Biaxially oriented polypropylene film for lid material

Abstract

Provided is a biaxially oriented polypropylene film for a lid material that is excellent in press-through properties, heat sealability, and printability, and is made of the same material as a bottom material to facilitate recycling. This biaxially oriented polypropylene film for a lid material comprises a polypropylene resin composition containing 90 mass% or more of a polypropylene resin, and satisfies the following (1) to (3). (1) The thickness is 5 μm to 25 μm inclusive. (2) The impact strength is 0.10 J to 0.85 J inclusive. (3) The thermal shrinkage rate in the width direction at 150 °C is -2.0% to 15% inclusive.

Description

Biaxially Oriented Polypropylene Film for Lid Material

[0001] The present invention relates to a biaxially oriented polypropylene film for a lid material used in a blister pack package (hereinafter referred to as a blister package). More specifically, it relates to a biaxially oriented polypropylene film for a lid material of a blister package used as a package for toiletries such as toothbrushes, medical appliances such as injection needle packs, pharmaceuticals such as tablets and capsules, electronic components, button batteries, stationery, etc.

[0002] Conventionally, as a package containing button batteries, stationery, toothbrushes, tablets, etc. as contents, a blister package is used, which consists of a bottom material made of a molded body of a plastic sheet having a recess for containing the contents and a lid material made of paper or aluminum foil for closing the recess of the bottom material.

[0003] For the bottom material of the blister package, a molded body having a recess for containing the contents, with a plastic sheet such as polyvinyl chloride resin, polypropylene resin, polystyrene resin, etc. as a molding material, is used. On the other hand, paper or aluminum foil is used for the lid material of the blister package. The contents of this blister package are taken out by methods such as tearing the lid material or peeling the adhered part between the lid material and the bottom material. The conventional blister package using a paper lid material has drawbacks such as the content taking-out operation not being easy because the contents are taken out by tearing the paper lid material or peeling the adhered part between the paper lid material and the bottom material, and the moisture-proof property not being perfect because a paper lid material is used. Also, there are problems such as paper powder generation when taking out the contents, and when the blister package gets wet, the contents get wet or the sterile state of the contents cannot be maintained.

[0004] On the other hand, in press-through packaging (sometimes abbreviated as PTP packaging), a type of blister packaging, aluminum foil is used as the lid material for tablets and other PTP packaging because of its excellent property of easily tearing the lid material by pushing out the tablets (hereinafter referred to as press-through property). However, while aluminum foil lids have excellent press-through and gas barrier properties, they are very fragile and easily tear due to their lack of elasticity, and can tear if unintentional force is applied to the molded part. In addition, aluminum foil is far more expensive than plastic film, which is another problem, and there is a strong demand for improvement. Furthermore, in blister packaging, printing is usually done on the lid material, but printing on aluminum foil is difficult, and detailed printing to enhance the design is extremely difficult. Moreover, when the bottom material is a molded plastic sheet, it is difficult to separate and collect the plastic sheet and aluminum foil, which can damage the incinerator during disposal. Therefore, from the perspective of plastic product recycling, recyclable, environmentally friendly blister packaging that uses the same plastic film material for both the lid and the bottom material is attracting attention. However, when using plastic film as a lid material, the press-through properties become poor, so countermeasures are necessary.

[0005] For example, Patent Document 1 discloses a lid material for PTP packaging that uses a sheet made of a resin composition containing a polypropylene resin and an inorganic substance to improve press-through properties as a base material, but it had the problem of being difficult to process and recycle. Patent Document 2 discloses a lid material containing a polypropylene resin film and a polyethylene film that have been degraded by radiation irradiation to improve press-through properties, but it also had the problem of being difficult to recycle. Patent Document 3 discloses Comparative Example 6, in which a biaxially oriented polypropylene film is used as the press-through lid material, but it is also disclosed that when the lid material of Comparative Example 6 is used, it has the problem of being inferior in press-through properties. On the other hand, Patent Document 3 discloses that in all examples, an unstretched polypropylene film with a thickness of 60 to 80 μm was used as the press-through lid material, but the unstretched polypropylene film had the problem that its impact strength became too low when the thickness was reduced to about 20 μm. In addition, although the unstretched polypropylene film has a small thermal shrinkage rate, it softens at high temperatures, so when heat-sealed at high temperatures, it has the problem of poor appearance.

[0006] JP 10-101133, JP 7-256842, JP 2024-67220

[0007] In view of the problems of conventional blister packaging lids, the present invention provides a biaxially oriented polypropylene film for lids that has press-through properties, heat-sealability, and printability, and is made of the same material as the bottom material, making it easily recyclable. Press-through properties are a required performance not only for PTP packaging but for blister packaging in general, and in this specification, "press-through properties" means the property that the lid can be easily broken and the tablets removed by pushing out the contents inside the blister packaging.

[0008] As a result of diligent research to achieve the above objective, the present inventors have arrived at the following inventions [1] to

[13] . [1] A biaxially oriented polypropylene film for lid material, comprising a polypropylene resin composition containing 90% by mass or more of polypropylene resin, wherein the biaxially oriented polypropylene film satisfies the following (1) to (3): (1) The thickness is 5 μm or more and 25 μm or less. (2) The impact strength is 0.10 J or more and 0.85 J or less. (3) The thermal shrinkage rate in the width direction at 150°C is -2.0% or more and 15% or less. [2] The biaxially oriented polypropylene film for lid material according to [1] above, wherein the storage modulus in the longitudinal direction at 140°C is 0.30 GPa or more and 1.0 GPa or less. [3] The biaxially oriented polypropylene film for lid material according to [1] or [2] above, wherein the mesopentad fraction of the polypropylene resin is 97.0% or more. [4] A biaxially oriented polypropylene film for lid material as described in any of [1] to [3] above, used for the lid of a blister packaging. [5] A biaxially oriented polypropylene film for lid material as described in any of [1] to [3] above, used for the lid of a press-through packaging. [6] A blister packaging comprising a lid made of the biaxially oriented polypropylene film for lid material as described in any of [1] to [3] above, and a bottom made of polypropylene resin. [7] Use of the biaxially oriented polypropylene film for lid material as described in any of [1] to [3] above as lid material. [8] A biaxially oriented polypropylene film for lid material made of a polypropylene resin composition containing 90% by mass or more of polypropylene resin, wherein the biaxially oriented polypropylene film satisfies the following (1) to (3): (1) The thickness is 5 μm or more and 25 μm or less. (2) The impact strength is 0.10 J or more and 0.85 J or less. (3) The longitudinal storage modulus at 140°C is 0.30 GPa or more and 1.0 GPa or less. [9] The biaxially oriented polypropylene film for lid material according to [8] above, wherein the mesopentade fraction of the polypropylene resin is 97.0% or more.

[10] The biaxially oriented polypropylene film for lid material according to [8] or [9] above, used for the lid of a blister packing.

[11] A biaxially oriented polypropylene film for lid material as described in [8] or [9] above, used as a lid for a press-through packaging body.

[12] A blister packaging body comprising a lid material made of the biaxially oriented polypropylene film for lid material as described in [8] or [9] above, and a bottom material made of polypropylene resin.

[13] Use of the biaxially oriented polypropylene film for lid material as described in [8] or [9] above as a lid material.

[0009] The biaxially oriented polypropylene film for lids of the present invention has excellent press-through properties, allowing for easy removal of contents without the need for scissors, notches, or perforations. It also possesses sufficient strength to facilitate post-processing such as printing. Furthermore, it exhibits a good appearance after heat-sealing the bottom and lid materials.

