WO2014024968A1 - インモールドラベル用ポリプロピレンフィルム - Google Patents
インモールドラベル用ポリプロピレンフィルム Download PDFInfo
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- WO2014024968A1 WO2014024968A1 PCT/JP2013/071506 JP2013071506W WO2014024968A1 WO 2014024968 A1 WO2014024968 A1 WO 2014024968A1 JP 2013071506 W JP2013071506 W JP 2013071506W WO 2014024968 A1 WO2014024968 A1 WO 2014024968A1
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- 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
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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
- B29C55/14—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial biaxial successively
- B29C55/143—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial biaxial successively firstly parallel to the direction of feed and then transversely thereto
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- 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
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2023/00—Use of polyalkenes or derivatives thereof as moulding material
- B29K2023/10—Polymers of propylene
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- 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
Definitions
- the present invention relates to a polypropylene film for in-mold labels excellent in heat resistance and mechanical properties.
- a conventional polypropylene film has a shrinkage rate of several tens of percent at 150 ° C., and has low heat resistance and low rigidity compared to PET, etc., so curling due to shrinkage is likely to occur during laminating, and this may cause defects. It was.
- Patent Document 1 a technique for producing a film having high-temperature rigidity and heat resistance by forming a stretched film using polypropylene having high stereoregularity and a narrow molecular weight distribution
- Patent Document 2 a technique for producing a film having high-temperature rigidity and heat resistance by forming a stretched film using polypropylene having high stereoregularity and a narrow molecular weight distribution
- Patent Document 2 a technology for producing a film having high-temperature rigidity and heat resistance by forming a stretched film using polypropylene having high stereoregularity and a narrow molecular weight distribution.
- Patent Documents 1 to 3 have difficulty in stretchability and inferior mechanical properties.
- Patent Documents 4 to 5 cannot be said to have sufficient heat resistance at high temperatures, and a polypropylene film having high heat resistance and excellent impact resistance and transparency has not been known. That is, they do not exceed the range of conventional polypropylene films, and their uses are limited. For example, no attention has been paid to heat resistance at high temperatures exceeding 150 ° C.
- the in-mold label method When affixing a label to the outer surface of a resin container, such as a polypropylene or polyethylene container, the in-mold label method is affixed to the outer surface of the container at the same time as the molding of the container. It is used favorably because it has many advantages such as being able to display an area label and being excellent in design, and by making the container thinner by increasing the rigidity of the container itself by the label. .
- paper, synthetic paper, plastic film, etc. are used as an in-mold label base material (for example, refer patent document 6, patent document 7, patent document 8, etc.).
- plastic film In the case of plastic film, the same plastic film is bonded together, or plastic films of various materials according to the label specifications are combined to form an in-mold label for printing, laminating, or bonding. Is widely implemented.
- a polypropylene film is often used from the viewpoint of adhesion to a container.
- the present invention has been made against the background of the problems of the prior art. That is, the objective of this invention is providing the polypropylene film suitable for an in-mold label use.
- the present invention is a film mainly composed of a polypropylene resin, the thermal shrinkage rate in the MD direction and TD direction at 150 ° C. is 9% or less, the Young's modulus in the MD direction is 2 GPa or more, A polypropylene film for an in-mold label, wherein the Young's modulus in the TD direction is 4 GPa or more and the haze is 6% or less.
- the lower limit of the isotactic mesopentad fraction of the polypropylene resin constituting the film is 96%, and the lower limit of the plane orientation coefficient of the film is 0.0125.
- the upper limit of the amount of the copolymerization monomer of the polypropylene resin constituting the film is 0.1 mol%.
- the polypropylene resin constituting the film has a normal temperature xylene-soluble content of 7% by mass or less.
- the polypropylene film of the present invention is difficult to stretch due to tension during printing or laminating, and the label after bonding is It can prevent curling.
- Example 2 is a DSC chart of a polypropylene film described in Example 1 and Comparative Example 1.
- the present invention relates to a polypropylene film for in-mold labels.
- the polypropylene film for an in-mold label of the present invention is a film mainly composed of a polypropylene resin, and the thermal shrinkage rate in the MD direction and the TD direction at 150 ° C. is 9% or less, and the Young's modulus in the MD direction. Is 2 GPa or more, Young's modulus in the TD direction is 4 GPa or more, and haze is 6% or less.
- the lower limit of the heat shrinkage rate at 150 ° C. in the MD direction and the TD direction of the polypropylene film of the present invention is preferably 0.5%, more preferably 1%, still more preferably 1.5%, particularly preferably. Is 2%, most preferably 2.5%.
- the MD direction is the film flow direction
- the TD direction is the direction perpendicular to the film flow direction.
- the upper limit of the heat shrinkage rate at 150 ° C. in the MD direction and the TD direction is 9%, preferably 8%, more preferably 7%, still more preferably 6%, and most preferably 5%. .
- the heat shrinkage rate is 9% or less, a film having excellent heat resistance can be obtained, and use in applications that may be exposed to a high temperature of about 150 ° C. becomes easier.
- the heat shrinkage at 150 ° C. is about 2.5% or more, for example, the low molecular weight polypropylene (hereinafter referred to as low molecular weight component) having a molecular weight of about 100,000 is increased, and the stretching conditions and heat setting conditions are adjusted.
- the thermal shrinkage rate at 150 ° C. in the MD direction and the TD direction exceeds 15%, and the thermal shrinkage rate at 120 ° C. is about 3%.
- the lower limit of the Young's modulus (23 ° C.) in the MD direction is 2 GPa, preferably 2.1 GPa, more preferably 2.2 GPa, and even more preferably 2.3 GPa. And most preferably 2.4 GPa.
- the upper limit of the Young's modulus in the MD direction is preferably 4 GPa, more preferably 3.7 GPa, even more preferably 3.5 GPa, particularly preferably 3.4 GPa, and most preferably 3.3 GPa. If the Young's modulus in the MD direction is 2 GPa or more and 4 GPa or less, it may be practically easy to manufacture or the MD-TD balance may be improved.
- the lower limit of the Young's modulus (23 ° C.) in the TD direction is 4 GPa, more preferably 4.2 GPa, and still more preferably 4.3 GPa.
- the upper limit of the Young's modulus in the TD direction is preferably 8 GPa, more preferably 7.5 GPa, still more preferably 7 GPa, and particularly preferably 6.5 GPa.
- the Young's modulus in the TD direction is 3.8 GPa or more and 8 GPa or less, it may be practically easy to manufacture or the MD-TD balance may be improved.
- the Young's modulus can be increased by increasing the stretching ratio. In the case of MD-TD stretching, the stretching ratio in the MD direction is set lower, and the Young's modulus in the TD direction is increased by increasing the stretching ratio in the TD direction. The rate can be increased.
- the lower limit as a practical value of the haze of the polypropylene film of the present invention is preferably 0.1%, more preferably 0.2%, still more preferably 0.3%, and particularly preferably 0.4%. %, And most preferably 0.5%.
- the upper limit of the haze of the film is 6%, preferably 5%, more preferably 4.5%, still more preferably 4%, and most preferably 3.5%.
- the haze is 6% or less, it may be easy to use in applications where transparency is required. For example, when the stretching temperature or the heat setting temperature is too high, the haze tends to increase when the cooling roll temperature is high and the cooling rate is slow, or when there are too many low molecular weight components. I can do it.
- the upper limit of the curl amount of the polypropylene film of the present invention is preferably 15 mm, more preferably 14 mm, still more preferably 13 mm, and most preferably 12 mm.
- the curl amount is 15 mm or less, the occurrence of film defects caused by curl can be suppressed. A method for measuring the curl amount will be described later.
- the polypropylene resin constituting the film of the present invention has a characteristic broad molecular weight distribution.
- Polypropylene resin used in the present invention for example, weight average molecular weight (M w) of 100,000 as low molecular weight polypropylene (low molecular weight component) as main, further for example M w of high molecular weight having a molecular weight extremely about 1.5 million Polypropylene (hereinafter referred to as a high molecular weight component) is preferably contained. Crystallinity can be greatly increased by mainly using a low molecular weight component, and it is considered that a polypropylene film having a high rigidity and high heat resistance, which has not been conventionally obtained, is obtained.
- a low molecular weight polypropylene resin has a low melt tension when softened by heating, and it is generally difficult to obtain a stretched film.
- the presence of several percent to several tens of percent of the high molecular weight component enables stretching, and the high molecular weight component serves as a crystal nucleus, further improving the crystallinity of the film. It is considered that a film can be easily obtained.
- Parameters representing the molecular weight of the polymer include number average molecular weight (M n ), mass average molecular weight (M w ), Z average molecular weight (M z ), Z + 1 average molecular weight (M z + 1 ), peak molecular weight (M p ).
- the lower limit of M z + 1 / M n is preferably 50, more preferably 60, still more preferably 70, particularly preferably 80, and most preferably 90. If M z + 1 / M n is less than 50, it may be difficult to obtain the effects of the present invention such as a low thermal shrinkage at a high temperature.
- the upper limit of M z + 1 / M n is preferably 300, more preferably 200. If M z + 1 / M n exceeds 300, it may actually be difficult to produce a resin.
- the lower limit of M z + 1 of the entire polypropylene resin constituting the film is preferably 2500,000, more preferably 3000,000, still more preferably 3300000, particularly preferably 3500000, and most preferably 3700000.
