Process for preparation of foamed article

Abstract

The invention relates to a process for the preparation of a foamed article, comprising the sequential steps of: • A) providing a polymer composition comprising a high melt strength polypropylene, • B) adding a blowing agent to the polymer composition, for example wherein the blowing agent is added in an amount >_ 0.10 wt% and <_ 20 wt% based on the polymer composition and • C) subjecting the mixture of the polymer composition and the blowing agent to a foaming process to form the foamed article, wherein the high melt strength polypropylene is prepared by • a) irradiation of a mixture comprising a polypropylene and a stabilizer, wherein the irradiation is performed with >_ 2.0 and <_ 20 Megarad electron-beam radiation in a reduced oxygen environment, wherein the amount of active oxygen is <_ 15% by volume with respect to the total volume of the reduced oxygen environment for a time sufficient for obtaining a long chain branched polypropylene and • b) deactivation of the free radicals in the long chain branched polypropylene to form the high melt strength polypropylene, wherein the stabilizer is or comprises vitamin E;

Description

[0001] PROCESS FOR PREPARATION OF FOAMED ARTICLE

[0002] The invention relates to a process for the preparation of a foamed article using a polymer composition.

[0003] Polymer foams are used in a wide range of applications, such as building and construction, automotive applications, household applications, such as food packaging and protective packaging; and consumer applications. Foams are popular because of their good mechanical rigidity, their good insulative properties and their cushioning against mechanical shock. In addition, the use of foams provides a significant contribution to the reduction in the use of raw materials. Moreover, the use of foams allows for a lightweight solution, which is not only of advantage from a cost perspective, but also from a transportation point of view as less energy is required to transport a lighter material.

[0004] Polypropylene foams are of advantage as compared to other polymer foams due to a number of reasons: polypropylene has good mechanical properties, in particular rigidity (stiffness), allows easy recycling (whereas, polystyrene for example requires further steps in waste separation processes), has a good chemical (oil and acid) resistance, a good thermal resistance and does not absorb water.

[0005] It is important for a foamed article to have good aesthetics and low density. It is further desirable that such foamed article can be obtained over a large temperature processing window.

[0006] Accordingly, the invention provides a process for the preparation of a foamed article, comprising the sequential steps of:

[0007] A) providing a polymer composition comprising a high melt strength polypropylene,

[0008] B) adding a blowing agent to the polymer composition, for example wherein the blowing agent is added in an amount > 0.10 wt% and < 20 wt% based on the polymer composition and

[0009] C) subjecting the mixture of the polymer composition and the blowing agent to a foaming process to form the foamed article, wherein the high melt strength polypropylene is prepared by a) irradiation of a mixture comprising a polypropylene and a stabilizer, wherein the irradiation is performed with > 2.0 and < 20 Megarad electron-beam radiation in a reduced oxygen environment, wherein the amount of active oxygen is < 15% by volume with respect to the total volume of the reduced oxygen environment for a time sufficient for obtaining a long chain branched polypropylene and b) deactivation of the free radicals in the long chain branched polypropylene to form the high melt strength polypropylene, wherein the stabilizer is or comprises vitamin E, wherein the polypropylene in the mixture to be irradiated in step a) is produced by a polymerization process in the presence of a catalyst comprising a catalyst comprising a procatalyst, a co-catalyst and optionally an external electron donor, wherein the procatalyst is obtainable by a process comprising the steps of: contacting a magnesium-containing support with a halogen-containing titanium compound, and an internal electron donor according to Formula I: wherein R1is a secondary alkyl group and R2is a non-secondary alkyl group having at least 5 carbon atoms, preferably R2is a non-secondary alkyl group having at least 5 carbon atoms and being branched at the 3-position or further positions; said procatalyst is prepared according to the following steps: i) contacting a compound R4zMgX42.zwith an alkoxy- or aryloxy-containing silane compound to give a first intermediate reaction product, being a solid Mg(ORa)xX12-x, wherein: Rais a linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and preferably has from 1 to 20 carbon atoms; wherein R4is a linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and preferably has from 1 to 20 carbon atoms, preferably R4is butyl; wherein X4and X1are each independently selected from the group of consisting of fluoride (F-), chloride (CI-), bromide (Br-) or iodide (I-), preferably chloride; z is in a range of larger than 0 and smaller than 2, being 0 < z < 2, x is an integer between 0 and 2; ii) optionally contacting the solid Mg(ORa)xX12.xobtained in step i) with at least one activating compound selected from the group formed by activating electron donors and metal alkoxide compounds of formula M1(ORb)v.w(OR3)w or M2(ORb)v.w(R3)w, to obtain a second intermediate product; wherein: M1is a metal selected from the group consisting of Ti, Zr, Hf, Al or Si; v is the valency of M1; M2is a metal being Si; v is the valency of M2; Rband R3are each a linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms, and preferably has from 1 to 20 carbon atoms; wherein w is smaller than v, preferably v being 3 or 4; iii) contacting the first or second intermediate reaction product, obtained respectively in step i) or ii), with a halogen-containing Ti-compound and said compound represented Formula I, as the internal electron donor.

[0010] The high melt strength polypropylene used in the process according to the invention is prepared by irradiating a mixture comprising vitamin E and a polypropylene made using a specific catalyst. It was surprisingly found that a foamed article with good aesthetics and low density can be obtained by the process according to the invention within a large temperature processing window.

[0011] The foamed article according to the invention may be a foamed sheet.

[0012] High melt strength polypropylene

[0013] Preferably, the high melt strength polypropylene used according to the invention is characterized by Mz determined on a sample which has not been subjected to a melt flow index measurement in accordance with ASTM D1238 (2013) at a temperature of 290°C under a load of 2.16 kg and molecular weight distribution curve obtained on a sample which has been subjected to a melt flow index measurement in accordance with ASTM D1238 (2013) at a temperature of 290°C under a load of 2.16 kg.

[0014] Preferably, the high melt strength polypropylene has Mz of at least 1500 kg / mol, preferably 2000 to 30000 kg / mol, more preferably 3000 to 25000 kg / mol, more preferably 5000 to 20000 kg / mol, more preferably 7500 to 17500 kg / mol, determined according to ASTM D6474-12 using SEC-MALS. This Mz is determined on a sample which has not been subjected to a melt flow index measurement in accordance with ASTM D1238 (2013) at a temperature of 290°C under a load of 2.16 kg.

[0015] Further, a molecular weight distribution curve is obtained for the high melt strength polypropylene by subjecting a sample of the high melt strength polypropylene to a melt flow index measurement in accordance with ASTM D1238 (2013) at a temperature of 290°C under a load of 2.16 kg to obtain a strand and subjecting the strand to SEC-MALS to determine molecular weight according to ASTM D6474-12 to obtain the molecular weight distribution curve.

