WO2015012324A1

WO2015012324A1 - Stretched polypropylene film

Info

Publication number: WO2015012324A1
Application number: PCT/JP2014/069485
Authority: WO
Inventors: 山田　浩司; 理木下; 多賀　敦; 健一船城
Original assignee: 東洋紡株式会社
Priority date: 2013-07-23
Filing date: 2014-07-23
Publication date: 2015-01-29
Also published as: KR102352439B1; TW201510034A; TWI629301B; KR20160034302A; JPWO2015012324A1; JP6477472B2

Abstract

A stretched polypropylene film that has a low shrinkage factor at 150°C that is comparable to that of polyethylene terephthalate (PET), the stretched polypropylene film being a stretched film that uses a propylene polymer satisfying conditions (a)—(c) and that satisfies conditions (d) and (e). (a) Meso pentad fraction is 96% or more. (b) Non-propylene comonomer content is 0.5 mol% or less. (c) Melt flow rate (MFR) is 0.5g/10 min. or more and 20g/10 min. or less. (d) When polypropylene α-crystal (110) surface scattering intensity as measured by wide-angle x-ray scattering is plotted against azimuth angle, the half width of the largest peak is 30 degrees or less. (e) Melting endothermic peak area (total heat of fusion) as measured using differential scanning calorimetry at a rate of temperature increase of 20°C/min. is 115J/g or more, and the ratio (heat of fusion at 150°C/total heat of fusion) of area at 150°C or less (heat of fusion at 150°C) to total heat of fusion is 0.12 or less.

Description

Stretched polypropylene film

The present invention relates to a stretched polypropylene film. More specifically, the present invention relates to a stretched polypropylene film excellent in heat resistance and mechanical properties, which can be suitably used in various fields where dimensional stability at high temperature and high rigidity are required.

Conventionally, stretched polypropylene films have been widely used for a wide range of applications such as packaging for food and various products, electrical insulation, and surface protection films. However, the conventional polypropylene film has a shrinkage rate of several tens of percent at 150 ° C., and has low heat resistance and low rigidity as compared with a polyethylene terephthalate (PET) film or the like.

By the way, various techniques for improving the physical properties of the polypropylene film have been proposed. For example, a technique is known in which a stretched film is formed using polypropylene having high stereoregularity and a narrow molecular weight distribution to obtain a high-temperature rigidity and heat-resistant film (see Patent Document 1).
Further, a technique is known that can be suitably used as a capacitor film having excellent electrical insulation, mechanical properties, etc. by using a polypropylene film having high stereoregularity and a broad molecular weight distribution as a stretched film. (See Patent Document 2).

Furthermore, a technology for forming a separator film using polypropylene having a low molecular weight and a soluble content of 0 ° C. by a temperature rising fractionation method in a specific range is known. This film has dimensions in a drying process and a printing process. It is said that it is excellent in stability (refer patent document 3).

However, the films described in Patent Documents 1 to 3 have difficulty in stretchability and inferior mechanical properties such as impact resistance.

In addition, by adding a small amount of long-chain branched or cross-linked polypropylene to the medium molecular weight component, it promotes the formation of a child lamella, improves stretchability, has excellent mechanical properties, heat resistance, withstand voltage properties, and uniform physical properties. A technique for producing a film having excellent properties is known (see Patent Document 4).

Furthermore, by using almost the same amount of high molecular weight component and low molecular weight component (or low low molecular weight component), broad molecular weight distribution, and using polypropylene with a small amount of decalin soluble, it is possible to obtain rigidity and workability. Is known (see Patent Document 5).

However, these films described in Patent Documents 4 to 5 still cannot be said to have sufficient heat resistance at high temperatures exceeding 150 ° C., have high heat resistance, and excellent impact resistance and transparency. Polypropylene film was not known. In other words, the films described in Patent Documents 4 to 5 do not exceed the range of conventional polypropylene films, and their uses are limited. For example, heat resistance at high temperatures exceeding 150 ° C. It was not done.

JP-A-8-325327 JP 2004-175932 A JP 2001-146536 A JP 2007-84813 A Special table 2008-540815

The present invention has been made against the background of the problems of the prior art. That is, an object of the present invention is to provide a stretched polypropylene film having a low shrinkage comparable to that of a polyethylene terephthalate (PET) film at 150 ° C. and having high rigidity.

As a result of intensive studies to achieve the above object, the present inventors have completed the present invention. That is, the stretched polypropylene film of the present invention is a stretched film using a propylene polymer that satisfies the following requirements (a) to (c), and satisfies the following requirements (d) and (e): Features.
(A) Mesopentad fraction is 96% or more.
(B) The content of comonomer other than propylene is 0.5 mol% or less.
(C) The melt flow rate (MFR) is 0.5 g / 10 min or more and 20 g / 10 min or less.
(D) The half-value width of the maximum peak when the scattering intensity of the 110 plane of the α-type crystal of polypropylene measured by the wide angle X-ray scattering method is plotted against the azimuth is 30 degrees or less.
(E) The melting endothermic peak area (total heat of fusion) measured at a heating rate of 20 ° C./min using a differential scanning calorimeter is 115 J / g or more and an area of 150 ° C. or less (150 ° C. heat of fusion) ) To the total heat of fusion (150 ° C. heat of fusion / total heat of fusion) is 0.12 or less.

A stretched film is a film having an orientation stretched by a method such as uniaxial, simultaneous biaxial, and sequential biaxial, industrially, and the degree of orientation is, for example, wide-angle X-ray diffraction or small-angle X-ray. It can be estimated from scattering, refractive index, and the like. In the present invention, the degree of orientation of the stretched film is defined by wide-angle X-ray diffraction.

In the present invention, it is preferable that the long-period size obtained from the long-period scattering peak in the main orientation direction measured by the small-angle X-ray scattering method is 40 nm or more. In the present invention, a film stretched at least uniaxially and having a thickness of 3 to 100 μm is preferable. Furthermore, in the present invention, it is preferable that the thermal shrinkage rate in the TD direction at 150 ° C. and the thermal shrinkage rate in the MD direction at 150 ° C. are both 10% or less. Furthermore, in the present invention, it is preferable that the haze of the film is 6% or less.

According to the stretched polypropylene film of the present invention, a low shrinkage rate and a high rigidity comparable to that of a polyethylene terephthalate (PET) film can be exhibited at 150 ° C., and thus thinning is possible.
Furthermore, since the stretched polypropylene film of the present invention can maintain various physical properties even when exposed to an environment of 150 ° C. or higher, it should be used in a high-temperature environment that has not been considered with conventional polypropylene films. And can be preferably applied in a wide range of applications. For example, the stretched polypropylene film of the present invention is used as a base material layer, and a heat seal layer or a gas barrier layer is laminated on the surface layer, so that it can be used for various packaging applications. It can also be used as a substrate for extrusion lamination. And when performing heat sealing on the stretched polypropylene film of the present invention or a laminated film using the same, the heat sealing strength is improved by setting the heat sealing temperature high, so that the line speed in bag making processing is increased. Can improve productivity. Furthermore, the amount of deformation of the bag can also be suppressed when high-temperature processing such as retort is performed after bag making.

