TW202136394A - Production method for biaxially-oriented polypropylene film - Google Patents

Abstract

The purpose of the present invention is to provide a biaxially-oriented polypropylene film which has high rigidity, has excellent heat resistance at temperatures as high as 150 DEG C, easily maintains a bag shape when formed into a packaging bag, and has few wrinkles in a sealed part when heat sealed. Provided is a production method for a biaxially-oriented polypropylene film, said production method comprising, in the given order: a step in which a polypropylene resin composition containing a polypropylene resin with a meso pentad fraction of at least 97.0% is extruded to obtain an unstretched sheet; a step in which the unstretched sheet is stretched in the length direction thereof; a preheating step in which the length-direction stretched film is heated to a preheat temperature in the range from Tm to Tm+25 DEG C; a step in which the preheated length-direction stretched film is stretched in the width direction by a factor of at least 10 at a temperature in the range from Tm-10 DEG C to the preheat temperature; a step in which the film is cooled at a temperature that is not greater than the width-direction stretching temperature when the width-direction stretching was completed and is in the range from Tm-80 DEG C to Tm-15 DEG C; and a heat treatment step.

Description

Manufacturing method of biaxially oriented polypropylene film

The present invention relates to a method for manufacturing a biaxially oriented polypropylene film with excellent rigidity and heat resistance. In detail, it relates to the following manufacturing method of a biaxially oriented polypropylene film. The biaxially oriented polypropylene film is easy to maintain the shape of the bag when it is made into a packaging bag, and there are few wrinkles in the sealing part during heat sealing, so it can More suitable for packaging bags.

Biaxially oriented polypropylene film is used for packaging or industrial applications because of its moisture resistance, and necessary rigidity and heat resistance. In recent years, with the expansion of use applications, higher performance is required, and in particular, the increase in rigidity is expected. In addition, out of consideration for the environment, it is required to maintain the strength even if the volume is reduced (the film thickness is thinned), but it is indispensable for this to increase the rigidity significantly. As a means to increase rigidity, it is known that the crystallinity and melting point of polypropylene resin can be improved by improving the catalyst or process technology during polymerization of polypropylene resin. However, despite this improvement, there has been no sufficient rigidity so far. Biaxially aligned polypropylene film.

The industry has proposed the following method: in the manufacturing step of the biaxially oriented polypropylene film, after stretching in the width direction, the film is relaxed below the temperature when the side is stretched in the width direction, and the heat treatment in the first stage is performed on the second stage. A method of heat-treating from the first stage temperature to the elongation temperature in the width direction (for example, refer to Patent Literature 1, etc.); and a method of extending in the length direction after stretching in the width direction (for example, refer to Patent Literature 2, etc.). However, although the film described in Patent Document 2 is excellent in rigidity, it is easy to produce wrinkles in the sealed portion after heat sealing, and the heat resistance is poor. In addition, the film described in Patent Document 1 has low orientation and insufficient rigidity. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] International Publication No. WO2016/182003. [Patent Document 2] JP 2013-177645 A.

[The problem to be solved by the invention]

The subject of the present invention is to solve the above-mentioned problems. That is, it relates to a method for manufacturing a biaxially oriented polypropylene film with excellent film rigidity, and further relates to a method for manufacturing a biaxially oriented polypropylene film with excellent film rigidity and heat resistance at high temperatures up to 150°C. In detail, the following method for manufacturing a biaxially oriented polypropylene film is provided. The biaxially oriented polypropylene film is easy to maintain the shape of the bag when it is made into a packaging bag, and has less wrinkles at the sealing portion and its surroundings during heat sealing. [Means to solve the problem]

The inventors of the present case have made diligent studies to achieve the above-mentioned object, and found that by the following manufacturing method, a biaxially oriented polypropylene film with excellent film rigidity can be obtained, and the rigidity of the film can be obtained at a high temperature of up to 150°C. Biaxially oriented polypropylene film with excellent heat resistance. That is, the present invention is a method for manufacturing a biaxially oriented polypropylene film, which in turn includes: a polypropylene resin composition containing a polypropylene resin with a meso pentad fraction of 97.0% or more The step of obtaining the unstretched sheet by extrusion, the step of extending the unstretched sheet in the length direction, the preheating step of heating the lengthwise stretched film to a preheating temperature in the range of Tm to Tm + 25°C, and the preheating step of the preheated length direction The step of stretching the stretched film at a temperature above Tm-10°C to below the preheating temperature with a magnification of 10 times or more in the width direction, and at the end of the width direction stretching at a temperature below the width direction stretching temperature and Tm-80°C above to Tm-15 The step of cooling the film at a temperature below ℃, and the step of heat treatment.

In this case, it is more appropriate that the crystallization temperature of the polypropylene resin constituting the biaxially oriented polypropylene film is 105°C or higher and the melting point is 160°C or higher.

In this case, it is more appropriate that the melt flow rate of the polypropylene resin constituting the biaxially oriented polypropylene film is 4.0 g/10 minutes or more.

In addition, in this case, it is more appropriate that the polypropylene resin constituting the biaxially oriented polypropylene film has a molecular weight of 100,000 or less and a component content of 35% by mass or more. [Efficacy of invention]

By applying the manufacturing method of the biaxially oriented polypropylene film of the present invention, a biaxially oriented polypropylene film can be obtained. Due to its high rigidity, it is easy to maintain the shape of the bag when it is made into a packaging bag, so it can be more suitably used for Packaging bag. Furthermore, it is possible to obtain a biaxially oriented polypropylene film, which has high rigidity and excellent heat resistance at high temperatures up to 150°C, so it is easy to maintain the shape of the bag when it is made into a packaging bag, and there are few wrinkles in the sealing portion during heat sealing. , So it can be more suitable for packaging bags. In addition, the biaxially oriented polypropylene film is also excellent in rigidity, can maintain strength even if the thickness of the film is reduced, and can be suitably used for applications requiring higher rigidity.

Hereinafter, the manufacturing method of the biaxially oriented polypropylene film of the present invention will be described in more detail.

The biaxially oriented polypropylene film obtained by the present invention is composed of a polypropylene resin composition with polypropylene resin as the main component. Furthermore, the so-called "main component" means that the proportion of polypropylene resin in the polypropylene resin composition is 90% by mass or more, more preferably 93% by mass or more, and even more preferably 95% by mass or more, especially It is 97% by mass or more.

[Polypropylene resin] The polypropylene resin used in the present invention may be a polypropylene homopolymer, or a copolymer of propylene, ethylene and/or α-olefin with 4 or more carbon atoms. Preferably, it is a propylene homopolymer that does not substantially contain ethylene and/or α-olefin with a carbon number of 4 or more, even when it contains ethylene and/or an α-olefin component with a carbon number of 4 or more, ethylene and/or carbon The amount of the α-olefin component having a number of 4 or more is also preferably 1 mol% or less. The upper limit of the component amount is more preferably 0.5 mol%, further preferably 0.3 mol%, and particularly preferably 0.1 mol%. If it is the said range, crystallinity will improve easily. Examples of the α-olefin component having 4 or more carbon atoms constituting the copolymer include 1-butene, 1-pentene, 3-methyl-1-pentene, and 3-methyl-1-butene , 1-hexene, 4-methyl-1-pentene, 5-ethyl-1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1- Hexadecene, 1-heptadecene, 1-octadecene, 1-eicosene, etc. As the polypropylene resin, two or more different polypropylene homopolymers, or copolymers of propylene, ethylene and/or α-olefins with 4 or more carbon atoms, and mixtures of these can be used.

[Three-dimensional regularity] The meso pentad fraction ([mmmm]%) of the polypropylene resin used in the present invention as an indicator of stereoregularity is preferably in the range of 97.0% to 99.9%, more preferably 97.5% to 99.7 In the range of %, more preferably in the range of 98.0% to 99.5%, and particularly preferably in the range of 98.5% to 99.3%. If it is 97.0% or more, the crystallinity of the polypropylene resin is improved, the melting point, crystallinity, and crystal orientation of the crystals in the film are improved, and it is easy to obtain rigidity and heat resistance at high temperatures. If it is 99.9% or less, it is easy to suppress the cost in the production of polypropylene, and it becomes difficult to break during film formation. More preferably, it is 99.5% or less. The meso pentad fraction is measured by the nuclear magnetic resonance method (the so-called NMR (Nuclear Magnetic Resonance) method). In order to make the meso pentad component ratio of the polypropylene resin within the above range, it is preferable to use a method of washing the obtained polypropylene resin powder with a solvent such as n-heptane, or suitable catalyst and/ Or the selection of the auxiliary catalyst, the selection of the components of the polypropylene resin composition, etc.

