JP7721079B2 - Resin film, laminate, and package or container - Google Patents

Description

The present invention relates to a resin film, a laminate, and a package or container having the laminate.

In the food and pharmaceutical packaging industries, sterilization processes such as retort sterilization and aseptic filling have traditionally been considered and put into practical use to prevent infection by bacteria such as E. coli in order to maintain the safety of the contents. However, in recent years, with the spread of infectious diseases, consumer awareness of hygiene has spread, and there is a demand for safe packaging materials. Furthermore, while inorganic compounds, silver, copper, and other substances are known to have antibacterial and antiviral properties, there is still room for improvement from the perspective of cost and food safety when used in packaging that comes into direct contact with food.

Tannin, a type of polyphenol, has long been used as a rust inhibitor and is known to form a stable film on the surface of zinc, for example. However, tannin is virtually insoluble in organic solvents, limiting its uses. Therefore, by substituting at least a portion of the hydroxyl groups in the tannin molecule with alkyl ethers or alkyl esters to create water-insoluble tannic acid derivatives, it is possible to broaden its uses (Patent Document 1).

However, the above-mentioned coating is believed to be formed by a film formed when gallic acid and other compounds in tannic acid react with zinc, and then a film formed when tannic acid undergoes coagulation or associative polymerization (Non-Patent Document 1). The hydroxyl groups of the gallic acid and other compounds contained in tannic acid are involved in these reactions. Therefore, if these hydroxyl groups are converted to alkyl ethers or the like, it becomes difficult to form a coating, and there are concerns that the rust prevention effect will be reduced. Even in Patent Document 1, the evaluation is solely in solution form.

In response, film-forming compositions have been proposed that contain tannic acid derivatives in which the hydrogen atoms in at least some of the hydroxyl groups of tannic acid are substituted with linear hydrocarbon groups having 3 to 18 carbon atoms (see, for example, Patent Document 2). This film-forming composition possesses film-forming properties and is said to be capable of forming stable films on a variety of substrates. This is thought to be because the tannic acid derivative molecules are aligned with their linear hydrocarbon groups aligned, resulting in an orderly orientation. This orientation provides film stability that more than compensates for the loss of hydroxyl groups, resulting in superior rust prevention, antibacterial, and bactericidal properties compared to aggregated tannic acid films.

Japanese Patent Application Laid-Open No. 2004-307362 International Publication No. 2016/076311

Metal Surface Technology, Vol. 29, No. 1, pp. 38-42 and Fig. 10, 1978

However, while the above-mentioned conventional film-forming compositions containing tannic acid derivatives enable cost reductions, their antibacterial reliability is not sufficient, and there is still room for improvement when used as packaging materials that come into direct contact with food, medical products, etc. In particular, packaging materials are provided with a sealing layer for attachment to containers or to other packaging materials, and when used in a manner that brings the contents into direct contact with the sealing layer, it is necessary to prevent contamination of the contents due to, for example, the elution of antibacterial substances contained in the sealing layer. Furthermore, in recent years, with the diversification of lifestyles and the need for preserved food in emergencies, the uses of food packaging materials have become more diverse, and there is a demand for food packaging materials that can exhibit sufficient rust prevention, antibacterial, and bactericidal properties for a variety of uses.

The object of the present invention is to provide a resin film, laminate, and packaging or container that exhibits sufficient antibacterial, sterilizing, and disinfecting properties, thereby achieving high reliability.

To achieve the above objective, the inventors conducted extensive research and discovered that by incorporating a polyolefin resin and a tannic acid derivative in which at least some of the multiple hydroxyl groups have been substituted with a chain hydrocarbon group having 1 to 18 carbon atoms into a resin film, the specific tannic acid derivative can be stably retained within the resin or on the resin surface, resulting in sufficient antibacterial, sterilizing, and disinfecting properties and achieving high reliability.

That is, the present invention provides the following configurations.
[1] A resin film comprising a polyolefin resin and a tannic acid derivative in which at least a portion of a plurality of hydroxyl groups is substituted with a chain hydrocarbon group having 1 to 18 carbon atoms.

[2] The resin film described in [1] above, wherein the polyolefin resin is one or more selected from polyethylene-based resins, polypropylene-based resins, and polybutylene-based resins.

[3] The resin film described in [1] or [2] above, wherein the tannic acid derivative is present in an amount of 0.5% by mass or more and 30% by mass or less relative to the total amount of the resin film.

[4] A package or container using the resin film described in any one of [1] to [3] above.

[5] A package or container comprising a container body and one or more of the resin films described in any one of [1] to [3] above attached to the container body.

