laminate

Abstract

To provide a laminate using polypropylene in the innermost layer and the outermost layer, which can widen tolerance of a heat-sealing temperature.SOLUTION: A laminate comprises at least a substrate layer, a middle layer and a sealant layer, where the substrate layer is arranged on the outermost surface of one side of the laminate, and the sealant layer is arranged on the outermost surface of the other side, all of the substrate layer, the middle layer and the sealant layer contain polypropylene, and a surface on the middle layer side of the substrate layer or at least one surface of the middle layer is equipped with an inorganic oxide layer and a gas-barrier coating layer. When the softening temperature of the substrate layer surface measured by local thermal analysis (LTA) of the substrate layer is T1, and the softening temperature of the sealant layer surface is T2, T1 and T2 satisfy the following conditions. T1>200°C and T2<150°CSELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a laminate and a packaging bag.

Background Art

[0002] A laminate including a biaxially stretched PET (polyethylene terephthalate) film excellent in heat resistance and toughness as a base film and a polyolefin film such as polyethylene or polypropylene as a sealant layer is known (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As the problem of plastic waste is attracting attention worldwide, the demand for environmentally friendly packaging materials is increasing more and more in order to realize a recycling-oriented society. Regarding packaging materials, many global companies have set goals for better plastic resource recycling and have introduced various measures. In addition, in the United States, a recycling route from the collection to the reuse of PE (polyethylene) has begun to be established, and the efforts towards recycling based on monomaterial (single material) are accelerating globally. That is, even in the case of a laminate for packaging that has conventionally been made to have high performance by combining various different materials, monomaterialization has come to be required.

[0005] When converting a conventional multi-material (composite material) packaging material into a monomaterial as a packaging material for retort, a change to a packaging material of a single PP (polypropylene) material can be considered from the viewpoint of sealant characteristics. However, when the packaging material is made into a monomaterial, the melting points of the innermost layer (the layer on the content side) and the outermost layer become very close.

[0006] Since the outermost layer is the part that is most heated during the heat-sealing process when making bags, a film that is difficult to heat-seal is used. However, if a high temperature is applied to fuse the sealant, which is the innermost layer, during the heat-sealing process, the outermost layer may be deformed due to heat shrinkage, causing problems such as the bag being distorted, the transportability decreasing, and the workability during the enclosure of the contents decreasing. Therefore, in a laminate using polypropylene for the innermost and outermost layers, the range (margin) of the heat-sealing temperature that can suppress the heat shrinkage of the laminate while ensuring sufficient seal strength is narrow. Even if the heat-sealing temperature deviates slightly from a predetermined value, a decrease in seal strength and heat shrinkage are likely to occur, and there is a problem that the mass productivity of the packaging bag is likely to decrease.

[0007] The present disclosure has been made in view of the above circumstances, and an object thereof is to provide a laminate using polypropylene for the innermost and outermost layers, which can widen the margin of the heat-sealing temperature, and a packaging bag using the same.

Means for Solving the Problems

[0008] In order to solve the above problems, the present disclosure provides the following laminate and packaging bag. [1] A laminate comprising at least a base material layer, an intermediate layer, and a sealant layer, wherein the base material layer is disposed on one outermost surface of the laminate, and the sealant layer is disposed on the other outermost surface. The base material layer, the intermediate layer, and the sealant layer all contain polypropylene, and an inorganic oxide layer and a gas barrier coating layer are provided on the surface of the base material layer on the intermediate layer side or at least one surface of the intermediate layer. The softening temperature of the surface of the base material layer measured by local thermal analysis (LTA) of the base material layer is T 1 , and the softening temperature of the surface of the sealant layer is T 2 . When 1 and T 2 satisfy the following conditions, the laminate. T 1 > 200 °C T 2 < 150 °C [2] T1 and T 2 The laminate according to [1] above, wherein satisfies the following conditions. (T 1 -T 2 ) > 53 °C [3] When heat sealing is performed under the conditions of an upper seal actual temperature of 145 °C, a lower seal actual temperature of 90 °C, a seal pressure of 0.3 MPa, and a heating time of 1 second, using a heat sealer with a metal upper side and a silicon rubber lower side, with the sealant layers of the laminate facing each other, the seal strength of the resulting seal part is 20 N / 15 mm or more. The laminate according to [1] or [2] above. [4] When heat sealing is performed under the conditions of an upper seal actual temperature of 160 °C, a lower seal actual temperature of 90 °C, a seal pressure of 0.3 MPa, and a heating time of 1 second, using a heat sealer with a metal upper side and a silicon rubber lower side, with the sealant layers of the laminate facing each other, the heat shrinkage rate of the resulting seal part is less than 3%. The laminate according to any one of [1] to [3] above. [5] When heat sealing is performed with the sealant layers of the laminate facing each other, using a heat sealer with a metal upper side and a silicon rubber lower side, under the conditions of a lower seal actual temperature of 90 °C, a seal pressure of 0.3 MPa, and a heating time of 1 second, while varying the upper seal actual temperature, the minimum temperature of the upper seal actual temperature at which the seal strength of the resulting seal part reaches 20 N / 15 mm is T L , and the maximum temperature of the upper seal actual temperature at which the heat shrinkage rate of the resulting seal part can be maintained at less than 3% is T H When, H -T L is 15 °C or more. The laminate according to any one of [1] to [4] above. [6] The laminate according to any one of [1] to [5] above, wherein T 2 satisfies the following conditions. T 2 ≥ 135 °C [7] The laminate according to any one of [1] to [6] above, wherein each of the base material layer, the intermediate layer, and the intermediate layer and the sealant layer are adhered via an adhesive layer using a two-component curable urethane-based adhesive. [8] The laminate according to [7] above, wherein at least one of the base material layer, the intermediate layer, and the intermediate layer and the sealant layer is adhered via an adhesive layer using a solvent-free two-component curable urethane-based adhesive. [9] A packaging bag formed by bagging the laminate according to any one of [1] to [8] above.

Advantages of the Invention

[0009] According to the present disclosure, there can be provided a laminate using polypropylene for the innermost layer and the outermost layer, which can widen the margin of the heat seal temperature, and a packaging bag using the same.

Brief Description of the Drawings

[0010]

Figure 1

Modes for Carrying Out the Invention

[0011] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the drawings as appropriate. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant descriptions are omitted. Also, the dimensional ratios in the drawings are not limited to the ratios shown.

