Composition comprising polypropylene and polyethylene

Abstract

The invention relates to a polyolefin composition comprising high melt strength polypropylene and polyethylene, wherein the high melt strength polypropylene is obtained by or obtainable by a process comprising melt-mixing a base polypropylene, a peroxide and a linear α-olefin composition comprising linear C20+ α-olefins.

Description

[0001] COMPOSITION COMPRISING POLYPROPYLENE AND POLYETHYLENE

[0002] The present invention relates to a polyolefin composition comprising polypropylene and polyethylene and articles comprising such composition.

[0003] Compositions of polypropylene and polyethylene are desirable as they allow tuning of the material properties by selecting the type and amounts of the individual components. However, it is well known that polyethylene and polypropylene are immiscible. It is further a disadvantage that polypropylene and polyethylene substantially do not interact so that a blend of polyethylene and polypropylene generally results in a two phase system having a polypropylene phase and a polyethylene phase with poor physical properties.

[0004] Accordingly attempts have been made to increase the interaction between the phases in such blends by adding a compatibilizer. Compatibilizers are materials that have affinity with both phases and enhance the bonding strength. As a result, a material with improved properties can be obtained.

[0005] Blends of polypropylene and polyethylene comprising a compatibilizer are known in the art. For example US 6,114,443 discloses a composition comprising a blend of polyethylene and an isotactic poly-alpha-olefin homopolymer (such as polypropylene), together with a diblock copolymer compatibilizer of polyethylene block and an atactic poly-alpha-olefin block.

[0006] WO2016188818 discloses a composition comprising polypropylene, polyethylene and a compatibilizer which is a non-aromatic polyester.

[0007] In view of the advantageous combination of mechanical properties and cost there is a continuous need for further compositions that can be manufactured relatively easy and with low cost.

[0008] It is therefore an object of the present invention to provide a composition comprising polypropylene and polyethylene, which composition has good mechanical properties.

[0009] Accordingly, the present invention provides a polyolefin composition comprising high melt strength polypropylene and polyethylene, wherein the high melt strength polypropylene is obtained by or obtainable by a process comprising melt-mixing a base polypropylene, a peroxide and a linear a-olefin composition comprising linear C20+ a- olefins.

[0010] It was surprisingly found that the high melt strength polypropylene used according to the invention can be blended with polyethylene to obtain a composition with good mechanical properties without a compatibilizer.

[0011] Linear C20+ a-olefins is herein meant as linear a-olefins with 20 or more carbon atoms.

[0012] The linear C20+ a-olefins used for making the high melt strength polypropylene according to the invention are generally obtained as byproducts of processes for the preparation of more commonly used lower carbon a-olefins. The linear C20+ a-olefins generally have relatively limited uses such as lubricant and waxes. The invention is highly advantageous in that new applications have been found for these byproducts.

[0013] High melt strength polypropylene

[0014] According to the invention, melt-mixing a base polypropylene with a peroxide and a linear a-olefin composition comprising linear C20+ a-olefins results in the linear C20+ a-olefins grafting onto the propylene polymer backbone, obtaining the high melt strength polypropylene.

[0015] Preferably, the process for obtaining the high melt strength polypropylene does not comprise adding inorganic nano-fillers, such as silica, organoclay and carbon nanotube, before, during and / or after the melt-mixing step.

[0016] Preferably, the process for obtaining the high melt strength polypropylene does not comprise irradiation of the polypropylene by an electron beam before, during and / or after the melt-mixing step. This advantageously avoids undesired degradation of the polypropylene.

[0017] Base polypropylene

[0018] The polypropylene to be melt-mixed with the peroxide and the linear a-olefin composition to obtain the high melt strength polypropylene is referred herein as the base polypropylene.

[0019] The base polypropylene may be or comprise a propylene homopolymer, a random propylene copolymer or a heterophasic propylene copolymer or any combinations thereof. In some preferred embodiments, the base polypropylene is a propylene homopolymer. In some preferred embodiments, the base polypropylene is a random propylene copolymer.

[0020] A propylene homopolymer can be obtained by polymerizing propylene under suitable polymerization conditions. A propylene copolymer can be obtained by copolymerizing propylene and ethylene or one or more other a-olefins under suitable polymerization conditions. The preparation of propylene homopolymers and copolymers is, for example, described in Moore, E. P. (1996) Polypropylene Handbook. Polymerization, Characterization, Properties, Processing, Applications, Hanser Publishers: New York.

