Easily openable composite film

Abstract

To provide an easily openable composite film which has stable seal strength and high sealability, causes no knocking occurrence when opened, and causes no problem such as film remaining and film cleavage.SOLUTION: A composite film is formed by laminating a sealant layer, an adjacent layer, and an outer layer in this order. The sealant layer is composed of a composition comprising an antiblocking agent and a glycol-modified polyethylene terephthalate (PET-G). An amount of the antiblocking agent in the composition has a ratio of 10,000-50,000 mass ppm. The adjacent layer is composed of at least one modified polyolefin resin selected from an acid-modified polyethylene, an ethylene-methyl acrylate copolymer (EMA), or an ethylene-acrylic acid-maleic acid anhydride three component copolymer. The composite film exhibits an easily openable property due to sealing of the sealant layer to an adherend and releasing of the adjacent layer from the sealant layer.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an easy-open composite film having excellent sealing properties and easy-open properties. [Background technology]

[0002] In order to protect the contents, it is important for the package to have a high level of sealing ability so that it can be easily opened and withstand external forces such as those caused by the sterilization process during food production, vibrations during transportation, and handling of the goods, and it is usually sealed by heat sealing. As a packaging material that enables such high heat sealing at low temperatures, JP 2017-178398 A (Patent Document 1) proposes a laminate of an oriented polyester film and an unoriented nylon 6 film having a predetermined crystallinity.

[0003] Along with such heat sealability, "easy-openability" that means that the package can be easily opened when in use is often required.

[0004] Various types of easy-to-open packaging have been proposed, and one of them, known as easy-peel packaging, uses a sealant film that is easy to open. It is widely used for a variety of applications, including as lids for cup containers for dessert foods such as jelly, yogurt, and pudding, and for rice, as well as inner lids for tube containers for wasabi, ginger, and mustard, and as packs for processed meat products such as ham and bacon, and the balance between sealability and ease of opening is important.

[0005] Therefore, from the viewpoints of heat sealing properties to plastics and preventing contamination of the contents, these composite films are required to not only be easy to open but also to have easy-open properties that prevent stringiness, residual fibers, fuzziness, etc.

[0006] The present applicant also proposed in JP 2012-116061 A (Patent Document 2) an easy-open film for medical packaging that eliminates stringiness when peeled off. Furthermore, Japanese Patent Application Laid-Open No. 2019-991 (Patent Document 3) proposes an easy-to-open composite film made of a composite material of a polyethylene material and a polybutene material, which has sealability and easy-to-open properties. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-178398 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-116061 [Patent Document 3] Japanese Patent Application Publication No. 2019-991 Summary of the Invention [Problem to be solved by the invention]

[0008] When used as a lid material for containers and a top material for deep-draw packaging, an easy-to-open composite film that combines airtightness and easy opening is desirable. Furthermore, it is desirable that the film does not require excessive strength to open, has stable sealing strength that does not peel with a small force, and leaves little film residue when peeled. However, such a film for packaging has not been available until now.

[0009] When opening the package, knocking peeling (also known as pulse peeling) occurs, which makes the peeling feel worse and can cause problems such as tearing of the top material film. Here, knocking peeling refers to the state in which a peeling sound (a tingling, pulsed peeling sound) occurs when peeling, and refers to the state in which stress is felt when peeling. Therefore, an object of the present invention is to provide an easy-to-open composite film that has sealability and easy-to-open properties, leaves no film residue when opened, and can eliminate problems such as knocking and film tearing. [Means for solving the problem]

[0010] In order to solve the above problems, the present invention is characterized by the following configuration. [1] A composite film comprising a sealant layer, an adjacent layer, and an outer layer laminated in this order; the sealant layer is made of a composition containing an antiblocking agent and glycol-modified polyethylene terephthalate (PET-G), and the amount of the antiblocking agent in the composition is in a ratio of 10,000 to 50,000 ppm by mass; the adjacent layer is made of at least one modified polyolefin resin selected from acid-modified polyethylene, ethylene-methyl acrylate copolymer (EMA), and ethylene-acrylic acid-maleic anhydride ternary copolymer; A composite film that seals an adherend with a sealant layer and exhibits easy-open properties by peeling the sealant layer from an adjacent layer.

