JP6241039B2 - Stretched polypropylene film - Google Patents

Description

  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, a stretched polypropylene film has been widely used in a wide range of applications such as packaging of 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., has lower heat resistance and lower rigidity than polyethylene terephthalate (PET) and the like, and thus has limited applications.

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, it promotes the formation of a child lamella, improves stretchability, and has excellent mechanical properties, heat resistance, withstand voltage characteristics, and excellent uniformity of physical properties The technique to do is known (refer 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, the films described in Patent Documents 4 to 5 still cannot be said to have sufficient heat resistance at a high temperature exceeding 150 ° C., and have high heat resistance approaching that of a PET film. In addition, a polypropylene film excellent in impact resistance and uniformity has not been known. That is, 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, attention is paid to 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 such prior art problems. 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 this object, the present inventor has found that the mesopentad fraction, the amount of copolymerizable monomers other than propylene, the melt flow rate (MFR), the mass average molecular weight (Mw) / number average molecular weight (Mn), And z + 1 average molecular weight (Mz + 1) / number average molecular weight (Mn) are each controlled to a predetermined range, and the plane orientation coefficient of the film is controlled to a predetermined range, the shrinkage rate and rigidity at 150 ° C. Has been found to be able to be improved to a level equivalent to that of a polyethylene terephthalate (PET) film, and the present invention has been completed.

That is, the stretched polypropylene film of the present invention is characterized in that the polypropylene resin constituting the film satisfies the following conditions 1) to 5), and the lower limit of the plane orientation coefficient of the film is 0.0125.
1) The lower limit of the mesopentad fraction is 96%.
2) The upper limit of the amount of copolymerization monomers other than propylene is 0.1 mol%.
3) The lower limit of the melt flow rate (MFR) measured at 230 ° C. and 2.16 kgf is 1 g / 10 min.
4) The lower limit of the mass average molecular weight (Mw) / number average molecular weight (Mn) is 5.5.
5) The lower limit of z + 1 average molecular weight (Mz + 1) / number average molecular weight (Mn) is 50.

  The stretched polypropylene film of the present invention is preferably biaxially stretched. In that case, the stretch ratio in the longitudinal direction is 3 to 8 times, and the stretch ratio in the width direction is 4 to 20 times. Is preferred.

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. Can be applied to a wide range of uses.

The present invention relates to a stretched polypropylene film excellent in dimensional stability at high temperatures and mechanical properties. The polypropylene resin constituting the stretched polypropylene film of the present invention has the following characteristics with respect to molecular weight distribution, melt flow rate, regularity, and constituent monomers.
(Molecular weight distribution of polypropylene resin)
One of the characteristics of the stretched polypropylene film of the present invention is the molecular weight distribution state of the polypropylene resin to be constituted.
The polypropylene resin constituting the stretched polypropylene film of the present invention mainly contains a low molecular weight component and further contains a high molecular weight component having a very high molecular weight. Crystallinity can be greatly increased by mainly using a low molecular weight component, and it is considered that a highly-stretched and heat-resistant stretched polypropylene film that has not been conventionally obtained is obtained. On the other hand, a low molecular weight polypropylene resin has a low melt tension when softened by heating and cannot generally be a stretched film. The high molecular weight component can be stretched by the presence of several percent to several tens of percent, and the high molecular weight component serves as a crystal nucleus, further increasing the crystallinity of the film, and the effect of the stretched film of the present invention. It is considered to have been achieved.

The polypropylene resin constituting the stretched polypropylene film of the present invention is characterized by a wide molecular weight distribution. In general, the breadth of the molecular weight distribution can be expressed as mass average molecular weight (Mw) / number average molecular weight (Mn).
In the present invention, it is important that the lower limit of Mw / Mn is 5.5. The lower limit of Mw / Mn is preferably 6, more preferably 6.5, still more preferably 7, and particularly preferably 7.2. If it is less than the above, the effects of the present application such as a low thermal shrinkage at high temperatures cannot be obtained. On the other hand, the upper limit of Mw / Mn is preferably 30, more preferably 25, still more preferably 20, particularly preferably 15, and most preferably 13. Exceeding the above may make it difficult to produce a realistic resin.

  An average molecular weight that places importance on high molecular weight components is Z + 1 average molecular weight (Mz + 1), and the degree of molecular weight distribution can be expressed more accurately by Mz + 1 / Mn.

  In the present invention, it is important that the lower limit of Mz + 1 / Mn is 50. The lower limit of Mz + 1 / Mn is preferably 60, more preferably 70, still more preferably 80, and particularly preferably 90. If it is less than the above, the effects of the present application such as a low thermal shrinkage at high temperatures cannot be obtained. On the other hand, the upper limit of Mz + 1 / Mn is preferably 300, more preferably 200. Exceeding the above may make it difficult to produce a realistic resin.

  The lower limit of Mn of the entire polypropylene resin constituting the stretched polypropylene film of the present invention is preferably 20000, more preferably 22000, still more preferably 24000, particularly preferably 26000, and most preferably 27000. . Within the above range, there are advantages that stretching is easy, uneven thickness is reduced, stretching temperature and heat setting temperature are easily increased, and thermal shrinkage is decreased. On the other hand, the upper limit of the total Mn is preferably 65000, more preferably 60000, still more preferably 55000, particularly preferably 53000, and most preferably 52000. Within the above range, the effects of the present application such as a low heat shrinkage rate at a high temperature exhibited by the low molecular weight component can be easily obtained, and stretching can be facilitated.

  The lower limit of Mw of the entire polypropylene resin constituting the stretched polypropylene film of the present invention is preferably 250,000, more preferably 260000, still more preferably 270000, particularly preferably 280000, and most preferably 290000. . Within the above range, there are advantages that stretching is easy, uneven thickness is reduced, stretching temperature and heat setting temperature are easily increased, and thermal shrinkage is decreased. On the other hand, the upper limit of the total Mw is preferably 500,000, more preferably 450,000, still more preferably 400,000, particularly preferably 380000, and most preferably 370000. Within the above range, the mechanical load is small and stretching becomes easy.

