WO2025211238A1 - Coating composition for forming gas barrier coating film and gas barrier laminate - Google Patents

Abstract

Provided are: a gas barrier laminate having a gas barrier coating film that has excellent oxygen barrier properties and transparency and also has water vapor barrier properties superior to those of conventional gas barrier coating films; and a coating composition that enables efficient formation of such a gas barrier coating film. The gas barrier laminate has a gas barrier coating film on a substrate and is characterized in that: the gas barrier laminate is free from coloration derived from an organic compound, such as an amine compound or a carboxylic acid compound; the ratio (P/Zr) of the Zr (Zr-Kα) and P (P-Kα) contents in fluorescent X-ray measurement of the coating film is in a range of 1.39-2.59; and the ratio (P2/P1) of a peak area (P2) in 2600-3700 cm^-1 and a peak area (P1) in 850-1350 cm^-1 in an infrared absorption spectrum of the coating film is less than 0.772.

Description

Coating composition for forming gas barrier coating film and gas barrier laminate

The present invention relates to a coating composition for forming a gas barrier coating film and a gas barrier laminate having a coating film made from this coating composition. More specifically, the present invention relates to a gas barrier laminate having a coating film that has excellent oxygen barrier properties and water vapor barrier properties as well as excellent transparency, and to a coating composition capable of forming such a coating film.

BACKGROUND ART Gas barrier laminates have been known which are formed by forming a film containing metal atoms and phosphorus atoms as constituent components on a plastic substrate.
For example, Patent Document 1 listed below describes a composite structure having a substrate (X) and a layer (Y) laminated on the substrate (X), wherein the layer (Y) contains a reaction product (R), and the reaction product (R) is a reaction product obtained by reacting at least a metal oxide (A) with a phosphorus compound (B), and the fraction (n ¹ ) at which infrared absorption is maximized in the infrared absorption spectrum of the layer (Y) in the range of 800 to 1400 cm ⁻¹ is in the range of 1080 to 1130 cm ⁻¹ , and the metal atom (M) constituting the metal oxide (A) is aluminum.

The composite structure disclosed in Patent Document 1 satisfies both the oxygen barrier property and the water vapor barrier property, but there are concerns about its stability against the acids and alkalis contained in the contents. Also, during the drying process of film formation, volatile acids contained in the paint are evaporated, which must be addressed, resulting in poor productivity.
The present inventors have proposed a coating composition that uses a composite structure consisting of a reaction product of a metal oxide and a phosphate compound to solve the above problems, and that, by incorporating specific additives, can exhibit even better oxygen barrier properties and water vapor barrier properties (Patent Document 2).

In the coating composition for forming a gas barrier coating film according to Patent Document 2, an amine compound containing polyvalent metal ions and an organic carboxylic acid is used as a specific additive. The polyvalent metal ions capture the metal ions, and the amine compound reacts with the metal ions, carboxylic acid, and phosphoric acid to become incorporated into a crosslinked structure and function as a binder between the metal oxide particles. This allows for the formation of a defect-free coating film, which can exhibit superior oxygen barrier properties and water vapor barrier properties.

Furthermore, as a further improvement over the coating composition of Patent Document 2, the present inventors have proposed a coating composition that contains at least one of a metal alkoxide, a hydrolyzate of a metal alkoxide, and a metal hydroxide, in addition to a metal oxide and a phosphate compound.

Patent No. 4961054 International Publication No. 2022/075352

A coating film made from the above coating composition can be efficiently formed that not only has excellent oxygen barrier properties and water vapor barrier properties due to the uniform and dense crosslinked structure of the metal oxide and phosphate compound, but also has excellent transparency and is free from yellowing due to the reaction between the amine compound and carboxylic acid. Through further research, the present inventors have found that the water vapor barrier properties of a coating film made from the above coating composition can be further improved.
Accordingly, an object of the present invention is to provide a gas barrier laminate provided with a gas barrier coating film that has excellent oxygen barrier properties and transparency, as well as water vapor barrier properties that are even better than those of conventional gas barrier coating films, and a coating composition that can efficiently form such a gas barrier coating film.

According to the present invention, there is provided a gas barrier laminate having a gas barrier coating film on a substrate, wherein the coating film comprises a reaction product obtained by reacting a metal alkoxide, a hydrolysate of a metal alkoxide, at least one metal hydroxide, zirconium oxide, and a phosphate compound or a sulfate compound, and wherein, in fluorescent X-ray measurement of the coating film, the content ratio (P/Zr) of Zr (Zr-Kα) and P (P-Kα) is in the range of 1.39 to 2.59, and in an infrared absorption spectrum of the coating film, the ratio (P2/P1) of the peak area (P2) between 2600 and 3700 cm ⁻¹ and the peak area (P1) between 850 and 1350 cm ⁻¹ is less than 0.772.

In the gas barrier laminate of the present invention,
[1] A gas barrier laminate having a substrate of a biaxially oriented polyethylene terephthalate film having a thickness of 25 μm and having the coating film formed on the substrate in an amount of 1.8 to 2.2 g/ ^m2 has a haze of less than 9.0%;
[2] The metal species of the metal alkoxide, the hydrolyzate of the metal alkoxide, or the metal hydroxide is aluminum, and the content ratio (Al/Zr) of Zr (Zr-Kα) and Al (Al-Kα) in the coating film measured by fluorescent X-rays is in the range of 0.15 to 0.58;
[3] The coating film has an infrared absorption peak in the range of 1000 to 1120 cm ⁻¹ in an infrared absorption spectrum;
[4] A gas barrier laminate having a biaxially oriented polyethylene terephthalate film of 25 μm in thickness as a substrate, a coating film of 1.8 to 2.2 g/ ^m2 formed on the substrate, and a biaxially oriented polyethylene terephthalate film of 25 μm in thickness further laminated via an adhesive layer thereon, has a water vapor permeability of less than 0.100 g/ ^m2 day (40°C, 90% RH),
is preferred.

The present invention also provides a deposition substrate comprising the gas barrier laminate.

The present invention further provides a coating composition for forming a gas barrier coating film, which contains a metal alkoxide, a hydrolyzate of a metal alkoxide, at least one metal hydroxide, a metal oxide, and a phosphoric acid compound or a sulfate compound, and is characterized in that the viscosity ratio (A/B) of the viscosity (A) at a spindle rotation speed of 50 rpm to the viscosity (B) at a spindle rotation speed of 200 rpm of the coating composition when dispersed in water/isopropanol (60/40) with a solids content of 5 to 7% by mass is less than 3.6, as measured at 25°C using a Brookfield viscometer.

In the coating composition for forming a gas barrier coating film of the present invention,
[1] The viscosity of the coating composition for forming a gas barrier coating film, when dispersed in water/isopropanol (60/40) with a solid content of 5 to 7% by mass, measured at a temperature of 25°C using a Brookfield viscometer at a spindle rotation speed of 50 rpm, is less than 113.9 mPa sec;
[2] The metal species of the metal alkoxide or metal hydroxide is at least one of aluminum, titanium, iron, and zirconium;
[3] The metal alkoxide is at least one of methoxide, ethoxide, propoxide, isopropoxide, butoxide, isobutoxide, sec-butoxide, and tert-butoxide;
[4] The metal alkoxide is aluminum isopropoxide;
[5] The metal hydroxide is aluminum hydroxide.
[6] The metal oxide is zirconium oxide or aluminum oxide,
[7] The metal oxide is a crystalline zirconium oxide.
[8] The phosphoric acid compound is at least one of orthophosphoric acid, metaphosphoric acid, polyphosphoric acid, and cyclic polyphosphoric acid;
is preferred.

The present invention also provides a method for producing the above-mentioned coating composition for forming a gas barrier coating film, which comprises mixing a metal alkoxide, a hydrolyzate of a metal alkoxide, at least one metal hydroxide, a metal oxide, and a phosphate compound or a sulfate compound, and then stirring the mixture so that the viscosity measured at a temperature of 25°C using a Brookfield viscometer with a spindle rotation speed of 50 rpm is less than 113.9 mPa·sec.

