Patent Description:
The incorporation of said butene-<NUM> polymer allows to achieve an improved melt flowability in the injection molding process, while enhancing some mechanical properties of the ethylene polymer.

Injection molding is commonly used for producing various kinds of polymer articles, in particular those having a complex shape.

Polyolefins, including polyethylene, are the most widely used plastics for injection molding.

In the injection molding process, heat and pressure are applied to the polymer, causing it to melt and flow. The melt is injected under high pressure into the mold.

Pressure is maintained on the material in the cavity until it cools and solidifies. When the temperatures have been reduced sufficiently below the polymer's distortion temperature, the mold opens and the molded article is ejected.

It is thus evident that in a polyolefin designed for injection molding, a high melt flowability is required, in order to obtain a high and consistent quality of the final articles with viable pressure and temperature conditions and to reduce the cycle time.

In the case of polyethylene, such effect is achieved by properly setting the molecular weights and the molecular weight distribution, but there is a continuous effort to obtain the best possible melt flowability under the injection molding process conditions, without reducing the mechanical properties.

Paraffinic waxes, such as Fischer-Tropsch waxes, are often used as additives to improve melt flowability of polyethylene in the injection molding process.

However, when the waxes are added to polyethylene in amounts over about <NUM>% by weight, it becomes increasingly difficult to obtain a homogeneous blend, so that the improvement in melt flowability is limited.

Moreover, the final mechanical properties are generally worsened.

While it is already known to add low amounts of butene-<NUM> polymers to polyethylene for the preparation of pipes, films and fibers, as reported in <CIT> and <CIT>, the use of butene-<NUM> polymers as processing aids in compositions for injection molding is not contemplated in the art. <CIT> discloses polyolefin compositions for injection moulding, which compositions comprise also a butene-<NUM> polymer, however, having relatively low melt flow rates.

It has now been found that by adding a butene-<NUM> polymer with a very high melt flow rate value to an ethylene polymer, it is possible to obtain a polymer composition for injection molding with an unexpected profile of properties.

Thus the present disclosure provides a polymer composition comprising:.

wherein the amounts of A) and B) are referred to the total weight of A) + B).

The said composition has high values of melt flowability, measured as spiral length, and of impact resistance, measured as Charpy impact strength.

As used herein, the expression "ethylene polymer" includes polymers selected from ethylene homopolymers and ethylene copolymers containing alpha-olefin comonomers different from ethylene, having preferably from <NUM> to <NUM> carbon atoms (preferably in amounts from <NUM>% to <NUM>% by weight with respect to the total weight of the copolymer) and their mixtures. Examples of the said alpha-olefin comonomers having from <NUM> to <NUM> carbon atoms are propylene, butene-<NUM>, pentene-<NUM>, hexene-<NUM>, octene-<NUM> and <NUM>-methylpentene-<NUM>.

Butene-<NUM> and hexene-<NUM> are preferred.

The expression "ethylene polymer" is also intended to embrace, as alternatives, both a polymer consisting of a single component, such kind of polymer being called "monomodal" polymer in the art, and a polymer (polymer composition) comprising two or more ethylene polymer components, preferably with different molecular weights, thus a "bimodal" or "multimodal" polymer.

As used herein, the expression "butene-<NUM> polymer" includes polymers selected from butene-<NUM> homopolymers and copolymers of butene-<NUM> containing alpha-olefin comonomers different from butene-<NUM>, preferably selected from ethylene, propylene, alpha-olefins having from <NUM> to <NUM> carbon atoms and mixtures thereof.

Examples of said alpha-olefins having from <NUM> to <NUM> carbon atoms are hexene-<NUM> and octene-<NUM>.

The expression "butene-<NUM> polymer" is also intended to embrace, as alternatives, both a polymer consisting of a single component and a polymer (polymer composition) comprising two or more butene-<NUM> polymer components, preferably with different amounts of comonomers.

