Propylene-based polymer composition, method for producing propylene-based polymer composition, and biaxially stretched film

Abstract

To provide a propylene-based polymer composition capable of obtaining a biaxial oriented film having comparatively good thermostability, to provide a manufacturing method of a propylene-based polymer composition, and to provide a biaxial oriented film having comparatively good thermostability.SOLUTION: A propylene-based polymer composition includes a propylene-based polymer, and satisfies the following requirements (1)-(4): (1) A melt flow rate measured at a temperature of 230°C and a load of 2.16 kg is 2 g / 10 min. to 10 g / 10 min.; (2) Isotactic pentad fraction is 98.0% or higher; (3) Expression (I), 3.0≤Mw / Mn≤20 (I), is satisfied; and (4) Expression (II), (Mw(CXS) / Mn(CXS)) / (Mw / Mn)≤0.70 (II), is satisfied.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a propylene-based polymer composition, a method for producing the propylene-based polymer composition, and a biaxially stretched film obtained using the propylene-based polymer composition. [Background technology]

[0002] Conventionally, for example, a film used in various packaging materials has been known that has a structure in which a polyethylene terephthalate (PET) biaxially oriented film is used as a base film and a polypropylene (PP) unoriented film is laminated to the base film as a sealant film. Films with such a structure can exhibit excellent functionality as various packaging bags because the base film has high rigidity and high heat resistance and the sealant film has low-temperature heat-sealability.

[0003] In recent years, there has been an increasing demand for recycling of this type of film, and the development of mono-material films is being sought. Specifically, it is considered preferable to use a polypropylene-based biaxially oriented film of the same type as the sealant film made of polypropylene as the base film.

[0004] However, polypropylene-based biaxially stretched films are inferior in rigidity and heat resistance to polyethylene terephthalate-based biaxially stretched films, and therefore, films using polypropylene-based biaxially stretched films as base films have the problem of limited applications.

[0005] As a propylene-based polymer used for forming a molded article having high rigidity and high heat resistance, for example, Patent Document 1 proposes a propylene-based polymer obtained by polymerizing propylene using a combination of a specific solid titanium catalyst component and a specific external donor, and having extremely long meso chains (propylene unit chains in which α-methyl carbons are oriented in the same direction) and a high-temperature eluting component as determined by temperature rising elution fractionation (TREF) in relation to MFR. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2019 / 004418 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the biaxially stretched film obtained using the resin composition containing the propylene-based polymer described in Patent Document 1 has room for improvement in heat shrinkage, particularly in the heat shrinkage in a direction (hereinafter also referred to as "TD direction") intersecting the machine direction (hereinafter also referred to as "MD direction") during production, and there is a demand for a film with better heat resistance.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a propylene-based polymer composition from which a biaxially stretched film having relatively excellent heat resistance can be obtained, a method for producing a propylene-based polymer composition, and further to provide a biaxially stretched film having relatively excellent heat resistance. [Means for solving the problem]

[0009] The propylene polymer composition according to the present invention is a propylene polymer composition containing a propylene polymer, and satisfies the following requirements (1) to (4). (1) The melt flow rate measured at a temperature of 230°C and a load of 2.16 kg is 2 g / 10 min to 10 g / 10 min. (2) The isotactic pentad fraction is 98.0% or more. (3) Satisfy the following formula (I): 3.0≦Mw / Mn≦20 (I) (In the formula, Mn represents the number average molecular weight of the propylene polymer composition measured by gel permeation chromatography. Mw represents the weight average molecular weight of the propylene polymer composition measured by gel permeation chromatography. (4) Satisfies the following formula (II): (Mw(CXS) / Mn(CXS)) / (Mw / Mn)≦0.70 (II) (In the formula, Mn and Mw have the same meanings as above. Mn(CXS) represents the polystyrene-equivalent number average molecular weight of the cold xylene soluble portion of the propylene-based polymer composition measured by gel permeation chromatography. Mw(CXS) indicates the weight average molecular weight of the cold xylene soluble portion of the propylene polymer composition measured by gel permeation chromatography, converted into polystyrene.

[0010] The method for producing the propylene polymer composition according to the present invention is a method for producing the above-mentioned propylene polymer composition, and includes the following step (11): (11) A step of polymerizing propylene in the presence of an olefin polymerization catalyst obtained by contacting a solid catalyst component for olefin polymerization with an organoaluminum compound and an external electron donor to obtain a propylene-based polymer, The external electron donor is a compound represented by the following formula (IV): SiR 1 n (OR 2 ) (4-n) (IV) (In the formula, n represents an integer of 1 to 3. R 1 represents a cyclic aliphatic hydrocarbon group having 3 to 10 carbon atoms. 1 When there are multiple groups, they may be the same or different. R 2 represents a hydrocarbon group having 1 to 20 carbon atoms. 2 If there are multiple, they may be the same or different.)

[0011] The biaxially stretched film according to the present invention can be obtained using the above-mentioned propylene polymer composition. [Effects of the Invention]

[0012] According to the present invention, a propylene-based polymer composition from which a biaxially stretched film having relatively excellent heat resistance can be obtained, a method for producing a propylene-based polymer composition, and a biaxially stretched film having relatively excellent heat resistance can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments.

[0014] [Propylene-based polymer composition] The propylene polymer composition according to this embodiment contains a propylene polymer.

[0015] The propylene-based polymer is a polymer containing more than 50% by mass of structural units derived from propylene, i.e., a propylene homopolymer or a propylene-based copolymer containing more than 50% by mass of structural units derived from propylene. From the viewpoint of improving the heat resistance and rigidity of the biaxially stretched film, the propylene-based polymer is preferably a propylene homopolymer. Examples of the propylene-based copolymer include those obtained by copolymerizing propylene with at least one monomer selected from ethylene and α-olefins having 4 to 20 carbon atoms.

[0016] Examples of the α-olefins having 4 to 20 carbon atoms include 1-butene, 2-methyl-1-propene, 1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 1-hexene, 2-ethyl-1-butene, 2,3-dimethyl-1-butene, 2-methyl-1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 3,3-dimethyl-1-butene, 1-heptene, methyl-1-hexene, dimethyl-1-pentene, ethyl-1-pentene, and trimethyl- Examples of the alkyl ester include 1-butene, methylethyl-1-butene, 1-octene, methyl-1-pentene, ethyl-1-hexene, dimethyl-1-hexene, propyl-1-heptene, methylethyl-1-heptene, trimethyl-1-pentene, propyl-1-pentene, diethyl-1-butene, 1-nonene, 1-decene, 1-undecene, and 1-dodecene. Of these, 1-butene, 1-pentene, 1-hexene, or 1-octene is preferred, and 1-butene is more preferred.

[0017] Examples of propylene copolymers include propylene-1-butene copolymer, propylene-1-hexene copolymer, propylene-1-octene copolymer, propylene-ethylene-1-butene copolymer, propylene-ethylene-1-hexene copolymer, and propylene-ethylene-1-octene copolymer, and preferably propylene-ethylene copolymer, propylene-1-butene copolymer, or propylene-ethylene-1-butene copolymer.

[0018] When the propylene-based copolymer is a propylene-ethylene copolymer, the content of structural units derived from ethylene is preferably 2.0% by mass or less, more preferably 1.0% by mass or less, and even more preferably 0.4% by mass or less, from the viewpoint of improving the heat resistance and rigidity of the biaxially stretched film.

