JP2023179896A - Laminate, packaging material, and packaging bag - Google Patents

Abstract

To provide a laminate that has superior recycling suitability and superior heat sealability.SOLUTION: A laminate comprises a protective layer, a substrate layer, and a sealant layer, laminated in the stated order. The substrate layer and the sealant layer each comprise polyethylene. The protective layer is a heated and dried product of a composition that comprises at least one of a hydroxy group-containing polymer compound and a hydrolysate thereof, and at least one selected from the group consisting of a metalalkoxide, a silane coupling agent and hydrolysates thereof. In the laminate, the content of the polyethylene is 90 mass% or more.SELECTED DRAWING: Figure 1

Description

The present invention relates to a laminate, a packaging material using the same, and a packaging bag. More specifically, the present invention relates to a laminate with excellent material recyclability and low environmental impact, and packaging materials and packaging bags using the same.

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.

JP 2020-55157 Publication

However, when the laminate described in Patent Document 1 is applied to a packaging bag, in the bag manufacturing process for forming the packaging bag, the heat seal layers (sealant layers) of the laminate are faced to each other, and the base material layer of the laminate is There is a process of thermally welding (heat sealing) by applying pressure from the outer surface using a high-temperature jig and sandwiching the material. The jig of a heat sealing machine is at a high temperature, and the outer surface of the base material layer that comes into direct contact with the jig is exposed to high temperatures, so in conventional laminates, the base material layer is affected by the heat and adheres to the jig. In some cases, problems such as wrinkles occurring in the heat-sealed portion may occur, and the heat-sealability was not sufficient. Therefore, there have been problems such as the narrow range of appropriate bag-making temperature conditions, poor productivity, and the fact that the strength of the packaging bag may not be sufficient.

Therefore, an object of the present invention is to provide a laminate having excellent recyclability and heat sealability, and a packaging material and a packaging bag using the same.

In order to solve the above problems, the present invention provides a laminate having a structure in which a protective layer, a base material layer, and a sealant layer are laminated in this order, wherein the base material layer and the sealant layer are made of polyethylene. and the protective layer contains at least one of a hydroxyl group-containing polymer compound and a hydrolyzate thereof, and at least one selected from the group consisting of a metal alkoxide, a silane coupling agent, and a hydrolyzate thereof. The present invention provides a laminate, which is a heat-dried product of a composition in which the proportion of polyethylene in the laminate is 90% by mass or more.

In the laminate, the composition may contain a silane coupling agent, and the silane coupling agent may contain 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate.

The laminate may include a vapor deposited layer located between the base layer and the sealant layer.

In the laminate, the vapor deposited layer may contain a metal oxide.

In the laminate, the thickness of the protective layer may be 0.4% or more and 2.0% or less of the total thickness of the laminate.

In the laminate, the base layer may contain high-density polyethylene or medium-density polyethylene.

In the laminate, the sealant layer may contain low density polyethylene.

In the laminate, at least one of the base layer and the sealant layer may be a layer made of an unstretched polyethylene film.

The laminate may include an intermediate layer located between the base layer and the sealant layer, and the intermediate layer may contain polyethylene.

In the laminate, the intermediate layer may include high-density polyethylene or medium-density polyethylene.

In the laminate, the intermediate layer may be a layer made of an unstretched polyethylene film.

The present invention also provides a packaging material containing the laminate of the present invention.

The present invention further provides a packaging bag made from the above packaging material.

According to the present invention, it is possible to provide a laminate having excellent recyclability and heat sealability, and a packaging material and a packaging bag using the same.

FIG. 1 is a schematic cross-sectional view of a laminate according to an embodiment of the present invention. It is a cross-sectional schematic diagram of the laminated body based on another example of one Embodiment of this invention.

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

FIG. 1 is a schematic cross-sectional view showing one embodiment of the laminate of the present invention. The laminate 1 shown in FIG. 1 includes a base layer 10 , a first adhesive layer 40 , an intermediate layer 20 , a second adhesive layer 50 , and a sealant layer 30 . A protective layer 11 is provided on the outer surface 10a side, and a vapor deposition layer 14 is provided on one surface of the intermediate layer 20. Furthermore, the laminate 1 includes a printed layer 12 on the inner surface 10b side of the base layer 10, and a gas barrier coating layer 15 on the opposite side of the vapor deposited layer 14 from the intermediate layer 20. Each layer will be explained below.

The base layer 10 is a layer containing polyethylene, and may be a non-stretched film made of polyethylene, for example. The base material layer 10 is a portion that becomes the outer surface when a packaging material is formed using the laminate 1. However, in the laminate 1 of this embodiment, the outer surface of the base material layer 10 is protected by a protective layer 11.

As the base material layer 10, 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.

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 laminate 1 can be improved. By setting the thickness of the base material layer 10 to 50 μm or less, the processability of the laminate 1 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. Since the melting point of the polyethylene that forms the base material layer 10 and the temperature of the heat seal bar are almost the same, if the base material layer 10 is made the outermost layer, there may be defects in appearance such as wrinkles or heat of the base material layer 10. There is a possibility that adhesion (removal) to the heat seal bar may occur due to welding.

