Polypropylene composition for stretched film and stretched film containing the same

Abstract

To provide a polypropylene composition which gives a stretched film having high heat resistance and rigidity, and to provide a stretched film containing the polypropylene composition.SOLUTION: The polypropylene composition for a stretched film contains a polypropylene selected from the group consisting of propylene homopolymers and propylene-ethylene copolymers containing 1.0 wt.% or less of an ethylene-derived unit. The polypropylene satisfies the following requirement (1): the molecular weight distribution Mw / Mn by GPC measurement and the amount γ (wt.%) of a component having a molecular weight of 1,000,000 or more by GPC measurement satisfy 0.4<(Mw / Mn)×γ<10.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a polypropylene composition for a stretched film and a stretched film containing the same.

Background Art

[0002] Stretched films made of polypropylene resin are widely used in a wide range of applications such as for electrical insulation, surface protection, packaging of various products such as food and industrial members. However, it has been pointed out that conventional stretched films made of polypropylene resin have low heat resistance. Stretched films made of polypropylene resin are greatly inferior in heat resistance compared to other materials, especially polyethylene terephthalate films, etc., and the heat shrinkage rate at 150 ° C is as large as several tens of %. In addition, due to low rigidity, the materials are sorted according to the application.

[0003] Various techniques have been proposed to improve the physical properties such as heat resistance and mechanical properties of biaxially stretched polypropylene-based films. For example, claim 1 of Patent Document 1 discloses a propylene polymer having a very advantageous balance of rigidity and processability for film applications including biaxially stretched polypropylene film applications, "a propylene polymer having a decalin-soluble content of 1.6% by weight or less and a polydispersity index (PI) of at least 5.0".

[0004] Further, claim 1 of Patent Document 2 discloses a biaxially stretched laminated polypropylene film having high heat resistance and rigidity, "the polypropylene resin constituting the film, a completely homopolypropylene resin containing no copolymer component and / or a polypropylene resin copolymerized with ethylene and / or an α-olefin having 4 or more carbon atoms satisfies the following conditions 1) to 4), and the lower limit of the surface orientation coefficient of the film is 0.0125, and the tensile elastic modulus in the transverse direction of the film is 5.1 GPa or more. A biaxially oriented stretched polypropylene film characterized by the above. 1) The lower limit of the mesopentad fraction is 96%. 2) The upper limit of the amount of copolymerized monomer other than propylene is 0.1 mol%. 3) The weight-average molecular weight (Mw) / number-average molecular weight (Mn) is 3.0 or more and 5.4 or less. 4) The melt flow rate (MFR) measured at 230 °C and 2.16 kgf is 6.5 g / 10 min or more and 9.0 g / 10 min or less.」 is disclosed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] The stretched films obtained from the polypropylene resins of Patent Documents 1 and 2 do not have sufficient heat resistance. For example, under high-temperature conditions exceeding 150 °C, they cannot maintain their shape, and there are problems such as printed characters, patterns, etc. being deformed and easily wrinkled. Also, in Patent Documents 1 and 2, it cannot be said that sufficient studies have been made on the structure, properties, etc. of preferred polypropylene or polypropylene compositions for improving heat resistance. An object of the present invention is to provide a polypropylene composition that gives a stretched film having high heat resistance and rigidity, and a stretched film containing the same.

Means for Solving the Problems

[0007] As a result of intensive studies, the present inventors have found that by setting the relationship between the molecular weight distribution Mw / Mn and the content of high-molecular-weight components within a predetermined range for polypropylene, a stretched film excellent in heat resistance and rigidity can be obtained, and the present invention has been completed. The present invention relates to the following [1] to [8].

[0008] A polypropylene composition for a stretched film, comprising polypropylene selected from the group consisting of a propylene homopolymer and a propylene-ethylene copolymer containing units derived from 1.0% by weight or less of ethylene, wherein the polypropylene satisfies the following requirement (1). (1) The molecular weight distribution Mw / Mn measured by GPC and the amount γ (wt%) of components having a molecular weight of 1,000,000 or more measured by GPC satisfy 0.4 < (Mw / Mn)·γ < 10. [2] The polypropylene composition for a stretched film according to [1], wherein the polypropylene satisfies the following requirement (2). (2) The melt flow rate measured at 230 °C and a load of 2.16 kg in accordance with JIS K7210 is 3.5 to 20 g / 10 min. [3] The polypropylene composition for a stretched film according to [1] or [2], wherein the polypropylene satisfies the following requirement (3). (3) 13 The isotactic mesopentad fraction (mmmm) measured by C-NMR is 95% or more. [4] The polypropylene composition for a stretched film according to any one of [1] to [3], wherein the polypropylene satisfies the following requirement (4). (4) Mw / Mn satisfies 2.0 < Mw / Mn < 5.0. [5] The polypropylene composition for a stretched film according to any one of [1] to [4], wherein the polypropylene satisfies the following requirement (5). (5) γ is less than 5.0% by weight. [6] A stretched film comprising the polypropylene composition for a stretched film according to any one of [1] to [5]. [7] Regarding the heat shrinkage rate of the stretched film measured in accordance with JIS K6782 in an environment at 150 °C for 30 minutes, the MD direction is 0 to 3.5% and the TD direction is 0 to 5.0%. The stretched film according to [6]. [8] Regarding the Young's modulus of the stretched film measured in accordance with JIS K7127, the TD direction is 5.6 GPa or more. The stretched film according to [6] or [7].

Advantages of the Invention

[0009] The polypropylene compositions for the stretched films of Aspects 1 to 5 exhibit high heat resistance and rigidity. The stretched films of Aspects 6 to 8 have high heat resistance and rigidity and can maintain their shapes even at high temperatures, so they are less likely to wrinkle and the characters, patterns, etc. of the printed matter do not deform.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0011] The polypropylene composition for the stretched film of the present invention is a polypropylene composition for the stretched film containing polypropylene selected from the group consisting of a propylene homopolymer and a propylene-ethylene copolymer containing units derived from 1.0% by weight or less of ethylene, wherein the polypropylene satisfies the following requirement (1). (1) The molecular weight distribution Mw / Mn by GPC measurement and the amount γ (weight%) of components having a molecular weight of 1,000,000 or more by GPC measurement satisfy 0.4 < (Mw / Mn)·γ < 10. By using the polypropylene composition for the stretched film, a stretched film having high heat resistance and rigidity can be obtained.

[0012] In the present invention, the propylene-based polymer means a propylene homopolymer or a propylene-ethylene copolymer containing units derived from ethylene in an amount of 1.0% by weight or less. Further, in the present invention, polypropylene means a polymer that satisfies the above requirement (1) among the propylene-based polymers.

