Polypropylene-based unstretched film and laminate using the same

Abstract

Provided are: a polypropylene-based non-stretched film that has, when used in a packaging bag that is for packaging a retort food and has less number of layers in consideration of the environment, excellent low-temperature heat sealability and high-temperature blocking resistance, excellent bag-making processability, and excellent retort suitability; and a laminate using the same. This polypropylene-based non-stretched film contains, as a main component, a propylene-based random copolymer having a melting temperature peak at 135-145°C, and has, as a heat seal surface on at least one surface, a surface that has a film surface average roughness Ra of at least 0.1 µm and a peak count of at least 100 peaks / 10 mm2 for 0.3 µm or higher peaks. Alternatively, the polypropylene-based non-stretched film according to claim 1 is formed of two layers, which are a base layer and a seal layer. The base layer contains at least 50 mass% of a propylene-ethylene block copolymer, and has a melting temperature peak at 150°C or higher. The range of the melting temperature peak of the seal layer is 135-145°C. The polypropylene-based non-stretched film has, as a heat seal surface, a surface in which the seal layer surface has a surface average roughness Ra of at least 0.1 µm, and, in terms of the peak count number RPc, the peak count is at least 100 peaks / 10 mm2 for 0.3 µm or higher peaks. In addition, this laminate has laminated therein a heat resistant base material having a melting point of 160°C or higher, and has a heat seal strength of at least 23 N / 15 mm at 170°C.

Description

[Technical Field]

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

[0002] Laminates and packaging bags for retort food packaging are made by laminating a heat-resistant substrate such as biaxially oriented polyethylene terephthalate film (hereinafter sometimes referred to as PET), biaxially oriented polyamide film (hereinafter sometimes referred to as ON), or aluminum foil (hereinafter sometimes referred to as AL foil) with a heat-sealable unoriented polypropylene film (hereinafter sometimes referred to as CPP), such as PET / ON / CPP or PET / ON / AL foil / CPP. The required properties of these packaging bags include heat resistance, impact resistance, high heat-seal strength, blocking resistance, and bag-making processability.

[0003] In recent years, environmentally friendly packaging legislation has come into force, making environmentally conscious design a necessity for packaging bags. This has led to increased demand for fewer layers in laminates, and bilayer structures such as PET / CPP, ON / CPP, and OPP / CPP are being investigated. Furthermore, there is a growing demand for mono-material packaging bags with excellent recyclability. Therefore, mono-material laminates, such as biaxially oriented polypropylene film / non-oriented polypropylene film, with an OPP / CPP structure, are being investigated. However, OPP has lower heat resistance than PET or ON, making it difficult to process under conventional bag-making conditions. Therefore, to maintain the same processability, there is a growing demand for non-oriented polypropylene film with low-temperature heat sealability, high-temperature blocking resistance, and retort suitability.

[0004] To solve the above problems, Patent Document 1 proposes a laminate in which a heat seal layer is laminated on one side of a biaxially oriented polypropylene film with high heat resistance and elastic modulus, but the laminate has insufficient low-temperature heat sealability, high-temperature blocking resistance, and retort suitability. Patent Document 2 also proposes a polypropylene-based multilayer sealant film for retort pouches in which inorganic particles are added to the heat seal layer to define the surface roughness, but there are concerns about particles falling off during the film-forming and laminating processes, and particles being mixed into food. Furthermore, the film's properties of low-temperature heat sealability, high-temperature blocking resistance, and retort suitability are insufficient, and the film is also poor in bag-making processability. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-7441 [Patent Document 2] Patent No. 5895590 Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, an object of the present invention is to provide a polypropylene-based unstretched film that has excellent low-temperature heat sealing properties, high-temperature blocking resistance, bag-making processability, and retort suitability, and a laminate using the same, as a packaging bag for retort food packaging with a reduced number of layers that is environmentally friendly. [Means for solving the problem]

[0007] The present inventors have achieved the above object by providing the following polypropylene-based unstretched film and a laminate using the same.

[0008] That is, the present invention is directed to a film having a propylene-based random copolymer as a main component, the melting temperature peak of which is 135°C or more and 145°C or less, and a film having an average surface roughness Ra of 0.1µm or more and a peak count of 0.3µm or more per 10mm on at least one side.2 The surface of the film is a non-stretched polypropylene film, and the heat-sealable surface is a surface of the film.

[0009] The seal layer has two layers: a base layer and a seal layer; the base layer contains 50% by mass or more of a propylene-ethylene block copolymer, has a melting temperature peak of 150°C or higher, and the seal layer has a melting temperature peak in the range of 135°C to 145°C; the seal layer surface has an average surface roughness Ra of 0.1 μm or higher, and the peak count of 0.3 μm or higher is 100 / 10 mm. 2 The polypropylene-based non-oriented film has the above surface as a heat seal surface. [Effects of the Invention]

[0010] By using a polypropylene-based unstretched film that has excellent low-temperature heat sealing properties and high-temperature blocking resistance for use in packaging retort foods, and a laminate using the film, it is possible to provide an environmentally friendly packaging bag for packaging retort foods that allows for a reduction in the amount of packaging material used. DETAILED DESCRIPTION OF THE INVENTION

[0011] The polypropylene-based non-oriented film and the laminate using the same of the present invention will be specifically described below.

[0012] The non-stretched polypropylene film of the present invention is mainly composed of a propylene random copolymer having a melting temperature peak in the range of 135° C. to 145° C. Here, the term "main component" means that the propylene random copolymer accounts for 50% by mass or more of the total amount of resin in the film.

[0013] 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 of 23 N / 15 mm or more at 170°C required for retort food applications cannot be obtained, and when the contents are filled into the bag and heat sterilized at 130°C or higher, the contents may scatter or leak.

[0014] The peak melting temperature of the propylene random copolymer is in the range of 135°C to 145°C, so that the heat seal strength at 170°C required for retort food applications of 23N / 15mm or more can be obtained, and the blocking shear strength at 130°C is 15N / 12cm. 2 This is preferable because it can be done as follows.

[0015] When the melting temperature peak is less than 135°C, the blocking shear force at 130°C is 15N / 12cm 2 If the peak melting temperature exceeds 145°C, when the heat seal surfaces are overlapped and heat sealed, the heat seal initiation temperature at which the heat seal strength is 3N / 15mm or more may reach 150°C or higher, slowing down the bag making speed.

[0016] 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 more preferably in the range of 2 to 20 g / 10 min, since this allows stable melt extrusion film formation.

[0017] The propylene random copolymer having a melting temperature peak in the range of 135°C to 145°C is preferably a propylene random copolymer composed of propylene and one or more comonomers, as this can achieve both high-temperature blocking resistance and heat seal strength.

