WO2021256349A1 - Biaxially-oriented polypropylene film - Google Patents

Abstract

[Problem] To provide a biaxially-oriented polypropylene film which has high rigidity and excellent heat resistance even at a temperature as high as 150°C, which easily maintains a bag shape when used as a packaging bag, which undergoes little pitch shift during printing and has few wrinkles in a seal part when heat sealed, and is not susceptible to electrostatic charge. [Solution] This biaxially-oriented polypropylene film: has stress (F5) when stretched 5% at 23°C of 40 MPa or more in the longitudinal direction, and 160 MPa or more in the width direction; heat shrinkage at 150°C of 10% or less in the longitudinal direction, and 30% or less in the width direction; and a surface intrinsic resistance of at least one surface of the film of 15Ω/□.

Description

Biaxially oriented polypropylene film

The present invention relates to a biaxially oriented polypropylene film having excellent rigidity and heat resistance. More specifically, the present invention relates to a biaxially oriented polypropylene film that can be suitably used for a packaging bag because it is easy to maintain the shape of the bag when it is used as a packaging bag, and there are few wrinkles in the sealed portion when it is heat-sealed and it is difficult to be charged.

Biaxially oriented polypropylene film has moisture resistance, and also has the necessary rigidity and heat resistance, so it is used for packaging and industrial applications. In recent years, as the applications used have expanded, higher performance has been required, and in particular, improvement in rigidity is expected. Further, from the consideration of the environment, it is required to maintain the strength even if the volume is reduced (the film thickness is thinned), but for that purpose, it is indispensable to significantly improve the rigidity. As a means for improving the rigidity, it is known that the crystallinity and melting point of the polypropylene resin are improved by improving the catalyst and the process technology at the time of polymerization of the polypropylene resin. No biaxially oriented polypropylene film had sufficient rigidity.

In the manufacturing process of biaxially oriented polypropylene film, after stretching in the width direction, the first stage heat treatment is performed while relaxing the film below the temperature at the time of width direction stretching, and in the second stage, heat treatment is performed at the first stage temperature to the width direction stretching temperature. (For example, see Reference 1 and the like), and a method of further stretching in the longitudinal direction after stretching in the width direction (see, for example, Reference 2 and the like) have been proposed. However, although the film described in Patent Document 2 is excellent in rigidity, wrinkles are likely to occur in the sealed portion after heat sealing, and the heat resistance is inferior. Further, the orientation of the film described in Patent Document 1 is low, and the rigidity is not sufficient.

WO2016 / 182003 International Bulletin Japanese Unexamined Patent Publication No. 2013-177645

The object of the present invention is to solve the above-mentioned problems. That is, the present invention relates to a biaxially oriented polypropylene film having excellent film rigidity and heat resistance at a high temperature of 150 ° C. More specifically, it is an object of the present invention to provide a biaxially oriented polypropylene film which can easily maintain the shape of a packaging bag, has less wrinkles in and around the sealed portion when heat-sealed, and is less likely to be charged.

As a result of diligent studies to achieve such an object, the present inventors have found that the stress (F5) at 5% elongation is 40 MPa or more in the longitudinal direction, 160 MPa or more in the width direction, and 150 at 23 ° C. A biaxially oriented polypropylene film having a heat shrinkage rate at ° C. of 10% or less in the longitudinal direction, 30% or less in the width direction, and a surface intrinsic resistance of at least one side of the film surface of 15 Ω / □ or less. As a result, it has been found that a biaxially oriented polypropylene film having excellent film rigidity and heat resistance at a high temperature of as high as 150 ° C. and being less likely to be charged can be obtained.

In this case, the heat shrinkage rate of the biaxially oriented polypropylene film at 120 ° C. is 2.0% or less in the longitudinal direction, 5.0% or less in the width direction, and the heat shrinkage rate at 120 ° C. in the longitudinal direction is It is preferably smaller than the heat shrinkage rate of 120 ° C. in the width direction.

Further, in this case, it is preferable that the refractive index Ny in the longitudinal direction of the biaxially oriented polypropylene film is 1.5230 or more and ΔNy is 0.0220 or more.

Furthermore, in this case, it is preferable that the haze of the biaxially oriented polypropylene film is 5.0% or less.

Furthermore, in this case, it is preferable that the mesopentad fraction of the main polypropylene resin constituting the base material layer (A) is 97.0% or more.

Furthermore, in this case, it is preferable that the crystallization temperature of the main polypropylene resin constituting the base material layer (A) is 105 ° C. or higher and the melting point is 161 ° C. or higher.

Furthermore, in this case, it is preferable that the melt flow rate of the main polypropylene resin constituting the base material layer (A) is 4.0 g / 10 minutes or more.

Furthermore, in this case, it is preferable that the component amount of the main polypropylene resin constituting the base material layer (A) having a molecular weight of 100,000 or less is 35% by mass or more.

The biaxially oriented polypropylene film of the present invention has high rigidity and excellent heat resistance at a high temperature of 150 ° C., so that it is easy to maintain the bag shape when it is used as a packaging bag, and wrinkles in the sealed portion when heat-sealed. A biaxially oriented polypropylene film that can be suitably used for a packaging bag can be obtained because the amount of the film is small and the laminating strength is excellent. Further, since the biaxially oriented polypropylene film has excellent rigidity, the strength can be maintained even if the thickness of the film is reduced, and it can be suitably used for applications requiring higher rigidity. ..

Hereinafter, the biaxially oriented polypropylene film of the present invention will be described in more detail.
The biaxially oriented polypropylene film of the present invention preferably has a structure including a base layer (A), an intermediate layer (B), and a surface layer (C), and the base layer (A), the intermediate layer (B), and the surface layer (C) are preferably included. The surface layer (C) is preferably adjacent in this order.

The base layer (A), the intermediate layer (B), and the surface layer (C) will be described in detail below.

(Base material layer (A))
The base material layer (A) of the biaxially oriented polypropylene film of the present invention comprises a polypropylene resin composition containing the following polypropylene homopolymer as a main component.

(Polypropylene homopolymer)
The polypropylene homopolymer used for the base material layer (A) is preferably a polypropylene polymer that does not substantially contain ethylene and / or an α-olefin having 4 or more carbon atoms, and ethylene and / or 4 or more carbon atoms. Even when the α-olefin component is contained, the amount of ethylene and / or the α-olefin component having 4 or more carbon atoms is preferably 0.3 mol% or less, more preferably 0.2 mol or less. More preferably, it is a polypropylene polymer having an amount of 0.1 mol or less. Within the above range, crystallinity tends to improve.
Examples of the α-olefin component having 4 or more carbon atoms constituting such a copolymer include 1-butene, 1-pentene, 3-methylpentene-1, 3-methylbutene-1, 1-hexene, and 4-methyl. Examples thereof include pentene-1,5-ethylhexene-1,1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-eicosene and the like.
As the polypropylene homopolymer, two or more different kinds of polypropylene homopolymers can be used.

(Tacticity)
The mesopentad fraction ([mmmm]%), which is an index of the stereoregularity of the polypropylene homopolymer used in the present invention, is preferably in the range of 97.0 to 99.9%, preferably 97.5 to 99. It is more preferably in the range of 0.7%, further preferably in the range of 98.0 to 99.5%, and particularly preferably in the range of 98.5 to 99.3%.
When it is 97.0% or more, the crystallinity of the polypropylene resin is enhanced, the melting point, crystallinity, and crystallinity of the crystals in the film are improved, and rigidity and heat resistance at high temperature can be easily obtained. When it is 99.9% or less, it is easy to suppress the cost in terms of polypropylene production, and it is difficult to break during film formation. The mesopentad fraction is measured by a nuclear magnetic resonance method (so-called NMR method).
In order to keep the mesopentad fraction of the polypropylene homopolymer within the above range, a method of washing the obtained polypropylene resin powder with a solvent such as n-heptane, selection of a catalyst and / or a co-catalyst, and a polypropylene resin composition. A method of appropriately selecting the components of the substance is preferably adopted.

(Melting temperature)
The lower limit of the melting temperature (Tm) of the polypropylene homopolymer constituting the biaxially oriented polypropylene film of the present invention is preferably 160 ° C, more preferably 161 ° C, still more preferably 162 ° C, and further. It is preferably 163 ° C, more preferably 164 ° C. When Tm is 160 ° C. or higher, rigidity and heat resistance at high temperature can be easily obtained. The upper limit of Tm is preferably 170 ° C., more preferably 169 ° C., still more preferably 168 ° C., even more preferably 167 ° C., and particularly preferably 166 ° C. When Tm is 170 ° C. or lower, it is easy to suppress an increase in cost in terms of polypropylene production, and it is difficult to break during film formation. By blending the crystal nucleating agent with the polypropylene resin described above, the melting temperature can be further increased.
Tm is measured by a differential scanning calorimeter (DSC). A sample of 1 to 10 mg is packed in an aluminum pan, set, melted at 230 ° C. for 5 minutes in a nitrogen atmosphere, and the scanning speed is -10 ° C./. It is the main peak temperature of the endothermic peak associated with melting observed when the temperature is lowered to 30 ° C. in minutes, held for 5 minutes, and the temperature is raised at a scanning rate of 10 ° C./min.

(Crystallization temperature)
The lower limit of the crystallization temperature (Tc) measured by DSC of the polypropylene homopolymer constituting the biaxially oriented polypropylene film of the present invention is 105 ° C, preferably 108 ° C, and more preferably 110 ° C. .. When Tc is 105 ° C. or higher, crystallization is likely to proceed in the stretching in the width direction and the subsequent cooling step, and rigidity and heat resistance at high temperature are easily obtained. The upper limit of Tc is preferably 135 ° C., more preferably 133 ° C., still more preferably 132 ° C., even more preferably 130 ° C., particularly preferably 128 ° C., and most preferably 127 ° C. Is. When Tc is 135 ° C. or lower, it is easy to suppress an increase in cost in terms of polypropylene production, and it is difficult to break during film formation. By blending the crystal nucleating agent with the above-mentioned polypropylene resin, the crystallization temperature can be further raised.
Tc is measured by DSC. A sample of 1 to 10 mg is packed in an aluminum pan, melted at 230 ° C for 5 minutes in a nitrogen atmosphere, and cooled to 30 ° C at a scanning speed of -10 ° C / min. It is the main peak temperature of the exothermic peak observed at the time of.

(Melt flow rate)
The melt flow rate (MFR) of the polypropylene homopolymer constituting the biaxially oriented polypropylene film of the present invention is measured in accordance with the condition M (230 ° C., 2.16 kgf) of JIS K 7210 (1995). 4.0 to 30 g / 10 minutes is preferable, 4.5 to 25 g / 10 minutes is more preferable, and 4.8 to 22 g / 10 minutes is more preferable, and 5.0 to 20 g / 10 minutes is preferable. Minutes are particularly preferable, and 6.0 to 20 g / 10 minutes are most preferable.
When the MFR of the polypropylene resin is 4.0 g / 10 minutes or more, it is easy to obtain a biaxially oriented polypropylene film having low heat shrinkage.
Further, when the MFR of the polypropylene resin is 30 g / 10 minutes or less, it is easy to maintain the film-forming property of the film.

From the viewpoint of film characteristics, the lower limit of the MFR (230 ° C., 2.16 kgf) of the polypropylene homopolymer constituting the film is preferably 5.0 g / 10 minutes, more preferably 5.5 g / 10 minutes, still more preferably. It is preferably 6.0 g / 10 minutes, particularly preferably 6.3 g / 10 minutes, and most preferably 6.5 g / 10 minutes.
When the MFR of the polypropylene resin is 5.0 g / 10 minutes or more, the amount of low molecular weight components of the polypropylene resin constituting the film increases. Therefore, by adopting the widthwise stretching step in the film forming step described later, In addition to the fact that the orientation crystallization of the polypropylene resin is more promoted and the degree of crystallization in the film is more likely to be increased, the polypropylene molecular chains in the amorphous portion are less entangled with each other, and the heat resistance is more likely to be increased. ..
In order to keep the MFR of the polypropylene homopolymer within the above range, it is preferable to adopt a method of controlling the average molecular weight and the molecular weight distribution of the polypropylene homopolymer.

That is, the lower limit of the amount of the component having a molecular weight of 100,000 or less in the gel permeation chromatography (GPC) integration curve of the polypropylene homopolymer constituting the film of the present invention is 35% by mass, preferably 38% by mass, and more. It is preferably 40% by mass, more preferably 41% by mass, and particularly preferably 42% by mass.
The upper limit of the amount of the component having a molecular weight of 100,000 or less in the GPC integration curve is preferably 65% by mass, more preferably 60% by mass, and further preferably 58% by mass. When the amount of the component having a molecular weight of 100,000 or less in the GPC integration curve is 65% by mass or less, the film strength is unlikely to decrease.
At this time, if a high molecular weight component or a long chain branching component having a long relaxation time is included, the amount of the component having a molecular weight of 100,000 or less contained in the polypropylene resin can be easily adjusted without significantly changing the overall viscosity, so that the rigidity is increased. It is easy to improve the film-forming property without significantly affecting the heat shrinkage.

(Molecular weight distribution)
The lower limit of the mass average molecular weight (Mw) / number average molecular weight (Mn), which is an index of the breadth of the molecular weight distribution of the polypropylene homopolymer used in the present invention, is preferably 3.5, more preferably 4.0. Yes, more preferably 4.5, and particularly preferably 5.0. The upper limit of Mw / Mn is preferably 30, more preferably 25, still more preferably 23, particularly preferably 21 and most preferably 20.
Mw / Mn can be obtained using GPC. When Mw / Mn is in the above range, it is easy to increase the amount of the component having a molecular weight of 100,000 or less.

For the molecular weight distribution of polypropylene homopolymers, components of different molecular weights can be polymerized in a series of plants in multiple stages, components of different molecular weights can be blended offline with a kneader, or catalysts with different performances can be blended. It can be adjusted by polymerization or by using a catalyst capable of achieving a desired molecular weight distribution. The shape of the molecular weight distribution obtained by GPC has a single peak in a GPC chart in which the horizontal axis is the logarithmic weight (M) log (logM) and the vertical axis is the differential distribution value (weight fraction per logM). It may have a gentle molecular weight distribution, or it may have a molecular weight distribution having a plurality of peaks and shoulders.

(Propylene resin composition)
Ethylene and / or propylene having an α-olefin component having 4 or more carbon atoms of more than 0.3% and ethylene and / or α-olefin having 4 or more carbon atoms in the propylene resin composition constituting the base material layer (A) When the copolymer with ethylene is mixed and used, the amount of ethylene and / or α-olefin component having 4 or more carbon atoms is 0.3 with respect to the entire polypropylene-based resin used for the base material layer (A). The content of the copolymer of propylene exceeding% and ethylene and / or α-olefin having 4 or more carbon atoms is preferably 5% by weight or less, more preferably 3% by weight or less, and 1% by weight. The following is more preferable, and 0% by weight is particularly preferable.

(Antistatic agent)
By using a specific diethanolamine fatty acid ester compound, a specific amine compound, and a specific glycerin monofatty acid ester compound in combination with the propylene resin composition constituting the base material layer (A) in a specific ratio, the initial antistatic property is sufficient. At the same time, an excellent antistatic property can be maintained for a long period of time, and the initial transparency is hardly deteriorated even when exposed to a high temperature, so that a non-sticky biaxially stretched polypropylene-based resin film can be obtained.

