JP7279363B2 - gas barrier film and packaging film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a gas barrier film, and more particularly to a gas barrier film having high resistance to hot water and pinholes and excellent lamination properties, and a packaging film using the same.

BACKGROUND ART Packaging materials using various plastic films, metal foils, paper, and the like have been developed for packaging foods, pharmaceuticals, and the like, which are highly airtight and prevent deterioration of the contents due to moisture and oxygen. In particular, retort packaging and boiling packaging, which are subjected to heat sterilization treatment such as retorting and boiling, are generally used as packaging forms that can be stored for a long period of time in food and pharmaceutical applications.

Properties required for retort and boil packaging materials include various gas barrier properties, hot water resistance, aroma retention, discoloration resistance, impact resistance, pressure resistance, puncture resistance, and bending resistance. A lamination configuration suitable for the object is designed.

As an example, a biaxially oriented polyethylene terephthalate (PET) film is used as a base material in order to impart hot water resistance, fragrance retention, printability, etc., and a water-soluble polymer is placed on the vapor deposition layer as a gas barrier layer, and one type of (I) is used. A gas barrier coating layer formed by applying a coating agent mainly composed of the above metal alkoxide or metal alkoxide hydrolyzate, (II) an aqueous solution containing tin chloride, or a water-alcohol mixed solution, and heating and drying the second layer. (Patent Document 1).

In order to impart impact resistance, pressure resistance, and pierce resistance to the boil/retort packaging material, a typical structure is that a nylon film and a sealant film are laminated on this gas barrier film via an adhesive. It has been put into practical use, and in this case, it is necessary to make it multilayered to three or more layers.

In addition, a gas barrier film produced using a sol-gel method, such as the gas barrier coating layer, generally has the property of curling due to dehydration condensation in the gas barrier coating layer when heat above a certain temperature is applied. Therefore, when heat treatment is applied in the dry lamination process, the film may warp toward the gas barrier coating surface, making it difficult to process more stably than with ordinary films.

Japanese Patent No. 2790054

As described above, both a PET film and an ONY (biaxially oriented nylon) film are generally used together as a packaging material for heat treatment, particularly retort treatment. This is because the PET film has the advantage of high hot water resistance, but has the disadvantage of low puncture resistance, and the ONY film has the advantage of high puncture resistance, but has the disadvantage of low hot water resistance. It is for complementing and using.
However, since both PET and ONY are used, the number of lamination steps increases, and there is concern about the impact on the environment, and there is a demand for improvement in terms of cost. It is also required that the gas barrier film produced by using the sol-gel method as the gas barrier coating layer has stable workability.

The present invention has been made in view of the above circumstances. To provide a gas barrier film exhibiting excellent gas barrier properties even when a material film is subjected to hot water treatment such as retort treatment, and having good suitability for dry lamination, and to provide a packaging film using the same. .

In a first aspect of the present invention, on a film substrate containing a polyester resin having a butylene terephthalate unit as a main structural unit,
an adhesion layer containing an anchor coating agent that is a polyester-based polyurethane resin;
A gas barrier film obtained by laminating at least a deposited layer containing silicon oxide and a gas barrier coating layer comprising a composition containing at least one of a water-soluble polymer and a metal alkoxide or a hydrolyzate thereof, wherein the gas barrier film comprises: In the gas barrier film, the tension applied to the film is set to 40 N/m, and the warp angle of the film edge after heating at temperatures of 70 ° C. and 100 ° C. for 1 minute is 0 ° or more and 60 ° or less toward the film substrate side. Yes,
The gas barrier film is characterized in that the vapor deposition layer containing silicon oxide has a thickness of 10 nm or more and 50 nm or less, and the gas barrier coating layer has a thickness of 100 nm or more and 1000 nm or less.

The second invention is
The gas barrier film is characterized in that the vapor deposition layer containing silicon oxide has a thickness of 10 nm or more and 50 nm or less, and the gas barrier coating layer has a thickness of 100 nm or more and 1000 nm or less.

The third invention is
A packaging film comprising the above gas barrier film.

The gas barrier film according to the present invention has high hot water resistance and pinhole resistance against physical impact, and can maintain excellent gas barrier properties even when subjected to retort treatment, boiling treatment, cooking, etc., and can be used in a dry lamination process. A gas barrier film having excellent processability was also made possible.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic cross-sectional view showing one aspect of a gas barrier film having excellent gas barrier properties according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic diagram which showed the one aspect|mode of the packaging film using the gas barrier film which concerns on this invention.

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic cross-sectional view of the gas barrier film according to this embodiment. In the gas barrier film 10 shown in FIG. 1, an adhesion layer 2, an inorganic deposition layer 3, and a gas barrier coating layer 4 are sequentially laminated on a base film 1. As shown in FIG. Each of these layers will be described in turn below.