[0018] 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.

[0019] From the viewpoint of 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 during unwinding.

[0020] The non-oriented polypropylene film of the present invention has an average surface roughness Ra of 0.1 μm or more on at least one surface to be heat-sealed, preferably in the range of 0.2 to 0.7 μm, because this provides good film slippage and good processability during film formation and lamination.

[0021] The polypropylene-based non-oriented film of the present invention has a peak count of 100 or more peaks of 0.3 μm or more per 10 mm on at least one side of the heat-sealable surface. 2 In this case, the blocking shear force at 130°C is 15N / 12cm 2 This is preferable because it is easy to open the bag, easy to fill the contents, and increases the bag-making speed when automatically filling the contents into the bag. 2 , more preferably 500 or more / 10mm 2 is.

[0022] In order to keep the average film surface roughness of the heat seal surface and the peak count of 0.3 μm or more within the preferred ranges, it is preferable that the film surface is not formed using inorganic or organic particles, as this can prevent particles from falling off during film formation and from being mixed into the contents.

[0023] In order to set the average surface roughness of the film and the peak count of 0.3 μm or more within the preferred range, for example, the propylene random copolymer is mixed with at least one polyethylene and an organic peroxide crosslinking agent, and the mixture is extruded at high temperature and high shear to prepare chips, which are then used to form a film using a T-die type film forming machine or an inflation film forming machine.

[0024] The polyethylene has a density of, for example, 0.900 g / cm 3 More than 0.945g / cm 3 Low density polyethylene, with a density of less than 0.945 g / cm 3 More than 0.970g / cm 3 Examples include high density polyethylene with a density of less than 0.900 g / cm 3 If less than this amount of polyethylene is mixed, it may not be possible to form the above-mentioned average surface roughness and peak count of the film.

[0025] The low-density polyethylene is a linear low-density polyethylene (hereinafter sometimes referred to as LLDPE), which is a copolymer of ethylene and an α-olefin, and has good dispersibility in a propylene-based random copolymer, and the peak count of 0.3 μm or more is 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.

[0026] The peak melting temperature 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, from the viewpoint of heat seal strength and blocking shear force at 130°C.

[0027] The melt flow rate of the polyethylene measured in accordance with JIS-K7210 (1999) at 190°C under a load of 21.18 N is preferably 0.2 to 10 g / 10 min, more preferably 0.5 to 5 g / 10 min, because this provides good dispersibility in the propylene-based random copolymer and makes it easier to obtain the film surface average roughness and peak count of 0.3 μm or more.

[0028] The amount of the linear low-density polyethylene (LLDPE) mixed into the propylene-based random copolymer is preferably less than 50% by mass, more preferably in the range of 5 to 40% by mass, and even more preferably in the range of 10 to 30% by mass, which makes it easier to obtain the average surface roughness of the film and a peak count of 0.3 μm or more, and the blocking shear force at 130° C. is 15 N / 12 cm 2 The following is likely to be the case, which is preferable.

[0029] The amount of the organic peroxide added is preferably in the range of 0.1 to 10% by mass of the resin component, more preferably 0.5 to 5% by mass, because this provides good dispersibility in the resin, allows the crosslinking agent to function effectively on the polyethylene, and makes it easier to achieve the average film surface roughness and peak count of 0.3 μm or more. If the amount is less than 1% by mass, the effect of the addition is difficult to see, while if it exceeds 40% by mass, poor dispersion is likely to occur and extrudability may deteriorate.

[0030] 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.

[0031] 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 ...

[0032] 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.

[0033] From the viewpoint of food hygiene when packaging retort food, it is preferable that the organic peroxide does not remain in the polypropylene-based unstretched film of the present invention.

[0034] Another method for achieving a preferred range of average film surface roughness Ra and peak count of 0.3 μm or more is to use a film-forming nip roller to impart an embossed pattern to one side of the film (heat-sealed surface). There are no particular limitations on the film-forming nip roller as long as it can form the heat-sealed surface of the present invention. 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.

[0035] The polypropylene-based non-oriented film of the present invention has a blocking shear strength of 15 N / 12 cm between heat-sealed surfaces at 130°C. 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. The blocking shear force at 130°C is preferably 15N / 12cm or less. 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.

[0036] In addition, in the case of packaging bags such as pouches, when the heat-sealable surfaces 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 lower, more preferably 145°C or lower.

[0037] The bag-making speed is preferably 40 spm or more, more preferably 45 spm or more. 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 preferable.

[0038] The polypropylene-based unstretched film of the present invention is preferred because the blocking shear force and heat seal strength at 130°C are within the preferred ranges of the present invention, and the addition of a thermoplastic elastomer improves the low-temperature heat sealability and impact resistance.

[0039] 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 effects of improving low-temperature heat sealing properties and impact resistance may not be observed, and if it exceeds 40% by mass, the heat sealing strength may decrease significantly during retort processing or heating in a microwave oven, etc., and liquid may leak from the packaging bag.

[0040] 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.

[0041] 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.

[0042] The MFR of the thermoplastic elastomer 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 the propylene-based random copolymer and blocking resistance.

[0043] The polypropylene-based non-oriented film of the present invention comprises two layers, a base layer and the polypropylene-based non-oriented film as a seal layer, wherein the base layer contains 50% by mass or more of a propylene-ethylene block copolymer, has a melting temperature peak of 150°C or higher, the seal layer has a melting temperature peak in the range of 135°C to 145°C, the seal layer has a surface average roughness Ra of 0.1µm or higher based on the roughness curve element, and the peak count RPc of 0.3µm or higher based on the roughness curve element is 100 / 10mm. 2 That's all.

[0044] The base layer preferably contains 50% by mass or more of a propylene-ethylene block copolymer. If the propylene-ethylene block copolymer content is less than 50% by mass, the laminate may have poor low-temperature impact resistance when laminated with a heat-resistant substrate and used as a packaging bag.

[0045] In order to obtain the properties of the laminate of the present invention, it is preferable that the propylene-ethylene block copolymer 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, the amount of the 20°C xylene soluble portion CXS of 10 mass% or more and 25.0 mass% or less, and the 20°C xylene insoluble portion CXIS of 1.5 dL / g or more and 2.2 dL / g or less.

[0046] 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).

[0047] The 20° C. xylene insoluble portion CXIS corresponds to the polypropylene alone, and the xylene soluble portion CXS corresponds to the rubber component.