[0013] [Polypropylene Composition] The polypropylene composition contains polypropylene selected from the group consisting of a propylene homopolymer and a propylene-ethylene copolymer containing units derived from ethylene in an amount of 1.0% by weight or less. In the present invention, the content ratio of the units derived from ethylene in the propylene-ethylene copolymer is a value calculated based on the following formula. Content ratio of units derived from ethylene (%) = Weight of units derived from ethylene / (Weight of units derived from propylene + Weight of units derived from ethylene) × 100 The propylene homopolymer and the propylene-ethylene copolymer may each be used alone or in combination of two or more.

[0014] The polypropylene composition may be in a form containing only one of the propylene homopolymer and the propylene-ethylene copolymer, or in a form containing both the propylene homopolymer and the propylene-ethylene copolymer, or in a form containing the propylene homopolymer and / or the propylene-ethylene copolymer as a main component and other components as sub-components. In the present invention, "contained as a main component" means that the total content ratio of the propylene homopolymer and the propylene-ethylene copolymer in 100% by weight of the polypropylene composition is 50% by weight or more. From the viewpoint of suppressing appearance defects due to sub-components or maintaining film physical properties such as heat resistance and rigidity, the total content ratio of the propylene homopolymer and the propylene-ethylene copolymer in 100% by weight of the polypropylene composition is preferably 80% by weight or more, more preferably 90% by weight or more. The upper limit of the total content ratio of the propylene homopolymer and the propylene-ethylene copolymer is 100% by weight.

[0015] <Polypropylene> From the viewpoints of the heat resistance and rigidity of the stretched film, the polypropylene is preferably a propylene homopolymer. When the polypropylene is a propylene-ethylene copolymer, the content ratio of the units derived from ethylene is 1.0% by weight or less, preferably 0.5% by weight or less, more preferably 0.3% by weight or less. When it is within the above range, the high rigidity of the stretched film can be maintained.

[0016] The polypropylene may be one obtained by polymerizing other monomers such as α-olefins having 4 or more carbon atoms and non-conjugated dienes as long as the object of the present invention is not impaired.

[0017] The polypropylene satisfies the following requirement (1). (1) The molecular weight distribution Mw / Mn by GPC measurement and the amount γ (weight%) of the components having a molecular weight of 1 million or more by GPC measurement satisfy 0.4 < (Mw / Mn)·γ < 10. By setting 0.4 < (Mw / Mn)·γ < 10, a stretched film having high rigidity and low heat shrinkage can be obtained. From the viewpoint of obtaining a stretched film having high rigidity and low heat shrinkage, preferably (Mw / Mn)·γ < 7, more preferably (Mw / Mn)·γ < 5, still more preferably (Mw / Mn)·γ < 4. Also, from the viewpoint of moldability such as breakage and uneven elongation during film molding, (Mw / Mn)·γ > 0.4, preferably (Mw / Mn)·γ > 0.6, and more preferably (Mw / Mn)·γ ≧ 1.0.

[0018] The values of Mn, Mw, and γ defined above are all obtained by gel permeation chromatography (GPC). The details of the measurement method and measurement instrument are as described in the examples. Here, Mn and Mw are the number-average molecular weight and weight-average molecular weight of polypropylene measured by GPC, and Mw / Mn can be an index of the molecular weight distribution of polypropylene. The Mn, Mw, and Mw / Mn of polypropylene can be easily adjusted by changing the temperature and pressure conditions of propylene polymerization, or, as the most common method, by adding a chain transfer agent such as hydrogen during propylene polymerization. Furthermore, when using two or more types of metallocene complexes, it can be controlled by changing the amount ratio. Also, Mn, Mw, and Mw / Mn can be adjusted by appropriately reducing a higher molecular weight propylene-based polymer.

[0019] γ is the amount (unit: wt%) of components with a molecular weight of 1 million or more in 100 wt% of polypropylene measured by GPC. Specifically, γ is a value obtained by multiplying the value obtained by subtracting the integral value up to a molecular weight (M) of 1 million (Log(M) = 6.0) from 1 in the integral molecular weight distribution curve (normalized to 1 for the total amount) obtained by GPC measurement by 100. An example of how to obtain γ is shown in Figure 2. γ can be adjusted, for example, by controlling the prepolymerization conditions, the amount of hydrogen during polymerization, etc. in addition to the selection, combination, and amount ratio of the catalyst, and also by appropriately reducing a higher molecular weight propylene-based polymer.

[0020] 0.4 < (Mw / Mn)·γ < 10 can be achieved by narrowing the molecular weight distribution of polypropylene and reducing the amount of high molecular weight components with a molecular weight of 1 million or more. By satisfying 0.4 < (Mw / Mn)·γ, the film-forming suitability on a biaxial stretching machine is improved, thus preventing troubles during film production, and further having the effect of improving the quality such as the film thickness accuracy. Also, by satisfying (Mw / Mn)·γ < 10, while suppressing the large viscosity due to the fraction of polymer molecules with a molecular weight of 1 million or more, the presence of a large amount of molecules with the same degree of molecular weight makes it possible to suppress the thermal shrinkage due to entropy, and it is considered that the low thermal shrinkage of the obtained stretched film is exhibited.

[0021] Polypropylene preferably satisfies the following requirements (2) to (5).

[0022] (2) It conforms to JIS K7210 and has a melt flow rate measured at 230 °C and a load of 2.16 kg of 3.5 to 20 g / 10 min. Polypropylene conforms to JIS K7210:1999, and the melt flow rate (MFR) measured at 230 °C and a load of 2.16 kg is preferably 3.5 to 20 g / 10 min, more preferably 5.0 to 18 g / 10 min, and even more preferably 7.0 to 15 g / 10 min. When it is within the above range, the moldability during film forming becomes good. The melt flow rate (MFR) of polypropylene can be easily adjusted by changing the polymerization temperature and pressure, or as a general method, by adding a chain transfer agent such as hydrogen during polymerization. Also, the melt flow rate (MFR) can be adjusted by appropriately reducing a higher molecular weight propylene-based polymer.

[0023] (3) 13 The isotactic mesopentad fraction (mmmm) measured by C-NMR is 95% or more. Polypropylene 13 The isotactic mesopentad fraction (mmmm) measured by C-NMR is preferably 95% or more, more preferably 96% or more, and even more preferably 97% or more. Also, mmmm can be 95 to 96%. When it is within the above range, the rigidity of the film becomes good. In this specification, the isotactic mesopentad fraction (mmmm) is a value measured by the following method.

