Biaxially oriented polypropylene resin film and packaging material using the same

Abstract

To provide a biaxially oriented polypropylene resin film suitable for an automatic packaging system, satisfactory in both heat seal strength after automatic packaging and heat seal strength in a melt-cutting sealing system, and superior in anti-fogging property, drip-proof property, slip property and blocking resistance.SOLUTION: A biaxially oriented polypropylene-based resin film has a base layer (A) made of a resin composition containing a polypropylene-based resin and a polyethylene-based resin, a seal layer (B) made of a polypropylene-based resin composition mainly composed of a propylene-butene-1 copolymer on one side of the base layer (A), and a surface layer (C) on the side of the base layer (A) opposite to the seal layer (B), and satisfies the following conditions a) to d): a) the polyethylene resin constituting the base layer (A) has a melt flow rate of 1.5 g / 10 min or more and 10 g / 10 min or less at 190°C and a density of 0.910 g / cm3 or more and 0.930 g / cm3 or less, and is contained in an amount of 1 wt.% or more and 20 wt.% or less relative to a total of 100 of the polypropylene resin and the polyethylene resin constituting the base layer (A); b) a thickness of the seal layer (B) is 1 μm or less; c) the polypropylene composition constituting the seal layer (B) contains 0.1 wt.% or more and 1.0 wt.% or less of an anti-fogging agent; and d) a thickness of the surface layer (C) is 1 μm or less.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a biaxially oriented polypropylene resin film and a package using the same, and in particular, to a package using the same that has heat sealability and anti-fogging effect, and is therefore suitable for packaging fresh produce such as vegetables, fruits, flowers, and other plants that require high freshness (hereinafter, referred to as "packaging" in this specification). This invention relates to a biaxially oriented polypropylene resin film suitable for packaging fruits and vegetables, and a package using the same. [Background technology]

[0002] 2. Description of the Related Art Biaxially oriented polypropylene resin films have been widely used in the field of packaging, such as food packaging and textile packaging, because of their excellent optical properties, mechanical properties, and packaging suitability. In particular, anti-fog films are widely used for packaging fruits and vegetables.

[0003] In particular, in the packaging of fruits and vegetables, there is a demand for labor saving in farm work due to the recent decline in the agricultural population, and automatic packaging methods are becoming more widespread. The so-called pillow packaging method is used as an automatic packaging method for fruits and vegetables, and it is possible to carry out the process of making bags by heat sealing and the process of filling the contents simultaneously.

[0004] As a material that can be applied to automatic packaging systems, a propylene-ethylene-butene copolymer with a melting point 10 to 90°C lower than that of the outer layer is melt-extruded onto a biaxially oriented film-like material whose main component is crystalline polypropylene resin. A laminated film obtained by performing a roll-up lamination process has been disclosed (see, for example, Patent Document 1).

[0005] A packaging film consisting of a laminate of two or more layers, which has a base layer mainly made of polypropylene resin and a heat seal layer mainly made of polyolefin resin using propylene-butene-1 copolymer and propylene-ethylene-butene-1 copolymer, has been disclosed as being suitable for automatic packaging systems and having excellent heat seal strength (see, for example, Patent Document 2).

[0006] Also, a packaging film that can be used for both automatic packaging methods such as pillow packaging and heat-seal packaging has been disclosed (see, for example, Patent Document 3). However, even in these conventional heat-sealable polypropylene laminate films, there has been a demand for further improvement in anti-fogging properties, particularly in drip resistance, slipperiness, and blocking resistance.

[0007] A biaxially oriented polypropylene film containing plant-derived polyethylene and having heat sealability has also been disclosed (see, for example, Patent Document 4). [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 3104166 [Patent Document 2] Patent No. 4385443 [Patent Document 3] Patent Publication No. 2019-166830 [Patent Document 4] Patent Publication No. 2019-6461 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been made in view of the problems of the conventional technology. That is, an object of the present invention is to provide a biaxially oriented polypropylene resin film which is suitable for an automatic packaging system, is satisfactory in terms of both heat seal strength after automatic packaging and heat seal strength in a melt-cutting sealing system, and has excellent drip-proofness, slipperiness, and blocking resistance. [Means for solving the problem]

[0010] In view of the above problems, the present inventors have conducted extensive research and have succeeded in obtaining a polypropylene-based laminate film that is particularly excellent in drip-proofness, slipperiness, and blocking resistance, and also has melt-cutting sealability and heat sealability, by setting the properties and respective ratios of the polypropylene-based resin and polyethylene-based resin constituting the base layer (A) and the properties of the sealing layer (B) and surface layer (C) within specific ranges, and by virtue of the properties of the sealing layer (B) and surface layer (C). That is, the present invention has the following configuration.

[0011] 1. A biaxially oriented polypropylene resin film having a base layer (A) made of a resin composition containing a polypropylene resin and a polyethylene resin, a seal layer (B) made of a polypropylene resin composition mainly composed of a propylene-butene-1 copolymer on one side of the base layer (A), and a surface layer (C) on the side of the base layer (A) opposite to the seal layer (B), and satisfying the following conditions a) to d): a) The polyethylene resin constituting the base layer (A) has a melt flow rate of 1.5 g / 10 min or more and 10 g / 10 min or less at 190° C. and a density of 0.910 g / cm 3 More than 0.930g / cm 3 The content is 1% by weight or more and 20% by weight or less relative to 100% by weight of the total of the polypropylene-based resin and the polyethylene-based resin constituting the base layer (A). b) The thickness of the sealing layer (B) is 1 μm or less. c) The polypropylene composition constituting the sealing layer (B) contains an anti-fogging agent in an amount of 0.1% by weight or more and 1.0% by weight or less. d) The surface roughness SRa (arithmetic mean roughness) of the surface layer (C) is 0.018 μm or more.

[0012] 2. The biaxially oriented polypropylene resin film according to 1., wherein the melting point of the propylene-butene-1 copolymer or the plurality of propylene-butene-1 copolymers is in the range of 120 to 130°C.

[0013] 3. The biaxially oriented polypropylene resin film according to 1 or 2, wherein the content of the propylene-butene-1 copolymer or the plurality of propylene-butene-1 copolymers is in the range of 50% by weight or more.

[0014] 4. The biaxially oriented polypropylene resin film according to any one of 1. to 3., wherein the thickness of the sealing layer (B) is 1.5% or more and 4% or less of the total thickness of the film.

[0015] 5. A biaxially oriented polypropylene resin film according to any one of 1. to 4., wherein the base layer (A) is made of a polypropylene resin composition mainly comprising at least one polypropylene resin selected from the group consisting of isotactic propylene homopolymers, propylene-ethylene copolymers, propylene-butene-1 copolymers, propylene-ethylene-butene-1 copolymers, and propylene-pentene copolymers.