[Melting temperature] The lower limit of the melting temperature (Tm) of the polypropylene resin constituting the biaxially oriented polypropylene film of the present invention measured by DSC (Differential Scanning Calorimetry) is preferably 160°C, more preferably 161°C, It is more preferably 162°C, and still more preferably 163°C. If Tm is 160°C or higher, it is easy to obtain rigidity and heat resistance at high temperatures. The upper limit of Tm is preferably 170°C, more preferably 169°C, still more preferably 168°C, still more preferably 167°C, and particularly preferably 166°C. If Tm is 170° C. or less, it is easy to suppress an increase in cost in the production of polypropylene, and it becomes difficult to break during film formation. The melting temperature can also be further increased by blending the crystallization nucleating agent in the aforementioned polypropylene resin. The so-called Tm means that 1mg to 10mg of the sample is loaded into an aluminum pan and set in a differential scanning calorimeter (DSC), melted at 230°C for 5 minutes under a nitrogen atmosphere, and cooled to a temperature of -10°C/min at a scanning speed After 30°C, hold for 5 minutes, and the main peak temperature of the endothermic peak with melting observed when the temperature is raised at a scanning speed of 10°C/min.

[Crystalization temperature] The lower limit of the crystallization temperature (Tc) of the polypropylene resin constituting the biaxially oriented polypropylene film of the present invention measured by DSC is 105°C, preferably 108°C, more preferably 110°C. If Tc is 105°C or higher, crystallization in the width direction stretching and subsequent cooling steps is easy to progress, and rigidity and heat resistance at high temperatures are easy to obtain. The upper limit of Tc is preferably 135°C, more preferably 133°C, still more preferably 132°C, still more preferably 130°C, particularly preferably 128°C, and most preferably 127°C. If Tc is 135°C or less, it is difficult to increase the cost in the production of polypropylene, and it becomes difficult to break during film formation. The so-called Tc refers to the observation when a sample of 1 mg to 10 mg is placed in an aluminum pan and set in a DSC, melted at 230°C for 5 minutes under a nitrogen atmosphere, and cooled to 30°C at a scanning speed of -10°C/min. The main peak temperature of the exothermic peak. The crystallization temperature can also be further increased by blending the crystallization nucleating agent in the aforementioned polypropylene resin.

[The melt flow rate] Regarding the melt flow rate (MFR; Melt Flow Rate) of the above-mentioned polypropylene resin constituting the biaxially oriented polypropylene film of the present invention, it was measured in accordance with the condition M (230°C, 2.16kgf) of JIS K 7210 (1995) In the case, it is preferably 4.0g/10min to 30g/10min, more preferably 4.5g/10min to 25g/10min, still more preferably 4.8g/10min to 22g/10min, particularly preferably 5.0 g/10 minutes to 20g/10 minutes, preferably 6.0g/10 minutes to 20g/10 minutes. If the melt flow rate (MFR) of the polypropylene resin is 4.0 g/10 minutes or more, it is easy to obtain a biaxially oriented polypropylene film with low heat shrinkage. In addition, if the melt flow rate (MFR) of the polypropylene resin is 30 g/10 minutes or less, it is easy to maintain the film formability of the film.

From the viewpoint of film characteristics, it is preferable to set the lower limit of the melt flow rate (MFR) (230°C, 2.16 kgf) of the polypropylene resin constituting the film to preferably 5.0 g/10 minutes, more preferably 5.5 g/10 minutes, more preferably 6.0 g/10 minutes, particularly preferably 6.3 g/10 minutes, most preferably 6.5 g/10 minutes. If the melt flow rate (MFR) of the polypropylene resin is 5.0 g/10 minutes or more, the amount of low molecular weight components of the polypropylene resin constituting the film increases. Therefore, by adopting the width direction stretching step in the film forming step described later, The alignment crystallization of the polypropylene resin is further promoted, and the degree of crystallinity in the film becomes easier to further increase. In addition, the entanglement of polypropylene molecular chains in the amorphous part becomes less, and it is easy to further improve the heat resistance. In order to make the melt flow rate (MFR) of the polypropylene resin within the above-mentioned range, a method of controlling the average molecular weight or molecular weight distribution of the polypropylene resin, etc. can be preferably adopted.

That is, the lower limit of the amount of components with a molecular weight of 100,000 or less in the GPC (Gel Permeation Chromatography) cumulative curve of the polypropylene resin constituting the membrane of the present invention is preferably 35% by mass, more preferably 38% by mass, more preferably 40% by mass, particularly preferably 41% by mass, most preferably 42% by mass. The upper limit of the amount of components with a molecular weight of 100,000 or less in the GPC cumulative curve is preferably 65% by mass, more preferably 60% by mass, and still more preferably 58% by mass. If the amount of components with a molecular weight of 100,000 or less in the GPC cumulative curve is 65% by mass or less, the film strength will not easily decrease. At this time, if a high molecular weight component or long chain branch component with a long relaxation time is included, it becomes easy to adjust the amount of the component with a molecular weight of 100,000 or less contained in the polypropylene resin without greatly changing the overall viscosity. Therefore, the rigidity or heat shrinkage is not affected and the film forming properties are easily improved.

[The molecular weight distribution] The lower limit of the mass average molecular weight (Mw)/number average molecular weight (Mn) of the polypropylene resin used in the present invention as an indicator of the breadth of the molecular weight distribution is preferably 3.5, more preferably 4.0, and even more preferably 4.5, especially Preferably it is 5.0. The upper limit of Mw/Mn is preferably 30, more preferably 25, still more preferably 23, particularly preferably 21, and most preferably 20. Mw/Mn can be obtained using gel permeation chromatography (GPC). If Mw/Mn is in the above range, it is easy to increase the amount of components with a molecular weight of 100,000 or less.

Furthermore, the molecular weight distribution of polypropylene resin can be adjusted by the following methods: the components of different molecular weights are polymerized in multiple stages using a series of equipment, or the components of different molecular weights are blended offline using a kneader, or blended. Combine catalysts with different properties for polymerization, or use a catalyst that can achieve the desired molecular weight distribution. As the shape of the molecular weight distribution obtained by GPC, the logarithm (logM) of molecular weight (M) is taken on the horizontal axis and the differential distribution value (weight fraction per logM) is taken on the vertical axis. It can be a GPC graph with a single peak A gentle molecular weight distribution can also be a molecular weight distribution with multiple peaks or shoulders.

[Method of making biaxially oriented polypropylene film] The method for producing the biaxially oriented polypropylene film of the present invention is preferably obtained by producing an unstretched sheet composed of a polypropylene resin composition mainly composed of the above-mentioned polypropylene resin, and performing biaxially extend. As a biaxial stretching method, it can be obtained by any of the inflation synchronous biaxial stretching method, the tenter synchronous biaxial stretching method, and the tenter gradual biaxial stretching method, but the film stability is , From the viewpoint of thickness uniformity, it is preferable to adopt the stenter gradual biaxial stretching method. It is particularly preferable to extend in the width direction after extending in the length direction, but it may also be a method of extending in the width direction and then in the length direction.

Next, the manufacturing method of the biaxially oriented polypropylene film of the present invention will be described below, but it is not necessarily limited to this. Furthermore, the biaxially oriented polypropylene film obtained by the present invention can also be a layer with other functions in at least a single area layer. The build-up layer can be single-sided or double-sided. In this case, the above-mentioned polypropylene resin composition may be used for the resin composition of the other side layer and the center layer. In addition, it may be different from the above-mentioned polypropylene resin composition. Regarding the number of layers of the build-up layer, one layer or two layers or three or more layers per single side may be used, but from the viewpoint of manufacturing, one layer or two layers is preferable. As a method of lamination, for example, co-extrusion using a feed block method or a multi-manifold method is preferred. Especially for the purpose of improving the processability of the biaxially oriented polypropylene film, it is possible to laminate a resin layer with heat sealability within the range of not degrading the characteristics. In addition, in order to impart printability, corona treatment may be applied to one side or both sides.

In the following, an example of a single-layer case will be described for the case where the tenter frame is used for the gradual biaxial stretching method. First, the resin composition containing polypropylene resin is heated and melted using a uniaxial or biaxial extruder, extruded from a T-die into a sheet, and brought into contact with a cooling roll for cooling and solidification. For the purpose of accelerating solidification, it is preferable to immerse the sheet cooled by a cooling roll in a water tank or the like and then cool it.

Then, using two pairs of stretching rollers that have heated the sheet, and increasing the rotation speed of the stretching roller at the back, the sheet is stretched in the longitudinal direction to obtain a uniaxially stretched film.

Then, after preheating the uniaxially stretched film, while holding the end of the film with a tenter-type stretcher, it stretches in the width direction at a specific temperature to obtain a biaxially stretched film. The step of extending in the width direction will be described in detail later.

After the width direction stretching step is completed, the biaxially stretched film is heat-treated at a specific temperature to obtain a biaxially aligned film. In the heat treatment step, the film may also be relaxed in the width direction.

For the biaxially oriented polypropylene film obtained in this way, if necessary, for example, after corona discharge treatment is performed on at least one side, it is wound up with a winder to obtain a film roll.