[0048] If the amount of 20°C xylene soluble portion CXS in the base layer is less than 10% by mass, the low-temperature impact resistance may be poor, and the decrease in heat seal strength at 100°C of the laminate 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, resulting in 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.

[0049] 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.

[0050] 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.

[0051] 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. under a load of 21.18 N from the viewpoints of extrusion stability and low-temperature impact resistance.

[0052] The base layer preferably contains 10% by mass or more and less than 50% by mass of a propylene-ethylene random copolymer, since this allows adjustment of the low-temperature impact resistance and heat seal strength of the retort packaging laminate.

[0053] The ethylene content of the propylene-ethylene random copolymer is preferably 1% by mass or more and 7% by mass or less, since this provides good miscibility with the propylene-ethylene block copolymer.

[0054] The MFR of the propylene-ethylene random copolymer is preferably in the range of 0.5 to 10 g / 10 min at 230° C. under a load of 21.18 N, from the viewpoints of extrusion stability and melt miscibility with the propylene-ethylene block copolymer.

[0055] The base layer preferably contains 10% by mass or more and 40% by mass or less of ethylene-α-olefin copolymer (where the total mass of the base layer resin is taken as 100% by mass), which is preferable because it allows adjustment of vapor permeability during microwave heating.

[0056] If the content of the ethylene-α-olefin copolymer is less than 10% by mass, the effect of the copolymer on vapor permeability during microwave heating may not be observed, whereas if the content 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.

[0057] The melting point of the ethylene-α-olefin copolymer is preferably 110° C. or higher and 140° 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 140° C., the heat seal strength at high temperatures may increase, resulting in poor steam permeability when heated in a microwave oven.

[0058] The ethylene-α-olefin copolymer is a copolymer of ethylene in a proportion of 50 to 95% by mass as a main component and an α-olefin as a copolymerizable monomer, and specifically, is preferably produced using a metallocene catalyst.

[0059] As the α-olefin, 1-butene, 1-hexene, 1-octene, and the like having 4 to 10 carbon atoms can be used, and a specific example thereof is linear low-density polyethylene (hereinafter sometimes referred to as LLDPE).

[0060] The MFR of the ethylene-α-olefin copolymer 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.

[0061] It is preferable to add a thermoplastic elastomer to the polypropylene-based non-stretched film, since this improves the low-temperature heat sealability and impact resistance.

[0062] 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 effects of improving low-temperature heat sealability and impact resistance may not be achieved, whereas if the content is more than 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.

[0063] 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.

[0064] 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.

[0065] 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 ethylene-based elastomers, and in the range of 0.5 to 10 g / 10 min at 230°C and a load of 21.18 N for propylene-based elastomers, from the viewpoints of miscibility with the polypropylene-based resin that is the main component of the sealing layer and film formation stability.

[0066] The polypropylene-based non-oriented 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.

[0067] 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).

[0068] 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).

[0069] 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.

[0070] The amount of antioxidant to be added may be set appropriately within the range of 100 to 10,000 ppm, depending on the type of antioxidant used.

[0071] As the neutralizing agent, hydrotalcite compounds, calcium hydroxide, etc. are preferred for reducing smoke generation during film formation.

[0072] The polypropylene-based non-oriented film of the present invention may contain a fatty acid amide-based lubricant in an amount of 100 to 1000 ppm 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-sealing strength. If the amount of fatty acid amide-based lubricant added is less than 100 ppm, the lubrication property may be deteriorated, whereas 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 heat-sealing strength.

[0073] Examples of the fatty acid amide lubricants include oleic acid amide, erucic acid amide, stearic acid amide, palmitic acid amide, and behenic acid amide.

[0074] 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 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 product 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.

[0075] The thickness of the polypropylene-based non-oriented film is preferably 20 μm or more and 150 μm or less, and the thickness ratio of the base layer to the seal layer is preferably 9:1 to 3:1, which allows stable film-forming properties, low-temperature impact resistance, and heat-sealing strength of the film to be obtained, and bag-forming properties to be maintained.

[0076] In a laminate obtained by laminating the polypropylene-based unoriented film of the present invention with 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, when the laminate is used as a retort packaging material, the heat seal strength may decrease due to a heat treatment at 130° C. or higher, which may result in scattering or leakage of the contents.

[0077] The heat-resistant substrate having a melting point of 160°C or higher 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, biaxially oriented polyester / polyamide hybrid film, uniaxially oriented polyamide film, uniaxially oriented polyethylene terephthalate film, uniaxially oriented polypropylene film, and uniaxially oriented polybutylene terephthalate, 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, and at least one substrate layer selected from the group consisting of synthetic paper and aluminum foil. Of the monomaterials, it is preferable to use a biaxially oriented polypropylene film or uniaxially oriented polypropylene film as the substrate.

[0078] The method for laminating the heat-resistant substrate and the polypropylene-based unstretched film of the present invention is not particularly limited, but a dry lamination method is preferred from the viewpoint of productivity.

[0079] The adhesive for dry lamination is not particularly limited, but examples thereof include a two-component reactive aromatic adhesive composed 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 a two-component reactive aliphatic adhesive; Examples of adhesives include polyurethane adhesives, acrylic adhesives, epoxy adhesives, polyolefin adhesives, elastomer adhesives, and fluorine adhesives.

[0080] 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.

[0081] The laminate can be used by processing it into a flat bag (flat pouch), a standing pouch, or the like, with the polypropylene-based non-oriented film of the present invention as the inner surface of the bag to be heat-sealed. [Example]

[0082] 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.

[0083] (1) Melting temperature peak Using a differential scanning calorimeter (Shimadzu DSC-60), the temperature was raised from 20°C at a rate of 10°C / min up to 250°C, and the highest peak temperature of the melting peaks when heated was taken as the melting temperature peak.

[0084] (2) Density of polyethylene (unit: g / cm 3 ) Measurement was carried out in accordance with Method A (water displacement method) of JIS-K7112:1999.

[0085] (3) Melt flow rate (MFR) According to JIS K7210:1999, measurements were carried out at a temperature of 230°C for propylene random copolymers, propylene-ethylene block copolymers, and propylene-α-olefin copolymer elastomers, and at a temperature of 190°C for polyethylene resins and ethylene-α-olefin copolymer elastomers, with a load of 21.18 N.

[0086] (4) 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%).

[0087] (5) 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.

[0088] (6) 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).

[0089] 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 said insolubles in (a))} × 100 / (Content of xylene solubles at 20°C in (a)) (Unit of content) Place: mass%).

[0090] (7) Density of polyethylene (unit: g / cm 3 ) Measurement was carried out in accordance with Method A (water displacement method) of JIS-K7112:1999.

