Heterophasic polypropylene composition with high melting point

Abstract

The present invention relates to a heterophasic polypropylene composition having a high melting temperature and concurrently moderate softness and high impact strength. In particular, the present invention relates to a heterophasic polypropylene composition comprising a propylene copolymer (A) matrix of propylene with ethylene and 1-butene comonomer units and a propylene ethylene elastomer (B) dispersed within the matrix. Further, the present invention also relates to a preparation process for the heterophasic polypropylene composition in the presence of a Ziegler-Natta catalyst, and to articles comprising the heterophasic polypropylene composition as well as to the use of the heterophasic polypropylene composition in an article.

Description

[0001] Heterophasic polypropylene composition with high melting point

[0002] The present invention relates to a heterophasic polypropylene composition having a high melting temperature and concurrently moderate softness and high impact strength. In particular, the present invention relates to a heterophasic polypropylene composition comprising a propylene copolymer (A) matrix of propylene with ethylene and 1 -butene comonomer units and a propylene ethylene elastomer (B) dispersed within the matrix. Further, the present invention also relates to a preparation process for the heterophasic polypropylene composition in the presence of a Ziegler-Natta catalyst, and to articles comprising the heterophasic polypropylene composition as well as to the use of the heterophasic polypropylene composition in an article.

[0003] Background

[0004] Plastic packaging is widely used in daily life due to its good cost / performance balance. Polyolefin polymers based on polypropylene and / or polyethylene are often used in these applications. For adjusting the properties of these polymers, other comonomers of higher alpha-olefins, such as 1 -butene and 1 -hexene, are often employed. Employment of such kind of higher alpha-olefins allows for excellent flexibility in improving the properties of choice in the final polymer.

[0005] Heterophasic propylene copolymers are very often used in packaging applications due to their good balance of properties. For example, EP-A-3126411 describes a heterophasic propylene copolymer comprising a matrix being a propylene - C4 to C12 alpha-olefin copolymer and a propylene ethylene elastomer as the dispersed phase. This heterophasic propylene polymer is prepared using a single-site solid particulate catalyst. The exemplified polymers are characterized by good mechanical properties such as moderate to high flexibility, although their impact strength may still be improved. Moreover, providing polymers for application in a broad temperature range is generally desired, why improving temperature features is an important issue.

[0006] Object of the invention

[0007] It is thus an object of the present invention to provide new polypropylene compositions for application in a broad temperature range, wherein the polypropylene compositions can simultaneously offer high impact strength at moderate softness. In particular, polypropylene compositions for application in the packaging field, such as molded articles or films, are desired. Further, polypropylene compositions which can offer these properties with a low number of different components are highly desirable, as less complex polymer compositions can easily be subjected to recycling processes after use.

[0008] Summary of the invention

[0009] It has been surprisingly found that the above-described object can be achieved by a heterophasic polypropylene composition comprising a propylene copolymer (A) matrix of propylene with ethylene and 1 -butene comonomer units and a propylene ethylene elastomer (B) dispersed within the matrix, the heterophasic polypropylene composition comprising from 25 to 50 wt.-%, based on the total weight of the heterophasic polypropylene composition and determined at 25 °C according to ISO 16152, of a xylene soluble fraction (XS) comprising propylene comonomer units and, based on the total weight of the xylene soluble fraction (XS), ethylene comonomer units in a content in the range of from 18.0 to 35.0 wt.-%, and the xylene soluble fraction (XS) having an intrinsic viscosity IV, determined according to ISO 1628-1 & 3, in the range of from 1.8 to 3.0 dl / g; and wherein the heterophasic polypropylene composition comprises, based on the total weight of the heterophasic polypropylene composition and determined by13C-NMR spectroscopy, a content of 1 -butene comonomer units in the range of from 3.0 to 10.0 wt.-%, and a content of ethylene comonomer units in the range of from 5.0 to 15.0 wt.-%, and wherein the heterophasic polypropylene has: i.) a melt flow rate MFR2 (230 °C), determined according to ISO 1 133, in the range of from 0.1 to 20.0 g / 10 min, and ii.) a melting temperature Tm, determined according to differential scanning calorimetry (DSC) described in the specification, in the range of from 157 to 170 °C.

[0010] Based on the particular selection of the comonomers and their content in the polymer and the ethylene content in the xylene soluble fraction (XS), polymers with the described good balance of properties are obtained. The polymers are characterized by a higher melting temperature, and are, thus, applicable in a broad temperature range. They are moderately soft and have a high impact strength.

[0011] Further, it has been found that the above-described object is achieved by a process for the preparation of the heterophasic polypropylene composition according to the present invention by a multi-stage polymerization process, comprising

[0012] I.) preparing a first propylene polymer fraction (A1 ) being a propylene homopolymer or a propylene copolymer of propylene with ethylene comonomer units in a bulk phase reactor, preferably a loop reactor, in a first polymerization stage in the presence of a Ziegler-Natta catalyst;

[0013] II.) transferring the first propylene polymer fraction (A1 ) to a second polymerization stage and preparing a second propylene polymer fraction (A2) being a propylene copolymer of propylene with ethylene comonomer units and 1 -butene comonomer units in the presence of a Ziegler-Natta catalyst in a first gas phase reactor (GPR1 ); and wherein the first propylene polymer fraction (A1 ) and the second propylene polymer fraction (A2) together form a propylene copolymer (A); and

[0014] III.) transferring the propylene copolymer (A) to a third polymerization stage and preparing a propylene ethylene elastomer (B) as a third propylene polymer fraction in the presence of a Ziegler-Natta catalyst in a second gas phase reactor (GPR2), to obtain the heterophasic polypropylene composition.

[0015] The use of a Ziegler-Natta catalyst in the claimed process further allows to obtain the desired properties. By using new generations of this catalyst, employment of phthalate compounds can be avoided, and the risk of contamination of the final products with phthalate can be minimized.

[0016] Articles, preferably films and molded articles, comprising the heterophasic polypropylene composition, as well as the use of the heterophasic polypropylene composition in an article allow to provide articles with the good properties. These articles are characterized by the desired high melting temperature and at the same time are characterized by high impact strength at moderate softness.

[0017] Description of the invention

[0018] Heterophasic polypropylene composition

[0019] The present invention relates to a heterophasic polypropylene composition.

[0020] The heterophasic polypropylene composition according to the present invention comprises or consists of a propylene copolymer (A) matrix of propylene with ethylene and 1 -butene comonomer units and a propylene ethylene elastomer (B) dispersed within the matrix. Thus, the heterophasic polypropylene composition is a terpolymer of propylene, ethylene and 1 -butene. The term ‘heterophasic polypropylene composition’ as used herein means that at least two distinct phases are present in the composition, i.e., a propylene copolymer (A) and a propylene ethylene elastomer (B). The propylene copolymer (A) forms a crystalline matrix of the heterophasic polypropylene composition and the propylene ethylene elastomer (B) is dispersed in the crystalline matrix. Presence of the distinct phases is easily detectable via DSC analysis: the crystalline matrix propylene copolymer (A) will show a melting point higher than that of the propylene ethylene elastomer (B).