[0024] ( 13 Measurement method of C-NMR) [Sample preparation and measurement conditions] 200 mg of the sample is dissolved in o-dichlorobenzene / deuterated benzene (C 6 D 5(Br) = 4 / 1 (volume ratio), 2.4 mL. It is placed in an NMR sample tube with an inner diameter of 10 mm φ together with hexamethyldisiloxane, which is a reference substance for chemical shift, and uniformly dissolved with a block heater at 150 °C. NMR measurement is carried out using an AV400 type NMR apparatus manufactured by Bruker BioSpin equipped with a 10 mm φ cryoprobe. 13 The measurement conditions for 13C-NMR are as follows: the sample temperature is 120 °C, the pulse angle is 90°, the pulse interval is 15 seconds, and the number of integration times is 1024 times. The measurement is carried out by the broadband decoupling method. The chemical shift is set with the 13C signal of hexamethyldisiloxane at 13 1.98 ppm, and the chemical shift of the signal by other 13C is based on this. 13

[0025] [Calculation method of isotactic mesopentad fraction (mmmm)] The isotactic mesopentad fraction (mmmm) of a five - chain propylene unit can be obtained by substituting the integration intensity of the 13C signal measured by 13C - NMR into the following formula (1). 13 13C - NMR measurement 13 mmmm(%)=(I mm - 2×I mrrm )×100 / (I mm + 3×I mrrm ) ··· Formula (1) Here, I mm represents the integration intensity of the 13C signal attributed to the bonding pattern of mm for a three - chain propylene unit, and is calculated as the integration intensity of the 13C signal in the range of chemical shift from 23.6 to 21.1 ppm (hereinafter referred to as "I 13 13 23.6~21.1 "). I mrrm represents the integration intensity of the 13C signal attributed to the bonding pattern of mrrm for a five - chain propylene unit, and is the value indicated by I 13 19.9~19.7 The spectral assignment can be made with reference to Polymer Journal, Vol. 16, p. 717 (1984), Asakura Shoten, Macromolecules, Vol. 8, p. 687 (1975), and Polymer, Vol. 30, p. 1350 (1989). The chemical shift range may shift slightly depending on the molecular weight of the polymer, etc., but the region can be easily identified.

[0026] (4) Mw / Mn satisfies 2.0 < Mw / Mn < 5.0. For polypropylene, Mw / Mn by GPC measurement is preferably 2.0 < Mw / Mn < 5.0, more preferably 2.3 ≦ Mw / Mn ≦ 4.8, and even more preferably 2.6 ≦ Mw / Mn ≦ 4.7. Mw / Mn is an index representing the molecular weight distribution, and the smaller this value, the narrower the molecular weight distribution. By reducing and optimizing Mw / Mn, the stretching of the film can be carried out uniformly and stably. When Mw / Mn < 5.0, the uniformity of the molecular chain length increases, and the external force applied during stretching is sufficiently propagated to the material, so the rigidity of the molded product is likely to improve. Also, when Mw / Mn > 2.0, the moldability improves, so the thickness accuracy and surface properties during film production are likely to improve.

[0027] (5) γ is less than 5.0% by weight. For polypropylene, the amount γ of components with a molecular weight of 1 million or more by GPC measurement is preferably less than 5.0% by weight, more preferably less than 3.0% by weight, even more preferably less than 2.0% by weight, and particularly preferably less than 1.5% by weight. Also, γ is preferably 0.01% by weight or more, more preferably 0.05% by weight or more, even more preferably more than 0.1% by weight, and particularly preferably 0.4% by weight or more. Within the above range, the stretching tension of polypropylene is small, and the equipment load during molding can be suppressed. Furthermore, when the molecular chains are oriented or the crystal structure such as lamellae is rearranged during stretching, it can be molded uniformly and stably, the rigidity of the film is likely to improve, and in terms of the higher-order structure, it can be made less likely to shrink during heating.

[0028] <Method for Producing Polypropylene> The propylene-based polymer can preferably be obtained by polymerizing propylene or copolymerizing propylene and a small amount of ethylene using a catalyst such as a Ziegler-Natta catalyst or a metallocene catalyst. When the propylene-based polymer thus obtained satisfies the above requirement (1), this propylene-based polymer can be used as the polypropylene of the present invention.

[0029] As an example of the Ziegler-Natta catalyst, there is included a solid component (a) containing magnesium, titanium, halogen, and an internal electron donor compound selected from phthalate-based compounds, diether-based compounds, succinate-based compounds, etc. The Ziegler-Natta catalyst may further contain an organoaluminum compound (b) and an external electron donor compound (c) as necessary in addition to the solid component (a). Furthermore, the solid component (a) may be subjected to a contact treatment with an alkoxysilane or a silane compound having an alkenyl group. Examples of the metallocene catalyst include a metallocene catalyst composed of a metallocene compound, at least one compound selected from organometallic compounds, organoaluminum oxy compounds, and compounds capable of reacting with the metallocene compound to form an ion pair, and further, if necessary, a particulate carrier. Among them, a metallocene catalyst capable of stereoregular polymerization such as an isotactic or syndiotactic structure is preferable.

[0030] As the polymerization method of the propylene-based polymer, a known method may be adopted. For example, a method of polymerizing in an inert solvent such as hexane, heptane, toluene, xylene, etc.; a method of polymerizing in a liquid monomer; a method of adding a catalyst to a gaseous monomer and polymerizing in a gas phase state; or a method of polymerizing by combining these, etc. may be mentioned. The polymerization of the propylene-based polymer may be a single-stage polymerization carried out in one reactor or a multi-stage polymerization carried out in a plurality of reactors. In the case of multi-stage polymerization, the polymerization conditions of each reactor may be the same or different. The reactor may be a reactor having a gradient of monomer concentration and polymerization conditions. The molecular weight of the propylene-based polymer may be adjusted using a chain transfer agent such as hydrogen.

[0031] When the obtained propylene-based polymer satisfies (Mw / Mn)·γ ≧ 10, the propylene-based polymer can be subjected to a reduction treatment with an organic peroxide to adjust Mw / Mn and γ so that 0.4 < (Mw / Mn)·γ < 10 is satisfied. In particular, due to the reduction treatment, molecular cleavage occurs in the relatively high molecular weight components (molecules) constituting the propylene-based polymer, so that γ becomes smaller and 0.4 < (Mw / Mn)·γ < 10 can be satisfied. When the obtained propylene-based polymer satisfies 0.4 < (Mw / Mn)·γ < 10, the reduction treatment with an organic peroxide is not essential, but the value of (Mw / Mn)·γ can be made to be in a more preferable range, and the reduction treatment may be performed in order to further improve the high rigidity and low heat shrinkage of the stretched film. Also, when (Mw / Mn)·γ ≦ 0.4, by mixing with a separately produced propylene-based polymer having a large Mw / Mn or γ and satisfying (Mw / Mn)·γ ≧ 10, the propylene-based polymer as a whole can be adjusted to satisfy 0.4 < (Mw / Mn)·γ < 10.

[0032] The propylene-based polymer before the reduction treatment is not particularly restricted as long as it is a propylene homopolymer or a propylene-ethylene copolymer containing units derived from ethylene of 1.0% by weight or less, but Mw / Mn is preferably 5 to 20, more preferably 6 to 15. Also, the melt flow rate (MFR) measured at 230°C and a load of 2.16 kg in accordance with JIS K7210:1999 is preferably 0.1 to 10 g / 10 min, more preferably 0.2 to 5 g / 10 min.

