JP7712752B2 - Laminated film for packaging materials and packaging bags - Google Patents

Description

This disclosure relates to a laminated film for packaging materials and a packaging bag, and more specifically to a laminated film for packaging materials laminated with a film made of a resin composition containing a plant-derived low-density polyethylene resin, and a packaging bag using the film.

For example, flexible packaging (light packaging) that is widely used as a packaging form for frozen foods such as dumplings, pan-fried shumai, stir-fried rice, and pizza is made of a flexible packaging material consisting of a sealant film and a base film.
However, many of the raw materials for flexible packaging materials are derived from petroleum, and there is a need to address environmental issues and conserve exhaustible resources such as petroleum.
Furthermore, a packaging bag containing a biodegradable resin composition containing a polylactic acid-based resin as a carbon-neutral material, which is intended to reduce the amount of petroleum resources used in packaging materials, and a specified amount of an ethylene-α-olefin copolymer and a polymer having an epoxy group is known (for example, Patent Document 1).

JP 2009-155516 A

By incorporating a biodegradable resin other than petroleum-derived raw materials in the resin composition constituting the packaging bag, the proportion of petroleum-derived raw materials can be reduced.
However, compared with those made from petroleum-based resins, such packaging bags are significantly inferior in processability, such as tensile strength, tear strength, seal strength, and stiffness, making it difficult to improve the productivity and durability of the bags.

The object of the present invention is to provide an environmentally friendly laminated film for packaging that conserves petroleum resources and reduces carbon dioxide emissions, and a packaging bag made of the film that has processing suitability and physical properties, particularly durability, comparable to those of packaging bags made of petroleum-based resins.

In order to solve the above problems, the present invention provides a laminated film for packaging material, which is obtained by laminating a base film and a sealant film made of a resin composition containing a plant-derived low-density polyethylene resin obtained by polymerizing plant-derived ethylene by a high-pressure method, and is characterized in that the laminated film for packaging material has a biomass content of at least 25% as calculated from the measured value of radiocarbon dating ^14C .

Furthermore, the plant-derived low-density polyethylene resin is characterized by having a biomass content of 10 to 100%.

Furthermore, the base film is characterized in that it is a film made of a resin composition containing a plant-derived polyethylene terephthalate resin obtained by condensation polymerization of plant-derived ethylene glycol and petroleum-derived terephthalic acid.

Furthermore, the sealant film contains 10 to 100% of the plant-derived low-density polyethylene resin.
The present invention is characterized in that the resin composition contains 00% by weight of a petroleum-derived low-density polyethylene resin and 0 to 90% by weight of a petroleum-derived low-density polyethylene resin, and is composed of either (A) or (B) below.
(A) A single-layer structure in which the resin composition and the petroleum-derived low-density polyethylene resin are mixed. (B) A multi-layer structure in which a middle layer is a layer in which the resin composition and the petroleum-derived low-density polyethylene resin are mixed, and an outer layer and an inner layer are made of the petroleum-derived low-density polyethylene resin.

Furthermore, the present invention is characterized in that an intermediate layer is further provided between the sealant film and the base film.

Furthermore, the packaging bag of the present invention is characterized by being made using the above-mentioned laminated film for packaging materials.

According to the present invention, a laminate film for packaging materials is provided by laminating a base film and a sealant film made of a resin composition containing a plant-derived low-density polyethylene resin obtained by polymerizing plant-derived ethylene by a high-pressure method, and the laminate film for packaging materials has a biomass content of at least 25% calculated from the measured value of ^14C radiocarbon dating. This reduces the consumption of petroleum resources, which are widely used as a raw material for the sealant film that constitutes the laminate film for packaging materials, and suppresses the emission of petroleum-derived carbon dioxide during the production and disposal of the film.
Furthermore, because its physical properties are comparable to those of petroleum-derived low-density polyethylene resin, the manufacturing process can be the same as that of existing laminated films for packaging materials, making it possible to switch raw materials without compromising the processing suitability of the packaging material.
Furthermore, the origin of the raw materials of the low-density polyethylene resin that constitutes the laminated film for packaging materials can be identified using this biomass degree as an indicator, making it possible to confirm the origin of the raw materials from the time of production of the film until its disposal.
Therefore, it is possible to provide a laminate film for packaging materials containing a low-density polyethylene resin that has a reduced environmental impact, is highly productively efficient, and allows the origin of the raw materials to be identified.

Furthermore, if the plant-derived low-density polyethylene resin has a biomass content of 10 to 100%, the petroleum-derived content of the low-density polyethylene resin that constitutes the sealant film can be further reduced, further reducing the amount of petroleum resources used and further suppressing petroleum-derived carbon dioxide emissions during film production and disposal.

Furthermore, if the base film is made of a resin composition containing plant-derived polyethylene terephthalate resin obtained by condensation polymerization of plant-derived ethylene glycol and petroleum-derived terephthalic acid, the proportion of petroleum-derived raw materials used in the base film can be reduced, further reducing the amount of petroleum resources used and further suppressing petroleum-derived carbon dioxide emissions during the production and disposal of the laminate film for packaging materials.
The laminated film for packaging materials has tensile strength, seal strength and stiffness suitable for use in packaging bags, for example, flexible packaging bags, and exhibits excellent processability.

Furthermore, the sealant film is produced by using a resin composition containing 10 to 100% by weight of a plant-derived low-density polyethylene resin and 0 to 90% by weight of a petroleum-derived low-density polyethylene resin, and is characterized in that the following (A) and (B) are used:
(A) A single layer structure in which a resin composition and a petroleum-derived low-density polyethylene resin are mixed. (B) A middle layer is a layer in which a resin composition and a petroleum-derived low-density polyethylene resin are mixed,
In the case of a multi-layer structure in which the outer layer and the inner layer are made of petroleum-derived low-density polyethylene resin, the proportion of petroleum-derived low-density polyethylene resin used in the laminated film for packaging can be reduced, thereby reducing the amount of petroleum resources used and suppressing petroleum-derived carbon dioxide emissions during the production and disposal of the film.
In addition, by using a petroleum-derived low-density polyethylene resin for the inner and outer layers constituting the sealant film such as (B), the film can be manufactured with the properties possessed by existing manufacturing processes.
Therefore, it is possible to provide a laminate film for packaging materials having superior processability.