[0021] The term ‘propylene copolymer" as used herein denotes a polymer comprising, based on the total weight of the polymer, at least 50 wt.-% of propylene monomer units and further alpha-olefin comonomer units different from propylene.

[0022] The wording ‘alpha-olefin’ units (e.g., propylene, ethylene, 1 -butene units etc.) as used herein for contents of the polymer is to be understood to teach these units for preparing the polymer. The resultant polymer contains the respective units derived from these alpha-olefin monomer units.

[0023] Unless otherwise indicated, percentages throughout this disclosure are percentages by weight (wt.-%) based on the total weight of the respectively described enclosing entity.

[0024] The heterophasic polypropylene composition comprises from 25 to 50 wt.-%, preferably from 28 to 45 wt.-% and more preferably from 30 to 40 wt.-%, based on the total weight of the heterophasic polypropylene composition and determined at 25 °C according to ISO 16152, of a xylene soluble fraction (XS).

[0025] The xylene soluble fraction (XS) comprises propylene comonomer units and, based on the total weight of the xylene soluble fraction (XS), ethylene comonomer units in a content in the range of from 18.0 to 35.0 wt.-%, preferably from 19.0 to 34.0 wt.-% and more preferably from 20.0 to 33.0 wt.-%.

[0026] The xylene soluble fraction (XS) may further comprise 1 -butene comonomer units. Preferably, the xylene soluble fraction (XS) further comprises, based on the total weight of the xylene soluble fraction (XS), 1 -butene comonomer units in a content in the range of from 0.0 to 8.0 wt.-%, preferably from 3.0 to 7.5 wt.-% and more preferably from 3.5 to 7.0 wt.-%.

[0027] Accordingly, the xylene soluble fraction (XS) comprises or consists of propylene comonomer units, ethylene comonomer units and, optionally, 1 -butene comonomer units.

[0028] Preferably, the total content of ethylene and 1 -butene comonomer units in the xylene soluble fraction (XS) is, based on the total weight of the xylene soluble fraction (XS), in the range of from 18.0 to 43.0 wt.-%, preferably from 22.0 to 41.5 wt.-% and more preferably from 23.5 to 40.0 wt.-%.

[0029] Generally, the xylene soluble fraction (XS) comprises the propylene ethylene elastomer (B). Preferably, the xylene soluble fraction (XS) comprises the propylene ethylene elastomer (B) in a content of at least 50 wt.-%, more preferably at least 60 wt.-% and up to 100 wt.-% of, based on the total weight of the xylene soluble fraction (XS).

[0030] The xylene soluble fraction (XS) has an intrinsic viscosity IV, determined according to ISO 1628-1 & 3, in the range of from 1.8 to 3.0 dl / g, preferably from 1.9 to 2.8 dl / g and more preferably from 2.0 to 2.6 dl / g.

[0031] Generally, the heterophasic polypropylene composition further comprises a xylene insoluble fraction (XI) that respectively amounts to 50 to 75 wt.-% of the heterophasic polypropylene composition, based on the total weight of the heterophasic polypropylene composition and determined at 25 °C according to ISO 16152. Preferably, the xylene insoluble fraction (XI) comprises or consists of propylene comonomer units, ethylene comonomer units and 1 -butene comonomer units.

[0032] Generally, the xylene insoluble fraction (XI) comprises a higher content of the propylene copolymer (A). Preferably, the xylene insoluble fraction (XI) comprises the propylene copolymer (A) in a content of at least 70 wt.-%, more preferably at least 80 wt.-% and up to 100 wt.-% of, based on the total weight of the xylene insoluble fraction (XI).

[0033] Preferably, the xylene insoluble fraction (XI) and the xylene soluble fraction (XS) add up to 100 wt.-% of the propylene polymer content of the heterophasic polypropylene composition. More preferably, they add up to 100 wt.-% of the entire polymer content of the heterophasic polypropylene composition. However, it is to be understood that additives may additionally be present in the heterophasic polypropylene composition as defined below.

[0034] Thus, preferably, the heterophasic polypropylene composition consists of the xylene insoluble fraction (XI) and the xylene soluble fraction (XS) and optional additives.

[0035] The heterophasic polypropylene composition comprises, based on the total weight of the heterophasic polypropylene composition and determined by13C- NMR spectroscopy, a content of 1 -butene comonomer units in the range of from 3.0 to 10.0 wt.-%, preferably from 3.5 to 8.0 wt.-% and more preferably from 4.0 to 6.5 wt.-%, and a content of ethylene comonomer units in the range of from 5.0 to 15.0 wt.-%, preferably from 5.5 to 12.0 wt.-% and more preferably from 6.0 to 10.0 wt.-%.

[0036] Preferably, the content of both comonomer units together, i.e. the 1 -butene comonomer units and the ethylene comonomer units, amounts to from 8.0 to 25.0 wt.-%, more preferably from 9.0 to 20.0 wt.-% and most preferably from 10.0 to 16.5 wt.-%.

[0037] The heterophasic polypropylene composition has a melt flow rate MFR2 (230 °C), determined according to ISO 1133, in the range of from 0.1 to 20.0 g / 10 min, preferably from 0.8 to 15.0 g / 10 min and more preferably from 1.0 to 10.0 g / 10 min.

[0038] The heterophasic polypropylene composition is characterized by a high melting temperature Tm.

[0039] Accordingly, the heterophasic polypropylene composition has a melting temperature Tm, determined according to differential scanning calorimetry (DSC) described herein, in the range of from 157 to 170 °C, preferably from 158 to 167 °C and more preferably from 159 to 165 °C.

[0040] The heterophasic polypropylene composition has a first glass transition temperature Tgiand a second glass transition temperature Tg2 which are determined according to ISO 6721 -7. The first glass transition temperature Tgiis the glass transition temperature of the propylene copolymer (A) matrix, while the second glass transition temperature Tg2 is the glass transition temperature of the propylene ethylene elastomer (B). The first glass transition temperature Tgiis generally higher than the second glass transition temperature Tg2.

[0041] Preferably, the first glass transition temperature Tgiis in the range of from - 12 to + 2 °C, more preferably from - 10 to 0 °C and even more preferably from - 8 to - 2 °C. Preferably, the second glass transition temperature Tg2 is in the range of from - 55 to - 35 °C, more preferably from - 52 to - 37 °C and even more preferably from - 50 to - 38 °C.

[0042] Preferably, the heterophasic polypropylene composition is free of phthalic acid esters and their respective decomposition products.

[0043] The heterophasic polypropylene composition is characterized by a high melting temperature and concurrently a medium softness.

[0044] Preferably, the heterophasic polypropylene composition has a flexural modulus, determined according to ISO 178, in the range of from 300 to 700 MPa, more preferably from 350 to 600 MPa and most preferably from 400 to 550 MPa. The heterophasic polypropylene composition is further characterized by a relatively high impact strength (determined as the Charpy notched impact strength).

[0045] Preferably, the heterophasic polypropylene composition has an impact strength at +23 °C, determined according to ISO 179 / 1 eA, in the range of from 65.0 to 120.0 kJ / m2, more preferably from 70.0 to 100.0 kJ / m2and most preferably from 75.0 to 95.0 kJ / m2.