In the gas barrier laminate of the present invention, the metal oxide is uniformly and highly dispersed without aggregation, which promotes the reaction between the metal oxide and the phosphate compound or sulfate compound, forming a uniform and dense crosslinked structure, thereby suppressing the permeation of nonpolar gas molecules and polar gas molecules and exhibiting excellent oxygen barrier property and water vapor barrier property. Furthermore, the amount of unreacted hydroxyl groups that serve as pathways for polar gases (water molecules) in the gas barrier coating film is reduced, further improving the water vapor barrier property. Furthermore, because aggregation of the metal oxide particles is suppressed, the transparency of the coating film is also excellent, and in the case of a laminate in which a coating film is formed on a 25 μm thick biaxially oriented polyethylene terephthalate substrate, the haze is less than 9.0%.
In the coating composition for forming a gas barrier coating film of the present invention, the metal oxide particles are uniformly and highly dispersed without agglomeration, resulting in reduced thixotropy. Therefore, the viscosity is adjusted to be lower than that of conventional coating compositions for forming a gas barrier coating film, and the composition is capable of forming a uniform, smooth coating film with excellent coatability and leveling properties. Furthermore, the excellent smoothness of the coating film suppresses light scattering on the coating film surface, which, combined with the absence of aggregation of the metal oxide particles, reduces the haze of the coating film and provides excellent transparency. Furthermore, the excellent coatability reduces the occurrence of coating film defects, and, combined with the formation of a uniform, dense crosslinked structure due to the high dispersion of the metal oxide particles as described above, allows the formation of a coating film with excellent oxygen barrier properties and water vapor barrier properties. Furthermore, since the coating composition does not contain a volatile acid, no special measures are required in the drying process, resulting in excellent productivity and safety.

1 is a diagram showing a cross-sectional structure of an example of the gas barrier laminate of the present invention. FIG. 2 is a diagram showing the cross-sectional structure of another example of the gas barrier laminate of the present invention.

(Gas barrier laminate)
An important feature of the gas barrier coating film formed on the substrate in the gas barrier laminate of the present invention is that the ratio (P2/P1) of the peak area (P2) from 2600 to 3700 ^cm to the peak area (P1) from 850 to 1350 ^cm in the infrared absorption spectrum is less than 0.772.
The gas barrier coating film in the gas barrier laminate of the present invention can be formed from a coating composition for forming a gas barrier coating film, which contains at least one of a metal alkoxide, a hydrolyzate of a metal alkoxide, and a metal hydroxide, together with a metal oxide and a phosphate compound, etc., as described below, and particularly a coating composition in which the metal oxide is zirconium oxide, and specifically, the coating film is formed by crosslinking a metal oxide with a phosphate compound or a sulfate compound to form a metal phosphate or a metal sulfate. Furthermore, metal alkoxides, etc., also react with phosphate compounds or sulfate compounds to form metal phosphates or metal sulfates, which are incorporated into the crosslinked structure and function as binders between metal oxide particles.
The peak area (P1) in the infrared absorption spectrum is the peak area of a metal phosphate or metal sulfate in FT-IR measurement of a coating film on a substrate, while the peak area (P2) is the peak area of a hydroxyl group in the coating film alone. A ratio of these (P2/P1) of less than 0.772 means, as mentioned above, that the reaction between the metal oxide and the phosphate compound or the like is efficiently promoted, and a dense crosslinked structure free from defects due to the generation of the metal phosphate or the like is efficiently formed, while the number of unreacted hydroxyl groups is reduced.

Furthermore, as described above, in the gas barrier laminate of the present invention, the dispersibility of zirconium oxide (hereinafter sometimes referred to as "metal oxide") in the coating film is excellent, so there is no aggregation of zirconium oxide particles (hereinafter sometimes referred to as "metal oxide particles") and the transparency of the coating film is improved, and in the case of a gas barrier laminate in which a coating film is formed in an amount of 1.8 to 2.2 g/ ^m2 on a biaxially stretched polyethylene terephthalate film with a thickness of 25 μm, the haze is less than 9.0%.

When the gas barrier coating film in the gas barrier laminate of the present invention uses zirconium oxide as the metal oxide, phosphoric acid as the phosphate compound or the like, and aluminum isopropoxide or aluminum hydroxide as the metal alkoxide or the like, it is preferable that the content ratio (Al/Zr) of Zr (Zr-Kα) of zirconium oxide measured by X-ray fluorescence to Al (Al-Kα) of aluminum alkoxide or the like measured by X-ray fluorescence is in the range of 0.15 or more and less than 0.60, particularly in the range of 0.33 to 0.58, and further in the range of 0.43 to 0.58.
When the content ratio (Al/Zr) is within the above range, it becomes possible to exhibit the above-described effects of the aluminum alkoxide and the like without impairing the dense cross-linked structure of the zirconium oxide and the phosphate compound, and it becomes possible to exhibit excellent oxygen barrier property and water vapor barrier property.

Furthermore, when the gas barrier coating film in the gas barrier laminate of the present invention uses zirconium oxide as the metal oxide, phosphoric acid as the phosphate compound or the like, and aluminum isopropoxide or aluminum hydroxide as the metal alkoxide or the like, it is preferable that the content ratio (P/Zr) of Zr (Zr-Kα) of the zirconium oxide measured by X-ray fluorescence to P (P-Kα) of the phosphate compound measured by X-ray fluorescence measurement is in the range of 1.39 or more and less than 2.68, particularly in the range of 1.49 to 2.59, and further in the range of 1.91 to 2.59.
When the content ratio (P/Zr) is within the above range, the phosphate compound reacts efficiently with the metal oxide in the coating film, neither too much nor too little, resulting in the formation of a uniform and dense coating film that can exhibit excellent oxygen barrier properties and water vapor barrier properties. That is, if the content ratio determined by fluorescent X-ray measurement is less than the above range and there is an insufficient amount of phosphate compound, the metal oxide particles will not be bonded together sufficiently, and defects will occur in the structure of the coating film, which could result in reduced oxygen barrier properties and water vapor barrier properties. On the other hand, if the content ratio determined by fluorescent X-ray measurement is greater than the above range and there is an excess of phosphate compound, the number of hydroxyl groups derived from the phosphate groups will increase, which could also result in reduced oxygen barrier properties and water vapor barrier properties.

The coating film in the gas barrier laminate of the present invention preferably has an infrared absorption peak in the range of 1000 to 1120 ^cm in the infrared absorption spectrum of the coating film on the substrate. That is, as described above, the coating film in the gas barrier laminate of the present invention has excellent dispersibility of metal oxides, and therefore a crosslinked structure based on the formation of metal phosphate is efficiently formed. Therefore, the coating film has a maximum absorption peak in the above range derived from the metal phosphate.

As described above, the gas barrier laminate of the present invention has a reduced number of hydroxyl groups derived from the phosphate compound and from the surfaces of metal oxide particles that are not used in the reaction in the coating film, and its uniform and dense structure makes it possible to inhibit the permeation of non-polar gas molecules and polar gas molecules, and therefore has excellent oxygen barrier properties and water vapor barrier properties, and is particularly excellent in water vapor barrier properties.
In addition, examples of gas molecules other than oxygen and water vapor that can be inhibited from permeating include, but are not limited to, hydrogen, helium, nitrogen, methane, ammonia, acidic gases such as hydrogen chloride, hydrogen sulfide, carbon dioxide, sulfur oxides, and nitrogen oxides.
For example, a gas barrier laminate having a substrate of a 25 μm-thick biaxially oriented polyethylene terephthalate film, on which a coating film with a coating amount of 1.8 to 2.2 g/ ^m2 is applied, and further having a 25 μm-thick biaxially oriented polyethylene terephthalate film formed via an adhesive layer, has a water vapor permeability of less than 0.100 g/ ^m2 ·day (40°C, 90% RH), and exhibits excellent water vapor barrier properties.
Furthermore, a gas barrier laminate having a substrate of a 25 μm-thick biaxially oriented polyethylene terephthalate film, on which a coating film with a coating amount of 1.8 to 2.2 g/ ^m2 and a 25 μm-thick biaxially oriented polyethylene terephthalate film formed via an adhesive layer, has an oxygen permeability of 25 cc/m2 ^day atm or less (40°C, 90% RH), demonstrating excellent oxygen barrier properties.

Furthermore, as described above, in the gas barrier laminate of the present invention, a gas barrier coating film is formed in a state in which the metal oxide particles are uniformly and highly dispersed without agglomeration, and as a result, a uniform and smooth coating film is formed, which has excellent optical properties. In addition to having a haze of less than 9.0%, a gas barrier laminate having a biaxially oriented polyethylene terephthalate film of 25 μm in thickness as a substrate and a coating film of 1.8 to 2.2 g/ ^m2 formed on said substrate has a total light transmittance of 80% or more and a gloss (glossiness) at an angle of 60° of 100 or more, thereby exhibiting excellent optical properties.

