Polypropylene-polyethylene blends with improved properties

Abstract

Polypropylene-polyethylene blends comprising A) 75 to 90 wt% of a blend of A1) polypropylene and A-2) polyethylene and B) 10 to 25 wt% of a compatibilizer which is a heterophasic polyolefin composition comprising B1) a polypropylene with an MFR2 between 1.0 and 300 g / 10 min (according to ISO 1133 at 230°C with a load of 2.16 kg) and B-2) an ethylene-propylene copolymer or C4 to C10 alpha olefin with a Tg (measured by dynamic mechanical thermal analysis, DMTA, according to ISO 6721-7) below -25 °C and an intrinsic viscosity (measured in decalin according to DIN ISO 1628 / 1 at 135 °C) of at least 3.0 dl / g, whereby the blend has simultaneously increased Charpy notched impact strength (according to ISO 179-leA, measured at 23°C), Flexural modulus (according to ISO 178) as well as heat deflection resistance (determined with DMTA according to ISO 6721-7).

Description

Polypropylene-polyethylene blends with improved properties The present invention relates to blends of polypropylene and polyethylene containing a specific type of compatibilizer. The addition of this specific compatibilizer results in a simultaneous increase in stiffness, impact resistance, and thermal deflection resistance. Furthermore, the present invention relates to recycled blends of polypropylene and polyethylene containing this specific type of compatibilizer. Polyolefins, such as polypropylene and polyethylene, are typical commercial polymers with many application areas and a remarkable growth rate. This is due not only to a favorable price / performance ratio, but also to the versatility of these materials and a very wide range of possible modifications, allowing for the adaptation of end-use properties across a broad spectrum. Chemical modifications, copolymerization, blending, stretching, heat treatment, and the combination of these techniques can convert common-quality polyolefins into valuable products with special properties. Polypropylene-polyethylene blends have generated considerable interest. It is well known that the impact strength of polypropylene (PP) increases at low temperatures with the addition of polyethylene (PE). Unfortunately, PP and PE are highly immiscible, resulting in a blend with poor adhesion between its phases, a coarse morphology, and consequently, poor mechanical properties. The compatibility between the phases of a blend can be improved by adding compatibilizers, resulting in a finer and more stable morphology, better adhesion between the blend phases, and consequently, improved properties of the final product. Several types of compatibilizers are known in the literature, such as block copolymers, e.g. an ethylene-propylene block copolymer and styrene-ethylene / butylene-styrene or triblock copolymers, or ethylene-propylene rubber (EPR), an ethylene / propylene-diene copolymer (EPDM), or an ethylene / vinyl acetate (EVA) copolymer. According to Wei Zhu et al.; Journal of Applied Polymer Science, vol. 58, pp. 515-521 (1995), adding an ethylene-propylene copolymer as a compatibilizer to polypropylene-polyethylene blends can mitigate the high incompatibility to some extent, and ethylene-propylene rubber (EPR) or ethylene-propylene-diene rubber (EPDM) can substantially improve the toughness of the blends, but at the expense of reduced modulus and tensile strength. As an improvement, the authors of this article suggest using a PP-block-PE copolymer prepared by sequential polymerization, whereby propylene is polymerized first, followed by ethylene in the second stage. The use of this compatibilizer leads to a small increase in elongation at break and tensile strength.Since the compatibilizer described has a very high molecular weight, expressed by its intrinsic viscosity, its addition also leads to a significant reduction in processability, expressed by the melt flow rate (MFR). Also according to Teh et al., Adv. Polym. Technol. vol. 13, pp. 1-23 (1994) the addition of ethylene propylene rubber (EPR) can be used to compatibilize polypropylene and polyethylene blends, resulting in improved toughness but lower moduli and heat resistance. While the compatibilizers described by Zhu et al. are not commercially available, it is commonly known that both EPR and EPDM are more expensive than the respective blending components, PP and PE, due to a more complex production process. For various applications, such as pipes, profiles, packaging, automotive components, or household items, it is of great importance that Pp / PE blends exhibit high stiffness, as well as high impact resistance and thermal deflection temperature. Therefore, one objective of the present invention was to simultaneously enhance these three properties of PP / PE blends. This objective has not yet been addressed in the literature. Furthermore, the demand for the use of recycled polyolefins, obtained from the recovery of plastic material waste derived from post-consumer and / or post-industrial waste, in a compound with virgin polymer has increased in recent years, especially because there are legal requirements in some segments such as automotive applications. One of the key challenges in polyolefin recycling, especially when dealing with post-consumer waste (PCW) material streams, is the difficulty of quantitatively separating polypropylene (PP) and polyethylene (PE). Commercial recyclables from PCW sources have been found to typically contain mixtures of PP and PE, with the smaller component reaching less than 50% by weight. Such recycled PP / PE blends typically exhibit impaired mechanical and optical properties, poor odor and taste performance, and generally poor compatibility between the main polymer phases, resulting in limited impact strength and thermal deflection resistance. This inferior performance is partly due to