JP2023017015A - biaxially oriented polypropylene film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biaxially stretched laminated polypropylene film having higher heat resistance and rigidity.

SOLUTION: In the biaxially oriented stretched polypropylene film, a polypropylene resin constituting the film and including a polypropylene resin obtained by copolymerizing complete homopolypropylene resin containing no copolymerization component and/or ethylene and/or α-olefin having 4 or more carbon atoms satisfies the following conditions 1) to 4), a lower limit of a plane orientation coefficient of the film is 0.0125, and a tensile elastic modulus in a transverse direction of the film is 5.1 GPa or more: 1) a lower limit of a mesopentad fraction is 96%; 2) an upper limit of copolymerizable monomer weight other than propylene is 0.1 mol%; 3) mass average molecular weight (Mw)/number average molecular weight (Mn) is 3.0 to 5.4, inclusive; and 4) a melt flow rate (MFR) measured at 230°C and 2.16 kgf is 6.5 g/10 min to 9.0 g/10 min, inclusive.

SELECTED DRAWING: None

COPYRIGHT: (C)2023,JPO&INPIT

Description

The present invention relates to a biaxially oriented laminated polypropylene film. Specifically, it relates to a biaxially oriented polypropylene film having excellent heat resistance and mechanical properties.

Conventionally, stretched polypropylene films have been widely used in a wide range of applications, such as packaging of foods and various products, electrical insulation, and surface protection films. However, conventional polypropylene films have a shrinkage rate of several tens of percent at 150° C., and are less heat-resistant and less rigid than polyethylene terephthalate (PET) films and the like.

Various techniques for improving the physical properties of polypropylene films have been proposed. For example, by forming a film using polypropylene containing approximately the same amount of high-molecular-weight components and low-molecular-weight components (or less low-molecular-weight components), having a wide molecular-weight distribution, and having a low decalin-soluble content, it is possible to achieve a combination of rigidity and workability. A technique of balancing is known (Patent Document 1). However, with this technology, the heat resistance at high temperatures exceeding 150°C is still not sufficient, and a polypropylene film with high heat resistance, impact resistance, and transparency was not known. .

As a result of intensive studies based on the above-mentioned prior art, the applicant of the present application has decided to provide a highly rigid and highly heat-resistant oriented polypropylene film by using a polypropylene-based polymer having a mesopentad fraction of 96% or more. It was successful (Patent Document 2). However, this film has room for improvement in heat resistance.

Japanese Patent Publication No. 2008-540815 WO2015/012324 Pamphlet

In view of the above circumstances, an object of the present invention is to provide a biaxially stretched laminated polypropylene film having higher heat resistance and rigidity.

The present invention, which has solved the above problems, is characterized in that the polypropylene resin constituting the film satisfies the following conditions 1) to 4), and the lower limit of the plane orientation coefficient of the film is 0.0125. It is a biaxially oriented polypropylene film.
1) The lower limit of the mesopentad fraction is 96%.
2) The upper limit of the amount of copolymerizable monomers other than propylene is 0.1 mol%.
3) The weight average molecular weight (Mw)/number average molecular weight (Mn) is 3.0 or more and 5.4 or less. 4) Melt flow rate (MFR) measured at 230° C. and 2.16 kgf is 6.2 g/10 min or more and 9.0 g/10 min or less.

In addition, the second aspect of the present invention, which has solved the above problems, is a base layer (A) containing a polypropylene-based resin as a main component and a base layer (A) containing a polypropylene-based resin as a main component on at least one surface of the base layer (A). The polypropylene resin constituting the base layer (A) satisfies the following conditions 1) to 4), and the lower limit of the plane orientation coefficient of the film is 0.0125. A biaxially oriented polypropylene film characterized by:
1) The lower limit of the mesopentad fraction is 96%.
2) The upper limit of the amount of copolymerizable monomers other than propylene is 0.1 mol%.
3) The weight average molecular weight (Mw)/number average molecular weight (Mn) is 3.0 or more and 5.4 or less. 4) Melt flow rate (MFR) measured at 230° C. and 2.16 kgf is 6.2 g/10 min or more and 9.0 g/10 min or less.

In this case, it is preferable that the film has a thermal shrinkage rate of 8% or less at 150° C. in the machine direction and the transverse direction.

In this case, it is preferable that the longitudinal tensile modulus of the film is 2.0 GPa or more and the transverse tensile modulus of the film is 4.5 GPa or more.

In this case, it is preferable that the film has a haze value of 5% or less.

The biaxially oriented polypropylene film of the present invention has a small molecular weight distribution and less entanglement of molecular chains, so the orientation is stronger, it has higher thermal dimensional stability and lateral rigidity, and less heat wrinkles. Because it is hard to break, it has excellent film processability.

The biaxially oriented polypropylene film of the first invention is characterized in that the polypropylene resin constituting the film satisfies the following conditions 1) to 4) and that the lower limit of the plane orientation coefficient of the film is 0.0125. and
1) The lower limit of the mesopentad fraction is 96%.
2) The upper limit of the amount of copolymerizable monomers other than propylene is 0.1 mol%.
3) The weight average molecular weight (Mw)/number average molecular weight (Mn) is 3.0 or more and 5.4 or less. 4) Melt flow rate (MFR) measured at 230° C. and 2.16 kgf is 6.2 g/10 min or more and 9.0 g/10 min or less.
In the biaxially oriented polypropylene film of the second invention, the substrate layer (A) containing a polypropylene resin as a main component and the surface containing a polypropylene resin as a main component on at least one surface of the base layer (A) layer (B), and that the polypropylene resin constituting the base layer (A) satisfies the following conditions 1) to 4), and that the lower limit of the plane orientation coefficient of the film is 0.0125. Characterized by
1) The lower limit of the mesopentad fraction is 96%.
2) The upper limit of the amount of copolymerizable monomers other than propylene is 0.1 mol%.
3) The weight average molecular weight (Mw)/number average molecular weight (Mn) is 3.0 or more and 5.4 or less. 4) Melt flow rate (MFR) measured at 230° C. and 2.16 kgf is 6.2 g/10 min or more and 9.0 g/10 min or less.
Further details are provided below.

(1) A polypropylene resin obtained by copolymerizing 0.5 mol % or less of ethylene and/or an α-olefin having 4 or more carbon atoms can also be used as the polypropylene resin used in the first invention. Such a copolymerized polypropylene resin is also included in the polypropylene resin of the present invention (hereinafter referred to as polypropylene resin). The content of the copolymer component is preferably 0.3 mol % or less, more preferably 0.1 mol % or less, and most preferably a complete homopolypropylene resin containing no copolymer component.
When ethylene and/or α-olefins having 4 or more carbon atoms are copolymerized in excess of 0.5 mol %, the crystallinity and rigidity are excessively lowered, and the thermal shrinkage at high temperatures may increase. A blend of such resins may be used.

The mesopentad fraction ([mmmm]%) measured by 13C-NMR, which is an index of the stereoregularity of the polypropylene resin, is preferably 96 to 99.5%. More preferably, it is 97% or more, and still more preferably 98% or more. If the mesopentad ratio of the polypropylene of the base material layer (A) is small, the elastic modulus will be low and the heat resistance may be insufficient. 99.5% is a realistic upper limit.