[0010] (1) Polypropylene resin composition The polypropylene resin composition constituting the biaxially oriented polypropylene film for lid material in the present invention may be a mixture of two or more different polypropylene polymers (polypropylene resins), for example, a mixture of two or more different polypropylene homopolymers, a mixture of two or more different polypropylene copolymers containing α-olefins other than propylene, or a mixture of one or more polypropylene homopolymers and one or more polypropylene copolymers containing α-olefins other than propylene.

[0011] The following describes the preferred physical properties of the polypropylene resin composition constituting the biaxially oriented polypropylene film for lid material in the present invention. When using two or more different polypropylene polymers, the physical properties other than the melt flow rate shall be the mass-averaged values ​​of the physical properties of each polypropylene polymer.

[0012] The melting point (hereinafter sometimes referred to as Tm) of the polypropylene resin composition constituting the biaxially oriented polypropylene film for lid material in the present invention is preferably 158 to 170°C, more preferably 159 to 169°C, even more preferably 160 to 168°C, particularly preferably 161 to 167°C, and most preferably 162 to 166°C. A melting point of 158°C or higher makes it easier to obtain flatness, rigidity, and heat resistance at high temperatures. A melting point of 170°C or lower makes it easier to suppress cost increases in polypropylene manufacturing and makes it less prone to breakage during film formation. The melting point of a polypropylene resin composition is the main peak temperature of the endothermic peak observed during melting, when 5 mg of the polypropylene resin composition is placed in an aluminum pan, set in a differential scanning calorimeter (DSC), heated from 30°C to 230°C at a heating rate of 20°C / min under a nitrogen atmosphere, held at 230°C for 5 minutes to melt the polypropylene resin composition, then cooled to 30°C at a cooling rate of -10°C / min and held at 30°C for 5 minutes, and then heated again at a heating rate of 10°C / min.

[0013] The crystallization temperature (hereinafter sometimes referred to as Tc) of the polypropylene resin composition constituting the biaxially oriented polypropylene film for lid material in the present invention is preferably 105 to 135°C, more preferably 108 to 133°C, even more preferably 110 to 132°C, even more preferably 112 to 130°C, particularly preferably 114 to 128°C, and most preferably 115 to 125°C. When the crystallization temperature is 105°C or higher, crystallization proceeds easily during the widthwise stretching and subsequent cooling process, making it easier to obtain rigidity and heat resistance at high temperatures. When the crystallization temperature is 135°C or lower, it is less likely to increase costs in terms of polypropylene manufacturing, and the film is less likely to break during film formation. The crystallization temperature of the polypropylene resin composition is the main peak temperature of the exothermic peak observed when 5 mg of the polypropylene resin composition is packed into an aluminum pan, set in a DSC, heated from 30°C to 230°C under a nitrogen atmosphere at a heating rate of 20°C / min, held at 230°C for 5 minutes to melt the polypropylene resin composition, and then cooled down to 30°C at a cooling rate of -10°C / min.

[0014] The melting point and crystallization temperature of the polypropylene resin composition may be increased to be within the above range by incorporating a crystal nucleating agent into the polypropylene resin composition.

[0015] The polypropylene resin composition constituting the biaxially oriented polypropylene film for lid material in the present invention preferably has a mesopentad fraction ([mmmm]%) of 97.0 to 99.9%, more preferably 97.5 to 99.7%, and even more preferably 98.0 to 99.5%, which is an indicator of stereoregularity. If it is less than 97.0%, there is a risk that high orientation cannot be achieved during stretching, and crystallization may be inhibited, potentially leading to a deterioration in rigidity and heat resistance. On the other hand, if it is 97.0% or more, the stereoregularity of the polypropylene resin composition is enhanced, improving the melting point, crystallinity, and crystal orientation of the crystals in the film, making it easier to obtain flatness, rigidity, and heat resistance at high temperatures. If it is 99.9% or less, it is easier to reduce the cost of polypropylene manufacturing and the film is less likely to break during film formation. The mesopentad fraction is measured by nuclear magnetic resonance (NMR) spectroscopy. To ensure that the mesopentade fraction of the polypropylene resin composition is within the above-mentioned range, methods such as washing the obtained polypropylene resin powder with a solvent such as n-heptane, or using an appropriate catalyst and / or co-catalyst can be employed.

[0016] The melt flow rate (MFR) of the polypropylene resin composition constituting the biaxially oriented polypropylene film for lid material in the present invention is preferably 4.0 to 30 g / 10 min, more preferably 4.5 to 25 g / 10 min, even more preferably 4.8 to 22 g / 10 min, even more preferably 5.0 to 20 g / 10 min, particularly preferably 6.0 to 20 g / 10 min, and most preferably 6.0 to 15 g / 10 min, when measured in accordance with the conditions M (230°C, 2.16 kgf) of JIS K 7210 (1995). When the MFR of the polypropylene resin composition is 4.0 g / 10 min or higher, a biaxially oriented polypropylene film with a low thermal shrinkage rate is easily obtained. Furthermore, when the MFR of the polypropylene resin composition is 30 g / 10 min or lower, the film-forming properties are easily maintained.

[0017] In the present invention, the amount of components with a molecular weight of 100,000 or less in the GPC integrated curve of the polypropylene resin composition constituting the biaxially oriented polypropylene film for lids is preferably 35% by mass or more, more preferably 38 to 65% by mass, even more preferably 38 to 60% by mass, particularly preferably 38 to 55% by mass, and most preferably 38 to 50% by mass. When the amount of components with a molecular weight of 100,000 or less is 35% by mass or more, the heat resistance is less likely to decrease. When the amount of components with a molecular weight of 100,000 or less is 65% by mass or less, the film strength is less likely to decrease. In this case, if high molecular weight components or long-chain branched components with long relaxation times are included, it becomes easier to adjust the amount of components with a molecular weight of 100,000 or less in the polypropylene resin composition without significantly changing the overall viscosity, so it is easier to improve film-forming properties without significantly affecting physical properties such as flatness, rigidity, and heat resistance.

[0018] The polypropylene resin composition constituting the biaxially oriented polypropylene film for lids in the present invention mainly consists of polypropylene resin. However, as long as the effects of the present invention are not impaired, additives such as resins other than polypropylene resin, known heat stabilizers, antioxidants, ultraviolet absorbers, nucleating agents, adhesives, antifogging agents, flame retardants, and inorganic or organic fillers may be added to the polypropylene resin composition constituting the biaxially oriented polypropylene film for lids in the present invention. However, these additions are preferably in small amounts, and in the polypropylene resin composition constituting the biaxially oriented polypropylene film for lids in the present invention, the amount of resins other than polypropylene resin is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 2% by mass or less, and particularly preferably 1% by mass or less. Furthermore, in the polypropylene resin composition constituting the biaxially oriented polypropylene film for lids in the present invention, the amount of additives other than resin is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 2% by mass or less, and particularly preferably 1% by mass or less. Examples of resins other than polypropylene resin include polyolefin resins other than polypropylene resin and various elastomers. These can be produced by sequential polymerization using a multi-stage reactor, by blending with polypropylene resin in a Henschel mixer, by diluting a master pellet prepared in advance using a melt-kneader with polypropylene resin to a predetermined concentration, or by pre-melting and kneading the entire amount before use.

[0019] (2) Polypropylene resin The biaxially oriented polypropylene film for lid material in the present invention consists of a polypropylene resin composition mainly composed of polypropylene resin. The term "main component" means that the proportion of polypropylene resin in the polypropylene resin composition is 90% by mass or more, preferably 93% by mass or more, more preferably 95% by mass or more, and even more preferably 97% by mass or more. If the polypropylene resin composition contains two or more different types of polypropylene resin, it is preferable that the total content of polypropylene resin in the polypropylene resin composition is within the above range.