Furthermore, by providing an intermediate layer between the sealant film and the base film, the laminate film for packaging can be configured to have various functions, such as gas barrier properties.

Furthermore, since the packaging bag of the present invention is made using the above-mentioned laminate film for packaging material, the proportion of petroleum-derived low-density polyethylene resin used in the laminate film for packaging material that constitutes the packaging bag can be reduced, thereby reducing the amount of petroleum resources used and suppressing petroleum-derived carbon dioxide emissions during the production and disposal of the packaging bag.
Furthermore, it is possible to reduce the ratio of petroleum-derived raw materials used in the construction of disposable packaging bags, which are widely available in the world. Furthermore, as described above, the processability and physical properties of the laminated film for packaging materials are comparable to those of petroleum-derived raw materials.
Therefore, it is possible to provide a packaging bag that contains a plant-derived low-density polyethylene resin that conserves petroleum resources and reduces the environmental impact, and that has processability and physical properties, particularly durability, that are comparable to those of petroleum-based resins.

1 is a flow chart illustrating the manufacturing process of sugarcane-derived low density polyethylene film. FIG. 1 is a cross-sectional view showing a sealant film containing a sugar cane-derived low-density polyethylene resin according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a schematic diagram of a film having a multilayer structure in which a middle layer is made of bio-based low-density polyethylene resin. 1 is a cross-sectional view showing a schematic example of a laminate film for packaging material according to the present embodiment. FIG. 1 is a flow chart illustrating a process for producing a plant-derived polyethylene terephthalate film. FIG. 1 is a cross-sectional view showing a schematic example of a packaging bag produced by heat-sealing a laminated film for packaging materials. 1 is a perspective view showing a four-side sealed bag as an example of a packaging bag formed using the packaging laminate film according to the present embodiment. FIG.

Below, an embodiment of the present invention will be described in detail with reference to the drawings.

Flexible packaging, which is widely used for foods and daily necessities, is made of laminated films. Some laminated films are made by laminating a sealant film (heat-sealable film) that serves as a heat-sealing material on the inner surface of the flexible packaging onto a base film. For example, polyester resins are used as the material for the base film.
On the other hand, the material of the sealant film is low density polyethylene (LDPE).
Low density polyethylene resin is inexpensive and has excellent flexibility, transparency, extrusion coating properties, and thermal adhesion properties.

Thus, low-density polyethylene resins and polyester-based resins are often used as materials for laminated films, and these low-density polyethylene resins and polyester-based resins are produced using petroleum as the starting material.
For example, low-density polyethylene is produced by addition polymerization of ethylene (ethene) obtained by refining crude oil or the like under high-temperature and high-pressure conditions, such as 300° C. and 2000 atmospheric pressure.

On the other hand, awareness of environmental issues such as the depletion of resources such as petroleum and global warming due to increased carbon dioxide emissions is growing year by year. In this context, the use of petroleum-derived low-density polyethylene resins means that large amounts of carbon dioxide fixed in petroleum are released into the atmosphere during the process from the manufacture to disposal of petrochemical products, and therefore is a lack of consideration for the environment.

Against this background, the development of technology to manufacture plastics from plants, which are carbon-neutral and renewable resources, has progressed, and the technology to produce polyethylene, the most widely used plastic, using biomass sugarcane as the starting material has been established (Compiled by the Processing Technology Research Group, Convertec 2009.9, pp. 63-67).
Carbon neutral means that the amount of carbon dioxide absorbed by a plant during growth is approximately the same as the amount of carbon dioxide emitted during combustion or decomposition, that is, the plant is neutral with respect to the amount of carbon circulated in the environment.

Next, a manufacturing process of the sealant film constituting the packaging laminate film according to this embodiment will be described.
FIG. 1 is a flow chart illustrating a manufacturing process of a sugarcane-derived low-density polyethylene film, and FIG. 2 is a cross-sectional view showing a sealant film containing a sugarcane-derived low-density polyethylene resin according to this embodiment.
In this embodiment, an example is shown in which sugar cane is used as the starting material for the packaging laminate film and the packaging bag.
However, the raw material for the laminated film for packaging material and the packaging bag according to this embodiment is not limited to sugar cane, but may be any plant that can be used as a raw material for producing low-density polyethylene resin, and further may be any renewable, biologically derived organic resource excluding fossil resources.

As shown in Figure 1, first, the sugar juice extracted from sugarcane harvested in the field is heated and concentrated, and a mixture of crystallized raw sugar and non-crystalline sugarcane blackstrap molasses 1 is separated in a centrifuge. This sugarcane blackstrap molasses 1, a by-product of sugar production, is used as the raw material.

Sugarcane molasses 1 is diluted with water to an appropriate concentration, fermented by yeast, and distilled to produce bioethanol 2 (step S101).

Bioethanol 2 is heated in the presence of a catalyst, and plant-derived bioethylene 3 is obtained through an intramolecular dehydration reaction (step S102).

Bioethylene 3 (monomer) is polymerized by a high-pressure method to obtain plant-derived bio-low-density polyethylene resin 10 (step S103).

In this way, the bio-based low-density polyethylene resin 10 used in the sealant film constituting the laminated film for packaging material according to this embodiment is produced from ethylene derived from plants such as sugar cane as a starting material. It has been confirmed that plant-derived ethylene and polyethylene have the same quality as petroleum-derived ethylene and polyethylene.
Therefore, the bio-based low-density polyethylene resin 10 can be produced in the same manner as low-density polyethylene resin is produced from petroleum-derived ethylene. That is, the bio-based low-density polyethylene resin 10 can be produced by addition polymerization of the bio-based ethylene 3 under high-temperature and high-pressure conditions such as 300° C. and 2000 atm.

The bio-based low-density polyethylene resin 10 can have various physical properties, such as a density d of 0.910 to 0.925 g/cm ³ and a melt flow rate (MFR) in the range of 0.5 to 8.0 g/10 min, more preferably 0.7 to 5.0 g/10 min, similar to petroleum-derived low-density polyethylene resins.

