WO2024111580A1 - Laminate and paper container for liquid - Google Patents

Abstract

This laminate exhibits high barrier characteristics and a high heat-sealability, while retaining a high paper ratio. The laminate has the following in the indicated sequence: a thermoplastic resin layer, a paper base layer, an adhesive resin layer, a vapor-deposited layer, and a sealant layer. The sealant layer is provided in an outermost layer of the laminate; the laminate has a protective layer between the adhesive resin layer and the vapor-deposited layer; and the sealant layer contains a metallocene-catalyzed linear low-density polyethylene.

Description

Laminate and liquid paper container

This disclosure relates to a laminate and a liquid paper container.

　Conventionally, a barrier laminate having a paper base layer is known that has a resin film having a vapor-deposited layer of a metal such as aluminum as a barrier layer.

For example, Patent Document 1 (JP 2011-001107 A) describes a packaging container material having a first film made of polypropylene obtained using a metallocene catalyst and a metal vapor deposition layer vapor-deposited on a first surface of the first film.

However, when using a resin film with a vapor deposition layer for packaging containers, as in the technology described in Patent Document 1 (JP Patent Publication 2011-001107), a sealant layer is also required to adhere the resin film. This increases the amount of resin film, which means that the paper ratio (biomass ratio) of the constituent components decreases.

The present disclosure relates to a laminate that has high barrier properties and heat sealability while maintaining a high paper ratio. The present disclosure also relates to a liquid paper container made using the above laminate.

The present disclosure relates to the following [1] to [10].
[1] A laminate having a thermoplastic resin layer, a paper base layer, an adhesive resin layer, a vapor deposition layer, and a sealant layer in this order,
the sealant layer is provided on the outermost layer of the laminate,
the laminate has a protective layer between the adhesive resin layer and the vapor deposition layer,
A laminate wherein the sealant layer comprises a metallocene-catalyzed linear low density polyethylene.
[2] The laminate according to [1], wherein the ratio of the paper base layer in the laminate is 80% by mass or more.
[3] The laminate according to [1] or [2], wherein the sealant layer has a melt flow rate of 1.0 to 6.0 g/10 min.
[4] The density of the sealant layer is 0.905 to 0.925 g/ ^cm3 ,
The laminate according to any one of [1] to [3], wherein the sealant layer has a Vicat softening point of 84 to 100° C.
[5] The laminate according to any one of [1] to [4], wherein the sealant layer is an inflation molded article.
[6] The laminate according to any one of [1] to [5], wherein the content of the metallocene-catalyzed linear low-density polyethylene in the sealant layer is 70 to 100 mass %.
[7] The laminate according to any one of [1] to [6], wherein the sealant layer contains 0 to 30 mass% of low-density polyethylene based on the mass of the sealant layer.
[8] The laminate according to any one of [1] to [7], wherein the vapor deposition layer contains at least one selected from the group consisting of silica, alumina, and diamond-like carbon.
[9] The laminate according to any one of [1] to [8], wherein the protective layer contains at least one resin selected from the group consisting of a polyurethane resin, a polyester resin, and an ethylene-vinyl alcohol copolymer resin.
[10] The laminate according to any one of [1] to [9], wherein the laminate has an undercoat layer between the vapor deposition layer and the sealant layer.
[11] The laminate according to any one of [1] to [10], which is for use in a paper container for liquids (for example, a paper container for aseptically filled liquids).
[12] A liquid-storing paper container using the laminate according to any one of [1] to [10].
[13] A method for producing a laminate having a thermoplastic resin layer, a paper base layer, an adhesive resin layer, a protective layer, a vapor deposition layer, and a sealant layer in this order, comprising:
forming the sealant layer comprising metallocene-catalyzed linear low density polyethylene;
forming the deposition layer on the sealant layer directly or via an undercoat layer;
forming the protective layer on the deposition layer to obtain a sealant film;
laminating the protective layer of the sealant film and the paper base layer via the adhesive resin layer;
The method for producing a laminate comprising the steps of:
[14] The method for producing a laminate according to [13], wherein the content of the metallocene-catalyzed linear low-density polyethylene in the sealant layer is 70 to 100 mass %.
[15] The method for producing a laminate according to [13] or [14], wherein the sealant layer contains 0 to 30 mass % of low-density polyethylene based on the mass of the sealant layer.
[16] The method for producing a laminate according to any one of [13] to [15], wherein the protective layer contains at least one resin selected from the group consisting of a polyurethane resin, a polyester resin, and an ethylene-vinyl alcohol copolymer resin.

Schematic cross-sectional view of a laminate

Hereinafter, preferred embodiments of the present disclosure will be described. In this specification, the description of "X or more and Y or less" or "X to Y" representing a numerical range means a numerical range including the lower and upper limits which are the endpoints, unless otherwise specified. When a numerical range is described in stages, the upper and lower limits of each numerical range can be combined in any way.
Furthermore, a description such as "at least one selected from the group consisting of A, B, and C" means any of A, B, C, A and B, A and C, B and C, or A, B, and C.

In addition, in this specification, "on a layer" means that it may be directly on top of a layer, or it may be on top of a layer via another layer. In addition, in this specification, (meth)acrylic is a general term for acrylic and methacrylic.

[Laminate]
The laminate according to the present embodiment has a thermoplastic resin layer, a paper base layer, an adhesive resin layer, a vapor deposition layer, and a sealant layer in this order, the sealant layer being provided on the outermost layer of the laminate, the laminate having a protective layer between the adhesive resin layer and the vapor deposition layer, and the sealant layer containing a metallocene-catalyzed linear low-density polyethylene. The laminate according to the present embodiment has high barrier properties and heat sealability while maintaining a high paper ratio, and can be suitably used, for example, as a paper container for liquids (particularly, a paper container for aseptically filled liquids).

A preferred embodiment of the laminate will be described with reference to the drawings. The laminate 10 shown in FIG. 1 has a thermoplastic resin layer 1, a paper base layer 2, an adhesive resin layer 3, a vapor deposition layer 12, and a sealant layer 11, in this order. The laminate also has a protective layer 13 between the adhesive resin layer 3 and the vapor deposition layer 12. The sealant layer 11, the vapor deposition layer 12, and the protective layer 13 may form a sealant film 4. For example, the laminate 10 may be a laminate in which the thermoplastic resin layer 1, the paper base layer 2, the adhesive resin layer 3, and the sealant film 4 are laminated in this order.

The sealant layer 11 is provided on the outermost layer of the laminate 10. That is, one surface of the laminate 10 may be the sealant layer 11, and the other surface may be the thermoplastic resin layer 1. In the laminate, other layers may be present between the above layers as long as they do not impair the effects of the present disclosure.
For example, as long as the paper ratio can be maintained high, the laminate may have an undercoat layer between the deposition layer 12 and the sealant layer 11. In this case, the laminate is formed by laminating a thermoplastic resin layer, a paper base layer, an adhesive resin layer, a protective layer, a deposition layer, an undercoat layer, and a sealant layer in this order.
For example, when used in a paper container for aseptically filled liquids, a printed layer may be provided on one side of the paper substrate. In this case, the laminate is formed by laminating a thermoplastic resin layer, a printed layer, a paper substrate layer, an adhesive resin layer, a protective layer, a vapor deposition layer, and a sealant layer in this order. The printed layer can be formed by a known coating method using a known pigment and binder.

