Propylene-based polymer composition, biaxially stretched film, and packaging bag

Abstract

The present invention provides a propylene-based polymer composition that is useful in production of a biaxially stretched film that has excellent dimensional stability at high temperatures. The propylene-based polymer composition comprises two or more types of propylene-based polymer and satisfies requirements (1) and (2) below. (1) The amount of components having a molecular weight of not more than 100,000, as measured by gel permeation chromatography, is 30-50 mass%. (2) The amount of components having a molecular weight of 100,000-800,000, as measured by gel permeation chromatography, is 35-52 mass%.

Description

Propylene-based polymer composition, biaxially stretched film and packaging bag

[0001] The present invention relates to a propylene polymer composition containing a propylene polymer, a biaxially stretched film using the propylene polymer composition, and a packaging bag using the biaxially stretched film.

[0002] Conventionally, for example, as a film used for various packaging materials, a structure in which a polyethylene terephthalate (PET) biaxially oriented film is used as a base film and a polypropylene (PP) unoriented film or a polyethylene (PE) unoriented film is laminated to the base film as a sealant film has been known. Films of this 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 biaxially oriented film, which is the same type of olefin-based resin as the sealant film made of olefin-based resins such as polypropylene and polyethylene, as the base film.

[0004] However, polypropylene-based biaxially stretched films have a larger heat shrinkage rate than polyethylene terephthalate-based biaxially stretched films, etc. Therefore, films using polypropylene-based biaxially stretched films as base films have had the problem of being limited in their applications.

[0005] A known example of a polypropylene-based biaxially stretched film with improved heat resistance is the film described in Patent Document 1. Specifically, Patent Document 1 discloses a method for improving heat shrinkability and rigidity by converting a highly stereoregular polypropylene into a stretched polypropylene film having a crystal orientation within a predetermined range.

[0006] However, the film described in Patent Document 1 does not have sufficient dimensional stability at high temperatures.

[0007] International Publication No. 2015 / 012324

[0008] Therefore, an object of the present invention is to provide a propylene-based polymer composition useful for producing a biaxially stretched film having excellent dimensional stability at high temperatures, a biaxially stretched film using the propylene-based polymer composition, and a packaging bag using the biaxially stretched film.

[0009] The present invention provides the following [1] to

[10] .

[0010] [1] A propylene polymer composition containing two or more propylene polymers and satisfying the following requirements (1) and (2): (1) The amount of components having a molecular weight of 100,000 or less as measured by gel permeation chromatography is 30% by mass to 50% by mass. (2) The amount of components having a molecular weight of 100,000 or more and 800,000 or less as measured by gel permeation chromatography is 35% by mass to 52% by mass. [2] The propylene polymer composition according to [1], which further satisfies the following requirement (3): (3) The amount of components having a molecular weight of 800,000 or more as measured by gel permeation chromatography is 4% by mass to 18% by mass. [3] The propylene polymer composition according to [1] or [2], comprising a propylene polymer (a) having a melt flow rate of 3 g / 10 min or less and / or an intrinsic viscosity of 2.0 dL / g or more, and a propylene polymer (b) having a melt flow rate of 15 g / 10 min or more and / or an intrinsic viscosity of 1.4 dL / g or less. [4] The propylene polymer composition according to any of [1] to [3], having a melt flow rate of 4 g / min to 20 g / min. [5] The propylene polymer composition according to any of [1] to [4], having an isotactic pentad fraction of 98.0% or more. [6] The propylene polymer composition according to any of [1] to [5], having an intrinsic viscosity of 1.3 dL / g to 2.3 dL / g. [7] The propylene polymer composition according to any of [1] to [6], further comprising a stretchability improver. [8] The propylene-based polymer composition according to [7], wherein the stretchability improver is at least one selected from the group consisting of a β-crystal nucleating agent and a hydrocarbon resin. [9] A biaxially stretched film containing the propylene-based polymer composition according to any one of [1] to [8].

[10] A packaging bag comprising the biaxially stretched film according to [9].

[0011] According to the present invention, it is possible to provide a propylene-based polymer composition useful for producing a biaxially stretched film having excellent dimensional stability at high temperatures, a biaxially stretched film using the propylene-based polymer composition, and a packaging bag using the biaxially stretched film.

[0012] The propylene polymer composition according to this embodiment contains two or more types of propylene polymers.

[0013] The propylene-based polymer is a polymer containing more than 50% by mass of monomer units derived from propylene. For example, the propylene-based polymer may be a propylene homopolymer or a propylene-based copolymer. From the viewpoint of the heat shrinkage rate 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 comonomer selected from ethylene and an α-olefin having 4 to 20 carbon atoms.

[0014] Examples of 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 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, 1-dodecene, and the like are included, and 1-butene, 1-pentene, 1-hexene, or 1-octene is preferred, and 1-butene is more preferred.

[0015] Examples of propylene copolymers include propylene-ethylene copolymers, propylene-α-olefin copolymers, etc. Examples of propylene-α-olefin copolymers include propylene-1-butene copolymers, propylene-1-hexene copolymers, propylene-1-octene copolymers, propylene-ethylene-1-butene copolymers, propylene-ethylene-1-hexene copolymers, propylene-ethylene-1-octene copolymers, etc., and preferred are propylene-ethylene copolymers, propylene-1-butene copolymers, and propylene-ethylene-1-butene copolymers.

