Butene-1 polymer masterbatch composition for foaming applications

Abstract

Provided is a masterbatch composition comprising: A) 25-80 wt.% of a butene-1 polymer composition comprising: a) a butene-1 homopolymer or copolymer having a copolymerized comonomer content (CA) of up to 5 mol%, and b) a copolymer of butene-1 having a copolymerized comonomer content (CB) of more than 5- 25 mol%, wherein the amount of polymer a) is in a range of 5-95 wt%, said butene-1 polymer composition having i) a total copolymerized comonomer content of 4-18 mol%, and ii) a fraction soluble in xylene at 0°C of 35-90 wt%, iii) a melt flow rate value of 30-1000 g / 10 min; B) 20-75 wt.% of at least one endothermic chemical blowing agent; and C) 0-50 wt.% of at least one nucleating agent.

Description

BUTENE- 1 POLYMER MASTERBATCH COMPOSITION FOR FOAMING APPLICATIONSFIELD OF THE INVENTION

[0001] The present disclosure relates to a polymer masterbatch composition suitable for foaming applications, specifically for foaming propylene polymers. The masterbatch composition of the instant disclosure comprises a butene- 1 polymer carrier and at least an endothermic chemical blowing agent. Optionally, the masterbatch composition also comprises a nucleating agent.BACKGROUND OF THE INVENTION

[0002] Polymer compositions comprising butene- 1 polymers exhibit advantageous properties such as chemical inertness and moisture barrier, as well as high flexibility and good mechanical properties over a wide range of temperatures.

[0003] EP2864403A1 discloses polymer foams based on butene and ethylene. The butene copolymer has melting temperatures comprised in the range of from 60 °C to 120 °C. The foam further comprises sodium bicarbonate as a chemical foaming agent to facilitate foaming and a talc additive.

[0004] GB 1277161 A discloses a process for the preparation of a molded polyolefin cellular foamed product. The olefinic polymer may be polyethylene, polypropylene or poly-butene. Sodium bicarbonate may be used as foaming agent.

[0005] US20030037633A1 shows a steering wheel comprising a rim portion, a spoke portion and a foamed padding material. The foamed padding material may comprise a thermoplastic polyolefin elastomer such as polybutylene as well as from 0.1% to 10% by weight of a gasified chemical foaming agent such as sodium bicarbonate.

[0006] It has now been found that by combining a butene- 1 polymer composition with specific total copolymerized comonomer content, fraction soluble in xylene at 0°C, and melt flow rate, with a chemical blowing agent, and optionally a nucleating agent, a masterbatch composition with an advantageous profile of properties is achieved.SUMMARY OF THE INVENTION

[0007] In a first aspect, the present disclosure provides a masterbatch composition comprising:

[0008] A) from 25 to 80 wt.% of a butene-1 polymer composition comprising:

[0009] (a) at least one butene-1 homopolymer, or copolymer of butene-1 with one or more comonomers selected from ethylene and higher alpha-olefins, the copolymer having a copolymerized comonomer content (CA) in a range of up to 5% by mole, and

[0010] (b) at least one copolymer of butene-1 with one or more comonomers selected from ethylene and higher alpha-olefins, having a copolymerized comonomer content (CB) in a range of more than 5% to 25% by mole,

[0011] wherein the amount of polymer (a) is in a range of from 5 to 95 % by weight, based on the total weight of polymers (a) and (b),

[0012] said butene-1 polymer composition having:

[0013] i) a total copolymerized comonomer content in a range of from 4% to 18% by mole, based on the total weight of polymers (a) and (b), and

[0014] ii) a fraction soluble in xylene at 0°C of from 35% to 90% by weight, based on the total weight of polymers (a) and (b),

[0015] iii) a melt flow rate value in a range of from 30 to 1000 g / 10 min, as measured according to ISO 1133 at 190°C with a load of 2.16 kg;

[0016] B) from 20 to 75 wt.% of at least one endothermic chemical blowing agent;

[0017] C) from 0 to 50 wt.% of at least one nucleating agent,

[0018] wherein the amounts of components A), B) and C) are based on the total weight of the masterbatch composition.

[0019] In a second aspect, the disclosure relates to a process for preparing the masterbatch composition.

[0020] In a third aspect, the disclosure relates to use of the masterbatch composition in a method of foaming thermoplastic polyolefins.

[0021] In a fourth aspect, the disclosure relates to a process for preparing a thermoplastic polyolefin foamed article.

[0022] The masterbatch composition of the instant disclosure shows very low volatiles and has a clean emission profile. Furthermore, the masterbatch compositions of the present disclosureare highly compatible with thermoplastic polyolefins, in particular with polypropylene, which are used in a wide number of foaming applications.

[0023] The foamed articles, obtained by adding the masterbatch composition of the present disclosure to a thermoplastic polyolefin base resin, show a structure with uniform distribution of fine cells.BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG. 1 provides a schematic representation of a foamed test specimen illustrating the method to determine the total thickness, the thickness of the skin, unfoamed layers and the thickness of the foamed layer of a foamed article.

[0025] FIG. 2 provides a SEM image of the foamed material of example El .

[0026] FIG. 3 provides a SEM image of the foamed material of example E2.

[0027] FIG. 4 provides a SEM image of the foamed material of example E3.

[0028] FIG. 5 provides a SEM image of the foamed material of example CE4.DETAILED DESCRIPTION OF THE INVENTION

[0029] In the context of the present disclosure;

[0030] - the total weight of a polymer composition or masterbatch sums up to 100% by weight, unless otherwise specified;

[0031] - the term “consisting” referred to a polymer or to a polymer composition, mixture or blend should be construed to mean “consisting or consisting essentially of’;

[0032] - the term “consisting essentially of’ means that, in addition to those components which are mandatory, other components may also be present in the material, provided that the essential characteristics of the material are not materially affected by their presence. Examples of components that, when present in customary amounts, do not materially affect the characteristics of a polymer or of a polyolefin composition, mixture or blend are catalyst residues, antistatic agents and processing aids;

[0033] - the term “copolymer” is referred to a polymer deriving from the intentional polymerization of at least two different comonomers, i.e. the term “copolymer” includes terpolymers;

[0034] - the term “masterbatch” refers to a powdered, granulate, or pelletized composition comprising a mixture of two or more components that is used to simplify the metering of at least one of the components into a base resin during the formation of the end product, like a foamed article.

