JP2022138700A - Laminated film and package - Google Patents

Abstract

To provide a laminated film which is excellent in gas barrier property while having a moderate interlayer strength.SOLUTION: A laminated body has at least three layers including a layer (A) containing a vinyl alcohol-based resin, a layer (B) containing an ionomer-based resin, and a layer (C) in this order.SELECTED DRAWING: None

Description

The present application relates to laminated films and packages.

2. Description of the Related Art Conventionally, various methods such as stretch packaging and shrink packaging have been used as packaging methods for perishable foods in the food packaging field. In recent years, in particular, the demand for gas-encapsulated packaging for long-term storage has increased due to the growing awareness of food loss reduction. By enclosing an inert gas such as nitrogen gas inside the food packaging, it is possible to suppress oxidation deterioration of the food and extend the storage period. For such food packaging films, films having oxygen gas barrier properties are preferably used so that the inert gas sealed inside the packaging does not leak and oxygen existing outside the packaging does not mix.

In recent years, the impact of plastics on the environment has become a social problem, and the use of plant-derived raw materials and biodegradable raw materials is on the rise, as opposed to the conventional use of petroleum-derived raw materials. In addition, it is important to implement the 3Rs (reduce, reuse, recycle) for used plastics, and it is especially important to separate them by type for recycling.

In order to reduce such food loss, as a laminated structure having oxygen gas barrier properties, in Patent Document 1, a vinyl alcohol-based resin is used to impart gas barrier properties, and by controlling the structure, stretchability and gas barrier properties are excellent. and However, in Patent Document 1, the focus is placed on the portion with strong interlayer adhesion, and no consideration is given to sorting and recycling at the time of disposal.

Patent Document 2 discloses a heat-shrinkable laminated film focused on interlayer strength. By controlling the interlaminar strength of the ethylene-vinyl alcohol copolymer resin, it is said to have excellent anti-fogging properties. However, it does not refer to the interlaminar strength with respect to vinyl alcohol-based resins, and, like Patent Document 1, does not assume sorting and recycling at the time of disposal.

JP-A-2006-312313 JP 2015-221507 A

The present invention has been made in view of the above problems, and an object of the present invention is to provide a laminated film and a package that have an appropriate interlayer strength and excellent gas barrier properties.

In order to solve the above-described problems and achieve the object, the laminated film according to the present invention comprises a layer (A) containing a vinyl alcohol resin, a layer (B) containing an ionomer resin, and a layer (C) in that order. It comprises at least three layers.

Here, it is preferable that the layer (A) and the layer (B) have an interlayer strength of 0.1 N/15 mm to 3.0 N/15 mm measured under an atmosphere of 23° C. at a tensile speed of 300 mm/min.

Moreover, it is preferable that the laminated film is stretched in at least one direction.

Further, it is preferable that the oxygen permeability measured in an atmosphere of 20° C.×50% RH based on JIS K7126-2 (2006) is 1.0 cc/m ² ·day·atm or less.

Moreover, it is preferable that the heat shrinkage ratio in the main shrinkage direction when immersed in hot water at 100° C. for 10 seconds is 30% or more.

Moreover, when the resin composition forming the layer (B) is taken as 100% by mass, the content of the ionomer-based resin is preferably 30% by mass or more.

Moreover, it is preferable that the layer (B) contains a polyethylene-based resin.

Moreover, it is preferable that the layer (C) contains a polyethylene-based resin.

Moreover, it is preferable that the polyethylene-based resin contains a plant-derived polyethylene-based resin.

Moreover, it is preferable to have at least five layers in this order of the layer (C), the layer (B), the layer (A) containing the vinyl alcohol resin, the layer (B), and the layer (C).

In order to solve the above-described problems and achieve the object, the laminated film according to the present invention comprises a layer (A) having gas barrier properties, a layer (B) containing an ionomer resin, and at least three layers (C) in that order. It is preferable that the laminated film has layers, and the interlayer strength measured in an atmosphere of 23° C. at a tensile speed of 300 mm/min for the layers (A) and (B) is 0.1 N/15 mm to 3 N/15 mm. .

Moreover, it is preferable that the laminated film has heat shrinkability.

Also, the laminated film is preferably for food packaging.

In order to solve the above-described problems and achieve the object, a package according to the present invention includes any one of the laminated films described above and a food packaging tray.

The laminated film of the present invention does not undergo delamination during actual use, and the layers (A) and (C) can be easily delaminated with a tape or the like at the time of disposal. In addition, by using a vinyl alcohol resin for the layer (A), it is water-soluble, so that the impact on the environment can be reduced at the time of disposal after sorting, and the environmental compatibility is high. Furthermore, by containing an ionomer resin in the layer (B), the metal species contained in the ionomer resin and the hydroxyl group of the vinyl alcohol resin used in the layer (A) form a coordinate bond, resulting in gas barrier properties. Improvement can be expected. In addition, by using a material having gas barrier properties for the layer (A) and containing an ionomer resin for the layer (B), there is no delamination during actual use, and the layer (A) can be easily attached to the layer (A) with a tape or the like at the time of disposal. (C) can be delaminated and is excellent in separability at the time of disposal.

The present invention will be described in detail below. However, the contents of the present invention are not limited to the embodiments described below.

In this specification, the term "main component" indicates that the component accounts for the largest amount by mass when the total of the constituent components is 100% by mass, and is preferably 50% by mass or more, and 60% by mass. The above is more preferable, and 70% by mass or more is even more preferable.

In addition, when described as “X to Y” (X and Y are arbitrary numbers), unless otherwise specified, “X or more and Y or less”, “preferably larger than X” and “preferably smaller than Y” ” is included.

