes using a stretched polyethylene film as a base material, and describes that printability can be improved thereby.

JP 2020-55157 Publication

When a polyethylene film is used as the base material layer of a laminate, the base material layer is likely to be thermally deformed during the laminate manufacturing process that involves heat drying due to the material's soft and easily heat-sealable properties. When the base material layer is thermally deformed, the dimensions of the pattern printed on the base material layer expand and contract, resulting in problems such as poor appearance and misalignment of the eye marks, making it impossible to make bags.

In addition, when a stretched polyethylene film is used for the base layer, it is easy to suppress the expansion and contraction of the base layer, but the adhesion between the base layer and the intermediate layer or sealant layer (heat seal layer) is insufficient. There is a problem in that when a packaging bag is formed, the bag is easily torn.

The present disclosure has been made in view of the problems of the prior art described above, and provides a laminate with good dimensional stability of printed patterns and lamination strength, a method for manufacturing the same, and a packaging bag using the laminate. The purpose is to provide.

In order to solve the above problems, the present disclosure provides the following laminate, method for manufacturing the same, and packaging bag.

[1] It has a structure in which a base material layer, a printing layer, a first adhesive layer, an intermediate layer, a second adhesive layer, and a sealant layer are laminated in this order; The material layer, the intermediate layer, and the sealant layer are all composed of unstretched polyethylene films, and the first adhesive layer is a layer formed using a solvent-free adhesive, and the first adhesive layer is a layer formed using a solvent-free adhesive, and the first adhesive layer is a layer formed using a solvent-free adhesive, and the first adhesive layer is a layer formed using a solvent-free adhesive, and A laminate in which the proportion of polyethylene is 90% by mass or more.
[2] The laminate according to [1] above, wherein the solvent-free adhesive is a two-component curable urethane adhesive.
[3] The laminate according to [1] or [2] above, wherein the base layer and the intermediate layer both contain high-density polyethylene or medium-density polyethylene.
[4] The laminate according to any one of [1] to [3] above, wherein the sealant layer contains low-density polyethylene.
[5] The laminate according to any one of [1] to [4] above, comprising an inorganic oxide layer on at least one surface of the intermediate layer, the inorganic oxide layer containing a metal oxide.
[6] The laminate according to [5] above, comprising a gas barrier coating layer between the inorganic oxide layer and the first adhesive layer or the second adhesive layer.
[7] The laminate according to any one of [1] to [6] above, wherein the second adhesive layer is a gas barrier adhesive layer formed using a gas barrier adhesive.
[8] A packaging bag made from the laminate according to any one of [1] to [7] above.
[9] A method for producing a laminate according to any one of [1] to [7] above, which comprises forming the printing layer on the substrate layer by a printing method using ink to form a printing substrate. and a laminating step of laminating the printing substrate and a laminated film including the intermediate layer, the second adhesive layer, and the sealant layer using the solvent-free adhesive. A method for manufacturing a laminate comprising:
[10] The above solvent-free adhesive is a two-part curing urethane adhesive, and the viscosity of the urethane adhesive immediately after mixing the two parts is 200 to 2500 mPa·s at 40°C. 9]. The method for producing a laminate according to item 9.
[11] In the above bonding step, the heating temperature of the solvent-free adhesive is within the range of 50 to 90°C so that the viscosity of the solvent-free adhesive at the heating temperature is 200 to 2000 mPa・s. The method for manufacturing a laminate according to the above [9] or [10], wherein the method is set as follows.

According to the present disclosure, it is possible to provide a laminate with good dimensional stability of a printed pattern and good lamination strength, a method for manufacturing the same, and a packaging bag using the laminate.

FIG. 1 is a schematic cross-sectional view showing an embodiment of a laminate of the present disclosure. FIG. 1 is a schematic cross-sectional view showing an embodiment of a laminate of the present disclosure.

Embodiments of the present disclosure will be described in detail below, with reference to the drawings as the case may be. However, the present disclosure is not limited to the following embodiments.

<Laminated body>
The laminate according to this embodiment has a structure in which a base layer, a printing layer, a first adhesive layer, an intermediate layer, a second adhesive layer, and a sealant layer are laminated in this order. The base layer, the intermediate layer, and the sealant layer are all made of unstretched polyethylene film, the first adhesive layer is a layer formed using a solvent-free adhesive, and the laminate It is a laminate in which the proportion of polyethylene is 90% by mass or more. According to the above laminate, by using an unstretched polyethylene film as the base layer, the adhesion between the base layer and the intermediate layer is improved compared to when a stretched polyethylene film is used, and good laminate strength is achieved. is obtained. Furthermore, better laminate strength can be obtained by using unstretched polyethylene films for all of the base layer, intermediate layer, and sealant layer. Further, according to the above-mentioned laminate, since the first adhesive layer is formed using a solvent-free adhesive, it is possible to form the first adhesive layer using a solvent-based adhesive. Heat drying (oven drying, etc.) for removing the solvent is not performed, and there is no residual solvent in the first adhesive layer. Therefore, even when an unstretched polyethylene film is used as the base layer, expansion and contraction of the base layer can be suppressed, and good dimensional stability of the printed pattern can be obtained. Further, since no residual solvent is present in the first adhesive layer, it is possible to suppress the occurrence of rubbing or bleeding in the printed pattern. Further, since there is no residual solvent, it is possible to suppress the odor of the solvent when it is packaged. Furthermore, the laminate having the above structure has excellent flexibility and can obtain good compressive strength.

FIGS. 1 and 2 are schematic cross-sectional views each showing an embodiment of the laminate of the present disclosure. The laminate 1 shown in FIG. 1 includes a base layer 10, a printed layer 12, a first adhesive layer 40, an intermediate layer 20, a second adhesive layer 50, and a sealant layer 30. The laminate 2 shown in FIG. 2 includes a base layer 10, a printed layer 12, a first adhesive layer 40, an intermediate layer 20, an anchor coat layer 13, an inorganic oxide layer 14, and a gas barrier coating. layer 15, a second adhesive layer 50, and a sealant layer 30. Here, the base layer 10, the intermediate layer 20, and the sealant layer 30 are all made of unstretched polyethylene film. Further, the first adhesive layer 40 is a layer formed using a solvent-free adhesive. Further, the proportion of polyethylene in the laminate is 90% by mass or more. Each layer will be explained below.

(Base material layer)
The base layer 10 is a layer made of an unstretched polyethylene film. The base material layer 10 is a portion that becomes the outer surface when a packaging bag is formed using the laminates 1 and 2.

From the viewpoint of strength and heat resistance, the base layer 10 is a film made of high density polyethylene (density 0.94 g/cm ³ or more) or medium density polyethylene (density 0.925 to 0.945 g/cm ³ ). can be used. These materials may be derived from petroleum or plants, or may be a mixture thereof. Further, the surface of the base material layer 10 can be subjected to adhesion-facilitating treatment by dry surface treatment such as corona treatment or atmospheric pressure plasma treatment. Furthermore, it is also possible to use as the base layer 10 a multilayered unstretched polyethylene film obtained by extruding polyethylenes having different densities by a coextrusion method.

Here, unstretched polyethylene film is a film that is not stretched during film formation, and has spherical crystals (spherulites) of about 10 to 100 μm composed of randomly folded polyethylene molecular chains, which are non-crystalline molecules. A polyethylene film that has an interconnected structure. An unstretched polyethylene film has the property that when it receives a strong impact, the spherulites are destroyed and the molecular chains are oriented and stretched, thereby preventing the film itself from tearing. Therefore, a package made of a laminate in which unstretched polyethylene films are laminated as the base layer 10, intermediate layer 20, and sealant layer 30 (a packaging bag is made, filled with contents, and sealed) cannot be dropped. It is characterized by excellent bag strength.

