Deep drawing package

Abstract

To provide a deep drawing package that exhibits stable peel strength when sealed within a temperature range of 120 to 160°C, even if a thermal history is applied to a bottom material during deep drawing molding.SOLUTION: A deep drawing package includes a top material and a bottom material. The top material is a composite film in which a sealant layer, an adjacent layer, and an outer layer are laminated in this order. The sealant layer is made of a composition containing glycol-modified polyethylene terephthalate (PET-G). The adjacent layer is made of a modified polyolefin resin containing at least one of acid-modified polyethylene, ethylene-acrylic ester copolymer, and ethylene-acrylic ester copolymer-maleic anhydride copolymer. The bottom material has a recessed part formed by deep drawing and includes PET-G in a layer facing the top material. The deep drawing package is sealed such that the sealant layer faces the bottom material, and the package has easy-to-open properties.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a deep-draw packaging body that has excellent sealing properties and easy-open properties, and has high sealing stability. [Background technology]

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

[0003] Along with such sealing properties, "easy opening" is often required, meaning that the container can be easily opened when in use.

[0004] Various easy-to-open packages have been proposed, and among them, packages called easy-peel use a sealant film that provides opening properties and are used for packaging various foods. For example, JP 2019-991 A (Patent Document 2) proposes an easy-to-open composite film made of a composite material of polyethylene and polybutene, which has sealing properties and easy opening properties. Deep-draw packaging using such easy-open composite films as the top material is widely used. Deep-draw packaging is a packaging form in which a recess corresponding to the content is made in the bottom material by vacuum forming, the content is placed in the recess, and then the top material is sealed from above and the edges are cut. In this packaging form, a polyester sheet or the like is used as the bottom material. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-178398 [Patent Document 2] Japanese Patent Application Publication No. 2019-991 Summary of the Invention [Problem to be solved by the invention]

[0006] Bottom materials for deep-draw packaging often undergo heat history during deep-draw molding, bonding to the top material, etc. When a polyester sheet is used for such bottom materials, the heat history can sometimes cause unstable peel strength between the bottom material and the top material. The present inventors considered that this was due to crystallization occurring on the surface of the bottom material due to thermal history, which reduced the sealing performance. Therefore, there has been a demand for the development of a package that combines a top material and a bottom material that have stable peel strength even when subjected to heat history. [Means for solving the problem]

[0007] The present inventors have conducted extensive research to solve the above problems and have discovered that a package that overcomes all of the above problems can be obtained by combining a predetermined top material and bottom material, thereby completing the present invention. 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 glycol-modified polyethylene terephthalate (PET-G); a top material in which the adjacent layer is a composite film made of a modified polyolefin resin containing at least one of acid-modified polyethylene, ethylene-acrylic acid ester copolymer, and ethylene-acrylic acid ester copolymer-maleic anhydride copolymer; It consists of a bottom material, the bottom material has a recess formed by deep drawing, and a layer facing the top material contains glycol-modified polyethylene terephthalate (PET-G); The deep-drawn package is sealed so that the sealant layer and the bottom material face each other and has easy-to-open properties. [2] The deep-draw packaging of [1], wherein the sealant layer of the top material further contains an antiblocking agent, and the amount of the antiblocking agent in the composition containing glycol-modified polyethylene terephthalate (PET-G) and the antiblocking agent is in a ratio of 10,000 to 50,000 mass ppm. [3] A deep-draw packaging body according to [1], wherein the thickness of the sealant layer of the top material is 10 μm or less, and the thickness of the entire composite film of the top material is in the range of 30 to 80 μm. [4] A deep-drawn package according to [1], in which the peripheral edge of the bottom material and the top material in contact with said peripheral edge are sealed, has stable peel strength when sealed at a temperature between 120°C and 160°C, even when the bottom material is subjected to a heat history during deep-draw molding. [Effects of the Invention]

[0008] According to the present invention, a deep-draw package can be provided in which deterioration of sealing properties due to the thermal history of the bottom material is suppressed and the sealing strength is stable even at low temperatures or when sealed for a short time. [Brief explanation of the drawings]

[0009] [Figure 1] A schematic diagram of the deep-draw packaging process is shown below. DETAILED DESCRIPTION OF THE INVENTION

[0010] The deep-draw packaging body of the present invention is composed of an easy-open composite film as a top material and a bottom material, with the sealant layer of the composite film being configured to face each other as the bottom material. [Packaging] Easy-to-open composite film The easy-open composite film that is the top material is a composite film in which a sealant layer, an adjacent layer, and an outer layer are laminated in this order.