the fact that PE, with its lower stiffness and melting point, forms the continuous phase even at PP concentrations of up to 65%, due to the typically higher viscosity of the PE components in PCW. This normally excludes the application for high-quality parts, and only allows use in low-cost and low-demand applications. Therefore, another objective of the present invention was to simultaneously increase the stiffness, as well as the impact strength and thermal deflection resistance of recycled PP / PE blends, in order to make them suitable for use in a composite with a virgin polymer, e.g. for automotive applications. The discovery of the present invention is that with a special type of compatibilizer, which is a heterophasic polyolefin composition comprising a combination of a polypropylene and an ethylene-propylene copolymer or a C4 to C10 alpha olefin, with specific properties, a simultaneous increase in stiffness, as well as impact resistance and thermal deflection resistance of virgin and recycled PP / PE blends can be achieved. Therefore, the present invention relates to polypropylene-polyethylene blends comprising Component A), 75 to 90% by weight of a blend of A-1), 30 to 70% by weight of polypropylene, and A-2), 70 to 30% by weight of polyethylene, wherein component (A) is not a heterophasic polymer; and Component B), 10 to 25 wt% of a compatibilizer that is a heterophasic polyolefin composition comprising B-1), 55 to 90 wt% of a polypropylene with an MFR2 between 1.0 and 300 g / 10 min (according to ISO 1133 at 230 °C with a 2.16 kg load), and B-2), 45 to 10 wt% of an ethylene-propylene copolymer or a C4 to C10 alpha olefin with a glass transition temperature Tg (measured by dynamic thermomechanical analysis, DMTA, according to ISO 6721-7) below -45 °C and an intrinsic viscosity (measured in decalin according to DIN ISO 1628 / 1 at 135 °C) of at least 3.3 dl / g,whereby the mixture has (i) a Charpy notched impact strength (according to ISO 179-1eA, measured at 23 °C) at least 2% higher than that of the same mixture without compatibilizer B) and, at the same time, (ii) a flexural modulus (according to ISO 178) at least 3% higher than that of the same mixture without compatibilizer B) and, additionally, (iii) a thermal deflection strength (determined by DMTA according to ISO 6721-7) expressed by the temperature at which the storage modulus G' of 40 MPa (T (G' = 40 MPa) is reached, which is at least 4 °C higher than that of the same mixture without compatibilizer B). In a preferred embodiment, Component A) is a recycled material, which is recovered from plastic material waste derived from post-consumer and / or post-industrial waste. A further embodiment of a heterophasic polyolefin composition comprising B-1), 55 to 90 wt% of a polypropylene having an MFR2 between 1.0 and 300 g / 10 min (according to ISO 1133 at 230 °C with a 2.16 kg load) and B-2), 45 to 10 wt% of an ethylene-propylene copolymer or a C4 to C10 alpha olefin having a Tg (measured by dynamic thermomechanical analysis, DMTA, according to ISO 6721-7) below -45 °C and an intrinsic viscosity (measured in decalin according to DIN ISO 1628 / 1 at 135 °C) of at least 3.3 dl / g, as a compatibilizer for polypropylene-polyethylene blends comprising component A), wherein component (A) does not is a heterophasic polymer, and whereby component (A) is present in an amount of 75 to 90% by weight with respect to the resulting polypropylene-polyethylene mixture, whereby component A) is a mixture of A-1),from 30 to 70% by weight of polypropylene, and A-2), from 70 to 30% by weight of polyethylene; and wherein the heterophasic polyolefin composition is used in an amount of 10 to 25% by weight with respect to the resulting polypropylene-polyethylene blend to simultaneously increase the Charpy notched impact strength (according to ISO 179-1eA, measured at 23 °C), the flexural modulus (according to ISO 178), and the thermal deflection strength (determined by DMTA according to ISO 6721-7), whereby the Charpy notched impact strength (according to ISO 179-1eA, measured at 23 °C) of the blend comprising component A) and component B) is at least 2% higher than the Charpy notched impact strength (according to ISO 179-1eA, measured at 23 °C) of the same blend A) without compatibilizer B), and whereby the flexural modulus (according to the ISO 178 standard,measured at 23 °C) of the mixture comprising component A) and component B) is at least 3% higher than that of the same mixture A) without compatibilizer B), and by which the heat deflection temperature (HDT, according to ISO 75 B) of the mixture comprising component A) and component B) is at least 4 °C higher than that of the same mixture A) without compatibilizer B). Another embodiment is the use of a blend, where Component A) is a recycled material, recovered from post-consumer and / or post-industrial plastic waste, in a compound with one or more virgin polymers and, optionally, mineral fillers or reinforcing fibers. These compounds can be used advantageously, for example, in automotive applications. Component A) Component A) of the mixture of the invention comprises A-1) 30 to 70% by weight of polypropylene and A-2) from 70 to 30% by weight of polyethylene, whereby component (A) is not a heterophasic polymer. A-1 polypropylene may comprise one or more polymeric materials selected from the following: I) isotactic or mainly isotactic propylene homopolymers; II) isotactic random copolymers of propylene with ethylene and / or C4-C10 alpha-olefins, preferably ethylene and / or C4-C8 alpha-olefins, such as, for example, 1-butene, 1-hexene, 1-octene, 4-methyl-1-pentene, wherein the total comonomer content ranges from 0.05 to 20% by weight, or mixtures of said copolymers with isotactic or mainly isotactic propylene homopolymers; III) heterophasic copolymers