KR101986868B1

KR101986868B1 - Stretched polypropylene film

Info

Publication number: KR101986868B1
Application number: KR1020147022521A
Authority: KR
Inventors: 오사무 기노시타; 히로카즈 오키; 고우지 야마다; 아츠시 다가
Original assignee: 도요보 가부시키가이샤
Priority date: 2012-01-24
Filing date: 2013-01-23
Publication date: 2019-06-07
Also published as: KR20140119117A; CN104105746A; TWI631151B; CN104105746B; WO2013111779A1; TW201339219A; JP6241039B2; HK1198701A1; JP2014055276A

Abstract

A stretched polypropylene film having a low shrinkage ratio comparable to that of polyethylene terephthalate (PET) at 150 DEG C and being high in strength. In the stretched polypropylene film, 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 meso pentad fraction is 96%.
2) The upper limit of the amount of copolymerized 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 the z + 1 average molecular weight (Mz + 1) / number average molecular weight (Mn) is 50.

Description

Stretched polypropylene film [0002]

The present invention relates to a stretched polypropylene film. And more particularly to a stretched polypropylene film excellent in heat resistance and mechanical properties, which can be suitably used in various fields requiring dimensional stability at a high temperature and high rigidity.

Background Art [0002] Conventional polypropylene stretched films have been widely used for a wide variety of applications such as packaging for food products and various products, electric insulation, and surface protective films. However, the conventional polypropylene film has a shrinkage rate at a temperature of 150 캜 of several tens% and has a limited use because it has low heat resistance and low rigidity as compared with polyethylene terephthalate (PET) and the like.

However, various techniques for improving the physical properties of the polypropylene film have been proposed. For example, there is known a technique of forming a stretched film having high stereoregularity and using a polypropylene having a narrow molecular weight distribution to obtain a film having high temperature rigidity and heat resistance (see Patent Document 1).

Further, there is known a technology in which polypropylene having a high stereoregularity and having a wide molecular weight distribution can be used as a stretched film and thus can be suitably used as a capacitor film having excellent electrical insulation and mechanical characteristics (see Patent Document 2).

Furthermore, there is known a technique of making a separator film using polypropylene having a low molecular weight and a soluble fraction of 0 占 폚 in a specific range at a temperature elevation fractionation method, and this film is considered to have excellent dimensional stability in a drying step and a printing step (See Patent Document 3).

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

There is also known a technique of forming a film having excellent mechanical properties, heat resistance and withstand voltage characteristics and excellent uniformity of physical properties by promoting the formation of a lamellar structure by improving the stretchability by adding a minute amount of a long chain branch or crosslinked polypropylene Patent Document 4).

In addition, it is also said that a film made of polypropylene containing almost the same amount of a high molecular weight component and a low molecular weight component (or having a low molecular weight component), a broad molecular weight distribution and a small amount of decalin soluble component is used to balance the rigidity and workability (See Patent Document 5).

However, the films described in Patent Documents 4 to 5 can not be said to have sufficient heat resistance at a high temperature exceeding 150 占 폚, so that they have high heat resistance close to the PET film, excellent productivity and excellent impact resistance and uniformity No good polypropylene film was known. That is, the films described in Patent Documents 4 to 5 do not exceed the range of the conventional polypropylene film, and their use is limited. For example, no consideration has been given to the heat resistance at a high temperature exceeding 150 캜.

Japanese Patent Application Laid-Open No. 8-325327 Japanese Patent Application Laid-Open No. 2004-175932 Japanese Patent Application Laid-Open No. 2001-146536 Japanese Patent Application Laid-Open No. 2007-84813 Japanese Patent Publication No. 2008-540815

SUMMARY OF THE INVENTION The present invention has been made in view of the above 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 a polyethylene terephthalate (PET) film at 150 DEG C and high rigidity.

(MFR), mass-average molecular weight (Mw) / number-average molecular weight (Mn), and z + weight average molecular weight (Mn) (Mz + 1) / number average molecular weight (Mn) of the polypropylene resin controlled to a predetermined range, and the surface orientation coefficient of the film is controlled to fall within a predetermined range, the shrinkage rate and rigidity Can be improved to a level equivalent to that of a polyethylene terephthalate (PET) film, and the present invention has been completed.

That is, the oriented polypropylene film of the present invention is characterized in that the polypropylene resin constituting the film satisfies the following conditions 1) to 5), and that the lower limit of the plane orientation coefficient of the film is 0.0125.

1) The lower limit of the meso pentad fraction is 96%.

2) The upper limit of the amount of copolymerized 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 the z + 1 average molecular weight (Mz + 1) / number average molecular weight (Mn) is 50.

The stretched polypropylene film of the present invention is preferably one obtained by biaxial stretching. In this case, the stretching ratio in the longitudinal direction is preferably 3 to 8 times, and the stretching ratio in the transverse direction is preferably 4 to 20 times.

According to the stretched polypropylene film of the present invention, it is possible to exhibit a low shrinkage ratio and high rigidity comparable to that of a polyethylene terephthalate (PET) film at 150 ° C, and further to thin films.

Further, since the stretched polypropylene film of the present invention can maintain its physical properties even when exposed to an environment of 150 ° C or higher, it can be used in a high temperature environment that can not be expected in conventional polypropylene films, and can be applied to a wide range of applications It becomes.

Fig. 1 is a differential scanning calorimetry (DSC) chart of a 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 and mechanical properties at a high temperature. The polypropylene resin constituting the stretched polypropylene film of the present invention has the following characteristics with regard to the molecular weight distribution, the melt flow rate, the regularity, and the constituent monomers.

(Molecular weight distribution of polypropylene resin)

One of the characteristics of the stretched polypropylene film of the present invention resides in the molecular weight distribution of the constituent polypropylene resin.

The polypropylene resin constituting the oriented 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. It is considered that the crystallinity can be largely increased by mainly using a low molecular weight component and a stretched polypropylene film of high rigidity and high heat resistance which has not been conventionally obtained is obtained. On the other hand, the low molecular weight polypropylene resin has a low melt tension in the case of heat softening and can not generally be a stretched film. It is believed that the presence of a high molecular weight component in an amount of several percent to several tens of percent enables the stretching and that the high molecular weight component plays a role of crystal nuclei and further increases the crystallinity of the film to achieve the effect of the stretched film of the present invention do.

