JP7677515B2 - Gas barrier laminate - Google Patents

Description

The present invention relates to a gas barrier laminate.

Conventionally, a gas barrier laminate has been known that includes a biaxially oriented polyethylene terephthalate film, which has excellent heat resistance and toughness, as a base film, and a sealant layer (see, for example, Patent Document 1).

JP 2017-178357 A

In recent years, however, growing environmental awareness stemming from the problem of marine plastic waste has led to a demand for more efficient sorting and recovery of plastic materials and recycling. In other words, there is now a demand for mono-materialization of packaging laminates, which have traditionally been made high-performance by combining a variety of different materials.

To achieve mono-material laminates, the constituent films must be made of the same material. For example, polyethylene film, a type of polyolefin film, is widely used as a packaging material, and there are hopes for mono-material laminates using polyethylene film. However, one of the basic physical properties of polyethylene film is that it has a low melting point, and is prone to stretching and deformation even at low temperatures. As a result, in the process of forming a barrier layer on polyethylene film by methods such as vapor deposition to impart high gas barrier properties, when the polyethylene film is wound up under tension, the roll transportability becomes poor, causing wrinkles in the film, which can often lead to problems with proper processing in post-processing.

The present invention was made in consideration of the above-mentioned circumstances, and aims to provide a gas barrier laminate that is useful for realizing mono-materialization, has good processing suitability, and is wrinkle-resistant.

The present invention provides a gas barrier laminate comprising a polyethylene-containing substrate layer and a barrier layer, the arithmetic mean roughness a of the surface of the polyethylene-containing substrate layer opposite the barrier layer being 3 μm or more. Such a gas barrier laminate has good film transportability during roll processing and is less prone to wrinkling.

If the arithmetic mean roughness of the surface of the polyethylene-containing substrate layer that contacts the barrier layer is b, a/b may be 3 or more.

The polyethylene-containing substrate layer may include unstretched polyethylene.

The barrier layer may include a gas barrier coating layer, or may include an inorganic vapor deposition layer.

The barrier layer may include, from the polyethylene-containing substrate layer side, an undercoat layer, an inorganic vapor deposition layer, and a gas barrier coating layer in this order.

The present invention can provide a gas barrier laminate that is suitable for processing and does not wrinkle easily.

FIG. 1 is a schematic cross-sectional view showing a gas barrier laminate according to one embodiment.

Below, a preferred embodiment of the present invention will be described in detail, with reference to the drawings where necessary. Note that in the drawings, the same or corresponding parts are given the same reference numerals, and duplicate explanations will be omitted. Also, the dimensional ratios of the drawings are not limited to those shown in the drawings.

<Gas Barrier Laminate>
Fig. 1 is a schematic cross-sectional view showing a gas barrier laminate according to one embodiment. The gas barrier laminate 10 shown in Fig. 1 includes a base layer 1 and a barrier layer 2. The base layer 1 contains polyethylene, and the arithmetic mean roughness a of the surface of the base layer opposite to the barrier layer is 3 µm or more.

[Base material layer]
The substrate layer 1 is a film serving as a support and contains polyethylene. The content of polyethylene in the substrate layer 1 may be 50% by mass or more, 80% by mass or more, or 100% by mass based on the total amount of the substrate layer 1. The substrate layer 1 may contain a polyethylene film or may be made of a polyethylene film. In addition, as the polyethylene, an acid-modified polyethylene obtained by graft-modifying polyethylene with an unsaturated carboxylic acid, an acid anhydride of an unsaturated carboxylic acid, an ester of an unsaturated carboxylic acid, or the like may be used.

The polyethylene contained in the base layer 1 is preferably high density polyethylene (HDPE). HDPE is preferable because it has excellent heat resistance, is less likely to stretch than other polyethylenes, and is more likely to be prevented from wrinkling. The density of the polyethylene contained in the base layer 1 may be, for example, 0.94 g/ ^cm2 or more, or 0.95 g/ ^cm2 or more.

The polyethylene contained in the base layer 1 may be stretched or unstretched, but is preferably unstretched. A base layer containing unstretched polyethylene ensures the rigidity of the packaging material and makes it easier to prevent bags from falling off or breaking.

The arithmetic mean roughness a of the surface of the base layer 1 opposite the barrier layer 2 is 3 μm or more. If the arithmetic mean roughness a is 3 μm or more, the polyethylene film will have excellent roll transportability when it is wound up under tension, and the occurrence of wrinkles in the film can be suppressed. From this perspective, the arithmetic mean roughness a of the surface of the base layer 1 opposite the barrier layer 2 is preferably 4 μm or more, and more preferably 5 μm or more. There is no particular upper limit to the arithmetic mean roughness a, and it may be, for example, 10 μm or less.

When the arithmetic mean roughness of the surface of the base layer 1 that contacts the barrier layer 2 is b, it is preferable that a/b is 3 or more. When a/b is 3 or more, it becomes easier to laminate the barrier layer 2 without impairing the barrier properties. From this viewpoint, a/b is more preferably 3.5 or more, and even more preferably 4 or more. There is no particular upper limit to a/b, and it may be, for example, 100 or less. In this specification, the arithmetic mean roughness is measured by measuring the front and/or back surfaces three times using an optical interference surface measuring device, and the maximum projection height (μm) that is the largest value among the three measurements is defined as the arithmetic mean roughness of the film.

