Process for preparing propylene composition

Abstract

The present invention relates to a process for the preparation of a polypropylene composition comprising a propylene-based polymer, which is a propylene homopolymer or a propylene-ethylene copolymer having an ethylene content of less than 1.0 wt%, based on the propylene-ethylene copolymer, the present invention relates to a process for preparing a polypropylene composition having a melt flow rate (MFR) in the range of from 0.50 to 110 dg / min wherein the melt flow rate is determined using ISO 1133-1: 2011 at 230 DEG C using 2.16 kg wherein the process comprises the step of polymerizing propylene and optionally an ethylene comonomer in the gas phase in the presence of a catalyst to obtain a propylene-based polymer, wherein the catalyst comprises a procatalyst, a co-catalyst and optionally an external electron donor, and wherein the procatalyst is obtainable by a process comprising the steps of contacting a magnesium-containing support with a halogen-containing titanium compound and an internal electron donor according to formula I, r1 is a secondary alkyl group and R2 is a non-secondary alkyl group having at least 5 carbon atoms, preferably R2 is a non-secondary alkyl group having at least 5 carbon atoms and is branched in position 3 or another position; the procatalyst is prepared according to the following steps: i) contacting a compound R < 4 > z Mg X < 4-z > with an alkoxy or aryloxy-containing silane compound to produce a first intermediate reaction product, namely solid Mg (ORa) xX < 12-x >, wherein: Ra is a linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxycarbonyl or alkylaryl groups and combinations of one or more thereof; wherein the hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms, and preferably have from 1 to 20 carbon atoms; wherein R4 is a linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxycarbonyl or alkylaryl groups and combinations of one or more thereof; wherein the hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and preferably have 1 to 20 carbon atoms, preferably R4 is butyl; wherein X4 and X1 are each independently selected from the group consisting of fluorine ion (F-), chloride ion (Cl-), bromide ion (Br-) or iodide ion (I-), preferably chloride ion; z is in a range greater than 0 and less than 2, i.e. 0 lt; zlt, zlt; x is an integer from 0 to 2; ii) optionally contacting the solid Mg (ORa) xX12-x obtained in step i) with at least one activating compound selected from the group consisting of an activating electron donor and a metal alkoxide compound of formula M1 (ORb) v-w (OR3) w or M2 (ORb) v-w (R3) w to obtain a second intermediate product; wherein: M1 is a metal selected from the group consisting of Ti, Zr, Hf, Al or Si; v is the valence of M1; m2 is metal Si; v is the valence of M2; each of Rb and R3 is a linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxycarbonyl or alkylaryl groups and combinations of one or more thereof; wherein the hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms, and preferably have from 1 to 20 carbon atoms; wherein w is less than v, preferably v is 3 or 4; iii) bringing the first intermediate reaction product or the second intermediate reaction product respectively obtained in step i) or ii) into contact with a halogen-containing Ti compound and the compound represented by formula I as an internal electron donor. # imgabs0 #

Description

Technical Field

[0001] The present invention relates to a process for preparing a composition comprising a propylene-based polymer, which is a propylene homopolymer or a propylene-ethylene copolymer having an ethylene content of up to 1.0 wt.-%, based on the propylene-ethylene copolymer.

[0002] In addition, the present invention also relates to an article comprising the polypropylene composition of the present invention. In addition, the present invention relates to the use of the polypropylene composition and to a method for preparing the article. The present invention also relates to the use of the polypropylene composition of the present invention for compounding with another polymer or for making a masterbatch. Background Art

[0003] Polymers, such as polypropylene, are increasingly being used in applications with different requirements. At the same time, there is a constant search for tailored polymers that meet the requirements of these applications, for example with high stiffness (as indicated by high isotacticity and low CXS). In addition, there is a constant push for high-yield processes, as these are more economically advantageous.

[0004] Therefore, there is a need in the art for a process for preparing a polypropylene composition comprising a propylene-based polymer, which is a propylene homopolymer or a propylene-ethylene copolymer having an ethylene content of up to 1.0 wt.-%, based on the propylene-ethylene copolymer, which can be produced with high catalyst yields, having high stiffness. Summary of the invention

[0005] It is therefore an object of the present invention to provide a process for preparing a polypropylene composition comprising a propylene-based polymer which is a propylene homopolymer or a propylene-ethylene copolymer having an ethylene content of less than 1.0 wt.-%, based on the propylene-ethylene copolymer, which can be produced with high catalyst yield and has high stiffness.

[0006] The object is achieved by a process for the preparation of a polypropylene composition comprising a propylene based polymer which is a propylene homopolymer or a propylene-ethylene copolymer having an ethylene content of up to 1.0 wt.-%, based on the propylene-ethylene copolymer,

[0007] Therein, the polypropylene composition preferably has at least more than 95 wt.-%, more preferably at least more than 96 wt.-%, even more preferably at least more than 97 wt.-%, even more preferably at least more than 98 wt.-% of propylene-based polymers based on the composition, and:

[0008] a melt flow rate (MFR) in the range of 0.50 to 110 dg / min, wherein the melt flow rate is determined using ISO 1133-1:2011 using 2.16 kg at 230°C, and

[0009] Wherein, the method comprises the step of polymerizing propylene and an optional ethylene comonomer in the gas phase in the presence of a catalyst to obtain a propylene-based polymer, wherein the catalyst comprises a procatalyst, a cocatalyst and an optional external electron donor, and the procatalyst can be obtained by a method comprising the following steps:

[0010] Contacting a magnesium-containing support with a halogen-containing titanium compound and an internal electron donor according to formula I:

[0011]

[0012] Wherein, R 1 is a secondary alkyl group and R 2 is a non-secondary alkyl group having at least 5 carbon atoms, preferably R 2 is a non-secondary alkyl group branched at the 3-position or another position;

[0013] Preparing the procatalyst according to the following steps:

[0014] i) Contacting the compound R 4 z MgX 4 2-z with a silane compound containing an alkoxy or aryloxy group to produce a first intermediate reaction product, namely solid Mg(OR a ) x X 1 2-x , wherein: R a is a straight-chain, branched or cyclic hydrocarbon group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxycarbonyl or alkylaryl groups and one or more combinations thereof; wherein the hydrocarbon group may be substituted or unsubstituted, may contain one or more heteroatoms and preferably has 1 to 20 carbon atoms; wherein R 4 is a straight-chain, branched or cyclic hydrocarbon group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxycarbonyl or alkylaryl groups and one or more combinations thereof; wherein the hydrocarbon group may be substituted or unsubstituted, may contain one or more heteroatoms and preferably has 1 to 20 carbon atoms, preferably R 4 is butyl; wherein X 4 and X 1 are each independently selected from the group consisting of fluoride ion (F-), chloride ion (Cl-), bromide ion (Br-) or iodide ion (I-), preferably chloride ion; z is in the range greater than 0 and less than 2, i.e., 0 < z < 2, and x is an integer from 0 to 2;

