Polypropylene composition with reduced stickiness

Abstract

The present application relates to a heterophasic polypropylene composition comprising from 30.0 to 60.0 wt.-% of a crystalline propylene homopolymer (A), from 35.0 to 60.0 wt.-% of an elastomeric propylene-ethylene copolymer (B) having an ethylene content of 15.0 to 42.0 wt.-%, based on the total weight of the elastomeric propylene-ethylene copolymer (B), and from 0.0 to 20.0 wt.-% of an elastomeric ethylene-propylene copolymer (C) having an ethylene content of from 45.0 to 80.0 wt.-%, based on the total weight of the elastomeric ethylene-propylene copolymer (C), all weight percentages being based on the total weight of the heterophasic polypropylene composition, a process for producing said heterophasic polypropylene composition, an article comprising said heterophasic polypropylene composition and the use of said heterophasic polypropylene composition for the production of an article.

Description

[0001] Polypropylene composition with reduced stickiness

[0002] The present application relates to a heterophasic polypropylene composition comprising from 30.0 to 60.0 wt.-% of a crystalline propylene homopolymer (A), from 35.0 to 60.0 wt.-% of an elastomeric propylene-ethylene copolymer (B) having an ethylene content of 15.0 to 42.0 wt.-%, based on the total weight of the elastomeric propylene-ethylene copolymer (B), and from 0.0 to 20.0 wt.-% of an elastomeric ethylene-propylene copolymer (C) having an ethylene content of from 45.0 to 80.0 wt.-%, based on the total weight of the elastomeric ethylene-propylene copolymer (C), all weight percentages being based on the total weight of the heterophasic polypropylene composition, a process for producing said heterophasic polypropylene composition, an article comprising said heterophasic polypropylene composition and the use of said heterophasic polypropylene composition for the production of an article.

[0003] Technical background

[0004] Propylene polymers are used in a broad variety of demanding applications, such as automotive applications, construction, medical applications or packaging due to their excellent properties and low costs. The demands can be challenging, since many polymer properties are directly or indirectly interrelated, i.e. improving a specific property can only be accomplished on the expense of another property. Stiffness can for instance be improved by increasing the crystallinity and / or the relative amount of homopolymer within the composition. As a consequence, the material becomes more brittle, thereby resulting in poor impact properties. It is known that impact strength of polypropylene can be improved by dispersing a rubber phase within the polymer matrix, thereby obtaining a heterophasic polypropylene composition.

[0005] Currently, most of the commercial reactor-made heterophasic polypropylene compositions are polymerized in the presence of a Ziegler-Natta catalyst in order to ensure proper reactivity of the catalyst in all stages in a multistage polymerization process of two or more sequential polymerization stages, in which the crystalline matrix phase and the elastomeric rubber phase are polymerized.

[0006] Current state of the art is to produce the polymer matrix in one or two sequential polymerization stages followed by two or three sequential polymerization stages for producing the rubber phase.

[0007] Several challenges arise from this type of practice: 1) stickiness: Normally if the ethylene content in the rubber phase is at a higher end, than the flowability of the resultant reactor powder is restricted and therefore fouling in the polymerization reactors especially at the end of the sequential multistage polymerization is significantly increased.

[0008] 2) life time of the catalyst: It is known that a multistage polymerization process with three or more (up to five) sequential polymerization stages means that the catalyst must have a long life time, which is very demanding and not too good solution.

[0009] Moreover, the many reactors running sequentially also means high energy consumption (CO2 emission).

[0010] Thus there is a need in the art to provide a heterophasic polypropylene composition which is easy to produce, shows a low stickiness, and has a high amount of rubber phase.

[0011] Another challenge is that the known products sometime have too low melting temperature, which, as a consequence, results in lower thermal resistance. Higher melting temperature is demanded for engineering applications such as automotive.

[0012] WO 2016 / 066453 discloses a heterophasic polypropylene composition with a high reactor powder flowability indicating low stickiness. However, the polymerization process requires at least three sequential main polymerization stages so that due to a reduced catalyst activity in the last polymerization stages the options for polymerizing the rubber phase are rather limited.

[0013] The present invention provides a different approach in which a heterophasic polypropylene composition is produced with crystalline propylene homopolymer (A), an elastomeric propylene-ethylene copolymer (B) and optionally an elastomeric ethylenepropylene copolymer (C) with a higher ethylene content than copolymer (B). The heterophasic polypropylene composition is produced in a sequential polymerization process with only two or three sequential polymerization stages. The heterophasic polypropylene composition shows high reactor powder flowability indicating low stickiness, high melting temperature and provides a stiffness-impact balance with a superior impact strength at sufficient stiffness.

[0014] Summary of the invention

[0015] In a first aspect the present invention relates to a heterophasic polypropylene composition comprising (A) from 30.0 to 60.0 wt.-%, preferably from 32.5 to 57.5 wt.-%, more preferably from 35.0 to 55.0 wt.-%, based on the total weight of the heterophasic polypropylene composition, of a crystalline propylene homopolymer;

[0016] (B) from 35.0 to 60.0 wt.-%, preferably from 37.5 to 57.5 wt.-%, more preferably from 40.0 to 55.0 wt.-%, based on the total weight of the heterophasic polypropylene composition, of an elastomeric propylene-ethylene copolymer having an ethylene content, determined by13C NMR spectroscopy, of from 15.0 to 42.0 wt.-%, preferably from 17.5 to 35.0 wt.-%, more preferably from 20.0 to 30.0 wt.-%, based on the total weight of the elastomeric propylene-ethylene copolymer (B); and

[0017] (C) from 0.0 to 20.0 wt.-%, preferably from 0.0 to 18.5 wt.-%, more preferably from 0.0 to 17.5 wt.-%, based on the total weight of the heterophasic polypropylene composition, of an elastomeric ethylene-propylene copolymer having an ethylene content, determined by13C NMR spectroscopy, of from 45.0 to 80.0 wt.-%, preferably from 55.0 to 77.5 wt.-%, more preferably from 60.0 to 75.0 wt.-%, based on the total weight of the elastomeric ethylene-propylene copolymer (C), wherein the heterophasic polypropylene composition has

[0018] • a content of xylene cold solubles (XCS) fraction, based on the total weight of the heterophasic polypropylene composition and determined at 25°C according to ISO 16152, of from 25.0 to 75.0 wt.-%, preferably from 27.5 to 65.0 wt.-%, more preferably from 30.0 to 55.0 wt.-%,

[0019] • an intrinsic viscosity of the xylene cold solubles (XCS) fraction (iV(XCS) of from 3.0 to 9.0, preferably from 3.5 to 8.0, more preferably from 4.0 to 7.5, determined according to ISO 1628 / 1 in decalin at 135°C, and

[0020] • a melt flow rate MFR2 of from 0.01 to 10.0 g / 10 min, preferably from 0.05 to 5.5 g / 10 min, more preferably from 0.1 to 3.5 g / 10 min, determined according to ISO 1133 at 230°C and 2.16 kg.

[0021] In a second aspect, the present invention relates to a process for producing the heterophasic polypropylene composition as described above or below comprising the steps of

[0022] • Polymerizing propylene monomer units in a first polymerization reactor in the presence of a Ziegler Natta catalyst system to produce the crystalline propylene homopolymer (A) in a weight amount of from 30.0 to 60.0 wt.-%, preferably from 32.5 to 57.5 wt.-%, more preferably from 35.0 to 55.0 wt.-%, based on the total weight of the heterophasic polypropylene composition;

[0023] • Transferring a first reaction mixture comprising the crystalline propylene homopolymer (A) and the Ziegler Natta catalyst system from the first polymerization reactor to a second polymerization reactor;

[0024] • Polymerizing propylene monomer units and ethylene monomer units in a molar ratio of ethylene monomer units to propylene monomer units (C2 / C3) of from 200 to less than 1250 mol / kmol, such as from 200 to 1000 mol / kmol, preferably from 250 to 650 mol / kmol, more preferably from 300 to 500 mol / kmol in the second polymerization reactor in the presence of the first reaction mixture to produce the elastomeric propylene-ethylene copolymer (B) in a weight amount of from 35.0 to 60.0 wt.-%, preferably from 37.5 to 57.5 wt.-%, more preferably from 40.0 to 55.0 wt.-%, based on the total weight of the heterophasic polypropylene composition;

[0025] • Withdrawing a reactor powder from the final polymerization reactor comprising crystalline propylene homopolymer (A), the elastomeric propylene-ethylene copolymer (B), and the Ziegler Natta catalyst system;

[0026] • Compounding the reactor powder optionally together with additives to obtain the heterophasic polypropylene composition.

[0027] In a third aspect the present invention relates to an article, preferably an injection moulded article, more preferably an injection moulded automotive article comprising the heterophasic polypropylene composition as defined above or below.

[0028] In a fourth aspect the present invention relates to the use of the heterophasic polypropylene composition as defined above or below for the production of an article, preferably an injection moulded article, more preferably an injection moulded automotive article.

[0029] Definitions

[0030] 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 claiming the present invention, the following terminology will be used in accordance with the definitions set out below.

[0031] Unless clearly indicated otherwise, use of the terms “a,” “an,” and the like refers to one or more.

[0032] In the following, amounts are given in % by weight (wt.-%) unless it is stated otherwise.

[0033] A heterophasic polypropylene is a propylene-based copolymer with a crystalline matrix phase, which can be a propylene homopolymer or a random copolymer of propylene and at least one alpha-olefin comonomer, and an elastomeric phase dispersed therein. The elastomeric phase can be a propylene copolymer with a high amount of comonomer, which is not randomly distributed in the polymer chain but are distributed in a comonomer-rich block structure and a propylene-rich block structure.

[0034] A heterophasic polypropylene usually differentiates from a one-phasic propylene copolymer in that it shows at least two distinct glass transition temperatures Tg, which are attributed to the matrix phase and the disperse elastomeric phase respectively.

[0035] A propylene homopolymer is a polymer, which essentially consists of propylene monomer units. Due to impurities especially during commercial polymerization processes a propylene homopolymer can comprise up to 0.1 mol-% comonomer units, preferably up to 0.05 mol-% comonomer units and most preferably up to 0.01 mol-% comonomer units.

[0036] A propylene copolymer is a copolymer of propylene monomer units and comonomer units, preferably selected from ethylene and C4-C8 alpha-olefins, in the present case ethylene. A propylene random copolymer is a propylene copolymer wherein the comonomer units are randomly distributed along the polymer chain, whilst a propylene block copolymer comprises blocks of propylene monomer units and blocks of comonomer units. Propylene random copolymers can comprise comonomer units from one or more comonomers different in their amounts of carbon atoms. Usually, a propylene polymer comprising at least two propylene polymer fractions (components), which have been produced under different polymerization conditions resulting in different (weight average) molecular weights and / or different comonomer contents for the fractions, preferably produced by polymerizing in multiple polymerization stages with different polymerization conditions, is referred to as “multimodal”. The prefix “multi” relates to the number of different polymer fractions the propylene polymer is consisting of. As an example of multimodal propylene polymer, a propylene polymer consisting of two fractions only is called “bimodal”, whereas a propylene polymer consisting of three fractions only is called “trimodal”.

[0037] A unimodal propylene polymer only consists of one fraction.

[0038] Thereby, the term “different” means that the propylene polymer fractions differ from each other in at least one property, preferably in the weight average molecular weight - which can also be measured in different melt flow rates of the fractions - or comonomer content or both.

[0039] An elastomer is a polymer with viscoelasticity and weak intermolecular forces. The term “elastomer” can be used interchangeably with “rubber”.

[0040] Polyolefin based elastomers, such as polypropylene based elastomers, or polyethylenebased elastomers, i.e. an elastomer with a molar majority of olefin monomer units, such as propylene monomer units or ethylene monomer units, are usually thermoplastic elastomers.

