JP7600554B2 - Resin film, laminate, and packaging bag - Google Patents

Description

The present invention relates to a resin film, a laminate including a resin film, and a packaging bag.

Resin films containing polyethylene terephthalate are widely used as packaging materials for packaging objects such as food, medicines, and cosmetics. In order to prevent deterioration of the object's quality, it is preferable that the packaging material has gas barrier properties that make it difficult for gases such as oxygen and water vapor to pass through. For this reason, a laminate of a resin film and a gas barrier layer including a metal film or a metal oxide film is used as a packaging material (see, for example, Patent Document 1).

JP 2019-81607 A

During the distribution process of packaged products, external forces that cause deformation such as bending or twisting of the packaging material may be repeatedly applied to the product, such as when the product is subjected to vibration during transportation. It is desirable for the deterioration of gas barrier properties caused by the application of such external forces to be minimal in laminates used as packaging materials.

The present invention aims to provide a resin film, a laminate, and a packaging bag that can suppress the deterioration of the gas barrier properties of the laminate.

The resin film that solves the above problem is a resin film that forms a laminate for packaging bags by laminating a gas barrier layer having gas barrier properties, contains polyethylene terephthalate, and in a storage elasticity curve showing the relationship between the storage elasticity of the resin film and temperature, the transition temperature from a glass state to a rubber state is 80°C or more and 88°C or less, and the storage elasticity at the transition temperature is 3.8 GPa or more and 4.1 GPa or less.

According to the above configuration, the strength of the elastic properties of the resin film is suitable in the environment in which the laminate is used as a packaging bag. In other words, since the contribution of the elasticity of the resin film in responding to an external force is not too large, even if an external force is repeatedly applied to a laminate including a resin film and a gas barrier layer, the movement of the gas barrier layer laminated on the resin film is suppressed, and the occurrence of defects in the gas barrier layer is suppressed. Therefore, the deterioration of the gas barrier properties of the laminate can be suppressed. On the other hand, since the elastic properties of the resin film are not too weak, the deterioration of the suitability of the laminate as a packaging material is easily suppressed.

In the above-described configuration, the resin film may contain polyethylene terephthalate having dicarboxylic acid units in the repeating units thereof that contain terephthalic acid and isophthalic acid.
According to the above-mentioned configuration, a resin film having a transition temperature and a storage modulus within the above-mentioned ranges can be suitably obtained.

The laminate that solves the above problem includes the above resin film and a gas barrier layer having gas barrier properties.
According to the above-mentioned configuration, even when an external force is repeatedly applied, deterioration of the gas barrier properties of the laminate is suppressed, and therefore the suitability of the laminate for use as a packaging material is improved.

In the above configuration, the gas barrier layer may have a first barrier layer containing at least one of aluminum oxide and silicon oxide, and a second barrier layer containing a polymer material.
According to the above-mentioned configuration, the gas barrier property of the laminate is further improved.

In the above configuration, the second barrier layer may be stacked adjacent to the first barrier layer.
According to the above-mentioned configuration, the second barrier layer can protect the first barrier layer and complement the gas barrier property.

In the above configuration, the second barrier layer may contain one or more silicon compounds represented by Si( ^OR1 ) ₄ or ^R2Si ( ^OR3 ) ₃ ( ^OR1 and ^OR3 are hydrolyzable groups, and ^R2 is an organic functional group) or hydrolysates thereof, and a water-soluble polymer having a hydroxyl group.
According to the above-mentioned configuration, the effect of the second barrier layer in protecting the first barrier layer and in complementing the gas barrier property is enhanced.

The packaging bag that solves the above problem is a packaging bag for packaging an object, and is made of the above laminate.

The above configuration prevents the gas barrier properties of the packaging bag from deteriorating due to vibrations during product transportation, etc. This prevents deterioration in the quality of the packaged object.

The present invention makes it possible to prevent deterioration of the gas barrier properties of the laminate.

FIG. 2 is a diagram showing a cross-sectional structure of a resin film according to an embodiment. FIG. 2 is a diagram showing a cross-sectional structure of a laminate according to an embodiment. FIG. 1 is a diagram showing a perspective structure of a packaging bag according to an embodiment. FIG. 4 is a diagram showing an example of storage elasticity curves in Examples and Comparative Examples. FIG. 4 is a diagram showing an example of a loss elasticity curve in an example and a comparative example. FIG. 4 is a diagram showing an example of a loss tangent curve in an example and a comparative example.

An embodiment of a resin film, a laminate, and a packaging bag will be described with reference to the drawings.
[Resin film]
The structure of the resin film 10 will be described with reference to Fig. 1. The resin film 10 contains recycled PET, which is recycled polyethylene terephthalate (PET). PET products that are subject to recycling include used PET bottles. The recycled PET contained in the resin film 10 is at least one of PET recycled by mechanical recycling and PET recycled by chemical recycling.

