Polypropylene composition with improved toughness / multiaxial impact at low temperature

Abstract

The present invention relates to a polypropylene composition comprising: a base polymer matrix comprising a first heterophasic propylene copolymer and a second heterophasic propylene copolymer, an impact modifier comprising a first rubber component and a second rubber component, and optionally an inorganic filler; the compositions exhibit an improved balance of impact properties and stiffness, in particular improved toughness / multi-axis instrument impact (MAI) at very low temperatures. The invention also relates to a method for preparing the polymer composition. The invention also relates to articles made from the polymer composition, and to the use of the polymer composition in automobiles, in particular for injection molded articles.

Description

[0001] The present invention relates to a polymer composition having an improved balance of impact properties and rigidity, in particular improved toughness / multiaxial instrumented impact (MAI) at low temperatures. The polymer composition comprises: a base polymer matrix comprising a first multiphase propylene copolymer and a second multiphase propylene copolymer; an impact modifier comprising a first rubber component and a second rubber component; and optionally an inorganic filler. The present invention also relates to a method for preparing the polymer composition. The present invention also relates to an article made from the polymer composition, and to the use of the polymer composition in the automotive industry, in particular for injection-molded articles.

[0002] Polypropylene has been widely used in different applications, such as packaging, construction and building, foams and lightweight articles, consumer goods, fibers, and automotive. For decades, the flexibility to design polypropylene characteristics and customize properties for various applications has been extensively developed. Compared to polyethylene, polypropylene compositions and articles made therefrom offer better rigidity, high heat resistance, and improved chemical resistance. However, especially at low temperatures, particularly in sub-zero environments, such as at -20 °C or -30 °C, the poor impact properties of polypropylene severely affect performance. Under such low-temperature conditions, injection-molded components generally have very little toughness, and even a small impact can cause component damage that may compromise safety. Therefore, several methods have been employed to achieve a balance of desired properties in polypropylene, such as producing polypropylene in a multistage reactor, performing post-reactor modification in an extruder, compounding or blending with elastomers and / or plastomers.

[0003] WO2012152803A1 discloses highly filled soft multiphase compositions having a Shore hardness D below 50, an elongation at break above 250%, and a tensile strength at break equal to or higher than 10 MPa. An improved balance of flexibility, toughness, and impact at low temperatures is also disclosed.

[0004] WO201591372A1 discloses thermoplastic polypropylene compositions and filled compositions thereof comprising talc as a mineral filler for producing molded articles for interior and exterior parts having good processability and improved surface properties.

[0005] WO2021130122A1 discloses a polypropylene (PP)-based polymer composition comprising a first multiphase PP copolymer, a second multiphase PP copolymer, and optionally an inorganic filler, having a high heat distortion temperature and good tiger stripe performance.

[0006] WO202213051A1 discloses a polypropylene composition comprising two different polypropylenes and an ethylene polymer (PE) selected from ethylene-based plastomers and LDPE, and articles made from said composition. Also disclosed is a polypropylene composition having good total light transmittance and a beneficial balance of stiffness and impact properties.

[0007] WO202234208A1 discloses a composition comprising: two heterophasic propylene copolymers, one produced using a metallocene catalyst and having a low total ethylene content, while the other heterophasic propylene copolymer has a higher ethylene content; a plastomer, talc and optionally high density polyethylene (HDPE). The composition is said to exhibit high scratch resistance and reduced emission values (VOC, FOG) for automotive articles, especially automotive interior articles, without compromising mechanical properties (stiffness and impact).

[0008] There is a continuing need to provide polymer compositions that can provide an improved balance of impact properties and stiffness, especially improved toughness or multi-axial instrumented impact at low temperatures while maintaining flowability.

[0009] Accordingly, an object of the present invention is to at least partially address one or more of the foregoing needs.

[0010] An object of the present invention is to provide a polymer composition having improved toughness / multi-axial instrumented impact at low temperatures while maintaining desired stiffness and flowability.

[0011] This object is achieved by a polymer composition comprising:

[0012] a base polymer matrix of 45.5 to 74.5 wt% based on the total weight of the polymer composition,

[0013] an impact modifier of 7.5 to 34.5 wt% based on the total weight of the polymer composition, and

[0014] optionally an inorganic filler;

[0015] wherein the base polymer matrix is a polypropylene-based heterophasic resin comprising a first heterophasic propylene copolymer (HECO1) and a second heterophasic propylene copolymer (HECO2);

[0016] wherein the first heterophasic propylene copolymer (HECO1) is 21.5 to 57.4 wt% and has a melt flow rate of 42.5 to 120.8 dg / min measured at 230 °C with a 2.16 kg load according to ISO1133-1:2011;

[0017] wherein the second multiphase propylene copolymer (HECO2) is from 10.2 to 45.4% by weight and has a melt flow rate of from 5.6 to 65 dg / min measured at 230 °C with a 2.16 kg load according to ISO 1133-1:2011;

[0018] wherein the impact modifier comprises a first rubber component (ER1) and a second rubber component (ER2) selected from ethylene-based copolymers, plastomers or elastomers and combinations thereof.

[0019] Surprisingly, it has been found that the polymer compositions according to the invention have high toughness / multi-axial instrumented impact at low temperatures while maintaining the desired rigidity and flowability.

[0020] Base polymer matrix

[0021] The amount of the base polymer matrix in the polymer composition is from 45.5 to 74.5% by weight, preferably from 48.6 to 70.8% by weight, more preferably from 51.2 to 68.7% by weight, even more preferably from 55.3 to 66.8% by weight, based on the total weight of the polymer composition.

[0022] The base polymer matrix is a polypropylene-based multiphase resin which comprises a first multiphase propylene copolymer (HECO1) and a second multiphase propylene copolymer (HECO2).

