Laminated films and packaging bags

Abstract

To provide a film that is easy to recycle while having barrier properties, a laminated film and a wrapper.SOLUTION: A film comprises a first resin layer formed from polyethylene (PE) and a second resin layer formed from ethylene-vinyl alcohol copolymer (EVOH), which are made adjacent to each other by co-extrusion, the film being drawn in the same direction.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a film, a laminated film, and a packaging bag. [Background technology]

[0002] Paragraph 0012 of Patent Document 1 and paragraph 0010 of Patent Document 2 describe a laminate film that has traditionally been used for packaging bags, in which a polyolefin resin such as low-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, polypropylene, or the like is laminated as a sealant layer on a substrate such as biaxially oriented polypropylene, biaxially oriented polyamide, or biaxially oriented polyester. It is also suggested that a metal layer, a ceramic layer, an ethylene-vinyl alcohol copolymer (EVOH), or the like may be laminated to enhance the barrier properties of the laminate film. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-265020 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-39932 Summary of the Invention [Problem to be solved by the invention]

[0004] The laminated film used in conventional packaging bags has a layer of heat-adhesive resin (sealant) such as polyethylene (PE) on the inside and a base material such as polyethylene terephthalate (PET), which has higher heat resistance than the sealant, on the outside. When heat-adhesive laminated films are bonded, the sealant is melted to bond the inside of the laminated film. However, packaging bags containing different resins have the problem of being difficult to recycle as plastic containers and packaging.

[0005] In recent years, mono-material containers and packaging made from a single resin have been proposed to facilitate recycling. However, packaging bags made from films using only polyethylene have poor barrier properties, limiting their applications. When EVOH film is laminated as a barrier film, the thickness is at least around 6 μm, reducing recyclability.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a film, a laminated film, and a packaging bag that can achieve both recyclability and barrier properties. [Means for solving the problem]

[0007] To solve the above problems, the present invention provides a film characterized in that a first resin layer formed from polyethylene (PE) and a second resin layer formed from ethylene-vinyl alcohol copolymer (EVOH) are adjacent to each other by coextrusion and stretched in the same direction.

[0008] The first resin layer may be laminated on both sides of the second resin layer. The first resin layer may be laminated on one surface of the second resin layer. The stretching ratio in the same direction may be 2 to 10 times. The second resin layer may have a thickness of 6 μm or less.

[0009] The present invention also provides a laminated film in which a sealant is laminated on a substrate, wherein at least one of the substrate and the sealant contains the film. A biaxially oriented polyethylene resin film may be further laminated on the substrate side of the laminated film relative to the sealant. The film laminated to the laminate film may be only a film having the first resin layer and the second resin layer, or may consist of a film having the first resin layer and the second resin layer and a polyethylene-based resin film, and the weight of the second resin layer may be 10% by weight or less of the entire laminate film. The present invention also provides a packaging bag, at least one member of which is formed from the laminated film. The packaging bag may be a stand-up pouch. [Effects of the Invention]

[0010] According to the present invention, the thickness of the second resin layer containing EVOH can be reduced, so that both recyclability and barrier properties can be achieved. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described below based on preferred embodiments. The film of the embodiment is characterized in that a first resin layer formed from polyethylene (PE) and a second resin layer formed from ethylene-vinyl alcohol copolymer (EVOH) are adjacent to each other by coextrusion and stretched in the same direction.

[0012] The laminate film of the embodiment may use the film of the embodiment as a substrate. In this case, the layers other than the second resin layer may be formed from a polyethylene-based resin layer mainly composed of a polyethylene-based resin. Therefore, the laminate film of the embodiment can be used to realize mono-material container packaging. Specific examples of the polyethylene-based resin layer include the first resin layer and a sealant layer, which will be described later, but are not limited to these.

[0013] The polyethylene resin forming the polyethylene resin layer may be a homopolymer of ethylene or a copolymer mainly composed of ethylene. Examples of monomers (comonomers) other than ethylene include one or more of α-olefins such as 1-butene, 1-hexene, and 1-octene, cyclic olefins such as norbornene, and vinyl monomers such as vinyl acetate, vinyl chloride, and acrylic acid. When a comonomer is used in the polyethylene resin, the comonomer may be one or more of different types.

