JP7649487B2 - Multilayer substrate, multilayer film comprising said multilayer substrate, laminate comprising said multilayer film, and packaging material comprising said laminate - Google Patents

Description

The present invention relates to a multilayer substrate, a multilayer film comprising the multilayer substrate, a laminate comprising the multilayer film, and the laminate.

Traditionally, films made of polyesters such as polyethylene terephthalate (hereinafter also referred to as polyester films) have been used as the base material for constructing laminates used in the production of packaging materials because they have excellent mechanical properties, chemical stability, heat resistance, and transparency, as well as being inexpensive.

Depending on the contents to be filled into the packaging material, the packaging material is required to have high gas barrier properties such as oxygen barrier properties and water vapor barrier properties, and in order to meet this requirement, it is common to form a vapor-deposited film containing alumina, silica, etc. on the surface of a polyester film (Patent Document 1).

In recent years, there has been a search for resin materials to replace polyester films, and their application to polyolefin film, particularly polypropylene film, as substrates, has been considered.

Japanese Patent Application Publication No. 2005-053223

The present inventors had been considering using a stretched polypropylene film (hereinafter also referred to as a stretched polypropylene film) instead of the conventional polyester film substrate, and discovered a new problem in that satisfactory gas barrier properties could not be obtained even when a vapor deposition film was formed on the surface of the stretched polypropylene film.
As a result of further investigations, the inventors discovered that in packaging materials using a laminated film in which a vapor-deposited film is provided on the stretched polypropylene film, a unique phenomenon not seen in conventional laminated films using a polyester film base material occurs, namely, delamination occurs between the stretched polypropylene film and the vapor-deposited film, and they came to the knowledge that this phenomenon causes insufficient gas barrier properties.

The inventors have discovered that by providing a surface resin layer containing a resin material having a melting point of 180°C or higher on the surface of a stretched polypropylene film, the adhesion of the vapor-deposited film formed on the surface resin layer is improved and the gas barrier properties are also improved.

The present invention was made based on this knowledge, and the problem it aims to solve is to provide a substrate that has excellent interlayer adhesion with the vapor-deposited film and high gas barrier properties.

Another problem to be solved by the present invention is to provide a laminate film comprising the substrate.
Another problem to be solved by the present invention is to provide a laminate comprising the laminate film.
A further object of the present invention is to provide a packaging material comprising the laminate.

The multilayer substrate of the present invention has been subjected to a stretching treatment,
The multilayer substrate includes at least a polypropylene resin layer and a surface resin layer,
The surface resin layer is characterized by containing a resin material having a melting point of 180° C. or higher.

In one embodiment, the melting point of the resin material is 265°C or less.

In one embodiment, the difference between the melting point of the resin material and the melting point of the polypropylene contained in the polypropylene resin layer is 20 to 80°C.

In one embodiment, the resin material has a polar group.

In one embodiment, the resin material is one or more resin materials selected from ethylene vinyl alcohol copolymer, polyvinyl alcohol, polyester, nylon 6, nylon 6,6, MXD nylon, and amorphous nylon.

In one embodiment, the ratio of the thickness of the surface resin layer to the total thickness of the multilayer substrate is 1% or more and 10% or less.

In one embodiment, the multilayer substrate is a co-extruded film.

In one embodiment, the multi-layer substrate is used in packaging applications.

The laminated film of the present invention is characterized by comprising the above-mentioned multilayer substrate and a vapor-deposited film made of an inorganic oxide, and having a vapor-deposited film on a surface resin layer.

In one embodiment, the inorganic oxide is silica or alumina.

In one embodiment, the laminate film of the present invention further comprises a barrier coat layer on the vapor deposition film.

The laminate of the present invention is characterized by comprising the laminate film and a sealant layer.

In one embodiment, the sealant layer is made of the same material as the polypropylene resin layer, which is polypropylene.

The packaging material of the present invention is characterized by comprising the above laminate.

According to the present invention, it is possible to produce a packaging material having excellent interlayer adhesion between a polypropylene film and a vapor-deposited film and high laminate strength, and it is also possible to provide a substrate having high gas barrier properties.
Furthermore, according to the present invention, a laminate film including the substrate can be provided.
Furthermore, according to the present invention, a laminate comprising the laminate film can be provided.
Furthermore, according to the present invention, a packaging material including the laminate can be provided.

FIG. 1 is a schematic cross-sectional view showing one embodiment of a multilayer base material of the present invention. FIG. 1 is a schematic cross-sectional view showing one embodiment of a multilayer base material of the present invention. 1 is a schematic cross-sectional view showing one embodiment of a laminated film of the present invention. 1 is a schematic cross-sectional view showing one embodiment of a laminated film of the present invention. 1 is a schematic cross-sectional view showing one embodiment of a laminate of the present invention. FIG. 1 is a perspective view showing one embodiment of a packaging material of the present invention. FIG. 1 is a perspective view showing one embodiment of a packaging material of the present invention.

