Biaxially oriented polypropylene film, and laminate

Abstract

Provided are: a laminate which has excellent laminate strength, has a heat seal portion with an excellent appearance, and is unlikely to cause contamination on a guide roll; and a biaxially oriented polypropylene film capable of forming such a laminate. The biaxially oriented polypropylene film comprises: a substrate layer A composed of a polypropylene-based resin composition; a surface layer B composed of a polypropylene-based resin composition; and a surface layer C composed of a polypropylene-based resin composition, and satisfies the following (1) to (4). (1) The heat shrinkage rate of the biaxially oriented polypropylene film at 150°C in the longitudinal direction is 0.0-10.0%. (2) The heat shrinkage rate of the biaxially oriented polypropylene film at 150°C in the width direction is 0.0-15.0%. (3) The anti-blocking agent falling rate in the surface layer B and the anti-blocking agent falling rate in the surface layer C are each 10% or less. (4) The laminate strength is at least 1.5 N / 15 mm.

Description

Biaxially oriented polypropylene film and laminate

[0001] The present disclosure relates to biaxially oriented polypropylene films and laminates.

[0002] Biaxially oriented polypropylene films have been widely used as packaging materials for foods, textile products, and other articles because of their excellent transparency and mechanical properties.

[0003] In food packaging, biaxially oriented polypropylene films are sometimes laminated with a gas barrier layer. Furthermore, in food packaging bags, biaxially oriented polypropylene films are sometimes laminated with a printing layer to improve the content display and design. For example, Patent Document 1 discloses a laminate having a structure of a printing substrate layer / printing layer / adhesive layer / inorganic thin film layer / deposition substrate layer / adhesive layer / sealant film, in which the substrate layers and the sealant film are made of the same polypropylene material from the viewpoint of recycling.

[0004] As a biaxially oriented polypropylene film with improved adhesion to printing ink, for example, Patent Document 2 discloses a film having a surface layer with a predetermined surface roughness and wetting tension. In addition, in the case of providing an aluminum vapor-deposited film on biaxially oriented polypropylene, for example, Patent Document 3 discloses a film with a surface layer having a relatively small surface roughness and a predetermined wetting tension as a film with excellent adhesion to the aluminum vapor-deposited film.

[0005] International Publication No. 2021 / 020400 International Publication No. 2018 / 142983 International Publication No. 2022 / 004340

[0006] However, the inventors' investigations have revealed that laminates obtained by laminating conventional biaxially oriented polypropylene films and heat-sealable films sometimes have insufficient lamination strength between the films. It has also been found that wrinkles may occur at the heat-sealed portion formed when such laminates are heat-sealed. It has also been found that the antiblocking agent may fall off when such laminates are wound up, causing staining of the guide roll. Therefore, an object of the present invention is to provide a laminate that has excellent lamination strength, excellent appearance at the heat-sealed portion, and is less likely to cause staining of the guide roll. Another object of the present invention is to provide a biaxially oriented polypropylene film that can be used to form such laminates.

[0007] The biaxially oriented polypropylene film according to the embodiment that can solve the above problems is as follows. [1] A biaxially oriented polypropylene film having a base layer A made of a polypropylene-based resin composition, a surface layer B made of a polypropylene-based resin composition, and a surface layer C made of a polypropylene-based resin composition, wherein the biaxially oriented polypropylene film satisfies the following (1) to (4): (1) The heat shrinkage rate at 150°C in the longitudinal direction of the biaxially oriented polypropylene film is 0.0% or more and 10.0% or less. (2) The heat shrinkage rate at 150°C in the width direction of the biaxially oriented polypropylene film is 0.0% or more and 15.0% or less. (3) The dropout rate of the antiblocking agent in the surface layer B and the dropout rate of the antiblocking agent in the surface layer C are each 10% or less. (4) The lamination strength is 1.5 N / 15 mm or more.

[0008] The biaxially oriented polypropylene film and laminate of the embodiment are preferably any of the following. [2] The biaxially oriented polypropylene film according to [1], wherein the surface layer B, the surface layer C, or both of them have a surface wet tension of 36 mN / m or more. [3] The biaxially oriented polypropylene film according to [1] or [2], wherein the surface layer B and the surface layer C each contain a polypropylene-based resin having a melting point of 130°C or more and 158°C or less in an amount of 25% by mass or more and 85% by mass or less. [4] The biaxially oriented polypropylene film according to any one of [1] to [3], wherein the surface layer B and the surface layer C each contain a polypropylene-based resin having a melting point of 159°C or more and 175°C or less in an amount of 15% by mass or more and 75% by mass or less. [5] The biaxially oriented polypropylene film according to [3], wherein the polypropylene-based resin of the surface layer B and the surface layer C is each a propylene-ethylene-butene copolymer. [6] The biaxially oriented polypropylene film according to any one of [1] to [5], wherein the base layer A contains 70% by mass or more of a polypropylene-based resin having a mesopentad fraction ([mmmm]%) of 95.0% to 99.9% and a melting point of 160°C to 175°C. [7] The biaxially oriented polypropylene film according to any one of [1] to [6], wherein the surface layer B, the surface layer C, or both have a surface resistance of 14.0 Log Ω or more and 18 Log Ω or less. [8] The biaxially oriented polypropylene film according to any one of [1] to [7], wherein the content of the antiblocking agent in the surface layer B is 100 ppm to 10,000 ppm, and the content of the antiblocking agent in the surface layer C is 100 ppm to 10,000 ppm. [9] The biaxially oriented polypropylene film according to [8], wherein the antiblocking agent in the surface layer B and the antiblocking agent in the surface layer C each contain particles having a pore volume of 0.2 mL / g to 3 mL / g.

[10] (4) The biaxially oriented polypropylene film according to any one of [1] to [9], wherein the lamination strength is 10 N / 15 mm or less.

[11] A laminate comprising the biaxially oriented polypropylene film according to any one of [1] to

[10] and a heat-sealable polyolefin film, wherein the surface layer B, the base layer A, the surface layer C, and the heat-sealable polyolefin film are laminated in this order.

[12] The laminate according to

[11] , further comprising a functional layer, wherein the functional layer, the surface layer B, the base layer A, the surface layer C, and the heat-sealable polyolefin film are laminated in this order.

[13] The laminate according to

[12] , wherein the functional layer is a printed layer, a vapor-deposited layer, or a coating layer.

[14] The laminate according to

[12] or

[13] , further comprising a stretched polyolefin film or a stretched polyester film, wherein the stretched polyolefin film or the stretched polyester film, the functional layer, the surface layer B, the base layer A, the surface layer C, and the heat-sealable polyolefin film are laminated in this order.

[0009] The above-mentioned configuration makes it possible to provide a laminate having excellent lamination strength, excellent appearance of the heat-sealed portion, and less likely to stain the guide roll, and also to provide a biaxially oriented polypropylene film capable of forming such a laminate.

[0010] An example of a 125x magnification microscope image of the surface of an aqueous ink printed layer with uniform dot size and no ink repellency. An example of a 125x magnification microscope image of the surface of an aqueous ink printed layer with uniform dot size and ink repellency. An example of a 125x magnification microscope image of the surface of an aqueous ink printed layer with non-uniform dot size and ink repellency. An enlarged view of the ink repellency area in Figure 2.

[0011] The biaxially oriented polypropylene film of the embodiment has a base layer A made of a polypropylene-based resin composition, a surface layer B made of a polypropylene-based resin composition, and a surface layer C made of a polypropylene-based resin composition. Each layer will be described in detail below.

[0012] (1) Substrate Layer A The substrate layer A is made of a polypropylene-based resin composition. The substrate layer A preferably enhances the thermal dimensional stability, mechanical strength, and transparency of the biaxially oriented polypropylene film. The polypropylene-based resin composition of the substrate layer A preferably contains a polypropylene-based resin in an amount of 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more, based on the entire substrate layer A. On the other hand, the polypropylene-based resin composition of the substrate layer A may contain a polypropylene-based resin in an amount of 100% by mass or less, 99.9% by mass or less, 99.8% by mass or less, or 99.6% by mass or less, based on the entire substrate layer A. When the polypropylene-based resin composition of the substrate layer A contains two or more types of polypropylene-based resins, the above content is the total value.

[0013] Various suitable physical properties of the polypropylene-based resin are described below, and when two or more different polypropylene-based resins are used, it is preferable that the mass-average physical property values ​​of each polypropylene-based resin fall within the numerical ranges described below. For example, when a polypropylene-based resin composition contains 50 mass% of a polypropylene-based resin having a melting point of 160°C and 50 mass% of a polypropylene-based resin having a melting point of 170°C, the mass-average melting point of the polypropylene-based resin composition is 165°C. The same applies to mass-average values ​​hereinafter.

[0014] The polypropylene resin contained in the base layer A preferably has a melting point of 160°C or higher and 175°C or lower, more preferably 164°C or higher and 173°C or lower, and even more preferably 166°C or higher and 171°C or lower. A melting point of 160°C or higher can improve thermal dimensional stability and mechanical strength. A melting point of 175°C or lower can easily suppress cost increases in polypropylene production and make the film less likely to break during film formation. The melting point can also be further increased by blending a crystal nucleating agent with the polypropylene resin. The melting point can be measured using a differential scanning calorimeter (DSC). Specifically, the melting point is the main peak temperature of the endothermic peak associated with melting, observed when a 5 mg sample is packed into an aluminum pan, melted at 230°C for 5 minutes under a nitrogen atmosphere, cooled to 30°C at a scanning rate of -10°C / min, held for 5 minutes, and then heated at a scanning rate of 10°C / min.

[0015] The polypropylene resin contained in the base layer A preferably has a mesopentad fraction ([mmmm]%), an index of stereoregularity, of 95.0 to 99.9%, more preferably 97.0 to 99.7%, even more preferably 97.5 to 99.5%, and particularly preferably 98.0 to 99.3%. When the mesopentad fraction is 95.0% or higher, the crystallinity of the polypropylene resin is enhanced, improving the melting point, crystallinity, and crystalline orientation of the crystals in the base layer A, thereby increasing thermal dimensional stability and mechanical strength. When the mesopentad fraction is 99.9% or lower, the cost of polypropylene production is easily reduced and the film is less likely to break during film formation. The mesopentad fraction is measured by nuclear magnetic resonance (NMR).