The gas barrier laminate of the present invention is a laminate comprising a substrate and a gas barrier layer comprising the gas barrier coating film described above formed on at least one surface thereof, and preferably, as shown in Figure 1, a gas barrier layer 3 is formed on substrate 1 via an anchor coat layer 2 described below. The anchor coat layer 2 is a coating film that has excellent adhesion to substrate 1, and by forming the gas barrier layer on this coating film, the interlayer adhesion between the gas barrier layer and the plastic substrate is significantly improved, delamination is suppressed in high temperature or high humidity environments, and peeling of the gas barrier layer from the substrate can be effectively prevented even when subjected to retort sterilization or the like.
In the gas barrier laminate of the present invention, it is preferable to form a resin layer 5 made of a thermoplastic resin on the gas barrier layer 3 via an adhesive layer 4, as shown in FIG. 2.

[Base material]
[0043] The substrate for the gas barrier laminate of the present invention may be any conventionally known substrate made of resins such as thermoplastic resins and thermosetting resins, or fibers such as paper or nonwoven fabric. Preferred examples include films, sheets, and any packaging materials and molded structures in the shape of a bottle, cup, tray, can, or the like, produced from thermoformable thermoplastic resins by means of extrusion molding, biaxially oriented film molding, cast film molding, injection molding, blow molding, stretch blow molding, press molding, or the like.

Examples of thermoplastic resins constituting the substrate include olefin copolymers such as low-, medium-, or high-density polyethylene, linear low-density polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-1-butene copolymer, ionomer, ethylene-vinyl acetate copolymer, and ethylene-vinyl alcohol copolymer; polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene terephthalate/isophthalate, and polyethylene naphthalate; polyamides such as nylon 6, nylon 6,6, nylon 6,10, and metaxylylene adipamide; polyimides such as diamine-carboxylic anhydride copolymers; styrene copolymers such as polystyrene, styrene-butadiene block copolymer, styrene-acrylonitrile copolymer, and styrene-butadiene-acrylonitrile copolymer (ABS resin); vinyl chloride copolymers such as polyvinyl chloride and vinyl chloride-vinyl acetate copolymer; acrylic copolymers such as polymethyl methacrylate and methyl methacrylate-ethyl acrylate copolymer; and polycarbonate.
In addition, in view of recent environmental concerns, chemically recycled polyethylene terephthalate, mechanically recycled polyethylene terephthalate, biomass-derived polyethylene terephthalate, biomass-derived olefin, recycled olefin, etc. can be used.
In the present invention, a sheet made of polyethylene terephthalate, polybutylene terephthalate or polypropylene can be particularly suitably used.

These thermoplastic resins may be used alone or in the form of a blend of two or more types, or in the form of a laminate of different resins. The plastic substrate may have a single layer structure or a laminate structure of two or more layers, for example, formed by co-melt extrusion or other lamination. Furthermore, the plastic material may be subjected to a strength-enhancing process such as uniaxial or biaxial stretching to improve heat resistance.
If desired, one or more additives such as pigments, antioxidants, antistatic agents, ultraviolet absorbers, lubricants, etc. may be added to the thermoformable thermoplastic resin in a total amount of 0.001 to 5.0 parts by mass per 100 parts by mass of the resin.
Furthermore, for example, in order to reinforce this container, one or more types of fiber reinforcing materials such as glass fiber, aromatic polyamide fiber, carbon fiber, pulp, cotton linter, etc., powder reinforcing materials such as carbon black, white carbon, etc., or flake-like reinforcing materials such as glass flakes, aluminum flakes, etc. can be blended in a total amount of 2 to 150 parts by mass per 100 parts by mass of the thermoplastic resin, and for the purpose of further increasing the weight, one or more types of heavy or soft calcium carbonate, mica, talc, kaolin, gypsum, clay, barium sulfate, alumina powder, silica powder, magnesium carbonate, etc. can be blended in a total amount of 5 to 100 parts by mass per 100 parts by mass of the thermoplastic resin according to a formulation known per se.
Furthermore, for the purpose of improving the gas barrier property, scaly inorganic fine powder, such as water-swellable mica or clay, may be blended in a total amount of 5 to 100 parts by mass per 100 parts by mass of the thermoplastic resin according to a known formulation.
Similarly, for the purpose of improving the gas barrier properties, there is no problem in providing a thin film layer of an inorganic material such as silicon oxide or aluminum oxide on a plastic substrate by physical or chemical vapor deposition.

The substrate may also be a final film, sheet, or molded product such as a container, or this coating may be applied in advance to a preformed article to be molded into a container. Examples of such preformed articles include cylindrical parisons with or without bottoms for biaxially stretched blow molding, pipes for molding plastic containers, sheets for vacuum forming, pressure forming, and plug-assist molding, or films for heat-sealed lids and bag making.

[Anchor coat layer]
The anchor coat layer formed on the surface of the substrate as needed can be an anchor coat layer that has been conventionally formed on gas barrier laminates, and can suitably be an anchor coat layer made of a conventionally known polyurethane resin that combines a hydroxyl group-containing compound as the main component, such as an acrylic resin or polyol, with an isocyanate curing agent, or an anchor coat layer further containing a silane coupling agent, or an anchor coat layer made of a hydrophilic group-containing resin and a silane coupling agent. The anchor coat layer-forming composition will be described later.

(Substrate for vapor deposition)
As described above, the gas barrier laminate of the present invention has excellent gas barrier properties, particularly excellent water vapor barrier properties, and therefore can be suitably used as a substrate on which a vapor-deposited film is formed.
The method for forming the vapor-deposited film on the substrate is not particularly limited, and the film can be formed by physical vapor deposition such as sputtering, vacuum deposition, ion plating, etc., or chemical vapor deposition such as plasma CVD, etc. Examples of the vapor-deposited film to be formed include, but are not limited to, gold, silver, copper, titanium, nickel, aluminum, silicon oxide, titanium oxide, aluminum oxide, a mixture of silica and alumina, indium tin oxide, diamond-like carbon, etc.

(Gas barrier coating film forming coating composition)
The coating composition for forming a gas barrier coating film, which is capable of forming a gas barrier coating film on the gas barrier laminate of the present invention, contains a metal alkoxide, a hydrolysate of a metal alkoxide, at least one metal hydroxide, a metal oxide, and a phosphoric acid compound or a sulfate compound, and an important feature of the coating composition for forming a gas barrier coating film is that when the coating composition is made into a water/isopropanol (60/40) dispersion having a solids content of 5 to 7% by mass, the viscosity ratio (A/B) of the viscosity (A) at a spindle rotation speed of 50 rpm to the viscosity (B) at a spindle rotation speed of 200 rpm is less than 3.6, as measured at 25°C using a Brookfield viscometer.
That is, paint compositions generally have thixotropy, and since this thixotropy depends on shear stress during dispersion treatment, the viscosity decreases when the rotation speed is high and high shear stress is applied, and increases when the rotation speed is low and shear stress is weak. The paint composition for forming gas barrier coatings of the present invention has low viscosity even at a low rotation speed (50 rpm), as described above, and is characterized by a viscosity ratio (A/B) of less than 3.6, because the metal alkoxides, metal oxides, phosphate compounds, etc. in the paint composition are highly dispersed and have reduced thixotropy.

The coating composition for forming a gas barrier coating film of the present invention, when dispersed in water/isopropanol (60/40) with a solids content of 5 to 7% by mass, preferably has a viscosity of less than 113.9 mPa·sec, particularly 26.2 to 96.0 mPa·sec, measured at 25°C using a Brookfield viscometer at a spindle rotation speed of 50 rpm. This allows the metal oxide particles and other particles in the coating composition for forming a gas barrier coating film to be uniformly dispersed without agglomeration, making it possible to form a coating film that exhibits excellent oxygen barrier properties and water vapor barrier properties. Furthermore, as mentioned above, excellent coatability and leveling properties can be achieved, making it possible to form a coating film without defects, which also contributes to the development of excellent oxygen barrier properties and water vapor barrier properties.