Hereinafter, each step will be described in detail. [Extrusion step] First, use a uniaxial or biaxial extruder to heat and melt a polypropylene resin composition with polypropylene resin as the main component in the range of 200°C to 300°C, and form a sheet of molten polypropylene resin from a T-die. The product is extruded and brought into contact with a metal cooling roll to cool and solidify. It is preferable to further put the obtained unstretched sheet into the water tank. The temperature of the cooling roll, or the cooling roll and the water tank is preferably in the range of 10°C to Tc. When the transparency of the film is to be improved, it is preferable to use a cooling roll with a temperature in the range of 10°C to 50°C for cooling and solidification. . When the cooling temperature is set to 50°C or lower, the transparency of the unstretched sheet is likely to increase, and it is preferably 40°C or lower, and more preferably 30°C or lower. In order to increase the degree of crystal alignment after the gradual biaxial stretching, it is sometimes preferable to set the cooling temperature to 40°C or higher, but use propylene with a meso pentad component ratio of 97.0% or higher as described above. In the case of a homopolymer, it is preferable to set the cooling temperature to 40°C or lower, more preferably to 30°C or lower, in terms of easy extension in subsequent steps and reduction in thickness unevenness. In terms of cooling efficiency, the thickness of the unstretched sheet is preferably 3500 μm or less, and more preferably 3000 μm or less, which can be appropriately adjusted according to the film thickness after gradual biaxial stretching. The thickness of the unstretched sheet can be controlled by the extrusion speed of the polypropylene resin composition and the width of the lip of the T-die.

[Length direction extension step] The lower limit of the stretching ratio in the length direction is preferably 3 times, more preferably 3.5 times, and particularly preferably 3.8 times. If it is the said range, it will become easy to improve strength, and film thickness unevenness will also become small. The upper limit of the stretching ratio in the length direction is preferably 8 times, more preferably 7.5 times, and particularly preferably 7 times. If it is the said range, the width direction extension in the width direction extension process will be easy to progress, and productivity will improve. The lower limit of the stretching temperature in the longitudinal direction is preferably Tm-40°C, more preferably Tm-37°C, and still more preferably Tm-35°C. If it is the said range, the width direction extending|stretching to be performed next becomes easy, and thickness unevenness also becomes small. The upper limit of the stretching temperature in the longitudinal direction is preferably Tm-7°C, more preferably Tm-10°C, and still more preferably Tm-12°C. If it is the said range, it will become easy to make a thermal contraction rate small, it will become difficult to extend|stretch by adhering to a stretching roll, or the roughness of a surface will increase, and the quality will fall in few cases. In addition, the stretching in the longitudinal direction can also be carried out by using three or more pairs of stretching rolls, divided into two or more stages.

[Preheating step] Before the step of stretching in the width direction, the uniaxially stretched film stretched in the length direction must be heated in the range of Tm to Tm+25°C to soften the polypropylene resin composition. By setting it to Tm or more, softening progresses and extension in the width direction becomes easy. By setting Tm+25°C or less, the alignment during lateral stretching can be performed and the rigidity can be easily expressed. It is more preferably Tm+2°C to Tm+22°C, and particularly preferably Tm+3°C to Tm+20°C. Here, the highest temperature in the preheating step is set as the preheating temperature.

[Width direction extension step] In the width direction extension step after the preheating step, a preferred method is as described below.

In the width direction stretching step, it is preferable to perform stretching at a temperature above Tm-10°C and below the preheating temperature. At this time, the beginning of the width direction extension may be the time when the preheating temperature is reached, or the time when the temperature is lowered after reaching the preheating temperature to reach a temperature lower than the preheating temperature. The lower limit of the temperature in the width direction stretching step is more preferably Tm-9°C, still more preferably Tm-7°C, and particularly preferably Tm-5°C. If the stretching temperature in the width direction is within this range, the rigidity of the biaxially oriented film obtained can be easily increased. The upper limit of the temperature in the width direction stretching step is preferably Tm+10°C, more preferably Tm+7°C, and particularly preferably Tm+5°C. If the elongation temperature in the width direction is within this range, uneven elongation is less likely to occur. At the end of the stretching in the width direction, that is, after reaching the final stretching magnification in the width direction, the film is immediately cooled. The cooling temperature at this time is preferably set to a temperature below the temperature in the width direction and Tm-80°C or more and Tm-15°C or less, more preferably set to a temperature of Tm-80°C or more and Tm-20°C or less, More preferably, it is set to the temperature of Tm-80 degreeC or more and Tm-30 degreeC or less, Especially preferably, it is set to the temperature of Tm-70 degreeC or more and Tm-40 degreeC or less. The temperature at the end of the stretching in the width direction may be gradually reduced to the temperature at the time of cooling, or it may be reduced stepwise or in one step. If the temperature is lowered stepwise or in one step, it is easy to increase the crystal orientation in the film, which is preferable.

The lower limit of the final width direction stretching magnification in the width direction stretching step is preferably 10 times, more preferably 11 times. If it is 10 times or more, the rigidity is easily increased, and the unevenness of the film thickness is also likely to decrease. The upper limit of the stretch magnification in the width direction is preferably 20 times, more preferably 17 times, and still more preferably 15 times. If it is 20 times or less, it is easy to reduce the thermal shrinkage rate, and it is difficult to break during stretching.

In this way, by using polypropylene resin with high stereoregularity and high melting point and high crystallinity, and adopting the above-mentioned width direction extension step, the molecules of the polypropylene resin are highly aligned in the main alignment direction (the above-mentioned width direction extension step is , Which is equivalent to the width direction) is arranged, so more crystals with strong crystal alignment and high melting point are easily generated in the obtained biaxial alignment film. In addition, the alignment of the amorphous portion between the crystals is also increased along the main alignment direction (in the above-mentioned width direction extending step, it corresponds to the width direction), so the rigidity is high. In addition, since there are many crystals with a high melting point around the amorphous part, at a temperature lower than the melting point of the crystal, the stretched polypropylene molecules in the amorphous part are not easy to relax, and it is easy to maintain the tension state of the polypropylene molecules. Therefore, the entire biaxial alignment film can maintain high rigidity even at high temperatures. In addition, it should be noted that by adopting such a width direction stretching step, the heat shrinkage rate at a high temperature of 150° C. is also likely to be further reduced. The reason is that there are more crystals with strong crystal alignment and high melting point around the amorphous part, so the stretched polypropylene resin molecules in the amorphous part are not easily relaxed at a temperature lower than the melting point of the crystal. Furthermore, it should be noted that the alignment of the amorphous portion between the crystals also increases along the main alignment direction (in the above-mentioned width direction stretching step, it is equivalent to the width direction), but it is not in an extremely tensioned state, so tensile fracture elongation The rate increases.

In addition, by increasing the low-molecular-weight component of the polypropylene resin, the crystallinity of the film is easily improved, and the entanglement of the molecular chains of the polypropylene resin in the amorphous part becomes less, and the heat shrinkage stress is reduced. The heat shrinkage rate is further reduced. Considering that in the prior art, if one of the characteristics of strength and heat shrinkage is improved, the other characteristic will decrease. The above improvement can be described as epoch-making.

[Heat treatment step] For a biaxially stretched film, if necessary, in order to further reduce the thermal shrinkage rate, heat treatment may be performed. The upper limit of the heat treatment temperature is preferably Tm + 10°C, more preferably Tm + 7°C, and particularly preferably Tm + 5°C. By setting Tm+10°C or less, it is easy to express rigidity, the roughness of the film surface does not become excessively large, and the film is not easy to whiten. The lower limit of the heat treatment temperature is preferably Tm-5°C, more preferably Tm-2°C, and particularly preferably Tm°C. If it does not reach Tm-5°C, the heat shrinkage rate may increase. By adopting the above-mentioned width-direction stretching step, even if the heat treatment is performed at a temperature between Tm-5°C and Tm+10°C, the crystals with high alignment generated in the stretching step are not easily melted, so that the rigidity of the obtained film can be prevented. Reduce, and make the thermal shrinkage rate smaller. For the purpose of adjusting the thermal shrinkage rate, the film may be relaxed (relaxed) in the width direction during heat treatment, and the upper limit of the relaxation rate is preferably 4%. If it is in the above range, the film strength is unlikely to decrease, and the film thickness fluctuation is likely to be small. It is more preferably 3%, still more preferably 2%, still more preferably 1%, and particularly preferably 0%.

[Film thickness] The thickness of the biaxially aligned polypropylene film obtained by the present invention can be set according to each application, but in terms of obtaining the strength of the film, the lower limit of the film thickness is preferably 2μm, more preferably 3μm, and more preferably 4μm, especially It is preferably 8 μm, most preferably 10 μm. If the film thickness is 2 μm or more, the rigidity of the film is easily obtained. The upper limit of the film thickness is preferably 100 μm, more preferably 80 μm, still more preferably 60 μm, particularly preferably 50 μm, and most preferably 40 μm. If the film thickness is 100 μm or less, the cooling rate of the unstretched sheet during the extrusion step is unlikely to decrease. The biaxially oriented polypropylene film obtained by the present invention is usually formed into a roll with a width of 2000 mm to 12000 mm and a length of about 1000 m to 50000 m, and is wound into a film roll shape. Furthermore, it is cut according to each application and provided in the form of a slitting roll with a width of 300mm to 2000mm and a length of 500mm to 5000m. The biaxially oriented polypropylene film of the present invention can obtain a longer-sized film roll.