[0021] The random propylene copolymer may comprise as the comonomer ethylene or an a- olefin chosen from the group of a-olefins having 4 to 12 C-atoms, preferably ethylene, 1 -butene, 1 -hexene, 1 -octene or any mixtures thereof. The amount of the comonomer is preferably at most 10 wt% based on the random propylene copolymer, for example in the range from 2.0 to 7.0 wt% based on the random propylene copolymer. In particularly preferred embodiments, the random propylene copolymer is a propyleneethylene random copolymer, preferably wherein the amount of the ethylene comonomer units is 2.0 to 7.0 wt% based on the random propylene copolymer.

[0022] Heterophasic propylene copolymers are generally prepared in one or more reactors, by polymerization of propylene in the presence of a catalyst and subsequent polymerization of an ethylene-a-olefin mixture. The resulting polymeric materials are heterophasic, but the specific morphology usually depends on the preparation method and monomer ratios used.

[0023] The heterophasic propylene copolymer comprises a propylene-based matrix and a dispersed ethylene-a-olefin copolymer. The propylene-based matrix typically forms the continuous phase in the heterophasic propylene copolymer. The propylene-based matrix consists of a propylene homopolymer and / or a propylene copolymer consisting of at least 90 wt% of propylene monomer units and at most 10 wt% of ethylene and / or a-olefin monomer units, based on the total weight of the propylene-based matrix. The a-olefin in the dispersed ethylene-a-olefin copolymer is preferably chosen from the group of a-olefins having 3 to 8 carbon atoms, preferably propylene.

[0024] Preferably, the base polypropylene has a melt flow index determined according to ISO1133-1 :2022 at 230 °C and 2.16 kg of 0.1 to 10 dg / min. Preferably, the base polypropylene has a density as determined according to ASTM D1505 of 895 to 930 kg / m3, for example 895 to 900 kg / m3or 900 to 915 kg / m3.

[0025] In some embodiments, the base polypropylene is a propylene homopolymer having a density as determined according to ASTM D1505 of 900 to 915 kg / m3.

[0026] In some embodiments, the base polypropylene is a random propylene copolymer having a density as determined according to ASTM D1505 of 895 to 900 kg / m3.

[0027] The base polypropylene may be or comprise a post consumer recycled (PCR) polypropylene.

[0028] Linear a-olefin composition

[0029] The linear a-olefin composition comprises linear a-olefins. Preferably, the amount of linear a-olefins in the linear a-olefin composition is at least 95 wt%, at least 97 wt%, at least 99 wt%, at least 99.5 wt% or 100 wt%.

[0030] Preferably, the amount of the linear C20+ a-olefins with respect to the total linear a- olefins in the linear a-olefin composition is at least 55 wt%, preferably at least 60 wt%, more preferably at least 70 wt%, more preferably at least 80 wt%, more preferably at least 90 wt%, more preferably at least 95 wt%.

[0031] The linear a-olefin composition may comprise C20-C30 linear a-olefins and C30+ linear a-olefins.

[0032] Preferably, the amount of the C20-C30 linear a-olefins with respect to the total linear a- olefins in the linear a-olefin composition is at least 55 wt%, preferably at least 60 wt%, more preferably at least 70 wt%, more preferably at least 80 wt%, for example 80 to 99 wt%, 80 to 95 wt% or 80 to 90 wt%.

[0033] Preferably, the amount of the C20-C24 linear a-olefins with respect to the total linear a- olefins in the linear a-olefin composition is 50 to 90 wt% or 65 to 75 wt% and the amount of the C26-C28 linear a-olefins with respect to the total linear a-olefins in the linear a-olefin composition is 5.0 to 25 wt% or 15 to 25 wt%. Preferably, the amount of the C30+ linear a-olefins with respect to the total linear a- olefins in the linear a-olefin composition is at most 20 wt%, for example 1 .0 to 15 wt% or 3.0 to 10 wt%.

[0034] The linear a-olefin composition may further comprise linear C4 to C19 a-olefins.

[0035] Preferably, the amount of the C4 to C19 linear a-olefins with respect to the total linear a-olefins in the linear a-olefin composition is at most 5.0 wt%, for example 0.1 to 5.0 wt% or 0.5 to 3.0 wt%.

