KR20240058955A - Biaxially oriented polypropylene film - Google Patents

Abstract

To provide a biaxially oriented laminated polypropylene film with higher heat resistance and rigidity. It is a biaxially oriented polypropylene film characterized in that the polypropylene resin constituting the film satisfies the conditions 1) to 4) below and the lower limit of the plane orientation coefficient of the film is 0.0125. 1) The lower limit of the mesopentad fraction is 96%. 2) The upper limit of the amount of copolymerized monomers other than propylene is 0.1 mol%. 3) Mass average molecular weight (Mw)/number average molecular weight (Mn) is 3.0 or more and 5.4 or less. 4) The melt flow rate (MFR) measured at 230°C and 2.16 kgf is more than 6.2 g/10 min and less than 9.0 g/10 min.

Description

Biaxially oriented polypropylene film {BIAXIALLY ORIENTED POLYPROPYLENE FILM}

The present invention relates to biaxially oriented laminated polypropylene films. In detail, it relates to a biaxially oriented polypropylene film with excellent heat resistance and mechanical properties.

Conventionally, stretched polypropylene films have been widely used for a wide range of purposes, such as for packaging food and various products, for electrical insulation, and as surface protection films. However, conventional polypropylene films have a shrinkage rate of several tens of percent at 150°C, and compared to polyethylene terephthalate (PET) films, etc., they have low heat resistance and low rigidity, so their uses have been limited.

Various technologies for improving the physical properties of polypropylene films have been proposed. For example, by making a film using polypropylene, which contains approximately equal amounts of high-molecular-weight components and low-molecular-weight components (or has a small amount of low-molecular-weight components), has a wide molecular weight distribution, and has a low decalin soluble content, rigidity and processability are balanced. The technology is known (patent document 1). However, this technology still cannot be said to have sufficient heat resistance at high temperatures exceeding 150°C, and no polypropylene film has been known to have high heat resistance and excellent impact resistance and transparency.

As a result of careful study based on the above-described prior art, the applicant of the present application succeeded in providing a stretched polypropylene film with high rigidity and high heat resistance by using a polypropylene-based polymer with a mesopentad fraction of 96% or more ( Patent Document 2). However, this film had room for improvement in heat resistance.

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

In view of the above-described circumstances, the present invention sets out as a task the provision of a biaxially oriented laminated polypropylene film with higher heat resistance and rigidity.

The present invention, which was able to solve the above problems, is a biaxially oriented polypropylene film characterized in that the polypropylene resin constituting the film satisfies the conditions 1) to 4) below and the lower limit of the plane orientation coefficient of the film is 0.0125. am.

1) The lower limit of the mesopentad fraction is 96%.

2) The upper limit of the amount of copolymerized monomers other than propylene is 0.1 mol%.

3) Mass average molecular weight (Mw)/number average molecular weight (Mn) is 3.0 or more and 5.4 or less.

4) The melt flow rate (MFR) measured at 230°C and 2.16 kgf is more than 6.2 g/10 min and less than 9.0 g/10 min.

In addition, the second present invention, which was able to solve the above problems, includes a base material layer (A) containing polypropylene resin as a main component and a surface layer containing polypropylene resin as a main component on at least one surface of the base layer (A) ( B), the polypropylene resin constituting the base layer (A) satisfies the conditions 1) to 4) below, and the lower limit of the plane orientation coefficient of the film is 0.0125. .

1) The lower limit of the mesopentad fraction is 96%.

2) The upper limit of the amount of copolymerized monomers other than propylene is 0.1 mol%.

3) Mass average molecular weight (Mw)/number average molecular weight (Mn) is 3.0 or more and 5.4 or less.

4) The melt flow rate (MFR) measured at 230°C and 2.16 kgf is more than 6.2 g/10 min and less than 9.0 g/10 min.

In this case, it is suitable that the heat shrinkage rate of the film in the longitudinal and transverse directions at 150°C is 8% or less.

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

In this case, it is suitable that the haze value of the film is 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, has higher thermal dimensional stability and rigidity in the transverse direction, has smaller heat distortion wrinkles, and has less wrinkles. Because it is difficult to break, film processability is very excellent.

The biaxially oriented polypropylene-based film of the first invention 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.

1) The lower limit of the mesopentad fraction is 96%.

2) The upper limit of the amount of copolymerized monomers other than propylene is 0.1 mol%.

3) Mass average molecular weight (Mw)/number average molecular weight (Mn) is 3.0 or more and 5.4 or less.

4) The melt flow rate (MFR) measured at 230°C and 2.16 kgf is more than 6.2 g/10 min and less than 9.0 g/10 min.

In addition, the biaxially oriented polypropylene film of the second invention includes a base material layer (A) containing polypropylene resin as a main component and a surface layer containing polypropylene resin as a main component on at least one surface of the base layer (A). (B), the polypropylene resin constituting the base layer (A) satisfies the conditions 1) to 4) below, and the lower limit of the plane orientation coefficient of the film is 0.0125.

1) The lower limit of the mesopentad fraction is 96%.

2) The upper limit of the amount of copolymerized monomers other than propylene is 0.1 mol%.

3) Mass average molecular weight (Mw)/number average molecular weight (Mn) is 3.0 or more and 5.4 or less.

4) The melt flow rate (MFR) measured at 230°C and 2.16 kgf is more than 6.2 g/10 min and less than 9.0 g/10 min.

This is explained in more detail below.

(1) The polypropylene resin used in the first invention can also be a polypropylene resin copolymerized with 0.5 mol% or less of ethylene and/or an α-olefin having 4 or more carbon atoms. Such copolymerized polypropylene resin is also included in the polypropylene resin (hereinafter referred to as polypropylene resin) of the present invention. The copolymerization component is preferably 0.3 mol% or less, more preferably 0.1 mol% or less, and a completely homopolypropylene resin containing no copolymerization component is most preferable.

When copolymerization of ethylene and/or α-olefin having 4 or more carbon atoms exceeds 0.5 mol%, crystallinity and rigidity may decrease too much, and heat shrinkage at high temperatures may increase. These resins may be blended and used.

