Polypropylene-based stretched film and package

Abstract

To provide a polypropylene-based stretched film which is thin and has high pinhole resistance, and a packaging body.SOLUTION: The polypropylene-based stretched film comprises a base layer, a surface layer laminated on one side of the base layer, and a seal layer laminated on the other side of the base layer, wherein the surface layer has a thickness of 4 μm or less and contains 80 wt% or more of a homopolypropylene having an isotactic index of 98% or more, the base layer contains 50 wt% or more of a homopolypropylene having an isotactic index of 96% or more, and has a melting temperature of less than 162 °C, and the seal layer contains a polypropylene-based random copolymer and has a tensile strength in the flow direction of the resin of 100 MPa or more and a total thickness of 25 μm or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a polypropylene-based stretched film and a packaging material. [Background technology]

[0002] Patent Document 1 discloses an example of a polypropylene-based stretched film, which includes a base layer and a heat-sealable layer laminated on the base layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-137074 Summary of the Invention [Problem to be solved by the invention]

[0004] From the viewpoint of environmental issues, it is required to reduce the amount of resin used in polypropylene-based stretched films. For this reason, it is preferable to make the polypropylene-based stretched film thin. However, if the polypropylene-based stretched film is made thin, there is a concern that the pinhole resistance will decrease.

[0005] An object of the present invention is to provide a thin, highly pinhole-resistant polypropylene-based stretched film and a package manufactured using the same. [Means for solving the problem]

[0006] A polypropylene-based stretched film according to a first aspect of the present invention comprises a base layer, a surface layer laminated on one side of the base layer, and a seal layer laminated on the other side of the base layer, wherein the surface layer has a thickness of 4 μm or less and contains 80% by weight or more of homopolypropylene having an isotactic index of 98% or more, the base layer contains more than 50% by weight of homopolypropylene having an isotactic index of 96% or more and has a melting point of less than 162°C, and the seal layer contains a polypropylene-based random copolymer and has a tensile strength of 100 MPa or more in the resin flow direction and an overall thickness of 25 μm or less.

[0007] The above-mentioned polypropylene-based stretched film has a total thickness of 25 μm or less, and is therefore thin. Furthermore, the above-mentioned polypropylene-based stretched film has the above-mentioned surface layer specifications, base layer specifications, and resin flow direction tensile strength, and therefore it has been confirmed that the pinhole resistance is enhanced. In other words, the above-mentioned polypropylene-based stretched film is thin and has high pinhole resistance.

[0008] A polypropylene-based stretched film according to a second aspect of the present invention is the polypropylene-based stretched film according to the first aspect, wherein the thickness of the seal layer exceeds 2 μm.

[0009] It was confirmed that the above-mentioned polypropylene-based stretched film can provide high heat seal strength.

[0010] A stretched polypropylene film according to a third aspect of the present invention is the stretched polypropylene film according to the first or second aspect, and has a heat seal strength at 130° C. of 5.0 N / 15 mm or more.

[0011] The above-mentioned polypropylene-based stretched film has high heat seal strength, and therefore can be firmly bonded.

[0012] A packaging body according to a fourth aspect of the present invention is produced using the stretched polypropylene film according to any one of the first to third aspects.

[0013] According to the above-mentioned package, the same effects as those of the polypropylene-based stretched film according to any one of the first to third aspects can be obtained. [Effects of the Invention]

[0014] The polypropylene-based stretched film and packaging material according to the present invention are thin and highly pinhole resistant. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 2 is a cross-sectional view of a polypropylene-based stretched film included in the packaging body of the embodiment. [Figure 2] 1 is a table showing the specifications and test results of polypropylene-based stretched films of the examples. [Figure 3] 1 is a table showing the specifications and test results of a comparative polypropylene-based stretched film. [Figure 4] Figure regarding wear testing. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, a polypropylene-based stretched film and a packaging material according to one embodiment of the present invention will be described with reference to the drawings.

