POLYOLEFIN COMPOSITION WITH HIGH TRANSPARENCY

FIELD OF THE INVENTION

[0001] The present disclosure relates to a polyolefin composition having a low haze, thus a high transparency, also referred to as optical clarity, comprising a propylene polymer, or a heterophasic polyolefin composition comprising said propylene polymer, a clarifying agent and low amounts of a butene- 1 polymer.

[0002] The incorporation of said butene- 1 polymer allows to achieve an improved transparency with respect to a polyolefin composition containing the clarifying agent only.

BACKGROUND OF THE INVENTION

[0003] Crystalline polyolefins, including polypropylene, are used in large amounts in the industrial production of a very wide range of finished or semi-finished articles, such as, for example, injection molded, extruded or blow molded articles, like containers, bottles, sheets, films and fibers.

[0004] In many application fields, for instance in injection molded, blown and extruded articles for medical uses and for packaging, it is often desirable to have a high transparency.

[0005] As reported in for instance in WO2016/025326, high transparency in propylene polymers can be achieved by adding a clarifying agent.

[0006] The clarifying agent has generally a crystal nucleating effect on the propylene polymer when it is melted, formed and cooled to obtain the final article.

[0007] Consequently, the size of crystals is decreased and the light scattering is reduced, even if some residual haze is still left.

[0008] It has now been found that the haze of a polyolefin composition comprising propylene polymers and a clarifying agent can be further reduced by adding low amounts of a butene- 1 polymer.

SUMMARY OF THE INVENTION

[0009] Thus the present disclosure provides a polyolefin composition comprising:

A) a propylene polymer, or a heterophasic polyolefin composition comprising said propylene polymer and an ethylene copolymer;

B) from 0.01% to 2% by weight, preferably from 0.015% to 1.5% by weight, more preferably from 0.02% to 0.5% by weight, most preferably from 0.02% to 0.3% by weight, in particular from 0.02% to 0.2% by weight, of a butene- 1 polymer; and

C) a clarifying agent; wherein the amounts of C) are referred to the total weight of A) + B) + C).

[0010] In addition to enhanced transparency, the said composition has also good mechanical properties.

DETAILED DESCRIPTION OF THE INVENTION

[0011] As previously explained, the addition of the butene- 1 polymer B) has the effect of reducing the haze of a polyolefin composition containing the components A) and C).

[0012] Thus, the present disclosure provides also the use of a butene- 1 polymer B) to reduce the haze of a polyolefin composition comprising:

A) a propylene polymer, or a heterophasic polyolefin composition comprising said propylene polymer and an ethylene copolymer; and

C) a clarifying agent;

[0013] the said butene- 1 polymer B) being added to the said polyolefin composition in amounts from 0.01% to 2% by weight, preferably from 0.015% to 1.5% by weight, more preferably from 0.02% to 0.5% by weight, most preferably from 0.02% to 0.3% by weight, in particular from 0.02% to 0.2% by weight with respect to the total weight of A) + B) + C).

[0014] As used herein, the expression “propylene polymer” includes polymers selected from propylene homopolymers, propylene copolymers, in particular random copolymers, and their mixtures.

[0015] Analogously, as used herein, the expression “butene-1 polymer” includes polymers selected from butene-1 homopolymers, butene-1 copolymers and their mixtures.

[0016] In the present polyolefin composition, when A) is a propylene copolymer, it contains one or more comonomer(s) preferably selected from ethylene and CH2=CHR alpha-olefins, where R is a C2-C8 alkyl radical, in particular butene-1, pentene- 1, 4-methyl-pentene-l, hexene- 1 and octene- 1.

[0017] Ethylene, butene-1 and hexene- 1 are preferred.

[0018] When B) is a butene copolymer, it contains one or more comonomer(s) preferably selected from ethylene, propylene and CH2=CHR alpha-olefins, where R is a Cs-Cs alkyl radical, in particular pentene-1, 4-methyl-pentene-l, hexene-1 and octene-1. [0019] Ethylene, propylene and hexene- 1 are preferred.

From the above definitions it is evident that the term “copolymer” includes polymers containing more than one kind of comonomers.

[0020] Other preferred features for the propylene polymer A), when selected from propylene homopolymers and copolymers, are: content of comonomer(s), when A) is a copolymer, from 0.5 to 15% by weight, more preferably from 1 to 12% by weight, in particular from 0.5 to 6% by weight when the comonomer is ethylene or hexene- 1; poly dispersity Index (P.I.) equal to or higher than 4, specifically from 4 to 20, more preferably from 4 to 15;

MIL from 0.1 to 400 g/10 min. in particular from 0.5 to 150 g/10 min. or from 10 to 100 g/10 min., where MIL is the melt flow index at 230 °C with a load of 2.16 kg, determined according to ISO 1133-2:2011; amount of fraction insoluble in xylene at 25°C equal to or higher than 85% by weight, more preferably equal to or higher than 90% by weight, in particular, in the case of propylene homopolymers, equal to or higher than 95% by weight, the upper limit being preferably of 99% for all homopolymers and 96% for all copolymers;

[0021] flexural modulus higher than 200 MPa, more preferably higher than 400 MPa, the upper limit being preferably of 2000 MPa in all cases.

[0022] Both the said propylene homopolymers and propylene copolymers are known in the art and commercially available.

[0023] Examples of commercially available homopolymers and copolymers of propylene are the polymer products sold by the LyondellBasell Industries with the trademark Moplen.

[0024] They can be prepared by using a Ziegler-Natta catalyst or a metallocene-based catalyst system in the polymerization process.

[0025] Typically a Ziegler-Natta catalyst comprises the product of the reaction of an organometallic compound of group 1, 2 or 13 of the Periodic Table of Elements with a transition metal compound of groups 4 to 10 of the Periodic Table of Elements (new notation). In particular, the transition metal compound can be selected among compounds of Ti, V, Zr, Cr and Hf and is preferably supported on MgCh.

[0026] Particularly preferred catalysts comprise the product of the reaction of said organometallic compound of group 1, 2 or 13 of the Periodic Table of Elements, with a solid catalyst component comprising a Ti compound and an electron donor compound supported on MgCh.

[0027] Preferred organometallic compounds are the aluminum alkyl compounds. [0028] Thus preferred Ziegler-Natta catalysts are those comprising the product of reaction of:

1) a solid catalyst component comprising a Ti compound, preferably a halogenated Ti compound, in particular TiCh, and an electron donor (internal electron-donor) supported on MgCh;

2) an aluminum alkyl compound (cocatalyst); and, optionally,

3) an electron-donor compound (external electron-donor).

[0029] The solid catalyst component (1) contains as electron-donor a compound generally selected among the ethers, ketones, lactones, compounds containing N, P and/or S atoms, and mono- and dicarboxylic acid esters.