(Multi-layer substrate)
As shown in FIG. 1, a multilayer substrate 10 of the present invention includes a polypropylene resin layer 11 and a surface resin layer 12 .
In one embodiment, the multilayer substrate 10 may further include an adhesive resin layer 13 between the polypropylene resin layer 11 and the surface resin layer 12, as shown in FIG.

The multi-layer substrate is subjected to a stretching treatment, and the stretching treatment may be uniaxial stretching or biaxial stretching.
The stretching ratio of the multilayer base material in the machine direction (MD direction) and the transverse direction (TD direction) is preferably 2 to 15 times, and more preferably 5 to 13 times.
By setting the stretching ratio to 2 times or more, the strength and heat resistance of the multi-layered substrate can be further improved, and the printability of the multi-layered substrate can also be improved.
From the viewpoint of the breaking limit of the multi-layered base material, the stretching ratio is preferably 15 times or less.

The surface resin layer of the multilayer substrate may be subjected to a surface treatment, which can improve adhesion to adjacent layers.
The method of the surface treatment is not particularly limited, and examples thereof include physical treatments such as corona discharge treatment, ozone treatment, low-temperature plasma treatment using oxygen gas and/or nitrogen gas, and glow discharge treatment, as well as chemical treatments such as oxidation treatment using chemicals.

The layers of the multilayer container of the present invention are described below.

(Polypropylene resin layer)
The polypropylene resin layer is made of polypropylene and may have a single-layer structure or a multi-layer structure.

The polypropylene contained in the polypropylene resin layer may be any of a homopolymer, a random copolymer, and a block copolymer.
A polypropylene homopolymer is a polymer of propylene alone, a polypropylene random copolymer is a random copolymer of propylene and an α-olefin other than propylene (e.g., ethylene, butene-1, 4-methyl-1-pentene, etc.), and a polypropylene block copolymer is a copolymer having a polymer block of propylene and a polymer block of the above-mentioned α-olefin other than propylene.
Among these polypropylenes, it is preferable to use homopolymers or random copolymers from the viewpoint of transparency. When the rigidity and heat resistance of the packaging bag are important, it is preferable to use homopolymers, and when the impact resistance and the like are important, it is preferable to use random copolymers.
It is also possible to use biomass-derived polypropylene and mechanically or chemically recycled polypropylene.

The polypropylene content in the polypropylene resin layer is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more.

As long as the properties of the present invention are not impaired, the polypropylene resin layer may contain a resin material other than polypropylene, and examples of such materials include polyolefins such as polyethylene, (meth)acrylic resins, vinyl resins, cellulose resins, polyamide resins, polyesters, and ionomer resins.
Furthermore, the polypropylene resin layer may contain additives, as long as the properties of the present invention are not impaired. Examples of such additives include crosslinking agents, antioxidants, antiblocking agents, slip agents, UV absorbers, light stabilizers, fillers, reinforcing agents, antistatic agents, pigments, and modifying resins.

The thickness of the polypropylene resin layer is preferably 10 μm or more and 50 μm or less, and more preferably 10 μm or more and 40 μm or less.
By making the thickness of the polypropylene resin layer 10 μm or more, the strength and heat resistance of the multi-layered base material can be further improved.
Furthermore, by setting the thickness of the polypropylene resin layer to 50 μm or less, the film-forming property and processability of the multi-layered base material can be further improved.

The polypropylene resin layer may have a printed layer on its surface. The image formed on the printed layer is not particularly limited, and may be a letter, a pattern, a symbol, or a combination thereof.
The printing layer on the substrate can be formed using ink derived from biomass, which reduces the environmental impact.
The method for forming the printed layer is not particularly limited, and examples of the method include conventionally known printing methods such as gravure printing, offset printing, and flexographic printing.

(Surface resin layer)
The multilayer substrate of the present invention has a surface protective layer on a polypropylene resin layer, the surface protective layer containing a resin material having a melting point of 180°C or higher (hereinafter also referred to as a high melting point resin material), and a vapor deposition film having high adhesion can be formed on the surface resin layer, thereby improving the gas barrier properties.
In addition, as described below, packaging materials produced using the multi-layer substrate of the present invention have high laminate strength.

The melting point of the high melting point resin material is more preferably 185° C. or higher, further preferably 190° C. or higher, and particularly preferably 205° C. or higher.
By setting the melting point of the high melting point resin material to 185° C. or higher, the adhesiveness of the vapor-deposited film can be further improved, the gas barrier property can be further improved, and the laminate strength of the packaging material can be further improved.
From the viewpoint of film-forming properties of the multi-layer substrate, the melting point of the high-melting-point resin material is preferably 265° C. or less, more preferably 260° C. or less, and even more preferably 250° C. or less.

