Blow film

Abstract

The present invention relates to a blown film comprising a polypropylene composition comprising an ethylene-propylene copolymer and a polyethylene-polyethylene glycol block copolymer.

Description

Technical Field

[0001] This invention relates to a blown film comprising a polypropylene composition comprising an ethylene-propylene copolymer and a polyethylene-polyethylene glycol block copolymer, and the use of the composition in the manufacture of a blown film. Background Technology

[0002] Blown film extrusion is a technique most commonly used in the manufacture of plastic films, particularly those for the packaging industry. The process involves extruding a preform of molten polymer (typically polyethylene or polypropylene) through a die, causing it to expand to several times its initial diameter to form a film bubble, which is then solidified by cooling and crystallization. This film bubble is then flattened for use as a liner film or can be made into bags. In principle, two main processes are known, the fundamental difference being the method of cooling the film bubble. The more common process uses air cooling, while a more complex process uses water cooling.

[0003] One challenge in blown film processing is melt fracture, which reduces performance and limits applications. To overcome this problem, processing aids based on fluoropolymers (such as Dynamar from 3M) are typically used. This solution has long been a perfect and cost-effective solution. However, it has recently been recognized that such processing aids pose health, safety, and environmental problems in blown film production due to the accumulation of fluorinated compounds in the produced film. Furthermore, these processing aids have a persistent effect in the extruder, posing a risk of cross-contamination in subsequent production processes.

[0004] Therefore, efforts have been made to replace these fluoropolymer processing aids. US2005070644A1 discloses an extrudable composition for manufacturing thermoplastic films, comprising thermoplastic polyethylene and polyethylene glycol. EP3234004B1 discloses a thermoplastic composition comprising polyethylene, and a polymer processing additive composition comprising polyethylene glycol and a metal salt of carboxylic acid, sulfonic acid, or alkyl sulfuric acid.

[0005] However, it is still necessary to find other processing aids to replace the fluoropolymers used in the production of polypropylene-based blown films, because the knowledge gained for polyethylene cannot be directly transferred to polypropylene.

[0006] There is a particular need for processing aids that can be used to produce blown films (based on polypropylene obtained using metallocene catalysts). Summary of the Invention

[0007] This invention relates to a blown film comprising a polypropylene composition, said polypropylene composition comprising:

[0008] a) at least 98.0 wt% of an ethylene-propylene copolymer, based on the total weight of the polypropylene composition; and

[0009] b) 0.01 to 1.0 wt% of a polymer processing aid, based on the total weight of the polypropylene composition, wherein the polymer processing aid is a polyethylene-polyethylene glycol block copolymer (PE-EO) represented by the following chemical formula: C n H 2n+z (OCH2CH2) y OH, where n averages ≥5, preferably n averages 5 to 100, more preferably n averages 10 to 50, z is -3 to 1, preferably z is 1, and y averages ≥25, preferably y averages 25 to 500, more preferably y averages 50 to 250.

[0010] The ethylene-propylene copolymer has the following characteristics:

[0011] i) Through 13 The ethylene content, as determined by C-NMR, ranged from 0.5% to 7.0 wt%.

[0012] ii) By 13 C-NMR measurements showed that the defects in the 2,1 reddish region ranged from >0.10 to 1.00 mol%; and

[0013] iii) The MFR2 (230 °C; 2.16 kg) measured according to ISO 1133 is 0.1 to 5.0 g / 10 min.

[0014] Preferred embodiments of the polypropylene composition for producing blown film are defined in the claims of claim 1.

[0015] Furthermore, the present invention relates to the use of the polypropylene compositions as described herein for the manufacture of films, and to a method for blown films using the polypropylene compositions of the present invention.

[0016] The invention is defined in more detail below. Detailed Implementation

[0017] blown film

[0018] Blown films are known to those skilled in the art. As described above, blown films are obtained by extrusion technology, wherein a preform of a molten polypropylene composition according to the invention is extruded through a die and expanded to several times its initial diameter to form a film bubble. This film bubble is then flattened to obtain a film. The film can be used, for example, as a paving film or can be converted into a bag. In the case of this application, air cooling of the film bubble is preferred. For information on the manufacture of blown films from polypropylene, please refer in particular to NelloPasquini's "Polypropylene Handbook," 2nd edition (pp. 412-414).

[0019] As described above, the present invention also relates to the use of the polypropylene composition of the present invention in the manufacture of blown films using process conditions well known in the art. Furthermore, the present invention also relates to a method for obtaining the blown film of the present invention, comprising the following steps:

[0020] I. Provide polypropylene compositions as defined herein;

[0021] II. Melt the polypropylene composition;

[0022] III. To expand the molten polypropylene composition into a thin film bubble;

[0023] IV. Air-cool the thin film bubble;

[0024] V. Flatten the film bubble to obtain a blown film.

[0025] Polypropylene composition

[0026] The blown film is made of a polypropylene composition, i.e., contains a polypropylene composition. The blown film according to the invention contains a polypropylene composition as its primary component. Therefore, preferably, the blown film contains at least 95 wt% of the polypropylene composition based on its total weight. More preferably, the blown film is composed of a polypropylene composition. The polypropylene composition of the invention is defined as follows.

[0027] First, the individual components of the polypropylene composition are described, followed by a description of the polypropylene composition itself.

[0028] ethylene-propylene copolymer

[0029] The majority of the polypropylene composition is an ethylene-propylene copolymer, that is, at least 98.0 wt%, more preferably at least 99.0 wt%, of the polypropylene composition is an ethylene-propylene copolymer.

[0030] The term "ethylene-propylene copolymer" indicates that the copolymer consists only of units derived from ethylene and propylene, wherein the propylene units constitute the major part of the ethylene-propylene copolymer. Therefore, through... 13 The ethylene content of the ethylene-propylene copolymer, as measured by C-NMR, is 0.5 to 7.0 wt%, preferably 0.7 to 4.0 wt%, more preferably 0.8 to 2.7 wt%, and even more preferably 0.9 to 2.3 wt%.

[0031] Furthermore, the ethylene-propylene copolymer of the present invention must be produced using a metallocene catalyst, which reflects the presence of 2,1-erythroid region defects in the polymer chain. More information regarding polymerization conditions is provided below. Therefore, the ethylene-propylene copolymer of the present invention is produced by... 13The 2,1 reddish region defects measured by C-NMR are >0.10 to 1.00 mol%, more preferably 0.35 to 0.85 mol%, and even more preferably 0.45 to 0.75 mol%.

[0032] Another characteristic of ethylene-propylene copolymers, due to the use of metallocene catalysts, is their relatively low content of xylene cold solubles. Therefore, the xylene cold soluble (XCS) fraction of the ethylene-propylene copolymer, as measured at 25 °C according to ISO 16152, is preferably 0.1 to 5.0 wt%, more preferably 0.2 to 3.0 wt%, and even more preferably 0.3 to 1.0 wt%.