[0016] Preferably, in this molecular weight distribution curve, the area under the curve at Log molecular weight of above 6.0 is at most 12.5 % of the area under the total curve, and / or the area under the curve at Log molecular weight of above 6.5 is at most 5.0 % of the area under the total curve.

[0017] Preferably, the area under the curve at Log molecular weight of above 6.0 is 5.0 to 12.2%, more preferably 5.5 to 10.0%, of the area under the total curve.

[0018] Preferably, the area under the curve at Log molecular weight of above 6.5 is 1.0 to 4.8%, more preferably 1.5 to 4.0%, of the area under the total curve.

[0019] Preferably, the high melt strength polypropylene has Mz determined from said molecular weight distribution curve of 2000 to 7000 kg / mol, more preferably 3000 to 5500 kg / mol.

[0020] A high melt strength polypropylene is branched and, thus, differs from a linear polypropylene in that the polypropylene backbone covers side chains whereas a nonbranched polypropylene, i.e. a linear polypropylene, does not cover side chains. The side chains have significant impact on the rheology of the polypropylene. Accordingly linear polypropylenes and high melt strength polypropylenes can be clearly distinguished by their flow behaviour under stress.

[0021] Branching can be generally achieved by using specific catalysts, i.e. specific single-site catalysts, or by chemical modification. Concerning the preparation of a branched polypropylene obtained by the use of a specific catalyst reference is made to EP 1 892 264. With regard to a branched polypropylene obtained by chemical modification it is referred to EP 0 879 830 A1 . In such a case the branched polypropylene is also called high melt strength polypropylene. Preferably, the high melt strength polypropylene has a branching index g’ of less than 1 .00, more preferably less than 0.90, more preferably less than 0.80, more preferably less than 0.75.

[0022] The branching index g' is explained e.g. in EP1847555A1. The branching index g' defines the degree of branching and correlates with the amount of branches of a polymer. The branching index g' is defined as g'=[IV]br / [l V]iinin which g' is the branching index, [IVbr] is the intrinsic viscosity of the branched polypropylene and [IV]iinis the intrinsic viscosity of the linear polypropylene having the same weight average molecular weight (within a range of ±10 %) as the branched polypropylene. Thereby, a low g'-value is an indicator for a high branched polymer. In other words, if the g'-value decreases, the branching of the polypropylene increases. Reference is made in this context to B.H. Zimm and W.H. Stockmeyer, J. Chem. Phys. 17,1301 (1949). This document is herewith included by reference. The intrinsic viscosity needed for determining the branching index g' is measured according to DIN ISO 1628 / 1 , October 1999 (in Decalin at 135 °C).

[0023] Preferably, the high melt strength polypropylene has a melt strength of > 30 cN. The melt strength of the high melt strength polypropylene is herein determined in accordance with ISO 16790:2005 at a temperature of 200°C, using a cylindrical capillary having a length of 20mm and a width of 2mm, a starting velocity vO of 7.5mm / s and an acceleration of 12mm / s2.

[0024] High melt strength polypropylene having a melt strength > 30 cN can for example be obtained by the process as disclosed in W02009 / 003930A1. W02009 / 003930A1 discloses an irradiated polymer composition comprising at least one polyolefin resin and at least one non-phenolic stabilizer, wherein the irradiated polymer composition is produced by a process comprising mixing the polyolefin resin with the non-phenolic stabilizer and irradiating this mixture in a reduced oxygen environment. In addition, a high melt strength polypropylene is available from SABIC as SABIC® PP UMS 561 P as of 18 February 2021.

[0025] The high melt strength polypropylene is prepared by a) irradiation of a mixture comprising a polypropylene and a stabilizer, wherein the irradiation is performed with > 2.0 and < 20 Megarad electron-beam radiation in a reduced oxygen environment, wherein the amount of active oxygen is < 15% by volume with respect to the total volume of the reduced oxygen environment for a time sufficient for obtaining a long chain branched polypropylene and b) deactivation of the free radicals in the long chain branched polypropylene to form the high melt strength polypropylene.

[0026] How to deactivate the free radicals is known in the art, for example by heating as described in W02009 / 003930A1 .

[0027] In some preferred embodiments, the stabilizer comprises a non-phenolic stabilizer. Preferably, the non-phenolic stabilizer is chosen from the group of hindered amines.

[0028] Examples of non-phenolic stabilizers are known in the art and are for example disclosed on pages 37 - 60 of W02009 / 003930A1 , hereby incorporated by reference. Preferably, the non-phenolic stabiizer is chosen from the group of hindered amines. More preferably, the non-phenolic stabilizer comprises at least one hindered amine selected from the group of Chimassorb® 944, Tinuvin® 622, Chimassorb® 2020, Chimassorb® 119, Tinuvin® 770, and mixtures thereof, separate or in combination with at least one hydroxylamine, nitrone, amine oxide, or benzofuranone selected from N.M- dehydrogenated tallow)amine (Irgastab® FS-042), an N,N- di(alkyl)hydroxylamine produced by a direct oxidation of N,N-di(hydrogenated tallow)amine (Irgastab® FS- 042), N-octadecyl-a-heptadecylnitrone, Genox™ EP, a di(C16 -C18 )alkyl methyl amine oxide, 3-(3,4-dimethylphenyl)-5,7-di-tert-butyl-benzofuran-2-one, Irganox® HP- 136 (BFI), and mixtures thereof, and separate or in combination with at least one organic phosphite or phosphonite selected from tris(2,4-di-tert-butylphenyl) phosphite (Irgafos® 168). Even more preferably, the non-phenolic stabilizers of the present subject matter can include those described in U.S. Patents 6,664,317 and 6,872,764, both of which are incorporated herein by reference in their entirety.

[0029] The stabilizer is or comprises vitamin E. The use of vitamin E was surprisingly found to allow obtaining a good surface quality of the foamed article within a particularly large temperature processing window. In particular, the use of vitamin E allows using low temperature for foaming during foaming process such as foam extrusion process.

[0030] The stabilizer may comprise a non-phenolic stabilizer and vitamin E.

[0031] Preferably, the melt strength of the high melt strength polypropylene is > 37 cN, preferably > 40 cN, preferably > 45 cN, > more preferably 50 cN, more preferably > 55 cN, even more preferably > 60 cN, most preferably > 65 cN and / or preferably the melt strength of the high melt strength polypropylene is <100 cN, for example < 95 cN, for example < 90 cN, for example < 87cN.

