Multilayer film, laminate, packaging bag, packaging product, and selection method of multilayer film

Abstract

To provide a laminate and a packaging bag which are excellent in recyclability and bag-making suitability, and have excellent gas barrier properties even after heat treatment.SOLUTION: There is provided a multilayer film having: an outermost layer containing a thermosetting resin or a thermoplastic resin having a melting point of 160°C or more; and a polyethylene layer containing a polyethylene-based resin, wherein when heated at 100°C for 15 minutes, an MD heat shrinkage rate calculated by the following formula (1) and a TD heat shrinkage rate calculated by the following formula (2) are less than 2%.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a multilayer film, a laminate, a packaging bag, a packaging product, and a method for selecting a multilayer film.

Background Art

[0002] In recent years, due to the increasing environmental awareness triggered by problems such as marine plastic waste, there has been a growing demand for more efficient separation, recycling, and resource recovery of plastic materials. Against this background, the development of packaging bags made of a single material has been desired. By realizing the use of a single material for packaging bags (monomaterialization), the recyclability of packaging bags can be enhanced.

[0003] For example, Patent Document 1 discloses a laminate including a base material and a heat-sealing layer, wherein the base material and the heat-sealing layer are made of the same type of resin material, the base material has a multilayer structure, the base material is a base material subjected to a stretching treatment, and the heat-sealing layer is a layer not subjected to a stretching treatment.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, when manufacturing a package, the heat-sealing layers (sealant layers) of the laminate are faced to each other, and pressure is applied to the laminate by a jig and pinched. Thereby, the heat-sealing layers are heat-welded (heat-sealed) to each other. The outermost layer of the laminate in contact with the jig is exposed to a high temperature.

[0006] The inventor selected a polyethylene-based resin as a material for realizing a single-material packaging bag. The inventor's study revealed that in a laminate using a polyethylene-based resin, problems such as distortion and whitening may occur in the heat-sealed portion due to exposure to high temperatures during heat sealing. Therefore, in a laminate using a polyethylene-based resin, the range of heat-sealing temperatures suitable for bag making is narrow, and there is room for improvement in terms of bag-making suitability.

[0007] In addition, the packaging bag is required to have excellent gas barrier properties even after heat treatment.

[0008] The present disclosure provides a laminate, a packaging bag, and a packaged product that are excellent in recyclability and bag-making suitability and also excellent in gas barrier properties even after heat treatment. Further, the present disclosure provides a multilayer film and a method for selecting the same, which, when used as a material for a laminate, result in a laminate that is excellent in recyclability and bag-making suitability and also excellent in gas barrier properties even after heat treatment. [Means for Solving the Problems]

[0009] One aspect of the present disclosure relates to the following multilayer film, laminate, packaging bag, packaged product, and method for selecting a multilayer film. [1] A multilayer film having an outermost layer containing a thermosetting resin or a thermoplastic resin having a melting point of 160°C or higher, and a polyethylene layer containing a polyethylene-based resin, wherein when heated at 100°C for 15 minutes, the MD heat shrinkage rate obtained by the following formula (1) and the TD heat shrinkage rate obtained by the following formula (2) are less than 2%. MD heat shrinkage rate (%) = (MD length before heating - MD length after heating) / MD length before heating × 100 …(1) TD heat shrinkage rate (%) = (TD length before heating - TD length after heating) / TD length before heating × 100 …(2) [2] The multilayer film according to [1], wherein the ratio of the thickness of the outermost layer to the total thickness of the multilayer film is 2% or more. [3] Comprising a multilayer film and a sealant layer, wherein the sealant layer contains a polyethylene-based resin, wherein the multilayer film is composed of the multilayer film according to [1] or [2], a laminate, wherein in the multilayer film, the polyethylene layer is disposed on the sealant layer side. [4] The laminate according to [3], further comprising a first adhesive layer between the multilayer film and the sealant layer. [5] Between the first adhesive layer and the sealant layer, further comprising an intermediate layer and a second adhesive layer in this order from the first adhesive side, the laminate according to [4], wherein the intermediate layer contains a polyethylene-based resin. [6] The laminate according to any one of [3] to [5], further comprising a gas barrier layer between the multilayer film and the sealant layer. [7] The laminate according to any one of [3] to [6], wherein the mass ratio of the polyethylene-based resin in the entire laminate is 90% by mass or more. [8] The laminate according to any one of [3] to [7], wherein the temperature T1 and the temperature T2 measured by the following measurement method satisfy the following formula (T). T2 - T1 ≧ 35°C ···(T) <Measurement method of the temperature T1> A measurement method comprising the following steps (a1) to (c1), and repeating the steps (a1) to (c1) while changing the heat seal temperature from 80°C to a higher temperature by 10°C at a time in the step (b1) until it is determined that peeling does not occur between the sealant layers in the step (c1), and adopting the highest heat seal temperature among those at which peeling is determined to occur between the sealant layers in the step (c1) as the temperature T1. (a1) A step of preparing two test pieces of the laminate having a size of 60 mm in width and 50 mm in length. (b1) A step of obtaining a sample by heat-sealing the two test pieces with a seal width of 10 mm, a seal pressure of 0.2 MPa, and a seal time of 1 second with the sealant layers facing each other. (c1) Step of performing a peel test on the above sample at 300 mm / min using a tensile testing machine in accordance with JIS Z1707:2019 <Measurement method of the above temperature T2> A measurement method comprising the following steps (a2) to (c2), and repeating the steps (a2) to (c2) while changing the heat seal temperature from 120 °C to a higher temperature in increments of 5 °C in the step (b2) until it is determined that there is a change in appearance in the step (c2), and adopting the highest heat seal temperature among those at which it is determined that there is no change in appearance in the step (c2) as the above temperature T2. (a2) Step of preparing two pieces of the above laminate with a size of 60 mm in width × 50 mm in length as test pieces (b2) Step of obtaining a sample by overlapping the two test pieces so that the sealant layers face each other, heat-sealing with a seal width of 10 mm, a seal pressure of 0.2 MPa, and a seal time of 1 second (c2) Step of checking for any change in the appearance of the above sample [9] A packaging bag obtained by bag-making the laminate according to any one of [3] to [8].

[10] A packaging product comprising the packaging bag according to [9] and the contents contained in the packaging bag.

[11] A method for selecting a multilayer film for packaging, having an outermost layer containing a thermosetting resin or a thermoplastic resin with a melting point of 160 °C or higher and a polyethylene layer containing a polyethylene-based resin, When the multilayer film to be evaluated is heated at 100 °C for 15 minutes, a method for selecting a multilayer film for packaging that determines a multilayer film with an MD heat shrinkage rate obtained by the following formula (1) and a TD heat shrinkage rate obtained by the following formula (2) of less than 2% as a qualified product. MD heat shrinkage rate (%) = (MD length before heating - MD length after heating) / MD length before heating × 100 …(1) TD heat shrinkage rate (%) = (TD length before heating - TD length after heating) / TD length before heating × 100 …(2)

Effects of the Invention

[0010] According to the present disclosure, there are provided a laminate, a packaging bag, and a packaging product that are excellent in recyclability and bag-making suitability, and also excellent in gas barrier properties even after heat treatment. Further, according to the present disclosure, there are provided a multilayer film and a method for selecting the same, which, when used as a material of the laminate, provide a laminate excellent in recyclability and bag-making suitability, and also excellent in gas barrier properties even after heat treatment.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings as appropriate. However, the present disclosure is not limited to the following embodiments.

