JP4730984B2 - Polypropylene film and method for producing the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polypropylene film and a method for producing the same, and more particularly, to a polypropylene film and a method for producing the same that are less likely to cause tarmi on the film even when roll-tightened due to shrinkage with time. .
[0002]
[Prior art]
Polypropylene film has a number of desirable properties, including excellent optical properties such as transparency and gloss, tensile properties, mechanical properties such as Young's modulus, and virtually non-toxic and odorless properties. ing. Therefore, the polypropylene film is widely used as a packaging material for food. In order to provide barrier properties and heat sealability against oxygen gas, water vapor, etc., vinylidene chloride copolymer, vinyl alcohol polymer, ethylene-vinyl alcohol copolymer, acrylic copolymer, etc. In some cases, it is used as a coating.
[0003]
However, these films are shipped in a roll-up state and are subjected to post-processing such as printing and laminating, but the roll tends to be tightened by shrinking with time during storage. The tightening condition becomes more prominent as the long roll is wound with higher tension and closer to the core. When such winding tightening occurs, a difference in shrinkage ratio appears as a film talmi in a portion with poor thickness accuracy. When such a roll is used in the printing process, pitch deviation occurs and normal printing cannot be performed.
[0004]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide a polypropylene film and a method for producing the same, which retains the excellent properties of the polypropylene film and hardly causes winding tarmi after storage for a long period of time.
[0005]
[Means for Solving the Problems]
As a result of intensive studies to achieve the above object, the present inventors have found that the degree of unevenness on the surface of the polypropylene film is greatly involved in the occurrence of tarmi, and have completed the present invention.
[0006]
That is, the present invention is a polypropylene film composed of three or more layers whose layer structure is a surface layer (A) / 1 or a core layer (C) / surface layer (B) composed of a plurality of layers. One surface layer (A) is composed of a polypropylene homopolymer, and the surface layer (A) contains 1,400 to 4,000 ppm of fine particles having an average particle diameter Td of 1 to 4 μm, The content of fine particles in layers other than the surface layer (A) is 2,000 ppm or less, and the ratio Ttotal / Ta of the total thickness Ttotal of the other layers to the thickness Ta of the surface layer (A) is 4 to 60, On the surface layer (B) opposite to the surface layer (A), the ratio Ta / Td of the thickness Ta of the surface layer (A) to the average particle diameter Td of the fine particles is 1/5 to 2. Vinylidene chloride polymer, ethylene-vinyl alcohol polymer and vinyl Providing a polypropylene-based film coating layer having a thickness of 0.25~5μm made from a polymer selected from the alcohol-based polymer is provided.
[0007]
Moreover, this invention is a manufacturing method of the polypropylene-type film which consists of three or more layers whose layer structure is a surface layer (A) / 1 or a core layer (C) / surface layer (B) comprised by several layers. And a step of laminating a layer containing 1,400 to 4,000 ppm of fine particles having an average particle diameter Td of 1 to 4 μm, which is composed of a polypropylene homopolymer, as a surface layer (A), and a surface On the surface layer (B) opposite to the layer (A), a coating layer having a thickness of 0.25 to 5 μm made of a polymer selected from vinylidene chloride polymer, ethylene-vinyl alcohol polymer and vinyl alcohol polymer together comprising the step of providing, the ratio Ttotal / Ta of total thickness Ttotal of other layers to the thickness Ta of the surface layer (a) and 4 to 60, the average particle diameter Td thickness Ta and fine particles the surface layer (a) The ratio Ta / Td and 1/5 to 2 in, and the content of the fine particles in the layer other than the surface layer (A) provides a method for producing a polypropylene film characterized by the following 2,000 ppm.
In the present specification, “ppm” indicates parts per million based on weight. Further, “film” is used to mean including a sheet.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The polypropylene film is composed of a polypropylene resin that is excellent in optical properties, mechanical properties, and packaging suitability. The polypropylene resin is preferably a crystalline resin. The polypropylene resin may be a propylene homopolymer, but other olefins such as ethylene, butene-1,3-methylpentene, 4-methylpentene and the like as long as they do not lose the rigidity. It may be a copolymer. The isotactic index (II) of the polypropylene resin may be in a range that does not impair the film properties, but is often 90% or more, and particularly preferably 94% or more. The melting point of the polypropylene resin is, for example, 150 ° C. or more, preferably 160 ° C. or more, and the MFR (melt flow rate) is, for example, 0.5 to 20 g / 10 minutes, preferably 1 to 15 g / 10 minutes, more preferably 2 to 10 g / 10 min.