[0011] [2] The easy-open composite film of [1], wherein the thickness of the sealant layer is 10 μm or less and the total thickness is in the range of 30 to 80 μm. [3] An easy-to-open composite film according to [1] or [2], wherein the outer layer is made of polyamide resin. [Effects of the Invention]

[0012] According to the present invention, an easy-to-open composite film can be provided that has stable seal strength, does not cause knocking when opened, and leaves little film residue. This film is less likely to tear than conventional films. When this film is combined with a bottom material as a top material, it can be widely used as a package or container for food, etc. DETAILED DESCRIPTION OF THE INVENTION

[0013] The easy-open composite film of the present invention is a composite film formed by laminating a sealant layer, an adjacent layer, and an outer layer in this order.

[0014] Sealant layer The sealant layer is made of a composition containing an antiblocking agent and glycol-modified polyethylene terephthalate (PET-G).

[0015] PET-G is a polymer in which part of the ethylene glycol component of PET resin has been replaced with cyclohexanedimethanol. The amount of cyclohexanedimethanol is appropriately selected depending on the purpose, but is typically 20 to 50 mol %, preferably 25 to 45 mol %, and more preferably 30 to 40 mol %, when the total with ethylene glycol is taken as 100 mol %. PET-G is a completely vitrified resin that does not crystallize even during molding and processing, making it an amorphous resin.

[0016] In the present invention, a composition containing an antiblocking agent is used together with the PET-G. The content of the antiblocking agent in the resin composition is desirably 10,000 to 50,000 ppm by mass, preferably 30,000 to 40,000 ppm by mass, from the viewpoint of contributing to the antiblocking effect and ensuring the seal strength.

[0017] Examples of antiblocking agents include aluminosilicate, talc, diatomaceous earth, zeolite, mica, clay, crosslinked silicone particles, crosslinked polyamide particles, crosslinked polyacrylic particles, and crosslinked polystyrene particles. These may be used alone or in combination of two or more. Amorphous aluminosilicates obtained by chemically modifying synthetic zeolites can be used as such antiblocking agents, such as the Shilton JC series manufactured by Mizusawa Industrial Chemicals. Furthermore, examples of antiblocking agents made of organic fine particles include fine particles containing a crosslinking agent made of, for example, polystyrene, polyethylene, polyamide, polyester, polyacrylate, polymethacrylate, epoxy resin, polyvinyl acetate, polyvinyl chloride, or the like, alone or as copolymers thereof.

[0018] The particle size of the antiblocking agent is not particularly limited, but for example, an antiblocking agent having an average particle size (measured with a Coulter counter) in the range of 1 to 10 μm, preferably 2 to 7 μm, is used. Note that even if the particle size of the antiblocking agent is larger than the film thickness of the sealant layer, this does not pose any problems in use as long as it is configured to be peeled off from the adjacent layer described below.

[0019] Adjacent layers The adjacent layer is made of at least one modified polyolefin resin selected from the group consisting of acid-modified polyethylene, ethylene-methyl acrylate copolymer (EMA), and ethylene-acrylic acid-maleic anhydride ternary copolymer. The acid-modified polyethylene may be a modified polyethylene resin obtained by copolymerizing or graft-polymerizing at least one monomer selected from the group consisting of unsaturated carboxylic acids (such as maleic anhydride) and derivatives thereof. Commercially available ethylene-methyl acrylate copolymers (EMA) or ethylene-acrylic acid-maleic anhydride ternary copolymers can be used. The quantitative relationship between ethylene and functional group-containing monomers in modified polyethylene resins is such that the content of functional group-containing monomers relative to the total resin is preferably in the range of 10% to 30% by weight, and more preferably 12.5% ​​to 27.5% by weight. Examples include the ET series of ethylene-acrylic acid-maleic anhydride ternary copolymers and the EMA series of ethylene-methyl acrylate copolymers, both of which are available under the "Rexpearl" brand manufactured by Japan Polyethylene Corporation. Among these, ethylene-acrylic acid-maleic anhydride ternary copolymers are preferred in the present invention.

[0020] In the present invention, the sealant layer is sealed to the adherend, thereby making it possible to peel the sealant layer from the adjacent layer.

[0021] ·Outer layer The outer layer is not particularly limited, but is preferably made of polyamide, etc. Examples of polyamide include nylon 6, nylon 66, nylon 610, nylon 6 / 66 copolymer, polymetaxylene adipamide, etc.

