TWI607021B - Polypropylene film - Google Patents

Description

Polypropylene film

This invention relates to a polypropylene film. More specifically, it relates to a polypropylene film which is excellent in heat resistance and mechanical properties in various fields which are applicable to dimensional stability and high rigidity in a desired high temperature.

Conventionally, polypropylene stretched films have been widely used in a wide range of applications such as packaging for foods and various products, electrical insulation, and surface protective films. However, the conventional polypropylene film has a shrinkage ratio of tens of % at 150 ° C, is lower in heat resistance than PET, and has low rigidity, and therefore, its use is limited.

In order to solve such problems, a technique of forming a film having high-temperature rigidity and heat resistance by using a polypropylene having a high stereoregularity and a narrow molecular weight distribution as a stretched film has been known (for example, see Patent Document 1).

In addition, it is known that a polypropylene film having excellent high electrical conductivity and mechanical properties can be used as a stretching film by using a polypropylene having a high stereoregularity and a wide molecular weight distribution (for example, see Patent Document 2). .

Further, a technique of using a polypropylene having a low molecular weight and a soluble fraction at a temperature of 0 ° C in a specific range as a separator is also known, and the film is excellent in dimensional stability in a drying step and a printing step (for example, Patent Document 3, etc.).

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

It is known that a long-chain branched or cross-linked polypropylene is added to a medium molecular weight component in a small amount to promote formation of a sub-layer and to improve elongation, and to provide excellent mechanical properties, heat resistance, and withstand voltage characteristics and various physical properties. A technique of a film having excellent uniformity (for example, see Patent Document 4).

Further, it is known to form a film by using a polypropylene containing a substantially equal amount of a high molecular weight component and a medium molecular weight component (low molecular weight component), a broad molecular weight distribution, and a small amount of decane soluble fraction, thereby balancing rigidity and workability. Technology (for example, refer to Patent Document 5, etc.).

The film described in the above-mentioned Patent Documents 4 to 5 is insufficient in heat resistance at a high temperature, and a polypropylene film having high heat resistance and excellent impact resistance and transparency has not been known. That is, those which do not exceed the range of the conventional polypropylene film are limited in use, for example, heat resistance at a high temperature exceeding 150 ° C is not noticed.

In order to improve the heat resistance of the film, a technique of setting the elongation at 120 ° C and a load of 0.5 kgf/mm ^{2 in a} TMA (thermomechanical analysis) measurement to 10% or less is known (for example, see Patent Document 6). However, the film described in Patent Document 6 does not have sufficient heat resistance when printing or processing.

Conventionally, when printing or laminating is performed on a polypropylene film, in the drying step, the film is stretched while being heated in a state in which the film is stretched, causing various problems. For example, it is known that the printed pattern overlaps the colors to be printed one by one, and when the film has no heat resistance, the overlap When printing, there may be problems such as uneven spacing or difficulty in adjustment. Further, when the film has a scar, it is generally processed at the time of processing by increasing the tension applied to the film to eliminate the appearance of the scar. However, if the film has no heat resistance at this time, there is a case where the film is excessively stretched, and when it is more extreme, it may be broken.

Due to such problems, it is known that a low tension is generally set in the printing or lamination of a polypropylene film, but if it is set to a low tension, the occurrence of scars or film defects may occur during processing.

Further, for example, when the printing pitch is a particularly important processed product, the surface substrate is not a polypropylene film, but a polyethylene terephthalate film made of a resin material excellent in heat resistance is used, so that the polypropylene film is used. The scope is limited.

[Previous Technical Literature]

[Patent Literature]

Patent Document 1: Japanese Laid-Open Patent Publication No. Hei 8-325327.

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

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

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

Patent Document 5: Japanese Laid-Open Patent Publication No. 2008-540815.

Patent Document 6: Japanese Laid-Open Patent Publication No. 2001-106804.

The present invention has been developed in the context of the problems related to the prior art. That is, the object of the present invention is to provide a polypropylene film suitable for printing processing and the like which is excellent in heat resistance and dimensional stability, and more particularly, to provide a polypropylene film. The polypropylene film has a low elongation under high temperature load, a low shrinkage rate at 150 ° C, and high rigidity.

The inventors of the present invention have completed the present invention by focusing on the results of the review in order to achieve the above object. That is, the polypropylene film of the present invention is characterized in that the haze is 6% or less, the heat shrinkage rate at 150 ° C is 15% or less, and the temperature is increased by 5 ° C / min and the load is 0.5 kg / mm ² . The heating elongation E (%) in the MD direction at the time of TMA (thermomechanical analysis) measurement satisfies the formula (1) at 120 ° C to 150 ° C.

Log(E)≦0.0275T-2.4839...(1) (only T is temperature (°C)).

At this time, the lower limit of the isotactic pentad fraction of the polypropylene resin constituting the above film is 96%, and the lower limit of the surface alignment coefficient of the film is preferably 0.0125.

Further, the upper limit of the amount of the comonomer of the polypropylene resin constituting the film at this time is preferably 0.1 mol%.

Further, at this time, the polypropylene resin constituting the film is preferably 7% by mass or less at room temperature.

Since the polypropylene film of the present invention is excellent in heat resistance and dimensional stability, it can suppress misalignment and deformation during printing, and remarkably improve the efficiency of printing processing.

Moreover, the polypropylene film of the present invention can maintain various physical properties even when exposed to an environment of 150 ° C or higher, so that it can be used in the conventional polypropylene film. Imagine using it in a high temperature environment.

Fig. 1 is a DSC chart of a polypropylene film described in Example 1 and Comparative Example 1.

[Formation for implementing the invention]

(film properties)

The present invention relates to a polypropylene film excellent in dimensional stability and mechanical properties at a high temperature, and the polypropylene film is subjected to TMA (thermomechanical analysis) measurement at a temperature increase rate of 5 ° C / min and a load of 0.5 kg / mm ² . The heating elongation E (%) in the MD direction satisfies the formula (1) in the range of 120 ° C to 150 ° C, preferably in the case of satisfying the formula (2), and more preferably in the formula (3).

Log(E)≦0.0275T-2.4839...(1)

Log(E)≦0.0263T-2.3572...(2)

Log(E)≦0.0239T-2.0776...(3) (in equations (1) to (3), T is temperature (°C))

When the heating elongation E (%) does not satisfy the formula (1), the deformation of the film in the printing step becomes large, and the precision and efficiency of printing are remarkably lowered.

The lower limit of the heating elongation E (%) is 1% at 120 ° C, 2% at 130 ° C, 5% at 140 ° C, and 8% at 150 ° C. When the heating elongation E (%) at each temperature is less than the above lower limit, the stability at the time of printing processing may be lowered.

The lower limit of the heat shrinkage ratio in the MD direction and the TD direction of the polypropylene film of the present invention at 150 ° C is preferably 0.5%, more preferably 1%, more preferably 1.5%, still more preferably 2%, and 2.5%. For the best. The above heat shrinkage rate is 0.5% In the above case, there is a case where the actual manufacturing such as the cost surface becomes easy, and the thickness variation becomes small. In addition, the MD direction means the flow direction of the film, and the TD direction means the direction perpendicular to the flow direction of the film.

