JP2024054520A - Laminate for gas barrier film, gas barrier film, packaging film, packaging container and packaging product - Google Patents

Abstract

To provide a laminate for gas barrier film, a gas barrier film, a packaging film, a packaging container and a packaging product which have excellent oxygen barrier property even after hot water treatment, and by which a gas barrier film having an excellent external appearance can be manufactured.SOLUTION: A laminate for gas barrier film for forming a gas barrier film together with an oxygen barrier film comprises a resin substrate, and an inorganic oxide layer on which an oxygen barrier film is formed, where a coefficient of dynamic friction between the inorganic oxide layer and stainless steel is 0.4 or less.SELECTED DRAWING: Figure 1

Description

This disclosure relates to laminates for gas barrier films, gas barrier films, packaging films, packaging containers, and packaging products.

Packaging containers such as packaging bags used for packaging food, medicines, etc. require gas barrier properties that block the intrusion of water vapor, oxygen, and other gases that can cause deterioration of the contents in order to prevent deterioration or spoilage of the contents and to maintain their functions and properties. For this reason, gas barrier films have traditionally been used in packaging containers.

As such a gas barrier film, for example, a barrier laminate comprising a multilayer substrate, a vapor deposition film, and a barrier coat layer provided on the vapor deposition film, in which the barrier coat layer is a gas barrier coating film composed of a resin composition of a metal alkoxide, a water-soluble polymer, and a silane coupling agent, is known (see Patent Document 1 below).

Japanese Patent No. 6902231

However, the gas barrier film described in Patent Document 1 above has room for improvement in terms of oxygen barrier properties after hot water treatment such as retort treatment, and appearance.

The present disclosure has been made in consideration of the above problems, and aims to provide a laminate for a gas barrier film, a gas barrier film, a packaging film, a packaging container, and a packaging product that can produce a gas barrier film that has excellent oxygen barrier properties even after hot water treatment and has an excellent appearance.

The inventors of the present disclosure have investigated the cause of the above-mentioned problem. First, the inventors of the present disclosure have found that when a gas barrier film laminate, which is formed by forming an inorganic oxide layer on a resin substrate, is transported by roll-to-roll transport through a guide roll, if the inorganic oxide layer of the gas barrier film laminate is brought into contact with the guide roll, wrinkles may occur in the gas barrier film laminate itself or scratches may occur on the surface of the inorganic oxide layer, and that if an oxygen barrier film is formed on the gas barrier film laminate to produce a gas barrier film, there is room for improvement in the appearance of the gas barrier film. In addition, the inventors of the present disclosure have considered that the wrinkles occurring in the gas barrier film laminate itself and the scratches occurring on the surface of the inorganic oxide layer may be caused by the large friction force between the guide roll and the inorganic oxide layer. Furthermore, when the gas barrier film laminate is transported by roll-to-roll transport, a stainless steel roll is often used as the guide roll. Therefore, the inventors of the present disclosure have found that the above-mentioned problem can be solved by the following present disclosure after extensive research.

The outline of this disclosure is as follows.
[1] A laminate for a gas barrier film that forms a gas barrier film together with an oxygen barrier coating, the laminate for a gas barrier film comprising a resin substrate and an inorganic oxide layer on which the oxygen barrier coating is formed, the coefficient of dynamic friction between the inorganic oxide layer and stainless steel being 0.4 or less.
[2] The gas barrier film laminate according to [1], wherein the resin substrate contains polypropylene or polyethylene terephthalate.
[3] The laminate for a gas barrier film according to [1] or [2], wherein the inorganic oxide layer has a thickness of 1 to 200 nm.
[4] The laminate for a gas barrier film according to any one of [1] to [3], wherein the inorganic oxide layer contains aluminum oxide or silicon oxide.
[5] The laminate for a gas barrier film according to any one of [1] to [4], further comprising an underlayer between the resin substrate and the inorganic oxide layer, the underlayer containing an organic polymer, the organic polymer containing at least one of a polyacrylic resin, a polyol resin, a polyurethane resin, a polyamide resin, and a reaction product of these resins, and the underlayer has a thickness of 0.01 to 1 μm.
[6] A gas barrier film comprising the laminate for gas barrier films according to any one of [1] to [5], and an oxygen barrier coating provided on the inorganic oxide layer of the laminate for gas barrier films.
[7] The gas barrier film according to [6], wherein the oxygen barrier coating is composed of an organic-inorganic composite film, and the organic-inorganic composite film is formed using a composition for forming an oxygen barrier coating film, the composition comprising at least one of a metal alkoxide and a hydrolysate of a metal alkoxide, and a water-soluble polymer.
[8] The gas barrier film according to [7] or [8], wherein the composition for forming an oxygen barrier coating film further contains at least one of a silane coupling agent and a hydrolysate of a silane coupling agent.
[9] The gas barrier film according to [6], wherein the oxygen barrier coating is composed of a polycarboxylic acid polyvalent metal salt coating containing a polycarboxylic acid polyvalent metal salt which is a reaction product between a carboxy group of a polycarboxylic acid polymer and a polyvalent metal compound.
[10] A packaging film comprising the gas barrier film according to any one of [6] to [9] and a sealant layer, the sealant layer being provided on the oxygen barrier coating of the gas barrier film.
[11] A packaging container obtained using the packaging film according to [10].
[12] A packaging product comprising the packaging container according to [11] and contents filled in the packaging container.