[0035] The masterbatch composition of the first aspect of the present disclosure comprises:

[0036] A) from 25 to 80 wt.% of a butene-1 polymer composition comprising:

[0037] (a) at least one butene-1 homopolymer, or copolymer of butene-1 with one or more comonomers selected from ethylene and higher alpha-olefins, the copolymer having a copolymerized comonomer content (CA) in a range of up to 5% by mole, and

[0038] (b) at least one copolymer of butene-1 with one or more comonomers selected from ethylene and higher alpha-olefins, having a copolymerized comonomer content (CB) in a range of more than 5% to 25% by mole,

[0039] wherein the amount of polymer (a) is in a range of from 5 to 95 % by weight, based on the total weight of polymers (a) and (b),

[0040] said butene-1 polymer composition having

[0041] i) a total copolymerized comonomer content in a range of from 4% to 18% by mole, based on the total weight of polymers (a) and (b), and

[0042] ii) a fraction soluble in xylene at 0°C of from 35% to 90% by weight, based on the total weight of polymers (a) and (b), and

[0043] iii) a melt flow rate value MFR( A) in a range of from 30 to 1000 g / 10 min, as measured according to ISO 1133 at 190°C with a load of 2.16 kg;

[0044] B) from 20 to 75 wt.% of at least one endothermic chemical blowing agent; and

[0045] C) from 0 to 50 wt.% of at least one nucleating agent,

[0046] wherein the amounts of components A), B) and C) are based on the total weight of the masterbatch composition.

[0047] Preferably, component A) comprises:

[0048] from 20% to 70% by weight, preferably from 30% to 60% by weight, of polymer (a), and

[0049] from 80% to 30% by weight, preferably from 70% to 40% by weight, of polymer (b), each based on the total weight of polymers (a) and (b).

[0050] In one embodiment, the component A) consists of polymer (a) and polymer (b), in the amounts disclosed above.

[0051] Preferably, i) the total copolymerized comonomer content is in a range of from 5% to 12% by mole, based on the total weight of polymers (a) and (b).

[0052] Preferably, ii) solubility in xylene at 0°C is in a range of from 48% to 62% by weight, based on the total weight of polymers (a) and (b).

[0053] It is preferred that component A) has a melt flow rate value MFR(A) in a range of from 40 to 800 g / 10 min, preferably from 100 to 300 g / lOmin, as measured according to ISO 1133 at 190°C with a load of 2.16 kg.

[0054] The specific melt flow rate values for polymers (a) and (b) can be broadly selected, provided that the melt flow rate value MFR(A) of the overall butene- 1 polymer composition A) are obtained.

[0055] In this respect, it is well known that the logarithm of the melt flow rate value of polyolefin blends in general, thus of blends of butene- 1 polymers as well, is given by the sum of the products of the weight fraction and the logarithm of the melt flow rate value of the single polymers.

[0056] Thus, the melt flow rate value of a polymer composition made of a blend of polymers (a) and (b) is determined by the following relation: log MFR(a+b) = WA log MFR(a) + WB log MFR(b) where MFR(a+b) is the melt flow rate value for the blend of (a) and (b), MFR (a) and MFR (b) are the melt flow rate values of polymers (a) and (b) respectively, and WA and WB are the respective weight fractions. For instance, WA and WB are 0.4 and 0.6 when the blend is made of 40% by weight of polymer (a) and 60% by weight of polymer (b).

[0057] The butene- 1 polymer composition has a measurable crystallinity, as demonstrated by the presence, in the Differential Scanning Calorimetry (DSC) pattern, of the melting temperature peaks of crystalline butene- 1 polymers.

[0058] In particular, the butene- 1 polymer composition A) shows one or more melting peaks in the second DSC heating scan measured as described in the experimental section. Such temperature peak or peaks are attributed to the melting point of crystalline form II of the butene- 1 polymers (Tm(II)) and the area under the peak (or peaks) is taken as the global melting enthalpy (DH Tm(II)). If more than one peak is present, the highest (most intense) one is taken as Tm(II).

[0059] It is preferred that component A) has a Tm(II) value in a range of from 70° to 105°C, preferably from 75° to 100°C, more preferably from 77° to 90°C, in particular in a range of from 79° to 85°C, as measured by DSC with a scanning speed of 10°C / min.

[0060] Specific global DH Tm(II) values for the butene- 1 polymer composition A) are equal to or lower than 15 J / g, in particular of 3 to 15 J / g, measured with a scanning speed of 10 °C / min.

[0061] Moreover, the butene- 1 polymer composition A) shows one or more melting peaks, occurring at temperatures equal to or greater than the temperatures Tm(II) attributed to the melting point of the crystalline form II, in a DSC heating scan carried out after aging. Such temperature peak or peaks are attributed to the melting point crystalline form I of the butene- 1 polymers (Tm(I)). If more than one peak is present, the highest (most intense) one is taken as Tm(I). Hence, for butene- 1 polymer composition A) the equation Tm(I) > Tm(II) is fulfilled.

[0062] The area under the peak (or peaks) is taken as the global melting enthalpy (DH Tm(I)). Specific global DH Tm(I) values for the butene-1 polymer composition A) are of 50 J / g or less, in particular of from 25 to 50 J / g, preferably from 30 to 50 J / g, measured with a scanning speed of 10 °C / min.