[0012] <Laminate> FIG. 1 is a schematic cross-sectional view showing a laminate according to an embodiment. The laminate 100 shown in FIG. 1 includes a base material layer 11, an intermediate layer 12, and a sealant layer 13 in this order. The base material layer 11 and the intermediate layer 12, and the intermediate layer 12 and the sealant layer 13 may be adhered with an adhesive layer S, respectively. The base material layer, the intermediate layer, and the sealant layer all contain polypropylene. The base material layer, the intermediate layer, and the sealant layer may include a polypropylene film. From the viewpoint of improving the gas barrier properties against water vapor and oxygen, the laminate includes an inorganic oxide layer and a gas barrier coating layer on the surface of the base material layer 11 on the intermediate layer 12 side, or at least one surface of the intermediate layer 12. The base material layer 11 is disposed on one outermost surface of the laminate 100, and the sealant layer 13 is disposed on the other outermost surface of the laminate 100. The base material layer 11 is also referred to as the outermost layer of the laminate 100 (the layer opposite to the content side when used as a packaging bag). The sealant layer 13 is also referred to as the innermost layer of the laminate 100 (the layer on the content side when used as a packaging bag).

[0013] [Base material layer 11] The base material layer is a layer that serves as one of the supports and contains polypropylene. The base material layer may include a polypropylene film and may be made of a polypropylene film.

[0014] The polypropylene film may be an acid-modified polypropylene film obtained by graft-modifying polypropylene with an unsaturated carboxylic acid, an acid anhydride of an unsaturated carboxylic acid, an ester of an unsaturated carboxylic acid, or the like. As the polypropylene, polypropylene-based resins such as homopolypropylene resin (PP), propylene-ethylene random copolymer, propylene-ethylene block copolymer, and propylene-α olefin copolymer can be used. Here, in the case of a random copolymer or a block copolymer, since the regularity of the molecular structure is disturbed due to the inclusion of different components, the softening temperature tends to decrease. Therefore, the polypropylene constituting the base material layer is preferably homopolypropylene.

[0015] Various additives such as flame retardants, slip agents, antiblocking agents, antioxidants, light stabilizers, tackifiers, antistatic agents, etc. may be added to the polypropylene film constituting the base material layer.

[0016] From the viewpoints of impact resistance, heat resistance, water resistance, dimensional stability, etc., the polypropylene film constituting the base material layer is preferably a stretched film. Thereby, it is possible to suppress the heat fusion of the base material layer in the heat sealing process during bag making. In addition, the laminate can be more suitably used for applications subjected to retort treatment or boiling treatment. The stretching method is not particularly limited, and any method may be used as long as a film with stable dimensions can be supplied, such as stretching by inflation, or uniaxial stretching, biaxial stretching, etc.

[0017] The thickness of the base material layer is not particularly limited. Depending on the application, the thickness can be set to 6 to 200 μm, but from the viewpoints of reducing material for environmental load reduction and obtaining excellent heat resistance, impact resistance, and gas barrier properties, it may be 9 to 50 μm, it may be 12 to 38 μm, or it may be 18 to 30 μm.

[0018] The base material layer may be subjected to various pretreatment such as corona treatment, plasma treatment, frame treatment, etc. on its laminated surface within a range that does not impair the barrier performance, or a coating layer such as an easy adhesion layer may be provided.

[0019] The surface softening temperature T 1 (°C) of the base material layer measured by local thermal analysis (LTA) needs to satisfy the following conditions. T 1 >200 °C T 1 Since T is higher than 200 °C, even when the heat sealing temperature is increased (for example, about 160 °C), the generation of heat shrinkage and distortion of the laminate can be suppressed. Therefore, the margin of the heat sealing temperature (heat sealing margin) of the laminate can be widened. From the viewpoint of further enhancing the above effects, T 1It may be 201°C or higher, 203°C or higher, 205°C or higher. T 1 The upper limit value of 1 is not particularly limited, and for example, it may be 220°C or lower. The softening temperature of the substrate surface may be 200°C or higher and 220°C or lower, 201°C or higher and 220°C or lower, 203°C or higher and 220°C or lower, 205°C or higher and 220°C or lower. The softening temperature of the substrate layer surface can be adjusted, for example, by the degree of crystallinity, molecular weight, and blending ratio of the copolymer. Note that the softening temperature can also be measured by differential scanning calorimetry (DSC: Differential Scanning Calorimetry), but the softening temperature measured by DSC is the softening temperature including information on other layers such as the intermediate layer, not just the surface of the substrate layer or the sealant layer. By measuring the softening temperature by LTA, the softening temperature of the surface of the substrate layer or the sealant layer can be selectively measured.

[0020] The melting point (melting peak temperature) of the substrate layer measured by differential scanning calorimetry (DSC) may be over 161°C, 163°C or higher, 165°C or higher. When the melting point is over 161°C, there is a tendency to obtain a desired surface softening temperature (over 200°C). The upper limit value of the melting point is not particularly limited, and for example, it may be 180°C or lower. The melting point of the substrate layer may be over 161°C and 180°C or lower, 163°C or higher and 180°C or lower, 165°C or higher and 180°C or lower. The melting point of the substrate layer can be adjusted, for example, by the degree of crystallinity, molecular weight, and blending ratio of the copolymer. The melting point of the substrate layer can be measured using a differential scanning calorimeter (for example, manufactured by Hitachi High-Tech Science Corporation, product name: DSC7000X) under the condition of a heating rate of 10°C / min.

[0021] [Softening Temperature Measurement Method] The softening temperature refers to the temperature at which a substance such as resin exhibits softening behavior. In the evaluation of the softening temperature in this embodiment, local thermal analysis (LTA) using an atomic force microscope is employed, and heating of the sample is performed by applying a voltage to a cantilever having a heater. In local thermal analysis (LTA), after measuring the shape of the measurement sample, a constant force (contact pressure) is applied to the sample surface with the cantilever at a predetermined location of the sample, heating is performed while keeping the contact pressure constant, and the temperature at which the height position (Z displacement) of the cantilever becomes maximum due to the change in the hardness of the sample surface before and after heating is calculated as the softening temperature. The height position of the cantilever changes due to the upward movement of the cantilever in the vertical direction due to the thermal expansion of the sample surface and the downward movement of the cantilever in the vertical direction due to the softening of the sample surface. That is, the sample reaches the softening temperature immediately before the position of the cantilever drops. Therefore, by converting the applied voltage of the heater of the cantilever when the height position of such a cantilever becomes maximum into temperature, the local and surface-near softening temperature in the nanoscale region can be known.

[0022] The apparatus uses an atomic force microscope (AFM) manufactured by Oxford Instruments, MFP-3D-SA (trade name), and Ztherm, which is a local thermal analysis option. The AC mode (tapping mode) is used for shape measurement, and the contact mode is used for softening temperature measurement.

[0023] The cantilever used is AN2-200 (trade name) manufactured by Anasys Instruments with a spring constant specification of 0.5 to 3.5 N / m.

