Polyolefin compositions for blown films

Abstract

The present invention is directed to a polyolefin composition for blown films comprising a metallocene catalyzed polyolefin and poly(tetrahydrofuran) as a polymer processing aid, a blown film comprising said polyolefin composition, and the use of poly(tetrahydrofuran) to decrease haze in a blown film consisting of the polyolefin composition.

Description

[0001] Polyolefin Compositions for Blown Films

[0002] The present invention is directed to a polyolefin composition for blown films comprising a polyolefin and poly(tetrahydrofuran) as a polymer processing aid, a blown film comprising said polyolefin composition, and the use of poly(tetrahydrofuran) to decrease haze in a blown film consisting of the polyolefin composition.

[0003] Technical Background

[0004] Blown film extrusion is a technology that is the most common method to make plastic films, especially for the packaging industry. The process involves extruding a tube of molten polymer, typically of polyethylene or polypropylene, through a die and inflating the same to several times its initial diameter to form a thin film bubble, which solidifies by cooling and crystallization. This bubble is then collapsed and used as a lay-flat film or can be made into bags. In principle two major processes are known, which basically differ in the kind of cooling of the film bubble. The more common process uses air cooling, and the more complex one water cooling.

[0005] One difficulty which occurs in the blown film process is melt fracture reducing the performance and limiting the application. To overcome this problem, typically processing aids based on fluoropolymers (e.g. Dynamar from 3M) are used. For long time being, this type of solution worked perfectly and cost efficiently. However, recently it was recognized that such processing aids cause healthy, safety and environmental problems in the production of blown films, due to the fluorine compounds, which accumulate in the produced films. Moreover, such processing aids have long lasting effects in extruders and risks the following production with cross contamination. Consequently, efforts have been made to substitute these fluoropolymer processing aids.

[0006] It was now surprisingly found that poly(tetrahydrofuran)s (poly(THF)) are excellent processing aids for polyolefin compositions for blown films that can prevent melt fracture in the blown films while also reducing the haze. While poly(tetrahydrofuran)s (poly(THF)) are known as possible additives in adhesive layers for surface protection films, e.g. as described in EP 1 099 738 A2 and WO 2002 / 092709 Al, it could not have been expected, that poly(tetrahydro- furan)s (poly(THF)) having a number average molecular weight Mnin the range of from 100 to 10,000 g moF1are ideal polymer processing aids for polyolefin compositions for blown films comprising a monophasic, semi-crystalline polyolefin.

[0007] Definitions

[0008] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although, any methods and materials similar or equivalent to those described herein can be used in practice for testing of the present invention, the preferred materials and methods are described herein. In describing and aspecting the present invention, the following terminology will be used in accordance with the definitions set out below.

[0009] For the purposes of the present invention, the term "consisting of" is considered to be a preferred embodiment of the term "comprising of". If hereinafter a group is defined to comprise at least a certain number of elements, this is also to be understood to disclose a group, which preferably consists only of these elements.

[0010] Where an indefinite or definite article is used when referring to a singular noun, e.g. "a", "an" or "the", this includes a plural of that noun unless something else is specifically stated.

[0011] The term "semi-crystalline polyolefin" indicates that the polyolefin is not amorphous. The term “monophasic” indicates that the polyolefin does not comprise polymer components, which are not miscible with each other, as this is the case for heterophasic polyolefins. Hence, the term “monophasic” indicates that the polyolefin is homogeneous, i.e., that the polyolefin is composed of a single phase.

[0012] The term “metallocene catalyzed” indicates that the respective polymer was produced in the presence of a metallocene catalyst. The skilled person is aware of the differences between metallocene catalyzed polymers and polymers catalyzed for example by a Ziegler-Natta catalyst.

[0013] For example, when using a metallocene catalyst to produce polypropylenes, the obtained polypropylene possesses regio-defects in amounts not found in Ziegler Natta catalyzed polypropylenes.

[0014] The regio-defects of propylene polymers can be of three different types, namely 2,1- erythro (2,le), 2,1-threo (2, It) and 3,1 defects. A detailed description of the structure and mechanism of formation of regio-defects in polypropylene can be found in Chemical Reviews 2000, 100(4), pages 1316 to 1327. These defects are measured using13C NMR as described in more detail below. The term "2,1 regio-defects" as used in the present invention defines the sum of 2,1 erythro regio-defects and 2,1 threo regio-defects.

[0015] Polyethylene polymers made using metallocene catalysis, as opposed to Ziegler Natta catalysis, also have characteristic features that allow them to be distinguished from Ziegler Natta materials. In particular, the comonomer distribution is more homogeneous. This can be shown using Temperature Rising Elution Fractionation (TREF) or Crystallization Analysis Fractionation (Crystaf) techniques.

[0016] Catalyst residues may also indicate the catalyst used.

[0017] For example, Ziegler Natta catalysts would not contain a Zr or Hf group (IV) metal. Summary of the invention

[0018] The present invention is directed to a polyolefin composition for blown films comprising a) 99.00 to 99.99 wt%, based on the total weight of the polyolefin composition, of a metallocene catalyzed polyolefin, being a propylene-ethylene copolymer having an ethylene content, measured by quantitative13C-NMR, in the range of 0.5 to 7.0 wt%, based on the total weight of the propylene-ethylene copolymer, and b) 0.01 to 1.00 wt%, based on the total weight of the polyolefin composition, of a polymer processing aid, wherein said polymer processing aid is a poly(tetrahydrofuran) having a number average molecular weight Mn, determined by gel permeation chromatography (GPC), in the range of from 100 to 10,000 g mol1, preferably of from 1,000 to 3,000 g mol1, wherein the polyolefin a) has i) a density, measured according to ISO 1183-1:2004 Method A on compression molded specimen prepared according to EN ISO 1872-2, in the range of 850 to 980 kg / m3, preferably 880 to 950 kg / m3, ii) a melting temperature Tm, determined according to ISO 11357 / part 3 / method C2, in the range of 125 to 162 °C, iii) an MFR2 measured according to ISO 1133 at 230 °C and a load of 2.16 kg, in the range of 0.1 to 5.0 g / lOmin, iv) a xylene cold soluble (XCS) fraction, determined at 25 °C, according to ISO 16152, in the range of 0.1 to 5.0 wt. %, and wherein the polyolefin composition preferably has an MFR2, measured according to ISO 1133 at 230 °C and a load of 2.16 kg, in the range of 0.1 to 5.0 g / 10 min, more preferably in the range of 0.5 to 4.0 g / 10 min, yet more preferably in the range of 0.8 to 3.5 g / 10 min. Further, the invention is directed to a blown film, wherein the blown film comprises the polyolefin composition as described above or below in an amount of more than 95 wt%, based on the total weight of the blown film, preferably consists of the polyolefin composition as described above or below.

[0019] Additionally, the invention is directed to the use of poly(tetrahydrofuran) having a number average molecular weight Mn, determined by gel permeation chromatography (GPC), in the range of from 100 to 10,000 g mol1, preferably of from 1,000 to 3,000 g mol1as a polymer processing aid for decreasing the haze in %, determined according to ASTM D 1003-00, of a blown film consisting of the polyolefin composition as described above or below by at least 1 %, preferably by 1.1 to 10 %, compared to a blown film consisting of a polyolefin composition being identical but without any polymer processing aid.

[0020] Detailed description of the invention

[0021] Polyolefin composition

[0022] The present invention is directed to a polyolefin composition for blown films comprising a) 99.00 to 99.99 wt%, based on the total weight of the polyolefin composition, of a metallocene catalyzed polyolefin, being a propylene-ethylene copolymer having an ethylene content, measured by quantitative13C-NMR, in the range of 0.5 to 7.0 wt%, based on the total weight of the propylene-ethylene copolymer, and b) 0.01 to 1.00 wt%, based on the total weight of the polyolefin composition, of a polymer processing aid, wherein said polymer processing aid is a poly(tetrahydrofuran) having a number average molecular weight Mn, determined by gel permeation chromatography (GPC), in the range of from 100 to 10,000 g mol1, preferably of from 1,000 to 3,000 g mol1, wherein the polyolefin a) has i) a density, measured according to ISO 1183-1:2004 Method A on compression molded specimen prepared according to EN ISO 1872-2, in the range of 850 to 980 kg / m3, preferably 880 to 950 kg / m3, ii) a melting temperature Tm, determined according to ISO 11357 / part 3 / method C2, in the range of 125 to 162 °C, iii) an MFR2 measured according to ISO 1133 at 230 °C and a load of 2.16 kg, in the range of 0.1 to 5.0 g / lOmin, and iv) a xylene cold soluble (XCS) fraction, determined at 25 °C, according to ISO 16152, in the range of 0.1 to 5.0 wt. %.