It is a chart for demonstrating the azimuth angle dependence and the half value width of the diffraction intensity of 110 plane of alpha type crystal in the wide angle X-ray diffraction pattern of a stretched polypropylene film. 2 is a differential scanning calorimetry (DSC) chart for the stretched polypropylene film obtained in Example 1 and Comparative Example 1. FIG.

The present invention relates to a stretched polypropylene film excellent in dimensional stability at high temperatures and mechanical properties. The characteristics of the stretched polypropylene film of the present invention are as follows: (1) The stretched polypropylene film of the present invention is a stretched film using a propylene polymer that satisfies the following requirements (a) to (c), and the following requirements ( d) and (e) are satisfied.
(A) Mesopentad fraction is 96% or more.
(B) The content of comonomer other than propylene is 0.5 mol% or less.
(C) The melt flow rate (MFR) is 0.5 g / 10 min or more and 20 g / 10 min or less.
(D) The half-value width of the maximum peak when the scattering intensity of the 110 plane of the α-type crystal of polypropylene measured by the wide angle X-ray scattering method is plotted against the azimuth is 30 degrees or less.
(E) The melting endothermic peak area (total heat of fusion) measured at a heating rate of 20 ° C./min using a differential scanning calorimeter is 115 J / g or more and an area of 150 ° C. or less (150 ° C. heat of fusion) ) To the total heat of fusion (150 ° C. heat of fusion / total heat of fusion) is 0.12 or less.

(2) Moreover, it is preferable that the long period size calculated | required from the long period scattering peak of the main orientation direction measured by a small angle X-ray scattering method is 40 nm or more,
(3) Furthermore, it is preferable that the film is a film stretched at least uniaxially with a thickness of 3 to 100 μm,
(4) Furthermore, it is preferable that the thermal shrinkage rate in the TD direction at 150 ° C. and the thermal shrinkage rate in the MD direction at 150 ° C. are both 10% or less,
(5) Further, it is preferable that the haze is 6% or less.

(Polypropylene resin)
The polypropylene resin used in the present invention is not particularly limited, and for example, a propylene homopolymer or a copolymer with ethylene and / or an α-olefin having 4 or more carbon atoms can be used.
As the polypropylene resin constituting the film, a propylene homopolymer substantially free of comonomer is preferable, and even when the comonomer is contained, the amount of comonomer is 0.5 mol% or less. The upper limit of the comonomer amount is preferably 0.3 mol%, more preferably 0.1 mol%. When it is in the above range, the crystallinity may be improved, and the thermal shrinkage at high temperatures may be reduced. In addition, a comonomer may be contained as long as it is a trace amount within a range in which the crystallinity is not significantly reduced.
The polypropylene resin constituting the film is more preferably a propylene homopolymer obtained only from a propylene monomer, and even the propylene homopolymer is most preferably free of heterogeneous bonds such as head-to-head bonds. .

(Stereoregularity of polypropylene resin)
The lower limit of the mesopentad fraction measured by ¹³ C-NMR, which is an index of stereoregularity of the polypropylene resin constituting the film, is 96%. The lower limit of the mesopentad fraction is preferably 96.5%, more preferably 97%. When it is within the above range, the crystallinity may be improved, and the thermal shrinkage rate at a high temperature may be lower. The upper limit of the mesopentad fraction is preferably 99.8%, more preferably 99.6%, still more preferably 99.5%. In the above range, realistic production may be easy.

The lower limit of the meso average chain length of the polypropylene resin constituting the film is preferably 100, more preferably 120, and still more preferably 130. When it is in the above range, the crystallinity may be improved, and the thermal shrinkage at high temperatures may be reduced. The upper limit of the meso average chain length is preferably 5000 from a practical aspect.

The lower limit of the xylene-soluble content of the polypropylene resin constituting the film is preferably 0.1% by mass from a practical aspect. The upper limit of the xylene-soluble content is preferably 7% by mass, more preferably 6% by mass, and further preferably 5% by mass. When it is in the above range, the crystallinity may be improved, and the thermal shrinkage at high temperatures may be reduced.

(Melt flow rate of polypropylene resin)
The lower limit of the melt flow rate (MFR) (230 ° C., 2.16 kgf) of the polypropylene resin is 0.5 g / 10 minutes. The lower limit of the MFR is preferably 1.0 g / 10 minutes, more preferably 1.3 g / 10 minutes, still more preferably 1.5 g / 10 minutes, still more preferably 2.0 g / 10 minutes. Yes, particularly preferably 4.0 g / 10 min, and preferably 6.0 g / 10 min. Within the above range, the mechanical load is small, and extrusion and stretching may be easy. The upper limit of MFR is 20 g / 10 minutes, preferably 17 g / 10 minutes, more preferably 16 g / 10 minutes, and further preferably 15 g / 10 minutes. When it is within the above range, stretching may be easy, thickness unevenness may be reduced, and the stretching temperature and heat setting temperature may be easily increased, resulting in a lower thermal shrinkage rate.

(Molecular weight of polypropylene resin)
The lower limit of the number average molecular weight (Mn) measured by gel permeation chromatography (GPC) of the polypropylene resin constituting the film is preferably 20000, more preferably 22000, still more preferably 24000, Preferably it is 26000, and most preferably 27000. When it is in the above range, there are the advantages that stretching becomes easy, thickness unevenness is reduced, stretching temperature and heat setting temperature are easily raised, and thermal shrinkage rate is lowered. The upper limit of Mn is preferably 200000, more preferably 170000, still more preferably 160000, and particularly preferably 150,000. Within the above range, the effects of the present application such as a low heat shrinkage rate at high temperature, which is an effect of a low molecular weight substance, may be easily obtained, or stretching may be facilitated.

The lower limit of the mass average molecular weight (Mw) measured by GPC of the polypropylene resin constituting the film is preferably 180000, more preferably 200000, still more preferably 230,000, still more preferably 240000, particularly Preferably it is 250,000, and most preferably 270000. When it is in the above range, there are the advantages that stretching becomes easy, thickness unevenness is reduced, stretching temperature and heat setting temperature are easily raised, and thermal shrinkage rate is lowered. The upper limit of Mw is preferably 500,000, more preferably 450,000, still more preferably 420,000, particularly preferably 410,000, and most preferably 400,000. Within the above range, the mechanical load is small and extrusion and stretching may be easy.

(Molecular weight distribution of polypropylene resin)
The polypropylene resin used in the present invention preferably has the following characteristics. That is, when the gel permeation chromatography (GPC) integration curve of the polypropylene resin constituting the film is measured, the lower limit of the amount of the component having a molecular weight of 100,000 or less is preferably 35% by mass, more preferably 38% by mass. Yes, more preferably 40% by mass, particularly preferably 41% by mass, and most preferably 42% by mass. Within the above range, the effects of the present application such as a low heat shrinkage rate at a high temperature, which is an effect of a low molecular weight substance, may be easily obtained, and stretching may be facilitated. The upper limit of the amount of a component having a molecular weight of 100,000 or less in the GPC integration curve is preferably 65% by mass, more preferably 60% by mass, still more preferably 58% by mass, and particularly preferably 56% by mass. Most preferably, it is 55 mass%. When it is within the above range, stretching may be easy, thickness unevenness may be reduced, and the stretching temperature and heat setting temperature may be easily increased, resulting in a low thermal shrinkage rate.

