Elimination of stress whitening in rtpo materials

Abstract

The present invention provides a polypropylene composition made of a specific reactor thermoplastic polyolefin (rTPO) that is recyclable, prevents or significantly reduces the tendency to SW, while showing improved mechanical properties of the material, especially in terms of improving impact strength at low temperatures and lower brittle to ductile transition temperature (BDTT), as well as a production method for the polypropylene composition, the use of the polypropylene composition and a film or article comprising the polypropylene composition.

Description

[0001] DESCRIPTION

[0002] Elimination of stress whitening in rTPO materials

[0003] Field of the invention

[0004] The present invention relates to a polypropylene composition (PPC) containing a reactor thermoplastic polyolefin (rTPO) reducing or eliminating stress whitening while maintaining good mechanical properties and broadening the brittle-to-ductile region. The present invention furthermore relates to a method for producing the polypropylene composition, the use of the polypropylene composition and a film or article comprising the polypropylene composition.

[0005] Technical background

[0006] Due to its numerous good properties, polypropylene (PP) has become one of the most widespread plastics and is widely used everywhere. Due to the wide range of applications, constantly increasing demands are placed on the material, resulting in a constant improvement and expansion of the property profile. One of the disadvantages that polypropylene has is the occurrence of stress whitening (SW), also called "blush", which occurs under tensile or impact loading and deteriorates the esthetic qualities of a product. This effect occurs with numerous PP grades, both PP homopolymer and copolymer and especially with multiphase systems, such as heterophasic copolymers and can severely hamper technical applicability, since SW can occur even with minor impact loads.

[0007] Heterophasic polypropylenes are known for their good impact properties especially at low temperatures. This arises from EPC (ethylene-propylene copolymer) elastomeric domains / fractions (amorphous fractions) that are dispersed within the (typically) homopolymer matrix. In-reactor methods have been developed for producing high elastomeric content thermoplastic polyolefins and the elastomeric component of thermoplastic polyolefin resins produced by these processes, termed rTPO resins, is finely and uniformly dispersed in the polypropylene matrix and without need for subjecting the resins to a compounding operation. Stress whitening (SW) is usually observed in polypropylene, especially in heterophasic copolymers due to their elastomeric phase, so that it is expected that a high elastomeric content unfavorably influences the SW. Mechanistically, SW is described as a cavitation effect related to the energy absorption in the material occurring in and around e.g. elastomer particles in heterophasic copolymers. While the elastomeric phase improves the toughness of PP and is desirable for applications such as automotive interior and rigid packaging designated for impact and low temperatures, it can enhance stress whitening (SW) due to the cavities present at the interface of the matrix and the elastomeric domains.

[0008] To overcome it, it is known that introducing various modifiers, e.g. high density polyethylene (HDPE; see Macromol. Symp. 312 (2012), 34-42), can drastically improve the situation, by improving the mechanical properties and reducing the stress whitening. However, with the current focus on design for recycling and mono-material approaches, the use of modifiers such as HDPE is unfavorable. Another approach which is more focused on polymer design is to reduce the incompatibility between the matrix and the elastomeric domains by making the elastomeric domains propylene (C3)-rich. This way the stress whitening is reduced. However, this would mean that the low temperature impact strength (e.g. -10°C) is worsened, which would limit the application for such a polymer.

[0009] Hence, regarding heterophasic copolymers, there is conventionally a contradiction between better SW and good mechanical properties, especially in terms of impact strength in a wide temperature range.

[0010] EP 1828304 Al relates to a PP composition comprising a crystalline propylene polymer, an elastomeric copolymer of ethylene and propylene and PE homopolymer or ethylene-propylene copolymer having a low comonomer content, but nothing is known about SW behavior. EP 3212713 Bl relates to a heterophasic polypropylene composition (HECO) with homo-homo-block (homopolymer, homopolymer, block copolymer) design with improved impact strength / stiffness balance and with high flowability, but nothing is known about SW behavior. EP 3212711 Bl relates to a heterophasic polypropylene composition (HECO) with homo-homo-block design focusing on improved stiffness / impact balance, but nothing is known about SW behavior. EP 3115411 Bl relates to a tube comprising a heterophasic polypropylene (HECO) composition (HECO) comprising a heterophasic polypropylene copolymer having a homo-homo-block design with an antioxidant comprising a sterically hindered phenol, but nothing is known about SW behavior. EP 3315551 Bl relates to a nucleated heterophasic polypropylene composition, which focuses on improved properties in view of mechanical and optical behavior as well as low amounts of extractable, but nothing is known about SW behavior. EP 3574025 Bl relates to a heterophasic propylene polymer (HECO) having a homo-homo-block design and aiming at improved optical properties, but nothing is known about SW behavior. EP 3953401 Al relates to a heterophasic polyolefin composition having a homo-homo-block design with improved mechanical and optical properties including low stress whitening. However, there is still room for improving stress whitening, impact strength at low temperatures and lowering the brittle to ductile transition temperature (BDTT).

[0011] Hence, there is a demand for improved PP products with lower stress whitening for better appearance and lifetime of finished products with good recyclability and good mechanical properties, so that there is a need for new and improved PP material.

[0012] Summary of the invention

[0013] It is therefore the object of the present invention to provide a polypropylene composition that is recyclable, prevents or significantly reduces the tendency to SW, while showing improved mechanical properties of the material, especially in terms of improved impact strength at low temperatures and lower brittle to ductile transition temperature (BDTT), as well as a production method for the polypropylene composition, the use of the polypropylene composition and a film or article comprising the polypropylene composition.

[0014] The inventors of the present invention surprisingly found that the object can be solved by providing a polypropylene composition (PPC), which comprises, based on the total weight of the PPC, 94.000 to 99.999 wt.-%, preferably 96.000 to 99.990 wt.-%, more preferably 97.000 to 99.950 wt.-%, most preferably 97.500 to 99.900 wt.-%, of (A) a reactor thermoplastic polyolefin (rTPO) comprising, based on the total weight of the rTPO, the following fractions:

[0015] (Al) 40.0 to 60.0 wt.-% of a polypropylene homopolymer fraction (PPH),

[0016] (A2) 30.0 to 45.0 wt.-% of a random ethylene / propylene (C2 / C3) polymer fraction (rEP), and

[0017] (A3) 10.0 to 25.0 wt.-% of a C2C3 elastomeric propylene copolymer fraction (EPC), wherein the PPC has: a soluble fraction (SF) and a crystalline fraction (CF), both determined by CRYSTEX measurement according to the description, wherein the soluble fraction is present in an amount of 18.0 to 40.0 wt.-%, a total ethylene (C2) content (C2tot), determined by CRYSTEX measurement calibrated with NMR according to the description, in the range of 10.0 to 20.0 wt.- %, of which an ethylene content of the soluble fraction (C2SF) is in the range of 25.0 to 80.0 wt.-% and wherein an intrinsic viscosity of the soluble fraction (IVSF), determined by CRYSTEX measurement according to the description, is in the range of 1.40 to 4.00 dL / g, and of which an ethylene content of the crystalline fraction (C2CF) is in the range of 2.5 to 20.0 wt.-% and wherein an intrinsic viscosity of the crystalline fraction (IVCF), determined by CRYSTEX measurement according to the description, is more than 2.50 and 6.00 dL / g or less, a stress whitening (SW) intensity, determined according to the description, in the range of 0 to 2.0, a brittle to ductile transition temperature (BDTT), determined according to ISO 179-2, in the range of -30.0°C to 10.0°C, a flexural modulus (FM), according to ISO 178, in the range of 600 to 900 MPa, and a melt flow rate MFR2, according to ISO 1133 at 230°C and 2.16 kg load, in the range of 1.0 to less than 5.0 g / 10 min.

[0018] By means of the above-identified configuration, in particular the tailored combination of a homopolymer (PPH) - random copolymer (rEP) arrangement (which is thought to form a matrix phase / fraction) with a high amount of specific elastomeric ethylene-enriched ethylene / propylene polymer fraction (EPC) (which is thought to be dispersed in the matrix phase), which can advantageously be polymerized as a reactor blend in a three-stage polymerization process such as the Borstar® technology, a reactor thermoplastic polyolefin (rTPO)-based composition essentially consisting of the rTPO (i.e. amount of 94.000 to 99.999 wt.-% in the composition) can be provided that achieves the surprising technical effects of preventing or significantly reducing the tendency for stress whitening (SW), improving impact strength especially at low temperatures and lower the brittle to ductile transition temperature (BDTT). Thus, with this tailored polymer, the stress whitening is essentially eliminated while maintaining good mechanical properties and broadening the brittle-to-ductile region.

[0019] The present invention further relates to a production method for the polypropylene composition, the use of the polypropylene composition and a film or article comprising the polypropylene composition.

[0020] Preferred embodiments of the invention are depicted in the dependent claims and a detailed description of the invention is provide in the following description.

[0021] Brief description of the drawings

[0022] Fig. 1 is a schematic representation of experimental set up for SW measurement.

[0023] Fig. 2 is a schematic diagram of the function recorded during SW experiment.

[0024] Fig. 3 is a brittle-to-ductile transition temperature (BDTT) overlay of the comparative Example CE1 and the inventive Examples IE1 to IE3.

[0025] Detailed Description

[0026] The term "comprising" (as well as terms "containing", "including" or "having") as used in the present invention does not exclude other components. For the purposes of the present invention, the term "consisting of" is considered to be a preferred embodiment of the term "comprising of" (as well as terms "containing", "including" or "having) unless specifically defined otherwise. Likewise, if hereinafter a group is defined to comprise at least a certain number of embodiments, this is also to be understood to disclose a group, which preferably consists only of these embodiments, unless specifically defined otherwise. Further, unless explicitly described otherwise, the description of the present invention is to be understood so that one or more of any of the described preferred embodiments of the invention can be combined with the invention described in its most general features.

[0027] Further, where an indefinite or definite article is used when referring to a singular noun, e.g. "a", "an" or "the", this includes a plural of that noun unless something else is specifically stated.

[0028] In the following amounts are given in % by weight (wt.-%) unless it is stated otherwise.

[0029] When reference is made to a method or step or stage or reactor or apparatus (or similar) "for" producing or forming a certain material (e.g. polymer fraction) or "for" performing a certain action, this shall be understood that this step (or stage or reactor, etc.) is adapted to (configured to) produce (or form) that certain material or to perform this certain action.