The polypropylene resin constituting the stretched polypropylene film of the present invention is first characterized by having a broad molecular weight distribution. Generally, the range 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 the 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 range, the effect of the present invention such as a low heat shrinkage rate at a high temperature can not 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. If it exceeds the above range, it may become difficult to produce a realistic resin.

The average molecular weight with an emphasis on high molecular weight components has a Z + 1 average molecular weight (Mz + 1), and the degree of molecular weight distribution can be more accurately represented 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, even more preferably 80, and particularly preferably 90. If it is less than the above range, the effect of the present invention such as a low heat shrinkage rate at a high temperature can not be obtained. On the other hand, the upper limit of Mz + 1 / Mn is preferably 300, more preferably 200. If it exceeds the above range, it may become difficult to produce a realistic resin.

The lower limit of Mn of the entire polypropylene resin constituting the oriented polypropylene film of the present invention is preferably 20,000, more preferably 22,000, still more preferably 24,000, particularly preferably 26,000, and most preferably, 27,000. Within this range, the stretching becomes easy, the thickness variation becomes small, and the stretching temperature and the heat fixing temperature can easily be increased, and the heat shrinkage rate is advantageously lowered. On the other hand, the upper limit of the total Mn is preferably 65,000, more preferably 60,000, still more preferably 55,000, particularly preferably 53,000, and most preferably 52,000. Within this range, the effect of the present invention such as a low heat shrinkage at a high temperature represented by a low molecular weight component can be easily obtained or the stretching can be facilitated.

The lower limit of the Mw of the entire polypropylene resin constituting the stretched polypropylene film of the present invention is preferably 250,000, more preferably 260,000, still more preferably 270,000, particularly preferably 280,000, and most preferably, 290,000. Within this range, the stretching becomes easy, the thickness variation becomes small, and the stretching temperature and the heat fixing temperature can easily be increased, and the heat shrinkage rate is advantageously lowered. 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 380,000, and most preferably 370,000. If it is in the above range, the mechanical load is small and the 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 2,500,000, more preferably 3,000,000, still more preferably 3,300,000, particularly preferably 3,500,000, and most preferably It is 3,700,000. Within this range, high molecular weight components are sufficient, and the effect of the present invention is easily obtained. On the other hand, the upper limit of the total Mz + 1 is preferably 40,000,000, more preferably 35,000,000, and even more preferably 30,000,000. If it is in the above-mentioned range, it is easy to produce a realistic resin, easy to stretch, or less fish eyes in the film.

The average molecular weight with an emphasis on high molecular weight components also has a Z average molecular weight (Mz). The lower limit of Mz / Mn is preferably 30, more preferably 35, further preferably 38, particularly preferably 40 , And most preferably < RTI ID = 0.0 > 41. Within this range, the effect of the present invention such as a low heat shrinkage at high temperature can be more readily obtained. On the other hand, the upper limit of Mz / Mn is preferably 100. Within this range, it is easy to produce a realistic resin.

The lower limit of Mz of the entire polypropylene resin constituting the stretched polypropylene film of the present invention is preferably 1,000,000, more preferably 1,200,000, still more preferably 1,300,000, particularly preferably 1,400,000, and most preferably, 1,500,000. Within this range, high molecular weight components are sufficient, and the effect of the present invention is easily obtained. While the upper limit of the total Mz is preferably 15,000,000. If it is in the above-mentioned range, it is easy to produce a realistic resin, easy to stretch, or less fish eyes in the film.

The lower limit of the peak value (Mp) in the molecular weight distribution curve of the polypropylene resin constituting the oriented polypropylene film of the present invention is preferably 50,000, more preferably 60,000, still more preferably 70,000, Is 75,000. Within this range, an advantage is obtained in that the stretching is facilitated, the thickness variation is reduced, or the stretching temperature and the heat fixing temperature are easily increased and the heat shrinkage ratio is further lowered. 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 this range, the effect of the present invention such as a low heat shrinkage at a high temperature represented by a low molecular weight component is more easily obtained, and the stretching is 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, Is 2.5% by mass, more preferably 3% by mass, particularly preferably 3.3% by mass, and most preferably 3.5% by mass. Within this range, the effect of the present invention such as a low heat shrinkage rate at a high temperature represented by a low molecular weight component can be easily obtained or the 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 integrated curve is preferably 20% by mass, more preferably 17% by mass, still more preferably 15% by mass, and particularly preferably 14% , And most preferably 13 mass%. Within this range, the stretching can be facilitated, the thickness variation can be reduced, or the stretching temperature and the heat fixing temperature can easily be increased, and the heat shrinkage can be suppressed to be lower.

Molecules having a molecular weight of about 10,000 or less do not contribute to the entanglement of molecular chains, but have the effect of solving entanglement between molecules in a plasticizer. The inclusion of molecules at the time of stretching is easily released and the stretching at a low stretching stress can be performed by incorporating a specific amount of the component having a molecular weight of 10,000 or less so that the residual stress is low and the shrinkage rate at high temperature can be made low do.

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, Is preferably 38% by mass, more preferably 40% by mass, particularly preferably 41% by mass, and most preferably 42% by mass. Within this range, the effect of the present invention such as a low heat shrinkage at a high temperature represented by a low molecular weight component can be easily obtained or the 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 integrated curve is preferably 65% by mass, more preferably 60% by mass, still more preferably 58% by mass, and particularly preferably 56% , And most preferably 55 mass%. Within this range, the stretching can be facilitated, the thickness variation can be reduced, or the stretching temperature and the heat fixing temperature can easily be increased, and the heat shrinkage can be suppressed to be lower.

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

[High molecular weight component]

The lower limit of the melt flow rate (MFR) of the high molecular weight component measured at 230 캜 and 2.16 kgf is preferably 0.0001 g / 10 min, more preferably 0.0005 g / 10 min, still more preferably 0.001 g / 10 min min, and particularly preferably 0.005 g / 10 min. If it is within the above-mentioned range, it is possible to easily manufacture the resin or reduce the fish eye of the film in reality.

In addition, the MFR of the high molecular weight component at 230 DEG C and 2.16 kgf is too small to make realistic measurement difficult. In such a case, the high load MFR at a load of 10 times (21.6 kgf) may be measured. In this case, the lower limit is preferably 0.1 g / 10 min, more preferably 0.5 g / 10 min, / 10 min, and particularly preferably 5 g / 10 min.