[0041] In a heterophasic polypropylene a matrix phase and a dispersed phase usually form due to the differences in intrinsic viscosity of the crystalline polypropylene compound forming the matrix phase and the elastomeric copolymer forming the dispersed phase, which reduces their miscibility.

[0042] “Reactor-made” means that the different polymers, i.e. the crystalline propylene homopolymer (A), the elastomeric propylene-ethylene copolymer (B) and the elastomeric ethylene-propylene copolymer (C) are prepared as different fractions in the same polymerization process.

[0043] In a multistage polymerization process the different polymer fractions are polymerized at different polymerization stages of the polymerization process. In a sequential polymerization process the different polymer fractions are polymerized sequential polymerization stages of the polymerization process, whereby the polymer fraction of a later polymerization stage is polymerized in the presence of a polymer fraction polymerized in an earlier polymerization stage.

[0044] Detailed description of the invention

[0045] Heterophasic polypropylene composition

[0046] The heterophasic polypropylene composition comprises a crystalline propylene homopolymer (A) in an amount of from 30.0 to 60.0 wt.-%, preferably from 32.5 to 57.5 wt.-%, more preferably from 25.0 to 55.0 wt.-%, an elastomeric propylene-ethylene copolymer (B) in an amount of from 35.0 to 60.0 wt.-%, preferably from 37.5 to 57.5 wt.- %, more preferably from 40.0 to 55.0 wt.-%, and optionally an elastomeric ethylenepropylene copolymer (C) in an amount of from 0.0 to 20.0 wt.-%, preferably from 0.0 to 18.5 wt.-%, more preferably from 0.0 to 17.5 wt.-%, all based on the total weight of the heterophasic polypropylene composition.

[0047] The elastomeric propylene-ethylene copolymer (B) and the optional elastomeric ethylene-propylene copolymer (C) thereby differ in their ethylene content.

[0048] It is preferred that the crystalline propylene homopolymer (A) forms at least the major part of the matrix phase of the heterophasic polypropylene composition, and that the elastomeric propylene-ethylene copolymer (B) and the optional elastomeric ethylenepropylene copolymer (C), if present, form at least the major part of the disperse phase of the heterophasic polypropylene composition.

[0049] As a consequence, the disperse phase of the heterophasic polypropylene composition in one embodiment, in the case that only the elastomeric propylene-ethylene copolymer (B) but not the elastomeric ethylene-propylene copolymer (C) is present, is unimodal, preferably in view of the differences in ethylene content and / or molecular weight.

[0050] In another embodiment the disperse phase of the heterophasic polypropylene composition in the case that both the elastomeric propylene-ethylene copolymer (B) and the elastomeric ethylene-propylene copolymer (C) are present, is multimodal, more preferably bimodal, in view of the differences in ethylene content and / or molecular weight. It is further preferred that the matrix phase of the heterophasic polypropylene composition is unimodal, preferably in view of the differences in ethylene content and / or molecular weight.

[0051] It is preferred that the heterophasic polypropylene composition is reactor-made, Preferably the heterophasic polypropylene composition is produced in a multistage polymerization process, which preferably has only two or three sequential polymerization stages.

[0052] The multistage polymerization process is preferably conducted in the presence of a Ziegler-Natta catalyst system.

[0053] In the following the crystalline propylene homopolymer (A) is also denoted component (A), the elastomeric propylene-ethylene copolymer (B) is also denoted component (B) and the elastomeric ethylene-propylene copolymer (C) is also denoted component (C).

[0054] The heterophasic polypropylene composition can further comprise polymeric components, which are different from the components (A), (B) and optionally (C), in an amount of preferably 0.0 to 10.0 wt.-% based on the total weight of the heterophasic polypropylene composition.

[0055] In a preferred embodiment the polymeric components of the heterophasic polypropylene composition consist of components (A), (B) and optionally (C).

[0056] Besides these polymeric components, the heterophasic polypropylene composition may comprise one or more additives in an amount of from 0.0 up to 5.0 wt.-%, based on the total weight of the heterophasic polypropylene composition. The one or more additives are preferably selected from acid scavengers, antioxidants, UV stabilizers, nucleating agents, pigments, antistatic agents, slip agents, etc. Such additives are commercially available and for example described in “Plastic Additives Handbook”, 6thedition 2009 of Hans Zweifel (pages 1141 to 1190).

[0057] Usually, these additives are added in quantities of 1 to 10000 ppm for each single component. Preferably, the heterophasic polypropylene composition contains from 0 to 4.00 wt.-%, more preferably from 0 to 2.50 wt.-% of one or more alpha-nucleating agents, based on the total amount of the heterophasic polypropylene composition.

[0058] The amount of pure alpha-nucleating agents in the heterophasic polypropylene composition (without optional carrier polymer of a master batch) is preferably in the range of from 0 to 5000 ppm, more preferably from 0 to 4000 ppm, based on the total amount of the heterophasic polypropylene composition.

[0059] The alpha-nucleating agent is generally not restricted.

[0060] Preferably, the alpha-nucleating agent or agents is resp. are selected from soluble alpha-nucleating agents and polymeric alpha-nucleating agents.

[0061] The alpha-nucleating agent is preferably selected from the group consisting of

[0062] (i) dibenzylidenesorbitol (e.g. 1 ,3 : 2,4 dibenzylidenesorbitol) and C-i-Cs-alkyl- substituted dibenzylidenesorbitol derivatives, such as methyldibenzylidenesorbitol, ethyldibenzylidenesorbitol or dimethyldibenzylidenesorbitol (e.g. 1 ,3 : 2,4 di(methylbenzylidene) sorbitol), or substituted nonitol-derivatives, such as 1 ,2,3- trideoxy-4,6:5,7-bis-0-[(4-propylphenyl)methylene]-nonitol, and

[0063] (ii) vinylcycloalkane polymer and vinylalkane polymer (as discussed in more detail below), and

[0064] (iii) mixtures thereof.

[0065] The alpha-nucleating agent or agents is resp. are preferably selected from the group consisting of dibenzylidenesorbitol (e.g. 1 ,3 : 2,4 dibenzylidene sorbitol), dibenzylidenesorbitol derivative, preferably dimethyldibenzylidenesorbitol (e.g. 1 ,3 : 2,4 di(methylbenzylidene) sorbitol), or substituted nonitol-derivatives, such as 1 ,2,3-trideoxy- 4,6:5,7-bis-O-[(4- propylphenyl)methylene]-nonitol, vinylcycloalkane polymer, vinylalkane polymer, and mixtures thereof.

[0066] Especially preferred are vinylcycloalkane polymers such as e.g. vinylcyclohexane (VCH) polymers. Such polymers can be added e.g. using Borealis Nucleation Technology (BNT).

[0067] The alpha-nucleating agent can be added to the heterophasic polypropylene composition as an isolated raw material or in a mixture with a carrier polymer, i.e. in a so-called master batch. The amount of the carrier polymer of the master batch thereby is calculated to the amount of the alpha-nucleating agent.

[0068] In one embodiment the heterophasic polypropylene composition comprises a single alpha-nucleating agent.

[0069] In said embodiment, the pure amount of alpha-nucleating agent is preferably in the range of from 0.1 to 5000 ppm, more preferably from 1 to 5000 ppm.

[0070] In another embodiment, the heterophasic polypropylene composition does not comprise an alpha-nucleating agent.

[0071] In said embodiment, the pure amount of alpha-nucleating agent is 0 ppm.

[0072] The one or more additives can be added to the polymeric components in a blending step.

[0073] Thereby, the one or more additives can be added to the polymeric components in form of master batches in which one or more additives are blended with a carrier polymer in concentrated amounts. Any optional carrier polymer is calculated to the amount of additives, based on the total weight of the heterophasic polypropylene composition.

[0074] The heterophasic polypropylene composition preferably has a total ethylene content, based on the total weight of the heterophasic polypropylene composition, of from 8.0 to 30.0 wt.-%, preferably 10.0 to 27.5 wt.-%, more preferably 12.0 to 25.0 wt.-%, determined by13C NMR spectroscopy.

[0075] Further, the heterophasic polypropylene composition preferably has a total propylene content, based on the total weight of the heterophasic polypropylene composition, of from 70.0 to 92.0 wt.-%, more preferably from 72.5 to 90.0 wt.-%, still more preferably from 75.0 to 88.0 wt.-%, determined by13C NMR spectroscopy.

[0076] It is preferred that the monomer units of the heterophasic polypropylene composition consist of propylene monomer units and ethylene comonomer units, so that the propylene monomer units and the ethylene comonomer units make up 100 wt.-% of the monomer units in the heterophasic polypropylene composition. The heterophasic polypropylene composition generally has a matrix phase and an elastomeric phase dispersed in said matrix phase.

[0077] The matrix phase preferably is a propylene homopolymer.

[0078] The heterophasic polypropylene composition has a content of xylene cold solubles (XCS) fraction, based on the total weight of the heterophasic polypropylene composition and determined at 25°C according to ISO 16152, of from 25.0 to 75.0 wt.-%, preferably from 27.5 to 65.0 wt.-%, more preferably from 30.0 to 55.0 wt.-%.

[0079] The xylene cold solubles (XCS) fraction has an intrinsic viscosity (iV(XCS)) of from 3.0 to 9.0 dl / g, preferably from 3.5 to 8.0 dl / g, more preferably from 4.0 to 7.5 dl / g, determined according to ISO 1628 / 1 in decalin at 135°C.

[0080] In some embodiments, the lower limit of the intrinsic viscosity (iV(XCS)) is preferably 4.3 dl / g, more preferably 4.5 dl / g, still more preferably 4.7 dl / g, determined according to ISO 1628 / 1 in decalin at 135°C.

[0081] Further, the xylene cold solubles (XCS) fraction preferably has an ethylene content (C2(XCS)), based on the total amount of monomer units in the xylene cold solubles (XCS) fraction and determined by13C NMR spectroscopy, of from 25.0 to 70.0 wt.-%, more preferably from 30.0 to 60.0 wt.-%, still more preferably from 35.0 to 50.0 wt.-%.

[0082] It is preferred that the propylene content and the ethylene content of the xylene cold solubles (XCS) fraction make up 100 wt.-% of the xylene cold solubles (XCS) fraction.

[0083] It is preferred that the heterophasic polypropylene composition has a content of a fraction insoluble in cold xylene (XCI) based on the total weight of the heterophasic polypropylene composition and determined at 25°C according to ISO 16152, of from 25.0 to 75.0 wt.-%, more preferably from 35.0 to 72.5 wt.-%, still more preferably from 45.0 wt.-% to 70.0 wt.-%.

[0084] The xylene cold solubles (XCS) fraction and the fraction insoluble in cold xylene (XCI) generally make up 100 wt.-% of the heterophasic polypropylene composition. The heterophasic polypropylene composition has a melt flow rate MFR2, determined according to ISO 1133 at 230°C and 2.16 kg of from 0.01 to 10.0 g / 10 min, preferably from 0.05 to 5.5 g / 10 min, more preferably from 0.1 to 3.5 g / 10 min.

[0085] Further, the heterophasic polypropylene composition preferably has a melting temperature Tm, determined by differential scanning calorimetry (DSC) analysis according to ISO 11357, of from 155.0 to 175.0°C, more preferably from 160.0 to 172.5°C, still more preferably from 163.0 to 170.0°C.

[0086] It has surprisingly been found that the heterophasic polypropylene composition combines high flowability of the reactor powder together with a favorable stiffness to impact balance.

[0087] The reactor powder of the heterophasic polypropylene composition preferably has a powder flowability, determined according to ISO 6186:1998, method A, nozzle diameter 15 mm, of from 5 to 20 s, preferably from 7 to 17 s.

[0088] Further, the reactor powder of the heterophasic polypropylene composition preferably shows an uninterrupted flow, determined according to ISO 6186:1998, method A, nozzle diameter 15 mm.

[0089] Still further, the heterophasic polypropylene composition preferably has a Charpy notched impact strength at 23°C of from 50.0 to 150.0 kJ / m2, more preferably from 65.0 to 125.0 kJ / m2, still more preferably from 70.0 to 100.0 kJ / m2, determined according to ISO 179-1 / 1 eA.