For example, a polyoxyethylene alkylamine mono obtained by adding 2 mol or more of ethylene oxide to 1 mol of the amine represented by the formula (1) with respect to 100 parts by weight of the polypropylene resin composition constituting the base material layer (A). 0.3 to 0.2 parts by weight of the fatty acid ester compound (A),

In the formula, R1 and R2 are alkyl groups having 7 to 21 carbon atoms, X and Y are integers of 1 to 29, respectively, and X + Y are integers of 2 to 30.

0.03 to 0.2 parts by weight of the glycerin monofatty acid ester compound (B) represented by the formula (2),

In the formula, R3 is an alkyl group having 7 to 21 carbon atoms.

0 to 0.2 parts by weight of the polyoxyethylene alkylamine difatty acid ester compound (C) to which 2 mol or more of ethylene oxide is added to 1 mol of the amine represented by the formula (3).

In the formula, R4, R5, and R6 are alkyl groups having 7 to 21 carbon atoms, X and Y are integers of 1 to 29, respectively, and X + Y are integers of 2 to 30.

0 to 0.2 parts by weight of the polyoxyethylene alkenylamine compound (D) to which 2 mol or more of ethylene oxide is added to 1 mol of the amine represented by the formula (4).

In the formula, R7 is an alkenyl group having 7 to 21 carbon atoms, X and Y are integers of 1 to 29, respectively, and X + Y is an integer of 2 to 30.
Is preferably contained.

The polyoxyethylene amine monoester compound (A) to which 2 mol of ethylene oxide is added to 1 mol of the amine used in the present invention is a nonionic antistatic agent represented by the formula (1) and is a group. It is contained in an amount of preferably 0.3 to 1.2 parts by weight, particularly preferably 0.3 to 1.1 parts by weight, based on 100 parts by weight of the polypropylene-based resin composition constituting the material layer (A). When the content of the compound (A) is 0.3 parts by weight or more, the antistatic effect is obtained for a long period of time, and when the content is 1.2 parts by weight or less, the bleeding amount is small and the transparency is lowered due to whitening. few.

The glycerin monofatty acid ester compound (B) used in the present invention is a nonionic antistatic agent represented by the formula (2), and R3 is a linear or branched alkyl group, preferably having 10 carbon atoms. Alkyl groups of ~ 21 are particularly preferably alkyl groups having 14 to 20 carbon atoms, and are preferably 0.03 to 0. With respect to 100 parts by weight of the polypropylene-based resin composition constituting the base material layer (A). It is contained in an amount of 3 parts by weight, particularly preferably 0.03 to 0.2 parts by weight. When the content of the compound (E) is 0.03 parts by weight or more, the antistatic property develops quickly and the antistatic effect can be obtained, and when the content is 0.3 parts by weight or less, the bleeding amount is small and the film surface becomes adhesive. It is unlikely to occur and there is little decrease in transparency due to whitening.

The polyoxyethylene alkyl diethanolamine compound (C) to which 2 mol or more of ethylene oxide is added to 1 mol of amine used in the present invention is a nonionic antistatic agent represented by the formula (3) and is a base material. The content is preferably 0 to 0.2 parts by weight, particularly preferably 0.002 to 0.15 parts by weight, based on 100 parts by weight of the polypropylene-based resin composition constituting the layer (A). When the content of the compound (C) is 0.2 parts by weight or less, the amount of bleeding is small and the decrease in transparency due to whitening is small.

It is a nonionic antistatic agent represented by the formula (4) of the polyoxyethylene alkenyl diethanolamine compound (D) in which 2 mol or more of ethylene oxide is added to 1 mol of the amine used in the present invention, and is a base material layer. It is preferably contained in an amount of 0 to 0.2 parts by weight, particularly preferably 0.002 to 0.15 parts by weight, based on 100 parts by weight of the polypropylene-based resin composition constituting (A). When the content of the compound (C) is 0.2 parts by weight or less, the amount of bleeding is small and the decrease in transparency due to whitening is small.

X and Y in the formulas (1) to (4) are integers of 1 to 29, respectively, and X + Y is an integer of 2 to 30, preferably an integer of 2 to 4.
R1 to R6 are linear or branched alkyl groups, particularly preferably alkyl groups having 13 to 25 carbon atoms, and particularly preferably alkyl groups having 13 to 18 carbon atoms.

Specific examples of the alkyl group of R1 to R6 in the formulas (1) to (3) include a methyl group, an ethyl group, a propyl group, a butyl group, an isobutyl group, a t-butyl group, a pentyl group, an isopentyl group and a nonyl group. Examples thereof include a group, a decyl group, an undecyl group, a lauryl group, a trilauryl group, a myristyl group, a pentadecyl group, a palmityl group, a heptadecyl group, a stearyl group, a nonadecyl group and an eicosyl group.

The alkenyl group of R7 in the formula (4) is preferably at least one selected from higher unsaturated aliphatic groups having 12 to 21 carbon atoms.

Further, as long as the effect of the present invention is not impaired, the polypropylene-based resin composition constituting the base material layer (A) has various additives for improving quality such as slipperiness, for example, improving productivity. It is also possible to add lubricants such as waxes and metal soaps, plasticizers, processing aids, known heat stabilizers usually added to polypropylene films, antioxidants, ultraviolet absorbers and the like.

(Middle layer (B))
(Polypropylene resin)
The polypropylene resin composition used for the intermediate layer (B) of the biaxially oriented polypropylene film of the present invention contains the polypropylene homopolymer described below and the common weight of propylene and ethylene and / or α-olefin having 4 or more carbon atoms. When coalesced, it is easy to improve the laminate strength while maintaining rigidity.

(Polypropylene homopolymer)
The polypropylene homopolymer used for the intermediate layer (B) is preferably a polypropylene polymer that does not substantially contain ethylene and / or an α-olefin having 4 or more carbon atoms, and has ethylene and / or 4 or more carbon atoms. Even when the α-olefin component is contained, the amount of ethylene and / or the α-olefin component having 4 or more carbon atoms is preferably 0.3 mol% or less, more preferably 0.2 mol% or less. More preferably, it is a polypropylene polymer having an amount of 0.1 mol or less. Within the above range, crystallinity tends to improve.
Examples of the α-olefin component having 4 or more carbon atoms constituting such a copolymer include 1-butene, 1-pentene, 3-methylpentene-1, 3-methylbutene-1, 1-hexene, and 4-methyl. Examples thereof include pentene-1,5-ethylhexene-1,1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-eicosene and the like.
As the polypropylene homopolymer, two or more different kinds of polypropylene homopolymers can be used.

The content of the polypropylene homopolymer is preferably 55% by weight or more, more preferably 55% by weight or more and 95% by weight or less, more preferably 60% by weight, based on the total polypropylene resin used in the intermediate layer (B). It is more preferably contained in an amount of% or more and 92% by weight or less, and particularly preferably contained in an amount of 65% by weight or more and 92% by weight or less.

(Tacticity)
The mesopentad fraction ([mmmm]%), which is an index of the stereoregularity of the polypropylene homopolymer, is preferably in the range of 97.0 to 99.9%, and preferably in the range of 97.5 to 99.7%. It is more preferably in the range of 98.0 to 99.5%, further preferably in the range of 98.5 to 99.3%, and particularly preferably in the range of 98.5 to 99.3%.
When it is 97.0% or more, the crystallinity of the polypropylene homopolymer is enhanced, the melting point, crystallinity, and crystallinity of the crystals in the film are improved, and rigidity and heat resistance at high temperature can be easily obtained. When it is 99.9% or less, it is easy to suppress the cost in terms of polypropylene production, and it is difficult to break during film formation. The mesopentad fraction is measured by a nuclear magnetic resonance method (so-called NMR method).
It is more preferably 99.5% or less. The mesopentad fraction is measured by a nuclear magnetic resonance method (so-called NMR method).
In order to keep the mesopentad fraction of the polypropylene homopolymer within the above range, a method of washing the obtained polypropylene homopolymer powder with a solvent such as n-heptane, selection of a catalyst and / or a co-catalyst, and polypropylene A method of appropriately selecting the components of the resin composition is preferably adopted.

(Melting temperature)
The lower limit of the melting temperature (Tm) measured by DSC of the polypropylene homopolymer is preferably 160 ° C., more preferably 161 ° C., still more preferably 162 ° C., and even more preferably 163 ° C. , More preferably 164 ° C. When Tm is 160 ° C. or higher, rigidity and heat resistance at high temperature can be easily obtained. The upper limit of Tm is preferably 170 ° C., more preferably 169 ° C., still more preferably 168 ° C., even more preferably 167 ° C., and particularly preferably 166 ° C. When Tm is 170 ° C. or lower, it is easy to suppress an increase in cost in terms of polypropylene production, and it is difficult to break during film formation. The melting temperature can be further increased by adding a crystal nucleating agent to the above-mentioned polypropylene homopolymer.
Tm is measured by a differential scanning calorimeter (DSC). A sample of 1 to 10 mg is packed in an aluminum pan, set in a differential scanning calorimeter (DSC), and melted at 230 ° C. for 5 minutes in a nitrogen atmosphere. This is the main peak temperature of the endothermic peak associated with melting, which is observed when the temperature is lowered to 30 ° C. at a scanning speed of −10 ° C./min, held for 5 minutes, and the temperature is raised at a scanning speed of 10 ° C./min.

(Crystallization temperature)
The lower limit of the crystallization temperature (Tc) measured by DSC of the polypropylene homopolymer is 105 ° C, preferably 108 ° C, and more preferably 110 ° C. When Tc is 105 ° C. or higher, crystallization is likely to proceed in the stretching in the width direction and the subsequent cooling step, and rigidity and heat resistance at high temperature are easily obtained. The upper limit of Tc is preferably 135 ° C., more preferably 133 ° C., still more preferably 132 ° C., even more preferably 130 ° C., particularly preferably 128 ° C., and most preferably 127 ° C. Is. If the Tc is 135 ° C. or lower, it is difficult to increase the cost in terms of polypropylene production, and it is difficult to break during film formation. The crystallization temperature can be further increased by adding a crystal nucleating agent to the above-mentioned polypropylene homopolymer.
Tc is measured by a differential scanning calorimeter (DSC). A sample of 1 to 10 mg is packed in an aluminum pan, set in the DSC, melted at 230 ° C. for 5 minutes in a nitrogen atmosphere, and the scanning speed is -10. It is the main peak temperature of the exothermic peak observed when the temperature is lowered to 30 ° C. at ° C./min.

(Melt flow rate)
The melt flow rate (MFR) of the polypropylene homopolymer shall be 4.0 to 30 g / 10 minutes when measured in accordance with the condition M (230 ° C., 2.16 kgf) of JIS K 7210 (1995). It is preferably 5.0 to 25 g / 10 minutes, more preferably 6.0 to 22 g / 10 minutes, particularly preferably 7.0 to 20 g / 10 minutes, and 8.0 to 20 g. Most preferably, it is / 10 minutes.
When the melt flow rate (MFR) of the polypropylene homopolymer is 4.0 g / 10 minutes or more, it is easy to obtain a biaxially oriented polypropylene film having low heat shrinkage.
Further, when the melt flow rate (MFR) of the polypropylene homopolymer is 30 g / 10 minutes or less, it is easy to maintain the film-forming property of the film.

The lower limit of the melt flow rate (MFR) (230 ° C., 2.16 kgf) of the polypropylene homopolymer is preferably 5.0 g / 10 minutes, more preferably 5.5 g / 10 minutes, and further, from the viewpoint of film characteristics. It is preferably 6.0 g / 10 minutes, particularly preferably 6.3 g / 10 minutes, and most preferably 6.5 g / 10 minutes.
When the melt flow rate (MFR) of the polypropylene homopolymer fat is 5.0 g / 10 minutes or more, the amount of the low molecular weight component of the polypropylene homopolymer fat constituting the film increases. By adopting the widthwise stretching step, the orientation crystallization of the polypropylene homopolymer is further promoted, the degree of crystallization in the film is more likely to be increased, and the polypropylene molecular chains in the amorphous portion are arranged with each other. There is less entanglement and it is easier to increase heat resistance.
In order to keep the melt flow rate (MFR) of the polypropylene homopolymer within the above range, it is preferable to adopt a method of controlling the average molecular weight and the molecular weight distribution of the polypropylene resin.

That is, the lower limit of the amount of the component having a molecular weight of 100,000 or less in the GPC integration curve of the polypropylene homopolymer is 35% by mass, preferably 38% by mass, more preferably 40% by mass, and further preferably 41% by mass. %, Especially preferably 42% by mass.
The upper limit of the amount of the component having a molecular weight of 100,000 or less in the GPC integration curve is preferably 65% by mass, more preferably 60% by mass, and further preferably 58% by mass. When the amount of the component having a molecular weight of 100,000 or less in the GPC integration curve is 65% by mass or less, the film strength is unlikely to decrease.
At this time, if a high molecular weight component or a long chain branched component having a long relaxation time is included, it becomes easy to adjust the amount of the component having a molecular weight of 100,000 or less contained in the polypropylene homopolymer without significantly changing the overall viscosity. , It is easy to improve the film-forming property without significantly affecting the rigidity and heat shrinkage.

(Molecular weight distribution)
In the polypropylene homopolymer, the lower limit of the mass average molecular weight (Mw) / number average molecular weight (Mn), which is an index of the breadth of the molecular weight distribution, is preferably 3.5, more preferably 4, and even more preferably 4. It is 4.5, and particularly preferably 5. The upper limit of Mw / Mn is preferably 30, more preferably 25, still more preferably 23, particularly preferably 21 and most preferably 20.
Mw / Mn can be obtained using gel permeation chromatography (GPC). When Mw / Mn is in the above range, it is easy to increase the amount of the component having a molecular weight of 100,000 or less.

Regarding the molecular weight distribution of polypropylene homopolymers, components of different molecular weights can be polymerized in a series of plants in multiple stages, components of different molecular weights can be blended offline with a kneader, or catalysts with different performances can be blended. It can be adjusted by polymerizing or using a catalyst capable of achieving a desired molecular weight distribution. The shape of the molecular weight distribution obtained by GPC has a single peak in a GPC chart in which the horizontal axis is the logarithmic weight (M) log (logM) and the vertical axis is the differential distribution value (weight fraction per logM). It may have a gentle molecular weight distribution, or it may have a molecular weight distribution having a plurality of peaks and shoulders.

(Copolymer of propylene and ethylene and / or α-olefin having 4 or more carbon atoms)
The copolymer of propylene used in the intermediate layer (B) with ethylene and / or an α-olefin having 4 or more carbon atoms has an ethylene and / or α-olefin component having 4 or more carbon atoms in an amount of 0.3 mol%. It is preferably a copolymer of more propylene and ethylene and / or an α-olefin having 4 or more carbon atoms.
Ethylene and / or a copolymer of ethylene and / or an α-olefin having 4 or more carbon atoms having an α-olefin component content of more than 0.3 mol% and ethylene and / or an α-olefin having 4 or more carbon atoms may have low crystallinity. Preferably, other α-olefins include, for example, ethylene, 1-butene, 1-pentene, 3-methylpentene-1,3-methylbutene-1,1-hexene, 4-methylpentene-1,5-ethylhexene. -1,1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-eicosene and the like can be mentioned.
The amount of ethylene and / or α-olefin component having 4 or more carbon atoms is preferably 0.4 mol% or more, more preferably 0.6 mol% or more. Within the above range, crystallinity tends to decrease.
Here, the copolymer is preferably a random or block copolymer obtained by polymerizing one or more of the α-olefins exemplified above with propylene, and is preferably a propylene / ethylene copolymer. It is preferably a propylene / butene-1 copolymer, a propylene / ethylene / butene-1 copolymer, or a propylene / penten-1 copolymer.
Among the copolymers of propylene and ethylene and / or α-olefin having 4 or more carbon atoms, the one having the lowest DSC melting point has a melting point peak temperature of 150 ° C. or higher and 160 ° C. or lower.