[6] The packaging or container described in [5] above, wherein the resin film constitutes a lid material for the container body.

[7] The packaging or container described in [5] above, wherein the resin film is attached to the outer surface of the container body.

[8] A package or container comprising an exterior portion formed by laminating one or more of the resin films described in any one of [1] to [3] above, and a storage portion formed inside the exterior portion.

[9] A laminated structure including the resin film according to any one of [1] to [3] above and a thermoplastic resin film,
A laminate having the resin film as an outermost layer.

[10] A package or container using the laminate described in [9] above.

[11] A package or container comprising a container body and one or more of the laminates described in [9] above attached to the container body.

[12] The packaging or container described in [11] above, wherein the laminate constitutes a lid material for the container body.

[13] The packaging or container described in [11] above, wherein the laminate is attached to the outer surface of the container body.

[14] A package or container comprising an exterior part formed by laminating one or more of the laminates described in [9] above, and a storage part formed inside the exterior part.

The present invention achieves sufficient antibacterial, sterilizing, and disinfecting properties, achieving high reliability.

FIG. 1 is a chemical reaction flow diagram showing an example of derivatization of tannic acid. FIG. 2A is a cross-sectional view showing an example of a specific configuration of a laminate according to an embodiment of the present invention. FIG. 2B is a cross-sectional view showing an example of another specific configuration of the laminate according to this embodiment. FIG. 3 is a perspective view showing an example of a specific configuration of a container using the laminate according to this embodiment. FIG. 4 is a perspective view showing another example of a specific configuration of a package using the laminate according to this embodiment. FIG. 5A is a perspective view showing another example of a specific configuration of a package using the laminate according to this embodiment. FIG. 5B is a cross-sectional view taken along line II of FIG. 5A. FIG. 6 is a perspective view showing another example of a specific configuration of a container using the laminate according to this embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings, but the present invention is not limited to the following embodiments.
<Resin film>
The resin film of this embodiment contains a polyolefin resin and a tannic acid derivative in which at least some of the hydroxyl groups are substituted with a chain hydrocarbon group having 1 to 18 carbon atoms.

[Polyolefin resin]
Specifically, the polyolefin resin used in this embodiment is preferably one or more types selected from polyethylene-based resins, polypropylene-based resins, and polybutylene-based resins, and more preferably a polyethylene-based resin or a polypropylene-based resin.

(Polyethylene resin)
An example of the polyethylene resin for the resin film is linear polyethylene. Linear polyethylene is obtained by copolymerizing ethylene monomer as the main component with an α-olefin such as 1-butene, 1-hexene, 1-octene, or 4-methylpentene as a comonomer by low-pressure radical polymerization using a single-site catalyst. The comonomer content in the linear polyethylene is preferably in the range of 0.5 to 20 mol%, and more preferably in the range of 1 to 18 mol%.

Examples of the single-site catalyst include various single-site catalysts, such as metallocene catalyst systems that combine metallocene compounds of transition metals from Group IV or V of the periodic table with organoaluminum compounds and/or ionic compounds. Furthermore, because single-site catalysts have uniform active sites, the molecular weight distribution of the resulting resin is sharper than with multi-site catalysts, which have non-uniform active sites. This results in less precipitation of low-molecular-weight components when formed into a film, and makes it possible to obtain a resin with excellent physical properties, such as stable seal strength and excellent blocking resistance.

The density of the linear polyethylene is preferably 0.900 to 0.945 g/ ^cm3 , and more preferably 0.910 to 0.940 g/ ^cm3 . A density within this range provides adequate rigidity, excellent mechanical strength such as heat seal strength and pinhole resistance, and improved film formability and extrusion suitability. The melting point of the linear polyethylene is generally preferably in the range of 60 to 130°C, and more preferably 70 to 120°C. A melting point within this range improves processing stability and flexibility, resulting in good pinhole resistance. Furthermore, the MFR (190°C, 21.18 N) of the ethylene resin is preferably 2 to 20 g/10 min, and more preferably 3 to 10 g/10 min. An MFR within this range improves the extrusion moldability of the film.

The linear polyethylene is preferably used in a resin film that is primarily composed of the resin, and preferably accounts for 70% by mass or more of the resin components, more preferably 80% by mass or more, and even more preferably 90% by mass or more.

In addition, resins other than linear polyethylene may be used in the resin film. Other resins that can be used in combination include polyethylene-based resins other than linear polyethylene, polypropylene-based resins, and the resins exemplified above as resins that can be used in combination.

When these other resins are used, they preferably account for no more than 30% by mass of the resin components contained in the resin film, more preferably no more than 20% by mass, and even more preferably no more than 10% by mass. There is no particular lower limit, but they may be used in an amount of 1% by mass or more depending on the desired properties.

