EP4634293A1

EP4634293A1 - Polypropylene composition with improved ductility/ multi-axial impact at low temperature

Info

Publication number: EP4634293A1
Application number: EP23821626.1A
Authority: EP
Inventors: Junhua Zhang; Jiaoyan ZHOU; Ting Huang; Bin Sun; Dimphna Johanna Maria Van Beek
Original assignee: SABIC Global Technologies BV
Current assignee: SABIC Global Technologies BV
Priority date: 2022-12-15
Filing date: 2023-12-11
Publication date: 2025-10-22
Also published as: WO2024126366A1; CN120359267A

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 exhibiting improved balance of impact and stiffness properties; particularly improved ductility/ multi-axial instrumented impact (MAI) at very low temperatures. The present invention further relates to a process for the preparation of the said polymer composition. The present invention further relates to articles made from the said polymer composition and applications of the said polymer composition in automotive, particularly for injection-molded articles.

Description

Polypropylene composition with improved ductility/ multi-axial impact at low temperature

[0001] The present invention relates to a polymer composition with improved balance of impact and stiffness properties particularly an improved ductility/ multi-axial instrumented impact (MAI) at low temperature. The polymer composition comprising Base polymer matrix comprising first heterophasic propylene copolymers and second heterophasic propylene copolymer, an impact modifier comprising first rubber component and second rubber component and optionally an inorganic filler. The present invention further relates to a process for the preparation of said polymer composition. The present invention further relates to articles made from said polymer composition and applications of the said polymer composition in automotive, particularly for injection-molded articles.

[0002] Polypropylene has been widely used for different applications such as packaging, building and construction, foam & lightweight articles, consumer goods, fibers, and automotive. The flexibility of designing the polypropylene features and tailoring properties for various applications have been significantly developed over several decades. Polypropylene compositions and articles prepared therefrom offer better stiffness, high heat resistance and improved chemical resistance compared to polyethylene. However, poor impact properties of polypropylene, particularly at low temperature severely affects the performance, particularly at subzero environments; for example at -20°C or -30°C. At such low temperature conditions, the injection-molded components usually have little ductility and even a small impact may cause damage to the components that may compromise the safety. Therefore, the balance of desired properties of polypropylene have been achieved via several methods such as producing polypropylene in multistage reactors, post-reactor modifications in extruder, compounding or blending with elastomers and/or plastomers.

[0003] WO2012152803A1 discloses highly filled soft heterophasic compositions having shore Hardness D lower than 50, elongation at break higher than 250% and tensile strength at break equal to or higher than 10 MPa. It further discloses an improved balance of flexibility, ductility and impact at low temperature.

[0004] WO201591372A1 discloses thermoplastic polypropylene compositions and filled compositions thereof, comprising talc as a mineral filler, for use in the production of molded articles for interior trims and exterior parts having, good processability and improved surface properties. [0005] WO2021130122A1 discloses a polypropylene (PP) based polymer composition comprising a first heterophasic PP copolymer, a second heterophasic PP copolymer and optionally an inorganic filler having high heat deflection temperature and good tiger stripe performance.

[0006]W0202213051A1 discloses a heterophasic polypropylene composition comprising two different heterophasic polypropylene and polymer of ethylene (PE) being selected from an ethylene-based plastomer and an LDPE, as well as articles made therefrom. It further relates to a heterophasic polypropylene composition with good total luminous transmittance and a beneficial balance of stiffness and impact properties.

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

[0008] There is a continuous need to provide a polymer composition providing improved balance of impact and stiffness properties, particularly improved ductility or multi-axial instrumented impact at low temperature while maintaining flowability.

[0009] It is therefore an object of the present invention to address at least in part one or more of the foregoing needs.

[0010] It is an object of the present invention to provide a polymer composition with improved ductility I multi-axial instrumented impact at low temperature while maintaining desired stiffness and flowability.

[0011] This object is achieved by a polymer composition comprising: from 45.5 to 74.5 wt. % of a base polymer matrix, based on the total weight of the polymer composition, from 7.5 to 34.5 wt. % of an impact modifier, based on the total weight of the polymer composition, and optionally an inorganic filler 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); wherein the first heterophasic propylene copolymer (HECO1) is in the range from 21.5 to 57.4 wt. % having a melt flow rate in the range from 42.5 to 120.8 dg/ min as measured according to ISO1133-1 :2011 at 230 °C with a 2.16 kg load; wherein the second heterophasic propylene copolymer (HECO2) is in the range from 10.2 to 45.4 wt. % having a melt flow rate in the range from 5.6 to 65 dg/ min as measured according to ISO1133-1 :2011 at 230 °C with a 2.16 kg load; wherein the impact modifier comprises a first rubber component (ER1) and a second rubber component (ER2) selected from a group consisting of an ethylene based copolymer, a plastomer or an elastomer and combinations thereof.

[0012] It was surprisingly found that the polymer composition according to the present invention has high ductility I multi-axial instrumented impact at low temperature while maintaining desired stiffness and flowability.

Base polymer matrix

[0013] The amount of base polymer matrix in the polymer composition ranges from 45.5 to 74.5 wt. %, preferably from 48.6 to 70.8 wt. %, more preferably from 51.2 to 68.7 wt. %, even more preferably from 55.3 to 66.8 wt. % based on the total weight of the polymer composition.