[0016] When the propylene-based copolymer is a propylene-ethylene copolymer, the ethylene content 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 the heat shrinkage rate and rigidity of the biaxially stretched film.

[0017] When the propylene-based copolymer is a propylene-α-olefin copolymer, the α-olefin content is preferably 8.0% by mass or less, more preferably 3.0% by mass or less, and even more preferably 1.0% by mass or less, from the viewpoint of the heat shrinkage rate and rigidity of the biaxially stretched film.

[0018] When the propylene-based copolymer is a propylene-ethylene-α-olefin copolymer, the total content of ethylene and α-olefin is preferably 4.0% by mass or less, more preferably 3.0% by mass or less, and even more preferably 1.0% by mass or less, from the viewpoint of the heat shrinkage rate and rigidity of the biaxially stretched film.

[0019] 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 1.5% by mass, and even more preferably 0.1% to 1.0% by mass. By setting the CXS within the above range, the biaxially stretched film can be produced with good stretchability and can exhibit high rigidity and excellent shrinkage at high temperatures. The CXS of the propylene polymer can be adjusted to the above range, for example, by selecting the type of external donor used during propylene polymerization. Specific examples of external donors include cyclohexylethyldimethoxysilane, dicyclopentyldimethoxysilane, and di-tert-butyldimethoxysilane. The CXS can be determined by the same method as the method for measuring the CXS of a propylene polymer composition described in the Examples section below.

[0020] The propylene polymer composition may contain two or more propylene polymers and other components. The total content of the two or more propylene polymers in the propylene polymer composition is preferably 80% by mass to 100% by mass, more preferably 90% by mass to 100% by mass, and even more preferably 99% by mass to 100% by mass. The propylene polymer composition usually contains a plurality of propylene polymers having different MFRs and / or intrinsic viscosities. The propylene polymer composition is preferably a propylene polymer composition containing a propylene polymer (a) having an MFR of 3 g / 10 min or less and / or an intrinsic viscosity of 2.0 dL / g or more, and a propylene polymer (b) having an MFR of 15 g / 10 min or more and / or an intrinsic viscosity of 1.4 dL / g or less, and more preferably a propylene polymer composition containing a propylene polymer (a) having an MFR of 0.003 to 1 g / 10 min and / or an intrinsic viscosity of 2.7 to 7.3 dL / g, and a propylene polymer (b) having an MFR of 30 to 800 g / 10 min and / or an intrinsic viscosity of 0.6 to 1.2 dL / g. The use of a propylene polymer composition containing multiple types of propylene polymers with different MFRs has the effect of exhibiting good stretchability during the production of a biaxially stretched film, and also exhibiting high rigidity and an excellent shrinkage rate at high temperatures in the biaxially stretched film. The MFR and intrinsic viscosity of the propylene polymer can be changed, for example, by adjusting the hydrogen concentration used during propylene polymerization. The MFR and intrinsic viscosity can be determined by the same method as the method for measuring the MFR and intrinsic viscosity of the propylene polymer composition described in the Examples below.

[0021] The contents of the propylene polymer (a) and the propylene polymer (b) in the propylene polymer composition are preferably 10% by mass to 65% by mass of the propylene polymer (a) and 35% by mass to 90% by mass of the propylene polymer (b), and more preferably 20% by mass to 60% by mass of the propylene polymer (a) and 40% by mass to 80% by mass of the propylene polymer (b), relative to the total content of the propylene polymer (a) and the propylene polymer (b).

[0022] A method for producing a propylene polymer composition containing two or more propylene polymers includes a method in which at least two propylene polymers are produced separately and the resulting propylene polymers are mixed to form a propylene polymer composition. Examples of methods for producing at least two propylene polymers separately include known polymerization methods. Examples include solvent polymerization carried out in the presence of an inert solvent, bulk polymerization carried out in the presence of a liquid monomer, and gas-phase polymerization carried out substantially in the absence of a liquid medium. Gas-phase polymerization is preferred. Examples of methods for producing a propylene polymer composition containing at least two propylene polymers include a polymerization method in which two or more of the above polymerization methods are combined, and a method in which a plurality of polymerization steps are carried out in multiple stages (multistage polymerization).

[0023] The method for mixing at least two types of propylene polymers produced separately may be any method that uniformly disperses these polymers. Examples include a method in which at least two types of propylene polymers are mixed using a ribbon blender, Henschel mixer, tumbler mixer, or the like, and the mixture is melt-kneaded using an extruder, etc.; a method in which at least two types of propylene polymers are melt-kneaded separately and pelletized, and the pellets are mixed and further melt-kneaded using the same method as above; a method in which at least two types of 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 processing machine; and a method in which at least two types of propylene polymers are melt-kneaded separately and pelletized, and the pellets are fed individually to the extruder of a film processing machine and mixed. Another example includes a method in which a masterbatch containing 100 parts by mass of one propylene polymer and 1 to 99 parts by mass of the other propylene polymer is previously prepared, and the two propylene polymers are mixed appropriately to achieve a predetermined concentration.