(Polypropylene resin)
Examples of polypropylene-based resins for the resin film include propylene homopolymers, propylene-ethylene copolymers, propylene-α-olefin random copolymers such as propylene-1-butene copolymers, ethylene-1-butene copolymers, and propylene-ethylene-1-butene terpolymers, and metallocene catalyst-based polypropylenes. These may be used alone or in combination of two or more.

The polypropylene resin preferably has an MFR (230°C) of 0.5 to 30.0 g/10 min and a melting point of 110 to 165°C, and more preferably an MFR (230°C) of 2.0 to 15.0 g/10 min and a melting point of 115 to 162°C. An MFR and melting point within these ranges improves processing stability, processability when co-extruded with other layers, and film formability.

When a resin film is primarily composed of polypropylene resin, other resins may be used in combination with it to improve adhesion with adhesives or printing inks when laminating it with other substrates using adhesives or when printing on it. Other resins that can be used in combination include, for example, linear polyethylenes such as linear low-density polyethylene (LLDPE) and low-density polyethylene (LDPE), branched polyethylenes, ethylene-vinyl acetate copolymer (EVA), ethylene-methyl methacrylate copolymer (EMMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl acrylate (EMA) copolymer, ethylene-ethyl acrylate-maleic anhydride copolymer (E-EA-MAH), ethylene-acrylic acid copolymer (EAA), and ethylene-methacrylic acid copolymer (EMAA); as well as ionomers of ethylene-acrylic acid copolymer, ionomers of ethylene-methacrylic acid copolymer, and copolymers of ethylene and monomers having a cyclic olefin structure, such as norbornene-based monomers. These may be used alone or in combination of two or more.

When these other resins are used, their content is preferably 35% by mass or less, and more preferably 20% by mass or less, of the total amount of resin components that make up the resin film. There is no particular lower limit, but they may be used in an amount of 1% by mass or more, depending on the desired properties.

[Tannic acid derivatives]
Tannin is a general term for plant components that produce polyphenols upon hydrolysis. Tannins are broadly classified into hydrolyzable tannins, in which gallic acid or ellagic acid is ester-bonded to sugars such as glucose and is easily hydrolyzed by acids or enzymes, and condensed tannins, in which compounds with a flavanol skeleton are polymerized. Derivatization in the present disclosure is possible with either type of tannin or a mixture thereof, and it is believed that the effects of the present disclosure can be achieved. Hydrolyzable tannins are preferred, and for example, those containing tannic acid represented by the following formula (1) as the main component are derivatized.

Tannic acid has multiple hydroxyl groups, and in the derivatives disclosed herein, the hydrogen atoms of at least some of the hydroxyl groups are substituted with linear hydrocarbon groups having 1 to 18 carbon atoms. The total number of hydroxyl groups in the raw tannic acid varies depending on the type. Preferably, 10% or more of the substituents are substituted, more preferably 20% or more, and particularly preferably 40% or more. For example, in the case of formula (1) above, there are a total of 25 hydroxyl groups, of which 1, preferably 3 or more, more preferably 5 or more, and particularly preferably 10 or more are substituted.

The upper limit on the number of substituents varies depending on the type of substituent, the substrate to which it is applied, and the intended use. All hydroxyl groups may be substituted as long as the desired adhesion to the substrate can be achieved. When applied to polar substrates such as metals and glass, it is preferable that 80% or less of the substituents be substituted, and more preferably 60% or less. For example, in the case of formula (1) above, the number is preferably 20 or less, and more preferably 15 or less.

A chain hydrocarbon group having 1 to 18 carbon atoms includes a linear or branched alkyl group, alkenyl group, or alkynyl group, which is bonded to the tannic acid backbone via a bond containing an oxygen atom derived from a hydroxyl group. Specific examples of the chain hydrocarbon group include butyl, hexyl, heptyl, octyl, isooctyl, nonyl, isononyl, decyl, undecyl, dodecyl, hexadecyl, propylene, hexylene, hexadecenyl, and octadecenyl groups. The chain hydrocarbon group preferably has 3 to 18 carbon atoms, more preferably 4 to 18, and even more preferably 6 to 16. Examples of the bond containing an oxygen atom include an ether bond, an ester bond, and a urethane bond.

The tannic acid derivative is preferably present in an amount of 0.5% by mass or more and 30% by mass or less, more preferably 2% by mass or more and 25% by mass or less, and even more preferably 5% by mass or more and 15% by mass or less, relative to the total amount of the resin film. When the tannic acid derivative content is 5% by mass or more and 15% by mass or less, the tannic acid derivative can be more stably retained in the resin and superior antibacterial properties can be exhibited.

