Polypropylene-based film and packaging laminate using the same

Abstract

To provide a polypropylene-based film and a packaging laminate using the same that achieve excellent low-temperature impact resistance, low-temperature heat sealability, high-temperature blocking resistance, and secondary processability.SOLUTION: A polypropylene-based film capable of constituting at least a seal layer, having a polypropylene-based resin as a main component, a surface property aspect ratio Str of 0.2 to 1.0, and a peak count number RPc in which a peak count number of peaks of 0.3 μm or more is 300 or more per 20 mm2, and having a melting start temperature peak of 130 to 145°C, and a packaging laminate using the same.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polypropylene film and a packaging laminate using the same. [Background technology]

[0002] Packaging films and packaging laminates using the same include laminates such as PET / ON / CPP, PET / ON / AL foil / CPP, and PT / gas barrier layer / CPP, which are made by laminating a heat-resistant substrate such as a biaxially oriented polyethylene terephthalate film (hereinafter sometimes referred to as PET), a biaxially oriented polyamide film (hereinafter sometimes referred to as ON), a biaxially oriented polypropylene film (hereinafter sometimes referred to as OPP), or an aluminum foil (hereinafter sometimes referred to as AL foil) with a heat-sealable unoriented polypropylene film (hereinafter sometimes referred to as CPP).

[0003] In recent years, laws related to environmentally friendly packaging have been enacted, making environmentally conscious design of packaging bags essential. This has led to an increasing demand for mono-material packaging bags made of the same material with excellent recyclability, and laminates of the same material, such as OPP / gas barrier layer / CPP, are being investigated. However, OPP has lower heat resistance than PET or ON, and therefore its poor secondary processability under conventional lamination and bag-making conditions is an issue. Therefore, in order to maintain the same secondary processability as before, there is an increasing demand for unoriented polypropylene film (CPP) with low-temperature impact resistance, low-temperature heat sealability, and high-temperature blocking resistance.

[0004] Furthermore, when a retort food packaging bag using the laminate is heated in a microwave oven, the bag is also required to have vapor permeability to prevent the bag from bursting due to internal steam pressure.

[0005] To solve these problems, Patent Document 1 proposes a laminate in which a heat-sealing layer is laminated on one side of a biaxially oriented polypropylene film with high heat resistance and elastic modulus, but the laminate is insufficient in low-temperature impact resistance, low-temperature heat-sealing property, high-temperature blocking resistance, retort suitability, etc. Patent Document 2 also proposes a polypropylene-based multilayer sealant film for retort pouches in which inorganic particles are added to impart blocking resistance to the heat-sealing layer to define the surface roughness, but there are concerns about particle shedding during the film-forming and laminating processes and particle contamination into food. Furthermore, the film's properties of low-temperature impact resistance, low-temperature heat-sealing property, high-temperature blocking resistance, and retort suitability are insufficient, and the film is also poor in bag-making processability and steam permeability during microwave heating. Patent Document 3 proposes a sealant film for retort pouch packaging with improved low-temperature impact resistance, heat-sealing property, citrus peel resistance, and blocking resistance, but the film fails to achieve both low-temperature heat-sealing property and high-temperature blocking resistance.

[0006] Furthermore, Patent Document 4 proposes an exterior material for an electricity storage device having a sealant layer made of a polypropylene resin containing a high-density polyethylene resin having a melt flow rate of 0.01 to 2 g / 10 min at 190°C to roughen the surface of the film. However, since the number of surface protrusions due to the high-density polyethylene is small, the secondary processability and high-temperature heat blocking resistance are insufficient. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2020-7441 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-236973 [Patent Document 3] Japanese Patent Application Laid-Open No. 2012-172124 [Patent Document 4] Patent Publication No. 2018-73649 Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, an object of the present invention is to provide a polypropylene film having excellent low-temperature impact resistance, low-temperature heat sealing property, high-temperature blocking resistance and secondary processability, and a packaging laminate using the same. [Means for solving the problem]

[0009] The present inventors have achieved the above object by providing the following polypropylene-based film and a packaging laminate using the same.

[0010] That is, the present invention is capable of constituting at least a sealing layer, and is mainly composed of a polypropylene resin, and has a surface texture aspect ratio Str of 0.2 to 1.0, and a peak count RPc of 300 peaks / 20 mm of 0.3 μm or more. 2 As described above, a polypropylene film having a peak melting temperature of 130 to 145°C is provided.

[0011] The present invention also provides a sheet-like laminate comprising at least two layers, a base layer and a seal layer, wherein the base layer contains 20% by mass or more of a propylene-ethylene block copolymer and is mainly composed of a polypropylene-based resin having a melting temperature peak of 140°C or higher, and the seal layer is mainly composed of a polypropylene-based resin, and has a surface texture aspect ratio Str of 0.2 to 1.0, and a peak count RPc of 300 peaks / 20mm of 0.3µm or more. 2 As described above, a polypropylene film having a peak melting temperature of 130 to 145°C is provided.

[0012] Furthermore, the present invention also provides a packaging laminate comprising the polypropylene film and a specific heat-resistant substrate, and a packaging laminate for mono-materialization. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a polypropylene-based film and a packaging laminate using the same that have excellent low-temperature impact resistance, low-temperature heat sealing properties, and high-temperature blocking resistance, and also have excellent bag-making processability, can be easily made into an environmentally friendly monomaterial, and can be heated in a microwave oven, and a laminate using the same. DETAILED DESCRIPTION OF THE INVENTION

[0014] The polypropylene film of the present invention and the packaging laminate using the same will be specifically described below.

[0015] The present invention is capable of constituting at least a sealing layer, and is mainly composed of a polypropylene resin, and the aspect ratio Str of the surface texture of the sealing layer surface is 0.2 to 1.0, and the peak count RPc is 300 / 20 mm 2 The polypropylene film has a peak melting temperature of 130 to 145°C.

[0016] The present invention also provides a sheet that is made up of at least two layers, a base layer and a seal layer, in which the base layer contains 20% by mass or more of a propylene-ethylene block copolymer and is mainly composed of a polypropylene-based resin having a melting temperature peak of 140°C or higher, and the seal layer is mainly composed of a polypropylene-based resin, has a surface texture aspect ratio Str of 0.2 to 1.0, and has a peak count RPc of 300 peaks / 20mm of 0.3μm or more. 2 The polypropylene film has a peak melting temperature of 130 to 145°C.

[0017] The term "polypropylene-based resin is the main component" means that the polypropylene-based resin accounts for 50% by mass or more of the total amount of the seal layer.

[0018] The polypropylene film of the sealing layer has a melting temperature peak in the range of 130° C. to 145° C. If the melting temperature peak of the sealing layer is less than 130° C., the blocking shear force at 130° C. when the sealing surfaces of the sealing layers are overlapped is 15 N / 12 cm.2 If the peak melting temperature exceeds 145°C, when the sealing surfaces of the sealing layers are overlapped and heat-sealed, the heat-sealing initiation temperature at which the heat-seal strength is 3N / 15mm or more may exceed 150°C, slowing down the bag-making speed.

[0019] Furthermore, the peak melting temperature of the sealing layer is preferably in the range of 130°C to 145°C, since this allows for a heat seal strength of 23N / 15mm or more at 170°C, which is necessary for use in retort pouch foods.

[0020] Here, the melting temperature peak refers to the highest peak temperature of the melting peak measured using a differential scanning calorimeter.

[0021] The polypropylene resin in the seal layer may be at least one of homopolypropylene, propylene-ethylene random copolymer, ethylene-propylene-butene random copolymer, propylene-ethylene block copolymer, etc., and preferably contains 50% or more by mass of propylene-ethylene random copolymer. If the proportion of propylene-ethylene random copolymer is less than 50% by mass, the heat seal strength of 23 N / 15 mm or more at 170°C required for retort food applications cannot be achieved, and the contents may splash or leak when the contents are filled into the bag and sterilized by heating at 130°C or higher.

[0022] The melt flow rate (hereinafter sometimes referred to as MFR) of the propylene-ethylene random copolymer is preferably in the range of 0.5 to 100 g / 10 min (230°C, load 2.18 N), and more preferably in the range of 2 to 20 g / 10 min, since this allows stable melt extrusion film formation.

[0023] The propylene-ethylene random copolymer having a melting temperature peak in the range of 130°C to 145°C is preferably a propylene-ethylene random copolymer mainly composed of propylene and one or more comonomers, as this copolymer can achieve both high-temperature blocking resistance and heat seal strength.

[0024] Examples of the comonomer include ethylene and α-olefins having 4 or more carbon atoms. Examples of the random copolymer include a propylene-ethylene random copolymer of propylene and ethylene, a random copolymer of propylene and an α-olefin having 4 or more carbon atoms, and a random copolymer of propylene, ethylene, and an α-olefin having 4 or more carbon atoms. Examples of the α-olefins having 4 or more carbon atoms constituting the random copolymer include 1-butene, 4-methylpentene-1, 1-octene, 1-hexene, etc., and 1-butene is preferred.

[0025] From the viewpoint of low-temperature heat seal strength, the copolymerization amount of the comonomer is preferably 1 mol % or more and 10 mol % or less. If the copolymerization amount is less than 1 mol %, the heat seal strength may be low, while if it exceeds 10 mol %, the slipperiness may be poor, the film may wrinkle easily when wound up, and the film may break due to blocking when unwound.

[0026] The aspect ratio Str of the surface texture of the sealing layer surface is 0.2 to 1.0, and the peak count RPc is 300 peaks / 20 mm of 0.3 μm or more. 2 This ensures good processability during film formation and lamination, and the blocking shear force at 130°C when the seal layer surfaces are overlapped is 15N / 12cm. 2 This is preferable because when automatically filling contents into bags, the bags are easy to open, the contents can be filled easily, and the bag production speed is high.

[0027] The aspect ratio Str of the surface texture of the sealing layer surface is 0.2 to 1.0, and the peak count RPc is 300 peak counts of 0.3 μm or more per 20 mm 2 To achieve the above, it is preferable that the film surface is not formed using inorganic or organic particles, since this can prevent particles from falling off during film formation or during the lamination process with a heat-resistant substrate, and can prevent particles from becoming mixed into the contents of the bag.

[0028] The aspect ratio Str of the surface texture represents the aspect ratio of the protrusions on the film surface when the film surface is observed with a laser microscope in accordance with ISO25178.

[0029] In addition, the peak count RPc of 0.3 μm or more is the peak count of 0.3 μm or more, measured on a 20 mm measurement area based on the roughness curve element, measured on the seal layer film surface in the direction (TD) perpendicular to the film flow direction (MD) using a fully automatic micro-profile measuring instrument according to the measurement method specified in JIS B0601:1982. 2 The peak counts of particles 0.3 μm or larger were calculated.

[0030] The aspect ratio Str of the surface texture of the sealing layer surface is 0.2 to 1.0, and the peak count RPc is 300 peaks / 20 mm of 0.3 μm or more. 2 To achieve the above, for example, the polypropylene resin is mixed with at least one polyethylene resin and an organic peroxide, and the mixture is subjected to high-temperature, high-shear extrusion using a single-screw extruder or a twin-screw extruder to prepare master chips in which the polyethylene resin is pseudo-crosslinked and finely dispersed, and the master chips are then used to form a film using a T-die film-forming machine or an inflation film-forming machine.

[0031] When the polyethylene resin is added to the polypropylene resin and mixed with the polypropylene resin and melt-extruded, the aspect ratio Str of the surface texture of the present invention is 0.2 to 1.0, and the peak count RPc is 300 peaks / 20 mm of 0.3 μm or more, even if the amount of the polyethylene resin added is increased. 2 It cannot be more than that.

[0032] The polyethylene resin may be, for example, a polyethylene having a density of 0.910 g / cm 3 ~0.970g / cm 3 In particular, polyethylene resins having a density of 0.935 g / cm 3 ~0.970g / cm 3 High density polyethylene is preferred.

[0033] The density of the polyethylene resin is 0.910 g / cm 3 If the film surface average roughness and peak count are less than 0.970 g / cm, the film surface average roughness and peak count may not be formed. 3 If it exceeds this value, the dispersibility in the polypropylene resin may be deteriorated, and the film formability may be deteriorated.

[0034] The melting temperature peak of the polyethylene resin is preferably in the range of 120°C to 145°C, more preferably in the range of 125°C to 145°C, from the viewpoints of heat seal strength and blocking shear force at 130°C.

[0035] The melt flow rate (MFR) of the polyethylene resin is preferably 0.2 to 20 g / 10 min, more preferably 0.5 to 10 g / 10 min, as measured at 190°C under a load of 21.18 N in accordance with JIS-K7210 (1999). This is because the polyethylene resin has good dispersibility in the polypropylene resin, the aspect ratio Str of the film surface property of the seal layer is 0.2 to 1.0, and the peak count Rpc of 0.3 μm or more is 300 / 20 mm. 2 It is easy to obtain a range of

[0036] The amount of the polyethylene resin mixed into the polypropylene resin is preferably in the range of 5 to 40% by mass, more preferably 10 to 30% by mass, and the aspect ratio Str of the film surface property of the seal layer is 0.2 to 1.0, and the peak count number Rpc of 0.3 μm or more is 300 / 20 mm 2 or more, and the blocking shear strength at 130°C is 15N / 12cm 2 The following is likely to be the case, which is preferable.

[0037] When the mixed amount of the polyethylene resin is less than 5% by mass, the aspect ratio Str of the surface texture is 0.2 to 1.0, and the peak count number Rpc of 0.3 μm or more is 300 / 20 mm 2 If the above cannot be achieved and the content exceeds 40% by mass, the heat seal strength may decrease.