[0016] The melt flow rate (MFR) of the polypropylene resin contained in the base layer A, when measured in accordance with JIS K 7210 (1995) Condition M (230°C, 2.16 kgf), is preferably 4.0 to 30 g / 10 min, more preferably 4.5 to 25 g / 10 min, even more preferably 4.8 to 22 g / 10 min, particularly preferably 5.0 to 20 g / 10 min, and most preferably 5.5 to 10 g / 10 min. When the MFR of the polypropylene resin is 4.0 g / 10 min or higher, the amount of low molecular weight components of the polypropylene resin contained in the base layer A increases, which further promotes oriented crystallization of the polypropylene resin, making it easier to increase the crystallinity in the base layer A, and reducing entanglement of polypropylene molecular chains in the amorphous portion, thereby improving thermal dimensional stability and mechanical strength. Furthermore, when the MFR of the polypropylene resin is 30 g / 10 min or lower, it is easy to maintain the film formability of the film.

[0017] The polypropylene resin contained in the base layer A preferably has a weight average molecular weight (Mw) of 180,000 to 500,000. If the Mw is less than 180,000, the melt viscosity is low, which may result in instability during casting and poor film formability. If the Mw exceeds 500,000, the amount of components with a molecular weight of 100,000 or less decreases, which may result in a high heat shrinkage rate at high temperatures. The Mw is more preferably 190,000 to 400,000, even more preferably 200,000 to 380,000, and particularly preferably 210,000 to 350,000.

[0018] The number average molecular weight (Mn) of the polypropylene resin contained in the base layer A is preferably 20,000 to 200,000. If it is less than 20,000, the melt viscosity is low, which may result in instability during casting and poor film formability. If it exceeds 200,000, the heat shrinkage rate at high temperatures may be high. Mn is more preferably 30,000 to 120,000, even more preferably 40,000 to 110,000, particularly preferably 50,000 to 100,000, and most preferably 60,000 to 90,000.

[0019] The polypropylene resin contained in the base layer A preferably has an Mw / Mn ratio, an index of molecular weight distribution, of 2.8 to 10. It is more preferably 3.0 to 8.0, even more preferably 3.2 to 6.0, and particularly preferably 3.5 to 5.0. When the Mw / Mn ratio of the polypropylene resin is 2.8 or higher, the proportion of low-molecular-weight components in the polypropylene resin contained in the base layer A increases, which further promotes oriented crystallization of the polypropylene resin, makes it easier to increase the crystallinity in the base layer A, and reduces entanglement of polypropylene molecular chains in the amorphous portion, thereby improving thermal dimensional stability and mechanical strength. The molecular weight distribution of the polypropylene resin can be adjusted by polymerizing components of different molecular weights in a series of plants in multiple stages, blending components of different molecular weights offline in a kneader, blending catalysts with different performances and polymerizing them, or using a catalyst that can achieve the desired molecular weight distribution.

[0020] (Polypropylene Homopolymer) The polypropylene-based resin contained in the base layer A is preferably a polypropylene homopolymer. The polypropylene homopolymer is a polypropylene that is substantially free of α-olefin components other than propylene. Specifically, the polypropylene homopolymer is a polypropylene copolymer having α-olefin components other than propylene in an amount of more than 0% but not more than 1 mol% and 99 mol% or more as structural units, or a polypropylene that does not contain any components other than propylene as structural units. Thus, in the present disclosure, the polypropylene homopolymer includes not only polypropylene that is completely free of α-olefin components other than propylene, but also polypropylene copolymers having α-olefin components other than propylene in an amount of more than 0% but not more than 1 mol% and 99 mol% or more as structural units. Even when the polypropylene homopolymer contains α-olefin components other than propylene, the content of the α-olefin components other than propylene (the total amount of ethylene and α-olefins having 4 or more carbon atoms) is, as described above, 1 mol% or less, preferably 0.3 mol% or less, more preferably 0.2 mol% or less, and even more preferably 0.1 mol% or less. Within the above range, crystallinity is likely to be improved. Examples of the α-olefin component having 4 or more carbon atoms include 1-butene, 1-pentene, 3-methyl-1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 5-ethyl-1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-eicosene, etc. As the polypropylene homopolymer, two or more different polypropylene homopolymers can also be used.

[0021] (Other than Polypropylene Homopolymer) The polypropylene-based resin composition constituting the base layer A may contain additives or may contain other resins other than polypropylene homopolymer. Examples of additives include antioxidants, UV absorbers, nucleating agents, adhesives, anti-fogging agents, flame retardants, inorganic or organic fillers, or mixtures thereof. Examples of other resins include polyolefin resins other than the polypropylene homopolymer used in the base layer A, and various elastomers. These may be sequentially polymerized using a multi-stage reactor, blended with a polypropylene-based resin using a Henschel mixer, master pellets prepared in advance using a melt kneader may be diluted with polypropylene to a predetermined concentration, or the entire amount may be melt-kneaded and used. If the surface resistivity of the polypropylene-based resin used in the base layer A is too high when used alone, a surfactant may be added to reduce the surface resistivity.

[0022] (2) Surface Layer B and Surface Layer C When a functional layer such as a printed layer, a vapor-deposited layer, or a coating layer is provided on the surface, it is preferable that surface layer B, surface layer C, or both of these have high adhesion to the functional layer, and it is also preferable that they are provided with slip properties and anti-blocking properties. Note that the functional layer is a layer having at least one function such as adhesion, coating properties, design properties, water vapor barrier properties, oxygen barrier properties, thermal conductivity, low dielectric properties, high dielectric properties, and heat resistance. Examples of the functional layer include a printed layer, a vapor-deposited layer, and a coating layer, and the functional layer is preferably a printed layer, a vapor-deposited layer, or a coating layer.

[0023] The surface layer B is made of a polypropylene-based resin composition. The surface layer C is made of a polypropylene-based resin composition. The raw material compositions and properties of the surface layers B and C will be described in detail below, but the raw material compositions and properties of the surface layers B and C may be the same or different. The raw material compositions and properties of the surface layers B and C can be changed depending on the purpose of each layer. For example, if the surface adhesiveness of the surface layer B is to be higher than that of the surface layer C, it is preferable to blend more polypropylene-based resin with a melting point of 130°C or higher and 158°C or lower in the surface layer B than polypropylene-based resin with a melting point of 130°C or higher and 158°C or lower in the surface layer C. The reverse is also possible. Furthermore, by adjusting the type, particle size, and blending amount of the antiblocking agent blended in the surface layers B and C, the gas barrier properties of the vapor deposition layer can be improved by reducing and smoothing the surface protrusions on one surface, and the surface protrusions on the other surface can be made larger to impart slip properties and antiblocking properties.

[0024] The surface layer B and the surface layer C each preferably contain a polypropylene resin having a melting point of 130° C. or higher and 158° C. or lower in an amount of 25% by mass or higher and 85% by mass or lower. The surface layer B and the surface layer C each preferably contain a polypropylene resin having a melting point of 159° C. or higher and 175° C. or lower in an amount of 15% by mass or higher and 75% by mass or lower. On the other hand, the content of the polypropylene resin having a melting point of 129° C. or lower in the surface layer B and the surface layer C is preferably low, specifically, preferably 20% by mass or lower, more preferably 10% by mass or lower, even more preferably 5% by mass or lower, particularly preferably 1% by mass or lower, and most preferably 0% by mass (no polypropylene resin of 129° C. or lower). In the following, the polypropylene resin contained in the surface layer B and the surface layer C having a melting point of 159°C or higher and 175°C or lower may be referred to as a "high melting point polypropylene resin," the polypropylene resin having a melting point of 130°C or higher and 158°C or lower may be referred to as a "mid-melting point polypropylene resin," and the polypropylene resin having a melting point of 129°C or lower may be referred to as a "low melting point polypropylene resin." The melting points of the polypropylene resins contained in the surface layer B and the surface layer C are rounded to one decimal place and are classified as high melting point polypropylene resin, mid-melting point polypropylene resin, or low melting point polypropylene resin. The high melting point polypropylene resin, mid-melting point polypropylene resin, and low melting point polypropylene resin may each be only one type of polypropylene resin, or two or more different types of polypropylene resins.

[0025] When surface layer B and surface layer C each contain a mid-melting point polypropylene resin in a content of 25% by mass or more and 85% by mass or less, adhesion to printed layers, vapor-deposited layers, coating layers, etc. can be further improved. By increasing the adhesiveness of both surfaces of surface layer B and surface layer C, the peel strength of a laminate obtained by laminating other components to both surfaces of a biaxially oriented polypropylene film can be dramatically increased. When the melting point of the mid-melting point polypropylene resin is 158°C or less, adhesion to the functional layer can be improved. When the melting point is 130°C or more, roughening of the film surface can be suppressed even when the longitudinal stretching temperature is increased during film formation, and by increasing the longitudinal stretching temperature, detachment of the antiblocking agent can be suppressed. The melting point of the mid-melting point polypropylene resin is preferably 134°C or more and 150°C or less, more preferably 138°C or more and 143°C or less. When the content of the mid-melting point polypropylene resin is 25% by mass or more, adhesion to heat-sealable films, printed layers, vapor-deposited layers, coating layers, etc. can be improved. The surface layer B and the surface layer C each preferably contain the mid-melting point polypropylene resin in an amount of 30% by mass or more and 80% by mass or less, and more preferably 35% by mass or more and 75% by mass or less.

[0026] On the other hand, in order to maintain the thermal dimensional stability and mechanical strength of the biaxially stretched polypropylene film, it is preferable that surface layer B and surface layer C each contain a high-melting-point polypropylene resin. The high-melting-point polypropylene resin has a melting point of 159°C to 175°C, preferably 160°C to 170°C, and more preferably 161°C to 165°C. Furthermore, surface layer B and surface layer C each preferably contain the high-melting-point polypropylene resin in an amount of 15% by mass to 75% by mass, more preferably 20% by mass to 70% by mass, and even more preferably 25% by mass to 65% by mass.

[0027] With respect to the total resin contained in surface layer B and surface layer C, the total amount of the high-melting point polypropylene resin and the mid-melting point polypropylene resin is preferably 60 to 100 mass%, more preferably 70 to 100 mass%, even more preferably 80 to 100 mass%, still more preferably 90 to 100 mass%, particularly preferably 95 to 100 mass%, and most preferably 98 to 100 mass%.