[0009]
In the polypropylene film, various additives such as an antioxidant, an ultraviolet absorber, an antistatic agent, a crystal nucleus growth agent, a styrene resin, and a terpene resin are used as long as bleed does not become a functional obstacle. , Petroleum resins, dicyclopentadiene resins, coumarone resins such as coumarone resin, phenolic resins, rosin and its derivatives and hydrocarbon polymers such as hydrogenated resins, plasticizers, waxes, fillers, anti-blocking agents, etc. May be included.
[0010]
Examples of the antioxidant include phenol-based, phosphorus-based and sulfur-based antioxidants. Examples of phenolic antioxidants include 2,6-di-t-butyl-p-cresol (BHT), tetrakis [methylene-3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl). ) Propionate] Methane (Nippon Ciba Geigy, trade name: Irganox 1010, etc.) is preferred. The amount of the antioxidant used is an amount that can contribute to the stability of film forming properties and film properties, for example, 0.01 to 0.30 parts by weight, preferably 0.02 to 100 parts by weight of polypropylene resin. 0.25 parts by weight.
[0011]
The polypropylene film is composed of two or more layers. For example, surface layer (A) / surface layer (B), surface layer (A) / core layer (C) / surface layer (B), etc. Can be illustrated. The core layer (C) may be composed of a plurality of layers.
[0012]
The main feature of the present invention is that one surface layer (A) of the film is composed of a homopolymer of polypropylene, and the surface layer (A) contains 1,400 to 10 fine particles having an average particle diameter Td of 1 to 10 μm. , 000 ppm. The average particle diameter Td is preferably about 1 to 5 μm, more preferably about 1 to 4 μm, and the content of the fine particles is preferably about 1,500 to 6,000 ppm, more preferably about 1,800 to 4,000 ppm. It is.
[0013]
In the present invention, since the surface layer (A) contains a specific amount of fine particles having a specific particle size, when the roll film shrinks and tightens, the fine particles protruding from the surface layer act as spacers, and break, deform, or film Excessive tension can be prevented from working by sinking inside. For this reason, even if the film is rewound, it is difficult for the film to be tarnished. If the average particle size of the fine particles is too small, a sufficient effect of preventing talmi cannot be obtained. On the other hand, if the average particle size is too large, slipperiness decreases and pinholes are likely to occur during printing. In addition, when the content of the fine particles is too small, a sufficient effect of preventing talmi is not exhibited, and when the content is too large, the transparency of the film is deteriorated.
[0014]
As the fine particles, ordinary antiblocking agents can be used. Examples thereof include silica, alumina, synthetic zeolite, kaolin, talc, zinc oxide, magnesium oxide, zirconium oxide, titanium oxide, aluminum hydroxide, quartz powder, Inorganic fine powders such as calcium carbonate, magnesium carbonate, barium sulfate; thermoplastic resins such as polyester, polyamide, polycarbonate, polyethersulfone, polyetherimide, polyphenylene sulfide, polyetheretherketone, polyamideimide, crosslinked acrylic resin, crosslinked Thermosetting resins such as melamine resin, benzoguanamine resin, urea resin, amino resin, furan resin, epoxy resin, phenol resin, unsaturated polyester, pinyl ester resin, diallyl phthalate resin, polyimide And the like.
[0015]
Among these fine particles, those that are easy to break or deform or sink into the film when the roll film is tightened are preferable, and those that are broken into secondary particles are particularly preferable. In the case of breaking into secondary particles, it is desirable that the average particle size is, for example, 1.0 μm or less, particularly 0.5 μm or less, and in particular 0.3 μm or less. If the particle size after destruction is too large, pinholes may be generated during printing or the roll may be soiled during processing. From such a point of view, the fine particles are particularly preferably agglomerated inorganic substances [for example, oxides (including composite oxides) such as silica].
[0016]
The fine particles are used alone or in combination of two or more. The fine particles may be spherical or indefinite, but if close to spherical particles are used, high blocking resistance is easily imparted without reducing transparency.
[0017]
The ratio Ta / Td between the thickness Ta of the surface layer (A) and the average particle diameter Td of the fine particles is preferably 1/5 to 2, more preferably about 1/4 to 1. If this ratio is too small, the fine particles are likely to fall off, and if it is too large, the probability that the fine particles protrude from the surface layer becomes small, so that it is difficult to exhibit a sufficient wound tarmi-preventing effect and anti-blocking effect.