[0030] The reactor thermoplastic polyolefin (rTPO) of the present invention is a polymer (polymer in-reactor blend) providing favorable properties (in particular prevented or significantly reduced tendency to SW and improved mechanical properties of the material, especially in terms of improving impact strength at low temperatures and lower brittle to ductile transition temperature (BDTT)) which does not require excessive additive addition and thus can be used with low amounts of additives.

[0031] As such, the polypropylene composition (PPC) of the present invention essentially consists of the rTPO, i.e. it comprises, based on the total weight of the PPC, 94.000 to 99.999 wt.-%, preferably 96.000 to 99.990 wt.-%, more preferably 97.000 to 99.950 wt.-%, most preferably 97.500 to 99.900 wt.-%, of the (A) reactor thermoplastic polyolefin (rTPO), thereby significantly facilitating the recycling of articles formed of the composition. A detailed description of the composition, the rTPO, the use and the method of the present invention will be provided below.

[0032] Polypropylene Composition

[0033] The polypropylene composition (PPC) of the present invention comprises, based on the total weight of the PPC, 94.000 to 99.999 wt.-%, preferably 96.000 to 99.990 wt.-%, more preferably 97.000 to 99.950 wt.-%, most preferably 97.500 to 99.900 wt.-%, of (A) a reactor thermoplastic polyolefin (rTPO) comprising, based on the total weight of the rTPO, the following fractions:

[0034] (Al) 40.0 to 60.0 wt.-%, preferably 42.0 to 58.0 wt.-%, more preferably 43.0 to 57.0 wt.-%, of a polypropylene homopolymer fraction (PPH),

[0035] (A2) 30.0 to 45.0 wt.-%, preferably 30.0 to 42.0 wt.-%, more preferably 31.0 to 41.0 wt.-%, of a random ethylene / propylene (C2 / C3) polymer fraction (rEP), and (A3) 10.0 to 25.0 wt.-%, preferably 12.0 to 23.0 wt.-%, more preferably 14.0 to 22.0 wt.-% of a C2C3 elastomeric propylene copolymer fraction (EPC), wherein the PPC has: a soluble fraction (SF) and a crystalline fraction (CF), both determined by CRYSTEX measurement according to the description, wherein the soluble fraction is present in an amount of 18.0 to 40.0 wt.-%, a total ethylene (C2) content (C2tot), determined by CRYSTEX measurement calibrated with NMR according to the description, in the range of 10.0 to 20.0 wt.- %, of which an ethylene content of the soluble fraction (C2SF) is in the range of 25.0 to 80.0 wt.-% and wherein an intrinsic viscosity of the soluble fraction (IVSF), determined by CRYSTEX measurement according to the description, is in the range of 1.40 to 4.00 diyg, and of which an ethylene content of the crystalline fraction (C2CF) is in the range of 2.5 to 20.0 wt.-% and wherein an intrinsic viscosity of the crystalline fraction (IVCF), determined by CRYSTEX measurement according to the description, is more than 2.50 and 6.00 dL / g or less, a stress whitening (SW) intensity, determined according to the description, in the range of 0 to 2.0, a brittle to ductile transition temperature (BDTT), determined according to ISO 179-2, in the range of -30.0°C to 10.0°C, a flexural modulus (FM), according to ISO 178, in the range of 600 to 900 MPa, and a melt flow rate MFR2, according to ISO 1133 at 230°C and 2.16 kg load, in the range of 1.0 to less than 5.0 g / 10 min.

[0036] That is, the polypropylene composition (PPC) in accordance with the present invention essentially consists of the reactor thermoplastic polyolefin (rTPO) (component (A)) and further contains other components such as nucleating agent(s) and / or additive(s). The requirement applies that the components (A) and the other components, as far as being present, add up to 100 wt.-%, provided that the amount of the rTPO accounts for at least 94.000 to 99.999 wt.-% of the PPC. It is to be understood that if various ranges are indicated, the lower and upper limit(s) of the various ranges can be suitable combined to form another range and this general principle applies throughout the entire application. Further, as apparent from the word "polypropylene composition (PPC)", the present invention does not aim at a composition of different polymers. Accordingly, the polypropylene composition comprises other components such as nucleating agent(s) and / or additives, but preferably no other polymer components than the rTPO, except for optional polymeric nucleating agent(s) and / or matrix polymers of a masterbatch for adding additive(s) and / or nucleating agent(s).

[0037] The present invention can achieve the herein described envisaged beneficial technical effects by providing the polypropylene composition (PPC) which essentially consists of the reactor thermoplastic polyolefin (rTPO).

[0038] Preferably, the polypropylene composition (PPC) comprises, based on the total weight of the PPC, up to 5.000 wt.-%, preferably 0.010 to 3.500 wt.-%, more preferably 0.025 to 2.500 wt.-%, yet more preferably 0.050 to 1.500 wt.-%, most preferably 0.075 to 0.750 wt.-%, additive(s) based on the PPC, said additive(s) being preferably selected from the group consisting of antioxidants, acid scavenges, UV-stabilizers, antistatic agents, and slip agents and mixtures thereof. Notably, it is possible that two or more functions can be combined in the same molecule and such a constitution may be preferred to reduce the overall amount of additives. The additive(s) may be added to the composition in pure form or in the form of a masterbatch in a carrier resin. Where applicable and appropriate, the additive(s) may already be added during the polymerization of the rTPO. Preferably, at least antioxidant(s), more preferably at least antioxidant(s) and acid scavenger(s), are present as additive(s). Such additives are well known in the art and ensure favorable stability and / or performance of the polypropylene composition in its designated application.

[0039] Preferably, the polypropylene composition (PPC) comprises 0.0001 to 0.1000 wt.- % (1 to 1000 pm), preferably 0.0005 to 0.0500 wt.-% (5 to 500 ppm), more preferably 0.0008 to 0.0100 wt.-% (8 to 100 ppm) of polymeric a-nucleating agent(s), based on the total weight of the PPC. Preferably, the polymeric a- nucleating agent(s) is / are at least one of poly(vinyl cyclohexane) and poly(vinyl cyclopentane). The polymeric a-nucleating agent(s) may be added to the composition in pure form or in the form of a masterbatch in a carrier resin. Preferably, the polymeric a-nucleating agent(s) may be incorporated as a polymer fraction (AIN) into the rTPO by means of pre-polymerization, more preferably by being pre-polymerized onto a Ziegler Natta catalyst system, as described herein.

[0040] The PPC may further comprise 0.0010 to 3.0000 wt.-%, 0.0100 to 2.5000 wt.-%, 0.0100 to 2.0000 wt.-%, 0.0500 to 1.8000 wt.-%, or 0.1000 to 1.5000 wt.-% of non-polymeric nucleating agent(s), based on the total weight of the PPC. Preferably, the polypropylene composition (PPC) is nucleated by polymeric a- nucleating agent(s) only and does not require to contain non-polymeric nucleating agent(s).

[0041] If present, the non-polymeric nucleating agent(s) preferably include at least or preferably are a-nucleating agent(s). The a-nucleating agent(s) is(are) preferably particulate dispersive a-nucleating agent(s), more preferably selected from the group consisting of low molecular weight organic type a-nucleating agents, such as organic carboxylic acid salts, organophosphoric acid salts or combinations thereof, and inorganic type nucleating agents, such as carbonates, silicates, aluminates or alumosilicates, or combinations thereof. Examples include salts of monocarboxylic acids, such as sodium benzoate or aluminum tert-butylbenzoate, salts of di- or polycarboxylic acids, such as the disodium salt of bicyclo (2.2.1) heptane-2,3-dicarboxylic acid or the calcium salt of 1,2-cyclohexane dicarboxylicacid, and salts of diesters of phosphoric acid, such as sodium 2,2'- methylenebis (4,6,-di-tert-butylphenyl) phosphate or aluminium-hydroxy- bis[2,2'-methylene-bis(4,6-di-t-butylphenyl)phosphate] ; in particular at least one of sodium benzoate, l,3:2,4-bis-(3,4-dimethyl-benzylidene)-sorbitol, sodium- 2,2'-methylenebis-(4,6-di-tert-butyl-phenyl)-phosphate, hydroxybis-(2,4,8,10- tetra-tert-butyl-6-hydroxy-12h-dibenzo- (d,g)(l,3,2)-dioxaphosphocin-oxidato)- aluminium, ADK STAB NA-21 (Adeka Palmarole, France), Hyperform HPN-20 E (Milliken, USA).

[0042] However, a skilled person and the present invention appreciates modifications e.g. in that the PPC comprises optional component(s) other than the above nucleating agent(s) and / or above additive(s), such as utilization agents, polymer additives, fillers, coloring agents, anti-block agents, processing aids, and modifiers commonly known in the art, as long as the claimed requirements of the PPC are satisfied. Thus, care must be taken not to add any optional component(s), which interfere with attaining the claimed properties of the PPC. In any case, the PPC preferably does not contain other polymer components than the rTPO (except for optional carrier polymer of a masterbatch and / or polymeric nucleating agent as discussed herein). That is, in the context of the present invention, a skilled person appreciates that e.g. the additive(s) and / or nucleating agent(s) (or optional other component(s)) can be added to the PPC in a polymer component in the form of a masterbatch (also referred to as carrier polymer of the masterbatch), while the carrier polymer of a masterbatch is preferably a polypropylene homopolymer. The amount of such masterbatch carrier polymer, if used, usually does not exceed 4.00 wt.-%, preferably is used in an amount of 3.00 wt.-% or less or 1.00 wt.-% or less, based on the total weight of the PPC.