The upper limit of the heat shrinkage rate at 150 ° C in the MD direction and the TD direction is 15%, preferably 13%, more preferably 12%, more preferably 11%, and most preferably 10%. When the heat shrinkage ratio is 15% or less, a film excellent in heat resistance can be obtained, and it is easier to use it in applications that may be exposed to a high temperature of about 150 °C. Further, when the heat shrinkage ratio at 150 ° C is about 2.5% or more, for example, a low molecular weight polypropylene having a molecular weight of about 100,000 (hereinafter referred to as a low molecular weight component) can be adjusted, and elongation conditions and heat setting conditions can be adjusted, but lower than When it is about 2.5%, it is preferable to perform annealing treatment on line off. Further, in the conventional polypropylene film, the heat shrinkage ratio at 150 ° C in the MD direction and the TD direction is 15% or more, and the heat shrinkage ratio at 120 ° C is about 3%.

The lower limit of the actual value of the haze of the polypropylene film of the present invention is preferably 0.1%, more preferably 0.2%, still more preferably 0.3%, most preferably 0.4%, and most preferably 0.5%. The upper limit of the haze of the film is 6%, preferably 5%, more preferably 4.5%, more preferably 4%, and most preferably 3.5%. The haze is 6% or less, and it is easy to use in applications where transparency is required. When the elongation temperature or the heat setting temperature is too high, the cooling roll temperature is high, and the cooling rate of the stretched film is slow, and the low molecular weight component is too large, the haze tends to be large, and the conditions can be adjusted within the above range. .

(polypropylene resin)

The polypropylene resin used in the present invention is mainly a low molecular weight polypropylene (low molecular weight component) having a mass average molecular weight (Mw) of about 100,000, for example. Further, it is preferable to contain, for example, a high molecular weight polypropylene (hereinafter referred to as a high molecular weight component) having an Mw of about 1.5 million and having a very high molecular weight. It is considered that the low molecular weight component is mainly used to greatly improve the crystallinity, and a polypropylene film having high rigidity and high heat resistance which has not been conventionally obtained can be obtained. Further, the low molecular weight polypropylene resin has a low melt tension when heated and softened, and it is generally difficult to form a stretched film. The high molecular weight component which is present in the range of several to several tens of % is stretched, and the high molecular weight component functions as a crystal nucleus, and has an effect of further improving the crystallinity of the film, and is considered to be suitable for obtaining the polypropylene of the present invention. The substance of the film.

Examples of the parameter indicating the molecular weight of the polymer include a number average molecular weight (Mn), a mass average molecular weight (Mw), a Z average molecular weight (Mz), a Z+1 average molecular weight (Mz+1), a peak molecular weight (Mp), and the like. These are defined by the number of molecules (Ni) of molecular weight (Mi) as follows.

Number average molecular weight: Mn = Σ (Ni‧Mi) / Σ Ni

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 )

Peak molecular weight: Mp (molecular weight at the peak position of the gel permeation chromatography (GPC) curve)

Then, as a parameter indicating the molecular weight distribution, the ratio of the average molecular weight is generally used, and examples thereof include Mw/Mn, Mz+1/Mn, and the like, but the molecular weight distribution of the characteristics of the polypropylene resin used in the present invention is represented. It is preferred to use Mz+1/Mn. The measurement method for such molecular weight and molecular weight distribution generally uses GPC.

The lower limit of Mz+1/Mn is preferably 50, more preferably 60, more preferably 70, more preferably 80, and 90 is the best. When Mz+1/Mn is less than 50, there is a case where it is difficult to obtain the effect of the present invention such as a low heat shrinkage rate at a high temperature. The upper limit of Mz+1/Mn is preferably 300, and more preferably 200. When Mz+1/Mn exceeds 300, there is a case where it is practically difficult to manufacture a resin.

The lower limit of Mz+1 of the polypropylene resin constituting the film is preferably 2,500,000, more preferably 3,000,000, more preferably 3,300,000, more preferably 3,500,000, and most preferably 3.7 million. When Mz+1 is 2,500,000 or more, the high molecular weight component is sufficient and the effect of the present invention can be easily obtained. The upper limit of Mz+1 of the polypropylene resin constituting the film is preferably 40,000,000, more preferably 35,000,000, and even more preferably 30,000,000. When Mz+1 is 4,000,000 or less, the resin can be easily produced or stretched easily, and the fisheye in the film is reduced.

The lower limit of Mn of the polypropylene resin constituting the film is preferably 20,000, more preferably 22,000, more preferably 24,000, more preferably 26,000, and most preferably 27,000. When Mn is 20,000 or more, the elongation is easy, the thickness unevenness is small, and the elongation temperature or the heat setting temperature can be easily increased to lower the heat shrinkage rate. The upper limit of Mn of the polypropylene resin constituting the film is preferably 65,000, more preferably 60, more preferably 55,000, more preferably 53,000, and most preferably 52,000. When Mn is 65,000 or less, the effect of a low molecular weight component can be more easily exhibited, and a heat shrinkage rate at a high temperature or the like can be easily obtained, and it is easy to extend.

The lower limit of the Mw of the entire polypropylene resin constituting the film is 250000 is better, with 260,000 is better, 270,000 is better, and 280,000 is especially good, with 290,000 being the best. When the Mw is 250,000 or more, the elongation is easy, the thickness unevenness is small, and the elongation temperature or the heat setting temperature is easily increased to lower the heat shrinkage rate. The upper limit of the Mw of the polypropylene resin constituting the film is preferably 500,000, more preferably 450,000, more preferably 400,000, more preferably 380000, and most preferably 370,000. When the Mw is 500,000 or less, there is a case where the mechanical load is small and it is easy to be extruded and extended.

The lower limit of the melt flow rate (MFR) (230 ° C, 2.16 kgf) of the polypropylene resin constituting the film is preferably 1 g/10 min, more preferably 1.2 g/10 min, and 1.4 g/10 min. Good, 1.5g/10 minutes is the best, 1.6g/10 minutes is the best. When the MFR is 1 g/10 min or more, the mechanical load is small and it is easy to extend. The upper limit of the MFR of the polypropylene resin constituting the film is preferably 11 g/10 min, more preferably 10 g/10 min, still more preferably 9 g/10 min, and particularly preferably 8.5 g/10 min. When the MFR is 11 g/10 minutes or less, the elongation is easy, the thickness unevenness is small, and the elongation temperature or the heat setting temperature is easily increased to lower the heat shrinkage rate.

When the gel permeation chromatography (GPC) accumulation curve of the entire polypropylene resin constituting the film is measured, the lower limit of the ratio of the molecular weight of 10,000 or less in the entire polypropylene resin is preferably 2% by mass, more preferably 2.5% by mass. It is preferably 3% by mass, more preferably 3.3% by mass, and most preferably 3.5% by mass. When the ratio of the molecular weight of 10,000 or less is 2% by mass or more, the effect of obtaining a low molecular weight substance can be more easily obtained. The heat shrinkage rate and the like of the present invention are easily extended.

The upper limit of the ratio of the molecular weight of 10,000 or less in the entire polypropylene resin in the GPC accumulation curve is preferably 20% by mass, more preferably 17% by mass, even more preferably 15% by mass, and particularly preferably 14% by mass. The mass % is the best. When the ratio of the component having a molecular weight of 10,000 or less is 20% by mass or less, the elongation is easy, the thickness unevenness is small, the elongation temperature or the heat setting temperature is easily increased, and the heat shrinkage ratio is lowered.