[0018]
In the polypropylene film of the present invention, layers other than the surface layer (A) [for example, the surface layer (B) opposite to the surface layer (A)] may also contain the fine particles (anti-blocking agent). Good. The content can be appropriately selected in consideration of the balance between transparency and blocking resistance of the film, and is, for example, 2,000 ppm or less (for example, about 500 to 2,000 ppm), preferably 1,500 ppm or less (for example, 800 to 1500 ppm). ). In addition, when a polypropylene film consists of three or more layers, layers (core layer (C) etc.) other than the surface layers (A) and (B) on both sides may not contain the fine particles. When fine particles are contained in a layer other than the surface layer (A), the kind of fine particles may be the same as or different from the surface layer (A).
[0019]
The total thickness of the polypropylene film of the present invention can be appropriately selected depending on the application, and is, for example, 1 to 250 μm, preferably 10 to 100 μm, and more preferably about 15 to 50 μm. In the sheet, for example, when a polypropylene film is used as the base polypropylene layer, the thickness of the layer may be about 0.1 to 5 mm.
[0020]
The thickness Ta of the surface layer (A) of the polypropylene film and the total thickness Ttotal of the other layers can be selected within a range that does not impair the properties of the composite film. For example, Ttotal / Ta is 4 or more (for example, 4 to 60). ), Preferably 5 to 50, more preferably about 10 to 30. When the ratio Ttotal / Ta is less than 4, when the waste generated during film production is reused, the physical property change of the film becomes large and it is difficult to produce a stable quality product.
[0021]
The coefficient of static friction between the (A)-(A) planes at 23 ° C. of the polypropylene film of the present invention (based on JIS K 7125) is preferably 0.25 to 0.55, preferably 0.30 to 0.50. More preferably, it is 0.35-0.45. If this value is too small, it depends on the friction coefficient of the surface layer (B) opposite to the surface layer (A), but the film tends to wrinkle during winding, and if it is too large, In addition to being easy to enter, problems with close contact with the roll are likely to occur during printing and lamination. The static friction coefficient can be adjusted by the average particle diameter, the content of the fine particles contained in the surface layer (A), the added amount of waxes, or the like.
[0022]
The polypropylene film may be unstretched, but is preferably stretched. The stretched film may be uniaxially stretched, but is preferably biaxially stretched. Moreover, the stretched film may be heat-treated as necessary.
[0023]
In addition, when the surface layer of the polypropylene film [for example, the surface layer (B)] is activated in consideration of post-processing, it is 36 dyne / cm or more, preferably 37 to 45 dyne / cm, more preferably 38 to It is desirable to develop a surface tension of about 42 dyne / cm. When the surface tension is less than 36 dyne / cm, adhesion with adhesives, printing inks, and various coating agents is hardly exhibited.
[0024]
In the polypropylene film of the present invention, a coating layer may be provided on the surface layer (B) in order to impart gas barrier properties, heat sealing properties, and the like. The polymer used for this coating layer can be selected according to the application, for example, vinylidene chloride polymer, ethylene-vinyl alcohol polymer, vinyl alcohol polymer, polyamide polymer, polyacrylonitrile polymer, urethane polymer, etc. Examples thereof include a gas barrier resin. Among these, vinylidene chloride polymers, ethylene-vinyl alcohol polymers, and vinyl alcohol polymers are particularly preferable.
[0025]
The vinylidene chloride polymer is a copolymer of vinylidene chloride and other polymerizable monomers. Examples of such polymerizable monomers include vinyl chloride, vinyl acetate, crotonic acid, acrylic acid, methyl acrylate, and ethyl acrylate. Examples include acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, tert-butyl acrylate, acrylonitrile, methacrylonitrile, methacrylic acid, and methacrylates corresponding to the above acrylates. Among these vinylidene chloride copolymers, vinylidene chloride-acrylonitrile copolymer, vinylidene chloride-methacrylic acid copolymer, vinylidene chloride-acrylate copolymer, vinylidene chloride-methacrylate copolymer, vinylidene chloride-vinyl acetate copolymer Polymers are particularly preferred.