The protective layer 11 is provided to prevent problems during heat sealing during bag making, filling and sealing, and to ensure suitability for heat sealing. Because of this role, the protective layer 11 may be provided as the outermost layer of the laminate.

The thickness of the laminate changes depending on the weight of the contents to be packaged. When packaging lightweight contents, the packaging is generally made thinner in consideration of cost, and when packing heavy items, it is generally made thicker in consideration of strength. As the thickness of the laminate increases, the amount of heat required to thermally melt the heat sealing surface of the sealant layer increases. For this reason, the thickness of the protective layer 11 is preferably changed in proportion to the total thickness of the laminate. The ratio of the thickness of the protective layer 11 to the total thickness of the laminate is preferably 0.4% or more and 2.0% or less. When this ratio is 0.4% or more, desired heat resistance can be easily obtained and better heat sealability can be obtained, and when this ratio is 2.0% or less, waste of material of the protective layer 11 can be avoided. At the same time, it is possible to suppress an increase in the amount of heat required for heat sealing.

The thickness of the protective layer 11 is adjusted according to the total thickness of the laminate as described above, but from the viewpoint of improving heat resistance and reducing the amount of heat required for heat sealing, the thickness is, for example, 0.1 to 5.0 μm. may be 0.2 to 4.0 μm, may be 0.3 to 2.0 μm, and may be 0.5 to 2.0 μm.

The protective layer 11 provided on the outer surface of the base layer 10 needs to have heat resistance that does not cause softening, melting, decomposition, etc. even when heated to, for example, 140° C. during heat sealing. Therefore, the protective layer 11 contains at least one of a hydroxyl group-containing polymer compound and a hydrolyzate thereof, and at least one selected from the group consisting of a metal alkoxide, a silane coupling agent, and a hydrolyzate thereof. This is a heat-dried product of the composition.

The hydroxyl group-containing polymer compound and its hydrolyzate, the metal alkoxide, the silane coupling agent, and their hydrolyzate undergo a dehydration condensation reaction to become insoluble in water and organic solvents (as a result, the protective layer 11 It is possible to obtain sufficient heat resistance to provide heat sealability. In addition, when a packaging bag made of a packaging material using a laminate provided with a protective layer according to the present invention is filled with contents, sealed by heat sealing, immersed in hot water, and subjected to boiling treatment in which heat sterilization is performed. A good appearance can be maintained without the protective layer 11 peeling off.

As a means for forming the protective layer 11, 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 coating) is used. (referred to as an agent). For example, the coating agent is prepared by directly or in advance 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 and 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.

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 a coating agent for the protective layer because it has particularly excellent heat sealability.

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 protective layer 11 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.

When the coating agent contains a silane coupling agent, the molecular chain formed by the dehydration condensation reaction between the hydroxyl group-containing polymer compound and its hydrolyzate, and the metal alkoxide and its hydrolyzate, becomes even higher-dimensional. Since the network structure is formed, the hot water resistance of the laminate 1 is improved. When the silane coupling agent contains 1,3,5-tris(3-trialkoxysilylalkyl) isocyanurate, the silane coupling agent in the coating agent has both the flexibility derived from the nurate skeleton and the coupling performance. Since peeling due to bending, rubbing, etc. that occurs during boiling processing can be prevented, the hot water resistance of the laminate 1 is further improved. When containing isocyanurate, hot water resistance is further improved.

From the viewpoint of adhesion to the base layer 10, the amount of metal alkoxide in the coating agent can be 1 to 4 parts by mass, and may be 2 to 3 parts by mass with respect to 1 part by mass of the hydroxyl group-containing polymer compound. It's fine. 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 coating agent should be 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 can be added to the coating agent as long as hot water resistance and water resistance are not impaired. be. Hot water resistance refers to the practical feasibility of boil sterilization, and when the laminate 1 or a packaging bag made using the laminate 1 is immersed in 80°C hot water and subjected to boil sterilization for 30 minutes. , meaning that the protective layer does not peel off, lift, or become rough.

The coating agent can 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. The coating formed by applying the coating 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 drying temperature within the above range, thermal shrinkage of the base layer 10 can be prevented.

The protective layer 11 may be formed using a coating 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 coating agent as necessary.