[0032] With polypropylene as used herein is meant propylene homopolymer, a copolymer of propylene with an a-olefin or a heterophasic propylene copolymer.

[0033] Preferably, the high melt strength polypropylene is polypropylene chosen from the group of propylene homopolymers and propylene copolymers comprising moieties derived from propylene and one or more comonomers chosen from the group of ethylene and alpha-olefins with > 4 and < 12 carbon atoms.

[0034] Preferably, the propylene copolymer comprises moieties derived from one or more comonomers chosen from the group of ethylene and alpha-olefins with > 4 and < 12 carbon atoms in an amount of < 10wt%, for example in an amount of > 1.0 and < 7.0wt% based on the propylene copolymer, wherein the wt% is determined using13C NMR. For example, the propylene copolymer comprises moieties derived from one or more comonomer chosen from the group of ethylene, 1 -butene, 1 -pentene, 1 -hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, 1-decene and 1-dodecene, preferably moieties derived from ethylene.

[0035] Polypropylenes and the processes for the synthesis of polypropylenes are known. A propylene homopolymer is obtained by polymerizing propylene under suitable polymerization conditions. A propylene copolymer is obtained by copolymerizing propylene and one or more other comonomers, for example ethylene, 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.

[0036] Propylene homopolymers, propylene copolymers and heterophasic propylene copolymers can be made by any known polymerization technique as well as with any known polymerization catalyst system. Regarding the techniques, reference can be given to slurry, solution or gas phase polymerizations; regarding the catalyst system reference can be given to Ziegler-Natta, metallocene or single-site catalyst systems. All are, in themselves, known in the art. Preferably, the high melt strength polypropylene has a melt flow rate > 0.50 and < 8.0 g / 1 Omin, more preferably > 0.70 and < 5.0 g / 1 Omin, most preferably > 1 .0 and < 4.0 g / 10min, most preferably > 1.5 and < 4.0 g / 1 Omin, as determined in accordance with ASTM D1238 (2013) at a temperature of 230°C under a load of 2.16 kg.

[0037] Preferably, the high melt strength polypropylene is present in an amount > 10wt% based on the polymer composition, preferably wherein the high melt strength polypropylene is present in an amount > 10wt% based on the polymer composition, more preferably in an amount < 99.5 wt% based on the polymer composition. For example, the amount of high melt strength polypropylene based on the polymer composition is > 15wt%, > 20wt%, > 25wt%, preferably > 30wt%, preferably > 40wt%, preferably > 50wt%, preferably > 60wt%, preferably > 70wt%, preferably > 80wt%, preferably > 90wt% and / or < 99.5wt%, < 99 wt%, < 98.5wt%, < 98.0wt%, < 97.0wt%, < 96.0wt%, < 95.0wt%.

[0038] Catalyst

[0039] The polypropylene in the mixture to be irradiated in step a) is produced by a polymerization process in the presence of a catalyst comprising a procatalyst, a cocatalyst and optionally an external electron donor, wherein the procatalyst is obtainable by a process comprising the steps of: contacting a magnesium-containing support with a halogen-containing titanium compound, and an internal electron donor according to Formula I: wherein R1is a secondary alkyl group and R2is a non-secondary alkyl group having at least 5 carbon atoms, preferably R2is a non-secondary alkyl group having at least 5 carbon atoms and being branched at the 3-position or further positions; said procatalyst is prepared according to the following steps: i) contacting a compound R4zMgX42.zwith an alkoxy- or aryloxy-containing silane compound to give a first intermediate reaction product, being a solid Mg(ORa)xX12-x, wherein: Rais a linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and preferably has from 1 to 20 carbon atoms; wherein R4is a linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and preferably has from 1 to 20 carbon atoms, preferably R4is butyl; wherein X4and X1are each independently selected from the group of consisting of fluoride (F-), chloride (CI-), bromide (Br-) or iodide (I-), preferably chloride; z is in a range of larger than 0 and smaller than 2, being 0 < z < 2, x is an integer between 0 and 2; ii) optionally contacting the solid Mg(ORa)xX12-x obtained in step i) with at least one activating compound selected from the group formed by activating electron donors and metal alkoxide compounds of formula M1(ORb)v.w(OR3)w or M2(ORb)v.w(R3)w, to obtain a second intermediate product; wherein: M1is a metal selected from the group consisting of Ti, Zr, Hf, Al or Si; v is the valency of M1; M2is a metal being Si; v is the valency of M2; Rband R3are each a linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms, and preferably has from 1 to 20 carbon atoms; wherein w is smaller than v, preferably v being 3 or 4; iii) contacting the first or second intermediate reaction product, obtained respectively in step i) or ii), with a halogen-containing Ti-compound and said compound represented Formula I, as the internal electron donor.

[0040] Such catalyst is described in detail in W02021 / 063930, incorporated herein by reference. The catalyst comprises a procatalyst, a co-catalyst and optionally an external electron donor.

[0041] In an embodiment, during step ii) as activating compounds an alcohol is used as activating electron donor and titanium tetraalkoxide is used as metal alkoxide compound.

[0042] In an embodiment, an activator is present. In an embodiment, said activator is ethyl benzoate. In an embodiment, said activator is a benzamide according to formula X:

[0043] Formula X wherein R70and R71are each independently selected from hydrogen or an alkyl, and R72, R73, R74, R75, R76are each independently selected from hydrogen, a heteroatom or a hydrocarbyl group, preferably selected from alkyl, alkenyl, aryl, aralkyl, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof, more preferably wherein R70and R71are both methyl and wherein R72, R73, R74, and R75are all hydrogen, being N,N’-dimethylbenzamide (Ba-2Me).

[0044] Preferably, the internal electron donor used is according to Formula I:

[0045] Formula I wherein R1is a secondary alkyl group having at least three carbon atoms and R2is a non-secondary alkyl group having at least 5 carbon atoms, preferably R1et R2is having at most seven carbon atoms, preferably at most six carbon atoms , preferably iso-propyl, iso-butyl, iso-pentyl, cyclopentyl, n-pentyl, and iso-hexyl, preferably R2is being branched at the 3-position or further positions.

[0046] In another embodiment, the internal electron donor is 3,3-bis(methoxymethyl)-2,6- dimethyl heptane, according to Formula I wherein R1 is iso-propyl being secondary alkyl and R2 is iso-pentyl being non-secondary and having a branch on the third carbon atom (abbreviated as iPiPen, wherein iP stands for iso-propyl and iPen stands for isopentyl, also known as 3-methyl-butyl). This compound iPiPen has a chemical formula of CI3H28O2; an exact mass of 216.21 and a molecular weight of 216.37. In a more preferred embodiment of the invention, iPiPen is used as internal donor and / or wherein the activating compound is preferably N,N-dimethylbenzamide.