- M z + 1 is 2500,000 or more, the high molecular weight component is sufficient, and the effects of the present invention are easily obtained.
- the upper limit of M z + 1 of the entire polypropylene resin constituting the film is preferably 40000000, more preferably 35000000, and further preferably 30000000.
- M z + 1 is 4000000 or less, the production of the resin is actually easy, stretching may be easy, and fish eyes in the film may be reduced.
- the lower limit of M n of the entire polypropylene resin constituting the film is preferably 20000, more preferably 22000, still more preferably 24000, particularly preferably 26000, and most preferably 27000.
- Mn is 20000 or more, there are the advantages that stretching is easy, thickness unevenness is small, stretching temperature and heat setting temperature are easily raised, and thermal shrinkage is lowered.
- the upper limit of M n of the entire polypropylene resin constituting the film is preferably 65000, more preferably 60000, still more preferably 55000, particularly preferably 53000, and most preferably 52000.
- M n is 65000 or less, the effect of a low molecular weight component is likely to be exhibited, and a low heat shrinkage rate at a high temperature is likely to be obtained, and stretching may be facilitated.
- the lower limit of M w of the entire polypropylene resin constituting the film is preferably 250,000, more preferably 260000, still more preferably 270000, particularly preferably 280000, and most preferably 290000.
- Mw is 250,000 or more, there are the advantages that stretching becomes easy, thickness spots are reduced, stretching temperature and heat setting temperature are easily raised, and thermal shrinkage rate is lowered.
- the upper limit of M w of the entire polypropylene resin constituting the film is preferably 500,000, more preferably 450,000, still more preferably 400,000, particularly preferably 380000, and most preferably 370000.
- M w of is that there is the mechanical load 500000 a small stretch easily.
- the lower limit of M w / M n is preferably 5.5, more preferably 6, still more preferably 6.5, particularly preferably 7, and most preferably 7.2.
- the upper limit of M w / M n is preferably 30, more preferably 25, still more preferably 20, particularly preferably 15, and most preferably 13.
- the lower limit of the melt flow rate (MFR) (230 ° C., 2.16 kgf) of the entire polypropylene resin constituting the film is preferably 1 g / 10 minutes, more preferably 1.2 g / 10 minutes, and even more preferably 1 0.4 g / 10 min, particularly preferably 1.5 g / 10 min, most preferably 1.6 g / 10 min.
- MFR melt flow rate
- the upper limit of the MFR of the entire polypropylene resin constituting the film is preferably 11 g / 10 minutes, more preferably 10 g / 10 minutes, still more preferably 9 g / 10 minutes, and most preferably 8.5 g / 10 minutes. It is. When the MFR is 11 g / 10 min or less, stretching may be facilitated, thickness unevenness may be reduced, and the stretching temperature and heat setting temperature may be easily increased, resulting in a lower thermal shrinkage rate.
- the lower limit of the ratio of components having a molecular weight of 10,000 or less in the entire polypropylene resin is preferably 2% by mass, more preferably 2 0.5% by mass, more preferably 3% by mass, particularly preferably 3.3% by mass, and most preferably 3.5% by mass.
- the ratio of the component having a molecular weight of 10,000 or less is 2% by mass or more, the effects of the present application such as a low heat shrinkage rate at a high temperature, which is an effect of a low molecular weight product, may be more easily obtained, and stretching may be facilitated.
- the upper limit of the ratio of components having a molecular weight of 10,000 or less in the entire polypropylene resin in the GPC integration curve is preferably 20% by mass, more preferably 17% by mass, still more preferably 15% by mass, and particularly preferably 14%. % By mass, most preferably 13% by mass.
- the ratio of the component having a molecular weight of 10,000 or less is 20% by mass or less, stretching may be facilitated, thickness unevenness may be reduced, and the stretching temperature and heat setting temperature may be easily increased, resulting in a low thermal shrinkage rate.
- Molecules with a molecular weight of 10,000 or less do not contribute to the entanglement between the molecular chains, and have the effect of loosening the entanglement between the molecules like a plasticizer.
- the inclusion of a specific amount of a component with a molecular weight of 10,000 or less facilitates the entanglement of molecules during stretching, and enables stretching with low stretching stress, resulting in low residual stress and low shrinkage at high temperatures. It
- the lower limit of the ratio of components having a molecular weight of 100,000 or less in the entire polypropylene resin in the GPC integration curve is preferably 35% by mass, more preferably 38% by mass, still more preferably 40% by mass, and particularly preferably 41%. % By mass, most preferably 42% by mass.
- the ratio of the component having a molecular weight of 100,000 or less is 35% by mass or more, the effect of a low molecular weight product is likely to be exhibited, and a low thermal shrinkage rate at a high temperature may be easily obtained, or stretching may be facilitated.
- the upper limit of the ratio of components having a molecular weight of 100,000 or less in the entire polypropylene resin in the GPC integration curve is preferably 65% by mass, more preferably 60% by mass, still more preferably 58% by mass, and particularly preferably 56% by mass. % By mass, most preferably 55% by mass.
- the ratio of the component having a molecular weight of 100,000 or less is 65% by mass or less, stretching is facilitated, thickness unevenness is reduced, stretching temperature and heat setting temperature are easily increased, and heat shrinkage rate is easily reduced. May be.
- a high molecular weight component and a low molecular weight component that are preferably used to obtain a polypropylene resin having such characteristics of molecular weight distribution will be described below.
- the lower limit of MFR (230 ° C., 2.16 kgf) of the high molecular weight component is preferably 0.0001 g / 10 minutes, more preferably 0.0005 g / 10 minutes, and further preferably 0.001 g / 10 minutes. Particularly preferred is 0.005 g / 10 min.
- MFR of the high molecular weight component is 0.0001 g / 10 min or more, the production of the resin may actually be easy, or the fish eyes of the film may be reduced.
- the MFR at 230 ° C. and 2.16 kgf, which is a high molecular weight component, is too small and may be difficult to measure in practice.
- the preferred lower limit is 0.1 g / 10 minutes, more preferably 0.5 g / 10 minutes, and even more preferably 1 g / 10. Minute, particularly preferably 5 g / 10 minutes.
- the upper limit of MFR (230 ° C., 2.16 kgf) of the high molecular weight component is preferably 0.5 g / 10 minutes, more preferably 0.35 g / 10 minutes, and further preferably 0.3 g / 10 minutes. Particularly preferably, it is 0.2 g / 10 minutes, and most preferably 0.1 g / 10 minutes.
- the MFR of the high molecular weight component is 0.5 g / 10 min or less, many high molecular weight components are not necessary to maintain the MFR of the entire polypropylene resin, and the effect of the low molecular weight component is easily manifested and is low at high temperatures. A thermal contraction rate or the like may be more easily obtained.
- the lower limit of M w of the high molecular weight component is preferably 500,000, more preferably 600,000, still more preferably 700,000, particularly preferably 800,000, and most preferably 1000000. Not require the amount of number of polymeric component to M w of the high molecular weight component to maintain MFR of the whole polypropylene resin If it is 500,000 or more, the effect of the low molecular weight component is likely to express, low thermal shrinkage at high temperatures The rate may be more easily obtained.
- the upper limit of M w of the high molecular weight component is preferably 10000000, more preferably 8000000, still more preferably 6000000, and particularly preferably 5000000. If the Mw of the high molecular weight component is 10000000 or less, the production of the resin may actually be easy, or the fish eyes of the film may be reduced.
- the lower limit of the amount of the high molecular weight component is preferably 2% by mass, more preferably 3% by mass, still more preferably 4% by mass, and particularly preferably 5% by mass.
- the upper limit of the amount of the high molecular weight component is preferably 30% by mass, more preferably 25% by mass, still more preferably 22% by mass, and particularly preferably 20% by mass.
- the amount of the high molecular weight component is 30% by mass or less, the effect of the low molecular weight component is likely to be exhibited, and a low heat shrinkage rate at a high temperature may be easily obtained.
- the ratio of the high molecular weight component to the entire polypropylene resin constituting the film is determined by performing peak separation from the molecular weight distribution curve measured using GPC, and the same applies to other components such as a low molecular weight component described later.
- a polypropylene resin having a long chain branching or a crosslinked structure can be used in place of the linear polypropylene resin, which is known as a high melt tension polypropylene, and is made by Borealis Corporation.
- a high melt tension polypropylene which is known as a high melt tension polypropylene, and is made by Borealis Corporation.
- Borealis Corporation There are “WB130HMS”, “WB135HMS” and the like.
- the lower limit of the low molecular weight component MFR (230 ° C., 2.16 kgf) is preferably 70 g / 10 min, more preferably 80 g / 10 min, still more preferably 100 g / 10 min, and particularly preferably 150 g / min. 10 minutes, most preferably 200 g / 10 minutes.
- MFR of the low molecular weight component is 70 g / 10 min or more, the crystallinity is improved and a low thermal shrinkage rate at a high temperature may be easily obtained.
- the upper limit of the MFR of the low molecular weight component is preferably 2000 g / 10 minutes, more preferably 1800 g / 10 minutes, still more preferably 1600 g / 10 minutes, and most preferably 1500 g / 10 minutes.