In the present specification, the term "film" is meant to include thick sheets to thin films.

As used herein, "at least one direction" means that in the manufacturing process of a laminated film, when the direction of flow from the extruder is the machine direction (MD) and the orthogonal direction is the transverse direction (TD), the machine direction and the transverse direction It means either one or both of the directions, and the "main shrinkage direction" means the direction in which the heat shrinkage rate is larger, out of the longitudinal direction and the transverse direction.

In addition, the upper limit and lower limit of the numerical range in this specification, even if slightly deviating from the numerical range specified by the present invention, as long as it has the same effect as within the numerical range, the present invention shall be included in the equivalent range of

<Laminated film>
A laminated film according to an example of an embodiment of the present invention (hereinafter sometimes referred to as "this film") comprises at least a layer (A), a layer (B), and a layer (C), and the layer (A) is It is a layer containing a vinyl alcohol resin, and the layer (B) is characterized by containing an ionomer resin. In this embodiment, the laminated film having heat-shrinkability, that is, the heat-shrinkable film will be described, but the film may be a non-heat-shrinkable film. That is, the present invention can be a laminated film comprising at least layer (A), layer (B), and layer (C).

(1) Thickness The upper limit of the thickness of the present film is preferably 100 µm or less, more preferably 70 µm or less, and even more preferably 50 µm or less. On the other hand, the lower limit is preferably 5 µm or more, more preferably 8 µm or more, and particularly preferably 10 µm or more. If the thickness is 100 μm or less, the transparency tends to be excellent. Further, if the thickness is 5 μm or more, there is a tendency that the handleability can be secured.

(2) Haze The upper limit of the haze of the present film is preferably 20% or less, more preferably 15% or less, and particularly preferably 10% or less. On the other hand, the lower limit is preferably 0.5% or more, more preferably 1% or more. If the haze is 20% or less, the transparency tends to be excellent. Further, when the haze is 0.5% or more, visibility tends to be ensured, and erroneous mixing into food during packaging can be prevented.

(3) Tensile strength and elongation The tensile strength of the present film is not particularly limited, but the upper limit is preferably 100 MPa or less, more preferably 90 MPa or less, and particularly preferably 80 MPa or less. On the other hand, the lower limit is preferably 10 MPa or more, more preferably 20 MPa or more. If the tensile strength is 100 MPa or less, there is a tendency that an appropriate degree of elongation can be secured and that the handling property is excellent. Moreover, if the tensile strength is 10 MPa or more, there is a tendency that the stiffness of the film can be secured.
The tensile elongation of the present film is not particularly limited, but the upper limit is preferably 300% or less, more preferably 250% or less. On the other hand, the lower limit is preferably 20% or more, more preferably 30% or more, and particularly preferably 40% or more. If the tensile elongation is 300% or less, there is a tendency for excellent hand tearability during use. Moreover, when the tensile elongation is 20% or more, there is a tendency that the handling property during use is excellent. Specifically, the tensile strength and tensile elongation can be measured by the methods described in Examples.

(4) Thermal shrinkage The upper limit of the thermal shrinkage of the film is preferably 70% or less, more preferably 60% or less, and particularly preferably 50% or less. On the other hand, the lower limit is preferably 10% or more, more preferably 20% or more. A heat shrinkage rate of 70% or less is preferable because excessive deformation of the container can be prevented when the film is shrunk. Moreover, if the heat shrinkage rate is 10% or more, there is a tendency that the packaging aptitude to follow the container is excellent during shrink packaging such as pillow packaging. Specifically, the thermal shrinkage can be measured by the method described in Examples.

(5) Oxygen permeability The upper limit of the oxygen permeability of the film is preferably 1.0 cc/m ² ·day·atm or less, more preferably 0.60 cc/m ² ·day·atm or less, and 0.20 cc/ m ² ·day·atm or less is more preferable, and 0.13 cc/m ² ·day·atm or less is particularly preferable. On the other hand, the lower limit is preferably 0.001 cc/m ² ·day·atm or more, more preferably 0.01 cc/m ² ·day·atm or more. If the oxygen permeability is 1.0 cc/m ² ·day·atm or less, oxidative deterioration due to oxygen after packaging can be sufficiently prevented. Moreover, if the oxygen permeability is 0.001 cc/m ² ·day·atm or more, it is possible to prevent an excessively sealed state.

(6) Water vapor permeability The upper limit of the water vapor permeability of the present film is preferably 50 g/m ² ·day or less, more preferably 35 g/m ² ·day or less, and particularly preferably 25 g/m ² ·day or less. On the other hand, the lower limit is preferably 0.1 g/m ² ·day or more, more preferably 1 g/m ² ·day or more. If the water vapor transmission rate is 50 g/m ² ·day or less, it is possible to sufficiently prevent the infiltration of external water vapor after packaging. Moreover, when the water vapor transmission rate is 0.1 g/m ² ·day or more, excessive sealing can be prevented.

(7) Interlaminar strength Interlaminar strength in the present film is important, and the upper limit is preferably 3.0 N/15 mm or less, more preferably 2.0 N/15 mm or less, further preferably 1.0 N/15 mm or less, and 0.8 N /15 mm or less is particularly preferable, and 0.6 N/15 mm or less is most preferable. On the other hand, the lower limit is preferably 0.2 N/15 mm or more, more preferably 0.3 N/15 mm or more. When the interlaminar strength is 3.0 N/15 mm or less, preferably 2.0 N/15 mm or less, the layer (A) can be easily separated from the other layers, and the separation at the time of disposal is excellent. Also, if the interlaminar strength is 0.2 N/15 mm or more, the film can be used without delamination. Specifically, the interlayer strength can be measured by the method described in Examples.