comprising an isotactic propylene homopolymer as (I), or random propylene copolymers as (II), and an elastomeric fraction comprising ethylene copolymers with propylene and / or a C4-C8 α-olefin, optionally containing small amounts of a diene, such as butadiene, 1,4-hexadiene, 1,5-hexadiene, ethylidene-1-norbornene. For example, a polypropylene suitable for use as component A-1) may have a density of 0.895 to 0.920 g / cm3, preferably 0.900 to 0.915 g / cm3, and more preferably 0.905 to 0.915 g / cm3 determined in accordance with ISO 1183, and a melt flow rate (MFR) of 0.5 to 300 g / 10 min, preferably 1.0 to 150 g / 10 min and, alternatively, 1.5 to 50 g / 10 min determined in accordance with ISO 1133 (at 230 °C; 2.16 kg load). Generally, the melting temperature of component A-1) is within the range of 135 to 170 °C, preferably in the range of 140 to 168 °C, more preferably in the range of 142 to 166 °C. In the case of a propylene homopolymer as in point (I) above, it will generally have a melting temperature of 150 to 170 °C, preferably 155 to 168 °C, and more preferably 160 to 165 °C as determined by differential scanning calorimetry (DSC) in accordance with ISO 11357-3.In the case of a random propylene copolymer as in point (II) above, it will generally have a melting temperature of 130 to 162 °C, preferably 135 to 160 °C, and more preferably 140 to 158 °C as determined by DSC in accordance with ISO 11357-3. Preferably, the polypropylene of A-1) does not comprise a heterophasic copolymer like point (III) above. The polyethylene of A-2) is preferably a high-density polyethylene (HDPE) or a linear low-density polyethylene (LLDPE) or a long-chain branched low-density polyethylene (LDPE). The comonomer content of A-2 is normally less than 50% by weight, preferably less than 25% by weight, and most preferably less than 15% by weight. In this document, HDPE suitable for use as A-2) in this disclosure has a density determined according to ISO 1183 equal to or greater than 0.941 g / m³, preferably from 0.941 to 0.965 g / cm³, more preferably from 0.945 to 0.960 g / cm³. In one embodiment, the HDPE is an ethylene homopolymer. HDPE suitable for use as A-2) in this disclosure may generally have an MFR determined by ISO 1133 (at 190 °C; 2.16 kg load) of 0.01 g / 10 min to 50 g / 10 min, preferably from 0.1 to 30 g / 10 min, as well as from 0.5 to 20 g / 10 min. HDPE can also be a copolymer, for example, a copolymer of ethylene with one or more alphaolefin monomers such as propylene, butene, hexene, etc. LLDPE suitable for use as A-2) in this disclosure may generally have a density determined by ISO 1183, of 0.900 to 0.920 g / cm³, or 0.905 to 0.918 g / cm³, or 0.910 to 0.918 g / m³, and an MFR determined by ISO 1133 (at 190 °C; 2.16 kg load), of 0.01 to 50 g / min, or 0.1 to 30 g / 10 min, or 0.5 to 20 g / 10 min. LLDPE is a copolymer, for example, a copolymer of ethylene with one or more alpha-olefin monomers such as propylene, butene, hexene, etc. An LDPE suitable for use as A-2) in this disclosure may generally have a density determined by ISO 1183, from 0.915 to 0.935 g / m3, and an Mf R determined by ISO 1133 (190 °C; 2.16 kg), from 0.01 to 20 g / min. LDPE is a homopolymer of ethylene. The melting temperature of component A-2) is preferably within the range of 100 to 135 °C, more preferably within the range of 105 to 132 °C. In a preferred embodiment, Component A) is a recycled material, which is recovered from plastic material waste derived from post-consumer and / or post-industrial waste. Such post-consumer and / or post-industrial waste may come from, among others, waste electrical and electronic equipment (WEEE) or end-of-life vehicles (ELVs), or from differentiated waste collection systems such as the German DSD system, the Austrian ARA system or the Italian "Raccolta Differenziata" system. The mixtures can be PP-rich materials or PE-rich materials or mixtures with approximately equivalent amounts of PP and PE. The term "waste" is used to designate polymeric materials that have undergone at least one transformation cycle into manufactured goods, as opposed to virgin polymers. As mentioned previously, all types of polyethylene may be present, preferably HDPE, LLDPE, or LDPE, or polypropylene. Such recycled materials are marketed, for example, by Corepla (Italian Consortium for the Collection, Recovery, and Recycling of Plastic Packaging Waste), Resource Plastics Corp. (Brampton, ON), Kruschitz GmbH, Plastics and Recycling (AT), Vogt Plastik GmbH (DE), etc. The quantities of component A-1 and component A-2 can be from 30 to 70% by weight of component A-1 of PP and from 70 to 30% by weight of component A-2 of PE, preferably from 40 to 60% by weight of component A-1 of PP and from 60 to 40% by weight of component A-2 of PE. Component A) of the mixture of the invention preferably has an MFR (230 °C, 2.16 kg, ISO 1133) of 0.5 to 150 g / 10 min, more preferably of 1 to 120 g / 10 min. Component (A) is not a heterophasic polymer. Component B) Component B) of the mixture according to the invention is a heterophasic polyolefin composition comprising B-1) 55 to 90% by weight of a polypropylene with an MFR2 (ISO 1133; 230 °C; 2.16 kg) between 1.0 and 300 g / 10 min, and B-2) 45 to 10% by weight of an ethylene and propylene copolymer or a C4 to C10 alpha olefin with a Tg (measured by DMTA according to ISO 6721-7) below -45 °C and an intrinsic viscosity (measured in decalin according to DIN ISO 1628 / 1 at 135 °C) of at least 3.3 dl / g. Heterophasic polyolefin compositions are generally characterized by a cold xylene soluble fraction (XCS) and a cold xylene insoluble fraction (XCI). For the purposes of this application, the cold xylene soluble (XCS) fraction of the heterophasic polyolefin compositions is essentially identical to Component B-2) of said heterophasic