WO2024257805A1 - 二軸配向ポリプロピレンフィルム - Google Patents

二軸配向ポリプロピレンフィルム Download PDF

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Publication number
WO2024257805A1
WO2024257805A1 PCT/JP2024/021368 JP2024021368W WO2024257805A1 WO 2024257805 A1 WO2024257805 A1 WO 2024257805A1 JP 2024021368 W JP2024021368 W JP 2024021368W WO 2024257805 A1 WO2024257805 A1 WO 2024257805A1
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Prior art keywords
film
biaxially oriented
temperature
oriented polypropylene
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English (en)
French (fr)
Japanese (ja)
Inventor
一仁 堀之内
徹 今井
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Toyobo Co Ltd
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Toyobo Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
    • B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
    • B29C55/10—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial
    • B29C55/12—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial biaxial
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/18—Manufacture of films or sheets
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
    • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
    • C08L23/10—Homopolymers or copolymers of propene
    • C08L23/12—Polypropene
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
    • C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
    • C08J2323/10—Homopolymers or copolymers of propene
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
    • C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
    • C08J2323/10—Homopolymers or copolymers of propene
    • C08J2323/12—Polypropene
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2423/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
    • C08J2423/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
    • C08J2423/10—Homopolymers or copolymers of propene
    • C08J2423/12—Polypropene
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L2203/00—Applications
    • C08L2203/16—Applications used for films
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L2205/00—Polymer mixtures characterised by other features
    • C08L2205/02—Polymer mixtures characterised by other features containing two or more polymers of the same C08L -group
    • C08L2205/025—Polymer mixtures characterised by other features containing two or more polymers of the same C08L -group containing two or more polymers of the same hierarchy C08L, and differing only in parameters such as density, comonomer content, molecular weight, structure

Definitions

  • the present invention relates to a biaxially oriented polypropylene film.
  • Biaxially oriented polypropylene film has excellent physical properties such as rigidity and heat resistance, so it has traditionally been used in a wide range of applications, including packaging and industrial uses.
  • Patent Documents 1 to 3 disclose biaxially oriented polypropylene films that can be used for packaging applications and have various excellent physical properties. Specifically, the film of Patent Document 1 has low heat shrinkage and excellent Young's modulus, the film of Patent Document 2 has low heat shrinkage and excellent Young's modulus, and the film of Patent Document 3 has low heat shrinkage and excellent stress at 5% elongation.
  • the object of the present invention is to provide a biaxially oriented polypropylene film in which the length of the film in the width direction hardly changes even during or at the end of the temperature increase.
  • a biaxially oriented polypropylene film having a longitudinal storage modulus of 2.8 GPa or more at 23°C, a transverse storage modulus of 8.0 GPa or more at 23°C, a longitudinal heat shrinkage of 4.5% or less at 150°C, and a transverse heat shrinkage of 9.0% or less at 150°C.
  • the biaxially oriented polypropylene film of the present invention has a high storage modulus at 23°C while a low thermal shrinkage rate at 150°C, so that the length of the film in the width direction hardly changes during or after the temperature increase, and the film maintains its flatness even after heating. Therefore, the biaxially oriented polypropylene film of the present invention can be suitably used for packaging, industrial purposes, etc.
  • FIG. 1 is a graph showing the relationship between temperature and length in the width direction of the film in Example 4, Comparative Example 1, and Comparative Example 8.
  • FIG. 1 is a diagram showing the relationship between temperature and loss modulus in Example 4 and Comparative Example 1.
  • FIG. 1 is a diagram showing the relationship between temperature and storage modulus in Example 4 and Comparative Example 8.
  • the biaxially oriented polypropylene film of the present invention is made of a polypropylene resin composition.
  • the polypropylene resin composition constituting the biaxially oriented polypropylene film of 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 ⁇ -olefins other than propylene, or a mixture of one or more polypropylene homopolymers and one or more polypropylene copolymers containing ⁇ -olefins other than propylene.
  • polypropylene polymers polypropylene resins
  • the physical properties other than the melt flow rate are the mass average values of the physical properties of each polypropylene polymer.
  • the melting point (hereinafter sometimes referred to as Tm) of the polypropylene resin composition constituting the biaxially oriented polypropylene film of 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.
  • Tm melting point
  • the melting point is 158°C or higher, flatness, rigidity, heat resistance at high temperatures, etc. are easily obtained.
  • the melting point is 170°C or lower, it is easy to suppress cost increase in terms of polypropylene production, and the film is less likely to break during film formation.
  • the melting point of the polypropylene resin composition is the main endothermic peak temperature associated with melting, which is observed when 5 mg of the polypropylene resin composition is packed into 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 in a nitrogen atmosphere, and held at 230°C for 5 minutes to melt the polypropylene resin composition, and then cooled to 30°C at a heating rate of -10°C/min, held at 30°C for 5 minutes, and then heated at a heating rate of 10°C/min.
  • DSC differential scanning calorimeter
  • the crystallization temperature (hereinafter sometimes referred to as Tc) of the polypropylene resin composition constituting the biaxially oriented polypropylene film of 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.
  • Tc The crystallization temperature of the polypropylene resin composition constituting the biaxially oriented polypropylene film of 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.
  • 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 at a heating rate of 20°C/min in a nitrogen atmosphere, and held at 230°C for 5 minutes to melt the polypropylene resin composition, and then cooled to 30°C at a heating rate of -10°C/min.
  • the melting point and crystallization temperature of the polypropylene resin composition may be increased to fall within the above range by incorporating a crystal nucleating agent into the polypropylene resin composition.
  • the polypropylene resin composition constituting the biaxially oriented polypropylene film of the present invention preferably has a mesopentad fraction ([mmmm]%), which is an index of stereoregularity, 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, or that crystallization is inhibited, resulting in a deterioration in rigidity and heat resistance.
  • a mesopentad fraction [mmmm]%), which is an index of stereoregularity, of 97.0 to 99.9%, more preferably 97.5 to 99.7%, and even more preferably 98.0 to 99.5%.
  • the crystallinity of the polypropylene resin composition increases, and the melting point, crystallinity, and crystal orientation of the crystals in the film improve, making it easier to obtain flatness, rigidity, heat resistance at high temperatures, and the like. If it is 99.9% or less, it is easier to reduce the cost of polypropylene production, and the film is less likely to break during film formation.
  • the mesopentad fraction is measured by nuclear magnetic resonance (NMR) spectroscopy.
  • the melt flow rate (MFR) of the polypropylene resin composition constituting the biaxially oriented polypropylene film of 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 7.5 to 15 g/10 min.
  • MFR melt flow rate
  • the amount of components with a molecular weight of 100,000 or less is preferably 35% by mass or more, more preferably 38 to 65% by mass, even more preferably 40 to 60% by mass, particularly preferably 41 to 55% by mass, and most preferably 42 to 50% by mass.