[0033] Examples of the organic peroxide include benzoyl peroxide, di-t-butyl peroxide, dicumyl peroxide, t-butyl cumyl peroxide, 1,1-bis-(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclohexane, 2,2-bis(t-butylperoxy)octane, n-butyl-4,4-bis(t-butylperoxy)valerate, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)-3-hexyne, 1,3-bis(t-butylperoxyisopropyl)benzene, α,α'-bis(t-butylperoxyisopropyl)benzene, t-butyl hydroperoxide, cumene hydroperoxide, lauroyl peroxide, di-t-butyl diperoxyphthalate, t-butyl peroxymaleic acid, t-butyl peroxyisopropyl carbonate, isopropyl percarbonate, and the like. These can be used not only singly but also in combination of two or more. Among these, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)-3-hexyne, 1,3-bis(t-butylperoxyisopropyl)benzene, or α,α'-bis(t-butylperoxyisopropyl)benzene is preferable.

[0034] For the subtractive treatment, 0.005 to 1.0 part by weight of the organic peroxide may be used with respect to 100 parts by weight of the propylene-based polymer, and both may be heated and kneaded at a temperature equal to or higher than the melting temperature of the polymer, for example, 180 to 300°C. As the method, a known method can be adopted, but it is particularly preferable to perform it in an extruder. Further, before heating and kneading, both may be mixed in advance using a mixer such as a Henschel mixer or a ribbon blender so that the organic peroxide is uniformly dispersed in the propylene-based polymer. Furthermore, in order to improve the dispersibility of the organic peroxide, a mixture of the organic peroxide and an appropriate medium can also be used.

[0035] The polypropylene thus obtained can be formed into pellets, powder, or other forms by known methods.

[0036] <Polypropylene composition> The polypropylene composition may consist only of the above polypropylene, or may contain the above polypropylene and other components. Examples of other components include additives and other polymers other than the above polypropylene. Examples of additives include antioxidants, lubricants, antistatic agents, antiblocking agents, ultraviolet absorbers, light stabilizers, chlorine absorbers, heat stabilizers, antifogging agents, flame retardants, dispersants, copper corrosion inhibitors, neutralizing agents, plasticizers, antifoaming agents, crosslinking agents, peroxides, oil extenders, pigments, and the like.

[0037] Examples of antioxidants include phenolic antioxidants and phosphite antioxidants. Examples of phenolic antioxidants include 2,6-di-t-butyl-p-cresol (BHT), tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane (manufactured by BASF Japan Ltd., trade name "IRGANOX (registered trademark) 1010"), n-octadecyl-3-(4'-hydroxy-3',5'-di-t-butylphenyl)propionate (manufactured by BASF Japan Ltd., trade name "IRGANOX (registered trademark) 1076"), and the like. Examples of phosphite antioxidants include bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite, tris(2,4-di-t-butylphenyl)phosphite, and the like. Examples of lubricants include higher fatty acid amides, higher fatty acid esters, and the like. Examples of antistatic agents include glycerin esters of fatty acids having 8 to 22 carbon atoms, sorbitan acid esters, polyethylene glycol esters, and the like. Examples of antiblocking agents include silica, calcium carbonate, talc, and the like.

[0038] Examples of ultraviolet absorbers include compounds such as triazole-based, benzophenone-based, salicylate-based, cyanoacrylate-based, nickel chelate-based, and inorganic fine particle-based compounds. Examples of triazole-based ultraviolet absorbers include 2-(2'-hydroxy-5'-methylphenyl)benzotriazole (manufactured by Sumitomo Chemical Co., Ltd., trade name: Sumisorb (registered trademark) 200; manufactured by BASF Japan Ltd., trade name: Tinuvin (registered trademark) P), 2-(2'-hydroxy-5'-t-octylphenyl)benzotriazole (manufactured by Sumitomo Chemical Co., Ltd., trade name: Sumisorb (registered trademark) 340; manufactured by BASF Japan Ltd., trade name: Tinuvin (registered trademark) 399), 2-(2'-hydroxy-3',5'-di-t-butylphenyl)benzotriazole (manufactured by Sumitomo Chemical Co., Ltd., trade name: Sumisorb (registered trademark) 320; manufactured by BASF Japan Ltd., trade name: Tinuvin (registered trademark) 320), 2-(2'-hydroxy-3',5'-di-t-amylphenyl)benzotriazole (manufactured by Sumitomo Chemical Co., Ltd., trade name: Sumisorb (registered trademark) 350; manufactured by BASF Japan Ltd., trade name: Tinuvin (registered trademark) 328), 2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)-5-chlorobenzotriazole (manufactured by Sumitomo Chemical Co., Ltd., trade name: Sumisorb (registered trademark) 300; manufactured by BASF Japan Ltd., trade name: Tinuvin (registered trademark) 326), and the like. Examples of benzophenone-based ultraviolet absorbers include 2-hydroxy-4-methoxybenzophenone (manufactured by Sumitomo Chemical Co., Ltd., trade name: Sumisorb (registered trademark) 110), 2-hydroxy-4-n-octoxybenzophenone (manufactured by Sumitomo Chemical Co., Ltd., trade name: Sumisorb (registered trademark) 130), and the like. Examples of salicylate-based ultraviolet absorbers include 4-t-butylphenyl salicylate (manufactured by Cipro Kasei Co., Ltd., trade name: Seasorb 202), and the like. Examples of cyanoacrylate-based ultraviolet absorbers include ethyl (3,3-diphenyl)cyanoacrylate (manufactured by Cipro Kasei Co., Ltd., trade name: Seasorb 501), and the like. Examples of nickel chelate type ultraviolet absorbers include nickel dibutyldithiocarbamate (manufactured by Sumitomo Chemical Co., Ltd., trade name: Antigen (registered trademark) NBC), etc. Examples of inorganic fine particle type ultraviolet absorbers include TiO 2 , ZnO 2 , CeO 2 , etc.