[0046] Preferably, the heterophasic polypropylene composition has a crystallization temperature Tc, determined according to differential scanning calorimetry (DSC) described herein, of above 1 14 °C for the non-nucleated heterophasic polypropylene composition, such as in the range of from 115 to 125 °C, more preferably from 1 15 to 124 °C and most preferably from 116 to 123 °C, and / or above 120 °C for the nucleated heterophasic polypropylene composition, such as in the range of from 121 to 135 °C, more preferably from 122 to 130 °C and most preferably from 123 to 129 °C. The term ‘nucleated’ refers to a-nucleation that may be conducted by the presence of an external nucleating agent, by the Borealis Nucleation Technology (BNT), or by a combination of both.

[0047] Preferably, propylene, 1 -butene and ethylene are the only monomers present in the heterophasic polypropylene composition. It is preferred that the heterophasic polypropylene composition is substantially free of units derived from other alphaolefin monomers (i.e., Cs to Cs alpha-olefin monomers), e.g., it comprises less than 0.10 wt.-%, preferably less than 0.05 wt.-%, and more preferably less than 0.01 wt.-% of other alpha-olefin monomers such as Cs to Cs alpha-olefin monomer units.

[0048] The comonomer contents in the heterophasic polypropylene composition, the xylene soluble fraction (XS) and in the propylene copolymers are determined by13C-NMR spectroscopy, as described in the method section.

[0049] The heterophasic polypropylene composition is preferably obtained by a polymerization process using a Ziegler-Natta catalyst. Preferably, the heterophasic polypropylene composition is produced using a Ziegler-Natta catalyst according to the preferred embodiments as described with respect to the preparation of the heterophasic polypropylene composition herein.

[0050] Preferably, the propylene copolymer (A) and the propylene ethylene elastomer (B) are the only propylene polymer components in the heterophasic polypropylene composition.

[0051] The weight ratio of the propylene ethylene elastomer (B) to the propylene copolymer (A) in the heterophasic polypropylene composition is preferably in the range of from 10:90 to 25:75, more preferably from 12:88 to 22:78. In other words, the heterophasic polypropylene composition preferably comprises, based on the total weight of the heterophasic polypropylene composition, from 75 to 90 wt.-%, more preferably from 78 to 88 wt.-%, of the propylene copolymer (A) and from 12 to 22 wt.-% of the propylene ethylene elastomer (B).

[0052] It is to be understood herein that the heterophasic polypropylene composition may comprise further components such as additives, which may optionally be added in a mixture with or without a carrier polymer (e.g., in a master batch).

[0053] Suitable additives include fillers, lubricants, processing aids, antioxidants, UV absorbers, light stabilizers, nucleating agents, foaming or blowing agents, clarifiers and pigments.

[0054] The additives may be present in a content in the range of from 0.1 to 10.0 wt.- %, preferably from 0.1 to 5.0 wt.-% and more preferably from 0.1 to 3.0 wt.-%, based on the total weight of the heterophasic polypropylene composition.

[0055] In one particular embodiment, a nucleating agent is used in a content of 0.05 to 0.2 wt.-%. One preferred nucleating agent is ADK STAB NA-71 , commercially available from Adeka, France, comprising more than 90 wt.-% of 2,2’- methylene bis-(2,6-di-tert. butylphenyl) phosphate lithium salt (CAS-No. 85209-93-4).

[0056] Propylene copolymer (A)

[0057] The propylene copolymer (A) forms the crystalline matrix of the heterophasic polypropylene composition. The propylene copolymer (A) is a copolymer of propylene with 1 -butene comonomer units and ethylene comonomer units.

[0058] Preferably, the propylene copolymer (A) has, based on the total weight of the propylene copolymer (A), a content of 1 -butene comonomer units in the range of from 2.0 to 6.0 wt.-%, more preferably from 2.5 to 5.5 wt.-%, and a content of ethylene comonomer units in the range of from 1 .0 to 3.9 wt.-%, more preferably from 1.5 to 3.5 wt.-%.

[0059] Preferably, propylene, 1 -butene and ethylene are the only comonomers present in the propylene copolymer (A). It is preferred that the propylene copolymer (A) is substantially free of units derived from other alpha-olefin monomers (i.e. , Cs to Cs alpha-olefin monomers), e.g., it comprises less than 0.10 wt.-%, preferably less than 0.05 wt.-%, and more preferably less than 0.01 wt.-% of other alphaolefin monomers such as Cs to Cs alpha-olefin monomer units.

[0060] The propylene copolymer (A) is preferably a multimodal polymer. The term ‘multimodal polymer" as used herein denotes a polymer composition comprising at least two polymer fractions, which have been produced under different polymerization conditions resulting in different (weight average) molecular weights and / or molecular weight distributions for the fractions and / or different comonomer contents. The prefix ‘multi’ relates to the number of different polymer fractions the polymer consists of. The term ‘multimodal polymer" comprises bimodal, trimodal, tetramodal etc. polymers.

[0061] More preferably, the propylene copolymer (A) is a bimodal polymer, i.e., it consists of or comprises two different polymer fractions, i.e., the first propylene polymer fraction (A1 ) and the second propylene polymer fraction (A2).

[0062] Preferably, the first propylene polymer fraction (A1 ) and the second propylene polymer fraction (A2) are prepared in an order of subsequent polymerization stages.

[0063] Preferably, the propylene copolymer (A) comprises, or consists of, from 30 to 70 wt.-%, based on the total weight of the propylene copolymer (A), of a first propylene polymer fraction (A1 ) being a propylene homopolymer or propylene copolymer of propylene with ethylene comonomer units, preferably being a propylene homopolymer, and from 30 to 70 wt.-%, based on the total weight of the propylene copolymer (A), of a second propylene polymer fraction (A2), being a propylene copolymer of propylene with ethylene comonomer units and 1- butene comonomer units.

[0064] In other words, the weight ratio of the first propylene polymer fraction (A1 ) to the second propylene polymer fraction (A2) in the propylene copolymer (A) is preferably in the range of from 30:70 to 70:30, more preferably from 35:65 to 65:35 and most preferably from 40:60 to 60:40.

[0065] The second propylene polymer fraction (A2) is different from the first propylene polymer fraction (A1 ). Preferably, the second propylene polymer fraction (A2) has a higher total content of comonomers than the first propylene polymer fraction (A1 ). More preferably, the second propylene polymer fraction (A2) has a higher content of ethylene comonomer units and 1 -butene comonomer units than the first propylene polymer fraction (A1 ).

[0066] Preferably, the propylene copolymer (A) has a molecular weight distribution Mw / Mn, being the ratio of the weight average molecular weight Mwand the number average molecular weight Mn, in the range of from 3.0 to 10.0, more preferably from 4.0 to 8.0 and most preferably 5.5 to 7.0.

[0067] The propylene copolymer (A) preferably has a melt flow rate MFR2 (230 °C), determined according to ISO 1133, in the range of from 0.5 to 30.0 g / 10 min, more preferably from 0.6 to 25.0 g / 10 min and most preferably from 0.7 to 20.0 g / 10 min. First propylene polymer fraction (A1)

[0068] The first propylene polymer fraction (A1 ) of the propylene copolymer (A) preferably consists of a single propylene polymer.