[0011] Sealant layer The sealant layer is made of a composition including glycol-modified polyethylene terephthalate (PET-G).

[0012] 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.

[0013] In the present invention, a composition containing an antiblocking agent together with the PET-G is preferred for the purpose of peeling the layer from the adjacent layer described below. 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 viewpoints of contributing to the antiblocking effect and ensuring the seal strength.

[0014] 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.

[0015] 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.

[0016] Adjacent layers The adjacent layer is made of at least one modified polyolefin resin selected from acid-modified polyethylene, ethylene-acrylic acid ester copolymer, and ethylene-acrylic acid ester copolymer-maleic anhydride 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. The quantitative relationship between ethylene and functional group-containing monomer in the modified polyolefin resin is such that the content of functional group-containing monomer is preferably in the range of 10% to 30% by weight, more preferably 12.5% ​​to 27.5% by weight, relative to the total weight of the resin. 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 "Rexpearl" manufactured by Japan Polyethylene Co., Ltd. Among these, ethylene-acrylic acid-maleic anhydride ternary copolymers are preferred in the present invention. 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.

[0017] ·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.

[0018] Other layers In the present invention, a sealant layer, an adjacent layer, and an 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 propylene or higher 1-olefins (having 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 for the purpose of adhering each layer. The adhesive resin is not particularly limited, but known resins can 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.

[0019] ·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.

[0020] 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.

[0021] ·Layer composition The thickness of the sealant layer of the top material is 10 μm or less, preferably in the range of 4 to 7 μm, and the thickness of the entire composite film of the top material is in the range of 30 to 80 μm, preferably in the range of 40 to 60 μm.

[0022] At this thickness, a composite film having good sealing properties and easy opening properties can be obtained. If the film is too thin, the strength is low and the film is prone to tearing, making it difficult to use, while if the film is too thick, the sealing properties and opening properties with the corresponding bottom material when contents are placed inside are poor.

[0023] 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.

[0024] The easy-open composite film of the top material can be produced by a conventional method such as a T-die method, a water-cooled or air-cooled inflation method, or the like. 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.

[0025] Bottom Material A polyester sheet is used for the bottom material. In the present invention, the layer facing the top material (i.e., the surface layer) contains glycol-modified polyethylene terephthalate (PET-G). The PET-G may be the same as or different from the top material, but it is usually preferable that they are the same. This surface layer serves as a sealant layer for the bottom material and is joined to the sealant layer of the top material to form the package. The surface layer may also be a layer composed of a glycol-modified polyethylene terephthalate (PET-G) composition. In the case of a composition, it is sufficient that the content is 50% by mass or more. The bottom material is usually made up of a laminated film of two or more layers, but may also be made up of a single layer. As the laminated film, a laminated polyethylene terephthalate of amorphous polyethylene terephthalate (A-PET) and glycol-modified polyethylene terephthalate is used because it is preferable in terms of processability and bonding to the easy-open composite film of the present invention. The thickness of the bottom material is selected appropriately depending on the purpose, but generally, if it is about 100 to 1000 μm, the strength of the bottom material can be maintained and deep drawing molding is possible. The thickness of the sealant layer of the bottom material is not particularly limited, but is 10 to 100 μm, preferably in the range of 20 to 50 μm. The bottom material is deep-drawn by thermoforming or the like to form a recess, into which the contents are placed and then sealed with the top material.

[0026] [Deep drawing molding and packaging] The deep-draw packaging body is formed, for example, as shown in FIG. The bottom material is heated and vacuum molded to form a recess for accommodating the contents. The recess is formed at a position facing the top material as described above.

[0027] After filling the recess with the contents, the above-mentioned easy-open composite film is used as the top material, and the surface layer of the bottom material containing PET-G faces the sealant layer of the top material. The top material is used as a lid, and the edges where the bottom material and the top material are in contact other than the recess are sealed by heat sealing or the like. If necessary, unnecessary edges can be cut off to create a package of the desired size.

[0028] In such deep-draw packaging, the bottom material has both a deep-draw molding section and a sealing section, so if a polyester-based sheet is used for the bottom material, the heat history applied in the molding section can cause recrystallization of the bottom material, resulting in a deterioration of sealing properties and a loss of sealing strength.However, in the present invention, a specified top material is used and combined with a specified bottom material, so after deep-draw molding, stable sealing and peeling are possible even at low temperatures of 120 to 160°C when sealing.