[0024] When mixing at least two kinds of propylene polymers produced separately, a stabilizer, a lubricant, an antistatic agent, an antiblocking agent, various inorganic or organic fillers, and the like may be added as needed.

[0025] As the catalyst used for polymerizing each of the at least two kinds of propylene polymers, a catalyst for stereoregular polymerization of propylene is used whether they are polymerized individually or in a multi-stage polymerization method.

[0026] Examples of the catalyst for stereoregular polymerization of propylene include catalyst systems in which a solid catalyst component, such as a titanium trichloride catalyst or a Ti-Mg catalyst containing titanium, magnesium, a halogen, and an electron donor as essential components, is combined with a third component, such as an organoaluminum compound and, if necessary, an electron donor compound, and metallocene catalysts.

[0027] Preferred are catalyst systems that combine a solid catalyst component containing magnesium, titanium, a halogen, and an electron donor as essential components, an organoaluminum compound, and an electron donor compound, and specific examples thereof include the catalyst systems described in JP-A Nos. 61-218606, 61-287904, 7-216017, and 2004-182876.

[0028] The propylene polymer composition according to this embodiment may contain, in addition to the propylene polymer, a stretchability improver, such as at least one selected from the group consisting of a β-crystal nucleating agent and a hydrocarbon resin.

[0029] 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 comprising component A, which is an organic dibasic acid, and component B, which is an oxide, hydroxide, or salt of a metal of Group IIA of the periodic table; and compositions comprising a cyclic phosphorus compound and a magnesium compound. One or more of these may be used in combination. Among the above β-crystal nucleating agents, the amide compounds N,N'-dicyclohexyl-2,6-naphthalenedicarboxyamide, N,N-dicyclohexylterephthalamide, and N,N'-diphenylhexanediamide are preferred, with N,N'-dicyclohexyl-2,6-naphthalenedicarboxyamide being more preferred.

[0030] When the propylene polymer composition of the present embodiment contains a β-crystal nucleating agent, the content of the β-crystal nucleating agent is preferably 50 ppm by mass to 5000 ppm by mass, more preferably 100 ppm by mass to 1500 ppm by mass, and further preferably 100 ppm by mass to 900 ppm by mass.

[0031] Examples of hydrocarbon resins include cyclopentadiene resins made from petroleum-based unsaturated hydrocarbons, and resins made primarily from higher olefin hydrocarbons.

[0032] When the propylene-based polymer composition of the present embodiment contains a hydrocarbon resin, the content of the hydrocarbon resin is preferably 0.1% by mass to 30% by mass, more preferably 0.3% by mass to 20% by mass, and even more preferably 0.5% by mass to 10% by mass.

[0033] The propylene polymer composition of the present embodiment satisfies the following requirements (1) and (2): (1) The amount of components having a molecular weight of 100,000 or less, as measured by gel permeation chromatography (hereinafter also referred to as GPC), is 30% by mass to 50% by mass; and (2) The amount of components having a molecular weight of 100,000 or more and 800,000 or less, as measured by gel permeation chromatography, is 35% by mass to 52% by mass. The amounts of components having a molecular weight of 100,000 or less and components having a molecular weight of 100,000 or more and 800,000 or less can be determined by the method described in [Examples] below.

[0034] The amount of components having a molecular weight of 100,000 or less as measured by GPC is preferably 35% by mass to 50% by mass, more preferably 40% by mass to 50% by mass. The amount of components having a molecular weight of 100,000 or less can be changed by, for example, mixing a plurality of propylene polymers having different MFRs to adjust the molecular weight and molecular weight distribution of the propylene polymer composition.

[0035] The amount of components having a molecular weight of 100,000 or more and 800,000 or less as measured by GPC is preferably 40% by mass to 52% by mass, more preferably 42% by mass to 52% by mass. The amount of components having a molecular weight of 100,000 or more and 800,000 or less can be changed by, for example, mixing a plurality of propylene polymers having different MFRs to adjust the molecular weight and molecular weight distribution of the propylene polymer composition.

[0036] The propylene polymer composition of the present embodiment preferably further satisfies the following requirement (3): (3) The amount of components having a molecular weight of 800,000 or more measured by gel permeation chromatography is 4% by mass to 18% by mass. The amount of components having a molecular weight of 800,000 or more can be determined by the method described in [Examples] below.

[0037] The amount of components having a molecular weight of 800,000 or more measured by GPC is preferably 4% by mass to 15% by mass, more preferably 7% by mass to 13% by mass. The amount of components having a molecular weight of 800,000 or more can be changed by, for example, mixing a plurality of propylene polymers having different MFRs to adjust the molecular weight and molecular weight distribution of the propylene polymer composition.

[0038] The melt flow rate (hereinafter abbreviated as MFR) of the propylene polymer composition is preferably 4 g / 10 min to 18 g / 10 min, more preferably 4 g / 10 min to 15 g / 10 min, and even more preferably 6 g / 10 min to 12 g / 10 min. By using a propylene polymer having an MFR within the above range, the polypropylene in a molten state has an appropriate viscosity, which results in good stretchability during the production of a biaxially stretched film, and the biaxially stretched film can exhibit high rigidity and an excellent shrinkage rate at high temperatures. The MFR of the propylene polymer composition can be varied by, for example, mixing multiple propylene polymers having different MFRs to adjust the molecular weight and molecular weight distribution of the propylene polymer composition. The MFR can be determined by the method described in the Examples section below.