[0033] The term "ethylene-propylene copolymer" should further indicate that the copolymer is not a multiphase system. Therefore, the ethylene-propylene copolymer of the present invention is monophase, as is well known to those skilled in the art. In other words, the ethylene-propylene copolymer does not contain polymer components that are immiscible with each other, which is precisely the case with multiphase propylene copolymers. Multiphase systems, compared to monophase systems, comprise a continuous polymer phase (e.g., polypropylene) in which other immiscible polymers (e.g., elastomeric polymers) are dispersed as inclusions. In contrast, a polypropylene system containing a polypropylene matrix and inclusions as a second polymer phase will be referred to as a multiphase system and is not part of the present invention. The presence of the second polymer phase, or so-called inclusions, can be observed, for example, by high-resolution microscopy (e.g., electron microscopy or atomic force microscopy) or dynamic mechanical thermal analysis (DMTA). Specifically, in DMTA, the presence of a multiphase structure can be identified by the presence of at least two distinct glass transition temperatures.

[0034] Furthermore, the molecular weight distribution (MWD) of the ethylene-propylene copolymer, as determined by gel permeation chromatography (GPC), is defined as the ratio between the weight-average molar mass (Mw) and the number-average molar mass (Mn), preferably in the range of 2.0 to 5.0, more preferably in the range of 2.1 to 4.5, and even more preferably in the range of 2.2 to 3.5.

[0035] Furthermore, the molecular weight of the ethylene-propylene copolymer must be high enough to allow the production of blown films from polypropylene compositions in which the ethylene-propylene copolymer is the main component. Therefore, the melt flow rate MFR2 (230 °C; 2.16 kg) of the ethylene-propylene copolymer, as measured according to ISO 1133, is preferably 0.1 to 5.0 g / 10 min, more preferably 0.5 to 4.0 g / 10 min, and even more preferably 0.8 to 3.2 g / 10 min.

[0036] In a preferred embodiment, the ethylene-propylene copolymer comprises two ethylene-propylene copolymer fractions. In other words, the ethylene-propylene copolymer comprises, preferably, the following components:

[0037] (a) The first ethylene-propylene copolymer fraction (F1), the first ethylene-propylene copolymer fraction (F1) is obtained by... 13 The ethylene content, as determined by C-NMR, is 0.2 to 1.0 wt%, preferably obtained by... 13 The ethylene content, as determined by C-NMR, ranged from 0.2 to 0.9 wt%; and

[0038] (b) Second ethylene-propylene copolymer fraction (F2)

[0039] in

[0040] - The ethylene content in the first ethylene-propylene copolymer fraction (F1) and the second ethylene-propylene copolymer fraction (F2) are different, provided that the ethylene content in the first ethylene-propylene copolymer fraction (F1) is lower than the ethylene content in the second ethylene-propylene copolymer fraction (F2);

[0041] - The weight ratio [(F1) / (F2)] between the first ethylene-propylene copolymer fraction (F1) and the second ethylene-propylene copolymer fraction (F2) is 70 / 30 to 50 / 50, preferably 65 / 35 to 55 / 45; and

[0042] - Based on the ethylene-propylene copolymer, the total amount of the first ethylene-propylene copolymer fraction (F1) and the second ethylene-propylene copolymer fraction (F2) is at least 98 wt%, preferably the ethylene-propylene copolymer is composed of the first propylene-ethylene copolymer fraction (F1) and the second ethylene-propylene copolymer fraction (F2).

[0043] Therefore, preferably, the ethylene-propylene copolymer conforms to formula (1) and preferred formula (1a):

[0044] (1)

[0045] (1a)

[0046] In the formula,

[0047] “C2(PPC)” represents the ethylene-propylene copolymer. 13 Ethylene content [wt%] as measured by C-NMR;

[0048] “C2(F1)” represents the first ethylene-propylene copolymer fraction (F1). 13 Ethylene content [wt%] as measured by C-NMR;

[0049] “(F1) / (PPC)” is the amount of the first ethylene-propylene copolymer fraction (F1) in the ethylene-propylene copolymer divided by the amount of ethylene-propylene copolymer.

[0050] Therefore, more preferably, the difference in ethylene content between the first ethylene-propylene copolymer fraction (F1) and the second ethylene-propylene copolymer fraction (F2) is 2.0 to 6.0 wt%, more preferably 2.0 to 5.0 wt%.

[0051] Therefore, the ethylene content of the second ethylene-propylene copolymer fraction (F2) is preferably 2.0 to 7.0 wt%, more preferably 2.2 to 6.0 wt%, and even more preferably 2.5 to 5.0 wt%.

[0052] catalyst

[0053] As described above, the ethylene-propylene copolymer of the present invention must be produced using a metallocene catalyst.

[0054] Preferably, ethylene-propylene copolymers are produced in a sequential polymerization process using a specific metallocene catalyst. Therefore, ethylene-propylene copolymers can be produced using metallocene catalysts disclosed in WO 2019 / 179959, which is incorporated herein by reference.

[0055] The particularly preferred metallocene catalyst complex is racemic-trans-dimethylsilanediyl[2-methyl-4,8-bis-(3',5'-dimethylphenyl)-1,5,6,7-tetrahydro-s-indene-1-yl][2-methyl-4-(3',5'-dimethylphenyl)-5-methoxy-6-tert-butylindene-1-yl]zirconium dichloride (MC-2).

[0056] WO 2019 / 179959 also discloses preferred co-catalysts.

[0057] Catalyst manufacturing

[0058] For information on catalyst manufacturing, please also refer to WO 2019 / 179959.

[0059] The preferred catalyst system (single-center catalyst system 1 (SSCS1)) is defined in the Examples section below.

[0060] The polymerization conditions in the sequential polymerization of ethylene-propylene copolymers are not specifically required and are well known to those skilled in the art. Typically, the first ethylene-propylene copolymer fraction (F1) is produced in a slurry reactor, and the second ethylene-propylene copolymer fraction (F2) is prepared in a gas-phase reactor in the presence of the first ethylene-propylene copolymer fraction. For such multi-stage processes, a preferred process is a "cyclic-gas-phase" process, such as the one developed by Borealis (Denmark) (called BORSTAR). ®(Technology), described in, for example, patent documents such as EP 0 887 379, WO 92 / 12182, WO 2004 / 000899, WO 2004 / 111095, WO 99 / 24478, WO 99 / 24479, WO 00 / 68315, WO 2015 / 082379 or WO 2015 / 01134.

[0061] As is well known, pre-aggregation can be performed before the main aggregation.

[0062] For information on pre-polymerization, please refer to WO 2015 / 011134.

[0063] In the case of a prepolymerization step, all catalyst mixtures are introduced into the prepolymerization step.

[0064] As described above, the first ethylene-propylene copolymer fraction (F1) is preferably prepared in the slurry phase polymerization step (i.e., in the liquid phase).

