Polypropylene film, packaging material, and package

Abstract

A polypropylene film comprising a core layer and a first skin layer, wherein the core layer contains polypropylene, the first skin layer contains polypropylene and an antiblocking agent, and the particle size distribution of the antiblocking agent in the first skin layer has two or more peak values.

Description

Polypropylene film, packaging material, and package

[0001] The present disclosure relates to a polypropylene film, a packaging material, and a package. This application claims priority based on Japanese Patent Application No. 2024-174683 filed in Japan on October 4, 2024, and incorporates its content herein by reference.

[0002] As a packaging material for foods, pharmaceuticals, industrial products, etc., or as a component of industrial products, polypropylene films are widely used. Examples of usage forms include a single-layer sheet made of a single-layer polypropylene film, a laminated sheet in which a polypropylene film is laminated with another sheet material, etc. Examples of other sheet materials laminated with the polypropylene film include polyester-based resin films, vinyl chloride films, paper, etc.

[0003] Generally, polypropylene films are stored in a roll form, but there were problems with storage stability and handling because the films adhered to each other during storage and became difficult to peel off (blocking). Anti-blocking agents are used to improve these problems. Patent Document 1 proposes a laminate for a gas barrier film including a base film containing a resin and an anti-blocking agent, and an inorganic oxide layer laminated on the base film. Patent Document 2 proposes a laminated film having a center layer, an outer layer portion, and an inner layer portion, wherein the first layer and the third layer of the inner layer portion contain an anti-blocking agent. Patent Document 3 proposes a laminated film including a base material containing an anti-blocking agent and a release layer laminated on the base material.

[0004] Japanese Patent Application Laid-Open No. 2024-58265, Japanese Patent Application Laid-Open No. 2024-68066, Japanese Patent Application Laid-Open No. 2024-59273

[0005] However, there is also a problem that the anti-blocking agent falls off from the film. Also, when pulling out the film from the roll, appropriate slipperiness (i.e., to improve handling) is necessary. An object of the present disclosure is to provide a film material that suppresses the dropout of the anti-blocking agent and has appropriate slipperiness.

[0006] The inventors diligently investigated methods for manufacturing films using non-petrochemical materials with low environmental impact as raw materials. As a result, they discovered that by including an antiblocking agent in such a way that it has at least two peaks in the particle size distribution, the shedding of the antiblocking agent can be suppressed, and a polypropylene film with appropriate slipperiness can be obtained, thus completing this disclosure.

[0007] This disclosure has the following aspects: [1] A polypropylene film comprising a core layer and a first skin layer, wherein the core layer comprises polypropylene, the first skin layer comprises polypropylene and an antiblocking agent, and the particle size distribution of the antiblocking agent in the first skin layer has two or more peak values. [2] The polypropylene film according to [1], wherein the thickness of the first skin layer is 0.5 to 5.0 μm. [3] The polypropylene film according to [1] or [2], wherein the particle size of the antiblocking agent is 0.01 to 50 μm. [4] The polypropylene film according to any one of [1] to [3], wherein the ratio A, expressed as (particle size R1 at the largest peak a in the range of 0.1 to 2.5 μm) / (thickness T1 of the first skin layer) in the particle size distribution of the antiblocking agent in the first skin layer, is 0.3 to 2.5. [5] The polypropylene film according to any one of [1] to [4], wherein the ratio B expressed as (particle size R2 at the largest peak b in the range of greater than 2.5 μm and less than or equal to 10 μm) / (thickness T1 of the first skin layer) in the particle size distribution of the antiblocking agent in the first skin layer is 1.0 to 6.0. [6] The polypropylene film according to any one of [1] to [5], wherein the ratio A expressed as (particle size R1 at the largest peak a in the range of 0.1 to 2.5 μm) / (thickness T1 of the first skin layer) to the ratio B expressed as (particle size R2 at the largest peak b in the range of greater than 2.5 μm and less than or equal to 10 μm) / (thickness T1 of the first skin layer) is expressed as B / A and is 1 to 10. [7] The polypropylene film according to any one of [1] to [6], wherein the antiblocking agent comprises at least one selected from the group consisting of resin particles, higher fatty acid particles, higher fatty acid amide particles, higher fatty acid metal salt particles, silica particles, talc particles, zeolite particles, kaolinite particles, and feldspar particles.[8] A polypropylene film according to any one of [1] to [7], further comprising a second skin layer, wherein the first skin layer, the core layer, and the second skin layer are laminated in this order. [9] A polypropylene film according to any one of [1] to [8], wherein the core layer contains biomass-derived propylene units, and the content of the biomass-derived propylene units is 10% by mass or more and 50% by mass or less with respect to the total mass of the polypropylene film.

[10] A polypropylene film according to any one of [1] to [9], wherein at least one of the core layer and the first skin layer contains a phosphorus-based antioxidant, and the content of the phosphorus-based antioxidant is 300 ppm by mass or more and 1000 ppm by mass or less with respect to the total mass of the polypropylene film.

[11] A packaging material comprising the polypropylene film according to any one of [1] to

[10] .

[12] A package in which an article is packaged with the packaging material according to

[11] .

[13] A method for producing a polypropylene film according to any one of [1] to

[10] , comprising forming the first skin layer on one surface of the core layer.

[0008] According to this disclosure, a polypropylene film can be obtained that suppresses the shedding of the antiblocking agent and has appropriate slipperiness.

[0009] Figure 3 is a schematic cross-sectional view showing an example of a polypropylene film according to the present disclosure. It shows an example of the particle size distribution when particle size (μm) is plotted on the horizontal axis and peak intensity (volume frequency) on the vertical axis. Figure 3 is a schematic perspective view showing an example of a packaging according to the present disclosure.

[0010] In this specification, the "~" indicating a numerical range means that the values ​​described before and after it are included as the lower and upper limits. The lower and upper limits of the numerical ranges disclosed in this specification can be arbitrarily combined to form new numerical ranges. In this specification, "biomass raw material" means a raw material obtained from biomass such as corn, sugarcane, and wood (for example, propylene). In this specification, "bio-naphtha" means naphtha produced using biomass as a raw material. "Petroleum naphtha" means naphtha produced using petroleum as a raw material. In this specification, "polypropylene" means a material mainly composed of propylene-based units, and means a homopolymer of propylene or a copolymer having 80% by mass or more of propylene-based units.

[0011] The propylene film of this disclosure comprises a first skin layer and a core layer. Figure 1 is a schematic cross-sectional view showing an example of the propylene film of this disclosure. In Figure 1, the propylene film F of this disclosure comprises a first skin layer S1 and a core layer C. The core layer C may have a second skin layer S2 on the side opposite to the first skin layer S1. The first skin layer S1 has a particle size distribution of antiblocking agents in the first skin layer with two or more peak values. The first skin layer S1 may contain, as an antiblocking agent, an antiblocking agent A1 with a smaller average particle size (hereinafter also referred to as the "first antiblocking agent") and an antiblocking agent A2 with a larger average particle size (hereinafter also referred to as the "second antiblocking agent").

[0012] <Core Layer> In this disclosure, the core layer is a layer containing polypropylene. Preferably, the core layer contains polypropylene having propylene units derived from biomass raw materials (hereinafter also referred to as "biomass-derived P units") (hereinafter also referred to as "first polypropylene (A)").

