JP7813093B2 - Odor-absorbing stretch film - Google Patents

Description

The present invention relates to an odor-adsorbing stretched film, and an odor-adsorbing stretched packaging material and an odor-adsorbing stretched package produced using the odor-adsorbing stretched film.
In particular, it has excellent adsorption properties for odorous substances such as aldehydes, ketones, sulfur compounds, and amines.

Packaging materials incorporating odor adsorbents have been proposed. In these packaging materials, odor adsorbents such as synthetic zeolite and activated carbon are kneaded into a resin material (see Patent Document 1). However, these materials have the problem of adsorbing not only odors but also atmospheric moisture, and desorbing the odors once adsorbed, so they do not achieve a sufficient odor adsorption effect.
Packaging materials containing an odor adsorbent made by supporting a chemical adsorbent on an inorganic porous material are also known (Patent Document 2), but the main substances to be adsorbed are only odor components having specific functional groups, and unless the resin material is selected appropriately, they are not able to sufficiently adsorb odor components of organic substances that do not have functional groups.

Patent No. 2538487 JP 2014-233408 A

The objective of the present invention is to solve the above-mentioned problems and provide a film that has an excellent balance of manufacturability, such as film-forming properties, suitability for filling machines, and a high odor adsorption effect over a long period of time against odorous substances such as aldehydes, ketones, sulfur-based compounds, and amines, as well as packaging materials and packages that use this film.

As a result of extensive investigations, the present inventors have found that a stretched film having a specific odor-absorbing layer can achieve the above object.
The present invention is characterized by the following points.
1. An odor-adsorbing stretched film capable of adsorbing odors of aldehydes, ketones, sulfur-based compounds, or amines,
The odor-adsorbing stretched film has at least an odor-adsorbing layer,
the odor absorbing layer contains a binder resin and an odor absorbing agent;
The odor adsorbent contains hydrophobic zeolite and/or a metal-supported inorganic porous material,
The odor-absorbing stretched film has a water vapor permeability of 10 g/( ^m2 ·day) or more.
Odor-absorbing stretch film.
2. The odor-adsorbing stretched film according to the above item 1, wherein the odor adsorbent further contains an amino group-supporting inorganic porous material.
3. The odor-absorbing stretched film according to item 1 or 2 ^above , wherein the binder resin is one or more resins selected from the group consisting of C4-LLDPE, C6-LLDPE, and C8-LLDPE, ^each having a density of 0.90 g/cm3 or more and 0.94 g/cm3 or less.
4. The odor-adsorbing stretched film according to any one of items 1 to 3 above, wherein the odor adsorbent is melt-kneaded in advance with the thermoplastic resin in a mass ratio of odor adsorbent/thermoplastic resin of 0.5/99.5 to 40/60.
5. The layer structure of the odor-absorbing stretched film is
a layer structure consisting of only the odor adsorption layer;
a layer structure having the odor adsorption layer and a heat seal layer on one surface thereof;
a layer structure having the odor adsorption layer and heat seal layers on both surfaces thereof;
Any layer structure selected from the group consisting of:
the heat seal layer contains a heat sealable resin but does not contain the odor adsorbent;
5. An odor-adsorbing stretched film according to any one of 1 to 4 above.
6. An odor-adsorbing stretched packaging material comprising the odor-adsorbing stretched film according to any one of 1 to 5 above.
7. An odor-absorbing stretched packaging body made using the odor-absorbing stretched packaging material described in 6 above.

The present invention provides a film that has an excellent balance of manufacturing suitability, including film-forming properties, suitability for filling machines, and a high odor adsorption effect over a long period of time for odorous substances such as aldehydes, ketones, sulfur-based compounds, and amines, as well as packaging materials and packages that use this film.

1 is a schematic cross-sectional view showing an example of the layer structure of an odor-adsorbing stretched film of the present invention. FIG. 2 is a schematic cross-sectional view showing another example of the layer structure of the odor-adsorbing stretched film of the present invention. FIG. 2 is a schematic cross-sectional view showing another example of the layer structure of the odor-adsorbing stretched film of the present invention. FIG. 1 is a diagram showing the adsorption mechanism of odorous substances by a chemical adsorbent-supporting inorganic porous material.

The odor-adsorbent stretched film of the present invention and the packaging material and package produced using the odor-adsorbent stretched film are described in detail below. Specific examples are provided for explanation, but the present invention is not limited to these.

<<Odor-absorbing stretched film>>
The odor-adsorbing stretched film of the present invention is a heat-sealable and odor-adsorbing stretched sealant film, which is particularly excellent in adsorbing odors of aldehydes, ketones, sulfur-based compounds, and amines.
The odor-adsorbing stretched film has a layer structure including at least an odor-adsorbing layer.
The odor-adsorbing stretched film may be a single-layer structure as shown in FIG. 1, which is composed only of an odor-adsorbing layer, or may be a laminate structure having a multi-layer structure. In the case of a multi-layer structure, it may have various layers other than the odor-adsorbing layer, as necessary.

The odor absorbing layer contains an odor absorbing agent and a binder resin, and may contain other components.
The odor adsorbing layer may be composed of a single layer containing a binder resin and an odor adsorbent, or may be composed of two or more layers having the same and/or different compositions, for example, two or more layers having different types or amounts of odor adsorbents.
Furthermore, for example, as shown in Figures 2 and 3, one or both surfaces of the odor-adsorbing stretched film may be a layer containing a heat-sealable resin but not an odor adsorbent (hereinafter referred to as a heat-sealable layer).
By providing a heat seal layer or an odor absorbing layer with a low odor absorbing agent content on the outer surface of the odor-absorbing stretched film, high heat sealability can be achieved.
The odor-absorbing stretched film may contain components other than the binder resin, heat-sealable resin, and odor absorbent, such as slip agents, antiblocking agents, antioxidants, solvents, and other additives in small amounts as needed.
Furthermore, the layers constituting the odor-adsorbing stretched film may be laminated via an adhesive layer.