[0065] The temperature during slurry polymerization is typically 50 to 110 °C, preferably 60 to 100 °C, and particularly 65 to 95 °C. The pressure is 1 to 150 bar, preferably 10 to 100 bar.

[0066] Slurry polymerization can be carried out in any known reactor used for slurry polymerization. Such reactors include continuous stirred tank reactors and loop reactors. Loop reactors are generally known in the art, and examples are given in, for example, US-A-4582816, US-A-3405109, US-A-3324093, EP-A-479186, and US-A-5391654.

[0067] The residence time in the aforementioned reactor region can vary. In one embodiment, the residence time in a slurry reactor (e.g., a ring reactor) is 0.5 to 5 hours, for example 0.5 to 2 hours, while the residence time in a gas-phase reactor is typically 1 to 8 hours, for example 1.5 to 4 hours.

[0068] As is known in the art, other components may also be introduced into the slurry polymerization stage. Therefore, hydrogen is added to control the molecular weight of the polymer.

[0069] The slurry polymerization stage is followed by a gas-phase polymerization stage, in which a second ethylene-propylene copolymer fraction (F2) is produced. Preferably, the slurry is introduced directly into the gas-phase polymerization zone, with no flash evaporation step between the two stages. This direct feeding method is described in EP-A-887379, EP-A-887380, EP-A-8877381, and EP-A-991684.

[0070] In other words, the reaction product of the slurry phase polymerization, namely the first ethylene-propylene copolymer fraction (F1), is preferably carried out in a ring reactor and then transferred to a subsequent gas phase reactor to produce the second ethylene-propylene copolymer fraction (F2).

[0071] Gas-phase polymerization can be carried out in a fluidized bed reactor, a fast fluidized bed reactor, or a settling bed reactor, or any combination of these reactors. When using a combination of reactors, the polymer is transferred from one polymerization reactor to another. However, it is preferable to produce a second ethylene-propylene copolymer fraction (F2) in a single gas-phase reactor.

[0072] Typically, the gas-phase reactor operates in a temperature range of 50 to 100 °C, preferably 65 to 95 °C. The pressure is suitably 10 to 40 bar, preferably 15 to 30 bar.

[0073] According to the present invention, a first ethylene-propylene copolymer fraction (F1) is produced in a first step (i.e., a first reactor, such as a ring reactor), while a second ethylene-propylene copolymer fraction (F2) is produced in a subsequent step (i.e., a second reactor, such as a gas-phase reactor). When the polymerization process of both the first ethylene-propylene copolymer fraction (F1) and the second ethylene-propylene copolymer fraction (F2) also includes a prepolymerization step, then the first ethylene-propylene copolymer fraction (F1) according to the present invention is the polymer produced in the prepolymerization and the polymer produced in the first reactor (such as a ring reactor) in the subsequent first step, while the second ethylene-propylene copolymer fraction (F2) is the product of the second reactor (such as a gas-phase reactor). The amount of polymer produced in the prepolymerization step is relatively small compared to the amount produced in the first reactor, and therefore has little impact on the properties of the ethylene-propylene copolymer from the first reactor.

[0074] The preferred properties of the first ethylene-propylene copolymer fraction (F1) and the second ethylene-propylene copolymer fraction (F2) have been mentioned above.

[0075] Polymer processing aids

[0076] Polymer processing aids are used to eliminate or at least reduce melt fracture, increase gloss, reduce surface defects, and improve surface smoothness. Fluoropolymers are typically the preferred choice for polymer processing aids. However, in this invention, it has been found that polymers composed of the following chemical formula C... n H 2n+z (OCH2CH2) y The polyethylene-polyethylene glycol block copolymer (PE-EO) represented by OH can serve as an excellent alternative to commonly used fluoropolymers for manufacturing the ethylene-propylene copolymer-based blown film of this invention.

[0077] In this invention, the amount of polymer processing aid is 0.01 to 1.0 wt%, preferably 0.05 to 0.8 wt%, based on the total weight of the polypropylene composition.

[0078] Polyethylene-polyethylene glycol block copolymer (PE-EO) is known in the art.

[0079] The blown film applicable to this invention is made of chemical formula C n H 2n+z (OCH2CH2) y The polyethylene-polyethylene glycol block copolymer (PE-EO) represented by OH must meet the following specific ranges for n, z, and y.

[0080] The length of the polyethylene block in the PE-EO block copolymer is defined by n.

[0081] According to the present invention, the average value of n is ≥5, preferably the average value of n is 5 to 100, and more preferably the average value of n is 10 to 50.

[0082] The polyethylene block comprises multiple ethylene units; however, carbon-carbon double bonds can be present in the polyethylene blocks of the PE-EO block copolymer. The number of double bonds is given by z, where z ranges from -3 to 1. When z = -3, there are two double bonds in the polyethylene block; when z = -1, there is one double bond; and when z = 1, the polyethylene consists only of ethylene units. Preferably, z = 1, in which case the polyethylene block consists only of ethylene units.

[0083] The length of the polyethylene glycol (PEG) blocks affects their applicability in reducing melt fracture in blown films. It has been found that the PEG blocks must have at least 25 PEG units. Therefore, an average y value of ≥25 is preferred, an average y value of 25 to 500 is more preferably an average y value of 50 to 250.

[0084] The number-average molar mass (Mn) of the polyethylene-polyethylene glycol block copolymer is preferably 2,000 to 25,000 g / mol, more preferably 3,000 to 20,000 g / mol.

[0085] The polyethylene-polyethylene glycol block copolymers of the present invention are commercially available. Their preparation is known to those skilled in the art. For example, the preparation of polyethylene-polyethylene glycol block copolymers is described in J. Milton Harris et al., “Purification of biomaterials by phase-partitioning with poly(ethyleneglycol)-alkyl ether” (Ind. Eng. Chem. Prod. Res. Dev. 1984, 23, 1, 86-88) or MHM Ahmed et al., “Preparation and characterization of some new surfactant derived from phenol” (Olaj, Szappan, Kozmetika 2011, 60(1), 17-22).

[0086] As described above, since polyethylene-polyethylene glycol block copolymers have been found to be excellent alternatives to fluoropolymer processing aids, the propylene compositions of the present invention preferably do not contain fluoropolymers.

[0087] Even more preferably, the polyethylene-polyethylene glycol block copolymer is the only polymer processing aid in the polypropylene composition.

[0088] α-nucleating agent

[0089] The polypropylene composition according to the invention can be further subjected to α-nucleation. In a preferred embodiment of the invention, the polypropylene composition further comprises an α-nucleating agent, wherein the α-nucleating agent is present in an amount of 0.0001 to 1.0 wt%, more preferably 0.0003 to 0.8 wt%, and even more preferably 0.0005 to 0.5 wt%, based on the total weight of the composition.

[0090] Preferred examples of α-nucleating agents are disclosed in Hans Zweifel's "Plastics Additives Handbook" (6th edition), pages 967-990.