The upper limit of the melt flow rate (MFR) of the high molecular weight component measured at 230 占 폚 at 2.16 kgf is preferably 0.5 g / 10 min, more preferably 0.35 g / 10 min, still more preferably 0.3 g / 10 min min, particularly preferably 0.2 g / 10 min, and most preferably 0.1 g / 10 min. In the above range, since the amount of the polymer component required to maintain the total MFR is small, the effect of the present invention such as a low heat shrinkage at a high temperature exhibited by the low molecular weight component is more easily obtained.

The lower limit of the 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. In the above range, since the amount of the polymer component required to maintain the total MFR is small, the effect of the present invention such as a low heat shrinkage at a high temperature exhibited by the low molecular weight component is more easily obtained. On the other hand, the upper limit of the Mw of the high molecular weight component is preferably 10,000,000, more preferably 8,000,000, still more preferably 6,000,000, and particularly preferably 5,000,000. If it is within the above-mentioned range, it is possible to easily manufacture the resin or reduce the fish eye of the film in reality.

The lower limit of the intrinsic viscosity (?) Of the high molecular weight component is preferably 3 dl / g, more preferably 3.2 dl / g, still more preferably 3.5 dl / g, particularly preferably 4 dl / g . In this range, since the amount of the polymer component necessary to maintain the MFR of the whole is small, the effect of the present invention such as a low heat shrinkage at a high temperature represented by a low molecular weight component is more easily obtained. On the other hand, the upper limit of the intrinsic viscosity (?) Of the high molecular weight component is preferably 15 dl / g, more preferably 12 dl / g, still more preferably 10 dl / g, particularly preferably 9 dl / to be. If it is within the above-mentioned range, it is possible to easily manufacture the resin or reduce the fish eye of the film in reality.

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. If 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 MFR of the whole, and the effect of the present invention such as low heat shrinkage at high temperature can be more easily obtained. On the other hand, the upper limit of the amount of the high molecular weight component is preferably 30% by mass, more preferably 25% by mass, still more preferably 22% by mass, and particularly preferably 20% by mass in 100% by mass of the polypropylene resin . Within this range, the effect of the present invention such as a low heat shrinkage at a high temperature represented by a low molecular weight component can be more easily obtained.

[Low molecular weight component]

The lower limit of the melt flow rate (MFR) of the low molecular weight component measured at 230 캜 and 2.16 kgf is preferably 70 g / 10 min, more preferably 80 g / 10 min, still more preferably 100 g / 10 min min, particularly preferably 150 g / 10 min, and most preferably 200 g / 10 min. Within this range, the crystallinity is improved, and the effect of the present invention such as a low heat shrinkage at a high temperature is more easily obtained. On the other hand, the upper limit of the melt flow rate (MFR) of the low molecular weight component measured at 230 ° C and 2.16 kgf is preferably 2,000 g / 10 min, more preferably 1,800 g / 10 min, still more preferably 1,600 g / 10 min, particularly preferably 1,500 g / 10 min, and most preferably 1,400 g / 10 min. If it is in the above range, the MFR of the whole can be easily maintained and the film-forming property is excellent.

The lower limit of the Mw of the low molecular weight component is preferably 50,000, more preferably 53,000, still more preferably 55,000, particularly preferably 60,000, and most preferably 70,000. If it is in the above range, the MFR of the whole can be easily maintained and the film-forming property is excellent. On the other hand, the upper limit of the Mw of the low molecular weight component is preferably 150,000, more preferably 140,000, still more preferably 130,000, particularly preferably 120,000, and most preferably 110,000. Within this range, the crystallinity is improved, and the effect of the present invention such as a low heat shrinkage rate at a high temperature is more easily obtained.

The lower limit of the intrinsic viscosity (?) 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, particularly preferably 0.55 dl / g , Most preferably 0.6 dl / g. If it is in the above range, the MFR of the whole can be easily maintained and the film-forming property is excellent. On the other hand, the upper limit of the intrinsic viscosity (?) Of the low molecular weight component is preferably 1.1 dl / g, more preferably 1.05 dl / g, still more preferably 1 dl / g, particularly preferably 0.95 dl / And most preferably 0.85 dl / g. Within this range, the crystallinity is improved, and the effect of the present invention such as a low heat shrinkage rate at a high temperature is more easily obtained.

The lower limit of the 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 this range, the effect of the present invention such as a low heat shrinkage at a high temperature represented by a low molecular weight component can be more easily obtained. 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 . In the above range, it is not necessary to increase the molecular weight of the low molecular weight component in order to maintain the total MFR, and the effect of the present invention such as a low heat shrinkage rate at high temperature is more easily obtained.

The lower limit of the ratio of the MFR (g / 10 min) of the low molecular weight component to the MFR (g / 10 min) of the high molecular weight component in the polypropylene resin is preferably 500, more preferably 1,000, Is 2,000, particularly preferably 4,000. Within this range, the effect of the present invention such as a low heat shrinkage at high temperature can be more readily obtained. On the other hand, the upper limit of the MFR ratio of the low molecular weight component to the MFR / high molecular weight component is preferably 1,000,000.

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

The polypropylene resin in the present invention may contain a high molecular weight component or a component having a molecular weight other than the low molecular weight component in order to adjust MFR as the whole polypropylene resin. Further, a polypropylene resin having a molecular weight of a low molecular weight component, particularly a molecular weight of about 30,000 or less, and further having a molecular weight of about 10,000 or less may be contained in order to facilitate entanglement of the molecular chains and control elongation and the like.

In order to obtain a desired molecular weight distribution of the polypropylene resin by 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, To adjust the distribution state, and to adjust the MFR to be easy to produce as a stretched film.

(Melt flow rate of polypropylene resin)

It is important that the lower limit of the melt flow rate (MFR) of the entire polypropylene resin constituting the stretched polypropylene film of the present invention measured at 230 캜 and 2.16 kgf 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. If it is in the above range, the mechanical load is small and the stretching becomes 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, Preferably 8 g / 10 min. In the above range, stretching becomes easy, the thickness variation becomes small, or the stretching temperature and the heat fixing temperature are easily increased, and the heat shrinkage ratio is further lowered.