In mechanical recycling, PET products are crushed and washed to remove surface dirt and foreign matter, and then the resin is exposed to high temperatures to remove contaminants remaining inside the resin. In chemical recycling, PET products are crushed and washed to remove surface dirt and foreign matter, and then the resin is depolymerized to return to intermediate raw materials, which are then refined and repolymerized to produce PET. Compared to chemical recycling, mechanical recycling does not require large-scale equipment for chemical reactions, so the costs and environmental impact of producing recycled PET are small. Therefore, it is preferable that the recycled PET contained in the resin film 10 is PET regenerated by mechanical recycling.

In addition to recycled PET, the resin film 10 may contain virgin PET, which is PET newly synthesized from raw materials such as petroleum. The mass proportion of recycled PET contained in the resin film 10 is preferably 60% or more and 100% or less of the total mass of the resin film 10.

The repeating units of PET include diol units and dicarboxylic acid units. In a resin film for packaging applications made of virgin PET, the diol units are ethylene glycol and the dicarboxylic acid units are terephthalic acid. On the other hand, the dicarboxylic acid used as the raw material for PET used in PET bottles is mixed with isophthalic acid in addition to terephthalic acid to improve the processability of the resin when it is molded into a bottle shape. That is, in PET bottles, the diol units are ethylene glycol and the dicarboxylic acid units include terephthalic acid and isophthalic acid. The inclusion of isophthalic acid suppresses crystallization of PET, improving processability. The diol units may also include diethylene glycol.

Therefore, the dicarboxylic acid units of recycled PET contain terephthalic acid and isophthalic acid. That is, the resin film 10 contains PET having dicarboxylic acid units containing terephthalic acid and isophthalic acid. It is preferable that the proportion of isophthalic acid in the total dicarboxylic acid units of the PET contained in the resin film 10 is 0.5 mol % or more and 5 mol % or less.

The average molecular weight of the PET contained in the resin film 10 is not particularly limited, but is preferably, for example, about 1,000 to 1,000,000. Note that the resin film 10 may contain resins other than PET and various additives such as plasticizers.

The resin film 10 may be composed of a single layer, or may be a laminate of multiple layers. When the resin film 10 has multiple layers, the constituent layers of the resin film 10 may have the same composition, or the constituent layers of the resin film 10 may include layers of different compositions. For example, the constituent layers of the resin film 10 may include a layer made of recycled PET and a layer made of virgin PET. Alternatively, the constituent layers of the resin film 10 may include multiple layers containing recycled PET in different proportions.

The thickness of the resin film 10 is selected according to the various resistances and processability required for the packaging bag. From the viewpoint of processability, the thickness of the resin film 10 is preferably from 3 μm to 100 μm in practical terms, and more preferably from 6 μm to 50 μm inclusive.

The method for forming the resin film 10 is not particularly limited, and any known film forming method such as extrusion molding may be used. In addition, as the method for extrusion and cooling, any known cooling method such as cooling rolls, air cooling, water cooling, etc. may be used.
Furthermore, the resin film 10 may be produced without stretching or by stretching. As the stretching method, a known stretching method such as uniaxial stretching or biaxial stretching is used.

[Laminate]
The structure of the laminate 20 will be described with reference to Fig. 2. The laminate 20 includes a resin film 10 and a gas barrier layer 11. The gas barrier layer 11 has a function of enhancing the gas barrier properties of the laminate 20.

The gas barrier layer 11 includes a first barrier layer made of, for example, an inorganic oxide or a metal. The inorganic oxide is, for example, an oxide of silicon, aluminum, magnesium, calcium, potassium, tin, sodium, boron, titanium, lead, zirconium, yttrium, or the like. The metal is, for example, aluminum, magnesium, tin, sodium, titanium, lead, zirconium, yttrium, gold, chromium, or the like. The first barrier layer may include two or more of these materials.

When a transparent packaging bag is formed from the laminate 20, a first barrier layer made of an inorganic oxide is used. In particular, a first barrier layer made of aluminum oxide or silicon oxide is preferably used. When a light-shielding property is to be imparted to the packaging bag formed from the laminate 20, a first barrier layer made of a metal is used. In particular, a first barrier layer made of aluminum is preferably used. The gas barrier layer 11 may include multiple first barrier layers made of the same or different materials.

The thickness of the first barrier layer is selected according to the material of the first barrier layer, etc. The thickness of the first barrier layer is preferably 5 nm or more and 300 nm or less, and more preferably 10 nm or more and 150 nm or less. If the thickness of the first barrier layer is equal to or more than the above lower limit, the first barrier layer is easily formed into a uniform film, and the thickness of the first barrier layer is sufficiently ensured, so that good gas barrier properties are obtained. If the thickness of the first barrier layer is equal to or less than the above upper limit, the flexibility of the first barrier layer is good, so that the occurrence of cracks in the first barrier layer due to external factors such as bending or pulling the laminate 20 is easily suppressed.