[0028] Various suitable physical properties of the mid-melting point polypropylene resin and the high-melting point polypropylene resin will be described below. When two or more different polypropylene resins are used as the mid-melting point polypropylene resin, it is preferable that the mass-averaged physical property values ​​of the respective polypropylene resins fall within the numerical ranges described below. When two or more different polypropylene resins are used as the high-melting point polypropylene resin, it is preferable that the mass-averaged physical property values ​​of the respective polypropylene resins fall within the numerical ranges described below.

[0029] The melt flow rate (MFR; 230°C, 2.16 kgf) of the mid-melting point polypropylene resin is preferably 2.0 g / 10 min or more and 10 g / 10 min or less, more preferably 3.0 g / 10 min or more and 8.0 g / 10 min or less, and even more preferably 4.0 g / 10 min or more and 7.0 g / 10 min or less. The melt flow rate (MFR; 230°C, 2.16 kgf) of the high-melting point polypropylene resin is preferably 2.0 g / 10 min or more and 10 g / 10 min or less, and more preferably 3.0 g / 10 min or more and 6.0 g / 10 min or less. Furthermore, the difference between the MFR of the mid-melting point polypropylene resin and the MFR of the high-melting point polypropylene resin is preferably 2.0 g / 10 min or less, more preferably 1.5 g / 10 min or less.

[0030] The weight-average molecular weight (Mw) of the mid-melting point polypropylene resin is preferably 180,000 to 500,000. It is more preferably 190,000 to 320,000, even more preferably 200,000 to 300,000, and particularly preferably 230,000 to 260,000. If the Mw is less than 180,000, the melt viscosity is low, which can result in instability during casting and poor film formability. If the Mw exceeds 500,000, the amount of components with a molecular weight of 100,000 or less becomes too small, which can result in a high heat shrinkage rate at high temperatures.

[0031] The Mw of the high-melting point polypropylene resin is preferably 180,000 to 500,000. It is more preferably 210,000 to 400,000, even more preferably 240,000 to 350,000, and particularly preferably 270,000 to 320,000. If the Mw is less than 180,000, the melt viscosity is low, resulting in instability during casting and poor film formability. If the Mw exceeds 500,000, the amount of components with a molecular weight of 100,000 or less becomes too small, which may result in a high heat shrinkage rate at high temperatures. It is also preferable that the Mw of the high-melting point polypropylene resin is higher than that of the mid-melting point polypropylene resin.

[0032] The number average molecular weight (Mn) of the mid-melting point polypropylene resin is preferably 20,000 to 200,000. It is more preferably 30,000 to 80,000, even more preferably 40,000 to 70,000, and particularly preferably 45,000 to 55,000. If Mn is less than 20,000, the melt viscosity is low, which may result in instability during casting and poor film formability. If Mn exceeds 200,000, the heat shrinkage rate at high temperatures may increase.

[0033] The Mn of the high-melting point polypropylene resin is preferably 20,000 to 200,000. It is more preferably 30,000 to 80,000, even more preferably 40,000 to 70,000, and particularly preferably 50,000 to 60,000. If the Mn is less than 20,000, the melt viscosity is low, which may result in instability during casting and poor film formability. If the Mn exceeds 200,000, the heat shrinkage rate at high temperatures may increase. It is also preferable that the Mn of the high-melting point polypropylene resin is higher than the Mn of the mid-melting point polypropylene resin.

[0034] The molecular weight distribution (Mw / Mn) of the mid-melting point polypropylene resin is preferably 2.8 to 10, more preferably 3.2 to 9.0, even more preferably 3.5 to 9.0, particularly preferably 4.0 to 8.0, and most preferably 4.5 to 6.0. The molecular weight distribution (Mw / Mn) of the high-melting point polypropylene resin is preferably 2.8 to 10, more preferably 3.2 to 9.0, even more preferably 3.5 to 9.0, particularly preferably 3.7 to 8.0, and most preferably 4.0 to 6.0. It is also preferable that the Mw / Mn of the high-melting point polypropylene resin is larger than the Mw / Mn of the mid-melting point polypropylene resin.

[0035] High-melting point polypropylene resins, mid-melting point polypropylene resins, and low-melting point polypropylene resins are obtained by polymerizing the raw material propylene using known catalysts such as Ziegler-Natta catalysts and metallocene catalysts. For example, to obtain a mid-melting point polypropylene resin, propylene may be copolymerized with ethylene, an α-olefin having 4 or more carbon atoms, or both. Alternatively, a polypropylene resin with reduced stereoregularity may be used depending on the catalyst used. However, a mid-melting point polypropylene resin can also be obtained without copolymerizing propylene with ethylene, an α-olefin having 4 or more carbon atoms, or both. The content of α-olefin components other than propylene in the mid-melting point polypropylene resin (specifically, the total amount of ethylene and the α-olefin having 4 or more carbon atoms) is preferably 0 to 15 mol%, more preferably 2 to 10 mol%. Specifically, a propylene-ethylene-butene copolymer is preferred. A propylene-ethylene-butene copolymer contains at least propylene structural units, ethylene structural units, and butene structural units. Similarly, the content of α-olefin components other than propylene in the low-melting-point polypropylene-based resin is preferably 0 to 15 mol%, more preferably 2 to 10 mol%. Specifically, the low-melting-point polypropylene-based resin is preferably a propylene-ethylene copolymer. The propylene-ethylene copolymer contains at least propylene structural units and ethylene structural units. The high-melting-point polypropylene-based resin is preferably a polypropylene homopolymer. The polypropylene homopolymer is polypropylene that does not substantially contain α-olefin components other than propylene, specifically a polypropylene copolymer having structural units of more than 0% but not more than 1 mol% of α-olefin components other than propylene and 99 mol% or more of propylene, or a polypropylene that does not contain structural units other than propylene.

[0036] From the viewpoint of imparting slip properties and anti-blocking properties to the surface layer B, the surface layer C, or both, it is preferable that the surface layer B, the surface layer C, or both contain an anti-blocking agent. Furthermore, the surface layer B, the surface layer C, or both may contain additives other than the anti-blocking agent, or may contain resins other than polypropylene-based resins. Examples of other additives include antioxidants, UV absorbers, nucleating agents, adhesives, anti-fogging agents, flame retardants, inorganic or organic fillers, or mixtures thereof. Examples of other resins include polyolefin-based resins other than the polypropylene-based resin used in the surface layer B, the surface layer C, or both, and various elastomers. These may be sequentially polymerized using a multi-stage reactor, blended with a polypropylene-based resin using a Henschel mixer, or master pellets prepared in advance using a melt kneader may be diluted with polypropylene to a predetermined concentration, or the entire amount may be melt-kneaded in advance before use. With respect to the total resin contained in surface layer B, surface layer C, or both, the total content of the high-melting point polypropylene resin and the mid-melting point polypropylene resin is preferably 70 to 100 mass%, more preferably 80 to 100 mass%, even more preferably 90 to 100 mass%, particularly preferably 95 to 100 mass%, and most preferably 98 to 100 mass%.

[0037] The antiblocking agent is preferably a particle having a pore volume of 0.2 mL / g to 3 mL / g, more preferably 0.5 mL / g to 2.5 mL / g, and even more preferably 1.1 mL / g to 1.8 mL / g. The antiblocking agent can be appropriately selected from inorganic and organic particles. Among these, silicon compounds are particularly preferred. Examples of silicon compounds include silica, silicates, compounds having a main skeleton formed by siloxane bonds, and mixtures thereof. Porous silica particles are particularly preferred. The porous silica preferably has a pore volume of 0.8 mL / g to 2 mL / g, more preferably 1.1 mL / g to 1.8 mL / g. The particle shape may be spherical or irregular, but irregular shapes are preferred. The average particle size of the particles is preferably 1 μm to 5 μm, more preferably 2 μm to 4 μm. The average particle size is determined by taking a photograph using a scanning electron microscope, measuring the Feret's diameter in the horizontal direction using an image analyzer, and averaging the results. The use of the antiblocking agent is preferred in that it can reduce the rate at which the antiblocking agent falls off and suppress guide roll contamination.

[0038] The content of the antiblocking agent is preferably 100 ppm to 10,000 ppm, more preferably 300 ppm to 6,000 ppm, even more preferably 800 ppm to 4,000 ppm, and particularly preferably 1,200 ppm to 2,700 ppm, based on the total mass of the surface layer B, the surface layer C, or both. By adjusting the content within the above ranges, the three-dimensional average roughness of the surface layer B, the surface layer C, or both, can be adjusted to the specified range described below. By adjusting the content of the antiblocking agent to 100 ppm or more, a film with excellent slip properties and blocking resistance can be obtained. By adjusting the content of the antiblocking agent to 10,000 ppm or less, the antiblocking agent can be reduced to fall off, thereby suppressing guide roll contamination. Furthermore, problems such as a decrease in light transmittance, penetration of the antiblocking agent through the functional layer when laminating the functional layer, and sparseness of the functional layer formed near the surface layer B due to the antiblocking agent protruding from the surface layer B, the surface layer C, or both are unlikely to occur, and a decrease in barrier properties and poor adhesion are unlikely to occur.

[0039] The dropout rate of the antiblocking agent in surface layer B and surface layer C is 10% or less, preferably 8% or less, more preferably 6% or less, and even more preferably 4% or less. A dropout rate of 10% or less can prevent guide roll contamination during post-processing such as coating or vapor deposition. Furthermore, the generation of voids due to dropout of the antiblocking agent can be prevented, and a laminate with excellent gas barrier properties can be obtained when a metal, a metal oxide, or both are vapor-deposited. The lower limit of the dropout rate is not particularly limited, but is, for example, 0.3% or more. The dropout rate of the antiblocking agent can be adjusted to the above range by adjusting the film-forming conditions in addition to the type, pore volume, particle size, and content of the antiblocking agent.