  The lower limit of Mz + 1 of the entire polypropylene resin constituting the stretched polypropylene film of the present invention is preferably 2500,000, more preferably 3000,000, still more preferably 3300000, particularly preferably 3500000, and most preferably 3700000. . Within the above range, the high molecular weight component is sufficient, and the effects of the present invention are easily obtained. On the other hand, the upper limit of the total Mz + 1 is preferably 40000000, more preferably 35000000, and further preferably 30000000. Within the above range, realistic resin production is easy, stretching is easy, and fish eyes in the film are reduced.

  Moreover, as an average molecular weight that places importance on the high molecular weight component, there is also a Z average molecular weight (Mz), and the lower limit of Mz / Mn is preferably 30, more preferably 35, still more preferably 38, and particularly preferably. 40, most preferably 41. Within the above range, the effects of the present application such as a low thermal contraction rate at high temperatures are more easily obtained. On the other hand, the upper limit of Mz / Mn is preferably 100. Within the above range, realistic resin production is facilitated.

  The lower limit of Mz of the entire polypropylene resin constituting the stretched polypropylene film of the present invention is preferably 1000000, more preferably 1200000, still more preferably 1300000, particularly preferably 1400000, and most preferably 1500000. . Within the above range, the high molecular weight component is sufficient, and the effects of the present invention are easily obtained. On the other hand, the upper limit of the overall Mz is preferably 15000000. Within the above range, realistic resin production is easy, stretching is easy, and fish eyes in the film are reduced.

  The lower limit of the peak value (Mp) in the molecular weight distribution curve of the polypropylene resin constituting the stretched polypropylene film of the present invention is preferably 50000, more preferably 60000, still more preferably 70000, and particularly preferably 75000. is there. Within the above range, advantages such as easy stretching, reduced thickness unevenness, easy increase in stretching temperature and heat setting temperature, and lower heat shrinkage rate can be obtained. On the other hand, the upper limit of Mp is preferably 150,000, more preferably 130,000, still more preferably 120,000, and particularly preferably 115,000. Within the above range, the effects of the present application such as a low heat shrinkage rate at a high temperature exhibited by the low molecular weight component can be obtained more easily, and stretching can be facilitated.

When the gel permeation chromatography (GPC) integration curve of the entire polypropylene resin constituting the stretched polypropylene film of the present invention is measured, 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 It is 2.5% by mass, more preferably 3% by mass, particularly preferably 3.3% by mass, and most preferably 3.5% by mass. Within the above range, the effects of the present application such as a low thermal shrinkage at a high temperature exhibited by the low molecular weight component can be more easily obtained, and stretching can be facilitated. On the other hand, the upper limit of the amount of the component having a molecular weight of 10,000 or less in the GPC integration curve is preferably 20% by mass, more preferably 17% by mass, still more preferably 15% by mass, and particularly preferably 14% by mass. And most preferably 13% by weight. Within the above range, stretching can be facilitated, thickness spots can be reduced, stretching temperature and heat setting temperature can be easily increased, and the heat shrinkage rate can be further reduced.
Molecules with a molecular weight of about 10,000 or less do not contribute to the entanglement between the molecular chains, and have the effect of loosening the entanglement between the molecules as a plasticizer. The inclusion of a specific amount of a component having a molecular weight of 10,000 or less facilitates the entanglement of molecules during stretching, and enables stretching at a low stretching stress, resulting in low residual stress and low shrinkage at high temperatures. It is considered a thing.

  When the gel permeation chromatography (GPC) integration curve of the entire polypropylene resin constituting the stretched polypropylene film of the present invention 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 It is 38% by mass, 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 exhibited by the low molecular weight component can be easily obtained, and stretching can be facilitated. On the other hand, the upper limit of the amount of the component having a molecular weight of 100,000 or less in the GPC integration curve is preferably 65% by mass, more preferably 60% by mass, still more preferably 58% by mass, and particularly preferably 56% by mass. And most preferably 55% by weight. Within the above range, stretching can be facilitated, thickness spots can be reduced, stretching temperature and heat setting temperature can be easily increased, and the heat shrinkage rate can be further reduced.

  A high molecular weight component and a low molecular weight component suitable for forming a polypropylene resin having such molecular weight distribution characteristics will be described.

[High molecular weight component]
The lower limit of the melt flow rate (MFR) measured at 230 ° C. and 2.16 kgf of the high molecular weight component is preferably 0.0001 g / 10 min, more preferably 0.0005 g / 10 min, and further preferably 0.001 g. / 10 min, particularly preferably 0.005 g / 10 min. Within the above range, it is practically easy to produce the resin, and the fish eyes of the film can be reduced.
The MFR at 230 ° C. and 2.16 kgf of the high molecular weight component may be too small to make practical measurement difficult. In such a case, the high load MFR at 10 times the load (21.6 kgf) may be measured, in which case the preferred lower limit is 0.1 g / 10 min, more preferably 0.5 g / 10 min. More preferably, it is 1 g / 10 min, and particularly preferably 5 g / 10 min.
The upper limit of the melt flow rate (MFR) measured at 230 ° C. and 2.16 kgf of the high molecular weight component is preferably 0.5 g / 10 min, 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. When the amount is within the above range, the amount of the polymer component necessary for maintaining the overall MFR is small, and the effects of the present application such as a low heat shrinkage rate at a high temperature exhibited by the low molecular weight component are more easily obtained.

  The lower limit of Mw of the high molecular weight component is preferably 500,000, more preferably 600,000, still more preferably 700,000, particularly preferably 800,000, and most preferably 1,000,000. When the amount is within the above range, the amount of the polymer component necessary for maintaining the overall MFR is small, and the effects of the present application such as a low heat shrinkage rate at a high temperature exhibited by the low molecular weight component are more easily obtained. On the other hand, the upper limit of Mw of the high molecular weight component is preferably 10000000, more preferably 8000000, still more preferably 6000000, and particularly preferably 5000000. Within the above range, it is practically easy to produce the resin, and the fish eyes of the film can be reduced.