[0013] [Multilayer Film] Hereinafter, the multilayer film according to the present disclosure will be described.

[0014] <First Embodiment> FIG. 1 is a schematic cross-sectional view of a multilayer film according to the first embodiment of the present disclosure. The multilayer film 1 shown in FIG. 1 has an outermost layer 10 and a polyethylene layer 11. The outermost layer 10 contains a thermosetting resin or a thermoplastic resin having a melting point of 160° C. or higher. The polyethylene layer 11 contains a polyethylene-based resin.

[0015] In the multilayer film 1, when heated at 100°C for 15 minutes, the MD heat shrinkage rate obtained by the following formula (1) and the TD heat shrinkage rate obtained by the following formula (2) are less than 2%. MD heat shrinkage rate (%) = (MD length before heating - MD length after heating) / MD length before heating × 100 …(1) TD heat shrinkage rate (%) = (TD length before heating - TD length after heating) / TD length before heating × 100 …(2)

[0016] MD is the machine direction of the outermost layer and the polyethylene layer, and TD is the transverse direction perpendicular thereto. For example, the film can be used to measure the orientation angle using a retardation measuring device (trade name: KOBRA, manufactured by Oji Scientific Instruments Co., Ltd.), and MD and TD can be distinguished from the orientation angle.

[0017] The laminate obtained using the multilayer film is excellent in recyclability and bag-making suitability, and also excellent in gas barrier properties even after heat treatment. The present inventor speculates as follows about the reason for such an effect. That is, the outermost layer 10 contains a thermosetting resin or a thermoplastic resin having a melting point of 160°C or higher. Thereby, while ensuring recyclability of the multilayer film, the occurrence of appearance defects such as heat shrinkage and wrinkles during bag-making is suppressed. Therefore, there is a tendency to widen the range of heat seal temperatures suitable for bag-making. Furthermore, the MD heat shrinkage rate and the TD heat shrinkage rate of the multilayer film are less than 2%. Thereby, the shrinkage of the heating portion during heat sealing is suppressed, and wrinkles and distortion of the laminate are less likely to occur. Also, in the laminate, curling toward the multilayer film side after heat treatment can be prevented and deterioration of the barrier layer can be prevented. As a result, the laminate is excellent in bag-making suitability and also excellent in gas barrier properties even after heat treatment even when a polyethylene-based resin is used.

[0018] The MD heat shrinkage rate and the TD heat shrinkage rate are preferably 1.5% or less, and more preferably 1.0% or less. Thereby, the laminate tends to be further excellent in bag-making suitability and gas barrier properties after heat treatment.

[0019] The above MD heat shrinkage rate and TD heat shrinkage rate can be appropriately adjusted by changing the density of the polyethylene resin contained in the polyethylene layer and changing the draw ratio of the multilayer film 1.

[0020] The thickness of the multilayer film 1 is not particularly limited and can be appropriately changed depending on the price and application while considering the suitability as a packaging material and the lamination suitability with other layers. The thickness of the multilayer film 1 is preferably 10 μm or more and 50 μm or less, and more preferably 15 μm or more and 40 μm or less. When the thickness of the multilayer film is greater than 15 μm, the stability in manufacturing tends to be sufficiently ensured. When the thickness of the multilayer film is less than 50 μm, the manufacturing cost tends to be suppressed.

[0021] The content ratio of the polyethylene resin in the multilayer film 1 may be 70% by mass or more, 80% by mass or more, or 90% by mass or more based on the total amount of the multilayer film 1.

[0022] The multilayer film 1 may be produced by forming a film of the materials constituting each layer by a coextrusion method such as the T-die method or the inflation method, or may be produced by a lamination method. The multilayer film 1 is preferably a coextruded multilayer film produced by forming a film by a coextrusion method. The coextruded multilayer film tends to be able to make the outermost layer thinner compared to the multilayer film obtained by lamination. As a result, the visibility of the printed pattern of the multilayer film 1 is improved, and the multilayer film 1 tends to be more excellent in ensuring the content of the polyethylene resin and in recyclability. Also, the coextruded multilayer film tends to be excellent in the adhesion strength between the polyethylene layer and the outermost layer compared to the multilayer film obtained by coating.

[0023] The multilayer film 1 may be unstretched or may be subjected to a stretching treatment. The stretching treatment may be uniaxial stretching or biaxial stretching. The multilayer film 1 is preferably subjected to biaxial stretching. Thereby, the generation of curl is suppressed, and the multilayer film 1 tends to be more excellent in gas barrier properties after heat treatment.

[0024] Various additives may be added to each layer of the multilayer film 1. Examples of such additives include flame retardants, slip agents, antiblocking agents, antioxidants, light stabilizers, and tackifiers.

[0025] The surface of the multilayer film 1 can be subjected to an easy adhesion treatment by a dry surface treatment such as corona treatment or atmospheric pressure plasma treatment.

[0026] Hereinafter, each layer of the multilayer film 1 will be described in detail.

[0027] (Outermost layer) The outermost layer 10 contains a thermosetting resin or a thermoplastic resin having a melting point of 160°C or higher. The outermost layer 10 is provided to prevent problems during heat sealing when making bags or filling and sealing, and to ensure heat sealing suitability. Due to such a role, the outermost layer 10 may be provided as the outermost layer of the laminate described later.

[0028] The ratio of the thickness of the outermost layer 10 to the total thickness of the multilayer film is preferably 2% or more, more preferably 3% or more, and still more preferably 4% or more. Thereby, the multilayer film 1 is likely to obtain the desired heat resistance and tends to obtain better heat sealability. The ratio of the thickness of the outermost layer 10 to the total thickness of the multilayer film is preferably 20% or less, more preferably 15% or less, and still more preferably 10% or less. Thereby, waste of the material of the outermost layer 10 can be suppressed, and the content of the polyethylene-based resin with respect to the whole laminate can be ensured, and the laminate tends to be more excellent in recyclability.

[0029] The thickness of the outermost layer 10 is adjusted according to the total thickness of the multilayer film as described above. From the viewpoints of improving heat resistance and reducing the amount of heat required for heat sealing, for example, it may be 0.1 to 5.0 μm, may be 0.2 to 4.0 μm, may be 0.3 to 4.0 μm, or may be 0.3 to 3.0 μm.

[0030] The outermost layer 10 contains a thermosetting resin or a resin with a melting point of 160°C or higher. The resin is preferably at least one resin selected from the group consisting of polyurethane, polyester, polyamide, polyamideimide, and epoxy.

[0031] When forming the outermost layer 10 using a resin with a melting point of 160°C or higher, the melting point of the resin may be 160°C or higher. However, from the perspective of obtaining higher heat resistance, the melting point may be 180°C or higher, or may be 200°C or higher.

[0032] Examples of polyurethane include dispersions such as Takelac W and WS series manufactured by Mitsui Chemicals, ETERNACOLL series manufactured by Ube Industries, Hydran series manufactured by DIC, and Adeka Bon Titizer HUX series manufactured by ADEKA, and solvent-based coating liquids such as Takelac E series manufactured by Mitsui Chemicals and Barnock series manufactured by DIC.

[0033] Examples of polyester include dispersions such as Byrnal manufactured by Toyobo, Aron Melt manufactured by Toagosei, and Eritel manufactured by Unitika, and solvent-based coating liquids such as Barnock series manufactured by DIC.

