TWI588185B - Biaxially oriented polypropylene film - Google Patents

Description

Biaxially stretched polypropylene film

This invention relates to an extended polypropylene film. More specifically, it relates to a biaxially stretched polypropylene film which is excellent in heat resistance and mechanical properties which can be suitably used in various fields requiring dimensional stability or high rigidity at high temperatures.

Conventionally, a stretch film of polypropylene has been generally used for a wide range of applications such as packaging for foods and various products, electrical insulation, and surface protection films. However, since the shrinkage ratio of the conventional polypropylene film at 150 ° C is several tens of %, the heat resistance is lower than that of PET, and the rigidity thereof is also low, and the use is limited.

In order to solve such problems, a technique is known in which a polypropylene film having a high stereoregularity and a narrow molecular weight distribution is used as a stretched film to form a film having high temperature rigidity and heat resistance (see, for example, Patent Document 1). ).

Further, a technique is known in which a polypropylene film having a high stereoregularity and a wide molecular weight distribution is used as an extension film, so that it can be suitably used as a capacitor film excellent in electrical insulation properties, mechanical properties, and the like (see, for example, a patent) Literature 2, etc.).

Still further, a technique is known which uses a low molecular weight and a soluble component amount of 0 ° C by a temperature rising method in a specific range. Polypropylene is used as a spacer film, and this film is considered to have excellent dimensional stability even in the drying step and the printing step (see, for example, Patent Document 3).

However, the films described in Patent Documents 1 to 3 are problematic in terms of elongation, and the mechanical properties such as impact resistance are also poor.

A technique is known in which a small amount of long-chain branches or cross-linked polypropylene is used to promote the formation of a lamella to improve the elongation, and to provide excellent mechanical properties, heat resistance, and withstand voltage characteristics. Further, a film having excellent uniformity of physical properties (see, for example, Patent Document 4).

Further, a technique is known in which a film is formed by using polypropylene having a substantially equal amount of a high molecular weight component and a low molecular weight component (having a low molecular weight component), a broad molecular weight distribution, and a small amount of decahydronaphthalene soluble component. A balance between rigidity and workability is obtained (see, for example, Patent Document 5).

The film described in the above-mentioned Patent Documents 4 to 5 is not sufficiently high in heat resistance at a high temperature, and a polypropylene film having high heat resistance, excellent impact resistance, and transparency is not known. That is, these still cannot escape the conventional polypropylene film field, and their use is limited, and the heat resistance at a high temperature of, for example, more than 150 ° C is not considered.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. Hei 8-325327

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2004-175932

[Patent Document 3] Japanese Laid-Open Patent Publication No. 2001-146536

[Patent Document 4] Japanese Laid-Open Patent Publication No. 2007-84813

[Patent Document 5] Japanese Patent Publication No. 2008-540815

The present invention has been completed in the light of the problems of the prior art. That is, it is an object of the present invention to provide an extended polypropylene film which has a low shrinkage ratio at a temperature of 150 ° C and a high rigidity.

The present inventors have completed the present invention as a result of intensive investigation to achieve the object. That is, the present invention is a biaxially stretched polypropylene film characterized in that the α2 type crystal amount measured by solid state NMR is 23% or more of all crystals, and the density is 0.910 g/cm ³ or more, and differential scanning calorimetry is used. The melting point measured by DSC was 168 ° C or higher, the heat shrinkage at 150 ° C was 15% or less, and the haze was 6% or less.

In this case, it is preferred that the lower limit of the mesogenic pentad sequence fraction of the polypropylene resin constituting the film is 96% and the lower limit of the face alignment coefficient of the film is 0.0125.

Further, in this case, the upper limit of the amount of the copolymerized monomer of the polypropylene resin constituting the film is preferably 0.1 mol%.

Further, in this case, it is preferred that the polypropylene resin constituting the film has a xylene soluble component of 7% by mass or less.

According to the present invention, the heat resistance and dimensional stability of the stretched polypropylene film are excellent, so that shrinkage due to heat sealing can be suppressed. The resulting deformation can also suppress misregister and deformation during printing, and the efficiency of printing processing is remarkably improved.

Further, the polypropylene film of the present invention can maintain various physical properties even when exposed to an environment of 150 ° C or higher, and can be used even in a high-temperature environment which cannot be imagined by a conventional polypropylene film.

Fig. 1 is an example of a solid state NMR spectrum of a polypropylene film described in Example 1.

[Formation of the Invention]

The present invention relates to an extended polypropylene film excellent in dimensional stability and mechanical properties at high temperatures. The extended polypropylene film of the present invention is a biaxially stretched polypropylene film characterized in that the α2 type crystal amount measured by solid state NMR is 23% or more of all crystals, and the density is 0.910 g/cm ³ or more, and differential scanning is performed. The melting point measured by a calorimeter (DSC) was 168 ° C or higher, the heat shrinkage ratio at 150 ° C was 15% or less, and the haze was 6% or less.

(polycrystalline crystal of polypropylene)

It is known that polypropylene has several crystal polymorphs, but usually α-form crystals are preferentially formed. Among the α-type crystals, α1 type and α2 type are known, but compared with α1 type crystal, the crystal of the α2 type crystal molecular chain having a uniform orientation and high order is considered to have high stability (Reference: M. Hikosaka & T. Seto, Polymer Journal, 111 (5), 1973). Therefore, it is expected that various physical properties can be enhanced by containing a large amount of α2-type crystals. The amount of α2 type crystal can be quantified by wide-angle X-ray diffraction or solid-state NMR, but because it is as thin It is difficult to quantify a sample by a wide-angle X-ray diffraction method, and it is preferable to use a solid state NMR method. The method for using solid state NMR is described in T. Miyoshi et. al., J. Phys. Chem. B, 114, 92-100 (2010).

On the other hand, the α1 type crystal is different from the range in which the α2 type crystal system is formed, and the crystallization temperature α1 type of 130° C. or less is mainly used, and when it exceeds 150° C., the α 2 type system is mainly generated. However, the higher the temperature, the lower the crystallization rate, and at a crystallization temperature of, for example, more than 140 ° C, it is considered that it is difficult to industrially produce a product having a large amount of α 2 type crystals because of the long time required for curing.

Therefore, it is necessary to increase the crystallization rate of the polypropylene at a high temperature, but for this reason, it is preferred to use a propylene homopolymer having improved stereoregularity. However, in particular, in the use of a stretched polypropylene film, in order to reduce the degree of crystallization of a raw material before stretching, from the viewpoint of productivity improvement or physical properties, etc., a comonomer such as ethylene may be carried out. Co-aggregation, or the reduction of stereoregularity. Therefore, the melting point becomes low, and elongation or heat fixation at a high temperature at which a large amount of α2 type crystals can be obtained becomes difficult.