Methods for forming the first barrier layer on the substrate include vacuum deposition, sputtering, ion plating, and plasma vapor deposition (CVD). In particular, vacuum deposition is preferred from the viewpoint of increasing productivity. As a heating means for the vacuum deposition, it is preferable to use any of the electron beam heating method, resistance heating method, and induction heating method. However, it is more preferable to use the electron beam heating method from the viewpoint of high freedom in selecting the evaporation material. In addition, in order to improve the adhesion between the first barrier layer and the substrate and the denseness of the first barrier layer, it is also possible to perform deposition using a plasma assist method or an ion beam assist method. In addition, in order to increase the transparency of the first barrier layer, reactive deposition may be used in which various gases such as oxygen are blown in during deposition.

When forming the first barrier layer on the resin film 10, the surface of the resin film 10 may be subjected to a surface treatment such as plasma treatment or corona treatment in order to increase the adhesion between the resin film 10 and the first barrier layer. In addition, an anchor coat layer may be formed between the resin film 10 and the first barrier layer in order to increase the adhesion between these layers. These configurations improve the adhesion between the layers after heat sterilization of the laminate 20, as well as the gas barrier properties and other performance properties.

The gas barrier layer 11 may include a second barrier layer containing a polymer material in addition to or instead of the first barrier layer. For example, a second barrier layer may be laminated on a first barrier layer made of an inorganic oxide in order to protect the first barrier layer and complement the gas barrier properties of the first barrier layer. In this case, the laminate 20 has a structure in which the first barrier layer and the second barrier layer are laminated in this order on the resin film 10. The first barrier layer and the second barrier layer are adjacent to each other. The material of the second barrier layer may be selected depending on the purpose of forming the second barrier layer. Below, a suitable configuration for the second barrier layer for protecting the above-mentioned first barrier layer and complementing the gas barrier properties will be described.

The second barrier layer contains a water-soluble polymer and an inorganic compound. The water-soluble polymer has a hydroxyl group. Examples of the water-soluble polymer include polyvinyl alcohol, polyvinylpyrrolidone, starch, methyl cellulose, carboxymethyl cellulose, and sodium alginate. In particular, polyvinyl alcohol (PVA) is preferable because it is excellent at improving gas barrier properties.

The inorganic compound contained in the second barrier layer is a silicon compound represented by Si(OR ¹ ) ₄ or R ² Si(OR ³ ) ₃ (OR ¹ and OR ³ are hydrolyzable groups, and R ² is an organic functional group), or a hydrolyzate thereof. The second barrier layer may contain two or more of the above silicon compounds or their hydrolyzates. As Si(OR ¹ ) ₄ , tetraethoxysilane [Si(OC ₂ H ₅ ) ₄ ] is preferably used because it is relatively stable in an aqueous solvent after hydrolysis. In addition, R ² in R ² Si(OR ³ ) ₃ is preferably selected from the group consisting of a vinyl group, an epoxy group, a methacryloxy group, a ureido group, and an isocyanate group.

The second barrier layer is formed by applying a mixed solution of the materials for the second barrier layer. The mixed solution is prepared by mixing a silicon compound, either directly or after a prior treatment such as hydrolysis, with a solution in which a water-soluble polymer is dissolved in water or a mixed solvent of water and alcohol. This mixed solution is applied onto the first barrier layer, and the resulting coating film is then heated and dried to form the second barrier layer. It is also possible to add known additives such as isocyanate compounds, silane coupling agents, dispersants, stabilizers, viscosity adjusters, and colorants to the mixed solution as necessary, provided that the gas barrier properties are not impaired.

When PVA is used as the water-soluble polymer, the proportion of PVA in the mixed solution is preferably 20 wt % to 50 wt %, and more preferably 25 wt % to 40 wt %, of the total solid content of the mixed solution. If the proportion of PVA is equal to or greater than the lower limit, the second barrier layer can have good flexibility, making it easy to form the second barrier layer. If the proportion of PVA is equal to or less than the upper limit, the second barrier layer can have good gas barrier properties.
The thickness of the second barrier layer is selected from the range of, for example, 0.05 μm or more and 30 μm or less.

In addition, the gas barrier layer 11 may include a layer made of another material, such as a metal nitride, in addition to the first barrier layer and the second barrier layer, or instead of the first barrier layer and the second barrier layer.