The laminated film of the present invention has a laminated structure having at least a layer (A), a layer (B) and a layer (C). Since the layer (B) contains an ionomer resin, it has an appropriate interlaminar strength, does not delaminate during actual use, and can be easily delaminated from the layer (A) and the layer (C) with a tape or the like at the time of disposal. be. In addition, by using an ionomer-based resin for the layer (B), the metal species contained in the ionomer-based resin and the hydroxyl group of the vinyl alcohol-based resin used for the layer (A) form a coordinate bond, resulting in gas barrier properties. can be expected to improve.

The layer structure of the laminated film of the present invention is not particularly limited, and not only a structure having at least the layer (A), the layer (B), and the layer (C), but also a multilayer structure of 4 layers, 5 layers, and more. It doesn't matter if it is. Regardless of the layer structure, if the layer (B) is provided as an adhesive layer for the layer (A), the laminated film will have an appropriate interlaminar strength. In the laminated film, it is preferable that the layer (B) is provided between two different layers, that is, the layer (B) is provided for each layer.

The thickness ratio of each layer (lamination ratio) of the laminated film of the present invention is not particularly limited.
The thickness ratio of the layer (A), the layer (B), and the layer (C) in the laminated film of the present invention can be appropriately adjusted depending on the application and purpose. From the viewpoint of obtaining the effect of the present invention, the thickness ratio [(A):(B):(C)] of layer (A), layer (B), and layer (C) is preferably 1:1 :1 to 0.01:0.1:1, more preferably 0.5:0.8:1 to 0.1:0.6:1. When the thickness ratio of the layer (A), the layer (B), and the layer (C) is within the above range, the gas barrier property of the vinyl alcohol resin used for the layer (A) and the thickness of the layer (A) and the layer (C) It has a good balance with interlaminar strength and is suitable for use as a food packaging material. In addition, when each layer has two or more layers, the thickness of each layer means the total thickness of each of the plurality of layers.
The thickness and thickness ratio of the layer (A), layer (B), and layer (C) in the laminated film can be controlled by adjusting the thickness of the nonporous film before stretching, the stretching conditions, and the like. .
The lamination ratio of the layer (A) to the total thickness is preferably 0.1% or more and 30% or less, more preferably 0.5% or more and 20% or less, and even more preferably 1% or more and 10% or less. The thickness of the layer (A) in the heat-shrinkable film is preferably 0.1-10 μm, more preferably 0.5-5 μm. If the thickness ratio of the layer (A) and the thickness in the film are within this range, it tends to be easy to obtain a laminated film with excellent gas barrier properties and processing suitability.

As long as the present film has the above structure, it may further include other layers.

Layer (A), layer (B) and layer (C) constituting the present film are described below. After that, a method for forming the present film as a manufacturing method will be described.

Each component constituting the present film will be described below.
<Layer (A)>
The layer (A) constituting the laminated film of the present invention contains a vinyl alcohol-based resin. Each component constituting the layer (A) will be described below.

<Vinyl alcohol resin>
The vinyl alcohol resin used in the layer (A) of the present invention is a resin mainly composed of vinyl alcohol structural units obtained by saponifying a polyvinyl ester resin obtained by copolymerizing a vinyl ester monomer. It is composed of vinyl alcohol structural units and vinyl ester structural units corresponding to the degree of saponification. Vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, and versatic acid. Vinyl and the like can be mentioned, but vinyl acetate is preferably used from the viewpoint of cost.

The vinyl alcohol resin used in the present invention preferably has an average degree of polymerization (measured according to JIS K6726 (1994)) of 150 to 3,000, more preferably 200 to 2,000, and particularly preferably 300 to 1,000. If the average degree of polymerization of the vinyl alcohol-based resin is 150 or more, it is preferable because the mechanical strength of the layer (A) tends to be maintained. In addition, when the average degree of polymerization of the vinyl alcohol resin is 3000 or less, there is a tendency to prevent the deterioration of the moldability due to the decrease in fluidity of the resin.

The degree of saponification (measured according to JIS K6726 (1994)) of the vinyl alcohol resin used in the present invention is preferably 80 to 100 mol%, more preferably 90 to 99.9 mol%, and more preferably 98 to 99.9 mol%. 5 mol % is particularly preferred. When the degree of saponification of the vinyl alcohol resin is 80 mol % or more, sufficient gas barrier properties can be maintained.

The melting point of the vinyl alcohol resin used in the present invention is preferably 140 to 250°C, more preferably 150 to 245°C, still more preferably 160 to 240°C, and particularly preferably 170 to 230°C. If the melting point is 140° C. or higher, there is a tendency for excellent shape stability during melt molding. If the melting point is 250° C. or less, there is a tendency to prevent deterioration of the resin during melt molding. The melting point of the vinyl alcohol-based resin can be measured with a differential scanning calorimeter (DSC) at a temperature raising/lowering rate of 10° C./min according to JIS K7121 (2012).

The vinyl alcohol resin used in the present invention is obtained by copolymerizing various monomers during production of the polyvinyl ester resin and saponifying it, or by post-modifying the unmodified vinyl alcohol resin with various functionalities. A modified vinyl alcohol resin into which a group has been introduced can also be used.