Molecules having a molecular weight of 10,000 or less do not intertwin the molecular chains, and have the effect of loosening the intertwining between the plasticizer molecules. It is considered that the content of the component having a molecular weight of 10,000 or less is a specific amount, and the entanglement of the molecules during stretching is easily released and can be extended by a low elongation stress, and as a result, the residual stress is also low, and the shrinkage ratio at a high temperature can be lowered.

The lower limit of the ratio of the molecular weight of 100,000 or less in the entire polypropylene resin in the GPC cumulative curve is preferably 35 mass%, more preferably 38 mass%, more preferably 40 mass%, more preferably 41 mass%, and 42 mass%. The mass % is the best. When the ratio of the component having a molecular weight of 100,000 or less is 35 mass% or more, it is easy to exhibit the effect of a low molecular weight product, and it is easy to obtain a low heat shrinkage rate at a high temperature and to easily extend.

The upper limit of the ratio of the molecular weight of 100,000 or less in the entire polypropylene resin in the GPC accumulation curve is preferably 65 mass%, more preferably 60 mass%, more preferably 58 mass%, and most preferably 56 mass%. 55% by mass is the best. When the ratio of the component having a molecular weight of 100,000 or less is 65% by mass or less, the elongation is easy, the thickness unevenness is small, the elongation temperature or the heat setting temperature is likely to be increased, and the heat shrinkage ratio is lowered.

Conventionally, polypropylene having a low molecular weight component as a main component cannot be sufficiently extended. It is considered that by using a polypropylene resin having a molecular weight distribution having such characteristics, even a polypropylene mainly composed of a low molecular weight component can be extended, and high polypropylene can be used. The heat is fixed at a temperature, and the heat shrinkage rate at a high temperature can be lowered by the synergistic effect of high crystallinity and strong heat fixation.

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

(high molecular weight component)

The lower limit of the MFR (230 ° C, 2.16 kgf) of the high molecular weight component is preferably 0.0001 g/10 min, more preferably 0.0005 g/10 min, more preferably 0.001 g/10 min, and 0.005 g/10 min. Very good. When the MFR of the high molecular weight component is 0.0001 g/10 min or more, the resin can be easily produced and the fish eye in the film can be reduced.

Further, the MFR of the high molecular weight component at 230 ° C and 2.16 kgf is too small, and it is actually difficult to measure. Preferably, the lower limit is 0.1 g/10 min, preferably 0.5 g/10 min, more preferably 1 g/10 min, and 5 g/10, if expressed by MFR at 10 times load (21.6 kgf) of 2.16 kgf. Minutes are especially good.

The upper limit of the MFR of the high molecular weight component is preferably 0.5 g/10 min, more preferably 0.35 g/10 min, more preferably 0.3 g/10 min, and particularly preferably 0.2 g/10 min, 0.1 g/ 10 minutes is the best. When the MFR of the high molecular weight component is 0.5 g/10 minutes or less, it is easy to exhibit low in order to maintain the MFR of the entire polypropylene resin without requiring a large amount of high molecular weight components. The effect of the molecular weight component is more likely to result in a lower heat shrinkage rate at a high temperature.

The lower limit of the Mw of the high molecular weight component is preferably 500,000, more preferably 600,000, more preferably 700,000, more preferably 800,000, and most preferably 1,000,000. When the Mw of the high molecular weight component is 500,000 or more, in order to maintain the MFR of the entire polypropylene resin, it is not necessary to have a large amount of high molecular weight component, and it is easy to exhibit a low molecular weight component, and it is possible to more easily obtain a low heat shrinkage rate at a high temperature.

The upper limit of the Mw of the high molecular weight component is preferably 10,000,000, more preferably 8,000,000, more preferably 6,000,000, and particularly preferably 5,000,000. When the Mw of the high molecular weight component is 10,000,000 or less, the resin can be easily produced, and the fish eye in 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. When the amount of the high molecular weight component is 2% by mass or more, in order to maintain the MFR of the entire polypropylene resin, it is not necessary to increase the molecular weight of the low molecular weight component, and it is more likely to obtain a low heat shrinkage rate at a high temperature.

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. When the amount of the high molecular weight component is 30% by mass or less, the effect of easily exhibiting a low molecular weight component is obtained, and the case where the low heat shrinkage rate at a high temperature is more easily obtained may be obtained. Further, the ratio of the high molecular weight component to the entire polypropylene resin constituting the film is determined by peak separation using a molecular weight distribution curve measured by GPC, and the following low molecular weight is obtained. The same is true for other ingredients.

Here, the high molecular weight component may also be a polypropylene resin having a long-chain branching or cross-linking structure in place of a linear polypropylene resin, which is known as a high-melt-tensile polypropylene, and a Daploy "WB130HMS" manufactured by Borealis Co., Ltd. "WB135HMS" and so on.

(low molecular weight component)

The lower limit of the MFR (230 ° C, 2.16 kgf) of the low molecular weight component is preferably 70 g/10 min, more preferably 80 g/10 min, more preferably 100 g/10 min, and particularly preferably 150 g/10 min. 200g/10 minutes is the best. When the MFR of the low molecular weight component is 70 g/10 min or more, the crystallinity is improved, and it is easier to obtain a low heat shrinkage ratio at a high temperature.

The upper limit of the MFR of the low molecular weight component is preferably 2000 g/10 min, more preferably 1800 g/10 min, more preferably 1600 g/10 min, more preferably 1500 g/10 min, and most preferably 1500 g/10 min. . When the MFR of the low molecular weight component is 2000 g/10 minutes or less, the MFR of the entire polypropylene resin 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, more preferably 55,000, more preferably 60,000, and most preferably 70,000. When the Mw of the low molecular weight component is 50,000 or more, the MFR of the entire polypropylene resin can be easily maintained, and the film forming property is excellent.

The upper limit of the Mw of the low molecular weight component is preferably 170,000, more preferably 165,000, more preferably 160,000, still more preferably 155,000, and most preferably 150,000. When the Mw of the low molecular weight component is 170,000 or less, the crystallinity is improved, and the low heat shrinkage rate at a high temperature is more easily obtained. shape.

The lower limit of the amount of the low molecular weight component is preferably 40% by mass, more preferably 50% by mass, still more preferably 55% by mass, and particularly preferably 60% by mass. When the amount of the low molecular weight component is 40% by mass or more, there is a case where the heat shrinkage rate at a high temperature which is more likely to obtain the effect of the low molecular weight component is obtained.

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. When the amount of the low molecular weight component is 98% by mass or less, in order to maintain the MFR of the entire polypropylene resin, it is not necessary to increase the molecular weight of the low molecular weight component, and it is more likely to obtain a low heat shrinkage rate at a high temperature.

The lower limit of the MFR ratio of the MFR/high molecular weight component of the low molecular weight component is preferably 500, more preferably 1,000, more preferably 2,000, and most preferably 4,000. When the ratio of the MFR of the low molecular weight component to the MFR of the high molecular weight component is 500 or more, it is more likely to obtain a low heat shrinkage rate at a high temperature. The upper limit of the ratio of the MFR of the low molecular weight component to the MFR of the high molecular weight component is preferably 1,000,000.

