CN109070568B

CN109070568B - Biaxially stretched laminated polypropylene film

Info

Publication number: CN109070568B
Application number: CN201780020590.6A
Authority: CN
Inventors: 木下理; 山田浩司; 多贺敦
Original assignee: Toyobo Co Ltd
Current assignee: Toyobo Co Ltd
Priority date: 2016-03-28
Filing date: 2017-03-21
Publication date: 2021-08-27
Anticipated expiration: 2037-03-21
Also published as: JP2024041794A; TW201801927A; JP7437115B2; CN109070568A; KR102434652B1; JP2023040009A; TWI711539B; WO2017169952A1; JPWO2017169952A1; JP2024041793A; JP7459919B2; KR20180122459A

Abstract

Provided is a biaxially stretched laminated polypropylene film having high rigidity, excellent heat resistance and excellent antistatic properties. The biaxially stretched laminated polypropylene film of the present invention is a laminated film comprising at least 2 or more layers of polypropylene resin compositions having different crystallinities, the biaxially stretched laminated polypropylene film comprising: a layer A formed from a polypropylene resin composition having a Δ H of 78.0J/g or more; and a B layer which is formed from a polypropylene resin composition having a Delta H of less than 82.0J/g and a Delta H of 2.0 to 40.0J/g lower than that of the A layer, and which is present on at least one outermost surface side, wherein the Delta H represents a melting endothermic peak area measured at a temperature rise rate of 20 ℃/min using a differential scanning calorimeter.

Description

Biaxially stretched laminated polypropylene film

Technical Field

The present invention relates to a biaxially stretched laminated polypropylene film. More specifically, the present invention relates to a biaxially stretched polypropylene film having excellent heat resistance, rigidity and antistatic properties.

Background

Conventionally, stretched polypropylene films have been used in a wide range of applications such as packaging of foods and various products, electrical insulation, and surface protection films. However, the conventional polypropylene film has a shrinkage of several tens% at 150 ℃, and has a low heat resistance and a low rigidity as compared with a polyethylene terephthalate (PET) film, etc., and thus, its application is limited.

Various techniques for improving the physical properties of polypropylene films have been proposed. For example, the following techniques are known: a balance between rigidity and processability is obtained by forming a film using polypropylene containing substantially equal amounts of a high molecular weight component and a low molecular weight component (or a small amount of a low molecular weight component), having a broad molecular weight distribution, and a small amount of a decalin-soluble component (patent document 1). However, in this technique, it can be said that the heat resistance at high temperatures such as above 150 ℃ is still insufficient, and a polypropylene film having high heat resistance and excellent impact resistance and transparency has not been known yet.

The present applicant has conducted extensive studies in view of the above-mentioned prior art, and as a result, has used the polypropylene resin as an index of stereoregularity of the film¹³A polypropylene-based polymer having a meso pentad fraction of 96% or more as measured by C-NMR has successfully provided a stretched polypropylene film having high rigidity and high heat resistance (patent document 2).

Documents of the prior art

Patent document

Patent document 1: japanese Kokai publication No. 2008-540815

Patent document 2: WO2015/012324 pamphlet

Disclosure of Invention

Problems to be solved by the invention

However, in the patent document 2, there is room for improvement in antistatic property.

In view of the above circumstances, the present invention describes the following problems: provided is a biaxially stretched laminated polypropylene film having high rigidity, excellent heat resistance and excellent antistatic properties.

Means for solving the problems

The present invention is configured as follows.

1. A biaxially stretched laminated polypropylene film characterized by comprising at least 2 or more layers of a laminated film comprising polypropylene resin compositions having different crystallinities,

the biaxially stretched laminated polypropylene film has:

a layer A formed from a polypropylene resin composition having a Δ H of 78.0J/g or more; and the combination of (a) and (b),

a layer B comprising a polypropylene resin composition having a Delta H of less than 82.0J/g and a Delta H of 2.0 to 40.0J/g lower than that of the layer A, and

the aforementioned B layer is present on at least one outermost surface side,

wherein Δ H represents a melting endothermic peak area measured at a temperature increase rate of 20 ℃/min using a differential scanning calorimeter.

2. The biaxially stretched laminated polypropylene film according to the above 1, wherein the ratio of the total thickness of the B layer to the total thickness of the A layer (total B layer/total A layer) is 0.01 to 0.5, and the total thickness of the B layer is 0.5 to 4 μm.

3. The biaxially stretched laminated polypropylene film according to 1 or 2, further comprising, on the outermost surface side of the layer B: a further layer having a thickness of 0.01 to 1.0 μm and formed of a polypropylene resin composition having a Δ H of more than 76.0J/g.

4. The biaxially stretched laminated polypropylene film according to any one of the above 1 to 3, wherein the Melt Flow Rate (MFR) of the whole film is 2.0 to 10.5g/10 min.

5. The biaxially stretched laminated polypropylene film according to any one of the above 1 to 4, wherein the surface resistivity value (Log. OMEGA.) of the whole film is 13.5 or less.

6. The biaxially stretched laminated polypropylene film according to any one of the above 1 to 5, wherein the dynamic friction coefficient of the whole film is 0.4 or less.

7. The biaxially stretched laminated polypropylene film according to any one of 1 to 6, wherein the heat shrinkage rate at 150 ℃ is 10.0% or less in both the MD direction and the TD direction, and wherein the tensile elastic modulus in the MD direction is 2.0GPa or more and the tensile elastic modulus in the TD direction is 3.8GPa or more.

8. The biaxially stretched laminated polypropylene film according to any one of the above 1 to 7, wherein the lamination strength in the MD direction after lamination is 1.2N/15mm or more.

ADVANTAGEOUS EFFECTS OF INVENTION

The polypropylene film of the present invention has at least 2 layers of the high-crystalline a layer and the low-crystalline B layer, and has a laminated structure in which the B layer is disposed on the outermost surface side, and therefore, the antistatic agent kneaded into at least one layer bleeds out on the surface of the low-crystalline B layer disposed on the outermost surface side. As a result, good antistatic properties can be exhibited while maintaining the excellent heat resistance and rigidity of the a layer having high crystallinity.

Detailed Description

The polypropylene film of the present invention is a biaxially stretched laminated polypropylene film, which is a laminated film comprising at least 2 or more layers of polypropylene resin compositions having different crystallinities, the biaxially stretched laminated polypropylene film comprising: a layer A formed from a polypropylene resin composition having a Δ H of 78.0J/g or more; and a B layer which is formed from a polypropylene resin composition having a Delta H of less than 82.0J/g and a Delta H of 2.0 to 40.0J/g lower than that of the A layer, and which is present on at least one outermost surface side, wherein the Delta H represents a melting endothermic peak area (total heat of fusion) measured at a temperature rise rate of 20 ℃/min using a Differential Scanning Calorimeter (DSC).