[0090] Furthermore, the heterophasic polypropylene composition preferably has a Charpy notched impact strength at -20°C of from 50.0 to 175.0 kJ / m2, more preferably from 75.0 to 150.0 kJ / m2, still more preferably from 80.0 to 125.0 kJ / m2, determined according to ISO 179-1 / 1 eA.

[0091] Additionally, the heterophasic polypropylene composition preferably has a flexural modulus of from 250 to 750 MPa, more preferably from 275 to 700 MPa, still more preferably from 300 to 650 MPa, determined according to ISO 178 method A. In a first embodiment the heterophasic polypropylene composition comprises the crystalline propylene homopolymer (A) and the elastomeric propylene-ethylene copolymer (B), wherein the elastomeric ethylene-propylene copolymer (C) is not present.

[0092] Thereby, it is preferred that in said first embodiment the polymeric part of the heterophasic polypropylene composition consists of the crystalline propylene homopolymer (A) and the elastomeric propylene-ethylene copolymer (B).

[0093] In said first embodiment the heterophasic polypropylene composition preferably comprises

[0094] (A) from 40.0 to 60.0 wt.-%, preferably from 42.5 to 57.5 wt.-%, more preferably from 45.0 to 55.0 wt.-%, based on the total weight of the heterophasic polypropylene composition, of the crystalline propylene homopolymer; and

[0095] (B) from 40.0 to 60.0 wt.-%, preferably from 42.5 to 57.5 wt.-%, more preferably from 45.0 to 55.0 wt.-%, based on the total weight of the heterophasic polypropylene composition, of the elastomeric propylene-ethylene copolymer; wherein the elastomeric ethylene-propylene copolymer (C) is not present.

[0096] In said first embodiment the heterophasic polypropylene composition preferably has one or more or all of the following properties:

[0097] • a total ethylene content, based on the total weight of the heterophasic polypropylene composition, of from 8.0 to 22.5 wt.-%, preferably 10.0 to 20.0 wt.-%, more preferably 12.0 to 17.5 wt.-%, determined by13C NMR spectroscopy;

[0098] • a content of xylene cold solubles (XCS) fraction, based on the total weight of the heterophasic polypropylene composition and determined at 25°C according to ISO 16152, of from 25.0 to 50.0 wt.-%, preferably from 27.5 to 45.0 wt.-%, more preferably from 30.0 to 40.0 wt.-%.

[0099] Further, the heterophasic polypropylene composition of said first embodiment preferably has the other properties as defined above or below in the accordant ranges as defined above or below. In a second embodiment the heterophasic polypropylene composition comprises the crystalline propylene homopolymer (A), the elastomeric propylene-ethylene copolymer (B), and the elastomeric ethylene-propylene copolymer (C).

[0100] Thereby, it is preferred that in said second embodiment the polymeric part of the heterophasic polypropylene composition consists of the crystalline propylene homopolymer (A), the elastomeric propylene-ethylene copolymer (B) and the elastomeric ethylene-propylene copolymer (C).

[0101] In said second embodiment the heterophasic polypropylene composition preferably comprises

[0102] (A) from 30.0 to 50.0 wt.-%, preferably from 32.5 to 47.5 wt.-%, more preferably from 25.0 to 45.0 wt.-%, based on the total weight of the heterophasic polypropylene composition, of a crystalline propylene homopolymer;

[0103] (B) from 35.0 to 55.0 wt.-%, preferably from 35.5 to 52.5 wt.-%, more preferably from 35.0 to 50.0 wt.-%, based on the total weight of the heterophasic polypropylene composition, of the elastomeric propylene-ethylene copolymer; and

[0104] (C) from 5.0 to 20.0 wt.-%, preferably from 7.5 to 18.5 wt.-%, more preferably from 10.0 to 17.5 wt.-%, based on the total weight of the heterophasic polypropylene composition, of the elastomeric ethylene-propylene copolymer.

[0105] In said second embodiment the heterophasic polypropylene composition preferably has one or more or all of the following properties:

[0106] • a total ethylene content, based on the total weight of the heterophasic polypropylene composition, of from 15.0 to 30.0 wt.-%, preferably 17.5 to 27.5 wt.- %, more preferably 20.0 to 25.0 wt.-%, determined by13C NMR spectroscopy;

[0107] • a content of xylene cold solubles (XCS) fraction, based on the total weight of the heterophasic polypropylene composition and determined at 25°C according to ISO 16152, of from 35.0 to 75.0 wt.-%, preferably from 37.5 to 65.0 wt.-%, more preferably from 40.0 to 55.0 wt.-%.

[0108] Further, the heterophasic polypropylene composition of said second embodiment preferably has the other properties as defined above or below in the accordant ranges as defined above or below.

[0109] The crystalline propylene homopolymer (A) is present in the heterophasic polypropylene composition in an amount of from 30.0 to 60.0 wt.-%, preferably from 32.5 to 57.5 wt.-%, more preferably from 35.0 to 55.0 wt.-%, based on the total weight of the heterophasic polypropylene composition.

[0110] The crystalline propylene homopolymer (A) preferably has a melt flow rate MFR2 determined according to ISO 1133 at 230°C and 2.16 kg of from 2.5 to 25.0 g / 10 min, more preferably from 3.5 to 20.0 g / 10 min, still more preferably from 5.0 to 15.0 g / 10 min.

[0111] Usually, the melt flow rate of the crystalline propylene homopolymer (A) can be measured directly from the polymerization mixture of the crystalline propylene homopolymer (A) in the first polymerization stage.

[0112] Further, the crystalline propylene homopolymer (A) preferably has a content of xylene cold solubles (XCS) fraction, determined according to ISO 16152 at 25°C of from 0.1 to 3.5 wt.-%, more preferably from 0.5 to 3.0 wt.-%, still more preferably from 0.8 to 2.5 wt.- %.

[0113] Elastomeric

[0114] The elastomeric propylene-ethylene copolymer (B) is present in the heterophasic polypropylene composition in an amount of from 35.0 to 60.0 wt.-%, preferably from 37.5 to 57.5 wt.-%, more preferably from 40.0 to 55.0 wt.-%, based on the total weight of the heterophasic polypropylene composition.

[0115] The elastomeric propylene-ethylene copolymer (B) has an ethylene content of from 15.0 to 42.0 wt.-%, preferably from 17.5 to 35.0 wt.-%, more preferably from 20.0 to 30.0 wt.- %, based on the total weight of the elastomeric propylene-ethylene copolymer (B).

[0116] Further, the elastomeric propylene-ethylene copolymer (B) preferably has a propylene content of from 58.0 to 85.0 wt,-%, more preferably from 65.0 to 82.5 wt.-%, still more preferably from 70.0 to 80.0 wt.-%, based on the total weight of the elastomeric propylene-ethylene copolymer (B). It is preferred that the propylene monomer units and the ethylene comonomer units make up 100 mol-% of the elastomeric propylene-ethylene copolymer (B).

[0117] The elastomeric propylene-ethylene copolymer (B) preferably has a melt flow rate MFR2 determined according to ISO 1133 at 230°C and 2.16 kg of from 0.01 to 2.50 g / 10 min, more preferably from 0.05 to 1 .00 g / 10 min, still more preferably from 0.10 to 0.50 g / 10 min.

[0118] The melt flow rate MFR2 of the elastomeric propylene-ethylene copolymer (B) can be calculated from the melt flow rate MFR2 of the crystalline propylene homopolymer (A) and the melt flow rate MFR2 of the polymerization mixture of the crystalline propylene homopolymer (A) and the elastomeric propylene-ethylene copolymer (B) in the second polymerization stage according to the formula disclosed in the determination methods below.

[0119] Elastomeric

[0120] The elastomeric ethylene-propylene copolymer (C) is present in the heterophasic polypropylene composition in an amount of from 0.0 to 20.0 wt.-%, preferably from 0.0 to 18.5 wt.-%, more preferably from 0.0 to 17.5 wt.-%, based on the total weight of the heterophasic polypropylene composition.

[0121] The elastomeric ethylene-propylene copolymer (C) has an ethylene content of from 45.0 to 80.0 wt.-%, preferably from 55.0 to 77.5 wt.-%, more preferably from 60.0 to 75.0 wt.- %, based on the total weight of the elastomeric ethylene-propylene copolymer (C).

[0122] The ethylene content of the elastomeric ethylene-propylene copolymer (C) is higher than the ethylene content of the elastomeric propylene-ethylene copolymer (B).

[0123] Further, the elastomeric ethylene-propylene copolymer (C) preferably has a propylene content of from 20.0 to 55.0 wt.-%, more preferably from 22.5 to 45.0 wt.-%, still more preferably from 25.0 to 40.0 wt.-%, based on the total weight of the elastomeric ethylene-propylene copolymer (C). With the molar majority of ethylene monomer units (i.e. at least 55 mol-%) the elastomeric ethylene-propylene copolymer (C) preferably qualifies as elastomeric ethylene-based copolymer.

[0124] It is preferred that the propylene monomer units and the ethylene comonomer units make up 100 mol-% of the elastomeric ethylene-propylene copolymer (C).

[0125] The elastomeric ethylene-propylene copolymer (C) preferably has a melt flow rate MFR2 determined according to ISO 1133 at 230°C and 2.16 kg of from 0.001 to 0.500 g / 10 min, more preferably from 0.005 to 0.250 g / 10 min, still more preferably from 0.010 to 0.100 g / 10 min.

[0126] The melt flow rate MFR2 of the elastomeric ethylene-propylene copolymer (C) can be calculated from the melt flow rate MFR2 of the polymerization mixture of the crystalline propylene homopolymer (A) and the elastomeric propylene-ethylene copolymer (B) in the second polymerization stage and the melt flow rate MFR2 of polymerization mixture of the crystalline propylene homopolymer (A), the elastomeric propylene-ethylene copolymer (B) and the ethylene-propylene copolymer (C) in the third polymerization stage, preferably of the heterophasic polypropylene composition, according to the formula disclosed in the determination methods below.

[0127] It is preferred that the elastomeric ethylene-propylene copolymer (C) has a lower melt flow rate MFR2 than the elastomeric propylene-ethylene copolymer (B).

[0128] Process

[0129] The present invention further relates to a process for producing a heterophasic polypropylene composition.

[0130] The process preferably comprises the steps of:

[0131] • Polymerizing propylene monomer units in a first polymerization reactor in the presence of a Ziegler Natta catalyst system to produce the crystalline propylene homopolymer (A) in a weight amount of from 30.0 to 60.0 wt.-%, preferably from 32.5 to 57.5 wt.-%, more preferably from 35.0 to 55.0 wt.-%, based on the total weight of the heterophasic polypropylene composition; • Transferring a first reaction mixture comprising the crystalline propylene homopolymer (A) and the Ziegler Natta catalyst system from the first polymerization reactor to a second polymerization reactor;

[0132] • Polymerizing propylene monomer units and ethylene monomer units in a molar ratio of ethylene monomer units to propylene monomer units (C2 / C3) of from 200 to less than 1250 mol / kmol, such as from 200 to 1000 mol / kmol, preferably from 250 to 650 mol / kmol, more preferably from 300 to 500 mol / kmol in the second polymerization reactor in the presence of the first reaction mixture to produce an elastomeric propylene-ethylene copolymer (B) in a weight amount of from 35.0 to 60.0 wt.-%, preferably from 37.5 to 57.5 wt.-%, more preferably from 40.0 to 55.0 wt.-%, based on the total weight of the heterophasic polypropylene composition;

[0133] • Withdrawing a reactor powder from the final polymerization reactor comprising crystalline propylene homopolymer (A), the elastomeric propylene-ethylene copolymer (B), and the Ziegler Natta catalyst system;

[0134] • Compounding the reactor powder optionally together with additives to obtain the heterophasic polypropylene composition.