  The lower limit of the intrinsic viscosity (η) of the high molecular weight component is preferably 3 dl / g, more preferably 3.2 dl / g, still more preferably 3.5 dl / g, and particularly preferably 4 dl / g. . When the amount is within the above range, the amount of the polymer component necessary for maintaining the overall MFR is small, and the effects of the present application such as a low heat shrinkage rate at a high temperature exhibited by the low molecular weight component are more easily obtained. On the other hand, the upper limit of the intrinsic viscosity (η) of the high molecular weight component is preferably 15 dl / g, more preferably 12 dl / g, still more preferably 10 dl / g, and particularly preferably 9 dl / g. Within the above range, it is practically easy to produce the resin, and the fish eyes 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 100% by mass of the polypropylene resin. . Within the above range, it is not necessary to increase the molecular weight of the low molecular weight component in order to maintain the overall MFR, and the effects of the present application such as a low heat shrinkage rate at a high temperature can be more easily obtained. On the other hand, the upper limit of the amount of the high molecular weight component is 100% by mass of the polypropylene resin, preferably 30% by mass, more preferably 25% by mass, still more preferably 22% by mass, and particularly preferably 20% by mass. It is. Within the above range, the effects of the present application such as a low heat shrinkage at a high temperature exhibited by the low molecular weight component can be obtained more easily.

[Low molecular weight component]
The lower limit of the melt flow rate (MFR) measured at 230 ° C. and 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. Preferably it is 150 g / 10min, Most preferably, it is 200g / 10min. When the content is in the above range, the crystallinity is improved, and the effects of the present application such as a low heat shrinkage rate at a high temperature are more easily obtained. On the other hand, the upper limit of the melt flow rate (MFR) measured at 230 ° C. and 2.16 kgf of the low molecular weight component is preferably 2000 g / 10 min, more preferably 1800 g / 10 min, and further preferably 1600 g / 10 min. Particularly preferred is 1500 g / 10 min, and most preferred is 1400 g / 10 min. Within the above range, the overall MFR is easily maintained, and the film-forming property is excellent.

  The lower limit of the Mw of the low molecular weight component is preferably 50000, more preferably 53000, still more preferably 55000, particularly preferably 60000, and most preferably 70000. Within the above range, the overall MFR is easily maintained, and the film-forming property is excellent. On the other hand, the upper limit of Mw of the low molecular weight component is preferably 150,000, more preferably 140000, still more preferably 130,000, particularly preferably 120,000, and most preferably 110,000. When the content is in the above range, the crystallinity is improved, and the effects of the present application such as a low heat shrinkage rate at a high temperature are more easily obtained.

  The lower limit of the intrinsic viscosity (η) of the low molecular weight component is preferably 0.46 dl / g, more preferably 0.48 dl / g, still more preferably 0.50 dl / g, and particularly preferably 0.55 dl. / G, most preferably 0.6 dl / g. Within the above range, the overall MFR is easily maintained, and the film-forming property is excellent. On the other hand, the upper limit of the intrinsic viscosity (η) of the low molecular weight component is preferably 1.1 dl / g, more preferably 1.05 dl / g, still more preferably 1 dl / g, and particularly preferably 0.95 dl. / G, most preferably 0.85 dl / g. When the content is in the above range, the crystallinity is improved, and the effects of the present application such as a low heat shrinkage rate at a high temperature are more easily obtained.

  The lower limit of the amount of the low molecular weight component is preferably 30% by mass, more preferably 40% by mass, still more preferably 50% by mass, and particularly preferably 55% by mass in 100% by mass of the polypropylene resin. . Within the above range, the effects of the present application such as a low heat shrinkage at a high temperature exhibited by the low molecular weight component can be obtained more easily. On the other hand, 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 100% by mass of the polypropylene resin. It is. Within the above range, it is not necessary to increase the molecular weight of the low molecular weight component in order to maintain the overall MFR, and the effects of the present application such as a low heat shrinkage rate at a high temperature can be more easily obtained.

  The lower limit of the ratio of low molecular weight component MFR (g / 10 min) / high molecular weight component MFR (g / 10 min) in the polypropylene resin is preferably 500, more preferably 1000, still more preferably 2000, Preferably it is 4000. Within the above range, the effects of the present application such as a low thermal contraction rate at high temperatures are more easily obtained. On the other hand, the upper limit of the low molecular weight component MFR / high molecular weight component MFR ratio is preferably 1,000,000.

The high molecular weight component and the low molecular weight component may be a mixture of two or more resins corresponding to each component, and in this case, the preferred range of the amount of each component described above is the total amount of the two or more resins. .
In addition, the polypropylene resin in the present invention may contain a component having a molecular weight other than the above-described high molecular weight component and low molecular weight component in order to adjust the MFR as the entire polypropylene resin. Further, in order to easily loosen the entanglement of the molecular chains and adjust the stretchability, a polypropylene resin having a molecular weight of the low molecular weight component or less, particularly a molecular weight of about 30,000 or less, and further a molecular weight of about 10,000 or less may be contained. .

  In order to achieve a preferable molecular weight distribution state of a polypropylene resin using a high molecular weight component and a low molecular weight component, for example, when the molecular weight of the low molecular weight component is low, the molecular weight of the high molecular weight component is increased, and the amount of the high molecular weight component is increased. It is preferable to adjust the MFR so that it can be easily manufactured as a stretched film.

(Melt flow rate of polypropylene resin)
It is important that the lower limit of the melt flow rate (MFR) measured at 230 ° C. and 2.16 kgf of the entire polypropylene resin constituting the stretched polypropylene film of the present invention is 1 g / 10 min. The lower limit of the total MFR is preferably 1.2 g / 10 min, more preferably 1.4 g / 10 min, still more preferably 1.5 g / 10 min, and particularly preferably 1.6 g / 10 min. Within the above range, the mechanical load is small and stretching is easy. On the other hand, the upper limit of the total 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, most preferably 8 g / min. 10 min. When it is within the above range, stretching becomes easy, thickness unevenness is reduced, and the stretching temperature and heat setting temperature are easily increased, resulting in a lower thermal shrinkage rate.

(Regularity of polypropylene resin)
It is important that the lower limit of the mesopentad fraction of the polypropylene resin constituting the stretched polypropylene film of the present invention is preferably 96%. The lower limit of the mesopentad fraction is preferably 96.5%, more preferably 97%. Within the above range, the crystallinity is improved, and the thermal shrinkage at high temperatures can be kept low. The upper limit of the mesopentad fraction is preferably 99.5%, more preferably 99.3%, still more preferably 99%. When it is in the above range, realistic production becomes easy.