[0038] The amount of the organic peroxide added is preferably in the range of 0.1 to 10% by mass, more preferably 0.5 to 5% by mass, based on the total amount of the resin components, so that the organic peroxide has good dispersibility in the resin, the effect of the crosslinking agent on the polyethylene resin can be exerted, and the aspect ratio Str of the surface properties of the film is 0.2 to 1.0 and the number of peak counts Rpc of 0.3 μm or more is 300 / 20 mm 2 If the amount added is less than 1% by mass, the effect of the addition is difficult to see, whereas if it exceeds 40% by mass, poor dispersion is likely to occur, and extrudability may deteriorate.

[0039] The organic peroxide is not particularly limited, and examples thereof include alkyl peroxides, diacyl peroxides, ester peroxides, carbonate peroxides, etc. Examples of alkyl peroxides include dicumyl peroxide, di-tert-butyl peroxide, di-tert-butylcumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di(tert-butyl-oxy)hexyne-3, tert-butylcumyl, 1,3-bis(tert-butylperoxyisopropyl)benzene, 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxonane, etc.

[0040] Examples of diacyl peroxides include benzoyl peroxide and lauroyl peroxide. Examples of peroxide esters include 1,1,3,3-tetramethylbutylperoxyneodecanoate, α-cumylperoxyneodecanoate, tert-butylperoxyneodecanoate, tert-butylperoxyneoheptanoate, tert-butylperoxypivalate, tert-hexylperoxypivalate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, tert-amylperoxy-2-ethylhexanoate, tert-butylperoxy-2-ethylhexanoate, tert-butylperoxyisobutyrate, di-tert-butylperoxyhexahydroterephthalate, tert-amylperoxy-3,5,5-trimethylhexanoate, tert-butylperoxy-3,5,5-trimethylhexanoate, tert-butylperoxyacetate, tert-Butyl peroxybenzoate, dibutylperoxytrimethyladipate Examples include:

[0041] Examples of peroxycarbonates include di-3-methoxybutyl peroxydicarbonate, di(2-ethylhexyl) peroxydicarbonate, diisopropyl peroxycarbonate, tert-butylperoxyisopropyl carbonate, di(4-t- butylcyclohexyl) peroxydicarbonate, dicetyl peroxydicarbonate, dimyristyl peroxydicarbonate, etc.

[0042] In view of food hygiene, it is preferable that the organic peroxide vaporizes during melt extrusion and does not remain in the polypropylene film of the present invention when used as a retort food package.

[0043] In addition, the aspect ratio Str of the surface quality of the sealing layer surface other than the above is 0.2 to 1.0, and the peak count Rpc of 0.3 μm or more is 300 / 20 mm 2One method for achieving the above is to use a film-forming nip roller to impart an embossed pattern to one side of the film (the seal layer surface). There are no particular limitations on the film-forming nip roller as long as it can form the seal layer surface of the present invention, but for example, the film-forming nip rollers disclosed in International Publication No. 2013 / 80925 and Japanese Patent Application Laid-Open No. 2020-55189 are preferably used. Specifically, an embossing nip roller having an arithmetic mean roughness Ra of 0.2 μm or less, a ten-point mean roughness Rz of 2 to 8 μm, and an average spacing Sm of irregularities of 90 μm or less is preferred.

[0044] The polypropylene film is preferably used by blending a propylene-ethylene block copolymer. The propylene-ethylene block copolymer preferably has an intrinsic viscosity [η]CXS of 2.5 dL / g to 3.5 dL / g of the 20°C xylene soluble portion CXS, an amount of the 20°C xylene soluble portion CXS of 10% by mass to 25.0% by mass, and an intrinsic viscosity [η]CXIS of 1.5 dL / g to 2.2 dL / g, because this improves low-temperature impact resistance and improves the retention of the bags after they are made into bags.

[0045] Here, with regard to the 20°C xylene insoluble portion CXIS and soluble portion CXS, when the polypropylene film is completely dissolved in boiling xylene, the temperature is lowered to 20°C, and the mixture is left to stand for 4 hours or more, and then the precipitate and solution are separated by filtration, the precipitate is referred to as the 20°C xylene insoluble portion CXIS (hereinafter, may be referred to as the xylene insoluble portion CXIS), and the portion obtained by drying the solution portion (filtrate) to dryness and under reduced pressure at 70°C is referred to as the 20°C xylene soluble portion CXS (hereinafter, may be referred to as the xylene soluble portion CXS).

[0046] The 20°C xylene insoluble portion CXIS corresponds to simple polypropylene, and the xylene soluble portion CXS corresponds to a rubber component. If the amount of the 20°C xylene soluble portion CXS is less than 10% by mass, the low-temperature impact resistance may be poor, and the decrease in heat seal strength at 100°C may be small, resulting in poor steam permeability when overheated in a microwave oven. If it exceeds 25.0% by mass, the decrease in heat seal strength at 100°C may be significant, resulting in liquid leakage from the packaging bag when heated in a microwave oven, etc. The amount of CXS is preferably in the range of 8% to 20.0% by mass.

[0047] The amount of the propylene-ethylene block copolymer mixed is preferably in the range of 1 to 30% by mass relative to the total amount of resin in the polypropylene film. If the amount is less than 1% by mass, the effect of the mixture is not observed, while if it exceeds 30% by mass, the low-temperature heat sealability and the above-mentioned normal properties may deteriorate.

[0048] It is preferable to add a thermoplastic elastomer to the polypropylene film, since this further improves the low-temperature heat sealability and impact resistance.

[0049] The content of the thermoplastic elastomer is preferably 5% by mass or more and 20% by mass or less. If the content is less than 5% by mass, the effect of improving low-temperature heat sealability and impact resistance may not be achieved, while if the content exceeds 20% by mass, the blocking shear force at 130°C when the seal layer surfaces are overlapped may increase, which may result in poor opening of the bag when filling the contents into a bag made using the laminate of the present invention and a decrease in bag making speed.

[0050] The thermoplastic elastomer is preferably a copolymer of 55 to 95% by mass of ethylene or propylene as a main component and 5 to 45% by mass of an α-olefin as a copolymerization monomer, specifically one produced using a metallocene catalyst.

[0051] The α-olefin may be ethylene, propylene, 1-butene, 1-hexene, 1-octene, or the like, which has 2 to 10 carbon atoms, and specific examples of the thermoplastic elastomer include ethylene-propylene copolymer elastomer, ethylene-butene copolymer elastomer, ethylene-octene copolymer elastomer, propylene-ethylene copolymer elastomer, propylene-butene copolymer elastomer, propylene-hexene copolymer elastomer, propylene-octene copolymer elastomer, etc. In particular, it is preferable to add an elastomer whose main component is propylene in view of heat seal strength and low-temperature impact resistance.

[0052] The MFR of the thermoplastic elastomer is preferably in the range of 0.5 to 10 g / 10 min at 190°C and a load of 21.18 N for elastomers containing ethylene as the main component, and in the range of 0.5 to 10 g / 10 min at 230°C and a load of 21.18 N for elastomers containing propylene as the main component, from the viewpoints of miscibility with the polypropylene-based resin as the main component and film formation stability.

[0053] The polypropylene-based film of the present invention comprises at least two layers: a base layer and a seal layer, the base layer containing 20% ​​by mass or more of a propylene-ethylene block copolymer and containing a polypropylene-based resin as a main component having a melting temperature peak of 140°C or higher, the seal layer having a surface property aspect ratio Str of 0.2 to 1.0, and a peak count RPc of 300 peaks / 20mm of 0.3µm or more. 2 The polypropylene film has a peak melting temperature of 130 to 145°C.

[0054] Here, the polypropylene resin of the base layer being the main component means that it accounts for 50% by mass or more of the total amount of the resin composition of the base layer.

[0055] The polypropylene resin having a melting temperature peak of 140°C or higher for the base layer refers to a resin containing 50% by mass of a propylene component. Examples of such a resin include homopolypropylene, propylene-ethylene block copolymer, propylene-ethylene random copolymer, and ethylene-propylene-butene random copolymer, and a mixture of one or more of these may be used.

[0056] By using a polypropylene resin having a peak melting temperature of 140°C or higher as the main component of the base layer, a laminate with fewer wrinkles and pitch deviations can be obtained when laminated with a heat-resistant substrate, improving bag-making processability and secondary processability, and also increasing the heat-seal strength at 170°C.

[0057] Here, the melting temperature peak refers to the highest peak temperature of the melting peak measured using a differential scanning calorimeter.

[0058] It is preferable to mix a propylene-ethylene random copolymer and a propylene-ethylene block copolymer in the polypropylene resin of the base layer, as this improves the interfacial adhesive strength with the seal layer, thereby increasing low-temperature impact resistance and heat seal strength.

[0059] The blend ratio of the propylene-ethylene random copolymer and the propylene-ethylene block copolymer may be in the range of 0 to 80 mass % of the propylene-ethylene random copolymer and 20 to 100 mass % of the propylene-ethylene block copolymer (where the total amount of polypropylene resins is 100 mass %).

[0060] The ethylene content of the propylene-ethylene random copolymer is preferably 1% by mass or more and 7% by mass or less, since this improves the interfacial adhesive strength with the seal layer and increases the heat seal strength.

[0061] The content of the propylene-ethylene block copolymer is preferably 20% by mass or more, since this improves low-temperature impact resistance and improves the retention rate of the contents packed in the bag.

[0062] The propylene-ethylene block copolymer preferably has an intrinsic viscosity [η]CXS of the 20°C xylene soluble portion CXS of 2.5 dL / g or more and 3.5 dL / g or less, an amount of the 20°C xylene soluble portion CXS of 10 mass% or more and 25.0 mass% or less, and an intrinsic viscosity [η]CXIS of the 20°C xylene insoluble portion CXIS of 1.5 dL / g or more and 2.2 dL / g or less, as these improve low-temperature impact resistance.

[0063] Here, with regard to the 20°C xylene insoluble portion CXIS and soluble portion CXS, when the polypropylene film is completely dissolved in boiling xylene, the temperature is lowered to 20°C, and the mixture is left to stand for 4 hours or more, and then the precipitate and solution are separated by filtration, the precipitate is referred to as the 20°C xylene insoluble portion CXIS (hereinafter, may be referred to as the xylene insoluble portion CXIS), and the portion obtained by drying the solution portion (filtrate) to dryness and under reduced pressure at 70°C is referred to as the 20°C xylene soluble portion CXS (hereinafter, may be referred to as the xylene soluble portion CXS).

[0064] The 20° C. xylene insoluble portion CXIS corresponds to the polypropylene alone, and the xylene soluble portion CXS corresponds to the rubber component.

[0065] If the amount of 20°C xylene soluble portion CXS in the base layer is less than 5% by mass, the low-temperature impact resistance may be poor, and the decrease in heat seal strength of the laminate at 100°C may be small, resulting in poor vapor permeability, while if it exceeds 25.0% by mass, the decrease in heat seal strength at 100°C may be significant, leading to leakage from the packaging bag when heated in a microwave oven, etc. The amount of CXS is preferably in the range of 8% by mass or more and 20.0% by mass or less.

[0066] If the intrinsic viscosity ([η]CXS) of the 20°C xylene soluble portion CXS in the base layer is less than 2.5 dL / g, low-temperature impact resistance may decrease, and if it is more than 3.5 dL / g, dispersibility in the xylene insoluble portion CXIS may decrease, resulting in poor melt extrusion properties.

[0067] Furthermore, if the intrinsic viscosity ([η]CXIS) of the 20°C xylene-insoluble portion CXIS in the polypropylene film is less than 1.5 dL / g, the low-temperature impact resistance may decrease, and if it is more than 2.2 dL / g, the dispersibility of the xylene-soluble portion CXS may deteriorate.

[0068] The melt flow rate (MFR) of the polypropylene resin is preferably in the range of 0.5 to 15 g / 10 min at 230° C. under a load of 21.18 N, from the viewpoint of extrusion stability and low-temperature impact resistance.

[0069] The base layer preferably contains 10% to 40% by mass of linear low-density polyethylene (hereinafter sometimes referred to as LLDPE) (where the total mass of the base layer resin is taken as 100% by mass). In this case, when used as a retort packaging material containing oily foods, the occurrence of orange peel can be suppressed, which is preferable, as it improves low-temperature impact resistance and allows adjustment of steam permeability during microwave heating.

[0070] If the LLDPE content is less than 10% by mass, the effect of the content on vapor permeability during microwave heating may not be observed, whereas if it exceeds 40% by mass, the heat seal strength may be significantly reduced during retort treatment or heating in a microwave oven, etc., which may result in liquid leakage from the packaging bag.

[0071] The melting point of the LLDPE is preferably 110° C. or higher and 145° C. or lower. If the melting point is lower than 110° C., the heat seal strength at high temperatures may decrease, resulting in packaging bags being torn, whereas if the melting point is higher than 145° C., the heat seal strength at high temperatures may increase, resulting in poor vapor permeability when heated in a microwave oven.

[0072] The LLDPE is a copolymer of 50 to 95% by mass of ethylene as a main component and an α-olefin as a copolymerization monomer, and specifically, it is preferably produced using a metallocene catalyst.

[0073] Examples of the α-olefin include those having 4 to 10 carbon atoms such as 1-butene, 1-hexene, and 1-octene.