[0069] The propylene polymer of the first propylene polymer fraction (A1 ) preferably is a propylene homopolymer or propylene copolymer of propylene with ethylene comonomer units and optionally 1 -butene comonomer units.

[0070] More preferably, the first propylene polymer fraction (A1 ) has, based on the total weight of the first propylene polymer fraction (A1 ), a content of ethylene comonomer units in the range of from 0 to below 2.0 wt.-%, more preferably from 0 to below 1.0 wt.-%, and most preferably the first propylene polymer fraction (A1 ) is a propylene homopolymer.

[0071] The first propylene polymer fraction (A1 ) preferably has a melt flow rate MFR2 (230 °C), determined according to ISO 1133, in the range of from 0.2 to 10.0 g / 10 min, more preferably from 0.5 to 8.0 g / 10 min and most preferably from 0.8 to 6.0 g / 10 min.

[0072] Second propylene polymer fraction (A2)

[0073] The second propylene polymer fraction (A2) of the propylene copolymer (A) preferably consists of a single propylene polymer.

[0074] The propylene polymer of the second propylene polymer fraction (A2) preferably is a propylene copolymer of propylene with 1 -butene comonomer units and ethylene comonomer units.

[0075] The second propylene polymer fraction (A2) preferably has a melt flow rate MFR2 (230 °C), determined according to ISO 1133, in the range of from 0.1 to 20.0 g / 10 min, preferably from 0.8 to 15.0 g / 10 min and more preferably from 1.0 to 10.0 g / 10 min.

[0076] The MFR2 Of the second propylene polymer fraction (A2), produced in the second polymerization stage is determined according to equation (1 ): equation (1 ) wherein

[0077] MFR(A) is the MFR2 of the propylene copolymer (A) w(A 1) and w(A2) are the weight fractions of the propylene polymer fractions (A1 ) and (A2) in the propylene copolymer (A) MFR(A 1) is the MFR2 of the propylene polymer fraction (A1 ) produced in the first polymerization stage.

[0078] Respectively adapted equations may be used to determine the parameters of the second propylene polymer fraction (A2) or of polymers prepared in further polymerization stages of a preparation process.

[0079] Preferably, the second propylene polymer fraction (A2) has, based on the total weight of the second propylene polymer fraction (A2), a content of 1 -butene comonomer units in the range of from 6.0 to 18.0 wt.-%, more preferably from 8.0 to 16.0 wt.-% and most preferably from 10.0 to 15.0 wt.-%, and a content of ethylene comonomer units in the range of from 4.0 to 15.0 wt.-%, more preferably from 5.0 to 13.0 wt.-% and most preferably from 6.0 to 12.0 wt.-%.

[0080] Propylene ethylene elastomer (B)

[0081] The heterophasic polypropylene composition further comprises a propylene ethylene elastomer (B). The propylene ethylene elastomer (B) forms the dispersed phase that is dispersed in the crystalline matrix.

[0082] The propylene ethylene elastomer (B) is a copolymer of propylene and ethylene. Preferably, the propylene ethylene elastomer (B) is a unimodal propylene copolymer.

[0083] Preferably, the ethylene content in the propylene ethylene elastomer (B), based on the total weight of the propylene ethylene elastomer (B), is in the range of from 20 to 60 wt.-%, more preferably from 22 to 50 wt.-% and most preferably from 25 to 45 wt.-%. The ethylene content is determined by13C-NMR spectroscopy, as described in the method section.

[0084] The propylene ethylene elastomer (B) may comprise 1 -butene comonomer units. The content of 1 -butene comonomer units in the propylene ethylene elastomer (B) is preferably in the range of from 0 to 5.0 wt.-%.

[0085] Preferably, propylene and ethylene and optionally 1 -butene are the only monomers present in the propylene ethylene elastomer (B). It is preferred that propylene ethylene elastomer (B) is substantially free of units derived from other alpha-olefin monomers (i.e., Cs to Cs alpha-olefin monomers), e.g., it comprises less than 0.10 wt.-%, preferably less than 0.05 wt.-%, and more preferably less than 0.01 wt.-% of other alpha-olefin monomers such as Cs to Cs alpha-olefin monomer units.

[0086] Preferably, the propylene ethylene elastomer (B) has a molecular weight distribution Mw / Mn, being the ratio of the weight average molecular weight Mw and the number average molecular weight Mn, in the range of from 3.0 to 10.0, more preferably from 4.0 to 8.0 and most preferably 5.5 to 7.0.

[0087] Preparation of the heterophasic polypropylene composition

[0088] The heterophasic polypropylene composition according to the present invention may be prepared by any known process in the art. Ideally, a process is used which produces a homogenous mixture of the various components. Typically, compounding is employed. Compounding usually involves mixing or / and blending the various components in a molten state, often by extrusion.

[0089] Preferably, the heterophasic polypropylene composition is produced in a multistage process wherein the propylene polymers are produced in an order of subsequent stages.

[0090] In a preferred embodiment, the heterophasic polypropylene composition in any of the above-described embodiments is prepared by a multi-stage polymerization process, comprising

[0091] I.) preparing a first propylene polymer fraction (A1 ) being a propylene homopolymer or a propylene copolymer of propylene with ethylene comonomer units in a bulk phase reactor, preferably a loop reactor, in a first polymerization stage in the presence of a Ziegler-Natta catalyst;

[0092] II.) transferring the first propylene polymer fraction (A1 ) to a second polymerization stage and preparing a second propylene polymer fraction (A2) being a propylene copolymer of propylene with ethylene comonomer units and 1 -butene comonomer units in the presence of a Ziegler-Natta catalyst in a first gas phase reactor (GPR1 ); and wherein the first propylene polymer fraction (A1 ) and the second propylene polymer fraction (A2) together form a propylene copolymer (A); and

[0093] III.) transferring the propylene copolymer (A) to a third polymerization stage and preparing a propylene ethylene elastomer (B) as a third propylene polymer fraction in the presence of a Ziegler-Natta catalyst in a second gas phase reactor (GPR2), to obtain the heterophasic polypropylene composition.

[0094] The present invention also relates to a process for the preparation of a heterophasic polypropylene composition by a multi-stage polymerization process, comprising the above-described steps I.), II.) and III.). The process may lead to a heterophasic polypropylene composition in any of the above-described embodiments.

[0095] Accordingly, in step I.) of the process, propylene and optionally ethylene are fed into the bulk phase reactor to prepare the first propylene polymer fraction (A1 ). In step II.) of the process, propylene, 1 -butene and ethylene are fed into the first gas phase reactor (GPR1 ), where the first propylene polymer fraction (A1 ) has been previously placed, to prepare the second propylene polymer fraction (A2). The two propylene polymer fractions (A1 ) and (A2) form the propylene copolymer (A).

[0096] The propylene copolymer (A) is placed in a second gas phase reactor (GPR2), and propylene, ethylene and optionally 1 -butene are added in step III.) of the process, to prepare the heterophasic polypropylene composition. The process may further comprise blending the heterophasic composition with additives, extruding and / or pelletizing the heterophasic composition.