In addition to the resin film 10 and the gas barrier layer 11, the laminate 20 may also include a sealing layer containing a thermoplastic resin, an adhesive layer for increasing the adhesion between the gas barrier layer 11 and the layer above or below it, and a layer for displaying decoration or information formed by printing. The sealing layer is melted when forming a packaging bag in which the ends of the laminate 20 are fused together by heat sealing.

The thickness of the laminate 20 is, for example, 30 μm or more and 300 μm or less. The thickness of the laminate 20 may be selected depending on various resistances and processability required for the packaging bag.
To form the laminate 20, various physical vapor deposition methods, various coating methods, dry lamination, extrusion lamination, and the like are used depending on the materials of the gas barrier layer 11 and other layers.

[Packaging bag]
The configuration of the packaging bag 30 will be described with reference to Fig. 3. The packaging bag 30 has a bag shape formed from the laminate 20 and is configured to be sealable. In the packaging bag 30, the gas barrier layer 11 is located on the inner side of the resin film 10. The shape and size of the packaging bag 30 are not particularly limited, and may be designed according to the object to be packaged. The object to be packaged is, for example, food, medicine, cosmetics, etc.

The method for joining the ends of the laminate 20 when forming the packaging bag 30 is not particularly limited, and heat sealing may be used as described above, or the ends of the laminate 20 may be joined by other methods. Figure 3 illustrates an example of a packaging bag 30 having a sealing portion 31 at its end where the ends of the laminate 20 are joined.

[Physical properties of resin film]
The inventors of the present application have found that the flexibility of the resin film 10 contributes to suppressing a decrease in the gas barrier property of the laminate 20. The inventors of the present application have focused on dynamic elastic moduli, that is, the storage elastic modulus G1, the loss elastic modulus G2, and the loss tangent (tan δ), as parameters for evaluating the flexibility of the resin film 10.

When an external force such as vibration is applied to the laminate 20, the gas barrier layer 11 deforms in response to the deformation of the resin film 10. The storage modulus G1 indicates the component of the energy generated by stress in an object that is stored inside the object, and the loss modulus G2 indicates the component of the energy that is diffused to the outside as heat. In other words, the magnitude of the storage modulus G1 indicates the strength of the properties of the resin film 10 as an elastic body, and the magnitude of the loss modulus G2 indicates the strength of the properties of the resin film 10 as a viscous body. Tan δ is the ratio of the loss modulus G2 to the storage modulus G1 (G2/G1), and indicates the balance between the properties of the resin film 10 as an elastic body and the properties of the viscous body.

The stronger the elastic properties of the resin film 10, the higher the responsiveness of the shape change to the application and release of an external force. That is, when the application and release of an external force to the resin film 10 is repeated in a short period of time, such as when the resin film 10 is subjected to vibration, the generation of strain due to the application of the external force and the recovery of the strain due to the release of the external force are repeated in the resin film 10 in a short period of time. Therefore, the movement of the gas barrier layer 11 following the resin film 10 becomes large, and as a result, defects such as pinholes are easily generated in the gas barrier layer 11, and the gas barrier properties of the laminate 20 are easily deteriorated.

On the other hand, when the resin film 10 has stronger viscous properties, the rate of deformation in response to the application of an external force becomes slower, and the deformation is less likely to return to its original state even when the external force is released. Therefore, even if the application and release of an external force to the resin film 10 is repeated in a short period of time, the movement of the resin film 10 and the gas barrier layer 11 is suppressed. In other words, the vibration absorption ability of the laminate 20 is improved. Therefore, the occurrence of defects in the gas barrier layer 11 is suppressed, and the deterioration of the gas barrier properties of the laminate 20 is suppressed.

However, if the viscous properties of the resin film 10 become too strong, the suitability of the laminate 20 as a packaging material, such as ease of processing and strength, decreases. As a result of extensive research, the inventors of the present application have found ranges of the storage modulus G1, loss modulus G2, and tan δ of the resin film 10 that can suppress a decrease in gas barrier properties while maintaining the suitability of the laminate 20 as a packaging material. The preferred ranges for each parameter are explained below.

In the storage elasticity curve showing the relationship between the storage elasticity modulus G1 and temperature of the resin film 10, the transition temperature T1 from the glass state to the rubber state is 80°C or more and 88°C or less, and the storage elasticity modulus G1 at the transition temperature T1 is 3.8 GPa or more and 4.1 GPa or less.

The temperature of the environment in which the packaging bag 30 is used is often lower than the transition temperature T1, i.e., the resin film 10 is used in a glassy state with low fluidity. Since the change in the storage modulus G1 when the resin film 10 is in a glassy state is small, the elastic properties of the resin film 10 when it is used as the packaging bag 30 can be appropriately evaluated by evaluating the storage modulus G1 at the transition temperature T1.