It is preferable that the heterogeneous bond of the polypropylene resin which comprises the stretched polypropylene film of this invention is not recognized. In addition, not being recognized here means that a peak is not seen by 500 MHz < ¹³ > C-NMR.

  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. On the other hand, 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 is improved and the thermal shrinkage rate at a high temperature is reduced.

  The lower limit of the isotactic chain length of the polypropylene resin constituting the stretched polypropylene film of the present invention is preferably 100, more preferably 120, and still more preferably 130. When it is in the above range, the crystallinity is improved and the thermal shrinkage rate at a high temperature is reduced. On the other hand, the upper limit of the isotactic chain length is preferably 5000 from a practical aspect.

(Component monomer of polypropylene resin)
The polypropylene resin constituting the stretched polypropylene film of the present invention is most preferably a complete homopolypropylene obtained only from a propylene monomer, but may be a copolymer with a copolymer monomer as long as it is in a trace amount. As the copolymerization monomer species, olefins such as ethylene and butene are preferable.

  It is important that the upper limit of the amount of comonomer other than propylene in the polypropylene resin is 0.1 mol%. The upper limit of the amount of copolymerization monomer is preferably 0.05 mol%, more preferably 0.01 mol%. When it is in the above range, the crystallinity is improved and the thermal shrinkage rate at a high temperature is reduced.

  Conventionally, a stretched polypropylene film is industrially produced because of the very narrow range of conditions that can be stretched, such as the high crystallinity of perfect homopolypropylene and the rapid drop in melt tension after melt softening. In general, about 0.5% of a copolymer component (mainly ethylene) was added. However, if the polypropylene resin has a molecular weight distribution as described above, even if it contains little or no copolymerization component, the tension drop after melt softening is moderate, and industrial stretching is possible.

  That is, in the present invention, by using a polypropylene resin having the characteristic molecular weight distribution as described above, it becomes possible to stretch polypropylene mainly composed of low molecular weight components, which could not be sufficiently stretched conventionally. In addition, it is considered that a high heat setting temperature can be adopted, and the heat shrinkage rate at high temperatures can be lowered by the synergistic effect of high crystallinity and strong heat setting.

(Production method of polypropylene resin)
The polypropylene resin is obtained by polymerizing propylene as a raw material using a Ziegler-Natta catalyst, a metallocene catalyst, or the like. In particular, in order to eliminate the heterogeneous bond, it is preferable to use a catalyst capable of highly regular polymerization, such as a Ziegler-Natta catalyst.
As a polymerization method of propylene, a method of polymerizing in an inert solvent such as hexane, heptane, toluene, xylene, a method of polymerizing in liquid propylene or ethylene, a catalyst is added to propylene or ethylene as a gas, The method of superposing | polymerizing in a phase state or the method of superposing | polymerizing combining these is mentioned.
The high molecular weight component and the low molecular weight component may be polymerized separately and then mixed, or may be polymerized in multiple stages in a single plant having a multistage reactor. In particular, a method of using a plant having a multi-stage reactor and polymerizing a low molecular weight component in the presence of the high molecular weight component first is preferable. The molecular weight can be adjusted by the amount of hydrogen mixed in the system during the polymerization.

(Film physical properties)
It is important that the lower limit of the plane orientation coefficient of the stretched polypropylene film of the present invention is 0.0125. The lower limit of the plane orientation coefficient is preferably 0.0126, more preferably 0.0127, and still more preferably 0.0128. On the other hand, the upper limit of the plane orientation coefficient is preferably 0.0155 as a practical value, more preferably 0.0150, still more preferably 0.0148, and particularly preferably 0.0145. The plane orientation coefficient can be set within the range by adjusting the draw ratio. Within this range, the thickness unevenness of the film is also good.

  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. On the other hand, the upper limit of Nx is preferably 1.52, 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. On the other hand, 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.

  The stretched polypropylene film of the present invention is characterized by being highly crystalline. That is, the lower limit of the film crystallinity is preferably 55%, more preferably 56%, still more preferably 57%, particularly preferably 58%, and most preferably 59%. If it is less than the above, the thermal shrinkage at high temperatures may increase. On the other hand, the upper limit of the film crystallinity is preferably 85%, more preferably 80%, still more preferably 79%, particularly preferably 78%, and most preferably 77%. If the above is exceeded, realistic manufacturing may become difficult. The crystallinity of the film is determined by a method such as reducing the amount of copolymerization monomer in the polypropylene resin to 0% by mass, increasing the low molecular weight component, or setting the stretching temperature and heat setting temperature to a high temperature. Can be inside.

  The lower limit of the melting point of the stretched polypropylene film of the present invention is preferably 168 ° C, more preferably 169 ° C. Within the above range, the thermal shrinkage rate at high temperatures is small. On the other hand, the upper limit of the melting point is preferably 180 ° C, more preferably 177 ° C, and further preferably 175 ° C. When it is in the above range, realistic production becomes easy. Melting point: Decrease the amount of copolymerization monomer in polypropylene resin or make it 0% by mass, increase the fraction of mesopentad, decrease the amount of xylene soluble at room temperature, increase the low molecular weight component, stretching temperature, heat setting It can be within the range by a method such as setting the temperature to a high temperature.

Even when the conventional polypropylene film has a melting point peak around 170 ° C., when measured by DSC, a peak rise (beginning of melting) is recognized from around 140 ° C., and at 140 ° C. Although heat resistance could be expected, the heat shrinkage rate increased rapidly at 150 ° C. However, the polypropylene film of the present invention has no peak rise even at 150 ° C., and low heat shrinkability at 150 ° C. is obtained. This is considered to be achieved by using a polypropylene resin with little or no copolymerization component, rapidly generating crystals with a high melting point due to a characteristic molecular weight distribution, and being able to be achieved in combination with a high heat setting temperature. . Furthermore, 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 in a high-temperature environment that has not been considered with conventional polypropylene films.
The melting start can be obtained from the DSC chart. As an example, the DSC chart of the stretched polypropylene film obtained in Example 1 and Comparative Example 1 described later is shown in FIG. In Example 1, a peak rise (melting start) is observed between 150 and 160 ° C. (around 155 ° C.), and in Comparative Example 1, a peak rise (melting start) is observed from around 140 ° C.