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

Since the protective layer 11 is a heat-dried product of the coating agent, the protective layer 11 contains carbon atoms and silicon atoms. The molar ratio of silicon atoms to carbon atoms (Si/C) on the surface of the protective layer 11 may be 0.1 or more and 1 or less, 0.2 or more and 0.9 or less, and 0.4 or more. It may be 0.8 or less, and may be 0.4 or more and 0.6 or less. When the Si/C on the surface of the protective layer 11 is 0.1 or more, the water resistance of the protective layer 11 is further improved, and as the Si/C becomes larger, the water resistance tends to further improve. When Si/C on the surface of the protective layer 11 is 1 or less, the brittleness of the surface of the protective layer 11 can be reduced, and as Si/C becomes smaller, the brittleness of the protective layer 11 tends to be further reduced. When the protective layer becomes brittle, the surface of the protective layer becomes powdery and detaches, which may lead to deterioration in appearance or damage to the laminate. If Si/C on the surface of the protective layer 11 is within the above range, for example, when a packaging bag is formed using the laminate 1 having the protective layer 11 as the outermost layer, deterioration in appearance and damage of the packaging bag can be suppressed. it is conceivable that. Si/C on the surface of the protective layer 11 can be measured by the method described in the examples below.

For the purpose of improving the adhesion between the base layer 10 and the protective layer 11, an adhesion imparting layer may be provided on the base layer 10 to the extent that recyclability is not impaired.

The printed layer 12 can be formed on the outer surface 10a of the base layer 10 on which the protective layer 11 is formed, or the inner surface 10b on the side on which the intermediate layer 20 is laminated. The method of forming the image is not particularly limited, and the image can be formed by ordinary gravure printing, flexographic printing, or the like, using ink suitable for each method. Inks include solvent-based inks and water-based inks, and from an environmental standpoint, it is preferable to use water-based inks. Further, the outer surface 10a or inner surface 10b of the base material 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.

The intermediate layer 20 is a layer containing polyethylene, and may be, for example, an unstretched film made of polyethylene. 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.

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 intermediate layer 20 is preferably 9 μm or more and 50 μm or less, more preferably 12 μm or more and 30 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.

In the laminate 1, a vapor deposition layer 14 is formed on at least one surface of the intermediate layer 20. In this embodiment, the vapor deposition layer 14 is formed on the surface of the intermediate layer 20 that faces the second adhesive layer 50, but may be formed on the opposite surface. The vapor deposited layer 14 provides the laminate 1 with oxygen barrier properties and water vapor barrier properties.

Examples of the structure of the vapor deposition layer 14 include a vapor deposition layer made of a 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 vapor deposition 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 1.

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 vapor deposited 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 vapor deposited layer is more preferably 7 nm or more and 15 nm or less.

The thickness of the deposited 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 vapor deposited layer is more preferably 20 nm or more and 40 nm or less.

The vapor deposition 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.

An anchor coat layer may be formed on the surface of the intermediate layer 20 on the side where the vapor deposition layer 14 is formed using a known anchor coat agent. Thereby, the adhesion of the vapor deposited layer made of metal oxide 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.

Furthermore, in order to improve the adhesion with the first adhesive layer 40, the second adhesive layer 50, the vapor deposition layer 14, the above-mentioned anchor coat layer, etc., the corresponding surfaces of the intermediate layer 20 are subjected to corona treatment. Surface treatment such as plasma treatment may also be performed.

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.

A gas barrier coating layer 15 may be provided on the vapor deposition layer 14 for the purpose of improving gas barrier properties and protecting the vapor deposition 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 may be a layer made of the same components as the protective layer 11.

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.

Regarding the hydroxyl group-containing polymer compound used in the preparation of the overcoat agent, the same explanation as for the hydroxyl group-containing polymer compound used in the preparation of the coating agent may be applied.

Regarding the metal alkoxides used in the preparation of the overcoat agent, the same explanations as for the metal alkoxides used in the preparation of the coating agent may apply.

As for the silane coupling agent used in the preparation of the overcoat agent, the same explanation as for the silane coupling agent used in the preparation of the coating agent may be applied.

The amount of metal alkoxide in the overcoat agent can be 1 to 4 parts by mass, and 2 to 3 parts by mass per 1 part by mass of the hydroxyl group-containing polymer compound, from the viewpoint of adhesion with the vapor deposited layer and maintenance of gas barrier properties. It may be a department. 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.

Overcoating agents can be applied in the same manner as coating agents. A coating formed by applying an overcoat agent can be dried in the same manner as a coating formed by applying a coating agent.

Once the overcoat agent has been applied, the temperature at which the coating film is dried can be, for example, 50 to 150°C, preferably 70 to 100°C. By controlling the drying temperature within the above range, it is possible to further suppress the occurrence of cracks in the vapor deposited layer and the gas barrier coating layer, and it is possible to exhibit excellent barrier properties.

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

The thickness of the gas barrier coating layer is preferably 50 to 1000 nm, more preferably 100 to 500 nm. When the thickness of the gas barrier coating layer 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.

The sealant layer 30 is made of polyethylene, and is bonded by heat sealing when the laminate 1 is used to form a packaging material such as a packaging bag. 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). Further, from the viewpoint of environmental load, it is preferable that biomass-derived polyethylene or recycled polyethylene 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 laminate 1 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 in the packaging material 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 laminate 1 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. Further, by setting the thickness to 200 μm or less, the processability of the laminate 1 can be improved, and it is further preferable to set the thickness to 150 μm.

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.