The density (d, unit: g/cm ³ ) was measured in accordance with JIS K 6760 (1981) using a sheet having a thickness of 1 mm obtained by press molding at 150° C.
Furthermore, the melt flow rate (MFR, unit: g/10 min) was measured in accordance with JIS K 7210 (1995) under conditions of a test temperature of 190° C. and a test load of 21.18 N.
The melt flow rate value is the amount (g) of a measurement object placed in a cylinder with a hole of 2 mm diameter at the bottom heated to 190° C. and extruded in 10 minutes under a load of 21.18 N. The higher the degree of polymerization of a polymer, the higher the viscosity when melted, and therefore the smaller the melt flow rate value tends to be.

The bio-based low-density polyethylene resin 10 having these physical properties is used to produce a sealant film constituting a laminate film for packaging material. In this case, petroleum-derived low-density polyethylene resin 11 is mixed therein as necessary.
The bio-based low-density polyethylene resin 10 is mixed with petroleum-derived low-density polyethylene resin 11 so that the content is an appropriate ratio of 10 to 100% by weight.

The resin composition containing 10 to 100% by weight of bio-based low-density polyethylene resin 10 mixed with petroleum-derived low-density polyethylene resin 11 is formed into a film F1 containing bio-based low-density polyethylene as shown in Figure 2 (step S104).

The method for producing the sealant film constituting the laminated film for packaging material according to this embodiment is not particularly limited, but it is preferable to use melt extrusion molding, and the inflation method, flat die method, etc. are preferably used. Furthermore, the sealant film may be processed into a multilayer structure in which multiple layers are stacked, in which case the co-extrusion method is preferably used.

In this embodiment, the plant-derived bio-based low-density polyethylene resin 10 obtained as described above is used to produce a sealant film constituting a laminate film for packaging materials.
As a result, this embodiment reduces the ratio of petroleum-derived resins used in the resin composition used in the laminate film for packaging materials, thereby reducing consumption of petroleum, which is a fossil resource (a depletable resource), and contributing to the prevention of global warming by reducing carbon dioxide emissions.

In this embodiment, a bio-based low-density polyethylene resin 10 having a biomass content of 80 to 100% as determined by ¹⁴ C radiocarbon dating is used.

Here, it is difficult to distinguish between plant (biomass)-derived resins and petroleum-derived resins based on physical properties such as molecular weight, mechanical properties, thermal properties, etc. Therefore, the biomass degree is used as a general index for distinguishing the content ratio of plant-derived resins in a resin composition.
This biomass content takes advantage of the fact that the carbon in petroleum-derived resins does not contain (remain in) ^14C (radioactive carbon-14, half-life 5,730 years), and is calculated by measuring the concentration of this ^14C using accelerator mass spectrometry.
Therefore, by measuring the biomass degree of a film, it is possible to identify whether or not plant-derived raw materials have been used and the content ratio of plant-derived resin in the resin composition.

In the first step of the biomass measurement, carbon dioxide, which is generated by burning the sample and purified in a vacuum line, is reduced with hydrogen using iron as a catalyst to produce graphite. This graphite is then attached to a tandem accelerator-based ¹⁴ C-AMS (Accelerator Mass Spectrometry) dedicated device (manufactured by NEC) to count ¹⁴ C and measure the concentration of ¹³ C ( ¹³ C/ ¹² C) and ¹⁴ C ( ¹⁴ C/ ¹² C).
From these measurements, the ratio of the ¹⁴ C concentration of the sample carbon to the standard modern carbon is calculated. In this measurement, the standard sample for ¹⁴ C measurement, oxalic acid (HOx) provided by the National Institute of Standards and Technology (NIST), is used.
II) is used to perform quantification.

In this embodiment, a sealant film having such a biomass content is used.
And whereas all the resins were petroleum-derived resins, in this embodiment, petroleum-derived low-density polyethylene resin 11 is hybridized (substituted) with bio-based low-density polyethylene resin 10, which is comparable to the petroleum-derived resin in terms of physical properties, etc.
As a result, in this embodiment, it is possible to reduce the amount of petroleum-derived carbon dioxide emissions during the production and disposal of the sealant film.

Furthermore, in this embodiment, a plant-derived low-density polyethylene having a density d of 0.910 to 0.925 g/ ^cm3 and a melt flow rate of 0.5 to 8.0 g/10 min is used as the bio-based low-density polyethylene resin 10 contained in the resin composition, which makes it possible to produce a plant-derived sealant film having physical properties comparable to those of petroleum-derived films using existing film production processes.
Therefore, the raw materials can be switched without impairing the processability of the packaging material. Furthermore, the plant-derived sealant film according to the present embodiment is comparable in durability to petroleum-derived sealant films.

Furthermore, in this embodiment, the sealant film has a biomass degree calculated from the measurement value of radiocarbon dating ^14C , so that this biomass degree can be used as an indicator to identify the origin of the raw materials of the low-density polyethylene resin that constitutes the sealant film, and the raw materials from which the film was made to the time of disposal can be confirmed.

In this embodiment, the melt flow rate (MFR) of the bio-low density polyethylene resin 10 constituting the sealant film is preferably 0.5 to 4.0 g/10 min. Furthermore, in order for the sealant film to have a high biomass content and to obtain good tensile strength and seal strength as a packaging bag, the melt flow rate (MFR) of the bio-low density polyethylene resin 10 is more preferably 0.7 to 3.8 g/10 min.

Next, in this embodiment, the above-mentioned bio-based low-density polyethylene resin 10 and petroleum-derived low-density polyethylene resin 11 can be used to form a sealant film as follows.
That is, the sealant film can be constructed in the manner described below in (A) and (B) so that the amount of bio-based low-density polyethylene resin 10 is 10 to 100% by weight and the amount of petroleum-derived low-density polyethylene resin 11 is 0 to 90% by weight relative to the entire film.

First, as shown in FIG. 2 above as film F1 (A), it can have a single layer structure made of a resin composition in which bio-based low-density polyethylene resin 10 and petroleum-derived low-density polyethylene resin 11 are mixed.
As described above, the resin composition constituting the film F1 contains 10 to 100% by weight of the bio-based low-density polyethylene resin 10 and 0 to 90% by weight of the petroleum-derived low-density polyethylene resin 11.
Therefore, when the content of the petroleum-derived low-density polyethylene resin 11 is 0% by weight, the film F1 has a single layer configuration of the bio-based low-density polyethylene resin 10 alone.