  By dividing the heat of fusion obtained as an endothermic peak area of 150 ° C. or higher by 209 J / g, the crystallinity in all samples at 150 ° C. can be obtained. The lower limit of the crystallinity at 150 ° C. of the stretched polypropylene film of the present invention is preferably 48%, more preferably 49%, still more preferably 50%, and particularly preferably 51%. Within the above range, the thermal contraction rate at high temperature becomes smaller. On the other hand, the upper limit of the 150 ° C. crystallinity is preferably 85%, more preferably 80%, still more preferably 79%, and particularly preferably 78%, from a practical viewpoint. The crystallinity at 150 ° C. is within the range by reducing the copolymer monomer amount in the polypropylene resin to 0% by mass, increasing the low molecular weight component, or setting the stretching temperature and heat setting temperature to a high temperature. It can be.

(Film characteristics)
150 ° C. thermal shrinkage rate in the MD direction of the stretched polypropylene film of the present invention (in the present specification, “MD direction” means the longitudinal direction of the film, and “MD direction” may be referred to as “longitudinal direction”). The lower limit is preferably 0.5%, more preferably 1%, still more preferably 1.5%, particularly preferably 2%, and most preferably 2.5%. If it is in the above range, realistic production may be easy in terms of cost or the like, and thickness unevenness may be reduced. On the other hand, the upper limit of the 150 ° C. heat shrinkage rate in the MD direction is preferably 8%, more preferably 7%, still more preferably 6.5%, particularly preferably 6%, and most preferably 5%. %. When it is in the above range, it is easier to use in applications that may be exposed to a high temperature of about 150 ° C.

150 ° C. thermal shrinkage rate in the TD direction of the stretched polypropylene film of the present invention (in the present specification, “TD direction” means the width direction of the film, and “TD direction” may be referred to as “lateral direction”). The lower limit is preferably 0.5%, more preferably 1%, still more preferably 1.5%, particularly preferably 2%, and most preferably 2.5%. If it is in the above range, realistic production may be easy in terms of cost or the like, and thickness unevenness may be reduced. On the other hand, the upper limit of 150 ° C. heat shrinkage in the TD direction is preferably 13%, more preferably 12%, still more preferably 11%, particularly preferably 10%, and most preferably 9%. is there. When it is in the above range, it is easier to use in applications that may be exposed to a high temperature of about 150 ° C.
If the heat shrinkage at 150 ° C is up to about 2.5%, it can be achieved by increasing the low molecular weight component, adjusting the stretching conditions and the fixing conditions. It is preferable to process.

  The lower limit of the impact resistance at room temperature (23 ° C.) of the stretched polypropylene film of the present invention is preferably 0.5 J, more preferably 0.6 J. Within the above range, the film has sufficient toughness and does not break during handling. On the other hand, the upper limit of impact resistance at room temperature (23 ° C.) may be 2J from a practical viewpoint, more preferably 1.5J, and still more preferably 1.2J. Impact resistance tends to decrease 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 high molecular weight components is low. These components can be adjusted to be within the range.

  When the stretched polypropylene film of the present invention is a biaxially stretched film, the lower limit of the Young's modulus in the MD direction at 23 ° C. is preferably 2 GPa, more preferably 2.1 GPa, still more preferably 2.2 GPa, Particularly preferred is 2.3 GPa, and most preferred is 2.4 GPa. On the other hand, the upper limit of the Young's modulus in the MD direction at 23 ° C. is preferably 4 GPa, more preferably 3.7 GPa, still more preferably 3.5 GPa, particularly preferably 3.4 GPa, and most preferably 3 GPa. .3 GPa. When it is in the above range, realistic production is easy, and the MD-TD balance is improved.

When the stretched polypropylene film of the present invention is a biaxially stretched film, the lower limit of the Young's modulus in the TD direction at 23 ° C. is preferably 3.8 GPa, more preferably 4 GPa, still more preferably 4.2 GPa, Particularly preferred is 4.3 GPa. On the other hand, 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 it is in the above range, realistic production is easy, and the MD-TD balance is improved.
The Young's modulus can be increased by increasing the draw ratio. In the case of MD-TD stretching, the MD stretch ratio is set lower, and the Young's modulus in the TD direction is increased by increasing the TD stretch ratio. Can do.

  The lower limit of the thickness uniformity 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%. On the other hand, the upper limit of thickness uniformity is preferably 20%, more preferably 17%, still more preferably 15%, particularly preferably 12%, and most preferably 10%. Within the above range, defects are unlikely to occur during post-processing such as coating and printing, and it is easy to use in applications that require precision. In addition, the thickness uniformity of a film is measured by the method mentioned later in an Example.

  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 0.8%. 4%, most preferably 0.5%. On the other hand, the upper limit of haze is preferably 6%, more preferably 5%, still more preferably 4.5%, particularly preferably 4%, and most preferably 3.5%. When it is in the above range, it becomes easy to use in applications requiring transparency. Haze tends to decrease when the stretching temperature and heat setting temperature are too high, when the CR temperature is high and the cooling rate is slow, or when the low molecular weight is too high, and by adjusting these, it can be within the above range. .

The lower limit of the density of the stretched polypropylene film of the present invention is preferably 0.91 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 . Within the above range, the crystallinity is high and the thermal shrinkage rate may be small. On the other hand, the upper limit of the film density is preferably 0.925 g / cm ^3, more preferably 0.922 g / cm ^3, more preferably from 0.920 g / cm ^3, particularly preferably 0.918 g / cm ³ . In the above range, realistic production may be easy. The film density can be increased by increasing the draw ratio and temperature, increasing the heat setting temperature, and further performing offline annealing.

(Method for producing stretched polypropylene film)
The stretched polypropylene film of the present invention can be produced by forming a film-forming resin composition containing a polypropylene resin into a film by a known method and stretching the resulting unstretched film. By using a stretched film, a film having a low thermal shrinkage rate can be obtained even at 150 ° C., which could not be expected with a conventional polypropylene film.