Monomers used for copolymerization with vinyl ester monomers include olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, α-octadecene, 3-buten-1-ol, 4-pentene. -1-ol, 5-hexen-1-ol, 3,4-dihydroxy-1-butene and other hydroxy group-containing α-olefins and their acylated derivatives, acrylic acid, methacrylic acid, crotonic acid, maleic acid , maleic anhydride, unsaturated acids such as itaconic acid, salts thereof, monoesters or dialkyl esters, nitriles such as acrylonitrile and methacrylonitrile, amides such as diacetone acrylamide, acrylamide, methacrylamide, ethylene sulfonic acid, allyl Sulfonic acid, olefin sulfonic acids such as methallylsulfonic acid or salts thereof, alkyl vinyl ethers, dimethyl allyl vinyl ketone, N-vinyl pyrrolidone, vinyl chloride, vinyl ethylene carbonate, 2,2-dialkyl-4-vinyl-1,3 -Vinyl compounds such as dioxolane, glycerol monoallyl ether, 3,4-diacetoxy-1-butene, isopropenyl acetate, substituted vinyl acetates such as 1-methoxyvinyl acetate, vinylidene chloride, 1,4-diacetoxy-2-butene , vinylene carbonate and the like.

Vinyl alcohol resins into which functional groups have been introduced by post-reaction include those having acetoacetyl groups by reaction with diketene, those having polyalkylene oxide groups by reaction with ethylene oxide, and hydroxyalkyls by reaction with epoxy compounds, etc. and those obtained by reacting an aldehyde compound having various functional groups with a vinyl alcohol-based resin. The content of the functional group introduced by the post-reaction in the modified vinyl alcohol resin varies depending on the modified species, so it cannot be generalized. It is preferably used.

The layer (A) of the present invention is a layer containing a vinyl alcohol-based resin as a main component, and preferably contains 50% by mass or more of the vinyl alcohol-based resin, more preferably 60% by mass or more, and more preferably 70% by mass or more. It is more preferable to contain 80% by mass or more, and it is most preferable to contain 95% by mass or more. By including the vinyl alcohol resin in the layer (A) as a main component, sufficient gas barrier properties can be ensured.

The vinyl alcohol resin used in the present invention may be of one type or a mixture of two or more types. In the case of a mixture of two or more types, a combination of the above-described unmodified vinyl alcohol resins, or a combination of unmodified vinyl alcohol resins and vinyl alcohol resins having different degrees of saponification, polymerization, modification, etc., is used. be able to. Among them, the vinyl alcohol resin used in the present invention is a resin mainly composed of vinyl alcohol structural units, and includes a vinyl alcohol structural unit corresponding to the degree of saponification, a vinyl acetate structural unit of the unsaponified portion, and a side chain. Those having at least a structural unit having a primary hydroxyl group are preferred.

Commercially available vinyl alcohol resins can be used. Examples of commercially available vinyl alcohol resins include Kuraray's Exeval (registered trademark) and Mitsubishi Chemical Corporation's G-polymer (registered trademark).

In the above-described embodiment, the preferred layer (A) contains a vinyl alcohol resin, but the layer (A) may be made of other materials as long as it has gas barrier properties.

<Layer (B)>
It is important that the layer (B) constituting the laminated film of the present invention contains an ionomer resin. By using an ionomer resin for the layer (B), the layer (A) and the layer (C) have an appropriate interlaminar strength. A) and layer (C) are delaminated and can be separated. In addition, by using an ionomer-based resin for the layer (B), the metal species contained in the ionomer-based resin and the hydroxyl group of the vinyl alcohol-based resin contained in the layer (A) form a coordinate bond, resulting in gas barrier properties. can be expected to improve. Each component constituting the layer (B) will be described below.

<Ionomer resin>
The ionomer resin used in the layer (B) of the present invention means a copolymer of ethylene and a small amount of acrylic acid or methacrylic acid crosslinked with metal ions such as zinc and sodium. The metal species contained in the ionomer-based resin is preferably a monovalent or divalent metal ion, and may contain two or more types of metal ions. The metal species contained in the ionomer-based resin more preferably contains a divalent metal ion represented by zinc. The metal ions contained in the ionomer-based resin tend to form coordination bonds with functional groups such as hydroxyl groups, making it difficult to dissociate, and an improvement in gas barrier properties can be expected due to cross-linking between polymers via metal ions. Furthermore, the inclusion of divalent metal ions facilitates cross-linking, which tends to reduce the free volume and further improve gas barrier properties. Furthermore, in order to improve gas barrier properties, compounds such as metal salts containing divalent metal ions may be added. Specifically, zinc compounds, copper compounds, nickel compounds, iron compounds, manganese compounds, and the like may be added.

The layer (B) of the present invention is a layer containing an ionomer resin, and preferably contains 30% by mass or more of the ionomer resin, more preferably 40% by mass or more, and particularly preferably 50% by mass or more. . If the content of the ionomer-based resin in the adhesive layer is 30% by mass or more, the interlayer strength preferably defined in the present application can be ensured.

Resins other than the ionomer-based resin used in the layer (B) of the present invention are not particularly limited, but polyolefin-based resins are preferably used. Polyolefin resins include low density polyethylene, linear low density polyethylene, medium density polyethylene, high density polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, ethylene-ethyl acrylate copolymer, Examples include ethylene-methyl acrylate copolymers, ethylene-ethyl acrylate-maleic anhydride copolymers, ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers, etc. Among them, polyethylene-based resins are preferred.