According to the gas barrier film laminate of the present disclosure, when the gas barrier film laminate is transported in a roll-to-roll manner through a guide roll made of stainless steel, even if the inorganic oxide layer is brought into contact with the guide roll, the frictional force between the guide roll and the inorganic oxide layer is sufficiently reduced. Therefore, according to the gas barrier film laminate of the present disclosure, compared to when the dynamic friction coefficient between the stainless steel and the inorganic oxide layer exceeds 0.4, it is possible to suppress the occurrence of wrinkles in the gas barrier film laminate and the occurrence of rubbing of the inorganic oxide layer by the guide roll, and the occurrence of damage to the inorganic oxide layer is suppressed. Therefore, when an oxygen barrier coating is formed on the inorganic oxide layer of the gas barrier film laminate thus obtained to form a gas barrier film, it is possible to produce a gas barrier film having excellent oxygen barrier properties and excellent appearance even after hot water treatment such as retort treatment.

The present disclosure provides a laminate for a gas barrier film, a gas barrier film, a packaging film, a packaging container, and a packaging product that can produce a gas barrier film that has excellent oxygen barrier properties even after hot water treatment.

1 is a cross-sectional view showing one embodiment of a laminate for a gas barrier film according to the present disclosure. FIG. 1 is a cross-sectional view showing one embodiment of a gas barrier film of the present disclosure. FIG. 1 is a cross-sectional view showing one embodiment of a packaging film of the present disclosure. FIG. 1 is a cross-sectional view illustrating one embodiment of a packaging product of the present disclosure.

Embodiments of the present disclosure are described in detail below.

<Laminate for gas barrier film>
First, an embodiment of the laminate for a gas barrier film of the present disclosure will be described with reference to Fig. 1. Fig. 1 is a cross-sectional view showing an embodiment of the laminate for a gas barrier film of the present disclosure. As shown in Fig. 1, the laminate for a gas barrier film 10 is a laminate for a gas barrier film that forms a gas barrier film together with an oxygen barrier coating, and includes a resin substrate 1 and an inorganic oxide layer 3 on which the oxygen barrier coating is formed. Here, the dynamic friction coefficient between the inorganic oxide layer 3 and stainless steel (hereinafter also referred to as "dynamic friction coefficient A") is 0.4 or less.
The gas barrier film laminate 10 may further include an underlayer 2 between the resin substrate 1 and the inorganic oxide layer 3 .

According to the gas barrier film laminate 10, when the gas barrier film laminate 10 is transported in a roll-to-roll manner through a guide roll made of stainless steel, even if the inorganic oxide layer 3 is brought into contact with the guide roll, the frictional force between the guide roll and the inorganic oxide layer 3 is sufficiently reduced. Therefore, compared to when the dynamic friction coefficient A exceeds 0.4, the gas barrier film laminate 10 can suppress the occurrence of wrinkles in the gas barrier film laminate 10 and the occurrence of rubbing against the inorganic oxide layer 3 by the guide roll, and suppresses the occurrence of damage to the inorganic oxide layer 3. Therefore, when an oxygen barrier film is formed on the inorganic oxide layer 3 of the gas barrier film laminate 10 thus obtained to form a gas barrier film, it is possible to produce a gas barrier film having excellent oxygen barrier properties and excellent appearance even after hot water treatment such as retort treatment.

The resin substrate 1, undercoat layer 2, and inorganic oxide layer 3 are described in detail below.

(1) Resin Substrate The resin substrate 1 is a layer that serves as a support for the inorganic oxide layer 3, and contains a resin. Examples of the resin include polyolefin resins, polyester resins, polyamide resins, polyether resins, acrylic resins, and natural polymer compounds (such as cellulose acetate). These can be used alone or in combination of two or more.

Examples of the polyolefin resin include polyethylene and polypropylene.
Examples of polyester resins include polyethylene terephthalate (PET) and polyethylene naphthalate (PEN).
The resin preferably contains polypropylene or polyethylene terephthalate. In this case, the mechanical strength of the packaging film containing the laminate for gas barrier films 10 can be further improved, and the resin substrate 1 can be made less likely to melt when the packaging film containing the laminate for gas barrier films 10 is heat-sealed.

The resin substrate 1 may further contain additives such as antiblocking agents, antistatic agents, UV absorbers, plasticizers, and lubricants, as necessary.

The resin substrate 1 may be a stretched film or a non-stretched film, but from the viewpoint of oxygen barrier properties, a stretched film is preferable. Examples of stretched films include uniaxially stretched films and biaxially stretched films, but biaxially stretched films are preferable because they improve heat resistance.

The dynamic friction coefficient (hereinafter also referred to as "dynamic friction coefficient B") of the surface of the resin substrate 1, i.e., the surface of the resin substrate 1 on the inorganic oxide layer 3 side, with respect to stainless steel is preferably smaller than the dynamic friction coefficient A. In this case, the dynamic friction coefficient A tends to be 0.4 or less.
The dynamic friction coefficient B can be adjusted, for example, by adjusting the content of a filler (such as an antiblocking agent) in the resin substrate 1 or by subjecting the surface of the resin substrate 1 to a smoothing treatment.

The thickness of the resin substrate 1 is not particularly limited, but may be, for example, 0.1 mm or less. In particular, the thickness of the resin substrate 1 is preferably 40 μm or less, more preferably 35 μm or less, and particularly preferably 30 μm or less. When the thickness of the resin substrate 1 is 40 μm or less, the flexibility of the gas barrier film laminate 10 is further improved compared to when the thickness of the resin substrate 1 exceeds 40 μm, and the oxygen gas barrier property of the gas barrier film laminate 10 after abuse can be further improved. However, from the viewpoint of improving strength, the thickness of the resin substrate 1 is preferably 10 μm or more, and more preferably 12 μm or more.

The resin substrate 1 may be a single layer or a laminate of multiple layers.