[0023] Multiphase propylene copolymer

[0024] Multiphase propylene copolymers generally have a two-phase structure which comprises a propylene-based semi-crystalline polymer as the matrix and an elastomer or rubber, usually an ethylene-α-olefin rubber, as the dispersed phase. Multiphase propylene copolymers are generally prepared in a multi-stage polymerization process.

[0025] First multiphase propylene copolymer (HECO1)

[0026] The amount of the first multiphase propylene copolymer (HECO1) is from 21.5 to 57.4% by weight, preferably from 23.6 to 55.8% by weight, more preferably from 25.2 to 52.7% by weight, even more preferably from 27.2 to 46.6% by weight, based on the total weight of the polymer composition.

[0027] The first multiphase propylene copolymer (HECO1) preferably comprises a first propylene polymer (a1) as the matrix and a first ethylene-α-olefin copolymer (a2) as the dispersed phase.

[0028] The amount of the first propylene polymer (a1) is preferably from 80 to 92% by weight, more preferably from 85 to 90% by weight, based on the total amount of the first multiphase propylene copolymer (HECO1).

[0029] In the first multiphase propylene copolymer (HECO1), the first propylene polymer (a1) can be a propylene homopolymer and / or a propylene-α-olefin copolymer, where the α-olefin has 2 or 4 to 20 carbon atoms. For example, the propylene-α-olefin can be a propylene-ethylene copolymer or a propylene-butene copolymer. Preferably, in the first multiphase propylene copolymer (HECO1), the first propylene polymer (a1) is a propylene homopolymer.

[0030] In the first multiphase propylene copolymer (HECO1), the melt flow rate (MFR) of the first propylene polymer (a1) is preferably 150 to 300 dg / min, more preferably 180 to 270 dg / min, and even more preferably 200 to 250 dg / min, measured according to ISO 1133-1:2011 at 230 °C with a 2.16 kg load.

[0031] The amount of the first ethylene-α-olefin copolymer (a2) is preferably 8 to 20% by weight, more preferably 10 to 15% by weight, based on the total amount of the first multiphase propylene copolymer (HECO1).

[0032] In the first multiphase propylene copolymer (HECO1), the amount of the structural part derived from ethylene is preferably 40 to 53% by weight, based on the total amount of the first ethylene-α-olefin copolymer (a2).

[0033] In the first multiphase propylene copolymer (HECO1), the α-olefin structural part in the first ethylene-α-olefin copolymer (a2) preferably is derived from at least one α-olefin having 3 to 20 carbon atoms. For example, the first ethylene-α-olefin copolymer (a2) can be an ethylene-propylene copolymer, for example, the first ethylene-α-olefin copolymer (a2) can be an ethylene-butene copolymer, for example, the first ethylene-α-olefin copolymer (a2) can be an ethylene-hexene copolymer, for example, the first ethylene-α-olefin copolymer (a2) can be an ethylene-octene copolymer, for example, the first ethylene-α-olefin copolymer (a2) can be an ethylene-propylene-butene copolymer, for example, the first ethylene-α-olefin copolymer (a2) can be an ethylene-propylene-hexene copolymer. Preferably, the first ethylene-α-olefin copolymer (a2) in the first multiphase propylene copolymer (HECO1) is an ethylene-propylene copolymer.

[0034] The MFR of the first multiphase propylene copolymer (HECO1) is 42.5 to 120.8 dg / min, more preferably 50.1 to 110.6 dg / min, and most preferably 60 - 100 dg / min, measured according to ISO 1133-1:2011 at 230 °C with a 2.16 kg load.

[0035] The first multiphase propylene copolymer (HECO1) can be divided into a xylene-soluble part (CXS1) and a first xylene-insoluble part (CXI1). The amount of the xylene-soluble part of the first multiphase propylene copolymer (HECO1) is 11.6 to 26.9% by weight, preferably 12.1 to 22.6% by weight, more preferably 12.5 to 18.7% by weight, even more preferably 13.2 to 16.8% by weight based on the total amount of the first multiphase propylene copolymer (HECO1) as determined according to ISO16152:2005. The amount of the first xylene-insoluble part based on the total amount of the first multiphase propylene copolymer is calculated by the following equation:

[0036] CXI1 = 100% by weight - CXS1

[0037] The ratio between the intrinsic viscosity IV CXS1 of the xylene-soluble part of the first multiphase propylene copolymer (HECO1) and the intrinsic viscosity IV CXI1 of the xylene-insoluble part of the first multiphase propylene copolymer (HECO1) is 2.1 to 7.5, preferably 3.2 to 5.1, more preferably 3.5 to 4.5, where IV CXS1 and IV CXI1 are measured according to ISO1628-1:2009 and ISO1628-3:2010 respectively.

[0038] The intrinsic viscosity IV CXI1 of the first xylene-insoluble part (CXI1) of the first multiphase propylene copolymer (HECO1) is 0.9 to 2.0 dl / g, preferably 1.0 to 1.8 dl / g, more preferably 1.0 to 1.5 dl / g, even more preferably 1.0 to 1.4 dl / g as measured according to ISO1628-3:2010.

[0039] The intrinsic viscosity (IV CXS1) of the xylene-soluble part of the first multiphase propylene copolymer (HECO1) is preferably 4.2 to 6.8 dl / g, more preferably 4.5 to 6.2 dl / g, even more preferably 4.8 to 6.0 dl / g as measured according to ISO1628-1:2009.

