Polypropylene-based unstretched film and laminate using same

Abstract

Provided are: a polypropylene-based unstretched film which has excellent low-temperature heat sealability, excellent high-temperature blocking resistance, excellent bag-making processability, and excellent cooking suitability, as a packaging bag for packaging cooked foods, in which the number of layers is reduced in consideration of the environment; and a laminate using the polypropylene-based unstretched film. A polypropylene-based unstretched film which comprises, as a main component, a propylene-based random copolymer having a melting temperature peak of 135-145 DEG C, and which has, as a heat-sealing surface, a surface having a film surface average roughness Ra of 0.1 [mu] m or more and a peak count of 0.3 [mu] m or more of 100 or more per 10 mm2 on at least one surface. Alternatively, the polypropylene-based unstretched film described in Request 1 is formed from two layers, i.e., a base layer containing 50 mass% or more of a propylene-ethylene block copolymer and having a melting temperature peak of 150 DEG C or more, and a sealant layer having a melting temperature peak in the range of 135 DEG C to 145 DEG C, and a heat sealing surface having a surface average roughness Ra of 0.1 [mu] m or more and a peak count of 0.3 [mu] m or more among the number of peak counts RPc of 100 / 10 mm2 or more. And a laminate in which a heat-resistant substrate having a melting point of 160 DEG C or more is laminated, and which has a heat seal strength at 170 DEG C of 23 N / 15 mm or more.

Description

Technical Field

[0001] The present invention relates to a polypropylene-based unstretched film for packaging retort foods and a laminate using the same. Background Art

[0002] Laminated products and packaging bags for retort foods are made by laminating heat-resistant substrates such as biaxially oriented polyethylene terephthalate film (hereinafter sometimes referred to as PET), biaxially oriented polyamide film (hereinafter sometimes referred to as ON), and aluminum foil (hereinafter sometimes referred to as AL foil) with heat-sealable unoriented polypropylene film (hereinafter sometimes referred to as CPP). These bags are manufactured using PET / ON / CPP or PET / ON / AL foil / CPP. Required properties for these bags include heat resistance, impact resistance, high heat seal strength, blocking resistance, and ease of bag production.

[0003] In recent years, laws related to environmentally friendly packaging have been implemented, necessitating environmentally friendly designs for packaging bags. Consequently, there has been a growing demand for reducing the number of layers in laminates, leading to research into two-layer constructions such as PET / CPP, ON / CPP, and OPP / CPP. Furthermore, there has been a growing demand for packaging bags made from a single material and featuring excellent recyclability, leading to research into homogeneous laminates such as biaxially oriented polypropylene film / unoriented polypropylene film, or OPP / CPP. However, OPP has lower heat resistance than PET and ON, resulting in poor processability under conventional bag-making conditions. Consequently, to maintain comparable processability, unoriented polypropylene films are now required to exhibit higher low-temperature heat sealability, high-temperature blocking resistance, and retortability.

[0004] To address the aforementioned issues, Patent Document 1 proposes a laminate comprising a heat-sealable layer laminated on one side of a biaxially oriented polypropylene film having high heat resistance and elastic modulus. However, low-temperature heat-sealability, high-temperature blocking resistance, and retortability are insufficient. Furthermore, Patent Document 2 proposes a retort-safe polypropylene multilayer sealing film in which inorganic particles are added to the heat-sealable layer to regulate surface roughness. However, there are concerns about particle shedding during the film-forming and lamination processes, as well as particle contamination of food. Furthermore, the film's low-temperature heat-sealability, high-temperature blocking resistance, and retortability are insufficient, and its bag-making processability is also poor.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2020-7441

[0008] Patent Document 2: Japanese Patent No. 5895590 Summary of the Invention

[0009] Problems to be solved by the invention

[0010] Therefore, the present invention aims to provide a polypropylene-based unstretched film and a laminate using the same, which are excellent in low-temperature heat sealing properties, high-temperature blocking resistance, bag-making processability, and retort suitability, as a packaging bag for retort food packaging with a reduced number of layers in consideration of the environment.

[0011] Means for solving problems

[0012] The inventors of the present application have solved the aforementioned problems by providing the following unstretched polypropylene film and a laminate using the same.

[0013] That is, the present invention is a polypropylene-based unstretched film, which has a propylene-based random copolymer having a melting temperature peak of 135°C or more and 145°C or less as a main component, and has a film surface average roughness Ra of 0.1 μm or more on at least one side, and a peak count of 0.3 μm or more per 10 mm. 2 The surface serves as a thermal cover.

[0014] The present invention also provides a polypropylene-based unstretched film comprising two layers, a base layer and a sealant layer, wherein the base layer contains 50% by mass or more of a propylene-ethylene block copolymer and has a melting temperature peak of 150° C. or higher, and the sealant layer has a melting temperature peak within a range of 135° C. to 145° C. The unstretched polypropylene film has a surface average roughness Ra of 0.1 μm or higher on the sealant layer, and a peak count of 0.3 μm or higher is 100 peaks / 10 mm. 2 The above surface serves as a heat shield.

[0015] Effects of the Invention

[0016] By using a polypropylene-based unstretched film having excellent low-temperature heat-sealability and high-temperature blocking resistance and a laminate using the same for retort food packaging, it is possible to provide a packaging bag for retort food packaging that is environmentally friendly and can reduce the amount of packaging materials. DETAILED DESCRIPTION

[0017] Hereinafter, the polypropylene-based unstretched film of the present invention and a laminate using the same will be described in detail.

[0018] The unstretched polypropylene film of the present invention contains as a main component a propylene random copolymer having a melting temperature peak in the range of 135° C. to 145° C. Here, the main component means that the propylene random copolymer accounts for 50% by mass or more of the total resin content of the film.

[0019] If the ratio of the propylene-based random copolymer having a melting temperature peak in the range of 135°C to 145°C is less than 50% by mass, the heat seal strength at 170°C, i.e., 23 N / 15 mm or higher, required for retort food applications, cannot be achieved. When the bagged product is filled with contents and heat-sterilized at 130°C or higher, the contents may scatter or leak.

[0020] By setting the melting temperature peak of the propylene random copolymer within the range of 135°C to 145°C, a heat seal strength of 23 N / 15 mm or more at 170°C, which is required for retort food applications, can be obtained. In addition, a blocking shear force of 15 N / 12 cm at 130°C can be achieved. 2 Below, so it is preferred.

[0021] If the melting temperature peak is less than 135°C, the shear force at 130°C will be 15N / 12cm. 2 If the melting temperature peak exceeds 145°C, when the heat seal sheets are overlapped and heat-sealed, the heat seal start temperature at which the heat seal strength reaches 3N / 15mm or more may be 150°C or higher, which slows the bag making speed.

[0022] The melt flow rate (hereinafter sometimes referred to as MFR) of the propylene random copolymer is preferably in the range of 0.5 to 100 g / 10 min (230°C, load 2.18 N), and a range of 2 to 20 g / 10 min is preferred because stable melt extrusion film formation can be achieved.

[0023] The propylene random copolymer having a melting temperature peak in the range of 135°C to 145°C is preferably a propylene random copolymer formed from propylene and one or more comonomers because it 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 propylene-ethylene random copolymers, random copolymers of propylene and ethylene and α-olefins having 4 or more carbon atoms, and random copolymers of propylene, ethylene, and α-olefins 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-methyl-1-pentene, 1-octene, and 1-hexene, with 1-butene being preferred.

[0025] The copolymerization amount of the aforementioned comonomer is preferably from 1 mol% to 10 mol% from the viewpoint of heat seal strength. If the copolymerization amount is less than 1 mol%, the heat seal strength may be reduced. If it exceeds 10 mol%, the slip properties may be deteriorated, and wrinkles may be easily generated during film winding. In addition, the film may be blocked from unwinding and break.

[0026] The polypropylene unstretched film of the present invention has an average surface roughness Ra of 0.1 μm or greater on at least one side of the film, the side to be heat-sealed. Preferably, a surface roughness within the range of 0.2 to 0.7 μm is preferred because the film has good slip properties and is easy to pass through during film production and lamination processes.

[0027] The polypropylene-based unstretched film of the present invention has a peak count of 0.3 μm or more on at least one side, which is the side to be heat-sealed, of 100 or more / 10 mm. 2 In this case, it is suitable to make the adhesion shear force at 130°C to be 15N / 12cm 2 The following is preferred when automatically filling the contents into the bagged product, because the bag opening property is excellent, the filling property of the contents is excellent, and the bag making speed is increased. The peak count of 0.3 μm or more is preferably 300 or more / 10 mm 2 , more preferably 500 or more / 10mm 2 .

[0028] In order to ensure that the average roughness of the film surface of the heat seal and the peak count of 0.3 μm or more are within the preferred range, it is preferred not to form the film surface using inorganic particles or organic particles. This is because it is possible to prevent particles from falling off during film formation and mixing into the contents.