As described above, the coating composition for forming a gas barrier coating film of the present invention contains at least one of a metal alkoxide, a hydrolysate of a metal alkoxide, and a metal hydroxide, together with a metal oxide and a phosphoric acid compound or a sulfate compound, so that a uniform and dense crosslinked structure is formed by the metal oxide and the phosphoric acid compound, etc., and by reacting the metal alkoxide, etc. with the phosphoric acid compound, etc., it is incorporated into the crosslinked structure and functions as a binder between the metal oxide particles, thereby enabling the composition to exhibit excellent oxygen barrier properties and water vapor barrier properties.
Furthermore, reactions of metal alkoxides and their hydrolysates, and metal hydroxides with phosphate compounds, etc., do not cause yellowing, making it possible to form colorless, transparent gas barrier coating films. Furthermore, compared to conventional coating film formation methods involving amine compounds and carboxylic acids, this method can be performed at lower temperatures and in a shorter time, making it superior in terms of productivity.

[Metal oxides]
The metal oxide used in the coating composition for forming a gas barrier coating film of the present invention is preferably an oxide of a divalent or higher metal atom, and includes, but is not limited to, oxides of magnesium, calcium, iron, zinc, aluminum, silicon, titanium, zirconium, etc., and zirconium oxide is particularly preferred.
The metal oxide used in this specification contains a structure represented by MOM as a main component, where M represents a metal atom and O represents an oxygen atom.
Zirconium oxide contains Zr and O as component elements, amorphous zirconium oxide contains zirconium hydroxide (Zr(OH) ₄ ) and/or zirconyl hydroxide (ZrO(OH) ₂ ) as the main component, and crystalline zirconium oxide contains hydrated zirconium oxide ( _ZrO2.xH2O ) and/or zirconium oxide ( _ZrO2 ) as _the main component. The term "main component" refers to a component contained in a proportion of 50% or more. The crystallinity of zirconium oxide and zirconium oxide formed into a gas barrier coating can be evaluated by identifying the X-ray peaks specific to crystalline zirconium using a conventionally known X-ray structural diffractometer.
In the present invention, either crystalline or amorphous zirconium oxide (zirconia) can be used as the zirconium oxide. However, from the viewpoint of efficiently suppressing the permeation of gas molecules, crystalline zirconium oxide is particularly preferably used.

In paints, zirconium oxide is used in the form of a sol in which zirconium oxide particles are used as a dispersoid and an inorganic acid such as nitric acid is blended as a stabilizer. However, in the present invention, in order to prevent the volatilization of the inorganic acid during coating film formation due to the inclusion of the inorganic acid, it is preferable to use a zirconium oxide sol that is substantially free of volatile acid and in which a carbonate, ammonium carbonate, organic dispersant, or the like is used instead of an inorganic acid such as nitric acid.
Furthermore, the binder component contains at least one of a metal alkoxide, a hydrolysate of a metal alkoxide, and a metal hydroxide, which are capable of providing many hydroxyl groups available for reaction with a phosphate compound or the like. Therefore, just as in the case of using amorphous zirconium oxide, even when crystalline zirconium oxide is used, it is possible to achieve both oxygen barrier properties and water vapor barrier properties equivalent to those achieved when amorphous zirconium oxide with many hydroxyl groups is used.

Furthermore, it is desirable that the zirconium oxide particles have an average primary particle size (D50) of 100 nm or less, preferably 50 nm or less, and more preferably 30 nm or less, which allows the formation of a uniform coating film with excellent transparency. The average particle size (D50) is the volume-average particle size measured by a laser diffraction/scattering method, and D50 is the 50% value in the volume-based particle size distribution. By using such fine particle-type zirconium oxide as a raw material, excellent transparency can be achieved.
Furthermore, by using the zirconium oxide particles, it is possible to form a uniform and smooth coating film, and since zirconium oxide has a high refractive index, it can be used as a refractive index adjusting layer.

[Phosphate Compounds]
Phosphoric acid compounds usable in the present invention include orthophosphoric acid, metaphosphoric acid, polyphosphoric acid, cyclic polyphosphoric acid, phosphorous acid, phosphonic acid, and their derivatives. Specific examples of polyphosphoric acid include pyrophosphoric acid, triphosphoric acid, and polyphosphoric acid condensed with four or more phosphoric acids. Examples of the above derivatives include salts, (partial) ester compounds, halides (e.g., chlorides), and dehydrates (e.g., diphosphorus pentoxide) of orthophosphoric acid, metaphosphoric acid, polyphosphoric acid, phosphorous acid, and phosphonic acid. Examples of phosphonic acid derivatives also include compounds in which the hydrogen atom directly bonded to the phosphorus atom of phosphonic acid (H-P(=O)(OH) ₂ ) is substituted with an alkyl group that may have various functional groups (e.g., nitrilotris(methylenephosphonic acid), N,N,N',N'-ethylenediaminetetrakis(methylenephosphonic acid)), as well as salts, (partial) ester compounds, halides, and dehydrates thereof. Furthermore, organic polymers containing phosphorus atoms, such as phosphorylated starch, can also be used. These phosphate compounds can be used alone or in combination of two or more.
In the present invention, it is particularly preferable to use at least one of orthophosphoric acid, metaphosphoric acid, polyphosphoric acid, and cyclic polyphosphoric acid.

[Sulfuric acid compound]
In the present invention, examples of sulfate compounds that can be used in place of the above-mentioned phosphoric acid compounds to form dense coating films upon reaction with metal oxides include compounds selected from the group consisting of sulfuric acid, sulfates, sulfate esters, alkyl sulfates, polyoxyethylene alkyl ether sulfates, and salts thereof. These sulfate compounds can be used alone or in combination of two or more.
In the present invention, sulfuric acid can be particularly preferably used.

[Metal alkoxide or its hydrolysate]
Metal alkoxides are generally represented by the following formula (1):
M ⁿ⁺ (OR) ⁿ -...(1)
In the formula, R represents an organic group having 1 to 8 carbon atoms, M represents a metal atom, and n represents an integer of 1 or more.

In the present invention, in the above formula (1), the metal atom M is preferably any one of aluminum, titanium, iron, and zirconium, and is particularly preferably aluminum.
In the above formula (1), the organic group R is preferably any one of a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group.
In the present invention, as described above, the metal alkoxide is preferably at least one metal alkoxide selected from methoxide, ethoxide, propoxide, isopropoxide, butoxide, isobutoxide, sec-butoxide, and tert-butoxide, and among these, aluminum isopropoxide can be preferably used.

[Metal hydroxide]
Metal hydroxides are generally represented by the following formula (2).
M ⁿ⁺ (OH) ⁿ -...(2)
In the formula, H represents a hydrogen atom, M represents a metal atom, and n represents an integer of 1 or more.
The metal hydroxide is preferably any of the hydroxides of aluminum, titanium, iron, and zirconium listed as examples of metal alkoxides, and among these, aluminum hydroxide is preferably used.

(Method for producing a coating composition for forming a gas barrier coating film)
The coating composition for forming a gas barrier coating film of the present invention may be either an aqueous or solvent-based composition as long as it contains the above-mentioned metal oxide, phosphate compound, etc. and metal alkoxide, etc., but is preferably an aqueous composition.
In the coating composition for forming a gas barrier coating film, it is desirable to use a sol containing metal oxide fine particles as the dispersoid as the metal oxide. Furthermore, it is preferable to use a sol containing metal oxide fine particles as the dispersoid that does not contain a volatile acid as a stabilizer, in order to prevent the adverse effects of acid generation on equipment and the working environment.
For the above reasons, it is desirable not to use, as a deflocculating agent, volatile acids such as nitric acid, hydrochloric acid, acetic acid, and trifluoroacetic acid, which have been used to prepare dispersions with excellent transparency and viscosity stability.

The coating composition for forming a gas barrier coating film of the present invention is prepared by mixing the above-mentioned metal oxide, phosphate compound, etc., and metal alkoxide, etc. in a solvent capable of dissolving the phosphate compound, etc. and the metal alkoxide, etc.
As such an aqueous medium, conventionally known aqueous solvents such as distilled water, ion-exchanged water, and pure water can be used. Similar to known aqueous compositions, the composition can contain organic solvents such as alcohols, polyhydric alcohols, derivatives thereof, and ketones. When such a co-solvent is used, it can be contained in an amount of 1 to 90 wt % relative to the aqueous solvent in the aqueous composition. By including a solvent in the above range, film-forming performance is improved. Preferred organic solvents are those having amphiphilic properties, such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol, tert-butyl alcohol, butyl cellosolve, propylene glycol monopropyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, 3-methyl-3-methoxybutanol, acetone, and methyl ethyl ketone.

