JP2023139596A - Laminate and packaging material - Google Patents

Abstract

To provide a laminate having excellent recyclability and heat-sealing properties.SOLUTION: There is provided a laminate obtained by laminating at least a base material layer, a first adhesive layer, an intermediate layer, a second adhesive layer and a sealant layer in this order, wherein a protective layer is provided on the outermost surface side of the base material layer, the protective layer is composed of a thermosetting resin, the base material layer, the intermediate layer and the sealant layer are composed of a polyethylene resin, the probe drop temperature on the surface of the base material layer is 180°C or more and 220°C or less, the probe drop temperature on the surface of the intermediate layer is 180°C or less and the ratio of polyethylene in the laminate is 90 mass% or more.SELECTED DRAWING: Figure 1

Description

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

JP2020-55157A

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 with excellent recyclability and heat sealability, and a packaging material using the same.

As a means for solving the above problems, a first aspect of the present invention is such that at least a base layer, a first adhesive layer, an intermediate layer, a second adhesive layer, and a sealant layer are laminated in this order. In the laminate, a protective layer is provided on the outermost surface side of the base layer, the protective layer is made of a thermosetting resin, the base layer, the intermediate layer, and the sealant layer are made of polyethylene resin, and The material layer has a probe drop temperature of 180°C or more and 220°C or less on the surface of the base material layer, and the intermediate layer has a probe drop temperature of 180°C or less on the surface of the intermediate layer, and the polyethylene content in the laminate is The laminate is characterized in that the proportion is 90% by mass or more.

In the laminate according to the present invention, by forming a thermosetting resin film serving as a protective layer on the outermost surface of the base material layer, thermal damage on the surface of the laminate during heat sealing is alleviated. In addition, the resin base material layer made of polyethylene with a probe fall temperature in the range of 180°C or more and 220°C or less has good transparency, so printing layers such as designs and letters can be printed on the inner surface of the base material. The placed packaging material also has high visibility. Further, the intermediate layer made of polyethylene having a needle drop temperature of 180° C. or lower has sufficient strength. Although the printed layer can be provided on either side of the base material as appropriate, this effect is more likely to be obtained in the case of a packaging material placed on the inner surface of the base material.

In a second aspect of the present invention, the protective layer comprises at least one of a metal alkoxide, a hydrolyzate of a metal alkoxide, and a reaction product of a metal alkoxide or a hydrolyzate of a metal alkoxide, and a water-soluble polymer. The laminate according to claim 1, comprising:

Further, a third aspect of the present invention is the laminate according to claim 1 or 2, characterized in that a gas barrier layer is provided on the surface of the base layer facing the sealant layer.

A fourth aspect of the present invention is the laminate according to claim 3, wherein the gas barrier layer includes an inorganic compound.

A fifth aspect of the present invention is the laminate according to claim 4, further comprising a coating layer on the inorganic compound layer.

In a sixth aspect of the present invention, the coating layer includes at least one of a metal alkoxide, a hydrolyzate of a metal alkoxide, and a reaction product of a metal alkoxide or a hydrolyzate of a metal alkoxide, and a water-soluble polymer. The laminate according to claim 5, comprising:

A seventh aspect of the present invention is a packaging material comprising the laminate according to any one of claims 1 to 6.

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

FIG. 1 is a schematic cross-sectional view showing one embodiment of a laminate according to the present invention. FIG. 2 is a schematic cross-sectional view of the laminate of Example 1.

The laminate according to the present invention will be explained in detail with reference to the drawings. FIG. 1 is a schematic sectional view showing one embodiment of a laminate according to the present invention, and FIG. 2 is a schematic sectional view of a laminate of Example 1 including a printed layer.

As shown in FIG. 1, the laminate 10 according to the present invention has a base material layer 1, a first adhesive layer 4, an intermediate layer 2, a second adhesive layer 6, and a sealant layer 3 laminated in this order, This is a laminate 10 in which a protective layer 7 is laminated on the outermost surface of a base layer 1 . Further, in the laminate 11 of Example 1 shown in FIG. 2, a printed layer 8 is provided on the back side of the base layer 1. The main components, the base layer 1, the intermediate layer 2, and the sealant layer 3, are all made of polyethylene resin.

<Method for measuring probe drop temperature>
Using an atomic force microscope equipped with a nanothermal microscope consisting of a cantilever with a heating mechanism, the cantilever is brought into contact with the surface of a resin base material in a solid state fixed to a sample stage, and a constant force ( When the sample is heated by applying tactile pressure and voltage, the sample surface thermally expands and the cantilever rises. When the cantilever is further heated, the sample surface softens and a large change in hardness is observed, and the cantilever descends and enters the sample surface. A sudden change in displacement at this time is detected. The point at which this displacement changes is the softening point, and by converting the voltage into temperature, it becomes the softening temperature, that is, the tip drop temperature.