[0014] The proportion of ethylene in the constituent monomers of the polyethylene resin is preferably 50% by weight or more, and may be, for example, 80 to 100% by weight. The ethylene or comonomer used in the polyethylene resin may be a compound derived from a fossil resource such as petroleum, or may be a compound derived from biomass such as plants. The resin contained in the polyethylene resin layer may be only a polyethylene resin.

[0015] The polyethylene resin layer may contain additives other than the resin. The additives are not particularly limited, but examples thereof include antioxidants, lubricants, antiblocking agents, flame retardants, UV absorbers, light stabilizers, antistatic agents, colorants, crosslinking agents, etc. The additives may be either components that are compatible with the resin or components that are not compatible with the resin.

[0016] The material forming the polyethylene-based resin layer may be one type of polyethylene-based resin or a blend of two or more types of polyethylene-based resin. The polyethylene-based resin layer can be made of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), or high-density polyethylene (HDPE), but HDPE is more preferable for the first resin layer in terms of physical strength and heat resistance. Recycled polyethylene may also be used as the polyethylene-based resin.

[0017] EVOH can be obtained by copolymerizing ethylene with a vinyl ester monomer, saponifying the resulting copolymer, and converting the vinyl ester units to vinyl alcohol units. Examples of vinyl ester monomers include vinyl carboxylates such as vinyl formate, vinyl acetate, vinyl butyrate, and vinyl benzoate. EVOH has improved barrier properties as the proportion of vinyl alcohol units increases, but its moisture resistance decreases, so it is preferable for it to have an appropriate ethylene content. The ethylene content of EVOH can be, for example, 20 to 60 mol%. The degree of saponification of EVOH is not limited to 100 mol%, but is preferably, for example, 80 mol% or higher.

[0018] In the film of the embodiment, a first resin layer (PE layer) and a second resin layer (EVOH layer) adjacent to each other are laminated by coextrusion and stretched in the same direction. This allows the thickness of the EVOH layer to be thin. Because the first resin layer (PE layer) and the second resin layer (EVOH layer) are integrated by coextrusion, a structure in which different resin layers are directly adjacent to each other is obtained without an adhesive layer or the like between the layers, resulting in excellent adhesion between the layers. In the following description, the film of the embodiment having the first resin layer and the second resin layer may be referred to as an "EVOH coextrusion stretched film."

[0019] The stretching direction of the EVOH coextrusion stretched film is not particularly limited, and may be either the machine direction (MD) or the transverse direction (TD). Biaxial stretching in the MD and TD directions is also possible. The stretching ratio is preferably 2 to 10 times, and more preferably 3 to 6 times. Since the first resin layer and the second resin layer are stretched after being laminated by coextrusion, the stretching direction and stretching ratio of the first resin layer and the second resin layer are the same. In the case of biaxial stretching, the stretching ratios in each stretching direction may be the same, or the stretching ratios in the MD and TD may be different. The stretching direction in uniaxial or biaxial stretching may be an oblique direction intersecting the MD and TD directions. In the case of uniaxial stretching, stretching in the MD direction is preferred in consideration of processability and printability.

[0020] The first resin layer may contain PE in a proportion of 50% by weight or more, or even 80 to 100% by weight. The second resin layer may contain EVOH in a proportion of 50% by weight or more, or even 80 to 100% by weight. The EVOH co-extruded stretched film may be a resin film consisting of only a PE layer and an EVOH layer. As described below, a layer such as a sealant layer may be laminated on the EVOH co-extruded stretched film.

[0021] The EVOH coextruded stretched film may have one first resin layer and one second resin layer. The EVOH coextruded stretched film may have two or more first resin layers and two or more second resin layers. The first resin layer may be laminated on both sides of the second resin layer, such as a film having three layers of "first resin layer / second resin layer / first resin layer." The first resin layer may be laminated on one side of the second resin layer, such as a film having two layers of "first resin layer / second resin layer." The second resin layer may be laminated on both sides of the first resin layer, such as a film having three layers of "second resin layer / first resin layer / second resin layer."

[0022] The thickness of the EVOH coextruded stretched film is not particularly limited, but may be, for example, about 10 to 200 μm. From the viewpoint of recyclability, the thinner the thickness of the second resin layer (EVOH layer), the better, and it may be 10 μm or less, further 6 μm or less, and more preferably 4 μm or less. From the viewpoint of barrier properties, the thickness of the second resin layer may be 1 μm or more, further 2 μm or more.