[0030] Catalysts having the above mentioned characteristics are well known in the patent literature; particularly advantageous are the catalysts described in US patent 4,399,054 and European patent 45977.

[0031] Particularly suited among the said internal electron-donor compounds are phthalic acid esters, preferably diisobutyl phthalate, and succinic acid esters.

[0032] Other internal electron-donors particularly suited are the 1,3-diethers, as illustrated in published European patent applications EP-A-361493 and 728769.

[0033] As cocatalysts (2), one preferably uses the trialkyl aluminum compounds, such as Al- triethyl, Al-triisobutyl and Al-tri-n-butyl.

[0034] The electron-donor compounds (3) that can be used as external electron-donors (added to the Al-alkyl compound) comprise the aromatic acid esters (such as alkyl benzoates), heterocyclic compounds (such as 2,2,6,6-tetramethylpiperidine and 2,6-diisopropylpiperidine), and in particular silicon compounds containing at least one Si-OR bond (where R is a hydrocarbon radical).

[0035] Useful examples of silicon compounds are (tert-butyl)2Si(OCH3)2, (cyclohexyl)(m ethyl) Si (OCH3)2, (phenyl)2Si(OCH3)2 and (cyclopentyl)2Si(OCH3)2.

[0036] The previously said 1,3- diethers are also suitable to be used as external electrondonors. In the case that the internal electron-donor is one of the said 1,3-diethers, the external electron-donor can be omitted.

[0037] The catalysts may be precontacted with small quantities of olefin (prepolymerization), maintaining the catalyst in suspension in a hydrocarbon solvent, and polymerizing at temperatures from room to 60°C, thus producing a quantity of polymer from 0.5 to 3 times the weight of the catalyst.

[0038] The operation can also take place in liquid monomer, producing, in this case, a quantity of polymer up to 1000 times the weight of the catalyst. [0039] Preferred examples of metallocene-based catalyst systems are disclosed in US20060020096 and W098040419.

[0040] The polymerization conditions to be used with the above said catalysts generally are well known also.

[0041] The said polymerization can be carried out in a single step, or in two or more steps under different polymerization conditions.

[0042] It can occur in liquid phase (e.g. using liquid propylene as diluent), in gas phase or liquid-gas phase.

[0043] Conventional molecular weight regulators known in the art, such as chain transfer agents (e.g. hydrogen or ZnEt2), may be used.

[0044] The polymerization temperature is preferably from 40 to 120°C; more preferably from 50 to 80°C.

[0045] The polymerization pressure can be atmospheric or higher.

[0046] If the polymerization is carried out in liquid propylene, the pressure is the one which competes with the vapor pressure of the liquid propylene at the operating temperature used, and may be modified by the vapor pressure of the small quantity of inert diluent used to feed the catalyst mixture, by the overpressure of optional monomers and by the hydrogen used as molecular weight regulator.

[0047] In particular, the propylene polymer A) can be produced by a polymerization process carried out in a gas-phase polymerization reactor comprising at least two interconnected polymerization zones, as is illustrated in EP application 782587.

[0048] In detail, the process is carried out in a first and in a second interconnected polymerization zones into which propylene and the optional comonomers are fed in the presence of the catalyst system and from which the polymer produced is discharged. In said process the growing polymer particles flow upward through one (first) of the said polymerisation zones (riser) under fast fluidisation conditions, leave said riser and enter another (second) polymerisation zone (downcomer) through which they flow downward in a densified form under the action of gravity, leave said downcomer and are reintroduced into the riser, thus establishing a circulation of polymer between the riser and the downcomer.

[0049] In the downcomer high values of density of the solid are reached, which approach the bulk density of the polymer. A positive gain in pressure can thus be obtained along the direction of flow, so that it becomes possible to reintroduce the polymer into the riser without the help of special mechanical means. In this way, a "loop" circulation is set up, which is defined by the balance of pressures between the two polymerization zones and by the head loss introduced into the system. [0050] Generally, the condition of fast fluidization in the riser is established by feeding a gas mixture comprising the relevant monomers to said riser. It is preferable that the feeding of the gas mixture is effected below the point of reintroduction of the polymer into said riser by the use, where appropriate, of gas distributor means. The velocity of transport gas into the riser is higher than the transport velocity under the operating conditions, preferably from 2 to 15 m/s.

[0051] Generally, the polymer and the gaseous mixture leaving the riser are conveyed to a solid/gas separation zone. The solid/gas separation can be effected by using conventional separation means. From the separation zone, the polymer enters the downcomer. The gaseous mixture leaving the separation zone is compressed, cooled and transferred, if appropriate with the addition of make-up monomers and/or molecular weight regulators, to the riser. The transfer can be carried out by means of a recycle line for the gaseous mixture.

[0052] The control of the polymer circulation between the two polymerization zones can be carried out by metering the amount of polymer leaving the downcomer using means suitable for controlling the flow of solids, such as mechanical valves.

[0053] The process can be carried out under operating pressures of between 0.5 and 10 MPa, preferably between 1.5 to 6 MPa.

[0054] Optionally, one or more inert gases, such as nitrogen or an aliphatic hydrocarbon, are maintained in the polymerization zones, in such quantities that the sum of the partial pressures of the inert gases is preferably between 5 and 80% of the total pressure of the gases.

[0055] The catalyst is fed up to the riser at any point of the said riser. However, it can also be fed at any point of the downcomer. The catalyst can be in any physical state, therefore catalysts in either solid or liquid state can be used.

[0056] Preferred examples of heterophasic polyolefin composition A) are compositions comprising: i) one or more propylene polymers selected from propylene homopolymers and propylene copolymers as previously defined and their mixtures, and ii) a copolymer or a composition of copolymers of ethylene with propylene and/or one or more CH2=CHR alpha-olefin(s), where R is a C2-C8 alkyl radical, and optionally with minor amounts of a diene (preferably from 1 to 10% by weight with respect to the weight of ii)), said copolymer or composition containing 15% by weight or more, preferably from 15% to 90% by weight, in particular from 25 to 85% by weight of ethylene with respect to the weight of ii).

[0057] Particularly preferred examples of said heterophasic polyolefin composition are those containing from 40 to 90% by weight of component i) and 10 to 60% by weight of component ii), referred to the total weight of i) + ii). [0058] The said CH2=CHR alpha-olefin which can be present in component ii) is the same as previously described for the propylene copolymers.

[0059] A particularly preferred example is butene- 1.

[0060] Preferred examples of dienes are butadiene, 1,4-hexadiene, 1,5-hexadiene and ethy li dene- 1 -norb omene .

[0061] The heterophasic polyolefin composition A) preferably has a MIL ranging from 0.1 to 50 g/10 minutes, more preferably from 0.5 to 20 g/10 minutes.

[0062] The elongation at break of the heterophasic polyolefin composition is preferably from 100% to 1000%.