The probe fall temperature is a temperature obtained by measuring the rising and falling behavior of the probe by locally performing thermal analysis. In order to evaluate the tip temperature drop, an atomic force microscope equipped with a nanothermal microscope consisting of a cantilever (probe) with a heating mechanism is used. When a cantilever is brought into contact with the surface of a solid sample fixed on a sample stage and heated by applying a certain force (touch pressure) to the cantilever (probe) in contact mode and applying a voltage, the sample is heated. The surface expands thermally and the cantilever rises. When the cantilever (probe) is further heated, the sample surface softens and a large change in hardness is observed, and the cantilever (probe) descends and penetrates the sample surface. A sudden change in displacement at this time is detected. The point at which this voltage changes is the point at which the probe starts to fall, and by converting the voltage into temperature, it becomes the temperature at which the probe falls. By performing such measurements, it is possible to know the probe drop temperature locally in the nanoscale region and near the surface.

As the atomic force microscope (AFM), MPF-3D-SA (trade name) and Ztherm system (trade name) manufactured by Oxford Instruments Co., Ltd. are used. The device is not particularly limited to this device, and Bruker Japan's Nano Thermal Analysis (trade name) series and nanoIR (trade name) series can also be used. Furthermore, it is also possible to attach Nano Thermal Analysis (trade name) as an accessory to other manufacturers' AFMs and perform measurements.

The cantilever (probe) used is AN2-200 (trade name) manufactured by Anasys Instruments. The present invention is not particularly limited to this cantilever, and other cantilevers (probes) may be used as long as they can sufficiently reflect laser light and apply voltage.

The voltage range to be applied to the cantilever (probe) depends on the resin to be measured, but it is preferably from 1V to 10V, and in order to reduce damage to the sample and measure with higher spatial resolution, it is recommended to range from 3V to 8V. More preferred.

Although the measurable probe drop temperature range depends on the resin to be measured, etc., it is generally possible to measure from a measurement start temperature of about 25°C, which is room temperature, to a measurement end temperature of about 400°C. The temperature range for calculating the probe drop temperature is preferably 25°C or more and 300°C or less.

To measure the tip temperature, heat is applied to the cantilever (probe) with a constant contact pressure.The contact pressure needs to be in contact with the sample, but it needs to be a force that does not destroy the surface. The spring constant of the cantilever (probe) is preferably 0.1 to 3.5 N/m, and in order to perform measurements in both tapping mode and contact mode, the spring constant is 0.5 to 3.5 N/m. It is preferable to use a cantilever (probe). The contact pressure is preferably 0.1 to 3.0V.

The heating rate of the cantilever (probe) depends on the heating mechanism provided by the cantilever (probe), but it is generally preferable to heat the cantilever at a heating rate of 0.1 V/sec or more and 10 V/sec or less. . It is more preferable to heat at a temperature increase rate of 0.2 V/sec or more and 5 V/sec or less. As the sample surface softens, the cantilever penetrates the sample and the needle descends. The amount of penetration of the cantilever (tip) must be deep enough to recognize the peak top of the softening curve, so it is preferably 3 to 500 nm. If the amount of penetration is large, the cantilever (tip) may be damaged. More preferably, it is 5 to 100 nm.

Although not limited to these, by approximating the expansion curve and the softening curve using functions as necessary, and calculating their intersection point, the tip descent starting point and tip descent temperature can be determined. It may be a method. Alternatively, an analysis method may be used in which the peak top of the displacement is used as the probe descent starting point or the probe descent temperature. In expansion or softening, it may be a displacement from a steady state to a certain constant value.

In order to accurately measure the temperature of the sample, a calibration curve was created after measuring the sample. There are four types of calibration samples: polycaprolactone (melting point: 55°C), low density polyethylene (LDPE, melting point: 110°C), polypropylene (PP, melting point: 164°C), and polyethylene terephthalate (PET, melting point: 235°C). was used. A calibration curve was created by measuring twice at different measurement positions, and using the average value as the probe drop temperature to create a calibration curve. Using this calibration curve, the voltage was taken as the tip drop starting point, which was converted into temperature and used as the tip drop temperature.