[0026]
The vinylidene chloride content in the vinylidene chloride copolymer is usually 85 to 99% by weight, preferably about 90 to 97% by weight. The coating liquid used for forming the coating layer may be acetone, methyl ethyl ketone, cyclohexanone, benzene, toluene, xylene, tetrahydrofuran, dioxane, diethyl ether, ethyl acetate, butyl acetate, dimethyl, depending on the type of copolymer. A solution such as a solution of formamide or a polymer dissolved in a mixed solution thereof or an emulsion type may be used, and the thickness of the coating layer (coating layer) does not impair desired characteristics (for example, gas barrier properties) and transparency. It is used after being prepared to be in the range.
[0027]
As the ethylene-vinyl alcohol polymer, a solvent-soluble resin is preferable, and the ethylene content thereof is usually 5 to 50 mol%, preferably 10 to 45%, more preferably about 25 to 35 mol%. The molecular weight is usually 10,000 to 100,000, preferably about 40,000 to 50,000, and the degree of saponification is preferably 99.5% or more. Such a solvent-soluble ethylene-vinyl alcohol polymer is soluble in water or a mixed solvent of water and alcohols such as methanol, ethanol, propanol, isopropanol, and cyclohexanol, and is coated with a thin film (coating layer). Can be formed.
[0028]
The coating layer can be formed using a conventional method such as coating or laminating. The coating layer may be composed of a single layer or a plurality of layers depending on desired properties (for example, gas barrier properties), and one layer may contain many kinds of resins. The coating method is not particularly limited, and conventional methods such as an air knife coating method, a roll coating method, a gravure coating method, a blade coater method, a dip coating method, and a spray method can be employed. After coating the surface of the surface layer (B) with a coating solution prepared according to the type of resin, for example, a barrier resin coating layer can be formed, for example, by drying at a temperature of about 50 to 150 ° C.
[0029]
The thickness of the said coating layer is 0.05-15 micrometers, for example, Preferably it is 0.1-10 micrometers, More preferably, it is about 0.25-5 micrometers. When the thickness is 0.05 μm or less, for example, sufficient gas barrier properties cannot be obtained, and when it exceeds 15 μm, it tends to be economically disadvantageous.
[0030]
The polypropylene film of the present invention can be produced by a step of laminating a layer containing 1,400 to 10,000 ppm of fine particles having an average particle diameter Td of 1 to 10 μm as the surface layer (A).
[0031]
Composite (lamination) of two or more layers of film is performed by a dry laminating method in which other layers are combined with a base polypropylene film layer using an anchor coat agent such as titanium, polyethyleneimine, or urethane. However, it can be preferably carried out by a co-extrusion method.
[0032]
In the coextrusion molding method, for example, a polypropylene resin constituting the surface layer (A) and a resin composition containing 1,400 to 10,000 ppm of fine particles having an average particle diameter Td of 1 to 10 μm and other layers are constituted. A composite film can be produced by subjecting a resin composition containing a polypropylene resin to coextrusion molding. The composite film is preferably subjected to a stretching process. For coextrusion molding, an extrusion molding machine equipped with a T die, a ring die, or the like can be used.
[0033]
In the example using a two-layer extruder, the resin composition constituting one surface layer (A) and the resin composition constituting the other surface layer (B) are individually charged, and the inside of the die is formed by an extruder. By melt extrusion, the resin compositions are combined in a flow path in the die to be multilayered and extruded out of the die. By cooling the multilayer film, a composite film having a layer structure of surface layer (A) / surface layer (B) is obtained. A composite film having a layer structure of surface layer (A) / core layer (C) / surface layer (B) and a composite film having four or more layers can also be produced according to the above.
[0034]
In the T-die method, the composite film can be stretched after cooling the composite film extruded from the die, and in the inflation method, it can be performed together with melt extrusion from the die.
[0035]
Examples of the stretching method include conventional stretching methods such as roll stretching, tenter stretching, tube stretching, and a combination of these. The draw ratio can be appropriately set according to the desired film properties, and the draw ratio in at least one direction is 2 times or more, preferably about 5 to 10 times.
[0036]
As the surface layer activation treatment, a conventional surface treatment such as corona discharge treatment, flame treatment, plasma treatment, ozone or ultraviolet irradiation treatment can be employed. A preferable surface treatment includes corona discharge treatment. The surface treatment may be performed prior to the stretching process of the film, but is often performed after the stretching process.