[0034] Examples of polyamide include nylon 6 and nylon 12 synthesized from combinations of ω-amino acids, and nylon 66 synthesized from combinations of diamines and dicarboxylic acids.

[0035] Examples of polyamideimide include the Byromax series manufactured by Toyobo.

[0036] Examples of epoxy include the Adeka New Coat series manufactured by ADEKA, the Denacol series manufactured by Nagase ChemteX, and the jER series manufactured by Mitsubishi Chemical.

[0037] In the outermost layer, the content of the thermosetting resin and the resin having a melting point of 160 °C or higher may be 70% by mass or more, 80% by mass or more, 90% by mass or more, or 100% by mass based on the total amount of the outermost layer.

[0038] (Polyethylene layer) The polyethylene layer contains a polyethylene-based resin. Examples of such a polyethylene-based resin include ultra-low density polyethylene resin (abbreviation: VLDPE, density: less than 0.910 g / cm 3 ), low density polyethylene resin (abbreviation: LDPE, density: 0.910 g / cm 3 or more and less than 0.930 g / cm 3 ), medium density polyethylene resin (abbreviation: MDPE, density: 0.930 g / cm 3 or more and less than 0.942 g / cm 3 ), linear low density polyethylene resin (abbreviation: LLDPE, density: 0.930 g / cm 3 or more and less than 0.942 g / cm 3 ), and high density polyethylene resin (abbreviation: HDPE, density: 0.942 g / cm 3 or more).

[0039] Further, the polyethylene layer may be an adhesive resin such as maleic anhydride graft-modified polyethylene. The polyethylene layer may contain a resin other than the polyethylene-based resin.

[0040] The content of the polyethylene-based resin may be 50% by mass or more, 70% by mass or more, 90% by mass or more, 95% by mass or more, or 100% by mass based on the total amount of the polyethylene layer.

[0041] <Second Embodiment> Hereinafter, the multilayer film according to the second embodiment will be described. Regarding points not described below, as long as there is no inconsistency, it is the same as the multilayer film according to the first embodiment. FIG. 2 is a schematic cross-sectional view of the multilayer film according to the second embodiment of the present disclosure. The multilayer film 2 shown in FIG. 2 has an outermost layer 10 and a polyethylene layer 11. The polyethylene layer includes a first polyethylene layer 11a and a second polyethylene layer 11b from the side of the outermost layer 10.

[0042] The first polyethylene layer 11a is preferably an adhesive resin, and the second polyethylene layer 11b is preferably a high-density polyethylene resin. Thereby, heat shrinkage is suppressed, and the laminate tends to be more excellent in bag-making suitability and gas barrier properties after heat treatment. Further, the first polyethylene layer 11a is preferably a maleic anhydride graft-modified high-density polyethylene resin. Thereby, the laminate tends to be more excellent in gas barrier properties after heat treatment.

[0043] As described above, the multilayer films according to the first and second embodiments have been described, but the multilayer film according to the present disclosure is not limited to the above embodiments. In the multilayer film, the polyethylene layer may be 3 layers, 4 layers, or 5 or more layers.

[0044] [Laminate] Hereinafter, the laminate according to the present disclosure will be described.

[0045] <First Embodiment> FIG. 3 is a schematic cross-sectional view of the laminate according to the first embodiment of the present disclosure. The laminate 100 shown in FIG. 3 includes a multilayer film 1, a first adhesive layer 40, a polyethylene film 20, a second adhesive layer 50, and a sealant layer 30. The laminate 100 includes an inorganic oxide layer 14 and a gas barrier coating layer 15 as gas barrier layers between the polyethylene film 20 and the sealant layer 30. In the multilayer film, the polyethylene layer 11 is disposed on the side of the sealant layer 30.

[0046] In the laminate 100, it is preferable that the temperature T1 and the temperature T2 measured by the following measurement method satisfy the following formula (T). Thereby, the laminate tends to be more excellent in bag-making suitability. From the same viewpoint, the left side of the following formula (T) is more preferably 40°C or higher, still more preferably 50°C or higher, and particularly preferably 70°C or higher.

[0047] T2 - T1 ≥ 35°C ···(T)

[0048] <Measurement method of temperature T1> It includes the following steps (a1) to (c1). Until it is determined that peeling does not occur between the sealant layers in the (c1) step, the steps (a1) to (c1) are repeated while changing the heat seal temperature from 80°C to a higher temperature in increments of 10°C in the (b1) step. The highest heat seal temperature among those determined to cause peeling between the sealant layers in the (c1) step is adopted as the temperature T1.

[0049] (a1) Step: Prepare two laminates 100 with a size of 60 mm in width × 50 mm in length as test pieces. (b1) Step: Overlap the two test pieces so that the sealant layers face each other, and perform heat sealing with a seal width of 10 mm, a seal pressure of 0.2 MPa, and a seal time of 1 second to obtain a sample. (c1) Step: Conduct a peel test on the sample using a tensile testing machine at 300 mm / min in accordance with JIS Z1707:2019.

[0050] <Measurement method of temperature T2> It includes the following steps (a2) to (c2). Until it is determined that there is a change in appearance in the (c2) step, the steps (a2) to (c2) are repeated while changing the heat seal temperature from 120°C to a higher temperature in increments of 5°C in the (b2) step. The highest heat seal temperature among those determined not to have a change in appearance in the (c2) step is adopted as the temperature T2.

[0051] (a2) Step: Prepare two laminates with a size of 60 mm in width × 50 mm in length as test pieces. (b2) Process: Overlay two test pieces so that the sealant layers face each other, and heat-seal them with a seal width of 10 mm, a seal pressure of 0.2 MPa, and a seal time of 1 second to obtain a sample. (c2) Process: Check whether there is any change in the appearance of the sample.

[0052] Since the laminate 100 includes the multilayer film 1, the polyethylene film 20, and the sealant layer 30 containing a polyethylene-based resin, the content ratio of the polyethylene-based resin in the laminate 100 is 90% by mass or more based on the total amount of the laminate 100. Thereby, the laminate 100 has high recyclability. When the multilayer film 1, the polyethylene film 20, and the sealant layer 30 are all made of only a polyethylene-based resin, the ratio (% by mass) of the polyethylene-based resin in the laminate 100 can be calculated by the following formula (3). (Mass of multilayer film 1 + Mass of polyethylene film 20 + Mass of sealant layer 30) / Mass of entire laminate 100 × 100 …(3)

[0053] Hereinafter, each layer of the laminate 100 will be described.

[0054] (Polyethylene Film) The polyethylene film 20 plays a role in improving the processing stability when providing the inorganic oxide layer 14. Further, the polyethylene film 20 plays a role in suppressing the deterioration of the gas barrier property after heat sterilization treatment. The polyethylene film 20 is a layer containing a polyethylene-based resin. The polyethylene-based resin contained in the polyethylene film 20 is not particularly limited, but from the viewpoints of excellent processing stability when providing a gas barrier layer and excellent heat resistance capable of maintaining the gas barrier property even after heat sterilization treatment, high-density polyethylene resin and medium-density polyethylene resin are preferable. These materials may be derived from petroleum, may be derived from plants, or may be a mixture thereof. The surface of the polyethylene film 20 can be subjected to an easy adhesion treatment by a dry surface treatment such as corona treatment or atmospheric pressure plasma treatment.