If the storage modulus G1 at the transition temperature T1 is 4.1 GPa or less, the contribution of elasticity in the resin film 10 in responding to external forces is not too great, and therefore the deterioration of the gas barrier properties of the laminate 20 is suppressed. On the other hand, if the storage modulus G1 at the transition temperature T1 is 3.8 GPa or more, the elastic properties of the resin film 10 are not too weak, and therefore the deterioration of the suitability of the laminate 20 as a packaging material is easily suppressed.

In the loss elasticity curve showing the relationship between the loss modulus G2 of the resin film 10 and temperature, it is preferable that the temperature T2 at the peak position is 95°C or more and 102°C or less, and the loss modulus G2 at the peak position is 0.30 GPa or more and 0.37 GPa or less.

The temperature T2 at the peak position in the loss elasticity curve is the temperature at which the viscous properties of the resin film 10 are significantly expressed. The higher the temperature T2, the less likely it is that flexibility due to viscosity will be expressed in the low temperature range that includes the temperature of the environment in which the packaging bag 30 is used. If the temperature T2 is 102° C. or lower and the loss modulus G2 at the peak position, i.e., the loss modulus G2 at temperature T2, is 0.30 GPa or higher, flexibility due to viscosity is likely to be well exhibited in the low temperature range. Therefore, deterioration of the gas barrier properties of the laminate 20 is suppressed.
Furthermore, if the loss modulus G2 at the peak position is 0.37 GPa or less, deterioration in the suitability of the laminate 20 as a packaging material is likely to be suppressed.

In the loss tangent curve showing the relationship between tan δ and temperature of the resin film 10, it is preferable that tan δ at the peak position is 0.160 or more and 0.190 or less. The temperature T3 at the peak position is preferably 108°C or more and 115°C or less.

Since tan δ is the ratio of the storage modulus G1 to the loss modulus G2, the influence of factors for each sample of the resin film 10 that cause errors in the dynamic modulus is eliminated. In other words, there is little variation in the shape of the curve between samples with the same configuration. Therefore, the dynamic modulus can be accurately evaluated by using tan δ.

The larger the tan δ, the greater the viscous properties of the resin film 10 relative to its elastic properties, i.e., the greater the vibration absorption. If the tan δ at the peak position is 0.160 or more, the ratio of the viscous contribution to the elastic contribution in the response to an external force in the resin film 10 is sufficiently large, so that the deterioration of the gas barrier properties of the laminate 20 is suppressed. On the other hand, if the tan δ at the peak position is 0.190 or less, the viscous properties of the resin film 10 relative to its elastic properties are not too great, so that the deterioration of the suitability of the laminate 20 as a packaging material is suppressed.

In addition, if the temperature T3 at the peak position is 115°C or lower, the flexibility of the resin film 10 due to its viscosity is likely to be well exhibited in the low temperature range that includes the temperature of the environment in which the packaging bag 30 is used.

The values of the storage modulus G1, loss modulus G2, and tan δ at each temperature T1, T2, and T3 can be adjusted by the composition of the resin film 10, the temperature and speed of extrusion and cooling, the stretching ratio, and other manufacturing conditions. For example, the higher the proportion of isophthalic acid in the total dicarboxylic units of PET contained in the resin film 10, the more it inhibits molecular orientation, the greater the flexibility of the resin film 10, and the stronger the properties of the resin film 10 as a viscous body. In terms of cooling temperature, a lower cooling temperature during the production of the resin film 10 can reduce the storage modulus G1 and increase tan δ. As a result, the flexibility of the resin film 10 can be increased even in the low temperature region, and the properties of the resin film 10 as a viscous body can be strengthened. In terms of cooling rate, rapid cooling rather than slow cooling can cause the resin to grow crystals appropriately while leaving the amorphous portion, so that the temperature T3 is lower, but tan δ and the loss modulus G2 can be increased. As a result, the flexibility of the resin film 10 is increased, and the properties of the resin film 10 as a viscous body can be strengthened. In terms of the stretching ratio, by reducing the stretching ratio during the production of the resin film 10, molecular orientation can be suppressed, so the transition temperature T1 can be lowered and the increase in the storage modulus G1 can be suppressed. As a result, the flexibility of the resin film 10 is increased, and the properties of the resin film 10 as a viscous body can be strengthened.

[Example]
The above-mentioned resin film and laminate will be described using specific examples and comparative examples.

Example 1
The three resin layers were laminated by coextrusion to form the resin film of Example 1. Each resin layer is a layer in which recycled PET regenerated by mechanical recycling and virgin PET are mixed. The three resin layers have the same composition. The mass ratio of recycled PET contained in the resin film of Example 1 is 80% of the total mass of the resin film. The thickness of the resin film of Example 1 is 12 μm.