[0135] In a first embodiment it is preferred that the second polymerization reactor is the final polymerization reactor, so that the reactor powder withdrawn from the final polymerization reactor is the reaction mixture of the second polymerization reactor comprising the crystalline propylene homopolymer (A), the elastomeric propylene- ethylene copolymer (B), and the Ziegler Natta catalyst system.

[0136] In said embodiment the heterophasic polypropylene composition comprises the crystalline propylene homopolymer (A) and the elastomeric propylene-ethylene copolymer (B), wherein an elastomeric ethylene-propylene copolymer (C) is not present. Thereby, in said first embodiment the polymeric part of the heterophasic polypropylene composition preferably consists of the crystalline propylene homopolymer (A) and the elastomeric propylene-ethylene copolymer (B).

[0137] In a second embodiment, the process further comprises the following steps:

[0138] • Transferring a second reaction mixture comprising the crystalline propylene homopolymer (A), the elastomeric propylene-ethylene copolymer (B) and the Ziegler Natta catalyst system from the second polymerization reactor to a third polymerization reactor; • Polymerizing propylene monomer units and ethylene monomer units in a molar ratio of ethylene monomer units to propylene monomer units (C2 / C3) of from 500 to less than 1250 mol / kmol, preferably from 600 to 1150 mol / kmol, more preferably from 700 to 1000 mol / kmol in the third polymerization reactor in the presence of the second reaction mixture to produce an elastomeric ethylene-propylene copolymer (C) in a weight amount of from 5.0 to 20.0 wt.-%, preferably from 7.5 to 18.5 wt.-%, more preferably from 10.0 to 17.5 wt.-%, based on the total weight of the heterophasic polypropylene composition;

[0139] • Withdrawing a reactor powder from the final polymerization reactor comprising crystalline propylene homopolymer (A), the elastomeric propylene-ethylene copolymer (B), the elastomeric ethylene-propylene copolymer (C) and the Ziegler Natta catalyst system;

[0140] • Compounding the reactor powder optionally together with additives to obtain the heterophasic polypropylene composition.

[0141] In said second embodiment it is preferred that the third polymerization reactor is the final polymerization reactor, so that the reactor powder withdrawn from the final polymerization reactor is the reaction mixture of the third polymerization reactor comprising the crystalline propylene homopolymer (A), the elastomeric propyleneethylene copolymer (B), the elastomeric ethylene-propylene copolymer (C) and the Ziegler Natta catalyst system.

[0142] In said second embodiment the heterophasic polypropylene composition comprises the crystalline propylene homopolymer (A), the elastomeric propylene-ethylene copolymer (B), and the elastomeric ethylene-propylene copolymer (C).

[0143] Thereby, in said second embodiment the polymeric part of the heterophasic polypropylene composition preferably consists of the crystalline propylene homopolymer (A), the elastomeric propylene-ethylene copolymer (B) and the elastomeric ethylene- propylene copolymer (C).

[0144] It is preferred that the product of the process of the first or second embodiment as described above is the heterophasic polypropylene composition in all embodiments and aspects as described above or below.

[0145] All aspects and embodiments of the process as described above or below preferably apply to the above described process. In a second aspect of the present invention, the present invention relates to a process for producing the heterophasic polypropylene composition as described above or below comprising the steps of

[0146] • Polymerizing propylene monomer units in a first polymerization reactor in the presence of a Ziegler Natta catalyst system to produce the crystalline propylene homopolymer (A) in a weight amount of from 30.0 to 60.0 wt.-%, preferably from 32.5 to 57.5 wt.-%, more preferably from 35.0 to 55.0 wt.-%, based on the total weight of the heterophasic polypropylene composition;

[0147] • Transferring a first reaction mixture comprising the crystalline propylene homopolymer (A) and the Ziegler Natta catalyst system from the first polymerization reactor to a second polymerization reactor;

[0148] • Polymerizing propylene monomer units and ethylene monomer units in a molar ratio of ethylene monomer units to propylene monomer units (C2 / C3) of from 200 to less than 1250 mol / kmol, such as from 200 to 1000 mol / kmol, preferably from 250 to 650 mol / kmol, more preferably from 300 to 500 mol / kmol in the second polymerization reactor in the presence of the first reaction mixture to produce the elastomeric propylene-ethylene copolymer (B) in a weight amount of from 35.0 to 60.0 wt.-%, preferably from 37.5 to 57.5 wt.-%, more preferably from 40.0 to 55.0 wt.-%, based on the total weight of the heterophasic polypropylene composition;

[0149] • Withdrawing a reactor powder from the final polymerization reactor comprising crystalline propylene homopolymer (A), the elastomeric propylene-ethylene copolymer (B), and the Ziegler Natta catalyst system;

[0150] • Compounding the reactor powder optionally together with additives to obtain the heterophasic polypropylene composition.

[0151] In a first embodiment of said second aspect it is preferred that the second polymerization reactor is the final polymerization reactor, so that the reactor powder withdrawn from the final polymerization reactor is the reaction mixture of the second polymerization reactor comprising the crystalline propylene homopolymer (A), the elastomeric propylene-ethylene copolymer (B), and the Ziegler Natta catalyst system.

[0152] In said embodiment the heterophasic polypropylene composition comprises the crystalline propylene homopolymer (A) and the elastomeric propylene-ethylene copolymer (B), wherein an elastomeric ethylene-propylene copolymer (C) is not present. Thereby, in said first embodiment the polymeric part of the heterophasic polypropylene composition preferably consists of the crystalline propylene homopolymer (A) and the elastomeric propylene-ethylene copolymer (B).

[0153] In a second embodiment of said second aspect the process further comprises the following steps:

[0154] • Transferring a second reaction mixture comprising the crystalline propylene homopolymer (A), the elastomeric propylene-ethylene copolymer (B) and the Ziegler Natta catalyst system from the second polymerization reactor to a third polymerization reactor;

[0155] • Polymerizing propylene monomer units and ethylene monomer units in a molar ratio of ethylene monomer units to propylene monomer units (C2 / C3) of from 500 to less than 1250 mol / kmol, preferably from 600 to 1150 mol / kmol, more preferably from 700 to 1000 mol / kmol in the third polymerization reactor in the presence of the second reaction mixture to produce an elastomeric ethylene-propylene copolymer (C) in a weight amount of from 5.0 to 20.0 wt.-%, preferably from 7.5 to 18.5 wt.-%, more preferably from 10.0 to 17.5 wt.-%, based on the total weight of the heterophasic polypropylene composition;

[0156] • Withdrawing a reactor powder from the final polymerization reactor comprising crystalline propylene homopolymer (A), the elastomeric propylene-ethylene copolymer (B), the elastomeric ethylene-propylene copolymer (C) and the Ziegler Natta catalyst system;

[0157] • Compounding the reactor powder optionally together with additives to obtain the heterophasic polypropylene composition.

[0158] The process in all aspects is further specified as follows:

[0159] The matrix phase of the heterophasic polypropylene composition is preferably polymerized in first polymerization reactor for producing a unimodal matrix phase. The elastomeric phase of the heterophasic polypropylene composition is preferably polymerized in the subsequent one or two polymerization reactors in the presence of the matrix phase for producing a unimodal elastomeric phase or a multimodal elastomeric phase, preferably a bimodal elastomeric phase. Preferably, the polymerization reactors are selected from slurry phase reactors, such as loop reactors and / or gas phase reactors such as fluidized bed reactors, more preferably from loop reactors and fluidized bed reactors.

[0160] A preferred sequential multistage polymerization 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

[0161] WO 2004 / 000899, WO 2004 / 111095, WO 99 / 24478, WO 99 / 24479 or in WO 00 / 68315.

[0162] It is particularly preferred that first polymerization reactor is a slurry phase reactor, more preferably a loop reactor.

[0163] It is preferred that the operating temperature in the first polymerization reactor, preferably the loop reactor, is in the range from 70 to 90 °C, more preferably in the range from 72 to 87 °C, still more preferably in the range from 75 to 85 °C.

[0164] Typically, the pressure in the first polymerization reactor, preferably in the loop reactor, is in the range from 20 to 80 bar, preferably 30 to 70 bar, like 35 to 65 bar.

[0165] In the first polymerization reactor, preferably the loop reactor, a propylene homopolymer is produced. Thus, the first propylene polymer fraction is a first propylene homopolymer fraction.

[0166] Preferably hydrogen is added in the first polymerization reactor in order to control the molecular weight, i.e. the melt flow rate MFR2.

[0167] Preferably the hydrogen to propylene ratio (H2 / C3 ratio) in the first polypropylene reactor, preferably the loop reactor, is in the range from 0.5 to 35.0 mol / kmol, more preferably 0.7 to 25.0 mol / kmol, still more preferably from 1.0 to 10.0 mol / kmol.

[0168] Due to the rather low amount of hydrogen, the melt flow rate of the first propylene polymer fraction is rather low.

[0169] It is preferred that the first propylene polymer fraction has a melt flow rate MFR2 (230°C, 2.16 kg, ISO 1133) in the range of 2.5 to 25.0 g / 10 min, preferably from 3.5 to 20.0 g / 10 min, more preferably from 5.0 to 15.0 g / 10 min. The second polymerization reactor preferably is a first gas phase reactor, such as a first fluidized bed gas phase reactor.

[0170] It is preferred that the operating temperature in the second polymerization reactor, preferably the first gas phase reactor, is in the range from 60 to 85 °C, more preferably in the range from 65 to 78 °C. Typically, the operating temperature in second polymerization reactor is lower than the operating temperature in the third polymerization reactor.

[0171] Typically, the pressure in the second polymerization reactor, preferably in the first gas phase reactor, is in the range from 5 to 50 bar, preferably 15 to 40 bar.

[0172] It is preferred that in the second polymerization reactor, preferably the first gas phase reactor, a propylene-ethylene copolymer is produced. Thus, it is preferred that the second propylene polymer fraction is a first propylene-ethylene copolymer fraction.

[0173] The ethylene to propylene ratio (C2 / C3 ratio) in the second polymerization reactor, preferably the first gas phase reactor, is in the range from 200 to less than 1250 mol / kmol, such as from 200 to 1000 mol / kmol, preferably from 250 to 650 mol / kmol, more preferably from 300 to 500 mol / kmol.

[0174] Due to the high ethylene to propylene ratio (C2 / C3 ratio) the second propylene polymer fraction preferably is an elastomeric block copolymer with propylene rich sections and ethylene rich sections. Thereby, the amount of propylene rich sections is preferably higher than the amount of ethylene rich sections.

[0175] Preferably hydrogen is added in the second polymerization reactor in order to control the molecular weight, i.e. the melt flow rate MFR2.

[0176] Preferably the hydrogen to propylene ratio (H2 / C2 ratio) in the second polypropylene reactor, preferably the first gas phase reactor, is in the range from 5.0 to 50.0 mol / kmol, more preferably 10.0 to 25.0 mol / kmol. It is preferred that the combined first and second propylene polymer fractions have a melt flow rate MFR2 (230°C, 2.16 kg, ISO 1133) in the range of 0.1 to 15.0 g / 10 min, preferably from 0.2 to 12.5 g / 10 min, more preferably from 0.5 to 10.0 g / 10 min.

[0177] The optional third polymerization reactor preferably is a second gas phase reactor, such as a second fluidized bed gas phase reactor.

[0178] It is preferred that the operating temperature in the optional third polymerization reactor, preferably the second gas phase reactor, is in the range from 60 to 85 °C, more preferably in the range from 65 to 78 °C. Typically, the operating temperature in the optional third polymerization reactor is comparable to the operating temperature in the second polymerization reactor.

[0179] Typically, the pressure in the optional third polymerization reactor, preferably in the second gas phase reactor, is in the range from 5 to 40 bar, preferably 10 to 30 bar.

[0180] In the optional third polymerization reactor, preferably the second gas phase reactor, an ethylene-propylene copolymer is produced. Thus, the optional third propylene polymer fraction is a first ethylene-propylene copolymer fraction.