[0020] The polypropylene resin that is the main component of the polypropylene resin composition constituting the biaxially oriented polypropylene film for lid material in the present invention may be a polypropylene homopolymer or a polypropylene copolymer containing α-olefins other than propylene, but it is preferable to use a polypropylene polymer that substantially does not contain α-olefin components other than propylene. Specifically, a "polypropylene polymer that substantially does not contain α-olefin components other than propylene" is a polypropylene (co)polymer whose constituent units are 1 mol% or less of α-olefin components other than propylene and 99 mol% or more of propylene. Even when α-olefin components other than propylene are included, the content of α-olefin components other than propylene (total amount of ethylene and α-olefins having 4 or more carbon atoms) is 1 mol% or less, preferably 0.5 mol% or less, more preferably 0.3 mol% or less, even more preferably 0.1 mol% or less, and particularly preferably 0 mol%. Crystallinity tends to improve within the above range. Examples of α-olefin components having 4 or more carbon atoms include 1-butene, 1-pentene, 3-methyl-1-pentene, 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, and 1-eicosene. The polypropylene resin, which is the main component of the polypropylene resin composition constituting the biaxially oriented polypropylene film for lid material in the present invention, may be a mixture of two or more different polypropylene polymers, for example, a mixture of two or more different polypropylene homopolymers, a mixture of polypropylene copolymers containing two or more different α-olefins other than propylene, or a mixture of one or more polypropylene homopolymers and one or more polypropylene copolymers containing α-olefins other than propylene. In the case of a mixture of two or more different polypropylene polymers, it is preferable that the total content of polypropylene polymers in the polypropylene resin composition is within the above range.

[0021] The following describes various suitable physical properties of the polypropylene resin, which is the main component of the polypropylene resin composition constituting the biaxially oriented polypropylene film for lid material in the present invention. When using two or more different polypropylene resins, the physical properties other than the melt flow rate shall be the mass average of the physical properties of each polypropylene resin.

[0022] The melting point of the polypropylene resin, which is the main component of the polypropylene resin composition constituting the biaxially oriented polypropylene film for lid material in the present invention, is preferably 158 to 170°C, more preferably 159 to 169°C, even more preferably 160 to 168°C, particularly preferably 161 to 167°C, and most preferably 162 to 166°C. A melting point of 158°C or higher makes it easier to obtain flatness, rigidity, and heat resistance at high temperatures. A melting point of 170°C or lower makes it easier to suppress cost increases in polypropylene manufacturing and makes it less likely to break during film formation. The melting point of polypropylene resin is the main peak temperature of the endothermic peak observed during melting, when 5 mg of polypropylene resin is packed into an aluminum pan, placed in a differential scanning calorimeter (DSC), heated from 30°C to 230°C in a nitrogen atmosphere at a heating rate of 20°C / min, held at 230°C for 5 minutes to melt the polypropylene resin, then cooled down to 30°C at a cooling rate of -10°C / min and held at 30°C for 5 minutes, and then heated up at a heating rate of 10°C / min.

[0023] The crystallization temperature of the polypropylene resin, which is the main component of the polypropylene resin composition constituting the biaxially oriented polypropylene film for lid material in the present invention, is preferably 105 to 135°C, more preferably 108 to 133°C, even more preferably 110 to 132°C, even more preferably 112 to 130°C, particularly preferably 114 to 128°C, and most preferably 116 to 127°C. When the crystallization temperature is 105°C or higher, crystallization proceeds easily during the widthwise stretching and subsequent cooling process, making it easier to obtain rigidity and heat resistance at high temperatures. When the crystallization temperature is 135°C or lower, it is less likely to increase the cost in terms of polypropylene manufacturing and the film is less likely to break during film formation. The crystallization temperature of polypropylene resin is the main peak temperature of the exothermic peak observed when 5 mg of polypropylene resin is packed into an aluminum pan, set in a DSC, heated from 30°C to 230°C under a nitrogen atmosphere at a heating rate of 20°C / min, held at 230°C for 5 minutes to melt the polypropylene resin, and then cooled down to 30°C at a cooling rate of -10°C / min.

[0024] By incorporating a nucleating agent into polypropylene resin, the melting point and crystallization temperature can be increased. When a nucleating agent is incorporated, it is preferable that the melting point and crystallization temperature of the polypropylene resin containing the nucleating agent fall within the above-mentioned range.

[0025] The polypropylene resin, which is the main component of the polypropylene resin composition constituting the biaxially oriented polypropylene film for lid material in the present invention, preferably has a mesopentad fraction ([mmmm]%) of 97.0 to 99.9%, more preferably 97.5 to 99.7%, and even more preferably 98.0 to 99.5%. If it is less than 97.0%, there is a risk that high orientation cannot be achieved during stretching, and crystallization may be inhibited, potentially worsening rigidity and heat resistance. On the other hand, if it is 97.0% or more, the stereoregularity of the polypropylene resin composition is enhanced, improving the melting point, crystallinity, and crystal orientation of the crystals in the film, making it easier to obtain flatness, rigidity, and heat resistance at high temperatures. If it is 99.9% or less, it is easier to reduce the cost of polypropylene manufacturing and the film is less likely to break during film formation. The mesopentad fraction is measured by nuclear magnetic resonance (NMR) spectroscopy. To keep the mesopentade fraction of the polypropylene resin within the above-mentioned range, methods such as washing the obtained polypropylene resin powder with a solvent such as n-heptane, or using an appropriate catalyst and / or co-catalyst can be employed.

[0026] The melt flow rate (MFR) of the polypropylene resin, which is the main component of the polypropylene resin composition constituting the biaxially oriented polypropylene film for lid material in the present invention, is preferably 4.0 to 30 g / 10 min, more preferably 4.5 to 25 g / 10 min, even more preferably 4.8 to 22 g / 10 min, even more preferably 5.0 to 20 g / 10 min, particularly preferably 6.0 to 20 g / 10 min, and most preferably 6.0 to 15 g / 10 min, when measured in accordance with the conditions M (230°C, 2.16 kgf) of JIS K 7210 (1995). When the MFR of the polypropylene resin is 4.0 g / 10 min or higher, a biaxially oriented polypropylene film with a low thermal shrinkage rate is easily obtained. Furthermore, when the MFR of the polypropylene resin is 30 g / 10 min or lower, the film-forming properties of the film are easily maintained.

[0027] (3) Method for manufacturing a biaxially oriented polypropylene film for lids The biaxially oriented polypropylene film for lids in the present invention is preferably obtained by preparing an unstretched sheet made of a polypropylene resin composition mainly composed of polypropylene resin and then biaxially stretching it. For biaxial stretching, it is preferable to stretch in the longitudinal direction first and then in the width direction, but it may also be stretched in the width direction first and then in the longitudinal direction. Examples of biaxial stretching methods include simultaneous inflation biaxial stretching, simultaneous tenter biaxial stretching, successive tenter biaxial stretching, and tube stretching, but successive tenter biaxial stretching is preferred from the viewpoint of film formation stability and thickness uniformity.

[0028] The following describes a method for producing a biaxially oriented polypropylene film for lid material according to the present invention. The following describes a method for producing a single-layer biaxially oriented polypropylene film using the tenter sequential biaxial stretching method, but the method is not limited to the method described below.