By providing the sealant layer 11, the deposition layer 12, and the protective layer 13 in this order in the laminate 10, there is no need to provide an additional sealant layer on a resin film with a deposition layer as in Patent Document 1 (JP Patent Publication 2011-001107). In addition, an adhesive layer for adhering the sealant layer is also not required. As a result, the amount of film used can be reduced, and the paper ratio (biomass ratio) of the constituent components is improved. Furthermore, productivity is improved because the number of layers can be reduced.

In addition, the sealant layer 11 of the laminate 10 of this embodiment contains metallocene-catalyzed linear low-density polyethylene, but such a sealant layer has the problem of low wettability and low adhesion to the deposition layer. In addition, since metallocene-catalyzed linear low-density polyethylene has low heat resistance, it is difficult to form a deposition layer without defects due to thermal expansion and contraction during deposition. According to the present disclosure, the adhesion to the deposition layer and heat resistance can be improved by performing a surface treatment (corona treatment, etc.) of the sealant layer described below or forming an undercoat layer, and defects in the deposition layer can be covered by providing a protective layer on the deposition layer, thereby solving the above problems and obtaining a laminate with excellent barrier properties.

In order to obtain such a laminate 10, for example, a method of forming a vapor deposition layer 12 on the sealant layer 11 can be mentioned. The vapor deposition layer 12 is preferably vapor-deposited on the sealant layer 11. When an undercoat layer is formed on the sealant layer, the vapor deposition layer is preferably vapor-deposited on the undercoat layer.

In a laminate, whether or not the vapor deposition layer has been vapor-deposited onto the sealant layer (or undercoat layer) can be confirmed by the following method. If there is no adhesive layer of 2 μm or more between the vapor deposition layer and the sealant layer (or undercoat layer) and an adhesive layer of 2 μm or more exists on the side of the vapor deposition layer opposite the sealant layer, it can be assumed that the vapor deposition layer has been vapor-deposited onto the sealant layer (or undercoat layer). Components of the adhesive layer include resins such as polyolefin resins, unsaturated polyolefin carboxylic acid copolymers, polyurethane resins, and epoxy resins, which are described below as adhesive resin layers. In addition, by checking the sealant layer (or undercoat layer) for traces of surface treatment such as corona discharge treatment, it is possible to estimate the surface on which the vapor deposition layer has been vapor-deposited.

The sealant layer 11 is provided on the outermost layer of the laminate 10. This allows it to exhibit sufficient heat sealability. The sealant layer 11 contains metallocene-catalyzed linear low-density polyethylene (m-LLDPE). m-LLDPE is a linear low-density polyethylene produced using a metallocene catalyst. The sealant layer 11 contains m-LLDPE, which allows it to obtain good low-temperature heat sealability. Furthermore, the sealant layer 11 contains m-LLDPE, which reduces volatile low-molecular-weight components and makes it easier to reduce odors, so it is thought that the transfer of odors to liquids when used in liquid paper containers can be suppressed.

From the viewpoint of the strength of the laminate, the laminate 10 preferably has a basis weight of 200 g/m ² or more and 1000 g/m ² or less.
From the viewpoint of maintaining the shape of the liquid paper container, the basis weight of the laminate 10 is more preferably 250 g/m ² or more, even more preferably 300 g/m ² or more, and even more preferably 350 g/m ² or more. From the viewpoint of processability and transportability, the basis weight of the laminate 10 is more preferably 800 g/m ² or less, and even more preferably 500 g/m ² or less.
The basis weight (g/m ² ) can be measured in accordance with JIS P 8124:2011.

The ratio of the paper base layer 2 in the laminate 10 is preferably 80% by mass or more, and more preferably 81% by mass or more. In addition, the upper limit of the ratio of the paper base layer 2 is not particularly limited, but is usually 99% by mass or less, and preferably 90% by mass or less, or may be 87% by mass or less. The above range indicates that the ratio of paper in the constituent components is very high.

From the viewpoint of more effectively ensuring the oxygen barrier properties of the laminate, the oxygen permeability of the laminate measured at 23°C and a relative humidity of 50% in accordance with JIS K 7126-2:2006 is preferably less than 5.0 mL/ ^m2 /day/atm, more preferably 3.0 mL/ ^m2 /day/atm or less, even more preferably 2.0 mL/ ^m2 /day/atm or less, even more preferably 1.6 mL/ ^m2 /day/atm or less, even more preferably 1.0 mL/ ^m2 /day/atm or less, and even more preferably 0.5 mL/ ^m2 /day/atm or less. The lower limit of the oxygen permeability is not particularly limited, but is usually 0 mL/ ^m2 /day/atm or more, may be 0.03 mL/ ^m2 /day/atm or more, or may be 0.1 mL/ ^m2 /day/atm or more.

From the viewpoint of more effectively ensuring the water vapor barrier properties of the laminate, the water vapor permeability of the laminate measured at 40°C and a relative humidity of 90% in accordance with JIS Z 0208: 1976 is preferably less than 5.0 g/ ^m2 /day, more preferably 3.0 g/ ^m2 /day or less, even more preferably 2.0 g/ ^m2 /day or less, even more preferably 1.5 g/ ^m2 /day or less, and even more preferably 1.0 g/ ^m2 /day or less. The lower limit of the water vapor permeability is not particularly limited, and is usually 0 g/ ^m2 /day or more, may be 0.1 g/ ^m2 /day or more, or may be 0.3 g/ ^m2 /day or more.
According to the present disclosure, it is possible to provide a laminate having high barrier properties and heat sealability while maintaining a high paper ratio, and a liquid paper container using the laminate.
Each layer constituting the laminate 10 will now be described.

[Thermoplastic resin layer]
The thermoplastic resin layer 1 may be present on the surface of the laminate. The thermoplastic resin layer is, for example, a layer that becomes the outer surface (printed surface) of the liquid paper container when the liquid paper container is molded. The thermoplastic resin layer 1 and the sealant layer 11 may be heat-sealed when the liquid paper container is molded.

There are no particular limitations on the resin used in the thermoplastic resin layer 1, and any known resin may be used. The resin used in the thermoplastic resin layer 1 is preferably one that can be heat-sealed with the sealant layer, and more preferably the thermoplastic resin layer itself has heat-sealability.
Specific examples include low density polyethylene (LDPE), linear low density polyethylene (LLDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), ethylene-propylene copolymer, ethylene-butene copolymer, propylene-butene copolymer, propylene homopolymer, propylene-ethylene random copolymer, propylene-ethylene block copolymer, propylene-ethylene-butene copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl methacrylate copolymer, cyclohexane dimethanol modified polyethylene tephthalate. Examples of suitable biodegradable resins include polyester resins such as acrylic acid copolymers, polymethylpentene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyester copolymers, polystyrene, polyvinyl chloride, acrylonitrile butadiene styrene (ABS) resins, acrylic resins, modified polyphenylene ether (PPE), and polyamide resins; biodegradable resins such as polylactic acid (PLA), polyhydroxybutyric acid (PHB), polybutylene succinate (PBS), poly(butylene adipate-co-butylene terephthalate) (PBAT), polycaprolactone (PCL), and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH); and mixtures thereof.

The method for forming the thermoplastic resin layer 1 is not particularly limited, and the above-mentioned resin may be laminated using a known method to form the thermoplastic resin layer 1. Alternatively, the thermoplastic resin layer 1 may be formed by coating an emulsion of the above-mentioned resin.
The resin used in the thermoplastic resin layer 1 is preferably at least one selected from the group consisting of polyethylene and biodegradable resins, more preferably at least one selected from the group consisting of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE) and biodegradable resins, even more preferably at least one selected from the group consisting of low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE), and even more preferably low-density polyethylene (LDPE). Polyethylene is preferably used as a liquid paper container material because it is low cost and has appropriate flexibility.