Fig. 3 is a cross-sectional view showing a film having a multilayer structure in which a middle layer is made of bio-based low-density polyethylene resin 10. As shown in Fig. 3 as film F2 of (B), a multilayer structure having a middle layer made of a resin composition in which bio-based low-density polyethylene resin 10 and petroleum-derived low-density polyethylene resin 11 are mixed, and outer and inner layers made of petroleum-derived low-density polyethylene resin 11 may also be used.
Here, similarly to film F1, the resin composition constituting the middle layer of film F2 contains 10 to 100% by weight of bio-based low-density polyethylene resin 10 and 0 to 90% by weight of petroleum-derived low-density polyethylene resin 11.
Therefore, when the content of the petroleum-derived low-density polyethylene resin 11 is 0% by weight, the middle layer of the film F2 has a single layer configuration of the bio-based low-density polyethylene resin 10 alone.

By adopting this configuration, the proportion of petroleum-derived raw materials used in the resin composition that constitutes films F1 and F2 can be reduced, and petroleum-derived carbon dioxide emissions during the production and disposal of the films can be suppressed.
In addition, by using petroleum-derived low-density polyethylene resin 11 for the inner and outer layers constituting film F2 as shown in (B), the film F2 can be manufactured, used, and processed with properties similar to those of existing films.
The multi-layered film F2 can be produced by coextrusion.

Next, in this embodiment, a laminate film for packaging material can be constructed using the above-mentioned films F1 and F2. Figure 4 is a cross-sectional view showing a schematic example of a laminate film for packaging material.

First, the laminate film for packaging material 12 basically comprises the above-mentioned film F1 or F2 laminated to a base film 14 as a sealant film 13. The laminate film for packaging material 12 according to this embodiment preferably has a biomass content of at least 25% as calculated from the measured value of radiocarbon dating ^14C .
With this configuration, it is possible to reduce the usage ratio of the petroleum-derived low-density polyethylene resin 11 constituting each film F1 and F2 of the sealant film 13 used for heat sealing.
The packaging laminate film 12 according to this embodiment can conserve petroleum resources and reduce petroleum-derived carbon dioxide emissions during its production, disposal, and the like.

Here, the Japan Bioplastics Association (JBPA) defines biomass plastics as "polymeric materials with a molecular weight (Mn) of 1,000 or more that contain substances derived from renewable organic resources as raw materials and are obtained by chemical or biological synthesis (excluding chemically unmodified non-thermoplastic natural organic polymeric materials)."
Furthermore, by containing 25.0% by weight or more of biomass-derived components in the raw material composition of biomass plastic or biomass-derived thermosetting plastic, the product can be made compliant with the "Biomass Plastic Mark."

The laminated film for packaging material 12 may have an intermediate layer 15. By changing the intermediate layer 15 in various ways, it is possible to impart various functions, such as gas barrier properties, impact resistance, pinhole resistance, aroma retention, and chemical resistance, to the laminated film for packaging material 12. For example, the intermediate layer 15 is made of a barrier material that suppresses the transmission of water vapor and oxygen.
For example, the barrier material may be a biaxially oriented polyamide (ONy: Oriented Nylon) film or a biaxially oriented polyethylene terephthalate (OPET: Oriented PolyEthylene Terephthalate) film as a barrier resin. Furthermore, the barrier material may be a vapor deposition film in which a vapor deposition film of silica, aluminum, or the like is formed on the surface of a barrier resin. Furthermore, the barrier material may be a metal foil such as aluminum, for example.

The intermediate layer 15 is laminated by being bonded to the sealant film 13 by an adhesive layer 16 and to the base film 14 by an adhesive layer 17. The materials of the adhesive layer 16 and the adhesive layer 17 are appropriately selected depending on the type of base material and the bonding method. Examples of lamination (bonding) methods include a dry lamination method and a melt extrusion lamination method.

Materials for adhesive layer 16, which serves as the lamination adhesive layer in the dry lamination method, and adhesive layer 17 include polyester-based adhesives and polyether-based adhesives, and from the viewpoint of adhesive strength, it is preferable to use a two-component curing urethane-based adhesive.
On the other hand, materials for adhesive layer 16, which becomes the melt-extruded resin layer in the melt extrusion lamination method, and adhesive layer 17 include polyethylene and polypropylene, and it is preferable to use low-density polyethylene from the viewpoint of substrate adhesion, although this depends on the type of substrate.
Furthermore, a dry lamination method or a melt extrusion lamination method may be used in combination. Before each layer is bonded, the surface may be subjected to a surface modification treatment such as a corona discharge treatment, an ozone treatment, a plasma treatment, etc., as necessary in order to improve adhesion, and an anchor coating agent or the like may be applied.

A printed layer 18 may be formed on any of the layers constituting the packaging laminate film 12. The printing of characters, figures, symbols, designs, etc. is not particularly limited as long as it is in a position that can be seen from the outside of the packaging container, and may be surface printing.
4, a printed layer 18 is formed on the inner side of the base film 14. A white underlayer may be provided on the printed layer 18. The printed layer 18 is formed by printing using gravure printing ink or the like by a printing method such as gravure printing, letterpress printing, screen printing, transfer printing, or flexographic printing.

In addition, the packaging laminate film 12 may have an outer layer (not shown) further laminated to the base film 14.

Examples of the base film 14 that can be used include various resin films and sheets such as polyethylene-based resins, polypropylene-based resins, cyclic polyolefin-based resins, polystyrene-based resins, acrylonitrile-styrene copolymers (AS resins), acrylonitrile-butadiene-styrene copolymers (ABS resins), polyvinyl chloride-based resins, fluorine-based resins, poly(meth)acrylic resins, polycarbonate-based resins, polyester-based resins such as polyethylene terephthalate and polyethylene naphthalate, polyamide-based resins such as various nylons, polyimide-based resins, polyamideimide resins, polyarylphthalate-based resins, silicone-based resins, polysulfone-based resins, polyphenylene sulfide-based resins, polyethersulfone-based resins, polyurethane-based resins, acetal-based resins, and cellulose-based resins.