[0029] First, a polypropylene resin composition is heated and melted in a single-screw or twin-screw extruder, extruded into a sheet from a T-die, and cooled and solidified on a cooling roll to obtain an unstretched sheet. Next, this unstretched sheet is stretched longitudinally using two heated stretching rolls, increasing the rotation speed of the rear stretching roll to obtain a uniaxially oriented film. Subsequently, the uniaxially oriented film is heated in a preheating step, then stretched in the width direction while gripping the film end with a tenter stretching machine, heat treated, and finally cooled to obtain a biaxially oriented polypropylene film. If necessary, a film roll can be obtained by surface treating at least one side of the biaxially oriented polypropylene film and then winding it with a winder. The following describes the extrusion process, longitudinal stretching process, preheating process, width stretching process, heat treatment process, and cooling process in that order.

[0030] <Extrusion Process> First, a polypropylene resin composition mainly composed of polypropylene resin is heated and melted in a single-screw or twin-screw extruder at a temperature of 200°C to 300°C. The sheet-like molten polypropylene resin composition is extruded from the T-die and pressed onto a metal cooling roll using a contact device such as an air knife, where it is cooled and solidified to obtain an unstretched sheet. The obtained unstretched sheet may be further placed in a water tank. The temperature of the cooling roll, or the temperature of the cooling roll and water tank, is preferably 10°C or higher and Tc°C or lower. If the transparency of the film is to be increased, it is preferable to cool and solidify it with a cooling roll at 10 to 50°C. When using a propylene homopolymer with a mesopentad fraction of 97.0% or higher, it is preferable to set the cooling temperature to 40°C or lower from the viewpoint of facilitating the stretching in the next process, and more preferably to 30°C or lower from the viewpoint of reducing thickness variations. However, when increasing the degree of crystal orientation after sequential biaxial stretching, it may be preferable to set the cooling temperature to 40°C or higher. From the viewpoint of cooling efficiency, the thickness of the unstretched sheet is preferably 3500 μm or less, and more preferably 3000 μm or less. The thickness of the unstretched sheet can be appropriately adjusted according to the film thickness after sequential biaxial stretching. The thickness of the unstretched sheet can be controlled by the extrusion speed of the polypropylene resin composition and the lip width of the T-die, etc.

[0031] <Longitudinal stretching process> The longitudinal stretching temperature is preferably Tm-30 to Tm-7°C, more preferably Tm-27 to Tm-10°C, and even more preferably Tm-26 to Tm-12°C. If Tm-30°C or higher, the subsequent widthwise stretching becomes easier and thickness unevenness is less likely to occur. Furthermore, if Tm-7°C or lower, the thermal shrinkage rate is easily reduced, and there is less chance of adhesion to the stretching roll making stretching difficult, or a decrease in quality due to increased surface roughness. Here, as mentioned above, Tm is the melting point of the polypropylene resin composition constituting the biaxially oriented polypropylene film in the present invention. The lower limit of the longitudinal stretching ratio is preferably 3.5 times or more, more preferably 4 times or more. If it is 3.5 times or more, thickness unevenness can be reduced. The upper limit of the longitudinal stretching ratio is preferably 8 times or less, more preferably 7 times or less. If it is 8 times or less, breakage is less likely to occur during the subsequent TD stretching, making production easier. Furthermore, while stretching in the longitudinal direction may be performed in two or more stages using three or more stretching rolls, it is preferable to stretch in one stage using two pairs of stretching rolls. When stretching in multiple stages, it is preferable that the highest stretching temperature is within the above range.

[0032] <Preheating Process> It is preferable to heat the uniaxially oriented film after longitudinal stretching in the preheating process to sufficiently soften the polypropylene resin composition before the widthwise stretching process. The heating temperature in the preheating process is preferably Tm to Tm+25°C, more preferably Tm+2 to Tm+20°C, and even more preferably Tm+3 to Tm+15°C. Setting the heating temperature in the preheating process above the melting point promotes softening and facilitates widthwise stretching. Setting the heating temperature in the preheating process below Tm+25°C promotes orientation during widthwise stretching, making it easier to achieve rigidity. If the preheating process consists of multiple zones, the temperature of the zone with the highest temperature among them is used as the preheating temperature.

[0033] <Stretching process in the width direction> The stretching temperature in the width direction is preferably Tm-10°C or higher and below the heating temperature in the preheating process. A temperature of Tm-10°C or higher makes it easier to improve the rigidity of the resulting film. Furthermore, a temperature of Tm-9 to Tm+10°C is more preferable, Tm-7 to Tm+7°C is even more preferable, and Tm-5 to Tm+5°C is particularly preferable. A temperature of Tm+10°C or lower makes it less likely for stretching to occur. In the stretching process in the width direction, it is preferable to add a later stretching process at a lower temperature following the stretching process in the width direction within the above temperature range (hereinafter sometimes referred to as the earlier stretching process). Providing a later stretching process makes it easier to increase the rigidity of the film. The lower limit of the stretching ratio in the width direction is preferably 7 times or more, more preferably 7.5 times or more, and even more preferably 8 times or more. A ratio of 7 times or more makes it less likely for thickness unevenness to occur. The upper limit of the TD stretching ratio is preferably 15 times or less, more preferably 12 times or less, and even more preferably 10 times or less. If the ratio exceeds 15 times, the thermal shrinkage rate may increase, or the material may break during stretching. If a later stretching process is added, it is preferable to ensure that the total stretching ratio falls within the above range.

[0034] <Heat Treatment Process> Heat treatment is performed after the stretching process in the width direction is completed. Specific methods of heat treatment include creating a zone with a higher temperature than the stretching zone after the stretching process in the width direction is completed, and raising the zone temperature in the latter half of the stretching process and then passing the film through a zone at the same temperature after the stretching process is completed to raise the film temperature. Methods of heating include blowing hot air and heating with an infrared heater, but the method is not particularly limited as long as it raises the film temperature above the time of the stretching process in the width direction.

[0035] The heat treatment process is preferably carried out immediately after the completion of the widthwise stretching process (i.e., immediately after the widthwise stretching reaches the final stretching ratio). The temperature in the heat treatment process is preferably higher than the temperature at the end of the widthwise stretching process, specifically, it is preferably at least 1°C higher than the widthwise stretching temperature. Furthermore, the heat treatment process is preferably carried out in two stages: an early heat treatment process and a late heat treatment process. In the early heat treatment process, the heat treatment is performed at a temperature higher than the temperature at the end of the widthwise stretching process, and then in the late heat treatment process, the heat treatment is performed at a temperature lower than the temperature in the early heat treatment process. The early heat treatment process and the late heat treatment process will be described below.

[0036] (Early Heat Treatment Process) The heating temperature in the early heat treatment process is preferably Tm to Tm+20°C, more preferably Tm+3 to Tm+18°C, even more preferably Tm+4 to Tm+14°C, and particularly preferably Tm+5 to Tm+13°C. Heating in the heat treatment process after the stretching process relaxes the molecular chain orientation formed during stretching, making crystallization more likely to occur in the later heat treatment process. If heating is performed at a temperature lower than Tm°C, relaxation will not proceed, so the tension of the molecular chains will remain strong, which may inhibit crystallization. On the other hand, if heating is performed at a temperature higher than Tm+20°C, melting will proceed, and many of the oriented molecular chains will relax, which tends to reduce rigidity. By performing heat treatment at a temperature of Tm to Tm + 20°C in the initial heat treatment step, and then performing heat treatment at a lower temperature than the initial heat treatment step in the later heat treatment step, it is possible to set the longitudinal storage modulus at 140°C to 0.30 GPa or more and 1.0 GPa or less, and the widthwise thermal shrinkage rate at 150°C to 15% or less. The temperature can be gradually increased from the temperature at the end of widthwise stretching to the heating temperature, but it can also be increased in steps or in one step. Increasing the temperature in steps or in one step is preferable because it makes it easier to control the orientation of molecular chains in the film. In the initial heat treatment step, the film may or may not be relaxed in the widthwise direction. Specifically, the relaxation rate is preferably 0 to 3%, more preferably 0 to 1%, and even more preferably 0% (no relaxation). Within the above range, the rigidity is less likely to decrease, and the variation in film thickness tends to be small. If the relaxation rate is higher than 3%, many of the oriented molecular chains are relaxed, so the rigidity tends to decrease. Furthermore, if you want to increase rigidity even more, you do not need to relax it. Also, if it does not impair the effects of the present invention, you may slightly expand it to suppress sagging of the film, etc.

