Polypropylene composition for stretch film and stretch film comprising the same

Abstract

Provided are a polypropylene composition that can provide a stretched film having high heat resistance and rigidity, and a stretched film including the same. A stretched film-use polypropylene composition includes 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, the polypropylene satisfying the following requirement (1).(1) The amount γ (%) by weight of a component having a molecular weight of 1 million or more, as determined using GPC, and the molecular weight distribution Mw / Mn, as determined using GPC, satisfy 0.4 < (Mw / Mn) · γ < 10.

Description

Technical Field

[0001] This invention relates to polypropylene compositions for stretch films and stretch films comprising the same. Background Technology

[0002] Polypropylene resin stretch films are widely used in a wide range of applications, including electrical insulation, surface protection, and packaging for various commodities such as food and industrial components. However, traditional polypropylene resin stretch films have been noted for their low heat resistance. Compared to other materials, especially polyethylene terephthalate (PET) films, polypropylene resin stretch films exhibit significantly poorer heat resistance, with a substantial shrinkage rate of several tens of percent at 150°C. Furthermore, due to their low rigidity, the materials are classified according to their intended applications.

[0003] Various techniques have been proposed to improve the heat resistance, mechanical properties, and other physical properties of biaxially oriented polypropylene films. For example, claim 1 of Patent Document 1 discloses a "propylene polymer having a rigidity-processability balance that is very advantageous for applications including biaxially oriented polypropylene films, particularly for film applications."

[0004] Furthermore, in claim 1 of Patent Document 2, as a biaxially oriented laminated polypropylene film with high heat resistance and rigidity, it is disclosed that: "A biaxially oriented stretched polypropylene film, characterized in that the polypropylene resin constituting the film, comprising a fully homopolymerized polypropylene resin without copolymer components and / or a polypropylene resin copolymerized with ethylene and / or α-olefins having 4 or more carbon atoms, satisfies the following conditions 1) to 4), and the lower limit of the planar orientation coefficient of the film is 0.0125, and the transverse tensile modulus of elasticity of the film is 5.1 GPa or higher."

[0005] 1) The lower limit of the percentage of the racemic pentaunit group is 96%.

[0006] 2) The upper limit for the amount of comonomers other than propylene is 0.1 mol.

[0007] 3) The mass-average molecular weight (Mw) / number-average molecular weight (Mn) is above 3.0 and below 5.4.

[0008] 4) The melt flow rate (MFR) measured at 230℃ and 2.16 kgf is greater than 6.5 g / 10 min and less than 9.0 g / 10 min.

[0009] Existing technical documents

[0010] Patent documents

[0011] Patent Document 1: Japanese Patent Publication No. 2008-540815

[0012] Patent Document 2: Japanese Patent Application Publication No. 2023-17015 Summary of the Invention

[0013] The problem the invention aims to solve

[0014] The heat resistance of the stretched films obtained from the polypropylene resins in Patent Documents 1 and 2 is not sufficient. For example, they cannot maintain their shape at high temperatures above 150°C, and printed text and patterns are prone to deformation and wrinkling. Furthermore, Patent Documents 1 and 2 do not adequately investigate the structure and properties of preferred polypropylene or polypropylene compositions used to improve heat resistance. The object of this invention is to provide a polypropylene composition that provides a stretched film with high heat resistance and rigidity, and a stretched film comprising the same.

[0015] Solution for solving the problem

[0016] The inventors conducted in-depth research and found that, for polypropylene, by setting the relationship between the molecular weight distribution Mw / Mn and the content of high molecular weight components within a specified range, a tensile film with excellent heat resistance and rigidity can be obtained, thus completing the present invention. The present invention relates to the following [1]~[8].

[0017] [1] A polypropylene composition for stretching film comprising polypropylene selected from the group consisting of propylene homopolymer and propylene-ethylene copolymer, wherein the propylene-ethylene copolymer contains less than 1.0% by weight of ethylene-derived units, wherein the polypropylene satisfies the following requirement (1).

[0018] (1) The molecular weight distribution Mw / Mn obtained by GPC and the amount γ (weight%) of components with a molecular weight of more than 1 million obtained by GPC satisfy 0.4 < (Mw / Mn)·γ < 10.

[0019] [2] The polypropylene composition for stretching film according to [1], wherein the polypropylene satisfies the following requirement (2).

[0020] (2) The melt flow rate measured at 230℃ and 2.16kg load based on JIS K7210 was 3.5~20g / 10min.

[0021] [3] The polypropylene composition for stretching film according to [1] or [2], wherein the polypropylene satisfies the following requirement (3).

[0022] (3)Use 13 The percentage (mmmm) of isotactic five-unit groups determined by C-NMR is over 95%.

[0023] [4] The polypropylene composition for stretching film according to any one of [1] to [3], wherein the polypropylene satisfies the following requirement (4).

[0024] (4) Mw / Mn satisfies 2.0 < Mw / Mn < 5.0.

[0025] [5] A polypropylene composition for stretching film according to any one of [1] to [4], wherein the polypropylene satisfies the following requirement (5).

[0026] (5) γ is less than 5.0% by weight.

[0027] [6] A stretching film comprising any one of the stretching film polypropylene compositions described in any one of [1] to [5].

[0028] [7] According to the stretching film described in [6], the heat shrinkage rate of the stretching film, measured based on JIS K6782 at 150°C for 30 minutes, is 0~3.5% in the MD direction and 0~5.0% in the TD direction.

[0029] [8] The stretched film according to [6] or [7], wherein the Young's modulus of the stretched film, as determined based on JIS K7127, is 5.6 GPa or more in the TD direction.

[0030] The effects of the invention

[0031] The polypropylene compositions used in stretch films of methods 1-5 exhibit high heat resistance and rigidity. The stretch films of methods 6-8 also exhibit high heat resistance and rigidity, and can maintain their shape even at high temperatures, thus they are less prone to wrinkling, and the text, patterns, etc. printed on them will not deform. Attached Figure Description

[0032] Figure 1 It is a graph that illustrates the baseline and interval of the chromatogram in GPC determination.

[0033] Figure 2 This is a graph showing an example of molecular weight distribution curves and cumulative molecular weight distribution curves.

[0034] Figure 3 This is a graph showing the molecular weight distribution curve of polypropylene in Example 1.

[0035] Figure 4 This is a graph showing the molecular weight distribution curve of the propylene polymer of Comparative Example 2.

[0036] Figure 5 Yes Figure 3 and Figure 4 The graph is obtained through comparison. Detailed Implementation

[0037] The polypropylene composition for stretching films of the present invention comprises polypropylene selected from the group consisting of propylene homopolymer and propylene-ethylene copolymer, wherein the propylene-ethylene copolymer contains less than 1.0% by weight of ethylene-derived units, and the polypropylene satisfies the following requirement (1).