The thickness of the thermoplastic resin layer 1 is not particularly limited, but from the viewpoint of adhesion to the sealant layer, it is preferably 5 μm or more, more preferably 10 μm or more, and from the viewpoint of reducing the environmental load, it is preferably 40 μm or less, more preferably 32 μm or less.
The basis weight of the thermoplastic resin layer 1 is not particularly limited, but from the viewpoint of adhesion to the sealant layer, it is preferably 5 g/ ^m2 or more, more preferably 10 g/ ^m2 or more, and from the viewpoint of reducing the environmental load, it is preferably 40 g/ ^m2 or less, more preferably 30 g/ ^m2 or less.

[Paper base layer]
The paper base layer 2 functions as a base layer that holds the laminate 10, and is preferably one that can impart strength to the laminate as a liquid paper container material. The material of the paper base layer 2 is not particularly limited, but known papers such as paperboard such as coated board, card paper, ivory paper, and manila board, milk carton base paper, cup base paper, kraft paper, and fine paper can be used.

The thickness of the paper base layer 2 is not particularly limited, but is preferably 100 to 1000 μm, and more preferably 300 to 800 μm.
The basis weight of the paper base layer 2 is preferably 100 g/m ² or more, more preferably 200 g/m ² or more, even more preferably 300 g/m ² or more, and preferably 1000 g/m ² or less, more preferably 700 g/m ² or less, and even more preferably 400 g/m ² or less. When the basis weight of the paper base layer 2 is 100 g/m ² or more, sufficient strength can be imparted to the laminate, and it can be suitably used for liquid paper container applications. Furthermore, since the ratio of the paper base layer 2 in the laminate 10 is high, it can be applied to applications where plastic-free is required. In addition, when the basis weight of the paper base layer 2 is 1000 g/m ² or less, it can be expected to be suitable for processing into liquid paper containers and to reduce the load during transportation.

[Adhesive resin layer]
The adhesive resin layer 3 bonds the paper base layer 2 and the protective layer 13 (e.g., the protective layer 13 in the sealant film 4). The adhesive resin layer 3 is not particularly limited as long as it can bond the paper base layer 2 and the protective layer 13, and any known resin can be used. Specifically, the resins mentioned above as the resin for the thermoplastic resin layer can be used.

The resin used for the adhesive resin layer 3 may be at least one selected from the group consisting of polyethylene such as low density polyethylene (LDPE), linear low density polyethylene (LLDPE), medium density polyethylene (MDPE), and high density polyethylene (HDPE); ethylene-acrylic acid copolymer; and ethylene-methacrylic acid copolymer (EMAA).
Preferably, it is at least one selected from the group consisting of low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and ethylene-methacrylic acid copolymer (EMAA), more preferably, it is at least one selected from the group consisting of low density polyethylene (LDPE) and ethylene-methacrylic acid copolymer (EMAA), and from the viewpoint of improving the adhesion between the paper base layer and the protective layer, it is even more preferably ethylene-methacrylic acid copolymer (EMAA).

The method for forming the adhesive resin layer 3 is not particularly limited, and the adhesive resin layer 3 may be formed by laminating the resin using a known method. Alternatively, the adhesive resin layer 3 may be formed by coating an emulsion of the resin on the paper base layer 2 or the protective layer 13.

The thickness of the adhesive resin layer 3 is not particularly limited, but from the viewpoint of adhesion to the sealant layer, it is preferably 5 μm or more, more preferably 10 μm or more, and from the viewpoint of reducing the environmental load, it is preferably 30 μm or less, more preferably 22 μm or less.
The basis weight of the adhesive resin layer 3 is not particularly limited, but from the viewpoint of adhesion to the sealant layer, it is preferably 5 g/ ^m2 or more, more preferably 10 g/ ^m2 or more, and from the viewpoint of reducing the environmental load, it is preferably 30 g/ ^m2 or less, more preferably 20 g/ ^m2 or less.

[Sealant film]
The laminate 10 may have a sealant film 4 formed by laminating a sealant layer 11, a vapor deposition layer 12, and a protective layer 13. For example, the sealant film 4 includes the sealant layer 11, the vapor deposition layer 12, and the protective layer 13 in this order, and has an undercoat layer between the vapor deposition layer 12 and the sealant layer 11 as necessary. The sealant film 4 may be a film consisting of only the sealant layer 11, the vapor deposition layer 12, and the protective layer 13, or may be a film consisting of only the sealant layer 11, the undercoat layer, the vapor deposition layer 12, and the protective layer 13. The sealant layer 11, the vapor deposition layer 12, the protective layer 13, and the undercoat layer will be described below. The sealant film may further have layers other than these layers.

[Deposition layer]
The vapor deposition layer 12 can be, for example, a barrier layer provided to suppress the transmission of oxygen or water vapor through the laminate 10. The vapor deposition layer 12 is preferably provided on the surface of the sealant layer 11 facing the paper base layer 2. The vapor deposition layer 12 preferably includes at least one selected from the group consisting of inorganic substances, and is more preferably formed of at least one selected from the group consisting of inorganic substances. Examples of inorganic substances include metals, metal oxides, non-metal oxides, and inorganic substances other than those mentioned above.
In the present disclosure, the deposition layer refers to a film formed by a deposition method in a broad sense, and includes not only films formed by vacuum deposition methods but also films formed by sputtering and the like.

Among the inorganic substances applied to the deposition layer 12, metals that can be used include, for example, aluminum (Al), magnesium (Mg), tin (Sn), sodium (Na), titanium (Ti), lead (Pb), zirconium (Zr), yttrium (Y), gold (Au), and chromium (Cr).

Among the inorganic substances applied to the deposition layer 12, the metal oxide may be any of the metals listed above, such as aluminum oxide (alumina) or titanium oxide. An example of a non-metal oxide is silica, which is an oxide of silicon (Si).
Other inorganic substances include carbon-based materials such as diamond-like carbon, graphite, graphene, etc. The deposition layer 12 preferably contains at least one selected from the group consisting of silica, alumina, and diamond-like carbon, and more preferably contains at least one selected from the group consisting of silica, alumina, and diamond-like carbon.

The thickness of the vapor deposition layer 12 varies depending on the type of material used, but is preferably 5 to 50 nm, more preferably 7 to 30 nm, and even more preferably 8 to 25 nm. By being equal to or greater than the lower limit, more sufficient barrier properties can be obtained. On the other hand, by being equal to or less than the upper limit, it is easier to increase the paper ratio while still obtaining sufficient barrier properties.

The method for forming the deposition layer 12 is not particularly limited, and known methods can be used. For example, physical vapor deposition methods (Physical Vapor Deposition method, PVD method) such as electron beam deposition method, vacuum deposition method, sputtering method, and ion plating method, or chemical vapor deposition methods (Chemical Vapor Deposition method, CVD method) such as plasma chemical vapor deposition method, thermal chemical vapor deposition method, and photochemical vapor deposition method can be mentioned.

[Sealant layer]
The sealant layer 11 is a layer that can become the inner surface (liquid-contacting surface) of the liquid-carton container when the liquid-carton container is formed, for example. When the liquid-carton container is formed, the thermoplastic resin layer 1 and the sealant layer 11 may be heat-sealed. As described above, the sealant layer 11 contains metallocene-catalyzed linear low-density polyethylene (m-LLDPE). There are no particular limitations on the m-LLDPE, and any known product may be used. The m-LLDPE may be either a commercially available product or a synthetic product. In the case of a synthetic product, it can be produced using a known method. The sealant layer 11 may be either a single layer or a multilayer, but is preferably a single layer.