[0015] ii) Optionally, the solid Mg(OR a ) xX 1 2-x and an activated electron donor selected from the group consisting of 1 (OR b ) v-w (OR 3 ) w or M 2 (OR b ) v-w (R 3 ) w to obtain a second intermediate product; wherein: M 1 is a metal selected from the group consisting of Ti, Zr, Hf, Al or Si; v is M 1 The valence of 2 is metal Si; v is M 2 The valence of b and R 3 Each is a straight chain, branched or cyclic hydrocarbon group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxycarbonyl or alkylaryl groups and one or more combinations thereof; wherein the hydrocarbon group may be substituted or unsubstituted, may contain one or more heteroatoms and preferably has 1 to 20 carbon atoms; wherein w is less than v, preferably v is 3 or 4;

[0016] iii) contacting the first intermediate reaction product or the second intermediate reaction product obtained in step i) or ii) respectively with a halogen-containing Ti compound and the compound represented by formula I as an internal electron donor.

[0017] The present invention also provides a polypropylene composition obtainable or obtainable by the process according to the present invention.

[0018] The present invention also provides a polypropylene composition comprising a propylene-based polymer which is a propylene homopolymer or a propylene-ethylene copolymer having an ethylene content of up to 1.0 wt.-%, based on the propylene-ethylene copolymer,

[0019] The polypropylene composition has

[0020] A melt flow rate (MFR) in the range of 0.50 to 110 dg / min, wherein the melt flow rate is determined using ISO 1133-1:2011 using 2.16 kg at 230°C, and

[0021] wherein the amount of Ti in the propylene-based polymer is at most 1.1 mg per 1 kg of the propylene-based polymer as measured by inductively coupled plasma mass spectrometry (ICP-MS).

[0022] According to the present invention, it has surprisingly been found that the use of a specific catalyst in a process for preparing a propylene-based polymer results in a combination of high catalyst yield and high isotacticity of the composition. Due to the use of such a low amount of catalyst, a polypropylene composition with a very low amount of Ti can be produced. Therefore, in another aspect, the present invention provides a polypropylene composition with a very low amount of Ti from the catalyst used in the preparation of the composition, which is advantageous for the high purity of the composition. DETAILED DESCRIPTION

[0023] Propylene-based polymers

[0024] The polypropylene composition according to the present invention comprises a propylene based polymer which is a propylene homopolymer or a propylene-ethylene copolymer having an ethylene content of less than 1.0 wt.-%, based on the propylene-ethylene copolymer.

[0025] Preferably, the polypropylene composition has a melt flow rate (MFR) of 0.50 to 110 dg / min, more preferably 0.5 to 50 dg / min as determined according to ISO 1133-1:2011 using 2.16 kg at 230 °C.

[0026] Preferably, the propylene-based polymer has a cold xylene soluble content (CXS) in the range of 1.0 to 5.0, more preferably in the range of 1.0 to 4.0 wt.%, more preferably in the range of 1.0 to 3.0 wt.%, as measured by the method described in the "CRYSTEX Method for Propylene Homopolymers" section of the Measurement Methods section of the present disclosure.

[0027] Preferably, the propylene-based polymer has a pentad isotacticity of at least 95.5 wt%, preferably at least 96 wt%, wherein the pentad isotacticity is expressed as 13 C NMR, and / or having a melt flow rate (MFR) in the range of 2 to 100 dg / min as measured according to ISO 1133-1:2011 using 2.16 kg at 230°C Hopol ).

[0028] Preferably, the polypropylene composition has a molecular weight distribution (Mw / Mn) in the range of 1.0 to 11.0, more preferably in the range of 4.0 to 9.0, wherein Mw denotes the weight average molecular weight and Mn denotes the number average molecular weight, and wherein Mw and Mn are measured according to ISO 16014-1(4):2003.

[0029] Process for preparing propylene-based polymers

[0030] The person skilled in the art knows how to prepare propylene homopolymers or propylene-ethylene copolymers. The preparation of propylene homopolymers and propylene-ethylene copolymers is described, for example, in Moore, EP (1996) Polypropylene Handbook. Polymerization, Characterization, Properties, Processing, Applications, Hanser Publishers: New York.

[0031] catalyst

[0032] The catalyst used for preparing the polypropylene composition according to the present invention is a catalyst described in detail in WO2021 / 063930, which is incorporated herein by reference. The catalyst comprises a main catalyst, a cocatalyst and optionally an external electron donor.

[0033] The procatalyst can be obtained by a process comprising contacting a magnesium-containing support with a halogen-containing titanium compound and an internal electron donor according to formula I:

[0034]

[0035] Where R 1 is a secondary alkyl group and R 2 is a non-secondary alkyl group having at least 5 carbon atoms, preferably R 2 is a non-secondary alkyl group having at least 5 carbon atoms and is branched at the 3-position or another position.

[0036] The method for providing the procatalyst follows the method described in WO2021 / 063930A1 (which is incorporated by reference) and comprises the following steps:

[0037] i) making the compound R 4 z MgX 4 2-z contacting with an alkoxy- or aryloxy-containing silane compound to produce a first intermediate reaction product, namely solid Mg(OR a ) x X 1 2-x , where: R a is a straight chain, branched or cyclic hydrocarbon group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxycarbonyl or alkylaryl groups and one or more combinations thereof; wherein the hydrocarbon group may be substituted or unsubstituted, may contain one or more heteroatoms and preferably has 1 to 20 carbon atoms; wherein R 4is a straight-chain, branched or cyclic hydrocarbon group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxycarbonyl or alkylaryl groups and one or more combinations thereof; wherein the hydrocarbon group may be substituted or unsubstituted, may contain one or more heteroatoms and preferably has 1 to 20 carbon atoms, preferably R 4 is butyl; wherein X 4 and X 1 are each independently selected from the group consisting of fluoride ion (F-), chloride ion (Cl-), bromide ion (Br-) or iodide ion (I-), preferably chloride ion; z is in the range greater than 0 and less than 2, i.e., 0 < z < 2, and x is an integer from 0 to 2;

[0038] ii) Optionally, the solid Mg(OR a ) x X 1 2-x obtained in step i) is contacted with at least one activating compound selected from the group consisting of activating electron donors and metal alkoxide compounds of the formula M 1 (OR b ) v-w (OR 3 ) w or M 2 (OR b ) v-w (R 3 ) w to obtain a second intermediate product; wherein: M 1 is a metal selected from the group consisting of Ti, Zr, Hf, Al or Si; v is the valence of M 1 ; M 2 is the metal Si; v is the valence of M 2 ; R b and R 3 are each independently a straight-chain, branched or cyclic hydrocarbon group selected from alkyl, alkenyl, aryl, aralkyl, alkoxycarbonyl or alkylaryl groups and one or more combinations thereof; wherein the hydrocarbon group may be substituted or unsubstituted, may contain one or more heteroatoms and preferably has 1 to 20 carbon atoms; wherein w is less than v, preferably v is 3 or 4;

[0039] iii) The first intermediate reaction product or the second intermediate reaction product obtained in step i) or ii) respectively is contacted with a halogen-containing Ti compound and the compound of formula I as an internal electron donor.