[0043] Preferably, the polypropylene composition (PPC) of the present invention has a soluble fraction (SF), determined by CRYSTEX measurement according to the description, in an amount of 19.0 to 35.0 wt.-%, preferably 20.0 to 30.0 wt.-%. In this case, due to a suitable and favorable adjusted amount of soluble fraction (SF), the effects of the present invention are more pronounced and / or their achievement is facilitated. Preferably, the polypropylene composition (PPC) of the present invention has a total ethylene (C2) content (C2tot), determined by CRYSTEX measurement calibrated with NMR according to the description, in the range of 10.0 to 15.0 wt.- %, of which an ethylene content of the soluble fraction (C2SF) is in the range of 26.0 to 60.0 wt.-%, preferably 28.0 to 50.0 wt.-%, and wherein an intrinsic viscosity of the soluble fraction (IVSF), determined by CRYSTEX measurement according to the description, is in the range of 1.60 to 3.00 diyg, preferably 1.70 to 2.50 dU / g, and of which an ethylene content of the crystalline fraction (C2CF) is in the range of 3.0 to 15.0 wt.-%, preferably 3.5 to 8.0 wt.-%, and wherein an intrinsic viscosity of the crystalline fraction (IVCF), determined by CRYSTEX measurement according to the description, is 2.50 to 5.00 dL / g, preferably 2.60 to 4.50 dU / g- In this case, due to suitably and favorably adjusting the ethylene contents and intrinsic viscosities of different fraction, the effects of the present invention are more pronounced and / or their achievement is facilitated. Especially by adjusting the most preferred ranges for e.g. C2tot, C2SF, and C2CF, it is possible to further improve BDTT.

[0044] Preferably, the polypropylene composition (PPC) of the present invention has a SW intensity, determined according to the description, of 0 to 1.0, more preferably 0. In this case, the present invention is able to achieve outstanding stress whitening properties and can thus be used in applications demanding high resistance to stress whitening.

[0045] Preferably, the polypropylene composition (PPC) of the present invention has a brittle to ductile transition temperature (BDTT), determined according to ISO 179- 2, in the range of -30.0°C to 0.0°C, more preferably -28.0 to -10.0°C. In this case, the present invention is achieve outstanding brittle to ductile properties and can thus be used in applications demanding ductile properties already at low temperatures. Preferably, the polypropylene composition (PPC) of the present invention has a flexural modulus (FM), according to ISO 178, in the range of 610 to 850 MPa. In this case, the present invention is achieve favorable stiffness / bending properties and can thus be used in applications requiring a certain stiffness behavior.

[0046] Preferably, the polypropylene composition (PPC) of the present invention has a MFR.2, according to ISO 1133 at 230°C and 2.16 kg load, in the range of 1.2 to 4.0 g / 10 min, more preferably 1.4 to 3.5 g / 10 min. In this case, due to suitably and favorably adjusting the melt behavior, the effects of the present invention are more pronounced and / or their achievement is facilitated, and the PPC can be used in applications requiring moderate melt flow properties.

[0047] Preferably, the polypropylene composition (PPC) of the present invention has a storage modulus G', as determined by dynamic mechanical analysis according to ISO 6721-7 at 23°C, in the range of 250 to 650 MPa, more preferably 350 to 550 MPa. In this case, the present invention is achieve favorable mechanical properties and can thus be used in applications requiring a certain stiffness behavior. Equally preferably, the rTPO has two glass transition temperatures Tg(d) relating to the disperse phase (EPC) and Tg(m) relating to the matrix phase, as determined by dynamic mechanical analysis according to ISO 6721-7. The respective Tg-values are peak values of the tangent of the loss angle, tan(6), as recorded in the same measurement as detailed below. Tg(d) preferably ranges from -70.0 to -35.0°C, more preferably -65.0 to -40.0°C, most preferred -60.0 to -45.0°C, and Tg(m) preferably ranges from -10 to 10°C, more preferably -5 to 5°C, most preferred -2.0 to 2.0°C

[0048] Preferably, the polypropylene composition (PPC) of the present invention has an impact strength, Charpy notched ISO 179-2 at -10°C, in the range of 8.0 to 80.0 kJ / m2, more preferably 9.0 to 75.0 kJ / m2, yet more preferably 25.0 to 70.0 kJ / m. In this case, the present invention is achieve favorable impact properties and can thus be used in applications requiring good impact properties already at low temperatures. Preferably, the polypropylene composition (PPC) of the present invention has an impact strength, Charpy notched ISO 179-2 at 20°C, in the range of 50.0 to 100.0 kJ / m2, more preferably 60.0 to 85.0 kJ / m2. In this case, the present invention is achieve favorable impact properties and can thus be used in applications requiring very good impact properties also at moderate (ambient) temperatures.

[0049] Preferably, the polypropylene composition (PPC) of the present invention has a crystallization temperature (Tc), according to DSC, in the range of 105.0 to 140.0°C, more preferably 115.0 to 135.0°C. In this case, due to suitably and favorably adjusting the crystallization temperature, the effects of the present invention are more pronounced and / or their achievement is facilitated.

[0050] Preferably, the polypropylene composition (PPC) of the present invention has a melting temperature (Tm), according to DSC, of 160.0 to 175.0°C, more preferably 161.0 to 170.0°C. In this case, due to suitably and favorably adjusting the crystallization temperature, the effects of the present invention are more pronounced and / or their achievement is facilitated.

[0051] Preferably, the polypropylene composition (PPC) of the present invention has an intrinsic viscosity IV, determined by CRYSTEX measurement according to the description, in the range of 2.00 to 3.0 dL / g, more preferably 2.20 to 2.80 dU - In this case, due to suitably and favorably adjusting the intrinsic viscosity, the effects of the present invention are more pronounced and / or their achievement is facilitated.

[0052] Needless to say that each of the above described properties of the PPC composition (e.g. SW intensity, BDTT, FM, MFR2, storage modulus G', impact strength at -10°C and at 20°, Tg(d), Tg(m), Tc, Tm, and IV) as well as the properties of the rTPO as described hereinafter may preferably be individually adjusted into a preferred or more preferred range, while it is even more preferred that two or more, most preferably all, of the above properties are adjusted into preferred and / or even more preferred ranges in combination. This principle generally applies throughout the entire application to other mentioned properties in connection with (preferred) quantifications. Reactor thermoplastic polyolefin (rTPO)

[0053] The polypropylene composition (PPC) of the present invention is characterized by comprising, based on the total weight of the PPC, 94.000 to 99.999 wt.-%, preferably 96.000 to 99.990 wt.-%, more preferably 97.000 to 99.950 wt.-%, most preferably 97.500 to 99.900 wt.-%, of (A) a reactor thermoplastic polyolefin (rTPO).

[0054] The reactor thermoplastic polyolefin (rTPO) itself comprises, based on the total weight of the rTPO, at least the following fractions:

[0055] (Al) 40.0 to 60.0 wt.-% of a polypropylene homopolymer fraction (PPH),

[0056] (A2) 30.0 to 45.0 wt.-% of a random ethylene / propylene (C2 / C3) polymer fraction (rEP), and

[0057] (A3) 10.0 to 25.0 wt.-% of a C2C3 elastomeric propylene copolymer fraction (EPC).

[0058] Preferably, the rTPO essentially consist of the PPH, the rEP, and the EPC (essentially consists meaning that the summed content thereof is 95.0 wt.-% or more based on the total weight of the rTPO). The summed content of PPH, rEP, and EPC in the rTPO is preferably 96.0 wt.-% or more, 97.0 wt.-% or more, 98.0 wt.-% or more, or 99.0 wt.-% or more, and may be even 100 wt.-%. For example, the summed content of PPH, rEP, and EPC in the rTPO may be in the range of from 95.0 wt.-% to 100 wt.-%, preferably 100 wt.-%. By applying the above-mentioned configuration, it is easier to accomplish the favorable balance between stiffness and impact strength and this balance is more pronounced.

[0059] Preferably, the rTPO determines the crystallization temperature of the PPC by having a crystallization temperature (Tc), according to DSC, in the range of 105.0 to 140.0°C, preferably 115.0 to 135.0°C, more preferably 118.0 to 131.0°C. In this case, due to suitably and favorably adjusting the crystallization temperature, the effects of the present invention are more pronounced and / or their achievement is facilitated. Preferably, the rTPO determines the melting temperature of the PPC by having a melting temperature (Tm), according to DSC, of 160.0 to 175.0°C, preferably 161.0 to 170.0°C. In this case, due to suitably and favorably adjusting the melting temperature, the effects of the present invention are more pronounced and / or their achievement is facilitated.

[0060] Preferably, the rTPO determines the MFR2 of the PPC by having a MFR2, according to ISO 1133 at 230°C and 2.16 kg load, in the range of 1.2 to 4.0 g / 10 min, more preferably 1.4 to 3.5 g / 10 min. In this case, due to suitably and favorably adjusting the melt behavior of the rTPO, the effects of the present invention are more pronounced and / or their achievement is facilitated, and the PPC comprising the same can be used in applications requiring moderate melt flow properties.

[0061] Preferably, the reactor thermoplastic polyolefin (rTPO) comprises, based on the total weight of the rTPO, 42.0 to 58.0 wt.-%, more preferably 43.0 to 57.0 wt.-%, of the polypropylene homopolymer fraction (PPH). In the present invention, the PPH is a polypropylene homopolymer in which preferably only propylene units are detectable (e.g. determined with13C NMR spectroscopy). However, a skilled person and the present invention appreciates that production methods commonly employed in the art may result in contamination with comonomers especially in case a prepolymerization step using comonomer(s) and / or nucleating agent monomer(s) is applied. Note that in the present invention, a prepolymerization is not considered to represent a main polymerization step of its own and the amount and properties (such as comonomer content etc.) of a prepolymer fraction produced in a prepolymerization step is counted to the amount (wt.-%) and properties of the main polymer fraction unless stated otherwise. In the present invention, the term polypropylene homopolymer is thus intended to refer to the constitution of the main polymerization fraction excluding an optional prepolymer fraction. That means that for instance the main polypropylene homopolymer fraction may be produced by supply of only propylene units (as polymerizing monomers) to give a propylene homopolymer fraction, while the prepolymer may be produced using propylene and comonomer(s) such as nucleating agent monomers as described later. In this case, although the monomer of a prepolymer fraction, if present, is accounted by definition to the main polypropylene homopolymer fraction, the PPH polypropylene homopolymer is still classified as homopolymer if the main polypropylene fraction is a homopolymer. Further, even though it is usually desired to keep such contaminations at a low level (i.e. in trace amounts), the homopolymer may contain certain amounts of contaminate comonomers, e.g. alpha-olefin comonomers, such as e.g. derived from prepolymerization. As such, the term homopolymer, as used herein, refers to a polypropylene polymer containing at least 99.0 wt.-%, preferably at least 99.8 wt.-%, more preferably at least 99.9 wt.-%, most preferably 100 wt.-% of propylene units (e.g. determined by quantitative13C NMR spectroscopy), as long as the claimed requirements of the PPH as well as that of the polypropylene composition are satisfied.