[0063] The flexural modulus of the heterophasic polyolefin composition is preferably from 500 to 1500 MPa, more preferably from 700 to 1500 MPa.

[0064] The copolymer or composition of copolymers ii) has preferably a solubility in xylene at 25°C of from 40% to 100% by weight, more preferably from 50% to 100% by weight, referred to the total weight of ii).

[0065] Said heterophasic polyolefin compositions are known in the art and commercially available.

[0066] Examples of commercially available heterophasic polyolefin compositions are the polymer products sold by the LyondellBasell Industries with the trademark Moplen.

[0067] They can be prepared by blending components i) and ii) in the molten state, that is to say at temperatures greater than their softening or melting point, or more preferably by sequential polymerization in the presence of a Ziegler-Natta catalyst as previously described.

[0068] Other catalysts that may be used are metallocene-type catalysts, as described in USP 5,324,800 and EP-A-0129368; particularly advantageous are bridged bis-indenyl metallocenes, for instance as described in USP 5,145,819 and EP-A-0485823. These metallocene catalysts may be used in particular to produce the component ii).

[0069] The above mentioned sequential polymerization process for the production of the heterophasic polyolefin composition comprises at least two stages, where in one or more stage(s) propylene is polymerized, optionally in the presence of the said CH2=CHR alpha-olefin comonomer(s), to form component i), and in one or more additional stage(s) mixtures of ethylene with propylene and/or the said CH2=CHR alpha-olefin comonomer(s), and optionally dienes, are polymerized to form component ii).

[0070] The polymerization process is carried out in liquid, gaseous, or liquid/gas phase. The polymerization temperature in the various stages of polymerization can be equal or different, and generally ranges from 40 to 90°C, preferably from 50 to 80°C for the production of component i), and from 40 to 60°C for the production of component ii). Examples of sequential polymerization processes are described in European patent applications EP-A-472946 and EP-A-400333 and in WO03/011962.

[0071] The butene-1 polymer B) is preferably a linear polymer which is highly isotactic, having in particular an isotacticity from 90 to 99%, more preferably from 93 to 99%, most prerably from 95 to 99%, measured as mmmm pentads/total pentads with ¹³ C-NMR operating at 150.91 MHz, or as quantity by weight of matter soluble in xylene at 0 °C.

[0072] The butene-1 polymer B) has preferably a MIE value of from 1 to 3000 g/10 min., more preferably from 50 to 3000 g/10 min., where MIE is the melt flow index at 190°C with a load of 2.16 kg, determined according to ISO 1133-2:2011.

[0073] Highly preferred MIE values for the butene-1 polymer B) are from 700 to 3000 g/10 min.

[0074] In one embodiment, the butene-1 polymer B) may be a copolymer having a comonomer content, in particular a copolymerized ethylene content, of from 0.5% to 5.0% by mole, preferably of from 0.7% to 3.5% by mole.

[0075] In one further embodiment, the butene-1 polymer B) may be a butene-1 polymer composition comprising:

Bl) a butene-1 homopolymer or a copolymer of butene-1 with at least one comonomer selected from ethylene, propylene, the previously defined CH2=CHR alpha-olefin and mixtures thereof, having a copolymerized comonomer content of up to 2% by mole;

B2) a copolymer of butene-1 with at least one comonomer selected from ethylene, propylene, the previously defined CH2=CHR alpha-olefin and mixtures thereof, having a copolymerized comonomer content of from 3 to 5% by mole; said composition having a total copolymerized comonomer content of 0.5 - 4.0% by mole, preferably of from 0.7 to 3.5% by mole, referred to the sum of Bl) + B2).

[0076] The relative amounts of Bl) and B2) may range from 10% to 40% by weight, in particular from 15% to 35% by weight of Bl) and from 90% to 60% by weight, in particular from 85% to 65% by weight of B2), said amounts being referred to the sum of Bl) + B2).

[0077] In one embodiment, the butene-1 polymer B) may have at least one of the following additional features: a) a molecular weight distribution (Mw/Mn) equal to or lower than 9, preferably equal to or lower than 4, more preferably equal to or lower than 3, most preferably equal to or lower than 2.5, the lower limit being preferably of 1.5 in all cases; b) melting point Tmll, measured by DSC (Differential Scanning Calorimetry) in the second heating run with a scanning speed of 10 °C/min., equal to or lower than 125°C, preferably equal to or lower than 110°C, the lower limit being preferably in all cases of 80°C; c) a Brookfield viscosity at 190°C of from 1500 to 20000 mPa-sec, in particular from 2000 to 15000 mPa-sec, or from 2500 to 10000 mPa-sec; d) 4,1 insertions not detectable using a ¹³ C-NMR operating at 150.91 MHz; e) X-ray crystallinity of from 25 to 65%; f) glass transition temperature (Tg) from - 40°C to - 10°C, preferably from -30°C to -10°C.

[0078] Optionally, the butene- 1 polymer B) may have at least one of the following further additional features: i) intrinsic viscosity (I V.) measured in tetrahydronaphtalene (THN) at 135°C, equal to or lower than 5 dl/g, preferably equal to or lower than 2 dl/g, more preferably equal to or lower than 0.6 dl/g, the lower limit being preferably of 0.2 dl/g in all cases; ii) Mw equal to or greater than 30.000 g/mol, in particular from 30.000 to 500.000 g/mol or from 30.000 to 100.000 g/mol; iii) melting point Tml, measured by DSC with a scanning speed of 10 °C/min., from 95°C to 110°C; iv) a density of 0.885-0.925 g/cm ³ , in particular of 0.890-0.920 g/cm ³ ;

[0079] Said butene- 1 polymer B) can be obtained using known processes and polymerization catalysts.

[0080] As a way of example, in order to produce the butene- 1 polymer B) one can use TiCh based Ziegler-Natta catalysts and aluminum derivatives, such as aluminum halides for example, as cocatalysts, as well as the catalytic systems supported on MgCh described above for the preparation of the propylene polymer A).

[0081] When said supported catalytic systems are used, additional examples of internal electron-donor compounds are diethyl or diisobutyl 3,3 - dimethyl glutarate.

[0082] Preferred examples of external electron-donor compounds are cyclohexyltrimethoxysilane, t-butyltrimethoxysilane diisopropyldrimethoxysilane and thexyltrimethoxysilane. The use of thexyltrimethoxysilane is particularly preferred.

[0083] Preferably, the butene- 1 polymer B) can be 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 alkyl metallocene cation; and, optionally,

- an organo aluminum compound.