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

Further, in addition to the above-described high molecular weight component and low molecular weight component, a component having a molecular weight other than the low molecular weight component and the high molecular weight component of the present invention may be added in order to adjust the MFR of the entire polypropylene resin. For example, polypropylene (hereinafter referred to as a medium molecular weight component) which is larger than the low molecular weight component and smaller than the Mw of the high molecular weight component may be contained. and Further, in order to facilitate the loosening of the molecular chain to adjust the elongation, etc., it is preferable to add a polypropylene resin having a Mw of less than 50,000, and it is more preferable to add a polypropylene resin having a Mw of 30,000 or less, and to add a polypropylene resin having a Mw of 10,000 or less. Very good.

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

The upper limit of the ratio of the medium molecular weight component to the entire polypropylene resin constituting the film is preferably 58% by mass, more preferably 56% by mass, even more preferably 54% by mass, and particularly preferably 52% by mass, and 50%. The mass % is the best. When the ratio of the medium molecular weight component is 58% by mass or less, the elongation is easy, the thickness unevenness is small, the elongation temperature and the heat setting temperature are easily increased, and the heat shrinkage ratio is lowered.

The lower limit of the ratio of the polypropylene having a Mw of less than 50,000 to the entire polypropylene resin constituting the film is preferably 0% by mass, more preferably 1% by mass, still more preferably 2% by mass, and particularly preferably 3% by mass. Good, 4% by mass is the best. The addition of the polypropylene having a Mw of less than 50,000 has a case where the effect of the present invention such as a low heat shrinkage rate at a high temperature is more easily obtained.

The upper limit of the ratio of the polypropylene having a Mw of less than 50,000 to the entire polypropylene resin constituting the film is preferably 20% by mass, and is 18%. The mass % is better, preferably 17% by mass, more preferably 16% by mass, and most preferably 15% by mass. When the ratio of the polypropylene having a Mw of less than 50,000 is 20% by mass or less, there is a case where the elongation is easy and the thickness unevenness is small.

Polypropylene molecules having a Mw of less than 50,000 are difficult to form intertwined molecular chains, and have the effect of loosening the inter-molecular entanglement of the plasticizer. It is considered that by arranging the amount of the component containing a specific amount of polypropylene having a Mw of less than 50,000, it is easy to loosen the inter-molecular entanglement during stretching, and it is possible to extend with a low elongation stress, and as a result, the residual stress is low and the high temperature can be lowered. The shrinkage rate in the middle.

In order to use a high molecular weight component and a low molecular weight component to form a preferred molecular weight distribution of the polypropylene resin, for example, when the molecular weight of the low molecular weight component to be used is low, the molecular weight of the high molecular weight component can be increased, and the amount of the high molecular weight component can be increased to adjust The state of the molecular weight distribution is simultaneously adjusted to become an MFR which is easy to manufacture the stretched film.

(stereoregularity of polypropylene resin)

The lower limit of the isotactic pentad fraction (hereinafter also referred to as mmmm) of the stereoregularity index of the polypropylene resin constituting the film is preferably 96%, more preferably 96.5%, and 97% or more. good. When the mmmm is 96% or more, the crystallinity is improved and the heat shrinkage rate at a high temperature is lowered.

The upper limit of mmmm is preferably 99.5%, more preferably 99.3%, and even more preferably 99%. When the mmmm is 99.5% or less, there is a case where it is actually easy to manufacture.

Among the polypropylene resins constituting the film, a heterogeneous bond such as a head-to-head bond such as a propylene monomer is not detected. Further, "no heterojunction was detected" means that no peak appeared in 13 ^C- NMR.

The lower limit of the isotactic mean chain length (hereinafter referred to as meso-average chain length) of the polypropylene resin constituting the film is preferably 100, more preferably 120, and even more preferably 130. When the meso-average chain length is 100 or more, the crystallinity is improved and the heat shrinkage rate at a high temperature is small. The upper limit of the meso-average chain length of the polypropylene resin constituting the film is preferably 5,000.

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 reality. The upper limit of the xylene soluble fraction is preferably 7 mass%, more preferably 6 mass%, and even more preferably 5 mass%. When the xylene solubility of the propylene resin is 7% by mass or less, the crystallinity is improved, and the heat shrinkage rate at a high temperature is small.

The polypropylene resin constituting the film is preferably a propylene homopolymer (completely homo-polypropylene) obtained only from a propylene monomer, but may also be a copolymer of a propylene monomer and a trace amount of a monomer other than the propylene monomer. Things. The monomer type (comonomer type) other than the propylene monomer may be ethylene, butene, hexene, octene or the like.

The upper limit of the proportion of the monomer other than the propylene monomer is preferably 0.1 mol%, more preferably 0.05 mol%, still more preferably 0.01 mol%. When the ratio of the monomer other than the propylene monomer is 0.1 mol% or less, the crystallinity is improved, and the heat shrinkage rate at a high temperature is small.

In the conventional polypropylene film, when a propylene homopolymer is used, since the high crystallinity and the melt tension after melt softening are rapidly lowered, the range of conditions that can be extended is extremely narrow, so that industrial film formation is difficult, and generally 0.5 mol is added. Copolymerization component of about % (mainly ethylene). However, in In the polypropylene resin having the molecular weight distribution state as described above, even if the copolymerization component is almost or completely absent, the tension after melt softening is lowered smoothly, and industrial elongation can be performed.

(Method for producing polypropylene resin)

The polypropylene resin is obtained by polymerizing a propylene raw material using a conventional catalyst such as a Ziegler-Natta catalyst or a metallocene catalyst. Among them, a catalyst which does not easily contain a heterojunction bond like a Ziegler-Natta catalyst and which can carry out polymerization with high stereoregularity is preferred.

The polymerization method of propylene can be a conventional polymerization method, and examples thereof include a method of polymerizing in an inert solvent such as hexane, heptane, toluene or xylene, a method of polymerizing in a liquid propylene or ethylene, and a gas. A method in which a catalyst is added to propylene or ethylene and polymerized in a gas phase state, or a method in which these are polymerized in combination, or the like.

The method for realizing the polypropylene having the molecular weight distribution of the present invention is not particularly limited, but it is essential to substantially contain a high molecular weight component and a low molecular weight component. For example, the high molecular weight component and the low molecular weight component may be separately polymerized and mixed, or may be produced in a series of equipment in a multistage reactor. In particular, in the case of using a device having a multistage reactor, it is preferred to polymerize the high molecular weight component and then polymerize the low molecular weight component in the presence of the polymer.

In the resin composition for molding a polypropylene film of the present invention, in addition to a polypropylene resin or the like, an additive and other resins may be added as needed, but the quality is preferably 30% by mass or less. Additive Examples thereof include antioxidants, ultraviolet absorbers, antistatic agents, lubricants, nucleating agents, adhesives, antifogging agents, flame retardants, anti-caking agents, inorganic or organic fillers, and the like. Examples of the other resin include a polypropylene resin other than the polypropylene resin used in the present invention, a random copolymer of a copolymer of propylene and ethylene and/or an α-olefin having 4 or more carbon atoms, various elastomers, and the like. Examples of the α-olefin having 4 or more carbon atoms include butene, hexene, and octene. These may be mixed with a polypropylene resin by a Henschel mixer, or may be diluted with polypropylene in such a manner that the masterbatch prepared by using a melt kneading machine is used in a predetermined concentration, or may be preliminarily made in whole amount. Used after melt kneading.