(Base film)
The base film 1 contains a polyester resin having butylene terephthalate (PBT) units as main structural units.

Here, the polyester resin having a butylene terephthalate unit as a main structural unit means that 60% by mass or more of the repeating units formed by bonding the dicarboxylic acid component and the glycol component of the resin are composed of butylene terephthalate units. there is

The polyester resin contained in the base film 1 is preferably a resin containing 60% by mass or more of polybutylene terephthalate, or a mixed resin of polybutylene terephthalate and polyethylene terephthalate. If the polybutylene terephthalate is less than 60% by mass, the impact strength and pinhole resistance are lowered, and the film properties are not sufficient. Further, the base film 1 may be biaxially stretched or uniaxially stretched, but biaxial stretching is more preferable in order to impart thermal stability.

Further, by using a polyester resin which is a mixed material of polybutylene terephthalate and polyethylene terephthalate, puncture resistance is also improved. For example, according to Japanese Unexamined Patent Application Publication No. 2002-179892, although it is a blend film of a polyester resin mainly composed of polyethylene terephthalate (PET) and a polyester resin mainly composed of polybutylene terephthalate (PBT), the PET phase and the PBT phase are independent. It is said that by having crystals, it is possible to obtain a polyester film that has both hot water resistance and flexibility, so that it has high puncture strength.

In order to obtain the independent crystals, it is necessary to melt them individually when producing the polyester film, which can be confirmed by individually detecting crystal melting peaks with a differential scanning calorimeter (DSC). can. A crystal peak of the PBT phase appears on the low temperature side, followed by a crystal peak of the PET phase. By using these two polyester resins, PET and PBT, the advantages of the PET phase and the PBT phase can be utilized because individual crystal melting occurs while ensuring compatibility to the extent that the glass transition fuses.

The thickness of the base film 1 is not particularly limited. Although the piercing strength improves as the thickness increases, a thickness of about 6 μm to 200 μm can be suitably used depending on the application. The base film 1 may be subjected to various pretreatments such as corona treatment, plasma treatment and flame treatment, or may be provided with an anchor coat layer such as an easy adhesion layer. In addition, a flattening layer may be separately provided to reduce unevenness of the base film 1 .

(Adhesion layer)
The adhesion layer 2 is provided on the base film 1 made of the polyester resin, and improves the adhesion performance between the base film 1 and the vapor deposition layer 3, and smoothes the plane to make the vapor deposition layer in the next process uniform without defects. It is a layer intended to obtain two effects of forming a film and exhibiting high barrier properties, and is a layer containing an anchor coating agent.

Examples of such adhesive layer 2 include polyester-based polyurethane resins and polyether-based polyurethane resins. Among these anchor coating agents, polyester-based polyurethane resins are preferable from the viewpoint of heat resistance and interlayer adhesive strength.

The thickness of the adhesive layer 2 is not particularly limited, but the thickness is preferably in the range of 0.01 to 5 μm, more preferably in the range of 0.03 to 3 μm, and more preferably 0.05 μm. A range of ~2 μm is particularly preferred. If the thickness of the adhesion layer 2 is less than the lower limit, the interlayer adhesive strength tends to be insufficient, while if it exceeds the upper limit, the desired gas barrier properties tend not to be exhibited.

In addition, as a method for coating the adhesion layer 2 on the base film 1, known coating methods can be used without particular limitation, such as immersion method (dipping method); spray, coater, printer, brush, etc. A method using The types of coaters and printing machines used in these methods and their coating methods include gravure coaters such as direct gravure, reverse gravure, kiss reverse gravure, and offset gravure, reverse roll coaters, and micro gravure. A coater, a coater combined with a chamber doctor, an air knife coater, a dip coater, a bar coater, a comma coater, a die coater and the like can be used.

Further, the coating amount of the adhesion layer 2 is preferably 0.01 to 5 g/m ² , and preferably 0.03 to 5 g/m ² , after the anchor coating agent is applied and dried. More preferably 3 g/m ² . If the mass per 1 m ² after coating and drying the anchor coating agent is less than the lower limit, film formation tends to be insufficient, while if it exceeds the upper limit, drying will be insufficient and the solvent will remain. tends to be easier.

In addition, the method for drying such an adhesion layer 2 is not particularly limited, but a method by natural drying, a method of drying in an oven set to a predetermined temperature, a dryer attached to the coater, such as an arch dryer, A method using a floating dryer, a drum dryer, an infrared dryer, or the like can be mentioned. Further, 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.

Coating agents for the anchor coat layer and the flattening layer include, for example, acrylic resins, epoxy resins, acrylic urethane resins, polyester polyurethane resins, and polyether polyurethane resins. Among these coating agents, acrylic urethane resins and polyester polyurethane resins are preferable from the viewpoint of heat resistance and interlayer adhesive strength.