Here, Δ H is a value that serves as an index of crystallinity. The higher the crystallinity, the larger the energy required for melting the crystal, and therefore, the larger Δ H, the higher the crystallinity. In the present invention, the raw materials used for film formation were measured for a DSC curve at a temperature rise rate of 20 ℃/min to obtain Δ H.

First, Δ H of the a layer and the B layer most added with the features of the present invention will be described.

The layer A is a highly crystalline layer which is responsible for heat resistance, rigidity, mechanical strength after lamination, etc., and Δ H is necessarily 78.0J/g or more, more preferably 80.0J/g or more, further preferably 81.0J/g or more, and further preferably 82.0J/g or more. When Δ H of the a layer is small, rigidity such as tensile elastic modulus becomes small, which is not preferable. Further, Δ H of the layer A is preferably 104.0J/g or less, more preferably 102.0J/g or less, and further preferably 100.0J/g or less. If Δ H of the a layer is too large, high-temperature long-time production is required, and actual industrial production may become difficult.

On the other hand, the B layer is a layer having lower crystallinity on the outermost surface side than the a layer, and the antistatic agent kneaded into the B layer having lower crystallinity (skin layer) naturally bleeds out on the surface of the B layer on the outermost surface side, and the antistatic agent kneaded into the a layer having higher crystallinity (core layer) bleeds out on the surface of the B layer on the outermost surface side, and plays a role of imparting excellent antistatic properties. Therefore, the layer B must have a Δ H lower than 82.0J/g and a Δ H lower than that of the layer A by 2.0 to 40.0J/g. When Δ H of the B layer is 82.0J/g or more, the amount of the antistatic agent oozed out is small, and the antistatic property becomes insufficient. Further, the film tends to have poor slidability, and there is a fear that stable film formation cannot be performed. Further, the later-described lamination strength may be reduced. The B layer preferably has a.DELTA.H of 81.0J/g or less, more preferably 80.0J/g or less, and particularly preferably less than 78.0J/g. The lower limit of Δ H of the B layer is not particularly limited, and Δ H is preferably 60.0J/g or more. When Δ H is less than 60.0J/g, the tensile modulus of elasticity becomes small, the heat shrinkage becomes large, the transparency is lowered, or the roller may be attached.

The difference between the Δ H of the layer A and the Δ H of the layer B (Δ H of the layer A- Δ H of the layer B) is 2.0 to 40.0J/g. When the difference is less than 2.0J/g, the effect of the present invention of achieving both the target heat resistance and antistatic property by laminating a high crystalline layer and a low crystalline layer may be insufficient. On the other hand, if the difference is more than 40.0J/g, the low crystalline layer is heated by heat during stretching, and thus, problems such as whitening occur. The preferable range of the difference in Δ H is 3.0 to 25J/g, and more preferably 4.0 to 15J/g.

In the biaxially stretched laminated polypropylene film of the present invention, in order to increase the crystallinity (Δ H) of the polypropylene resin of the layer a, there are: reducing the molecular weight of the layer A; reducing the comonomer in the polypropylene resin; increasing the meso pentad fraction which is an index of the stereoregularity of the resin; increasing the amount of low molecular weight components having a molecular weight of about 10 ten thousand or less; and the like. This is because the low-molecular-weight component having a molecular weight of about 10 ten thousand or less has a large effect of accelerating the crystallization rate. Further, since the high molecular weight component having a molecular weight of about 100 ten thousand or more acts as a crystal nucleating agent and promotes the crystallization rate of the low molecular weight component, it is also effective to mix the low molecular weight component with a small amount of the high molecular weight component to increase the molecular weight distribution (Mw/Mn).

On the other hand, in order to reduce the crystallinity (Δ H) of the polypropylene resin of the B layer, there are: increasing the molecular weight of the B layer; increasing the copolymerization component in the polypropylene resin; reducing the meso pentad fraction; and the like.

The laminated film of the present invention has the following features as described above: Δ H (total heat of fusion) of the a layer and the B layer, and the difference therebetween, the melting endothermic peak temperature in the DSC curve also become one of the criteria for crystallinity. The melting endothermic peak temperature of the A layer is preferably 160 ℃ or more, more preferably 163 ℃ or more. Further, it is preferably 176 ℃ or lower, more preferably 173 ℃ or lower, and still more preferably 170 ℃ or lower.

On the other hand, in the case of the B layer, the melting endothermic peak temperature is preferably 166 ℃ or less, more preferably 164 ℃ or less. Further, it is preferably 120 ℃ or higher, more preferably 130 ℃ or higher.

Hereinafter, the layer a and the layer B constituting the laminated film of the present invention will be described in more detail.

(layer A)

The polypropylene resin used in the layer a of the present invention may be not only a polypropylene homopolymer but also a polypropylene obtained by copolymerizing ethylene and/or an α -olefin having 4 or more carbon atoms in an amount of 0.5 mol% or less. Such a copolymerized polypropylene is also included in the polypropylene resin of the present invention (hereinafter, sometimes referred to simply as polypropylene). Examples of the α -olefin having 4 or more carbon atoms include 1-butene, 1-hexene, 4-methylpent-1-ene, and 1-octene. In the case of the a layer, it is preferable to decrease the comonomer in the polypropylene resin to increase Δ H as described above, and therefore, the ethylene, the α -olefin having 4 or more carbon atoms, and the other copolymerization component are preferably 0.3 mol% or less, more preferably 0.1 mol% or less, and most preferably completely homopolymerized polypropylene (polypropylene homopolymer) containing no copolymerization component. When ethylene and/or an α -olefin having 4 or more carbon atoms is copolymerized in an amount exceeding 0.5 mol%, Δ H becomes small, crystallinity and rigidity excessively decrease, and the heat shrinkage rate at high temperature sometimes becomes large. Further, resins satisfying the above characteristics (e.g., completely homo-polypropylene and co-polypropylene) may be blended and used.

Use as an indicator of the stereoregularity of the polypropylene constituting the layer A of the present invention¹³Meso pentad fraction ([ mmmm ] determined by C-NMR]%) is preferably 98-99.5 percent. More preferably 98.1% or more, and still more preferably 98.2% or more. When the meso pentad fraction of the polypropylene in the layer a is small, the elastic modulus is lowered, and the heat resistance may be insufficient. 99.5% is a realistic upper limit.