Mw/Mn, which is an index of molecular weight distribution, is preferably 3.0 to 5.4 for polypropylene resins. It is more preferably 3.0 to 5.0, still more preferably 3.2 to 4.5, and particularly preferably 3.3 to 4.0.
When the Mw/Mn of the entire polypropylene resin constituting the biaxially oriented polypropylene film of the present invention exceeds 5.4, if the Mw/Mn is too large, the high molecular weight component increases and the heat shrinkage rate may increase. Also, the tensile modulus (Young's modulus) in the width direction (TD) tends to decrease. When a molecular weight component is present, the high molecular weight component promotes the crystallization of the low molecular weight component, but the entanglement between molecules becomes stronger, and there is also a tendency for the thermal shrinkage to increase even if the crystallinity is high.
When the Mw/Mn of the entire polypropylene resin constituting the biaxially oriented polypropylene film of the present invention is less than 3.0, film formation becomes difficult.
Mw means weight average molecular weight and Mn means number average molecular weight.

The weight average molecular weight (Mw) of polypropylene resin is preferably 180,000 to 500,000. A more preferable lower limit of Mw is 190,000, more preferably 200,000, and a more preferable upper limit of Mw is 320,000, more preferably 300,000, and particularly preferably 250,000.

The number average molecular weight (Mn) of polypropylene resin is preferably 20,000 to 200,000. A more preferable lower limit of Mn is 30,000, more preferably 40,000, particularly preferably 50,000, and a more preferable upper limit of Mn is 80,000, more preferably 70,000, particularly preferably 60,000. be.

When the gel permeation chromatography (GPC) integrated curve of the entire polypropylene resin constituting the biaxially oriented polypropylene film of the first invention is measured, the lower limit of the amount of components having a molecular weight of 100,000 or less is preferably 35% by mass. , more preferably 38% by mass, still more preferably 40% by mass, particularly preferably 41% by mass, and most preferably 42% by mass.
On the other hand, the upper limit of the amount of components having a molecular weight of 100,000 or less in the GPC integration curve is preferably 65% by mass, more preferably 60% by mass, still more preferably 58% by mass, and particularly preferably 56% by mass. and most preferably 55% by mass. Within the above range, stretching is facilitated, thickness unevenness is reduced, stretching temperature and heat setting temperature are easily raised, and heat shrinkage can be suppressed to a lower level.

At this time, the polypropylene resin preferably has a melt flow rate (MFR; 230° C., 2.16 kgf) of 6.2 g/10 minutes to 10.0 g/10 minutes.
The lower limit of the MFR of the polypropylene resin is more preferably 6.5 g/10 minutes, still more preferably 7 g/10 minutes, and particularly preferably 7.5 g/10 minutes. The upper limit of the MFR of the polypropylene resin is more preferably 9 g/10 minutes, still more preferably 8.5 g/10 minutes, and particularly preferably 8.2 g/10 minutes.
When the melt flow rate (MFR; 230° C., 2.16 kgf) is 6.2 g/10 minutes or more, the thermal shrinkage at high temperatures can be further reduced. Furthermore, since the degree of orientation of the film caused by stretching is increased, the rigidity of the film, particularly the tensile elastic modulus (Young's modulus) in the width (TD) direction is increased. Moreover, when the melt flow rate (MFR; 230° C., 2.16 kgf) is 9.0 g/10 minutes or less, the film can be easily formed without breakage.
The molecular weight distribution of polypropylene resin can be adjusted by polymerizing components with different molecular weights in multiple stages in a series of plants, by blending components with different molecular weights offline using a kneader, or by blending catalysts with different performance. It is possible to adjust the molecular weight distribution by polymerizing with a catalyst or by using a catalyst capable of realizing a desired molecular weight distribution.

The polypropylene resin used in the present invention is obtained by polymerizing raw material propylene using a known catalyst such as a Ziegler-Natta catalyst or a metallocene catalyst. Among them, it is preferable to use a Ziegler-Natta catalyst in order to eliminate heterogeneous bonds, and to use a catalyst capable of polymerizing with high stereoregularity.
As a method for polymerizing propylene, known methods may be adopted. For example, a method of polymerizing in an inert solvent such as hexane, heptane, toluene, or xylene, a method of polymerizing in a liquid monomer, a method of polymerizing a gaseous monomer with a catalyst and polymerizing in a gas phase, or a method of polymerizing by combining these.

The polypropylene resin may contain additives and other resins. Examples of additives include antioxidants, ultraviolet absorbers, nucleating agents, adhesives, antifog agents, flame retardants, inorganic or organic fillers, and the like. Other resins include polypropylene resins other than the polypropylene resin used in the present invention, random copolymers that are copolymers of propylene and ethylene and/or α-olefins having 4 or more carbon atoms, and various elastomers. These are polymerized sequentially using a multi-stage reactor, blended with polypropylene resin in a Henschel mixer, or prepared in advance using a melt kneader and diluted with polypropylene to a predetermined concentration. Alternatively, the entire amount may be previously melted and kneaded before use.

(2) The polypropylene resin used for the base material layer (A) of the second invention may also be a polypropylene resin obtained by copolymerizing 0.5 mol% or less of ethylene and/or an α-olefin having 4 or more carbon atoms. . Such a copolymerized polypropylene resin is also included in the polypropylene resin of the present invention (hereinafter referred to as polypropylene resin). The content of the copolymer component is preferably 0.3 mol % or less, more preferably 0.1 mol % or less, and most preferably a complete homopolypropylene resin containing no copolymer component.
When ethylene and/or α-olefins having 4 or more carbon atoms are copolymerized in excess of 0.5 mol %, the crystallinity and rigidity are excessively lowered, and the thermal shrinkage at high temperatures may increase. A blend of such resins may be used.

The mesopentad fraction ([mmmm]%) measured by 13C-NMR, which is an index of the stereoregularity of the polypropylene resin, is preferably 96 to 99.5%. More preferably, it is 97% or more, and still more preferably 98% or more. If the mesopentad ratio of the polypropylene of the base material layer (A) is small, the elastic modulus will be low and the heat resistance may be insufficient. 99.5% is a realistic upper limit.

Mw/Mn, which is an index of molecular weight distribution, is preferably 3.0 to 5.4 for polypropylene resins. It is more preferably 3.0 to 5.0, still more preferably 3.2 to 4.5, and particularly preferably 3.3 to 4.0.
If the Mw/Mn of the entire polypropylene resin constituting the base material layer (A) exceeds 5.4, if the Mw/Mn is too large, the high-molecular-weight component increases and the heat shrinkage rate may increase. There is a tendency that the tensile elastic modulus (Young's modulus) in the width direction (TD) may become small.
When a molecular weight component is present, the high molecular weight component promotes the crystallization of the low molecular weight component, but the entanglement between molecules becomes stronger, and there is also a tendency for the thermal shrinkage to increase even if the crystallinity is high.
When the Mw/Mn of the entire polypropylene resin constituting the biaxially oriented polypropylene film of the present invention is less than 3.0, film formation becomes difficult. Mw means weight average molecular weight and Mn means number average molecular weight.

The weight average molecular weight (Mw) of polypropylene resin is preferably 180,000 to 500,000. A more preferable lower limit of Mw is 190,000, more preferably 200,000, and a more preferable upper limit of Mw is 320,000, more preferably 300,000, and particularly preferably 250,000.