The structure of the base material layer 1 may be appropriately multi-layered, for example, taking into consideration the processing suitability, rigidity, waist strength, heat resistance, powder fall during transportation, etc., of the film constituting the base material layer 1. The structure of the base material layer 1 may be, for example, a multi-layer structure including multiple layers (films) each containing polyethylene with different densities. The film constituting the base material layer 1 may be appropriately selected from high density polyethylene (HDPE), medium density polyethylene, low density polyethylene, etc. When the density of the base material is measured as the base material layer 1, the density is preferably 0.94 g/cm ² or more. In addition, when a slip agent, an antistatic agent, etc. are contained, the content of the agent may be changed in each layer and laminated. The base material layer 1 having multiple layers can be laminated to a film by extrusion coating, co-extrusion coating, sheet molding, co-extrusion blow molding, etc.

The thickness of the substrate layer 1 may be, for example, 10 to 100 μm, or 15 to 50 μm.

The laminated surface of the base material layer 1 may be subjected to various pretreatments such as corona treatment, plasma treatment, and frame treatment, as long as the barrier performance is not impaired, and a coating layer such as an easy-adhesion layer may be provided.

[Barrier layer]
The barrier layer 2 is a layer capable of imparting gas barrier properties to the gas barrier laminate, and may include, for example, a gas barrier coating layer, an inorganic vapor deposition layer, etc. The barrier layer 2 may include, from the substrate layer 1 side, an undercoat layer 3, an inorganic vapor deposition layer 4, and a gas barrier coating layer 5 in this order, as shown in FIG. 1. The oxygen permeability of the barrier layer 2 is preferably 20 cc/ ^m2 day atm or less, more preferably 10 cc/ ^m2 day atm or less, even more preferably ⁵ cc/m2 day atm or less, and particularly preferably ² cc/m2 day atm or less. By having the oxygen permeability within the above range, the gas barrier properties of the gas barrier laminate can be sufficiently ensured.

(subbing layer)
The undercoat layer (anchor coat layer) 3 can achieve the effects of improving the adhesion performance between the substrate layer 1 and the inorganic vapor deposition layer 4, improving the smoothness of the surface of the substrate layer 1, and suppressing the occurrence of cracks in the inorganic vapor deposition layer 4 due to elongation of the substrate layer 1. The improved smoothness makes it easier to form the inorganic vapor deposition layer 4 uniformly without defects, and makes it easier to exhibit high barrier properties. The undercoat layer 3 can be formed using a composition for forming an undercoat layer (anchor coat agent).

Examples of anchor coating agents include acrylic resins, epoxy resins, acrylic urethane resins, polyester polyurethane resins, polyether polyurethane resins, etc. From the viewpoints of heat resistance and interlayer adhesive strength, acrylic urethane resins and polyester polyurethane resins are preferred as anchor coating agents.

The thickness of the undercoat layer 3 is not particularly limited, but is preferably in the range of 0.01 to 5 μm, more preferably in the range of 0.03 to 3 μm, and even more preferably in the range of 0.05 to 2 μm. If the thickness of the undercoat layer 3 is equal to or greater than the lower limit, more sufficient interlayer adhesive strength tends to be obtained, while if the thickness is equal to or less than the upper limit, the desired gas barrier properties are likely to be achieved.

As a method for applying the undercoat layer 3 onto the substrate layer 1, known application methods can be used without particular limitation, and examples thereof include immersion methods (dipping methods); methods using a spray, a coater, a printer, a brush, etc. In addition, examples of the types of coaters and printers used in these methods and the application methods thereof include gravure coaters such as direct gravure methods, reverse gravure methods, kiss reverse gravure methods, and offset gravure methods, reverse roll coaters, microgravure coaters, coaters combined with chamber doctor, air knife coaters, dip coaters, bar coaters, comma coaters, die coaters, etc.

The coating amount of the undercoat layer 3 is preferably 0.01 to 5 g/ ^m2 , and more preferably 0.03 to 3 g/ ^m2 , in terms of the mass per ^m2 after the anchor coating agent is applied and dried. If the mass per ^m2 after the anchor coating agent is applied and dried is equal to or greater than the above lower limit, the film formation tends to be sufficient, whereas if it is equal to or less than the above upper limit, the film tends to be sufficiently dried and the solvent is less likely to remain.

The method for drying the undercoat layer 3 is not particularly limited, but examples include natural drying, drying in an oven set at a predetermined temperature, and using a dryer attached to the coater, such as an arch dryer, floating dryer, drum dryer, or infrared dryer. Furthermore, the drying conditions can be appropriately selected depending on the drying method. For example, in the method of drying in an oven, it is preferable to dry at a temperature of 60 to 100°C for about 1 second to 2 minutes.

