JP7707611B2 - High heat resistance, low odor, gas adsorption sealant film - Google Patents

Description

The present invention relates to a highly heat-resistant, low-odor, gas-adsorbing sealant film that adsorbs gases generated by itself and gases from adjacent spaces, and releases only a small amount of gas even when heated, without causing any change in the odor or taste of the contents.

In recent years, packaging materials containing odor adsorbents that adsorb odors have been proposed to prevent the contents of the package from being contaminated, deteriorated, or changed in odor and taste (Patent Document 1). In such packaging materials, odor adsorbents such as synthetic zeolite and activated carbon are kneaded into a resin material.
Packaging materials containing an odor adsorbent comprising a chemical adsorbent supported on an inorganic porous body are also known (Patent Document 2), but the main object of adsorption is only to adsorb odorous components having specific functional groups. In a situation where the resin material is not selected, the amount of organic matter not having functional groups generated cannot be suppressed, and odorous components cannot be sufficiently adsorbed.
Furthermore, hygroscopic packaging materials that suppress the generation of unpleasant odors due to hydrolysis of the contents are also known (Patent Document 3), but although they have the effect of suppressing odor generation, the generated odor components remain as they are, so a sufficient odor improvement effect was not obtained. Furthermore, for applications used in high-temperature sterilization processes such as retort sterilization and high-temperature boiling, a covering film having a functional resin layer containing an oxygen absorbent and a gas adsorbent has been proposed to reduce the remaining odor in the package and improve the odor (Patent Document 4), but it is unable to adsorb all of the resin decomposition components that are generated when the oxygen absorption properties are expressed, and furthermore, because it is a covering film, an easy-peel layer is formed on the inner layer surface, so it is not suitable for general-purpose use.

Patent No. 2538487 JP 2014-233408 A JP 2006-327690 A Patent No. 5046098

The objective of the present invention is to provide a sealant film that has high heat resistance capable of withstanding the temperatures (90-110°C) used in boiling and semi-retort heating processes, emits little gas from itself, adsorbs gases from the outside in contact with it, and suppresses changes in the taste and odor of the contents.

As a result of various investigations, the present inventors have found that a sealant film containing at least a specific highly heat-resistant, low odor resin and a gas adsorbent can achieve the above object.
That is, the present invention is characterized in the following points.
1. A highly heat-resistant, low-odor, gas-adsorbing sealant film,
The highly heat-resistant, low-odor, gas-adsorbing sealant film contains a highly heat-resistant, low-odor resin having heat-sealing properties and a gas adsorbent, and adsorbs gases generated from itself and gases from the outside.
the gas is one or a combination of two or more selected from the group consisting of hydrocarbons, aldehydes, ketones, and carboxylic acids;
The high heat resistance and low odor resin has a density of 0.920 g/ ^cm3 or more and 0.960 g/ ^cm3 or less,
The highly heat-resistant, low-odor, gas-adsorbing sealant film is characterized in that the concentration of leachable total organic carbon (TOC) contained in the film made of the highly heat-resistant, low-odor resin is 1.5 ppm or more and 250 ppm or less, and is leachable by boiling treatment at 90 to 110°C for 30 minutes and storing the film at 35°C.
2. The content of the high heat resistance, low odor resin in the total resin contained in the high heat resistance, low odor gas adsorption sealant film is 70 mass% or more and 100 mass% or less,
The gas adsorbent is contained in a layer containing the gas adsorbent in an amount of 0.1% by mass or more and 30% by mass or less.
2. The highly heat-resistant, low odor, gas-adsorbing sealant film according to 1 above.
3. The highly heat-resistant, low-odor, gas-adsorbing sealant film according to the above item 1 or 2, characterized in that the highly heat-resistant, low-odor resin is a polyethylene-based resin.
4. The high heat resistant, low odor gas adsorption sealant film according to 1 or 2 above, characterized in that the high heat resistant, low odor resin is one or a combination of two or more selected from the group consisting of high density polyethylene, medium density polyethylene, low density polyethylene, and linear low density polyethylene.
5. The highly heat-resistant and low odor gas adsorption sealant film according to any one of 1 to 4 above, characterized in that the gas adsorbent comprises one or a combination of two or more selected from the group consisting of hydrophobic zeolite, molecular sieve, metal-organic framework (MOF), and activated carbon.
6. The highly heat-resistant, low odor gas adsorption sealant film has a gas adsorption layer and a heat seal layer,
the gas adsorption layer is a layer containing the high heat resistant, low odor resin and the gas adsorbent,
the heat seal layer contains the highly heat resistant, low odor resin and has heat sealability;
At least one outermost layer of the highly heat-resistant, low odor, gas-adsorbing sealant film is a heat seal layer,
The high heat resistant, low odor resin contained in the gas adsorption layer and the high heat resistant, low odor resin contained in the heat seal layer are the same or different.
6. A highly heat-resistant, low odor, gas-adsorbing sealant film according to any one of 1 to 5 above.
7. The heat shrinkage rate when boiled for 10 minutes or more and 60 minutes or less at a temperature of 90 ° C. or more and 100 ° C. or less is 0% or more and 10% or less,
The surface is free of any orange peel-like changes.
7. A highly heat-resistant, low odor, gas-adsorbing sealant film according to any one of 1 to 6 above.
8. A highly heat-resistant, low odor, gas-adsorbing sealant film for boiling sterilization or semi-retort sterilization, using the highly heat-resistant, low odor, gas-adsorbing sealant film according to any one of 1 to 7 above.

The present invention makes it possible to obtain a sealant film that has high heat resistance capable of withstanding the temperatures (90-110°C) used in boiling and semi-retort heating processes, emits little gas from itself, adsorbs gases from the outside in contact with it, and suppresses changes in the odor and taste of the contents.

FIG. 1 is a schematic cross-sectional view showing an example of the layer structure of a highly heat-resistant, low odor gas-adsorbing sealant film of the present invention. FIG. 2 is a schematic cross-sectional view showing an example of another embodiment of the layer structure of the highly heat-resistant and low odor gas-adsorbing sealant film of the present invention. FIG. 2 is a schematic cross-sectional view showing another example of the layer structure of the highly heat-resistant and low odor gas-adsorbing sealant film of the present invention.