The number average molecular weight (Mn) of polypropylene resin is preferably 20,000 to 200,000. A more preferable lower limit of Mn is 30,000, more preferably 40,000, particularly preferably 50,000, and a more preferable upper limit of Mn is 80,000, more preferably 70,000, particularly preferably 60,000. be.

When the gel permeation chromatography (GPC) integrated curve of the entire polypropylene resin constituting the base material layer (A) is measured, the lower limit of the amount of the component having a molecular weight of 100,000 or less is preferably 35% by mass, more preferably It is 38% by mass, more preferably 40% by mass, particularly preferably 41% by mass, and most preferably 42% by mass.
On the other hand, the upper limit of the amount of components having a molecular weight of 100,000 or less in the GPC integration curve is preferably 65% by mass, more preferably 60% by mass, still more preferably 58% by mass, and particularly preferably 56% by mass. and most preferably 55% by mass. Within the above range, stretching is facilitated, thickness unevenness is reduced, stretching temperature and heat setting temperature are easily raised, and heat shrinkage can be suppressed to a lower level.

At this time, the polypropylene resin preferably has a melt flow rate (MFR; 230° C., 2.16 kgf) of 6.2 g/10 minutes to 10.0 g/10 minutes.
The lower limit of the MFR of the polypropylene resin is more preferably 6.5 g/10 minutes, still more preferably 7 g/10 minutes, and particularly preferably 7.5 g/10 minutes. The upper limit of the MFR of the polypropylene resin is more preferably 9 g/10 minutes, still more preferably 8.5 g/10 minutes, and particularly preferably 8.2 g/10 minutes.
When the melt flow rate (MFR; 230° C., 2.16 kgf) is 6.2 g/10 minutes or more, the thermal shrinkage at high temperatures can be further reduced. Furthermore, since the degree of orientation of the film caused by stretching is increased, the rigidity of the film, particularly the tensile elastic modulus (Young's modulus) in the width (TD) direction is increased. Moreover, when the melt flow rate (MFR; 230° C., 2.16 kgf) is 9.0 g/10 minutes or less, the film can be easily formed without breakage.
The molecular weight distribution of polypropylene resin can be determined by polymerizing components with different molecular weights in multiple stages in a series of plants, by blending components with different molecular weights offline in kneaders, and by blending catalysts with different performance. or by using a catalyst capable of realizing a desired molecular weight distribution.

The polypropylene resin used in the base material layer (A) is obtained by polymerizing raw material propylene using a known catalyst such as a Ziegler-Natta catalyst or a metallocene catalyst. Among them, it is preferable to use a Ziegler-Natta catalyst in order to eliminate heterogeneous bonds, and to use a catalyst capable of polymerizing with high stereoregularity.
As a method for polymerizing propylene, known methods may be adopted. For example, a method of polymerizing in an inert solvent such as hexane, heptane, toluene, or xylene, a method of polymerizing in a liquid monomer, a method of polymerizing a gaseous monomer with a catalyst and polymerizing in a gas phase, or a method of polymerizing by combining these.

The polypropylene resin may contain additives and other resins. Examples of additives include antioxidants, ultraviolet absorbers, nucleating agents, adhesives, antifog agents, flame retardants, inorganic or organic fillers, and the like. Other resins include polypropylene resins other than the polypropylene resin used in the present invention, random copolymers that are copolymers of propylene and ethylene and/or α-olefins having 4 or more carbon atoms, and various elastomers. These are polymerized sequentially using a multi-stage reactor, blended with polypropylene resin in a Henschel mixer, or prepared in advance using a melt kneader and diluted with polypropylene to a predetermined concentration. Alternatively, the entire amount may be previously melted and kneaded before use.

(3) The surface roughness of the surface layer (B) of the second invention is preferably 0.027 μm or more and 0.40 μm or less. If the thickness is less than 0.027 μm, the adhesion to printing ink and adhesion to adhesives used for lamination with films of other members will be insufficient, and if the thickness exceeds 0.40 μm, problems such as color developability and discoloration will occur. occur.
In order for the surface roughness of the surface layer (B) to be 0.027 μm or more and 0.40 μm or less, the melt flow rate (MFR) of the polypropylene resin composition forming the surface layer (B) is It is preferred to use a mixture of two or more different polypropylene resins. In this case, the difference in MFR is preferably 3 g/10 minutes or more, more preferably 3.5 g/10 minutes or more.
By using such a mixture, it is assumed that the surface roughness of the surface layer (B) becomes 0.027 μm or more due to the difference in crystallization rate.
Polypropylene obtained by copolymerizing ethylene and/or an α-olefin having 4 or more carbon atoms can also be used as the polypropylene resin having a higher MFR. Examples of α-olefins having 4 or more carbon atoms include 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene.
Polypropylene obtained by copolymerizing ethylene and/or an α-olefin having 4 or more carbon atoms can also be used as the polypropylene resin having a smaller MFR. Examples of α-olefins having 4 or more carbon atoms include 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene.
In addition, maleic acid or the like having polarity may be used as another copolymerization component.
The total content of ethylene, α-olefins having 4 or more carbon atoms, and other copolymer components is preferably 8.0 mol % or less. If it is copolymerized in excess of 8.0 mol %, the film may turn white and have a poor appearance, or may become sticky and difficult to form.
Two or more of these resins may be blended for use. When blended, individual resins may be copolymerized in excess of 8.0 mol%, but the blend preferably contains 8.0 mol% or less of monomers other than propylene in monomer units. .

The polypropylene resin composition of the surface layer (B) preferably has an MFR of 1.0 g/10 minutes to 8 g/10 minutes. The lower limit of the MFR of the polypropylene resin composition for the surface layer (B) is more preferably 2 g/10 minutes, and even more preferably 3 g/10 minutes. The upper limit of the MFR of the polypropylene resin composition for the surface layer (B) is more preferably 7 g/10 minutes, and even more preferably 6.0 g/10 minutes. Within this range, the film formability is good, and the thermal shrinkage at high temperatures can be kept small. When the MFR of the polypropylene resin composition of the surface layer (B) is less than 1.0 g/10 min, when the MFR of the polypropylene of the base layer (A) is large, the difference between the base layer (A) and the surface layer (B) Since the difference in viscosity becomes large, unevenness (raw fabric unevenness) tends to occur during film formation. When the MFR of the polypropylene resin composition of the surface layer (B) exceeds 8 g/10 minutes, the adhesion to the cooling roll deteriorates, air is entrained, and the smoothness is poor, resulting in many defects. There is a risk.

The polypropylene resin used in the surface layer (B) is obtained by polymerizing raw material propylene using a known catalyst such as a Ziegler-Natta catalyst or a metallocene catalyst. Among them, it is preferable to use a Ziegler-Natta catalyst in order to eliminate heterogeneous bonds, and to use a catalyst capable of polymerizing with high stereoregularity.
As a method for polymerizing propylene, known methods may be adopted. For example, a method of polymerizing in an inert solvent such as hexane, heptane, toluene, or xylene, a method of polymerizing in a liquid monomer, a method of polymerizing a gaseous monomer with a catalyst and polymerizing in a gas phase, or a method of polymerizing by combining these.