The content of the copolymer of ethylene and / or propylene having an α-olefin component content of 4 or more carbon atoms of more than 0.3 mol% and ethylene and / or α-olefin having 4 or more carbon atoms is the intermediate layer (B). ), It is preferably 45% by weight or less, more preferably 5% by weight or more and 45% by weight or less, and 8% by weight or more and 40% by weight or less with respect to the entire polypropylene resin composition used in). It is more preferably 8% by weight or more, and particularly preferably 35% by weight or less.

(Polypropylene resin composition)
The ratio of the α-olefin monomer-derived component to the total of the propylene monomer-derived component and the α-olefin monomer-derived component of the entire polypropylene resin composition used in the intermediate layer (B) is 0.03 mol% or more, 0.4 mol%. It is preferably 0.04 mol% or more and 0.3 mol% or less, and more preferably 0.05 mol% or more and 0.2 mol% or less.

The isotactic mesopentad fraction of the entire polypropylene resin composition constituting the intermediate layer (B) is preferably 95% or more from the viewpoint of rigidity. Further, from the viewpoint of film forming property, it is preferably 99.5% or less.

Further, the melt flow rate (MFR) of the polypropylene resin composition used in the intermediate layer (B) is preferably 5.0 g / 10 min or more from the viewpoint of fusing sealability. By doing so, it is possible to achieve both rigidity and heat resistance at high temperatures at a higher level. It is more preferably 6.0 g / 10 min or more, particularly preferably 7.0 g / 10 min or more, and most preferably 8.0 g / 10 min or more.

(Antistatic agent)
By using a specific amine ester compound, a specific amine compound, and a specific glycerin monofatty acid ester compound in combination with the propylene resin composition constituting the intermediate layer (B) in a specific ratio, the antistatic property can be further improved. ..

For example, a polyoxyethylene alkylamine mono obtained by adding 2 mol or more of ethylene oxat to 1 mol of the amine represented by the general formula (1) with respect to 100 parts by weight of the polypropylene resin composition constituting the intermediate layer (B). 0.3 to 1.2 parts by weight of fatty acid ester compound (A),

In the formula, R1 and R2 are alkyl groups having 7 to 21 carbon atoms, X and Y are integers of 1 to 29, respectively, and X + Y are integers of 2 to 30.

Glycerin monofatty acid ester compound (B) represented by the general formula (2) 0.03 to 1.2 parts by weight,

In the formula, R3 is an alkyl group or an alkenyl group having 7 to 21 carbon atoms.

0 to 0.2 parts by weight of the polyoxyethylene alkylamine difatty acid ester compound (C) to which 2 mol or more of ethylene oxalate is added to 1 mol of the amine represented by the general formula (3).

In the formula, R4, R5, and R6 are alkyl groups having 7 to 21 carbon atoms, X and Y are integers of 1 to 29, respectively, and X + Y are integers of 2 to 30.

0 to 0.2 parts by weight of the polyoxyethylene alkenylamine compound (D) to which 2 mol or more of ethylene oxide is added to 1 mol of the amine represented by the general formula (4).

In the formula, R7 is an alkenyl group having 7 to 21 carbon atoms, X and Y are integers of 1 to 29, respectively, and X + Y is an integer of 2 to 30.
Is preferably contained.

The polyoxyethylene amine monoester compound (A) in which 2 mol of ethylene oxalate is added to 1 mol of amine used in the present invention is a nonionic antistatic agent represented by the formula (1) and is intermediate. The content is preferably 0.3 to 1.2 parts by weight, particularly preferably 0.3 to 1.1 parts by weight, based on 100 parts by weight of the polypropylene-based resin composition constituting the layer (B). When the content of compound (A) is 0.3 parts by weight or more, an antistatic effect can be obtained for a long period of time, and when the content is 1.2 parts by weight or less, the amount of bleeding is small and the transparency is lowered by whitening. few.

The glycerin monofatty acid ester compound (B) used in the present invention is a nonionic antistatic agent represented by the formula (2), and R3 is a linear or branched alkyl group, preferably having 10 carbon atoms. It is an alkyl group of to 21 to, particularly preferably an alkyl group having 14 to 20 carbon atoms, and is preferably 0.03 to 0.3 weight by weight with respect to 100 parts by weight of the polypropylene resin composition constituting the intermediate layer (B). It is contained in an amount of 0.03 to 0.2 parts by weight, particularly preferably 0.03 to 0.2 parts by weight. When the content of the compound (E) is 0.03 part by weight or more, the antistatic property develops quickly and the antistatic effect can be obtained, and when the content is 1.2 parts by weight or less, the bleeding amount is small and the film surface becomes adhesive. It is less likely to occur and the transparency due to whitening is less likely to decrease.

The polyoxyethylene alkyl diethanolamine compound (C) to which 2 mol or more of ethylene oxalate is added to 1 mol of amine used in the present invention is a nonionic antistatic agent represented by the formula (3) and is an intermediate layer. It is preferably contained in an amount of 0 to 0.2 parts by weight, particularly preferably 0.002 to 0.15 parts by weight, based on 100 parts by weight of the polypropylene resin composition constituting (B). When the content of the compound (C) is 0.2 parts by weight or less, the amount of bleeding is small and the decrease in transparency due to whitening is small.

The polyoxyethylene alkenyldiethanolamine compound (D) to which 2 mol or more of ethylene oxalate is added to 1 mol of amine used in the present invention is a nonionic antistatic agent represented by the formula (4) and is an intermediate layer. It is preferably contained in an amount of 0 to 0.2 parts by weight, particularly preferably 0.002 to 0.15 parts by weight, based on 100 parts by weight of the polypropylene resin composition constituting (B). When the content of the compound (C) is 0.2 parts by weight or less, the amount of bleeding is small and the decrease in transparency due to whitening is small.

X and Y in the equations (1) to (4) are integers of 1 to 29, respectively, and X + Y is an integer of 2 to 30, preferably an integer of 2 to 4. R1 is a linear or branched alkyl group, particularly preferably an alkyl group having 13 to 25 carbon atoms, and particularly preferably an alkyl group having 13 to 18 carbon atoms.

Specific examples of the alkyl group of R1 to R6 in the formulas (1) to (3) include a methyl group, an ethyl group, a propyl group, a butyl group, an isobutyl group, a t-butyl group, a pentyl group, an isopentyl group and a nonyl group. Examples thereof include a group, a decyl group, an undecyl group, a lauryl group, a trilauryl group, a myristyl group, a pentadecyl group, a palmityl group, a heptadecyl group, a stearyl group, a nonadecyl group and an eicosyl group.

The alkenyl group of R7 in the formula (4) is preferably at least one selected from higher unsaturated aliphatic groups having 12 to 21 carbon atoms.

Further, as long as the effect of the present invention is not impaired, the polypropylene-based resin composition constituting the intermediate layer (B) has various additives for improving quality such as slipperiness, for example, improving productivity. Therefore, it is also possible to add lubricants such as waxes and metal soaps, plasticizers, processing aids, known heat stabilizers usually added to polypropylene films, antioxidants, ultraviolet absorbers and the like.

(Surface layer (C))
(Polypropylene resin)
The polypropylene resin composition used for the surface layer (C) of the biaxially oriented polypropylene film of the present invention contains the polypropylene homopolymer described below and the common weight of propylene and ethylene and / or α-olefin having 4 or more carbon atoms. When coalesced, it is easy to improve the laminate strength while maintaining rigidity.

(Polypropylene homopolymer)
The polypropylene homopolymer used for the surface layer (C) is preferably a polypropylene polymer that does not substantially contain ethylene and / or an α-olefin having 4 or more carbon atoms, and has ethylene and / or 4 or more carbon atoms. Even when the α-olefin component is contained, the amount of ethylene and / or the α-olefin component having 4 or more carbon atoms is preferably 0.3 mol% or less, more preferably 0.2 mol% or less. More preferably, it is a polypropylene polymer having an amount of 0.1 mol or less. Within the above range, crystallinity tends to improve.
Examples of the α-olefin component having 4 or more carbon atoms constituting such a copolymer include 1-butene, 1-pentene, 3-methylpentene-1, 3-methylbutene-1, 1-hexene, and 4-methyl. Examples thereof include pentene-1,5-ethylhexene-1,1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-eicosene and the like.
As the polypropylene homopolymer, two or more different kinds of polypropylene homopolymers can be used.

The content of the polypropylene homopolymer is preferably 90% by weight or less, more preferably 40% by weight or more and 90% by weight or less, more preferably 50% by weight or less, based on the total polypropylene resin used for the surface layer (C). It is more preferably contained in an amount of% by weight or more and 80% by weight or less, and particularly preferably 60% by weight or more and 70% by weight or less.

(Tacticity)
The mesopentad fraction ([mmmm]%), which is an index of the stereoregularity of the polypropylene homopolymer, is preferably in the range of 97.0 to 99.9%, and preferably in the range of 97.5 to 99.7%. It is more preferably in the range of 98.0 to 99.5%, further preferably in the range of 98.5 to 99.3%, and particularly preferably in the range of 98.5 to 99.3%.
When it is 97.0% or more, the crystallinity of the polypropylene resin is enhanced, the melting point, crystallinity, and crystallinity of the crystals in the film are improved, and rigidity and heat resistance at high temperature can be easily obtained. When it is 99.9% or less, it is easy to suppress the cost in terms of polypropylene production, and it is difficult to break during film formation. The mesopentad fraction is measured by a nuclear magnetic resonance method (so-called NMR method).
It is more preferably 99.5% or less. The mesopentad fraction is measured by a nuclear magnetic resonance method (so-called NMR method).
In order to keep the mesopentad fraction of the polypropylene homopolymer within the above range, a method of washing the obtained polypropylene homopolymer powder with a solvent such as n-heptane, selection of a catalyst and / or a co-catalyst, and polypropylene A method of appropriately selecting the components of the resin composition is preferably adopted.

(Melting temperature)
The lower limit of the melting temperature (Tm) measured by DSC of the polypropylene homopolymer is preferably 160 ° C., more preferably 161 ° C., still more preferably 162 ° C., and even more preferably 163 ° C. , More preferably 164 ° C. When Tm is 160 ° C. or higher, rigidity and heat resistance at high temperature can be easily obtained. The upper limit of Tm is preferably 170 ° C., more preferably 169 ° C., still more preferably 168 ° C., even more preferably 167 ° C., and particularly preferably 166 ° C. When Tm is 170 ° C. or lower, it is easy to suppress an increase in cost in terms of polypropylene production, and it is difficult to break during film formation. The melting temperature can be further increased by adding a crystal nucleating agent to the above-mentioned polypropylene homopolymer.
Tm is measured by a differential scanning calorimeter (DSC). A sample of 1 to 10 mg is packed in an aluminum pan, set in a differential scanning calorimeter (DSC), and melted at 230 ° C. for 5 minutes in a nitrogen atmosphere. This is the main peak temperature of the endothermic peak associated with melting, which is observed when the temperature is lowered to 30 ° C. at a scanning speed of −10 ° C./min, held for 5 minutes, and the temperature is raised at a scanning speed of 10 ° C./min.

(Crystallization temperature)
The lower limit of the crystallization temperature (Tc) of the polypropylene homopolymer is 105 ° C, preferably 108 ° C, and more preferably 110 ° C. When Tc is 105 ° C. or higher, crystallization is likely to proceed in the stretching in the width direction and the subsequent cooling step, and rigidity and heat resistance at high temperature are easily obtained. The upper limit of Tc is preferably 135 ° C., more preferably 133 ° C., still more preferably 132 ° C., even more preferably 130 ° C., particularly preferably 128 ° C., and most preferably 127 ° C. Is. If the Tc is 135 ° C. or lower, it is difficult to increase the cost in terms of polypropylene production, and it is difficult to break during film formation. The crystallization temperature can be further increased by adding a crystal nucleating agent to the above-mentioned polypropylene homopolymer.
Tc is measured by a differential scanning calorimeter (DSC). A sample of 1 to 10 mg is packed in an aluminum pan, set in the DSC, melted at 230 ° C. for 5 minutes in a nitrogen atmosphere, and the scanning speed is -10. It is the main peak temperature of the exothermic peak observed when the temperature is lowered to 30 ° C. at ° C./min.

(Melt flow rate)
The MFR of the polypropylene homopolymer is preferably 4.0 to 30 g / 10 minutes when measured in accordance with the condition M (230 ° C., 2.16 kgf) of JIS K 7210 (1995). It is more preferably 5 to 25 g / 10 minutes, further preferably 4.8 to 22 g / 10 minutes, particularly preferably 5.0 to 20 g / 10 minutes, and 6.0 to 20 g / 10 minutes. And most preferable.
When the MFR of the polypropylene homopolymer is 4.0 g / 10 minutes or more, it is easy to obtain a biaxially oriented polypropylene film having low heat shrinkage.
Further, when the MFR of the polypropylene tree homopolymer is 30 g / 10 minutes or less, it is easy to maintain the film-forming property of the film.

The lower limit of the MFR (230 ° C., 2.16 kgf) of the polypropylene homopolymer is preferably 5.0 g / 10 minutes, more preferably 5.5 g / 10 minutes, still more preferably 6.0 g from the viewpoint of film characteristics. It is preferably / 10 minutes, particularly preferably 6.3 g / 10 minutes, and most preferably 6.5 g / 10 minutes.
When the MFR of the polypropylene homopolymer is 5.0 g / 10 minutes or more, the amount of low molecular weight components of the polypropylene tree homopolymer constituting the film increases. By adopting it, the orientation crystallization of the polypropylene resin is further promoted, the degree of crystallization in the film is more likely to be increased, and the polypropylene molecular chains in the amorphous portion are less entangled with each other, resulting in heat resistance. It is easier to enhance sex.
In order to keep the MFR of the polypropylene homopolymer within the above range, it is preferable to adopt a method of controlling the average molecular weight and the molecular weight distribution of the polypropylene resin.

That is, the lower limit of the amount of the component having a molecular weight of 100,000 or less in the gel permeation chromatography (GPC) integration curve of the polypropylene homopolymer is 35% by mass, preferably 38% by mass, and more preferably 40% by mass. It is more preferably 41% by mass, and particularly preferably 42% by mass.
The upper limit of the amount of the component having a molecular weight of 100,000 or less in the GPC integration curve is preferably 65% by mass, more preferably 60% by mass, and further preferably 58% by mass. When the amount of the component having a molecular weight of 100,000 or less in the GPC integration curve is 65% by mass or less, the film strength is unlikely to decrease.
At this time, if a high molecular weight component or a long chain branched component having a long relaxation time is included, it becomes easy to adjust the amount of the component having a molecular weight of 100,000 or less contained in the polypropylene homopolymer without significantly changing the overall viscosity. , It is easy to improve the film-forming property without significantly affecting the rigidity and heat shrinkage.