[0019] When the propylene-based copolymer is a propylene-α-olefin copolymer, the content of structural units derived from α-olefin is preferably 8.0 mass% or less, more preferably 3.0 mass% or less, and even more preferably 1.0 mass% or less, from the viewpoint of improving the heat resistance and rigidity of the biaxially stretched film.

[0020] When the propylene-based copolymer is a propylene-ethylene-α-olefin copolymer, the total content of structural units derived from ethylene and α-olefin is preferably 8.0 mass% or less, more preferably 3.0 mass% or less, and even more preferably 1.0 mass% or less, from the viewpoint of improving the heat resistance and rigidity of the biaxially stretched film.

[0021] The cold xylene solubles content (hereinafter abbreviated as CXS) of the propylene polymer is preferably 2.0% by mass or less, more preferably 0.1% to 1.0% by mass, and even more preferably 0.3% to 1.0% by mass. By setting the CXS within the above range, good stretchability is exhibited during the production of a biaxially stretched film, and the biaxially stretched film can be made to exhibit high rigidity and heat resistance. The CXS of the propylene polymer can be determined by dissolving the propylene polymer in boiling xylene, cooling the mixture, and quantifying the propylene polymer dissolved in the filtrate of the resulting mixture using liquid chromatography (LC).

[0022] The propylene polymer preferably has a melt flow rate (hereinafter abbreviated as MFR) measured at a temperature of 230°C under a load of 2.16 kg of 1 g / 10 min to 50 g / 10 min, more preferably 1 g / 10 min to 20 g / 10 min, and even more preferably 2 g / 10 min to 15 g / 10 min. By using a propylene polymer having an MFR within the above range, the molten polypropylene has an appropriate viscosity, which provides good stretchability during the production of a biaxially stretched film and allows the biaxially stretched film to exhibit high rigidity and heat resistance. The MFR of the propylene polymer is measured according to Method A specified in JIS K7210-1:2014.

[0023] The propylene polymer composition may contain only one type of propylene polymer, or may contain two or more types of propylene polymers differing in the type and content of structural units. The propylene polymer composition may also contain components other than the propylene polymer. The content of the propylene polymer in the propylene polymer composition is preferably 80% by mass to 99.9% by mass, more preferably 90% by mass to 99.9% by mass, and even more preferably 99% by mass to 99.9% by mass. The propylene polymer composition may contain, for example, multiple types of propylene polymers with different MFRs. A preferred example is a propylene polymer composition containing a propylene polymer (a) having an MFR of 4 g / 10 min or less and a propylene polymer (b) having an MFR of 20 g / 10 min to 500 g / 10 min.

[0024] The contents of the propylene polymer (a) and the propylene polymer (b) in the propylene polymer composition are preferably 50% by mass to 90% by mass and 10% by mass to 50% by mass, more preferably 50% by mass to 85% by mass and 15% by mass to 50% by mass, based on the total content of the propylene polymer (a) and the propylene polymer (b). Use of a propylene polymer composition containing multiple propylene polymers with different MFRs reduces thickness unevenness during stretching in the production of a biaxially stretched film, imparts good stretchability, and enables the biaxially stretched film to exhibit high rigidity and heat resistance.

[0025] The CXS of the propylene polymer composition is preferably 2.0% by mass or less, more preferably 0.1% to 1.0% by mass, and even more preferably 0.3% to 1.0% by mass. By setting the CXS within the above range, good stretchability is exhibited during the production of a biaxially stretched film, and the biaxially stretched film can be made to exhibit high rigidity and heat resistance. The CXS of the propylene polymer composition can be determined by dissolving the propylene polymer composition in boiling xylene, cooling the mixture, and quantifying the propylene polymer dissolved in the filtrate of the resulting mixture using liquid chromatography (LC).

[0026] The propylene polymer composition according to the present embodiment may contain a stretchability improver in addition to the propylene polymer as described above. Examples of the stretchability improver include at least one selected from the group consisting of a β-crystal nucleating agent and a hydrocarbon resin, and a β-crystal nucleating agent is preferred.

[0027] The β-crystal nucleating agent is a compound capable of forming β-crystals having a hexagonal crystal structure in a propylene polymer. The β-crystal nucleating agent is not particularly limited, and various conventionally known β-crystal nucleating agents can be used. Examples of the pigment include amide compounds represented by N,N'-dicyclohexyl-2,6-naphthalenedicarboxyamide, N,N'-dicyclohexylterephthalamide, and N,N'-diphenylhexanediamide; tetraoxaspiro compounds; quinacridones represented by quinacridone and quinacridonequinone; nanoscale iron oxide; alkali or alkaline earth metal salts of carboxylic acids represented by calcium pimelate, potassium 1,2-hydroxystearate, magnesium benzoate, magnesium succinate, and magnesium phthalate; aromatic sulfonic acid compounds represented by sodium benzenesulfonate and sodium naphthalenesulfonate; diesters or triesters of di- or tribasic carboxylic acids; phthalocyanine pigments represented by phthalocyanine blue; two-component compounds consisting of component A, which is an organic dibasic acid, and component B, which is an oxide, hydroxide, or salt of a metal from Group IIA of the periodic table; and compositions consisting of a cyclic phosphorus compound and a magnesium compound. One or more of these may be used in combination. Among the above-mentioned β-crystal nucleating agents, the amide compounds N,N'-dicyclohexyl-2,6-naphthalenedicarboxyamide, N,N-dicyclohexylterephthalamide, and N,N'-diphenylhexanediamide are preferred, and N,N'-dicyclohexyl-2,6-naphthalenedicarboxyamide is more preferred.

[0028] Examples of hydrocarbon resins include cyclopentadiene resins made from petroleum-based unsaturated hydrocarbons, and resins made primarily from higher olefin hydrocarbons.

[0029] From the viewpoint of improving the heat resistance of the film, the propylene polymer composition satisfies the following requirement (1), and preferably satisfies the following requirement (1'). (1) The melt flow rate measured at a temperature of 230°C and a load of 2.16 kg is 2 g / 10 min to 10 g / 10 min. (1') The melt flow rate measured at a temperature of 230°C and a load of 2.16 kg is 2 g / 10 min to 4 g / 10 min.

[0030] An example of a method for increasing the MFR of a propylene polymer composition is to increase the hydrogen concentration used during polymerization in the production method of a propylene polymer composition described below. On the other hand, an example of a method for decreasing the MFR of a propylene polymer composition is to decrease the hydrogen concentration used during polymerization in the production method of a propylene polymer composition described below. The MFR of a propylene polymer composition is measured according to Method A specified in JIS K7210-1:2014.

[0031] From the viewpoint of improving the heat resistance of the film, the propylene polymer composition satisfies the following requirement (2), and preferably satisfies the following requirement (2'). (2) The isotactic pentad fraction is 98.0% or more. (2') The isotactic pentad fraction is 99.0% or more.

[0032] The isotactic pentad fraction (hereinafter abbreviated as [mmmm]) of a propylene polymer composition is the fraction of propylene monomer units at the center of an isotactic sequence in pentad units in the molecular chain of a propylene polymer, i.e., the fraction of propylene monomer units in a sequence in which five consecutive propylene monomer units are meso-bonded. Methods for increasing the [mmmm] of a propylene polymer composition include, for example, increasing the polymerization temperature and decreasing the ratio of the amount of external electron donor used (mmol / h) to the amount of organoaluminum compound used (mmol / h). The [mmmm] of a propylene polymer composition is 13 It is measured by C-NMR.