[0063] The butene-1 polymer composition A) preferably also has a detectable content of crystalline form III. Crystalline form III is detectable via the X-ray diffraction method described in the Journal of Polymer Science Part B: Polymer Letters Volume 1, Issue 11, pages 587-591, November 1963, or Macromolecules, Vol. 35, No. 7, 2002.

[0064] Preferably, butene-1 polymer composition A) has a Brookfield viscosity in a range of from 10,000 to 270,000 mPa-s, preferably in a range of from 15,000 to 250,000 mPa-s, more preferably in a range of from 20,000 to 200,000 mPa-s, in particular in a range of from 25,000 to 150,000 mPa-s, such as in a range of from 30,000 to 100,000 mPa-s, or from 35,000 to 50,000 mPa-s, each measured at 190°C according to ASTM D3236-15 (2021).

[0065] In a preferred embodiment, polymer (a) of the butene-1 polymer composition A) has from 1% to 4% by mole of copolymerized comonomer (CA).

[0066] Preferably, polymer (b) of component A) has from 8% to 20% by mole of copolymerized comonomer (CB).

[0067] Preferably, when both (a) and (b) are copolymers, the difference between the percent values of the copolymerized comonomer contents of (a) and (b) satisfies the following relation: (CB) - (CA) > 5; or, preferably, (CB) - (CA) > 6.

[0068] Preferably, the comonomer comprised in polymer (a) and polymer (b) of component A) is ethylene.

[0069] Specific examples of higher alpha-olefins that can be present as comonomers in polymers (a) and (b), in addition or in alternative to ethylene, are the alpha-olefins of the formula CH2 = CHR, wherein R is methyl or an alkyl radical containing 3 to 8 or 3 to 6 carbon atoms, like propylene, hexene- 1 and octene- 1.

[0070] In a preferred embodiment, component A) has a density equal to or greater than 0.89 g / cm3, preferably in a range of from 0.89 to 0.92 g / cm3.

[0071] Preferably, component A) has an Mw / Mn value, where Mw is the weight average molecular mass and Mn is the number average molecular mass both measured by GPC, equal to or lower than 4, in particular equal to or lower than 3, or equal to or lower than 2.5, the lower limit being of 1.5 in all cases.

[0072] Moreover, the butene- 1 polymer composition A) preferably has at least one, more preferably all, of the following further features:

[0073] - Mw equal to or greater than 50.000, in particular from 50.000 to 180.000 g / mol, like from 70.000 to 150.000 g / mol; and / or

[0074] - Mz equal to or greater than 90.000 g / mol, in particular from 90.000 to 200.000 g / mol, like from 100.000 to 190.000 g / mol; and / or

[0075] - an intrinsic viscosity (IV) measured according to ASTM D2857-22 in tetrahydronaphthalene (THN) at 135°C equal to or lower than 0.7 dl / g, in particular from 0.2 dl / g to 0.7 dl / g, like from 0.5 dl / g to 0.6 dl / g; and / or

[0076] - isotactic pentads (mmmm) measured with13C-NMR operating at 150.91 MHz higher than 90%, in particular higher than 93%, like higher than 95%; and / or

[0077] - 4,1 insertions not detectable using a13C-NMR operating at 150.91 MHz; and / or

[0078] - a Shore D value equal to or lower than 50, in particular from 25 to 50, like from 25 to45, measured according to ISO 868:2003; and / or

[0079] - a tensile modulus, measured at 23°C according to ISO 527-1,-2:2019, offrom 30 MPa to 150 MPa, in particular from 50 MPa to 120 MPa.

[0080] The butene- 1 polymer polymers (a) and (b) are preferably obtained by polymerizing the monomer(s) in the presence of a metallocene catalyst system obtainable by contacting:- a stereorigid metallocene compound;- an alumoxane or a compound capable of forming an alkylmetallocene cation; and, optionally,- an organo-aluminum compound.

[0081] Preferably the stereorigid metallocene compound belongs to the following formula (I):wherein:M is an atom of a transition metal selected from those belonging to group 4; preferably M is zirconium;X, equal to or different from each other, is a hydrogen atom, a halogen atom, a R, OR, OR’O, OSO2CF3, OCOR, SR, NR2 or PR2 group wherein R is a linear or branched, saturated or unsaturated Ci-C2o-alkyl, C3-C2o-cycloalkyl, Ce-C2o-aryl, C7-C2o-alkylaryl or C?-C2o-arylalkyl radical, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; and R’ is a Ci-C2o-alkylidene, C6-C2o-arylidene, C?-C2o-alkylarylidene, or C7-C2o-arylalkylidene radical; preferably X is a hydrogen atom, a halogen atom, a OR’O or R group; more preferably X is chlorine or a methyl radical;R1, R2, R5, R6, R7, R8and R9, equal to or different from each other, are hydrogen atoms, or linear or branched, saturated or unsaturated Ci-C2o-alkyl, C3-C2o-cycloalkyl, Ce-C2o-aryl, C7-C2o-alkylaryl or C7-C2o-arylalkyl radicals, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; or R5and R6, and / or R8and R9optionally form a saturated or unsaturated, 5 or 6 membered rings, said ring optionally bearing C1-C20 alkyl radicals as substituents; with the proviso that at least one of R6or R7is a linear or branched, saturated or unsaturated Ci-C2o-alkyl radical, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; preferably a Ci-Cio-alkyl radical;R3and R4, equal to or different from each other, are linear or branched, saturated or unsaturated Ci-C2o-alkyl radicals, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; preferably R3and R4equal to or different from each other are Ci-Cio-alkylradicals; more preferably R3is a methyl, or ethyl radical; and R4is a methyl, ethyl or isopropyl radical.