[0181] The ethylene to propylene ratio (C2 / C3 ratio) in the optional third polymerization reactor, preferably the second gas phase reactor, is in the range from 500 to less than 1250 mol / kmol, preferably from 600 to 1150 mol / kmol, more preferably from 700 to 1000 mol / kmol.

[0182] Due to the high ethylene to propylene ratio (C2 / C3 ratio) the third propylene polymer fraction preferably is an elastomeric block copolymer with propylene rich sections and ethylene rich sections. Thereby, the amount of ethylene rich sections is preferably higher than the amount of propylene rich sections.

[0183] Preferably hydrogen is added in the third polymerization reactor in order to control the molecular weight, i.e. the melt flow rate MFR2.

[0184] Preferably, the hydrogen to ethylene ratio (H2 / C2 ratio) in the third polymerization reactor, preferably the second gas phase reactor, is in the range from 25 to 150 mol / kmol, more preferably 50 to 100 mol / kmol. It is preferred that the combined first, second and third propylene polymer fractions have a melt flow rate MFR2 (230°C, 2.16 kg, ISO 1133) in the range of 0.01 to 10.0 g / 10 min, preferably from 0.05 to 5.5 g / 10 min, more preferably from 0.1 to 3.5 g / 10 min.

[0185] The combined first, second and optional third propylene polymer fractions preferably form the polymeric components of the heterophasic polypropylene composition.

[0186] It is preferred that the main polymerization stages of the process consist of two sequential main polymerization stages in the first polymerization reactor and the second polymerization reactor or of three sequential main polymerization stages in the first polymerization reactor, the second polymerization reactor and the third polymerization reactor.

[0187] The preparation of the first, second and optional third propylene polymer fractions can comprise in addition to the (main) polymerization stages in the at least two, preferably two or three polymerization reactors prior thereto a pre-polymerization in a prepolymerization reactor upstream to the first polymerization reactor.

[0188] In the pre-polymerization reactor, a polypropylene is produced. The pre-polymerization is preferably conducted in the presence of the Ziegler-Natta catalyst system. According to this embodiment, the Ziegler-Natta catalyst system is introduced to the pre- polymerization step. However, this shall not exclude the option that at a later stage for instance further co-catalyst is added in the polymerization process, for instance in the first polymerization reactor. In one embodiment, all components of the Ziegler-Natta catalyst system are only added in the pre-polymerization reactor, if a pre-polymerization is applied.

[0189] The pre-polymerization reaction is typically conducted at a temperature of 0 to 50 °C, preferably from 10 to 40 °C, and more preferably from 15 to 25 °C.

[0190] The pressure in the pre-polymerization reactor is not critical but must be sufficiently high to maintain the reaction mixture in liquid phase. Thus, the pressure may be from 20 to 100 bar, for example 30 to 70 bar. In a preferred embodiment, the pre-polymerization is conducted as bulk slurry polymerization in liquid propylene, i.e. the liquid phase mainly comprises propylene, optionally with inert components dissolved therein.

[0191] It is possible to add other components also to the pre-polymerization stage. Thus, hydrogen may be added into the pre-polymerization stage to control the molecular weight of the polypropylene as is known in the art. Further, antistatic additives may be used to prevent the particles from adhering to each other or to the walls of the reactor.

[0192] The precise control of the pre-polymerization conditions and reaction parameters is within the skill of the art.

[0193] Due to the above defined process conditions in the pre-polymerization, preferably a mixture of the Ziegler-Natta catalyst system and the polypropylene produced in the pre- polymerization reactor is obtained. Preferably, the Ziegler-Natta catalyst system is (finely) dispersed in the polypropylene. In other words, the Ziegler-Natta catalyst system particles introduced into the pre-polymerization reactor are split into smaller fragments that are evenly distributed within the growing polypropylene. The sizes of the introduced Ziegler-Natta catalyst system as well as of the obtained fragments are not of essential relevance for the instant invention and within the skilled knowledge.

[0194] As mentioned above, if a pre-polymerization is used, subsequent to said pre- polymerization, the mixture of the Ziegler-Natta catalyst system and the polypropylene produced in the pre-polymerization reactor is transferred to the first polymerization reactor. Typically the total amount of the polypropylene produced in the pre- polymerization reactor in the first, second and third propylene polymer fractions is rather low and typically not more than 3.0 wt.-%, more preferably not more than 2.0 wt.-%, still more preferably in the range from 0.2 to 2.0 wt.-%, like in the range 0.5 of to 1 .5 wt.-%.

[0195] In case that pre-polymerization is not used, propylene and the other ingredients such as the Ziegler-Natta catalyst system are directly introduced into the first polymerization reactor. The residence times of the polymerization mixtures in the different polymerization stages are adjusted to obtain the amounts of the first, second, third and fourth polymer fractions in the combined first, second and third polymer fractions.

[0196] The Ziegler-Natta catalyst system will be now described in more detail.

[0197] It is appreciated that there are no specific restrictions regarding the catalyst system as long as a Ziegler-Natta catalyst system is used. As regards Ziegler-Natta catalyst systems suitable for preparing the heterophasic polypropylene composition, reference is made to e.g. WO 2014 / 023603, EP 491566, EP 591224, EP 586390, WO 2012 / 007430, EP 2610271 , EP 2610273 and EP 2610272.

[0198] The Ziegler-Natta catalyst system can be supported or self-self-supported.

[0199] In one specific embodiment, the Ziegler-Natta is self-supported and preferably prepared as described below:

[0200] The catalyst is preferably a solid Ziegler-Natta catalyst, which comprises compounds of a transition metal of Group 4 to 6 of IUPAC, like titanium, a Group 2 metal compound, like a magnesium, and an internal donor being preferably a non-phthalic compound, more preferably a non-phthalic acid ester, still more preferably being a diester of non- phthalic dicarboxylic acids as described in more detail below. Thus, the catalyst is fully free of undesired phthalic compounds. Further, the solid catalyst is free of any external support material, like silica or MgCI2, but the catalyst is self-supported.

[0201] The Ziegler-Natta catalyst (ZN-C) can be further defined by the way it is obtained.

[0202] Accordingly, the Ziegler-Natta catalyst (ZN-C) is preferably obtained by a process comprising the steps of a) a-i) providing a solution of at least a Group 2 metal alkoxy compound (Ax) being the reaction product of a Group 2 metal compound and a monohydric alcohol (A) comprising in addition to the hydroxyl moiety at least one ether moiety optionally in an organic liquid reaction medium; or

[0203] 32) a solution of at least a Group 2 metal alkoxy compound (Ax’) being the reaction product of a Group 2 metal compound and an alcohol mixture of the monohydric alcohol (A) and a monohydric alcohol (B) of formula ROH, optionally in an organic liquid reaction medium; or as) providing a solution of a mixture of the Group 2 alkoxy compound (Ax) and a Group 2 metal alkoxy compound (Bx) being the reaction product of a Group 2 metal compound and the monohydric alcohol (B), optionally in an organic liquid reaction medium; or

[0204] 34) providing a solution of Group 2 alkoxide of formula M(ORi)n(OR2)mX2-n-m or mixture of Group 2 alkoxides M(ORi)nX2-n’ and M(OR2)mX2-m’, where M is Group 2 metal, X is halogen, R1 and R2 are different alkyl groups of C2 to C16 carbon atoms, and 0 < n < 2, 0 < m < 2 and n+m+(2-n-m) = 2, provided that both n and m 0, 0 < n’ < 2 and 0 < m’ < 2; and b) adding said solution from step a) to at least one compound of a transition metal of Group 4 to 6 and c) obtaining the solid catalyst component particles, and adding an internal electron donor, preferably a non-phthalic internal donor, at any step prior to step c).

[0205] The internal donor or precursor thereof is added preferably to the solution of step a).

[0206] According to the procedure above the Ziegler-Natta catalyst can be obtained via precipitation method or via emulsion (liquid / liquid two-phase system) - solidification method depending on the physical conditions, especially temperature used in steps b) and c).

[0207] In both methods (precipitation or emulsion-solidification) the catalyst chemistry is the same.

[0208] In precipitation method combination of the solution of step a) with at least one transition metal compound in step b) is carried out and the whole reaction mixture is kept at least at 50°C, more preferably in the temperature range of 55°C to 110°C, more preferably in the range of 70°C to 100°C, to secure full precipitation of the catalyst component in form of a solid particles (step c). In emulsion - solidification method in step b) the solution of step a) is typically added to the at least one transition metal compound at a lower temperature, such as from -10 to below 50°C, preferably from -5 to 30°C. During agitation of the emulsion the temperature is typically kept at -10 to below 40°C, preferably from -5 to 30°C. Droplets of the dispersed phase of the emulsion form the active catalyst composition.

[0209] Solidification (step c) of the droplets is suitably carried out by heating the emulsion to a temperature of 70 to 150°C, preferably to 80 to 110°C.

[0210] The catalyst prepared by emulsion - solidification method is preferably used in the present invention.

[0211] In a preferred embodiment in step a) the solution of a2) or as) are used, i.e. a solution of (Ax’) or a solution of a mixture of (Ax) and (Bx).

[0212] Preferably the Group 2 metal is magnesium.

[0213] The magnesium alkoxy compounds (Ax), (Ax’) and (Bx) can be prepared in situ in the first step of the catalyst preparation process, step a), by reacting the magnesium compound with the alcohol(s) as described above, or said magnesium alkoxy compounds can be separately prepared magnesium alkoxy compounds or they can be even commercially available as ready magnesium alkoxy compounds and used as such in the catalyst preparation process of the invention.

[0214] Illustrative examples of alcohols (A) are monoethers of dihydric alcohols (glycol monoethers). Preferred alcohols (A) are C2 to C4 glycol monoethers, wherein the ether moieties comprise from 2 to 18 carbon atoms, preferably from 4 to 12 carbon atoms. Preferred examples are 2-(2-ethylhexyloxy)ethanol, 2-butyloxy ethanol, 2-hexyloxy ethanol and 1 ,3-propylene-glycol-monobutyl ether, 3-butoxy-2-propanol, with 2-(2- ethylhexyloxy)ethanol and 1 ,3-propylene-glycol-monobutyl ether, 3-butoxy-2-propanol being particularly preferred.

[0215] Illustrative monohydric alcohols (B) are of formula ROH, with R being straight-chain or branched Ce-C alkyl residue. The most preferred monohydric alcohol is 2-ethyl-1 - hexanol or octanol. Preferably a mixture of Mg alkoxy compounds (Ax) and (Bx) or mixture of alcohols (A) and (B), respectively, are used and employed in a mole ratio of Bx:Ax or B:A from 8:1 to 2:1 , more preferably 5:1 to 3:1.

[0216] Magnesium alkoxy compound may be a reaction product of alcohol(s), as defined above, and a magnesium compound selected from dialkyl magnesiums, alkyl magnesium alkoxides, magnesium dialkoxides, alkoxy magnesium halides and alkyl magnesium halides. Alkyl groups can be a similar or different C1-C20 alkyl, preferably C2- C10 alkyl. Typical alkyl-alkoxy magnesium compounds, when used, are ethyl magnesium butoxide, butyl magnesium pentoxide, octyl magnesium butoxide and octyl magnesium octoxide. Preferably the dialkyl magnesiums are used. Most preferred dialkyl magnesiums are butyl octyl magnesium or butyl ethyl magnesium.

[0217] It is also possible that magnesium compound can react in addition to the alcohol (A) and alcohol (B) also with a polyhydric alcohol (C) of formula R”(OH)mto obtain said magnesium alkoxide compounds. Preferred polyhydric alcohols, if used, are alcohols, wherein R” is a straight-chain, cyclic or branched C2 to C10 hydrocarbon residue, and m is an integer of 2 to 6.