[0017] <1. Structure of polypropylene-based stretched film> FIG. 1 is a cross-sectional view showing an example of the layer structure of a polypropylene-based stretched film 10 included in a package 1 of this embodiment. The polypropylene-based stretched film 10 of this embodiment is used, for example, as a packaging bag for products, a packaging bag for fruits and vegetables (such as cut cabbage), or a hanging bag for display in a retail store. The polypropylene-based stretched film 10 is a laminated film including a base layer 20, a surface layer 30, and a seal layer 40. The polypropylene-based stretched film 10 of this embodiment is configured to have a thin overall thickness in order to reduce the amount of resin used. The overall thickness of the polypropylene-based stretched film 10 is 25 μm or less. The overall thickness of the polypropylene-based stretched film 10 is preferably 23 μm or less, and more preferably 20 μm or less.

[0018] The base layer 20 contains more than 50 wt % of homopolypropylene with an isotactic index (mesopentide fraction) of 96% or more and a melting point below 162°C. This improves the stretchability of the polypropylene-based stretched film 10. To improve the stretchability of the polypropylene-based stretched film 10, the base layer 20 preferably contains 60 wt % or more, and even more preferably 70 wt % or more, of homopolypropylene with an isotactic index of 96% or more but less than 98%. The melting point of the base layer 20, as measured by differential scanning calorimetry, is preferably 150°C or more but less than 162°C, and even more preferably 152°C or more but less than 160°C. The crystallization temperature of the base layer 20 is preferably less than 115°C. The homopolypropylene constituting the base layer 20 may contain at least one of plant-derived raw materials and biomass raw materials, and may also contain recycled raw materials such as polypropylene-based stretched films. The melt mass flow rate (MFR) of the homopolypropylene material constituting the base layer 20 is preferably 10 g / 10 min or less, more preferably 7 g / 10 min or less, and even more preferably less than 4 g / 10 min. The crystallization temperature of the base layer 20 is preferably 100°C or more and 140°C or less, more preferably 110°C or more and 130°C or less. The thickness of the base layer 20 is preferably 10 μm or more and 20 μm or less, more preferably 12 μm or more and 18 μm or less.

[0019] The material constituting the base layer 20 may further contain an olefin-based elastomer and a petroleum resin. The content of the olefin-based elastomer and petroleum resin is preferably 1% by weight or more to 40% by weight, more preferably 3% by weight or more to 30% by weight or less, based on 100% by weight of the resin components constituting the base layer 20. Furthermore, as the olefin-based elastomer, an ethylene / α-olefin copolymer elastomer or a propylene / α-olefin copolymer elastomer is preferably used. The copolymer may be a block copolymer or a random copolymer. The ethylene / α-olefin copolymer elastomer and the propylene / α-olefin copolymer elastomer are elastomers containing 15 mol % or more of an α-olefin copolymer component having 4 or more carbon atoms. Examples of α-olefins include butene-1, pentene-1, hexene-1, octene-1, and 4-methylpentene-1. Among these, an ethylene / butene copolymer elastomer and a propylene / butene copolymer elastomer are preferred.

[0020] The surface layer 30 is laminated to one side of the base layer 20. The surface layer 30 may be laminated to the base layer 20 via, for example, an adhesive layer or the like. The surface layer 30 has a thickness of 4 μm or less. This improves the stretchability of the polypropylene-based stretched film 10. To improve the stretchability of the polypropylene-based stretched film 10, the thickness of the surface layer 30 is preferably 3 μm or less. The surface layer 30 contains 80% by weight or more of homopolypropylene having an isotactic index of 98% or more. The use of homopolypropylene having a high isotactic index in the surface layer 30 improves the pinhole resistance of the polypropylene-based stretched film 10. To improve the pinhole resistance of the polypropylene-based stretched film 10, the surface layer 30 is preferably composed solely of homopolypropylene having an isotactic index of 98% or more. To improve the pinhole resistance, the lower limit of the thickness of the surface layer 30 is preferably 1 μm or more, more preferably 1.5 μm or more. The melt mass flow rate (MFR) of the homopolypropylene material constituting the surface layer 30 is preferably 10 g / 10 min or less, more preferably 7 g / 10 min or less, and even more preferably less than 4 g / 10 min.

[0021] The sealing layer 40 is laminated on the other side of the base layer 20. The sealing layer 40 may be laminated on the base layer 20 via, for example, an adhesive layer or the like. The sealing layer 40 contains a polypropylene random copolymer. The thickness of the sealing layer 40 can be selected as desired. From the viewpoint of increasing the heat seal strength, the thickness of the sealing layer 40 is preferably more than 2 μm and less than 5 μm. The heat seal strength of the sealing layer 40 can be selected as desired. To ensure strong bonding, the heat seal strength of the sealing layer 40 is preferably 5.0 N / 15 mm or more at 130°C. The heat seal strength of the sealing layer 40 is more preferably 6.0 N / 15 mm or more at 130°C.