The difference between the melting point of the high melting point resin material contained in the multi-layer base material and the melting point of the polypropylene contained in the polypropylene resin layer is preferably 20 to 80°C, and more preferably 20 to 60°C.
By setting the difference between the melting point of the high melting point resin material contained in the multilayer base material and the melting point of the polypropylene contained in the polypropylene resin layer to 20° C. or more, the adhesion of the vapor-deposited film can be further improved, the gas barrier property can be further improved, and the laminate strength of the packaging material can be further improved.
Furthermore, by making the difference between the melting point of the high melting point resin material contained in the multilayer base material and the melting point of the polypropylene contained in the polypropylene resin layer 80° C. or less, the film formability of the multilayer base material can be further improved.

The high melting point resin material preferably has a polar group.
In the present invention, the polar group refers to a group containing one or more heteroatoms, and examples thereof include an ester group, an epoxy group, a hydroxyl group, an amino group, an amide group, a carboxyl group, a carbonyl group, a carboxylic anhydride group, a sulfone group, a thiol group, and a halogen group.
Among these, from the viewpoint of the laminate strength of the packaging material, a hydroxyl group, an ester group, an amino group, an amide group, a carboxyl group and a carbonyl group are preferred, and a hydroxyl group is more preferred.

The high melting point resin material can be used without any particular limitation as long as it has a melting point of 180°C or higher, and examples include vinyl resin, polyamide, polyimide, polyester, (meth)acrylic resin, cellulose resin, polyolefin resin, and ionomer resin.

In the present invention, a resin material having a melting point of 180° C. or higher and having a polar group is particularly preferred, and amide resins such as ethylene-vinyl alcohol copolymer, polyvinyl alcohol, nylon 6, nylon 6,6, MXD nylon, and amorphous nylon are preferred, with ethylene-vinyl alcohol copolymer and polyvinyl alcohol being particularly preferred.
By using such a resin material, the adhesion of the evaporated film formed on the coating layer can be significantly improved, and the gas barrier properties of the film can be effectively improved.

The content of the high melting point resin material in the surface resin layer is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more.

As long as the characteristics of the present invention are not impaired, the surface resin layer may contain a resin material other than the high melting point resin material.
Furthermore, within the scope of not impairing the characteristics of the present invention, the surface resin layer may contain additives, such as crosslinking agents, antioxidants, antiblocking agents, slip agents, ultraviolet absorbers, light stabilizers, fillers, reinforcing agents, antistatic agents, pigments, and modifying resins.

The ratio of the thickness of the surface resin layer to the total thickness of the multilayer base material is preferably 1% or more and 10% or less, and more preferably 1% or more and 5% or less.
By making the ratio of the thickness of the surface resin layer to the total thickness of the multilayer substrate 1% or more, the adhesion of the vapor-deposited film can be improved, the gas barrier properties can be improved, and the laminate strength of the packaging material can be improved.
In addition, by setting the ratio of the thickness of the surface resin layer to the total thickness of the multilayer substrate to 10% or less, the film-forming property and processability of the multilayer substrate can be further improved. In addition, as described below, the recyclability of a packaging material produced using a laminate of the multilayer substrate of the present invention and a sealant layer made of polypropylene can be improved.

The thickness of the surface resin layer is preferably 0.1 μm or more and 5 μm or less, and more preferably 0.1 μm or more and 4 μm or less.
By making the thickness of the surface resin layer 0.1 μm or more, the adhesion of the evaporated film can be improved, the gas barrier property can be improved, and the laminate strength of the packaging material can be improved.
In addition, by making the thickness of the surface resin layer 5 μm or less, the film-forming property and processing suitability of the multilayer substrate can be further improved. In addition, as described below, the recyclability of a packaging material produced using a laminate of the multilayer substrate of the present invention and a sealant layer made of polypropylene can be improved.

(Adhesive Resin Layer)
In one embodiment, the multilayer substrate of the present invention may include an adhesive resin layer between the polypropylene resin layer and the surface resin layer, thereby improving the adhesion between these layers.

The adhesive resin layer can be formed by using an adhesive resin such as polyether, polyester, silicone resin, epoxy resin, polyurethane, vinyl resin, phenol resin, and polyolefin.
Of the above, and as described below, from the viewpoint of the recyclability of packaging materials produced using a laminate of the multilayer base material of the present invention and a sealant layer made of polypropylene, polyolefins and acid-modified products thereof are preferred, and polypropylene and acid-modified products thereof are particularly preferred.
As the adhesive polypropylene, commercially available products can be used, for example, the Admer series manufactured by Mitsui Chemicals, Inc.