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

Additionally, Mw/Mn, which is an indicator of molecular weight distribution, is preferably 3.0 to 5.4 for polypropylene resin. More preferably, it is 3.0 to 5.0, further preferably is 3.2 to 4.5, and particularly preferably is 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 Mw/Mn becomes too large, the high molecular weight component increases, and the heat shrinkage rate may increase, or may shrink in the width direction ( There is a tendency for the tensile modulus (Young's modulus) of TD) to become small. When a high molecular weight component is present, the high molecular weight component promotes the crystallization of the low molecular weight component, but the entanglement of the molecules becomes stronger, and the heat shrinkage rate also tends to increase even if crystallinity is high.

If Mw/Mn of the entire polypropylene resin constituting the biaxially oriented polypropylene film of the present invention is less than 3.0, film forming becomes difficult.

Mw means mass average molecular weight, and Mn means number average molecular weight.

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

When measuring the gel permeation chromatography (GPC) integration curve of the entire polypropylene resin constituting the biaxially oriented polypropylene film of the first invention, the lower limit of the amount of the component with a molecular weight of 100,000 or less is preferably 35% by mass. , more preferably 38 mass%, further preferably 40 mass%, particularly preferably 41 mass%, and most preferably 42 mass%.

On the other hand, the upper limit of the amount of the component with a molecular weight of 100,000 or less in the GPC integration curve is preferably 65% by mass, more preferably 60% by mass, further preferably 58% by mass, and especially preferably 56% by mass. %, and most preferably 55 mass%. Within the above range, stretching becomes easy, thickness unevenness decreases, and the stretching temperature or heat setting temperature tends to rise, and the heat shrinkage rate can be suppressed to a lower level.

At this time, the melt flow rate (MFR; 230°C, 2.16 kgf) of the polypropylene resin is preferably 6.2 g/10 min to 10.0 g/10 min.

The lower limit of the MFR of the polypropylene resin is more preferably 6.5 g/10 min, more preferably 7 g/10 min, and particularly preferably 7.5 g/10 min. The upper limit of the MFR of the polypropylene resin is more preferably 9 g/10 min, more preferably 8.5 g/10 min, and particularly preferably 8.2 g/10 min.

If the melt flow rate (MFR; 230°C, 2.16 kgf) is 6.2 g/10 minutes or more, the thermal contraction rate at high temperature can also be reduced. Additionally, because the degree of orientation of the film generated by stretching becomes stronger, the rigidity of the film, especially the tensile modulus (Young's modulus) in the width (TD) direction, increases. Additionally, if the melt flow rate (MFR; 230°C, 2.16 kgf) is 9.0 g/10 minutes or less, it is easy to form a film without breaking.

In addition, the molecular weight distribution of polypropylene resin can be determined by polymerizing components of different molecular weights in a series of plants in multiple stages, blending components of different molecular weights with a kneader off-line, blending catalysts with different performances, or polymerizing the desired molecular weight distribution. It is possible to adjust it by using a catalyst that can realize.

The polypropylene resin used in the present invention is obtained by polymerizing propylene as a raw material using a known catalyst such as a Ziegler-Natta catalyst or a metallocene catalyst. Among them, in order to eliminate heterogeneous bonds, it is preferable to use a Ziegler-Natta catalyst and a catalyst capable of polymerization with high stereoregularity.

As a method for polymerizing propylene, known methods may be employed, for example, polymerizing in an inert solvent such as hexane, heptane, toluene, or xylene, polymerizing in a liquid monomer, adding a catalyst to the gas monomer, Examples include a method of polymerizing in a gaseous state or a method of polymerizing by combining these methods.

Polypropylene resin may contain additives or other resins. Examples of additives include antioxidants, ultraviolet absorbers, nucleating agents, adhesives, antifogging agents, flame retardants, inorganic or organic fillers, etc. 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 with 4 or more carbon atoms, and various elastomers. These are sequentially polymerized using a multi-stage reactor, blended with polypropylene resin using a Henschel mixer, diluted with polypropylene to a predetermined concentration of master pellets previously produced using a melt kneader, or melt-kneaded in full in advance. You can use it.

(2) The polypropylene resin used in the base material layer (A) of the second invention can also be a polypropylene resin copolymerized with 0.5 mol% or less of ethylene and/or an α-olefin having 4 or more carbon atoms. Such copolymerized polypropylene resin is also included in the polypropylene resin (hereinafter referred to as polypropylene resin) of the present invention. The copolymerization component is preferably 0.3 mol% or less, more preferably 0.1 mol% or less, and a completely homopolypropylene resin containing no copolymerization component is most preferable.

When copolymerization of ethylene and/or α-olefin having 4 or more carbon atoms exceeds 0.5 mol%, crystallinity and rigidity may decrease too much, and heat shrinkage at high temperatures may increase. These resins may be blended and used.

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

Additionally, Mw/Mn, which is an indicator of molecular weight distribution, is preferably 3.0 to 5.4 for polypropylene resin. More preferably, it is 3.0 to 5.0, further preferably is 3.2 to 4.5, and particularly preferably is 3.3 to 4.0.

If the Mw/Mn of the entire polypropylene resin constituting the base layer (A) exceeds 5.4, if Mw/Mn becomes too large, the high molecular weight components may increase, and the heat shrinkage rate may increase, or the tensile strength in the width direction (TD) may increase. There is a tendency for the elastic modulus (Young's modulus) to become small.

When a high molecular weight component is present, the high molecular weight component promotes the crystallization of the low molecular weight component, but the entanglement of the molecules becomes stronger, and the heat shrinkage rate also tends to increase even if crystallinity is high.

If Mw/Mn of the entire polypropylene resin constituting the biaxially oriented polypropylene film of the present invention is less than 3.0, film forming becomes difficult. Mw means mass average molecular weight, and Mn means number average molecular weight.

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

When measuring the gel permeation chromatography (GPC) integration curve of the entire polypropylene resin constituting the base layer (A), the lower limit of the amount of components with a molecular weight of 100,000 or less is preferably 35% by mass, more preferably It is 38 mass%, more preferably 40 mass%, especially preferably 41 mass%, and most preferably 42 mass%.