Specific examples of layer configurations of odor-adsorbing stretched films include a single-layer configuration consisting of an odor-adsorbing layer, a two-layer configuration consisting of a heat-sealing layer/odor-adsorbing layer, and a three-layer configuration consisting of a heat-sealing layer/odor-adsorbing layer/heat-sealing layer.

The odor adsorbent content in the odor adsorption layer is preferably 0.3% by mass or more and 15% by mass or less, and more preferably 0.5% by mass or more and 14% by mass or less. If the content is less than this range, the odor adsorption effect will be difficult to achieve, and if the content is more than this range, film formability may be impaired.

The thickness of the odor-adsorbing stretched film of the present invention is preferably 10 μm to 60 μm, more preferably 15 μm to 50 μm, in order to achieve a good balance between heat-sealing properties and odor adsorption properties. If the thickness is thinner than this range, the film is prone to tearing, while if the thickness is thicker than this range, the film is too rigid and is likely to be inferior in suitability for packaging applications.
The thickness of the odor adsorption layer is preferably 5 μm or more and 40 μm or less. If the thickness is thinner than this range, the heat sealability and/or odor adsorption properties may be insufficient, and if the thickness is thicker than this range, the laminate may be too rigid.

The odor-adsorbing stretched film of the present invention is preferably a stretched film, which improves the strength, dimensional stability, and heat resistance of the odor-adsorbing stretched film and allows it to have a high water vapor permeability.
The stretching treatment may be, for example, stretching by a tenter system or a tubular system, and the stretching ratio is preferably 1.5 to 4 times. The stretching direction may be uniaxial or biaxial.
If the stretching ratio is less than the above range, the water vapor transmission rate may not be sufficiently high, and if it is greater than the above range, the uniformity of odor adsorption, water vapor transmission rate, heat sealing properties, etc. may be insufficient.
The water vapor permeability of the odor-adsorbing stretched film is preferably 10 g/( ^m2 ·day) or more. If the water vapor permeability is lower than this range, it may be difficult to maintain a low humidity level inside the package.
Regarding the upper limit, even when the value is higher than the upper limit of measurement of 300 g/( ^m2 ·day) using a general water vapor transmission rate measuring device, the film can be used without any problems as an odor-absorbing stretched film. Therefore, although it can be said that the value is greater than 300 g/( ^m2 ·day), it is not possible to set an exact upper limit.

The odor-adsorbing stretched film of the present invention preferably has a porous structure.
This porous structure exists mainly in the resin matrix of the odor adsorption layer, and can be created by stretching the odor-adsorbing stretched film and peeling off the surrounding resin that is in contact with the odor adsorbent particles.
The odor-adsorbing stretched film has a porous structure, which allows it to have a high water vapor permeability.

[Odor adsorption]
In the present invention, odor adsorption ability refers to the ability to physically adsorb odorous substances, the ability to chemically adsorb odorous substances, or the ability to decompose and deodorize them by oxidation-reduction reaction.
The odorous substances to be adsorbed in the present invention are aldehydes, ketones, sulfur-based compounds, and amines.

Specific examples of aldehyde compounds include trans-4,5-epoxy-(E)-2-decenal, 2-methylpropanal, 3-methylbutanal, acetaldehyde, and formaldehyde.
Specific examples of ketone compounds include 1-octen-3-one, diacetyl (acetoin), acetone, nonenal, MEK, MIBK, and 3,3-dimethyl-2-butanone.
Specific examples of sulfur-based compounds include hydrogen sulfide, methanethiol, dimethyl sulfide, propanethiol, and dimethyl disulfide.
Specific examples of amine compounds include ammonia, dimethylamine, pyridine, and trimethylamine.

(Suitable for filling machines)
Filling machine suitability refers to the suitability for manufacturing without defects such as poor heat sealing or pinholes occurring in a process using a filling machine that continuously produces sterilization-generated odor-absorbing packaging and fills it with the contents.

[Odor absorbent]
In the present invention, the odor adsorbent may be a physical odor adsorbent and/or a chemical odor adsorbent.
The physical odor adsorbent is an odor adsorbent that physically adsorbs odorous substances, preferably exhibiting a neutralizing effect, and specific examples of such compounds include hydrophobic zeolite inorganic porous materials.
The chemical odor adsorbent is an odor adsorbent that chemically adsorbs odorous substances and preferably decomposes the odorous substances through an oxidation-reduction reaction, and examples thereof include deodorizing glass having an oxidation-reduction action, a mixture of metal salts and metal oxides, and inorganic porous bodies carrying a chemical adsorbent.
Examples of the inorganic porous material carrying a chemical adsorbent include an amino group-carrying inorganic porous material and a metal-carrying inorganic porous material.
The odor adsorption layer of the present invention can contain one or more odor adsorbents selected from the above group, and preferably contains a hydrophobic zeolite and/or a metal-supported inorganic porous material. It is even more preferable that the layer further contains an amino group-supported inorganic porous material, if necessary.

(Hydrophobic Zeolite)
In the present invention, the hydrophobic zeolite has a function of mainly physically adsorbing odorous substances.
Hydrophobic zeolites have excellent adsorption performance for aldehydes, ketones, sulfur-based compounds, and amines, and are particularly excellent in adsorption performance for aldehydes, ketones, and sulfur-based compounds.
In the present invention, the hydrophobic zeolite used as the odor adsorbent preferably has a SiO ₂ /Al ₂ O ₃ molar ratio of 400/1 to 10,000/1. When the molar ratio is within the above range, the hydrophobicity and pore size are well balanced, and good odor adsorption properties can be achieved.
The hydrophobic zeolite maintains its effect of adsorbing odorous components even when the laminate of the present invention is 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. However, from the viewpoints of uniform dispersibility, kneading properties, film-forming properties, and the like when dispersed in a resin, a powder form is preferred.

In the present invention, the average particle size of the hydrophobic zeolite can be selected appropriately depending on the application, but the average particle size is preferably 0.01 μm to 15 μm. Here, the average particle size is a value measured by dynamic light scattering.
If the average particle size is smaller than the above range, the hydrophobic zeolite tends to aggregate and the dispersibility tends to decrease, whereas if the average particle size is larger than the above range, the film-forming properties of the layer containing the hydrophobic zeolite tend to be poor, making it difficult to add a large amount of hydrophobic zeolite, and furthermore, the surface area is reduced, which may result in insufficient deodorizing effect.