The base film 14 is preferably made of a biaxially oriented polypropylene film (OPP: Oriented Polypolypropylene) or a biaxially oriented polyethylene terephthalate film (OPET).
The biaxially oriented polypropylene film is excellent in moisture resistance, water resistance, chemical resistance, etc., and is highly versatile and inexpensive. The biaxially oriented polyethylene terephthalate has low moisture absorption and excellent aroma retention in addition to scratch resistance, heat resistance, water resistance, etc. The packaging laminate film 12 using these base films 14 has tensile strength, seal strength, and stiffness suitable for packaging bags, for example, soft packaging bags, and shows excellent processability.

Furthermore, in this embodiment, the raw material for the biaxially oriented polyethylene terephthalate used in the base film 14 may be plant-derived.

Next, a manufacturing process of the plant-derived base film 14 constituting the packaging laminate film 12 according to this embodiment will be described.
Fig. 5 is a flow chart illustrating a process for producing a plant-derived polyethylene terephthalate film. Note that, in this example, sugar cane is used as the starting material for the plant-derived polyethylene terephthalate film, i.e., the bio-PET film F3 (see Fig. 1).
However, the raw material for the bio-PET film F3 in this embodiment is not limited to sugar cane, but may be any plant that can be used as a raw material for producing polyethylene terephthalate resin, and may further be any renewable, biologically derived organic resource excluding fossil resources.

First, bioethylene 3 is obtained through steps S101 and S102 in FIG. 1 described above.

Bioethylene oxide 4 (1,2-epoxyethane) is obtained by oxidizing bioethylene 3 (step S201). Bioethylene oxide 4 can be obtained, for example, by pressurizing and heating bioethylene 3 to 1 to 3 MPa and 200 to 300° C. in the presence of a silver catalyst and catalytically oxidizing the bioethylene 3 with molecular oxygen or a molecular oxygen-containing gas.
The bioethylene oxide 4 may be produced by reacting the bioethylene 3 with hydrogen peroxide or a peracid.

Bioethylene oxide 4 is hydrolyzed under an acid catalyst to obtain plant-derived bioethylene glycol 5 (MEG: Mono Ethylene Glycol) (ethane-1,2-diol) (step S202). The biomass content of this bioMEG 5 can be set to 100%.

On the other hand, paraxylene 6, a secondary product of petroleum, is oxidized and refined to a high purity to obtain purified terephthalic acid (PTA) 7 (step S203).

The bio-PET resin 19 containing plant-derived raw materials is obtained by condensation polymerization of the bio-MEG 5 and the purified terephthalic acid (PTA) 7 (step S204). Note that the bio-PET resin 19 has a biomass content of 30% since 30% of the raw materials are the bio-MEG 5 and 70% are the purified terephthalic acid (PTA) 7.

The bio-PET resin 19 is formed into a film to form a bio-PET film F3 (step S205). The bio-PET film F3 thus obtained is used as the base film 14 constituting the laminate film for packaging material 12, as necessary. In this way, the present embodiment further reduces the ratio of petroleum-derived resin to the resin composition used in the laminate film for packaging material 12, thereby further reducing consumption of petroleum, which is a fossil resource (a depletable resource), and contributing to the prevention of global warming by reducing carbon dioxide emissions.
More specifically, Bio-PET Film F3 can reduce _{CO2 emissions} by approximately 10% over its entire life cycle, from raw material procurement to disposal, compared to petroleum-derived PET film.

In addition, Bio-PET film F3 has 2 carbon atoms derived from Bio-MEG5 and 8 carbon atoms derived from purified terephthalic acid (PTA)7, so the biomass ratio is 20%. On the other hand, the molecular weight of the PET structural unit is 192, and the molecular weight derived from ethylene glycol is 60. Therefore, the biomass ratio calculated by the gravimetric method is 60/192 = 31.25%.

6 is a cross-sectional view showing a schematic example of a packaging bag produced by heat sealing the packaging laminate film 12. The packaging laminate film 12 is produced by heat sealing (thermocompression bonding) the outer peripheral edge of the packaging laminate film 12.
In this example, the packaging laminate film 12 is formed of two layers, a sealant film 13 and a base film 14. An adhesive layer is not shown in the figure.

One laminate film 12 for packaging material is folded or two laminate films 12 for packaging material are overlapped so that the surfaces of the sealant film 13, which is the inner layer of the laminate film 12 for packaging material, face each other, and the outer edges are heat-sealed.
The heat sealing method may be bar sealing, rotary roll sealing, belt sealing, impulse sealing, high frequency sealing, ultrasonic sealing, etc. Fig. 6 shows an example in which two sheets of the packaging laminate film 12A and 12B are overlapped.

Heating and pressure are applied from the sides of the base films 14A and 14B, which are the outer layers of the two laminated films for packaging material 12A and 12B, using a heating roller or the like (not shown). The heat melts the sealant films 13A and 13B, and the pressure causes the sealant films 13A and 13B to adhere to each other. This forms a seal portion 21 at the outer peripheral ends of the two laminated films for packaging material 12A and 12B.

Such a seal portion 21 is formed on three sides of, for example, two rectangular sheets of the packaging laminate film 12A and 12B, and the remaining side is used as a filling port for the contents. Then, a further seal portion 21 is formed on the side after the contents are filled through the filling port, thereby forming a completed packaging bag (four-side sealed bag 20).

Figure 7 is a perspective view showing a four-sided sealed bag 20 as an example of a packaging bag formed using the packaging laminate film 12 according to this embodiment. In this way, a soft packaging bag can be formed using the soft packaging material consisting of the sealant film 13 according to this embodiment and the base film 14, into which frozen foods such as fried rice can be filled and packaged.

With this configuration, it is possible to reduce the usage ratio of petroleum-derived raw materials in the laminate film for packaging material 12 constituting the packaging bag, thereby saving petroleum resources and suppressing petroleum-derived carbon dioxide emissions during the manufacture and disposal of the packaging bag. In particular, since flexible packaging bags tend to be disposable, the laminate film for packaging material 12 according to this embodiment, which reduces the usage of petroleum resources and suppresses petroleum-derived carbon dioxide emissions, can provide an effect of providing an environmentally friendly packaging bag.
Furthermore, as described above, the processability and physical properties of the laminate film for packaging materials 12 according to this embodiment are comparable to those of petroleum-derived materials.
Therefore, according to the configuration of this embodiment, a packaging bag can be provided that contains bio-low density polyethylene resin 10, which conserves petroleum resources and reduces the environmental impact, and has processing suitability and physical properties, particularly durability, that are comparable to those of petroleum-based resins.