[0091] (8) Average film surface roughness Ra, peak count RPc based on roughness curve elements, peak count of 0.3 μm or more Using a fully automatic microscopic shape measuring instrument (SURFCORDER ET4000A) manufactured by Kosaka Laboratory Ltd., the film surface was measured in the direction perpendicular to the film flow direction (TD) according to the measurement method specified in JIS B-0601:1982 under the conditions below, and the average roughness Ra of the film surface and the peak count RPc of 0.3 μm or more based on the roughness curve element were determined. Measuring length: 2 mm Y direction measurement length: 10mm Y-direction measurement pitch: 0.1 mm Number of scans: 100.

[0092] (9) Film thickness and thickness composition The film thickness was measured at 10 randomly selected locations on the film using a dial gauge in accordance with JIS K7130 (1992) A-2 method, and the average value was taken as the film thickness.

[0093] (10) Temperature at which heat seal strength is 3N / 15mm or more In accordance with JIS Z1713:1999, samples of polypropylene-based unoriented film were overlapped with their heat-sealed surfaces facing each other and heat-sealed at different temperatures, and the heat-seal strength was measured at a peeling 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.

[0094] (11) Heat seal strength at 170°C A heat-resistant base layer and a polypropylene-based unstretched film were bonded together by a standard dry lamination method using an aliphatic ester 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 produce a laminate. The polypropylene-based unstretched films of the laminate were overlapped and heat-sealed at 170°C to prepare a sample, which was measured for heat-seal strength at a peel rate of 300 mm / min using a Tensilon manufactured by Orientec Co., Ltd. A value of 23 N / 15 mm or more was deemed suitable for retort packaging.

[0095] (12) Blocking shear force at 130°C A 30mm wide and 100mm long film sample was prepared from a polypropylene-based unstretched film. The seal layers were overlapped over an area of ​​30mm x 40mm, and a 10g load was applied. The sample was then heated in an oven at 130°C for 30 minutes, and then left in an atmosphere at 23°C and 65% humidity for 30 minutes or more. The shear peel strength was then measured at a pulling rate of 300mm / min using a Tensilon manufactured by Orientec Co., Ltd. The shear peel strength measured by this method was 15N / 12cm. 2 If the temperature was below this, the high-temperature blocking resistance was judged to be good.

[0096] (13) Bag making speed A heat-resistant substrate layer and a polypropylene-based non-oriented film were bonded together by a conventional dry lamination method using an aliphatic ester adhesive (Takelac A385 / Takenate A50, adhesive layer thickness 2.5 μm, manufactured by Mitsui Chemicals, Inc.), and aged for 3 days at 40 ° C. to produce a long laminate. Next, using the laminate, depending on the heat-resistant substrate, a bag making machine was used to make a bottom seal temperature (bottom part) of 140 ° C. or higher and 230 ° C. or lower, a vertical seal temperature of 130 ° C. or higher and 230 ° C. or lower, and a top seal temperature (sealed part after filling the contents) of 130 ° C. or higher and 230 ° C. or lower. The number of packaging bags filled with 200 g of saline solution per minute was determined as the bag making speed spm (shots per minute), and a value of 40 spm or higher was evaluated as good high-speed bag making.

[0097] (14) Bag breakage retention rate (low temperature impact resistance) A 60 μm thick unstretched polypropylene film was laminated to one side of a heat-resistant substrate layer of a 15 μm thick biaxially oriented polyamide film using an aliphatic ester adhesive (Mitsui Chemicals, Takelac A385 / Takenate A50, adhesive layer thickness 2.5 μm) using the conventional dry lamination method, and the laminate was aged at 40°C for 3 days to create a laminate.

[0098] Using this laminate, 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 10 drops of a 1 kg load from a height of 20 cm (base shape: 152 mm x 152 mm) 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 and no 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.

[0099] (15) Heat seal strength in a 100°C atmosphere (steam permeability when heated in a microwave oven) Using the packaging bag obtained in (14) 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.

[0100] The compositions of various raw materials used in the present invention are described below. Table 1 also shows the properties of the polypropylene-based unstretched films and laminates produced from the raw material formulations.

[0101] (1) Propylene-ethylene block copolymer (a1) MFR: 2.1 g / 10 min (230°C) CXS amount: 20% by mass [η]CXIS:1.8dl / g [η]CXS:3.2dl / g Melting temperature peak: 163℃ (2) Propylene-ethylene block copolymer (a2) MFR: 2.7 g / 10 min (230°C) CXS amount: 27% by mass [η]CXIS:1.9dl / g [η]CXS:3.0dl / g Melting temperature peak: 155℃ (3) Propylene-based random copolymer (a3) Ethylene-propylene random copolymer.

[0102] Ethylene content: 4% by mass MFR: 3.0 g / 10 min (230°C) Melting temperature peak: 142℃ (4) Propylene-based random copolymer (a4) Ethylene-propylene random copolymer Ethylene content: 6% by mass MFR: 3.0 g / 10 min (230°C) Melting temperature peak: 135℃ (5) Propylene-based random copolymer (a5) Ethylene-propylene-butene random copolymer Propylene content: 90.7% by mass, ethylene content: 2.5% by mass, butene content: 6.8% by mass MFR: 3.5g / 10min (230℃) Melting temperature peak: 132℃ (6) Polyethylene (b1) Linear low-density polyethylene copolymerized with 1-octene MFR: 0.8g / 10min (190℃) Density: 0.925g / cm 3 Melting temperature peak: 125℃ (7) Polyethylene (b2) High-density polyethylene MFR: 1.1 g / 10 min (190°C) Density: 0.950g / cm 3 Melting temperature peak: 132℃ (8) Polyethylene (b3) High-pressure low-density polyethylene MFR: 7.0g / 10min (190℃) Density: 0.905g / cm 3 Melting temperature peak: 106℃ (9) Ethylene-butene copolymer elastomer (c1) "Tafmer" (registered trademark) manufactured by Mitsui Chemicals, Inc. MFR: 3.6 g / 10 min (190°C) Melting temperature peak: 66℃ (10) Propylene-butene copolymer elastomer (c2) "Tafmer" (registered trademark) manufactured by Mitsui Chemicals, Inc. MFR: 7g / 10min (230℃) Peak melting temperature: 75°C.

[0103] [Example 1] The composition of the polypropylene-based unstretched film was 67.6 mass% of ethylene-propylene random copolymer (a3), which was propylene-based random copolymer thoroughly cooled with liquid nitrogen and then pulverized into powder using an impeller mill, 30 mass% of linear low-density polyethylene (b1), and 2.4 mass% of Perhexa 25B (manufactured by Nippon Oil & Fats Co., Ltd., chemical name: 2,5-dimethyl-2,5-di(t-butylperoxy)hexane) as a peroxide.