- the MFR of the low molecular weight component is 2000 g / 10 min or less, it becomes easy to maintain the MFR in the entire polypropylene resin, and the film forming property may be excellent.
- the lower limit of M w of the low molecular weight component is preferably 50000, more preferably 53000, still more preferably 55000, particularly preferably 60000, and most preferably 70000.
- the upper limit of the M w of the low molecular weight component is preferably 170000, more preferably 165000, still more preferably 160000, particularly preferably 155000, and most preferably 150,000.
- the Mw of the low molecular weight component is 170000 or less, the crystallinity is improved, and a low heat shrinkage rate at a high temperature may be more easily obtained.
- the lower limit of the amount of the low molecular weight component is preferably 40% by mass, more preferably 50% by mass, still more preferably 55% by mass, and particularly preferably 60% by mass.
- the upper limit of the amount of the low molecular weight component is preferably 98% by mass, more preferably 97% by mass, still more preferably 96% by mass, and particularly preferably 95% by mass.
- the amount of the low molecular weight component is 98% by mass or less, it is not necessary to increase the molecular weight of the low molecular weight component in order to maintain the MFR of the entire polypropylene resin, and it becomes easier to obtain a low heat shrinkage rate at a high temperature. There is.
- the lower limit of the low molecular weight component MFR / high molecular weight component MFR ratio is preferably 500, more preferably 1000, still more preferably 2000, and particularly preferably 4000.
- the upper limit of the MFR ratio of the low molecular weight component / the MFR ratio of the high molecular weight component is preferably 1,000,000.
- the high molecular weight component and the low molecular weight component may be a mixture of two or more resins corresponding to each component, and the blending amount in that case is a total amount.
- a component having a molecular weight other than the low molecular weight component and high molecular weight component of the present invention may be added in order to adjust the MFR of the entire polypropylene resin.
- polypropylene hereinafter, referred to as a medium molecular weight component having a M w that is larger than the low molecular weight component and smaller than the high molecular weight component may be included.
- M w 5 million in less than a polypropylene resin to adjust and to stretchability easily loosened entanglement of molecular chains more preferably M w 3 10,000 or less polypropylene resin, particularly preferably M w 1 10,000 or less Polypropylene resin may be added.
- the lower limit of the ratio of the medium molecular weight component to the entire polypropylene resin constituting the film depends on the Mw of the medium molecular weight component used, but is preferably 5% by mass, more preferably 10% by mass, and still more preferably 13%. % By weight, particularly preferably 15% by weight, and most preferably 16% by weight. When the ratio of the medium molecular weight component is 5% by mass or more, fish eyes may be reduced or stretching may be facilitated.
- the upper limit of the ratio of the medium molecular weight component to the entire polypropylene resin constituting the film is preferably 58% by mass, more preferably 56% by mass, still more preferably 54% by mass, and particularly preferably 52% by mass. Most preferably, it is 50 mass%.
- the lower limit of the ratio of polypropylene having an M w of less than 50,000 to the total polypropylene resin constituting the film is preferably 0% by mass, more preferably 1% by mass, still more preferably 2% by mass, and particularly preferably 3%.
- % By weight most preferably 4% by weight.
- the upper limit of the ratio of polypropylene having a Mw of less than 50,000 to the total polypropylene resin constituting the film is preferably 20% by mass, more preferably 18% by mass, still more preferably 17% by mass, and particularly preferably 16% by mass.
- % By mass most preferably 15% by mass.
- Polypropylene molecules having an Mw of less than 50,000 are difficult to form entanglement between molecular chains, and have an effect of loosening the entanglement between molecules like a plasticizer.
- a specific amount of polypropylene component of less than 50,000 Mw it is easy to entangle the molecules at the time of stretching, and it is possible to stretch at a low stretching stress. As a result, the residual stress is also low and the shrinkage rate at high temperature is reduced. It is thought that it is made low.
- the molecular weight of the high molecular weight component is increased. It is possible to adjust the molecular weight distribution by increasing the MFR and adjust the MFR so that it can be easily produced as a stretched film.
- the lower limit of the isotactic mesopentad fraction (hereinafter sometimes referred to as mmmm), which is an index of the stereoregularity of the polypropylene resin constituting the film, is preferably 96%, more preferably 96.5%, More preferably, it is 97%.
- mmmm is 96% or more, the crystallinity is improved, and the thermal shrinkage rate at a high temperature may be lower.
- the upper limit of mmmm is preferably 99.5%, more preferably 99.3%, and still more preferably 99%. When mmmm is 99.5% or less, production may be facilitated in practice.
- no heterogeneous bond such as a head-to-head bond of a propylene monomer is observed in the polypropylene resin constituting the film. Note that “no heterogeneous bond is observed” means that no peak is observed in 13 C-NMR.
- the lower limit of the isotactic meso average chain length (hereinafter referred to as meso average chain length) of the polypropylene resin constituting the film is preferably 100, more preferably 120, and still more preferably 130.
- meso average chain length is 100 or more, the crystallinity is improved, and the thermal shrinkage rate at high temperature may be reduced.
- the upper limit of the meso average chain length of the polypropylene resin constituting the film is preferably 5000 from a practical aspect.
- the lower limit of the room temperature xylene soluble content of the polypropylene resin constituting the film is preferably 0.1% by mass from a practical aspect.
- the upper limit of the xylene-soluble content is preferably 7% by mass, more preferably 6% by mass, and further preferably 5% by mass.
- the xylene-soluble content of the propylene resin is 7% by mass or less, the crystallinity is improved, and the thermal shrinkage rate at a high temperature may be reduced.
- the polypropylene resin constituting the film is most preferably a propylene homopolymer (complete homopolypropylene) obtained only from propylene monomer, but may be a copolymer of a propylene monomer and a small amount of monomer other than propylene monomer.
- a propylene homopolymer complete homopolypropylene obtained only from propylene monomer
- ethylene, butene, hexene, octene and the like can be used.
- the upper limit of the proportion of monomers other than propylene monomer is preferably 0.1 mol%, more preferably 0.05 mol%, and still more preferably 0.01 mol%.
- the proportion of the monomer other than the propylene monomer is 0.1 mol% or less, the crystallinity may be improved and the thermal shrinkage rate at high temperature may be reduced.
- the polypropylene resin is obtained by polymerizing propylene as a raw material using a known catalyst such as a Ziegler-Natta catalyst or a metallocene catalyst. Among these, it is preferable to use a catalyst such as a Ziegler-Natta catalyst that is unlikely to contain heterogeneous bonds and can be polymerized with high stereoregularity.
- a known polymerization method can be used, but a method of polymerizing in an inert solvent such as hexane, heptane, toluene, xylene, a method of polymerizing in liquid propylene or ethylene, or a gas.
- Examples thereof include a method in which a catalyst is added to propylene and ethylene and polymerization is performed in a gas phase state, or a method in which these are combined for polymerization.
- the method for realizing the polypropylene having the molecular weight distribution of the present invention is not particularly limited, but it is necessary to substantially include a high molecular weight component and a low molecular weight component.
- the high molecular weight component and the low molecular weight component may be separately polymerized and then mixed, or may be produced in a series of plants using a multistage reactor.
- a method is preferred in which a plant having a multi-stage reactor is used, and a high molecular weight component is first polymerized and then a low molecular weight component is polymerized in the presence thereof.
- additives and other resins may be added to the polypropylene film molding resin composition of the present invention as necessary, but the mass of these may be 30% by mass or less.
- the additive include an antioxidant, an ultraviolet absorber, an antistatic agent, a lubricant, a nucleating agent, an adhesive, an antifogging agent, a flame retardant, an antiblocking agent, and an inorganic or organic filler.
- the other resin examples include polypropylene resins other than the polypropylene resin used in the present invention, random copolymers that are copolymers of propylene and ethylene and / or ⁇ -olefins having 4 or more carbon atoms, and various elastomers.
- the ⁇ -olefin having 4 or more carbon atoms include butene, hexene, octene and the like. These can be blended with polypropylene resin and a Henschel mixer, or master pellets prepared using a melt kneader in advance can be diluted with polypropylene to a predetermined concentration, or the total amount can be melt-kneaded in advance. Also good.
- the lower limit of the plane orientation coefficient of the polypropylene film of the present invention is preferably 0.0125, more preferably 0.0126, still more preferably 0.0127, and particularly preferably 0.0128.
- the upper limit of the plane orientation coefficient of the polypropylene film of the present invention is preferably 0.0155 as a realistic value, more preferably 0.0150, still more preferably 0.0148, and particularly preferably 0.0145. is there.
- the plane orientation coefficient can be adjusted by adjusting the draw ratio in the MD direction and the TD direction. When the plane orientation coefficient of the film is 0.0125 or more and 0.0155 or less, the thickness unevenness of the film is good.
- the lower limit of the refractive index (Nx) in the MD direction of the polypropylene film of the present invention is preferably 1.502, more preferably 1.503, and still more preferably 1.504.
- the upper limit of Nx is preferably 1.520, more preferably 1.517, and even more preferably 1.515.
- the lower limit of the refractive index (Ny) in the TD direction of the polypropylene film of the present invention is preferably 1.523, more preferably 1.525.
- the upper limit of Ny is preferably 1.535, more preferably 1.532.
- the lower limit of the refractive index (Nz) in the thickness direction of the polypropylene film of the present invention is preferably 1.480, more preferably 1.490, and still more preferably 1.501.