The ends of the packaging bag may be provided with a cut line for opening using a laser or the like. Furthermore, the packaging bag according to this embodiment may be optionally equipped with a one-piece or two-piece type spout, a fastener for resealing, or the like. Naturally, bio-low-density polyethylene resin 10 or bio-PET resin 19 may be used as the material for these.

In addition to the four-sided sealed bag 20 illustrated in FIG. 7, various types of packaging bags according to this embodiment can be manufactured by heat sealing using a heat seal type such as a side seal type, a two-sided seal type, a three-sided seal type, an envelope seal type, a grommet seal type (pillow seal type), a pleated seal type, a flat bottom seal type, a square bottom seal type, and others.
Furthermore, in this embodiment, by using the above-mentioned laminated film 12 for packaging material, it is possible to produce self-supporting packaging bags (standing pouches), containers including tube containers and liquid paper containers, container lids, and container labels.
Furthermore, the contents of the packaging bag according to this embodiment are not limited to the exemplified foods and beverages, but can also contain cosmetics, medicines, miscellaneous goods, etc., thereby further reducing the proportion of petroleum-derived materials used and significantly suppressing petroleum-derived carbon dioxide emissions.

In this embodiment, it is preferable that the biomass ratio of the entire packaging material is 25% or more. Therefore, when the base film 14 is made of the bio-PET film F3 having a biomass ratio of 20%, the sealant film 13 may contain, for example, about 35% of the bio-low-density polyethylene resin 10.
On the other hand, when the biomass degree of the base film 14 is 0%, the ratio of the bio-based low-density polyethylene resin 10 in the sealant film 13 is increased to, for example, 70%. In this manner, in this embodiment, the biomass degree of the entire packaging material is set to at least 25%.

The present disclosure will be described in more detail and specifically below with reference to examples. However, the present disclosure is not limited to the following examples.

[Example 1]
(1) Resin composition A resin composition was prepared by thoroughly kneading 50.0 parts by weight of low-density polyethylene (LC525 manufactured by Japan Polyethylene Corporation: density d = 0.923 g/ ^cm3 , melt flow rate (MFR) = 3.5 g/10 min) and 50.0 parts by weight of biomass low-density polyethylene (SEB853 manufactured by Braskem Corporation: density d = 0.923 g/ ^cm3 , melt flow rate (MFR) = 2.7 g/10 min).

(2) Film Next, the resin composition prepared in (1) was used to produce a monolayer film having a thickness of 30 μm according to this example using a single-layer top-blown air-cooled inflation co-extrusion film-forming machine. That is, the monolayer film according to Example 1 is a film F1 containing bio-based low-density polyethylene as shown in Figure 2. One surface of the produced monolayer film was subjected to a corona discharge surface treatment (hereinafter referred to as corona treatment).

(3) Laminated material One side of a 15 μm thick biaxially oriented nylon 6 film was subjected to a corona treatment, and the desired printed pattern was formed on the corona-treated surface using a conventional gravure ink composition by gravure printing.Then, the entire surface including the printed pattern was coated with a two-component curing polyurethane-based laminating adhesive using a gravure roll coating method to a thickness of 4.0 g/ ^m2 (dry state) to form a laminating adhesive layer.The corona-treated side of the single-layer film produced in (2) was then placed against the laminating adhesive layer surface, and the two were then dry laminated to produce a laminated material.

(4) Flexible Package Product Next, two sheets of the laminate produced in (3) were prepared and overlapped with the film sides of (2) facing each other, and then the edges around the periphery were heat-sealed on three sides to form a sealed portion 21 and produce a three-sided sealed flexible packaging bag having an opening at the top. Snacks were filled and packaged in the three-sided sealed flexible packaging bag through the opening, and then the edges of the opening were heat-sealed to form the sealed portion 21, producing a flexible packaging product.

[Example 2]
(1) Resin composition A resin composition was prepared by thoroughly kneading 30.0 parts by weight of low-density polyethylene (LC522 manufactured by Japan Polyethylene Corporation: density d = 0.923 g/ ^cm3 , melt flow rate (MFR) = 4.0 g/10 min) and 70.0 parts by weight of biomass low-density polyethylene (SPB681 manufactured by Braskem Corporation: density d = 0.922 g/ ^cm3 , melt flow rate (MFR) = 3.8 g/10 min).

(2) Film Next, a monolayer film having a thickness of 50 μm according to this embodiment was produced using the resin composition prepared in (1) by using a single-layer top-blown air-cooled inflation co-extrusion film-forming machine. That is, the monolayer film according to Example 2 is a film F1 containing bio-based low-density polyethylene as shown in Figure 2. One surface of the produced monolayer film was subjected to a corona treatment.

(3) Laminated material One side of a biaxially oriented PET film with a thickness of 12 μm was subjected to a corona treatment, and the desired printed pattern was formed on the corona-treated surface using a conventional gravure ink composition by gravure printing.Then, the entire surface including the printed pattern was coated with a two-component curing polyurethane-based laminating adhesive using a gravure roll coating method to a thickness of 4.0 g/ ^m2 (dry state) to form a laminating adhesive layer.The corona-treated side of the single-layer film produced in (2) was then placed against the laminating adhesive layer surface, and the two were then dry laminated to produce a laminated material.

(4) Flexible Package Product Next, two sheets of the laminate produced in (3) were prepared and overlapped with the film sides of (2) facing each other, and then the edges around the periphery were heat-sealed on three sides to form a sealed portion 21 and produce a three-sided sealed flexible packaging bag having an opening at the top. Snacks were filled and packaged in the three-sided sealed flexible packaging bag through the opening, and then the edges of the opening were heat-sealed to form a sealed portion 21, producing a flexible packaging product.