  • the amount of components with a molecular weight of 100,000 or less is 35% by mass or more, heat resistance is unlikely to decrease.
  • the amount of components with a molecular weight of 100,000 or less is 65% by mass or less, film strength is unlikely to decrease.
  • a high molecular weight component with a long relaxation time or a long-chain branched component is included, it is easy to adjust the amount of components with a molecular weight of 100,000 or less contained in the polypropylene resin composition without significantly changing the overall viscosity, so that it is easy to improve film formability without significantly affecting physical properties such as flatness, rigidity, and heat resistance.
  • the polypropylene resin composition constituting the biaxially oriented polypropylene film of the present invention is mainly composed of polypropylene resin, but 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, anti-fogging agents, flame retardants, inorganic or organic fillers, etc. may be added to the polypropylene resin composition constituting the biaxially oriented polypropylene film of 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.
  • 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.
  • resins other than polypropylene resin include polyolefin resins other than polypropylene resins, various elastomers, etc. These may be sequentially polymerized using a multi-stage reactor, blended with polypropylene resin in a Henschel mixer, master pellets prepared in advance using a melt kneader are diluted with polypropylene resin to a predetermined concentration, or the entire amount may be melt kneaded in advance before use.
  • the biaxially oriented polypropylene film of the present invention is made of a polypropylene resin composition containing a polypropylene resin as a main component.
  • the term "main component" means that the proportion of the polypropylene resin in the polypropylene resin composition is 90% by mass or more, more preferably 93% by mass or more, even more preferably 95% by mass or more, and particularly preferably 97% by mass or more.
  • the polypropylene resin composition contains two or more different polypropylene resins, it is preferable that the total content of the polypropylene resins in the polypropylene resin composition is within the above range.
  • polypropylene resin which is the main component of the polypropylene resin composition constituting the biaxially oriented polypropylene film of the present invention
  • a polypropylene homopolymer or a polypropylene copolymer containing an ⁇ -olefin other than propylene may be used, but it is preferable to use a polypropylene polymer that does not substantially contain an ⁇ -olefin component other than propylene.
  • the "polypropylene polymer that does not substantially contain an ⁇ -olefin component other than propylene” is a polypropylene (co)polymer having 1 mol% or less of an ⁇ -olefin component other than propylene and 99 mol% or more of propylene as constituent units.
  • the content of the ⁇ -olefin component other than propylene (the total amount of ethylene and an ⁇ -olefin 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%.
  • the crystallinity is likely to be improved.
  • Examples of the ⁇ -olefin component 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 of 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 ⁇ -olefins other than propylene, or a mixture of one or more polypropylene homopolymers and one or more polypropylene copolymers containing one or more ⁇ -olefins other than propylene.
  • the total content of the polypropylene polymers in the polypropylene resin composition is within the above range.
  • the polypropylene resin which is the main component of the polypropylene resin composition that constitutes the biaxially oriented polypropylene film of the present invention.
  • the physical properties other than the melt flow rate are the mass average values of the physical properties of each polypropylene resin.
  • the melting point of the polypropylene resin which is the main component of the polypropylene resin composition constituting the biaxially oriented polypropylene film of 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.
  • the melting point is 158°C or higher, flatness, rigidity, heat resistance at high temperatures, etc. are easily obtained.
  • the melting point is 170°C or lower, it is easy to suppress cost increases in terms of polypropylene production, and the film is less likely to break during film formation.
  • the melting point of the polypropylene resin is the main endothermic peak temperature associated with melting, which is observed when 5 mg of the polypropylene resin is packed into 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 in a nitrogen atmosphere, and held at 230°C for 5 minutes to melt the polypropylene resin, and then cooled to 30°C at a heating rate of -10°C/min, held at 30°C for 5 minutes, and then heated at a heating rate of 10°C/min.
  • DSC differential scanning calorimeter
  • the crystallization temperature of the polypropylene resin which is the main component of the polypropylene resin composition constituting the biaxially oriented polypropylene film of 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.
  • crystallization temperature is 105°C or higher, crystallization is likely to proceed during the width direction stretching and the subsequent cooling process, and rigidity and heat resistance at high temperatures are likely to be obtained.
  • the crystallization temperature of the polypropylene resin is the main peak temperature of the exothermic peak observed when 5 mg of the polypropylene resin is packed into an aluminum pan, set in a DSC, heated from 30°C to 230°C at a heating rate of 20°C/min in a nitrogen atmosphere, and held at 230°C for 5 minutes to melt the polypropylene resin, and then cooled to 30°C at a heating rate of -10°C/min.
  • the melting point and crystallization temperature can be increased.
  • the melting point and crystallization temperature of the polypropylene resin to which the nucleating agent is blended are within the above ranges.
  • the polypropylene resin which is the main component of the polypropylene resin composition constituting the biaxially oriented polypropylene film of the present invention, preferably has a mesopentad fraction ([mmmm]%), which is an index of stereoregularity, 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, or that crystallization is inhibited, resulting in a deterioration in rigidity and heat resistance.
  • a mesopentad fraction [mmmm]%), which is an index of stereoregularity, of 97.0 to 99.9%, more preferably 97.5 to 99.7%, and even more preferably 98.0 to 99.5%.
  • the crystallinity of the polypropylene resin composition increases, and the melting point, crystallinity, and crystal orientation of the crystals in the film improve, making it easier to obtain flatness, rigidity, heat resistance at high temperatures, and the like. If it is 99.9% or less, it is easier to reduce the cost of polypropylene production, and the film is less likely to break during film formation.
  • the mesopentad fraction is measured by nuclear magnetic resonance (NMR) spectroscopy.
  • 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 of the present invention, when measured in accordance with condition M (230°C, 2.16 kgf) of JIS K 7210 (1995), 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 7.5 to 15 g/10 min.
  • the MFR of the polypropylene resin is 4.0 g/10 min or more, it is easy to obtain a biaxially oriented polypropylene film with a low thermal shrinkage rate.
  • the MFR of the polypropylene resin is 30 g/10 min or less, it is easy to maintain the film formability of the film.
  • the biaxially oriented polypropylene film of the present invention is preferably obtained by preparing an unstretched sheet made of a polypropylene resin composition mainly composed of a polypropylene resin, and biaxially stretching the sheet.
  • the biaxial stretching it is preferable to stretch the sheet in the longitudinal direction and then in the width direction, but it may also be stretched in the width direction and then in the longitudinal direction.
  • the biaxial stretching method include an inflation simultaneous biaxial stretching method, a tenter simultaneous biaxial stretching method, a tenter sequential biaxial stretching method, and a tube stretching method, and from the viewpoint of film-forming stability and thickness uniformity, the tenter sequential biaxial stretching method is preferable.
  • the method for producing the biaxially oriented polypropylene film of the present invention is described below.