(2) Underlayer The underlayer 2 is a layer for improving the adhesion between the resin substrate 1 and the inorganic oxide layer 3, and is provided between the resin substrate 1 and the inorganic oxide layer 3.

The material constituting the undercoat layer 2 includes an organic polymer. The organic polymer may be at least one of a polyacrylic resin, a polyol resin, a polyurethane resin, a polyamide resin, or a reaction product of these resins.

The polyurethane resin may contain a reaction product of a polyol compound and an isocyanate compound. From the viewpoint of transparency, the polyol compound is preferably an acrylic polyol. The isocyanate compound mainly functions as a crosslinking agent or a curing agent.

The proportion of organic polymers in the material constituting the undercoat layer 2 may be 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more.

The thickness of the underlayer 2 is not particularly limited as long as it is capable of improving the adhesion between the resin substrate 1 and the inorganic oxide layer 3, and may be 0.01 μm or more. In this case, compared to when the thickness of the underlayer 2 is less than 0.01 μm, it is possible to further improve the smoothness of the surface of the underlayer 2 compared to the surface of the resin substrate 1, and it is possible to make the thickness of the inorganic oxide layer 3 more uniform, and it is also possible to further improve the oxygen barrier property. Therefore, the oxygen barrier property of the gas barrier film laminate 10 can be further improved. The thickness of the underlayer 2 may be 0.03 μm or more, 0.04 μm or more, or 0.05 μm or more. By increasing the thickness of the underlayer 2, it is possible to further suppress the deterioration of the water vapor barrier property when an external force such as stretching is applied. The thickness of the underlayer 2 may be 1 μm or less. In this case, compared to when the thickness of the underlayer 2 exceeds 1 μm, the flexibility of the gas barrier film laminate 10 is further improved, and the oxygen gas barrier property of the gas barrier film laminate 10 after abuse can be further improved. The thickness of the underlayer 2 may be 0.3 μm or less, or 0.2 μm or less.

(3) Inorganic Oxide Layer The inorganic oxide layer 3 is a layer containing an inorganic oxide. By having the inorganic oxide layer 3, the laminate for gas barrier films 10 can further improve the gas barrier properties.

The dynamic friction coefficient (dynamic friction coefficient A) between the inorganic oxide layer 3 and the stainless steel is 0.4 or less. In this case, the laminate 10 for gas barrier film can suppress the occurrence of rubbing and wrinkles due to contact with the guide roll. Therefore, compared with the case where the dynamic friction coefficient A exceeds 0.4, a gas barrier film having excellent oxygen barrier properties even after hot water treatment can be produced. In addition, since the laminate 10 for gas barrier film can suppress the occurrence of rubbing and wrinkles due to contact with the guide roll, when a gas barrier film is produced by forming an oxygen barrier coating on the inorganic oxide layer 3, the gas barrier film can also have an excellent appearance.
The dynamic friction coefficient A may be 0.35 or less, 0.30 or less, or 0.25 or less. In this case, scratches or wrinkles due to rubbing or the like are unlikely to occur even if the laminate for gas barrier film 10 comes into contact with a guide roll during transportation, and the oxygen barrier property after hot water treatment is further improved.
The dynamic friction coefficient A may be greater than 0, and may be 0.10 or more, 0.15 or more, or 0.20 or more. The dynamic friction coefficient A is preferably 0.10 or more. In this case, the laminate 10 for gas barrier films is less likely to meander when transported.
The dynamic friction coefficient is an average value of dynamic friction coefficients measured three times in accordance with JIS K7125 using a friction tester (Friction Tester TR-2, manufactured by Toyo Seiki Seisakusho Co., Ltd.). The dynamic friction coefficient for each measurement is specifically measured as follows. That is, first, a sled with a laminate formed by attaching the laminate 10 for gas barrier films to the underside of a sled (weight) weighing 200 g is placed on a stainless steel plate having a horizontal surface, so that the inorganic oxide layer 3 of the laminate 10 for gas barrier films contacts the stainless steel plate on a surface having an area of 6.3 cm long x 6.3 cm wide. Then, the sled with the laminate is slid on the stainless steel plate at a speed of 100 mm/min for a running distance of 60 mm, and the dynamic friction coefficient is calculated based on the dynamic friction force measured at this time.

The dynamic friction coefficient A can be adjusted, for example, by adjusting the value of the dynamic friction coefficient B of the resin substrate 1.

The ratio of the coefficient of friction B to the coefficient of dynamic friction A (hereinafter also referred to as "r") may be 1.2 or less, or 0.9 or less.
r may be 0.3 or greater, or 0.5 or greater.

Examples of inorganic oxides include oxides of at least one metal selected from the group consisting of Si, Al, Mg, Sn, Ti, and In, and non-metal-added metal oxides obtained by adding non-metals such as carbon or phosphorus to metal oxides. From the viewpoint of water vapor barrier properties, the metal oxide is preferably aluminum oxide or silicon oxide. Among these, from the viewpoint of oxygen barrier properties after hot water treatment, aluminum oxide is more preferable.
The inorganic oxide layer 3 may be composed of a single layer or multiple layers.

The thickness of the inorganic oxide layer 3 is not particularly limited, but is preferably 1 nm or more. In this case, the oxygen barrier property of the gas barrier film laminate 10 is further improved compared to when the thickness of the inorganic oxide layer 3 is less than 1 nm. The thickness of the inorganic oxide layer 3 may be 5 nm or more, 8 nm or more, or 10 nm or more.
The thickness of the inorganic oxide layer 3 is preferably 200 nm or less. In this case, the flexibility of the laminate for gas barrier films 10 is improved and the oxygen barrier property of the laminate for gas barrier films 10 after abuse can be improved more than when the thickness of the inorganic oxide layer 3 exceeds 200 nm. The oxygen barrier property of the laminate for gas barrier films 10 after hot water treatment can also be improved more. The thickness of the inorganic oxide layer 3 may be 80 nm or less, 70 nm or less, 60 nm or less, 50 nm or less, 40 nm or less, or 30 nm or less.