As a result of intensive review by the present inventors, it has been found that by using a polypropylene homopolymer having a wide molecular weight distribution and stretching or heat-fixing at a high temperature, a film containing a large amount of α2 type crystal can be produced, and the present invention can be completed.

(crystal structure of the film)

The lower limit of the amount of the α2 type crystal contained in the film is 23% of the total amount of crystallization, preferably 25%, more preferably 26%, still more preferably 27%. If the α2 type crystal is less than 23%, the heat resistance will be insufficient. Α2 type knot contained in the film The upper limit of the amount of crystals is preferably 90% of the total amount of crystallization, more preferably 85%, still more preferably 70% or less. In order to increase the amount of the α2 type crystal by more than 90%, it is necessary that the crystallization time becomes remarkably long and the productivity is deteriorated. The amount of crystallization of the α2 type can be increased by increasing the extension temperature or the heat setting temperature or performing off-line annealing.

(film properties)

The lower limit of the density of the polypropylene film of the present invention is 0.910 g/cm ³ , more preferably 0.911 g/cm ³ , still more preferably 0.912 g/cm ³ , and particularly preferably 0.913 g/cm ³ . If it is the above range, the crystallinity will become high and the heat shrinkage rate will become small.

The upper limit of the film density is preferably 0.925 g/cm ³ , more preferably 0.922 g/cm ³ , still more preferably 0.920 g/cm ³ , and particularly preferably 0.918 g/cm ³ . If it is the above range, the actual manufacturing will become easy. The film density can be increased by increasing the stretching ratio or temperature, increasing the heat setting temperature, or even performing off-line annealing.

The melting point (melting peak temperature) of the film can be obtained by using a differential scanning calorimeter (DSC) to obtain a melting endothermic curve obtained by raising the temperature from room temperature to 230 ° C at a rate of 20 ° C/min. Got it. The lower limit of the melting point is 168 ° C, preferably 169 ° C, more preferably 170 ° C. If it is the above range, the heat shrinkage rate at a high temperature becomes small. The upper limit of the melting point is preferably 180 ° C, more preferably 178 ° C, still more preferably 177 ° C. If it is the above range, the actual manufacturing will become easy. The melting point can be set within the above range by reducing the amount of the copolymerizable monomer or not, or by setting the elongation temperature and the heat setting temperature to a high temperature.

The MD direction and the TD direction of the polypropylene film of the present invention The lower limit of the heat shrinkage ratio at 150 ° C is preferably 0.5%, more preferably 1%, still more preferably 1.5%, particularly preferably 2%, most preferably 2.5%. If it is in the above range, manufacturing in the real world such as a cost surface becomes easy, or thickness unevenness becomes small. The upper limit of the heat shrinkage ratio at 150 ° C in the MD direction and the TD direction is 15%, more preferably 13%, still more preferably 12%, particularly preferably 11%, and most preferably 10%. If it is in the above range, it will be easier to use in applications where it is likely to be exposed to a high temperature of about 150 °C. In addition, if the heat shrinkage ratio at 150 ° C is about 2.5%, the amount of the low molecular weight component can be increased, and the stretching conditions and the fixing conditions can be changed. However, it is preferable to perform the annealing treatment offline.

The haze of the stretched film of the present invention is preferably 0.1%, more preferably 0.2%, still more preferably 0.3%, particularly preferably 0.4%, most preferably 0.5%, in terms of practical values. The upper limit of the haze is 6%, more preferably 5%, still more preferably 4.5%, particularly preferably 4%, and most preferably 3.5%. If it is in the above range, it will become easy to use in applications requiring transparency. When the temperature is too high and the heat setting temperature is too high, the temperature of the cooling roll is high and the cooling rate is slow. The case where the low molecular weight component is excessive tends to be deteriorated, and it can be set to the above range by adjusting the temperature. Inside.

The lower limit of the surface alignment coefficient of the polypropylene film of the present invention is preferably 0.0125, more preferably 0.0126, still more preferably 0.0127, and particularly preferably 0.0128. The upper limit of the surface alignment coefficient is preferably 0.0155, more preferably 0.0150, still more preferably 0.0148, and particularly preferably 0.0145. The surface alignment coefficient can be set within the range by the adjustment of the stretching ratio. As long as it is within this range, the thickness unevenness of the film is at least good.

MD refractive index of the polypropylene film of the present invention The lower limit of (Nx) is preferably 1.502, more preferably 1.503, still more preferably 1.504. The upper limit of Nx is preferably 1.520, more preferably 1.517, still more preferably 1.515.

The lower limit of the refractive index (Ny) in the TD direction is preferably 1.523, more preferably 1.525. The upper limit of Ny is preferably 1.535, more preferably 1.532.

The lower limit of the refractive index (Nz) in the thickness direction is preferably 1.480, more preferably 1.489, still more preferably 1.500. The upper limit of Nz is preferably 1.510, more preferably 1.507, still more preferably 1.505.

The lower limit of the impact resistance (room temperature, 23 ° C) of the stretched film of the present invention is preferably 0.5 J, more preferably 0.6 J. If it is the above range, it will have sufficient toughness as a film, and it will not fracture at the time of use. The upper limit of the impact resistance is preferably 2 J from the actual surface, more preferably 1.8 J, still more preferably 1.6 J, and particularly preferably 1.5 J. When the impact resistance is large in the case where the amount of the low molecular weight component is large, the molecular weight in the whole is low, the high molecular weight component is small, or the molecular weight of the high molecular weight component is low, the impact resistance tends to be lowered, and the impact resistance may be matched. Use to adjust these components to be within the range.

When the stretched film is a biaxially stretched film, the lower limit of the Young's ratio (23 ° C) in the MD direction is preferably 2 GPa, more preferably 2.1 GPa, still more preferably 2.2 GPa, particularly preferably 2.3 GPa, and most preferably 2.4 GPa. . The upper limit of the Young's rate in the MD direction is preferably 4 GPa, more preferably 3.7 GPa, still more preferably 3.5 GPa, particularly preferably 3.4 GPa, and most preferably 3.3 GPa. If it is the above range, it is easy to manufacture in reality, or the balance of MD-TD is favorable.

When the stretched film is a biaxially stretched film, the lower limit of the Young's ratio (23 ° C) in the TD direction is preferably 3.8 GPa, more preferably 4 GPa, and further The best is 4.2GPa, and the best is 4.3GPa. The upper limit of the Young's rate in the TD direction is preferably 8 GPa, more preferably 7.5 GPa, still more preferably 7 GPa, and particularly preferably 6.5 GPa. If it is the above range, it is easy to manufacture in reality, or the balance of MD-TD is favorable.

In addition, the Young's rate can be increased by increasing the stretching ratio. In the case of MD-TD extension, the Young's rate in the TD direction can be increased by setting the MD stretching ratio to be lower and increasing the TD stretching ratio. Big.