[0037] (Late Heat Treatment Process) The heating temperature in the late heat treatment process is preferably Tm-40 to Tm+10°C, more preferably Tm-30 to Tm+10°C, even more preferably Tm-20 to Tm+10°C, particularly preferably Tm-10 to Tm+10°C, and most preferably Tm-3 to Tm+10°C. Heating at a temperature higher than Tm+10°C does not promote crystallization and the thermal shrinkage rate does not decrease easily. On the other hand, heat treating at a temperature lower than Tm-40°C does not promote lamellar thickening and the melting point of the film does not increase easily. In other words, the heat resistance at high temperatures is impaired. In the late heat treatment process, the film may be relaxed in the width direction for the purpose of adjusting the thermal shrinkage rate. If relaxed, the relaxation rate is preferably 1 to 8%, more preferably 2 to 8%, and even more preferably 3 to 8%. Within the above range, the rigidity does not decrease easily and the variation in film thickness tends to be small. However, if you want to increase the rigidity further, you do not need to relax the film.

[0038] In the stretching process in the width direction, the molecular chains are oriented by stretching, but strong entanglement remains, resulting in an excessively constrained state of the molecular chains. When a heat treatment process is performed in this state, the degree of crystallinity does not increase easily due to the large number of excessively constrained molecular chains resulting from entanglement, and the thickness of the lamellae in the crystalline region does not increase easily, forming a crystalline region that melts at a lower temperature, so sufficient heat resistance cannot be achieved at high temperatures. Therefore, in conventional film-forming processes, crystallization was promoted by relaxing the film by several percent to tens of percent in the heat treatment process to resolve the entanglement of molecular chains after stretching in the width direction. However, relaxing the film reduces the orientation of the molecular chains generated in the stretching process in the width direction, reducing the rigidity of the film, making it difficult to achieve both heat resistance and rigidity in conventional film-forming processes. In addition, there was a problem of excessive melting and whitening of the film when heat treatment was performed at high temperatures. To resolve this issue, it is preferable to perform a heat treatment immediately after the widthwise stretching process at a higher temperature than the widthwise stretching process, with a relaxation rate of 3% or less, thereby resolving the constraint of molecular chains due to excessive entanglement while preserving the orientation of the molecular chains. Performing this heat treatment process reduces the presence of constrained molecular chains due to entanglement, thereby increasing the degree of crystallinity, making it easier to increase the thickness of the lamellae in the crystalline region, and enabling sufficient heat resistance even at high temperatures.

[0039] Furthermore, increasing the amount of low molecular weight polypropylene components (components with a molecular weight of 100,000 or less) in the polypropylene resin composition constituting the biaxially oriented polypropylene film is preferable because it reduces the entanglement of molecular chains, thereby weakening the thermal shrinkage stress in parts other than the lamellae of the crystalline region and further reducing the thermal shrinkage rate.

[0040] (Cooling step) It is preferable to cool the film immediately after the heat treatment step. The cooling temperature is preferably 10°C to 140°C, more preferably 15°C to 135°C, even more preferably 20°C to 130°C, particularly preferably 20°C to 80°C, and most preferably 20°C to 50°C. By providing a cooling step, the molecular orientation state within the film can be fixed.

[0041] The manufacturing method in the case of using the biaxially oriented polypropylene film for lid materials in the present invention as a single layer has been described above. However, the biaxially oriented polypropylene film for lid materials in the present invention may have layers having other functions (hereinafter referred to as functional layers) laminated on at least one side. The functional layer may be laminated on only one side or on both sides. When the functional layer contains a resin, the resin may be the polypropylene resin constituting the biaxially oriented polypropylene film for lid materials, or a resin other than the polypropylene resin constituting the biaxially oriented polypropylene film for lid materials. The number of laminated functional layers may be 1 layer, 2 layers, or 3 or more layers on one side, but from the viewpoint of ease of manufacture, it is preferably 1 layer or 2 layers. The lamination method is not particularly limited, and for example, coextrusion by a feed block method or a multi-manifold method is preferable. Further, for imparting printability, corona treatment can also be performed on one side or both sides of the film.

[0042] The biaxially oriented polypropylene film for lid materials in the present invention can also be made into a film roll having a width of 2000 to 12000 mm and a length of about 1000 to 50000 m by winding it in a roll shape, and it is possible to obtain a long film roll. Also, it can be slit according to each application to form a slit roll having a width of 300 to 2000 mm and a length of about 500 to 5000 m.

[0043] (4) Physical properties of the biaxially oriented polypropylene film for lid materials The biaxially oriented polypropylene film for lid materials of the present invention preferably has the following characteristics. Here, in the biaxially oriented polypropylene film in the present invention, the "machine direction (MD direction)" corresponds to the flow direction in the film manufacturing process, and the "transverse direction (TD direction)" is the direction orthogonal to the flow direction in the film manufacturing process, and the same applies hereinafter. For a polypropylene film whose flow direction in the film manufacturing process is unknown, wide-angle X-rays are incident perpendicular to the film surface, and the scattering peak derived from the (110) plane of the α-type crystal is scanned in the circumferential direction. The direction in which the diffraction intensity of the obtained diffraction intensity distribution is the largest is defined as the "machine direction", and the direction orthogonal to it is defined as the "transverse direction".

[0044] <Thickness> The thickness of the biaxially oriented polypropylene film for lid material of the present invention is 5 μm or more and 25 μm or less. The upper limit of the thickness is preferably 23 μm or less, more preferably 20 μm or less, and even more preferably 18 μm or less. If the thickness is 25 μm or less, the press-through properties are good and the contents can be easily removed from the packaging. The lower limit of the thickness is preferably 10 μm or more, and more preferably 14 μm or more. If the thickness is 5 μm or more, the occurrence of film tearing and wrinkles can be suppressed during printing and bag making.

[0045] <Impact Strength> The impact strength of the biaxially oriented polypropylene film for lid material of the present invention is 0.10 J or more and 0.85 J or less. The upper limit of the impact strength is preferably 0.82 J or less, more preferably 0.80 J or less, even more preferably 0.75 J or less, and particularly preferably 0.60 J or less. If the impact strength is 0.85 J or less, the press-through properties are good, and the contents can be easily removed from the packaging. The lower limit of the impact strength is preferably 0.15 J or more, and more preferably 0.20 J or more. If the impact strength is 0.10 J or more, film tearing and wrinkle formation can be suppressed during printing and bag making.