[0029] In order to make the average roughness of the surface of the aforementioned film and the peak count of 0.3 μm or more within the preferred range, for example, it can be illustrated that: at least one kind of polyethylene and a cross-linking agent of an organic peroxide are mixed with the aforementioned propylene-based random copolymer and subjected to high-temperature high-shear extrusion to form a chip, and using this chip, a film is formed using a T-die film machine or an inflation film machine.

[0030] Examples of the polyethylene include polyethylene having a density of 0.900 g / cm 3 Above and less than 0.945g / cm 3 Low-density polyethylene with a density of 0.945g / cm 3 Above and less than 0.970g / cm 3 High density polyethylene, etc. When the mixed density is less than 0.900g / cm 3In the case of polyethylene, the above-mentioned average roughness and peak count of the film surface may not be achieved.

[0031] As the low-density polyethylene, a linear low-density polyethylene (hereinafter sometimes referred to as LLDPE) which is a copolymer of ethylene and α-olefin has good dispersibility in the propylene-based random copolymer, and it is easy to make the peak count of 0.3 μm or more 100 or more / 10 mm. 2 Examples of the α-olefin constituting the linear low-density polyethylene include 1-butene, 1-hexene, and 1-octene.

[0032] From the viewpoint of heat seal strength and blocking shear force at 130°C, the melting temperature peak of the polyethylene is preferably 100°C or higher and lower than 140°C, more preferably 120°C or higher and lower than 140°C.

[0033] The melt flow rate of the polyethylene measured at 190°C and a load of 21.18N in accordance with JIS-K7210 (1999) is preferably 0.2 to 10 g / 10 min, more preferably 0.5 to 5 g / 10 min. This allows for good dispersibility in the propylene-based random copolymer, making it easy to obtain the average surface roughness of the film and a peak count of 0.3 μm or more, and is therefore preferred.

[0034] The amount of the linear low-density polyethylene (LLDPE) mixed in the propylene random copolymer is preferably less than 50% by mass, more preferably 5 to 40% by mass, and even more preferably 10 to 30% by mass. This makes it easy to obtain the average surface roughness of the film and a peak count of 0.3 μm or more, and the adhesion shear strength at 130°C is easily 15 N / 12 cm. 2 The following are preferred.

[0035] 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, relative to the resin component. This provides good dispersibility in the resin, allows the crosslinking agent to act on the polyethylene, and facilitates achieving an average surface roughness of the film and a peak count of 0.3 μm or greater. An amount less than 1% by mass may not produce significant effects, while an amount exceeding 40% by mass may result in poor dispersion and deterioration in extrudability.

[0036] The organic peroxide is not particularly limited, and examples thereof include alkyl peroxides, diacyl peroxides, peroxyesters, and peroxycarbonates. Examples of the alkyl peroxide 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-butylperoxy)-3-hexyne, tert-butylcumyl peroxide, 1,3-bis(tert-butylperoxyisopropyl)benzene, and 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane.

[0037] Examples of the diacyl peroxides include benzoyl peroxide, lauroyl peroxide, and decanoyl peroxide. Examples of the peroxyesters include 1,1,3,3-tetramethylbutyl peroxyneodecanoate, α-cumyl peroxyneodecanoate, t-butyl peroxyneodecanoate, t-butyl peroxyneoheptanoate, t-butyl peroxypivalate, t-hexyl peroxypivalate, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, t-amyl peroxy-2-ethylhexanoate, t-butyl peroxy-2-ethylhexanoate, t-butyl peroxyisobutyrate, di-t-butyl peroxyhexahydroterephthalate, t-amyl peroxy-3,5,5-trimethylhexanoate, t-butyl peroxy-3,5,5-trimethylhexanoate, t-butyl peroxyacetate, t-butyl peroxybenzoate, and dibutyl peroxytrimethyladipate.

[0038] Examples of the peroxycarbonates include di-3-methoxybutyl peroxydicarbonate, di(2-ethylhexyl) peroxydicarbonate, diisopropyl peroxycarbonate, tert-butyl peroxyisopropyl carbonate, di(4-tert-butylcyclohexyl) peroxydicarbonate, dicetyl peroxydicarbonate, and dimyristyl peroxydicarbonate.

[0039] Note that, from the perspective of food hygiene in retort food packaging, it is preferred that the organic peroxide does not remain in the unstretched polypropylene film of the present invention.

[0040] In addition, as a method other than the above-mentioned method for making the average roughness Ra of the film surface and the peak count of 0.3 μm or more within a preferred range, a method for giving an embossed shape to one side (hot cover) of the film using a film-making nip roller can be cited. As long as it is a film-making nip roller that can form the hot cover in the present invention, there is no particular restriction. For example, the film-making nip roller disclosed in International Publication No. 2013 / 80925 and Japanese Patent Application Publication No. 2020-55189 can be preferably utilized. Specifically, it is preferably an embossing nip roller having an arithmetic mean roughness Ra of less than 0.2 μm, a ten-point average roughness Rz of 2 to 8 μm, and an average interval Sm of concave and convex of less than 90 μm.

[0041] The polypropylene-based unstretched film of the present invention preferably has a shear strength of 15 N / 12 cm when the heat seals are bonded together at 130°C. 2 In this case, the bag is easy to open when the bag is automatically filled with the contents, and the filling of the contents is easy. If the adhesion shear force at 130°C exceeds 15N / 12cm 2 , when automatically filling the bagged product with contents, the bag mouth may not be opened and the contents may spill out, and the bag making speed may be reduced.

[0042] In packaging bags such as pouches, when heat-sealing the heat-sealed sheets together, the heat-sealing initiation temperature at which the heat-seal strength reaches 3 N / 15 mm or more is preferably 150° C. or lower, more preferably 145° C. or lower.

[0043] The bag making speed is preferably 40 spm or higher, more preferably 45 spm or higher. If the bag making speed is less than 40 spm, the product yield may be poor and the manufacturing cost may increase, which is not preferred.

[0044] The polypropylene-based unstretched film of the present invention preferably has the adhesion shear force and heat seal strength at 130° C. within the preferred ranges of the present invention and preferably further contains a thermoplastic elastomer, because low-temperature heat sealability and impact resistance are improved.

[0045] The content of the thermoplastic elastomer is preferably 5% by mass or more and 40% 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 observed. If the content exceeds 40% by mass, the heat seal strength may be significantly reduced during retorting, heating in a microwave oven, or the like, and leakage from the packaging bag may occur.

[0046] 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 comonomer. Specifically, it is preferably produced using a metallocene catalyst.

[0047] As the aforementioned α-olefin, ethylene, propylene, 1-butene, 1-hexene, 1-octene, etc. having 2 to 10 carbon atoms can be used. Specific examples of the thermoplastic elastomer include ethylene-propylene copolymer elastomers, ethylene-butene copolymer elastomers, ethylene-octene copolymer elastomers, propylene-ethylene copolymer elastomers, propylene-butene copolymer elastomers, propylene-hexene copolymer elastomers, and propylene-octene copolymer elastomers. In particular, from the perspectives of heat seal strength and low-temperature impact resistance, it is preferred to additionally add an elastomer containing propylene as the main component.

[0048] 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, from the viewpoint of compatibility with the propylene-based random copolymer and blocking resistance.

[0049] The polypropylene-based unstretched film of the present invention is composed of two layers, a base layer and the aforementioned polypropylene-based unstretched film as a sealing layer, wherein the base layer contains 50% by mass or more of a propylene-ethylene block copolymer and has a melting temperature peak of 150° C. or more, the melting temperature peak of the aforementioned sealing layer is within the range of 135° C. to 145° C., the surface average roughness Ra of the sealing layer based on the roughness curve element is 0.1 μm or more, and the peak count number RPc based on the roughness curve element, of peaks with a surface roughness of 0.3 μm or more, is 100 / 10 mm. 2 above.

[0050] The base layer preferably contains 50% by mass or more of a propylene-ethylene block copolymer. If the propylene-ethylene block copolymer is less than 50% by mass, the laminated product with a heat-resistant substrate may have poor low-temperature impact resistance when used as a packaging bag.

[0051] With respect to the aforementioned propylene-ethylene block copolymer, in order to obtain the characteristics of the laminate of the present invention, it is preferred that the intrinsic viscosity [η]CXS of the 20°C xylene-soluble portion CXS is 2.5 dl / g or more and 3.5 dl / g or less, the amount of the aforementioned 20°C xylene-soluble portion CXS is 10% by mass or more and 25.0% by mass or less, and the intrinsic viscosity [η]CXIS of the 20°C xylene-insoluble portion CXIS is 1.5 dl / g or more and 2.2 dl / g or less.

[0052] Here, regarding the aforementioned 20°C xylene-insoluble portion CXIS and soluble portion CXS, when the aforementioned polypropylene film is completely dissolved in boiling xylene, cooled to 20°C, allowed to stand for more than 4 hours, and then filtered to separate into a precipitate and a solution, the precipitate is referred to as the 20°C xylene-insoluble portion CXIS (hereinafter, sometimes referred to as the xylene-insoluble portion CXIS), and the portion obtained by solidifying the solution portion (filtrate) and drying it at 70°C under reduced pressure is referred to as the 20°C xylene-soluble portion CXS (hereinafter, sometimes referred to as the xylene-soluble portion CXS).