[0038] (1) The molecular weight distribution Mw / Mn obtained by GPC and the amount γ (weight%) of components with a molecular weight of more than 1 million obtained by GPC satisfy 0.4 < (Mw / Mn)·γ < 10.

[0039] By using a polypropylene composition for stretching films, it is possible to obtain stretching films with high heat resistance and rigidity.

[0040] In this invention, propylene-based polymers refer to propylene homopolymers or propylene-ethylene copolymers, wherein the propylene-ethylene copolymers contain less than 1.0% by weight of ethylene-derived units. Furthermore, in this invention, polypropylene refers to a propylene-based polymer that satisfies the above requirement (1).

[0041] [Polypropylene Composition]

[0042] The polypropylene composition comprises polypropylene selected from the group consisting of propylene homopolymers and propylene-ethylene copolymers containing less than 1.0% by weight of ethylene-derived units. In this invention, the proportion of ethylene-derived units in the propylene-ethylene copolymer is a value calculated based on the following formula.

[0043] The percentage of units derived from ethylene (%) = (Weight of units derived from ethylene / (Weight of units derived from propylene + Weight of units derived from ethylene)) × 100

[0044] Both propylene homopolymers and propylene-ethylene copolymers can be used alone or in combination of two or more.

[0045] The polypropylene composition may be composed of either propylene homopolymer or propylene-ethylene copolymer, or it may be composed of both propylene homopolymer and propylene-ethylene copolymer, or it may be composed of propylene homopolymer and / or propylene-ethylene copolymer as the main components and other components as minor components.

[0046] In this invention, "comprising...as a main component" means that the total content of propylene homopolymer and propylene-ethylene copolymer in 100% by weight of the polypropylene composition is 50% by weight or more. From the viewpoint of suppressing poor appearance caused by minor components or maintaining the heat resistance and rigidity of the film, the total content of propylene homopolymer and 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 of propylene homopolymer and propylene-ethylene copolymer is 100% by weight.

[0047] <Polypropylene>

[0048] From the viewpoint of heat resistance and rigidity of the stretched film, polypropylene is preferably a propylene homopolymer. When the polypropylene is a propylene-ethylene copolymer, the content of ethylene-derived units is 1.0% by weight or less, preferably 0.5% by weight or less, and more preferably 0.3% by weight or less. Within the above range, high rigidity of the stretched film can be maintained.

[0049] In polypropylene, other monomers such as α-olefins with more than 4 carbon atoms and non-conjugated dienes can be polymerized without prejudice to the purpose of this invention.

[0050] Polypropylene meets the following requirement (1).

[0051] (1) The molecular weight distribution Mw / Mn obtained by GPC and the amount γ (weight%) of components with a molecular weight of more than 1 million obtained by GPC satisfy 0.4 < (Mw / Mn)·γ < 10.

[0052] By setting the value to 0.4 < (Mw / Mn)·γ < 10, a stretched film with high rigidity and low thermal shrinkage can be obtained. From the viewpoint of obtaining a stretched film with high rigidity and low thermal shrinkage, it is preferable that (Mw / Mn)·γ < 7, more preferably (Mw / Mn)·γ < 5, and even more preferably (Mw / Mn)·γ < 4.

[0053] Furthermore, from the viewpoint of the formability of the film during forming, such as fracture and uneven elongation, (Mw / Mn)·γ>0.4 is preferred, (Mw / Mn)·γ>0.6 is more preferred, and (Mw / Mn)·γ≥1.0 is even more preferred.

[0054] The values ​​of Mn, Mw, and γ defined above are all obtained using gel permeation chromatography (GPC). Details of the determination methods and equipment are described in the examples.

[0055] Here, Mn and Mw are the number-average molecular weight and weight-average molecular weight of polypropylene determined by GPC, and Mw / Mn can be used as an indicator 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, more generally, by adding chain transfer agents such as hydrogen during propylene polymerization. Furthermore, they can be controlled by changing the ratio of the metallocene complexes used, or, when using two or more complexes. Additionally, Mn, Mw, and Mw / Mn can also be adjusted by appropriately degrading higher molecular weight propylene polymers.

[0056] γ is the amount (in weight percent) of the component with a molecular weight of 1 million or more in 100% of polypropylene, as determined by GPC. Specifically, γ is the value obtained by subtracting the integral value from 1 (normalized to 1) of the cumulative molecular weight distribution curve obtained by GPC, up to 1 million (Log(M) = 6.0), and then multiplying the result by 100. An example of how γ is determined is shown below. Figure 2 Besides being adjustable through factors such as the selection, combination, and ratio of catalysts, γ can also be adjusted by controlling prepolymerization conditions, the amount of hydrogen during polymerization, and so on, and by conducting polymerization. Additionally, γ can also be adjusted by appropriately degrading higher molecular weight propylene polymers.

[0057] The property 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 of the biaxial stretching machine is improved, thus preventing defects during film production and improving film quality such as thickness accuracy. In addition, by satisfying (Mw / Mn)·γ < 10, the large viscosity caused by the polymer molecules with a molecular weight of 1 million or more is suppressed, and the presence of a large number of molecules with similar molecular weights can suppress entropy-induced thermal shrinkage, resulting in a stretched film that exhibits low thermal shrinkage.

[0058] Polypropylene preferably meets the following requirements (2) to (5).

[0059] (2) The melt flow rate measured at 230℃ and 2.16kg load based on JIS K7210 was 3.5~20g / 10min.

[0060] The melt flow rate (MFR) of polypropylene, measured according to JIS K7210:1999 at 230°C and 2.16 kg load, 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. Within these ranges, the formability when forming a film becomes good.

[0061] 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 chain transfer agents such as hydrogen during polymerization. Alternatively, the melt flow rate (MFR) can also be adjusted by appropriately degrading higher molecular weight propylene-based polymers.

[0062] (3)Use 13 The percentage (mmmm) of isotactic five-unit groups determined by C-NMR is over 95%.

[0063] Polypropylene, utilization 13 The percentage of isotactic pentads (mmmm) measured by C-NMR is preferably 95% or more, more preferably 96% or more, and even more preferably 97% or more. Additionally, mmmm can be 95-96%. When it is within the above range, the rigidity of the film becomes good.

[0064] In this specification, the percentage of isotactic five-unit groups (mmmm) is a value determined by the following method.

[0065] ( 13 C-NMR determination method)

[0066] [Sample preparation and measurement conditions]

[0067] 200 mg of the sample was added to an NMR tube with an inner diameter of 10 mm φ along with 2.4 mL of o-dichlorobenzene / deuterated brominated benzene (C6D5Br) = 4 / 1 (volume ratio) and hexamethyldisiloxane as the chemical shift reference. The mixture was then dissolved until homogeneous using a heating block at 150 °C.