[Thickness uniformity] The lower limit of the thickness uniformity of the biaxially oriented polypropylene film obtained by the present invention is preferably 0%, more preferably 0.1%, further preferably 0.5%, and particularly preferably 1%. The upper limit of the thickness uniformity is preferably 20%, more preferably 17%, further preferably 15%, particularly preferably 12%, and most preferably 10%. If it is in the above range, defects are less likely to occur during post-processing such as coating or printing, and it is easy to use for applications requiring precision. The measurement method is as follows. A test piece of 40 mm in the width direction was cut from a constant area where the physical properties of the film were stable along the length of the film. The film supply device manufactured by MIKURON Measuring Instruments Co., Ltd. (use product model: A90172) and the film thickness manufactured by Anritsu Co., Ltd. were used. The measuring device (product name: K-313A wide-range high-sensitivity electronic micrometer) continuously measures the film thickness within a range of 20,000 mm, and calculates the thickness uniformity from the following formula. Thickness uniformity (%)=[(maximum thickness-minimum thickness)/average thickness]×100

[Film characteristics] The biaxially oriented polypropylene film of the present invention has the following characteristics. Here, the so-called "length direction" in the biaxially oriented polypropylene film of the present invention refers to the direction corresponding to the direction of travel in the film manufacturing step, and the so-called "width direction" refers to the travel in the aforementioned film manufacturing step. Orthogonal direction. For a polypropylene film whose traveling direction is unknown in the film manufacturing step, a wide-angle X-ray is incident in a direction perpendicular to the film surface, and the scattering peak originating from the (110) plane of the α-type crystal is scanned in the circumferential direction to obtain The direction of the maximum diffraction intensity of the diffraction intensity distribution is set as the "length direction", and the direction orthogonal to the "length direction" is set as the "width direction".

[150℃ heat shrinkage rate] The upper limit of the thermal shrinkage rate of the biaxially oriented polypropylene film of the present invention in the length direction at 150°C is 10%, preferably 7.0%, more preferably 6.0%, still more preferably 5.0%, particularly preferably 4.0% or less . The upper limit of the thermal shrinkage in the width direction at 150° C. is preferably 30%, more preferably 24%, still more preferably 21%, and particularly preferably 18% or less. If the thermal shrinkage rate in the longitudinal direction is 10% or less and the thermal shrinkage rate in the width direction is 30% or less, wrinkles will not easily occur during heat sealing, especially if the thermal shrinkage rate in the longitudinal direction at 150°C is 8.0% or less and The heat shrinkage rate in the width direction at 150°C is 20% or less, and the strain at the time of welding the clip chain part at the opening part is small, which is preferable. In order to reduce the heat shrinkage rate at 150°C, it is effective to measure the lower limit of the amount of components with a molecular weight of 100,000 or less in the case of the gel permeation chromatography (GPC) cumulative curve of the polypropylene resin constituting the membrane. Set to 35% by mass, and adjust the stretching ratio, stretching temperature, and heat fixing temperature.

[Tensile breaking strength at 23℃] The thermal shrinkage rate (%) of the biaxially oriented polypropylene film in the width direction at 150°C and the tensile breaking strength (MPa) in the width direction at 23°C of the present invention must satisfy the following formula. By satisfying the following formula, the rigidity is higher and the heat shrinkage rate at high temperature is smaller. Therefore, the ease of maintaining the shape of the bag when it is made into a packaging bag is further improved, and the film is less likely to be deformed during processing such as printing. The tensile breaking strength in the width direction at 23°C (MPa) ≧The heat shrinkage in the width direction at 150°C (%)×6.2＋300

The lower limit of the tensile breaking strength of the biaxially oriented polypropylene film of the present invention at 23° C. in the longitudinal direction is preferably 90 MPa, more preferably 100 MPa, further preferably 110 MPa, and particularly preferably 120 MPa. If it is 90 MPa or more, it becomes less likely that the printing pitch deviation occurs when the printing ink is transferred, and the durability of the packaging bag is also likely to be excellent. The actual value of the upper limit of the tensile strength at break in the longitudinal direction is preferably 200 MPa, more preferably 180 MPa, and still more preferably 160 MPa. If it is 200 MPa or less, the breakage of the film or the breakage of the packaging bag is likely to decrease. The lower limit of the tensile breaking strength of the biaxially oriented polypropylene film of the present invention in the width direction at 23° C. is preferably 380 MPa, more preferably 400 MPa, further preferably 430 MPa, and particularly preferably 450 MPa. If it is 380 MPa or more, it becomes difficult to produce print pitch deviation when transferring the printing ink, and the durability of the packaging bag is also likely to be excellent. The actual value of the upper limit of the tensile breaking strength in the width direction is preferably 550 MPa, more preferably 520 MPa, and still more preferably 500 MPa. If it is less than 550MPa, the breakage of the film or the breakage of the packaging bag is likely to decrease. In order to increase the tensile strength at break, it is effective to set the lower limit of the amount of components with a molecular weight of 100,000 or less when the cumulative curve of the gel permeation chromatography (GPC) of polypropylene resin constituting the film is measured 35 mass%, and adjust the stretching ratio, stretching temperature, and heat fixing temperature.

The biaxially oriented polypropylene film of the present invention more preferably has the following characteristics and structure. [Stress at 5% elongation at 23℃] The lower limit of the stress (F5) of the biaxially oriented polypropylene film of the present invention at 5% elongation in the longitudinal direction at 23°C is preferably 40 MPa, more preferably 42 MPa, furthermore preferably 44 MPa, and even more preferably 46 MPa, especially Preferably, it is 48 MPa. If it is 40 MPa or more, since the rigidity is high, it is easy to maintain the shape of the bag when it is made into a packaging bag, and the film is unlikely to be deformed during processing such as printing. The upper limit of F5 in the length direction is preferably 70 MPa, more preferably 65 MPa, still more preferably 62 MPa, and particularly preferably 60 MPa. If it is 70 MPa or less, actual manufacturing becomes easier, and the longitudinal-width balance is easily improved. The lower limit of F5 in the width direction of the biaxially oriented polypropylene film of the present invention at 23° C. is preferably 160 MPa, more preferably 170 MPa, further preferably 180 MPa, and particularly preferably 190 MPa. If it is 160 MPa or more, since the rigidity is high, it is easy to maintain the shape of the bag when it is made into a packaging bag, and the film is unlikely to be deformed during processing such as printing. The upper limit of F5 in the width direction is preferably 250 MPa, more preferably 230 MPa, and still more preferably 220 MPa. If it is 250 MPa or less, actual manufacturing is easy, and the longitudinal-width balance is easy to improve. F5 can be in the range by adjusting the stretching ratio or relaxation ratio, or adjusting the temperature at the time of film formation.

[23℃ tensile elongation at break] The lower limit of the tensile elongation at break of the biaxially oriented polypropylene film of the present invention at 23° C. in the longitudinal direction is preferably 195%, more preferably 200%, more preferably 210%, and particularly preferably 220% or more. If it is more than 195%, the breakage of the film or the breakage of the packaging bag is likely to decrease. The actual value of the upper limit of the tensile elongation at break in the longitudinal direction is preferably 300%, more preferably 280%.

The lower limit of the tensile elongation at break in the width direction of the biaxially oriented polypropylene film of the present invention at 23° C. is preferably 25%, more preferably 30%, still more preferably 32%, and particularly preferably 35% or more. If it is more than 25%, the breakage of the film or the breakage of the packaging bag is likely to decrease. The upper limit of the tensile elongation at break in the width direction is preferably 60%, more preferably 55%, and still more preferably 50%. If it is 60% or less, it becomes less likely to produce print pitch deviation when transferring the printing ink, and the durability of the packaging bag is also likely to be excellent. The tensile elongation at break can be adjusted within the range by adjusting the stretching ratio, the stretching temperature, and the heat-fixing temperature.

[120℃ heat shrinkage rate] The upper limit of the thermal shrinkage rate of the biaxially oriented polypropylene film of the present invention at 120° C. in the longitudinal direction is preferably 2.0%, more preferably 1.5%, further preferably 1.2%, and particularly preferably 1.0%. If it is 2.0% or less, it becomes less likely to cause print pitch deviation when printing ink is transferred. The upper limit of the thermal shrinkage in the width direction at 120°C is 5.0%, preferably 4.0%, more preferably 3.5%, and particularly preferably 2.5%. If it is 5.0% or less, wrinkles are less likely to occur during heat sealing. If the thermal shrinkage rate in the longitudinal direction at 120°C is smaller than the thermal shrinkage rate in the width direction at 120°C, the printing pitch deviation will be less likely to occur when the printing ink is transferred. The heat shrinkage rate at 120°C and the length direction-width direction balance of the heat shrinkage rate can be adjusted within the range by adjusting the stretching ratio, stretching temperature, and heat fixing temperature.

[Refractive Index] The lower limit of the refractive index (Nx) in the length direction of the biaxially oriented polypropylene film of the present invention is preferably 1.4950, more preferably 1.4970, and still more preferably 1.4980. If it is 1.4950 or more, it is easy to increase the rigidity of the film. The upper limit of the refractive index (Nx) in the length direction is preferably 1.5100, more preferably 1.5070, and still more preferably 1.5050. If it is 1.5100 or less, the balance between the longitudinal direction and the width direction of the film tends to be excellent.