In the method for producing a coating composition for forming a gas barrier coating film of the present invention, it is important that the metal oxide, phosphate compound, etc. are uniformly and highly dispersed without aggregation after mixing in a solvent, and therefore it is preferable to carry out a dispersion treatment. In the dispersion treatment, stirring is carried out so that the viscosity measured at a temperature of 25°C using a Brookfield viscometer with a spindle rotation speed of 50 rpm is less than 113.9 mPa sec, particularly in the range of 26.2 to 96.0 mPa sec.
As a dispersion treatment method, any conventionally known dispersion treatment can be used as long as it can adjust the viscosity to the above range. Examples of the dispersion treatment that can be used include, but are not limited to, a method of crushing fine particles by cavitation using an ultrasonic homogenizer, a mechanical dispersion treatment using a disperser with rotating blades, and dispersion using a mill with glass or zirconia beads. In particular, an ultrasonic homogenizer can be preferably used.

In the coating composition for forming a gas barrier coating film of the present invention, a phosphate compound and a metal alkoxide may be added to the metal oxide within a range that does not impair the oxygen barrier property and water vapor barrier property.
The amount of the phosphate compound or the like to be added varies depending on the type of phosphate compound or the like used and cannot be generally specified. However, when zirconium oxide is used as the metal oxide, phosphoric acid as the phosphate compound or the like, and aluminum isopropoxide as the metal alkoxide or the like, it is preferable to blend in an amount of 53.5 to 90.9 parts by mass, and particularly 69.5 to 90.9 parts by mass, of the nonvolatile content of phosphoric acid per 100 parts by mass of the solid content of zirconium oxide.

The amount of metal alkoxide or the like to be added varies depending on the type of metal alkoxide or the like used and cannot be generally specified. However, when zirconium oxide is used as the metal oxide, phosphoric acid is used as the phosphate compound or the like, and aluminum isopropoxide is used as the metal alkoxide or the like, it is preferable to add aluminum isopropoxide in an amount of 44.7 to 76.0 parts by mass, particularly 58.1 to 76.0 parts by mass, per 100 parts by mass of the solid content of zirconium oxide.
In the coating composition for forming a gas barrier coating film of the present invention, by ensuring that the contents of the phosphate compound and metal alkoxide, which serve as binder components, are within the above-mentioned ranges, it is possible to prepare a coating composition that can form a suitable coating film that has excellent transparency and gas barrier properties.

In the coating composition for forming a gas barrier coating film of the present invention, it is desirable that the binder components such as the phosphoric acid compound and the metal alkoxide are within the above ranges, but even within the above ranges, a higher content is particularly desirable because this allows for a reduction in the viscosity of the coating composition.
Therefore, in the coating composition for forming a gas barrier coating film of the present invention, by employing the above-mentioned high dispersion treatment or an increased amount of binder component, or both, it is possible to suitably prepare a coating composition having the desired viscosity characteristics.
Furthermore, by increasing the contents of the phosphate compound and metal alkoxide, the crosslinked structures formed in the coating film increase, and the crosslinked structures of the metal phosphate, which is the reaction product of the phosphate compound and the metal alkoxide, etc., which acts as a binder between the metal compound particles, also increase, making it possible to provide a coating composition that can form a defect-free coating film. Note that if the contents of the phosphate compound and metal alkoxide, etc., are greater than the above ranges, not only will no further effects be obtained, but there is also a risk of defects in the barrier structure of the coating film compared to when they are within the above ranges.

Furthermore, the coating composition for forming a gas barrier coating film of the present invention preferably contains a catalyst capable of promoting the reaction between the metal oxide or metal alkoxide used and the phosphoric acid compound, etc. This promotes the crosslinking reaction of the coating composition, making it possible to reduce the heating temperature and heating time required for forming the coating film.
Examples of such catalysts include acid catalysts such as paratoluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, dinonylnaphthalenedisulfonic acid, and cumenesulfonic acid, as well as amine neutralization products of these acids. Of these, paratoluenesulfonic acid is particularly preferred.
The acid catalyst is preferably contained in an amount of 0.1 to 10 parts by mass, particularly 1 to 3 parts by mass, per 100 parts by mass of the solid content of zirconium oxide.
In addition to the above components, the coating composition for forming a gas barrier coating film may also contain a crosslinking agent, a metal complex, a condensation accelerator, a polymer compound, a filler, a plasticizer, an antioxidant, an ultraviolet absorber, a flame retardant, an antifoaming agent, a colorant, etc.

(Method for producing gas barrier laminate)
In the method for producing a gas barrier laminate of the present invention, the coating composition for forming a gas barrier coating film of the present invention can be applied directly to at least one surface of the above-mentioned substrate, but it is preferable to apply a composition for forming an anchor coat layer, which will be described later, prior to applying the coating composition for forming a gas barrier coating film.
The amount of the anchor coat layer-forming composition to be applied is determined by the content of the polyurethane resin or carboxyl group-containing polyester resin, and the silane coupling agent in the composition, and cannot be generally specified, but it is preferable to apply so that the solids weight of the coating film is in the range of 0.05 to 1.00 g/m ² , particularly 0.10 to 0.50 g/m ^2. If the anchor coat application amount is less than the above range, there is a risk that the anchor coat layer will not be able to be fixed to the substrate as compared with when it is within the above range, while if the anchor coat application amount is more than the above range, it will be less economical.
The anchor coat layer-forming composition applied to the substrate is dried at a temperature of 80 to 150°C for 1 to 60 seconds to remove the solvent from the composition, although this depends on the composition and amount applied. This allows the anchor coat layer to be economically formed without affecting the substrate, even if it is made of a plastic with a low melting point, such as polypropylene.

Next, a coating composition for forming a gas barrier coating film is applied onto the anchor coat layer-forming composition, which has been dried after the solvent has been removed. The amount of coating composition for forming a gas barrier coating film to be applied is determined by the contents of metal oxides, phosphate compounds, etc., and metal alkoxides, etc. in the composition and cannot be generally specified, but it is preferable to apply it so that the solids weight of the coating film is in the range of 0.05 to 3.0 g/m ² , and particularly 0.1 to 2.5 g/m ² . If the amount applied is less than the above range, sufficient barrier properties cannot be obtained. On the other hand, if the amount applied is greater than the above range, it will only be less economical and will not offer any particular advantage.

In the coating composition for forming a gas barrier coating film of the present invention, a gas barrier layer can be formed by heating at a temperature of 80 to 220°C, preferably 140 to 220°C, for 1 second to 10 minutes, depending on the composition and application amount of the metal oxides, phosphate compounds, and metal alkoxides used in the composition. This reduces the difference in shrinkage due to heating between the gas barrier layer and the anchor coat layer, improving the crack resistance of the gas barrier layer and significantly improving the interlayer adhesion between the gas barrier layer and the anchor coat layer, preventing peeling of the gas barrier layer from the substrate even when subjected to retort sterilization, etc. Furthermore, a coating film can be formed efficiently at a lower temperature and in a shorter time than conventional gas barrier layers.

The application of the anchor coat layer forming composition and the gas barrier coating film forming coating composition, and the drying or heat treatment can be carried out by a conventionally known method.
The application method is not limited to these, but for example, spray coating, immersion, or application with a bar coater, roll coater, gravure coater, or the like is possible.
The drying or heating treatment can be carried out by oven drying (heating), infrared heating, high frequency heating, vacuum drying, superheated steam, or the like.

[Anchor coat layer forming composition]
As the anchor coat layer-forming composition to be applied to the surface of the substrate as needed, as described above, an anchor coat layer-forming composition made of a conventionally known polyurethane resin that is a combination of a hydroxyl group-containing compound that serves as a main component, such as an acrylic resin or polyol, and an isocyanate-based curing agent, or an anchor coat layer-forming composition that further contains a silane coupling agent, or a hydrophilic group-containing resin and a silane coupling agent can be suitably used.

<Polyurethane resin>
As the polyurethane resin constituting the anchor coat layer, a polyurethane resin composed of a hydroxyl group-containing compound as a main component, such as a known acrylic resin or polyol, which has been conventionally used as an anchor coat layer, and an isocyanate compound can be used.
In the present invention, it is desirable to use a polyurethane resin having a glass transition temperature (Tg) of 80° C. or higher, particularly in the range of 80 to 120° C. If the glass transition temperature is lower than the above range, the heat resistance of the anchor coat layer will be inferior compared to when the glass transition temperature is within the above range, and when the gas barrier layer is dried, cracks may occur in the gas barrier layer when the gas barrier coating film shrinks due to heating, resulting in a decrease in barrier properties.