  The film-forming resin composition contains the above-mentioned polypropylene resin as a main component, but additives and other resins may be added as necessary. 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 other resins include polypropylene resins other than the specific polypropylene resin used in the present invention, random copolymers that are copolymers of ethylene and α-olefin, and various elastomers. It is preferable that the addition amount of an additive and other resin is 50 mass parts or less in total in 100 mass parts of resin compositions for film forming. These are blended with polypropylene resin and Henschel mixer, etc., or master pellets prepared in advance using a melt kneader are diluted with polypropylene to a predetermined concentration, or the entire amount is melt kneaded in advance. be able to.

  Stretching may be uniaxial stretching that stretches in either the longitudinal direction or the width direction of the film, or may be biaxial stretching that stretches in both the longitudinal direction or the width direction. In this case, sequential biaxial stretching or simultaneous biaxial stretching may be used. The stretched polypropylene film of the present invention is preferably a biaxially stretched film.

In the following, a method for producing a film of sequential biaxial stretching of longitudinal stretching and transverse stretching, which is a particularly preferred example, will be described.
First, a polypropylene resin is heated and melted with a monoaxial or biaxial extruder and extruded onto a chill roll to obtain an unstretched film. In the case of melt extrusion, for example, it is preferable to extrude into a sheet form from a T die so that the resin temperature is 200 to 280 ° C., and to cool and solidify with a cooling roll having a temperature of 10 to 100 ° C. Next, for example, the film is stretched 3 to 8 times in the longitudinal (MD) direction with a stretching roll of 120 to 165 ° C., and subsequently 155 ° C. to 175 ° C. (more preferably 158 ° C. to 170 ° C.) in the width (TD) direction. It is preferable to stretch 4 to 20 times at temperature. Further, it is preferable to perform heat treatment while allowing relaxation of 1 to 15% at an atmospheric temperature of preferably 165 to 175 ° C (more preferably 166 to 173 ° C). The stretched polypropylene film thus obtained can be subjected to a corona discharge treatment on at least one side, and then a roll sample can be obtained by winding with a winder.

  The lower limit of the draw ratio in the MD direction is preferably 3 times, more preferably 3.5 times. If it is less than the above, film thickness unevenness may occur. On the other hand, the upper limit of the draw ratio in the MD direction is preferably 8 times, more preferably 7 times. If the above is exceeded, it may be difficult to continue stretching in the TD direction.

  The lower limit of the stretching temperature in the MD direction is preferably 120 ° C, more preferably 125 ° C, and further preferably 130 ° C. If it is less than the above, the mechanical load may be increased, the thickness unevenness may be increased, or the film may be roughened. On the other hand, the upper limit of the stretching temperature in the MD direction is preferably higher in terms of heat shrinkage, but it may be difficult to stretch by adhering to the roll, and is preferably 165 ° C, more preferably 160 ° C. More preferably, it is 155 degreeC, Most preferably, it is 150 degreeC.

  The lower limit of the draw ratio in the TD direction is preferably 4 times, more preferably 5 times, and even more preferably 6 times. If it is less than the above, thickness unevenness may occur. On the other hand, the upper limit of the stretching ratio in the TD direction is preferably 20 times, more preferably 17 times, still more preferably 15 times, and particularly preferably 12 times. If the above is exceeded, the thermal shrinkage rate may be increased or the film may be broken during stretching.

  In the stretching in the TD direction, preheating is preferably performed, and the preheating temperature is preferably set higher by 10 to 15 ° C. than the stretching temperature in order to quickly raise the film temperature in the vicinity of the stretching temperature.

  The stretching in the TD direction is performed at a higher temperature than the conventional polypropylene film. The lower limit of the stretching temperature in the TD direction is preferably 155 ° C, more preferably 157 ° C, and further preferably 158 ° C. If it is less than the above, it may break without being sufficiently softened, or the thermal shrinkage rate may be increased. On the other hand, the upper limit of the stretching temperature in the TD direction is preferably 175 ° C, more preferably 170 ° C, and even more preferably 168 ° C. In order to lower the heat shrinkage rate, the temperature is preferably higher, but if it exceeds the above, the low molecular weight component may melt and recrystallize, and the surface roughness or the film may be whitened.

  The film after stretching is preferably heat-set. The heat setting can be performed 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, the thermal shrinkage rate may increase. In addition, a long heat setting process is required to reduce the heat shrinkage rate, and productivity may be inferior. On the other hand, the upper limit of the heat setting temperature is preferably 175 ° C, more preferably 173 ° C. When the above is exceeded, the low molecular weight component may melt and recrystallize, and the surface roughness and the film may be whitened.

  During heat setting, it is preferable to relax. The lower limit of relaxation is preferably 1%, more preferably 2%, and even more preferably 3%. If it is less than the above, the thermal shrinkage rate may increase. On the other hand, the upper limit of relaxation is preferably 15%, more preferably 10%, and even more preferably 8%. When the above is exceeded, the thickness unevenness may increase.

Furthermore, in order to reduce the heat shrinkage rate, the film manufactured in the above process can be once wound up in a roll shape 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 it is less than the above, the effect of annealing may not be obtained. On the other hand, the upper limit of the offline annealing temperature is preferably 175 ° C, more preferably 174 ° C, and further preferably 173 ° C. When the above is exceeded, the transparency may decrease, or the thickness unevenness may increase.

  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 it is less than the above, the effect of annealing may not be obtained. On the other hand, the upper limit of the offline annealing time is preferably 30 minutes, more preferably 25 minutes, and further preferably 20 minutes. When the above is exceeded, productivity may be reduced.

  Although the thickness of a film is set according to each use, the minimum of film thickness becomes like this. Preferably it is 2 micrometers, More preferably, it is 3 micrometers, More preferably, it is 4 micrometers. The upper limit of the film thickness is preferably 300 μm, more preferably 250 μm, still more preferably 200 μm, particularly preferably 100 μm, and most preferably 50 μm.