[0097] Generally, polymers produced in a multi-stage process are also designated as ‘in-situ’ blends. The resulting end product consists of an intimate mixture of the polymers from the three or more reactors. These three or more polymers may have different molecular weight distribution curves, and / or they may differ in terms of comonomer content or type. The end product thus contains a mixture of three or more polymers with differing properties, i.e. , it is a multimodal polymer mixture.

[0098] The first polymerization stage for producing the first propylene polymer fraction (A1 ) is preferably a slurry polymerization step. The slurry polymerization usually takes place in a liquid mixture of the employed monomers, preferably without the presence of an inert diluent, like a hydrocarbon diluent.

[0099] The temperature in the first polymerization stage is typically from 60 to 100 °C, preferably from 60 to 80 °C. An excessively high temperature should be avoided to prevent partial dissolution of the polymer into the liquid phase, the fouling of the reactor and early deactivation of the catalyst. The pressure is typically from 1 to 150 barg, preferably from 40 to 80 barg.

[0100] The slurry polymerization may be conducted in any known reactor used for slurry polymerization, such as any bulk phase reactor. Such reactors include a continuous stirred tank reactor and a loop reactor. It is especially preferred to conduct the polymerization in a loop reactor. In such reactors the slurry is circulated with a high velocity along a closed pipe by using a circulation pump. Loop reactors are generally known in the art and examples are given, for instance, in the patent applications US-A-4582816, US-A-3405109, US-A- 3324093, EP-A-479186 and US-A-5391654. It is thus preferred to conduct the first polymerization stage as a slurry polymerization in a loop reactor.

[0101] The slurry may be withdrawn from the reactor either continuously or intermittently. A preferred way of intermittent withdrawal is the use of settling legs where the slurry is allowed to concentrate before withdrawing a batch of the concentrated slurry from the reactor. The use of settling legs is disclosed, among others, in US-A-337421 1 , US-A-3242150 and EP-A-1310295. Continuous withdrawal is disclosed, among others, in EP-A-891990, EP-A-1415999, EP-A- 1591460 and WO-A-2007 / 025640. The continuous withdrawal is advantageously combined with a suitable concentration method, as disclosed in EP-A-1310295 and EP-A-1591460. It is preferred to withdraw the slurry from the first polymerization stage continuously.

[0102] Hydrogen is typically introduced into the first polymerization stage for controlling the MFR2 of the polymer. The amount of hydrogen needed to reach the desired MFR2 depends on the catalyst used and the polymerization conditions, as will be appreciated by the skilled worker.

[0103] The average residence time in the first polymerization stage is typically from 20 to 120 minutes, preferably from 30 to 80 minutes. As it is well known in the art the average residence time T can be calculated from equation (2) below: equation (2) wherein

[0104] VR is the volume of the reaction space (in case of a loop reactor, the volume of the reactor, in case of the fluidized bed reactor, the volume of the fluidized bed),

[0105] Qo is the volumetric flow rate of the product stream (including the polymer product and the fluid reaction mixture).

[0106] The production rate is suitably controlled with the catalyst feed rate. It is also possible to influence the production rate by suitable selection of the monomer concentration. The desired monomer concentration can then be achieved by suitably adjusting the propylene feed rate.

[0107] The first propylene polymer fraction (A1 ) is transferred to the second polymerization stage for producing the second propylene polymer fraction (A2) in a gas phase polymerization step, i.e. , carried out in a first gas-phase reactor (GPR1 ). Any suitable gas phase reactor known in the art may be used, such as a fluidized bed gas phase reactor.

[0108] For gas phase reactors, the reaction temperature used will generally be in the range 60 to 115 °C (e.g. 70 to 1 10 °C), the reactor pressure will generally be in the range 10 to 30 barg, and the residence time will generally be 1 to 8 hours. The gas used will commonly be a non-reactive gas such as nitrogen or low boiling point hydrocarbons such as propane together with monomer. A chain transfer agent (e.g., hydrogen) is typically added to the second polymerization stage.

[0109] In the first gas-phase reactor (GPR1 ), a mixture of the first propylene polymer fraction (A1 ) and the second propylene polymer fraction (A2) is formed being the propylene copolymer (A).

[0110] The propylene copolymer (A) is transferred to the third polymerization stage for producing the propylene ethylene elastomer (B) in a gas phase polymerization step, i.e. , carried out in a second gas-phase reactor (GPR2). Any suitable gas phase reactor known in the art may be used, such as a fluidized bed gas phase reactor. The condition range described above for the first gas phase reactor are similarly used for the second gas phase reactor.

[0111] A preferred multistage process is the above-identified slurry-gas phase process, such as developed by Borealis and known as the Borstar® technology. In this respect, reference is made to the European patent applications EP-A-0887379 and EP-A-0517868.

[0112] The process may comprise one or more further polymerization stage(s) / step(s). Particularly preferred is a prepolymerization step, which precedes the polymerization step I.).

[0113] The purpose of the prepolymerization is to polymerize a small amount of polymer onto the catalyst at a low temperature and / or a low monomer concentration. By prepolymerization, it is possible to improve the performance of the catalyst in slurry and / or modify the properties of the final polymer. The prepolymerization step is typically conducted in slurry.

[0114] Thus, the prepolymerization step may be conducted in a loop reactor. The prepolymerization is again preferably conducted in liquid propylene, without the presence of an inert diluent, like a hydrocarbon diluent.

[0115] The temperature in the prepolymerization step is typically from 0 to 60 °C, preferably from 10 to 50 °C and more preferably from 15 to 40 °C.

[0116] The pressure is not critical and is typically from 1 to 150 barg, preferably from 40 to 80 barg.

[0117] The amount of monomer is typically such that from 0.1 to 1000 grams of monomer per one gram of solid catalyst component is polymerized in the prepolymerization step. As the person skilled in the art knows, the catalyst particles recovered from a continuous prepolymerization reactor do not all contain the same amount of prepolymer. Instead, each particle has its own characteristic amount which depends on the residence time of that particle in the prepolymerization reactor. As some particles remain in the reactor for a relatively long time and some for a relatively short time, then also the amount of prepolymer on different particles is different and some individual particles may contain an amount of prepolymer which is outside the above limits. However, the average amount of prepolymer on the catalyst typically is within the limits specified above.

[0118] The molecular weight of the prepolymer may be controlled by hydrogen as it is known in the art. Further, antistatic additives may be used to prevent the particles from adhering to each other or the walls of the reactor, as disclosed in WO-A- 96 / 19503 and WO-A-96 / 32420.

[0119] The catalyst components are preferably all introduced to the prepolymerization step when a prepolymerization step is present. However, where the solid catalyst component and the cocatalyst can be fed separately it is possible that only a part of the cocatalyst is introduced into the prepolymerization stage and the remaining part into subsequent polymerization stages. In such cases it is necessary to introduce as much cocatalyst into the prepolymerization stage that a sufficient polymerization reaction is obtained therein.

[0120] It is understood within the scope of the invention, that the amount of polymer produced in the prepolymerization typically lies within 1 .0 to 5.0 wt.-%, based on the total weight of the heterophasic propylene composition. This polymer is counted as part of the first propylene polymer fraction (A1 ).