As the acrylic resin, polymers and copolymers synthesized by solution polymerization or suspension polymerization using a conventionally known radical initiator or the like can be used.
The glass transition temperature of the acrylic resin is preferably −50 to 100° C., more preferably 40 to 100° C. The number average molecular weight of the acrylic resin is preferably 500,000 to 100,000, more preferably 500,000 to 80,000 The hydroxyl value of the acrylic resin is preferably 10 to 200 mgKOH/g, more preferably 80 to 180 mgKOH/g.
The monomer for forming the copolymer is not particularly limited, but copolymers of methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, acrylic acid, methacrylic acid, itaconic acid, maleic acid, 2-hydroxyethyl methacrylate, tert-butyl acrylate, and the like, combined as necessary, can be used.
Examples of polyols include glycols, polyester polyols, polyether polyols, acrylic polyols, and urethane-modified versions of these, with acrylic polyols and glycols being particularly preferred.

The glass transition temperature of the polyester polyol is preferably −50 to 100° C., more preferably −20 to 80° C. The number average molecular weight of these polyester polyols is preferably 500,000 to 100,000, more preferably 500,000 to 80,000.
Examples of glycols include ethylene glycol, propylene glycol, diethylene glycol, butylene glycol, neopentyl glycol, and 1,6-hexanediol.

As the isocyanate component which is a curing agent for polyurethane resins, aromatic diisocyanates, araliphatic diisocyanates, alicyclic diisocyanates, aliphatic diisocyanates, etc. can be used.
Examples of aromatic diisocyanates include tolylene diisocyanate (2,4- or 2,6-tolylene diisocyanate or a mixture thereof) (TDI), phenylene diisocyanate (m-, p-phenylene diisocyanate or a mixture thereof), 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate (NDI), diphenylmethane diisocyanate (4,4'-, 2,4'-, or 2,2'-diphenylmethane diisocyanate or a mixture thereof) (MDI), 4,4'-toluidine diisocyanate (TODI), and 4,4'-diphenyl ether diisocyanate.
Examples of the araliphatic diisocyanate include xylene diisocyanate (1,3- or 1,4-xylene diisocyanate or a mixture thereof) (XDI), tetramethyl xylene diisocyanate (1,3- or 1,4-tetramethyl xylene diisocyanate or a mixture thereof) (TMXDI), ω,ω'-diisocyanato-1,4-diethylbenzene, and the like.

Examples of alicyclic diisocyanates include 1,3-cyclopentene diisocyanate, cyclohexane diisocyanate (1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate), 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate, IPDI), methylene bis(cyclohexyl isocyanate) (4,4'-, 2,4'-, or 2,2'-methylene bis(cyclohexyl isocyanate)) (hydrogenated MDI), methyl cyclohexane diisocyanate (methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate), bis(isocyanatomethyl)cyclohexane (1,3- or 1,4-bis(isocyanatomethyl)cyclohexane or a mixture thereof) (hydrogenated XDI), and the like.

Aliphatic diisocyanates include, for example, trimethylene diisocyanate, 1,2-propylene diisocyanate, butylene diisocyanate (tetramethylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate), hexamethylene diisocyanate, pentamethylene diisocyanate, 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, and 2,6-diisocyanate methyl caffeate.

The polyisocyanate component may also be a polyfunctional polyisocyanate compound such as an isocyanurate, biuret, or allophanate derived from the above polyisocyanate monomer, or a polyfunctional polyisocyanate compound having a terminal isocyanate group obtained by reaction with a trifunctional or higher polyol compound such as trimethylolpropane or glycerin.
The polyisocyanate component preferably has a glass transition temperature (Tg) of 50° C. or higher and a number average molecular weight (Mn) of 400 or higher, and more preferably has a glass transition temperature (Tg) of 60° C. or higher and a number average molecular weight (Mn) of 500 or higher.
In the present invention, it is preferable to use xylene diisocyanate among the above isocyanate components.

<Hydrophilic group-containing resin>
Examples of hydrophilic group-containing resins include, but are not limited to, water-dispersible or water-soluble polyester resins, water-dispersible or water-soluble acrylic resins, and water-dispersible or water-soluble polyurethane resins. In the present invention, polyester resins are preferred, and carboxyl group-containing polyester resins are particularly preferred.

The carboxyl group-containing polyester resin can be prepared by combining a carboxylic acid anhydride such as phthalic anhydride, succinic anhydride, maleic anhydride, trimellitic anhydride, itaconic anhydride, or citraconic anhydride with a monomer component typically used in the polymerization of polyester resins.
Examples of such monomer components include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, and naphthalenedicarboxylic acid; aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, and dimer acid; unsaturated dicarboxylic acids such as maleic acid (anhydride), fumaric acid, and terpene-maleic acid adducts; alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, tetrahydrophthalic acid, hexahydroisophthalic acid, and 1,2-cyclohexenedicarboxylic acid; and trivalent or higher polycarboxylic acids such as trimellitic acid (anhydride), pyromellitic acid (anhydride), and methylcyclohexene tricarboxylic acid. One or more of these may be selected and used. In the present invention, from the viewpoint of heat resistance, etc., it is preferable that the proportion of aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, and naphthalenedicarboxylic acid in the polycarboxylic acid components constituting the polyester resin is 50 mol% or more.

The polyhydric alcohol components that make up the polyester resin are not particularly limited and may be ethylene glycol, propylene glycol (1,2-propanediol), 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2-ethyl-2-butyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, 1-methyl-1,8-octanediol, 3-methyl-1,6-hexanediol, 4-methyl-1,7-heptanediol, 4-methyl These polyhydric alcohols may be used singly or in combination of two or more thereof. Examples of suitable polyhydric alcohols include aliphatic glycols such as 1,8-octanediol, 4-propyl-1,8-octanediol, and 1,9-nonanediol; ether glycols such as diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; alicyclic polyalcohols such as 1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, tricyclodecane glycols, and hydrated bisphenols; and trihydric or higher polyalcohols such as trimethylolpropane, trimethylolethane, and pentaerythritol. Among the above polyhydric alcohol components, ethylene glycol, propylene glycol, and neopentyl glycol are preferred for use in the present invention.

Carboxyl group-containing polyester resins can be produced by known methods, such as polycondensing one or more of the above polycarboxylic acid components with one or more of the polyhydric alcohol components; depolymerizing the resulting mixture after polycondensation with a polycarboxylic acid component, such as terephthalic acid, isophthalic acid, trimellitic anhydride, trimellitic acid, or pyromellitic acid; or ring-opening addition of an acid anhydride, such as phthalic anhydride, maleic anhydride, trimellitic anhydride, or ethylene glycol bistrimellitate dianhydride, after polycondensation.

The carboxyl group-containing polyester resin preferably has an acid value of 1 to 80 KOHmg/g, particularly 10 to 30 KOHmg/g, and a glass transition temperature (Tg) of 0 to 120°C, particularly 67 to 80°C.
The carboxyl group-containing polyester resin used may be a blended polyester resin, so long as the acid value and Tg after blending are within the above ranges.
The carboxyl group-containing polyester resin is preferably an amorphous polyester.

<Silane coupling agent>
As the silane coupling agent used in the anchor coat layer, an epoxy-based silane coupling agent can be suitably used.
Examples of such epoxy-based silane coupling agents that can be used include β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, and 3-glycidoxypropyltrimethoxysilane.
Other silane coupling agents include tetramethoxysilane, tetraethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, and 3-isocyanatepropyltriethoxysilane, and can be used as needed.
Furthermore, for the purpose of improving hot water resistance adhesion, the silane coupling agent used may be hydrolyzed as necessary to promote a condensation reaction of the silane coupling agent.