[0082] Preferably the compounds of formula (I) have formula (la):wherein:M, X, R1, R2, R5, R6, R8and R9are as described above;R3is a linear or branched, saturated or unsaturated Ci-C2o-alkyl radical, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; preferably R3is a Ci-Cio-alkyl radical; more preferably R3is a methyl, or ethyl radical.

[0083] Specific examples of metallocene compounds are dimethylsilyl {(2,4, 7-trimethyl-l- indenyl)-7-(2,5-dimethyl-cyclopenta[l,2-b:4,3-b’]-dithiophene)} zirconium dichloride; dimethylsilanediyl {(1 -(2,4, 7-trimethylindenyl)-7-(2, 5-dimethyl-cyclopenta[l, 2-b:4,3-b’]- dithiophene)} Zirconium dichloride or dimethylsilanediyl {(1 -(2, 4, 7-trimethylindenyl)-7-(2, 5- dimethyl-cyclopenta[l,2-b:4,3-b’]-dithiophene)}zirconium dimethyl.

[0084] Preferred alumoxanes are methylalumoxane (MAO), tetra-(isobutyl)alumoxane (TIBAO), tetra-(2,4,4-trimethyl-pentyl)alumoxane (HO AO), tetra-(2,3-dimethylbutyl)alumoxane (TDMBAO) and tetra-(2,3,3-trimethylbutyl)alumoxane (TTMBAO).

[0085] Examples of compounds able to form an alkylmetallocene cation are compounds of formula D+E', wherein D+is a Bronsted acid, able to donate a proton and to react irreversibly with a substituent X of the metallocene of formula (I) and E' is a compatible anion, which is able to stabilize the active catalytic species originating from the reaction of the two compounds, and which is sufficiently labile to be removed by an olefinic monomer. Preferably, the anion E" comprises of one or more boron atoms.

[0086] Examples organo-aluminum compound are trimethylaluminum (TMA), triisobutylaluminum (UBA), tris(2,4,4-trimethyl-pentyl)aluminum (HOA), tris(2,3-dimethylbutyl)aluminum (TDMBA) and tris(2,3,3-trimethylbutyl)aluminum (TTMBA).

[0087] Examples of the catalyst system and of polymerization processes employing such catalyst system is to be found in W02004 / 099269 and W02009 / 000637.

[0088] By operating under known polymerization conditions in the presence of the above described catalyst system, in one embodiment the two polymers (a) and (b) of are prepared separately and then blended together in the molten state by using known polymer processing apparatuses, such as mono- and twin screw extruders.

[0089] Preferably, the butene- 1 polymer composition A) is prepared directly in polymerization (reactor blend).

[0090] The polymerization process for producing the composition thus comprises at least two sequential polymerization stages, carried out in two or more reactors connected in series, wherein polymers (a) and (b) are prepared in separate subsequent stages, operating in each stage, except for the first stage, in the presence of the polymer formed and the catalyst used in the preceding stage.

[0091] When the butene- 1 polymer composition A) is a reactor blend, the amounts of polymer (a) and (b) in the butene- 1 polymer composition A) correspond to the split between the polymerization stages.

[0092] The polymerization process is preferably carried out in liquid phase, optionally in the presence of an inert hydrocarbon solvent, or in gas phase, using fluidized bed or mechanically agitated gas phase reactors. Liquid polymerization is preferred.

[0093] The catalyst is preferably added in the first reactor only, or, less preferably, in more than one reactor.

[0094] In liquid polymerization, when a hydrocarbon solvent is used, it is either aromatic, like toluene, or aliphatic, like propane, hexane, heptane, isobutane, cyclohexane and 2,2,4- trimethylpentane, isododecane). Preferably, the polymerization process is carried out using liquid butene- 1 as polymerization medium.

[0095] The polymerization temperature is preferably from 20°C to 150°C, in particular between 50°C and 90°C, like from 65°C to 82°C.

[0096] The concentration of hydrogen in the liquid phase during the polymerization reaction (molar ppm H2 / butene- 1 monomer) is preferably from 1000 ppm to 6000 ppm, in particular from 1900 ppm to 5500 ppm, like from 1100 to 1800 ppm.

[0097] When a copolymer is prepared, the amount of comonomer, in particular ethylene, in the liquid phase is preferably from 0.1% to 8% by weight, in particular from 0.2% to 7% by weight, with respect to the total weigh of comonomer and butene- 1 monomer present in the polymerization reactor.

[0098] Preferably, component B) is selected from the group consisting of an alkali-metal citrate, an alkali-metal bicarbonate and combinations thereof. In a preferred embodiment, B) is sodium citrate, or is a mixture of sodium citrate with sodium bicarbonate.

[0099] In one embodiment, the masterbatch composition comprises from 1 to 50 wt.% of component C). Preferably, component C) is talc.

[0100] Preferably, the masterbatch composition comprises:

[0101] - from 35% to 65% by weight, more preferably from 40% to 55% by weight, in particular from 45% to 50% by weight, of component A),

[0102] - from 20% to 40% by weight, preferably from 25% to 35% by weight, in particular from 27% to 33% by weight, of component B), and

[0103] - from 10% to 45% by weight, preferably from 15% to 35% by weight, in particular from 17% to 30% by weight, of component C),

[0104] each based on the total weight of the masterbatch composition.

[0105] The masterbatch composition optionally further comprises up to and including 15% by weight, preferably from 1 to 15%by weight, more preferably from 5 to 12% by weight, based on the total weight of the masterbatch composition, of at least one wax D), wherein the wax is preferably a polyolefin wax, like Licowax PE 520 marketed by Clariant.

[0106] The masterbatch composition optionally further comprises up to and including 5% by weight, like from 0.1 to 5% by weight, based on the total weight of the masterbatch composition, of at least one additive E) selected from selected from the group consisting of antioxidants, light stabilizers, slipping agents, anti-acids, melt stabilizers, and combinations thereof, like CaO.