[0033] From the viewpoint of improving the heat resistance of the film, the propylene polymer composition satisfies the following requirement (3), preferably the following requirement (3'), and more preferably the following requirement (3''). (3) Satisfy the following formula (I): 3.0≦Mw / Mn≦20 (I) (3') Satisfies the following formula (I'): 3.0≦Mw / Mn≦10 (I') (3'') Satisfies the following formula (I''). 3.0≦Mw / Mn≦5.0 (I'')

[0034] In the formulas (I), (I'), and (I''), Mn represents the number average molecular weight of the propylene polymer composition measured by gel permeation chromatography. Mw represents the weight average molecular weight of the propylene polymer composition measured by gel permeation chromatography.

[0035] Methods for increasing Mw / Mn include, for example, lowering the polymerization temperature, decreasing the ratio of the amount of external electron donor used (mmol / h) to the amount of organoaluminum compound used (mmol / h), separately producing high-molecular-weight polymers and low-molecular-weight polymers, continuously producing high-molecular-weight polymers and low-molecular-weight polymers and mixing them, etc. On the other hand, methods for decreasing Mw / Mn include, for example, increasing the polymerization temperature, increasing the ratio of the amount of external electron donor used (mmol / h) to the amount of organoaluminum compound used (mmol / h), etc.

[0036] From the viewpoint of improving the heat resistance of the film, the propylene polymer composition satisfies the following requirement (4), and preferably satisfies the following requirement (4'). (4) Satisfies the following formula (II): (Mw(CXS) / Mn(CXS)) / (Mw / Mn)≦0.70 (II) (4') Satisfies the following formula (II'): 0.50≦(Mw(CXS) / Mn(CXS)) / (Mw / Mn)≦0.70 (II')

[0037] In formulas (II) and (II'), Mn and Mw have the same meanings as above. Mn(CXS) represents the polystyrene-equivalent number average molecular weight of the cold xylene-soluble portion of the propylene polymer composition measured by gel permeation chromatography. Mw(CXS) represents the polystyrene-equivalent weight average molecular weight of the cold xylene-soluble portion of the propylene polymer composition measured by gel permeation chromatography.

[0038] Examples of methods for increasing (Mw(CXS) / Mn(CXS)) / (Mw / Mn) include increasing the ratio of the amount of organoaluminum compound used (mmol / h) to the amount of solid catalyst component used (g / h) for olefin polymerization, decreasing the ratio of the amount of external electron donor used (mmol / h) to the amount of organoaluminum compound used (mmol / h), and decreasing the concentration of hydrogen used during polymerization in the production method for a propylene polymer composition described below. On the other hand, examples of methods for decreasing (Mw(CXS) / Mn(CXS)) / (Mw / Mn) include using an external electron donor having a cyclic aliphatic hydrocarbon group, decreasing the ratio of the amount of organoaluminum compound used (mmol / h) to the amount of solid catalyst component used (g / h), increasing the ratio of the amount of external electron donor used (mmol / h) to the amount of organoaluminum compound used (mmol / h), and increasing the concentration of hydrogen used during polymerization in the production method for a propylene polymer composition described below.

[0039] From the viewpoint of improving the heat resistance of the film, the propylene polymer composition preferably satisfies the following requirement (5). (5) Satisfies the following formula (III): Mw(CXS) / Mn(CXS)<3.0 (III)

[0040] The ratio Mw(CXS) / Mn(CXS) is preferably 1.5 or more, more preferably 1.8 or more, and more preferably 2.5 or less.

[0041] Examples of methods for reducing Mw(CXS) / Mn(CXS) include using an external electron donor having a cyclic aliphatic hydrocarbon group in the production method of a propylene polymer composition described below, reducing the ratio of the amount of the organoaluminum compound used (mmol / h) to the amount of the solid catalyst component used (g / h) for olefin polymerization, and increasing the ratio of the amount of the external electron donor used (mmol / h) to the amount of the organoaluminum compound used (mmol / h).

[0042] [Method for producing propylene polymer composition] The method for producing a propylene polymer composition according to this embodiment includes the following step (11). (11) A step of obtaining a propylene-based polymer by polymerizing propylene in the presence of an olefin polymerization catalyst obtained by contacting a solid catalyst component for olefin polymerization with an organoaluminum compound and an external electron donor, wherein the external electron donor is a compound represented by the following formula (IV): SiR 1 n (OR 2 ) (4-n) (IV)

[0043] In formula (IV), n represents an integer of 1 to 3. 1 represents a cyclic aliphatic hydrocarbon group having 3 to 10 carbon atoms. 1 When there are multiple R, they may be the same or different. 2 represents a hydrocarbon group having 1 to 20 carbon atoms. 2 When there are multiple groups, they may be the same or different.

[0044] The method for producing the propylene polymer composition according to this embodiment may further include the following step (12). (12) A step of mixing the propylene polymer obtained in the step (11) with at least one selected from the group consisting of a stretchability improver, a stabilizer, a lubricant, an antistatic agent, an antiblocking agent, an inorganic filler, and an organic filler to obtain a propylene polymer composition.

[0045] <Olefin polymerization catalyst> The olefin polymerization catalyst can be produced by contacting a solid catalyst component for olefin polymerization with an organoaluminum compound and an external electron donor. That is, the olefin polymerization catalyst comprises a solid catalyst component for olefin polymerization, an organoaluminum compound, and an external electron donor.

[0046] <Solid catalyst component for olefin polymerization> The solid catalyst component for olefin polymerization comprises a titanium atom, a magnesium atom, a halogen atom and an internal electron donor.

[0047] The solid catalyst component for olefin polymerization means a component that exists as a solid in at least toluene and constitutes an olefin polymerization catalyst when brought into contact with an organoaluminum compound and an external electron donor.

[0048] A part or all of the titanium atoms in the solid catalyst component for olefin polymerization are derived from a titanium halide compound.A part or all of the halogen atoms in the solid catalyst component for olefin polymerization are derived from a titanium halide compound.

[0049] Examples of the titanium halide compound include titanium tetrahalide, monoalkoxytitanium trihalide, dialkoxytitanium dihalide, and trialkoxytitanium monohalide, and are preferably titanium tetrahalide or monoalkoxytitanium trihalide, and more preferably titanium tetrahalide. The titanium halide compounds may be used alone or in combination of two or more.

[0050] Some or all of the magnesium atoms in the solid catalyst component for olefin polymerization are derived from the magnesium compound, and some of the halogen atoms in the solid catalyst component for olefin polymerization may be derived from the magnesium compound.

[0051] Examples of the magnesium compound include dialkyl magnesium, magnesium dialkoxide, alkyl magnesium halide, alkoxy magnesium halide, aryloxy magnesium halide, and magnesium halide, and magnesium halide is preferred.

[0052] The magnesium compounds may be used alone or in combination of two or more.

[0053] The internal electron donor refers to an organic compound capable of donating electron pairs to one or more metal atoms contained in the solid catalyst component for olefin polymerization. Examples of the internal electron donor include monoester compounds, dicarboxylic acid ester compounds, diol diester compounds, β-alkoxy ester compounds, and diether compounds.

[0054] The monoester compound means an organic compound having one ester bond (—CO—O—) in the molecule, and is preferably an aromatic carboxylic acid ester compound or an aliphatic carboxylic acid ester compound.

[0055] The dicarboxylic acid ester compound means a compound having two ester bonds (-CO-O-) in the molecule, and having a structure in which two carboxyl groups of a dicarboxylic acid are esterified with a monohydric alcohol, and is preferably an aromatic dicarboxylic acid ester compound or an aliphatic dicarboxylic acid ester compound.