<Method of manufacturing laminate for gas barrier film>
Next, a method for producing the gas barrier film laminate 10 will be described.

First, prepare a resin substrate 1. At this time, it is preferable to use a resin substrate 1 in which the dynamic friction coefficient (dynamic friction coefficient B) of the surface of the resin substrate 1 on which the undercoat layer 2 is to be formed with respect to stainless steel is smaller than the dynamic friction coefficient A.

Next, the underlayer 2 is formed on one surface of the resin substrate 1 to form a resin substrate with an underlayer.
Specifically, a composition for forming the underlayer 2 is applied onto one surface of the resin substrate 1, and then heated and dried to form the underlayer 2. At this time, the heating temperature may be, for example, 50 to 200° C., and the drying time may be, for example, about 10 seconds to 10 minutes.
The resin substrate with the undercoat layer thus formed is wound up on a roll.

Next, an inorganic oxide layer 3 is formed on the undercoat layer 2 of the undercoat layer-attached resin substrate unwound from a roll, thereby obtaining a laminate 10 for a gas barrier film.
The inorganic oxide layer 3 can be formed by, for example, a vacuum film formation method. Examples of the vacuum film formation method include a physical vapor deposition method and a chemical vapor deposition method. Examples of the physical vapor deposition method include a vacuum deposition method, a sputtering deposition method, and an ion plating method. As the physical vapor deposition method, a vacuum deposition method is particularly preferably used. Examples of the vacuum deposition method include a resistance heating vacuum deposition method, an EB (Electron Beam) heating vacuum deposition method, and an induction heating vacuum deposition method. Examples of the chemical vapor deposition method include a thermal CVD method, a plasma CVD method, and a photo CVD method.
The laminate 10 for a gas barrier film thus obtained is passed through a guide roll made of stainless steel and wound up on a roll with the inorganic oxide layer 3 in contact with the guide roll.

<Gas barrier film>
Next, an embodiment of the gas barrier film of the present disclosure will be described with reference to Fig. 2. In Fig. 2, the same components as those in Fig. 1 are denoted by the same reference numerals, and duplicated description will be omitted.

Figure 2 is a cross-sectional view showing one embodiment of the gas barrier film of the present disclosure. As shown in Figure 2, the gas barrier film 20 includes a laminate 10 for gas barrier film and an oxygen barrier coating 4, and the oxygen barrier coating 4 is disposed on the inorganic oxide layer 3 of the laminate 10 for gas barrier film.

This gas barrier film 20 has the above-mentioned gas barrier film laminate 10, so it has excellent oxygen barrier properties even after hot water treatment such as retort treatment.

(4) Oxygen Barrier Film There are no particular limitations on the oxygen barrier film 4 as long as it is a film having oxygen barrier properties. Examples of such oxygen barrier films 4 include organic-inorganic composite films and films of polyvalent metal salts of polycarboxylic acids.

The organic-inorganic composite film is preferably formed using a composition for forming an oxygen barrier film containing at least one of a metal alkoxide and a hydrolyzate of a metal alkoxide and a water-soluble polymer, which can effectively improve the oxygen barrier property and water vapor barrier property of the gas barrier film 20.
From the viewpoint of more adequately maintaining the gas barrier properties after hot water treatment such as retort treatment, the composition for forming an oxygen barrier film preferably contains at least one of a silane coupling agent and a hydrolysate thereof.

Examples of water-soluble polymers include polyvinyl alcohol, polyvinylpyrrolidone, starch, methyl cellulose, carboxymethyl cellulose, and sodium alginate. Among these, polyvinyl alcohol (PVA) is particularly preferred because it is easy to improve the oxygen barrier properties of the gas barrier film.

The metal alkoxide is represented by the following general formula (1).
M(OR ¹ ) _m ... (1)
In the above general formula (1), R ¹ is each independently a monovalent organic group having 1 to 8 carbon atoms, and is preferably an alkyl group such as a methyl group or an ethyl group. M represents an n-valent metal atom such as Si, Ti, Al, or Zr. m is an integer from 1 to n. When there are multiple R ^1s , the R ^1s may be the same or different.

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

The silane coupling agent is represented by the following general formula (2) and functions as a curing agent.
( ^R2Si ( ^OR3 ) ₃ ) _n ... (2)

In general formula (2), R ² represents a monovalent organic functional group, and R ³ represents an alkyl group or —C ₂ H ₄ OCH ₃ .
In this case, it is possible to improve the adhesion between the oxygen barrier film 4 and the inorganic oxide layer 3, and delamination between layers in the gas barrier film laminate 10 can be suppressed.
^R2 and ^R3 may be the same or different. ^R3s may be the same or different.

Examples of the monovalent organic functional group represented by ^R2 include a vinyl group, an epoxy group, a mercapto group, an amino group, or a monovalent organic functional group containing an isocyanate group. Among them, the monovalent organic functional group is preferably a monovalent organic functional group containing an isocyanate group. In this case, the composition can have better hot water resistance by curing, and it is possible to impart greater lamination strength to the gas barrier film laminate 10 even after hot water treatment such as retort treatment.