(Regularity of polypropylene resin)

It is important that the lower limit of the meso pentad fraction of the polypropylene resin constituting the stretched polypropylene film of the present invention is preferably 96%. The lower limit of the meso pentad fraction is preferably 96.5%, more preferably 97%. Within this range, the crystallinity is improved and the heat shrinkage rate at high temperature can be suppressed to a low level. The upper limit of the meso pentad fraction is preferably 99.5%, more preferably 99.3%, still more preferably 99%. If it is in the above range, it is easy to manufacture realistically.

It is preferable that the polypropylene resin constituting the stretched polypropylene film of the present invention is not identified. Also, the fact that it is not confirmed here means that no peak is observed at 500 MHz ¹³ C-NMR.

The lower limit of the xylene-soluble fraction of the polypropylene resin constituting the film is preferably 0.1% by mass from the viewpoint of practical use. On the other hand, the upper limit of the xylene-soluble component is preferably 7% by mass, more preferably 6% by mass, and still more preferably 5% by mass. If it is in the above range, the crystallinity is improved and the heat shrinkage rate at high temperature becomes small.

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. If it is in the above range, the crystallinity is improved and the heat shrinkage rate at high temperature becomes small. On the other hand, the upper limit of the isotactic chain length is preferably 5,000 from a practical point of view.

(Constituent monomers of polypropylene resin)

The polypropylene resin constituting the stretched polypropylene film of the present invention is most preferably a homopolypropylene obtained only from propylene monomers, but may be a copolymer with a copolymerized monomer if it is a very small amount. As the copolymerizable monomer species, olefins such as ethylene and butene are preferable.

It is important that the upper limit of the amount of the copolymerized monomer other than propylene in the polypropylene resin is 0.1 mol%. The upper limit of the amount of the copolymerized monomer is preferably 0.05 mol%, more preferably 0.01 mol%. If it is in the above range, the crystallinity is improved and the heat shrinkage rate at high temperature becomes small.

In addition, conventionally stretched polypropylene films have a high crystallinity in a completely homopolypropylene industrially, but are difficult to form because of a very narrow range of stretching conditions, such as a rapid decrease in melt tension after melt-softening. % Of the copolymerization component (mainly ethylene). However, in the case of the polypropylene resin having a molecular weight distribution as described above, the tensile strength after softening and softening is mild, even if it contains little or no copolymerization component, and industrial drawing is possible.

That is, in the present invention, by using the polypropylene resin having the characteristic molecular weight distribution as described above, it is possible to stretch the polypropylene mainly composed of a low molecular weight component which has not been sufficiently stretched in the past, And it is considered that the heat shrinkage rate at high temperature can be lowered by the high crystallinity, strong open and positive synergy effect.

(Production method of polypropylene resin)

The polypropylene resin is obtained by polymerizing propylene as a starting material by using a Ziegler-Natta catalyst, a metallocene catalyst or the like. Among them, it is preferable to use a catalyst capable of polymerization with high regularity such as a Ziegler-Natta catalyst in order to eliminate heterogeneous bonds.

Examples of the polymerization method of propylene include a method of polymerization in an inert solvent such as hexane, heptane, toluene and xylene, a method of polymerization in liquid propylene or ethylene, a method of adding a catalyst in gaseous propylene or ethylene and polymerization in a gaseous state, Followed by polymerization.

The high molecular weight component and the low molecular weight component may be separately polymerized and then mixed, or may be polymerized in multiple stages in a series of plants having a multi-stage reactor. In particular, it is preferable to polymerize a high molecular weight component first in a plant having a multi-stage reactor and then polymerize a low molecular weight component in the presence thereof. The molecular weight can be controlled by adjusting the amount of hydrogen mixed in the system at the time of polymerization.

(Film properties)

It is important that the lower limit of the plane orientation coefficient of the oriented 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 a realistic value of preferably 0.0155, 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 adjustment of the drawing magnification. Within this range, the thickness variation of the film is also good.

The lower limit of the refractive index (Nx) in the MD direction of the oriented polypropylene film of the present invention is preferably 1.502, more preferably 1.503, and further preferably 1.504. On the other hand, the upper limit of Nx is preferably 1.52, more preferably 1.517, and still more preferably 1.515.

The lower limit of the refractive index (Ny) in the TD direction of the drawn 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, more preferably 1.532.

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

The stretched polypropylene film of the present invention has a characteristic of high crystallinity. 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 range, the heat shrinkage ratio at a high temperature may be increased. 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 it exceeds the above-mentioned range, it may become difficult to realize realistic production. Further, the film crystallinity can be set within a range by a method of reducing the amount of copolymerized monomers in the polypropylene resin to 0% by mass, a method of increasing a low molecular weight component, a stretching temperature, a method of setting a heat fixing temperature at a high temperature,

The lower limit of the melting point of the oriented polypropylene film of the present invention is preferably 168 占 폚, and more preferably 169 占 폚. If it is in the above range, the heat shrinkage rate at a high temperature is reduced. On the other hand, the upper limit of the melting point is preferably 180 占 폚, more preferably 177 占 폚, and further preferably 175 占 폚. If it is in the above range, it is easy to manufacture realistically. The melting point is determined by a method of decreasing the copolymerized monomer content in the polypropylene resin to 0% by mass, a method of increasing the meso pentad fraction, a method of reducing the room temperature xylene solubles, a method of increasing the low molecular weight component, Or by setting the fixing temperature at a high temperature.

In the conventional polypropylene film, even when the melting point peak is located near 170 DEG C, the start of melting (start of melting) is observed from the vicinity of 140 DEG C when measured by DSC, and heat resistance at 140 DEG C is expected The heat shrinkage rate was rapidly increased at 150 ° C. However, in the polypropylene film of the present invention, no peaks start even at 150 占 폚, and a low heat shrinkability at 150 占 폚 is obtained. It is considered that the polypropylene resin having little or no copolymerization component can be used to rapidly produce a crystal having a high melting point due to a characteristic molecular weight distribution and achieve a high heat fixation temperature. In addition, the polypropylene film of the present invention can maintain its physical properties even when exposed to an environment of 150 ° C or higher, and can be used even under a high temperature environment which can not be expected in conventional polypropylene films.

The melting initiation can also be obtained from a DSC chart. 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, the start of the peak (initiation of melting) was confirmed at 150 to 160 ° C (near 155 ° C), and in Comparative Example 1, the peak (start of melting) was observed at around 140 ° C.