In each drawing, the size and ratio of the components may be changed or exaggerated for ease of understanding. Also, for ease of understanding, parts that are not necessary for the explanation or repeated reference numerals may be omitted.
Although not shown in the drawings, an adhesive layer may be provided between each layer.
Furthermore, if necessary, in order to strengthen the adhesive strength (adhesion strength) between each layer, the laminated surfaces of each layer may be previously subjected to physical surface treatments such as corona discharge treatment, ozone treatment, plasma treatment, glow discharge treatment, sandblasting treatment, etc., or chemical surface treatments such as oxidation treatment using chemicals.

The highly heat-resistant, low odor, gas-adsorbing sealant film of the present invention will be described in more detail below. Specific examples will be given, but the present invention is not limited thereto.
In the present invention, the terms film and sheet are used synonymously.

<High heat resistance, low odor, gas adsorption sealant film>
The highly heat-resistant, low odor, gas-adsorbing sealant film of the present invention contains a highly heat-resistant, low odor resin with heat sealing properties and a gas adsorbent, and therefore has excellent heat sealing properties, high heat resistance that can withstand temperatures from boiling to semi-retort heating treatment (90 to 110°C), little thermal shrinkage, suppression of the occurrence of citrus peel, and little gas emission (including elution) from the film itself, and can adsorb gases from the outside that it comes into contact with, thereby suppressing changes in the taste and odor of the packaged contents caused by these gases.

The highly heat-resistant, low odor, gas-adsorbing sealant film may have a single layer structure or a multi-layer structure of two or more layers.
For example, it may be composed of a single layer of a gas adsorption layer containing a highly heat-resistant, low-odor resin and a gas adsorbent, or it may be composed of two layers, that is, a gas adsorption layer containing a highly heat-resistant, low-odor resin and a gas adsorbent, and a heat seal layer containing a highly heat-resistant, low-odor resin, or it may have a three-layer structure in which a gas adsorption layer is sandwiched between two heat seal layers.

The content of the high heat resistance, low odor resin in the resin contained in the total high heat resistance, low odor gas adsorption sealant film is preferably 70% by mass or more and 100% by mass or less, more preferably 80% by mass or more and 100% by mass or less, and even more preferably 90% by mass or more and 100% by mass or less. If it is less than the above range, the low gas release properties of the high heat resistance, low odor gas adsorption sealant film may be insufficient, and if it is more than the above range, it is difficult to balance the various physical properties and workability, but the low gas release properties are not significantly improved.

The content of the gas adsorbent in the layer containing the gas adsorbent is preferably 0.1% by mass or more and 30% by mass or less, and more preferably 0.5% by mass or more and 28% by mass or less. If the content is less than the above range, the gas adsorption effect may be insufficient, and if the content is more than the above range, the film formability may be deteriorated.
Here, the layer containing a gas adsorbent refers to the entire highly heat-resistant, low odor, gas-adsorbing sealant film when the highly heat-resistant, low odor, gas-adsorbing sealant film is composed of only one layer, and refers to, for example, the gas adsorption layer when the highly heat-resistant, low odor, gas-adsorbing sealant film has a multi-layer structure having a gas adsorption layer and a heat seal layer, etc.

When the highly heat-resistant, low odor, gas-adsorbing sealant film of the present invention has a multi-layer structure having a gas adsorption layer, a heat seal layer, etc., in order to improve heat sealability and lamination properties, it is preferable that the outermost layer on at least one side of the highly heat-resistant, low odor, gas-adsorbing sealant film is a heat seal layer, and it is more preferable that the outermost layers on both sides are heat seal layers.
Furthermore, the highly heat-resistant, low odor resin contained in the gas adsorption layer and the highly heat-resistant, low odor resin contained in the heat seal layer may be the same or different.

The high heat resistance, low odor, gas adsorption sealant film can adjust its gas adsorption and outgassing properties by adjusting the film thickness.
The thickness of the highly heat-resistant, low odor gas adsorption sealant film is preferably 25 μm or more and 150 μm or less, more preferably 30 μm or more and 100 μm or less, in order to have a good balance between heat sealability, gas adsorption, and low gas release. If the thickness is thinner than the above range, the heat sealability and/or gas adsorption may be insufficient, and if the thickness is thicker than the above range, the low gas release may be inferior.

And, the high heat resistant, low odor, gas adsorption sealant film may further contain small amounts of slip agents, antiblocking agents, antioxidants, solvents, and other additives.
The high heat resistant, low odor gas adsorption sealant film of the present invention preferably contains an antioxidant in order to suppress the generation of gases emitted due to resin deterioration in a high temperature environment. Conversely, it is preferable to limit the use of additives that may increase the amount of gas emitted at high temperatures.

(Gas to be adsorbed)
The gas components to be adsorbed in the present invention are mainly gas components originally contained in the highly heat-resistant, low odor, gas-adsorbing sealant film of the present invention, and gas components consisting of resin decomposition products generated by decomposition of the resin in the highly heat-resistant, low odor, gas-adsorbing sealant film by heating such as heat sealing, boiling, semi-retort treatment, etc., or by irradiation with UV or EB, etc.
Here, examples of gas components originally contained in the highly heat-resistant, low odor, gas-adsorbing sealant film include gas components contained in the raw materials that constitute the highly heat-resistant, low odor, gas-adsorbing sealant film, and gas components generated due to the thermal history, etc., when forming the highly heat-resistant, low odor, gas-adsorbing sealant film.
In particular, these include gas components that are originally contained in the highly heat-resistant, low odor, gas-adsorbing sealant film, gas components that were contained in the raw materials that make up the highly heat-resistant, low odor, gas-adsorbing sealant film, and gas components that are generated due to the thermal history, etc., when forming the low outgassing gas-adsorbing sealant film.