[0023] Aspects of the polyolefin composition according to the present invention are described in the following.

[0024] First the individual components of the polyolefin composition are described and subsequently the polyolefin composition as such.

[0025] Metallocene catalyzed polyolefin

[0026] The major component of the polyolefin composition for blown films is a metallocene catalyzed polyolefin, which is a propylene-ethylene copolymer.

[0027] The term “propylene-ethylene copolymer” indicates that said copolymer consists only of units derived from ethylene and propylene, wherein the propylene units make up the major part of the propylene-ethylene copolymer.

[0028] The ethylene content of the propylene-ethylene copolymer is in the range of 0.5 to 7.0 wt%, preferably in the range of 0.7 to 4.0 wt%, more preferably in the range of 0.8 to 2.7 wt%, still more preferably in the range of 0.9 to 2.3 wt%, based on the total weight of the propylene-ethylene copolymer, measured by quantitative13C-NMR. The ethylene content of the propylene-ethylene copolymer is typical for a semicrystalline polyolefin, i.e., for a semi-crystalline propylene-ethylene copolymer.

[0029] The polyolefin has a density, measured according to ISO 1183-1:2004 Method A on compression molded specimen prepared according to EN ISO 1872-2, in the range of 850 to 980 kg / m3, preferably 880 to 950 kg / m3, more preferably 895 to 910 kg / m3.

[0030] Further, the melting temperature Tm, determined according to ISO 11357 / part 3 / method C2, is in the range of 125 to 162 °C, preferably 130 to 150 °C.

[0031] The molecular weight of the polyolefin must be high enough that a blown film can be produced from the polyolefin composition. Accordingly, the MFR2 (230 °C; 2.16 kg), measured according to ISO 1133, of the polyolefin is in the range of 0.1 to 5.0 g / 10 min, preferably of 0.5 to 4.0 g / 10 min, more preferably in the range of 0.8 to 3.2 g / 10 min.

[0032] The polyolefin has low xylene cold soluble (XCS) content, determined at 25 °C, according to ISO 16152, which is in the range of 0.1 to 5.0 wt%, preferably of 0.2 to 1.0 wt%.

[0033] Such a low xylene cold soluble (XCS) content is typical for semi-crystalline propylene homopolymers and propylene random copolymers, such as the propylene- ethylene copolymer of the inventive polyolefin composition. Given such low xylene cold soluble (XCS) content, the presence of an elastomeric polymer in the propylene- ethylene copolymer, resulting in a heterophasic propylene copolymer, is excluded, at least a considerable amount thereof, since an elastomeric polymer would contribute to the xylene cold soluble (XCS) content. Given the ethylene content of the propylene-ethylene copolymer and the low xylene cold soluble (XCS) content, a skilled person would understand that the propyleneethylene copolymer is monophasic and semi-crystalline, i.e., that the propyleneethylene copolymer of the inventive polyolefin composition is monophasic and semicrystalline.

[0034] The polyolefin, i.e., the propylene-ethylene copolymer, is preferably semicrystalline.

[0035] The polyolefin, i.e., the propylene-ethylene copolymer, is preferably monophasic as is well understood by the skilled person. In contrast to monophasic systems, heterophasic systems comprise a continuous polymer phase, like a polypropylene, in which a further non-miscible polymer, like an elastomeric polymer, is dispersed as inclusions. Said polyolefin systems containing a polyolefin matrix and inclusions as a second polymer phase would by contrast be called heterophasic and are not part of the present invention. The presence of a second polymer phase or the so-called inclusions is for instance visible by high resolution microscopy, like electron microscopy or atomic force microscopy, or by 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.

[0036] Preferably, the molecular weight distribution (MWD), determined by Gel Permeation Chromatography (GPC) is in the range of 2.0 to 5.0, preferably 2.5 to 3.5.

[0037] The propylene-ethylene copolymer is produced with a metallocene catalyst, which is reflected by the presence of 2,1 regio-defects in the polymer chain. Metallocene catalysts are single site catalysts. Further information regarding the polymerization conditions is provided in detail below. Accordingly, the propylene-ethylene copolymer has 2,1 regio-defects, measured by quantitative13C NMR, preferably in the range of > 0.10 to 1.00 mol%, more preferably in the range of 0.35 to 0.85 mol%, yet more preferably in the range of 0.45 to 0.75 mol%.

[0038] In a preferred embodiment, the propylene-ethylene copolymer comprises two propylene-ethylene copolymer fractions. That is, the propylene-ethylene copolymer comprises, preferably consists of,

[0039] (a) a first propylene-ethylene copolymer fraction (Fl) having an ethylene content, measured by quantitative13C-NMR, in the range of 0.4 to 5.0 wt%, preferably in the range of 0.5 to 2.0 wt%, more preferably in the range of 0.6 to 1.5 wt%, based on the total weight of the first propylene-ethylene copolymer fraction (Fl) and

[0040] (b) a second propylene-ethylene copolymer fraction (F2), wherein the amount of ethylene in the first propylene-ethylene copolymer fraction (Fl) and the second propylene-ethylene copolymer fraction (F2) is different, with the proviso that the ethylene content in the first propylene- ethylene copolymer fraction (Fl) is lower than in the second propylene- ethylene copolymer fraction (F2), the weight ratio between the first propylene-ethylene copolymer fraction (Fl) and the second propylene-ethylene copolymer fraction (F2) [(F1) / (F2)] is in the range of 70 / 30 to 50 / 50, preferably in the range of 65 / 35 to 55 / 45, and the total amount of the first propylene-ethylene copolymer fraction (Fl) and the second propylene-ethylene copolymer fraction (F2) together, based on the propylene-ethylene copolymer, is at least 98 wt%, preferably the propylene-ethylene copolymer consists of the first propylene ethylenecopolymer fraction (Fl) and the second propylene-ethylene copolymer fraction (F2).

[0041] Accordingly, it is preferred that the propylene-ethylene copolymer complies with the equation (1), preferably with the equation (la)

[0042] C2 (PPC)

[0043] > 3.00 (1)

[0044] (C2 (Fl) X [(Fl) / (PPC)])

[0045] C2 (PPC)

[0046] 5.00 > > 3.00 (la)

[0047] (C2 (Pl) X [(Fl) / (PPC)]) wherein

[0048] “C2 (PPC)” is the ethylene content [wt%], measured by quantitative13C NMR, of the propylene-ethylene copolymer;

[0049] “C (Fl)” is the ethylene content [wt%], measured by quantitative13C NMR, of the first propylene-ethylene copolymer fraction (Fl);

[0050] “(F1) / (PPC)” is the amount of the first propylene-ethylene copolymer fraction (Fl) in the propylene-ethylene copolymer divided by the amount of the propylene-ethylene copolymer.

[0051] Accordingly, it is further preferred that the ethylene content between the first propylene-ethylene copolymer fraction (Fl) and the second propylene-ethylene copolymer fraction (F2) differs in the range of 1.5 to 6.0 wt%, more preferably in the range of 2.0 to 5.0 wt%.

[0052] Therefore, it is preferred that the ethylene content of the second propylene-ethylene copolymer fraction (F2) is in the range of 1.9 to 11.0 wt%, more preferably in the range of 2.2 to 10.0 wt%, still more preferably in the range of 2.5 to 6.0 wt%. Catalyst

[0053] According to this invention, the polyolefin a) is produced with a metallocene catalyst.

[0054] Preferably, the polyolefin, i.e., the propylene-ethylene copolymer, is produced in a sequential polymerization process using a specific metallocene catalyst. Accordingly, the polyolefin, i.e., the propylene-ethylene copolymer, can be produced with a metallocene catalyst, for example as disclosed in WO 2019 / 179959 or WO 2020 / 239602, which is incorporated by reference herewith.