(Method for producing tannic acid derivatives)
Tannic acid derivatives can be obtained by the Williamson ether synthesis, a type of alkylation reaction. Specifically, they can be produced by reacting tannic acid with an alkyl halide in the presence of a basic catalyst in a solvent such as tetrahydrofuran or dimethyl sulfoxide. _The basic catalyst can be one or more catalysts selected from the group consisting of MH, _M2CO3 , and M (M: alkali metal). For example, _K2CO3 can convert an OH group to O ^- M ⁺ , promoting the nucleophilic reaction of the O-group to an alkyl halide (X-R1: X: halogen, R1: alkyl group). Examples of alkyl _halides that can be used include alkyl iodides. Alternatively, alkyl halides containing a sulfonyl group or other leaving group can also be used. Alkylation reactions other than the Williamson ether synthesis can also be used. Furthermore, dehydration condensation reactions with carboxylic acids using condensing agents such as N,N'-dicyclohexylcarbodiimide (DCC) or condensation reactions with isocyanates can also be used.

The reaction is carried out at a temperature between 70°C and 100°C for approximately 1 hour. Figure 1 shows an example of the derivatization of tannic acid of formula (1). It shows an example of synthesizing a derivative having _nine decyl groups (TA( _C10 ) ₉ ) by using _K2CO3 as a basic catalyst and heating to 85°C in DMF. By changing the molar ratio of alkyl halide to tannic acid, the value of n, which represents the number of alkyl groups introduced into tannic acid, can be set to the desired value.

[Other additives]
The resin film of this embodiment may contain one or more of the following components, as long as the object of the present invention is not impaired: antistatic agents, heat stabilizers, nucleating agents, antioxidants, lubricants, antiblocking agents, release agents, UV absorbers, colorants, etc. In particular, to ensure processability during film formation and packaging suitability in filling machines, the coefficient of friction of the film surface is preferably 1.5 or less, and more preferably 1.0 or less. Therefore, it is preferable to appropriately contain a lubricant, an antiblocking agent, and/or an antistatic agent. The content of these additives in the resin film is preferably 5% by mass or less, more preferably 3% by mass or less. For this reason, the content of the resin component in the resin film (the total content of the resin component and the antifogging agent when an antifogging agent is contained) is preferably 95% by mass or more, more preferably 97% by mass or more.

<Method of manufacturing resin film>
The method for producing the resin film of the present embodiment is not particularly limited, but for example, a masterbatch pellet obtained by melt-kneading a polyolefin resin and a tannic acid derivative in an extruder or the like can be obtained as is, or other additives can be added to polyolefin resin pellets and the film can be obtained by an extrusion method.

<Laminate>
The laminate of this embodiment has a laminate structure including the above-mentioned resin film and thermoplastic resin film, with the resin film as the outermost layer. The total number of layers in the laminate is not particularly limited as long as it includes a resin film and a thermoplastic resin film. It may be composed of two layers of a resin film and a thermoplastic resin film, or it may be composed of three layers of a resin film (surface layer), a thermoplastic resin film (sealing layer), and an intermediate film (intermediate layer) between the resin film and the thermoplastic resin film. Furthermore, the laminate may be composed of four or more layers including a resin film and a thermoplastic resin film.

[Thermoplastic resin film]
Specifically, the thermoplastic resin film is preferably one or two types selected from polyethylene-based resins and polypropylene-based resins, and more preferably a polyethylene-based resin or a polypropylene-based resin.

(Polyethylene resin)
Examples of polyethylene resins for the thermoplastic resin film include polyethylene resins such as very low density polyethylene (VLDPE), linear low density polyethylene (LLDPE), linear medium density polyethylene (LMDPE), low density polyethylene (LDPE), medium density polyethylene (MDPE), and high density polyethylene (HDPE); ethylene copolymers such as ethylene-vinyl acetate copolymer (EVA), ethylene-methyl methacrylate copolymer (EMMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl acrylate (EMA) copolymer, ethylene-ethyl acrylate-maleic anhydride copolymer (E-EA-MAH), ethylene-acrylic acid copolymer (EAA), and ethylene-methacrylic acid copolymer (EMAA); and ionomers of ethylene-acrylic acid copolymers and ionomers of ethylene-methacrylic acid copolymers. These may be used alone or in combination of two or more. Among these, LLDPE, LMDPE, and HDPE are preferred from the viewpoints of tearability and pinhole resistance and rigidity as a multilayer film.