The lower limit of the thickness uniformity of the stretched 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%, most preferably 10%. If it is in the above range, it is less likely to cause defects during processing after coating, printing, etc., and it is easy to use for applications requiring precision.

(polypropylene resin)

The polypropylene resin constituting the film may be a copolymer of a propylene individual polymer or a copolymerized monomer in a range in which crystallization does not inhibit the formation of an α2-type crystal at a high temperature. The copolymerizable monomer source can be ethylene, butene, hexene, octene or the like.

The polypropylene resin constituting the film of the present invention has a special broad molecular weight distribution. Examples of the parameter indicating the molecular weight of the polymer include a number average molecular weight (M _n ), a mass average molecular weight (M _w ), a Z average molecular weight (M _z ), and a Z+1 average molecular weight (M _z+1 ). The peak molecular weight (M _p ) or the like is defined by the number of molecules (N _i ) of the molecular weight (M _i ) as follows.

Number average molecular weight: M _n = Σ(N _i ‧M _i )/ΣN _i

Mass average molecular weight: M _w = Σ (N _i ‧ M _i ² ) / Σ (N _i ‧ M _i )

Z average molecular weight: M _z = Σ (N _i ‧ M _i ³ ) / Σ (N _i ‧ M _i ² )

Z+1 average molecular weight: M _z+1 = Σ (N _i ‧ M _i ⁴ ) / Σ (N _i ‧ M _i ³ )

Peak molecular weight: M _p (molecular weight at the peak position of the GPC curve)

Further, as the parameter indicating the molecular weight distribution, the ratio of these average molecular weights is generally used, and examples thereof include M _w /M _n , M _z /M _w , M _z /M _n and the like. For the measurement method of such molecular weight or molecular weight distribution, gel permeation chromatography (GPC) is generally used.

The polypropylene resin used in the present invention preferably contains, for example, a low molecular weight component, and further contains a high molecular weight component having a very high molecular weight. It is considered that by using a low molecular weight component as a main component, not only the crystallinity can be greatly improved, but also an α2 type crystal amount can be obtained, and an extended polypropylene film having an unprecedented high rigidity and high heat resistance can be obtained. On the other hand, the low molecular weight polypropylene resin has a low melt tension in the case of heat softening, and it is generally difficult to form a stretched film. It is considered that the high molecular weight component is present in a number of % to tens of %, and particularly in the high temperature conditions favorable for the formation of the α 2 type crystal, the function of easily extending and allowing the high molecular weight component to realize the crystal nucleus is increased. The crystallization speed at a high temperature achieves the efficacy of the stretched film of the present invention.

So it is an indicator of molecular weight distribution, the use-based attention as M _{z + 1-average} molecular weight of the high molecular weight component, M _z is preferably obtained with M _n ratio of _{+ 1} / M _n. The lower limit of M _z+1 /M _n is preferably 50, more preferably 60, still more preferably 70, particularly preferably 80, most preferably 90. If it is less than the above, it becomes difficult to obtain the effect of the present invention such as a low heat shrinkage rate at a high temperature. The upper limit of M _z+1 /M _n is preferably 300, more preferably 200. If it is larger than the above, the production of the resin becomes difficult in reality.

The lower limit of M _z+1 of the entire polypropylene resin constituting the film is preferably 2,500,000, more preferably 3,000,000, still more preferably 3,300,000, particularly preferably 3,500,000, and most preferably 3,300,000. When M _z+1 is 2,500,000 or more, the high molecular weight component is sufficient, and the effect of the present invention can be easily obtained. The upper limit of the overall M _z+1 is preferably 40000000, more preferably 35000000, still more preferably 30000000. When M _z+1 is 40,000,000 or less, in actuality, the production of the resin is easy, or the elongation is easy, or the fish eyes in the film are reduced.

The lower limit of the preferred configuration of the entire polypropylene resin film of M _n 20,000, more preferably 22,000, further more preferably 24,000, particularly preferably 26,000, most preferably 27,000. When the M _n of the above-described range will be generated extending facilitated, the thickness unevenness becomes smaller, easy to make the stretching temperature or the heat setting temperature rise rate of the thermal shrinkage becomes low. The upper limit of all of M _n is preferably from 65,000, more preferably 60,000, further more preferably 55,000, particularly preferably 53,000, most preferably 52,000. Efficacy low thermal shrinkage rate under the above-described range if M _n of efficacy would easily obtain high-temperature low molecular weight component of the present invention, or can be easily extended.

The lower limit of the M _w of the entire polypropylene resin constituting the film is preferably 250,000, more preferably 260,000, still more preferably 270,000, particularly preferably 280,000, and most preferably 290,000. When it is in the above range, the elongation becomes easy, the thickness unevenness is small, and the elongation temperature or the heat setting temperature is likely to increase, and the heat shrinkage rate is lowered. The upper limit of the overall M _w is preferably 500000, more preferably 450,000, still more preferably 400,000, particularly preferably 380,000, and most preferably 370,000. If it is the above range, the mechanical load is small and it is easy to extend.

The lower limit of the melt flow rate (MFR) (230 ° C, 2.16 kgf) of the entire polypropylene resin constituting the film is preferably 1 g/10 min, more preferably 1.2 g/10 min, still more preferably 1.4 g/10 min. It is particularly preferably 1.5 g/10 min, and most preferably 1.6 g/10 min. If it is the above range, the mechanical load is small and it is easy to extend. The upper limit of the overall MFR is preferably 11 g/10 min, more preferably 10 g/10 min, still more preferably 9 g/10 min, particularly preferably 8.5 g/10 min, and most preferably 8 g/10 min. When it is in the above range, the elongation becomes easy, the thickness unevenness becomes small, and the elongation temperature or the heat fixation temperature is likely to rise and the heat shrinkage rate is changed to be low.

In the case of measuring the GPC integrated curve of the entire polypropylene resin constituting the film, the lower limit of the amount of the component having a molecular weight of 10,000 or less is preferably 2% by mass, more preferably 2.5% by mass, still more preferably 3% by mass, particularly preferably It is 3.3% by mass, and most preferably 3.5% by mass. If it is in the above range, the effect of the present invention, such as a low heat shrinkage rate at a high temperature, which is effective as a low molecular weight component, becomes easy to obtain, or the elongation becomes easy. The upper limit of the amount of the component having a molecular weight of 10,000 or less in the GPC integrated curve is preferably 20% by mass, more preferably 17% by mass, still more preferably 15% by mass, particularly preferably 14% by mass, most preferably 13% by mass. . If it is in the above range, the elongation becomes easy, the thickness unevenness becomes small, and the elongation temperature or the heat fixation temperature is likely to increase and the heat shrinkage rate is lowered.