The linear low density polyethylene is usually a copolymer of ethylene and an α-olefin. The α-olefin is preferably an α-olefin having 3 to 20 carbon atoms, such as propylene, butene-1, 3-methylbutene-1, 3-methylpentene-1, 4-methylpentene-1, hexene-1, octene-1, pentene-1, decene-1, tetradecene-1, hexadecene-1, octadecene-1, and eicosene-1. The α-olefins may be used alone or in combination of two or more.

In addition to m-LLDPE, the sealant layer 11 may contain other resins to the extent that the effects of the present disclosure are not impaired. The content of linear low density polyethylene (m-LLDPE) in the sealant layer is preferably 70% by mass or more, more preferably 75% by mass or more, from the viewpoint of low-temperature heat sealability, and, as described below, is preferably 100% by mass or less, more preferably 90% by mass or less, even more preferably 85% by mass or less, and even more preferably 80% by mass or less, from the viewpoint of the formation efficiency of the sealant layer.
The content of m-LLDPE in the sealant layer is preferably 70 to 100% by mass, more preferably 70 to 90% by mass, even more preferably 75 to 90% by mass, still more preferably 75 to 85% by mass, and particularly preferably 75 to 80% by mass.

The resin other than m-LLDPE is not particularly limited as long as it has heat sealability. For example, the resins listed in the above [Thermoplastic resin layer] can be used.
The other resin preferably includes at least one selected from the group consisting of low density polyethylene (LDPE) and linear low density polyethylene (LLDPE), and more preferably includes low density polyethylene (LDPE). The content of the other resin (e.g., LDPE) in the sealant layer is preferably 30% by mass or less, more preferably 25% by mass or less, from the viewpoint of low temperature heat sealability, and is preferably 0% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and even more preferably 20% by mass or more, from the viewpoint of the formation efficiency of the sealant layer, as described later.
The sealant layer preferably contains 0 to 30 mass %, more preferably 10 to 30 mass %, even more preferably 10 to 25 mass %, still more preferably 15 to 25 mass %, and particularly preferably 20 to 25 mass %, of another resin (e.g., low-density polyethylene) based on the mass of the sealant layer.

When forming the sealant layer 11 by melt extrusion, m-LLDPE alone has low fluidity, so a highly mixed screw must be used in the extruder, and changing from a standard screw may result in a decrease in work efficiency. From this perspective, it is preferable to melt extrude m-LLDPE together with other resins (e.g., LDPE). In other words, from the perspective of the efficiency of forming the sealant layer, it is preferable that the sealant layer 11 contains m-LLDPE and other resins (e.g., LDPE). In this case, the preferred content of each resin in the sealant layer is as described above.

The melt flow rate (MFR) of the sealant layer is preferably 1.0 to 6.0 g/10 min, more preferably 1.5 to 5.0 g/10 min, and even more preferably 1.7 to 4.2 g/10 min. When the MFR is within the above range, odors generated from the sealant layer are easily suppressed. Therefore, the sealant layer is preferable as a liquid paper container for storing food.
For the same reason, the melt flow rate (MFR) of the m-LLDPE contained in the sealant layer is also preferably within the above range. The MFR of m-LLDPE is mainly affected by the molecular weight of LLDPE, and the higher the molecular weight, the lower the MFR tends to be, and the lower the molecular weight, the higher the MFR tends to be. The molecular weight can be adjusted within a desired range by appropriately selecting the manufacturing method of m-LLDPE (for example, high pressure method, gas phase method, etc.), the raw material (the above-mentioned α-olefin), and the type and amount of catalyst added. In order to set the MFR of the sealant layer within the above range, it is preferable to lower the molding temperature from the viewpoint of maintaining a high molecular weight.

The density of the sealant layer is preferably 0.905 to 0.925 g/ ^cm3 , and more preferably 0.906 to 0.915 g/ ^cm3 . When the density is in the above range, a sealant layer with high sealing performance can be obtained. The density of the sealant layer can be controlled by the type of resin used and the addition of additives. For the same reason, the density of the m-LLDPE contained in the sealant layer is also preferably within the above range. The density of the m-LLDPE can be adjusted to within a desired range by appropriately selecting the production method of the m-LLDPE (for example, the high pressure method, the gas phase method, etc.), the raw material (the above-mentioned α-olefin), the type and amount of the catalyst, etc.

The Vicat softening point of the sealant layer is preferably 84 to 100°C, and more preferably 86 to 98°C. With a Vicat softening point in the above range, a sealant layer with excellent low-temperature sealing properties and hot tack can be obtained. The Vicat softening point of the sealant layer can be controlled by the type of resin used and the addition of additives. For the same reason, the Vicat softening point of the m-LLDPE contained in the sealant layer is also preferably within the above range. The Vicat softening point of the m-LLDPE can be adjusted to within the desired range by appropriately selecting the manufacturing method of m-LLDPE (for example, high pressure method, gas phase method, etc.), raw material (the above-mentioned α-olefin), type and amount of catalyst, etc.

The method for forming the sealant layer is not particularly limited, and m-LLDPE (or a mixture of m-LLDPE and other resins) can be formed by a known method. It is preferable that linear low-density polyethylene synthesized by a high-pressure method using a metallocene catalyst is melted together with other resins (for example, LDPE) as necessary in an extruder such as a single-screw extruder, and then film-formed by an inflation method. That is, the sealant layer is preferably an inflation molded product.
In the inflation method, for example, a heated and molten resin is extruded from an opening in a mold while cooling air is blown into it, thereby obtaining a film-like molded product.

The temperature at which linear low-density polyethylene (or a mixture of m-LLDPE and other resins) is melted is preferably 130 to 200°C, more preferably 140 to 190°C, and even more preferably 150 to 180°C. The temperature at which film is formed by inflation molding is preferably 130 to 200°C, and more preferably 150 to 180°C. The above temperature range for inflation molding is a relatively low temperature, which makes it easy to suppress odors originating from low molecular weight components generated by thermal decomposition. Therefore, it is preferable for use in liquid paper containers.

The thickness of the sealant layer 11 is not particularly limited, but from the viewpoint of heat sealability, it is preferably 15 μm or more, more preferably 25 μm or more, and from the viewpoint of reducing the environmental load, it is preferably 50 μm or less, more preferably 35 μm or less.
The basis weight of the sealant layer 11 is not particularly limited, but from the viewpoint of heat sealability, it is preferably 10 g/ ^m2 or more, more preferably 20 g/ ^m2 or more, and from the viewpoint of reducing the environmental load, it is preferably 50 g/ ^m2 or less, more preferably 30 g/ ^m2 or less.

The deposition layer 12 can be formed, for example, by directly depositing the inorganic material described above on the sealant layer 11 using the electron beam deposition method described above.
When the deposition layer 12 is provided directly on the sealant layer 11 as described above, the surface of the sealant layer 11 may be pretreated as necessary, and it is preferable to pretreat the surface from the viewpoint of improving the wettability of the sealant layer and increasing the adhesion between the sealant layer and the deposition layer as described above. That is, the surface of the sealant layer 11 facing the deposition layer 12 may be surface-treated, and it is preferable to surface-treat the surface from the viewpoint of improving the wettability of the sealant layer and increasing the adhesion between the sealant layer and the deposition layer as described above. Specific examples of the surface treatment include physical treatments such as corona discharge treatment, ozone treatment, low-temperature plasma treatment using oxygen gas or nitrogen gas, and glow discharge treatment, and chemical treatments such as oxidation treatment using chemicals. Corona discharge treatment is preferable.
The corona discharge treatment conditions may be appropriately adjusted taking into account the above-mentioned points, and the discharge amount is preferably 20 to 100 W·min/ ^m2 , and more preferably 40 to 80 W·min/ ^m2 .