[0013] (Polypropylene) The first polypropylene (A) contained in the core layer is mainly composed of propylene-based units, and is a homopolymer of propylene or a copolymer having 80% by mass or more of propylene-based units. The copolymer is, for example, a copolymer having propylene-based units and units based on one or more α-olefins. Examples of α-olefins include ethylene, 1-butene, 1-hexene, 1-octene, 4-methylpentene-1, etc. The propylene-based units are preferably 85% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, relative to the total units of the polypropylene. It may also be 100% by mass.

[0014] The content of the first polypropylene (A) relative to the total mass of the core layer is preferably 10 to 100% by mass, more preferably 15 to 100% by mass, and even more preferably 20 to 100% by mass. When the content is below the upper limit, the effect of reducing environmental impact obtained from biomass-derived P units is superior. When the content is above the lower limit, it becomes easier to suppress changes in color and strength over time caused by biomass-derived P units, thus making it easier to prevent a decrease in the commercial value of the product. In addition, it is easier to further improve the excellent physical properties obtained from petroleum naphtha-derived P units.

[0015] The content of biomass-derived P units relative to the total mass of the core layer is preferably 11% to 50% by mass, more preferably 11% to 45% by mass, even more preferably 11% to 40% by mass, and particularly preferably 11% to 35% by mass. When the content of biomass-derived P units is above the lower limit, the effect of reducing environmental impact obtained from biomass-derived P units is superior. Furthermore, when the content of biomass-derived P units is below the upper limit, it becomes easier to suppress changes in color and strength over time caused by biomass-derived P units, thus making it easier to prevent a decrease in the commercial value of the product.

[0016] The first polypropylene (A) may contain biomass-derived P units, and may also contain petroleum naphtha-derived propylene units (hereinafter also referred to as "petroleum naphtha-derived P units"). It is preferable to contain both biomass-derived P units and petroleum naphtha-derived P units because the resulting polypropylene film has excellent physical properties.

[0017] The content of biomass-derived P units relative to the total units of the first polypropylene (A) is preferably 20 to 90% by mass, more preferably 30 to 80% by mass, and even more preferably 40 to 70% by mass. When the content of biomass-derived P units is above the lower limit, the effect of reducing environmental impact obtained from the biomass-derived P units is superior. When the content of biomass-derived P units is below the upper limit, it becomes easier to suppress changes in color and strength over time caused by the biomass-derived P units, thus making it easier to prevent a decrease in the commercial value of the product.

[0018] The content of petroleum naphtha-derived P units relative to the total units of the first polypropylene (A) is preferably 10 to 80% by mass, more preferably 20 to 70% by mass, and even more preferably 30 to 60% by mass. When the content of petroleum naphtha-derived P units is above the lower limit, it becomes easier to suppress changes in color and strength over time caused by biomass-derived P units, thus making it easier to prevent a decrease in the commercial value of the product. In addition, it is easier to further improve the excellent physical properties obtained by petroleum naphtha-derived P units. When the content of petroleum naphtha-derived P units is below the upper limit, the effect of reducing environmental impact obtained by biomass-derived P units is superior.

[0019] The mass ratio expressed as [petroleum naphtha-derived P units] / [biomass-derived P units] is preferably 0.1 to 4, more preferably 0.2 to 2.3, and even more preferably 0.4 to 1.5. When the mass ratio is below the above upper limit, the effect of reducing environmental burden obtained from biomass-derived P units is superior. When the mass ratio is above the above lower limit, it becomes easier to prevent a decrease in the physical properties of the polypropylene film caused by biomass-derived P units, and thus easier to prevent a decrease in the commercial value of the product.

[0020] The first polypropylene (A) may be a copolymer having other units based on monomers other than propylene. The total content of biomass-derived P units and petroleum naphtha-derived P units relative to the total units of the first polypropylene (A) is preferably 80% by mass or more, more preferably 85% by mass, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more. It may also be 100% by mass.

[0021] The first polypropylene (A) preferably contains units based on propylene produced from a mixture of bionaphtha and petroleum naphtha. Propylene produced using a mixture of bionaphtha and petroleum naphtha as raw material naphtha is a mixture of biomass-derived propylene and petroleum naphtha-derived propylene. The ratio of bionaphtha to petroleum naphtha in the raw material naphtha determines the ratio of biomass-derived propylene to petroleum naphtha-derived propylene in the produced propylene. For example, propylene (50 / 50) produced from a mixture consisting of 50% by mass of bionaphtha and 50% by mass of petroleum naphtha is a mixture of 50% by mass of biomass-derived propylene and 50% by mass of petroleum naphtha-derived propylene. With respect to the total units of polypropylene obtained by polymerizing the propylene (50 / 50), the content of biomass-derived P units is 50% by mass and the content of petroleum naphtha-derived P units is 50% by mass.

[0022] The first polypropylene (A) contained in the core layer may be of one type or two or more types. The content of the first polypropylene (A) in the core layer can be designed so that the biomass-derived P units are 10% by mass or more and 50% by mass or less relative to the mass of the polypropylene film.

[0023] The mass-average molecular weight of polypropylene in the core layer is preferably 100,000 to 800,000, more preferably 200,000 to 700,000, and even more preferably 200,000 to 600,000. If the mass-average molecular weight of polypropylene in the core layer is above the lower limit, the mechanical strength of the film is easily improved. If it is below the upper limit, the fluidity of the resin is appropriate, resulting in good sheet moldability and making it easier to improve thickness accuracy during film formation. In this specification, mass-average molecular weight refers to the weight-average molecular weight on a standard polystyrene basis, measured by gel permeation chromatography (GPC).

[0024] (Phosphorus-based antioxidant) The core layer may contain a phosphorus-based antioxidant. The content of the phosphorus-based antioxidant relative to the total mass of the core layer is preferably 300 ppm by mass or more and 1000 ppm by mass or less, and more preferably 300 ppm by mass or more and 700 ppm by mass or less. When the content of the phosphorus-based antioxidant is above the lower limit, it is excellent in suppressing changes in color and strength over time. When the content of the phosphorus-based antioxidant exceeds the upper limit, bleed-out over time is likely to occur, leading to a decrease in transparency and printing properties.

[0025] Examples of phosphorus-based antioxidants include tris(nonylphenyl) phosphite, tris(2,4-di-t-butylphenyl) phosphite, distearyl pentaerythritol diphosphite, bis(2,4-di-t-butylphenyl) pentaerythritol diphosphite, bis(2,4-di-t-butyl-6-methylphenyl) pentaerythritol diphosphite, bis(2,6-di-t-butyl-4-methylphenyl) pentaerythritol diphosphite, bis(2,4-dicumylphenyl) pentaerythritol diphosphite, and tetrakis(2,4-di-t-butylphenyl). Examples include -4,4'-diphenylenediphosnite, 2,2'-methylenebis(4,6-di-t-butylphenyl)2-ethylhexyl phosphite, 2,2'-ethylidenebis(4,6-di-t-butylphenyl)fluorophosphite, bis(2,4-di-t-butyl-6-methylphenyl)ethyl phosphite, 2-(2,4,6-tri-t-butylphenyl)-5-ethyl-5-butyl-1,3,2-oxaphosphorinane, and 2,2',2''-nitrilo[triethyl-tris(3,3',5,5'-tetra-t-butyl-1,1'-biphenyl-2,2'-diyl)phosphite. Among these, tris(2,4-di-t-butylphenyl)phosphite is particularly preferred. It is preferable that the phosphorus-based antioxidant contains tris(2,4-di-t-butylphenyl)phosphite. The proportion of tris(2,4-di-t-butylphenyl) phosphite relative to the total mass of phosphorus-based antioxidants contained in the core layer is preferably 80% by mass or more, more preferably 85% by mass, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more. It may also be 100% by mass.