The thickness of the base material layer 10 is preferably 10 μm or more and 50 μm or less, more preferably 12 μm or more and 35 μm or less. By setting the thickness of the base material layer 10 to 10 μm or more, the strength of the laminates 1 and 2 can be improved. By setting the thickness of the base material layer 10 to 50 μm or less, the processability of the laminates 1 and 2 can be improved.

The base material layer 10 can be produced by forming polyethylene into a film by a T-die method, an inflation method, or the like. When producing the base material layer 10 by the T-die method, the melt flow rate (MFR) of polyethylene is preferably 3 g/10 minutes or more and 20 g/10 minutes or less. By setting the MFR to 3 g/10 minutes or more, the processability of the laminate can be improved. Further, by setting the MFR to 20 g/10 minutes or less, it is possible to prevent the fabricated base layer 10 from breaking.

When producing the base material layer 10 by an inflation method, the MFR of polyethylene is preferably 0.5 g/10 minutes or more and 5 g/10 minutes or less. By setting the MFR to 0.5 g/10 minutes or more, the processability of the laminate can be improved. Furthermore, by setting the MFR to 5 g/10 minutes or less, film formability can be improved.

The melting points of high-density polyethylene and medium-density polyethylene used as the base material layer 10 are approximately 120°C to 140°C. On the other hand, the melting point of low density polyethylene used as the sealant layer 30 described below is approximately 90°C to 120°C. In order to heat seal the laminate of the base material layer 10 and the sealant layer 30, a heat seal bar, which is a jig of a heat sealing machine, is heated to about 130°C to 140°C, and the base material layer 10 and the intermediate layer to be described later are Heat is conducted to the sealant layer 30 through the sealant layer 20, and the sealant layer 30 is thermally welded.

When the base material layer 10 is stretched under a temperature environment of 70° C. with a tension of 100 N/m, it is preferable that the base layer 10 elongates by 3% or more in the tensile direction. Since the base material layer 10 is composed of an unstretched polyethylene film, it can have an elongation rate of 3% or more when stretched under the above conditions. The base material layer having the above elongation rate has excellent adhesion to the intermediate layer 20 compared to a base material layer made of a stretched polyethylene film having an elongation rate of less than 3%. The elongation rate of the base material layer 10 is preferably 3% or more, but may be 4% or more, or 4.5% or more. Moreover, the elongation rate of the base material layer 10 may be 10% or less, or 8% or less. The elongation rate of the base material layer 10 can be measured using, for example, a thermal analyzer.

(Printing layer)
The printed layer 12 is formed on the surface of the base layer 10 on the first adhesive layer 40 side. The pattern can be formed by any printing method such as ordinary gravure printing or flexographic printing, using ink suitable for each printing method, without any particular limitation. Inks include solvent-based inks and water-based inks, and from an environmental standpoint, it is preferable to use water-based inks. Further, the surface of the base layer 10 may be subjected to surface treatment such as corona treatment or plasma treatment in order to improve the adhesion of the printed layer 12.

(First adhesive layer)
The first adhesive layer 40 is a layer formed using a solvent-free adhesive, and is provided between the base layer 10 and the intermediate layer 20 to bond them together. As the solvent-free adhesive, either a one-component curing type or a two-component curing type adhesive can be used. Examples of solvent-free adhesives include urethane adhesives, epoxy adhesives, silicone adhesives, etc. From the viewpoint of impact resistance, urethane adhesives are preferred, and two-component curing urethane adhesives are preferred. Particularly preferred are agents.

The two-component curable urethane-based solventless adhesive includes a polyol component as a main ingredient and a polyisocyanate component as a curing agent.

The polyol component may be one or a mixture of two or more selected from the group consisting of polyester polyol, polyether polyol, polyether ester polyol, and polyurethane polyol.

The polyester polyol may be, for example, an ester reaction product of a polycarboxylic acid, a dialkyl ester of a polycarboxylic acid, or a mixture thereof, and a glycol solvent. The polyhydric carboxylic acid may be, for example, succinic acid, glutaric acid, isophthalic acid, terephthalic acid, adipic acid, pimelic acid, corkic acid, azelaic acid, sebacic acid, dodecanedioic acid, dimer acid. The glycol solvent may be, for example, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, butylene glycol, neopentyl glycol, 1,6-hexanediol.

The polyether polyol may be, for example, a polymer of an oxirane compound and a low-molecular polyol. The oxirane compound may be, for example, ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran. The low molecular weight polyol may be water, ethylene glycol, propylene glycol, trimethylolpropane, glycerin.

The polyether ester polyol may be obtained, for example, by reacting a polycarboxylic acid, a dialkyl ester of a polycarboxylic acid, or a mixture thereof with a polyether polyol.

Polyurethane polyols may be, for example, reaction products of polyester polyols, polyether polyols, polyether ester polyols and polyisocyanate monomers.

The polyisocyanate component may be an aliphatic polyisocyanate, an aromatic polyisocyanate, or a mixture thereof.

The aliphatic polyisocyanate may be, for example, a polyisocyanate monomer, a polyisocyanate derivative, or a polyisocyanate-terminated prepolymer. The polyisocyanate monomer may be, for example, tetramethylene diisocyanate, isopropylene diisocyanate, 1,6-hexamethylene diisocyanate, dodecamethylene diisocyanate, trimethylhexamethylene diisocyanate. The polyisocyanate derivative may be 1,3-cyclohexylene diisocyanate, 1,4-cyclohexylene diisocyanate, lysine diisocyanate, isophorone diisocyanate.

The aromatic polyisocyanate may be, for example, a polyisocyanate monomer, a polyisocyanate derivative, or a polyisocyanate-terminated prepolymer. The polyisocyanate monomer may be, for example, tolylene diisocyanate, phenylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate. The polyisocyanate derivative may be, for example, an isocyanurate derived from a polyisocyanate monomer. The polyisocyanate-terminated prepolymer may be a difunctional polyisocyanate containing terminal isocyanate groups obtained by reacting a polyisocyanate monomer with a difunctional polyol compound such as polypropylene glycol. Further, the polyisocyanate-terminated prepolymer may be a polyfunctional polyisocyanate containing terminal isocyanate groups obtained by reacting a polyisocyanate monomer with a trifunctional or higher functional polyol compound such as trimethylolpropane.

The solvent-free adhesive is preferably a urethane adhesive containing adipic acid and isophthalic acid from the viewpoint of further improving lamination strength. Furthermore, when a urethane adhesive containing adipic acid and isophthalic acid is used, it is possible to improve resistance to heat sterilization treatments such as boiling treatment and retort treatment, and to suppress a decrease in laminate strength due to heat sterilization treatment. Can be done.

Further, the solvent-free adhesive does not need to contain glycidoxyalkylalkoxysilane. Examples of glycidoxyalkylalkoxysilane include 3-glycidyloxypropyltrimethoxysilane (GPTMS), 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, 2-(3,4-epoxy Examples include cyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, and the like. Many common adhesives contain glycidoxyalkylalkoxysilane as an adhesion aid, but in the laminate of this embodiment, the solvent-free adhesive does not contain glycidoxyalkylalkoxysilane. Even if it is not, sufficient lamination strength can be obtained. In particular, when the solvent-free adhesive is a urethane-based adhesive containing adipic acid and isophthalic acid, even if the solvent-free adhesive does not contain glycidoxyalkylalkoxysilane, more sufficient lamination strength can be achieved. Obtainable.