[0036] In particularly preferred embodiments, the amount of the linear C4 to C19 a-olefins with respect to the total linear a-olefins in the linear a-olefin composition is 0.1 to 5.0 wt%, the amount of the linear C20-C24 a-olefins with respect to the total linear a-olefins in the linear a-olefin composition is 65 to 80 wt%, the amount of the linear C26-C28 a-olefins with respect to the total linear a-olefins in the linear a-olefin composition is 10 to 20 wt% and the amount of the linear C30+ a-olefins with respect to the total linear a-olefins in the linear a-olefin composition is 3.0 to 10 wt%.

[0037] Preferably, the amount of the linear a-olefin composition with respect to the base polypropylene is 0.5 to 10 wt%, more preferably 1 .0 to 5.0 wt%.

[0038] Preferably, the amount of the linear C20+ a-olefins with respect to with respect to the base polypropylene is 0.5 to 10 wt%, more preferably 1.0 to 5.0 wt%.

[0039] Preferably, the amount of the linear C20-C30 a-olefins with respect to the base polypropylene is 0.5 to 10 wt%, more preferably 1 .0 to 5.0 wt%.

[0040] Peroxide

[0041] The peroxide may be any known peroxide used for increasing the melt flow of polypropylene. The peroxide may e.g. be selected from the group consisting of 2,5- dimethyl-2,5-bis(tert. butyl- peroxy)hexane (DHBP) (for instance sold under the tradenames Luperox 101 and Trigonox 101 ), 2,5-dimethyl-2,5-bis(tert.butyl- peroxy)hexyne-3 (DYBP) (for instance sold under the tradenames Luperox 130 and Trigonox 145), dicumyl-peroxide (DCUP) (for instance sold under the tradenames Luperox DC and Perkadox BC), di-tert.butyl-peroxide (DTBP) (for instance sold under the tradenames Trigonox B and Luperox Di), tert.butyl-cumyl-peroxide (BCUP) (for instance sold under the tradenames Trigonox T and Luperox 801 ) and 1 ,3-bis (tert.butylperoxy-isopropyl)benzene (DIPP) (for instance sold under the tradenames Perkadox 14S and Luperox DC).

[0042] Preferably, the amount of the peroxide with respect to the base polypropylene is 0.01 to 1 .00 wt%, more preferably 0.05 to 0.50 wt%.

[0043] Polyethylene

[0044] The polyethylene may be any one or combinations of high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE) and low-density polyethylene (LDPE). The production processes of HDPE, LLDPE and LDPE are summarized in Handbook of Polyethylene by Andrew Peacock (2000; Dekker; ISBN 0824795466) at pages 43-66.

[0045] The polyethylene may be or comprise a post consumer recycled (PCR) polyethylene.

[0046] HDPE

[0047] The polyethylene may be or comprise HDPE.

[0048] HDPE may be an ethylene homopolymer or may comprise a comonomer, for example 1 -butene or 1 -hexene.

[0049] Preferably, the HDPE has a density of 940-960 kg / m3, more preferably 940-955 kg / m3, measured according to ASTM D1505.

[0050] Preferably, the HDPE has a melt flow index determined according to ISO1133-1 :2022 at 190 °C and 5 kg of 0.1-4.0 g / 10 min, more preferably 0.1-1.0 g / 10 min.

[0051] Preferably, the HDPE has a melt flow index determined according to ISO1133-1 :2022 at 230 °C and 21.6 kg of 5.0-15 g / 10 min, more preferably 0.1-1.0 g / 10 min.

[0052] LLDPE

[0053] The polyethylene may be or comprise LLDPE.

[0054] The technologies suitable for the LLDPE manufacture include gas-phase fluidized-bed polymerization, polymerization in solution, polymerization in a polymer melt under very high ethylene pressure, and slurry polymerization.

[0055] The LLDPE comprises ethylene and a C3-C10 a-olefin comonomer (ethylene- a-olefin copolymer). Suitable a-olefin comonomers include 1-butene, 1- hexene, 4-methyl pentene and 1 -octene. The preferred comonomer is 1-butene.

[0056] Preferably, the a-olefin comonomer is present in an amount of about 5.0 to about 20 percent by weight of the ethylene-alpha olefin copolymer, more preferably an amount of from about 7.0 to about 15 wt% of the ethylene-a-olefin copolymer.

[0057] Preferably, the LLDPE has a density of 900-940 kg / m3, more preferably 905-930 kg / m3, more preferably 910-925 kg / m3, determined according to ASTM D1505.