[0055] A specifically preferred metallocene catalyst complex is rac-anti- dimethylsilanediyl[2-methyl-4, 8-bis-(3’, 5’ -dimethylphenyl)- 1,5,6, 7-tetrahydro-s- indacen- 1 -yl] [2-methyl-4-(3 ’ , 5 ’ -dimethylphenyl)-5-methoxy-6-tert-buty linden- 1 -yl] zirconium dichloride (e.g. MC-2 in WO 2019 / 179959 or complex C2 in WO 2020 / 239602).

[0056] The preferred cocatalysts are also disclosed e.g. in WO 2019 / 179959 or

[0057] WO 2020 / 239602.

[0058] Catalyst Manufacture

[0059] Regarding catalyst manufacture, reference is also made to WO 2019 / 179959 or WO 2020 / 239602.

[0060] The most preferred metallocene catalyst system is defined in the example section below (single site catalyst system 1 (SSCS1)).

[0061] The polymerization conditions in the sequential polymerization of the propylene- ethylene copolymer are nothing specific and well known to the skilled person. Typically, the first propylene-ethylene copolymer fraction (Fl) is produced in a slurry reactor and the second propylene-ethylene copolymer fraction (F2) is produced in a gas phase reactor in the presence of the first propylene-ethylene copolymer fraction (Fl). Regarding such multistage processes a preferred process is a “loop-gas phase”-process, such as developed by Borealis A / S, Denmark (known as BORSTAR® technology) described e.g. in patent literature, such as in 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 in WO 2015 / 011134.

[0062] It is well known that prior to the main polymerization, a prepolymerization may take place.

[0063] Regarding the prepolymerization, reference is made to WO 2015 / 011134.

[0064] In case a prepolymerization step is performed, all of the catalyst mixture is introduced to the prepolymerization step.

[0065] As mentioned above, the first propylene-ethylene copolymer fraction (Fl) is preferably produced in a slurry phase polymerization step, i.e., in the liquid phase.

[0066] The temperature in the slurry polymerization is typically from 50 to 110 °C, preferably from 60 to 100 °C and in particular from 65 to 95 °C. The pressure is from 1 to 150 bar, preferably from 10 to 100 bar.

[0067] The slurry polymerization may be conducted in any known reactor used for slurry polymerization. Such reactors include a continuous stirred tank reactor and a loop reactor. Loop reactors are generally known in the art and examples are given, for instance, in US 4582 816 A, US 3 405 109 A, US 3 324 093 A, EP 479 186 A, and US 5 391 654 A.

[0068] The residence time can vary in the reactor zones identified above. In one embodiment, the residence time in the slurry reactor, for example a loop reactor, is in the range of from 0.5 to 5 hours, for example 0.5 to 2 hours, while the residence time in the gas phase reactor generally will be in the range from 1 to 8 hours, like from 1.5 to 4 hours.

[0069] Into the slurry polymerization stage other components may also be introduced as it is known in the art. Thus, hydrogen is added to control the molecular weight of the polymer.

[0070] The slurry polymerization stage is followed by the gas phase polymerization stage in which the second propylene-ethylene copolymer fraction (F2) is produced. It is preferred to conduct the slurry directly into the gas phase polymerization zone without a flash step between the stages. This kind of direct feed is described in EP 887 379 A, EP 887 380 A, EP 887 381 A and EP 991 684 A.

[0071] That is, the reaction product of the slurry phase polymerization, i.e., the first propylene-ethylene copolymer fraction (Fl), which preferably is carried out in a loop reactor, is then transferred to the subsequent gas phase reactor in which the second propylene-ethylene copolymer fraction (F2) is produced.

[0072] The polymerization in gas phase may be conducted in fluidized bed reactors, in fast fluidized bed reactors or in settled bed reactors or in any combination of these. When a combination of reactors is used then the polymer is transferred from one polymerization reactor to another. However, it is preferred that the second propylene- ethylene copolymer fraction (F2) is produced in one gas phase reactor.

[0073] Typically, the gas phase reactor is operated at a temperature within the range of from 50 to 100 °C, preferably from 65 to 95 °C. The pressure is suitably from 10 to 40 bar, preferably from 15 to 30 bar. According to this invention, it is preferred that the first propylene-ethylene copolymer fraction (Fl) is produced in the first step, i.e., in a first reactor, e.g. the loop reactor, whereas the second propylene-ethylene copolymer fraction (F2) is produced in the subsequent step, i.e., in the second reactor, e.g. the gas phase reactor. In case the polymerization process of the first propylene-ethylene copolymer fraction (Fl) and the second propylene-ethylene copolymer fraction (F2) contains also a prepolymerization step, then the first propylene-ethylene copolymer fraction (Fl) according to this invention is the polymer produced in the prepolymerization together with the polymer produced in the subsequent first step, in the first reactor, e.g. the loop reactor, whereas the second propylene-ethylene copolymer fraction (F2) is the product of the second reactor, e.g. the gas phase reactor. The amount of polymer produced in the prepolymerization step is comparatively small compared to the quantities produced in the first reactor and therefore has no great influence on the properties of the propylene-ethylene copolymer from the first reactor.

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

[0075] The polymer processing aid

[0076] Polymer processing aids are used to eliminate or at least to reduce melt fracture, to increase gloss and to reduce surface defects, thereby improving surface smoothness. Typically fluoropolymers are the first choice as polymer processing aid. However, in the present invention it has been found that a poly(tetrahydrofuran) is an excellent alternative to the commonly used fluoropolymers, for the manufacture of blown films based on the polyolefin composition as described above or below.

[0077] Poly(tetrahydrofuran)s and their manufacture are known in the art. The poly(tetrahydrofuran) suitable as a polymer processing aid in the polyolefin composition has a number average molecular weight Mn, determined by gel permeation chromatography (GPC), in the range of from 100 to 10,000 g mol1, preferably of from 1,000 to 3,000 g mol1.

[0078] Such poly(tetrahydrofuran)s are commercially available for example from Sigma- Aldrich (CAS-no. 25190-06-1).

[0079] Since poly(tetrahydrofuran) has been found to be an excellent alternative to fluoropolymer processing aids, the polyolefin composition of the present invention preferably does not contain fluoropolymers.

[0080] Even more preferably, the poly(tetrahydrofuran) is the sole polymer processing aid in the polyolefin composition.

[0081] Besides the reduction in melt fracture, it was also found that poly(tetrahydrofuran) as described above or below can reduce the haze of a blown film consisting of the polyolefin composition as described above or below.

[0082] Accordingly, the present invention is also directed to the use of poly(tetrahydrofuran) having a number average molecular weight Mn, determined by gel permeation chromatography (GPC), in the range of from 100 to 10,000 g mol1, preferably of from 1,000 to 3,000 g moE1as a polymer processing aid for decreasing the haze in %, determined according to ASTM D 1003-00, of a blown film consisting of the polyolefin composition as described above or below by at least 1 %, preferably at least 1.2 % compared to a blown film consisting of a polyolefin composition being identical but without any polymer processing aid. The haze reduction is determined by the taking the difference between the haze in % of the blown film consisting of the unmodified polyolefin composition and the haze in % of the blown film consisting of the modified polyolefin composition.

[0083] Haze reduction = Haze (unmodifed) - Haze (modified)

[0084] “Modified” indicates the presence of poly(tetrahydrofuran) as the polymer processing aid.

[0085] Thus, the disclosed decrease in haze is the absolute decrease of the haze in % and the “%” does not indicate a relative decrease of the total haze by that percentage.

[0086] Alpha-nucleating agent

[0087] The polyolefin composition according to this invention may be further alphanucleated. In a preferred embodiment of the present invention, the polyolefin composition comprises additionally an alpha-nucleating agent, which is present in the range of 0.0001 to 0.99 wt%, more preferably in the range of 0.0003 to 0.8 wt%, yet more preferably in the range of 0.0005 to 0.5 wt%, based on the total weight of the composition.

[0088] Preferred examples of the alpha-nucleating agents are disclosed in “Plastics Additives Handbook”, Hans Zweifel, 6thEdition, p. 967 - 990.