[0040] The first multiphase propylene copolymer (HECO1) is preferably a non-degradative cracking multiphase propylene copolymer. The term "non-degradative cracking" is known in the art, but for the sake of clarity, it means that the material is not treated to directly modify the molecular weight and / or molecular weight distribution of the polymer after polymerization. In other words, the non-degradative cracking polymer is not treated with peroxides, radiation, or any other initiator source that causes chain-breaking reactions. One advantage of non-degradative cracking polypropylene compared to degradative cracking polypropylene is that the former generally suffers less from the release of low molecular weight materials, such as those inherently generated during degradative cracking, and is not expected to be used in automotive applications. For the sake of clarity, the term "reactor grade" indicates that the copolymer is non-degradative cracking. The first multiphase propylene copolymer (HECO1) is preferably a reactor grade multiphase propylene copolymer.

[0041] Methods for producing the first multiphase propylene copolymer (HECO1) are known in the art. Preferably, the first multiphase propylene copolymer (HECO1) is produced in a sequential polymerization process comprising at least two reactors, and more preferably the polypropylene of the present invention is produced in a sequential polymerization process comprising at least three reactors.

[0042] The catalysts used in the preparation of the first multiphase propylene copolymer (HECO1) are also known in the art, such as Ziegler-Natta catalysts, metallocene catalysts. Preferably, the catalyst used to produce the first multiphase propylene copolymer does not contain phthalates, for example the catalyst comprises compounds of transition metals of Groups 4 to 6 of the IUPAC Periodic Table of the Elements, Group 2 metal compounds, and internal donors, where the internal donors include but are not limited to: 1,3-diether, such as 9,9-bis(methoxymethyl)fluorene, optionally substituted malonates, maleates, succinates, glutarates, benzoates, cyclohexene-1,2-dicarboxylates, benzoates, citraconates, aminobenzoates, silyl esters, and their derivatives and / or mixtures.

[0043] For example, the catalyst used in the preparation of the first multiphase propylene copolymer (HECO1) is a Ziegler-Natta catalyst, which comprises a main catalyst, at least one external donor, a cocatalyst, and optionally an internal donor, where the external electron donor is selected from compounds having the structure according to Formula III: (R 90 )2N-Si(OR 91 )3, compounds having the structure according to Formula IV: (R 92 )Si(OR 93 )3, and mixtures thereof, where R 90 , R 91 , R 92 and R 93Each of the groups is independently a straight-chain, branched-chain or cyclic substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, preferably a straight-chain unsubstituted alkyl group having 1 to 8 carbon atoms, preferably ethyl, methyl or n-propyl.

[0044] In one embodiment, R 90 and R 91 are each ethyl (the compound of formula III is diethylaminotriethoxysilane, DEATES). In another embodiment, R 92 is n-propyl, and R 93 are each ethyl (the compound of formula IV is n-propyltriethoxysilane, nPTES), or in another embodiment, R 92 is n-propyl, and R 93 are each methyl (the compound of formula IV is n-propyltrimethoxysilane, nPTMS).

[0045] Preferably, the heterophasic propylene copolymer of the present invention is prepared by a catalyst system comprising a Ziegler-Natta catalyst and at least one external electron donor selected from compounds having a structure according to formula III: (R 90 )2N-Si(OR 91 )3, compounds having a structure according to formula IV: (R 92 )Si(OR 93 )3 and mixtures thereof.

[0046] "Cocatalyst" is a term well-known in the art of Ziegler-Natta catalyst technology and is considered a substance capable of converting a main catalyst into an active polymerization catalyst. Generally, a cocatalyst is an organometallic compound containing a metal of Group 1, 2, 12, or 13 of the Periodic System (Handbook of Chemistry and Physics, 70th Edition, CRC Press, 1989 - 1990). The cocatalyst can include any compound known in the art to be used as a "cocatalyst", such as hydrides, alkylates, or arylates of aluminum, lithium, zinc, tin, cadmium, beryllium, magnesium, and combinations thereof. The cocatalyst can be a hydrocarbyl aluminum cocatalyst, such as: triisobutylaluminum, trihexylaluminum, diisobutylaluminum hydride, dihexylaluminum hydride, isobutylaluminum dihydride, hexylaluminum dihydride, diisobutylhexylaluminum, isobutyldihexylaluminum, trimethylaluminum, triethylaluminum, tripropylaluminum, triisopropylaluminum, tri-n-butylaluminum, trioctylaluminum, tridecylaluminum, tris(dodecyl)aluminum, tribenzylaluminum, triphenylaluminum, trinaphthylaluminum, and tritolylaluminum. In one embodiment, the cocatalyst is selected from triethylaluminum, triisobutylaluminum, trihexylaluminum, diisobutylaluminum hydride, and dihexylaluminum hydride. More preferably, trimethylaluminum, triethylaluminum, triisobutylaluminum, and / or trioctylaluminum. Most preferably, triethylaluminum (abbreviated as TEAL). The cocatalyst can also be a hydrocarbyl aluminum compound, such as: tetraethylaluminum dihydride, methylaluminoxane, isobutylaluminoxane, tetra-isobutylaluminum dihydride, diethylethoxyaluminum, diisobutylaluminum chloride, methyldichloroaluminum, diethylaluminum chloride, ethylaluminum dichloride, and dimethylaluminum chloride; preferably TEAL.

[0047] For example, the main catalyst can be prepared by a method including the following steps: providing a magnesium-based support, and contacting the magnesium-based support with a Ziegler-Natta type catalytic substance, an internal donor, and an activator to produce the main catalyst. For example, the examples of Dow's US 5,093,415 disclose improved methods for preparing the main catalyst. Preferably, the main catalyst is a compound containing titanium.

[0048] In the context of the present invention, the molar ratio between Si and Ti elements in the catalyst system is preferably from 0.1 to 40, preferably from 0.1 to 20, even more preferably from 1 to 20, and most preferably from 2 to 10. Preferably, the molar ratio between Al and Ti elements in the catalyst system is from 5 to 500, preferably from 15 to 200, more preferably from 30 to 160, and most preferably from 50 to 140.