(film properties)

The lower limit of the surface alignment coefficient of the polypropylene film of the present invention is preferably 0.0125, more preferably 0.0126, still more preferably 0.0127, and particularly preferably 0.0128. The upper surface of the polypropylene film of the present invention has an upper limit, and the upper limit is preferably 0.015, more preferably 0.0150, more preferably 0.0148, and particularly preferably 0.0145. The surface alignment coefficient can be adjusted by adjusting the stretching ratio in the MD direction and the TD direction. When the surface alignment coefficient of the film is 0.0125 or more and 0.0155 or less, the thickness unevenness of the film is also good.

The lower limit of the refractive index (Nx) in the MD direction of the polypropylene film of the present invention is preferably 1.502, more preferably 1.503, and even more preferably 1.504. The upper limit of Nx is preferably 1.520, more preferably 1.517, and even better at 1.515.

The polypropylene film of the present invention has a refractive index (Ny) in the TD direction The limit is preferably 1.523 and better at 1.525. The upper limit of Ny is preferably 1.535 and more preferably 1.532.

The lower limit of the refractive index (Nz) in the thickness direction of the polypropylene film of the present invention is preferably 1.480, more preferably 1.489, and even more preferably 1.501. The upper limit of Nz is preferably 1.510, more preferably 1.507, and even better at 1.505.

(film crystallinity)

The polypropylene film of the present invention has various high crystallinity characteristics as follows.

The lower limit of the degree of crystallization of the polypropylene film of the present invention is preferably 55%, more preferably 56%, more preferably 57%, still more preferably 58%, and most preferably 59%. When the degree of crystallization of the film is less than 55%, the heat shrinkage rate at a high temperature may become large. The upper limit of the degree of crystallization of the polypropylene film of the present invention is preferably 85%, more preferably 80%, more preferably 79%, more preferably 78%, and most preferably 77%. When the degree of crystallization of the film exceeds 85%, it is actually difficult to manufacture. The adjustment of the degree of crystallization of the film can be carried out by reducing or removing comonomer, increasing the low molecular weight component, and setting the extension temperature and the heat setting temperature to a high temperature.

The lower limit of the melting peak temperature of the polypropylene film of the present invention is preferably 168 ° C, more preferably 169 ° C. When the melting peak temperature of the film is 168 ° C or higher, the heat shrinkage rate at a high temperature becomes small. The upper limit of the melting peak temperature of the polypropylene film of the present invention is preferably 180 ° C, more preferably 177 ° C, still more preferably 175 ° C. When the melting peak temperature of the film is 180 ° C or lower, it is actually easy to manufacture. The adjustment of the dissolution peak temperature can be It is carried out by reducing or removing comonomer, setting the elongation temperature and the heat setting temperature to a high temperature.

In the conventional polypropylene film, for example, when the melting peak temperature is around 170 ° C, when a differential scanning calorimeter (hereinafter also referred to as DSC) is used, a peak appears near 140 ° C (starting melting), and even 140 can be expected. The heat resistance at °C will increase sharply at 150 °C. However, the polypropylene film of the present invention does not exhibit a peak even at 150 ° C, and it is considered that the polypropylene film of the present invention has a low heat shrinkage rate at 150 ° C.

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 in which a conventional polypropylene film cannot be imagined. Moreover, the beginning of the melt can be obtained from the DSC chart.

The lower limit of the degree of crystallization at 150 ° C is preferably 48%, more preferably 49%, and even more preferably 50%. 51% is especially good. When the degree of crystallization in 150 ° C is 48% or more, the heat shrinkage rate at a high temperature may become small. The upper limit of the degree of crystallization in 150 ° C is preferably 85% from the actual surface, more preferably 80%, and even more preferably 79%. It is especially good at 78%. The degree of crystallization in 150 ° C can be set within a range by reducing or removing comonomer, increasing a low molecular weight component, and setting the elongation temperature and the heat setting temperature to a high temperature.

The melting peak temperature (Tmp), the degree of crystallization of the film, and the degree of crystallization in 150 ° C can be determined using a differential scanning calorimeter (DSC).

When the temperature is raised from room temperature to 230 ° C in a ratio of 20 ° C / minute The endothermic peak temperature is melted as Tmp. Then, the heat of fusion was determined from the area of the endothermic peak, and the degree of crystallization was determined by dividing the heat of fusion by the heat of crystallization of 209 J/g of the complete crystallization of polypropylene. Further, among the endothermic peak areas, the heat of fusion is obtained from an endothermic peak area of 150 ° C or higher, and by dividing the heat of fusion by the heat of crystallization of 203 J/g of the complete crystal of polypropylene, all of 150 ° C can be obtained. The degree of crystallization in the sample. Further, for the heat of fusion of the complete crystallization of polypropylene, the values described in H. Bu, SZDCheng, B. Wunderlich et al., Makromoleculare Chemie, Rapid Communication, Vol. 9, p. 75 (1988) are used, in the examples described later. The same value is also used.

The impact resistance of the polypropylene film mostly depends on the thickness of the film. When the thickness is generally 20 μm, the lower limit of the impact resistance (23 ° C) of the polypropylene film of the present invention is preferably 0.5 J, more preferably 0.6 J. . When the impact resistance of the film is 0.5 J or more, it has sufficient toughness as a film and does not break during handling. The upper limit of the impact resistance can be 2 J in the actual surface, preferably 1.5 J, and more preferably 1.2 J. When the low molecular weight component is large, the molecular weight of the whole is low, the high molecular weight component is small, and the molecular weight of the high molecular weight component is low, the impact resistance tends to be lowered, so that the components can be adjusted depending on the application. And set in the range.

When the polypropylene film is a biaxially stretched film, the lower limit of the Young's modulus (23 ° C) in the MD direction is preferably 2 Gpa, more preferably 2.1 Gpa, more preferably 2.2 Gpa, and 2.3 Gpa is preferred, 2.4. Gpa is the best. The upper limit of the Young's modulus in the MD direction is preferably 4Gpa, 3.7Gpa More preferably, it is better with 3.5Gpa, 3.4Gpa is the best, and 3.3Gpa is the best. When the Young's modulus in the MD direction is 2 GPa or more and 4 GPa or less, there is a case where the manufacturing is easy and the balance of the MD-TD is improved.

When the polypropylene film is a biaxially stretched film, the lower limit of the Young's modulus (23 ° C) in the TD direction is preferably 3.8 GPa, more preferably 4 Gpa, more preferably 4.2 Gpa, and particularly preferably 4.3 Gpa. The upper limit of the Young's coefficient in the TD direction is 8Gpa, preferably 7.5Gpa, 7Gpa and 6.5Gpa. When the Young's modulus in the TD direction is 3.8 GPa or more and 8 GPa or less, there is a case where the manufacturing is easy and the MD-TD balance is improved.

Moreover, increasing the stretching ratio increases the Young's modulus, and when the MD-TD is extended, the stretching ratio in the MD direction can be set to a low value, and by increasing the stretching ratio in the TD direction, the Young's modulus in the TD direction can be increased.

The lower limit of the thickness unevenness of the polypropylene film of the present invention is preferably 0%, more preferably 0.1%, still more preferably 0.5%, and particularly preferably 1%. The upper limit of the thickness unevenness of the polypropylene film of the present invention is preferably 20%, more preferably 17%, still more preferably 15%, more preferably 12%, and most preferably 10%. When the thickness unevenness of the film is 0% or more and 20% or less, it is less likely to cause defects during post-processing such as coating or printing, and it is easy to use it in applications requiring precision.