(Polypropylene resin)
Examples of polypropylene-based resins for thermoplastic resin films include propylene homopolymers; propylene-ethylene copolymers; propylene-α-olefin random copolymers such as propylene-1-butene copolymers, ethylene-1-butene copolymers, and propylene-ethylene-1-butene terpolymers; and metallocene-catalyzed polypropylenes. These may be used alone or in combination of two or more. Among these, propylene-α-olefin random copolymers are preferred, and propylene-α-olefin random polymers polymerized using a metallocene catalyst are particularly preferred. When these polypropylene-based resins are used as thermoplastic resin films, the heat resistance of the film is improved and the softening temperature can be increased. Therefore, these polypropylene-based resins can be suitably used as laminating films for packaging materials, which have excellent steam and high-pressure heat sterilization properties, such as boiling or hot filling at temperatures below 100°C, or retort sterilization at temperatures above 100°C.

The thermoplastic resin film obtained as described above may be laminated to another substrate film for use. There are no particular limitations on the other substrate film that can be used in this case, but from the perspective of easily achieving the effects of the present invention, it is preferable to use a plastic substrate, particularly a biaxially stretched thermoplastic resin film. Furthermore, for applications that do not require transparency, aluminum foil can also be used alone or in combination.

Examples of stretched thermoplastic resin films include biaxially oriented polyester (PET), biaxially oriented polypropylene (OPP), biaxially oriented polyamide (PA), co-extruded biaxially oriented polypropylene with a central layer of ethylene-vinyl alcohol copolymer (EVOH), biaxially oriented ethylene-vinyl alcohol copolymer (EVOH), and co-extruded biaxially oriented polypropylene coated with polyvinylidene chloride (PVDC). These may be used alone or in combination.

When the resin film is (F1) and the thermoplastic resin film is (F2), the laminate may have the following specific configurations, but is not limited to these.
Resin film (f1) of polyethylene resin and tannic acid derivative/polypropylene resin (f2)
Resin film (f1) of polyethylene resin and tannic acid derivative/polyethylene resin (f2)
Resin film (f1) of polypropylene resin and tannic acid derivative/polypropylene resin (f2)
Resin film (f1) of polypropylene resin and tannic acid derivative/polyethylene resin (f2)
Resin film (f1) of polyester resin and tannic acid derivative/polyethylene resin (f2)
Resin film (f1) of polyester resin and tannic acid derivative/polypropylene resin (f2)
Resin film of polystyrene resin and tannic acid derivative (f1)/polyethylene resin (f2)
Resin film of polystyrene resin and tannic acid derivative (f1)/polypropylene resin (f2)

<Method of manufacturing laminate>
The method for producing the laminate of the present embodiment is not particularly limited, but the laminate can be produced by, for example, a co-extrusion method in which a polyolefin resin and a tannic acid derivative are melt-kneaded in an extruder or the like to obtain masterbatch pellets, and then the masterbatch pellets and each resin or resin mixture used in the laminate are heated and melted in separate extruders, and laminated in a molten state while being heated and melted using a co-extrusion multilayer die method, a feed block method, or the like, and then formed into a film by inflation, a T-die chill roll method, or the like.

[Specific configurations of laminate and packaging or container]
The packaging or container according to this embodiment uses the above-mentioned resin film or the above-mentioned laminate, and the form thereof is not particularly limited. Hereinafter, a packaging or container using a laminate will be described as an example. A packaging or container using a resin film is similar to a packaging or container using a laminate, and therefore a description thereof will be omitted.
2A and 2B are cross-sectional views showing an example of a specific configuration of the laminate according to this embodiment.
2A, laminate 10 has a layered structure including resin film 11 and thermoplastic resin film 12, with resin film 11 being the outermost layer. Resin film 11 contains (1) a polyolefin resin and (2) a tannic acid derivative in which at least a portion of a plurality of hydroxyl groups has been substituted with a chain hydrocarbon group having 1 to 18 carbon atoms. This makes it possible to inhibit the proliferation of bacteria, viruses, and the like with a simplified layer structure.

Also, as shown in FIG. 2B , it may have a laminated structure including a resin film 11, a thermoplastic resin film 12, and an intermediate film 13 arranged between the resin film 11 and the thermoplastic resin film 12, with the resin film 11 being the outermost layer.
The intermediate film 13 is not particularly limited, but is preferably a polyethylene-based resin or a polypropylene-based resin. Examples of the polyethylene-based resin for the intermediate film include polyethylene resins such as very low-density polyethylene (VLDPE), linear low-density polyethylene (LLDPE), linear medium-density polyethylene (LMDPE), low-density polyethylene (LDPE), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE); ethylene-vinyl acetate copolymer (EVA), ethylene-methyl methacrylate copolymer (EMMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl acrylate (EMA) copolymer, ethylene-ethyl acrylate-maleic anhydride copolymer (E-EA-MAH), ethylene-acrylic acid copolymer (EAA), and ethylene-methacrylic acid copolymer (EMAA); and ionomers of ethylene-acrylic acid copolymers and ionomers of ethylene-methacrylic acid copolymers.