[0068] NMR measurements were performed using a Bulker BioSpin AV400 NMR apparatus equipped with a 10 mm φ cryopreservation probe.

[0069] 13 The C-NMR measurement conditions were set as follows: sample temperature 120℃, pulse angle 90°, pulse interval 15 seconds, and cumulative number of pulses 1024. The measurement was carried out using the broadband decoupling method.

[0070] Regarding chemical shift, hexamethyldisiloxane... 13 The C signal was set to 1.98 ppm, and the others... 13The chemical shift of the C signal is based on this.

[0071] [Calculation method for the percentage of isomorphic five-element units (mmmm)]

[0072] The percentage (mmmm) of isotactic pentads of propylene units can be obtained by utilizing... 13 Measured by C-NMR. 13 The integral intensity of the C signal is obtained by substituting it into the following equation (1).

[0073] mmmm(%)=(I mm -2×I mrrm )×100 / (I mm +3×I mrrm Equation (1)

[0074] Here, I mm This indicates that the propylene unit triplet belongs to the bonding mode of mm. 13 The integrated intensity of the C signal, as a chemical shift in the range of 23.6–21.1 ppm. 13 The integral intensity of the C signal (hereinafter referred to as "I") 23.6~21.1 Use “” to calculate.

[0075] I mrrm This indicates that the propylene unit pentad belongs to the MRRM bonding mode. 13 The integral intensity of the C signal is I. 19.9~19.7 The value shown.

[0076] The spectral attribution can be found in the following: Polymer Journal, Vol. 16, p. 717 (1984), Asakura Shoten; Macromolecules, Vol. 8, p. 687 (1975); Polymer, Vol. 30, p. 1350 (1989).

[0077] Although the chemical shift range may vary due to factors such as the molecular weight of the polymer, the region is relatively easy to identify.

[0078] (4) Mw / Mn satisfies 2.0 < Mw / Mn < 5.0.

[0079] The Mw / Mn ratio of polypropylene, as determined by GPC, 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 indicator of molecular weight distribution; a smaller value means a narrower molecular weight distribution. By reducing Mw / Mn and selecting an appropriate value, film stretching can be performed uniformly and stably. When Mw / Mn < 5.0, the uniformity of molecular chain length increases, and the external force applied through stretching is fully propagated to the material, thus making it easier to improve the rigidity of the molded product. Furthermore, when Mw / Mn > 2.0, formability becomes good, thus making it easier to improve the thickness accuracy and surface properties during film manufacturing.

[0080] (5) γ is less than 5.0% by weight.

[0081] The amount of polypropylene with a molecular weight of 1 million or more as determined by GPC, γ, 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. Furthermore, γ is preferably 0.01% by weight or more, more preferably 0.05% by weight or more, even more preferably greater than 0.1% by weight, and particularly preferably 0.4% by weight or more. When within the above range, the tensile tension of polypropylene is low, which can suppress the load on the molding apparatus. Furthermore, when the molecular chain orientation or crystal structure such as lamellars rearranges during stretching, uniform and stable molding is possible, easily improving the rigidity of the film. In addition, in advanced structures, shrinkage is less likely to occur during heating.

[0082] <Manufacturing Method of Polypropylene>

[0083] Propylene polymers can preferably be obtained by polymerizing propylene using catalysts such as Ziegler-Natta catalysts or metallocene catalysts, or by copolymerizing propylene with a small amount of ethylene. When the propylene polymer obtained in this way meets the above requirement (1), the propylene polymer can be used as the polypropylene of the present invention.

[0084] As an example of a Ziegler-Natta catalyst, a solid component (a) may be included, containing magnesium, titanium, halogens, and an internal electron-donating compound selected from phthalate compounds, diether compounds, and succinate compounds. In addition to the aforementioned solid component (a), the Ziegler-Natta catalyst may, as needed, include an organoaluminum compound (b) and an external electron-donating compound (c). Furthermore, the solid component (a) may be contacted with alkoxysilanes or alkenyl silane compounds.

[0085] Examples of metallocene catalysts include metallocene compounds and at least one compound selected from organometallic compounds, organoalumina compounds, and compounds capable of reacting with metallocene compounds to form ion pairs, as well as a particulate support used as needed. Among these, metallocene catalysts capable of stereoregular polymerization, such as isotropic or synisotropic structures, are preferred.

[0086] As for the polymerization method of propylene-based polymers, well-known methods can be used. For example, methods of polymerization in inert solvents such as hexane, heptane, toluene, and xylene can be listed; methods of polymerization in liquid monomers can be listed; methods of polymerization in the gas phase by adding a catalyst to the monomer gas; or methods of polymerization by combining these methods.

[0087] The polymerization of propylene polymers can be a single-stage polymerization using one reactor, or a multi-stage polymerization using multiple reactors. In multi-stage polymerization, the polymerization conditions in each reactor can be the same or different. The reactor can be a reactor with gradients in monomer concentration and polymerization conditions.

[0088] The molecular weight of propylene polymers can also be adjusted using chain transfer agents such as hydrogen.

[0089] For the obtained propylene polymers, when (Mw / Mn)·γ ≥ 10, the propylene polymers can be degraded using organic peroxides to adjust Mw / Mn and γ, thereby satisfying 0.4 < (Mw / Mn)·γ < 10. In particular, through degradation treatment, the relatively high molecular weight components (molecules) constituting the propylene polymer undergo molecular breakage, thus reducing γ and satisfying 0.4 < (Mw / Mn)·γ < 10.

[0090] When the obtained propylene polymer satisfies 0.4 < (Mw / Mn)·γ < 10, degradation treatment with organic peroxides is not necessary, but the above degradation treatment can be performed in order to set the value of (Mw / Mn)·γ to a more preferred range and further improve the high rigidity and low thermal shrinkage of the stretched film.

[0091] In addition, when (Mw / Mn)·γ≤0.4, the entire propylene polymer can be adjusted to satisfy 0.4<(Mw / Mn)·γ<10 by mixing it with separately manufactured propylene polymers with large Mw / Mn or γ and satisfying (Mw / Mn)·γ≥10.

[0092] The propylene polymer before degradation treatment is not particularly restricted as long as it is a propylene homopolymer or a propylene-ethylene copolymer containing less than 1.0% by weight of ethylene-derived units. The Mw / Mn ratio is preferably 5 to 20, more preferably 6 to 15. In addition, the melt flow rate (MFR) measured based on JIS K7210:1999 at 230°C and 2.16 kg load is preferably 0.1 to 10 g / 10 min, more preferably 0.2 to 5 g / 10 min.