[0058] Preferably, the LLDPE has a melt flow index determined according to ISO1133-1 :2022 at 190 °C and 2.16 kg of 0.1 to 3.0 g / 10min, more preferably 1.0 to 3.0 g / 10min.

[0059] LDPE

[0060] The polyethylene may be or comprise LDPE.

[0061] The LDPE may be produced by use of autoclave high pressure technology and by tubular reactor technology.

[0062] LDPE may be an ethylene homopolymer or may comprise a comonomer, for example 1-butene or 1 -hexene.

[0063] Preferably, the LDPE has a density of 916-940 kg / m3, more preferably 920-935 kg / m3, determined according to ASTM D1505.

[0064] Preferably, the LDPE has a melt flow index determined according to ISO1133-1 :2022 at 190 °C and 2.16 kg of 0.1 to 3.0 g / 10min, more preferably 1.0 to 3.0 g / 10min.

[0065] Blend of HMS-PP and PE

[0066] According to the invention, a blend of the high melt strength polypropylene and polyethylene can be made. Accordingly, in some preferred embodiments of the invention, the total amount of the high melt strength polypropylene and the polyethylene with respect to the total polyolefins in the polyolefin composition is at least 90 wt%, for example 95 to 99.9 wt%. The weight ratio between the high melt strength polypropylene to the polyethylene in the polyolefin composition may e.g. be 5:95 to 95:5, for example 5:95 to 50:50 or 50:50 to 95:5.

[0067] HMS-PP as compatibilizer for PP and PE

[0068] Further according to the invention, the high melt strength polypropylene can be used as a compatibilizer for blending polypropylene and a polyethylene. Accordingly, the invention provides use of the high melt strength polypropylene as a compatibilizer for blending polypropylene and a polyethylene.

[0069] In some embodiments, the polyolefin composition comprises a further polypropylene, wherein the amount of the high melt strength polypropylene with respect to the total of said further polypropylene and the polyethylene is 0.5 to 10 wt%, preferably 5 to 10 wt%.

[0070] The weight ratio between the total of the high melt strength polypropylene and the further polypropylene to the polyethylene in the polyolefin composition may e.g. be 5:95 to 95:5, for example 5:95 to 50:50 or 50:50 to 95:5.

[0071] As the further polypropylene, any type of polypropylene can be used. Suitable examples of the further polypropylene are those described for the base polypropylene.

[0072] Optional components

[0073] The polyolefin composition according to the invention may be obtained by melt-mixing the high melt strength polypropylene and the polyethylene, optionally with any other optional components.

[0074] The polyolefin composition may comprise components other than the high melt strength polypropylene and the polyethylene, such as additives and fillers. Examples of the additives include nucleating agents; stabilizers, e.g. heat stabilizers, anti-oxidants, UV stabilizers; colorants, like pigments and dyes; clarifiers; surface tension modifiers; lubricants; flame-retardants; mold-release agents; flow improving agents; plasticizers; anti-static agents; external elastomeric impact modifiers; blowing agents; and / or components that enhance interfacial bonding between polymer and filler, such as a maleated polyethylene. The amount of the additives is typically 0 to 5.0 wt%, for example 1 .0 to 3.0 wt%, with respect to the total composition. Examples of fillers include glass fibers, talc and mica. The amount of fillers may e.g. be 0 to 40 wt%, for example 5 to 30 wt% or 10 to 25 wt%, with respect to the total polyolefin composition.

[0075] Accordingly, in some embodiments, the polyolefin composition further comprises 0 to 5.0 wt% of additives and 0 to 40 wt% of fillers.

[0076] In some embodiments, the polyolefin composition according to the invention has little or no fillers, i.e. the polyolefin composition according to the invention has less than 5.0 wt%, less than 3.0 wt%, less than 1 .0 wt%, less than 0.5 wt%, less than 0.1 wt% or 0 wt% of fillers.

[0077] Preferably, the total amount of the high melt strength polypropylene, the polyethylene, the optional additives, the optional fillers and the optional further polypropylene is 100 wt% with respect to the total polyolefin composition.

[0078] The invention further provides a process for making the polyolefin composition according to the invention, comprising melt-mixing the high melt strength polypropylene and the polyethylene and optionally additives, fillers and / or further polypropylene. Some or all of the optional components may be added to the high melt strength polypropylene and / or the polyethylene before the high melt strength polypropylene and the polyethylene are melt-mixed.