  • the following describes a method for producing a single-layer biaxially oriented polypropylene film using a tenter sequential biaxial stretching method, but is not limited to the following production method.
  • the polypropylene resin composition is heated and melted in a single-screw or twin-screw extruder, extruded from a T-die into a sheet, and cooled and solidified by being grounded on a cooling roll to obtain an unstretched sheet.
  • the unstretched sheet is stretched in the longitudinal direction by two pairs of heated stretching rolls, by increasing the rotation speed of the rear stretching roll, to obtain a uniaxially stretched film.
  • the uniaxially stretched film is heated in a preheating step, and then stretched in the width direction while holding the film ends with a tenter-type stretching machine, heat-treated, and finally cooled to obtain a biaxially oriented polypropylene film.
  • At least one side of the biaxially oriented polypropylene film may be subjected to a surface treatment, and then the film may be wound up on a winder to obtain a film roll.
  • the extrusion step, the longitudinal stretching step, the preheating step, the widthwise stretching step, the heat treatment step, and the cooling step will be described in this order below.
  • a polypropylene resin composition mainly composed of polypropylene resin is heated and melted in a range of 200°C to 300°C in a single-screw or twin-screw extruder, and the sheet-shaped molten polypropylene resin composition is extruded from a T-die, and is brought into contact with a metallic cooling roll using a contacting device such as an air knife, and 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 cooling roll and water bath is preferably 10° C. or higher and Tc° C.
  • the cooling temperature is preferably 40° C. or lower from the viewpoint of facilitating the stretching in the next step, and more preferably 30° C. or lower from the viewpoint of reducing thickness unevenness.
  • a cooling temperature of 40° C. or higher may be preferable.
  • the thickness of the unstretched sheet is preferably 3500 ⁇ m or less, more preferably 3000 ⁇ m or less.
  • the thickness of the unstretched sheet may be appropriately adjusted according to the thickness of the film after the 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.
  • 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-25 to Tm-12°C. If the temperature is Tm-30°C or higher, the subsequent widthwise stretching becomes easy and the film thickness unevenness tends to be reduced. If the temperature is Tm-7°C or lower, the heat shrinkage rate is easily reduced, and the film is less likely to be difficult to stretch by applying it to the stretching rolls or to have a large surface roughness, resulting in a decrease in quality.
  • the stretching ratio in the longitudinal direction is preferably 3.5 to 8.0 times, more preferably 3.8 to 7.0 times, and even more preferably 4.2 to 6.0 times.
  • the longitudinal stretching may be performed in two or more stages using three or more pairs of stretching rolls, it is preferable to perform stretching in one stage using two pairs of stretching rolls.
  • the highest stretching temperature is within the above range.
  • ⁇ Preheating process> It is preferable to heat the uniaxially stretched film after the longitudinal stretching in the preheating step, and to sufficiently soften the polypropylene resin composition before the widthwise stretching step.
  • the heating temperature in the preheating step 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.
  • the stretching temperature in the width direction is preferably Tm-10°C or higher and equal to or lower than the heating temperature in the preheating step. If the temperature is Tm-10°C or higher, the rigidity of the resulting film is easily improved. Also, it is more preferably Tm-9 to Tm+10°C, even more preferably Tm-7 to Tm+7°C, and particularly preferably Tm-5 to Tm+5°C. If the temperature is Tm+10°C or lower, stretching unevenness is less likely to occur.
  • a width direction stretching step in the above temperature range hereinafter sometimes referred to as an early stretching step
  • a later stretching step in which stretching is performed at a lower temperature.
  • the rigidity of the film can be easily increased.
  • the stretching ratio in the width direction is preferably 10 to 20 times, more preferably 11 to 17 times, further preferably 12 to 15 times, and particularly preferably 12.5 to 15 times. If it is 10 times or more, the rigidity is easily increased and the film thickness unevenness is easily reduced. Also, if it is 20 times or less, the heat shrinkage rate is easily reduced and the film is less likely to break during stretching.
  • the total stretch ratio is set within the above range.
  • Heat treatment is performed after the end of the width direction stretching process.
  • Specific means for heat treatment include a method of providing a zone with a higher temperature than the stretching zone after the end of the width direction stretching, a method of increasing the zone temperature in the latter half of stretching and passing the film through a zone of the same temperature after the end of stretching to increase the temperature of the film, etc.
  • heating means include a method of blowing hot air and a method of heating with an infrared heater, but there is no particular limitation as long as the method is a method of increasing the temperature of the film from the end of the width direction stretching process.
  • the heat treatment step is preferably carried out immediately after the widthwise stretching step is completed (i.e., immediately after the widthwise stretching has reached the final stretch ratio).
  • the temperature in the heat treatment step is preferably higher than that at the end of the widthwise stretching step, and more specifically, is preferably the widthwise stretching temperature +1°C or more.
  • the heat treatment step is preferably carried out in two stages, an early heat treatment step and a later heat treatment step, and it is preferable that the early heat treatment step is performed at a temperature higher than that at the end of the widthwise stretching step, and then the later heat treatment step is performed at a temperature lower than that in the early heat treatment step.
  • the early heat treatment step and the later heat treatment step are described below.
  • the heating temperature in the early heat treatment step 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 + 10 ° C.
  • the temperature can be gradually increased from the temperature at the end of the width direction stretching to the temperature during heating, but it can also be increased in stages or in one stage. It is preferable to increase the temperature in stages or in one stage because it is easy to control the orientation of the molecular chains in the film.
  • the film may or may not be relaxed (relaxed) in the width direction.
  • the relaxation rate is preferably 0 to 3%, more preferably 0 to 1%, and even more preferably 0% (not relaxed).
  • the rigidity is less likely to decrease and the film thickness fluctuation is likely to be small. If the relaxation rate is higher than 3%, many of the oriented molecular chains are relaxed, so the rigidity is likely to decrease. If it is desired to further increase the rigidity, the film may not be relaxed. In addition, the film may be slightly expanded to suppress sagging, etc., as long as it does not impair the effects of the present invention.
  • the heating temperature in the latter heat treatment step is preferably Tm-70 to Tm°C, more preferably Tm-50 to Tm-1°C, further preferably Tm-40 to Tm-2°C, and particularly preferably Tm-30 to Tm-3°C.
  • Tm°C crystallization does not proceed and the heat shrinkage rate is unlikely to decrease.
  • Tm-70°C lamellar thickening does not proceed and the melting point of the film is unlikely to increase. In other words, heat resistance at high temperatures is impaired.
  • the film may be relaxed in the width direction for the purpose of adjusting the thermal shrinkage rate.
  • the relaxation rate is preferably 1 to 8%, more preferably 2 to 6%, and even more preferably 3 to 5%, but the film may not be relaxed. If the relaxation rate is within the above range, the rigidity is unlikely to decrease and the film thickness variation is likely to be small. However, if the rigidity is desired to be increased, the film may not be relaxed.