The thickness of the adhesive resin layer is not particularly limited, but can be, for example, 1 μm or more and 15 μm or less. By making the thickness of the adhesive resin layer 1 μm or more, the adhesion between the polypropylene resin layer and the surface resin layer can be further improved. By making the thickness of the adhesive layer 15 μm or less, the processability of the multilayer substrate can be improved.

In one embodiment, the multilayer substrate of the present invention is a co-extruded film, which can be produced by forming a resin film using a T-die method, an inflation method, or the like, and then stretching the film.
By forming the film by the inflation method, the resin film can be stretched at the same time.

(Laminated film)
As shown in FIG. 3 , the laminated film 20 of the present invention comprises the above-mentioned multilayer substrate 10 and a vapor-deposited film 21 containing an inorganic oxide, and is characterized in that the vapor-deposited film 21 is provided on a surface resin layer 12.
In one embodiment, the laminate film 20 may further include a barrier coat layer 22 on the vapor deposition film 21 as shown in FIG.

Each layer of the laminated film will be described below. Note that the multilayer substrate has been described above, so a detailed description will be omitted here.

(Vapor-deposited film)
The laminated film of the present invention has a vapor-deposited film made of an inorganic oxide on the surface resin layer. This improves the gas barrier properties of the laminated film, specifically, the oxygen barrier properties and water vapor barrier properties. In addition, the weight loss of the contents filled in the packaging material produced using the laminated film of the present invention can be suppressed.

Examples of inorganic oxides include aluminum oxide (alumina), silicon oxide (silica), magnesium oxide, calcium oxide, zirconium oxide, titanium oxide, boron oxide, hafnium oxide, and barium oxide.
Of the above, silica and alumina are preferred.
Moreover, silica is particularly preferable because it does not require aging treatment after the deposition film is formed.

The thickness of the evaporated film is preferably 1 nm or more and 150 nm or less, more preferably 5 nm or more and 60 nm or less, and even more preferably 10 nm or more and 40 nm or less.
By making the thickness of the vapor-deposited film 1 nm or more, the oxygen barrier property and water vapor barrier property of the laminate can be further improved.
In addition, by making the thickness of the vapor-deposited film 150 nm or less, the occurrence of cracks in the vapor-deposited film can be prevented. Furthermore, as described below, the recyclability of a packaging material produced using a laminate of the multilayer base material of the present invention and a sealant layer made of polypropylene can be improved.

The deposition film can be formed by a conventional method, for example, physical vapor deposition methods (PVD method) such as vacuum deposition, sputtering, and ion plating, as well as chemical vapor deposition methods (CVD method) such as plasma chemical vapor deposition, thermal chemical vapor deposition, and photochemical vapor deposition.

Also, for example, a composite film consisting of two or more layers of vapor-deposited films of different inorganic oxides can be formed and used by combining both physical vapor deposition and chemical vapor deposition. The degree of vacuum in the vapor deposition chamber is preferably about 10 ^-2 to 10 ^-8 mbar before oxygen is introduced, and about 10 ^-1 to 10 ^-6 mbar after oxygen is introduced. The amount of oxygen introduced varies depending on the size of the vapor deposition machine. For the oxygen to be introduced, an inert gas such as argon gas, helium gas, or nitrogen gas may be used as a carrier gas to the extent that no problems occur. The film transport speed can be about 10 to 800 m/min.

It is preferable that the surface of the deposited film is subjected to the above-mentioned surface treatment. This can improve adhesion to adjacent layers.

(Barrier Coat Layer)
The laminated film of the present invention may further include a barrier coat layer on the vapor-deposited film, which can improve the oxygen barrier property and water vapor barrier property of the laminated film.

In one embodiment, the barrier coat layer contains a gas barrier resin such as an ethylene-vinyl alcohol copolymer (EVOH), polyvinyl alcohol, polyacrylonitrile, polyamides such as nylon 6, nylon 6,6, and polymetaxylylene adipamide (MXD6), polyester, polyurethane, and (meth)acrylic resin. Among these, polyvinyl alcohol is preferred from the viewpoints of oxygen barrier property and water vapor barrier property.
Furthermore, by including polyvinyl alcohol in the barrier coat layer, the occurrence of cracks in the vapor-deposited film can be effectively prevented.

The content of the gas barrier resin in the barrier coat layer is preferably 50% by mass or more and 95% by mass or less, and more preferably 75% by mass or more and 90% by mass or less. By making the content of the gas barrier resin in the barrier coat layer 50% by mass or more, the oxygen barrier property and water vapor barrier property of the substrate can be further improved.

The barrier coat layer may contain the above additives as long as they do not impair the properties of the present invention.

The thickness of the barrier coat layer is preferably 0.01 μm or more and 10 μm or less, and more preferably 0.1 μm or more and 5 μm or less.
By making the thickness of the barrier coat layer 0.01 μm or more, the oxygen barrier property and water vapor barrier property of the laminated film can be further improved. By making the thickness of the barrier coat layer 10 μm or less, the processability of the laminated film can be improved. In addition, the recyclability of the packaging material produced using the laminate of the multilayer base material of the present invention and the sealant layer made of polypropylene can be improved.