[0040] In one embodiment, during step ii), as the activating compound, an alcohol is used as the activating electron donor and a tetraalkyl titanate is used as the metal alkoxide compound.

[0041] In one embodiment, an activator is present. In one embodiment, the activator is ethyl benzoate. In one embodiment, the activator is a benzamide according to formula X:

[0042]

[0043] Where R 70 and R 71 are each independently selected from hydrogen or alkyl, and R 72 , R 73 , R 74 , R 75 , R 76 Each is independently selected from hydrogen, a heteroatom or a hydrocarbon group, which is preferably selected from an alkyl, alkenyl, aryl, aralkyl, alkoxycarbonyl or alkylaryl group and one or more combinations thereof, more preferably wherein R 70 and R 71 are all methyl and R 72 , R 73 , R 74 and R 75 All are hydrogen, namely N,N'-dimethylbenzamide (Ba-2Me).

[0044] Preferably, the internal electron donor used is according to formula I:

[0045]

[0046] Where R 1 is a secondary alkyl group having at least three carbon atoms and R 2 is a non-secondary alkyl group having at least 5 carbon atoms, preferably R 1 and R 2 having up to seven carbon atoms, preferably up to six carbon atoms, preferably isopropyl, isobutyl, isopentyl, cyclopentyl, n-pentyl and isohexyl, preferably R 2 Branching at position 3 or another position.

[0047] In another embodiment, the internal electron donor is 3,3-bis(methoxymethyl)-2,6-dimethylheptane, according to Formula I, wherein R1 is isopropyl, i.e., a secondary alkyl group, and R2 is isopentyl, i.e., a non-secondary alkyl group and having a branch on the third carbon atom (abbreviated as iPiPen, where iP represents isopropyl and iPen represents isopentyl, also known as 3-methyl-butyl). The compound iPiPen has C 13 H 28 Chemical formula of O2; exact mass of 216.21 and molecular weight of 216.37. In a more preferred embodiment of the present invention, the iPiPen is used as an internal donor and / or wherein the activating compound is preferably N,N-dimethylbenzamide.

[0048]

[0049] In another embodiment, the internal electron donor is (1-methoxy-2-(methoxymethyl)-5-methylhexan-2-yl)cyclopentane, according to Formula I, wherein R 1 is a secondary alkyl cyclopentyl and R 2 is a secondary cyclopentyl group (abbreviated as CPiPen, where CP represents cyclopentyl and iPen represents isopentyl, also known as 3-methyl-butyl). 15 H 30 Chemical formula of O2; exact mass of 242.22 and molecular weight of 242.40. In a more specific embodiment, CPiPen is used as internal donor and N,N-dimethylbenzamide is preferably used as activator.

[0050]

[0051] In another embodiment, the internal electron donor is 3,3-bis(methoxymethyl)-2,7-dimethyloctane, according to Formula I, wherein R 1 isopropyl secondary alkyl and R 2 is a non-secondary isohexyl radical with a branch on the fourth carbon atom (abbreviated as iPiHex, where iP represents isopropyl and iHex represents isohexyl, also known as 4-methyl-pentyl). The compound iPiHex has C 14 H 30 Chemical formula of O2; exact mass of 230.22 and molecular weight of 230.39. In a more specific embodiment, iPiHex is used as internal donor and N,N-dimethylbenzamide is preferably used as activating agent.

[0052]

[0053]

[0054] In another embodiment, the internal electron donor is 3,3-bis(methoxymethyl)-2-methyloctane, according to Formula I, wherein R 1 isopropyl secondary alkyl and R 2 is a non-secondary non-branched n-pentyl group (abbreviated as iPnPen, wherein iP represents isopropyl and nPen represents n-pentyl). The compound iPnPen has C 13 H 28 Chemical formula of O2; exact mass of 216.21 and molecular weight of 216.37. In a more specific embodiment, iPnPen is used as internal donor and N,N-dimethylbenzamide is preferably used as activator.

[0055]

[0056] In another embodiment, the internal electron donor is 3,3-bis(methoxymethyl)-2,6-dimethyloctane, according to Formula I, wherein R 1 isopropyl secondary alkyl and R 2 is a non-secondary branched hexyl group with a branch at the third carbon atom (abbreviated as iP3Hex, wherein iP represents an isopropyl group and wherein 3Hex represents a hexyl group with a branch at the third carbon atom, also known as 3-methyl-pentyl). The compound iPiHex has C 14 H 32 Chemical formula of O2; exact mass of 230.22 and molecular weight of 230.39. In a more preferred embodiment, iP3Hex is used as internal donor and / or N,N-dimethylbenzamide is preferably used as activating agent.

[0057]

[0058] In another embodiment, the procatalyst used according to the present invention provides a polymer yield of at least 50 kg polymer per gram of procatalyst used.

[0059] In one embodiment, the substituent R 1 is isopropyl or cyclopentyl. In one embodiment, the substituent R 2 The following table shows the above embodiments together with their abbreviations and R 1 and R 2 groups, whether these groups are secondary and whether they are branched.

[0060] According to the present invention, it is also preferred that R 1 is a secondary alkyl group and R 2 is a non-secondary alkyl group, which is branched at the 3-position or another position.

[0061]

[0062] Preferably, the catalyst comprises an external electron donor, and the molar ratio of the cocatalyst to the external electron donor is greater than 1 and at most 120, or greater than 3 and at most 90.

[0063] Preferably, the cocatalyst is selected from trimethylaluminum, triethylaluminum, triisobutylaluminum, trihexylaluminum, diisobutylaluminum hydride, trioctylaluminum, dihexylaluminum hydride and mixtures thereof.