[0062] Preferably, the PPH forms a matrix phase of the rTPO. The PPH may usually have an MFR.2, according to ISO 1133 at 230°C and 2.16 kg load, in the range of 2.00 to 8.00 g / 10 min, preferably 2.50 to 6.50 g / 10 min. The PPH is preferably formed in a loop reactor in the presence of a Ziegler- Natta catalyst.

[0063] Preferably, the reactor thermoplastic polyolefin (rTPO) comprises, based on the total weight of the rTPO, 30.0 to 42.0 wt.-%, more preferably 31.0 to 41.0 wt.-%, of the random ethylene / propylene (C2 / C3) polymer fraction (rEP).

[0064] Preferably, also the rEP forms a matrix phase of the rTPO together with the PPH. The rEP may usually have an MFR.2, according to ISO 1133 at 230°C and 2.16 kg load, in the range of 0.20 to 1.80 g / 10 min, preferably 0.30 to 1.00 g / 10 min. The rEP is preferably formed in a gas phase reactor in the presence of a Ziegler- Natta catalyst.

[0065] Preferably, the random ethylene / propylene (C2 / C3) polymer fraction (rEP) has a C2 content (C2rEp), as determined by quantitative NMR according to the description, of 6.00 to 12.00 wt.-%, more preferably 6.50 to 10.50 wt.-%. In this case, due to suitably and favorably adjusting the C2 content of the second polymer fraction constituting a matrix phase, the effects of the present invention are more pronounced and / or their achievement is facilitated by suitably setting the compatibility of the matrix phase of the rTPO to the elastomeric dispersed phase. In the present invention, the rEP is formed predominantly of ethylene and propylene units, but may contain other units of a-olefins with 4-10 carbon atoms. In particular, the rEP refers to a polypropylene polymer containing at least 90.0 wt.-%, preferably at least 95.0 wt.-%, more preferably at least 99.0 wt.-%, most preferably 100 wt.-% of ethylene and propylene units (e.g. determined by quantitative13C NMR spectroscopy), so that the rEP may be a copolymer consisting of ethylene and propylene units. The monomer units are distributed randomly.

[0066] Preferably, the reactor thermoplastic polyolefin (rTPO) comprises, based on the total weight of the rTPO, 13.0 to 24.0 wt.-%, more preferably 14.0 to 22.0 wt.-%, of a C2C3 elastomeric propylene copolymer fraction (EPC).

[0067] Preferably, the EPC forms a dispersed phase (elastomeric phase) of the rTPO, that is particles dispersed in the polymer matrix. The EPC may usually have an MFR2, according to ISO 1133 at 230°C and 2.16 kg load, in the range of 1.00 to 20.00 g / 10 min, preferably 1.20 to 15.00 g / 10 min. The EPC is preferably formed in a gas phase reactor in the presence of a Ziegler-Natta catalyst.

[0068] Preferably, the C2C3 elastomeric propylene copolymer fraction (EPC) has a C2 content (C2EPC), as determined by quantitative NMR according to the description, of 40.00 wt.-% to 96.00 wt.-%, more preferably 41.00 to 75.00 wt.-%, most preferably 42.00 to 65.00 wt.-%. In this case, due to suitably and favorably adjusting the C2 content of the elastomeric polymer fraction which is dispersed in the matrix phase, the effects of the present invention are more pronounced and / or their achievement is facilitated. Especially by adjusting the more or most preferred range, it is possible to further improve BDTT.

[0069] In the present invention, the EPC is formed predominantly of ethylene and propylene units, but may contain other units of a-olefins with 4-10 carbon atoms. In particular, the EPC refers to a polypropylene polymer containing at least 90.0 wt.-%, preferably at least 95.0 wt.-%, more preferably at least 99.0 wt.-%, most preferably 100 wt.-% of ethylene and propylene units (e.g. determined by quantitative13C NMR spectroscopy), so that the EPC may be a copolymer consisting of ethylene and propylene units.

[0070] The polymerization method of reactor thermoplastic polyolefin (rTPO) is not especially limited as long as the essential characteristics (and preferably also the preferred characteristics) of the rTPO and its polymer fractions as described herein are obtained.

[0071] Preferably, the rTPO is (thus having the characteristics of) a reactor blend made in a three-stage polymerization process applying a slurry reactor (SR) - gas phase reactor (GPR1) - gas phase reactor (GPR2) cascade, such that the PPH is made in the SR, the rEP is made in the GPR1 and the EPC is made in the GPR2, preferably in the presence of a Ziegler Natta catalyst system. A more detailed description regarding the polymerization method of the rTPO is given in the context of the following 'Method for producing the polypropylene composition (PPC)'.

[0072] Method for producing the polypropylene composition (PPC)

[0073] The method for producing the polypropylene composition (PPC) is essentially characterized by comprising producing the reactor thermoplastic polyolefin (rTPO), which is the essential component of the PPC.

[0074] In general, the rTPO may be produced by a series of reactions to create an inreactor blend of polymers which results in an arrangement comprising a matrix fraction (or matrix phase) and a dispersed fraction (dispersed phase). The rTPO is a reactor blend (in-reactor blend) made in a polymerization process (also referred to as polymerization method) comprising at least three stages, in the presence of a catalyst system. The catalyst system is preferably a Ziegler Natta catalyst system.

[0075] The polymerization by using a Ziegler Natta catalyst system may be effected in three or more, e.g. 3, 4 or more, polymerization reactors, using conventional polymerization techniques, e.g. gas phase, solution phase, slurry or bulk polymerization. A combination of slurry (or bulk) and at least two gas phase reactors (GPRs) may be used, particularly with the reactor sequence in the order of a slurry (or bulk) reactor and two or more, more preferably only two, GPRs, optionally and preferably with a pre-polymerization reactor prior to the slurry (or bulk) reactor. Note that the pre-polymerization is not considered to represent a main polymerization step of its own. The polymerization may preferably further comprise pre-polymerizing the Ziegler-Natta catalyst system with a suitable monomer, preferably vinyl cyclohexane or vinyl cyclopentane, to produce a polymeric a-nucleating agent. Note that the pre-polymerization to produce a polymeric a-nucleating agent is also not considered to represent a main polymerization step of its own.

[0076] In the context of producing the polypropylene composition (PPC) of the present invention, the reactor thermoplastic polyolefin (rTPO) is preferably produced by a process comprising the steps of: a) Polymerizing propylene in the presence of a Ziegler-Natta type catalyst system in a first polymerization reactor, for producing the polypropylene homopolymer fraction (PPH) as a first polymer fraction (Al); b) Transferring the polymerization mixture comprising the Ziegler-Natta type catalyst system and the first polymer fraction from the first polymerization reactor to a second polymerization reactor; c) Polymerizing propylene and ethylene in the presence of the Ziegler-Natta type catalyst system in the second polymerization reactor for producing the random ethylene / propylene (C2 / C3) polymer fraction (rEP) as a second polymer fraction (A2); d) Transferring the polymerization mixture comprising the Ziegler-Natta type catalyst system and the first and second polymer fractions from the second polymerization reactor to a third polymerization reactor; e) Polymerizing propylene and ethylene in the presence of the Ziegler-Natta type catalyst system in the third polymerization reactor for producing the C2C3 elastomeric propylene copolymer fraction (EPC) as a third polymer fraction (A3), which is dispersed in the first and second polymer fractions acting as matrix; f) Withdrawing the polymerization mixture comprising the Ziegler-Natta type catalyst system, the first, second and third polymer fractions (Al, A2, and A3) from the third polymerization reactor; and g) Obtaining the reactor thermoplastic polyolefin (rTPO) comprising the polypropylene homopolymer fraction (PPH) and the random ethylene / propylene (C2 / C3) polymer fraction (rEP) as matrix and the C2C3 elastomeric propylene copolymer fraction (EPC) being dispersed in the matrix.

[0077] Preferably, the process further comprising a pre-polymerization step prior to the first polymerization step in the first polymerization reactor, wherein a mixture of the Ziegler-Natta catalyst system and a polypropylene pre-polymer produced in a pre-polymerization reactor is obtained and subsequent to the pre-polymerization, the mixture of the Ziegler-Natta catalyst system and the polypropylene prepolymer produced in the pre-polymerization reactor is transferred to the first polymerization reactor. That is, the main polymerization steps may preferably be preceded by the pre-polymerization step. The purpose of the pre-polymerization is to polymerize a small amount of polymer onto the catalyst at a low temperature and / or a low monomer concentration. By pre-polymerization, it is possible to improve the performance of the catalyst in slurry and / or modify the properties of the final polymer. The pre-polymerization step is preferably conducted in slurry and the amount of polymer produced in a pre-polymerization step is counted to the amount (wt.-%) of the polymer fraction produced in the first main polymerization reactor (i.e. PPH). It is understood that the amount of polymer produced in the pre-polymerization may be within 0.5 to 5.0 wt.-%, preferably 1.0 to 2.5 wt.-%, in respect to the final rTPO. Further, in a preferred case that the rTPO is nucleated by polymeric a-nucleating agent(s) being incorporated as a polymer fraction (AIN) into the rTPO by means of pre-polymerization, more preferably by being pre-polymerized onto a Ziegler Natta catalyst system, the amount of the polymeric a-nucleating agent fraction (AIN) is counted to the amount (wt.-%) of the polymer fraction produced in the first main polymerization reactor (i.e. PPH).

[0078] Preferably, the first polymerization reactor is a slurry reactor (SR) (e.g. a loop reactor), the second polymerization reactor is a first gas phase reactor (GPR1) and the third polymerization reactor is a second reactor gas phase reactor (GPR2). Therefore, the rTPO is preferably a reactor blend made in a three-stage polymerization process applying a slurry reactor (SR) - gas phase reactor (GPR1) - gas phase reactor (GPR2) cascade, such that the PPH is made in the SR, the rEP is made in the GPR1 and the EPC is made in the GPR2, preferably in the presence of a Ziegler Natta catalyst system.