[0074] The MFR of the LLDPE is preferably in the range of 0.5 to 10 g / 10 min at 190° C. under a load of 21.18 N, from the viewpoints of miscibility with polypropylene resins and blocking resistance.

[0075] Adding 1% to 20% by mass of a thermoplastic elastomer to the base layer (where the total mass of the base layer resin is taken as 100% by mass) improves the interfacial adhesion with the seal layer, and thus improves heat seal strength and low-temperature impact resistance, which is preferable. If the content is less than 1% by mass, the effects of improving heat seal strength and low-temperature impact resistance may not be achieved, while if it exceeds 20% by mass, heat resistance may decrease, resulting in poor lamination processability and increased blocking at 130°C.

[0076] Examples of the thermoplastic elastomer include ethylene-α-olefin copolymer elastomers and propylene-α-olefin copolymer elastomers, and propylene-α-olefin copolymer elastomers are particularly preferred because they improve the interfacial adhesive strength with the seal layer and further improve the heat seal strength and low-temperature impact resistance.

[0077] The propylene-α-olefin copolymer elastomer is preferably a copolymer of 55 to 95 mass % of propylene as a main component and 5 to 45 mass % of an α-olefin as a copolymerization monomer, and specifically, is preferably produced using a metallocene catalyst.

[0078] The α-olefin may be ethylene, 1-butene, 1-hexene, 1-octene, or the like, which has 2 to 10 carbon atoms, and specific examples of the propylene-α-olefin include propylene-ethylene copolymer elastomer, propylene-butene copolymer elastomer, propylene-octene copolymer elastomer, etc. In particular, propylene-butene copolymer elastomer is preferred from the viewpoint of heat seal strength and low-temperature impact resistance.

[0079] The propylene-α-olefin copolymer elastomer has a density of 0.87 to 0.90 g / cm 3 In this range, those having a melting point of 70 to 100°C, an MFR of 230°C, and an MFR of 0.5 to 20g / 10min under a load of 21.18N are preferred as they have good compatibility with the polypropylene resin.

[0080] The base layer may contain 100 to 1000 ppm of a fatty acid amide lubricant relative to the total amount of resin composition, as long as the amount does not deteriorate the film-forming property due to contamination in the film-forming process caused by heat scattering during melt extrusion or reduce the heat seal strength. If the amount of fatty acid amide lubricant added is less than 100 ppm, the slipperiness may be deteriorated, while if it exceeds 1000 ppm, the amount of heat scattering during melt extrusion increases, causing contamination in the film-forming process, resulting in deterioration of the film-forming property and a decrease in the laminate strength with the heat-resistant substrate.

[0081] Examples of the fatty acid amide lubricants include oleic acid amide, erucic acid amide, stearic acid amide, palmitic acid amide, and behenic acid amide.

[0082] The base layer can be made by crushing recovered film generated during the film production process to remove foreign matter, and then returning the recovered raw material to the base layer. A recovery rate of 50% by mass or less is preferred to maintain the film properties.

[0083] The sealing layer, which is a multi-layer structure consisting of a base layer and a sealing layer, is mainly composed of a polypropylene resin, and has a surface property in which the aspect ratio Str of the sealing layer surface is 0.2 to 1.0, and the peak count RPc is 300 / 20 mm of 0.3 μm or more. 2 The melting start temperature peak is 130 to 145°C.

[0084] The peak melting temperature of the sealing layer is in the range of 130°C to 145°C, so that the heat seal strength at 170°C required for retort food applications, which is 23N / 15mm or more, can be obtained, and the blocking shear force at 130°C is 15N / 12cm. 2 This is preferable because it can be done as follows:

[0085] Here, the melting temperature peak refers to the highest peak temperature of the melting peak measured using a differential scanning calorimeter.

[0086] The polypropylene resin in the seal layer may be at least one of propylene-ethylene random copolymer, ethylene-propylene-butene random copolymer, propylene-ethylene block copolymer, etc., and preferably contains 50% or more by mass of propylene-ethylene random copolymer. If the proportion of propylene-ethylene random copolymer is less than 50% by mass, the heat seal strength of 23 N / 15 mm or more at 170°C required for retort food applications cannot be achieved, and the contents may splash or leak when the contents are filled into the bag and sterilized by heating at 130°C or higher.

[0087] Furthermore, by having the melting temperature peak of the polypropylene resin of the seal layer in the range of 130°C to 145°C, it is possible to obtain a heat seal strength of 23N / 15mm or more at 170°C, which is necessary for use in retort food products, and it is also preferable because the blocking shear force at 130°C can be 15N / 12cm2 or less. If the melting temperature peak is less than 130°C, the blocking shear force at 130°C when the seal layer surfaces are overlapped will be 15N / 12cm2 or less. 2 If the peak melting temperature exceeds 145°C, when the seal layer surfaces are overlapped and heat sealed, the heat seal initiation temperature at which the heat seal strength is 3N / 15mm or more may exceed 150°C, slowing down the bag making speed.

[0088] The melt flow rate (hereinafter sometimes referred to as MFR) of the propylene-ethylene random copolymer is preferably in the range of 0.5 to 100 g / 10 min (230°C, load 2.18 N), and more preferably in the range of 2 to 20 g / 10 min, since this allows stable melt extrusion film formation.

[0089] The propylene-ethylene random copolymer having a melting temperature peak in the range of 135°C to 145°C is preferably a propylene-ethylene random copolymer mainly composed of propylene and one or more comonomers, as this copolymer can achieve both high-temperature blocking resistance and heat seal strength.

[0090] Examples of the comonomer include ethylene and α-olefins having 4 or more carbon atoms. Examples of the random copolymer include a propylene-ethylene random copolymer of propylene and ethylene, a random copolymer of propylene and an α-olefin having 4 or more carbon atoms, and a random copolymer of propylene, ethylene, and an α-olefin having 4 or more carbon atoms. Examples of the α-olefins having 4 or more carbon atoms constituting the random copolymer include 1-butene, 4-methylpentene-1, 1-octene, 1-hexene, etc., and 1-butene is preferred.

[0091] From the viewpoint of low-temperature heat seal strength, the copolymerization amount of the comonomer is preferably 1 mol % or more and 10 mol % or less. If the copolymerization amount is less than 1 mol %, the heat seal strength may be low, while if it exceeds 10 mol %, the slipperiness may be poor, the film may wrinkle easily when wound up, and the film may break due to blocking when unwound.

[0092] The aspect ratio Str of the surface texture of the sealing layer surface is 0.2 to 1.0, and the peak count RPc is 300 peaks / 20 mm of 0.3 μm or more. 2 The above results in good processability during film formation and lamination, and the blocking shear force at 130°C when the sealing surfaces of the sealing layers are overlapped is 15N / 12cm. 2 This is preferable because when automatically filling contents into bags, the bags are easy to open, the contents can be filled easily, and the bag production speed is high.

[0093] The aspect ratio Str of the surface texture of the sealing layer surface is 0.2 to 1.0, and the peak count RPc is 300 peak counts of 0.3 μm or more per 20 mm 2 To achieve the above, it is preferable that the film surface is not formed using inorganic or organic particles, since this can prevent particles from falling off during film formation or the lamination process with a heat-resistant substrate, and can prevent particles from becoming mixed into the contents of the bag.

[0094] The aspect ratio Str of the surface texture represents the aspect ratio of the protrusions on the film surface when the film surface is observed with a laser microscope in accordance with ISO25178.

[0095] In addition, the peak count RPc of 0.3 μm or more is the peak count of 0.3 μm or more, measured on a 20 mm measurement area based on the roughness curve element, measured on the seal layer film surface in the direction (TD) perpendicular to the film flow direction (MD) using a fully automatic micro-profile measuring instrument according to the measurement method specified in JIS B0601:1982. 2 The peak counts of particles 0.3 μm or larger were calculated.

[0096] The aspect ratio Str of the surface quality of the sealing layer surface is 0.2 to 1.0, and the peak count RPc is 300 / 20 mm of 0.3 μm or more. 2 To achieve the above, for example, the polypropylene resin is mixed with at least one polyethylene resin and an organic peroxide, and the mixture is subjected to high-temperature, high-shear extrusion using a single-screw extruder or a twin-screw extruder to prepare master chips, and the master chips are then used to form films using a T-die type film forming machine or an inflation film forming machine.

[0097] When the polyethylene resin is added to the polypropylene resin and mixed and melt-extruded, the surface texture aspect ratio Str of the present invention is 0.2 to 1.0, and the peak count RPc is 300 peaks / 20 mm of 0.3 μm or more, even if the amount of polyethylene resin added is increased. 2 It cannot be more than that.

[0098] The polyethylene resin may be, for example, a polyethylene having a density of 0.910 g / cm 3 ~0.970g / cm 3 In particular, polyethylene resins having a density of 0.935 g / cm 3 ~0.970g / cm 3 High density polyethylene is preferred.

[0099] The density of the polyethylene resin is 0.910 g / cm 3 If the film surface average roughness and peak count are less than 0.970 g / cm, the film surface average roughness and peak count may not be formed. 3 If it exceeds this value, the dispersibility in the polypropylene resin may deteriorate, and the surface roughness Str may exceed 1.0.

[0100] The melting temperature peak of the polyethylene resin is preferably in the range of 120°C to 145°C, more preferably in the range of 125°C to 145°C, from the viewpoints of heat seal strength and blocking shear force at 130°C.

[0101] The melt flow rate (MFR) of the polyethylene resin is preferably 0.2 to 20 g / 10 min, more preferably 0.5 to 10 g / 10 min, as measured at 190°C under a load of 21.18 N in accordance with JIS-K7210 (1999). This is because the resin has good dispersibility in the propylene-ethylene random copolymer, the aspect ratio Str of the film surface property of the seal layer is 0.2 to 1.0, and the peak count Rpc of 0.3 μm or more is 300 / 20 mm. 2 It is easy to obtain a range of

[0102] The amount of the polyethylene resin mixed into the polypropylene resin is preferably in the range of 5 to 40% by mass, more preferably 10 to 30% by mass, and the aspect ratio Str of the film surface property of the seal layer is 0.2 to 1.0, and the peak count number Rpc of 0.3 μm or more is 300 / 20 mm 2 or more, and the blocking shear strength at 130°C is 15N / 12cm 2The following is likely to be the case, which is preferable.

[0103] When the mixed amount of the polyethylene resin is less than 5% by mass, the aspect ratio Str of the surface texture is 0.2 to 1.0, and the peak count number Rpc of 0.3 μm or more is 300 / 20 mm 2 If the above cannot be achieved and the content exceeds 40% by mass, the heat seal strength may decrease.

[0104] The amount of the organic peroxide added is preferably in the range of 0.1 to 10% by mass, more preferably 0.5 to 5% by mass, based on the total amount of resin components. This is because the organic peroxide has good dispersibility in the resin, the crosslinking agent can exert its effect on the polyethylene resin, and the film has a surface roughness Str of 0.2 to 1.0 and a peak count Rpc of 0.3 μm or more of 300 / 20 mm 2 If the amount added is less than 1% by mass, the effect of the addition is difficult to see, whereas if it exceeds 40% by mass, poor dispersion is likely to occur, and extrudability may deteriorate.

[0105] The organic peroxide is not particularly limited, and examples thereof include alkyl peroxides, diacyl peroxides, ester peroxides, carbonate peroxides, etc. Examples of alkyl peroxides include dicumyl peroxide, di-tert-butyl peroxide, di-tert-butylcumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di(tert-butyl-oxy)hexyne-3, tert-butylcumyl, 1,3-bis(tert-butylperoxyisopropyl)benzene, 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxonane, etc.

[0106] Examples of diacyl peroxides include benzoyl peroxide, lauroyl peroxide, decanoyl peroxide, etc. Examples of peroxide esters include 1,1,3,3-tetramethylbutylperoxyneodecanoate, α-cumylperoxyneodecanoate, tert-butylperoxyneodecanoate, tert-butylperoxyneoheptanoate, tert-butylperoxypivalate, tert-hexylperoxypivalate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, tert-amylperoxyl-2-ethylhexanoate, tert-amylperoxyl-2-ethylhexanoate, tert-butylperoxypivalate, tert-butylperoxyneodecanoate, tert-butylperoxyneoheptanoate, tert-butylperoxypivalate, tert-hexylperoxypivalate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, tert-amylperoxyl-2-ethylhexanoate, tert-butylperoxyneodecanoate, tert-butylperoxyneodecanoate, tert-butylperoxyneoheptanoate, tert-butylperoxypivalate, tert-hexylperoxypivalate, tert-tetramethylbutylperoxy-2-ethylhexanoate, tert-amylperoxyl-2-ethylhexanoate, tert-butylperoxyneodec ... peroxymethyl tert-butyl ether, tert-butyl ...

[0107] Examples of peroxycarbonates include di-3-methoxybutyl peroxydicarbonate, di(2-ethylhexyl) peroxydicarbonate, diisopropyl peroxydicarbonate, tert-butylperoxyisopropyl carbonate, di(4-t-butylcyclohexyl) peroxydicarbonate, dicetyl peroxydicarbonate, and dimyristyl peroxydicarbonate.

[0108] In view of food hygiene, it is preferable that the organic peroxide vaporizes during melt extrusion and does not remain in the polypropylene film of the present invention when used as a retort food package.