[0064] Preferably, the external electron donor is selected from the group of compounds having the structure according to:

[0065] -Formula III: (R 90 )2N—Si(OR91 )3,

[0066] -Formula IV: (R 92 )Si(OR 93 )3,

[0067] -Formula V:Si(OR a ) 4-n R b n ,and

[0068] - mixtures thereof,

[0069] Among them, R 90 , R 91 , R 92 and R 93 Each of the groups is independently a linear, branched or cyclic, substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, preferably wherein R 90 , R 91 , R 92 and R 93 The groups are each independently a straight-chain unsubstituted alkyl group having 1 to 8 carbon atoms,

[0070] Where n can be 0 to 2, and R a and R b Each of independently represents an alkyl or aryl group, optionally containing one or more heteroatoms, such as O, N, S or P, having, for example, 1 to 20 carbon atoms.

[0071] Preferably, the molar ratio of Al in the promoter to Si in the external electron donor is greater than 1 and at most 120, or greater than 3 and at most 90.

[0072] For example, ethyl, methyl or n-propyl, such as diethylaminotriethoxysilane (DEATES), n-propyltriethoxysilane (nPTES), n-propyltrimethoxysilane (nPTMS); and having the general formula Si(OR a ) 4-n R b n An organosilicon compound wherein n may be 0 to 2, and R a and R bEach of the above independently represents an alkyl or aryl group, which optionally contains one or more heteroatoms, such as O, N, S or P, and has, for example, 1 to 20 carbon atoms; such as diisobutyldimethoxysilane (DiBDMS), tert-butylisopropyldimethoxysilane (tBuPDMS), cyclohexylmethyldimethoxysilane (CHMDMS), dicyclopentyldimethoxysilane (DCPDMS) or di(isopropyl)dimethoxysilane (DiPDMS). More preferably, the external electron donor is selected from di(isopropyl)dimethoxysilane (DiPDMS) or diisobutyldimethoxysilane (DiBDMS).

[0073] Preferably, the external donor comprises or consists of a compound selected from the list comprising organosilicon compounds, silanes, alkoxysilanes, alkylsilanes, alkylalkoxysilanes and aliphatic / aromatic esters, for example dicyclopentyldimethoxysilane, di-tert-butyldimethoxysilane, methylcyclohexyldimethoxysilane, ethylcyclohexyldimethoxysilane, diphenyldimethoxysilane, diisopropyldimethoxysilane, di-n-propyldimethoxysilane, diisobutyldimethoxysilane, di-n-butyldimethoxysilane, cyclopentyltrimethoxysilane, isopropyltrimethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, ethyltriethoxysilane, tetramethoxysilane, tetraethoxysilane, cyclopentylpyrrolidinodimethoxysilane, bis(pyrrolidino)dimethoxysilane, and mixtures thereof, preferably di(isopropyl)dimethoxysilane (DiPDMS).

[0074] The compounds mentioned above as examples of external electron donors are sometimes referred to as selectivity control agents (SCA). The external electron donor may consist of SCA. Alternatively, in addition to SCA, the external electron donor may additionally include a compound referred to as an activity limiting agent (ALA). Preferably, the activity limiting agent (ALA) is selected from the group consisting of ethyl acetate, ethyl benzoate, ethyl p-ethoxybenzoate, methyl trimethylacetate, isopropyl myristate, di-n-butyl sebacate, (poly)(alkylene glycol) mono- or diacetate, (poly)(alkylene glycol) mono- or dimyristate, (poly)(alkylene glycol) mono- or dilaurate, (poly)(alkylene glycol) mono- or dioleate, triacetin, a mixed glyceride of linoleic acid, oleic acid, palmitic acid and stearic acid, and a mixture thereof. More preferably, the activity limiting agent (ALA) is isopropyl myristate.

[0075] The ratio of selectivity control agent (SCA) to activity limiting agent (ALA) is not critical in principle, with best results being obtained with a SCA / ALA ratio in the range of 0.010 to 100, more preferably in the range of 0.10 to 20.

[0076] The molar ratio of Al in the promoter to Si in the external electron donor may be, for example, 1 to 120.

[0077] In some preferred embodiments, the molar ratio of Al in the promoter to Si in the external electron donor is greater than 1, preferably greater than 3, even more preferably greater than 4 and up to 120, preferably up to 110, more preferably 90, more preferably up to 70, more preferably up to 60. The molar ratio of Al in the promoter to Si in the external electron donor is in the range of 1 to 120, or 1 to 110, or 1 to 90, or 1 to 70, or 1 to 60, 3 to 60, or 3 to 90, or 4 to 90, or 4 to 70, or 4 to 60, or 5 to 120, or 5 to 110, or 5 to 90, or 5 to 70, or 5 to 60.

[0078] In some preferred embodiments, the molar ratio of Al in the promoter to Si in the external electron donor is greater than 15 and up to 120, or greater than 20, or greater than 25 and up to 120, or up to 100, or up to 90, or up to 70, or up to 60. The molar ratio of Al in the promoter to Si in the external electron donor is in the range of 15 to 120, or 15 to 100, or 15 to 90, or 15 to 70, or 15 to 60, or 20 to 120, or 20 to 100, or 20 to 90, or 20 to 70, 20 to 60, or 25 to 120, or 25 to 100, or 25 to 90, or 25 to 70, or 25 to 60.

[0079] In some embodiments, the molar ratio of Al in the co-catalyst to Si in the external electron donor is in the range of 1 to 25, or 1 to 14, or 1 to 10, or 3 to 10, or 3 to 14, or 3 to 20, or 3 to 25, or 4 to 10, or 4 to 14, or 4 to 20, or 4 to 25, or 5 to 10, or 5 to 14, or 5 to 20, or 5 to 25.

[0080] It is well known in the art of polypropylene catalysts that an increased Al / Si molar ratio leads to increased catalyst productivity and decreased isotacticity (and hence stiffness) of the polypropylene.

[0081] However, it has surprisingly been observed that the present invention allows the use of high molar ratios of Al / Si while maintaining high isotacticity and having increased catalyst productivity.

[0082] Catalyst productivity (CY) Ti*Productivity / Mass retention:

[0083] In a preferred embodiment, the process has a CY Ti (KgPP / g catalyst)*productivity (Kg / h) / mass hold-up (Kg) of at least 25, more preferably at least 30, more preferably at least 35, more preferably at least 40, wherein CY Ti (KgPP / g catalyst) is calculated according to equation (1):

[0084]

[0085] The Ti content in the catalyst and the Ti content in the obtained polymer were measured by inductively coupled plasma mass spectrometry (ICP-MS).

[0086] Preferably, the amount of Ti in the propylene-based polymer is at most 1.1 mg per 1 kg of the propylene-based polymer as measured by inductively coupled plasma mass spectrometry (ICP-MS).