On the other hand, the upper limit of the amount of the component with a molecular weight of 100,000 or less in the GPC integration curve is preferably 65% by mass, more preferably 60% by mass, further preferably 58% by mass, and especially preferably 56% by mass. %, and most preferably 55 mass%. Within the above range, stretching becomes easy, thickness unevenness decreases, and the stretching temperature or heat setting temperature tends to rise, and the heat shrinkage rate can be suppressed to a lower level.

At this time, the melt flow rate (MFR; 230°C, 2.16 kgf) of the polypropylene resin is preferably 6.2 g/10 min to 10.0 g/10 min.

The lower limit of the MFR of the polypropylene resin is more preferably 6.5 g/10 min, more preferably 7 g/10 min, and particularly preferably 7.5 g/10 min. The upper limit of the MFR of the polypropylene resin is more preferably 9 g/10 min, more preferably 8.5 g/10 min, and particularly preferably 8.2 g/10 min.

If the melt flow rate (MFR; 230°C, 2.16 kgf) is 6.2 g/10 minutes or more, the thermal contraction rate at high temperature can also be reduced. Additionally, because the degree of orientation of the film generated by stretching becomes stronger, the rigidity of the film, especially the tensile modulus (Young's modulus) in the width (TD) direction, increases. Additionally, if the melt flow rate (MFR; 230°C, 2.16 kgf) is 9.0 g/10 minutes or less, it is easy to form a film without breaking.

In addition, the molecular weight distribution of polypropylene resin can be determined by polymerizing components of different molecular weights in a series of plants in multiple stages, blending components of different molecular weights with a kneader off-line, blending catalysts with different performances, or polymerizing the desired molecular weight distribution. It is possible to adjust it by using a catalyst that can realize.

The polypropylene resin used in the base material layer (A) is obtained by polymerizing propylene as a raw material using a known catalyst such as a Ziegler-Natta catalyst or a metallocene catalyst. Among them, in order to eliminate heterogeneous bonds, it is preferable to use a Ziegler-Natta catalyst and a catalyst capable of polymerization with high stereoregularity.

As a method for polymerizing propylene, known methods may be employed, for example, polymerizing in an inert solvent such as hexane, heptane, toluene, or xylene, polymerizing in a liquid monomer, adding a catalyst to the gas monomer, Examples include a method of polymerizing in a gaseous state or a method of polymerizing by combining these methods.

Polypropylene resin may contain additives or other resins. Examples of additives include antioxidants, ultraviolet absorbers, nucleating agents, adhesives, antifogging agents, flame retardants, inorganic or organic fillers, etc. 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 with 4 or more carbon atoms, and various elastomers. These are sequentially polymerized using a multi-stage reactor, blended with polypropylene resin using a Henschel mixer, diluted with polypropylene to a predetermined concentration of master pellets previously produced using a melt kneader, or melt-kneaded in full in advance. You can use it.

(3) It is suitable that the surface roughness of the surface layer (B) of the second invention is 0.027 μm or more and 0.40 μm or less. If it is less than 0.027 μm, the adhesion to printing ink or the adhesive used for lamination with other member films is not sufficient, and if it exceeds 0.40 μm, problems such as color development and discoloration 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 polypropylene resin composition forming the surface layer (B) is composed of two or more types of polypropylene resins having different melt flow rates (MFR). It is preferable to use a mixture. In this case, the difference in MFR is preferably 3 g/10 minutes or more, and more preferably 3.5 g/10 minutes or more.

It is estimated that by using this mixture, the surface roughness of the surface layer (B) will be 0.027 μm or more due to the difference in crystallization rate.

As a polypropylene-based resin with a larger MFR, polypropylene copolymerized with ethylene and/or an α-olefin having 4 or more carbon atoms can also be used. Examples of α-olefins having 4 or more carbon atoms include 1-butene, 1-hexene, 4-methyl·1-pentene, and 1-octene.

Additionally, as a polypropylene-based resin with a smaller MFR, polypropylene copolymerized with ethylene and/or an α-olefin having 4 or more carbon atoms can also be used. Examples of α-olefins having 4 or more carbon atoms include 1-butene, 1-hexene, 4-methyl·1-pentene, and 1-octene.

Additionally, polar maleic acid or the like may be used as other copolymerization components.

It is preferable that the total amount of ethylene, α-olefins with 4 or more carbon atoms, and other copolymerization components is 8.0 mol% or less. If copolymerization exceeds 8.0 mol%, the film may whiten and have a poor appearance, or stickiness may occur, making film forming difficult.

Additionally, two or more types of these resins may be blended and used. In the case of blending, individual resins may be copolymerized in an amount exceeding 8.0 mol%, but the blend preferably contains 8.0 mol% or less of monomers other than propylene on a monomer basis.

Additionally, the polypropylene resin composition of the surface layer (B) preferably has an MFR of 1.0 g/10 min to 8 g/10 min. The lower limit of the MFR of the polypropylene resin composition of the surface layer (B) is more preferably 2 g/10 min, and even more preferably 3 g/10 min. The upper limit of the MFR of the polypropylene resin composition of the surface layer (B) is more preferably 7 g/10 min, and even more preferably 6.0 g/10 min. If it is within this range, film forming properties are good and the heat shrinkage rate at high temperature can be kept small. If the MFR of the polypropylene resin composition of the surface layer (B) is less than 1.0 g/10 min, and the MFR of the polypropylene of the base layer (A) is large, the viscosity difference between the base layer (A) and the surface layer (B) increases. , unevenness (fabric unevenness) is likely to occur during film forming. If the MFR of the polypropylene resin composition of the surface layer (B) exceeds 8 g/10 min, there is a risk that the adhesion to the cooling roll will deteriorate, air will be incorporated, smoothness will be poor, and defects that originate from this will increase.

The polypropylene resin used in the surface layer (B) is obtained by polymerizing propylene as a raw material using a known catalyst such as a Ziegler-Natta catalyst or a metallocene catalyst. Among them, in order to eliminate heterogeneous bonds, it is preferable to use a Ziegler-Natta catalyst and a catalyst capable of polymerization with high stereoregularity.