[0039] Examples of light stabilizers include compounds such as sebacate type, butanetetracarboxylate type, succinic acid polyester type, and triazine type. Examples of sebacate type light stabilizers include bis(2,2,6,6 - tetramethyl - 4 - piperidyl) sebacate (manufactured by ADEKA Corporation, trade name: Adeka Stab (registered trademark) LA - 77; manufactured by BASF Japan Ltd., trade name: Tinuvin (registered trademark) 770), bis(1,2,2,6,6 - pentamethyl - 4 - piperidyl) sebacate (manufactured by BASF Japan Ltd., trade name: Tinuvin (registered trademark) 765), etc. Examples of butanetetracarboxylate type light stabilizers include tetrakis(2,2,6,6 - tetramethyl - 4 - piperidyl) - 1,2,3,4 - butanetetracarboxylate (manufactured by ADEKA Corporation, trade name: Adeka Stab (registered trademark) LA - 57), tetrakis(1,2,2,6,6 - pentamethyl - 4 - piperidyl) - 1,2,3,4 - butanetetracarboxylate (manufactured by ADEKA Corporation, trade name: Adeka Stab (registered trademark) LA - 52), a condensate of 1,2,3,4 - butanetetracarboxylic acid with 2,2,6,6 - tetramethyl - 4 - piperidinol and tridecyl alcohol (manufactured by ADEKA Corporation, trade name: Adeka Stab (registered trademark) LA - 67), a condensate of 1,2,3,4 - butanetetracarboxylic acid with 1,2,2,6,6 - pentamethyl - 4 - piperidinol and tridecyl alcohol (manufactured by ADEKA Corporation, trade name: Adeka Stab (registered trademark) LA - 62), etc. Examples of succinic acid polyester type light stabilizers include a condensation polymer of succinic acid with 1 - (2 - hydroxyethyl) - 4 - hydroxy - 2,2,6,6 - tetramethylpiperidine, etc. Examples of triazine-based light stabilizers include N,N'-bis(3-aminopropyl)ethylenediamine·2,4-bis{N-butyl-N-(1,2,2,6,6-pentamethyl-4-piperidyl)amino}-6-chloro-1,3,5-triazine condensate (manufactured by BASF Japan Ltd., trade name: Chimasorb® 199), poly{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl}{(2,2,6,6-tetramethyl-4-piperidyl)imino}hexamethylene{(2,2,6,6-tetramethyl-4-piperidyl)imino} (manufactured by BASF Japan Ltd., trade name: Chimasorb® 944), poly(6-morpholino-s-triazine-2,4-diyl){(2,2,6,6-tetramethyl-4-piperidyl)imino}hexamethylene{(2,2,6,6-tetramethyl-4-piperidyl)imino} (manufactured by BASF Japan Ltd., trade name: Chimasorb® 3346), and the like.

[0040] Examples of other polymers include polypropylene-based resins other than the polypropylene according to the present invention, polyethylene, propylene-based or ethylene-based elastomers, and the like. Examples of propylene-based or ethylene-based elastomers include ethylene-α-olefin copolymers, binary random copolymers of propylene and an α-olefin having 4 to 12 carbon atoms, and ternary random copolymers of propylene, ethylene, and an α-olefin having 4 to 12 carbon atoms.

[0041] The content of the additive in 100% by weight of the polypropylene composition is preferably 5% by weight or less, more preferably 3% by weight or less, and even more preferably 1% by weight or less. The content of other polymers in 100% by weight of the polypropylene composition is preferably 49% by weight or less, more preferably 20% by weight or less, and even more preferably 10% by weight or less.

[0042] When the polypropylene composition contains an additive or other polymer, the polypropylene and the additive or other polymer can be mixed or melt-kneaded to produce a polypropylene composition. Examples of the mixing method include mixing with a Henschel mixer, V blender, ribbon blender, tumbler blender, etc. Examples of the melt-kneading method include melt-kneading with a kneader such as a single-screw extruder, multi-screw extruder, kneader, Banbury mixer, etc. The polypropylene composition thus obtained can be formed into pellets, powder, etc. by known methods. The additive may be added during the polymerization of the propylene-based polymer, may be added simultaneously or separately with an organic peroxide during the degradation treatment of the propylene-based polymer, or may be added to the polypropylene after the degradation treatment. Also, other polymers are usually added to the polypropylene after the degradation treatment. In any case, the mixing method is not particularly limited as long as the effects of the present invention are not impaired.

[0043] [Stretched film] The stretched film contains a polypropylene composition. The content ratio of the polypropylene composition in 100% by weight of the stretched film is preferably 50% by weight or more, more preferably 80% by weight or more. The upper limit of the content ratio of the polypropylene composition in 100% by weight of the stretched film is 100% by weight. The stretched film can be produced by using a known melt extrusion film-forming method for the polypropylene composition to produce an unstretched film and then stretching the film. The stretched film may be a uniaxially stretched film or a biaxially stretched film, and is preferably a biaxially stretched film from the viewpoint of the synthetic balance in the MD direction and TD direction. In the case of a biaxially stretched film, either a simultaneous biaxial stretching method or a sequential biaxial stretching method may be employed.

[0044] Regarding the heat shrinkage rate of the stretched film measured under the environment of 150°C for 30 minutes in accordance with JIS K6782, the heat shrinkage rate in the MD direction is preferably 0 to 3.5%, more preferably 0 to 3.0%. Also, regarding the heat shrinkage rate, the heat shrinkage rate in the TD direction is preferably 0 to 5.0%, more preferably 0 to 3.0%, and even more preferably 0 to 1.5%. Among them, the heat shrinkage rate is preferably such that the MD direction is 0 to 3.5% and the TD direction is 0 to 5.0%, more preferably the MD direction is 0 to 3.0% and the TD direction is 0 to 3.0%, and even more preferably the MD direction is 0 to 3.0% and the TD direction is 0 to 1.5%. When it is within the above range, it becomes possible to use it for applications that require high heat resistance and could not be used with conventional OPP films. For example, there is an advantage that it can be used as an alternative to PET films.

[0045] Regarding the Young's modulus of the stretched film measured in accordance with JIS K7127, the Young's modulus in the MD direction is preferably 2 GPa or more, more preferably 2.2 GPa or more, and even more preferably 2.5 GPa or more. Regarding the Young's modulus of the stretched film measured in accordance with JIS K7127, the Young's modulus in the TD direction is preferably 5.6 GPa or more, more preferably 6.0 GPa or more, and even more preferably 6.5 GPa or more. When it is within the above range, it becomes possible to use it for applications that require high heat resistance and could not be used with conventional OPP films. For example, there is an advantage that it can be used as an alternative to PET films.

[0046] In the present invention, the MD direction is the flow direction of the film (which may also be referred to as the length direction or the longitudinal direction), and the TD direction is the direction perpendicular to the flow direction and the thickness direction of the film (which may also be referred to as the transverse direction or the width direction).

[0047] The stretched film may be a single layer containing a polypropylene composition or a multilayer in which each layer contains a polypropylene composition. In the case of a multilayer film, the polypropylene compositions constituting each layer may be the same or different. Also, the stretched film may be a laminated film further laminated with other layers. In the case of a multilayer film or a laminated film, after performing a stretching treatment on a single-layer film containing a polypropylene composition, it may be used as a multilayer film or a laminated film, or after forming a multilayer film or a laminated film, a stretching treatment may be performed.

[0048] When the stretched film is a single-layer film, its thickness is preferably 5 to 200 μm, more preferably 10 to 150 μm, still more preferably 12 to 100 μm, and even more preferably 15 to 80 μm.

[0049] When the stretched film is incorporated into a multilayer film each containing a polypropylene composition, or a laminated film in which the stretched film and other layers are laminated, the thickness of each stretched film is preferably 5 to 150 μm, more preferably 10 to 100 μm, still more preferably 12 to 80 μm, and even more preferably 15 to 60 μm. When it is a multilayer film or a laminated film, its total thickness is preferably 5 to 200 μm, more preferably 10 to 150 μm, still more preferably 12 to 120 μm, and even more preferably 15 to 100 μm.