[0039] The isotactic pentad fraction (hereinafter abbreviated as [mmmm]) of the propylene polymer composition is preferably 98.3% or more, more preferably 98.5% to 100%. Use of a propylene polymer composition having an [mmmm] within the above range has the effect of enabling a biaxially stretched film to exhibit high rigidity and excellent shrinkage at high temperatures. The [mmmm] of the propylene polymer composition can be adjusted to fall within the above range by selecting the type of external donor used during propylene polymerization. Specific examples of external donors include cyclohexylethyldimethoxysilane, dicyclopentyldimethoxysilane, and di-tert-butyldimethoxysilane. [mmmm] can be determined by the method described in [Examples] below.

[0040] The intrinsic viscosity of the propylene polymer composition is preferably 1.3 dL / g to 2.1 dL / g, more preferably 1.3 dL / g to 1.9 dL / g, and even more preferably 1.4 dL / g to 1.8 dL / g. A propylene polymer composition having an intrinsic viscosity within the above range has the effect of exhibiting excellent fluidity and processability. The intrinsic viscosity of the propylene polymer composition can be changed by mixing multiple propylene polymers having different intrinsic viscosities and adjusting the molecular weight and molecular weight distribution of the propylene polymer composition. The intrinsic viscosity can be determined by the method described in [Examples] below.

[0041] The cold xylene solubles content (CXS) of the propylene polymer composition is preferably 3.0% by mass or less, more preferably 0.1% by mass to 2.0% by mass, and even more preferably 0.3% by mass to 1.5% 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 exhibit high rigidity and an excellent shrinkage rate at high temperatures. The CXS can be determined by the method described later in [Examples].

[0042] The biaxially stretched film according to this embodiment can be obtained by biaxially stretching the propylene polymer composition according to this embodiment. Specific methods for biaxial stretching will be described later.

[0043] The thickness of the biaxially stretched film according to this embodiment is preferably 10 μm to 70 μm, and more preferably 10 μm to 30 μm.

[0044] The method for producing the biaxially stretched film according to this embodiment may be a sequential biaxial stretching method or a simultaneous biaxial stretching method.

[0045] The method for producing a biaxially stretched film according to this embodiment includes an extrusion step in which the propylene-based polymer composition according to this embodiment is heated and melted using an extruder and extruded onto a cooling roll to obtain an unstretched sheet. In the extrusion step, for example, the propylene-based polymer composition is heated and melted using an extruder and extruded through a T-die onto a cooling roll, where it is cooled and fixed into a sheet, thereby obtaining an unstretched sheet.

[0046] The method for producing a biaxially stretched film according to this embodiment also includes an MD stretching step in which the unstretched sheet obtained in the extrusion step is stretched in the MD direction by 4 to 10 times, preferably 5 to 10 times, using a stretching roll to obtain a uniaxially stretched sheet.

[0047] The method for producing a biaxially stretched film according to this embodiment also includes 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, thereby obtaining a biaxially stretched film.

[0048] The method for producing a biaxially stretched film according to this embodiment may also 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 3% to 30%, preferably 3% 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 3%, the shrinkage rate during heating will be high, and a biaxially stretched film with excellent heat resistance will not be obtained. Furthermore, if the relaxation rate exceeds 30%, the film thickness unevenness will tend to increase. The relaxation rate can be calculated using the following formula (X): Relaxation rate=(L1−L2) / L1×100 (X) (where L1 is the distance between the chucks in the TD direction before relaxing the film, and L2 is the distance between the chucks in the TD direction after relaxing the film.)

[0049] Furthermore, the method for producing a biaxially stretched film according to this embodiment may include a step of performing corona treatment or the like, if necessary.

[0050] 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 chill roll when the propylene polymer composition extruded from the T-die is cooled and fixed into a sheet is preferably 10 to 100°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.

[0051] 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.

[0052] The biaxially stretched film according to this embodiment can be used as various packaging materials. For example, a packaging bag formed from the multilayer film can be used to package any object to be packaged, such as food, clothing, or miscellaneous goods.

[0053] The propylene-based polymer composition, biaxially stretched film, and packaging bag 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-described 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 other embodiments).

[0054] The measured values ​​of each item in the examples and comparative examples were measured by the following methods.

[0055] (1) Molecular weight, amount of components at specific molecular weights Various molecular weights (number average molecular weight Mn, weight average molecular weight Mw, z-average molecular weight Mz) and amount of components at specific molecular weights (wt%) of the propylene polymer composition were measured using gel permeation chromatography (GPC) under the following conditions. Note that, based on the description of ISO 16014-1, the baseline on the chromatogram was defined to designate the peak derived from the propylene polymer. (GPC Apparatus and Software) Apparatus: HLC-8321 GPC / HT (Tosoh) Software: HLC-8321 GPC / HT Program Version 2.02 (Tosoh) (Measurement Conditions) GPC column: TSKgel GMHHR-H(S)HT 7.8 mm I.D. x 300 mm (Tosoh), 3 tubes. Mobile phase: ortho-dichlorobenzene (Fujifilm Wako Pure Chemical Industries, Ltd., special grade) supplemented with BHT at a concentration of 0.1 g / 100 mL. Flow rate: 1 mL / min. Column oven temperature: 140°C. Autosampler temperature: 140°C. System oven temperature: 40°C. Detector: Refractive index detector (RID). RID cell temperature: 140°C. Sample solution injection volume: 300 μL (Sample solution preparation conditions). Solvent: ortho-dichlorobenzene supplemented with BHT at 0.1 g / 100 mL. - Sample solution concentration: 1 mg / mL - Dissolution conditions: 5 mg of sample was sealed in a 1000 mesh SUS wire mesh bag, the wire mesh 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, the test tube was placed in an automatic dissolution shaker DF-8020 (Tosoh), and stirred at a stirring rate of 60 reciprocations per minute at 140°C for 120 minutes. (Analysis method) As standard substances for GPC column calibration, 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 and the mixture was left to stand at room temperature for 120 minutes to dissolve.