Examples of the alkyl group represented by ^R3 include a methyl group and an ethyl group. Among them, a methyl group is preferable because hydrolysis is rapid.

n represents an integer of 1 or more. When n is 1, the silane coupling agent represents a monomer, whereas when n is 2 or more, the silane coupling agent represents a polymer. n is preferably 3. In this case, the hot water resistance of the oxygen barrier coating 4 can be further improved, and it is possible to impart greater laminate strength to the gas barrier film laminate 10 even after hot water treatment such as retort treatment.

The silane coupling agent is preferably a trimer 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate in the above general formula (2), in which ^R2 is NCO- ^R4- , ^R4 is an alkylene group whose carbon number is an integer of 1 or more, and n is 3. In this case, the wet heat resistance of the oxygen barrier coating 4 is improved, and the lamination strength (adhesion strength) of the oxygen barrier coating 4 to the resin substrate 1 after hot water treatment such as retort treatment is improved.

The silane coupling agent may be 3-glycidoxypropyltrialkoxysilane in which ^R2 in the above general formula (2) is a 3-glycidoxypropyl group and n is 1. In this case, the wet heat resistance of the oxygen barrier coating is improved, and the lamination strength (adhesion strength) of the oxygen barrier coating 4 to the resin substrate 1 after hot water treatment such as retort treatment is improved.

Examples of silane coupling agents include silane coupling agents having a vinyl group such as vinyltrimethoxysilane and vinyltriethoxysilane; silane coupling agents having an epoxy group such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, and 3-glycidoxypropylethyldiethoxysilane; silane coupling agents having a mercapto group such as 3-mercaptopropyltrimethoxysilane and 3-mercaptopropylmethyldimethoxysilane; silane coupling agents having an amino group such as 3-aminopropyltrimethoxysilane and 3-aminopropyltriethoxysilane; and silane coupling agents having an isocyanate group such as 3-isocyanatepropyltriethoxysilane and 1,3,5-tris(3-methoxysilylpropyl)isocyanurate. These silane coupling agents may be used alone or in combination of two or more.

(Polycarboxylic acid polyvalent metal salt coating)
The polycarboxylic acid polyvalent metal salt film is a film containing a polyvalent metal salt of a carboxylic acid, which is a reaction product between a carboxy group of a polycarboxylic acid polymer and a polyvalent metal compound. The polycarboxylic acid polyvalent metal salt film can be formed by applying an oxygen barrier film-forming material in which a polycarboxylic acid polymer and a polyvalent metal compound are mixed, and then heating and drying the material, or by applying an oxygen barrier film-forming material mainly composed of a polycarboxylic acid polymer and drying the material to form a first film, applying an oxygen barrier film-forming material mainly composed of a polyvalent metal compound and drying the material to form a second film, and then allowing a crosslinking reaction between the first film and the second film.

A polycarboxylic acid polymer is a polymer having multiple carboxy groups in the molecule. Examples of polycarboxylic acid polymers include (co)polymers of ethylenically unsaturated carboxylic acids; and copolymers of ethylenically unsaturated carboxylic acids and other ethylenically unsaturated monomers. Examples of ethylenically unsaturated carboxylic acids include acrylic acid and methacrylic acid. Examples of ethylenically unsaturated monomers copolymerizable with ethylenically unsaturated carboxylic acids include ethylene and propylene. These polycarboxylic acid polymers may be used alone or in combination of two or more.

The polyvalent metal compound is not particularly limited as long as it is a compound that reacts with the carboxyl group of the polycarboxylic acid polymer to form a polyvalent metal salt of the polycarboxylic acid. Examples of such polyvalent metal compounds include zinc oxide and magnesium oxide. These can be used alone or in combination of two or more. From the viewpoint of the oxygen barrier properties of the oxygen barrier film 4, zinc oxide is preferred as the polyvalent metal compound.

The oxygen barrier film-forming composition may further contain known additives such as dispersants, stabilizers, viscosity adjusters, and colorants as necessary, to the extent that the gas barrier properties of the oxygen barrier film 4 are not impaired.

The oxygen barrier film-forming composition may further contain a liquid that dissolves or disperses the solid content. An aqueous medium is usually used as such a liquid. Examples of the aqueous medium include water, a hydrophilic organic solvent, or a mixture of these. Examples of the hydrophilic organic solvent include alcohols such as methanol, ethanol, and isopropanol; ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran; cellosolves; carbitols; and nitriles such as acetonitrile. These can be used alone or in combination of two or more.

The aqueous medium is preferably an aqueous medium consisting of water alone or an aqueous medium containing water as the main component. When the aqueous medium contains water as the main component, the water content in the aqueous medium is preferably 70% by mass or more, and more preferably 80% by mass or more.

The thickness of the oxygen barrier film 4 is not particularly limited, but is preferably 50 nm or more.
In this case, the oxygen barrier properties of the gas barrier film 20 are further improved, compared to when the thickness of the oxygen barrier coating 4 is less than 50 nm.

From the viewpoint of improving the gas barrier property, the thickness of the oxygen barrier film 4 is more preferably 100 nm or more, and particularly preferably 200 nm or more.
On the other hand, the thickness of the oxygen barrier coating 4 is preferably 700 nm or less. Compared with a thickness of the oxygen barrier coating 4 exceeding 700 nm, the flexibility of the gas barrier film 20 is improved, and the oxygen barrier property of the gas barrier film 20 after abuse can be improved. In addition, the oxygen barrier property of the gas barrier film 20 after hot water treatment such as retort treatment can be improved.

From the viewpoint of further improving the flexibility of the gas barrier film 20, the thickness of the oxygen barrier coating 4 is preferably 500 nm or less, and particularly preferably 400 nm or less.