The coating amount of the first adhesive layer 40 is preferably 0.5 g/m ² or more and 3.0 g/m ² or less, more preferably 1.0 g/m ² or more and 2.0 g/m ^{2 or} less. If the coating amount of the first adhesive layer 40 is 0.5 g/m ² or more, the effect of suppressing delamination between the base layer 10 and the intermediate layer 20 can be enhanced. If the coating amount of the first adhesive layer 40 is 3.0 g/m ² or less, it is possible to suppress the occurrence of winding misalignment during processing of the laminate, and to improve the appearance quality of the laminate. In addition, appropriate lamination strength can be obtained.

(middle class)
The intermediate layer 20 is a layer made of an unstretched polyethylene film. The polyethylene contained in the intermediate layer 20 is preferably high-density polyethylene or medium-density polyethylene from the viewpoint of strength and heat resistance. These materials may be derived from petroleum or plants, or may be a mixture thereof. As the intermediate layer 20, similarly to the base material layer 10, it is also possible to use an unstretched polyethylene film with a multilayer structure obtained by extruding polyethylenes having different densities by a coextrusion method. Further, the surface of the intermediate layer 20 can be subjected to adhesion-facilitating treatment by dry surface treatment such as corona treatment or atmospheric pressure plasma treatment.

The thickness of the intermediate layer 20 is preferably 9 μm or more and 50 μm or less, more preferably 12 μm or more and 35 μm or less. By setting the thickness of the intermediate layer 20 to 9 μm or more, the strength and heat resistance of the laminate can be improved. By setting the thickness of the intermediate layer 20 to 50 μm or less, the processability of the laminate can be improved.

The intermediate layer 20 can be produced by forming a polyethylene film by a T-die method, an inflation method, or the like. When producing the intermediate layer 20 by the T-die method, the melt flow rate (MFR) of polyethylene is preferably 3 g/10 minutes or more and 20 g/10 minutes or less. By setting the MFR to 3 g/10 minutes or more, the processability of the laminate can be improved. Further, by setting the MFR to 20 g/10 minutes or less, it is possible to prevent the produced film from breaking.

When producing the intermediate layer 20 by the inflation method, the MFR of polyethylene is preferably 0.5 g/10 minutes or more and 5 g/10 minutes or less. By setting the MFR to 0.5 g/10 minutes or more, the processability of the laminate can be improved. Furthermore, by setting the MFR to 5 g/10 minutes or less, film formability can be improved.

(Anchor coat layer)
In the laminate 2, an anchor coat layer 13, an inorganic oxide layer 14, and a gas barrier coating layer 15 are formed on at least one surface of the intermediate layer 20. In this embodiment, the anchor coat layer 13 can be formed using a known anchor coat agent. By forming the inorganic oxide layer 14 on the intermediate layer 20 via the anchor coat layer 13, the adhesion of the inorganic oxide layer 14 to the intermediate layer 20 can be improved.

Examples of the anchor coating agent include polyester polyurethane resins and polyether polyurethane resins. From the viewpoint of heat resistance and interlayer adhesive strength, polyester-based polyurethane resins are preferred.

A polyvinyl alcohol resin may be used as the anchor coating agent. The polyvinyl alcohol resin may be any resin having a vinyl alcohol unit formed by saponifying a vinyl ester unit, and examples thereof include polyvinyl alcohol (PVA) and ethylene-vinyl alcohol copolymer (EVOH).

When polyvinyl alcohol resin is used as the anchor coating agent, methods for forming the anchor coating layer include coating using a polyvinyl alcohol resin solution, multilayer extrusion, and the like. In the case of multilayer extrusion, the layers may be laminated via an adhesive resin such as maleic anhydride graft-modified polyethylene.

(Inorganic oxide layer)
The inorganic oxide layer 14 provides the laminate 2 with oxygen barrier properties and water vapor barrier properties. In the laminate 2, the anchor coat layer 13, the inorganic oxide layer 14, and the gas barrier coating layer 15 are formed on the surface of the intermediate layer 20 facing the second adhesive layer 50; You can.

Examples of the structure of the inorganic oxide layer 14 include a vapor deposited layer made of metal oxide such as aluminum oxide, silicon oxide, magnesium oxide, and tin oxide. From the viewpoint of transparency and barrier properties, the metal oxide may be selected from the group consisting of aluminum oxide, silicon oxide, and magnesium oxide. Furthermore, in consideration of cost, aluminum oxide and silicon oxide are selected. Furthermore, from the viewpoint of excellent tensile stretchability during processing, it is more preferable to use a layer using silicon oxide. By using the inorganic oxide layer 14 as a barrier film made of a metal oxide, high barrier properties can be obtained with a very thin layer that does not affect the recyclability of the laminate 2.

Because the vapor-deposited layer made of metal oxide is transparent, compared to the vapor-deposited layer made of metal, the user holding the packaging material made of the laminate may misunderstand that metal foil is used. It has the advantage of being difficult to do.

The thickness of the inorganic oxide layer made of aluminum oxide is preferably 5 nm or more and 30 nm or less. When the film thickness is 5 nm or more, sufficient gas barrier properties can be obtained. Moreover, when the film thickness is 30 nm or less, it is possible to suppress generation of cracks due to deformation due to internal stress of the thin film, and to suppress deterioration of gas barrier properties. It should be noted that if the film thickness exceeds 30 nm, the cost tends to increase due to an increase in the amount of materials used, a longer film formation time, etc., which is not preferable from an economic point of view. From the same viewpoint as above, the thickness of the inorganic oxide layer made of aluminum oxide is more preferably 7 nm or more and 15 nm or less.

The thickness of the inorganic oxide layer made of silicon oxide is preferably 10 nm or more and 50 nm or less. When the film thickness is 10 nm or more, sufficient gas barrier properties can be obtained. Furthermore, when the film thickness is 50 nm or less, it is possible to suppress the occurrence of cracks due to deformation of the thin film due to internal stress, and to suppress deterioration of gas barrier properties. It should be noted that if the film thickness exceeds 50 nm, the cost tends to increase due to an increase in the amount of materials used, a longer film formation time, etc., which is not preferable from an economic point of view. From the same viewpoint as above, the thickness of the inorganic oxide layer made of silicon oxide is more preferably 20 nm or more and 40 nm or less.

The inorganic oxide layer 14 can be formed, for example, by vacuum film formation. In vacuum film formation, a physical vapor deposition method or a chemical vapor deposition method can be used. Examples of the physical vapor deposition method include, but are not limited to, a vacuum evaporation method, a sputtering method, an ion plating method, and the like. Examples of the chemical vapor deposition method include, but are not limited to, a thermal CVD method, a plasma CVD method, a photo CVD method, and the like.

The above vacuum film formation methods include resistance heating vacuum evaporation, EB (Electron Beam) heating vacuum evaporation, induction heating vacuum evaporation, sputtering, reactive sputtering, dual magnetron sputtering, and plasma chemical vapor deposition. (PECVD method) etc. are particularly preferably used. However, in terms of productivity, vacuum evaporation is currently the best method. As a heating means for the vacuum evaporation method, it is preferable to use one of an electron beam heating method, a resistance heating method, and an induction heating method.

(Gas barrier coating layer)
In the laminate 2, a gas barrier coating layer 15 is provided on the inorganic oxide layer 14 for the purpose of improving gas barrier properties and protecting the inorganic oxide layer 14. Although not particularly limited, the gas barrier coating layer 15 may contain a hydroxyl group-containing polymer compound, specifically, at least one of a hydroxyl group-containing polymer compound and its hydrolyzate, metal alkoxide, silane, etc. It may be a heat-dried product of a composition containing at least one selected from the group consisting of a coupling agent and a hydrolyzate thereof.