[0079] Pipe

[0080] The present invention further provides an article comprising the composition according to the invention, preferably a molded article, such as a pipe or a film.

[0081] The pipe may be a multilayer pipe having an innermost layer comprising the composition according to the invention and one or more outer layers.

[0082] The term “pipe” is herein understood as a hollow elongated article. The cross section may be of various shapes e.g. be circular, elliptical, square, rectangular or triangular. The pipe according to the invention may have an outer diameter in the range of 2.5 to 255 cm and / or an inner diameter of 2 to 250 cm and / or the pipe may have one or more layers with a total layer thickness in the range of 0.3 to 100 mm. The outer layer may e.g. have a thickness of 0.3 to 50 mm, 1 to 30 mm or 5 to 20 mm. At least one of the outer layers may be steel, ceramic or polymer. Any kind of polymer may be used for the outer layer(s). Preferably, the outer layer or layers comprises polypropylene or polyethylene. Preferably, the outer layer adjacent to the innermost layer comprises polypropylene or polyethylene.

[0083] A tie layer may be present between the innermost layer and the adjacent outer layer. The tie layer may be comprise anhydride- or acid-grafted materials. However, the composition according to the invention in the innermost layer allows eliminating the need for such tie layer when the adjacent outer layer comprises polypropylene and / or polyethylene.

[0084] Accordingly, in preferred embodiments, the adjacent outer layer comprises polypropylene and / or polyethylene and is directly bonded to the innermost layer.

[0085] The pipe according to the invention may be produced by any suitable process, e.g. as described in US9488310. The pipe according to the invention may be produced by a pipe extrusion manufacturing process.

[0086] The film may be a multilayer pipe having a surface layer (the layer which is at the surface of the film) comprising the composition according to the invention.

[0087] It is noted that the invention relates to the subject-matter defined in the independent claims alone or in combination with any 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.

[0088] 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.

[0089] 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.

[0091] Materials: hPP1 : propylene homopolymer having a melt flow index of 0.3 dg / min (ISO1133-1 : 2022, 230 °C, 2.16 kg) and a density of 905 kg / m3(SABIC® PP531 P) rPP1 : random propylene-ethylene copolymer having a melt flow index of 0.3 dg / min (ISO1133-1 : 2022, 230 °C, 2.16 kg) and a density of 898 kg / m3, ethylene content 4 wt% (SABIC® Vestolen P9421)

[0092] LAO: linear a-olefin composition having the following composition:

[0093] The IR absorbance of a sample of LAO showed strong absorbance at 1642cm1attributed to unsaturated (C=C) functional group present in LAO.

[0094] Peroxide: polypropylene masterbatch comprising 40 wt% of 1 ,3-bis (tertbutylperoxyisopropyl) benzene

[0095] Materials shown in Table 1 were melt-mixed at a temperature of 200 °C for 8 minutes.

[0096] FTIR test was conducted on the obtained polypropylene to confirm that the C20+ linear a-olefins have grafted on the polypropylene. The samples made using LAO and peroxide showed peaks at 720 cm1while the samples made using peroxide without LAO. The grafting percentage was quantified by counting the ethylene print content. The rheological behavior of the obtained polypropylene samples was studied by ARES rheometer which uses rotational force to measure the storage and loss moduli as well as the complex viscosity of the studied samples. The temperature was fixed at 180 °C and the frequency was increased from 0.5 rad / s to 500 rad / s while measuring the complex viscosity and storage and loss moduli at each frequency. Zero Shear viscosity was extrapolated from the obtained results and shown in Table 1.

[0097] MFI of the samples was measured according to IS01133-1 (2022) at 230 °C, 2.16 kg and shown in Table 1.

[0098] Table 1

[0099] The polypropylene obtained with the addition of C20+ linear alpha-olefins according to the invention has a higher zero shear viscosity than the corresponding polypropylene obtained without the addition of C20+ linear alpha-olefins, indicating that the melt strength of the polypropylene obtained with the addition of alpha-olefin is higher.

[0100] The obtained samples of polypropylene were melt-mixed with polyethylene were melt- mixed at a temperature of 220 °C for 6 minutes to obtain compositions shown in T able 2.