[0053] The 20° C. xylene-insoluble portion CXIS corresponds to the polypropylene monomer, and the xylene-soluble portion CXS corresponds to the rubber component.

[0054] If the amount of the 20°C xylene-soluble portion CXS in the base layer is less than 10% by mass, low-temperature impact resistance may be poor, the decrease in heat seal strength at 100°C of the laminate may be small, and vapor permeability may be poor. If it exceeds 25.0% by mass, the decrease in heat seal strength at 100°C may be significant, and liquid leakage from the packaging bag may occur when heated in a microwave oven or the like. The amount of CXS is preferably within the range of 8% to 20.0% by mass.

[0055] If the intrinsic viscosity ([η]CXS) of the 20°C xylene-soluble portion CXS in the aforementioned base layer is less than 2.5 dl / g, the low-temperature impact resistance may be reduced. If it is greater than 3.5 dl / g, the dispersibility in the xylene-insoluble portion CXIS may be reduced, thereby worsening the melt extrusion properties.

[0056] In addition, if the intrinsic viscosity ([η]CXIS) of the 20°C xylene-insoluble portion CXIS in the above-mentioned polypropylene film is less than 1.5 dl / g, the low-temperature impact resistance may be reduced, and if it is greater than 2.2 dl / g, the dispersibility of the xylene-soluble portion CXS may be deteriorated.

[0057] From the viewpoint of extrusion stability and low-temperature impact resistance, the melt flow rate (hereinafter sometimes referred to as MFR) of the propylene-ethylene block copolymer is preferably in the range of 0.5 to 10 g / 10 min at 230°C and a load of 21.18 N.

[0058] It is preferred that the base layer contains 10% by mass or more and less than 50% by mass of a propylene-ethylene random copolymer because the low-temperature impact resistance and heat seal strength of the retort packaging laminate can be adjusted.

[0059] When the ethylene content of the propylene·ethylene random copolymer is 1% by mass or more and 7% by mass or less, the miscibility with the propylene·ethylene block copolymer is good and it is preferable.

[0060] The MFR of the propylene / ethylene random copolymer is preferably in the range of 0.5 to 10 g / 10 min at 230° C. and a load of 21.18 N, from the viewpoint of extrusion stability and melt compatibility with the propylene / ethylene block copolymer.

[0061] The base layer preferably contains 10% to 40% by mass of an ethylene-α-olefin copolymer (wherein the total mass of the base layer resin is 100% by mass). In this case, the vapor permeability during microwave heating can be adjusted, which is preferred.

[0062] If the content of the ethylene-α-olefin copolymer is less than 10% by mass, no improvement in vapor permeability during microwave heating may be observed. If the content exceeds 40% by mass, the heat seal strength may be significantly reduced during retorting, microwave heating, etc., and liquid leakage may occur from the packaging bag.

[0063] The melting point of the ethylene-α-olefin copolymer is preferably from 110°C to 140°C. If the melting point is less than 110°C, the heat seal strength at high temperatures is reduced, and the packaging bag may break. If the melting point exceeds 140°C, the heat seal strength at high temperatures is increased, and the vapor permeability during microwave heating may deteriorate.

[0064] The ethylene / α-olefin copolymer is a copolymer of 50 to 95% by mass of ethylene as a main component and an α-olefin as a comonomer, and specifically, is preferably produced using a metallocene catalyst.

[0065] As the α-olefin, 1-butene, 1-hexene, 1-octene, etc. having 4 to 10 carbon atoms can be used, and specific examples include linear low-density polyethylene (hereinafter sometimes referred to as LLDPE).

[0066] The MFR of the ethylene / α-olefin copolymer is preferably within a range of 0.5 to 10 g / 10 min at 190° C. and a load of 21.18 N from the viewpoint of compatibility with the polypropylene resin and blocking resistance.

[0067] It is preferred to add a thermoplastic elastomer to the unstretched polypropylene film because the low-temperature heat sealability and impact resistance are improved.

[0068] The content of the thermoplastic elastomer is preferably 5% by mass or more and 40% 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 observed. If the content exceeds 40% by mass, the heat seal strength may be significantly reduced during retorting, heating in a microwave oven, or the like, and leakage from the packaging bag may occur.

[0069] 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 comonomer. Specifically, it is preferably produced using a metallocene catalyst.

[0070] As the aforementioned α-olefin, ethylene, propylene, 1-butene, 1-hexene, 1-octene, etc. having 2 to 10 carbon atoms can be used. Specific examples of the thermoplastic elastomer include ethylene-propylene copolymer elastomers, ethylene-butene copolymer elastomers, ethylene-octene copolymer elastomers, propylene-ethylene copolymer elastomers, propylene-butene copolymer elastomers, propylene-hexene copolymer elastomers, and propylene-octene copolymer elastomers. In particular, from the perspectives of heat seal strength and low-temperature impact resistance, it is preferred to additionally add an elastomer containing propylene as the main component.

[0071] Regarding the MFR of the aforementioned thermoplastic elastomer, from the viewpoint of compatibility with the polypropylene resin serving as the main component of the aforementioned sealant layer and from the viewpoint of film forming stability, it is preferred that the MFR of the elastomer containing ethylene as the main component be in the range of 0.5 to 10 g / 10 minutes at 190°C and a load of 21.18 N, and that of the elastomer containing propylene as the main component be in the range of 0.5 to 10 g / 10 minutes at 230°C and a load of 21.18 N.

[0072] The polypropylene-based unstretched film of the present invention may contain antioxidants, heat stabilizers, neutralizers, antistatic agents, hydrochloric acid absorbers, antiblocking agents, lubricants, etc., within the scope of not impairing the purpose of the present invention. These additives may be used alone or in combination of two or more.

[0073] Here, specific examples of the antioxidant include hindered phenol-based antioxidants such as 2,6-di-tert-butylphenol (BHT), n-octadecyl-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl) propionate ("Irganox" 1076, "Sumilizer" BP-76), tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate]methane ("Irganox" 1010, "Sumilizer" BP-101), and tris(3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate ("Irganox" 3114, Mark AO-20).

[0074] Examples of phosphite-based (phosphorus-based) antioxidants include tris(2,4-di-tert-butylphenyl)phosphite ("Irgafos" 168, Mark 2112), tetrakis(2,4-di-tert-butylphenyl)-4,4'-biphenyl-diphosphonite ("Sandstab" P-EPQ), bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite ("Ultranox" 626, Mark PEP-24G), and distearylpentaerythritol diphosphite (Mark PEP-8).

[0075] Among these, 6-[3-(3-tert-butyl-4-hydroxy-5-methyl)propoxy]-2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]-dioxaphosphepane ("Sumilizer" GP) and 2[1-2-hydroxy-3,5-di-tert-pentylphenyl]ethyl]-4,6-di-tert-pentylphenyl acrylate ("Sumilizer" GS), which have both the functions of hindered phenol and phosphite, are preferred. Their combined use is particularly preferred because they are effective in suppressing resin decomposition during film formation and contribute to achieving both heat seal strength and blocking resistance.

[0076] The amount of the antioxidant to be added may be appropriately set within the range of 100 to 10,000 ppm, although it depends on the type of antioxidant used.

[0077] As the neutralizing agent, hydrotalcite compounds, calcium hydroxide, etc. are preferable in order to reduce smoke generation during film formation.

[0078] The unstretched polypropylene film of the present invention may contain 100 to 1000 ppm of a fatty acid amide lubricant relative to the total resin composition, within a range that does not deteriorate film forming properties due to contamination during the film forming process caused by heat dissipation during melt extrusion, nor does it reduce heat seal strength. If the amount of fatty acid amide lubricant added is less than 100 ppm, slidability may deteriorate. If it exceeds 1000 ppm, heat dissipation during melt extrusion increases, contaminating the film forming process, deteriorating film forming properties, and reducing heat seal strength.

[0079] Examples of the fatty acid amide-based lubricant include oleamide, erucamide, stearamide, palmitic acid amide, and behenamide.

[0080] Examples of methods for obtaining the polypropylene-based unstretched film of the present invention include: a method in which the resin and additive composition are melted and kneaded using a single-screw extruder, a twin-screw co-rotating extruder, or a twin-screw counter-rotating extruder, followed by extrusion from a T-type spinneret onto a cooling drum and cooling and solidification; and a method in which the film is melt-extruded onto a heat-resistant substrate and laminated. In the present invention, the method in which the film is extruded from a T-type spinneret onto a cooling drum and cooled and solidified is preferred because the heat seal strength is increased.

[0081] The unstretched polypropylene film preferably has a thickness of 20 μm to 150 μm, and the thickness ratio of the base layer to the sealant layer is preferably 9:1 to 3:1. This ensures stable film formability, low-temperature impact resistance, and heat-seal strength, while maintaining bag-forming properties.