(Molecular weight distribution)
In the polypropylene homopolymer, the lower limit of the mass average molecular weight (Mw) / number average molecular weight (Mn), which is an index of the breadth of the molecular weight distribution, is preferably 3.5, more preferably 4, and even more preferably 4. It is 4.5, and particularly preferably 5. The upper limit of Mw / Mn is preferably 30, more preferably 25, still more preferably 23, particularly preferably 21 and most preferably 20.
Mw / Mn can be obtained using gel permeation chromatography (GPC). When Mw / Mn is in the above range, it is easy to increase the amount of the component having a molecular weight of 100,000 or less.

Regarding the molecular weight distribution of polypropylene homopolymers, components of different molecular weights can be polymerized in a series of plants in multiple stages, components of different molecular weights can be blended offline with a kneader, or catalysts with different performances can be blended. It can be adjusted by polymerizing or using a catalyst capable of achieving a desired molecular weight distribution. The shape of the molecular weight distribution obtained by GPC has a single peak in a GPC chart in which the horizontal axis is the logarithmic weight (M) log (logM) and the vertical axis is the differential distribution value (quantity fraction per logM). It may have a gentle molecular weight distribution, or it may have a molecular weight distribution having a plurality of peaks and shoulders.

(Copolymer of propylene and ethylene and / or α-olefin having 4 or more carbon atoms)
The copolymer of propylene used in the surface layer (C) with ethylene and / or an α-olefin having 4 or more carbon atoms is ethylene and / or propylene having an α-olefin component content of 4 or more carbon atoms of more than 0.3 mol. And / or a copolymer of ethylene and / or an α-olefin having 4 or more carbon atoms is preferable.
The copolymer of ethylene and / or an α-olefin having 4 or more carbon atoms and having an α-olefin component of more than 0.3 mol and ethylene and / or an α-olefin having 4 or more carbon atoms is preferably low in crystallinity. Examples of other α-olefins include ethylene, 1-butene, 1-pentene, 3-methylpentene-1, 3-methylbutene-1, 1-hexene, 4-methylpentene-1, 5-ethylhexene-1. , 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-eicosene and the like.
The amount of ethylene and / or α-olefin component having 4 or more carbon atoms is preferably 0.4 mol% or more, more preferably 0.5 mol% or more. Within the above range, crystallinity tends to decrease.
Here, the copolymer is preferably a random or block copolymer obtained by polymerizing one or more of the α-olefins exemplified above with propylene, and is preferably a propylene / ethylene copolymer. It is preferably a propylene / butene-1 copolymer, a propylene / ethylene / butene-1 copolymer, or a propylene / penten-1 copolymer.

Among the copolymers of propylene and ethylene and / or α-olefin having 4 or more carbon atoms, the one having the lowest DSC melting point preferably has a melting point peak temperature of 150 ° C. or higher and 160 ° C. or lower.

The content of the copolymer of ethylene and / or the copolymer of ethylene and / or the α-olefin having 4 or more carbon atoms and the α-olefin having more than 0.3 mol and the ethylene and / or the α-olefin having 4 or more carbon atoms is in the surface layer (C). It is preferably 10% by weight or more, more preferably 10% by weight or more and 60% by weight or less, and further preferably 20% by weight or more and 50% by weight or less with respect to the entire polypropylene resin used. It is preferable, and it is particularly preferable that it is 30% by weight or more and 50% by weight or less.

(Polypropylene resin composition)
The ratio of the α-olefin monomer-derived component to the total of the propylene monomer-derived component and the α-olefin monomer-derived component of the entire polypropylene resin composition used in the surface layer (C) is 0.10 mol% or more and 0.4 mol%. It is preferably 0.15 mol% or more and 0.2 mol% or less, and further preferably 0.2 mol% or more and 0.25 mol% or less.

The isotactic mesopentad fraction of the entire polypropylene resin composition constituting the surface layer (C) is preferably 95% or more from the viewpoint of rigidity. Further, from the viewpoint of film forming property, it is preferably 99.5% or less.

Further, the melt flow rate (MFR) of the polypropylene resin composition used in the surface layer (C) is preferably 5.0 g / 10 min or more from the viewpoint of fusing sealability. By doing so, it is possible to achieve both rigidity and heat resistance at high temperatures at a higher level. It is more preferably 6.0 g / 10 min or more, particularly preferably 7.0 g / 10 min or more, and most preferably 8.0 g / 10 min or more.

(Antistatic agent)
By using a specific amine ester compound, a specific amine compound, and a specific glycerin monofatty acid ester compound in combination with the propylene resin composition constituting the surface layer (C) in a specific ratio, the antistatic property can be further improved. ..

For example, a polyoxyethylene alkylamine mono obtained by adding 2 mol or more of ethylene oxat to 1 mol of the amine represented by the general formula (1) with respect to 100 parts by weight of the polypropylene resin composition constituting the surface layer (C). 0.3 to 1.2 parts by weight of fatty acid ester compound (A),

In the formula, R1 and R2 are alkyl groups having 7 to 21 carbon atoms, X and Y are integers of 1 to 29, respectively, and X + Y are integers of 2 to 30.

0.03 to 1.2 parts by weight of the glycerin monofatty acid ester compound (B) represented by the following formula (2),

In the formula, R3 is an alkyl group having 7 to 21 carbon atoms.

0 to 0.2 parts by weight of the polyoxyethylene alkylamine difatty acid ester compound (C) to which 2 mol or more of ethylene oxalate is added to 1 mol of the amine represented by the following formula (3).

In the formula, R4, R5, and R6 are alkyl groups having 7 to 21 carbon atoms, X and Y are integers of 1 to 29, respectively, and X + Y are integers of 2 to 30.

0 to 0.2 parts by weight of the polyoxyethylene alkenylamine compound (D) to which 2 mol or more of ethylene oxide is added to 1 mol of the amine represented by the following formula (4).

In the formula, R7 is an alkenyl group having 7 to 21 carbon atoms, X and Y are integers of 1 to 29, respectively, and X + Y is an integer of 2 to 30.
Is preferably contained.

The polyoxyethylene alkylamine monofatty acid ester compound (A) in which 2 mol of ethylene oxalate is added to 1 mol of amine used in the present invention is a nonionic antistatic agent represented by the formula (1). , The content is preferably 0.3 to 1.2 parts by weight, particularly preferably 0.3 to 1.1 parts by weight, based on 100 parts by weight of the polypropylene-based resin composition constituting the surface layer (C). .. When the content of compound (A) is 0.3 parts by weight or more, an antistatic effect can be obtained for a long period of time, and when the content is 1.2 parts by weight or less, the amount of bleeding is small and the transparency is lowered by whitening. few.

The glycerin monofatty acid ester compound (B) used in the present invention is a nonionic antistatic agent represented by the formula (2), and R3 is a linear or branched alkyl group, preferably having 10 carbon atoms. It is an alkyl group of ~ 21, particularly preferably an alkyl group having 14 to 20 carbon atoms, and is preferably 0.03 to 0.3 weight by weight with respect to 100 parts by weight of the polypropylene resin composition constituting the surface layer (C). It is contained in an amount of 0.03 to 0.2 parts by weight, particularly preferably 0.03 to 0.2 parts by weight. When the content of the compound (E) is 0.03 part by weight or more, the antistatic property is rapidly developed and the antistatic effect is obtained, and when the content is 1.2 parts by weight or less, the bleeding amount is small and the film surface is adhesive. It is less likely to occur and the transparency due to whitening is less likely to decrease.

The polyoxyethylene alkylamine difatty acid ester compound (C) to which 2 mol or more of ethylene oxalate is added to 1 mol of amine used in the present invention is a nonionic antistatic agent represented by the formula (3). , The content is preferably 0 to 0.2 parts by weight, and particularly preferably 0.002 to 0.15 parts by weight with respect to 100 parts by weight of the polypropylene resin composition constituting the surface layer (C). When the content of the compound (C) is 0.2 parts by weight or less, the amount of bleeding is small and the decrease in transparency due to whitening is small.

The polyoxyethylene alkenylamine compound (D) in which 2 mol or more of ethylene oxalate is added to 1 mol of the amine used in the present invention is a nonionic antistatic agent represented by the formula (4) and is a surface layer. It is preferably contained in an amount of 0 to 0.2 parts by weight, particularly preferably 0.002 to 0.15 parts by weight, based on 100 parts by weight of the polypropylene resin composition constituting (C). When the content of compound (D) is 0.2 parts by weight or less, the amount of bleeding is small and the decrease in transparency due to whitening is small.

X and Y in the equations (1) to (4) are integers of 1 to 29, respectively, and X + Y is an integer of 2 to 30, preferably an integer of 2 to 4. R1 is a linear or branched alkyl group, particularly preferably an alkyl group having 13 to 25 carbon atoms, and particularly preferably an alkyl group having 13 to 18 carbon atoms.

Specific examples of the alkyl group of R1 to R6 in the formulas (1) to (3) include a methyl group, an ethyl group, a propyl group, a butyl group, an isobutyl group, a t-butyl group, a pentyl group, an isopentyl group and a nonyl group. Examples thereof include a group, a decyl group, an undecyl group, a lauryl group, a trilauryl group, a myristyl group, a pentadecyl group, a palmityl group, a heptadecyl group, a stearyl group, a nonadecyl group and an eicosyl group.

The alkenyl group of R7 in the formula (4) is preferably at least one selected from higher unsaturated aliphatic groups having 12 to 21 carbon atoms.

Further, as long as the effect of the present invention is not impaired, the polypropylene-based resin composition constituting the surface layer (C) has various additives for improving quality such as slipperiness, for example, improving productivity. For this purpose, lubricants such as waxes and metal soaps, plasticizers, processing aids, known heat stabilizers usually added to polypropylene films, antioxidants, ultraviolet absorbers, inorganic and organic fine particles, etc. are blended. It is also possible.

Examples of the inorganic fine particles include silicon dioxide, calcium carbonate, titanium dioxide, talc, kaolin, mica, and zeolite, and these shapes can be spherical, elliptical, conical, or amorphous. As for the particle size, a desired particle size can be used and blended depending on the intended use and usage of the film.
Further, as the organic fine particles, crosslinked particles such as acrylic, methyl acrylate, and styrene-butadiene can be used, and various particles such as inorganic fine particles can be used in terms of shape and size. It is possible. Further, it is possible to apply various surface treatments to the surface of these inorganic or organic fine particles, and these can be used alone or in combination of two or more. The above is also applicable to the surface layer (B) described later.

(Film layer composition)
The biaxially oriented polypropylene-based film of the present invention has a three-layer structure of a base layer (A) / intermediate layer (B) / surface layer (C), and a surface layer (C) / base layer (A) / intermediate layer ( It has a four-layer structure of B) / surface layer (C) and a six-layer structure of surface layer (C) / intermediate layer (B) / base layer (A) / intermediate layer (B) / surface layer (C). May be good.

(Film thickness)
The total layer thickness of the biaxially oriented polypropylene resin film of the present invention varies depending on its use and usage, but is preferably 10 μm or more, more preferably 15 μm or more, and more preferably 20 μm from the viewpoint of film strength, sealing property or water vapor barrier property. The above is more preferable.
Further, in terms of high-speed packaging processability or visibility, 60 μm or less is preferable, 50 μm or less is further preferable, 45 μm or less is particularly preferable, and 40 μm or less is most preferable.

The thickness of the base material layer (A) varies depending on the application and the method of use, but is preferably 10 μm or more in terms of the rigidity of the film and the water vapor barrier property. In terms of transparency and influence on the environment, 50 μm or less is preferable, 45 μm or less is more preferable, 40 μm or less is further preferable, and 37 μm or less is particularly preferable.
The thickness of the intermediate layer (B) varies depending on its use and method of use, but is preferably 1 μm or more, more preferably 2 μm or more, still more preferably 4 μm or more, in terms of film laminating strength and antistatic property.

The thickness of the intermediate layer (B) varies depending on its use and method of use, but is preferably 8 μm or less, more preferably 6 μm or less, in terms of film rigidity and heat resistance at high temperatures.
The ratio of the thickness of the intermediate layer (B) to the thickness of all the biaxially oriented polypropylene-based resin films is preferably 5% or more, more preferably 10% or more, and more preferably 10% or more from the viewpoint of rigidity and heat resistance at high temperatures. % Or more is more preferable.

The ratio of the thickness of the intermediate layer (B) to the thickness of the entire biaxially oriented polypropylene-based resin film is preferably 30% or less, more preferably 25% or less, from the viewpoint of rigidity and heat resistance at high temperatures.
The thickness of the surface layer (C) varies depending on its use and usage, but is preferably 0.3 μm or more, more preferably 0.5 μm or more, and more preferably 0.8 μm or more in terms of film laminating strength and antistatic property. More preferred.
The thickness of the surface layer (C) varies depending on the application and the method of use, but is preferably 4 μm or less, more preferably 3 μm or less, in terms of the rigidity of the film and the heat resistance at high temperatures.

The ratio of the thickness of the surface layer (C) to the thickness of the entire biaxially oriented polypropylene resin film is preferably 2% or more from the viewpoint of rigidity and heat resistance at high temperature, and more preferably 3% or more. % Or more is more preferable.
The ratio of the thickness of the surface layer (C) to the thickness of the entire biaxially oriented polypropylene-based resin film is preferably 20% or less, more preferably 15% or less from the viewpoint of rigidity and heat resistance at high temperatures.

(Method for forming biaxially oriented polypropylene film)
The biaxially oriented polypropylene film of the present invention is preferably obtained by preparing an unstretched sheet made of the polypropylene resin composition containing the above-mentioned polypropylene resin as a main component and biaxially stretching the film. As a biaxial stretching method, any of the inflation simultaneous biaxial stretching method, the tenter simultaneous biaxial stretching method, and the tenter sequential biaxial stretching method can be obtained, but from the viewpoint of film forming stability and thickness uniformity, the tenter sequential biaxial stretching method can be obtained. It is preferable to adopt the axial stretching method. In particular, it is preferable to stretch in the longitudinal direction and then in the width direction, but a method of stretching in the width direction and then stretching in the longitudinal direction may also be used.

Next, the method for producing the biaxially oriented polypropylene film of the present invention will be described below, but the present invention is not necessarily limited thereto.
The following is an example of the case of the surface layer (C) / intermediate layer (B) / base layer (A) / intermediate layer (B) / surface layer (C) when the tenter sequential biaxial stretching method is adopted. Will be described.
First, a molten polypropylene resin composition multilayer sheet having a structure of a surface layer (C) / intermediate layer (B) / base layer (A) / intermediate layer (B) / surface layer (C) is extruded from a T-die.
As a method, for example, thermoplastic resins fed from different flow paths using six extruders are laminated in multiple layers using a multi-layer feed block, a static mixer, a multi-layer multi-manifold die, or the like. A co-extruding method or the like can be used.
It is also possible to introduce the above-mentioned multilayer device into the melt line from the extruder to the T-type die by using only one extruder.
From the viewpoint of stabilizing back pressure and suppressing thickness fluctuation, a method of installing a gear pump in the polymer flow path is preferable.
The molten sheet co-extruded from the T-die into a sheet is grounded on a metal cooling roll to be cooled and solidified. For the purpose of promoting solidification, it is preferable to further cool the sheet cooled by a cooling roll by immersing it in a water tank or the like.