[0055] The thickness of the polyethylene film 20 is not particularly limited and can be appropriately determined according to price and use, while considering suitability as a packaging material and suitability for lamination with other layers. However, 5 μm to 100 μm is preferable, 10 μm to 60 μm is more preferable, and 15 μm to 40 μm is even more preferable. When the thickness of the polyethylene film 20 is 5 μm or more, the laminate 100 is further excellent in heat resistance and tends to increase the stability in manufacturing. When the thickness of the polyethylene film 20 is 100 μm or less, an increase in manufacturing cost can be suppressed.

[0056] The polyethylene film 20 can be produced by forming a film from a polyethylene-based resin by a coextrusion method such as the T-die method or the inflation method. When producing the polyethylene film 20 by the T-die method, the melt flow rate (MFR) of the polyethylene-based resin is preferably 3 g / 10 min or more and 20 g / 10 min or less. By setting the MFR to 3 g / 10 min or more, the processability of the laminate can be improved. Also, by setting the MFR to 20 g / 10 min or less, it is possible to prevent the produced film from breaking.

[0057] When producing the polyethylene film 20 by the inflation method, the MFR of the polyethylene-based resin is preferably 0.1 g / 10 min or more and 5 g / 10 min or less. By setting the MFR to 0.1 g / 10 min or more, the processability of the laminate can be improved. Also, by setting the MFR to 5 g / 10 min or less, the film-forming property can be improved.

[0058] The content of the polyethylene-based resin may be 90% by mass or more, 95% by mass or more, or 100% by mass based on the total amount of the polyethylene film 20.

[0059] The polyethylene film 20 may contain various additives such as a flame retardant, a slip agent, an antiblocking agent, an antioxidant, a light stabilizer, and an adhesion promoter. The polyethylene film 20 may have functions such as gas barrier property, oxygen absorption property, high rigidity, and light shielding property. Such functions may be appropriately changed according to the use of the laminate 100.

[0060] The polyethylene film 20 may be unstretched or may be subjected to a stretching treatment. That the polyethylene film 20 is unstretched means that the absolute value of the molecular orientation degree of the polyethylene film 20 is less than 1.07. When the polyethylene film 20 is unstretched (the absolute value of the molecular orientation degree is less than 1.07), the inorganic oxide layer 14 is less likely to peel off, and the adhesiveness with the sealant layer 30 tends to improve. The absolute value of the molecular orientation degree can be measured by a molecular orientation meter.

[0061] (Inorganic oxide layer) In the laminate 100, the inorganic oxide layer 14 is formed on at least one surface of the polyethylene film 20. The inorganic oxide layer 14 imparts oxygen barrier properties and water vapor barrier properties to the laminate 100. The laminate 100 includes the inorganic oxide layer 14 and the gas barrier coating layer 15 between the polyethylene film 20 and the sealant layer 30, so that when used as a packaging bag, even if it is bent by the contents, the tensile force applied to the gas barrier layer is reduced. As a result, the packaging bag has excellent gas barrier properties.

[0062] Examples of the configuration of the inorganic oxide layer 14 include a vapor deposition layer made of a metal oxide such as aluminum oxide, silicon oxide, magnesium oxide, and tin oxide. From the viewpoints of transparency and barrier properties, the metal oxide may be selected from the group consisting of aluminum oxide, silicon oxide, and magnesium oxide. Further, considering cost, it is selected from aluminum oxide and silicon oxide. Furthermore, by forming the inorganic oxide layer 14 as a barrier film made of a metal oxide, a very thin layer within a range that does not affect the recyclability of the laminate 100 can obtain high barrier properties.

[0063] The film thickness of the vapor deposition layer made of aluminum oxide is preferably 5 nm or more and 30 nm or less. When the film thickness is 5 nm or more, sufficient gas barrier properties can be obtained. Also, when the film thickness is 30 nm or less, it is possible to suppress the generation of cracks due to deformation caused by the internal stress of the thin film and suppress the deterioration of the gas barrier properties. Note that when the film thickness exceeds 30 nm, the cost tends to increase due to an increase in the amount of material used and a longer film formation time, etc., so it is not preferable from an economic point of view. From the same viewpoint as above, the film thickness of the vapor deposition layer is more preferably 7 nm or more and 15 nm or less.

[0064] The film thickness of the inorganic oxide layer made of silicon oxide is preferably 5 nm or more and 100 nm or less. When the film thickness is 5 nm or more, sufficient gas barrier properties can be obtained. Also, when the film thickness is 100 nm or less, even if an external load such as bending or pulling is applied after forming the inorganic oxide layer 21, it is possible to suppress the occurrence of cracks in the inorganic oxide layer 21 and suppress the deterioration of the gas barrier properties. Note that when the film thickness exceeds 100 nm, the cost tends to increase due to an increase in the amount of material used and a longer film formation time, etc., so it is not preferable from an economic point of view. From the same viewpoint as above, the film thickness of the vapor deposition layer is more preferably 10 nm or more and 50 nm or less.

[0065] The inorganic oxide layer 14 can be formed, for example, by vacuum film formation. In vacuum film formation, a physical vapor deposition method or a chemical vapor deposition method can be used. Examples of the physical vapor deposition method include, but are not limited to, vacuum evaporation, sputtering, ion plating, etc. Examples of the chemical vapor deposition method include, but are not limited to, thermal CVD, plasma CVD, photo CVD, etc.

[0066] In the above-mentioned vacuum film formation, a resistance heating type vacuum evaporation method, an EB (Electron Beam) heating type vacuum evaporation method, an induction heating type vacuum evaporation method, a sputtering method, a reactive sputtering method, a dual magnetron sputtering method, a plasma chemical vapor deposition method (PECVD method), etc. are particularly preferably used. However, considering productivity, at present, the vacuum evaporation method is the most excellent. As the heating means of the vacuum evaporation method, it is preferable to use any one of an electron beam heating method, a resistance heating method, and an induction heating method.

[0067] A subbing layer may be formed on the surface of the polyethylene film 20 on the side where the inorganic oxide layer 14 is formed, using a coating liquid for forming a known subbing layer. The subbing layer can be formed, for example, by a coating liquid containing a resin such as an acrylic resin, an epoxy resin, an acrylic urethane resin, a polyester-based polyurethane resin, or a polyether-based polyurethane resin. The subbing layer may be formed by a coating liquid containing an acrylic urethane resin or a polyester-based polyurethane resin from the viewpoints of heat resistance and interlayer adhesion strength.

[0068] The method of applying the coating liquid for forming the subbing layer may be a known coating method, and examples include a dipping method, spraying, a coater, a printing machine, a method using a brush, etc. Also, as the types of coaters and printing machines used in these methods and their coating methods, there are gravure coaters such as a direct gravure method, a reverse gravure method, a kiss reverse gravure method, an offset gravure method, a reverse roll coater, a micro gravure coater, a chamber doctor combined coater, an air knife coater, a dip coater, a bar coater, a comma coater, a die coater, etc.

[0069] The method for drying the undercoat layer is not particularly limited, and examples thereof include a method by natural drying, a method of drying in an oven set at a predetermined temperature, and a method using a dryer attached to a coater, such as an arch dryer, a floating dryer, a drum dryer, an infrared dryer, etc. The drying conditions can be appropriately selected depending on the drying method. For example, in the method of drying in an oven, it may be dried at 60 to 100°C for about 1 second to 2 minutes.

[0070] From the viewpoint of easily obtaining sufficient adhesion between layers, the thickness of the undercoat layer is preferably 0.01 μm or more, 0.03 μm or more, or 0.05 μm or more. From the viewpoint of excellent gas barrier properties, the thickness of the undercoat layer is preferably 5 μm or less, 3 μm or less, or 2 μm or less.