[0050] The method for producing the stretched film is not particularly limited. For example, an unstretched film made of the polypropylene composition can be prepared and stretched in a uniaxial or biaxial direction by a known method to obtain a stretched film. The molding temperature when stretching the unstretched film is preferably 140 to 180 °C, more preferably 150 to 175 °C, and still more preferably 155 to 170 °C. An MD stretching step of obtaining a uniaxially stretched film by stretching the unstretched film 2 to 10 times, preferably 4 to 7 times, in the MD direction using stretching rolls may be provided. Further, the uniaxially stretched film obtained in the MD stretching step can be stretched 4 to 20 times, preferably 4 to 10 times, in the TD direction in a heating furnace using two rows of chucks arranged along the MD direction to obtain a biaxially stretched film. A TD stretching step may be provided.

[0051] In order to improve processability, the stretched film may be subjected to a discharge treatment such as corona or plasma, a flame treatment, an ozone treatment, etc. on the surface of the film.

[0052] The stretched film can be used as one layer of a multilayer film or a laminated film. The laminated film is obtained by laminating an arbitrary layer on one or both sides of a layer made of a stretched film. Examples of methods for producing a multilayer film or a laminated film include commonly used coextrusion methods, extrusion lamination methods, thermal lamination methods, dry lamination methods, and inflation methods that perform cooling in a water or air atmosphere.

[0053] For example, an arbitrary layer such as a sealant layer, a gas barrier layer, an adhesive layer, a printing layer, etc. can be laminated on the stretched film to form a laminated film. Among them, it is preferable to laminate a sealant layer made of an olefin resin on the layer made of the stretched film, and the obtained laminated film has the effect of being easy to recycle. The stretched film can be used as various packaging materials. For example, the packaging material formed of the above laminated film can be suitably used for packaging any packaging object such as food, clothing, and miscellaneous goods.

Examples

[0054] Hereinafter, as examples, the present invention will be described more specifically, but the present invention is not limited only to the examples. Hereinafter, for propylene-based polymers, those satisfying 0.4 < (Mw / Mn)·γ < 10 will be referred to as "polypropylene", and those not satisfying it will be referred to as "propylene-based polymers".

[0055] [Measurement methods for physical properties] The physical property measurements and analytical values of each item in the examples were in accordance with the following methods.

[0056] (1) MFR (unit: g / 10 min) Using pellets of polypropylene or propylene-based polymers, the MFR was measured under the following conditions in accordance with Table 1 of Appendix A and Condition M of JIS K7210:1999. Test temperature: 230 °C, nominal load: 2.16 kg Die shape: diameter 2.095 mm, length 8.000 mm

[0057] (2) GPC measurement GPC measurement was performed using pellets of polypropylene or a propylene-based polymer to determine the number average molecular weight Mn, weight average molecular weight Mw, Mw / Mn, and γ. The details of the measuring equipment are as follows. Apparatus: GPC (ALC / GPC, 150C) manufactured by Waters Detector; MIRAN, 1A, IR detector manufactured by FOXBORO (measurement wavelength: 3.42 μm) Column: AD806M / S (3 pieces) manufactured by Showa Denko Mobile phase solvent; o-dichlorobenzene (ODCB) Measurement temperature; 140 °C Flow rate; 1.0 mL / min Injection volume: 0.2 mL

[0058] The sample was prepared by using pellets of polypropylene or a propylene-based polymer and ODCB (containing 0.5 mg / mL of dibutylhydroxytoluene (BHT)) to prepare a 1 mg / mL solution, which was dissolved at 140 °C for about 1 hour. Note that the baseline and interval of the obtained chromatogram were performed as shown in Figure 1. In addition, the conversion from retention volume to molecular weight obtained by GPC measurement was performed using a calibration curve prepared in advance with standard polystyrene. The standard polystyrene used is the following brand manufactured by Tosoh Corporation. Brand: F380, F288, F128, F80, F40, F20, F10, F4, F1, A5000, A2500, A1000 A calibration curve was prepared by injecting 0.2 mL of a solution dissolved in ODCB (containing 0.5 mg / mL of BHT) so that each would be 0.5 mg / mL. The calibration curve used a cubic equation obtained by approximating with the least squares method. For the conversion to molecular weight, a universal calibration curve was used with reference to "Size Exclusion Chromatography" by Sadao Mori (Kyoritsu Shuppan). The viscosity formula used for the conversion to molecular weight ([η]=K×M α ) used the following values. (A) When creating a calibration curve using standard polystyrene PS: K = 1.38×10 -4 , α = 0.70 (B) When measuring a sample of polypropylene or a propylene-based polymer PP: K = 1.03×10 -4 , α = 0.78

[0059] γ is the value obtained by multiplying by 100 the value obtained by subtracting from 1 the integrated value up to a molecular weight (M) of 1,000,000 (Log(M)=6.0) in the integrated molecular weight distribution curve (normalized to 1 for the total amount) obtained by GPC measurement. An example of how to obtain γ is shown in Figure 2.

[0060] (3) 13 Isotactic mesopentad fraction (mmmm) measured by C-NMR Using pellets of polypropylene or a propylene-based polymer, the isotactic mesopentad fraction (mmmm) was determined as follows. ( 13 Measurement method of C-NMR) [Sample preparation and measurement conditions] 200 mg of the sample was placed in an NMR sample tube with an inner diameter of 10 mmφ together with 2.4 mL of o-dichlorobenzene / deuterated bromobenzene (C 6 D 5 Br)=4 / 1 (volume ratio) and hexamethyldisiloxane as a reference substance for chemical shift, and uniformly dissolved with a block heater at 150°C. NMR measurement was performed using a Bruker Biospin AV400 type NMR apparatus equipped with a 10 mmφ cryoprobe. 13 The measurement conditions for C-NMR were a sample temperature of 120°C, a pulse angle of 90°, a pulse interval of 15 seconds, and an integration number of 1024 times, and the measurement was carried out by the broad-band decoupling method. The chemical shift was set to 1.98 ppm for the C signal of hexamethyldisiloxane, and the chemical shifts of the signals due to the other C were based on this. 13 13

[0061] [Calculation method for isotactic mesopentad fraction (mmmm)] The isotactic mesopentad fraction (mmmm) of a pentad of propylene units was determined by substituting the integrated intensity of the C signal measured by 13C-NMR into the following formula (1). 13 13 mmmm (%) = (I mm - 2×I mrrm ) × 100 / (I mm + 3×I mrrm ) ··· Formula (1) Here, I mm represents the integrated intensity of the C signal assigned to the bonding pattern of mm for a triad of propylene units, and is the integrated intensity of the C signal in the range of chemical shifts from 23.6 to 21.1 ppm. I 13 13 mrrm represents the integrated intensity of the C signal assigned to the bonding pattern of mrrm for a pentad of propylene units, and is the integrated intensity of the C signal in the range of chemical shifts from 19.9 to 19.7 ppm. 13 13

[0062] (4) Film thickness For the biaxially stretched films of Examples 1 to 5 and Comparative Examples 1 to 5, the film thickness was measured using ID-SX2 manufactured by Mitutoyo Corporation.