[0014] The base polymer matrix is a polypropylene-based heterophasic resin comprising a first heterophasic propylene copolymer (HECO1) and a second heterophasic propylene copolymer (HECO2).

Heterophasic propylene copolymer

[0015] A heterophasic propylene copolymer typically has a two-phase structure that comprises a propylene-based semi-crystalline polymer as a matrix and an elastomer or rubber as the dispersed phase, usually an ethylene-a-olefin rubber. Heterophasic propylene copolymers are usually prepared in a multistage polymerization process.

The first heterophasic propylene copolymer (HECO1)

[0016] The amount of first heterophasic propylene copolymer (HECO1) is in the range from 21.5 to 57.4 wt. %, preferably from 23.6 to 55.8 wt. %, more preferably from 25.2 to 52.7 wt. %, even more preferably from 27.2 to 46.6 wt. % based on the total weight of the polymer composition.

[0017] The first heterophasic propylene copolymer (HECO1) preferably comprises a first propylene polymer (a1) as matrix and a first ethylene-a-olefin copolymer (a2) as dispersed phase.

[0018] The amount of the first propylene polymer (a1) is preferably in the range from 80 to 92 wt. %, more preferably in the range from 85 to 90 wt. % based on the total amount of the first heterophasic propylene copolymer (HECO1).

[0019] The first propylene polymer (a1) in the first heterophasic propylene copolymer (HECO1) can be a propylene homopolymer or/and a propylene-a-olefin copolymer wherein the a-olefin has 2 or 4 to 20 carbon atoms, for example the propylene-a-olefin can be a propylene-ethylene copolymer or a propylene-butene copolymer. Preferably, the first propylene polymer (a1) in the first heterophasic propylene copolymer (HECO1) is a propylene homopolymer. [0020] The melt flow rate (MFR) of the first propylene polymer (a1) in the first heterophasic propylene copolymer (HECO1) is preferably in the range from 150 to 300 dg/ min, preferably from 180 to 270 dg/ min, more preferably from 200 to 250 dg/min as determined according to ISO1133- 1 :2011 at 230 °C with 2.16 kg load.

[0021] The amount of the first ethylene-a-olefin copolymer (a2) is preferably in the range from 8 to 20 wt. %, preferably from 10 to 15 wt. % based on the total amount of the first heterophasic propylene copolymer (HECO1).

[0022] In the first heterophasic propylene copolymer (HECO1), the amount of the moiety derived from ethylene is preferably in the range from 40 to 53 wt. % based on the total amount of the first ethylene-a-olefin copolymer (a2).

[0023] The moiety of a-olefin in the first ethylene-a-olefin copolymer (a2) in the first heterophasic propylene copolymer (HECO1) is preferably derived from at least one a-olefin having 3 to 20 carbon atoms, for example the first ethylene-a-olefin copolymer (a2) can be an ethylenepropylene copolymer, for example the first ethylene-a-olefin copolymer (a2) can be an ethylenebutene copolymer, for example the first ethylene-a-olefin copolymer (a2) can be an ethylenehexene copolymer, for example the first ethylene-a-olefin copolymer (a2) can be an ethyleneoctene copolymer, for example the first ethylene-a-olefin copolymer (a2) can be an ethylene- propylene-butene copolymer, for example the first ethylene-a-olefin copolymer (a2) can be an ethylene-propylene-hexene copolymer. Preferably, the first ethylene-a-olefin copolymer (a2) in the first heterophasic propylene copolymer (HECO1) is an ethylene-propylene copolymer.

[0024]The MFR of the first heterophasic propylene copolymer (HECO1) is in the range from 42.5 to 120.8 dg/ min, more preferably from 50.1 to 110.6 dg/ min, most preferably from 60-100 dg/ min, as determined according to ISO1133-1 :2011 at 230 °C with a 2.16 kg load.

[0025]The first heterophasic 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 heterophasic propylene copolymer (HECO1) is in the range from 11.6 to 26.9 wt. %, preferably from 12.1 to 22.6 wt. %, more preferably from 12.5 to 18.7 wt. %, even more preferably from 13.2 to 16.8 wt. % based on the total amount of the first heterophasic propylene copolymer (HECO1) as determined according to 15016152:2005. The amount of the first xylene-insoluble part based on the total amount of the first heterophasic propylene copolymer is calculated by the following equation:

CXI1 = 100 wt. % - CXS1

[0026] The ratio between the intrinsic viscosity of the xylene-soluble part of the first heterophasic propylene copolymer (HECO1) IV CXS1 and the intrinsic viscosity of the xylene-insoluble part of the first heterophasic propylene copolymer (HECO1) IV CXI1 is in the range from 2.1 to 7.5, preferably from 3.2 to 5.1 , more preferably from 3.5 to 4.5, wherein IV CXS1 and IV CXI1 are measured according to IS01628-1 :2009 and IS01628-3:2010 respectively.

[0027] The intrinsic viscosity of the first xylene-insoluble part (CXI1) of the first heterophasic propylene copolymer (HECO1) IV CXI1 is in the range from 0.9 to 2.0 dl/ g, preferably in the range from 1.0 to 1.8 dl/ g, more preferably from 1 .0 to 1.5 dl/ g, even more preferably in the range from 1.0 to 1.4 dl/ g as measured according to IS01628-3:2010.