[0071] (Gas barrier coating layer) The gas barrier coating layer 15 plays a role in improving the gas barrier property and protecting the inorganic oxide layer 14. The gas barrier coating layer 15 is not particularly limited, but may contain a hydroxyl group-containing polymer compound. Specifically, it may be a heat-dried product of a composition containing at least one of a hydroxyl group-containing polymer compound and its hydrolyzate, and at least one selected from the group consisting of metal alkoxides, silane coupling agents, and their hydrolyzates.

[0072] The gas barrier coating layer 15 can be formed, for example, using a composition (hereinafter referred to as an overcoat agent) obtained by adding a hydroxyl group-containing polymer compound and a metal alkoxide and / or a silane coupling agent to water or a water / alcohol mixed solution. The overcoat agent can be prepared by mixing, for example, a solution in which a hydroxyl group-containing polymer compound, which is a water-soluble polymer, is dissolved in an aqueous (water or water / alcohol mixed) solvent, and a metal alkoxide and / or a silane coupling agent, either directly or after performing treatments such as hydrolyzing them in advance.

[0073] Examples of the hydroxyl group-containing polymer compound include polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyvinyl pyrrolidone, starch, methyl cellulose, carboxymethyl cellulose, sodium alginate, and the like. Among these, when polyvinyl alcohol (PVA) is used as an overcoat agent for the gas barrier coating layer, it is preferable because of its particularly excellent gas barrier properties.

[0074] Examples of the metal alkoxide include compounds represented by the following general formula (I). M(OR 1 ) m (R 2 ) n-m …(I) In the above general formula (I), R 1 and R 2 are each independently a monovalent organic group having 1 to 8 carbon atoms, and are preferably an alkyl group such as a methyl group or an ethyl group. M represents an n-valent metal atom such as Si, Ti, Al, or Zr. m is an integer of 1 to n. When there are a plurality of R 1 or R 2 , R 1 each other or R 2 each other may be the same or different.

[0075] Specific examples of the metal alkoxide include tetraethoxysilane [Si(OC2H5)4], triisopropoxyaluminum [Al(O-2'-C3H7)3], and the like. Tetraethoxysilane and triisopropoxyaluminum are preferable because they are relatively stable in an aqueous solvent after hydrolysis.

[0076] Examples of the silane coupling agent include compounds represented by the following general formula (II). Si(OR 11 ) p (R 12 ) 3-p R 13 …(II) In the above general formula (II), R 11 represents an alkyl group such as a methyl group or an ethyl group, and R 12represents a monovalent organic group such as an alkyl group, an aralkyl group, an aryl group, an alkenyl group, an alkyl group substituted with an acryloxy group, or an alkyl group substituted with a methacryloxy group, and R 13 represents a monovalent organic functional group, and p represents an integer from 1 to 3. Note that R 11 or R 12 When there are multiple, R 11 each other or R 12 each other may be the same or different. The monovalent organic functional group represented by R 13 includes a glycidyloxy group, an epoxy group, a mercapto group, a hydroxyl group, an amino group, an alkyl group substituted with a halogen atom, or a monovalent organic functional group containing an isocyanate group. The silane coupling agent may be a multimer such as a dimer and a trimer of the above-described silane coupling agent.

[0077] Specific examples of the silane coupling agent include silane coupling agents such as vinyltrimethoxysilane, γ-chloropropylmethyldimethoxysilane, γ-chloropropyltrimethoxysilane, glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and γ-methacryloxypropylmethyldimethoxysilane.

[0078] When the water-soluble polymer is PVA, the content of PVA in the mixed solution may be 20 to 50% by mass or 25 to 40% by mass based on the total solid content of the mixed solution. When the content of PVA is 20% by mass or more, it becomes easier to form the gas barrier coating layer 15. When the content of PVA is 50% by mass or less, the laminate 100 tends to have excellent gas barrier properties.

[0079] To the overcoat agent, known additives such as an isocyanate compound, a dispersant, a stabilizer, a viscosity modifier, and a colorant can be added as necessary within a range that does not impair the gas barrier properties.

[0080] The overcoat agent can be applied by, for example, dipping method, roll coating method, gravure coating method, reverse gravure coating method, air knife coating method, comma coating method, die coating method, screen printing method, spray coating method, gravure offset method, etc. The coating film formed by applying the overcoat agent can be dried by, for example, hot air drying method, hot roll drying method, high-frequency irradiation method, infrared irradiation method, UV irradiation method, or a combination thereof.

[0081] When drying the above coating film, the temperature can be, for example, 50 to 150 °C, and preferably 60 to 100 °C. By setting the temperature during drying within the above range, the generation of cracks in the inorganic oxide layer and the gas barrier coating layer can be further suppressed, and excellent barrier properties can be exhibited.

[0082] The gas barrier coating layer may be formed using an overcoat agent containing a hydroxyl group-containing polymer compound (for example, polyvinyl alcohol resin) and a silane compound. An acid catalyst, an alkali catalyst, a photoinitiator, etc. may be added to the overcoat agent as necessary.

[0083] Examples of the silane compound include silane coupling agents, polysilazanes, siloxanes, etc., and specifically, tetramethoxysilane, tetraethoxysilane, glycidoxypropyltrimethoxysilane, acryloxypropyltrimethoxysilane, hexamethyldisilazane, etc.

[0084] The thickness of the gas barrier coating layer is preferably 50 to 1000 nm, and more preferably 100 to 500 nm. When the thickness of the gas barrier coating layer is 50 nm or more, there is a tendency to obtain more sufficient gas barrier properties, and when it is 1000 nm or less, there is a tendency to maintain sufficient flexibility.

[0085] (Sealant layer) The sealant layer 30 is made of a polyethylene-based resin and is joined by heat fusion (heat sealing) when forming a packaging material such as a packaging bag using the laminate 100. From the viewpoint of heat sealability, the polyethylene-based resin constituting the sealant layer 30 is preferably a low-density polyethylene resin, a linear low-density polyethylene resin, or an ultra-low-density polyethylene resin. Also, from the viewpoint of environmental load, it is preferable that a polyethylene-based resin derived from biomass or a recycled polyethylene-based resin is used for the sealant layer 30. The sealant layer 30 may be composed of an unstretched polyethylene film. A copolymer of ethylene and other monomers can be used for the sealant layer 30 within a range that does not impair the properties of the laminate 100.

[0086] The thickness of the sealant layer 30 can be appropriately changed according to the weight of the contents filled in the packaging material to be produced. For example, when producing a packaging bag filled with 1 g or more and 200 g or less of contents, the thickness of the sealant layer 30 is preferably 20 μm or more and 60 μm or less. By setting the thickness to 20 μm or more, it is possible to prevent the filled contents from leaking due to damage to the sealant layer 30. By setting the thickness to 60 μm or less, the processability of the laminate 100 can be improved.

[0087] As another example, when producing a standing pouch filled with 50 g or more and 2000 g or less of contents, the thickness of the sealant layer 30 is preferably 50 μm or more and 200 μm or less. By setting the thickness to 50 μm or more, it is possible to prevent the filled contents from leaking due to damage to the sealant layer 30. Also, by setting the thickness to 200 μm or less, the processability of the laminate 100 can be improved, and it is more preferably 150 μm.