In the laminate 10, the sealant layer 11 may be one layer or two or more layers. Preferably, it is one layer. When the laminate has two or more sealant layers, the resins used in each sealant layer may be the same or different.

[Protective Layer]
The laminate 10 has a protective layer 13 on (preferably directly on) the deposition layer 12. The protective layer 13 can protect the deposition layer 12. The protective layer 13 can achieve high barrier properties. If the protective layer 13 is not present, the barrier properties tend to decrease. The inventors have found that although it is preferable to use a material with barrier properties for the protective layer 13, even if the protective layer 13 itself is a material with low barrier properties (such as polyester resin), it is possible to maintain the barrier properties of the deposition layer 12 at a very high level. The inventors believe that this is because the protective layer 13 is present on (preferably directly on) the deposition layer 12, which suppresses the occurrence of fine cracks in the deposition layer 12, or fills in the cracks in the deposition layer 12. In Patent Document 1, the deposition layer and the paper base layer are extrusion laminated with a molten adhesive resin without providing a protective layer on the deposition layer. In this case, the deposition layer is damaged by heat during lamination, and the barrier properties are thought to decrease.

The material of the protective layer 13 is not particularly limited, and for example, a known resin material can be used. The protective layer preferably contains a resin. For example, this means that the resin content in the protective layer is, for example, 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, particularly preferably 90% by mass or more, and most preferably 95% by mass or more. The upper limit of the resin content in the protective layer is not particularly limited, and is, for example, 100% by mass or less, and may be 100% by mass.

The resins used in the protective layer are not particularly limited, but include alkyd resins; (meth)acrylic (co)polymers, styrene-(meth)acrylic resins; olefin-unsaturated carboxylic acid copolymers such as ethylene-acrylic acid copolymers and ethylene-methacrylic acid copolymers; vinyl alcohol resins such as polyvinyl alcohol and ethylene-vinyl alcohol copolymer resins (ethylene-modified polyvinyl alcohol); cellulose resins; polyurethane resins; polyester resins such as polylactic acid; etc.

Among these, it is preferable that the protective layer contains one or more resins selected from the group consisting of polyurethane resins, polyester resins, and ethylene-vinyl alcohol copolymer resins. These resins can achieve very good barrier properties. From the viewpoint of further improving the barrier properties (particularly the oxygen barrier properties), it is more preferable that the protective layer contains one or more resins selected from the group consisting of polyurethane resins and ethylene-vinyl alcohol copolymer resins.

<Polyester resin>
The polyester resin contained in the protective layer is not particularly limited, and examples thereof include polyester resins that can be dispersed (including emulsified) in organic solvents or aqueous solvents.

Commercially available polyester resins may be used, such as the "Elitel UE Series (product name)" manufactured by Unitika Ltd., and a specific example is Elitel UE9800-30EA.

<Polyurethane resin>
The polyurethane resin contained in the protective layer is not particularly limited, and preferable examples include polyurethane resins that can be dispersed (including emulsified) in organic solvents or aqueous solvents.

The polyurethane resin may have hydroxy groups, and the hydroxyl value is preferably 50 mgKOH/g or more, more preferably 100 mgKOH/g or more, and even more preferably 150 mgKOH/g or more. The upper limit of the hydroxyl value of the polyurethane resin is not particularly limited, but is preferably 1000 mgKOH/g or less, more preferably 800 mgKOH/g or less, and even more preferably 600 mgKOH/g or less. It is preferable that the hydroxyl value of the polyurethane resin is within the above range, since it has excellent oxygen barrier properties.

As polyurethane resins, commercially available products may be used, such as "Takelac W series (product name)", "Takelac WPB series (product name)", and "Takelac WS series (product name)" manufactured by Mitsui Chemicals, Inc., and a specific example is Takelac WPB-341. Other commercially available polyurethane resins include "HPU W-003" (hydroxyl value 235 mg KOH/g) manufactured by Dainichiseika Chemicals Mfg. Co., Ltd.

<Ethylene vinyl alcohol copolymer resin>
The ethylene-vinyl alcohol copolymer resin (hereinafter also referred to as EVOH-based resin) is not particularly limited, and a preferred example is an ethylene-vinyl alcohol copolymer that can be dispersed (including emulsified) in an organic solvent or an aqueous solvent.
As the ethylene-vinyl alcohol copolymer resin, a commercially available product may be used, for example, "Eversolve (product name)" manufactured by Nippon Cima Co., Ltd., which is a paint in which an ethylene-vinyl alcohol copolymer resin is dissolved in a water/alcohol mixed solvent.

The method for forming the protective layer is not particularly limited. From the viewpoint of protecting the deposition layer, a method in which a solution or dispersion of the above-mentioned resin (preferably an aqueous dispersion) is applied by a known method and then dried is preferred. The protective layer is preferably a coating layer.
The protective layer may contain other components in addition to the above resins, as long as the effects of the present disclosure are not impaired. Examples of other components include silane coupling agents, surfactants, dispersants, pigments, antioxidants, antistatic agents, dyes, plasticizers, lubricants, and release agents.

(Amount of protective layer)
The amount of the protective layer in the laminate (e.g., coating amount) is not particularly limited, but is preferably 0.1 g/m ² or more, more preferably 0.3 g/m ² or more, even more preferably 0.4 g/m ² or more, and preferably 3.0 g/m ² or less, more preferably 1.0 g/m ² or less, even more preferably 0.7 g/m ² or less, and even more preferably 0.6 g/m ² or less, calculated on a solid content basis. The thickness of the protective layer is preferably less than 2 μm, and preferably 0.1 μm or more.
Even if the protective layer is very thin as in the above range, the oxygen barrier property and water vapor barrier property of the laminate can be made very high, which makes it easy to maintain a high paper ratio.

[Undercoat layer]
The laminate may have an undercoat layer between the deposition layer 12 and the sealant layer 11. The undercoat layer can further improve the barrier properties of the deposition layer. The present inventors believe that this is because the deposition layer is densely constructed by providing the undercoat layer due to high chemical affinity between the undercoat layer material on the sealant layer surface and the deposition material.

The material of the undercoat layer is not particularly limited, and for example, a known resin material can be used. The undercoat layer preferably contains a resin. For example, this means that the resin content in the undercoat layer is, for example, 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, particularly preferably 90% by mass or more, and most preferably 95% by mass or more. The upper limit of the resin content in the undercoat layer is not particularly limited, and is, for example, 100% by mass or less, and may be 100% by mass.

The resin used for the undercoat layer is not particularly limited, and the resin materials exemplified for the protective layer can be used. The method for forming the undercoat layer can be the same as that for the protective layer.
For the same reasons as described for the protective layer, the undercoat layer preferably contains one or more resins selected from the group consisting of polyurethane-based resins, polyester-based resins, and ethylene-vinyl alcohol copolymer resins, more preferably contains one or more resins selected from the group consisting of polyurethane-based resins and ethylene-vinyl alcohol copolymer resins, and even more preferably contains a polyurethane-based resin.