(evaporation layer)
The vapor-deposited layer 3 made of an inorganic oxide used in the gas barrier film 10 of the present invention may be a metal oxide represented by SiOx, AlOx, or a mixture thereof, but in particular should be silicon oxide.

When the gas barrier film of the present invention is used in the next process such as printing or lamination, the gas barrier film layer 4 produced by the sol-gel method described later undergoes dehydration condensation due to heating, and stress is generated. There are concerns that the film may warp on the side of the gas-barrier coating layer, resulting in poor winding appearance in the printing process, and in the lamination process, the film may overlap the laminate surface, making processing impossible. On the other hand, the deposited layer 3 containing silicon oxide generates stress on the side of the PBT substrate layer opposite to the gas barrier coating layer 4, so that the warpage of the film when the gas barrier coating layer 4 is heated is reduced. Therefore, the deposition layer 3 is preferably made of silicon oxide.

The O/Si atomic ratio of silicon oxide is desirably 1.7 or more. If it is less than 1.7, the amount of metallic Si is large and the transparency is impaired. Also, the O/Si atomic ratio must be 2.0 or less. If it is 2.0 or more, the crystallinity of SiO becomes high, the deposited film becomes hard, and the tensile resistance is poor, so that cracks occur when laminating the gas barrier coating layer in the next step.

The O/Si atomic ratio measurement method of the deposited film is determined by X-ray photoelectron spectroscopy (XPS). The measuring device is, for example, an X-ray photoelectron spectrometer (manufactured by JEOL Ltd., JPS-90MXV). Measured at line power. Quantitative analysis to determine the O/Si atomic ratio is performed using relative sensitivity factors of 2.28 for O1s and 0.9 for Si2p, respectively.

The film thickness of the vapor deposition layer 3 is preferably 10 nm or more and 50 nm or less. If the film thickness is less than 10 nm, the stress on the film substrate side is smaller than the stress on the gas barrier coating layer after heating, so that the film warps toward the gas barrier coating layer side. Furthermore, sufficient water vapor barrier properties cannot be obtained. On the other hand, if the thickness is larger than 50 nm, cracks may occur due to deformation due to internal stress of the thin film, and the water vapor barrier property may deteriorate. Furthermore, the cost increases due to an increase in the amount of material used and a longer film forming time, which is not preferable from an economic point of view.

The deposition layer 3 must be formed by vacuum deposition. A physical vapor deposition method or a chemical vapor deposition method can be used in vacuum deposition. Examples of the physical vapor deposition method include a vacuum deposition method, a sputtering method, an ion plating method, and the like, but are not limited to these. Examples of chemical vapor deposition methods include thermal CVD, plasma CVD, and optical CVD, but are not limited to these.

In the vacuum film formation, a resistance heating vacuum deposition method, an EB (Electron Beam) heating vacuum deposition method, an induction heating vacuum deposition method, a sputtering method, a reactive sputtering method, a dual magnetron sputtering method, and a plasma chemical vapor deposition method. (PECVD method) and the like are particularly preferably used. However, considering the productivity, the vacuum deposition method is the best at present. As a heating means for the vacuum evaporation method, it is preferable to use any one of an electron beam heating method, a resistance heating method, and an induction heating method.

(Gas barrier coating layer)
The gas barrier film layer 4 is a transparent film formed on the vapor deposition layer 3, and is made of a mixture containing a transparent resin and an inorganic substance such as an inorganic oxide. By providing the gas barrier coating layer 4, a transparent gas barrier film 10 having higher gas barrier properties can be obtained.
The gas-barrier film layer 4 is formed, for example, on the vapor-deposited layer 3 containing silicon oxide, and is mainly composed of an aqueous solution or a water/alcohol mixed solution containing a water-soluble polymer and one or more metal alkoxides or hydrolysis products thereof. It can be obtained by applying and drying a coating liquid.

Examples of water-soluble polymers that can be used include polyvinyl alcohol (PVA), polyvinylpyrrolidone, starch, methylcellulose, carboxymethylcellulose, sodium alginate, or mixtures thereof. In particular, when PVA is used, the gas barrier coating layer 4 having the most excellent gas barrier properties can be formed. The PVA referred to here is typically obtained by saponifying polyvinyl acetate.

As this PVA, various saponified PVA can be used, from partially saponified PVA in which several tens of percent of acetyl groups remain to complete PVA in which only several percent of acetyl groups remain.
There is no limit to the molecular weight of PVA, and for example, PVA with a degree of polymerization in the range of 300 to several thousand can be used. In general, high-molecular-weight PVA having a high degree of saponification and a high degree of polymerization can provide excellent water resistance.