[0104] 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, and the mixture was mixed for 3 minutes using a Henschel mixer.

[0105] The mixture was then fed into a twin-screw extruder controlled at 260°C for melt kneading, extruded at 250°C through a T-die at 60 m / min, brought into contact with a cooling roll at 45°C for cooling and solidification, and then corona discharge treated on one side to obtain a 60 μm thick unstretched polypropylene film.

[0106] The polypropylene-based unstretched film was bonded to a 12 μm thick transparent vapor-deposited biaxially oriented polyethylene terephthalate film (Barrierox SBR2 (registered trademark)) as a heat-resistant substrate using an aliphatic ester-based adhesive (Takelac A385 / Takenate A50 manufactured by Mitsui Chemicals, Inc., adhesive layer thickness 2.5 μm) by a conventional dry lamination method, and then aged at 40°C for 3 days to obtain a laminate.

[0107] 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 unoriented film and the properties of the laminate with a heat-resistant substrate are shown in Table 1.

[0108] The polypropylene-based non-stretched film has a melting temperature peak of 142°C, an average film surface roughness Ra of 0.29µm on the heat seal surface, and a peak count of 2690 / 10mm of 0.3µm or more. 2 The peak count is very high, and when the heat seal surfaces are overlapped and heat sealed, the heat seal strength reaches 3N / 15mm or more at 144°C, which is excellent in low-temperature heat sealing properties. The blocking shear strength at 130°C is 2.4N / 12cm. 2 The film had excellent high-temperature blocking resistance, a high heat seal strength of 60 N / 15 mm at 170°C, making it suitable for retort packaging, and a bag-making speed of 45 spm, providing excellent bag-making properties, satisfying all of the required properties of the present invention.

[0109] [Example 2] An unstretched polypropylene film was obtained in the same manner as in Example 1, except that the ethylene-propylene random copolymer of the propylene-based random copolymer (a3) ​​was replaced with an ethylene-propylene random copolymer of the propylene-based random copolymer (a4). A laminate was also obtained in the same manner as in Example 1, except that a 20 μm-thick biaxially oriented polypropylene film (Pylenfilm-OT (registered trademark)) P2171 commercially available from Toyobo Co., Ltd. was used as the heat-resistant substrate. The heat-seal strength of the laminate was confirmed at 170°C, and bag formability was evaluated in the same manner as in Example 1, using a bag-making machine at a bottom seal temperature (bottom edge) of 145°C, a vertical seal temperature of 145°C, and a top seal temperature (sealed portion after filling with contents) of 150°C. The properties of the obtained polypropylene-based unstretched film and the properties of the laminate with the heat-resistant substrate are shown in Table 1.

[0110] [Example 3] An unstretched polypropylene 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. A laminate was also 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.

[0111] [Example 4] A polypropylene-based unstretched film was obtained in the same manner as in Example 1, except that the mixed composition in Example 1 was changed to 89 mass% of ethylene-propylene random copolymer as propylene-based random copolymer (a3), 10 mass% of linear low-density polyethylene as polyethylene (b1), and 1 mass% of Perhexa 25B (manufactured by NOF Corporation, chemical name: 2,5-dimethyl-2,5-di(t-butylperoxy)hexane) as a peroxide, totaling 100 mass parts. 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.

[0112] [Example 5] A polypropylene-based unstretched film was obtained in the same manner as in Example 1, except that the mixed composition in Example 1 was changed to 67.6 mass% of an ethylene-propylene random copolymer (a3), 20 mass% of a linear low-density polyethylene (b1), 10 mass% of an ethylene-butene copolymer elastomer (c1), and 2.4 mass% of Perhexa 25B (manufactured by NOF Corporation, chemical name: 2,5-dimethyl-2,5-di(t-butylperoxy)hexane) as a peroxide, totaling 100 mass parts. Furthermore, a laminate was 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.

[0113] [Example 6] The composition of the polypropylene-based unstretched film was 100 parts by mass of a mixed resin consisting of 70% by mass of an ethylene-propylene random copolymer (propylene-based random copolymer (a3)), 20% by mass of a linear low-density polyethylene (polyethylene (b1)), and 10% by mass of an ethylene-butene copolymer elastomer (c1). To this mixture, 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, and the mixture was mixed for 3 minutes using a Henschel mixer.

[0114] The mixture is then fed into a twin-screw extruder controlled at 260°C, melted and kneaded, and extruded. A stainless steel core having a heat transfer medium flow path is coated with HTV silicone rubber to a thickness of 8 mm, and then covered with a PFA heat-shrinkable tube having a thickness of 0.2 mm. The PFA surface is buffed and then sprayed with steel spheres to create a surface with a depth of 1.0 μm and a number of 10 mm recesses. 2Using an embossing rubber roller with 1,400 rollers per roller, the film was extruded between a mirror-finished metal roll and the embossing rubber roller to obtain a 60 μm thick polypropylene-based non-stretched film. A laminate was also obtained in the same manner as in Example 1. The properties of the obtained polypropylene-based non-stretched film and the properties of the laminate with the heat-resistant substrate are shown in Table 1.

[0115] [Comparative Example 1] The composition of the polypropylene-based unstretched film was 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) mixed resin (100 parts by mass total). The inorganic particles were added to the mixed resin: 0.4 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 60 μm thick polypropylene-based unstretched film. 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 the heat-resistant substrate are shown in Table 1.

[0116] The polypropylene-based non-oriented film has a melting temperature peak of 142°C, an average roughness Ra of the heat seal surface of 0.04µm, and a peak count of 0.3µm or more of 68 / 10mm. 2 Therefore, the blocking shear force at 130°C is 42N / 12cm 2 The high-temperature blocking resistance was poor, and the bag-making speed was 35 spm, which was poor in bag-making properties.

[0117] Comparative Example 2 A polypropylene-based non-oriented film was obtained in the same manner as in Example 1, except that the ethylene-propylene random copolymer of the propylene-based random copolymer (a3) ​​was replaced with an ethylene-propylene-butene random copolymer of the propylene-based random copolymer (a5) in the composition of the polypropylene-based non-oriented film. A laminate was also obtained in the same manner as in Example 1. The properties of the obtained polypropylene-based non-oriented film and the properties of the laminate with the heat-resistant substrate are shown in Table 1.