The first adhesive layer 40 is a layer containing at least one type of adhesive, and is provided between the base layer 10 and the intermediate layer 20 to bond them together. 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. Any adhesive such as a one-component curing type or a two-component curing type urethane adhesive can be used for the first adhesive layer 40 and the second adhesive layer 50. These adhesives may contain a layered inorganic compound for the purpose of further enhancing barrier properties.

The first adhesive layer 40 and the second adhesive layer 50 can also be formed using an adhesive that can exhibit gas barrier properties after curing. In particular, if the adhesive layer in contact with the vapor deposited layer is formed using an adhesive that exhibits gas barrier properties, it is possible to further suppress the deterioration of the gas barrier properties due to the occurrence of cracks in the vapor deposited layer. Thereby, the gas barrier performance of the laminate 1 can be further improved. 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 thickness of the first adhesive layer 40 and 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 1.0 μm or more and 4 μm or less. More preferably, it is .5 μm or less. Improving the adhesiveness of the first adhesive layer 40 and the second adhesive layer 50 by setting the thickness of the first adhesive layer 40 and the second adhesive layer 50 to 0.5 μm or more. I can do it. By setting the thickness of the first adhesive layer 40 and the second adhesive layer 50 to 6 μm or less, the processability of the laminate 1 can be improved.

The first adhesive layer 40 and the second adhesive layer 50 can be formed using various known methods such as a direct gravure roll coating method, a gravure roll coating method, a kiss coating method, a reverse roll coating method, a Fontaine method, and a transfer roll coating method. It can be formed by any method.

In the laminate 1 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 proportion of polyethylene in the laminate 1 is 90% by mass. % or more. Thereby, the laminate 1 has 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 laminate 1 can be calculated by the following formula (1).
(Mass of base layer 10 + mass of intermediate layer 20 + mass of sealant layer 30)/mass of entire laminate 1 x 100...(1)

When one laminate 1 is folded with the sealant layers 30 facing each other, or two laminates 1 are stacked with the sealant layers 30 facing each other, the sealant layer at the periphery is removed, leaving the filled part with the contents. By joining 30 by heat sealing, a packaging bag made of the laminate 1 can be formed. By performing the above-described joining while sandwiching the folded bottom film, a standing pouch can be formed. In addition, it can be used as various other packaging bags such as pillow packaging, four-sided seals, three-sided seals, and gusset bags. In this way, the laminate 1 can be applied to various packaging bags.

By providing the protective layer 11 as the outermost layer on the outer surface of the base material layer 10 containing polyethylene, the laminate of the present invention can improve the heat resistance of the heat-sealed part and facilitate bag making under appropriate conditions. This makes it possible to improve the strength and appearance required for packaging bags. In addition, by combining the intermediate layer 20 made of a non-stretched film with the vapor-deposited layer 14, the packaging bag containing liquid will not be easily torn due to impact when dropped, and the packaging This increases the strength of the bag.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. For example, the laminate may not include one or more of the printed layer, intermediate layer, vapor deposited layer, and gas barrier coating layer. If the laminate does not include an intermediate layer, the first adhesive layer is not necessary and the vapor deposited layer may be provided on the base layer. Further, when the laminate does not include a gas barrier coating layer, the laminate may be as shown in FIG. 2.

The laminate 2 shown in FIG. 2 is obtained by removing the gas barrier coating layer 15 from the laminate 1. In place of removing the gas barrier coating layer 15, the laminate 2 includes a second adhesive layer 60 formed using an adhesive (the above-mentioned gas barrier adhesive) that can exhibit gas barrier properties after curing. Thereby, it is possible to suppress deterioration of gas barrier properties due to the occurrence of cracks in the vapor deposited layer 14. The thickness, formation method, etc. of the second adhesive layer 60 may be the same as those of the second adhesive layer 50.

The laminate 1 can be suitably used to form a packaging bag for packaging contents. Examples of the contents include liquid seasonings, toiletries, soups, liquid detergents and other liquids, boiled foods and other solids, and curry and other liquid and solid mixtures.

Examples of the packaging bag include flat pouch-shaped packaging bags, pillow packaging bags, and the like.

The flat pouch-shaped packaging bag may be made into a bag shape by folding one laminate 1 in half so that the sealant films face each other and then heat-sealing three sides. The laminate 1 may be stacked so that the sealant films face each other, and then heat-sealed on four sides to form a bag shape.

The pillow packaging bag formed from the laminate 1 may include a main body having a cylindrical shape, and a flange extending along the axial direction of the main body and projecting from the main body. The pillow packaging bag can be formed using, for example, a known pillow packaging and filling machine.