[0093] Examples of organic peroxides include benzoyl peroxide, di-tert-butyl peroxide, dicumyl peroxide, tert-butylisocumyl peroxide, 1,1-bis-(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-butylperoxy)cyclohexane, 2,2-bis(tert-butylperoxy)octane, 4,4-bis(tert-butylperoxy)valerate, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, and 2,5 Dimethyl-2,5-di(benzoylperoxy)hexane, 2,5-dimethyl-2,5-di(tert-butylperoxy)-3-hexyne, 1,3-bis(tert-butylperoxyisopropyl)benzene, α,α´-bis(tert-butylperoxyisopropyl)benzene, tert-butyl-hydrogen peroxide, cumene-hydrogen peroxide, lauroyl peroxide, di-tert-butyl dipperoxyphthalate, tert-butyl maleic acid peroxide, tert-butyl peroxyisopropyl carbonate, isopropyl percarbonate, etc.

[0094] These are not limited to one type, and two or more types can be used in combination. Among these, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di(tert-butylperoxy)-3-hexyne, 1,3-bis(tert-butylperoxyisopropyl)benzene or α,α´-bis(tert-butylperoxyisopropyl)benzene are preferred.

[0095] The degradation treatment can be performed by heating and mixing 0.005 to 1.0 parts by weight of organic peroxide with 100 parts by weight of the propylene polymer at a temperature above the melt temperature of the polymer, for example, 180 to 300°C. Known methods can be used, and it is particularly preferred to carry out the process in an extruder. Furthermore, to ensure uniform dispersion of the organic peroxide in the propylene polymer, the two materials can be pre-mixed using a Henschel mixer, belt mixer, or similar mixer before heating and mixing. Moreover, to improve the dispersibility of the organic peroxide, a mixture obtained by mixing the organic peroxide with a suitable medium can be used.

[0096] The resulting polypropylene can be processed into granules, powders, or other forms using known methods.

[0097] <Polypropylene Composition>

[0098] The polypropylene composition may contain only the polypropylene described above, or it may contain the polypropylene described above and other components.

[0099] Other components may include additives and polymers other than polypropylene mentioned above. Examples of additives include antioxidants, lubricants, antistatic agents, anti-blocking agents, UV absorbers, light stabilizers, chlorine absorbers, heat stabilizers, antifogging agents, flame retardants, dispersants, copper toxicity preventers, neutralizers, plasticizers, anti-bubble agents, crosslinking agents, peroxides, oil fillers, and pigments.

[0100] Examples of antioxidants include phenolic antioxidants and phosphite antioxidants. Examples of phenolic antioxidants include 2,6-di-tert-butyl-p-cresol (BHT), tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]methane (manufactured by BASF Japan, trade name "IRGANOX (registered trademark) 1010"), and octadecyl 3-(4'-hydroxy-3',5'-di-tert-butylphenyl)propionate (manufactured by BASF Japan, trade name "IRGANOX (registered trademark) 1076"). Examples of phosphite antioxidants include bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite and tris(2,4-di-tert-butylphenyl)phosphite.

[0101] Examples of lubricants include higher fatty acid amides and higher fatty acid esters.

[0102] Examples of antistatic agents include glycerides of fatty acids with 8 to 22 carbon atoms, sorbitol esters, and polyethylene glycol esters.

[0103] Examples of anti-blocking agents include silica, calcium carbonate, and talc.

[0104] Examples of compounds that can be used as ultraviolet absorbers include triazole compounds, benzophenone compounds, salicylates, cyanoacrylates, nickel chelates, and inorganic microparticles.

[0105] 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, trade name: Tinuvin (registered trademark) P), 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole (manufactured by Sumitomo Chemical Co., Ltd., trade name: SUMISORB (registered trademark) 340; manufactured by BASF Japan, trade name: Tinuvin (registered trademark) 399), and 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)benzotriazole (manufactured by Sumitomo Chemical Co., Ltd., trade name: SUMISORB). RB (registered trademark) 320; manufactured by BASF Japan, trade name: Tinuvin (registered trademark) 320), 2-(2'-hydroxy-3',5'-di-tert-pentylphenyl)benzotriazole (manufactured by Sumitomo Chemical Co., Ltd., trade name: SUMISORB (registered trademark) 350; manufactured by BASF Japan, trade name: Tinuvin (registered trademark) 328), 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole (manufactured by Sumitomo Chemical Co., Ltd., trade name: SUMISORB (registered trademark) 300; manufactured by BASF Japan, trade name: Tinuvin (registered trademark) 326), etc.

[0106] Examples of benzophenone-based ultraviolet absorbers include 2-hydroxy-4-methoxybenzophenone (manufactured by Sumitomo Chemical Co., Ltd., trade name: SUMISORB (registered trademark) 110) and 2-hydroxy-4-n-octyloxybenzophenone (manufactured by Sumitomo Chemical Co., Ltd., trade name: SUMISORB (registered trademark) 130).

[0107] Examples of salicylate-based ultraviolet absorbers include 4-tert-butylphenyl salicylate (manufactured by Shipro KaseiKaisha, Ltd., trade name: SEESORB 202).

[0108] Examples of cyanoacrylate-based ultraviolet absorbers include ethyl (3,3-diphenyl)cyanoacrylate (manufactured by Shipro Kasei Kaisha, Ltd., trade name: SEESORB 501).

[0109] Examples of nickel chelate-based ultraviolet absorbers include nickel dibutyldithiocarbamate (manufactured by Sumitomo Chemical Co., Ltd., trade name: Anchigen (registered trademark) NBC).

[0110] Examples of inorganic particulate ultraviolet absorbers include TiO2, ZnO2, and CeO2.

[0111] Examples of light stabilizers include sebacic acid esters, butanetetracarboxylic acid esters, succinic acid polyesters, and triazine compounds.

[0112] Examples of sebacate-type light stabilizers include bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate (manufactured by ADEKA Corporation, trade name: ADEKA STAB (registered trademark) LA-77; manufactured by BASF Japan Corporation, trade name: tinuvin (registered trademark) 770) and bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate (manufactured by BASF Japan Corporation, trade name: tinuvin (registered trademark) 765).