[0109] In addition, the aspect ratio Str of the surface quality of the sealing layer surface other than the above is 0.2 to 1.0, and the peak count Rpc of 0.3 μm or more is 300 / 20 mm 2One method for achieving the above is to use a film-forming nip roller to impart an embossed pattern to one side of the film (the seal layer surface). There are no particular limitations on the film-forming nip roller as long as it can form the seal layer surface of the present invention, but for example, the film-forming nip rollers disclosed in International Publication No. 2013 / 80925 and Japanese Patent Application Laid-Open No. 2020-55189 are preferably used. Specifically, an embossing nip roller having an arithmetic mean roughness Ra of 0.2 μm or less, a ten-point mean roughness Rz of 2 to 8 μm, and an average spacing Sm of irregularities of 90 μm or less is preferred.

[0110] The sealing layer is preferably made of a propylene-ethylene block copolymer, and the propylene-ethylene block copolymer preferably has an intrinsic viscosity [η]CXS of 2.5 dL / g to 3.5 dL / g of the 20°C xylene soluble portion CXS, an amount of the 20°C xylene soluble portion CXS of 10% by mass to 25.0% by mass, and an intrinsic viscosity [η]CXIS of the 20°C xylene insoluble portion CXS of 1.5 dL / g to 2.2 dL / g, because this improves low-temperature impact resistance.

[0111] Here, with regard to the 20°C xylene insoluble portion CXIS and soluble portion CXS, when the polypropylene film is completely dissolved in boiling xylene, the temperature is lowered to 20°C, and the mixture is left to stand for 4 hours or more, and then the precipitate and solution are separated by filtration, the precipitate is referred to as the 20°C xylene insoluble portion CXIS (hereinafter, may be referred to as the xylene insoluble portion CXIS), and the portion obtained by drying the solution portion (filtrate) to dryness and under reduced pressure at 70°C is referred to as the 20°C xylene soluble portion CXS (hereinafter, may be referred to as the xylene soluble portion CXS).

[0112] The 20°C xylene insoluble portion CXIS corresponds to simple polypropylene, and the xylene soluble portion CXS corresponds to a rubber component. If the amount of the 20°C xylene soluble portion CXS is less than 10% by mass, the low-temperature impact resistance may be poor, and the decrease in heat seal strength at 100°C may be small, resulting in poor steam permeability when overheated in a microwave oven. If it exceeds 25.0% by mass, the decrease in heat seal strength at 100°C may be significant, resulting in liquid leakage from the packaging bag when heated in a microwave oven, etc. The amount of CXS is preferably in the range of 8% to 20.0% by mass.

[0113] The amount of the propylene-ethylene block copolymer mixed is preferably in the range of 1 to 30% by mass relative to the total amount of resin in the polypropylene film. If the amount is less than 1% by mass, the effect of the mixture is not observed, while if it exceeds 30% by mass, the low-temperature heat sealability and the above-mentioned normal properties may deteriorate.

[0114] It is preferable to add a thermoplastic elastomer to the sealing layer, since this further improves the low-temperature heat sealability and impact resistance.

[0115] The content of the thermoplastic elastomer is preferably 5% by mass or more and 20% by mass or less. If the content is less than 5% by mass, the effect of improving low-temperature heat sealability and impact resistance may not be achieved, while if the content exceeds 20% by mass, the blocking shear force at 130°C when the seal layer surfaces are overlapped may increase, which may result in poor opening of the bag when filling the contents into a bag made using the laminate of the present invention and a decrease in bag making speed.

[0116] The thermoplastic elastomer is preferably a copolymer of 55 to 95% by mass of ethylene or propylene as a main component and 5 to 45% by mass of an α-olefin as a copolymerization monomer, specifically one produced using a metallocene catalyst.

[0117] The α-olefin may be ethylene, propylene, 1-butene, 1-hexene, 1-octene, or the like, which has 2 to 10 carbon atoms, and specific examples of the thermoplastic elastomer include ethylene-propylene copolymer elastomer, ethylene-butene copolymer elastomer, ethylene-octene copolymer elastomer, propylene-ethylene copolymer elastomer, propylene-butene copolymer elastomer, propylene-hexene copolymer elastomer, propylene-octene copolymer elastomer, etc. In particular, it is preferable to add an elastomer whose main component is propylene in view of heat seal strength and low-temperature impact resistance.

[0118] The MFR of the thermoplastic elastomer is preferably in the range of 0.5 to 10 g / 10 min at 190°C and a load of 21.18 N for elastomers containing ethylene as the main component, and in the range of 0.5 to 10 g / 10 min at 230°C and a load of 21.18 N for elastomers containing propylene as the main component, from the viewpoints of miscibility with the polypropylene-based resin as the main component and film formation stability.

[0119] The polypropylene film is a single layer or a multi-layer of a base layer and a seal layer, and the 719 cm -1 Peak at 973cm -1 The value obtained by dividing the peak at 719 cm by the peak at 719 cm on the surface of the sealing layer by infrared absorptiometry is preferably in the range of 0.3 to 0.8. -1 Peak at 973cm -1 When the value obtained by dividing the value by the peak is in the range of 0.3 to 0.8, it is possible to achieve both low-temperature heat sealing property, low-temperature impact resistance, and high-temperature blocking resistance.

[0120] The polypropylene film is preferably a single layer or a multilayer film consisting of a base layer and a seal layer, and the external haze of the seal layer of the film is preferably in the range of 5 to 20%. By having the external haze of the seal layer of the film in the range of 5 to 20%, the film alone and the laminate maintain their blocking resistance at high temperatures, and adhesion or inclusion of foreign matter can be visually confirmed.

[0121] The polypropylene film is a single layer or a multi-layer of a base layer and a seal layer, and the blocking shear strength between the seal surfaces of the seal layers at 130°C is 15N / 12cm 2 In this case, the bag is easy to open and the filling of the contents is excellent when automatically filling the contents into the bag. 2 If the time exceeds this, the opening of the bag may not open during automatic filling of the contents into the bag, causing the contents to spill out, and the bag making speed may decrease.

[0122] Furthermore, in the case of packaging bags such as pouches, when the sealing surfaces of the sealing layers are overlapped and heat-sealed, the heat-sealing initiation temperature at which the heat-sealing strength is 3 N / 15 mm or more is preferably 150° C. or less, more preferably 145° C. or less. By setting the heat-sealing initiation temperature at 150° C. or less at which the heat-sealing strength is 3 N / 15 mm or more, conventional bag-making speeds can be maintained.

[0123] The conventional bag-making speed is preferably 40 spm (shots per minute) or more, more preferably 45 spm or more. A bag-making speed of less than 40 spm is not preferable because it may result in poor product yield and high manufacturing costs.

[0124] The polypropylene film of the present invention preferably has a total thickness of 20 to 150 μm in a single layer or a multilayer structure of a base layer and a seal layer. The thickness ratio of the base layer to the multilayer structure of the seal layer is preferably 9:1 to 3:1. This ensures stable film-forming properties, impact resistance, and heat-sealing strength, while maintaining bag-forming properties.

[0125] The polypropylene film of the present invention may contain antioxidants, heat stabilizers, neutralizing agents, antistatic agents, hydrochloric acid absorbers, antiblocking agents, lubricants, etc. These additives may be used alone or in combination of two or more, provided that the object of the present invention is not impaired.

[0126] Specific examples of antioxidants include hindered phenols such as 2,6-di-t-butylphenol (BHT), n-octadecyl-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate (Irganox 1076, Sumilizer BP-76), tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane (Irganox 1010, Sumilizer BP-101), and tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate (Irganox 3114, Mark AO-20).

[0127] Examples of phosphite (phosphorus) antioxidants include tris(2,4-di-t-butylphenyl)phosphite ("Irgafos" 168, Mark 2112), tetrakis(2,4-di-t-butylphenyl)-4,4'-biphenylene-diphosphonite ("Sandstab" P-EPQ), bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite ("Ultranox" 626, Mark PEP-24G), and distearyl pentaerythritol diphosphite (Mark PEP-8).

[0128] Among these, 6-[3-(3-t-butyl-4-hydroxy-5-methyl)propoxy]-2,4,8,10-tetra-t-butyldibenz[d,f][1,3,2]-dioxaphosphepine ("Sumilizer" GP) and 2[1-2-hydroxy-3,5-di-t-pentylphenyl]ethyl]-4,6-di-t-pentylphenyl acrylate ("Sumilizer" GS) are preferred, as they combine the functions of both hindered phenols and phosphites. The combined use of these two is particularly preferred, as it is effective in suppressing resin decomposition during film formation and contributes to achieving both heat seal strength and blocking resistance.

[0129] In the single sealing layer and the multi-layer structure of the base layer and the sealing layer, the amount of antioxidant added to each layer may be appropriately set in the range of 100 to 10,000 ppm, depending on the type of antioxidant used.

[0130] As the neutralizing agent, hydrotalcite compounds, calcium hydroxide, etc. are preferred for reducing smoke generation during film formation.

[0131] Examples of methods for obtaining the polypropylene-based film of the present invention include a method in which the resin and additive composition are melted and kneaded in a single-screw extruder, a twin-screw co-rotating extruder, or a twin-screw counter-rotating extruder, and then extruded from a T-type nozzle onto a cooling drum and cooled to solidify, or a method in which the melt-extruded composition is laminated onto a heat-resistant substrate. In the present invention, the method in which the resin and additive composition are extruded from a T-type nozzle onto a cooling drum and then cooled to solidify is preferred because it provides higher heat seal strength.

[0132] The polypropylene film can also be uniaxially or biaxially stretched as needed. In the case of uniaxial stretching, it is preferable to stretch the film 3 to 10 times in the longitudinal direction at a stretching temperature of 120 to 150°C, and in the case of biaxial stretching, it is preferable to stretch the film 10 to 50 times in the longitudinal and transverse directions combined at a stretching temperature of 140 to 165°C.

[0133] In the laminate in which a heat-resistant substrate having a melting temperature peak of 160°C or higher is laminated on the side opposite to the seal surface of the seal layer of the polypropylene film, the heat seal strength is preferably 23 N / 15 mm or higher when the seal surfaces of the seal layers are overlapped and heat-sealed at 170°C. If the heat seal strength at 170°C is less than 23 N / 15 mm, when used as a retort packaging material, the heat seal strength may be reduced by heat treatment at 130°C or higher, which may result in scattering or leakage of the contents.

[0134] The heat-resistant substrate is preferably at least one selected from the group consisting of biaxially oriented polyamide film, biaxially oriented polyethylene terephthalate film, biaxially oriented polypropylene film, biaxially oriented polybutylene terephthalate film, biaxially oriented polyester / polyamide hybrid film, uniaxially oriented polyamide film, uniaxially oriented polyethylene terephthalate film, uniaxially oriented polypropylene film, and uniaxially oriented polybutylene terephthalate film, and a substrate having at least one gas barrier layer applied to the film, selected from the group consisting of metal vapor deposition, inorganic vapor deposition, inorganic metal transparent vapor deposition, and gas barrier resin, and at least one layer selected from the group consisting of synthetic paper and aluminum foil.

[0135] Furthermore, the heat-resistant substrate is preferably a substrate comprising at least one film selected from the group consisting of biaxially oriented polyamide film, biaxially oriented polyethylene terephthalate film, biaxially oriented polypropylene film, biaxially oriented polybutylene terephthalate film, biaxially oriented polyester / polyamide hybrid film, uniaxially oriented polyamide film, uniaxially oriented polyethylene terephthalate film, uniaxially oriented polypropylene film, and uniaxially oriented polybutylene terephthalate film, to which at least one gas barrier layer selected from the group consisting of metal vapor deposition, inorganic oxide vapor deposition, and gas barrier resin is applied.

[0136] As an environmentally friendly design for the laminate, it is preferable to use the polypropylene film and a biaxially oriented polypropylene film or a uniaxially oriented polypropylene film of a polypropylene resin as a mono-material with excellent recyclability. For example, it is preferable to configure a packaging laminate in which a surface layer made of a biaxially oriented polypropylene film, a gas barrier layer made of a biaxially oriented polypropylene film having a vapor deposition layer, and an inner layer made of a polypropylene film are laminated in this order.

[0137] The method of laminating a heat-resistant substrate on the side opposite the sealing surface of the sealing layer of the polypropylene-based film, and the method of laminating a heat-resistant substrate and a heat-resistant substrate provided with a gas barrier layer on the side opposite the sealing surface of the sealing layer of the polypropylene-based film are not particularly limited, but a dry lamination method is preferred from the viewpoint of productivity.

[0138] Dry laminating adhesives are not particularly limited, but examples include two-component reactive aromatic adhesives consisting of a first component made of one or more polyols selected from the group consisting of polyurethane polyols, polyester polyols, and polyether polyols, and a second component (curing agent) made of isocyanate, or two-component reactive aliphatic adhesives, polyurethane adhesives, polyester-polyurethane adhesives, polyether-polyurethane adhesives, acrylic adhesives, epoxy adhesives, polyolefin adhesives, elastomer adhesives, and fluorine-based adhesives.

[0139] The thickness of the adhesive layer is preferably 0.5 to 5 μm, more preferably 0.5 to 3 μm. If the thickness of the adhesive layer is 0.5 μm or more, it becomes easy to control the film thickness, and if it is 5 μm or less, it becomes easy to shorten the drying time and reduce production costs while imparting sufficient adhesive strength.

[0140] The laminate of the heat-resistant substrate and at least one gas barrier layer selected from the group consisting of metal vapor deposition, inorganic oxide vapor deposition, and gas barrier resin has a heat shrinkage rate of 7% or less at 150°C in the longitudinal direction and a water vapor permeability of 5 g / m 2 / day / atm or less, oxygen permeability is 5cc / m 2 / day / atm or less is preferable because it can be processed into gas barrier packaging bags, flat bags (flat pouches) for retort, standing pouches, and the like.