<Base material layer, intermediate layer>
As a result of measuring the probe drop temperature of various polyethylene resins, the inventors found that when the probe drop temperature is 180°C or higher, the haze of the base layer 1 is small, transparency is developed, and visibility is sufficient. It was found that transparency was further improved when the temperature was 200°C or higher. It becomes possible to arrange the printed layer 8 on the inner surface side of the base material layer 1. It has been found that this makes it easier to obtain the effects of the present invention. Note that the position of the printed layer 8 does not necessarily have to be on the back side of the base layer 1.

It has been found that the intermediate layer 2 has good drop impact strength when the probe fall temperature is 180° C. or less, leading to the completion of the present invention.

The base layer 1 and the intermediate layer 2 are made of high-density polyethylene and medium-density polyethylene having a density of 0.925 g/cm ³ or more. The thickness 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 to 10 μm or more, the strength of the laminate can be improved. By setting the thickness to 50 μm or less, the processability of the laminate can be improved.

The base layer 1 and the intermediate layer 2 are preferably surface-treated. According to this treatment, the adhesion between the base layer 1 and the intermediate layer 2 with adjacent layers can be improved. The method of surface treatment is not particularly limited. Examples of surface treatments include physical treatments such as corona discharge treatment, ozone treatment, low-temperature plasma treatment using oxygen gas and/or nitrogen gas, glow discharge treatment, and chemical treatment such as oxidation treatment using chemicals. One example is processing.

<Gas barrier layer>
In the layer structure shown in FIG. 1, it is desirable that the surface of the intermediate layer 2 facing the sealant layer 3 is provided with a gas barrier layer 5 made of an inorganic compound layer or an inorganic compound layer and a coating layer. The gas barrier layer 5 functions as a barrier layer that suppresses permeation of oxygen and water vapor.

Examples of the inorganic compound contained in the inorganic compound layer include a vapor deposited 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. By using the inorganic compound layer as a barrier film using a metal oxide, high barrier properties can be obtained with a very thin layer that does not affect the recyclability of the laminate 10.

The inorganic compound layer 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 thickness of the inorganic compound 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 compound layer is more preferably 7 nm or more and 15 nm or less.

The thickness of the inorganic compound 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 compound layer is more preferably 20 nm or more and 40 nm or less.

An anchor coat layer may be formed on the side of the intermediate layer 2 on which the inorganic compound layer is formed using a known anchor coat agent. Thereby, the adhesion of the inorganic compound 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.

The coating layer protects the inorganic compound layer and exhibits barrier properties independently of the inorganic compound layer. The coating layer can be formed using an aqueous solution containing at least one selected from the group consisting of hydroxyl group-containing polymer compounds, metal alkoxides, silane coupling agents, and hydrolysates thereof.

The thickness of the 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.

<Protective layer>
One main surface of the protective layer 7 constitutes the outermost surface of the laminate 10. The protective layer 7 contains a thermosetting resin and has excellent heat resistance. Examples of thermosetting resins include polyurethane resins, polyester resins, polyamide resins, polyamideimide resins, acrylic resins, epoxy resins, hydroxyl group-containing polymers, and organosilicon compounds. The protective layer 7 may contain one type of the above thermosetting resin, or may contain two or more types. As the thickness of the protective layer 7 becomes thinner, it tends to become difficult to achieve high heat resistance. In order to reduce or alleviate thermal damage during heat sealing, the thickness of the protective layer 7 is preferably 0.3 μm or more. Furthermore, as the thickness of the protective layer 7 increases, it tends to become difficult to sufficiently dry the resin coating during the manufacturing process of the laminate 10. From the viewpoint of productivity, the thickness of the protective layer 7 is preferably 3 μm or less.

Even when polyethylene with poor heat resistance is used as the base material layer 1, the provision of the protective layer 7 made of thermosetting resin on the outermost surface prevents thermal damage during heat sealing on the surface of the laminate. The reduction has been eased, and countermeasures such as slowing down the bag making speed are no longer necessary, and productivity no longer decreases.

<Print layer>
A printed layer 8 can be provided on the back side of the base layer 1 . The printing layer 8 is made of a conventionally used ink binder resin such as urethane-based, acrylic-based, nitrocellulose-based, rubber-based, or vinyl chloride-based ink, and various pigments, extender pigments, plasticizers, drying agents, and stabilizers. This layer is made of ink to which additives such as agents are added, and displays patterns such as letters and pictures. As the ink, it is preferable to use an ink derived from biomass.
Examples of methods for forming the printing layer 8 include well-known printing methods such as offset printing, gravure printing, flexographic printing, and silk screen printing, and well-known coating methods such as roll coating, knife edge coating, and gravure coating. method can be used. In particular, water-based flexographic printing is preferable because it imposes a small printing load on the base material layer and is also environmentally friendly.