[0087] Composition

[0088] The polypropylene composition has a melt flow rate (MFR) in the range of 0.50 to 110 dg / min, wherein the melt flow rate is determined using ISO 1133-1:2011 using 2.16 kg at 230°C. In some preferred embodiments, the MFR of the polypropylene composition measured using ISO 1133-1:2011 using 2.16 kg at 230°C is from 0.50 to 30 dg / min. In some preferred embodiments, the MFR of the polypropylene composition measured using ISO 1133-1:2011 using 2.16 kg at 230°C is from 30 to 110 dg / min.

[0089] Preferably, the amount of propylene-based polymer is at least 95 wt-%, more preferably at least 96 wt-%, even more preferably at least 97 wt-%, even more preferably at least 98 wt-%, based on the polypropylene composition.

[0090] Inorganic fillers

[0091] The composition according to the present invention may comprise an inorganic filler. Suitable examples of inorganic fillers include, but are not limited to, talc.

[0092] The composition according to the invention may be free or substantially free of inorganic fillers. For example, the composition according to the invention may comprise less than 1.0 wt%, less than 0.1 wt% or less than 0.01 wt% of inorganic fillers.

[0093] additive

[0094] In some embodiments, the polypropylene composition additionally comprises additives, e.g. in an amount of 0.10 to 2.0 wt.-%, based on the polypropylene composition.

[0095] Additives include stabilizers. Stabilizers may, for example, be selected from heat stabilizers, antioxidants and / or UV stabilizers, all of which are known to those skilled in the art.

[0096] Additives may further include nucleating agents, colorants such as pigments and dyes; clarifying agents; surface tension adjusting agents; lubricants; flame retardants; mold release agents; flow improvers; plasticizers; antistatic agents; foaming agents; and slip agents.

[0097] In one aspect, the invention provides articles comprising the polypropylene composition of the present invention. Preferably, the amount of the polypropylene composition is at least 95% by weight based on the article. Preferably, the article is prepared by injection molding. Preferably, the article is a household article, such as a vacuum cleaner housing, household chemicals and paint, or a packaged article, such as a container, a crate, a box, a battery shell, a bucket, a flower pot, a food container / package, an ice cream container, a thin-walled package, a lid and a closure, a health care package, or a health care article, such as a drug delivery article, a laboratory ware, a medical device, a medical diagnostic article or an automotive interior article, such as a dashboard bracket, a door panel, a dashboard, a dashboard bracket, a door cladding, a door fixture, an armrest, a pillar cladding, a seat cladding, a luggage cladding, an interior decoration, and an application in heating, ventilation, and air conditioning (HVAC) applications.

[0098] In one aspect, the present invention relates to the use of the polypropylene composition of the present invention for preparing articles. Preferably, the amount of the polypropylene composition is at least 95% by weight based on the article. Preferably, the article is prepared by injection molding. Preferably, the article is a household article, such as a vacuum cleaner housing, household chemicals and paint, or a packaged article, such as a container, a crate, a box, a battery shell, a bucket, a flower pot, a food container / package, an ice cream container, a thin-walled package, a lid and a closure, a health care package, or a health care article, such as a drug delivery article, a laboratory ware, a medical device, a medical diagnostic article or an automotive interior article, such as a dashboard bracket, a door panel, a dashboard, a dashboard bracket, a door cladding, a door fixture, an armrest, a pillar cladding, a seat cladding, a luggage cladding, an interior decoration, and applications in heating, ventilation, and air conditioning (HVAC) applications.

[0099] In one aspect, the present invention provides a method for preparing an article, comprising the steps of:

[0100] a. Provide a polypropylene composition of the present invention, and

[0101] b. Converting the polypropylene composition into an article, for example by using extrusion or injection molding processes.

[0102] The present invention also relates to the use of the inventive polypropylene composition for compounding with another polymer, such as another polypropylene, or for the preparation of a masterbatch.

[0103] It is further noted that the present invention relates to any possible combination of features described herein, preferably in particular those combinations of features presented in the claims. Thus, it will be appreciated that all combinations of features relating to the composition according to the invention, all combinations of features relating to the method according to the invention and all combinations of features relating to the composition according to the invention with features relating to the method according to the invention are described herein.

[0104] It is also noted that the term "comprising / including / containing" does not exclude the presence of other elements. However, it is also understood that a description of a product / composition comprising certain components also discloses a product / composition consisting of these components. A product / composition consisting of these components may be advantageous because it provides a simpler and more economical method for preparing the product / composition. Similarly, it is also understood that a description of a method comprising certain steps also discloses a method consisting of these steps. A method consisting of these steps may be advantageous because it provides a simpler and more economical method.

[0105] The invention is now explained with the aid of the following examples without, however, being restricted thereto.

[0106] Example

[0107] Method for preparing primary catalyst

[0108] For Examples E2 to E6 of the present invention: The main catalyst is prepared according to the method disclosed in Example 1 of WO2021 / 063930A1

[0109] For Example E1: The procatalyst was prepared according to the method disclosed in Example 1 of WO 2021 / 063930 A1, but without using an external donor. This example is therefore not part of the present invention.

[0110] For Comparative Example CE1, a catalyst was prepared according to Comparative Example 1 in EP0728770B1 using a micropheroidal MgCl2.2.1 EtOH support having an average particle size of 15 microns.

[0111] Process conditions of E1 to E5 and CE1

[0112] The gas phase polymerization was carried out in a horizontal stirred gas phase reactor (plus covered secondary reactor) with a downstream powder handling unit for powder collection (= degassing and catalyst deactivation).

[0113] The temperature of the powder bed is measured by a series of internal thermocouples. The data from these thermocouples is used to control the quench flow to the various quench nozzles.

[0114] Hydrogen was fed to the reactor to control the melt flow rate.

[0115] The obtained propylene homopolymer was collected and its properties were measured.

[0116] E6 Tm Process conditions

[0117] The gas phase polymerization was carried out in a series of two horizontal cylindrical stirred bed gas phase reactors connected in series to prepare the heterophasic propylene copolymer E6.

[0118] In the first reactor (R1) a homopolymer is formed and in the second reactor (R2) an ethylene-propylene copolymer rubber is formed to produce a heterophasic propylene copolymer. Both reactors are operated in continuous mode.

[0119] During operation, the polypropylene powder produced in the first reactor is discharged into the second reactor through the powder discharge system.

[0120] The temperature of the powder bed is measured by a series of internal thermocouples. The data from these thermocouples is used to control the quench flow to the various quench nozzles.

[0121] Hydrogen was fed independently to the two reactors to control the melt flow index ratio of the homopolymer powder and the copolymer powder.