Specific examples of gases to be adsorbed include organic substances with relatively small molecular weights.
The organic matter is a gas component derived from the highly heat-resistant, low-odor, gas-adsorbing sealant film, and the gas component compounds often have 1 to 16 carbon atoms, and examples of the types include hydrocarbons, aldehydes, ketones, and carboxylic acids.

Specific examples of hydrocarbons include propane, propene, butane, isobutane, 2-methylbutane, butene, isobutene, 2-methylpentane, 3-ethylpentane, 2,2-dimethylpentane, 3,3-dimethylpentane, hexane, cyclohexane, 2-methylhexane, 3-methylhexane, 2,5-dimethylhexane, heptane, 2-methylheptane, 3-methylheptane, 3-ethylheptane, 2,2,4,6,6-pentamethylheptane, 3-ethyl-3-methylheptane, 3-methylheptene, octane, 2-methyloctane, 4-ethyloctane, nonane, 3-methylnonane, decane, and dodecane.

Specific examples of aldehydes include formaldehyde, acetaldehyde, 2-methylpropanal, and 3-methylbutanal.

Specific examples of ketones include acetone, MEK, MIBK, and 3,3-dimethyl-2-butanone.

Specific examples of carboxylic acids include acetic acid, isovaleric acid, 2-methylpropanoic acid, 2,2-
Dimethylpropanoic acid and the like.

Hydrocarbons, aldehydes, ketones, and carboxylic acids originate from the thermal history of the highly heat-resistant, low-odor, gas-adsorbing sealant film.

[Gas adsorption layer]
The gas adsorption layer is a layer containing a gas adsorbent and having high gas adsorption properties, and preferably further contains a highly heat-resistant, low odor resin as a binder resin in order to maintain low gas release properties. However, other resins and various additives such as antioxidants can be contained within a range that does not significantly impair the gas adsorption properties and low gas release properties.
The highly heat-resistant, low odor gas-adsorbing sealant film may contain one gas-adsorbing layer or two or more layers having the same or different compositions.

In order to exhibit good gas adsorption properties, the thickness of the gas adsorption layer is preferably 5 μm or more and 80 μm or less, and more preferably 7 μm or more and 75 μm or less. If it is thinner than the above range, there is a risk that the gas adsorption properties will be insufficient, and if it is thicker than the above range, there is a risk that the gas adsorption properties will not improve significantly and the rigidity of the high heat resistance, low odor gas adsorption sealant film will become too strong, resulting in reduced workability.

[Heat seal layer]
The heat seal layer is a layer containing a highly heat resistant, low odor resin and has high heat sealability. In order to have high heat sealability, it is preferable that the heat seal layer does not contain a gas adsorbent.
In order to achieve both high heat sealability and low gas release, the heat sealable resin contained is preferably a highly heat resistant, low odor resin.
However, various additives such as gas adsorbents, other resins, and antioxidants may be contained within the range that does not significantly impair the heat sealability and low gas release properties.
The highly heat-resistant, low odor, gas-adsorbing sealant film may contain one heat seal layer or two or more layers having the same or different compositions.

In order to exhibit good heat sealability, the thickness of the heat seal layer is preferably 3 μm or more and 30 μm or less, and more preferably 5 μm or more and 20 μm or less. If it is thinner than the above range, the heat sealability may be insufficient, and if it is thicker than the above range, the heat sealability may not be significantly improved and the rigidity of the high heat resistance, low odor gas adsorption sealant film may become too weak, resulting in reduced workability.

[High heat resistant low odor resin]
A highly heat-resistant, low-odor resin is a resin that has high heat resistance and emits a small amount of gas, and the amount of gas emitted varies depending on the shape and thermal history of the resin.
By incorporating a high heat resistant, low odor resin having heat sealing properties into a high heat resistant, low odor, gas adsorption sealant film, the high heat resistant, low odor, gas adsorption sealant film is imparted with heat sealing properties, the amount of gas released is reduced, and the passage and release of gas can be suppressed.

The amount of gas released from the highly heat-resistant, low-odor resin is highly correlated with the concentration of leachable total organic carbon (TOC) contained in the highly heat-resistant, low-odor resin, which leach out during boiling or semi-retort treatment.
TOC is the concentration of the total amount of organic matter (organic carbon) in water that can be oxidized, expressed as a carbon concentration, and is used as one of the representative water quality indicators, and is standardized in JIS K0805 (Total Organic Carbon (TOC) Automatic Meter) and other standards.

The total extractable organic carbon (
The TOC concentration is preferably 1.5 ppm or more and 250 ppm or less, more preferably 5 ppm or more and 200 ppm or less. It is difficult to prepare a concentration lower than the above range, and it is difficult to show a significant difference in practical effect. If it is higher than the above range, the gas release property of the high heat resistance and low odor resin may be insufficient.

The reason why the concentration of leachable TOC for the high heat resistant, low odor resin as a single raw material is measured in a filmed state rather than in the raw material pellet state, etc., is that when the high heat resistant, low odor resin is made into a film to form a low outgassing gas adsorption sealant layer, etc., it is subjected to various thermal histories, which can increase the amount of leachable TOC.

The concentration of extractable total organic carbon (TOC) contained in the film made of the above-mentioned highly heat-resistant low odor resin can be measured as follows.
For example, a film made of the highly heat-resistant, low-odor resin of the present invention is filled in a gas sampling bag with distilled water as the filling water, boiled to elute organic carbon bodies, cooled, and then stored, and the TOC concentration in the filled water is measured.The TOC concentration of the filled water before filling is subtracted as a blank to calculate the increase in TOC concentration, and the concentration of leachable TOC contained in the film made of the highly heat-resistant, low-odor resin can be calculated.

Specific conditions are boiling temperature of 90°C to 100°C, boiling time of 10 to 60 minutes, storage temperature of 25°C to 50°C, storage period of 1 day to 4 weeks, and it is preferable to measure the TOC concentration of the filled water using a total organic carbon meter or HS-GC.