[0107] In the second aspect, the disclosure relates to the process for preparing the masterbatch composition of the first aspect, comprising:

[0108] a) optionally obtaining a blend of components B) and component C); and

[0109] b) compounding component B) or the blend of step a), with component A);

[0110] wherein step b) takes place at a temperature in a range of from 80°C to 150°C.

[0111] Optionally, the at least one wax D) and / or the at least one additive E) are blended with component B) and optionally component C) in step a).

[0112] Preferably, the process of the second aspect comprises a step (c) of pelletizing the compound of step (b).

[0113] The process for preparing the masterbatch composition is carried out using known compounding devices, like extruders.

[0114] In the third aspect, the disclosure relates to the use of the masterbatch composition according to the first aspect in a method of foaming thermoplastic polyolefins.

[0115] In the fourth aspect, the disclosure relates to the process for preparing a thermoplastic polyolefin foamed article, comprising:

[0116] i) providing a foamable blend by dispersing the masterbatch composition according to the first aspect into a base resin comprising at least one thermoplastic polyolefin at a temperature of at least 150°C, preferably ranging from 150° to 230°C,

[0117] ii) filling the cavity of a mould with the foamable blend, and

[0118] iii) foaming the foamable blend, preferably by dropping the pressure into the mould.

[0119] In one embodiment, the process of the fourth aspect is a foam injection molding process, in which the foaming step iii) is carried out by expanding the foamable blend with low hold pressure of the mold.

[0120] In a preferred embodiment, the process of the fourth aspect is a core-back foam injection molding process, wherein the foaming step iii) is carried out by depressurization of the mould cavity.

[0121] Preferably, step i) is carried out by dispersing from 1 to 10% by weight, preferably from 2 to 7% by weight, based on the total weight of the foamable blend, of the masterbatch composition of the first aspect into the base resin.

[0122] It is preferred that the thermoplastic polyolefin of the base resin has a melting point comprised in the range of from 150°C to 230°C.

[0123] In a further preferred embodiment, the base resin comprises at least one propylene polymer, more preferably at least one propylene polymer having melting temperature equal to or greater than 150°C, like comprised in the range of from 150°C to 170°C.

[0124] Thermoplastic polyolefin foamed articles obtained from the process of the fourth aspect have small cell size, uniform cell size distribution and high ratio of the thickness of the core layer to the total thickness of the article, resulting in light weight of the foamed article and good mechanical properties.

[0125] Thermoplastic polyolefin foamed articles obtained from the process of the fourth aspect, particularly polypropylene foamed articles, find application preferably in the automotive field, like in interior parts.

[0126] While multiple embodiments are disclosed, still other embodiments will become apparent to those skilled in the art from the following detailed description. As will be apparent, certain embodiments, as disclosed herein, are capable of modifications in various obvious aspects, all without departing from the spirit and scope of the claims as presented herein. Accordingly, the following detailed description is to be regarded as illustrative in nature and not restrictive.EXAMPLES

[0127] The following examples are given to illustrate the present invention without limiting purpose.

[0128] CHARACTERIZATION METHODS : the following methods are used to determine the properties indicated in the description, claims and examples.

[0129] Comonomer content of polybutene-1: determined by FT-IR. The test specimens are pressed films. Films are obtained with a hydraulic press that can be heated up to 200°C (Carver or equivalent). The spectrum of the sample vs. an air background is recorded and plotted in absorbance vs. wavenumbers (resolution 2 cm'1). The following measurements are used to calculate the ethylene content:- area (At) of the combination absorption bands between 4482 and 3950 cm'1which is used for spectrometric normalization of film thickness;- factor of subtraction (FCRc2): the digital subtraction between the spectrum of the polymer sample and the absorption band due to the sequences BEE and BEB (B: 1 -butene units, E: ethylene units) of the methylenic groups (CH2 rocking vibration);- area (AC2, block) of the residual band after subtraction of the C2PB spectrum. It comes from the sequences EEE of the methylenic groups (CH2 rocking vibration).Sample preparationA sheet is obtained by pressing 1.5 g of polymer between two aluminum foils. A minimum of two pressing operations are recommended. A small portion is cut from this sheet to mold a film. Film thickness ranges between 0.1-0.3 mm. Pressing temperature is 140±10°C. IR spectrums is recorded right after film preparation.Calibration of (BEB+BEE) sequencesA calibration straight line is obtained by plotting %(BEB + BEE)wt vs. FCRc2 / At. The slope Gr and the intercept Ir are calculated from linear regression.Calibration of EEE sequencesA calibration straight line is obtained by plotting %(EEE)wt vs. Ac2, block / At. The slope GH and the intercept In are calculated from linear regression.CalculationCalculate the concentration by weight of the BEE + BEB sequences of ethylene units:FCRc%(BEE + BEB)wt = Gr - + EAtCalculate the residual area (AC2, block) after the subtraction described above, using a baseline between the shoulders of the residual band.Calculate the concentration by weight of the EEE sequences of ethylene units:Calculate the total amount of ethylene percent by weight:0 / oC2wt = [° / 0(BEE+ BEB) t + %(EEE) t\

[0130] Fraction soluble in xylene at 0°C: 2.5 g of polymer and 250 cm3of o-xylene are introduced in a glass flask equipped with a refrigerator and a magnetic stirrer. The temperature is raised in 30 minutes up to the boiling point of the solvent. The so obtained clear solution is then kept under reflux and stirring for further 30 minutes. The closed flask is then cooled to 100°C in air for 10 to 15 minute under stirring and then kept for 30 minutes in thermostatic water bath at 0°C for 60 minutes as well. The so formed solid is filtered on quick filtering paper at 0°C. 100 cm3of the filtered liquid is poured in a previously weighed aluminum container which is heated on a heating plate under nitrogen flow, to remove the solvent by evaporation. The percent by weight of polymer soluble at 0°C (XS 0°C) is calculated with respect to the initial weight of the sample.