Instead of the above-mentioned resins, a polyvinyl alcohol-based resin can be used as the undercoat layer 3. The polyvinyl alcohol-based resin may be any resin that has vinyl alcohol units formed by saponifying vinyl ester units, such as polyvinyl alcohol (PVA) and ethylene-vinyl alcohol copolymer (EVOH).

Examples of PVA include resins obtained by polymerizing vinyl esters such as vinyl acetate, vinyl formate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl pivalate, and vinyl versatate alone and then saponifying them. The PVA may be a modified PVA that has been copolymerized or post-modified. The modified PVA can be obtained, for example, by copolymerizing a vinyl ester with an unsaturated monomer that is copolymerizable with the vinyl ester and then saponifying it. Examples of unsaturated monomers copolymerizable with vinyl esters include olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, and α-octadecene; hydroxyl group-containing α-olefins such as 3-buten-1-ol, 4-pentyn-1-ol, and 5-hexen-1-ol; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, and undecylenic acid; nitriles such as acrylonitrile and methacrylonitrile; diacetone acrylamide, acrylonitrile, and the like. amides such as arylamide and methacrylamide; olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid, and methallyl sulfonic acid; vinyl compounds such as alkyl vinyl ethers, dimethylallyl vinyl ketone, N-vinylpyrrolidone, vinyl chloride, vinyl ethylene carbonate, 2,2-dialkyl-4-vinyl-1,3-dioxirane, glycerin monoallyl ether, and 3,4-diacetoxy-1-butene; vinylidene chloride, 1,4-diacetoxy-2-butene, and vinylene carbonate.

The polymerization degree of PVA is preferably 300 to 3000. If the polymerization degree is less than 300, the barrier properties tend to decrease, and if it exceeds 3000, the viscosity is too high and the coating suitability tends to decrease. The saponification degree of PVA is preferably 90 mol% or more, more preferably 95 mol% or more, and even more preferably 99 mol% or more. The saponification degree of PVA may be 100 mol% or less, or 99.9 mol% or less. The polymerization degree and saponification degree of PVA can be measured in accordance with the method described in JIS K 6726 (1994).

EVOH is generally obtained by saponifying copolymers of ethylene and vinyl acid esters such as vinyl acetate, vinyl formate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl pivalate, and vinyl versatate.

The degree of polymerization of EVOH is preferably 300 to 3000. If the degree of polymerization is less than 300, the barrier property is likely to decrease, and if it exceeds 3000, the viscosity is too high and the coating suitability is likely to decrease. The degree of saponification of the vinyl ester component of EVOH is preferably 90 mol % or more, more preferably 95 mol % or more, and even more preferably 99 mol % or more. The degree of saponification of EVOH may be 100 mol % or less, or may be 99.9 mol % or less. The degree of saponification of EVOH is determined by nuclear magnetic resonance ( ¹ H-NMR) measurement, from the peak area of hydrogen atoms contained in the vinyl ester structure and the peak area of hydrogen atoms contained in the vinyl alcohol structure.

The ethylene unit content of EVOH is preferably 10 mol% or more, more preferably 15 mol% or more, even more preferably 20 mol% or more, and particularly preferably 25 mol% or more. The ethylene unit content of EVOH is preferably 65 mol% or less, more preferably 55 mol% or less, and even more preferably 50 mol% or less. When the ethylene unit content is 10 mol% or more, the gas barrier property or dimensional stability can be maintained well under high humidity. On the other hand, when the ethylene unit content is 65 mol% or less, the gas barrier property can be improved. The ethylene unit content of EVOH can be determined by the NMR method.

When a polyvinyl alcohol resin is used as the undercoat layer 3, the undercoat layer 3 can be formed by coating a polyvinyl alcohol resin solution or by multi-layer extrusion.

(Inorganic vapor deposited layer)
Examples of materials constituting the inorganic vapor deposition layer 4 include inorganic oxides such as aluminum oxide, silicon oxide, magnesium oxide, and tin oxide. From the viewpoints of transparency and barrier properties, the inorganic oxide may be selected from the group consisting of aluminum oxide, silicon oxide, and magnesium oxide. From the viewpoint of excellent tensile extensibility during processing, it is preferable that the inorganic vapor deposition layer 4 is a layer using silicon oxide. By using the inorganic vapor deposition layer 4, high barrier properties can be obtained with a very thin layer that does not affect the recyclability of the gas barrier laminate.

The O/Si ratio of the inorganic vapor deposition layer 4 is preferably 1.7 or more. When the O/Si ratio is 1.7 or more, the content of metal Si is suppressed, and good transparency is easily obtained. In addition, the O/Si ratio is preferably 2.0 or less. When the O/Si ratio is 2.0 or less, the crystallinity of SiO is high, and the inorganic vapor deposition layer is prevented from becoming too hard, and good tensile resistance is obtained. This makes it possible to suppress the occurrence of cracks in the inorganic vapor deposition layer 4 when laminating the gas barrier coating layer 5. In addition, even after forming into a packaging bag, the base layer 1 may shrink due to heat during the boiling process, but when the O/Si ratio is 2.0 or less, the inorganic vapor deposition layer easily follows the above shrinkage, and the deterioration of the barrier property can be suppressed. From the viewpoint of obtaining these effects more fully, the O/Si ratio of the inorganic vapor deposition layer 4 is preferably 1.75 to 1.9, and more preferably 1.8 to 1.85.