Examples of polypropylene-based resins for the intermediate film include propylene homopolymers; propylene-ethylene copolymers; propylene-α-olefin random copolymers such as propylene-1-butene copolymers, ethylene-1-butene copolymers, and propylene-ethylene-1-butene terpolymers; and metallocene-catalyzed polypropylenes.

FIG. 3 is a perspective view showing an example of a specific configuration of a container using the laminate 10 according to this embodiment.
As shown in FIG. 3 , the container 30 includes a container body 31 and a laminate 10 attached to the container body 31 .
The laminate 10 has a laminated structure including a resin film 11 and a thermoplastic resin film 12, with the resin film 11 being the outermost layer. The thermoplastic resin film 12 constitutes the innermost layer of the lid. In this embodiment, the laminate 10 constitutes the lid of a container body 31 and is attached to the container body 31 so as to close an opening 32 of the container body 31. At this time, the thermoplastic resin film 12 seals the internal space 33, isolating it from the outside, and the internal space 33 is maintained in a sealed or airtight state.

In this embodiment, the resin film 11 constitutes the outermost layer of the lid material, and the specific tannic acid derivative is retained inside or on the surface of the resin of the resin film 11. This allows the resin film 11 to suppress the growth of bacteria, viruses, etc. in the container 30.

FIG. 4 is a perspective view showing another example of a specific configuration of a package using the laminate 10 according to this embodiment.
As shown in Fig. 4, the package 40 includes an exterior portion 41 formed by bonding together a plurality of laminates 10, and a storage portion 42 formed inside the exterior portion 41. The laminate 10 has a laminated structure including a resin film 11 and a thermoplastic resin film 12, with the resin film 11 being the outermost layer. The storage portion 42 is formed, for example, by bonding together a laminate 10 located at the bottom and a laminate 10 located at the outer periphery.

The thermoplastic resin film 12 is provided on part of the surface of the resin film 11 and is positioned in the opening 43 of the exterior part 41. After the contents are placed in the storage part 42 of the package 40, the opening 43 is closed and the thermoplastic resin films 12 are heat-sealed while abutting each other, isolating the storage part 42 from the outside and maintaining the storage part 42 in a sealed or airtight state.

In this embodiment, the resin film 11 constitutes the outermost layer of the packaging body 40, and the specific tannic acid derivative is retained inside or on the surface of the resin of the resin film 11. With this configuration, the resin film 11 inhibits the growth of bacteria, viruses, and the like in the packaging body 40.

FIG. 5A is a perspective view showing another example of a specific configuration of a package using the laminate 10 according to this embodiment, and FIG. 5B is a cross-sectional view taken along line II in FIG. 5A.
5A and 5B , the package 50 includes an exterior part 51 formed by bonding two sheets of the laminate 10 together, and a storage part 52 formed inside the exterior part 21. The storage part 52 can store contents C, such as food, medicine, etc. The storage part 52 may contain a gas such as air, or may be in a reduced pressure state such as a vacuum.

The laminate 10 has a laminate structure including a resin film 11 and a thermoplastic resin film 12, with the resin film 11 being the outermost layer.

The exterior portion 51 is formed, for example, by bonding two thermoplastic resin films 12 provided on two laminates 10 together. By sealing these thermoplastic resin films 12, the storage portion 52 is isolated from the outside, and the storage portion 52 is maintained in an airtight or sealed state.

In this embodiment, the resin film 11 constitutes the outermost layer of the packaging body 50, and the specific tannic acid derivative is held inside or on the surface of the resin of the resin film 11. With this configuration, the resin film 11 suppresses the growth of bacteria, viruses, etc. in the packaging body 50. In addition, the layer configuration can be simplified, allowing for weight and cost reductions of the packaging body.

FIG. 6 is a perspective view showing another example of a specific configuration of a container using the laminate 10 according to this embodiment.
As shown in FIG. 6, the container 60 includes a container body 61 and two laminated bodies 10-1 and 10-2 attached to the container body 61.

Laminate 10-1 has a laminated structure including resin film 11 and thermoplastic resin film 12, with resin film 11 as the outermost layer. Laminate 10-1 forms the lid of container body 61 and is attached to container body 61 so as to close opening 62 of container body 61. At this time, the thermoplastic resin film 12 seals, isolating internal space 63 from the outside, and maintaining the internal space 63 in a sealed or airtight state.