As a method for polymerizing propylene, known methods may be employed, for example, polymerization in an inert solvent such as hexane, heptane, toluene, or xylene, polymerization in liquid monomer, or adding a catalyst to the gaseous monomer, Examples include a method of polymerizing in a gaseous state or a method of polymerizing by combining these methods.

The surface layer (B) may contain additives or other resins. Examples of additives include antioxidants, ultraviolet absorbers, nucleating agents, adhesives, antifogging agents, flame retardants, inorganic or organic fillers, etc. 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 with 4 or more carbon atoms, and various elastomers. These are sequentially polymerized using a multi-stage reactor, blended with polypropylene resin using a Henschel mixer, diluted with polypropylene to a predetermined concentration of master pellets previously produced using a melt kneader, or melt-kneaded in full in advance. You can use it.

It is preferable that the wetting tension of the surface of the surface layer (B) is 38 mN/m or more.

When the wetting tension is 38 mN/m or more, adhesion to printing ink or adhesive improves.

It is more preferable that the wetting tension is 16LogΩ or more. In order to increase the wetting tension to 38 mN/m or more, additives such as antistatic agents and surfactants are usually used. However, since it has the effect of lowering the surface specific resistance, surface treatment such as corona treatment or flame treatment is used. You can.

For example, corona treatment is preferably performed in the air using a preheating roll and a treatment roll.

It is preferable that the center plane ridge height SRp + center plane valley depth SRv of the surface 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 of the surface of the surface layer (B), the center plane peak height SRp, and the center plane valley depth SRv are calculated using a three-dimensional roughness meter, with a stylus pressure of 20 mg, a measurement length in the X direction of 1 mm, and a feed pitch in the Y direction of 2. Measurements were made with 99 lines recorded in ㎛, a height direction magnification of 20000 times, and a cutoff of 80 ㎛, and the arithmetic mean roughness was determined according to the definition of the arithmetic mean roughness described in JISB0601 (1994).

The center surface ridge height SRp + center surface valley depth SRv of the surface of the surface layer (B) is an index of the state of the large uneven portion formed by the lubricant, and in the state of the roll film, the slip when in contact with the base material layer (A) It is related to sex.

If the center surface ridge height SRp + center 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 if it is 2.0 μm or less, transparency is maintained.

The center plane ridge height SRp + center plane valley depth SRv of the surface of the surface layer (B) is preferably 1.1 μm or more, more preferably 1.2 μm or more, and especially preferably 1.3 μm or more.

In order to keep the center surface ridge height SRp + center surface valley depth SRv of the surface layer (B) from 1.0 ㎛ to 2.0 ㎛, a suitable method is to mix an anti-blocking agent into the polypropylene resin composition forming the surface layer (B). .

The anti-blocking agent can be appropriately selected from among inorganic anti-blocking agents such as silica, calcium carbonate, kaolin, and zeolite, and organic anti-blocking agents such as acrylic, polymethacrylic, and polystyrene. Among these, it is particularly preferable to use silica.

The preferred average particle diameter of the anti-blocking agent is 1.0 to 2.0 ㎛, more preferably 1.0 to 1.5 ㎛.

The anti-blocking agent is preferably used in a mass of 3000 ppm in the polypropylene resin composition. The method of measuring the average particle size here is to take a picture with a scanning electron microscope, measure the horizontal ferret diameter using an image analyzer, and display it as the average value.

(4) Biaxially oriented polypropylene film

The overall thickness of the biaxially oriented polypropylene film of the present invention is preferably 9 to 200 m, more preferably 10 to 150 μm, further preferably 12 to 100 μm, and particularly preferably 12 to 80 μm.

As the ratio of the thickness of the surface layer (B) and the base layer (A) in the biaxially oriented polypropylene film of the second invention, the total surface layer (B)/total base layer (A) is preferably 0.01 to 0.5, It is more preferable that it is 0.03 to 0.4, and it is still more preferable that it is 0.05 to 0.3. When the total surface layer (B)/total base layer (A) exceeds 0.5, the shrinkage rate tends to increase. Additionally, the thickness of the entire base layer (A) relative to the thickness of the entire film is preferably 50 to 99%, more preferably 60 to 97%, and particularly preferably 70 to 95%. The remainder becomes the surface layer (B) or the surface layer (B) and other layers (for example, C layer). The actual thickness of the entire surface layer (B) is preferably 0.5 to 4 μm, more preferably 1 to 3.5 μm, and still more preferably 1.5 to 3 μm.

As the ratio of the thickness of the surface layer (B) and the base layer (A) in the biaxially oriented polypropylene film of the second invention, the total surface layer (B)/total base layer (A) is preferably 0.01 to 0.5, It is more preferable that it is 0.03 to 0.4, and it is still more preferable that it is 0.05 to 0.3. When the total surface layer (B)/total base layer (A) exceeds 0.5, the shrinkage rate tends to increase. Additionally, the thickness of the entire base layer (A) relative to the thickness of the entire film is preferably 50 to 99%, more preferably 60 to 97%, and particularly preferably 70 to 95%. The remainder becomes the surface layer (B) or the surface layer (B) and other layers (for example, C layer).

The actual thickness of the entire surface layer (B) is preferably 0.5 to 4 μm, more preferably 1 to 3.5 μm, and still more preferably 1.5 to 3 μm.

The biaxially oriented polypropylene film of the second invention may be a film with a two-layer structure having one base layer (A) and one surface layer (B), or may have a structure of three or more layers. Preferred is a two-layer structure of base layer (A)/surface layer (B). Additionally, it may be a three-layer structure of surface layer (B)/A layer/surface layer (B), /base layer (A)/middle layer (C)/surface layer (B), or a multilayer structure of more than that.

Additionally, when there are multiple base layers (A) or surface layers (B), the compositions may be different as long as each layer satisfies its properties.

(5) Film properties

The thermal contraction rate of the biaxially oriented polypropylene film of the present invention at 150°C in the longitudinal and transverse directions is preferably 8% or less, and more preferably 7% or less. By setting the heat shrinkage rate to 8% or less, heat distortion wrinkles during processing can be reduced.