[0218] The magnesium alkoxy compounds of step a) are thus selected from the group consisting of magnesium dialkoxides, diaryloxy magnesiums, alkyloxy magnesium halides, aryloxy magnesium halides, alkyl magnesium alkoxides, aryl magnesium alkoxides and alkyl magnesium aryloxides. In addition a mixture of magnesium dihalide and a magnesium dialkoxide can be used.

[0219] The solvents to be employed for the preparation of the present catalyst may be selected among aromatic and aliphatic straight chain, branched and cyclic hydrocarbons with 5 to 20 carbon atoms, more preferably 5 to 12 carbon atoms, or mixtures thereof. Suitable solvents include benzene, toluene, cumene, xylol, pentane, hexane, heptane, octane and nonane. Hexanes and pentanes are particular preferred. Mg compound is typically provided as a 10 to 50 wt% solution in a solvent as indicated above. Typical commercially available Mg compound, especially dialkyl magnesium solutions are 20 - 40 wt% solutions in toluene or heptanes.

[0220] The reaction for the preparation of the magnesium alkoxy compound may be carried out at a temperature of 40° to 70°C. Most suitable temperature is selected depending on the Mg compound and alcohol(s) used.

[0221] The transition metal compound of Group 4 to 6 is preferably a titanium compound, most preferably a titanium halide, like TiCU.

[0222] The non-phthalic internal donor used in the preparation of the catalyst used in the present invention is preferably selected from (di)esters of non-phthalic carboxylic (di)acids, 1 ,3-diethers, derivatives and mixtures thereof. Especially preferred donors are diesters of mono-unsaturated dicarboxylic acids, in particular esters belonging to a group comprising malonates, maleates, succinates, citraconates, glutarates, cyclohexene-1 ,2-dicarboxylates and benzoates, and any derivatives and / or mixtures thereof. Preferred examples are e.g. substituted maleates and citraconates, most preferably citraconates.

[0223] In emulsion method, the two phase liquid-liquid system may be formed by simple stirring and optionally adding (further) solvent(s) and additives, such as the turbulence minimizing agent (TMA) and / or the emulsifying agents and / or emulsion stabilizers, like surfactants, which are used in a manner known in the art for facilitating the formation of and / or stabilize the emulsion. Preferably, surfactants are acrylic or methacrylic polymers. Particular preferred are unbranched C12 to C20 (meth)acrylates such as poly(hexadecyl)- methacrylate and poly(octadecyl)-methacrylate and mixtures thereof. Turbulence minimizing agent (TMA), if used, is preferably selected from a-olefin polymers of a-olefin monomers with 6 to 20 carbon atoms, like polyoctene, polynonene, polydecene, polyundecene or polydodecene or mixtures thereof. Most preferable it is polydecene.

[0224] The solid particulate product obtained by precipitation or emulsion - solidification method may be washed at least once, preferably at least twice, most preferably at least three times with an aromatic and / or aliphatic hydrocarbons, preferably with toluene, heptane or pentane. The catalyst can further be dried, as by evaporation or flushing with nitrogen, or it can be slurried to an oily liquid without any drying step.

[0225] The finally obtained Ziegler-Natta catalyst is desirably in the form of particles having generally an average particle size range of 5 to 200 pm, preferably 10 to 100. Particles are compact with low porosity and have surface area below 20 g / m2, more preferably below 10 g / m2. Typically the amount of Ti is 1 to 6 wt.-%, Mg 10 to 20 wt.-% and internal donor 10 to 40 wt.-% of the catalyst composition.

[0226] The Ziegler-Natta catalyst is preferably used in association with an alkyl aluminum cocatalyst and optionally external donors.

[0227] As further component in the instant polymerization process an external donor is preferably present. Suitable external donors include certain silanes, ethers, esters, amines, ketones, heterocyclic compounds and blends of these. It is especially preferred to use a silane. It is most preferred to use silanes of the general formula

[0228] RapRbqSi(ORc)(4-p-q) wherein Ra, Rband Rcdenote a hydrocarbon radical, in particular an alkyl or cycloalkyl group, and wherein p and q are numbers ranging from 0 to 3 with their sum p + q being equal to or less than 3. Ra, Rband Rccan be chosen independently from one another and can be the same or different. Specific examples of such silanes are (tert- butyl)2Si(OCH3)2, (cyclohexyl)(methyl)Si(OCH3)2, (phenyl)2Si(OCH3)2 and (cyclopentyl)2Si(OCH3)2, or of general formula

[0229] Si(OCH2CH3)3(NR3R4) wherein R3and R4can be the same or different a represent a hydrocarbon group having 1 to 12 carbon atoms.

[0230] R3and R4are independently selected from the group consisting of linear aliphatic hydrocarbon group having 1 to 12 carbon atoms, branched aliphatic hydrocarbon group having 1 to 12 carbon atoms and cyclic aliphatic hydrocarbon group having 1 to 12 carbon atoms. It is in particular preferred that R3and R4are independently selected from the group consisting of methyl, ethyl, n-propyl, n-butyl, octyl, decyl, iso-propyl, iso-butyl, iso-pentyl, tert.-butyl, tert.-amyl, neopentyl, cyclopentyl, cyclohexyl, methylcyclopentyl and cycloheptyl.

[0231] More preferably both R1and R2are the same, yet more preferably both R3and R4are an ethyl group.

[0232] Especially preferred external donors are the dicyclopentyl dimethoxy silane donor (D- donor) or the cyclohexylmethyl dimethoxy silane donor (C-Donor).

[0233] In addition to the Ziegler-Natta catalyst and the optional external donor a co-catalyst can be used. The co-catalyst is preferably a compound of group 13 of the periodic table (IUPAC), e.g. organo aluminum, such as an aluminum compound, like aluminum alkyl, aluminum halide or aluminum alkyl halide compound. Accordingly, in one specific embodiment the co-catalyst is a trialkylaluminium, like triethylaluminium (TEAL), dialkyl aluminium chloride or alkyl aluminium dichloride or mixtures thereof. In one specific embodiment the co-catalyst is triethylaluminium (TEAL).

[0234] Preferably the ratio between the co-catalyst (Co) and the external donor (ED) [Co / ED] and / or the ratio between the co-catalyst (Co) and the transition metal (TM) [Co / TM] should be carefully chosen.

[0235] Accordingly,

[0236] (a) the mol-ratio of co-catalyst (Co) to external donor (ED) [Co / ED] is preferably in the range of 5 to 45, more preferably is in the range of 5 to 35, still more preferably is in the range of 5 to 25; and optionally

[0237] (b) the mol-ratio of co-catalyst (Co) to titanium compound (TC) [Co / TC] is preferably in the range of above 80 to 500, more preferably is in the range of 100 to 350, still more preferably is in the range of 120 to 300.

[0238] In said one specific embodiment the Ziegler-Natta catalyst system preferably comprises (a) a Ziegler-Natta catalyst comprising compounds (TC) of a transition metal of Group 4 to 6 of IUPAC, a Group 2 metal compound and an internal donor, wherein said internal donor is a non-phthalic compound, preferably is a non-phthalic acid ester and still more preferably is a diester of non-phthalic dicarboxylic acids;

[0239] (b) a co-catalyst (Co), and

[0240] (c) optionally an external donor (ED).

[0241] It is preferred that the internal donor (ID) is selected from optionally substituted malonates, maleates, succinates, glutarates, cyclohexene-1 ,2-dicarboxylates, benzoates and derivatives and / or mixtures thereof, preferably the internal donor (ID) is a citraconate. Additionally or alternatively, the molar-ratio of co-catalyst (Co) to external donor (ED) [Co / ED] is 5 to 45.

[0242] In one embodiment an additional nucleating agent is introduced to the composition during the polymerization process of the polymeric components of the heterophasic polypropylene composition. The additional nucleating agent is preferably a polymeric nucleating agent, which is preferably produced by polymerizing a vinyl compound. The additional nucleating agent is preferably introduced to the heterophasic polypropylene composition by first polymerizing the vinyl compound, preferably vinylcycloalkane, as defined below, in the presence of the Ziegler-Natta catalyst system and the obtained reaction mixture of the polymer of the vinyl compound, preferably vinyl cyclohexane (VCH) polymer, and the catalyst system is then used for producing the polymeric components of the heterophasic polypropylene composition.

[0243] With regard to the polymeric nucleating agents reference is made to the international applications WO 99 / 24478, WO 99 / 24479 and particularly WO 00 / 68315. According to this technology a catalyst system, preferably a Ziegler-Natta procatalyst, can be modified by polymerizing a vinyl compound in the presence of the catalyst system, comprising in particular the special Ziegler-Natta procatalyst, an external donor and a cocatalyst, which vinyl compound has the formula: CH2=CH-CHR1R2wherein R1and R2, together with the carbon atom they are attached to, form an optionally substituted saturated or unsaturated or aromatic ring or a fused ring system, wherein the ring or fused ring moiety contains four to 20 carbon atoms, preferably 5 to 12 membered saturated or unsaturated or aromatic ring or a fused ring system or independently represent a linear or branched C4-C30 alkane, C4- C20 cycloalkane or C4- C20 aromatic ring. Preferably R1and R2, together with the C-atom wherein they are attached to, form a five- or six-membered saturated or unsaturated or aromatic ring or independently represent a lower alkyl group comprising from 1 to 4 carbon atoms. Preferred vinyl compounds for the preparation of a polymeric nucleating agent to be used in accordance with the present invention are in particular vinyl cycloalkanes, in particular vinyl cyclohexane (VCH), vinyl cyclopentane, and vinyl-2-methyl cyclohexane, 3-methyl-1 -butene, 3-ethyl-1 -hexene, 3-methyl-1 -pentene, 4-methyl-1 -pentene or mixtures thereof. VCH is a particularly preferred monomer.

[0244] The polymerized vinyl compound acts as an alpha-nucleating agent. The weight ratio of vinyl compound to solid catalyst component in the modification step of the catalyst is preferably of up to 5 (5:1), preferably up to 3 (3:1) most preferably from 0.5 (1 :2) to 2 (2:1). The most preferred vinyl compound is vinylcyclohexane (VCH).

[0245] The reactor powder from the last polymerization stage preferably has a powder flowability, determined according to ISO 6186:1998, method A, nozzle diameter 15 mm, of from 5 to 20 s, more preferably from 7 to 17 s.

[0246] Further, the reactor powder from the last polymerization stage preferably shows an uninterrupted flow determined according to ISO 6186:1998, method A, nozzle diameter 15 mm.

[0247] The good flowability of the reactor powder from the last polymerization stage indicates that the reactor powder during the whole polymerization process show reduced stickiness so that reactor fouling also in the last polymerization stages is reduced or even avoided.

[0248] The reactor powder comprising the crystalline propylene homopolymer, the elastomeric propylene-ethylene copolymer and optionally the elastomeric ethylene-propylene copolymer are blended with optional additives to produce the heterophasic polypropylene composition. Thereby, the blending conditions are preferably in the usual range for blending such heterophasic polypropylene compositions and can be easily adapted by one skilled in the art.

[0249] Article

[0250] In a third aspect the present invention relates to an article, preferably an injection moulded article, more preferably an injection moulded automotive article comprising the heterophasic polypropylene composition as defined above or below. The article preferably comprises the heterophasic polypropylene composition in an amount of from 25 to 100 wt.-%.

[0251] In one embodiment the article preferably comprises the heterophasic polypropylene composition in an amount of from 90 to 100 wt.-%, more preferably from 95 to 100 wt.- %.

[0252] In said embodiment, the article preferably shows the same properties as described above or below for the heterophasic polypropylene composition.

[0253] It is preferred that all aspects and embodiments of the heterophasic polypropylene composition and the process for producing the heterophasic polypropylene composition as described above and below also apply to the article of the third aspect of the invention.

[0254] Use

[0255] In a fourth aspect the present invention relates to the use of the heterophasic polypropylene composition as defined above or below for the production of an article, preferably an injection moulded article, more preferably an injection moulded automotive article.