The laminate, packaging material, and packaging bag according to one aspect of the present invention are as described in, for example, [1] to [14] below, and have been described in detail based on the above embodiments.
[1] A laminate having a structure in which a protective layer, a base material layer, and a sealant layer are laminated in this order,
the base layer and the sealant layer contain polyethylene,
The protective layer comprises at least one of a hydroxyl group-containing polymer compound and a hydrolyzate thereof;
A heat-dried product of a composition containing at least one selected from the group consisting of metal alkoxides, silane coupling agents, and hydrolysates thereof,
A laminate in which the proportion of polyethylene in the laminate is 90% by mass or more.
[2] The laminate according to [1], wherein the composition contains a silane coupling agent.
[3] The laminate according to [2], wherein the silane coupling agent contains 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate.
[4] The laminate according to any one of [1] to [3], comprising a vapor deposition layer located between the base material layer and the sealant layer.
[5] The laminate according to [4], wherein the vapor deposition layer contains a metal oxide.
[6] The laminate according to any one of [1] to [5], wherein the thickness of the protective layer is 0.4% or more and 2.0% or less of the total thickness of the laminate.
[7] The laminate according to any one of [1] to [6], wherein the base layer contains high-density polyethylene or medium-density polyethylene.
[8] The laminate according to any one of [1] to [7], wherein the sealant layer contains low-density polyethylene.
[9] The laminate according to any one of [1] to [8], wherein at least one of the base layer and the sealant layer is a layer made of an unstretched polyethylene film.
[10] The laminate according to any one of [1] to [9], comprising an intermediate layer located between the base layer and the sealant layer, the intermediate layer containing polyethylene.
[11] The laminate according to [10], wherein the intermediate layer contains high-density polyethylene or medium-density polyethylene.
[12] The laminate according to [10] or [1], wherein the intermediate layer is a layer made of an unstretched polyethylene film.
[13] A packaging material comprising the laminate according to any one of [1] to [12].
[14] A packaging bag made of the packaging material according to [13].

However, one aspect of the present invention is not limited to the above embodiments and [1] to [14] above. One aspect of the present invention can be further modified without departing from the spirit thereof.

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

(Preparation of 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.

(Preparation of 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 (SiO ₂ (conversion) 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-trimethoxysilylpropyl)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.

(Preparation of intermediate film A)
The above-mentioned anchor coating agent was applied by gravure coating to one side of a 25 μm thick unstretched polyethylene film (three-layer structure of HDPE/MDPE/HDPE=5 μm/15 μm/5 μm) which had been corona treated on both sides as an intermediate layer. It was coated and dried to form an anchor coat layer with a thickness of 0.1 μm. Next, a transparent vapor deposition layer of silicon oxide 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 vapor deposited layer was set to 1.8 by adjusting the type of vapor deposition material. The above-mentioned overcoat agent was applied onto the vapor deposited layer by a gravure coating method 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 a vapor deposited layer of silica was formed was obtained.

(Preparation of intermediate film B)
An anchor coating agent was applied to one side of the same unstretched polyethylene film as intermediate film A by gravure coating and dried to provide an anchor coating layer with a thickness of 0.1 μm. Next, a transparent vapor deposition layer of aluminum oxide with a thickness of 10 nm was formed on the anchor coat layer using a vacuum vapor deposition apparatus using an electron beam heating method using aluminum as a vapor deposition source. The O/Al ratio of the deposited layer was set to 1.5 by adjusting the amount of oxygen introduced. Furthermore, an overcoat agent was applied onto the vapor deposited 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 B in which a vapor deposited layer made of alumina was formed was obtained.

(Preparation of intermediate film C)
Intermediate film C was obtained in the same manner as intermediate film A except that no gas barrier coating layer was formed.

(Preparation of coating liquid (coating agent) for forming protective layer)
The following solutions A, B, and C were each prepared.
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 (SiO ₂ (conversion) 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-trimethoxysilylpropyl)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.

(Preparation of adhesive A)
Adhesive A, which is a urethane adhesive, was prepared by mixing 100 parts by mass of Takelac A525, manufactured by Mitsui Chemicals, with 11 parts by mass of Takenate A52, manufactured by Mitsui Chemicals, and 84 parts by mass of ethyl acetate.

(Adhesive B)
Adhesive B, which is an epoxy gas barrier adhesive, was prepared by mixing 16 parts by mass of Maxive C93T manufactured by Mitsubishi Gas Chemical Company and 5 parts by mass of Maxive M-100 manufactured by Mitsubishi Gas Chemical Company.

(Example 1-1)
As a base material layer, a 25 μm thick unstretched polyethylene film (3-layer configuration of HDPE/MDPE/HDPE=5 μm/15 μm/5 μm), both sides of which were corona treated, was prepared. A coating liquid for forming a protective layer is prepared by mixing liquid A and liquid B, which were prepared as the coating liquid for forming a protective layer, in a mass ratio of 65/35 on the corona-treated outer surface of the base layer. This was applied by gravure coating, dried and cured to form a protective layer with a thickness of 0.5 μm. Furthermore, a printed layer (thickness: 1 μm) was formed on the corona-treated inner surface of the base layer by gravure printing using urethane ink. Ink was applied to the entire surface without forming an image.