In the biaxially oriented polypropylene film of the present invention, the thermal contraction rate in the longitudinal direction at 150°C is preferably 0.2 to 8%, and more preferably 0.3 to 7%. If the heat shrinkage rate is within the above range, the film can be said to have excellent heat resistance and can be used even in applications that may be exposed to high temperatures. In addition, if the heat shrinkage rate at 150°C is up to about 1.5%, it can be achieved by adjusting the stretching conditions and heat setting conditions, for example by increasing the low molecular weight component, but to lower it below that, it is necessary to perform an offline annealing treatment, etc. desirable.

In the biaxially oriented polypropylene film of the present invention, the heat shrinkage rate in the transverse direction at 150°C is preferably 0.2 to 8%, more preferably 0.3 to 7%, further preferably 0.4 to 6%, and 0.5%. to 5% is particularly preferred. If the heat shrinkage rate is within the above range, the film can be said to be particularly excellent in heat resistance and can be used even in applications that may be exposed to high temperatures. In addition, if the heat shrinkage rate at 150°C is up to about 1.5%, it can be achieved by adjusting the stretching conditions and heat setting conditions, for example by increasing the low molecular weight component, but to lower it below that, it is necessary to perform an offline annealing treatment, etc. desirable.

The tensile modulus of elasticity in the longitudinal direction 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, further preferably 2.2 to 3.5 GPa, and 2.3 to 3.4 GPa. is particularly preferable. The measurement method is described later.

The tensile modulus of elasticity in the transverse direction 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, further preferably 4.7 to 7 GPa, and still more preferably 4.8 to 6.5 GPa. is particularly preferable. If the tensile modulus of elasticity in the transverse direction is within the above range, it becomes possible to produce a film that is difficult to fold.

The difficulty in folding 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 drag force by ring crush measurements detected by a load cell. The measurement method is 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%, further preferably 0.3 to 4.5%, and especially preferably 0.4 to 4%. If it is within the above range, it may be easier to use for applications requiring transparency. Haze tends to worsen when, for example, the stretching temperature and heat setting temperature are too high, the cooling roll (CR) temperature is high and the cooling rate of the stretched fabric sheet is slow, or there are too many low molecular weight components, so these can be adjusted. By doing so, it can be within the above range. The haze measurement method is described later.

The lower limit of the plane orientation coefficient of the biaxially oriented laminated polypropylene film of the present invention is preferably 0.011, more preferably 0.012, and even more preferably 0.013. Within the above range, the heat resistance and rigidity of the film tend to increase.

Stretched laminated polypropylene films generally have a crystal orientation, and the direction or degree has a significant influence on the film properties. The degree of crystal orientation tends to change depending on the molecular structure of the polypropylene used and the process and conditions in film production, and can be adjusted to fall within the above range. The measurement method is described later.

The ink adhesion of the biaxially oriented polypropylene film of the present invention was evaluated by performing a peeling test on gravure-printed printing ink and measuring the number of peeled parts out of a total of 25 locations. The number of peeling points is preferably 15 or less, more preferably 5 or less, and most preferably 0. If there are more than 15, the degree of ink peeling increases and becomes a problem. The evaluation method of ink adhesion is described later.

The longitudinal lamination strength after lamination for 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 even more preferably 1.4 to 2.5 N/mm. desirable. The method for measuring laminate strength is 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. If the dynamic friction coefficient is 0.5 or less, unwinding of the film from the roll film can be performed smoothly and printing processing is easy. The method of measuring the dynamic friction coefficient will be described later.

(6) Manufacturing method

The biaxially oriented laminated polypropylene film of the present invention can be obtained by melting and extruding a polypropylene resin using an extruder to form an unstretched sheet, stretching the unstretched sheet by a predetermined method, and heat treating it.

In the case of the second invention, a polypropylene raw material for the base layer (A) (polypropylene-based resin composition for the base layer (A)) and a polypropylene raw material for the surface layer (B) (polypropylene-based resin composition for the surface layer (B)) Each can be obtained by melt extruding using a separate extruder to form a laminated unstretched sheet, stretching the unstretched sheet by a predetermined method, and then heat treating it.

Unstretched sheets are obtained by using multiple extruders, feed blocks, or 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 layer within this temperature range, the viscosity difference (MFR difference) between the polypropylene raw material for the base layer (A) and the polypropylene raw material for the surface layer (B) is determined. It is desirable to keep it below 6g/10min. If the viscosity difference is greater than 6 g/10 minutes, the layer is likely to be disturbed, resulting in poor appearance. More preferably, it is 5.5 g/10 minutes or less, and even more preferably, it is 5 g/10 minutes or less.

The cooling roll surface temperature is preferably 25 to 35°C, and more preferably 27 to 33°C. Next, the film is stretched 3 to 8 times in the longitudinal (MD) direction, preferably 3 to 7 times, with a stretching roll at 120 to 165°C, and then stretched in the TD direction at 155 to 175°C, more preferably 160 to 163°C. Stretching is performed 4 to 20 times, preferably 6 to 12 times. Additionally, heat setting is performed at 165 to 176°C, more preferably 170 to 176°C, and still more preferably 172 to 175°C, while providing 2 to 10% relaxation. A film roll can be obtained by subjecting the biaxially oriented laminated polypropylene film obtained in this way to corona discharge, plasma treatment, flame treatment, etc., as necessary, and then winding it with a winder.

The lower limit of the MD draw ratio is preferably 3 times, and more preferably 3.5 times. If it is less than the above, film thickness may become uneven. The upper limit of MD stretch ratio is preferably 8 times, more preferably 7 times. If it exceeds the above, continuous TD stretching may become difficult. The lower limit of the stretching temperature of MD is preferably 120°C, more preferably 125°C, and still more preferably 130°C. If it is less than the above, mechanical load may increase, thickness unevenness may increase, or the surface of the film may become rough. The upper limit of the stretching temperature of MD is preferably 160°C, more preferably 155°C, and still more preferably 150°C. A higher temperature is preferable for lowering the thermal shrinkage rate, but there are cases where it adheres to the roll and cannot be stretched, or surface roughness may occur.