The O/Si ratio of the inorganic vapor deposition layer 4 can be determined by X-ray photoelectron spectroscopy (XPS). For example, the measurement can be performed using an X-ray photoelectron spectrometer (manufactured by JEOL Ltd., product name: JPS-90MXV) with a non-monochromated MgKα (1253.6 eV) X-ray source and an X-ray output of 100 W (10 kV-10 mA). For quantitative analysis to determine the O/Si ratio, relative sensitivity factors of 2.28 for O1s and 0.9 for Si2p can be used.

The thickness of the inorganic vapor deposition layer 4 is preferably 10 nm or more and 50 nm or less. If the thickness is 10 nm or more, sufficient gas barrier properties can be obtained. Furthermore, if the thickness is 50 nm or less, the occurrence of cracks due to deformation caused by internal stress in the thin film can be suppressed, and the deterioration of gas barrier properties can be suppressed. Note that if the thickness exceeds 50 nm, costs are likely to increase due to an increase in the amount of material used and a longer film formation time, and this is not preferable from an economic standpoint. From the same standpoint as above, it is more preferable that the thickness of the inorganic vapor deposition layer is 20 nm or more and 40 nm or less.

The inorganic deposition layer 4 can be formed, for example, by vacuum deposition. In vacuum deposition, physical vapor deposition or chemical vapor deposition can be used. Examples of physical vapor deposition include, but are not limited to, vacuum deposition, sputtering, and ion plating. Examples of chemical vapor deposition include, but are not limited to, thermal CVD, plasma CVD, and photo CVD.

In the above vacuum film formation, the resistive heating vacuum deposition method, the EB (Electron Beam) heating vacuum deposition method, the induction heating vacuum deposition method, the sputtering method, the reactive sputtering method, the dual magnetron sputtering method, the plasma enhanced chemical vapor deposition method (PECVD method), etc. are particularly preferably used. However, in terms of productivity, the vacuum deposition method is currently the most superior. As the heating means for the vacuum deposition method, it is preferable to use any of the following methods: the electron beam heating method, the resistive heating method, or the induction heating method.

(Gas barrier coating layer)
The gas barrier coating layer 5 protects the inorganic vapor deposition layer 4 and prevents the inorganic oxide layer from cracking when bent.

The gas barrier coating layer 5 is a layer that has gas barrier properties. By providing a gas barrier coating layer, the gas barrier properties of the gas barrier laminate can be improved.

The gas barrier coating layer 5 may be formed using a composition for forming a gas barrier coating layer (hereinafter also referred to as a coating agent) whose main component is an aqueous solution or a water/alcohol mixed solution containing at least one selected from the group consisting of a hydroxyl group-containing polymer compound, a metal alkoxide, a silane coupling agent, and their hydrolysates.

Specific examples of hydroxyl group-containing polymer compounds include water-soluble polymers such as ethylene vinyl alcohol, polyvinyl alcohol, polyvinylpyrrolidone, starch, methyl cellulose, carboxymethyl cellulose, and sodium alkynate, with polyvinyl alcohol (PVA) being particularly preferred due to its excellent barrier properties.

The metal alkoxide is preferably formed from a composition containing at least one selected from the group consisting of metal alkoxides represented by the following general formula (1) and their hydrolysates or polymers.
M (OR ¹ ) _m (R ² ) _nm ...(1)
In the above general formula (1), ^R1 and ^R2 are each independently a monovalent organic group having 1 to 8 carbon atoms, and are preferably an alkyl group such as a methyl group or an ethyl group. M represents an n-valent metal atom such as Si, Ti, Al, or Zr. m is an integer from ¹ to n. When there are multiple R1s or ^R2s , the ^R1s or ^R2s may be the same or different.

Specific examples of metal alkoxides include tetraethoxysilane [Si(OC ₂ H ₅ ) ₄ ] and triisopropoxyaluminum [Al(O-2'-C ₃ H ₇ ) ₃ ]. The metal alkoxide is preferably tetraethoxysilane or triisopropoxyaluminum, since it is relatively stable in an aqueous solvent after hydrolysis. Examples of hydrolyzates of metal alkoxides include silicic acid (Si(OH) ₄ ), which is a hydrolyzate of tetraethoxysilane, and aluminum hydroxide (Al(OH) ₃ ), which is a hydrolyzate of tripropoxyaluminum. These can be used alone or in combination of two or more.

The silane coupling agent includes a compound represented by the following general formula (2).
Si(OR ¹¹ ) _p (R ¹² ) _3-p R ¹³ ...(2)
In the above general formula (2), R ¹¹ represents an alkyl group such as a methyl group or an ethyl group, R ¹² represents a monovalent organic group such as an alkyl group, an aralkyl group, an aryl group, an alkenyl group, an alkyl group substituted with an acryloxy group, or an alkyl group substituted with a methacryloxy group, R ¹³ represents a monovalent organic functional group, and p represents an integer of 1 to 3. When a plurality of R ¹¹ or R ¹² are present, the R ^11s or the R ^12s may be the same or different. Examples of the monovalent organic functional group represented by R ¹³ include a monovalent organic functional group containing a glycidyloxy group, an epoxy group, a mercapto group, a hydroxyl group, an amino group, an alkyl group substituted with a halogen atom, or an isocyanate group.