[0121] The heterophasic polymer composition is preferably obtained by a polymerization process using a Ziegler-Natta catalyst. In a preferred embodiment, a Ziegler-Natta catalyst is used in all stages of the polymerization process.

[0122] Preferably, the Ziegler-Natta catalyst comprises: a) compound(s) of a transition metal of Group 4 to 6 of IIIPAC; b) a Group 2 metal compound; c) an internal donor, wherein said internal donor is a non-phthalic compound, preferably is a non-phthalic acid ester; d) a co-catalyst; and e) optionally an external donor.

[0123] The internal donor is preferably selected from (di)esters of non-phthalic carboxylic (di)acids, 1 ,3-diethers, derivatives and mixtures thereof. Most preferred internal donors are (di)esters of citraconic acid. Preferably, the Ziegler-Natta catalyst does not comprise phthalic acid esters, and the heterophasic polypropylene composition is free of phthalic acid esters and their respective decomposition products.

[0124] Suitable Ziegler-Natta catalysts for use in the above-described polymerization reactions and preparation thereof are described in EP-A-3562850.

[0125] It will be appreciated that the propylene polymers may contain standard polymer additives as described above.

[0126] After preparation, the obtained polymer is typically extruded and pelletized. The extrusion may be conducted in the manner generally known in the art, preferably in a twin screw extruder. One example of suitable twin screw extruders is a corotating twin screw extruder. Those are manufactured, among others, by Coperion or Japan Steel Works. Another example is a counter-rotating twin screw extruder. Such extruders are manufactured, among others, by Kobe Steel and Japan Steel Works. Before the extrusion at least part of the desired additives, as mentioned above, are preferably mixed with the polymer. The extruders typically include a melting section where the polymer is melted and a mixing section where the polymer melt is homogenized. Melting and homogenization are achieved by introducing energy into the polymer. Suitable level of specific energy input (SEI) is from about 150 to about 450 kWh / ton polymer, preferably from 175 to 350 kWh / ton.

[0127] Article and use

[0128] The present invention also relates to an article comprising the heterophasic polypropylene composition according to the invention in any of the abovedescribed embodiments, and to the use of the heterophasic polypropylene composition in an article. Preferable articles include films and molded articles.

[0129] The articles according to the invention may be employed in a number of end applications, in particular food and non-food packaging applications as well as medical packaging applications.

[0130] As used herein the term 'molded article’ denotes an article that is produced by any conventional molding technique, e.g., injection molding, extrusion blow molding, stretch molding, compression molding, rotomolding or injection stretch blow molding. Articles produced by injection molding, extrusion blow molding, or injection stretch blow molding are preferred. Articles produced by extrusion blow molding are especially preferred. The molded articles preferably are thin-walled articles having a wall thickness of 300 pm to 2 mm. More preferably, the thinwalled articles have a wall thickness of 300 pm to 1400 pm, and even more preferably the thin-walled articles have a wall thickness of 500 pm to 900 pm. The molded articles of the present invention can be containers, such as bottles, canisters, wide-mouth containers, jars, or the like.

[0131] The films may be prepared by any method known in the art, such as cast film extrusion or blown film extrusion, the latter being preferred. The films may be multilayer or monolayer films, with the core layer consisting of the heterophasic polypropylene composition according to the invention. Preferably, the films are non-oriented films. In one embodiment, the films are monolayer films consisting of the heterophasic polypropylene composition according to the invention as the sole polymer component. Generally, the articles are characterized by a moderate softness and application thereof at higher temperatures (e.g. of about 150 °C) is possible.

[0132] Measurement methods

[0133] All parameters mentioned in the description of the invention or the examples were measured according to the methods described below.

[0134] Melt Flow Rate

[0135] The melt flow rate (MFR) was determined according to ISO 1133 and is indicated in g / 10 min. The MFR is an indication of the melt viscosity of the polymer. The MFR is determined at 190 °C for PE and 230 °C for PP. The load under which the melt flow rate is determined is usually indicated as a subscript, for instance MFR2 is measured under 2.16 kg load (condition D).

[0136] Description of microstructure quantification by NMR spectroscopy

[0137] Quantitative nuclear-magnetic resonance (NMR) spectroscopy was used to quantify the comonomer content of the polymers.

[0138] Quantitative13C{1H} NMR spectra were recorded in the molten-state using a Bruker Avance III 500 NMR spectrometer operating at 500.13 and 125.76 MHz for1H and13C respectively. All spectra were recorded using a13C optimised 7 mm magic-angle spinning (MAS) probehead at 180°C using nitrogen gas for all pneumatics. Approximately 200 mg of material was packed into a 7 mm outer diameter zirconia MAS rotor and spun at 4 kHz. This setup was chosen primarily for the high sensitivity needed for rapid identification and accurate quantification {klimke06, parkinson07, castignolles09}. Standard single-pulse excitation was employed utilising the NOE at short recycle delays of 3s {pollard04, klimke06} and the RS-HEPT decoupling scheme {fillip05, griffin07}. A total of 1024 (1 k) transients were acquired per spectra.

[0139] Quantitative13C{1H} NMR spectra were processed, integrated and relevant quantitative properties determined from the integrals. All chemical shifts are internally referenced to the methyl isotactic pentad (mmmm) at 21.85 ppm and assignments done according {brandoliniOl , randall89, resconiOO}.

[0140] Characteristic signals corresponding to the incorporation of 1 -butene were observed and the comonomer content quantified in the following way. The amount isolated 1 -butene incorporated in PBP sequences was quantified using the integral of the aB2 sites at 43.6 ppm accounting for the number of reporting sites per comonomer:

[0141] B = l«B2 / 2 If observed the amount consecutively incorporated 1 -butene in PBBP sequences was quantified using the integral of the aaB2 site at 40.6 ppm accounting for the number of reporting sites per comonomer:

[0142] BB = 2 * laaB2

[0143] In case of presence of consecutively incorporated 1 -butene (BB) the isolated incorporated butene (B) needs to be corrected due to influencing signals by subtracting BB / 2.

[0144] Characteristic signals corresponding to different incorporations of ethylene were observed and the comonomer content quantified utilising following assignments and equations for the respective sequences:

[0145] The amount of P was quantified based on the Saa methylene site including additional propene units not covered by Saa:

[0146] P= Isacc + B + (0.5*BB) + E + (0.5*EE)

[0147] The total amount of comonomers was then calculated as follows:

[0148] Btotai = B + B B Etotai = E + E E + E E E Ptotai = P

[0149] B[mol%] = 100* Btotai I ( Btotai + Etotal + Ptotai)

[0150] E[mol%] = 100* Etotal I ( Btotai + Etotal + Ptotai)

[0151] P[mol%] = 100* Ptotai I ( Btotai + Etotal + Ptotai)

[0152] The weight percent comonomer incorporation was calculated from the mol%:

[0153] B [wt.-%] = 100*(B[mol%]*56.11 ) / ((E[mol%] *28.05) + (B[mol%] *56.11 ) + (P[mol%]*42.08))

[0154] For e.g. xylene soluble fraction where butene was not observed the related equations collapse to the following:

[0155] P= Iscca + E + (0.5*EE)

[0156] The total amount of comonomer was then calculated as follows:

[0157] Etotal = E + E E + E E E Ptotal = P

[0158] E[mol%] = 100* Etotal I ( Etotal + Ptotal)

[0159] P[mol%] = 100* Ptotal I ( Etotal + Ptotal)

[0160] The weight percent comonomer incorporation was calculated from the mol%:

[0161] E [wt.-%] = 100*(E[mol%]*28.05) / ((E[mol%] *28.05) + (P[mol%]*42.08))

[0162] References klimke06 : Klimke, K., Parkinson, M., Piel, C., Kaminsky, W., Spiess, H.W., Wilhelm, M., Macromol. Chem. Phys. 2006;207:382. parkinson07: Parkinson, M., Klimke, K., Spiess, H.W., Wilhelm, M., Macromol. Chem. Phys. 2007;208:2128. pollard04: Pollard, M., Klimke, K., Graf, R., Spiess, H.W., Wilhelm, M., Sperber, O., Piel, C., Kaminsky, W., Macromolecules 2004;37:813. filip05: Filip, X., Tripon, C., Filip, C., J. Mag. Resn. 2005, 176, 239 griffin07: Griffin, J.M., Tripon, C., Samoson, A., Filip, C., and Brown, S.P., Mag. Res. in Chem. 2007 45, S1 , S198 castignolles09: Castignolles, P., Graf, R., Parkinson, M., Wilhelm, M., Gaborieau, M., Polymer 50 (2009) 2373 resconiOO: Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253 randall89: J. Randall, Macromol. Sci., Rev. Macromol. Chem. Phys. 1989, C29, 201. brandoliniOl : A. J. Brandolini, D.D. Hills, “NMR spectra of polymers and polymer additives”, Marcel Deker Inc., 2000 abis86: L. Abis, Mackromol. Chem. 187, 1877-1886 (1986)

[0163] Molecular weight and molecular weight distribution

[0164] Molecular weight averages (Mz, Mwand Mn), Molecular weight distribution (MWD) and its broadness, described by polydispersity index, PDI= Mw / Mn(wherein Mnis the number average molecular weight and Mw is the weight average molecular weight) were determined by Gel Permeation Chromatography (GPC) according to ISO 16014-1 :2003, ISO 16014-2:2003, ISO 16014-4:2003 and ASTM D 6474- 12 using the following formulas:

[0165] For a constant elution volume interval AV,, where At, and Mi are the chromatographic peak slice area and polyolefin molecular weight (MW), respectively associated with the elution volume, Vi, where N is equal to the number of data points obtained from the chromatogram between the integration limits.

[0166] A high temperature GPC instrument, equipped with either infrared (IR) detector (IR4 or IR5) from PolymerChar (Valencia, Spain) or differential refractometer (Rl) from Agilent Technologies, equipped with 3x Agilent-PLgel Olexis and 1x Agilent- PLgel Olexis Guard columns was used. As the solvent and mobile phase 1 ,2,4- trichlorobenzene (TCB) stabilized with 250 mg / L 2,6-Di-tert-butyl-4-methyl- phenol) was used. The chromatographic system was operated at 160 °C and at a constant flow rate of 1 mL / min. 200 pL of sample solution was injected per analysis. Data collection was performed using either Agilent Cirrus software version 3.3 or PolymerChar GPC-IR control software.

[0167] The column set was calibrated using universal calibration (according to ISO 16014-2:2003) with 19 narrow MWD polystyrene (PS) standards in the range of 0.5 kg / mol to 11500 kg / mol. The PS standards were dissolved at room temperature over several hours. The conversion of the polystyrene peak molecular weight to polyolefin molecular weights is accomplished by using the Mark Houwink equation and the following Mark Houwink constants:

[0168] KPS = 19 x 10~3mL / g, aPS= 0.655

[0169] KPE= 39 x 10-3mL / g, aPE= 0. 725

[0170] KPP= 19 x 10-3mL / g, aPP= 0. 725

[0171] A third order polynomial fit was used to fit the calibration data. All samples were prepared in the concentration range of 0.5 to 1 mg / ml and dissolved at 160 °C for 2.5 hours (PP) or 3 hours (PE) under continuous gentle shaking.

[0172] Flexural Modulus (FM)

[0173] The flexural modulus was determined in a 3-point-bending test at 23 °C according to ISO 178 on 80x10x4 mm3test bars injection molded in line with ISO 1873-2.

[0174] Glass transition temperature (Tg)

[0175] The glass transition temperatures Tgiand Tg2 were determined by dynamic mechanical analysis according to ISO 6721 -7.

[0176] The measurements were done in torsion mode on compression molded samples (40x10x1 mm3) between -100 °C and +150 °C with a heating rate of 2 °C / min and a frequency of 1 Hz.

[0177] Differential scanning calorimetry (DSC)

[0178] Differential scanning calorimetry (DSC) analysis, melting temperature (Tm), melt enthalpy (Hm) and crystallization temperature (Tc) were 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 / cool / heat cycle with a scan rate of 10 °C / min in the temperature range of -30 to +225 °C. Crystallization temperature (Tc) was determined from the cooling step, while melting temperature (Tm) and melt enthalpy (Hm) were determined from the second heating step.

[0179] Throughout the present description, the term Tm is understood as peak temperature of melting as determined by DSC at a heating rate of 10 K / min.

[0180] Throughout the present description, the term Tc is understood as peak temperature of crystallization as determined by DSC at a cooling rate of 10 K / min.

[0181] Notched Impact Strength (NIS)

[0182] The Charpy notched impact strength (NIS) was measured according to ISO 179 1 eA at +23 °C using injection molded bar test specimens of 80x10x4 mm3prepared in accordance with ISO 1873-2. Xylene soluble fraction (XS) and xylene insoluble fraction (XI)

[0183] The xylene soluble fraction (XS) and xylene insoluble fraction (XI) were determined according to ISO 16152 at 25 °C.

[0184] Intrinsic viscosity (IV)

[0185] The IV of the xylene solubles was measured at 135 °C in decalin according to ISO 1628-1 & 3.

[0186] Examples

[0187] Preparation of the heterophasic polypropylene composition

[0188] Two heterophasic polypropylene compositions according to the invention were prepared as Inventive Examples IE1 and IE2 in a multi-stage polymerization process as described above, under the conditions outlined in Table 1. The catalyst was a Ziegler-Natta catalyst prepared as described in EP-A-3562850. The solid catalyst component was used along with triethylaluminium (TEAL) as co-catalyst and dicyclo pentyl dimethoxy silane (D-donor) as external donor.

[0189] Additionally, Comparative Examples CE1 and CE2 were prepared as outlined in Table 1 . The process for the preparation of the comparative examples contained the similar number of stages as the process for the preparation of the inventive examples. However, the comparative examples are random-heterophasic copolymers comprising only propylene and ethylene.

[0190] Table 1: Process conditions

[0191] The polymers prepared above were mixed with 0.25 wt.-% of Irganox B215 (a synergistic 2: 1 blend of antioxidants Irgafos 168 (tris(2,4- ditertbutylphenyl)phosphite, CAS No: 31570-04-4) and Irganox 1010 (pentaerythritol tetrakis[3-[3,5-di-tert-butyl-4-hydroxyphenyl]propionate], CAS No: 6683-19-8, commercially available from BASF SE, Germany) and 0.05 wt.- % of CEASIT Fl (Ca-stearate, CAS No: 1592-23-0, commercially available from Baerlocher GmbH, Germany), and then compounded in a twin screw extruder ZSK 18, with melt temperature of 200-220 °C and throughput of 7 kg / h. Pelletization of the polymers took place in the presence or absence of a nucleating agent (as indicated in Table 2).