[0131] Melt flow rate: MFR is determined according to ISO 1133-1:2011, with a load of 2.16 kg at 190°C for polybutene-1 and with a load of 2.16 kg at 230°C for polypropylene.

[0132] Thermal properties (melting temperatures and enthalpies): were determined by Differential Scanning Calorimetry (D.S.C.) on a Perkin Elmer DSC-7 instrument. The melting temperatures of butene- 1 copolymers and of the HMA compositions were determined according to the following method:

[0133] - Tmll (melting temperature / s measured in second heating run): a weighted sample (5-10 mg) obtained from the polymerization (or a weighted sample of the HMA composition) was sealed into aluminium pans and heated at 200°C with a scanning speed corresponding to 10°C / minute. The sample was kept at 200°C for 5 minutes to allow a complete melting of all the crystallites thus cancelling the thermal history of the sample. Successively, after cooling to -20°C with a scanning speed corresponding to 10°C / minute, the peak temperature was taken as crystallization temperature (Tc). After standing 5 minutes at - 20°C, the sample was heated for the second time at 200°C with a scanning speed corresponding to 10°C / min. In this second heating run, the peak temperature measured were marked as (Tmll). If more than one peak was present, the highest one (most intense) was taken as Tmll. The area under the peak (or peaks) as global melting enthalpy (DH Tmll).

[0134] - The melting enthalpy and the melting temperature were measured also after aging(without cancelling the thermal history) as follows by using the Differential Scanning Calorimetry (D.S.C.) on an Perkin Elmer DSC-7 instrument. A weighted sample (5-10 mg) obtained from the polymerization (or a weighted sample of the HMA composition) was sealed into aluminium pans and heated at 200°C with a scanning speed corresponding to 10°C / minute. The sample was kept at 200°C for 5 minutes to allow a complete melting of all the crystallites and cooled down to 20°C at a cooling rate of 10°C / min. The sample was then stored for 10 days at room temperature. After 10 days the sample was subjected to DSC, it was cooled to -20°C, and then it was heated at 200°C with a scanning speed corresponding to 10°C / min. In this heating run, the peak temperature was recorded as the melting temperatures (Tml). If more than one peak was present, the highest one (most intense) was taken as Tml. The area under the peak (or peaks) as global melting enthalpy after 10 days (DH Tml).

[0135] Brookfield viscosity: determined at 190°C according to the ASTM D3236-15 (2021). Test instrument: cylindrical spindle rotational viscometer type Brookfield HA or HB,Ametek / Benelux Scientific model DV2T can be taken as reference. Testing conditions: spindle SC4-27; software Rheocalc T 1.2.19. Preheat the sample chamber and spindle at the testing temperature for at least 15 min. Load 10.5±0.1 g of polymer to be tested into the sample chamber and insert the spindle. Preheat for further 3 min. Start the rotation at low speed and keep the speed constant for 3 minutes. Increase the RPM stepwise until 80% of Torque value is reached according to the table below:Torque decreases during test progression, and the value of viscosity is the mean value in the last 20 min. of testing.

[0136] Molecular weight distribution: measured by way of Gel Permeation Chromatography in 1 ,2, 4-tri chlorobenzene (TCB). Molecular weight parameters (Mn, Mw and Mz) and molecular weight distributions for all the samples are measured by using a GPC-IR apparatus by PolymerChar, which is equipped with a column set of four PLgel Olexis mixed-bed (Polymer Laboratories) and an IR5 infrared detector (PolymerChar). The dimensions of the columns are 300 x 7.5 mm and their particle size 13 / im. The mobile phase flow rate is kept at 1.0 ml / min. All the measurements are carried out at 150°C. Solution concentrations are 2.0 mg / ml (at 150°C) and 0.3 g / 1 of 2,6-diterbuthyl-p-chresole are added to prevent degradation. For GPC calculation, a universal calibration curve is obtained using 12 polystyrene (PS) standard samples supplied by PolymerChar (peak molecular weights ranging from 266 to 1,220,000). A third order polynomial fit is used for interpolate the experimental data and obtain the calibration curve. Data acquisition and processing is done by using Empower 3 (Waters). The Mark-Houwink equation is used to determine the molecular weight distribution and the average molecular weights. For butene / ethylene copolymers, it is assumed for each sample that the composition is constant in the whole range of molecular weight and the K value of the Mark-Houwink equation is calculated using a linear combination:where KEB is the constant of the copolymer, KPE (4.06 x 10'4, dl / g) and KPB (1.78 x 10'4dl / g) are the constants of polyethylene (PE) and PB, xE and xB are the ethylene and the butene- 1 weight relative amounts, with xE + xB = 1. The Mark-Houwink exponents a = 0.725 was used for all the butene / ethylene copolymers independently on their composition. For polystyrene KPS = 1.21 x 10"4dl / g and a = 0.706 are used.

[0137] Density: measured according to ISO 1183-1 :2019. Test specimens were taken from compression molded plaques conditioned for 10 days at 25°C before carrying out the density measurement.

[0138] Intrinsic viscosity: determined according to ASTM D2857-22 in tetrahydronaphthalene (THN) at 135°C.

[0139] Shore D: measured according to ISO 868:2003 (15 sec) 10 days after moulding on compression molded specimens.

[0140] Tensile modulus: measured at 23°C according to ISO 527-1,-2:2019 10 days after moulding on compression molded specimens.

[0141] Thickness of foamed layers: measured on a magnified image of the cross-section of a test specimens using an optical microscope, Zeiss Axio Zoom. VI 6, equipped with a camera, Axiocam 305 color. On each test specimen, the following parameters were determined:- total thickness of the test specimen (L): the distance between the opposite surfaces of the specimens is measured in two points, see lines (A) and (B) in FIG.1. The total thickness (L) is calculated as the arithmetic mean value of the two measures;- thickness of the skin, unfoamed layers (S): for each surface, the distance between the surface and the edge of the foam cell closer to said surface is measured, (si) and (s2) in FIG.l. The thickness (S) of each skin layer is calculated as the arithmetic mean value of si and s2;- the thickness of the foamed layer F is calculated from the formula F = L - 2S.