[0141] The laminate is suitable for monomaterial recyclability and comprises a surface layer made of a biaxially stretched polypropylene film, a heat-resistant substrate made of a biaxially stretched polypropylene film having an inorganic oxide vapor deposition layer, and a seal layer made of a polypropylene film. The laminate has a heat shrinkage rate of 7% or less at 150°C in the longitudinal direction, and a water vapor permeability of 5 g / m 2 / day / atm or less, oxygen permeability is 10cc / m 2 / day / atm or less, and can be processed into bags such as gas barrier packaging bags, flat bags (flat pouches) for retort, and standing pouches.

[0142] In this case, it is preferable for the proportion of polypropylene-based resin in the laminate suitable for monomaterial recyclability to be 70% by mass or more, as this provides excellent recyclability.

[0143] Examples of the vapor-deposited layer formed on the heat-resistant substrate include metals such as aluminum, magnesium, titanium, tin, indium, silicon, and zinc, as well as their oxides, which may be used alone or in combination. The vapor-deposited layer is preferably a compound containing a metal oxide or a metal nitride. The vapor-deposited layer preferably contains a metal oxide or a metal nitride, because it improves resistance to heat applied during boiling and retorting. Examples of metal oxides include aluminum oxide, magnesium oxide, titanium oxide, tin oxide, indium oxide alloys, silicon oxide, and silicon oxynitride. Examples of metal nitrides include aluminum nitride, titanium nitride, and silicon nitride. These inorganic oxides may be used alone or in combination. Of these, it is more preferable for the vapor-deposited layer of the present invention to contain aluminum and / or silicon, because this improves resistance to heat applied during the boiling and retorting processes.

[0144] The thickness of the vapor-deposited layer is preferably 1 nm or more and 150 nm or less, more preferably 5 nm or more and 60 nm or less, and even more preferably 10 nm or more and 40 nm or less. By making the thickness of the vapor-deposited layer 1 nm or more, the oxygen barrier property and water vapor barrier property of the laminate for packaging materials of the present invention can be obtained. Furthermore, by making the thickness of the vapor-deposited layer 150 nm or less, the occurrence of cracks in the vapor-deposited layer can be prevented and productivity can be improved.

[0145] When the vapor-deposited layer is an aluminum vapor-deposited layer, its OD (Optical Density) value is preferably 2 or more and 3.5 or less, which makes it possible to improve the oxygen barrier property and water vapor barrier property while maintaining the productivity of the laminate for packaging materials of the present invention.

[0146] The OD value is measured by an optical densitometer in accordance with JIS-K-7361. A perpendicular transmitted light beam is irradiated onto a sample, and the ratio to the state without the sample is expressed in log (logarithm).

[0147] The vapor deposition layer can be formed using a conventionally known method, for example, physical vapor deposition methods (PVD methods) such as vacuum deposition, sputtering, and ion plating, and chemical vapor deposition methods (CVD methods) such as plasma chemical vapor deposition, thermal chemical vapor deposition, and photochemical vapor deposition.

[0148] Furthermore, for example, a composite film consisting of two or more vapor-deposited layers of different inorganic oxides can be formed by combining physical vapor deposition and chemical vapor deposition. The degree of vacuum in the deposition chamber is 10 -2 ~10 -8 After oxygen is introduced, the pressure is preferably about 10 -1 ~10 -6A pressure of about mbar is preferred. The amount of oxygen introduced varies depending on the size of the deposition machine. An inert gas such as argon gas, helium gas, or nitrogen gas may be used as a carrier gas for the oxygen introduced, provided that this does not cause any problems. The film transport speed can be about 10 to 800 m / min.

[0149] When providing a vapor-deposited layer on the heat-resistant substrate, it is preferable to provide an anchor treatment layer on the surface of the heat-resistant substrate, provide the vapor-deposited layer thereon, and further provide a protective layer on the surface of the vapor-deposited layer, thereby preventing cracks from occurring in the vapor-deposited layer, maintaining gas barrier properties, and improving adhesion to the polypropylene film.

[0150] Examples of the anchor treatment layer and the surface protection layer include liquid curing or two-component curing adhesives, non-curing adhesives, and solventless adhesives, and from the viewpoint of environmental load, solventless adhesives are preferably used.

[0151] Examples of the solvent-free adhesive include polyether adhesives, polyester adhesives, silicone adhesives, epoxy adhesives, and urethane adhesives, and among these, two-component curing urethane adhesives can be preferably used.

[0152] Examples of the solvent-based adhesive include rubber-based adhesives, vinyl-based adhesives, silicone-based adhesives, epoxy-based adhesives, phenol-based adhesives, and olefin-based adhesives.

[0153] By setting the thickness of the anchor treatment layer and the surface protection layer in the range of 0.3 to 5 μm, the bending load resistance of the vapor deposition layer can be improved.

[0154] The anchor treatment layer and the surface protection layer can be formed by applying and drying on the substrate by a conventionally known method such as a direct gravure roll coating method, a gravure roll coating method, a kiss coating method, a reverse roll coating method, a Fontaine method, or a transfer roll coating method.

[0155] Gas barrier resins used in the gas barrier resin layer provided on the heat-resistant substrate include, for example, water-soluble resins such as polyvinyl alcohol resins, ethylene-vinyl alcohol copolymer resins, and modified polyvinyl alcohol resins, vinyl chloride resins, and vinylidene chloride resins. These polymers may be used alone or in mixtures of two or more. Vinyl alcohol polymers (including modified polyvinyl alcohol) are preferred. Vinyl alcohol polymers (including modified polyvinyl alcohol) are generally obtained by saponifying polyvinyl acetate. They may be partially saponified by saponifying a portion of the acetate groups, or completely saponified, but a higher degree of saponification is preferred. The degree of saponification is preferably 90% or higher, more preferably 95% or higher. A low degree of saponification and a high content of acetate groups with significant steric hindrance may increase the free volume of the gas barrier resin layer. The degree of polymerization of the vinyl alcohol resin is preferably 1,000 to 3,000, more preferably 1,000 to 2,000. If the degree of polymerization is low, the polymer may be difficult to fix, making it difficult to exhibit gas barrier properties.

[0156] Furthermore, the gas barrier resin layer preferably further contains a metal alkoxide in addition to the gas barrier resin. Examples of metal alkoxides include alkoxides of aluminum, silicon, titanium, zinc, tin, zirconium, etc., with silicon alkoxides being particularly preferred from the standpoints of ease of handling and compatibility with the gas barrier resin. Examples of silicon alkoxides include those represented by Si(OR)4. R in the silicon alkoxide is preferably a lower alkyl group, such as a methyl group, an ethyl group, an n-propyl group, or an n-butyl group. Specific examples of silicon alkoxides include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane, which may be used alone or in combination of two or more.

[0157] Silicon alkoxide is hydrolyzed in the presence of Si(OR)4, water, a catalyst, and an organic solvent. The amount of water used for hydrolysis is preferably 0.8 to 5 equivalents, more preferably 1.0 to 4 equivalents, relative to the alkoxy group of Si(OR)4. If the amount of water is less than 0.8 equivalents, the hydrolysis may not proceed sufficiently. If the amount of water is more than 4 equivalents, the hydrolysis may proceed too rapidly, resulting in a hydrolyzed liquid that is poorly compatible with the gas barrier resin.

[0158] The catalyst used for hydrolysis is preferably an acid catalyst. Examples of acid catalysts include, but are not limited to, hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, acetic acid, and tartaric acid. Generally, the hydrolysis and polycondensation reaction of silicon alkoxides can be carried out using either an acid or a base catalyst. However, when an acid catalyst is used, the monomers in the system tend to be hydrolyzed evenly and become linear. On the other hand, when a base catalyst is used, the reaction mechanism favors the hydrolysis and polycondensation reaction of alkoxides bonded to the same molecule, so the reaction proceeds randomly and the reaction product tends to have many voids. The amount of catalyst used is preferably 0.1 mol% or more and 0.5 mol% or less based on the total molar amount of silicon alkoxide.

[0159] The organic solvent used for hydrolysis may be an alcohol such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, or n-butyl alcohol that is miscible with water and silicon alkoxide.

[0160] The hydrolysis temperature is preferably 20° C. or higher and 45° C. or lower. If the reaction is carried out at a temperature lower than 20° C., the reactivity is low and the hydrolysis of Si(OR)4 may not proceed easily. On the other hand, if the reaction is carried out at a temperature higher than 45° C., the hydrolysis and polycondensation reaction may proceed too rapidly, resulting in gelation.

[0161] The gas barrier resin layer of the present invention can be obtained by coating and drying a coating liquid containing the components. The drying temperature for the coating liquid may be selected appropriately from 100°C to 200°C depending on the type of heat-resistant substrate. However, when the coating liquid is applied to the aforementioned biaxially stretched polypropylene film, the drying temperature is preferably 100°C to 180°C, and even more preferably 120°C to 180°C, taking into consideration the heat resistance of the film. If the drying temperature is less than 100°C, the water contained as a solvent (described below) may not evaporate sufficiently, and the layer may not harden. Furthermore, to improve the gas barrier properties, the gas barrier resin layer can be further heat-treated after formation. The heat treatment temperature is preferably 30°C to 100°C, and more preferably 40°C to 80°C. The heat treatment time is preferably 1 day to 14 days, and more preferably 3 days to 7 days. If the heat treatment temperature is below 30°C, the thermal energy required to promote the reaction may be insufficient and the effect may be small. If the temperature exceeds 100°C, the substrate may curl, oligomers and additives may bleed out, and the costs for equipment and production may increase.

[0162] The solvent used in the coating liquid for the gas barrier resin layer may be any solvent that can uniformly dissolve the gas barrier resin and metal alkoxide (including hydrolyzates of metal alkoxides) described above. In particular, when the gas barrier resin layer is made of a water-soluble resin and a metal alkoxide (including hydrolyzates of metal alkoxides), water or a water / alcohol mixed solvent is preferred, and examples of the alcohol used in the mixed solvent include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, and n-butyl alcohol.

[0163] The method for applying the coating liquid containing the components of the gas barrier resin layer is not particularly limited, and any known method can be used, such as a direct gravure method, a reverse gravure method, a microgravure method, a rod coating method, a bar coating method, a die coating method, or a spray coating method. The gas barrier resin layer according to the present invention may contain a leveling agent, a crosslinking agent, a curing agent, an adhesion agent, a stabilizer, an ultraviolet absorber, an antistatic agent, etc., as long as the gas barrier properties are not impaired.

[0164] The thickness of the gas barrier resin layer in the present invention may be appropriately selected depending on the type of heat-resistant substrate and the type of gas barrier resin, but is preferably 10 nm to 1,000 nm, more preferably 100 nm to 600 nm, and even more preferably 250 nm to 500 nm. If the thickness is less than 10 nm, sufficient gas barrier properties may not be exhibited. On the other hand, if the thickness exceeds 1,000 nm, the thickness may cause curling of the substrate.

[0165] When the laminate in which the heat-resistant substrate layer is made of biaxially oriented polypropylene is used as a retort packaging bag, the bag-making speed is 40 spm or more, which is equivalent to the bag-making speed of a laminate in which a conventional polyester film is used as a heat-resistant substrate. [Example]

[0166] The present invention will be described in detail below with reference to examples, but the scope of the present invention is not limited thereto. In addition, the measurement values ​​of each evaluation item in the detailed description of the present invention and the examples were measured by the following methods.

[0167] (1) Melting temperature peak Using a differential scanning calorimeter (DSC-60 manufactured by Shimadzu Corporation), the resin compositions of the base layer and the seal layer were heated from 20°C at a rate of 10°C / min, and the highest peak temperature of the melting peak when heated to 250°C was taken as the melting temperature peak.

[0168] (2) Content of 20°C xylene soluble fraction CXS and insoluble fraction CXIS Five grams of film or polymer was completely dissolved in 500 ml of boiling xylene (grade 1, manufactured by Kanto Chemical Co., Ltd.), cooled to 20°C, and left to stand for at least four hours. The precipitate and solution were then filtered to separate the xylene-soluble and xylene-insoluble portions. The mass of the xylene-insoluble portion was determined by drying the precipitate at 70°C under reduced pressure, then measuring its mass at 23°C to determine its content (mass%). The xylene-soluble portion CXS was determined by drying the filtrate to dryness, then measuring its mass under reduced pressure at 70°C, and then measuring its mass to determine its content (mass%).

[0169] (3) Intrinsic viscosity of xylene-insoluble portion CXIS and soluble portion CXS of film and polymer Using the sample separated by the above method, measurements were carried out in tetralin at 135°C using an Ubbelohde viscometer.

[0170] (4) Ethylene content The values ​​were determined by infrared spectroscopy according to the method described on page 616 and subsequent pages of the Polymer Analysis Handbook (published by Kinokuniya Shoten in 1995). The ethylene content (mass%) in the 20°C xylene soluble portion of the propylene-ethylene block copolymer (a) was calculated using the following formula: (Ethylene content contained in xylene solubles at 20°C) = {(Ethylene content contained in (a)) - (Ethylene content contained in xylene insolubles at 20°C) × (Content of insolubles in (a))} × 100 / (Content of xylene solubles at 20°C in (a)) (Content unit: mass%)

[0171] (5) Density of resin (unit: g / cm 3 ) Measurement was carried out in accordance with Method A (water displacement method) of JIS-K7112:1999.