The density of the high heat resistance, low odor resin is preferably 0.920 g/cm ³ or more and 0.960 g/cm ³ or less, and more preferably 0.925 g/cm ³ or more and 0.955 g/cm ³ or less. If the density is in the above range, the amount of gas released can be reduced.

The MFR (melt flow rate) of the high heat resistance, low odor resin is preferably 0.2 g/10 min or more and 10 g/10 min or less, and more preferably 0.5 g/10 min or more and 7 g/10 min or less. If the MFR is within the above range, even if it is mixed with other resins or gas adsorbents, it can maintain a good MFR and exhibit good film-forming properties and adhesive properties.

As the highly heat-resistant, low-odor resin, a polyethylene-based resin (low gas emission polyethylene-based resin) is preferred because it has excellent heat sealability, resistance to UV or EB irradiation and heating, and resistance to decomposition.
The low gas release polyethylene resin originally contains a small amount of gas that can be released, and is resistant to UV or EB irradiation and heating and is not easily decomposed, so that the amount of gas released can be reduced.

Specific examples of polyethylene species in low gas emission polyethylene resins include, but are not limited to, low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl methacrylic acid copolymer, ethylene-propylene copolymer, and other low gas emission products, as well as mixtures of these resins.

Among the above, one or a combination of two or more selected from the group consisting of HDPE, MDPE, LDPE and LLDPE is preferred.
The LLDPE is preferably one or a combination of two or more selected from the group consisting of C4-LLDPE, C6-LLDPE, and C8-LLDPE.
E is more preferred.

Here, C4-LLDPE is a linear low-density polyethylene made of a copolymer of ethylene and 1-butene, C6-LLDPE is a linear low-density polyethylene made of a copolymer of ethylene and 1-hexene and/or 4-methyl-1-pentene, and C8-LLDPE is a linear low-density polyethylene made of a copolymer of ethylene and 1-octene.
Each of the molecular structures has an ethylene-derived LLDPE main chain with side chains having 4, 6 and 8 carbon atoms derived from 1-butene, 1-hexene and/or 4-methyl-1-pentene and 1-octene, respectively.

In order to keep the amount of released gas contained in the resin low, for example, it is effective to reduce the amount of unreacted raw materials, low molecular weight products, and by-products, and to remove the polymerization catalyst when producing the resin.Specific examples of such methods include improving the purity of raw materials, precisely controlling conditions such as reaction temperature and pressure, removing unreacted raw materials, low molecular weight products, by-products, and polymerization catalysts by distillation or washing, and preventing oxidation due to exposure to oxygen in the air at high temperatures.
Another method is to limit the use of additives that may increase the amount of outgassing when the resin is pelletized or filmed, and to prevent oxidation due to high temperatures. Specific additives include lubricants, antioxidants, antiblocking agents, solvents, etc.

[Gas adsorbent]
In the present invention, the gas adsorbent preferably contains one or a combination of two or more selected from the group consisting of hydrophobic zeolite, molecular sieve, metal organic framework (MOF), and activated carbon.

(Hydrophobic Zeolite)
In the present invention, the hydrophobic zeolite used as the gas adsorbent preferably has a _SiO2 / _{Al2O3 molar} ratio of 2/1 to 10,000/1, more preferably 30/1 to 2,000/1. When the molar ratio is within the above range, the hydrophobicity and pore size are well balanced, and good gas adsorption properties can be achieved.
Hydrophobic zeolite is preferably used because it maintains its gas component adsorption effect even when exposed to temperatures of 230° C. or higher.
The hydrophobic zeolite may have any external shape, such as a sphere, a rod, an ellipse, or the like, and may be in any form, such as a powder, a lump, or a granule. From the viewpoints of uniform dispersibility, kneading characteristics, film-forming properties, and the like, when dispersed in a resin, the powder form is preferred.

In the present invention, the average particle size of the hydrophobic zeolite can be appropriately selected from any average particle size depending on the application, but the average particle size is preferably 0.01 μm or more and 30 μm or less, and more preferably 0.1 μm or more and 20 μm or less. Here, the average particle size is a value measured by a dynamic light scattering method.
If the average particle size is smaller than the above range, the hydrophobic zeolite is likely to aggregate and the dispersibility tends to decrease.If the average particle size is larger than the above range, the film-forming property of the layer containing the hydrophobic zeolite tends to be poor, so it tends to be difficult to add a large amount of hydrophobic zeolite, and the surface area is also reduced, so there is a possibility that a sufficient gas adsorption effect cannot be obtained.

Because hydrophobic zeolite is hydrophobic, it is difficult for it to adsorb highly polar water molecules, but on the other hand, it has a high affinity for organic gases with low polarity, and it does not adsorb other gas components with low polarity, hydrophobic gases, or lipophilic gases (
Zeolite has a high affinity with gases (including solvent-based gases) and is therefore easy to adsorb. In other words, it has an excellent function of adsorbing gas components that do not have functional groups. Furthermore, when alkali metals or alkaline earth metals such as Ca, Na, and K are present on the zeolite surface, the zeolite surface exhibits basicity and is easy to adsorb acidic gases through a neutralization reaction.

(Molecular sieve)
Molecular sieves are a type of hydrophilic zeolite that adsorb highly polar molecules into their porous pores, and are particularly adsorbent of water (water vapor) molecules.
Molecular sieves are designated as 3A, 4A, 5A, or 13X depending on the type of raw zeolite, where the number indicates the approximate pore diameter (angstroms) and the capital letters indicate the type of zeolite, with A representing LTA zeolite and X representing FAU zeolite.
3A is suitable for adsorbing acetonitrile and ethanol, 5A is suitable for adsorbing aromatic compounds, and 13X is suitable for adsorbing large molecules such as long-chain tertiary amines.