The degree of crystallization in the entire sample at 150 占 폚 can be obtained by dividing the heat of fusion obtained as an endothermic peak area of 150 占 폚 or higher by 209 J / g. The lower limit of the crystallinity at 150 캜 of the drawn polypropylene film of the present invention is preferably 48%, more preferably 49%, still more preferably 50%, and particularly preferably 51%. If it is in the above range, the heat shrinkage rate at a high temperature becomes smaller. On the other hand, the upper limit of the crystallinity at 150 캜 is preferably 85%, more preferably 80%, still more preferably 79%, and particularly preferably 78% in view of practicality. The degree of crystallization at 150 占 폚 can be set within a range by a method of reducing the copolymerized monomer content in the polypropylene resin to 0% by mass, a method of increasing a low molecular weight component, a stretching temperature, a method of setting a heat fixing temperature at a high temperature,

(Film characteristics)

In the stretched polypropylene film of the present invention, the 150 占 폚 heat shrinkage ratio in the MD direction (in this specification, "MD direction" means the longitudinal direction of the film and "MD direction" is sometimes referred to as "longitudinal direction" Is preferably 0.5%, more preferably 1%, still more preferably 1.5%, particularly preferably 2%, and most preferably 2.5%. If the thickness is in the above-mentioned range, the manufacturing may be facilitated at a cost or the like, or the thickness deviation may be reduced. On the other hand, the upper limit of the heat shrinkage at 150 占 폚 in the MD direction is preferably 8%, more preferably 7%, still more preferably 6.5%, particularly preferably 6%, and most preferably 5% to be. Within this range, it is easier to use for applications that are likely to be exposed to a high temperature of about 150 ° C.

In the stretched polypropylene film of the present invention, the 150 占 폚 heat shrinkage ratio in the TD direction (in this specification, "TD direction" means width direction of the film and "TD direction" is sometimes referred to as "transverse direction" Is preferably 0.5%, more preferably 1%, still more preferably 1.5%, particularly preferably 2%, and most preferably 2.5%. If the thickness is in the above-mentioned range, the manufacturing may be facilitated at a cost or the like, or the thickness deviation may be reduced. On the other hand, the upper limit of the heat shrinkage at 150 캜 in the TD direction is preferably 13%, more preferably 12%, still more preferably 11%, particularly preferably 10%, and most preferably 9% to be. Within this range, it is easier to use for applications that are likely to be exposed to a high temperature of about 150 ° C.

When the heat shrinkage at 150 ° C is up to about 2.5%, it is possible to increase the number of low molecular weight components to adjust the stretching conditions and fixing conditions. However, in order to further reduce the heat shrinkage, it is preferable to perform the annealing at off-line.

The lower limit of the impact resistance at room temperature (23 캜) of the drawn polypropylene film of the present invention is preferably 0.5 J, and more preferably 0.6 J. If it is within the above range, the film has sufficient toughness and is not broken at the time of handling. On the other hand, the upper limit of the impact resistance at room temperature (23 캜) may be 2 J, more preferably 1.5 J, and more preferably 1.2 J in view of practicality. Impact resistance tends to be lowered when the molecular weight of the whole low molecular weight component is low, when the high molecular weight component is low, when the molecular weight of the high molecular weight component is low, To be within the range.

When the oriented 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 캜 is preferably 2 ㎬, more preferably 2.1 ㎬, more preferably 2.2 ㎬, Preferably 2.3 ㎬, and most preferably 2.4.. On the other hand, the upper limit of the Young's modulus in the MD direction at 23 캜 is preferably 4 ㎬, more preferably 3.7 ㎬, more preferably 3.5,, particularly preferably 3.4 ㎬, and most preferably 3.3 ㎬. to be. In the above range, it is easy to manufacture realistically or 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 캜 is preferably 3.8 ㎬, more preferably 4 ㎬, more preferably 4.2 ㎬, It is preferably 4.3.. 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. In the above range, it is easy to manufacture realistically or MD-TD balance is improved.

Also, the Young's modulus can be increased by increasing the drawing magnification. In the case of MD-TD drawing, the Young's modulus in the TD direction can be increased by setting the MD drawing magnification to a little lower and increasing the TD drawing magnification.

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 the thickness uniformity is preferably 20%, more preferably 17%, still more preferably 15%, particularly preferably 12%, and most preferably 10%. Within the above range, defects are unlikely to occur at the time of post-processing such as coating or printing, so that it is easy to use for applications requiring precision. Further, the thickness uniformity of the film is measured by a method described later in Examples.

The haze of the stretched polypropylene film of the present invention is a practical value and the lower limit is preferably 0.1%, more preferably 0.2%, still more preferably 0.3%, particularly preferably 0.4%, and most preferably, 0.5%. On the other hand, the upper limit of the haze is preferably 6%, more preferably 5%, still more preferably 4.5%, particularly preferably 4%, and most preferably 3.5%. If it is in the above range, it is easy to use for applications requiring transparency. The haze tends to decrease when the drawing temperature and the heat fixing temperature are excessively high, when the cooling rate is low due to the high CR temperature, and when the low molecular weight is excessively large.

The lower limit of the density of the oriented polypropylene film of the present invention is preferably 0.91 g / cm3, more preferably 0.911 g / cm3, still more preferably 0.912 g / cm3, and particularly preferably 0.913 g / cm3 . If it is in the above range, the crystallinity is high and the heat shrinkage ratio may be small. On the other hand, the upper limit of the film density is preferably 0.925 g / cm3, more preferably 0.922 g / cm3, still more preferably 0.920 g / cm3, particularly preferably 0.918 g / cm3. If it is in the above-mentioned range, it may be easy to make the production realistically. The film density can be increased by increasing the stretching magnification or the temperature, by increasing the heat fixing temperature, and further by offline annealing.

(Production method of stretched polypropylene film)

The stretched polypropylene film of the present invention can be produced by forming a resin composition for film molding comprising a polypropylene resin by a known method and stretching the obtained non-stretched film. By using the stretched film, a film having a low heat shrinkage rate even at 150 DEG C, which is unpreferable in a conventional polypropylene film, can be obtained.