A first barrier layer made of aluminum oxide was laminated on the resin film of Example 1 by using a vacuum deposition method. The thickness of the first barrier layer was 10 nm. Furthermore, a second barrier layer was formed on the first barrier layer by using a direct gravure coating method. In detail, a mixed solution for forming the second barrier layer was prepared by mixing a hydrolysis solution obtained by adding hydrochloric acid to tetraethoxysilane and stirring for 30 minutes to hydrolyze it, and a PVA solution obtained by dissolving polyvinyl alcohol in a mixed solvent of water and isopropyl alcohol at a ratio of 60:40. The mixed solution was applied on the first barrier layer by using a bar coater, and the formed coating film was dried at 120°C for 1 minute by using a dryer to form a second barrier layer. The thickness of the second barrier layer was 300 nm.
This resulted in the production of the laminate of Example 1. That is, the laminate of Example 1 included a resin film and a gas barrier layer including a first barrier layer and a second barrier layer.

Example 2
The resin film of Example 2 was formed by laminating three resin layers so that the second resin layer was sandwiched between two first resin layers. The first resin layer is a layer made of recycled PET regenerated by chemical recycling. The second resin layer is a layer in which recycled PET regenerated by mechanical recycling is mixed with a small amount of recycled PET regenerated by chemical recycling. The mass ratio of recycled PET contained in the resin film of Example 2 is 100% of the total mass of the resin film. The thickness of the resin film of Example 2 is 12 μm.

Example 3
The resin film of Example 3 was formed by laminating three resin layers so that the second resin layer was sandwiched between two first resin layers. The first resin layer was a layer made of virgin PET. The second resin layer was a layer made of recycled PET regenerated by chemical recycling. The mass ratio of recycled PET contained in the resin film of Example 3 was 70% of the total mass of the resin film. The thickness of the resin film of Example 3 was 12 μm.

Comparative Example
A resin film of the comparative example was obtained by forming a single resin layer made of virgin PET. The resin film of the comparative example did not contain recycled PET. The thickness of the resin film of the comparative example was 12 μm.

A comparative laminate was obtained by laminating a first barrier layer and a second barrier layer to the resin film of the comparative example using the same materials and manufacturing method as in Example 1. That is, the comparative laminate includes a resin film and a gas barrier layer having the same configuration as in Example 1.

<Measurement of dynamic elastic modulus>
A strip-shaped test piece was prepared from the resin film of each Example and Comparative Example. The length of the test piece was 20 mm, and the width of the test piece was 10 mm. The flow direction (MD direction) during the formation of the resin film was set as the length direction of the test piece. Using a thermomechanical analyzer (Hitachi High-Tech Science Corporation: DMA7100), the storage modulus G1 and loss modulus G2 of each test piece were measured, and tan δ was calculated. The measurement conditions are as follows.
Frequency: 10Hz
Tension condition: Strain amplitude 10μm
: Minimum tension/compression force 50 mN
: Tension/compression gain 1.2
: Initial force amplitude 50 mN
Heating conditions: temperature rise rate 2°C/min
:Heating temperature 30℃～180℃

<Evaluation of gas barrier properties>
Test pieces were prepared from the laminates of Example 1 and Comparative Example, and a Gelbo Flex test was carried out to evaluate the flexibility of the laminates. The test method is described below. Then, to evaluate the gas barrier properties of the laminates, the oxygen permeability and water vapor permeability were measured for the laminates before and after the Gelbo Flex test. The measurement method is described below.

(Flexibility evaluation)
The flexibility of the laminate was evaluated using a flexibility evaluation device (Gelbo Flex Tester, manufactured by Tester Sangyo Co., Ltd.). First, a test piece was attached to the fixed head of the evaluation device so as to be cylindrical. Next, while holding both ends of the test piece, the laminate was bent by repeating the operation of twisting the test piece by 440 degrees at an initial gripping distance of 175 mm and a stroke of 87.5 mm 10 times at a speed of 40 times/min.

(Measurement of water vapor permeability)
The water vapor permeability of the laminate was measured using a water vapor permeability measuring device (PERMATRAN 3/31, manufactured by Modern Control) under conditions of a temperature of 40° C. and a relative humidity of 90%. The measurement method was in accordance with JIS K-7129 and ASTM F1249-90, and the unit of the measurement was [g(STP)/ ^m2 ·day].

(Oxygen permeability measurement)
The oxygen permeability of the laminate was measured using an oxygen permeability measuring device (OXTRAN 2/20, manufactured by Modern Control) at a temperature of 30° C. and a relative humidity of 70%. The measurement method was in accordance with JIS K-7126 B method (constant pressure method) and ASTM D3985-81, and the unit of the measurement was [cm ³ (STP)/m ² ·day·MPa].