Specific examples of silane coupling agents include vinyltrimethoxysilane, γ-chloropropylmethyldimethoxysilane, γ-chloropropyltrimethoxysilane, glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and γ-methacryloxypropylmethyldimethoxysilane.

The silane coupling agent may also be a polymer formed by polymerizing the compound represented by the general formula (2) above. The polymer is preferably a trimer, and more preferably 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate. This is a condensation polymer of 3-isocyanate alkylalkoxysilane. It is known that this 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate has no chemical reactivity in the isocyanate portion, but the reactivity is ensured by the polarity of the nurate portion. In general, it is added to adhesives, etc., in the same way as 3-isocyanate alkylalkoxysilane, and is known as an adhesion improver. Therefore, by adding 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate to a hydroxyl group-containing polymer compound, the water resistance of the gas barrier coating layer 5 can be improved by hydrogen bonding. 3-isocyanate alkyl alkoxy silanes are highly reactive and have low liquid stability, whereas 1,3,5-tris (3-trialkoxy silyl alkyl) isocyanurates are not water-soluble due to the polarity of the nurate moiety, but are easily dispersed in aqueous solutions and can maintain a stable liquid viscosity. In addition, the water resistance of 3-isocyanate alkyl alkoxy silanes is equivalent to that of 1,3,5-tris (3-trialkoxy silyl alkyl) isocyanurates.

1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate is produced by thermal condensation of 3-isocyanatepropylalkoxysilane, and may contain the raw material 3-isocyanatepropylalkoxysilane, but this does not pose any particular problems. More preferred is 1,3,5-tris(3-trialkoxysilylpropyl)isocyanurate, and even more preferred is 1,3,5-tris(3-trimethoxysilylpropyl)isocyanurate. This methoxy group has a fast hydrolysis rate, and those containing propyl groups are relatively inexpensive, so 1,3,5-tris(3-trimethoxysilylpropyl)isocyanurate is practically advantageous.

In addition, known additives such as isocyanate compounds, dispersants, stabilizers, viscosity adjusters, and colorants may be added to the coating agent as long as the gas barrier properties are not impaired.

The coating agent may contain water-swellable mica. Mica is a type of inorganic layered mineral in which extremely thin unit crystal layers overlap to form a single layered particle. Micas include natural mica and synthetic mica. Examples include muscovite, phlogopite, biotite, potassium phlogopite, potassium tetrasilicic mica, potassium taeniolite, potassium sodium fluorine tetrasilicic mica, fluorine tetrasilicic mica, sodium phlogopite, sodium tetrasilicic mica, and sodium hectorite. One of these types of mica may be used, or two or more different types of mica may be used in combination.

As the mica, those which swell and cleave in water are preferred, and among these, water-swellable mica having swelling properties in water is particularly preferred. More specifically, it is a synthetic mica having the property of absorbing and swelling water by coordinating water between extremely thin unit crystal layers, and is generally a compound in which a layer in which Si ⁴⁺ is coordinated to O ^2- to form a tetrahedral structure and a layer in which Al ³⁺ , Mg ²⁺ , Fe ²⁺ , and Fe ³⁺ are coordinated to O ^2- and ^OH- to form an octahedral structure are bonded in a 1:1 or 2:1 ratio and stacked to form a layered structure. For example, sodium fluorine tetrasilicic mica is preferred.

When water-swellable mica is included, the coating agent preferably contains a hydroxyl-containing polymer compound. If the total mass of the gas barrier coating layer 5 is 100 parts by mass, the content of water-swellable mica may be within the approximate range of, for example, 20 parts by mass to 50 parts by mass. In this case, the gas barrier coating layer 5 may be formed using a coating liquid containing, as solids, a hydroxyl-containing polymer compound and water-swellable mica. The solids ratio of water-swellable mica out of the total solids of this coating liquid may be within the approximate range of, for example, 20% by mass to 50% by mass.

The area-average diameter of the water-swellable mica is, for example, within the approximate range of 0.5 μm to 5 μm, and may be within the approximate range of 1.5 μm to 2.5 μm. The aspect ratio of the water-swellable mica is, for example, within the approximate range of 10 to 200.

The thickness of the gas barrier coating layer 5 is preferably 50 to 1000 nm, and more preferably 100 to 500 nm. If the thickness of the gas barrier coating layer 5 is 50 nm or more, there is a tendency for more sufficient gas barrier properties to be obtained, and if it is 1000 nm or less, there is a tendency for sufficient flexibility to be maintained.

The coating agent for forming the gas barrier coating layer 5 can be applied by, for example, dipping, roll coating, gravure coating, reverse gravure coating, air knife coating, comma coating, die coating, screen printing, spray coating, gravure offset, etc. The coating film obtained by applying this coating agent can be dried by, for example, hot air drying, hot roll drying, high frequency irradiation, infrared irradiation, UV irradiation, or a combination of these. Considering high speed processability, it is most preferable to dry the coating film by hot air drying.