[0016] 6. A biaxially oriented polypropylene resin film according to any one of 1. to 5., wherein the surface layer (C) is made of a resin composition mainly containing at least one polypropylene resin selected from the group consisting of propylene-ethylene-butene-1 copolymers, propylene-butene-1 copolymers, and propylene-ethylene copolymers.

[0017] 7. The biaxially oriented polypropylene resin film according to any one of 1. to 6., wherein the melting point of the polypropylene resin constituting the surface layer (C) is in the range of 130 to 140°C.

[0018] 8. The biaxially oriented polypropylene resin film according to any one of 1. to 7., wherein the thickness of the surface layer (C) is 1.5% or more and 4% or less of the total thickness of the film.

[0019] 9. A polypropylene-based laminate film described in any one of 1. to 8., in which the heat seal strength when the seal layers (B) of the biaxially oriented polypropylene-based resin film are heat sealed together at 120°C is 3.5 N / 15 mm or more.

[0020] 10. A polypropylene-based laminate film described in any one of 1. to 9., wherein the blocking value measured for the sealing layer (B) and the surface layer (C) of the biaxially oriented polypropylene-based resin film together is 110 mN / 200 mm or less.

[0021] 11. The polypropylene-based laminate film according to any one of 1. to 10., wherein the coefficient of friction between the surface layers (C) of the biaxially oriented polypropylene-based resin film is 0.35 or less.

[0022] 12. A packaging material using the biaxially oriented polypropylene resin film according to any one of 1. to 11. Effect of the Invention

[0023] The biaxially oriented polypropylene resin film of the present invention has excellent slip properties and blocking resistance, and is satisfactory in terms of both heat seal strength after automatic packaging and heat seal strength when using a fusion-cutting seal method. It also has less clouding due to water droplets after packaging vegetables, making it suitable for preserving the freshness of vegetables. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] The biaxially oriented polypropylene-based resin film of the present invention has a base layer (A) made of a resin composition containing a polypropylene-based resin and a polyethylene-based resin, a seal layer (B) made of a resin composition mainly composed of a propylene-butene-1 copolymer on one side of the base layer (A), and a surface layer (C) on the side of the base layer (A) opposite to the seal layer (B).

[0025] (Base material layer (A)) [Polypropylene resin] In the present invention, the resin composition constituting the substrate layer (A) contains a polypropylene-based resin. The polypropylene resin preferably comprises at least one resin selected from the group consisting of n-heptane-insoluble isotactic propylene homopolymers and copolymers of propylene and other α-olefins containing 70 mol % or more of propylene. n-Heptane insolubility is an index of the crystallinity of polypropylene and also indicates its safety when used for food packaging. In the present invention, it is preferable to use polypropylene that satisfies the n-heptane insolubility criteria specified in Notification No. 20 of the Ministry of Health and Welfare of February 1982 (the eluted amount when extracted at 25°C for 60 minutes is 150 ppm or less [30 ppm or less for those used at temperatures exceeding 100°C]).

[0026] When an isotactic propylene homopolymer and a copolymer of propylene and other α-olefins containing 70 mol % or more of propylene are mixed and used, the content of the copolymer of propylene and other α-olefins containing 70 mol % or more of propylene is desirably 50 wt % or more, more preferably 70 wt % or more, and even more preferably 90 wt % or more, based on the entire resin composition used in the base layer (A).

[0027] The α-olefin copolymerization component of the copolymer of propylene and another α-olefin is preferably an α-olefin having 2 to 8 carbon atoms, such as ethylene, butene-1, pentene-1, hexene-1, or 4-methyl-1-pentene. The copolymer is preferably a random or block copolymer obtained by polymerizing one or more of the above-listed α-olefins with propylene, and is preferably a propylene-ethylene copolymer, a propylene-butene-1 copolymer, a propylene-ethylene-butene-1 copolymer, or a propylene-pentene copolymer. The ratio of the α-olefin monomer-derived component to the total of the propylene monomer-derived component and the α-olefin monomer-derived component of the polypropylene-based resin used in the base layer (A) is preferably 0.3 mol% or more from the viewpoint of anti-fogging properties, particularly drip-proof properties. This makes it possible to achieve both rigidity and melt-cutting sealability at a high level. It is more preferably 0.4 mol% or more, and even more preferably 0.5 mol% or more. The melting point of the polypropylene resin used in the base layer (A) is preferably 156° C. or higher. The melting point is measured by the method described in the Examples below. When the melting point is 156° C. or higher, it is easy to make the film transport smoother in automatic packaging processing, and the obtained bag product is less likely to have wrinkles. The ratio of the α-olefin monomer derived component to the total of the propylene monomer derived component and the α-olefin monomer derived component of the polypropylene resin used in the base layer (A) is preferably 1.0 mol% or less from the viewpoint of melting point. This makes it easier to obtain melt-cutting sealability. It is more preferably 0.9 mol% or less, and even more preferably 0.8 mol% or more. In addition, the melt flow rate (MFR) can be exemplified as being in the range of 0.1 to 100 g / 10 min, preferably 0.5 to 20 g / 10 min, and more preferably 1.0 to 10 g / 10 min.

[0028] [Polyethylene resin] In the present invention, the resin composition constituting the substrate layer (A) contains a polyethylene-based resin. The polyethylene-based resin is a resin mainly composed of ethylene, and can be, for example, any ethylene homopolymer such as high-pressure low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, and high-density polyethylene, or can be a crystalline or low-crystalline or non-crystalline random or block copolymer with a monomer such as α-olefins such as propylene, butene-1, pentene-1, hexene-1, 3-methylbutene-1, 4-methylpentene-1, and octene-1, vinyl acetate, (meth)acrylic acid, or (meth)acrylic acid ester, or a mixture thereof.

[0029] The polyethylene resin is preferably contained in an amount of 1% by weight or more and 20% by weight, based on 100% by weight of the total of the polypropylene resin and the polyethylene resin constituting the base layer (A). When it is 1% by weight or more, the heat seal strength, slipperiness, blocking resistance, and drip resistance are improved. It is more preferably 5% by weight or more, and even more preferably 8% by weight. When it is 20% by weight or less, it is easy to maintain rigidity. It is more preferably 18% by weight or less, and even more preferably 15% by weight. The following is the result.

[0030] The melting point of the polyethylene resin is preferably in the range of 100° C. to 135° C., more preferably 105° C. to 130° C., from the viewpoints of heat resistance, transparency, mechanical properties, and film formability. The density is measured according to JIS K7112 and is 0.90 g / cm. 3 More than 0.94g / cm 3 Less than 0.91 g / cm is preferred. 3 More than 0.94g / cm 3 The following is more preferred:

[0031] The density was measured according to JIS K7112 and was 0.90 g / cm 3 More than 0.94g / cm 3 Less than 0.91 g / cm is preferred. 3 More than 0.94g / cm 3 The following is more preferred: The melt flow rate (MFR) of the polyethylene resin, measured in accordance with ASTM D1238 under conditions of 190°C and a load of 2.16 kg, is preferably 0.5 g / 10 min or more, more preferably 1 g / 10 min or more, and even more preferably 2 g / 10 min or more. From the viewpoint of further stabilizing moldability, it is preferably 20 g / 10 min or less, more preferably 15 g / 10 min or less, and even more preferably 10 g / 10 min or less.