[0049] In one embodiment, the molar ratio between Si and Ti elements is the molar ratio between the external donor and the main catalyst.

[0050] In one embodiment, the molar ratio between Al and Ti elements is the molar ratio between the cocatalyst and the main catalyst.

[0051] Second multiphase propylene copolymer (HECO2)

[0052] The amount of the second multiphase propylene copolymer (HECO2) is 10.2 to 45.4% by weight, preferably 11.6 to 41.8% by weight, more preferably 15.3 to 37.7% by weight, even more preferably 22.4 to 35.8% by weight, based on the total weight of the polymer composition.

[0053] The second multiphase propylene copolymer (HECO2) preferably comprises a second propylene polymer (b1) as the matrix and a second ethylene-α-olefin copolymer (b2) as the dispersed phase.

[0054] The amount of the second propylene polymer (b1) is preferably 65 to 81% by weight, preferably 70 to 76% by weight, based on the total amount of the second multiphase propylene copolymer (b).

[0055] In the second multiphase propylene copolymer (HECO2), the second propylene polymer (b1) can be a propylene homopolymer and / or a propylene-α-olefin copolymer, where the α-olefin has 2 or 4 to 20 carbon atoms. For example, the propylene-α-olefin can be a propylene-ethylene copolymer or a propylene-butene copolymer. Preferably, in the second multiphase propylene copolymer (HECO2), the second propylene polymer (b1) is a propylene homopolymer.

[0056] The MFR of the second propylene polymer (b1) in the second multiphase propylene copolymer (HECO2) is preferably 20 to 150 dg / min, preferably 50 to 100 dg / min, more preferably 60 to 90 dg / min, measured at 230 °C with a load of 2.16 kg according to ISO 1133-1:2011.

[0057] The amount of the second ethylene-α-olefin copolymer (b2) is preferably 19 to 35% by weight, preferably 24 to 30% by weight, based on the total amount of the second multiphase propylene copolymer (b).

[0058] In the second multiphase propylene copolymer (b), the amount of the structural part derived from ethylene is preferably 55 to 68% by weight, based on the total amount of the second ethylene-α-olefin copolymer (b2).

[0059] In the second multiphase propylene copolymer (HECO2), the α-olefin structural moiety in the second ethylene-α-olefin copolymer (b2) is preferably derived from at least one α-olefin having 3 to 20 carbon atoms. For example, the second ethylene-α-olefin copolymer (b2) can be an ethylene-propylene copolymer. For example, the second ethylene-α-olefin copolymer (b2) can be an ethylene-butene copolymer. For example, the second ethylene-α-olefin copolymer (b2) can be an ethylene-hexene copolymer. For example, the second ethylene-α-olefin copolymer (b2) can be an ethylene-octene copolymer. For example, the second ethylene-α-olefin copolymer (b2) can be an ethylene-propylene-butene copolymer. For example, the second ethylene-α-olefin copolymer (b2) can be an ethylene-propylene-hexene copolymer. Preferably, in the second multiphase propylene copolymer (HECO2), the second ethylene-α-olefin copolymer (b2) is an ethylene-propylene copolymer.

[0060] The MFR of the second multiphase propylene copolymer (HECO2) is 5.6 to 65 dg / min as measured at 230 °C with a 2.16 kg load in accordance with ISO 1133-1:2011, more preferably 7.2 to 53.8 dg / min, more preferably 10.3 to 39.6 dg / min, and most preferably 12.5 to 27 dg / min.

[0061] The second multiphase propylene copolymer (HECO2) can be divided into a xylene-soluble fraction (CXS2) and a xylene-insoluble fraction (CXI2). The amount of the xylene-soluble fraction of the second multiphase propylene copolymer (HECO2) is 15.3 to 30.8% by weight, preferably 16.2 to 27.7% by weight, more preferably 18.3 to 25.7% by weight, based on the total amount of the second multiphase propylene copolymer (a) as measured in accordance with ISO 16152:2005.

[0062] CXI2 = 100% by weight - CXS2

[0063] The ratio between the intrinsic viscosity IV CXS2 of the xylene-soluble fraction of the second multiphase propylene copolymer (HECO2) and the intrinsic viscosity IV CXI2 of the xylene-insoluble fraction of the second multiphase propylene copolymer (HECO2) is 1.7 to 4.5, preferably 2.6 to 3.9, more preferably 2.8 to 3.4, where IV CXS2 and IV CXI2 are measured in accordance with ISO 1628-1:2009 and ISO 1628-3:2010, respectively.

[0064] The intrinsic viscosity IV CXI2 of the xylene-insoluble fraction (CXI2) of the second multiphase propylene copolymer (HECO2) is 1.1 to 1.7 dl / g, preferably 1.2 to 1.5 dl / g, more preferably 1.2 to 1.5 dl / g, as measured in accordance with ISO 1628-3:2010.

[0065] The intrinsic viscosity IV CXS2 of the xylene-soluble fraction (CXS2) of the second heterophasic propylene copolymer (HECO2) is from 2.9 to 4.9 dl / g, preferably from 3.5 to 4.6 dl / g, more preferably from 3.8 to 4.6 dl / g, measured according to ISO 1628-1:2009.

[0066] The second heterophasic propylene copolymer (HECO2) is different from the first heterophasic propylene copolymer (HECO1).

[0067] The second heterophasic propylene copolymer (HECO2) is preferably a reactor-grade heterophasic propylene copolymer.

[0068] The second heterophasic propylene copolymer (HECO2) can be produced by methods and catalysts known in the art.