[0046] <Heat Shrinkage Rate at 150°C> The longitudinal heat shrinkage rate of the biaxially oriented polypropylene film for lid material of the present invention at 150°C is preferably 15% or less, more preferably 8.0% or less. It is even more preferably 6.0% or less, particularly preferably 5.0% or less, and most preferably 4.0% or less. A rate of 15% or less makes it less likely for printing pitch misalignment to occur when transferring printing ink. Furthermore, a rate of 15% or less improves processability when heat-sealing the bottom material and lid material for blister packaging, and also suppresses deformation of the film (lid material) even after processing, thereby suppressing the occurrence of wrinkles in the bottom material of the blister packaging. A lower longitudinal heat shrinkage rate at 150°C is preferable, and although there is no particular lower limit, due to technical difficulties, it is, for example, -2.0% or more, and preferably 0.5% or more. The longitudinal heat shrinkage rate at 150°C can be set to -2.0% or more and 15% or less by adjusting the stretching ratio, stretching temperature, and heat treatment temperature.

[0047] The heat shrinkage rate in the width direction of the biaxially oriented polypropylene film for the lid material of the present invention at 150°C is preferably 15% or less, more preferably 12% or less, still more preferably 8.5% or less, and particularly preferably 6.5% or less. When it is 15% or less, the processability when heat-sealing the bottom material and the lid material for blister packaging can be improved, and even after processing, the deformation of the film (lid material) can be suppressed, so that the occurrence of wrinkles in the bottom material of the blister package can be suppressed. The lower limit of the heat shrinkage rate in the width direction at 150°C is preferably -2.0% or more, more preferably 1% or more. The heat shrinkage rate in the width direction at 150°C can be made -2.0% or more and 15% or less by adjusting the draw ratio, draw temperature, and heat treatment temperature.

[0048] <Storage Modulus at 140°C> The storage modulus of the biaxially oriented polypropylene film for lids of the present invention was determined by dynamic viscoelasticity measurement. Specifically, with a measurement load of 10 g and a frequency of 10 Hz, the temperature was raised from -60°C to 160°C at a heating rate of 5°C / min under a nitrogen atmosphere, and the storage modulus at each temperature during the heating process was measured. The longitudinal storage modulus of the biaxially oriented polypropylene film for lids of the present invention at 140°C is preferably 0.30 GPa or more and 1.0 GPa or less, and more preferably 0.31 GPa or more and 0.90 GPa or less. If the longitudinal storage modulus at 140°C is 0.30 GPa or more and 1.0 GPa or less, the longitudinal dimensional stability at high temperatures will be good. The storage modulus in the width direction of the biaxially oriented polypropylene film for lids of the present invention is preferably 0.30 GPa or more and 1.0 GPa or less at 140°C, and more preferably 0.31 GPa or more and 0.90 GPa or less. If the storage modulus in the width direction at 140°C is 0.30 GPa or more and 1.0 GPa or less, the dimensional stability in the width direction at high temperatures will be good. The storage modulus in the longitudinal and width directions of the biaxially oriented polypropylene film for lids of the present invention is preferably 0.30 GPa or more and 1.0 GPa or less at 140°C, and more preferably 0.31 GPa or more and 0.90 GPa or less. If the storage modulus in the longitudinal and width directions at 140°C is both 0.30 GPa or more and 1.0 GPa or less, the dimensional stability in the longitudinal and width directions at high temperatures will be good, the flatness of the film will not deteriorate easily, and the processability of the film can be improved.

[0049] The sum of the storage moduli in the longitudinal and width directions at 140°C for the biaxially oriented polypropylene film for lids of the present invention is preferably 0.8 GPa or more and 3.0 GPa or less, more preferably 0.9 GPa or more and 2.0 GPa or less, and even more preferably 0.93 GPa or more and 1.5 GPa or less. When the sum of the storage moduli in the longitudinal and width directions at 140°C is within the above range, the strength at high temperatures tends to increase, and printing pitch misalignment is less likely to occur when transferring high-temperature printing ink during printing. In addition, the flatness of the film is less likely to deteriorate, and the processability of the film can be improved.

[0050] <Stress (F5) at 5% Elongation> The stress (F5) in the longitudinal direction at 23°C of the biaxially oriented polypropylene film for lid material of the present invention at 5% elongation is preferably 40 MPa or more and 70 MPa or less, more preferably 42 MPa or more and 65 MPa, even more preferably 42 MPa or more and 62 MPa or less, and particularly preferably 42 MPa or more and 60 MPa or less. At 40 MPa or more, the rigidity is high, making it easier to maintain the shape of the bag when made into a packaging bag, and less likely for the film to deform during processing such as printing. At 70 MPa or less, practical manufacturing becomes easier, and the balance between the longitudinal direction and the width direction is easily improved. The longitudinal F5 can be kept within the above range by adjusting the stretching ratio and relaxation rate, or by adjusting the temperature during film formation. The biaxially oriented polypropylene film for lids of the present invention has a stress (F5) in the width direction at 23°C when stretched to 5%. Preferably, the F5 is 90 MPa or more and 150 MPa or less, more preferably 95 MPa or more and 140 MPa or less, even more preferably 100 MPa or more and 130 MPa or less, and particularly preferably 105 MPa or more and 120 MPa or less. At 90 MPa or more, the rigidity is high, making it easier to maintain the shape of the bag when made into a packaging bag, and less likely for the film to deform during processing such as printing. At 150 MPa or less, practical manufacturing becomes easier, and the balance between the longitudinal and width directions is easily improved. The F5 in the width direction can be kept within the above range by adjusting the stretching ratio and relaxation rate, or by adjusting the temperature during film formation. The sum of the stress (F5) in the longitudinal and width directions at 5% elongation at 23°C for the biaxially oriented polypropylene film for lid material of the present invention is preferably 100 MPa or more and 200 MPa or less, more preferably 110 MPa or more and 190 MPa or less, even more preferably 120 MPa or more and 180 MPa or less, and particularly preferably 140 MPa or more and 170 MPa or less. At 100 MPa or more, the rigidity is high, making it easy to maintain the shape of the bag when made into a packaging bag, and the film is less likely to deform during processing such as printing. At 200 MPa or less, practical manufacturing becomes easier, and the balance between the longitudinal and width directions is easily improved. The F5 in the longitudinal and width directions can be kept within the above range by adjusting the stretching ratio and relaxation rate, or by adjusting the temperature during film formation.

[0051] <Tensile Elongation at Break> The longitudinal tensile elongation at break of the biaxially oriented polypropylene film for lids of the present invention is preferably 240% or more and 500% or less, more preferably 260% or more and 400%, even more preferably 280% or more and 370% or less, and particularly preferably 300% or more and 345% or less. At 240% or more, film breakage and packaging bag rupture can be reduced. At 500% or less, misalignment of the printing pitch when transferring printing ink is less likely to occur, and the durability of the packaging bag is also increased. The widthwise tensile elongation at break of the biaxially oriented polypropylene film for lids of the present invention is preferably 25% or more and 150% or less, more preferably 30% or more and 120% or less, even more preferably 35% or more and 100% or less, and particularly preferably 40% or more and 70% or less. At 25% or more, film breakage and packaging bag rupture can be reduced. At a ratio of 150% or less, misalignment of the print pitch during ink transfer is less likely to occur, and the durability of the packaging bag is also increased.