[0047] In another embodiment, the internal electron donor is (1-methoxy-2-(methoxymethyl)-5- methylhexan-2-yl)cyclopentane, according to Formula I wherein R1is secondary alkyl cyclopentyl and R2is secondary cyclopentyl (abbreviated as CPiPen, wherein CP stands for cyclopentyl and iPen stands for iso-pentyl, also known as 3-methyl-butyl). This compound CPiPen has a chemical formula of CI5H30O2; an exact mass of 242.22 and a molecular weight of 242.40. In a more specific embodiment, CPiPen is used as internal donor and / V, / V-dimethylbenzamide is preferably used as activator.

[0048] In another embodiment, the internal electron donor is 3,3-bis(methoxymethyl)-2,7- dimethyloctane, according to Formula I wherein R1is the secondary alkyl iso-propyl and R2is non-secondary iso-hexyl with a branch on the four carbon atom (abbreviated as iPiHex, wherein iP stands for iso-propyl and iHex stands for iso-hexyl, also known as 4-methyl-pentyl). This compound iPiHex has a chemical formula of CI4H30O2; an exact mass of 230.22 and a molecular weight of 230.39. In a more specific embodiment, iPiHex is used as internal donor and / V, / V-dimethylbenzamide is preferably used as activator.

[0049] In another embodiment, the internal electron donor is 3,3-bis(methoxymethyl)-2- methyloctane, according to Formula I wherein R1is secondary alkyl iso-propyl and R2is non-secondary non-branched n-pentyl (abbreviated as iPnPen, wherein iP stands for iso-propyl and nPen stands for n-pentyl). This compound iPnPen has a chemical formula of CI3H28O2; an exact mass of 216.21 and a molecular weight of 216.37. In a more specific embodiment, iPnPen is used as internal donor and / V, / V-dimethylbenzamide is preferably used as activator. iPnPen

[0050] In another embodiment, the internal electron donor is 3,3-bis(methoxymethyl)-2,6- dimethyloctane, according to Formula I wherein R1is secondary alkyl iso-propyl and R2is non-secondary branched hexyl having a branch at the third carbon atom (abbreviated as iP3Hex, wherein iP stands for iso-propyl and wherein 3Hex stands for hexyl having a branch at the third carbon atom, also known as 3-methyl-pentyl). This compound iPiHex has a chemical formula of C14H32O2 ; an exact mass of 230.22 and a molecular weight of 230.39. In a more preferred embodiment, iP3Hex is used as internal donor and / or / V, / V-dimethylbenzamide is preferably used as activator. iP3Hex

[0051] In an embodiment, the substituent R1is isopropyl or cyclopentyl. In an embodiment, the substituent R2is isopentyl or isohexyl. The below table shows the embodiments above with their abbreviations and the R1and R2groups as well if these groups are secondary or not and branched or not.

[0052] It is further preferred that R1is a secondary alkyl group and R2is a non-secondary alkyl group being branched at the 3-position or further positions. Preferably, the catalyst comprises the external electron donor and the molar ratio of cocatalyst to external electron donor is more than 1 and at most 120 or more than 3 and at most 90.

[0053] Preferably, the molar ratio of Al in the co-catalyst to Si in the external electron donor is more than 1 and at most 120 or more than 3 and at most 90.

[0054] Preferably, the co-catalyst is selected from the group consisting of trimethylaluminum, triethylaluminum, triisobutylaluminum, trihexylaluminum, di-isobutylaluminum hydride, trioctylaluminium, dihexylaluminum hydride and mixtures thereof.

[0055] Preferably, the external electron donors are chosen from the group of compounds having a structure according to:

[0056] - Formula III : (R90)2N— Si(OR91)3,

[0057] - Formula IV: (R92)Si(OR93)3, Formula V: Si(ORa)4.nRbn, and mixtures thereof, wherein each of R90, R91, R92and R93groups are each independently a linear, branched or cyclic, substituted or unsubstituted alkyl having between 1 and 10 carbon atoms, preferably wherein R90, R91, R92and R93groups are each independently a linear unsubstituted alkyl having between 1 and 8 carbon atoms, wherein n can be from 0 up to 2, and each of Raand Rb, independently, represents an alkyl or aryl group, optionally containing one or more hetero atoms for instance O, N, S or P, with, for instance, 1-20 carbon atoms, for example ethyl, methyl or n-propyl, for example diethylaminotriethoxysilane (DEATES), n-propyl triethoxysilane, (nPTES), n-propyl trimethoxysilane (nPTMS); and organosilicon compounds having general formula Si(ORa)4.nRbn, wherein n can be from 0 up to 2, and each of Raand Rb, independently, represents an alkyl or aryl group, optionally containing one or more hetero atoms for instance O, N, S or P, with, for instance, 1-20 carbon atoms; such as diisobutyl dimethoxysilane (DiBDMS), t-butyl isopropyl dimethyxysilane (tBuPDMS), cyclohexyl methyldimethoxysilane (CHMDMS), dicyclopentyl dimethoxysilane (DCPDMS) or di(iso-propyl) dimethoxysilane (DiPDMS). More preferably, the external electron donor is chosen from the group of di(iso-propyl) dimethoxysilane (DiPDMS) or diisobutyl dimethoxysilane (DiBDMS).

[0058] Preferably, the external donor comprises or consists of a compound selected from the list comprising organo-silicon compounds, silanes, alkoxy silanes, alkyl silane, alkyl alkoxy silane and aliphatic / aromatic ester, for example dicyclopentyldimethoxysilane, di-tert-butyldimethoxysilane, methylcyclohexyldimethoxysilane, ethylcyclohexyldimethoxysilane, diphenyldimethoxysilane, diisopropyldimethoxysilane, di-n-propyldimethoxysilane, diisobutyldimethoxysilane, di-n-butyldimethoxysilane, cyclopentyltrimethoxysilane, isopropyltrimethoxysilane, npropyltrimethoxysilane, n- propyltriethoxysilane, ethyltriethoxysilane, tetramethoxysilane, tetraethoxysilane, cyclopentylpyrrolidinodimethoxysilane, bis(pyrrolidino )-dimethoxysilane, and mixtures thereof, preferentially di(iso-propyl) dimethoxysilane (DiPDMS)

[0059] The compounds mentioned above as examples of the external electron donor are sometimes referred as Selectivity Control Agent (SCA). The external electron donor may consist of SCA. Alternatively, in addition to SCA, the external electron donor may further comprise compounds known as an activity limiting agent (ALA). Preferably, the Activity Limiting Agent (ALA) is selected from the group consisting of: ethyl acetate, ethyl benzoate, p-ethoxy ethyl benzoate, methyl trimethylacetate, isopropyl myristate, di-n-butyl sebacate, (poly)(alkylene glycol) mono- or diacetates, (poly)(alkylene glycol) mono- or di-myristates, (poly)(alkylene glycol) mono- or di- laurates, (poly)(alkylene glycol) mono- or di-dioleates, glyceryl tri(acetate), mixed glycerides of linoleic, oleic, palmitic and stearic acids, and mixtures thereof. More preferably, the Activity Limiting Agent (ALA) is isopropyl myristate.