[0256] It is preferred that all aspects and embodiments of the heterophasic polypropylene composition, the process for producing the heterophasic polypropylene composition and the article as described above and below also apply to the use of the fourth aspect of the invention.

[0257] Experimental Section

[0258] The following Examples are included to demonstrate certain aspects and embodiments of the invention as described in the claims. It should be appreciated by those of skill in the art, however, that the following description is illustrative only and should not be taken in any way as a restriction of the invention.

[0259] 1. Determination methods 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.

[0260] Quantification of microstructure by NMR spectroscopy

[0261] Quantitative nuclear-magnetic resonance (NMR) spectroscopy was used to quantify the comonomer content and comonomer sequence distribution of the polymers. 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 probehead at 125°C using nitrogen gas for all pneumatics. Approximately 200 mg of material was dissolved in 3 ml of 7,2-tetrachloroethane-c / 2 (TCE-c ) along with chromium-(lll)- acetylacetonate (Cr(acac)3) resulting in a 65 mM solution of relaxation agent in solvent (Singh, G., Kothari, A., Gupta, V., Polymer Testing 28 5 (2009), 475). To ensure a homogenous solution, after initial sample preparation in a heat block, the NMR tube was further heated in a rotatory 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 and quantitatively needed for accurate ethylene content quantification. Standard single-pulse excitation was employed without NOE, using an optimised tip angle, 1 s recycle delay and a 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, 1128). A total of 6144 (6k) transients were acquired per spectra.

[0262] Quantitative13C{1H} NMR spectra were processed, integrated and relevant quantitative properties determined from the integrals using proprietary computer programs. All chemical shifts were indirectly referenced to the central methylene group of the ethylene block (EEE) at 30.00 ppm using the chemical shift of the solvent. This approach allowed comparable referencing even when this structural unit was not present. Characteristic signals corresponding to the incorporation of ethylene were observed Cheng, H. N., Macromolecules 17 (1984), 1950).

[0263] With characteristic signals corresponding to 2,1 erythro regio defects observed (as described in L. Resconi, L. Cavallo, A. Fait, F. Piemontesi, Chem. Rev. 2000, 100 (4), 1253, in Cheng, H. N., Macromolecules 1984, 17, 1950, and in W-J. Wang and S. Zhu, Macromolecules 2000, 33 1157) the correction for the influence of the regio defects on determined properties was required. Characteristic signals corresponding to other types of regio defects were not observed.

[0264] 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.

[0265] 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:

[0266] E = 0.5(Spp + Spy + Spb + O.5(Sa + Say))

[0267] Through the use of this set of sites the corresponding integral equation becomes:

[0268] E = 0.5(IH+IG + 0.5(lc + 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.

[0269] The mole percent comonomer incorporation was calculated from the mole fraction: E [mol%] = 100 * fE

[0270] The weight percent comonomer incorporation was calculated from the mole fraction: E [wt%] = 100 * (fE * 28.06) I ((fE * 28.06) + ((1 -fE) * 42.08))

[0271] The comonomer sequence distribution at the triad level was determined using the analysis method of Kakugo et al. (Kakugo, M., Naito, Y., Mizunuma, K., Miyatake, T. Macromolecules 15 (1982) 1150). This method was chosen for its robust nature and integration regions slightly adjusted to increase applicability to a wider range of comonomer contents.

[0272] The relative content of isolated to block ethylene incorporation was calculated from the triad sequence distribution using the following relationship (equation (I)): wherein 1(E) is the relative content of isolated to block ethylene sequences [in %]; fPEP is the mol fraction of propylene / ethylene / propylene sequences (PEP) in the sample; fPEE is the mol fraction of propylene / ethylene / ethylene sequences (PEE) and of ethylene / ethylene / propylene sequences (EEP) in the sample; fEEE is the mol fraction of ethylene / ethylene / ethylene sequences (EEE) in the sample

[0273] The C2 content of a fraction (X) produced in the presence of a fraction (Y) is calculated using the measured values of the C2 content of fraction (Y) and the mixture received after producing fraction (X) (final):

[0274] C2finat=CX■ weight fraction (X) + C2y■ weight fraction (K)

[0275] Thereby in the heterophasic polypropylene composition of the present invention the C2 content of elastomeric propylene-ethylene copolymer (B) as fraction (X) is calculated according to the above formula with fraction (Y) being the crystalline propylene homopolymer (A) and C2fjnaibeing the C2 content of the polymerization mixture of the second polymerization stage (R2).

[0276] Further, in the heterophasic polypropylene composition of the present invention the C2 content of optional elastomeric ethylene-propylene copolymer (C) as fraction (X) is calculated according to the above formula with fraction (Y) being the polymerization mixture of the second polymerization stage (R2) and C2fjnaibeing the C2 content of the polymerization mixture of the second polymerization stage (R3).

[0277] Melt Flow Rate

[0278] The melt flow rate (MFR) was determined according to ISO 1133 and was 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 polypropylene was determined at a temperature of 230 °C and a load of 2.16 kg.

[0279] The MFR2 of a fraction (X) produced in the presence of a fraction (Y) is calculated using the measured values of MFR2 of fraction (Y) and the mixture received after producing fraction (X) (“final”):

[0280] Log(MFRfinal) = weight fraction(X) * Log(MFRx) + weight fraction(Y) * Log(MFRY) Thereby in the heterophasic polypropylene composition of the present invention the MFR2 of elastomeric propylene-ethylene copolymer (B) as fraction (X) is calculated according to the above formula with fraction (Y) being the crystalline propylene homopolymer (A) and MFRfjnaibeing the MFR2 of the polymerization mixture of the second polymerization stage (R2).

[0281] Further, in the heterophasic polypropylene composition of the present invention the MFR2 of the optional elastomeric ethylene-propylene copolymer (C) as fraction (X) is calculated according to the above formula with fraction (Y) being the polymerization mixture of the second polymerization stage (R2) and MFRfjnaibeing the MFR2 of the polymerization mixture of the second polymerization stage (R3).

[0282] DSC analysis, melting temperature (Tm) and heat of fusion (Hf), crystallization temperature (Tc) and heat of crystallization (Hc): measured with a TA Instrument Q200 differential scanning calorimetry (DSC) on 5 to 7 mg samples. DSC was run according to ISO 113571 part 3 / method C2 in a heat I cool I heat cycle with a scan rate of 10 °C / min in the temperature range of -30 to +225 °C. Crystallization temperature (Tc) and crystallization enthalpy (Hc) were determined from the cooling step, while melting temperature (Tm) and melting enthalpy (Hm) were determined from the second heating step.

[0283] The glass transition temperature Tg and storage modulus G’ at 23 °C were determined by dynamic mechanical analysis according to ISO 6721-7. The measurements were done in torsion mode on compression moulded samples (40x10x1 mm3) between -100 °C and +150 °C with a heating rate of 2 °C / min and frequency of 1 Hz.

[0284] The Flexural Modulus was determined according to ISO 178 method A (3-point bending test) on 80 mm x 10 mm x 4 mm specimens. Following the standard, a test speed of 2 mm / min and a span length of 16 times the thickness was used. The testing temperature was 23±20C. Injection moulding was carried out according to ISO 19069-2 using a melt temperature of 230 °C for all materials irrespective of material melt flow rate. Notched impact strength (NIS)

[0285] The Charpy notched impact strength (NIS) was measured according to ISO 179 1eA at +23 °C or -20 °C, using injection moulded bar test specimens of 80x10x4 mm3prepared in accordance with ISO 19069-2 using a melt temperature of 230 °C for all materials irrespective of material melt flow rate.

[0286] The xylene soluble fraction at room temperature (XCS, wt.-%)

[0287] The amount of the polymer soluble in xylene was determined at 25 °C according to ISO 16152; 5thedition; 2005-07-01.

[0288] Intrinsic viscosity

[0289] Intrinsic viscosity was measured according to DIN ISO 1628 / 1 , October 1999 (in Decalin at 135 °C).

[0290] Powder flowability

[0291] The flowability of the reactor powder from the last polymerization stage was measured according to ISO 6186:1998, method A, the nuzzle diameter is 15 mm. The test was done at 23°C, 50% relative humidity. Before the test, the reactor powder was conditioned at the same condition for 24h. To determine the flow time, 150.0±0.1 g of reactor powder were weighted and poured into the funnel, and the tests were started without vibration. When the funnel is empty then the test is finished and time is recorded. For each sample three tests were done and the average is reported as tsis- Moreover, the flow mode is also recorded

[0292] U: materials flow uniformly

[0293] I: materials flow intermittently

[0294] P: materials does not flow at the test condition

[0295] 2. Preparation of the heterophasic polypropylene compositions Catalyst

[0296] The catalyst used in the polymerization process for examples IE1 , IE2 and CE1 has been produced as follows:

[0297] First, 0.1 mol of MgChx 3 EtOH was suspended under inert conditions in 250 ml of decane in a reactor at atmospheric pressure. The solution was cooled to the temperature of -15°C and 300 ml of cold TiCU was added while maintaining the temperature at said level. Then, the temperature of the slurry was increased slowly to 20 °C. At this temperature, 0.02 mol of dioctylphthalate (DOP) was added to the slurry. After the addition of the phthalate, the temperature was raised to 135 °C during 90 minutes and the slurry was allowed to stand for 60 minutes. Then, another 300 ml of TiCU was added and the temperature was kept at 135 °C for 120 minutes. After this, the catalyst was filtered from the liquid and washed six times with 300 ml heptane at 80 °C. Then, the solid catalyst component was filtered and dried. Catalyst and its preparation concept is described in general e.g. in patent publications EP491566, EP591224 and EP586390.

[0298] Polymerization was performed in a Borstar PP pilot plant, comprising a prepolymerization reactor, a loop reactor and two (or one) gas phase reactor(s). The polymerization conditions are also indicated in Table 1.

[0299] Table 1 : Polymerization conditions of IE1 , IE2 and CE1

[0300] The reactor powders from R2 for IE1 , R3 for IE2 and R4 for CE1 were subjected to the powder flowability test as described above in the determination methods. For determining the properties of the heterophasic polypropylene compositions the reactor powders of IE1 , IE2 and CE1 were compounded with 1500 ppm of an antioxidant blend of pentaerythrityl-tetrakis(3-(3’,5’-di-tert. butyl-4-hydroxyphenyl)- propionate (Cas. No. 6683-19-8) and tris (2,4-di-f-butylphenyl) phosphite (Cas. No. 31570-04-4) in weight ratio of 1 :2 and 500 ppm calcium stearate (Cas. No. 1592-23-0) and the properties of the resultant heterophasic polypropylene compositions were determined. The properties of the compounded heterophasic polypropylene compositions of IE1 , IE2 and CE1 are listed in Table 2 below.

[0301] Further listed in Table 2 are the properties of commercial heterophasic propylene copolymer resins Adflex C 200 F, commercially available from LyondellBasell, as RE1 , and SA232CF, commercially available from Borealis AG, as RE2.

[0302] RE1 is a heterophasic polypropylene resin developed for the central layer of tough, transparent co-extruded cast-film structures and suitable for co-extruded cast-film for food packaging, hygiene applications, surface protection.

[0303] RE2 is a heterophasic polypropylene resin with a random ethylene-propylene copolymer matrix suitable for use on conventional blown film lines with air cooling.

[0304] Table 2: Properties of the compositions of IE1 , CE1 and RE1 n.d. = not determined

[0305] ‘measured on the powder as described in Table 1.

[0306] The reactor powders of IE1 and IE2 show an improved flowability compared to the reactor powder of CE1 .

[0307] Further the inventive heterophasic polypropylene compositions IE1 and IE2 show an improved stiffness / impact balance with an improved impact strength especially at low temperatures at acceptable flexural modulus.

[0308] Thereby, it has been found that for soft applications the flexural modulus can be reduced without considerable impact on the impact properties or flowability by applying the third reactor stage for producing the elastomeric ethylene-propylene copolymer in IE2.