[0032] It is preferable to use a polyethylene resin made from plant-derived ethylene as the raw material for the polyethylene resin. The bio-based content of the polyethylene resin measured in accordance with ISO 16620 is preferably 50% or more and 100% or less, more preferably 70% or more and 100% or less, and even more preferably 80% or more and 100% or less.

[0033] According to the investigations of the present inventors, when the polypropylene resin composition constituting the base layer (A) contains a polypropylene resin and a specific polyethylene resin, fine surface irregularities are formed on the surfaces of the sealing layer (B) and the surface layer (C), thereby improving the slip properties and blocking resistance. Furthermore, the melting point of polyethylene resin is lower than that of polypropylene resin, and the heat seal strength is higher. For example, if a polyethylene resin with a melting point of about 120°C is used, the heat seal strength when heat sealed at 120°C is higher. In addition, it was discovered that when the polypropylene resin composition constituting the base layer (A) contains a polypropylene resin and a specific polyethylene resin, fogging is less likely to occur even when the amount of water droplets adhering to the film surface in a low-temperature environment. The reason for this is thought to be that the crystallinity of the polypropylene resin composition constituting the base layer (A) is reduced, which promotes and sustains the migration (bleed-out) of the anti-fogging agent to the seal layer (B) and surface layer (C).

[0034] [Anti-fogging agent] The resin composition constituting the substrate layer (A) preferably contains an antifogging agent. By containing an antifogging agent in the resin composition constituting the substrate layer (A), the antifogging agent in the substrate layer (A) migrates successively to the seal layer (B) and the surface layer (C), and the antifogging property of the film surface is easily maintained. Typical examples of the antifogging agent include fatty acid esters of polyhydric alcohols, amines of higher fatty acids, amides of higher fatty acids, ethylene oxide adducts of amines or amides of higher fatty acids, etc. The amount of such antifogging agent in the substrate layer (A) is preferably 0.1 to 1.0% by weight, more preferably 0.2 to 0.8% by weight, further preferably 0.3 to 0.8% by weight, and particularly preferably 0.4 to 0.8% by weight, calculated based on the total layer.

[0035] [Thickness of base layer (A)] The thickness of the substrate layer (A) is preferably 10 μm or more and 100 μm or less, more preferably 15 μm or more and 50 μm or less, and even more preferably 15 μm or more and 25 μm or less.

[0036] (Sealing layer (B)) [Polypropylene resin] The polypropylene resin composition that constitutes the seal layer (B) is mainly composed of propylene-butene-1 copolymer. By using propylene-butene-1 copolymer as the main component, the seal layers (B) are easily mixed together, making it difficult for interfaces to form and allowing the heat seal strength to be achieved. In addition, propylene-butene-1 copolymer has a small amount of copolymerization components, making it difficult for peeling to occur at the interface with the base layer (A). Therefore, even if the thickness of the seal layer (B) is made thin, sufficient heat seal strength can be obtained. As the propylene-butene-1 copolymer, a plurality of propylene-butene-1 copolymers can be used, but it is preferable to use a single type of propylene-butene-1 copolymer. The melting point of these propylene-butene-1 copolymers is preferably in the range of 120 to 130° C. If the melting point is 130° C. or lower, the heat seal rise temperature is unlikely to become too high even if an anti-fogging agent is included, and if the melting point is 120° C. or higher, the heat seal rise temperature is unlikely to become too low. The content of propylene-butene-1 copolymer in the polypropylene resin composition constituting the seal layer is preferably 90% by weight or more in order to improve the heat seal strength, and more preferably 95% by weight or more.

[0037] From the viewpoint of heat seal strength, a polypropylene-based resin composition mainly composed of propylene-butene-1 copolymer is used for the seal layer, but in order to achieve a heat seal rise temperature of 115 to 125°C, it is important to make the anti-fog agent in the seal layer (B) 0.3% by weight or more so that the heat seal rise temperature does not become too low. If the amount of anti-fog agent is less than 0.3% by weight, the heat seal rise temperature will decrease. It is preferably 0.3 to 0.8% by weight, more preferably 0.45 to 0.7% by weight. In this case, when the fruits and vegetables are packaged and displayed in supermarkets or distributed, it is possible to prevent the inside from becoming cloudy due to physiological actions of the contents.

[0038] [Anti-fogging agent] The polypropylene resin composition constituting the sealing layer (B) contains an anti-fogging agent, which is effective when used to package fruits and vegetables, which are characterized by their continued physiological activity even after harvest. By adding an anti-fog agent only to the base layer (A) during the production of the biaxially oriented polypropylene resin film of the present invention, the anti-fog agent will migrate (bleed out) sequentially to the seal layer (B) during the film production and during storage after the film formation, and the film surface will have anti-fog properties. The anti-fog agent may be added to all of the base layer (A), seal layer (B), and surface layer (C) during the film production.

[0039] In order to maintain excellent anti-fogging properties over the long term during distribution, it is preferable to store the package at room temperature rather than in a frozen state. Therefore, it is preferable to select an anti-fogging agent that will continue to exhibit anti-fogging properties over the course of repeated temperature changes between 5 and 30°C, taking into consideration changes in temperature during storage and distribution. Typical examples of the antifogging agent include fatty acid esters of polyhydric alcohols, amines of higher fatty acids, amides of higher fatty acids, ethylene oxide adducts of amines or amides of higher fatty acids, etc. The amount of such antifogging agent in the sealing layer (B) is preferably 0.1 to 1.0% by weight, more preferably 0.2 to 0.8% by weight, further preferably 0.3 to 0.8% by weight, and particularly preferably 0.4 to 0.8% by weight, calculated based on the total weight of the layer.

[0040] [Additives] In addition, various additives for improving qualities such as slipperiness and antistatic properties, for example, lubricants such as wax and metal soaps for improving productivity, plasticizers, processing aids, and known heat stabilizers, antioxidants, antistatic agents, and ultraviolet absorbers that are usually added to polypropylene-based films, can also be blended within a range that does not impair the effects of the present invention. In order to ensure the blocking resistance and slipperiness of the film, it is preferable to compound inorganic or organic fine particles.

[0041] Examples of inorganic fine particles include silicon dioxide, calcium carbonate, titanium dioxide, talc, kaolin, mica, and zeolite, and the shape of these particles may be any type, such as spherical, elliptical, conical, or amorphous, and the particle size thereof may be selected according to the application and method of use of the film. As organic fine particles, crosslinked particles of acrylic, methyl acrylate, styrene-butadiene, etc. can be used, and as with inorganic fine particles, various shapes and sizes can be used. In addition, the surfaces of these inorganic or organic fine particles can be subjected to various surface treatments, and these can be used alone or in combination of two or more kinds.