[0122] The propylene homopolymer from the first reactor was collected and its properties were measured.

[0123] Table 1 shows the catalysts used in the polymerization process and various properties of the homopolymers obtained.

[0124] Table 1 Polymerization reaction conditions and polymer properties

[0125]

[0126]

[0127] Al / Ti is the molar ratio of co-catalyst (TEA) to main catalyst

[0128] Si / Ti is the molar ratio of external donor (DiPDMS) to main catalyst

[0129] Al / Si is the molar ratio of co-catalyst (TEA) to external donor (DiPDMS)

[0130] H2 / C3 is the molar ratio of hydrogen to propylene

[0131] NA: Not analyzed

[0132] It can be seen that the process of preparing E2-E6 using a catalyst comprising the procatalyst of the present invention has a higher catalyst productivity (expressed by CY Ti* productivity / mass retention) than CE1 prepared using a catalyst comprising a different procatalyst, while resulting in compositions with comparable rigidity, as can be understood from the comparable values ​​of CXS and isotacticity.

[0133] From the comparison of E2-E6, it can be seen that a higher Al / Si molar ratio (lower amount of Si (external donor)) in the catalyst leads to a higher catalyst productivity. In this regard, it is noteworthy that E6, which uses a lower Al / Si molar ratio (higher amount of Si) in the catalyst than CE1, leads to a higher catalyst productivity than CE1. This shows that the type of procatalyst in the catalyst leads to differences in catalyst productivity.

[0134] From the comparison of E1 with E2 to E6, it can be seen that the use of Si external donor reduces the catalyst productivity, but it is still higher than CE1.

[0135] In addition, the amount of Ti detected in E1 to E6 is lower than that in CE1, which means that the polypropylene according to the present invention contains less impurities than polypropylene prepared with other catalysts, such as the catalyst used in Comparative Example 1 in EP0728770B1, which uses a microspherical MgCl2.2.1EtOH carrier with an average particle size of 15 microns. Therefore, the polypropylene produced by the method according to the present invention can be suitable for applications requiring fewer impurities without further additional purification methods.

[0136] Measurement method

[0137] MFR

[0138] MFR is measured according to ISO 1133 (2.16 kg / 230° C.).

[0139] CRYSTEX method for propylene homopolymer

[0140] The CRYSTEX method described below can determine the following properties of PP homopolymers:

[0141] - amount of crystalline insoluble fraction in PP homopolymer (CXI equivalent to the whole sample; HT fraction);

[0142] -Amount of amorphous soluble fraction in PP homopolymer (CXS equivalent to the whole sample)

[0143] The properties can be measured according to the CRYSTEX method by a CRYSTEX QC instrument of CRYSTEX QC Polymer Char (Valencia, Spain). A schematic diagram of the CRYSTEX QC instrument is given in Del Hierro, P.; Ortin, A.; Monrabal, B.; 'Soluble Fraction Analysis in polypropylene, The Column', February 2014, pp. 18-23.

[0144] The CRYSTEX QC instrument includes an infrared detector (IR4) and an online double capillary viscometer. Quantification of HT fraction, LT fraction, TC2 whole, TC2-HT fraction, TC2-LT fraction can be performed by an infrared detector that detects IR absorbance in two different bands (CH3 and CH2). IV whole, IV-HT fraction, IV-LT fraction can be measured by an online double capillary viscometer.

[0145] A sample of the PP homopolymer to be analyzed was weighed at a concentration of 10 mg / mL. After automatically filling the vial with 1,2,4-TCB containing 250 mg / L 2,6-tert-butyl-4-methylphenol (BHT) as an antioxidant, the sample was dissolved at 170°C until complete dissolution was achieved, for 60 min, while continuously stirring at 800 rpm.

[0146] A defined volume of the sample solution is injected into a column filled with an inert carrier, where crystallization of the sample and separation of the soluble fraction from the crystalline portion are performed. This process is repeated twice.

[0147] During the first injection, the entire sample was subjected to the elevated temperature measurement to determine the IV bulk [dl / g] and TC2 bulk (m / m %) of the PP homopolymer. However, TC2 is not relevant for homopolymer PP.

[0148] During the second injection, the measurement was performed at low temperature to determine the amorphous soluble fraction (CXS equivalent to the whole sample) (m / m %), followed by the measurement at high temperature to determine the crystalline insoluble fraction (CXI equivalent to the whole sample (m / m %)).

[0149] The crystalline insoluble fraction and the amorphous soluble fraction were separated by temperature cycling of dissolution at 165°C, crystallization at 40°C and redissolution in 1,2,4-trichlorobenzene (1,2,4-TCB) at 165°C.

[0150] The CXS content was determined by calibrating the instrument with various PP polymers having known CXS content determined by the standard gravimetric method according to ISO16152.

[0151] Isotacticity 13 C NMR

[0152] 175 mg of polypropylene pellets were dissolved in 3 ml of deuterated tetrachloroethylene (C2D2Cl4) containing 2,6-di-tert-butyl-4-methylphenol (BHT) at 130°C (5 mg BHT in 200 ml C2D2CL). The spectra were recorded on a Bruker Avance 500 spectrometer equipped with a cryogenically cooled probe head operating at 125°C. 13 C NMR spectroscopy.

[0153] The isotacticity of the mmmm pentad level is given by 13 C NMR spectroscopy, in % based on total pentad content.

[0154] Catalyst productivity (CY) Ti (KgPP / g catalyst) * productivity (Kg / h) / mass retention (Kg)

[0155] The Ti content in the catalyst and the Ti content in the obtained polymer were measured by ICP. The ICP procedure was as follows: approximately 250 mg of each sample was digested in 6 mL of concentrated nitric acid (trace metal grade) using an Anton Paar Multiwave PRO equipped with a closed high pressure quartz digestion vessel by microwave assisted acid digestion. After the microwave digestion run, the acid analysis was transferred to a pre-cleaned plastic centrifuge tube containing 1 mL of internal standard solution and diluted to the 50 mL mark with MilliQ water. The elements in the samples were quantified using an Agilent 8900 ICP-MS system using a multi-element calibration set from Inorganic Ventures.

[0156] Then calculate CY according to equation (1)

[0157]

[0158] The production rate (Kg / h) and mass holdup (Kg) were measured.

[0159] The production rate (Kg / h) / mass hold-up (Kg) corresponds to the polymer residence time.