Claims

Claims1 . A heterophasic polypropylene composition comprising(A) from 30.0 to 60.0 wt.-%, preferably from 32.5 to 57.5 wt.-%, more preferably from 35.0 to 55.0 wt.-%, based on the total weight of the heterophasic polypropylene composition, of a crystalline propylene homopolymer;(B) from 35.0 to 60.0 wt.-%, preferably from 37.5 to 57.5 wt.-%, more preferably from 40.0 to 55.0 wt.-%, based on the total weight of the heterophasic polypropylene composition, of an elastomeric propylene-ethylene copolymer having an ethylene content, determined by13C NMR spectroscopy, of from 15.0 to 42.0 wt.-%, preferably from 17.5 to 35.0 wt.-%, more preferably from 20.0 to 30.0 wt.-%, based on the total weight of the elastomeric propyleneethylene copolymer (B); and(C) from 0.0 to 20.0 wt.-%, preferably from 0.0 to 18.5 wt.-%, more preferably from 0.0 to 17.5 wt.-%, based on the total weight of the heterophasic polypropylene composition, of an elastomeric ethylene-propylene copolymer having an ethylene content, determined by13C NMR spectroscopy, of from 45.0 to 80.0 wt.-%, preferably from 55.0 to 77.5 wt.-%, more preferably from 60.0 to 75.0 wt.-%, based on the total weight of the elastomeric ethylenepropylene copolymer (C), wherein the heterophasic polypropylene composition has• a content of xylene cold solubles (XCS) fraction, based on the total weight of the heterophasic polypropylene composition and determined at 25°C according to ISO 16152, of from 25.0 to 75.0 wt.-%, preferably from 27.5 to 65.0 wt.-%, more preferably from 30.0 to 55.0 wt.-%,• an intrinsic viscosity of the xylene cold solubles (XCS) fraction (iV(XCS) of from 3.0 to 9.0 dl / g, preferably from 3.5 to 8.0 dl / g, more preferably from 4.0 to 7.5 dl / g, determined according to ISO 1628 / 1 in decalin at 135°C, and• a melt flow rate MFR2 of from 0.01 to 10.0 g / 10 min, preferably from 0.05 to 5.5 g / 10 min, more preferably from 0.1 to 3.5 g / 10 min, determined according to ISO 1133 at 230°C and 2.16 kg.

2. The heterophasic polypropylene composition according to claim 1 , wherein the xylene cold solubles (XCS) fraction has an ethylene content (C2(XCS)), based onthe total amount of monomer units in the xylene cold solubles (XCS) fraction and determined by13C NMR spectroscopy, of from 25.0 to 70.0 wt.-%, preferably from 30.0 to 60.0 wt.-%, more preferably from 35.0 to 50.0 wt.-%.

3. The heterophasic polypropylene composition according to claims 1 or 2 having one or more or all of the following properties:• a total ethylene content, based on the total weight of the heterophasic polypropylene composition, of from 8.0 to 30.0 wt.-%, preferably 10.0 to 27.5 wt.-%, more preferably 12.0 to 25.0 wt.-%, determined by13C NMR spectroscopy;• a melting temperature Tm, determined by DSC analysis according to ISO 11357, of from 155.0 to 175.0°C, preferably from 160.0 to 172.5°C, more preferably from 163.0 to 170.0°C.• a Charpy notched impact strength at 23°C of from 50.0 to 150.0 kJ / m2, preferably from 65.0 to 125.0 kJ / m2and more preferably from 70.0 to 100.0 kJ / m2, determined according to ISO 179-1 / 1 eA;• a Charpy notched impact strength at -20°C of from 50.0 to 175.0 kJ / m2, preferably from 75.0 to 150.0 kJ / m2and more preferably from 80.0 to 125.0 kJ / m2, determined according to ISO 179-1 / 1 eA;• a flexural modulus of from 250 to 750 MPa, preferably from 275 to 700 MPa, more preferably from 300 to 650 MPa, determined according to ISO 178 method A.

4. The heterophasic polypropylene composition according to any one of claims 1 to 3, wherein the crystalline propylene homopolymer (A) has a melt flow rate MFR2 determined according to ISO 1133 at 230°C and 2.16 kg of from 2.5 to 25.0 g / 10 min, preferably from 3.5 to 20.0 g / 10 min, more preferably from 5.0 to 15.0 g / 10 min.

5. The heterophasic polypropylene composition according to any one of claims 1 to 4, wherein the elastomeric propylene-ethylene copolymer (B) has a melt flow rate MFR2 determined according to ISO 1133 at 230°C and 2.16 kg of from 0.01 to 2.50 g / 10 min, preferably from 0.05 to 1.00 g / 10 min, more preferably from 0.10 to 0.50 g / 10 min.

6. The heterophasic polypropylene composition according to any one of claims 1 to 5, wherein the elastomeric ethylene-propylene copolymer (C) has a melt flow rate MFR2 determined according to ISO 1133 at 230°C and 2.16 kg of from 0.001 to 0.500 g / 10 min, preferably from 0.005 to 0.250 g / 10 min, more preferably from 0.010 to 0.100 g / 10 min.

7. The heterophasic polypropylene composition according to any one of claims 1 to 6 comprising(A) from 40.0 to 60.0 wt.-%, preferably from 42.5 to 57.5 wt.-%, more preferably from 45.0 to 55.0 wt.-%, based on the total weight of the heterophasic polypropylene composition, of the crystalline propylene homopolymer; and(B) from 40.0 to 60.0 wt.-%, preferably from 42.5 to 57.5 wt.-%, more preferably from 45.0 to 55.0 wt.-%, based on the total weight of the heterophasic polypropylene composition, of the elastomeric propylene-ethylene copolymer; wherein the elastomeric ethylene-propylene copolymer (C) is not present, and the heterophasic polypropylene composition has• a total ethylene content, based on the total weight of the heterophasic polypropylene composition, of from 8.0 to 22.5 wt.-%, preferably 10.0 to 20.0 wt.-%, more preferably 12.0 to 17.5 wt.-%, determined by13C NMR spectroscopy; and / or• a content of xylene cold solubles (XCS) fraction, based on the total weight of the heterophasic polypropylene composition and determined at 25°C according to ISO 16152, of from 25.0 to 50.0 wt.-%, preferably from 27.5 to 45.0 wt.-%, more preferably from 30.0 to 40.0 wt.-%.

8. The heterophasic polypropylene composition according to any one of claims 1 to 6 comprising(A) from 30.0 to 50.0 wt.-%, preferably from 32.5 to 47.5 wt.-%, more preferably from 35.0 to 45.0 wt.-%, based on the total weight of the heterophasic polypropylene composition, of a crystalline propylene homopolymer;(B) from 35.0 to 55.0 wt.-%, preferably from 37.5 to 52.5 wt.-%, more preferably from 40.0 to 50.0 wt.-%, based on the total weight of the heterophasicpolypropylene composition, of the elastomeric propylene-ethylene copolymer; and(C) from 5.0 to 20.0 wt.-%, preferably from 7.5 to 18.5 wt.-%, more preferably from 10.0 to 17.5 wt.-%, based on the total weight of the heterophasic polypropylene composition, of the elastomeric ethylene-propylene copolymer, wherein the heterophasic polypropylene composition has• a total ethylene content, based on the total weight of the heterophasic polypropylene composition, of from 15.0 to 30.0 wt.-%, preferably 17.5 to 27.5 wt.-%, more preferably 20.0 to 25.0 wt.-%, determined by13C NMR spectroscopy; and / or• a content of xylene cold solubles (XCS) fraction, based on the total weight of the heterophasic polypropylene composition and determined at 25°C according to ISO 16152, of from 35.0 to 75.0 wt.-%, preferably from 37.5 to 65.0 wt.-%, more preferably from 40.0 to 55.0 wt.-%.

9. The heterophasic polypropylene composition according to any one of claims 1 to 8, wherein the heterophasic polypropylene composition is reactor-made.

10. A process for producing the heterophasic polypropylene composition according to any one of claims 1 to 9 comprising the steps of• Polymerizing propylene monomer units in a first polymerization reactor in the presence of a Ziegler Natta catalyst system to produce the crystalline propylene homopolymer (A) in a weight amount of from 30.0 to 60.0 wt.-%, preferably from 32.5 to 57.5 wt.-%, more preferably from 35.0 to 55.0 wt.-%, based on the total weight of the heterophasic polypropylene composition;• Transferring a first reaction mixture comprising the crystalline propylene homopolymer (A) and the Ziegler Natta catalyst system from the first polymerization reactor to a second polymerization reactor;• Polymerizing propylene monomer units and ethylene monomer units in a molar ratio of ethylene monomer units to propylene monomer units (C2 / C3) of from 200 to less than 1250 mol / kmol, such as from 200 to 1000 mol / kmol, preferably from 250 to 550 mol / kmol, more preferably from 300 to 500 mol / kmol in the second polymerization reactor in the presence of the first reaction mixture to produce the elastomeric propylene-ethylene copolymer (B) in a weight amountof from 35.0 to 60.0 wt.-%, preferably from 37.5 to 57.5 wt.-%, more preferably from 40.0 to 55.0 wt.-%, based on the total weight of the heterophasic polypropylene composition;• Withdrawing a reactor powder from the final polymerization reactor comprising crystalline propylene homopolymer (A), the elastomeric propylene-ethylene copolymer (B), and the Ziegler Natta catalyst system;• Compounding the reactor powder optionally together with additives to obtain the heterophasic polypropylene composition.11 . The process according to claim 10 further comprising the following steps:• Transferring a second reaction mixture comprising the crystalline propylene homopolymer (A), the elastomeric propylene-ethylene copolymer (B) and the Ziegler Natta catalyst system from the second polymerization reactor to a third polymerization reactor;• Polymerizing propylene monomer units and ethylene monomer units in a molar ratio of ethylene monomer units to propylene monomer units (C2 / C3) of from 500 to less than 1250 mol / kmol, preferably from 600 to 1150 mol / kmol, more preferably from 700 to 1000 mol / kmol in the third polymerization reactor in the presence of the second reaction mixture to produce an elastomeric ethylenepropylene copolymer (C) in a weight amount of from 5.0 to 20.0 wt.-%, preferably from 7.5 to 18.5 wt.-%, more preferably from 10.0 to 17.5 wt.-%, based on the total weight of the heterophasic polypropylene composition;• Withdrawing a reactor powder from the final polymerization reactor comprising crystalline propylene homopolymer (A), the elastomeric propylene-ethylene copolymer (B), the elastomeric ethylene-propylene copolymer (C) and the Ziegler Natta catalyst system;• Compounding the reactor powder optionally together with additives to obtain the heterophasic polypropylene composition.

12. The process according to claims 10 or 11 , wherein the reactor powder has a powder flowability, determined according to ISO 6186:1998, method A, nuzzle diameter 15 mm, of from 5 to 20 s, preferably from 7 to 17 s, and shows an uninterrupted flow.

13. The process according to any one of claims 10 to 12, wherein the hydrogen to propylene ratio (H2 / C3 ratio) in the first polypropylene reactor is in the range from 0.5 to 35.0 mol / kmol, more preferably 0.7 to 25.0 mol / kmol, still more preferably from 1.0 to 10.0 mol / kmol, and / or the hydrogen to propylene ratio (H2 / C2 ratio) in the second polypropylene reactor is in the range from 5.0 to 50.0 mol / kmol, more preferably 10.0 to 25.0 mol / kmol.

14. The process according to any one of claims 12 to 13, wherein the hydrogen to ethylene ratio (H2 / C2 ratio) in the third polymerization reactor is in the range from 25 to 150 mol / kmol, more preferably 50 to 100 mol / kmol.

15. An article, preferably an injection moulded article, more preferably an injection moulded automotive article comprising the heterophasic polypropylene composition according to any one of claims 1 to 14.

16. The use of the heterophasic polypropylene composition according to any one of claims 1 to 14 for the production of an article, preferably an injection moulded article, more preferably an injection moulded automotive article.

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