The polypropylene constituting the layer A of the present invention preferably has a mass average molecular weight (Mw) of 180000 to 500000. When the amount is less than 180000, the melt viscosity is low, and therefore, the casting is unstable, and the film-forming property may be deteriorated. When Mw exceeds 500000, extrusion is sometimes difficult and film formability is poor, which is not preferable. When Mw is high, the amount of low molecular weight components having a molecular weight of 10 ten thousand or less in a Gel Permeation Chromatography (GPC) integration curve is small, and the heat shrinkage rate may be high. The lower limit of Mw is more preferably 190000, still more preferably 200000, and the upper limit of Mw is more preferably 450000, still more preferably 420000, particularly preferably 410000.

In order to easily obtain a desired low heat shrinkage ratio at high temperature or reduce thickness unevenness, the content ratio of the low-molecular weight component in the a layer is preferably 35% by weight or more, more preferably 38% by weight or more, and still more preferably 42% by weight or more.

The number average molecular weight (Mn) of the polypropylene constituting the A layer of the present invention is preferably 20000 to 200000. When the melt viscosity is less than 20000, the melt viscosity is low, and therefore, the melt viscosity is unstable during casting, and the film-forming property may be deteriorated. When the amount exceeds 200000, extrusion is sometimes difficult, and film formability is poor, which is not preferable. When Mn is high, the thermal shrinkage may be high. The lower limit of Mn is more preferably 30000, still more preferably 40000, particularly preferably 50000, and the upper limit of Mn is more preferably 170000, still more preferably 160000, particularly preferably 150000.

Further, the Mw/Mn, which is an index of molecular weight distribution, of the polypropylene of the A layer is preferably 2.8 to 30. More preferably 3 to 15, still more preferably 3.2 to 10, and particularly preferably 3.5 to 6.

As described above, by mixing the low molecular weight component with a small amount of the high molecular weight component, the Mw/Mn can be increased here. That is, the low-molecular weight component having a molecular weight of about 10 ten thousand or less has a large effect of accelerating the crystallization rate, and if the high-molecular weight component having a molecular weight of about 100 ten thousand or more is added, it acts as a crystal nucleating agent and can accelerate the effect of adding the low-molecular weight component. When a low molecular weight component is mixed with a small amount of a high molecular weight component, Mw/Mn becomes large. When the amount of the low-molecular-weight component is large, entanglement of molecules becomes strong, and even if the crystallinity is high, the heat shrinkage tends to be large. When Mw/Mn is too large, the amount of high molecular weight component increases, and the heat shrinkage ratio may become large, which is not preferable. In this case, the Mw/Mn is preferably 8 to 30, more preferably 8 to 15. The MFR in this case is preferably 2 to 6g/10 min.

The molecular weight distribution of the polypropylene can be adjusted as follows: the adjustment can be made by polymerizing the different molecular weight components in multiple stages in a series of plants, or by blending the different molecular weight components off-line in a compounder, or by blending and polymerizing catalysts having different properties, or by using catalysts that achieve the desired molecular weight distribution.

The melt flow rate (MFR; 230 ℃, 2.16kgf) of the polypropylene of the A layer is preferably 0.5 to 20g/10 min. The lower limit of MFR is more preferably 2g/10 min, still more preferably 4g/10 min, particularly preferably 5g/10 min, most preferably 6g/10 min. The upper limit of MFR of the polypropylene of the layer A is more preferably 15g/10 min, still more preferably 12g/10 min, particularly preferably 10g/10 min, most preferably 9.5g/10 min. Within this range, the adhesiveness to the cooling roll is also good, the film forming property is excellent, and the heat shrinkage rate at high temperature can be kept small.

(layer B)

The polypropylene resin used in the layer B of the present invention may be a polypropylene obtained by copolymerizing ethylene and/or an α -olefin having 4 or more carbon atoms, in addition to a polypropylene homopolymer. Examples of the α -olefin having 4 or more carbon atoms include 1-butene, 1-hexene, 4-methylpent-1-ene, and 1-octene. Further, as other copolymerization components, maleic acid having polarity or the like may be used. In the case of the B layer, the total amount of ethylene, α -olefin having 4 or more carbon atoms, and other copolymerization components (hereinafter, sometimes represented by copolymerization components) is preferably 8.0 mol% or less, and more preferably 6.0 mol% or less. When the copolymerization is carried out at more than 8.0 mol%, the film may be whitened to cause poor appearance or tackiness, which may make film formation difficult. Further, resins satisfying the above characteristics (e.g., completely homo-polypropylene and co-polypropylene) may be blended and used. In the case of blending, each resin may be copolymerized in an amount exceeding 8.0 mol%, and the blend is preferably such that the monomer other than propylene in the monomer unit is 8.0 mol% or less.

The polypropylene of the B layer of the present invention preferably has MFR of 0.5 to 10g/10 min. The lower limit of MFR of the polypropylene of the B layer is more preferably 2g/10 min, still more preferably 3g/10 min. The upper limit of MFR of the polypropylene of the B layer is more preferably 8g/10 min, still more preferably 5.5g/10 min. Within this range, the film formability is also good, and the heat shrinkage rate at high temperature can be kept small. On the other hand, when the MFR of the polypropylene of the B layer is less than 0.5g/10 min, and the MFR of the polypropylene of the a layer is large, the viscosity difference between the a layer and the B layer becomes large, and therefore, unevenness (coil unevenness) is likely to occur during film formation. When the MFR of the B layer exceeds 10g/10 min, the adhesiveness to the cooling roll is deteriorated, air is mixed in, smoothness is deteriorated, and defects which become starting points may be increased.

The meso pentad fraction of the polypropylene in the B layer is preferably 98.2% or less. More preferably 98.0% or less, and still more preferably 97.8% or less. When the meso pentad fraction of the polypropylene in the B layer is large, the crystallinity becomes too high, and the antistatic agent is less likely to bleed out, and the antistatic property may be lowered. Further, the sliding property and the lamination strength tend to be lowered. The meso pentad fraction of the polypropylene in the B layer is not particularly limited from the above-mentioned viewpoint, and is preferably 90% or more in consideration of film appearance, film formability, and the like.

The mass average molecular weight (Mw) of the polypropylene constituting the B layer of the present invention is preferably 200000 to 500000. If the amount is less than 200000, the adhesion to the cooling roll may be poor, air may be mixed in, the smoothness may be poor, and defects which become starting points may be increased. When Mw exceeds 500000, extrusion is sometimes difficult, and unevenness (web unevenness) is likely to occur during film formation, which is not preferable. The lower limit of Mw is more preferably 220000, still more preferably 240000, and the upper limit of Mw is more preferably 450000, still more preferably 420000, particularly preferably 410000.