In the polypropylene resin used in the present invention, the lower limit of mass average molecular weight (Mw) / number average molecular weight (Mn), which is generally an indicator of the breadth of molecular weight distribution, is preferably 4, more preferably 4.5. Yes, more preferably 5, particularly preferably 5.5, and most preferably 6. The upper limit of Mw / Mn is preferably 30, more preferably 25, still more preferably 22, particularly preferably 21, and most preferably 20. When Mw / Mn is in the above range, realistic production is easy.
The molecular weight distribution of polypropylene is such that components with different molecular weights are polymerized in a series of plants in multiple stages, components with different molecular weights are blended offline in a kneader, or catalysts with different performances are blended for polymerization. Or by using a catalyst capable of realizing a desired molecular weight distribution.

The stretched polypropylene film in the present invention is characterized by its structure, particularly the orientation of the film.
(Film orientation)
The stretched polypropylene film generally has a crystal orientation, and its direction and degree greatly affect the physical properties of the film. The degree of crystal orientation varies depending on the molecular structure of the polypropylene used and the process and conditions in film production. Further, the orientation direction of the stretched polypropylene film can be determined by measuring the azimuth angle dependency of the scattering peak derived from the crystal by making X-rays incident perpendicular to the film surface by wide-angle X-ray diffraction method. it can. Specifically, the stretched polypropylene film typically has a monoclinic α-type crystal structure. The α-type crystal has a strong orientation mainly in one axis when the azimuth angle dependence of the scattering intensity of 110 planes (plane spacing: 6.65 Å) is measured by wide-angle X-ray diffraction. That is, when the scattering intensity derived from the 110 plane of the α-type crystal is plotted against the azimuth angle, the strongest peak is observed in the direction perpendicular to the orientation of the molecular axis. In the present invention, the degree of orientation is defined by the half width of the maximum peak.
A typical pattern is shown in FIG. 1 for the azimuth angle dependence of scattering from the 110 plane of the α-type crystal of polypropylene. Further, FIG. 1 shows the full width at half maximum of the main peak (maximum peak) of the azimuth angle dependency of the 110 plane.

In the stretched polypropylene film of the present invention, the half-value width of the maximum peak when plotting the scattering intensity of the 110 plane measured by the wide-angle X-ray scattering method against the azimuth is 30 degrees or less. The upper limit of the half width is preferably 29 degrees, more preferably 28 degrees. When the FWHM of the azimuth angle dependence of the scattering intensity derived from the 110 plane is larger than the above range, the orientation is not sufficient, and the heat resistance and rigidity are not sufficient. The lower limit of the FWHM of the azimuth angle dependence of the scattering intensity derived from the 110 plane is preferably 5 degrees, more preferably 7 degrees, and even more preferably 8 degrees. If the full width at half maximum of the 110 plane is smaller than the above range, impact resistance may be lowered and orientation cracks may occur.

(Wide-angle X-ray diffractometer)
The half width defined in the present invention is preferably measured using X-rays with high parallelism, and radiant light is preferably used.
As an X-ray generation source used for wide-angle X-ray diffraction measurement, a general apparatus such as a tube type or a rotary type used in a laboratory may be used, but a high-intensity light source capable of emitting high-intensity synchrotron radiation. Is preferably used. With synchrotron radiation, X-rays do not spread easily and the brightness is high, so measurements can be performed with high accuracy and in a short time. For example, even a film sample with a thickness of several tens of microns can be measured on a single film without overlapping the films. In addition, since a highly accurate measurement is possible, detailed crystal orientation evaluation is possible. On the other hand, with X-rays with low brightness, when measuring film samples with a thickness of several tens of microns, it takes a long time to measure unless multiple sheets are stacked. Thus, the peak when the scattering intensity of the 110 plane is plotted against the azimuth angle becomes broad, and the obtained half-value width tends to increase.
Large-scale synchrotron radiation facilities such as SPring-8, High Energy Accelerator Research Organization, Aichi Synchrotron Light Center, Saga Kyushu Synchrotron Light Research Center For example, in SPring-8, it is preferable to measure the full width at half maximum of the present invention using a beam line BL03XU owned by the Frontier Soft Matter Development Industry-University Federation (FSBL).

(Long-period structure, small-angle X-ray scattering (SAXS))
In the stretched polypropylene film of the present invention, it is preferable that the long period size is large. Generally, a crystalline polymer has a regular laminated structure (periodic structure) composed of repeating crystals and amorphous. Here, the size of the repeating unit composed of a crystal and an amorphous is called a long period size. The long period size can be obtained from the scattering peak angle derived from the long period structure in the main orientation direction measured by the small angle X-ray scattering method.

The long-period scattering peak by the small-angle X-ray scattering measurement of the stretched polypropylene film of the present invention needs to be clearly observed in the main orientation direction. Here, the main orientation direction indicates a direction in which scattering due to the long period of the polymer crystal is more strongly observed in the two-dimensional X-ray scattering pattern. In the case of uniaxial stretching, the main orientation direction often coincides with the stretching direction. In the case of sequential biaxial stretching of longitudinal stretching and transverse stretching, depending on the respective stretching ratios, the main orientation direction in the transverse stretching direction. Often match. It is shown that a long-period structure with high ordering is formed as the long-period peak attributed to the polymer crystal is clearly observed.

In the stretched polypropylene film of the present invention, the long period size obtained from the long period scattering peak is preferably 40 nm or more. The lower limit of the long period size is more preferably 41 nm, and still more preferably 43 nm. When the long period size is smaller than the above range, the melting peak temperature is low, and thus the heat resistance is not sufficient. The upper limit of the long period size is preferably 100 nm, more preferably 90 nm, and further preferably 80 nm. When the long cycle size is larger than the above range, it takes a long time for crystallization or heat treatment, and thus realistic manufacturing becomes difficult.

(Small angle X-ray diffractometer)
The X-ray generation source used for the small-angle X-ray scattering measurement is not particularly limited, and a general apparatus such as a tube type or a rotary type used in a laboratory can be used. It is preferable to use a high-intensity light source capable of irradiating radiation with high luminance, similar to the X-ray generation source used in the above. In particular, since the stretched polypropylene film of the present invention has a large long period, X-ray scattering derived from the long period structure is in a smaller angle region. Therefore, since it is difficult to measure with a laboratory X-ray apparatus having a large X-ray beam diameter and a short camera length, X-rays are difficult to spread, the beam diameter can be reduced to several hundred microns or less, and It is preferable to measure an ultra-small angle region under a long camera length using synchrotron radiation having high luminance. At this time, the camera length is preferably 7 m or longer.