The lower limit of the draw ratio of TD is preferably 4 times, more preferably 5 times, and still more preferably 6 times. If it is less than the above, thickness may become uneven. The upper limit of the TD draw ratio is preferably 20 times, more preferably 17 times, further preferably 15 times, and especially preferably 12 times. If it exceeds the above, the heat shrinkage rate may increase or it may break during stretching. The preheating temperature in TD stretching quickly raises the film temperature to around the stretching temperature, so it is preferably set 5 to 15°C higher than the stretching temperature. TD stretching is performed at a higher temperature than that of conventional biaxially oriented polypropylene films. The lower limit of the stretching temperature of TD is preferably 155°C, more preferably 157°C, further preferably 158°C, and particularly preferably 160°C. If it is less than the above, it may not be sufficiently softened and may break, or the heat shrinkage rate may increase. The upper limit of the TD stretching temperature is preferably 170°C, more preferably 168°C, and still more preferably 163°C. In order to lower the heat shrinkage rate, a higher temperature is preferable, but if the temperature exceeds the above temperature, the low molecular weight component melts and recrystallizes, which not only reduces the orientation, but also causes surface roughness and whitening of the film.

The film after stretching is heat set. Heat setting can be performed at a higher temperature 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. Additionally, in order to lower the heat shrinkage rate, long-term processing is required, which may reduce productivity. The upper limit of the heat setting temperature is preferably 176°C, more preferably 175°C. If the above amount is exceeded, the low molecular weight component may melt and recrystallize, resulting in roughening of the surface or whitening of the film.

When heat setting, it is desirable to relax. 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%. If it exceeds the above, thickness unevenness may increase.

Additionally, in order to reduce heat shrinkage, the film manufactured through the above process may be wound into a roll and then annealed offline. The lower limit of the temperature for offline annealing is preferably 160°C, more preferably 162°C, and 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, and still more preferably 173°C. If it exceeds the above, transparency may decrease or thickness unevenness may increase.

The lower limit of the offline annealing time is preferably 0.1 minute, more preferably 0.5 minute, 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, and even more preferably 20 minutes. If the above amount is exceeded, productivity may decrease.

Example

Hereinafter, the present invention will be described in more detail by way of examples. However, the following examples do not limit the present invention, and any modifications made without departing from the spirit of the present invention are included in the present invention. In addition, the measuring method of the film properties obtained in the examples and comparative examples is as follows.

1) Stereoregularity

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

2) Melt flow rate (MFR; g/10 min)

In accordance with JIS K7210, measurement was performed at a temperature of 230°C and a load of 2.16 kgf.

The resin was used as pellets (powder) by measuring the required amount.

After cutting the required amount of film, a sample cut into a square with a side of about 5 mm was used.

3) Molecular weight and molecular weight distribution

Molecular weight and molecular weight distribution were determined based on monodisperse polystyrene using gel permeation chromatography (GPC) and converted to polypropylene values. The measurement conditions for the column and solvent used in GPC measurement are as follows.

Solvent: 1,2,4-trichlorobenzene

Column: TSKgel GMHHR-H(20)HT×3

Flow rate: 1.0ml/min

Detector: RI

Measurement temperature: 140℃

The number average molecular weight (Mn), mass average molecular weight (Mw), and molecular weight distribution are each defined by the following equation by the number of molecules (Ni) of the molecular weight (Mi) at each elution position of the GPC curve obtained through the molecular weight calibration curve.

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, it was decided to set the baseline in the range from the lowest position on the high molecular weight side of the elution peak on the high molecular weight side closest to the elution peak of the standard substance.

4) Thickness

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

5) Heat shrinkage rate (%)

Based on JIS Z1712, it was measured by the following method. The film was cut to a width of 20 mm and a length of 200 mm in each of the MD and TD directions, hung in a hot air oven at 150°C, and heated for 5 minutes. The length after heating was measured, and the heat shrinkage rate was calculated as the ratio of the shrunken length to the original length.

6) Tensile modulus (Young’s modulus (unit: ㎬))

In accordance with JIS K7127, the Young's modulus in the MD and TD directions of the film was measured at 23°C.

7) Ring Crush (g)

Using a digital ring crush tester (manufactured by Tester Sangyo), prepare a film sample size of 12.7 mm Insert along the circumference. At 23°C, the maximum load when the compression plate was compressed at a downward speed of 12 mm/min. was taken as the ring crush measurement value.

8) Haze (unit: %)

Measured according to JIS K7105.

9) Dynamic friction coefficient

In accordance with JIS K7125, the corona-treated sides of the film were overlapped and measured at 23°C.

10) Refractive index, plane orientation coefficient

Measurement was made using an Atago Abbe refractometer according to JIS K7142-1996 5.1 (Method A). The refractive indices along the MD and TD directions were set to Nx and Ny, respectively, and the refractive indices in the thickness direction were set to Nz. The plane orientation coefficient (ΔP) was determined as (Nx+Ny)/2-Nz.

11) Surface roughness

The surface roughness of the obtained film was evaluated using a three-dimensional roughness meter (manufactured by Kosaka Kensho, model number ET-30HK) at a stylus pressure of 20 mg, a measurement length of 1 mm in the Measurements were made with a feed pitch of 2 ㎛, 99 recorded lines, a height direction magnification of 20000 times, and a cutoff of 80 ㎛.

The three-dimensional roughness was measured three times, and the arithmetic average roughness (SRa), central peak height (SRp), and central valley depth (SRv) were evaluated by their average values.

12) Surface specific resistance value (LogΩ)

In accordance with JIS K6911, the corona-treated surface of the film was measured after aging the film at 23°C for 24 hours.

13) Wet tension (mN/m)

In accordance with JIS K6768:1999, the film was aged at 23°C and relative humidity of 50% for 24 hours, and then the corona-treated surface of the film was measured in the following procedure.

1) Measurements are performed in a standard laboratory atmosphere (refer to JIS K7100) with 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 spread it by pulling the wire bar.

When spreading the test mixture using a cotton swab or brush, the liquid quickly spreads over an area of at least 6 cm2. The amount of liquid should be such that it forms a thin layer without forming a puddle.

Wetting tension is determined by observing the liquid film of the test liquid mixture in a bright place and examining the state of the liquid film after 3 seconds. Those that do not cause tearing of the liquid film and maintain the state when applied for more than 3 seconds are in a wet state. If the wet state is maintained for more than 3 seconds, the next step is to proceed to the mixed solution with high surface tension. Conversely, if the liquid film is torn in 3 seconds or less, the next step is to proceed to the next mixed solution with low surface tension.