[0024] The voltage application acceleration (heating rate) of the cantilever in the measurement of the softening temperature is set to 0.5 V / second.

[0025] In Ztherm, the contact pressure of the cantilever (the change in the amount of deflection of the cantilever) is measured while being constantly controlled. However, since the amount of deflection of the cantilever changes due to the applied voltage even without contacting the sample, it is necessary to control the contact pressure after subtracting the amount of deflection of the cantilever caused by the applied voltage. Ztherm has a Detrend correction function for obtaining the change in the amount of deflection of the cantilever with respect to the applied voltage. With the cantilever not in contact with the sample surface, the maximum applied voltage used for measurement is applied to the cantilever and Detrend correction is performed. In this embodiment, after the shape measurement and before the softening temperature measurement, Detrend correction is performed at the maximum applied voltage used for measurement and the voltage application acceleration (heating rate) of 0.5 V / second, and then the measurement is carried out. The contact pressure is set to 0.5 V.

[0026] The set value of the downward displacement amount of the cantilever for stopping the measurement is 50 nm.

[0027] The softening point is the point where the height (Z displacement) of the cantilever in the vertical direction is the maximum, and the applied voltage at this point is read.

[0028] In order to convert the applied voltage of the cantilever heater into the softening temperature, a calibration curve of the applied voltage and the melting point (melting peak temperature) is created. As calibration samples, samples for which the values of the melting point (melting peak temperature) have already been measured with a differential scanning calorimeter (DSC) are used. For each calibration sample, the softening temperature is measured while changing the measurement position, and a calibration curve is created by approximating the average value of the applied voltage at the softening point and the melting point (melting peak temperature) with a cubic function by the least squares method. The calibration samples are polycaprolactone pellets (melting point: 60 °C), low-density polyethylene pellets (melting point: 112 °C), polypropylene pellets (melting point: 166 °C), and biaxially stretched films of polyethylene terephthalate (melting point: 255 °C), and cross-section samples created in an environment below the glass transition temperature are used for each. For the creation of the cross-section samples, an ultramicrotome and a cryo system are used, and cross-section cutting is performed on polycaprolactone at -80 °C, low-density polyethylene at -140 °C, polypropylene at -40 °C, and polyethylene terephthalate at room temperature of 25 °C.

[0029] Using this calibration curve of the applied voltage and the melting point (melting peak temperature), the applied voltage at the softening point is converted into temperature to obtain the softening temperature.

[0030] [Adhesion layer] When the laminate includes an inorganic oxide layer on the base material layer, an adhesion layer (anchor coat layer) may be provided on the surface of the base material layer where the inorganic oxide layer is laminated. The adhesion layer is provided on the base material layer, and two effects can be obtained: improvement of the adhesion performance between the base material layer and the inorganic oxide layer, and improvement of the smoothness of the surface of the base material layer. Note that by improving the smoothness, it becomes easier to form the inorganic oxide layer uniformly without defects, and it is easier to exhibit high barrier properties. The adhesion layer can be formed using an anchor coat agent.

[0031] Examples of the anchor coat agent include polyester-based polyurethane resins and polyether-based polyurethane resins. From the viewpoints of heat resistance and interlayer adhesion strength, polyester-based polyurethane resins are preferred as the anchor coat agent.

[0032] The thickness of the adhesion layer is not particularly limited, but it is preferably in the range of 0.01 to 5 μm, more preferably in the range of 0.03 to 3 μm, and particularly preferably in the range of 0.05 to 2 μm. When the thickness of the adhesion layer is equal to or greater than the above lower limit value, sufficient interlayer adhesion strength tends to be obtained. On the other hand, when it is equal to or less than the above upper limit value, the desired gas barrier property tends to be easily exhibited.

[0033] As a method for coating the adhesion layer on the base material layer, known coating methods can be used without particular limitation, including dipping method; methods using spray, coater, printing machine, brush, etc. In addition, as for the types of coaters and printing machines used in these methods and their coating methods, there are gravure coaters such as direct gravure method, reverse gravure method, kiss reverse gravure method, offset gravure method, reverse roll coater, micro gravure coater, chamber doctor combined coater, air knife coater, dip coater, bar coater, comma coater, die coater, etc.

[0034] The coating amount of the adhesion layer is such that the mass per 1 m 2 after coating and drying the anchor coating agent is preferably 0.01 to 5 g / m 2 and more preferably 0.03 to 3 g / m 2 When the mass per 1 m 2 after coating and drying the anchor coating agent is equal to or greater than the above lower limit, film formation tends to be sufficient. On the other hand, when it is equal to or less than the above upper limit, it tends to dry sufficiently and it is difficult for the solvent to remain.

[0035] The method for drying the adhesion 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 the coater, such as an arch dryer, a floating dryer, a drum dryer, an infrared dryer, etc. Further, as the drying conditions, they can be appropriately selected according to the drying method. For example, in the method of drying in an oven, it is preferable to dry at a temperature of 60 to 100 °C for about 1 second to 2 minutes.

[0036] As the adhesion layer, instead of the above polyurethane resin, a polyvinyl alcohol-based resin can be used. The polyvinyl alcohol-based resin may be any resin having a vinyl alcohol unit formed by saponifying a vinyl ester unit. Examples thereof include polyvinyl alcohol (PVA) and ethylene-vinyl alcohol copolymer (EVOH).

[0037] When a polyvinyl alcohol-based resin is used as the adhesion layer, examples of the method for forming the adhesion layer include coating using a polyvinyl alcohol-based resin solution and multilayer extrusion.

[0038] [Inorganic Oxide Layer] The inorganic oxide layer contributes to the improvement of gas barrier properties. Examples of the inorganic oxide contained in the inorganic oxide layer include aluminum oxide, silicon oxide, magnesium oxide, tin oxide, etc. From the viewpoints of transparency and barrier properties, the inorganic oxide may be selected from the group consisting of aluminum oxide, silicon oxide, and magnesium oxide. Also, from the viewpoint of excellent tensile stretchability during processing, it is preferable that the inorganic oxide layer is a layer using silicon oxide. By using an inorganic oxide layer containing silicon oxide, a very thin layer within a range that does not affect the recyclability of the laminate can obtain higher barrier properties.