[0172] (6) Melt flow rate (MFR) According to JIS K7210:1999, measurements were taken at a temperature of 230°C for polypropylene resins, and at a temperature of 190°C for polyethylene resins and ethylene-α-olefin copolymer elastomers, with a load of 21.18N for each.

[0173] (7) Aspect ratio Str of film surface texture based on roughness curve element The aspect ratio Str of the film surface was determined when the film surface was observed under the following conditions based on ISO 25178 using a laser microscope VK-100 / VK-X150 manufactured by KEYENCE Corporation. Observation magnification: 50x Observation area: 0.0625mm 2

[0174] (8) Peak count based on roughness curve elements: Peak count of 0.3 μm or more in RPc Using a fully automatic microscopic shape measuring instrument (SURFCORDER ET4000A) manufactured by Kosaka Laboratory Co., Ltd., the surface of the seal layer film was measured in the direction perpendicular to the flow direction of the film (TD) under the following conditions according to the measurement method specified in JIS B0601:1982, and the number of peak counts of 0.3 μm or more in the peak count number RPc based on the roughness curve element was determined. Measuring length: 2 mm Y direction measurement length: 10mm Y-direction measurement pitch: 0.1 mm Number of scans: 100.

[0175] (9) Film thickness and thickness composition The film thickness was measured using a dial gauge at 10 random locations on the film according to JIS K7130 (1992) A-2. The average value was used as the film thickness. The thickness composition of the base layer and the seal layer was determined by cutting a cross section of the film with a microtome, taking a cross-sectional photograph of the cross section at 1000x magnification using a VHX-100 digital microscope (Keyence Corporation), measuring the thickness direction distance of each layer, and calculating the thickness of each layer from the magnification. The thickness of each layer was calculated by using five cross-sectional photographs taken at five random locations from different measurement fields of view, and averaging these.

[0176] (10) Temperature at which heat seal strength is 3N / 15mm or more In accordance with JIS Z1713:1999, the seal surfaces of the polypropylene film seal layers were overlapped and the heat seal temperature was changed in 1°C increments, and the heat seal strength of these samples was measured at a peel speed of 300 mm / min using a Tensilon made by Orientec Co., Ltd. A heat seal initiation temperature of 150°C or less at which the heat seal strength at 23°C was 3 N / 15 mm or more using this measurement method was considered to have good low-temperature heat sealability.

[0177] (11) Blocking shear force at 130°C A 30mm wide and 100mm long polypropylene film sample was prepared, and the sealing surfaces of the sealing layers were overlapped in an area of ​​30mm x 40mm, with a 10g load placed on the sample. The sample was then heated in an oven at 130°C for 30 minutes, and left in an atmosphere at 23°C and 65% humidity for at least 30 minutes. The shear peel strength was then measured at a pulling rate of 300mm / min using a Tensilon manufactured by Orientec Co., Ltd. This measurement method resulted in a shear peel strength of 15N / 12cm. 2 If the temperature was below this, the high-temperature blocking resistance was judged to be good.

[0178] (12) External haze of the sealing layer The external haze of the sealing layer was measured by the following method using a Heze-meter HM-150 manufactured by Murakami Color Research Laboratory. (i) The total haze (i) of the entire film is measured. (ii) Measure the internal haze (ii) (measure by immersing the sample in a quartz cell containing liquid paraffin). (iii) Liquid paraffin is applied to the seal layer and the haze (iii) is measured (internal haze + base layer haze). (iv) External haze of sealing layer = Total haze (i) - Internal haze (ii) - Haze (iii)

[0179] (13) Preparation of laminate with heat-resistant substrate A gas-barrier, heat-resistant substrate ("Barrierox" 110 SBR2, manufactured by Toray Advanced Film Co., Ltd.), consisting of a 12-μm-thick biaxially oriented polyethylene terephthalate film coated with aluminum oxide vapor deposition and a gas-barrier resin, and a 15-μm-thick biaxially oriented polyamide film (Bonyl® Q, manufactured by Kohjin Co., Ltd.), were laminated together using a standard dry lamination method with an aliphatic ester-based adhesive (Takelac A385 / Takenate A50, manufactured by Mitsui Chemicals, Inc., adhesive layer thickness: 2.5 μm). A 60-μm-thick polypropylene film was then laminated to the 15-μm-thick biaxially oriented polyamide film surface using a standard dry lamination method with an aliphatic ester-based adhesive (Takelac A385 / Takenate A50, manufactured by Mitsui Chemicals, Inc., adhesive layer thickness: 2.5 μm), and the laminate was aged at 40°C for 3 days to produce a laminate.

[0180] Furthermore, for the purpose of producing a monomaterial, a laminate was created by laminating a 20 μm thick biaxially oriented polypropylene (Pylen Film-OT (registered trademark) P2171 manufactured by Toyobo Co., Ltd.), a 20 μm thick biaxially oriented polypropylene film in which a gas barrier resin resin made of polyvinyl alcohol resin to which silicon alkoxide and a crosslinking agent have been added on an aluminum oxide vapor deposition layer, and a 60 μm thick polypropylene film using an aliphatic ester adhesive (Takelac A385 / Takenate A50 manufactured by Mitsui Chemicals, Inc., adhesive layer thickness 2.5 μm) using a conventional dry lamination method, and aging at 40°C for 3 days.

[0181] (14) Secondary processability In the step (13) of laminating the heat-resistant substrate and the polypropylene film, process contamination due to particles and resin falling onto the metal rolls and nip rolls of the lamination process line was visually confirmed.

[0182] (15) Heat seal strength when heat sealed at 170°C Using the laminate obtained in (13) above, the sealing surfaces of the sealing layers of the polypropylene-based films of the laminate were overlapped and heat-sealed at 170°C (seal plate: flat plate, one side: constant 80°C). After leaving the sample in an atmosphere of 23°C for 1 hour, the heat-seal strength was measured at a peel rate of 300 mm / min using a Tensilon manufactured by Orientec Co., Ltd. in an atmosphere of 23°C, and a value of 23 N / 15 mm or more was deemed suitable for retort packaging.

[0183] (16) 150°C heat shrinkage rate in the longitudinal direction of the laminate Using the laminate (13), a 100 x 100 mm mark was made in the center of a 200 x 200 mm film, which was then held in a 150°C oven for 5 minutes, removed, and left at room temperature at 23°C for 1 hour.The length in the machine direction (MD) was then measured to determine the shrinkage rate.

[0184] (17) Bag making speed Using the laminate (13) described above, depending on the heat-resistant substrate, a bag making machine was used under the conditions of a bottom seal temperature (bottom part) of 140°C or more and 230°C or less, a vertical seal temperature of 130°C or more and 230°C or less, and a top seal temperature (sealed part after filling with contents) of 130°C or more and 230°C or less. The number of packaging bags filled with 160g of saline solution as contents that could be produced in one minute was defined as the bag making speed spm (shots per minute), and a speed of 40 spm or more was evaluated as good high-speed bag making ability.

[0185] (18) Bag breakage retention rate (low temperature impact resistance) Using the laminate (13), a three-sided bag measuring 150 mm long x 130 mm wide was heat-sealed on three sides at 210°C, filled with 160 g of saline solution, and then sealed using an impulse sealer set to 210°C to obtain a packaging bag. The resulting packaging bag was subjected to a 1 kg load from a 20 cm height (base dimension: 152 mm x 152 mm) drop 10 times in a 5°C atmosphere using a DuPont drop impact tester, and the bag breakage retention rate was measured. Laminates with a bag breakage retention rate of 50% or higher without liquid leakage were evaluated as having good low-temperature impact resistance, while laminates with a bag breakage retention rate of less than 50% due to bag rupture or liquid leakage from the seal were evaluated as having poor low-temperature impact resistance.

[0186] (19) Heat seal strength in a 100°C atmosphere (steam permeability when heated in a microwave oven) Using the packaging bag obtained in (18) above, the heat seal strength was measured at a peel rate of 300 mm / min in an atmosphere of 100°C using a Tensilon manufactured by Orientec Co., Ltd. A value of 30 N / 15 mm or less was evaluated as good steam permeability when heated in a microwave oven, and a value of 30 N / 15 mm or more was evaluated as poor steam permeability.

[0187] (20) OD value (optical density) Metallized film is measured using an optical densitometer in accordance with JIS-K-7361. A perpendicular transmitted light beam is irradiated onto the sample, and the ratio to the value when there is no sample is expressed as log (logarithm). The higher the optical density, the lower the transmittance; 100% transmittance means the optical density is 0.

[0188] (21) Thickness of inorganic vapor deposition layer, thickness of protective layer The thickness of the protective layer and the inorganic vapor deposition layer were measured by observing the cross section using a TEM. First, a sample for cross-sectional observation was prepared by FIB using a microsampling system (Hitachi, Ltd., FB-2000A) (specifically, based on the method described in "Polymer Surface Processing Science" (by Akira Iwamori), pp. 118-119). Next, a transmission electron microscope (Hitachi, Ltd., H-9000UHRII) was used to observe the cross section at an accelerating voltage of 300 kV. The magnification was adjusted so that the layer thickness accounted for 30-70% of the observed image. A total of five samples were measured in the same manner, and the average values ​​of all five were calculated. These values, converted to nm, were used as the protective layer thickness and the inorganic vapor deposition layer thickness.

[0189] (22) Oxygen permeability The oxygen transmission rate (hereinafter sometimes abbreviated as OTR) of the laminate with the heat-resistant substrate obtained in (13) above was measured at a temperature of 23°C and a humidity of 90%RH using an oxygen transmission rate measuring device ("OX-TRAN" (registered trademark) 2 / 21) manufactured by MOCON, based on JIS K7126-2 (2006). The measurement was performed twice for each of two test pieces, and the average of the four measured values ​​was taken as the oxygen transmission rate.

[0190] (23) Water vapor transmission rate (hereinafter sometimes abbreviated as WVTR) The water vapor transmission rate (hereinafter sometimes abbreviated as WVTR) of the laminate with the heat-resistant substrate obtained in (13) above was measured at a temperature of 40°C and a humidity of 90%RH using a water vapor transmission rate measuring device ("PERMATRAN" (registered trademark)-W 3 / 31) manufactured by MOCON in accordance with JIS K7129-2 (2019). The measurement was performed twice for each of the two test pieces, and the average of the four measured values ​​was used as the water vapor transmission rate.

[0191] The compositions of the various raw materials used in the present invention are described below. Tables 1 and 2 summarize the properties of the polypropylene films and retort laminates produced from the raw material formulations.

[0192] (1) Propylene-ethylene block copolymer (a1) MFR: 2.1g / 10min CXS amount: 20% by mass [η]CXIS:1.8dl / g [η]CXS:3.2dl / g Peak melting temperature: 162°C.

[0193] (2) Propylene-ethylene random copolymer (a2) Ethylene content: 4% by mass MFR: 3.0g / 10min Peak melting temperature: 142°C.

[0194] (3) Propylene-ethylene random copolymer (a3) Ethylene content: 6% by mass MFR: 3.0g / 10min Peak melting temperature: 132°C.

[0195] (4) Propylene-ethylene random copolymer (a4) Ethylene content: 2% by mass MFR: 2.5g / 10min Melting temperature peak: 150°C.

[0196] (5) Propylene-ethylene-butene random copolymer (a5) Propylene content: 90.7% by mass, ethylene content: 3.5% by mass, butene content: 8% by mass MFR: 3.5g / 10min Melting temperature peak: 128°C.

[0197] (6) Linear low-density polyethylene (b1) MFR: 2.2g / 10min Density: 0.921g / cm 3 Peak melting temperature: 120°C.

[0198] (7) Linear low-density polyethylene (b2) MFR: 4.2g / 10min Density: 0.923g / cm 3 Peak melting temperature: 118°C.

[0199] (8) High-density polyethylene resin (b3) MFR: 1.1g / 10min Density: 0.955g / cm 3 Peak melting temperature: 135°C.

[0200] (9) High-density polyethylene resin (b4) MFR: 0.2g / 10min Density: 0.938g / cm 3 Peak melting temperature: 1°C.

[0201] (10) High-pressure low-density polyethylene (b5) MFR: 7.0g / 10min Density: 0.905g / cm 3 Peak melting temperature: 106°C.

[0202] (11) Propylene-butene copolymer elastomer (c1) MFR: 7.0g / 10min Density: 0.880g / cm 3 Melting temperature peak: 70℃

[0203] [Example 1] The polypropylene film composition was made up of 87.5% by mass of a propylene-ethylene random copolymer (a2) with a melting temperature peak of 142°C, which had been thoroughly cooled with liquid nitrogen and then pulverized using an impeller mill to form a powder, 10% by mass of high-density polyethylene (b3), and 2.5% by mass of Perhexa 25B (registered trademark, manufactured by Nippon Oil & Fats Co., Ltd.; chemical name: 2,5-dimethyl-2,5-di(t-butylperoxy)hexane) as a peroxide. To a total of 100 parts by mass of the mixed composition, 0.05 parts by mass of tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane ("Sumilizer" BP-101) and 0.01 parts by mass of Irganox 1076 (manufactured by Ciba Specialty Chemicals) were added, mixed for 3 minutes in a Henschel mixer, and then fed into a twin-screw extruder temperature-controlled at 260°C, where the mixture was melt-kneaded at high temperature and high shear to produce master chips.