A molecule having a molecular weight of about 10,000 or less does not contribute to the entanglement of the molecular chains, and has the effect of disintegrating the molecules with each other like a plasticizer. It is considered that the amount of the component having a molecular weight of 10,000 or less is contained in a specific amount, so that the entanglement of the molecule during stretching is easily released, and the elongation under low elongation stress becomes possible, and as a result, the residual stress is also Low and low shrinkage at high temperatures.

The lower limit of the amount of the component having a molecular weight of 100,000 or less in the GPC integrated curve is preferably 35 mass%, more preferably 38 mass%, still more preferably 40 mass%, particularly preferably 41 mass%, and most preferably 42 mass%. . If it is in the above range, the effect of the present invention, such as a low heat shrinkage rate at a high temperature, which is effective for a low molecular weight component, becomes easy to obtain, or the elongation becomes easy. The upper limit of the amount of the component having a molecular weight of 100,000 or less in the GPC integrated curve is preferably 65 mass%, more preferably 60 mass%, still more preferably 58 mass%, particularly preferably 56 mass%, and most preferably 55 mass%. . If it is in the above range, the elongation becomes easy, the thickness unevenness becomes small, and the elongation temperature or the heat fixation temperature is likely to increase and the heat shrinkage rate is lowered.

The high molecular weight component and the low molecular weight component which are preferably used in order to obtain a polypropylene resin having such a molecular weight distribution are described below.

(high molecular weight component)

The lower limit of the MFR (230 ° C, 2.16 kgf) of the high molecular weight component is preferably 0.0001 g/10 min, more preferably 0.0005 g/10 min, still more preferably 0.001 g/10 min, particularly preferably 0.005 g/10 min. . If it is the above range, the production of the resin in reality is easy, or the fisheye of the film can be reduced. Further, the MFR at 230 ° C and 2.16 kgf of the high molecular weight component may be too small, and it is difficult to measure it in reality. If expressed by MFR at a load of 10 times (21.6 kgf), a preferred lower limit is 0.1 g/10 min, more preferably 0.5 g/10 min, still more preferably 1 g/10 min, and particularly preferably 5 g. /10 minutes.

The upper limit of the MFR of the high molecular weight component is preferably 0.5 g/10 min. The clock is more preferably 0.35 g/10 min, still more preferably 0.3 g/10 min, particularly preferably 0.2 g/10 min, and most preferably 0.1 g/10 min. In the above range, in order to maintain the entire MFR, the amount of the high molecular weight component is not required, and the effect of the present invention such as the low heat shrinkage rate at a high temperature of the effect of the low molecular weight component becomes more readily available.

The lower limit of the M _w of the high molecular weight component is preferably 500,000, more preferably 600,000, still more preferably 700,000, particularly preferably 800,000, most preferably 1,000,000. In the above range, in order to maintain the entire MFR, a large amount of a high molecular weight component is not required, and the effect of the present invention, such as a low heat shrinkage rate at a high temperature, which is effective as a low molecular weight component, becomes more easily obtained.

The upper limit of the M _w of the high molecular weight component is preferably 10,000,000, more preferably 8,000,000, still more preferably 6,000,000, and particularly preferably 5,000,000. If it is the above range, the production of the resin in reality is easy, or the fisheye of the film can be reduced.

The lower limit of the amount of the high molecular weight component is preferably 2% by mass, more preferably 3% by mass, still more preferably 4% by mass, and particularly preferably 5% by mass. In the above range, it is not necessary to increase the molecular weight of the low molecular weight component in order to maintain the entire MFR, and the effect of the present invention such as a low heat shrinkage rate at a high temperature is more easily obtained.

The upper limit of the amount of the high molecular weight component is preferably 30% by mass, more preferably 25% by mass, still more preferably 22% by mass, and particularly preferably 20% by mass. If it is the above range, the effect of the present invention becomes easier to obtain, such as a low heat shrinkage rate at a high temperature, which is an effect of a low molecular weight component.

Here, the high molecular weight component can also be used with a long chain branch or cross A polypropylene resin having a joint structure is used in place of a linear polypropylene resin, and is widely known as a high melt tension polypropylene, and examples thereof include Daploy WB130HMS and WB135HMS manufactured by Borealis.

(low molecular weight component)

The lower limit of the MFR (230 ° C, 2.16 kgf) of the low molecular weight component is preferably 70 g/10 min, more preferably 80 g/10 min, still more preferably 100 g/10 min, particularly preferably 150 g/10 min, most preferably 200g/10 minutes. If it is the above range, the crystallinity becomes good, and at the high temperature, the heat shrinkage rate and the like, the effect of the present invention becomes more readily available.

The upper limit of the MFR of the low molecular weight component is preferably 2,000 g/10 min, more preferably 1800 g/10 min, still more preferably 1600 g/10 min, particularly preferably 1500 g/10 min, most preferably 1500 g/10 min. When it is in the above range, the MFR in the whole is easily maintained, and the film forming property is excellent.

The lower limit of the M _w of the low molecular weight component is preferably 50,000, more preferably 53,000, still more preferably 55,000, particularly preferably 60,000, most preferably 70,000. When it is in the above range, the MFR in the whole is easily maintained, and the film forming property is excellent.

The upper limit of the M _w of the low molecular weight component is preferably 150,000, more preferably 140,000, still more preferably 130,000, particularly preferably 120,000, and most preferably 110,000. If it is the above range, the crystallinity becomes good, and at the high temperature, the heat shrinkage rate and the like, the effect of the present invention becomes more readily available.

The lower limit of the amount of the low molecular weight component is preferably 40% by mass, more preferably 50% by mass, still more preferably 55% by mass, and particularly preferably 60% by mass. If it is the above range, the effect of the present invention becomes easier to obtain, such as a low heat shrinkage rate at a high temperature, which is an effect of a low molecular weight component.

The upper limit of the amount of the low molecular weight component is preferably 98% by mass, more preferably 97% by mass, still more preferably 96% by mass, and particularly preferably 95% by mass. In the above range, it is not necessary to increase the molecular weight of the low molecular weight component in order to maintain the entire MFR, and the effect of the present invention such as a low heat shrinkage rate at a high temperature is more easily obtained.

The lower limit of the MFR ratio of the MFR/high molecular weight component of the low molecular weight component is preferably 500, more preferably 1,000, still more preferably 2,000, and particularly preferably 4,000. If it is in the above range, the effect of the present invention such as a low heat shrinkage rate at a high temperature becomes more readily available. Further, the upper limit of the MFR ratio of the MFR/high molecular weight component of the low molecular weight component is preferably 1,000,000.

The high molecular weight component and the low molecular weight component may be a mixture of two or more kinds of resins corresponding to the respective components, and in this case, the blending amount is a total amount.