The lower limit of the refractive index (Ny) in the width direction of the biaxially oriented polypropylene film of the present invention is 1.5230, preferably 1.5235, and more preferably 1.5240. If it is 1.5230 or more, it is easy to increase the rigidity of the film. The upper limit of the refractive index (Ny) in the width direction is preferably 1.5280, more preferably 1.5275, and still more preferably 1.5270. If it is 1.5280 or less, it will become easy to be excellent in the balance of the characteristic of the length direction-width direction of a film.

The lower limit of the refractive index (Nz) in the thickness direction of the biaxially oriented polypropylene film of the present invention is preferably 1.4960, more preferably 14965, and still more preferably 1.4970. If it is 1.4960 or more, it is easy to increase the rigidity of the film. The upper limit of the refractive index (Nz) in the thickness direction is preferably 1.5020, more preferably 1.5015, and still more preferably 1.5010. If it is 1.5020 or less, it is easy to improve the heat resistance of the film. The refractive index can be within the range by adjusting the stretching ratio, stretching temperature, and heat fixing temperature.

[ΔNy] The lower limit of ΔNy of the biaxially oriented polypropylene film of the present invention is 0.0220, preferably 0.0225, more preferably 0.0228, and still more preferably 0.0230. If it is 0.0220 or more, the rigidity of the film tends to increase. The actual value of the upper limit of ΔNy is preferably 0.0270, more preferably 0.0265, still more preferably 0.0262, and particularly preferably 0.0260. If it is 0.0270 or less, uneven thickness will also easily become good. ΔNy can be in the range by adjusting the stretching ratio, stretching temperature, and heat-fixing temperature of the film. ΔNy means that the refractive index along the length, width, and thickness of the film is set to Nx, Ny, and Nz, respectively, and calculated using the following formula, and the overall alignment of the length, width, and thickness of the film The degree of alignment in the width direction. ΔNy=Ny－[(Nx＋Nz)/2]

[Face Orientation Coefficient] The lower limit of the plane alignment coefficient (ΔP) of the biaxially oriented polypropylene film of the present invention is preferably 0.0135, more preferably 0.0138, and still more preferably 0.0140. If it is 0.0135 or more, the balance of the plane direction of the film will be good, and thickness unevenness will also be good. The actual value of the upper limit of the surface alignment coefficient (ΔP) is preferably 0.0155, more preferably 0.0152, and still more preferably 0.0150. If it is 0.0155 or less, heat resistance at high temperatures is likely to be excellent. The surface alignment coefficient (ΔP) can be within the range by adjusting the stretching ratio, stretching temperature, and heat fixing temperature. In addition, the surface alignment coefficient (ΔP) is calculated using (formula) [(Nx+Ny)/2]-Nz.

[Haze] The upper limit of the haze of the biaxially oriented polypropylene film of the present invention is preferably 5.0%, more preferably 4.5%, still more preferably 4.0%, particularly preferably 3.5%, and most preferably 3.0%. If it is 5.0% or less, it is easy to use in applications requiring transparency. The actual value of the lower limit of the haze is preferably 0.1%, more preferably 0.2%, further preferably 0.3%, and particularly preferably 0.4%. If it is 0.1% or more, it is easy to manufacture. The haze can be adjusted by adjusting the cooling roll (CR) temperature, the width direction stretching temperature, the preheating temperature before the width direction stretching of the tenter, the width direction stretching temperature, or the heat fixing temperature, or the molecular weight of the polypropylene resin is less than 100,000. The amount of the component is within the range, but it may increase due to the addition of an anti-blocking agent or the provision of a sealing layer.

[The half-value width of the diffraction peak derived from the alignment crystal] The biaxially oriented polypropylene film of the present invention utilizes wide-angle X-ray measurement perpendicularly incident on the film surface to determine the azimuth angle of the scattering peak of the (110) surface of the polypropylene α-type crystal, which is derived from the width direction of the film. The upper limit of the half-value width (Wh) of the diffraction peak of the alignment crystal is preferably 25°, more preferably 24°, more preferably 23°, and particularly preferably 22°. If the half-value width (Wh) is 25° or less, it is easy to increase the rigidity of the film. The lower limit of Wh is preferably 16°, more preferably 17°, and still more preferably 18°.

[X-ray orientation] The lower limit of the X-ray alignment calculated from the Wh of the biaxially aligned polypropylene film of the present invention using the following formula is preferably 0.860, more preferably 0.867, and still more preferably 0.872. By setting it to 0.860 or more, it is easy to increase the rigidity. X-ray orientation=(180－Wh)/180 The upper limit of the X-ray orientation is preferably 0.911, more preferably 0.906, and still more preferably 0.900. By setting it to 0.911 or less, film formation is easy to be stable.

[Practical characteristics of the membrane] The practical characteristics of the biaxially oriented polypropylene film of the present invention will be described.

[Wrinkles during heat sealing] In forming a bag for packaging food, the bag is filled with contents, heated to melt the film, and welded and sealed. In addition, in many cases, the above-mentioned steps are also performed in the same manner when the bag is made while filling the food. Usually, a sealant film made of polyethylene or polypropylene is laminated on a base film, and the surfaces of the sealant film are welded to each other. The heating method is to apply pressure from the base film side with a hot plate and press the film to seal, and in many cases the seal width is set to about 10 mm. At this time, since the base film is also heated, the shrinkage at this time causes wrinkles. In terms of the durability of the bag, the number of wrinkles is better, and in order to increase the desire to buy, the number of wrinkles is also better. Although there are cases where the sealing temperature is around 120°C, in order to increase the processing speed of the bag, a higher sealing temperature is required. Even in this case, the shrinkage is preferably small. When the zipper is welded to the opening of the bag, it is required to seal at a higher temperature.

[Printing pitch deviation] As the composition of the packaging film, in most cases, the basic composition is composed of a laminated film of a base film on which printing is performed and a sealant film. In the aspect of bag making, bag making machines are used, such as three-side sealing bags, standing bags, gusset bags, etc., and various bag making machines are used. It can be considered that the printing pitch deviation is caused by the fact that tension or heat is applied to the film during the printing step, so that the base material of the film expands and contracts. In terms of effective use of resources, it is important to eliminate defective products caused by deviations in printing pitch, and it is also important to increase the desire to buy.

[Film Processing] The printing of the biaxially oriented polypropylene film of the present invention can be performed by relief printing, offset printing, gravure printing, stencil printing, or transfer printing according to the application. In addition, unstretched sheets composed of low density polyethylene, linear low density polyethylene, ethylene-vinyl acetate copolymer, polypropylene, polyester, uniaxially stretched film, and biaxially stretched film can also be laminated as a sealant The film is used in the form of a laminate imparted with heat sealability. Furthermore, when it is desired to improve gas barrier properties or heat resistance, an aluminum foil or a combination of polyvinylidene chloride, nylon, ethylene-vinyl alcohol copolymer, polyvinyl alcohol can be provided between the biaxially oriented polypropylene film and the sealant film. The unstretched sheet, uniaxially stretched film, and biaxially stretched film constitute the intermediate layer. For bonding the sealant film, an adhesive applied by a dry lamination method or a hot melt lamination method can be used. In terms of improving gas barrier properties, aluminum or inorganic oxide can also be vapor-deposited on a biaxially oriented polypropylene film, an intermediate layer film, or a sealant film. The evaporation method can be vacuum evaporation, sputtering, ion plating, and vacuum evaporation of silicon dioxide, aluminum oxide, or a mixture of these is particularly preferred.

For the biaxially oriented polypropylene film of the present invention, for example, by adding fatty acid esters of polyhydric alcohols, amines of higher fatty acids, amides of higher fatty acids, amines of higher fatty acids, or ethylene oxide adducts of amides The amount of anti-fogging agent in the film is set in the range of 0.2% by mass to 5% by mass, which can be suitable for packaging fresh products composed of vegetables, fruits, flowers and other plants requiring high freshness.

In addition, as long as the effect of the present invention is not impaired, various additives to improve sliding properties or antistatic properties can also be formulated, such as waxes, metal soaps and other lubricants and plasticizers that are formulated to improve productivity. , Processing aids or heat stabilizers, antioxidants, antistatic agents, ultraviolet absorbers, etc.

[Industry Availability] The biaxially oriented polypropylene film of the present invention has excellent characteristics as described above, so it can be preferably used for packaging bags, and the thickness of the film can be made thinner than before.

Furthermore, it is also suitable for insulating films of capacitors and motors, back cover sheets of solar cells, barrier films of inorganic oxides, base films of transparent conductive films such as ITO (Indium Tin Oxide), etc., which are used at high temperatures. , Or isolation film and other applications that require rigidity. In addition, the use of coating agents, inks, laminating adhesives, etc., which were previously difficult to use, enables coating or printing processing at high temperatures, so that production efficiency can be expected. [Example]

Hereinafter, the present invention will be explained in detail with examples. In addition, the characteristics were measured and evaluated by the following methods. (1) Melt flow rate The melt flow rate (MFR) is measured in accordance with JISK7210 at a temperature of 230°C and a load of 2.16 kgf.