The barrier coat layer can be formed by dissolving or dispersing the above-mentioned materials in water or a suitable solvent, applying the solution, and drying the solution. The barrier coat layer can also be formed by applying a commercially available barrier coat agent and drying the solution.

In another embodiment, the barrier coat layer is a gas barrier coating film containing at least one resin composition such as a hydrolysate of a metal alkoxide or a hydrolysis condensate of a metal alkoxide obtained by polycondensing a mixture of a metal alkoxide and a water-soluble polymer by a sol-gel method in the presence of a sol-gel catalyst, water, an organic solvent, etc.
By providing such a barrier coat layer on the vapor-deposited film, the occurrence of cracks in the vapor-deposited film can be effectively prevented.

In one embodiment, the metal alkoxide is represented by the following general formula:
R ¹ _n M(OR ² ) _m
(In the formula, R ¹ and R ² each represent an organic group having 1 to 8 carbon atoms, M represents a metal atom, n represents an integer of 0 or more, m represents an integer of 1 or more, and n+m represents the atomic valence of M.)

As the metal atom M, for example, silicon, zirconium, titanium, aluminum, etc. can be used.
Examples of the organic group represented by R ¹ and R ² include alkyl groups such as a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, and an i-butyl group.

Examples of metal alkoxides satisfying the above general formula include tetramethoxysilane (Si( _OCH3 ) ₄ ), tetraethoxysilane (mass %) Si( _OC2H5 ) ₄ ), _{tetrapropoxysilane (Si(OC3H7 ) 4} ), and _{tetrabutoxysilane} ( _Si ( _OC4H9 ) ₄ ).

It is also preferable to use a silane coupling agent together with the metal alkoxide.
As the silane coupling agent, a known organoalkoxysilane containing an organic reactive group can be used, and in particular, an organoalkoxysilane having an epoxy group is preferred. Examples of organoalkoxysilane having an epoxy group include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane.

Two or more of the above silane coupling agents may be used, and it is preferable to use the silane coupling agent in an amount within the range of about 1 to 20 parts by mass per 100 parts by mass of the total amount of the alkoxide.

As water-soluble polymers, polyvinyl alcohol and ethylene-vinyl alcohol copolymers are preferred, and from the viewpoints of oxygen barrier properties, water vapor barrier properties, water resistance, and weather resistance, it is preferable to use these in combination.

The content of the water-soluble polymer in the gas barrier coating film is preferably 5 parts by mass or more and 500 parts by mass or less per 100 parts by mass of the metal alkoxide.
By making the content of the water-soluble polymer in the gas barrier coating film 5 parts by mass or more per 100 parts by mass of the metal alkoxide, the oxygen barrier property and water vapor barrier property of the laminated film can be further improved. Also, by making the content of the water-soluble polymer in the gas barrier coating film 500 parts by mass or less per 100 parts by mass of the metal alkoxide, the film formability of the gas barrier coating film can be improved.

The thickness of the gas barrier coating film is preferably 0.01 μm or more and 100 μm or less, and more preferably 0.1 μm or more and 50 μm or less, which can further improve the oxygen barrier property and water vapor barrier property while maintaining recyclability.
By making the thickness of the gas barrier coating film 0.01 μm or more, the oxygen barrier property and water vapor barrier property of the laminated film can be improved, and the occurrence of cracks in the vapor deposition film can be prevented.
By setting the thickness of the gas barrier coating film to 100 μm or less, the recyclability of a packaging material produced using a laminate of the multilayer base material of the present invention and a sealant layer made of polypropylene can be improved.

The gas barrier coating film can be formed by applying a composition containing the above-mentioned materials by a conventionally known means such as roll coating using a gravure roll coater or the like, spray coating, spin coating, dipping, brushing, bar coding, or an applicator, and then polycondensing the composition by a sol-gel method.
The sol-gel catalyst is preferably an acid or an amine compound. As the amine compound, a tertiary amine that is substantially insoluble in water and soluble in an organic solvent is preferable, and examples thereof include N,N-dimethylbenzylamine, tripropylamine, tributylamine, and tripentylamine. Among these, N,N-dimethylbenzylamine is preferable.
The sol-gel catalyst is preferably used in the range of 0.01 to 1.0 part by mass, and more preferably 0.03 to 0.3 part by mass, per 100 parts by mass of the metal alkoxide.
By using a sol-gel catalyst in an amount of 0.01 part by mass or more per 100 parts by mass of the metal alkoxide, the catalytic effect can be improved, and by using a sol-gel catalyst in an amount of 1.0 part by mass or less per 100 parts by mass of the metal alkoxide, the thickness of the gas barrier coating film formed can be made uniform.