A metal alkoxide is a compound represented by the general formula M(OR)n. Here, M represents a metal such as Ti, Al, Zr or Si, and R represents _an alkyl group such as _CH3 group, _C2H5 group. Also, n indicates the valence of the element M.
Examples of metal alkoxides include tetraethoxysilane [Si(OC ₂ H ₅ ) ₄
], triisopropoxyaluminum [Al(O-2′-C ₃ H ₇ ) ₃ ], among others, tetraethoxysilane and triisopropoxyaluminum are relatively stable in a solution containing water after hydrolysis. can exist in

When alkoxysilane is used as the metal alkoxide, the alkoxysilane can be, for example, a compound represented by Si(OR ¹ ) ₄ or R ² Si(OR ³ ) ₃ or a mixture thereof.
Here, R ¹ and R ³ represent hydrolyzable groups such as CH ₃ group, C ₂ H ₅ group and C ₂ H ₄ OCH ₃ group, and R ² represents an organic functional group.

Since the metal oxide film obtained by hydrolyzing and condensing the metal alkoxide is hard, cracks are likely to occur due to strain due to external force or volume reduction during condensation. Therefore, it is very difficult to form this metal oxide film with a uniform thickness without causing cracks or the like.

On the other hand, a film formed using a coating liquid containing a polymer, a metal alkoxide and/or its hydrolyzate, and water is more flexible than a metal oxide film, and therefore cracks do not occur. It's hard. However, in this film, the metal oxide is not uniformly dispersed microscopically, and high gas barrier properties may not be obtained.

When a water-soluble polymer is used as this polymer, the strong hydrogen bond between the hydroxyl group of the polymer and the hydroxyl group of the hydrolyzate of the metal alkoxide is used to convert the metal oxide into the polymer during condensation. can be evenly distributed in the Therefore, a gas barrier property close to that of a metal oxide film can be achieved. Therefore, when such a gas-barrier film layer 4 is formed on the vapor-deposited layer 3, it is possible to achieve much higher gas-barrier properties than when they are used alone.

However, the gas barrier coating layer 4 obtained using the coating liquid containing the metal alkoxide and/or its hydrolysis product, the water-soluble polymer having a hydroxyl group, and water forms hydrogen bonds. When used in harsh environments, water intrusion can cause swelling and eventual dissolution. Therefore, even if this gas barrier laminate 10 achieves a high gas barrier property by laminating the vapor deposition layer 3 and the gas barrier film layer 4, under severe conditions such as a high temperature and high humidity environment, adhesion is not possible. properties and gas barrier properties may easily deteriorate.

On the other hand, if an alkoxysilane represented by, for example, R ² Si(OR ³ ) ₃ is used as the metal alkoxide, the gas-barrier film layer 4 is resistant to swelling even when water penetrates and is excellent in water resistance. be able to. Especially when the organic functional group ^R2 is a water-insoluble functional group such as vinyl group, epoxy group, methacryloxy group, ureido group and isocyanate group, higher water resistance can be achieved. When the organic functional group ^R2 is vinyl or methacryloxy, ionizing radiation such as ultraviolet rays or electron beams is applied during the manufacturing process. Water and a catalyst (acid or alkali) are generally used as reaction accelerators for hydrolysis of metal alkoxide.

In addition, when a tetraalkoxysilane represented by Si(OR ¹ ) ₄ is used as the metal alkoxide, for example, it is difficult to swell even when water penetrates, and the gas barrier coating has excellent water resistance and extremely high barrier properties. Layer 4 can be obtained. In particular, when the hydrolyzable group R ¹ is a CH ₃ group or a C ₂ H ₅ group, higher water resistance and excellent barrier properties can be achieved. Water and a catalyst (acid or alkali) are generally used as reaction accelerators for hydrolysis of metal alkoxide.

When two kinds of metal alkoxides, namely, a tetraalkoxysilane represented by the general formula Si(OR ¹ ) ₄ and a trialkoxysilane represented by the general formula R ² Si(OR ³ ) ₃ are used, these alkoxysilanes _The ^ratio _{is ,} ^{for example} _, ^{R 2 _} _{_} ^_ The ratio of Si(OH) ₃ equivalent mass may be set to be within the range of 1% to 50%. If this ratio is less than 1%, the water resistance will be low, and if it exceeds 50%, the organic functional group ^R2 will become pores in the gas barrier and the gas barrier properties will be reduced.

The mixing ratio of the tetraalkoxysilane represented by the general formula Si(OR ¹ ) ₄ and the trialkoxysilane represented by the general formula R ² Si(OR ³ ) ₃ is 5% to 30%. It may be set to be within the range. In this case, the liquid content or water-containing content can be sterilized by boiling or pressurized/heat sterilized, and water resistance and high barrier properties sufficient for long-term storage in a hot and humid environment can be achieved.