[0079] Such a process is in general described inter alia in WO 2017 / 198633 Al, WO 2017 / 148970 Al, WO 2020 / 207825 Al and details of how to prepare Ziegler Natta catalysed bi- and multimodal polymers can be found in these references. A suitable and preferred process is the Borstar® process. Another suitable slurry-gas phase polymerization process is the Speripol® process of Basell.

[0080] That is, the components (polymer fractions) are preferably produced under different polymerization conditions resulting in different properties of the polymer fractions to result in bi- or multimodal polymers. The term "bimodal" or "multimodal" the context of bi- or multimodal polymers means herein bi- or multimodality with respect to a polymer property such as melt flow rate (MFR2) (e.g. the first fraction (PPH) and a second fraction (rEP) have different MFR2values), density, Mw, comonomer, comonomer content etc..

[0081] Conditions for operating a slurry reactor (e.g. loop reactor) and a GPR and how to adjust and fine-tune final polymer properties are known to the skilled person or can be determined by orientating experimentation. Preferred operation conditions in the slurry reactor may be as follows:

[0082] • temperature within the range of 55 to 95°C, more preferably 60 to 90°C, most preferably 65 to 85°C, e.g. 75±5°C,

[0083] • pressure within the range of 30 to 75 barg, more preferably 40 to 70 barg, most preferably 45 to 60 parg, e.g. 53±5 barg,

[0084] • hydrogen can be added for controlling the molar mass in a manner known per se.

[0085] Preferred operation conditions in the GPR may be as follows:

[0086] • temperature within the range of 50 to 130°C, more preferably 60 to 100°C, most preferably 70 to 90°C, e.g. 80±5°C, • pressure within the range of 5 to 45 barg, more preferably 15 to 40 barg, e.g. 23±5 barg,

[0087] • hydrogen can be added for controlling the molar mass in a manner known per se.

[0088] The rTPO is preferably prepared in the presence of a Ziegler-Natta catalyst system as descried in the following "Catalyst".

[0089] Further, the process of compounding the rTPO with other components such as the additive(s) and / or nucleating agent(s) is in the skilled knowledge and the PPC can for instance be obtained by mixing the rTPO and other component(s) such as the additive(s) and / or nucleating agent(s) before, during or after melting the rTPO, and / or the other component(s) may in the individual case be added or incorporated already during the polymerization of the rTPO. For mixing, a conventional compounding or blending apparatus, such as e.g. a Banbury® mixer, a 2-roll rubber mill, Buss-co-kneader, a single screw extruder e.g. with special mixing segments or a twin screw extruder may be used. The PPH composition recovered from compounding or blending apparatus (e.g. the extruder) can be in the form of pellets or powder.

[0090] Catalyst

[0091] As said above, the rTPO is preferably prepared in the presence of a Ziegler-Natta catalyst system (which may also be abbreviated as Ziegler-Natta catalyst).

[0092] There exists a crucial difference in the chain-microstructure between polypropylenes produced by a single site catalyst such as a metallocene catalyst and a Ziegler-Natta catalyst. The chain regularity of metallocene-based polypropylene is usually reduced by stereo- and regio-defects, whereas the chain regularity of Ziegler-Natta based polypropylenes is only reduced by stereo defects usually leading to highly isotactic polypropylene polymer. There is also a differences in the uniformity of the concentrations of defects (such as stereo- and / or region-errors) in relation to the kind of catalyst used.

[0093] The Ziegler-Natta catalyst system preferably comprises (a) a Ziegler-Natta catalyst (ZN-C) comprising compounds (TC) of a transition metal of Group 4 to 6 (according to IUPAC), a Group 2 metal compound (MC) and an internal donor (ID),

[0094] (b) a co-catalyst (Co).

[0095] The Ziegler-Natta catalyst system preferably further comprises an external donor (ED).

[0096] The Ziegler-Natta catalyst (system) is preferably present in the first polymerization stage, i.e. in a pre-polymerization or in a first main polymerization (e.g. when preparing the PPH). Further, as already stated above, polymeric a-nucleating agent(s) may preferably be pre-polymerized onto a Ziegler Natta catalyst system, which is known as BNT-technology and with regard to the BNT-technology, reference is made to WO2017 / 148970 Al and the respective information provided therein.

[0097] It is particularly preferred that the rTPO is polymerized (prepared) in the presence of a Ziegler-Natta catalyst that does not comprise phthalate-based electron donors. As such, it is preferred that the rTPO is free of phthalic esters and their decomposition products. Suitable non-phthalate Ziegler-Natta type catalysts are inter alia described in WO 2014 / 187687 Al, WO2017 / 198633 Al and WO2017 / 148970 Al, see e.g. the Examples of these documents.

[0098] The catalyst used in the present invention is thus preferably a solid Ziegler-Natta catalyst (ZN-C), which comprises compounds (TC) of a transition metal of Group 4 to 6 (IUPAC), like titanium, a Group 2 metal compound (MC), like a magnesium, and an internal donor (ID) preferably being 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 preferably fully free of (undesired) phthalic compounds. Further, the solid catalyst is preferably free of any external support material, like silica or MgCh, but the catalyst is self-supported. A self-supported catalyst is not necessarily free of magnesium halides, since these are formed during the reaction between the magnesium compound and TiCk; however, the presence of magnesium halides as external support media is preferably excluded.

[0099] The Ziegler-Natta catalyst (ZN-C) can be further defined by the way as obtained. Accordingly, the Ziegler-Natta catalyst (ZN-C) is preferably obtained by a process comprising the steps of a) al) providing a solution of at least a Group 2 metal alkoxy compound (Ax) being the reaction product of a Group 2 metal compound (MC) and an alcohol (A) comprising in addition to the hydroxyl moiety at least one ether moiety optionally in an organic liquid reaction medium; or a2) a solution of at least a Group 2 metal alkoxy compound (Ax') being the reaction product of a Group 2 metal compound (MC) and an alcohol mixture of the alcohol (A) and a monohydric alcohol (B) of formula R.OH, optionally in an organic liquid reaction medium; or a3) 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 (MC) and the monohydric alcohol (B), optionally in an organic liquid reaction medium; and b) adding said solution from step a) to at least one compound (TC) of a transition metal of Group 4 to 6 and c) obtaining the solid catalyst component particles, and adding a preferably non-phthalic internal electron donor (ID) at any (arbitrary) step prior to step c).

[0100] The internal donor (ID) or precursor thereof is added preferably to the solution of step a).

[0101] According to the procedure above, the Ziegler-Natta catalyst (ZN-C) 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). In both methods (precipitation or emulsionsolidification) the catalyst chemistry is the same. In precipitation method combination of the solution of step a) with at least one transition metal compound (TC) 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 to 110°C, more preferably in the range from 70 to 100°C, to secure full precipitation of the catalyst component in form of a solid particles (step c).

[0102] In emulsion - solidification method in step b) the solution of step a) is typically added to the at least one transition metal compound (TC) 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. 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. The catalyst prepared by emulsion - solidification method is preferably used in the present invention.

[0103] In a preferred embodiment in step a) the solution of a2) or a3) are used, i.e. a solution of (Ax') or a solution of a mixture of (Ax) and (Bx). Preferably the Group 2 metal (MC) is magnesium.

[0104] 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.

[0105] 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. Illustrative monohydric alcohols (B) are of formula ROH, with R being straightchain or branched Ce -Cio alkyl residue. The most preferred monohydric alcohol is 2-ethyl-l-hexanol or octanol.

[0106] 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.

[0107] 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 Ci - C20 alkyl, preferably C2 - Cio alkyl. Typical alkyl-alkoxy magnesium compounds, when used, are ethyl magnesium butoxide, butyl magnesium pentoxide, octyl magnesium butoxide and octyl magnesium octoxide. Preferably, dialkyl magnesiums are used. Most preferred dialkyl magnesiums are butyl octyl magnesium or butyl ethyl magnesium.

[0108] 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 Cio hydrocarbon residue, and s is an integer of 2 to 6.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] The transition metal compound of Group 4 to 6 is preferably a titanium compound, most preferably a titanium halide, like TiCk.

[0114] The internal donor (ID) 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-l,2-dicarboxylates and benzoates, and any derivatives and / or mixtures thereof. Preferred examples are e.g. substituted maleates and citraconates, most preferably citraconates.

[0115] 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 u-olefin polymers of u-olefin monomers with 6 to 20 carbon atoms, like polyoctene, polynonene, polydecene, polyundecene or polydodecene or mixtures thereof. Most preferable it is polydecene.

[0116] 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.

[0117] 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 pm. Particles preferably 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.-%, the amount of Mg is 10 to 20 wt.-% and the amount of donor is 10 to 40 wt.-% of the catalyst composition.

[0118] Detailed description of preparation of catalysts is disclosed in WO2017 / 148970 Al, W02012 / 007430 Al, EP2610271 Al, EP261027 Al and EP2610272 Al which are incorporated here by reference.

[0119] The Ziegler-Natta catalyst (ZN-C) is preferably used in association with an alkyl aluminum cocatalyst and optionally external donors.

[0120] As further component in the instant polymerization process, an external donor (ED) is preferably present. Suitable external donors (ED) 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

[0121] R%RbqSi(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

[0122] Si(OCH2CH3)3(NR3R4) wherein R3and R4can be the same or different a represent a hydrocarbon group having 1 to 12 carbon atoms.

[0123] 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, decanyl, iso-propyl, iso-butyl, iso-pentyl, tert. -butyl, tert. -amyl, neopentyl, cyclopentyl, cyclohexyl, methylcyclopentyl and cycloheptyl. More preferably, both R3and R4are the same, yet more preferably both R3and R4are an ethyl group.

[0124] Especially preferred external donors (ED) are the dicyclopentyl dimethoxy silane donor (D donor) or the cyclohexylmethyl dimethoxy silane donor (C-Donor). In addition to the Ziegler-Natta catalyst (ZN-C) and the optional external donor (ED) a cocatalyst 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 (Co) is a trialkylaluminium, like triethylaluminium (TEAL), dialkyl aluminium chloride or alkyl aluminium dichloride or mixtures thereof. In one specific embodiment the co- catalyst (Co) is triethylaluminium (TEAL).