The composition may further contain an acid, which is used as a catalyst in the sol-gel process, mainly for the hydrolysis of alkoxides, silane coupling agents, etc.
The acid may be a mineral acid such as sulfuric acid, hydrochloric acid, or nitric acid, or an organic acid such as acetic acid, tartaric acid, etc. The amount of the acid used is preferably 0.001 mol or more and 0.05 mol or less based on the total molar amount of the alkoxide and the alkoxide portion (e.g., silicate portion) of the silane coupling agent.
The amount of acid used is 0.001 moles or more relative to the total molar amount of the alkoxide and the alkoxide portion (e.g., silicate portion) of the silane coupling agent, thereby improving the catalytic effect. Also, the amount of acid used is 0.05 moles or less relative to the total molar amount of the alkoxide and the alkoxide portion (e.g., silicate portion) of the silane coupling agent, thereby making the thickness of the gas barrier coating film formed uniform.

The composition preferably contains water in an amount of 0.1 to 100 moles, more preferably 0.8 to 2 moles, per mole of the total amount of alkoxides.
By controlling the water content to 0.1 mole or more per mole of the total molar amount of the alkoxides, the oxygen barrier property and water vapor barrier property of the laminate of the present invention can be improved. Also, by controlling the water content to 100 moles or more per mole of the total molar amount of the alkoxides, the hydrolysis reaction can be carried out quickly.

The composition may also contain an organic solvent. Examples of the organic solvent that can be used include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, and n-butanol.

Hereinafter, one embodiment of the method for forming a gas barrier coating film will be described.
First, a composition is prepared by mixing a metal alkoxide, a water-soluble polymer, a sol-gel catalyst, water, an organic solvent, and optionally a silane coupling agent, etc. In the composition, a polycondensation reaction gradually proceeds.
Next, the composition is applied onto the vapor-deposited film by the above-mentioned conventionally known method and dried. This drying process further advances the polycondensation reaction between the alkoxide and the water-soluble polymer (and the silane coupling agent, if the composition contains a silane coupling agent) to form a composite polymer layer.
Finally, the composition is heated at a temperature of 20 to 250° C., preferably 50 to 220° C., for 1 second to 10 minutes to form a gas barrier coating film.

The barrier coat layer may have a printed layer formed thereon. The method for forming the printed layer is as described above.

(Laminate)
As shown in FIG. 5, the laminate 30 of the present invention is characterized by comprising the laminate film 20 and a sealant layer 31 .

Each layer of the laminate will be described below. Note that the laminate film has been described above, so a detailed description will be omitted here.

(Sealant Layer)
In one embodiment, the sealant layer can be formed of a resin material that can be fused to each other by heat, and examples of such resin materials include low density polyethylene (LDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), linear low density polyethylene (LLDPE), ethylene-α-olefin copolymers polymerized using a metallocene catalyst, random or block copolymers of ethylene and polypropylene, polypropylene, ethylene-vinyl acetate copolymers (EVA), ethylene-acrylic acid copolymers (EAA), ethylene-ethyl acrylate copolymers (EEA), ethylene-methacrylic acid copolymers (EMAA), ethylene, and the like. Examples of the resin include ethylene-methyl methacrylate copolymer (EMMA), ionomer resins, heat-sealable ethylene-vinyl alcohol resins, or copolymerized resins such as methylpentene resins, ethylene-propylene copolymers, methylpentene polymers, polybutene polymers, polyethylene, polypropylene, and cyclic olefin copolymers; acid-modified polyolefins obtained by modifying polyolefins with unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, and itaconic acid; polyesters such as PET; polyvinyl acetate resins; poly(meth)acrylic resins; and polyvinyl chloride resins.
Conventionally, a laminate in which a substrate and a sealant layer are made of different resin materials has been used to produce a packaging material. However, since it is difficult to separate the substrate and the sealant layer after collecting the used packaging material, the current situation is that the laminate is not actively recycled.
By forming the substrate and the sealant layer from the same material, it is not necessary to separate the substrate and the sealant layer, and therefore the recycling suitability can be improved.
That is, from the viewpoint of the recyclability of the packaging material produced using the laminate, it is preferable that the sealant layer be made of polypropylene among the above-mentioned resin materials.

The sealant layer may contain the above additives as long as the properties of the present invention are not impaired.

The sealant layer may have a single layer structure or a multilayer structure.

The thickness of the sealant layer is preferably 20 μm or more and 100 μm or less, and more preferably 30 μm or more and 70 μm or less.
By making the thickness of the sealant layer 20 μm or more, the laminate strength of the packaging material including the laminate of the present invention can be further improved.
Moreover, by setting the thickness of the sealant layer to 100 μm or less, the processability of the laminate of the present invention can be further improved.