<Packaging film>
Next, an embodiment of the packaging film of the present disclosure will be described with reference to Fig. 3. In Fig. 3, the same components as those in Fig. 1 or 2 are denoted by the same reference numerals, and duplicated description will be omitted.

Figure 3 is a cross-sectional view showing one embodiment of the packaging film of the present disclosure. As shown in Figure 3, the packaging film 30 includes a gas barrier film 20 and a sealant layer 21 laminated to the gas barrier film 20, and the sealant layer 21 is disposed on the oxygen barrier coating 4 of the gas barrier film 20. As shown in Figure 2, in the gas barrier film 20, the oxygen barrier coating 4 and the sealant layer 21 may be bonded to each other by an adhesive layer 22.

This packaging film 30 includes the gas barrier film 20, which has excellent oxygen barrier properties even after hot water treatment such as retort treatment. Therefore, the packaging film 30 can have excellent oxygen barrier properties even after hot water treatment.

Materials for the adhesive layer 22 include, for example, polyester-isocyanate resins, urethane resins, and polyether resins. To use the packaging film 30 for retort applications, it is preferable to use a two-component curing urethane adhesive that is resistant to retort processing.

(Sealant Layer)
Examples of the material of the sealant layer 21 include thermoplastic resins such as polyolefin resins and polyester resins, but polyolefin resins are generally used. Specifically, examples of the polyolefin resin include ethylene-based resins such as low-density polyethylene resin (LDPE), medium-density polyethylene resin (MDPE), linear low-density polyethylene resin (LLDPE), ethylene-vinyl acetate copolymer (EVA), ethylene-α-olefin copolymer, and ethylene-(meth)acrylic acid copolymer, and polypropylene-based resins such as homopolypropylene resin (PP), propylene-ethylene random copolymer, propylene-ethylene block copolymer, and propylene-α-olefin copolymer, and mixtures thereof. The material of the sealant layer 21 can be appropriately selected from the above-mentioned thermoplastic resins depending on the intended use and temperature conditions such as boiling and retorting.

The thermoplastic resin constituting the sealant layer 21 may be stretched or unstretched, but from the viewpoint of lowering the melting point and facilitating heat sealing of the packaging film 30, it is preferable that it is unstretched.

The thickness of the sealant layer 21 is determined appropriately depending on the mass of the contents and the shape of the packaging bag, and is not particularly limited, but is preferably 30 to 150 μm from the viewpoint of the flexibility and adhesiveness of the packaging film 30.

<Packaged products>
Next, an embodiment of the packaging product of the present disclosure will be described with reference to Fig. 4. Fig. 4 is a cross-sectional view showing one embodiment of the packaging product of the present disclosure. In Fig. 4, the same components as those in Figs. 1 to 3 are denoted by the same reference numerals, and duplicated descriptions will be omitted.
As shown in Fig. 4, a packaged product 50 includes a packaging container 40 and a content C filled in the packaging container 40. The packaging container 40 shown in Fig. 4 is obtained by using a pair of packaging films 30 and heat-sealing the peripheral portions of the packaging films 30 with the sealant layers 21 facing each other. Note that the adhesive layer 22 of the packaging films 30 is omitted in Fig. 4.

This packaged product 50 includes a packaging container 40, which is formed using a packaging film 30. Therefore, the packaged product 50 has excellent oxygen barrier properties even after hot water treatment.

The packaging container 40 can also be obtained by folding one packaging film 30 and heat sealing the peripheral portion of the packaging film 30 with the sealant layers 21 facing each other.

Examples of packaging containers 40 include packaging bags, laminated tube containers, and liquid paper containers.

Contents C are not particularly limited, and examples of contents C include food, liquids, medicines, electronic parts, etc.

The present disclosure is not limited to the above embodiment. For example, in the above embodiment, in the packaging film 30, the sealant layer 21 is disposed on the oxygen barrier coating 4 of the gas barrier film 20, but the sealant layer 21 may be disposed on the opposite side of the resin substrate 1 to the oxygen barrier coating 4.

The present disclosure will be explained in detail below with reference to examples, but the present disclosure is not limited to these examples.

<Preparation of oxygen barrier film composition>
Liquids A to F for preparing the oxygen barrier film-forming compositions used in the Examples and Comparative Examples were prepared as follows.

(Liquid A)
Polyvinyl alcohol (product name: Kuraray Poval 60-98, manufactured by Kuraray Co., Ltd., hereinafter also referred to as "PVA") was mixed with water to prepare liquid A having a solid content of 5% by mass.

(Liquid B)
Tetraethoxysilane (product name: "KBE04", solid content: 100 mass%, manufactured by Shin-Etsu Chemical Co., Ltd., hereinafter also referred to as "TEOS") as a metal alkoxide, methanol (manufactured by Kanto Chemical Co., Ltd.), and 0.1N hydrochloric acid (manufactured by Kanto Chemical Co., Ltd.) were mixed in a mass ratio of 17/10/73 to prepare liquid B having a solid content of 5 mass%. At this time, the solid content was calculated by converting TEOS to _SiO2 .

(Liquid C)
1,3,5-tris(3-methoxysilylpropyl)isocyanurate (SC agent A) as a silane coupling agent was added to a mixed solvent of water/IPA=1/1 (mass ratio) to obtain a 5 mass% solid content liquid C. The solid content was calculated by converting the silane coupling agent into (NCO(CH ₂ ) ₃ Si(OH) ₃ ) ₃ .