[0091] Among all α-nucleating agents, the preferred ones are: calcium salts of 1,2-cyclohexanedicarboxylate, such as those used in, for example, the Hyperform family of Milliken (e.g., HPN-20E); aluminum bis[2,4,8,10-tetrakis(1,1-dimethylethyl)-6-hydroxy-12H-dibenzo-[d,g]-dioxa-phosphine-6-oxide]hydroxyaluminum, such as those used in nucleating agents ADK NA-21, NA-21 E, NA-21 F, etc.; metal salts of 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate, such as sodium 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate (ADK NA-11), aluminum bis[2,2'-methylenebis(4,6-di-tert-butylphenyl)-phosphate]hydroxyaluminum, and lithium 2,2'-methylenebis(2,6-di-tert-butylphenyl) phosphate (e.g., ADK STAB). (Used in NA-71); sorbitol-based nucleating agents, namely di(alkylbenzyl)sorbitols, such as 1,3:2,4-25-dibenzylsorbitol, 1,3:2,4-di(4-methylbenzyl)sorbitol, 1,3:2,4-di(4-ethylbenzyl)sorbitol, and 1,3:2,4-bis(3,4-dimethylbenzyl)sorbitol; nonanol derivatives, such as 1,2,3-trideoxy-4,6 ;5,7-bis-O-[(4-propylphenyl)methylene]nonanol; and benzotriamides, such as substituted 1,3,5-benzenetriamides, such as N,N',N''-tritert-butyl-1,3,5-benzenetricarboxamide, N,N',N''-tricyclohexyl-1,3,5-benzenetricarboxamide and N-[3,5-bis(2,2-dimethyl-propamido)-phenyl]-2,2-dimethyl-propamidamide. Particularly preferred are: metal salts of 2,2'-methylene bis(4,6-di-tert-butylphenyl) phosphate, such as lithium 2,2'-methylene bis-(2,6-di-tert-butylphenyl) phosphate (e.g., NA-71), calcium 1,2-cyclohexanedicarboxylate (e.g., HPN-20E), aluminum bis[2,4,8,10-tetra(1,1-dimethylethyl)-6-hydroxy-12H-dibenzo-[d,g]-dioxa-phosphine-6-oxide]hydroxyaluminum (e.g., NA-21), and polymer nucleating agents selected from vinyl cycloalkane polymers and vinyl alkane polymers.

[0092] Preferably, the polymer composition comprises at least one α-nucleating agent selected from the following: a metal salt of 2,2'-methylene bis(4,6-di-tert-butylphenyl) phosphate, bis[2,4,8,10-tetra(1,1-dimethylethyl)-6-hydroxy-12H-dibenzo-[d,g]-dioxa-phosphine-6-oxide]aluminum hydroxyl (e.g., NA-21), and the polymer nucleating agent calcium 1,2-cyclohexanedicarboxylate (HPN-20E). More preferably, the α-nucleating agent is selected from the following: lithium 2,2'-methylene bis(2,6-di-tert-butylphenyl) phosphate (e.g., NA-71), disodium bicyclo(2.2.1)heptane-2,3-dicarboxylate (e.g., HPN-E20), and polyvinylcyclohexane (p-VCH). Even more preferably, the α-nucleating agent present in the polymer composition is selected from the following: lithium 2,2'-methylene bis-(2,6-di-tert-butylphenyl) phosphate (e.g., NA-71), aluminum bis[2,4,8,10-tetra(1,1-dimethylethyl)-6-hydroxy-12H-dibenzo-[d,g]-dioxaphosphine-6-oxide]hydroxyaluminum (e.g., NA-21), calcium 1,2-cyclohexane dicarboxylate (HPN-20E), and polyvinylcyclohexane (p-VCH).

[0093] Therefore, particularly preferably, the α-nucleating agent present in the polypropylene composition is selected from the following: bis[2,4,8,10-tetra(1,1-dimethylethyl)-6-hydroxy-12H-dibenzo-[d,g]-dioxa-phosphine-6-oxide]aluminum hydroxyl (e.g., NA-21), polyvinylcyclohexane (p-VCH), lithium 2,2'-methylenebis-(2,6-di-tert-butylphenyl)phosphate (e.g., NA-71), and calcium 1,2-cyclohexanedicarboxylate (HPN-20E); wherein, further, the total amount of the α-nucleating agent is preferably 0.0005 to 0.5 wt% based on the total weight of the polypropylene composition.

[0094] Other components

[0095] As described above, the polypropylene composition must contain an ethylene-propylene copolymer as a major component and polymer processing aids. Furthermore, the polypropylene composition may contain α-nucleating agents as described above and typical additives other than α-nucleating agents, such as antioxidants, antistatic agents, and antifogging agents. Therefore, the term "additives" according to the invention does not include α-nucleating agents and polymer processing aids. Such additives may be premixed with a carrier material, which is typically polypropylene. According to the invention, such a carrier material (e.g., this additional polypropylene) is considered part of the additives.

[0096] Generally, based on the polypropylene composition, the total amount of additives (including the amount of carrier material) should not exceed 1.0 wt%, preferably 0.05 to 1.0 wt%.

[0097] Therefore, the polypropylene composition of the present invention comprises, preferably, the following components:

[0098] (a) Based on the total weight of the composition, at least 98.0 wt%, more preferably at least 99.0 wt%, of an ethylene-propylene copolymer;

[0099] (b) Based on the total weight of the polypropylene composition, 0.01 to 1.0 wt%, more preferably 0.05 to 0.8 wt%, of a polymer processing aid, said polymer processing aid being a polyethylene-polyethylene glycol block copolymer (PE-EO) represented by the following chemical formula: C n H 2n+z (OCH2CH2) y OH, where n averages ≥5, preferably n averages 5 to 100, more preferably n averages 10 to 50, z is -3 to 1, preferably z is 1, and y averages ≥25, preferably y averages 25 to 500, more preferably y averages 50 to 250.

[0100] (c) Based on the total weight of the polypropylene composition, 0.0001 to 1.0 wt%, more preferably 0.0005 to 0.5 wt%, of an α-nucleating agent, preferably selected from bis[2,4,8,10-tetrakis(1,1-dimethylethyl)-6-hydroxy-12H-dibenzo-[d,g]-dioxaphosphine-6-oxide]aluminum hydroxide, polyvinylcyclohexane (p-VCH), lithium 2,2'-methylenebis-(2,6-di-tert-butylphenyl)phosphate and calcium 1,2-cyclohexanedicarboxylate and mixtures thereof; and

[0101] (d) 0.05 to 1.0 wt% of additives based on the total weight of the polypropylene composition;

[0102] Wherein, based on the total weight of the composition, the total amount of (b), (c) and (d) does not exceed 2.0 wt%, preferably not more than 1.0 wt%.