(Packaging materials)
The packaging material of the present invention is characterized by comprising the laminate. Examples of the packaging material include packaging products (packaging bags), lids, and laminate tubes.

Examples of packaging bags include standing pouch type, side seal type, two-sided seal type, three-sided seal type, four-sided seal type, envelope seal type, grommet seal type (pillow seal type), pleated seal type, flat bottom seal type, square bottom seal type, and gusset type.

A standing pouch, which is an example of a packaging bag comprising the laminate of the present invention, will be described. FIG. 6 is a diagram showing a simplified example of the configuration of a standing pouch. As shown in FIG. 6, a standing pouch 40 is composed of a body portion (side sheet) 41 and a bottom portion (bottom sheet) 42. The side sheet 41 and bottom sheet 42 of the standing pouch 20 may be composed of the same material, or may be composed of different materials.

In one embodiment, the body 41 of the standing pouch 40 can be formed by bag making so that the heat seal layer of the laminate of the present invention becomes the innermost layer.
In another embodiment, the side sheet 41 can be formed by preparing two sheets of the laminate of the present invention, overlapping them with their heat seal layers facing each other, inserting two sheets of laminate folded in a V shape into both ends of the overlapped laminate so that the heat seal layers are on the outside, and heat sealing them. According to this production method, a stand pouch having a body with a gusset 43 as shown in Figure 7 can be obtained.

In one embodiment, the bottom sheet 22 of the standing pouch 20 can be formed by inserting the laminate of the present invention between pre-formed side sheets and heat sealing the laminate.
More specifically, the laminate can be formed by folding the laminate into a V shape so that the heat seal layer is on the outside, inserting it between side sheets that have been made into a bag, and heat sealing it.

Heat sealing can be performed by known methods such as bar sealing, rotary roll sealing, belt sealing, impulse sealing, high frequency sealing, and ultrasonic sealing.

The contents filled into the packaging material are not particularly limited, and may be liquid, powder, or gel. The contents may also be food or non-food.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

Example 1
A multilayer substrate was produced by co-extruding polyamide (polyamide 6, manufactured by Ube Industries, Ltd., melting point: 220°C), adhesive resin (Admer QF500, manufactured by Mitsui Chemicals, Inc., maleic anhydride modified polypropylene), and polypropylene (Novatec FL203D, manufactured by Japan Polypropylene Corporation, melting point: 160°C) and then stretching the extrusions 5 times in the machine direction (MD) and 10 times in the transverse direction (TD) using a sequential biaxial stretching device.
The multi-layered substrate prepared as described above had a surface resin layer made of polyamide, an adhesive resin layer made of adhesive resin, and a polypropylene resin layer made of polypropylene, and had a total thickness of 20 μm.
The ratio of the thickness of the surface resin layer made of polyamide to the thickness of the multilayer substrate was 2%.

Example 2
A multilayer substrate was produced in the same manner as in Example 1, except that the polyamide was changed to polyvinyl alcohol (manufactured by Nippon Vinyl Acetate Bhopal Co., Ltd., Bhopal JC-33, melting point: 200° C.) and a surface resin layer was formed.

Example 3
A multilayer substrate was prepared in the same manner as in Example 1, except that the polyamide was changed to ethylene vinyl alcohol (EVAL F171B, manufactured by Kuraray Co., Ltd., melting point: 183° C.) and a surface resin layer was formed.

Example 4
A multilayer substrate was produced in the same manner as in Example 1, except that the polyamide was changed to a non-crystalline polyester (Vylon RN-9300, manufactured by Toyobo Co., Ltd., melting point: 198° C.) and a surface resin layer was formed.

Comparative Example 1
Polypropylene (Novatec FL203D, manufactured by Japan Polypropylene Corporation, melting point: 160° C.) was co-extruded and then stretched 5 times in the machine direction (MD direction) and 10 times in the transverse direction (TD direction) using a sequential biaxial stretching device to produce a substrate with a thickness of 20 μm.

<<Gas barrier property evaluation>>
The multi-layer substrate and the polypropylene film obtained in the above examples were placed in a test machine, and a silica vapor deposition film was formed on the surface resin layer and on the polypropylene film obtained in the above comparative example by a batch-type parallel plate CVD method. The deposition conditions for the CVD method were as follows.
(Deposition conditions)
Input power: 100W
・Raw material gas: HMDSO
Carrier gas flow rate: Ar 3.0 sccm
Oxygen gas flow rate: 50 sccm
・Deposition pressure 15 Pa

After the deposition film was formed, the oxygen permeability (cc/m ² ·day·atm) and water vapor permeability (g/m ² ·day) were measured by the following methods. The results are shown in Table 1.