(Metal-organic framework (MOF))
For metal organic frameworks (MOFs), a salt composed of a metal ion and an organic ligand is preferably used.
The metal-organic framework can have a porous structure with a smaller pore size and a larger specific surface area compared to common activated carbon or zeolite.
Specific examples of the metal organic framework include aluminum fumarate, zirconium fumarate, copper trimesate, aluminum trimesate, zirconium trimesate, iron trimesate, aluminum terephthalate, zirconium terephthalate, 2-methylimidazole zinc, magnesium formate, zinc benzene-1,3,5-tribenzoate, zinc 2,6-naphthalene-dicarboxylate, aluminum aminobenzene-1,4-dicarboxylate, magnesium 2,5-dioxidobenzene-1,4-dicarboxylate, and magnesium 4,4-dioxidobiphenyl-3,3-dicarboxylate. One or a combination of two or more selected from this group can be used.

The pore diameter of the metal organic framework is preferably 0.3 nm or more and 3.0 nm or less, and more preferably 0.3 nm or more and 2.0 nm or less. For example, the pore diameters are 1.1 nm and 0.6 nm for 2-methylimidazole zinc salt, 0.90 nm or 0.3 nm and 0.5 nm for copper trimesate, 0.8 nm and 0.5 nm for aluminum terephthalate, 1.1 nm and 0.5 nm for aluminum fumarate, 0.7 nm and 0.6 nm for aluminum trimesate, 0.46 nm, 1.15 nm, and 1.8 nm for zirconium trimesate, 0.3 nm and 0.4 nm for magnesium formate, and 2.5 nm and 2.9 nm for iron trimesate.

The specific surface area of the metal organic framework can be expressed by a BET specific surface area or a Langmuir specific surface area. In the case of the BET specific surface area, it is preferably 400 m ² /g or more and 4000 m ² /g or less, and more preferably 900 m ² /g or more and 2100 m ² /g or less.
The Langmuir specific surface area is preferably 500 m ² /g or more and 5000 m ² /g or less, and more preferably 1200 m ² /g or more and 2400 m ² /g or less.

For example, the BET specific surface areas are 1,350 ^{m 2} /g for zinc 2-methylimidazole, 1,500 ^{m 2} /g for copper trimesate, 950 ^{m 2} /g for aluminum terephthalate, 1,000 ^{m 2} /g for aluminum fumarate, 1,100 ^{m 2} /g for aluminum trimesate, 2,060 ^{m 2} /g for zirconium trimesate, 400 m ² /g for magnesium formate, and 3,600 m ² /g for zinc benzene-1,3,5-tribenzoate.
For example, the Langmuir specific surface areas are 1,800 m ² /g for zinc 2-methylimidazole, 2,000 ^{m 2} /g for copper trimesate, 1,500 ^{m 2} /g for aluminum terephthalate, 1,200 ^{m 2} /g for aluminum fumarate, 1,500 ^{m 2} /g for aluminum trimesate, 2,390 ^{m 2} /g for zirconium trimesate, 500 ^{m 2} /g for magnesium formate, and 5,000 m ² /g for zinc benzene-1,3,5-tribenzoate.

The above metal organic frameworks can absorb gases in amounts that correspond to the molecular size and specific surface area of their pores. For example, 2-methylimidazole zinc salt is excellent at absorbing lower hydrocarbons and carbon dioxide, copper trimesate is excellent at absorbing lower hydrocarbons (especially methane) and carbon dioxide, aluminum terephthalate is excellent at absorbing methane, water vapor, and carbon dioxide, aluminum fumarate and zircon trimesate are excellent at absorbing water vapor, and aluminum trimesate is excellent at absorbing lower hydrocarbons (especially methane) and water vapor.

In the present invention, among the above metal organic frameworks, it is preferable to use one or a combination of two or more selected from the group consisting of 2-methylimidazole zinc salt, copper trimesate, and aluminum terephthalate.

(activated carbon)
Activated carbon is a porous material that is primarily composed of carbon and also contains oxygen, hydrogen, calcium, etc., and has been chemically or physically processed. Because it is porous, it has a large surface area relative to its volume, and therefore has the ability to adsorb many substances.
Since the surface of activated carbon is non-polar, it has a low adsorption power for polar molecules and is more likely to selectively adsorb granular organic matter that is smaller than the pores of activated carbon.

(Improved dispersion by making gas adsorbent into a master batch)
The gas adsorbent may be directly mixed with other components of the high heat resistant, low odor gas adsorbing sealant film and melt-kneaded, but it is preferable to increase the dispersibility of the gas adsorbent in the high heat resistant, low odor gas adsorbing sealant film by mixing the gas adsorbent with a thermoplastic resin at a high concentration and then melt-kneading (melt blending) to prepare a master batch, and then mixing this with other components of the high heat resistant, low odor gas adsorbing sealant film in a ratio corresponding to the target content and melt-kneading, a so-called master batch method.
By adopting the master batch method, even when a gas adsorbent that is prone to aggregation is used, the gas adsorbent can be efficiently and uniformly dispersed in the highly heat-resistant, low odor gas adsorbing sealant film.

The mass ratio of the gas adsorbent to the thermoplastic resin in the master batch is not particularly limited, but is preferably from 3/97 to 50/50, more preferably from 5/95 to 40/60.
As a method for kneading the gas adsorbent and the thermoplastic resin, various kneading methods can be applied.
The thermoplastic resin used in the masterbatch can be of a type and content within a range that does not significantly adversely affect the heat sealability, film formability, gas adsorption, and low gas release properties of the entire high heat resistance, low odor gas adsorption sealant film, but a resin that is highly compatible with other resins such as heat sealable resins and high heat resistance, low odor resins contained in the high heat resistance, low odor gas adsorption sealant film and has the same degree of heat sealability is preferred, and may be the same as or different from these. For example, it may be a high heat resistance, low odor resin.

Specific examples of thermoplastic resins used in masterbatches include polyolefin resins such as general-purpose polyethylene, polypropylene, methylpentene polymers, and acid-modified polyolefin resins, as well as mixtures of these resins, but are not limited to these resins, and the type of thermoplastic resin can be selected according to the purpose.

The MFR (melt flow rate) of the thermoplastic resin used in the master batch is preferably 0.2 g/10 min or more and 10 g/10 min or less. If the MFR is in this range, melt mixing with the gas adsorbent is easy, the gas adsorbent is easily dispersed in the high heat resistant, low odor gas adsorbent sealant film, and the film formability of the high heat resistant, low odor gas adsorbent sealant film is easily maintained.