The temperature and tension when drying the coating film can be, for example, a coating film surface temperature of 30 to 120°C and a tension of 10 to 100 N/m, and it is preferable that the coating film surface temperature is 40 to 70°C and the tension is 10 to 70 N/m. By keeping the coating film surface temperature and tension during drying within the above ranges, the occurrence of cracks in the inorganic vapor deposition layer 4 and the gas barrier coating layer 5 can be further suppressed, and excellent barrier properties can be achieved.

When the gas barrier coating layer 5 is formed by high-speed processing, the temperature and tension when drying the coating can be, for example, an oven temperature of 50 to 180°C and a tension of 10 to 100 N/m, and preferably an oven temperature of 70 to 150°C and a tension of 10 to 70 N/m. By keeping the oven temperature and tension during drying within the above ranges, the occurrence of cracks in the inorganic vapor deposition layer 4 and the gas barrier coating layer 5 can be further suppressed when processing at a high speed of 100 m/min or more over a wide width of 500 mm or more, and excellent barrier properties can be achieved.

The gas barrier coating layer 5 and the inorganic vapor deposition layer 4 are preferably in direct contact (with no other layers interposed therebetween) from the viewpoint of preventing cracking of the inorganic vapor deposition layer 4. Therefore, the gas barrier coating layer 5 is preferably formed by applying the above-mentioned adhesive onto the inorganic vapor deposition layer 4, and drying and curing it. Similarly, the inorganic vapor deposition layer 4 and the undercoat layer 3 are preferably in direct contact (with no other layers interposed therebetween) from the viewpoint of preventing cracking of the inorganic vapor deposition layer 4.

The gas barrier laminate according to this embodiment may include a sealant layer or a printing layer on the barrier layer.

The sealant layer is a layer that provides heat sealing to the gas barrier laminate. The sealant layer may contain a polyolefin, which may be polyethylene.

As the material for the sealant layer, polyolefin-based resins are generally used among thermoplastic resins. Specifically, ethylene-based resins such as low-density polyethylene resin (LDPE), medium-density polyethylene resin (MDPE), direct-locked low-density polyethylene resin (LLDPE), ethylene-vinyl acetate copolymer (EVA), ethylene-α-olefin copolymer, and ethylene-(meth)acrylic acid copolymer, blend resins of polyethylene and polybutene, and polypropylene-based resins such as homopolypropylene resin (PP), propylene-ethylene random copolymer, propylene-ethylene block copolymer, and propylene-α-olefin copolymer can be used. These thermoplastic resins can be appropriately selected depending on the intended use and temperature conditions such as boiling treatment.

The sealant layer may contain various additives such as flame retardants, slip agents, antiblocking agents, antioxidants, light stabilizers, and tackifiers.

The thickness of the sealant layer is determined by the weight of the contents and the shape of the package, but a thickness of approximately 30 to 150 μm is preferable.

The sealant layer can be formed by any of the known lamination methods, including a method in which a sealant layer on a film made of the above-mentioned thermoplastic resin is laminated with an adhesive for forming the above-mentioned gas barrier coating layer 5, a dry lamination method in which the sealant layer is laminated with an adhesive such as a one-component curing or two-component curing urethane adhesive, a non-solvent dry lamination method in which the sealant layer on a film is laminated with a solvent-free adhesive, and an extrusion lamination method in which the above-mentioned thermoplastic resin is heated and melted, extruded into a curtain shape, and laminated.

The printing layer is provided at a position visible from the outside of the gas barrier laminate for the purpose of displaying information about the contents, identifying the contents, or improving the design of the packaging bag. There are no particular limitations on the printing method and printing ink, and they are appropriately selected from known printing methods and printing inks taking into consideration the printability on the film, design such as color tone, adhesion, and safety as a food container. Examples of printing methods that can be used include gravure printing, offset printing, gravure offset printing, flexographic printing, and inkjet printing. Among these, gravure printing is preferably used from the viewpoints of productivity and high definition of the image.

To improve the adhesion of the printed layer, the surface of the layer that forms the printed layer may be subjected to various pretreatments such as corona treatment, plasma treatment, and frame treatment, or a coating layer such as an easy-adhesion layer may be provided.

As described above, the film constituting the gas barrier laminate according to this embodiment can be a mono-material packaging material that is highly recyclable. The gas barrier laminate can be suitably used for various applications such as packaging products such as containers and bags, sheet molded products such as decorative sheets and trays, optical films, resin plates, various label materials, lid materials, and laminate tubes, and is particularly suitable for use in packaging products. Examples of packaging products include pillow bags, standing pouches, three-sided sealed bags, and four-sided sealed bags.

<Packaging bag>
The packaging bag is obtained by forming the above-mentioned gas barrier laminate into a bag. The packaging bag may be one gas barrier laminate folded in half so that the sealant layers face each other, and then heat-sealed on three sides to form a bag shape, or two gas barrier laminates stacked together so that the sealant layers face each other, and then heat-sealed on four sides to form a bag shape. The packaging bag can contain food, medicine, and other contents. The packaging bag can be subjected to a heat sterilization treatment such as boiling.