[0125] 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 adjusted within certain limits. More specifically,

[0126] (a) the mol-ratio of co-catalyst (Co) to external donor (ED) [Co / ED] should preferably be in the range from 5 to 45, preferably is in the range from 5 to 35, more preferably is in the range from 5 to 25; and optionally (b) the mol-ratio of co-catalyst (Co) to titanium compound (TC) [Co / TC] should preferably be in the range from above 80 to 500, preferably is in the range from 100 to 350, still more preferably is in the range from 120 to 300.

[0127] When employing a Ziegler-Natta catalyst system in a multi-reactor arrangement as pointed out above, it is preferred that at least part of, preferably all of, the Ziegler-Natta catalyst (ZN-C) be fed into the first polymerization reactor and is transferred with the polymer (slurry) obtained in the first polymerization reactor into the subsequent reactors, should any subsequent reactors be used. If the process covers also a pre-polymerization step, it is preferred that at least part of, preferably all of, the Ziegler-Natta catalyst (ZN-C) be fed into the prepolymerization reactor. Subsequently the pre-polymerization product containing the Ziegler-Natta catalyst (ZN-C) is transferred into the first polymerization reactor. Co-catalyst and, if present, external donor, are preferably fed together with the ZN-C.

[0128] A preferable catalyst system for producing the rTPO of the present invention (as well as a production method for such a catalyst system) is described in WO2017 / 148970 Al and EP4141068 Al, which is herewith incorporated by reference.

[0129] Use and Articles

[0130] The PPC of the present invention may be used for producing a film. Preferably, the use comprises obtaining a film by casting or extrusion. The rTPO and / or the PPC of the present invention may be used for producing a molded article. The use preferably comprises obtaining the molded article by blow molding or injection molding, more preferably by injection molding.

[0131] The present invention thus also refers to a film or article, comprising the PPC of the present invention. Preferably, at least 80.0 wt.-%, more preferably at least 90.0 wt.-%, yet more preferably at least 95.0 wt.-% of the film or article is made of the PPC described above and it also possible and most preferred that the film or article is made of, i.e. consists of the PPC. Appropriate film forming and molding processes for preparing the molded article of the present invention are commonly known to the skilled person. The film may e.g. be a packaging film for consumer goods or medical packaging, preferably obtained by casting or extrusion, such as extrusion blow molding. The article is preferably a molded article, more preferably an injection molded article.

[0132] Measuring Methods

[0133] Melt flow rate (MFR)

[0134] The melt flow rate (MFR2) of propylene based polymers was measured at 230°C with a load of 2.16 kg according to ISO 1133. Calculation of the MFR.2 of a polymer fraction (e.g. rEP), e.g. if it cannot be measured, because it cannot be isolated from the mixture, can be done in line with the principle and systematic of the formulas in WO 2017 / 148970 Al (see section "calculations"); see also Kim McAuley's equation 25 in K. K. McAuley and J. F. McGregor: On-line Inference of Polymer Properties in an Industrial Polyethylene Reactor, AIChE Journal, June 1991 , Vol. 37, No, 6, pages 825-835).

[0135] DSC analysis, melting temperature (Tm), melting enthalpy (Hm), crystallization temperature (Tc) and crystallization enthalpy (Hc)

[0136] Melting peak temperatures (Tm), melting enthalpies (Hm), crystallization peak temperature (Tc) and crystallization enthalpy (Hc) was measured with a TA Instrument Q200 differential scanning calorimetry (DSC) on 5 to 7 mg samples. DSC was run according to ISO 11357 I 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 peak temperature (Tc) and crystallization enthalpy (Hc) were determined from the cooling step, while melting peak temperature(s) (Tm) and melting enthalpy(ies) (Hm) were determined from the second heating step.

[0137] Flexural Modulus (FM)

[0138] The flexural modulus was determined according to ISO 178 method A (3-point bending test) on 80 x 10 x 4 mm3specimens. 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±2° C. Injection molding was carried out according to ISO 19069-2 using a melt temperature of 230°C for all materials irrespective of material melt flow rate.

[0139] Dynamic Mechanical Thermal Analysis (DMTA) - glass transition temperature (Tg) and Storage Modulus

[0140] The glass transition temperature Tgwas determined by dynamic mechanical thermal analysis (DMTA) according to ISO 6721-7. The measurements were done in torsion mode on compression molded samples (35x10x1 mm3) between -130°C and +160°C with a heating rate of 2°C / min and a frequency of 1 Hz.

[0141] Storage modulus G' was determined at +23°C according ISO 6721-7: 1996. The measurements were the same as for Tgin which it was calculated at the peaks of tan delta (=G" / G').

[0142] Comonomer content

[0143] Quantitative13C{1H} NMR spectra were recorded in the solution-state using a Bruker Avance NEO 400 NMR spectrometer operating at 400.15 and 100.62 MHz forXH and13C respectively. All spectra were recorded using a13C optimised 10 mm extended temperature probe head at 125°C using nitrogen gas for all pneumatics. Approximately 200 mg of material was dissolved in 3 ml of 1,2-tetrachloroethane- d2 (TCE-d2) along with chromium-(III)-acetylacetonate (Cr(acac)3) resulting in a 60 mM solution of relaxation agent in solvent {8} and with approximately 3 mg BHT (2,6-di-tert-butyl-4-methylphenol CAS 128-37-0). 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 {3, 4}. A total of 6144 (6k) transients were acquired per spectra.

[0144] 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 {7}.

[0145] The comonomer fraction was quantified using the method of Wang et. al. {6} 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 regiodefects when needed. Integral regions were slightly adjusted to increase applicability across the whole range of encountered comonomer contents.

[0146] 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:

[0147] E = 0.5 (Spp + Spy + SP5 + 0.5(Sop + Soy))

[0148] Through the use of this set of sites the corresponding integral equation becomes: E = 0.5 (IH+IG + 0.5(Ic+ ID)) using the same notation used in the article of Wang et al. {6}. Equations used for absolute propylene content were not modified.

[0149] The mole percent comonomer incorporation was calculated from the mole fraction: E [mol%] = 100 * fE

[0150] The weight percent comonomer incorporation was calculated from the mole fraction :

[0151] E [wt.-%] = 100 * (fE * 28.06 ) / ( (fE * 28.06) + ((1-fE) * 42.08) ) Bibliographic references:

[0152] 1) Busico, V., Cipullo, R., Prog. Polym. Sci. 26 (2001) 443.

[0153] 2) Busico, V., Cipullo, R., Monaco, G., Vacatello, M., Segre, A.L., Macromolecules 30 (1997) 6251.

[0154] 3) Zhou, Z., Kuemmerle, R., Qiu, X., Redwine, D., Cong, R., Taha, A., Baugh, D. Winniford, B., J. Mag. Reson. 187 (2007) 225.

[0155] 4) Busico, V., Carbonniere, P., Cipullo, R., Pellecchia, R., Severn, J., Talarico, G., Macromol. Rapid Commun. 2007, 28, 1128.

[0156] 5) Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253.

[0157] 6) Wang, W-J., Zhu, S., Macromolecules 33 (2000), 1157. 7) Cheng, H. N., Macromolecules 17 (1984), 1950.

[0158] 8) Singh, G., Kothari, A., Gupta, V., Polymer Testing 28 5 (2009), 475.

[0159] 9) Kakugo, M., Naito, Y., Mizunuma, K., Miyatake, T. Macromolecules 15 (1982) 1150.

[0160] 10) Randall, J. Macromol. Sci., Rev. Macromol. Chem. Phys. 1989, C29, 201.

[0161] 11) Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253.

[0162] Calculation of the comonomer (e.g. ethylene) content of a polymer fraction (e.g. EPC), e.g. if it cannot be measured, because it cannot be isolated from the mixture, can be done in line with the principle and systematic of the formulas in WO 2017 / 148970 Al (see section "calculations").

[0163] CRYSTEX Method - Determination of crystalline and soluble fractions and their respective properties (Intrinsic Viscosity (IV) and ethylene (C2) content)

[0164] Note: Crystallization extraction (CRYSTEX) analyses the polymeric part of each component, with non-polymeric parts, such as any fillers or particulate pigments, not contributing to the reported CRYSTEX data presented.

[0165] The crystalline (CF) and soluble fractions (SF) of the polypropylene compositions (PPC) as well as the comonomer content and intrinsic viscosities of the respective fractions were analyzed by use of the Crystex (crystallisation extraction) method. Potential instruments that can be used are Crystex QC or Crystex 42 (Polymer Char; Valencia, Spain). Details of the technique and the method can be found in literature (Ljiljana Jeremie, Andreas Albrecht, Martina Sandholzer & Markus Gahleitner (2020) Rapid characterization of high-impact ethylene-propylene copolymer composition by crystallization extraction separation: comparability to standard separation methods, International Journal of Polymer Analysis and Characterization, 25:8, 581-596).

[0166] The crystalline and amorphous fractions are separated through temperature cycles of dissolution at 160°C, crystallization at 40°C and re-dissolution in 1,2,4- trichlorobenzene at 160°C. Quantification of SF and CF and determination of ethylene content (C2) are achieved by means of an integrated infrared detector (IR4) and for the determination of the intrinsic viscosity (IV) an online 2-capillary viscometer is used. The IR4 detector is a multiple wavelength detector measuring IR absorbance at two different bands (CH3stretching vibration (centred at app. 2960 cm ) and the CH stretching vibration (2700-3000 cm4) that are serving for the determination of the concentration and the ethylene content in Ethylene-Propylene (EP) copolymers. The IR4 detector is calibrated with series of 8 EP copolymers with known ethylene content in the range of 2 wt.-% to 69 wt.-% (determined by13C- NMR) and each at various concentrations, in the range of 2 and 13 mg / ml. To encounter for both features, concentration and ethylene content at the same time for various polymer concentration expected during Crystex analyses the following calibration equations were applied:

[0167] Cone = a + b*Abs(CH) + c*(Abs(CH))2+ d*Abs(CH3) + e*(Abs(CH3)2+ f*Abs(CH)*Abs(CH3) (Equation 1)

[0168] CH3 / 1000C = a + b*Abs(CH) + c* Abs(CH3) + d * (Abs(CH3) / Abs(CH)) + e*(Abs(CH3) / Abs(CH))2(Equation 2)

[0169] The constants a to e for equation 1 and a to f for equation 2 were determined by using least square regression analysis.