[0039] When the inorganic oxide layer contains silicon oxide, the O / Si ratio of the inorganic oxide layer is preferably 1.7 or more. When the O / Si ratio is 1.7 or more, the content ratio of metallic Si is suppressed and good transparency is easily obtained. Also, the O / Si ratio is preferably 2.0 or less. When the O / Si ratio is 2.0 or less, the crystallinity of SiO becomes high and it is possible to prevent the inorganic oxide layer from becoming too hard, and good tensile resistance can be obtained. Thereby, it is possible to suppress the occurrence of cracks in the inorganic oxide layer when laminating the gas barrier coating layer. Further, even after being formed into a packaging bag, the base material layer or the intermediate layer may shrink due to heat during boiling or retort treatment, but when the O / Si ratio is 2.0 or less, the inorganic oxide layer easily follows the above shrinkage, and a decrease in barrier properties can be suppressed. From the viewpoint of obtaining these effects more sufficiently, the O / Si ratio of the inorganic oxide layer is preferably 1.75 or more and 1.9 or less, and more preferably 1.8 or more and 1.85 or less.

[0040] The O / Si ratio of the inorganic oxide layer can be determined by X-ray photoelectron spectroscopy (XPS). For example, the measuring apparatus can be an X-ray photoelectron spectrometer (manufactured by JEOL Ltd., trade name: JPS-90MXV), the X-ray source can use non-monochromatized MgKα (1253.6 eV), and measurement can be performed with an X-ray output of 100 W (10 kV - 10 mA). For quantitative analysis to obtain the O / Si ratio, relative sensitivity factors of 2.28 for O1s and 0.9 for Si2p can be used.

[0041] The film thickness of the inorganic oxide layer is preferably 10 nm or more and 50 nm or less. When the film thickness is 10 nm or more, sufficient water vapor barrier properties can be obtained. Also, when the film thickness is 50 nm or less, it is possible to suppress the occurrence of cracks due to deformation caused by internal stress of the thin film and suppress a decrease in water vapor barrier properties. Note that when the film thickness exceeds 50 nm, the cost tends to increase due to an increase in the amount of material used and a long film formation time, etc., which is not preferable from an economic viewpoint. From the same viewpoint as above, the film thickness of the inorganic oxide layer is more preferably 20 nm or more and 40 nm or less.

[0042] The inorganic oxide layer can be formed, for example, by vacuum deposition. In vacuum deposition, 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.

[0043] In the above-mentioned vacuum deposition, 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.

[0044] [Gas barrier coating layer] The gas barrier coating layer is for protecting the inorganic oxide layer, contributing to the improvement of the gas barrier property, and exhibiting a high gas barrier property due to the synergistic effect with the inorganic oxide layer. The gas barrier coating layer may be a layer formed using a gas barrier coating layer forming composition containing at least one selected from the group consisting of a hydroxyl group-containing polymer compound, a metal alkoxide, a silane coupling agent, and their hydrolyzates.

[0045] The gas barrier coating layer can be formed using a composition for forming a gas barrier coating layer (hereinafter also referred to as a coating agent) mainly composed of an aqueous solution or a water / alcohol mixed solution containing at least one selected from the group consisting of a hydroxyl group-containing polymer compound, a metal alkoxide, a silane coupling agent, and their hydrolyzates. From the viewpoint of more sufficiently maintaining the gas barrier property after heat water treatment such as retort treatment, the coating agent preferably contains at least a silane coupling agent or its hydrolyzate, and more preferably contains at least one selected from the group consisting of a hydroxyl group-containing polymer compound, a metal alkoxide, and their hydrolyzates, and a silane coupling agent or its hydrolyzate, and still more preferably contains a hydroxyl group-containing polymer compound or its hydrolyzate, a metal alkoxide or its hydrolyzate, and a silane coupling agent or its hydrolyzate. The coating agent can be prepared, for example, by mixing 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 with a product obtained by directly treating or previously hydrolyzing a metal alkoxide and a silane coupling agent.

[0046] Examples of the hydroxyl group-containing polymer compound used in the coating agent include polyvinyl alcohol, polyvinyl pyrrolidone, starch, methyl cellulose, carboxymethyl cellulose, sodium alginate, etc. Among these, when polyvinyl alcohol (PVA) is used as the coating agent for the gas barrier coating layer, it is preferable because the gas barrier property is particularly excellent.

[0047] Examples of the metal alkoxide include tetraethoxysilane [Si(OC 2 H 5 ) 4 , triisopropoxyaluminum [Al(O-2’-C 3 H 7 ) 3 , etc. Tetraethoxysilane and triisopropoxyaluminum are preferable because they are relatively stable in an aqueous solvent after hydrolysis.

[0048] Examples of the silane coupling agent include vinyltrimethoxysilane, γ-chloropropylmethyldimethoxysilane, γ-chloropropyltrimethoxysilane, glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane and the like. The silane coupling agent may be a multimer thereof.

[0049] In the coating agent, within a range not impairing the gas barrier property, it is also possible to add an isocyanate compound or known additives such as a dispersant, a stabilizer, a viscosity modifier, and a colorant as necessary. An acid catalyst, an alkali catalyst, a photoinitiator or the like may be added to the coating agent as necessary.

[0050] From the viewpoint of obtaining excellent gas barrier properties while making the content of polypropylene in the laminate 90% by mass or more, the thickness of the gas barrier coating layer is preferably 50 to 1000 nm, more preferably 100 to 500 nm. When the thickness of the gas barrier coating layer is 50 nm or more, there is a tendency that more sufficient gas barrier properties can be obtained, and when it is 1000 nm or less, there is a tendency that sufficient flexibility can be maintained.

[0051] The coating agent for forming the gas barrier coating layer can be applied, for example, by a dipping method, a roll coating method, a gravure coating method, a reverse gravure coating method, an air knife coating method, a comma coating method, a die coating method, a screen printing method, a spray coating method, a gravure offset method or the like. The coating film formed by applying this coating agent can be dried, for example, by a hot air drying method, a hot roll drying method, a high frequency irradiation method, an infrared irradiation method, a UV irradiation method, or a combination thereof.

[0052] When drying the above coating film, the temperature can be, for example, 50 to 150°C, preferably 70 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.

[0053] [Intermediate layer 12] Regarding the configuration of the intermediate layer, the above content described for the configuration of the base material layer can be appropriately referred to. Further, the above-described adhesion layer, inorganic oxide layer, and gas barrier coating layer may be provided on at least one surface of the intermediate layer. By providing the laminate with an intermediate layer, deformation of the laminate during bag making can be further reduced as compared with the case where the intermediate layer is not provided.

[0054] The thickness of the intermediate layer is not particularly limited, but may be the same as the thickness of the base material layer. The ratio of the thicknesses of these layers (thickness of the base material layer / thickness of the intermediate layer) may be 1.00 or more, may be more than 1.00, may be 1.25 or more, or may be 1.50 or more. The base material layer is a part that directly contacts or is close to the heat seal bar during heat sealing, and is a part that is particularly heated among the layers of the laminate. Therefore, it is likely to shrink thermally during heat sealing. Therefore, by making the base material layer thicker than the intermediate layer, thermal shrinkage of the base material layer can be suppressed.