In order to use a high molecular weight component and a low molecular weight component, the molecular weight distribution of a polypropylene resin is a preferable state. For example, when the molecular weight of the low molecular weight component to be used is low, the molecular weight of the high molecular weight component can be increased or increased. The amount of the molecular weight component or the like is adjusted to adjust the state of the molecular weight distribution, and is adjusted to facilitate the production of the MFR as the stretched film.

Further, in addition to the above-described high molecular weight component or low molecular weight component, in order to adjust the MFR in the entire polypropylene resin, a component having a molecular weight other than the low molecular weight component or the high molecular weight component of the present invention may be added. System may contain, for example: lower molecular weight component of the large and small components of higher molecular weight M _w of polypropylene (hereinafter, referred to as molecular weight component).

The lower limit of the ratio of the medium molecular weight component to the entire polypropylene resin constituting the film varies depending on the M _w of the molecular weight component used, but is preferably 5% by mass, more preferably 10% by mass, further preferably It is 13% by mass, particularly preferably 15% by mass, and most preferably 16% by mass. When the ratio of the medium molecular weight component is 5% by mass or more, the fish eye can be reduced or the elongation can be facilitated.

The upper limit of the ratio of the medium molecular weight component to the entire polypropylene resin constituting the film is preferably 58% by mass, more preferably 56% by mass, still more preferably 54% by mass, particularly preferably 52% by mass, most preferably 50%. quality%. When the ratio of the medium molecular weight component is 58% by mass or less, the elongation becomes easy and the thickness unevenness becomes small, and the elongation temperature or the heat fixation temperature is likely to increase and the heat shrinkage rate is lowered.

Further, in order to facilitate the untangling of the molecular chain to adjust the elongation, etc., it is also possible to add a polypropylene having a _{Mw of} less than 50,000, more preferably a polypropylene resin having a M _{w of} 30,000 or less, particularly preferably A polypropylene resin having a M _{w of} less than 10,000.

The lower limit of the ratio of the polypropylene having a M _{w of} less than 50,000 is preferably 0% by mass, more preferably 1% by mass, still more preferably 2% by mass, particularly preferably 3% by mass, based on the entire polypropylene resin constituting the film. The best is 4% by mass. By adding polypropylene having a _{Mw of} less than 50,000, the effect of the present invention such as low heat shrinkage at a high temperature becomes more readily available.

The upper limit of the ratio of the polypropylene having a M _{w of} less than 50,000 is preferably 50% by mass, more preferably 45% by mass, still more preferably 40% by mass, particularly preferably 35% by mass, based on the entire polypropylene resin constituting the film. The best is 30% by mass. When the ratio of the polypropylene having a M _{w of} less than 50,000 is 50% by mass or less, the elongation becomes easy, or the thickness unevenness becomes small.

A polypropylene molecule having a M _{w of} less than 50,000 is difficult to form a molecular chain to each other, and has a plasticizer-like effect of uncoupling the molecules. It is considered that the amount of the component of the polypropylene containing a specific amount of M _{w of} less than 50,000 makes it possible to extend under low elongation stress, and as a result, the residual stress is low and the shrinkage rate at a high temperature is lowered. By.

(stereoregularity of polypropylene resin)

The lower limit of the sequence ratio of the meso-pentome group of the stereoregularity index of the polypropylene resin constituting the film is preferably 96%, more preferably 96.5%, still more preferably 97%. If it is the above range, crystallinity and melting point will increase, and the heat shrinkage rate at a high temperature will become lower. The upper limit of the sequence fraction of the mesocyclic pentad in the same row is preferably 99.5%, more preferably 99.3%, still more preferably 99%. If it is the above range, the actual manufacturing will become easy.

It is preferred not to allow heterogeneous bonding of the polypropylene resin constituting the film. Further, here, the heterogeneous binding system is not allowed to mean that no peak is observed in the ¹³ C-NMR.

The lower limit of the xylene soluble component of the polypropylene resin constituting the film is preferably 0.1% by mass from the actual surface. The upper limit of the xylene soluble component is preferably 7% by mass, more preferably 6% by mass, still more preferably 5% by mass. If it is the above range, the crystallinity will increase, and the heat shrinkage rate at a high temperature will become small.

The lower limit of the meso-average chain length of the same row of the polypropylene resin constituting the film is preferably 100, more preferably 120, still more preferably 130. If it is the above range, the crystallinity will increase, and the heat shrinkage rate at a high temperature will become small. The upper limit of the meso-average chain length in the same row is preferably 5,000 from the actual side.

The polypropylene resin constituting the film is preferably a completely homopolypropylene obtained only from a propylene monomer, but may be a copolymer with a copolymerized monomer if it is a trace amount. As the copolymerization monomer, ethylene or butene is preferred.

The upper limit of the amount of the copolymerized monomer is preferably 0.1 mol%, more preferably 0.05 mol%, still more preferably 0.01 mol%. If it is the above range, the crystallinity will increase, and the heat shrinkage rate at a high temperature will become small.

Further, when the conventional stretched polypropylene film is industrially completely homopolypropylene, the range of conditions that can be extended is extremely narrow due to the high degree of crystallinity or the melt tension after melt softening, and it is difficult to form a film. Usually, a copolymerization component (mainly ethylene) of 0.5 mol% is copolymerized. However, as described above, the polypropylene resin in the molecular weight distribution state of the present invention can be industrially extended even if the copolymerization component after melt softening is mildly reduced even if it has almost no copolymerization component.

(Method for producing polypropylene resin)

The polypropylene resin is obtained by polymerizing propylene as a raw material using a conventional catalyst such as a Nigler-Natta catalyst or a metallocene catalyst. Further, in order to prevent the above heterogeneous combination from being present, a 戚Geller-Natcata catalyst is used, and among them, a catalyst capable of performing polymerization with high stereoregularity is preferably used.

Examples of the polymerization method of propylene include a method of polymerizing in an inert solvent such as hexane, heptane, toluene or xylene; a method of polymerizing in liquid propylene or ethylene; and a gas of propylene or ethylene. A method of adding a catalyst to polymerize in a gas phase state; or a method of combining these polymerizations.

The high molecular weight component and the low molecular weight component may be mixed after being separately polymerized, or may be produced in a series of apparatuses in a multistage reactor. Particularly preferred is a method of polymerizing a low molecular weight component in the presence of a polymer having a multistage reactor after initially polymerizing the high molecular weight component. Further, the adjustment of the molecular weight can be carried out by the amount of hydrogen mixed in the polymerization.