- the upper limit of Nz is preferably 1.510, more preferably 1.507, and even more preferably 1.505.
- the polypropylene film of the present invention has the following highly crystalline characteristics.
- the lower limit of the crystallinity of the polypropylene film of the present invention is preferably 55%, more preferably 56%, still more preferably 57%, particularly preferably 58%, most preferably 59%. . If the degree of crystallinity of the film is less than 55%, the thermal shrinkage at high temperatures may increase.
- the upper limit of the crystallinity of the polypropylene film of the present invention is preferably 85%, more preferably 80%, still more preferably 79%, particularly preferably 78%, and most preferably 77%. . When the crystallinity of the film exceeds 85%, realistic production may be difficult.
- the crystallinity of the film can be adjusted by techniques such as reducing or eliminating copolymerization monomers, increasing the amount of low molecular weight components, and setting the stretching temperature and heat setting temperature to a high temperature.
- the lower limit of the melting peak temperature of the polypropylene film of the present invention is preferably 168 ° C, more preferably 169 ° C. When the melting peak temperature of the film is 168 ° C. or higher, the thermal shrinkage rate at a high temperature may be small.
- the upper limit of the melting peak temperature of the polypropylene film of the present invention is preferably 180 ° C, more preferably 177 ° C, and further preferably 175 ° C. When the melting peak temperature of the film is 180 ° C. or lower, production may be facilitated in practice.
- the melting peak temperature can be adjusted by techniques such as reducing or eliminating the copolymerization monomer, increasing the low molecular weight component, and setting the stretching temperature and heat setting temperature to a high temperature.
- the conventional polypropylene film has a melting peak temperature around 170 ° C., for example, when measured with a differential scanning calorimeter (hereinafter also referred to as DSC), the peak rises from around 140 ° C. ( Although the heat resistance at 140 ° C. could be expected, the heat shrinkage rate increased rapidly at 150 ° C.
- the polypropylene film of the present invention does not have a peak at 150 ° C., and the polypropylene film of the present invention is considered to have low heat shrinkage even at 150 ° C.
- the polypropylene film of the present invention can maintain various physical properties even when exposed to an environment of 150 ° C. or higher, and can be used in a high-temperature environment that has not been considered with conventional polypropylene films.
- the melting start can be obtained from the DSC chart.
- the lower limit of crystallinity at 150 ° C. is preferably 48%, more preferably 49%, still more preferably 50%, and particularly preferably 51%. When the degree of crystallinity at 150 ° C. is 48% or more, the thermal shrinkage rate at high temperatures may be smaller.
- the upper limit of the degree of crystallinity at 150 ° C. is preferably 85%, more preferably 80%, still more preferably 79%, and particularly preferably 78% from a practical aspect.
- the degree of crystallinity at 150 ° C. can be kept within the range by techniques such as reducing or eliminating the copolymerization monomer, increasing the low molecular weight component, and setting the stretching temperature and heat setting temperature to a high temperature.
- the melting peak temperature (Tmp), the crystallinity of the film, and the crystallinity at 150 ° C. can be determined using a differential scanning calorimeter (DSC).
- DSC differential scanning calorimeter
- the melting endothermic peak temperature obtained when the temperature was raised from room temperature to 230 ° C. at a rate of 20 ° C./min was defined as Tmp.
- the heat of fusion is obtained from the endothermic peak area, and the degree of crystallinity can be obtained by dividing the heat of fusion by 209 J / g which is the heat of fusion of the complete polypropylene crystal. Further, among the endothermic peak areas, the heat of fusion is obtained from the endothermic peak area of 150 ° C.
- the lower limit of the thickness unevenness of the polypropylene film of the present invention is preferably 0%, more preferably 0.1%, still more preferably 0.5%, and particularly preferably 1%.
- the upper limit of the thickness unevenness of the polypropylene film of the present invention is preferably 20%, more preferably 17%, still more preferably 15%, particularly preferably 12%, and most preferably 10%.
- the thickness unevenness of the film is 0% or more and 20% or less, defects are unlikely to occur during post-processing such as coating and printing, and it is easy to use in applications that require precision.
- the lower limit of the density of the polypropylene film of the present invention is preferably 0.910 g / cm 3 , more preferably 0.911 g / cm 3 , still more preferably 0.912 g / cm 3 , and particularly preferably 0.8. 913 g / cm 3 .
- the upper limit of the density of the polypropylene film of the present invention is preferably 0.925 g / cm 3, more preferably 0.922 g / cm 3, more preferably from 0.920 g / cm 3, particularly preferably 0. 918 g / cm 3 .
- the density of the film can be increased by increasing the draw ratio and temperature, increasing the heat setting temperature, and further performing offline annealing.
- the polypropylene film of the present invention may be a uniaxially stretched film in the longitudinal direction (MD direction) or the transverse direction (TD direction), but is preferably a biaxially stretched film.
- biaxial stretching sequential biaxial stretching or simultaneous biaxial stretching may be used.
- a method for producing a film of sequential biaxial stretching of longitudinal stretching and transverse stretching which is the most preferred example, will be described, but the method for producing a polypropylene film is not limited thereto.
- a polypropylene resin is heated and melted with a single or twin screw extruder and extruded onto a chill roll to obtain an unstretched sheet.
- the melt extrusion conditions are such that the resin temperature is 200 to 280 ° C.
- the sheet is extruded from a T-die and cooled and solidified with a cooling roll having a temperature of 10 to 100 ° C.
- the film is stretched 3 to 8 times in the length direction (MD direction) with a stretching roll at 120 to 160 ° C., and subsequently 155 ° C. to 175 ° C., preferably 157 ° C. to 170 ° C. in the width direction (TD direction). Stretch 4 to 15 times at temperature. Further, heat treatment (heat setting) is performed while relaxing (relaxing) 1 to 15% at an ambient temperature of 165 to 175 ° C., preferably 166 to 173 ° C.
- a roll film can be obtained by subjecting the polypropylene film thus obtained to corona discharge treatment on at least one side as necessary, and then winding it with a winder.
- the lower limit of the draw ratio in the MD direction is preferably 3 times, more preferably 3.5 times. If the draw ratio in the MD direction is less than 3 times, thickness unevenness may occur.
- the upper limit of the draw ratio in the MD direction is preferably 8 times, more preferably 7 times. If the stretching ratio in the MD direction exceeds 8 times, it may be difficult to continue stretching in the TD direction.
- the lower limit of the temperature during stretching in the MD direction (hereinafter referred to as stretching temperature) is preferably 120 ° C, more preferably 125 ° C, and further preferably 130 ° C.
- the upper limit of the stretching temperature in the MD direction is preferably 160 ° C, more preferably 155 ° C, and further preferably 150 ° C.
- a higher stretching temperature in the MD direction is preferable for lowering the thermal shrinkage, but may adhere to the roll and cannot be stretched.
- the preheating temperature (hereinafter referred to as the preheating temperature) is preferably set 10 to 15 ° C. higher than the stretching temperature in the TD direction.
- the lower limit of the draw ratio in the TD direction is preferably 4 times, more preferably 5 times, and even more preferably 6 times. If the draw ratio in the TD direction is less than 4 times, thickness unevenness may occur.
- the upper limit of the draw ratio in the TD direction is preferably 15 times, more preferably 14 times, and still more preferably 13 times. When the draw ratio in the TD direction exceeds 15 times, the thermal shrinkage rate may be increased or the film may be broken during stretching.
- the stretching in the TD direction can be performed at a higher temperature than the conventional polypropylene film, and the lower limit of the stretching temperature in the TD direction is preferably 155 ° C, more preferably 157 ° C. If the stretching temperature in the TD direction is less than 155 ° C., the film may be broken without being sufficiently softened or the heat shrinkage rate may be increased.
- the upper limit of the stretching temperature in the TD direction is preferably 175 ° C, more preferably 170 ° C. In order to lower the heat shrinkage rate, a higher temperature is preferable, but when the stretching temperature in the TD direction exceeds 175 ° C., low molecular components may melt and recrystallize, resulting in surface roughness and whitening of the film. .
- the stretched film is preferably heat-set by heat treatment.
- the heat setting can be performed at a temperature higher than that of a conventional polypropylene film, and the lower limit of the heat treatment temperature for performing the heat setting (hereinafter referred to as the heat setting temperature) is preferably 165 ° C., more preferably 166 ° C. .
- the heat setting temperature is lower than 165 ° C.
- the upper limit of the heat setting temperature is preferably 175 ° C, more preferably 173 ° C.
- the heat setting temperature exceeds 175 ° C., low molecular weight components may melt and recrystallize, resulting in surface roughness and whitening of the film.
- the lower limit of the relaxation rate is preferably 1%, more preferably 2%. If the relaxation rate is less than 1%, the thermal shrinkage rate may increase.
- the upper limit of the relaxation rate is preferably 15%, more preferably 10%. If the relaxation rate exceeds 15%, the thickness unevenness may increase.
- the film produced in the above process can be once wound up into a roll and then annealed offline.
- the lower limit of the annealing temperature (hereinafter referred to as offline annealing temperature) is preferably 160 ° C., more preferably 162 ° C., and further preferably 163 ° C. If the offline annealing temperature is lower than 160 ° C., the effect of annealing may not be obtained.