The gas barrier coating layer 15 is made of, for example, a composition obtained by adding a hydroxyl group-containing polymer compound, a metal alkoxide, and/or a silane coupling agent to water or a water/alcohol mixture (hereinafter referred to as an overcoat agent). ). For example, the overcoat agent can be made by directly combining a solution of a hydroxyl group-containing polymer compound, which is a water-soluble polymer, in an aqueous (water or water/alcohol mixed) solvent with a metal alkoxide and/or a silane coupling agent; It can be prepared by mixing these with those that have been subjected to a treatment such as hydrolysis in advance.

Examples of the hydroxyl group-containing polymer compound include polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyvinylpyrrolidone, starch, methylcellulose, carboxymethylcellulose, sodium alginate, and the like. Among these, it is preferable to use polyvinyl alcohol (PVA) as an overcoat agent for the gas barrier coating layer since it has particularly excellent gas barrier properties.

Examples of the metal alkoxide include compounds represented by the following general formula (I).
M(OR ¹ ) _m (R ² ) _nm ...(I)
In the above general formula (I), R ¹ and R ² are each independently a monovalent organic group having 1 to 8 carbon atoms, and are preferably an alkyl group such as a methyl group or an ethyl group. M represents an n-valent metal atom such as Si, Ti, Al, and Zr. m is an integer from 1 to n. In addition, when a plurality of R ¹ or R ² exist, R ¹ or R ² may be the same or different.

Specific examples of the metal alkoxide include tetraethoxysilane [Si(OC ₂ H ₅ ) ₄ ], triisopropoxyaluminum [Al(O-2′-C ₃ H ₇ ) ₃ ], and the like. Tetraethoxysilane and triisopropoxyaluminum are preferred because they are relatively stable in aqueous solvents after hydrolysis.

Examples of the silane coupling agent include compounds represented by the following general formula (II).
Si(OR ¹¹ ) _p (R ¹² ) _3-p R ¹³ ...(II)
In the above general formula (II), R ¹¹ represents an alkyl group such as a methyl group or an ethyl group, and R ¹² represents an alkyl group, an aralkyl group, an aryl group, an alkenyl group, an alkyl group substituted with an acryloxy group, or a methacryloxy group. represents a monovalent organic group such as an alkyl group substituted with a group, R ¹³ represents a monovalent organic functional group, and p represents an integer of 1 to 3. In addition, when a plurality of R ¹¹ or R ¹² exist, R ¹¹ or R ¹² may be the same or different. The monovalent organic functional group represented by ^R13 is a monovalent organic functional group containing a glycidyloxy group, an epoxy group, a mercapto group, a hydroxyl group, an amino group, an alkyl group substituted with a halogen atom, or an isocyanate group. Examples include groups.

Specifically, the silane coupling agent includes vinyltrimethoxysilane, γ-chloropropylmethyldimethoxysilane, γ-chloropropyltrimethoxysilane, glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, Examples include silane coupling agents such as γ-methacryloxypropylmethyldimethoxysilane.

Moreover, the silane coupling agent may be a polymer obtained by polymerizing the compound represented by the above general formula (II). The multimer is preferably a trimer, more preferably 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate. This is a condensation polymer of 3-isocyanatealkylalkoxysilane. It is known that in this 1,3,5-tris(3-trialkoxysilylalkyl) isocyanurate, the isocyan moiety has no chemical reactivity, but the reactivity is ensured by the polarity of the nurate moiety. Generally, like 3-isocyanate alkyl alkoxylane, it is added to adhesives, etc., and is known as an adhesion improver. Therefore, by adding 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate to the hydroxyl group-containing polymer compound, the water resistance of the gas barrier coating layer 15 can be improved due to hydrogen bonding. 3-Isocyanate alkyl alkoxyrane has high reactivity and low liquid stability, whereas 1,3,5-tris(3-trialkoxysilylalkyl) isocyanurate is not water-soluble due to the polarity of the nurate moiety. However, it is easily dispersed in aqueous solutions and can maintain stable liquid viscosity. Furthermore, the water resistance properties of 3-isocyanatealkylalkoxyrane and 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate are equivalent.

1,3,5-Tris(3-trialkoxysilylalkyl)isocyanurate is sometimes produced by thermal condensation of 3-isocyanatepropylalkoxysilane, and may also contain the raw material 3-isocyanatepropylalkoxysilane. However, there is no particular problem. More preferred is 1,3,5-tris(3-trialkoxysilylpropyl)isocyanurate, and even more preferred is 1,3,5-tris(3-trimethoxysilylpropyl)isocyanurate. 1,3,5-tris(3-trimethoxysilylpropyl)isocyanurate is practically advantageous because the methoxy group has a high hydrolysis rate and those containing a propyl group are available at relatively low cost.

The amount of metal alkoxide in the overcoat agent can be 1 to 4 parts by mass per 1 part by mass of the hydroxyl group-containing polymer compound from the viewpoint of adhesion with the inorganic oxide layer 14 and maintaining gas barrier properties, and 2 It may be up to 3 parts by weight. Similarly, the amount of the silane coupling agent can be 0.01 to 1 part by weight, and may be 0.1 to 0.5 part by weight, per 1 part by weight of the hydroxyl group-containing polymer compound. When using a silane compound (alkoxysilane) as the metal alkoxide, the amount of the silane compound (metal alkoxide and silane coupling agent) in the overcoat agent is 1 to 4 parts by mass per 1 part by mass of the hydroxyl group-containing polymer compound. The amount may be 2 to 3 parts by mass.

If necessary, known additives such as isocyanate compounds, dispersants, stabilizers, viscosity modifiers, and colorants may be added to the overcoat agent within a range that does not impair gas barrier properties.

The overcoat agent may be applied by, for example, a dipping method, a roll coating method, a gravure coating method, a reverse gravure coating method, an air knife coating method, a comma coating method, a die coating method, a screen printing method, a spray coating method, a gravure offset method, etc. Can be done. The coating film formed by applying the overcoat agent can be dried by, for example, a hot air drying method, a hot roll drying method, a high frequency irradiation method, an infrared irradiation method, a UV irradiation method, or a combination thereof.

The temperature at which the coating film is dried can be, for example, 50 to 150°C, preferably 70 to 100°C. By setting the temperature during drying within the above range, it is possible to further suppress the occurrence of cracks in the inorganic oxide layer 14 and the gas barrier coating layer 15, and it is possible to exhibit excellent barrier properties.

The gas barrier coating layer 15 may be formed using an overcoat agent containing a hydroxyl group-containing polymer compound (eg, polyvinyl alcohol resin) and a silane compound. An acid catalyst, an alkali catalyst, a photoheavy initiator, etc. may be added to the overcoat agent as necessary.

Examples of the silane compound include silane coupling agents, polysilazane, siloxane, etc. Specifically, tetramethoxysilane, tetraethoxysilane, glycidoxypropyltrimethoxysilane, acryloxypropyltrimethoxysilane, hexamethyldisilazane, etc. etc.

The thickness of the gas barrier coating layer 15 is preferably 50 to 1000 nm, more preferably 100 to 500 nm. When the thickness of the gas barrier coating layer 15 is 50 nm or more, it tends to be able to obtain more sufficient gas barrier properties, and when it is 1000 nm or less, it tends to be able to maintain sufficient flexibility.

(Second adhesive layer)
The second adhesive layer 50 is a layer containing at least one type of adhesive, and is provided between the intermediate layer 20 and the sealant layer 30 to bond them together. Either a one-component curing type or a two-component curing type adhesive can be used for the second adhesive layer 50. Examples of the adhesive include urethane adhesive, epoxy adhesive, silicone adhesive, and the like. These adhesives may contain a layered inorganic compound for the purpose of further enhancing barrier properties.