In the resin composition for film formation of the present invention, an additive or other resin may be added as needed, but these components are preferably 30% by mass or less. Examples of the additives include antioxidants, ultraviolet absorbers, antistatic agents, slip agents, nucleating agents, adhesives, antifogging agents, flame retardants, anti-caking agents, inorganic or organic fillers, and the like. . Examples of the other resin include a polypropylene resin other than the polypropylene resin used in the present invention, a random copolymer with a copolymer of ethylene or an α-olefin, or various elastomers. The α-olefin may, for example, be butene, hexene or octene. These may be mixed with a polypropylene resin in a Henschel mixer, or a masterbatch prepared by using a melt kneader in advance with a polypropylene to a predetermined concentration, or may be used by melt-kneading a whole amount in advance.

It is considered that by using a polypropylene resin having a molecular weight distribution having such a characteristic, it is possible to extend a polypropylene having a low molecular weight component as a main component which cannot be sufficiently extended in the past, and a high heat setting temperature can be employed. The synergistic effect of high crystallinity and strong heat fixation reduces the heat shrinkage rate at high temperatures.

(Method for producing polypropylene film)

For the stretched film of the present invention, the length direction (MD) Uniaxially stretched film in the direction) or in the transverse direction (TD direction), but is preferably a biaxially stretched film. The biaxial extension may be a sequential biaxial extension or a simultaneous biaxial extension.

By forming a stretched film, a film which is unimaginable in the conventional polypropylene film and which has a low heat shrinkage rate even at 150 ° C can be obtained.

The method for producing the longitudinally extending-laterally extending sequential biaxially stretched film of the best case will be described below.

First, the polypropylene resin was heated and melted in a uniaxial or biaxial extruder, and extruded on a cooling roll to obtain an unstretched film.

The melt-extruding conditions are obtained by extruding a resin into a sheet shape by a T-die at a temperature of, for example, 200 to 280 ° C, and cooling and solidifying at a temperature of 10 to 100 ° C by a cooling roll. Next, the film is stretched in the length (MD) direction by 3 to 8 times with a stretching roller of 120 to 160 ° C, and then at a temperature of 155 ° C to 175 ° C, preferably 157 ° C to 170 ° C in the width (TD) direction. 4~15 times extension.

Further, heat treatment is applied while allowing relaxation of 1 to 15% at an ambient temperature of 165 to 175 ° C, preferably 166 to 173 ° C.

The corrugated film can be obtained by applying a corona discharge treatment to at least one side of the polypropylene film thus obtained, and then winding it up by a coiler.

The lower limit of the stretching ratio of MD is preferably 3 times, more preferably 3.5 times. If it is less than the above, the film thickness will become uneven. The upper limit of the stretching ratio of MD is preferably 8 times, more preferably 7 times. If it is larger than the above, the subsequent TD extension becomes difficult.

The lower limit of the extension temperature of the MD is preferably 120 ° C, more preferably 125 ° C, still more preferably 130 ° C. If it is less than the above, the mechanical burden It will become larger, or the thickness will become larger, and the surface crack of the film will occur. The upper limit of the extension temperature of the MD is preferably 165 ° C, more preferably 160 ° C, still more preferably 155 ° C, and particularly preferably 150 ° C. The higher temperature is better at lowering the heat shrinkage rate, but it adheres to the roll and cannot be extended.

The lower limit of the stretching ratio of TD is preferably 4 times, more preferably 5 times, still more preferably 6 times. If it is less than the above, the film thickness will become uneven. The upper limit of the TD stretching ratio is preferably 15 times, more preferably 14 times, still more preferably 13 times. If it is larger than the above, the heat shrinkage rate becomes high, or it may break when it is extended.

The preheating temperature during the extension of the TD is such that the film temperature is rapidly raised to near the extension temperature, and is preferably set to be 5 to 15 ° C higher than the extension temperature. The extension of TD is carried out at a higher temperature than conventional polypropylene films. The lower limit of the extension temperature of TD is preferably 155 ° C, more preferably 157 ° C, still more preferably 158 ° C. If it is less than the above, not only the amount of formation of the α2-type crystal in the obtained film may be insufficient, but in the elongation process, the film may not be sufficiently softened and broken, or the heat shrinkage rate may become high.

The upper limit of the TD extension temperature is preferably 175 ° C, more preferably 170 ° C, still more preferably 168 ° C. In order to lower the heat shrinkage rate, it is preferable that the temperature is high. However, if it is larger than the above, not only the low molecular weight component is melted and recrystallized, but the surface is cracked or the film is whitened, and crystallization does not progress during stretching, and the α2 type crystal is not crystallized. The fraction does not increase and the heat resistance decreases.

The extended film is heat-fixed. The heat setting can be carried out at a higher temperature than the conventional polypropylene film. The lower limit of the heat setting temperature is preferably 165 ° C, more preferably 166 ° C. If it is less than the above, not only the amount of formation of the α2-type crystal in the obtained film may be insufficient, but the melting point may become low. Or the rate of heat shrinkage becomes higher. Further, it takes a long time to lower the heat shrinkage rate, and the productivity is deteriorated.

The upper limit of the heat setting temperature is preferably 175 ° C, more preferably 173 ° C. If it is larger than the above, the low molecular weight component melts and recrystallizes to cause surface cracking or film whitening.

It is preferred to relax (relax) when heat is fixed. The lower limit of relaxation is preferably 1%, more preferably 2%, still more preferably 3%. If it is less than the above, the heat shrinkage rate will become high. Relax The upper limit is preferably 15%, more preferably 10%, still more preferably 8%. If it is larger than the above, the thickness unevenness will become large.

Further, in order to lower the heat shrinkage rate, the film produced in the above step may be annealed off-line once it is wound into a roll shape.

The lower limit of the off-line annealing temperature is preferably 160 ° C, more preferably 162 ° C, still more preferably 163 ° C. If it is less than the above, the effect of annealing cannot be obtained. The upper limit of the off-line annealing temperature is preferably 175 ° C, more preferably 174 ° C, still more preferably 173 ° C. If it is larger than the above, the transparency will be lowered, or the thickness unevenness will become large.

The lower limit of the off-line annealing time is preferably 0.1 minute, more preferably 0.5 minute, still more preferably 1 minute. If it is less than the above, the effect of annealing cannot be obtained. The upper limit of the off-line annealing time is preferably 30 minutes, more preferably 25 minutes, still more preferably 20 minutes. If it is larger than the above, productivity will decrease.

The thickness of the film is set for various uses, but the lower limit of the film thickness is preferably 2 μm, more preferably 3 μm, still more preferably 4 μm. . The upper limit of the film thickness is preferably 300 μm, more preferably 250 μm, still more preferably 200 μm, particularly preferably 100 μm, most preferably 50 μm.

The polypropylene film obtained in this manner is usually formed into a roll having a width of 2000 to 12000 mm and a length of about 1000 to 50,000 m, and is wound into a roll shape. Further, it is cut for various uses, and is used as a cutting reel having a width of 300 to 2000 mm and a length of 500 to 5000 m.