[0204] Next, 70% by mass of the master chip, 20% by mass of a propylene-ethylene block copolymer (a1), and 10% by mass of a propylene-butene copolymer elastomer (c1) were mixed, fed into a twin-screw extruder controlled at 260°C, melt-kneaded, and extruded from a T-type nozzle at 250°C and 60 m / min. The mixture was then brought into contact with a cooling roll at 45°C to cool and solidify, and one side (the non-sealed side) was subjected to a corona discharge treatment to obtain a 60 μm-thick polypropylene film.

[0205] Next, a 12 μm-thick biaxially oriented polyethylene terephthalate film (Barrierox® 110 SBR2, manufactured by Toray Advanced Film Co., Ltd.) coated with aluminum oxide vapor deposition and a gas barrier resin and having a melting temperature peak of 260°C and a 15 μm-thick biaxially oriented polyamide film (Bonyl® Q, manufactured by Kohjin Co., Ltd.) was used as a heat-resistant substrate. An aliphatic ester-based adhesive (Takelac A385 / Takenate A50, manufactured by Mitsui Chemicals, Inc., adhesive layer thickness 2.5 μm) was used to bond the biaxially oriented polyamide film surface to the corona-treated side of the polypropylene film using an aliphatic ester-based adhesive (Takelac A385 / Takenate A50, manufactured by Mitsui Chemicals, Inc., adhesive layer thickness 2.5 μm) using a conventional dry lamination method. The laminate was then aged at 40°C for 3 days to obtain a laminate.

[0206] Using the laminate, the heat seal strength at 170°C was confirmed, and bag formability was confirmed by using a bag making machine with a bottom seal temperature (bottom part) of 210°C, a vertical seal temperature of 210°C, and a top seal temperature (sealed part after filling with contents) of 210°C, and evaluating the bag making speed (spm (shots per minute)) as the number of packaging bags filled with 200 g of saline solution as the contents.

[0207] The properties of the obtained polypropylene film and the properties of the laminate with the heat-resistant substrate are shown in Table 1.

[0208] The polypropylene-based film had excellent low-temperature heat sealing properties, excellent high-temperature blocking resistance, high heat sealing strength at 170°C as a laminate, excellent low-temperature impact resistance, excellent bag formability, low water vapor permeability and oxygen permeability resulting in excellent gas barrier properties, and excellent steam permeability when heated in a microwave oven, satisfying all of the required properties of the present invention for use in retort packaging.

[0209] [Example 2] A polypropylene film and laminate were obtained in the same manner as in Example 1, except that the seal layer composition was a master chip (90 mass %) prepared by melt-kneading 77.5 mass % of propylene-ethylene random copolymer (a2), 10 mass % of high-density polyethylene (b4), 10 mass % of propylene-ethylene block copolymer (a1), and 2.5 mass % of Perhexa 25B (registered trademark) as a peroxide at high temperature and high shear, to which 10 mass % of the propylene-ethylene block copolymer (a1) was added. The properties of the obtained polypropylene film and the properties of the laminate with the heat-resistant substrate are shown in Table 1.

[0210] The polypropylene-based film had excellent low-temperature heat sealing properties, excellent high-temperature blocking resistance, high heat sealing strength at 170°C as a laminate, excellent low-temperature impact resistance, excellent bag formability, low water vapor permeability and oxygen permeability resulting in excellent gas barrier properties, and excellent steam permeability when heated in a microwave oven, satisfying all of the required properties of the present invention for use in retort packaging.

[0211] [Example 3] A polypropylene film and a laminate were obtained in the same manner as in Example 1, except that the seal layer composition was a mixture of 80% by mass of a master chip prepared by mixing 87.5% by mass of propylene-ethylene random copolymer (a2), 10% by mass of high-density polyethylene (b2), and 2.5% by mass of peroxide and melt-kneading the mixture at high temperature and high shear, 10% by mass of a propylene-ethylene block copolymer (a1), and 10% by mass of a propylene-butene copolymer elastomer (c1). The properties of the obtained polypropylene film and the properties of the laminate with the heat-resistant substrate are shown in Table 1.

[0212] The polypropylene-based film had excellent low-temperature heat sealing properties, excellent high-temperature blocking resistance, high heat sealing strength at 170°C as a laminate, excellent low-temperature impact resistance, excellent bag formability, low water vapor permeability and oxygen permeability resulting in excellent gas barrier properties, and excellent steam permeability when heated in a microwave oven, satisfying all of the required properties of the present invention for use in retort packaging.

[0213] [Example 4] An unstretched polypropylene film was obtained in the same manner as in Example 1, except that the propylene-ethylene random copolymer (a2) in the master chip was changed to the propylene-ethylene random copolymer (a3). The properties of the obtained polypropylene film and the properties of the laminate with the heat-resistant substrate are shown in Table 1.

[0214] The polypropylene film has excellent high-temperature heat sealing properties, excellent high-temperature blocking resistance, high heat sealing strength at 170°C as a laminate, excellent low-temperature impact resistance, excellent bag formability, low water vapor permeability and oxygen permeability for excellent gas barrier properties, and excellent steam permeability when heated in a microwave oven, and satisfies all of the required properties of the present invention for use in retort packaging.

[0215] [Example 5] An unstretched polypropylene film was obtained in the same manner as in Example 1, except that the master chips used in Example 1 were 80% by mass, which were prepared by mixing 57.5% by mass of propylene-ethylene random copolymer (a2), 40% by mass of high-density polyethylene (b2), and 2.5% by mass of peroxide and melt-kneading the mixture at high temperature and high shear. The properties of the obtained polypropylene film and the properties of the laminate with the heat-resistant substrate are shown in Table 1.

[0216] The polypropylene-based film had excellent low-temperature heat sealing properties, excellent high-temperature blocking resistance, high heat sealing strength at 170°C as a laminate, excellent low-temperature impact resistance, excellent bag formability, low water vapor permeability and oxygen permeability resulting in excellent gas barrier properties, and excellent steam permeability when heated in a microwave oven, satisfying all of the required properties of the present invention for use in retort packaging.

[0217] [Example 6] In Example 1, a master chip was prepared using a mixture of 87.6% by mass of propylene-ethylene random copolymer (a2), 10% by mass of high-density polyethylene (b2), and 2.4% by mass of Perhexa 25B (manufactured by NOF Corporation, chemical name: 2,5-dimethyl-2,5-di(t-butylperoxy)hexane) as a peroxide. A polypropylene-based unstretched film was obtained in the same manner as in Example 1, except that the seal layer composition was a mixture of 55% by mass of the master chip, 30% by mass of propylene-ethylene block copolymer (a1), and 15% by mass of propylene-butene copolymer elastomer (c1). A laminate was also obtained in the same manner as in Example 1. The properties of the obtained polypropylene-based unstretched film and the properties of the laminate with a heat-resistant substrate are shown in Table 1.

[0218] The polypropylene-based film had excellent low-temperature heat sealing properties, excellent high-temperature blocking resistance, high heat sealing strength at 170°C as a laminate, excellent low-temperature impact resistance, excellent bag formability, low water vapor permeability and oxygen permeability resulting in excellent gas barrier properties, and excellent steam permeability when heated in a microwave oven, satisfying all of the required properties of the present invention for use in retort packaging.

[0219] [Example 7] The polypropylene film used had a resin composition for the base layer, consisting of 72% by mass of a propylene-ethylene block copolymer (a1) with a peak melting temperature of 162°C, 18% by mass of linear low-density polyethylene (b1), and 10% by mass of a propylene-butene copolymer elastomer (c1). The seal layer was made of 87.5% by mass of a propylene-ethylene random copolymer (a2) with a peak melting temperature of 142°C and 10% by mass of high-density polyethylene (b3), which had been thoroughly cooled with liquid nitrogen and then pulverized to powder using an impeller mill, and 2.5% by mass of Perhexa 25B (registered trademark) (manufactured by NOF Corporation, chemical name: 2,5-dimethyl-2,5-di(t-butylperoxy)hexane) as the peroxide. To a total of 100 parts by mass of the mixed composition, 0.05 parts by mass of tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane ("Sumilizer" BP-101) and 0.01 parts by mass of Irganox 1076 (manufactured by Ciba Specialty Chemicals) were added, mixed for 3 minutes in a Henschel mixer, and then fed into a twin-screw extruder temperature-controlled at 260°C, where the mixture was melt-kneaded at high temperature and high shear to produce master chips. Next, a resin composition obtained by mixing 70% by mass of the master chip, 20% by mass of a propylene-ethylene block copolymer (a1), and 10% by mass of a propylene-butene copolymer elastomer (c1) was separately fed into an extruder and melt-kneaded at 260°C. The resulting mixture was extruded from a T-type two-layer die with a base layer to seal layer thickness ratio of 6:1, brought into contact with a cooling roll at 45°C, and taken up at 60 m / min to cool and solidify. The surface of the base layer (non-sealed surface) was then corona discharge treated to obtain a 60 μm-thick polypropylene film.

[0220] Next, a heat-resistant substrate was prepared by laminating two heat-resistant substrates, one made of a 12-μm-thick biaxially oriented polyethylene terephthalate film with a melting temperature peak of 260°C and coated with aluminum oxide vapor and a gas barrier resin (Barrierox (registered trademark) 110 SBR2, manufactured by Toray Advanced Film Co., Ltd.) and the other made of a 15-μm-thick biaxially oriented polyamide film (ON), using an aliphatic ester-based adhesive (Takelac A385 / Takenate A50, manufactured by Mitsui Chemicals, Inc., adhesive layer thickness 2.5 μm) using a standard dry lamination method. The corona-treated side of the base layer of the polypropylene film was then laminated to the biaxially oriented polyamide film using an aliphatic ester-based adhesive (Takelac A385 / Takenate A50, manufactured by Mitsui Chemicals, Inc., adhesive layer thickness 2.5 μm) using a standard dry lamination method, and the laminate was then aged at 40°C for 3 days to obtain a laminate.

[0221] Using the laminate, the heat seal strength at 170°C was confirmed, and bag formability was confirmed by testing a bag-making machine at a bottom seal temperature (bottom edge) of 210°C, a vertical seal temperature of 210°C, and a top seal temperature (sealed portion after filling) of 210°C, evaluating the number of packaging bags filled with 200g of saline solution as the bag-making speed (spm) as shots per minute. The properties of the obtained polypropylene-based film and the properties of the laminate with the heat-resistant substrate are shown in Table 1.

[0222] The polypropylene-based film had excellent low-temperature heat sealing properties, excellent high-temperature blocking resistance, high heat sealing strength at 170°C as a laminate, excellent low-temperature impact resistance, excellent bag formability, low water vapor permeability and oxygen permeability resulting in excellent gas barrier properties, and excellent steam permeability when heated in a microwave oven, satisfying all of the required properties of the present invention for use in retort packaging.

[0223] [Example 8] In Example 7, the base layer was made of a resin composition containing 35% by mass of a propylene-ethylene block copolymer (a1) having a melting temperature peak of 162°C, 50% by mass of a propylene-ethylene random copolymer (a2), and 15% by mass of a linear low-density polyethylene (b2). The seal layer was made of 77.5% by mass of a propylene-ethylene random copolymer (a2), 10% by mass of a high-density polyethylene (b4), 10% by mass of a propylene-ethylene block copolymer (a1), and 25% by mass of perhexa as a peroxide. 90% by mass of master chips, which had been melt-kneaded with 2.5% by mass of B (registered trademark), were mixed with 10% by mass of propylene-ethylene block copolymer (a1). These resin compositions were separately fed into an extruder and melt-kneaded at 260°C, extruded from a T-type two-layer die with a base layer to seal layer thickness ratio of 6:1, brought into contact with a cooling roll at 45°C, and taken up at 60 m / min to cool and solidify. The surface of the base layer (non-sealed surface) was then corona discharge treated to obtain a 60 μm-thick polypropylene film.

[0224] Next, a laminate with a heat-resistant substrate was obtained in the same manner as in Example 7. The properties of the obtained polypropylene-based film and the properties of the laminate with the heat-resistant substrate are shown in Table 1.

[0225] The polypropylene-based film had excellent low-temperature heat sealing properties, excellent high-temperature blocking resistance, high heat sealing strength at 170°C as a laminate, excellent low-temperature impact resistance, excellent bag formability, low water vapor permeability and oxygen permeability resulting in excellent gas barrier properties, and excellent steam permeability when heated in a microwave oven, satisfying all of the required properties of the present invention for use in retort packaging.

[0226] [Example 9] For the purpose of preparing a monomaterial, a 20 μm-thick biaxially oriented polypropylene (Pylen Film-OT (registered trademark) P2171 manufactured by Toyobo Co., Ltd.) and a 20 μm-thick biaxially oriented polypropylene film heat-resistant substrate, in which a gas barrier resin made of polyvinyl alcohol resin to which silicon alkoxide and a crosslinking agent have been added on an aluminum oxide vapor-deposited layer, was coated, and the base layer surface of the 60 μm-thick polypropylene film of Example 7 was laminated by a standard dry lamination method using an aliphatic ester-based adhesive (Takelac A385 / Takenate A50 manufactured by Mitsui Chemicals, Inc., adhesive layer thickness 2.5 μm), and then aged at 40°C for 3 days to form a laminate, and the laminate was evaluated in the same manner as in Example 7. The laminate had excellent low-temperature heat sealing properties, excellent high-temperature blocking resistance, high heat sealing strength at 170°C as a laminate, excellent low-temperature impact resistance, excellent bag formability, low water vapor permeability and oxygen permeability resulting in excellent gas barrier properties, and excellent steam permeability when heated in a microwave oven, satisfying all of the required properties of the present invention for use in retort packaging.