Next, the surface of the base material layer on which the printed layer was formed and the corona-treated surface of the intermediate film A on which the vapor deposited layer was not formed were adhered by a dry rate method using adhesive A. This adhesive layer was designated as the first adhesive layer. The thickness of the first adhesive layer was 3 μm.

Furthermore, a single-sided corona-treated unstretched polyethylene film (LLDPE single-layer structure) with a thickness of 60 μm was prepared as a sealant layer. The surface of the intermediate film A on the vapor-deposited layer side and the corona-treated surface of the sealant layer were bonded together by a dry rate method using adhesive A as the second adhesive layer. Through the above steps, a laminate of Example 1-1 was obtained.

(Example 1-2)
A laminate of Example 1-2 was obtained in the same manner as in Example 1-1 except that the thickness of the protective layer was 2 μm and the thickness of the sealant layer was 150 μm.

(Example 1-3)
A laminate of Example 1-3 was obtained in the same manner as Example 1-1 except that intermediate film B was used instead of intermediate film A.

(Example 1-4)
A laminate of Example 1-4 was obtained in the same manner as Example 1-1 except that intermediate film C was used instead of intermediate film A and adhesive B was used as the second adhesive layer. .

(Example 1-5)
The thickness of the protective layer was 4 μm, and instead of intermediate film A, a 25 μm thick unstretched polyethylene film (3-layer configuration of HDPE/MDPE/HDPE = 5 μm/15 μm/5 μm) with corona treatment on both sides was used. A laminate of Example 1-5 was obtained in the same manner as Example 1-1 except that the thickness of the sealant layer was 150 μm.

(Example 2-1)
The laminate of Example 2-1 was prepared in the same manner as in Example 1-1 except that liquid A, liquid B, and liquid C were mixed at a mass ratio of 65/25/10 as the coating liquid for forming a protective layer. Obtained.

(Example 2-2)
A laminate of Example 2-2 was obtained in the same manner as in Example 2-1 except that the thickness of the protective layer was 2 μm and the thickness of the sealant layer was 150 μm.

(Example 2-3)
A laminate of Example 2-3 was obtained in the same manner as Example 2-1 except that intermediate film B was used instead of intermediate film A.

(Example 2-4)
A laminate of Example 2-4 was obtained in the same manner as in Example 2-1 except that intermediate film C was used instead of intermediate film A and adhesive B was used as the second adhesive layer. .

(Example 2-5)
The thickness of the protective layer was 4 μm, and instead of intermediate film A, a 25 μm thick unstretched polyethylene film (3-layer configuration of HDPE/MDPE/HDPE = 5 μm/15 μm/5 μm) with corona treatment on both sides was used. A laminate of Example 2-5 was obtained in the same manner as Example 2-1 except that the thickness of the sealant layer was 150 μm.

(Example 3-1)
The laminate of Example 3-1 was prepared in the same manner as in Example 1-1 except that liquid A, liquid B, and liquid C were mixed at a mass ratio of 45/45/10 as the coating liquid for forming a protective layer. Obtained.

(Example 3-2)
A laminate of Example 3-2 was obtained in the same manner as Example 3-1 except that the thickness of the protective layer was 2 μm and the thickness of the sealant layer was 150 μm.

(Example 3-3)
A laminate of Example 3-3 was obtained in the same manner as Example 3-1 except that intermediate film B was used instead of intermediate film A.

(Example 3-4)
A laminate of Example 3-4 was obtained in the same manner as in Example 3-1 except that intermediate film C was used instead of intermediate film A and adhesive B was used as the second adhesive layer. .

(Example 3-5)
The thickness of the protective layer was 4 μm, and instead of intermediate film A, a 25 μm thick unstretched polyethylene film (3-layer configuration of HDPE/MDPE/HDPE = 5 μm/15 μm/5 μm) with corona treatment on both sides was used. A laminate of Example 3-5 was obtained in the same manner as Example 3-1 except that the thickness of the sealant layer was 150 μm.

(Comparative Examples 1 to 5)
Laminates of Comparative Examples 1 to 5 were obtained in the same manner as in Examples 1-1 to 1-5, except that the coating liquid for forming the protective layer was replaced only with Liquid B.

(Comparative Examples 6 to 10)
Laminates of Comparative Examples 6 to 10 were obtained in the same manner as in Examples 1-1 to 1-5, except that no protective layer was formed.

(Example 4-1)
As a base material layer, a 25 μm thick unstretched polyethylene film (3-layer configuration of HDPE/MDPE/HDPE=5 μm/15 μm/5 μm), both sides of which were corona treated, was prepared. The above-mentioned anchor coating agent was applied to one side of the base layer by gravure coating and dried to provide an anchor coating layer with a thickness of 0.1 μm. Next, a transparent vapor deposition 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 vapor deposited layer was set to 1.8 by adjusting the type of vapor deposition material. The above-mentioned overcoat agent was applied onto the vapor deposited layer by a gravure coating method and dried to form a gas barrier coating layer (overcoat layer) having a gas barrier function and having a thickness of 0.3 μm.