The undercoat layer may contain other components in addition to the above resins, as long as the effects of the present disclosure are not impaired. Examples of other components include silane coupling agents, surfactants, dispersants, pigments, antioxidants, antistatic agents, dyes, plasticizers, lubricants, and release agents.

The amount of the undercoat layer (e.g., coating amount) is also the same as that of the protective layer. The amount of the undercoat layer is preferably 0.1 g/m ² or more, more preferably 0.3 g/m ² or more, even more preferably 0.4 g/m ² or more, and also preferably 3.0 g/m ² or less, more preferably 1.0 g/m ² or less, even more preferably 0.7 g/m ² or less, and even more preferably 0.6 g/m ² or less, in terms of solid content. The thickness of the undercoat layer is preferably less than 2 μm, and preferably 0.1 μm or more.

Even when the undercoat layer is very thin as in the above range, it is possible to provide the laminate with very high oxygen barrier properties and water vapor barrier properties, which makes it easy to maintain a high paper ratio.
It is preferable to form an undercoat layer on the sealant layer (which may be a surface-treated sealant layer), and then form a vapor deposition layer thereon.

[Liquid carton]
The laminate of the present disclosure has excellent oxygen barrier properties and appropriate strength, and therefore can be suitably used for liquid containers such as milk cartons (hereinafter also referred to as liquid paper containers), cups, trays, dishes, lids, laminated tubes, and other packaging containers. The contents to be packaged may be liquid, solid, or gel. Due to its high barrier properties, the laminate of the present disclosure is preferably used for aseptically filled liquid paper containers.
That is, the liquid-storing paper container is preferably made using the laminate. Moreover, the laminate is preferably for use in a liquid-storing paper container.

The shape of the liquid paper container is not particularly limited, and may be, for example, a roof type (gable top type), a rectangular parallelepiped type (flat top type, brick type, straight type, etc.), a triangular pyramid type, a slant top type, a regular tetrahedron type, a cup type, a tray type, etc. Furthermore, the liquid paper container may be equipped with a straw insertion hole, a spout, a lid material, etc., as long as the gas barrier properties are not impaired.

The liquid contained in the liquid paper container may be either food or non-food. The liquid contained in the liquid paper container is not particularly limited, and may include alcoholic beverages such as sake, shochu, and wine, dairy beverages such as milk, and beverages such as juice, coffee, tea, and black tea; liquid foods such as instant foods, microwaveable foods, beverages (yogurt, jelly, pudding, etc.), and prepared dishes; pharmaceuticals; and chemical products such as car wax, shampoo, rinse, detergent, bath additives, hair dye, and toothpaste.

The liquid paper container may be, for example, a sterile filled liquid paper container. There are no particular limitations on the manufacturing method of the sterile filled liquid paper container, but for example, a continuous laminate (hereinafter, packaging material) in a strip shape is scored, the packaging material with the scored lines is fed to a filling processing device and sterilized continuously with hydrogen peroxide, and after sterilization with hydrogen peroxide, a vertical seal is applied in the lengthwise direction in a sterile chamber to form the packaging material into a tube, the tubular packaging material is filled with the contents, horizontal seals are applied at predetermined intervals in the horizontal direction of the tubular packaging material, the packaging material is cut along the horizontal seals, and folded along the creases to form the final shape, thereby obtaining a liquid paper container.

[Method of manufacturing laminate]
The method for producing the laminate is not particularly limited. It is sufficient to form a thermoplastic resin layer, a paper base layer, an adhesive resin layer, a protective layer, a vapor deposition layer, and a sealant layer in this order. The method for producing the laminate is preferably as follows:
forming a sealant layer comprising metallocene-catalyzed linear low density polyethylene;
The method includes a step of forming a vapor deposition layer on the sealant layer directly or via an undercoat layer, and a step of forming a protective layer on the resulting vapor deposition layer to obtain a sealant film 4.
The manufacturing method preferably includes a step of laminating the protective layer of the obtained sealant film 4 and a paper base layer (or a paper base layer on which a thermoplastic resin layer has been formed) via an adhesive resin layer. The lamination method is not particularly limited, and may be a lamination method as described above. After laminating the sealant film 4 and the paper base layer, a thermoplastic resin layer may be formed on the paper base layer.
In the method for producing a laminate according to this embodiment, the preferred aspects of each step are as described above.

The features of the present invention are explained in more detail below with reference to examples and comparative examples. The materials, amounts used, ratios, processing contents, processing procedures, etc. shown in the following examples can be modified as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the specific examples shown below. Furthermore, unless otherwise specified, "%" and "parts" in the following recipes represent "% by mass" and "parts by mass", respectively. Furthermore, the operations of the examples and comparative examples were carried out at room temperature (20-25°C) and normal humidity (40-50% RH) unless otherwise specified.

The measurement and evaluation methods for each physical property are described below.
[Oxygen permeability]
The oxygen permeability (mL/m 2 /day/atm) of the laminate was measured using an oxygen permeability measuring device (OX-TRAN2/22, manufactured by MOCON) in accordance with JIS K7126-2:2006 under conditions of a temperature of ²³ ° C. and a relative humidity of 50%.

[Water vapor permeability]
The water vapor permeability (g/ ^m2 /day) of the laminates obtained in the examples and comparative examples was measured with the sealant layer facing inside in accordance with JIS-Z-0208:1976 (cup method) Method B (40°C±0.5°C, relative humidity 90%±2%).

[Mass ratio of paper base material]
The mass ratio of the paper substrate was calculated as a percentage based on the total mass of the laminate as follows.
(Ratio of the mass of the paper substrate)=(Mass of the paper substrate)/(Mass of the laminate)×100

[Odor evaluation]
The laminate was sealed on three sides using a heat sealer at 150°C for 2 seconds, and 250 mL of water was poured into it and sealed to form a 1000 mL pillow bag. This sample was then stored at 23°C and 50% RH for 24 hours, after which the water was diluted to 1000 mL (4-fold dilution), and the odor of the water was evaluated by 10 panelists using the three-point discrimination method.
The three-point discrimination method was performed as follows.
After storing the samples as described above, three water samples were prepared, designated X, Y, and Y, with the test samples obtained in the Examples and Comparative Examples designated X and the comparison sample (using packaging material made of ordinary LLDPE that produces an odor) designated Y. Ten panelists were asked to select which of these water samples did not have a water odor. If seven or more of the ten panelists selected X, the corresponding test sample X was judged to be "A: the water does not have an odor derived from the packaging material." Otherwise, it was judged to be "B: the water has an odor derived from the packaging material."

[Evaluation of low-temperature heat sealability]
Two laminates were stacked together with the sealant layers facing each other, and heat-sealed using a heat seal tester (TP-701-B, manufactured by Tester Sangyo) at 110°C, 0.4 MPa, and 1 second. The heat-sealed test piece was left to stand in a room at a temperature of 23°C±1°C and a humidity of 50%±2% for at least 4 hours.
The heat-sealed test pieces were then cut to a width of 15 mm, and subjected to T-peel at a tensile speed of 300 mm/min using a tensile tester (Shimadzu AGX-F), and the fracture behavior was visually evaluated. When the paper substrate was broken, it was judged to be good because the adhesion between the layers was high.
A: The paper base is destroyed.
B: The paper base material was not destroyed, and the sealant layers were peeled off from each other.