The polypropylene film of the present invention has excellent characteristics as described above as never before.

When used as a packaging film, it can be made thinner due to high rigidity, and can be reduced in cost and weight.

Moreover, since it is high in heat resistance, it can be dried at a high temperature during drying of coating or printing, and productivity can be improved, and a coating agent, an ink, a laminate adhesive, etc. which were conventionally difficult to use can be used.

Further, it is also possible to use a base film which is an insulating film such as a capacitor or a generator, a back sheet of a solar cell, a barrier film of an inorganic oxide, or a transparent conductive film such as ITO.

In addition, the present application claims priority from the patent application No. 2012-281685 filed on Dec. 25, 2012. The entire contents of the specification of Japanese Patent Application No. 2012-281685, filed on Dec. 25, 2012, are hereby incorporated by reference.

[Examples]

Hereinafter, the present invention will be described in detail based on examples, but the present invention is not limited to the examples. The measurement method of the physical properties in the examples is as follows.

1) Melt flow rate (MFR, g/10 minutes)

The MFR was measured at a temperature of 230 ° C in accordance with JIS K7210.

2) Molecular weight and molecular weight distribution

The molecular weight and molecular weight distribution were determined by using GPC and using a monodisperse polystyrene standard.

The column and solvent used in the GPC measurement are as follows.

Solvent: 1,2,4-trichlorobenzene

Column: TSKgel GMH _HR -H(20)HT×3

Flow rate: 1.0ml/min

Detector: RI

Measuring temperature: 140 ° C

The number average molecular weight (M _n ), the mass average molecular weight (M _w ), the Z average molecular weight (M _z ), and the Z+1 average molecular weight (M _z+1 ) are each obtained by using a GPC curve obtained by a molecular weight calibration curve. The number of molecules (N _i ) of the molecular weight (M _i ) at each dissolution position is defined by the following formula.

Number average molecular weight: M _n = Σ(N _i .M _i )/ΣN _i

Mass average molecular weight: M _w = Σ (N _i .M _i ² ) / Σ (N _i .M _i )

Z average molecular weight: M _z = Σ (N _i .M _i ³ ) / Σ (N _i .M _i ² )

Z+1 average molecular weight: M _z+1 = Σ (N _i .M _i ⁴ ) / Σ (N _i .M _i ³ )

Further, the molecular weight at the peak position of the GPC curve was defined as M _p .

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

From the obtained GPC curve, peak separation was performed for two components having different molecular weights. The molecular weight distribution of each component is assumed to be a Gauss constant, and is set such that the peak width thereof is M _w / M _n = 4. The average molecular weight was calculated from the curves of the respective components obtained.

Moreover, the GPC curve of the entire polypropylene resin constituting the film is obtained. The ratio of the component having a molecular weight of 10,000 or less and the ratio of the component having a molecular weight of 100,000 or less in the entire polypropylene resin constituting the film.

3) Stereo regularity

In the same row, the racemic pentad sequence fraction (the meso pentad sequence fraction, [mmmm]) and the same row meso average chain length (meso average chain length) were determined using ¹³ C- NMR was carried out. The same-order meso-pentome sequence fraction is based on the method described by Zambelli et al., Macromolecules, Vol. 6, p. 925 (1973). The same meso-average chain length is in accordance with JCRandall's "Polymer Sequence Distribution". Calculated by the method described in Chapter 2 (1977) (Academic Press, New York).

The NMR measurement was carried out using AVANCE 500 manufactured by BRUKER Co., Ltd., and a 200 mg sample was dissolved at 135 ° C in an 8:2 mixture of o-dichlorobenzene and deuterated benzene, and subjected to ¹³ C-NMR measurement at 110 °C.

4) Solid state NMR measurement

After each sample was uniformly and tightly packed into a ZrO ₂ rotating device, it was inserted into a solid-state nuclear magnetic resonance device. Thereafter, the rotating device was tilted only to the magic angle (54.7°) to the external magnetic field, and rotated at a speed of 4000 Hz, and ¹³ C-NMR measurement was performed using the CP/MAS method. The conditions are listed below.

Device name: AVANCE300 made by BRUKER

Measuring core: ¹³ C

Measurement frequency: 75.5MHz

Number of rotations: 4000Hz

Waiting time (D1): 5 seconds

Data reading time (Aq): 34.9ms

Flip angle: 90°

The total number of calculations: 3000~10000 times

Measuring temperature: room temperature

The ¹³ C-NMR spectrum obtained was applied to an analytical method of J. Phys. Chem. B, 114, 92-100 (2010) by using T. Miyoshi et al., and the ratio of α2 type crystal was calculated. A standard sample having a ratio of α1 type crystals of 100% was used as a control sample preparation.

5) Density (g/cm ³ )

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

6) Melting point (Tmp, °C)

The thermal measurement was performed using a DSC-60 differential scanning calorimeter manufactured by Shimadzu Corporation. A sample of about 5 mg was cut out from the film and sealed in an aluminum pan for measurement. The temperature was raised from room temperature to 230 ° C at a rate of 20 ° C / minute, and the melting endothermic peak temperature of the sample was set to Tmp.

7) Cold xylene soluble component (CXS, mass%)

1 g of the polypropylene sample was dissolved in 200 ml of boiling xylene and allowed to cool, and then recrystallized in a constant temperature water bath at 20 ° C for 1 hour, and the ratio of the mass dissolved in the filtrate to the original sample amount was set to CXS (mass %).

8) Thermal shrinkage rate (%)

It was measured in accordance with JIS Z 1712. That is, the stretched film was cut in the MD and TD directions with a length of 200 mm and a width of 200 mm, and hung in a hot air oven for 5 minutes. The length after heating was measured, and the heat shrinkage ratio was determined from the ratio of the length of the shrinkage to the original length.

9) Impact resistance

The measurement was carried out at 23 ° C using a Toyo Seiki Film Impact Tester.

10) Young's rate (unit: GPa)

The tensile strengths of MD and TD were measured at 23 ° C according to JIS K 7127.

11) Haze (unit: %)

It is measured in accordance with JIS K7105.

12) Refractive index

It was measured using an Abe refractometer manufactured by ATAGO. The refractive indices in the MD and TD directions are each Nx and Ny, and the refractive index in the thickness direction is Nz.

13) Surface alignment coefficient

The Nx and Ny measured in the above 12) are calculated from the formula of [(Nx+Ny)/2]-Nz by Nz from the thickness direction.

14) Uneven thickness

A square sample having a length of 1 m was cut out from the wound film roll, and 100 sheets of measurement samples each divided into 10 equal portions in the MD direction and the TD direction were prepared. The thickness of the near-center portion of the sample for measurement was measured by a contact film thickness meter.