(Method for producing a highly heat-resistant, low odor, gas-adsorbing sealant film)
For example, a gas adsorption layer resin composition for the gas adsorption layer and a high heat resistance, low odor resin for the heat seal layer are separately prepared, and a high heat resistance, low odor gas adsorption sealant film having the following layer structure can be obtained by an inflation method.
Layer structure: heat seal layer 1/gas adsorption layer/heat seal layer 2
Alternatively, the gas adsorbing layer resin composition for the gas adsorbing layer and the highly heat-resistant, low odor resin for the heat seal layer may be laminated on a release film by extrusion coating or co-extrusion, and the release film may be removed. In the case of the extrusion coating method, lamination may be performed via an adhesive layer as necessary.

<Heat resistance measurement of highly heat-resistant, low odor gas adsorption sealant film>
The highly heat-resistant, low odor, gas-adsorbing sealant film of the present invention can have a thermal shrinkage rate of 0% or more and 10% or less when cut to, for example, 10 cm x 10 cm and boiled or heated at a temperature of 90 to 110°C for 10 to 60 minutes, and can suppress the occurrence of orange peel-like changes on the surface.
The thermal shrinkage rate is the rate of change in length, and may be, for example, the average value of the thermal shrinkage rates of the lengths of each side.
In the present invention, heat resistance does not simply mean that there is little thermal deformation or thermal decomposition at high temperatures, but also includes that the resin releases little gas components originally contained therein and that gas adsorption properties are maintained.
For example, even if a package containing contents made using a highly heat-resistant, low-odor, gas-adsorbing sealant film is subjected to a high-temperature boiling process at 90°C to 100°C or a heat treatment such as a semi-retort process at 100°C to 110°C, the generation of odor of decomposition products is suppressed and the small amount of odor of decomposition products that is generated and the oxidized odor of the contents can be adsorbed, thereby suppressing changes in the odor and taste of the contents.

<Measurement and calculation of elutable TOC concentration contained in highly heat-resistant, low-odor resin film and highly heat-resistant, low-odor gas-adsorbing sealant film>
The concentration of leachable total organic carbon (TOC) contained in the above-mentioned highly heat-resistant, low odor resin film and highly heat-resistant, low odor gas adsorption sealant film can be measured and calculated as follows.
The high heat resistance, low odor resin film and the high heat resistance, low odor gas adsorption sealant film are collectively referred to as test piece film.
First, the test piece film is placed in a gas sampling bag, which is filled with distilled water as filling water, and then sealed.
The water is then boiled to elute the organic carbon, and the water is then cooled to room temperature (about 35° C.) and left to stand for a certain period of time, after which the TOC concentration in the water is measured.
Next, the TOC concentration of the filling water before filling is subtracted as a blank to calculate the increase in TOC concentration, and the concentration of soluble TOC contained in the test piece film is calculated.
As the gas sampling bag, a SMART BAG manufactured by GL Sciences Inc. or the like can be used, and as the filling water, distilled water for high performance liquid chromatography can be used.
The TOC concentration of the filling water can be measured by a total organic carbon meter or HS-GC, for example, a TOC-L total organic carbon meter (manufactured by Shimadzu Corporation, etc.).

Specific conditions are a boiling temperature of 90°C to 100°C, a boiling time of 10 to 60 minutes, a storage temperature of 25°C to 50°C, and a storage period of 1 day to 4 weeks. In the case where the test piece film is a resin film made of a highly heat-resistant, low-odor resin, the boiling conditions are preferably 90°C, 30 minutes, and the storage conditions are 35°C, 2 weeks.
When the test piece film is a highly heat-resistant, low odor, gas-adsorbing sealant film, the boiling conditions are preferably 90° C. for 30 minutes and the storage conditions are preferably room temperature (35° C.) for 2 weeks.

The following shows an example in which the concentration C of soluble TOC contained in a test piece film is calculated from the increased concentration of TOC in the filling water.
Filled water (distilled water) weight: W1 = 1000 [g]
Test piece film
Density: S [g/cm ³ ]
Size: 15cm x 44cm x 50μm thickness, 2 sheets
Weight: W2 = 15 x 44 x 50 x 10 ^-4 x 2 x S = 6.6 x S [g]
Concentration of elutable TOC: C [ppm]
Increase in TOC concentration in filling water: X [ppm]
Then,
Total weight of elutable TOC contained in the test piece film = C x W2 [g]
This dissolves in W1 [g] of water, so
X=C×W2/W1=C×6.6×S×10 ^-3 [ppm]
The TOC concentration C of the soluble TOC contained in the test piece film is calculated from the following formula:
C=X/(6.6×S×10 ^-3 ) [ppm]
For example, when the density S of the test piece film is 1.00 [g/cm ³ ] and the increase X in the TOC concentration of the filling water is 0.01 [ppm],
C=0.01/(6.6×1.00×10 ^-3 )=1.51 [ppm]
It is calculated as follows:

The elutable TOC concentration in the high heat resistance, low odor gas adsorption sealant film measured under the above conditions is preferably 0.01 ppm or more and 1.5 ppm or less, and more preferably 0.02 ppm or more and 1.2 ppm or less. It is difficult to produce a film with a concentration lower than the above range, and it is difficult to show a significant difference in practical effect. If it is higher than the above range, the low odor property of the high heat resistance, low odor gas adsorption sealant film may be insufficient. From the viewpoint of achieving both cost and performance, the above range is preferable.

Details of the raw materials used in the examples are as follows.
[High heat resistant low odor resin]
High heat resistance and low odor resin 1: Ultzexx 3520L, manufactured by Prime Polymer Co., Ltd. C6-LLDPE, density 0.931 g/cm ³ , MFR 2.1 g/10 min. Extractable TOC concentration contained in the resin film 42.3 ppm.
High heat resistance and low odor resin 2: Ultzex 4020L, manufactured by Prime Polymer Co., Ltd. C6-LLDPE, density 0.937 g/cm ³ , MFR 2.3 g/10 min. Extractable TOC concentration contained in the resin film 32.5 ppm.
High heat resistance and low odor resin 3: Hi-Zex 3300F, manufactured by Prime Polymer Co., Ltd. HDPE, density 0.949 g/cm ³ , MFR 1.1 g/10 min. Extractable TOC concentration contained in the resin film 24.4 ppm.