[0037]
The composite polypropylene-based film of the present invention thus obtained exhibits an excellent effect in preventing winding tarmi, despite its simple composition and structure. Therefore, it can be suitably used for a wide range of applications such as various packaging materials in the food field, pharmaceutical field, precision electronic component field and the like.
[0038]
【The invention's effect】
According to the present invention, the polypropylene film is composed of two or more layers, and one surface layer contains fine particles having a specific particle size, so that the excellent characteristics of the polypropylene film are maintained over time. Can prevent the occurrence of heavy winding tarmi.
[0039]
【Example】
Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.
[0040]
Example 1
The following composition was used as a raw material for the surface layer (A), the surface layer (B), and the core layer (C).
Raw material of surface layer (A): polypropylene homopolymer (MFR = 8 g / 10 min, isotactic index 97%, melting point 163 ° C.) 100 parts by weight, antioxidant 0.23 parts by weight and fine particles (anti-blocking) Raw material of the composition surface layer (B) to which 0.30 part by weight of an aggregation type silica having an average particle size of 2.7 μm was added as an agent): a polypropylene random copolymer containing 2% ethylene component (MFR = 15, melting point 150 ° C., (Crystallinity 47%) A composition core layer in which 0.02 part by weight of an antioxidant and 0.10 part by weight of PMMA (polymethyl methacrylate) having an average particle size of 2 μm as an antiblocking agent are added to 100 parts by weight (C ) Raw material: Polypropylene homopolymer (MFR = 2 g / 10 min, isotactic index 97%, melting point 163 ° C.) 100 parts by weight of antioxidant A composition comprising 0.23 parts by weight of a stopper and 0.13 parts by weight of silica having an average particle size of 2.2 μm as an antiblocking agent.
The raw materials of each of the layers (A), (B), and (C) are respectively supplied to an extruder equipped with a T die, and are coextruded at a temperature of 250 to 260 ° C. to form a layer structure (A) / ( C) / (B) 3 types and 3 layers sheets were prepared. The obtained sheet was stretched 5 times in the longitudinal direction at 130 to 160 ° C., then stretched 10 times in the lateral direction at 160 ° C., and then heat-treated at 160 ° C. for 10 seconds. Furthermore, the surface of the (B) layer of the film was subjected to corona discharge treatment to produce a multilayer film having a surface wetting tension of 40 dyne / cm. The total thickness of the obtained film was 20 μm [(A) layer thickness 0.8 μm, (B) layer thickness 1.2 μm, (C) layer thickness 18 μm]. The haze (4 layers) of this film was 8%, and the coefficient of static friction between (A) and (A) (based on JIS K 7125) was 0.40.
[0041]
Rolls (width 760 mm, length 4,000 m) with varying film thickness accuracy (TV) and winding hardness (tension) were prepared. The obtained roll was allowed to stand at 40 ° C. for 1 month, and then the occurrence of tarmi was observed while the film was rewound. The TV value representing the thickness accuracy was obtained by the following equation.
TV (%) = (maximum thickness−minimum thickness) / average thickness × 100
The winding hardness was measured with an Asker C-type rubber / plastic hardness meter (manufactured by Kobunshi Keiki Co., Ltd.) (measured with a load of 50 g per 1 cm ² ).
The result is shown in FIG. As apparent from the figure, no tarmi was generated unless the thickness accuracy was extremely poor or the winding hardness was not high. In the figure, a square mark indicates that no talmi was observed, and a triangle mark indicates that talmi was observed (hereinafter the same).
Further, when the surface layer (A) of the film left to stand at 40 ° C. for 1 month was observed, about 5% of the added fine particles were decomposed into secondary particles having an average particle diameter of 0.1 μm.
[0042]
Comparative Example 1
A multilayer film was prepared in the same manner as in Example 1 except that the fine particles in the raw material of the surface layer (A) were silica having an average particle diameter of 2.2 μm and the addition amount was 0.13 parts by weight. This film had a haze of 4% and a static friction coefficient between (A) and (A) of 0.56. Rolls with varying thickness accuracy (TV) and winding hardness (tension) (width 760 mm, length 4,000 m) were allowed to stand at 40 ° C. for one month, and then the occurrence of tarmi was observed while the film was rewound. . The result is shown in FIG. As is clear from the figure, tarmi was generated even in a film having a relatively good thickness accuracy and a low winding hardness.