[0026] The core layer may, depending on quality requirements, contain materials other than the first polypropylene (A) and phosphorus-based antioxidants, to the extent that they do not impair the effects of the present disclosure. Examples of other materials include polypropylene other than the first polypropylene (A) (hereinafter also referred to as "second polypropylene (B)") and resin components such as other resins; as well as optional components such as pigments, dyes, lubricants, antiblocking agents, antistatic agents, ultraviolet absorbers, plasticizers, freshness preservatives, deodorants, compatibilizers, resins other than polypropylene, and antioxidants other than phosphorus-based antioxidants. From the viewpoint of improving adhesion to the skin layer, it is preferable that the core layer does not contain antiblocking agents.

[0027] (Resin components) When the core layer contains resin components other than the first polypropylene (A), the content of the resin components other than the first polypropylene (A) is preferably 10 to 80% by mass, more preferably 30 to 70% by mass, and even more preferably 50 to 60% by mass, relative to the total mass of the core layer. When the content is below the above upper limit, the effect of reducing environmental impact obtained from biomass-derived P units is superior. When the content is above the above lower limit, it is easier to suppress changes in color and strength over time caused by biomass-derived P units, thus making it easier to prevent a decrease in the commercial value of the product. In addition, it is easier to further improve the excellent physical properties obtained from petroleum naphtha-derived P units.

[0028] • Second Polypropylene (B) The polypropylene included in the core layer preferably includes, in addition to the first polypropylene (A), a second polypropylene (B) which contains petroleum naphtha-derived P units but does not contain biomass-derived P units. The second polypropylene (B) included in the core layer mainly consists of propylene-based units and is a propylene homopolymer or a copolymer having 80% by mass or more of propylene-based units. The second polypropylene (B) may also be a copolymer having other units based on monomers other than propylene. Examples of monomers other than propylene are the same as those for α-olefins described for the first polypropylene (A). The content of petroleum naphtha-derived P units relative to the total units of the second polypropylene (B) is preferably 80% by mass or more, more preferably 85% by mass, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more. It may also be 100% by mass.

[0029] The second polypropylene (B) contained in the polypropylene film of this disclosure may be one type or two or more types. The content of the second polypropylene (B) in the polypropylene film of this disclosure can be designed such that the biomass-derived P units in the first polypropylene (A) are 10% by mass or more and 50% by mass or less relative to the mass of the polypropylene film of this disclosure.

[0030] (Optional components) If the core layer contains optional components, the total content of the optional components relative to the mass of the core layer is preferably 3% by mass or less, and more preferably 2% by mass or less. It may also be zero.

[0031] The core layer thickness is preferably 10 to 70 μm, more preferably 12 to 65 μm, and even more preferably 15 to 60 μm. If the core layer thickness is below the above upper limit, it becomes easier to suppress changes in color and strength over time caused by biomass-derived P units, thus making it easier to prevent a decrease in the commercial value of the product. If the core layer thickness is above the above lower limit, the effect of reducing environmental impact obtained from biomass-derived P units is superior.

[0032] <First Skin Layer> In this disclosure, the first skin layer is a layer comprising polypropylene and an antiblocking agent. In this disclosure, the particle size distribution of the antiblocking agent in the first skin layer has two or more peak values.

[0033] (Polypropylene) The polypropylene used in the first skin layer is the same as that used in the core layer. The first skin layer preferably contains the second polypropylene (B) and does not contain the first polypropylene (A). The content of the second polypropylene (B) relative to the total mass of the first skin layer is preferably 80% by mass or more, more preferably 85% by mass, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more. It may also be 100% by mass. If the content of the second polypropylene (B) is below the above upper limit, it is easier to maintain excellent physical properties. If the content of the second polypropylene (B) is above the above lower limit, it is easier to further improve the excellent physical properties obtained from petroleum naphtha-derived P units.

[0034] The mass-average molecular weight of polypropylene in the first skin layer is preferably 50,000 to 800,000, more preferably 100,000 to 700,000, and even more preferably 100,000 to 600,000. If the mass-average molecular weight of polypropylene in the first skin layer is above the lower limit, the mechanical strength of the film is easily improved. If it is below the upper limit, the fluidity of the resin is appropriate, resulting in good sheet moldability and making it easier to improve thickness accuracy during film formation.

[0035] (Anti-blocking agent) In this disclosure, the first skin layer includes an anti-blocking agent. The anti-blocking agent prevents the films from sticking together (blocking) when the films are rolled up and stacked, by forming protrusions on the surface of the polypropylene film. This prevents a deterioration in the quality of the film product due to blocking. In addition, the anti-blocking agent prevents the generation of static electricity when the rolled film is pulled out for use, by forming protrusions on the surface of the polypropylene film. This prevents a deterioration in the handling of the film product due to static electricity.

[0036] Examples of antiblocking agents include inorganic antiblocking agents and organic antiblocking agents. Examples of inorganic antiblocking agents include silica particles, talc particles, zeolite particles, kaolinite particles, and feldspar particles. Examples of organic antiblocking agents include polymethyl methacrylate (PMMA), polysilicon resin, resin particles such as cross-linked polystyrene, higher fatty acid particles, higher fatty acid amide particles, and higher fatty acid metal salt particles. One antiblocking agent may be used, or two or more may be used. When two or more types are used, two or more inorganic antiblocking agents may be used, inorganic antiblocking agents and organic antiblocking agents may be used in combination, or two or more organic antiblocking agents may be used.

[0037] In the first skin layer, the particle size of the antiblocking agent is preferably 0.01 to 50 μm, more preferably 0.1 to 30 μm, and even more preferably 0.3 to 20 μm. When the particle size of the antiblocking agent is below the above upper limit, the difference between the convex and smooth parts on the surface of the skin layer becomes smaller, resulting in better adhesion to the core layer. When the particle size of the antiblocking agent is above the above lower limit, the difference between the convex and smooth parts on the surface of the skin layer becomes of an appropriate size, resulting in better blocking resistance. In this specification, "particle size" refers to an absolute value, not an average value, and can be measured by laser diffraction / scattering.

[0038] In the first skin layer, the average particle size of the antiblocking agent is preferably 0.1 to 10 μm, more preferably 0.2 to 6.0 μm, and even more preferably 0.4 to 4.5 μm. When the average particle size of the antiblocking agent is below the above upper limit, the adhesion to the core layer is superior. When the average particle size of the antiblocking agent is above the above lower limit, the blocking resistance is superior. In this specification, the "average particle size of the antiblocking agent" can be measured by laser diffraction / scattering.

[0039] In this disclosure, the particle size distribution of the antiblocking agent in the first skin layer has two or more peak values. Having two or more peak values ​​forms protrusions of different heights on the surface of the first skin layer. This makes it possible to achieve antiblocking properties and slipperiness, prevention of detachment of the antiblocking agent, adhesion to the core layer, and ease of winding when rolled (excellent handling).