The number average molecular weight (Mn) of the polypropylene constituting the B layer of the present invention is preferably 50000 to 200000. If the melt viscosity is less than 50000, the melt viscosity is low, and therefore, the melt viscosity is unstable during casting, and the adhesiveness to a cooling roll is deteriorated, air is mixed, the smoothness is deteriorated, and defects which become starting points may be increased. When the amount exceeds 200000, extrusion is sometimes difficult, and film formability is poor, which is not preferable. The lower limit of Mn is more preferably 60000, still more preferably 70000, and the upper limit of Mn is more preferably 170000, still more preferably 160000, and particularly preferably 150000.

In the B layer, the Mw/Mn is preferably 3.5 to 30, more preferably 3.7 to 20, and further preferably 3.7 to 15.

(laminated film)

The biaxially stretched laminated polypropylene film of the present invention has the above-mentioned a layer and B layer, and the B layer is disposed so as to be at least one outermost surface side. Here, "the B layer exists on at least one outermost surface side" means that the B layer is closer than the a layer if viewed from at least one side. The "outermost surface side" means that, in the relationship between the a layer and the B layer constituting the laminated film, the B layer is located on the outermost surface than the a layer, and includes not only the case where the B layer is disposed on the outermost surface (top) of the laminated film but also the case where other layers (other than the a layer and the B layer) are disposed on the outermost surface (top) of the B layer. That is, the laminated film of the present invention may have a multilayer structure of 3 or more layers in addition to a 2-layer structure.

Specifically, the laminated film of the present invention may include, as resin components: when the layer is formed only of the a layer and the B layer, the film may have a 2-layer structure including 1 layer each of the a layer (core layer) and the B layer (skin layer) (that is, the B layer is provided on one of the a layers), or may have a sandwich structure (B layer/a layer/B layer) including 2 layers and 3 skin layers each including the B layer on both of the a layers (core layer) (that is, the B layer is provided on both of the a layers). Alternatively, for example, a sandwich structure of 2 kinds of 5 layers (B layer/a layer/B layer) or the like may be used, and a multilayer structure of more than this may also be used. Of course, the present invention is not limited to these examples, and examples thereof include: various modes of the B layer on the outermost surface side, for example, modes of a layer/B layer, a layer/B layer, and the like, are possible. Among them, 2 kinds of 3-layer structures of B layer/a layer/B layer are preferable. When the laminated film has a plurality of a layers and B layers, the respective layers may be the same type of resin or different types of resins.

Alternatively, the biaxially stretched laminated polypropylene film of the present invention may have a polypropylene resin layer other than the above-mentioned a layer and B layer (the layers other than the above are collectively referred to as the C layer for convenience). By providing such a C layer on the outermost layer, the heat resistance of the outermost layer can be further ensured without substantially preventing the bleeding of the antistatic agent. The C layer has a Δ H of more than 76.0J/g and does not belong to any of the A and B layers. The C layer may be disposed at any position, and may be disposed between the a layer and the B layer, on the core side of the a layer, or on the outermost surface side of the B layer. The C layer is preferably disposed on the outermost surface side of the B layer, and may be, for example, a film having a 3-layer structure of 3 types including the C layer, the B layer, and the a layer in this order from the outermost surface side. As the raw material used for the layer C, the raw materials described for the layers a and B can be suitably used. For example, the polypropylene resin composition used for the layer A may be used for the polypropylene resin composition of the layer C, or may be different from that used for the layer A.

The thickness of the entire film is preferably 9 to 200. mu.m, more preferably 10 to 150. mu.m, still more preferably 12 to 100. mu.m, and particularly preferably 12 to 80 μm.

The ratio of the thicknesses of the B layer and the a layer is preferably 0.01 to 0.5, more preferably 0.03 to 0.4, and further preferably 0.05 to 0.3 for the total B layer (the total thickness of a plurality of B layers in the case of a plurality of a layers)/the total a layer (the total thickness of a plurality of a layers in the case of a plurality of a layers). When the total B layer/total a layer exceeds 0.5, the elastic modulus tends to decrease. The thickness of the total a layer is preferably 50 to 99%, more preferably 60 to 97%, and particularly preferably 70 to 95% of the thickness of the entire film. The remaining portion becomes a B layer, or a C layer other than the a layer and the B layer.

The substantial thickness of the total A layer is preferably 5 to 50 μm, more preferably 10 to 45 μm, and further preferably 15 to 40 μm.

The substantial thickness of the total B layer is preferably 0.1 μm or more, more preferably 0.5 μm or more, further preferably 1 μm or more, further more preferably 1.5 μm or more; preferably 4 μm or less, more preferably 3.5 μm or less, further preferably 3 μm or less, and further more preferably 2 μm or less.

When a C layer is further present, the thickness of the C layer is preferably 0.01 to 1.0. mu.m, more preferably 0.05 μm or more, and still more preferably 0.1 μm or more. The thickness of the C layer is preferably thinner than the B layer, and preferably less than 0.5. mu.m.

The MFR of the whole film is preferably 2.0 to 10.5g/10 min. When the amount is less than 2.0g/10 minutes, film formability is poor, and the heat shrinkage of the resulting film tends to be large. The lower limit of MFR is more preferably 3.0g/10 min. On the other hand, when the amount exceeds 10.5g/10 minutes, the adhesiveness to the cooling roll is lowered, and the film formation stability tends to be poor, or defects such as foreign matters tend to increase.

The polypropylene used in the present invention is obtained by polymerizing propylene as a raw material using a known catalyst such as a ziegler-natta catalyst or a metallocene catalyst. Among them, a Ziegler-Natta catalyst is used for eliminating heterozygosity, and a catalyst capable of polymerization with high stereoregularity is preferably used.

As the polymerization method of propylene, known methods can be used, and examples thereof include: a method of polymerizing in an inactive solvent such as hexane, heptane, toluene, xylene, etc.; a method of carrying out polymerization in a liquid monomer; a method of adding a catalyst to a gas monomer and polymerizing the monomer in a gas phase; or a method of polymerizing a combination of these.

The biaxially stretched laminated polypropylene film of the present invention contains an antistatic agent. The content of the antistatic agent in the entire film is preferably 0.01 to 3.0 mass%, more preferably 0.05 to 2.8 mass%, and still more preferably 0.10 to 2.5 mass%. The antistatic agent is not particularly limited, and amine surfactants and fatty acid monoglycerides are preferable examples.