[0043]
Example 2
0.1 parts by weight of PMMA fine particles having an average particle diameter of about 2 μm are added to 100 parts by weight of vinylidene chloride polymer on the surface layer (B) of the film having different thickness accuracy prepared under the same conditions as in Example 1. The coating solution was coated to form a vinylidene chloride polymer layer having a thickness of 1 μm. The haze (4 sheets) of this film was 8%, and the static friction coefficient between (A) and (A) was 0.40. Using the obtained film, rolls (width 760 mm, length 4,000 m) with varying winding hardness (tension) were prepared. After leaving these at 40 ° C. for 1 month, the occurrence of tarmi was observed while rewinding the film. As a result, the same profile as in FIG. 1 was obtained, and almost no tarmi was generated.
Further, when the surface layer (A) of the film left to stand at 40 ° C. for 1 month was observed, about 5% of the added fine particles were decomposed into secondary particles having an average particle diameter of 0.1 μm.
[0044]
Comparative Example 2
A vinylidene chloride polymer layer was formed under the same conditions as in Example 2 on the surface layer (B) of the film having different thickness accuracy prepared under the same conditions as in Comparative Example 1. This film had a haze of 4% and a static friction coefficient between (A) and (A) of 0.56. Using the obtained film, rolls (width 760 mm, length 4,000 m) with varying winding hardness (tension) were prepared. After these were left at 40 ° C. for 1 month, the occurrence of tarmi was observed while rewinding the film. As a result, the profile was the same as in FIG.
[0045]
Comparative Example 3
Films having different thickness accuracy were prepared under the same conditions as in Example 1 except that the single layer configuration using only the raw material of the surface layer (A) was used. Using this film, rolls (width 760 mm, length 4,000 m) with varying winding hardness (tension) were prepared. The obtained roll was left to stand at 40 ° C. for 1 month, and then the occurrence of tarmi was observed while the film was rewound. % Or more and lack of transparency.
[Brief description of the drawings]
1 is a graph showing the relationship between winding hardness and thickness accuracy and occurrence of tarmi in the film of Example 1. FIG.
2 is a graph showing the relationship between the winding hardness and thickness accuracy and the occurrence of tarmi in the film of Comparative Example 1. FIG.

Claims (4)

It is a polypropylene film composed of three or more layers whose layer structure is a surface layer (A) / 1 or a core layer (C) / surface layer (B) composed of a plurality of layers , one surface layer ( A) is composed of a polypropylene homopolymer, and the surface layer (A) contains 1,400 to 4,000 ppm of fine particles having an average particle diameter Td of 1 to 4 μm, except for the surface layer (A). The content of fine particles in this layer is 2,000 ppm or less, the ratio Ttotal / Ta of the total thickness Ttotal of the other layers to the thickness Ta of the surface layer (A) is 4 to 60, and the surface layer (A) The ratio Ta / Td between the thickness Ta and the average particle diameter Td of the fine particles is 1/5 to 2, and on the surface layer (B) opposite to the surface layer (A), a vinylidene chloride polymer, ethylene -Vinyl alcohol polymers and vinyl alcohol polymers Polypropylene-based film coating layer having a thickness 0.25~5μm is provided consisting of a polymer selected from the.    The polypropylene film according to claim 1, wherein the coefficient of static friction between (A) and (A) at 23 ° C is 0.25 to 0.55. The polypropylene film according to claim 1 or 2, wherein the fine particles comprise an agglomerated inorganic material. A method for producing a polypropylene film comprising three or more layers, wherein the layer structure is a surface layer (A) / 1 or a core layer (C) / surface layer (B) composed of a plurality of layers, A step of laminating a surface layer (A) comprising a layer composed of a homopolymer and containing 1,400 to 4,000 ppm of fine particles having an average particle diameter Td of 1 to 4 μm, and the surface layer (A) And a step of providing a coating layer having a thickness of 0.25 to 5 μm made of a polymer selected from a vinylidene chloride polymer, an ethylene-vinyl alcohol polymer and a vinyl alcohol polymer on the surface layer (B) on the opposite side. , the ratio Ttotal / Ta of total thickness Ttotal of other layers to the thickness Ta of the surface layer (a) and 4 to 60, the ratio Ta / Td between the average particle diameter Td thickness Ta and fine particles the surface layer (a) 1/5 to 2 and then, and method for producing a polypropylene film characterized in that the content of the fine particles in the layer other than the surface layer (A) or less 2,000 ppm.

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