(2) The meso five-element component ratio The meso pentad fraction ([mmmm]%) of the polypropylene resin is measured using 13C-NMR (13C-Nuclear Magnetic Resonance; 13C-nuclear magnetic resonance). The meso pentad fraction was calculated according to the method described in Zambelli et al. Macromolecules, Vol. 6, page 925 (1973). 13C-NMR measurement was performed using AVANCE500 manufactured by BRUKER, 200 mg of the sample was dissolved in an 8:2 mixture of o-dichlorobenzene and deuterated benzene at 135°C, and the measurement was performed at 110°C.

(3) The number-average molecular weight, weight-average molecular weight, component amount with a molecular weight of 100,000 or less, and molecular weight distribution of polypropylene resin. Use gel permeation chromatography (GPC) to obtain PP( polypropylene; polypropylene) converted molecular weight. When the reference line is not clear, the reference line is set within the range from the elution peak on the high molecular weight side that is closest to the elution peak of the standard substance until it reaches the lowest position of the hem portion on the high molecular weight side. The GPC measurement conditions are as follows. Device: HLC-8321PC/HT (manufactured by Tosoh Co., Ltd.) Detector: RI (Refractive Index detector) Solvent: 1,2,4-trichlorobenzene + dibutylhydroxytoluene (0.05%) Column: TSKgelguardcolumnHHR(30)HT(7.5mmI.D.×7.5cm)×1 piece + TSKgelGMHHR-H(20)HT(7.8mmI.D.×30cm)×3 pieces Flow rate: 1.0mL/min Injection volume: 0.3mL Measurement temperature: 140℃ The number average molecular weight (Mn) and mass average molecular weight (Mw) are respectively determined by the molecular weight (Mi) of each dissolution position of the GPC curve obtained through the molecular weight calibration curve and the number of molecules (Ni) using the following formula To define. Number average molecular weight: Mn=Σ(Ni·Mi)/ΣNi Mass average molecular weight: Mw=Σ(Ni·Mi ² )/Σ(Ni·Mi) Here, the molecular weight distribution can be obtained by Mw/Mn. In addition, based on the integral curve of the molecular weight distribution obtained by GPC, the ratio of components with a molecular weight of 100,000 or less was determined.

(4) Crystallization temperature (Tc), melting temperature (Tm) Using a Q1000 differential scanning calorimeter manufactured by TA Instruments, thermal measurement was performed in a nitrogen atmosphere. Cut out about 5 mg from polypropylene resin pellets and seal it in an aluminum pan for measurement. After raising the temperature to 230°C for 5 minutes, cooling to 30°C at a rate of -10°C/min, and setting the exothermic peak temperature as the crystallization temperature (Tc). In addition, the heat of crystallization (ΔHc) is determined by setting the reference line so as to smoothly connect from the start of the exothermic peak to the end of the exothermic peak, and the area of the exothermic peak is obtained. In this state, the temperature was maintained at 30°C for 5 minutes, the temperature was increased to 230°C at 10°C/min, and the main endothermic peak temperature was set as the melting temperature (Tm).

(5) Film thickness Using Millitron 1202D manufactured by SEIKO EM, the thickness of the film was measured.

(6) Haze NDH5000 manufactured by Nippon Denshoku Industry Co., Ltd. was used, and the measurement was performed at 23°C in accordance with JISK7105.

(7) Tensile test In accordance with JIS K 7127, the tensile strength in the longitudinal direction and the width direction of the film was measured at 23°C. The sample was cut out from the film to a size of 15 mm×200 mm, and set in a tensile tester (two-column tabletop tester Instron 5965 manufactured by Instron Japan Co., Ltd.) with a chuck width of 100 mm. The tensile test was performed at a tensile speed of 200 mm/min. According to the obtained strain-stress curve, the stress at 5% elongation is set to F5. Tensile breaking strength and tensile breaking elongation are respectively taken as the strength and elongation at the point when the sample breaks.

(8) Heat shrinkage rate According to JIS Z 1712, the following method is used for measurement. The film was cut with a width of 20 mm and a length of 200 mm along the length and width directions of the film, respectively, and hung in a hot air oven at 120°C or 150°C and heated for 5 minutes. The length after heating was measured, and the heat shrinkage rate was calculated|required by the ratio of the length after shrinking to the original length.

(9) Refractive index, ΔNy, surface alignment coefficient The measurement was performed using an Abbe refractometer manufactured by ATAGO Co., Ltd. at a wavelength of 589.3 nm and a temperature of 23°C. Let the refractive index along the length direction and the width direction of the film be Nx and Ny, respectively, and let the refractive index in the thickness direction be Nz. ΔNy is obtained by using Nx, Ny, and Nz, and using (formula) Ny-[(Nx+Nz)/2]. In addition, the surface alignment coefficient (ΔP) is calculated using (formula) [(Nx+Ny)/2]-Nz.

(10) X-ray half-value width and orientation An X-ray diffraction device (RINT2500 manufactured by Rigaku Co., Ltd.) was used for the measurement by the transmission method. X-rays with a wavelength of 1.5418Å are used, and the detector uses a scintillation counter. The film was laminated so as to have a thickness of 500 μm to prepare a sample. Place the sample table at the position of the diffraction peak (diffraction angle 2θ=14.1°) of the (110) plane of the α-type crystal of polypropylene resin, and rotate the sample 360° with the thickness direction of the film as the axis to obtain the (110) plane The azimuth angle of the diffraction strength depends on the nature. The half-value width Wh of the diffraction peak derived from the aligned crystals in the width direction of the film is determined from the dependence of the azimuth angle. In addition, using Wh, the X-ray orientation degree was calculated from the following equation. X-ray orientation=(180－Wh)/180

[Example 1] As polypropylene resin, polypropylene homopolymer PP-1 (manufactured by Sumitomo Chemical Co., Ltd., Sumitomo Noblen FLX80E4) with MFR=7.5g/10min, [mmmm]=98.9%, Tc=116.2°C, Tm=162.5°C 80 parts by weight, mixed with 20 parts by weight of propylene homopolymer PP-2 (manufactured by Sumitomo Chemical Co., Ltd., EL80F5) with MFR = 11g/10 minutes, [mmmm] = 98.8%, Tc = 116.5°C, Tm = 161.5°C Use together. Extrude from a T-die at 250°C into a sheet, put it in contact with a cooling roll at 20°C, and put it directly into a water tank at 20°C. Then, it stretched 4.5 times in the length direction with two pairs of rolls at 142°C, and then clamped both ends with clamps, introduced into a hot air oven, preheated at 170°C, and stretched 12 times in the width direction at 167°C as the first stage. After stretching in the width direction, it was immediately cooled at 100°C while still being held by the clamp, and then heat-treated at 165°C without relaxation in the width direction. The thickness of the film thus obtained was 20.3 μm. Table 1 shows the structure of the polypropylene resin, and Table 2 shows the film forming conditions. As shown in Table 3, a film with high rigidity and low heat shrinkage at high temperature was obtained.

[Example 2] Except for stretching at 162°C in the width direction and heat treatment at 170°C, it was carried out in the same manner as in Example 1. The thickness of the obtained film was 20.8 μm. Table 1 shows the structure of the polypropylene resin, and Table 2 shows the film forming conditions. As shown in Table 3, a film with high rigidity and low heat shrinkage at high temperature was obtained.

[Example 3] Stretching was carried out at 162°C in the width direction, and except for this, it was carried out in the same manner as in Example 1. The thickness of the obtained film was 20.7 μm. Table 1 shows the structure of the polypropylene resin, and Table 2 shows the film forming conditions. As shown in Table 3, a film with high rigidity and low heat shrinkage at high temperature was obtained.

[Example 4] Except for stretching at 162°C in the width direction and cooling at 140°C, it was carried out in the same manner as in Example 1. The thickness of the obtained film was 20.6 μm. Table 1 shows the structure of the polypropylene resin, and Table 2 shows the film forming conditions. As shown in Table 3, a film with high rigidity and low heat shrinkage at high temperature was obtained.

[Comparative Example 1] As polypropylene resin, polypropylene homopolymer PP-1 (manufactured by Sumitomo Chemical Co., Ltd., Sumitomo Noblen FLX80E4) with MFR=7.5g/10min, [mmmm]=98.9%, Tc=116.2°C, Tm=162.5°C was used . Extrude from a T-die at 250°C into a sheet, put it in contact with a cooling roll at 20°C, and put it directly into a water tank at 20°C. Then, stretched 4.5 times in the length direction with two pairs of rollers at 145°C, then clamped both ends with clamps, introduced into a hot air oven, preheated at 170°C, and stretched 6 times in the width direction as the first stage at 160°C in the width direction , And then stretched 1.36 times at 145°C as the second stage, thereby performing a total of 8.2 times of stretching. After extending in the width direction, it was immediately cooled at 100°C while still being held by the clamp, and then heat-fixed at 163°C. The thickness of the film thus obtained was 18.7 μm. Table 1 shows the structure of the polypropylene resin, and Table 2 shows the film forming conditions. The first-stage extension of the horizontal stretching step is set as the early period, and the second-stage extension is set as the late period. The physical properties of the film are shown in Table 3, and the heat shrinkage rate at 150°C is poor.