<Measurement results>
Figures 4 to 6 show curves obtained by measuring the dynamic modulus of elasticity for the resin films of each Example and Comparative Example. Figure 4 shows a storage elasticity curve, Figure 5 shows a loss elasticity curve, and Figure 6 shows a loss tangent curve. The dynamic modulus of elasticity was measured for three test pieces for each Example and Comparative Example. The curves shown in Figures 4 to 6 are representative curves obtained by measuring the three test pieces.

Table 1 shows the analysis results of the storage elasticity, loss elasticity, and tan δ for the resin films of each example and comparative example. Each value in the analysis results is the average value obtained from measurements on three test pieces.

The analytical values of storage elasticity are the transition temperature T1 in the storage elasticity curve and the storage elastic modulus G1 at the transition temperature T1. The transition temperature T1 was determined as the temperature at the intersection of the approximation line of the glass region, which is on the lower temperature side of the inflection point in the storage elasticity curve, and the approximation line of the transition region, which is on the higher temperature side of the inflection point. The approximation line on the low temperature side was created by approximating the group of measurement points between the inflection point and a point about 10 degrees lower to a point about 5 degrees lower than the inflection point. The approximation line on the high temperature side was created by approximating the group of measurement points between the inflection point and a point about 5 degrees higher to a point about 10 degrees higher than the inflection point.

The analytical value of loss elasticity is the temperature T2 and the loss modulus G2 at the peak position on the loss elasticity curve. The analytical value of tan δ is the temperature T3 and the value of tan δ at the peak position on the loss tangent curve.

Table 2 shows the measurement results of oxygen permeability and water vapor permeability for the laminates of Example 1 and Comparative Example. For Example 1 before the Gelbo Flex test, and for Example 1 and Comparative Example after the Gelbo Flex test, the permeability was measured for two test pieces, and the average value was calculated.

As shown in Table 1, in Examples 1 to 3, which contain recycled PET, the transition temperature T1 in the storage elasticity curve is 80°C or higher and 88°C or lower, and the storage elasticity modulus G1 at the transition temperature T1 is 3.8 GPa or higher and 4.1 GPa or lower. On the other hand, the storage elasticity modulus G1 of the comparative example, which does not contain recycled PET, is greater than 4.1 GPa. In other words, this suggests that the resin film of the comparative example has stronger elastic properties than the resin films of Examples 1 to 3.

In addition, in Examples 1 to 3, the temperature T2 at the peak position in the loss elasticity curve is 95°C or more and 102°C or less, and the loss modulus G2 at the peak position is 0.30 GPa or more and 0.37 GPa or less. On the other hand, the temperature T2 in the comparative example is greater than 102°C. In other words, it is suggested that the resin film of the comparative example has difficulty in exhibiting flexibility due to viscosity in the low temperature region. Note that the loss modulus G2 at the peak position of the comparative example is greater than 0.37, but compared to the difference in storage modulus G1 between the examples and the comparative example, the difference in loss modulus G2 is small, and it is difficult to say that the properties as a viscous body are significantly stronger in the comparative example.

In addition, in Examples 1 to 3, the temperature T3 at the peak position in the loss tangent curve is 108°C or more and 115°C or less, and the tan δ at the peak position is 0.160 or more and 0.190 or less. On the other hand, the tan δ at the peak position in the comparative example is smaller than 0.160. In other words, compared to Examples 1 to 3, the comparative example has smaller viscous body properties relative to elastic body properties, suggesting that the contribution of viscosity to the response to external forces is smaller. In addition, the temperature T3 in the comparative example is greater than 115°C, suggesting that the resin film of the comparative example has difficulty in exhibiting flexibility in the low temperature range.

As shown in Table 2, Example 1 shows a smaller decrease in oxygen permeability before and after the Gelbo Flex test than the Comparative Example. Also, Example 1 shows a smaller decrease in water vapor permeability before and after the Gelbo Flex test than the Comparative Example. Therefore, it was confirmed that Example 1 suppresses the decrease in gas barrier properties before and after the Gelbo Flex test more than the Comparative Example. In other words, it was shown that if the parameters of storage elasticity, loss elasticity, and tan δ are within the above ranges, the flexibility of the resin film 10 can be suitably obtained, and as a result, the decrease in gas barrier properties of the laminate against the application of external force can be suppressed.

As described above in the embodiments and examples, the resin film, laminate, and packaging bag can provide the following effects.
(1) In the storage elasticity curve of the resin film 10, the transition temperature T1 is 80° C. or more and 88° C. or less, and the storage elastic modulus G1 at the transition temperature T1 is 3.8 GPa or more and 4.1 GPa or less. This makes the strength of the properties of the resin film 10 as an elastic body suitable in the environment in which the packaging bag 30 is used. That is, since the contribution of the elasticity of the resin film 10 in response to an external force is not too large, even if an external force is repeatedly applied to the laminate 20, the movement of the gas barrier layer 11 laminated on the resin film 10 is suppressed, and the occurrence of defects in the gas barrier layer 11 is suppressed. Therefore, the deterioration of the gas barrier property of the laminate 20 can be suppressed. On the other hand, since the properties of the resin film 10 as an elastic body are not too weak, the deterioration of the suitability of the laminate 20 as a packaging material is easily suppressed.