[0170] The CH3 / 1000C is converted to the ethylene content in wt.-% using the following relationship: wt.-% (ethylene in copolymer) = 100 - CH3 / 1000TC*0.3 (Equation 3)

[0171] Amounts of Soluble fraction (SF) and Crystalline Fraction (CF) are correlated through the XS calibration to the "Xylene Cold Soluble" (XCS) quantity and respectively Xylene Cold Insoluble (XCI) fractions, determined according to standard gravimetric method as per ISO16152. XS calibration is achieved by testing various EP copolymers with XCS content in the range 2-31 wt.-%. A linear calibration curve is used.

[0172] Intrinsic viscosity (IV) of the parent EP copolymer and its soluble and crystalline fractions are determined with a use of an online 2-capillary viscometer and are correlated to corresponding IV's determined by standard method in decalin according to ISO 1628-3 at 135°C. Calibration is achieved with various EP copolymers and PP polymers with IV = 2-4 dL / g- The determined calibration curve is linear.

[0173] The samples to be analyzed are weighed out in concentrations of lOmg / ml to 20 mg / ml. After automated filling of the vial with 1,2,4-trichlorbenzole (TCB) containing 250 mg / l 2,6-tert-butyl-4-methylphenol (BHT) as antioxidant, the sample is dissolved at 170°C until complete dissolution is achieved with either constant stirring or gentle shaking. To avoid sample degradation, polymer solution is blanketed with the N2 atmosphere during dissolution.

[0174] For a PP composition containing inorganic fillers or pigments or any other non-TCB soluble polymeric substances removal of these is required. This can be done by hot filtration prior injection.

[0175] A defined volume of the sample solution is injected into the column filled with inert support where the crystallization of the sample and separation of the soluble fraction from the crystalline part is taking place. This process is repeated two times. During the first injection the whole sample is measured at high temperature, determining the IV[dl / g] and the C2[wt.-%] of the PP composition. During the second injection the soluble fraction (at low temperature) and the crystalline fraction (at high temperature) with the crystallization cycle are measured (wt.-% SF, wt.-% C2, IV).

[0176] Brittle to ductile transition temperature (BDTT) - Impact Strength

[0177] The determination of the brittle to ductile transition temperature (BDTT) is based on the a(cN) values as determined from Charpy instrumented impact strength according to ISO 179-2:2000 on V-notched specimen with a geometry of 80x10x4 mm3as set forth in ISO 179-leA. The a(cN) values were determined in intervals of 3°C from -40°C to +41°C with an impact velocity of 1.5 m / s and plotted over temperature, calculating the BDTT the average value of the step increase. For a detailed description of the determination of the BDTT reference is made to Grein, C. et al, Impact Modified Isotactic Polypropylene with Controlled Rubber Intrinsic Viscosities: Some New Aspects About Morphology and Fracture, J Appl Polymer Sci, 87 (2003), 1702-1712. Stress whitening (SW)

[0178] Stress whitening was determined by a modified three point bending test, namely the reversed three point bending test (cf. Fig. 1).

[0179] The reversed three point bending test was carried out on a universal testing machine (Zwick Z010) at 50 mm / min. The samples were 2 mm thick injection molded UL94 specimens (125x12.5x2mm).

[0180] The experimental set-up consisted of the reversed three point bending test coupled with an optical detection system.

[0181] The mechanical set up consisted of:

[0182] A fix part (1), with a span (2) of 40 mm, a moving part including a loading edge (3) with a light source (4) and an optical sensor (5) fixed on the moving part closely above and beneath the specimen (6) by a vertical rod. This ensures that the distance between light source and optical sensor remains constant during the test, which is a prerequisite for a good reproducibility of the measurements.

[0183] The force-deflection and the optical signal-deflection curves are recorded. At the beginning of the test, the optical signal (7) is calibrated to 100 % (7a), regardless of the initial transparency / haziness of the inserted sample.

[0184] Occurrence of stress whitening is correlated with a sharp drop in the optical signaldeflection curve (cf. Fig. 2).

[0185] Three different parameters were determined: a) Stress whitening angle b) Residual size (width) of the blushing zones c) Stress whitening intensity a) The stress whitening angle [°], (also: bending angle or onset-angle) indicates, at which bending angle stress whitening (SW) occurs. The occurrence of stress whitening is correlated with a sharp drop of the optical response (light transmission) during bending (cf. Fig. 2).

[0186] The onset angle for stress whitening is determined according to formula (VI): Onset angle -0.9997 (VI) wherein

[0187] "s" denominates the deflection of the loading edge, at which the light transmission curve drops and is determined as illustrated in Fig. 2.

[0188] At the beginning of the test, the optical signal (7) is calibrated to 100% (7a), regardless of the initial transparency / haziness of the inserted sample. The deflection of the loading edge (s), at which the light transmission curve drops is determined by the abscissa-value (8) of the intersection between the tangent of the slope of the optical signal (7b) and the 100% line of the initial optical signal (7a). b) Residual size (width) of the blushing zones immediately after a bending of 90°, measured in [mm], also denominated as "Res-SW 90°" or "residual stress whitening".

[0189] The width of a blushing zone (b) is determined as follows:

[0190] Tests are conducted to a deflection corresponding to an angle of 90° according to the formula (VI) above. Then the specimen is abruptly unloaded with a crosshead speed of 400 mm / min. The width of the blushing area is measured immediately after testing using a slide gage. c) Stress whitening intensity: this is the residual intensity of the blushing zone immediately after a bending of 90° (visual appreciation from 0 to 5, with 0: no remaining blush, 5: intensive whitening), also denominated as "SW-intensity".

[0191] Evaluation of the stress whitening intensity:

[0192] A mark of 0 is attributed when there is no residual blushing; a note of 5 when the whitening of the deformed zone is extremely pronounced. The obtained value is entered manually in a result sheet; average calculations are automated. The determination of these parameters is somewhat subjective and dependent on an operator. Although the obtained values are somewhat subjective, they give essential information on the elastic recovery potential of the material.

[0193] What is important to notice, is: a. an intensity of 0 is remarkably low (i.e. no blushing visible); b. an intensity of up to 1 is excellent; c. an intensity between 1.1 and 1.5 is good; d. an intensity between 1.6 and 3 is acceptable; e. an intensity higher than 3 is insufficient.

[0194] Examples

[0195] The following Examples are included to demonstrate certain aspects and favorable 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. Nevertheless, values, such as properties and conditions, disclosed in the Examples may be combined with ranges disclosed in a more general context (e.g. claims or general description) to give new (more limited or different) ranges without any limitation.

[0196] The polymers of inventive examples IE1 to IE3 were prepared in a Borstar® PP pilot unit with sequential process comprising a pre-polymerization reactor, a loop reactor and two gas phase reactors (i.e. 3-main reactor set-up of Ioop+GPR1+GPR2) and the polymer of comparative example CE1 was prepared in a Borstar® PP pilot unit with sequential process comprising a pre-polymerization reactor, a loop reactor and a gas phase reactor (i.e. 2-main reactor set-up of loop + GPR). The reaction conditions are summarized in Table 1 together with the properties of the final polymer (powder form) and of the polymer.

[0197] The catalyst used was a Ziegler-Natta catalyst (system) as used and described for the inventive examples of WO 2016 / 066446 Al, pre-polymerized with vinylcyclohexane to achieve nucleation with poly(vinylcyclohexane). Nucleation by prepolymerization with vinylcyclohexane is described in EP 2 960 256 Bl and EP 2 960 279 Bl in detail. The catalyst systems defined above was used in combination with triethyl-aluminium (TEAL) as co-catalyst and dicyclopentadienyl-dimethoxy silane (donor D) as external donor.

[0198] Table 1 For producing the polymer compositions (PPC), the polymers C-PP, PPI, PP2 and PP3 (99.8 wt.-%) of Table 1 were each compounded with 0.075 wt.-% of antioxidant pentaerythritol tetrakis[3-[3,5-di-tert-butyl-4-hydroxyphenyl] propionate] (Irganox® 1010, CAS No: 6683-19-8, available from BASF), 0.075 wt.- % of antioxidant tris(2,4-di-tert-butylphenyl)phosphite (Irgafos® 168, CAS No: 31570-04-4, available from BASF) and 0.05 wt.-% of acid scavenger calcium stearate (Ceasit AV-FI, CAS No: 1592-23-0, available from Baerlocher). Specifically, polymer powders C-PP, PPI, PP2 and PP3 were each mixed with the above defined additives, and then compounded in a TSE 16 twin screw extruder, with a melt temperature of 210°C, and production rate of 2 kg / h. The properties of the pelletized polymer compositions are shown in Table 2.

[0199] Table 2 - Properties of the pelletized PPCs.

[0200] Figure 3 shows the overlay of BDTT curves for all materials. The 1stderivates of the BDTT curves were computed to determine the onset transition temperatures, which are summarized in Table 3 together with other properties of the polymer compositions. It is clearly shown in Fig. 3 that the transition to the ductile region occurs at lowers temperatures for the IES compared to the CE.

[0201] Table 3 - Summary of the mechanical properties and SW intensities.

[0202] As can be seen from Fig. 3 and Tables 2 and 3, the PPCs of the present invention show that having higher soluble fraction (SF) improves the impact properties while reducing the stiffness without significant loss thereof. However, it was expected that increasing the soluble fraction would worsen the stress whitening intensity due to the elastomeric phase. This was unexpectedly not the case as demonstrated by the IEs. Further, IE3, which has a further C2-enriched elastomeric fraction (EPC) in comparison to IE1 and IE2, shows a slightly higher and thus less favorable, but still improved BDTT.