[0042] The average particle size of the inorganic or organic fine particles is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 3 μm or more. The average particle size is preferably 5 μm or less, and more preferably 4 μm or less. The average particle size of the fine particles was measured as follows. The particles were dispersed in ion-exchanged water stirred at a specified rotation speed (approximately 5000 rpm) using a high-speed stirrer, and the dispersion was added to isotone (physiological saline) and further dispersed using an ultrasonic disperser. The particle size distribution was then determined using the Cole counter method, and the average particle size was calculated. The content of the fine particles is preferably 0.3% by weight or more, more preferably 0.5% by weight or more, even more preferably 0.7% by weight or more, and even more preferably 1.0% by weight or more, and is preferably 3.0% by weight or less, more preferably 2.0% by weight or less, and even more preferably 1.7% by weight or less, based on the polypropylene resin composition constituting the sealing layer (B).

[0043] [Thickness of seal layer (B)] The presence of the sealing layer (B) and surface layer (C) promotes the migration (bleed-out) of the anti-fog agent to the film surface, and the thicker the layer, the greater the effect on drip resistance, but the thickness of the sealing layer (B) must be 1 μm or less. If the thickness exceeds 1 μm, the strength of the welded seal when making bags using the welded seal method will be insufficient, and fine surface irregularities will be formed on the surface of the sealing layer (B), improving the slipperiness and blocking resistance. The thickness of the seal layer (B) is preferably 1.5% or more of the total film thickness in terms of heat seal strength after automatic packaging, and 4% or less in terms of heat-cut seal strength. The strength of the heat-sealing is also greatly affected by the size of the fused resin portion, called the "polyester pool," that occurs during heat-sealing. The thickness of the sealing layer (B) is preferably 0.1 μm or more. The sealing layer (B) needs to be provided on only one side of the base layer (A). If it is provided on both sides of the base layer (A), the film will stick to the sealing bar during the automatic packaging process, which can easily result in packaging defects.

[0044] (Surface layer (C)) [Polypropylene resin] The surface layer (C) can be mainly composed of at least one polypropylene resin selected from the group consisting of propylene-ethylene-butene-1 copolymer, propylene-butene-1 copolymer, and propylene-ethylene copolymer. Using one of these resins makes it easier for the seal layers to mix together, makes it difficult for an interface to form, and makes it easier to achieve heat seal strength. The melting point of the polypropylene resin is preferably in the range of 130 to 140° C. If the melting point is 140° C. or lower, the heat seal rise temperature is unlikely to become too high even if an anti-fogging agent is contained, and if the melting point is 130° C. or higher, the heat seal rise temperature is unlikely to become too low. The content of at least one polypropylene resin selected from the group consisting of propylene-ethylene-butene-1 copolymer, propylene-butene-1 copolymer, and propylene-ethylene copolymer in the polypropylene resin composition constituting the surface layer (C) is preferably 90% by weight or more in terms of improving the heat seal strength, and more preferably 95% by weight or more.

[0045] The heat seal rising temperature of the surface layer (C) is preferably 130°C or more and 140°C or less. The heat seal rising temperature of the surface layer (C) is the temperature at which the heat seal strength becomes 1N / 15mm when the surfaces of the surface layers (C) of the film of the present invention are placed face to face and heat sealed at a heat seal pressure of 1kg / cm2 for 1 second. When the heat seal rising temperature of the surface layer (C) is 130°C or more, the surface layer (C) is less likely to fuse to the seal bar during heat sealing of pillow packaging, making it easy to make bags. When the heat seal rising temperature is 140°C or less, the back-pasted part is easily fused to the exterior part of the package during pillow packaging, resulting in a good appearance, and the back-pasted part does not get caught when the packages are stacked, so there is no problem of the seal peeling off.

[0046] [Anti-fogging agent] It is preferable that the surface of the surface layer (C) has anti-fogging properties, which improves the appearance of the packaged fruits and vegetables when they become cloudy due to condensation when they are displayed in a supermarket or the like. Typical examples of the antifogging agent include fatty acid esters of polyhydric alcohols, amines of higher fatty acids, amides of higher fatty acids, ethylene oxide adducts of amines or amides of higher fatty acids, etc. The amount of such antifogging agent present in the surface layer (C) is preferably 0.1 to 1.0% by weight, more preferably 0.2 to 0.8% by weight, further preferably 0.3 to 0.8% by weight, and particularly preferably 0.4 to 0.8% by weight, calculated based on the total layer.

[0047] [Additives] In addition, various additives for improving qualities such as slipperiness and antistatic properties, for example, lubricants such as wax and metal soaps for improving productivity, plasticizers, processing aids, and known heat stabilizers, antioxidants, antistatic agents, and ultraviolet absorbers that are usually added to polypropylene-based films, can also be blended within a range that does not impair the effects of the present invention. In order to ensure the blocking resistance and slipperiness of the film, it is preferable to compound inorganic or organic fine particles.

[0048] Examples of inorganic fine particles include silicon dioxide, calcium carbonate, titanium dioxide, talc, kaolin, mica, and zeolite, and the shape of these particles may be any type, such as spherical, elliptical, conical, or amorphous, and the particle size thereof may be selected according to the application and method of use of the film. As organic fine particles, crosslinked particles of acrylic, methyl acrylate, styrene-butadiene, etc. can be used, and as with inorganic fine particles, various shapes and sizes can be used. In addition, the surfaces of these inorganic or organic fine particles can be subjected to various surface treatments, and these can be used alone or in combination of two or more kinds.

[0049] The average particle size of the inorganic or organic fine particles is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 3 μm or more. The average particle size is preferably 5 μm or less, and more preferably 4 μm or less. The average particle size of the fine particles was measured as follows. The particles were dispersed in ion-exchanged water stirred at a specified rotation speed (approximately 5000 rpm) using a high-speed stirrer, and the dispersion was added to isotone (physiological saline) and further dispersed using an ultrasonic disperser. The particle size distribution was then determined using the Cole counter method, and the average particle size was calculated. The content of the fine particles is preferably 0.3% by weight or more, more preferably 0.5% by weight or more, even more preferably 0.7% by weight or more, and even more preferably 1.0% by weight or more, and is preferably 3.0% by weight or less, more preferably 2.0% by weight or less, and even more preferably 1.7% by weight or less, based on the polypropylene resin composition constituting the surface layer (C).

[0050] (Thickness of surface layer (C)) When the polypropylene resin composition constituting the base layer (A) contains a polypropylene resin and a specific polyethylene resin, fine surface irregularities are formed on the surface of the surface layer (C), and therefore the smaller the thickness of the surface layer (C), the larger the surface irregularities will be, but the less likely it is to exhibit anti-fogging properties, so the surface layer (C) is essential. However, if the thickness of the surface layer (C) is too large, the surface irregularities will be small, so it is also necessary to control the thickness. The thickness of the surface layer (C) is preferably 1 μm or less. When the thickness is 1 μm or less, the heat-cutting seal strength is easily obtained, and fine surface irregularities are formed on the surface of the surface layer (C), thereby improving the slipperiness and blocking resistance. The thickness of the surface layer (C) is preferably 1.5% or more of the total film thickness in terms of heat seal strength after automatic packaging, and 4% or less in terms of heat seal strength when the film is made into a bag by a heat seal method. The thickness of the surface layer (C) is preferably 0.1 μm or more.