[0082] In the laminate formed by laminating the unstretched polypropylene film of the present invention and a heat-resistant substrate having a melting point of 160°C or higher, the heat seal strength at 170°C is preferably 23 N / 15 mm or higher. If the heat seal strength at 170°C is less than 23 N / 15 mm, the heat seal strength may be reduced by heating at 130°C or higher when used as a retort packaging material, which may cause the contents to scatter or leak.

[0083] The heat-resistant substrate having a melting point of 160°C or higher is preferably a substrate layer comprising at least one material selected from the group consisting of biaxially stretched polyamide film, biaxially stretched polyethylene terephthalate film, biaxially stretched polypropylene film, biaxially stretched polybutylene terephthalate film, biaxially stretched polyester / polyamide composite film, uniaxially stretched polyamide film, uniaxially stretched polyethylene terephthalate film, uniaxially stretched polypropylene film, and uniaxially stretched polybutylene terephthalate film; films obtained by applying at least one gas barrier layer selected from the group consisting of metal vapor deposition, inorganic vapor deposition, transparent metal oxide vapor deposition, and gas barrier resin to these films; synthetic paper; and aluminum foil. From the perspective of a single material, a substrate made of biaxially stretched polypropylene film or uniaxially stretched polypropylene film is preferred.

[0084] The method for laminating the heat-resistant substrate and the unstretched polypropylene film of the present invention is not particularly limited, but dry lamination is preferred from the viewpoint of productivity.

[0085] There are no particular limitations on the adhesive for dry lamination, and examples thereof include a two-liquid reactive aromatic adhesive consisting of a first liquid (containing one or more polyols selected from the group consisting of polyurethane polyols, polyester polyols, and polyether polyols) and a second liquid (a curing agent containing isocyanate), or a two-liquid reactive aliphatic adhesive, a polyurethane adhesive, an acrylic adhesive, an epoxy adhesive, a polyolefin adhesive, an elastic adhesive, a fluorine-based adhesive, and the like.

[0086] The thickness of the adhesive layer is preferably 0.5 to 5 μm, more preferably 0.5 to 3 μm. When the thickness of the adhesive layer is 0.5 μm or more, the film thickness is easily controlled, while when it is 5 μm or less, sufficient adhesive strength is imparted while shortening the drying time and reducing production costs.

[0087] The above-mentioned laminate can be used by processing the bag made of the polypropylene-based unstretched film of the present invention into a flat bag (flat bottom bag), a self-supporting bag, etc. so that the inner surface of the bag serves as a heat seal.

[0088] Example

[0089] Hereinafter, the present invention will be described in detail with reference to Examples, but the scope of the present invention is not limited thereto. In addition, the measured values ​​of each evaluation item in the detailed description of the present invention and Examples were measured by the following methods.

[0090] (1) Melting temperature peak

[0091] Using a differential scanning calorimeter (DSC-60 manufactured by Shimadzu Corporation), the temperature was raised 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 defined as the melting temperature peak.

[0092] (2) Density of polyethylene (unit: g / cm 3 )

[0093] The measurement was carried out in accordance with Method A (water displacement method) of JIS-K7112:1999.

[0094] (3) Melt flow rate (MFR)

[0095] According to JIS K7210:1999, propylene random copolymers, propylene·ethylene block copolymers, and propylene·α-olefin copolymer elastomers were measured at a temperature of 230°C with a load of 21.18N, and polyethylene resins and ethylene·α-olefin copolymer elastomers were measured at a temperature of 190°C with a load of 21.18N.

[0096] (4) Content of xylene-soluble fraction CXS and insoluble fraction CXIS at 20°C

[0097] 5 g of the membrane or polymer was completely dissolved in 500 ml of boiling xylene (grade 1 manufactured by Kanto Chemical Co., Ltd.), cooled to 20°C, and allowed to stand for at least 4 hours. The precipitate and solution were then filtered to separate the xylene-soluble portion and the xylene-insoluble portion. The xylene-insoluble portion was determined by drying the precipitate at 70°C under reduced pressure and measuring its mass at 23°C to determine its content (mass %). Furthermore, the xylene-soluble portion CXS was determined by drying the filtrate to a solid state, drying it at 70°C under reduced pressure, and measuring its mass to determine its content (mass %).

[0098] (5) Intrinsic viscosity of the xylene-insoluble fraction CXIS and the xylene-soluble fraction CXS of the film and polymer

[0099] The sample separated by the above method was used to perform the measurement in tetralin at 135°C using an Ubbelohde viscometer.

[0100] (6) Ethylene content

[0101] The content was determined by infrared spectroscopy using the method described on page 616 and thereafter of Handbook of Polymer Analysis (published by Kinokuniya Bookstore in 1995).

[0102] The content (mass %) of ethylene contained in the 20°C xylene-soluble portion of the propylene·ethylene block copolymer (a) is calculated according to the following formula.

[0103] (The content of ethylene contained in the xylene soluble portion at 20°C) = {(the content of ethylene contained in (a)) - (the content of ethylene contained in the xylene insoluble portion at 20°C) × (the content of the insoluble portion in (a))} × 100 / (the content of the xylene soluble portion at 20°C in (a)) (unit of content: mass %).

[0104] (7) Density of polyethylene (unit: g / cm 3 )

[0105] The measurement was carried out in accordance with Method A (water displacement method) of JIS-K7112:1999.

[0106] (8) Average surface roughness Ra of the film, peak counts of 0.3 μm or greater in the peak counts RPc based on the roughness curve elements

[0107] Using a fully automatic micro-shape measuring machine (SURFCORDER ET4000A) manufactured by Kosaka Laboratory Co., Ltd., and utilizing the measuring method specified in JISB-0601:1982, the membrane surface was measured in a direction (TD) perpendicular to the flow direction of the membrane under the following conditions to determine the average roughness Ra of the membrane surface and the peak count RPc of 0.3 μm or greater based on the peak count number RPc of the roughness curve elements.

[0108] Measuring length: 2mm

[0109] Measuring length in Y direction: 10mm

[0110] Y direction measurement spacing: 0.1mm

[0111] Number of scans: 100 times.

[0112] (9) Film thickness and thickness composition

[0113] The film thickness was measured at 10 random locations on the film using a micrometer in accordance with JIS K7130 (1992) A-2 method, and the average value was taken as the film thickness.

[0114] (10) Temperature at which the heat seal strength reaches 3N / 15mm or higher

[0115] In accordance with JIS Z1713:1999, heat seal strength was measured using a Tensilon manufactured by ORIENTEC at a peel rate of 300 mm / min for samples formed by overlapping heat-sealing sheets of unstretched polypropylene film and varying the heat-sealing temperature. This method considers good low-temperature heat sealability when the heat seal strength at 23°C reaches 3 N / 15 mm or higher and the heat seal initiation temperature is 150°C or lower.

[0116] (11) Heat seal strength at 170°C

[0117] A heat-resistant substrate layer and an unstretched polypropylene film were laminated using a conventional dry lamination method using an aliphatic ester adhesive (Mitsui Chemicals, Inc., Takelac A385 / Takenate A50, adhesive layer thickness 2.5 μm). The laminate was then aged at 40°C for 3 days to produce a laminate. Samples of the unstretched polypropylene films of this laminate were stacked and heat-sealed at 170°C. The heat seal strength was measured using Tensilon (Orientec) at a peel rate of 300 mm / min. A value of 23 N / 15 mm or higher was considered suitable for retort packaging applications.

[0118] (12) Adhesion shear force at 130°C

[0119] A film sample with a width of 30 mm and a length of 100 mm was prepared from a polypropylene unstretched film. The sealant layers were overlapped to form a 30 mm x 40 mm area. A load of 10 g was applied and the film was heated in an oven at 130°C for 30 minutes. The film was then left in an atmosphere of 23°C and 65% humidity for at least 30 minutes. The shear peel strength was measured using a Tensilon manufactured by ORIENTEC at a tensile speed of 300 mm / min. In this measurement method, the shear peel strength was 15 N / 12 cm. 2 When the value is less than 50%, the high-temperature blocking resistance is considered to be good.

[0120] (13) Bag making speed

[0121] A heat-resistant substrate layer and a polypropylene unstretched film were laminated using a conventional dry lamination method using an aliphatic ester adhesive (Mitsui Chemicals, Inc., Takelac A385 / Takenate A50, adhesive layer thickness 2.5 μm). The laminate was then aged at 40°C for 3 days to form a long laminate. This laminate was then used in a bag-making machine under the following conditions: a bottom seal temperature (bottom edge) of 140°C to 230°C, a longitudinal seal temperature of 130°C to 230°C, and a top seal temperature (sealed portion after filling) of 130°C to 230°C, depending on the heat-resistant substrate. The number of packaging bags filled with 200 g of saline solution that could be completed in one minute was measured as the bag-making speed (shots per minute). A value of 40 spm or higher was evaluated as indicating good high-speed bag-making performance.