Claims

CLAIMS1. A polypropylene composition (PPC), which comprises, based on the total weight of the PPC, 94.000 to 99.999 wt.-%, preferably 96.000 to 99.990 wt.-%, more preferably 97.000 to 99.950 wt.-%, most preferably 97.500 to 99.900 wt.- %, of (A) a reactor thermoplastic polyolefin (rTPO) comprising, based on the total weight of the rTPO, the following fractions:(Al) 40.0 to 60.0 wt.-% of a polypropylene homopolymer fraction (PPH),(A2) 30.0 to 45.0 wt.-% of a random ethylene / propylene (C2 / C3) polymer fraction (rEP), and(A3) 10.0 to 25.0 wt.-% of a C2C3 elastomeric propylene copolymer fraction (EPC), wherein the PPC has: a soluble fraction (SF) and a crystalline fraction (CF), both determined by CRYSTEX measurement according to the description, wherein the soluble fraction is present in an amount of 18.0 to 40.0 wt.-%, a total ethylene (C2) content (C2tot), determined by CRYSTEX measurement calibrated with NMR according to the description, in the range of 10.0 to 20.0 wt.- %, of which an ethylene content of the soluble fraction (C2SF) is in the range of 25.0 to 80.0 wt.-% and wherein an intrinsic viscosity of the soluble fraction (IVSF), determined by CRYSTEX measurement according to the description, is in the range of 1.40 to 4.00 dU / g, and of which an ethylene content of the crystalline fraction (C2CF) is in the range of 2.5 to 20.0 wt.-% and wherein an intrinsic viscosity of the crystalline fraction (IVCF), determined by CRYSTEX measurement according to the description, is more than 2.50 and 6.00 dU / g or less, a stress whitening (SW) intensity, determined according to the description, in the range of 0 to 2.0, a brittle to ductile transition temperature (BDTT), determined according to ISO 179-2, in the range of -30.0°C to 10.0°C,a flexural modulus (FM), according to ISO 178, in the range of 600 to 900 MPa, and a melt flow rate MFR2, according to ISO 1133 at 230°C and 2.16 kg load, in the range of 1.0 to less than 5.0 g / 10 min.

2. The polypropylene composition (PPC) according to claim 1, wherein the random ethylene / propylene (C2 / C3) polymer fraction (rEP) has a C2 content (C2rEp), as determined by quantitative NMR according to the description, of 6.00 to 12.00 wt.-%, preferably 6.50 to 10.50 wt.-%.

3. The polypropylene composition (PPC) according to claim 1 or 2, wherein the C2C3 elastomeric propylene copolymer fraction (EPC) has a C2 content(C2EPC), as determined by quantitative NMR according to the description, of 40.00 wt.-% to 96.00 wt.-%, preferably 41.00 to 75.00 wt.-%, more preferably 42.00 to 65.00 wt.-%.

4. The polypropylene composition (PPC) according to any of claims 1 to 3, wherein the PPC has one or more, preferably all of the below properties: a soluble fraction (SF), determined by CRYSTEX measurement according to the description, in an amount of 19.0 to 35.0 wt.-%, preferably 20.0 to 30.0 wt.- %, , a total ethylene (C2) content (C2tot), determined by CRYSTEX measurement calibrated with NMR according to the description, in the range of 10.0 to 15.0 wt.- %, of which an ethylene content of the soluble fraction (C2SF) is in the range of 26.0 to 60.0 wt.-%, preferably 28.0 to 50.0 wt.-%, and wherein an intrinsic viscosity of the soluble fraction (IVSF), determined by CRYSTEX measurement according to the description, is in the range of 1.60 to 3.00 dL / g, preferably 1.70 to 2.50 dMg, and of which an ethylene content of the crystalline fraction (C2CF) is in the range of 3.0 to 15.0 wt.-%, preferably 3.5 to 8.0 wt.-%, and wherein an intrinsic viscosity of the crystalline fraction (IVCF), determined by CRYSTEX measurement according to the description, is 2.50 to 5.00 dU / g, preferably 2.60 to 4.50 dU / g,a stress whitening intensity, determined according to the description, in the range of 0 to 1.0, preferably 0, a brittle to ductile transition temperature (BDTT), determined according to ISO 179-2, in the range of -30.0°C to 0.0°C, preferably -28.0 to -10.0°C, a flexural modulus (FM), according to ISO 178, in the range of 610 to 850 MPa, and a MFR2, according to ISO 1133 at 230°C and 2.16 kg load, in the range of 1.2 to 4.0 g / 10 min, preferably 1.4 to 3.5 g / 10 min.

5. The polypropylene composition (PPC) according to any one of claims 1 to 4, wherein the PPC has one or more, preferably all of the below properties: a storage modulus G', as determined by dynamic mechanical analysis according to ISO 6721-7 at 23°C, in the range of 250 to 650 MPa, preferably 350 to 550 MPa, an impact strength, Charpy notched ISO 179-2 at -10°C, in the range of 8.0 to 80.0 kJ / m2, preferably 9.0 to 75.0 kJ / m2, more preferably 25.0 to 70.0 kJ / m2, and an impact strength, Charpy notched ISO 179-2 at 20°C, in the range of 50.0 to 100.0 kJ / m2, preferably 60.0 to 85.0 kJ / m2.

6. The polypropylene composition (PPC) according to any one of claims 1 to 5, wherein the PPC has one or more, preferably all of the below properties: a crystallization temperature (Tc), according to DSC, in the range of 105.0 to 140.0°C, preferably 115.0 to 135.0°C, more preferably 118.0 to 131.0°C, a melting temperature (Tm), according to DSC, of 160.0 to 175.0°C, preferably 161.0 to 170.0°C, and / or, preferably and an intrinsic viscosity IV, determined by CRYSTEX measurement according to the description, in the range of 2.00 to 3.0 dL / g, preferably 2.20 to 2.80 dL / g.

7. The polypropylene composition (PPC) according to any one of claims 1 to 6, wherein the rTPO is a reactor blend made in a three-stage polymerization process applying a slurry reactor (SR) - gas phase reactor (GPR1) - gas phase reactor (GPR2) cascade, such that the PPH is made in the SR, the rEP is made in the GPR1and the EPC is made in the GPR2, preferably in the presence of a Ziegler Natta catalyst system.

8. The polypropylene composition (PPC) according to any one of claims 1 to 7, wherein the PPC comprises 0.0001 to 0.1000 wt.-%, preferably 0.0005 to 0.0500 wt.-%, more preferably 0.0008 to 0.0100 wt.-% of polymeric a-nucleating agent(s), based on the total weight of the PPC, preferably at least one of poly(vinyl cyclohexane) and poly(vinyl cyclopentane); and / or the PPC comprises 0.0010 to 3.0000 wt.-%, 0.0100 to 2.5000 wt.-%, 0.0100 to 2.0000 wt.-%, 0.0500 to 1.8000 wt.-%, or 0.1000 to 1.5000 wt.-% of non-polymeric nucleating agent(s), based on the total weight of the PPC, preferably at least a-nucleating agent(s).

9. The polypropylene composition (PPC) composition according to any one of claims 1 to 8, wherein the PPC comprises, based on the total weight of the PPC, up to 5.000 wt.- %, preferably 0.010 to 3.500 wt.-%, more preferably 0.025 to 2.500 wt.-%, more preferably 0.050 to 1.500 wt.-%, most preferably 0.075 to 0.750 wt.-%, additive(s) based on the PPC, said additive(s) being preferably selected from the group consisting of antioxidants, acid scavenges, UV-stabilizers, antistatic agents, and slip agents and mixtures thereof.

10. Method for producing the polypropylene composition (PPC) as defined by one of claims 1 to 9, comprising producing the reactor thermoplastic polyolefin (rTPO) by a process comprising the steps of: a) Polymerizing propylene in the presence of a Ziegler-Natta type catalyst system in a first polymerization reactor, for producing the polypropylene homopolymer fraction (PPH) as a first polymer fraction (Al); b) Transferring the polymerization mixture comprising the Ziegler-Natta type catalyst system and the first polymer fraction from the first polymerization reactor to a second polymerization reactor; c) Polymerizing propylene and ethylene in the presence of the Ziegler-Natta type catalyst system in the second polymerization reactor for producing therandom ethylene / propylene (C2 / C3) polymer fraction (rEP) as a second polymer fraction (A2); d) Transferring the polymerization mixture comprising the Ziegler-Natta type catalyst system and the first and second polymer fractions from the second polymerization reactor to a third polymerization reactor; e) Polymerizing propylene and ethylene in the presence of the Ziegler-Natta type catalyst system in the third polymerization reactor for producing the C2C3 elastomeric propylene copolymer fraction (EPC) as a third polymer fraction (A3), which is dispersed in the first and second polymer fractions acting as matrix; f) Withdrawing the polymerization mixture comprising the Ziegler-Natta type catalyst system, the first, second and third polymer fractions (Al, A2, and A3) from the third polymerization reactor; and g) Obtaining the reactor thermoplastic polyolefin (rTPO) comprising the polypropylene homopolymer fraction (PPH) and the random ethylene / propylene (C2 / C3) polymer fraction (rEP) as matrix and the C2C3 elastomeric propylene copolymer fraction (EPC) being dispersed in the matrix, the process optionally further comprising a pre-polymerization step prior to the first polymerization step in the first polymerization reactor, wherein a mixture of the Ziegler-Natta catalyst system and a polypropylene pre-polymer produced in a pre-polymerization reactor is obtained and subsequent to the prepolymerization, the mixture of the Ziegler-Natta catalyst system and the polypropylene pre-polymer produced in the pre-polymerization reactor is transferred to the first polymerization reactor.

11. Method for producing polypropylene composition (PPC) according to claim 10, wherein the process further comprises pre-polymerizing the Ziegler-Natta catalyst system with a suitable monomer, preferably vinyl cyclohexane or vinyl cyclopentane, to produce the polymeric a-nucleating agent fraction (AIN).

12. Method for producing polypropylene composition (PPC) according to claim 10 or 11, whereinthe first reactor is preferably a slurry reactor, the second reactor is a first gas phase reactor (GPR1) and the third reactor is a second reactor gas phase reactor (GPR3).

13. Method for producing polypropylene composition (PPC) according to any one of claims 10 to 12, wherein the Ziegler-Natta catalyst system comprises(a) a Ziegler-Natta catalyst (ZN-C) comprising compounds (TC) of a transition metal of Group 4 to 6 (according to IUPAC), a Group 2 metal compound (MC) and an internal donor (ID),(b) a co-catalyst (Co), and(c) optionally an external donor (ED).

14. Use of the polypropylene composition (PPC) composition according to any one of claims 1 to 9 for producing a film, preferably obtained by casting or extrusion, or producing a molded article, preferably obtained by blow or injection molding, more preferably by injection molding.

15. Film or article, comprising the polypropylene composition (PPC) composition according to any one of claims 1 to 9, wherein the film is a packaging film for consumer goods or medical packaging, preferably obtained by casting or extrusion, such as extrusion blow molding, or wherein the article is a molded article, preferably an injection molded article.

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