Unlike non-hydrophobic (hydrophilic) zeolites, in which odorous substances and water vapor are adsorbed to the same adsorption sites, hydrophobic zeolites are hydrophobic and therefore have difficulty adsorbing highly polar molecules such as water molecules. Conversely, they have a high affinity for less polar odorous molecules, hydrophobic gases, and lipophilic gases (including solvent-based gases), which are easily adsorbed. Furthermore, due to the effect of alkali metals and alkaline earth metals such as Ca, Na, and K present on the zeolite surface, the zeolite surface exhibits basicity, making it easy to adsorb acidic gases through a neutralization reaction.

(Inorganic porous material)
Examples of inorganic porous materials used in deodorants include activated clay and activated bentonite.
Activated clay is a type of clay that is porous, has a large specific surface area, and has excellent adsorption properties. It is obtained by heat treating acid clay, whose main component is naturally occurring montmorillonite, with inorganic acids such as sulfuric acid or hydrochloric acid.
Activated clay having a large specific surface area is preferred, and although there is no particular restriction on the specific surface area, clay with a specific surface area of 50 to 400 m ² /g is readily available. The pH (5% suspension) is preferably 2.5 to 9, more preferably 3 to 7.
Activated bentonite is made by artificially converting Ca-type bentonite into Na-type bentonite by adding a few wt % of sodium carbonate, and exhibits properties similar to those of Na-type bentonite.
Here, bentonite is a substance whose main component is the clay mineral montmorillonite and contains minerals such as quartz and feldspar as impurities, and is broadly divided into two types: Na-type bentonite, which contains a large amount of Na ⁺ ions, and Ca-type bentonite, which contains a large amount of Ca2 ⁺ ions. Basic bentonite is preferred, with a pH of 8 to 13, more preferably 9 to 12, and even more preferably 10 to 11.

(Deodorizing glass)
Deodorizing glass is a glassy inorganic material with deodorizing effects, and contains compounds in which phosphorus, copper, silicon, and other metal salts are supported on inorganic materials. Trace amounts of the contained metal elements are ionized to exert a deodorizing effect.
The metal components in the deodorizing glass are ionized and act as a catalyst to accelerate the decomposition reaction of odorous substances.

(Metal salt/metal oxide mixture)
Examples of the metal salt/metal oxide mixture include a mixture of a salt consisting of a metal cation and an inorganic acid anion with a metal oxide, and specifically, a mixture of alum (AlK(SO ₄ ) ₂ ) with CaO and ZnO.
The metal components in the metal salt/metal oxide mixture are ionized, and act as a catalyst to accelerate the decomposition of odorous sulfur compounds.

(Chemical adsorbent-supporting inorganic porous material)
In the present invention, the chemical adsorbent-supported inorganic porous material is an inorganic porous material that supports an organic compound or a metal compound and has the function of mainly chemically adsorbing odorous substances, and examples thereof include amino group-supported inorganic porous materials and metal-supported inorganic porous materials.
In the present invention, the organic compound used in the chemical adsorbent-supported inorganic porous material is a compound that has a reactive functional group that chemically reacts with and bonds to odorous substances and that can be supported on the inorganic porous material.
More specifically, it is an organic compound having a functional group that is reactive to bond with aldehydes, ketones, carboxylic acids, or alcohols, and examples of such compounds include organic compounds containing an amino group, metal compounds, etc.

As a method for supporting the chemical adsorbent, a known or commonly used supporting method can be applied. For example, the chemical adsorbent can be supported by impregnating the inorganic porous body with a solution containing the chemical adsorbent described below and drying the resultant.
In the present invention, by using a chemical adsorbent-supported inorganic porous material, the adsorption capacity per unit mass of the odor adsorbent can be significantly increased, the content of the odor adsorbent in the laminate can be reduced, and physical adsorption properties in the pores of the inorganic porous material can also be expected.
These properties make it possible to maintain excellent film-forming properties, and in some cases to maintain a balance with coatability, heat-sealability, and the like.

The chemical adsorbent-supporting inorganic porous material may have any external shape, such as spherical, rod-like, or elliptical, and may be in any form, such as powder, lump, or granule. However, from the viewpoints of the above-mentioned film-forming properties, uniform dispersibility, kneading characteristics, etc., a powder form is preferred.

The average particle size of the chemical adsorbent-supporting inorganic porous material can be selected appropriately depending on the application, but in the present invention, the average particle size is preferably 0.01 μm to 15 μm, more preferably 0.1 μm to 13 μm, and even more preferably 1 μm to 12 μm. Here, the average particle size is a value measured by dynamic light scattering.
If the average particle size is smaller than the above range, the chemical adsorbent-supporting inorganic porous material is likely to aggregate, and dispersibility tends to decrease.
Furthermore, if the average particle size is larger than the above range, the film-forming properties will be poor, making it difficult to incorporate a large amount of the chemical adsorbent-supporting inorganic porous material, and there is a possibility that a sufficient adsorption effect will not be obtained.

The mechanism by which the chemical adsorbent-carrying inorganic porous material adsorbs odorous substances will be explained in more detail using specific examples shown in FIG. 4, but the present invention is not limited to these.
Fig. 4 shows the case where aldehyde odorous substances are chemically adsorbed to an inorganic porous material carrying amino groups. The aldehyde groups of the aldehyde odorous substances and the amino groups of the inorganic porous material carrying amino groups undergo a chemical reaction to bond, and the aldehyde odorous substances are adsorbed.

The chemical adsorbent-carrying inorganic porous material is chemically adsorbed, so that once adsorbed odorous substances are difficult to desorb, and odor adsorption can be carried out efficiently.
Furthermore, since odorants bind to specific functional groups of the chemical adsorbent, it is less susceptible to the effects of various substances that reduce odor adsorption capacity, such as water vapor.