polyolefin compositions. Therefore, when referring to the intrinsic viscosity and ethylene content of B-2) of the heterophasic polyolefin compositions, it means the intrinsic viscosity and ethylene content of the cold xylene soluble (XCS) fraction of said heterophasic polyolefin compositions. The polypropylenes suitable for use as Component B-1) may include any type of isotactic or predominantly isotactic polypropylene homopolymer or random copolymer known in the art. Thus, the polypropylene may be a propylene homopolymer or an isotactic random copolymer of propylene with ethylene and / or C4 to Ce alpha-olefins, such as, for example, 1-butene, 1-hexene, or 1-octene, wherein the total comonomer content ranges from 0.05 to 10% by weight. A polypropylene suitable for use as component B-1) may have a density of 0.895 to 0.920 g / cm3, preferably 0.900 to 0.915 g / m3, and more preferably 0.905 to 0.915 g / m3 determined in accordance with ISO 1183. Typically, component B-1) has a melting temperature of 130 to 170 °C, more preferably 135 to 168 °C and most preferably 140 to 165 °C. If it is a propylene homopolymer, it shall have a melting point of 150 to 170 °C, preferably 155 to 168 °C, as well as 160 to 165 °C, determined by differential scanning calorimetry (DSC) in accordance with ISO 11357-3. If it is a random copolymer of propylene with ethylene and / or C4 to C8 alpha-olefins, it shall have a melting point of 130 to 162 °C, preferably 135 to 160 °C, as well as 140 to 158 °C, determined by DSC in accordance with ISO 11357-3. The melt flow index of component B-1) ranges from 1.0 to 300 g / 10 min, preferably from 2.0 to 200 g / 10 min and, more preferably, from 4.0 to 150.0 g / 10 min, e.g., from 4.5 to 150.0 g / 10 min, determined according to ISO 1133 (230 °C; 2.16 kg). In one embodiment, the melt flow index of component B-1) ranges from 4.0 to 75 g / 10 min determined according to ISO 1133 (230 °C; 2.16 kg). As Component B-2) an ethylene-propylene copolymer or a C4 to C10 alpha olefin is used. The alpha olefin is preferably butene, hexene or octene, more preferably butene or octene and most preferably octene. B-2 copolymers have a glass transition temperature Tg (measured with DMTA according to ISO 6721-7) of -45 °C and an intrinsic viscosity (measured in decalin according to DIN ISO 1628 / 1 at 135 °C) of 3.3 dl / g. The glass transition temperature Tg (measured with DMTA according to ISO 6721-7) of B-2 copolymers is normally -65 °C or higher, preferably -60 °C or higher, and most preferably -58 °C or higher. The intrinsic viscosity (measured in decalin according to DIN ISO 1628 / 1 at 135 °C) of the B-2 copolymers is normally 10.0 or lower, more preferably 9.0 or lower, and most preferably 8.5 or lower. In the event that the copolymer of B-2) is an ethylene-propylene copolymer, it has an ethylene content of 10 to 55% by weight, preferably 15 to 50% by weight, more preferably 18 to 48% by weight, and most preferably 20 to 46% by weight. In the event that the copolymer of B-2) is a copolymer of ethylene and a C4-C10 alpha olefin, it has an ethylene content of 60 to 95% by weight, preferably 65 to 90% by weight and more preferably 70 to 85% by weight. Component B-2 differs from component A-2). Typically, component B-2 differs from A-2) in its comonomer content, expressed as a weight percentage. Preferably, the comonomer content of A-2) is lower than that of B-2), more preferably the comonomer content of A-2) is at least 2 percentage points lower than that of B-2), and most preferably the comonomer content of A-2) is at least 5 percentage points lower than that of B-2). In the suitable heterophasic polyolefin composition as component B), B-1) is present in an amount of 55 to 90% by weight, preferably in an amount of 60 to 88% by weight and more preferably in an amount of 65 to 85% by weight and most preferably in an amount of 65 to 80% by weight, and B-2) is present in an amount of 10 to 45% by weight, more preferably in an amount of 12 to 40% by weight, more preferably in an amount of 15 to 40% by weight, even more preferably in an amount of 15 to 35% by weight and most preferably in an amount of 20 to 35% by weight. Component B) preferably has an ethylene homopolymer content not exceeding 10% by weight, more preferably not exceeding 5% by weight, and most preferably component B) is free of ethylene homopolymers. The suitable heterophasic polyolefin composition as component B) can be prepared by mechanically mixing component B-1) and component B-2). Suitable polypropylene homopolymers or copolymers as component B-1) for mechanical blending are marketed, among others, by Borealis Ag or can be prepared by known processes, such as in a one-phase or two-phase polymerization process comprising a loop reactor or a loop reactor with a downstream gas-phase reactor, in the presence of highly stereospecific Ziegler-Natta catalysts or single-site catalysts such as metallocene catalysts, known to those skilled in the art. Suitable copolymers as component B-2) for mechanical blending can be any copolymer of ethylene and propylene or ethylene and a C4 to C10 alpha olefin with the properties defined above, which may be marketed, among others, by Borealis Plastomers (NL) under the trade name Queo®, by DOW Chemical Corp (USA) under the trade name Engage®, or by ENI SpA (IT). Alternatively, these copolymers can be prepared by known processes, in a one-phase or two-phase polymerization process, comprising solution polymerization, suspension polymerization, gas-phase polymerization, or combinations thereof, in the presence of highly stereospecific Ziegler-Natta catalysts, suitable vanadium oxide catalysts, or single-site catalysts such as metallocene or restricted geometry catalysts, known to those skilled in the art. In another embodiment, the suitable heterophasic