Commercially available ionomer resins can be used. As a commercially available ionomer-based resin, Himilan (registered trademark) manufactured by Mitsui-Dow Polychemicals, etc. can be used. The melt flow rate (MFR) of the ionomer resin is not particularly limited, but usually the MFR is preferably 0.5 g/10 minutes to 10 g/10 minutes, and 1.0 g/10 minutes to 8.0 g/10 minutes. More preferably, it is 0 g/10 minutes. By setting the MFR to 0.5 g/10 minutes or more, it is possible to have a sufficient melt viscosity during molding and ensure high productivity. On the other hand, by setting the MFR to 10 g/10 minutes or less, it is possible to have sufficient strength. The MFR is measured under conditions of a temperature of 190° C. and a load of 2.16 kg according to JIS K7210-1 A method (2014).
The melting point of the ionomer resin is preferably 70°C to 120°C, more preferably 75°C to 115°C, as measured at a heating rate of 10°C/min in differential scanning calorimetry. By setting the melting point within the above range, both transparency and moisture resistance can be achieved. The melting point can be measured using a differential scanning calorimeter at a heating rate of 10° C./min according to JIS K7121 (2012).

<Layer (C)>
The layer (C) of the present invention is not particularly limited, but it is a layer that imparts heat sealability to the laminated film and functions as a support layer during stretching, and is preferably the outermost layer of the laminated film. To position. A known thermoplastic resin can be used for the layer (C). For example, ethylene-α-olefin copolymer, high-density polyethylene, low-density polyethylene, linear low-density polyethylene, ethylene-acrylic acid copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer. Polyethylene resins such as coalescence, ethylene-methacrylic acid copolymer, ethylene-methyl methacrylate copolymer, ethylene-vinyl acetate copolymer, polypropylene resin, polyamide resin, aliphatic aromatic polyester resin, Biodegradable resins such as aliphatic polyesters and these plant-derived resins can be used. Among them, it is preferable to use biodegradable resins and plant-derived resins from the viewpoint of environmental consideration. In particular, the biodegradable resin is preferably used in the present invention because it can be biodegraded in the soil after delamination and separation of only the layer (C) after it is used as a laminated film.

The biodegradable resin that can be suitably used for the layer (C) of the present invention is not particularly limited, and commonly available biodegradable resins can be used. Examples thereof include polycaprolactone, cellulose ester, lactic acid polyester resin, aliphatic polyester resin, and aliphatic aromatic polyester resin. Among them, it is preferable to use an aliphatic aromatic polyester resin, an aliphatic polyester resin, or a lactic acid polyester resin in consideration of productivity and workability when producing a film and biodegradability after use.

The plant-derived resin that can be suitably used in the laminated film of the present invention is not particularly limited, and generally available plant-derived resins can be suitably used. Examples thereof include polyethylene-based resins, polypropylene-based resins, polyamide-based resins, aliphatic polyester-based resins, and aliphatic-aromatic polyester-based resins. Among them, it is preferable to use a polyethylene-based resin in consideration of productivity, workability, and economic efficiency when producing a film. The melt flow rate (MFR) of the polyethylene resin is not particularly limited, but usually the MFR is preferably 0.5 g/10 minutes to 15 g/10 minutes, and 1.0 g/10 minutes to 10 g/10 minutes. More preferably 10 minutes. By setting the MFR to 0.5 g/10 minutes or more, it is possible to have a sufficient melt viscosity at the time of molding and to ensure high productivity. On the other hand, by setting the MFR to 15 g/10 minutes or less, it is possible to have sufficient strength. The MFR is measured under conditions of a temperature of 190° C. and a load of 2.16 kg according to JIS K7210-1 A method (2014).
The polyethylene resin preferably has a melting point of 110° C. to 135° C., more preferably 115° C. to 130° C., measured at a heating rate of 10° C./min in differential scanning calorimetry. By setting the melting point within the above range, both transparency and moisture resistance can be achieved. The melting point can be measured using a differential scanning calorimeter at a heating rate of 10° C./min according to JIS K7121 (2012).
The density of the polyethylene resin is preferably 0.850 g/cm ³ or more and 0.970 g/cm ³ or less, more preferably 0.880 g/cm ³ or more and 0.960 g/cm ³ or less, and 0.900 g. /cm 3 or more and 0.950 g/cm ³ or less. By setting the density within the above range, both mechanical strength and flexibility can be achieved. Density can be measured according to JIS K7112 (1999).

<Method for producing laminated film>
The method for producing the laminated film of the present invention will be explained. The following explanation is an example of the method for producing the laminated film of the present invention, and the laminated film of the present invention is limited to the laminated film produced by such a production method. not something.

In the method for producing a laminated film according to an example of the embodiment of the present invention (hereinafter sometimes referred to as the present film production method), the layer (A), the layer (B), and the layer (C) are A laminated film is obtained by kneading and melt-molding using an extruder or the like under temperature conditions below the decomposition temperature.

Since the present film manufacturing method only needs to include the steps described above, it may further include other steps and treatments.

Further, in the present invention, other resins may be allowed to be mixed in the layer (A), the layer (B) and the layer (C) within a range that does not impair the effects of the present invention.
Other resins include polyethylene resins, polypropylene resins, polystyrene resins, polyvinyl chloride resins, polyvinylidene chloride resins, chlorinated polyethylene resins, polyester resins, polycarbonate resins, polyamide resins, and polyacetal resins. Resin, acrylic resin, ethylene vinyl acetate copolymer, polymethylpentene resin, polyvinyl alcohol resin, cyclic olefin resin, polylactic acid resin, polybutylene succinate resin, polyacrylonitrile resin, polyethylene oxide resin , cellulose resin, polyimide resin, polyurethane resin, polyphenylene sulfide resin, polyphenylene ether resin, polyvinyl acetal resin, polybutadiene resin, polybutene resin, polyamideimide resin, polyamide bismaleimide resin, polyarylate resin Examples include resins, polyetherimide resins, polyetheretherketone resins, polyetherketone resins, polyethersulfone resins, polyketone resins, polysulfone resins, aramid resins, fluorine resins, and the like.