[Oxygen permeability]
Using an oxygen permeability measuring device (OX-TRAN2/20, manufactured by MOCON), the test piece was set so that the substrate layer surface was the oxygen supply side, and the oxygen permeability was measured in an environment of 23° C. and relative humidity of 90% RH in accordance with JIS K 7126.
[Water vapor permeability]
Using a water vapor transmission rate measuring device (MOCON Corporation, PERMATRAN-w 3/33), the test piece was set so that the substrate layer surface was on the water vapor supply side, and the water vapor transmission rate was measured in accordance with JIS K 7129 under an environment of 40°C and a relative humidity of 90% RH.

In addition, silica vapor deposition films and alumina vapor deposition films were formed by PVD in the test machine, and the oxygen permeability (cc/ ^m2 ·day·atm) and water vapor permeability (g/ ^m2 ·day) were similarly measured. The results are summarized in Table 1.

<<Laminate strength test>>
In the gas barrier property evaluation, a 40 μm-thick unstretched polypropylene film was dry laminated onto the silica vapor-deposited film formed by the CVD method to form a sealant layer, thereby producing a laminate.
The laminate was cut into a 15 mm wide rectangular sample, and the lamination strength (N/15 mm) between the vapor-deposited film and the surface resin layer, and between the vapor-deposited film and the polypropylene film was measured using a tensile tester (Tensilon universal material testing machine, manufactured by Orientec Co., Ltd.) in accordance with JIS K6854-2, using 90° peeling (T-peel method) at a peel speed of 50 mm/min. The measurement results are summarized in Table 1.
A 40 μm-thick unstretched polypropylene film was dry-laminated onto the silica vapor-deposited film and alumina vapor-deposited film formed by the PVD method to prepare a laminate, and the laminate strength was measured in the same manner as above. The measurement results are shown in Table 1.

<<Film-forming property evaluation>>
In the above-mentioned Examples and Comparative Examples, the occurrence of unevenness in the flow of the resin during film formation was visually observed and evaluated based on the following evaluation criteria. The evaluation results are summarized in Table 1.
(Evaluation Criteria)
◯: Flow unevenness was observed.
×: No flow unevenness was observed.

10: Multilayer base material, 11: Polypropylene resin layer, 12: Surface resin layer, 13: Adhesive resin layer, 20: Laminated film, 21: Vapor deposition film, 22: Barrier coat layer, 30: Laminate, 31: Sealant layer, 40: Packaging material, 41: Body (side sheet), 42: Bottom (bottom sheet), 43: Gusset

Claims (14)

A multi-layer substrate used as the substrate of a laminate having at least a substrate, a vapor-deposited film, and a sealant layer in this order ,
The multilayer base material has been subjected to a stretching treatment,
Furthermore, the multilayer base material includes at least a polypropylene resin layer and a surface resin layer,
the surface resin layer contains a resin material having a melting point of 180° C. or more,
The content of the resin material in the surface resin layer is 80% by mass or more,
A multi-layer substrate, characterized in that the ratio of the thickness of the surface resin layer to the total thickness of the multi-layer substrate is 1% or more and 10% or less . The multilayer substrate according to claim 1, wherein the melting point of the resin material is 265°C or less. The multilayer substrate according to claim 1 or 2, wherein the difference between the melting point of the resin material and the melting point of the polypropylene contained in the polypropylene resin layer is 20 to 80°C. The multilayer substrate according to any one of claims 1 to 3, wherein the resin material has a polar group. The multilayer substrate according to any one of claims 1 to 4, wherein the resin material is one or more resin materials selected from ethylene vinyl alcohol copolymer, polyvinyl alcohol, polyester, nylon 6, nylon 6,6, MXD nylon, and amorphous nylon. The multi-layer substrate according to any one of claims 1 to 5 , wherein the multi-layer substrate is a co-extruded film. The multi-layer substrate according to any one of claims 1 to 6 , which is used for packaging material applications. A laminate film comprising the multilayer substrate according to any one of claims 1 to 7 and a vapor-deposited film made of an inorganic oxide, the vapor-deposited film being provided on the surface resin layer. The laminate includes a multilayer substrate used as the substrate of a laminate including at least a substrate, a vapor-deposited film, and a sealant layer in this order, and a vapor-deposited film made of an inorganic oxide;
The multilayer base material is subjected to a stretching treatment,
Furthermore, the multilayer base material includes at least a polypropylene resin layer and a surface resin layer,
the surface resin layer contains a resin material having a melting point of 180° C. or more,
A laminated film comprising the vapor-deposited film on the surface resin layer. The laminated film according to claim 8 or 9, wherein the inorganic oxide is silica or alumina. The laminate film according to any one of claims 8 to 10, further comprising a barrier coat layer on the vapor-deposited film. A laminate comprising the laminate film according to any one of claims 8 to 11 and a sealant layer. The laminate of claim 12, wherein the sealant layer is comprised of polypropylene . A packaging material comprising the laminate according to claim 12 or 13.