The resin composition for film molding contains the polypropylene resin as a main component, but additives and other resins may be added as needed. Examples of the additive include an antioxidant, an ultraviolet absorber, an antistatic agent, a lubricant, a nucleating agent, a pressure-sensitive adhesive, an anti-fogging agent, a flame retardant, an antiblocking agent, and an inorganic or organic filler. Examples of the other resin include a polypropylene resin other than the specific polypropylene resin used in the present invention, a random copolymer as a copolymer of ethylene and an? -Olefin, and various elastomers. The amount of the additive and other resin added is preferably 50 parts by mass or less in total in 100 parts by mass of the resin composition for film forming. These may be blended with a polypropylene resin and a Henschel mixer or may be used by diluting the master pellets prepared in advance using a melt mixer with polypropylene so as to have a predetermined concentration or by melting and kneading the entire amount beforehand.

The stretching may be uniaxial stretching in which stretching is performed in either the longitudinal direction or the transverse direction of the film, or biaxial stretching in both the longitudinal direction and the transverse direction. In the case of biaxial stretching, the stretching may be biaxial stretching or simultaneous biaxial stretching . The stretched polypropylene film of the present invention is preferably a biaxially stretched film.

Described below is a particularly preferable example of a method for producing a continuous biaxially stretched film of longitudinal stretching-transverse stretching.

First, the polypropylene resin is heated and melted by a single-screw or twin-screw extruder, and extruded on chill roll to obtain an unstretched film. At the time of melt extrusion, for example, it is preferable that the resin is extruded into a sheet form from a T-die at a temperature of 200 to 280 DEG C and cooled and solidified by a cooling roll at a temperature of 10 to 100 DEG C. The film is stretched in the MD direction by 3 to 8 times with a stretching roll of, for example, 120 to 165 ° C and then stretched in the width direction (TD) by 155 to 175 ° C (more preferably, 158 to 170 ° C) The stretching is preferably carried out at a temperature of 4 to 20 times. It is also preferable to conduct the heat treatment while allowing a 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 at least on one side, and then rolled into a winder to obtain a roll sample.

The lower limit of the draw ratio in the MD direction is preferably 3 times, more preferably 3.5 times. If the thickness is less than the above range, a film thickness deviation 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 it is more than the above range, 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 占 폚, more preferably 125 占 폚, and still more preferably 130 占 폚. If it is less than the above range, the mechanical load may increase, the thickness variation may increase, or the surface of the film may be roughened. On the other hand, the upper limit of the stretching temperature in the MD direction is preferably 165 ° C, more preferably 160 ° C, and more preferably 160 ° C, since the higher the temperature is preferable from the viewpoint of the heat shrinkage, Lt; RTI ID = 0.0 > 150 C, < / RTI >

The lower limit of the draw ratio in the TD direction is preferably 4 times, more preferably 5 times, and still more preferably 6 times. If the thickness is less than the above range, a thickness variation may occur. On the other hand, the upper limit of the stretching magnification in the TD direction is preferably 20 times, more preferably 17 times, still more preferably 15 times, particularly preferably 12 times. If it exceeds the above-mentioned range, the heat shrinkage ratio may be increased, or may be broken at the time of stretching.

Preheating is preferably performed at the time of stretching in the TD direction, and the preheating temperature is set to be 10 to 15 DEG C higher than the stretching temperature, in order to rapidly raise the film temperature to about the stretching temperature.

The stretching in the TD direction is performed at a temperature higher than that of a conventional polypropylene film. The lower limit of the stretching temperature in the TD direction is preferably 155 占 폚, more preferably 157 占 폚, and still more preferably 158 占 폚. If it is less than the above range, it may not be sufficiently softened and may be broken or the heat shrinkage ratio may be increased. On the other hand, the upper limit of the stretching temperature in the TD direction is preferably 175 占 폚, more preferably 170 占 폚, and further preferably 168 占 폚. In order to lower the heat shrinkage rate, it is preferable that the temperature is high, but if it is higher than the above range, the low molecular weight component may be melted and recrystallized to cause surface roughening or film whitening.

The stretched film is preferably heat-set. The hot fix can be performed at a higher temperature than the conventional polypropylene film. The lower limit of the heat setting temperature is preferably 165 占 폚, and more preferably 166 占 폚. If it is less than the above range, the heat shrinkage ratio may be increased. Further, in order to lower the heat shrinkage rate, it is necessary to perform the heat setting treatment for a long period of time, and productivity may be deteriorated. On the other hand, the upper limit of the heat fixing temperature is preferably 175 占 폚, and more preferably 173 占 폚. If it exceeds the above range, the low molecular weight component may melt and recrystallize, resulting in surface roughness and film whitening.

It is desirable to relax (relax) when opened and on time. The lower limit of the relax is preferably 1%, more preferably 2%, still more preferably 3%. If it is less than the above range, the heat shrinkage ratio may be increased. On the other hand, the upper limit of the relax is preferably 15%, more preferably 10%, still more preferably 8%. If the thickness exceeds the above range, the thickness deviation may become large.

In addition, in order to lower the heat shrinkage ratio, the film produced in the above step may be wound into a roll shape and annealed at off-line.

The lower limit of the offline annealing temperature is preferably 160 占 폚, more preferably 162 占 폚, and still more preferably 163 占 폚. If it is less than the above range, the effect of annealing may not be obtained. On the other hand, the upper limit of the offline annealing temperature is preferably 175 占 폚, more preferably 174 占 폚, and further preferably 173 占 폚. If it exceeds the above-mentioned range, the transparency may be lowered or the thickness deviation may be increased.

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

The thickness of the film is set for each application, but the lower limit of the film thickness is preferably 2 占 퐉, more preferably 3 占 퐉, further preferably 4 占 퐉. The upper limit of the film thickness is preferably 300 占 퐉, more preferably 250 占 퐉, still more preferably 200 占 퐉, particularly preferably 100 占 퐉, and most preferably 50 占 퐉.

The stretched polypropylene film thus obtained is usually formed into a roll having a width of about 2,000 to 12,000 mm and a length of about 1,000 to about 50,000 m and wound in a roll form. It is also provided as a slit roll having a width of 300 to 2,000 mm and a length of 500 to 5,000 m in accordance with each application.

The stretched polypropylene film of the present invention has excellent characteristics as described above. Therefore, when it is used as a packaging film, it is highly rigid and can be made thinner, so that 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 coating or printing, so that it is possible to use a coating agent, an ink, a laminate adhesive or the like which has been difficult to be used conventionally. Further, it can be used as an insulating film such as a capacitor or a motor, a back sheet of a solar cell, a barrier film of an inorganic oxide, or a base film of a transparent conductive film such as ITO.