Among the alkoxysilanes represented by the general formula Si(OR ¹ ) ₄ , tetraethoxysilane is a hydrolysis product that can exist relatively stably in an aqueous solvent. is relatively easy.

An alkoxysilane represented by the general formula Si(OR ¹ ) ₄ , an alkoxysilane represented by the general formula R ² Si(OR ³ ) ₃ , and a water-soluble The polymers can be mixed in any order. For example, alkoxysilanes represented by the general formula Si(OR ¹ ) ₄ and alkoxysilanes represented by the general formula R ² Si(OR ³ ) ₃ are separately hydrolyzed, and then They may be added in solution. This method is excellent in terms of dispersibility of silicon oxide and efficiency of hydrolysis.

For the coating liquid for forming the gas barrier coating layer 4, consideration is given to improving the wettability and adhesion of the gas barrier coating layer 4 to ink or adhesives, and preventing cracks from occurring due to contraction of the gas barrier coating 4. Then, the additive may be added. Examples of such additives include isocyanate compounds, colloidal silica, clay minerals such as smectites, stabilizers, colorants, rheology modifiers, and mixtures thereof.

If the thickness of the gas barrier coating layer 4 is small, it is difficult to form the gas barrier coating layer 4 as a uniform continuous film, and sufficient gas barrier properties cannot be obtained. When the thickness is large, cracks are likely to occur in the film. The thickness of gas barrier coating layer 4 is, for example, within the range of 100 nm to 5000 nm.

Furthermore, the thicker the gas barrier coating layer, the more likely the film is to warp toward the gas barrier coating layer due to dehydration condensation during heating. In order to prevent this warping during heating, the inventors conducted extensive studies and found that the thickness of the gas barrier coating layer 4 laminated on the deposited layer containing silicon oxide and having a thickness of 10 nm or more and 50 nm or less should be 100 nm or more and 1000 nm or less. Preferably.
If the film thickness is 1000 nm or more, the stress applied to the coating surface side of the gas barrier coating layer becomes dominant over the stress applied to the film substrate side of the vapor deposition layer, and processing problems may occur during dry lamination, which is not preferable.

The coating liquid for forming the gas barrier coating layer 4 is, for example, a dipping method, a roll coating method, a gravure coating method, a reverse gravure coating method, an air knife coating method, a comma coating method, a die coating method, a screen printing method, and a spray coating method. , gravure offset method, or the like. A coating film obtained by applying this coating liquid can be dried by, for example, a hot air drying method, a hot roll drying method, a high frequency irradiation method, an infrared irradiation method, a UV irradiation method, or a combination thereof.

(packaging film)
FIG. 2 is a schematic cross-sectional view of the packaging film according to this embodiment. In the packaging film 100 shown in FIG. 2, a print layer 20, an adhesive layer 30, and a sealant film 40 are sequentially laminated on the gas barrier film layer of the gas barrier film 10. As shown in FIG. The present invention is not limited to the following embodiments, and functional layers other than these may be added.

(Print layer)
A printed layer 20 can be provided on the gas barrier film layer side of the gas barrier film 10 . Printing is provided on the layer visible from the outside of the packaging film for the purpose of displaying information about the contents, identifying the contents, or improving the design. Although there are no particular restrictions on the printing method and printing ink, any known printing method may be selected as appropriate considering printability on film, design properties such as color tone, adhesion, safety as a food container, etc. For example, gravure printing, offset printing, gravure offset printing, flexographic printing, inkjet printing, etc. can be used. Among them, the gravure printing method can be preferably used in terms of productivity and high definition of the pattern.

Furthermore, in order to increase the adhesion between the gas barrier coating layer and the ink, various pretreatments such as corona treatment, plasma treatment and flame treatment, and a coating layer such as an easy adhesion layer may be provided on the gas barrier coating layer. I do not care.

(adhesive layer)
A sealant film 40 can be laminated via the adhesive layer 30 . Examples of adhesive materials that can be used include polyester-isocyanate resins, urethane resins, polyether resins, and the like. For use in retort applications, a two-liquid curable urethane-based adhesive that is resistant to retort can be preferably used.

(sealant film)
Among thermoplastic resins, polyolefin resins are generally used as the material of the sealant film 40. Specifically, low-density polyethylene resin (LDPE), medium-density polyethylene resin (MDPE), linear low-density polyethylene Resin (LLDPE), ethylene-based resin such as ethylene-vinyl acetate copolymer (EVA), ethylene-α-olefin copolymer, ethylene-methacrylic acid resin copolymer, blended resin of polyethylene and polybutene, homopolypropylene Polypropylene resins such as resins (PP), propylene-ethylene random copolymers, propylene-ethylene block copolymers, and propylene-α-olefin copolymers can be used. It can be selected as appropriate depending on the temperature conditions.