[0051] (film thickness) The film thickness of the biaxially oriented polypropylene-based resin film of the present invention varies depending on its application and method of use, but a polypropylene-based film used as a packaging film is generally about 10 to 100 μm, and in terms of mechanical strength and transparency, it is more preferably about 15 to 50 μm, even more preferably about 15 to 40 μm, and particularly preferably about 15 to 25 μm.

[0052] (Method for producing biaxially oriented polypropylene resin film) The biaxially oriented polypropylene resin film of the present invention can be produced under the same film-forming conditions as those for general polyolefins. For example, the film can be produced by melt laminating the film by a T-die method, an inflation method, or the like using an extruder suitable for the number of layers, followed by cooling by a cooling roll method, a water cooling method, or an air cooling method to form a laminated film, which can then be stretched by a sequential biaxial stretching method, a simultaneous biaxial stretching method, a tube stretching method, or the like. Here, as an example of the conditions for manufacturing by the sequential biaxial stretching method, the resin melt-extruded from a T-shaped die is cooled and solidified in a casting machine to produce a raw sheet. In this case, the roll temperature for melt casting is preferably set between 15°C and 40°C in order to suppress crystallization of the resin and improve transparency. Next, the raw sheet is heated to a temperature suitable for stretching, and then stretched in the sheet flow direction by utilizing the speed difference between the stretching rolls. In this case, the stretching ratio is preferably set between 3 and 6 times in consideration of stable production without uneven stretching. Next, both edges of the longitudinally stretched sheet are held by tenter clips, and the sheet is stretched while being successively expanded in the direction perpendicular to the sheet flow while being heated to a temperature suitable for stretching with hot air. In this case, the transverse stretching ratio is preferably set between 7 and 10 times in consideration of thickness variation and productivity.

[0053] The biaxially oriented polypropylene resin film of the present invention can be surface-treated to improve printability, lamination, etc. Examples of the surface treatment method include corona discharge treatment, plasma treatment, flame treatment, acid treatment, etc., and are not particularly limited. It is preferable to carry out corona discharge treatment, plasma treatment, or flame treatment, which can be performed continuously and can be easily carried out before the winding step in the production process of this film.

[0054] (Film characteristics) The biaxially oriented polypropylene resin film of the present invention preferably has the following properties.

[0055] (Heat seal start temperature) In the present invention, the heat seal rise temperature of the seal layer (B) is preferably 115° C. or higher and 125° C. or lower. The heat seal rise temperature of the seal layer (B) is the temperature at which the heat seal strength becomes 1 N / 15 mm when the faces of the seal layers (B) of the film of the present invention are placed face to face and heat sealed at a heat seal pressure of 1 kg / cm2 for a time of 1 second.

[0056] When the heat seal start temperature of the sealing layer (B) is 125°C or less, sufficient strength is maintained even at a low heat seal temperature, making it easy to heat seal, and making it easy to operate at high speeds when automatically packaging.In addition, the sealing part has excellent sealing properties, and this, combined with the anti-fogging properties, maintains the freshness of fresh produce, the appearance of the contents is also good, and the package is easy to handle. When the heat seal start temperature of the sealing layer (B) is 125°C or less, the difference in melting point with the base layer (A) mainly made of polypropylene resin becomes large, making it easy to sufficiently increase the operating speed of automatic packaging without raising the temperature of the sealing bar, and since there is no need to set a high temperature to increase the heat seal strength, the entire laminated film is less likely to shrink during heat sealing, wrinkles are less likely to occur in the heat sealed area, and sealing defects in the heat sealed area are less likely to occur. When the heat seal start temperature of the sealing layer (B) is less than 115°C, the heat seal strength decreases when bags are made using the heat seal method, making it difficult to use both the automatic packaging method and the heat seal method.

[0057] (120℃ heat seal strength) In order to prevent the contents from dropping out, the biaxially oriented polypropylene resin film of the present invention preferably has a heat seal strength of 3.5 N / 15 mm or more in the longitudinal and transverse directions at 120°C, as measured by the measurement method described below. The longitudinal direction here means the direction in which the film flows from the step of casting the raw material resin composition to the step of winding the stretched film, and the transverse direction means the direction perpendicular to the flow direction. The same applies to the following distance characteristics.

[0058] (Anti-fogging) The biaxially oriented polypropylene resin film of the present invention is preferably rated as rank 3 or higher in anti-fogging property by the measurement method described below, more preferably rank 2 or higher, and even more preferably rank 1.

[0059] (Anti-fog unevenness) The biaxially oriented polypropylene resin film of the present invention is preferably rated at rank 2 or lower for anti-fog unevenness measured by the measurement method described below.

[0060] (Waterproof) The biaxially oriented polypropylene resin film of the present invention is preferably rated as rank 3 or lower in drip-proofness by the measurement method described below, more preferably rank 2 or lower, and even more preferably rank 1.

[0061] (Suitable for automatic packaging) The biaxially oriented polypropylene resin film of the present invention is preferably evaluated as ◯ or Δ in terms of automatic packaging suitability as measured by the measurement method described below, and more preferably ◯.

[0062] (Welding seal strength) The biaxially oriented polypropylene resin film of the present invention preferably has a heat-seal strength measured by the measurement method described below of 25 N / 15 mm or more, more preferably 28 N / 15 mm or more, and even more preferably 29 N / 15 mm or more.

[0063] (Heat shrinkage rate at 120℃) The biaxially oriented polypropylene resin film of the present invention preferably has a thermal shrinkage rate in the longitudinal direction at 120°C measured by the measurement method described below of 3.7% or less, more preferably 3.5% or less, even more preferably 3.0% or less, and particularly preferably 2.5% or less. The thermal shrinkage rate at 120°C in the width direction measured by the method described below is preferably 3.5% or less, more preferably 3.0% or less, even more preferably 2.0% or less, still more preferably 1.6% or less, and particularly preferably 1.3% or less.

[0064] (Hayes) The biaxially oriented polypropylene resin film of the present invention preferably has a haze of 8% or less, more preferably 7% or less, even more preferably 6% or less, and even more preferably 5% or less, as measured by the method described below.

[0065] (Kinematic friction coefficient) The biaxially oriented polypropylene resin film of the present invention preferably has a dynamic friction coefficient in both the longitudinal and transverse directions, as measured by the method described below, of 0.38 or less, more preferably 0.35 or less, even more preferably 0.32 or less, still more preferably 0.30 or less, and particularly preferably 0.28 or less.