[Melt flow rate of sealant layer]
The melt flow rate is calculated by measuring the amount of resin extruded from the orifice at the bottom of a cylinder, which is heated and pressurized at a constant temperature. The melt flow rate of the sealant layer in the laminate can be measured by the following procedure.
First, the sealant layer present on the surface of the laminate was cut out with a microtome, and the obtained sealant layer was used as a sample. Then, using a Melt Indexer G-02 manufactured by Toyo Seiki Seisakusho Co., Ltd., a mass measurement was performed under conditions of a temperature of 190° C. and a load of 2.16 kg according to JIS K 7210-01.

[Sealant layer density]
The density of the sealant layer in the laminate can be measured by the following procedure.
The sealant layer present on the surface of the laminate is cut out with a microtome, and the resulting sealant layer is used as a sample. Then, in accordance with JIS K7112, measurement is performed by an underwater displacement method using, for example, an automatic specific gravity meter DSG-1 manufactured by Toyo Seiki Seisakusho.

[Vicat softening point of sealant layer]
The Vicat softening point of the sealant layer in the laminate can be measured by the following procedure.
The sealant layer present on the surface of the laminate is cut out with a microtome, and the obtained sealant layer is used as a sample. The Vicat softening point is measured using a Vicat tester HVT305 manufactured by Beijing United Test Co., Ltd. The specific conditions are as follows: the test is performed in accordance with JIS K 7206:2016.

Example 1
Linear low density polyethylene (m-LLDPE, density 0.907 g/cm ³ , MFR 2.0 g/10 min., Vicat softening point 88°C) synthesized by a high pressure method using a metallocene catalyst was melted at 180°C in a single screw extruder. Then, using a Sumitomo Heavy Industries Modern Co., Ltd. Co-RT type, a sealant layer was formed into a film by the inflation method at an extrusion speed of 150 m/min. and a temperature of 170°C to produce an m-LLDPE film with a thickness of 30 μm (basis weight approximately 27.2 g/m ² ). The low temperature heat sealability and hot tackiness of the m-LLDPE were evaluated by the following method.
The obtained m-LLDPE film was subjected to a corona discharge treatment once using a laboratory corona treatment machine (TEC-4AX, manufactured by Kasuga Denki) at a speed of 4.5 m/min and a discharge amount of 64.8 W min/ ^m2 , and then subjected to silica deposition (SiOx) by electron beam deposition to form a deposition layer on the film surface. The silica deposition layer had a thickness of 20 nm.
Furthermore, a urethane resin (Takelac WPB-341, manufactured by Mitsui Chemicals) was applied onto the deposition layer so as to have a solid content of 0.5 g/ ^m2 , and then dried for 1 minute in a 120°C air dryer to form a protective layer, thereby obtaining a sealant film.

The above sealant film was attached to one side of a paper substrate (milk carton base paper, basis weight 330 g/ ^m2 , thickness 400 μm) by polysand lamination using low-density polyethylene (LDPE) (Novatec LD LC600A, manufactured by Japan Polyethylene Co., Ltd.) so that the protective layer of the sealant film faced the paper substrate. The thickness of the low-density polyethylene adhesive resin layer was 20 μm (basis weight 18.4 g/ ^m2 ).
Finally, a low-density polyethylene (Novatec LD LC600A, manufactured by Japan Polyethylene Co., Ltd.) was applied to the opposite side of the paper substrate to the side to which the sealant film was attached, to a thickness of 30 μm (basis weight: approximately 27.6 g/ ^m2 ) as a thermoplastic resin layer by extrusion lamination to obtain a laminate. The basis weight of the laminate was 403.8 g/ ^m2 .

[Evaluation of low-temperature heat sealability of the resin in the sealant layer]
Laminated paper was produced by extrusion laminating corona-treated kraft paper (75 g/ ^m2 ) with the same resin composition as that used for the sealant layer at 320°C to a thickness of 20 μm. The sealant layers of the resulting laminated paper were overlapped and heat-sealed at 2 kg/ ^cm2 for 1 second at 10°C intervals from 100°C to 160°C, and the heat seal strength of the heat seal was measured. Test pieces were cut to a width of 15 mm and T-peeled at a tensile speed of 300 mm/min using a tensile tester (Shimadzu AGX-F) to measure the heat seal strength.
The rise temperature is the minimum temperature at which the heat seal strength is greater than zero using the above sample.
The heat seal strength at 150°C is the heat seal strength when a test piece heat-sealed at 150°C is used.

[Evaluation of hot tack of resin in sealant layer] (Heat seal condition: 0.4 MPa-1 sec)
Using a hot tack tester manufactured by Tester Sangyo, a corona-treated kraft paper (75 g/m ² ) was extrusion-laminated at 320° C. with the same resin composition as that used for the sealant layer to a thickness of 20 μm to produce laminated paper. The obtained laminated paper was cut to a width of 25 mm.
The resulting sealant layers of the laminated paper were overlapped and heat sealed at a sealing temperature of 120°C, a sealing pressure of 0.4 MPa/ ^cm2 , and a sealing time of 1 second using a Tester Sangyo TE-503. Immediately after (375 milliseconds), the heat seal strength was measured at 180° peeling at a pulling speed of 200 mm/min using a Tester Sangyo TE-503. The heat seal strength (N/25 mm) obtained here was used to evaluate the hot tackiness.

Example 2
A laminate was obtained in the same manner as in Example 1, except that the resin used for the adhesive resin layer was an ethylene-methacrylic acid copolymer (EMAA, Nucrel N0908C, manufactured by Mitsui DuPont Polychemicals) having a thickness of 20 μm (basis weight of about 18.6 g/m ² ).

Example 3
A laminate was obtained in the same manner as in Example 1, except that the resin used for the adhesive resin layer was an ethylene-methacrylic acid copolymer (EMAA, Nucrel N0908C, manufactured by DuPont-Mitsui Polychemicals) of 15 μm (basis weight: approximately 14.0 g/ ^m2 ), and the thermoplastic resin layer was a low-density polyethylene (Novatec LD LC600A, manufactured by Japan Polyethylene Corporation) of 20 μm (basis weight: approximately 18.4 g/ ^m2 ) applied by extrusion lamination.

Example 4
A laminate was obtained in the same manner as in Example 2, except that the m-LLDPE film was subjected to a corona discharge treatment under the same conditions as in Example 1, and then a diamond-like carbon (DLC) deposition layer (deposition thickness 10 nm) was formed by chemical vapor deposition using toluene instead of the silica deposition layer.

Example 5
A laminate was obtained in the same manner as in Example 2, except that the m-LLDPE film was subjected to a corona discharge treatment under the same conditions as in Example 1, and then a deposition layer (deposition thickness 10 nm) was formed by electron beam deposition using alumina (AlOx) instead of silica.

Example 6
A laminate was obtained in the same manner as in Example 2, except that the coating material for the protective layer was a polyester resin (Eliteru UE9800-30EA, manufactured by Unitika Ltd.) and was applied so as to give a solid content of 0.5 g/ ^m2 .

(Example 7)
A laminate was obtained in the same manner as in Example 2, except that the coating material for the protective layer was an EVOH-based resin (Eversolve, manufactured by Nippon Cima Co., Ltd.) and was applied so as to be 0.5 g/ ^m2 in terms of solid content.

(Example 8)
A laminate was obtained in the same manner as in Example 2, except that a sealant layer was formed into a film (thickness 30 ^μm , basis weight approximately 27.4 g/ ^m2 ) by an inflation method using linear low-density polyethylene (density 0.913 g/cm3, MFR 4.0 g/10 min., Vicat softening point 97°C) synthesized by a high-pressure method using a metallocene catalyst.