Specific examples of the amine-based surfactant include diethanolamine myristate, diethanolamine palmitate, diethanolamine stearate, diethanolamine oleate, diethanolamine arachidate and diethanolamine behenate, more preferably diethanolamine palmitate, diethanolamine stearate and diethanolamine oleate, and 2 or more selected from these surfactants can be used as a mixture.

Specific examples of the monoglyceride include glycerol monolaurate, glycerol monomyristate, glycerol monopalmitate, glycerol monostearate, glycerol monoarachate, and glycerol monobehenate, and more preferably glycerol monostearate, and 2 or more of these may be selected and used as a mixture.

If the amount of the antistatic agent is less than 0.01% by mass, the film tends to be poor in antistatic properties, and if the amount is more than 3% by mass, the roll may be contaminated during film formation or processing, or the film surface may be sticky, which is not preferable. In addition, since the above-mentioned problems are easily caused when a large amount of the antistatic agent is added to the layer B during production, it is preferable that the antistatic agent is not added to the polypropylene resin composition for the layer B, the amount of the antistatic agent to be added is reduced, or the antistatic agent is added to the layer a within the above-mentioned amount range during production. Even in this case, the antistatic agent contained in the layer a diffuses and migrates into the layer B, and further may exude to the surface of the laminated film through the layer B. When the Δ H of the B layer is less than 82.0J/g and the difference between the Δ H of the A layer and the Δ H of the B layer (Δ H of the A layer- Δ H of the B layer) is 2.0 to 40.0J/g, the diffusion, migration, and bleeding of the antistatic agent to the B layer are promoted, and sufficient antistatic properties can be obtained.

In the layer B, an antiblocking agent may be added. The anti-blocking agent may be suitably selected from inorganic anti-blocking agents such as silica, calcium carbonate, kaolin, zeolite, and the like, and organic anti-blocking agents such as aliphatic fatty acid esters, ethylene bisamides, acrylic acids, polystyrenes, and the like. The preferable average particle diameter of the anti-blocking agent is 0.5 to 5.0. mu.m, more preferably 1.0 to 3.0. mu.m. If the average particle size is less than 0.5. mu.m, a large amount of an antiblocking agent is required for obtaining good slidability, and conversely, if it exceeds 5.0. mu.m, the surface roughness of the film becomes too large, and the practical properties may not be satisfied, which is not preferable. The antiblocking agent is preferably 0.01 to 0.3% by mass in the layer B. When the amount is less than 0.01% by mass, the film is less likely to slip, and when the amount is more than 0.3% by mass, the film may be whitened, which is not preferable.

The layer a and/or the layer B (in the case of further including other layers than these layers, the other layers) of the present invention may contain other additives and other resins. Examples of the other additives include antioxidants, ultraviolet absorbers, nucleating agents, adhesives, antifogging agents, flame retardants, inorganic or organic fillers, and the like. Examples of the other resin include polypropylene resins other than the polypropylene resin used in the present invention, random copolymers which are copolymers of propylene and ethylene and/or α -olefins having 4 or more carbon atoms, and various elastomers. These may be used by polymerizing sequentially using a multistage reactor, blending with a polypropylene resin using a henschel mixer, diluting a master batch pellet prepared in advance using a melt kneader with polypropylene so as to have a predetermined concentration, or melt kneading the whole amount in advance.

(method for producing film)

The biaxially stretched laminated polypropylene film of the present invention can be obtained as follows: the polypropylene material for layer a (the polypropylene resin composition for layer a), the polypropylene material for layer B (the polypropylene resin composition for layer B), and if necessary, the other material for layer C (the resin composition for layer C) are melt-extruded by an extruder to form an unstretched sheet, and the unstretched sheet is stretched by a predetermined method and heat-treated to obtain the polypropylene resin composition for layer a. The unstretched laminated film can be obtained by using a plurality of extruders, a feed block, and a manifold. The melt extrusion temperature is preferably about 200 to 280 ℃, and in order to obtain a laminate film having a good appearance without causing random lamination in this temperature range, it is preferable to perform the melt extrusion so that the difference in viscosity (MFR difference) between the polypropylene material for the a layer and the polypropylene material for the B layer becomes 6g/10 min or less. When the viscosity difference is more than 6g/10 minutes, the layer is easily disturbed to cause appearance defects. More preferably 5.5g/10 min or less, and still more preferably 5g/10 min or less.

The surface temperature of the cooling roll is preferably 25 to 35 ℃, and more preferably 27 to 33 ℃. Then, the film is preferably stretched 3 to 8 times (more preferably 3 to 7 times) in the longitudinal (MD) direction by a 120 to 165 ℃ stretching roll, and then stretched 4 to 20 times, more preferably 6 to 12 times in the width (TD) direction at 155 to 175 ℃, more preferably 160 to 163 ℃.

Further, the heat fixation is performed at a relaxation rate of preferably 165 to 176 ℃, more preferably 170 to 176 ℃, and still more preferably 172 to 175 ℃, preferably 2 to 10%. The biaxially stretched laminated polypropylene film thus obtained is subjected to corona discharge, plasma treatment, flame treatment, and the like as necessary, and then wound up by a winder to obtain a film roll.

As described above, the lower limit of the MD stretching ratio is preferably 3 times, and more preferably 3.5 times. If the amount is less than the above, film thickness unevenness may occur. The upper limit of the stretching magnification in the MD is preferably 8 times, and more preferably 7 times. If the amount exceeds the above range, TD stretching to be performed subsequently may become difficult. The lower limit of the MD stretching temperature is preferably 120 ℃, more preferably 125 ℃, and still more preferably 130 ℃. When the amount is less than the above range, the mechanical load becomes large, the thickness unevenness becomes large, or the surface of the film may be rough. The upper limit of the MD stretching temperature is preferably 165 ℃, more preferably 160 ℃, still more preferably 155 ℃, and yet more preferably 150 ℃. In order to reduce the heat shrinkage, it is preferable that the temperature is high, but the film cannot adhere to a roll and is stretched, or surface roughness may occur.