- the upper limit of the offline annealing temperature is preferably 175 ° C., more preferably 174 ° C., and further preferably 173 ° C. When the offline annealing temperature exceeds 175 ° C., the transparency may be lowered or the thickness unevenness may be increased.
- the lower limit of the time for annealing offline (hereinafter referred to as offline annealing time) is preferably 0.1 minutes, more preferably 0.5 minutes, and even more preferably 1 minute. If the offline annealing time is less than 0.1 minute, the effect of annealing may not be obtained.
- the upper limit of the offline annealing time is preferably 30 minutes, more preferably 25 minutes, and further preferably 20 minutes. If the offline annealing time exceeds 30 minutes, the productivity may decrease.
- the thickness of the film is set according to each application, but the lower limit of the thickness of the film is preferably 2 ⁇ m, more preferably 3 ⁇ m, and further preferably 4 ⁇ m.
- the upper limit of the thickness of the film is preferably 300 ⁇ m, more preferably 250 ⁇ m, still more preferably 200 ⁇ m, particularly preferably 150 ⁇ m, and most preferably 100 ⁇ m.
- the polypropylene film thus obtained is usually formed as a roll having a width of 2000 to 12000 mm and a length of 1000 to 50000 m, and is wound into a roll. Furthermore, it is slit according to each application, and is provided as a slit roll having a width of 300 to 2000 mm and a length of about 500 to 5000 m.
- the polypropylene film of the present invention has excellent characteristics such as those described above which are not present in the prior art.
- the polypropylene film of the present invention When used as an in-mold label film, it has high heat resistance, so that the film shrinkage due to heat during in-mold processing is not observed, the appearance is good, and the curl is small.
- the rigidity since the rigidity is high, the handling property at the time of in-mold processing is improved.
- the measuring method of the physical property in an Example is as follows.
- M n ⁇ (N i ⁇ M i ) / ⁇ N i
- Mass average molecular weight: M w ⁇ (N i ⁇ M i 2 ) / ⁇ (N i ⁇ M i )
- M p The molecular weight at the peak position of the GPC curve was defined as M p .
- the baseline should be set in a range up to the lowest position on the high molecular weight side of the elution peak closest to the elution peak of the standard substance.
- the ratio of the component used as the molecular weight of 10,000 or less in the whole polypropylene resin which comprises a film, and the ratio of the component used as a molecular weight of 100,000 or less were calculated
- mmmm is in accordance with the method described in Zambelli et al., Macromolecules, Vol. 6, 925 (1973). C. It was calculated according to the method described in Randall, “Polymer Sequence Distribution”, Chapter 2 (1977) (Academic Press, New York). NMR measurement was carried out at 110 ° C. using AVANCE 500 manufactured by BRUKER, dissolving 200 mg of a sample in an 8: 2 mixture of o-dichlorobenzene and heavy benzene at 135 ° C.
- Tmp Melting peak temperature
- Crystallinity Degree of crystallinity is obtained by obtaining the heat of fusion ( ⁇ Hm, J / g) from the endothermic peak area in the DSC melting profile and dividing the value of ⁇ Hm by 209 J / g which is the heat of fusion of the complete polypropylene crystal. Asked. Further, by obtaining the heat of fusion ( ⁇ Hm ′, J / g) from the endothermic peak area of 150 ° C. or higher in the DSC melting profile, and dividing the value of ⁇ Hm ′ by 209 J / g, which is the heat of fusion of polypropylene complete crystal, The crystallinity in all samples at 150 ° C. was determined.
- Refractive index It measured using the Atago Co., Ltd. Abbe refractometer.
- the refractive indexes along the MD and TD directions were Nx and Ny, respectively, and the refractive index in the thickness direction was Nz.
- Thickness spot A square sample having a length of 1 m was cut out from the wound film roll, and was divided into 10 equal parts in the MD direction and the TD direction to prepare 100 measurement samples. The thickness was measured with a contact-type film thickness meter at the approximate center of the measurement sample. The average value of the 100 points of data obtained was obtained, the difference between the minimum value and the maximum value (absolute value) was obtained, and the value obtained by dividing the absolute value of the difference between the minimum value and the maximum value by the average value was obtained. It was.
- PP-1 a propylene homopolymer
- the thickness of the film thus obtained was 20 ⁇ m, the properties and the like of the polypropylene resin are shown in Tables 1 and 2, the film forming conditions are shown in Table 3, and the physical properties of the obtained film are shown in Table 5. As shown in Table 5, a film having a low thermal shrinkage and a high Young's modulus was obtained.
- the DSC chart of the stretched propylene film of Example 1 is shown in FIG.
- An adhesive (TM-386 manufactured by Toyo Morton Co., Ltd.) was applied to one side of the polypropylene film of Example 1, and a polypropylene film was further stacked thereon to produce a laminate film of polypropylene film / adhesive / polypropylene film.
- the laminating conditions are a gravure laminator, an unwinding tension of 50 N / m, a winding tension of 55 N / m, an adhesive application amount of 0.6 g / m 2 , a drying temperature of 90 ° C., and a drying time of 10 seconds.
- This laminated product was heat-aged at an ambient temperature of 40 ° C.
- the strips were seasoned at 23 ° C. in a 65% Rh environment, and the curl amount was measured on a horizontal table.
- the curl amount the amount of lift from the horizontal platform when the film with the adhesive applied first is up is read in millimeters, the average value at the four corners of the label is taken as the curl amount, and the curl amount of the label is shown in Table 5. It was shown to.
- Example 2 10 parts by weight of low molecular weight polypropylene having a molecular weight of 10,000 (high wax “NP105” manufactured by Mitsui Chemicals, Inc.) is added to 90 parts by weight of “PP-1” to make a total of 100 parts by weight, and a 30 mm twin screw extruder And kneaded to obtain pellets of the mixture “PP-2”.
- a film was obtained from the pellets in the same manner as in Example 1. Properties and the like of the polypropylene resin are shown in Tables 1 and 2, film forming conditions are shown in Table 3, and physical properties of the obtained film and label curl amount are shown in Table 5.
- Example 4 A film was obtained in the same manner as in Example 1 except that “PP-1” was used, the preheating temperature was 173 ° C., the stretching temperature in the TD direction and the heat setting temperature were 167 ° C. Properties and the like of the polypropylene resin are shown in Tables 1 and 2, film forming conditions are shown in Table 3, and physical properties of the obtained film and label curl amount are shown in Table 5.
- Example 5 A film was obtained in the same manner as in Example 2 except that the film was stretched 5.5 times in the length direction and 12 times in the transverse direction. Properties and the like of the polypropylene resin are shown in Tables 1 and 2, film forming conditions are shown in Table 3, and physical properties of the obtained film and label curl amount are shown in Table 5.
- Example 6 The film produced in Example 1 was subjected to heat treatment (offline annealing) at 170 ° C. for 5 minutes in a tenter hot air oven. Properties and the like of the polypropylene resin are shown in Tables 1 and 2, film forming conditions are shown in Table 3, and physical properties of the obtained film and label curl amount are shown in Table 5.
- Comparative Example 2 A film was produced in the same manner as in Comparative Example 1, except that the preheating temperature was 171 ° C, the stretching temperature in the TD direction was 160 ° C, and the heat setting temperature was 165 ° C. Properties and the like of the polypropylene resin are shown in Tables 1 and 2, film forming conditions are shown in Table 4, and physical properties of the obtained film and label curl amount are shown in Table 6.
- the polypropylene film of the present invention has high heat resistance and high rigidity, so it is not only suitable for in-mold labels with small curl, but it also eliminates the need to use a thick film to prevent curling, or uses an intermediate product. There is no need to do this, and you can expect advantages such as lowering the cost of labels.