[0056] The diol diester compound means a compound having two ester bonds (-CO-O-) in the molecule, and having a structure in which each of the two hydroxyl groups of the diol esterifies a carboxyl group of a monocarboxylic acid or dicarboxylic acid.

[0057] The β-alkoxy ester compound means a compound having an alkoxycarbonyl group and an alkoxy group at the β-position of the alkoxycarbonyl group.

[0058] The diether compound means a compound having two ether bonds in the molecule.

[0059] Further examples include the internal electron donors described in JP-A-2011-246699.

[0060] Among the above internal electron donors, dicarboxylic acid ester compounds, diol diester compounds, and β-alkoxy ester compounds are preferred. The internal electron donors may be used alone or in combination of two or more.

[0061] The median particle size of the solid catalyst component for olefin polymerization is usually 60 μm or less, preferably 20 to 50 μm, and more preferably 30 to 40 μm.

[0062] The median particle size of the solid catalyst component for olefin polymerization can be controlled by the particle size of the magnesium compound in the solid catalyst component for olefin polymerization.

[0063] <Organoaluminum compounds> The organoaluminum compound is a compound having one or more carbon-aluminum bonds, and specific examples thereof include the compounds described in JP-A-10-212319. The organoaluminum compound is preferably a trialkylaluminum, a mixture of a trialkylaluminum and a dialkylaluminum halide, or an alkylalumoxane, and more preferably triethylaluminum, triisobutylaluminum, a mixture of triethylaluminum and diethylaluminum chloride, or tetraethyldialumoxane.

[0064] <External electron donor> The external electron donor is a compound represented by the above formula (IV). Specific examples of the compound include dicyclobutyldimethoxysilane, dicyclopentyldimethoxysilane, cyclohexyltriethoxysilane, and cyclopentyltriethoxysilane, and preferably dicyclopentyldimethoxysilane. The external electron donors may be used alone or in combination of two or more.

[0065] When producing an olefin polymerization catalyst, the method for contacting the solid olefin polymerization catalyst component, the organoaluminum compound, and the external electron donor is not particularly limited, as long as an olefin polymerization catalyst is produced. The contact is carried out in the presence or absence of a solvent. A contact mixture of these components may be fed to a polymerization vessel, or each component may be fed separately to a polymerization vessel and contacted in the polymerization vessel, or a contact mixture of any two components and the remaining component may be fed separately to a polymerization vessel and contacted in the polymerization vessel.

[0066] <Preactivation of solid catalyst components for olefin polymerization> When producing a catalyst for olefin polymerization, the solid catalyst component for olefin polymerization may be contacted with an organoaluminum compound in the presence of a small amount of olefin to preactivate the solid catalyst component for olefin polymerization.

[0067] The method for supplying a small amount of olefin may be to supply a small amount of olefin into the system after contacting the solid catalyst component for olefin polymerization with an organoaluminum compound, or may be to supply a small amount of olefin into the system after contacting the solid catalyst component for olefin polymerization with a small amount of olefin. The method for supplying a small amount of olefin may be to supply a small amount of olefin while maintaining the reaction system at a predetermined pressure, or may be to supply a small amount of olefin initially.

[0068] The amount of the organoaluminum compound used is usually 0.5 to 700 mol, preferably 0.8 to 500 mol, and more preferably 1 to 200 mol per mol of titanium atom in the solid catalyst component for olefin polymerization.

[0069] The amount of olefin used is usually 0.01 to 1000 g, preferably 0.05 to 500 g, and more preferably 0.1 to 200 g per 1 g of the solid catalyst component for olefin polymerization.

[0070] In preactivating the solid catalyst component for olefin polymerization, an electron donor compound may be brought into contact with the solid catalyst component for olefin polymerization, if necessary.

[0071] Examples of the electron donor compound include oxygen-containing compounds, nitrogen-containing compounds, phosphorus-containing compounds, and sulfur-containing compounds, with oxygen-containing compounds and nitrogen-containing compounds being preferred. Examples of the oxygen-containing compound include alkoxysilanes, ethers, esters, and ketones, with alkoxysilanes and ethers being preferred. The electron donor compound may be the same as or different from the external electron donor described below.

[0072] The amount of the electron donor compound used is usually 0.003 to 5 mol, preferably 0.005 to 3 mol, and more preferably 0.01 to 2 mol, per 1 mol of the organoaluminum compound.

[0073] The method for supplying the electron donor compound is not particularly limited, and the organoaluminum compound and the electron donor compound may be supplied separately, or the organoaluminum compound and the electron donor compound may be contacted in advance and then supplied. The olefin used in preactivating the solid catalyst component for olefin polymerization may be the same as or different from the olefin used in polymerization.

[0074] <Olefin polymerization process> The amount of the solid catalyst component for olefin polymerization used may be appropriately determined depending on the specifications of the polymerization reactor and the amount of polymer produced.

[0075] The amount of the organoaluminum compound used is usually 1 to 1000 mol, preferably 5 to 600 mol, per mol of titanium atoms in the solid catalyst component.

[0076] The amount of the external electron donor used is usually 0.1 to 2000 mol, preferably 0.3 to 1000 mol, and more preferably 0.5 to 800 mol per mol of titanium atoms in the solid catalyst component.

[0077] The ratio of the amount of the organoaluminum compound used (mmol / h) to the amount of the solid catalyst component used (g / h) for olefin polymerization is preferably 10 to 40, more preferably 15 to 35, and even more preferably 20 to 30, from the viewpoint of reducing (Mw(CXS) / Mn(CXS)) / (Mw / Mn) and improving the heat resistance of the biaxially stretched film.

[0078] The ratio of the amount of external electron donor used (mmol / h) to the amount of organoaluminum compound used (mmol / h) is preferably 0.20 to 0.40, more preferably 0.22 to 0.35, and even more preferably 0.25 to 0.30, from the viewpoint of reducing (Mw(CXS) / Mn(CXS)) / (Mw / Mn) and improving the heat resistance of the biaxially stretched film.

[0079] <Polymerization of propylene polymer> In the step (11), propylene may be polymerized alone, or propylene may be copolymerized with at least one monomer selected from ethylene and α-olefins having 4 to 20 carbon atoms.

[0080] As the polymerization method, known polymerization methods can be used. For example, solvent polymerization using an inert solvent represented by a hydrocarbon compound such as hexane, heptane, octane, decane, cyclohexane, methylcyclohexane, benzene, toluene, or xylene, bulk polymerization using a liquid monomer as a solvent, or gas-phase polymerization carried out in a gaseous monomer are listed. Bulk polymerization or gas-phase polymerization, which facilitate post-treatment, are preferred. These polymerization methods may be batch or continuous.

[0081] When gas phase polymerization is used as the polymerization method in step (11), the effective hydrogen concentration during polymerization (hydrogen concentration / (hydrogen concentration+propylene concentration)) is preferably more than 1.5 mol%, more preferably 1.6 to 3.0 mol%, and even more preferably 1.6 to 2.0 mol%, from the viewpoint of reducing (Mw(CXS) / Mn(CXS)) / (Mw / Mn) and improving the heat resistance of the biaxially stretched film.