[0040] (3) Layer Structure and Thickness Structure of Biaxially Oriented Polypropylene Film When a biaxially oriented polypropylene film has a surface layer B on one side of a base layer A, the surface layer B may be laminated directly on the surface of the base layer A, or another layer may be interposed between the base layer A and the surface layer B. When a biaxially oriented polypropylene film has a surface layer C on the other side of the base layer A, the surface layer C may be laminated directly on the surface of the base layer A, or another layer may be interposed between the base layer A and the surface layer C. For example, the biaxially oriented polypropylene film may have a three-layer structure consisting of only the surface layer B / base layer A / surface layer C, or may have a multi-layer structure of four or more layers including layers other than the base layer A, surface layer B, and surface layer C. An example of a four-layer structure is surface layer B / intermediate layer D / base layer A / surface layer C, and an example of a five-layer structure is surface layer B / intermediate layer D / base layer A / intermediate layer D / surface layer C. By providing the intermediate layer D, the adhesive strength between the base layer A and the surface layer B, the surface layer C, or both of these can be increased.

[0041] The overall thickness of the biaxially oriented polypropylene film is preferably 5 to 100 μm, more preferably 10 to 80 μm, and even more preferably 18 to 50 μm. Within the above range, the film has sufficient rigidity and is suitable as a substrate for packaging and industrial use.

[0042] The thickness of surface layer B and surface layer C is preferably 0.3 μm to 10 μm, more preferably 0.5 μm to 3 μm, and even more preferably 0.8 μm to 2 μm. A thickness of 0.3 μm or more can improve the adhesion between surface layer B and surface layer C and the functional layer, making them suitable as a substrate for packaging or industrial use that requires the addition of a functional layer through vapor deposition processing or coating processing, etc. If the thickness of surface layer B is greater than 10 μm, the thickness ratio of substrate layer A may be relatively low, which may result in a decrease in the rigidity and thermal dimensional stability of the film.

[0043] The thickness of the base layer A is preferably 5 to 90 μm, more preferably 10 to 50 μm, and even more preferably 15 to 30 μm. A thickness of 5 μm or more can improve the thermal dimensional stability and mechanical strength of the film. If the thickness of the base layer A is greater than 90 μm, the thermal dimensional stability and mechanical strength can be improved, but the effects may saturate.

[0044] (4) Method for producing biaxially oriented polypropylene film The biaxially oriented polypropylene film can be obtained by melt-extruding the polypropylene resin compositions constituting each of the base layer A, surface layer B, and surface layer C using separate extruders, co-extruding them through a die, and cooling them with a cooling roll to form an unstretched sheet, stretching the unstretched sheet in the longitudinal direction (MD) and width direction (TD), and then heat-setting the sheet.

[0045] The melt extrusion temperature is preferably about 200 to 280°C. When layers A, B, and C are co-extruded within this temperature range, in order to obtain a film with good appearance without layer disorder, it is preferable that the difference between the MFR of base layer A and the MFR of surface layer B and surface layer C (hereinafter referred to as MFR difference) is 5.0 g / 10 min or less. If the MFR difference is greater than 5.0 g / 10 min, the layers tend to become disordered, resulting in poor appearance. It is more preferably 4.0 g / 10 min or less, and even more preferably 3.0 g / 10 min or less. Furthermore, when surface layer C is present, it is preferable that the difference between the maximum and minimum MFRs of the three polypropylene resin compositions constituting base layer A, surface layer B, and surface layer C is 5.0 g / 10 min or less, and more preferably 3.0 g / 10 min or less.

[0046] The surface temperature of the chill roll is preferably 20 to 50°C, more preferably 30 to 40°C, and even more preferably 30 to 35°C. When the chill roll temperature is 50°C or less, crystallization of the unstretched sheet and growth of spherulites can be suppressed, allowing for a high stretch ratio and producing a film with a high tensile modulus. In addition, the occurrence of large surface irregularities due to spherulites can be suppressed, producing a film with an appropriate surface roughness.

[0047] The lower limit of the stretching ratio in the longitudinal direction (MD) is preferably 3.5 times or more, more preferably 4 times or more. If it is 3.5 times or more, thickness unevenness can be reduced. The upper limit of the stretching ratio in the MD is preferably 8 times or less, more preferably 7 times or less. If it is 8 times or less, breakage is less likely to occur in the subsequent TD stretching, making production easier.

[0048] The lower limit of the MD stretching temperature is preferably 120°C or higher, more preferably 130°C or higher, and even more preferably 135°C or higher. At 120°C or higher, thickness unevenness is less likely to increase and the film surface is less likely to become rough. A higher MD stretching temperature makes it less likely that voids will be formed around the antiblocking agent particles, preventing roll contamination during processing due to the antiblocking agent particles falling off the film surface. Furthermore, good gas barrier properties are obtained when aluminum is vapor-deposited.

[0049] The upper limit of the MD stretching temperature is preferably 150°C or less, more preferably 145°C or less, and even more preferably 140°C or less. If the MD stretching temperature is too high, the film may start to stick to the MD stretching rolls, causing stick-slip and resulting in spots and surface roughness on the film. If the MD stretching temperature is further increased, the film may stick to the stretching rolls, making it impossible to stretch.

[0050] The lower limit of the stretching ratio in the transverse direction (TD) is preferably 6 times or more, more preferably 7 times or more, and even more preferably 8 times or more. If it is 6 times or more, thickness unevenness is unlikely to become large. The upper limit of the TD stretching ratio is preferably 15 times or less, more preferably 13 times or less, and even more preferably 11 times or less. If it exceeds the above range, the heat shrinkage rate may become high and there is a risk of frequent breakage during stretching.

[0051] It is preferable to heat the uniaxially stretched film after longitudinal stretching to sufficiently soften the polypropylene resin composition before the widthwise stretching step. The heating temperature in the preheating step is preferably 160°C or higher and 180°C or lower, and more preferably 165°C or higher and 175°C or lower. By setting the heating temperature in the preheating step to 160°C or higher, softening progresses and widthwise stretching becomes easier. The lower limit of the TD stretching temperature is preferably 150°C or higher, more preferably 152°C or higher, even more preferably 154°C or higher, and particularly preferably 156°C or higher. At 150°C or higher, the film is easily softened sufficiently, and is less likely to break or have an increased heat shrinkage rate. The upper limit of the TD stretching temperature is preferably 170°C or lower, more preferably 168°C or lower, and even more preferably 166°C or lower.

[0052] To reduce the heat shrinkage rate, a higher heat setting temperature is preferred, more preferably 160°C or higher, and even more preferably 162°C or higher. If the temperature is 160°C or higher, the heat shrinkage rate is less likely to increase. The upper limit of the heat setting temperature is preferably 180°C or lower, more preferably 175°C or lower. If the temperature is 180°C or lower, surface roughening and whitening of the film are less likely to occur.

[0053] It is preferable to relax the film during heat setting. The lower limit of the relaxation rate is preferably 2% or more, more preferably 3% or more, and even more preferably 5% or more. If it is 2% or more, the thermal shrinkage rate is unlikely to become high. The upper limit of the relaxation rate is preferably 10% or less, more preferably 8% or less. If it is 10% or less, thickness unevenness is unlikely to become large.

[0054] Furthermore, in order to reduce the thermal shrinkage rate, the film produced by the above process may be wound into a roll and then annealed offline.

[0055] The film thus obtained may be subjected to corona discharge, plasma treatment, flame treatment, etc., as required, and then wound up with a winder to obtain a biaxially oriented polypropylene film roll. Note that the method for producing the biaxially oriented polypropylene film is not limited to the above-mentioned method.

[0056] (5) Various Properties of Biaxially Oriented Polypropylene Film (Haze) The haze of the biaxially oriented polypropylene film is preferably 8% or less, more preferably 5% or less, even more preferably 4% or less, and particularly preferably 3% or less. A haze within the above range makes it easy to use in applications requiring transparency. Haze tends to deteriorate when the stretching temperature or heat setting temperature is too high, when the cooling roll temperature is high and the cooling rate of the unstretched (raw) sheet is slow, or when there is too much low-molecular-weight component with a molecular weight of 100,000 or less. By adjusting these conditions, the haze can be kept within the above range.

[0057] (Tensile Modulus) The tensile modulus of the biaxially oriented polypropylene film in the longitudinal direction is preferably 1.0 GPa or more, more preferably 1.5 GPa or more, even more preferably 1.8 GPa or more, and particularly preferably 2.0 GPa or more. There is no particular upper limit, and it is, for example, 5.0 GPa or less. The tensile modulus of the biaxially oriented polypropylene film in the width direction is preferably 3.0 GPa or more, more preferably 3.2 GPa or more, and even more preferably 3.5 GPa or more. There is no particular upper limit, and it is, for example, 10 GPa or less. The sum of the tensile modulus of the biaxially oriented polypropylene film in the longitudinal direction and the width direction is preferably 5.8 to 12.0 Pa, and more preferably 6.0 to 10.0 GPa. If the tensile modulus is within the above range, the film will have a strong stiffness, and it can be used even if it is thin, which ultimately enables cost reduction. In addition, the "longitudinal direction" of a biaxially oriented polypropylene film refers to the direction corresponding to the flow direction in the film manufacturing process, and the "width direction" refers to the direction perpendicular to the flow direction in the film manufacturing process, and the same applies below.

[0058] (Heat Shrinkage Rate) The heat shrinkage rate of the biaxially oriented polypropylene film in the longitudinal direction at 150°C is preferably 10.0% or less, more preferably 9.0% or less, even more preferably 7.0% or less, and particularly preferably 5.0% or less. Within the above range, the film can be used in applications where it may be exposed to high temperatures. Furthermore, even when a functional layer is laminated on the film, the degradation of the barrier property of the functional layer can be suppressed, thereby improving the barrier property of the laminate. The lower limit of the heat shrinkage rate of the biaxially oriented polypropylene film in the longitudinal direction at 150°C is preferably 0%. From the perspective of productivity in production, it is preferably 1% or more, more preferably 3% or more. The heat shrinkage rate of the biaxially oriented polypropylene film in the width direction at 150°C is 15.0% or less, more preferably 10.0% or less, even more preferably 8.0% or less, and particularly preferably 5% or less. The lower limit of the heat shrinkage rate in the width direction at 150°C is -5%, preferably 0%. From the perspective of productivity in production, it is preferably 3%, more preferably 5%. Within the above range, the film can be used in applications where it may be exposed to high temperatures. Furthermore, even when a functional layer is laminated on the film, the barrier properties of the functional layer can be prevented from decreasing, resulting in improved barrier properties of the laminate. The sum of the heat shrinkage rates in the longitudinal and width directions of the biaxially oriented polypropylene film at 150°C is preferably 25.0% or less, more preferably 23.0% or less, even more preferably 20.0% or less, even more preferably 15.0% or less, and particularly preferably 12.0% or less. The lower limit of the sum of the heat shrinkage rates in the longitudinal and width directions at 150°C is 0% or more. From the perspective of production productivity, 4% is preferred, and 8% is more preferred. Within the above range, the film can be used in applications where it may be exposed to high temperatures. Furthermore, even when a functional layer is laminated on the film, the barrier properties of the functional layer can be prevented from decreasing, resulting in improved barrier properties of the laminate.