  • the molecular chains are oriented by stretching, but the entanglement remains strong, so the molecular chains are in an excessively constrained state. If the heat treatment process is performed in this state, the degree of crystallization is difficult to increase due to the large number of molecular chains that are excessively constrained due to entanglement, and further, the thickness of the lamella in the crystalline portion is difficult to increase, and a crystalline portion that melts at a lower temperature is formed, so that sufficient heat resistance cannot be exhibited at high temperatures.
  • the film in order to eliminate the entanglement of the molecular chains after stretching in the width direction, the film is relaxed by several percent to several tens of percent in the heat treatment process to promote crystallization.
  • the orientation of the molecular chains generated in the width direction stretching process is reduced by the relaxation, and the rigidity of the film is reduced, so that it is difficult to achieve both heat resistance and rigidity in the conventional film-forming process.
  • a heat treatment at a temperature higher than that of the width direction stretching immediately after the end of the width direction stretching step, with a relaxation rate of 3% or less, thereby eliminating the constraint of the molecular chains due to excessive entanglement while retaining the molecular chain orientation.
  • this heat treatment step is carried out, the presence of constrained molecular chains due to entanglement of the molecular chains is reduced, so that the degree of crystallization increases, making it easier to increase the thickness of the lamellae in the crystalline portion, and sufficient heat resistance can be exhibited even at high temperatures.
  • the entanglement of molecular chains can be reduced, which is preferable as it weakens the heat shrinkage stress in the parts other than the lamellae of the crystalline parts and further reduces the heat shrinkage rate.
  • the cooling temperature is preferably from 10° C. to 140° C., more preferably from 15° C. to 135° C., even more preferably from 20° C. to 130° C., particularly preferably from 20° C. to 80° C., and most preferably from 20° C. to 50° C.
  • the cooling temperature is preferably from 10° C. to 140° C., more preferably from 15° C. to 135° C., even more preferably from 20° C. to 130° C., particularly preferably from 20° C. to 80° C., and most preferably from 20° C. to 50° C.
  • the biaxially oriented polypropylene film of the present invention may have a layer having another function (hereinafter referred to as a functional layer) laminated on at least one side.
  • the functional layer may be laminated on only one side or on both sides.
  • the resin may be the polypropylene resin constituting the biaxially oriented polypropylene film, or a resin other than the polypropylene resin constituting the biaxially oriented polypropylene film may be used.
  • the number of functional layers may be one, two, or three or more layers per side, but from the viewpoint of ease of production, one or two layers is preferred.
  • the lamination method is not particularly limited, and for example, coextrusion using a feed block method or a multi-manifold method is preferred. As long as the effect of the present invention is not impaired, a resin layer having heat sealability can be laminated as a functional layer in order to improve the processability of the biaxially oriented polypropylene film. In addition, corona treatment can be performed on one or both sides of the film to impart printability.
  • the biaxially oriented polypropylene film of the present invention can be wound into a roll to produce a film roll with a width of 2000 to 12000 mm and a length of about 1000 to 50000 m, making it possible to obtain a long film roll. It can also be slit to suit each application to produce a slit roll with a width of 300 to 2000 mm and a length of about 500 to 5000 m.
  • the biaxially oriented polypropylene film of the present invention preferably has the following properties.
  • the "longitudinal direction (MD direction)" of the biaxially oriented polypropylene film of the present invention is the direction corresponding to the flow direction in the film production process
  • the "width direction (TD direction)” is the direction perpendicular to the flow direction in the film production process, and the same applies below.
  • MD direction the direction corresponding to the flow direction in the film production process
  • TD direction width direction
  • ⁇ Width direction length> In a thermomechanical analysis, when the temperature is raised from 30°C to 130°C at a heating rate of 10°C/min, the width direction length of the biaxially oriented polypropylene film of the present invention at 30°C is X0 , the maximum width direction length during the heating is X1 , and the minimum width direction length during the heating is X2 .
  • the percentage of ( X1 - X0 )/ X0 is preferably 0.20% or less, more preferably 0.19% or less, even more preferably 0.18% or less, particularly preferably 0.17% or less, and most preferably 0.16% or less.
  • the percentage of (X 2 -X 0 )/X 0 is preferably -0.50% or more, more preferably -0.45% or more, even more preferably -0.40% or more, particularly preferably -0.35% or more, and most preferably -0.30% or more. If it is -0.50% or more, deformation of the film can be suppressed even after the film is heated at high temperatures during heat processing with a roll, printing, or heat sealing, so that the flatness of the film is unlikely to deteriorate and the processability of the film can be improved.
  • the larger (X 2 -X 0 )/X 0 is, the more preferable it is, and the upper limit is not particularly limited, but is, for example, 0.00% or less.
  • the temperature at which the width direction length of the biaxially oriented polypropylene film of the present invention becomes 0.9950X 0 or less is preferably 129°C or more, more preferably 130°C or more, even more preferably 131°C or more, particularly preferably 132°C or more, and most preferably 133°C or more.
  • the "temperature at which the width direction length becomes 0.9950X 0 or less” refers to the lowest temperature at which the width direction length becomes 0.9950X 0 or less when the temperature is increased from 30°C to 160°C at a heating rate of 10°C/min.
  • the temperature at which the width direction length becomes 0.9950X 0 or less is 129°C or more, deformation of the film can be suppressed even after the film is heated at a high temperature such as during heat processing with a roll, printing, or heat sealing, and the flatness of the film is not easily deteriorated and the processability of the film can be improved.
  • the temperature at which the shrinkage becomes 0.9950X 0 or less is preferably high, and the upper limit is not particularly limited, but is, for example, 160° C. or less, preferably 156° C. or less. At 160° C. or less, practical manufacturing is easy and transparency is easily maintained. If the length in the width direction never becomes 0.9950X 0 or less even when the temperature is raised from 30° C. to 160° C., the temperature at the time of 0.5% shrinkage is determined to exceed 160° C.
  • the loss modulus was determined by dynamic viscoelasticity measurement. Specifically, the temperature was raised from -60°C to 160°C at a heating rate of 5°C/min in a nitrogen atmosphere under a measurement load of 10 g and a frequency of 10 Hz, and the loss modulus was measured at each temperature during the heating process.
  • the present inventors have found that by using highly stereoregular polypropylene and employing the above-mentioned width direction stretching process, it is possible to increase the orientation in the film, i.e., to increase the value of the loss modulus from -25°C to 25°C.
  • E"(A) is preferably 0.40 GPa or more, more preferably 0.42 GPa or more, even more preferably 0.44 GPa or more, particularly preferably 0.46 GPa or more, and most preferably 0.48 GPa or more.
  • E"(A) is 0.40 GPa or more, the rigidity tends to be high.