(Film crystallinity)
The stretched film of the present invention has the following highly crystalline characteristics. For example, the total heat of fusion in the temperature rise measurement with a differential scanning calorimeter (DSC) can be used as an index of crystallinity.
The total heat of fusion corresponds to the melting endothermic peak area measured by a differential scanning calorimeter at a rate of temperature increase of 20 ° C./min. The lower limit of the total heat of fusion is 115 J / g, preferably 117 J / g, more preferably 120 J / g. When the total heat of fusion is smaller than the above range, the degree of crystallinity is not sufficient, and the heat resistance and rigidity are lowered. The upper limit of the total heat of fusion is preferably 150 J / g, more preferably 145 J / g, and even more preferably 140 J / g. When the total heat of fusion is higher than the above range, a high-temperature and long-time manufacturing process is required, and realistic manufacturing may be difficult. The total heat of fusion is, for example, within the above range by a technique such as reducing or not using the amount of copolymerization monomer, increasing stereoregularity, setting the stretching temperature and heat setting temperature to a high temperature, and performing offline annealing. Can be controlled.

Of the melting endothermic peak area, the area of 150 ° C. or lower corresponds to 150 ° C. heat of fusion. In the present invention, the upper limit of the ratio of 150 ° C. heat of fusion and total heat of fusion (150 ° C. heat of fusion / total heat of fusion) obtained as an endothermic peak partial area of 150 ° C. or lower is 0.12, preferably 0.11. Yes, more preferably 0.10. If it is larger than this, the heat resistance at high temperatures may be lowered. The lower limit of the 150 ° C. heat of fusion / total heat of fusion is preferably 0, more preferably 0.005, and even more preferably 0.01. The heat of fusion at 150 ° C. can be controlled by, for example, techniques such as reducing or not using the amount of copolymerization monomer, setting the stretching temperature and heat setting temperature to a high temperature, and performing offline annealing.

In the conventional stretched polypropylene film, even when the melting peak temperature is in the vicinity of 170 ° C., when measured by DSC, the rise of the peak due to the start of melting is recognized from around 140 ° C., and at 140 ° C. Although the heat resistance of can be expected, the thermal shrinkage rate increased rapidly at 150 ° C. However, in the stretched polypropylene film of the present invention, the peak rise is small even at 150 ° C., and it is considered that low heat shrinkability at 150 ° C. is obtained. That is, the stretched polypropylene film of the present invention can maintain various physical properties even when exposed to an environment of 150 ° C. or higher, and should be used even in a high temperature environment that could not be considered with a conventional stretched polypropylene film. Can do. The start of melting can be determined from the DSC curve. FIG. 2 shows the DSC chart of Example 1 as an example of the stretched film of the present invention. *

(Film melting peak temperature)
The lower limit of the melting peak temperature measured with a differential scanning calorimeter at a rate of temperature rise of 20 ° C./min is preferably 165 ° C., more preferably 167 ° C. When the melting peak temperature is within the above range, the thermal shrinkage rate at a high temperature may be small. The upper limit of the melting peak temperature is preferably 180 ° C, more preferably 178 ° C, and further preferably 177 ° C. When the melting peak temperature is within the above range, realistic production may be facilitated. The melting peak temperature is within the above range by, for example, a technique in which the amount of copolymerization monomer is reduced or not used, the stereoregularity is increased, the stretching temperature and the heat setting temperature are set to a high temperature, and offline annealing is performed. Can be controlled within.

(Film physical properties)
The stretched polypropylene film of the present invention exhibits the following physical properties. The following physical properties can be measured and evaluated by, for example, the methods described later in Examples.
(Heat shrinkage)
The stretched polypropylene film of the present invention is a stretched film mainly composed of a polypropylene resin, and preferably has a thermal shrinkage of 10% or less in the MD direction and the TD direction at 150 ° C. Here, the MD direction is a film flow direction (also referred to as a length direction or a longitudinal direction), and a TD direction is a direction perpendicular to the film flow direction (a lateral direction or a width direction). There is also. In the conventional stretched polypropylene film, the 150 ° C. heat shrinkage rate in the MD direction and the TD direction is 15% or more, and the 120 ° C. heat shrinkage rate is about 3%. By setting the heat shrinkage rate to 10% or less, a film having excellent heat resistance can be obtained.

The lower limit of the 150 ° C. heat shrinkage rate in the MD direction and the TD direction of the stretched polypropylene film of the present invention is preferably 0.2%, more preferably 0.3%, still more preferably 0.5%. Yes, particularly preferably 0.7%, most preferably 1.0%. When the 150 ° C. heat shrinkage ratio is in the above range, realistic manufacturing may be facilitated in terms of cost or the like, and thickness unevenness may be reduced. The upper limit of the 150 ° C. heat shrinkage in the MD direction and the TD direction is preferably 10%, more preferably 9%, still more preferably 8%, particularly preferably 7%, and most preferably 5%. %. When the 150 ° C. heat shrinkage ratio is in the above range, it is easier to use in applications and processing that may be exposed to a high temperature of about 150 ° C. If the heat shrinkage at 150 ° C. is up to about 1.5%, for example, it is possible to increase the low molecular weight component, and adjust the stretching conditions and heat setting conditions. It is preferable to perform an annealing treatment offline.

(Impact resistance)
The lower limit of the impact resistance (23 ° C.) of the stretched polypropylene film of the present invention is preferably 0.6 J, more preferably 0.7 J. When the impact resistance is within the above range, the film has sufficient toughness and does not break during handling. The upper limit of impact resistance is preferably 2 J, more preferably 1.8 J, even more preferably 1.6 J, and particularly preferably 1.5 J from the practical viewpoint. For example, when there are many low molecular weight components, when the overall molecular weight is low, when there are few high molecular weight components, and when the molecular weight of the high molecular weight component is low, the impact resistance tends to decrease. By adjusting these components according to the above, it is possible to control within the above range.

(Haze)
The lower limit of the haze of the stretched polypropylene film of the present invention is preferably 0.1% as a practical value, more preferably 0.2%, still more preferably 0.3%, and particularly preferably 0. 4%. The upper limit of haze is preferably 6%, more preferably 5%, still more preferably 4.5%, particularly preferably 4%, and most preferably 3.5%. If the haze is in the above range, it may be easy to use in applications where transparency is required. For example, when the stretching temperature and the heat setting temperature are too high, the haze tends to be deteriorated when the cooling roll (CR) temperature is high and the stretching rate of the stretched raw sheet is slow, or when the low molecular weight is too large. By adjusting, it can control within the said range.

(Young's modulus)
When the stretched polypropylene film of the present invention is a biaxially stretched film, the lower limit of the Young's modulus (23 ° C.) in the MD direction is preferably 2 GPa, more preferably 2.1 GPa, and even more preferably 2.2 GPa. Yes, particularly preferably 2.3 GPa, and most preferably 2.4 GPa. The upper limit of the Young's modulus 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. . When the Young's modulus in the MD direction is within the above range, realistic production may be easy or the MD-TD balance may be improved.