[0103] Properties of Polypropylene Compositions

[0104] The polypropylene compositions of the present invention have been tailored to suit the manufacture of blown films. Therefore, the melt flow rate MFR2 (230 °C; 2.16 kg) of the polypropylene compositions of the present invention, as measured according to ISO 1133, is preferably 0.1 to 5 g / 10 min, more preferably 0.5 to 4.0 g / 10 min, and even more preferably 0.8 to 3.5 g / 10 min.

[0105] The polypropylene composition according to the invention can be further defined by its melt behavior.

[0106] Preferably, the melting temperature T of the propylene composition is... m The temperature ranges from 120 to 162 ℃.

[0107] Furthermore, at least one melting peak temperature (T) of the polypropylene composition of the present invention p,m The temperature is preferably 120 to 162 °C, more preferably 132 to 155 °C.

[0108] In particular, the polypropylene composition of the present invention is characterized by having at least two melting peak temperatures, wherein one melting peak temperature (T) p1,m The melting peak temperature is 145 to 155 °C, more preferably 147 to 153 °C, and another melting peak temperature (T) is... p2,m The temperature is 132 to 142 °C, more preferably 134 to 140 °C.

[0109] Properties of blown film

[0110] The combination of the polymer processing aids described above with the ethylene-propylene copolymer described above achieves the good optical properties of the corresponding blown films.

[0111] Therefore, the haze of the membrane, as measured according to ASTM D 1003-00, is preferably ≤8%, more preferably ≤7%, and even more preferably 0.1% to 6.0%.

[0112] Furthermore, the transparency of the blown film, as measured according to ASTM D1003:21, is preferably ≥80%, more preferably ≥85%, and even more preferably 85% to 99%.

[0113] Any combination of the preferred features and embodiments described herein falls within the scope of this invention.

[0114] Preferred Implementation

[0115] Some particularly preferred embodiments of the present invention are listed below.

[0116] Therefore, the present invention relates to a blown film composed of a polypropylene composition, said polypropylene composition comprising:

[0117] a) at least 98.0 wt% of an ethylene-propylene copolymer, based on the total weight of the polypropylene composition; and

[0118] b) 0.01 to 1.0 wt% of a polymer processing aid, based on the total weight of the polypropylene composition, wherein the polymer processing aid is a polyethylene-polyethylene glycol block copolymer (PE-EO) represented by the following chemical formula: C n H 2n+z (OCH2CH2) y OH, where n averages ≥5, preferably n averages 5 to 100, more preferably n averages 10 to 50, z is -3 to 1, preferably z is 1, and y averages ≥25, preferably y averages 25 to 500, more preferably y averages 50 to 250.

[0119] The ethylene-propylene copolymer has the following characteristics:

[0120] i) Through 13 The ethylene content, as determined by C-NMR, ranged from 0.5% to 7.0 wt%.

[0121] ii) By 13 C-NMR measurements showed that the defects in the 2,1 reddish region ranged from >0.10 to 1.00 mol%; and

[0122] iii) The MFR2 (230 °C; 2.16 kg) measured according to ISO 1133 is 0.1 to 5.0 g / 10 min.

[0123] This invention particularly relates to a blown film composed of a polypropylene composition, said polypropylene composition comprising:

[0124] (a) Based on the total weight of the composition, at least 98.0 wt%, more preferably at least 99.0 wt%, of an ethylene-propylene copolymer;

[0125] (b) Based on the total weight of the polypropylene composition, 0.01 to 1.0 wt%, more preferably 0.05 to 0.8 wt%, of a polymer processing aid, said polymer processing aid being a polyethylene-polyethylene glycol block copolymer (PE-EO) represented by the following chemical formula: C n H 2n+z (OCH2CH2) y OH, where n averages ≥5, preferably n averages 5 to 100, more preferably n averages 10 to 50, z is -3 to 1, preferably z is 1, and y averages ≥25, preferably y averages 25 to 500, more preferably y averages 50 to 250.

[0126] (c) Based on the total weight of the polypropylene composition, 0.0001 to 1.0 wt%, more preferably 0.0005 to 0.5 wt%, of an α-nucleating agent, preferably selected from bis[2,4,8,10-tetra(1,1-dimethylethyl)-6-hydroxy-12H-dibenzo-[d,g]-dioxa-phosphine-6-oxide]aluminum hydroxide, polyvinylcyclohexane (p-VCH), lithium 2,2'-methylenebis-(2,6-di-tert-butylphenyl) phosphate and calcium 1,2-cyclohexane dicarboxylate and mixtures thereof;

[0127] The ethylene-propylene copolymer has the following characteristics:

[0128] i) Through 13 The ethylene content, as determined by C-NMR, ranged from 0.5% to 7.0 wt%.

[0129] ii) By 13 C-NMR measurements showed that the defects in the 2,1 reddish region ranged from >0.10 to 1.00 mol%; and

[0130] iii) The MFR2 (230 °C; 2.16 kg) measured according to ISO 1133 is 0.1 to 5.0 g / 10 min.

[0131] Even more preferably, the present invention relates to a blown film composed of a polypropylene composition, said polypropylene composition comprising:

[0132] (a) Based on the total weight of the composition, at least 98.0 wt%, more preferably at least 99.0 wt%, of an ethylene-propylene copolymer;

[0133] (b) Based on the total weight of the polypropylene composition, 0.01 to 1.0 wt%, more preferably 0.05 to 0.8 wt%, of a polymer processing aid, said polymer processing aid being a polyethylene-polyethylene glycol block copolymer (PE-EO) represented by the following chemical formula: C n H 2n+z (OCH2CH2) y OH, where n averages ≥5, preferably n averages 5 to 100, more preferably n averages 10 to 50, z is -3 to 1, preferably z is 1, and y averages ≥25, preferably y averages 25 to 500, more preferably y averages 50 to 250.

[0134] (c) Based on the total weight of the polypropylene composition, 0.0001 to 1.0 wt%, more preferably 0.0005 to 0.5 wt%, of an α-nucleating agent, preferably selected from bis[2,4,8,10-tetrakis(1,1-dimethylethyl)-6-hydroxy-12H-dibenzo-[d,g]-dioxa-phosphine-6-oxide]aluminum hydroxide, polyvinylcyclohexane (p-VCH), lithium 2,2'-methylenebis-(2,6-di-tert-butylphenyl)phosphate and calcium 1,2-cyclohexanedicarboxylate and mixtures thereof; and

[0135] (d) 0.05 to 1.0 wt% of additives based on the total weight of the polypropylene composition;

[0136] The ethylene-propylene copolymer has the following characteristics:

[0137] i) Through 13 The ethylene content, as determined by C-NMR, ranged from 0.5% to 7.0 wt%.

[0138] ii) By 13 C-NMR measurements showed that the defects in the 2,1 reddish region ranged from >0.10 to 1.00 mol%; and

[0139] iii) The MFR2 (230 °C; 2.16 kg) measured according to ISO 1133 is 0.1 to 5.0 g / 10 min;

[0140] Wherein, based on the total weight of the composition, the total amount of (b), (c) and (d) does not exceed 2.0 wt%, preferably not more than 1.0 wt%.