[0059] (Three-dimensional average roughness) The lower limit of the three-dimensional average roughness SRa of the surface layer B, the surface layer C, or both of the biaxially oriented polypropylene film is preferably 15 nm. It is more preferably 20 nm, even more preferably 25 nm, and even more preferably 30 nm. When the three-dimensional average roughness of the surface layer B, the surface layer C, or both of them is 15 nm or more, the film has good slipperiness and can suppress the occurrence of wrinkles when wound into a roll or during post-processing such as vapor deposition. Furthermore, the upper limit of the three-dimensional average roughness of the surface layer B, the surface layer C, or both of them is preferably 100 nm. When it is 100 nm or less, the film has good transparency and can suppress the film from becoming too slippery when wound into a roll or during post-processing such as vapor deposition, thereby preventing deterioration of workability. The three-dimensional average roughness SRa can be controlled by adjusting the type, particle size, amount, and film-forming conditions of the antiblocking agent. When a biaxially oriented polypropylene film is vapor-deposited to impart gas barrier properties, the gas barrier properties of the vapor-deposited layer can be improved by making the surface protrusions on the vapor-deposited surface small and smooth, and the surface protrusions on the other surface can be made large to impart slip properties and anti-blocking properties. In this case, the three-dimensional average roughness SRa of the vapor-deposited surface can be less than 15 nm.

[0060] (Antiblocking Agent Dropout Rate) The dropout rate of the antiblocking agent in surface layer B and surface layer C is 10% or less, preferably 8% or less, more preferably 6% or less, and even more preferably 4% or less. A dropout rate of 10% or less can prevent guide roll contamination during post-processing such as coating or vapor deposition. In addition, the generation of voids due to dropout of the antiblocking agent can be prevented, and a laminate with excellent gas barrier properties can be obtained when a metal, a metal oxide, or both are vapor-deposited. The lower limit of the dropout rate is not particularly limited, but is, for example, 0.3% or more.

[0061] (Wet Tension) The wet tension of the surface layer B, surface layer C, or both of the biaxially oriented polypropylene film is preferably 36 mN / m or more, more preferably 38 mN / m or more, and even more preferably 40 mN / m or more. The wet tension may be appropriately set depending on the type of functional layer to be formed on the surface layer B, surface layer C, or both. When an inorganic thin film layer such as an aluminum thin film layer is formed by a thermal vapor deposition method or the like, setting the surface to 36 mN / m or more tends to improve adhesion with the inorganic vapor deposition layer, etc. Similarly, when a heat-sealable film sealant film is laminated on the surface layer B, surface layer C, or both of them, the wet tension may be appropriately set depending on the type of adhesive used for lamination, but setting it to 36 mN / m or more tends to improve adhesion. To achieve a wet tension of 36 mN / m or more, surface treatments such as corona treatment, flame treatment, and anchor coating treatment can be performed. Since a wet tension that is too high may deteriorate slip properties and anti-blocking properties, it is preferably 46 mN / m or less.

[0062] (Surface Resistivity) The surface resistance of the surface layer B and the surface layer C of the biaxially oriented polypropylene film is preferably 14 Log Ω or more, more preferably 14.5 Log Ω or more, and even more preferably 15 Log Ω or more. If the film contains additives or impurities such as antistatic agents, they may bleed out onto the film surface due to surface treatment, resulting in poor adhesion. A surface resistance of 14 Log Ω or more reduces bleed-out of additives and the like onto the film surface, which is preferable in terms of adhesion to the functional layer. The preferred upper limit of the surface resistance of the surface layer B and the surface layer C is not particularly limited, but is 18 Log Ω or less for manufacturing reasons.

[0063] (Dynamic friction coefficient) The dynamic friction coefficient of the biaxially oriented polypropylene film is preferably 0.5 or less, more preferably 0.48 or less, and particularly preferably 0.45 or less. When the dynamic friction coefficient is 0.5 or less, the film can be smoothly unwound from the roll film, facilitating printing processing. The dynamic friction coefficient of the biaxially oriented polypropylene film can be adjusted by the raw material composition and film-forming conditions. In particular, it can be adjusted by the amount and particle size of the antiblocking agent blended in surface layer B, surface layer C, or both. The dynamic friction coefficient of the biaxially oriented polypropylene film is the dynamic friction coefficient when surface layer B and surface layer C are in contact with each other, and can be measured by the method described in the examples.

[0064] (6) Laminate A laminate according to an embodiment includes the biaxially oriented polypropylene film of any of the above-described embodiments. Preferably, the laminate further includes a heat-sealable polyolefin film, with the surface layer B, base layer A, surface layer C, and heat-sealable polyolefin film laminated in this order. Preferably, the laminate further includes a functional layer, with the functional layer, surface layer B, base layer A, surface layer C, and heat-sealable polyolefin film laminated in this order. The functional layer is preferably a printed layer, a vapor-deposited layer, or a coating layer. More preferably, the laminate further includes a heat-sealable polyolefin film, with the functional layer, surface layer B, surface layer A, surface layer C, and heat-sealable polyolefin film laminated in this order. More preferably, the laminate further includes a stretched polyolefin film or stretched polyester film, with the stretched polyolefin film or stretched polyester film, the functional layer, surface layer B, surface layer A, surface layer C, and heat-sealable polyolefin film laminated in this order. The functional layer, heat-sealable film, and stretched film of the laminate will be described below.

[0065] (7) Functional Layer Biaxially oriented polypropylene films are not limited to packaging applications and can be used for industrial purposes. In addition, when it is desired to improve the gas barrier properties or design properties of the biaxially oriented polypropylene film, a functional layer such as a printed layer, a vapor deposition layer, or a coating layer can be provided to form a laminate.

[0066] A printed layer can be provided on the biaxially oriented polypropylene film. Water-based inks are preferred from an environmental perspective. When using water-based inks, it is necessary that the printed layer does not repellent (printability) and that it has sufficient adhesion to the film. Biaxially oriented polypropylene films have excellent printability and adhesion to water-based inks. When gravure printing is performed on the surface of the film using water-based ink and the shape of the printed dots is observed to evaluate the dot size and the degree of ink repellency, a uniform dot size is preferred, and a uniform dot size and no repellency are even more preferred.

[0067] When it is desired to improve the gas barrier property, it is preferable to laminate a vapor deposition layer, a coating layer, or both of them on the biaxially oriented polypropylene film. The vapor deposition layer can be produced by any known production method, such as a PVD method (physical vapor deposition method) such as a vacuum deposition method, a sputtering method, or an ion plating method, or a CVD method (chemical vapor deposition method). However, the physical vapor deposition method is preferable, and the vacuum vapor deposition method is more preferable. For example, in the vacuum vapor deposition method, aluminum, Al ２ O ３ , SiO ｘ (X<2), Al ２ O ３ and SiO ２ A mixture of Al and SiO ２ A mixture of these materials or the like can be used, and known heating methods such as resistance heating, high-frequency induction heating, and electron beam heating can be used. Furthermore, oxygen, nitrogen, water vapor, or the like can be introduced as a reactive gas, and reactive vapor deposition using ozone addition, ion-assisted deposition, or other methods can be used. Furthermore, the production conditions can be changed as long as the objectives of the present disclosure are not impaired, such as by applying a bias to the biaxially oriented polypropylene film or by increasing or decreasing the temperature of the biaxially oriented polypropylene film. The same applies to other production methods such as sputtering and CVD.

[0068] When a vapor-deposited layer is provided on a biaxially oriented polypropylene film, the vapor-deposited layer preferably contains a metal, a metal oxide, or both of them, and aluminum, Al ２ O ３, SiOx (X<2), Al ２ O ３ and SiO ２ or a mixture of Al and SiO ２ More preferably, it contains a mixture of aluminum or Al and SiO ２ The thickness of the vapor-deposited layer is preferably 5 to 40 nm, more preferably 10 to 30 nm. When a metal or inorganic oxide is vapor-deposited, it is preferably vapor-deposited on the side of the biaxially oriented polypropylene film that has the smaller surface roughness.

[0069] Examples of materials for the coating layer when it is desired to improve the gas barrier property include polyvinylidene chloride, nylon, butanediol-vinyl alcohol copolymer, ethylene-vinyl alcohol copolymer, polyvinyl alcohol, etc. In the case of the coating layer, the coating amount after drying is 0.03 to 3 g / m ２ It is preferable that the density is 0.1 to 0.3 g / m ２ It is more preferable that:

[0070] The upper limit of oxygen permeability of a laminate in which an inorganic thin film layer or a coating layer is provided on a biaxially oriented polypropylene film at a temperature of 23°C and a relative humidity of 65% is 50 mL / m ２ / day / MPa, and more preferably 39 mL / m ２ / day / MPa, and more preferably 30 mL / m ２ / day / MPa, and particularly preferably 25 mL / m ２ / day / MPa. The upper limit of oxygen permeability is 50 mL / m ２ The lower limit of the oxygen permeability of the vapor-deposited film at a temperature of 23°C and a relative humidity of 65% is not particularly limited, but from the viewpoint of productivity, it is preferably 0.1 mL / m ２ / day / MPa. In a laminate in which an inorganic thin film layer is provided on a biaxially oriented polypropylene film, the adhesion at the interface between the inorganic thin film layer or coating layer and the biaxially oriented polypropylene film is preferably high, and high adhesion can keep the above-mentioned oxygen permeability low. The adhesion at the interface between the inorganic thin film layer or coating layer and the biaxially oriented polypropylene film is measured by attaching an adhesive tape to the inorganic thin film layer and evaluating the degree of peeling of the inorganic thin film layer or coating layer by a 90° peeling method, and it is preferable that the inorganic thin film layer or coating layer only peels partially, and more preferably that the inorganic thin film layer or coating layer does not peel.