[0066] (Blocking resistance) The biaxially oriented polypropylene resin film of the present invention preferably has a blocking value of 110 mN / 200 mm or less, more preferably 100 mN / 200 mm or less, as measured by the method described below.

[0067] (Surface roughness SRa) The biaxially oriented polypropylene resin film of the present invention preferably has a surface roughness SRa measured by the measurement method described below of 0.018 μm or more, more preferably 0.0019 μm or more. EXAMPLES

[0068] The present invention will be described in more detail below with reference to the following examples. The present invention is not limited to the following examples unless otherwise stated. The characteristics in this specification were evaluated by the following methods.

[0069] (1) Layer thickness The biaxially oriented polypropylene resin film was cut into a size of 1 cm x 1 cm, embedded in UV-curable resin, and cured by irradiating UV for 5 minutes. After that, a cross-sectional sample was prepared using a microtome and observed using a differential interference microscope to measure the thickness of the entire film layer, the seal layer (B), and the surface layer (C). Five points were measured for the sample, and the average value was calculated.

[0070] (2) Heat seal start temperature The heat seal strength is the temperature at which the heat seal strength becomes 1N / 15mm when the seal layers (B) of the biaxially oriented polypropylene resin film are stacked facing each other and heat sealed using a thermal gradient tester (manufactured by Toyo Seiki Co., Ltd.) at a heat seal pressure of 1kg / cm2, a time of 1 second, and a temperature increased by 5°C from 80°C. The heat seal layer surfaces of a 5cm x 20cm film were placed facing each other and heat sealed simultaneously using five heat seal bars (seal surface 1cm x 3cm) set at temperatures in 5°C increments, and the center was cut to a width of 15mm, attached to the upper and lower chucks of a tensile tester, and pulled at a tensile speed of 200mm / min, the strength of each was measured, and the heat seal strength was calculated (unit: N / 15mm). A linear graph was drawn with temperature on the horizontal axis and heat seal strength on the vertical axis, and the temperature at which the heat seal strength exceeded 1 N / 15 mm was determined as the heat seal start temperature.

[0071] (3) 120℃ heat seal strength The sealing layers (B) of the biaxially oriented polypropylene resin film were placed face to face and heat sealed at 120°C using a thermal gradient tester (manufactured by Toyo Seiki Co., Ltd.) with a heat seal pressure of 1 kg / cm2 and a time of 1 second. The center of the heat seal was cut to a width of 15 mm, attached to the upper and lower chucks of a tensile tester, and pulled at a tensile speed of 200 mm / min. The heat seal strength was calculated (units are N / 15 mm).

[0072] (4) Anti-fogging properties 1) Pour 300cc of 50°C warm water into a 500cc open-top container. 2) The opening of the container is sealed with the film, with the anti-fogging property measurement surface of the film facing inward. 3) Leave in a cold room at 5°C. 4) After the warm water in the container had completely cooled to the ambient temperature, the degree of condensation on the film surface was evaluated on a 5-point scale. Grade 1: No dew on the entire surface (0 surface area) Grade 2: Some dew adhesion (up to 1 / 4 of surface area) Grade 3: Dew adhesion to about 1 / 2 (up to 2 / 4 of the adhesion area) Grade 4: Almost all dew is attached (up to 3 / 4 of the surface area) Grade 5: Dew on the entire surface (3 / 4 or more of the surface area)

[0073] (5) Anti-fog unevenness 1) Pour 300cc of 50°C warm water into a 500cc open-top container. 2) The opening of the container is sealed with the film, with the anti-fogging property measurement surface of the film facing inward. 3) Leave at 20°C for 20 seconds. 4) The degree of dew adhesion on the film surface was evaluated on a 5-point scale. Grade 1: No dew on the entire surface (0 surface area) Grade 2: Some dew adhesion (up to 1 / 4 of surface area) Grade 3: Dew adhesion to about 1 / 2 (up to 2 / 4 of the adhesion area) Grade 4: Almost all dew is attached (up to 3 / 4 of the surface area) Grade 5: Dew on the entire surface (3 / 4 or more of the surface area)

[0074] (6) Water resistance 1) Pour 300cc of 30°C warm water into a 500cc open-top container. 2) The opening of the container is sealed with the film, with the anti-fogging property measurement surface of the film facing inward. 3) Leave in a cold room at 5°C. 4) After the warm water in the container had completely cooled to the ambient temperature, the degree of condensation on the film surface was evaluated on a 5-point scale. Grade 1: No dew on the entire surface (0 surface area) Grade 2: Some dew adhesion (up to 1 / 4 of surface area) Grade 3: Dew adhesion to about 1 / 2 (up to 2 / 4 of the adhesion area) Grade 4: Almost all dew is attached (up to 3 / 4 of the surface area) Grade 5: Dew on the entire surface (3 / 4 or more of the surface area) The drip-proofness evaluation uses 30°C warm water, so the amount of water droplets adhering to the film surface is less than when 50°C warm water is used, resulting in a stricter evaluation judgment.

[0075] (7) Suitability for automatic packaging The heat seal layers of the biaxially oriented polypropylene resin films were placed face to face and heat sealed using a thermal gradient tester (manufactured by Toyo Seiki Co., Ltd.) at a heat seal pressure of 1 kg / cm2 for 1 second. At that time, the presence or absence of fusion of the surface layer (C) to the seal bar and the heat seal start temperature were evaluated according to the following criteria. ○: No adhesion to the seal bar. Start-up temperature: 115℃ to 125℃ △: No adhesion to the seal bar. Start-up temperature is less than 115℃ or more than 125℃. ×: There is adhesion to the seal bar

[0076] (8) Strength of melt-cut seal Using a welding seal machine (Kyoei Printing Machinery Materials Co., Ltd.: PP500 type), a welding seal bag was made from biaxially oriented polypropylene resin film. Conditions: Cutting blade; cutting edge angle 60° Sealing temperature: 370℃ Shot rate: 120 bags / min The above-mentioned heat-sealed bag was cut into a width of 15 mm, and both ends were clamped in the clamping parts of a tensile tester (grip interval: 200 mm) with any slack removed. The specimen was pulled at a pulling speed of 200 mm / min, and the strength at which the seal broke was used to calculate the melt-cutting seal strength (N / 15 mm). Measurements were carried out five times and averaged. A strength of 20N / 15mm or more was determined to be suitable for welding and sealing.

[0077] (9) Heat shrinkage rate The measurement was performed according to the following method in accordance with JIS Z1712. A biaxially oriented polypropylene resin film was cut into a width of 20 mm and a length of 200 mm in each of the MD and TD directions, and was hung in a hot air oven at 120°C and heated for 5 minutes. The length after heating was measured, and the heat shrinkage rate was calculated as the ratio of the shrunken length to the original length.

[0078] (10) Hayes Measurements were performed in accordance with JIS K7105.