[0141] The present invention will now be described through examples.

[0142] A. Measurement Method

[0143] Unless otherwise defined, the following definitions of terms and methods apply to the above general description of the invention, including the claims, and the following embodiments.

[0144] Quantitative analysis of microstructure using NMR spectroscopy

[0145] Quantitative nuclear magnetic resonance (NMR) spectroscopy was used to quantify the isotactic regularity and regional regularity of ethylene-propylene copolymers.

[0146] Recordings were performed at 400.15 MHz and 100.62 MHz using a Bruker Advance III 400 NMR spectrometer. 1 H and 13 Quantitative analysis of C in solution state 13 C{1 H⁺ NMR spectroscopy. Using… 13 A C-optimized 10 mm extended temperature probe was used to record all spectra at 125 °C, and nitrogen was used for all pneumatic devices.

[0147] Approximately 200 mg of material was dissolved in 1,2-tetrachloroethane-d2 (TCE-d2). To ensure homogeneity of the solution, after preliminary sample preparation in a heating block, the NMR tube was further heated in a rotary thermostat for at least 1 hour. The tube was then inserted into a magnet and rotated at 10 Hz. This setup was chosen primarily for the high resolution required for quantification of stereoregularity distribution (Busico, V., Cipullo, R., Prog. Polym. Sci. 26 (2001) 443; Busico, V.; Cipullo, R., Monaco, G., Vacatello, M., Segre, AL, Macromolecules 30 (1997) 6251). Using a decoupling scheme of NOE and two-stage WALTZ16, standard single-pulse excitation was employed (Zhou, Z., Kuemmerle, R., Qiu, X., Redwine, D., Cong, R., Taha, A., Baugh, D. Winniford, B., J.Mag. Reson. 187 (2007) 225; Busico, V., Carbonniere, P., Cipullo, R.,Pellecchia, R., Severn, J., Talarico, G., Macromol. Rapid Commun. 2007, 28,11289). A total of 8192 (8k) transients were acquired for each spectrum.

[0148] Using proprietary computer programs for quantitative analysis 13 The C{1H}NMR spectra were processed, integrated, and the relevant quantitative properties were determined by the integration.

[0149] All chemical shifts are internally referenced to the methyl isotactic pentatonic group (mmmm) at 21.85 ppm.

[0150] Characteristic signals corresponding to regional defects were observed (Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253; Wang, WJ., Zhu, S., Macromolecules 33 (2000), 1157; Cheng, HN, Macromolecules 17 (1984), 1950) or comonomers.

[0151] Stereoregularity distribution was quantified by integrating the methyl region between 23.6 and 19.7 ppm, correcting for any sites unrelated to the stereo sequence of interest (Busico, V., Cipullo, R., Prog. Polym. Sci. 26(2001) 443; Busico, V., Cipullo, R., Monaco, G., Vacatello, M., Segre, AL, Macromolecules 30 (1997) 6251).

[0152] Specifically, the influence of regional defects and copolymers on the quantitative distribution of stereoregularity was corrected by subtracting representative regional defects and comonomer integrals from specific integral regions of the stereo sequence.

[0153] Isosteric regularity was measured at the quintet level and reported as the percentage of isosteric quintet (mmmm) sequences relative to all quintet sequences:

[0154]

[0155] The presence of two methyl sites at 17.7 and 17.2 ppm indicates the presence of a 2,1-type erythromorphic defect, which is corroborated by other characteristic sites. No characteristic signals corresponding to other types of erythromorphic defects were observed (Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253).

[0156] The amount of defects in the 2,1 erythromorph region was quantified by averaging the integrals of the two characteristic methyl sites at 17.7 and 17.2 ppm.

[0157]

[0158] The amount of propylene incorporated into primary doping (1, 2) was quantified based on the methyl region, and corrections were made for sites within this region unrelated to primary doping and primary doping sites outside this region.

[0159]

[0160] The total amount of propylene is quantified as the sum of primary propylene inclusions and all other existing regional defects:

[0161]

[0162] 2,1 The molar percentage of defects in the reddish region was quantified relative to all propylene:

[0163]

[0164] Through the 13 Multiple signals across the entire spectral region of the C{1H} spectrum were integrated, and the comonomer fraction was quantified using the method of Wang et al. (Wang, WJ., Zhu, S., Macromolecules 33 (2000), 1157). This method was chosen because of its robustness and ability to account for regional defects when needed. Slight adjustments were made to the integration region to improve applicability across the entire comonomer content range.

[0165] For systems where only isolated ethylene is observed in the PPEPP sequence, the method of Wang et al. was modified to reduce the influence of non-zero integrals from sites that are known to be absent. This method reduces the overestimation of ethylene content in such systems by reducing the number of sites used to determine absolute ethylene content to the following:

[0166]

[0167] By using this set of sites, the corresponding integral equation becomes:

[0168]

[0169] The same notation as that used in the article by Wang et al. (Wang, WJ., Zhu, S., Macromolecules 33 (2000), 1157) is used. The equations used to calculate the absolute propylene content are not modified.

[0170] Calculate the molar percentage of comonomer incorporated from the molar fraction:

[0171]

[0172] Calculate the weight percentage of comonomer incorporated from the mole fraction:

[0173]

[0174] melt flow rate

[0175] Melt flow rate (MFR) was determined according to ISO 1133, with units of g / 10 min. MFR characterizes the flowability of a polymer, and thus its processing properties. A higher melt flow rate generally corresponds to a lower polymer viscosity. The MFR2 of polypropylene was determined at 230 °C and a load of 2.16 kg.

[0176] The melt flow rate MFR2 (230 °C) of the second polypropylene (PP2) was calculated:

[0177]

[0178] In the formula

[0179] w(PP1) is the weight fraction [wt%] of the first ethylene-propylene copolymer fraction (F1);

[0180] w(PP2) is the weight fraction [wt%] of the second ethylene-propylene copolymer fraction (F2);

[0181] MFR(PP1) is the melt flow rate MFR2 (230 °C) [g / 10min] of the first ethylene-propylene copolymer fraction (F1);

[0182] MFR(PP) is the melt flow rate MFR2 (230 °C) [g / 10min] of the reactor powder of ethylene-propylene copolymer;

[0183] MFR(PP2) is the calculated melt flow rate MFR2 (230 °C) [g / 10 min] of the second ethylene-propylene copolymer fraction (F2).

[0184] Molar mass (ethylene-propylene copolymer)

[0185] According to ISO 16014-4:2003 and ASTM D 6474-99, the average molar mass (M) is determined by gel permeation chromatography (GPC) using the following formula. z M w and M n ) and molecular weight distribution (MWD) (i.e. M w / M n ):

[0186]

[0187]

[0188]

[0189] In the formula, Ai and Mi represent the chromatographic peak slice area and the molecular weight (MW) of the polyolefin.