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Abstract
Description
また、高立体規則性を持ち、分子量分布の広いポリプロピレンを用いて延伸フィルムとすることにより電気絶縁性、機械特性等に優れたキャパシターフィルムとして好適に用いることができるという技術が知られていた(例えば特許文献2等参照)。
従来、インモールドラベル基材としては、紙、合成紙、プラスチックフィルム等が用いられている(例えば特許文献6、特許文献7、特許文献8等参照)。
プラスチックフィルムの場合は、印刷やラミネート加工、あるいは、接着加工などを施すため、同じプラスチックフィルム同士を貼り合わたり、ラベル仕様に応じた様々な素材のプラスチックフィルムを貼り合わせてインモールドラベルを構成することが広く実施されている。このプラスチックフィルムとしては、容器との接着性の観点からポリプロピレンフィルムが多く使用されている。
カール抑制のためには、印刷やラミネート加工では、加工条件を頻度高く調整したり、ポリプロピレンフィルムの厚みを厚くしたり、ポリプロピレンフィルムの幅方向中央部を選りすぐってインモールドラベル基材として使用するなどの方法を取らざるを得ないため、ラベルとしてはコスト高な構成を強いられてきた。
本発明のポリプロピレンフィルムのMD方向およびTD方向の150℃における熱収縮率の下限は好ましくは0.5%であり、より好ましくは1%であり、さらに好ましくは1.5%であり、特に好ましくは2%であり、最も好ましくは2.5%である。上記熱収縮率が0.5%以上であると、コスト面などで現実的な製造が容易となったり、厚み斑が小さくなったりすることがある。なお、MD方向とは、フィルムの流れ方向であり、TD方向とは、フィルムの流れ方向に垂直な方向である。
MD方向およびTD方向の150℃における熱収縮率の上限は9%であり、好ましくは8%であり、より好ましくは7%であり、さらに好ましくは6%であり、最も好ましくは5%である。上記熱収縮率が9%以下であると、耐熱性の優れたフィルムを得ることができ、150℃程度の高温に晒される可能性のある用途での使用がより容易になる。なお、150℃における熱収縮率は2.5%程度以上の場合は、例えば分子量が10万程度の低分子量ポリプロピレン(以下、低分子量成分という)を多くする、延伸条件、熱固定条件を調整することで可能であるが、2.5%程度よりも低い場合はオフラインでアニール処理をすることが好ましい。なお、従来のポリプロピレンフィルムでは、MD方向およびTD方向の150℃における熱収縮率は15%を超えており、120℃における熱収縮率は3%程度である。
なお、延伸倍率を高くすることでヤング率を大きくすることができ、MD-TD延伸の場合はMD方向の延伸倍率を低めに設定し、TD方向の延伸倍率を高くすることでTD方向のヤング率を大きくすることができる。
高分子の分子量を表すパラメータとしては、数平均分子量(Mn)、質量平均分子量(Mw)、Z平均分子量(Mz)、Z+1平均分子量(Mz+1)、ピーク分子量(Mp)などが挙げられ、これらは、分子量(Mi)の分子数(Ni)により以下のように定義される。
数平均分子量:Mn=Σ(Ni・Mi)/ΣNi
質量平均分子量:Mw=Σ(Ni・Mi 2)/Σ(Ni・Mi)
Z平均分子量:Mz=Σ(Ni・Mi 3)/Σ(Ni・Mi 2)
Z+1平均分子量:Mz+1=Σ(Ni・Mi 4)/Σ(Ni・Mi 3)
ピーク分子量:Mp(ゲル・パーミエーション・クロマトグラフィー(GPC)曲線のピーク位置の分子量)
そして、分子量分布を表すパラメータとしては、これらの平均分子量の比が一般的に用いられ、例えば、Mw/Mn、Mz+1/Mnなどが挙げられるが、本発明に用いられるポリプロピレン樹脂の特徴的な分子量分布を表すにはMz+1/Mnが好適である。このような分子量や分子量分布の測定方法としては、GPCが一般的に用いられる。
Mw/Mnの上限は好ましくは30であり、より好ましくは25であり、さらに好ましくは20であり、特に好ましくは15であり、最も好ましくは13である。
GPC積算カーブでのポリプロピレン樹脂全体における分子量1万以下の成分の比率の上限は好ましくは20質量%であり、より好ましくは17質量%であり、さらに好ましくは15質量%であり、特に好ましくは14質量%であり、最も好ましくは13質量%である。分子量1万以下の成分の比率が20質量%以下であると延伸が容易となったり、厚み斑が小さくなったり、延伸温度や熱固定温度が上げられやすく熱収縮率が低くなることがある。
分子量1万以下の分子は分子鎖同士の絡み合いには寄与せず、可塑剤的に分子同士の絡み合いをほぐす効果がある。分子量1万以下の成分の量が特定量含まれることで延伸時の分子の絡み合いがほどけやすく、低い延伸応力での延伸が可能となり、その結果として残留応力も低く高温での収縮率を低くできているものと考えられる。
GPC積算カーブでのポリプロピレン樹脂全体における分子量10万以下の成分の比率の上限は好ましくは65質量%であり、より好ましくは60質量%であり、さらに好ましくは58質量%であり、特に好ましくは56質量%であり、最も好ましくは55質量%である。分子量10万以下の成分の比率が65質量%以下であると延伸が容易となったり、厚み斑が小さくなったり、延伸温度や熱固定温度が上げられやすく熱収縮率を低くすることが容易となることがある。
高分子量成分のMFR(230℃、2.16kgf)の下限は好ましくは0.0001g/10分であり、より好ましくは0.0005g/10分であり、さらに好ましくは0.001g/10分であり、特に好ましくは0.005g/10分である。高分子量成分のMFRが0.0001g/10分以上であると現実的に樹脂の製造が容易であったり、フィルムのフィッシュアイを低減できることがある。
なお、高分子量成分の230℃、2.16kgfでのMFRは小さすぎて現実的には測定が困難となる場合がある。2.16kgfの10倍の荷重(21.6kgf)でのMFRであらわすと、好ましい下限は0.1g/10分であり、より好ましくは0.5g/10分であり、さらに好ましくは1g/10分であり、特に好ましくは5g/10分である。
高分子量成分のMFR(230℃、2.16kgf)の上限は好ましくは0.5g/10分であり、より好ましくは0.35g/10分であり、さらに好ましくは0.3g/10分であり、特に好ましくは0.2g/10分であり、最も好ましくは0.1g/10分である。高分子量成分のMFRが0.5g/10分以下であるとポリプロピレン樹脂全体のMFRを維持するために多くの高分子量成分が必要でなく、低分子量成分の効果が発現しやすく、高温での低い熱収縮率などがより得られやすくなることがある。
高分子量成分のMwの上限は好ましくは10000000であり、より好ましくは8000000であり、さらに好ましくは6000000であり、特に好ましくは5000000である。高分子量成分のMwが10000000以下であると現実的に樹脂の製造が容易であったり、フィルムのフィッシュアイを低減できることがある。
高分子量成分の量の上限は好ましくは30質量%であり、より好ましくは25質量%であり、さらに好ましくは22質量%であり、特に好ましくは20質量%である。高分子量成分の量が30質量%以下であると低分子量成分の効果が発現しやすく、高温での低い熱収縮率などがより得られやすくなることがある。なお、フィルムを構成するポリプロピレン樹脂全体に対する高分子量成分の比率は、GPCを用いて測定した分子量分布曲線からピーク分離を行って求めるものとし、後述の低分子量成分など他の成分でも同様である。
低分子量成分のMFR(230℃、2.16kgf)の下限は好ましくは70g/10分であり、より好ましくは80g/10分であり、さらに好ましくは100g/10分であり、特に好ましくは150g/10分であり、最も好ましくは200g/10分である。低分子量成分のMFRが70g/10分以上であると結晶性が良くなり、高温での低い熱収縮率などがより得られやすくなることがある。
低分子量成分のMFRの上限は好ましくは2000g/10分であり、より好ましくは1800g/10分であり、さらに好ましくは1600g/10分であり、最も好ましくは1500g/10分である。低分子量成分のMFRが2000g/10分以下であるとポリプロピレン樹脂全体でのMFRを維持しやすくなり、製膜性に優れることがある。
低分子量成分のMwの上限は好ましくは170000であり、より好ましくは165000であり、さらに好ましくは160000であり、特に好ましくは155000であり、最も好ましくは150000である。低分子量成分のMwが170000以下であると結晶性が良くなり、高温での低い熱収縮率がより得られやすくなることがある。
低分子量成分の量の上限は好ましくは98質量%であり、より好ましくは97質量%であり、さらに好ましくは96質量%であり、特に好ましくは95質量%である。低分子量成分の量が98質量%以下であるとポリプロピレン樹脂全体でのMFRを維持するために低分子量成分の分子量を上げる必要がなく、高温での低い熱収縮率などがより得られやすくなることがある。
また、上記の高分子量成分や低分子量成分以外に、ポリプロピレン樹脂全体でのMFRを調整するために本発明の低分子量成分や高分子量成分以外の分子量を有する成分を添加しても良い。例えば、低分子量成分よりも大きく高分子量成分よりも小さいMwであるポリプロピレン(以下、中分子量成分という)を含んでいてもよい。さらに、分子鎖の絡み合いをほぐしやすくして延伸性などを調節するために好ましくはMw5万未満のポリプロピレン樹脂、さらに好ましくはMw3万以下のポリプロピレン樹脂、特に好ましくはMw1万以下のポリプロピレン樹脂を添加しても良い。