[0122] (14)Bag breaking retention rate (low temperature impact resistance)

[0123] A 60 μm polypropylene unstretched film was adhered to one side of a heat-resistant substrate layer of a 15 μm thick biaxially stretched polyamide film using a conventional dry lamination method using an aliphatic ester adhesive (Mitsui Chemicals, Inc. Takelac A385 / Takenate A50, adhesive layer thickness 2.5 μm). The laminate was then aged at 40°C for 3 days to form a laminate.

[0124] The laminate was heat-sealed on three sides at 210°C, and 160 g of saline was filled into the resulting three-sided bag of 150 mm in length and 130 mm in width. The bag was then sealed at 210°C using an impulse sealer to obtain a packaging bag. The resulting packaging bag was dropped 10 times from a height of 20 cm using a DuPont drop hammer impact tester at 5°C, with a drop plate (bottom shape: 152 mm × 152 mm) with a load of 1 kg. The bag retention rate at this time was measured. A laminate with a bag retention rate of 50% or more without leakage was evaluated as having good low-temperature impact resistance, and a laminate with a bag rupture rate of less than 50% due to bag rupture and leakage from the sealed portion was evaluated as having poor low-temperature impact resistance.

[0125] (15) Heat seal strength at 100°C (vapor permeability during microwave heating)

[0126] The packaging bag obtained in the above (14) was used, and Tensilon manufactured by ORIENTEC was used to measure the heat seal strength in an atmosphere of 100°C at a peeling speed of 300 mm / min. A value of 30 N / 15 mm or less was evaluated as good vapor permeability during microwave heating, and a value of 30 N / 15 mm or more was evaluated as poor vapor permeability.

[0127] The compositions of various raw materials used in the present invention are described below. Table 1 summarizes the properties of the unstretched polypropylene films and laminates produced based on these raw material formulations.

[0128] (1) Propylene-ethylene block copolymer (a1)

[0129] MFR: 2.1g / 10min (230℃)

[0130] CXS amount: 20 mass%

[0131] [η]CXIS:1.8dl / g

[0132] [η]CXS:3.2dl / g

[0133] Melting temperature peak: 163°C

[0134] (2) Propylene-ethylene block copolymer (a2)

[0135] MFR: 2.7g / 10min (230℃)

[0136] CXS amount: 27 mass%

[0137] [η]CXIS:1.9dl / g

[0138] [η]CXS:3.0dl / g

[0139] Melting temperature peak: 155°C

[0140] (3) Propylene-based random copolymer (a3)

[0141] Ethylene-propylene random copolymer.

[0142] Ethylene content: 4% by mass

[0143] MFR: 3.0g / 10min (230℃)

[0144] Melting temperature peak: 142°C

[0145] (4) Propylene-based random copolymer (a4)

[0146] Ethylene-propylene random copolymer

[0147] Ethylene content: 6% by mass

[0148] MFR: 3.0g / 10min (230℃)

[0149] Melting temperature peak: 135°C

[0150] (5) Propylene-based random copolymer (a5)

[0151] Ethylene·propylene·butene random copolymer

[0152] Propylene content: 90.7% by mass, ethylene content: 2.5% by mass, butene content: 6.8% by mass

[0153] MFR: 3.5g / 10min (230℃)

[0154] Melting temperature peak: 132°C

[0155] (6) Polyethylene (b1)

[0156] 1-octene copolymerized linear low-density polyethylene

[0157] MFR: 0.8g / 10min (190℃)

[0158] Density: 0.925g / cm 3

[0159] Melting temperature peak: 125℃

[0160] (7) Polyethylene (b2)

[0161] High-density polyethylene

[0162] MFR: 1.1g / 10min (190℃)

[0163] Density: 0.950g / cm 3

[0164] Melting temperature peak: 132°C

[0165] (8) Polyethylene (b3)

[0166] High-pressure low-density polyethylene

[0167] MFR: 7.0g / 10min (190℃)

[0168] Density: 0.905g / cm 3

[0169] Melting temperature peak: 106°C

[0170] (9) Ethylene-butene copolymer elastomer (c1)

[0171] Mitsui Chemicals, Inc. "Tafmer" (registered trademark)

[0172] MFR: 3.6g / 10min (190℃)

[0173] Melting temperature peak: 66°C

[0174] (10) Propylene-butene copolymer elastomer (c2)

[0175] Mitsui Chemicals, Inc. "Tafmer" (registered trademark)

[0176] MFR: 7g / 10min (230℃)

[0177] Melting temperature peak: 75°C.

[0178] [Example 1]

[0179] The composition of the polypropylene-based unstretched film was as follows: 67.6% by mass of an ethylene-propylene random copolymer (a3) ​​obtained by sufficiently cooling with liquid nitrogen and then pulverizing it with an impeller mill to form a powder; 30% by mass of a linear low-density polyethylene (b1); and 2.4% by mass of Perhexa 25B (manufactured by NOF Corporation, chemical name: 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane) as a peroxide.

[0180] To 100 parts by mass of the total amount of the mixed composition, 0.05 parts by mass of tetrakis(methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate)methane ("Sumilizer" BP-101) and 0.01 parts by mass of Irganox 1076 (manufactured by Ciba Specialty Chemicals) were added, and the mixture was mixed for 3 minutes using a Henschel mixer.

[0181] The resulting film was then supplied to a twin-screw extruder adjusted to a temperature of 260°C for melt kneading, extruded from a T-die at 250°C at a rate of 60 m / min, cooled and solidified by contact with a cooling roll at 45°C, and then subjected to corona discharge treatment on one side to obtain a polypropylene unstretched film having a thickness of 60 μm.

[0182] The unstretched polypropylene film was laminated onto a heat-resistant substrate, a transparent vapor-deposited biaxially stretched polyethylene terephthalate film (Barrialox SBR2 (registered trademark)) having a thickness of 12 μm, using a conventional dry lamination method using an aliphatic ester adhesive (Takelac A385 / Takenate A50 manufactured by Mitsui Chemicals, Inc., adhesive layer thickness 2.5 μm). The laminate was then aged at 40°C for 3 days to obtain a laminate.

[0183] The heat seal strength at 170°C was confirmed using the laminate, and the bag-making speed (shots per minute) was evaluated as a measure of bag-making performance. The spm refers to the number of packaging bags containing 200 g of saline solution that can be formed using a bag-making machine at a bottom seal temperature (bottom edge) of 210°C, a longitudinal seal temperature of 210°C, and a top seal temperature (sealed after filling) of 210°C. The properties of the resulting unstretched polypropylene film and the laminate with a heat-resistant substrate are shown in Table 1.

[0184] The melting temperature peak of the unstretched polypropylene film is 142°C, the average surface roughness Ra of the heat-sealed film is 0.29 μm, and the peak count of 0.3 μm and above is as high as 2690 / 10 mm. 2 , which is a very large number of peak counts. The temperature at which the heat seal strength becomes 3N / 15mm or more when the heat seal covers are overlapped and heat sealed is 144°C. The low temperature heat sealability is excellent, and the adhesion shear force at 130°C is 2.4N / 12cm 2 , excellent high temperature adhesion resistance, heat sealing strength at 170 ℃ up to 60N / 15mm, suitable for cooking packaging purposes, also achieved a bag making speed of 45spm, excellent bag making properties, meeting all the required characteristics of the present invention.

[0185] [Example 2]

[0186] In Example 1, the ethylene / propylene random copolymer of the propylene random copolymer (a3) ​​was replaced with the ethylene / propylene random copolymer of the propylene random copolymer (a4), thereby obtaining a polypropylene-based unstretched film. Furthermore, a laminate was obtained in the same manner as in Example 1, except that a commercially available biaxially stretched polypropylene film (PYRENFILM-OT (registered trademark)) P2171 manufactured by Toyobo Co., Ltd., having a thickness of 20 μm, was used as the heat-resistant substrate. Heat seal strength at 170°C was confirmed using the laminate. Furthermore, as a measure of bag-forming properties, bag-forming properties were evaluated in the same manner as in Example 1 using a bag-making machine under the following conditions: a bottom seal temperature (bottom edge) of 145°C, a longitudinal seal temperature of 145°C, and a top seal temperature (sealed portion after filling with contents) of 150°C.

[0187] Table 1 shows the properties of the obtained unstretched polypropylene film and the properties of the laminate with the heat-resistant substrate.

[0188] [Example 3]

[0189] A polypropylene unstretched film was obtained in the same manner as in Example 1, except that the propylene random copolymer (a3) ​​was changed to 87.6% by mass of an ethylene-propylene random copolymer and the polyethylene (b1) was changed to 10% by mass of a linear low-density polyethylene. Furthermore, a laminate was obtained in the same manner as in Example 1. The properties of the obtained polypropylene unstretched film and the properties of the laminate with the heat-resistant substrate are shown in Table 1.

[0190] [Example 4]

[0191] In Example 1, the same procedures as in Example 1 were followed, except that the total weight of the mixed composition was changed to 100 parts by weight, consisting of 89% by weight of an ethylene-propylene random copolymer (propylene random copolymer) as the propylene random copolymer (a3), 10% by weight of a linear low-density polyethylene (polyethylene (b1)), and 1% by weight of Perhexa 25B (manufactured by NOF Corporation, chemical name: 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane) as a peroxide. A polypropylene unstretched film was obtained in the same manner as in Example 1. Furthermore, a laminate was obtained in the same manner as in Example 1. The properties of the obtained polypropylene unstretched film and the properties of the laminate with the heat-resistant substrate are shown in Table 1.