The second adhesive layer 50 (gas barrier adhesive layer) having gas barrier properties can also be formed using an adhesive that can exhibit gas barrier properties after curing. Thereby, the gas barrier performance of the laminate 2 can be further improved. Further, when the second adhesive layer 50 is a gas barrier adhesive layer, the laminate 2 does not need to include the gas barrier coating layer 15. By forming an adhesive layer in contact with the inorganic oxide layer 14 with an adhesive that exhibits gas barrier properties, deterioration of gas barrier properties due to cracking in the inorganic oxide layer 14 can be suppressed even without the gas barrier coating layer 15. is possible. Examples of such gas barrier adhesives include epoxy adhesives and polyester/polyurethane adhesives. Specific examples include "Maxive" manufactured by Mitsubishi Gas Chemical Co., Ltd. and "Paslim" manufactured by DIC Corporation.

The second adhesive layer 50 may be formed using a solvent-free adhesive. As the solvent-free adhesive, the same adhesive as used for forming the first adhesive layer 40 can be used.

The thickness of the second adhesive layer 50 is preferably 0.5 μm or more and 6 μm or less, more preferably 0.8 μm or more and 5 μm or less, and even more preferably 1.0 μm or more and 4.5 μm or less. preferable. By setting the thickness of the second adhesive layer 50 to 0.5 μm or more, the adhesiveness of the second adhesive layer 50 can be improved. By setting the thickness of the second adhesive layer 50 to 6 μm or less, the processability of the laminate 2 can be improved.

(Sealant layer)
The sealant layer 30 is a layer made of an unstretched polyethylene film, and is joined by heat sealing when forming a packaging material such as a packaging bag using the laminates 1 and 2. From the viewpoint of heat-sealability, the polyethylene constituting the sealant layer 30 is preferably low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), or very low-density polyethylene (VLDPE). Furthermore, from the viewpoint of environmental impact, biomass-derived polyethylene or recycled polyethylene may be used for the sealant layer 30. The sealant layer 30 may be composed of an unstretched polyethylene film.

As the low density polyethylene, polyethylene having a density of 0.900 g/cm ³ or more and less than 0.925 g/cm ³ can be used. As the linear low density polyethylene, polyethylene having a density of 0.900 g/cm ³ or more and less than 0.925 g/cm ³ can be used. As the ultra-low density polyethylene, polyethylene having a density of less than 0.900 g/cm ³ can be used. For the sealant layer 30, a copolymer of ethylene and other monomers can be used as long as the properties of the laminates 1 and 2 are not impaired.

The thickness of the sealant layer 30 can be changed as appropriate depending on the weight of the contents to be filled into the packaging bag to be produced. For example, when producing a packaging bag filled with contents of 1 g or more and 200 g or less, the thickness of the sealant layer 30 is preferably 20 μm or more and 60 μm or less. By setting the thickness to 20 μm or more, it is possible to prevent the filled contents from leaking due to damage to the sealant layer 30. By setting the thickness to 60 μm or less, the processability of the laminates 1 and 2 can be improved.

As another example, when producing a standing pouch filled with contents of 50 g or more and 2000 g or less, the thickness of the sealant layer 30 is preferably 50 μm or more and 200 μm or less. By setting the thickness to 50 μm or more, it is possible to prevent the filled contents from leaking due to damage to the sealant layer 30. Moreover, by setting the thickness to 200 μm or less, the processability of the laminates 1 and 2 can be improved, and it is further preferable to set the thickness to 180 μm or less.

Additives such as an antioxidant, an antistatic agent, a nucleating agent, and an ultraviolet absorber may be added to the polyethylene used for the base layer 10, the intermediate layer 20, and the sealant layer 30.

In the laminates 1 and 2 of this embodiment configured as described above, the base layer 10, the intermediate layer 20, and the sealant layer 30 are made of polyethylene, so that the polyethylene content in the laminates 1 and 2 is The proportion is 90% by mass or more. Thereby, the laminates 1 and 2 have high recyclability. When the base layer 10, the intermediate layer 20, and the sealant layer 30 are all made of polyethylene, the proportion (mass %) of polyethylene in the laminates 1 and 2 can be calculated by the following formula (1).
Proportion of polyethylene in the laminate (mass%) = (mass of base layer + mass of intermediate layer + mass of sealant layer) / mass of entire laminate x 100...(1)

It is preferable that the laminates 1 and 2 of this embodiment configured as described above have a solvent content of 5 mg/m ² or less. Thereby, the dimensional stability of the printed pattern can be improved. In the laminates 1 and 2 of this embodiment, since the first adhesive layer 40 is formed of a solvent-free adhesive, the solvent content can be reduced to 5 mg/m ² or less. Note that even if the second adhesive layer 50 is formed of a solvent-based adhesive, the laminates 1 and 2 of this embodiment can satisfy the above-described solvent content conditions. The solvent content of the laminates 1 and 2 may be 4.5 mg/m ² or less, or 4 mg/m ² or less. The solvent content of the laminates 1 and 2 can be measured using, for example, a gas chromatograph under the following conditions.

(Gas chromatograph measurement conditions)
Equipment: Gas chromatograph (GC) with headspace autosampler
Model number: Headspace autosampler 7697A (manufactured by Agilent Technologies)
GC7890B (manufactured by Agilent Technologies)
Measurement method: Cut the laminate into 10 cm squares, seal the finely cut pieces in a 20 mL vial, and heat them at 80° C. for 20 minutes. 1.0 mL of the headspace gas generated by heating was subjected to GC analysis, and the remaining solvent was determined using a calibration curve of each standard substance (toluene, ethyl acetate, 2-propanol (IPA), methanol, MEK, etc.) prepared in advance. Quantify the content.

<Method for manufacturing laminate>
Next, a method for manufacturing the laminate will be described. The method for manufacturing a laminate according to the present embodiment includes a printing step of forming a printing layer on a substrate layer by a printing method using ink to obtain a printing substrate, a printing substrate, an intermediate layer, and a second layer. The method includes a bonding step of bonding together a laminated film including an adhesive layer and a sealant layer using a solvent-free adhesive.

When producing the laminates 1 and 2, a laminate film production process is performed to produce a laminate film including an intermediate layer, a second adhesive layer, and a sealant layer before the bonding process. In addition, when manufacturing the laminate 2, an anchor coat layer 13, an inorganic oxide layer 14, and a gas barrier coating layer 15 are formed on the intermediate layer 20 before the laminate film manufacturing process to obtain an intermediate film. Perform the film production process. In the intermediate film production step, the anchor coat layer 13, the inorganic oxide layer 14, and the gas barrier coating layer 15 can be formed on the intermediate layer 20 by a known method.

In the laminated film production process, the intermediate layer 20 or the intermediate film and the sealant layer 30 are bonded together by a method corresponding to the adhesive used.

When using a solvent-based adhesive as the adhesive, the solvent-based adhesive is applied onto the intermediate layer 20 or the intermediate film and bonded to the sealant layer 30 using a general dry lamination method, and the solvent is removed by heat drying. By doing so, a laminated film can be obtained. Thermal drying can be carried out using an oven or the like, for example, at a temperature of 50 to 80° C., an oven length of 5 to 20 m, and a processing speed of 50 to 200 m/min.

When using a solvent-free adhesive as the adhesive, by applying the solvent-free adhesive onto the intermediate layer 20 or the intermediate film and bonding it with the sealant layer 30 in the same manner as the above-mentioned bonding process, A laminated film can be obtained.