The present invention is described in Japanese Patent Application No. 2012-12117 filed on January 24, 2012, Japanese Patent Application No. 2012-146801 filed on June 29, 2012, and Application filed on August 17, 2012 Japanese Patent Application No. 2012-180971, which is incorporated herein by reference in its entirety. Japanese Patent Application No. 2012-12117 filed on January 24, 2012, Japanese Patent Application No. 2012-146801 filed on June 29, 2012, and Japanese Patent Application filed on August 17, 2012 The entire contents of the specification of Patent Application No. 2012-180971 are hereby incorporated by reference.

Example

EXAMPLES The present invention will be described in more detail with reference to the following examples and comparative examples. However, the present invention is not limited to the following examples, and the present invention may be carried out by appropriately modifying it in a range that is suitable for the following purposes Of course, all of which are included in the technical scope of the present invention.

In the following Examples and Comparative Examples, methods for measuring physical properties are as follows.

(1) Melt flow rate (MFR) (g / 10 min)

MFR was measured at 230 캜 according to JIS-K7210.

(2) Intrinsic viscosity (?) (Dl / g)

The intrinsic viscosity was measured at 135 占 폚 by dissolving the sample in tetralin according to JIS K7367-1: 2002.

(3) Molecular weight and molecular weight distribution

Molecular weight and molecular weight distribution were determined on the basis of monodisperse polystyrene using gel permeation chromatography (GPC). The measurement conditions of the column, solvent, etc. used in the GPC measurement are as follows.

Solvent: 1,2,4-trichlorobenzene

Column: TSKgel GMH _HR- H (20) HT 3

Flow rate: 1.0 ml / min

Detector: RI

Measuring 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) of each of the GPC curves obtained through the molecular weight calibration curve (Ni). &Lt; / RTI >

Number average molecular weight: Mn =? (Ni 占)) /? Ni

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

(4) stereoregularity

Measurement of the meso pentad fraction (isotactic meso pentad fraction) and meso chain length (meso average chain length) was carried out by using ¹³ C-NMR. According to the method described in Zambelli et al., Macromolecules, Vol. 6, p. 925 (1973), the isotactic meso pentad fraction is determined by the method described in " Polymer Sequence Distribution " (1977) (Academic Press, New York). &Quot;

¹³ C-NMR measurement was carried out at 110 占 폚 using "AVANCE500" manufactured by BRUKER, and 200 mg of the sample was dissolved in a mixture of o-dichlorobenzene and heptane at a volume ratio of 8: 2 (volume ratio) at 135 占 폚.

(5) Density (g / cm3)

The density of the film was measured by density gradient method according to JIS-K7112.

(6) Melting point (Tmp) (占 폚), crystallinity (%) and crystallinity (%) at 150 占 폚

Thermal measurement was performed using a differential scanning calorimeter (" DSC-60 " manufactured by Shimadzu Corporation). Approximately 5 mg of the sample film was cut out and sealed in an aluminum pan for measurement. The temperature was raised from room temperature to 230 ° C at a rate of 20 ° C / minute, and the melting endothermic peak temperature of the sample was determined as the melting point Tmp. The crystallization degree is 209 J / g of the heat of fusion of the polypropylene perfect crystal described in Die Makromolekulare Chemie, Rapid Communications, vol.9, page 75 (1988) by H. Bu, SZD Cheng, B. Wunderlich et al. , And the ratio of the heat of fusion of the DSC melting profile obtained from the melting peak area (? Hm) obtained in the above-mentioned heat measurement was expressed as a percentage. The degree of crystallization at 150 ° C was determined from the heat of fusion at 150 ° C or higher of the DSC melting profile.

(7) Cold Xylene Soluble Part (CXS) (% by mass)

1 g of the polypropylene sample was dissolved in 200 ml of boiling xylene, and after cooling, recrystallized in a constant temperature water bath at 20 캜 for 1 hour. The ratio of the mass dissolved in the filtrate to the original sample was CXS (mass%).

(8) Heat shrinkage (%)

And measured according to JIS-Z1712. That is, the stretched film was cut in a MD direction and a TD direction with a length of 20 mm and a length of 200 mm, respectively, and was suspended in a hot air oven and heated for 5 minutes. The length after heating was measured to determine the heat shrinkage rate at the ratio of the shrunk length to the original length.

(9) Impact resistance (J)

The film was measured at 23 캜 using a film impact tester manufactured by Toyo Seiki.

(10) Young's modulus (㎬)

The tensile strength in the MD direction and the TD direction was measured at 23 占 폚 according to JIS-K7127.

(11) Haze (%)

And measured according to JIS-K7105.

(12) Refractive indexes (Nx, Ny, Nz)

Was measured using an Abbe refractometer (Atago). The refractive indices in the MD and TD directions are Nx and Ny, respectively, and the refractive index in the thickness direction is Nz.

(13) Plane orientation coefficient

[(Nx + Ny) / 2] -Nz was calculated from Nx, Ny and Nz measured in (12) above.

(14) Thickness deviation (Thickness uniformity) (%)

A square sample having a length of 1 m was cut out from the wound film roll, and divided into 10 pieces in the MD direction and 100 pieces in the TD direction, and 100 samples for measurement were prepared. The thickness of the almost center portion of the measurement sample was measured with a contact type film thickness meter. Then, the difference (B / A) × 100 between the minimum value and the maximum value was obtained by obtaining the average value A of the obtained data of 100 points, and the value calculated by using the formula (B / A) × 100 was regarded as the film thickness deviation.

(Example 1)

A polypropylene homopolymer having a Mw / Mn ratio of 7.7, Mz + 1 / Mn = 140, MFR = 5.0 g / 10 min and a mesopentad fraction [mmmm] = 97.3% Novatech (registered trademark) PP SA4L ": 0 mol% of copolymerized monomer; hereinafter abbreviated as" PP-1 ") was used.