[0118] The polypropylene-based non-stretched film has a melting temperature peak of 132°C, and therefore the blocking shear force at 130°C is 17N / 12cm. 2 The product had poor high-temperature blocking resistance, a low heat seal strength of 20N / 15mm at 170°C, leakage of the contents occurred during retort treatment at 130°C, and the bag-making speed was 32 spm, making the product poor in bag-making properties.

[0119] Comparative Example 3 A polypropylene-based non-oriented film was obtained in the same manner as in Example 1, except that the linear low-density polyethylene of polyethylene (b1) was changed to a high-pressure low-density polyethylene of polyethylene (b3) in the composition of the polypropylene-based non-oriented film. A laminate was also obtained in the same manner as in Example 1. The properties of the obtained polypropylene-based non-oriented film and the properties of the laminate with the heat-resistant substrate are shown in Table 1.

[0120] The polypropylene-based non-oriented film has a low average roughness Ra of 0.08 μm, and the melting temperature of the mixed high-pressure low-density polyethylene is low at 106 ° C., so the blocking shear force at 130 ° C is 25 N / 12 cm 2 The heat seal strength at 170°C was low at 20N / 15mm, causing leakage of the contents during retort treatment at 130°C, and the bag-making speed was also poor at 37 spm, resulting in poor bag-making properties.

[0121] Comparative Example 4 A polypropylene-based non-oriented film was obtained in the same manner as in Example 1, except that the composition of the polypropylene-based non-oriented film was 100 parts by mass of a mixed resin consisting of 85% by mass of an ethylene-propylene block copolymer of a propylene-based block copolymer (a1), 5% by mass of high-density polyethylene, and 10% by mass of an ethylene-butene copolymer elastomer (c1). A laminate was also obtained in the same manner as in Example 1. The properties of the obtained polypropylene-based non-oriented film and the properties of the laminate with a heat-resistant substrate are shown in Table 1.

[0122] The polypropylene-based unstretched film had an average roughness Ra that satisfied the range specified in the present invention, but the peak count of 0.3 μm or more was below the range specified in the present invention, and the blocking shear force at 130° C. was 40 N / 12 cm 2 However, the melting temperature of the main component, ethylene-propylene block copolymer, is high at 163°C, so the temperature at which the heat seal strength reaches 3N / 15mm or more is high at 170°C, resulting in poor low-temperature heat sealability.The heat seal strength at 170°C is low at 4N / 15mm, so it was not possible to obtain bags under the above bag-making conditions.

[0123] [Example 7] The base layer composition of the polypropylene-based unstretched film was 100 parts by mass of a mixed resin consisting 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 polyethylene resin (b1), and 500 ppm of "Sumilizer" GP and 750 ppm of "Sumilizer" GS were mixed for 3 minutes in a Henschel mixer, and the mixture was fed into a twin-screw extruder controlled at a temperature of 260°C and melt-kneaded.

[0124] The sealing layer composition was made up of 57.5% by mass of a propylene-ethylene random copolymer (a3) ​​with a peak melting temperature of 142°C, which had been thoroughly cooled with liquid nitrogen and then pulverized using an impeller mill to form a powder, 40% by mass of 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(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 in a Henschel mixer for 3 minutes, and then fed into a twin-screw extruder temperature-controlled at 260°C for melt-kneading to produce master chips.

[0125] Next, 25% by mass of the propylene-ethylene random copolymer (a3) ​​was mixed with 75% by mass of the master chips, and the mixture was fed into a twin-screw extruder whose temperature was adjusted to 260°C and melt-kneaded.

[0126] Next, the melt-mixed base layer resin and seal layer resin were extruded at a ratio of 6:1 from a multi-layer T-type two-layer die at 250°C and 60 m / min, and then brought into contact with a cooling roll at 45°C to cool and solidify.The base layer surface was then corona discharge treated to obtain a 60 μm thick polypropylene-based unstretched film.

[0127] The above polypropylene-based unstretched film was bonded to a 15 μm-thick biaxially oriented polyamide film as a heat-resistant substrate using an aliphatic ester-based adhesive (Takelac A385 / Takenate A50, manufactured by Mitsui Chemicals, Inc., adhesive layer thickness 2.5 μm) by a conventional dry lamination method, and then aged at 40°C for 3 days to obtain a laminate.

[0128] Using the above 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 edge) of 210°C, a vertical seal temperature of 210°C, and a top seal temperature (sealed part after filling) of 210°C, and evaluating the number of packaging bags filled with 200g of saline solution as the bag forming speed (spm) (shots per minute). The properties of the obtained polypropylene-based unoriented film and the properties of the laminate with a heat-resistant substrate are shown in Table 2.

[0129] The polypropylene-based non-oriented film has excellent low-temperature heat sealing properties, excellent high-temperature blocking resistance, and as a laminate has high heat sealing strength at 170°C, excellent low-temperature impact resistance, excellent bag formability, 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.

[0130] [Example 8] A polypropylene-based unstretched film and a laminate were obtained in the same manner as in Example 7, except that the base layer contained 60 mass% of propylene-ethylene block copolymer (a1), 20 mass% of propylene-ethylene random copolymer (a3), and 20 mass% of linear low-density polyethylene (b1). The properties of the obtained polypropylene-based unstretched film and the properties of the laminate with the heat-resistant substrate are shown in Table 2.

[0131] The polypropylene-based non-oriented film has excellent low-temperature heat sealing properties, excellent high-temperature blocking resistance, and as a laminate has high heat sealing strength at 170°C, excellent low-temperature impact resistance, excellent bag formability, 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.

[0132] [Example 9] An unstretched polypropylene film was obtained in the same manner as in Example 1, except that in Example 7, 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. A laminate was also obtained in the same manner as in Example 7. The properties of the obtained unstretched polypropylene film and the properties of the laminate with the heat-resistant substrate are shown in Table 2.

[0133] The polypropylene-based non-oriented film has excellent low-temperature heat sealing properties, excellent high-temperature blocking resistance, and as a laminate has high heat sealing strength at 170°C, excellent low-temperature impact resistance, excellent bag formability, 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.

[0134] [Example 10] An unstretched polypropylene film was obtained in the same manner as in Example 1, except that in Example 7, the propylene-ethylene random copolymer (a3) ​​having a peak melting temperature of 142°C in the seal layer was replaced with a propylene-ethylene random copolymer (a4) having a peak melting temperature of 135°C. A laminate was also obtained in the same manner as in Example 7. The properties of the obtained unstretched polypropylene film and the properties of the laminate with the heat-resistant substrate are shown in Table 2.

[0135] The polypropylene-based non-oriented film has excellent low-temperature heat sealing properties, excellent high-temperature blocking resistance, and as a laminate has high heat sealing strength at 170°C, excellent low-temperature impact resistance, excellent bag formability, 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.