[0084] 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-Cio-aryl, C?-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, Ce-C2o-arylidene, C?-C2o-alkylarylidene, or C?-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;

R ¹ , R ² , R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ , equal to or different from each other, are hydrogen atoms, or linear or branched, saturated or unsaturated Ci-C2o-alkyl, C3-C2o-cycloalkyl, Ce-Cio-aryl, C?-C2o-alkylaryl or C?-C2o-arylalkyl radicals, optionally containing heteroatoms belonging to groups 13-17 of the Periodic Table of the Elements; or R ⁵ and R ⁶ , and/or R ⁸ and R ⁹ can optionally form a saturated or unsaturated, 5 or 6 membered rings, said ring can bear C1-C20 alkyl radicals as substituents; with the proviso that at least one of R ⁶ or R ⁷ is 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;

R ³ and R ⁴ , 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 R ³ and R ⁴ equal to or different from each other are Ci-Cio-alkyl radicals; more preferably R ³ is a methyl, or ethyl radical; and R ⁴ is a methyl, ethyl or isopropyl radical.

[0085] Preferably the compounds of formula (I) have formula (la):

(la)

Wherein:

M, X, R ¹ , R ² , R ⁵ , R ⁶ , R ⁸ and R ⁹ have been described above;

R ³ is 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 R ³ is a Ci-Cio-alkyl radical; more preferably R ³ is a methyl or ethyl radical.

[0086] Specific examples of metallocene compounds are dimethylsilyl{(2,4,7-trimethyl-l- indenyl)-7-(2,5-dimethyl-cyclopenta[l,2-b:4,3-b’]-dithioph ene)} zirconium dichloride; dimethylsilanediyl{(l-(2,4,7-trimethylindenyl)-7-(2,5-dimeth yl-cyclopenta[l,2-b:4,3-b’]- dithiophene)}Zirconium dichloride and dimethylsilanediyl{(l-(2,4,7-trimethylindenyl)-7-(2,5- dimethyl-cyclopenta[l,2-b:4,3-b’]-dithiophene)}zirconium dimethyl.

[0087] Examples of alumoxanes are methylalumoxane (MAO), tetra-(isobutyl)alum oxane (TIBAO), tetra-(2,4,4-trimethyl-pentyl)alumoxane (TIOAO), tetra-(2,3-dimethylbutyl)alumoxane (TDMBAO) and tetra-(2,3,3-trimethylbutyl)alumoxane (TTMBAO).

[0088] 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 able to be removed by an olefinic monomer. Preferably, the anion E" comprises of one or more boron atoms.

[0089] Examples organo aluminum compound are trimethylaluminum (TMA), triisobutylaluminium (TIBA), tris(2,4,4-trimethyl-pentyl)aluminum (TIOA), tris(2,3- dimethylbutyl)aluminium (TDMBA) and tris(2,3,3-trimethylbutyl)aluminum (TTMBA).

[0090] Examples of the said catalyst system and of polymerization processes employing such catalyst system can be found in W02004099269 and W02009000637. [0091] The polymerization process can be carried out with the said catalysts by operating 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.

[0092] The hydrocarbon solvent can be either aromatic (such as toluene) or aliphatic (such as propane, hexane, heptane, isobutane, cyclohexane and 2,2,4-trimethylpentane, isododecane).

[0093] Preferably, the polymerization process is carried out by using liquid butene- 1 as polymerization medium.

[0094] The polymerization temperature can be from 20°C to 150°C, in particular from 50°C to 90°C, for example from 65°C to 82°C.

[0095] To control the molecular weights, a molecular weight regulator, in particular hydrogen, is fed to the polymerization environment.

[0096] It is also possible to operate according to a multistep polymerization process, wherein butene-1 polymers with different composition and/or molecular weights are prepared in sequence in two or more reactors with different reaction conditions, such as the concentration of molecular weight regulator and/or comonomer fed in each reactor.

[0097] In particular, when the present butene-1 polymer comprises the previously said two components Bl) and B2), the polymerization process can be carried out in two or more reactors connected in series, wherein components Bl) and B2) 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.

[0098] The catalyst can be added in the first reactor only, or in more than one reactor.

[0099] For all the previously described polymer components, high melt index values can be obtained directly in polymerization or by subsequent chemical treatment (chemical visbreaking).

[0100] The chemical visbreaking of the polymer is carried out in the presence of free radical initiators, such as the peroxides.

[0101] The peroxides which are most conveniently used in the polymer visbreaking process have a decomposition temperature preferably ranging from 150°C to 250°C. Examples of said peroxides are di-tert-butyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di(tert- butylperoxy)hexyne and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, all of which are commercially available.

[0102] The quantity of peroxide necessary for the visbreaking process preferably ranges from 0.001 to 0.5% by weight of the polymer, more preferably from 0.001 to 0.2%.

[0103] With the term “clarifying agent” it is intended any additive which gives rise to a haze decrease when added to propylene polymers or to heterophasic compositions comprising said propylene polymers. [0104] Preferably, the clarifying agent has the effect of reducing the haze values of said polymers by at least 20%, more preferably by at least 30%, in particular by at least 50%.

[0105] Said reduction is preferably achieved when the clarifying agent is added to a propylene polymer in amounts from 0.025% to 0.2% by weight with respect to the total weight of the propylene polymer and the clarifier.

[0106] As previously said, the clarifying agents usually belong to the class of nucleating agents.

[0107] Suitable clarifying agents include the derivatives, in particular the acetals, of polyols, preferably of sorbitol, xylitol and nonitol, phosphate ester salts and carboxylic acid salts.

[0108] Specific examples of acetals of sorbitol and xylitol include dibenzylidene sorbitol; di(alkylbenzylidene) sorbitols, in particular di(p-methylbenzylidene) sorbitol, di(o- methylbenzylidene) sorbitol and di(p-ethylbenzylidene) sorbitol; bis(3,4-dialkylbenzylidene) sorbitols, in particular l,3;2,4-Bis(3,4-dimethylbenzylidene) sorbitol and bis(3,4- diethylbenzylidene) sorbitol; bis(5',6',7',8'-tetrahydro-2-naphthylidene) sorbitol; bis(trimethylbenzylidene) xylitol and bis(trimethylbenzylidene) sorbitol.

[0109] Said sorbitol and xylitol acetals and their use as clarifying agents are disclosed in US patent 5,310,950.

[0110] Examples of commercial products include MILLAD® 3988, powdered 1,3;2,4- Bis(3,4-dimethylbenzylidene) sorbitol; MILLAD® NX™ 8000, l,2,3-trideoxy-4,6:5,7-bis-O-[(4- propylphenyl)methylene]-nonitol and MILLAD® NX™ 8500E, another nonitol-based clarifying agent.

[0111] Examples of commercially available phosphate ester salts for use as clarifying agents include stabilizers NA-11, sodium 2,2'-methylene-bis-(4,6-di- tert-butylphenyl)phosphate, NA- 21, aluminum hydroxy bis[2,2'-methylene-bis-(4,6-di-tert- butylphenyl)phosphate] and NA-71, all available from Adeka Corporation.