The thickness of the sealant film 40 is determined according to the weight of the contents, the shape of the packaging bag, etc., but a thickness of approximately 30 to 150 μm is preferable.

As a method for forming the sealant layer, a dry lamination method in which a film made of the above resin is laminated with a one-component curing type or two-component curing type urethane adhesive, or a non-solvent bonding method using a non-solvent adhesive. A dry lamination method, an extrusion lamination method in which the above-mentioned resin is heated and melted, extruded in a curtain shape, and laminated together can be formed by a known lamination method.

(dry lamination processing)
The dry lamination method is preferable for retort treatment, particularly high-temperature hot water treatment at 120° C. or higher.
In dry lamination, the film is heated in an oven while being tensioned. The heating temperature is generally in the range of 60° C. to 100° C., although it depends on the processing speed, and the processing temperature is set while checking the amount of residual solvent and the degree of shrinkage of the film. Moreover, the tension when processing the gas barrier film is preferably in the range of 10 N/m to 70 N/m. If the tension is higher than 70 N/m, the barrier layer may crack and deteriorate, which is not preferable.

It is most preferable that the edges of the gas barrier film used in dry lamination do not warp when heated. It is preferable to warp at an angle of 60° or more, and within this range, it is possible to suppress the warpage of the film edges by means of guide rolls. On the other hand, when the film edge warps toward the gas barrier coating layer, the warping cannot be suppressed by the guide rolls, which may cause problems in processing.

Examples of heat sterilization methods for packaging films include retort treatment and boiling treatment. Retort processing is a method of autoclave sterilization of microorganisms such as molds, yeasts and bacteria, generally for the purpose of preserving food and the like. Usually, the gas barrier laminate packaging material containing food is autoclaved at 105 to 140° C. and 0.15 to 0.30 MPa for 10 to 120 minutes.

There are two types of retort equipment: a steam type using heated steam and a hot water type using pressurized heated water. Boiling treatment is a wet heat sterilization method for preserving foods and the like.

Usually, depending on the contents, the gas barrier laminate packaging material packed with food or the like is subjected to moist heat sterilization at 60 to 100° C. under atmospheric pressure for 10 to 120 minutes. Boiling treatment is usually carried out using a hot water bath, but there are two types: a batch type in which the water is immersed in a hot water bath at a constant temperature and taken out after a certain period of time, and a continuous type in which the hot water is sterilized through a tunnel.

Examples and comparative examples according to the present invention are shown below.

First, the coating solution 1 for the adhesion layer was prepared by the following procedure.

Coating liquid 1:
Adhesive solution (polyester-based polyurethane resin) manufactured by Mitsui Chemicals, Inc.
(Main agent: Takelac A-525 (50% by mass of urethane resin precursor, 50% by mass of ethyl acetate) / Curing agent: Takenate A-52 (55% by mass of urethane resin curing agent, 45% by mass of ethyl acetate) / solvent: ethyl acetate)
These were blended with A-525:A-52:ethyl acetate=9:1:165 (solid content concentration 3% by mass).

Next, the coating liquid 2 for the gas barrier coating layer was prepared by the following procedure.

Coating liquid 2:
(a) Tetraethoxysilane (Si( _{OC2H5 ) 4} ; hereinafter abbreviated as TEOS) 17.9
72.1 g of 0.1N hydrochloric acid was added to g and 10 g of methanol, and the mixture was stirred for 30 minutes to hydrolyze the hydrolyzed solution with a solid content of 5% (in terms of weight ratio of SiO ₂ ).
(b) A 5% (weight ratio) solution of polyvinyl alcohol (hereinafter abbreviated as PVA) in water/methanol = 95/5 (weight ratio).
(c) 1,3,5-tris(3-trialkoxysilylalkyl)isocyanurate was added to a water/isopropyl alcohol = 1/1 solution to a solid content of 5% (weight ratio converted to R ² Si(OH) ₃ ). Prepared hydrolysis solution.
The mixing ratio of the above solutions (a) to (c) is mixed so that a solution / b solution / c solution = 70/20/10 (solid content weight ratio), and coating solution 2 used in Example 1 got

Examples and comparative examples are shown below.

(Example 1)
A mixed resin containing PBT and PET as the main material was formed into a film by a casting method, then biaxially stretched in the MD and TD directions while being heated, and then heat-set to obtain a biaxially stretched PBT film having a thickness of 15 μm. . One side of this biaxially stretched film was subjected to a corona treatment, and the treated side was coated with the coating liquid 1 by a gravure roll coating method, and 0.1 g/m ² of a polyester polyurethane resin was cured.
Next, a vapor deposition layer of silicon oxide having a thickness of 20 nm was formed using a vacuum vapor deposition apparatus using an electron beam heating system. Further, the coating solution 2 was applied by gravure roll coating, heated and dried in an oven, and a 300 nm gas barrier coating layer was laminated to prepare a gas barrier film of the present invention.