[0060] The ratio of Selectivity Control Agent (SCA) to Activity Limiting Agent (ALA) is in principle not critical, best results are obtained for a SCA / ALA ratio in the range from 0.010 to 100, more preferably in the range from 0.10 to 20.

[0061] The molar ratio of Al in the co-catalyst to Si in the external electron donor may e.g. be 1 to 120.

[0062] In some preferred embodiments, the molar ratio of Al in the co-catalyst to Si in the external electron donor is more than 1 , preferably more than 3, even more preferably more than 4 and at most 120, preferably at most 110, more preferably 90, more preferably at most 70, more preferably at most 60. the molar ratio of Al in the co- catalyst to Si in the external electron donor is in the range from 1 to 120, or 1 to 110 or 1 to 90 or 1 to 70 or 1 to 60, 3 to 60, or 3 to 90, or 4 to 90, or 4 to 70, or 4 to 60, or 5 to 120, or 5 to 110, or 5 to 90, or 5 to 70, or 5 to 60, or.

[0063] In some preferred embodiments, the molar ratio of Al in the co-catalyst to Si in the external electron donor is more than 15 and at most 120 or more than 20, or more than 25 and at most 120, or at most 100, or at most 90, or at most 70, or at most 60. The molar ratio of Al in the co-catalyst to Si in the external electron donor is in the range from 15 to 120, or 15 to 100, or 15 to 90 or 15 to 70, or 15 to 60, or 20 to 120, or 20 to 100, or 20 to 90, or 20 to 70, 20 to 60, or 25 to 120, or 25 to 100, or 25 to 90 or 25 to 70, or 25 to 60

[0064] In some embodiment the molar ratio of Al in the co-catalyst to Si in the external electron donor is in the range from 1 to 25, or from 1 to 14, or from 1 to 10, or from 3 to 10, or 3 to 14, or 3 to 20, or 3 to 25, or from 4 to 10, or 4 to 14, or 4 to 20, or 4 to 25, or from 5 to 10, or 5 to 14, or 5 to 20, or 5 to 25.

[0065] Further components in polymer composition

[0066] The polymer composition may further comprise additives, such as for example flame retardants, pigments, lubricants, slip agents flow promoters, antistatic agents, processing stabilizers, long term stabilisers and / or UV stabilizers. The additives may be present in any desired amount to be determined by the man skilled in the art, but are preferably present > 0.001 wt% and < 5.0 wt%, more preferably > 0.01 wt% and < 4.0 wt%, even more preferably > 0.01 wt% and < 3.0 wt%, even more preferably > 0.01 wt% and < 2.0 wt% based on the polymer composition.

[0067] The polymer composition may further comprise a nucleating agent. A nucleating agent may be desired to increase the cell density and to modify the dynamics of bubble formation and growth. (Gendron, Thermoplastic foam Processing, 2005, page 209).

[0068] The amount of nucleating agent may for example be > 0.010 wt% and < 5.0 wt%, for example > 0.030 wt% and < 4.0 wt%, for example > 0.050 wt% and < 3.0 wt%, preferably > 0.10 wt% and < 2.5 wt%, more preferably > 0.30 wt% and < 1 .5 wt% based on the polymer composition, most preferably > 0.50 wt% and < 1 ,2wt% based on the polymer composition.

[0069] Suitable nucleating agents include but are not limited to talc, silica and a mixture of sodium bicarbonate and citric acid. Other suitable nucleating agents include amides, for example azo dicarbonamide, amines and / or esters of a saturated or unsaturated aliphatic (C10-C34) carboxylic acid. Examples of suitable amides include fatty acid (bis)amides such as for example stearamide, caproamide, caprylamide, undecylamide, lauramide, myristamide, palmitamide, behenamide and arachidamide, hydroxystearamides and alkylenediyl-bis-alkanamides, preferably (C2-C32) alkylenediyl- bis-(C2-C32) alkanamides, such as for example ethylene bistearamide (EBS), butylene bistearamide, hexamethylene bistearamide, ethylene bisbehenamide and mixtures thereof. Suitable amines include or instance (C2-Ci8) alkylene diamines such as for example ethylene biscaproamine and hexamethylene biscaproamine. Preferred esters of a saturated or unsaturated aliphatic (C10-C34) carboxylic acid are the esters of an aliphatic (C16-C24) carboxylic acid. Preferably, the nucleating agent is chosen from the group of talc, sodium bicarbonate, citric acid, azodicarbonamide and mixtures thereof, more preferably, the nucleating agent is talc.

[0070] For the preparation of the foamed article, it may be desired to use a cell stabilizer. Cell stabilizers are permeability modifiers which retard the diffusion of for example hydrocarbons such as isobutane to create dimensionally stable foams. (Gendron, Thermoplastic foam Processing, 2005, pages 31 and 149) Preferred cell stabilizers include but are not limited to glycerol monostearate (GMS), glycerol monopalmitate (GMP), palmitides and / or amides. Suitable amides are for example stearyl stearamide, palmitide and / or stearamide. Suitable mixtures include for example a mixture comprising GMS and GMP or a mixture comprising stearamide and palmitamide. Preferably, in case a cell stabilizer is used, the cell stabilizer is glycerol monostearate or stearamide.

[0071] The amount of cell stabilizer to be added depends on desired cell size and the polymer composition used for the preparation of the foamed article. Generally, the cell stabiliser may be added in an amount > 0.10 and < 3.0 wt % relative to the polymer composition. Preferably, the polymer composition is present in the foamed article in an amount > 95 wt% based on the foamed article. For example, the polymer composition is present in the foamed article in an amount > 96 wt%, > 97 wt%, > 98 wt%, > 99 wt%, > 99.5 wt% based on the foamed article. The foamed article may also consist of the polymer composition.

[0072] The polymer composition may further comprise a further polypropylene which is not a high melt strength polypropylene.