Further, in the present invention, in addition to the above-described components, generally used additives can be appropriately added within a range that does not significantly impair the effects of the present invention. Examples of the additives include recycled resins generated from trimming loss such as selvages, pigments, flame retardants, and weather resistance stabilizers, which are added for the purpose of improving and adjusting molding processability, productivity, and various physical properties of laminated films. agents, heat stabilizers, antistatic agents, melt viscosity improvers, cross-linking agents, lubricants, nucleating agents, plasticizers, anti-aging agents, antioxidants, light stabilizers, UV absorbers, neutralizers, anti-fogging agents, Additives such as antiblocking agents, slip agents, and colorants are included.

The machine used for kneading is not particularly limited. For example, known extruders such as single-screw extruders, twin-screw extruders and multi-screw extruders can be used. In addition, depending on the facility structure and necessity, a pressure reducer may be connected to the vent port to remove moisture and other low-molecular-weight substances.

The film-forming process and the stretching process will be sequentially described below.

(1) Film Forming Process Examples of the method of heating and melting the material resin include a T-die method and an inflation method. Practically, it is preferable to melt-extrude the material resin from a round die and perform balloon molding by air cooling.

When the T-die method is used as a specific method for forming a film, the sheets of molten resin extruded from the T-die are laminated and brought into close contact with a rotating cast roll (chill roll, cast drum). A method of forming into a take-off sheet-like material can be mentioned.

A touch roll, an air knife, an electric contact device, or the like may be attached to the cast roll in order to adhere the film material to the cast roll.
When forming a film while cooling the kneaded material, the temperature of the cast rolls is preferably 70° C. or lower. It is more preferably 60° C. or lower, still more preferably 50° C. or lower. By setting the temperature of the cast roll to 70° C. or less to obtain a laminated film material with a low degree of crystallinity, breakage in the subsequent stretching process can be suppressed, which is preferable.

In the resulting unstretched film, the thickness of the effective portion excluding both ends is preferably 700 μm to 100 μm, more preferably 600 μm to 125 μm, and even more preferably 500 μm to 150 μm.
If the thickness of the unstretched film is 100 µm or more, the film is too thin to cause breakage during stretching. can prevent

Regarding the layer structure of the original film of the laminated film of the present invention, not only the layer structure described above but also a structure in which other layers are combined may be used.

(2) Stretching Step Next, the obtained nonporous membrane is uniaxially stretched or biaxially stretched. The uniaxial stretching may be vertical uniaxial stretching or horizontal uniaxial stretching. Biaxial stretching may be simultaneous biaxial stretching or sequential biaxial stretching. Simultaneous biaxial stretching is more preferable from the viewpoint of productivity when producing a laminated film, which is the object of the present invention. The stretching of the film in the machine direction (MD) is called "longitudinal stretching", and the stretching in the direction perpendicular to the machine direction (TD) is called "transverse stretching".

When sequential biaxial stretching is used, the stretching temperature must be appropriately selected according to the composition of the resin composition to be used, the crystalline melting peak temperature, the degree of crystallinity, etc. However, the balance with other physical properties such as mechanical strength and shrinkage ratio is necessary. Easy to take.

The stretching temperature in longitudinal stretching is preferably in the range of approximately 10 to 100°C, more preferably 15 to 90°C, still more preferably 20 to 80°C. If the stretching temperature in the longitudinal stretching is 10° C. or higher, breakage during stretching is suppressed and uniform stretching is performed, which is preferable. On the other hand, if the stretching temperature in the longitudinal stretching is 100° C. or less, stretching can be performed without excessive sticking to the rolls.

The longitudinal draw ratio can be arbitrarily selected, but the draw ratio per uniaxial drawing is preferably 1.1 to 10 times, more preferably 1.5 to 8.0 times, and still more preferably 2.0 to 6.0 times. 0 times. A film that shrinks due to heat can be obtained by setting the draw ratio per uniaxial drawing to 1.1 times or more. Moreover, by making it 10 times or less, it is possible to obtain a laminated film in which excessive shrinkage is suppressed.

The transverse stretching temperature is preferably 50 to 150°C, more preferably 60 to 140°C. When the lateral stretching temperature is within the specified range, stretching can be performed while preventing the film from breaking after longitudinal stretching.

The transverse draw ratio can be arbitrarily selected, but is preferably 1.1 to 10 times, more preferably 1.5 to 9.0 times, still more preferably 2.0 to 8.0 times. A film that shrinks due to heat can be obtained by stretching at a specified transverse draw ratio.
Furthermore, the laminated film of the present invention can be subjected to corona treatment, plasma treatment, printing, coating, surface treatment such as vapor deposition, perforation, etc., if necessary, as long as the present invention is not impaired. It is also possible to stack several laminated films of the present invention depending on the conditions.

Examples and Comparative Examples are shown below to describe the laminated film of the present invention in more detail, but the present invention is not limited in any way.