[0088] (First and second adhesive layers) The first adhesive layer 40 is a layer containing at least one type of adhesive, and is provided between the multilayer film 1 and the polyethylene film 20 to bond the two. The second adhesive layer 50 is a layer containing at least one type of adhesive, and is provided between the polyethylene film 20 and the sealant layer 30 to bond the two. Any adhesive such as a one-component curable or two-component curable urethane-based adhesive can be used for the first adhesive layer 40 and the second adhesive layer 50. These adhesives may contain a layered inorganic compound for the purpose of further enhancing the barrier properties.

[0089] The first adhesive layer 40 and the second adhesive layer 50 can also be formed using an adhesive capable of exhibiting gas barrier properties after curing. In particular, when an adhesive layer that exhibits gas barrier properties and contacts the inorganic oxide layer is formed, it is possible to further suppress a decrease in gas barrier properties due to crack generation in the inorganic oxide layer. Thereby, the gas barrier performance of the laminate 100 can be further improved. Examples of such gas barrier adhesives include epoxy-based adhesives and polyester-polyurethane-based adhesives. Specific examples include "Maxiseal" manufactured by Mitsubishi Gas Chemical Company and "Paslim" manufactured by DIC Corporation.

[0090] The thickness of the first adhesive layer 40 and the second adhesive layer 50 is preferably 0.5 μm or more and 6 μm or less, more preferably 0.8 μm or more and 5 μm or less, and even more preferably 1.0 μm or more and 4.5 μm or less. By setting the thickness of the first adhesive layer 40 and the second adhesive layer 50 to 0.5 μm or more, the adhesiveness of the first adhesive layer 40 and the second adhesive layer 50 can be improved. By setting the thickness of the first adhesive layer 40 and the second adhesive layer 50 to 6 μm or less, the processability of the laminate 100 can be improved.

[0091] The first adhesive layer 40 and the second adhesive layer 50 can be formed by various known methods such as the direct gravure roll coating method, the gravure roll coating method, the kiss coating method, the reverse roll coating method, the fountain method, and the transfer roll coating method.

[0092] <Second Embodiment> Hereinafter, the laminate according to the second embodiment will be described. Regarding points not described below, unless there is an inconsistency, it is the same as the laminate according to the first embodiment. FIG. 4 is a schematic cross-sectional view of the laminate according to the second embodiment of the present disclosure. The laminate 200 shown in FIG. 4 is different from the laminate 100 in that the polyethylene film 20 has a surface layer 20a, an intermediate layer 20b, and a back layer 20c in this order.

[0093] The surface layer 20a preferably contains a polyethylene-based resin having a density of 0.926 g / cm 3 or more, and preferably contains at least one selected from the group consisting of medium-density polyethylene resin and high-density polyethylene resin. The back layer 20c preferably contains at least one selected from the group consisting of medium-density polyethylene resin and high-density polyethylene resin. The intermediate layer 20b preferably contains a high-density polyethylene resin. By these, while having the surface smoothness of the polyethylene film 20, the processing stability and heat resistance when providing the inorganic oxide layer 14 can be improved.

[0094] The density of the entire polyethylene film 20 is preferably 0.942 g / cm 3 or more from the viewpoint of heat resistance.

[0095] The thickness of the intermediate layer 20b preferably has 1 / 3 or more of the entire polyethylene film 20 from the viewpoint of heat resistance.

[0096] In the polyethylene film 20, the probe drop temperature of the intermediate layer 20b is preferably higher than the probe drop temperature of the surface layer 20a and equal to or higher than the probe drop temperature of the back layer 20c. Thereby, the surface of the surface layer 20a of the polyethylene film 20 is less likely to be rough, defects are less likely to occur when forming the inorganic oxide layer 14, and excellent heat resistance tends to be realized. As a result, the laminate 200 is less likely to generate wrinkles, has excellent processing stability, and is more likely to maintain the gas barrier property even after heat sterilization treatment.

[0097] The probe lowering temperature is measured as follows. That is, using an atomic force microscope equipped with a nano-thermal microscope composed of a cantilever (probe) having a heating mechanism, the cantilever (probe) is brought into contact with the surface of a polyethylene film (sample) fixed to a sample stage, and a constant force (contact pressure) is applied to the cantilever (probe) in contact mode, and heating is carried out by applying a voltage. Then, as the sample surface thermally expands, the cantilever (probe) rises. Further heating the cantilever (probe) causes the sample surface to soften and a large change in hardness is observed, and the cantilever (probe) descends and penetrates into the sample surface. The abrupt change in displacement at this time is detected. This voltage change point is the probe lowering start point, and by converting the voltage to temperature, the probe lowering temperature is obtained.

[0098] As described above, the laminate according to the first and second embodiments has been described, but the laminate according to the present disclosure is not limited to the above embodiments. For example, the laminate may include a multilayer film 2 instead of the multilayer film 1. The laminate may further include a printing layer. Also, the laminate may not include one or more of the polyethylene film, the inorganic oxide layer, and the gas barrier coating layer. When the laminate does not include a polyethylene film, the first adhesive layer is unnecessary, and the inorganic oxide layer may be provided on the multilayer film. Also, the gas barrier layer may be provided between the multilayer film and the polyethylene film. In that case, the laminate may be as shown in FIG. 5.

[0099] The laminate 300 shown in FIG. 5 includes an inorganic oxide layer 14 and a gas barrier coating layer 15 between the multilayer film 1 and the polyethylene film 20. Thereby, the obtained packaging bag can suppress the influence of the contents on the gas barrier layer, and there is a tendency for the gas barrier property to be improved. The polyethylene film 20 is arranged such that the surface layer 20a faces the inorganic oxide layer 14 side and the back layer 20c faces the second adhesive layer 50 side.

[0100] <Packaging bag> The packaging bag according to this embodiment is obtained by bag-making a laminate 100. Specifically, while opposing the sealant layers 30, when one laminate 100 is bent or two laminates 100 are overlapped, and the sealant layers 30 at the peripheral portions are joined by heat sealing leaving the filling portion for the contents, a packaging bag made of the laminate 100 can be formed. By performing the above-described joining while sandwiching the bent bottom film, a standing pouch can be formed. In addition, it can be used as various packaging bags such as pillow packaging, four-side seal, three-side seal, and gusset bag. Thus, the laminate 100 can be applied to various packaging bags. The laminate 100 can be suitably used for a packaging bag for applications where boiling treatment (for example, boiling temperature: 95°C or higher) is performed.

[0101] <Packaging product> The packaging product according to this embodiment includes the packaging bag according to the above embodiment and the contents accommodated in the packaging bag. Examples of the contents include food, liquid, pharmaceuticals, and electronic components.

[0102] <Method for selecting a multilayer film for packaging> Hereinafter, the method for selecting a multilayer film for packaging according to this embodiment will be described. In the selection method according to this embodiment, when the multilayer film to be evaluated is heated at 100°C for 15 minutes, a multilayer film in which the MD heat shrinkage rate obtained by the above formula (1) and the TD heat shrinkage rate obtained by the above formula (2) are less than 2% is determined as a qualified product.

[0103] The layer configuration, the materials constituting the multilayer film, the thickness of each layer, etc. may be the same as those of the multilayer film according to the above embodiment.

Examples

[0104] Hereinafter, the present disclosure will be specifically described with reference to examples, but the present disclosure is not limited to these examples.