[0073] Preferably, the density of the foamed article is < 650 kg / m3and > 20kg / m3preferably < 500 kg / m3and > 30kg / m3, wherein the density is determined according to ASTM D792 (2008).

[0074] Preferably, the foamed article has an open cell content of < 15.0 % , preferably < 12.0%, more preferably < 10.0%, even more preferably < 7.0%, even more preferably < 5.0%, even more preferably < 4.0%, even more preferably < 3.0%, even more preferably < 2.0%, wherein the open cell content is determined according to ASTM D6226-10.

[0075] Process

[0076] The foamed article according to the invention is obtained by subjecting the polymer composition to a foaming process preferably selected from foam extrusion, foam blow molding, foam injection molding, bead foam extrusion and autoclave bead foaming.

[0077] Preferably, the foamed article according to the invention is obtained by foam extrusion of the polymer composition.

[0078] Processes for the preparation of foamed articles such as foamed sheets are within the knowledge of the person skilled in the art. In such a process, a melt of a composition of the high melt strength polypropylene mixed with a gaseous or liquid blowing agent is suddenly expanded through a pressure drop. Continuous foaming processes as well as discontinuous processes may be applied. In a continuous foaming process, the polymer composition is melted and laden with gas in an extruder under pressures typically above 20 bar before being extruded through a die where the pressure drop causes the formation of a foam. The mechanism of foaming polypropylene in such foam extrusion process is explained, for example, in H. E. Naguib, C. B. Park, N. Reichelt, Fundamental foaming mechanisms governing the volume expansion of extruded polypropylene foams, Journal of Applied Polymer Science, 91 , 2661-2668 (2004 ). Processes for foaming are outlined in S. T. Lee, Foam Extrusion, Technomic Publishing (2000 ). In a discontinuous foaming process, the polypropylene composition (micro-)pellets are laden with foaming agent under pressure and heated below melting temperature before the pressure in the autoclave is suddenly relaxed. The dissolved foaming agent forms bubbles and creates a foam structure.

[0079] During the extrusion, parameters such as the die opening size and the pulling speed may be adjusted such that sufficient shear stress is applied to result in anisotropic properties, e.g. higher stiffness in the extrusion direction than the thickness direction, of the foamed article obtained.

[0080] Preferably, the foamed article is prepared by a process comprising the sequential steps of: A) providing the polymer composition,

[0081] B) adding a blowing agent to the polymer composition, for example wherein the blowing agent is added in an amount > 0.10 wt% and < 20 wt% based on the polymer composition and

[0082] C) subjecting the mixture of the polymer composition and the blowing agent to a foaming process, preferably a foam extrusion process, to form the foamed article.

[0083] The amount of blowing agent for example depends on the desired density and the polymer composition used. For example, the blowing agent may be used in an amount > 0.10 wt% and < 20 wt% based on the polymer composition.

[0084] Examples of suitable physical blowing agents include, but are not limited to isobutane, CO2, pentane, butane, nitrogen and / or a fluorohydrocarbon. Preferably, the physical blowing agent is isobutane and / or CO2, most preferably isobutane.

[0085] Examples of suitable chemical blowing agents include, but are not limited to citric acid or a citric acid-based material (e.g. mixtures of citric acid and sodium bicarbonate) and azo dicarbonamide. Such chemical blowing agents are for example commercially available from Clariant Corporation under for example the name Hydrocerol ™ CF- 40E™ or Hydrocerol™ CF-05E™.

[0086] Preferably, step C) is a foam extrusion process comprising melt mixing the mixture at temperatures in the range of 180 to 300°C and foaming the melt mixture at temperatures in the range of 130 to 210°C. More preferably, step C) is a foam extrusion process comprising melt mixing the mixture at temperatures in the range of 240 to 290°C and foaming the melt mixture at temperatures in the range of 155 to 210°C.

[0087] In some embodiments, the foaming of the melt mixture in the foam extrusion process of step C) is performed at temperatures in the range of 170 to 210 °C, for example 170 to 195 °C.

[0088] In some embodiments, the foaming of the melt mixture in the foam extrusion process of step C) is performed at temperatures below 180 °C, for example 160 to 175 °C.

[0089] In some embodiments, the foaming of the melt mixture in the foam extrusion process of step C) is performed at temperatures below 170 °C, for example 155 to 169 °C or 159 to 164 °C. Such low temperature range advantageously results in a low density of the foamed article obtained.

[0090] The foamed article thus prepared may be stretched monoaxially or biaxially using a manner known per se. This further enhances the anisotropy of the compression strength of the foamed article.

[0091] Therefore, the foamed article may be prepared by a process comprising the sequential steps of:

[0092] A) providing the polymer composition of the invention,

[0093] B) adding a blowing agent to the polymer composition, for example wherein the blowing agent is added in an amount > 0.10 wt% and < 20 wt% based on the polymer composition and

[0094] C) subjecting the mixture of the polymer composition and the blowing agent to a foam extrusion process to form the foamed article and

[0095] D) stretching the foamed article in at least one direction.

[0096] The foamed article may be a foamed sheet which has been stretched in at least one direction, for example wherein the foamed sheet has been monoaxially stretched (for example in the machine direction) or for example the foamed sheet has been biaxially stretched, for example in both the machine direction (MD) and in the transverse direction (TD). As is known to the person skilled in the art, the stretching in MD and TD may be carried out simultaneously, or in consecutive steps.

[0097] The draw ratio in MD may for example be > 1.1 and < 7.0, for example > 1.1 and < 3.0. The draw ratio in transverse direction may for example be > 1.1 and < 7.0, for example > 1.1 and < 3.0.

[0098] The foamed article or the foamed sheet of the invention can suitably be used in applications such as building and construction, automotive applications, household applications, such as food packaging and protective packaging; and consumer applications. For example, the sheets can be used for the preparation of cups, trays, containers, bottles, seals, returnable boxes. Other applications of the sheets of the invention are for example: sandwich panels, pipe insulations, concrete joint fillers, insulation materials for houses, water tanks or floors (floor underlayments). The very good cushioning properties of the foamed article or the foamed sheet of the invention offer the user safety and comfort. The foamed article or the foamed sheet is applicable in multiple applications requiring non-slip performance, such as footwear, protective guards, sports floor mats and foam rollers.

[0099] The foamed article or the foamed sheet of the invention can be used as a replacement for applications wherein polystyrene foam is typically used, such as disposable food containers.

[0100] 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 compositions according to the invention; all combinations of features relating to the processes according to the invention and all combinations of features relating to the compositions according to the invention and features relating to the processes according to the invention are described herein.