・ A-1: Polyvinyl alcohol (grade name; G-Polymer BVE8049P, MFR: 4.0 g/10 min [230°C, 2.16 kg load], melting point: 185°C, manufactured by Mitsubishi Chemical Corporation)
・ B-1: Na-based ionomer (grade name: Himilan 1605, MFR: 2.8 g/10 min [190 ° C., 2.16 kg load], melting point: 92 ° C., Mitsui Dow Polychemical Co., Ltd.)
・ B-2: Zn-based ionomer (grade name: Himilan 1705, MFR: 5.0 g/10 min [190 ° C., 2.16 kg load], melting point: 91 ° C., manufactured by Mitsui Dow Polychemicals)
・ D-1: polyethylene (ADMER NF614, melting point: 122 ° C., manufactured by Mitsui Chemicals, Inc.)
・D-2: Polyethylene (grade name: Novatec LL UF240, MFR: 2.1 g/10 min [190°C, 2.16 kg load], density: 0.920 g/cm ³ , manufactured by Japan Polyethylene Co., Ltd.) (C-2 using the same raw materials as
D-3: Plant-derived polyethylene (grade name; SPB681, MFR: 3.8 g/10 min [190°C, 2.16 kg load], density: 0.922 g/cm ³ , manufactured by Braskem) (C-4 and using the same raw materials)
・C-1: Polyethylene (grade name: Evolue SP2120, MFR: 2.2 g/10 minutes [190°C, 2.16 kg load], density: 0.921 g/cm ³ , manufactured by Prime Polymer Co., Ltd.)
・C-2: Polyethylene (grade name: Novatec LL UF240, MFR: 2.1 g/10 min [190°C, 2.16 kg load], density: 0.920 g/cm ³ , manufactured by Japan Polyethylene Co., Ltd.)
・C-3: Plant-derived polyethylene (grade name; SLH218, MFR: 2.3 g/10 min [190°C, 2.16 kg load], density: 0.916 g/cm ³ , manufactured by Braskem)
・C-4: Plant-derived polyethylene (grade name; SPB681, MFR: 3.8 g/10 min [190°C, 2.16 kg load], density: 0.922 g/cm ³ , manufactured by Braskem)

(Example 1)
100 parts by mass of vinyl alcohol resin (A-1) in the intermediate layer side extruder with a T die with a lip opening of 1 mm, 50 parts by mass of ionomer resin (B-2) in the adhesive layer side extruder and polyethylene resin (D -3) Melt extrusion molding at 210 ° C. using a mixture of 50 parts by mass and a mixture of 60 parts by mass of polyethylene resin (C-1) and 40 parts by mass of polyethylene resin (C-2) in the extruder on the front and back layers. Conducted and guided to cast rolls at 40°C. A laminated film material having a thickness of 200 μm and having a 3-kind 5-layer structure was obtained. Thereafter, the laminated film-like material was longitudinally stretched by using a longitudinal stretching machine at a draw ratio of 100% (total longitudinal stretching ratio of 2.0 times) between rolls set at 65°C. The longitudinally stretched film was preheated at a preheating temperature of 80°C for a preheating time of 12 seconds in a film tenter facility (manufactured by Kyoto Kikai Co., Ltd.), then stretched 5.0 times in the transverse direction at a stretching temperature of 80°C, and stretched 80 times. A laminated film was obtained by heat-treating at ℃. Table 1 summarizes the evaluation results of the obtained laminated film.

(Examples 2-4, Comparative Examples 1-3)
A mixture was prepared at the raw material compounding ratio shown in the table, and a laminated film material was obtained in the same manner as in Example 1. After that, the laminated film material was stretched longitudinally and transversely at a predetermined magnification in the same manner as in Example 1 to obtain a laminated film. A comparative example was made with a material that did not contain an ionomer as an adhesive layer. Table 1 summarizes the evaluation results of the obtained laminated film.

Film thickness, haze, tensile strength, heat shrinkage, oxygen permeability, water vapor permeability, interlaminar strength, packaging suitability, recyclability, and comprehensive evaluation of the films obtained in Examples and Comparative Examples were evaluated by the following methods. was measured and evaluated.

(1) Film thickness 10 points were randomly measured using a dial gauge of 1/1000 mm, and the average value was taken as the thickness.

(2) Haze The haze value of the obtained laminated film was measured according to JIS K7136 (2000).

(3) Tensile Strength and Elongation The obtained laminated film was cut into a size of 120 mm in MD and 15 mm in TD, and according to JIS K7127 (1999), at a tensile speed of 200 mm/min and an ambient temperature of 23°C, the MD of the film was subjected to tensile breakage. The strength and tensile elongation at break were measured, and the average value of five measurements was calculated.
In addition, the resulting laminated film was cut into a size of 15 mm MD and 120 mm TD, and in accordance with JIS K7127 (1999), at a tensile speed of 200 mm / min, at an ambient temperature of 23 ° C. The tensile breaking strength of TD of the film, tensile breaking elongation The degree was measured and the average value of 5 measurements was calculated.

(4) Thermal Shrinkage Rate The obtained laminated film was cut into strips having an MD of 200 mm and a TD of 10 mm, and marked lines were marked at intervals of 100 mm in MD. After that, each strip-shaped film was immersed in a hot water bath set at a temperature of 100 ° C. for 10 seconds, and the marked line spacing after shrinkage was measured, and the amount of shrinkage (= marked line spacing before shrinkage - marked line spacing after shrinkage). was measured. The thermal shrinkage rate was calculated as the ratio of the amount of shrinkage to the interval between marked lines before shrinkage (=(amount of shrinkage/interval between marked lines before shrinkage)×100%).
Also, the obtained laminated film was cut into a size of 10 mm in MD and 200 mm in TD, and a reference line was marked on the TD at an interval of 100 mm. After that, the same measurement as the MD thermal shrinkage measurement was performed to measure the TD thermal shrinkage.

(5) Oxygen Permeability The obtained laminated film is measured in accordance with JIS K7126-2 (2006) using an OXY-TRAN100 type oxygen permeability measuring device manufactured by Modern Control Co., Ltd. under an atmosphere of 23° C. and 50% RH. , the oxygen permeability of the laminated film was measured.