The resin film 11 of the laminate 10-1 constitutes the outermost layer of the container 60, and the specific tannic acid derivative is retained inside or on the surface of the resin film 11.

Like laminate 10-1, laminate 10-2 has a laminate structure including resin film 11 and thermoplastic resin film 12, with resin film 11 as the outermost layer. Laminate 10-2 is attached to the outer surface, for example, the outer peripheral surface, of container body 61. Resin film 11 of laminate 10-2 constitutes the outermost layer of container 60, and the specific tannic acid derivative is retained within or on the resin surface of resin film 11. With this configuration, the resin films 11, 11 of laminates 10-1, 10-2 can suppress the growth of bacteria, viruses, and the like in container 60.

The following describes examples of the present invention. The present invention is not limited to the examples shown below. In the examples, "parts" means mass % unless otherwise specified.

(Synthesis of tannic acid derivatives)
[Synthesis Example 1]
35 parts of tannic acid (Tokyo Chemical Industry Co., Ltd.) and 65 parts of n-methyl iodide were dissolved in N,N-dimethylformamide (hereinafter referred to as DMF), 63 parts of potassium carbonate was added, and the mixture was reacted for 10 hours at 85° C. Thereafter, the DMF was distilled under reduced pressure, washed with water, and dried to obtain a tannic acid derivative (TA1-5) substituted with 5 equivalents (20% of the number of substituents) of an alkyl group having one carbon atom.

(Preparation of antibacterial masterbatch "antibacterial agent MB (1)" based on propylene-ethylene copolymer)
[Preparation Example 1]
A propylene-ethylene copolymer (MFR (230°C) 7 g/10 min, melting point 130°C) and a tannic acid derivative (TA1-5) were mixed in a mass ratio of 80/20, melted and kneaded in an extruder, and then subjected to a granulator to obtain antibacterial master batch pellets (hereinafter referred to as antibacterial agent MB(1)).

(Preparation of antibacterial masterbatch "antibacterial agent MB (2)" based on linear polyethylene)
[Preparation Example 2]
Linear polyethylene (MFR (190°C) 4 g/10 min, density 0.905 g/cm3) and a tannic acid derivative (TA1-5) were mixed in a mass ratio of 80/20, melt-kneaded in an extruder, and then processed in a granulator to obtain antibacterial master batch pellets (hereinafter referred to as antibacterial agent MB(2)).

Example 1
The following resins were used as resin components for the surface layer, intermediate layer, and seal layer to prepare resin mixtures for forming each layer. These mixtures were fed into three extruders and co-extruded to form a 30 μm-thick laminate, with the average thicknesses of the surface layer, intermediate layer, and seal layer being 7 μm, 18 μm, and 5 μm, respectively.

Surface layer: a mixture of 15 parts by mass of propylene-ethylene copolymer (ethylene-derived component content: 4.2%, density: 0.90 g/cm ³ , melt index (hereinafter referred to as MI): 6 g/10 min, melting point 140°C), 25 parts by mass of propylene-ethylene-1-butene terpolymer (density: 0.90 g/cm ³ , MFR: 5.4 g/10 min (190°C, 21.18 N)), 10 parts by mass of crystalline ethylene-1-butene copolymer (density: 0.88 g/cm ³ , MI: 4 g/10 min), and 50 parts by mass of antibacterial agent MB (1). Middle layer: a mixture of 75 parts by mass of propylene homopolymer (density: 0.90 g/cm ³ , MFR: 7.5 g/10 min), and propylene-ethylene copolymer (ethylene content: 5.2%, density: 0.90 g/cm ³ Sealing layer: a resin mixture of 10 parts by mass of a propylene-ethylene copolymer (ethylene-derived component content: 5.0 mass%, density: 0.90 g/cm ³ , MFR (measurement temperature 230°C): 7 g/10 min) and 30 parts by mass of a propylene-1-butene copolymer (density: 0.90 g/cm ³ , MFR (measurement temperature 230°C): 4 g/ ¹⁰ min).

Example 2
The following resins were used as resin components for the surface layer, intermediate layer, and seal layer to prepare resin mixtures for each layer. These mixtures were fed into three extruders and co-extruded so that the average thicknesses of the surface layer, intermediate layer, and seal layer laminates were 7 μm, 18 μm, and 5 μm, respectively, to form a 30 μm-thick laminate. The surface layer of the resulting laminate was then subjected to corona discharge treatment to obtain a surface energy of 35 mN/m, thereby obtaining a laminate.