[0071] The adhesion between the vapor-deposited layer and the substrate layer of a vapor-deposited film provided with a vapor-deposited layer is preferably high, since high adhesion can reduce the oxygen permeability. The adhesion of the vapor-deposited layer can be evaluated by attaching an adhesive tape to the vapor-deposited layer of the film and measuring the degree of peeling of the vapor-deposited layer using a 90° peeling method. It can also be evaluated by measuring the oxygen permeability after subjecting the vapor-deposited surface of the vapor-deposited film to an abrasion test; it is preferable that the aluminum vapor-deposited layer does not peel off partially, and more preferably that the aluminum vapor-deposited layer does not peel off at all.

[0072] A printed layer can be provided on biaxially oriented polypropylene film. Water-based ink is preferred from an environmental perspective. When using water-based ink, it is necessary that the printed layer does not repellent (printability) and that it has sufficient adhesion to the film. Biaxially oriented polypropylene film has excellent printability and adhesion to water-based ink.

[0073] (8) Heat-sealable film, stretched film Biaxially oriented polypropylene film or a laminate having a printed layer, an inorganic thin film layer, or a coating layer laminated thereon can be processed into a heat-sealable laminate, such as a packaging bag, by laminating a heat-sealable film. The heat-sealable film laminated on the biaxially oriented polypropylene film is preferably a heat-sealable polyolefin film. When both surfaces of the biaxially oriented polypropylene film have excellent adhesiveness, it is preferably used as part of a laminate having a heat-sealable polyolefin film on the outermost surface. In particular, it is preferable to use the biaxially oriented polypropylene film as part of a laminate further having a stretched polyolefin film or stretched polyester film arranged on the side opposite to the side on which the heat-sealable polyolefin film is arranged. For example, the biaxially oriented polypropylene film is preferably used as a substrate in a laminate consisting of a substrate for a front printing layer / heat-sealable film, or as a substrate for a gas barrier film in an intermediate layer in a laminate consisting of a substrate for a back printing layer / gas barrier film / heat-sealable film.

[0074] Examples of heat-sealable films include unstretched films, uniaxially stretched films, and biaxially stretched films made of polyolefins such as low-density polyethylene, linear low-density polyethylene, and polypropylene, ethylene-vinyl acetate copolymers, polyesters, or combinations thereof. Heat-sealable polyolefin films that are unstretched or uniaxially stretched films made of low-density polyethylene, linear low-density polyethylene, or polypropylene are particularly preferred. Polypropylene is particularly preferred in terms of ease of recycling.

[0075] The surface of the biaxially oriented polypropylene film to which the heat-sealable film is laminated may be either the surface layer B side or the surface layer C side. The heat-sealable film is preferably laminated via an adhesive layer. Examples of adhesives that can be used include ester-based adhesives, urethane-based adhesives, acrylic-based adhesives, and polyethyleneimine-based adhesives. Examples of lamination methods that can be used include dry lamination, extrusion lamination, and co-extrusion.

[0076] A biaxially oriented polypropylene film or a laminate obtained by laminating a functional layer such as a printed layer, an inorganic thin film layer, or a coating layer, and a heat-sealable film onto the biaxially oriented polypropylene film can be processed into a packaging bag and used as a packaging container with excellent suitability for filling and packaging and preserving various items such as food and beverages, pharmaceuticals, detergents, shampoos, oils, toothpaste, adhesives, and pressure-sensitive adhesives.

[0077] The laminate strength of the biaxially oriented polypropylene film, measured by the method described below, is 1.5 N / 15 mm or more, preferably 2.0 N / 15 mm or more, more preferably 2.5 N / 15 mm or more, even more preferably 2.7 N / 15 mm or more, and particularly preferably 2.8 N / 15 mm or more. There is no particular upper limit, but 10 N / 15 mm or less is sufficient. In this case, it is preferable to have a heat-sealable film on the surface layer C side. Furthermore, the laminate strength of a laminate having a functional layer such as a printed layer, an inorganic thin film layer, or a coating layer on a biaxially oriented polypropylene film, measured by the method described below, is 1.5 N / 15 mm or more, preferably 2.0 N / 15 mm or more, more preferably 2.5 N / 15 mm or more, even more preferably 2.7 N / 15 mm or more, and particularly preferably 2.8 N / 15 mm or more. There is no particular upper limit, but 10 N / 15 mm or less is sufficient. In this case, it is preferable to have a heat-sealable film on the surface layer C side.

[0078] A biaxially oriented polypropylene film or a laminate having a functional layer such as a printed layer, an inorganic thin film layer, or a coating layer on the biaxially oriented polypropylene film and a heat-sealable film is less likely to wrinkle in the sealed portion even when the heat-sealing temperature is high when processed into a packaging bag. Because the sum of the heat shrinkage rate at 150°C in the longitudinal direction and the heat shrinkage rate at 150°C in the transverse direction of the biaxially oriented polypropylene film is 0.0% or more and 25.0% or less, even when the temperature of the seal bar is increased, there is little wrinkling or deformation in the sealed portion, allowing for faster bag production.

[0079] An example of a laminate configuration having a functional layer on one side of a biaxially oriented polypropylene film and a heat-sealable film on the other side is a laminate in which a biaxially oriented polypropylene film of the present disclosure provided with a gas barrier layer as a functional layer is disposed between another biaxially oriented polypropylene film provided with a printed layer and a heat-sealable film such as a non-oriented polypropylene film or a non-oriented linear low-density polyethylene film. Examples include (OPP or PET / printed layer) / adhesive layer / (aluminum or inorganic oxide vapor-deposited layer / OPP*) / adhesive layer / (CPP or LLDPE), (OPP or PET / printed layer) / adhesive layer / (gas barrier coating layer / OPP*) / adhesive layer / (CPP or LLDPE), etc. A laminate can also be formed by bonding a heat-sealable film such as a non-oriented polypropylene film or a non-oriented linear low-density polyethylene film to a biaxially oriented polypropylene film of the present disclosure provided with a printed layer as a functional layer. For example, a laminate used as a surface printing substrate, such as (printing layer / OPP*) / adhesive layer / (CPP or LLDPE), can be mentioned. In the above layer structure, " / " indicates the boundary between different members, and the abbreviations used are as follows: OPP*: biaxially oriented polypropylene film of the present disclosure OPP or PET: general biaxially oriented polypropylene film or biaxially oriented polyethylene terephthalate film CPP: unstretched polypropylene film LLDPE: linear low-density polyethylene film

[0080] This application claims the benefit of priority based on Japanese Patent Application No. 2024-011278 filed on January 29, 2024, and Japanese Patent Application No. 2024-012919 filed on January 31, 2024. The entire contents of the specifications of Japanese Patent Application No. 2024-011278 filed on January 29, 2024, and Japanese Patent Application No. 2024-012919 filed on January 31, 2024 are incorporated herein by reference.

[0081] The present disclosure will be described below with reference to examples, but the present disclosure is not limited to these examples.

[0082] (Measurement Methods) The physical properties of the raw materials used and the resulting films in the Examples and Comparative Examples were measured by the following methods. Note that in the following 1) to 5), the physical properties of the polypropylene resin used in each layer were measured, and in 6) to 17), the physical properties of the biaxially oriented polypropylene film were measured. In 18) to 21), evaluations were made during post-processing, such as laminating other layers such as a functional layer onto the biaxially oriented polypropylene film.

[0083] 1) Melting Point Using a PerkinElmer DSC8500 differential scanning calorimeter, 5 mg of a sample was packed into an aluminum pan and set therein, and melted at 230°C for 5 minutes under a nitrogen atmosphere. The sample was then cooled to 30°C at a scanning rate of -10°C / min, maintained at this temperature for 5 minutes, and then heated at a scanning rate of 10°C / min. The main peak temperature of the endothermic peak accompanying melting was taken as the melting point (Tm).

[0084] 2) Mesopentad fraction (mmmm) The mesopentad fraction is measured as follows: １３ The mesopentad fraction was calculated according to the method described in "Zambelli et al., Macromolecules, Vol. 6, p. 925 (1973)". １３ C-NMR measurement was performed using an AVANCE 500 manufactured by BRUKER at 110°C by dissolving 200 mg of a sample in a mixed solution of o-dichlorobenzene and deuterated benzene in a ratio of 8:2 (volume ratio) at 135°C.

[0085] 3) Melt flow rate (MFR) Measured in accordance with JIS K7210 at a temperature of 230°C and a load of 2.16 kgf.

[0086] 4) Number average molecular weight (Mn), weight average molecular weight (Mw), and molecular weight distribution (Mw / Mn) The molecular weight and molecular weight distribution of the polypropylene resin were determined using gel permeation chromatography (GPC) with monodisperse polystyrene as the standard. The measurement conditions for the column, solvent, etc. used in the GPC measurement are as follows: Solvent: 1,2,4-trichlorobenzene Column: TSKgel GMHHR-H(20)HT x 3 Flow rate: 1.0 ml / min Detector: RI Measurement temperature: 140°C

[0087] 5) Molecular weight, molecular weight distribution Number average molecular weight (Mn), weight average molecular weight (Mw), and molecular weight distribution (Mw / Mn) are defined by the following formulas, respectively, using the number of molecules (Ni) of the molecular weight (Mi) at each elution position of the GPC curve obtained via the molecular weight calibration curve. Number average molecular weight: Mn = Σ(Ni·Mi) / ΣNi Weight average molecular weight: Mw = Σ(Ni·Mi) ２ ) / Σ(Ni·Mi) Molecular weight distribution: Mw / Mn When the baseline was unclear, the baseline was set in the range up to the lowest point of the high molecular weight base of the elution peak on the high molecular weight side closest to the elution peak of the standard substance.

[0088] 6) Thickness A cross section of a film solidified with a modified urethane resin was cut out with a microtome and observed with a differential interference microscope to measure the thickness of each layer.

[0089] 7) Haze The haze of the film was measured at 23° C. using a haze meter (300A manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K 7105. The measurement was carried out twice, and the average value was calculated.