(Amino group-supported inorganic porous material)
The amino group-supported inorganic porous material is an inorganic porous material that supports amino groups on the surface, and is capable of chemically adsorbing odorous substances that chemically react with the amino groups.
The amino group-supporting inorganic porous material can be prepared, for example, by using a compound having an amino group.
Examples of compounds containing an amino group include alkylamines, cyclic amines, polyamines, and alcoholamines, such as ethylenediamine, tetramethylenediamine, metaphenylenediamine, diethylenetriamine, triethylenetriamine, tetraethylenepentamine, ethanolamine, piperazine, and piperidine.
The amino group-supported inorganic porous material has excellent adsorption performance for aldehydes and ketones.
Aldehydes and ketones react chemically with amino groups via the Schiff reaction and are adsorbed.

(Metal-supported inorganic porous material)
The metal-supported inorganic porous material is an inorganic porous material that supports a metal element in the state of metal, metal ion, or metal oxide.
Metal-supported inorganic porous materials have excellent adsorption performance for sulfur-based compounds, ketones, and amines.
The metal species to be supported preferably contains one or more metals selected from the group consisting of copper, zinc, silver, platinum, iron and cobalt.
In the present invention, by using a metal-supported inorganic porous material, the adsorption capacity per unit mass of the odor adsorbent can be significantly increased, the content in the laminate can be reduced, and physical adsorption properties in the pores of the inorganic porous material can also be expected.
Furthermore, the metal-supported inorganic porous material may have any external shape, such as a spherical, rod-like, or elliptical shape, and may be in any form, such as a powder, a lump, or a granule. However, from the viewpoints of the above-mentioned film-forming properties, uniform dispersibility, kneading properties, etc., a powder form is preferred.

The metal-supported inorganic porous material can be selected from those with any average particle size depending on the application, but in the present invention, those with an average particle size of 0.01 μm to 15 μm are particularly preferred, those with an average particle size of 0.1 μm to 13 μm are more preferred, and those with an average particle size of 1 μm to 12 μm are even more preferred. Here, the average particle size is a value measured by dynamic light scattering.
If the average particle size is smaller than the above range, the metal-supported inorganic porous material is likely to aggregate, and dispersibility tends to decrease.
If the average particle size is larger than the above range, the film-forming properties will be poor, making it difficult to incorporate a large amount of the metal-supported inorganic porous material, and there is a possibility that a sufficient adsorption effect will not be obtained.

(Inorganic porous material used in chemical adsorbent-supporting inorganic porous material)
In the present invention, the inorganic porous material used in the chemical adsorbent-supporting inorganic porous material can be any inorganic compound having a large number of pores on its surface. Examples include zeolite, silicon dioxide, silicates, activated carbon, titania, inorganic phosphates such as calcium phosphate, alumina, aluminum hydroxide, magnesium hydroxide, and mixtures thereof. In particular, aluminum hydroxide, zeolites, and silicates are preferably used in view of the pore state having pore sizes effective for the molecular size or cluster size of the substance to be adsorbed, and from the viewpoint of safety.
In the above, the zeolite is preferably hydrophobic, and more preferably has a SiO ₂ /Al ₂ O ₃ molar ratio of 400/1 to 10,000/1.
In particular, aluminum hydroxide, zeolite, and silicates are preferably used from the viewpoint of safety and having a porous state with pores of an effective size relative to the molecular size or cluster size of the substance to be adsorbed.

The inorganic porous body may have any external shape, such as a spherical shape, a rod shape, an elliptical shape, or the like, and may be in any form, such as a powder shape, a lump shape, or a granular shape. However, a powder shape is preferred from the viewpoints of the film-forming properties, uniform dispersion, kneading properties, and the like, after the inorganic porous body is made by supporting the chemical adsorbent.
The inorganic porous material can be appropriately selected from those with any average particle size depending on the application. In order to achieve the average particle size of the chemical adsorbent-supporting inorganic porous material described above, the average particle size is preferably 0.01 μm to 15 μm, more preferably 0.1 μm to 13 μm, and even more preferably 1 μm to 12 μm.

(Improved dispersibility through masterbatch of odor adsorbent)
The odor adsorbent may be directly mixed with the other components of the odor adsorption layer and melt-kneaded, but it is preferable to increase the dispersibility of the odor adsorbent in the odor adsorption layer by using the so-called masterbatch method, in which the odor adsorbent is mixed at a high concentration with a thermoplastic resin and then melt-kneaded (melt-blended) to prepare a masterbatch, and this is then mixed with the other components of the odor adsorption layer in a ratio corresponding to the target content and melt-kneaded.
By employing the masterbatch method, even when an odor adsorbent that is prone to aggregation is used, the odor adsorbent can be dispersed efficiently and uniformly in the odor adsorption layer.

The mass ratio of gas adsorbent to thermoplastic resin in the masterbatch is not particularly limited, but is preferably 0.5/99.5 to 40/60, and more preferably 1/99 to 35/65.
As a method for kneading the odor adsorbent and the thermoplastic resin, a known or commonly used kneading method 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, odor adsorption properties, or low elution properties of the entire odor adsorption layer.

The MFR (melt flow rate) of the thermoplastic resin is preferably 0.2 g/10 min or more and 10 g/10 min or less. An MFR within this range facilitates melt-kneading with the odor adsorbent, makes it easy to disperse the odor adsorbent in the odor adsorption layer, and helps maintain the film-forming properties of the odor adsorption layer.

Specific examples of the thermoplastic resin include, for example, general-purpose polyethylene, polypropylene, methylpentene polymer, polyolefin resins such as acid-modified polyolefin resins, and mixtures of these resins, but are not limited to these resins, and the type of thermoplastic resin can be selected depending on the purpose.
It is also possible and preferable to use the heat-sealable resin contained in the odor adsorption layer as the thermoplastic resin.