Next, on the corona-treated side of the base material layer opposite to the side on which the vapor deposited layer was formed, liquid A and liquid B prepared as coating liquids for forming a protective layer are mixed in a mass ratio of 65/35, respectively. A layer-forming coating solution was prepared, applied by gravure coating, dried and cured to form a protective layer with a thickness of 0.3 μm. Further, as a sealant layer, a 20 μm thick single-sided corona-treated unstretched polyethylene film (single layer structure of LLDPE) was prepared. The gas barrier coating layer and the corona-treated surface of the sealant layer were bonded together by a dry rate method using adhesive A as the adhesive layer. Through the above steps, a laminate of Example 4-1 was obtained.

(Example 4-2)
A laminate of Example 4-2 was obtained in the same manner as in Example 4-1 except that the vapor deposited layer was changed to a 10 nm thick transparent vapor deposited layer made of aluminum oxide.

(Example 4-3)
A laminate of Example 4-3 was obtained in the same manner as Example 4-1 except that the gas barrier coating layer was not provided and the adhesive A was replaced with the above-mentioned adhesive B.

(Example 4-4)
A laminate of Example 4-4 was obtained in the same manner as Example 4-1 except that the base material layer was not provided with a vapor deposition layer and a gas barrier coating layer (overcoat layer).

(Example 5-1)
The laminate of Example 5-1 was prepared in the same manner as in Example 4-1 except that liquid A, liquid B, and liquid C were mixed at a mass ratio of 65/25/10 as the coating liquid for forming a protective layer. Obtained.

(Example 5-2)
A laminate of Example 5-2 was obtained in the same manner as in Example 5-1 except that the vapor deposited layer was changed to a 10 nm thick transparent vapor deposited layer made of aluminum oxide.

(Example 5-3)
A laminate of Example 5-3 was obtained in the same manner as Example 5-1 except that the gas barrier coating layer was not provided and the adhesive A was replaced with the above-mentioned adhesive B.

(Example 5-4)
A laminate of Example 5-4 was obtained in the same manner as Example 5-1 except that the base material layer was not provided with a vapor deposition layer and a gas barrier coating layer (overcoat layer).

(Example 6-1)
The laminate of Example 6-1 was prepared in the same manner as in Example 4-1 except that liquid A, liquid B, and liquid C were mixed at a mass ratio of 45/45/10 as the coating liquid for forming a protective layer. Obtained.

(Example 6-2)
A laminate of Example 6-2 was obtained in the same manner as Example 6-1 except that the vapor deposited layer was changed to a 10 nm thick transparent vapor deposited layer made of aluminum oxide.

(Example 6-3)
A laminate of Example 6-3 was obtained in the same manner as Example 6-1 except that the gas barrier coating layer was not provided and the adhesive A was replaced with the above-mentioned adhesive B.

(Example 6-4)
A laminate of Example 6-4 was obtained in the same manner as Example 6-1 except that the base material layer was not provided with a vapor deposition layer and a gas barrier coating layer (overcoat layer).

(Comparative Examples 11 to 14)
Laminates of Comparative Examples 11 to 14 were obtained in the same manner as in Examples 4-1 to 4-4, except that the coating liquid for forming the protective layer was replaced only with liquid B.

(Comparative Examples 15 to 18)
Laminates of Comparative Examples 15 to 18 were obtained in the same manner as in Examples 4-1 to 4-4, except that no protective layer was formed.

<Evaluation>
The following evaluations were performed on the laminates of each example and comparative example. The results are shown in Tables 1 to 10.

(Ratio of silicon atoms to carbon atoms (Si/C))
In order to obtain Si/C, first, a spectrum was obtained by performing narrow analysis on the exposed surface of the protective layer using the following measurement equipment and under the following measurement conditions. The ratio of Si and C was calculated from the obtained spectrum. Note that the ratio of silicon atoms to carbon atoms (Si/C) is a molar ratio.
<Measuring equipment>
JEOL Ltd., JPS-9030 type photoelectron spectrometer <Measurement conditions>
(Spectrum acquisition conditions)
Incident X-ray: MgKα (monochromatic X-ray, hν=1253.6eV)
X-ray output: 10W (10kV/10mA)
X-ray scanning area (measurement area): Circular area with a diameter of 6 mm Photoelectron capture angle: 90°

(Recyclability)
Based on the above formula (1), the proportion (mass %) of polyethylene in the laminate of each example was calculated. The evaluation was made in the following two stages.
A: The content of polyethylene is 90% by mass or more.
C: The content of polyethylene is less than 90% by mass.