Then, the sheet is stretched in the longitudinal direction by increasing the rotation speed of the rear stretching rolls with two pairs of stretching rolls in which the sheet is heated to obtain a uniaxially stretched film.

Subsequently, after preheating the uniaxially stretched film, the film is stretched in the width direction at a specific temperature while grasping the end of the film with a tenter type stretcher to obtain a biaxially stretched film. This width direction stretching step will be described in detail later.

After the width direction stretching step is completed, the biaxially stretched film is heat-treated at a specific temperature to obtain a biaxially oriented film. In the heat treatment step, the film may be relaxed in the width direction.

A film roll can be obtained by subjecting the biaxially oriented polypropylene film thus obtained to, for example, corona discharge treatment on at least one side thereof and then winding it with a winder.

Each process will be described in detail below.
(Extrusion process)
The temperature of the cooling roll or the cooling roll and the water tank is preferably in the range of 10 ° C to Tc, and if it is desired to increase the transparency of the film, it is cooled and solidified with a cooling roll having a temperature in the range of 10 to 50 ° C. Is preferable. When the cooling temperature is 50 ° C. or lower, the transparency of the unstretched sheet tends to increase, preferably 40 ° C. or lower, and more preferably 30 ° C. or lower. In order to increase the degree of crystal orientation after sequential biaxial stretching, it may be preferable to set the cooling temperature to 40 ° C. or higher, but as described above, a propylene homopolymer having a mesopendat fraction of 97.0% or higher is used. In this case, the cooling temperature is preferably 40 ° C. or lower, which is preferable in terms of facilitating stretching in the next step and reducing thickness unevenness, and more preferably 30 ° C. or lower.
The thickness of the unstretched sheet is preferably 3500 μm or less, more preferably 3000 μm or less in terms of cooling efficiency, and can be appropriately adjusted according to the film thickness after sequential biaxial stretching. The thickness of the unstretched sheet can be controlled by the extrusion speed of the polypropylene resin composition, the lip width of the T-die, and the like.

(Longitudinal stretching step)
The lower limit of the longitudinal stretching ratio is preferably 3 times, more preferably 3.5 times, and particularly preferably 3.8 times. Within the above range, the strength can be easily increased and the film thickness unevenness can be reduced. The upper limit of the longitudinal stretching ratio is preferably 8 times, more preferably 7.5 times, and particularly preferably 7 times. Within the above range, the width direction stretching in the width direction stretching step is easy, and the productivity is improved.
The lower limit of the longitudinal stretching temperature is preferably Tm-40 ° C, more preferably Tm-37 ° C, and even more preferably Tm-35 ° C. Tm is the melting point of the polypropylene homopolymer constituting the base material layer. Within the above range, the subsequent stretching in the width direction becomes easy and the thickness unevenness is reduced. The upper limit of the longitudinal stretching temperature is preferably Tm-7 ° C, more preferably Tm-10 ° C, and even more preferably Tm-12 ° C. Within the above range, the heat shrinkage rate is likely to be reduced, and it is unlikely that the heat shrinkage will be reduced due to the difficulty in stretching by being attached to the stretching roll or the surface roughness becoming large.
The longitudinal stretching may be performed by using three or more pairs of stretching rolls and stretching in two or more stages.

(Preheating process)
Prior to the widthwise stretching step, it is necessary to heat the uniaxially stretched film after longitudinal stretching in the range of Tm to Tm + 25 ° C. to soften the polypropylene resin composition. When it is set to Tm or more, softening progresses and stretching in the width direction becomes easy. By setting the temperature to Tm + 25 ° C. or lower, the orientation at the time of lateral stretching progresses, and the rigidity is easily developed. It is more preferably Tm + 2 to Tm + 22 ° C, and particularly preferably Tm + 3 to Tm + 20 ° C. Here, the maximum temperature in the preheating process is defined as the preheating temperature.

(Width direction stretching step)
In the width direction stretching step after the preheating step, a preferable method is as follows.

In the width direction stretching step, a section (first half section) for stretching at a temperature of Tm-10 ° C. or higher and a preheating temperature or lower is provided. At this time, the start of the first half section may be at the time when the preheating temperature is reached, or at the time when the temperature is lowered after reaching the preheating temperature and reaches a temperature lower than the preheating temperature.
The lower limit of the temperature in the early section in the width direction stretching step is preferably Tm ° C, more preferably Tm + 1 ° C, and further preferably Tm + 3 ° C. When the stretching temperature in the first half section is in this range, the shrinkage at a high temperature is reduced, the plane orientation coefficient does not become too high, and the antistatic property is likely to be improved.
Following the first half section, a section (late section) that is lower than the temperature of the first half section and stretches at a temperature of Tm-70 ° C or higher and Tm-5 ° C or lower may be provided, or the temperature in the first half section may be used as it is. Lateral stretching may be continued.
The upper limit of the stretching temperature in the latter section is preferably Tm-8 ° C, more preferably Tm-10 ° C. If the stretching temperature in the latter section is in this range, rigidity is likely to be developed.
The lower limit of the stretching temperature in the latter section is preferably Tm-65 ° C, more preferably Tm-60 ° C, and even more preferably Tm-55 ° C. When the stretching temperature in the latter section is in this range, the film formation is likely to be stable.

It is preferable to cool the film at the end of the late section or immediately after the film is continuously stretched at the temperature in the early section and the final stretching ratio in the width direction is reached. The cooling temperature at this time is preferably a temperature of Tm-80 ° C or higher and Tm-15 ° C or lower, preferably Tm-80 ° C or higher and Tm-20 ° C or lower, which is lower than the temperature of the latter section. It is more preferably Tm-80 ° C. or higher and Tm-30 ° C. or lower, and particularly preferably Tm-70 ° C. or higher and Tm-40 ° C. or lower.
The temperature in the early section and the temperature in the late section can be gradually lowered, but can also be lowered stepwise or in one step, and may be constant. When the temperature is gradually lowered, the film is less likely to break and the thickness variation of the film is likely to be reduced. Further, it is preferable because the heat shrinkage rate is easy to be small and the film is less whitened. The temperature at the end of the early section in the width direction stretching step can be gradually lowered to the temperature at the start of the late section, but it can also be lowered stepwise or in one step.

When the latter section is provided, the lower limit of the draw ratio at the end of the first section of the width direction stretching step is preferably 5 times, more preferably 6 times, and further preferably 7 times. The upper limit of the draw ratio at the end of the first half section is preferably 15 times, more preferably 14 times, and further preferably 13 times.

When the latter section is provided, the lower limit of the final width direction stretching ratio in the width direction stretching step is preferably 7 times, more preferably 8 times, still more preferably 9 times, and particularly preferably 10 times. .. If it is 7 times or more, the rigidity is likely to be increased and the film thickness unevenness is likely to be reduced. The upper limit of the stretch ratio in the width direction is preferably 20 times, more preferably 17 times, and further preferably 15 times. When it is 20 times or less, the heat shrinkage rate is likely to be reduced, and it is difficult to break during stretching.

When the lateral stretching is continued as it is at the temperature in the early section without providing the latter section, the lower limit of the final width drawing magnification in the width direction stretching step is preferably 10 times, more preferably 11 times. .. If it is 10 times or more, the rigidity is likely to be increased and the film thickness unevenness is likely to be reduced. The upper limit of the stretch ratio in the width direction is preferably 20 times, more preferably 17 times, and further preferably 15 times. When it is 20 times or less, the heat shrinkage rate is likely to be reduced, and it is difficult to break during stretching.

As described above, by using the polypropylene resin having high stereoregularity and high crystallinity and adopting the above-mentioned stretching step in the width direction, the molecules of the polypropylene resin do not need to be extremely increased in stretching ratio. Is highly aligned in the main orientation direction (the width direction is applicable in the above-mentioned width direction stretching step), so that the crystal orientation in the obtained biaxially oriented film is very strong and crystals with a high melting point are likely to be produced. ..
In addition, the orientation of the amorphous part between the crystals also increases in the main orientation direction (the width direction corresponds to the above-mentioned width direction stretching step), and many crystals having a high melting point exist around the amorphous part. At a temperature lower than the melting point, the elongated polypropylene molecule in the amorphous part is difficult to relax and tends to maintain its tense state. Therefore, the entire biaxially oriented film can maintain high rigidity even at high temperatures.
Further, it should be noted that by adopting such a stretching step in the width direction, the heat shrinkage rate at a high temperature of 150 ° C. tends to decrease. The reason is that since many crystals with a high melting point exist around the amorphous part, the elongated polypropylene resin molecules in the amorphous part are difficult to relax at a temperature lower than the melting point of the crystals, and the molecules are less entangled with each other. be.

It should be further noted that by increasing the low molecular weight component of the polypropylene resin, the crystallinity of the film is more likely to increase, and the entanglement of the polypropylene resin molecular chains in the amorphous portion is reduced, resulting in heat shrinkage stress. By weakening it, the heat shrinkage rate can be further reduced. Conventionally, it can be said that it is epoch-making considering that if either the strength or the heat shrinkage rate is improved, the other property tends to be deteriorated.

(Heat treatment process)
If necessary, the biaxially stretched film can be heat-treated to further reduce the heat shrinkage. The upper limit of the heat treatment temperature is preferably Tm + 10 ° C, more preferably Tm + 7 ° C. By setting the temperature to Tm + 10 ° C. or lower, rigidity is easily developed, the roughness of the film surface does not become too large, and the film is less likely to whiten. The lower limit of the heat treatment temperature is preferably Tm-10 ° C, more preferably Tm-7 ° C. If the temperature is lower than Tm-10 ° C, the heat shrinkage rate may increase.
By adopting the above-mentioned width direction stretching step, even if heat treatment is performed at a temperature between Tm-10 ° C. and Tm + 10, the highly oriented crystals produced in the stretching step are difficult to melt, and the rigidity of the obtained film is reduced. The heat shrinkage can be made smaller without lowering. For the purpose of adjusting the heat shrinkage rate, the film may be relaxed (relaxed) in the width direction during the heat treatment. The upper limit of the relaxation rate is preferably 10%. Within the above range, the film strength is unlikely to decrease, and the film thickness variation tends to be small. It is more preferably 8%, further preferably 7%, even more preferably 3%, particularly preferably 2%, and most preferably 0%.

(Film thickness)
The thickness of the biaxially oriented polypropylene film of the present invention is set according to each application, but in order to obtain the strength of the film, the lower limit of the film thickness is preferably 10 μm, more preferably 12 μm, still more preferably. It is 14 μm, particularly preferably 16 μm. When the film thickness is 2 μm or more, the rigidity of the film can be easily obtained. The upper limit of the film thickness is preferably 100 μm, more preferably 70 μm, still more preferably 50 μm, particularly preferably 40 μm, and most preferably 30 μm. When the film thickness is 100 μm or less, the cooling rate of the unstretched sheet during the extrusion process is unlikely to decrease.
The biaxially oriented polypropylene film of the present invention is usually formed as a roll having a width of 2000 to 12000 mm and a length of about 1000 to 50000 m, and is wound into a film roll. Further, it is slit according to each application and is provided as a slit roll having a width of 300 to 2000 mm and a length of about 500 to 5000 m. The biaxially oriented polypropylene film of the present invention can obtain a longer film roll.

The antistatic biaxially stretched polypropylene resin film used in the present invention is subjected to surface treatment by conventionally known methods such as corona discharge treatment, plasma treatment, ozone treatment, chemical treatment, and known anchor treatment, depending on the purpose. Anchor treatment or the like using an agent may be applied.
In particular, antistatic properties can be improved by performing corona discharge treatment, plasma treatment, and ozone treatment.
For example, a corona processing machine manufactured by Sophthal Corona & Plasma GmbH, etc. was used on the film surface on the side of the obtained biaxially oriented polypropylene film in contact with the cooling roll, and the applied current value was 0.30 to 2. Corona treatment is preferably performed under the condition of 0.0A, more preferably 0.50 to 2.0A, still more preferably 0.80 to 2.0A, and particularly preferably 1.5 to 2.0A.

(Thickness uniformity)
The lower limit of the thickness uniformity of the biaxially oriented polypropylene film of the present invention is preferably 0%, more preferably 0.1%, still more preferably 0.5%, and particularly preferably 1%. The upper limit of the thickness uniformity is preferably 20%, more preferably 17%, still more preferably 15%, particularly preferably 12%, and most preferably 10%. Within the above range, defects are less likely to occur during post-processing such as coating and printing, and it is easy to use for applications that require precision.
The measurement method was as follows. A test piece having a width of 40 mm is cut out from a constant region where the film physical characteristics are stable in the length direction of the film, and a film feeder manufactured by Micron Measuring Instruments Co., Ltd. (using the product number: A90172) and a film manufactured by Anritsu Co., Ltd. Using a continuous thickness measuring device (product name: K-313A wide-range high-sensitivity electronic micrometer), the film thickness was continuously measured over 20000 mm, and the thickness uniformity was calculated from the following formula.
Thickness uniformity (%) = [(maximum thickness-minimum thickness) / average thickness] x 100

(Film characteristics)
The biaxially oriented polypropylene film of the present invention is characterized by the following characteristics. Here, the "longitudinal direction" in the biaxially oriented polypropylene film of the present invention is a direction corresponding to the flow direction in the film manufacturing process, and the "width direction" is a direction orthogonal to the flow direction in the film manufacturing process. Is. For polypropylene films whose flow direction is unknown in the film manufacturing process, wide-angle X-rays are incident in the direction perpendicular to the film surface, and the scattering peak derived from the (110) plane of the α-type crystal is scanned in the circumferential direction. The direction in which the diffraction intensity of the obtained diffraction intensity distribution is the largest is referred to as the "width direction", and the direction orthogonal to it is referred to as the "longitudinal direction".

(Stress at 23 ° C 5% elongation)
The lower limit of the stress (F5) of the biaxially oriented polypropylene film of the present invention at 5% elongation in the longitudinal direction at 23 ° C. is 40 MPa, preferably 42 MPa, more preferably 43 MPa, still more preferably 44 MPa. It is particularly preferably 45 MPa. At 40 MPa or more, the rigidity is high, so that the bag shape when used as a packaging bag is easily maintained, and the film is less likely to be deformed during processing such as printing. The upper limit of F5 in the longitudinal direction is preferably 70 MPa, more preferably 65 MPa, still more preferably 62 MPa, particularly preferably 61 MPa, and most preferably 60 MPa. At 70 MPa or less, realistic manufacturing is easy and the vertical-width balance is easy to improve.

The lower limit of F5 in the width direction of the biaxially oriented polypropylene film of the present invention at 23 ° C. is 160 MPa, preferably 165 MPa, more preferably 168 MPa, and further preferably 170 MPa. At 160 MPa or higher, the rigidity is high, so that the bag shape when used as a packaging bag is easily maintained, and the film is less likely to be deformed during processing such as printing. The upper limit of F5 in the width direction is preferably 250 MPa, more preferably 245 MPa, and even more preferably 240 MPa. If it is 250 MPa or less, realistic manufacturing is easy and the vertical width balance is easy to improve.
F5 is within the range by adjusting the stretching ratio and the relaxing rate, and adjusting the temperature at the time of film formation.