[0040] It is preferable that the first skin layer contains two or more antiblocking agents with different average particle sizes (hereinafter, the antiblocking agent with the smaller average particle size will also be referred to as the "first antiblocking agent," and the antiblocking agent with the larger average particle size will also be referred to as the "second antiblocking agent"). The two or more different antiblocking agents may be of the same type or of different types.

[0041] Figure 2 is a schematic diagram showing the particle size distribution of two or more antiblocking agents with different average particle sizes. It is an example of a particle size distribution when particle size (μm) is plotted on the horizontal axis (x axis) and peak intensity (volume frequency) is plotted on the vertical axis (y axis). As shown in Figure 2, the particle size distribution has at least two peaks. (Method for measuring particle size peaks) The dispersion of the antiblocking agent is measured using a particle size distribution analyzer (for example, Nikkiso Co., Ltd. Microtrac MT3300EX2) by laser diffraction / scattering method, and a volume-based particle size distribution graph is created. In the present invention, the peaks of the particle size distribution of the antiblocking agent are defined as follows. In the particle size distribution graph, a protrusion of 5% or more of the particle frequency of the highest peak particle size is considered a peak. The largest peak in the range of 0.1 to 2.5 μm is considered peak a, and the largest peak in the range of over 2.5 μm and up to 10 μm is considered peak b. The number of peaks may be more than two, but two is preferred. If there are more than two peaks, the difference in height of the protrusions is mitigated, making it easier to improve slipperiness. However, if there are two peaks, a moderate difference in height of the protrusions is created, making it easier to enhance the anti-blocking effect.

[0042] The average particle diameter of the first anti-blocking agent is preferably 0.1 to 2.5 μm, more preferably 0.3 to 2.4 μm, and even more preferably 0.6 to 2.2 μm. When the average particle diameter of the first anti-blocking agent is below the above upper limit value, an appropriate particle size difference occurs with the average particle diameter of the second anti-blocking agent, so that the difference between the convex portion and the smooth portion on the surface of the skin layer becomes an appropriate size, and thus the anti-blocking property is more excellent. When the average particle diameter of the first anti-blocking agent is above the above lower limit value, the difference from the average particle diameter of the second anti-blocking agent becomes small, so that the difference between the convex portion and the smooth portion on the surface of the skin layer becomes small, and thus the adhesiveness with the core layer is more excellent. Further, since the difference from the average particle diameter of the second anti-blocking agent becomes small, it is easy to suppress the dropout of the anti-blocking agent.

[0043] The average particle diameter of the second anti-blocking agent is preferably more than 2.5 μm and at most 10 μm, more preferably 2.8 to 6 μm, even more preferably 2.8 to 5 μm, particularly preferably 2.9 to 4.5 μm, and most preferably 2.9 to 4.2 μm. When the average particle diameter of the second anti-blocking agent is below the above upper limit value, the difference from the average particle diameter of the first anti-blocking agent becomes small, so that the difference between the convex portion and the smooth portion on the surface of the skin layer becomes small, and thus the adhesiveness with the core layer is more excellent. Further, since the difference from the average particle diameter of the first anti-blocking agent becomes small, it is easy to suppress the dropout of the anti-blocking agent. When the average particle diameter of the second anti-blocking agent is above the above lower limit value, an appropriate particle size difference occurs with the average particle diameter of the first anti-blocking agent, so that the difference between the convex portion and the smooth portion on the surface of the skin layer becomes an appropriate size, and thus the anti-blocking property is more excellent.

[0044] - First antiblocking agent The average particle size of the first antiblocking agent is preferably 0.1 to 2.5 μm, more preferably 0.3 to 2.3 μm, and even more preferably 0.5 to 2.2 μm. If the average particle size of the first antiblocking agent is below the above upper limit, an appropriate particle size difference is created between it and the average particle size of the second antiblocking agent, resulting in an appropriate difference in size between the convex and smooth areas on the surface of the skin layer, thereby improving blocking resistance. If the average particle size of the first antiblocking agent is above the above lower limit, the difference with the average particle size of the second antiblocking agent becomes smaller, resulting in a smaller difference between the convex and smooth areas on the surface of the skin layer, thereby improving adhesion to the core layer.

[0045] The content of the first antiblocking agent relative to the total mass of the first skin layer is preferably 0.05 to 0.7% by mass, more preferably 0.07 to 0.5% by mass, and even more preferably 0.1 to 0.3% by mass. When the content of the first antiblocking agent is below the above upper limit, the difference between the convex and smooth parts on the surface of the skin layer becomes of an appropriate size, making it easier to improve the blocking resistance of the second antiblocking agent. When the content of the first antiblocking agent is above the above lower limit, it becomes easier to improve the blocking resistance of the first antiblocking agent, and the difference between the convex and smooth parts on the surface of the skin layer becomes smaller, resulting in better adhesion to the core layer.

[0046] The ratio A, expressed as (particle size R1 at the largest peak a in the range of 0.1 to 2.5 μm) / (thickness T1 of the first skin layer), is preferably 0.2 to 2.5, more preferably 0.25 to 2.0, and even more preferably 0.3 to 1.5. When the ratio A is below the upper limit, the difference between the convex and smooth portions on the surface of the skin layer becomes of an appropriate size, resulting in superior blocking resistance. When the ratio A is above the lower limit, the difference between the convex and smooth portions on the surface of the skin layer becomes smaller, resulting in superior adhesion to the core layer.

[0047] When the first anti-blocking agent is resin particles, the mass average molecular weight of the resin is preferably from 1,000 to 2,000,000, more preferably from 10,000 to 1,500,000, and still more preferably from 100,000 to 1,000,000. When the mass average molecular weight of the resin is at least the above lower limit value, the heat resistance and abrasion resistance are excellent and the durability is easily improved. When it is at most the above upper limit value, the processability is excellent and the dispersibility is easily improved.

[0048] - Second anti-blocking agent The average particle diameter of the second anti-blocking agent is preferably more than 2.5 μm and at most 10 μm, more preferably from 2.8 to 6 μm, still more preferably from 2.8 to 5 μm, particularly preferably from 2.9 to 4.5 μm, and most preferably from 2.9 to 4.2 μm. When the average particle diameter of the second anti-blocking agent is at most the above upper limit value, it is easy to prevent the second anti-blocking agent from dropping off from the first skin layer. Further, since the difference from the average particle diameter of the first anti-blocking agent becomes small, the difference between the convex portion and the smooth portion on the skin layer surface becomes small, and thus the adhesiveness to the core layer is more excellent. When the average particle diameter of the second anti-blocking agent is at least the above lower limit value, an appropriate particle diameter difference occurs between the average particle diameter of the second anti-blocking agent and that of the first anti-blocking agent. As a result, the difference between the convex portion and the smooth portion on the skin layer surface becomes an appropriate size, and thus the anti-blocking property is more excellent.

[0049] With respect to the total mass of the first skin layer, the content of the second anti-blocking agent is preferably from 0.01 to 0.4% by mass, more preferably from 0.02 to 0.3% by mass, and still more preferably from 0.02 to 0.2% by mass. When the content of the second anti-blocking agent is at most the above upper limit value, it is easy to prevent the second anti-blocking agent from dropping off from the first skin layer, and it is easy to enhance the anti-blocking property by the first anti-blocking agent. The difference between the convex portion and the smooth portion on the skin layer surface becomes small, and thus the adhesiveness to the core layer is more excellent. When the content of the second anti-blocking agent is at least the above lower limit value, it is easy to enhance the anti-blocking property by the second anti-blocking agent, and the difference between the convex portion and the smooth portion on the skin layer surface becomes an appropriate size, and thus it is easy to enhance the anti-blocking property.