[0136] [Example 11] An unstretched polypropylene film was obtained in the same manner as in Example 1, except that in Example 7, the propylene-ethylene random copolymer (a3) ​​in the seal layer was changed to 87.5% by mass and the linear low-density polyethylene in the polyethylene resin (b1) was changed to 10% by mass. A laminate was also obtained in the same manner as in Example 7. The properties of the obtained unstretched polypropylene film and the properties of the laminate with the heat-resistant substrate are shown in Table 2. The polypropylene-based non-oriented film has excellent low-temperature heat sealing properties, excellent high-temperature blocking resistance, and as a laminate has high heat sealing strength at 170°C, excellent low-temperature impact resistance, excellent bag formability, 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.

[0137] [Example 12] In Example 7, a polypropylene-based non-oriented film was obtained in the same manner as in Example 1, except that the seal layer contained 89 mass% of propylene-ethylene random copolymer (a3), 10 mass% of linear low-density polyethylene as polyethylene resin (b1), and 1 mass% of Perhexa 25B, totaling 100 mass parts. A laminate was also obtained in the same manner as in Example 7. The properties of the obtained polypropylene-based non-oriented film and the properties of the laminate with a heat-resistant substrate are shown in Table 2.

[0138] The polypropylene-based non-oriented film has excellent low-temperature heat sealing properties, excellent high-temperature blocking resistance, and as a laminate has high heat sealing strength at 170°C, excellent low-temperature impact resistance, excellent bag formability, 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.

[0139] [Example 13] In Example 7, a polypropylene-based unstretched film was obtained in the same manner as in Example 1, except that the seal layer was changed to a mixed composition of 77.5 mass% of propylene-ethylene random copolymer (a1), 15 mass% of linear low-density polyethylene (polyethylene resin (b1)), 5 mass% of ethylene-butene copolymer elastomer (c1), and 2.5 mass% of Perhexa 25B, totaling 100 mass parts. A laminate was also obtained in the same manner as in Example 7. The properties of the obtained polypropylene-based unstretched film and the properties of the laminate with a heat-resistant substrate are shown in Table 2.

[0140] The polypropylene-based non-oriented film has excellent low-temperature heat sealing properties, excellent high-temperature blocking resistance, and as a laminate has high heat sealing strength at 170°C, excellent low-temperature impact resistance, excellent bag formability, 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.

[0141] [Example 14] In Example 7, the seal layer composition was 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 were added as antioxidants to a total of 100 parts by mass of the mixed composition in a Henschel mixer for 3 minutes, and the mixture was then fed to a twin-screw extruder controlled at 260°C for melt-kneading.

[0142] Next, a stainless steel core metal that holds the heat transfer medium flow path is coated with HTV silicone rubber to a thickness of 8 mm, and then covered with a PFA heat-shrinkable tube with a thickness of 0.2 mm. After buffing the surface of the PFA, steel spheres are sprayed onto it to create a surface with a depth of 1.0 μm and a number of 10 mm 2The film was extruded at 50 m / min through a multilayer T-die between an embossing rubber roller (1,400 per roller) and a mirror-finished metal roll, with the sealing layer facing the rubber roll, to obtain a 60 μm-thick unstretched polypropylene film. A laminate was also obtained in the same manner as in Example 7. The properties of the obtained unstretched polypropylene film and the properties of the laminate with the heat-resistant substrate are shown in Table 2.

[0143] The polypropylene-based non-oriented film has excellent low-temperature heat sealing properties, excellent high-temperature blocking resistance, and as a laminate has high heat sealing strength at 170°C, excellent low-temperature impact resistance, excellent bag formability, 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.

[0144] [Example 15] In Example 7, the base layer composition was 100 parts by mass of a mixed resin consisting of 72% by mass of a propylene-ethylene block copolymer (a1), 18% by mass of a linear low-density polyethylene (polyethylene resin (b1)), and 10% by mass of a propylene-butene copolymer elastomer. This was mixed with 500 ppm of "Sumilizer" GP and 750 ppm of "Sumilizer" GS as antioxidants in a Henschel mixer for 3 minutes, and then fed to a twin-screw extruder controlled at 260°C for melt-kneading.

[0145] The seal layer composition consisted of 87.5% by mass of a propylene-ethylene random copolymer (a3) ​​with a peak melting temperature of 142°C, which had been thoroughly cooled with liquid nitrogen and then pulverized using an impeller mill to form a powder. It also contained 10% by mass of high-density polyethylene (b2), 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 this mixture, 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. The mixture was mixed for 3 minutes in a Henschel mixer and then fed into a twin-screw extruder regulated at 260°C for melt-kneading to produce a master chip.

[0146] Next, 70% by mass of the master chips was mixed with 20% by mass of a propylene-ethylene block copolymer and 10% by mass of a propylene-butene copolymer elastomer, and the mixture was fed into a twin-screw extruder controlled at 260°C for melt-kneading.

[0147] Next, the melt-mixed base layer resin and seal layer resin were extruded at a ratio of 6:1 from a multi-layer T-type two-layer die at 250°C and 60 m / min, and then brought into contact with a cooling roll at 45°C to cool and solidify.The base layer surface was then corona discharge treated to obtain a 60 μm thick polypropylene-based unstretched film.

[0148] The above polypropylene-based unstretched film was laminated with a biaxially oriented polyamide film having a thickness of 15 μm in the same manner as in Example 7. The properties of the obtained polypropylene-based unstretched film and the properties of the laminate with the heat-resistant substrate are shown in Table 2.

[0149] The polypropylene-based non-oriented film has excellent low-temperature heat sealing properties, excellent high-temperature blocking resistance, and as a laminate has high heat sealing strength at 170°C, excellent low-temperature impact resistance, excellent bag formability, 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.

[0150] Comparative Example 5 An unstretched polypropylene film was obtained in the same manner as in Example 7, except that the base layer contained 40% by mass of the propylene-ethylene block copolymer (a1) and 30% by mass of the propylene-ethylene random copolymer (a3). A laminate was also 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 2.

[0151] The above-mentioned polypropylene-based unstretched film has a low content of propylene-ethylene block copolymer in the base layer, so some bags leak when heat-treated at 130°C, and it also has poor low-temperature impact resistance.

[0152] Comparative Example 6 In Example 7, a polypropylene-based unstretched film was obtained in the same manner as in Example 1, except that the base layer was made of a mixed resin of 70 mass% of propylene-ethylene random copolymer (a3) ​​and 30 mass% of linear low-density polyethylene (b1), a polyethylene-based resin. A laminate was also obtained in the same manner as in Example 7. The properties of the obtained polypropylene-based unstretched film and the properties of the laminate with the heat-resistant substrate are shown in Table 2.