[0069] In one embodiment, the second heterophasic propylene copolymer (HECO2) is produced by the same method and the same catalyst as the first heterophasic propylene copolymer (HECO1).

[0070] Impact modifier

[0071] Polypropylene is a semi-crystalline polymer that exhibits a very attractive cost-performance balance and ease of processing. However, in order to meet the requirements of different applications / industries, polypropylene requires improved impact resistance at ambient or low temperatures.

[0072] The nature of impact modifiers is elastic or rubbery, which is why they can absorb or dissipate the energy of impact. Impact modifiers are substances that improve the durability of molded or extruded plastics, especially plastic parts that are constantly subjected to extreme conditions and impact forces, such as low-temperature conditions. Impact modifiers are added to compounded materials to provide improved mechanical properties, such as durability and toughness. They provide strength and fracture resistance to the polymers to which they are added. They also provide stiffness to the product to prevent it from warping or sagging during daily use.

[0073] The amount of impact modifier added to the polymer depends on the level of impact resistance required for the end-use application. The main applications of impact modifiers are in packaging, construction, automotive, and consumer goods.

[0074] The impact modifier present in the polymer composition is from 7.5 to 34.5% by weight, preferably from 10.2 to 30.8% by weight, more preferably from 12.4 to 28.7% by weight, even more preferably from 15.3 to 25.8% by weight, based on the total weight of the polymer composition.

[0075] The impact modifier of the present invention is different from the elastic phase of the first heterophasic propylene copolymer and the elastic phase of the second heterophasic propylene copolymer.

[0076] The impact modifier of the present invention comprises a first rubber component (ER1) and a second rubber component (ER2) selected from ethylene-based copolymers, plastomers or elastomers and combinations thereof.

[0077] As used in this specification and the appended claims, the term "ethylene-based copolymer" refers to an ethylene-α-olefin copolymer, wherein the α-olefin has 4 to 10 carbon atoms. Preferably, the ethylene-based copolymer can be an ethylene-1-butene copolymer, an ethylene-1-hexene copolymer or an ethylene-1-octene copolymer.

[0078] As used in this specification and the appended claims, the term "elastomer" refers to a polymer with a low degree of crystallinity having a density of 0.85 to 0.88 g / cm 3 as determined by ASTM D792 and exhibiting elastic properties.

[0079] As used in this specification and the appended claims, the term "plastomer" refers to a class of ethylene / α-olefin copolymers having a density of 0.87 - 0.91 g / cm 3 as determined by ASTM D792. Plastomers are also characterized by a melt flow index (at 190 °C, 2.16 kg) of 0.2 - 80 dg / min.

[0080] Impact modifiers containing ethylene-based copolymers or elastomers or plastomers can be prepared using methods known in the art, for example by using single-site catalysts, i.e., catalysts in which the transition metal component is an organometallic compound and in which at least one ligand has a cyclopentadienyl anion structure, such ligands being bonded and coordinated to the transition metal cation through the anion structure. This type of catalyst is also referred to as a "metallocene" catalyst. Metallocene catalysts are described, for example, in U.S. Patent Nos. 5,017,714 and 5,324,820. Polyolefin-based elastomers can also be prepared using conventional types of heterogeneous multi-site Ziegler-Natta catalysts.

[0081] The first rubber component (ER1)

[0082] The first rubber component (ER1) of the impact modifier is a copolymer of ethylene and an α-olefin having 4 to 10 carbon atoms. Preferably, the first rubber component is selected from ethylene-1-butene copolymers, ethylene-1-hexene copolymers, ethylene-1-octene copolymers and mixtures thereof. More preferably, the first rubber component is an ethylene-1-butene copolymer.

[0083] The first rubber component (ER1) is 3.3 to 16.8 wt%, preferably 5.1 to 12.6 wt%, more preferably 6.2 to 11.6 wt%, and even more preferably 7.1 to 10.2 wt%.

[0084] The density of the first rubber component (ER1) is 0.830 to 0.895 g / cm as determined according to ASTM D792-13 3 , preferably 0.840 to 0.885 g / cm 3 , more preferably 0.850 to 0.875 g / cm 3 .

[0085] The MFR of the first rubber component (ER1) is 0.1 to 2.6 dg / min as determined according to ASTM D1238-13 at 190 °C with a 2.16 kg load, preferably 0.2 to 1.5 dg / min, more preferably 0.3 to 1.1 dg / min, and even more preferably 0.3 to 0.9 dg / min.

[0086] The second rubber component (ER2)

[0087] The second rubber component (ER2) of the impact modifier is a copolymer of ethylene and an α-olefin having 4 to 10 carbon atoms. Preferably, the second rubber component is selected from ethylene-1-butene copolymers, ethylene-1-hexene copolymers, ethylene-1-octene copolymers, and mixtures thereof. More preferably, the second rubber component is an ethylene-1-octene copolymer.

[0088] The second rubber component (ER2) is 8.2 to 22.8% by weight, preferably 9.1 to 20.8% by weight, more preferably 10.3 to 18.6% by weight, and even more preferably 12.2 to 16.7% by weight.

[0089] The density of the second rubber component (ER2) is 0.830 to 0.895 g / cm as determined according to ASTM D792-13 3 , preferably 0.840 to 0.885 g / cm 3 , more preferably 0.850 to 0.875 g / cm 3 .

[0090] The MFR of the second rubber component (ER2) is 1.2 to 10.5 dg / min as determined according to ASTM D1238-13 at 190 °C with a 2.16 kg load, preferably 2.3 to 8.5 dg / min, more preferably 3.2 to 7.8 dg / min, and even more preferably 3.8 to 6.7 dg / min.