The lower limit of density of the polypropylene film of the present invention to 0.910g / cm ³ preferably, more preferably to 0.911g / cm ^3, to 0.912g / cm ³ and more preferably to 0.913g / cm ³ is particularly preferred. When the density of the film is 0.910 g/cm ³ or more, the crystallinity is high and the heat shrinkage rate is small.

The upper limit of the density of the polypropylene film of the present invention is preferably 0.925 g/cm ^{3 , more} preferably 0.922 g/cm ³ , still more preferably 0.920 g/cm ^{3 ,} and particularly preferably 0.918 g/cm ³ . When the density of the film is 0.925 g/cm ³ or less, it is actually easy to manufacture. The density of the film can be improved by an increase in the stretching ratio or temperature, an increase in the heat setting temperature, and further off-line annealing.

(Method for producing polypropylene film)

The polypropylene film of the present invention may be a uniaxially stretched film in the longitudinal direction (MD direction) or the width direction (TD direction), but a biaxially stretched film is preferred. In the case of biaxial stretching, it may be a sequential biaxial extension or a simultaneous biaxial extension.

By extending the polypropylene film, it is possible to obtain a film having a low heat shrinkage rate at 150 ° C which is unpredictable in the conventional polypropylene film.

Hereinafter, a method for producing a longitudinally extending-laterally extending sequential biaxially stretched film of a preferred embodiment will be described, but the method for producing the polypropylene film is not limited thereto.

First, the polypropylene resin was heated and melted in a uniaxial or biaxial extruder, and extruded on a cooling roll to obtain an unstretched sheet. The melt-extruding conditions were such that the resin temperature was 200 to 280 ° C, extruded into a sheet shape by a T-die, and solidified by a cooling roll at a temperature of 10 to 100 ° C. Next, the film is stretched 3 to 8 times in the longitudinal direction (MD direction) by an extension roller of 120 to 160 ° C, followed by a temperature in the width direction (TD direction) of 155 ° C to 175 ° C, more preferably 157 ° C to 170 ° C. Extend 4 to 15 times.

Also, at 165 to 175 ° C, the ambient temperature is preferably 166 to 173 ° C to relax (release) 1 to 15% while performing heat treatment (thermosetting) set).

In the polypropylene film thus obtained, after at least one side is subjected to a corona discharge treatment, a film roll can be obtained by winding up by a winder.

The lower limit of the stretching ratio in the MD direction is preferably 3 times, more preferably 3.5 times. When the stretching ratio in the MD direction is less than 3 times, there is a case where the thickness is uneven. The upper limit of the stretching ratio in the MD direction is preferably 8 times, more preferably 7 times. When the stretching ratio in the MD direction is more than 8 times, it is difficult to extend the subsequent TD direction.

The lower limit of the temperature at which the MD direction is extended (hereinafter referred to as the elongation temperature) is preferably 120 ° C, more preferably 125 ° C, and even more preferably 130 ° C. When the extension temperature in the MD direction is less than 120 ° C, there is a case where the mechanical load becomes large, the thickness unevenness becomes large, or the surface of the film becomes thick. The upper limit of the extension temperature in the MD direction is preferably 160 ° C, more preferably 155 ° C, and even more preferably 150 ° C. The high elongation temperature in the MD direction is preferable for the decrease in the heat shrinkage rate, but there is a case where it is not attached to the roll and cannot be stretched.

The film should be preheated before the TD direction is extended. In order to rapidly increase the temperature of the film to the extension temperature in the TD direction, it is preferred to set the preheating temperature (hereinafter referred to as preheating temperature) to a temperature higher by 10 to 15 ° C than the extension temperature in the TD direction.

The lower limit of the stretching ratio in the TD direction is preferably 4 times, more preferably 5 times, and more preferably 6 times. When the stretching ratio in the TD direction is less than 4 times, there is a case where the thickness is uneven. The upper limit of the stretching ratio in the TD direction is preferably 15 times, more preferably 14 times, and even more preferably 13 times. When the stretching ratio in the TD direction exceeds 15 times, the heat shrinkage rate becomes high and the elongation is broken. The situation of cracking.

The extension in the TD direction can be carried out at a higher temperature than the conventional polypropylene film, and the lower limit of the extension temperature in the TD direction is preferably 155 ° C, more preferably 157 ° C. When the extension temperature in the TD direction is less than 155 ° C, the film may not be sufficiently softened and broken, and the heat shrinkage rate may become high. The upper limit of the extension temperature in the TD direction is preferably 175 ° C, more preferably 170 ° C. In order to lower the heat shrinkage rate, it is preferable that the temperature is higher, but when the extension temperature in the TD direction exceeds 175 ° C, the low molecular weight component is melted and recrystallized, and the surface is rough and the film is whitened.

It is preferred that the stretched film is heat-fixed by heat treatment. The heat setting can be carried out at a higher temperature than the conventional polypropylene film, and the lower limit of the heat treatment temperature (hereinafter referred to as heat setting temperature) for heat setting is preferably 165 ° C, more preferably 166 ° C. When the heat setting temperature is less than 165 ° C, the heat shrinkage rate becomes high. Further, in order to reduce the heat shrinkage rate, it takes a long time to process, and there is a case where productivity is deteriorated. The upper limit of the heat setting temperature is preferably 175 ° C, more preferably 173 ° C. When the heat setting temperature exceeds 175 ° C, the low molecular weight component will melt and recrystallize, and the surface may be rough and the film may be whitened.

It is preferable to moderate the heat when it is fixed. The lower limit of the relaxation rate is preferably 1%, more preferably 2%. When the relaxation rate is less than 1%, the heat shrinkage rate becomes high. The upper limit of the mitigation rate is preferably 15%, and 10% is better. When the relaxation rate exceeds 15%, there is a case where the thickness unevenness is increased.

Further, in order to lower the heat shrinkage rate, the film produced in the above step may be wound into a round shape and then annealed off-line.

The lower limit of the temperature at which annealing is performed offline (hereinafter referred to as offline annealing temperature) is preferably 160 ° C, more preferably 162 ° C, still more preferably 163 ° C. When the off-line annealing temperature is less than 160 ° C, there is a case where an annealing effect cannot be obtained. The upper limit of the off-line annealing temperature is preferably 175 ° C, more preferably 174 ° C, and even more preferably 173 ° C. When the off-line annealing temperature exceeds 175 ° C, the transparency is lowered and the thickness unevenness is increased.

The lower limit of the time for annealing offline (hereinafter referred to as offline annealing time) is preferably 0.1 minutes, more preferably 0.5 minutes, and still more preferably 1 minute. When the off-line annealing time is less than 0.1 minutes, there is a case where an annealing effect cannot be obtained. The upper limit of the off-line annealing time is preferably 30 minutes, more preferably 25 minutes, and even more preferably 20 minutes. When the off-line annealing time exceeds 30 minutes, there is a case where productivity is lowered.

The film thickness is set for various purposes, but the lower limit of the film thickness is preferably 2 μm, more preferably 3 μm, and even more preferably 4 μm. The upper limit of the film thickness is preferably 300 μm, more preferably 250 μm, still more preferably 200 μm, particularly preferably 150 μm, and most preferably 100 μm.

The polypropylene film thus obtained is generally formed into a roll having a width of 2,000 to 12,000 mm and a length of about 1,000 to 50,000 m and wound into a wheel shape. Further, slitting is performed for each use, and a slit roll having a width of 300 to 2000 mm and a length of 500 to 5000 m is prepared for use.