[0142] Average cell size: measured on a magnified image of the cross-section of the test specimens using an optical microscope, Zeiss Axio Zoom. VI 6, equipped with a camera, Axiocam 305 color. For each foam cell, the cell size is determined as the diameter of the representing sphere, i.e. the sphere that has the same surface area of the foam cell. Five foam cells are selected which are representative for the cells population; the average cell size is the arithmetic mean of five cell sizes.

[0143] Odor: measured accordingly to the standard PV 3900, VW Norm 50180:2019-04.

[0144] MATERIALS USED

[0145] Component A): three different butene- 1 polymer compositions were tested as carrier resins in a masterbatch composition:

[0146] - PB(A1) was prepared according to example 1 of WO2019 / 025583,

[0147] - PB(A2) was prepared according to example 1 of WO2019 / 025585, and

[0148] - PB(A3) was prepared according to example 1 of WO2018 / 007279.

[0149] The properties of the three butene- 1 polymer compositions are reported in Table la and lb.

[0150] Component B): Sodium citrate and / or sodium bicarbonate, as specified below.

[0151] Component C): Talc Luzenac A7 C

[0152] Additives: CaO.Table laTable lb

[0153] Examples E1-E3 and comparative example CE4

[0154] Compounding: to prepare the polybutene-1 masterbatch composition, compounding was carried out under standard conditions, i.e. under water granulation. The compounding temperature was typically greater than the melting point Tm(II) of the lowest melting polymer, e.g. greater than 80°C, more typically from 81° to 150°C. The nucleating agent, the chemical blowing agent and the additives were first formulated into a blend, and then the blend was added to the polybutene-1 carrier. The masterbatch compositions are reported in table 2.

[0155] Foaming: The chemical foaming experiment was conducted on an injection molding machine Krauss Maffei KM 350 CX 2000, equipped with a single screw and gravimetric dosing system. The screw diameter was 70 mm with an L / D ratio of 20. The temperature profile was typically from 200° - 230°C. Panels were made from a starting wall thickness of 2 mm. The mold was opened to a final wall thickness of 3 mm, with a set expansion stroke of 1 mm. The masterbatch composition was dosed at 4 wt.% to a foamable base resin comprising polypropylene and 15 wt.% talc. The expansion gas was created by thermal decomposition of the blowing agent. The decomposition reaction typically took place from 150° - 230 °C. After injection and mold opening, the expansion started because of the pressure drop. Thickness of the layers, average cell size and odor are illustrated in table 2.

[0156] The foamed items of examples E1-E3 and comparative example CE4 are illustrated in FIG.2 to FIG.5. The foamed items of examples El and E2, FIG.2 and FIG.3 respectively, show a fine cell distribution comparable with that of an item foamed with ITP825, a commercial foaming masterbatch.Table 2

[0157] Examples E5-E7

[0158] Compounding and foaming were carried out as in Examples E1-E3. The masterbatch compositions and the foaming test results are summarized in table 3.Table 3

[0159] Examples E8 and E9

[0160] Masterbatch compounding and foaming tests were carried out as in Examples E1-E3.The masterbatch compositions and the foaming test results are summarized in table 4.Table 4

Claims

CLAIMSWhat is claimed is:

1. A masterbatch composition comprising:A) from 25% to 80% by weight of a butene- 1 polymer composition comprising: a) at least one butene- 1 homopolymer, or copolymer of butene- 1 with one or more comonomers selected from ethylene and higher alpha-olefins, the copolymer having a copolymerized comonomer content (CA) in a range of up to 5% by mole, and b) at least one copolymer of butene- 1 with one or more comonomers selected from ethylene and higher alpha-olefins, having a copolymerized comonomer content (CB) in a range of more than 5% to 25% by mole, wherein the amount of polymer a) is in a range of from 5 to 95 % by weight, based on the total weight of polymers a) and b), said butene- 1 polymer composition having i) a total copolymerized comonomer content in a range of from 4% to 18% by mole, preferably from 5% to 12% by mole, based on the total weight of polymers a) and b), and ii) a fraction soluble in xylene at 0°C of from 35% to 90% by weight, preferably from 48% to 62% by weight, based on the total weight of polymers a) and b), iii) a melt flow rate value in a range of from 30 to 1000 g / 10 min, as measured according to ISO 1133 at 190°C with a load of 2.16 kg;B) from 20% to 75% by weight of at least one endothermic chemical blowing agent;C) from 0 to 50% by weight of at least one nucleating agent, wherein the amounts of components A), B) and C) are based on the total weight of the masterbatch composition.

2. The masterbatch composition of claim 1, wherein component A) comprises from 20% to 70% by weight, preferably from 30% to 60% by weight, of polymer a), and from 80% to 30% by weight, preferably from 70% to 40% by weight, of polymer b), each based on the total weight of polymers a) and b).

3. The masterbatch composition of claim 1 or 2, wherein component A) has a melt flow rate in a range of from 40 to 800 g / 10 min, preferably from 100 to 300 g / lOmin, as measured according to ISO 1133 at 190°C with a load of 2.16 kg.

4. The masterbatch composition of any of the preceding claims, wherein component A) has a Tm(II) value in a range of from 70° to 105°C, preferably in a range of from 75° to 100°C, more preferably in a range of from 77° to 90°C, in particular in a range of from 79° to 85°C, as measured by DSC with a scanning speed of 10°C / min.