[General-purpose polyethylene]
General-purpose polyethylene 1: Evolu SP4020 manufactured by Prime Polymer Co., Ltd. C6-LLDPE, density 0.937 g/cm ³ , MFR 1.7 g/10 min. TOC concentration of extracted water 2
.85 ppm, and the elutable TOC concentration contained in the resin film was 461 ppm.
General-purpose polyethylene 2: Evolue SP1520 manufactured by Prime Polymer Co., Ltd. C6-LLDPE, density 0.913 g/cm ³ , MFR 2.0 g/10 min. TOC concentration of tree extract water 3.05 ppm, elutable TOC concentration contained in resin film 506 ppm.

[Gas adsorbent]
Hydrophobic zeolite 1: Mizuka Sieves EX-122, a hydrophobic zeolite manufactured by Mizusawa Chemical Industry Co., Ltd. SiO ₂ /Al ₂ O ₃ molar ratio=32/1, average particle size 2.5 to 5.5 μm.
Hydrophobic zeolite 2: Silton MT400, a hydrophobic zeolite manufactured by Mizusawa Chemical Industry Co., Ltd. SiO ₂ /Al ₂ O ₃ molar ratio=400/1, average particle size 5 to 7 μm.
Hydrophobic zeolite 3: Silton MT-2000, a hydrophobic zeolite manufactured by Mizusawa Chemical Industry Co., Ltd. SiO ₂ /Al ₂ O ₃ molar ratio=2000/1, average particle size 0.8 μm.

[Preparation of Masterbatch]
The masterbatch used in the gas adsorption layer was prepared as follows.

(Preparation of Masterbatch 1)
High heat resistant, low odor resin 1 and hydrophobic zeolite 1 were melt blended in the following ratio to obtain master batch 1 (MB1).
High heat resistance, low odor resin 1 70 parts by weight Hydrophobic zeolite 1 30 parts by weight

[Preparation of Masterbatches 2 to 5]
According to the formulation in Table 1, the raw materials were melt-blended in the same manner as for Masterbatch 1 to obtain Masterbatches 2 to 5 (MB2 to 5).

Example 1
[Preparation of Gas Adsorption Layer Resin Composition]
MB1 and highly heat-resistant, low-odor resin 1 were dry-blended in the following ratio to obtain a gas adsorbing layer resin composition 1 to be used in the gas adsorbing layer.
MB1 5.6 parts by mass High heat resistant low odor resin 1 94.4 parts by mass

[Preparation of high heat resistance, low odor, gas adsorption sealant film]
Using the gas adsorbing layer resin composition 1 and the high heat resistant, low odor resin 1 obtained above, a high heat resistant, low odor gas adsorbing sealant film 1 having the following layer structure was obtained by an inflation method.
The obtained highly heat-resistant, low odor gas-adsorbing sealant film 1 was used to evaluate film-forming properties, heat shrinkability, TOC elution amount, and odor functionality.
Layer structure of high heat resistance, low odor gas adsorption sealant film 1: Heat seal layer 1/gas adsorption layer/heat seal layer 2=high heat resistance low-type resin 1 (10 μm thick)/gas adsorption layer resin composition 1 (30 μm thick)/high heat resistance low odor resin 1 (10 μm thick)

<Examples 2 to 9 and Comparative Examples 1 to 4>
A gas adsorption layer resin composition was prepared according to the layer structure of the entire film shown in Tables 2 to 4, and a highly heat-resistant, low odor gas adsorption sealant film was obtained by the inflation method in the same manner as in Example 1 using the gas adsorption layer resin composition and/or resin, and was evaluated in the same manner.

<Evaluation method>
[Film forming property]
The appearance of the highly heat-resistant, low odor, gas-adsorbing sealant film was observed and evaluated sensorily. The evaluation criteria were as follows:
○: Film formation is possible without wrinkles or bumps.
×: Numerous wrinkles and bumps were generated, making film formation difficult.

[Heat sealability]
The highly heat-resistant, low odor, gas-adsorbing sealant film was cut into a size of 10 cm x 10 cm, and one side of the film was adhered to a PET film (PET film, Espet T4102, thickness 12 μm, manufactured by Toyobo Co., Ltd.) by dry lamination bonding using a dry lamination adhesive (Adlock RU77T/H7, manufactured by Rock Paint Co., Ltd., a polyester-based adhesive) to obtain a laminate.
Two sheets of the laminate prepared above were then overlapped with their heat-sealed surfaces facing each other, and a 1 cm x 10 cm area was heat-sealed under the following conditions using a heat seal tester (TP-701-A manufactured by Tester Sangyo Co., Ltd.), to prepare a test piece for peel strength in which the ends were not heat-sealed or bonded, and the ends were split into two.
This test piece was cut into a strip of 15 mm width, and each bifurcated end was attached to a tensile tester to measure the peel strength (N/15 mm) under the conditions described below, and the pass/fail judgment was made according to the pass/fail judgment criteria described below.
Heat sealing conditions Temperature: 160°C
Pressure: 1 kgf/ ^cm2
Time: 1 second Test conditions Test speed: 300 mm/min Load range: 50 N
Pass/fail criteria: ◯: 30N/15mm or more, passed.
×: Less than 30N/15mm, not acceptable.

[Heat shrinkage state after boiling]
A highly heat-resistant, low-odor, gas-adsorbing sealant film cut to 10 cm x 10 cm was boiled in hot water at 90 to 100°C for 10 minutes, and the average shrinkage rate of each side after boiling was calculated and judged as pass or fail according to the following criteria.
Good: Heat shrinkage rate is 10% or less. Passed.
×: The heat shrinkage rate is more than 10%, or the film is welded and measurement is impossible.