<Silica vapor deposition>
In forming the vapor deposition layer, the vapor deposition material type was changed, and a vapor deposition film having an O/Si atomic ratio of 1.8 was formed. In order to deposit this silica deposition film, the conditions were obtained by varying the types of deposition materials and deposition conditions in advance. The O/Si atomic ratio was determined by an X-ray photoelectron spectrometer (manufactured by JEOL Ltd., JPS-90MXV), using non-monochromatic MgKα (1253.6 eV) as the X-ray source, and 100 W (10 kV-10 mA). Measured by X-ray output. Quantitative analysis to determine the O/Si atomic ratio was performed using relative sensitivity factors of 2.28 for O1s and 0.9 for Si2p, respectively.

(Example 2)
A gas barrier film was obtained in the same manner as in Example 1, except that a 100% PBT material was used as the base film and a film was formed by stretching in a tubular method.

(Example 3)
A gas barrier film was obtained in the same manner as in Example 1, except that the vapor deposition layer was a SiOx vapor deposition film with a thickness of 40 nm.

(Example 4)
A gas barrier film was obtained in the same manner as in Example 1, except that the gas barrier coating layer had a thickness of 800 nm.

(Comparative example 1)
A gas barrier film was obtained in the same manner as in Example 1, except that no deposited layer of silicon oxide was provided.

(Comparative example 2)
A gas barrier film was obtained in the same manner as in Example 1, except that the deposited layer was made of aluminum oxide.

(Comparative Example 3)
A gas barrier film was obtained in the same manner as in Example 1, except that the vapor deposition layer was an SiOx vapor deposition film having a thickness of 5 nm.

(Comparative Example 4)
A gas barrier film was obtained in the same manner as in Example 1, except that the gas barrier coating layer had a thickness of 3000 nm.

(Comparative Example 5)
A gas barrier film was obtained in the same manner as in Example 1, except that a PET film (manufactured by Toray Industries, Inc., P60) was used as the base layer of the gas barrier film.

(Comparative Example 6)
A gas barrier film was obtained in the same manner as in Example 1, except that an ONY (biaxially oriented nylon) film (ONM manufactured by Unitika Ltd.) was used as the base layer of the gas barrier film.

[Experiment 1]
<Evaluation of dry lamination processability of gas barrier film>
Using a dry laminator, a two-component adhesive (Mitsui Chemicals A525/A52) was applied on the gas barrier coating layer of the gas barrier film by gravure roll coating, drying temperature 70 ° C., tension 40 N / m. to cure the adhesive 4 g / m ² for 1 minute, and laminated with an unstretched polypropylene film (CPP: Torayfan NO ZK207 manufactured by Toray Advanced Film Co., Ltd., thickness 60 μm), [transparent gas barrier laminate / adhesive layer / A laminate film for packaging having a structure of CPP (60 μm) was obtained.
In addition, dry lamination was carried out in the same manner except that the drying temperature was set to 100° C. to obtain a packaging laminate film having the same structure.

<Warp angle evaluation>
In the dry lamination, the warp angle of the film was measured after heating for 1 minute under each temperature and tension condition. In addition, as a measuring method, when the edge of the film is in a horizontal state, the angle of the edge where the film is turned up from the horizontal plane of the film is measured, and when the film warps toward the PBT base layer side, + ( plus), and - (minus) when the film warped toward the gas barrier coating layer.

<Processing suitability evaluation>
Regarding evaluation of processing suitability, the gas barrier film during lamination was judged according to the following criteria.
◯: The gas barrier film and the CPP film can be laminated with a predetermined processing width.
x: The gas barrier film was laminated in a curled state, and a predetermined processing width could not be obtained.

Table 1 shows the evaluation results of the dry lamination processability of Examples 1 to 4 and Comparative Examples 1 to 6.

From Table 1, the gas barrier films of Examples 1 to 4 and Comparative Examples 5 and 6 were heated at 70° C. and 100° C. for 1 minute at a tension of 40 N/m, which is a general dry lamination tension, in dry lamination. The warp angles of the film edges after heating were all within 0° to +60° toward the film substrate side, and curling was suppressed by the guide rolls, so stable lamination was possible.
However, in Comparative Example 1, there was no vapor deposition layer, and the stress of dehydration condensation of the gas barrier coating layer due to heating was applied strongly, so that the ends of the film broke and processing was not possible.
In Comparative Examples 2, 3, and 4, lamination was possible at a heating temperature of 70°C, but edge breakage occurred at a heating temperature of 100°C, making processing impossible.