[0089] Among all alpha-nucleating agents, 1,2-cyclohexane-dicarboxylic acid calcium salt as for instance used in Hyperform familiy of Milliken (e.g. HPN-20E), hydroxy- bis[2,4,8, 10-tetrakis( 1 , l-dimethylethyl)-6-hydroxy- 12H-dibenzo-[d,g]-dioxa- phoshocin-6-oxidato] aluminium as used in the nucleating agents ADK NA-21, NA- 21 E, NA-21 F, etc., metal salts of 2,2'-methylene bis(4,6-di-tert- butylphenyl)phosphat, like sodium-2,2'-methylene-bis(4,6-di-t- butylphenyl)phosphate (ADK NA-11), aluminium-hydroxy-bis[2,2'-mcthylcnc- bis(4,6-di-t-butyl-phenyl)-phosphate], 2,2’- methylene bis-(2,6-di-tert. butylphenyl) phosphate lithium salt (as used in ADK STAB NA-71), sorbitol-based nucleating agents, i.e. di(alkylbenzylidene) sorbitols like 1,3:2,4-25 dibenzylidene sorbitol, l,3:2,4-di(4-methylbenzylidene) sorbitol, l,3:2,4-di(4- ethylbenzylidene) sorbitol and l,3:2,4-Bis(3,4-dimethylbenzylidene) sorbitol, as well as nonitol derivatives, like l,2,3-trideoxy-4,6;5,7-bis-O-[(4-propylphenyl)methylene] nonitol, and benzenetrisamides like substituted 1,3,5-benzenetrisamides as N,N’,N”-tris-tert-butyl- 1,3,5- benzenetricarboxamide, N,N’,N”-tris-cyclohexyl-l,3,5-benzene-tricarboxamide and N-[3,5-bis-(2,2-dimethyl-propionylamino)-phenyl]-2,2-dimethyl-propionamide, wherein metal salts of 2,2'-methylene bis(4,6-di-tert-butylphenyl)phosphat, like 2,2’ - methylene bis-(2,6-di-tert. butylphenyl) phosphate lithium salt (e.g. NA-71), 1,2- cyclohexane-dicarboxylic acid, calcium salt (e.g. HPN-20E), hydroxy -bis [2, 4,8,10- tetrakis(l,l-dimethylethyl)-6-hydroxy-12H-dibenzo-[d,g]-dioxa-phoshocin-6- oxidato] aluminium( e.g. NA-21), and polymeric nucleating agents selected from the group consisting of vinylcycloalkane polymers and vinylalkane polymers are particularly preferred.

[0090] Preferably, the polyolefin composition contains at least one alpha-nucleating agent selected from the group consisting of metal salt of 2,2'-methylene bis(4,6-di-tert- butylphenyl)phosphate, hydroxy-bis[2,4,8,10-tetrakis(l,l-dimethylethyl)-6-hydroxy- 12H-dibenzo-[d,g]-dioxa-phoshocin-6-oxidato] aluminium (e.g. NA-21), polymeric nucleating agent and 1,2-cyclohexane-dicarboxylic acid, calcium salt (HPN-20E). Still more preferably the alpha-nucleating agent(s) is / are selected from the group consisting of 2,2’- methylene bis-(2,6-di-tert. butylphenyl) phosphate lithium salt (e.g. NA-71), bicyclo (2.2.1) heptane -2, 3-dicarboxylic acid, di-sodium salt (e.g. HPN-E20) and poly vinylcyclohexane (p-VCH). Yet more preferably, the alphanucleating agent(s) present in the polymer composition is / are selected from the group consisting of 2,2’- methylene bis-(2,6-di-tert. butylphenyl) phosphate lithium salt (e.g. NA-71), hydroxy-bis[2,4,8,10-tetrakis(l,l-dimethylethyl)-6-hydroxy-12H- dibenzo-[d,g]-dioxa-phoshocin-6-oxidato] aluminium (like NA-21), 1,2- cyclohexane-dicarboxylic acid, calcium salt (HPN-20E) and poly-vinylcyclohexane (p-VCH).

[0091] Thus, it is especially preferred that the alpha-nucleating agent(s) present in the polypropylene composition is / are selected from the group consisting of hydroxy - bis[2,4,8, 10-tetrakis( 1 , l-dimethylethyl)-6-hydroxy- 12H-dibenzo-[d,g]-dioxa- phoshocin-6-oxidato] aluminium (e.g. NA-21), poly-vinylcyclohexane (p-VCH), 2,2’- methylene bis-(2,6-di-tert. butylphenyl) phosphate lithium salt (e.g. NA-71) and 1,2-cyclohexane-dicarboxylic acid calcium salt (HPN-20E) or mixtures thereof, wherein further the total amount of the alpha-nucleating agent(s), based on the total weight of the polypropylene composition, is in the range of 0.0005 to 0.5 wt%.

[0092] Since the polyolefin composition of the present invention comprises the metallocene catalyzed, monophasic, semi-crystalline polyolefin in an amount of 99.00 to 99.99 wt%, the combined amount of the nucleating agents and the polymer processing aid in the polyolefin composition does not exceed 1.00 wt%.

[0093] Further components

[0094] As stated above, the polyolefin composition must comprise the metallocene catalyzed polyolefin as the main component and a polymer processing aid. Accordingly, when only the metallocene catalyzed polyolefin and the polytetrahydrofuran as the polymer processing aid are present in the polyolefin composition, their amounts add up to 100 wt%, based on the total weight of the polyolefin composition.

[0095] Additionally, the polypropylene composition may comprise an alpha-nucleating agent as mentioned above and typical additives other than the alpha-nucleating agent, like antioxidants, antistatic agents and antifogging agents. Accordingly, the term “additive(s)” according to this invention does not cover alpha-nucleating agents and polymer processing aids. Such additives may be premixed with a carrier material, which is typically a polypropylene. According to this invention such carrier material, e.g. such additional polypropylene, is considered as being part of the additives.

[0096] Typically, the total amount of additives, which also includes the amount of carrier material, based on the polyolefin composition, does not exceed 0.5 wt% and is preferably in the range of 0.01 to 0.5 wt%.

[0097] Accordingly, in a preferred embodiment the polyolefin composition according to this invention comprises, preferably consists of,

[0098] (a) 99.00 to 99.99 wt%, based on the total weight of the polyolefin composition, of the metallocene catalyzed propylene-ethylene copolymer as further defined herein,

[0099] (b) 0.05 to 0.8 wt%, based on the total weight of the polyolefin composition, of a polymer processing aid, wherein said polymer processing aid is a poly(tetrahydrofuran) having a number average molecular weight Mn, determined by gel permeation chromatography (GPC), in the range of from 100 to 10,000 g mol preferably of from 1,000 to 3,000 g mol

[0100] (c) 0.0005 to 0.5 wt%, based on the total weight of the polyolefin composition, of an alpha-nucleating agent, said alpha-nucleating agent being preferably selected from the group consisting of hydroxy - bis[2,4,8, 10-tetrakis( 1 , l-dimethylethyl)-6-hydroxy- 12H-dibenzo-[d,g]- dioxa-phoshocin-6-oxidato] aluminium, poly-vinylcyclohexane (p-VCH), 2,2’- methylene bis-(2,6-di-tert. butylphenyl) phosphate lithium salt, and 1,2-cyclohexane-dicarboxylic acid calcium salt, and mixtures thereof, and

[0101] (d) 0.01 to 0.5 wt%, based on the total weight of the polyolefin composition, of further additives, wherein the combined amount of (b), (c) and (d), based on the total weight of the composition, does not exceed 1.0 wt%.

[0102] Properties of the polyolefin composition

[0103] The polyolefin composition according to this invention has been tailored to be suited for the manufacture of blown films. Hence, the polyolefin composition according to this invention preferably has a melt flow rate MFR2 (230 °C; 2.16 kg), measured according to ISO 1133, in the range of 0.1 to 5 g / 10 min, more preferably in the range of 0.5 to 4.0 g / 10 min, still more preferably in the range of 0.8 to 3.5 g / 10 min. The polyolefin composition according to this invention can be defined further by its melting behavior. The polyolefin composition has a melting temperature Tm in the range of 125 to 162 °C. It is in particular preferred that the polyolefin composition according to this invention has at least one melting peak temperature (Tp,m) in the range of 125 to 150 °C, more preferably in the range of 130 to 148 °C.