(150 ° C heat shrinkage rate)
The upper limit of the heat shrinkage in the longitudinal direction at 150 ° C. of the biaxially oriented polypropylene film of the present invention is 10%, preferably 7.0%, more preferably 6.0%, and particularly preferably 4. It is 5.5%, most preferably 3.0%. The upper limit of the heat shrinkage in the width direction at 150 ° C. is 30%, preferably 16%, more preferably 15%, particularly preferably 12%, and most preferably 10%. When the heat shrinkage rate in the longitudinal direction is 10% or less and the heat shrinkage rate in the width direction is 30% or less, wrinkles are less likely to occur during heat sealing, and the heat shrinkage rate in the longitudinal direction at 150 ° C. is 8. When the heat shrinkage rate in the width direction at 0% or less and 150 ° C. is 15% or less, the strain when the chuck portion is fused to the open portion is extremely small, which is preferable. In order to reduce the heat shrinkage at 150 ° C, the lower limit of the amount of components with a molecular weight of 100,000 or less when measuring the gel permeation chromatography (GPC) integration curve of the polypropylene resin constituting the film is set to 35% by mass. It is effective to do.

(Surface specific resistance test)
The surface intrinsic resistance of the biaxially oriented polypropylene film of the present invention is 15Ω / □ or less, preferably 14.5Ω / □ or less, more preferably 14.0Ω / □ or less, and 13.5Ω / □ or less. □ The following is particularly preferable. When it is 15Ω / □ or less, the film roll and the film being processed are less charged, the bag making process is easy, and the obtained bag is also easy to have few defects. The lower limit of the surface intrinsic resistance length is preferably 10 N / 15 mm as a realistic value, and more preferably 11 N / 15 mm.

It is better that the biaxially oriented polypropylene film of the present invention has the following characteristics and structure.

(120 ° C. heat shrinkage rate)
The upper limit of the heat shrinkage in the longitudinal direction at 120 ° C. of the biaxially oriented polypropylene film of the present invention is preferably 2.0%, more preferably 1.7%, still more preferably 1.5%. , Particularly preferably 1.0%. When it is 2.0% or less, the printing pitch shift when transferring the printing ink is less likely to occur. The upper limit of the heat shrinkage in the width direction at 120 ° C. is 5.0%, preferably 4.0%, more preferably 3.0%, still more preferably 2.0%, and particularly. It is preferably 1.5%. When it is 5.0% or less, wrinkles at the time of heat sealing are less likely to occur.
When the longitudinal heat shrinkage rate at 120 ° C. is smaller than the width direction heat shrinkage rate at 120 ° C., the printing pitch shift when transferring the printing ink is less likely to occur. The balance between the heat shrinkage rate at 120 ° C. and the heat shrinkage rate in the longitudinal direction and the width direction can be within the range by adjusting the stretching ratio, the stretching temperature, and the heat fixing temperature.

(Refractive index)
The lower limit of the refractive index (Nx) in the longitudinal direction of the biaxially oriented polypropylene film of the present invention is preferably 1.4970, more preferably 1.4990, still more preferably 1.5000, and particularly preferably 1.5000. It is 1.5020. If it is 1.4970 or more, it is easy to increase the rigidity of the film. The upper limit of the refractive index (Nx) in the longitudinal direction is preferably 1.5100, more preferably 15070, and even more preferably 1.5050. If it is 1.5100 or less, the balance of the characteristics in the longitudinal direction and the width direction of the film tends to be excellent.

The lower limit of the refractive index (Ny) in the width direction of the biaxially oriented polypropylene film of the present invention is 1.5230, preferably 1.5240, and more preferably 1.5250. If it is 1.5230 or more, it is easy to increase the rigidity of the film. The upper limit of the refractive index (Ny) in the width direction is preferably 1.5280, more preferably 1.5275, and even more preferably 1.5270. If it is 1.5280 or less, the balance of the characteristics in the longitudinal direction and the width direction of the film tends to be excellent.

The lower limit of the refractive index (Nz) in the thickness direction of the biaxially oriented polypropylene film of the present invention is preferably 1.4960, more preferably 14970, still more preferably 1.4990, and particularly preferably 1. It is 5000. If it is 1.4960 or more, it is easy to increase the rigidity of the film. The upper limit of the refractive index (Nz) in the thickness direction is preferably 1.5020, more preferably 1.5015, and even more preferably 1.5010. If it is 1.5020 or less, it is easy to increase the heat resistance of the film.
The refractive index can be set within the range by adjusting the stretching ratio, the stretching temperature, and the heat fixing temperature.

(△ Ny)
The lower limit of ΔNy, which is the degree of orientation of the biaxially oriented polypropylene film of the present invention in the width direction, is 0.0220, preferably 0.0230, more preferably 0.0235, and even more preferably. Is 0.0240. If it is 0.0220 or more, the rigidity of the film tends to be high. The upper limit of ΔNy is preferably 0.0270, more preferably 0.0265, still more preferably 0.0262, and particularly preferably 0.0260 as a realistic value. If it is 0.0270 or less, the thickness unevenness tends to be good. ΔNy can be set within the range by adjusting the stretch ratio, the stretch temperature, and the heat fixing temperature of the film.
ΔNy is calculated by the following formula, where the refractive indexes along the longitudinal direction, the width direction, and the thickness direction of the film are Nx, Ny, and Nz, respectively. It means the degree of orientation in the direction.
ΔNy = Ny- [(Nx + Nz) / 2]

(Surface orientation coefficient)
The lower limit of the plane orientation coefficient (ΔP) of the biaxially oriented polypropylene film of the present invention is preferably 0.0135, more preferably 0.0138, and even more preferably 0.0140. When it is 0.0135 or more, the balance in the surface direction of the film is good and the thickness unevenness is also good. The upper limit of the plane orientation coefficient (ΔP) is preferably 0.0155, more preferably 0.0152, and even more preferably 0.0150 as a realistic value. If it is 0.0155 or less, the heat resistance at high temperature is likely to be excellent. The plane orientation coefficient (ΔP) can be set within the range by adjusting the stretching ratio, stretching temperature, and heat fixing temperature.
The plane orientation coefficient (ΔP) was calculated using (Equation) [(Nx + Ny) / 2] -Nz.

(Haze)
The upper limit of the haze of the biaxially oriented polypropylene film of the present invention is preferably 5.0%, more preferably 4.5%, still more preferably 4.0%, and particularly preferably 3.5%. Yes, most preferably 3.0%. If it is 5.0% or less, it is easy to use in applications where transparency is required. The lower limit of the haze is preferably 0.1%, more preferably 0.2%, still more preferably 0.3%, and particularly preferably 0.4% as a practical value. If it is 0.1% or more, it is easy to manufacture. The haze adjusts the cooling roll (CR) temperature, the width stretching temperature, the preheating temperature before stretching in the tenter width direction, the stretching temperature in the width direction, or the heat fixing temperature, or the amount of the component having a polypropylene resin molecular weight of 100,000 or less. However, it may increase due to the addition of a blocking inhibitor or the addition of a seal layer.

(Practical characteristics of film)
The practical characteristics of the biaxially oriented polypropylene film of the present invention will be described.
(Tensile breaking strength)
The lower limit of the tensile breaking strength in the longitudinal direction of the biaxially oriented polypropylene film of the present invention is preferably 90 MPa, more preferably 95 MPa, and further preferably 100 MPa. If it is 90 MPa or more, the printing pitch shift when transferring the printing ink is less likely to occur, and the durability of the packaging bag is likely to be excellent. The upper limit of the tensile breaking strength in the longitudinal direction is preferably 200 MPa, more preferably 190 MPa, and further preferably 180 MPa as a realistic value. If it is 200 MPa or less, the breakage of the film and the breakage of the packaging bag are likely to decrease.

The lower limit of the tensile breaking strength in the width direction of the biaxially oriented polypropylene film of the present invention is preferably 320 MPa, more preferably 340 MPa, and further preferably 350 MPa. If it is 320 MPa or more, the printing pitch shift when transferring the printing ink is less likely to occur, and the durability of the packaging bag is likely to be excellent. The upper limit of the tensile breaking strength in the width direction is preferably 500 MPa, more preferably 480 MPa, and further preferably 470 MPa as a realistic value. If it is 500 MPa or less, the breakage of the film and the breakage of the packaging bag are likely to decrease.
The tensile breaking strength can be set within the range by adjusting the draw ratio, the draw temperature, and the heat fixing temperature.

(Tension breaking elongation)
The lower limit of the tensile elongation at break in the longitudinal direction of the biaxially oriented polypropylene film of the present invention is preferably 50%, more preferably 55%, still more preferably 60%. If it is 50% or more, the breakage of the film and the breakage of the packaging bag are likely to decrease. The upper limit of the tensile elongation at break in the longitudinal direction is preferably 230%, more preferably 220%, and even more preferably 210% as a realistic value. If it is 230% or less, the printing pitch shift when transferring the printing ink is less likely to occur, and the durability of the packaging bag is likely to be excellent.

The lower limit of the tensile elongation at break in the width direction of the biaxially oriented polypropylene film of the present invention is preferably 10%, more preferably 15%, still more preferably 17%. If it is 10% or more, the breakage of the film and the breakage of the packaging bag are likely to decrease. The upper limit of the tensile elongation at break in the width direction is preferably 60%, more preferably 55%, and even more preferably 50%. If it is 60% or less, the printing pitch shift when transferring the printing ink is less likely to occur, and the durability of the packaging bag is likely to be excellent.
The tensile elongation at break can be within the range by adjusting the draw ratio, the draw temperature, and the heat fixing temperature.

(Loop stefness stress)
The lower limit of the longitudinal loop stefness stress S (mN) at 23 ° C. of the biaxially oriented polypropylene film of the present invention is preferably 0.00020 × t, where t (μm) is the thickness of the biaxially oriented polypropylene film. ^{It is 3} , more preferably 0.00025 × t ³ , still more preferably 0.00030 × t ³ , and particularly preferably 0.00035 × t ³ . When it is 0.00020 × t ³ or more, it is easy to maintain the shape of the package. The upper limit of the longitudinal loop stefness stress S (mN) at 23 ° C. is preferably 0.00080 × t ³ , more preferably 0.00075 × t ³ , and even more preferably 0.00072 × t. ^{It is 3} , and particularly preferably 0.00070 × t ³ . If it is 0.00080 × ^{t 3} below, realistic and easy to manufacture.
The lower limit of the loop stefness stress S (mN) in the width direction of the biaxially oriented polypropylene film at 23 ° C. is preferably 0.0010 × t, where t (μm) is the thickness of the biaxially oriented polypropylene film. ^{It is 3} , more preferably 0.0011 × t ³ , still more preferably 0.0012 × t ³ , and particularly preferably 0.0013 × t ³ . When it is 0.0010 × t ³ or more, it is easy to maintain the shape of the package. The upper limit of the loop stepness stress S (mN) in the width direction at 23 ° C. is preferably 0.0020 × t ³ , more preferably 0.0019 × t ³ , and even more preferably 0.0018 × t. ^{It is 3} , and particularly preferably 0.0017 × t ³ . When it is 0.0020 × t ³ or less, it is practically easy to manufacture.

The loop stefness stress is an index showing the waist feeling of the film, but it also depends on the thickness of the film. The measurement method is as follows. Two strips of 110 mm × 25.4 mm were cut out, with the longitudinal direction of the film as the long axis of the strip (loop direction) and the width direction of the film as the long axis of the strip (loop direction). For measuring loops in which one side of the film is the inner surface of the loop and the other side is the inner surface of the loop, with these sandwiched between clips, and the long axis of the strip is in the longitudinal and width directions of the film. Made. Set the measurement loop with the long axis of the strip in the longitudinal direction of the film on the chuck of Loop Steph Nestester DA manufactured by Toyo Seiki Co., Ltd. with the width direction perpendicular, remove the clip, and the chuck interval is 50 mm. The loop stepness stress was measured with a pushing depth of 15 mm and a compression rate of 3.3 mm / sec.
In the measurement, the loop stefness stress and the thickness were measured 5 times with one side of the film being the inner surface of the loop, and then 5 times with the other side being the inner surface of the loop. Using the data for a total of 10 times, plot the cube of the thickness (μm) of each test piece on the horizontal axis and the loop stepness stress (mN) on the vertical axis, and approximate it with a straight line that becomes the intercept 0. The inclination a was obtained. The inclination a means a characteristic value peculiar to the film that does not depend on the thickness that determines the rigidity. The inclination a was used as the evaluation value of the feeling of waist. The measurement loop in which the long axis of the strip is in the width direction of the film was measured in the same manner.

(Wrinkles during heat sealing)
To form a bag for packaging food, the pre-made bag is filled with the contents and heated to melt the film, fuse it and seal it. In many cases, the same procedure is used when making a bag while filling food. Usually, a sealant film made of polyethylene, polypropylene, or the like is laminated on the base film, and the sealant film surfaces are fused to each other. In the heating method, pressure is applied from the base film side with a heating plate to press the film to seal it, but the sealing width is often about 10 mm. At this time, the base film is also heated, and the shrinkage at that time causes wrinkles. It is better to have less wrinkles in the durability of the bag, and it is better to have less wrinkles in order to increase purchasing motivation. The sealing temperature may be about 120 ° C., but in order to increase the bag making processing speed, a higher sealing temperature is required, and even in that case, it is preferable that the shrinkage is small. When the chuck is fused to the open portion of the bag, sealing at a higher temperature is required.

(Laminate strength)
The lower limit of the longitudinal lamination strength of the biaxially oriented polypropylene film of the present invention is preferably 1.2N / 15mm, more preferably 1.3N / 15mm, still more preferably 1.4N / 15mm, and more. It is more preferably 1.5 N / 15 mm, and particularly preferably 1.6 N / 15 mm. If it is 1.2 N / 15 mm or more, the number of broken packaging bags tends to decrease. The upper limit of the laminating strength in the longitudinal direction is preferably 2.7 N / 15 mm as a realistic value, and more preferably 2.5 N / 15 mm.

The lower limit of the laminating strength in the width direction of the biaxially oriented polypropylene film of the present invention is preferably 1.0 N / 15 mm, more preferably 1.1 N / 15 mm, still more preferably 1.2 N / 15 mm, and more. It is more preferably 1.3 N / 15 mm, particularly preferably 1.4 N / 15 mm, and most preferably 1.5 N / 15 mm. If it is 1.0 N / 15 mm or more, the number of broken packaging bags tends to decrease. The upper limit of the laminating strength in the width direction is preferably 2.5 N / 15 mm as a realistic value, and more preferably 2.2 N / 15 mm.

(Surface specific resistance test)
The surface intrinsic resistance of the surface of the biaxially oriented polypropylene film of the present invention is preferably 15Ω / □ or less, more preferably 14.5Ω / □ or less, further preferably 14.0Ω / □ or less, and particularly preferably 13.5Ω / □ or less. preferable. When it is 15Ω / □ or less, the film roll and the film being processed are less charged, the bag making process is easy, and the obtained bag is also easy to have few defects. The lower limit of the surface intrinsic resistance length is preferably 10 N / 15 mm as a realistic value, and more preferably 11 N / 15 mm.

(Print pitch shift)
As a basic structure of the packaging film, it is often composed of a laminated film of a printed base film and a sealant film. A bag making machine is used to manufacture bags, and there are three-way bags, standing bags, gusset bags, etc., and various bag making machines are used. It is considered that the printing pitch shift occurs because the base material of the film expands and contracts because tension and heat are applied to the film during the printing process. Eliminating defective products due to print pitch deviation is important in terms of effective use of resources, and is also important in increasing purchasing motivation.