[0082] The polymerization method in step (11) may be a multi-stage polymerization method (multi-stage polymerization method) using the above-mentioned polymerization method, comprising a first step and a second step and subsequent steps. The polymerization method in the first step and the polymerization methods in the second step and subsequent steps may be the same or different. From the viewpoint of polymerization activity and ease of post-treatment, preferably, the first step is a step in which polymerization is carried out in the absence of an inert solvent, and the second step and subsequent steps are steps in which polymerization is carried out in a gas phase. Furthermore, the polymerization in the first step and the polymerization in the second step and subsequent steps may be carried out in the same polymerization tank (reactor) or in different polymerization tanks (reactors).

[0083] Examples of the multistage polymerization method include solvent-solvent polymerization, bulk-bulk polymerization, gas-gas phase polymerization, solvent-gas phase polymerization, bulk-gas-gas phase polymerization, solvent-gas-gas phase polymerization, and bulk-gas-gas phase polymerization, and preferably the bulk-gas phase polymerization, gas-gas phase polymerization, and bulk-gas-gas phase polymerization.

[0084] The polymerization temperature in the first step is not particularly limited, but is preferably 20°C to 180°C, and more preferably 30°C to 100°C from the viewpoint of productivity.

[0085] The polymerization temperature in the second and subsequent steps may be the same as or different from the polymerization temperature in the first step, but is preferably 20°C to 180°C, more preferably 30°C to 100°C.

[0086] In the method for producing a propylene polymer composition according to this embodiment, when a propylene polymer composition containing at least two propylene polymers is produced, examples of the method include a method in which the at least two propylene polymers are polymerized separately using the polymerization method described above and the resulting propylene polymers are mixed to produce a propylene polymer composition. The method for mixing at least two propylene polymers polymerized separately may be any method that uniformly disperses these polymers. Examples of the method include a method in which the at least two propylene polymers are mixed using a ribbon blender, Henschel mixer, tumbler mixer, or the like, and then melt-kneaded in an extruder or the like; a method in which the at least two propylene polymers are melt-kneaded separately and pelletized, and the pellets are mixed and further melt-kneaded in the same manner as above; a method in which the at least two propylene polymers are melt-kneaded separately and pelletized, and the pellets are blended by dry blending or the like, and then directly mixed in a film processor; and a method in which the at least two propylene polymers are melt-kneaded separately and pelletized, and the pellets are fed individually to the extruder of a film processor for mixing. Another method is to prepare a masterbatch in advance containing 100 parts by mass of one propylene polymer and 1 to 99 parts by mass of the other propylene polymer, and then mix them appropriately to obtain a predetermined concentration.

[0087] The method for producing a propylene polymer composition according to this embodiment may include post-treatment steps such as catalyst deactivation, desolvation, demonomerization, drying, and granulation, as needed.

[0088] [Biaxially oriented film] The biaxially stretched film according to this embodiment is obtained using the above-mentioned propylene-based polymer composition.

[0089] The thickness of the biaxially stretched film is preferably 10 μm to 70 μm, and more preferably 10 μm to 30 μm.

[0090] The method for producing the biaxially stretched film may be a sequential biaxial stretching method.

[0091] The method for producing a biaxially stretched film includes an extrusion step in which a propylene-based polymer composition is heated and melted using an extruder and extruded onto a cooling roll to obtain an unstretched sheet. In the extrusion step, for example, a propylene-based polymer composition is heated and melted using an extruder and extruded onto a cooling roll through a T-die to be cooled and fixed into a sheet, thereby obtaining an unstretched sheet.

[0092] The method for producing a biaxially stretched film may further include an MD stretching step in which the unstretched sheet obtained in the extrusion step is stretched in the MD direction by 6 to 10 times, preferably 8 to 10 times, using a stretching roll to obtain a uniaxially stretched sheet.

[0093] The method for producing a biaxially stretched film may also include a TD stretching step in which the uniaxially stretched sheet obtained in the MD stretching step is stretched in the TD direction by 4 to 20 times, preferably 4 to 10 times, in a heating furnace using two rows of chucks aligned along the MD direction to obtain a biaxially stretched film. In the TD stretching step, for example, both TD edge portions of the uniaxially stretched sheet are gripped with two rows of chucks aligned along the MD direction, and the uniaxially stretched sheet is stretched in the TD direction by the above-mentioned stretching ratio in a heating furnace equipped with a preheating section, a stretching section, and a heat treatment section to obtain a biaxially stretched film.

[0094] The method for producing a biaxially stretched film may further include a relaxation step in which the TD stretching of the biaxially stretched film obtained in the TD stretching step is relaxed in the TD direction by 16% to 30%, preferably 18% to 25%, using two rows of chucks aligned along the MD in a heating furnace. In this relaxation step, the TD stretching is relaxed by the above-mentioned ratio by narrowing the TD distance between the two rows of chucks gripping both TD end portions of the biaxially stretched film obtained in the TD stretching step. If the relaxation rate is less than 16%, the shrinkage rate during heating will be high, and a biaxially stretched film with excellent heat resistance may not be obtained. If the relaxation rate exceeds 30%, the thickness unevenness of the biaxially stretched film may become significant. The relaxation rate can be calculated using the following formula (X): Relaxation rate=(L1-L2) / L1×100...(X) (In the formula, L1 is the distance between the chucks in the TD direction before the film is relaxed, and L2 is the distance between the chucks in the TD direction after the film is relaxed.

[0095] Furthermore, the method for producing a biaxially stretched film may include a step of performing corona treatment, etc., as necessary.

[0096] In the above production method, the melting temperature when the propylene polymer composition is heated and melted in an extruder is preferably 230 to 290°C. The temperature of the cooling roll when the propylene polymer composition extruded from the T-die is cooled and fixed into a sheet is preferably 10 to 60°C. The temperature of the stretching roll when the unstretched sheet is stretched in the MD direction is preferably 110 to 165°C. The heating temperature when the uniaxially stretched sheet is stretched in the TD direction is preferably 150 to 200°C, and the heating temperature when the sheet is relaxed in the TD direction is preferably 150 to 200°C.

[0097] The biaxially stretched film according to this embodiment can be used as one layer of a multilayer film. The multilayer film is obtained by laminating an optional layer on a layer made of the biaxially stretched film according to this embodiment. For example, a multilayer film can be constructed by laminating an optional layer such as a sealant layer, a gas barrier layer, an adhesive layer, or a printed layer on the biaxially stretched film according to this embodiment. In particular, it is preferable to laminate a sealant layer using an olefin-based film on a layer made of the biaxially stretched film according to this embodiment, and the obtained multilayer film has the effect of being easily recycled. Examples of methods for producing a multilayer film using the biaxially stretched film according to this embodiment include commonly used extrusion lamination, heat lamination, dry lamination, and the like.

[0098] The biaxially stretched film according to this embodiment can be used as various packaging materials. For example, a packaging bag formed from the above multilayer film can be used to package any object to be packaged, such as food, clothing, or miscellaneous goods.

[0099] The propylene polymer composition, the method for producing the propylene polymer composition, and the biaxially stretched film according to the present embodiment are not limited to the above-described embodiment, and various modifications are possible without departing from the gist of the present invention. Furthermore, it goes without saying that the configurations, methods, etc. of the above and following embodiments may be arbitrarily adopted and combined (the configurations, methods, etc. of one embodiment may be applied to the configurations, methods, etc. of another embodiment). [Example]

[0100] The measured values ​​of each item in the examples and comparative examples were measured by the following methods.

[0101] (1) Melt flow rate (MFR, unit: g / 10 min) The MFR of the propylene-based polymer composition was measured at a temperature of 230°C and a load of 2.16 kg in accordance with Method A specified in JIS K7210-1:2014.