(Evaluation of heat sealability)
Each of the produced laminates was cut into 10 cm square pieces, folded in half so that the sealant layer was on the inside, and heat sealed using a heat seal tester at a temperature of 140°C, a pressure of 0.1 MPa, and a heating time of 1 second. . However, Example 1-2, Example 1-5, Example 2-2, Example 2-5, Example 3-2, Example 3-5, Comparative Example 2, Comparative Example 5, Comparative Example 7, The heating time in Comparative Example 10 was 3 seconds. The heat-sealed portion of the obtained sample was visually observed, and the heat-sealability was evaluated based on the presence or absence of adhesion of the laminate to the heat-sealed bar and the presence or absence of wrinkles in the heat-sealed portion. Evaluation was performed based on the following criteria.
(1) Adhesion to the heat seal bar A: Melting adhesion of the laminate to the heat seal bar was not observed.
B: The laminate is pseudo-adhered to the heat seal bar, but can be separated without melt adhesion.
C: The laminate was melted and adhesion to the heat seal bar was observed.
(2) Wrinkles A in the heat-sealed part: No wrinkles were observed in the heat-sealed part.
C: Wrinkles are observed in the heat-sealed portion.

(Impact resistance)
Using the laminates of each example, ten packaging bags measuring 100 mm x 150 mm with heat-sealed peripheral edges were produced. Heat sealing was performed under the same conditions as in the above heat sealability evaluation. This packaging bag was filled with 200 g of distilled water, sealed with a heat seal, and stored at 5° C. for 1 day. After storage, each packaging bag was dropped from a height of 1.5 m 50 times, and the number of torn packaging bags was recorded.

(Hot water resistance)
Using the laminates of each example, ten packaging bags measuring 100 mm x 150 mm with heat-sealed peripheral edges were produced. Heat sealing was performed under the same conditions as in the above heat sealability evaluation. This packaging bag was filled with 200 g of distilled water, sealed by heat sealing, immersed in warm water at 80°C, boiled for sterilization for 30 minutes, and the surface condition of the package after treatment was observed. Evaluation was performed based on the following criteria.
A: No difference observed in the protective layer before and after treatment.
B: Slight lifting and roughness of the protective layer is observed.
C: Peeling, lifting, and roughness were observed in the protective layer.

(water resistance)
Using the laminates of each example, ten packaging bags measuring 100 mm x 150 mm with heat-sealed peripheral edges were produced. Heat sealing was performed under the same conditions as in the above heat sealability evaluation. This packaging bag was filled with 200 g of distilled water, sealed by heat sealing, and immersed in tap water (without temperature control). After 12 hours, the bag was taken out and the surface condition after the immersion treatment was observed. Evaluation was performed based on the following criteria.
A: No difference observed in the protective layer before and after treatment.
B: Slight lifting and roughness of the protective layer is observed.
C: Peeling, lifting, and roughness were observed in the protective layer.

(Oxygen permeability: OTR)
Oxygen permeability 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 a vapor deposited layer.

(Water vapor transmission rate: WVTR)
Water vapor permeability 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 a vapor deposited layer.

As shown in Tables 1 to 10, all of the Examples and Comparative Examples had high recyclability and excellent impact resistance and gas barrier properties, but when the protective layer was made of PVA only, the protective layer The hot water resistance and water resistance were poor, and the laminate of the comparative example without a protective layer had poor heat sealability. In Examples 2-1 to 2-5, 3-1 to 3-5, 5-1 to 5-4, and 6-1 to 6-4 in which the coating agent contains liquid C, the hot water resistance test result was A. Met.

DESCRIPTION OF SYMBOLS 1, 2... Laminate, 10... Base material layer, 10a... Base material layer outer surface, 10b... Base material layer inner surface, 11... Protective layer, 12... Printing layer, 14... Vapor deposition layer, 15... Gas barrier coating layer, 20 ... intermediate layer, 30 ... sealant layer, 40 ... first adhesive layer, 50, 60 ... second adhesive layer.

Claims (14)

A laminate having a structure in which a protective layer, a base material layer, and a sealant layer are laminated in this order,
the base layer and the sealant layer contain polyethylene,
The protective layer is
At least one of a hydroxyl group-containing polymer compound and a hydrolyzate thereof,
A heat-dried product of a composition containing at least one selected from the group consisting of metal alkoxides, silane coupling agents, and hydrolysates thereof,
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 composition contains a silane coupling agent. The laminate according to claim 2, wherein the silane coupling agent includes 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate. The laminate according to claim 1, comprising a vapor deposited layer located between the base layer and the sealant layer. The laminate according to claim 4, wherein the vapor deposition layer contains a metal oxide. The laminate according to claim 1, wherein the thickness of the protective layer is 0.4% or more and 2.0% or less of the total thickness of the laminate. The laminate according to claim 1, wherein the base layer contains 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, wherein at least one of the base layer and the sealant layer is a layer made of an unstretched polyethylene film. The laminate according to claim 1, comprising an intermediate layer located between the base layer and the sealant layer, the intermediate layer comprising polyethylene. The laminate according to claim 10, wherein the intermediate layer comprises high density polyethylene or medium density polyethylene. The laminate according to claim 10, wherein the intermediate layer is a layer made of an unstretched polyethylene film. A packaging material comprising the laminate according to any one of claims 1 to 12. A packaging bag made of the packaging material according to claim 13.

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