[0101] 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.

[0102] The invention is now elucidated by way of the following examples, without however being limited thereto.

[0103] Materials used

[0104] High melt strength polypropylene: UMS1-4

[0105] UMS1 and 2 were prepared by preparing polypropylene and adding stabilizers in amounts shown in Table 1 and irradiating the mixture with an electron beam, as generally described in W02009003930A1 . UMS3 and 4 are commercially available products. UMS1

[0106] Procatalyst

[0107] A procatalyst was prepared according to the method described in W02021 / 063930A1 , example 1 (p.29, 1.30 to p.30, 1.11).

[0108] Polymerization method

[0109] Gas-phase polymerizations were performed in one horizontally stirred gas-phase reactor (plus the secondary reactor blanketed) with downstream powder processing units (= degassing & catalyst deactivation) for powder collection. The temperature of the powder bed is measured via a series of internal thermocouples. The data from these thermocouples is used to control the quench flow to the individual quench nozzles. Hydrogen was fed to the reactor to control the melt flow rate. The propylene homopolymer obtained was collected and its properties were measured. Below table shows the catalyst used in the polymerization process of the homopolymers obtained.

[0110] UMS2

[0111] The preparation method of UMS2 was identical with that of UMS1 except for the stabilizers used were as shown in Table 1 .

[0112] UMS3 is a long chain branched propylene homopolymer which is commercially available from Borealis as Daploy™ WB140HMS. It has a melt flow rate of MFR230 of 2.1 g / 10min and a melt strength of 36 cN. UMS4 is a polypropylene which is commercially available from Exxon as Achieve PP6302E1 HMS.

[0113] Mz, Mn, Mw

[0114] Mw, Mn and Mz were determined for i) pellets of the compositions provided above (without thermal and shear treatment described below) and ii) strands obtained from the pellets of i) by subjected them to a thermal and shear treatment described below.

[0115] Mw, Mn and Mz were all determined in accordance with ASTM D6474-12 (Standard Test Method for Determining Molecular Weight Distribution and Molecular Weight Averages of Polyolefins by High Temperature Gel Permeation Chromatography) using SEC-MALS as described below.

[0116] SEC-MALS (Size-Exclusion Chromatography with Multi-Angle Light Scattering) A Multi Angle Light Scattering detector is used. Two columns of Polymer Laboraties 20pm PLMixed ALS, 300 x 7.5 mm are used in series with 1 ,2,4-trichlorobenzene stabilized with 1 g / L butylhydroxytoluene (also known as 2.6-di-tert-butyl-4- methylphenol or BHT) as eluens. Injection volume is 200pl, flowrate 0.5 ml / min. Detectors ( concentration detector PolymerChar IR5 and light scattering detector, Wyatt Dawn Helios 18 angles) and columns are operated at 160°C.

[0117] Molar mass is determined from the intensity of scattered light at zero scattering angle along with the concentration; intensity at zero angle is obtained by the extrapolation to zero of intensities measured at several different angles, and concentration is typically measured with an IR5 detector, in-line with the MALS detector. RMS radius is calculated from the slope of angular variation of the scattered light intensity.

[0118] Thermal and shear treatment

[0119] Samples were subjected to a thermal and shear treatment by means of a MFI measurement. The MFI measurement was performed in accordance with ASTM D1238 (2013) at a temperature of 290°C (MFR290) under a load of 2.16 kg. The extruded strand from the MFI measurement was subjected to a measurement of Mn, Mw and Mz.

[0120] For the samples obtained after the thermal and shear treatment, a molecular weight distribution curve was made of dW / dlogM versus log Molecular weight. Form this molecular weight distribution curve, the proportion of the surface area in the high molecular fraction with respect to the total surface area was calculated. Specifically, the proportion of the surface area under log Mw of above 6.0 with respect to the total surface area and the proportion of the surface area under log Mw of above 6.5 with respect to the total surface area were calculated.

[0121] Table 1

[0122] Preparation of foamed polypropylene sheet by a foam extrusion process

[0123] For examples E1 - E15, the components shown in Table 3 were dosed in a co-rotating twin-screw extruder. The extruder was a 30mm double screw foam extruder from Theysohn having a length over diameter ratio (L / D) of 40. This extruder consists of nine electrical heating zones equipped with water cooling followed by a cooling section a static mixer and an adjustable slit die. The polymer and talc were dosed at the start of the extruder. At a latter zone of the extruder, the physical blowing agent, isobutane, is metered and mixed with the molten polymer. The molten mixture as obtained was then cooled using a melt cooler set. After cooling, the melt was extruded through a slit die having an adjustable die gap. The die gap was set to have a resultant die pressure of 25 bar at a throughput of 10 kg / hour. A foamed extruded sheet was obtained after cooling. The foam samples were extruded with the setting show in table 2.

[0124] POLYBATCH® FPE 50 T is a 50% masterbatch of talcum based nucleating agent, which is commercially available from LyondellBasell.

[0125] Table 2

[0126] Table 3

[0127] Density

[0128] The density of the foamed article was determined in accordance with ASTM D792 (2008).

[0129] Surface roughness

[0130] Surface roughness is defined as the level of irregularities on the foam surface (other than irregularities caused by corrugation or the underlying foam morphology) which are noticeable to the human eye. In the table, + indicates good results and - indicates bad results. It can be understood that use of UMS with a low proportion of the surface area under log molecular weight of above 6.0 and above 6.5 after MFI measurement (UMS1 and UMS2) results in a good surface quality. It can further be understood that the low temperature of the melt cooler results in a lower foam density.

[0131] It can further be understood that the use of Genox-EP (UMS1) allows obtaining a good surface quality at a large temperature window, but the use of vitamin E (UMS2) allows use of an even larger temperature window.