[0022] In the production of the stretched polypropylene-based film 10, from the viewpoint of improving orientation, the stretching ratio in the MD (Machine Direction) is preferably, for example, about 4.0 to 8.0, and more preferably about 4.5 to 6.5. This improves the stiffness of the stretched polypropylene-based film 10. Since MD stretching of the stretched polypropylene-based film 10 is the first step in stretching the film 10, it is easier to perform than TD (Transverse Direction) stretching, although the load on the rolls is greater. In the production of the stretched polypropylene-based film 10, from the viewpoint of improving orientation, the stretching ratio in the TD is preferably, for example, about 5.0 to 10.0. Furthermore, the tensile strength of the stretched polypropylene-based film 10 in the MD, in other words, in the direction of resin flow, is 100 MPa or more. This results in high mechanical strength.

[0023] From the viewpoint of increasing mechanical strength, the stretching ratio in MD of the polypropylene-based stretched film 10 is preferably 4.5 times or more. From the same viewpoint, the Young's modulus in MD of the polypropylene-based stretched film 10 is preferably 2.0 GPa or more, and the Young's modulus in TD is preferably 5.0 GPa or more. From the same viewpoint, the loop stiffness in MD of the polypropylene-based stretched film 10 is preferably 0.000200 or more, and the loop stiffness in TD is preferably 0.000450 or more.

[0024] <2. Method for producing stretched polypropylene film> There are no particular limitations on the method for producing the stretched polypropylene-based film 10 of this embodiment, and any known method can be used. From the viewpoints of productivity and the physical properties of the stretched polypropylene-based film 10, it is preferable to produce the stretched polypropylene-based film 10 by extruding a flat sheet and then sequentially biaxially stretching it.

[0025] In this embodiment, for example, a resin composition for the surface layer 30, a resin composition for the base layer 20, and a resin composition for the seal layer 40 are respectively charged into three extruders set at appropriate temperatures. The resins are melted and kneaded in the extruders, and then extruded into a sheet through a T-die at 210°C to 250°C. In this case, to form a three-layer structure, a feed block method or a multi-manifold method may be used. The extruded sheet is cooled and solidified by cooling rolls at 25°C and sent to the MD stretching process. MD stretching is performed using heating rolls set at 130°C to 140°C, and the sheet is stretched in the MD due to the speed difference between the rolls. There is no particular limitation on the number of heating rolls, but at least two, one on the low-speed side and one on the high-speed side, are required. As mentioned above, the stretch ratio in MD stretching is preferably approximately 4.0 to 8.0 times, more preferably approximately 4.5 to 6.5 times. Next, the sheet is sent to a TD stretching step using a tenter and stretched in the TD. The tenter is divided into a preheating zone, a stretching zone, and an annealing zone. The temperature of the preheating zone is set to 165°C to 170°C. The temperature of the stretching zone is set to 165°C to 170°C. The temperature of the annealing zone is set to 165°C to 170°C. As mentioned above, the stretching ratio in the stretching zone is preferably about 5.0 to 10.0 times. After being stretched, the sheet is cooled and fixed in the annealing zone and taken up by a winder to form a film roll.

[0026] <3. Functions and Effects of Polypropylene-Based Stretched Film> The polypropylene-based stretched film 10 is thin, having an overall thickness of 25 μm or less. Furthermore, the polypropylene-based stretched film 10 has the above-described specifications of the surface layer 30, the base layer 20, and the MD tensile strength, and therefore has enhanced pinhole resistance. In other words, the polypropylene-based stretched film 10 is thin and has high pinhole resistance.

[0027] <4. Example> The inventor(s) of the present application produced stretched polypropylene-based films of Examples and Comparative Examples and conducted tests to measure the physical properties of the stretched polypropylene-based films. For convenience, the components of the stretched polypropylene-based films of Examples and Comparative Examples may be described below using the same reference numerals as in the embodiments.