[0102] (2) Isotactic pentad fraction ([mmmm], unit: %) The [mmmm] of the propylene polymer composition is determined under the following conditions: 13 The NMR absorption peaks of the propylene polymer contained in the propylene polymer composition were determined by the method published by A. Zambelli et al. (Macromolecules, Vol. 8, p. 687, 1975). Model: Bruker AVANCE600 Probe: 10mm cryoprobe ·Measurement temperature: 135℃ Pulse repetition time: 4 seconds Pulse width: 45° Accumulation count: 256 times

[0103] (3) Molecular weight (unit: g / mol) and molecular weight distribution (unit: none) The molecular weights of the propylene polymer composition (number-average molecular weight Mn, weight-average molecular weight Mw, z-average molecular weight Mz) were measured using gel permeation chromatography (GPC) under the following conditions. Peaks were designated by defining the baseline on the chromatogram in accordance with ISO 16014-1. (GPC equipment and software) Equipment: HLC-8321GPC / HT (Tosoh) Software: HLC-8321 GPC / HT Program Version 2.02 (Tosoh) (Measurement conditions) GPC columns: TSKgel GMHHR-H(S)HT 7.8mm ID x 300mm (Tosoh), 3 columns Mobile phase: Orthodichlorobenzene (Wako, special grade) with BHT added at a concentration of 0.1 g / 100 mL was used. ·Flow rate: 1mL / min Column oven temperature: 140℃ Autosampler temperature: 140℃ System oven temperature: 40°C Detection: Refractive index detector (RID) RID cell temperature: 140℃ Sample solution injection volume: 300 μL (Sample solution preparation conditions) Solvent: Orthodichlorobenzene (Wako, special grade) with 0.1 g / 100 mL of BHT added. Sample solution concentration: 1mg / mL Dissolution conditions: 5 mg of sample was sealed in a 1000 mesh SUS wire bag, the wire bag containing the sample was placed in a test tube, 5 mL of solvent was added to the test tube, the test tube was covered with aluminum foil, and the test tube was placed in a DF-8020 automatic dissolution shaker (Tosoh) and stirred at a stirring speed of 60 strokes per minute at 140°C for 120 minutes. (Analysis method) As standard substances for calibrating the GPC column, standard polystyrenes manufactured by Tosoh were weighed out in the combinations shown in the table below, and 5 mL of orthodichlorobenzene (same composition as the mobile phase) was added, followed by standing at room temperature for 120 minutes to dissolve.

[0104] [Table 1]

[0105] Using a calibration curve obtained from a standard substance, the polystyrene-equivalent average molecular chain lengths An, Aw, and Az of the propylene-based polymer composition were determined. The polystyrene-equivalent average molecular chain lengths were each multiplied by the polypropylene Q factor of 26.4 to obtain the polystyrene-equivalent average molecular weights Mn, Mw, and Mz. Various molecular weight distributions (Mw / Mn, Mz / Mn) were calculated from the obtained Mn, Mw, and Mz.

[0106] (4-1) Cold xylene solubles (CXS, unit: mass%) The propylene polymer composition was dissolved in boiling xylene, and the resulting xylene solution was cooled to precipitate the cold xylene insoluble matter. The resulting mixture was filtered, and the olefin polymer (cold xylene soluble matter) dissolved in the resulting filtrate was quantified using liquid chromatography (LC).

[0107] (Pretreatment conditions) Sample size: 1g Solvent: 100 mL of xylene (Fujifilm Wako Pure Chemical Industries, Ltd., special grade) containing 2 mg / 100 mL of dibutylhydroxytoluene (BHT). Dissolution conditions: Reflux for 30 minutes after boiling Temperature conditions: After cooling with ice water for 20 minutes, heat to 20°C and stir for 1 hour Filtration conditions: Filtration through filter paper (No. 50) and measurement using LC

[0108] (LC measurement conditions) Liquid transfer pump: LC-20AD (Shimadzu Corporation) Degasser: DGU-20A3 (Shimadzu Corporation) Autosampler: SIL-20A HT (Shimadzu Corporation) Column oven: CTO-20A (Shimadzu Corporation) Refractive index detector: RID-10A (Shimadzu Corporation) System controller: CBM-20A (Shimadzu Corporation) Measurement and analysis software: LC solution ver. 1.24 SP1 Column: SHODEX GPC KF-801 (upper exclusion limit molecular weight 1500) Eluent: Tetrahydrofuran (Kanto Chemical Co., Ltd., special grade, stabilizer-free) Column oven temperature: 40℃ Sample injection volume: 130 μL ·Flow rate: 1mL / min Detector: Differential refractometer

[0109] (4-2) Molecular weight (unit: g / mol) and molecular weight distribution (unit: none) of cold xylene soluble fraction The molecular weights of the cold xylene-soluble fraction of the propylene polymer composition (number-average molecular weight Mn(CXS), weight-average molecular weight Mw(CXS), z-average molecular weight Mz(CXS)) were measured using gel permeation chromatography (GPC) under the following conditions. Peaks were designated by defining the baseline on the chromatogram, in accordance with ISO 16014-1.

[0110] (Measurement sample) The filtrate obtained in the CXS measurement of the propylene polymer composition described above was used as a measurement sample.

[0111] (GPC measurement conditions) Liquid transfer pump: LC-20AD (Shimadzu Corporation) Degasser: DGU-20A3 (Shimadzu Corporation) Autosampler: SIL-20A HT (Shimadzu Corporation) Column oven: CTO-20A (Shimadzu Corporation) Refractive index detector: RID-10A (Shimadzu Corporation) System controller: CBM-20A (Shimadzu Corporation) Measurement and analysis software: LC solution ver. 1.24 SP1 (Shimadzu Corporation) GPC columns: Plus Pore Series Poly Pore 7.5mm ID x 300mm (Agilent Technologies), 2 columns Mobile phase: Tetrahydrofuran (Kanto Chemical, special grade, stabilizer-free) ·Flow rate: 1mL / min Column oven temperature: 35℃ Detection: Differential refractive index detector Refractive index detector cell temperature: 35℃ Sample solution injection volume: 300 μL GPC column calibration standard: PStQuick Kit-H (Tosoh Corporation)

[0112] (Analysis method) To prepare the calibration curve samples, 1 mL of tetrahydrofuran (Kanto Chemical, special grade, stabilizer-free) was added to each vial of the Tosoh standard polystyrene kit PStQuick Kit-H (PStQuickA: polystyrene mixture with weight-average molecular weights of 1,090,000, 190,000, 18,100, and 2,420; PStQuickB: polystyrene mixture with weight-average molecular weights of 706,000, 96,400, 10,200, and 1,010; PStQuickC: polystyrene mixture with weight-average molecular weights of 427,000, 37,900, 5,970, and 500). The calibration curve was calculated using a third-order approximation equation. Based on the calibration curve, the average molecular weights Mn(CXS), Mw(CXS), and Mz(CXS) of the cold xylene soluble portion in terms of polystyrene were obtained. From the obtained Mn(CXS), Mw(CXS), and Mz(CXS), various molecular weight distributions (Mw / Mn(CXS), Mz / Mn(CXS)) were calculated.

[0113] In the chromatogram of the GPC measurement, the peaks derived from the components in the propylene-based polymer composition were defined as the peaks from the rise of the target peak to just before the rise of the BHT peak.