[0050] The ratio B, expressed as (particle size R2 at the largest peak b in the range of over 2.5 μm and under 10 μm) / (thickness T1 of the first skin layer), is preferably 0.6 to 6.0, more preferably 0.8 to 5.0, and even more preferably 1.0 to 4.5. When the ratio B is below the upper limit, it becomes easier to prevent the second antiblocking agent from falling off the first skin layer, and the difference between the convex and smooth parts on the surface of the skin layer becomes smaller, resulting in better adhesion to the core layer. When the ratio B is above the lower limit, the difference between the convex and smooth parts on the surface of the skin layer becomes of an appropriate size, resulting in better blocking resistance.

[0051] The ratio of ratio A, expressed as (particle diameter R1 at the largest peak a in the range of 0.1 to 2.5 μm) / (thickness T1 of the first skin layer) to ratio B, expressed as (particle diameter R2 at the largest peak b in the range of greater than 2.5 μm and less than or equal to 10 μm) / (thickness T1 of the first skin layer), is preferably 1 to 10, more preferably 1.3 to 8, and even more preferably 1.5 to 7, expressed as B / A. When B / A is less than or equal to the above upper limit, it becomes easier to prevent the second antiblocking agent from falling off the first skin layer, and the difference between the convex and smooth parts on the surface of the skin layer becomes smaller, resulting in better adhesion to the core layer. When B / A is greater than or equal to the above lower limit, the difference between the convex and smooth parts on the surface of the skin layer becomes an appropriate size, resulting in better blocking resistance.

[0052] The particle size ratio, expressed as (particle size R2 at the largest peak b in the range of over 2.5 μm and under 10 μm) / (particle size R1 at the largest peak a in the range of 0.1 to 2.5 μm), is preferably 1 to 10, more preferably 1.3 to 8, and even more preferably 1.5 to 7, expressed as R2 / R1. When R2 / R1 is below the above upper limit, it becomes easier to prevent the second antiblocking agent from falling off the first skin layer, and the difference between the convex and smooth parts on the surface of the skin layer becomes smaller, resulting in better adhesion to the core layer. When R2 / R1 is above the above lower limit, the difference between the convex and smooth parts on the surface of the skin layer becomes an appropriate size, resulting in better blocking resistance.

[0053] The particle size difference, expressed as (particle size R2 at the largest peak b in the range of over 2.5 μm and under 10 μm) - (particle size R1 at the largest peak a in the range of 0.1 to 2.5 μm), is preferably 0.1 to 6.0, more preferably 0.1 to 4.0, and even more preferably 0.2 to 3.5, expressed as R2 - R1. When R2 - R1 is below the above upper limit, it becomes easier to prevent the second antiblocking agent from falling off the first skin layer, and the difference between the convex and smooth parts on the surface of the skin layer becomes smaller, resulting in better adhesion to the core layer. When R2 - R1 is above the above lower limit, the difference between the convex and smooth parts on the surface of the skin layer becomes an appropriate size, resulting in better blocking resistance.

[0054] The mass ratio expressed as (content of first antiblocking agent) / (content of second antiblocking agent) is preferably 1 to 10, more preferably 1 to 5, and even more preferably 1 to 3. When the mass ratio is below the upper limit, it becomes easier to prevent the second antiblocking agent from falling off the first skin layer, and the difference between the convex and smooth parts on the surface of the skin layer becomes smaller, resulting in better adhesion to the core layer. When the mass ratio is above the lower limit, it becomes easier to improve the blocking resistance of the second antiblocking agent, and the difference between the convex and smooth parts on the surface of the skin layer becomes an appropriate size, resulting in better blocking resistance.

[0055] When the second antiblocking agent is resin particles, the mass-average molecular weight of the resin is preferably 1,000 to 2,000,000, more preferably 10,000 to 1,500,000, and even more preferably 100,000 to 1,000,000. If the mass-average molecular weight of the resin is above the lower limit, it is easy to improve heat resistance, abrasion resistance, and durability. If it is below the upper limit, it is easy to improve processability and dispersibility.

[0056] (Phosphorus-based antioxidant) The first skin layer may contain a phosphorus-based antioxidant. The content of the phosphorus-based antioxidant relative to the total mass of the first skin layer is preferably 300 ppm by mass or more and 1000 ppm by mass or less, and more preferably 300 ppm by mass or more and 700 ppm by mass or less. When the content of the phosphorus-based antioxidant is above the lower limit, it is excellent in suppressing changes in color and strength over time. When the content of the phosphorus-based antioxidant exceeds the upper limit, bleed-out over time is likely to occur, leading to a decrease in transparency and printing properties.

[0057] In this disclosure, the thickness of the first skin layer is preferably 0.5 to 5.0 μm, more preferably 0.6 to 4.5 μm, and even more preferably 0.7 to 4.0 μm. When the thickness of the first skin layer is below the above upper limit, it becomes easier to further improve the blocking resistance derived from the antiblocking agent. When the thickness of the first skin layer is above the above lower limit, it becomes easier to maintain the mechanical strength of the polypropylene film.

[0058] <Second Skin Layer> In this disclosure, the polypropylene film may have a second skin layer on the side of the core layer opposite to the first skin layer. Preferably, the second skin layer contains a second polypropylene (B) and does not contain the first polypropylene (A). The same material as the first skin layer can be used for the second skin layer. The composition of the first skin layer and the composition of the second skin layer may be the same or different, but it is preferable that they be the same. The thickness of the first skin layer and the thickness of the second skin layer may be the same or different, but it is preferable that they be the same.

[0059] ≪Characteristics of Polypropylene Film≫ Polypropylene film may be uniaxially oriented or biaxially oriented. The stretching ratio is preferably 3 to 6 times in the MD direction and 8 to 12 times in the TD direction. The density of the polypropylene film is not particularly limited, but for example, 0.90 to 0.92 g / cm³ is preferable. ３ The density is a value measured using a dry densimeter or density gradient tube. The thickness of the polypropylene film is not particularly limited, but for example, it is 15 μm to 80 μm.

[0060] The resistance of the antiblocking agent to shedding of the polypropylene film, as measured by the method described in the examples, is preferably grade 3 or lower, more preferably grade 2 or lower, and even more preferably grade 1. If the shedding of the antiblocking agent is below the above upper limit, it becomes easier to prevent a decrease in the commercial value of the product, and thus it is easier to maintain excellent physical properties.

[0061] The YI value change rate (%) of the polypropylene film of this disclosure, which can be measured by the method described in the examples, is preferably 20% or less, more preferably 15% or less, and even more preferably 10% or less. It may also be 0%. When the YI value change rate (%) is below the above upper limit, it is easier to suppress changes in color and strength over time caused by biomass-derived P units, thereby making it easier to prevent a decrease in the commercial value of the product, and also provides a superior effect in reducing the environmental burden obtained from biomass-derived P units.