Claims

CLAIMS1 . A process for the preparation of a foamed article, comprising the sequential steps of:A) providing a polymer composition comprising a high melt strength polypropylene,B) adding a blowing agent to the polymer composition, for example wherein the blowing agent is added in an amount > 0.10 wt% and < 20 wt% based on the polymer composition andC) subjecting the mixture of the polymer composition and the blowing agent to a foaming process to form the foamed article, wherein the high melt strength polypropylene is prepared by a) irradiation of a mixture comprising a polypropylene and a stabilizer, wherein the irradiation is performed with > 2.0 and < 20 Megarad electron-beam radiation in a reduced oxygen environment, wherein the amount of active oxygen is < 15% by volume with respect to the total volume of the reduced oxygen environment for a time sufficient for obtaining a long chain branched polypropylene and b) deactivation of the free radicals in the long chain branched polypropylene to form the high melt strength polypropylene, wherein the stabilizer is or comprises vitamin E, wherein the polypropylene in the mixture to be irradiated in step a) is produced by a polymerization process in the presence of a catalyst comprising a catalyst comprising a procatalyst, a co-catalyst and optionally an external electron donor, wherein the procatalyst is obtainable by a process comprising the steps of: contacting a magnesium-containing support with a halogen-containing titanium compound, and an internal electron donor according to Formula I:Formula I wherein R1is a secondary alkyl group and R2is a non-secondary alkyl group having at least 5 carbon atoms, preferably R2is a non-secondary alkyl group having at least 5 carbon atoms and being branched at the 3-position or further positions; said procatalyst is prepared according to the following steps: i) contacting a compound R4zMgX42.zwith an alkoxy- or aryloxy-containing silane compound to give a first intermediate reaction product, being a solid Mg(ORa)xX12-x,wherein: Rais a linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and preferably has from 1 to 20 carbon atoms; wherein R4is a linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and preferably has from 1 to 20 carbon atoms, preferably R4is butyl; wherein X4and X1are each independently selected from the group of consisting of fluoride (F-), chloride (CI-), bromide (Br-) or iodide (I-), preferably chloride; z is in a range of larger than 0 and smaller than 2, being 0 < z < 2, x is an integer between 0 and 2; ii) optionally contacting the solid Mg(ORa)xX12-x obtained in step i) with at least one activating compound selected from the group formed by activating electron donors and metal alkoxide compounds of formula M1(ORb)v.w(OR3)w or M2(ORb)v.w(R3)w, to obtain a second intermediate product; wherein: M1is a metal selected from the group consisting of Ti, Zr, Hf, Al or Si; v is the valency of M1; M2is a metal being Si; v is the valency of M2; Rband R3are each a linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms, and preferably has from 1 to 20 carbon atoms; wherein w is smaller than v, preferably v being 3 or 4; iii) contacting the first or second intermediate reaction product, obtained respectively in step i) or ii), with a halogen-containing Ti-compound and said compound represented Formula I, as the internal electron donor.

2. The process according to claim 1 , wherein the foaming process is selected from foam extrusion, foam blow molding, foam injection molding, bead foam extrusion and autoclave bead foaming.

3. The process according to any one of the preceding claims, wherein the foaming process is a foam extrusion process.

4. The process according to any one of the preceding claims, wherein the foaming process is a foam extrusion process comprising melt mixing the mixture attemperatures in the range of 180 to 300 °C, preferably 240 to 290°C, and foaming the melt mixture at temperatures in the range of 130 to 210 °C, preferably 155 to 210°C.

5. The process according to claim 4, wherein the foaming of the melt mixture is performed at temperatures below 170 °C.

6. The process according to claim 4 or 5, wherein the foaming of the melt mixture is preferred at temperatures in the range of 155 to 169 °C or 159 to 164 °C.

7. The process according to any one of the preceding claims, wherein the high melt strength polypropylene has Mz of at least 1500 kg / mol determined according to ASTM D6474-12 using SEC-MALS.

8. The process according to any one of the preceding claims, wherein the high melt strength polypropylene shows a molecular weight distribution curve in which the area under the curve at Log (molecular weight) of above 6.0 is at most 12.5 % of the area under the total curve and / or the area under the curve at Log (molecular weight) of above 6.5 is at most 5.0 % of the area under the total curve, wherein the molecular weight distribution curve is obtained by subjecting a sample of the high melt strength polypropylene to a melt flow index measurement in accordance with ASTM D1238 (2013) at a temperature of 290°C under a load of 2.16 kg to obtain a strand and subjecting the strand to SEC-MALS to determine molecular weight according to ASTM D6474-12 to obtain the molecular weight distribution curve.

9. The foamed article according to any one of the preceding claims, wherein the area under the curve at Log molecular weight of above 6.0 is 5.0 to 12.2%, preferably 5.5 to 10.0%, of the area under the total curve, and / or the area under the curve at Log molecular weight of above 6.5 is 1 .0 to 4.8%, preferably 1 .5 to 4.0%, of the area under the total curve.

10. The foamed article according to any one of the preceding claims, wherein the high melt strength polypropylene has Mz determined from said molecular weight distribution curve of 2000 to 7000, preferably 3000 to 5500 kg / mol.1 1 . The process according to any one of the preceding claims, wherein an activator is present, the activator preferably being a benzamide according to formula X:Formula X wherein R70and R71are each independently selected from hydrogen or an alkyl, and R72, R73, R74, R75, R76are each independently selected from hydrogen, a heteroatom or a hydrocarbyl group, preferably selected from alkyl, alkenyl, aryl, aralkyl, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof, more preferably wherein R70and R71are both methyl and wherein R72, R73, R74, and R75are all hydrogen, being / V, / V-dimethylbenzamide (Ba-2Me).

12. The process according to any one of the preceding claims, wherein the high melt strength polypropylene has a melt strength determined in accordance with ISO 16790:2005 at a temperature of 200°C, using a cylindrical capillary having a length of 20mm and a width of 2mm, a starting velocity vO of 7.5mm / s and an acceleration of 12mm / s2of > 30 cN, preferably > 40 cN, more preferably > 45 cN, > even more preferably 50 cN, even more preferably > 55 cN, even more preferably > 60 cN, most preferably > 65 cN and / or the melt strength of the high melt strength polypropylene is <100 cN, for example < 95 cN, for example < 90 cN, for example < 87cN, and / or the high melt strength polypropylene has a branching index g’ of less than 1 .00 wherein g'=[I ]br / [l V]iinin which g' is the branching index, [IVbr] is the intrinsic viscosity of the branched polypropylene and [IV]iinis the intrinsic viscosity of the linear polypropylene having the same weight average molecular weight (within a range of ±10 %) as the branched polypropylene.

13. The process according to any one of the preceding claims, wherein the high melt strength polypropylene is present in an amount > 10wt% based on the polymer composition, preferably wherein the high melt strength polypropylene is present in an amount > 10wt% based on the polymer composition, for example in an amount < 99.5 wt% based on the polymer composition.

14. The process according to any one of the preceding claims, wherein the polymer composition further comprises a nucleating agent, preferably wherein the nucleating agent is present in an amount > 0.01 wt% and < 5.0 wt% based on the composition and / or preferably wherein the nucleating agent is the nucleating agent is chosen from the group of talc, sodium bicarbonate, citric acid, azodicarbonamide and mixtures thereof.

15. The process according to any one of the preceding claims, wherein the polymer composition is present in the foamed article in an amount > 95 wt% based on the foamed article.

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