[Example 3]
(1) Resin Composition First, the following resin compositions (a), (b), and (c) were prepared.
(a) Resin composition constituting the first layer A resin composition was prepared by thoroughly kneading 100.0 parts by weight of low-density polyethylene (LC522 manufactured by Japan Polyethylene Corporation: density d = 0.923 g/ ^cm3 , melt flow rate (MFR) = 4.0 g/10 min), 0.5 parts by weight of synthetic silica, and 0.05 parts by weight of erucamide.
(b) Resin composition constituting second layer: 100.0 parts by weight of biomass low-density polyethylene (SPB681 manufactured by Braskem Corporation: density d=0.922 g/cm ³ , melt flow rate (MFR)=3.8 g/10 min) was prepared.
(c) Resin composition constituting third layer A resin composition was prepared by thoroughly kneading 100.0 parts by weight of low-density polyethylene (LC522 manufactured by Japan Polyethylene Corporation: density d = 0.923 g/ ^cm3 , melt flow rate (MFR) = 4.0 g/10 min), 0.5 parts by weight of synthetic silica, and 0.05 parts by weight of erucamide.

(2) Film Next, the resin compositions prepared in (1) were used, and these were co-extruded using a three-kind, three-layer, top-blown, air-cooled inflation co-extrusion film-forming machine to produce a layer of the resin composition (a) at 10 μm, a layer of the resin composition (b) at 30 μm, and a layer of the resin composition (c) at 10 μm, respectively, to produce a multilayer laminate film according to this embodiment, which is a co-extruded inflation film with a total thickness of 50 μm for the three layers. That is, the multilayer laminate film according to Example 3 is a film F2 having a multilayer structure in which the middle layer is a bio-low density polyethylene resin 10 as shown in FIG. 3. The surface of the first layer (a) of the produced multilayer laminate film was subjected to a corona treatment.

(3) Laminated material One side of a biaxially oriented PET film having a thickness of 12 μm was subjected to a corona treatment, and the desired printed pattern was formed on the corona-treated surface using a conventional gravure ink composition by a gravure printing method.Then, the entire surface including the printed pattern was coated with a two-component curing polyurethane-based laminating adhesive using a gravure roll coating method to a thickness of 4.0 g/ ^m2 (in a dry state) to form a laminating adhesive layer.The corona-treated surface of the layer made of the resin composition of the first layer (i) of the multilayer laminate resin film produced in (2) was then laminated against the laminating adhesive layer surface, and the two were then dry laminated to produce a laminated material.

(4) Flexible Package Product Next, two sheets of the laminated material produced in (3) were prepared, and the surfaces of the third layers (c) of each were overlapped facing each other, and then the edges around the periphery were heat-sealed on three sides to form a sealed portion 21 and produce a three-sided sealed flexible packaging bag having an opening at the top. Snacks were filled and packaged in the three-sided sealed flexible packaging bag through the opening, and then the edges of the opening were heat-sealed to form a sealed portion 21, producing a flexible packaging product.

[Example 4]
(1) Resin composition Low density polyethylene (LC520 manufactured by Japan Polyethylene Corporation: density d = 0.923 g
A resin composition was prepared by thoroughly kneading 30.0 parts by weight of a biomass low-density polyethylene (SEB853 manufactured by Braskem Corporation: density d = 0.923 g/ ^cm3 , melt flow rate (MFR) = 3.6 g/10 min) and 70.0 parts by weight of a biomass low-density polyethylene (SEB853 manufactured by Braskem Corporation: density d = 0.923 g/ ^cm3 , melt flow rate (MFR) = 2.7 g/10 min).

(2) Film Next, a monolayer film having a thickness of 50 μm according to this embodiment was produced using the resin composition prepared in (1) by using a single-layer top-blown air-cooled inflation co-extrusion film-forming machine. That is, the monolayer film according to Example 4 is a film F1 containing bio-based low-density polyethylene as shown in Figure 2. One surface of the produced monolayer film was subjected to a corona treatment.

(3) Laminated Material One side of a biaxially stretched PET film having a thickness of 12 μm was subjected to a corona treatment, and a two-component curing type polyurethane-based laminating adhesive was applied to the corona-treated surface to a thickness of 3.0 g/m ² (dry state) to form an adhesive layer, and then a biaxially stretched PET film having a thickness of 12 μm and having been corona-treated on both sides was laminated on the surface of the adhesive layer, and further, in the same manner as above, a two-component curing type polyurethane-based laminating adhesive was applied to a thickness of 3.0 g/m ² (dry state) to form an adhesive layer on the surface of the biaxially stretched PET film laminated on both sides to form a base film 14. The adhesive layer surface of the base film 14 and the corona-treated surface of the single layer film produced in (2) were placed opposite each other and laminated to obtain a multilayer laminate film in which the base film 14 of this example was laminated.

(4) Flexible Package Product Next, two sheets of the laminate produced in (3) were prepared and overlapped with the film sides of (2) facing each other, and then the edges around the periphery were heat-sealed on three sides to form a sealed portion 21 and produce a three-sided sealed flexible packaging bag having an opening at the top. Snacks were filled and packaged in the three-sided sealed flexible packaging bag through the opening, and then the edges of the opening were heat-sealed to form the sealed portion 21, producing a flexible packaging product.

[Example 5]
(1) Resin Composition First, the following resin compositions (a), (b), and (c) were prepared.
(a) Resin composition constituting the first layer A resin composition was prepared by thoroughly kneading 100.0 parts by weight of low-density polyethylene (LC522 manufactured by Japan Polyethylene Corporation: density d = 0.923 g/ ^cm3 , melt flow rate (MFR) = 4.0 g/10 min), 0.5 parts by weight of synthetic silica, and 0.05 parts by weight of erucamide.
(b) Resin composition constituting second layer: 100.0 parts by weight of biomass low-density polyethylene (SPB681 manufactured by Braskem Corporation: density d=0.922 g/cm ³ , melt flow rate (MFR)=3.8 g/10 min) was prepared.
(c) Resin composition constituting third layer A resin composition was prepared by thoroughly kneading 100.0 parts by weight of low-density polyethylene (LC522 manufactured by Japan Polyethylene Corporation: density d = 0.923 g/ ^cm3 , melt flow rate (MFR) = 4.0 g/10 min), 0.5 parts by weight of synthetic silica, and 0.05 parts by weight of erucamide.