[0028] The polypropylene-based stretched film in each example is a polypropylene-based stretched film of an embodiment. FIG. 2 is a table showing the specifications and test results of the polypropylene-based stretched films of Examples 1 to 7. FIG. 3 is a table showing the specifications and test results of the polypropylene-based stretched films of Comparative Examples 1 to 6. In FIGS. 2 and 3, the isotactic index value is referred to as "II value." The thicknesses of the base layer 20, surface layer 30, and seal layer 40 in FIGS. 2 and 3 are the thicknesses of the polypropylene-based stretched film after it has been stretched.

[0029] In addition, the specifications of the materials indicated by symbols in Figures 2 and 3 are as follows: PP-1: Homopolypropylene (II value: 99%, MFR: 3.0g / 10min) PP-2: Homopolypropylene (II value: 98%, MFR: 3.0g / 10min) PP-3: Homopolypropylene (II value: 97%, MFR: 3.0g / 10min) PP-4: Homopolypropylene (II value: 96%, MFR: 3.0g / 10min) PP-5: Homopolypropylene (II value: 95%, MFR: 2.5g / 10min) PP-6: Propylene / butene copolymer elastomer (MFR: 7.0g / 10min) PP-7: Propylene / ethylene / butene random copolymer (MFR: 5.0g / 10min) PE-1: Linear low-density polyethylene (MFR: 3.5g / 10min) ·HC-1: Petroleum resin

[0030] The polypropylene-based stretched film of Example 1 was prepared by feeding the resin compositions constituting each layer according to the formulation shown in FIG. 2 into three extruders, coextruding them through a three-layer T-die at 230°C so that the surface layer 30, base layer 20, and seal layer 40 were laminated in that order. The extrusions were then cooled and solidified using a cooling roll at 25°C to obtain a raw sheet. This sheet was then heated to 130°C and stretched 5.3 times in the MD direction. It was then preheated in a tenter at a set temperature of 165°C and stretched 6 times in the TD direction at a set temperature of 165°C. The sheet was then annealed at a set temperature of 165°C, and after exiting the tenter, it was subjected to a corona discharge treatment and wound up on a winder to obtain a polypropylene-based stretched film. The resulting polypropylene-based stretched film had an overall thickness of 20 μm. The thicknesses of the surface layer 30 and seal layer 40 were 2 μm, and the thickness of the base layer 20 was 16 μm. The polypropylene-based stretched films of Examples 2 to 7 and Comparative Examples 1 to 6 were obtained in the same manner as in Example 1, except that the composition, overall thickness, thickness of each layer, or stretching ratio was changed as shown in Figures 2 and 3.

[0031] The MFR of the materials constituting the polypropylene-based stretched films of Examples 1 to 7 and Comparative Examples 1 to 6 was measured in accordance with JIS K-7210 (2014) under conditions of 230°C and 2.16 kg. The isotactic index was calculated as the isotactic fraction of pentad units from nuclear magnetic resonance spectroscopy (C-NMR) measurements using carbon isotopes. C-NMR measurements were performed using a nuclear magnetic resonance apparatus while heating to 135°C. The isotactic index was determined from the resulting chart by calculating the ratio of the peak height at 21.82 ppm to the sum of the peak heights at 21.82, 21.57, 21.31, 21.03, 20.82, 20.64, 20.29, 20.17, and 19.88 ppm.

[0032] The melting points and crystallization temperatures of the materials constituting the base layers of the polypropylene-based stretched films of Examples 1 to 7 and Comparative Examples 1 to 6 can be measured using a differential scanning calorimeter (Shimadzu Corporation, DSC-60) at a temperature rise rate of 10°C / min.

[0033] <5. Test> The inventor(s) of the present application conducted tests to measure the following items for the stretched polypropylene films of Examples 1 to 7 and Comparative Examples 1 to 6.

[0034] <5-1. Tensile strength and tensile elongation> The stretched polypropylene films of Examples 1 to 7 and Comparative Examples 1 to 6 were cut to a size of 40 mm gauge interval and 10 mm width to obtain test specimens. The obtained test specimens were measured using a Strograph VE-1D manufactured by Toyo Seiki Seisaku-sho, Ltd., in accordance with a method conforming to JIS K-6732. However, the measurement was performed at an ambient temperature of 5°C and a test speed of 100 mm / min. Tensile strength and tensile elongation were measured using five test specimens for each Example and Comparative Example, and the average values ​​were calculated.