Surface layer: A mixture of 50 parts by mass of a propylene-ethylene block copolymer resin (propylene-derived component content: 90% by mass, density: 0.90 g/cm ³ , MFR (measurement temperature 230°C): 5 g/10 min) and 50 parts by mass of an antibacterial agent MB (1). Middle layer: A resin mixture of 50 parts by mass of a propylene-ethylene block copolymer (density: 0.90 g/cm 3 , MI: 8 g/10 min, melting point 160°C), 40 parts by mass of a propylene-ethylene random copolymer (ethylene content: 5.2%, density: 0.90 g/cm ³ , MFR: 5.4 g/10 min), and 10 parts by mass of a linear low-density polyethylene (density: 0.905 g/cm ³ , MFRI: 4.0 g/10 min). Sealing layer: A resin mixture of propylene-ethylene random copolymer (ethylene-derived component content: 5.0% by mass, density: 0.90 g/cm ³ , a resin mixture of 70 parts by mass of a propylene-1-butene copolymer (density: 0.90 g/cm 3 , MFR (measurement temperature: 230° C.): 7 g/10 min) and 30 parts by mass of a propylene-1-butene copolymer (density: 0.90 g/cm ³ , MFR (measurement temperature: 230° C.): 4 g/10 min).

Example 3
The following resins were used as resin components for the surface layer, intermediate layer, and seal layer to prepare resin mixtures for each layer. These mixtures were fed into three extruders and co-extruded to form a 30 μm-thick laminate, with the average layer thicknesses of the surface layer, intermediate layer, and seal layer being 10/16/4 μm. The surface layer of the resulting laminate was then subjected to corona discharge treatment to achieve a surface energy of 39 mN/m. A 12 μm polyester film was then attached using Dikdry LX510/KR90 adhesive to obtain a laminate.

Surface layer: (laminate layer) resin: a mixture of 50 parts by mass of linear low-density polyethylene (density: 0.935 g/cm ³ , MFR: 4.0 g/10 min) and 50 parts by mass of antibacterial agent MB (2) Intermediate layer: 100 parts by mass of linear low-density polyethylene (density 0.933 g/cm ³ , MFR 5.0 g/10 min) Heat seal layer: 100 parts by mass of propylene-ethylene copolymer [MFR (230°C) 7 g/10 min, melting point 130°C]

As a result, in all of Examples 1 to 3, it was confirmed that when a surface layer was formed using a mixture of a polyolefin resin containing a tannic acid derivative substituted with an alkyl group having one carbon atom, a resin film that stably retains tannic acid could be formed. Therefore, it is presumed that the resin film or a laminate containing this resin film inhibits bacterial growth and exhibits sufficient antibacterial properties.

10 Laminate 10-1 Laminate 10-2 Laminate 11 Resin film 12 Thermoplastic resin film 13 Intermediate film 20 Package 21 Exterior part 22 Storage part 30 Container 31 Container body 32 Opening 33 Internal space 40 Package 41 Exterior part 42 Storage part 43 Opening 50 Package 51 Exterior part 52 Storage part 60 Container 61 Container body 62 Opening 63 Internal space

Claims (14)

A resin film comprising a polyolefin resin and a tannic acid derivative in which at least a portion of a plurality of hydroxyl groups of tannic acid are substituted with a chain hydrocarbon group having 1 to 18 carbon atoms. The resin film according to claim 1, wherein the polyolefin resin is one or more selected from polyethylene-based resins, polypropylene-based resins, and polybutylene-based resins. The resin film according to claim 1 or 2, wherein the tannic acid derivative is present in an amount of 0.5% by mass or more and 30% by mass or less relative to the total amount of the resin film. A package or container using the resin film described in any one of claims 1 to 3. A packaging body or container comprising a container body and one or more resin films described in any one of claims 1 to 3 attached to the container body. The packaging or container described in claim 5, wherein the resin film constitutes a lid material for the container body. The packaging or container described in claim 5, wherein the resin film is attached to the outer surface of the container body. A package or container comprising an exterior portion formed by laminating one or more resin films described in any one of claims 1 to 3, and a storage portion formed inside the exterior portion. A laminated structure including the resin film according to any one of claims 1 to 3 and a thermoplastic resin film,
A laminate having the resin film as an outermost layer. A package or container using the laminate described in claim 9. A package or container comprising a container body and one or more laminates according to claim 9 attached to the container body. The packaging or container described in claim 11, wherein the laminate constitutes a lid material for the container body. The packaging or container described in claim 11, wherein the laminate is attached to the outer surface of the container body. A package or container comprising an exterior portion formed by laminating one or more of the laminates described in claim 9 together, and a storage portion formed inside the exterior portion.