polyolefin composition as component B) can be prepared by sequential polymerization, comprising at least two reactors in which polypropylene B-1) is produced first and copolymer B-2) is produced second in the presence of polypropylene B-1). A preferred sequential polymerization process comprises at least one loop reactor and at least one downstream gas-phase reactor. Such a process may have up to 3 gas-phase reactors. The polypropylene polymer B-1) is produced first, i.e., in the loop reactor, and is subsequently transferred to at least one gas-phase reactor, where the polymerization of ethylene, propylene, or a C4 to C10 alpha olefin or mixtures thereof takes place in the presence of the polypropylene polymer B-1). The polymer thus produced may be transferred to a second gas-phase reactor. Another possibility is that the polypropylene polymer B-1) is produced in the loop reactor and the first downstream gas-phase reactor. The polypropylene polymer B-1) is then transferred to at least a second gas-phase reactor where polymerization of ethylene and propylene or a C4 to C10 alpha olefin or mixtures thereof takes place in the presence of the polypropylene polymer B-1). The polymer thus produced may be transferred to a third gas-phase reactor. In a specific embodiment, the suitable heterophasic polyolefin composition as component B) is prepared by sequential polymerization comprising at least four reactors, wherein the polypropylene polymer B-1) is first produced in the loop reactor and the first subsequent gas-phase reactor. The polypropylene polymer B-1) is then transferred to the second gas-phase reactor where polymerization of ethylene and propylene or a C4 to C10 alpha olefin or mixtures thereof takes place in the presence of the polypropylene polymer B-1). The polymer thus produced is then transferred to the optional third gas-phase reactor where polymerization of ethylene and propylene or a C4 to C10 alpha olefin or mixtures thereof takes place in the presence of the product obtained in the second gas-phase reactor. Polymerization takes place in the presence of highly stereospecific Ziegler-Natta catalysts or single-site catalysts such as metallocene catalysts, known to experts in the field. A suitable sequential polymerization process is, among others, the Borstar® process from Borealis AG. Preferably, the heterophasic polyolefin composition B) is produced by sequential polymerization if the copolymer B-2) is an ethylene-propylene copolymer. If copolymer B-2) is a C4 to C10 ethylene-alpha olefin, the heterophasic polyolefin composition B) is preferably produced by mechanical mixing. Mixtures The polypropylene-polyethylene blends A) of the present invention comprising component B) as a compatibilizer have improved mechanical properties compared to blends comprising only component A). Component A) is present in an amount of 75 to 90% by weight, preferably 80 to 90% by weight, and component B) is present in an amount of 10 to 25% by weight, preferably 10 to 20% by weight. Components A) and B) are therefore normally different. The mixtures comprising component A) as well as component B) have greater Charpy notch impact strength (according to ISO 179-1eA, measured at 23 °C), as well as a higher flexural modulus (according to ISO 178, measured at 23 °C) and greater thermal deflection strength expressed by DMTA (according to ISO 6721-7) and by the thermal deflection temperature (HDT, according to ISO 75) compared to mixtures comprising only component A). The Charpy notch impact strength (according to ISO 179-1eA, measured at 23 °C) of the mixture according to the invention (comprising components A) and B) ) is at least 2% higher, preferably at least 3% higher, than the Charpy notch impact strength (according to ISO 179-1eA, measured at 23 °C) of the same mixture A) without compatibilizer B) . At the same time, the flexural modulus (according to ISO 178, measured at 23 °C) of the mixture according to the invention (comprising components A) and B) ) is at least 3% higher, preferably at least 4% higher, than that of the same mixture A) without compatibilizer B) . Also, in DMTA (according to ISO 6721-7) the temperature dependence of the storage module G' of the mixture according to the invention (comprising components A) and B) ) shows a greater resistance to thermal deflection expressed by the temperature at which the storage module G' of 40 MPa is reached (T (G' = 40 MPa) which is at least 4 °C higher, preferably at least 6 °C higher, than that of the same mixture A) without compatibilizer B) . Preferably, the heat deflection temperature (HDT, according to ISO 75 B) of the mixture according to the invention (comprising components A) and B) ) is at least 3 °C higher, preferably at least 4 °C higher, more preferably at least 10 °C higher than that of the same mixture A) without compatibilizer B) . The mixtures according to the present invention can be advantageously used in a composite with one or more virgin polymers, e.g., in automotive applications, pipes, or profiles for construction applications. In addition to virgin polyethylene and / or polypropylene, the composite may further comprise inorganic or organic reinforcements such as talc, glass fibers, or wood fibers. Optionally, the polypropylene-polyethylene blends according to the present invention further comprise inorganic reinforcing agents, typically inorganic fillers. The total amount of inorganic reinforcing agents is preferably from 1 to 20% by weight, more preferably from 2 to 15% by weight, based on the total amount of the polypropylene-polyethylene blend. Suitable inorganic fillers are talc, chalk, clay, mica, wood fibers or glass fibers and carbon fibers up to a length of 6 mm. The average particle size d50 of the load can be selected between 0.5 and 40 m, preferably between 0.7 and 20 m