[0114] (5) Heat shrinkage rate (unit: %) An A4-sized (297 mm x 210 mm) film was cut from the biaxially stretched film so that the long axis was parallel to the MD direction, and 200 mm gauge lines were drawn in both the MD and TD directions. The film was then hung in a 150°C oven for 30 minutes. The film was then removed and cooled at room temperature for 30 minutes, after which the gauge line lengths were measured. The heat shrinkage in each direction was calculated using the following formula: Heat shrinkage rate (%) = {(200 - gauge length after heating (mm)) / 200} x 100 The smaller the heat shrinkage rate, the more excellent the heat resistance.

[0115] (6) Young's modulus (unit: GPa) A 120mm x 20mm biaxially stretched film was taken so that the long side direction (120mm) coincided with the measurement direction (MD direction, TD direction). A tensile test was carried out using an A&D UNIVERSAL TESTING MACHINE STB-1225 at 23°C and 50% humidity, with a grip distance of 60mm and a tensile speed of 5mm / min. The Young's modulus (MD direction, TD direction) was measured from the tangent at the zero point of the tensile-stress curve.

[0116] <Production Example 1: Solid catalyst component 1 for olefin polymerization> A solid catalyst component 1 for olefin polymerization was obtained according to the method described in Example 1 of JP-A-2009-173870.

[0117] <Production Example 2: Solid catalyst component 2 for olefin polymerization> According to the method described in Example 1 of JP-A No. 2004-067850, a solid catalyst component 2 for olefin polymerization was obtained.

[0118] <β-crystal nucleating agent masterbatch> Propylene was polymerized by gas-phase polymerization using a Ziegler-Natta catalyst, triethylaluminum as a cocatalyst, and cyclohexylethyldimethoxysilane as an external donor under a hydrogen concentration of 0.95 mol% to obtain a propylene-based polymer. 95 parts by mass of the resulting propylene-based polymer was blended with 5 parts by mass of NU-100 (β-nucleating agent, manufactured by New Japan Chemical Co., Ltd.), 0.005 parts by mass of DHT-4C (neutralizing agent, manufactured by Kyowa Chemical Industry Co., Ltd.), 0.09 parts by mass of IRGANOX 1010 (antioxidant, manufactured by BASF Japan Ltd.), and 0.05 parts by mass of Sumilizer GP (antioxidant, manufactured by Sumitomo Chemical Co., Ltd.), followed by melt extrusion to obtain pelletized β-nucleating agent masterbatch.

[0119] <Example 1: Propylene-based polymer composition 1> (Preactivation of catalyst components for olefin polymerization) Dehydrated and degassed n-hexane (1.5 L), triethylaluminum (36.9 mmol), dicyclopentyldimethoxysilane (8.1 mmol) as an external electron donor, and the above-mentioned olefin polymerization catalyst component 1 (15.4 g) were placed in a 2 L autoclave equipped with a stirrer. After the temperature inside the autoclave was brought to 3-10°C, propylene (53.9 g) was continuously fed over 30 minutes to perform preactivation, yielding a prepolymerized catalyst slurry. The resulting prepolymerized catalyst slurry was transferred to a 160 L autoclave equipped with a stirrer and diluted with liquid butane (130 L).

[0120] (Polymerization process) Internal volume 1.4m 3 A gas-phase fluidized-bed reactor equipped with a stirrer was used. The fluidized-bed polymer load was 54 kg, the polymerization temperature was 86°C, the polymerization pressure was 1.9 MPaG, and the superficial gas velocity inside the reactor was 0.15 m / s. Propylene and hydrogen were supplied at an effective hydrogen concentration in the gas phase (hydrogen concentration / (hydrogen concentration + propylene concentration)) of 1.7 mol%. Triethylaluminum (27 mmol / h), dicyclopentyldimethoxysilane (5.9 mmol / h) as an external electron donor, and the above prepolymerization catalyst slurry (0.70 g / h as the mass of olefin polymerization catalyst component 1) were supplied, thereby producing a propylene polymer (13 kg / h). The propylene polymer was then continuously transferred to a post-treatment process.

[0121] (Post-processing process) The propylene polymer transferred from the gas-phase fluidized bed reactor to the drying tank was supplied with water (100 mL / h) and nitrogen gas (20 m 3 / h) was supplied to dry the propylene polymer and deactivate the catalyst.

[0122] 0.01 part by mass of DHT-4C (manufactured by Kyowa Chemical Industry Co., Ltd.), 0.09 part by mass of IRGANOX1010 (manufactured by BASF Japan Ltd.), and 0.05 part by mass of IRGAFOS168 (manufactured by BASF Japan Ltd.) were blended with 100 parts by mass of the obtained propylene polymer, and the blend was melt-extruded to obtain pelletized propylene polymer composition 1. The production conditions for propylene polymer composition 1 are shown in Table 2. The physical properties of propylene polymer composition 1 are shown in Table 3.

[0123] (Preparation of biaxially stretched film) Propylene polymer composition 1 was heated and melted at a resin temperature of 260°C using a T-die film-forming machine equipped with an extruder, and extruded onto a cooling roll at 30°C to obtain an unstretched sheet with a thickness of 0.5 mm. From the obtained unstretched sheet, a 10 cm square sheet was cut out. The four sides of the sheet were clamped with chucks and preheated for 3 minutes in a heating oven heated to 157°C, and then simultaneously stretched 6 times in both the MD and TD directions to obtain a biaxially stretched film. The evaluation results of the biaxially stretched film are shown in Table 3.

[0124] <Example 2: Propylene-based polymer composition 2> (Preactivation of catalyst components for olefin polymerization) Dehydrated and degassed n-hexane (1.5 L), triethylaluminum (36.9 mmol), cyclohexylethyldimethoxysilane (3.3 mmol) as an external electron donor, and the above-mentioned olefin polymerization catalyst component 2 (18.5 g) were placed in a 2 L autoclave equipped with a stirrer. After the temperature inside the autoclave was brought to 3-10°C, propylene (18.5 g) was continuously fed over 30 minutes to perform preactivation, yielding a prepolymerized catalyst slurry. The resulting prepolymerized catalyst slurry was transferred to a 160 L autoclave equipped with a stirrer and diluted with liquid butane (130 L).

[0125] (Polymerization process) Using a 163 L vessel-type reactor equipped with a stirrer, propylene (35 kg / h), hydrogen (37 NL / h), triethylaluminum (14 mmol / h), dicyclopentyldimethoxysilane (3.9 mmol / h), and the slurry of the prepolymerized catalyst components (0.69 g / h as the amount of catalyst components for olefin polymerization) were continuously fed into the reactor at a polymerization temperature of 72.5°C to obtain a propylene polymer (17 kg / h). The propylene polymer was continuously transferred to a post-treatment process.

[0126] (Post-processing process) The propylene polymer was transferred from the reactor to the drying tank, and water (100 mL / h) and nitrogen gas (20 Nm 3 / h) was supplied to dry the propylene polymer and deactivate the catalyst.

[0127] 0.01 part by mass of DHT-4C (manufactured by Kyowa Chemical Industry Co., Ltd.), 0.09 part by mass of IRGANOX1010 (manufactured by BASF Japan Ltd.), and 0.05 part by mass of IRGAFOS168 (manufactured by BASF Japan Ltd.) were blended with 100 parts by mass of the obtained propylene polymer, and the blend was melt-extruded to obtain pellets of propylene polymer composition 2. The production conditions for propylene polymer composition 2 are shown in Table 2. The physical properties of propylene polymer composition 2 are shown in Table 3.