[0090] 8) Appearance A bromine light (VIDEO LIGHT VLG301 100V 300W, manufactured by LPL) was irradiated onto the film surface at an angle of approximately 45 degrees, and the appearance of the film was evaluated by visual observation according to the following criteria: A: No unevenness in appearance that would be problematic for the product was observed. B: Many unevenness in transparency due to stick-slip occurring on the longitudinal stretching rolls was observed. C: Very many unevenness in transparency due to stick-slip occurring on the longitudinal stretching rolls was observed, to a level that was not acceptable for use as a product.

[0091] 9) Tensile Modulus A sample measuring 10 mm in width and 180 mm in length was cut from the film using a razor. Measurements were performed in accordance with JIS K 7127. After leaving the film in an atmosphere of 23°C and 65% relative humidity for 12 hours, measurements were performed under conditions of 23°C, 65% relative humidity, a chuck distance of 100 mm, and a pulling speed of 200 mm / min. The average value of five measurements was calculated and used as the longitudinal tensile modulus. The measuring device used was an Autograph AG5000A manufactured by Shimadzu Corporation. A sample measuring 180 mm in width and 10 mm in length was also cut from the film using a razor, and the widthwise tensile modulus was determined using the same method as for the longitudinal tensile modulus.

[0092] 10) Heat shrinkage was measured according to JIS Z 1712 by the following method. A film was cut into 20 mm wide and 200 mm long pieces along the longitudinal or transverse direction of the film to obtain multiple samples, which were then hung in a hot air oven at 150°C and heated for 5 minutes. The length of each sample after heating was measured, and the ratio of the shrunken length to the original length was taken as the heat shrinkage.

[0093] 11) Wet Tension (mN / m) According to JIS K 6768 (1999), the film was aged at 23° C. and a relative humidity of 50% for 24 hours, and then the wet tension of the surface of the surface layer B and the surface layer C was measured.

[0094] 12) Surface Resistivity Value According to JIS K 6911 (1995), the film was aged at 23° C. and a relative humidity of 65% for 24 hours, and then the surface resistivity values ​​of the surface layer B and the surface layer C were measured.

[0095] 13) Three-dimensional average roughness SRa Using a contact-type three-dimensional surface roughness meter (manufactured by Kosaka Laboratory Co., Ltd.: Model ET-4000A), the average roughness SRa of surface layer B and surface layer C was measured by the stylus method under the following conditions: stylus tip radius: 0.5 μm, stylus pressure: 50 μN, cutoff value: 800 μm, measurement length: 500 μm, measurement speed: 0.1 μm / sec, measurement interval: 5 μm

[0096] 14) Antiblocking agent drop rate Using a universal tensile tester (Toyo Baldwin STM-T-50BP), a 0.5 kg weight (contact surface: 63 mm x 63 mm) with a bettin fabric attached was placed over the measurement surface of the film, and a friction test was carried out under the following conditions: Temperature: 23°C, Relative humidity: 50%, Number of frictions: 5 times consecutively on the part to be evaluated, Pulling speed: 200 mm / min

[0097] After the above treatment, the film was observed at a magnification of 600x using a tabletop microscope (Hitachi, Ltd., "TM3030Plus Miniscope"), and the number of all antiblocking agents in the observed film and the number of antiblocking agents that had fallen off the film were counted, and the rate of antiblocking agent detachment was calculated using the following formula: Rate of antiblocking agent detachment (%) = (number of antiblocking agents that have fallen off the film) / (total number of antiblocking agents observed in the film and the number of antiblocking agents that have fallen off the film) × 100

[0098] 15) Dynamic friction coefficient Two films were prepared, and the surface layer B of one film was superimposed on the surface of the surface layer C of the other film. The coefficient of dynamic friction was measured in accordance with JIS K 7125 (1999) using a universal tensile tester STM-T-50BP (manufactured by Toyo Baldwin) in an atmosphere of 23°C and relative humidity of 50%.

[0099] 16) Wrinkles in film rolls The produced biaxially oriented polypropylene film was wound up using a slitter to a width of 600 mm and a roll length of 1,500 m to produce a film roll, and the wrinkles on the surface layer of the film roll were visually evaluated according to the following criteria: A+: No wrinkles. A: There were weak wrinkles, but the wrinkles disappeared when a tension of about 5 N / m was applied to the drawn-out film. B: There were weak wrinkles, but the wrinkles disappeared when a tension of about 20 N / m was applied to the drawn-out film. C: There were strong wrinkles, and the wrinkles did not disappear even when a tension of about 20 N / m was applied to the drawn-out film.

[0100] 17) Guide roll soiling After a 500 m length of film was passed through a slitter (NS-SLITTER FN-105 manufactured by Nishimura Manufacturing Co., Ltd.), the soiling of the guide roll was evaluated. A: No soiling of the guide roll. B: Slight soiling in parts of the guide roll. C: Soiling over the entire surface of the guide roll.

[0101] 18) Evaluation of water-based ink printability Water-based ink gravure printing was carried out on the surface layer B of the film at a speed of 50 m / min using a gravure printing machine (manufactured by Fuji Machinery Co., Ltd.). A process chart plate was used for the printing design. The inks and diluents used are as follows: Water-based ink: Toyo Ink Co., Ltd., product name JW291 Aquaecol R39 (registered trademark) Dilution solvent: Toyo Ink Co., Ltd., product name AQ602F

[0102] (Microscope Observation) Using a KEYENCE Digital Microscope VHX-200, the shapes of the printed dots were observed at a magnification of 125x, and the dot size and the degree of ink repellency were evaluated. A three-level evaluation standard is shown. Figures 1 to 3 show examples of dot shapes for each evaluation. Regarding ink repellency, Figure 4 shows an enlarged view of the ink repellency area in Figure 2. A: Dot size is uniform, no ink repellency (Figure 1) B: Dot size is uniform, ink repellency is present (Figure 2) C: Dot size is non-uniform, ink repellency is present (Figure 3)

[0103] 19) Evaluation of water-based ink adhesion The adhesion of the ink gravure printed in 18) was evaluated by cross-cut peeling (25 x 2 mm squares, 90° peeling method using 18 mm wide Cellotape (registered trademark) rcv manufactured by Nichiban Co., Ltd.), and the following ranking was given based on practicality: A: 0 to 5 cross-cut peeled areas B: 6 to 15 cross-cut peeled areas C: 15 or more cross-cut peeled areas

[0104] 20) Adhesion of aluminum vapor-deposited film A 105 mm x 105 mm film was cut out from the obtained film roll, and vapor deposition was performed on the surface of surface layer B using a small vacuum vapor deposition device (VWR-400 / ERH manufactured by ULVAC) to a film thickness of 30 nm, thereby obtaining a vapor-deposited film having an aluminum vapor-deposited film on surface layer B. An 18 mm wide piece of Cellotape (registered trademark) manufactured by Nichiban Co., Ltd. was attached to the aluminum vapor-deposited film of the vapor-deposited film, and the adhesion of the aluminum vapor-deposited film was evaluated by the 90° peeling method. A: No peeling of the aluminum vapor-deposited film was observed. B: Partial peeling of the aluminum vapor-deposited film was observed. C: Peeling of the aluminum vapor-deposited film was observed over the entire surface.

[0105] 21) Oxygen permeability of aluminum vapor-deposited film The oxygen permeability of a vapor-deposited film produced by the manufacturing method described in 20) above was measured in an atmosphere at a temperature of 23°C and a relative humidity of 65% using an oxygen permeability measuring device (OX-TRAN 2 / 20 manufactured by MOCON Corp.) in accordance with the electrolytic sensor method (Appendix A) of JIS K 7126-2. The oxygen permeability was measured in the direction in which oxygen permeated from the substrate layer A side to the aluminum vapor-deposited layer.

[0106] 22) Laminate Strength The laminate strength was measured using the following procedure. Procedure 1) Preparation of a laminate of a biaxially oriented polypropylene film and a non-oriented polypropylene film (heat-sealable film). This was performed using a continuous dry laminating machine as follows. The biaxially oriented polypropylene films obtained in the Examples and Comparative Examples were gravure-coated with an adhesive on the surface layer C side so that the dry coating amount was 2.8 g / m2, and then introduced into a drying zone and dried at 80°C for 5 seconds. Subsequently, the film was laminated with a heat-sealable film between rolls installed downstream (roll pressure: 0.2 MPa, roll temperature: 50°C). The resulting laminate film was wound up and aged for 3 days at 40°C. However, for the film of Example 5, the surface layer C was corona-treated immediately before gravure coating with the adhesive so that the wetting tension was 40 mN / m. The adhesive used was a urethane adhesive obtained by mixing 28.9% by weight of the base agent (TM569, manufactured by Toyo-Morton Co., Ltd.), 4.00% by weight of the curing agent (CAT10L, manufactured by Toyo-Morton Co., Ltd.), and 67.1% by weight of ethyl acetate. The heat-sealable film used was a non-oriented polypropylene film (P1193, thickness 40 μm) manufactured by Toyobo Co., Ltd. Procedure 2) Measurement of Laminate Strength The laminate film obtained above was cut into strips 200 mm long and 15 mm wide, with the longitudinal direction of the biaxially oriented polypropylene film as the long side. Using a tensile tester (Tensilon, manufactured by Orientec Co., Ltd.), the peel strength was measured at a T-peel speed of 200 mm / min under an environment of 23 ° C. and 65% relative humidity. The measurement was performed three times, and the average value was taken as the laminate strength.

[0107] 23) Appearance Evaluation of Heat-Sealed Portions An adhesive (TM329 / CAT8B manufactured by Toyo-Morton Co., Ltd.) was applied to the resulting film, and a 30 μm-thick unstretched polypropylene film (P1128 manufactured by Toyobo Co., Ltd.) was dry-laminated on a metal roll heated to 60°C as a heat-sealable film. The laminate was then aged at 40°C for 3 days to obtain a laminate for evaluation. The heat-sealable films of the laminate were heat-sealed together using a heat sealer to create a 130 mm x 180 mm three-sided sealed bag. The seal was applied at a pressure of 0.2 MPa for 1 second, with a seal bar width of 10 mm and a heat-sealing temperature of 150°C. The appearance of wrinkles in the heat-sealed portions was visually evaluated. A: No wrinkles were observed in the heat-sealed portions in either the width or length direction of the film. B: Wrinkles were observed in the heat-sealed portions in only one of the width or length directions of the film. C: Wrinkles were observed in the heat-sealed portions in both the width and length directions of the film.