[0104] Preferably, the present polyolefin composition is especially characterized by the presence of at least two, preferably two melting peak temperatures, whereby one melting peak temperature (Tpi,m) is in the range of 141 to 150 °C, more preferably in the range of 143 to 148 °C and another melting peak temperature (TP2,m) is in the range of 130 to 139 °C, more preferably in the range of 131 to 137 °C.

[0105] Thereby, the lower melting peak temperature (TP2,m) relates to the y-phase content and the higher melting peak temperature (Tpi,m) to the a-phase content in the polyolefin composition.

[0106] Further, the polyolefin composition can be characterized by the presence of at least two, preferably two peak melting enthalpies (Hp,m), whereby one peak melting enthalpy (Hpi,m) is in the range of 10 to 40 J / g, more preferably in the range of 15 to 30 J / g and another peak melting enthalpy (HP2,m) is in the range of 50 to 90 J / g, more preferably in the range of 60 to 75 J / g. Any combination of preferred features and embodiments, as described herein, is within the disclosure of this invention.

[0107] Preferred embodiments

[0108] In the following, some especially preferred embodiments of the invention are listed. Accordingly, the present invention is directed to polyolefin composition for blown films comprising a) 99.00 to 99.99 wt%, based on the total weight of the polyolefin composition, of a metallocene catalyzed, monophasic, semicrystalline propylene-ethylene copolymer having an ethylene content, measured by quantitative13C-NMR, in the range of 0.5 to 7.0 wt%, based on the total weight of the propylene-ethylene copolymer, and b) 0.01 to 1.00 wt%, based on the total weight of the polyolefin composition, of a polymer processing aid, wherein said polymer processing aid is a poly(tetrahydrofuran) having a number average molecular weight Mn, determined by gel permeation chromatography (GPC), in the range of from 100 to 10,000 g mol1, preferably of from 1,000 to 3,000 g mol"1, wherein the polypropylene a) has i) a density, measured according to ISO 1183-1:2004 Method A on compression molded specimen prepared according to EN ISO 1872-2, in the range of 850 to 980 kg / m3, preferably 880 to 950 kg / m3, more preferably 895 to 910 kg / m3, ii) a melting temperature Tm, determined according to 11357 / part 3 / method C2, in the range of 125 to 162 °C, preferably 130 to 150 °C, iii) a MFR2 (230 °C; 2.16 kg), measured according to ISO 1133, in the range of 0.1 to 5.0 g / lOmin, preferably of 0.5 to 4.0 g / lOmin, more preferably of 0.8 to 3.2 g / 10 min, iv) a xylene cold soluble (XCS) fraction, determined at 25 °C, according to ISO 16152, in the range of 0.1 to 5.0 wt%, and v) 2,1 regio-defects, measured by13C NMR, in the range of

[0109] > 0.10 to 1.00 mol%, preferably in the range of 0.35 to 0.85 mol%, more preferably in the range of 0.45 to 0.75 mol%.

[0110] In particular, the invention is directed to a polyolefin composition for blown films wherein the polyolefin composition consists of a) 99.00 to 99.99 wt%, based on the total weight of the composition, of a metallocene catalyzed, monophasic, semi-crystalline propylene-ethylene copolymer having an ethylene content, measured by quantitative13C- NMR, in the range of 0.5 to 7.0 wt%, based on the total weight of the propylene-ethylene copolymer, b) 0.05 to 0.8 wt%, based on the total weight of the polyolefin composition, of a polymer processing aid, wherein said polymer processing aid is a poly(tetrahydrofuran) having a number average molecular weight Mn, determined by gel permeation chromatography (GPC), in the range of from 100 to 10,000 g mol1, preferably of from 1,000 to 3,000 g mol1, c) 0.0005 to 0.5 wt%, based on the total weight of the polyolefin composition, of an alpha-nucleating agent, said alpha-nucleating agent being preferably selected from the group consisting of hydroxy - bis[2,4,8, 10-tetrakis( 1 , l-dimethylethyl)-6-hydroxy- 12H-dibenzo-[d,g]- dioxa-phoshocin-6-oxidato] aluminium, poly vinylcyclohexane (p-VCH), 2,2’- methylene bis-(2,6-di-tert. butylphenyl) phosphate lithium salt, and 1,2-cyclohexane-dicarboxylic acid calcium salt, and mixtures thereof, and d) 0.01 to 0.5 wt%, based on the total weight of the polyolefin composition, of additives, wherein the combined amount of (b), (c) and (d), based on the total weight of the composition, does not exceed 1.0 wt%, and wherein the polypropylene a) has i) a density, measured according to ISO 1183-1:2004 Method A on compression molded specimen prepared according to EN ISO 1872-2, in the range of 850 to 980 kg / m3, preferably 880 to 950 kg / m3, more preferably 895 to 910 kg / m3, ii) a melting temperature Tm, determined according to 11357 / part 3 / method C2, in the range of 125 to 162 °C, preferably 130 to 150 °C, iii) a MFR2 (230 °C; 2.16 kg), measured according to ISO 1133, in the range of 0.1 to 5.0 g / lOmin, preferably of 0.5 to 4.0 g / lOmin, more preferably of 0.8 to 3.2 g / 10 min, iv) a xylene cold soluble (XCS) fraction, determined at 25 °C, according to ISO 16152, in the range of 0.1 to 5.0 wt%, and v) 2,1 regio-defects, measured by13C NMR, in the range of

[0111] > 0.10 to 1.00 mol%, preferably in the range of 0.35 to 0.85 mol%, more preferably in the range of 0.45 to 0.75 mol%.

[0112] In a further preferred embodiment, the polyolefin composition for blown films comprises a) 99.00 to 99.99 wt%, based on the total weight of the polyolefin composition, of a metallocene catalyzed, monophasic, semicrystalline propylene-ethylene copolymer having an ethylene content, measured by quantitative13C-NMR, in the range of 0.5 to 7.0 wt%, based on the total weight of the propylene-ethylene copolymer, and b) 0.01 to 1.00 wt%, based on the total weight of the polyolefin composition, of a polymer processing aid, wherein said polymer processing aid is a poly(tetrahydrofuran) having a number average molecular weight Mn, determined by gel permeation chromatography (GPC), in the range of from 100 to 10,000 g mol1, preferably of from 1,000 to 3,000 g mol"1, wherein the propylene-ethylene copolymer a) has i) a density, measured according to ISO 1183-1:2004 Method A on compression molded specimen prepared according to EN ISO 1872-2, in the range of 850 to 980 kg / m3, preferably 880 to 950 kg / m3, more preferably 895 to 910 kg / m3, ii) a melting temperature Tm, determined according to 11357 / part 3 / method C2, in the range of 125 to 162 °C, preferably 130 to 150 °C, iii) a MFR2 (230 °C; 2.16 kg), measured according to ISO 1133, in the range of 0.1 to 5.0 g / lOmin, preferably of 0.5 to 4.0 g / lOmin, more preferably of 0.8 to 3.2 g / 10 min, iv) a xylene cold soluble (XCS) fraction, determined at 25 °C, according to ISO 16152, in the range of 0.1 to 5.0 wt%, and v) 2,1 regio-defects, measured by13C NMR, in the range of

[0113] > 0.10 to 1.00 mol%, preferably in the range of 0.35 to 0.85 mol%, more preferably in the range of 0.45 to 0.75 mol%.