[0052] (5) Packaging (blister packaging) The biaxially oriented polypropylene film for lids of the present invention has excellent press-through properties and can therefore be suitably used as a lid for blister packaging. It can be particularly suitably used as a lid for press-through packaging used for tablets, capsules, etc. The blister packaging comprises a lid made of the biaxially oriented polypropylene film for lids of the present invention and a bottom made of polypropylene resin. For example, it can be manufactured by overlapping the flange portion of a bottom sheet having a recess and a flange portion with the biaxially oriented polypropylene film for lids of the present invention and heat sealing them. The heat sealing temperature is preferably 80°C or higher and 180°C or lower. If it is 80°C or higher, sufficient heat sealing strength can be obtained. If it is 180°C or lower, a packaging without wrinkles or deformation can be obtained. The heat sealing time is preferably 0.05 seconds or higher and 3 seconds or lower. If it is 0.05 seconds or higher, sufficient sealing strength can be obtained. If it is 3 seconds or lower, a packaging without wrinkles or deformation can be obtained. The heat sealing pressure is preferably 0.1 MPa or higher and 0.6 MPa or lower. If the pressure is 0.1 MPa or higher, sufficient seal strength can be obtained. If the pressure is 0.6 MPa or lower, a package without wrinkles or deformation can be obtained. The bottom sheet is preferably a polypropylene sheet. If the bottom material is the same material as the lid material, recycling is easy. From the viewpoint of recycling, a blister package comprising a lid made of the biaxially oriented polypropylene film of the present invention and a bottom material made of a polypropylene resin composition containing 90% by mass or more of polypropylene resin is preferred. It is more preferable that the resin composition constituting the lid material and the resin composition constituting the bottom material both contain 93% by mass or more of polypropylene resin, even more preferable that they contain 95% by mass or more, particularly preferable that they contain 97% by mass or more, and most preferable that they contain 100% by mass (the resin composition constituting the lid material and the resin composition constituting the bottom material both consist only of polypropylene resin). Furthermore, it is even more preferable that the resin constituting the lid material and the resin constituting the bottom material both consist only of polypropylene resin. When the resin constituting the lid material and the resin constituting the bottom material both consist only of polypropylene resin (no resins other than polypropylene resin are included), the cost of recycling can be significantly reduced because no resins other than polypropylene resin are present.

[0053] The film used as the lid material for blister packaging requires openability (press-through capability). The biaxially oriented polypropylene film for lid materials of the present invention has good press-through capability. When blister packaging is manufactured by heat sealing, if the thermal dimensional stability of the lid material film is poor, wrinkles may occur in the flange and recessed areas. Since the biaxially oriented polypropylene film for lid materials of the present invention has excellent heat resistance, it can suppress the occurrence of wrinkles even at high heat sealing temperatures that allow for high production speeds.

[0054] This application claims the benefit of priority based on Japanese Patent Application No. 2024-166573 and No. 2024-166574, filed on 25 September 2024, and Japanese Patent Application No. 2024-225585 and No. 2024-225586, filed on 20 December 2024. The entire contents of the specifications of Japanese Patent Application No. 2024-166573 and No. 2024-166574, filed on 25 September 2024, and Japanese Patent Application No. 2024-225585 and No. 2024-225586, filed on 20 December 2024 are incorporated herein by reference.

[0055] The present invention will be described in detail below with reference to examples. The present invention is not limited to these examples. The evaluation methods used in each example and comparative example are as follows. In addition, in (2) to (4) below, various physical properties of polypropylene resins were measured, and for polypropylene resin compositions using two types of polypropylene resins, the mass average of the physical properties of each polypropylene resin was used as the physical property value of the polypropylene resin composition. On the other hand, in (1) below, for polypropylene resin compositions using two types of polypropylene resins, the melt flow rate was measured in the state in which the two types of polypropylene resins were blended.

[0056] (1) Melt flow rate The melt flow rate (MFR) was measured in accordance with JIS K7210 at a temperature of 230°C and a load of 2.16 kgf.

[0057] (2) Mesopentad fraction The measurement of the mesopentad fraction ([mmmm]%) is as follows: １３ The analysis was performed using 1C-NMR. Mesopentadi fractions were calculated according to the method described in Zamberli et al., Macromolecules, Vol. 6, p. 925 (1973). １３ ¹³C-NMR measurements were performed using a BRUKER AVANCE 500 analyzer. 200 mg of the sample was dissolved at 135°C in an 8:2 mixture of o-dichlorobenzene and deuterated benzene, and the measurements were carried out at 110°C.

[0058] (3) Amount of components with a molecular weight of 100,000 or less Gel permeation chromatography (GPC) was used to determine the amount of components with a molecular weight of 100,000 or less from the integral curve of the molecular weight obtained by GPC, using monodisperse polystyrene as the basis and expressing it as polypropylene-equivalent molecular weight. The GPC measurement conditions were as follows: ・Apparatus: Tosoh HLC-8321PC / HT ・Detector: RI ・Solvent: 1,2,4-trichlorobenzene + dibutylhydroxytoluene (0.05%) ・Column: TSKgelguardcolumnHHR(30)HT (7.5 mm I.D. × 7.5 cm) × 1 + TSKgelGMHHR-H(20)HT (7.8 mm I.D. × 30 cm) × 3 ・Flow rate: 1.0 mL / min ・Injection volume: 0.3 mL ・Measurement temperature: 140℃

[0059] (4) Melting point and crystallization temperature Thermal measurements were performed using a Q1000 differential scanning calorimeter manufactured by T.A. Instruments. Approximately 5 mg was cut from the pellet and placed in an aluminum pan for measurement, then set in the differential scanning calorimeter. Under a nitrogen atmosphere, the temperature was increased from 30°C to 230°C at a heating rate of 20°C / min and held at 230°C for 5 minutes to melt the resin. Then, the temperature was cooled down to 30°C at a heating rate of -10°C / min and held at 30°C for 5 minutes, and then increased to 230°C at a heating rate of 10°C / min. The melting point was defined as the main peak temperature of the endothermic peak observed during the second heating cycle. The crystallization temperature was defined as the main peak temperature of the exothermic peak observed when the temperature was cooled from 230°C to 30°C.

[0060] (5) Film thickness The film thickness was measured using a Seiko EM Millitron 1202D.

[0061] (6) Impact strength A film impact tester manufactured by Toyo Seiki Seisakusho Co., Ltd. was used to measure the strength when the film was punched out in an environment with a temperature of 23°C and a relative humidity of 65%, in accordance with ASTM D3420.

[0062] (7) Heat shrinkage rate The heat shrinkage rate of the film in the longitudinal and width directions at 150°C was measured in accordance with JIS Z1712 by the following method. The film was cut so that the measurement direction was 200 mm and the direction perpendicular to it was 20 mm, and it was suspended in a 150°C hot air oven and heated for 5 minutes. The length after heating was measured, and the heat shrinkage rate at 150°C was determined as the ratio of the length shrunk to the original length.

[0063] (8) Storage modulus at 140°C by dynamic viscoelasticity measurement (DMA) The storage modulus in the longitudinal and width directions of the film was measured by the following method. The film was cut so that the measurement direction was 40 mm and the direction perpendicular to it was 4 mm, and set in an RSA-G2 manufactured by T.A. Instrument Japan Co., Ltd. with a chuck width of 10 mm. The temperature was raised from -60°C to 160°C at a heating rate of 5°C / min under a nitrogen atmosphere with a measurement load of 10 g and a frequency of 10 Hz, and the storage modulus at 140°C was determined. In addition, the sum of the storage modulus at 140°C in the longitudinal direction and the storage modulus at 140°C in the width direction was calculated from the obtained values.

[0064] (9) Stress (F5) and tensile elongation at 5% elongation In accordance with JIS K7127, the film was cut so that the measurement direction was 200 mm and the direction perpendicular to it was 15 mm. The chuck width was 100 mm, and the film was set on a tensile testing machine (Instron 5965 dual-column benchtop testing machine manufactured by Instron Japan Company Limited) and a tensile test was performed at a tensile speed of 200 mm / min. From the obtained strain-stress curve, the stress (F5) at 5% elongation in the longitudinal and width directions of the film was measured at 23°C. In addition, the elongation at the time the sample broke in the obtained strain-stress curve was defined as the tensile elongation at fracture.