5. The masterbatch composition of any of the preceding claims, wherein component A) has a Brookfield viscosity in a range of from 10,000 to 270,000 mPa-s, preferably in a range of from 15,000 to 250,000 mPa-s, more preferably in a range of from 20,000 to 200,000 mPa-s, in particular in a range of from 25,000 to 150,000 mPa-s, such as in a range of from 30,000 to 100,000 mPa-s, or from 35,000 to 50,000 mPa-s, each measured at 190°C (ASTM D3236-15 (2021)).

6. The masterbatch composition of any of the preceding claims, wherein polymer a) of component A) has from 1% to 4% by mole of copolymerized comonomer (CA).

7. The masterbatch composition of any of the preceding claims, wherein polymer b) of component A) has from 8% to 20% by mole of copolymerized comonomer (CB).

8. The masterbatch composition of any of the preceding claims, wherein polymers (a) and (b) are copolymers and the difference between the percent values of the copolymerized comonomer contents of (a) and (b) satisfies the following relation: (CB) - (CA) > 5, or preferably, (CB) - (CA) > 6.

9. The masterbatch composition of any of the preceding claims, wherein the comonomer comprised in polymer (a) and polymer (b) is ethylene.

10. The masterbatch composition of any of the preceding claims, wherein component A) has a density equal to or greater than 0.89 g / cm3, preferably in a range of from 0.89 to 0.92 g / cm3.

11. The masterbatch composition of any of the preceding claims, wherein component A) has an Mw / Mn value, where Mw is the weight average molecular mass and Mn is the number average molecular mass both measured by GPC, equal to or lower than 4, in particular equal to or lower than 3, or equal to or lower than 2.5, the lower limit being of 1.5 in all cases.

12. The masterbatch composition of any of the preceding claims, wherein component A) has at least one, more preferably all, of the following features:- Mw equal to or greater than 50.000, in particular from 50.000 to 180.000 g / mol, like from 70.000 to 150.000 g / mol; and / or- Mz equal to or greater than 90.000 g / mol, in particular from 90.000 to 200.000 g / mol, like from 100.000 to 190.000 g / mol; and / or- an intrinsic viscosity (IV) measured according to ASTM D2857-22 in tetrahydronaphthalene (THN) at 135°C equal to or lower than 0.7 dl / g, in particular from 0.2 dl / g to 0.7 dl / g, like from 0.5 dl / g to 0.6 dl / g; and / or- isotactic pentads (mmmm) measured with 13C-NMR operating at 150.91 MHz higher than 90%, in particular higher than 93%, like higher than 95%; and / or- 4,1 insertions not detectable using a 13C-NMR operating at 150.91 MHz; and / or- a Shore D value equal to or lower than 50, in particular from 25 to 50, like from 25 to 45, measured according to ISO 868:2003; and / or- a tensile modulus, measured at 23°C according to ISO 527-1,-2:2019, of from 30 MPa to 150 MPa, in particular from 50 MPa to 120 MPa.

13. The masterbatch composition of any of the preceding claims, wherein component B) is selected from the group consisting of an alkali-metal citrate, an alkali-metal bicarbonate and combinations thereof.

14. The masterbatch composition of any of the preceding claims, wherein component B) is sodium citrate or a mixture of sodium citrate and sodium bicarbonate.

15. The masterbatch composition of any of the preceding claims, wherein component C) is talc.

16. The masterbatch composition of any of the preceding claims, comprising:- from 35% to 65% by weight, preferably from 40% to 55% by weight, in particular from 45% to 50% by weight, of component A),- from 20% to 40% by weight, preferably from 25% to 35% by weight, in particular from 27% to 33% by weight, of component B), and- from 10% to 45% by weight, preferably from 15% to 35% by weight, in particular from 17% to 30% by weight, of component C), each based on the total weight of the masterbatch composition.

17. The masterbatch composition of any of the preceding claims further comprising up to and including 15% by weight, preferably from 1 to 15%by weight, more preferably from 5 to 12% by weight, based on the total weight of the masterbatch composition, of at least one wax D), wherein the wax is preferably a polyolefin wax.

18. The masterbatch composition of any of the preceding claims further comprising up to and including 5% by weight, preferably from 0.1 to 5% by weight, based on the total weight of the masterbatch composition, of at least one additive E) selected from selected from the group consisting of antioxidants, light stabilizers, slipping agents, anti-acids, melt stabilizers, and combinations thereof.

19. A process for preparing the masterbatch composition of any of the preceding claims, comprising: a. optionally, obtaining a blend of component B) and component C); b. compounding component B) or the blend of step a), with component A); wherein step b) takes place at a temperature in a range of from 80°C to 150°C.

20. The process of claim 19, comprising the step c) of pelletizing the compound of step (b).

21. Use of the masterbatch composition of any of claims 1 to 18 in a method of foaming thermoplastic polyolefins.

22. A process for preparing a thermoplastic polyolefin foamed article, comprising: i) providing a foamable blend by dispersing the masterbatch composition according to any one of claims 1 to 18 into a base resin comprising at least one thermoplastic polyolefin at a temperature of at least 150°C, preferably ranging from 150° to 230°C, ii) filling the cavity of a mould with the foamable blend, and iii) foaming the foamable blend, preferably by dropping the pressure into the mould.

23. The process of claim 22 in which the foaming step iii) is carried out by expanding the foamable blend with low hold pressure of the mold.

24. The process of claim 22 or 23, wherein step i) is carried out by dispersing from 1 to 10% by weight, preferably from 2 to 7% by weight, based on the total weight of the foamable blend, of the masterbatch composition into the base resin.

25. The process of any one of claims from 22 to 24, wherein the base resin comprises at least one propylene polymer, more preferably at least one propylene polymer having melting temperature equal to or greater than 150°C, more preferably comprised in the range of from 150°C to 170°C.

26. A thermoplastic polyolefin foamed article obtained from the process according to any one of claims from 22 to 25.

Images