[0190] The PolymerChar GPC instrument, equipped with an infrared (IR) detector, was used with Polymer Laboratories' 3×Olexis and 1×Olexis-Guard columns, 1,2,4-trichlorobenzene (TCB, stabilized with 250 mg / L 2,6-di-tert-butyl-4-methylphenol) as solvent, at a temperature of 160 °C and a constant flow rate of 1 ml / min. 200 µL of sample solution was injected for each analysis. The column assembly was calibrated using a universal calibration method (according to ISO 16014-2:2003) using at least 15 narrow MWD polystyrene (PS) standards ranging from 0.5 kg / mol to 11500 kg / mol. The Mark Houwink constants for PS, PE, and PP were as described in ASTM D 6474-99. All samples were prepared as follows: 5.0 to 9.0 mg of polymer was dissolved in 8 ml of stable TCB (same as the mobile phase) at 160 °C for 2.5 h (PP) or 3 h (PE) in the autosampler of the GPC instrument with continuous gentle shaking.

[0191] Molar mass (polyethylene-polyethylene glycol block copolymer):

[0192] The average molar mass of polyethylene-polyethylene glycol block copolymers (M z M w and M n The molecular weight distribution was determined by gel permeation chromatography (GPC) in chloroform (CHCl3) at 23°C.

[0193] Xylene room temperature soluble fraction (XCS, wt%):

[0194] According to ISO 16152 (5th edition; 2005-07-01), the amount of xylene-soluble polymers is determined at 25 °C.

[0195] DSC analysis, melting peak temperature (T) p,m ) and enthalpy of fusion (H m ), crystallization peak temperature (T) p,c ) and enthalpy of crystallization (H c): 5-7 mg samples were measured using a TAInstrument Q200 differential scanning calorimeter (DSC). The DSC was operated according to ISO 11357 / Part 3 / Method C2 in a heating / cooling / heating cycle at a scan rate of 10 °C / min over a temperature range of -30 to +225 °C. The crystallization peak temperature (T) was determined by the cooling step. p,c ) and enthalpy of crystallization (H c The melting peak temperature (T) is determined by the second heating step. p1,m ), melting peak temperature (T) p2,m ) and enthalpy of fusion (H m1 / 2 ).

[0196] Haze

[0197] As described below, haze is measured on the membrane according to ASTM D 1003-00.

[0198] transparency

[0199] As described below, the transparency of the film was measured according to ASTM D1003:21.

[0200] B. Preparation of polymer compositions

[0201] Catalyst used in embodiments of the present invention

[0202] Catalyst complex

[0203] As described in WO 2019 / 179959, the following metallocene complexes were used:

[0204]

[0205] Preparation of MAO silica carrier

[0206] The steel reactor, equipped with a mechanical stirrer and filter, was flushed with nitrogen, and the reactor temperature was set to 20 °C. Next, 5.0 kg of silica-grade DM-L-303 from AGC Si Tech Co., pre-calcined at 600 °C, was added from the feed tank, followed by careful pressurization and depressurization with nitrogen using a manual valve. Then, 22 kg of toluene was added. The mixture was stirred for 15 minutes. Next, a 30 wt% MAO toluene solution (9.0 kg) from Lanxess was added over 70 minutes via the feed line at the top of the reactor. The reaction mixture was then heated to 90 °C and stirred at 90 °C for another two hours. The slurry was allowed to settle, and the mother liquor was filtered off. The catalyst was washed twice with toluene (22 kg) at 90 °C, followed by settling and filtration. The reactor was cooled to 60 °C, and the solids were washed with heptane (22.2 kg). Finally, the MAO-treated SiO2 was dried at 60 °C under a nitrogen stream for 2 hours, followed by stirring under vacuum (-0.5 bar) for 5 hours. The MAO-treated support was collected as a free-flowing white powder containing 12.2% Al (by weight).

[0207] Preparation of single-center catalyst system 1 (SSCS1)

[0208] At 20 °C, 30 wt% MAO (0.7 kg) in toluene was added to a steel nitrogen-covered reactor via a burette. Then, toluene (5.4 kg) was added with stirring. The aforementioned metallocene complex (93 g) was added from a metal cylinder and then washed with 1 kg of toluene. The mixture was stirred at 20 °C for 60 minutes. Then, triphenylmethyl tetratetra(pentafluorophenyl)borate (91 g) was added from a metal cylinder and then washed with 1 kg of toluene. The mixture was stirred at room temperature for 1 hour. The resulting solution was added to a stirred cake of MAO silica carrier prepared as described above within 1 hour. The cake was left to stand for 12 hours, then dried under a nitrogen stream at 60 °C for 2 hours, and then dried under vacuum (-0.5 bar) with stirring for 5 hours.

[0209] The dried catalyst, in the form of a pink free-flowing powder containing 13.9% Al and 0.11% Zr, was sampled.

[0210] Table 1: Aggregation Conditions

[0211]

[0212] In a ZSK 57 twin-screw extruder with a melt temperature of 210 °C, ethylene-propylene copolymers were mixed with different additives mentioned in Table 2 to obtain polypropylene compositions of Examples CE1, CE2 and IE1.

[0213] Table 2: Properties of Polymer Compositions and Blown Films

[0214]

[0215] "AO1" is a mixture of sterically hindered pentaerythritol tetrakis(3-(3',5'-di-tert-butyl-4-hydroxyphenyl)-propionate (CAS No. 6683-19-8, commercially available from BASF SE, Germany as Irganox 1010) and the phosphorus-based antioxidant tris(2,4-di-tert-butylphenyl) phosphite (CAS No. 31570-04-4, commercially available from BASF SE, Germany as Irgafos 168) in a weight ratio of 1:2.

[0216] "SHT" is Hycite 713, an acid remover from BASF SE in Germany. It is a magnesium / aluminum hydrotalcite (CAS No. 11097-59-9).

[0217] "NA" refers to ADK STAB NA-71, a commercial α-nucleating agent from Adeka Corporation of Japan, which is a mixture containing lithium 2,2'-methylene bis(2,6-di-tert-butylphenyl) phosphate (CAS No. 85209-93-4).

[0218] “Brij ® 20” is a polyethylene-polyethylene glycol block copolymer (CAS No. 9005-00-9) purchased from Sigma-Aldrich, which has a linear C 18 H 37 (OCH2CH2) y OH, where y averages 20, and number-average molecular weight M n It is 1150 g / mol.

[0219] “Brij ® 100” is a polyethylene-polyethylene glycol block copolymer (CAS No. 9005-00-9) purchased from Sigma-Aldrich, which has a linear C 18 H 37 (OCH2CH2) y OH, where y averages 100, and number-average molecular weight M n It is 4670 g / mol.