Example 9
100 parts by mass of linear low-density polyethylene (density 0.907 g/cm ³ , MFR 2.0 g/10 min., Vicat softening point 88° C.) synthesized by a high-pressure method using a metallocene catalyst was mixed with 30 parts by mass of low-density polyethylene (Novatec LD LF441MD, manufactured by Japan Polyethylene Co., Ltd., density 0.924 g/cm ³ , MFR 2.0 g/10 min., Vicat softening point: 98° C.). The mixture was melted at 180° C. in a single-screw extruder, and then a sealant layer was formed into a film by the inflation method using a Sumitomo Heavy Industries Modern Co., Ltd. Co-RT type at a discharge speed of 150 m/min. and a temperature of 170° C., to obtain a sealant layer having a thickness of 30 μm (basis weight about 27.2 g/m ^{2 ). A laminate was obtained in the same manner as in Example 2, except that the mixture was melted at 180° C. in a single-screw extruder, and then a sealant layer having a thickness of 30 μm (basis weight about 27.2 g/m 2} ) was obtained.

Example 10
A laminate was obtained in the same manner as in Example 2, except that a linear low-density polyethylene (density 0.907 g/cm ³ , MFR 2.0 g/10 min., Vicat softening point 88° C.) synthesized by a high-pressure method using a metallocene catalyst was extruded into a film at a melt temperature of 320° C. using a T-die to obtain a sealant layer (thickness 30 μm, basis weight approximately 27.2 g/m ² ).

(Example 11)
The obtained m-LLDPE film was subjected to a corona discharge treatment, and then a urethane resin (Takelac WPB-341, manufactured by Mitsui Chemicals, Inc.) was applied thereto so as to give a coating amount of 0.5 g/ ^m2 in terms of solid content, and the coating was dried for 1 minute in a 120°C air dryer to form an undercoat layer. Except for this, a laminate was obtained in the same manner as in Example 2.

Example 12
A laminate was obtained in the same manner as in Example 11, except that the coating material for the protective layer was "HPU W-003" manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd., and was applied so as to have a solid content of 0.5 g/m2.

(Comparative Example 1)
A laminate was obtained in the same manner as in Example 2, except that a sealant layer (thickness 30 μm, basis weight approximately 27.6 g/m ² ) was obtained using linear low-density polyethylene (density 0.920 g/cm ³ , MFR 2.1 g/10 min., Vicat softening point 102° C.) produced by a gas phase process using a Ziegler-Natta catalyst instead of a metallocene catalyst for the sealant film.

(Comparative Example 2)
A solvent-based non-gas barrier adhesive (DIC Dry LX-500/KW-75, DIC Graphics Corporation) was applied to the alumina-vapor-deposited surface of a 12 μm single-sided alumina-vapor-deposited PET film (Barrierox 1011HGCW, Toray Industries, Inc.) to a dry weight of 4 g/ ^m2 to form an adhesive layer. The m-LLDPE film (basis weight approximately 27.2 g/ ^m2 ) described in Example 1 was attached to the adhesive layer surface as a sealant layer to obtain a laminated film.
An adhesive layer of ethylene-methacrylic acid copolymer (EMAA, Nucrel N0908C, manufactured by DuPont-Mitsui Polychemicals) was formed on one side of a paper substrate (milk carton base paper, basis weight 330 g/m ² , thickness 400 μm) by extrusion sand lamination to a thickness of 20 μm (basis weight approximately 18.6 g/m ² ). The obtained laminated film and the paper substrate with the adhesive layer formed thereon were bonded together by dry lamination so that the paper surface and the PET surface were bonded to each other.
Furthermore, a polyethylene resin (Novatec LD LC600A, manufactured by Japan Polyethylene Corporation) was applied to the other surface of the paper base material by extrusion lamination to a thickness of 30 μm (basis weight approximately 27.4 g/m ² ) to form a resin layer (LDPE layer), thereby obtaining a laminate.

(Comparative Example 3)
A laminate was obtained in the same manner as in Example 2, except that no protective layer was laminated on the vapor-deposited layer.

(Comparative Example 4)
A laminate was obtained in the same manner as in Example 2, except that the protective layer was formed directly on the m-LLDPE film without SiOx deposition.

The physical properties and evaluation results of the laminates obtained in the examples and comparative examples are shown in Tables 1 to 3.
In the table, the molding method indicates the method for molding the sealant layer.

The unit of oxygen permeability is mL/m ² /day/atm, and the unit of water vapor permeability is g/m ² /day.

10: Laminate, 1: Thermoplastic resin layer, 2: Paper base layer, 3: Adhesive resin layer, 4: Sealant film, 11: Sealant layer, 12: Vapor deposition layer, 13: Protective layer

Claims (16)

1. A laminate having a thermoplastic resin layer, a paper base layer, an adhesive resin layer, a vapor deposition layer, and a sealant layer in this order,
   the sealant layer is provided on the outermost layer of the laminate,
   the laminate has a protective layer between the adhesive resin layer and the vapor deposition layer,
   A laminate wherein the sealant layer comprises a metallocene-catalyzed linear low density polyethylene.
2. The laminate according to claim 1, wherein the ratio of the paper base layer in the laminate is 80% by mass or more.
3. The laminate according to claim 1 or 2, wherein the melt flow rate of the sealant layer is 1.0 to 6.0 g/10 min.
4. The density of the sealant layer is 0.905 to 0.925 g/ ^cm3 ;
   The laminate according to any one of claims 1 to 3, wherein the sealant layer has a Vicat softening point of 84 to 100°C.
5. The laminate according to any one of claims 1 to 4, wherein the sealant layer is an inflation molded body.
6. The laminate according to any one of claims 1 to 5, wherein the content of the metallocene-catalyzed linear low-density polyethylene in the sealant layer is 70 to 100 mass %.
7. The laminate according to any one of claims 1 to 6, wherein the sealant layer contains 0 to 30 mass% low-density polyethylene based on the mass of the sealant layer.
8. The laminate according to any one of claims 1 to 7, wherein the vapor deposition layer contains at least one selected from the group consisting of silica, alumina, and diamond-like carbon.
9. The laminate according to any one of claims 1 to 8, wherein the protective layer contains at least one resin selected from the group consisting of polyurethane resins, polyester resins, and ethylene-vinyl alcohol copolymer resins.
10. The laminate according to any one of claims 1 to 9, wherein the laminate has an undercoat layer between the deposition layer and the sealant layer.
11. The laminate according to any one of claims 1 to 10, which is for use in a liquid paper container.
12. A liquid paper container made using the laminate described in any one of claims 1 to 10.
13. A method for producing a laminate having a thermoplastic resin layer, a paper base layer, an adhesive resin layer, a protective layer, a vapor deposition layer, and a sealant layer in this order, comprising:
    forming the sealant layer comprising metallocene-catalyzed linear low density polyethylene;
    forming the deposition layer on the sealant layer directly or via an undercoat layer;
    forming the protective layer on the deposition layer to obtain a sealant film;
    laminating the protective layer of the sealant film and the paper base layer via the adhesive resin layer;
    The method for producing a laminate comprising the steps of:
14. The method for producing a laminate according to claim 13, wherein the content of the metallocene-catalyzed linear low-density polyethylene in the sealant layer is 70 to 100% by mass.
15. The method for manufacturing a laminate according to claim 13 or 14, wherein the sealant layer contains 0 to 30% by mass of low-density polyethylene based on the mass of the sealant layer.
16. The method for producing a laminate according to any one of claims 13 to 15, wherein the protective layer contains at least one resin selected from the group consisting of polyurethane resins, polyester resins, and ethylene-vinyl alcohol copolymer resins.

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