[0113] Examples of butanetetracarboxylic acid ester-type light stabilizers include tetrakis(2,2,6,6-tetramethyl-4-piperidinyl)-1,2,3,4-butanetetracarboxylic acid ester (manufactured by ADEKA Corporation, trade name: ADEKA STAB (registered trademark) LA-57), tetrakis(1,2,2,6,6-pentamethyl-4-piperidinyl)-1,2,3,4-butanetetracarboxylic acid ester (manufactured by ADEKA Corporation, trade name: ADEKA STAB (registered trademark) LA-52), and condensates of 1,2,3,4-butanetetracarboxylic acid with 2,2,6,6-tetramethyl-4-piperidinol and tridecanol (manufactured by ADEKA Corporation, trade name: ADEKA). STAB (registered trademark) LA-67), condensate of 1,2,3,4-butanetetracarboxylic acid with 1,2,2,6,6-pentamethyl-4-piperidinol and tridecanol (manufactured by ADEKA Co., Ltd., trade name: ADEKA STAB (registered trademark) LA-62), etc.

[0114] Examples of succinic acid polyester-type light stabilizers include condensation polymers of succinic acid and 1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidine.

[0115] Examples of triazine-type light stabilizers include N,N'-bis(3-aminopropyl)ethylenediamine·2,4-bis{N-butyl-N-(1,2,2,6,6-pentamethyl-4-piperidinyl)amino}-6-chloro-1,3,5-triazine condensate (manufactured by BASF Japan, trade name: Chimasorb (registered trademark) 199), poly{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl}{(2,2,6,6-tetramethyl-4-piperidinyl)... Examples of imino compounds include hexamethylene {(2,2,6,6-tetramethyl-4-piperidinyl)imino} (manufactured by BASF Japan, trade name: Chimasorb (registered trademark) 944), poly(6-morpholino-triazine-2,4-diyl) {(2,2,6,6-tetramethyl-4-piperidinyl)imino} hexamethylene {(2,2,6,6-tetramethyl-4-piperidinyl)imino} (manufactured by BASF Japan, trade name: Chimasorb (registered trademark) 3346), etc.

[0116] Other polymers include polypropylene resins other than the polypropylene of this invention, polyethylene, propylene-based or ethylene-based elastomers, etc.

[0117] Examples of propylene-based or ethylene-based elastomers include ethylene-α-olefin copolymers, binary random copolymers of propylene and α-olefins having 4 to 12 carbon atoms, and ternary random copolymers of propylene, ethylene, and α-olefins having 4 to 12 carbon atoms.

[0118] The additive content 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.

[0119] When a polypropylene composition contains additives or other polymers, the polypropylene can be mixed or melt-blended with the additives or other polymers to produce the polypropylene composition. Examples of mixing methods include mixing using a Henschel mixer, a V-type mixer, a belt mixer, and a drum mixer.

[0120] Examples of melt mixing methods include using single-screw extruders, multi-screw extruders, kneaders, Banbury mixers, and other mixing mills. The resulting polypropylene compositions can then be formulated into granules, powders, or other forms using known methods.

[0121] Additives can be added during the polymerization of propylene-based polymers, or simultaneously or separately with organic peroxides during the degradation treatment of propylene-based polymers, or added to the degraded polypropylene. Additionally, other polymers are typically added to the degraded polypropylene. In any case, the mixing method is not particularly limited as long as it does not impair the effects of the invention.

[0122] [Stretched film]

[0123] The stretch film contains a polypropylene composition. The proportion of the polypropylene composition in 100% by weight of the stretch film is preferably 50% by weight or more, more preferably 80% by weight or more. The upper limit of the proportion of the polypropylene composition in 100% by weight of the stretch film is 100% by weight.

[0124] Stretched films can be produced by stretching an unstretched film made from a polypropylene composition using a known melt extrusion film method. The stretched film can be uniaxially stretched or biaxially stretched; from the viewpoint of balancing synthesis in the MD and TD directions, biaxially stretched films are preferred. In the case of biaxially stretched films, either simultaneous biaxial stretching or successive biaxial stretching can be used.

[0125] Regarding the heat shrinkage rate of the stretched film measured at 150°C for 30 minutes based on JIS K6782, the MD direction is preferably 0~3.5%, more preferably 0~3.0%. Furthermore, the aforementioned heat shrinkage rate in the TD direction is preferably 0~5.0%, more preferably 0~3.0%, and even more preferably 0~1.5%. Specifically, the aforementioned heat shrinkage rate is preferably 0~3.5% in the MD direction and 0~5.0% in the TD direction, more preferably 0~3.0% in the MD direction and 0~3.0% in the TD direction, and even more preferably 0~3.0% in the MD direction and 0~1.5% in the TD direction. When it falls within the above range, it can be used in applications requiring high heat resistance where conventional OPP films cannot be used; for example, it has the advantage of being able to replace PET films.

[0126] Regarding the Young's modulus of the stretched film as measured based on JIS K7127, it is preferably 2 GPa or higher in the MD direction, more preferably 2.2 GPa or higher, and even more preferably 2.5 GPa or higher. Regarding the Young's modulus of the stretched film as measured based on JIS K7127, it is preferably 5.6 GPa or higher in the TD direction, more preferably 6.0 GPa or higher, and even more preferably 6.5 GPa or higher. When it is within the above range, it can be used in applications requiring high heat resistance where conventional OPP films cannot be used; for example, it has the advantage of being able to replace PET films.

[0127] In this invention, the MD direction refers to the direction of travel of the film (sometimes also called the length direction or long side direction), and the TD direction refers to the direction perpendicular to the direction of travel and the thickness direction of the film (sometimes also called the transverse or width direction).

[0128] The stretched film can be a single layer containing a polypropylene composition, or it can be a multilayer film in which each layer contains a polypropylene composition. In the case of a multilayer film, the polypropylene compositions constituting each layer can be the same or different. In addition, the stretched film can be a laminated film with other layers also stacked on top of it.

[0129] In the case of multilayer or laminated films, a single-layer film containing a polypropylene composition can be stretched to form a multilayer or laminated film, or the multilayer or laminated film can be stretched after it has been formed.

[0130] When the stretched film is a single-layer film, its thickness is preferably 5~200μm, more preferably 10~150μm, even more preferably 12~100μm, and even more preferably 15~80μm.

[0131] When the stretched films are respectively integrated into a multilayer film containing a polypropylene composition or into a laminated film formed by stacking the stretched films and other layers, the thickness of each stretched film is preferably 5 to 150 μm, more preferably 10 to 100 μm, even more preferably 12 to 80 μm, and even more preferably 15 to 60 μm.

[0132] When the film is a multilayer film or a laminated film, its total thickness is preferably 5~200μm, more preferably 10~150μm, even more preferably 12~120μm, and even more preferably 15~100μm.