Boiling is a method of moist heat sterilization for preserving food, medicines, etc. Typically, although it depends on the contents, packaging bags containing food, etc. are subjected to moist heat sterilization at 60-100°C and atmospheric pressure for 10-120 minutes. Boiling is usually performed using a hot water bath at 100°C or less. Methods include a batch type in which the bag is immersed in a hot water bath at a constant temperature and treated for a certain period of time before being removed, and a continuous type in which the bag is passed through a tunnel-type hot water bath for treatment. The packaging bag of this embodiment can also be used suitably for applications requiring boiling treatment.

The packaging bag may also have a shape with a bent portion (folded portion) such as a standing pouch. The packaging bag of this embodiment can maintain high gas barrier properties even when it has a shape with a bent portion.

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

[Base material layer]
Substrate A: GAP (Charter NEX, thickness: 32 μm, unstretched HDPE)
Substrate B: SMUQ (Tokyo Ink Co., Ltd., thickness: 25 μm, stretched HDPE)
Substrate C: UB-3 (manufactured by Tamapoly Co., Ltd., thickness: 40 μm, unstretched MDPE)
Substrate D: JINDAL (manufactured by JINDAL, thickness: 25 μm, stretched HDPE)

<Measurement of arithmetic mean roughness of base layer>
Using an optical interference surface measuring instrument (Vertscan R3300h Lite, manufactured by Ryoka Systems Co., Ltd.) and a 5x objective lens, the front and back surfaces were each measured three times, and the largest maximum protrusion height (μm) among the three measurements was taken as the protrusion height (arithmetic mean roughness) of the film.

[Preparation of composition for forming undercoat layer]
Acrylic polyol and tolylene diisocyanate were mixed so that the number of NCO groups in tolylene diisocyanate was equal to the number of OH groups in the acrylic polyol, and the mixture was diluted with ethyl acetate so that the total solid content (total amount of acrylic polyol and tolylene diisocyanate) was 5 mass%. β-(3,4 epoxycyclohexyl)trimethoxysilane was further added to the diluted mixture in an amount of 5 mass parts per 100 mass parts of the total amount of acrylic polyol and tolylene diisocyanate, and these were mixed to prepare a composition for forming an undercoat layer (anchor coating agent).

[Preparation of gas barrier coating layer forming composition (coating agent)]
Composition A for forming gas barrier coating layer:
A gas barrier coating layer A was prepared by mixing the following liquids A, B and C in a mass ratio of 70/20/10.
Liquid A: A hydrolysis solution with a solid content of 5 mass % (SiO2 equivalent) obtained by adding 72.1 g of 0.1N hydrochloric acid to 17.9 g of tetraethoxysilane (Si( _OC2H5 ) ₄ ) _and 10 g of methanol and hydrolyzing the mixture by stirring for 30 minutes.
Solution B: 5% by mass of polyvinyl alcohol in water/methanol (mass ratio of water:methanol is 95:5)
Liquid C: A hydrolysis solution obtained by diluting 1,3,5-tris(3-trialkoxysilylpropyl)isocyanurate with a mixed liquid of water/isopropyl alcohol (water:isopropyl alcohol mass ratio 1:1) to a solid content of 5 mass%.

Composition B for forming gas barrier coating layer:
The polyurethane resin, 5% PVA aqueous solution, and silane coupling agent were mixed in a solids ratio of 60:35:5, and the mixture was diluted with water and isopropanol to a solids concentration of 5%, to prepare gas barrier coating layer forming composition B. At this time, the amount of isopropanol was 10% of the total gas barrier coating layer forming composition B.

Composition C for forming gas barrier coating layer:
A polyvinyl alcohol resin (PVA, Selvol-325 (saponification degree: 98 to 99%, polymerization degree 1700), manufactured by Sekisui Specialty Chemicals America, LLC.) was used as the hydroxyl group-containing polymer compound. The polyvinyl alcohol resin and water were mixed and heated to 95° C. to dissolve the polyvinyl alcohol resin in water. After cooling to room temperature, the mixture was diluted with water and isopropanol (mass ratio 1:1) so that the final solid content concentration was 5 mass %, thereby preparing component (A).
As the water-swellable mica, water-swellable synthetic mica (Somasif MEB-3, manufactured by Co-op Agri Co., Ltd.) was used. The water-swellable synthetic mica was treated using a bead mill so that the areal particle size was 2 μm. Thereafter, water was mixed so that the final solid content concentration was 8 mass %, to prepare component (B).
Components (A) and (B) were diluted with water and methanol (mass ratio 1:1) so that the content of water-swellable synthetic mica in the final gas barrier coating layer would be 15 mass %, to prepare composition C for forming a gas barrier coating layer.