[0112] Examples of carboxylic acid salts are dicarboxylic acid salts, in particular bicyclo[2.2.1]heptane dicarboxylate salts, like Hyperform® HPN-68L, which is based on endo- Norbornane-2, 3 -dicarboxylic acid disodium salt, and cyclohexane dicarboxylate salts, like Hyperform® HPN-20E, which is based on cyclohexane- 1,2-dicarboxylic acid calcium salt.

[0113] Particularly preferred clarifying agents are the di(alkylbenzylidene) sorbitols, the bis(3,4-dialkylbenzylidene) sorbitols, in particular 1, 3-0-2, 4-bis(3,4-dimethylbenzylidene) sorbitol, and the nonitol derivatives, in particular l,2,3-trideoxy-4,6:5,7-bis-O-[(4- propylphenyl)methylene] -nonitol . [0114] Preferred amounts of clarifying agent C) are from 0.02% to 0.3% by weight, in particular from 0.05% to 0.25% by weight, or from 0.05% to 0.2% by weight, or from 0.1% to 0.2% by weight, with respect to the total weight of A) + B) + C).

[0115] Thus, in a preferred embodiment the present polyolefin composition comprises:

A) from 97.7% to 99.97% by weight, preferably from 98.25% to 99.935 % by weight, more preferably from 99.3% to 99.93% by weight, most preferably from 99.5% to 99.88% by weight, of a propylene polymer, or a heterophasic polyolefin composition comprising said propylene polymer and an ethylene copolymer;

B) from 0.01% to 2% by weight, preferably from 0.015% to 1.5% by weight, more preferably from 0.02% to 0.5% by weight, most preferably from 0.02% to 0.3% by weight, in particular from 0.02% to 0.2% by weight of a butene-1 polymer; and

C) from 0.02% to 0.3% by weight, preferably from 0.05% to 0.25% by weight, more preferably from 0.05% to 0.2% by weight, most preferably from 0.1% to 0.2% by weight, of a clarifying agent; wherein the amounts of A), B) and C) are referred to the total weight of A) + B) + C). [0116] Preferably the weight ratio C)/B) is from 0.5 to 4, more preferably from 1 to 3.5.

[0117] The present polyolefin composition can also contain additives, fillers and pigments commonly used for olefin polymers, such as stabilizing agents (against heat, light, U.V.), plasticizers, antiacids, antistatic and water repellant agents, organic and inorganic pigments.

[0118] Preferably, the present polyolefin composition has at least one of the following features:

Haze values, measured according to ASTM D 1003 - 13 on 1 mm plaque, equal to or lower than 20%, more preferably equal to or lower than 15%, the lower limit being preferably of 2% in both cases;

MIL from 0.1 to 400 g/10 min. in particular from 0.5 to 150 g/10 min. or from 10 to 100 g/10 min.;

Elongation at break, according to ISO 527-1:2019 on compression molded plaques, measured 10 days after molding, from 500 to 1500%;

Charpy notched at 23°C, according to ISO 179/leA:2010 , measured 48 hours after molding, from 2 to 10 kJ/m ² ;

Charpy notched at 0°C, according to ISO 179/leA:2010, measured 48 hours after molding, from 1 to 5 kJ/m ² ; Melting temperature from 142 to 153 °C;

Crystallization temperature from 114 to 120°C.

[0119] The present polyolefin composition can be prepared by blending the components at temperatures generally of from 180 to 310°C, preferably from 190 to 280°C, more preferably from 200 to 250°C. Any known apparatus and technology can be used for this purpose.

[0120] Useful melt-blending apparatuses in this context are in particular extruders or kneaders, and particular preference is given to twin-screw extruders. It is also possible to premix the components at room temperature in a mixing apparatus.

[0121] The present polyolefin composition in form of the premixed components can also be directly fed to the processing equipment used to prepare the final article, thus omitting a previous melt blending step.

[0122] The present polyolefin composition can be processed in conventional polymer processing machines.

[0123] In particular, the present polyolefin composition is particularly suited for preparing injection molded articles, including injection blow molded and injection stretch blow molded articles, like formed articles in general (for instance housewares), bottles and containers.

[0124] Thus the present disclosure provides also an injection molded article comprising the said polyolefin composition. Such injection molded article is preferably characterized by a wall thickness equal to or greater than 0.1 mm, more preferably equal to or greater than 0.5 mm.

[0125] The injection molded article is typically prepared by using processes and apparatuses well known in the art. Generally the injection molding process comprises a step where the polymer is molten and a subsequent step where the molten polymer is injected in the mold under pressure. It is also possible to produce an injection molded tubular structure and to blow air into it while softened at a suited temperature, in order to force the softened tube to conform to the inside walls of the mold.

Temperatures and pressures are those usually employed in the injection molding processes. In particular it is possible to operate at melt temperatures from 180 to 230°C with injection pressures from 1 to 150 MPa.

EXAMPLES

[0126] Various embodiments, compositions and methods as provided herein are disclosed below in the following examples. These examples are illustrative only, and are not intended to limit the scope of the invention.

[0127] The following analytical methods are used to characterize the polymer compositions.

[0128] MIE and MIP [0129] Determined according to norm ISO 1133-2:2011 under the specified temperature and load.

[0130] Comonomer contents

[0131] Propylene polymer A)

[0132] For propylene copolymers the comonomer content was determined by infrared spectroscopy by collecting the IR spectrum of the sample vs. an air background with a Fourier Transform Infrared spectrometer (FTIR). The instrument data acquisition parameters were: purge time: 30 seconds minimum; collect time: 3 minutes minimum; apodization: Happ-Genzel; resolution: 2 cm' ¹ .

[0133] Sample Preparation

[0134] Using a hydraulic press, a thick sheet was obtained by pressing about g 1 of sample between two aluminum foils. If homogeneity is in question, a minimum of two pressing operations are recommended. A small portion was cut from this sheet to mold a film. Recommended film thickness ranges between 0.02-:0.05 cm (8 - 20 mils).

[0135] Pressing temperature was 180±10°C (356°F) and about 10 kg/cm ² (142.2 PSI) pressure for about one minute. Then the pressure was released and the sample was removed from the press and cooled to the room temperature.

[0136] The spectrum of a pressed film of the polymer was recorded in absorbance vs. wavenumbers (cm' ¹ ). The following measurements were used to calculate ethylene and butene- 1 content:

Area (At) of the combination absorption bands between 4482 and 3950 cm ^-1 which was used for spectrometric normalization of film thickness.

If ethylene was present, Area (AC2) of the absorption band between 750-700 cm' ¹ after two proper consecutive spectroscopic subtractions of an isotactic non additivated polypropylene spectrum and then, if butene- 1 was present, of a reference spectrum of a butene- 1 -propylene random copolymer in the range 800-690 cm' ¹ .