[0079] (11) Coefficient of kinetic friction Two sheets of biaxially oriented polypropylene resin films were placed together with the surface layer (C) faces facing each other, and measured in accordance with JIS K7125 at 23° C. Five sets of samples were measured, and the average value was calculated.

[0080] (12) Blocking value A biaxially oriented polypropylene resin film was cut into a length of 150 mm in the longitudinal direction and 200 mm in the transverse direction, the seal layer (B) and the surface layer (C) were placed together and sandwiched from above and below, a 20 kg weight was placed in the center, and the film was placed in an oven at 60°C. After 24 hours, it was removed and seasoned for 1 hour at a temperature of 23°C and a humidity of 65%, and a 6.35Φ test bar was fixed to the bonded portion. Using a tensile tester (Instron 5965 dual column tabletop tester), the film was held with a gripping distance of 200 mm between the film and the fixture, and pulled at a tensile speed of 100 mm / min. The strength at which the films peeled off was taken as the blocking value (mN / 200 mm). Measurements were taken at three points on the sample, and the average value was calculated.

[0081] (12) Surface roughness SRa The surface roughness of the obtained biaxially oriented polypropylene resin film was evaluated using a three-dimensional roughness meter (manufactured by Kosaka Laboratory, model number ET-30HK) with a stylus pressure of 20 mg, a measurement length in the X direction of 1 mm, a feed speed of 100 μm / sec, a feed pitch in the Y direction of 2 μm, 99 recorded lines, a height direction magnification of 20,000 times, and a cutoff of 80 μm, and was calculated in accordance with the definition of arithmetic mean roughness described in JIS B 0601 (1994). Surface roughness SRa was evaluated by the average value after three trials.

[0082] Example 1 (1)Resin used The polypropylene resin, polyethylene resin, and additives used as raw materials for constituting each layer in the following production examples are as follows: (1) Base material layer (A) [PP-1]: Propylene-ethylene random copolymer: "FS2011DG3" manufactured by Sumitomo Chemical Co., Ltd., ethylene content: 0.6 mol%, MFR: 2.7 g / 10 min, melting point: 158°C, mesopentad fraction: 97.0% [Anti-fog agent-1]: Glycerin monostearate (Matsumoto Yushi Pharmaceutical Co., Ltd., TB-123) [Anti-fog agent-2]: Polyoxyethylene (2) stearylamine (Matsumoto Yushi Pharmaceutical Co., Ltd., TB-12) [Anti-fogging agent-3]: Polyoxyethylene (2) stearylamine monostearate (Matsumoto Yushi Seiyaku Co., Ltd., Elex 334) [PE-1]: Ethylene homopolymer: Braskem "SLH218", MFR: 2.3g / 10min, melting point: 126℃, bio-based content: 84%

[0083] (2) Sealing layer (B) [PP-2]: Propylene-butene-1 copolymer: "SPX78J1" manufactured by Sumitomo Chemical Co., Ltd., butene content: 25 mol%, MFR: 8.5 g / 10 min, melting point: 128°C [Anti-fog agent-1]: Glycerin monostearate (Matsumoto Yushi Pharmaceutical Co., Ltd., TB-123)

[0084] (4) Surface layer (C) resin composition [PP-3]: Propylene-ethylene-butene random copolymer: "FSX66E8" manufactured by Sumitomo Chemical Co., Ltd., ethylene content: 2.5 mol%, butene content: 7 mol%, MFR: 3.1 g / 10 min, melting point: 133°C [Anti-fog agent-1]: Glycerin monostearate (Matsumoto Yushi Pharmaceutical Co., Ltd., TB-123) [Organic polymer particles]: Cross-linked acrylic particles: CS30: Sumitomo Chemical Co., Ltd., Particle size: 3.5 μm

[0085] The raw materials used for the base layer (A), seal layer (B), and surface layer (C) were mixed in the ratios shown in Table 1. Three melt extruders were used, and the mixed raw materials for the base layer (A) were melt extruded from the first extruder at a resin temperature of 280 ° C., the mixed raw materials for the surface layer (C) were melt extruded from the second extruder at a resin temperature of 250 ° C., and the mixed raw materials for the seal layer (B) were melt extruded from the third extruder at a resin temperature of 250 ° C., and the layers were laminated and extruded in the order of surface layer (C) / base layer (A) / seal layer (B) from the chill roll contact surface so that the thickness ratio was surface layer (C) / base layer (A) / seal layer (B) = 0.6 / 18.7 / 0.7 in the T-die, and cooled and solidified with a 30 ° C. cooling roll to obtain an unstretched sheet. The film was then stretched 4.5 times in the machine direction by utilizing the difference in peripheral speed between metal rolls heated to 130°C, and then introduced into a tenter stretching machine where it was stretched 9.5 times in the transverse direction. The preheating zone temperature of the tenter stretching machine was 168°C, and the stretching zone temperature was 155°C. After stretching, the film was heat-set at 163°C.

[0086] The surface of the surface layer (C) was subjected to a corona discharge treatment using a corona discharge treatment machine manufactured by Kasuga Electric Co., Ltd., and then the sealing layer (B) was subjected to a similar corona discharge treatment, and a biaxially oriented polypropylene-based resin film that could be wound up by a film winder and automatically packaged was obtained. The final film thickness was 20 μm, and the thickness ratio of the sealing layer (B) to the entire film was 3.5%. The obtained multilayer film satisfied the requirements of the present invention, and had sufficient suitability for automatic packaging, heat-cutting and sealing, anti-fogging properties, and drip-proofing properties for packaging of fruits and vegetables. The film composition and physical properties are shown in Table 1.

[0087] Example 2 A laminated film was obtained in the same manner as in Example 1, except that the content of [PE-1] in the base layer (A) was 10% by weight. The obtained multilayer film satisfied the requirements of the present invention, and the suitability for automatic packaging, suitability for welding and sealing, anti-fogging properties, and drip-proofing properties were at a level that did not pose a problem when packaging fruits and vegetables. The film composition and physical properties are shown in Table 1.

[0088] Example 3 A laminated film was obtained in the same manner as in Example 1, except that the content of [PE-1] in the base layer (A) was 20% by weight. The obtained multilayer film satisfied the requirements of the present invention, and the suitability for automatic packaging, suitability for welding and sealing, anti-fogging properties, and drip-proofing properties were at a level that did not pose a problem when packaging fruits and vegetables. The film composition and physical properties are shown in Table 1.

[0089] Example 4 A laminated film was obtained in the same manner as in Example 1, except that the mixed raw materials for the sealing layer (B) contained 80% by weight of [PP-2] and 20% by weight of [PP-3]. The obtained multilayer film satisfied the requirements of the present invention, and had sufficient suitability for automatic packaging, heat-cutting and sealing, anti-fogging properties, and drip-proofing properties for packaging of fruits and vegetables. The film composition and physical properties are shown in Table 1.