[0105] [Production of multilayer film] (Examples 1 to 5, Comparative Example 1) The materials shown in Table 1 were prepared. Using each material, a co-extruded multilayer film was produced by the co-extrusion air-cooled inflation method. Specifically, Extruders 1 to 3 were prepared. The materials shown in Tables 2 and 3 were filled into each extruder as the materials constituting the outermost layer, the first and the second polyethylene layers. The filled materials were melt-kneaded (temperature: 190 to 230 °C). The melted materials were extruded from each extruder, laminated, and air-cooled to obtain a film (layer structure: outermost layer / first polyethylene layer / second polyethylene layer). The thickness of each layer was made to be the values shown in Tables 2 and 3. The surface on the second polyethylene layer side of the multilayer film was corona-treated. Thereby, a co-extruded multilayer film having the heat shrinkage rates shown in Tables 2 and 3 was obtained.

[0106] (Examples 6, 7, Comparative Examples 2, 3) A film (layer structure: outermost layer / first polyethylene layer / second polyethylene layer) that was corona-treated in the same manner as in Examples 1 to 5 and Comparative Example 1 was obtained. The film was uniaxially stretched at a magnification of 2 to 7 times in the MD or TD direction. Thereby, a co-extruded multilayer film having the heat shrinkage rates shown in Tables 2 and 3 was obtained.

[0107] (Examples 8, 10 to 13, Comparative Example 4) A film (layer structure: outermost layer / first polyethylene layer / second polyethylene layer) that was corona-treated in the same manner as in Examples 1 to 5 and Comparative Example 1 was obtained. The film was biaxially stretched at a magnification of 2 to 7 times in the MD and TD directions. Thereby, a co-extruded multilayer film having the heat shrinkage rates shown in Tables 2 and 3 was obtained.

[0108] (Example 9) The materials shown in Table 1 were prepared. Using each material, a co-extruded multilayer film was produced by the co-extrusion air-cooled inflation method. Specifically, Extruders 1 to 5 were prepared. The materials shown in Table 2 were filled into each extruder as the materials constituting the outermost layer, the first to fourth polyethylene layers. The filled materials were melt-kneaded (temperature: 190 to 230 °C). The materials melted from each extruder were extruded and laminated, and then air-cooled to obtain a film (layer structure: outermost layer / first polyethylene layer / second polyethylene layer / third polyethylene layer / fourth polyethylene layer). The thickness of each layer was made to be the value shown in Table 2. The surface on the fourth polyethylene layer side of the multilayer film was subjected to corona treatment. The film was biaxially stretched at a magnification of 2 to 7 times in the MD and TD directions. Thereby, a co-extruded multilayer film having the heat shrinkage rate shown in Table 2 was obtained.

[0109]

Table 1

[0110] [Fabrication of laminate] (Examples 1 to 13, Comparative Examples 1 to 4) <Fabrication of polyethylene film> A polyethylene film having a surface layer, an intermediate layer, and a back layer was produced by the co-extrusion air-cooled inflation method. Specifically, Extruders 1 to 3 were prepared. As the materials constituting the surface layer, the intermediate layer, and the back layer, MDPE, HDPE, and MDPE shown in Table 1 were prepared, respectively. MDPE, HDPE, and MDPE were filled into Extruders 1 to 3, respectively. The filled materials were melt-kneaded (temperature: 190 to 230 °C). The materials melted from each extruder were extruded and laminated, and then air-cooled to obtain a polyethylene film (layer structure: MDPE / HDPE / MDPE).

[0111] <Formation of undercoat layer> A composition for forming an undercoat layer was coated on one surface of the polyethylene film by the gravure coating method to form a coating film, and the coating film was dried to form an undercoat layer having a thickness of 0.1 μm.

[0112] <Formation of inorganic oxide layer> A transparent inorganic oxide layer made of silicon oxide with a thickness of 30 nm was formed on the above-described undercoat layer by means of a vacuum evaporation apparatus using an electron beam heating method.

[0113] <Formation of Gas Barrier Coating Layer> An overcoat agent was applied onto the above-described inorganic oxide layer by a gravure coating method to form a coating film, and the coating film was dried to form a gas barrier coating layer with a thickness of 0.3 μm having a gas barrier function.

[0114] The surface of the polyethylene film on the side of the gas barrier coating layer and the sealant layer were pasted together using a urethane-based adhesive by a dry lamination method to obtain a first laminate. The surface of the first laminate on the side opposite to the sealant layer and the surface of the coextruded multilayer film on the side opposite to the outermost layer were pasted together using a urethane-based adhesive by a dry lamination method to obtain a second laminate. The second laminate was aged (temperature: 40 °C, period: 4 days) to obtain a third laminate. The thickness of each adhesive layer was 3 μm.

[0115] [Measurement of Temperature T1] Two samples with a width of 60 mm × a length of 50 mm were cut out from the third laminate. The two samples were overlapped so that the sealant layers faced each other. Heat sealing was performed on the two samples under the following conditions using a seal bar to obtain a fused body. A total of three measurement samples A with a width of 15 mm were collected from the obtained fused body.

[0116] (Sealing Conditions) · Seal bar width: 10 mm · Seal time: 1 second · Seal pressure: 0.2 MPa · Seal temperature: 80 °C

[0117] For each of the three prepared measurement samples A, a peeling test was performed to peel the two samples at a test speed of 300 mm / min in accordance with JIS Z1707:2019 "Heat Seal Strength Test".

[0118] Next, the seal temperature was changed to 10°C higher, and a measurement sample A was prepared in the same manner as above, and a peel test was conducted in the same manner as above. Thereafter, the above operation was repeated. Then, when peeling did not occur between the sealant layers during the peel test of the measurement sample A, and peeling occurred between the polyethylene layer and the sealant layer or the sample broke, the measurement was terminated. And the average value of the seal temperatures of the three measurement samples A on which the peel test was conducted immediately before the measurement sample A was defined as "temperature T1". The results are shown in Tables 2 and 3.

[0119] [Measurement of Temperature T2] Two pieces of the third laminate with a size of 60 mm in width and 50 mm in length were cut out. The two samples were overlapped so that the sealant layers faced each other. Heat sealing was performed on the two samples under the following conditions using a seal bar to obtain a fused body.

[0120] (Sealing Conditions) · Seal bar width: 10 mm · Seal time: 1 second · Seal pressure: 0.2 MPa · Seal temperature: 120°C

[0121] [Appearance Evaluation] The change in the appearance of the fused body was visually confirmed. Next, the seal temperature was changed to 5°C higher, and a fused body was prepared in the same manner as above, and the presence or absence of an appearance change was confirmed. Thereafter, the above operation was repeated. Then, when it was confirmed that there was an appearance change, the measurement was terminated. And the highest heat seal temperature at which it was determined that there was no appearance change was defined as "temperature T2". The results are shown in Tables 2 and 3. In addition, it was determined that there was no appearance change when none of the following states 1 to 6 occurred, and it was determined that there was an appearance change when any of states 1 to 6 occurred.