[0091] Optional inorganic filler

[0092] The polymer composition according to the present invention may further comprise an inorganic filler. The inorganic filler is 2.5 to 31% by weight, preferably 5.1 to 24.8% by weight, more preferably 8.1 to 19.8% by weight.

[0093] Suitable examples of inorganic fillers include, but are not limited to: talc, calcium carbonate, wollastonite, barium sulfate, kaolin, glass flakes, layered silicates (bentonite, montmorillonite, smectite) and mica. For example, the inorganic filler is selected from talc, calcium carbonate, wollastonite, mica and mixtures thereof.

[0094] More preferably, the inorganic filler is talc. According to sedimentation analysis according to Stokes' law (ISO 13317-3:2001), the median particle size (D50) of talc is preferably from 0.1 to 10.2 μm, preferably from 0.3 to 8.1 μm, more preferably from 0.5 to 5.2 μm, even more preferably from 0.6 to 2.5 μm.

[0095] Optional additives

[0096] The polymer composition according to the invention may also contain additives such as nucleating agents and clarifying agents, stabilizers, release agents, plasticizers, antioxidants, lubricants, antistatic agents, crosslinking agents, scratch-resistant agents, high-performance fillers, pigments and / or colorants, flame retardants, blowing agents, acid scavengers, recycling additives, antimicrobial agents, antifogging additives, slip additives, antiblocking additives, polymer processing aids and the like. Such additives are well known in the art. The amount of additive is preferably at most 5.0% by weight, preferably at most 4.5% by weight, more preferably at most 4% by weight, even more preferably at most 3.8% by weight, based on the total amount of the polymer composition. The reason for the preference for a small amount of additive is that the additive does not have a negative impact on the desired properties of the polymer composition according to the invention in such amounts.

[0097] Polymer composition

[0098] Polymer compositions, especially polypropylene-based polymer compositions, are widely used in the automotive industry because of their excellent mechanical and chemical properties. Polypropylene-based polymer compositions having a high flexural modulus at low temperatures and improved multiaxial impact are preferred for automotive applications because such compositions are less likely to deform under low temperature conditions or when subjected to impact.

[0099] Therefore, for automotive applications that require a certain level of rigidity, it is preferred that the polymer composition has a balance between flexural modulus, rigidity and impact at low temperatures while maintaining fluidity to achieve good processability in an extruder.

[0100] The polymer composition has one or more of the following properties:

[0101] - The melt flow rate is from 5.5 to 120 dg / min, preferably from 10.3 to 80.6 dg / min, more preferably from 14.2 to 70.3 dg / min, even more preferably from 15.3 to 35.7 dg / min, measured at 230 °C with a 2.16 kg load according to ISO 1133-1:2011;

[0102] - The flexural modulus is at least 1100 MPa, preferably 1200 to 1800 MPa, more preferably 1300 to 1700 MPa, measured according to ISO 178 at 23 °C;

[0103] - The Izod notched impact strength at 23 °C is 54.3 to 71.6 kJ / m measured according to ISO 179 / 1eA 2 ;

[0104] - The Izod notched impact strength at -40 °C is 3.5 to 9.5 kJ / m measured according to ISO 179 / 1eA 2 。

[0105] The present invention relates to the use of a combination of a first multiphase propylene copolymer (HECO1) and a second multiphase propylene copolymer (HECO2) in a compound, which further contains a first rubber component (ER1) and a second rubber component (ER2) and optionally an inorganic filler such as talc, the amount of the combination being effective to enable the manufacture of molded automotive parts having improved multiaxial instrument impact, especially at low temperatures, as defined in the specification.

[0106] The polymer composition according to the present invention can be prepared, for example, in an extrusion process by melt mixing in an extruder the first multiphase propylene copolymer, the second multiphase propylene copolymer, the first rubber component, the second rubber component, the optional inorganic filler and the optional additives.

[0107] The present invention also relates to a method for preparing an article, preferably an automotive part, which comprises the following sequential steps:

[0108] - Providing the polymer composition according to the present invention;

[0109] - Injection molding the polymer composition according to the present invention into an article.

[0110] The present invention also relates to the use of the polymer composition according to the present invention for automotive applications.

[0111] The present invention also relates to an article comprising the polymer composition according to the present invention, preferably the article is an automotive part, wherein the amount of the polymer composition according to the present invention is at least 95% by weight, preferably at least 98% by weight, based on the total amount of the article.

[0112] To avoid any confusion, in the context of the present invention, the term "amount" can be understood as "weight"; "melt flow index (MFI)" refers to the same physical property as "melt flow rate (MFR)".

[0113] It should be noted that the present invention relates to all possible combinations of the features described herein, preferably in particular those combinations of features presented in the claims. Thus, it will be understood that all combinations of features relating to the compositions according to the invention, all combinations of features relating to the methods according to the invention, and all combinations of features relating to the compositions according to the invention and features relating to the methods according to the invention are described herein.

[0114] It should also be noted that the term "comprising / including / containing" does not exclude the presence of other elements. However, it should also be understood that the description of a product / composition containing certain components also discloses a product / composition consisting of these components. A product / composition consisting of these components may be advantageous as it provides a simpler and more economical method for preparing the product / composition. Similarly, it should also be understood that the description of a method comprising certain steps also discloses a method consisting of these steps. A method consisting of these steps may be advantageous as it provides a simpler and more economical method. When values are mentioned for a lower limit and an upper limit of a parameter, it is also understood that the ranges resulting from combinations of the values of the lower limit and the upper limit are disclosed.

[0115] The present invention is now illustrated by means of the following examples, but the present invention is not limited thereto.