Repeat this operation to select a mixture that can accurately wet the surface of the test piece for 3 seconds.

3) A new swab is used for each test. Brushes or wire bars are cleaned with methanol and dried after each use, as residual liquid changes composition and surface tension by evaporation.

4) Perform the operation of selecting a mixture that can wet the surface of the test piece for 3 seconds at least three times. The surface tension of the liquid mixture selected in this way is reported as the wetting tension of the film.

14) Ink adhesion

On the film, full-side gravure printing (printing ink amount: 2 g/m2) was performed at a speed of 50 m/min using a gravure printer (manufactured by Mitani Tekkosho). The ink at this time is water-based ink (Dainipbon Ink Kagaku Kogyo Co., Ltd.: brand name: Eco Fine 709 Bag). Using this print sample, it was evaluated (in more detail) by checkerboard peeling (90° peeling method using 25 squares of 2 mm, 18 mm wide cellophane tape (registered trademark) manufactured by Nichiban) and judged from practicality. Thus, the following rank separation was performed.

checkerboard eye peeling part 0… ◎: Excellent printing ink adhesion.

〃 1 to 5… ○: Good printing ink adhesion.

〃 6 to 15… △: Printing ink adhesion is poor.

〃 16 or more… ×: There is no printing ink adhesion.

15) Laminate strength

The laminate strength was measured by the following procedure.

1) Production of laminate film with sealant film

It was carried out as follows using a continuous dry laminating machine.

The corona surface of the biaxially oriented polypropylene film obtained in Examples and Comparative Examples was gravure-coated with an adhesive so that the drying application amount was 3.0 g/m2, then guided to a drying zone and dried at 80°C for 5 seconds. Subsequently, it was bonded with a sealant film between rolls installed on the downstream side (roll pressure 0.2 MP, roll temperature: 60°C). The obtained laminate film was subjected to aging treatment at 40°C for 3 days in a wound state.

In addition, the adhesive used was an ether-based adhesive obtained by mixing 17.9% by mass of base material (TM329, manufactured by Toyo Moton), 17.9% by mass of hardener (CAT8B, manufactured by Toyo Moton), and 64.2% by mass of ethyl acetate, and the sealant film was Mui manufactured by Toyobo. An axially oriented polypropylene film (Pylene (registered trademark) CT P1128, thickness 30 μm) was used.

2) Measurement of laminate strength

The laminated film obtained above was cut into rectangles (length 200 mm, width 15 mm) having long sides in the longitudinal direction of the biaxially oriented polypropylene film, and tested at 23° C. using a tensile tester (Tensilon, manufactured by Orientec). The peel strength (N/15 mm) when peeled in a T shape at a tensile speed of 200 mm/min under an environment was measured. The measurement was performed three times, and the average value was taken as the laminate strength.

(Example 1)

A mixture of 99% by weight of the polypropylene homopolymer PP-1 shown in Table 1 and 1% by weight of an antistatic agent (stearyldiethanolamine stearate (KYM-4K, Matsumoto Yushi Co., Ltd.)) was used.

This mixture was melted at 250°C using a 60 mm extruder, co-extruded from a T die into a sheet, cooled and solidified with a cooling roll at 30°C, and then stretched 4.5 times in the machine direction (MD) at 135°C. did. Next, in the tenter, both ends of the film in the width direction are clipped, preheated at 175°C, stretched 8.2 times in the width direction (TD) at 160°C, and heated at 170°C while relaxing by 6.7% in the width direction (TD). Fixed. The film forming conditions at this time were set 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 the condition of an applied current value of 0.75 A, and then wound with a winder. This was used as the biaxially oriented single-layer polypropylene film of the present invention. 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 materials were melted at 250°C using a 60 mm extruder, and co-extruded into a sheet form from a T die at 30°C. After cooling and solidifying with a cooling roll, it was stretched 4.5 times in the longitudinal direction (MD) at 125°C. Next, in the tenter, both ends of the film in the width direction are clipped, preheated at 170°C, stretched 8.2 times in the width direction (TD) at 158°C, and heated at 165°C while relaxing by 6.7% in the width direction (TD). Except for fixing, a biaxially oriented single-layer polypropylene film was obtained in the same manner as in Example 1. The film forming conditions at this time were set as film forming condition b and are shown in Table 2. The physical properties of the obtained film are as shown in Table 3.

(Example 3)

In the base material layer (A), 99% by weight of polypropylene homopolymer PP-1 shown in Table 1 and 1% by weight of antistatic agent (stearyldiethanolamine stearate (KYM-4K, Matsumoto Yushi Co., Ltd.)) were mixed. one was used. Additionally, in the surface layer (B), 99.7% by weight of polypropylene homopolymer PP-1 shown in Table 1 and 0.3% by weight of an anti-blocking agent (commercially available silica particles (average particle diameter: 1.3 μm)) were used. .

The mixed raw materials used for the base layer (A) are melted at 250°C using a 60 mm extruder, and the mixed raw materials used for the surface layer (B) are melted at 250°C and co-extruded into a sheet form from a T die. After cooling and solidifying with a cooling roll at 30°C, it was stretched 4.5 times in the longitudinal direction (MD) at 135°C. Next, in the tenter, both ends of the film in the width direction are clipped, preheated at 175°C, stretched 8.2 times in the width direction (TD) at 160°C, and heated at 170°C while relaxing by 6.7% in the width direction (TD). Fixed. It was formed under the film forming conditions a shown in Table 2 and wound with a winder to obtain a biaxially oriented laminated polypropylene film of the present invention in which the base layer (A) and the surface layer (B) were laminated one layer each. After corona treatment was performed on the surface side of the surface layer (B) of the obtained biaxially oriented polypropylene film using a corona treatment machine manufactured by Softal Corona & Plasma GmbH under the condition of an applied current value of 0.75 A, wine What was wound further was used as the biaxially oriented single-layer polypropylene film of the present invention. The physical properties of the obtained film are as shown in Table 3.