[0192] [Example 5]

[0193] In Example 1, the following procedures were followed, except that the total weight of the mixed composition was changed to 100 parts by weight: 67.6% of the ethylene-propylene random copolymer (a3), 20% of the linear low-density polyethylene (b1), 10% of the ethylene-butene elastomer copolymer (c1), and 2.4% of Perhexa 25B (manufactured by NOF Corporation, chemical name: 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane) as a peroxide. A polypropylene unstretched film was obtained in the same manner as in Example 1. Furthermore, a laminate was obtained in the same manner as in Example 1. The properties of the obtained polypropylene unstretched film and the properties of the laminate with the heat-resistant substrate are shown in Table 1.

[0194] [Example 6]

[0195] As the composition of the polypropylene-based unstretched film, 0.05 parts by mass of tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]methane ("Sumilizer" BP-101) and 0.01 parts by mass of Irganox 1076 (manufactured by Ciba Specialty Chemicals) were added to 100 parts by mass of a total mixed resin of 70% by mass of an ethylene-propylene random copolymer (a3), 20% by mass of a linear low-density polyethylene (b1), and 10% by mass of an ethylene-butene copolymer elastomer (c1), and the mixture was mixed for 3 minutes using a Henschel mixer.

[0196] The material was then fed into a twin-screw extruder controlled at 260°C for melt kneading and extrusion. A stainless steel mandrel with a heat medium flow path was coated with HTV silicone rubber to a thickness of 8 mm, and then with a 0.2 mm thick PFA heat shrink tube. The PFA surface was polished and then sprayed with steel spheres to create a surface concave portion with a depth of 1.0 μm and a thickness of 10 mm. 2 The film was extruded between a mirror-finished metal roll and the embossing rubber roll, which had 1400 concave portions, to obtain a 60 μm thick unstretched polypropylene film. Separately, the same procedures as in Example 1 were followed to obtain a laminate. The properties of the resulting unstretched polypropylene film and the laminate with the heat-resistant substrate are shown in Table 1.

[0197] [Comparative Example 1]

[0198] The composition of the polypropylene-based unstretched film was as follows: 0.4 parts by weight of spherical silica having a particle size of 2 μm as inorganic particles, 0.05 parts by weight of tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]methane (Sumilizer BP-101), and 0.01 parts by weight of Irganox 1076 (manufactured by Ciba Specialty Chemicals) were added to 100 parts by weight of a total mixed resin of 70% by weight of an ethylene-propylene random copolymer (a3), 20% by weight of a linear low-density polyethylene (b1), and 10% by weight of an ethylene-butene copolymer elastomer (c1). The mixture was mixed for 3 minutes in a Henschel mixer and then supplied to a twin-screw extruder adjusted to a temperature of 260°C for melt kneading. The extruder was then extruded from a T-die at 250°C at a rate of 60 m / min and cooled and solidified by contact with a cooling roll at 45°C. Then, one side was subjected to corona discharge treatment to obtain a 60 μm thick unstretched polypropylene film. Furthermore, the same procedures as in Example 1 were followed to obtain a laminate. The properties of the obtained unstretched polypropylene film and the laminate with the heat-resistant substrate are shown in Table 1.

[0199] The melting temperature peak of the polypropylene unstretched film was 142°C, but the average roughness Ra of the heat seal was 0.04 μm, and the number of peaks larger than 0.3 μm was 68 / 10 mm. 2 Therefore, the adhesion shear force at 130℃ is 42N / 12cm 2 , high temperature blocking resistance is poor, the bag making speed becomes 35spm, and the bag making performance is poor.

[0200] [Comparative Example 2]

[0201] A polypropylene unstretched film was obtained in the same manner as in Example 1, except that the ethylene-propylene random copolymer (a3) ​​of the propylene random copolymer was replaced with an ethylene-propylene-butene random copolymer (a5) of the propylene random copolymer. Furthermore, a laminate was obtained in the same manner as in Example 1. The properties of the obtained polypropylene unstretched film and the properties of the laminate with the heat-resistant substrate are shown in Table 1.

[0202] The melting temperature peak of the polypropylene unstretched film is 132°C, so the adhesion shear force at 130°C is 17N / 12cm. 2 , high temperature blocking resistance is poor, the heat seal strength at 170 ℃ is as low as 20N / 15mm, leakage of contents occurs during the cooking process at 130 ℃, and the bag making speed becomes 32spm, and the bag making performance is poor.

[0203] [Comparative Example 3]

[0204] A polypropylene unstretched film was obtained in the same manner as in Example 1, except that the linear low-density polyethylene (b1) was replaced with a high-pressure low-density polyethylene (b3) as the composition of the polypropylene unstretched film. Furthermore, a laminate was obtained in the same manner as in Example 1. The properties of the obtained polypropylene unstretched film and the properties of the laminate with the heat-resistant substrate are shown in Table 1.

[0205] The average roughness Ra of the polypropylene unstretched film is as low as 0.08 μm, and the melting temperature of the high-pressure low-density polyethylene mixed therein is as low as 106°C. Therefore, the adhesion shear force at 130°C is 25 N / 12 cm. 2 , high temperature blocking resistance is poor, the heat seal strength at 170 ℃ is as low as 20N / 15mm, leakage of contents occurs during the cooking process at 130 ℃, and the bag making speed becomes 37spm, and the bag making performance is poor.

[0206] [Comparative Example 4]

[0207] A polypropylene unstretched film was obtained in the same manner as in Example 1, except that the composition of the unstretched polypropylene film was 100 parts by mass of a mixed resin comprising 85% by mass of an ethylene-propylene block copolymer (a1), 5% by mass of a high-density polyethylene, and 10% by mass of an ethylene-butene elastomer copolymer (c1). Furthermore, a laminate was obtained in the same manner as in Example 1. The properties of the obtained unstretched polypropylene film and the properties of the laminate with the heat-resistant substrate are shown in Table 1.

[0208] The average roughness Ra of the polypropylene unstretched film satisfies the range specified in the present invention, but the peak count of 0.3 μm or more is below the range specified in the present invention, and the adhesion shear strength at 130°C is 40 N / 12 cm. 2 The high-temperature blocking resistance is poor. The melting temperature of the main component ethylene-propylene block copolymer is as high as 163°C. Therefore, the temperature at which the heat seal strength becomes more than 3N / 15mm is as high as 170°C. The low-temperature heat sealability is poor, and the heat seal strength at 170°C is as low as 4N / 15mm. It is impossible to obtain bagged products under the above bag making conditions.

[0209] [Example 7]

[0210] The base layer composition of the polypropylene-based unstretched film is a mixed resin of 50% by mass of a propylene·ethylene block copolymer (a1), 20% by mass of a propylene·ethylene random copolymer (a3), and 30% by mass of a linear low-density polyethylene of a polyethylene-based resin (b1) is set to 100 parts by mass. 500 ppm of "Sumilizer" GP and 750 ppm of "Sumilizer" GS as antioxidants are mixed for 3 minutes using a Henschel mixer, and the mixture is supplied to a twin-screw extruder adjusted to a temperature of 260°C and melt-kneaded.

[0211] The sealant layer composition consisted of 57.5% by mass of a propylene / ethylene random copolymer (a3) ​​having a melting temperature peak of 142°C, which had been sufficiently cooled with liquid nitrogen and then pulverized using an impeller mill to form a powder; 40% by mass of a linear low-density polyethylene (b1); and 2.5% by mass of Perhexa 25B (registered trademark) (manufactured by NOF Corporation, chemical name: 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane) as a peroxide. To 100 parts by mass of this mixed composition, 0.05 parts by mass of tetrakis(methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate)methane (Sumilizer BP-101) and 0.01 parts by mass of Irganox 1076 (manufactured by Ciba Specialty Chemicals) were added, and the mixture was mixed using a Henschel mixer for 3 minutes. The mixture was then supplied to a twin-screw extruder adjusted to 260°C for melt kneading to prepare a masterbatch.

[0212] Next, 75% by mass of the masterbatch was mixed with 25% by mass of the propylene / ethylene random copolymer (a3), and the mixture was supplied to a twin-screw extruder adjusted to a temperature of 260° C. and melt-kneaded.

[0213] Next, the melt-mixed base layer resin and sealing layer resin are extruded from a multi-layer T-type 2-layer spinneret at a ratio of 6:1 at 250°C and 60 m / min, brought into contact with a cooling roller at 45°C. After cooling and solidification, the base layer surface is subjected to corona discharge treatment to obtain a polypropylene-based unstretched film with a thickness of 60 μm.