  The stretched polypropylene film thus obtained is usually formed as a roll 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 is provided 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 that are not present in the past. Therefore, when it is used as a packaging film, it is highly rigid, so that it can be thinned, and cost and weight can be reduced. In addition, since it has high heat resistance, it can be dried at a high temperature during drying of a coat or 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 has been difficult to use. Furthermore, it can also 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. 2012-12117 filed on January 24, 2012, Japanese Patent Application No. 2012-146801 filed on June 29, 2012, and August 17, 2012. Claims the benefit of priority based on Japanese Patent Application No. 2012-180971 filed in. Japanese Patent Application No. 2012-12117 filed on January 24, 2012, Japanese Patent Application No. 2012-146801 filed on June 29, 2012, and August 17, 2012 The entire contents of the specification of Japanese Patent Application No. 2012-180971 are incorporated herein by reference.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited by the following examples and the like, and is appropriately within a range that can meet the above and the following purposes. Of course, it is possible to carry out with modifications, and these are all included in the technical scope of the present invention.
In addition, the measuring method of the physical property in a following example and a comparative example is as follows.

(1) Melt flow rate (MFR) (g / 10 min)
MFR was measured at a temperature of 230 ° C. in accordance with JIS-K7210.
(2) Intrinsic viscosity (η) (dl / g)
The intrinsic viscosity was measured at 135 ° C. by dissolving the sample in tetralin according to JIS K7367-1: 2002.

(3) 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), the Z average molecular weight (Mz), and the Z + 1 average molecular weight (Mz + 1) are molecular weights (Mi) at the respective elution positions of the GPC curve obtained through the molecular weight calibration curve. It is defined by the following formula by the number of molecules (Ni).
Number average molecular weight: Mn = Σ (Ni · Mi) / ΣNi
Mass average molecular weight: Mw = Σ (Ni · Mi ² ) / Σ (Ni · Mi)
Z average molecular weight: Mz = Σ (Ni · Mi ³ ) / Σ (Ni · Mi ² )
Z + 1 average molecular weight: Mz + 1 = Σ (Ni · Mi ⁴ ) / Σ (Ni · Mi ³ )
Molecular weight distribution: Mw / Mn, Mz + 1 / Mn, Mz / 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.

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

(5) Density (g / cm ³ )
The density of the film was measured by a density gradient tube method according to JIS-K7112.

(6) Melting point (Tmp) (° C.), crystallinity (%) and 150 ° C. crystallinity (%)
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 of the sample was defined as the melting point Tmp. The degree of crystallinity is H.264. Bu, S .; Z. D. Cheng, B.M. The melting peak area obtained by the above thermal measurement with the heat of fusion of 209 J / g of the complete polypropylene crystal described in Wiederich et al., Die Makromolekulare Chemie, Rapid Communications, Vol. 9, page 75 (1988) as 100%. It calculated | required by showing the ratio of the heat of fusion of the DSC melting profile calculated | required from ((DELTA) Hm) in percentage. The 150 ° C. crystallinity was determined from the heat of fusion of 150 ° C. or higher in the DSC melting profile.

(7) Cold xylene soluble part (CXS) (mass%)
Dissolve 1 g of polypropylene sample in 200 ml of boiling xylene, allow to cool, recrystallize in a constant temperature water bath at 20 ° C. for 1 hour, and calculate the ratio of the mass dissolved in the filtrate to the original sample amount by CXS (mass%) It was.

(8) Thermal shrinkage (%)
It measured based on JIS-Z1712. That is, the stretched film was cut in the MD direction and the TD direction with a length of 20 mm and a length of 200 mm, respectively, suspended in a hot air oven and heated for 5 minutes. The length after heating was measured, and the thermal contraction rate was determined by the ratio of the contracted length to the original length.

(9) Impact resistance (J)
It measured at 23 degreeC using the Toyo Seiki film impact tester.

(10) Young's modulus (GPa)
Based on JIS-K7127, the tensile strength of MD direction and TD direction was measured at 23 degreeC.

(11) Haze (%)
It measured according to JIS-K7105.

(12) 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.
(13) Plane orientation coefficient It calculated using the formula of [(Nx + Ny) / 2] -Nz from Nx, Ny, and Nz measured by said (12).

(14) Thickness unevenness (thickness uniformity) (%)
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 of the substantially central portion of the measurement sample was measured with a contact-type film thickness meter. Then, the average value A of the obtained 100 points of data was obtained, and 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 obtained. Thick spots.

Example 1
As a polypropylene resin, a polypropylene homopolymer with Mw / Mn = 7.7, Mz + 1 / Mn = 140, MFR = 5.0 g / 10 min, mesopentad fraction [mmmm] = 97.3% (manufactured by Nippon Polypro Co., Ltd.) “NOVATEC (registered trademark) PP SA4L”: the amount of copolymerization monomer was 0 mol%; hereinafter abbreviated as “PP-1”) was used.
This polypropylene resin was extruded into a sheet form from a T-die at 250 ° C using a 65 mm extruder, cooled and solidified with a cooling roll at 30 ° C, and then longitudinally (lengthwise) 4.5 times longer at 135 ° C. Stretched, then clipped at both ends, led into a hot air oven, preheated at 170 ° C., then transversely stretched 8.2 times in the width direction (lateral direction) at 160 ° C., then 6.7 in the width direction % Heat treatment at 168 ° C. while relaxing. One side of the film thus obtained was subjected to corona treatment and wound up with a winder to obtain the stretched polypropylene film of the present invention.
The thickness of the obtained film was 20 μm, and the physical properties were as shown in Table 1, Table 2, and Table 3. From the results of the table, it can be seen that this film has a low thermal shrinkage and a high Young's modulus. Moreover, the chart obtained by the differential scanning calorimetry (DSC) of this film is shown in FIG.

(Example 2)
Low molecular weight propylene homopolymer having a narrow molecular weight distribution and a viscosity average molecular weight of 10,000 (90% by weight of the polypropylene homopolymer (PP-1) used in Example 1 (“High Wax NP105” manufactured by Mitsui Chemicals, Inc.): Except that the amount of copolymerization monomer is 0 mol%) and 10 parts by mass of the pelletized mixture (PP-2) obtained by melt kneading in a 30 mm twin screw extruder is used as the polypropylene resin. In the same manner as in Example 1, a stretched polypropylene film of the present invention was obtained.
The thickness of the obtained film was 20 μm, and the physical properties were as shown in Table 1, Table 2, and Table 3. From the results of the table, it can be seen that this film has a low thermal shrinkage and a high Young's modulus.