The surface layer (B) may contain additives and other resins. Examples of additives include antioxidants, ultraviolet absorbers, nucleating agents, adhesives, antifog agents, flame retardants, inorganic or organic fillers, and the like. Other resins include polypropylene resins other than the polypropylene resin used in the present invention, random copolymers that are copolymers of propylene and ethylene and/or α-olefins having 4 or more carbon atoms, and various elastomers. These are polymerized sequentially using a multi-stage reactor, blended with polypropylene resin in a Henschel mixer, or prepared in advance using a melt kneader and diluted with polypropylene to a predetermined concentration. Alternatively, the entire amount may be previously melted and kneaded before use.

The wetting tension of the surface of the surface layer (B) is preferably 38 mN/m or more.
When the wet tension is 38 mN/m or more, the adhesion with printing inks and adhesives is improved.
More preferably, the wetting tension is 16 LogΩ or more. Additives such as antistatic agents and surfactants are usually used to increase the wetting tension to 38 mN/m or more. For example, surface treatment such as
For example, corona treatment is preferably carried out in air using a preheated roll and a treatment roll.

It is preferable that the center surface peak height SR) + the center surface valley depth SRv of the surface layer (B) of the biaxially oriented polypropylene film of the present invention is 1.0 μm or more and 2.0 μm or less.
Here, the surface roughness center surface peak height SRp and center surface valley depth SRv of the surface of the surface layer (B) are measured length in the X direction using a three-dimensional roughness meter at a stylus pressure of 20 mg. Measured with a height of 1 mm, a feed pitch in the Y direction of 2 μm, 99 recorded lines, a magnification of 20000 times in the height direction, and a cutoff of 80 μm. .

The central surface peak height SRp+the central surface valley depth SRv of the surface of the surface layer (B) is an index of the state of large irregularities formed by the lubricant, and in the state of the roll film, the base layer (A) and the It is related to slipperiness at the time of contact.
When the central surface peak height SRp + central surface valley depth SRv of the surface of the surface layer (B) is 1.0 μm or more, the unwindability from the roll film is improved, and when it is 2.0 μm or less, the transparency is maintained. be done.
The central surface peak height SRp+the central surface valley depth SRv of the surface of the surface layer (B) is preferably 1.0 μm or more, 1.1 μm or more, more preferably 1.2 μm or more, and particularly preferably 1.3 μm or more.

In order to make the central surface peak height SRp + central surface valley depth SRv of the surface of the surface layer (B) 1.0 μm or more and 2.0 μm or less, an antiblocking agent is added to the polypropylene resin composition forming the surface layer (B). Compounding is the preferred method.
The anti-blocking agent is appropriately selected from inorganic anti-blocking agents such as silica, calcium carbonate, kaolin, and zeolite, and organic anti-blocking agents such as acrylic, polymethacrylic, and polystyrene. can do. Among these, it is particularly preferable to use silica.
The average particle size of the antiblocking agent is preferably 1.0-2.0 μm, more preferably 1.0-1.5 μm.
It is preferable that the antiblocking agent has a mass of 3000 ppm in the polypropylene resin composition. The method of measuring the average particle diameter as used herein is to take a photograph with a scanning electron microscope, measure the Feret diameter in the horizontal direction using an image analyzer, and display the average value.

(4) Biaxially oriented polypropylene film The thickness of the entire biaxially oriented polypropylene film of the present invention is preferably 9 to 200 m, more preferably 10 to 150 µm, still more preferably 12 to 100 µm, and particularly preferably 12 to 80 µm.

The ratio of the thickness of the surface layer (B) to the substrate layer (A) in the biaxially oriented polypropylene film of the second invention is 0.01 to 0 for the total surface layer (B)/total substrate layer (A). It is preferably 0.5, more preferably 0.03 to 0.4, even more preferably 0.05 to 0.3. When the total surface layer (B)/total base layer (A) ratio exceeds 0.5, the shrinkage tends to increase. The thickness of the entire base layer (A) is preferably 50 to 99%, more preferably 60 to 97%, and particularly preferably 70 to 95% of the thickness of the entire film. The rest will be the surface layer (B) or the surface layer (B) and other layers (for example, C layer). The substantial thickness of the entire surface layer (B) is preferably 0.5-4 μm, more preferably 1-3.5 μm, and even more preferably 1.5-3 μm.

The ratio of the thickness of the surface layer (B) to the substrate layer (A) in the biaxially oriented polypropylene film of the second invention is 0.01 to 0 for the total surface layer (B)/total substrate layer (A). It is preferably 0.5, more preferably 0.03 to 0.4, even more preferably 0.05 to 0.3. When the total surface layer (B)/total base layer (A) ratio exceeds 0.5, the shrinkage tends to increase. The thickness of the entire base layer (A) is preferably 50 to 99%, more preferably 60 to 97%, and particularly preferably 70 to 95% of the thickness of the entire film. The rest will be the surface layer (B) or the surface layer (B) and other layers (for example, C layer).
The substantial thickness of the entire surface layer (B) is preferably 0.5-4 μm, more preferably 1-3.5 μm, and even more preferably 1.5-3 μm.
The biaxially oriented polypropylene film of the second invention may be a two-layer structure film having one substrate layer (A) and one surface layer (B), but may have three or more layers. . A two-layer structure of base layer (A)/surface layer (B) is preferred. In addition, even if it is a three-layer structure of surface layer (B) / layer A / surface layer (B) / base layer (A) / intermediate layer (C) / surface layer (B) or a multilayer structure of more than that good.
In addition, when there are a plurality of substrate layers (A) and surface layers (B), the composition may be different as long as each layer satisfies its properties.

(5) Film properties The heat shrinkage rate at 150°C in the machine direction and the transverse direction of the biaxially oriented biaxially oriented polypropylene film of the present invention is preferably 8% or less, more preferably 7% or less, 8% or less is particularly preferred. By setting the heat shrinkage rate to 8% or less, wrinkles caused by heat during processing can be reduced.

In the biaxially oriented polypropylene film of the present invention, the heat shrinkage rate in the machine direction at 150° C. is preferably 0.2 to 8%, more preferably 0.3 to 7%. If the heat shrinkage rate is within the above range, the film can be said to be excellent in heat resistance and can be used in applications where there is a possibility of being exposed to high temperatures. If the 150° C. heat shrinkage rate is up to about 1.5%, it is possible, for example, by increasing the low molecular weight component and adjusting the stretching conditions and heat setting conditions. Treatment or the like is preferable.

In the biaxially oriented polypropylene film of the present invention, the lateral heat shrinkage at 150° C. is preferably 0.2 to 8%, more preferably 0.3 to 7%, and 0.4 to 6%. is more preferred, and 0.5 to 5% is particularly preferred. If the heat shrinkage ratio is within the above range, the film can be said to be particularly excellent in heat resistance, and can be used in applications that may be exposed to high temperatures. If the 150° C. heat shrinkage rate is up to about 1.5%, it is possible, for example, by increasing the low molecular weight component and adjusting the stretching conditions and heat setting conditions. Treatment or the like is preferable.

The longitudinal tensile modulus of the biaxially oriented polypropylene film of the present invention is preferably 1.8 to 4 GPa, more preferably 2.1 to 3.7 GPa, and 2.2 to 3.5 GPa. more preferably 2.3 to 3.4 GPa. The measuring method will be described later.