[0062] The percentage change in strength (%) of the polypropylene film of this disclosure, as measured by the method described in the examples, is preferably 20% or less, more preferably 15% or less, and even more preferably 10% or less. It may also be 0%. When the percentage change in strength (%) is below the above upper limit, it is easier to suppress the decrease in mechanical strength caused by biomass-derived P units, thereby making it easier to prevent a decrease in the commercial value of the product, and also provides a superior effect in reducing the environmental burden obtained from biomass-derived P units.

[0063] The transparency change rate (%) of the polypropylene film of this disclosure, as measured by the method described in the examples, is preferably 8% or less, more preferably 6% or less, and even more preferably 4% or less. It may also be 0%. When the YI value change rate (%) is below the above upper limit, it becomes easier to suppress changes in color and strength over time caused by biomass-derived P units, thereby making it easier to prevent a decrease in the commercial value of the product, and also provides a superior effect in reducing the environmental burden obtained from biomass-derived P units.

[0064] The haze value (%) of the polypropylene film disclosed herein, as measured by the method described in the examples, is preferably 20% or less, more preferably 10% or less, and even more preferably 5% or less. When the haze value (%) is below the above upper limit, the visibility of the contents and printed materials is improved when laminated to packaging bags or printed materials, resulting in superior functionality as a film product.

[0065] The blocking resistance of the polypropylene film disclosed herein, as measured by the method described in the examples, is preferably grade 3 or lower, more preferably grade 2 or lower, and even more preferably grade 1. When the blocking resistance is below the above upper limit, it is easier to prevent the films from sticking together and becoming difficult to peel off during storage, thus maintaining the quality of the product, and thus providing better storage and handling properties.

[0066] The slipperiness of the polypropylene film of this disclosure, as measured by the method described in the examples, is preferably 0.70 or less, more preferably 0.60 or less, and even more preferably 0.50 or less. When the slipperiness is below the above upper limit, the handling of the film product is excellent in processes such as printing and bag making, and it is easier to prevent wrinkles from forming when manufacturing or molding the film. When the slipperiness is above the above lower limit, it prevents misalignment of the film during manufacturing or molding, resulting in better work efficiency.

[0067] ≪Method for Manufacturing Polypropylene Film≫ The method for manufacturing the polypropylene film according to the present disclosure includes: forming a resin composition for a core layer containing polypropylene into a sheet to obtain an unstretched sheet; biaxially stretching the unstretched sheet to obtain a polypropylene film for a core layer; forming a resin composition for a first skin layer containing polypropylene and an antiblocking agent into a sheet to obtain an unstretched sheet; biaxially stretching the unstretched sheet to obtain a polypropylene film for a first skin layer; and laminating and bonding the obtained polypropylene film for a core layer and the polypropylene film for a first skin layer to obtain a laminate. As a biaxial stretching method, for example, the tenter sequential biaxial stretching method is preferred. From the viewpoint of adhesion between the core layer and the skin layer, the method for manufacturing the polypropylene film according to the present disclosure is preferably the tenter sequential biaxial stretching method using a co-extrusion die. Specifically, a preferred method includes co-extruding the resin composition for a core layer and the resin composition for a first skin layer to obtain a laminate. By using a co-press die, the polypropylene resin for the core layer can more easily conform to the irregularities on the surface of the polypropylene resin for the first skin layer, resulting in superior adhesion between the first skin layer and the core layer. When a second skin layer is present, a preferred method includes co-pressing the resin composition for the core layer, the resin composition for the first skin layer, and the resin composition for the second skin layer to obtain a laminate.

[0068] (Core layer resin composition) The core layer resin composition contains polypropylene. Preferably, the polypropylene contains the first polypropylene (A). The content of the first polypropylene (A) relative to the total mass of the core layer resin composition is preferably 10 to 100% by mass, more preferably 15 to 100% by mass, and even more preferably 20 to 100% by mass. If the content is below the upper limit, the effect of reducing environmental impact obtained from biomass-derived P units is superior. If the content is above the lower limit, it is easier to suppress changes in color and strength over time caused by biomass-derived P units, thus making it easier to prevent a decrease in the commercial value of the product. In addition, it is easier to further improve the excellent physical properties obtained from petroleum naphtha-derived P units.

[0069] The content of phosphorus-based antioxidants relative to the total mass of the core layer resin composition is preferably 300 ppm by mass or more and 1000 ppm by mass or less, and more preferably 300 ppm by mass or more and 700 ppm by mass or less. When the content of phosphorus-based antioxidants is above the lower limit, it is excellent in suppressing changes in color and strength over time. When the content of phosphorus-based antioxidants exceeds the upper limit, bleed-out over time is likely to occur, leading to a decrease in transparency and printing properties.

[0070] The content of resin components other than the first polypropylene (A) relative to the total mass of the core layer resin composition is preferably 5 to 90% by mass, more preferably 10 to 85% by mass, and even more preferably 15 to 80% by mass. When the content is below the upper limit, the environmental impact reduction effect obtained from biomass-derived P units is superior. When the content is above the lower limit, it becomes easier to suppress changes in color and strength over time caused by biomass-derived P units, thus making it easier to prevent a decrease in the commercial value of the product. In addition, it is easier to further improve the excellent physical properties obtained from petroleum naphtha-derived P units.

[0071] (Resin composition for the first skin layer) The resin composition for the first skin layer contains polypropylene and an antiblocking agent. The content of the second polypropylene (B) relative to the total mass of the resin composition for the first skin layer is preferably 80% by mass or more, more preferably 85% by mass, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more. It may also be 100% by mass. If the content of the second polypropylene (B) is below the above upper limit, it is easier to maintain excellent physical properties. If the content of the second polypropylene (B) is above the above lower limit, it is easier to further improve the excellent physical properties obtained from petroleum naphtha-derived P units.

[0072] The content of the first antiblocking agent relative to the total mass of the resin composition for the first skin layer is preferably 0.05 to 0.7% by mass, more preferably 0.07 to 0.5% by mass, and even more preferably 0.1 to 0.3% by mass. If the content of the first antiblocking agent is below the above upper limit, it becomes easier to improve the blocking resistance of the second antiblocking agent. If the content of the first antiblocking agent is above the above lower limit, the adhesion to the core layer is better.

[0073] The content of the second antiblocking agent relative to the total mass of the resin composition for the first skin layer is preferably 0.01 to 0.4% by mass, more preferably 0.02 to 0.3% by mass, and even more preferably 0.02 to 0.2% by mass. When the content of the second antiblocking agent is below the above upper limit, the adhesion to the core layer is superior. When the content of the second antiblocking agent is above the above lower limit, it becomes easier to improve the blocking resistance by the second antiblocking agent.

[0074] (Resin composition for the second skin layer) The resin composition for the second skin layer may be the same as that for the first skin layer.

[0075] ≪Laminate≫ A laminate according to one embodiment of the present disclosure is a laminate comprising a plurality of layers, wherein at least one layer consists of the polypropylene film of the present disclosure. Examples include a laminate obtained by laminating a plurality of polypropylene films of the present disclosure together, and a laminate obtained by laminating one or more layers consisting of the polypropylene film of the present disclosure and one or more layers consisting of a material different from the polypropylene film of the present disclosure. Examples of layers consisting of a material different from the polypropylene film of the present disclosure include resin films other than the polypropylene film of the present disclosure, paper, etc. Methods for manufacturing the laminate include lamination with other films, such as dry lamination and hot melt lamination. Among these, dry lamination using gravure roll coating equipment is preferred.