When the stretched polypropylene film of the present invention is a biaxially stretched film, the lower limit of the Young's modulus (23 ° C.) in the TD direction is preferably 3.8 GPa, more preferably 4 GPa, and even more preferably 4.1 GPa. Yes, and particularly preferably 4.2 GPa. The upper limit of the Young's modulus in the TD direction is preferably 8 GPa, more preferably 7.5 GPa, still more preferably 7 GPa, and particularly preferably 6.5 GPa. When the Young's modulus in the TD direction is within the above range, realistic production may be easy or the MD-TD balance may be improved. The Young's modulus can be increased, for example, by increasing the stretching ratio. In the case of MD-TD stretching, the MD stretching ratio is set to a lower value, and the TD stretching ratio is set to a higher value. The Young's modulus of can be increased.

(Thickness uniformity)
The lower limit of the uniformity of the thickness of the stretched polypropylene film of the present invention is preferably 0%, more preferably 0.1%, still more preferably 0.5%, and particularly preferably 1%. The upper limit of the thickness uniformity is preferably 20%, more preferably 17%, still more preferably 15%, particularly preferably 12%, and most preferably 10%. When the thickness uniformity is within the above range, defects are unlikely to occur during post-processing such as coating and printing, and it is easy to use for applications that require precision.

(Film density)
The lower limit of the density of the stretched polypropylene film of the present invention is preferably 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 . When the film density is in the above range, the crystallinity is high and the thermal shrinkage rate may be small. The upper limit of the film density is preferably 0.930 g / cm ³ , more preferably 0.928 g / cm ³ , still more preferably 0.926 g / cm ³ , and particularly preferably 0.925 g / cm ^3. It is. If the film density exceeds the upper limit, production may be difficult in practice. The film density can be increased by increasing the stretching ratio and stretching temperature, increasing the heat setting temperature, and further performing offline annealing.

(Refractive index)
The lower limit of the refractive index (Nx) in the MD direction of the stretched polypropylene film of the present invention is preferably 1.502, more preferably 1.503, and still more preferably 1.504. The upper limit of Nx is preferably 1.520, more preferably 1.517, and even more preferably 1.515.
The lower limit of the refractive index (Ny) in the TD direction of the stretched polypropylene film of the present invention is preferably 1.523, more preferably 1.525. The upper limit of Ny is preferably 1.535, and more preferably 1.532.
The lower limit of the refractive index (Nz) in the thickness direction of the stretched polypropylene film of the present invention is preferably 1.480, more preferably 1.490, and even more preferably 1.500. The upper limit of Nz is preferably 1.510, more preferably 1.507, and even more preferably 1.505.

(Plane orientation coefficient)
The lower limit of the plane orientation coefficient of the stretched 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 plane orientation coefficient is preferably 0.0155, more preferably 0.0150, even more preferably 0.0148, and particularly preferably 0.0145 as a practical value. The plane orientation coefficient can be set within the range by adjusting the draw ratio. When the plane orientation coefficient is within this range, the thickness unevenness of the film is also good.

(Production method of polypropylene resin)
The polypropylene resin is obtained by polymerizing propylene as a raw material using a known catalyst such as a Ziegler-Natta catalyst or a metallocene catalyst. Among these, in order to eliminate heterogeneous bonds, it is preferable to use a Ziegler-Natta catalyst and a catalyst capable of polymerization with high stereoregularity.
As a polymerization method of propylene, a known method may be employed. For example, a method of polymerizing in an inert solvent such as hexane, heptane, toluene, xylene, a method of polymerizing in a liquid monomer, a gas monomer Examples thereof include a method of adding a catalyst and polymerizing in a gas phase state, or a method of polymerizing by combining these.

(Additive)
If necessary, additives and other resins may be added to the film-forming resin composition of the present invention. Examples of the additive include an antioxidant, an ultraviolet absorber, an antistatic agent, a lubricant, a nucleating agent, an adhesive, an antifogging agent, a flame retardant, an antiblocking agent, and an inorganic or organic filler. Examples of the other resin include polypropylene resins other than the polypropylene resin used in the present invention, random copolymers that are copolymers of propylene and ethylene and / or α-olefins having 4 or more carbon atoms, and various elastomers. These are sequentially polymerized using a multistage reactor, blended with a polypropylene resin and a Henschel mixer, or master pellets prepared in advance using a melt kneader are diluted with polypropylene to a predetermined concentration. Alternatively, the entire amount may be melt-kneaded before use.

(Method for producing stretched polypropylene film)
The stretched film of the present invention may be a uniaxially stretched film in the longitudinal direction (MD direction) or the transverse direction (TD direction), but is preferably a biaxially stretched film. In the case of biaxial stretching, sequential biaxial stretching or simultaneous biaxial stretching may be used. In the present invention, by stretching at least uniaxially, it is possible to obtain a film having a low thermal shrinkage even at 150 ° C., which could not be expected with a conventional polypropylene film.

A method for producing a longitudinally-laterally stretched sequential biaxially stretched film which is the most preferred example will be described below.
First, a polypropylene resin is heated and melted with a single or twin screw extruder and extruded onto a chill roll to obtain an unstretched sheet. The melt extrusion conditions are such that the resin temperature is 200 to 280 ° C., the sheet is extruded from a T-die and cooled and solidified with a cooling roll having a temperature of 10 to 100 ° C. Next, the film is stretched 3 to 8 times, preferably 3 to 7 times in the length (MD) direction with a stretching roll at 120 to 165 ° C., and then 155 ° C. to 175 ° C., preferably 158 in the width (TD) direction. The film is stretched 4 to 20 times, preferably 6 to 12 times at a temperature of from 0 to 170 ° C. Furthermore, heat treatment is performed at an ambient temperature of 165 to 175 ° C., preferably 166 to 173 ° C. while allowing relaxation of 1 to 15%. A roll sample can be obtained by subjecting the polypropylene film thus obtained to a corona discharge treatment on at least one surface, if necessary, and then winding it with a winder.

The lower limit of the MD draw ratio is preferably 3 times, more preferably 3.5 times. If the MD draw ratio is less than the above, film thickness unevenness may occur. The upper limit of the MD draw ratio is preferably 8 times, more preferably 7 times. If the MD draw ratio exceeds the above, subsequent TD stretching may be difficult.
The lower limit of the MD stretching temperature is preferably 120 ° C, more preferably 125 ° C, and even more preferably 130 ° C. If the MD stretching temperature is lower than the above, the mechanical load may increase, the thickness unevenness may increase, or the film may become rough. The upper limit of the MD stretching temperature is preferably 165 ° C, more preferably 160 ° C, still more preferably 155 ° C, and particularly preferably 150 ° C. A higher stretching temperature is preferable for lowering the thermal shrinkage, but it may adhere to the roll and cannot be stretched, or surface roughness may occur.

The lower limit of the stretching ratio of TD is preferably 4 times, more preferably 5 times, and further preferably 6 times. If the draw ratio of TD is less than the above, thickness unevenness may occur. The upper limit of the TD stretch ratio is preferably 20 times, more preferably 17 times, still more preferably 15 times, and particularly preferably 12 times. When the draw ratio of TD exceeds the above, the thermal shrinkage rate may be increased or the film may be broken during stretching.
The preheating temperature in TD stretching is preferably set to be 5 to 15 ° C. higher than the stretching temperature in order to quickly raise the film temperature in the vicinity of the stretching temperature.