[0114] In a further embodiment, the polyolefin composition for blown films consists of a) 99.00 to 99.99 wt%, based on the total weight of the composition, of a metallocene catalyzed, monophasic, semi-crystalline propylene-ethylene copolymer having an ethylene content, measured by quantitative13C- NMR, in the range of 0.5 to 7.0 wt%, based on the total weight of the propylene-ethylene copolymer, b) 0.05 to 0.8 wt%, based on the total weight of the polyolefin composition, of a polymer processing aid, wherein said polymer processing aid is a poly(tetrahydrofuran) having a number average molecular weight Mn, determined by gel permeation chromatography (GPC), in the range of from 100 to 10,000 g mol preferably of from 1,000 to 3,000 g mol c) 0.0005 to 0.5 wt%, based on the total weight of the polyolefin composition, of an alpha-nucleating agent, said alpha-nucleating agent being preferably selected from the group consisting of hydroxy - bis[2,4,8, 10-tetrakis( 1 , l-dimethylethyl)-6-hydroxy- 12H-dibenzo-[d,g]- dioxa-phoshocin-6-oxidato] aluminium, poly vinylcyclohexane (p-VCH), 2,2’- methylene bis-(2,6-di-tert. butylphenyl) phosphate lithium salt, and 1,2-cyclohexane-dicarboxylic acid calcium salt, and mixtures thereof, and d) 0.01 to 0.5 wt%, based on the total weight of the polyolefin composition, of additives, wherein the combined amount of (b), (c) and (d), based on the total weight of the composition, does not exceed 1.0 wt%, and wherein the propylene-ethylene copolymer a) has i) a density, measured according to ISO 1183-1:2004 Method A on compression molded specimen prepared according to EN ISO 1872-2, in the range of 850 to 980 kg / m3, preferably 880 to 950 kg / m3, more preferably 895 to 910 kg / m3, ii) a melting temperature Tm, determined according to 11357 / part 3 / method C2, in the range of 125 to 162 °C, preferably 130 to 150 °C, iii) a MFR2 (230 °C; 2.16 kg), measured according to ISO 1133, in the range of 0.1 to 5.0 g / lOmin, preferably of 0.5 to 4.0 g / lOmin, more preferably of 0.8 to 3.2 g / 10 min, iv) a xylene cold soluble (XCS) fraction, determined at 25 °C, according to ISO 16152, in the range of 0.1 to 5.0 wt%, and v) 2,1 regio-defects, measured by13C NMR, in the range of

[0115] > 0.10 to 1.00 mol%, preferably in the range of 0.35 to 0.85 mol%, more preferably in the range of 0.45 to 0.75 mol%.

[0116] Blown film

[0117] Blown films are known to the skilled person. As stated above, blown films are obtained by extrusion technology in which a tube of the molten polypropylene composition according to this invention is extruded through a die and inflated to several times its initial diameter to form a thin film bubble. This bubble is then collapsed obtaining a film. Said film can be for instance used as a lay-flat film or can be converted into bags. In the present case air cooling of the film bubble is preferred. Regarding the manufacture of blown films from polypropylene reference is made inter alia to the “Polypropylene Handbook” of “Nello Pasquini, 2ndedition (pages 412 to 414).

[0118] The blown film of this invention comprises the polyolefin composition as described above or below in an amount of more than 95 wt%, based on the total weight of the blown film, preferably consists of the polyolefin composition as described above or below.

[0119] Preferably, the film has a haze, as determined according to ASTM D 1003-00 on a 50 pm blown film, of < 4.0%, more preferably < 3.5%, yet more preferably in the range of 0.1 % to 3.0 %. In the following the invention is described by way of examples.

[0120] A. Measuring methods

[0121] The following definitions of terms and determination methods apply for the above general description of the invention including the claims as well as to the below examples unless otherwise defined.

[0122] Quantification of microstructure by NMR spectroscopy

[0123] Quantitative nuclear-magnetic resonance (NMR) spectroscopy was used to quantify the isotacticity and regio-regularity of the propylene-ethylene copolymer. Quantitative13C {1H } NMR spectra were recorded in the solution-state using a Bruker Advance III 400 NMR spectrometer operating at 400.15 and 100.62 MHz for1H and13C respectively. All spectra were recorded using a13C optimised 10 mm extended temperature probe head at 125 °C using nitrogen gas for all pneumatics. Approximately 200 mg of material was dissolved in 7,2-tetrachloroethane-6?2 (TCE- <C). To ensure a homogenous solution, after initial sample preparation in a heat block, the NMR tube was further heated in a rotatary oven for at least 1 hour. Upon insertion into the magnet the tube was spun at 10 Hz. This setup was chosen primarily for the high resolution needed for tacticity distribution quantification (Busico, V., Cipullo, R., Prog. Polym. Sci. 26 (2001) 443; Busico, V.; Cipullo, R., Monaco, G., Vacatello, M., Segre, A.L., Macromolecules 30 (1997) 6251). Standard single-pulse excitation was employed utilising the NOE and bi-level WALTZ16 decoupling scheme (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 per spectra. Quantitative13C {1H } NMR spectra were processed, integrated and relevant quantitative properties determined from the integrals using proprietary computer programs.

[0124] All chemical shifts are internally referenced to the methyl isotactic pentad (mmmm) at 21.85 ppm.

[0125] Characteristic signals corresponding to regio defects (Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253; Wang, W-J., Zhu, S., Macromolecules 33 (2000), 1157; Cheng, H. N., Macromolecules 17 (1984), 1950) or comonomer were observed.

[0126] The tacticity distribution was quantified through integration of the methyl region between 23.6-19.7 ppm correcting for any sites not related to the stereo sequences of interest (Busico, V., Cipullo, R., Prog. Polym. Sci. 26 (2001) 443; Busico, V., Cipullo, R., Monaco, G., Vacatello, M., Segre, A.L., Macromolecules 30 (1997) 6251).

[0127] Specifically the influence of regio-defects and comonomer on the quantification of the tacticity distribution was corrected for by subtraction of representative regiodefect and comonomer integrals from the specific integral regions of the stereo sequences.

[0128] The isotacticity was determined at the pentad level and reported as the percentage of isotactic pentad (mmmm) sequences with respect to all pentad sequences: [mmmm] % = 100 * (mmmm / sum of all pentads)

[0129] The presence of 2,1 erythro regio-defects was indicated by the presence of the two methyl sites at 17.7 and 17.2 ppm and confirmed by other characteristic sites. Characteristic signals corresponding to other types of regio-defects were not observed (Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253).

[0130] The amount of 2,1 erythro regio-defects was quantified using the average integral of the two characteristic methyl sites at 17.7 and 17.2 ppm: Pile = (Ie6 + Ie8) / 2

[0131] The amount of 1,2 primary inserted propene was quantified based on the methyl region with correction undertaken for sites included in this region not related to primary insertion and for primary insertion sites excluded from this region: P12 = IcH3 + P12e

[0132] The total amount of propene was quantified as the sum of primary inserted propene and all other present regio-defects:

[0133] Ptotal = P12 + P21e

[0134] The mole percent of 2, 1 erythro regio-defects was quantified with respect to all propene:

[0135] [21e] mol% = 100 * (P2ie / Ptotal)

[0136] The comonomer fraction was quantified using the method of Wang et. al. (Wang, W- J., Zhu, S., Macromolecules 33 (2000), 1157) through integration of multiple signals across the whole spectral region in the13C {1H } spectra. This method was chosen for its robust nature and ability to account for the presence of regio-defects when needed. Integral regions were slightly adjusted to increase applicability across the whole range of encountered comonomer contents.

[0137] For systems where only isolated ethylene in PPEPP sequences was observed the method of Wang et. al. was modified to reduce the influence of non-zero integrals of sites that are known to not be present. This approach reduced the overestimation of ethylene content for such systems and was achieved by reduction of the number of sites used to determine the absolute ethylene content to:

[0138] E = 0.5(Spp + Spy + Sp5 + 0.5(Sap + Say))

[0139] Through the use of this set of sites the corresponding integral equation becomes:

[0140] E = 0.5(IH +IG + 0.5(Ic + ID)) using the same notation used in the article of Wang et. al. (Wang, W-J., Zhu, S., Macromolecules 33 (2000), 1157). Equations used for absolute propylene content were not modified. The mole percent comonomer incorporation was calculated from the mole fraction:

[0141] E [mol%] = 100 * fE

[0142] The weight percent comonomer incorporation was calculated from the mole fraction:

[0143] E [wt%] = 100 * (fE* 28.06) / ((fE* 28.06) + ((l-fE) * 42.08))

[0144] Melt Flow Rate

[0145] The melt flow rate (MFR) was determined according to ISO 1133 and is indicated in g / 10 min. The MFR is an indication of the flowability, and hence the processability, of the polymer. The higher the melt flow rate, the lower the viscosity of the polymer. The MFR2 of the polyolefin was determined at a temperature of 230 °C and a load of 2.16 kg.