(Liquid D)
0.1N hydrochloric acid (manufactured by Kanto Chemical Co., Ltd.) was added to an isopropanol (IPA) solution of 3-glycidoxypropyltrimethoxysilane (SC agent B) as a silane coupling agent, and the resulting solution was stirred for 30 minutes to hydrolyze the SC agent B, and then added to a mixed solvent of water/IPA = 1/1 (mass ratio) to obtain a liquid D with a solid content of 5 mass %. The solid content was calculated by converting the SC agent B to (CH ₂ O)CH ₂ OC ₃ H ₆ Si(OH) ₃ .

(Liquid E)
20 parts by mass of an aqueous polyacrylic acid solution having a number average molecular weight of 200,000 (Aron A-10H, manufactured by Toagosei Co., Ltd., solid content concentration 25% by mass) was diluted with 58.9 parts by mass of distilled water to obtain a diluted aqueous polyacrylic acid solution. Then, 0.44 parts by mass of aminopropyltrimethoxysilane (APTMS, manufactured by Aldrich Co., Ltd.) was added and stirred to obtain a liquid E mainly composed of a polycarboxylic acid polymer.

(Liquid F)
100 parts by mass of an aqueous dispersion of zinc oxide particles (ZE143, manufactured by Sumitomo Osaka Cement Co., Ltd.) and 2 parts by mass of a hardener (Liofol HAERTER UR 5889-21, manufactured by Henkel) were mixed to prepare liquid F containing a polyvalent metal compound as a main component.

<Preparation of Undercoat Layer Forming Composition>
The undercoat layer-forming composition was prepared as follows.
Acrydic CL-1000 (DIC Corporation) as an acrylic polyol and a tolylene diisocyanate (TDI) type curing agent (Coronate 2030, Tosoh Corporation) as an isocyanate compound were mixed in a solid content mass ratio of 6:4, and diluted with ethyl acetate as a dilution solvent to a solid content (total amount of acrylic polyol and isocyanate compound) of 2 mass%. In this way, a composition for forming an undercoat layer was prepared.

<Preparation of Gas Barrier Film>
Example 1
First, a biaxially oriented polypropylene film (PP) having a dynamic friction coefficient B of the surface on which the undercoat layer was to be formed, the value being shown in Table 1, was prepared as a resin substrate.
Next, the composition for forming the undercoat layer prepared as described above was applied onto the surface of the resin substrate using a gravure coating method to form a coating film, and the coating film was dried in an oven at 100°C for 10 seconds to form an undercoat layer having a thickness of 0.1 µm. The obtained resin substrate with undercoat layer was wound onto a roll to obtain a resin substrate roll with undercoat layer.
Next, the resin substrate with the undercoat layer was unwound from the resin substrate roll with the undercoat layer, and silicon oxide was deposited as an inorganic oxide on the undercoat layer by an electron beam vacuum deposition method using an electron beam heating method to form an inorganic oxide layer with a thickness of 25 nm, thereby obtaining a laminate for a gas barrier film. The obtained laminate for a gas barrier film was then wound up on a take-up roll while being guided through a guide roll made of stainless steel. At this time, the laminate for a gas barrier film was guided with the inorganic oxide layer in contact with the guide roll, and was wound up at a speed of 600 m/min while applying a tension of 100 N/m.

Liquids A to D were then mixed in the ratios (unit: mass%) shown in Table 1 to prepare a mixed liquid, which was then applied to the surface of the inorganic oxide layer of the gas barrier film laminate by gravure coating and dried at 60°C for 60 seconds to form an organic-inorganic composite film as an oxygen barrier film with a thickness of 0.3 μm. In this way, a gas barrier film was obtained in which the resin substrate, underlayer, inorganic oxide layer, and oxygen barrier film were laminated in this order.

(Examples 2 to 5 and Comparative Example 1)
A gas barrier film was obtained in the same manner as in Example 1, except that the material of the resin substrate, the dynamic friction coefficient B, the thickness, the presence or absence of an underlayer, the material of the inorganic oxide layer, the dynamic friction coefficient A, the proportions (mass %) of Liquids A to D for forming the organic-inorganic composite coating as the oxygen barrier coating, and the type of the oxygen barrier coating were as shown in Table 1.

(Examples 6 to 7 and Comparative Example 2)
A gas barrier film was obtained in the same manner as in Example 1, except that the material, dynamic friction coefficient B, thickness, presence or absence of an underlayer, the material of the inorganic oxide layer, and dynamic friction coefficient A of the resin substrate were as shown in Table 1, the type of oxygen barrier coating was a coating of a polyvalent metal salt of a polycarboxylic acid, and the coating of a polyvalent metal salt of a polycarboxylic acid was formed as follows.
That is, Liquid E was applied onto the inorganic oxide layer using a gravure coating method to form a coating film, which was then passed through an oven at 100° C. for 10 seconds to dry, thereby forming a polycarboxylic acid polymer film having a thickness of 0.2 μm. Next, Liquid F was applied onto the polycarboxylic acid polymer film using a gravure coating method to form a polyvalent metal compound film, which was then passed through an oven at 100° C. for 10 seconds to dry, thereby forming a polyvalent metal salt film of polycarboxylic acid having a thickness of 0.2 μm.
In addition, since Liquids A to D were not used in Examples 6 to 7 and Comparative Example 2, in Table 1, the proportions (mass %) of Liquids A to D that form the organic-inorganic composite coating are indicated as "-."

(Example 8 and Comparative Example 3)
A gas barrier film was obtained in the same manner as in Example 1, except that the material of the resin substrate, the dynamic friction coefficient B, the presence or absence of an underlayer, the material of the inorganic oxide layer, the dynamic friction coefficient A, the mass ratios (mass %) of Liquids A to D forming the organic-inorganic composite coating as the oxygen barrier coating, and the type of the oxygen barrier coating were as shown in Table 1.