Next, in the bonding step, the printing base material and the laminated film are bonded together using a solvent-free adhesive. The printing substrate and the laminated film may be bonded together, for example, using a laminator for solvent-free adhesives equipped with a device for applying a heat-melted solvent-free adhesive to the substrate to be coated by roll coating. Can be done.

When the solvent-free adhesive is, for example, a two-component curing urethane adhesive, the main agent containing a polyol component and the curing agent containing a polyisocyanate component are normally supplied separately, and then supplied to the coating section of the laminating machine. mixed before serving. The mixed adhesive is supplied, for example, between a doctor roll and a metering roll that rotate in opposite directions of the laminating device. The supplied adhesive is transferred from the metering roll to the coating roll, and is applied to the surface of the printing layer 12 side of the printing base material supplied between the coating roll and the impression roll.

The printing substrate coated with the adhesive is bonded to the laminated film and wound up by a winder to obtain a laminated body. The obtained laminate is preferably aged at 20 to 50°C for 24 to 96 hours. In addition, the doctor roll, metaling roll, and coating roll mentioned above are examples of the structure of a lamination apparatus, and may differ depending on the lamination apparatus used.

Here, in order to make the solvent-free adhesive so low in viscosity that it can be applied without a solvent, metal rolls such as doctor rolls and coating rolls are heated, and the solvent-free adhesive is melted by the temperature. It is preferable to lower the viscosity and perform coating and bonding.

Therefore, the heating temperature of the solvent-free adhesive in the bonding process should be set within the range of 50 to 90°C so that the viscosity of the solvent-free adhesive at the heating temperature is 200 to 2000 mPa・s. preferable. The heating temperature is more preferably a temperature at which the viscosity of the solvent-free adhesive is 300 to 1,500 mPa·s, and more preferably 500 to 1,000 mPa·s, from the viewpoint of obtaining a laminate with a more uniform coated appearance. More preferably, it is temperature. Further, the heating temperature is more preferably 50 to 80°C, more preferably 50 to 70°C, from the viewpoint of further improving the lamination strength of the laminate and further suppressing expansion and contraction of the printing base material. More preferred.

Furthermore, when the solvent-free adhesive is a two-component curing urethane adhesive, the viscosity of the urethane adhesive immediately after mixing the two components is preferably 200 to 2,500 mPa·s at 40°C, and preferably 500 to 2,500 mPa·s. It is more preferably 2000 mPa·s, and even more preferably 800 to 1500 mPa·s. Thereby, the above-mentioned heating temperature during application of the solvent-free adhesive in the bonding process can be lowered, and expansion and contraction of the printing base material can be further suppressed. The viscosity of a solvent-free adhesive can be measured, for example, by using a Visco Tester (for high viscosity) VT-04FS (manufactured by Rion Co., Ltd.) by inserting a measuring rotor into the adhesive at a predetermined temperature.

In the above bonding step, since a solvent-free adhesive is used, long-term heat drying (oven drying, etc.) at high temperature to remove the solvent is not performed. Therefore, expansion and contraction of the printing base material can be suppressed, and a laminate with good dimensional stability of the printed pattern can be obtained.

Through the above steps, the laminates 1 and 2 according to this embodiment can be manufactured.

<Packaging bag>
The packaging bag according to this embodiment is made by bag-making the laminate according to this embodiment. The packaging bag is prepared by folding one laminate 1 and 2 with the sealant layer 30 facing each other, or by stacking two laminates 1 and 2 with the sealant layer 30 facing each other, so that the packaging bag is not filled with the contents. It can be formed by joining the sealant layer 30 at the peripheral edge portion by heat sealing, leaving the remaining portions. Further, by performing the above-described joining while sandwiching the folded bottom film, a standing pouch can be formed as a packaging bag. In addition, the laminates 1 and 2 can be used to form various packaging bags such as pillow packaging, four-sided seals, three-sided seals, and gusset bags. In this way, the laminates 1 and 2 can be applied to various packaging bags.

Although the preferred embodiments of the present disclosure have been described above, the present disclosure is not limited to the above embodiments. For example, in the laminate 2 shown in FIG. 2, the anchor coat layer 13, the inorganic oxide layer 14, and the gas barrier coating layer 15 disposed on the second adhesive layer 50 side of the intermediate layer 20 may have a structure disposed on the first adhesive layer 40 side. Further, the laminate may have a structure in which one or more of the anchor coat layer 13, the inorganic oxide layer 14, and the gas barrier coating layer 15 are removed from the laminate 2 shown in FIG. 2.

The laminate may have a structure in which the gas barrier coating layer 15 is removed from the laminate 2 shown in FIG. In this case, the second adhesive layer 50 is preferably a layer (gas barrier adhesive layer) formed using the above-described adhesive (gas barrier adhesive) that can exhibit gas barrier properties after curing. Thereby, deterioration in gas barrier properties due to cracking in the inorganic oxide layer 14 can be suppressed.

EXAMPLES Hereinafter, the present disclosure will be explained in more detail with reference to examples, but the present disclosure is not limited to these examples.

Each material used in Examples and Comparative Examples is shown below.

(Solvent-free adhesive A)
As the solvent-free adhesive A, the product name "LA7735" (polyisocyanate component) manufactured by Henkel Japan Ltd. and the product name "LA6159" (polyol component) manufactured by Henkel Japan Ltd. were blended at a mass ratio of 100:45. A two-component curing urethane adhesive was used. The viscosity of the solvent-free adhesive A was 1500 mPa·s at 40°C immediately after mixing the two liquids, and 800 mPa·s at 60°C during lamination. Viscosity was measured using a Viscotester.

(Solvent-free adhesive B)
As a solvent-free adhesive B, the product name "LA7735" (polyisocyanate component) manufactured by Henkel Japan Ltd. and the product name "LA6088" (polyol component) manufactured by Henkel Japan Ltd. were blended at a mass ratio of 100:40. A two-component curing urethane adhesive was used. The viscosity of the solvent-free adhesive B was 4500 mPa·s at 40°C immediately after mixing the two liquids, and 2000 mPa·s at 60°C during lamination.

(solvent adhesive)
As a solvent-based adhesive, a urethane adhesive was used in which 100 parts by mass of Takelac A525 manufactured by Mitsui Chemicals, 11 parts by mass of Takenate A52 manufactured by Mitsui Chemicals, and 84 parts by mass of ethyl acetate were mixed. .

(Gas barrier adhesive)
As a solvent-type gas barrier adhesive, an epoxy gas barrier adhesive was used, which was a mixture of 16 parts by mass of Maxive C93T manufactured by Mitsubishi Gas Chemical Co., Ltd. and 5 parts by mass of Maxive M-100 manufactured by Mitsubishi Gas Chemical Company. Using.

(Anchor coating agent)
Acrylic polyol and tolylene diisocyanate are mixed so that the number of NCO groups in tolylene diisocyanate is equal to the number of OH groups in acrylic polyol, and the total solid content (total amount of acrylic polyol and tolylene diisocyanate) is ) was diluted with ethyl acetate to 5% by mass. Further, β-(3,4 epoxycyclohexyl)trimethoxysilane was added to the diluted mixed solution in an amount of 5 parts by mass based on 100 parts by mass of the total amount of acrylic polyol and tolylene diisocyanate, and these were mixed. An anchor coating agent was prepared by doing this.