(Example 3)
Mw / Mn = 4.6, Mz + 1 / Mn = 22, MFR = 120 g / 10 min, mesopentad fraction [mmmm] = 98 with respect to 70 parts by mass of the polypropylene homopolymer (PP-1) used in Example 1. 30% by weight of a polypropylene homopolymer (“Sumitomo Nobrene (registered trademark) U501E1” manufactured by Sumitomo Chemical Co., Ltd .: the amount of copolymerized monomer is 0 mol%) of 1% and dry blended (PP- A stretched polypropylene film of the present invention was obtained in the same manner as in Example 1 except that 3) was used as a polypropylene resin.
The thickness of the obtained film was 20 μm, and the physical properties were as shown in Table 1, Table 2, and Table 3. From the results of the table, it can be seen that this film has a low thermal shrinkage and a high Young's modulus.

Example 4
In Example 1, the stretched polypropylene film of the present invention was obtained in the same manner as in Example 1 except that the preheating temperature in transverse stretching was 173 ° C., and the stretching temperature and heat treatment temperature were 167 ° C.
The thickness of the obtained film was 20 μm, and the physical properties were as shown in Table 1, Table 2, and Table 3. From the results of the table, it can be seen that this film has a low thermal shrinkage and a high Young's modulus.

(Example 5)
In Example 2, the stretched polypropylene film of the present invention was obtained in the same manner as in Example 2 except that the film was stretched 5.5 times in the longitudinal direction (length direction) and 12 times in the width direction (lateral direction). .
The thickness of the obtained film was 20 μm, and the physical properties were as shown in Table 1, Table 2, and Table 3. From the results of the table, it can be seen that this film has a low thermal shrinkage and a high Young's modulus.

(Example 6)
The stretched polypropylene film obtained in Example 1 was further heat-treated at 170 ° C. for 5 minutes in a tenter hot air oven.
The thickness of the obtained film was 20 μm, and the physical properties were as shown in Table 1, Table 2, and Table 3.

(Example 7)
As a polypropylene resin, a polypropylene homopolymer having a Mw / Mn = 8.9, Mz + 1 / Mn = 110, MFR = 3.0 g / 10 min, and a mesopentad fraction [mmmm] = 97.2% (“HU300 manufactured by Samsung Central Co., Ltd.) The amount of copolymerization monomer is 0 mol%), 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. The stretched polypropylene film of the present invention was obtained.
The thickness of the obtained film was 20 μm, and the physical properties were as shown in Table 1, Table 2, and Table 3.

(Comparative Example 1)
As a polypropylene resin, a polypropylene polymer having Mw / Mn = 4, Mz + 1 / Mn = 21, MFR = 2.5 g / 10 min (“Sumitomo Nobrene (registered trademark) FS2011DG3” manufactured by Sumitomo Chemical Co., Ltd.): amount of copolymerization monomer Is 0.6 mol%), and the stretched polypropylene film for comparison was prepared in the same manner as in Example 1 except that the preheating temperature in transverse stretching was 168 ° C, the stretching temperature was 155 ° C, and the heat treatment temperature was 163 ° C. Obtained.
The thickness of the obtained film was 20 μm, and the physical properties were as shown in Table 1, Table 2, and Table 3. Moreover, the chart obtained by the differential scanning calorimetry (DSC) of this film is shown in FIG.

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

(Comparative Example 3)
As a polypropylene resin, a polypropylene polymer having Mw / Mn = 2.8, Mz + 1 / Mn = 9.2, MFR = 30 g / 10 min (“Novatech (registered trademark) PP SA03” manufactured by Nippon Polypro Co., Ltd.): copolymerization An attempt was made to obtain a stretched polypropylene film in the same manner as in Example 1 except that the amount of the monomer was 0 mol%). However, the film was broken by the transverse stretch and could not be biaxially stretched.

The stretched polypropylene film of the present invention can be widely used in packaging applications and industrial applications, but is particularly suitable for applications where cost reduction and weight reduction are required because it is highly rigid and can be thinned.
In addition, the stretched polypropylene film of the present invention has high heat resistance and can be dried at a high temperature at the time of drying when coating treatment or printing is performed, so that production efficiency can be improved and coating agents and inks that have been difficult to adopt conventionally are used. A treatment using a laminate adhesive or the like can be applied.
Furthermore, the stretched 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, base films for transparent conductive films such as ITO, and the like.

2 is a differential scanning calorimetry (DSC) chart for the stretched polypropylene film obtained in Example 1 and Comparative Example 1. FIG.

Claims (5)

A stretched polypropylene film, wherein the polypropylene resin constituting the film satisfies the following conditions 1) to 6), and the lower limit of the plane orientation coefficient of the film is 0.0125.
1) The lower limit of the mesopentad fraction is 96%.
2) The upper limit of the amount of copolymerization monomers other than propylene is 0.1 mol%.
3) The lower limit of the melt flow rate (MFR) measured at 230 ° C. and 2.16 kgf is 1 g / 10 min.
4) The lower limit of the mass average molecular weight (Mw) / number average molecular weight (Mn) is 5.5.
5) The lower limit of z + 1 average molecular weight (Mz + 1) / number average molecular weight (Mn) is 50.
6) The lower limit of z + 1 average molecular weight (Mz + 1) is 2500,000. 2. The stretched polypropylene film according to claim 1, wherein the lower limit of the amount of a component having a molecular weight of 100,000 or less is 35 mass% when a gel permeation chromatography (GPC) integration curve of the entire polypropylene resin constituting the stretched polypropylene film is measured. .   The stretched polypropylene film according to claim 1 or 2, wherein the upper limit of the plane orientation coefficient of the film is 0.0155.   The stretched polypropylene film according to any one of claims 1 to 3, which is biaxially stretched.   The stretched polypropylene film according to claim 4, wherein a stretch ratio in the longitudinal direction is 3 to 8 times, and a stretch ratio in the width direction is 4 to 20 times.