[0160] Ethylene content

[0161] use 13C-NMR spectroscopy measures ethylene content. For this purpose, about 150 mg of material was dissolved in 1,1,2,2-tetrachloroethane-d2 (TCE-d2). In order to ensure a uniform solution, sample preparation was carried out in a heated rotary oven. NMR measurements were performed in a solution state using a Bruker 500Advance III HD spectrometer, which ran 1H and 13C at 500.16 and 125.78 MHz, respectively, and was equipped with a 10 mm dual cryogenically cooled probe running at 125 ° C. 13C-NMR experiments were performed using standard single pulse excitation using NOE and dual-level WALTZ16 decoupling schemes (Zhou Z. et al. J. Mag. Reson 187 (2007) 225. A total of 512 transients were obtained for each spectrum. The spectrum was calibrated by setting the central signal of the triplet state of TCE at 74.2 ppm. A proprietary computer program was used to process, integrate, and determine relevant quantitative properties from the integration of quantitative 13C NMR spectra.

[0162] Flexural modulus (parallel and perpendicular orientation)

[0163] For the purposes of the present invention, the stiffness of the particles is determined by measuring the flexural modulus according to ASTM D790-10. The flexural modulus is determined according to ISO 37 / 2, parallel and perpendicular orientation, on 3.2 mm thick specimens.

[0164] Izod notched impact strength (parallel and perpendicular orientation)

[0165] For the purposes of the present invention, the impact strength is determined according to ISO 180 4A by measuring the notched Izod impact strength of the granules at 23° C., test geometry: 65*12.7*3.2 mm, notch 45°, parallel and perpendicular orientation according to ISO 37 / 2.

[0166] Tensile test method

[0167] For the purposes of the present invention, tensile properties are determined according to ISO 527-2 / 5A on 3.2 mm thick specimens.

Claims

1. A process for preparing a polypropylene composition comprising a propylene-based polymer, said propylene-based polymer being a propylene homopolymer or a propylene-ethylene copolymer having an ethylene content of less than 1.0 wt.-%, based on said propylene-ethylene copolymer, in, The polypropylene composition has a melt flow rate (MFR) in the range of 0.50 to 110 dg / min, wherein the melt flow rate is determined using ISO 1133-1:2011 using 2.16 kg at 230°C, wherein the process comprises the step of polymerizing propylene and optionally an ethylene comonomer in the presence of a catalyst in a gas phase to obtain the propylene-based polymer, wherein the catalyst comprises a procatalyst, a cocatalyst and optionally an external electron donor, wherein the procatalyst is obtainable by a process comprising the steps of: The magnesium-containing support is contacted with a halogen-containing titanium compound and an internal electron donor according to formula I: Among them, R 1 is a secondary alkyl group and R 2 is a non-secondary alkyl group having at least 5 carbon atoms, preferably R 2 is a non-secondary alkyl group having at least 5 carbon atoms and is branched at the 3-position or another position; The main catalyst is prepared according to the following steps: i) contacting the compound R 4 z MgX 4 2-z with an alkoxy- or aryloxy-containing silane compound to produce a first intermediate reaction product, namely solid Mg(OR a ) x X 1 2-x , where: R a is a straight-chain, branched or cyclic hydrocarbon group independently selected from the group consisting of alkyl, alkenyl, aryl, aralkyl, alkoxycarbonyl or alkylaryl groups and one or more combinations thereof; wherein the hydrocarbon group may be substituted or unsubstituted, may contain one or more heteroatoms and preferably has 1 to 20 carbon atoms; wherein R 4 is a straight-chain, branched or cyclic hydrocarbon group independently selected from the group consisting of alkyl, alkenyl, aryl, aralkyl, alkoxycarbonyl or alkylaryl groups and one or more combinations thereof; wherein the hydrocarbon group may be substituted or unsubstituted, may contain one or more heteroatoms and preferably has 1 to 20 carbon atoms, preferably R 4 is butyl; wherein X 4 and X 1 are each independently selected from the group consisting of fluoride ion (F-), chloride ion (Cl-), bromide ion (Br-) or iodide ion (I-), preferably chloride ion; z is in the range greater than 0 and less than 2, i.e., 0 < z < 2, and x is an integer from 0 to 2; ii) optionally subjecting the solid Mg(OR) obtained in step i) to a ) x X 1 2-x and an activated electron donor selected from the group consisting of 1 (OR b ) v-w (OR 3 ) w or M 2 (OR b ) v-w (R 3 ) w to obtain a second intermediate product; wherein: M 1 is a metal selected from the group consisting of Ti, Zr, Hf, Al or Si; v is M 1 The valence of M 2 is metal Si; v is M 2 The valence of b and R 3 Each is a straight chain, branched or cyclic hydrocarbon group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxycarbonyl or alkylaryl groups and one or more combinations thereof; wherein the hydrocarbon group may be substituted or unsubstituted, may contain one or more heteroatoms and preferably has 1 to 20 carbon atoms; wherein w is less than v, preferably v is 3 or 4; iii) contacting the first intermediate reaction product or the second intermediate reaction product obtained in step i) or ii) respectively with a halogen-containing Ti compound and the compound represented by formula I as an internal electron donor.

2. The process according to claim 1, wherein the co-catalyst is selected from the group consisting of trimethylaluminum, triethylaluminum, triisobutylaluminum, trihexylaluminum, diisobutylaluminum hydride, trioctylaluminum, dihexylaluminum hydride and mixtures thereof.

3. The process of claim 2, wherein the catalyst comprises an external electron donor, and wherein the molar ratio of the co-catalyst to the external electron donor is in the range of 1 to 25, or 1 to 15, or 1 to 10, or 3 to 10, or 3 to 15, or 3 to 20, or 3 to 60, or 3 to 90, or 4 to 70, or 5 to 110, or 5 to 60, or 15 to 120, or 15 to 120, or 20 to 120, or 25 to 100, or 20 to 60.

4. The process according to claim 2 or 3, wherein the catalyst comprises an external donor, wherein the external electron donor is a silane-containing external donor, preferably wherein the external electron donor is selected from the group of compounds having the structure according to: Formula III: (R 90 )2N—Si(OR 91 )3, Formula IV: (R 92 )Si(OR 93 )3, Formula V: Si(OR a ) 4-n R b n , and mixtures thereof, in, R 90 , R 91 , R 92 and R 93 Each of the groups is independently a linear, branched or cyclic, substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, preferably wherein R 90 , R 91 , R 92 and R 93 The groups are each independently a straight-chain unsubstituted alkyl group having 1 to 8 carbon atoms, Where n can be 0 to 2, and R a and R b Each of which independently represents an alkyl or aryl group, optionally containing one or more heteroatoms, such as O, N, S or P, having, for example, 1 to 20 carbon atoms, and The molar ratio of Al in the promoter to Si in the external electron donor is greater than 1 and at most 120, preferably greater than 15 and at most 120, or in the range of 1 to 14. 5 . The process according to claim 1 , wherein during step ii) as activating compound an alcohol is used as activating electron donor and a tetraalkyl titanate is used as metal alkoxide compound.