[0055] [Printing layer] The laminate may include a printing layer. The printing layer can be provided on at least one surface of the base material layer or on at least one surface of the intermediate layer. The printing layer is provided at a position visible from the outside of the laminate for the purpose of displaying information about the contents, identifying the contents, improving concealment, or improving the design of the packaging bag. The printing method and printing ink are not particularly limited, and are appropriately selected from known printing methods and printing inks in consideration of printability on the film, design properties such as color tone, adhesion, and safety as a food container. As the printing method, for example, a gravure printing method, an offset printing method, a gravure offset printing method, a flexographic printing method, an inkjet printing method, etc. can be used. Among them, the gravure printing method can be preferably used from the viewpoints of productivity and high definition of the pattern.

[0056] In order to enhance the adhesion of the printing layer, various pretreatment processes such as corona treatment, plasma treatment, and flame treatment may be performed on the surface of the layer provided with the printing layer, or a coating layer such as an easy - adhesion layer may be provided. The surface of the layer provided with the printing layer includes the surface of the base material layer or the intermediate layer, and the surface of the gas - barrier coating layer.

[0057] [Adhesive layer S] The base material layer and the intermediate layer can be laminated via an adhesive layer. As the material of the adhesive, for example, polyester - isocyanate - based resin, urethane resin, polyether - based resin, etc. can be used. For using the packaging bag for retort applications, a two - component curable urethane - based adhesive with retort resistance can be preferably used. When a two - component curable urethane - based adhesive is used, the cross - linking density is higher than when a one - component curable urethane - based adhesive is used, so it is easier to obtain high adhesion even after retort treatment. Also, as the two - component curable urethane - based adhesive, a solvent - free two - component curable urethane - based adhesive may be used. Note that from the perspective of environmental consideration, the adhesive may not contain 3 - glycidyloxypropyltrimethoxysilane (GPTMS).

[0058] The thickness of the adhesive layer is not particularly limited. For example, it may be 0.5 to 5 μm, or it may be 0.3 to 7 μm. When the thickness of the adhesive layer is 0.5 μm or more, it is easy to improve the adhesion between the base material layer and the intermediate layer. When it is 5 μm or less, it is easy to improve the barrier property and recyclability of the laminate.

[0059] [Sealing layer 13] The sealing layer is a layer that imparts heat - sealability in the laminate and contains polypropylene. The sealing layer may contain a polypropylene film and may be composed of a polypropylene film.

[0060] The polypropylene film may be an acid-modified polypropylene film obtained by graft-modifying polypropylene with an unsaturated carboxylic acid, an acid anhydride of an unsaturated carboxylic acid, an ester of an unsaturated carboxylic acid, or the like. As the polypropylene, polypropylene-based resins such as homopolypropylene resin (PP), propylene-ethylene random copolymer, propylene-ethylene block copolymer, and propylene-α-olefin copolymer can be used.

[0061] From the viewpoint of enhancing the sealing property by heat sealing, the polypropylene film constituting the sealant layer is preferably an unstretched film.

[0062] Various additives such as a flame retardant, a slip agent, an antiblocking agent, an antioxidant, a light stabilizer, a tackifier, and an antistatic agent may be added to the polypropylene film constituting the sealant layer.

[0063] The thickness of the sealant layer is determined by the mass of the contents, the shape of the packaging bag, etc., but may generally be a thickness of 30 to 150 μm, may be a thickness of 40 to 100 μm, and may be a thickness of 50 to 80 μm.

[0064] As a method for forming the sealant layer, a dry lamination method in which a film-shaped sealant layer made of the above-mentioned polypropylene is bonded with an adhesive such as a one-component curing type or two-component curing type urethane-based adhesive, a non-solvent lamination method in which a film-shaped sealant layer is bonded using a non-solvent adhesive, an extrusion lamination method in which the above-mentioned polypropylene is heated and melted, extruded in a curtain shape, and bonded, etc. can all be formed by known lamination methods. In the non-solvent lamination method, a non-solvent type two-component curing type urethane-based adhesive may be used as the non-solvent adhesive. These lamination methods can also be used when laminating the base material layer and the intermediate layer.

[0065] When the non-solvent lamination method is used, since the adhesive component does not contain an organic solvent, the amount of residual solvent in the laminate can be reduced. Also, when producing a laminate comprising a base layer made of stretched polypropylene and an intermediate layer made of stretched polypropylene using the dry lamination method, in order to prevent heat shrinkage of the laminate compared to a laminate using a polyester-based material, it is necessary to lower the temperature during its drying. In this case, the solvent in the adhesive may not be sufficiently volatilized and removed, remaining in the laminate, and an odor due to the residual solvent may remain. By using a solvent-free adhesive, such an amount of residual solvent can be further reduced.

[0066] Also, by using the non-solvent lamination method, the adhesive layer can be made thinner compared to the case of using the dry lamination method. Thereby, the content ratio of polypropylene in the entire laminate can be further improved. Furthermore, by making the adhesive layer thinner, when performing heat sealing, the heat conduction from the heat-sealing bar is improved, the sealing time and sealing temperature can be reduced, and the occurrence of wrinkles and the like associated with heat sealing can be suppressed. Such a laminate is suitable for producing a mono-material packaging bag.

[0067] The sealant layer and the intermediate layer can be laminated via the adhesive layer S described above. The adhesion between the sealant layer and the intermediate layer is performed by applying an adhesive to the intermediate layer and then laminating the sealant layer. When the adhesive is a solvent-free two-component curable urethane-based adhesive, the intermediate layer is not subjected to the heat load during solvent drying. Therefore, since it is difficult to cause breakage of the inorganic oxide layer or the gas barrier coating layer due to dimensional changes in the intermediate layer, the barrier properties are less likely to deteriorate.

[0068] The sealant layer needs to satisfy the following conditions for the softening temperature T 2 (°C) of the surface measured by local thermal analysis (LTA). T 2 <150 °C T 2Since it is less than 150°C, even when the heat seal temperature is lowered (for example, to about 145°C), sufficient seal strength can be obtained. Therefore, the heat seal margin of the laminate can be widened. From the viewpoint of further enhancing the above effects, T 2 may be 148°C or lower, and may be 147°C or lower. On the other hand, from the viewpoint of suppressing the fusion of the sealant layers and the bleed-out of additives during retort processing and boiling processing, T 2 may be 80°C or higher, and may be 100°C or higher. The softening temperature T 2 of the surface of the sealant layer may be 80°C or higher and less than 150°C, may be 80°C or higher and 148°C or lower, may be 80°C or higher and 147°C or lower, may be 100°C or higher and less than 150°C, may be 100°C or higher and 148°C or lower, and may be 100°C or higher and 147°C or lower. The softening temperature of the surface of the sealant layer can be adjusted, for example, by the degree of crystallinity, molecular weight, and blending ratio of the copolymer. The method for measuring the softening temperature is as described above.