<Preparation of packaging film>
A 60 μm-thick unstretched polypropylene film (trade name "TORAYFAN (registered trademark) ZK207", manufactured by Toray Industries, Inc.) was attached to the surface of the oxygen barrier coating of the gas barrier films obtained in Examples 1 to 8 and Comparative Examples 1 to 3 using a two-component adhesive (trade name "Takelac A-525/Takenate A-52", manufactured by Mitsui Chemicals SKC Polyurethanes, Inc.) to produce a packaging film with a surface width of 210 mm.

<Evaluation of oxygen barrier properties of packaging film after retort treatment>
For the packaging film obtained as described above, the oxygen permeability was measured before and after retort treatment as described below to evaluate the oxygen barrier property.

(1) Oxygen Permeability Before Retort Treatment The oxygen permeability before retort treatment was measured for the packaging film prepared as described above as follows.
That is, the oxygen permeability of the packaging film was measured using an oxygen permeability measuring device (product name "OX-TRAN2/20", manufactured by Modern Control) under conditions of a temperature of 30°C and a relative humidity of 70%. The measurement was performed in accordance with JIS K-7126-2. The results are shown in Table 1.
(2) Oxygen permeability after retort treatment The packaging film prepared as described above was subjected to retort treatment as follows, and then the packaging film was measured for oxygen permeability as described above. The results are shown in Table 1.
(Retort processing)
The retort treatment was carried out for 30 minutes at 121° C. using a hot water retort kettle for the test sample obtained as described below. After the retort treatment, an A4 size sheet (297 mm long side × 210 mm short side) was cut out from the test sample, and this sheet was used as a packaging film for measuring oxygen permeability.
(Preparation of test samples)
The test samples were prepared as follows.
First, an A4 size sheet (297 mm long x 210 mm short) was cut out from the packaging film prepared as described above, and the sheet was folded in half so that the short sides at both ends overlapped each other, and the overlapping long sides were heat-sealed to prepare a three-sided pouch with an opening. Then, 150 mL of a 0.6% by mass cysteine aqueous solution was poured into the three-sided pouch through the opening, and the short sides were heat-sealed. In this way, a test sample was prepared.

<Appearance>
The gas barrier films obtained in Examples 1 to 8 and Comparative Examples 1 to 3 were wound up on a roll for 1000 m with the oxygen barrier coating facing outward, and then visually observed for appearance. Gas barrier films in which wrinkles or scratches were found were rated as "X", and gas barrier films in which neither wrinkles nor scratches were found were rated as "O". The results are shown in Table 1.

As shown in Table 1, the gas barrier films of Examples 1 to 8 had sufficiently low oxygen permeability after retort treatment and good appearance compared to Comparative Examples 1 to 3.

From the above, it has been confirmed that the laminate for gas barrier film disclosed herein has a dynamic friction coefficient (dynamic friction coefficient A) between the inorganic oxide layer and the stainless steel of 0.4 or less, and thus it is possible to produce a gas barrier film that has excellent oxygen barrier properties even after hot water treatment such as retort treatment, and also has an excellent appearance.

Reference Signs List 1: resin substrate, 2: undercoat layer, 3: inorganic oxide layer, 4: oxygen barrier coating, 10: laminate for gas barrier film, 20: gas barrier film, 21: sealant layer, 30: packaging film, 40: packaging container, 50: packaged product.

Claims (12)

A laminate for a gas barrier film which forms a gas barrier film together with an oxygen barrier coating,
a resin substrate and an inorganic oxide layer on which the oxygen barrier coating is formed,
The laminate for a gas barrier film, wherein the dynamic friction coefficient between the inorganic oxide layer and stainless steel is 0.4 or less. The gas barrier film laminate according to claim 1, wherein the resin substrate contains polypropylene or polyethylene terephthalate. The gas barrier film laminate according to claim 1, wherein the inorganic oxide layer has a thickness of 1 to 200 nm. The gas barrier film laminate according to claim 1, wherein the inorganic oxide layer contains aluminum oxide or silicon oxide. A base layer is further provided between the resin substrate and the inorganic oxide layer,
the underlayer comprises an organic polymer;
the organic polymer includes at least one of a polyacrylic resin, a polyol resin, a polyurethane resin, a polyamide resin, and a reaction product of these resins;
2. The gas barrier film laminate according to claim 1, wherein the underlayer has a thickness of 0.01 to 1 μm. The gas barrier film laminate according to claim 1 ,
and an oxygen barrier coating provided on the inorganic oxide layer of the gas barrier film laminate. the oxygen barrier coating is composed of an organic-inorganic composite film,
7. The gas barrier film according to claim 6, wherein the organic-inorganic composite film is formed using a composition for forming an oxygen barrier coating film, the composition comprising at least one of a metal alkoxide and a hydrolysate of a metal alkoxide, and a water-soluble polymer. The gas barrier film according to claim 7, wherein the composition for forming an oxygen barrier coating further contains at least one of a silane coupling agent and a hydrolysate of a silane coupling agent. The gas barrier film according to claim 6, wherein the oxygen barrier coating is composed of a polycarboxylic acid polyvalent metal salt coating containing a polycarboxylic acid polyvalent metal salt which is a reaction product between a carboxy group of a polycarboxylic acid polymer and a polyvalent metal compound. A gas barrier film according to any one of claims 6 to 9, and a sealant layer,
A packaging film, wherein the sealant layer is provided on the oxygen barrier coating of the gas barrier film. A packaging container obtained using the packaging film according to claim 10. A packaging product comprising the packaging container according to claim 11 and contents filled in the packaging container.

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