[0220] The blown film was produced on a semi-commercial blown film production line at Windmöller & Hölscher (W&H) with a blow ratio of 1:2.5 and a film thickness of 50 µm. The melt temperature was set at 220 °C, and the take-up rate was 14 m / min. The surface quality of the film was observed by those skilled in the art.

[0221] As shown in Table 2, compared with films without polyethylene-polyethylene glycol block copolymers (CE1) or films with polyethylene-polyethylene glycol block copolymers (CE2, n~20) having shorter polyethylene glycol blocks, polyethylene-polyethylene glycol block copolymers (IE1, n~100) resulted in films with lower haze and higher transparency. Furthermore, IE1 exhibited a glossy and smooth surface without visible melt fracture, while CE1 and CE2 showed clearly visible melt fracture.

Claims

1. A blown film comprising a polypropylene composition, said polypropylene composition comprising: a) at least 98.0 wt% of an ethylene-propylene copolymer, based on the total weight of the polypropylene composition; and b) 0.01 to 1.0 wt% of a polymer processing aid, based on the total weight of the polypropylene composition, wherein the polymer processing aid is a polyethylene-polyethylene glycol block copolymer (PE-EO) represented by the following chemical formula: C n H 2n+z (OCH2CH2) y OH, where n averages ≥5, preferably n averages 5 to 100, more preferably n averages 10 to 50, z is -3 to 1, preferably z is 1, and y averages ≥25, preferably y averages 25 to 500, more preferably y averages 50 to 250. in, The ethylene-propylene copolymer has the following characteristics: i) Through 13 The ethylene content, as determined by C-NMR, ranged from 0.5% to 7.0 wt%. ii) By 13 C-NMR measurements showed that the defects in the 2,1 reddish region ranged from >0.10 to 1.00 mol%; and iii) The MFR2 (230 °C; 2.16 kg) measured according to ISO 1133 is 0.1 to 5.0 g / 10 min.

2. The blown film according to any one of the preceding claims, wherein, The number-average molar mass (Mn) of the PE-EO block copolymer, as measured by GPC, is 2000 to 25000 g / mol, preferably 3000 to 20000 g / mol.

3. The blown film according to any one of the preceding claims, wherein, The polypropylene composition does not contain fluoropolymers, and preferably contains only PE-EO block copolymers as polymer processing aids.

4. The blown film according to any one of claims 1 to 4, wherein, The polypropylene composition: - The MFR2 (230 °C; 2.16 kg) measured according to ISO 1133 is 0.1 to 5.0 g / 10 min; and - Optionally, the melting temperature T is measured according to ISO 11357-3. m The temperature ranges from 125 to 162 degrees Celsius.

5. The blown film according to any one of the preceding claims, wherein, The ethylene-propylene copolymer: - The molecular weight distribution (MWD), determined by gel permeation chromatography (GPC), ranged from 2.0 to 5.0; and - Optionally, the xylene cold solubles (XCS) grade, as determined by ISO 16152 at 25 °C, is from 0.2 to 3.0 wt%.

6. The blown film according to any one of the preceding claims, wherein, The blown film has a haze of ≤8%, preferably ≤7%, and more preferably 0.1% to 6.0%, as measured according to ASTM D 1003-00.

7. The blown film according to any one of the preceding claims, wherein, The blown film has a transparency of ≥80%, preferably ≥85%, and more preferably 85% to 99%, as measured according to ASTM D1003:

21.

8. The blown film according to any one of the preceding claims, wherein, Based on the total amount of the polypropylene composition, the polypropylene composition further comprises 0.0001 to 1.0 wt% of an α-nucleating agent.

9. The blown film according to claim 8, wherein, The α-nucleating agent is selected from bis[2,4,8,10-tetra(1,1-dimethylethyl)-6-hydroxy-12H-dibenzo-[d,g]-dioxa-phosphine-6-oxide]aluminum hydroxyl, polyvinylcyclohexane (p-VCH), lithium 2,2'-methylenebis-(2,6-di-tert-butylphenyl) phosphate and calcium 1,2-cyclohexane dicarboxylate and mixtures thereof.

10. The blown film according to any one of the preceding claims, wherein, The polypropylene composition has at least one melting peak temperature (T) measured according to ISO 11357-3. p,m The temperature is 132 to 150 °C. Preferably, the polypropylene composition has at least two melting peak temperatures, one of which is a melting peak temperature (T0). p1,m The melting peak temperature is 145 to 155 °C, and another melting peak temperature (T) is... p2,m The temperature ranges from 132 to 142 ℃.

11. The blown film according to any one of the preceding claims, wherein, The ethylene-propylene copolymer comprises, preferably, the following components: (a) The first ethylene-propylene copolymer fraction (F1), the first ethylene-propylene copolymer fraction (F1) is obtained by... 13 The ethylene content, as determined by C-NMR, ranged from 0.2 to 1.0 wt%; and (b) Second ethylene-propylene copolymer fraction (F2) in - The ethylene content in the first ethylene-propylene copolymer fraction (F1) and the second ethylene-propylene copolymer fraction (F2) are different, provided that the ethylene content in the first ethylene-propylene copolymer fraction (F1) is lower than the ethylene content in the second ethylene-propylene copolymer fraction (F2); - The weight ratio [(F1) / (F2)] between the first ethylene-propylene copolymer fraction (F1) and the second ethylene-propylene copolymer fraction (F2) is 70 / 30 to 50 / 50; and - Based on the ethylene-propylene copolymer, the total amount of the first ethylene-propylene copolymer fraction (F1) and the second ethylene-propylene copolymer fraction (F2) is at least 98 wt%, preferably the ethylene-propylene copolymer is composed of the first propylene-ethylene copolymer fraction (F1) and the second ethylene-propylene copolymer fraction (F2).

12. The blown film according to claim 11, wherein, The ethylene-propylene copolymer conforms to formula (1): In the formula "C2(PPC)" indicates the ethylene-propylene copolymer. 13 Ethylene content [wt%] as measured by C-NMR; "C2(F1)" refers to the first ethylene-propylene copolymer fraction (F1). 13 Ethylene content [wt%] as measured by C-NMR; "(F1) / (PPC)" is the amount of the first propylene-ethylene copolymer fraction (F1) in the ethylene-propylene copolymer divided by the amount of ethylene-propylene copolymer.

13. The blown film according to claim 11 or 12, wherein, The difference in ethylene content between the first ethylene-propylene copolymer fraction (F1) and the second ethylene-propylene copolymer fraction (F2) is 2.0 to 6.0 wt%.

14. Use of the polypropylene composition according to any one of claims 1 to 5 or 8 to 13 for the manufacture of blown films.

15. A method for obtaining a blown film, the method comprising the following steps: I. Providing a polypropylene composition according to any one of claims 1 to 5 or 8 to 13; II. Melt the polypropylene composition; III. To expand the molten polypropylene composition into a thin film bubble; IV. Air-cool the thin film bubble; V. Flatten the film bubble to obtain a blown film.

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