[0069] Also, from the viewpoint of suppressing the occurrence of inner surface fusion during retort processing (adhesion of unsealed heat seal surfaces due to heat during retort processing), T 2 may satisfy the following conditions. T 2 ≥135°C

[0070] In the laminate, the difference (T 1 ) between the softening temperature T 2 of the surface of the base material layer and the softening temperature T 1 of the surface of the sealant layer (T 2 ) preferably satisfies the following conditions. (T 1 -T 2 )>53°C T 1 -T 2 If it is greater than 53°C, it is possible to widen the margin of the heat seal temperature that can suppress the heat shrinkage of the laminate while ensuring sufficient seal strength. From the viewpoint of further enhancing the above effects, T 1 -T 2 may be 55°C or higher, may be 58°C or higher, and may be 60°C or higher.

[0071] The laminate may be such that 90% by mass or more of the total amount of the laminate is polypropylene. Thus, the laminate can be said to be a packaging material made of a single material (monomaterial) and is excellent in recyclability. From the viewpoint of further improving recyclability, the content of polypropylene in the laminate may be 95% by mass or more based on the total amount of the laminate.

[0072] When heat sealing is performed on the laminate with the sealant layers facing each other, using a heat sealer with a metal upper side and a silicon rubber lower side, under the conditions of an actual upper seal temperature of 145°C, an actual lower seal temperature of 90°C, a seal pressure of 0.3 MPa, and a heating time of 1 second, it is preferable that the seal strength of the obtained seal portion is 20 N / 15 mm or more, and more preferably 25 N / 15 mm or more. By satisfying the above conditions, the heat sealing margin of the laminate can be widened.

[0073] When heat sealing is performed on the laminate with the sealant layers facing each other, using a heat sealer with a metal upper side and a silicon rubber lower side, under the conditions of an actual upper seal temperature of 160°C, an actual lower seal temperature of 90°C, a seal pressure of 0.3 MPa, and a heating time of 1 second, it is preferable that the heat shrinkage rate of the obtained seal portion is less than 3%, and more preferably 2.8% or less. By satisfying the above conditions, the heat sealing margin of the laminate can be widened.

[0074] When heat sealing is performed on the laminate with the sealant layers facing each other, using a heat sealer with a metal upper side and a silicon rubber lower side, under the conditions of an actual lower seal temperature of 90°C, a seal pressure of 0.3 MPa, and a heating time of 1 second, while varying the actual upper seal temperature, and the minimum temperature of the actual upper seal temperature at which the seal strength of the obtained seal portion reaches 20 N / 15 mm is T L and the maximum temperature of the actual upper seal temperature at which the heat shrinkage rate of the obtained seal portion can be maintained at less than 3% is T H then, T H -T LIt is preferably 15°C or higher, more preferably 20°C or higher. By satisfying the above conditions, the heat seal margin of the laminate can be widened.

[0075] The laminate according to this embodiment has a wide margin of heat seal temperature that can suppress the heat shrinkage of the laminate while ensuring sufficient seal strength. Therefore, it is possible to suppress the deterioration of packaging material quality such as bag-making distortion and reduction of barrier properties during heat sealing, and the reduction of mass productivity of the packaging bag. That is, according to the present disclosure, it is possible to provide a laminate (packaging laminate) having a wide heat seal margin and excellent mass production stability of the packaging bag even with a PP single-material packaging material.

[0076] <Packaging bag> The packaging bag is formed by bag-making the above-described laminate, and there is no particular limitation on the shape. For example, it may be formed into a bag shape by folding a single laminate in half so that the sealant layers face each other and then heat-sealing three sides, or it may be formed into a bag shape by overlapping two laminates so that the sealant layers face each other and then heat-sealing four sides. It may also be a self-standing standing pouch that overlaps two laminates so that the sealant layers face each other and seals with a bottom material sandwiched therebetween. The packaging bag can contain contents such as food and pharmaceuticals as the contents and can be subjected to heat sterilization treatment such as retort treatment and boiling treatment.

[0077] Retort processing is generally a method of sterilizing microorganisms such as molds, yeasts, and bacteria under pressure to preserve foods, pharmaceuticals, etc. Usually, a packaging bag containing foods, etc. is subjected to a pressure sterilization treatment under the conditions of 105 to 140 °C and 0.15 to 0.30 MPa for 10 to 120 minutes. Retort devices include a steam type that uses heating steam and a hot water type that uses pressurized heated water, and they are appropriately selected according to the sterilization conditions of foods, etc. that are the contents. Boiling treatment is a method of sterilizing by moist heat to preserve foods, pharmaceuticals, etc. Usually, although it depends on the contents, a packaging bag containing foods, etc. is subjected to a moist heat sterilization treatment under the conditions of 60 to 100 °C and atmospheric pressure for 10 to 120 minutes. Boiling treatment is usually carried out at 100 °C or lower using a hot water tank. As methods, there are a batch type in which it is immersed in a hot water tank at a constant temperature, treated for a certain period of time, and then taken out, and a continuous type in which it is passed through the hot water tank in a tunnel type for treatment.

[0078] Since the above packaging bag has little deformation during bag making, it is excellent in transportability and workability during content enclosing.

Example

[0079] The present disclosure will be described in more detail by the following examples, but the present disclosure is not limited to these examples.

[0080] <Preparation of Composition for Adhesion Layer Formation> An acrylic polyol and tolylene diisocyanate were mixed so that the number of NCO groups of tolylene diisocyanate was equal to the number of OH groups of the acrylic polyol, and it was diluted with ethyl acetate so that the total solid content (the total amount of acrylic polyol and tolylene diisocyanate) was 5% by mass. To the diluted mixture, β-(3,4-epoxycyclohexyl)trimethoxysilane was further added so as to be 5 parts by mass with respect to 100 parts by mass of the total amount of acrylic polyol and tolylene diisocyanate, and these were mixed to prepare a composition for adhesion layer formation (anchor coating agent).

[0081] <Preparation of Composition for Gas Barrier Coating Layer Formation> A liquid, B liquid, and C liquid described below were mixed at a mass ratio of 65 / 25 / 10 to prepare a composition for forming a gas barrier coating layer. Liquid A: 17.9 g of tetraethoxysilane (Si(OC 2 H 5 )) 4 and 10 g of methanol were added with 72.1 g of 0.1N hydrochloric acid and stirred for 30 minutes for hydrolysis to obtain a hydrolysis solution with a solid content of 5 mass% (in terms of SiO 2 conversion). Liquid B: A 5 mass% water / methanol solution of polyvinyl alcohol (mass ratio of water:methanol is 95:5). Liquid C: A hydrolysis solution obtained by diluting 1,3,5-tris(3-trialkoxysilylpropyl)isocyanurate with a mixture of water / isopropyl alcohol (mass ratio of water:isopropyl alcohol is 1:1) to a solid content of 5 mass%.