[Whether or not the skin is soft after boiling]
A highly heat-resistant, low odor, gas-adsorbing sealant film cut to a size of 10 cm x 10 cm was boiled in hot water at 90 to 100°C for 10 minutes, and the appearance was visually observed to check for the occurrence of orange peel.
O: No yuzu skin, passed.
×: Yuzu skin, fail

[Elutable TOC concentration]
A gas sampling bag (GL Sciences, SMART BAG) was filled with the following size of high heat resistant, low odor gas adsorption sealant film and water, sealed, boiled at 90°C for 30 minutes, cooled to room temperature, and stored at 35°C for 2 weeks, after which the TOC concentration of the filled water was measured and the increase in TOC concentration was determined.
High heat resistance, low odor, gas adsorption sealant film Size: 15cm x 44cm x 50μm thick x 2 sheets.
Filling water: Distilled water for high performance liquid chromatography manufactured by Junsei Chemical Co., Ltd. 1000 g.
TOC concentration measuring device: TOC-L total organic carbon meter manufactured by Shimadzu Corporation.
Next, from the increase in TOC concentration in the filling water obtained above, the concentration of elutable TOC contained in the highly heat-resistant, low odor gas adsorption sealant film was calculated by the following formula.
C = X × W1/W2
= X × W1 / (6.6 × S)
C: concentration of elutable TOC contained in the highly heat-resistant, low-odor, gas-adsorbing sealant film [ppm]
X: Increased concentration of TOC in the filling water [ppm]
W1: Filled water weight = 1000 [g]
W2: High heat resistance, low odor, gas adsorption sealant film weight = 15 x 44 x 50 x 10
^-4 ×2×S=6.6×S[g]
S: density of the highly heat-resistant, low odor, gas-adsorbing sealant film [g/cm ³ ]

[Odor and Taste Sensory Evaluation]
A pouch (external dimensions: 13 cm x 17 cm) made from a gas sampling bag (GL Sciences, SMART BAG) was filled with two sheets of highly heat-resistant, low-odor gas adsorption sealant film cut to 11 cm x 15 cm and 100 ml of water (Japanese natural water, Suntory) as filling water to prepare a packaged liquid filling, which was then boiled at 90°C for 30 minutes and then stored for one week in a room temperature environment, after which a sensory evaluation of the odor and taste of the filled water was conducted.
The evaluation indicators are as follows:
1: Strong odor 2: Odor slightly reduced 3: Odor significantly reduced 4: Same as natural water before filling

<Summary of results>
The highly heat-resistant, low odor gas-adsorbing sealant films of all the Examples exhibited excellent film-forming properties, heat-sealing properties, low thermal shrinkage after boiling, appearance after boiling, extractable TOC concentration, and odor and taste functionality.
However, the sealant films of Comparative Examples 1, 2 and 3 using general-purpose resins showed poor results in any one of low heat shrinkage after boiling, appearance after boiling, extractable TOC concentration and taste and odor functionality.
Moreover, the sealant film of Comparative Example 4, which contained too much gas adsorbent, showed poor film-forming properties and heat sealability.

1 High heat resistance, low odor gas adsorption sealant film 4a Gas adsorption layer 4b Gas adsorbent 4c Heat seal layer

Claims (5)

A highly heat-resistant, low-odor, gas-adsorbing sealant film,
The highly heat-resistant, low-odor, gas-adsorbing sealant film contains a highly heat-resistant, low-odor resin having heat-sealing properties and a gas adsorbent, and adsorbs gases generated from itself and gases from the outside.
the gas is one or a combination of two or more selected from the group consisting of hydrocarbons, aldehydes, ketones, and carboxylic acids;
The high heat resistance and low odor resin has a density of 0.920 g/ ^cm3 or more and 0.960 g/ ^cm3 or less,
the gas adsorbent is a hydrophobic zeolite ;
The content of the high heat resistance, low odor resin in the total resin contained in the high heat resistance, low odor gas adsorption sealant film is 70 mass% or more and 100 mass% or less,
The content of the gas adsorbent in the layer containing the gas adsorbent is 0.1% by mass or more and less than 27.50% by mass ,
The concentration of leachable total organic carbon (TOC) contained in the film made of the highly heat-resistant, low-odor resin is 24.4 ppm or more and 42.3 ppm or less, and is leachable by boiling at 90 to 110°C for 30 minutes and by storing the film at rest at 35°C.
The heat shrinkage rate is 0% or more and 10% or less when boiled for 10 minutes or more and 60 minutes or less at a temperature of 90°C or more and 100°C or less, and the surface does not have an orange peel-like change.
The highly heat-resistant, low odor, gas-adsorbing sealant film. The highly heat-resistant, low-odor, gas-adsorbing sealant film according to claim 1, characterized in that the highly heat-resistant, low-odor resin is a polyethylene-based resin. The highly heat-resistant, low-odor gas-adsorbing sealant film according to claim 1, characterized in that the highly heat-resistant, low-odor resin is one or a combination of two or more selected from the group consisting of high-density polyethylene, medium-density polyethylene, low-density polyethylene, and linear low-density polyethylene. The highly heat-resistant, low odor gas adsorption sealant film has a gas adsorption layer and a heat seal layer,
the gas adsorption layer is a layer containing the high heat resistant, low odor resin and the gas adsorbent,
the heat seal layer contains the highly heat resistant, low odor resin and has heat sealability;
At least one outermost layer of the highly heat-resistant, low odor, gas-adsorbing sealant film is a heat seal layer,
The high heat resistant, low odor resin contained in the gas adsorption layer and the high heat resistant, low odor resin contained in the heat seal layer are the same or different.
The highly heat-resistant, low odor, gas-adsorbing sealant film according to any one of claims 1 to 3. A highly heat-resistant, low-odor, gas-adsorbing sealant film for boiling sterilization or semi-retort sterilization, using the highly heat-resistant, low-odor, gas-adsorbing sealant film according to any one of claims 1 to 4.