[0116] Materials

[0117] Polymers A, B and D are multiphase propylene copolymers prepared by the Innovene TM process in a sequential two-reactor setup. Propylene homopolymer is produced in the first reactor and propylene-ethylene copolymer is produced in the second reactor in the presence of the propylene homopolymer.

[0118] There are three components present in the catalyst system during the polymerization process: the main catalyst, the external electron donor, and the cocatalyst. The main catalyst is prepared according to the description in WO2016198344, page 36, paragraph "Main Catalyst III"; the external electron donor for polymers A and B is diisopropyl dimethoxysilane (DiPDMS), and the external electron donor for polymer D is n-propyl triethoxysilane (nPTES); the cocatalyst is triethylaluminum (TEAL).

[0119] The process conditions for polymers A, B and D are provided in Table 1:

[0120] Table 1: Process Conditions for Multiphase Propylene Copolymers (HECO)

[0121] Polymer Polymer A Polymer B Polymer D R1 Temperature (°C) 66 66 69.5 R1 Pressure (bar) 24 24 24 Al / Ti (mol / mol) 135 135 135 Si / Ti (mol / mol) 10 10 10 R1 H2 / C3 (mol / mol) 0.08 0.05 0.065 R1 Split (wt%) 80 74 86 R2 Temperature (°C) 66 57 59 R2 Pressure (bar) 24 24 24 R2 H2 / C3 (mol / mol) 0.132 0.005 0.0042 R2 C2 / C3 (mol / mol) 0.63 0.33 0.31 R2 Split (wt%) 20 26 14

[0122] In Table 1, R1 refers to the first reactor, R2 refers to the second reactor, Al / Ti is the molar ratio of cocatalyst to main catalyst, Si / Ti is the molar ratio of external donor to main catalyst, H2 / C3 is the molar ratio of hydrogen to propylene, C2 / C3 is the molar ratio of ethylene to propylene, and fractionation is the amount of material produced in R1 or R2 based on the amount of total polymer A or B or D, respectively. The properties of polymers A, B, and D are provided in Table 2.

[0123] Table 2: Properties of the heterophasic propylene copolymer (HECO)

[0124] Details Polymer A Polymer B Polymer D MFR (g / 10min) 40 14 77 PP Homopolymer Matrix (wt%) 80 74 86 CXS Fraction (wt%) 18 22 14 IV CXS (dl / g) 2.38 4.59 5.35 IV CXI (dl / g) 1.2 1.29 1.04 IV CXS / IV CXI 1.98 3.56 5.14

[0125] Sample preparation

[0126] Compounding

[0127] The pellets of the examples were prepared by compounding the components in the indicated amounts in Table 4 in a KraussMaffei Berstorff ZE40A_UTX 43D twin-screw extruder using the following settings: screw speed 400 rpm, throughput 150 kg / h, torque 38%, temperature 235 °C, and discharge pressure 13 bar.

[0128] Specimen preparation

[0129] The specimens for measurement were prepared by injection molding the pellets of the examples. The dimensions of the specimens for the tensile test are defined in ISO 527-2 type 1(a); the dimensions of the specimens for the impact resistance test are defined in ISO180 / 1A; the dimensions of the specimens for the measurement of the multi-axial instrumented impact fracture type are defined in ISO 6603-A2. The details of the different measurement methods are provided in Table 3.

[0130] Table 3: Measurement methods

[0131]

[0132] ISO 6603-2 curve type evaluation is a common method for characterizing the force / deflection data obtained from the puncture test experiment. It provides four typical curve series types that are usually observable during data evaluation. Generally, these range from ductile to brittle and focus on information such as yield, crack initiation, and crack propagation. The data obtained have been classified into these four categories, outlined below:

[0133] Fracture type:

[0134] YD: Yield, followed by deep drawing (ductile) - most preferred

[0135] YS: Yield, followed by stable cracking (semi-ductile) - preferred

[0136] YU: Yield, followed by unstable cracking (semi-brittle) - less preferred

[0137] NY: No yield (brittle) - not preferred

[0138] Table 4: Properties of the invention and comparative examples

[0139]

[0140] n.m. = not measured

[0141] ER1: An ethylene-1-butene elastomer, Tafmer DF605 commercially available from Mitsui Chemicals, with a density of 0.861 g / cm 3 (ASTM D792-13), MFI of 0.5 dg / min (ASTM D1238-13, 2.16 kg, 190 °C), and shore A hardness of 58 (ASTM D2240-15).

[0142] ER2: An ethylene-1-octene elastomer, Fortify5070T commercially available from SABIC, with a density of 0.868 g / cm 3 (ASTM D792-13), MFR of 5.0 dg / min (ASTM D1238-13, 2.16 kg, 190 °C), and shore A hardness of 63 (ASTM D2240-15); or Engage 8200 commercially available from Dow, with a density of 0.870 g / cm 3 (ASTM D792-13), MFR of 5.0 dg / min (ASTM D1238-13, 2.16 kg, 190 °C), and shore A hardness of 66 (ASTM D2240-15).

[0143] Talc: Luzenac HAR T84, a high aspect ratio talc commercially available from Imerys Talc. The median particle size (D50) of the talc measured by sedimentation analysis according to Stokes' law (ISO 13317-3:2001) is 2 microns.

[0144] Additive: The composite additive used consists of 50 wt% masterbatch, 20 wt% heat and processing stabilizer, 10 wt% UV stabilizer, and 20 wt% processing aid based on the total amount of the composite additive.

[0145] According to the information in Table 4, the polymer compositions of the present invention exemplified by Invention Examples IE1 to IE3 have an improved balance of rigidity, impact properties and flowability. Compared to Comparative Examples CE1 to CE3, the inventive compositions have surprisingly high impact properties, especially the multi-axial instrument impact values at -20 °C and -30 °C. More than 50% of the samples of Invention Examples IE1 to IE3 exhibited YD yield behavior at -20 °C, and 100% of the samples exhibited YS yield behavior at -30 °C, which is beneficial for automotive applications.