[0090] Example 5 A laminated film was obtained in the same manner as in Example 1, except that the thickness of the base layer (A) was 38.7 μm, the film thickness was 40 μm, and the thickness ratio of the seal layer (B) was 1.8%. The obtained multilayer film satisfied the requirements of the present invention, and the suitability for automatic packaging, suitability for melt-cutting and sealing, anti-fogging properties, and drip-proofing properties were at a level that did not pose a problem when packaging fruits and vegetables. The film composition and physical properties are shown in Table 1.

[0091] Example 6 A laminated film was obtained in the same manner as in Example 2, except that the thickness of the base layer (A) was increased to 38.7 μm, the film thickness was 40 μm, and the thickness ratio of the seal layer (B) was 1.8%. The obtained multilayer film satisfied the requirements of the present invention, and the suitability for automatic packaging, weld-cut sealing, anti-fogging properties, and drip-proofing properties were at a level that did not pose a problem when packaging fruits and vegetables. The film composition and physical properties are shown in Table 1.

[0092] Example 7 A laminated film was obtained in the same manner as in Example 3, except that the thickness of the base layer (A) was 38.7 μm, the film thickness was 40 μm, and the thickness ratio of the seal layer (B) was 1.8%. The obtained multilayer film satisfied the requirements of the present invention, and the suitability for automatic packaging, suitability for melt-cutting and sealing, anti-fogging properties, and drip-proofing properties were at a level that did not pose a problem when packaging fresh produce. The film composition and physical properties are shown in Table 1.

[0093] Comparative Example 1 A laminated film was obtained in the same manner as in Example 1, except that the amount of [PE-1] added to the base layer (A) was 0% by weight. The obtained laminated film had poor drip-proofing, slipperiness, and blocking resistance. The film composition and physical properties are shown in Table 1.

[0094] Comparative Example 2 A laminated film was obtained in the same manner as in Example 5, except that the amount of [PE-1] added to the base layer (A) was 0% by weight. The obtained laminated film also had poor drip resistance, slipperiness, and blocking resistance. The film composition and physical properties are shown in Table 1.

[0095] Comparative Example 3 A laminated film was obtained in the same manner as in Example 1, except that the thickness of the substrate layer (A) was 19.3 μm and the thickness of the surface layer (C) was 0.0 μm. The antifogging properties of the obtained laminated film were significantly deteriorated. The film composition and physical properties are shown in Table 1.

[0096] Comparative Example 4 A laminated film was obtained in the same manner as in Example 1, except that the thickness of the substrate layer (A) was 18.1 μm and the thickness of the surface layer (C) was 1.2 μm. The obtained laminated film had poor melt-cutting seal strength, slipperiness, and blocking resistance. The film composition and physical properties are shown in Table 1.

[0097] Comparative Example 5 A laminated film was obtained in the same manner as in Example 5, except that the thickness of the substrate layer (A) was 39.3 μm and the thickness of the surface layer (C) was 0.0 μm. The antifogging properties of the obtained laminated film were significantly deteriorated. The film composition and physical properties are shown in Table 1.

[0098] Comparative Example 6 A laminated film was obtained in the same manner as in Example 5, except that the thickness of the substrate layer (A) was 38.1 μm and the thickness of the surface layer (C) was 1.2 μm. The obtained laminated film had poor melt-cutting seal strength, slipperiness, and blocking resistance. The film composition and physical properties are shown in Table 1.

[0099] [Table 1] [Industrial Applicability]

[0100] The biaxially oriented polypropylene resin film of the present invention, which can be used for automatic packaging, has excellent anti-fogging and drip-proof properties, excellent slip properties and blocking resistance, and has high heat seal strength at 120°C, and is suitable for packaging food, particularly vegetables.

Claims

1. A biaxially oriented polypropylene-based resin film having a base layer (A) made of a resin composition containing a polypropylene-based resin and a polyethylene-based resin, a seal layer (B) made of a polypropylene-based resin composition mainly composed of a propylene-butene-1 copolymer on one side of the base layer (A), and a surface layer (C) on the side of the base layer (A) opposite to the seal layer (B), and satisfying the following conditions a) to d): a) The polyethylene resin constituting the base layer (A) has a melt flow rate of 1.5 g / 10 min or more and 10 g / 10 min or less at 190 ° C. and a density of 0.910 g / cm ３ 0.930g / cm or more ３ The content is 1% by weight or more and 20% by weight or less relative to 100% by weight of the total of the polypropylene-based resin and the polyethylene-based resin constituting the base layer (A). b) The thickness of the sealing layer (B) is 1 μm or less. c) The polypropylene composition constituting the sealing layer (B) contains an anti-fogging agent in an amount of 0.1% by weight or more and 1.0% by weight or less. d) The thickness of the surface layer (C) is 1 μm or less.

2. 2. The biaxially oriented polypropylene resin film according to claim 1, wherein the melting point of the propylene-butene-1 copolymer is in the range of 120 to 130°C.

3. 3. The biaxially oriented polypropylene resin film according to claim 1, wherein the content of the propylene-butene-1 copolymer is in the range of 50% by weight or more.

4. 4. The biaxially oriented polypropylene resin film according to claim 1, wherein the thickness of the sealing layer (B) is 1.5% or more and 4% or less of the total thickness of the film.

5. The biaxially oriented polypropylene resin film according to any one of claims 1 to 4, wherein the base layer (A) is made of a resin composition mainly composed of at least one polypropylene resin selected from the group consisting of isotactic propylene homopolymer, propylene-ethylene copolymer, propylene-butene-1 copolymer, propylene-ethylene-butene-1 copolymer, or propylene-pentene copolymer.

6. The biaxially oriented polypropylene resin film according to any one of claims 1 to 5, wherein the surface layer (C) is made of a resin composition mainly composed of at least one polypropylene resin selected from the group consisting of propylene-ethylene-butene-1 copolymer, propylene-butene-1 copolymer, and propylene-ethylene copolymer.

7. The biaxially oriented polypropylene resin film according to any one of claims 1 to 6, wherein the melting point of the polypropylene resin constituting the surface layer (C) is in the range of 130 to 140°C.

8. The biaxially oriented polypropylene resin film according to any one of claims 1 to 7, wherein the thickness of the surface layer (C) is 1.5% or more and 4% or less of the total thickness of the film.

9. The polypropylene-based laminate film according to any one of claims 1 to 8, wherein the heat seal strength when the seal layers (B) of the biaxially oriented polypropylene-based resin film are heat-sealed to each other at 120 ° C. is 3.5 N / 15 mm or more.

10. The polypropylene-based laminate film according to any one of claims 1 to 9, wherein the blocking value measured by combining the seal layer (B) and the surface layer (C) of the biaxially oriented polypropylene-based resin film is 110 mN / 200 mm or less.

11. The polypropylene-based laminate film according to any one of claims 1 to 10, wherein the friction coefficient between the surface layers (C) of the biaxially oriented polypropylene-based resin film is 0.35 or less.

12. A packaging material using the biaxially oriented polypropylene resin film according to any one of claims 1 to 11.

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