[Binder resin]
The binder resin contained in the odor adsorption layer is preferably a thermoplastic resin that can disperse the odor adsorbent and form the odor adsorption layer.
When the odor adsorption layer has heat-sealing properties, it is preferable to use a heat-sealing resin as the binder resin.
Examples of binder resins include polyolefins, olefin copolymers, copolymers of olefins and vinyl compounds, copolymers of olefins and various (meth)acrylic compounds, copolymers of olefins and unsaturated carboxylic acids, ionomer resins, terpolymer resins of olefins, various (meth)acrylic compounds, and various unsaturated carboxylic acids, polyethylene terephthalate (PET), polyacrylonitrile (PAN), etc. These may be used alone or in combination of two or more.
Among the above, polyolefins and olefin copolymers are preferred, olefin copolymers are more preferred, and among olefin copolymers, polyethylene resins are even more preferred. These resins also have excellent heat-sealing properties.
Specific examples of polyethylene-based resins include low-density polyethylene (LDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), 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 mixtures of these resins, but are not limited to these resins.
Among the polyethylene resins described above, LLDPE is more preferred, and ^{one or more} resins selected from the group consisting of C4-LLDPE, C6-LLDPE, and C8-LLDPE, each having a density of 0.90 g/cm or more and 0.94 g/cm or less, are even more preferred. These resins also have excellent heat-sealing properties.
By setting the density within the above range, good stretchability due to good softness can be obtained. If the density is below the above range, the softening point may be too low, making it difficult to maintain the layer structure, and if the density is above the above range, there is a risk that the stretchability will decrease.
The MFR (melt flow rate) of the binder resin is preferably 1 g/10 min or more and 10 g/10 min or less, and more preferably 1.5 g/10 min or more and 7 g/10 min or less. If the MFR is in the above range, even when mixed with the odor adsorbent, the binder resin can maintain a good MFR and exhibit good film-forming properties and adhesive properties.

<Heat seal layer>
The heat-sealable layer is a layer having excellent heat-sealability that is laminated on one or both surfaces of the odor-adsorbing stretched film of the present invention.
The heat seal layer is a layer containing a heat sealable resin and no or a low content of an odor adsorbent.

(Heat-sealable resin)
Examples of heat-sealable resins include polyolefins, olefin copolymers, copolymers of olefins and vinyl compounds, copolymers of olefins and various (meth)acrylic compounds, copolymers of olefins and unsaturated carboxylic acids, ionomer resins, terpolymer resins of olefins, various (meth)acrylic compounds, and various unsaturated carboxylic acids, polyethylene terephthalate (PET), polyacrylonitrile (PAN), etc. These may be used alone or in combination of two or more.
Among the above, polyolefins and olefin copolymers are preferred, olefin copolymers are more preferred, and among olefin copolymers, polyethylene resins are even more preferred.
Specific examples of polyethylene-based resins include low-density polyethylene (LDPE), medium-density polyethylene (MDPE), high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), 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 mixtures of these resins, but are not limited to these resins.
Among the above polyethylene resins, LLDPE is more preferred, and one or more selected from the group consisting of C4-LLDPE, C6-LLDPE, and C8-LLDPE, each having a density of 0.90 g/ ^cm3 or more and 0.94 g/cm3 or ^less , are even more preferred.
By setting the density within the above range, good stretchability due to good softness can be obtained. If the density is below the above range, the softening point may be too low, making it difficult to maintain the layer structure, and if the density is above the above range, there is a risk that the stretchability will decrease.
The MFR (melt flow rate) of the heat-sealable resin is preferably 1 g/10 min or more and 10 g/10 min or less, and more preferably 1.5 g/10 min or more and 7 g/10 min or less. If the MFR is in the above range, even when mixed with an odor adsorbent, the resin can maintain a good MFR and exhibit good film-forming properties and adhesive properties.

Details about LLDPE, polyolefins, vinyl compounds, and unsaturated carboxylic acids used in binder resins and heat-sealable resins are provided below.

(LLDPE)
LLDPE is a copolymer of repeating units of ethylene and some amount of an α-olefin.
More specifically, C4-LLDPE is a linear low-density polyethylene made from a copolymer of ethylene and 1-butene as an α-olefin, C6-LLDPE is a linear low-density polyethylene made from a copolymer of ethylene and 1-hexene and/or 4-methyl-1-pentene, and C8-LLDPE is a linear low-density polyethylene made from a copolymer of ethylene and 1-octene.
Each of these molecular structures has an ethylene-derived LLDPE main chain with side chains of 4, 6, and 8 carbon atoms derived from 1-butene, 1-hexene and/or 4-methyl-1-pentene, and 1-octene, respectively.
Among common polyethylenes, there are those with densities smaller than 0.90 g/ ^cm3 , with the upper limit being approximately 0.96 g/ ^cm3 . JIS K6899-1:2000 defines the density of LLDPE as 0.910 to 0.925, but in the present invention, even polyethylenes with densities outside this range are treated as LLDPE.

(Polyolefin)
In the present invention, polyolefin refers to a resin whose main chain is composed of repeating units derived from one or more types of monomers.
Examples of the polyethylene include polyethylene, polypropylene, methylpentene polymer, cyclic polyolefin resin, etc. Examples of the polyethylene include low-density polyethylene (LDPE), medium-density polyethylene (MDPE), high-density polyethylene (MDPE), linear low-density polyethylene (LLDPE), metallocene polyethylene, etc. These may be used alone or in combination of two or more.

(vinyl compounds)
The vinyl compound is a compound having a vinyl group, and specific examples thereof include vinyl acetate, vinyl alcohol, etc., and various (meth)acrylic compounds include (meth)acrylic acid, (meth)acrylic acid esters, etc. These may be used alone or in combination of two or more.

(Unsaturated carboxylic acid)
The unsaturated carboxylic acid is a carboxylic acid having an unsaturated carbon-carbon bond, and specific examples thereof include maleic acid, fumaric acid, and anhydrides thereof. These may be used alone or in combination of two or more.

<Adhesive layer>
In the present invention, it is also possible to provide adhesive layers between the layers constituting the laminate and between layers within each layer.
Furthermore, before forming the adhesive layer, an anchor coat layer may be formed in advance on the surface of the layer to be adhered in order to improve adhesiveness.