The transverse tensile modulus of the biaxially oriented polypropylene film of the present invention is preferably 4.5 to 8 GPa, more preferably 4.6 to 7.5 GPa, and 4.7 to 7 GPa. is more preferred, and 4.8 to 6.5 GPa is particularly preferred. If the tensile elastic modulus in the lateral direction is within the above range, it is possible to obtain a film that is difficult to break.

The resistance to folding of the biaxially oriented polypropylene film of the present invention was evaluated by holding the film in a ring shape and compressing it, and measuring the ring crush resistance detected by a load cell. The measuring method will be described later.

The haze of the biaxially oriented polypropylene film of the present invention is preferably 5% or less, more preferably 0.2 to 5%, even more preferably 0.3 to 4.5%, and particularly preferably 0.4 to 4%. Within the above range, it may be easy to use in applications where transparency is required. Haze tends to be worsened, for example, when the stretching temperature and heat setting temperature are too high, when the chill roll (CR) temperature is high and the cooling rate of the stretched raw sheet is slow, and when the low molecular weight component is too much, these are adjusted. By doing so, it is possible to make it within the above range. A method for measuring haze will be described later.

The lower limit of the impact resistance (23°C) of the stretched polypropylene film of the present invention is preferably 0.6J, more preferably 0.7J. Within the above range, the film has sufficient toughness and is not broken during handling.
The upper limit of the impact resistance is preferably 3J, more preferably 2.5J, still more preferably 2.2J, and particularly preferably 2J from a practical point of view. Impact resistance tends to decrease, for example, when there are many low molecular weight components, when the overall molecular weight is low, when there are few high molecular weight components, or when the molecular weight of the high molecular weight components is low. These components can be adjusted to be within range.

The lower limit of the plane orientation coefficient of the biaxially stretched laminated polypropylene film of the present invention is preferably 0.011, more preferably 0.012, and still more preferably 0.013. Within the above range, the heat resistance and rigidity of the film tend to be increased.
A stretched laminated polypropylene film generally has a crystal orientation, and the direction and degree of the orientation greatly affect the physical properties of the film. The degree of crystal orientation tends to change depending on the molecular structure of the polypropylene used, the process and conditions in film production, and can be made within the above range by adjusting these. The measuring method will be described later.

The ink adhesion of the biaxially oriented polypropylene film of the present invention was evaluated by conducting a peeling test of the printing ink used for gravure printing, and evaluating the number of peeled portions out of 25 locations in total. The number of peeled portions is preferably 15 or less, more preferably 5 or less, and most preferably 0. If the number is 15 or more, the degree of ink peeling increases, which is problematic. A method for evaluating ink adhesion will be described later.

The lamination strength in the longitudinal direction after lamination to the biaxially oriented polypropylene film of the present invention is preferably 1.2 to 2.5 N/15 mm, more preferably 1.3 to 2.5 N/mm, and 1.4 to 2 0.5 N/mm is more preferred. A method for measuring the lamination strength will be described later.

The dynamic friction coefficient of the biaxially oriented polypropylene film of the present invention is preferably 0.5 or less, more preferably 0.48 or less, and particularly preferably 0.45 or less. When the coefficient of dynamic friction is 0.5 or less, the film can be smoothly unwound from the roll film, and printing can be easily performed. A method for measuring the coefficient of dynamic friction will be described later.

(4) Production method The biaxially stretched laminated polypropylene film of the present invention is produced by melt extruding a polypropylene resin with an extruder to form an unstretched sheet, stretching the unstretched sheet by a predetermined method, and heat-treating it. Obtainable.
In the case of the second invention, polypropylene raw material for the base layer (A) (polypropylene resin composition for the base layer (A)) and polypropylene raw material for the surface layer (B) (polypropylene resin composition for the surface layer (B) It can be obtained by melt-extruding each of the products with a separate extruder to form a laminated unstretched sheet, and stretching and heat-treating the unstretched sheet by a predetermined method.
An unstretched sheet is obtained by using multiple extruders, feed blocks, and multi-manifolds. The melt extrusion temperature is preferably about 200 to 280°C.
In the second invention, in order to obtain a laminated film with a good appearance without disturbing the layers within this temperature range, the viscosity difference (MFR difference) is preferably 6 g/10 minutes or less. If the viscosity difference is more than 6 g/10 minutes, the layers tend to be disordered and the appearance is poor. It is more preferably 5.5 g/10 minutes or less, still more preferably 5 g/10 minutes or less.

The chill roll surface temperature is preferably 25 to 35°C, more preferably 27 to 33°C. Then, the film is stretched 3 to 8 times, preferably 3 to 7 times, in the machine direction (MD) with stretching rolls at 120 to 165°C, and subsequently stretched in the TD direction at 155 to 175°C, more preferably 160 to 163°C. 4 to 20 times, preferably 6 to 12 times. Furthermore, heat setting is performed at 165 to 176° C., more preferably 170 to 176° C., still more preferably 172 to 175° C., with 2 to 10% relaxation. The biaxially oriented laminated polypropylene film obtained in this way can be subjected, if necessary, to corona discharge, plasma treatment, flame treatment, etc., and then wound up with a winder to obtain a film roll.

The lower limit of the draw ratio in MD is preferably 3 times, more preferably 3.5 times. If it is less than the above, the film thickness may become uneven. The upper limit of the MD draw ratio is preferably 8 times, more preferably 7 times. If the above is exceeded, it may become difficult to perform subsequent TD stretching. The lower limit of the MD stretching temperature is preferably 120°C, more preferably 125°C, and still more preferably 130°C. If it is less than the above, the mechanical load may increase, the thickness unevenness may increase, and the surface of the film may become rough. The upper limit of the MD stretching temperature is preferably 160°C, more preferably 155°C, still more preferably 150°C. A higher temperature is preferable for lowering the heat shrinkage, but the film may adhere to the rolls, making it impossible to stretch or roughening the surface.

The lower limit of the TD draw ratio is preferably 4 times, more preferably 5 times, and still more preferably 6 times. If it is less than the above, thickness unevenness may occur. The upper limit of the TD draw ratio is preferably 20 times, more preferably 17 times, still more preferably 15 times, and particularly preferably 12 times. If the above is exceeded, the heat shrinkage rate may increase, or breakage may occur during stretching. The preheating temperature in TD stretching is preferably set 5 to 15° C. higher than the stretching temperature in order to quickly raise the film temperature to the vicinity of the stretching temperature. TD stretching is performed at a higher temperature than conventional biaxially oriented polypropylene films. The lower limit of the TD stretching temperature is preferably 155°C, more preferably 157°C, still more preferably 158°C, and particularly preferably 160°C. If it is less than the above, it may be broken without sufficiently softening, or the heat shrinkage rate may increase. The upper limit of the TD stretching temperature is preferably 170°C, more preferably 168°C, still more preferably 163°C. In order to lower the heat shrinkage rate, a higher temperature is preferable, but if the above temperature is exceeded, the low-molecular-weight components melt and recrystallize, which not only lowers the orientation but also causes surface roughness and whitening of the film.

The stretched film is heat set. Heat setting can be performed at higher temperatures than conventional biaxially oriented polypropylene films. The lower limit of the heat setting temperature is preferably 165°C, more preferably 166°C. If it is less than the above, the heat shrinkage rate may increase. In addition, a long time of treatment is required to reduce the heat shrinkage, which may result in poor productivity. The upper limit of the heat setting temperature is preferably 176°C, more preferably 175°C. If the above is exceeded, the low-molecular-weight components may melt and recrystallize, resulting in surface roughness and whitening of the film.