<First adhesive layer, second adhesive layer>
The first adhesive layer 4 and the second adhesive layer 6 contain at least one type of adhesive. The adhesive may be a one-component curable adhesive, a two-component curable adhesive, or a non-curable adhesive. Further, the adhesive may be a solvent-free adhesive or a solvent-based adhesive.

As the first adhesive layer 4 and the second adhesive layer 6, epoxy adhesives such as polyether adhesives, polyester adhesives, silicone adhesives, polyamine adhesives, urethane adhesives, Examples include rubber adhesives, vinyl adhesives, silicone adhesives, epoxy adhesives, phenolic adhesives, and olefin adhesives.

The second adhesive layer 6 may be a cured product of a resin composition containing a polyester polyol, an isocyanate compound, and a phosphoric acid modified compound. Such an adhesive can further improve the oxygen barrier properties and water vapor barrier properties of the laminate 10.

The thickness of the first adhesive layer 4 and the second adhesive layer 6 is preferably within the range of 0.1 μm to 20 μm, more preferably within the range of 0.5 μm to 10 μm, More preferably, the thickness is in the range of 5 μm to 5 μm.

The first adhesive layer 4 and the second adhesive layer 6 can be formed by conventionally 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 coating and drying on the sealant layer 3.

<Heat seal layer>
The laminate having barrier properties obtained as described above can be further provided with a heat-sealing layer 3 and used as a packaging material. The heat seal layer 3 is made of polyethylene, and is bonded by heat sealing when forming a packaging material such as a packaging bag using the laminate. From the viewpoint of heat-sealability, the polyethylene constituting the heat-sealing layer is preferably low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), or very low-density polyethylene (VLDPE).

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. The heat seal layer may be a single layer or may have a multilayer structure. By having a multilayer structure, bag-making suitability and strength can be further improved while maintaining heat-sealability. From the viewpoint of environmental impact, biomass-derived polyethylene or recycled polyethylene is preferable.
The thickness of the heat-sealing layer 3 can be appropriately set in consideration of the shape of the packaging bag to be manufactured, the mass of the contents to be accommodated, etc., and can be set to, for example, 30 to 150 μm.

Tests conducted in connection with the present invention will be described below.
(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 coating liquid for forming protective layer and coating layer)
A coating solution for forming a protective layer and a coating layer (hereinafter referred to as "coating solution") was prepared by mixing the following solutions 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-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.

<Example 1>
First, as the base layer 1, corona treatment was performed on the surface side of a polyethylene film (SMUQ manufactured by Tokyo Ink Co., Ltd., thickness 25 μm) with a probe drop temperature of 211°C, and then the above-mentioned coating liquid was applied by gravure coating. This was dried to form a protective layer 7 with a thickness of 0.5 μm. Next, a corona treatment was performed on the opposite surface of the base layer 1, and a pattern was printed using water-based flexo ink to form a printed layer 8.

Next, as the intermediate layer 2, a film commercially available under the trade name "GAP" (Charter
Next Generation, Inc.) was prepared. The film commercially available under the trade name "GAP" is made of polyethylene, has a probe drop temperature of 160°C as measured by the method described above, a thickness of 25 μm, a density of 0.950 g/cm ³ , and a single-sided film. Corona treated.

Next, the above-described anchor coating agent was applied onto the intermediate layer 2 by a gravure coating method to form an anchor coating layer having a thickness of 0.1 μm (in a dry state). Next, a 40 nm thick inorganic compound layer composed of a silicon oxide (SiOx) vapor deposited film is formed as the gas barrier layer 5, and the above-mentioned coating liquid is further applied to form a 0.3 μm thick (dry state) coating. formed a layer.

Next, a urethane adhesive is applied on the printed layer 8 to form the first adhesive layer 4, and the intermediate layer 2 and the base material layer are bonded to each other via the printed layer 8 and the first adhesive layer 4. 1 was pasted together.

Next, a sealant layer 3 is prepared, a urethane adhesive is applied on the barrier layer 5 of the intermediate layer 2 to form a second adhesive layer 6, and the intermediate layer 2 and sealant layer 3 are bonded together. Ta. Linear low density polyethylene (LLDPE) was used as the material for the sealant layer.
In this way, the laminate according to Example 1 was manufactured.