(2) In the loss elasticity curve of the resin film 10, the temperature T2 at the peak position is 95°C or more and 102°C or less, and the loss elasticity G2 at the peak position is 0.30 GPa or more and 0.37 GPa or less. This makes it easier for the flexibility due to the viscosity of the resin film 10 to be well exhibited in the low temperature range that includes the temperature of the environment in which the packaging bag 30 is used. This prevents a decrease in the gas barrier properties of the laminate 20. In addition, because the viscous properties of the resin film 10 do not become too strong, a decrease in the suitability of the laminate 20 as a packaging material is easily prevented.

(3) The tan δ at the peak position in the loss tangent curve of the resin film 10 is 0.160 or more and 0.190 or less. This provides an appropriate ratio of the properties of the resin film 10 as a viscous body relative to the properties of an elastic body. That is, in the resin film 10, the ratio of the contribution of viscosity to the contribution of elasticity in responding to an external force becomes sufficiently large, so that the vibration absorption is improved. Therefore, the deterioration of the gas barrier property of the laminate 20 can be suppressed. In addition, the temperature T3 at the peak position in the loss tangent curve of the resin film 10 is 108°C or more and 115°C or less. As a result, the temperature T3 at the peak position is not too high, so that the flexibility of the resin film 10 due to viscosity is easily exhibited in the environment in which the packaging bag 30 is used.

(4) If the laminate 20 includes the resin film 10 and the gas barrier layer 11, the deterioration of the gas barrier properties of the laminate 20 is suppressed even when external forces are repeatedly applied. Therefore, the suitability of the laminate 20 for use as a packaging material is improved.

(5) The gas barrier layer 11 has a first barrier layer containing at least one of aluminum oxide and silicon oxide, and a second barrier layer containing a polymeric material, thereby improving the gas barrier properties of the laminate 20.

(6) Since the second barrier layer is laminated adjacent to the first barrier layer, the second barrier layer can protect the first barrier layer and complement the gas barrier properties.
(7) The second barrier layer contains one or more silicon compounds represented by Si( ^OR1 ) ₄ or ^R2Si ( ^OR3 ) ₃ ( ^OR1 and ^OR3 are hydrolyzable groups, and ^R2 is an organic functional group) or hydrolysates thereof, and a water-soluble polymer having a hydroxyl group, thereby enhancing the effect of the second barrier layer in protecting the first barrier layer and complementing the gas barrier properties.

(8) If the packaging bag 30 is made of the laminate 20, the deterioration of the gas barrier properties of the packaging bag 30 due to vibration during transportation of the product is suppressed. Therefore, deterioration of the quality of the packaged object is suppressed.

REFERENCE SIGNS LIST 10: Resin film 11: Gas barrier layer 20: Laminate 30: Packaging bag

Claims (7)

A resin film that constitutes a laminate for a packaging bag by laminating a gas barrier layer having gas barrier properties,
It has three layers of polyethylene terephthalate resin,
At least one of the three resin layers contains recycled polyethylene terephthalate,
The mass ratio of the recycled polyethylene terephthalate contained in the resin film is 70% or more of the total mass of the resin film,
In a storage elasticity curve showing the relationship between the storage elastic modulus and temperature of the resin film, a transition temperature from a glassy state to a rubbery state is 80° C. or more and 88° C. or less, and the storage elastic modulus at the transition temperature is 3.8 GPa or more and 4.1 GPa or less. The recycled polyethylene terephthalate contains terephthalic acid and isophthalic acid in the dicarboxylic acid units in the repeating units.
The resin film according to claim 1 . The resin film according to claim 1 or 2,
A gas barrier layer having gas barrier properties;
A laminate comprising: The gas barrier layer is
a first barrier layer including at least one of aluminum oxide and silicon oxide;
and a second barrier layer comprising a polymeric material. The laminate according to claim 4 , wherein the second barrier layer is laminated adjacent to the first barrier layer. 6. The laminate according to claim 4, wherein the second barrier layer comprises one or more silicon compounds represented by Si( ^OR1 ) ₄ or ^R2Si ( ^OR3 ) ₃ ( ^OR1 and ^OR3 are hydrolyzable groups, and ^R2 is an organic functional group) or hydrolysates thereof, and a water-soluble polymer having a hydroxyl group. A packaging bag for packaging an object,
A packaging bag comprising the laminate according to any one of claims 3 to 6.