The adhesive (adhesive composition) forming the adhesive layer may be of a heat-curable type, an ultraviolet-curable type, an electron beam-curable type, or the like, and may be in any form such as an aqueous type, a solution type, an emulsion type, or a dispersion type. In addition, the adhesive may be in any form such as a film/sheet type, a powder type, or a solid type. Furthermore, the adhesive mechanism may be in any form such as a chemical reaction type, a solvent evaporation type, a thermal melting type, or a thermal pressure type.
Examples of such adhesives include polyvinyl acetate adhesives such as polyvinyl acetate and vinyl acetate-ethylene copolymers, polyacrylic acid adhesives made from copolymers of polyacrylic acid and polystyrene, polyester, polyvinyl acetate, etc., cyanoacrylate adhesives, ethylene copolymer adhesives made from copolymers of ethylene and monomers such as vinyl acetate, ethyl acrylate, acrylic acid, and methacrylic acid, cellulose adhesives, polyurethane adhesives, polyester adhesives, polyamide adhesives, polyimide adhesives, polyolefin adhesives, amino resin adhesives made from urea resin or melamine resin, phenol resin adhesives, epoxy adhesives, reactive (meth)acrylic adhesives, elastomer adhesives made from chloroprene rubber, nitrile rubber, styrene-butadiene rubber, etc., silicone adhesives, and inorganic adhesives made from alkali metal silicates, low-melting point glass, etc.

In one embodiment of the present invention, the adhesive layer may be a layer made of any of an adhesive for EC (extrusion coating), an adhesive for dry lamination, an adhesive for non-solvent lamination, and the like.
When an EC adhesive is used, there are no particular limitations, but for example, the adhesive is first heated and melted, expanded and stretched in the required width direction using a T-die or the like, and extruded in a curtain shape, allowed to flow down onto the layer to be adhered, and then sandwiched between a rubber roll and a cooled metal roll, thereby simultaneously forming an adhesive layer and adhering and laminating to the layer to be adhered.

In another embodiment, the adhesive layer may be formed by sand lamination. In this case, any resin that can be heated and melted and applied in an extruder can be used for the adhesive layer. Specifically, the resins listed above as thermoplastic resins with heat sealability can be preferably used.

When using a dry laminating adhesive, the adhesive dispersed or dissolved in a solvent is applied to one film and dried, and then the other film is placed on top of it and laminated. After that, the adhesive is cured by aging at 30 to 120°C for several hours to several days, allowing the two films to bond and laminate.

When using a non-solvent laminating adhesive, the adhesive itself is applied to the layer to be adhered without being dispersed or dissolved in a solvent, and then dried. The film that will form the other layer is then laminated on top of it, and the adhesive is then cured and laminated by aging at 30-120°C for several hours to several days.

The dry laminating adhesive or non-solvent laminating adhesive can be used by coating, for example, by roll coating, gravure roll coating, kiss coating, etc., and the coating amount is preferably 0.1 to 10 g/m ² (dry state). By setting the coating amount within the above range, good adhesion can be obtained.

(Anchor coat layer)
The anchor coat layer can be formed from any anchor coat agent.
Examples of anchor coating agents that can be used include organic titanium-based, isocyanate (urethane-based), polyethyleneimine-based, acid-modified polyethylene-based, polybutadiene-based, polyacrylic-based, polyester-based, epoxy-based, polyvinyl acetate-based, cellulose-based, and other anchor coating agents.

<<Odor-absorbing stretch packaging material>>
The odor-adsorbing stretched packaging material of the present invention is a packaging material made using the odor-adsorbing stretched film of the present invention, and may be the same as the odor-adsorbing stretched film, and may further have a base layer, various intermediate layers, a printed layer, etc., as necessary.
The odor-adsorbing stretched packaging material of the present invention can also be subjected to lamination (dry lamination or extrusion lamination), bag-making, and other post-treatments.

[Method for producing odor-absorbing stretched film or odor-absorbing stretched packaging material]
For example, an example of producing an odor-adsorbing stretched film (packaging material) having a layer structure of heat seal layer/odor adsorption layer/heat seal layer will be described.
The manufacturing method described below is an example and does not limit the present invention.
As long as the layers are laminated in this order, the order in which the layers are formed and laminated may be arbitrary.
First, a heat-sealable resin and a resin composition for an odor-adsorbing layer are laminated by inflation film formation to obtain an odor-adsorbing sealant film having a layer structure of heat-sealing layer/odor-adsorbing layer/heat-sealing layer.

The lamination of each layer described above can be carried out by any lamination method used in the production of ordinary packaging materials, such as wet lamination, dry lamination, solventless dry lamination, extrusion lamination, T-die coextrusion molding, coextrusion lamination, inflation molding, or the like.
Next, the odor-adsorbing sealant film obtained above is placed in a roll stretching machine at 50 to 130°C and stretched longitudinally by 2 to 4 times in the film-forming direction, to obtain a uniaxially stretched odor-adsorbing stretched film.
The biaxial stretching treatment can be carried out, for example, by longitudinally stretching the film to 2 to 4 times its original size using a roll stretching machine at 50 to 130° C., then transversely stretching the film to 3 to 5 times its original size using a tenter stretching machine in an atmosphere at 90 to 150° C., and subsequently heat-treating the film using the same tenter in an atmosphere at 100 to 240° C. The stretching treatment may be simultaneous biaxial stretching or sequential biaxial stretching.
Next, an aging treatment may be carried out as necessary.
In this manner, an odor-absorbing stretched film or odor-absorbing stretched packaging material can be produced.

The odor-adsorbing stretched film or odor-adsorbing packaging material obtained as described above can be subjected to secondary processing in order to impart surface functions such as chemical functions, electrical functions, magnetic functions, mechanical functions, friction/wear/lubrication functions, optical functions, thermal functions, and biocompatibility.
Examples of secondary processing include embossing, painting, adhesive, printing, metallizing (plating, etc.), machining, and surface treatment (antistatic treatment, corona discharge treatment, plasma treatment, photochromic treatment, physical vapor deposition, chemical vapor deposition, coating, etc.).

<<Odor-absorbing stretch packaging>>
The odor-adsorbing stretch packaging of the present invention is a packaging made using the odor-adsorbing stretch packaging material of the present invention.