[0146] Calculation of melt flow rate MFR2 (230 °C) of the second polypropylene (PP2), i.e. second propylene-ethylene copolymer fraction (F2): wherein w(PPl) is the weight fraction [in wt%] of the first propylene-ethylene copolymer fraction (Fl) , w(PP2) is the weight fraction [in wt%] of the second propylene-ethylene copolymer fraction (F2) ,

[0147] MFR(PPl) is the melt flow rate MFR2 (230 °C) [in g / lOmin] the first propyleneethylene copolymer fraction (Fl),

[0148] MFR(PP) is the melt flow rate MFR2 (230 °C) [in g / lOmin] of the reactor powder of the propylene-ethylene copolymer,

[0149] MFR(PP2) is the calculated melt flow rate MFR2 (230 °C) [in g / lOmin] of the second propylene-ethylene copolymer fraction (F2). Molar mass (Polyolefin)

[0150] Average molecular weights (Mz, Mw and Mn) and molecular weight distribution (MWD), i.e. Mw / Mn, were determined by Gel Permeation Chromatography (GPC) according to ISO 16014-4:2003 and ASTM D 6474-99 using the following formulas: where Ai and Mi are the chromatographic peak slice area and polyolefin molecular weight (MW).

[0151] A PolymerChar GPC instrument, equipped with infrared (IR) detector was used with 3 x Olexis and lx Olexis Guard columns from Polymer Laboratories and 1,2,4- trichlorobenzene (TCB, stabilized with 250 mg / 1 2,6-Di-tert-butyl-4-methyl-phenol) as solvent at 160 °C and at a constant flow rate of 1 ml / min. 200 pL of sample solution were injected per analysis. The column set was calibrated using universal calibration (according to ISO 16014-2:2003) with at least 15 narrow MWD polystyrene (PS) standards in the range of 0.5 kg / mol to 11500 kg / mol. Mark Houwink constants used for PS, PE and PP are as described per ASTM D 6474-99. All samples were prepared by dissolving 5.0 to 9.0 mg of polymer in 8 ml (at 160 °C) of stabilized TCB (same as mobile phase) for 2.5 hours for PP or 3 hours for PE at 160 °C under continuous gentle shaking in the autosampler of the GPC instrument.

[0152] Molar mass (Polytetrahydrofuran):

[0153] The number average molecular weight (Mn) of the polytetrahydrofuran was determined by gel permeation chromatography (GPC) in chloroform (CHCh) at 23

[0154] °C. The xylene soluble content at room temperature (XCS, wt%):

[0155] The amount of the polymer soluble in xylene was determined at 25 °C according to ISO 16152; 5th edition; 2005-07-01.

[0156] DSC analysis, melting peak temperature (Tp,m) and melting enthalpy (Hm), crystallization peak temperature (Tp,c) and crystallization enthalpy (Hc): measured with a TA Instrument Q200 differential scanning calorimetry (DSC) on 5 to 7 mg samples. DSC was run according to ISO 11357 / part 3 / method C2 in a heat / cool / heat cycle with a scan rate of 10 °C / min in the temperature range of -30 to +225 °C. Crystallization peak temperature (Tp,c) and crystallization enthalpy (Hc) were determined from the cooling step, while the melting peak temperatures (Tpi,m) and (Tp2,m) and the peak melting enthalpies (Hpi,m) and (HP2,m) were determined from the second heating step.

[0157] Density

[0158] Density of the polymer was measured according to ISO 1183-1:2004 Method A on compression molded specimen prepared according to EN ISO 1872-2 (Feb 2007) and is given in kg / m3.

[0159] Haze

[0160] Haze was determined according to ASTM D 1003-00 on the film as described below.

[0161] B. Preparation of the polyolefin composition

[0162] Catalyst for the inventive examples

[0163] Catalyst complex

[0164] The following metallocene complex has been used as described in WO 2020 / 239602 (complex C2):

[0165] Preparation of MAO-silica support

[0166] A steel reactor equipped with a mechanical stirrer and a filter net was flushed with nitrogen and the reactor temperature was set to 20 °C. Next silica grade DM-L-303 from AGC Si-Tech Co, pre-calcined at 600 °C (5.0 kg) was added from a feeding drum followed by careful pressuring and depressurising with nitrogen using manual valves. Then toluene (22 kg) was added. The mixture was stirred for 15 min. Next 30 wt% solution of MAO in toluene (9.0 kg) from Lanxess was added via feed line on the top of the reactor within 70 min. The reaction mixture was then heated up to 90 °C and stirred at 90 °C for additional 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, following by settling and filtration. The reactor was cooled off to 60 °C and the solid was washed with heptane (22.2 kg). Finally MAO treated SiO was dried at 60 °C under nitrogen flow for 2 hours and then for 5 hours under vacuum (- 0.5 barg) with stirring. MAO treated support was collected as a free-flowing white powder found to contain 12.2% Al by weight. Single site catalyst system 1 (SSCS1) preparation (ICS3 of WO 2020 / 239602)

[0167] 30 wt% MAO in toluene (0.7 kg) was added into a steel nitrogen blanked reactor via a burette at 20 °C. Toluene (5.4 kg) was then added under stirring. The metallocene complex as described above (93 g) was added from a metal cylinder followed by flushing with 1 kg toluene. The mixture was stirred for 60 minutes at 20°C. Trityl tetrakis(pentafluorophenyl) borate (91 g) was then added from a metal cylinder followed by a flush with 1 kg of toluene. The mixture was stirred for 1 h at room temperature. The resulting solution was added to a stirred cake of MAO-silica support prepared as described above over 1 hour. The cake was allowed to stay for 12 hours, followed by drying under N2 flow at 60°C for 2 h and additionally for 5 h under vacuum (-0.5 barg) under stirring. Dried catalyst was sampled in the form of pink free flowing powder containing 13.9% Al and 0.11% Zr.

[0168] Table 1: Polymerization conditions

[0169] The propylene-ethylene copolymer was compounded in a ZSK 57 twin screw extruder, with a melt temperature of 210°C, together with different additives mentioned in table 2 to obtain the polypropylene compositions of examples CE1 and IE1 to IE2.

[0170] Table 2: Polymer composition and blown film properties

[0171] “AO1” is a mixture of the sterically hindered phenol pentaerythrityl-tetrakis(3-(3’,5’- di-tert. butyl-4-hydroxyphenyl)-propionate (CAS-no. 6683-19-8, commercially available as Irganox 1010 from BASF SE, Germany) and the phosphorous based antioxidant tris (2,4-di-t-butylphenyl) phosphite (CAS-no. 31570-04-4, commercially available as Irgafos 168 from BASF SE, Germany) in the weight ratio of 1:2;

[0172] “SHT” is the acid scavenger Hycite 713 of BASF SE, Germany, a magnesium / aluminium-hydrotalcite (CAS-no. 11097-59-9);

[0173] “NA” is the commercial alpha-nucleating agent ADK STAB NA-71 of Adeka Corporation, Japan, a mixture comprising 2,2'-Methylenebis(2,6-di-tert- butylphenyl)phosphate lithium salt (CAS-no. 85209-93-4);

[0174] “Poly(THF)” is a poly( tetrahydrofuran) with an number average molecular weight Mnof 2,000 g / mol, (CAS-no. 25190-06-1) commercially available from Sigma- Aldrich.

[0175] *Haze reduction = Haze (unmodifed) - Haze (modified)

[0176] The blown films were produced on a Windmbller & Hblscher (W&H) semicommercial blown film line, with blow-up ratio of 1:2.5 and film thickness of 50 pm. The melt temperature was fixed at 220 °C and the uptake speed was 14m / min. The surface quality of the films were observed by person skilled in the art.

[0177] As shown in Table 2, the poly(tetrahydrofuran) decreases the haze of the blown films significantly (IE1 and IE2). Further, while the blown film of the unmodified CE1 has clear visible melt fracture, the blown films of IE1 and IE2 have a glossy and smooth surface and show no signs of visible melt fracture.