(overcoat agent)
An overcoat agent was prepared by mixing the following liquids A, B, and C at a mass ratio of 70/20/10, respectively.
Solution A: 72.1 g of 0.1N hydrochloric acid was added to 17.9 g of tetraethoxysilane (Si(OC ₂ H ₅ ) ₄ ) and 10 g of methanol, and the mixture was stirred for 30 minutes to be hydrolyzed, resulting in a solid content of 5% by mass (SiO2 equivalent). ) hydrolysis solution.
Solution B: 5% by mass water/methanol solution of polyvinyl alcohol (mass ratio of water:methanol is 95:5).
Solution C: 1,3,5-tris(3-trialkoxysilylpropyl)isocyanurate was diluted to a solid content of 5% by mass with a mixed solution of water/isopropyl alcohol (mass ratio of water:isopropyl alcohol was 1:1). Hydrolysis solution.

(Intermediate film A)
The above-mentioned anchor coating agent was applied by gravure coating to the corona-treated surface of an unstretched high-density polyethylene (HDPE) film (manufactured by Tamapoly Co., Ltd., product name: HS31, thickness: 30 μm, one side corona-treated) as an intermediate layer. It was coated and dried to provide an anchor coat layer with a thickness of 0.05 μm. Next, a transparent vapor deposition layer (inorganic oxide layer) made of silicon oxide and having a thickness of 30 nm was formed on the anchor coat layer using a vacuum vapor deposition apparatus using an electron beam heating method. The O/Si ratio of the inorganic oxide layer was set to 1.8 by adjusting the type of vapor deposition material. Next, the above-mentioned overcoat agent was applied onto the inorganic oxide layer by gravure coating and dried to form a gas barrier coating layer (overcoat layer) having a gas barrier function and having a thickness of 0.3 μm. As a result of the above, an intermediate film A in which the intermediate layer/anchor coat layer/inorganic oxide layer (SiO _x )/gas barrier coating layer was laminated was obtained.

(Intermediate film B)
The intermediate layer was prepared in the same manner as the above intermediate film A except that a 10 nm thick transparent vapor deposited layer (inorganic oxide layer) made of aluminum oxide was formed on the anchor coat layer using a vacuum evaporation apparatus using an electron beam heating method. An intermediate film B was obtained in which the following layers were laminated: /anchor coat layer/inorganic oxide layer (AlO _x )/gas barrier coating layer.

(Intermediate film C)
Intermediate film B, in which intermediate layer/anchor coat layer/inorganic oxide layer (SiO _x ) were laminated, was obtained in the same manner as intermediate film A except that no gas barrier coating layer was formed.

(Intermediate film D)
An intermediate film B in which an intermediate layer/anchor coat layer/inorganic oxide layer (AlO _x ) was laminated was obtained in the same manner as the above intermediate film B except that a gas barrier coating layer was not formed.

[Example 1]
As a base material layer, an unstretched high-density polyethylene (HDPE) film (manufactured by Tamapoly Co., Ltd., trade name: HS31, thickness: 30 μm, one side corona treated) was prepared. A pattern was printed on the corona-treated surface of the base material layer by a flexographic printing method to form a 1 μm thick printed layer to obtain a printed base material. On the other hand, as a sealant layer, a single-sided corona-treated unstretched polyethylene film (manufactured by Tamapori Co., Ltd., trade name: SE620, single-layer structure of LLDPE) having a thickness of 60 μm was prepared.

Next, the polyisocyanate component and polyol component of the above-mentioned solvent-free adhesive A were mixed using a two-component mixing supply device, and the solution temperature was set to 40°C. An unstretched high-density polyethylene (HDPE) film (manufactured by Tamapoly Co., Ltd., product name: Solvent-free adhesive A (adhesive that forms the second adhesive layer) was applied to the corona-treated surface of HS31 (thickness: 30 μm, one side corona treated) at a coating amount of 2.1 g/ ^m2 . The intermediate layer and sealant layer were bonded together. Thereafter, by aging at 40° C. for one day, a laminated film in which the intermediate layer and the sealant layer were laminated via the second adhesive layer was obtained.

Next, the polyisocyanate component and polyol component of the above-mentioned solvent-free adhesive A were mixed using a two-component mixing supply device, and the solution temperature was set to 40°C. Using a laminator for solvent-free adhesives, under the conditions of a processing speed of 100 m/min and a doctor roll and coating roll temperature of 60°C, solvent-free adhesive A (first adhesive layer) was applied onto the printing layer of the printing base material. The printing base material and the laminated film were bonded together by applying a coating amount of 2.1 g/m ² (forming adhesive) to the printed base material and the laminated film. Thereafter, by aging at 40° C. for 2 days, a laminate having a laminate structure of base material layer/printed layer/first adhesive layer/intermediate layer/second adhesive layer/sealant layer was obtained.

[Example 2]
A printing base material and a sealant layer were prepared in the same manner as in Example 1. Next, the polyisocyanate component and polyol component of the above-mentioned solvent-free adhesive A were mixed using a two-component mixing supply device, and the solution temperature was set to 40°C. Using a laminator for solvent-free adhesives, under the conditions of processing speed 100 m/min, doctor roll and coating roll temperature 60°C, solvent-free adhesive A (second An adhesive (forming an adhesive layer) was applied in an amount of 2.1 g/m ² , and the intermediate film A and the sealant layer were bonded together. Thereafter, by aging at 40° C. for one day, a laminated film in which the intermediate film A and the sealant layer were laminated via the second adhesive layer was obtained.

Next, the polyisocyanate component and polyol component of the above-mentioned solvent-free adhesive A were mixed using a two-component mixing supply device, and the solution temperature was set to 40°C. Using a laminator for solvent-free adhesives, under the conditions of a processing speed of 100 m/min and a doctor roll and coating roll temperature of 60°C, solvent-free adhesive A (first adhesive layer) was applied onto the printing layer of the printing base material. The printing base material and the laminated film were bonded together by applying a coating amount of 2.1 g/m ² (forming adhesive) to the printed base material and the laminated film. Thereafter, by aging at 40°C for 2 days, the substrate layer/printed layer/first adhesive layer/intermediate layer/anchor coat layer/inorganic oxide layer/gas barrier coating layer/second adhesive layer/ A laminate having a laminate structure of sealant layers was obtained.

[Example 3]
Substrate layer/print layer/first adhesive layer/intermediate layer/anchor coat layer/inorganic oxide layer/gas barrier was prepared in the same manner as in Example 2 except that intermediate film B was used instead of intermediate film A. A laminate having a laminate structure of adhesive coating layer/second adhesive layer/sealant layer was obtained.

[Example 4]
A printing base material and a sealant layer were prepared in the same manner as in Example 1. Next, the surface of the inorganic oxide layer side of the intermediate film C described above and the sealant layer were adhered by the dry nate method using the gas barrier adhesive described above (the adhesive forming the second adhesive layer). . Adhesion was performed using a dry laminator at a drying temperature of 50° C. and a processing speed of 100 m/min. Moreover, the thickness of the second adhesive layer was 2.1 μm. Thereby, a laminated film in which the intermediate film C and the sealant layer were laminated via the second adhesive layer was obtained.

Next, the polyisocyanate component and polyol component of the above-mentioned solvent-free adhesive A were mixed using a two-component mixing supply device, and the solution temperature was set to 40°C. Using a laminator for solvent-free adhesives, under the conditions of a processing speed of 100 m/min and a doctor roll and coating roll temperature of 60°C, solvent-free adhesive A (first adhesive layer) was applied onto the printing layer of the printing base material. The printing base material and the laminated film were bonded together by applying a coating amount of 2.1 g/m ² (forming adhesive) to the printed base material and the laminated film. Thereafter, by aging at 40°C for 2 days, a laminated structure of base material layer/print layer/first adhesive layer/intermediate layer/anchor coat layer/inorganic oxide layer/second adhesive layer/sealant layer is formed. A laminate having the following properties was obtained.