[0065] (10) Openability (Press-through capability) A PTP package was prepared by molding an unstretched polypropylene sheet (thickness 300 μm) to create a base material measuring 100 mm x 40 mm with 10 recesses in two rows, each 9 mm in diameter and 4 mm deep. A biaxially oriented polypropylene film for the lid material, coated with heat-seal adhesive, was heat-sealed to the flange portion of the base material at 160°C, and no contents were filled into the package. The recesses of the prepared PTP package were pressed with a finger, and a sensory evaluation was conducted to determine how easily the lid material film could be torn. The evaluation criteria were as follows: A: Can be opened without any problems. B: Requires force to open and is difficult to open. C: Cannot be opened because the lid material cannot be torn.

[0066] (11) Visual evaluation of the heat-sealed portion The presence or absence of wrinkles in the flange portion and recess portion of the PTP packaging obtained above was visually evaluated. A: No wrinkles were observed in either the flange portion or the recess portion. B: Wrinkles were observed in the recess portion. C: Wrinkles were observed in either the flange portion or the recess portion.

[0067] (Materials Used) The polypropylene resins that make up each layer used in the following implementation and comparative examples are as follows: ・PP-1: Propylene homopolymer (manufactured by Sumitomo Chemical Co., Ltd., mesopentad fraction: 98.9%, melting point: 162.5℃, MFR: 7.5g / 10min, amount of components with molecular weight of 100,000 or less: 40.5%). ・PP-2: Propylene homopolymer (manufactured by Sumitomo Chemical Co., Ltd., mesopentad fraction: 98.8%, melting point: 163.0℃, MFR: 2.7g / 10min, amount of components with molecular weight of 100,000 or less: 30.0%). • PP-3: Propylene homopolymer (manufactured by Nippon Polypropylene Co., Ltd., mesopentad fraction: 94.8%, melting point: 160.6°C, MFR: 3.0 g / 10 min, amount of components with molecular weight of 100,000 or less: 37.1%) • PP-4: Antiblocking agent masterbatch (containing 95% by mass of propylene homopolymer (mesopentad fraction: 94.8%, melting point: 160.6°C, MFR: 3.0 g / 10 min), and 5% by mass of porous silica particles (average particle size 2.9 μm, pore volume 0.55 ml / g))

[0068] (Example 1) As the polypropylene resin, 80 parts by mass of PP-1, 17 parts by mass of PP-2, and 3 parts by mass of PP-4 were blended and used as the raw material. The blended raw material was extruded into a sheet from a T-die at 250°C, brought into contact with a cooling roll at 20°C, and then immediately placed in a 20°C water bath. After that, it was stretched 4.0 times in the longitudinal direction using two pairs of rolls at 140°C, then both ends were clipped and it was introduced into a hot air oven, preheated to 173°C, and then stretched 9.6 times in the width direction at 162°C. Immediately after stretching in the width direction, it was heat-treated at 174°C without relaxation while still held by the clips, and then heat-treated at 170°C to relax in the width direction by a relaxation rate of 6.5%. Finally, it was cooled at room temperature (23°C). The thickness of the resulting film was 16.2 μm. Table 1 shows the manufacturing conditions of the film and the characteristics of the film. As shown in Table 1, the PTP packaging made using the film from Example 1 as the lid material exhibited good press-through properties and no wrinkles were generated due to heat sealing.

[0069] (Examples 2 and 3) In Examples 2 and 3, the film manufacturing conditions were changed to those described in Table 1, and biaxially oriented polypropylene films were produced. Table 1 shows the film manufacturing conditions and film properties. As shown in Table 1, the PTP packaging made using the films of Examples 2 and 3 as lid material had good press-through properties and no wrinkles were generated by heat sealing.

[0070] (Comparative Example 1) In Comparative Example 1, a film with a thickness of 26.7 μm was obtained by increasing the discharge amount of the raw material resin under the same manufacturing conditions as in Example 2. Table 1 shows the manufacturing conditions and physical properties of the film. As shown in Table 1, the PTP packaging made using the film of Comparative Example 1 as the lid material had very poor press-through properties.

[0071] (Comparative Example 2) In Comparative Example 2, a film with a thickness of 20.1 μm was obtained using the same manufacturing method as in Example 2, except that the film manufacturing conditions were changed to those shown in Table 1. Table 1 shows the film manufacturing conditions and the physical properties of the film. As shown in Table 1, the PTP packaging made using the film of Comparative Example 2 as the lid material had poor press-through properties and wrinkles occurred when heat-sealed.

[0072] (Comparative Example 3) In Comparative Example 3, a film with a thickness of 20.0 μm was obtained using the same manufacturing method as in Example 2, except that the film manufacturing conditions were changed to those shown in Table 1. Table 1 shows the film manufacturing conditions and the physical properties of the film. As shown in Table 1, the PTP packaging made using the film of Comparative Example 3 as the lid material had poor press-through properties and wrinkles occurred due to heat sealing.

[0073] (Comparative Example 4) In Comparative Example 4, a biaxially oriented polypropylene film was manufactured using raw materials with low stereoregularity and a low melting point under the manufacturing conditions described in Table 1. Table 1 shows the manufacturing conditions and physical properties of the film. As shown in Table 1, the PTP packaging made using the film of Comparative Example 4 as the lid material had very poor press-through properties, and wrinkles occurred when heat-sealed.

[0074] (Comparative Example 5) In Comparative Example 5, a commercially available biaxially oriented polypropylene film (manufactured by Toyobo Co., Ltd., P2161, thickness 20.2 μm) was used as the lid material. As shown in Table 1, the PTP packaging made using the film of Comparative Example 5 as the lid material had very poor press-through properties, and wrinkles occurred due to heat sealing.

[0075]

[0076] The biaxially oriented polypropylene film for lids of the present invention has excellent press-through properties, allowing for easy removal of contents without the need for scissors, notches, or perforations. It also possesses sufficient strength for easy post-processing such as printing, and has excellent thermal dimensional stability, making it widely usable as a lid material for blister packaging. When used as a lid material for the bottom of blister packaging made of polypropylene sheets, it is easy to recycle as it is made of the same material, and its thinness contributes to plastic reduction, making it usable as an environmentally friendly packaging material.

Claims

A biaxially oriented polypropylene film for lid material, comprising a polypropylene resin composition containing 90% by mass or more of polypropylene resin, wherein the biaxially oriented polypropylene film satisfies the following (1) to (3). (1) The thickness is 5 μm or more and 25 μm or less. (2) The impact strength is 0.10 J or more and 0.85 J or less. (3) The thermal shrinkage rate in the width direction at 150°C is -2.0% or more and 15% or less. 　 The biaxially oriented polypropylene film for lid material according to claim 1, wherein the longitudinal storage modulus at 140°C is 0.30 GPa or more and 1.0 GPa or less. 　 The biaxially oriented polypropylene film for lid material according to claim 1 or 2, wherein the mesopentad fraction of the polypropylene resin is 97.0% or more. 　 A biaxially oriented polypropylene film for use as a lid material for a blister packaging, as described in claim 1 or 2. 　 A biaxially oriented polypropylene film for use as a lid material for press-through packaging, as described in claim 1 or 2. 　 A blister packaging comprising a lid made of a biaxially oriented polypropylene film for lids as described in claim 1 or 2, and a bottom made of polypropylene resin.

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