Claims

Claims1. A polyolefin composition for blown films comprising a) 99.00 to 99.99 wt%, based on the total weight of the polyolefin composition, of a metallocene catalyzed polyolefin, being a propylene-ethylene copolymer having an ethylene content, measured by quantitative13C-NMR, in the range of 0.5 to 7.0 wt%, based on the total weight of the propylene-ethylene copolymer, and b) 0.01 to 1.00 wt%, based on the total weight of the polyolefin composition, of a polymer processing aid, wherein said polymer processing aid is a poly(tetrahydrofuran) having a number average molecular weight Mn, determined by gel permeation chromatography (GPC), in the range of from 100 to 10,000 g mol1, preferably of from 1,000 to 3,000 g mol1, wherein the polyolefin a) has i) a density, measured according to ISO 1183-1:2004 Method A on compression molded specimen prepared according to EN ISO 1872-2, in the range of 850 to 980 kg / m3, preferably 880 to 950 kg / m3, ii) a melting temperature Tm, determined according to 11357 / part 3 / method C2, in the range of 125 to 162 °C, iii) an MFR2, measured according to ISO 1133 at 230 °C and a load of 2.16 kg, in the range of 0.1 to 5.0 g / 10 min, iv) a xylene cold soluble (XCS) fraction, determined at 25 °C, according to ISO 16152, in the range of 0.1 to 5.0 wt%, and wherein the polyolefin composition preferably has an MFR2, measured according to ISO 1133 at 230 °C and a load of 2.16 kg, in the range of 0.1 to 5.0 g / 10 min, more preferably in therange of 0.5 to 4.0 g / 10 min, yet more preferably in the range of 0.8 to 3.5 g / 10 min.

2. The polyolefin composition for blown films according to claim 1, wherein the metallocene catalyzed polyolefin is a metallocene catalyzed, monophasic, semi-crystalline polyolefin.

3. The polyolefin composition for blown films according to claim 1 or 2, wherein the polyolefin composition comprises additionally c) an alpha-nucleating agent in the range of 0.0001 to 0.99 wt%, based on the total amount of the polyolefin composition, wherein the alphanucleating agent is preferably selected from the group consisting of hydroxy-bis[2,4,8, 10-tetrakis( 1 , l-dimethylethyl)-6-hydroxy- 12H- dibenzo-[d,g]-dioxa-phoshocin-6-oxidato] aluminium, poly vinylcyclohexane (p-VCH), 2,2’ -methylene bis-(2,6-di-tert. butylphenyl)phosphate lithium salt, and 1,2-cyclohexane-dicarboxylic acid calcium salt, and mixtures thereof, wherein the combined amount of (b) and (c), based on the total weight of the composition, does not exceed 1.00 wt%.

4. The polyolefin composition for blown films according to anyone of claims 1 to3, wherein the polyolefin a) has a molecular weight distribution (MWD), determined by Gel Permeation Chromatography (GPC) in the range of 2.0 to 5.0, preferably 2.5 to 3.5.

5. The polyolefin composition for blown films according to anyone of claims 1 to4, wherein the polyolefin a) hasa xylene cold soluble (XCS) fraction, determined at 25 °C, according to ISO 16152, in the range of 0.2 to 1.0 wt%.

6. The polyolefin composition for blown films according to anyone of claims 1 to 5, wherein the polyolefin a) is a polypropylene and has 2,1 regio-defects, measured by13C NMR, in the range of > 0.10 to 1.00 mol%, preferably in the range of 0.35 to 0.85 mol%, more preferably in the range of 0.45 to 0.75 mol%.

7. The polyolefin composition for blown films according to anyone of claims 1 to 6, wherein the polyolefin a) is a propylene-ethylene copolymer having an ethylene content, measured by quantitative13C-NMR, in the range of 0.7 to 4.0 wt%, preferably in the range of 0.8 to 2.7 wt%, based on the total weight of the propylene-ethylene copolymer.

8. The polyolefin composition for blown films according to claim 7, wherein the propylene-ethylene copolymer comprises, preferably consists of,(a) a first propylene-ethylene copolymer fraction (Fl) having an ethylene content, measured by quantitative13C-NMR, in the range of 0.4 to 5.0 wt%, preferably in the range of 0.5 to 2.0 wt%, more preferably in the range of 0.6 to 1.5 wt%, based on the total weight of the first propylene- ethylene copolymer fraction (Fl) and(b) a second propylene-ethylene copolymer fraction (F2), wherein the amount of ethylene in the first propylene-ethylene copolymer fraction (Fl) and the second propylene-ethylene copolymer fraction (F2) is different, with the proviso that the ethylene content in the first propylene-ethylene copolymerfraction (Fl) is lower than in the second propylene-ethylene copolymer fraction (F2), the weight ratio between the first propylene-ethylene copolymer fraction (Fl) and the second propylene-ethylene copolymer fraction (F2) [(F1) / (F2)] is in the range of 70 / 30 to 50 / 50, preferably in the range of 65 / 35 to 55 / 45, and the total amount of the first propylene-ethylene copolymer fraction (Fl) and the second propylene-ethylene copolymer fraction (F2) together, based on the propylene-ethylene copolymer, is at least 98 wt%, preferably the propylene- ethylene copolymer consists of the first propylene ethylenecopolymer fraction (Fl) and the second propylene-ethylene copolymer fraction (F2).

9. The polyolefin composition for blown films according to claim 8, wherein the propylene-ethylene copolymer complies with the equation (1)3.00wherein“C2 (PPC)” is the ethylene content in wt%, measured by quantitative13C NMR, of the propylene-ethylene copolymer;“C2 (Fl)” is the ethylene content in wt%, measured by quantitative13C NMR, of the first propylene-ethylene copolymer fraction (Fl);“(F1) / (PPC)” is the amount of the first propylene-ethylene copolymer fraction (Fl) in the propylene-ethylene copolymer divided by the amount of the propylene-ethylene copolymer.

10. The polyolefin composition for blown films according to claims 8 or 9, wherein the ethylene content between the first propylene-ethylene copolymer fraction (Fl) and the second propylene-ethylene copolymer fraction (F2) differs in the range of 1.5 to 6.0 wt%, preferably in the range of 2.0 to 5.0 wt%.

11. The polyolefin composition for blown films according to anyone of claims 1 to 10, wherein the composition has at least two, preferably two melting peak temperatures, determined according to ISO 11357 / part 3 / method C2, whereby one melting peak temperature (Tpi,m) is in the range of 141 to 150 °C, more preferably in the range of 143 to 148 °C, and another melting peak temperature (Tp2,m) is in the range of 130 to 139 °C, more preferably in the range of 131 to 137 °C.

12. The polyolefin composition for blown films according to anyone of claims 1 to 11, wherein the polyolefin composition consists of a) 99.00 to 99.99 wt%, based on the total weight of the composition, of the polyolefin, b) 0.05 to 0.8 wt%, based on the total weight of the polyolefin composition, of the poly (tetrahydrofuran), c) 0.0005 to 0.5 wt%, based on the total weight of the polyolefin composition, of an alpha-nucleating agent, said alpha-nucleating agent being preferably selected from the group consisting of hydroxy - bis[2,4,8, 10-tetrakis( 1 , l-dimethylethyl)-6-hydroxy- 12H-dibenzo- [d,g]-dioxa-phoshocin-6-oxidato] aluminium, poly vinylcyclohexane (p-VCH), 2,2’ -methylene bis-(2,6-di-tert. butylphenyl)phosphate lithium salt, and 1,2-cyclohexane-dicarboxylic acid calcium salt, and mixtures thereof, andd) 0.01 to 0.5 wt%, based on the total weight of the polyolefin composition, of additives, wherein the combined amount of (b), (c) and (d), based on the total weight of the composition, does not exceed 1.0 wt%.

13. A blown film, wherein the blown film comprises the polyolefin composition anyone of claims 1 to 12 in an amount of more than 95 wt% based on the total weight of the blown film, preferably consists of the polyolefin composition according to anyone of claims 1 to 12.

14. The blown film according to claim 13, wherein the film has a haze, as determined according to ASTM D 1003-00 on a 50 pm blown film, of< 4.0%, preferably < 3.5%, more preferably in the range of 0.1 % to 3.0 %.

15. Use of poly(tetrahydrofuran) having a number average molecular weight Mn, determined by gel permeation chromatography (GPC), in the range of from 100 to 10,000 g mol-1, preferably of from 1,000 to 3,000 g mol-1, as a polymer processing aid for decreasing the haze in %, determined according to ASTM D 1003-00, of a blown film consisting of the polyolefin composition according to anyone of the claims 1 to 12 by at least 1 %, preferably by at least 1.1 to 10 %, compared to a blown film consisting of a polyolefin composition being identical but without any polymer processing aid.

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