6. A method according to any one of the preceding claims, wherein: An activator is present, preferably a benzamide according to formula X: Where R 70 and R 71 are each independently selected from hydrogen or alkyl, and R 72 , R 73 , R 74 , R 75 , R 76 Each is independently selected from hydrogen, a heteroatom or a hydrocarbon group, which is preferably selected from an alkyl, alkenyl, aryl, aralkyl, alkoxycarbonyl or alkylaryl group and one or more combinations thereof, more preferably wherein R 70 and R 71 are all methyl and R 72 , R 73 , R 74 and R 75 All are hydrogen, namely N,N'-dimethylbenzamide (Ba-2Me).

7. The method according to any one of the preceding claims, wherein the amount of Ti in the propylene-based polymer is at most 1.1 mg per 1 kg of the propylene-based polymer as determined by inductively coupled plasma mass spectrometry (ICP-MS).

8. The process according to any one of the preceding claims, wherein the process has a catalyst productivity (CY)Ti (KgPP / g catalyst)*Productivity (kg / h) / Mass Hold-up (kg) of at least 25, more preferably at least 30, more preferably at least 35, more preferably at least 40, wherein CY Ti (kgPP / g catalyst) is calculated according to equation (1): in, The Ti content in the catalyst and the Ti content in the obtained polymer were determined by inductively coupled plasma mass spectrometry (ICP-MS).

9. The method of any one of the preceding claims, wherein the propylene-based polymer has a cold xylene soluble content (CXS) of 1.0 to 4.0 wt%, preferably 1.0 to 3.0 wt%, as measured by the method described in the "CRYSTEX Method for Propylene Homopolymers" section of the Measurement Methods section of this disclosure.

10. The method of any one of the preceding claims, wherein the propylene-based polymer has a. at least 95.5% by weight, preferably at least 96% by weight, of the pentad isotacticity, wherein the pentad isotacticity is used 13 C NMR, and / or b. The melt flow rate (MFR) of the propylene portion of the propylene-based polymer determined according to ISO 1133-1:2011 using 2.16 kg at 230°C in the range of 2 to 100 dg / min Hopol ).

11. The method according to any one of the preceding claims, wherein the internal donor is 3,3-bis(methoxymethyl)-2,6-dimethylheptane and / or wherein the activating compound is N,N-dimethylbenzamide.

12. The method according to any one of the preceding claims, wherein the external donor comprises or consists of a compound selected from the list comprising: Silicone Compounds, silanes, alkoxysilanes, alkylsilanes, alkylalkoxysilanes and aliphatic / aromatic esters, for example dicyclopentyldimethoxysilane, di-tert-butyldimethoxysilane, methylcyclohexyldimethoxysilane, ethylcyclohexyldimethoxysilane, diphenyldimethoxysilane, diisopropyldimethoxysilane, di-n-propyldimethoxysilane, diisobutyldimethoxysilane, di-n-butyldimethoxysilane, cyclopentyltrimethoxysilane, isopropyltrimethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, ethyltriethoxysilane, tetramethoxysilane, tetraethoxysilane, cyclopentylpyrrolidinyldimethoxysilane, bis(pyrrolidinyl)dimethoxysilane, and mixtures thereof, preferably di(isopropyl)dimethoxysilane (DiPDMS).

13. The method according to any one of the preceding claims, wherein the external donor further comprises a compound selected from the group consisting of ethyl acetate, ethyl benzoate, ethyl p-ethoxybenzoate, methyl pivalate, isopropyl myristate, di-n-butyl sebacate, (poly)(alkylene glycol) mono- or diacetate, (poly)(alkylene glycol) mono- or dimyristate, (poly)(alkylene glycol) mono- or dilaurate, (poly)(alkylene glycol) mono- or dioleate, triacetin, mixed glycerides of linoleic acid, oleic acid, palmitic acid and stearic acid, and mixtures thereof; preferably isopropyl myristate.

14. Polypropylene composition obtainable or obtainable by a process according to any one of the preceding claims.

15. A polypropylene composition comprising a propylene-based polymer which is a propylene homopolymer or a propylene-ethylene copolymer having an ethylene content of up to 1.0 wt.-%, based on the propylene-ethylene copolymer, wherein the polypropylene composition has a melt flow rate (MFR) in the range of 0.50 to 110 dg / min, wherein the melt flow rate is determined using ISO 1133-1:2011 using 2.16 kg at 230°C, and wherein the amount of Ti in the propylene-based polymer is at most 1.1 mg per 1 kg of the propylene-based polymer as measured by inductively coupled plasma mass spectrometry (ICP-MS).

16. An article comprising the polypropylene composition according to claim 14 or 15, wherein the amount of the polypropylene composition is at least 95 wt.%, based on the article, and / or wherein the article is prepared by injection molding, and / or wherein the article is a household article, such as a vacuum cleaner housing, household chemicals and paints, or a packaging article, such as a container, a crate, a box, a battery housing, a bucket, a flower pot, a food container / packaging, an ice cream container, a thin wall packaging, a lid and a closure, a healthcare packaging, or a healthcare article, such as a drug delivery article, a laboratory ware, a medical device, a medical diagnostic article, or an automotive interior article, such as a dashboard tray, a door panel, an instrument panel, a dashboard tray, a door covering, a door fixture, an armrest, a pillar covering, a seat covering, a trunk covering, an interior trim, and applications in heating, ventilation, and air conditioning (HVAC) applications.

17. Use of the polypropylene composition according to claim 14 or 15 for preparing an article, wherein the amount of the polypropylene composition is at least 95 wt.%, based on the article, and / or wherein the article is prepared by injection molding, and / or wherein the article is a household article, such as a vacuum cleaner housing, household chemicals and paints, or a packaging article, such as a container, a crate, a box, a battery housing, a bucket, a flower pot, a food container / packaging, an ice cream container, a thin wall packaging, a lid and a closure, a healthcare packaging, or a healthcare article, such as a drug delivery article, a laboratory ware, a medical device, a medical diagnostic article, or an automotive interior article, such as a dashboard tray, a door panel, an instrument panel, a dashboard tray, a door covering, a door fixture, an armrest, a pillar covering, a seat covering, a trunk covering, an interior trim, and applications in heating, ventilation, and air conditioning (HVAC) applications.

18. A method for preparing an article, comprising the steps of: a. providing a polypropylene composition according to claim 14 or 15, and b. converting the polypropylene composition into an article, for example by using extrusion or injection molding processes.

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