This polypropylene resin was extruded from a T-die at 250 캜 into a sheet form using a 65 mm extruder, cooled and solidified by a cooling roll at 30 캜, longitudinally stretched at 135 캜 in the longitudinal direction (longitudinal direction) 4.5 times, Both ends were inserted between clips and introduced into a hot air oven. After being preheated at 170 ° C, they were transversely stretched at a temperature of 160 ° C in the width direction (transverse direction) by 8.2 times and then subjected to heat treatment at 168 ° C while applying a relaxation of 6.7% . One side of the thus obtained film was subjected to corona treatment and wound with a winder to obtain a stretched polypropylene film of the present invention.

The thickness of the obtained film was 20 占 퐉, and physical properties thereof were as shown in Tables 1, 2 and 3. From the results of the table, it can be seen that the film has a low heat shrinkage and a high Young's modulus. A chart obtained by differential scanning calorimetry (DSC) of this film is shown in Fig.

(Example 2)

A low molecular weight propylene homopolymer having a narrow molecular weight distribution and a viscosity average molecular weight of 10,000 ("Hi-wax NP105" manufactured by Mitsui Chemicals, Inc.: the amount of copolymerized monomer was 0 (mass%)) relative to 90 parts by mass of the polypropylene homopolymer (PP-2) obtained by adding 10 parts by mass of a polypropylene resin (10% by mass) to a polypropylene resin obtained by melt kneading with a 30 mm twin-screw extruder was used as a polypropylene resin. A polypropylene film was obtained.

The thickness of the obtained film was 20 占 퐉, and physical properties thereof were as shown in Tables 1, 2 and 3. From the results of the table, it can be seen that the film has a low heat shrinkage and a high Young's modulus.

(Example 3)

Mw / Mn = 4.6, Mz + 1 / Mn = 22, MFR = 120 g / 10 min, and mesopentad fraction [mmmm] = 70 parts by mass based on 70 parts by mass of the polypropylene homopolymer (PP- (PP-3) obtained by adding 30 parts by weight of a polypropylene homopolymer (SUMITOMONOBLEN (registered trademark) U501E1 manufactured by Sumitomo Chemical Co., Ltd., a copolymerized monomer amount of 0 mol%) of 98.1% A stretched polypropylene film of the present invention was obtained in the same manner as in Example 1, except that it was used as a resin.

(Example 4)

A stretched polypropylene film of the present invention was obtained in the same manner as in Example 1 except that the preheating temperature in the transverse stretching was 173 deg. C, the stretching temperature and the heat treatment temperature were 167 deg.

(Example 5)

The stretched polypropylene film of the present invention was obtained in the same manner as in Example 2 except that the stretched polypropylene film of Example 2 was stretched 5.5 times in the longitudinal direction (longitudinal direction) and 12 times in the transverse direction (transverse direction).

(Example 6)

The stretched polypropylene film obtained in Example 1 was further heat treated in a tenter-type hot air oven at 170 DEG C for 5 minutes.

The thickness of the obtained film was 20 占 퐉, and physical properties thereof were as shown in Tables 1, 2 and 3.

(Example 7)

Polypropylene homopolymer ("HU300" manufactured by Samsung Total Co., Ltd.) having a Mw / Mn ratio of 8.9, a Mz + 1 / Mn of 110, a MFR of 3.0 g / 10 min and a mesopentaded fraction [mmmm] Except that the amount of the copolymerized monomer was 0 mol%), the preheating temperature of the transverse stretching was 171 캜, the transverse stretching temperature was 161 캜, and the heat treatment temperature after the transverse stretching was 170 캜. Of a stretched polypropylene film.

(Comparative Example 1)

(Sumitomo Blend (registered trademark) FS2011DG3 manufactured by Sumitomo Chemical Co., Ltd.) having a Mw / Mn of 4, a Mz + 1 / Mn of 21 and an MFR of 2.5 g / 10 min as a polypropylene resin: a copolymerized monomer Was used in place of the polypropylene film used in Example 1, and the preheating temperature in the transverse stretching was 168 占 폚, the stretching temperature was 155 占 폚, and the heat treatment temperature was 163 占 폚. &Lt; / RTI >

The thickness of the obtained film was 20 占 퐉, and physical properties thereof were as shown in Tables 1, 2 and 3. A chart obtained by differential scanning calorimetry (DSC) of this film is shown in Fig.

(Comparative Example 2)

A stretched polypropylene film for comparison was obtained in the same manner as in Comparative Example 1 except that the preheating temperature in the transverse stretching was 171 캜, the stretching temperature was 160 캜, and the heat treatment temperature was 165 캜.

(Comparative Example 3)

(Novatech (registered trademark) PP SA03 manufactured by Japan Polypropylene Co., Ltd.) having a Mw / Mn of 2.8, Mz + 1 / Mn of 9.2 and MFR of 30 g / 10 min as a polypropylene resin The amount of the monomer was 0 mol%). In the same manner as in Example 1, an attempt was made to obtain a stretched polypropylene film. However, the film was broken during transverse stretching and biaxial stretching could not be performed.

The stretched polypropylene film of the present invention can be widely used for packaging and industrial use, but is particularly suitable for applications requiring cost reduction and weight reduction because it is highly rigid and thin.

Further, since the stretched polypropylene film of the present invention has high heat resistance, it can be dried at a high temperature during drying when coating or printing is performed, so that it is possible to improve the efficiency of production and to provide a coating agent, an ink, a laminate A treatment using an adhesive or the like can be applied.

Further, the stretched polypropylene film of the present invention is also suitable as an insulating film such as a capacitor or a motor, a back sheet of a solar cell, a barrier film of an inorganic oxide, a base film of a transparent conductive film such as ITO, and the like.

Claims

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 meso pentad fraction is 96%.
2) The upper limit of the amount of copolymerized 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 the z + 1 average molecular weight (Mz + 1) / number average molecular weight (Mn) is 50.
6) z + 1 The lower limit of the average molecular weight (Mz + 1) is 2,500,000.

The method according to claim 1,
Wherein the lower limit of the amount of the component having a molecular weight of 100,000 or less is 35% by mass when the gel permeation chromatography (GPC) integration curve of the entire polypropylene resin constituting the stretched polypropylene film is measured.

3. The method according to claim 1 or 2,
Wherein the upper limit of the face orientation coefficient of the film is 0.0155.

3. The method according to claim 1 or 2,
Wherein the stretched polypropylene film is biaxially stretched.

5. The method of claim 4,
A stretching ratio in the longitudinal direction of 3 to 8 times and a stretching ratio in the transverse direction of 4 to 20 times.