(2) Film Next, the resin compositions prepared in (1) were used, and these were co-extruded using a three-kind, three-layer top-blown, air-cooled inflation co-extrusion film-forming machine to produce a layer of the resin composition (a) at 10 μm, a layer of the resin composition (b) at 30 μm, and a layer of the resin composition (c) at 10 μm, respectively, to produce a multilayer laminate film according to this embodiment, which is a co-extruded inflation film with a total thickness of 50 μm for the three layers. That is, the multilayer laminate film according to Example 5 is a film F2 having a multilayer structure in which the middle layer is a bio-low density polyethylene resin 10 as shown in FIG. 3. The surface of the first layer (a) of the produced multilayer laminate film was subjected to a corona treatment.

(3) Laminated Material One side of a biaxially oriented PET film having a thickness of 12 μm was subjected to a corona treatment, and a two-component curing type polyurethane-based laminating adhesive was applied to the corona-treated surface to a thickness of 3.0 g/m ² (dry state) to form an adhesive layer, and then a biaxially oriented nylon 6 film having a thickness of 15 μm and having been corona-treated on both sides was superposed on the surface of the adhesive layer, and further, in the same manner as above, a two-component curing type polyurethane-based laminating adhesive was applied to a thickness of 3.0 g/m ² (dry state) to form an adhesive layer on the surface of the biaxially oriented nylon 6 film having been corona-treated on both sides, to obtain a substrate film 14. The adhesive layer surface of the substrate film 14 and the corona-treated surface of the coextruded multilayer laminate film (2) were superposed facing each other to obtain a multilayer laminate film laminated with the substrate film 14 of this example.

(4) Flexible Package Product Next, two sheets of the laminated material produced in (3) were prepared, and the surfaces of the third layers (c) of each were overlapped facing each other, and then the edges around the periphery were heat-sealed on three sides to form a sealed portion 21, and a three-side sealed flexible packaging bag having an opening at the top was produced. The three-side sealed flexible packaging bag was filled and packaged with quick-frozen fried rice through the opening, and then the edges of the opening were heat-sealed to form a sealed portion 21, producing a flexible packaging product.

[Example 6]
(1) Resin composition A resin composition was prepared by thoroughly kneading 20.0 parts by weight of low-density polyethylene (LC525 manufactured by Japan Polyethylene Corporation: density d = 0.923 g/ ^cm3 , melt flow rate (MFR) = 3.5 g/10 min) and 80.0 parts by weight of biomass low-density polyethylene (SEB853 manufactured by Braskem Corporation: density d = 0.923 g/ ^cm3 , melt flow rate (MFR) = 2.7 g/10 min).

(2) Film Next, using each of the resin compositions prepared in (1), a monolayer film having a thickness of 30 μm according to this example was produced using a single-layer top-blown air-cooled inflation co-extrusion film-forming machine. That is, the monolayer film according to Example 6 is a film F1 containing bio-based low-density polyethylene as shown in Figure 2. One surface of the produced monolayer film was subjected to a corona treatment.

(3) Laminated material One side of a 12 μm thick biaxially stretched biomass PET film (Bio-PET film F3) was subjected to a corona treatment, and the desired printed pattern was formed on the corona-treated surface using a conventional gravure ink composition by gravure printing.Then, the entire surface including the printed pattern was coated with a two-component curing polyurethane-based laminating adhesive using a gravure roll coating method to a thickness of 4.0 g/ ^m2 (dry state) to form a laminating adhesive layer.The corona-treated surface of the single-layer film produced in (2) was then placed against the laminating adhesive layer surface, and the two were then dry laminated to produce a laminated material.

(4) Flexible Package Product Next, two sheets of the laminated material produced in (3) were prepared, and the surfaces of the film sides of each of them in (2) were overlapped facing each other, and then the edges around the periphery were heat-sealed on three sides to form a sealed portion 21, and a three-side sealed type flexible packaging bag having an opening at the top was produced. The three-side sealed type flexible packaging bag was filled and packaged with quick-frozen fried rice through the opening, and then the edges of the opening were heat-sealed to form a sealed portion 21, thereby producing a flexible packaging product.

As described above in detail, the films F1 and F2 made of the low-density polyethylene resin of the present disclosure are made of a resin composition containing a bio-low-density polyethylene resin 10 obtained by a high-pressure polymerization method. These films F1 and F2 are made into a sealant film 13, and laminated with a base film 14 to make a laminate film 12 for packaging material, and the packaging bag is made of this laminate film 12 for packaging material.

This disclosure can be applied to any product that uses polyethylene resin, such as a film made of polyethylene resin, or a packaging bag or container made of this film.

10 Bio-based low-density polyethylene resin 11 Petroleum-derived low-density polyethylene resin 12 Laminated film for packaging material 13 Sealant film 14 Base film 19 Bio-based PET resin 20 Four-side sealed bag (packaging bag)
F1, F2 film (sealant film)
F3 Bio PET film

Claims (4)

A laminated film for packaging materials having a base film, an intermediate layer, and a sealant film in this order,
The base film is made of a polyester resin,
The intermediate layer is a barrier resin,
The sealant film has an outer layer, a middle layer (excluding linear low-density polyethylene), and an inner layer,
The resin constituting the outer layer and the inner layer is made of a petroleum-derived low-density polyethylene resin,
The resin composition constituting the middle layer comprises, as resin components, 10 to 80 % by weight of a plant-derived high-pressure low-density polyethylene resin and 20 to 90% by weight of a petroleum-derived high-pressure low-density polyethylene resin;
The petroleum-derived high-pressure low-density polyethylene resin has a density d of 0.910 to 0.925 g/cm ³ and a melt flow rate (MFR) of 0.5 to 8.0 g/10 min.,
The plant-derived high-pressure low-density polyethylene resin has a density d of 0.910 to 0.925 g/ ^cm3 and a melt flow rate (MFR) of 0.7 to 3.8 g/10 min;
The sealant film does not contain 0.2% by mass or more of silica, 5.0% by mass or more of titanium oxide, an ionomer, or an ethylene-methacrylic acid copolymer;
The biomass content of the entire laminated film for packaging is 25% or more.
Laminated film for packaging materials. 2. The laminated film for packaging materials according to claim 1 , wherein the plant-derived low-density polyethylene resin has a biomass ratio of 80 to 100%. A container comprising the laminated film for packaging material according to claim 1 or 2 . A covering material comprising the laminated film for packaging materials according to claim 1 or 2 .