[0056]

[0057] 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 polypropylene-equivalent average molecular weights Mn, Mw, and Mz. Furthermore, the total area between the molecular weight distribution curve derived from the propylene-based polymer and the baseline was defined as 100%, and an integral distribution curve was obtained to determine the amount of components at specific molecular weights in the propylene-based polymer composition. This determined the amount of components with polypropylene-equivalent molecular weights of 100,000 or less, the amount of components from 100,000 to 800,000, and the amount of components with polypropylene-equivalent molecular weights of 800,000 or more.

[0058] (2) 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.

[0059] (3) Isotactic pentad fraction ([mmmm], unit: %) The [mmmm] of the propylene-based polymer composition was measured by 13C-NMR under the following conditions. The NMR absorption peaks of the propylene-based polymer contained in the propylene-based polymer composition were assigned according to the method published by A. Zambelli et al. (Macromolecules, Vol. 8, p. 687, 1975). [Measurement conditions] Model: Bruker AVANCE600 Probe: 10 mm cryoprobe Measurement temperature: 135°C Pulse repetition time: 4 seconds Pulse width: 45° Number of accumulations: 256 Magnetic field strength: 600 MHz

[0060] (4) Intrinsic Viscosity ([η], Unit: dL / g) The intrinsic viscosity of a propylene polymer or a propylene polymer composition was measured in tetralin at 135° C. using an Ubbelohde viscometer.

[0061] (5) Cold xylene solubles (CXS, unit: mass %) 0.1 g or 1 g of the propylene polymer composition was completely dissolved in 100 ml of boiling xylene, and then the temperature was lowered to 20°C and the mixture was stirred for 1 hour. The resulting mixture was separated into a precipitate and a solution by filtration, and the amount of components dissolved in the solution was quantified by liquid chromatography under the following conditions to determine the CXS. Column: SHODEX GPC KF-801 Eluent: tetrahydrofuran Column oven temperature: 40°C Sample injection amount: 130 μL Flow rate: 1 mL / min Detector: differential refractometer

[0062] (6) Film Thickness (unit: μm) The thickness of the biaxially stretched film was measured using a contact type film thickness meter in accordance with Method A described in JIS K7130-1999.

[0063] (7) Young's modulus (unit: GPa) A 120 mm × 20 mm biaxially stretched film was taken so that the long side direction (120 mm) coincided with the measurement direction (flow direction during film production / hereinafter: MD direction), and a tensile test was carried out using an A&D UNIVERSAL TESTING MACHINE STB-1225 in an atmosphere of 23 ° C. and 50% humidity, with a grip spacing of 60 mm and a tensile speed of 5 mm / min, and the Young's modulus was measured from the tangent at the zero point of the tensile-stress curve.

[0064] (8) Heat shrinkage (unit: %) A biaxially stretched film having a size of 100 mm square (100 mm length x 100 mm width) was taken, a gauge line of 80 mm in the MD direction was drawn, and the film was hung in an oven at 150°C for 30 minutes. The film was then taken out and cooled at room temperature for 30 minutes, after which the length of each gauge line was measured. The heat shrinkage in each direction was calculated using the following formula. A small heat shrinkage indicates excellent dimensional stability at high temperatures. Heat shrinkage (%) = {80 - gauge line length after heating (mm)) / 80} x 100

[0065] The components used in the examples and comparative examples are as follows.

[0066] Example 1 Preparation of Propylene Polymer Composition 1 and Biaxially Stretched Film 1 A bulk polymerization tank and a gas-phase polymerization tank were connected in series, and polymerization was carried out according to the following procedure. Using a Ziegler-Natta catalyst, triethylaluminum as a co-catalyst, and dicyclopentyldimethoxysilane as an external donor, propylene and hydrogen were supplied by bulk polymerization at a ratio of 1 NL (normal liter) to 10 kg of propylene, and propylene was polymerized to obtain Propylene Polymer 1-1. A portion of Propylene Polymer 1-1 was sampled and analyzed, and the intrinsic viscosity was found to be 3.6 dL / g. The propylene polymer 1-1 was continuously transferred to a gas-phase polymerization vessel without being deactivated, and a propylene polymer 1-2 was polymerized by gas-phase polymerization in an environment where the effective hydrogen concentration in the gas phase (hydrogen concentration / (hydrogen concentration+propylene concentration)) was 13.2 mol %, thereby obtaining a propylene polymer composition (containing propylene polymer 1-1 and propylene polymer 1-2). The content of propylene polymer 1-1 in 100 parts by mass of the propylene polymer composition was 36 parts by mass, and the content of propylene polymer 1-2 was 64 parts by mass. The intrinsic viscosity of propylene polymer 1-2 was calculated from the following formula and was found to be 0.8 dL / g. [η] １－２ = ([η] Ｔ ×100-[η] １－１ ×W １－１ ) / W １－２ (In the formula, [η] １－２ indicates the intrinsic viscosity (dL / g) of the propylene polymer 1-2. Ｔ represents the intrinsic viscosity (dL / g) of the propylene polymer composition. １－１ indicates the intrinsic viscosity (dL / g) of the propylene polymer 1-1. １－１ indicates the content (mass%) of propylene polymer 1-1. １－２ indicates the content (mass%) of propylene polymer 1-2.)