TD stretching is preferably performed at a higher temperature than a conventional stretched polypropylene film. The lower limit of the TD stretching temperature is preferably 155 ° C, more preferably 157 ° C, and even more preferably 158 ° C. When the stretching temperature of TD is less than the above, it may break without being sufficiently softened or the thermal shrinkage rate may be increased. The upper limit of the TD stretching temperature is preferably 175 ° C, more preferably 170 ° C, and even more preferably 168 ° C. In order to lower the heat shrinkage rate, it is preferable that the TD stretching temperature is higher. However, if the temperature exceeds the above, not only the low molecular weight component is melted and recrystallized, but the orientation is lowered, and the surface roughness and the film are whitened. There are things to do.

The stretched film is usually heat-set. In the present invention, heat setting can be performed at a higher temperature than conventional stretched polypropylene films. The lower limit of the heat setting temperature is preferably 165 ° C, more preferably 166 ° C. When the heat setting temperature is lower than the above, the heat shrinkage rate may be increased. In addition, a long time treatment is required to lower the heat shrinkage rate, and productivity may be inferior. The upper limit of the heat setting temperature is preferably 175 ° C, more preferably 173 ° C. If the heat setting temperature exceeds the above, the low molecular weight component may melt and recrystallize, resulting in surface roughness and whitening of the film.

時には It is preferable to relax when relaxing. The lower limit of relaxation is preferably 2%, more preferably 3%. If the relaxation is less than the above, the heat shrinkage rate may be high. The upper limit of relaxation is preferably 10%, more preferably 8%. When the relaxation is more than the above, thickness unevenness may increase.

Furthermore, in order to reduce the thermal shrinkage rate, the film manufactured in the above process can be once rolled up and then annealed offline. The lower limit of the offline annealing temperature is preferably 160 ° C., more preferably 162 ° C., and further preferably 163 ° C. If the offline annealing temperature is lower than the above, the effect of annealing may not be obtained. The upper limit of the offline annealing temperature is preferably 175 ° C, more preferably 174 ° C, and further preferably 173 ° C. When the off-line annealing temperature exceeds the above, transparency may be reduced or thickness unevenness may be increased.

The lower limit of the offline annealing time is preferably 0.1 minutes, more preferably 0.5 minutes, and even more preferably 1 minute. If the offline annealing time is less than the above, the annealing effect may not be obtained. The upper limit of the offline annealing time is preferably 30 minutes, more preferably 25 minutes, and further preferably 20 minutes. When the offline annealing time exceeds the above, productivity may be reduced.

Although the thickness of the film is set according to each application, the lower limit of the film thickness is preferably 2 μm, more preferably 3 μm, and further preferably 4 μm. The upper limit of the film thickness is preferably 300 μm, more preferably 250 μm, still more preferably 200 μm, further preferably 150 μm, particularly preferably 100 μm, and most preferably 50 μm.

The stretched polypropylene film obtained in this way is usually formed into a film having a width of about 2000 to 12000 mm and a length of about 1000 to 50000 m, and wound into a roll. Furthermore, it is slit according to each application and used as a slit roll having a width of 300 to 2000 mm and a length of about 500 to 5000 m.

The stretched polypropylene film of the present invention has excellent properties such as those described above which are not present in the prior art. When used as a packaging film, it is highly rigid and can be thinned, thereby reducing costs and weight.
In addition, since the stretched polypropylene film of the present invention has high heat resistance, it can be processed at a high temperature during coating and printing, and it is possible to use a coating agent, an ink, a laminating adhesive, or the like, which has been difficult to use conventionally, or production. it can. Furthermore, the stretched polypropylene film of the present invention can be used as an insulating film for capacitors and motors, a back sheet for solar cells, a barrier film for inorganic oxides, and a base film for transparent conductive films such as ITO.

The present application is Japanese Patent Application No. 2013-152929 filed on July 23, 2013, Japanese Patent Application No. 2013-152980 filed on July 23, 2013, July 25, 2013. Japanese Patent Application No. 2013-154673 filed, Japanese Patent Application No. 2013-154673 filed on July 25, 2013, Japanese Patent Application No. 2013- filed on July 29, 2013 No. 157049 and Japanese Patent Application No. 2013-157050 filed on Jul. 29, 2013 are all claimed. Japanese Patent Application No. 2013-152929 filed on July 23, 2013, Japanese Patent Application No. 2013-152980 filed on July 23, 2013, filed on July 25, 2013 Japanese Patent Application No. 2013-154673, Japanese Patent Application No. 2013-154673 filed on July 25, 2013, Japanese Patent Application No. 2013-1557049 filed on July 29, 2013, and The entire contents of Japanese Patent Application No. 2013-157050 filed on July 29, 2013 are incorporated herein by reference.

Hereinafter, the present invention will be described in detail based on examples, but the present invention is not limited to such examples. The measuring method of the physical property in an Example is as follows.

1) Stereoregularity The mesopentad fraction ([mmmm]%) and meso average chain length were measured using ¹³ C-NMR. The mesopentad fraction was determined according to the method described in “Zambelli et al., Macromolecules, Vol. 6, 925 (1973)”, and the meso average chain length was determined according to Chapter 2 of “Polymer Sequence Distribution” by “J. (1977) (Academic Press, New York) ". ^{The 13} C-NMR measurement was performed at 110 ° C. using “AVANCE 500” manufactured by BRUKER, and dissolving 200 mg of the sample in an 8: 2 (volume ratio) mixture of o-dichlorobenzene and heavy benzene at 135 ° C.

2) Xylene solubles (unit: mass%)
1 g of a polypropylene sample is dissolved in 200 ml of boiling xylene, allowed to cool, 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 is determined as the xylene solubles ( Mass%).

3) Melt flow rate (MFR) (unit: g / 10 min)
MFR was measured at a temperature of 230 ° C. and a load of 2.16 kgf in accordance with JIS K7210.

4) Molecular weight and molecular weight distribution The molecular weight and molecular weight distribution were determined on the basis of monodisperse polystyrene using gel permeation chromatography (GPC). The measurement conditions such as the column used and the solvent in GPC measurement are as follows.
Solvent: 1,2,4-trichlorobenzene Column: TSKgel GMH _HR —H (20) HT × 3
Flow rate: 1.0 ml / min
Detector: RI
Measurement temperature: 140 ° C

The number average molecular weight (Mn), the mass average molecular weight (Mw), and the Z + 1 average molecular weight (Mz + 1) are determined by the molecular number (Ni) of the molecular weight (Mi) at each elution position of the GPC curve obtained through the molecular weight calibration curve. It is defined by the following formula.
Number average molecular weight: Mn = Σ (Ni · Mi) / ΣNi
Mass average molecular weight: Mw = Σ (Ni · Mi ² ) / Σ (Ni · Mi)
Z + 1 average molecular weight: Mz + 1 = Σ (Ni · Mi ⁴ ) / Σ (Ni · Mi ³ )
Molecular weight distribution: Mw / Mn
The molecular weight at the peak position of the GPC curve was defined as Mp.
When the baseline was not clear, the baseline was set in the range from the elution peak closest to the elution peak of the standard substance to the lowest position of the bottom of the high molecular weight side.