[Method for producing odor-absorbing stretched packaging]
An example of a method for producing an odor-adsorbing stretched packaging body is a method for producing a packaging bag by forming an odor-adsorbing stretched packaging material into a bag.
First, the odor-absorbing stretch packaging material can be prepared by folding or overlapping two sheets, preferably with the heat-sealable layers facing each other, and heat-sealing the peripheral edges.
Examples of the form of the packaging bag include a side seal type, a two-sided seal type, a three-sided seal type, a four-sided seal type, an envelope seal type, a palm seal type (pillow seal type), a pleated seal type, a flat bottom seal type, a square bottom seal type, and a gusset type.
As the heat sealing method, known methods such as bar sealing, rotary roll sealing, belt sealing, impulse sealing, high frequency sealing, ultrasonic sealing, etc. can be used.

Details of the raw materials used in the examples are as follows:

[Heat-sealable resin]
Heat-sealable resin 1: Ultzex 1520L, manufactured by Prime Polymer Co., Ltd. C6-LLDPE, density 0.916 g/cm ³ , MFR 2.3 g/10 min.
Heat-sealable resin 2: manufactured by Ube Maruzen Polyethylene Co., Ltd., Yumerit 720FT, C4-LLDPE, density 0.918 g/cm ³ , MFR 4 g/10 min.
Heat-sealable resin 3: Ube Maruzen Polyethylene Co., Ltd., Yumerit 125NF, HAO-LLDPE (copolymerized LLDPE with a comonomer higher α-olefin having 6 or more carbon atoms such as C6 or C8), density 0.924 g/cm ³ , MFR 2.2 g/10 min.
Heat-sealable resin 4: HI-ZEX 3300F, manufactured by Prime Polymer Co., Ltd., density 0.949 g/cm ³ , MFR 1.1 g/10 min.

[Odor absorbent]
Hydrophobic zeolite 1: Silton MT400, a hydrophobic zeolite manufactured by Mizusawa Industrial Chemicals, Ltd. _{SiO 2} /Al ₂ O ₃ molar ratio = 400/1, average particle size = 5 to 7 μm.
Hydrophobic zeolite 2: Silton MT-8000 hydrophobic zeolite manufactured by Mizusawa Industrial Chemicals, Ltd. SiO ₂ /Al ₂ O ₃ molar ratio = 8000/1, average particle size = 0.8 μm.
General-purpose zeolite 1: Mizuka Sieves 5AP, a zeolite manufactured by Mizusawa Industrial Chemicals, Ltd. _{SiO 2} /Al ₂ O ₃ molar ratio = 2/1, average particle size 5 μm.
Amino group-supported inorganic porous material 1: Kesmon NS-241, manufactured by Toagosei Co., Ltd. Average particle size: 3.5 μm. Amino group-supported silica dioxide.
Metal-supported inorganic porous material: Dashlight CZU, manufactured by Sinanen Zeomic Co., Ltd. CuO, ZnO-supported zeolite, average particle size = 3 to 5 μm.

[Preparation of Masterbatch]
The masterbatch used in the odor adsorption layer was prepared as follows.
(Preparation of Masterbatch 1)
Heat-sealable resin 1 and hydrophobic zeolite 1 were melt-blended in the following ratio to obtain masterbatch 1 (MB1).
Heat-sealable resin 1 70 parts by weight Hydrophobic zeolite 1 30 parts by weight

[Preparation of Masterbatches 2 to 5]
According to the formulations in Table 1, melt blending was carried out in the same manner as for Masterbatch 1 to obtain Masterbatches 2 to 5 (MB2 to 5).

[Preparation of odor absorbing layer resin composition]
By dry blending the raw materials in the formulations shown in Tables 2 and 3, resin compositions 1 to 13 for the odor absorbing layer were obtained.

<Preparation and evaluation of odor-absorbing stretched film>
[Example 1]
The odor absorbing layer resin composition 1 and heat sealable resin 1 obtained above were laminated together by inflation film formation at 160° C. to obtain a film 1 having the following three-layer structure.
Layer structure of film 1: heat seal layer 1/odor adsorption layer/heat seal layer 2=heat sealable resin 1 (10 μm)/odor adsorption layer resin composition 1 (30 μm)/heat sealable resin 1 (10 μm).
Next, the film 1 obtained above was placed in a stretching machine (Toyo Seiki Co., Ltd., biaxial stretching tester: EX10-S2) and stretched twice in the film production direction to obtain an odor-adsorbing stretched film 1 with a thickness of 25 μm.
Layer structure of odor-adsorbing stretched film 1: heat seal layer/odor-adsorbing layer/heat seal layer=heat sealable resin 1 (5 μm)/odor-adsorbing layer resin composition 1 (15 μm)/heat sealable resin 1 (5 μm).

[Examples 2 to 7, 11 to 13, Comparative Examples 1 and 4]
An odor-adsorbing stretched film was obtained in the same manner as in Example 1 and evaluated in the same manner.

[Examples 8 to 10, Comparative Examples 2 and 3]
According to the film layer structure shown in Tables 5 and 6, the same procedure as in Example 1 was repeated to obtain odor-adsorbing stretched films, except that heat seal layer 1 and/or heat seal layer 2 was not provided, and the films were evaluated in the same manner.

<Summary of results>
All of the odor-adsorbing stretched films of the present invention exhibited a good balance of film-forming properties, stretchability, water vapor permeability, odor adsorption effect, and odor diffusion suppression effect.
Comparative Example 1, which contained general-purpose zeolite instead of hydrophobic zeolite, showed poor odor adsorption performance.
The laminates of Comparative Examples 2 and 3, which did not have an odor adsorption layer, showed low water vapor permeability and inferior odor adsorption effect and odor diffusion suppression effect.
The laminate of Comparative Example 4, in which the concentration of the odor adsorbent was too high, showed poor film-forming properties, heat-sealing properties and stretchability.

<Evaluation method>
[Film forming property]
The appearance of the odor-absorbing stretched film was observed and evaluated sensorily according to the following criteria:
◯: Odor-absorbing stretched film can be formed without wrinkles or bumps.
×: Numerous wrinkles and bumps occurred in the odor-absorbing stretched film, making film formation difficult.