[0122] State 1: Sticking to the seal bar State 2: Wrinkles in the sealed part State 3: Bubbles in the sealed part State 4: Whitening of the sealed part State 5: Shrinkage of the sealed part State 6: Breakage of the seal part

[0123] [Suitability for bag making] Using a three-side seal automatic bag making machine and a third laminate, a standing pouch composed of two side wall laminates and one two-folded bottom laminate with a peripherally heat-sealed edge was produced. The standing pouch had a height of 240 mm, a width of 160 mm, and a bottom fold-in (depth of the valley fold part of the bottom laminate) of 40 mm. The temperature of the heat seal bar was set to a value obtained by adding 15 °C to the temperature at which the heat seal strength was obtained. 200 bags were produced in continuous operation. The recovery rate of non-defective products without distortion, bubbles, whitening, or tearing in the heat seal part was evaluated according to the following criteria. The results are shown in Tables 2 and 3. The temperature at which the heat seal strength is obtained is measured as follows. That is, using a tensile testing machine, the heat seal strength of the heat seal part of the standing pouch is measured under the condition of a tensile speed of 300 mm / min. The temperature when the heat seal strength of the standing pouch reaches 15 N / 15 mm or more is defined as the temperature at which the heat seal strength is obtained.

[0124] (Criteria) A: The non-defective product rate is 100% B: The non-defective product rate is 95% or more and less than 100% C: The non-defective product rate is less than 95%

[0125] [Heat shrinkage rate] Three samples of the multilayer film cut to A4 size were prepared. A 100×100 mm cross mark indicating MD and TD was made at the center of each sample. Each sample was left standing in a constant temperature bath heated to 100 °C for 15 minutes and then taken out. The dimensions of each side of the mark were measured to calculate the dimensional change rate due to heating. The average value of the dimensional change rates of the three samples was taken as the heat shrinkage rate. The larger value of the heat shrinkage rates of MD and TD was adopted. The results are shown in Tables 2 and 3.

[0126] [Boiling evaluation] Two samples measuring 15 cm × 10 cm were cut out from the third laminate. The two samples were stacked so that their sealant layers faced each other, and triple impulse sealing was performed to form a pouch. 200 ml of tap water was put into the pouch as the contents, and the remaining side was impulse sealed to produce a four-sided sealed pouch (packaging bag). The obtained pouch was subjected to boiling treatment at 95°C for 30 minutes using a boiling treatment device. After boiling, the pouch was opened, the tap water inside was discarded, and it was dried thoroughly. The laminate was cut out from the pouch. The oxygen transmission rate of the cut-out laminate was measured using an oxygen transmission rate measuring device (manufactured by MOCON, device name: OXTRAN 2 / 21). The measurement atmosphere was 23°C and 70% RH. The measurement results were evaluated according to the following criteria. The results are shown in Tables 2 and 3. In the tables, the unit of the oxygen transmission rate is cc / (m 2 ·day).

[0127] (Criteria) A: The oxygen transmission rate is less than 1.0 cc / (m 2 ·day). B: The oxygen transmission rate is 1.0 cc / (m 2 ·day) or more and less than 2.0 cc / (m 2 ·day). C: The oxygen transmission rate is 2.0 cc / (m 2 ·day) or more.

[0128] [Recyclability] The mass ratio of the polyethylene-based resin in the entire third laminate was determined. The mass ratio of the polyethylene-based resin in each example and comparative example was 90% by mass or more. That is, the third laminate of each example and comparative example is excellent in recyclability.

[0129]

Table 2

[0130]

Table 3

Description of Symbols

[0131] 1, 2... multi-layer film, 100, 200, 300... laminate, 10... outermost layer, 11, 11a, 11b... polyethylene layer, 20b... intermediate layer, 30... sealant layer.

Claims

1. An outermost layer containing a thermosetting resin or a thermoplastic resin having a melting point of 160°C or higher, a polyethylene layer containing a polyethylene-based resin, A multilayer film having, When heated at 100°C for 15 minutes, the MD heat shrinkage rate obtained by the following formula (1) and the TD heat shrinkage rate obtained by the following formula (2) are less than 2%, a multilayer film. MD heat shrinkage rate (%) = (MD length before heating - MD length after heating) / MD length before heating × 100 …(1) TD heat shrinkage rate (%) = (TD length before heating - TD length after heating) / TD length before heating × 100 …(2)

2. The multilayer film according to claim 1, wherein the ratio of the thickness of the outermost layer to the total thickness of the multilayer film is 2% or more.

3. Comprising a multilayer film and a sealant layer, The sealant layer contains a polyethylene-based resin, The multilayer film is composed of the multilayer film according to claim 1, In the multilayer film, the polyethylene layer is disposed on the sealant layer side, a laminate.

4. The laminate according to claim 3, further comprising a first adhesive layer between the multilayer film and the sealant layer.

5. Between the first adhesive layer and the sealant layer, from the first adhesive layer side, an intermediate layer and a second adhesive layer are further provided in this order, The laminate according to claim 4, wherein the intermediate layer contains a polyethylene-based resin.

6. The laminate according to claim 3, further comprising a gas barrier layer between the multilayer film and the sealant layer.

7. The laminate according to claim 3, wherein the mass ratio of the polyethylene-based resin in the entire laminate is 90% by mass or more.

8. The laminate according to claim 3, wherein the temperature T1 and the temperature T2 measured by the following measurement method satisfy the following formula (T). T2 - T1 ≧ 35°C...(T) <Measurement method of the temperature T1> A measurement method comprising the following steps (a1) to (c1), and repeating the steps (a1) to (c1) while changing the heat seal temperature from 80°C to a higher temperature in increments of 10°C in the step (b1) until it is determined that peeling does not occur between the sealant layers in the step (c1), and adopting the highest heat seal temperature among the heat seal temperatures at which it is determined that peeling occurs between the sealant layers in the step (c1) as the temperature T1. (a1) A step of preparing two test pieces of the laminate having a size of 60 mm in width × 50 mm in length Step (b1): Stack the two test pieces so that the sealant layers face each other, and perform heat sealing at a seal width of 10 mm, a seal pressure of 0.2 MPa, and a seal time of 1 second to obtain a sample. Step (c1): Perform a peel test on the sample using a tensile testing machine at 300 mm / min in accordance with JIS Z1707:2019. <Method for Measuring the Temperature T2> A measuring method comprising the following steps (a2) to (c2). Until it is determined that there is a change in appearance in step (c2), repeat steps (a2) to (c2) while changing the heat sealing temperature from 120 °C to a higher temperature in increments of 5 °C in step (b2), and adopt the highest heat sealing temperature at which it is determined that there is no change in appearance in step (c2) as the temperature T2. Step (a2): Prepare two test pieces of the laminate having a size of 60 mm in width × 50 mm in length. Step (b2): Stack the two test pieces so that the sealant layers face each other, and perform heat sealing at a seal width of 10 mm, a seal pressure of 0.2 MPa, and a seal time of 1 second to obtain a sample. Step (c2): Check whether there is a change in the appearance of the sample.

9. A packaging bag obtained by bagging the laminate according to any one of claims 3 to 8.

10. A packaging product comprising the packaging bag according to claim 9 and the contents accommodated in the packaging bag.

11. A method for selecting a multilayer film for packaging, comprising an outermost layer containing a thermosetting resin or a thermoplastic resin having a melting point of 160 °C or higher, and a polyethylene layer containing a polyethylene-based resin, When the multilayer film to be evaluated is heated at 100 °C for 15 minutes, a multilayer film having an MD heat shrinkage rate obtained by the following formula (1) and a TD heat shrinkage rate obtained by the following formula (2) of less than 2% is judged as a qualified product. A method for selecting a multilayer film for packaging. MD heat shrinkage rate (%) = (MD length before heating - MD length after heating) / MD length before heating × 100... (1) TD heat shrinkage rate (%) = (TD length before heating - TD length after heating) / TD length before heating × 100... (2)

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