  • E"(A) is 0.40 GPa or more, the rigidity tends to be high.
  • a realistic value is, for example, 0.70 GPa or less, and preferably 0.60 GPa or less.
  • the present inventors have found that by using a polypropylene with high stereoregularity and adopting the above-mentioned width direction stretching process, it is possible to reduce the amount of crystals melting in the above-mentioned low temperature range, and the change in loss modulus from the glass transition temperature to 75°C is reduced.
  • E"(B) is preferably 0.26 GPa or more, more preferably 0.27 GPa or more, even more preferably 0.28 GPa or more, particularly preferably 0.29 GPa or more, and most preferably 0.30 GPa or more. If E"(B) is 0.26 GPa or more, the thermal shrinkage rate is likely to decrease. Furthermore, if E"(B) is 0.26 GPa or more, fewer crystals melt in the low temperature region, so planarity can be improved. There is no particular upper limit for E"(B), but a realistic value is, for example, 0.60 GPa or less, and preferably 0.50 GPa or less.
  • E"(C) is preferably 0.28 to 0.80 GPa, more preferably 0.29 to 0.75 GPa, even more preferably 0.30 to 0.70 GPa, particularly preferably 0.31 to 0.65 GPa, and most preferably 0.32 to 0.60 GPa. If E"(C) is 0.28 GPa or more, the film will be more rigid, and the shape of the bag will be easily maintained when it is made into a packaging bag, and the film will be less likely to deform during processing such as printing. If E"(C) is 0.80 GPa or less, practical manufacturing will be easier and the film will be less likely to tear in the width direction.
  • E"(C)/E"(A) is preferably 0.60 to 1.30, more preferably 0.62 to 1.20, even more preferably 0.64 to 1.10, particularly preferably 0.66 to 1.00, and most preferably 0.68 to 0.90.
  • E"(C)/E"(A) is 0.60 or more, the film has high rigidity, so that the shape of the bag is easily maintained when it is made into a packaging bag, and the film is less likely to deform during processing such as printing.
  • E"(C)/E"(A) is 1.30 or less, practical manufacturing is easy and the film is less likely to tear in the width direction.
  • E"(B)/E"(C) is preferably 0.60 to 1.30, more preferably 0.61 to 1.25, even more preferably 0.62 to 1.20, particularly preferably 0.63 to 1.15, and most preferably 0.64 to 1.10.
  • E"(B)/E"(C) is 0.60 or more, there are few crystals that melt in the low temperature range, so that relaxation associated with melting is less likely to occur, and as a result, relaxation of the amorphous portion is also suppressed. As a result, even when treated at high temperatures, the mobility of the amorphous portion is low, and flatness and heat resistance can be improved.
  • E"(B)/E"(C) is 1.30 or less, rigidity is less likely to decrease, and thickness fluctuation of the film is likely to be small.
  • the storage modulus was determined by dynamic viscoelasticity measurement. Specifically, the temperature was raised from ⁇ 60° C. to 160° C. at a 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 was measured at each temperature during the temperature rise.
  • the storage modulus in the longitudinal direction of the biaxially oriented polypropylene film of the present invention at 23° C. is 2.8 GPa or more, preferably 2.8 to 5.0 GPa, more preferably 2.8 to 4.5 GPa, even more preferably 2.8 to 4.3 GPa, particularly preferably 2.8 to 4.2 GPa, and most preferably 3.0 to 4.0 GPa.
  • the storage modulus in the width direction of the biaxially oriented polypropylene film of the present invention at 23° C. is 8.0 GPa or more, preferably 8.0 to 15.0 GPa, more preferably 8.2 to 14.0 GPa, even more preferably 8.4 to 13.5 GPa, and particularly preferably 8.6 to 13.0 GPa.
  • the strength of the biaxially oriented polypropylene film is significantly increased, and even if the film is thin, it can maintain its stiffness and strength, which contributes greatly to reducing the volume of the film. In addition, the flatness of the film is unlikely to deteriorate, and the processability of the film can be improved.
  • the storage modulus in the longitudinal direction of the biaxially oriented polypropylene film of the present invention at 120°C is preferably 0.5 to 2.5 GPa, more preferably 0.6 to 2.3 GPa, even more preferably 0.7 to 2.1 GPa, and particularly preferably 0.8 to 2.0 GPa.
  • the strength at high temperatures tends to be large, and printing pitch deviation is less likely to occur when transferring high-temperature printing ink during printing.
  • the storage modulus in the width direction of the biaxially oriented polypropylene film of the present invention at 120°C is preferably 2.1 to 8.0 GPa, more preferably 2.2 to 7.8 GPa, even more preferably 2.3 to 7.6 GPa, and particularly preferably 2.4 to 7.4 GPa.
  • the strength at high temperatures tends to be large, and printing pitch deviation is less likely to occur when transferring high-temperature printing ink during printing.
  • the flatness of the film is less likely to deteriorate, and the processability of the film can be improved.
  • the storage modulus in the longitudinal direction of the biaxially oriented polypropylene film of the present invention at 140° C. is preferably 0.3 to 1.5 GPa, more preferably 0.35 to 1.45 GPa, even more preferably 0.4 to 1.4 GPa, and particularly preferably 0.45 to 1.35 GPa.
  • the storage modulus in the width direction of the biaxially oriented polypropylene film of the present invention at 140° C. is preferably 1.3 to 5.0 GPa, more preferably 1.35 to 4.6 GPa, even more preferably 1.4 to 4.2 GPa, and particularly preferably 1.45 to 3.8 GPa.
  • the storage modulus at 140°C in the longitudinal and transverse directions is within the above range, the strength at high temperatures is likely to be large, and printing pitch deviation is unlikely to occur when transferring high-temperature printing ink during printing. In addition, the flatness of the film is unlikely to deteriorate and the processability of the film can be improved.
  • the storage modulus in the longitudinal direction of the biaxially oriented polypropylene film of the present invention at 150° C. is preferably 0.1 to 1.0 GPa, more preferably 0.15 to 0.9 GPa, even more preferably 0.2 to 0.8 GPa, and particularly preferably 0.25 to 0.7 GPa.
  • the storage modulus in the width direction of the biaxially oriented polypropylene film of the present invention at 150° C. is preferably 0.85 to 2.5 GPa, more preferably 0.9 to 2.4 GPa, even more preferably 0.95 to 2.3 GPa, and particularly preferably 1.0 to 2.2 GPa.
  • the storage modulus at 150°C in the longitudinal and transverse directions is within the above range, the strength at high temperatures is likely to be large, and printing pitch deviation is unlikely to occur when transferring high-temperature printing ink during printing. In addition, the flatness of the film is unlikely to deteriorate and the processability of the film can be improved.