[0023] The EVOH coextruded stretched film can be used as at least one of the substrate and sealant of a laminated film. Both the substrate and the sealant may be EVOH coextruded stretched films. The substrate or the sealant may be a polyethylene resin film formed from a polyethylene resin.

[0024] The EVOH coextruded stretched film substrate may have a three-layer structure such as "first resin layer / second resin layer / first resin layer" or a two-layer structure such as "first resin layer / second resin layer." The substrate may be bonded to the sealant on the first resin layer side. The substrate may be bonded to the sealant on the second resin layer side. When the outer surface of the substrate is the second resin layer, the heat resistance of the substrate is improved, and workability in heat sealing of the laminated film, bag making, etc. can be expected to be improved. When the outer surface of the substrate is the first resin layer, the second resin layer is protected by the first resin layer, making it easier to maintain barrier properties.

[0025] The substrate is laminated on the outer side of the sealant in the thickness direction of the laminate film. The substrate preferably reinforces the mechanical strength of the laminate film when the laminate film is transported in the lengthwise direction for use. The thickness of the substrate is not particularly limited, but may be, for example, about 10 to 50 μm. Conventional laminate films use a PET film or the like as the substrate, but in the laminate film of the embodiment, the first resin layer is formed from a polyethylene-based resin, thereby improving recyclability. Furthermore, the second resin layer contains EVOH, thereby providing excellent barrier properties.

[0026] The sealant can be used to bond laminated films. The EVOH co-extruded stretched film of the sealant may have a three-layer structure such as "first resin layer / second resin layer / first resin layer" or a two-layer structure such as "first resin layer / second resin layer." It is preferable that the inner surface of the sealant is the first resin layer in terms of sealing properties, etc.

[0027] When the sealant is a polyethylene-based resin, examples include polyethylene-based resins with relatively low density, such as linear low-density polyethylene (LLDPE) and low-density polyethylene (LDPE), or unstretched polyethylene-based resins. The thickness of the sealant is not particularly limited, but may be, for example, about 50 to 180 μm. The sealant may be a single-layer sealant film (sealant layer) or a multi-layer sealant film. A multi-layer sealant film can be formed by laminating two or more layers of film-like sealant resins using methods such as coextrusion, extrusion lamination, sandwich lamination, and thermal lamination.

[0028] The substrate and the sealant may be bonded via an adhesive layer by dry lamination or the like. When laminating an EVOH co-extruded stretched film and a polyethylene-based resin layer, extrusion lamination, thermal lamination, or the like may be used without an adhesive layer. When extrusion lamination, thermal lamination, or the like is performed, an adhesive layer may be provided on the EVOH co-extruded stretched film side, or at least one of the EVOH co-extruded stretched film and the polyethylene-based resin layer may be subjected to a surface treatment such as ozone treatment, plasma treatment, corona treatment, discharge treatment, or flame treatment.

[0029] The adhesive layer may be formed from an adhesive or an anchor coating agent. Materials for forming the adhesive layer are not particularly limited, but include urethane compounds, epoxy compounds, isocyanate compounds, polyethyleneimine, and organic titanium compounds such as titanium alkoxide. Examples of the thickness of the adhesive layer include approximately 0.1 to 10 μm, approximately 1 to 6 μm, and approximately 3 to 4 μm. The adhesive layer may contain a resin, or may be a resin-free adhesive layer.

[0030] In the laminate film of the embodiment, the film laminated on the laminate film may be only an EVOH coextruded stretched film. When the films laminated on the laminate film are an EVOH coextruded stretched film and another film, the other film may be a polyethylene-based resin film. The weight of the second resin layer is preferably 10% by weight or less, more preferably 5% by weight or less, of the entire laminate film. In this case, a container packaging that is close to a mono-material can be realized using a minimum amount of EVOH.

[0031] One or more layers of polyethylene-based resin film and one or more layers of EVOH co-extruded stretched film may be laminated on the outer side of the sealant in the thickness direction of the laminate film. For example, the laminate may be formed as sealant film / EVOH co-extruded stretched film / polyethylene-based resin film. The laminate may be formed as sealant film / polyethylene-based resin film / EVOH co-extruded stretched film. These films may be bonded together via an adhesive layer. The polyethylene-based resin film laminated on the outer side of the sealant may be a stretched film such as uniaxially stretched or biaxially stretched. If a biaxially stretched polyethylene-based resin film or an extruded polyethylene layer is further laminated on the substrate side of the sealant of the laminate film, it becomes easier to obtain strength sufficient for use as a bottom film for a stand-up pouch.