[Comparative Example 2] As polypropylene resin, 80 parts by weight of PP-1, and MFR = 11g/10 minutes, [mmmm] = 98.8%, Tc = 116.5 ℃, Tm = 161.5 ℃ propylene homopolymer PP-2 (Sumitomo Chemical Co., Ltd. Manufactured by Co., Ltd., EL80F5) 20 parts by weight blended and used. Except that the stretching temperature in the longitudinal direction was 142°C, the stretching temperature in the first step in the width direction was 162°C, and the heat setting temperature was 165°C, the same procedure was performed as in Comparative Example 1 except that. The thickness of the obtained film was 21.3 μm. Table 1 shows the structure of the polypropylene resin, and Table 2 shows the film forming conditions. The physical properties of this film are shown in Table 3, and the tensile breaking strength is poor.

[Comparative Example 3] During the heat fixing, 3% relaxation was performed, and other than that, it was performed in the same manner as in Comparative Example 2. The thickness of the obtained film was 21.1 μm. Table 1 shows the structure of the polypropylene resin, and Table 2 shows the film forming conditions. The physical properties of this film are shown in Table 3, and the tensile breaking strength is poor.

[Comparative Example 4] The stretching temperature in the longitudinal direction was set to 145°C, and the cooling temperature immediately after the stretching in the width direction was set to 140°C. Except for this, it was performed in the same manner as in Comparative Example 2. The thickness of the obtained film was 18.9 μm. Table 1 shows the structure of the polypropylene resin, and Table 2 shows the film forming conditions. The physical properties of this film are shown in Table 3, and the tensile breaking strength is poor.

[Comparative Example 5] After extending in the width direction, without cooling, it was heat-fixed at 165°C while still being held by the jig. Except for this, it was performed in the same manner as in Comparative Example 2. The thickness of the obtained film was 19.5 μm. Table 1 shows the structure of the polypropylene resin, and Table 2 shows the film forming conditions. The physical properties of the film are shown in Table 3, and the heat shrinkage rate at 150°C is poor.

[Comparative Example 6] Except that the stretching temperature of the second stage in the width direction was 155°C, it was carried out in the same manner as in Comparative Example 2. The thickness of the film thus obtained was 20.3 μm. Table 1 shows the structure of the polypropylene resin, and Table 2 shows the film forming conditions. The physical properties of this film are shown in Table 3, and the tensile breaking strength is poor.

[Comparative Example 7] Except for setting the stretching ratio in the longitudinal direction to 4.8 times, the same procedure as in Comparative Example 2 was carried out. The thickness of the obtained film was 19.1 μm. Table 1 shows the structure of the polypropylene resin, and Table 2 shows the film forming conditions. The physical properties of this film are shown in Table 3, and the tensile breaking strength is poor.

[Comparative Example 8] In the width direction stretching, the stretching magnification of the first stage was set to 6.6 times, and the stretching magnification of the second stage was set to 1.5 times, so that a total of 9.9 times was stretched. Except for this, it was performed in the same manner as in Comparative Example 2. . The thickness of the obtained film was 20.1 μm. Table 1 shows the structure of the polypropylene resin, and Table 2 shows the film forming conditions. The physical properties of this film are shown in Table 3, and the tensile breaking strength is poor.

[Comparative Example 9] As a polypropylene resin, PP-1 was used, extruded from a T-die at 250°C into a sheet, contacted with a cooling roll at 20°C, and directly poured into a water tank at 20°C. Then, stretching was performed 4.5 times in the longitudinal direction at 143°C, and the preheating temperature during the width direction stretching in the tenter was set at 170°C and the stretching temperature was set to 158°C to perform 8.2 times stretching, and then heat at 168°C. fixed. The thickness of the obtained film was 18.6 μm. Table 1 shows the structure of the polypropylene resin, Table 2 shows the film forming conditions, and Table 3 shows the physical properties. The physical properties of this film are shown in Table 3, and the tensile breaking strength is poor.

[Comparative Example 10] As the polypropylene resin, 80 parts by weight of PP-1 and 20 parts by weight of PP-2 were blended and used. The thickness of the obtained film was 20.0 μm. Table 1 shows the structure of the polypropylene resin, Table 2 shows the film forming conditions, and Table 3 shows the physical properties. The physical properties of this film are shown in Table 3, and the tensile breaking strength is poor.

[Comparative Example 11] As the polypropylene resin, PP-3 (manufactured by Japan Polypropylene Co., Ltd., FL203D) with MFR = 3 g/10 minutes, [mmmm] = 94.8%, Tc = 117.2°C, and Tm = 160.6°C was used. Extrude from a T-die at 250°C into a sheet, put it in contact with a cooling roll at 20°C, and put it directly into a water tank at 20°C. Then, it was stretched 4.5 times at 135°C along the length direction, and in the width direction stretching using a tenter, the preheating temperature was set to 166°C, and as the first stage of stretching, it was stretched 6 times at 155°C. As the second-stage stretching, it was stretched 1.36 times at 139°C to perform a total stretch of 8.2 times. After stretching in the width direction, it was immediately cooled at 95°C while still being held by the clamp, and then heat-treated at 158°C without relaxation in the width direction. The thickness of the obtained film was 19.2 μm. Table 1 shows the structure of the polypropylene resin, Table 2 shows the film forming conditions, and Table 3 shows the physical properties. The physical properties of the film are shown in Table 3, and the heat shrinkage rate at 150°C is poor.

[Comparative Example 12] As a polypropylene raw material, PP-4 (manufactured by Sumitomo Chemical Co., Ltd., FS2012) with MFR=2.7g/10min, [mmmm]=98.7%, Tc=114.7°C, and Tm=163.0°C was used. Extrude from a T-die at 250°C into a sheet, put it in contact with a cooling roll at 20°C, and put it directly into a water tank at 20°C. Then, it stretched 4.5 times in the length direction at 145°C, and in the width direction stretching using the tenter, the preheating temperature was set to 170°C, and the stretching was performed at 160°C for 6 times as the first stage of the stretching. As the second-stage stretching, it was stretched 1.36 times at 145°C to perform a total stretch of 8.2 times. After stretching in the width direction, it was immediately cooled at 100°C while still being held by the clamp, and then heat-treated at 163°C without relaxation in the width direction. The thickness of the obtained film was 21.2 μm. Table 1 shows the structure of the polypropylene resin, Table 2 shows the film forming conditions, and Table 3 shows the physical properties. The physical properties of the film are shown in Table 3, and the heat shrinkage rate at 150°C is poor.

[Comparative Example 13] As the polypropylene resin, PP-4 was used. Extrude from a T-die at 250°C into a sheet, put it in contact with a cooling roll at 20°C, and put it directly into a water tank at 20°C. Then, the film was stretched 5.8 times in the length direction at 130°C, and the film was heated using a tenter with the preheating temperature set to 167°C. Then, the film was stretched 8.6 times in the width direction at a stretching temperature of 161°C, and then 10 relaxation was applied on one side. % One side is heat-fixed at 130°C, and then the second stage of heat-fixing is performed at 140°C. The thickness of the obtained film was 13.4 μm. Table 1 shows the structure of the polypropylene resin, Table 2 shows the film forming conditions, and Table 3 shows the physical properties. The physical properties of the film are shown in Table 3, and the heat shrinkage rate at 150°C is poor.

[Comparative Example 14] Except that the stretching was performed 8 times at 162°C in the width direction, and cooling was performed at 140°C, it was carried out in the same manner as in Example 1 except for the above. The thickness of the obtained film was 19.7 μm. Table 1 shows the structure of the polypropylene resin, and Table 2 shows the film forming conditions. The physical properties of this film are shown in Table 3, and the tensile breaking strength is poor.

[Comparative Example 15] Stretching was performed 8 times in the width direction at 162° C., except for this, it was performed in the same manner as in Example 1. The thickness of the obtained film was 20.1 μm. Table 1 shows the structure of the polypropylene resin, and Table 2 shows the film forming conditions. The physical properties of this film are shown in Table 3, and the tensile breaking strength is poor.