and more preferably between 1.0 and 15 m. The mean particle size (or median) is the particle diameter where 50% of the particles are larger and 50% are smaller. It is denoted as d50 or D50. In principle, this value can be determined by any particle measurement technique, for example, measurement techniques based on the principle of light diffraction. Other techniques for determining particle size include, for example, granulometry, in which a uniform suspension of a small quantity of the powder to be investigated is prepared in a suitable dispersion medium and then subjected to sedimentation. The percentage distribution of particle sizes can be estimated from the correlation between the size and density of spherical particles and their settling velocity, determined by Stokes' Law, and the settling time. Other methods for determining particle size include microscopy, electron microscopy, sieve analysis, sedimentation analysis, surface density determination, and similar techniques. The particle size data appearing in this descriptive report were obtained in a well-known manner using a standard test procedure that employs Stokes' law of sedimentation by settling the particulate material in a fully dispersed condition in an aqueous medium using a Sedigraph 5100 machine supplied by Micromeritics Instruments Corporation, Norcross, Ga, USA (phone: +1 770 662 3620; website: www.micromeritics.com), referred to herein as the "Micromeritics Sedigraph 5100 unit". Preferably talc, glass fibers or wood fibers, most preferably talc, are used as inorganic filler. Before adding talc, it can be treated with various surface treatment agents, such as organic titanate coupling agents, silane coupling agents, fatty acids, metallic salts of fatty acids, fatty acid esters, and the like, in a manner known in the prior art. Talc can also be added without surface treatment. Preferably, talc is added without surface treatment. Experimental section: 1. METHODS The MFR was measured according to ISO 1133 with a load of 2.16 kg, at 230 °C for pure PP components and all compositions, but at 190 °C for all pure PE components. The Charpy notch impact strength was determined according to ISO 179 1eA at 23 °C using 80 x 10 x 4 mm3 injection-molded test bars according to EN ISO 1873-2. The flexural modulus was determined in three-point bending according to ISO 178 using 80 x 10 x 4 mm3 injection-molded test bars according to EN ISO 1873-2. The tensile modulus was determined according to ISO 527-2 (crosshead speed = 50 mm / min; 23 °C) using injection-molded specimens as described in EN ISO 1873-2 (dog bone shape, 4 mm thick). The heat deflection temperature (HDT) was determined according to ISO 75 B with a load of 0.64 MPa using 80 x 10 x 4 mm3 injection-molded test bars according to EN ISO 1873-2. The cold xylene solubles (XCS) content was determined at 25 °C according to ISO 16152; first edition; 01-07-2005. The intrinsic viscosity (N) was measured according to DIN ISO 1628 / 1, October 1999 (in decalin at 135 °C). The glass transition temperature (Tg) and storage modulus (G') were determined by dynamic mechanical analysis (DMTA) according to ISO 6721-7. Measurements were performed in torsion mode on compression-molded samples (40 x 10 x 1 mm³) between -100 °C and +150 °C with a heating rate of 2 °C / min and a frequency of 1 Hz. While Tg was determined from the loss angle curve (tan(8)), the storage modulus (G') curve was used to determine the temperature for a G' of 40 MPa, which represents a measure of resistance to thermal deflection. The melting temperature (Tm) and crystallization temperature (Tc) were measured using a Mettler TA820 differential scanning calorimetry (DSC) device on 5–10 mg samples. DSC was performed according to ISO 11357-3:1999 in a heat / cool / heat cycle with a scan rate of 10 °C / min in the temperature range of +23–+210 °C. The crystallization temperature and heat of crystallization (Hc) were determined from the cooling stage, while the melting temperature and heat of fusion (Hf) were determined from the second heating stage. Comonomer content, particularly ethylene content, was measured using Fourier transform infrared spectroscopy (FTIR) calibrated with 13C NMR. For measuring ethylene content in polypropylene, a thin film of the sample (approximately 250 µm thick) was prepared by hot pressing. The area of ​​the 720 and 733 cirr1 absorption peaks for propylene-ethylene copolymers was measured using a Perkin Elmer FTIR 1600 spectrometer. The polyethylene content of the recycled material was determined using the DSC technique described above to determine the melting temperature (Tm) and the crystallization temperature (Tc). For recycling, the polyethylene content was calculated from the enthalpy of fusion of PE in DSC (Hm (PE) ) associated with the lower melting point of the composition (Tm (PE) ) in the range of 110 to 130 °C. For the determination of the present invention for fully crystalline PE, an enthalpy of fusion of 298 J / g and an average degree of crystallinity of 50% were assumed. 