[Stretchability]
The stretched state of the odor-adsorbing stretched film in the stretching machine was observed and evaluated sensorily.
◯: The odor-absorbing stretched film was not torn and could be stretched.
×: The odor-adsorbing stretched film was torn and difficult to stretch.

[Water vapor permeability]
The water vapor permeability was measured by the MOCON method from the heat seal layer 1 side when the heat seal layer 1 was present, and from the heat seal layer 2 or odor adsorption side when the heat seal layer 1 was not present, and the pass/fail judgment was made. The judgment criteria were as follows.
Good: The water vapor transmission rate is 10 g/(m ² ·day) or more, and the test is passed.
×: The water vapor transmission rate was less than 10 g/(m ² ·day), and the sample was unacceptable.

[Odor component concentration]
The odor-adsorbing stretched films (4 cm × 10 cm × 5 sheets) were placed in gas sampling bags (SMART BAG PA AKK-10, manufactured by GL Sciences Inc., pouch area A4 size), and the gas sampling bags were filled with 1000 ml of test odor gas (acetaldehyde: 100 ppm, hydrogen sulfide: 25 ppm, ammonia concentration: 30 ppm) and sealed.
After leaving the container at room temperature for 48 hours, the concentration of each gas component was measured using the following measuring device.
Acetaldehyde concentration: detector tube (Gastec Corporation, No. 92M)
Hydrogen sulfide concentration: detector tube (Gastec Corporation, No. 4LK)
Ammonia concentration: detector tube (Gastec Corporation, No. 3L)

[Odor diffusion]
Using the odor-adsorbing stretched film, if heat-seal layer 1 was present, the heat-seal layers 1 were stacked facing each other; if heat-seal layer 1 was not present, the heat-seal layers 2 were stacked facing each other, the heat-seal layer 2 and the odor-adsorbing layer, or the odor-adsorbing layers were stacked facing each other in that order; if heat-seal layer 1 was not present, the odor-adsorbing layers were stacked facing each other to prepare a pouch half the size of A4. 200 ml of the test odor gas (acetaldehyde: 100 ppm, hydrogen sulfide: 25 ppm, ammonia concentration: 30 ppm) was filled into this pouch to prepare an odor-gas-filled pouch. The odor-gas-filled pouch was then sealed in a gas sampling bag (GL Sciences, Inc., SMART BAG PA AKK-10, pouch area: A4 size), and after 48 hours of storage at room temperature, a sensory evaluation was performed on the state of odor leaking between the odor-gas-filled pouch and the gas sampling bag.
Sensory evaluation index:
1. Strong odor 2. Odor 3. Slight odor 4. No odor

[Heat sealability]
The odor-adsorbing stretched film was cut into 10 cm x 10 cm pieces, and when heat-sealing layer 1 was present, the heat-sealing layers 1 were overlapped facing each other; when heat-sealing layer 1 was not present, the heat-sealing layers 2 were overlapped facing each other, or the heat-sealing layer 2 and the odor-adsorbing layer, or the odor-adsorbing layers were overlapped facing each other in that order of priority. A 1 cm x 10 cm area was heat-sealed using a heat-sealing tester (TP-701-A manufactured by Tester Sangyo Co., Ltd.) under the following conditions, and a test piece for peel strength was prepared in which the ends were not heat-sealed or bonded and were divided into two.
This test piece was cut into a 15 mm wide strip, and each bifurcated end was attached to a tensile tester to measure the peel strength (N/15 mm) under the following conditions, and the result was judged as pass/fail according to the following pass/fail criteria.
Heat sealing conditions Temperature: 160°C
Pressure: 1 kgf/cm
Time: 1 second Test conditions Test speed: 300 mm/min Load range: 50 N
Pass/fail criteria: ◯: 10N/15mm or more, passed.
×: Less than 10N/15mm, unacceptable.

1 odor-absorbing stretched film, odor-absorbing stretched packaging material 2 odor-absorbing layer 3 heat-seal layer 10 chemical adsorbent-carrying inorganic porous body

Claims (7)

An odor-adsorbing stretched film capable of adsorbing odors of aldehydes, ketones, sulfur-based compounds, or amines,
The odor-adsorbing stretched film has heat-sealing properties,
The odor-adsorbing stretched film has at least an odor-adsorbing layer,
the odor absorbing layer contains a binder resin and an odor absorbing agent;
the binder resin contains a heat-sealable resin,
The odor adsorbent contains a hydrophobic zeolite, or contains a hydrophobic zeolite and a metal-supported inorganic porous material,
The SiO ₂ /Al ₂ O ₃ molar ratio of the hydrophobic zeolite is 400/1 to 10,000/1;
the content of the odor adsorbent in the odor adsorption layer is 15% by mass or less;
The odor-adsorbing stretched film has a water vapor permeability of 10 g/( ^m2 ·day) or more.
Odor-absorbing stretch film. 2. The odor-adsorbing stretched film according to claim 1, wherein the odor adsorbent further comprises an inorganic porous material carrying an amino group -containing compound. 3. The odor-absorbing stretched film according to claim 1, wherein the binder resin is ^one or more resins selected from the group consisting of C4-LLDPE, C6-LLDPE, and C8-LLDPE, ^each having a density of 0.90 g/cm or more and 0.94 g/cm or less. The odor-adsorbing stretched film according to any one of claims 1 to 3, wherein the odor adsorbent is used as a masterbatch that is pre-melted and kneaded with a thermoplastic resin capable of forming an odor adsorption layer as the binder resin in a mass ratio of odor adsorbent/thermoplastic resin of 0.5/99.5 to 40/60. The layer structure of the odor-adsorbing stretched film is
a layer structure consisting of only the odor adsorption layer;
a layer structure having the odor adsorption layer and a heat seal layer on one surface thereof;
a layer structure having the odor adsorption layer and heat seal layers on both surfaces thereof;
Any layer structure selected from the group consisting of:
the heat seal layer contains a heat sealable resin but does not contain the odor adsorbent;
The odor-adsorbing stretched film according to any one of claims 1 to 4. An odor-absorbing stretched packaging material made using the odor-absorbing stretched film described in any one of claims 1 to 5. An odor-absorbing stretched package made using the odor-absorbing stretched packaging material described in claim 6.