The composition for forming the anchor coat layer may be either water-based or solvent-based, but from the viewpoint of the working environment, it is preferable to use an aqueous composition.
When the above-mentioned polyurethane resin is used in the composition for forming the anchor coat layer, it is preferable that the composition further contains an epoxy-based silane coupling agent. In addition, the polyurethane resin used is preferably a water-soluble or water-dispersible polyurethane.
On the other hand, when the above-mentioned hydrophilic group-containing resin is used in the composition for forming the anchor coat layer, it is desirable that the composition be prepared by containing, among others, a carboxyl group-containing polyester resin and an epoxy-based silane coupling agent.
The epoxy-based silane coupling agent is preferably contained in an amount of 1 to 80 parts by mass per 100 parts by mass of the solid content of the polyurethane-based resin, while it is preferably contained in an amount of 100 to 400 parts by mass, particularly 150 to 300 parts by mass, per 100 parts by mass of the solid content of the carboxyl group-containing polyester resin.
If the amount of epoxy silane coupling agent is less than the above range, the crack resistance when dried cannot be obtained satisfactorily compared with the case where the amount is within the above range. On the other hand, if the amount of epoxy silane coupling agent is more than the above range, it is difficult to further improve the adhesion and crack resistance, and there is a risk that the hot water resistance will be impaired, and furthermore, it will be inferior from the viewpoint of economic efficiency.

The aqueous medium may contain the same conventionally known aqueous medium as that used in the gas barrier layer-forming composition, as well as organic solvents such as alcohols, polyhydric alcohols, and derivatives thereof.
In addition to the above components, the anchor coat layer-forming composition may also contain known curing-accelerating catalysts, fillers, softeners, antioxidants, stabilizers, adhesion promoters, leveling agents, antifoaming agents, plasticizers, inorganic fillers, tackifying resins, fibers, colorants such as pigments, pot life extenders, etc.

The present invention will be further explained using the following examples, but the present invention is not limited in any way by these examples. The various measurement and evaluation methods used in the examples and comparative examples are as follows:

Example 1
[Preparation of coating composition for forming gas barrier coating film]
A gas barrier coating film-forming coating composition (hereinafter referred to as "barrier coat coating") was prepared using zirconium oxide sol (Zirconia sol ZSL-00120B (crystalline zirconium oxide, tetragonal system, solids content ( _ZrO2 equivalent) = 20%) manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.) as the metal oxide. First, the zirconium oxide sol was prepared using water and isopropanol solvent so that the solids content was 5-7% and the water/isopropanol ratio was 60/40. Next, 44.7 parts by mass of aluminum isopropoxide (manufactured by Wako Pure Chemical Industries, Ltd.) as an additive and 53.5 parts by mass of phosphoric acid (manufactured by Wako Pure Chemical Industries, Ltd., concentration = 75%) as a phosphate compound were added per 100 parts by mass of the solids content of the zirconium oxide sol, and the mixture was dispersed using a homogenizer for a predetermined time to obtain a barrier coat coating.

[Method for producing gas barrier laminate]
A gas barrier laminate was produced using the prepared barrier coating paint as follows: The barrier coating paint was applied to a substrate of 25 μm thick biaxially oriented polyester film (E5102, manufactured by Toyobo Co., Ltd.) using a bar coater so that the coating amount was 1.8 to 2.2 g/ ^m2 , and the coating was then dried by heating in a box oven at 200°C for 2 minutes to obtain a gas barrier laminate.

[Method of producing samples for evaluating gas barrier properties, etc.]
A sample for evaluation of gas barrier properties and the like (hereinafter referred to as "evaluation sample") was prepared by applying a urethane adhesive (Takenate A-315/Takenate A- ⁵⁰ manufactured by Mitsui Chemicals, Inc.) in an amount of 4.0 g/m2 to the barrier coat surface of the gas barrier laminate using a bar coater, drying the adhesive using a dryer, and then laminating the 25 μm thick biaxially oriented polyester film. This gave a sample for evaluation of gas barrier properties and the like.

Example 2
A gas barrier laminate and an evaluation sample were obtained in the same manner as in Example 1, except that 47.0 parts by mass of aluminum isopropoxide (manufactured by Wako Pure Chemical Industries, Ltd.) was added as an additive, and phosphoric acid (manufactured by Wako Pure Chemical Industries, Ltd., concentration=75%) was added as a phosphate compound so that the non-volatile content of the phosphoric acid was 56.1 parts by mass relative to 100 parts by mass of the solid content of the zirconium oxide sol.

Example 3
A gas barrier laminate and an evaluation sample were obtained in the same manner as in Example 1, except that 53.7 parts by mass of aluminum isopropoxide (manufactured by Wako Pure Chemical Industries, Ltd.) was added as an additive, and phosphoric acid (manufactured by Wako Pure Chemical Industries, Ltd., concentration=75%) was added as a phosphate compound so that the non-volatile content of the phosphoric acid was 64.2 parts by mass relative to 100 parts by mass of the solid content of the zirconium oxide sol.

Example 4
A gas barrier laminate and an evaluation sample were obtained in the same manner as in Example 1, except that 58.1 parts by mass of aluminum isopropoxide (manufactured by Wako Pure Chemical Industries, Ltd.) was added as an additive, and phosphoric acid (manufactured by Wako Pure Chemical Industries, Ltd., concentration=75%) was added as a phosphate compound so that the non-volatile content of the phosphoric acid was 69.5 parts by mass relative to 100 parts by mass of the solid content of the zirconium oxide sol.

Example 5
A gas barrier laminate and an evaluation sample were obtained in the same manner as in Example 1, except that 67.1 parts by mass of aluminum isopropoxide (manufactured by Wako Pure Chemical Industries, Ltd.) was added as an additive, and phosphoric acid (manufactured by Wako Pure Chemical Industries, Ltd., concentration=75%) was added as a phosphate compound so that the non-volatile content of the phosphoric acid was 80.2 parts by mass relative to 100 parts by mass of the solid content of the zirconium oxide sol.

Example 6
A gas barrier laminate and an evaluation sample were obtained in the same manner as in Example 1, except that 71.5 parts by mass of aluminum isopropoxide (manufactured by Wako Pure Chemical Industries, Ltd.) was added as an additive, and phosphoric acid (manufactured by Wako Pure Chemical Industries, Ltd., concentration=75%) was added as a phosphate compound so that the non-volatile content of the phosphoric acid was 85.5 parts by mass relative to 100 parts by mass of the solid content of the zirconium oxide sol.

Example 7
A gas barrier laminate and an evaluation sample were obtained in the same manner as in Example 1, except that 76.0 parts by mass of aluminum isopropoxide (manufactured by Wako Pure Chemical Industries, Ltd.) was added as an additive, and phosphoric acid (manufactured by Wako Pure Chemical Industries, Ltd., concentration=75%) was added as a phosphate compound so that the non-volatile content of the phosphoric acid was 90.9 parts by mass relative to 100 parts by mass of the solid content of the zirconium oxide sol.

(Example 8)
A gas barrier laminate and an evaluation sample were obtained in the same manner as in Example 1, except that 8.5 parts by mass of aluminum hydroxide (manufactured by Wako Pure Chemical Industries, Ltd.) was added as an additive, and phosphoric acid (manufactured by Wako Pure Chemical Industries, Ltd., concentration=75%) was added as a phosphate compound so that the non-volatile content of the phosphoric acid was 53.5 parts by mass relative to 100 parts by mass of the solid content of the zirconium oxide sol.

(Comparative Example 1)
A gas barrier laminate and an evaluation sample were obtained in the same manner as in Example 1, except that 40.3 parts by mass of aluminum isopropoxide (manufactured by Wako Pure Chemical Industries, Ltd.) was added as an additive, and phosphoric acid (manufactured by Wako Pure Chemical Industries, Ltd., concentration=75%) was added as a phosphate compound so that the non-volatile content of the phosphoric acid was 48.1 parts by mass, relative to 100 parts by mass of the solid content of the zirconium oxide sol.

(Comparative Example 2)
A gas barrier laminate and an evaluation sample were obtained in the same manner as in Example 1, except that the dispersion treatment using a rotary blade was carried out for a predetermined period of time.

(Comparative Example 3)
A gas barrier laminate and an evaluation sample were obtained in the same manner as in Example 1, except that 80.5 parts by mass of aluminum isopropoxide (manufactured by Wako Pure Chemical Industries, Ltd.) was added as an additive, and phosphoric acid (manufactured by Wako Pure Chemical Industries, Ltd., concentration=75%) was added as a phosphate compound so that the non-volatile content of the phosphoric acid was 96.2 parts by mass relative to 100 parts by mass of the solid content of the zirconium oxide sol.

(Evaluation method)
The gas barrier laminates and evaluation samples were evaluated using the following evaluation methods, as shown in Tables 1 and 2.

[Oxygen permeability]
The evaluation samples obtained in the examples and comparative examples were measured using an oxygen permeability measuring device (OX-TRAN2/21 manufactured by Modern Control) under the measurement conditions of a temperature of 40°C and a relative humidity of 90%.