The lower limit of the TD stretching ratio is preferably 4 times, more preferably 5 times, and still more preferably 6 times. When the amount is less than the above range, the thickness may be uneven. The upper limit of the TD stretching ratio is preferably 20 times, more preferably 17 times, further preferably 15 times, and particularly preferably 12 times. When the amount exceeds the above range, the heat shrinkage rate becomes high, or the film may be broken during stretching. In order to rapidly raise the film temperature to the vicinity of the stretching temperature, the preheating temperature in TD stretching is preferably set to be 5 to 15 ℃ higher than the stretching temperature. The TD stretching is performed at a higher temperature than the conventional stretched polypropylene film. The lower limit of the TD stretching temperature is preferably 155 ℃, more preferably 157 ℃, still more preferably 158 ℃, and particularly preferably 160 ℃. If the amount is less than the above range, the resin composition may not be softened sufficiently and may be broken or the heat shrinkage rate may be increased. The upper limit of the TD stretching temperature is preferably 175 ℃, more preferably 170 ℃, still more preferably 168 ℃, and yet more preferably 163 ℃. In order to reduce the heat shrinkage, it is preferable that the temperature is high, but if it exceeds the above, the low molecular weight component melts and recrystallizes, and not only the orientation is reduced, but also the surface is rough and the film is whitened in some cases.

The stretched film was heat-set. The heat-setting can be performed at a higher temperature than the conventional stretched polypropylene film. The lower limit of the thermal setting temperature is preferably 165 ℃ and more preferably 166 ℃. When the amount is less than the above, the heat shrinkage rate may be high. In addition, in order to reduce the heat shrinkage rate, a long treatment time is required, and the productivity is poor. The upper limit of the thermal setting temperature is preferably 176 deg.C, more preferably 175 deg.C. If the amount exceeds the above range, the low-molecular-weight component melts and recrystallizes, and the surface may be rough, or the film may be whitened.

At the time of heat setting, relaxation (relax) is preferably performed. The lower limit of the relaxation is preferably 2%, more preferably 3%. When the amount is less than the above, the heat shrinkage rate may be high. The upper limit of the relaxation is preferably 10%, more preferably 8%. If the thickness exceeds the above range, the thickness unevenness may be large.

Further, in order to reduce the thermal shrinkage, the film produced in the above step may be once wound in a roll shape and then annealed off-line. The lower limit of the temperature of the off-line annealing is preferably 160 ℃, more preferably 162 ℃, and still more preferably 163 ℃. If the amount is less than the above range, the annealing effect may not be obtained. The upper limit of the off-line annealing temperature is preferably 175 ℃, more preferably 174 ℃, and still more preferably 173 ℃. If the amount exceeds the above range, the transparency may be reduced or the thickness unevenness may be increased.

The lower limit of the off-line annealing time is preferably 0.1 minute, more preferably 0.5 minute, and further preferably 1 minute. If the amount is less than the above range, the annealing effect may not be obtained. The upper limit of the off-line annealing time is preferably 30 minutes, more preferably 25 minutes, and further preferably 20 minutes. If the amount exceeds the above range, the productivity may be lowered.

(Properties of film)

In the biaxially stretched laminated polypropylene film of the present invention, the heat shrinkage rate in the MD at 150 ℃ is preferably 0.2 to 10%, more preferably 0.3 to 9%, still more preferably 0.5 to 8%, particularly preferably 0.7 to 7%, most preferably 1 to 5%. The same applies to the thermal shrinkage in the TD direction at 150 ℃. When the heat shrinkage ratio is in the above range, it can be said that the film is excellent in heat resistance and can be used for applications where there is a possibility of exposure to high temperatures. Incidentally, if the heat shrinkage at 150 ℃ is up to about 1.5%, it can be achieved by, for example, increasing the low molecular weight component, adjusting the stretching conditions and the heat-setting conditions, and in order to reduce the molecular weight to less than this, it is preferable to perform an annealing treatment or the like offline.

In the biaxially stretched laminated polypropylene film of the present invention, the surface resistivity value is preferably 9.5 to 13.5(Log Ω), more preferably 10 to 13(Log Ω), and still more preferably 10.5 to 12.5(Log Ω). When the surface resistivity value exceeds 13.5(Log Ω), antistatic performance sometimes becomes insufficient.

The haze of the biaxially stretched laminated polypropylene film of the present invention is preferably 0.1 to 6%, more preferably 0.2 to 5%, further preferably 0.3 to 4.5%, particularly preferably 0.4 to 4%, most preferably 0.4 to 3.5%. When the amount is within the above range, the composition is easily used in applications where transparency is required. For example, when the stretching temperature or the heat-set temperature is too high, when the Cooling Roll (CR) temperature is high and the cooling rate of the stretched web sheet is low, or when the low-molecular-weight component is too high, the haze tends to be poor, and these can be adjusted to fall within the above range.

The lower limit of the plane orientation coefficient of the biaxially stretched laminated polypropylene film of the present invention is preferably 0.013, more preferably 0.014, and still more preferably 0.015. If the amount is less than the above range, the film will have low heat resistance and rigidity, and poor processability, resulting in poor appearance, and the effects of the present invention will not be sufficiently obtained.

Stretched laminated polypropylene films generally have crystal orientation, and the direction and degree of this crystal orientation have a large influence on the film properties. The degree of crystal orientation tends to vary depending on the molecular structure of the polypropylene used, the process and conditions in the production of the film, and can be adjusted to fall within the above-mentioned range.

The biaxially stretched laminated polypropylene film of the present invention has a tensile elastic modulus in the MD direction of preferably 2.0 to 4GPa, more preferably 2.1 to 3.7GPa, still more preferably 2.2 to 3.5GPa, particularly preferably 2.3 to 3.4GPa, and most preferably 2.4 to 3.3 GPa. The tensile modulus in the TD direction is preferably 3.8 to 8GPa, more preferably 4 to 7.5GPa, still more preferably 4.1 to 7GPa, and particularly preferably 4.2 to 6.5 GPa.

The dynamic friction coefficient of the biaxially stretched laminated polypropylene film of the present invention is preferably 0.2 to 0.4, more preferably 0.22 to 0.38, and still more preferably 0.24 to 0.36. This improves the processability of the film.

The biaxially stretched laminated polypropylene film of the present invention can be used as a base film (base layer) for use in sealant films, insulating films for capacitors, motors, and the like, back sheets for solar cells, barrier films for inorganic oxides, transparent conductive films for ITO, and the like. The lamination strength of the laminated film laminated with the film in the MD direction is preferably 1.2 to 2.5N/15mm, more preferably 1.3 to 2.3N/mm, and still more preferably 1.4 to 2.1N/mm. The method of measuring the lamination strength is as follows.

The present application claims benefit based on priority from Japanese patent application No. 2016-. The specification of the Japanese patent application No. 2016-.