[0076] ≪Packaging Material≫ The packaging material of this disclosure comprises the polypropylene film of this disclosure. The polypropylene film may be used as a packaging material as is, or the polypropylene film (F) may be processed in some way to become a packaging material. Known processing methods can be applied as processing. For example, the edges of the polypropylene film may be bonded together using an adhesive or heat-sealed to form a bag-shaped packaging material. Alternatively, the edges of the polypropylene film of this disclosure may be bonded together or heat-sealed to form a bag-shaped packaging material.

[0077] ≪Packaging≫ A packaging according to one embodiment of the present disclosure is one in which an article is packaged in the packaging material of the present disclosure. Figure 3 is a schematic perspective view showing an example of the packaging of the present disclosure. As shown in Figure 3, the packaging P is in which an article G is packaged in the packaging material PM of the present disclosure. The internal space may be filled with an inert gas such as nitrogen gas, or it may be an unfilled, vacuum-packed space. Examples of articles include general merchandise, food products, clothing, etc. Known packaging methods can be applied as the packaging method.

[0078] ≪Effects≫ The polypropylene film of this disclosure contains an antiblocking agent having at least two different particle sizes in the first skin layer. The effects obtained by using antiblocking agents with two different particle sizes are presumed to be as follows, although the detailed mechanism is not clear. When only an antiblocking agent with a large particle size is used, sufficient blocking resistance can be obtained, but adhesion to the core layer and ease of winding when rolled (handling) are poor, and because only large protrusions are formed, the antiblocking agent is prone to falling off due to frictional forces generated during handling. On the other hand, when only an antiblocking agent with a small particle size is used, sufficient adhesion to the core layer and ease of winding when rolled can be obtained, but because only small protrusions are formed, blocking resistance is poor. In order to balance these, it is presumed that by using antiblocking agents with two different particle sizes, blocking resistance and slipperiness, prevention of antiblocking agent detachment, adhesion to the core layer, and ease of winding when rolled can be achieved. Furthermore, even when the polypropylene film disclosed herein contains polypropylene derived from biomass raw materials in the core layer, it does not reduce color or tensile strength, and has excellent adhesion to the first skin layer containing an antiblocking agent, making it resistant to peeling. This prevents a decrease in product value and reduces environmental impact.

[0079] The present disclosure will be specifically explained below with reference to examples. However, this disclosure is not limited in any way to these examples. Unless otherwise specified, the unit of content, "%", refers to "mass%". The measurement and evaluation methods used in each example are shown below.

[0080] (1) Resistance to detachment of antiblocking agent The detachment resistance of the antiblocking agent was measured by rubbing the film surfaces together using the friction fastness tester "RT-300" manufactured by Daiei Kagaku Seiki Seisakusho Co., Ltd. Two types of samples were prepared: one for the friction element and one for the measurement stand. The sample for the friction element was cut to a size of 20 mm in the width direction and 70 mm in the flow direction. The sample for the measurement stand was cut to a size of 200 mm in the width direction and 170 mm in the flow direction. The surface of each sample was rubbed 10 times back and forth under the conditions of a 200 g load, a sliding distance of 120 mm, and a reciprocating speed of 30 cycles / min. After rubbing, the area of ​​scratches on the surface of the measurement stand sample was checked with a digital microscope "VHX-2000" manufactured by Keyence Corporation, and the detachment resistance of the antiblocking agent was determined according to the following criteria. Grade 1: No scratches Grade 2: Scratches occur, but within less than 10% of the friction area Grade 3: Scratches occur, but within 10% to less than 25% of the friction area Grade 4: Scratches occur, but within 25% to less than 50% of the friction area Grade 5: Scratches occur in an area exceeding 50% of the friction area The resistance of the antiblocking agent to shedding was evaluated according to the following criteria: ○: Antiblocking agent shedding resistance is Grade 2 or lower ×: Antiblocking agent shedding resistance exceeds Grade 2

[0081] (2) Color The YI value of the film was measured using a spectrochromatic colorimeter / haze meter "COH7700" manufactured by Nippon Denshoku Industries Co., Ltd. The film was stored at 23°C for 3 months, and the YI value at the start of storage (initial YI) and the YI value after 3 months (YI after 3 months) were measured. The rate of change in the YI value (unit: %) was calculated using the following formula. The effect of suppressing the change in color over time was evaluated according to the following criteria. Rate of change in YI value = (YI after 3 months - initial YI) / initial YI × 100 ○: YI value change rate after 3 months at 23°C is within 20% ×: YI value change rate after 3 months at 23°C exceeds 20%

[0082] (3) Tensile Strength The tensile strength in the flow direction was measured using a tensile testing machine in accordance with JIS K7127. The sample was cut to a size of 15 mm in the width direction and 200 mm in the flow direction, and the test was performed under the condition of a tensile speed of 200 mm / min. The strength at which the film broke was measured. The film was stored at 90°C for one month, and the strength at the start of storage (initial strength) and the strength after one month (strength after one month) were measured, and the strength change rate (unit: %) was calculated using the following formula. The effect of suppressing the change in tensile strength over time was evaluated according to the following criteria. Strength change rate = (initial strength - strength after one month) / initial strength × 100 ○: Strength change rate after one month at 90°C is within 20% ×: Strength change rate after one month at 90°C exceeds 20%

[0083] (4) Transparency The transparency of the film was measured using a transparency meter "CLARITY-METER TM-1D (product name)" manufactured by Murakami Color Technology Research Institute. The film was stored at 23°C for 3 months, and the transparency at the start of storage (initial transparency) and the transparency after 3 months (transparency after 3 months) were measured. The transparency change rate (unit: %) was calculated using the following formula. The effect of suppressing the change in transparency over time was evaluated according to the following criteria. Transparency change rate = (initial transparency - transparency after 3 months) / initial transparency × 100 ○: Transparency change rate after 3 months at 23°C is within 8% ×: Transparency change rate after 3 months at 23°C exceeds 8%

[0084] (5) Haze was measured according to the method described in JIS K 7136:2000.

[0085] (6) Blocking resistance samples were cut to a size of 50 mm in the width direction x 50 mm in the flow direction, and two films were stacked with their measurement surfaces aligned. A 2 kg weight was placed on top of the stack and stored at 40°C, 70% RH for 24 hours, and the degree of blocking was measured by peeling by hand. Grade 1: Peels off without resistance Grade 2: Peels off with some resistance Grade 3: Peels off with considerable resistance Grade 4: Does not peel off. After peeling once, it slides when stacked again Grade 5: Does not peel off. After peeling once, it does not slide even when stacked again Blocking resistance was evaluated according to the following criteria: ○: Blocking degree of 3 or less ×: Blocking degree of 3 or more

[0086] (7) The coefficient of friction for sliding properties was measured using a tensile testing machine. Two types of samples were prepared: one for the sliding side and one for the testing stand side. The sample for the sliding side was cut to a size of 120 mm in the width direction and 70 mm in the flow direction. The sample for the testing stand side was cut to a size of 150 mm in the width direction and 200 mm in the flow direction. The sample for the sliding side was wrapped in a 63 mm square, 1.96 N sliding piece, and the friction force was measured at a friction distance of 100 mm under conditions of 23°C, 50% RH and a tensile speed of 200 mm / min. The coefficient of dynamic friction was calculated using the following formula: Coefficient of dynamic friction = Friction force at 100 mm friction / Weight of the sliding piece. The sliding properties were evaluated according to the following criteria: ○: Coefficient of dynamic friction is 0.70 or less ×: Coefficient of dynamic friction is greater than 0.70

[0087] (8) Reduction of environmental impact ○: Contains biomass-derived polypropylene, resulting in a low environmental impact. ×: Does not contain biomass-derived polypropylene, resulting in a high environmental impact.