[0028] The intrinsic viscosity of the xylene-soluble part (IV CXS1) of the first heterophasic propylene copolymer (HECO1) is preferably in the range from 4.2 to 6.8 dl/ g, more preferably in the range from 4.5 to 6.2 dl/ g, even more preferably in the range from 4.8 to 6.0 dl/ g as measured according to IS01628-1 :2009.

[0029]The first heterophasic propylene copolymer (HECO1) is preferably a non-visbroken heterophasic propylene copolymer. The term non-visbroken is known in the art, yet for the avoidance of doubt, it means that the material was not treated to modify the molecular weight and/or the molecular weight distribution of the polymer directly after polymerisation. In other words, non-visbroken polymers are not treated with peroxides, radiation, or any other initiating source for chain breaking reactions to occur. An advantage of non-visbroken polypropylenes over vis-broken polypropylenes is that the former generally suffer less from the release of low molecular weight materials, such as those that are inherently produced upon visbreaking, and is not desired for automotive application. For the avoidance of doubt, the term reactor grade indicates that the copolymer is non-visbroken. The first heterophasic propylene copolymer (HECO1) is preferably a reactor grade heterophasic propylene copolymer.

[0030] The process to produce the first heterophasic propylene copolymer (HECO1) is known in the art. Preferably, the first heterophasic propylene copolymer (HECO1) is produced in a sequential polymerization process comprising at least two reactors, more preferably the polypropylene of the present invention is produced in a sequential polymerization process comprising at least three reactors.

[0031] The catalyst used in the preparation of the first heterophasic propylene copolymer (HECO1) is also known in the art, for example Ziegler-Natta catalyst, metallocene catalyst. Preferably, the catalyst used to produce the first heterophasic propylene copolymer is free of phthalate, for example the catalyst comprises compounds of a transition metal of Group 4 to 6 of IIIPAC periodic table elements, a Group 2 metal compound and an internal donor wherein the said internal donor include but are not limited to 1 ,3-diethers, for example 9,9-bis (methoxymethyl) fluorene, optionally substituted malonates, maleates, succinates, glutarates, benzoic acid esters, cyclohexene- 1 ,2-dicarboxylates, benzoates, citraconates, aminobenzoates, silyl esters and derivatives and/or mixtures thereof.

[0032] For example the catalyst used in the preparation of the first heterophasic propylene copolymer (HECO1) is a Ziegler-Natta catalyst comprising a procatalyst, at least one external donor, a co-catalyst and an optional internal donor wherein the external electron donor is chosen from the group consisting of a compound having a structure according to Formula III (R⁹⁰)₂N- Si(OR⁹¹)s , a compound having a structure according to Formula IV: (R⁹²)Si(OR⁹³)3 and mixtures thereof, wherein each of R⁹⁰, R⁹¹, R⁹² and R⁹³ groups are each independently a linear, branched or cyclic, substituted or unsubstituted alkyl having between 1 and 10 carbon atoms, preferably a linear unsubstituted alkyl having between 1 and 8 carbon atoms, preferably ethyl, methyl or n- propyl.

[0033] In one embodiment, R⁹⁰ and R⁹¹ are each ethyl (compound of Formula III is diethylaminotriethoxysilane, DEATES). In another embodiment, R⁹² is n-propyl and R⁹³ are each ethyl (compound of Formula IV is n-propyl triethoxysilane, nPTES) or in another embodiment R⁹² is n-propyl and R⁹³ are each methyl (compound of Formula IV is n-propyl trimethoxysilane, nPTMS).

[0034] Preferably, the heterophasic propylene copolymer of the invention is prepared by a catalyst system comprising a Ziegler-Natta catalyst and at least one external electron donor chosen from the group of a compound having a structure according to Formula III (R⁹⁰)₂N- Si(OR⁹¹)3, a compound having a structure according to Formula IV: (R⁹²)Si(OR⁹³)3 and mixtures thereof. [0035] A "co-catalyst" is a term well-known in the art in the field of Ziegler-Natta catalysts and is recognized to be a substance capable of converting the procatalyst to an active polymerization catalyst. Generally, the co-catalyst is an organometallic compound containing a metal from group 1 , 2, 12 or 13 of the Periodic System of the Elements (Handbook of Chemistry and Physics, 70th Edition, CRC Press, 1989- 1990). The co-catalyst may include any compounds known in the art to be used as “co-catalysts”, such as hydrides, alkyls, or aryls of aluminium, lithium, zinc, tin, cadmium, beryllium, magnesium, and combinations thereof. The co-catalyst may be a hydrocarbyl aluminium co-catalyst, such as triisobutylaluminium, trihexylaluminium, di-isobutylaluminium hydride, dihexylaluminium hydride, isobutylaluminium dihydride, hexylaluminium dihydride, diisobutylhexylaluminium, isobutyl dihexylaluminium, trimethylaluminium, triethylaluminium, tripropylaluminium, triisopropylaluminium, tri-n-butylaluminium, trioctylaluminium, tridecylaluminium, tridodecylaluminium, tribenzylaluminium, triphenylaluminium, trinaphthylaluminium, and tritolylaluminium. In an embodiment, the cocatalyst is selected from triethylaluminium, triisobutylaluminium, trihexylaluminium, di-isobutylaluminium hydride and dihexylaluminium hydride. More preferably, trimethylaluminium, triethylaluminium, triisobutylaluminium, and/or trioctylaluminium. Most preferably, triethylaluminium (abbreviated as TEAL). The co-catalyst can also be a hydrocarbyl aluminium compound such as tetraethyl- dialuminoxane, methylaluminoxane, isobutylaluminoxane, tetraisobutyl-dialuminoxane, diethylaluminiumethoxide, diisobutylaluminium chloride, methylaluminium dichloride, diethylaluminium chloride, ethylaluminium dichloride and dimethylaluminium chloride, preferably TEAL.