If butene-1 was present, the height (DC4) of the absorption band at 769 cm' ¹ (maximum value), after two proper consecutive spectroscopic subtractions of an isotactic non additivated polypropylene spectrum and then, if ethylene was present, of a reference spectrum of an ethyl ene-propylene random copolymer in the range 800-690 cm' ¹ . [0137] In order to calculate the ethylene and butene- Icontent, calibration straight lines for ethylene and butene- 1 obtained by using samples of known amount of ethylene and butene- 1 are needed.

[0138] Butene- 1 polymer B)

[0139] Comonomer contents were determined via FT-IR.

[0140] The spectrum of a pressed film of the polymer was recorded in absorbance vs. wavenumbers (cm ^-1 ). The following measurements were used to calculate the ethylene content: a) area (At) of the combination absorption bands between 4482 and 3950 cm' ¹ which is used for spectrometric normalization of film thickness. b) factor of subtraction (FCRc2) of 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 (CEE rocking vibration). c) Area (Ac2, block) of the residual band after subtraction of the C2PB spectrum. It comes from the sequences EEE of the methylenic groups (CEE rocking vibration).

[0141] APPARATUS

[0142] A Fourier Transform Infrared spectrometer (FTIR) was used, which is capable of providing the spectroscopic measurements above reported.

[0143] A hydraulic press with platens heatable to 200 °C (Carver or equivalent) was used.

[0144] METHOD

[0145] Calibration of (BEB + BEE) sequences

[0146] A calibration straight line was obtained by plotting %(BEB + BEE)wt vs. FCRc2/At. The slope Gr and the intercept Ewere calculated from a linear regression.

[0147] Calibration of EEE sequences

[0148] A calibration straight line was obtained by plotting %(EEE)wt vs. Ac2, block/ At. The slope GH and the intercept IH were calculated from a linear regression.

[0149] Sample preparation

[0150] Using a hydraulic press, a thick sheet was obtained by pressing about g 1.5 of sample between two aluminum foils. If homogeneity is in question, a minimum of two pressing operations are recommended. A small portion was cut from this sheet to mold a film. Recommended film thickness ranges between 0.1-0.3 mm.

[0151] The pressing temperature was 140 ± 10 °C.

[0152] A crystalline phase modification takes place with time, therefore it is recommended to collect the IR spectrum of the sample film as soon as it is molded.

[0153] Procedure [0154] The instrument data acquisition parameters were as follows:

Purge time: 30 seconds minimum.

Collect time: 3 minutes minimum.

Apodization: Happ-Genzel.

Resolution: 2 cm' ¹ .

Collect the IR spectrum of the sample vs. an air background.

[0155] CALCULATION

[0156] Calculate the concentration by weight of the BEE + BEB sequences of ethylene units:

[0157] Calculate the residual area (AC2, block) after the subtraction described above, using a baseline between the shoulders of the residual band.

[0158] Calculate the concentration by weight of the EEE sequences of ethylene units:

°/o(EEE)wt = GH ■ ^AC2 ’ ^BIOCK _{+ IH}

At

[0159] Calculate the total amount of ethylene percent by weight:

[0160] °/oC2wt = °/<>( EE + BEB)wt + °/o(EEE)wt\

[0161] Haze

[0162] Measured according to ASTM D 1003 - 13 on 1 mm plaque. According to the method used, 7.5 x 7.5 cm specimens were cut from molded plaques 1 mm thick and the haze value was measured using a Gardner photometric unit connected to a Hazemeter type UX- 10 or an equivalent instrument having G.E. 1209 light source with filter “C”. Reference samples of known haze were used for calibrating the instrument.

[0163] The plaques to be tested were produced according to the following method.

[0164] 75x75x1 mm plaques were molded with a GBF Plastiniector G235/90 Injection

Molding Machine, 90 tons under the following processing conditions:

Screw rotation speed: 120 rpm;

Back pressure: lO bar;

Melt temperature: 230°C;

Injection time: 5 sec;

Switch to hold pressure: 50 bar;

First stage hold pressure: 43 bar;

Second stage pressure: 20 bar; Hold pressure profile: First stage 5 sec;

Second stage 10 sec;

Cooling time: 20 sec;

Mold water temperature: 40°C.

[0165] Gloss

[0166] Specular gloss properties were measured at an angle of 60° using a micro-TRI-gloss meter made by BYK-Gardner GmbH in conformance with ASTM D 523 - 14(2018) using a black felt backing. The gloss meter was calibrated using a black glass.

[0167] Tensile modulus

[0168] Measured according to ISO 527-2:2012.

[0169] Charpy impact strength

[0170] According to ISO 179/leA:2010 at 23°C and 0 °C, measured 48 hours after molding.

[0171] Tensile stress and elongation at yield and at break

[0172] According to norm ISO 527-1:2019 on compression molded plaques, measured 10 days after molding.

[0173] Flexural modulus

[0174] According to norm ISO 178:2019, measured 48 hours after molding.

[0175] Brookfield viscosity

[0176] Measured at 190°C by means of a Cylindrical Spindle Rotational Viscometer HA Ametek/Benelux Scientific model DV2T, equipped with a drive motor capable of variable testing speed and a set of spindles capable of achieving and maintaining a torque at about 80%.

[0177] The selected spindle/chamber combination was SC4-27 / SC4-13R/RP.

[0178] During the test, the sample was subjected to a stepwise rotation increase until a torque value of around 80% was reached and maintained. Rotation started at 10 RPM then increased stepwise by 2 RPM every 5 seconds.

[0179] The Brookfield viscosity, expressed in mPa*s, was calculated as Shear Stress (mPa) / Shear Rate (sec-1) ratio and was determined by averaging the results obtained during the last 20 minutes of acquisition (1 datapoint / minute).

[0180] Intrinsic viscosity (I. V.)

[0181] Determined according to norm ASTM D 2857 - 16 in tetrahydronaphthalene at 135 °C.

[0182] Poly dispersity Index (PI)

[0183] Determined at a temperature of 200°C by using a parallel plates rheometer model RMS-

800 marketed by RHEOMETRICS (USA), operating at an oscillation frequency increasing from 0.1 rad/sec to 100 rad/sec. From the crossover modulus one can derive the P.I. by way of the equation: in which Gc is the crossover modulus which is defined as the value (expressed in Pa) at which G’=G” wherein G' is the storage modulus and G" is the loss modulus.

[0184] Fractions soluble and insoluble in xylene at 25 °C (XS-25°C)

[0185] 2.5 g of polymer were dissolved in 250 ml of xylene at 135° C under agitation. After 20 minutes the solution was allowed to cool to 25° C, still under agitation, and then allowed to settle for 30 minutes. The precipitate was filtered with filter paper, the solution evaporated in nitrogen flow, and the residue dried under vacuum at 80° C until constant weight was reached. Thus, one calculates the percent by weight of polymer soluble (Xylene Solubles - XS) and insoluble at room temperature (25° C).