  • the sum of the longitudinal storage modulus at 23°C and the longitudinal storage modulus at 140°C of the biaxially oriented polypropylene film of the present invention is preferably 3.0 to 8.0 GPa, more preferably 3.1 to 7.5 GPa, even more preferably 3.2 to 7.0 GPa, and particularly preferably 3.3 to 6.5 GPa.
  • the sum of the storage modulus in the width direction at 23°C and the storage modulus in the width direction at 140°C of the biaxially oriented polypropylene film of the present invention is preferably 8.9 to 19.0 GPa, more preferably 9.2 to 18.0 GPa, even more preferably 9.8 to 17.0 GPa, and particularly preferably 10.0 to 16.0 GPa.
  • the strength at high temperatures is likely to be large, and printing pitch deviation is unlikely to occur when transferring high-temperature printing ink during printing.
  • the flatness of the film is unlikely to deteriorate and the processability of the film can be improved.
  • the thickness of the biaxially oriented polypropylene film of the present invention is not particularly limited and may be appropriately set according to the application, but is preferably 2 to 100 ⁇ m, more preferably 3 to 80 ⁇ m, even more preferably 4 to 60 ⁇ m, particularly preferably 8 to 50 ⁇ m, and most preferably 10 to 40 ⁇ m.
  • the thickness is 2 ⁇ m or more, the film is easily rigid, and as a result, the film is easily strong.
  • the thickness is 100 ⁇ m or less, the cooling rate of the unstretched sheet during the extrusion process is not easily reduced.
  • the stress (F5) at 5% elongation in the longitudinal direction of the biaxially oriented polypropylene film of the present invention at 23°C is preferably 40 to 70 MPa, more preferably 42 to 65 MPa, even more preferably 46 to 62 MPa, and particularly preferably 48 to 60 MPa.
  • the film has high rigidity, so that the shape of the bag when made into a packaging bag is easily maintained, and the film is less likely to deform during processing such as printing.
  • 70 MPa or less practical production becomes easy, and the balance between the longitudinal direction and the width direction is easily improved.
  • the F5 in the longitudinal direction can be set within the above range by adjusting the stretch ratio or relaxation rate, or by adjusting the temperature during film formation.
  • the stress at 5% elongation in the width direction (F5) of the biaxially oriented polypropylene film of the present invention at 23°C is preferably 150 to 280 MPa, more preferably 152 to 250 MPa, even more preferably 154 to 230 MPa, particularly preferably 156 to 210 MPa, and most preferably 158 to 200 MPa.
  • the film has high rigidity, making it easier 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.
  • 280 MPa or less practical manufacturing is easy and the film is less likely to tear in the width direction.
  • the F5 in the width direction can be set within the above range by adjusting the stretch ratio and relaxation rate, or by adjusting the temperature during film formation.
  • the thermal shrinkage rate in the longitudinal direction of the biaxially oriented polypropylene film of the present invention at 120°C is preferably 2.5% or less, more preferably 2.0% or less, even more preferably 1.7% or less, and particularly preferably 1.5% or less. If it is 2.5% or less, printing pitch deviation is unlikely to occur when transferring printing ink.
  • the thermal shrinkage rate in the longitudinal direction at 120°C is preferably low, and the lower limit is not particularly limited, but is, for example, 0.1% or more, preferably 0.3% or more, from the viewpoint of technical difficulties.
  • the thermal shrinkage rate in the longitudinal direction at 120°C can be set within the above range by adjusting the stretch ratio, stretching temperature, and heat treatment temperature.
  • the heat shrinkage rate in the width direction of the biaxially oriented polypropylene film of the present invention at 120°C is preferably 1.1% or less, more preferably 1.0% or less, even more preferably 0.7% or less, particularly preferably 0.5% or less, and most preferably 0.3% or less. If it is 1.1% or less, wrinkles are less likely to occur during heat sealing.
  • the lower limit of the heat shrinkage rate in the width direction at 120°C is not particularly limited, but is, for example, -0.2%.
  • the heat shrinkage rate in the width direction at 120°C can be kept within the above range by adjusting the stretch ratio, stretching temperature, and heat treatment temperature.
  • the thermal shrinkage rate in the longitudinal direction of the biaxially oriented polypropylene film of the present invention at 150°C is 4.5% or less, and preferably 4.0% or less. If it is 4.5% or less, printing pitch deviation is less likely to occur when transferring printing ink.
  • a lower thermal shrinkage rate in the longitudinal direction at 150°C is preferable, and although there is no particular lower limit, it is, for example, 0.1% or more, and preferably 0.5% or more, due to technical difficulties.
  • the thermal shrinkage rate in the longitudinal direction at 150°C can be adjusted to be within the above range by adjusting the stretch ratio, stretching temperature, and heat treatment temperature.
  • the heat shrinkage rate in the width direction of the biaxially oriented polypropylene film of the present invention at 150°C is 9.0% or less, and more preferably 8.5% or less. If it is 9.0% or less, wrinkles are less likely to occur during heat sealing.
  • the heat shrinkage rate in the width direction at 150°C can be adjusted to be within the above range by adjusting the stretch ratio, stretching temperature, and heat treatment temperature.
  • the heat shrinkage rate in the longitudinal direction at 150°C is 4.5% or less and the heat shrinkage rate in the transverse direction is 9.0% or less, wrinkles are less likely to occur during heat sealing, and distortion is reduced when a zipper is fused to the opening of the bag, particularly when the bag is used as a packaging bag.
  • it is effective to set the amount of components with a molecular weight of 100,000 or less to 35% by mass or more when measuring the gel permeation chromatography (GPC) cumulative curve of the polypropylene resin composition that constitutes the film.
  • GPC gel permeation chromatography
  • the lower limit of the thickness uniformity of the biaxially oriented polypropylene film of the present invention is preferably 0%, more preferably 0.1%, even more preferably 0.5%, and particularly preferably 1%.
  • the upper limit of the thickness uniformity is preferably 20%, more preferably 17%, even more preferably 15%, particularly preferably 12%, and most preferably 10%. Within the above range, defects are unlikely to occur during post-processing such as coating and printing, and the film is easily used in applications requiring precision.
  • the biaxially oriented polypropylene film of the present invention exhibits little dimensional change over the entire temperature range from room temperature to 130° C. Therefore, even after heating at high temperatures such as during heat processing with a roll, printing, and heat sealing, deformation of the film can be suppressed, the flatness of the film is unlikely to deteriorate, and the processability of the film can be improved. In addition, it is possible to make the film thinner, which contributes to reducing the volume of packaging materials. From the above, when the biaxially oriented polypropylene film of the present invention is used, the bag shape is easily maintained when it is made into a packaging bag, the film is unlikely to deform during processing such as heat sealing at high temperatures, and printing pitch deviation is unlikely to occur during printing, making it suitable for packaging. In addition, the flatness is unlikely to be lost even after a silicone release agent is applied and dried by heating, making it suitable as a release film for optical applications and other applications where a high degree of flatness is required.