It is preferable to relax (relieve) at the time of heat setting. The lower limit of relaxation is preferably 2%, more preferably 3%. If it is less than the above, the heat shrinkage rate may increase. The upper limit of relaxation is preferably 10%, more preferably 8%. When the above is exceeded, thickness unevenness may become large.

Furthermore, in order to reduce the thermal shrinkage, the film produced by the above process can be wound into a roll and then annealed off-line. The lower limit of the offline annealing temperature is preferably 160°C, more preferably 162°C, still more preferably 163°C. If it is less than the above, the effect of annealing may not be obtained. The upper limit of the offline annealing temperature is preferably 175°C, more preferably 174°C, still more preferably 173°C. When the above is exceeded, the transparency may be lowered and the thickness unevenness may be increased.

The lower limit of the offline annealing time is preferably 0.1 minutes, more preferably 0.5 minutes, and still more preferably 1 minute. If it is less than the above, the effect of annealing may not be obtained. The upper limit of the offline annealing time is preferably 30 minutes, more preferably 25 minutes, still more preferably 20 minutes. If the above is exceeded, productivity may decrease.

The present invention will be described in more detail below with reference to examples, but the following examples do not limit the present invention, and are included in the present invention when modified within the scope of the gist of the present invention. Methods for measuring physical properties of films obtained in Examples and Comparative Examples are as follows.

1) Stereoregularity Mesopentad fraction ([mmmm]%) was measured using 13C-NMR. The mesopentad fraction was calculated according to the method described in "Zambelli et al., Macromolecules, Vol. 6, p.925 (1973)". 13C-NMR measurement was performed at 110°C by dissolving 200 mg of a sample in a mixture of o-dichlorobenzene and deuterated benzene at 8:2 (volume ratio) at 135°C using "AVANCE500" manufactured by BRUKER.

2) Melt flow rate (MFR; g/10 minutes)
It was measured at a temperature of 230° C. and a load of 2.16 kgf according to JIS K7210.
As the resin, pellets (powder) were directly weighed and used.
After cutting out the necessary amount of the film, a sample cut to about 5 mm square was used.

3) Molecular Weight and Molecular Weight Distribution Molecular weight and molecular weight distribution were determined by monodisperse polystyrene standards using gel permeation chromatography (GPC) and converted to polypropylene values. Measurement conditions such as columns and solvents used in GPC measurement are as follows.
Solvent: 1,2,4-trichlorobenzene Column: TSKgel GMHHR-H (20) HT x 3
Flow rate: 1.0ml/min
Detector: RI
Measurement temperature: 140°C

The number average molecular weight (Mn), mass average molecular weight (Mw), and molecular weight distribution are expressed by the following equations according to the number of molecules (Ni) at each elution position of the GPC curve obtained through the molecular weight calibration curve. Defined.
Number average molecular weight: Mn = Σ (Ni · Mi) / ΣNi
Mass average molecular weight: Mw = Σ (Ni · Mi ² ) / Σ (Ni · Mi)
Molecular weight distribution: Mw/Mn
When the baseline was not clear, the baseline was set in the range up to the lowest point of the high-molecular-weight elution peak closest to the elution peak of the standard substance.

4) Thickness The thickness of each layer of the substrate layer (A) and the surface layer (B) was measured by cutting out a cross section of a biaxially oriented laminated polypropylene film solidified with a modified urethane resin with a microtome and observing it with a differential interference microscope. .

5) Thermal shrinkage rate (%)
It was measured by the following method according to JIS Z1712. The film was cut into a width of 20 mm and a length of 200 mm in each of the MD direction and the TD direction, suspended in a hot air oven at 150° C. and heated for 5 minutes. The length after heating was measured, and the thermal shrinkage rate was determined as the ratio of the shrinkage length to the original length.

6) Tensile modulus (Young's modulus (unit: GPa))
The Young's modulus of the film in the MD and TD directions was measured at 23° C. according to JIS K7127.
7) Ring crush (g)
Prepare a film sample size of 12.7 mm x 152 mm with a digital ring crush tester (manufactured by Tester Sangyo Co., Ltd.), set the attachment spacer on the sample table according to the thickness of the film sample, and set the MD and TD directions. In each, a film sample is inserted circumferentially. At 23°C, the compression plate was lowered at a speed of 12 mm/min. The maximum load when compressed at 100 mm was taken as the ring crush measurement value.

8) Haze (unit: %)
It was measured according to JIS K7105.

9) Dynamic Friction Coefficient In accordance with JIS K7125, the corona-treated surfaces of the films were superimposed and measured at 23°C.
10) Impact resistance Measured at 23°C using a film impact tester manufactured by Toyo Seiki.

11) Refractive index and plane orientation coefficient Measured according to JIS K7142-1996 5.1 (method A) using an Abbe refractometer manufactured by Atago. Nx and Ny are the refractive indices along the MD and TD directions, respectively, and Nz is the refractive index in the thickness direction. The plane orientation coefficient (ΔP) was obtained by (Nx+Ny)/2−Nz.

12) Surface roughness The surface roughness of the obtained film is evaluated using a three-dimensional roughness meter (manufactured by Kosaka Laboratory Co., Ltd., model number ET-30HK), with a stylus pressure of 20 mg. 1 mm, a feed rate of 100 μm/sec, a feed pitch in the Y direction of 2 μm, 99 recorded lines, a magnification of 20,000 in the height direction, and a cutoff of 80 μm.
The three-dimensional roughness was measured three times, and the arithmetic average roughness (SRa), center plane peak height (SRp), and center plane valley depth (SRv) were evaluated by their average values.

13) Surface resistivity (LogΩ)
According to JIS K6911, after the film was aged at 23° C. for 24 hours, the corona-treated surface of the film was measured.

14) Wetting tension (mN/m)
After the film was aged at 23° C. and 50% relative humidity for 24 hours according to JIS K6768:1999, the corona-treated surface of the film was measured by the following procedure.
1) Measurements are performed in a standard laboratory atmosphere (see JIS K7100) at a temperature of 23°C and a relative humidity of 50%.
2) Place the test piece on the substrate of the hand coater (4.1), drop a few drops of the test mixture on the test piece, and immediately pull the wire bar to spread it.
If a cotton swab or brush is used to spread the test mixture, spread the liquid quickly over an area of at least 6 ^cm2 . The amount of liquid should be such that it forms a thin layer without pooling.
Wetting tension is determined by observing the liquid film of the mixed solution for testing in a bright place and observing the state of the liquid film after 3 seconds. If the applied state is maintained for 3 seconds or more without breaking the liquid film, it means that the liquid is wet. If the wetness is maintained for 3 seconds or more, the mixture proceeds to the next higher surface tension mixture, and conversely, if the liquid film breaks in 3 seconds or less, the mixture proceeds to the next lower surface tension mixture.
Repeat this operation and select a mixture that can wet the surface of the test piece accurately in 3 seconds.
3) Use a new swab for each test. Brushes or wire bars should be cleaned with methanol and dried between uses, as residual liquid will change composition and surface tension upon evaporation.
4) The operation of selecting a mixture that can wet the surface of the test piece in 3 seconds is performed at least 3 times. The surface tension of the mixture thus selected is reported as the wetting tension of the film.