[0035] <5-2.Young's Modulus> The stretched polypropylene films of Examples 1 to 7 and Comparative Examples 1 to 6 were cut into samples measuring MD 250 mm × TD 5 mm and MD 5 mm × TD 250 mm, respectively, to obtain two types of test pieces. The obtained test pieces were measured using a Strograph VE-1D manufactured by Toyo Seiki Seisakusho, Ltd., in accordance with a method conforming to ASTM D882. Young's modulus was measured using seven test pieces for each Example and Comparative Example, and the average value was calculated.

[0036] <5-3. Loop Stiffness> Ten 200 mm x 25.0 mm strips were cut out from each of the stretched polypropylene films of Examples 1 to 7 and Comparative Examples 1 to 6, with the longitudinal direction (MD) of the strip as the long axis (loop direction) or the width direction (TD) of the stretched polypropylene film as the long axis (loop direction) of the strip. These were then clamped between clips to create measurement loops, one with one side of the film forming the inner surface of the loop and the other with the other side forming the inner surface of the loop, with the long axis of the strip aligned in the longitudinal and width directions of the film. The test specimens with the long axis of the strip aligned in the longitudinal direction of the stretched polypropylene film were placed in the chuck of a loop stiffness tester DA manufactured by Toyo Seiki Co., Ltd., with the width direction perpendicular. The clips were then removed, and the loop stiffness stress was measured. The chuck spacing was 80 mm. The indentation depth was 30 mm. The compression speed was 3.3 mm / sec. The loop stiffness was measured five times for a specimen placed so that one side of the polypropylene-based stretched film was the inner surface of the loop. Then, the loop stiffness was measured five times for a specimen placed so that the other side was the inner surface of the loop. Using the data from these 10 measurements, the cube of the thickness (μm) of each specimen was plotted on the horizontal axis and the stress of the loop stiffness (mN) on the vertical axis. An approximate curve was obtained passing through the origin, and the slope of the curve was calculated as the measured value of the loop stiffness. The same measurement was also performed on a specimen whose long axis was in the width direction of the polypropylene-based stretched film.

[0037] <5-4. Pinhole resistance> The pinhole resistance was confirmed by an abrasion test. Figure 4 shows the equipment used for the abrasion test. In the abrasion test, a polypropylene-based stretched film F from each example and comparative example was attached to a cone-shaped aluminum jig 100, and the apex 100A of the cone was brought into contact with cardboard 120 fixed by a fixture 110 via the polypropylene-based stretched film F. Next, a 20 g weight 130 was placed on the jig 100. In this state, the jig 100 was slid at a speed of 2700 mm / min over a range of 45 mm under 65% humidity conditions, and the number of slides until a pinhole was formed was counted. The occurrence of a pinhole was determined by dropping a penetrant liquid onto the polypropylene-based stretched film F where the apex of the jig 100 had been in contact.

[0038] <5-5. Heat seal strength> For each of Examples 1 to 7 and Comparative Examples 1 to 6, two polypropylene-based stretched films were stacked with the seal layers 40 facing each other, and then heat-sealed using a heat seal tester (HG-100, manufactured by Toyo Seiki Seisaku-sho, Ltd.) to obtain test specimens. The temperature was 130°C, the pressure was 0.2 MPa, and the sealing time was 1.0 second. The obtained test specimens were cut to dimensions of 200 mm in length and 15 mm in width, and heat seal strength was measured using a T-peel tester (Peeling Tester HEIDON-17, manufactured by Shinto Scientific Co., Ltd.) at a tensile speed of 200 mm / min. Five measurements were performed for each Example and Comparative Example, and the average value was taken as the seal strength (N / 15 mm).

[0039] <5-6. Test Results> The polypropylene-based stretched films of each Example had an overall thickness of 25 μm or less, and the number of times that pinholes appeared when sliding was 150 to 200 times under a load of 20 g. Therefore, the polypropylene-based stretched films of each Example were thin and had high pinhole resistance. This is thought to be because the specifications of the surface layer 30, the specifications of the base layer 20, and the MD tensile strength of the polypropylene-based stretched films of each Example satisfied the requirements set forth in the embodiments.