[0214] The above-mentioned unstretched polypropylene film was laminated onto a biaxially stretched polyamide film having a thickness of 15 μm and serving as a heat-resistant substrate using a conventional dry lamination method using an aliphatic ester adhesive (Takelac A385 / Takenate A50 manufactured by Mitsui Chemicals, Inc., adhesive layer thickness 2.5 μm). The laminate was then aged at 40°C for 3 days to obtain a laminate.

[0215] The heat seal strength at 170°C was confirmed using the laminate, and the bag-making speed (shots per minute) was evaluated as a measure of bag-making performance. The spm refers to the number of packaging bags containing 200 g of saline solution that can be formed using a bag-making machine at a bottom seal temperature (bottom edge) of 210°C, a longitudinal seal temperature of 210°C, and a top seal temperature (sealed portion after filling) of 210°C. Table 2 shows the properties of the resulting unstretched polypropylene film and the properties of the laminate with a heat-resistant substrate.

[0216] The above-mentioned polypropylene-based unstretched film has 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-making properties, and excellent vapor permeability when heated in a microwave oven. For use in cooking packaging, it meets all the required properties of the present invention.

[0217] [Example 8]

[0218] In Example 7, the same procedures as in Example 7 were followed, except that the base layer was changed to 60% by mass of a propylene / ethylene block copolymer (a1), 20% by mass of a propylene / ethylene random copolymer (a3), and 20% by mass of a linear low-density polyethylene (b1), to obtain a polypropylene-based unstretched film and a laminate. Table 2 shows the properties of the obtained polypropylene-based unstretched film and the properties of the laminate with the heat-resistant substrate.

[0219] The above-mentioned polypropylene-based unstretched film has 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-making properties, and excellent vapor permeability when heated in a microwave oven. For use in cooking packaging, it meets all the required properties of the present invention.

[0220] [Example 9]

[0221] In Example 7, a polypropylene-based unstretched film was obtained in the same manner as in Example 7, except that the propylene-ethylene block copolymer (a1) having a melting temperature peak of 162°C in the base layer was replaced with a propylene-ethylene block copolymer (a2) having a melting temperature peak of 155°C. Furthermore, a laminate was obtained in the same manner as in Example 7. Table 2 shows the properties of the obtained polypropylene-based unstretched film and the properties of the laminate with the heat-resistant substrate.

[0222] The above-mentioned polypropylene-based unstretched film has 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-making properties, and excellent vapor permeability when heated in a microwave oven. For use in cooking packaging, it meets all the required properties of the present invention.

[0223] [Example 10]

[0224] In Example 7, a polypropylene-based unstretched film was obtained in the same manner as in Example 7, except that the propylene-ethylene random copolymer (a3) ​​having a melting temperature peak of 142°C in the sealant layer was replaced with a propylene-ethylene random copolymer (a4) having a melting temperature peak of 135°C. Furthermore, a laminate was obtained in the same manner as in Example 7. Table 2 shows the properties of the obtained polypropylene-based unstretched film and the properties of the laminate with the heat-resistant substrate.

[0225] The above-mentioned polypropylene-based unstretched film has 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-making properties, and excellent vapor permeability when heated in a microwave oven. For use in cooking packaging, it meets all the required properties of the present invention.

[0226] [Example 11]

[0227] In Example 7, the same procedures as in Example 7 were followed, except that the sealant layer was modified to contain 87.5% by mass of the propylene / ethylene random copolymer (a3) ​​and 10% by mass of the linear low-density polyethylene as the polyethylene resin (b1), to obtain a polypropylene-based unstretched film. Furthermore, the same procedures as in Example 7 were followed to obtain a laminate. Table 2 shows the properties of the obtained polypropylene-based unstretched film and the properties of the laminate with the heat-resistant substrate.

[0228] The above-mentioned polypropylene-based unstretched film has 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-making properties, and excellent vapor permeability when heated in a microwave oven. For use in cooking packaging, it meets all the required properties of the present invention.

[0229] [Example 12]

[0230] In Example 7, the sealant layer was modified to a total of 100 parts by mass of a mixture of 89% by mass of the propylene / ethylene random copolymer (a3), 10% by mass of a linear low-density polyethylene (b1) polyethylene resin, and 1% by mass of Perhexa 25B. A polypropylene unstretched film was obtained in the same manner as in Example 7. A laminate was also obtained in the same manner as in Example 7. Table 2 shows the properties of the obtained polypropylene unstretched film and the properties of the laminate with the heat-resistant substrate.

[0231] The above-mentioned polypropylene-based unstretched film has 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-making properties, and excellent vapor permeability when heated in a microwave oven. For use in cooking packaging, it meets all the required properties of the present invention.

[0232] [Example 13]

[0233] In Example 7, the sealant layer was modified to a total of 100 parts by mass of a mixture of 77.5% by mass of a propylene / ethylene random copolymer (a1), 15% by mass of a linear low-density polyethylene resin (b1), 5% by mass of an ethylene / butene elastomer copolymer (c1), and 2.5% by mass of Perhexa 25B. A polypropylene unstretched film was obtained in the same manner as in Example 7. A laminate was also obtained in the same manner as in Example 7. Table 2 shows the properties of the obtained polypropylene unstretched film and the properties of the laminate with the heat-resistant substrate.

[0234] The above-mentioned polypropylene-based unstretched film has 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-making properties, and excellent vapor permeability when heated in a microwave oven. For use in cooking packaging, it meets all the required properties of the present invention.

[0235] [Example 14]

[0236] In Example 7, the sealant layer composition consisted of 60% by mass of a propylene-ethylene random copolymer (a3) ​​and 40% by mass of a linear low-density polyethylene (b1). 500 ppm of "Sumilizer" GP and 750 ppm of "Sumilizer" GS as antioxidants were mixed with 100 parts by mass of this mixed composition using a Henschel mixer for 3 minutes, and the mixture was fed to a twin-screw extruder adjusted to 260°C for melt kneading.

[0237] Next, a stainless steel core shaft with a heat medium flow path was coated with HTV silicone rubber to a thickness of 8 mm, and then with a PFA heat shrink tube with a thickness of 0.2 mm. The PFA surface was polished and then sprayed with a steel sphere to form a concave portion with a depth of 1.0 μm and a thickness of 10 mm. 2 An embossing rubber roller having 1400 concave portions was used. The sealant layer was extruded from a multilayer T-type spinneret at a rate of 50 m / min between the embossing rubber roller and a mirror-finished metal roller, with the sealant layer facing the rubber roller. This produced a 60 μm thick unstretched polypropylene film. Separately, the same procedures as in Example 7 were followed to produce a laminate. Table 2 shows the properties of the resulting unstretched polypropylene film and the properties of the laminate with the heat-resistant substrate.

[0238] The above-mentioned polypropylene-based unstretched film has 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-making properties, and excellent vapor permeability when heated in a microwave oven. For use in cooking packaging, it meets all the required properties of the present invention.

[0239] [Example 15]

[0240] In Example 7, as the base layer composition, a mixed resin of 72 mass% of propylene·ethylene block copolymer (a1), 18 mass% of linear low-density polyethylene of polyethylene resin (b1), and 10 mass% of propylene·butene copolymer elastomer is set to 100 mass parts, and 500 ppm of "Sumilizer" GP and 750 ppm of "Sumilizer" GS as antioxidants are mixed for 3 minutes using a Henschel mixer and supplied to a twin-screw extruder adjusted to a temperature of 260°C for melt mixing.

[0241] The sealant layer composition consisted of 87.5% by mass of a propylene / ethylene random copolymer (a3) ​​having a melting temperature peak of 142°C, which had been fully cooled with liquid nitrogen and then pulverized using an impeller mill to form a powder; 10% by mass of a high-density polyethylene (b2); and 2.5% by mass of Perhexa 25B (registered trademark) (manufactured by NOF Corporation, chemical name: 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane) as a peroxide. To 100 parts by mass of this mixed composition, 0.05 parts by mass of tetrakis(methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate)methane (Sumilizer BP-101) and 0.01 parts by mass of Irganox 1076 (manufactured by Ciba Specialty Chemicals) were added. The mixture was mixed for 3 minutes using a Henschel mixer and then supplied to a twin-screw extruder adjusted to 260°C for melt kneading to produce a masterbatch.

[0242] Next, 20% by mass of a propylene-ethylene block copolymer and 10% by mass of a propylene-butene elastomer were mixed with 70% by mass of the masterbatch, and the mixture was fed to a twin-screw extruder adjusted to 260° C. and melt-kneaded.

[0243] Next, the melt-mixed base layer resin and sealing layer resin are extruded from a multi-layer T-type 2-layer spinneret at a ratio of 6:1 at 250°C and 60 m / min, and after being cooled and solidified by contact with a 45°C cooling roller, the base layer surface is subjected to corona discharge treatment to obtain a polypropylene-based unstretched film with a thickness of 60 μm.

[0244] The above unstretched polypropylene film was laminated with a 15 μm thick biaxially stretched polyamide film in the same manner as in Example 7. Table 2 shows the properties of the obtained unstretched polypropylene film and the properties of the laminate with the heat-resistant substrate.

[0245] The above-mentioned polypropylene-based unstretched film has 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-making properties, and excellent vapor permeability when heated in a microwave oven. For use in cooking packaging, it meets all the required properties of the present invention.