[0036] For example, the procatalyst may be prepared by a process comprising the steps of providing a magnesium-based support, contacting said magnesium-based support with a Ziegler- Natta type catalytic species, an internal donor, and an activator, to yield the procatalyst. For example, the Examples of US 5,093,415 of Dow discloses an improved process to prepare a procatalyst. Preferably, the procatalyst is a chemical compound comprising titanium.

[0037] In the context of the present invention, the molar ratio between Si and Ti element in the catalyst system is preferably in the range 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 element in the catalyst system is in the range from 5 to 500, preferably from 15 to 200, more preferably from 30 to 160, most preferably from 50 to 140.

[0038] In one embodiment, the molar ratio between Si and Ti element is the molar ratio between the external donor and the procatalyst.

[0039] In one embodiment, the molar ratio between Al and Ti element is the molar ratio between the co-catalyst and the procatalyst.

The second heterophasic propylene copolymer (HECO2)

[0040] The amount of second heterophasic propylene copolymer (HECO2) is in the range from 10.2 to 45.4 wt. %, preferably from 11.6 to 41.8 wt. %, more preferably from 15.3 to 37.7 wt. %, even more preferably from 22.4 to 35.8 wt. % based on the total weight of the polymer composition.

[0041] The second heterophasic propylene copolymer (HECO2) preferably comprises a second propylene polymer (b1) as matrix and a second ethylene-a-olefin copolymer (b2) as dispersed phase.

[0042] The amount of the second propylene polymer (b1) is preferably in the range from 65 to 81 wt. %, preferably in the range from 70 to 76 wt. % based on the total amount of the second heterophasic propylene copolymer (b).

[0043] The second propylene polymer (b1) in the second heterophasic propylene copolymer (HECO2) can be a propylene homopolymer or/and a propylene-a-olefin copolymer wherein the a-olefin has 2 or 4 to 20 carbon atoms, for example the propylene-a-olefin can be a propyleneethylene copolymer or a propylene-butene copolymer. Preferably, the second propylene polymer (b1) in the second heterophasic propylene copolymer (HECO2) is a propylene homopolymer.

[0044] The MFR of the second propylene polymer (b1) in the second heterophasic propylene copolymer (HECO2) is preferably in the range from 20 to 150 dg/ min, preferably from 50 to 100 dg/ min, more preferably from 60 to 90 dg/ min as measured according to ISO1133-1 :2011 at 230 °C with a 2.16 kg load.

[0045] The amount of the second ethylene-a-olefin copolymer (b2) is preferably in the range from 19 to 35 wt. %, preferably from 24 to 30 wt. % based on the total amount of the second heterophasic propylene copolymer (b).

[0046] In the second heterophasic propylene copolymer (b), the amount of the moiety derived from ethylene is preferably in the range from 55 to 68 wt. % based on the total amount of the second ethylene-a-olefin copolymer (b2).

[0047] The moiety of a-olefin in the second ethylene-a-olefin copolymer (b2) in the second heterophasic propylene copolymer (HECO2) is preferably derived from at least one a-olefin having 3 to 20 carbon atoms, for example the second ethylene-a-olefin copolymer (b2) can be an ethylene-propylene copolymer, for example the second ethylene-a-olefin copolymer (b2) can be an ethylene-butene copolymer, for example the second ethylene-a-olefin copolymer (b2) can be an ethylene-hexene copolymer, for example the second ethylene-a-olefin copolymer (b2) can be an ethylene-octene copolymer, for example the second ethylene-a-olefin copolymer (b2) can be an ethylene-propylene-butene copolymer, for example the second ethylene-a-olefin copolymer (b2) can be an ethylene-propylene-hexene copolymer. Preferably, the second ethylene-a-olefin copolymer (b2) in the second heterophasic propylene copolymer (HECO2) is an ethylenepropylene copolymer.

[0048] The MFR of the second heterophasic propylene copolymer (HECO2) is in the range from 5.6 to 65 dg/ min, more preferably in the range from 7.2 to 53.8 dg/ min, more preferably in the range from 10.3 to 39.6 dg/ min, most preferably in the range from 12.5 to 27 dg/min, as determined according to ISO1133-1 :2011 at 230 °C with a 2.16 kg load.

[0049] The second heterophasic propylene copolymer (HECO2) can be divided into a xylene- soluble part (CXS2) and a xylene-insoluble part (CXI2). The amount of the xylene-soluble part of the second heterophasic propylene copolymer (HECO2) is in the range from 15.3 to 30.8 wt. %, preferably in the range from 16.2 to 27.7 wt. %, more preferably in the range from 18.3 to 25.7 wt. % based on the total amount of the second heterophasic propylene copolymer (a) as determined according to 15016152:2005.