[0040] The polypropylene-based stretched film of Example 6 has a surface layer 30 with a thickness of 3 μm, which is thicker than the surface layer 30 of the polypropylene-based stretched films of Examples 1 to 5 and 7. The polypropylene-based stretched film of Example 6 has lower stretchability than the polypropylene-based stretched films of Examples 1 to 5 and 7, and therefore has slightly lower productivity. From this point of view, it can be seen that the thickness of the surface layer 30 is preferably 2 μm or less.

[0041] The polypropylene-based stretched film of Example 7 has a seal layer 40 with a thickness of 2 μm, which is thinner than the seal layer 40 of the polypropylene-based stretched films of Examples 1 to 6. Therefore, the polypropylene-based stretched film of Example 7 has a lower heat seal strength than the polypropylene-based stretched films of Examples 1 to 6. From this point of view, it can be seen that the thickness of the seal layer 40 is preferably greater than 2 μm.

[0042] In the stretched polypropylene film of Comparative Example 1, the isotactic index of the homopolypropylene material constituting the surface layer 30 is less than 98%. Also, the isotactic index of the homopolypropylene constituting the base layer 20 is less than 96%. Therefore, pinhole resistance is low.

[0043] The stretched polypropylene film of Comparative Example 2 had a thickness of more than 4 μm for the surface layer 30. Since the surface layer 30 was too thick and the stretchability was reduced, the stretched polypropylene film of Comparative Example 2 could not be produced.

[0044] The polypropylene-based stretched film of Comparative Example 3 contains 50% by weight of homopolypropylene with an isotactic index of 99%. The melting point of the base layer 20 is 162°C. Due to the reduced stretchability, the polypropylene-based stretched film of Comparative Example 3 could not be produced.

[0045] The polypropylene-based stretched film of Comparative Example 4 has an overall thickness of more than 25 μm. Heat is not easily transferred to the sealing layer 40, and therefore the sealing strength at low temperatures is low at 1.3 N / 15 mm.

[0046] In the polypropylene-based stretched film of Comparative Example 5, the material constituting the surface layer 30 is homopolypropylene with an isotactic index of 98% or more, but the content is less than 80% by weight, which results in low pinhole resistance.

[0047] The stretched polypropylene film of Comparative Example 6 was produced at a stretching ratio of 3.6 times and had an MD tensile strength of less than 100 MPa, resulting in low pinhole resistance.

[0048] The above-described embodiments are merely examples of possible forms of the polypropylene-based stretched film and packaging body of the present invention, and are not intended to limit the forms. The polypropylene-based stretched film and packaging body of the present invention may have forms different from those exemplified in the embodiments. Examples of such forms include forms in which part of the configuration of the embodiments is replaced, modified, or omitted, or forms in which a new configuration is added to each embodiment. [Explanation of symbols]

[0049] 1: Packaging 10: Polypropylene oriented film 20: Base material layer 30: Surface layer 40: Sealing layer

Claims

1. a substrate layer; a surface layer laminated on one side of the base material layer; a seal layer laminated on the other side of the base material layer, The surface layer has a thickness of 4 μm or less and an isotactic index of 98% or more. Contains 80% by weight or more of homopolypropylene, The base layer is made of homopolypropylene having an isotactic index of 96% or more. % by weight and has a melting point of less than 162°C; the sealing layer contains a polypropylene-based random copolymer, The Young's modulus of the resin in the flow direction is 2.0 GPa or more, and the overall thickness is 25 μm or less. R Polypropylene oriented film.

2. a substrate layer; a surface layer laminated on one side of the base material layer; a seal layer laminated on the other side of the base material layer, The surface layer has a thickness of 4 μm or less and an isotactic index of 98% or more. Contains 80% by weight or more of homopolypropylene, The base layer is made of homopolypropylene having an isotactic index of 96% or more. % by weight and has a melting point of less than 162°C; the sealing layer contains a polypropylene-based random copolymer, The loop stiffness in the direction of resin flow is 0.000200 or more, and the overall thickness is 25 μm or less. Polypropylene oriented film.

3. The thickness of the sealing layer is greater than 2 μm. The stretched polypropylene film according to claim 1 or 2.

4. Heat seal strength at 130°C is 5.0 N / 15 mm or more The stretched polypropylene film according to claim 1 or 2.

5. A packaging product produced using the stretched polypropylene film according to claim 1 or 2.

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