[0029] When the package is opened, the sealant layer of the easily peelable composite film, which is the top material, breaks at the sealed portion, causing interlayer peeling between the adjacent layers, and therefore the package is opened. For this reason, an unjoined portion may be provided between the easily peelable composite film and the base material. If the unbonded portion is pinched and the bottom and top materials are pulled in opposite directions, separation occurs. In the present invention, because the inner layer of the top material contains a specific antiblocking agent, the sealant layer breaks at the bonded portion, allowing separation at the interface with the adjacent layer, making it possible to open the package. Furthermore, stable seal strength can be achieved even at low temperatures, even if the bottom material has been subjected to heat history. [Example]

[0030] 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.

[0031] Top material 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) The thickness of the composite film was measured at five points on a piece of film (F1) using a dial gauge (PEACOCK UPRIGHT 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 anti-blocking agent. It was mixed with PET-G or polyethylene to obtain the content shown in Table 1. A polyether adhesive was used as the adhesive.

[0032] Bottom Material The bottom material used was a laminated or single layer film of the following materials with the thicknesses shown in Table 1. The sealant layer was a sheet made of glycol-modified polyethylene terephthalate (PET-G, ESTER, Eastman Chemical) (Shin-ei Kasei Co., Ltd.). Sheets made by mixing amorphous polyethylene terephthalate (A-PET) and PET-G in the ratios shown in Table 1 (Shin-ei Kasei Co., Ltd. and Sanbo Kasei Co., Ltd.) A-PET: amorphous polyethylene terephthalate (Sanbo Kasei Co., Ltd.)

[0033] [Examples 1-4, Comparative Examples 1 and 2] The materials shown in Table 1 were laminated by co-extrusion water-cooled inflation to produce a composite film, which was then laminated with OPET to form the top material. Multilayer or multilayer extrusion-molded bottom materials were also used. Using the top and bottom materials, the sealant layer of the top material was stacked so that it faced the sealant layer of the bottom material, and heat-sealing was performed at 300 kPa for 2 seconds using a seal tester ("Heat Seal Tester" manufactured by Tester Sangyo Co., Ltd.) at each sealing temperature shown in Table 1. Test specimens (50 mm x 15 mm) for measuring seal strength were cut out from the resulting laminated film. Peel tests were performed on the sealed portion of these test specimens using a Tensilon tensile tester ("Autograph" manufactured by Shimadzu Corporation) at a tensile speed of 300 mm / min at the temperatures shown in Table 1. Before the sealing, a pre-heat treatment was performed by applying a hot plate to the bottom material at 100° C. for 10 minutes, and the change in seal strength due to the presence or absence of heat history was measured. The results are shown in Table 1.

[0034] [Table 1]

[0035] In the packaging body of the example, the deterioration of the sealing property due to the thermal history of the bottom material is suppressed, and the sealing strength is stable even when sealed at low temperatures.

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 glycol-modified polyethylene terephthalate (PET-G); a top material in which the adjacent layer is a composite film made of a modified polyolefin resin containing at least one of acid-modified polyethylene, ethylene-acrylic acid ester copolymer, and ethylene-acrylic acid ester copolymer-maleic anhydride copolymer; It consists of a bottom material, the bottom material has a recess formed by deep drawing, and a layer facing the top material contains glycol-modified polyethylene terephthalate (PET-G); The deep-drawn package is sealed so that the sealant layer and the bottom material face each other and has easy-to-open properties.

2. The deep-draw packaging body according to claim 1, wherein the sealant layer of the top material further contains an antiblocking agent, and the amount of the antiblocking agent in the composition containing glycol-modified polyethylene terephthalate (PET-G) and the antiblocking agent is in a ratio of 10,000 to 50,000 ppm by mass.

3. 2. The deep-draw packaging body according to claim 1, wherein the thickness of the sealant layer of the top material is 10 μm or less, and the thickness of the entire composite film of the top material is in the range of 30 to 80 μm.

4. A deep-drawn package according to claim 1, in which the peripheral edge of the bottom material and the top material in contact with said peripheral edge are sealed, has stable peel strength when sealed at a temperature in the range of 120°C to 160°C even when the bottom material is subjected to a heat history during deep-draw molding.

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