CXI2 = 100 wt. % - CXS2

[0050] The ratio between the intrinsic viscosity of the xylene-soluble part of the second heterophasic propylene copolymer (HECO2) IV CXS2 and the intrinsic viscosity of the xylene- insoluble part of the second heterophasic propylene copolymer (HECO2) IV CXI2 is in the range from 1.7 to 4.5, preferably from 2.6 to 3.9, more preferably from 2.8 to 3.4, wherein IV CXS2 and IV CXI2 are measured according to IS01628-1 :2009 and IS01628-3:2010 respectively. [0051] The intrinsic viscosity of the xylene-insoluble part (CXI2) of the second heterophasic propylene copolymer (HECO2) IV CXI2 is in the range from 1.1 to 1.7 dl/ g, preferably in the range from 1.2 to 1.5 dl/ g, more preferably in the range from 1.2 to 1.5 dl/ g as measured according to IS01628-3:2010.

[0052] The intrinsic viscosity of the xylene-soluble part (CXS2) of the second heterophasic propylene copolymer (HECO2) IV CXS2 is in the range 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 as measured according to IS01628-1 :2009.

[0053] The second heterophasic propylene copolymer (HECO2) is different from the first heterophasic propylene copolymer (HECO1).

[0054] The second heterophasic propylene copolymer (HECO2) is preferably a reactor grade heterophasic propylene copolymer.

[0055] The second heterophasic propylene copolymer (HECO2) can be produced by a process and catalyst known in the art.

[0056] In one embodiment, the second heterophasic propylene copolymer (HECO2) is produced by the same process and same catalyst as the first heterophasic propylene copolymer (HECO1).

Impact Modifier

[0057] Polypropylene is a semi-crystalline polymer exhibiting a very attractive cost-performance balance and easy processability. However, to fulfill different application/ industry needs, polypropylene requires improved impact resistance at ambient or low temperatures.

[0058] Impact modifiers are elastomeric or rubbery in nature, which is why they can absorb the energy of an impact or dissipate it. Impact modifiers are substances that increase the durability of moulded or extruded plastics, especially plastic parts that are constantly subjected to extreme conditions and impact forces like low temperature conditions. Impact modifiers are added to compounded materials to provide improved mechanical performance like durability and toughness. They provide strength and break resistance to the polymers into which they are added. They also provide rigidity to the product to prevent it from warping or sagging during everyday use.

[0059] The amount of impact modifier added to the polymers depends upon the level of impact resistance needed for end-use applications. The major applications of impact modifiers are for packaging, construction, automotive, and consumer goods.

[0060]The impact modifier present in the polymer composition ranges from 7.5 to 34.5 wt. %, preferably from 10.2 to 30.8 wt. %, more preferably from 12.4 to 28.7 wt. %, even more preferably from 15.3 to 25.8 wt. % based on the total weight of the polymer composition.

[0061] The impact modifier of the present invention is different from the elastomeric phase of the first heterophasic propylene copolymer and the elastomeric phase of the second heterophasic propylene copolymer.

[0062] The impact modifier of the present invention comprises a first rubber component (ER1) and a second rubber component (ER2) selected from a group consisting of an ethylene based copolymer, a plastomer or an elastomer and combinations thereof.

[0063] The term "ethylene based copolymer", as used in this description and the appended claims refers to an ethylene-a-olefin copolymer and wherein the a-olefin has 4 to 10 carbon atoms. Preferably, ethylene based copolymer can be ethylene- 1 -butene copolymer or ethylene-1 -hexene copolymer or ethylene- 1 -octene copolymer.

[0064] The term "elastomer", as used in this description and the appended claims refers to a polymer with low crystallinity exhibiting elastic properties with a density range from 0.85 to 0.88 g/cm³ as determined according to ASTM D792.

[0065] The term "plastomer" as used in this description and the appended claims refers to a class of ethylene/a-olefin copolymers with a density of 0.87-0.91 g/cm³ as determined according to ASTM D792. Plastomers are further characterised by a melt flow index of 0.2-80 dg/ min (190 °C, 2.16 kg).

[0066] The impact modifier comprising the ethylene based copolymer or elastomer or plastomer may be prepared using methods known in the art, for example by using a single site catalyst, i.e. , a catalyst the transition metal components of which is an organometallic compound and at least one ligand of which has a cyclopentadienyl anion structure through which such ligand bondingly coordinates to the transition metal cation. This type of catalyst is also known as "metallocene" catalyst. Metallocene catalysts are for example described in U.S. Patent Nos. 5,017,714 and 5,324,820. The polyolefin based elastomer may also be prepared using traditional types of heterogeneous multi-sited Ziegler-Natta catalysts.

First rubber component (ER1)

[0067] The first rubber component (ER1) of the impact modifier is a copolymer of ethylene and an a-olefin having 4 to 10 carbon atoms, preferably the first rubber component is selected from the group consisting of ethylene-1 -butene copolymer, ethylene- 1 -hexene copolymer, ethylene-1- octene copolymer and mixtures thereof. More preferably, first rubber component is an ethylene- 1 -butene copolymer.

[0068] The first rubber component (ER1) is in the range of 3.3 to 16.8 wt.%, preferably in the range of 5.1 to 12.6 wt.%, more preferably in the range of 6.2 to 11.6 wt.%, even more preferably in the range of 7.1 to 10.2 wt.%.