Example 1
The above-mentioned composition for forming an undercoat layer was applied by gravure roll coating on the surface of the substrate A with a small maximum projection height, and dried and cured at 60°C to form an undercoat layer with a coating amount of 0.1 g/ ^m2 . A transparent inorganic deposition layer (silica deposition film) made of silicon oxide with a thickness of 30 nm was formed on the above-mentioned undercoat layer by a vacuum deposition device using an electron beam heating method. As the silica deposition film, a deposition film with O/Si of 1.8 was formed by preparing a deposition material type. The composition A for forming a gas barrier coating layer was applied on the above-mentioned inorganic deposition layer by gravure roll coating, and heated and dried in an oven under conditions of a tension of 20 N/n and a temperature of the coated coating surface of 60°C to form a gas barrier coating layer with a thickness of 0.3 μm. The heat drying was performed by attaching a heat label (manufactured by Micron Co., Ltd.) to the coating surface before drying, checking the temperature after drying, and adjusting the oven temperature to an arbitrary temperature (60°C in this example). As a result, a gas barrier laminate having a laminate structure of substrate layer/undercoat layer/inorganic vapor deposition layer/gas barrier coating layer was obtained.

Example 2
A gas barrier laminate was obtained in the same manner as in Example 1, except that composition B for forming a gas barrier coating layer was used instead of composition A for forming a gas barrier coating layer.

Example 3
A gas barrier laminate was obtained in the same manner as in Example 1, except that composition C for forming a gas barrier coating layer was used instead of composition A for forming a gas barrier coating layer.

Example 4
A gas barrier laminate was obtained in the same manner as in Example 1, except that the gas barrier coating layer was not formed.

Example 5
A gas barrier laminate was obtained in the same manner as in Example 3, except that no inorganic vapor deposition layer was formed on the undercoat layer.

(Comparative Example 1)
Substrate B was used in place of substrate A, and an undercoat layer, an inorganic vapor deposition layer and a gas barrier coating layer were formed on the surface having the greater maximum projection height in the same manner as in Example 1 to obtain a gas barrier laminate.

(Comparative Example 2)
Substrate C was used in place of substrate A, and an undercoat layer, an inorganic vapor deposition layer and a gas barrier coating layer were formed on the surface having the smaller maximum projection height in the same manner as in Example 1, to obtain a gas barrier laminate G.

(Comparative Example 3)
Substrate D was used in place of substrate A, and an undercoat layer, an inorganic vapor deposition layer and a gas barrier coating layer were formed on the surface having the smaller maximum projection height in the same manner as in Example 1, to obtain gas barrier laminate H.

<Evaluation of processing suitability>
When the gas barrier laminates A to H produced in Examples 1 to 5 and Comparative Examples 1 to 3 were laminated by roll-to-roll lamination using a gravure coating machine, those which could be laminated without any problems were marked with "O", and those which had wrinkles during winding and the winding shape was deformed were marked with "X". The results are shown in Table 1.

<Evaluation of oxygen barrier properties>
The oxygen barrier properties of the gas barrier laminates according to the examples, which had good processing suitability, were measured by JIS K7126, Method B (constant pressure method). The measurement was performed using an OXTRAN 2/20 made by MOCON at a temperature of 30°C and a relative humidity of 70%. The results are shown in Table 1 (unit: cc/ ^m2 day atm).

<Dynamic friction coefficient>
The dynamic friction coefficients of the back surface of the base layer and the barrier layer on the side opposite to the base layer in the gas barrier laminates according to the Examples, which had good processing suitability, were measured under the following conditions, assuming that the gas barrier laminates would be wound up on a roll or the like. The dynamic friction coefficients are shown in Table 1.
Measurement speed: 100 mm/min. Slider: 63 x 63 mm
Slider mass: 200g
Dynamic friction force: Average load from the start of relative displacement between the contact surfaces until 60 mm (N = 3 times)
Coefficient of kinetic friction: kinetic friction force divided by 1.96

1...substrate layer, 2...barrier layer, 3...undercoat layer, 4...inorganic vapor deposition layer, 5...gas barrier coating layer, 10...gas barrier laminate.

Claims (7)

A base layer made of a polyethylene film having a thickness of 15 μm to 50 μm and having a first surface and a second surface;
an inorganic vapor deposition layer provided on the second surface side of the base layer;
Equipped with
The arithmetic mean roughness a of the first surface of the base layer is 3 μm to 10 μm,
The inorganic deposition layer has a thickness of 10 nm to 50 nm;
The gas barrier laminate for packaging bags further comprises an undercoat layer between the substrate layer and the inorganic vapor deposition layer. 2. The gas barrier laminate for packaging bags according to claim 1, wherein the base layer is made of a polyethylene film having a density of 0.940 g/ ^cm3 or more. The gas barrier laminate for packaging bags according to claim 1 or 2, wherein the base layer is made of a multi-layered polyethylene film. The gas barrier laminate for packaging bags according to any one of claims 1 to 3, wherein the undercoat layer contains a polyvinyl alcohol-based resin. The gas barrier laminate for packaging bags according to any one of claims 1 to 4, further comprising a sealant layer containing a polyethylene resin on the second surface side of the base layer. The gas barrier laminate for packaging bags according to claim 5, wherein the sealant layer is a layer formed by an extrusion lamination method. The gas barrier laminate for packaging bags according to claim 5, wherein the sealant layer is a layer formed by a non-solvent lamination method.

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