[0032] When two or more layers of EVOH coextrusion stretched film are laminated to the laminate film, the barrier properties can be improved by the second resin layer. In the case of a laminate film that combines an EVOH coextrusion stretched film with a polyethylene-based resin film, the proportion of polyethylene contained in the laminate film can be increased to improve recyclability. A polyethylene-based resin layer may be laminated on one or both sides of the EVOH coextrusion stretched film.

[0033] The laminated film may be laminated with a printed film made of a polyethylene resin film having a printed layer. The printed film may also serve as the substrate. The printed film may be laminated between the substrate and the sealant. The printed layer may be formed on the inner surface of the printed film or on the outer surface of the printed film. Laminating the printed layer on the inner surface of the printed film is preferable because the printed layer is protected by the printed film.

[0034] The printed layer can be formed by printing ink in a solid or patterned manner using a printing method such as gravure printing, letterpress printing, offset printing, screen printing, or inkjet printing. The thickness of the printed layer is not particularly limited, but may be about 0.5 to 10 μm. The printed layer may be formed on the entire surface of the laminated film, or may be formed on a portion of the surface of the laminated film. Two or more printed layers may be superimposed. The printed layer may be omitted.

[0035] The ink for forming the printing layer may contain a colorant such as a pigment or dye, and a binder. Examples of binders include, but are not limited to, polyamide, polyurethane, polyester, polyvinyl chloride, polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, acrylic polymer, polybutadiene, and cyclized rubber. The ink may contain a solvent such as water, an organic solvent, or vegetable oil. After printing, the ink can be dried by volatilizing the solvent or hardening the ink. Heating, ultraviolet irradiation, or the like may be performed to accelerate the drying of the ink. The printing layer may contain a resin, or may not contain a resin.

[0036] The laminate film may have laminated thereon layers of different materials other than the resin layer, such as adhesive layers, printed layers, vapor-deposited layers, and coated layers. Examples of different materials include metals such as aluminum, and inorganic compounds such as silica and alumina. The printed layer, coated layer, adhesive layer, and the like may contain resins other than polyethylene as materials for ink, paint, adhesive, and the like. The method for forming the laminate film is not particularly limited, and examples include dry lamination, extrusion lamination, thermal lamination, co-extrusion, and coating. Different methods may be used to laminate each layer.

[0037] The laminated film of the embodiment can be used to produce a packaging bag. At least one component of the packaging bag may be formed from the laminated film of the embodiment. The packaging bag may have a body member and a bottom member. For example, the bottom member may be folded in half along a fold line at the bottom of the packaging bag and joined between the pair of body members. To make it easier to open the packaging bag, a slit such as a notch may be formed around the periphery of the opening portion. Forming a slit in the seal portion where the inner surface of the laminated film is joined can ensure the hermeticity of the packaging bag.

[0038] The dimensions of the packaging bag are not particularly limited, but for example, in the case of use as a refill container, the height in the vertical direction is about 100 to 500 mm, the width in the horizontal direction is about 70 to 300 mm, and the filling amount is 100 cm 3 ~5000cm 3 The state of the contents may be fluid, such as liquid, powder, or granules. The type of contents is not particularly limited, but may include detergents, medicines, cosmetics, pharmaceuticals, beverages, seasonings, inks, paints, fuels, etc.

[0039] The packaging bag may have a filling opening, a pouring opening, etc. For example, an opening may be formed at the top of the packaging bag between the front and rear body members, which can be used to fill or pour out the contents. After filling the contents, the body members may be joined together to seal the packaging bag. When opening the packaging bag, the laminated film has good hand tearability, so the joined portion between the body members can be easily torn. The pouring opening may be formed in a thin protruding shape at the top or corner of the packaging bag.

[0040] While the present invention has been described above based on preferred embodiments, the present invention is not limited to the above-described embodiments and various modifications can be made without departing from the spirit of the present invention. Modifications include addition, substitution, omission, and other changes of components.