[0069] The density of the first rubber component (ER1) is in the range of 0.830 to 0.895 g/ cm³, preferably in the range of 0.840 to 0.885 g/ cm³, more preferably in the range of 0.850 to 0.875 g/ cm³ as determined according to ASTM D792-13.

[0070] The MFR of the first rubber component (ER1) is in the range from 0.1 to 2.6 dg/min, preferably in the range from 0.2 to 1.5 dg/min, more preferably in the range from 0.3 to 1.1 dg/min, even more preferably in the range from 0.3 to 0.9 dg/min, as determined according to ASTM D1238-13 at 190 °C with a 2.16 kg load.

Second rubber component (ER2)

[0071] The second rubber component (ER2) of the impact modifier is a copolymer of ethylene and an a-olefin having 4 to 10 carbon atoms, preferably the second rubber component is selected from the group consisting of ethylene- 1 -butene copolymer, ethylene-1-hexene copolymer, ethylene- 1 -octene copolymer and mixtures thereof. More preferably, second rubber component is an ethylene- 1 -octene copolymer.

[0072] The second rubber component (ER2) is in the range of 8.2 to 22.8 wt.%, preferably in the range of 9.1 to 20.8 wt.%, more preferably in the range of 10.3 to 18.6 wt.%, even more preferably in the range of 12.2 to 16.7 wt.%.

[0073] The density of the second rubber component (ER2) is in the range of 0.830 to 0.895 g/ cm³, preferably in the range of 0.840 to 0.885 g/ cm³, more preferably in the range of 0.850 to 0.875 g/ cm³ as determined according to ASTM D792-13.

[0074] The MFR of the second rubber component (ER2) is in the range from 1.2 to 10.5 dg/min, preferably in the range from 2.3 to 8.5 dg/min, more preferably in the range from 3.2 to 7.8 dg/min, even more preferably in the range from 3.8 to 6.7 dg/min, as determined according to ASTM D1238-13 at 190 °C with a 2.16 kg load.

Optional inorganic filler

[0075] The polymer composition according to the present invention may further comprise an inorganic filler. The inorganic filler is in the range of 2.5 to 31 wt.%; preferably in the range of 5.1 to 24.8 wt.%, more preferably in the range of 8.1 to 19.8 wt.%.

[0076] Suitable examples of inorganic fillers include but are not limited to talc, calcium carbonate, wollastonite, barium sulfate, kaolin, glass flakes, laminar silicates (bentonite, montmorillonite, smectite) and mica. For example, the inorganic filler is selected from the group of talc, calcium carbonate, wollastonite, mica and mixtures thereof.

[0077] More preferably, the inorganic filler is talc. The mean particle size of talc (D50) of talc is preferably in the range from 0.1 to 10.2 micron, preferably from 0.3 to 8.1 micron, more preferably from 0.5 to 5.2 micron, even more preferably from 0.6 to 2.5 micron according to sedimentation analysis, Stokes’ law (ISO 13317-3:2001).

Optional additives

[0078] The polymer composition according to the present invention may further contain additives, for instance nucleating agents and clarifiers, stabilizers, release agents, plasticizers, anti-oxidants, lubricants, anti-statics, cross linking agents, scratch resistance agents, high performance fillers, pigments and/or colorants, flame retardants, blowing agents, acid scavengers, recycling additives, anti-microbials, anti-fogging additives, slip additives, antiblocking additives, polymer processing aids and the like. Such additives are well known in the art. The amount of the additives is preferably to be at most 5.0 wt. %, preferably at most 4.5 wt. %, more preferably at most 4 wt. %, even more preferably at most 3.8 wt. % based on the total amount of the polymer composition. The reason for the preference of the low amount of additives is that at this amount, additives do not have negative influence on the desired properties of the polymer composition according to the present invention.

Polymer composition

[0079] Polymer compositions, especially polymer compositions based on polypropylene are widely used in automotive industry thanks to their excellent mechanical and chemical properties. Polymer compositions based on polypropylene with a high flexural modulus and improved multi- axial impact at low temperature are preferred for automotive applications because such compositions are not to prone to deform in a low temperature condition or by the impact.

[0080] For automotive applications a certain level of stiffness is needed, hence it is preferred that the polymer composition have balance between flexural modulus, stiffness, and impact at low temperature while maintaining flowability for good processability in extruder.

[0081] The polymer composition has one or more of the following properties:

- a melt flow rate is in the range 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 as measured according to ISO1133-1:2011 at 230 °C with a 2.16 kg load;

- a flexural modulus of at least 1100 MPa, preferably from 1200 to 1800 MPa, more preferably from 1300 to 1700 MPa as measured according to ISO 178 @ 23°C;

- a Charpy Notched Impact strength at 23°C is in the range of 54.3 to 71.6 kJ/ m2 as measured according to ISO 179/1eA;

- a Charpy Notched Impact strength at -40°C is in the range of 3.5 to 9.5 kJ/ m2 as measured according to ISO 179/1eA;

[0082]The present invention relates to the use of a combination of the first heterophasic propylene copolymer (HECO1) and second heterophasic propylene copolymer (HECO2) in a compound, further containing the first rubber component (ER1) and the second rubber component (ER2) and optionally an inorganic filler such as talc in amounts effective so as to enable the manufacture of moulded automotive parts having an improved multi-axial instrumented impact, particularly at low temperature as defined in the specification.