(Film processing)
The biaxially oriented polypropylene film of the present invention can be printed by letterpress printing, lithographic printing, intaglio printing, stencil printing, and transfer printing, depending on the application.
In addition, low-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, polypropylene, unstretched sheet made of polyester, uniaxially stretched film, and biaxially stretched fill are bonded as a sealant film to impart heat-sealing properties. It can also be used as a laminated body. If you want to further improve gas barrier properties and heat resistance, use aluminum foil, polyvinylidene chloride, nylon, ethylene-vinyl alcohol copolymer, unstretched sheet made of polyvinyl alcohol, uniaxially stretched film, and biaxially stretched film as biaxially oriented polypropylene film. It can be provided as an intermediate layer between the and the sealant film. An adhesive applied by a dry lamination method or a hot melt lamination method can be used for laminating the sealant film.
In order to enhance the gas barrier property, aluminum or an inorganic oxide can be vapor-deposited on a biaxially oriented polypropylene film, an intermediate layer film, or a sealant film. Vacuum vapor deposition, sputtering, and ion plating can be adopted as the vapor deposition method, but silica, allumina, or a mixture thereof is particularly preferable.

The biaxially oriented polypropylene film of the present invention contains, for example, antifogging agents such as fatty acid esters of polyhydric alcohols, amines of higher fatty acids, amides of higher fatty acids, amines of higher fatty acids and ethylene oxide adducts of amide. By setting the abundance in the film in the range of 0.2 to 5% by mass, it is possible to make it suitable for packaging fresh products made of plants that require high freshness such as vegetables, fruits, and flowers. can.

Further, as long as the effect of the present invention is not impaired, various additives for improving quality such as slipperiness and antistatic property, for example, lubricants such as wax and metal soap for improving productivity, and plasticizers. It is also possible to add agents, processing aids, heat stabilizers, antioxidants, antistatic agents, ultraviolet absorbers and the like.

(Industrial applicability)
Since the biaxially oriented polypropylene film of the present invention has excellent properties as described above, it can be preferably used for packaging bags, and the thickness of the film can be made thinner than before.

Furthermore, it is required to be used at high temperatures such as insulating films for capacitors and motors, back sheets for solar cells, barrier films for inorganic oxides, and base films for transparent conductive films such as ITO, and to have rigidity such as separate films. It is also suitable for various applications. In addition, it is possible to coat and print at high temperatures by using coating agents, inks, laminating adhesives, etc., which have been difficult to use in the past, and it is expected that production efficiency will be improved.

Hereinafter, the present invention will be described in detail with reference to Examples. The characteristics were measured and evaluated by the following methods.
(1) Melt flow rate The melt flow rate (MFR) was measured at a temperature of 230 ° C. and a load of 2.16 kgf in accordance with JIS K7210.

(2) Mesopendat fraction The mesopentad fraction ([mmmm]%) of the polypropylene resin was measured ^{using 13} C-NMR. The mesopentad fraction was calculated according to the method described in Zambelli et al., Macromolecules, Vol. 6, p. 925 (1973). ¹³ C-NMR measurement was carried out using AVANCE 500 manufactured by BRUKER, in which 200 mg of a sample was dissolved in an 8: 2 mixture of o-dichlorobenzene and heavy benzene at 135 ° C. and 110 ° C.

(3) Number average molecular weight, weight average molecular weight, component weight of 100,000 or less, and molecular weight distribution of polypropylene resin It was determined as a PP-equivalent molecular weight based on monodisperse polystyrene using gel permeation chromatography (GPC). When the baseline is not clear, it was decided to set the baseline up to the lowest position of the skirt 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.
The GPC measurement conditions are as follows.
Equipment: HLC-8321PC / HT (manufactured by Tosoh Corporation)
Detector: RI
Solvent: 1,2,4-trichlorobenzene + dibutylhydroxytoluene (0.05%) Column: TSKgelgoldvolume HHR (30) HT (7.5 mm ID x 7.5 cm) x 1 + TSKgelGMHR-H (20) HT (7.8 mm ID × 30 cm) × 3 Flow rate: 1.0 mL / min
Injection volume: 0.3 mL
Measurement temperature: 140 ° C
Defined by the following equation by the number average molecular weight (Mn), weight average molecular weight (Mw) molecular weight, respectively of the elution position of GPC curve obtained via the molecular weight calibration curve the number of molecules _(Mi) (N i) ..
The number average molecular _{weight: Mn = Σ (N i ·} M i) / ΣNi
Weight average molecular _{weight: Mw = Σ (N i ·} M i 2) / Σ (N i · M i)
Here, the molecular weight distribution can be obtained by Mw / Mn.
Further, the ratio of the components having a molecular weight of 100,000 or less was obtained from the integral curve of the molecular weight distribution obtained by GPC.

(4) Crystallization temperature (Tc), melting temperature (Tm)
Thermal measurements were performed in a nitrogen atmosphere using a Q1000 differential scanning calorimeter manufactured by TA Instruments. Approximately 5 mg was cut out from the polypropylene resin pellet and sealed in an aluminum pan for measurement. The temperature was raised to 230 ° C. and held for 5 minutes, then cooled to 30 ° C. at a rate of −10 ° C./min, and the exothermic peak temperature was defined as the crystallization temperature (Tc). The amount of heat of crystallization (ΔHc) was determined by setting a baseline so that the area of the exothermic peak could be smoothly connected from the start to the end of the peak. The temperature was kept as it was at 30 ° C. for 5 minutes, the temperature was raised to 230 ° C. at 10 ° C./min, and the main endothermic peak temperature was defined as the melting temperature (Tm).

(5) Film thickness The thickness of the film was measured using a Millitron 1202D manufactured by Seiko EM.

(6) Haze Using NDH5000 manufactured by Nippon Denshoku Kogyo Co., Ltd., the measurement was carried out at 23 ° C. according to JIS K7105.

(7) Tensile test The tensile strength in the longitudinal direction and the width direction of the film was measured at 23 ° C. according to JIS K7127. The sample was cut out from a film to a size of 15 mm × 200 mm, had a chuck width of 100 mm, and was set in a tensile tester (dual column desktop tester Instron 5965 manufactured by Instron Japan Company Limited). A tensile test was performed at a tensile speed of 200 mm / min. From the obtained strain-stress curve, the stress at 5% elongation was defined as F5. The tensile breaking strength and the tensile breaking elongation were taken as the strength and elongation at the time when the sample broke, respectively.

(8) Heat shrinkage rate Measured by the following method according to JISZ1712. The film was cut with a width of 20 mm and a length of 200 mm in the longitudinal direction and the width direction of the film, respectively, and hung in a hot air oven at 120 ° C. or 150 ° C. and heated for 5 minutes. The length after heating was measured, and the heat shrinkage rate was determined by the ratio of the contracted length to the original length.

(9) Refractive index, ΔNy, plane orientation coefficient Measured at a wavelength of 589.3 nm and a temperature of 23 ° C. using an Abbe refractometer manufactured by Atago Co., Ltd. The refractive indexes along the longitudinal direction and the width direction of the film were Nx and Ny, respectively, and the refractive indexes in the thickness direction were Nz. ΔNy, which is the degree of orientation in the width direction, was determined using (Equation) ΔNy = Ny− [(Nx + Nz) / 2] using Nx, Ny, and Nz. The plane orientation coefficient (ΔP) was calculated using (Equation) ΔP = [(Nx + Ny) / 2] −Nz.

(12) Loop stepness stress 10 strip-shaped test pieces of 110 mm × 25.4 mm each with the longitudinal direction of the film as the long axis of the strip (loop direction) or the width direction of the film as the long axis of the strip (loop direction). I cut it out one by one. For measuring loops in which one side of the film is the inner surface of the loop and the other side is the inner surface of the loop, with these sandwiched between clips, and the long axis of the strip is in the longitudinal and width directions of the film. Made. Set the measurement loop with the long axis of the strip in the longitudinal direction of the film on the chuck part of Loop Stef Nestester DA manufactured by Toyo Seiki Seisakusho Co., Ltd. with the width direction perpendicular, remove the clip, and set the chuck interval. The loop stepness stress was measured at 50 mm, a pushing depth of 15 mm, and a compression rate of 3.3 mm / sec.
The measurement was performed so that one side of the film was the inner surface of the loop, but the loop stefness stress and the thickness were measured 5 times, and then the other side of the film was measured 5 times. Using the data for a total of 10 times, plot the thickness (μm) of each test piece on the horizontal axis and the loop stepness stress (mN) on the vertical axis, and approximate it with a straight line that becomes the intercept 0. The inclination a was obtained. The inclination a was used as the evaluation value of the feeling of waist. The measurement loop in which the long axis of the strip is in the width direction of the film was measured in the same manner.

(13) Laminate strength The laminate strength was measured by the following procedure.
1) Preparation of laminated film with sealant film The following was performed using a continuous dry laminating machine. First, an adhesive was gravure-coated on the corona surface of the biaxially oriented polypropylene films obtained in Examples and Comparative Examples so that the amount applied during drying was 3.0 g / m ^2, and then the adhesive was guided to a drying zone at 80 ° C. It dried in 5 seconds. Subsequently, it was bonded to the sealant film between the rolls provided on the downstream side (roll pressure 0.2 MP, roll temperature: 60 ° C.). The obtained laminated film was aged 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 adhesive was used, and a non-biaxially oriented polypropylene film (Pyrene (registered trademark) CT P1128, thickness 30 μm) manufactured by Toyobo Co., Ltd. was used as the sealant film.
The laminated film obtained above is cut into strips (length 200 mm, width 15 mm) having long sides in the longitudinal direction and the width direction of the biaxially oriented polypropylene film, and a tensile tester (Tensilon, manufactured by Orientec) is used. The peel strength (N / 15 mm) when peeled by 90 ° (T-shaped) at a tensile speed of 200 mm / min in an environment of 23 ° C. was measured. The measurement was performed three times, and the average value was taken as the laminating strength in the longitudinal direction and the width direction.

(14) Surface intrinsic resistance test The surface intrinsic resistance (Ω / □) of the obtained film surface was measured on the corona surface of the biaxially oriented polypropylene films obtained in Examples and Comparative Examples in accordance with ASTM D257. The measured temperature and humidity were 23 ° C. × 65% RH.

(Example 1)
[Base layer (A)]
As a polypropylene resin, MFR = 7.5 g / 10 minutes, [mmmm] = 98.9%, Tc = 116.2 ° C., Tm = 162.5 ° C., propylene homopolymer PP-1 (Sumitomo Chemical Co., Ltd.) , FLX80E4) with 80 parts by weight, MFR = 11 g / 10 minutes, [mmmm] = 98.8%, Tc = 116.5 ° C, Tm = 161.5 ° C. Polypropylene homopolymer PP-2 (Sumitomo) A blend of 20 parts by weight of EL80F5 manufactured by Chemical Co., Ltd. in 100 parts by weight, stearylamine monostearic acid ester as an antifogging agent as compound (A) (manufactured by Toho Chemical Industry Co., Ltd .: Anstex SA321) ) To 0.9912 parts by weight and 0.156 parts by weight of glycerin monostearate (manufactured by Toho Chemical Industry Co., Ltd .: Anstex MG100) as the compound (B), and then an extruder with a pelletizer. Was melt-kneaded and granulated to obtain pellets of the polypropylene composition, which was used as a polypropylene-based resin composition for the base material layer (A).
[Middle layer (B)]
As a polypropylene resin, MFR = 7.5 g / 10 minutes, [mmmm] = 98.9%, Tc = 116.2 ° C., Tm = 162.5 ° C., propylene homopolymer PP-1 (Sumitomo Chemical Co., Ltd.) Made of FLX80E4) 70 by weight, MFR = 11 g / 10 minutes, [mmmm] = 98.8%, Tc = 116.5 ° C, Tm = 161.5 ° C. Polypropylene homopolymer PP-2 (Sumitomo) 20 parts by weight of EL80F5) manufactured by Kagaku Co., Ltd., MFR = 7.5 g / 10 minutes, Tc = 111.7 ° C, Tm = 158 ° C. A blend of 10 parts by weight of the copolymer PP-3 (WF836DG3 manufactured by Sumitomo Chemical Co., Ltd.) in 100 parts by weight, and stearylamine monostearic acid ester as the compound (A) (manufactured by Toho Chemical Industry Co., Ltd .: Anse). Tex SA321) is 1.000 parts by weight, glycerin monostearate (manufactured by Toho Chemical Industry Co., Ltd .: Anstex MG100) is 0.155 parts by weight, and compound (C) is stearyl, which is an antifogging agent. 0.0400 parts by weight of diethanolamine (manufactured by Toho Kagaku Kogyo Co., Ltd .: Anstex SA20) is blended, mixed, melt-kneaded and granulated using an extruder with a pelletizer to obtain pellets of the polypropylene composition, and an intermediate layer is obtained. The polypropylene-based resin composition for (B) was used.
[Surface layer (C)]
As a polypropylene resin, MFR = 7.5 g / 10 minutes, [mmmm] = 98.9%, Tc = 116.2 ° C., Tm = 162.5 ° C., propylene homopolymer PP-1 (Sumitomo Chemical Co., Ltd.) Made of FLX80E4) with 64 parts by weight, MFR = 7.5 g / 10 minutes, Tc = 111.7 ° C., Tm = 158 ° C., and polypropylene / ethylene copolymer PP containing 0.6 mol% of ethylene monomer-derived components. -3 (WF836DG3 manufactured by Sumitomo Chemical Co., Ltd.) blended with 36 parts by weight is melt-kneaded and granulated using an extruder with a pelletizer to obtain pellets of a polypropylene composition, which is used for the surface layer (C). Was used as the polypropylene-based resin composition of.
First, the polypropylene resin composition constituting each of the surface layer (C) / base layer (A) / intermediate layer (B) / surface layer (C) is extruded at 250 ° C. and 250 ° C. using a multilayer feed block. It was heated and melted at ° C. and 250 ° C., and coextruded into a sheet at 250 ° C. while laminating the molten polypropylene resin composition from the T die.
The surface layer (C) on the base layer (A) side of the molten sheet was brought into contact with a cooling roll at 20 ° C. and was put into a water tank at 20 ° C. as it was. Then, after preheating to 137 ° C, it is stretched 4.5 times in the longitudinal direction with two pairs of rolls at 142 ° C, then both ends are clipped and guided into a hot air oven, preheated at 170 ° C, and then in the width direction. As the first step, it was stretched 7 times at 168 ° C., and then as the second step, it was stretched 1.43 times at 145 ° C., so that a total of 10 times was stretched. Immediately after stretching in the width direction, the mixture was cooled at 100 ° C. while being held by the clip, and then heat-fixed at 165 ° C. while relaxing by 3% in the width direction.
Using a corona processing machine manufactured by Sophthal Corona & Plasma GmbH on the film surface on the side of the obtained biaxially oriented polypropylene film in contact with the cooling roll, the corona was applied under the condition of an applied current value of 0.75 A. After the treatment, the film wound with a winder was obtained as a biaxially stretched single-layer polypropylene film of the present invention. The thickness of the obtained film was 20 μm.
The thickness of the film thus obtained was surface layer (C) / substrate layer (A) / intermediate layer (B) / surface layer (C) = 1/16/2/1 μm. Table 1 shows the structure of the polypropylene resin, Table 2 shows the raw materials for each layer, and Table 3 shows the film forming conditions. As shown in Table 4, a film having high rigidity, low heat shrinkage at high temperature, and less easily charged was obtained.