[0153] The polypropylene-based non-oriented film has a low melting temperature peak of the base layer, so that the heat during bag making causes deformation of the bag product, which reduces the bag making speed and results in a low bag break retention rate.

[0154] Comparative Example 7 In Example 7, for the sealing layer, 100 parts by mass of a mixed resin consisting of 80% by mass of ethylene-propylene random copolymer (a5) and 20% by mass of linear low-density polyethylene (b1) was added with 0.4 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) as inorganic particles. The mixture was mixed in a Henschel mixer for 3 minutes, then fed to a twin-screw extruder controlled at 260°C for melt-kneading, and subsequently extruded at 250°C through a T-die at 60 m / min and cooled and solidified by contacting with a cooling roll at 45°C. One side was then subjected to a corona discharge treatment to obtain a 60 μm thick polypropylene-based unstretched film. A laminate was also obtained in the same manner as in Example 7. The properties of the obtained polypropylene-based unstretched film and the properties of the laminate with the heat-resistant substrate are shown in Table 2.

[0155] The polypropylene-based non-stretched film has a seal layer with a melting temperature peak of 150°C, an average roughness Ra of 0.04µm, and a peak count of 0.3µm or more of 68 / 10mm. 2 Therefore, the blocking shear force at 130°C is 42N / 12cm 2 The bag-making speed was 35 spm, which meant poor bag-making properties, and the heat-seal strength in a 100°C atmosphere was high, so the steam permeability when heated in a microwave oven was poor.

[0156] [Comparative Example 8] An unstretched polypropylene 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 seal layer was replaced with an ethylene-propylene-butene random copolymer, i.e., a propylene-ethylene random copolymer (a6) having a melting temperature peak of 132°C. A laminate was also 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 2.

[0157] The sealing layer of the above polypropylene-based non-oriented film has a peak melting temperature of 132°C, so the blocking shear force at 130°C is 17N / 12cm. 2 The laminate had poor high-temperature blocking resistance, and the heat seal strength at 170°C was low at 20N / 15mm. When the produced bag was retorted at 130°C, leakage of the contents occurred, and the bag production speed was 32 spm, resulting in poor bag production properties.

[0158] Comparative Example 9 An unstretched polypropylene film was obtained in the same manner as in Example 7, except that the linear low-density polyethylene of the polyethylene resin (b1) in the seal layer was changed to a high-pressure low-density polyethylene of the polyethylene resin (b3). A laminate was also 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 2.

[0159] The above polypropylene-based non-oriented film has a low average roughness Ra of 0.08 μm for the seal layer, and the melting temperature of the mixed high-pressure low-density polyethylene is low at 106°C, so the blocking shear force at 130°C is 25 N / 12 cm 2 The heat seal strength of the laminate at 170°C was low at 20N / 15mm, and the contents leaked during retort treatment at 130°C in the produced bags. The bag production speed was also poor at 37 spm, resulting in poor bag production properties.

[0160] [Comparative Example 10] In Example 7, a polypropylene-based non-oriented film was obtained in the same manner as in Example 1, except that the seal layer contained 85 mass% of ethylene-propylene block copolymer (a1), 5 mass% of high-density polyethylene, and 10 mass% of ethylene-butene copolymer elastomer (c1), for a total resin content of 100 parts by mass. A laminate was also obtained in the same manner as in Example 7. The properties of the obtained polypropylene-based non-oriented film and the properties of the laminate with the heat-resistant substrate are shown in Table 2.

[0161] The average roughness Ra of the seal layer and the peak count of 0.3 μm or more of the above polypropylene-based unstretched film satisfied the ranges specified in the present invention. However, because the melting temperature was as high as 162°C, the temperature at which the heat seal strength reached 3 N / 15 mm or more was as high as 162°C, resulting in poor low-temperature heat sealing properties. The heat seal strength of the laminate at 170°C was as low as 4 N / 15 mm, and it was not possible to obtain a bag product under the above bag-making conditions.

[0162] [Table 1]

[0163] [Table 2] [Industrial Applicability]

[0164] The present invention can provide an unstretched polypropylene film and a laminate using the same, which can be used as an environmentally friendly packaging bag for retort food packaging with a reduced number of layers, and which has excellent low-temperature heat sealing properties, high-temperature blocking resistance, and excellent bag-making processability, and which has high heat sealing strength at 170°C as a laminate, excellent low-temperature impact resistance, excellent steam permeability when heated in a microwave oven, and excellent retort suitability.

Claims

1. The polymer comprises a propylene-based random copolymer as a main component, the melting temperature peak of which is 135°C or higher and 145°C or lower, Contains polyethylene having a melting temperature peak exceeding 106°C, At least one side of the film has an average surface roughness Ra of 0.1 μm or more and a peak count of 0.3 μm or more of 100 or more / 10 mm ２ A polypropylene-based unstretched film having a surface which is a heat seal surface.

2. The blocking shear strength between the heat-sealed surfaces at 130°C is 15 N / 12 cm ２ The polypropylene-based unstretched film according to claim 1, wherein:

3. It consists of two layers: a base layer and a seal layer. the base layer contains 50% by mass or more of a propylene-ethylene block copolymer and has a peak melting temperature of 150°C or higher; The melting temperature peak of the sealing layer is in the range of 135°C to 145°C, The sealing layer contains polyethylene having a melting temperature peak exceeding 106°C, The average surface roughness Ra of the sealing layer surface is 0.1 μm or more, and the peak count of 0.3 μm or more is 100 / 10 mm ２ A polypropylene-based unstretched film having the above surface as a heat seal surface.

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

5. The polypropylene-based unstretched film according to claim 1, having a film thickness of 20 μm or more and 150 μm or less.

6. The polypropylene-based unstretched film according to claim 3, wherein the film thickness is 20 μm or more and 150 μm or less, and the thickness ratio of the base layer to the seal layer is 9:1 to 3:

1.

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

8. 8. The laminate according to claim 7, wherein the heat-resistant substrate is at least one selected from the group consisting of any one 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; films obtained by subjecting any one of these films to metal vapor deposition, inorganic vapor deposition, transparent metal oxide vapor deposition, or gas barrier resin; synthetic paper; and aluminum foil.

9. A polypropylene-based unstretched film as described in claim 1, containing linear low-density polyethylene.

10. A polypropylene-based unstretched film as described in claim 3, wherein the sealing layer contains linear low-density polyethylene or high-density polyethylene.

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