[0083]The polymer composition according to the present invention can for example be prepared in an extrusion process by melt-mixing the first heterophasic propylene copolymer, the second heterophasic propylene copolymer, the first rubber component, the second rubber component, the optional inorganic filler and the optional additives in an extruder. [0084]The present invention further relates to a process for the preparation of an article, preferably an automotive part, comprising the sequential steps of:

- Providing the polymer composition according to the present invention;

- Injection molding the polymer composition according to the present invention in to the article.

[0085]The present invention further relates to the use of the polymer composition according to the present invention for automotive applications.

[0086]The present invention further 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 wt%, preferably at least 98 wt% based on the total amount of the article.

[0087] For the avoidance of 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)”.

[0088] It is noted that the invention relates to all possible combinations of features described herein, preferred in particular are those combinations of features that are present in the claims. It will therefore be appreciated that all combinations of features relating to the composition according to the invention; all combinations of features relating to the process according to the invention and all combinations of features relating to the composition according to the invention and features relating to the process according to the invention are described herein.

[0089] It is further noted that the term ‘comprising’ does not exclude the presence of other elements. However, it is also to be understood that a description on a product/composition comprising certain components also discloses a product/composition consisting of these components. The product/composition consisting of these components may be advantageous in that it offers a simpler, more economical process for the preparation of the product/composition. Similarly, it is also to be understood that a description on a process comprising certain steps also discloses a process consisting of these steps. The process consisting of these steps may be advantageous in that it offers a simpler, more economical process. When values are mentioned for a lower limit and an upper limit for a parameter, ranges made by the combinations of the values of the lower limit and the values of the upper limit are also understood to be disclosed.

[0090]The invention is now elucidated by way of the following examples, without however being limited thereto.

Materials

[0091] Polymer A, B, and D are heterophasic propylene copolymers prepared in an Innovene™ process, wherein a sequential two-reactor setup was employed. Propylene homopolymers were produced in first reactor and propylene-ethylene copolymers were produced in the second reactor in presence of propylene homopolymer.

[0092] There are three components in the catalyst system in the polymerization process: A procatalyst, an external electron donor and a co-catalyst. The procatalyst was prepared according to the description in WO2016198344, page 36, “Procatalyst III” paragraph; The external electron donor used for Polymer A and B was di(iso-propyl) dimethoxysilane (DiPDMS), the external electron donor used for Polymer D was n-propyltriethoxysilane (nPTES); the cocatalyst was triethylaluminium (TEAL).

[0093] The process conditions of Polymer A, B, and D provided in Table 1 :

Table 1 : Process conditions of Heterophasic propylene copolymer (HECO)

[0094] In Table 1 , R1 refers to the first reactor, R2 refers to the second reactor, Al/Ti is the molar ratio of the co-catalyst to the procatalyst, Si/Ti is the molar ratio of the external donor to the procatalyst, H2/C3 is the molar ratio of hydrogen to propylene, C2/C3 is the molar ratio of ethylene to propylene, split is the amount of substance produced in R1 or R2 based on the amount of the total Polymer A or B or D respectively. The properties of Polymer A, B, and D provided in Table 2.

Table 2: Properties of Heterophasic propylene copolymer (HECO) Sample preparation

Compounding [0095] Pellets of the Examples were prepared by compounding the components in amounts as indicated in Table 4 in a KraussMaffei Berstorff ZE40A_UTX 43D twin-screw extruder with the following setting: 400 rpm screw speed, 150kg/ h throughput, 38% torque, 235 °C as temperature and 13 bar as head pressure.

Specimen preparation

[0096] Specimens for the measurements were prepared by injection molding the pellets of examples. The dimensions of the specimens used in tensile test are defined in ISO 527-2 type 1(a); the dimensions of the specimens used in impact resistance test are defined in ISO180/1A; the dimensions of the specimens used in multi-axial instrumented impact break type measurement are defined in ISO 6603-A2. The details of the different measurement methods provided in table 3.

Table 3: Measurement methods [0097] The ISO 6603-2 curve type evaluation is a common method to characterize the force/ deflection data obtained by puncture test experiments. It provides four typical types of curve progression that can usually be observed during data evaluation. In general, these range from ductile to brittle and focus on information like yielding, crack initiation and crack propagation. Obtained data has been divided into these four categories, which are summarized below :

Break types:

YD : Yielding followed by deep drawing (Ductile) - most preferred

YS : Yielding followed by stable cracking (Semi-ductile) - preferred YU : Yielding followed by unstable cracking (Semi-brittle) - least preferred

NY : No yielding (Brittle) - not preferred

Table 4: Properties of Inventive and Comparative Examples n.m. = not measured

[0098]ER1 - is an ethylene- 1 -butene elastomer, Tafmer DF605 commercially available from Mitsui Chemicals, having a density of 0.861 g/ cm³ (ASTM D792-13), a MFR of 0.5 dg/ min (ASTM D1238-13, 2.16 kg, 190°C) and a shore A hardness of 58 (ASTM D2240-15).

[0099] ER2 - Fortify 5070T is an ethylene- 1 -octene elastomer commercially available from SABIC, having a density of 0.868 g/ cm³ (ASTM D792-13), a MFR of 5.0 dg/ min (ASTM D1238- 13, 2.16 kg, 190°C) and a shore A hardness of 63 (ASTM D2240-15) OR Engage 8200 commercially available from Dow, having a density of 0.870 g/ cm³ (ASTM D792-13), a MFR of 5.0 dg/ min (ASTM D1238-13, 2.16 kg, 190°C) and a shore A hardness of 66 (ASTM D2240-15).