[Experiment 2]
<Evaluation of physical properties of laminated film for packaging>
In Experiment 1, the laminated film obtained at a temperature enabling lamination (described in Table 2) was impulse-sealed on three sides into a 15 cm x 10 cm pouch, 200 ml of tap water was added to the contents, and the remaining side was impulse-sealed. A 4-way pouch was thus prepared. This pouch was subjected to retort treatment at 0.2 MPa and 121° C. for 30 minutes using a retort device.

After the retort treatment, the gas barrier properties of the pouches to be evaluated were evaluated after the tap water was discarded and the pouches were thoroughly dried.

<1> Evaluation of gas barrier property: [Method for measuring oxygen permeability]
Using an oxygen permeability measuring device (OXTRAN2/20 manufactured by Modern Control), the measurement was performed under the conditions of a temperature of 30°C and a relative humidity of 70%. The measurement method conforms to JIS K-7126, B method (isobaric method), and the measured value is expressed in units [cc/m ² ·day · MPa] (n = 3 average values).

<2> Evaluation of gas barrier property: [Method for measuring water vapor permeability]
Using a water vapor transmission rate measuring device (PERMATRAN3/33 manufactured by Modern Control), the measurement was performed under the conditions of a temperature of 40°C and a relative humidity of 90%. The measurement method conforms to JIS K-7126, B method (isobaric method), and the measured value is expressed in the unit [g/m ² ·day] (n = 3 average values).

<3> Evaluation of puncture strength:
A 5 cm square piece of gas barrier laminate after retort treatment was cut out and fixed to a jig for puncture measurement. The needle was pierced at a speed of 5 mm, and the load [N] until the needle penetrated was measured. (n = 3 average values)

Table 2 shows the physical property evaluation results of Examples 1 to 4 and Comparative Examples 2 to 6 after retort treatment.
The comprehensive evaluation items on the right end will be described later.

From Table 2, the gas barrier films of Examples 1 to 4 and Comparative Example 4 exhibited high barrier properties after retort treatment, and the puncture strength was also higher than that of the PET substrate of Comparative Example 5. It shows a strength equivalent to that of the ONY substrate.

However, in Comparative Example 2, although the base material is the same as that in Examples 1 to 4, the vapor deposition layer is aluminum oxide, so the retort resistance is inferior to that of silicon oxide.
Further, in Comparative Example 3, since the film thickness of the deposited layer is as thin as 5 nm, the water vapor barrier property is not exhibited.
In Comparative Example 5, the PET base material has good barrier properties, but the puncture strength is inferior to that of the PBT and ONY base materials.
In Comparative Example 6, the puncture strength was good because of the ONY base material, but the resistance to retort was low and the barrier properties were greatly deteriorated.

<Comprehensive evaluation>
Furthermore, based on the results described above, based on both the workability of the gas barrier film in Table 1 and the evaluation of physical properties in Table 2, the comprehensive evaluation in Table 2 was determined according to the following criteria.
○: Both workability and physical properties are excellent.
Δ: Physical properties are excellent, but workability has some problems.
x: Processability or physical properties are inferior, and there are one or more items that pose problems in practice.

In the comprehensive evaluation, Examples 1 to 4 were excellent in both workability and physical properties.
However, Comparative Examples 2, 3 and 4 were inferior in workability, Comparative Examples 2, 3 and 6 were inferior in barrier properties, and Comparative Example 5 was inferior in puncture strength.

As shown in Tables 1 and 2 above, the gas barrier film of the present invention has barrier properties and pinhole resistance that complement the features of both PET and ONY, and is dry laminated when producing a packaging film. It can be used as a film with good processability.

1 base film
2 adhesion layer
3 vapor deposition layer 4 gas barrier coating layer 10 gas barrier film 20 printed layer 30 adhesive layer 40 sealant film 100 packaging film

Claims (2)

On a film substrate containing a polyester resin having a butylene terephthalate unit as a main structural unit,
an adhesion layer containing an anchor coating agent that is a polyester-based polyurethane resin;
A gas barrier film comprising at least a vapor deposited layer containing silicon oxide and a gas barrier coating layer comprising a composition containing at least one of a water-soluble polymer and a metal alkoxide or a hydrolyzate thereof, said gas barrier film being laminated. In the film, the force applied to the film is 40 N / m, and the degree of warpage of the film edge after heating at temperatures of 70 ° C. and 100 ° C. for 1 minute is 0 ° or more and 60 ° or less toward the film substrate side. ,
The silicon oxide has an O/Si atomic ratio of 1.7 or more and 2.0 or less,
A gas barrier film, wherein the deposited layer containing silicon oxide has a thickness of 10 nm or more and 50 nm or less, and the gas barrier coating layer has a thickness of 100 nm or more and 1000 nm or less. A packaging film comprising the gas barrier film according to claim 1.

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