<Example 2>
Example 1 except that a film commercially available under the trade name "HD200" (manufactured by Jindal Films, Inc.) was used as the base layer 1 instead of a film commercially available under the trade name "XCC". A laminate according to Example 2 was created by the same method as the laminate according to Example 2, and evaluated in the same manner. The film commercially available under the trade name "HD200" is made of polyethylene, has a probe drop temperature of 203°C as measured by the method described above, a haze of 5.9%, a thickness of 25 μm, and a density of is 0.950 g/cm ³ , and one side is corona treated.

<Comparative example 1>
The protective layer 7 was not provided, and instead of the film commercially available under the trade name "GAP", a film commercially available under the trade name "HD200" (manufactured by Jindal Films, Inc.) was used as the intermediate layer 2. A laminate according to Comparative Example 1 was prepared in the same manner as the laminate according to Example 2, except that the following was used, and evaluated in the same manner. The film commercially available under the trade name "HD200" is made of polyethylene, has a probe drop temperature of 203°C as measured by the method described above, a haze of 5.9%, a thickness of 25 μm, and a density of is 0.950 g/cm ³ , and one side is corona treated.

<Comparative example 2>
The protective layer 7 was not provided, and instead of the film commercially available under the trade name "HD200", a film commercially available under the trade name "GAP" (Charter Next Generation, Inc.) was used as the base layer 1. A laminate according to Comparative Example 2 was prepared in the same manner as the laminate according to Comparative Example 1, except that a laminate (manufactured by M.P. Co., Ltd.) was used, and evaluated in the same manner. The film commercially available under the trade name "GAP" is made of polyethylene, has a probe drop temperature of 160°C as measured by the method described above, a haze of 21.5%, a thickness of 25 μm, and a density of is 0.950 g/cm ³ , and one side is corona treated.

(Evaluation of sealability, print visibility, drop strength and recyclability)
A small piece of the laminate sample was folded in half with the sealant layer facing inside and heat sealed. The sealability of the seal surface, print visibility, puncture strength, and recyclability were evaluated.
・Sealability 〇: There are no wrinkles on the surface, and it does not stick to the seal bar. Characteristic ○: Proportion of polyethylene 90% by mass or more ×: Proportion of polyethylene less than 90% by mass / Drop strength Using each laminate, 10 packaging bags of 100 mm x 150 mm with heat-sealed peripheral portions were produced. This packaging bag was filled with 200 ml of tap water and sealed by heat sealing, and after being stored at 5°C for 1 day, it was dropped from a height of 1.5 m 50 times, and the number of torn packaging bags was recorded.

The above results are summarized in Table 1.

As shown in Table 1, all of the Examples and Comparative Examples had high recyclability, but the laminates of Comparative Examples 1 and 2, which did not have a protective layer, had poor sealing performance and drop strength. It can be seen that the laminates of Examples 1 and 2 according to the invention are excellent in all of sealing properties, print visibility, and drop strength, and have high existence value as packaging materials.

1... Base material layer 2... Intermediate layer 3... Sealant layer 4... First adhesive layer 5... Gas barrier layer 6... Second adhesive layer 7... Protective layer 8 ...Printing layers 10, 11...Laminated body

Claims (7)

At least, in a laminate in which a base material layer, a first adhesive layer, an intermediate layer, a second adhesive layer, and a sealant layer are laminated in this order,
A protective layer is provided on the outermost side of the base layer,
The protective layer is made of a thermosetting resin,
The base layer, the intermediate layer and the sealant layer are made of polyethylene resin,
The base material layer has a probe drop temperature on the surface of the base material layer of 180°C or more and 220°C or less,
The intermediate layer has a probe drop temperature of 180° C. or less on the surface of the intermediate layer,
A laminate characterized in that the proportion of polyethylene in the laminate is 90% by mass or more. The laminate according to claim 1, wherein the protective layer contains at least one of a metal alkoxide, a hydrolyzate of a metal alkoxide, and a reaction product of a metal alkoxide or a hydrolyzate of a metal alkoxide, and a water-soluble polymer. . The laminate according to claim 1 or 2, further comprising a gas barrier layer on at least one surface of the intermediate layer. The laminate according to claim 3, wherein the gas barrier layer includes an inorganic compound. The laminate according to claim 4, further comprising a coating layer on the inorganic compound layer. The laminate according to claim 5, wherein the coating layer contains at least one of a metal alkoxide, a hydrolyzate of a metal alkoxide, and a reaction product of a metal alkoxide or a hydrolyzate of a metal alkoxide, and a water-soluble polymer. . A packaging material comprising the laminate according to any one of claims 1 to 6.

Images