[0128] (Preparation of biaxially stretched film) A biaxially stretched film was obtained using the propylene polymer composition 2 in the same manner as in Example 1. Table 3 shows the evaluation results of the biaxially stretched film.

[0129] <Production Example 1': Propylene-Based Polymer Composition 1'> A propylene polymer composition 1′ was obtained in the same manner as in Example 1, except that the production conditions were changed as shown in Table 2.

[0130] <Comparative Example 1: Propylene-Based Polymer Composition C1> A propylene-based polymer composition C1 was obtained in the same manner as in Example 1, except that the production conditions were changed as shown in Table 2. The physical properties of the propylene-based polymer composition C1 are shown in Table 3. Then, a biaxially stretched film was obtained in the same manner as in Example 1. The evaluation results of the biaxially stretched film are shown in Table 3.

[0131] <Comparative Example 2: Propylene-Based Polymer Composition C2> A propylene polymer composition C2 was obtained in the same manner as in Example 1, except that the production conditions were changed as shown in Table 2. The physical properties of the propylene polymer composition C2 are shown in Table 3. Then, a biaxially stretched film was obtained in the same manner as in Example 1. The evaluation results of the biaxially stretched film are shown in Table 3.

[0132] [Table 2]

[0133] In Table 2, "-" means that there are no applicable conditions or no data.

[0134] [Table 3]

[0135] <Example 3: Propylene-based polymer composition 3> The propylene polymer composition 1 (99 parts by mass) and the β-crystal nucleating agent masterbatch (1 part by mass) were melt-kneaded to obtain the propylene polymer composition 3. The physical properties of the propylene polymer composition 3 are shown in Table 4.

[0136] (Preparation of biaxially stretched film) Propylene-based polymer composition 3 was heated and melted at a resin temperature of 260°C using a T-die film-forming machine equipped with an extruder, and extruded onto a cooling roll at 30°C to obtain an unstretched sheet. The unstretched sheet was stretched 8 times in the MD direction using a stretching roll heated to 142°C to obtain a uniaxially stretched film. Both side edges of the uniaxially stretched film were gripped with two rows of chucks aligned along the MD, and the distance between the two rows of chucks was increased in the TD direction in a heating furnace heated to 170°C, thereby stretching the uniaxially stretched film 8 times in the TD direction. Subsequently, the distance between the two rows of chucks was narrowed in a heating furnace heated to 165°C, and the film was relaxed 19.5% in the TD direction to obtain a biaxially stretched film. The evaluation results of the biaxially stretched film are shown in Table 4.

[0137] <Example 4: Propylene-based polymer composition 4> Propylene polymer composition 1' (99 parts by mass) and a β-crystal nucleating agent masterbatch (1 part by mass) were melt-kneaded to obtain propylene polymer composition 4. The physical properties of propylene polymer composition 4 are shown in Table 4. Next, a biaxially stretched film was obtained in the same manner as in Example 3. The evaluation results of the biaxially stretched film are shown in Table 4.

[0138] <Comparative Example 3: Propylene-Based Polymer Composition C3> The propylene polymer composition C2 (99 parts by mass) and the β-crystal nucleating agent masterbatch (1 part by mass) were melt-kneaded to obtain a propylene polymer composition C3. The physical properties of the propylene polymer composition C3 are shown in Table 4. Next, a biaxially stretched film was obtained in the same manner as in Example 3. The evaluation results of the biaxially stretched film are shown in Table 4.

[0139] [Table 4]

[0140] As can be seen from the results in Tables 3 and 4, the biaxially stretched films of each Example that satisfy all of the constituent requirements of the present invention have a smaller heat shrinkage rate, particularly in the TD direction, than the biaxially stretched films of each Comparative Example, and are therefore superior in heat resistance.

Claims

1. A propylene-based polymer composition containing a propylene-based polymer, which satisfies the following requirements (1) to (4): (1) The melt flow rate measured at a temperature of 230° C. and a load of 2.16 kg is 2 g / 10 min to 10 g / 10 min. (2) The isotactic pentad fraction is 98.0% or more. (3) Satisfy the following formula (I). 3.0≦Mw / Mn≦20 (I) (In the formula, Mn represents the number average molecular weight of the propylene polymer composition measured by gel permeation chromatography. Mw represents the weight average molecular weight of the propylene polymer composition measured by gel permeation chromatography. (4) The following formula (II) is satisfied. (Mw(CXS) / Mn(CXS)) / (Mw / Mn)≦0.70 (II) (In the formula, Mn and Mw have the same meanings as above. Mn(CXS) represents the number average molecular weight of the cold xylene soluble portion of the propylene polymer composition measured by gel permeation chromatography, expressed in terms of polystyrene. Mw(CXS) represents the weight average molecular weight of the cold xylene soluble portion of the propylene polymer composition measured by gel permeation chromatography in terms of polystyrene.

2. The propylene polymer composition according to claim 1, which satisfies the following requirement (1'): (1') The melt flow rate measured at a temperature of 230°C and a load of 2.16 kg is 2 g / 10 min to 4 g / 10 min.

3. The propylene polymer composition according to claim 1 or 2, which satisfies the following requirement (2'): (2') The isotactic pentad fraction is 99.0% or more.

4. The propylene polymer composition according to any one of claims 1 to 3, which satisfies the following requirement (3'): (3') The following formula (I') is satisfied. 3.0≦Mw / Mn≦10 (I') (In the formula, Mn and Mw have the same meanings as above.)

5. The propylene polymer composition according to claim 4, which satisfies the following requirement (3''): (3'') Satisfies the following formula (I''). 3.0≦Mw / Mn≦5.0 (I'') (In the formula, Mn and Mw have the same meanings as above.)

6. The propylene polymer composition according to any one of claims 1 to 5, which satisfies the following requirement (4'): (4') Satisfies the following formula (II'). 0.50≦(Mw(CXS) / Mn(CXS)) / (Mw / Mn)≦0.70 (II') (In the formula, Mn, Mw, Mn(CXS), and Mw(CXS) have the same meanings as above.)

7. The propylene polymer composition according to any one of claims 1 to 6, which satisfies the following requirement (5): (5) Satisfies the following formula (III). Mw(CXS) / Mn(CXS)<3.0 (III) (In the formula, (CXS) and Mw(CXS) have the same meanings as above.)

8. The propylene polymer composition according to any one of claims 1 to 7, further comprising a stretchability improver.

9. The propylene polymer composition according to claim 8, wherein the stretchability improver is a β-crystal nucleating agent.

10. A method for producing the propylene polymer composition according to any one of claims 1 to 9, comprising: A method for producing a propylene-based polymer composition, comprising the following step (11): (11) A process for obtaining a propylene-based polymer by polymerizing propylene in the presence of an olefin polymerization catalyst obtained by contacting a solid catalyst component for olefin polymerization with an organoaluminum compound and an external electron donor, the process comprising: The external electron donor is a compound represented by the following formula (IV): SiR １ ｎ (OR ２ ) （４－ｎ） (IV) (In the formula, n represents an integer of 1 to 3. R １ represents a cyclic aliphatic hydrocarbon group having 3 to 10 carbon atoms. １ When there are multiple groups, they may be the same or different. R ２ represents a hydrocarbon group having 1 to 20 carbon atoms. ２ When there are multiple, they may be the same or different.)

11. A biaxially stretched film obtained using the propylene polymer composition according to any one of claims 1 to 9.

Images