(6) Water vapor permeability The obtained laminated film was measured for water vapor permeability in an atmosphere of 40°C and 90% RH using PERMATRAN manufactured by MOCON based on JIS K7129 (2008).

(7) Gas Barrier Properties The gas barrier properties of the obtained laminate films were evaluated according to the following criteria based on the oxygen permeability.
A: The oxygen permeability of the laminated film is 0.10 cc/m ² ·day·atm or less.
◯: The oxygen permeability of the laminated film is 1.0 cc/m ² ·day·atm or less.
x: The oxygen permeability of the laminated film is 10 cc/m ² ·day·atm or less.

(8) Interlaminar strength The obtained laminated film was cut into a size of 50 mm MD and 15 mm TD, and T-type peeling was performed with a chuck distance of 10 mm and a tensile speed of 300 mm / min, and the interlaminar strength of the film at an ambient temperature of 23 ° C. was measured. Then, the average value of 5 measurements was calculated.

(9) Packaging suitability For a 100 mL wide-mouth bottle made of high-density polyethylene resin with the lid removed (manufactured by AS ONE, mouth inner diameter 33.8 x body diameter 50 x total height 93 (mm)), a laminated film is placed at the opening of the wide-mouth bottle. It was covered and immersed in a warm water bath set at a temperature of 100° C. for 10 seconds to perform shrink packaging. The suitability for packaging was determined by the following evaluation method.
◯: The laminated film was able to be wrapped without wrinkles, tears, or insufficient tension.
x: Any of wrinkles, tearing, or insufficient tension occurred in the laminated film, and packaging was difficult.

(10) Recyclability Based on the interlaminar strength of the laminated film obtained, whether or not each layer can be separated was judged as recyclability according to the following criteria.
○: The interlayer strength of the laminated film is 3.0 N/15 mm or less, and the recycling is excellent.
x: The interlaminar strength of the laminated film exceeds 3.0 N/15 mm (including the case where delamination is not possible).

(11) Environmental suitability The environmental suitability of the laminated film obtained was judged according to the following criteria.
◯: A biodegradable resin or a resin made from a plant-derived raw material is contained in layers other than the layer (A) of the laminated film.
Δ: Layers other than the layer (A) of the laminated film do not contain a biodegradable resin or a resin made from a plant-derived raw material.

(12) Comprehensive evaluation Comprehensive evaluation of the laminated film obtained was determined according to the following criteria.
○: The laminated film satisfies the range specified in the present application.
x: The laminated film does not satisfy the range specified in the present application.

Table 1 shows the evaluation results of Examples and Comparative Examples.

The laminated film defined in the present application from the examples has an appropriate interlayer strength, so that it does not peel during actual use, and the layers can be easily peeled off with a tape or the like at the time of disposal, and the separation is excellent. On the other hand, in Comparative Example 1, in which only the polyethylene resin was used for the adhesive layer, the interlayer adhesion was not sufficient, so that the interlayer peeling occurred during stretching, making it difficult to evaluate as a laminated film. Further, in Comparative Examples 2 and 3, since the interlayer strength of the film is strong, the film cannot be peeled off with a tape or the like, and there is a risk of causing a problem in sortability at the time of disposal. In Comparative Examples 2 and 3, peeling did not occur even when pulled at 10 N/15 mm.

The laminated film of the present invention can be suitably used as a food packaging film for perishable foods.

Claims (14)

A laminated film comprising at least three layers in this order: a layer (A) containing a vinyl alcohol resin, a layer (B) containing an ionomer resin, and a layer (C). 2. The laminate film according to claim 1, wherein the layer (A) and the layer (B) have an interlaminar strength of 0.1 N/15 mm to 3.0 N/15 mm measured under an atmosphere of 23° C. at a tensile speed of 300 mm/min. 3. The laminated film according to claim 1, wherein the laminated film is stretched in at least one direction. According to JIS K7126-2 (2006), the oxygen permeability measured in an atmosphere of 20° C.×50% RH is 1.0 cc/m ² ·day·atm or less, according to any one of claims 1 to 3. Laminated film as described. The laminated film according to any one of claims 1 to 4, which has a heat shrinkage rate of 30% or more in the main shrinkage direction when immersed in hot water at 100°C for 10 seconds. The laminated film according to any one of claims 1 to 5, wherein the content of the ionomer resin is 30% by mass or more when the resin composition forming the layer (B) is 100% by mass. The laminated film according to any one of Claims 1 to 6, wherein the layer (B) contains a polyethylene resin. The laminated film according to any one of Claims 1 to 7, wherein the layer (C) contains a polyethylene resin. The laminated film according to claim 7 or 8, wherein the polyethylene-based resin contains a plant-derived polyethylene-based resin. 10. Any one of claims 1 to 9, comprising at least five layers in this order of the layer (C), the layer (B), the layer (A) containing the vinyl alcohol resin, the layer (B), and the layer (C). or the laminated film according to item 1. A laminated film comprising at least three layers in this order: a layer (A) having gas barrier properties, a layer (B) containing an ionomer resin, and a layer (C), wherein the tensile speed of the layers (A) and (B) A laminated film having an interlaminar strength of 0.1 N/15 mm to 3 N/15 mm measured in an atmosphere of 300 mm/min and 23°C. 12. The laminated film according to any one of claims 1 to 11, which is heat-shrinkable. The laminated film according to any one of claims 1 to 12, which is for food packaging. A package comprising the laminated film according to any one of claims 1 to 13 and a food packaging tray.