[0133] The manufacturing method of the stretched film is not particularly limited. For example, an unstretched film containing the above-described polypropylene composition can be prepared and stretched along a uniaxial or biaxial direction using a known method to obtain a stretched film. The forming temperature for stretching the unstretched film is preferably 140-180°C, more preferably 150-175°C, and even more preferably 155-170°C. The following MD stretching process can be included: stretching the unstretched film along the MD direction by 2 to 10 times, preferably 4 to 7 times, using stretching rollers to obtain a uniaxial stretched film. In addition, the following TD stretching process can be included: stretching the uniaxial stretched film obtained by the above MD stretching process along the TD direction by 4 to 20 times, preferably 4 to 10 times, using two rows of clamping members arranged along the MD direction in a heating furnace to obtain a biaxial stretched film.

[0134] To improve processability, the surface of the stretched film can be treated with corona discharge, plasma discharge, flame treatment, ozone treatment, etc.

[0135] Stretched films can be used as one layer in multilayer or laminated films. Laminated films are films in which arbitrary layers are stacked on one or both sides of a layer containing a stretched film. Commonly used methods for producing multilayer or laminated films include co-extrusion, extrusion lamination, hot lamination, dry lamination, and blow-blowing with cooling in water and / or atmospheric atmosphere.

[0136] For example, a laminated film can be formed by stacking any layer such as a sealing layer, a gas barrier layer, an adhesive layer, or a printing layer on a stretched film. Preferably, a sealing layer containing an olefin resin is stacked on the layer containing the stretched film, and the resulting laminated film has the effect of easy recycling.

[0137] Stretch films can be used as various packaging materials. For example, packaging materials formed from the above-mentioned laminated films can be suitable for packaging any kind of object, such as food, clothing, or groceries.

[0138] Example

[0139] The present invention will be further described in detail below by way of examples, but the present invention is not limited to the examples. Hereinafter, regarding propylene polymers, those that satisfy 0.4 < (Mw / Mn)·γ < 10 will be referred to as "polypropylene", and those that do not satisfy this condition will be referred to as "propylene polymers".

[0140] [Methods for determining physical properties]

[0141] The physical properties and analytical values ​​of each item in the examples were determined and analyzed according to the following methods.

[0142] (1) MFR (unit: g / 10 minutes)

[0143] Using granules of polypropylene or propylene-based polymers, the MFR was determined under the following conditions according to Table 1, Condition M, of Annex A of JIS K7210:1999.

[0144] Test temperature: 230℃ Nominal load: 2.16kg

[0145] Die head shape: Diameter 2.095mm, Length 8.000mm

[0146] (2) GPC determination

[0147] GPC was performed using polypropylene or propylene-based polymer granules to determine the number-average molecular weight (Mn), weight-average molecular weight (Mw), Mw / Mn, and γ. Details of the measuring equipment are as follows.

[0148] Equipment: Waters GPC (ALC / GPC, 150C)

[0149] Detector: FOXBORO MIRAN 1A IR detector (measurement wavelength: 3.42 μm)

[0150] Columns: Showa Denko AD806M / S (3 pieces)

[0151] Mobile phase solvent: o-dichlorobenzene (ODCB)

[0152] Temperature measured: 140℃

[0153] Flow rate: 1.0 mL / min

[0154] Injection volume: 0.2 mL

[0155] The sample was prepared as follows: a 1 mg / mL solution was prepared using polypropylene or propylene-based polymer granules and ODCB (containing 0.5 mg / mL butylated hydroxytoluene (BHT)), and dissolved at 140 °C for about 1 hour.

[0156] It should be noted that the baseline and interval of the obtained chromatogram, such as Figure 1 Do it that way.

[0157] In addition, a pre-prepared standard curve based on standard polystyrene was used to convert the retention volume to molecular weight obtained by GPC. The standard polystyrene used was of the following type manufactured by Tosoh Corporation.

[0158] Varieties: F380, F288, F128, F80, F40, F20, F10, F4, F1, A5000, A2500, A1000

[0159] Inject 0.2 mL of a solution prepared by dissolving 0.5 mg / mL of ODCB (containing 0.5 mg / mL BHT) and construct a calibration curve. The calibration curve is a cubic curve obtained by least squares approximation.

[0160] In the molecular weight conversion, the general calibration curve from Mori Sadao's "Size Exclusion Chromatography" (Kyoritsu Publishing) was used as a reference. The viscosity formula used in the molecular weight conversion ([η]=K×M) was... α The following values ​​were used in the data.

[0161] (i) When using standard polystyrene to prepare calibration curves

[0162] PS: K = 1.38 × 10 -4 α = 0.70

[0163] (ii) When determining samples of polypropylene or propylene-based polymers

[0164] PP: K = 1.03 × 10-4 α = 0.78

[0165] r is: the value obtained by subtracting the integral value of the cumulative molecular weight distribution curve (normalized to 1) obtained by GPC from 1, up to 1 million (Log(M) = 6.0), and then multiplying the result by 100. An example of how to determine γ is shown below. Figure 2 .

[0166] (3)Use 13 Percentage of isotactic five-unit groups determined by C-NMR (mmmm)

[0167] When using granules of polypropylene or propylene-based polymers, determine the percentage of isotactic five-unit groups (mmmm) as follows.

[0168] ( 13 C-NMR determination method)

[0169] [Sample preparation and measurement conditions]

[0170] 200 mg of the sample was added to an NMR tube with an inner diameter of 10 mm φ along with 2.4 mL of o-dichlorobenzene / deuterated brominated benzene (C6D5Br) = 4 / 1 (volume ratio) and hexamethyldisiloxane as a reference substance for chemical shift. The mixture was then dissolved until homogeneous using a heating block at 150 °C.

[0171] NMR measurements were performed using a Bulker BioSpin AV400 NMR apparatus equipped with a 10 mm φ cryopreservation probe.

[0172] 13 The C-NMR measurement conditions were set as follows: sample temperature 120℃, pulse angle 90°, pulse interval 15 seconds, and cumulative number of pulses 1024. The measurement was carried out using the broadband decoupling method.

[0173] Regarding chemical shift, hexamethyldisiloxane... 13 The C signal was set to 1.98 ppm, and the others... 13 The chemical shift of the C signal is based on this.

[0174] [Calculation method for the percentage of isomorphic five-element units (mmmm)]

[0175] The percentage of isotactic five-unit groups of propylene unit pentads (mmmm) is obtained by utilizing... 13 Measured by C-NMR. 13 The integral intensity of the C signal is obtained by substituting it into the following equation (1).

[0176] mmmm(%)=(I mm -2×I mrrm)×100 / (I mm +3×I mrrm Equation (1)

[0177] Here, I mm This indicates that the propylene unit triplet belongs to the bonding mode of mm. 13 The integrated intensity of the C signal is for chemical shifts in the range of 23.6–21.1 ppm. 13 The integral intensity of the C signal, I mrrm This indicates that the propylene unit pentad belongs to the MRRM bonding mode. 13 The integrated intensity of the C signal is for chemical shifts in the range of 19.9–19.7 ppm. 13 The integral intensity of the C signal.