(Example 2)
The procedure was the same as in Example 1 except that the antistatic agent was not added to the intermediate layer (B). Table 1 shows the structure of the polypropylene resin, Table 2 shows the raw materials for each layer, and Table 3 shows the film forming conditions. As shown in Table 4, a film having high rigidity, low heat shrinkage at high temperature, and less easily charged was obtained.

(Example 3)
No antistatic agent was added to the intermediate layer (B), and as a polypropylene resin, MFR = 7.5 g / 10 minutes, [mmmm] = 98.9%, Tc = 116.2 ° C., Tm = 162.5 ° C. 64 parts by weight of propylene homopolymer PP-1 (manufactured by Sumitomo Chemical Co., Ltd., FLX80E4) and ethylene monomer-derived components having MFR = 7.5 g / 10 minutes, Tc = 111.7 ° C., Tm = 158 ° C. A blend of 0.6 mol% propylene / ethylene copolymer PP-3 (WF836DG3 manufactured by Sumitomo Chemical Co., Ltd.) with 36 parts by weight, and 100 parts by weight of stearylamine monostearic acid ester (sterylamine monostearic acid ester) as compound (A). Toho Kagaku Kogyo Co., Ltd .: Anstex SA321) is blended in 1.0752 parts by weight, mixed, melt-kneaded and granulated using an extruder with a pelletizer to obtain pellets of the polypropylene composition, and the surface layer (C). ), Except for the polypropylene-based resin composition, the same procedure as in Example 1 was carried out. Table 1 shows the structure of the polypropylene resin, Table 2 shows the raw materials for each layer, and Table 3 shows the film forming conditions. As shown in Table 4, a film having high rigidity, low heat shrinkage at high temperature, and less easily charged was obtained.

(Example 4)
The film thickness was the same as in Example 1 except that the surface layer (C) / base layer (A) / intermediate layer (B) / surface layer (C) = 3/16/2/3 μm. Table 1 shows the structure of the polypropylene resin, Table 2 shows the raw materials for each layer, and Table 3 shows the film forming conditions. As shown in Table 4, a film having high rigidity, low heat shrinkage at high temperature, and less easily charged was obtained.

(Example 5)
The thickness of the film is surface layer (C) / base layer (A) / intermediate layer (B) / surface layer (C) = 1/14/4/1 μm, and the film is stretched at 164 ° C. as the first step in the width direction. The same procedure as in Example 1 was carried out except that the heat fixing temperature was set to 168 ° C. Table 1 shows the structure of the polypropylene resin, Table 2 shows the raw materials for each layer, and Table 3 shows the film forming conditions. As shown in Table 4, a film having high rigidity, low heat shrinkage at high temperature, and less easily charged was obtained.

(Example 6)
The thickness of the film is surface layer (C) / base layer (A) / intermediate layer (B) / surface layer (C) = 1/12/6/1 μm, and the film is stretched at 164 ° C. as the first step in the width direction. The same procedure as in Example 1 was carried out except that the heat fixing temperature was set to 168 ° C. Table 1 shows the structure of the polypropylene resin, Table 2 shows the raw materials for each layer, and Table 3 shows the film forming conditions. As shown in Table 4, a film having high rigidity, low heat shrinkage at high temperature, and less easily charged was obtained.

(Example 7)
The same procedure as in Example 1 was carried out except that the first step was stretched at 166 ° C. in the width direction and then the second step was double stretched at 162 ° C. Table 1 shows the structure of the polypropylene resin, Table 2 shows the raw materials for each layer, and Table 3 shows the film forming conditions. As shown in Table 4, a film having high rigidity, low heat shrinkage at high temperature, and less easily charged was obtained.

(Example 8)
As a polypropylene resin, a propylene / ethylene copolymer PP-3 (Sumitomo Chemical Co., Ltd.) containing 0.6 mol% of ethylene monomer-derived components having MFR = 7.5 g / 10 minutes, Tc = 111.7 ° C., and Tm = 158 ° C. WF836DG3) manufactured by Co., Ltd. was carried out in the same manner as in Example 1 except that 100 parts by weight was used as a polypropylene-based resin composition for the surface layer (C). Table 1 shows the structure of the polypropylene resin, Table 2 shows the raw materials for each layer, and Table 3 shows the film forming conditions. As shown in Table 4, a film having high rigidity and low heat shrinkage at high temperature but not easily charged was obtained.

(Comparative Example 1)
1.2974 parts of stearylamine monostearic acid ester (manufactured by Toho Chemical Industry Co., Ltd .: Anstex SA321) as compound (A) was added to the intermediate layer (B) without adding an antistatic agent to the base material layer (A). , 0.155 parts by weight of glycerin monostearate (manufactured by Toho Chemical Industry Co., Ltd .: Anstex MG100) as compound (B), and stearyldiethanolamine (manufactured by Toho Chemical Industry Co., Ltd .: Anstex SA20) as compound (C). The same procedure as in Example 1 was carried out except that 0.0400 parts by weight was blended. Table 1 shows the structure of the polypropylene resin, Table 2 shows the raw materials for each layer, and Table 3 shows the film forming conditions. As shown in Table 4, a film having high rigidity, low heat shrinkage at high temperature, and high laminating strength which is easily charged was obtained.

(Comparative Example 2)
As a polypropylene resin, MFR = 7.5 g / 10 minutes, [mmmm] = 98.9%, Tc = 116.2 ° C., Tm = 162.5 ° C., propylene homopolymer PP-1 (Sumitomo Chemical Co., Ltd.) , FLX80E4) with 80 parts by weight, MFR = 11 g / 10 minutes, [mmmm] = 98.8%, Tc = 116.5 ° C, Tm = 161.5 ° C. Polypropylene homopolymer PP-2 (Sumitomo) 0.9912 of stearylamine monostearic acid ester (manufactured by Toho Chemical Industry Co., Ltd .: Anstex SA321) as compound (A) in 100 parts by weight of a blend of 20 parts by weight of EL80F5 manufactured by Chemical Co., Ltd. 0.156 parts by weight and 0.156 parts by weight of glycerin monostearate (manufactured by Toho Chemical Industry Co., Ltd .: Anstex MG100) as compound (B) are mixed, and then melt-kneaded and granulated using an extruder with a pelletizer. The same procedure as in Example 1 was carried out except that pellets of the polypropylene composition were obtained and used as the polypropylene-based resin composition for the intermediate layer (B). Table 1 shows the structure of the polypropylene resin, Table 2 shows the raw materials for each layer, and Table 3 shows the film forming conditions. As shown in Table 4, a film having high rigidity and low heat shrinkage at high temperature, but easily charged was obtained.

(Comparative Example 3)
As a polypropylene resin, MFR = 7.5 g / 10 minutes, [mmmm] = 98.9%, Tc = 116.2 ° C., Tm = 162.5 ° C., propylene homopolymer PP-1 (Sumitomo Chemical Co., Ltd.) , FLX80E4) with 30 parts by weight, MFR = 11 g / 10 minutes, [mmmm] = 98.8%, Tc = 116.5 ° C, Tm = 161.5 ° C. Polypropylene homopolymer PP-2 (Sumitomo) 20 parts by weight of EL80F5) manufactured by Kagaku Co., Ltd., MFR = 7.5 g / 10 minutes, Tc = 111.7 ° C, Tm = 158 ° C. A blend of 50 parts by weight of the copolymer PP-3 (WF836DG3 manufactured by Sumitomo Chemical Co., Ltd.) in 100 parts by weight, and stearylamine monostearic acid ester as the compound (A) (manufactured by Toho Chemical Industry Co., Ltd .: Anse). Tex SA321) is 0.9554 parts by weight and glycerin monostearate (manufactured by Toho Chemical Industry Co., Ltd .: Anstex MG100) is 0.153 parts by weight as compound (B), and stearyldiethanolamine (Toho Chemical Co., Ltd.) is used as compound (C). Industrial Co., Ltd .: Anstex SA20) is blended in 0.120 parts by weight, mixed, melt-kneaded and granulated using an extruder with a pelletizer to obtain pellets of the polypropylene composition, and used for the intermediate layer (B). The same procedure as in Example 1 was carried out except that the polypropylene-based resin composition of the above was used. Table 1 shows the structure of the polypropylene resin, Table 2 shows the raw materials for each layer, and Table 3 shows the film forming conditions. As shown in Table 4, a film having low rigidity was obtained.

(Comparative Example 4)
As a polypropylene resin, a propylene / ethylene copolymer PP-3 (Sumitomo Chemical Co., Ltd.) containing 0.6 mol% of ethylene monomer-derived components having MFR = 7.5 g / 10 minutes, Tc = 111.7 ° C., and Tm = 158 ° C. WF836DG3) manufactured by Co., Ltd., 0.800 parts by weight of stearylamine monostearate ester (manufactured by Toho Chemical Industry Co., Ltd .: Anstex SA321) as compound (A) and glycerin monostearate as compound (B) in 100 parts by weight. (Toho Chemical Industry Co., Ltd .: Anstex MG100) is mixed in an amount of 0.157 parts by weight, and compound (C) is mixed with stearyldiethanolamine (manufactured by Toho Chemical Industry Co., Ltd .: Anstex SA20) in an amount of 0.200 parts by weight. After that, the polypropylene composition was melt-kneaded and granulated using an extruder with a pelletizer to obtain pellets of the polypropylene composition, and the same procedure as in Example 1 was carried out except that the polypropylene-based resin composition for the intermediate layer (B) was obtained. Table 1 shows the structure of the polypropylene resin, Table 2 shows the raw materials for each layer, and Table 3 shows the film forming conditions. As shown in Table 4, a film having low rigidity was obtained.

(Comparative Example 5)
As a polypropylene resin, MFR = 7.5 g / 10 minutes, [mmmm] = 98.9%, Tc = 116.2 ° C., Tm = 162.5 ° C., propylene homopolymer PP-1 (Sumitomo Chemical Co., Ltd.) , FLX80E4) with 80 parts by weight, MFR = 11 g / 10 minutes, [mmmm] = 98.8%, Tc = 116.5 ° C, Tm = 161.5 ° C. Polypropylene homopolymer PP-2 (Sumitomo) 0.9912 of stearylamine monostearic acid ester (manufactured by Toho Kagaku Kogyo Co., Ltd .: Anstex A321) as compound (A) in 100 parts by weight of a blend of 20 parts by weight of EL80F5 manufactured by Kagaku Co., Ltd. 0.156 parts by weight and 0.156 parts by weight of glycerin monostearate (manufactured by Toho Chemical Industry Co., Ltd .: Anstex MG100) as compound (B) are mixed, and then melt-kneaded and granulated using an extruder with a pelletizer. Pellets of the polypropylene composition were obtained to obtain a polypropylene-based resin composition for the intermediate layer (B), and as the polypropylene resin, MFR = 7.5 g / 10 minutes, [mm mm] = 98.9%, Tc = 116.2. 94 parts by weight of polypropylene homopolymer PP-1 (manufactured by Sumitomo Chemical Co., Ltd., FLX80E4) at ° C., Tm = 162.5 ° C., MFR = 7.5 g / 10 minutes, Tc = 111.7 ° C., Tm A blend of 6 parts by weight of propylene / ethylene copolymer PP-3 (WF836DG3 manufactured by Sumitomo Chemical Co., Ltd.) containing 0.6 mol% of an ethylene monomer-derived component at 158 ° C. is used for the surface layer (C). The same procedure as in Example 1 was carried out except that the polypropylene-based resin composition of No. 1 was used. Table 1 shows the structure of the polypropylene resin, Table 2 shows the raw materials for each layer, and Table 3 shows the film forming conditions. As shown in Table 4, a film having high rigidity and low heat shrinkage at high temperature, but easily charged was obtained.

(Comparative Example 6)
As a polypropylene resin, MFR = 7.5 g / 10 minutes, [mmmm] = 98.9%, Tc = 116.2 ° C., Tm = 162.5 ° C., propylene homopolymer PP-1 (Sumitomo Chemical Co., Ltd.) Made of FLX80E4) in 94 parts by weight, MFR = 7.5 g / 10 minutes, Tc = 111.7 ° C, Tm = 158 ° C. Polypropylene / ethylene copolymer PP with 0.6 mol% of ethylene monomer-derived component. -3 (WF836DG3 manufactured by Sumitomo Chemical Co., Ltd.) was blended with 6 parts by weight to prepare a polypropylene-based resin composition for the surface layer (C), and the same procedure as in Example 1 was carried out. Table 1 shows the structure of the polypropylene resin, Table 2 shows the raw materials for each layer, and Table 3 shows the film forming conditions. As shown in Table 4, a film having high rigidity and low heat shrinkage at high temperature, but easily charged was obtained.

(Comparative Example 7)
It was carried out in the same manner as in Example 1 except that it was stretched at 162 ° C. as the first step in the width direction. Table 1 shows the structure of the polypropylene resin, and Table 2 shows the film forming conditions. As shown in Table 3, a film having high rigidity but high heat shrinkage at high temperature and easily charged was obtained.

(Comparative Example 8)
The same procedure as in Example 1 was carried out except that the temperature was stretched at 162 ° C. in the width direction, the heat fixing temperature was set to 168 ° C., and the temperature was relaxed by 5% in the width direction. Table 1 shows the structure of the polypropylene resin, Table 2 shows the raw materials for each layer, and Table 3 shows the film forming conditions. As shown in Table 4, a film having low rigidity was obtained.

Claims (8)

1. The stress (F5) at 5% elongation is 40 MPa or more in the longitudinal direction at 23 ° C., 160 MPa or more in the width direction, and the heat shrinkage rate at 150 ° C. is 10% or less in the longitudinal direction, in the width direction. A biaxially oriented polypropylene film having a surface intrinsic resistance of 30% or less and at least one side of the film surface having a surface intrinsic resistance of 15Ω / □ or less.
2. The heat shrinkage rate of the biaxially oriented polypropylene film at 120 ° C. is 2.0% or less in the longitudinal direction, 5.0% or less in the width direction, and the heat shrinkage rate at 120 ° C. in the longitudinal direction is 120 in the width direction. The biaxially oriented polypropylene film according to claim 1, which is smaller than the ° C. heat shrinkage rate.
3. The biaxially oriented polypropylene film according to claim 1 or 2, wherein the refractive index Ny in the width direction of the biaxially oriented polypropylene film is 1.5230 or more and ΔNy is 0.0220 or more.
4. The biaxially oriented polypropylene film according to any one of claims 1 to 3, wherein the haze of the biaxially oriented polypropylene film is 5.0% or less.
5. The biaxially oriented polypropylene film according to any one of claims 1 to 4, wherein the main polypropylene resin constituting the base material layer (A) has a mesopentad fraction of 97.0% or more.
6. The biaxially oriented polypropylene film according to any one of claims 1 to 5, wherein the main polypropylene resin constituting the base material layer (A) has a crystallization temperature of 105 ° C. or higher and a melting point of 160 ° C. or higher.
7. The biaxially oriented polypropylene film according to any one of claims 1 to 6, wherein the melt flow rate of the main polypropylene resin constituting the base material layer (A) is 4.0 g / 10 minutes or more.
8. The biaxially oriented polypropylene film according to any one of claims 1 to 7, wherein the main polypropylene resin constituting the base material layer (A) has a molecular weight of 100,000 or less and a component amount of 35% by mass or more.