15) Ink Adhesion Gravure printing was performed on the film using a gravure printer (manufactured by Mitani Iron Works Co., Ltd.) at a speed of 50 m/min (printing ink amount: 2 g/m ² ). The ink at this time is a water-based ink (manufactured by Dainippon Ink and Chemicals Co., Ltd.: trade name Ecofine 709 White). Using this printed sample, evaluation was made by peeling off a grid (25 pieces of 2 mm squares, 90° peeling method using Cellotape (registered trademark) manufactured by Nichiban Co., Ltd., 18 mm width). were ranked.
Cross-cut peeled portion: 0 ⊚: Excellent adhesion to printing ink.
〃 1 to 5 ◯: Adhesion of printing ink is good.
"6 to 15" △: Poor adhesion of printing ink.
〃 1 or more ... ×: There is no printing ink adhesion.

16) Laminate strength Laminate strength was measured by the following procedure.
1) Preparation of laminate film with sealant film A continuous dry lamination machine was used as follows.
The corona surface of the biaxially oriented polypropylene film obtained in Examples and Comparative Examples was gravure-coated with an adhesive so that the dry coating amount was 3.0 g/m ² , and then led to a drying zone at 80°C for 5 seconds. dried with Subsequently, it was laminated with a sealant film between rolls provided downstream (roll pressure: 0.2 MP, roll temperature: 60°C). The obtained laminated film was subjected to aging treatment at 40° C. for 3 days in a wound state.
The adhesive was obtained by mixing 17.9% by mass of the main agent (TM329, manufactured by Toyo-Morton Co., Ltd.), 17.9% by mass of the curing agent (CAT8B, manufactured by Toyo-Morton Co., Ltd.), and 64.2% by mass of ethyl acetate. An ether-based adhesive was used, and a non-biaxially oriented polypropylene film (Pylen (registered trademark) CT P1128, thickness 30 μm) manufactured by Toyobo Co., Ltd. was used as the sealant film.
2) Measurement of laminate strength The laminate film obtained above was cut into strips (length 200 mm, width 15 mm) having long sides in the longitudinal direction of the biaxially oriented polypropylene film, and a tensile tester (Tensilon, manufactured by Orientec) ) was used to measure the peel strength (N/15 mm) when T-shaped peeling was performed at a tensile speed of 200 mm/min in an environment of 23°C. The measurement was performed three times, and the average value was taken as the laminate strength.

(Comparative Example 7)
A mixture of 99% by weight of the polypropylene homopolymer PP-1 shown in Table 1 and 1% by weight of an antistatic agent (stearyl diethanolamine stearate (KYM-4K, manufactured by Matsumoto Yushi Co., Ltd.)) was used.
Using a 60 mm extruder, the raw material resin was melted at 250° C., co-extruded into a sheet from a T-die, cooled and solidified with a cooling roll at 30° C., then extruded at 135° C. in the machine direction (MD) 4. Stretched 5 times. Then, in a tenter, both ends of the film in the width direction are clipped, and after preheating at 175 ° C., the film is stretched 8.2 times in the width direction (TD) at 160 ° C. while relaxing 6.7% in the width direction (TD). , and heat-set at 170°C. The film forming conditions at this time were designated as film forming conditions a, and are shown in Table 2.
One surface side of the obtained biaxially oriented polypropylene film was subjected to corona treatment using a corona treatment machine manufactured by Softal Corona & Plasma GmbH under conditions of an applied current value of 0.75 A, and then subjected to a winder. A biaxially oriented single-layer polypropylene film of the present invention was obtained by winding the film. The physical properties of the obtained film are as shown in Table 3.

(Example 2)
The polypropylene homopolymer PP-1 shown in Table 1 was changed to polypropylene resin PP-2, the mixed raw material was melted at 250 ° C. using a 60 mm extruder, and co-extruded into a sheet from a T die, and the temperature of 30 ° C. After cooling and solidifying with cooling rolls, the film was stretched 4.5 times in the machine direction (MD) at 125°C. Then, in a tenter, both ends of the film in the width direction are clipped, and after preheating at 170 ° C., the film is stretched 8.2 times in the width direction (TD) at 158 ° C. while relaxing 6.7% in the width direction (TD). A biaxially stretched monolayer polypropylene film was obtained in the same manner as in Comparative Example 7, except that the film was heat-set at 165°C. The film forming conditions at this time were designated as film forming conditions b, and are shown in Table 2. The physical properties of the obtained film are as shown in Table 3.

(Comparative Example 8)
In the base material layer (A), 99% by weight of the polypropylene homopolymer PP-1 shown in Table 1 and 1% by weight of an antistatic agent (stearyl diethanolamine stearate (Matsumoto Yushi Co., Ltd. KYM-4K)) are mixed. I used what I did. The surface layer (B) contains 99.7% by weight of the polypropylene homopolymer PP-1 shown in Table 1 and 0.3% of an antiblocking agent (commercially available silica particles (average particle diameter: 1.3 μm)). % by mass was used.
A 60 mm extruder is used for the mixed raw material used for the base material layer (A), and a 65 mm extruder is used for the mixed raw material used for the surface layer (B). After co-extrusion and solidification by cooling with a cooling roll at 30°C, it was stretched 4.5 times in the machine direction (MD) at 135°C. Then, in a tenter, both ends of the film in the width direction are clipped, and after preheating at 175 ° C., the film is stretched 8.2 times in the width direction (TD) at 160 ° C. while relaxing 6.7% in the width direction (TD). , and heat-set at 170°C. A film was formed under the film forming conditions a shown in Table 2 and wound up with a winder to obtain a biaxially oriented laminated polypropylene film of the present invention in which one base layer (A) and one surface layer (B) were laminated one by one. . The surface side of the surface layer (B) of the obtained biaxially oriented polypropylene film was subjected to corona treatment using a corona treatment machine manufactured by Softal Corona & Plasma GmbH under conditions of an applied current value of 0.75 A. After application, the film was taken up by a winder to obtain a biaxially oriented monolayer polypropylene film of the present invention. The physical properties of the obtained film are as shown in Table 3.

(Example 4)
A biaxially stretched laminated polypropylene film was obtained in the same manner as in Comparative Example 8, except that the raw material used for the substrate layer (A) did not contain an antistatic agent. The physical properties of the obtained film are as shown in Table 3.

(Comparative Example 9)
The base material layer (A) contains 99% by mass of the polypropylene homopolymer PP-1 shown in Table 1 and 1% by mass of an antistatic agent (stearyl diethanolamine stearate (Matsumoto Yushi Co., Ltd. KYM-4K)). A mixture was used. Further, the surface layer (B) contains 48.7% by weight of the polypropylene homopolymer PP-6 shown in Table 1, 51% by weight of the ethylene copolymerized polypropylene polymer PP-7 shown in Table 1, and an antiblocking agent. , Commercially available silica particles (average particle diameter: 1.3 μm) in the same manner as in Comparative Example 8, except that the compound was used with respect to the composition mixed at a ratio of 0.3 parts by mass. A biaxially oriented laminated polypropylene film was obtained.

(Example 6)
A biaxially stretched monolayer polypropylene film was obtained in the same manner as in Comparative Example 7, except that the film thickness was 30 μm. The physical properties of the obtained film are as shown in Table 3.