(Example 4)

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

(Example 5)

In the base material layer (A), 99% by mass of polypropylene homopolymer PP-1 shown in Table 1 and 1% by mass of antistatic agent (stearyldiethanolamine stearate (KYM-4K, Matsumoto Yushi Co., Ltd.)) were mixed. one was used. In addition, 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 commercially available silica as an anti-blocking agent. A biaxially oriented laminated polypropylene film was obtained in the same manner as in Example 3, except that 0.3% by mass of particles (average particle diameter: 1.3 μm) were used.

(Example 6)

A biaxially oriented single-layer polypropylene film was obtained in the same manner as in Example 1, 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 oriented single-layer polypropylene film was obtained in the same manner as in Example 1, except that the film thickness was 40 μm. The physical properties of the obtained film are as shown in Table 3.

(Comparative Example 1)

A biaxially oriented single-layer polypropylene film was obtained in the same manner as in Example 1, 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 oriented single-layer polypropylene film was formed in the same manner as in Example 1 except that the polypropylene resin PP-1 shown in Table 1 was changed to the polypropylene resin PP-4 shown in Table 1, but during stretching It broke and the film could not be obtained.

(Comparative Example 3)

A biaxially oriented single-layer polypropylene film was obtained in the same manner as in Example 1, 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 material resin was melted at 250°C using a 60 mm extruder, and co-extruded from a T die into a sheet shape. After cooling and solidifying with a cooling roll at 30°C, it was stretched 4.5 times in the longitudinal direction (MD) at 125°C. Next, in the tenter, both ends of the film in the width direction are clipped, preheated at 170°C, stretched 8.2 times in the width direction (TD) at 158°C, and heated at 165°C while relaxing by 6.7% in the width direction (TD). Except for fixing, a biaxially oriented single-layer polypropylene film was obtained in the same manner as in Example 1. 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 co-extruded from a T die into a sheet shape. After cooling and solidifying with a cooling roll at 30°C, it was stretched 4.5 times in the longitudinal direction (MD) at 140°C. Next, in the tenter, both ends of the film in the width direction are clipped, preheated at 170°C, stretched 8.2 times in the width direction (TD) at 160°C, and heated at 168°C while relaxing by 6.7% in the width direction (TD). Except for fixing, a biaxially oriented single-layer polypropylene film was obtained in the same manner as in Example 1. The film forming conditions at this time were set 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 material resin was melted at 250°C using a 60 mm extruder, and co-extruded from a T die into a sheet shape. After cooling and solidifying with a cooling roll at 30°C, it was stretched 4.5 times in the longitudinal direction (MD) at 135°C. Next, in the tenter, both ends of the film in the width direction are clipped, preheated at 170°C, stretched 8.2 times in the width direction (TD) at 160°C, and heated at 168°C while relaxing by 6.7% in the width direction (TD). Except for fixing, a biaxially oriented single-layer polypropylene film was obtained in the same manner as in Example 1. The film forming conditions at this time were set 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 1 to 5 had a small thermal contraction rate and a large Young's modulus. Among them, the laminated films obtained in Examples 3 to 5 were films with better lamination strength and ink adhesion.

In contrast, the film obtained in Comparative Example 1 had a large thermal contraction rate in the width direction (TD). The film obtained in Comparative Example 3 had a high thermal contraction rate in the width direction (TD) and a low Young's modulus in the width direction (TD). The film obtained in Comparative Example 4 has a high thermal contraction rate and a low Young's modulus in the width direction (TD) and the longitudinal direction (MD).

The film obtained in Comparative Example 5 had a small Young's modulus in the width direction (TD). The film obtained in Comparative Example 6 had a large thermal contraction rate in the width direction (TD).

The biaxially oriented laminated polypropylene film of the present invention has higher heat resistance and rigidity, has smaller heat distortion wrinkles, and is less prone to folding, so it is excellent in processability.

The biaxially oriented polypropylene-based film of the present invention can be used not only for food packaging used in standing pouches, etc., but also for label purposes.

Claims (4)

The polypropylene resin constituting the film satisfies the following conditions 1) to 4), the lower limit of the plane orientation coefficient of the film is 0.0125, the tensile modulus of elasticity in the transverse direction of the film is 5.0 GPa or more, and the longitudinal elasticity of the film is 5.0 GPa or more. A biaxially oriented polypropylene film characterized by a heat shrinkage rate of 8% or less at 150°C in the direction and transverse direction.
1) The lower limit of the mesopentad fraction is 96%.
2) The upper limit of the amount of copolymerized monomers other than propylene is 0.1 mol%.
3) Mass average molecular weight (Mw)/number average molecular weight (Mn) is 3.0 or more and 5.0 or less.
4) The melt flow rate (MFR) measured at 230°C and 2.16 kgf is more than 6.2 g/10 min and less than 9.0 g/10 min. It has a base layer (A) containing polypropylene resin as a main component and a surface layer (B) containing polypropylene resin as a main component on at least one surface of the base layer (A), and constitutes the base layer (A). The polypropylene resin satisfies the conditions 1) to 4) below,
The center surface ridge height SRp + the center surface valley depth SRv of the surface of the surface layer (B) is 1.0 ㎛ or more and 2.0 ㎛ or less,
A biaxial film characterized in that the lower limit of the plane orientation coefficient of the film is 0.0125, the tensile modulus of elasticity in the transverse direction of the film is 4.9 GPa or more, and the heat shrinkage rate at 150 ° C. in the longitudinal and transverse directions of the film is 8% or less. Oriented polypropylene film.
1) The lower limit of the mesopentad fraction is 96%.
2) The upper limit of the amount of copolymerized monomers other than propylene is 0.1 mol%.
3) Mass average molecular weight (Mw)/number average molecular weight (Mn) is 3.0 or more and 5.0 or less.
4) The melt flow rate (MFR) measured at 230°C and 2.16 kgf is more than 6.2 g/10 min and less than 9.0 g/10 min. The biaxially oriented polypropylene film according to claim 1 or 2, wherein the film has a longitudinal tensile modulus of elasticity of 2.0 GPa or more. The biaxially oriented polypropylene film according to claim 1 or 2, wherein the film has a haze value of 5% or less.