[0022] Other layers In the present invention, layers other than the sealant layer, adjacent layer, and outer layer (other layers) may be provided as appropriate. For example, a layer of polyethylene resin or the like may be provided as an additional layer between the adjacent layer and the outer layer. Polyethylene resins include not only ethylene homopolymers but also copolymers of ethylene and 1-olefins having propylene or more (3 or more carbon atoms). Generally, polyethylene resins contain about 15 mol% or less of comonomer. Furthermore, a layer made of an adhesive resin may be provided to bond the various layers together. The adhesive resin is not particularly limited, but known resins may be used. For example, a modified polyolefin resin obtained by graft polymerization of at least one monomer selected from the group consisting of unsaturated carboxylic acids (e.g., maleic anhydride) and their derivatives is preferred.

[0023] ·Outermost layer An outermost layer may be further provided on the outer surface of the outer layer. The outermost layer is not particularly limited, but is preferably formed from a substrate resin such as a polyamide resin or polyester resin. The substrate resin may be used alone or in combination with two or more. When two or more substrate resins are used in combination, they may be mixed to form a single mixed resin substrate layer, or a resin substrate layer having two or more resin layers may be formed. Furthermore, a vapor-deposited film of an inorganic material such as aluminum, aluminum oxide, silicon oxide, indium oxide, tin oxide, or zirconium oxide may be formed, or a metal layer such as aluminum, iron, copper, or tin may be provided. The substrate may be appropriately selected depending on the purpose, such as to maintain the film shape, to be printed on the surface, to prevent films from sticking together, to reduce the coefficient of friction of the film to make it slippery, or to shield the contents from view.

[0024] Furthermore, the easy-open composite film of the present invention may contain various additives such as antioxidants, ultraviolet absorbers, light stabilizers, flame retardants, fillers, and colorants in any of its layers, as needed.

[0025] Layer composition In the easy-open composite film of the present invention, the thickness of the sealant layer is 10 μm or less, preferably in the range of 4 to 7 μm. The overall thickness of the composite film is in the range of 30 to 80 μm, preferably in the range of 40 to 60 μm.

[0026] With such a thickness, a composite film can be obtained that has good sealing properties and is easy to open, leaves no film residue when opened, and eliminates problems such as knocking and film tearing. If the film is too thin, it will be difficult to use because of its low strength and prone to film tearing, while if it is too thick, it will be difficult to bond to the corresponding bottom material and easy to open when contents are placed inside.

[0027] The thickness of the adjacent layer is appropriately selected taking into consideration the overall thickness and the thickness of the sealant layer, but is generally in the range of 1 to 30 μm, preferably in the range of 2 to 15 μm. The thickness of the outer layer is also appropriately selected taking into consideration the overall thickness and the thickness of the sealant layer, but is preferably in the range of 10 to 30 μm, and more preferably in the range of 15 to 20 μm. The thickness of the other layers is appropriately selected taking into consideration the overall thickness and the thickness of the sealant layer. The thickness of the outermost layer is appropriately selected depending on the purpose, and the thickness of the outermost layer is not included in the total thickness.

[0028] The easy-open composite film of the present invention can be produced by conventional methods such as the T-die method, water-cooled or air-cooled inflation method, etc. In the present invention, the co-extrusion water-cooled inflation method is particularly preferred from the viewpoint of ease of production control, etc. To meet needs such as printing, the outermost layer can also be laminated with a film such as OPET by lamination or pressure bonding.

[0029] Such an easy-open composite film of the present invention can be used as a variety of packaging materials. For example, the easy-open composite film can be used as a top material, and can be combined with a known bottom material to seal the edges to form a packaging material. The bottom material may have a deep-drawn recess depending on the contents to be filled.

[0030] The package is opened by peeling away the sealant layer from the easily peelable composite film at the joint. Because the sealant layer of the easily peelable composite film contains a specific antiblocking agent, the sealant layer peels away at the joint, making it possible to open the package. Furthermore, no film remains when the package is opened, and knocking and film tearing are also reduced. [Example]

[0031] The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0032] The materials shown in Table 1 were prepared as materials for forming the composite film. Polyamide: 6 nylon UBE NYLON (UBE Corporation) Polyethylene (PE): LLDPE Evolue (Prime Polymer Co., Ltd.) Adhesive resin: Maleic anhydride modified polyolefin resin Modic (Mitsubishi Chemical Corporation) Ethylene-methyl acrylate copolymer (EMA) resin: Ethylene-methyl acrylate-maleic anhydride copolymer Rexpearl (Japan Polyethylene Co., Ltd.) Modified polyethylene: Maleic anhydride modified polyolefin resin Admer (Mitsui Chemicals (KK)) PET-G: Glycol-modified polyethylene terephthalate ESTER (Eastman Chemical Company) Antiblocking agent: Synthetic zeolite Shilton (Mizusawa Industrial Chemicals, Ltd.) Biaxially oriented polyethylene terephthalate film (OPET; average thickness 12 μm) Biaxially oriented nylon film (ONY; average film thickness 15 μm)