[0186] The percent by weight of polymer insoluble in xylene at room temperature (25°C) is considered the isotactic index of the polymer. This value corresponds substantially to the isotactic index determined by extraction with boiling n-heptane, which by definition constitutes the isotactic index of propylene polymers.

[0187] Fractions soluble and insoluble in xylene at 0°C (XS-0°C)

[0188] 2.5 g of the polymer sample were dissolved in 250 ml of xylene at 135°C under agitation. After 30 minutes the solution was allowed to cool to 100°C, still under agitation, and then placed in a water and ice bath to cool down to 0°C. Then, the solution was allowed to settle for 1 hour in the water and ice bath. The precipitate was filtered with filter paper. During the filtering, the flask was left in the water and ice bath so as to keep the flask inner temperature as near to 0°C as possible. Once the filtering is finished, the filtrate temperature was balanced at 25°C, dipping the volumetric flask in a water-flowing bath for about 30 minutes and then, divided in two 50 ml aliquots. The solution aliquots were evaporated in nitrogen flow, and the residue dried under vacuum at 80° C until constant weight was reached. The weight difference in between the two residues must be lower than 3%; otherwise the test has to be repeated. Thus, one calculates the percent by weight of polymer soluble (Xylene Solubles at 0°C = XS 0°C) from the average weight of the residues. The insoluble fraction in o-xylene at 0°C (xylene Insolubles at 0°C = XI%0°C) is:

[0189] XI%0°C=100-XS%0°C.

[0190] Melting and crystallization temperatures of butene- 1 polymer B) via differential scanning calorimetry (DSC)

[0191] Differential scanning calorimetric (DSC) data were obtained with a Perkin Elmer DSC- 7 instrument, using a weighted sample (5-10 mg) sealed into aluminum pans.

[0192] In order to determine the melting temperature of the polybutene- 1 crystalline form I (Tml), the sample was heated to 200°C with a scanning speed corresponding to 10°C/minute, kept at 200°C for 5 minutes and then cooled down to 20°C with 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 to 200°C with a scanning speed corresponding to 10°C/min. In this heating run, the highest temperature peak in the thermogram was taken as the melting temperature (Tml).

[0193] In order to determine the melting temperature of the polybutene- 1 crystalline form II (Tmll) and the crystallization temperature T _c , the sample was heated to 200°C with a scanning speed corresponding to 10°C/minute and 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, by cooling to -20°C with a scanning speed corresponding to 10°C/minute, the peak temperature was taken as crystallization temperature (T _c ) and the area as the crystallization enthalpy. After standing 5 minutes at -20°C, the sample was heated for the second time to 200°C with a scanning speed corresponding to 10°C/min. In this second heating run, the peak temperature was taken as the melting temperature of the polybutene- 1 crystalline form II (Tmll) and the area as the melting enthalpy (AHfll).

[0194] NMR analysis of chain structure

[0195] ¹³ C NMR. spectra were acquired on a Bruker AV-600 spectrometer equipped with cryo- probe, operating at 150.91 MHz in the Fourier transform mode at 120°C.

[0196] The peak of the Tps carbon (nomenclature according to C. J. Carman, R. A. Harrington and C. E. Wilkes, Macromolecules, 10, 3, 536 (1977)) was used as internal reference at 37.24 ppm. The samples were dissolved in l,l,2,2-tetrachloroethane-< 2 at 120°C with a 8 % wt/v concentration. Each spectrum was acquired with a 90° pulse, 15 seconds of delay between pulses and CPD to remove coupling. About 512 transients were stored in 32K data points using a spectral window of 9000 Hz.

[0197] The assignments of the spectra, the evaluation of triad distribution and the composition were made according to Kakugo [M. Kakugo, Y. Naito, K. Mizunuma and T. Miyatake, Macromolecules, 16, 4, 1160 (1982)] and Randall [J. C. Randall, Macromol. Chem Phys., C30, 211 (1989)] using the following:

BBB = 100 (Tpp)/S = 15

BBE = lOOTpg/S = 14

EBE = 100 P55 /S = 114 BEB = 100 Spp/S = 113 BEE= 100 Sas/S = 17 EEE = 100(0.25 S _Y5 +0.5 S ₅₅ )/S = 0.25 19+ 0.5110

[0198] To a first approximation, the mmmm was calculated using 2B2 carbons as follows: mmmm = Bi*100/(Bi+B2-2*A4-A?-Ai4)

[0199] Molecular weights determination by GPC

[0200] Measured by way of Gel Permeation Chromatography (GPC) in 1, 2, 4-tri chlorobenzene (TCB). Molecular weight parameters (Mn, Mw) and molecular weight distributions Mw/Mn for all the samples were measured by using a GPC-IR apparatus by PolymerChar, which was equipped with a column set of four PLgel Olexis mixed-bed (Polymer Laboratories) and an IR5 infrared detector (PolymerChar). The dimensions of the columns were 300 x 7.5 mm and their particle size was 13 «m. The mobile phase flow rate was kept at 1.0 mL/min. All the measurements were carried out at 150 °C. Solution concentrations were 2.0 mg/mL (at 150 °C) and 0.3 g/L of 2,6-diterbuthyl- -chresole were added to prevent degradation. For GPC calculation, a universal calibration curve was obtained using 12 polystyrene (PS) standard samples supplied by PolymerChar (peak molecular weights ranging from 266 to 1220000). A third-order polynomial fit was used for interpolate the experimental data and obtain the relevant calibration curve. Data acquisition and processing was done by using Empower 3 (Waters). The Mark-Houwink relationship was used to determine the molecular weight distribution and the relevant average molecular weights: the K values were Kps = 1.21 x 10' ⁴ dL/g and KPB = 1.78 x 10' ⁴ dL/g for PS and polybutene (PB) respectively, while the Mark-Houwink exponents a = 0.706 for PS and a = 0.725 for PB were used.

[0201] For butene/ethylene copolymers, as far as the data evaluation is concerned, it was assumed for each sample that the composition was constant in the whole range of molecular weight and the K value of the Mark-Houwink relationship was calculated using a linear combination as reported below: where KEB is the constant of the copolymer, KPE (4.06 x 10' ⁴ , dL/g) and KPB (1.78 x 10' ⁴ dL/g) are the constants of polyethylene (PE) and PB, XE and XB are the ethylene and the butene weight relative amount with XE + XB = 1. The Mark-Houwink exponents a = 0.725 was used for all the butene/ethylene copolymers independently on their composition. End processing data treatment was fixed for all samples to include fractions up at 1000 in terms of molecular weight equivalent. Fractions below 1000 were investigated via GC.

[0202] Determination of X-ray crystallinity

[0203] The X-ray crystallinity was measured with an X-ray Diffraction Powder Diffractometer (XDPD) that uses the Cu-Kal radiation with fixed slits and able to collect spectra between diffraction angle 20 = 5° and 20 = 35° with step of 0.1° every 6 seconds.