  • a sealant film made of polyethylene resin or polypropylene resin is laminated to the base film (the biaxially oriented polypropylene film of the present invention), and the sealant film surfaces are fused together.
  • the heating method is to apply pressure from the base film side with a heating plate to hold down the film and seal it, and the seal width is often about 10 mm.
  • the base film is also heated, and the expansion and contraction at that time causes wrinkles. Fewer wrinkles are better for the durability of the bag, and fewer wrinkles are also better for increasing purchasing desire.
  • the sealing temperature may be around 120°C, but a higher sealing temperature is required to increase the bag-making processing speed, and even in that case, it is preferable for the expansion and contraction to be small. If a zipper is to be fused to the opening of the bag, sealing at an even higher temperature is required.
  • an unstretched sheet, uniaxially stretched film, or biaxially stretched film made of low-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, polypropylene, or polyester can be laminated as a sealant film to the biaxially oriented polypropylene film of the present invention to form a laminate having heat sealability.
  • an intermediate layer of aluminum foil, an unstretched sheet, a uniaxially stretched film, or a biaxially stretched film can be provided between the biaxially oriented polypropylene film of the present invention and the sealant film.
  • the raw materials constituting the unstretched sheet, uniaxially stretched film, and biaxially stretched film include polyvinylidene chloride, nylon, ethylene-vinyl alcohol copolymer, and polyvinyl alcohol.
  • an adhesive applied by the dry lamination method or the hot melt lamination method can be used to attach the sealant film.
  • inorganic oxides such as aluminum, silica, and alumina can be vapor-deposited onto the biaxially oriented polypropylene film, the intermediate layer, or the sealant film.
  • Vacuum deposition, sputtering, ion plating, and other known methods can be used as the vapor deposition method.
  • the biaxially oriented polypropylene film of the present invention can be made suitable as a packaging material for vegetables, fruits, flowers, and other fresh produce by incorporating anti-fogging agents such as fatty acid esters of polyhydric alcohols, amines of higher fatty acids, amides of higher fatty acids, and ethylene oxide adducts of amines or amides of higher fatty acids in the range of 0.2 to 5 mass %.
  • anti-fogging agents such as fatty acid esters of polyhydric alcohols, amines of higher fatty acids, amides of higher fatty acids, and ethylene oxide adducts of amines or amides of higher fatty acids in the range of 0.2 to 5 mass %.
  • the present invention will be described in detail below with reference to examples. Of course, the present invention is not limited to these examples.
  • the evaluation methods used in each example and comparative example are as follows.
  • (2) to (4) various physical properties of the polypropylene resin were measured, and for polypropylene resin compositions using two types of polypropylene resin, the mass average of the physical property values of each polypropylene resin was used as the physical property value of the polypropylene resin composition.
  • the melt flow rate was measured when the two types of polypropylene resin were blended.
  • melt flow rate (MFR) was measured in accordance with JIS K7210 at a temperature of 230° C. and a load of 2.16 kgf.
  • the mesopentad fraction ([mmmm]%) was measured using 13 C-NMR.
  • the mesopentad fraction was calculated according to the method described in Zambelli et al., Macromolecules, Vol. 6, p. 925 (1973).
  • 13 C-NMR measurement was performed at 110° C. using an AVANCE 500 manufactured by BRUKER, by dissolving 200 mg of a sample in a mixed solution of o-dichlorobenzene and deuterated benzene in a ratio of 8:2 at 135° C.
  • Amount of components with molecular weight of 100,000 or less Calculated as polypropylene-equivalent molecular weight using gel permeation chromatography (GPC) with monodisperse polystyrene as the standard.
  • GPC gel permeation chromatography
  • the baseline was set to the lowest position of the high molecular weight side tail of the elution peak on the high molecular weight side closest to the elution peak of the standard substance.
  • the GPC measurement conditions are as follows. Equipment: Tosoh HLC-8321PC/HT Detector: RI Solvent: 1,2,4-trichlorobenzene + dibutylhydroxytoluene (0.05%) Column: TSK gelguard column HHR (30) HT (7.5 mm I.D.
  • the melting point was the main peak temperature of the endothermic peak associated with melting observed when the temperature was raised for the second time.
  • the crystallization temperature was the main peak temperature of the exothermic peak observed when the temperature was lowered from 230 ° C. to 30 ° C.
  • TMA Thermomechanical analysis
  • the maximum value of the length between the chucks during the temperature increase was defined as X 1 (mm), and the minimum value of the length between the chucks during the temperature increase was defined as X 2 (mm), and the percentages of (X 1 -10)/10((X 1 -X 0 )/X 0 ) and (X 2 -10)/10((X 2 -X 0 )/X 0 ) were calculated.
  • Thermomechanical analysis (TMA) measurement (temperature measurement at 0.5% shrinkage) A film was cut out so that the width direction of the film was 40 mm and the length direction of the film was 4 mm, and the film was set in a thermomechanical analyzer TMA-60 manufactured by Shimadzu Corporation so that the chuck width was 10 mm. The temperature was raised from 30°C to 160°C at a heating rate of 10°C/min with a measuring load of 0.5 g, and the length of the sample in the width direction during the heating was continuously measured. From the measurement results, the lowest temperature at which the length of the sample in the width direction was 9.95 mm or less was determined to be the temperature at which the sample contracted by 0.5%.
  • TMA thermomechanical analysis
  • Loss modulus by dynamic mechanical analysis A film was cut so that the width direction of the film was 40 mm and the length direction of the film was 4 mm, and the film was set in RSA-G2 manufactured by TA Instruments Japan Co., Ltd. so that the chuck width was 10 mm.
  • the film was heated 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 loss modulus during heating in the width direction of the film was measured.
  • a graph was drawn with temperature on the horizontal axis and loss modulus on the vertical axis, and the maximum value E"(A) of the loss modulus from -25°C to 25°C, the minimum value E"(B) of the loss modulus from 25°C to 75°C, and the maximum value E"(C) of the loss modulus at 100°C or higher were obtained.
  • the values of E"(C)/E"(A) and E"(B)/E"(C) were also calculated.
  • Heat shrinkage rate The heat shrinkage rate of the film in the longitudinal direction and the width direction at 120°C was measured according to JIS Z1712 by the following method. A film was cut so that the measurement direction was 200 mm and the direction perpendicular thereto was 20 mm, and the film was hung in a hot air oven at 120°C and heated for 5 minutes. The length after heating was measured, and the heat shrinkage rate at 120°C was calculated as the ratio of the shrunken length to the original length. The heat shrinkage at 150°C was measured in the same manner as the heat shrinkage at 120°C, except that the sample was hung in a hot air oven at 150°C.
  • the pressure was 0.2 MPa for 1 second, the width of the seal bar was 10 mm, and the heat seal temperature was 150° C.