[0178] (4) Film thickness

[0179] For the biaxially stretched films of Examples 1-5 and Comparative Examples 1-5, the thickness of the films was measured using the ID-SX2 film manufactured by Mitutoyo Corporation.

[0180] (5) Gloss (%)

[0181] For the biaxially stretched films of Examples 1-5 and Comparative Examples 1-5, the gloss of the films was measured at an incident angle of 60° using a GLOSS Gloss Meter VG2000 manufactured by Nippon Denshoku Kogyo Co., Ltd., based on JIS Z8741:1997.

[0182] (6) Haze (%)

[0183] For the biaxially stretched films of Examples 1-5 and Comparative Examples 1-5, the haze of the films was measured based on JIS K7136:2000.

[0184] (7) Young's modulus (tensile modulus of elasticity) (MPa)

[0185] For the biaxially stretched films of Examples 1-5 and Comparative Examples 1-5, based on the method described in JIS K7127 (1999) "Plastics - Test methods for tensile properties - Part 3: Test conditions for films and sheets", after a 24-hour conditioning period at 23°C and 50%RH, strip-shaped test pieces with a length of 150 mm and a width of 15 mm were cut in both the MD and TD directions. The clamping distance of the tensile testing machine was set to 100 mm, and the tensile speed was set to 1 mm / min. The Young's modulus (tensile elastic modulus) in the MD and TD directions of the film was measured. A higher Young's modulus indicates better rigidity. The Young's modulus was determined using the following criteria.

[0186] ◎: The Young's modulus in the MD direction is above 2.5 GPa and the Young's modulus in the TD direction is above 6.5 GPa, indicating that the biaxially stretched film has excellent rigidity.

[0187] ○: The Young's modulus in the MD direction is above 2.2 GPa and the Young's modulus in the TD direction is above 5.6 GPa and less than 6.5 GPa, indicating excellent rigidity of the biaxially stretched film.

[0188] ×: The Young's modulus in the TD direction is above 5.0 GPa and less than 5.6 GPa, indicating poor rigidity of the biaxially stretched film.

[0189] ××: The Young's modulus in the TD direction is less than 5.0 GPa, and the rigidity of the biaxially stretched film is significantly poor.

[0190] (8) Heat shrinkage rate (%)

[0191] For the biaxially stretched films of Examples 1-5 and Comparative Examples 1-5, the heat shrinkage rate was determined according to JIS K6782 using the following method. The films were cut into pieces 20 mm wide and 200 mm long in both the MD and TD directions, and then placed in a hot air oven at 150°C and heated for 30 minutes. The length was measured immediately after heating, and the ratio of the shrunken length to the original length was taken as the heat shrinkage rate. A smaller value indicates a lower heat shrinkage rate and better heat resistance and dimensional stability during heating. The heat shrinkage rate was determined based on the following criteria.

[0192] ◎: The heating shrinkage rate in the MD direction is 0~3.0% and the heating shrinkage rate in the TD direction is 0~1.5%, indicating that the heating shrinkage rate of biaxially stretched films is excellent.

[0193] ○: The heating shrinkage rate in the MD direction is 0~3.5% and the heating shrinkage rate in the TD direction is greater than 1.5% and less than 5.0%, indicating that the biaxially stretched film has excellent heating shrinkage rate.

[0194] ×: The heating shrinkage rate in the MD direction is greater than 3.5 and less than 5.0% or the heating shrinkage rate in the TD direction is greater than 5.0 and less than 10.0%, indicating a difference in heating shrinkage rate between biaxially stretched films.

[0195] ××: The heating shrinkage rate in the MD direction is greater than 5.0% and the shrinkage rate in the TD direction is greater than 10.0%, while the heating shrinkage rate of biaxially stretched films is significantly worse.

[0196] [Resin used]

[0197] The following describes the various resins used in the examples and comparative examples.

[0198] [Polypropylene]

[0199] A-1: 100 parts by weight of PP (brand name: Novatec, registered trademark) manufactured by Japan Polypropylene Corporation, grade EA9HD (propylene homopolymer using Ziegler-Natta catalyst, MFR (230°C, 2.16 kg load) = 0.4 g / 10 min), with 0.048 parts by weight of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane added as an organic peroxide, were mixed using a Henschel mixer. The resulting mixture was melt-extruded using a TECHNOVEL KZW-25 twin-screw extruder with a 25 mm screw diameter at a screw speed of 300 rpm and a mixing temperature of 150°C / 180°C / 230°C / 230°C / 180°C from the bottom of the hopper (C1 / C2 / C3~C7 / head / die) to obtain polypropylene granules. The resulting granules had an MFR of 10 g / 10 min.

[0200] A-2: 100 parts by weight of PP manufactured by Japan Polypropylene Corporation, trade name Novatec (registered trademark), grade FY6H (propylene homopolymer using Ziegler-Natta catalyst, MFR (230°C, 2.16 kg load) = 1.8 g / 10 min), grade FY6H, were mixed with 0.025 parts by weight of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane as an organic peroxide, using a Henschel mixer. Polypropylene granules were obtained by the same method as for polypropylene (A-1), except that the resulting mixture was used. The resulting granules had an MFR of 11.8 g / 10 min.

[0201] A-3: 100 parts by weight of PP manufactured by Japan Polypropylene Corporation, trade name Novatec (registered trademark), grade FL1105F (propylene homopolymer using Ziegler-Natta catalyst, MFR (230°C, 2.16 kg load) = 3.5 g / 10 min), with 0.007 parts by weight of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane as an organic peroxide added, were mixed using a Henschel mixer. Polypropylene granules were obtained by the same method as for polypropylene (A-1), except that the resulting mixture was used. The resulting granules had an MFR of 7.3 g / 10 min.

[0202] A-4: 100 parts by weight of PP manufactured by Japan Polypropylene Corporation, trade name Novatec (registered trademark), grade FL1105F (propylene homopolymer using Ziegler-Natta catalyst, MFR (230°C, 2.16 kg load) = 3.5 g / 10 min), with 0.014 parts by weight of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane as an organic peroxide added, were mixed using a Henschel mixer. Polypropylene granules were obtained by the same method as for polypropylene (A-1), except that the resulting mixture was used. The resulting granules had an MFR of 10.1 g / 10 min.