[0063] (5) Gloss (%) For the biaxially stretched films of Examples 1 to 5 and Comparative Examples 1 to 5, in accordance with JIS Z8741:1997, the gloss of the film was measured at an incident angle of 60° using a GLOSS meter Gloss Meter VG2000 manufactured by Nippon Denshoku Industries Co., Ltd.

[0064] (6) Haze (%) For the biaxially stretched films of Examples 1 to 5 and Comparative Examples 1 to 5, the haze of the films was measured in accordance with JIS K7136:2000.

[0065] (7) Young's modulus (tensile elastic modulus) (MPa) For the biaxially stretched films of Examples 1 to 5 and Comparative Examples 1 to 5, after conditioning for 24 hours in an environment of 23°C and 50% RH in accordance with the method described in JIS K7127 (1999) "Plastics - Test methods for tensile properties - Part 3: Test conditions for films and sheets", strip-shaped test pieces with a length of 150 mm and a width of 15 mm were cut out for each of the MD direction and the TD direction. The Young's modulus (tensile elastic modulus) of the films in the MD direction and the TD direction was measured with the chuck distance of the tensile testing machine being 100 mm and the tensile speed being 1 mm / min. The larger the Young's modulus, the better the rigidity. The Young's modulus was judged according to the following criteria. ◎: The Young's modulus in the MD direction is 2.5 GPa or more and the Young's modulus in the TD direction is 6.5 GPa or more, and the rigidity of the biaxially stretched film is extremely excellent. ○: The Young's modulus in the MD direction is 2.2 GPa or more and the Young's modulus in the TD direction is 5.6 GPa or more and less than 6.5 GPa, and the rigidity of the biaxially stretched film is excellent. ×: The Young's modulus in the TD direction is 5.0 GPa or more and less than 5.6 GPa, and the rigidity of the biaxially stretched film is inferior. ××: The Young's modulus in the TD direction is less than 5.0 GPa, and the rigidity of the biaxially stretched film is significantly inferior.

[0066] (8) Heat shrinkage rate (%) For the biaxially stretched films of Examples 1 to 5 and Comparative Examples 1 to 5, the heat shrinkage rate was measured by the following method in accordance with JIS K6782. The film was cut into pieces with a width of 20 mm and a length of 200 mm in each of the MD direction and the TD direction, and left standing in a hot air oven at 150°C for 30 minutes for heating. The length immediately after heating was measured, and the ratio of the shrunk length to the original length was taken as the heat shrinkage rate. The smaller the obtained value, the lower the heat shrinkage rate, which means excellent heat resistance and dimensional stability during heating. The heat shrinkage rate was judged according to the following criteria. ◎: The heat shrinkage rate in the MD direction is 0 - 3.0% and the heat shrinkage rate in the TD direction is 0 - 1.5%, and the heat shrinkage rate of the biaxially stretched film is extremely excellent. ○: The heat shrinkage rate in the MD direction is 0 - 3.5% and the heat shrinkage rate in the TD direction is over 1.5 - 5.0%, and the heat shrinkage rate of the biaxially stretched film is excellent. ×: The heat shrinkage rate in the MD direction is over 3.5 - 5.0% or the heat shrinkage rate in the TD direction is over 5.0 - 10.0%, and the heat shrinkage rate of the biaxially stretched film is inferior. ××: The heat shrinkage rate in the MD direction is over 5.0% and the shrinkage rate in the TD direction is over 10.0%, and the heat shrinkage rate of the biaxially stretched film is significantly inferior.

[0067] [Resin used] The various resins used in the examples and comparative examples are described below. [Polypropylene] A - 1: Manufactured by Japan Polypropylene Corporation, trade name Novatec (registered trademark) PP, grade name EA9HD (propylene homopolymer by Ziegler - Natta catalyst, MFR (230°C, 2.16 kg load) = 0.4 g / 10 min). To 100 parts by weight, 0.048 parts by weight of 2,5 - dimethyl - 2,5 - di(t - butylperoxy)hexane, an organic peroxide, was added and mixed in a Henschel mixer. For the obtained mixture, using a "KZW - 25" twin - screw extruder manufactured by Techno - bel with a screw diameter of 25 mm, screw rotation speed: 300 rpm, kneading temperature: from the hopper, C1 / C2 / C3~C7 / head / die = 150°C / 180°C / 230°C / 230°C / 180°C, melt extrusion was carried out to obtain polypropylene pellets. The MFR of the obtained pellets was 10 g / 10 min. A-2: 100 parts by weight of Novatec (registered trademark) PP, grade FY6H (homopolymer of propylene by Ziegler-Natta catalyst, MFR (230 °C, 2.16 kg load) = 1.8 g / 10 min) manufactured by Japan Polypropylene Corporation was mixed with 0.025 parts by weight of 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, an organic peroxide, using a Henschel mixer. Polypropylene pellets were obtained in the same manner as polypropylene (A-1), except that the resulting mixture was used. The MFR of the obtained pellets was 11.8 g / 10 min. A-3: 100 parts by weight of Novatec (registered trademark) PP, grade FL1105F (homopolymer of propylene by Ziegler-Natta catalyst, MFR (230 °C, 2.16 kg load) = 3.5 g / 10 min) manufactured by Japan Polypropylene Corporation was mixed with 0.007 parts by weight of 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, an organic peroxide, using a Henschel mixer. Polypropylene pellets were obtained in the same manner as polypropylene (A-1), except that the resulting mixture was used. The MFR of the obtained pellets was 7.3 g / 10 min. A-4: 100 parts by weight of Novatec (registered trademark) PP, grade FL1105F (homopolymer of propylene by Ziegler-Natta catalyst, MFR (230 °C, 2.16 kg load) = 3.5 g / 10 min) manufactured by Japan Polypropylene Corporation was mixed with 0.014 parts by weight of 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, an organic peroxide, using a Henschel mixer. Polypropylene pellets were obtained in the same manner as polypropylene (A-1), except that the resulting mixture was used. The MFR of the obtained pellets was 10.1 g / 10 min. A-5: 100 parts by weight of polypropylene manufactured by Japan Polypropylene Corporation, trade name Novatec (registered trademark) PP, grade name FL1105F (propylene homopolymer by Ziegler-Natta catalyst, MFR (230 °C, 2.16 kg load) = 3.5 g / 10 min) was mixed with 0.020 parts by weight of 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, an organic peroxide, using a Henschel mixer. Polypropylene pellets were obtained in the same manner as polypropylene (A-1), except that the resulting mixture was used. The MFR of the obtained pellets was 13.1 g / 10 min.