[0088] (9) The content of phosphorus-based antioxidants in the polypropylene film was determined by extracting the antioxidants from the film and measuring them by HPLC-PDA analysis.

[0089] The biomass-derived P unit content in the polypropylene film was calculated based on the biomass-derived P unit content in each raw material resin composition and the blending ratio of each raw material resin composition. It can also be measured by measuring the C14 concentration using accelerator mass spectrometry (AMS).

[0090] <Raw Materials> [Raw material resin composition containing the first polypropylene (A)] The following bioPP (A1) is a resin composition containing polypropylene produced by polymerizing propylene generated from raw material naphtha, which is a mixture of 50% by mass of bionaphtha and 50% by mass of petroleum naphtha, and tris(2,4-di-t-butylphenyl) phosphite, which is a phosphorus-based antioxidant. The content of biomass-derived P units relative to the total units of polypropylene is 50% by mass. BioPP (A1): Polypropylene (mass average molecular weight: 270,000) 99.20% by mass, phosphorus-based antioxidant 0.10% by mass, additives other than phosphorus-based antioxidant 0.70% by mass.

[0091] [Second raw material resin composition containing polypropylene (B)] The following petroleum PP (B1) is a resin composition containing polypropylene produced by polymerizing propylene generated from 100% petroleum naphtha raw material naphtha, and tris(2,4-di-t-butylphenyl) phosphite, which is a phosphorus-based antioxidant. Petroleum PP (B1): Polypropylene (mass average molecular weight: 300,000) 99.16% by mass, phosphorus-based antioxidant 0.04% by mass, additives other than phosphorus-based antioxidant 0.80% by mass.

[0092] [First Antiblocking Agent] Organic antiblocking agent (PMMA) (particle size: 0.4-4.0 μm, average particle size: 1.8 μm, mass-average molecular weight: 300,000, manufactured by Sankyo Chemical Industry Co., Ltd.)

[0093] [Second Antiblocking Agent] Organic antiblocking agent (PMMA) (particle size: 0.6-10 μm, average particle size: 3.0 μm, mass-average molecular weight: 300,000, manufactured by Sankyo Chemical Industry Co., Ltd.)

[0094] <Example 1> Using the configuration shown in Table 1, the raw material resin composition was melted at 230°C in an extruder, and the layers were laminated in the extruder so that the thickness ratio of the first skin layer / core layer / second skin layer was 5 / 90 / 5, and an extruded laminated sheet was obtained from a co-extrusion die. The core layer consisted of a mixture of petroleum PP (B1) and bio PP (A1). The laminated sheet was cooled by contact with a roll at 30°C, then longitudinally stretched 4.7 times at 140°C, and subsequently transversely stretched 10 times at 165°C, resulting in a thickness of 30 μm and a density of 0.90 g / cm³. ３ A biaxially oriented polypropylene film was obtained. In this example, the biomass-derived P unit content was 10% by mass of the polypropylene film, and the phosphorus-based antioxidant content was 350 ppm.

[0095] <Examples 2-9> Biaxially oriented polypropylene films were prepared in the same manner as in Example 1, except that the raw material composition and thickness were changed to match the compositions shown in Tables 1 and 2.

[0096] <Evaluation> Each polypropylene film obtained in Examples 1 to 9 was evaluated for the items listed in the table. The results are shown in Tables 2 and 3.

[0097]

[0098]

[0099]

[0100] As shown in the results above, the polypropylene films of Examples 1 to 9 had a low environmental impact and showed minimal changes in color, mechanical properties, and transparency over time. Furthermore, they exhibited excellent storage and handling properties, suppressed the shedding of antiblocking agents, and demonstrated superior blocking resistance and slipperiness.

[0101] The polypropylene film disclosed herein is a polypropylene film that suppresses the shedding of antiblocking agents and has moderate slipperiness, making it useful as an excellent packaging material.

[0102] A1 First antiblocking agent A2 Second antiblocking agent S1 First skin layer C Core layer S2 Second skin layer P Packaging G Article PM Packaging material

Claims

1. A polypropylene film comprising a core layer and a first skin layer, wherein the core layer comprises polypropylene, the first skin layer comprises polypropylene and an antiblocking agent, and the particle size distribution of the antiblocking agent in the first skin layer has two or more peak values.

2. The polypropylene film according to claim 1, wherein the thickness of the first skin layer is 0.5 to 5.0 μm.

3. The polypropylene film according to claim 1, wherein the particle size of the antiblocking agent is 0.01 to 50 μm.

4. The polypropylene film according to claim 1, wherein the ratio A, expressed as (particle size R1 at the largest peak a in the range of 0.1 to 2.5 μm) / (thickness T1 of the first skin layer) in the particle size distribution of the antiblocking agent in the first skin layer, is 0.3 to 2.

5.

5. The polypropylene film according to claim 1, wherein the ratio B expressed as (particle size R2 at the largest peak b in the range of greater than 2.5 μm and less than or equal to 10 μm) / (thickness T1 of the first skin layer) in the particle size distribution of the antiblocking agent in the first skin layer is 1.0 to 6.

0.

6. The polypropylene film according to claim 1, wherein, in the particle size distribution of the antiblocking agent in the first skin layer, the ratio of the ratio A, expressed as (particle size R1 at the largest peak a in the range of 0.1 to 2.5 μm) / (thickness T1 of the first skin layer) to the ratio B, expressed as (particle size R2 at the largest peak b in the range of greater than 2.5 μm and less than or equal to 10 μm) / (thickness T1 of the first skin layer), is expressed as B / A and is between 1 and 10.

7. The polypropylene film according to claim 1, wherein the antiblocking agent comprises at least one selected from the group consisting of resin particles, higher fatty acid particles, higher fatty acid amide particles, higher fatty acid metal salt particles, silica particles, talc particles, zeolite particles, kaolinite particles, and feldspar particles.

8. The polypropylene film according to claim 1, further comprising a second skin layer, wherein the first skin layer, the core layer, and the second skin layer are laminated in this order.

9. The polypropylene film according to claim 1, wherein the core layer contains biomass-derived propylene units, and the content of the biomass-derived propylene units is 10% by mass or more and 50% by mass or less with respect to the total mass of the polypropylene film.

10. The polypropylene film according to claim 1, wherein at least one of the core layer and the first skin layer contains a phosphorus-based antioxidant, and the content of the phosphorus-based antioxidant is 300 ppm by mass or more and 1000 ppm by mass or less with respect to the total mass of the polypropylene film.

11. A packaging material comprising the polypropylene film according to any one of claims 1 to 10.

12. A package in which an article is packaged with the packaging material described in claim 11.

13. A method for producing a polypropylene film according to any one of claims 1 to 10, comprising forming the first skin layer on one surface of the core layer.

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