[0227] [Example 10] In Example 9, a laminate was evaluated in the same manner as in Example 7, except that the multilayer polypropylene film of the base layer and seal layer of Example 8 was laminated with a heat-resistant substrate. The laminate had excellent low-temperature heat sealing properties, excellent high-temperature blocking resistance, high heat sealing strength at 170°C as a laminate, excellent low-temperature impact resistance, excellent bag formability, low water vapor permeability and oxygen permeability resulting in excellent gas barrier properties, and excellent steam permeability when heated in a microwave oven, satisfying all of the required properties of the present invention for retort packaging.

[0228] [Comparative Example 1] The polypropylene film was prepared by mixing 100 parts by mass of a mixed resin consisting of 70% by mass of a propylene-ethylene random copolymer (a2), 20% by mass of a high-pressure low-density polyethylene (b5), and 10% by mass of a propylene-butene copolymer elastomer (c1). To this was added 2 parts by mass of spherical silica having a particle size of 2 μm, 0.05 parts by mass of tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane ("Sumilizer" BP-101), and 0.01 parts by mass of Irganox 1076 (manufactured by Ciba Specialty Chemicals). The mixture was mixed for 3 minutes in a Henschel mixer, then fed to a twin-screw extruder controlled at 260°C for melt kneading. The mixture was then extruded at 250°C through a T-die at 60 m / min and cooled and solidified by contacting with a 45°C cooling roll. One side was then subjected to a corona discharge treatment to obtain a polypropylene film having a thickness of 60 μm. A laminate was also obtained in the same manner as in Example 1. The properties of the obtained polypropylene film and the properties of the laminate with the heat-resistant substrate are shown in Table 2.

[0229] The polypropylene film has a melting temperature peak of 142°C, which is within the range of the present invention. However, despite the high content of inorganic particles, the average roughness Str of the heat seal surface is 0.18, which is less than 0.2, and the peak count of 0.3 μm or more is 230 / 20 mm. 2 Because it is so small, the blocking shear force at 130°C is 20N / 12cm 2 The film had poor high-temperature blocking resistance, a bag-making speed of 35 spm, and poor bag-making performance. The inorganic particles caused process contamination during lamination, resulting in poor secondary processability. Furthermore, the high content of inorganic particles resulted in a deterioration in the heat-sealing properties of the laminate. Furthermore, when the laminate was unwound from the roll after being laminated with the heat-resistant substrate, pinholes were formed in the gas barrier layer due to the inorganic particles in the polypropylene film, resulting in a deterioration in oxygen permeability and water vapor permeability.

[0230] Comparative Example 2 A polypropylene film was obtained in the same manner as in Example 1, except that the propylene-ethylene random copolymer (a2) having a melting temperature peak of 142°C was replaced with a propylene-ethylene-butene random copolymer (a5) having a melting temperature peak of 128°C. A laminate was also obtained in the same manner as in Example 1. The properties of the obtained polypropylene film and the properties of the laminate with the heat-resistant substrate are shown in Table 2.

[0231] The polypropylene film has a peak melting temperature of 128°C, and therefore the blocking shear force at 130°C is 16N / 12cm 2 The heat seal strength at 170°C was low at 30N / 15mm, leakage of contents occurred during retort treatment at 130°C, the bag-making speed was 30 spm, and bag-break retention was also low. Furthermore, when the laminate was unwound from the roll that had been laminated with the heat-resistant substrate, blocking occurred, forming pinholes in the gas barrier layer, and deterioration of the oxygen permeability and water vapor permeability was observed.

[0232] Comparative Example 3 A polypropylene film was obtained in the same manner as in Example 1, except that the propylene-ethylene random copolymer (a2) having a melting temperature peak of 142°C was replaced with an ethylene-propylene-butene random copolymer (a4) having a melting temperature peak of 150°C. A laminate was also obtained in the same manner as in Example 1. The properties of the obtained polypropylene film and the properties of the laminate with the heat-resistant substrate are shown in Table 2.

[0233] The above polypropylene film had a film surface property aspect ratio Str and peak count RPc, and the peak count of 0.3 μm or more satisfied the ranges specified in the present invention. However, because the main component, propylene-ethylene random copolymer, had a high melting temperature of 150°C, the temperature at which the heat seal strength reached 3 N / 15 mm or more was as high as 155°C, resulting in poor low-temperature heat sealing properties. The heat seal strength at 170°C was low at 15 N / 15 mm, and leakage of the contents occurred during retort treatment at 130°C. The bag-making speed was also poor at 25 spm, resulting in poor bag-making properties, and the bag break retention rate was also low.

[0234] Comparative Example 4 A laminate was obtained in the same manner as in Example 1, except that the propylene-ethylene random copolymer (a2) contained 80% by mass of propylene-ethylene random copolymer and 20% by mass of high-density polyethylene (b2). The properties of the obtained polypropylene film and the properties of the laminate with the heat-resistant substrate are shown in Table 2.

[0235] The polypropylene film did not contain peroxide and was extruded under conventional conditions with a high concentration of high-density polyethylene. However, the peak count of 0.3 μm or more was 210 / 20 mm. 2 Because it is so thin, it is prone to wrinkling when laminated with a heat-resistant substrate, making it inferior for secondary processing. The blocking shear force at 130°C is 18N / 12cm. 2 The bag-making speed was 35 spm, which resulted in poor bag-making properties.

[0236] Comparative Example 5 In Example 7, a polypropylene film was obtained in the same manner as in Example 1, except that the base layer was made of a mixed resin of 10 mass% propylene-ethylene block copolymer (a1), 70 mass% propylene-ethylene-butene random copolymer (a5) having a melting temperature peak of 128°C, and 20 mass% linear low-density polyethylene (b1). A laminate was also obtained in the same manner as in Example 7. The properties of the obtained polypropylene film and the properties of the laminate with the heat-resistant substrate are shown in Table 2.

[0237] The polypropylene film mentioned above has a low content of propylene-ethylene block copolymer in the base layer, and is mainly composed of a propylene-ethylene-butene random copolymer with a low melting temperature peak. Because the seal layer is also thin, wrinkles appear when laminating with a heat-resistant substrate, resulting in poor oxygen and water vapor permeability. Furthermore, the heat seal strength at 170°C is low, and the bag deformation during bag making causes a decrease in the bag making speed and a low bag breakage retention rate.

[0238] Comparative Example 6 A polypropylene film was obtained in the same manner as in Example 1, except that in Example 7, the propylene-ethylene random copolymer (a2) with a peak melting temperature of 142°C in the seal layer was replaced with a propylene-ethylene-butene random copolymer (a5) with a peak melting temperature of 128°C. A laminate was also obtained in the same manner as in Example 9, consisting of a 20 μm-thick biaxially oriented polypropylene (Toyobo Co., Ltd., Pylen Film-OT (registered trademark) P2171) and a 20 μm-thick heat-resistant substrate of biaxially oriented polypropylene film, in which a gas barrier resin composed of polyvinyl alcohol resin to which silicon alkoxide and a crosslinking agent had been added was coated on an aluminum oxide vapor-deposited layer. The properties of the resulting polypropylene film and the properties of the laminate with the heat-resistant substrate are shown in Table 2.

[0239] The polypropylene film has a low melting temperature peak of the sealing layer, so the blocking shear force at 130°C is 16N / 12cm 2 The heat seal strength at 170°C was low at 30 N / 15 mm, leakage of the contents occurred during retort treatment at 130°C, and the bag-making speed was also poor at 30 spm. Furthermore, when the laminate was unwound from the roll on which it was laminated with the heat-resistant substrate, blocking occurred, forming pinholes in the gas barrier layer and deteriorating the oxygen permeability and water vapor permeability.

[0240] Comparative Example 7 A polypropylene film was obtained in the same manner as in Example 1, except that in Example 7, the propylene-ethylene random copolymer (a2) with a peak melting temperature of 142°C in the seal layer was replaced with a propylene-ethylene random copolymer (a4) with a peak melting temperature of 150°C. A laminate was also obtained in the same manner as in Example 9, consisting of a 20 μm-thick biaxially oriented polypropylene (Pylen Film-OT (registered trademark) P2171, manufactured by Toyobo Co., Ltd.) and a 20 μm-thick heat-resistant substrate of a biaxially oriented polypropylene film in which a gas barrier resin composed of polyvinyl alcohol resin to which silicon alkoxide and a crosslinking agent had been added was coated on an aluminum oxide vapor-deposited layer. The properties of the resulting polypropylene film and the properties of the laminate with the heat-resistant substrate are shown in Table 2.

[0241] The polypropylene-based film had a film surface property aspect ratio Str and peak count RPc, and the peak count of 0.3 μm or more satisfied the ranges specified in the present invention. However, because the melting temperature of the main component, propylene-ethylene random copolymer, was high at 150°C, the temperature at which the heat seal strength reached 3 N / 15 mm or more was high at 155°C, resulting in poor low-temperature heat sealing properties. The heat seal strength at 170°C was low at 12 N / 15 mm, and leakage of the contents occurred during retort treatment at 130°C. The bag-making speed was also poor at 25 spm, resulting in poor bag-making properties, and the bag break retention rate was also low.

[0242] [Table 1]

[0243] [Table 2] [Industrial Applicability]

[0244] The present invention can provide a polypropylene-based film having excellent low-temperature heat sealing properties, high-temperature blocking resistance, excellent bag-making processability, and excellent retort suitability, and a laminate using the same, which can be used for packaging bags for retort food packaging, battery exterior materials, etc.

Claims

1. At least a seal layer can be formed, the main component is polypropylene resin, the surface shape aspect ratio Str is 0.2 to 1.0, and the peak count RPc is 300 / 20 mm ２ The polypropylene film has a peak melting temperature of 130 to 145°C.

2. The seal layer is made up of at least two layers, a base layer and a seal layer, and the base layer contains 20% by mass or more of a propylene-ethylene block copolymer and is mainly composed of a polypropylene-based resin having a melting temperature peak of 140°C or higher. The seal layer is mainly composed of a polypropylene-based resin, and has a surface texture aspect ratio Str of 0.2 to 1.0 and a peak count RPc of 300 peaks / 20mm of 0.3 μm or more. ２ The polypropylene film has a peak melting temperature of 130 to 145°C.

3. The surface that will become the seal layer is measured by infrared absorption spectroscopy at 719 cm -1 The peak is 973 cm -1 The polypropylene film according to claim 1 or 2, wherein the value obtained by dividing by the peak is in the range of 0.3 to 0.

8.

4. The polypropylene-based film according to claim 1 or 2, wherein the external haze of the sealing layer is in the range of 5 to 20%.

5. The blocking shear force between the sealing surfaces of the sealing layer at 130°C is 15 N / 12 cm ２ The polypropylene-based film according to claim 1 or 2, wherein:

6. 3. The polypropylene-based film according to claim 1, wherein the heat-sealing initiation temperature at which the heat-sealing strength is 3 N / 15 mm or more when the sealing surfaces of the sealing layers are overlapped and heat-sealed is 150°C or less.

7. The polypropylene film according to claim 1 or 2, having a film thickness of 20 μm or more and 150 μm or less.

8. The polypropylene-based film according to claim 2, wherein the thickness ratio of the base layer to the seal layer is 9:1 to 3:

1.

9. 3. A packaging laminate comprising a polypropylene-based film according to claim 1 or 2, and a heat-resistant substrate having a melting temperature peak of 160°C or higher laminated on the side opposite the sealing surface of the sealing layer, the heat-sealing strength of which is 23 N / 15 mm or higher when the sealing surfaces of the sealing layers are overlapped and heat-sealed at 170°C.

10. 10. The packaging laminate according to claim 9, wherein the heat-resistant substrate comprises at least one selected from the group consisting of a biaxially oriented polyamide film, a biaxially oriented polyethylene terephthalate film, a biaxially oriented polypropylene film, a biaxially oriented polybutylene terephthalate film, a biaxially oriented polyester / polyamide hybrid film, a uniaxially oriented polyamide film, a uniaxially oriented polyethylene terephthalate film, a uniaxially oriented polypropylene film, and a uniaxially oriented polybutylene terephthalate film, and a substrate having at least one gas barrier layer applied to the film, the gas barrier layer being selected from the group consisting of metal vapor deposition, inorganic vapor deposition, transparent metal oxide vapor deposition, and a gas barrier resin, and at least one layer selected from the group consisting of synthetic paper and aluminum foil.

11. 10. The packaging laminate according to claim 9, wherein the heat-resistant substrate is a substrate comprising at least one film selected from the group consisting of biaxially oriented polyamide film, biaxially oriented polyethylene terephthalate film, biaxially oriented polypropylene film, biaxially oriented polybutylene terephthalate film, biaxially oriented polyester / polyamide hybrid film, uniaxially oriented polyamide film, uniaxially oriented polyethylene terephthalate film, uniaxially oriented polypropylene film, and uniaxially oriented polybutylene terephthalate film, to which at least one gas barrier layer selected from the group consisting of metal vapor deposition, inorganic oxide vapor deposition, and gas barrier resin has been applied.

12. 10. The packaging laminate according to claim 9, wherein a surface layer made of a biaxially stretched polypropylene film, a gas barrier layer made of a biaxially stretched polypropylene film having a vapor deposition layer, and an inner layer made of a polypropylene film are laminated in this order.

13. 13. The packaging laminate according to claim 12, wherein the proportion of the polypropylene-based resin is 70% by mass or more.

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