[0082] (Example 1) The above adhesion layer forming composition was coated on the corona-treated surface of a stretched polypropylene film (thickness 20 μm) with corona treatment on one side as an intermediate layer by the gravure roll coating method, dried and cured at 60°C, and an adhesion layer made of a polyester-based polyurethane resin with a coating amount of 0.1 g / m 2 was formed. Next, a transparent inorganic oxide layer (silica vapor deposition layer) made of silicon oxide with a thickness of 30 nm was formed by a vacuum vapor deposition apparatus using an electron beam heating method. As the silica vapor deposition layer, a vapor deposition layer with an O / Si ratio of 1.8 was formed by adjusting the vapor deposition material type. The O / Si ratio was measured with an X-ray photoelectron spectroscopy analyzer (manufactured by JEOL Ltd., product name: JPS-90MXV), using a non-monochromatized MgKα (1253.6 eV) as the X-ray source and an X-ray output of 100 W (10 kV - 10 mA). For the quantitative analysis to obtain the O / Si ratio, relative sensitivity factors of 2.28 for O1s and 0.9 for Si2p were used.

[0083] Next, the composition for forming the gas barrier coating layer was applied onto the inorganic oxide layer by a gravure roll coating method, and then heat-dried in an oven under the conditions of a tension of 20 N / m and a drying temperature of 120°C to form a gas barrier coating layer with a thickness of 0.3 μm. Thereby, a gas barrier film having a laminated structure of an intermediate layer / adhesion layer / inorganic oxide layer / gas barrier coating layer was obtained.

[0084] Next, a stretched polypropylene film (thickness: 20 μm) as a base material layer was laminated onto the gas barrier coating layer of the above gas barrier film by a dry lamination method through a two-component curable adhesive (manufactured by Mitsui Chemicals, Inc., trade name: main agent A525 / hardener A52). Subsequently, the non-corona-treated surface of the intermediate layer was subjected to corona treatment, and a non-stretched polypropylene film (thickness: 60 μm) as a sealant layer was laminated onto the intermediate layer by a dry lamination method through a two-component curable adhesive (manufactured by Mitsui Chemicals, Inc., trade name: main agent A525 / hardener A52). Thereby, a laminate having a laminated structure of a base material layer / adhesive layer / gas barrier coating layer / inorganic oxide layer / adhesion layer / intermediate layer / adhesive layer / sealant layer was manufactured. The thickness of each adhesive layer was 3 μm. As the base material layer, a stretched polypropylene film having the melting point and surface softening temperature shown in Table 1 below was used. As the sealant layer, a non-stretched polypropylene film having the surface softening temperature shown in Table 1 below was used.

[0085] (Examples 2 to 9 and 11, and Comparative Examples 1 to 2) A laminate was manufactured in the same manner as in Example 1, except that a stretched polypropylene film having the melting point and surface softening temperature shown in Table 1 below was used as the base material layer, and a non-stretched polypropylene film having the surface softening temperature shown in Table 1 below was used as the sealant layer.

[0086] (Example 10) In the same manner as in Example 1, a gas barrier film having a laminated structure of an intermediate layer / adhesion layer / inorganic oxide layer / gas barrier coating layer was obtained. Next, a stretched polypropylene film (thickness: 20 μm) as a base material layer was laminated on the gas barrier coating layer of the gas barrier film by a non-solvent lamination method via a two-component solventless curable urethane adhesive (manufactured by Toyo Morton Co., Ltd., trade name: TSN-4864A / TSN-4864B3). The two-component solventless adhesive was applied using a roll coater. Next, the non-corona-treated surface of the intermediate layer was subjected to corona treatment, and an unstretched polypropylene film (thickness: 60 μm) as a sealant layer was laminated on the intermediate layer by a non-solvent lamination method via a two-component solventless curable urethane adhesive (manufactured by Toyo Morton Co., Ltd., trade name: TSN-4864A / TSN-4864B3). The two-component solventless adhesive was applied using a roll coater. Thus, a laminate having a laminated structure of a base material layer / adhesive layer / gas barrier coating layer / inorganic oxide layer / adhesion layer / intermediate layer / adhesive layer / sealant layer was produced. The thickness of each adhesive layer was 2 μm. The same materials as those in Example 1 were used for the base material layer and the sealant layer.

[0087] <Measurement of melting point> The melting point of the base material layer was measured by the method shown below. The base material layer was cut from the laminates produced in the examples and comparative examples to obtain measurement samples. Using these measurement samples, the melting point (melting peak temperature) was measured by differential scanning calorimetry (DSC) under the condition of a heating rate of 10 °C / min. As the differential scanning calorimeter, DSC7000X (trade name) manufactured by Hitachi High-Tech Science Corporation was used.

[0088] <Measurement of surface softening temperature> The softening temperatures of the substrate layer surface and the sealant layer surface were measured by the following method using local thermal analysis (LTA) with an atomic force microscope. When measuring the softening temperature of the substrate layer surface using the laminate produced in the examples and comparative examples, after corona-treating the sealant layer side, it was fixed to a metal disk with an epoxy adhesive. When measuring the softening temperature of the sealant layer surface, after corona-treating the substrate layer side, it was fixed to a metal disk with an epoxy adhesive to obtain a measurement sample. The corona treatment was carried out using a corona treatment machine (product name: CT-0212) manufactured by Kasuga Electric Co., Ltd. under the condition of 0.20 kW.

[0089] The atomic force microscope (AFM) was an MFP-3D-SA (product name) manufactured by Oxford Instruments Co., Ltd., the local thermal analysis option was a Ztherm system, and the cantilever was an AN2-200 (product name) manufactured by Anasys Instruments Co., Ltd. with a spring constant of 0.5 to 3.5 N / m. The softening temperature was measured for the surface of each measurement sample.

[0090] When the surface of the sample was heated after Detrend correction with the contact pressure of the cantilever (change in the deflection amount of the cantilever) being 0.2 V, the voltage application acceleration (heating rate) being 0.5 V / second, and the maximum applied voltage being 6.0 V, the surface of the sample expanded and the position of the cantilever rose. When the surface of the sample was further heated and the surface of the sample softened and the position of the cantilever dropped by 30 nm, the measurement was terminated. When the Z displacement did not drop by 30 nm from the change point and reached the maximum applied voltage, the maximum applied voltages at the time of Detrend correction and measurement were increased by 0.5 V and the measurement was carried out again.