2. Examples Materials used Component A) For the virgin PP / PE blend, the following two components a) and b) were used as a 1:1 (weight ratio) mixture: a) HB600TF: PP homopolymer marketed by Borealis AG, Austria, which has an MFR2 (230 °C) of 2.0 g / 10 min, a melting point (DSC) of 165 °C and a density of 0.905 g / cm3. This has been produced with a 4th generation Ziegler-Natta type catalyst and lacks nucleating agents. b) MG7547S: HDPE homopolymer marketed by Borealis AG, Austria, having an MFR2 of 2.0 g / 10 min, a melting point (DSC) of 135 °C and a density of 0.945 g / cm3. Recycled material: PO Krublend MFR 3.1-5.0 (grey regranulate) was used: typical polyolefin regranulate marketed by Kruschitz GmbH, Austria, having an MFR2 (230 °C) of 3.4 g / 10 min, comprising approximately equal amounts of PP and PE. Dipolen S is a blend of recycled polymers comprising polyethylene and polypropylene obtained from mtm plastics GmbH, Niedergebra, Germany, and had a polyethylene content of 40% by weight as determined by DSC analysis. The melting points determined by DSC were 162 °C (PP) and 128 °C (PP). Talc: Luzenac HAR W92 with a mean (or median) particle size of 11, m Component B) Compatibilizers: Heterophasic copolymer 1 (HECO-1): HECO-1 was produced in a PP Borstar pilot plant with a prepolymerization reactor, a suspension loop reactor, and two gas-phase reactors. The catalyst used to prepare HECO-1 was produced as follows: First, 0.1 mol of MgChL x 3 EtOH was suspended under inert conditions in 250 mL of decane in a reactor at atmospheric pressure. The solution was cooled to -15 °C, and 300 mL of cold TiCl4 was added while maintaining the temperature at this level. The temperature of the suspension was then slowly raised to 20 °C. At this temperature, 0.02 mol of dioctyl phthalate (DOP) was added to the suspension. After the addition of the phthalate, the temperature was raised to 135 °C for 90 minutes, and the suspension was allowed to stand for 60 minutes. Then, another 300 mL of TiCl4 was added, and the temperature was maintained at 135 °C for 120 minutes. After this, the catalyst was separated from the liquid by filtration and washed six times with 300 ml of heptane at 80 °C. The solid catalyst component was then filtered and dried.(Ti content: 1.9% by weight and Mg content: 22.0% by weight). The catalyst and the concept of its preparation are described in general terms, for example, in patent publications EP491566, EP591224 and EP586390. The catalyst was used in combination with dicyclopentyldimethoxysilane [Si(OCH3)2(cyclopentyl)2] as an external donor (ED) and triethylaluminum (TEAL) as an activator and scrubber in the proportions indicated in Table 1. The catalyst was modified by polymerizing a vinyl compound in the presence of the catalytic system. The corresponding process is described in EP 1028984 and EP 1183307. Table 2: Pr il lim rr il nhrfi HE -1 B l PR1 GPR2 Heterophasic copolymer 2 (HECO-2): HECO-2 was prepared as described for HECO-1, but without passing through the first gas-phase reactor (GPR1). The specific reaction parameters can be seen in Table 3. T l : Pr rinl li r il nhrfi HE -2 Heterophasic copolymer 3 (HECO-3): A mixture of HF955MO (PP homopolymer marketed by Borealis AG, Austria, with an MFR2 (230 °C) of 20 g / 10 min, a melting point (d Sc ) of 165 °C and a density of 0.905 g / cm3) and Queo® 8210 (ethylene / octene plastomer marketed by Borealis AG, Austria, with an MFR2 (190 °C) of 10 g / 10 min, a melting point (DSC) of 75 °C and a density of 0.882 g / cm3; the plastomer has a Tg (DMTA) of -45 °C and an intrinsic viscosity of 3.1 dl / g) was used in varying compositions as indicated in Table 4. Heterophasic copolymer 4 (HECO-4) HECO-4 was produced in a PP Borstar® pilot plant with a prepolymerization reactor, a suspension loop reactor, and three gas-phase reactors. The catalyst used to prepare HECO-4 was produced as follows: First, 0.1 mol of MgChL x 3 EtOH was suspended under inert conditions in 250 mL of decane in a reactor at atmospheric pressure. The solution was cooled to -15 °C, and 300 mL of cold TiCU were added while maintaining the temperature at this level. The temperature of the suspension was then slowly raised to 20 °C. At this temperature, 0.02 mol of dioctyl phthalate (DOP) was added to the suspension. After the addition of the phthalate, the temperature was raised to 135 °C for 90 minutes, and the suspension was allowed to stand for 60 minutes. Then, another 300 mL of TiCU was added, and the temperature was maintained at 135 °C for 120 minutes. After this, the catalyst was separated from the liquid by filtration and washed six times with 300 ml of heptane at 80 °C. The solid catalyst component was then filtered and dried.(Ti content: 1.9% by weight and Mg content: 22.0% by weight). The catalyst and the concept of its preparation are described in general terms, for example, in patent publications EP491566, EP591224 and EP586390. The catalyst was used in combination with dicyclopentyldimethoxysilane [Si(OCH3)2(cyclopentyl)2] as an external donor (ED) and triethylaluminum (TEAL) as an activator and scrubber in the proportions indicated in Table 1. The catalyst was modified by polymerizing a vinyl compound in the presence of the catalytic system. The corresponding process is described in EP 1028984 and EP 1183307. T l 4: Pr rinl lim rr il nhrfi HE -4 continuation The MFR (230 °C, 2, 16 kg, ISO 1133) of the GPR1 product was 70 g / 10 min. Comparative example (CE 1) For the comparative example CE 1, BF970MO was used: a heterophasic ethylene-propylene impact copolymer (PP-HECO) marketed by Borealis AG, Austria, with an MFR2 (230 °C) of 20 g / 10 min, a melting point (DSC) of 165 °C and a density of 0.905 g / cm3. The polymer has an XCS content of 17.5 wt% with 34 wt% C2 and an intrinsic viscosity of 2.6 dl / g. The mixtures of component A) and component B) were prepared in a Coperion ZSK 25 co-rotation twin-screw extruder equipped with a mixing screw configuration with an L / D ratio of 25. A melting temperature of 200-220 °C was used during mixing, solidifying the melt strands in a water bath followed by pelletizing the strands. The quantities of the different components and the mechanical properties of the mixtures can be seen in Tables 4 and 5. As demonstrated in Ref. 2 through Ref. 5, the addition of talc in quantities of 10, 20, and 30% by weight leads to higher tensile and flexural modulus. However, impact resistance deteriorates simultaneously. The use of the polymer according to the present invention leads to the desired balance of good impact properties and stiffness.