フィルムを構成するポリプロピレン樹脂全体に対する中分子量成分の比率の下限は、用いる中分子量成分のMwにもよるが、好ましくは5質量%であり、より好ましくは10質量%であり、さらに好ましくは13質量%であり、特に好ましくは15質量%であり、最も好ましくは16質量%である。中分子量成分の比率が5質量%以上であるとフィッシュアイが低減できたり、延伸が容易となることがある。
フィルムを構成するポリプロピレン樹脂全体に対する中分子量成分の比率の上限は好ましくは58質量%であり、より好ましくは56質量%であり、さらに好ましくは54質量%であり、特に好ましくは52質量%であり、最も好ましくは50質量%である。中分子量成分の比率が58質量%以下であると延伸が容易となったり、厚み斑が小さくなったり、延伸温度や熱固定温度が上げられやすく熱収縮率が低くなることがある。
フィルムを構成するポリプロピレン樹脂全体に対するMw5万未満のポリプロピレンの比率の下限は好ましくは0質量%であり、より好ましくは1質量%であり、さらに好ましくは2質量%であり、特に好ましくは3質量%であり、最も好ましくは4質量%である。Mw5万未満のポリプロピレンを添加することにより高温での低い熱収縮率など本発明の効果がより得られやすくなることがある。
フィルムを構成するポリプロピレン樹脂全体に対するMw5万未満のポリプロピレンの比率の上限は好ましくは20質量%であり、より好ましくは18質量%であり、さらに好ましくは17量%であり、特に好ましくは16質量%であり、最も好ましくは15質量%である。Mw5万未満のポリプロピレンの比率が20質量%以下であると延伸が容易となったり、厚み斑が小さくなることがある。
Mw5万未満のポリプロピレン分子は分子鎖同士の絡み合いが形成しにくく、可塑剤的に分子同士の絡み合いをほぐす効果がある。Mw5万未満のポリプロピレンの成分の量が特定量含まれることで延伸時に分子の絡み合いがほどけやすく、低い延伸応力での延伸が可能となり、その結果として残留応力も低く高温での収縮率を低くできているものと考えられる。
フィルムを構成するポリプロピレン樹脂の立体規則性の指標であるアイソタックメソペンタッド分率(以下、mmmmということがある)の下限は好ましくは96%であり、より好ましくは96.5%であり、さらに好ましくは97%である。mmmmが96%以上であると結晶性が向上し、高温での熱収縮率がより低くなることがある。
mmmmの上限は好ましくは99.5%であり、より好ましくは99.3%であり、さらに好ましくは99%である。mmmmが99.5%以下であると現実的に製造が容易となることがある。
ポリプロピレン樹脂は、チーグラー・ナッタ触媒やメタロセン触媒等の公知の触媒を用いて、原料となるプロピレンを重合させて得られる。中でも、チーグラー・ナッタ触媒のような、異種結合を含みにくく、かつ、立体規則性の高い重合が可能な触媒を用いることが好ましい。
プロピレンの重合方法としては、公知の重合方法を用いることができるが、ヘキサン、ヘプタン、トルエン、キシレン等の不活性溶剤中で重合する方法、液状のプロピレンやエチレン中で重合する方法、気体であるプロピレンやエチレン中に触媒を添加し、気相状態で重合する方法、または、これらを組み合わせて重合する方法等が挙げられる。
本発明の分子量分布を有するポリプロピレンを実現する方法は特に限定されるものではないが、実質的に高分子量成分、低分子量成分を含む必要がある。例えば、高分子量成分、低分子量成分を別々に重合した後に混合しても良く、多段階の反応器で一連のプラントで製造しても良い。特に、多段階の反応器を持つプラントを用い、高分子量成分を最初に重合した後にその存在下で低分子量成分を重合する方法が好ましい。
本発明のポリプロピレンフィルムは以下の様な高結晶性の特徴を有する。
本発明のポリプロピレンフィルムの結晶化度の下限は好ましくは55%であり、より好ましくは56%であり、さらに好ましくは57%であり、特に好ましくは58%であり、最も好ましくは59%である。フィルムの結晶化度が55%未満であると高温での熱収縮率が大きくなることがある。本発明のポリプロピレンフィルムの結晶化度の上限は好ましくは85%であり、より好ましくは80%であり、さらに好ましくは79%であり、特に好ましくは78%であり、最も好ましくは77%である。フィルムの結晶化度が85%を超えると現実的な製造が困難となることがある。フィルムの結晶化度の調整は、共重合モノマーを少なくする、またはなくす、低分子量成分を多くする、延伸温度、熱固定温度を高温に設定するなどの手法により行うことが出来る。
本発明のポリプロピレンフィルムは150℃以上の環境下にさらされても諸物性を維持することができ、従来のポリプロピレンフィルムでは考えられなかったような高温の環境下でも使用することができる。なお、融解開始はDSCチャートから求めることができる。
室温から20℃/分の割合で230℃まで昇温した際に得られる融解吸熱ピーク温度をTmpとした。そして、吸熱ピーク面積から融解熱を求め、その融解熱をポリプロピレン完全結晶の融解熱である209J/gで除することにより、結晶化度を求めることができる。また、上記吸熱ピーク面積のうち、150℃以上の吸熱ピーク面積から融解熱を求め、その融解熱をポリプロピレン完全結晶の融解熱である209J/gで除することにより、150℃での全試料中の結晶化度を求めることができる。なお、ポリプロピレン完全結晶の融解熱については、H.Bu,S.Z.D.Cheng,B.WunderlichらによるMakromoleculare Chemie, Rapid Communication,第9巻,75頁(1988)に記載されている値を用いており、後述の実施例においても同様の値を用いた。
本発明のポリプロピレンフィルムの密度の上限は好ましくは0.925g/cm3であり、より好ましくは0.922g/cm3であり、さらに好ましくは0.920g/cm3であり、特に好ましくは0.918g/cm3である。フィルムの密度が0.925g/cm3以下であると現実的に製造が容易となることがある。フィルムの密度は延伸倍率や温度を高くする、熱固定温度を高くする、さらにはオフラインアニールすることで高めることができる。
本発明のポリプロピレンフィルムとしては長手方向(MD方向)もしくは横方向(TD方向)の一軸延伸フィルムでも良いが、二軸延伸フィルムであることが好ましい。二軸延伸の場合は逐次二軸延伸であっても同時二軸延伸であっても良い。
延伸してポリプロピレンフィルムを製造することで、従来のポリプロピレンフィルムでは予想できなかった150℃でも熱収縮率が低いフィルムを得ることができる。
まず、ポリプロピレン樹脂を単軸または二軸の押出機で加熱溶融させ、チルロール上に押し出して未延伸シートを得る。溶融押出条件としては、樹脂温度として200~280℃となるようにして、Tダイよりシート状に押出し、10~100℃の温度の冷却ロールで冷却固化する。ついで、120~160℃の延伸ロールでフィルムを長さ方向(MD方向)に3~8倍に延伸し、引き続き幅方向(TD方向)に155℃~175℃、好ましくは157℃~170℃の温度で4~15倍に延伸する。
さらに、165~175℃、好ましくは166~173℃の雰囲気温度で1~15%の緩和(リラックス)させながら熱処理(熱固定)を施す。
こうして得られたポリプロピレンフィルムに、必要に応じて少なくとも片面にコロナ放電処理を施した後、ワインダーで巻取ることによりロールフィルムを得ることができる。
オフラインでアニールさせる温度(以下、オフラインアニール温度という)の下限は好ましくは160℃であり、より好ましくは162℃であり、さらに好ましくは163℃である。オフラインアニール温度が160℃未満であるとアニールの効果が得られないことがある。オフラインアニール温度度の上限は好ましくは175℃であり、より好ましくは174℃であり、さらに好ましくは173℃である。オフラインアニール温度が175℃を超えると透明性が低下したり、厚み斑が大きくなったりすることがある。
本発明のポリプロピレンフィルムをインモールドラベル用フィルムとして用いた場合には、耐熱性が高いため、インモールド加工時の熱によるフィルム収縮が見られず、外観が良好であり、カールも小さくなる。また、剛性が高いため、インモールド加工時のハンドリング性が改善される。
JIS K 7210に準拠し、温度230℃、荷重2.16kgfで測定した。
分子量および分子量分布は、ゲル・パーミエーション・クロマトグラフィー(GPC)を用いて単分散ポリスチレン基準により求めた。
GPC測定での使用カラム、溶媒は以下のとおりである。
溶媒:1,2,4-トリクロロベンゼン
カラム:TSKgel GMHHR-H(20)HT×3
流量:1.0ml/min
検出器:RI
測定温度:140℃
数平均分子量(Mn)、質量平均分子量(Mw)、Z平均分子量(Mz)、Z+1平均分子量(Mz+1)はそれぞれ、分子量校正曲線を介して得られたGPC曲線の各溶出位置の分子量(Mi)の分子数(Ni)により次式で定義される。
数平均分子量:Mn=Σ(Ni・Mi)/ΣNi
質量平均分子量:Mw=Σ(Ni・Mi 2)/Σ(Ni・Mi)
Z平均分子量:Mz=Σ(Ni・Mi 3)/Σ(Ni・Mi 2)
Z+1平均分子量:Mz+1=Σ(Ni・Mi 4)/Σ(Ni・Mi 3)
分子量分布:Mw/Mn、Mz+1/Mn
また、GPC曲線のピーク位置の分子量をMpとした。
ベースラインが明確でないときは、標準物質の溶出ピークに最も近い高分子量側の溶出ピークの高分子量側のすそ野の最も低い位置までの範囲でベースラインを設定することとする。
得られたGPC曲線から、分子量の異なる2つ以上の成分にピーク分離を行った。各成分の分子量分布はガウス関数を仮定し、それぞれのピーク幅がMw/Mn=4となるように設定した。得られた各成分のカーブから平均分子量をそれぞれ計算した。