[0100] Talc - Luzenac HAR T84 is a high aspect ratio talc commercially available from Imerys Talc. The mean particle size (D50) of talc is 2 micron as measured according to sedimentation analysis, Stokes’ law (ISO 13317-3:2001).

[0101] Additives - The additive package used consists of 50 wt. % color masterbatch, 20 wt. % heat and process stabilizers, 10 wt. % UV stabilizer, 20 wt. % processing aid based on the total amount of the additive package.

[0102] According to the information in Table 4, the polymer composition of the invention as exemplified by inventive examples IE1 to IE3 have improved balance of stiffness, impact properties and flowability. The inventive compositions have surprisingly high impact properties, particularly multi-axial instrumented impact values at -20°C and -30°C in comparison with the comparative examples from CE1 to CE3. The inventive examples IE1 to IE3 exhibited YD yield behavior at -20°C for more than 50% of the samples and exhibited YS yield behavior at -30°C for 100% of the samples, which is beneficial for automotive applications.

Claims

Claims A polymer composition comprising: from 45.5 to 74.5 wt. % of a base polymer matrix, based on the total weight of the polymer composition, from 7.5 to 34.5 wt. % 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 heterophasic resin comprising a first heterophasic propylene copolymer (HECO1) and a second heterophasic propylene copolymer (HECO2); wherein the first heterophasic propylene copolymer (HECO1) is in the range from 21.5 to 57.4 wt. % having a melt flow rate in the range from 42.5 to 120.8 dg/ min as measured according to ISO1133-1 :2011 at 230 °C with a 2.16 kg load; wherein the second heterophasic propylene copolymer (HECO2) is in the range from 10.2 to 45.4 wt. % having a melt flow rate in the range from 5.6 to 65 dg/ min as measured according to ISO1133-1 :2011 at 230 °C with a 2.16 kg load; wherein the second heterophasic propylene copolymer (HECO2) fulfills the following conditions; b1. a xylene-soluble part (CXS2) in the range from 15.3 to 30.8 wt. % as determined by 18016152:2005; b2. a ratio between the intrinsic viscosity of the xylene-soluble part (IV CXS2) to the the intrinsic viscosity of the xylene-insoluble part (IV CXI2) is between 1 .7 to 4.5, wherein the intrinsic viscosity of the xylene-soluble part (IV CXS2) is in the range from 2.9 to 4.9 dl/ g and the intrinsic viscosity of the xylene-insoluble part (IV CXI2) is in the range from 1.1 to 1.7 dl/ g as measured according to ISO1628-3:2010 in decalin at 135 °C; wherein the impact modifier comprises a first rubber component (ER1) and a second rubber component (ER2) selected from a group consisting of an ethylene based copolymer, a plastomer or an elastomer and combinations thereof. The polymer composition according to claim 1 , wherein the first heterophasic propylene copolymer (HECO1) fulfills the following conditions; a1. a xylene-soluble part (CXS1) in the range from 11.6 to 26.9 wt. % as measured by 18016152:2005; a2. a ratio between the intrinsic viscosity of the xylene-soluble part (IV CXS1) to the the intrinsic viscosity of the xylene-insoluble part (IV CXI1) is between 2.1 to 7.5, wherein the intrinsic viscosity of the xylene-soluble part (IV CXS1) is in the range from 4.

2 to 6.8 dl/ g as measured according to IS01628-1 :2009; and the intrinsic viscosity of the xylene- insoluble part (IV CXI1) is in the range from 0.9 to 2.0 dl/ g as measured according to IS01628-3:2010 in decalin at 135 °C.

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

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

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

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

7. The polymer composition according to claims 1 to 6, wherein the inorganic filler is one selected from the group consisting of talc, calcium carbonate, mica, barium sulfate, calcium sulfate and a combination thereof and/or wherein the inorganic filler has an median diameter (D50) in a range from 0.1 pm to 10.2 pm as measured according to ISO 13317-3:2001.

8. The polymer composition according to claims 1 to 7, further comprising additives selected from the group comprising of an antioxidant, a UV absorbent, a nucleating agent, a coupling agent, a dispersant, a light stabilizer, a processed lubricant, an inorganic pigment, a colour masterbatch and a combination thereof.

9. The polymer composition according to claims 1 to 8 having one or more of the following properties: a melt flow rate in the range 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 as measured according to ISO1133-1 :2011 at 230 °C with a 2.16 kg load; a flexural modulus of at least 1100 MPa, preferably from 1200 to 1800, more preferably from 1300 to 1700 as measured according to ISO 178 @ 23°C;

- a Charpy Notched Impact strength at 23°C in the range of 54.3 to 71.6 kJ/m2 as measured according to ISO 179/1eA;

- a Charpy Notched Impact strength at -40°C in the range of 3.5 to 9.5 kJ/m2 as measured according to ISO 179/1eA.

10. The polymer composition according to claims 1 to 9 further comprises a third heterophasic propylene copolymer (HECO3).

11 . A process for the preparation of an article comprising the sequential steps of: providing the polymer composition of any one of claims 1 to 10; injection molding the polymer composition of any one of claims 1 to 10 into the article.

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

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