[Water vapor permeability]
The gas barrier property evaluation samples obtained in the Examples and Comparative Examples were measured using a water vapor transmission rate measuring device (MODERN CONTROL PERMATRAN-W3/34, TECHNOLOX Deltaperm-UH, and SEMPA HiBarSens 2.0) at a temperature of 40°C and a relative humidity of 90%.

[Infrared absorption spectrum]
For each of the gas barrier laminates obtained in the Examples and Comparative Examples, the infrared absorption spectrum of the gas barrier coating film applied to the polyester substrate was measured using a Fourier transform infrared spectrophotometer (FT/IR-6600, manufactured by JASCO Corporation).
<Measurement conditions for FT-IR device>
Equipment used: JASCO FT/IR-6600
Measurement conditions: Method: ATR (Ge prism)
Detector MCT
Attachment Thunder Dome
Wavenumber range: 800 to 4000 cm ^-1
Film measurement surface Barrier coating surface

[Optical properties]
For each of the gas barrier laminates obtained in the examples and comparative examples, the total light transmittance (%), haze (%) and gloss were measured using a haze meter (NDH8000 manufactured by Nippon Denshoku Industries Co., Ltd.) and a gloss meter (VG8000 manufactured by Nippon Denshoku Industries Co., Ltd.) with the polyester film substrate side as the detector side for measurement.

[X-ray fluorescence evaluation]
As a method for evaluating the elements contained in each gas barrier laminate obtained in the Examples and Comparative Examples, the phosphorus, aluminum, and zirconium elements can be quantified using a commercially available X-ray fluorescence analyzer. The net strength obtained by measuring each gas barrier laminate was converted into P/Zr for P and Zr, and into Al/Zr for Al and Zr, to calculate the content ratio of each element in the coating film, which was used for evaluation.
<Measurement conditions for fluorescent X-ray analyzer>
Equipment used: Rigaku Corporation ZSX Primus IV
Measurement conditions: Measurement target P-Kα line, Al-Kα line,
Zr-Kα wire measurement diameter 10mm
Measurement X-ray Rh (4.0 kW)
Film measurement surface: Measurement is performed by irradiating X-rays from the barrier coating surface side

[viscosity]
The viscosity of each barrier coating material obtained in the examples and comparative examples was measured using a Brookfield DV2T type viscometer (manufactured by EKO Seiko Co., Ltd.) under the following measurement conditions: temperature 25°C, spindle SC4-18, chamber 13R, and rotation speeds of 50 rpm and 200 rpm.

The various measurements and evaluation results for the above examples and comparative examples are shown in Tables 1 and 2.

[Abbreviations in Tables 1 and 2]
NV: solid content of metal oxide in metal oxide sol, ZSL-00120B: crystalline zirconium oxide, TT: total light transmittance, Hz: haze, Gs (60°): gloss at an angle of 60°, P/Zr: content ratio of phosphorus element (P) derived from the phosphate compound to zirconium element (Zr) in the metal oxide in the gas barrier laminate, Al/Zr: content ratio of aluminum element (Al) derived from the additive to zirconium element (Zr) in the metal oxide in the gas barrier laminate.

The coating composition for forming a gas barrier coating film of the present invention is capable of forming a coating film that has excellent oxygen barrier properties and water vapor barrier properties, and can be suitably used as a transparent high-barrier packaging material.
Furthermore, because the gas barrier laminate has particularly excellent water vapor barrier properties, its uses include, but are not limited to, food packaging containers, packaging materials for retort pouches, pharmaceutical packaging materials, deposition substrates, electronic devices, circuit board materials, semiconductor materials, solar cell components, organic EL light-emitting element components, organic EL lighting components, electronic paper, and battery exteriors.

REFERENCE SIGNS LIST 1 substrate, 2 anchor coat layer, 3 gas barrier layer, 4 adhesive layer, 5 resin layer

Claims (16)

A gas barrier laminate having a gas barrier coating film on a substrate,
the coating film comprises a reaction product obtained by reacting at least one of a metal alkoxide, a hydrolyzate of a metal alkoxide, and a metal hydroxide, zirconium oxide, and a phosphate compound or a sulfate compound;
the coating film has a Zr (Zr-Kα) to P (P-Kα) content ratio (P/Zr) in a range of 1.39 to 2.59 as measured by fluorescent X-rays;
The gas barrier laminate is characterized in that the ratio (P2/P1) of the peak area (P2) from 2600 to 3700 cm ⁻¹ to the peak area (P1) from 850 to 1350 cm ⁻¹ in the infrared absorption spectrum of the coating film is less than 0.772. 2. The gas barrier laminate according to claim 1, wherein the gas barrier laminate has a haze of less than 9.0%, and the gas barrier laminate has a biaxially oriented polyethylene terephthalate film having a thickness of 25 μm as a substrate and the coating film formed on the substrate in a coating amount of 1.8 to 2.2 g/ ^m2 . The gas barrier laminate according to claim 1 or 2, wherein the metal species of the metal alkoxide, metal alkoxide hydrolysate, or metal hydroxide is aluminum, and the Zr (Zr-Kα) to Al (Al-Kα) content ratio (Al/Zr) of the coating film measured by fluorescent X-ray analysis is in the range of 0.15 to 0.58. 3. The gas barrier laminate according to claim 1, wherein the coating film has an infrared absorption peak in the range of 1000 to 1120 cm ⁻¹ in an infrared absorption spectrum. 3. The gas barrier laminate according to claim 1 or ² , which has a biaxially oriented polyethylene terephthalate film of 25 μm in thickness as a substrate, and a biaxially oriented polyethylene terephthalate film of 25 μm in thickness laminated via an adhesive layer on the coating film formed on the substrate in a coating amount of 1.8 to 2.2 g/m2, and has a water vapor permeability of less than 0.100 g/ ^m2 day (40°C, 90% RH). A deposition substrate comprising the gas barrier laminate of claim 1 or 2. A coating composition for forming a gas barrier coating film, comprising a metal alkoxide, a hydrolyzate of a metal alkoxide, at least one metal hydroxide, a metal oxide, and a phosphoric acid compound or a sulfate compound, wherein the coating composition for forming a gas barrier coating film, when dispersed in water/isopropanol (60/40) with a solids content of 5 to 7% by mass, has a viscosity ratio (A/B) of less than 3.6, measured at 25°C using a Brookfield viscometer, where the viscosity (A) is at a spindle rotation speed of 50 rpm and the viscosity (B) is at a spindle rotation speed of 200 rpm. The coating composition for forming a gas barrier coating according to claim 7, wherein the viscosity of the coating composition for forming a gas barrier coating when dispersed in water/isopropanol (60/40) with a solids content of 5 to 7% by mass is less than 113.9 mPa·sec, measured at a temperature of 25°C using a Brookfield viscometer at a spindle rotation speed of 50 rpm. The coating composition for forming a gas barrier coating film according to claim 7 or 8, wherein the metal species of the metal alkoxide or metal hydroxide is at least one of aluminum, titanium, iron, and zirconium. The coating composition for forming a gas barrier coating film according to claim 7 or 8, wherein the metal alkoxide is at least one of methoxide, ethoxide, propoxide, isopropoxide, butoxide, isobutoxide, sec-butoxide, and tert-butoxide. The coating composition for forming a gas barrier coating film according to claim 7 or 8, wherein the metal alkoxide is aluminum isopropoxide. The coating composition for forming a gas barrier coating film according to claim 7 or 8, wherein the metal hydroxide is aluminum hydroxide. The coating composition for forming a gas barrier coating film according to claim 7 or 8, wherein the metal oxide is zirconium oxide or aluminum oxide. The coating composition for forming a gas barrier coating film according to claim 7 or 8, wherein the metal oxide is crystalline zirconium oxide. The coating composition for forming a gas barrier coating film according to claim 7 or 8, wherein the phosphoric acid compound is at least one of orthophosphoric acid, metaphosphoric acid, polyphosphoric acid, and cyclic polyphosphoric acid. 8. A method for producing a coating composition for forming a gas barrier coating film according to claim 7, comprising mixing a metal alkoxide, a hydrolysate of a metal alkoxide, at least one metal hydroxide, a metal oxide, and a phosphoric acid compound or a sulfate compound, and then stirring the mixture so that the viscosity measured at a temperature of 25°C using a Brookfield viscometer at a spindle rotation speed of 50 rpm is less than 113.9 mPa sec.