Claims

1. Polypropylene-polyethylene blends comprising component A), 75 to 90% by weight of a blend of A-1) 30 to 70% by weight of polypropylene and A-2) 70 to 30% by weight of polyethylene; wherein component (A) is not a heterophasic polymer, and (B) 10 to 25 wt% of a compatibilizer is a heterophasic polyolefin composition comprising (B-1) 55 to 90 wt% of a polypropylene having an MFR2 of between 1.0 and 300 g / 10 min (according to ISO 1133 at 230 °C with a load of 2.16 kg) and (B-2) 45 to 10 wt% of an ethylene-propylene copolymer or a C4 to C10 alpha olefin having a glass transition temperature (Tg) (measured by dynamic thermomechanical analysis, DMTA, according to ISO 6721-7) below -45 °C and an intrinsic viscosity (measured in decalin according to DIN ISO 1628 / 1 at 135 °C) of at least 3. 3 dl / g,whereby the mixture has (i) a Charpy notched impact strength (according to ISO 179-1eA, measured at 23 °C) at least 2% higher than that of the same mixture without compatibilizer B) and at the same time (ii) a flexural modulus (according to ISO 178) at least 3% higher than that of the same mixture without compatibilizer B) and additionally (iii) a thermal deflection strength (determined by DMTA according to ISO 6721-7) expressed by the temperature at which the storage modulus G' of 40 MPa (T (G' = 40 MPa) is reached, which is at least 4 °C higher than that of the same mixture without compatibilizer B).

2. Polypropylene-polyethylene blends according to claim 1 having a heat deflection temperature (HDT, according to ISO 75 B) at least 3 °C higher than that of the same blend without compatibilizer B).

3. Polypropylene-polyethylene blends according to claim 1 or 2,where Component A) is a recycled material, which is recovered from plastic material waste derived from post-consumer and / or post-industrial waste.

4. Polypropylene-polyethylene blends according to any of claims 1 to 3 above, wherein Component B-1) is selected from isotactic or predominantly isotactic polypropylene homopolymers or random copolymers of propylene with ethylene and / or C4 to C8 alpha-olefins, wherein the total comonomer content ranges from 0.05 to 10% by weight, wherein the polypropylenes have a density of 0.895 to 0.920 g / cm3 (according to ISO 1183) and, in the case of propylene homopolymers, have a melting point of 150 to 170 °C (determined by differential scanning calorimetry (DSC) according to ISO 11357-3) and, in the case of random copolymers of propylene with ethylene and / or C4 to C8 alpha-olefins,having a melting point of 130 to 162 °C (determined by DSC in accordance with ISO 11357-3).

5. Polypropylene-polyethylene blends according to any of claims 1 to 4, wherein Component B) is selected from (i) an in-reactor blend obtained by a sequential polymerization process in at least two reactors, whereby polypropylene B-1) is produced first and ethylene-propylene copolymer B-2) is produced second in the presence of polypropylene B-1), or (ii) a mechanical blend of polypropylene B-1) and ethylene-C4 to C10 alpha-olefin copolymer B-2).

6. Polypropylene-polyethylene blends according to any of claims 1 to 5,wherein Component A) is present in an amount of 80 to 90% by weight and Component B) is present in an amount of 10 to 20% by weight.

7. Polypropylene-polyethylene blends according to any of claims 1 to 6 above, wherein in Component B), component B-1) is present in an amount of 60 to 88% by weight and component B-2) is present in an amount of 12 to 40% by weight.

8. Use of a heterophasic polyolefin composition comprising B-1) 55 to 90 wt% of a polypropylene having an MFR2 of between 1.0 and 300 g / 10 min (according to ISO 1133 at 230 °C with a load of 2.16 kg) and B-2) 45 to 10 wt% of an ethylene-propylene copolymer or a C4 to C10 alpha olefin having a Tg (measured by dynamic thermomechanical analysis, DMTA, according to ISO 6721-7) below -45 °C and an intrinsic viscosity (measured in decalin according to DIN ISO 1628 / 1 at 135 °C) of at least 3,3 dl / g, as a compatibilizer for polypropylene-polyethylene blends comprising component A), wherein component (A) is not a heterophasic polymer, and wherein component (A) is present in an amount of 75 to 90% by weight with respect to the resulting polypropylene-polyethylene blend, wherein component A) is a blend of A-1) 30 to 70% by weight polypropylene and A-2) 70 to 30% by weight polyethylene; and wherein the heterophasic polyolefin composition is used in an amount of 10 to 25% by weight with respect to the resulting polypropylene-polyethylene mixture to simultaneously increase the Charpy notch impact strength (according to ISO 179-1eA, measured at 23 °C), the flexural modulus (according to ISO 178) as well as the thermal deflection resistance (determined by DMTA according to ISO 6721-7),whereby the Charpy notch impact strength (according to ISO 179-1eA, measured at 23 °C) of the mixture comprising component A) and component B) is at least 2% higher than the Charpy notch impact strength (according to ISO 179-1eA, measured at 23 °C) of the same mixture A) without compatibilizer B) , and whereby the flexural modulus (according to ISO 178, measured at 23 °C) of the mixture comprising components A) and B) ) is at least 3% higher than that of the same mixture A) without compatibilizer B) and whereby the heat deflection temperature (HDT, according to ISO 75 B) of the mixture comprising components A) and B) ) is at least 4 °C higher than that of the same mixture A) without compatibilizer B) .

9. Use according to claim 8, wherein the polypropylene-polyethylene mixture A) is a recycled material,that is recovered from plastic waste material derived from post-consumer and / or post-industrial waste.

10. Use of a mixture according to any one of claims 1 to 6 in a compound with one or more virgin polymers for automotive applications, pipes, or profiles for construction applications.

11. Use according to claim 10, wherein the mixture is a mixture as claimed in claim 3.

12. Use according to claims 10 or 11, wherein such a compound may further comprise inorganic or organic reinforcements selected from talc, glass fibers, or wood fibers.