[0101] PE1 : LLDPE having melt flow index of 2 dg / min (IS01133-1 : 2022, 190 °C, 2.16 kg) and density of 918 kg / m3, copolymer: 1 -butene (SABIC® LLDPE 218B)

[0102] Tensile elongation at break was measured according to ASTM D638 and the results are shown in Table 2. Table 2

[0103] The composition of CEx 11 made by blending PE with polypropylene treated with peroxide of CEx 4 has a lower tensile elongation at break than the composition of CEx 10 made by blending PE with PP which has not been treated with peroxide.

[0104] The composition of Ex 12 made by blending PE with the high melt strength polypropylene grafted with a-olefins has a higher tensile elongation at break than the compositions of CEx 10 and CEx 11 .

Claims

CLAIMS1 . A polyolefin composition comprising high melt strength polypropylene and polyethylene, wherein the high melt strength polypropylene is obtained by or obtainable by a process comprising melt-mixing a base polypropylene, a peroxide and a linear a-olefin composition comprising linear C20+ a-olefins.

2. The composition according to claim 1 , wherein the base polypropylene comprises or is a propylene homopolymer.

3. The composition according to any one of the preceding claims, wherein the base polypropylene comprises or is a random copolymer of propylene and a comonomer selected from ethylene and C4-C12 a-olefins, preferably a random propyleneethylene copolymer.

4. The composition according to any one of the preceding claims, wherein the base polypropylene has a melt flow index determined according to ISO1133-1 : 2022 at 230 °C and 2.16 kg of 0.1 to 10 dg / min.

5. The composition according to any one of the preceding claims, wherein the amount of the linear C20+ a-olefins with respect to the total linear a-olefins in the linear a-olefin composition is at least 55 wt%, preferably at least 60 wt%, more preferably at least 70 wt%, more preferably at least 80 wt%, more preferably at least 90 wt%, more preferably at least 95 wt%, preferably wherein the linear a-olefin composition further comprises linear C4 to C19 a-olefins in an amount of at most 5.0 wt%, for example 0.1 to 5.0 wt% or 0.1 to 3.0 wt%, with respect to the total linear a-olefins in the linear a-olefin composition.

6. The composition according to any one of the preceding claims, wherein the amount of C20-C24 linear a-olefins with respect to the total linear a-olefins in the linear a- olefin composition is 50 to 90 wt% or 65 to 75 wt% and the amount of C26-C28 linear a-olefins with respect to the total linear a-olefins in the linear a-olefin composition is 5.0 to 25 wt% or 15 to 25 wt%7. The composition according to any one of the preceding claims, wherein the amount of the linear C20+ a-olefins with respect to the base polypropylene is 0.5 to 10 wt%, more preferably 1 .0 to 5.0 wt%.

8. The composition according to any one of the preceding claims, wherein the amount of the peroxide with respect to the base polypropylene is 0.01 to 1 .00 wt%, more preferably 0.05 to 0.50 wt%.

9. The composition according to any one of the preceding claims, wherein the polyethylene is selected from the group consisting of high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE) and low-density polyethylene (LDPE) and combinations thereof.

10. The composition according to any one of the preceding claims, wherein the polyethylene has a melt flow index determined according to ISO1133-1 :2022 at 190 °C and 2.16 kg of 0.1 to 10 dg / min.11 . The composition according to any one of claims 1 to 10, wherein the total amount of the high melt strength polypropylene and the polyethylene with respect to the total polyolefins in the polyolefin composition is at least 90 wt%, for example 95 to 99.9 wt%.

12. The composition according to any one of claims 1 to 10, wherein the polyolefin composition comprises a further polypropylene, wherein the amount of the high melt strength polypropylene with respect to the total of said further polypropylene and the polyethylene is 0.5 to 10 wt%, preferably 5 to 10 wt%.

13. Use of high melt strength polypropylene as a compatibilizer for blending polypropylene and a polyethylene, wherein the high melt strength polypropylene is obtained by or obtainable by a process comprising melt-mixing a base polypropylene, a peroxide and a linear a-olefin composition comprising linear C20+ a-olefins.

14. An article comprising the composition according to any one of claims 1 to 12, preferably wherein the article is selected from a pipe and a film.

15. The article according to claim 14, wherein the article is a multilayer pipe having an innermost layer comprising the composition and one or more outer layers, preferably wherein the adjacent outer layer comprises polypropylene and / or polyethylene and is directly bonded to the innermost layer.

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