[Example 5]
In the same manner as in Example 4 except that intermediate film D was used instead of intermediate film C, base layer/print layer/first adhesive layer/intermediate layer/anchor coat layer/inorganic oxide layer/first A laminate having a laminate structure of two adhesive layers/sealant layers was obtained.

[Example 6]
A substrate was prepared in the same manner as in Example 2, except that solvent-free adhesive B was used instead of solvent-free adhesive A when forming the first adhesive layer and the second adhesive layer. A laminate having a laminate structure of layer/printed layer/first adhesive layer/intermediate layer/anchor coat layer/inorganic oxide layer/gas barrier coating layer/second adhesive layer/sealant layer was obtained.

[Comparative example 1]
The same procedure as in Example 1 was used except that a stretched high-density polyethylene (HDPE) film (manufactured by Tokyo Ink Co., Ltd., product name: SMUQ, thickness: 25 μm, one side corona treated) was used as the base layer and the intermediate layer. As a result, a laminate having a laminate structure of base material layer/printed layer/first adhesive layer/intermediate layer/second adhesive layer/sealant layer was obtained.

[Comparative example 2]
A printing base material and a sealant layer were prepared in the same manner as in Example 1. Next, the surface of the gas barrier coating layer side of the intermediate film A described above and the sealant layer were adhered by the dry nate method using the above-mentioned solvent-based adhesive (the adhesive forming the second adhesive layer). . Adhesion was performed using a dry laminator at a drying temperature of 50° C. and a processing speed of 100 m/min. Moreover, the thickness of the second adhesive layer was 3.5 μm. Thereby, a laminated film in which the intermediate film A and the sealant layer were laminated via the second adhesive layer was obtained.

Next, by the drynate method using the above-mentioned solvent-based adhesive (the adhesive forming the first adhesive layer), the surface of the printing layer side of the above-mentioned printing base material and the intermediate layer side of the above-mentioned laminated film are bonded. I glued the sides together. Adhesion was performed using a dry laminator at a drying temperature of 50° C. and a processing speed of 100 m/min. Moreover, the thickness of the first adhesive layer was 3.5 μm. As a result, a laminate having a laminated structure of base material layer/printed layer/first adhesive layer/intermediate layer/anchor coat layer/inorganic oxide layer/gas barrier coating layer/second adhesive layer/sealant layer is obtained. I got it.

[evaluation]
The obtained laminate was evaluated as follows. The results are shown in Table 1.

<Recyclability>
Based on the following formula (1), the proportion of polyethylene (% by mass) in the laminate obtained in each Example and Comparative Example was calculated. The evaluation was made in the following two stages.
Proportion of polyethylene in the laminate (mass%) = (mass of base layer + mass of intermediate layer + mass of sealant layer) / mass of entire laminate x 100...(1)
A: The content of polyethylene is 90% by mass or more.
C: The content of polyethylene is less than 90% by mass.

<Printed pattern dimensional stability>
The patterns of the laminates obtained in each Example and Comparative Example were visually observed, and the dimensional stability was evaluated based on the following evaluation criteria.
A: The expansion and contraction of the pattern was very small, and the difference between the circumferential length of the plate cylinder in flexographic printing and the corresponding pattern dimension of the laminate was ±3 mm or less, and the pattern was very good.
B: The pattern showed little expansion and contraction, and the difference between the circumferential length of the plate cylinder in flexographic printing and the corresponding pattern dimension of the laminate was more than ±3 mm and less than ±6 mm, and the pattern was good.
C: The pattern showed significant expansion and contraction, and the difference between the circumferential length of the plate cylinder in flexographic printing and the corresponding pattern dimension of the laminate exceeded ±6 mm, and the pattern was distorted.

<Lamination strength>
In accordance with JIS K6854, a strip-shaped test piece with a width of 15 mm was cut out from the laminate obtained in each example and comparative example, and the test piece was tested using a Tensilon universal testing machine RTC-1250 manufactured by Orientec. The interlayer peel strength (laminate strength) was measured as an index of adhesion. The measurement was performed using T-type peeling under normal conditions (23° C., 50% RH) at a peeling rate of 300 mm/min.

<Pressure test>
The laminates obtained in the Examples and Comparative Examples were cut into two 90 mm square pieces, the sealant layers were made to face each other, and three outer sides were sealed, then 100 g of tap water was filled, and the remaining one side was sealed. . The sealing conditions were 130° C., 0.2 MPa, and 1 second, and the width of the seal was 5 mm from the outer periphery. Thereby, a test pouch was obtained.

The obtained pouch was subjected to a static load test of 80 kgf for 3 minutes in accordance with JIS Z0238, and the compressive strength was evaluated based on the presence or absence of bag breakage according to the following criteria.
A: No bag breakage after static load test of 80 kgf for 3 minutes.
C: Bag broke during static load test at 80 kgf for 3 minutes.

<Oxygen permeability: OTR>
The oxygen permeability of the laminates obtained in Examples and Comparative Examples was measured by the Mocon method under conditions of 30° C. and 70% RH (relative humidity). However, the oxygen permeability was not measured for the laminate that did not have an inorganic oxide layer.

<Water vapor transmission rate: WVTR>
The water vapor permeability of the laminates obtained in Examples and Comparative Examples was measured by the Mocon method under conditions of 40° C. and 90% RH (relative humidity). However, the water vapor permeability was not measured for the laminate that did not have an inorganic oxide layer.

DESCRIPTION OF SYMBOLS 1, 2... Laminate, 10... Base material layer, 12... Print layer, 13... Anchor coat layer, 14... Inorganic oxide layer, 15... Gas barrier coating layer, 20... Intermediate layer, 30... Sealant layer, 40... 1st adhesive layer, 50... 2nd adhesive layer.

Claims (11)

It has a structure in which a base material layer, a printing layer, a first adhesive layer, an intermediate layer, a second adhesive layer, and a sealant layer are laminated in this order,
The base layer, the intermediate layer, and the sealant layer are all made of an unstretched polyethylene film,
The first adhesive layer is a layer formed using a solvent-free adhesive,
A laminate in which the proportion of polyethylene in the laminate is 90% by mass or more. The laminate according to claim 1, wherein the solvent-free adhesive is a two-part curable urethane adhesive. The laminate according to claim 1, wherein the base layer and the intermediate layer both contain high-density polyethylene or medium-density polyethylene. The laminate of claim 1, wherein the sealant layer comprises low density polyethylene. The laminate according to claim 1, further comprising an inorganic oxide layer on at least one surface of the intermediate layer, the inorganic oxide layer containing a metal oxide. The laminate according to claim 5, further comprising a gas barrier coating layer between the inorganic oxide layer and the first adhesive layer or the second adhesive layer. The laminate according to claim 1, wherein the second adhesive layer is a gas barrier adhesive layer formed using a gas barrier adhesive. A packaging bag made from the laminate according to any one of claims 1 to 7. A method for producing a laminate according to any one of claims 1 to 7, comprising:
a printing step of forming the printing layer on the substrate layer by a printing method using ink to obtain a printing substrate;
a laminating step of laminating the printing base material and a laminated film including the intermediate layer, the second adhesive layer, and the sealant layer using the solvent-free adhesive;
A method for manufacturing a laminate having: According to claim 9, the solvent-free adhesive is a two-component curing urethane adhesive, and the urethane adhesive has a viscosity of 200 to 2500 mPa·s at 40° C. immediately after mixing the two components. A method for manufacturing a laminate. In the bonding step, the heating temperature of the solvent-free adhesive is set within a range of 50 to 90 ° C. so that the viscosity of the solvent-free adhesive at the heating temperature is 200 to 2000 mPa s. A method for manufacturing a laminate according to claim 9.

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