  • the appearance of wrinkles in the heat-sealed portion was visually evaluated.
  • C Wrinkles were observed in the heat-sealed portion in both the width and length directions of the film.
  • Example 1 As the polypropylene resin, 80 parts by mass of propylene homopolymer PP-1 (Sumitomo Noblen FLX80E4 manufactured by Sumitomo Chemical Co., Ltd.) having an MFR of 7.5 g / 10 min, [mmmm] of 98.9%, melting point of 162.5 ° C., crystallization temperature of 116.2 ° C., and a molecular weight of 100,000 or less was 40.5% by mass, and 20 parts by mass of propylene homopolymer PP-2 (EL80F5 manufactured by Sumitomo Chemical Co., Ltd.) having an MFR of 11 g / 10 min, [mmmm] of 98.8%, melting point of 161.5 ° C., crystallization temperature of 116.5 ° C., and a molecular weight of 100,000 or less was 53.1% by mass.
  • propylene homopolymer PP-1 Suditomo Noblen FLX80E4 manufactured by Sumitomo Chemical Co., Ltd.
  • the sheet was extruded from a T-die at 250°C into a sheet, contacted with a cooling roll at 20°C, and then put into a water bath at 20°C. Thereafter, the film was stretched 4.5 times in the longitudinal direction with two pairs of rolls at 142°C, then both ends were clamped with clips, introduced into a hot air oven to preheat at 172°C, and then stretched 12.7 times in the width direction at 162°C. Immediately after the width direction stretching, the film was heat-treated at 170°C without relaxation while being held by the clips, and then heat-treated at 140°C to perform relaxation in the width direction at a relaxation rate of 3%. Finally, the film was cooled at room temperature (23°C).
  • the thickness of the film thus obtained was 20.0 ⁇ m.
  • Table 1 shows the production conditions of the film, and Table 2 shows the physical properties of the film.
  • the film of Example 1 had excellent flatness after treatment at 130° C., and was therefore suitable for applications requiring heat resistance, such as release films and process papers.
  • the three-side sealed bags produced using the film of Example 1 had a good heat-sealed appearance, and the resulting bags had excellent stiffness, and therefore had good handleability.
  • Examples 2 to 7 the films were produced by the same production method as in Example 1, except that the production conditions were changed to those shown in Table 1.
  • Table 1 shows the film production conditions
  • Table 2 shows the physical properties of the films.
  • all of the films of Examples 2 to 7 had excellent flatness after treatment at 130°C, and were therefore suitable for applications requiring heat resistance, such as release films and process papers.
  • all of the three-side sealed bags produced using the films of Examples 2 to 7 had good heat-sealed appearance, and the resulting bags had excellent stiffness, making them easy to handle.
  • the biaxially oriented polypropylene films produced in Examples 1 to 7 were used to produce laminates having the following configurations (1) to (9), and the laminates (1) to (9) were used to produce 130 mm x 180 mm three-sided seal type, pillow type, and gusset type packaging bags. Regardless of which biaxially oriented polypropylene film of each Example was used, packaging bags with good seal strength and good appearance of the sealed part could be produced.
  • Biaxially oriented PP film layer/printed layer/adhesive layer/unoriented PP film sealant layer were produced.
  • Biaxially oriented PET film layer/printed layer/adhesive layer/biaxially oriented PP film layer/adhesive layer/unoriented PP film sealant layer (3) Biaxially oriented PET film layer/printed layer/adhesive layer/biaxially oriented PP film layer/adhesive layer/unoriented PP film sealant layer. (4) Biaxially oriented PET film layer/printed layer/adhesive layer/biaxially oriented PP film layer/adhesive layer/linear low density PE film sealant layer. (5) Biaxially oriented PP film layer/anchor coat layer/inorganic thin film layer/inorganic thin film protective layer/printed layer/adhesive layer/linear low density PE film sealant layer.
  • Comparative Examples 1 to 5 In Comparative Examples 1 to 5, the films were produced by the same production method as in Example 1, except that the production conditions were changed to those shown in Table 1. Table 1 shows the film production conditions, and Table 2 shows the physical properties of the films. In Comparative Example 1 and Comparative Example 9 described later, the heat treatment was performed at 100° C. in the first stage of the heat treatment, which means that the first stage of the heat treatment is essentially cooling.
  • Example 6 The film was produced by the same production method as in Example 1, except that only PP-3 (WF836DG3 manufactured by Sumitomo Chemical Co., Ltd.) having an MFR of 7 g/10 min, [mmmm] of 95.2%, melting point of 157.8° C., crystallization temperature of 111.2° C., ethylene monomer content of 0.4 mol%, and component amount of molecular weight of 100,000 or less was 39.1 mass% was used as the polypropylene resin, and the film production conditions were changed to the production conditions shown in Table 1. The film production conditions are shown in Table 1, and the physical properties of the film are shown in Table 2.
  • Example 7 The film was produced by the same production method as in Example 1, except that the production conditions were changed to those shown in Table 1. Immediately after stretching in the width direction, the film was cooled (heat treated) at 120° C. while still held by the clips, and then re-stretched to 1.1 times in the width direction at 177° C. Table 1 shows the production conditions of the film, and Table 2 shows the physical properties of the film.
  • Example 8 The film was introduced into a hot air oven and preheated at 177°C, then stretched 6.8 times in the width direction at 169°C, and immediately after the width direction stretching, it was heat-treated at 170°C while still held by the clips to relax 16% in the width direction, except for the above, the same procedures as in Example 1.
  • Table 1 shows the production conditions of the film
  • Table 2 shows the physical properties of the film.
  • Example 9 The film was introduced into a hot air oven and preheated at 170°C, and then stretched 6.0 times in the width direction at 162°C in the first stage, followed by 1.36 times stretching at 145°C in the second stage for a total stretching of 8.16 times, and immediately after the width direction stretching, the film was heat-treated at 100°C while still held by the clips without relaxation, and then heat-treated at 165°C without relaxation, in the same manner as in Example 1.
  • Table 1 shows the production conditions of the film
  • Table 2 shows the physical properties of the film.
  • Fig. 1 is a diagram showing the relationship between temperature and the length in the width direction of the film in Example 4, Comparative Example 1, and Comparative Example 8 , and more precisely, the relationship between temperature and the percentage of (X- X0 )/X0 (X: film length in the width direction at that temperature, X0 : 10 (mm)).
  • Fig. 2 is a diagram showing the relationship between temperature and loss modulus in Example 4 and Comparative Example 1
  • Fig. 3 is a diagram showing the relationship between temperature and storage modulus in Example 4 and Comparative Example 8.

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WO2021261313A1 (ja) * 2020-06-25 2021-12-30 東洋紡株式会社 二軸配向ポリプロピレンフィルムの製造方法
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