[0033] The thickness of the composite film was measured at five points on one piece of film (F1) using a dial gauge (PEACOCK UP RIGHT DIAL GUAGE, Ozaki Seisakusho Co., Ltd.) according to a method conforming to JIS C2151. The average of the measurement results was used as the thickness of the entire film, and the thickness of each layer was calculated from the ratio of each material. Synthetic zeolite was used as the antiblocking agent, and was mixed with PET-G or polyethylene to obtain the content shown in Table 1. The adhesive used was a polyether adhesive.

[0034] [Examples 1-5, Comparative Examples 1-2] Each material was laminated by a coextrusion water-cooled inflation method to produce a composite film having the thickness and layer structure shown in Table 1. An OPET film was laminated as a substrate on the outermost layer of the composite film.

[0035] Comparative Example 3 A laminate consisting of a layer made of EMA resin and a polyethylene layer containing an antiblocking agent was laminated with an ONY film by adhering the polyethylene layer and the ONY film with an adhesive (a polyether adhesive), and an OPET film was further laminated on the surface of the ONY film to which the polyethylene layer was not adhered, to produce a composite film.

[0036] evaluation (1) Peel strength The composite films obtained in the examples and comparative examples were placed on an amorphous polyethylene terephthalate (A-PET) sheet (200 μm: manufactured by Sanbo Kasei) with the sealant layer of the composite film facing the A-PET sheet, and heat-sealed for 2 seconds at 140°C and 300 kPa using a seal tester ("Heat Seal Tester" manufactured by Tester Sangyo Co., Ltd.). A test piece (50 mm × 15 mm) for measuring seal strength was cut out from the obtained laminated film. A 180°C peel test was carried out on the sealed portion of this test piece using a Tensilon tensile tester ("Autograph" manufactured by Shimadzu Corporation) at a tensile speed of 300 mm / min.

[0037] (2) Remaining film A PET cup (200 μm) was used as the bottom material, and the sealant layer of the composite film obtained in the examples and comparative examples was joined to the bottom material at 160°C for 1 second at 200 kPa to seal it. After that, when the package was opened, the remaining film was visually observed and evaluated as follows. 〇: No film remains ×: Film remains

[0038] (3) Knocking A PET cup (200 μm) was used as the bottom material, and the sealant layer of the composite film obtained in the examples and comparative examples was joined and sealed at 160°C for 1 second at 200 kPa. After that, an evaluator listened to the sound generated when the package was opened and evaluated whether or not knocking occurred based on the following criteria. 〇: No knocking occurs ×: Knocking occurs

[0039] (4) Film tear A PET cup (200 μm) was used as the bottom material, and the sealant layer of the composite film obtained in the Examples and Comparative Examples was joined and sealed at 160°C for 1 second at 200 kPa. After that, the composite film was visually inspected for tears when opened, and the following evaluations were performed. 〇: No cracks ×: There is a crack The results are also shown in Table 1.

[0040] [Table 1] *Comparative Example 3 contains an antiblocking agent in the PE of the adjacent layer. Other examples and comparative examples use a sealant layer of PET-G.

[0041] The composite films of the examples of the present invention had a peel strength that was neither too high nor too low, and therefore had stable seal strength and high sealing performance, and did not cause knocking, film residue, or film tearing when opened. In contrast, the composite films of the comparative examples caused film residue and caused knocking and film tearing when opened.

Claims

1. a composite film comprising a sealant layer, an adjacent layer, and an outer layer laminated in this order; the sealant layer is made of a composition containing an antiblocking agent and glycol-modified polyethylene terephthalate (PET-G), and the amount of the antiblocking agent in the composition is in a ratio of 10,000 to 50,000 ppm by mass; the adjacent layer is made of at least one modified polyolefin resin selected from acid-modified polyethylene, ethylene-methyl acrylate copolymer (EMA), and ethylene-acrylic acid-maleic anhydride ternary copolymer; A composite film that seals an adherend with a sealant layer and exhibits easy-open properties by peeling the sealant layer from an adjacent layer.

2. 2. The easy-open composite film according to claim 1, wherein the thickness of the sealant layer is 10 μm or less and the total thickness is in the range of 30 to 80 μm.

3. 3. The easy-open composite film according to claim 1, wherein the outer layer is made of a polyamide resin.

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