[0067] 0.01 part by mass of DHT-4C (neutralizing agent, manufactured by Kyowa Chemical Industry Co., Ltd.), 0.18 part by mass of IRGANOX1010 (manufactured by BASF Japan Ltd.), and 0.25 part by mass of IRGAFOS168 (manufactured by BASF Japan Ltd.) were blended with 100 parts by mass of the obtained propylene polymer composition, and the blend was melt-extruded to obtain pellets of propylene polymer composition 1. The propylene polymer composition 1 had an Mn of 50,000, an Mw of 280,000, and an Mz of 960,000. The physical properties of the obtained propylene polymer composition 1 are shown in Table 2 below.

[0068] Propylene polymer composition 1 was heated and melted at a resin temperature of 250°C using a T-die film-forming machine equipped with an extruder with a screw diameter of 20 mmφ, and extruded onto a cooling roll at 80°C to obtain an unstretched sheet with a thickness of 0.5 mm. The four sides of the obtained unstretched sheet were gripped with chucks and preheated for 3 minutes in a heating oven heated to 157°C, and then simultaneously stretched 6 times in each of the MD and TD directions (directions perpendicular to the flow during film formation) to obtain biaxially stretched film 1. The production conditions and measured physical properties of the obtained biaxially stretched film 1 are shown in Table 3 below.

[0069] Example 2 Preparation of Propylene Polymer Composition 2 and Biaxially Stretched Film 2 A bulk polymerization tank and a gas-phase polymerization tank were connected in series, and polymerization was carried out according to the following procedure. Using a Ziegler-Natta catalyst, triethylaluminum as a co-catalyst, and cyclohexylethyldimethoxysilane as an external donor, propylene was polymerized by bulk polymerization without supplying hydrogen, to obtain propylene polymer 2-1. A portion of propylene polymer 2-1 was sampled and analyzed, and the intrinsic viscosity was found to be 7.1 dL / g. The propylene polymer 2-1 was continuously transferred to a gas-phase polymerization tank without being deactivated, and propylene polymer 2-2 was polymerized by gas-phase polymerization in an environment with an effective hydrogen concentration of 4.9 mol% in the gas phase, to obtain a propylene polymer composition (containing propylene polymer 2-1 and propylene polymer 2-2). The content of propylene polymer 2-1 in 100 parts by mass of the propylene polymer composition was 20 parts by mass, and the content of propylene polymer 2-2 was 80 parts by mass. The intrinsic viscosity of propylene polymer 2-2 was calculated in the same manner as for propylene polymer composition 1, and was found to be 0.9 dL / g.

[0070] 0.01 part by mass of DHT-4C (neutralizing agent, manufactured by Kyowa Chemical Industry Co., Ltd.), 0.18 part by mass of IRGANOX1010 (manufactured by BASF Japan Ltd.), and 0.25 part by mass of IRGAFOS168 (manufactured by BASF Japan Ltd.) were blended with 100 parts by mass of the obtained propylene polymer composition, and the blend was melt-extruded to obtain pellets of propylene polymer composition 2. The propylene polymer composition 2 had an Mn of 49,000, an Mw of 320,000, and an Mz of 1,420,000. The physical properties of the obtained propylene polymer composition 2 are shown in Table 2 below.

[0071] Biaxially stretched film 2 was obtained under the same conditions as in Example 1, except that propylene polymer composition 1 in Example 1 was changed to propylene polymer composition 2. The production conditions and measured values ​​of physical properties of the obtained biaxially stretched film 2 are shown in Table 3 below.

[0072] Synthesis Example 1 Preparation of Propylene Polymer Composition 3-1 Using a Ziegler-Natta catalyst, triethylaluminum as a co-catalyst, and cyclohexylethyldimethoxysilane as an external donor, propylene was polymerized by gas phase polymerization under an environment with an effective hydrogen concentration of 9.3 mol% in the gas phase, to obtain a propylene polymer 3-1. The propylene polymer 3-1 had an intrinsic viscosity of 0.9 dL / g. 0.01 part by mass of DHT-4C (neutralizing agent, manufactured by Kyowa Chemical Industry Co., Ltd.) and 0.125 part by mass of IRGANOX 1010 (manufactured by BASF Japan Ltd.) were blended with 100 parts by mass of the obtained propylene polymer 3-1, followed by melt extrusion to obtain a pellet-shaped propylene polymer composition 3-1.