(Example 7)
A biaxially stretched monolayer polypropylene film was obtained in the same manner as in Comparative Example 7, except that the film thickness was changed to 40 μm. The physical properties of the obtained film are as shown in Table 3.

(Comparative example 1)
A biaxially oriented monolayer polypropylene film was obtained in the same manner as in Comparative Example 7, except that the polypropylene resin PP-1 shown in Table 1 was changed to the polypropylene resin PP-3 shown in Table 1. The physical properties of the obtained film are as shown in Table 4.

(Comparative example 2)
A biaxially stretched single-layer polypropylene film was formed in the same manner as in Comparative Example 7, except that the polypropylene resin PP-1 shown in Table 1 was changed to the polypropylene resin PP-4 shown in Table 1, but the film was broken during stretching. I couldn't get the film.

(Comparative Example 3)
A biaxially stretched monolayer polypropylene film was obtained in the same manner as in Comparative Example 7, except that the polypropylene resin PP-1 shown in Table 1 was changed to the polypropylene resin PP-5 shown in Table 1. The physical properties of the obtained film are as shown in Table 4.

(Comparative Example 4)
The polypropylene resin PP-1 shown in Table 1 was changed to the polypropylene resin PP-6 shown in Table 1, the raw resin was melted at 250 ° C. using a 60 mm extruder, and coextruded into a sheet from a T die, and 30 After cooling and solidifying with cooling rolls at 125°C, the film was stretched 4.5 times in the machine direction (MD) at 125°C. Then, in a tenter, both ends of the film in the width direction are clipped, and after preheating at 170 ° C., the film is stretched 8.2 times in the width direction (TD) at 158 ° C. while relaxing 6.7% in the width direction (TD). A biaxially stretched monolayer polypropylene film was obtained in the same manner as in Comparative Example 7, except that the film was heat-set at 165°C. The physical properties of the obtained film are as shown in Table 4.

(Comparative Example 5)
The polypropylene resin PP-1 shown in Table 1 was changed to the polypropylene resin PP-8 shown in Table 1, the raw material resin was melted at 250 ° C. using a 60 mm extruder, and coextruded into a sheet from a T die, and 30 After cooling and solidifying with cooling rolls at 140°C, the film was stretched 4.5 times in the machine direction (MD) at 140°C. Then, in a tenter, both ends of the film in the width direction are clipped, preheated at 170 ° C., stretched at 160 ° C. in the width direction (TD) to 8.2 times, and relaxed by 6.7% in the width direction (TD). A biaxially stretched monolayer polypropylene film was obtained in the same manner as in Comparative Example 7, except that the film was heat-set at 168°C. The film-forming conditions at this time were designated as film-forming conditions c, and are shown in Table 2. The physical properties of the obtained film are as shown in Table 4.

(Comparative Example 6)
The polypropylene resin PP-1 shown in Table 1 was changed to the polypropylene resin PP-9 shown in Table 1, the raw resin was melted at 250 ° C. using a 60 mm extruder, and coextruded into a sheet from a T die, and 30 After cooling and solidifying with cooling rolls at 135°C, the film was stretched 4.5 times in the machine direction (MD) at 135°C. Then, in a tenter, both ends of the film in the width direction are clipped, preheated at 170 ° C., stretched at 160 ° C. in the width direction (TD) to 8.2 times, and relaxed by 6.7% in the width direction (TD). A biaxially stretched monolayer polypropylene film was obtained in the same manner as in Comparative Example 7, except that the film was heat-set at 168°C. The film forming conditions at this time were designated as film forming conditions d, and are shown in Table 2. The physical properties of the obtained film are as shown in Table 4.

The biaxially oriented polypropylene films obtained in Examples 2, 4, 6 and 7 had small heat shrinkage and large Young's modulus. Among them, the laminated film obtained in Example 4 was a film having even better lamination strength and ink adhesion.
In contrast, the film obtained in Comparative Example 1 had a large heat shrinkage rate in the width direction (TD). The film obtained in Comparative Example 3 had a large heat shrinkage rate in the width direction (TD) and a small Young's modulus in the width direction (TD). The film obtained in Comparative Example 4 has a large heat shrinkage rate and a small Young's modulus in the width direction (TD) and the machine direction (MD).
The film obtained in Comparative Example 5 had a small Young's modulus in the transverse direction (TD). The film obtained in Comparative Example 6 had a large heat shrinkage rate in the width direction (TD).

The biaxially stretched laminated polypropylene film of the present invention has higher heat resistance and rigidity, less wrinkles caused by heat, and is less likely to break, and thus has excellent workability.
The biaxially oriented polypropylene film of the present invention can be used not only for food packaging such as standing pouches, but also for labels and the like.

Claims (5)

A polypropylene resin composed of a complete homopolypropylene resin that does not contain a copolymer component and/or a polypropylene resin obtained by copolymerizing ethylene and/or an α-olefin having 4 or more carbon atoms, which constitutes the film, satisfies the following conditions 1) to 4). filling and
the lower limit of the plane orientation coefficient of the film is 0.0125;
A biaxially oriented polypropylene film characterized by having a transverse tensile modulus of 5.1 GPa or more.
1) The lower limit of the mesopentad fraction is 96%.
2) The upper limit of the amount of copolymerizable monomers other than propylene is 0.1 mol %.
3) The weight average molecular weight (Mw)/number average molecular weight (Mn) is 3.0 or more and 5.4 or less.
4) Melt flow rate (MFR) measured at 230° C. and 2.16 kgf is 6.5 g/10 min or more and 9.0 g/10 min or less. A substrate layer (A) and a substrate layer mainly composed of a polypropylene resin composed of a complete homopolypropylene resin containing no copolymer component and/or a polypropylene resin obtained by copolymerizing ethylene and/or an α-olefin having 4 or more carbon atoms. A polypropylene-based resin consisting of a complete homopolypropylene resin containing no copolymer component on at least one surface of (A) and/or a polypropylene resin obtained by copolymerizing ethylene and/or an α-olefin having 4 or more carbon atoms as a main component. A complete homopolypropylene resin containing no copolymer component and / or ethylene and / or an α-olefin having 4 or more carbon atoms is copolymerized, which constitutes the base layer (A). The polypropylene resin made of polypropylene resin satisfies the following conditions 1) to 4), and
the lower limit of the plane orientation coefficient of the film is 0.0125;
A biaxially oriented polypropylene film characterized by having a transverse tensile modulus of 4.8 GPa or more.
1) The lower limit of the mesopentad fraction is 96%.
2) The upper limit of the amount of copolymerizable monomers other than propylene is 0.1 mol %.
3) The weight average molecular weight (Mw)/number average molecular weight (Mn) is 3.0 or more and 5.4 or less.
4) Melt flow rate (MFR) measured at 230° C. and 2.16 kgf is 6.2 g/10 min or more and 9.0 g/10 min or less. 3. The biaxially oriented polypropylene film according to claim 1 or 2, wherein the heat shrinkage at 150[deg.] C. in the longitudinal and transverse directions of the film is 8% or less. The biaxially oriented polypropylene film according to any one of claims 1 to 3, which has a longitudinal tensile modulus of 2.0 GPa or more and a transverse tensile modulus of 4.5 GPa or more. The biaxially oriented polypropylene film according to any one of claims 1 to 4, which has a haze value of 5% or less.