Examples

The present invention will be described in more detail below with reference to examples, but the following examples are not intended to limit the present invention and modifications are possible without departing from the scope of the present invention. The physical properties of the films obtained in examples and comparative examples were measured as follows.

1) Tacticity

Meso pentad fraction ([ mmmm [)]% measurement of the chemical composition¹³C-NMR was conducted. The meso pentad fraction was calculated by the method described in "Zambelli et al, Macromolecules, vol.6, p.925 (1973)".¹³The C-NMR measurement was carried out as follows: 200mg of a sample was dissolved in o-dichlorobenzene and deuterated benzene at 135 ℃ by using "AVANCE 500" manufactured by BRUKER corporation: 2 (volume ratio) at 110 ℃.

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

Measured at a temperature of 230 ℃ and a load of 2.16kgf in accordance with JIS K7210.

The resin was used by directly weighing a desired amount of pellets (powder).

After cutting a desired amount of the film, the film was cut into about 5mm squares and used as a sample.

3) Molecular weight and molecular weight distribution

Molecular weight and molecular weight distribution were as follows: the molecular weight was determined by Gel Permeation Chromatography (GPC) based on monodisperse polystyrene. Measurement conditions using a column, a solvent, and the like in the GPC measurement are as follows.

Solvent: 1,2, 4-trichlorobenzene

Column: TSKgel GMH_HR-H(20)HT×3

Flow rate: 1.0 ml/min

A detector: RI (Ri)

Measuring temperature: 140 deg.C

The number average molecular weight (Mn), mass average molecular weight (Mw), and molecular weight distribution were as follows: the molecular weight (Mi) at each elution position in the GPC curve obtained from the molecular weight calibration curve is defined by the following formula.

Number average molecular weight: mn ∑ (Ni · Mi)/Σ Ni

Mass average molecular weight: mw ═ Σ (Ni · Mi)²)/Σ(Ni·Mi)

Molecular weight distribution: Mw/Mn

When the base line is not clear, the base line is set in a range from the lowest position of the substrate on the high molecular weight side of the elution peak closest to the high molecular weight side of the elution peak of the standard substance.

4) Differential Scanning Calorimetry (DSC)

The heat measurement was carried out by a differential scanning calorimeter ("DSC-60" manufactured by Shimadzu corporation). About 5mg of the raw material of the sample film was sealed in an aluminum pan for measurement. The temperature of the material for layer A and the material for layer B was raised from room temperature to 230 ℃ at a rate of 20 ℃ per minute, and the temperature was maintained for 5 minutes. Thereafter, the temperature was decreased at a rate of 20 ℃ per minute to room temperature, and the temperature was increased again at a rate of 20 ℃ per minute from room temperature to 230 ℃ to measure the melting endothermic peak temperature (. degree. C.) and the melting endothermic peak area (. DELTA.H (J/g) and the total heat of fusion of the sample at that time. Here, the baseline is set so that the curves are smoothly connected at the temperature before and after melting from the start of the endothermic peak to the end of the peak.

5) Thickness of

The thickness of each of the a and B layers was determined as follows: the cross section of the biaxially stretched laminated polypropylene film fixed with the modified polyurethane resin was cut with a microtome and observed with a differential interference microscope to measure the thickness.

6) Thermal shrinkage at 150 ℃ (%)

The measurement was carried out according to JIS Z1712 by the following method. The film was cut into a width of 20mm and a length of 200mm in each of the MD direction and TD direction, and was suspended in a hot air oven at 150 ℃ and heated for 5 minutes. The heated length was measured, and the heat shrinkage ratio was determined as the ratio of the shrunk length to the original length.

7) Tensile elastic modulus (Young's modulus (unit: GPa))

Young's moduli in the MD direction and TD direction of the film were measured at 23 ℃ in accordance with JIS K7127. For measuring Young's modulus, a film was cut into test pieces having a width of 15mm and a length of 200mm in the MD direction and TD direction, respectively.

8) Surface resistivity value (Log omega)

The film was aged at 23 ℃ for 24 hours in accordance with JIS K6911, and then the corona-treated surface of the film was measured.

9) Haze (unit: %)

Measured according to JIS K7105.

10) Coefficient of dynamic friction

The surfaces of the films subjected to the corona treatment were superposed on each other in accordance with JIS K7125, and the measurement was carried out at 23 ℃.

11) Film Density (g/cm)³)

The density of the film was measured by a density gradient tube method in accordance with JIS K7112.

12) Refractive index and surface orientation factor

Measured by JIS K7142-19965.1 (method A) using an Abbe refractometer manufactured by Atago. The refractive indices in the MD and TD directions are Nx and Ny, respectively, and the refractive index in the thickness direction is Nz. The plane orientation factor (. DELTA.P) was determined as (Nx + Ny)/2-Nz.

13) Appearance of the surface

The appearance of the surface was as follows: in the evaluation target area (width 1000mm, length 4000mm), light was applied from one side of the film surfaceAnd transmitting, and observing a portion shielded from light due to a defect of the thin film in the form of a black spot with a camera on the opposite side. The measuring area exceeds 25mm²In the case of the total number of defects of (4), the total number of defects is evaluated to be good at less than 200 and evaluated to be "x" at 200 or more.

14) Lamination strength in MD

The lamination strength was measured by the following procedure.

(a) Lamination with sealant films

The use of a continuous dry laminator was performed as follows.

The adhesive was applied at a dry weight of 3.0g/m²The biaxially stretched laminated polypropylene films obtained in examples and comparative examples were gravure-coated on the corona surface thereof, and then introduced into a drying zone and dried at 80 ℃ for 5 seconds. Subsequently, the sealant film was adhered to the downstream roll (roll pressure 0.2MP, roll temperature 60 ℃ C.). The obtained laminate film was subjected to aging treatment at 40 ℃ for 3 days in a wound state.

The adhesive used was an ether adhesive obtained by mixing 17.9 mass% of a base (TM 329 available from Toyo Morton ltd.), 17.9 mass% of a curing agent (TM 8B available from Toyo Morton ltd.), and 64.2 mass% of ethyl acetate, and the sealant film used was a non-stretched polypropylene film (Pylenct (registered trademark) CT P1128, thickness 30 μm) available from toyobo co.

(b) Measurement of lamination Strength

The laminate film obtained above was cut into a strip shape having a long side (length 200mm, width 15mm) in the MD direction, and peeled between the laminate film and the sealant film with tweezers, and T-peeled at a tensile speed of 200 mm/min under an environment of 23 ℃ using a tensile tester (Tensilon, Orientec co., ltd.), and the peel strength (N/15mm) at that time was measured. The measurement was performed 3 times, and the average value was defined as the lamination strength.