[0073] Synthesis Example 2: Preparation of Propylene Polymer Intermediate Composition 3-2 Using a Ziegler-Natta catalyst, triethylaluminum as a co-catalyst, and cyclohexylethyldimethoxysilane as an external donor, propylene was polymerized by gas phase polymerization under an effective hydrogen concentration of 0.14 mol% in the gas phase, to obtain a propylene polymer 3-2. The propylene polymer 3-2 had an intrinsic viscosity of 2.4 dL / g. 100 parts by mass of the obtained propylene polymer 3-2 were blended with 0.01 parts by mass of DHT-4C (neutralizing agent, manufactured by Kyowa Chemical Industry Co., Ltd.), 0.05 parts by mass of IRGANOX 1010 (antioxidant, manufactured by BASF Japan Ltd.), and 0.1 parts by mass of Sumilizer GP (antioxidant, manufactured by Sumitomo Chemical Co., Ltd.), followed by melt extrusion to obtain pellets of a propylene polymer composition 3-2.

[0074] Example 3 Preparation of Propylene Polymer Composition 3 and Biaxially Stretched Film 3 Propylene polymer composition 3-1 (55 parts by mass) and propylene polymer composition 3-2 (45 parts by mass) were mixed to prepare propylene polymer composition 3. The propylene polymer composition 3 had an Mn of 44,000, an Mw of 220,000, and an Mz of 640,000. The physical properties of pellets obtained by melt-extruding propylene polymer composition 3 are shown in Table 2 below.

[0075] Biaxially stretched film 3 was obtained under the same conditions as in Example 1, except that propylene polymer composition 1 in Example 1 was changed to propylene polymer composition 3. The production conditions and measured values ​​of physical properties of the obtained biaxially stretched film 3 are shown in Table 3 below.

[0076] Comparative Example 1: Preparation of Propylene Polymer Composition C1 and Biaxially Stretched Film C1 Propylene was polymerized by gas phase polymerization using a Ziegler-Natta catalyst, triethylaluminum as a co-catalyst, and cyclohexylethyldimethoxysilane as an external donor in an environment with a hydrogen concentration of 0.98 mol%, to obtain a propylene polymer C1-1. The propylene polymer C1-1 had an intrinsic viscosity of 1.7 dL / g. Propylene was polymerized by gas phase polymerization using a Ziegler-Natta catalyst, triethylaluminum as a co-catalyst, and cyclohexylethyldimethoxysilane as an external donor in an environment with an effective hydrogen concentration in the gas phase of 0.014 mol%, to obtain a propylene polymer C1-2. The propylene polymer C1-2 had an intrinsic viscosity of 3.6 dL / g. Propylene polymer C1-1 (91 parts by mass), propylene polymer C1-2 (9 parts by mass), 0.01 part by mass of DHT-4C (neutralizing agent, manufactured by Kyowa Chemical Industry Co., Ltd.), 0.18 part by mass of IRGANOX1010 (manufactured by BASF Japan Ltd.), and 0.25 part by mass of IRGAFOS168 (manufactured by BASF Japan Ltd.) were blended and then mixed to prepare propylene polymer composition C1. The propylene polymer composition C1 had an Mn of 66,000, an Mw of 250,000, and an Mz of 660,000. The physical properties of pellets obtained by melt-extruding the propylene polymer composition C1 are shown in Table 2 below.

[0077] A biaxially stretched film C1 was obtained under the same conditions as in Example 1, except that the propylene polymer composition 1 in Example 1 was changed to the propylene polymer composition C1. The production conditions and measured values ​​of the physical properties of the obtained biaxially stretched film C1 are shown in Table 3 below.

[0078] Synthesis Example 3: Preparation of β-crystal nucleating agent masterbatch Using a Ziegler-Natta catalyst, triethylaluminum as a co-catalyst, and cyclohexylethyldimethoxysilane as an external donor, propylene was polymerized by gas phase polymerization under an effective hydrogen concentration of 0.98 mol% in the gas phase to obtain a propylene-based polymer. The intrinsic viscosity of the obtained propylene-based polymer was 1.7 dL / g. 95 parts by mass of the obtained propylene-based polymer was blended with 5 parts by mass of NU-100 (β-crystal 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 IRGANOX1010 (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 a pellet-shaped β-crystal nucleating agent masterbatch.

[0079] Example 11 Preparation of Propylene Polymer Composition 11 and Biaxially Stretched Film 11 The propylene polymer composition (containing propylene polymer 1-1 and propylene polymer 1-2) (99 parts by mass) used in preparing the propylene polymer composition 1, a β-crystal nucleating agent masterbatch (1 part by mass), 0.01 parts by mass of DHT-4C (neutralizing agent, manufactured by Kyowa Chemical Industry Co., Ltd.), 0.18 parts by mass of IRGANOX1010 (manufactured by BASF Japan Ltd.), and 0.25 parts by mass of IRGAFOS168 (manufactured by BASF Japan Ltd.) were blended and then mixed to prepare propylene polymer composition 11. The propylene polymer composition 11 had an Mn of 53,000, an Mw of 270,000, and an Mz of 870,000. The physical properties of pellets obtained by melt-extruding the propylene polymer composition 11 are shown in Table 2 below.