The polypropylene film of the present invention has excellent characteristics as described above in the past.

When the polypropylene film of the present invention is used as a packaging film, it can be made thinner due to high rigidity, and can be reduced in cost and weight.

Further, since the polypropylene film of the present invention has high heat resistance, it can be subjected to high-temperature treatment at the time of coating or printing, and production efficiency can be improved or a coating agent, an ink, a laminating adhesive, or the like which has been difficult to use in the past can be used.

Further, the polypropylene film of the present invention may be used as a base film of an insulating film such as a capacitor or a motor, a back seat of a solar cell, a barrier film of an inorganic oxide, or a transparent conductive film such as ITO.

[Examples]

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

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

It was measured in accordance with JIS K 7210 at a temperature of 230 ° C and a load of 2.16 kgf.

2) Molecular weight and molecular weight distribution

The molecular weight and molecular weight distribution were determined by gel permeation chromatography (GPC) on a monodisperse polystyrene basis.

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

Solvent: 1,2,4-trichlorobenzene

Column: TSKgel GMH _HR -H(20)HT×3

Flow rate: 1.0ml/min

Detector: RI

Measuring temperature: 140 ° C

The number average molecular weight (Mn), the mass average molecular weight (Mw), the Z average molecular weight (Mz), and the Z+1 average molecular weight (Mz+1) are the molecular weights of the respective precipitation positions of the GPC curve obtained by the molecular weight calibration curve, respectively. The number of molecules (Ni) of (Mi) is defined by the following formula.

Number average molecular weight Mn = Σ (Ni‧Mi) / Σ Ni

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

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

When the baseline is not clear, the range from the lowest position of the peak of the high molecular weight side of the precipitation peak on the nearest high molecular weight side of the peak of the standard substance is set as the baseline.

From the obtained GPC curve, two or more components having different molecular weights were subjected to peak separation. The molecular weight distribution of each component is assumed to be a Gaussian function, and each peak width is set such that Mw/Mn = 4. The average molecular weight was calculated from the curves of the obtained components.

Further, the GPC curve of the entire polypropylene resin constituting the film is determined to have a molecular weight of 10,000 or less in the entire polypropylene resin constituting the film. The ratio of the components and the ratio of the components having a molecular weight of 100,000 or less.

3) Stereo regularity

The measurement of mmmm and meso average chain length was carried out using ¹³ C-NMR. Mmmmm is based on the method described by Zambelli et al. in Macromolecules, Vol. 6, p. 925 (1973). The meso-average chain length is based on JCRandall in "Polymer Sequence Distribution" Chapter 2 (1977) (Academic Press, New York). The method described is calculated.

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

4) Heating elongation (%)

The heating elongation was measured by TMA, and the TMA measurement was carried out using TMA-60 manufactured by Shimadzu Corporation. A strip having a length of 20 mm in the MD direction and a width of 4 mm in the TD direction was cut out from the film as a sample. The chuck distance was set to 10 mm, and the dimensional change in the MD direction was measured from a room temperature at a temperature increase rate of 5 ° C/min at a fixed load of 0.5 kg/mm ² , and the temperature was raised relative to the room temperature (23 ° C). The rate of dimensional change in the MD direction of the sample at temperature was taken as the heating elongation E (%).

5) Density (g/cm ³ )

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

6) Melting peak temperature (Tmp, °C)

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

7) Crystallization degree

The heat of fusion (ΔHm, J/g) was determined from the area of the endothermic peak in the DSC melting profile, and the degree of crystallization was determined by dividing the value of ΔHm by the heat of dissolution of 203 J/g of the complete crystal of polypropylene.

Further, the heat of fusion (ΔHm', J/g) was determined from the endothermic peak area of 150 ° C or more in the DSC melting profile, and the value of the ΔHm' was divided by the heat of dissolution of the completely crystallized polypropylene of 209 J/g. The degree of crystallization in the entire sample at 150 ° C was determined.

8) Cold xylene soluble part (CXS, mass%)

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

9) Thermal shrinkage rate (%)

The measurement was carried out in accordance with JIS Z 1712. That is, the polypropylene film was cut into a width of 20 mm and a length of 200 mm in the MD and TD directions, respectively, and suspended in a hot air oven for 5 minutes. The length after heating was measured, and the ratio of the shrinkage length to the original length was determined to obtain the heat shrinkage ratio.

10) Impact resistance

A film impact tester manufactured by Toyo Seiki Seisakusho Co., Ltd. was used and measured at 23 °C.

11) Young's coefficient (GPa)

The Young's modulus in the MD and TD directions was measured at 23 ° C according to JIS K 7127.

12) Haze (%)

The measurement was carried out in accordance with JIS K 7105.

13) Refractive index

The measurement was carried out using an Abbe refractometer manufactured by ATAGO. The refractive indices in the MD and TD directions are respectively set to Nx and Ny, and the refractive index in the thickness direction is set to Nz.

14) Surface alignment coefficient

From the Nx, Ny, and Nz measured in the above 13), the plane alignment coefficient (P) was calculated using the following formula.

P=[(Nx+Ny)/2]-Nz

15) Uneven thickness

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

Calculate the average value of the data of 100 points, and find the difference between the minimum value and the maximum value (absolute value), and divide the absolute value of the difference between the minimum value and the maximum value by the average value as the thickness unevenness of the film. .

(Example 1)

As the polypropylene resin, a propylene homopolymer having Mw/Mn = 7.7, Mz+1/Mn = 140, MFR = 5.0/10 minutes, and mmmm = 97.3% was used (manufactured by Japan POLYPRO Co., Ltd.: Novatec (registered trademark) PP "SA4L") (hereinafter referred to as "PP-1"). Using a 60 mm extruder, extruding into a sheet shape at 250 ° C in a T die, cooling and solidifying with a chill roll at 30 ° C, and then extending 4.5 times in the longitudinal direction (MD direction) at 135 ° C, and then clamping the ends with a chuck. Live, import In the hot air oven, after preheating at 170 ° C, it was extended 8.2 times in the width direction (TD direction) at 160 ° C, followed by relaxation at a relaxation rate of 6.7%, while heat treatment was performed at 168 ° C. Then, the film was subjected to corona treatment on one side and taken up by a coiler. The thickness of the film thus obtained was 20 μm, the characteristics of the polypropylene and the like are shown in Tables 1 and 2, and the film formation conditions are shown in Table 3. As shown in Table 5, a film having a low heat shrinkage rate and a high Young's modulus can be obtained. The DSC chart of the stretched propylene film of Example 1 is shown in Fig. 1.

(Example 2)

A film was obtained in the same manner as in Example 1 except that the thickness was changed to 13 μm. The properties and the like of the polypropylene resin are shown in Tables 1 and 2, and the film formation conditions are shown in Table 3. The obtained film properties are shown in Table 5.

(Example 3)

A film was obtained in the same manner as in Example 1 except that the thickness was 4 μm and the preheating temperature was 169 °C. The properties and the like of the polypropylene resin are shown in Tables 1 and 2, and the film formation conditions are shown in Table 3. The obtained film properties are shown in Table 5.