[0091] The applied voltage at the point where the height (Z displacement) in the vertical direction of the cantilever was maximum was taken as the applied voltage at the softening point, and the voltage value was read.

[0092] To calculate the softening temperature of the sample, a calibration curve was created. As calibration samples, four types were used: polycaprolactone (melting point: 60 °C), low-density polyethylene (LDPE, melting point: 112 °C), polypropylene (PP, melting point: 166 °C), and polyethylene terephthalate (PET, melting point: 255 °C). The maximum applied voltage during Detrend correction was 3.5 V for polycaprolactone, 5.5 V for low-density polyethylene, 6.7 V for polypropylene, and 7.9 V for polyethylene terephthalate. The contact pressure of the cantilever (change in the deflection amount of the cantilever) was 0.2 V, and the voltage application acceleration (heating rate) was 0.5 V / second. The measurement position of the calibration sample was changed and measured 20 times, and a calibration curve was created by approximating the average value of the applied voltage at the softening point and the melting point with a cubic function by the least squares method.

[0093] Using the calibration curve of the applied voltage and the melting point (melting peak temperature), the applied voltage at the softening point on the surface of the base material layer and the sealant layer was converted to temperature to obtain the softening temperature. The softening temperature was measured at 12 or more points within a 10-μm field of view, and the average value was calculated to obtain the surface softening temperature of each measurement sample.

[0094]

Table 1

[0095] <Production of Heat Seal Sample> The laminates obtained in the examples and comparative examples were cut into 60 mm × 120 mm so that the MD direction was the longitudinal direction. The cut laminate was bent in half by bending the central part in the longitudinal direction so that the sealant layers faced each other, and one side (however, at a position more than 3 mm away from the end) on the side opposite to the bent part was heat-sealed over a width of 10 mm using a heat sealer (model number: TP-701-B) manufactured by Tester Sangyo Co., Ltd. The heat seal conditions were as follows. Then, the bent part was cut with scissors so that the overlapping laminates had approximately the same length up and down, and the upper and lower laminates were separated. Thereby, a heat seal sample was obtained. (Heat Seal Conditions) Upper sealing bar: A sealing bar made of metal (aluminum alloy 2000 series (Al-Cu)) with a width of 10 mm was used, and the sealing temperature was changed in 5°C increments from 130°C to 165°C at the actual temperature. Lower sealing bar: A sealing bar made of silicon rubber with a width of 50 mm was used, and the sealing temperature was fixed at 90°C at the actual temperature. Sealing pressure: 0.3 MPa Heating time: 1.0 second

[0096] <Measurement of sealing strength> The heat-sealed sample was cut with a cutter to a width of 15 mm × a length of 60 mm to obtain a strip-shaped sample for measuring the sealing strength. The width direction of the sample for measuring the sealing strength is perpendicular to the width direction of the sealed part. For the obtained sample for measuring the sealing strength, using a tensile universal testing machine (manufactured by Shimadzu Corporation, product name: AGS-100NX), a peeling test of the sealed part was carried out under normal conditions (23°C, 50% RH) with a chuck distance of 10 mm and a peeling speed of 100 m / min. The sealing strength at each actual sealing temperature is shown in Table 2. When the sealing strength is 20 N / 15 mm or more, it is judged that there is no problem in practical use, and the lowest temperature of the upper sealing actual temperature at which a sealing strength of 20 N / 15 mm or more can be obtained is T L (°C) and recorded. T L The value of is shown in Table 3.

[0097] <Measurement of thermal shrinkage rate> The length A (mm) in the TD direction (the direction perpendicular to the width direction of the sealed part) of the sealed part of the heat-sealed sample, and the lengths B, C (mm) in the TD direction of the non-sealed parts 3 mm away from both ends in the width direction of the sealed part were measured, and the thermal shrinkage rate of the sealed part was calculated by the following formula. Note that the lengths B and C are the lengths of the parts that are sufficiently separated from the sealed part and not affected by heat. Thermal shrinkage rate (%) = [1 - A / {(B + C) / 2}] × 100 The thermal shrinkage rates at each actual sealing temperature (155 - 165°C) are shown in Table 2. When the thermal shrinkage rate is less than 3%, it is judged that there is no problem in practical use, and the highest temperature of the upper sealing actual temperature at which a thermal shrinkage rate of less than 3% can be maintained is T H (°C) and recorded. TH The values are shown in Table 3.

[0098] <Evaluation of distortion> The presence or absence of distortion (heat wrinkle) in the seal part of the heat seal sample at the upper seal actual temperature of 160°C was visually observed and evaluated according to the following criteria. If the evaluation is B or higher, it is at a level with no practical problems. The results are shown in Table 3. A: No distortion (heat wrinkle) is observed in either the seal part or the non-seal part near the seal part. B: Slight distortion (heat wrinkle) is observed in the seal part, but no distortion (heat wrinkle) is observed in the non-seal part near the seal part. C: Distortion (heat wrinkle) is observed in both the seal part and the non-seal part near the seal part.

[0099] <Heat seal margin> The maximum temperature T of the upper seal actual temperature at which the heat shrinkage rate of the seal part can be maintained below 3% H and the minimum temperature T of the upper seal actual temperature at which the seal strength of the seal part reaches 20 N / 15 mm or more L The difference (T H - T L ) was evaluated as the heat seal margin of the laminate according to the following criteria. If the evaluation is B or higher, it is at a level with no practical problems. The results are shown in Table 3. A: T H - T L is 20°C or higher B: T H - T L is 15°C or higher and less than 20°C C: T H - T L is 10°C or higher and less than 15°C D: T H - T L is less than 10°C

[0100]

Table 2

[0101]

Table 3

Description of Symbols

[0102] 11…Base material layer, 12…Intermediate layer, 13…Sealant layer, S…Adhesive layer, 100…Laminate.

Claims

[Claim 1] A laminate comprising at least a base layer, an intermediate layer, and a sealant layer, the base material layer is disposed on one outermost surface of the laminate, and the sealant layer is disposed on the other outermost surface of the laminate; the base layer, the intermediate layer and the sealant layer all comprise polypropylene; an inorganic oxide layer and a gas barrier coating layer are provided on a surface of the base layer facing the intermediate layer or on at least one surface of the intermediate layer; The softening temperature of the surface of the substrate layer measured by local thermal analysis (LTA) of the substrate layer is defined as T １ The softening temperature of the sealant layer surface is T ２ Then, T １ and T ２ A laminate satisfying the following conditions. T １ >200℃ T ２ <150℃

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