[0204] The samples were diskettes of about 1.5-2.5 mm of thickness and 2.5-4.0 cm of diameter made by compression moulding. The diskettes were aged at room temperature (23°C) for 96 hours.

[0205] After this preparation the specimen was inserted in the XDPD sample holder. The XRPD instrument set in order to collect the XRPD spectrum of the sample from diffraction angle 20 = 5° to 20 = 35° with steps of 0.1° by using counting time of 6 seconds, and at the end the final spectrum was collected. [0206] Defining Ta as the total area between the spectrum profile and the baseline expressed in counts/sec’20 and Aa as the total amorphous area expressed in counts/sec20, Ca is total crystalline area expressed in counts/sec20.

[0207] The spectrum or diffraction pattern was analyzed in the following steps:

1) define a suitable linear baseline for the whole spectrum and calculate the total area (Ta) between the spectrum profile and the baseline;

2) define a suitable amorphous profile, along the whole spectrum, that separate , the amorphous regions from the crystalline ones according to the two phase model;

3) calculate the amorphous area (Aa) as the area between the amorphous profile and the baseline;

4) calculate the crystalline area (Ca) as the area between the spectrum profile and the amorphous profile as Ca = Ta- Aa

5) Calculate the degree of crystallinity (%Cr) of the sample using the formula:

%Cr = lOO x Ca / Ta

[0208] Density

[0209] Measured according to ISO 1183-1 :2012 at 23°C.

[0210] Glass transition temperature via DMTA (Dynamic Mechanical Thermal Analysis) Molded specimens of 76 mm by 13 mm by 1 mm were fixed to the DMTA machine for tensile stress. The frequency of the tension and relies of the sample was fixed at 1 Hz. The DMTA translates the elastic response of the specimen starting from -100 °C to 130 °C. In this way it is possible to plot the elastic response versus temperature. The elastic modulus for a viscoelastic material is defined as E=E’+iE”. The DMTA can split the two components E’ and E” by their resonance and plot E’ vs temperature and E’ ZE” = tan (6) vs temperature.

The glass transition temperature Tg was assumed to be the temperature at the maximum of the curve E’ZE” = tan (6) vs temperature.

[0211] Melting temperature and crystallization temperatures of the polyolefin composition

[0212] Measured by using a DSC instrument according to ISO 11357-3:2018, at scanning rate of 20°C/min both in cooling and heating, on a sample of weight between 5 and 7 mg, under inert N2 flow. Instrument calibration made with Indium.

[0213] Materials

[0214] The hereinafter described materials were used in the following examples.

[0215] Propylene polymer A)

[0216] Copolymer of propylene with 3% by weight of ethylene, having the following properties:

- MIL of 75 g/10min.;

- Haze of 56.4%; - Gloss of 97.1;

- Fraction insoluble in xylene at 25°C of 94% by weight;

- Flexural modulus of about 1000 MPa.

[0217] Butene- 1 polymer B)

[0218] Two different polymers were used, namely butene- 1 polymer B)-I and butene- 1 polymer B)-II.

[0219] Butene- 1 polymer B)-I

[0220] Prepared as reported hereinafter.

[0221] Preparation of the catalytic solution

[0222] Under nitrogen atmosphere, 6400 g of a 33 g/L solution of triisobutylaluminium

(TIBA) in isododecane and 567 g of 30% wt/wt solution of methylalumoxane (MAO) in toluene were loaded in a 20 L jacketed glass reactor, stirred by means of an anchor stirrer, and allowed to react at room temperature for about 1 hour under stirring.

[0223] After this time, 1.27 g of metallocene dimethylsilyl{(2,4,7-trimethyl-l-indenyl)-7-(2,5- dimethyl-cyclopenta[l,2-b:4,3-b']-dithiophene)} zirconium dichloride, prepared according to Example 32 of WO0147939, was added and dissolved under stirring for about 30 minutes.

[0224] The final solution was discharged from the reactor into a cylinder through a filter to remove eventual solid residues.

[0225] The composition of the solution resulted to be:

[0226] Polymerization

[0227] The polymerization was carried out in two stirred reactors operated in series, in which liquid butene-1 constituted the liquid medium. The catalyst solution described above was fed in both reactors. The polymerization conditions are reported in Table 1. The butene-1 /ethylene copolymer was recovered as melt from the solution and cut in pellets. The copolymer was further characterized and the data are reported in Table 2. Table 1

Note: C2- = ethylene; kg/gMe = kilograms of polymer per gram of metallocene; Split = amount of polymer produced in the concerned reactor.

Table 2 [0228] Butene- 1 polymer B)-II

[0229] Using the same catalytic solution and the same polymerization equipment as used for the preparation of the butene- 1 polymer B)-I, the polymerization was carried out in the said two stirred reactors operated in series, in which liquid butene-1 constituted the liquid medium. The catalyst solution was injected in both reactors and the polymerization was carried out in continuous at a polymerization temperature of 75°C. The residence time in each reactor was in a range of 12CU200 min. The concentration of hydrogen during polymerization was 4900 ppm mol H2/(C4-) bulk, where C4- = butene-1. The comonomer was fed to the reactors in an amount of C2-/C4- 0.35%wt. The ethylene comonomer was almost immediately copolymerized (C2- "stoichiometric" feed to the reactor). The catalyst yield (mileage) was of 2000 kg/g metallocene active component. The butene-1 copolymer was recovered as melt from the solution and cut in pellets. The copolymer was further characterized and the data are reported in Table 3.

Table 3

[0230] Clarifying agent C)

[0231] l,3;2,4-Bis(3,4-dimethylbenzylidene) sorbitol, sold by Milliken with trademark Millad 3988.

[0232] Preparation of the polyolefin compositions

[0233] Examples 1 - 4 and Comparative Example 1

[0234] The previously described components A), B) and C) were blended in the amounts reported in the following Table 4, wherein also the final properties of the resulting polyolefin compositions are reported. [0235] Blending was carried out by extrusion with a conventional composition of stabilizing additives in a twin screw extruder Berstorff ZE 25 (length/diameter ratio of screws: 34) under nitrogen atmosphere in the following conditions:

[0236] Rotation speed: 250 rpm;

[0237] Extruder output: 15 kg/hour;

[0238] Melt temperature: 245 °C.

[0239] Said composition of stabilizing additives was made of 500 ppm of Irganox 1010, pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), commercially available from BASF, 1000 ppm of Irgafos 168, tris(2,4-di-tert-butylphenyl) phosphite, commercially available from BASF, 500 ppm of calcium stearate and 1000 ppm of GMS90 (glycerol monostearate) commercially available from Croda, summing up to 0.3% by weight of stabilizing additives, referred to the total weight of the polyolefin composition.

Table 4

* with respect to the total weight of the polyolefin composition;

** with respect to total weight of A) + B) + C).