[0068] [Propylene-based polymer] B-1: Polypropylene manufactured by Japan Polypropylene Corporation, trade name Novatec (registered trademark) PP, grade name SA3D (propylene homopolymer by Ziegler-Natta catalyst, MFR (230 °C, 2.16 kg load) = 11 g / 10 min) B-2: Polypropylene manufactured by Japan Polypropylene Corporation, trade name Novatec (registered trademark) PP, grade name FL1105F (propylene homopolymer by Ziegler-Natta catalyst, MFR (230 °C, 2.16 kg load) = 3.5 g / 10 min) B-3: Polypropylene manufactured by Japan Polypropylene Corporation, trade name Novatec (registered trademark) PP, grade name FL4 (propylene homopolymer by Ziegler-Natta catalyst, MFR (230 °C, 2.16 kg load) = 4.2 g / 10 min) B-4: Polypropylene manufactured by Japan Polypropylene Corporation, trade name Novatec (registered trademark) PP, grade name FL203D (propylene homopolymer by Ziegler-Natta catalyst, MFR (230 °C, 2.16 kg load) = 3.0 g / 10 min) B-5: 100 parts by weight of polypropylene homopolymer manufactured by Japan Polypropylene Corporation, trade name Novatec (registered trademark) PP, grade name FL1105F (propylene homopolymer by Ziegler-Natta catalyst, MFR (230 °C, 2.16 kg load) = 3.5 g / 10 min) was mixed with 0.003 parts by weight of 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, an organic peroxide, using a Henschel mixer. Pellets of the propylene-based polymer were obtained in the same manner as polypropylene (A-1), except that the resulting mixture was used. The MFR of the obtained pellets was 5.2 g / 10 min.

[0069] Example 1 Using a three-layer co-extrusion machine, polypropylene (A-1) was introduced into each layer and melt-extruded at a resin temperature of 240 °C for each layer, followed by rapid cooling with a cooling roll at 30 °C to produce a one-type three-layer unstretched film. For the obtained unstretched film, a biaxially stretched film was obtained using a biaxially stretched film forming machine (tenter) manufactured by Mitsubishi Heavy Industries, Ltd. with the roll temperature adjusted to 110 °C. The extrusion conditions, stretching conditions, and the thickness of the biaxially stretched film are as follows. Extrusion conditions Extrusion temperature: 240 °C, die width: 300 mm, lip opening: 2.0 mm, cooling roll temperature: 30 °C, cooling roll speed: 3 m / min Stretching conditions Stretching roll temperature: 110 °C, stretching ratio in the MD direction: 5 times, stretching ratio in the TD direction: 8 times, take-up speed: 15 m / min, tenter chamber temperature: preheating, stretching, and heat setting in all three zones at 165 °C Film thickness Total thickness 20 μm. Among them, the thicknesses of the first layer and the third layer are each 2 μm.

[0070] Example 2 In Example 1, polypropylene (A-1) was changed to polypropylene (A-2) to obtain the biaxially stretched film of Example 2.

[0071] Example 3 In Example 1, polypropylene (A-1) was changed to polypropylene (A-3) to obtain the biaxially stretched film of Example 3.

[0072] Example 4 In Example 1, polypropylene (A-1) was changed to polypropylene (A-4) to obtain the biaxially stretched film of Example 4.

[0073] Example 5 In Example 1, polypropylene (A-1) was changed to polypropylene (A-5) to obtain the biaxially stretched film of Example 5.

[0074] Comparative Example 1 In Example 1, polypropylene (A-1) was changed to propylene-based polymer (B-1) to obtain the biaxially stretched film of Comparative Example 1.

[0075] Comparative Example 2 In Example 1, polypropylene (A-1) was changed to propylene-based polymer (B-2) to obtain the biaxially stretched film of Comparative Example 2.

[0076] Comparative Example 3 In Example 1, polypropylene (A-1) was changed to propylene-based polymer (B-3) to obtain the biaxially stretched film of Comparative Example 3.

[0077] Comparative Example 4 In Example 1, polypropylene (A-1) was changed to propylene-based polymer (B-4) to obtain the biaxially stretched film of Comparative Example 4.

[0078] Comparative Example 5 In Example 1, polypropylene (A-1) was changed to propylene-based polymer (B-5) to obtain the biaxially stretched film of Comparative Example 5.

[0079] The physical properties of the polypropylene and propylene-based polymers used in the examples and comparative examples, and the biaxially stretched films obtained therefrom are shown in Table 1.

[0080] [Table 1]

[0081] [Consideration of Results of Examples and Comparative Examples] From Table 1, it can be seen that the biaxially stretched films of Examples 1 to 5 formed from polypropylene satisfying 0.4 < (Mw / Mn)·γ < 10 have an extremely high Young's modulus in the TD direction, small heat shrinkage rates in both the MD and TD directions, and excellent rigidity and heat resistance. On the other hand, the biaxially stretched films of Comparative Examples 1 to 5 formed from a propylene-based polymer with (Mw / Mn)·γ of 10 or more were inferior in Young's modulus in the TD direction and heat shrinkage rates in the MD and TD directions. [Industrial Applicability]

[0082] The polypropylene composition can be suitably used as a raw material for stretched films.

Claims

1. A polypropylene composition for a stretched film, comprising a polypropylene selected from the group consisting of a propylene homopolymer and a propylene-ethylene copolymer containing 1.0% by weight or less of units derived from ethylene, wherein the polypropylene satisfies the following requirement (1): (1) The molecular weight distribution Mw / Mn as determined by GPC and the amount γ (wt %) of components having a molecular weight of 1,000,000 or more as determined by GPC satisfy 0.4<(Mw / Mn)·γ<10.

2. The polypropylene composition for stretched films according to claim 1, wherein the polypropylene satisfies the following requirement (2): (2) The melt flow rate, measured in accordance with JIS K7210 at 230° C. under a load of 2.16 kg, is 3.5 to 20 g / 10 min.

3. The polypropylene composition for stretched films according to claim 2, wherein the polypropylene satisfies the following requirement (3): (3) １３ The isotactic mesopentad fraction (mmmm) measured by C-NMR is 95% or more.

4. The polypropylene composition for stretched films according to claim 3, wherein the polypropylene satisfies the following requirement (4): (4) Mw / Mn satisfies 2.0 < Mw / Mn < 5.

0.

5. The polypropylene composition for stretched films according to claim 4, wherein the polypropylene satisfies the following requirement (5): (5) γ is less than 5.0% by weight.

6. A stretched film comprising the polypropylene composition for stretched films according to any one of claims 1 to 5.

7. The stretched film according to claim 6, wherein the heat shrinkage of the stretched film measured in an environment of 150°C for 30 minutes in accordance with JIS K6782 is 0 to 3.5% in the MD direction and 0 to 5.0% in the TD direction.

8. 8. The stretched film according to claim 7, wherein the Young's modulus of the stretched film in the TD direction, measured in accordance with JIS K7127, is 5.6 GPa or more.

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