(example 1)

The polypropylene homopolymer PP-1 shown in Table 1 was used for the layer A, and the polypropylene homopolymer PP-2 shown in Table 1 was used for the layer B. In addition, 0.5 mass% of stearic acid diethanolamine as an antistatic agent was blended in the layer a raw material. In addition, 0.15 mass% of silica as an antiblocking agent was blended in the layer B. The layer A was extruded from a T die into a sheet form at 250 ℃ using a 60mm extruder and the layer B was extruded from a 65mm extruder, cooled and solidified on a 30 ℃ cooling roll, and then stretched 4.5 times in the MD direction at 135 ℃. Subsequently, both ends in the film width direction were held by clips in a tenter, preheated at 175 ℃, and then stretched 8.2 times in the film width direction at 160 ℃, and heat-set at 170 ℃ while 6.7% relaxation was performed. A biaxially stretched laminated polypropylene film in which the layer a and the layer B were laminated in each 1 layer was obtained. The B-side of the laminated polypropylene film was subjected to corona treatment and wound up by a winder. The thickness of the resulting film was 20 μm. The structure of polypropylene constituting the film is shown in table 1, and the film forming conditions are shown in table 2. The physical properties of the obtained film are shown in Table 3.

(examples 2 to 10, comparative examples 1 to 3)

A biaxially stretched laminated polypropylene film was obtained in the same manner as in example 1 except that the polypropylene shown in tables 1 and 3 was used and the production conditions shown in tables 2 and 3 were used. Examples 9 and 10 are 2-3-layer films using a feedblock comprising a core layer of layer a and skin layers of layer B. Comparative example 3 is an example in which the B layer is not laminated. The film properties are shown in Table 3.

[ Table 1]

[ Table 2]

Film forming conditions	a	b
			Resin temperature (. degree.C.)	250	250
Chill roll temperature (. degree. C.)	30	30
			MD stretch ratio (times)	4.5	4.5
MD stretching temperature (. degree. C.)	135	125
			TD stretch ratio (multiple)	8.2	8.2
TD Pre-heating temperature (. degree. C.)	175	170
			TD stretching temperature (. degree. C.)	160	155
Heat set temperature (. degree. C.)	170	163
			Relaxation Rate (%)	6.7	6.7

[ Table 3A ]

[ Table 3B ]

The biaxially stretched laminated polypropylene films obtained in examples 1 to 10 were low in heat shrinkage and high in Young's modulus (rigidity). Further, the sheet has a small surface resistivity, excellent antistatic properties, a small coefficient of dynamic friction, excellent bag-making processability, and a high lamination strength.

In contrast, the film of comparative example 1 was produced using the a layer having a Δ H smaller than that of the B layer as the core layer and having a heat-set temperature lower than a preferable temperature, and therefore the young's modulus was decreased.

The film of comparative example 2 has a large surface resistivity and a large coefficient of dynamic friction because a B layer having a Δ H larger than that of the a layer is used as the outermost layer (skin layer).

The film of comparative example 3 is an example of a single-layer film having only the a layer, and the surface resistivity and the coefficient of dynamic friction become large, and the lamination strength also becomes low.

The film of comparative example 4 was the same as the layer a in Δ H, that is, the difference in Δ H was 0. Therefore, the surface resistivity becomes large.

Industrial applicability

The biaxially stretched laminated polypropylene film of the present invention is excellent not only in heat resistance but also in antistatic properties. Further, since the rigidity is high, when the film is used as a packaging film, the film can be thinned, and cost reduction and weight reduction can be achieved. Further, since high-temperature treatment can be performed during coating and printing, not only production efficiency can be improved, but also a coating agent, ink, a laminating adhesive, and the like, which have been difficult to use in the past, can be used. The biaxially stretched laminated polypropylene film of the present invention can also be used for insulating films for capacitors, motors and the like, back sheets for solar cells, barrier films for inorganic oxides, base films for transparent conductive films such as ITO and the like, and the like.

Claims

the biaxially stretched laminated polypropylene film has:

a layer A formed from a polypropylene resin composition having a Δ H of 78.0J/g or more and 100.0J/g or less; and the combination of (a) and (b),

a layer B comprising a polypropylene resin composition having a Δ H of less than 82.0J/g and a Δ H of 2.0 to 40.0J/g lower than the Δ H of the layer A, and

the B layer is present on at least one of the outermost surfaces,

wherein Δ H represents a melting endothermic peak area measured at a temperature increase rate of 20 ℃/min using a differential scanning calorimeter,

the melting endotherm peak areas were determined as follows: 5mg of the raw material of the sample thin film was sealed in an aluminum pan for measurement, and the raw material for layer A and the raw material for layer B were heated from room temperature to 230 ℃ at a rate of 20 ℃/min, respectively, and held for 5 minutes, and then cooled to room temperature at a rate of 20 ℃/min, and then heated from room temperature to 230 ℃ at a rate of 20 ℃/min, and the melting endothermic peak area of the sample at that time was measured by a differential scanning calorimeter.

2. The biaxially stretched laminated polypropylene film according to claim 1, wherein the ratio of the total thickness of said B layer to the total thickness of said A layer (total B layer/total A layer) is 0.01 to 0.5, and the total thickness of said B layer is 0.5 to 4 μm.

3. The biaxially stretched laminated polypropylene film according to claim 1 or 2, further comprising, on the outermost surface side of said B layer: a further layer having a thickness of 0.01 to 1.0 μm and formed of a polypropylene resin composition having a Δ H of more than 76.0J/g.

4. The biaxially stretched laminated polypropylene film according to claim 1 or 2, wherein the Melt Flow Rate (MFR) of the whole film is 2.0 to 10.5g/10 min.

5. The biaxially stretched laminated polypropylene film according to claim 1 or 2, wherein the surface resistivity value (Log Ω) of the whole film is 13.5 or less.

6. The biaxially stretched laminated polypropylene film according to claim 1 or 2, wherein the dynamic friction coefficient of the whole film is 0.4 or less.

7. The biaxially stretched laminated polypropylene film according to claim 1 or 2, wherein the heat shrinkage at 150 ℃ is 10.0% or less in both the MD direction and the TD direction, and wherein the tensile elastic modulus in the MD direction is 2.0GPa or more and the tensile elastic modulus in the TD direction is 3.8GPa or more.

8. The biaxially stretched laminated polypropylene film according to claim 1 or 2, wherein the lamination strength in the MD direction after lamination is 1.2N/15mm or more.