Find the average value of the obtained 100-point data, and find the difference (absolute value) between the minimum value and the maximum value, and divide the absolute value of the difference between the minimum value and the maximum value by the value of the average value as the thickness unevenness of the film. .

(Example 1)

A propylene single polymer of M _w /M _n =7.7, Mz ₊₁ /M _n =140, MFR=5.0 g/10 min, [mmmm]=97.3% (made by Japan Polypropylene: "NOVATEC ^TM PP" ⁾ SA4L") as a polypropylene resin. It was extruded into a sheet shape by a T die at 250 ° C using a 60 mm extruder, cooled and solidified by a cooling roll at 30 ° C, and then extended to 4.5 times in the longitudinal direction at 135 ° C. Next, the ends were clamped by a jig and introduced into a hot blast stove. After preheating at 170 ° C, it was extended to 8.2 times in the transverse direction at 160 ° C, and then heat-treated at 168 ° C while relaxing at 6.7%. Thereafter, one side of the film was subjected to corona treatment and taken up by a coiler. The thickness of the film obtained in this manner was 20 μm, and as shown in Table 1, Table 2, and Table 3, a film having a low heat shrinkage rate and a high Young's ratio was obtained. The spectrum of the spectrum obtained by solid state NMR and the sample of 100% of the α1 type crystal are overlapped in Fig. 1 . The area ratio of this is equal to the fraction (%) of the α2-type crystal in all the crystals.

(Example 2)

To 90 parts by mass of SA4L, 10 parts by mass of a low molecular weight propylene individual polymer having a narrow molecular weight distribution and a molecular weight of 10,000 was added, and melted and kneaded in a 30 mm biaxial extruder to obtain pellets of the mixture. This pellet was obtained in the same manner as in Example 1 to obtain a film. The properties of the polypropylene resin and the physical properties of the obtained film are shown in Table 1, Table 2, and Table 3.

(Example 3)

For 70 parts by mass of SA4L, 30 parts by mass of propylene individual polymer of M _w /M _n =4.6, M _z+1 /M _n =22, MFR=120 g/10 min, [mmmm]=98.1% was added, and dry type was added. After mixing, a film was obtained in the same manner as in Example 1. The properties of the polypropylene resin and the physical properties of the obtained film are shown in Tables 1, 2 and 3.

(Example 4)

A film was obtained in the same manner as in Example 1 except that SA4L was used, and the preheating temperature at the time of the lateral stretching was 173 ° C, and the elongation temperature and the heat treatment temperature were 167 ° C. The properties of the polypropylene resin and the physical properties of the obtained film are shown in Table 1, Table 2, and Table 3.

(Example 5)

A film was obtained in the same manner as in Example 2 except that it was 5.5 times in the longitudinal direction and 12 times in the transverse direction. The properties of the polypropylene resin and the physical properties of the obtained film are shown in Table 1, Table 2, and Table 3.

(Example 6)

Using the film prepared in Example 1, heat treatment was carried out at 170 ° C for 5 minutes in a tenter type hot blast stove. The properties of the polypropylene resin and the physical properties of the obtained film are shown in Table 1, Table 2, and Table 3.

(Example 7)

In addition to the polypropylene resin, propylene alone polymer (Samsung Total "HU300" using M _w /M _n =8.9, M _z+1 /M _n =110, MFR=3.0 g/10 min, mmmm=97.1% was used. A polypropylene film was obtained in the same manner as in Example 1 except that the preheating temperature was 171 ° C, the extension temperature in the TD direction was 161 ° C, and the heat setting temperature was 170 ° C. The properties of the polypropylene resin and the physical properties of the obtained film are shown in Tables 1, 2 and 3.

(Comparative Example 1)

In addition to using the polypropylene-based resin manufactured by Sumitomo Chemical (shares) manufactured by the "SUMITOMO ^TM NOBLEN ^TM FS2011DG3", and let the longitudinal stretching temperature was 125 deg.] C, preheating the lateral stretching temperature was 168 deg.] C, an elongation temperature of 155 deg.] C, the heat treatment temperature is A film was obtained in the same manner as in Example 1 except for 163 °C. Its M _w /M _n =4, M _z+1 /M _n =21, MFR = 2.5 g/10 min. The properties of the polypropylene resin and the physical properties of the obtained film are shown in Table 1, Table 2, and Table 3.

(Comparative Example 2)

A film was produced in the same manner as in Comparative Example 1, except that the preheating temperature was 171 ° C, the elongation temperature was 160 ° C, and the heat treatment temperature was 165 ° C. Will gather The properties of the propylene resin and the physical properties of the obtained film are shown in Table 1, Table 2, and Table 3.

(Comparative Example 3)

Biaxial stretching was attempted in the same manner as in Example 1 except that "NOVATEC ^TM PP SA03" (MFR = 30 g/10 min) manufactured by Polypropylene Co., Ltd., Japan, and a longitudinal extension temperature of 130 ° C were used. When the transverse stretch is broken, the film cannot be obtained.

As is apparent from the above examples, the biaxially oriented polypropylene film of the present invention has a high crystal fraction of α2 type and excellent heat resistance.

[Industrial availability]

The biaxially stretched polypropylene film of the present invention can be widely used for packaging applications and industrial applications, and is particularly suitable for heat sealing applications, printing processes, and the like at high temperatures because of excellent heat resistance and dimensional stability.

Moreover, since it is high in heat resistance, it can be dried at a high temperature during drying of coating or printing, and it is possible to improve production efficiency and use a coating agent, an ink, a laminate adhesive, or the like which has been difficult to use in the past.

Furthermore, it is also applicable to an insulating film such as a capacitor or a generator, a back sheet of a solar cell, a barrier film of an inorganic oxide, or a base film of a transparent conductive film such as ITO.

Claims (5)

A biaxially stretched polypropylene film characterized in that the α2 type crystal amount measured by solid state NMR is 23% or more of all crystals, and the density is 0.910 g/cm ³ or more, which is measured by a differential scanning calorimeter (DSC). The melting point is 168 ° C or higher, the heat shrinkage ratio at 150 ° C is 15% or less, and the haze is 6% or less. The biaxially stretched polypropylene film of claim 1, wherein the lower limit of the mesogenic pentad sequence fraction of the polypropylene resin constituting the film is 96%, and the lower limit of the face alignment coefficient of the film is 0.0125. The biaxially stretched polypropylene film of claim 1 or 2, wherein the upper limit of the amount of the copolymerized monomer of the polypropylene resin constituting the film is 0.1 mol%. The biaxially stretched polypropylene film according to claim 1 or 2, wherein the polypropylene resin constituting the film has a xylene soluble component of 7% by mass or less. The biaxially stretched polypropylene film of claim 3, wherein the polypropylene resin constituting the film has a xylene soluble component of 7% by mass or less.