Claims

1. A polymer composition comprising: 45.5 to 74.5% by weight of a base polymer matrix based on the total weight of the polymer composition, 7.5 to 34.5% by weight of an impact modifier based on the total weight of the polymer composition, and an inorganic filler; wherein the base polymer matrix is a polypropylene-based multiphase resin comprising a first multiphase propylene copolymer (HECO1) and a second multiphase propylene copolymer (HECO2); wherein the first multiphase propylene copolymer (HECO1) is 21.5 to 57.4% by weight and has a melt flow rate of 42.5 to 120.8 dg / min measured at 230 °C with a 2.16 kg load according to ISO 1133-1:2011; wherein the second multiphase propylene copolymer (HECO2) is 10.2 to 45.4% by weight and has a melt flow rate of 5.6 to 65 dg / min measured at 230 °C with a 2.16 kg load according to ISO 1133-1:2011; wherein the second multiphase propylene copolymer (HECO2) satisfies the following conditions: b1. 15.3 to 30.8% by weight of the xylene-soluble fraction (CXS2) determined by ISO 16152:2005; b2. The ratio of the intrinsic viscosity (IV CXS2) of the xylene-soluble fraction to the intrinsic viscosity (IV CXI2) of the xylene-insoluble fraction is 1.7 to 4.5, wherein the intrinsic viscosity (IV CXS2) of the xylene-soluble fraction is 2.9 to 4.9 dl / g and the intrinsic viscosity (IV CXI2) of the xylene-insoluble fraction is 1.1 to 1.7 dl / g measured in decalin at 135 °C according to ISO 1628-3:2010; wherein the impact modifier comprises a first rubber component (ER1) and a second rubber component (ER2) selected from ethylene-based copolymers, plastomers or elastomers and combinations thereof.

2. The polymer composition according to claim 1, wherein the first multiphase propylene copolymer (HECO1) satisfies the following conditions: a1. 11.6 to 26.9% by weight of the xylene-soluble fraction (CXS1) measured by ISO 16152:2005; a2. The ratio of the intrinsic viscosity (IV CXS1) of the xylene-soluble fraction to the intrinsic viscosity (IV CXI1) of the xylene-insoluble fraction is 2.1 to 7.5, wherein the intrinsic viscosity (IV CXS1) of the xylene-soluble fraction is 4.2 to 6.8 dl / g measured according to ISO 1628-1:2009; and the intrinsic viscosity (IV CXI1) of the xylene-insoluble fraction is 0.9 to 2.0 dl / g measured in decalin at 135 °C according to ISO 1628-3:2010.

3. The polymer composition according to claims 1 to 2, wherein, based on the total weight of the polymer composition, the first rubber component is 3.3 to 16.8% by weight and the second rubber component is 8.2 to 22.8% by weight.

4. The polymer composition according to any one of claims 1 to 3, wherein the rubber component of the impact modifier is a copolymer of ethylene and an α-olefin having 4 to 10 carbon atoms, and preferably the rubber component is selected from ethylene-1-butene copolymers, ethylene-1-hexene copolymers, ethylene-1-octene copolymers, and mixtures thereof.

5. The polymer composition according to any one of claims 1 to 4, wherein the melt flow rate of the first rubber component is 0.1 to 2.6 dg / min and the melt flow rate of the second rubber component is 1.2 to 10.5 dg / min as measured at 190 °C with a 2.16 kg load according to ASTM D1238-13.

6. The polymer composition according to any one of claims 1 to 5, wherein the amount of the inorganic filler is 2.5 to 31% by weight, preferably 5.1 to 24.8% by weight, more preferably 8.1 to 19.8% by weight based on the total weight of the polymer composition.

7. The polymer composition according to any one of claims 1 to 6, wherein the inorganic filler is one selected from talc, calcium carbonate, mica, barium sulfate, calcium sulfate, and combinations thereof, and / or wherein the inorganic filler has a median particle size (D50) of 0.1 μm to 10.2 μm measured according to ISO 13317-3:2001.

8. The polymer composition according to any one of claims 1 to 7, which further comprises additives selected from the following: antioxidants, UV absorbers, nucleating agents, coupling agents, dispersants, light stabilizers, processing lubricants, inorganic pigments, masterbatches, and combinations thereof.

9. The polymer composition according to any one of claims 1 to 8, which has one or more of the following properties: - The melt flow rate is 5.5 to 120 dg / min, preferably 10.3 to 80.6 dg / min, more preferably 14.2 to 70.3 dg / min, even more preferably 15.3 to 35.7 dg / min as measured at 230 °C with a 2.16 kg load according to ISO 1133-1:2011; - The flexural modulus is at least 1100 MPa, preferably 1200 to 1800, more preferably 1300 to 1700 as measured at 23 °C according to ISO 178; - The notched Izod impact strength at 23 °C is 54.3 to 71.6 kJ / m measured according to ISO 179 / 1eA 2 ; - The notched Izod impact strength at -40 °C is 3.5 to 9.5 kJ / m measured according to ISO 179 / 1eA 2 .

10. The polymer composition according to any one of claims 1 to 9, which further comprises a third multiphase propylene copolymer (HECO3).

11. A method for preparing an article, which comprises the following sequential steps: - Providing the polymer composition according to any one of claims 1 to 10; - Injection molding the polymer composition according to any one of claims 1 to 10 into the article.

12. An article comprising the polymer composition according to any one of claims 1 to 11, and preferably the article is an injection molded article.

13. Use of the polymer composition according to any one of claims 1 to 12 for automotive applications.

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