(Example 4)

10 parts by weight of a low molecular weight polypropylene (Hi-wax "NP105" manufactured by Mitsui Chemicals Co., Ltd.) having a molecular weight of 10,000 was added to 90 parts by weight of the above-mentioned "PP-1" to prepare 100 parts by weight, and 30 mm of biaxial extrusion was carried out. The machine was melt-kneaded to obtain a pellet of the mixture "PP-2". The pellet was obtained in the same manner as in Example 1 to obtain a film. The properties and the like of the polypropylene resin are shown in Tables 1 and 2, and the film formation conditions are shown in Table 3. The obtained film properties are shown in Table 5.

(Example 5)

To 70 parts by weight of the above "PP-1", 30 parts by weight of a propylene homopolymer having Mw/Mn = 4.6, Mz+1/Mn = 22, MFR = 120 g/10 min, and mmmm = 98.1% was added, and dry blending was carried out. The mixture "PP-3" was obtained. A film was obtained in the same manner as in Example 1 using "PP-3". The properties and the like of the polypropylene resin are shown in Tables 1 and 2, and the film formation conditions are shown in Table 3. The obtained film properties are shown in Table 5.

(Example 6)

Using the above "PP-1", a film was obtained in the same manner as in Example 1 except that the preheating temperature was set to 173 ° C, the extension temperature in the TD direction, and the heat setting temperature were set to 167 ° C. The properties and the like of the polypropylene resin are shown in Tables 1 and 2, and the film formation conditions are shown in Table 3. The obtained film properties are shown in Table 5.

(Example 7)

A film was obtained in the same manner as in Example 4 except that it was extended 5.5 times in the longitudinal direction and 12 times in the width direction. The properties and the like of the polypropylene resin are shown in Tables 1 and 2, and the film formation conditions are shown in Table 3. The obtained film properties are shown in Table 5.

(Example 8)

Using the film produced in Example 1, heat treatment (offline annealing) was performed at 170 ° C for 5 minutes in a tenter type hot air oven. The properties and the like of the polypropylene resin are shown in Tables 1 and 2, and the film formation conditions are shown in Table 3. The obtained film properties are shown in Table 5.

(Example 9)

In addition to the polypropylene resin, a propylene homopolymer (SAMSUNG) having Mw/Mn=8.9, Mz+1/Mn=110, MFR=3.0/10 minutes, and mmmm=97.1% was used. "HU300" manufactured by TOTAL (hereinafter referred to as "PP-4"), the preheating temperature is 171 °C, the extension temperature in the TD direction is 161 °C, and the heat setting temperature is 170 °C. A polypropylene film was obtained in the same manner as in Example 1. The properties and the like of the polypropylene resin are shown in Tables 1 and 2, the film formation conditions are shown in Table 3, and the physical properties thereof are shown in Table 5.

The polypropylene film described in Examples 1 to 9 has high rigidity and heat resistance, and the film is less deformed during printing.

(Comparative Example 1)

In addition to the polypropylene resin, Sumitomo Nobrene (registered trademark) manufactured by Sumitomo Chemical Co., Ltd. using Mw/Mn=4, Mz+1/Mn=21, MFR=2.5 g/10 min, and ethylene amount = 0.6 mol%. FS2011DG3" (hereinafter referred to as "PP-5"), MD extension temperature is 125 °C, preheating temperature is 168 °C, extension temperature in TD direction is 155 °C, and heat setting temperature is 163 °C. A film was obtained in the same manner as in Example 1. The properties and the like of the polypropylene resin are shown in Tables 1 and 2, and the film formation conditions are shown in Table 4. The physical properties of the obtained film are shown in Table 6. The DSC chart of the stretched propylene film of Comparative Example 1 is shown in Fig. 1.

(Comparative Example 2)

A film was obtained in the same manner as in Comparative Example 1, except that the thickness was set to 12 μm and the preheating temperature was set to 167 °C. The properties and the like of the polypropylene resin are shown in Tables 1 and 2, and the film formation conditions are shown in Table 4, and the physical properties of the obtained film are shown in Table 6.

(Comparative Example 3)

In addition to setting the thickness to 4 μm, the preheating temperature is set to 165 ° C, A film was obtained in the same manner as in Comparative Example 1. The properties and the like of the polypropylene resin are shown in Tables 1 and 2, and the film formation conditions are shown in Table 4, and the physical properties of the obtained film are shown in Table 6.

(Comparative Example 4)

A film was obtained in the same manner as in Comparative Example 1, except that the preheating temperature was 171 ° C, the extension temperature in the TD direction was 160 ° C, and the heat setting temperature was 165 ° C. The properties and the like of the polypropylene resin are shown in Tables 1 and 2, and the film formation conditions are shown in Table 4, and the physical properties of the obtained film are shown in Table 6.

(Comparative Example 5)

As the polypropylene resin, a propylene homopolymer (hereinafter referred to as "PP-6") having Mw/Mn = 4.3, Mz+1/Mn = 28, MFR = 0.5 g/10 min, and mmmm = 97.0% was used and implemented. The film was obtained under the same conditions as in Example 9. The properties and the like of the polypropylene resin are shown in Tables 1 and 2, and the film formation conditions are shown in Table 4. The physical properties of the obtained film are shown in Table 6.

(Comparative Example 6)

Novatec PP "SA03" manufactured by Japan POLYPRO Co., Ltd., which uses a polypropylene homopolymer of Mw/Mn = 2.8, Mz+1/Mn = 9.2, MFR = 30 g/10 min, and mmmm = 97.9%, as a polypropylene resin. In the case of "PP-7", biaxial stretching was attempted in the same manner as in Example 1, but when it was extended in the width direction, it was broken and a film could not be obtained. The properties and the like of the polypropylene resin are shown in Tables 1 and 2, and the film formation conditions are shown in Table 4.

The polypropylene film described in Comparative Examples 1 to 5 was low in rigidity and heat resistance, and the deformation of the film during printing was also large.

[Industrial availability]

The polypropylene film of the present invention can be widely used in packaging applications and industrial applications, and is particularly excellent in heat resistance and dimensional stability, and is therefore suitable for printing processing.

Further, since the polypropylene film of the present invention has high heat resistance, it can be treated at a high temperature during coating or printing, and productivity can be improved, and a coating agent, an ink, a laminating adhesive, etc. which have been difficult to use in the past can be used. It is used on the polypropylene film of the present invention.

Further, it can be applied to an insulating film such as a capacitor or a motor, a base of a solar cell, a barrier film of an inorganic oxide, or a base film of a transparent conductive film such as ITO.

Claims (4)

A polypropylene film characterized by having a haze of 6% or less, a heat shrinkage ratio of 150 ° C or less of 15% or less, and thermomechanical analysis under the conditions of a temperature increase rate of 5 ° C / min and a load of 0.5 kg / mm ² The heating elongation E (%) in the longitudinal direction satisfies the formula (1) at 120 ° C to 150 ° C: Log (E) ≦ 0.0275T - 2.4839 (1) T is the temperature (° C.). The polypropylene film according to claim 1, wherein the lower limit of the isotactic meso-component ratio of the polypropylene resin constituting the film is 96%, and the lower limit of the surface alignment coefficient of the film is 0.0125. The polypropylene film according to claim 1 or 2, wherein the upper limit of the amount of the comonomer of the polypropylene resin constituting the film is 0.1 mol%. The polypropylene film according to claim 1 or 2, wherein the polypropylene resin constituting the film has a room temperature xylene soluble fraction of 7 mass% or less.