[0080] Propylene polymer composition 11 was heated and melted at a resin temperature of 250°C using a T-die film-forming machine equipped with an extruder with a screw diameter of 20 mmφ, and extruded onto a cooling roll at 80°C to obtain an unstretched sheet with a thickness of 0.5 mm. The four sides of the obtained unstretched sheet were gripped with chucks and preheated for 3 minutes in a heating oven heated to 153°C, and then simultaneously stretched 6 times in each of the MD and TD directions to obtain biaxially stretched film 11. The production conditions and measured physical properties of the obtained biaxially stretched film 11 are shown in Table 3 below.

[0081] Example 12 Preparation of Propylene Polymer Composition 12 and Biaxially Stretched Film 12 The propylene polymer composition (containing propylene polymer 2-1 and propylene polymer 2-2) (99 parts by mass) used in preparing the propylene polymer composition 2, a β-crystal nucleating agent masterbatch (1 part by mass), 0.01 parts by mass of DHT-4C (neutralizing agent, manufactured by Kyowa Chemical Industry Co., Ltd.), 0.18 parts by mass of IRGANOX1010 (manufactured by BASF Japan Ltd.), and 0.25 parts by mass of IRGAFOS168 (manufactured by BASF Japan Ltd.) were blended and then mixed to prepare the propylene polymer composition 12. The propylene polymer composition 12 had an Mn of 47,000, an Mw of 300,000, and an Mz of 1,250,000. The physical properties of pellets obtained by melt-extruding the propylene polymer composition 12 are shown in Table 2 below.

[0082] A biaxially stretched film 12 was obtained under the same conditions as in Example 11, except that the propylene-based polymer composition 11 in Example 11 was changed to the propylene-based polymer composition 12. The production conditions and measured values ​​of the physical properties of the obtained biaxially stretched film 12 are shown in Table 3 below.

[0083] Example 13 Preparation of Propylene Polymer Composition 13 and Biaxially Stretched Film 13 Propylene polymer composition 3-1 (54 parts by mass), propylene polymer composition 3-2 (45 parts by mass), and a β-crystal nucleating agent masterbatch (1 part by mass) were mixed to prepare propylene polymer composition 13. The propylene polymer composition 13 had an Mn of 47,000, an Mw of 220,000, and an Mz of 630,000. The physical properties of pellets obtained by melt-extruding the propylene polymer composition 13 are shown in Table 2 below.

[0084] A biaxially stretched film 13 was obtained under the same conditions as in Example 11, except that the propylene-based polymer composition 11 in Example 11 was changed to the propylene-based polymer composition 13. The production conditions and measured values ​​of the physical properties of the obtained biaxially stretched film 13 are shown in Table 3 below.

[0085]

[0086]

[0087] From Table 2 above, it can be seen that the biaxially stretched films of each Example have a smaller heat shrinkage rate than the biaxially stretched films of the Comparative Examples. In other words, it can be seen that the biaxially stretched films of each Example have excellent dimensional stability at high temperatures. It can also be seen that the biaxially stretched films of each Example have a Young's modulus equal to or greater than that of the biaxially stretched films of the Comparative Examples. In other words, it can be seen that the biaxially stretched films of each Example also have excellent rigidity.

[0088] The propylene-based polymer composition of the present invention, the biaxially stretched film containing the propylene-based polymer composition, and the packaging bag containing the biaxially stretched film can be used to package any object to be packaged, such as food, clothing, and miscellaneous goods, and are highly applicable in various industrial fields.

Claims

1. Contains two or more propylene polymers, A propylene-based polymer composition satisfying the following requirements (1) and (2): (1) The amount of components having a molecular weight of 100,000 or less as measured by gel permeation chromatography is 30% by mass to 50% by mass. (2) The amount of components having a molecular weight of 100,000 or more and 800,000 or less as measured by gel permeation chromatography is 35% by mass to 52% by mass.

2. The propylene polymer composition according to claim 1, further satisfying the following requirement (3): (3) The amount of components having a molecular weight of 800,000 or more as measured by gel permeation chromatography is 4% by mass to 18% by mass.

3. a propylene polymer (a) having a melt flow rate of 3 g / 10 min or less and / or an intrinsic viscosity of 2.0 dL / g or more; The propylene polymer composition according to claim 1, further comprising a propylene polymer (b) having a melt flow rate of 15 g / 10 min or more and / or an intrinsic viscosity of 1.4 dL / g or less.

4. The propylene polymer composition according to claim 1, which has a melt flow rate of 4 g / min to 20 g / min.

5. The propylene-based polymer composition according to claim 1, wherein the isotactic pentad fraction is 98.0% or more.

6. 2. The propylene polymer composition according to claim 1, wherein the propylene polymer composition has an intrinsic viscosity of 1.3 dL / g to 2.3 dL / g.

7. The propylene-based polymer composition according to claim 1, further comprising a stretchability improver.

8. The propylene-based polymer composition according to claim 7, wherein the stretchability improver is at least one selected from the group consisting of a β-crystal nucleating agent and a hydrocarbon resin.

9. A biaxially stretched film comprising the propylene polymer composition according to any one of claims 1 to 8.

10. A packaging bag comprising the biaxially stretched film according to claim 9.