5) Wide-angle X-ray diffraction In the embodiment of the present invention, in the second hatch of the beamline BL03XU owned by the Frontier Soft Matter Development Industry-University Federation (FSBL) in the large synchrotron radiation facility SPring-8, A measurement film was set so that the angle formed with the film surface was vertical, and wide-angle X-ray (WAXS) measurement was performed. The measurement conditions are shown below.
The X-ray wavelength was 0.1 nm, and the detector was an imaging plate (RIGAKU R-AXIS VII) or a CCD camera with an image intensifier (Hamamatsu Photonics V7739P + ORCA R2). The transmittance was calculated. The obtained two-dimensional image was subjected to air scattering correction in consideration of dark current (dark noise) and transmittance. The camera length was measured using cerium oxide (CeO ₂ ) and Fit 2D (European Synchrotron Radiation Facility software [http://www.esrf.eu/computing/scientific/FIT2D/]) (110) The azimuth profile of was calculated.

6) Long-period size by small-angle X-ray scattering method In the second hatch of the beamline BL03XU owned by the Frontier Soft Matter Development Industry-University Federation (FSBL) in the large synchrotron radiation facility SPring-8, The measurement film was set so that the angle between the X-ray source direction and the film surface was perpendicular with the TD direction as the left and right, and small-angle X-ray (SAXS) measurement was performed. The measurement conditions are shown below.
X-ray wavelength is 0.2 nm, camera length is about 7.7 m, imaging plate (RIGAKU R-AXIS VII) is used as a detector, and scattering vector q is in the range of 0.01 to 0.5 (nm ⁻¹ ). A scattering image of was obtained. Here, the scattering vector q is calculated by the equation q = 4π sin θ / λ, where θ is half of the scattering angle 2θ, π is the circularity, and λ is the wavelength of the X-ray. Air scattering correction was performed on the obtained scattered image in consideration of dark current and transmittance in the same manner as the WAXS measurement, and collagen calibrated separately with silver behenate was used for accurate camera length measurement. . A profile in the width direction of the sample was calculated using the Fit2d software described above, and plotted with the scattering vector q (nm ⁻¹ ) on the horizontal axis and the common logarithm of intensity I (q) on the vertical axis. Here, the calculation range of the profile was ± 5 degrees from the width direction.

7) Differential scanning calorimetry (DSC)
Thermal measurement was performed using a differential scanning calorimeter (“DSC-60” manufactured by Shimadzu Corporation). About 5 mg was cut out from the sample 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./min, and the melting endothermic peak temperature and melting endothermic peak area (total heat of fusion) of the sample were measured. Here, the baseline was set so that the curve smoothly connected at the temperature before and after melting from the end of the endothermic peak to the end of the peak. Of the melting endothermic peak area, the area of 150 ° C. or lower was defined as 150 ° C. heat of fusion.

8) Thermal shrinkage (unit:%)
Measurement was carried out according to JIS Z 1712 by the following method. The stretched film was 20 mm wide and 200 mm long, cut in the MD and TD directions, suspended in a hot air oven at 150 ° C. and heated for 5 minutes. The length after heating was measured, and the ratio (percentage) of the contracted length to the original length was defined as the thermal contraction rate.

9) Young's modulus (unit: GPa)
The Young's modulus in the MD direction and TD direction of the film was measured at 23 ° C. in accordance with JIS K 7127.

10) Impact resistance (Unit: J)
It measured at 23 degreeC using the Toyo Seiki "film impact tester".

11) Thickness uniformity (thickness unevenness) (unit:%)
A square sample having a length of 1 m was cut out from the wound film roll, and divided into 10 parts each in the MD direction and the TD direction, and 100 measurement samples were prepared. The thickness was measured with a contact-type film thickness meter at the approximate center of the measurement sample. The average value A of the obtained 100 points of data was obtained, the difference (absolute value) B between the minimum value and the maximum value was obtained, and the value calculated using the formula of (B / A) × 100 was used as the thickness variation of the film. It was.

12) Haze (Unit:%)
It measured according to JIS K7105.

13) Film density (unit: g / cm ³ )
The density of the film was measured by a density gradient tube method according to JIS K7112.

14) Refractive index (Nx, Ny, Nz)
Measurement was performed using an Abbe refractometer (manufactured by Atago Co., Ltd.). The refractive indexes along the MD and TD directions were Nx and Ny, respectively, and the refractive index in the thickness direction was Nz.

15) Plane orientation coefficient P
Using Nx, Ny, and Nz measured in the above 12), calculation was performed from the formula: P = [(Nx + Ny) / 2] −Nz.

Example 1
As a polypropylene resin, a propylene homopolymer having Mw / Mn = 7.7, Mz + 1 / Mn = 140, MFR = 5.0 g / 10 min, and mesopentad fraction [mmmm] = 97.3% (Nippon Polypro Corp.) “NOVATEC (registered trademark) PP SA4L” manufactured by Kobayashi Co., Ltd .: the amount of copolymerization monomer was 0 mol%;
This polypropylene resin was extruded into a sheet form from a T-die at 250 ° C. using a 60 mm extruder, cooled and solidified with a cooling roll at 30 ° C., and then 4.5 times in the length direction (MD direction) at 135 ° C. Longitudinal stretching, then clipped at both ends, guided into a hot air oven, preheated at 170 ° C, transversely stretched 8.2 times in the transverse direction (TD direction) at 160 ° C, and then relaxed by 6.7% And then heat treated at 168 ° C. Then, the corona treatment was performed on one side of the film, and it was wound up with a winder to obtain the stretched polypropylene film of the present invention.
The thickness of the obtained film was 20 μm. Table 1 shows the structure of the polypropylene constituting the film, and Table 2 shows the film forming conditions. The physical properties of the obtained film are as shown in Table 3. The heat shrinkage rate was low and the Young's modulus was high. Moreover, the chart obtained by the differential scanning calorimetry (DSC) of this film is shown in FIG.

(Example 2)
As a polypropylene resin, a propylene homopolymer (MU / Mn = 8.9, Mz + 1 / Mn = 110, MFR = 3.0 g / 10 min, [mmmm] = 97.1%, “HU300 manufactured by Samsung Sumtal Co., Ltd.) ": The amount of copolymerization monomer is 0 mol%; hereinafter abbreviated as" PP-2 "), the preheating temperature for transverse stretching is 171 ° C, the transverse stretching temperature is 161 ° C, and the heat treatment temperature after transverse stretching is 170 ° C A stretched polypropylene film of the present invention was obtained in the same manner as in Example 1 except that.
The thickness of the obtained film was 20 μm. Table 1 shows the structure of the polypropylene constituting the film, and Table 2 shows the film forming conditions. The physical properties of the obtained film were as shown in Table 3.