[0041] The laminate film of the embodiment is mainly made of a polyethylene-based resin and can be used for a variety of applications, including but not limited to packaging bags such as pouches, bags, and containers, and packaging laminate films. When the laminate film is flexible, it can be used to form a flexible packaging bag. The packaging bag may be formed from the laminate film alone, or may be combined with accessories such as labels, tags, straws, and outer boxes. From the viewpoint of recycling, it is preferable that the accessories can be separated from the packaging bag. [Example]

[0042] The present invention will be explained in more detail below using examples, but it should be understood that the present invention is not limited to these examples.

[0043] (Laminated film of Example 1) The EVOH co-extruded stretched film of the embodiment was used as a substrate, and a printed layer was optionally formed on the inner surface of the substrate.The EVOH co-extruded stretched film of the embodiment was used as a sealant, and the substrate and the sealant were laminated via an adhesive layer by dry lamination to produce a laminated film of Example 1.

[0044] (Laminated film of Example 2) The EVOH co-extruded stretched film of the embodiment was used as a substrate, and a printed layer was optionally formed on the inner surface of the substrate. A PE resin film such as LLDPE was used as a sealant film, and the substrate and sealant were laminated via an adhesive layer by dry lamination to produce a laminated film of Example 2.

[0045] (Laminated film of Example 3) The EVOH co-extruded stretched film of the embodiment was used as a substrate, and a printed layer was optionally formed on the inner surface of the substrate. A PE-based resin film such as LLDPE was used as a sealant film, and a biaxially stretched film made of a PE-based resin such as HDPE was placed between the substrate and the sealant film. The films were then laminated together via an adhesive by dry lamination to produce the laminated film of Example 3.

[0046] (Laminated film of Comparative Example 1) A stretched polyethylene (PE) resin film was used as the substrate, and a printed layer was formed on the inner surface of the substrate. A PE resin film such as LLDPE was used as the sealant, and the substrate and the sealant were laminated via an adhesive layer by dry lamination to produce the laminated film of Comparative Example 1.

[0047] (Laminated film of Comparative Example 2) A polyester resin film such as oriented PET was used as the substrate, and a barrier layer of aluminum, EVOH, etc. was formed on the inner surface of the substrate. A PE resin film such as LLDPE was used as the sealant film, and the substrate and sealant were laminated via an adhesive layer by dry lamination to produce the laminate film of Comparative Example 2.

[0048] The laminate film of Comparative Example 1 has good recyclability but poor barrier properties. The laminate film of Comparative Example 2 is not easy to recycle because different types of resins (PE and polyester) are laminated together. The laminate films of Examples 1 and 2 can achieve both recyclability and barrier properties by laminating the EVOH layer with the PE layer by coextrusion. Furthermore, the laminate film of Example 3 can improve strength properties.

[0049] When constructing a standing pouch, the laminated film of Example 1 or Example 2 can be used as a body film, and the laminated film of Example 3 can be used as a bottom film of the standing pouch. In the above configuration, the bottom film is not limited to the laminated film of Example 3, and may be made of a film having barrier properties.

Claims

1. A laminated film in which a sealant is laminated on a substrate, the substrate is a film in which a first resin layer formed from polyethylene (PE) and a second resin layer formed from ethylene-vinyl alcohol copolymer (EVOH) are adjacent to each other by coextrusion, the film is stretched in the same direction, and the thickness of the second resin layer is 6 μm or less; A laminate film characterized in that the film laminated on the laminate film is only a film having the first resin layer and the second resin layer, or is composed of a film having the first resin layer and the second resin layer and a polyethylene-based resin film, and the weight of the second resin layer is 10% by weight or less of the entire laminate film.

2. A laminated film as described in Claim 1, characterized in that in a film having the first resin layer and the second resin layer, the first resin layer is laminated on both sides of the second resin layer.

3. A laminated film as described in Claim 1, characterized in that in a film having the first resin layer and the second resin layer, the first resin layer is laminated on one side of the second resin layer.

4. A laminated film described in any one of claims 1 to 3, characterized in that in a film having the first resin layer and the second resin layer, the stretching ratio in the same direction is 2 to 10 times.

5. The laminated film according to any one of claims 1 to 4, further comprising a biaxially oriented polyethylene resin film laminated on the substrate side of the laminated film relative to the sealant.

6. A packaging bag, wherein at least one member is formed from the laminated film according to any one of claims 1 to 5.

7. 7. The packaging bag according to claim 6, wherein the packaging bag is a stand-up pouch.