[0246] [Comparative Example 5]

[0247] In Example 7, the same procedures as in Example 7 were followed, except that the propylene / ethylene block copolymer (a1) was changed to 40% by mass and the propylene / ethylene random copolymer (a3) ​​was changed to 30% by mass in the base layer, to obtain a polypropylene-based unstretched film. Furthermore, the same procedures as in Example 7 were followed to obtain a laminate. Table 2 shows the properties of the obtained polypropylene-based unstretched film and the properties of the laminate with the heat-resistant substrate.

[0248] The above-mentioned polypropylene-based unstretched film has a low content of propylene-ethylene block copolymer in the base layer, so that when the bag product is heat-treated at 130°C, leakage may occur. In addition, the low-temperature impact resistance is poor.

[0249] [Comparative Example 6]

[0250] In Example 7, the same procedures as in Example 7 were followed, except that the base layer was a mixed resin composed of 70% by mass of a propylene / ethylene random copolymer (a3) ​​and 30% by mass of a linear low-density polyethylene (b1) as a polyethylene resin, to obtain a polypropylene-based unstretched film. Separately, the same procedures as in Example 7 were followed to obtain a laminate. Table 2 shows the properties of the obtained polypropylene-based unstretched film and the properties of the laminate with the heat-resistant substrate.

[0251] The polypropylene-based unstretched film has a low melting temperature peak of the base layer, so the bag product is deformed by the heat during bag making, the bag making speed is reduced, and the bag break retention rate is low.

[0252] [Comparative Example 7]

[0253] In Example 7, the sealant layer was prepared by adding 0.4 parts by mass of spherical silica having a particle size of 2 μm as inorganic particles, 0.05 parts by mass of tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]methane (Sumilizer BP-101), and 0.01 parts by mass of Irganox 1076 (manufactured by Ciba Specialty Chemicals) to 100 parts by mass of a mixed resin comprising 80% by mass of the propylene / ethylene random copolymer (a5) and 20% by mass of the linear low-density polyethylene (b1). The mixture was mixed for 3 minutes using a Henschel mixer and then melt-kneaded in a twin-screw extruder regulated at 260°C. The mixture was then extruded from a T-die at 250°C at a speed of 60 m / min and cooled and solidified by contact with a cooling roll at 45°C. One side of the mixture was then subjected to corona discharge treatment to obtain a 60 μm thick unstretched polypropylene film. A laminate was obtained in the same manner as in Example 7. Table 2 shows the properties of the obtained unstretched polypropylene film and the properties of the laminate with the heat-resistant substrate.

[0254] The sealing layer of the unstretched polypropylene film had a melting temperature peak of 150°C, an average roughness Ra of 0.04 μm, and a peak count of 0.3 μm or greater of 68 / 10 mm. 2 Therefore, the adhesion shear force at 130℃ is 42N / 12cm 2, poor high temperature blocking resistance, bag making speed of 35spm, poor bag making performance, high heat sealing strength under 100℃ atmosphere, and poor steam permeability when heated in a microwave oven.

[0255] [Comparative Example 8]

[0256] In Example 7, the same procedures as in Example 7 were followed, except that the propylene / ethylene random copolymer (a3) ​​having a melting temperature peak of 142°C was replaced with an ethylene / propylene / butene random copolymer (a6) having a melting temperature peak of 132°C in the sealant layer, to produce a polypropylene-based unstretched film. Separately, the same procedures as in Example 7 were followed to produce a laminate. Table 2 shows the properties of the resulting unstretched polypropylene film and the properties of the laminate with the heat-resistant substrate.

[0257] In the case of the polypropylene-based unstretched film, the melting temperature peak of the sealant layer is 132°C, and thus the adhesion shear force at 130°C is 17 N / 12 cm. 2 , high temperature blocking resistance is poor, the heat sealing strength of the laminate at 170°C is as low as 20N / 15mm, the bag-making products leak during the cooking process at 130°C, and the bag-making speed becomes 32spm, and the bag-making performance is poor.

[0258] [Comparative Example 9]

[0259] In Example 7, the same procedures as in Example 7 were followed, except that the linear low-density polyethylene of the polyethylene resin (b1) was replaced with a high-pressure low-density polyethylene of the polyethylene resin (b3) for the sealant layer, to obtain a polypropylene unstretched film. Furthermore, the same procedures as in Example 7 were followed to obtain a laminate. Table 2 shows the properties of the obtained polypropylene unstretched film and the properties of the laminate with the heat-resistant substrate.

[0260] The average roughness Ra of the sealant layer of the polypropylene unstretched film is as low as 0.08 μm, and the melting temperature of the high-pressure low-density polyethylene mixed therein is as low as 106°C. Therefore, the adhesion shear force at 130°C is 25 N / 12 cm. 2 , high temperature blocking resistance is poor, the heat sealing strength of the laminate at 170°C is as low as 20N / 15mm, the bag-making products leak during the cooking process at 130°C, and the bag-making speed becomes 37spm, and the bag-making performance is poor.

[0261] [Comparative Example 10]

[0262] In Example 7, the same procedures as in Example 7 were followed, except that the sealant layer was prepared using a mixed resin composition of 85% by mass of an ethylene-propylene block copolymer (a1), 5% by mass of a high-density polyethylene, and 10% by mass of an ethylene-butene elastomer copolymer (c1) to a total of 100 parts by mass. A polypropylene unstretched film was obtained. Furthermore, a laminate was obtained in the same manner as in Example 7. Table 2 shows the properties of the obtained polypropylene unstretched film and the properties of the laminate with the heat-resistant substrate.

[0263] Regarding the above-mentioned polypropylene-based unstretched film, the average roughness Ra and the peak count of 0.3 μm or more of the sealing layer meet the ranges specified in the present invention. However, the melting temperature is as high as 162°C, so the temperature at which the heat seal strength becomes 3N / 15mm or more is as high as 162°C. The low-temperature heat sealability is poor, and the heat seal strength of the laminate at 170°C is as low as 4N / 15mm. Under the above-mentioned bag-making conditions, no bagged product can be obtained.

[0264] [Table 1]

[0265]

[0266] [Table 2]

[0267]

[0268] Industrial applicability

[0269] The present invention provides a packaging bag for retort foods that reduces the number of layers with environmental considerations. The present invention can provide an unstretched polypropylene film having excellent low-temperature heat sealability, high-temperature blocking resistance, and bag-making processability. The film also exhibits high heat seal strength at 170°C as a laminate, excellent low-temperature impact resistance, excellent vapor permeability during microwave heating, and excellent retort compatibility, as well as a laminate using the film.

Claims

1. A polypropylene-based unstretched film comprising a propylene-based random copolymer having a melting temperature peak of 135° C. to 145° C. as a main component, The polypropylene-based unstretched film has a film surface average roughness Ra of 0.1 μm or more on at least one side, and a peak count of 0.3 μm or more per 10 mm. 2 The surface serves as a thermal cover.

2. The unstretched polypropylene film according to claim 1, wherein The shear force of the heat seals at 130°C is 15N / 12cm 2 the following.

3. Polypropylene-based unstretched film, which is composed of two layers: a base layer and a sealant layer, The base layer contains 50% by mass or more of a propylene-ethylene block copolymer and has a melting temperature peak of 150° C. or more. The melting temperature peak of the sealing layer is within the range of 135°C to 145°C, and the surface average roughness Ra of the sealing layer of the unstretched polypropylene film is 0.1 μm or more, and the peak count of 0.3 μm or more is 100 / 10 mm. 2 The above surface serves as a heat shield.

4. The unstretched polypropylene film according to claim 1 or 3, wherein When the heat seal sheets are overlapped and heat-sealed, the heat seal initiation temperature at which the heat seal strength reaches 3 N / 15 mm or more is 150° C. or less. The unstretched polypropylene film according to claim 1 , wherein the film thickness is from 20 μm to 150 μm. The unstretched polypropylene film according to claim 3 , wherein the film thickness is 20 μm to 150 μm, and the thickness ratio of the base layer to the sealant layer is 9:1 to 3:

1.

7. A laminate comprising the unstretched polypropylene film according to claim 1 or 3 and a heat-resistant substrate having a melting point of 160°C or higher, wherein the laminate has a heat seal strength of 23 N / 15 mm or higher at 170°C.

8. The laminate according to claim 7, wherein The heat-resistant substrate is at least one selected from the group consisting of a biaxially stretched polyamide film, a biaxially stretched polyethylene terephthalate film, a biaxially stretched polypropylene film, a biaxially stretched polybutylene terephthalate film, a biaxially stretched polyester / polyamide composite film, a uniaxially stretched polyamide film, a uniaxially stretched polyethylene terephthalate film, a uniaxially stretched polypropylene film, and a uniaxially stretched polybutylene terephthalate film; a film obtained by applying metal vapor deposition, inorganic vapor deposition, transparent metal oxide vapor deposition, or a gas barrier resin to these films; synthetic paper; and aluminum foil.

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