Example 3
Low molecular weight propylene having a molecular weight of 10,000 (high wax “NP105” manufactured by Mitsui Chemicals, Inc .: amount of copolymerization monomer is 0 mol%) with respect to 90 parts by mass of the propylene homopolymer (PP-1) used in Example 1 10 parts by mass to make a total of 100 parts by mass, melt kneaded in a 30 mm twin screw extruder, Mw / Mn = 11, Mz + 1 / Mn = 146, MFR = 7.0 g / 10 min, [mmmm] = A pellet of a mixture of 96.5% propylene polymer (hereinafter abbreviated as “PP-3”) was obtained. A stretched polypropylene film of the present invention was obtained in the same manner as in Example 1 except that this pellet was used as a polypropylene resin.
The thickness of the obtained film was 20 μm. Table 1 shows the structure of the polypropylene constituting the film, and Table 2 shows the film forming conditions. The physical properties of the obtained film were as shown in Table 3.

Example 4
A stretched polypropylene film of the present invention was obtained in the same manner as in Example 3 except that the film was stretched 5.5 times in the length direction and 12 times in the transverse direction.
The thickness of the obtained film was 20 μm. Table 1 shows the structure of the polypropylene constituting the film, and Table 2 shows the film forming conditions. The physical properties of the obtained film were as shown in Table 3.

(Example 5)
The stretched polypropylene film produced in Example 1 was heat-treated at 170 ° C. for 5 minutes in a tenter hot air oven to obtain a stretched polypropylene film of the present invention.
The thickness of the obtained film was 20 μm. Table 1 shows the structure of the polypropylene constituting the film, and Table 2 shows the film forming conditions. The physical properties of the obtained film were as shown in Table 3.

(Example 6)
As a polypropylene resin, a propylene homopolymer having Mw / Mn = 4.0, Mz + 1 / Mn = 23, MFR = 6.0 g / 10 min, [mmmm] = 98.7% (the amount of the comonomer is 0 mol%) ; Hereinafter abbreviated as “PP-4”), a stretched polypropylene film of the present invention was obtained in the same manner as in Example 1.
The thickness of the obtained film was 20 μm. Table 1 shows the structure of the polypropylene constituting the film, and Table 2 shows the film forming conditions. The physical properties of the obtained film were as shown in Table 3.

(Comparative Example 1)
As a polypropylene resin, a propylene-ethylene copolymer (Sumitomo Chemical Co., Ltd., “Sumitomo Noblen” (Mw / Mn = 4, Mz + 1 / Mn = 21, MFR = 2.5 g / 10 min, [mmmm] = 97%) (Registered trademark) FS2011DG3 ”: 0.6 mol% copolymer monomer amount; hereinafter abbreviated as“ PP-5 ”), the longitudinal stretching temperature is 125 ° C., the preheating temperature in the transverse stretching is 168 ° C., and the transverse stretching temperature is A stretched polypropylene film was obtained in the same manner as in Example 1 except that the heat treatment temperature after 155 ° C and transverse stretching was 163 ° C.
The thickness of the obtained film was 20 μm. Table 1 shows the structure of the polypropylene constituting the film, and Table 2 shows the film forming conditions. The physical properties of the obtained film were as shown in Table 3. Moreover, the chart obtained by the differential scanning calorimetry (DSC) of this film is shown in FIG.

(Comparative Example 2)
A stretched polypropylene film was obtained in the same manner as in Comparative Example 1 except that the preheating temperature in transverse stretching was 171 ° C, the transverse stretching temperature was 160 ° C, and the heat treatment temperature after transverse stretching was 165 ° C.
The thickness of the obtained film was 20 μm. Table 1 shows the structure of the polypropylene constituting the film, and Table 2 shows the film forming conditions. The physical properties of the obtained film were as shown in Table 3.

(Comparative Example 3)
As a polypropylene resin, propylene homopolymer having Mw / Mn = 4.3, Mz + 1 / Mn = 28, MFR = 0.5 g / 10 min, [mmmm] = 97% (copolymerization monomer amount is 0 mol%; A stretched polypropylene film was obtained in the same manner as in Comparative Example 2, except that “PP-6” was used.
The thickness of the obtained film was 20 μm. Table 1 shows the structure of the polypropylene constituting the film, and Table 2 shows the film forming conditions. The physical properties of the obtained film were as shown in Table 3.

(Comparative Example 4)
As a polypropylene resin, a polypropylene polymer (Mip / Mn = 2.8, Mz + 1 / Mn = 9.2, MFR = 30 g / 10 min, [mmmm] = 97.9%, manufactured by Nippon Polypro Co., Ltd.) A stretched polypropylene film is obtained in the same manner as in Example 1 except that “NOVATEC (registered trademark) PP SA03”: the amount of copolymerization monomer is 0 mol%; hereinafter abbreviated as “PP-7”) is used. However, the film was broken by transverse stretching, and biaxial stretching could not be performed.

The polypropylene film of the present invention can be widely used for packaging applications, industrial applications, and the like, but can be reduced in thickness because of its particularly high rigidity, and cost and weight can be reduced. In addition, since the polypropylene film of the present invention has high heat resistance, it can be processed at a high temperature during coating or printing, and it is possible to use a coating agent, ink, a laminating adhesive, or the like, which has been difficult to use conventionally, or production. it can. Furthermore, the polypropylene film of the present invention is also suitable for insulating films such as capacitors and motors, back sheets for solar cells, barrier films for inorganic oxides, and base films for transparent conductive films such as ITO.

Claims

A stretched polypropylene film characterized by being a stretched film using a propylene polymer satisfying the following requirements (a) to (c) and satisfying the following requirements (d) and (e).
(A) Mesopentad fraction is 96% or more.
(B) The content of comonomer other than propylene is 0.5 mol% or less.
(C) The melt flow rate (MFR) is 0.5 g / 10 min or more and 20 g / 10 min or less.
(D) The half-value width of the maximum peak when the scattering intensity of the 110 plane of the α-type crystal of polypropylene measured by the wide angle X-ray scattering method is plotted against the azimuth is 30 degrees or less.
(E) The melting endothermic peak area (total heat of fusion) measured at a heating rate of 20 ° C./min using a differential scanning calorimeter is 115 J / g or more and an area of 150 ° C. or less (150 ° C. heat of fusion) ) To the total heat of fusion (150 ° C. heat of fusion / total heat of fusion) is 0.12 or less.
The stretched polypropylene film according to claim 1, wherein a long-period size obtained from a long-period scattering peak in a main orientation direction measured by a small-angle X-ray scattering method is 40 nm or more.
3. The stretched polypropylene film according to claim 1, wherein the stretched polypropylene film is stretched at least uniaxially with a thickness of 3 to 100 μm.
The stretched polypropylene film according to any one of claims 1 to 3, wherein the thermal shrinkage in the TD direction at 150 ° C and the thermal shrinkage in the MD direction at 150 ° C are both 10% or less.
The stretched polypropylene film according to any one of claims 1 to 4, wherein the haze is 6% or less.