[0192] Properties of the heterophasic polypropylene composition

[0193] Properties of the polymer compositions (prepared as pellets) were measured and are summarized in Table 2 below. Table 2: Properties of the polymer compositions

[0194] *IE2 contains 1000 ppm ADK STAB NA-71 , commercially available from Adeka, France, as the nucleating agent

[0195] **CE2 was prepared using the Borealis Nucleation Technology (BNT), as described e.g. in EP 2960279.

[0196] The inventive examples have high melting temperatures of above 160 °C, while the comparative examples have melting temperatures of 15 to 20 °C lower. All examples have a flexural modulus in a moderate softness range, with the inventive examples being softer. The Charpy notched impact strength is increased in the inventive examples.

Claims

Claims1. A heterophasic polypropylene composition comprising a propylene copolymer (A) matrix of propylene with ethylene and 1 -butene comonomer units and a propylene ethylene elastomer (B) dispersed within the matrix, the heterophasic polypropylene composition comprising from 25 to 50 wt.-%, based on the total weight of the heterophasic polypropylene composition and determined at 25 °C according to ISO 16152, of a xylene soluble fraction (XS) comprising propylene comonomer units and, based on the total weight of the xylene soluble fraction (XS), ethylene comonomer units in a content in the range of from 18.0 to 35.0 wt.-%, and the xylene soluble fraction (XS) having an intrinsic viscosity IV, determined according to ISO 1628-1 & 3, in the range of from 1 .8 to 3.0 dl / g; and wherein the heterophasic polypropylene composition comprises, based on the total weight of the heterophasic polypropylene composition and determined by13C-NMR spectroscopy, a content of 1 -butene comonomer units in the range of from 3.0 to 10.0 wt.-%, and a content of ethylene comonomer units in the range of from 5.0 to 15.0 wt.-%, and wherein the heterophasic polypropylene has: i.) a melt flow rate MFR2, determined according to ISO 1133 at 230 °C, in the range of from 0.1 to 20.0 g / 10 min, and ii.) a melting temperature Tm, determined according to differential scanning calorimetry (DSC) described in the specification, in the range of from 157 to 170 °C.

2. The heterophasic polypropylene composition according to claim 1 , wherein the heterophasic polypropylene composition has a first glass transition temperature Tgi, determined according to ISO 6721 -7, in the range of from - 12 to + 2 °C and second glass transition temperature Tg2 in the range of from - 55 to - 35 °C.

3. The heterophasic polypropylene composition according to any one of the preceding claims, wherein the heterophasic polypropylene composition has a flexural modulus, determined according to ISO 178, in the range of from 300 to 700 MPa.

4. The heterophasic polypropylene composition according to any one of the preceding claims, wherein the heterophasic polypropylene composition has an impact strength at +23 °C, determined according to ISO 179 / 1 eA, in the range of from 65.0 to 120.0 kJ / m2.

5. The heterophasic polypropylene composition according to any one of the preceding claims, wherein the heterophasic polypropylene composition has a crystallization temperature Tc, determined according to differential scanning calorimetry (DSC) described in the specification, in the range of from 115 to 125 °C for the non-nucleated heterophasic polypropylene composition and / or in the range of from 121 to 135 °C for the nucleated heterophasic polypropylene composition.

6. The heterophasic polypropylene composition according to any one of the preceding claims, wherein the heterophasic polypropylene composition is free of phthalic acid esters and their respective decomposition products.

7. The heterophasic polypropylene composition according to any one of the preceding claims, wherein the propylene copolymer (A) is a multimodal propylene copolymer, and / or the propylene ethylene elastomer (B) is a unimodal propylene copolymer.

8. The heterophasic polypropylene composition according to any one of the preceding claims, wherein the heterophasic polypropylene composition comprises, based on the total weight of the heterophasic polypropylene composition, from 75 to 90 wt.-% of propylene copolymer (A) and from 10 to 25 wt.-% of propylene ethylene elastomer (B).

9. The heterophasic polypropylene composition according to any one of the preceding claims, wherein the propylene copolymer (A) comprises two different propylene polymer fractions: a) 30 to 70 wt.-%, based on the total weight of the propylene copolymer (A), of a first propylene polymer fraction (A1 ) being a propylene homopolymer or propylene copolymer of propylene with ethylene comonomer units, preferably being a propylene homopolymer, and b) 30 to 70 wt.-%, based on the total weight of the propylene copolymer (A), of a second propylene polymer fraction (A2), being a propylene copolymer of propylene with ethylene comonomer units and 1 -butene comonomer units.

10. The heterophasic polypropylene composition according to any one of the preceding claims, wherein the propylene copolymer (A) comprises, based on the total weight of the propylene copolymer (A) and determined by13C- NMR spectroscopy, a content of 1 -butene comonomer units in the range of from 2.0 to 6.0 wt.-%, and a content of ethylene comonomer units in the range of from 1 .0 to 3.9 wt.-%.

11. A process for the preparation of the heterophasic polypropylene composition according to any one of the preceding claims by a multi-stage polymerization process, comprisingI.) preparing a first propylene polymer fraction (A1 ) being a propylene homopolymer or a propylene copolymer of propylene with ethylene comonomer units in a bulk phase reactor, preferably a loop reactor, in a first polymerization stage in the presence of a Ziegler-Natta catalyst;II.) transferring the first propylene polymer fraction (A1 ) to a second polymerization stage and preparing a second propylene polymer fraction (A2) being a propylene copolymer of propylene with ethylene comonomer units and 1 -butene comonomer units in the presence of a Ziegler-Natta catalyst in a first gas phase reactor (GPR1 ); and wherein the first propylene polymer fraction (A1 ) and the second propylene polymer fraction (A2) together form a propylene copolymer (A); andIII.) transferring the propylene copolymer (A) to a third polymerization stage and preparing a propylene ethylene elastomer (B) as a third propylene polymer fraction in the presence of a Ziegler-Natta catalyst in a second gas phase reactor (GPR2), to obtain the heterophasic polypropylene composition.

12. The process according to claim 1 1 , wherein the Ziegler-Natta catalyst comprises: a) compound(s) of a transition metal of Group 4 to 6 of IIIPAC; b) a Group 2 metal compound; c) an internal donor, wherein said internal donor is a non-phthalic compound, preferably is a non-phthalic acid ester; d) a co-catalyst; and e) optionally an external donor.

13. The process according to claim 12, wherein the internal donor is preferably selected from (di)esters of non-phthalic carboxylic (di)acids, 1 ,3-diethers, derivatives and mixtures thereof.

14. An article comprising the heterophasic polypropylene composition according to any one of claims 1 to 10, preferably being a film or a molded article.

15. Use of the heterophasic polypropylene composition according to any one of claims 1 to 10 in an article, preferably being a film or a molded article.

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