[Table 1] PP-1 PP-2 PP-3 PP-4 Copolymerization amount of components other than propylene (mol%) 0 0 0 0 MFR (g/10 minutes) 7.5 11 3 2.7 [mmmm](%) 98.9 98.8 94.8 98.7 Tc(℃) 116.2 116.5 117.2 114.7 Tm(℃) 162.5 161.5 160.6 163.0 ΔHc(J/g) 104.8 107.8 94.9 102.4 Ingredients with a molecular weight of less than 10,000 (mass%) 4.0 6.9 3.0 3.5 Ingredients with a molecular weight of less than 100,000 (mass%) 40.5 53.1 37.1 30.0

[Table 2] Example 1 Example 2 Example 3 Example 4 Comparative example 1 Comparative example 2 Comparative example 3 Comparative example 4 Comparative example 5 Comparative example 6 Comparative example 7 Comparative example 8 Comparative example 9 Comparative example 10 Comparative example 11 Comparative example 12 Comparative example 13 Comparative example 14 Comparative example 15 Raw material polypropylene resin PP-1 80 80 80 80 100 80 80 80 80 80 80 80 100 80 - - - 80 80 PP-2 20 20 20 20 - 20 20 20 20 20 20 20 - 20 - - - 20 20 PP-3 - - - - - - - - - - - - - - 100 - - - - PP-4 - - - - - - - - - - - - - - - 100 100 - - Mixed polypropylene resin Melt flow rate (g/10 minutes) 8.5 8.5 8.5 8.5 7.5 8.5 8.5 8.5 8.5 8.5 8.5 8.5 7.5 8.5 3 2.7 2.7 8.5 8.5 Ingredients with a molecular weight of less than 100,000 (mass%) 43.0 43.0 43.0 43.0 40.5 43.0 43.0 43.0 43.0 43.0 43.0 43.0 40.5 43.0 37.1 30.0 30.0 43.0 43.0 Extrusion step Extrusion temperature (℃) 250 250 250 250 250 250 250 250 250 250 250 250 250 250 250 250 250 250 250 Cooling temperature (℃) 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 Length extension step Length extension temperature (℃) 142 142 142 142 145 142 142 145 142 142 142 142 143 143 135 145 130 142 142 Length extension ratio (times) 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.8 4.5 4.5 4.5 4.5 4.5 5.8 4.5 4.5 Warm-up step Preheating temperature (℃) 170 170 170 170 170 170 170 170 170 170 170 170 170 170 166 170 167 170 170 Width direction extension step Extension temperature in the width direction of the previous interval (℃) 167 162 162 162 160 162 162 162 162 162 162 162 158 158 155 160 161 162 162 Stretching magnification in the width direction of the previous interval (times) - - - - 6 6 6 6 6 6 6 6.6 6 6 6 6 6.2 - - Lateral section width direction extension temperature (℃) 167 162 162 162 145 145 145 145 145 155 145 145 158 158 139 145 161 162 162 Extension magnification in the width direction of the later section (times) - - - - 1.36 1.36 1.36 1.36 1.36 1.36 1.36 1.5 1.36 1.36 1.36 1.36 1.39 - - Stretching magnification in the final width direction (times) 12.0 12.0 12.0 12.0 8.2 8.2 8.2 8.2 8.2 8.2 8.2 9.9 8.2 8.2 8.2 8.2 8.6 8 8 Temperature immediately after the width direction stretch (℃) 100 100 100 140 100 100 100 140 - 100 100 100 - - 95 100 - 140 100 Heat treatment steps Heat treatment temperature (℃) 165 170 165 165 163 165 165 165 165 165 165 165 168 168 158 163 130 165 165 Relaxation rate during heat treatment (%) 0 0 0 0 0 0 3 0 0 0 0 0 0 0 0 0 10 0 0 Heat treatment 2 temperature (℃) - - - - - - - - - - - - - - - - 140 - -

[table 3] Example 1 Example 2 Example 3 Example 4 Comparative example 1 Comparative example 2 Comparative example 3 Comparative example 4 Comparative example 5 Comparative example 6 Comparative example 7 Comparative example 8 Comparative example 9 Comparative example 10 Comparative example 11 Comparative example 12 Comparative example 13 Comparative example 14 Comparative example 15 Thickness (μm) 20.3 20.8 20.7 20.6 18.7 21.3 21.1 18.9 19.5 20.3 19.1 20.1 18.6 20 19.2 21.2 13.4 19.7 20.3 Haze (%) 1.1 0.9 1.2 1.0 0.7 2.2 2.0 2.0 2.1 2.1 2.2 2.0 1.0 1.1 0.4 0.4 0.6 1.5 1.4 23℃F5(width direction)(MPa) 182 189 207 205 193 180 169 171 183 175 184 188 133 131 158 183 210 157 168 23℃F5(length direction)(MPa) 48 49 49 49 49 44 46 46 46 45 45 46 44 44 39 46 55 47 48 Tensile breaking strength (width direction) (MPa) 422 466 473 458 450 397 366 396 435 373 379 391 336 344 414 430 476 357 379 Tensile breaking strength (length direction) (MPa) 124 124 128 123 134 106 105 111 114 106 117 113 118 124 163 160 182 117 112 Tensile elongation at break (width direction) (%) 29 40 34 31 27 26 twenty two 32 29 twenty four twenty one twenty two 37 44 29 27 33 40 38 Tensile elongation at break (length direction) (%) 261 239 238 232 178 176 172 179 199 182 173 190 188 219 201 192 160 191 180 120℃ heat shrinkage rate (width direction) (%) 2.0 1.7 3.0 3.3 4.0 3.0 2.2 3.0 3.0 3.3 3.0 2.7 0.7 1.0 9.8 6.5 2.7 2.5 2.3 120℃ heat shrinkage rate (length direction) (%) 0.2 0,3 0.8 0.5 1.0 1.0 1.0 0.8 1.0 1.0 1.0 0.8 1.3 1.3 4.0 1.7 1.5 0.5 0.3 Thermal shrinkage at 150°C (width direction) (%) 15.5 19.8 22.0 20.2 27.3 twenty two 18.2 17.8 24.7 18.3 17.7 17.3 11.7 13.2 57 43 37.8 16.7 18.7 Thermal shrinkage at 150°C (length direction) (%) 3.3 4.5 4.8 3.7 7 5 4.2 5.2 5.3 5.8 3.5 4.3 4.7 4.3 34 17 13.7 3.5 4.3 Width direction refractive index Ny 1.5254 1.5249 1.5249 1.5251 1.5245 1.5254 1.5258 1.5250 1.5261 1.5260 1.5249 1.5259 1.5252 1.5245 1.5187 1.5215 1.5251 1.5246 1.5241 Length direction refractive index Nx 1.5010 1.5011 1.5003 1.5001 1.5020 1.5028 1.5034 1.5030 1.5020 1.5031 1.5031 1.5020 1.5050 1.5056 1.4991 1.5010 1.4997 1.5025 1.5027 Refractive index in thickness direction Nz 1.4991 1.4990 1.4980 1.4980 1.4985 1.5001 1.5001 1.5000 1.4997 1.5007 1.4998 1.4999 1.5012 1.5010 1.4952 1.4973 1.4980 1.5001 1.4991 ΔNy 0.0254 0.0248 0.0257 0.0261 0.0243 0.0240 0.0240 0.0235 0.0253 0.0241 0.0234 0.0250 0.0221 0.0212 0.0216 0.0224 0.0262 0.0233 0.0232 Surface orientation coefficient ΔP 0.0141 0.0139 0.0146 0.0146 0.0148 0.0140 0.0145 0.0140 0.0144 0.0139 0.0142 0.0141 0.0139 0.0141 0.0137 0.0140 0.0144 0.0134 0.0143 X-ray half-value width (°) 20.9 20.1 20.7 20.0 20.6 22.2 23.0 23.8 20.2 23.6 23.6 21.8 28.6 28.9 23.9 24.4 21.2 25.8 25.3 X-ray orientation 0.884 0.888 0.885 0.889 0.886 0.877 0.872 0.868 0.888 0.869 0.869 0.879 0.841 0.839 0.867 0.864 0.882 0.857 0.859 A: Thermal shrinkage rate at 150℃ in the width direction×6.2+300 396 423 436 425 469 436 413 410 453 413 410 407 373 382 653 567 534 404 416 Width direction tensile breaking strength-A 26 43 36 32 -19 -39 -47 -14 -18 -40 -31 -16 -37 -38 -239 -137 -58 -47 -37

Claims (5)

A method for manufacturing a biaxially oriented polypropylene film, which sequentially includes the steps of extruding a polypropylene resin composition containing a polypropylene resin with a meso pentad component ratio of 97.0% or more to obtain an unstretched sheet; The step of extending the unstretched sheet along the length direction, the preheating step of heating the lengthwise stretched film to a preheating temperature in the range of Tm to Tm+25℃, and the preheated lengthwise stretched film above Tm-10℃ to preheating The step of stretching the film at a temperature below the temperature at a magnification of 10 times or more in the width direction, the step of cooling the film at a temperature below Tm-80°C and above Tm-15°C at the end of the width-direction stretching in the width direction, and Heat treatment step. The method for producing a biaxially oriented polypropylene film as described in claim 1, wherein the polypropylene resin constituting the biaxially oriented polypropylene film has a crystallization temperature of 105°C or higher and a melting point of 160°C or higher. The method for producing a biaxially oriented polypropylene film as described in claim 1 or 2, wherein the melt flow rate of the polypropylene resin constituting the biaxially oriented polypropylene film is 4.0 g/10 minutes or more. The method for producing a biaxially oriented polypropylene film as described in claim 1 or 2, wherein the polypropylene resin constituting the biaxially oriented polypropylene film has a molecular weight of 100,000 or less and a component content of 35% by mass or more. The method for producing a biaxially oriented polypropylene film as described in claim 3, wherein the polypropylene resin constituting the biaxially oriented polypropylene film has a molecular weight of 100,000 or less and a component content of 35% by mass or more.