[0203] A-5: 100 parts by weight of PP manufactured by Japan Polypropylene Corporation, trade name Novatec (registered trademark), grade FL1105F (propylene homopolymer using Ziegler-Natta catalyst, MFR (230°C, 2.16 kg load) = 3.5 g / 10 min), with 0.020 parts by weight of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane as an organic peroxide added, were mixed using a Henschel mixer. Polypropylene granules were obtained by the same method as for polypropylene (A-1), except that the resulting mixture was used. The resulting granules had an MFR of 13.1 g / 10 min.

[0204] [Propylene polymers]

[0205] B-1: Manufactured by Japan Polypropylene Corporation, trade name Novatec (registered trademark) PP, grade name SA3D (propylene homopolymer using Ziegler-Natta catalyst, MFR (230℃, 2.16kg loading) = 11g / 10min).

[0206] B-2: Manufactured by Japan Polypropylene Corporation, trade name Novatec (registered trademark) PP, grade name FL1105F (propylene homopolymer using Ziegler-Natta catalyst, MFR (230℃, 2.16kg loading) = 3.5g / 10min).

[0207] B-3: Manufactured by Japan Polypropylene Corporation, trade name Novatec (registered trademark) PP, grade FL4 (propylene homopolymer using Ziegler-Natta catalyst, MFR (230℃, 2.16kg loading) = 4.2g / 10min).

[0208] B-4: Manufactured by Japan Polypropylene Corporation, trade name Novatec (registered trademark) PP, grade name FL203D (propylene homopolymer using Ziegler-Natta catalyst, MFR (230℃, 2.16kg loading) = 3.0g / 10min).

[0209] B-5: 100 parts by weight of propylene homopolymer manufactured by Japan Polypropylene Corporation, trade name Novatec (registered trademark), grade FL1105F (propylene homopolymer using Ziegler-Natta catalyst, MFR (230°C, 2.16 kg load) = 3.5 g / 10 min), with 0.003 parts by weight of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane as an organic peroxide added, were mixed using a Henschel mixer. Except for using the resulting mixture, propylene polymer pellets were obtained by the same method as for polypropylene (A-1). The resulting pellets had an MFR of 5.2 g / 10 min.

[0210] Example 1

[0211] Polypropylene (A-1) was fed into each layer using a 3-layer co-extruder. After melt extrusion at a resin temperature of 240°C for each layer, the mixture was rapidly cooled using cooling rollers at 30°C to produce a 3-layer unstretched film. The resulting unstretched film was then used in a biaxial stretching film forming machine (tentor) manufactured by Mitsubishi Heavy Industries with the roller temperature adjusted to 110°C to obtain a biaxially stretched film.

[0212] The extrusion conditions, stretching conditions, and film thickness after biaxial stretching are described below.

[0213] Extrusion conditions: Extrusion temperature: 240℃, Die width: 300mm, Die lip opening: 2.0mm, Cooling roller temperature: 30℃, Cooling roller speed: 3m / min

[0214] Stretching conditions: Stretching roll temperature: 110℃; MD direction stretch ratio: 5 times; TD direction stretch ratio: 8 times; Traction speed: 15m / min; Tensile chamber temperature: 165℃ for all three zones (preheating, stretching, and heat setting).

[0215] The total thickness of the film is 20 μm. The thickness of the first and third layers is 2 μm each.

[0216] Example 2

[0217] In Example 1, polypropylene (A-1) was replaced with polypropylene (A-2) to obtain the biaxially stretched film of Example 2.

[0218] Example 3

[0219] In Example 1, polypropylene (A-1) was replaced with polypropylene (A-3) to obtain the biaxially stretched film of Example 3.

[0220] Example 4

[0221] In Example 1, polypropylene (A-1) was replaced with polypropylene (A-4) to obtain the biaxially stretched film of Example 4.

[0222] Example 5

[0223] In Example 1, polypropylene (A-1) was replaced with polypropylene (A-5) to obtain the biaxially stretched film of Example 5.

[0224] Comparative Example 1

[0225] In Example 1, polypropylene (A-1) was replaced with a propylene polymer (B-1) to obtain the biaxially stretched film of Comparative Example 1.

[0226] Comparative Example 2

[0227] In Example 1, polypropylene (A-1) was replaced with a propylene-based polymer (B-2) to obtain the biaxially stretched film of Comparative Example 2.

[0228] Comparative Example 3

[0229] In Example 1, polypropylene (A-1) was replaced with a propylene polymer (B-3) to obtain the biaxially stretched film of Comparative Example 3.

[0230] Comparative Example 4

[0231] In Example 1, polypropylene (A-1) was replaced with a propylene polymer (B-4) to obtain the biaxially stretched film of Comparative Example 4.

[0232] Comparative Example 5

[0233] In Example 1, polypropylene (A-1) was replaced with a propylene polymer (B-5) to obtain the biaxially stretched film of Comparative Example 5.

[0234] The polypropylene and propylene-based polymers used in the examples and comparative examples, and the properties of the biaxially stretched films obtained from them, are shown in Table 1.

[0235] [Table 1]

[0236]

[0237] [Examination of Results from Examples and Comparative Examples]

[0238] As shown in Table 1, the biaxially stretched films of Examples 1 to 5 formed by polypropylene satisfying 0.4 < (Mw / Mn)·γ < 10 have extremely high Young's modulus in the TD direction, small heating shrinkage in both the MD and TD directions, and excellent rigidity and heat resistance.

[0239] On the other hand, the Young's modulus in the TD direction and the difference in heating shrinkage in the MD and TD directions of the biaxially stretched films of Comparative Examples 1 to 5 formed from propylene polymers with (Mw / Mn)·γ of 10 or more are also considered.

[0240] Industrial availability

[0241] Polypropylene compositions can be suitably used as raw materials for stretch films.

Claims

1. A polypropylene composition for stretch film comprising polypropylene selected from the group consisting of propylene homopolymer and propylene-ethylene copolymer, the propylene-ethylene copolymer containing less than 1.0% by weight of ethylene-derived units, said polypropylene satisfying the following requirement (1): (1) The molecular weight distribution Mw / Mn obtained by GPC and the amount γ (weight%) of components with a molecular weight of more than 1 million obtained by GPC satisfy 0.4 < (Mw / Mn)·γ < 10.

2. The polypropylene composition for stretching films according to claim 1, wherein, The polypropylene satisfies the following requirement (2): (2) The melt flow rate measured at 230℃ and 2.16kg load based on JIS K7210 was 3.5~20g / 10min.

3. The polypropylene composition for stretching films according to claim 1 or 2, wherein, The polypropylene satisfies the following requirement (3): (3)Use 13 The percentage (mmmm) of isotactic five-unit groups determined by C-NMR is over 95%.

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

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

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

8. The stretched film according to claim 7, wherein, The Young's modulus of the stretched film, measured based on JIS K7127, is above 5.6 GPa in the TD direction.

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