また、フィルムを構成するポリプロピレン樹脂全体のGPC曲線から、フィルムを構成するポリプロピレン樹脂全体における分子量1万以下となる成分の比率及び分子量10万以下となる成分の比率を求めた。
mmmmおよびメソ平均連鎖長の測定は、13C-NMRを用いて行った。mmmmは、Zambelliら、Macromolecules,第6巻,925頁(1973)に記載の方法に従い、メソ平均連鎖長は、J.C.Randallによる、“Polymer Sequence Distribution”第2章(1977年)(Academic Press,New York)に記載の方法に従って算出した。
NMR測定は、BRUKER社製AVANCE500を用い、試料200mgをo-ジクロロベンゼンと重ベンゼンの8:2の混合液に135℃で溶解し、110℃で実施した。
フィルムの密度は、JIS K7112に従って密度勾配管法により測定した。
(株)島津製作所製DSC-60示差走査熱量計を用いて熱測定を行った。フィルムから約5mgを切り出してサンプルとし、そのサンプルを測定用のアルミパンに封入した。20℃/分の割合で室温から230℃まで昇温し、サンプルの融解ピーク温度をTmpとした。
DSC融解プロファイルにおける吸熱ピーク面積から融解熱(ΔHm、J/g)を求め、そのΔHmの値をポリプロピレン完全結晶の融解熱である209J/gで除することにより、結晶化度を求めた。
また、DSC融解プロファイルにおける150℃以上の吸熱ピーク面積から融解熱(ΔHm’、J/g)を求め、そのΔHm’の値をポリプロピレン完全結晶の融解熱である209J/gで除することにより、150℃での全試料中の結晶化度を求めた。
ポリプロピレン試料1gを沸騰キシレン200mlに溶解して放冷後、20℃の恒温水槽で1時間再結晶化させ、ろ過液に溶解している質量の、元の試料量に対する割合をCXS(質量%)とした。
JIS Z 1712に準拠して測定した。すなわち、ポリプロピレンフィルムを20mm巾で200mmの長さでMD、TD方向にそれぞれカットし、熱風オーブン中に吊るして5分間加熱した。加熱後の長さを測定し、元の長さに対する収縮した長さの割合で熱収縮率を求めた。
JIS K 7127に準拠してMDおよびTD方向のヤング率を23℃で測定した。
JIS K 7105に従って測定した。
(株)アタゴ製アッベ屈折計を用いて測定した。MD、TD方向に沿った屈折率をそれぞれNx、Nyとし、厚み方向の屈折率をNzとした。
上記11)で測定したNx、Ny、Nzから、面配向係数(P)を以下の式を用いて計算した。
P=[(Nx+Ny)/2]-Nz
巻き取ったフィルムロールから長さが1mの正方形のサンプルを切り出し、MD方向およびTD方向にそれぞれ10等分して測定用サンプルを100枚用意した。測定用サンプルのほぼ中央部を接触式のフィルム厚み計で厚みを測定した。
得られた100点のデータの平均値を求め、また最小値と最大値の差(絶対値)を求め、最小値と最大値の差の絶対値を平均値で除した値をフィルムの厚み斑とした。
ポリプロピレン樹脂として、Mw/Mn=7.7、Mz+1/Mn=140、MFR=5.0/10分、mmmm=97.3%であるプロピレン単独重合体(日本ポリプロ(株)製:ノバテック(登録商標)PP 「SA4L」)(以下、「PP-1」という)を用いた。60mm押出機を用いて、250℃でTダイよりシート状に押出し、30℃の冷却ロールで冷却固化した後、135℃で長さ方向(MD方向)に4.5倍に延伸し、ついで両端をクリップで挟み、熱風オーブン中に導いて、170℃で予熱後、160℃で横方向(TD方向)に8.2倍に延伸し、ついで6.7%の緩和率で緩和させながら168℃で熱処理した。その後、フィルムの片面にコロナ処理を行い、ワインダーで巻き取った。こうして得られたフィルムの厚みは20μmであり、ポリプロピレン樹脂の特性等を表1、2に、製膜条件を表3に、得られたフィルムの物性を表5に示した。表5に示すとおり、熱収縮率が低く、ヤング率が高いフィルムが得られた。実施例1の延伸プロピレンフィルムのDSCチャートを図1に示した。
このラミネート加工条件は、グラビア型ラミネーターを用い、巻き出し張力50N/m、巻き取り張力55N/m、接着剤塗布量は0.6g/m2、乾燥温度90℃、乾燥時間10秒である。このラミネート加工製品を40℃の雰囲気温度下で24時間加熱エージングを行った後に、流れ方向(MD方向)に5cm、垂直方向(TD方向)に10cmの大きさの短冊に切り出した。その後、短冊を23℃で65%Rh環境下でシーズニングを行い、水平台の上でカール量を測定した。カール量は、最初に接着剤を塗布したフィルムを上にした時の上側への水平台からの浮き上がり量をミリ単位で読み取り、ラベル四隅の平均値をカール量とし、ラベルのカール量を表5に示した。
上記「PP-1」90質量部に対して、分子量10000である低分子量ポリプロピレン(三井化学(株)製ハイワックス「NP105」)を10質量部加えて合計100質量部とし、30mm二軸押出機にて溶融混錬して、混合物「PP-2」のペレットを得た。このペレットを、実施例1と同様の方法でフィルムを得た。ポリプロピレン樹脂の特性等を表1、2に、製膜条件を表3に、得られたフィルムの物性およびラベルのカール量を表5に示した。
上記「PP-1」70質量部に対して、Mw/Mn=4.6、Mz+1/Mn=22、MFR=120g/10分、mmmm=98.1%であるプロピレン単独重合体を30質量部添加し、ドライブレンドして混合物「PP-3」を得た。「PP-3」を用いて、実施例1と同様の方法でフィルムを得た。ポリプロピレン樹脂の特性等を表1、2に、製膜条件を表3に、得られたフィルムの物性およびラベルのカール量を表5に示した。
上記「PP-1」を用い、予熱温度を173℃、TD方向の延伸温度及び熱固定温度を167℃とした以外は、実施例1と同様の方法でフィルムを得た。ポリプロピレン樹脂の特性等を表1、2に、製膜条件を表3に、得られたフィルムの物性およびラベルのカール量を表5に示した。
長さ方向に5.5倍、横方向に12倍延伸した以外は、実施例2と同様の方法でフィルムを得た。ポリプロピレン樹脂の特性等を表1、2に、製膜条件を表3に、得られたフィルムの物性およびラベルのカール量を表5に示した。
実施例1で作製したフィルムを用いて、テンター式熱風オーブン中で、170℃で5分間熱処理(オフラインアニール)を行った。ポリプロピレン樹脂の特性等を表1、2に、製膜条件を表3に、得られたフィルムの物性およびラベルのカール量を表5に示した。
ポリプロピレン樹脂として、Mw/Mn=8.9、Mz+1/Mn=110、MFR=3.0g/10分、mmmm=97.1%であるプロピレン単独重合体(サムスントタル(株)製「HU300」)(以下「PP-4」という)を用い、予熱温度を171℃、TD方向の延伸温度を161℃、熱固定温度を170℃とした以外は、実施例1と同様の方法でポリプロピレンフィルムを得た。ポリプロピレン樹脂の特性等を表1、2に、製膜条件を表3に、得られたフィルムの物性およびラベルのカール量を表5に示した。
ポリプロピレン樹脂として、Mw/Mn=4、Mz+1/Mn=21、MFR=2.5g/10分、エチレン量=0.6mol%である住友化学(株)製の住友ノーブレン(登録商標)「FS2011DG3」(以下「PP-5」という)を用い、MD延伸温度を125℃、予熱温度を168℃、TD方向の延伸温度を155℃、熱固定温度を163℃とした以外は、実施例1と同様の方法でフィルムを得た。ポリプロピレン樹脂の特性等を表1、2に、製膜条件を表4に、得られたフィルムの物性およびラベルのカール量を表6に示した。比較例1の延伸プロピレンフィルムのDSCチャートを図1に示す。
予熱温度を171℃、TD方向の延伸温度を160℃、熱固定温度を165℃とした以外は、比較例1と同様にフィルムを作製した。ポリプロピレン樹脂の特性等を表1、2に、製膜条件を表4に、得られたフィルムの物性およびラベルのカール量を表6に示した。
ポリプロピレン樹脂として、Mw/Mn=4.3、Mz+1/Mn=28、MFR=0.5g/10分、mmmm=97.0%であるプロピレン単独重合体(以下「PP-6」という)を用い、実施例7と同様の条件でフィルムを得た。ポリプロピレン樹脂の特性等を表1、2に、製膜条件を表4に、得られたフィルムの物性およびラベルのカール量を表6に示した。
ポリプロピレン樹脂として、Mw/Mn=2.8、Mz+1/Mn=9.2、MFR=30g/10分、mmmm=97.9%のプロピレン単独重合体である日本ポリプロ(株)製のノバテックPP「SA03」(以下「PP-7」という)を用い、実施例1と同様に二軸延伸を試みたが、横方向への延伸時に破断してフィルムを得ることができなかった。ポリプロピレン樹脂の特性等を表1、2に、製膜条件を表4に示した。
Claims (4)
- ポリプロピレン樹脂を主体として構成されたフィルムであって、150℃でのMD方向およびTD方向の熱収縮率が共に9%以下であり、MD方向のヤング率が2GPa以上であり、TD方向のヤング率が4GPa以上であり、ヘイズが6%以下であることを特徴とするインモールドラベル用ポリプロピレンフィルム。
- フィルムを構成するポリプロピレン樹脂のアイソタクチックメソペンタッド分率の下限が96%であり、フィルムの面配向係数の下限が0.0125である請求項1に記載のポリプロピレンフィルム。
- フィルムを構成するポリプロピレン樹脂の共重合モノマー量の上限が0.1mol%である請求項1または2に記載のポリプロピレンフィルム。
- フィルムを構成するポリプロピレン樹脂の常温キシレン可溶分が、7質量%以下である請求項1~3のいずれかに記載のポリプロピレンフィルム。
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