[0108] (Raw Material Resins) Details of polypropylene resins PP-1 to PP-7, which are raw materials used in the following Examples and Comparative Examples, are shown in Table 1. The antiblocking agent masterbatch (manufactured by Nippon Pigment Co., Ltd., hereinafter referred to as MB-1) used PP-3 shown in Table 1 as the polypropylene resin, and porous silica particles with an average particle size of 2.9 μm and a pore volume of 1.6 mL / g as the antiblocking agent (AB agent), and the content of the antiblocking agent in MB-1 was 5.0 mass%.

[0109]

[0110] Example 1 A base layer A was made by blending PP-1 at a ratio of 70% by mass and PP-2 at a ratio of 30% by mass. A surface layer B and a surface layer C were made by blending PP-3 at a ratio of 26% by mass, PP-4 at a ratio of 20% by mass, PP-5 at a ratio of 50% by mass, and MB-1 at a ratio of 4% by mass. The base layer A was made by a 45 mm extruder, the surface layer B was made by a 25 mm extruder, and the surface layer C was made by a 20 mm extruder. The raw material resins were melted at 250°C and co-extruded from a T-die into a sheet, and the surface layer B was cooled and solidified so that it came into contact with a cooling roll at 30°C, and then stretched 4.5 times in the longitudinal direction (MD) at 135°C. Next, in a tenter, both ends of the film in the width direction were clamped with clips, preheated to 173 ° C, stretched 8.2 times in the width direction (TD) at 164 ° C, and then heat-set at 171 ° C while relaxing 6.7% in the width direction (TD) to obtain a three-layer laminate consisting of surface layer B / base layer A / surface layer C. The surfaces of surface layer B and surface layer C of the laminate were subjected to corona treatment using a corona treater manufactured by Softal Corona & Plasma GmbH at an applied current of 0.75 A, and then wound up on a winder to obtain a biaxially oriented polypropylene film. The total thickness of the obtained biaxially oriented polypropylene film was 20 μm (thicknesses of surface layer B / base layer A / surface layer C were 1.3 μm / 17.4 μm / 1.3 μm).

[0111] Examples 2 to 7 Biaxially oriented polypropylene films were obtained in the same manner as in Example 1, except that the raw material compositions and film-forming conditions for the surface layer B and the surface layer C were as shown in Tables 2 and 3.

[0112] Comparative Examples 1, 3, and 4 Biaxially oriented polypropylene films were obtained under the same conditions as in Example 1, except that the raw material compositions of the surface layer B and the surface layer C were changed as shown in Table 2.

[0113] (Comparative Example 2) The same as in Example 1 except that the raw material composition of the surface layer B and the surface layer C was changed to 26 mass% of PP-3, a polypropylene resin having a melting point of 163 ° C, 20 mass% of PP-4, a polypropylene resin having a melting point of 159 ° C, and 50 mass% of PP-7, a polypropylene resin having a melting point of 140 ° C, and the film forming conditions were changed to the conditions shown in Table 3. A biaxially oriented polypropylene film was obtained under the same conditions as in Example 1.

[0114] (Comparative Example 5) A biaxially oriented polypropylene film was obtained under the same conditions as in Example 1, except that the raw material composition of the base layer A was changed as shown in Table 2 and only PP-4, a polypropylene-based resin having a melting point of 159°C, was used as the raw material of the base layer A.

[0115] The raw material composition of each layer of the films of the Examples and Comparative Examples, the thickness of each layer, and the film production conditions are shown in Tables 2 and 3, and various physical properties and evaluations of the films of the Examples and Comparative Examples are shown in Table 4.

[0116]

[0117]

[0118]

[0119] The biaxially oriented polypropylene films obtained in Examples 1 to 7 either did not produce guide roll staining or produced extremely little guide roll staining. Furthermore, the resulting film rolls had few wrinkles, and films cut from the film rolls had little water-based ink repellency on Layer B and good adhesion. Furthermore, when aluminum was vapor-deposited, the aluminum vapor-deposited film exhibited excellent adhesion, and the oxygen permeability of the aluminum vapor-deposited film was low, resulting in an excellent gas barrier. Furthermore, when a non-oriented polypropylene film was laminated on the surface layer C, the lamination strength with the non-oriented polypropylene film was high, and the appearance of the heat-sealed portion was also good.

[0120] In contrast, the film of Comparative Example 1 had a low content of polypropylene resin having a melting point of 130° C. or higher and 158° C. or lower in surface layers B and C, and therefore had poor water-based ink printability and adhesion on surface layer B, and also had poor adhesion to the aluminum vapor-deposited film, and the oxygen barrier property of the aluminum vapor-deposited film was inferior to that of the Examples. Furthermore, when an unstretched polypropylene film was further laminated on surface layer C, the lamination strength with the unstretched polypropylene film was poor.

[0121] In Comparative Example 2, a biaxially oriented polypropylene film could be obtained even when the longitudinal stretching temperature, widthwise stretching preheating temperature, and heat setting temperature were lowered, but the antiblocking agent loss rate was high and there was a lot of guide roll contamination. In addition, the water-based ink printability and aluminum vapor deposition film adhesion on the surface layer B were poor.

[0122] In Comparative Example 3, the surface layer B and the surface layer C did not contain a polypropylene-based resin having a melting point of 130° C. or higher and 158° C. or lower, and therefore the water-based ink printability and adhesion on the surface layer B were poor, and the adhesion of the aluminum vapor-deposited film was also poor, and the oxygen barrier property of the aluminum vapor-deposited film was inferior to that of the Examples. Furthermore, when an unstretched polypropylene film was further laminated on the surface layer C, the lamination strength with the unstretched polypropylene film was poor.

[0123] In Comparative Example 4, the surface layer C did not contain a polypropylene-based resin having a melting point of 130° C. or more and 158° C. or less, and therefore the laminate strength was low.

[0124] The film of Comparative Example 5 had a high heat shrinkage rate at 150°C in both the longitudinal and transverse directions because the base layer A was made of a polypropylene resin with a melting point of 159°C. As a result, the laminated laminate had many wrinkles in the heat-sealed area, resulting in a poor appearance and making it unusable as a packaging bag. Furthermore, the oxygen barrier properties of the aluminum vapor-deposited film were also inferior to those of the Examples.

[0125] The biaxially oriented polypropylene film of the embodiment has excellent lamination strength when functional layers such as printed layers, inorganic thin film layers, and coating layers, and heat-sealable films are laminated on both sides to form a laminate, and therefore can be used as a base film for laminates suitable for various uses such as food packaging, labels, and industrial applications, and is therefore industrially useful.

Claims

1. A biaxially oriented polypropylene film having a base layer A made of a polypropylene-based resin composition, a surface layer B made of a polypropylene-based resin composition, and a surface layer C made of a polypropylene-based resin composition, the biaxially oriented polypropylene film satisfying the following (1) to (4): (1) The heat shrinkage rate at 150°C in the longitudinal direction of the biaxially oriented polypropylene film is 0.0% or more and 10.0% or less. (2) The heat shrinkage rate at 150°C in the width direction of the biaxially oriented polypropylene film is 0.0% or more and 15.0% or less. (3) The dropout rate of the antiblocking agent in the surface layer B and the dropout rate of the antiblocking agent in the surface layer C are each 10% or less. (4) The lamination strength is 1.5 N / 15 mm or more.

2. The biaxially oriented polypropylene film according to claim 1, wherein the surface layer B, the surface layer C, or both of these have a wetting tension of 36 mN / m or more.

3. A biaxially oriented polypropylene film as described in claim 1, wherein the surface layer B and the surface layer C each contain a polypropylene-based resin having a melting point of 130°C or higher and 158°C or lower in an amount of 25% by mass or higher and 85% by mass or lower.

4. A biaxially oriented polypropylene film as described in claim 3, wherein the surface layer B and the surface layer C each contain a polypropylene-based resin having a melting point of 159°C or higher and 175°C or lower in an amount of 15% by mass or higher and 75% by mass or lower.

5. The biaxially oriented polypropylene film according to claim 3, wherein the polypropylene resins of the surface layer B and the surface layer C are each a propylene-ethylene-butene copolymer.

6. A biaxially oriented polypropylene film as described in claim 1, wherein the base layer A contains 70% by mass or more of a polypropylene-based resin having a mesopentad fraction ([mmmm]%) of 95.0% or more and 99.9% or less and a melting point of 160°C or more and 175°C or less.

7. The biaxially oriented polypropylene film according to claim 1, wherein the surface resistivity of the surface layer B, the surface layer C, or both of them is 14.0 Log Ω or more and 18 Log Ω or less.

8. A biaxially oriented polypropylene film as described in claim 1, wherein the content of the antiblocking agent in the surface layer B is 100 ppm or more and 10,000 ppm or less, and the content of the antiblocking agent in the surface layer C is 100 ppm or more and 10,000 ppm or less.

9. The biaxially oriented polypropylene film according to claim 8, wherein the antiblocking agent in surface layer B and the antiblocking agent in surface layer C each contain particles having a pore volume of 0.2 mL / g to 3 mL / g.

10. (4) A biaxially oriented polypropylene film according to claim 1, wherein the lamination strength is 10 N / 15 mm or less.

11. A laminate comprising the biaxially oriented polypropylene film according to any one of claims 1 to 10, and further comprising a heat-sealable polyolefin film, in which the surface layer B, the base layer A, the surface layer C, and the heat-sealable polyolefin film are laminated in this order.

12. The laminate according to claim 11, further comprising a functional layer, wherein the functional layer, the surface layer B, the base layer A, the surface layer C, and the heat-sealable polyolefin film are laminated in this order.

13. The laminate according to claim 12, wherein the functional layer is a printed layer, a vapor-deposited layer, or a coated layer.

14. The laminate according to claim 12, further comprising a stretched polyolefin film or a stretched polyester film, wherein the stretched polyolefin film or the stretched polyester film, the functional layer, the surface layer B, the base layer A, the surface layer C, and the heat-sealable polyolefin film are laminated in this order.

Images