Particularly preferred amounts of A) and B) are:.

wherein all the amounts of A) and B) are referred to the total weight of A) + B).

Preferred values of density for the ethylene polymer A) are from <NUM> to <NUM>/cm<NUM>, in particular from <NUM> to <NUM>/cm<NUM>, measured according to ISO <NUM>-<NUM>:<NUM> at <NUM>.

Particularly preferred values of MIP for the ethylene polymer A) are:.

Optionally, the ethylene polymer A) may have at least one of the following further additional features:.

The present ethylene polymer A) is available on the market. It belongs to the family of the polymers (homo- and copolymers) that can be obtained by way of polymerization processes in the presence of coordination catalysts. Said processes and the polymers obtained from them are widely described in the art.

In particular it is possible to carry out the polymerization process in the presence of a Ziegler-Natta catalyst.

As known, the Ziegler-Natta polymerization catalysts comprise the reaction product of an organic compound of a metal of Groups I-III of the Periodic Table (for example, an aluminum alkyl), and an inorganic compound of a transition metal of Groups IV-VIII of the Periodic Table (for example, a titanium halide), preferably supported on a Mg halide. The polymerization conditions to be used with such catalysts generally are well known also.

The said polymerization can be carried out in a single step, to prepare a monomodal ethylene polymer, or in two or more steps under different polymerization conditions, to prepare a multimodal ethylene polymer.

The present butene-<NUM> polymer B) preferably has a Brookfield viscosity at <NUM> of from <NUM> to <NUM> mPa·sec, in particular from <NUM> to <NUM> mPa·sec, or from <NUM> to <NUM> mPa·sec.

In one embodiment, the butene-<NUM> polymer B) may be a copolymer having a copolymerized comonomer content, in particular a copolymerized ethylene content, of from <NUM>% to <NUM>% by mole, preferably of from <NUM>% to <NUM>% by mole.

In one further embodiment, the butene-<NUM> polymer B) may be a butene-<NUM> copolymer composition comprising:.

The relative amounts of B1) and B2) may range from <NUM>% to <NUM>% by weight, in particular from <NUM>% to <NUM>% by weight of B1) and from <NUM>% to <NUM>% by weight, in particular from <NUM>% to <NUM>% by weight of B2), said amounts being referred to the sum of B1) + B2).

Highly preferred MIP values for the butene-<NUM> polymer B) are equal to or higher than <NUM>/<NUM>. , in particular from <NUM> to <NUM>/<NUM>.

Preferably, the butene-<NUM> polymer B) may have at least one of the following additional features:.

Optionally, the butene-<NUM> polymer B) may have at least one of the following further additional features:.

The butene-<NUM> polymer B) can be obtained by polymerizing the monomer(s) in the presence of a metallocene catalyst system obtainable by contacting:.

Preferably the stereorigid metallocene compound belongs to the following formula (I):
<CHM>
wherein:.

Preferably the compounds of formula (I) have formula (Ia):
<CHM>
Wherein:.

Specific examples of metallocene compounds are dimethylsilyl{(<NUM>,<NUM>,<NUM>-trimethyl-<NUM>-indenyl)-<NUM>-(<NUM>,<NUM>-dimethyl-cyclopenta[<NUM>,<NUM>-b:<NUM>,<NUM>-b']-dithiophene)} zirconium dichloride; dimethylsilanediyl{(<NUM>-(<NUM>,<NUM>,<NUM>-trimethylindenyl)-<NUM>-(<NUM>,<NUM>-dimethyl-cyclopenta[<NUM>,<NUM>-b:<NUM>,<NUM>-b']-dithiophene)}Zirconium dichloride and dimethylsilanediyl{(<NUM>-(<NUM>,<NUM>,<NUM>-trimethylindenyl)-<NUM>-(<NUM>,<NUM>-dimethyl-cyclopenta[<NUM>,<NUM>-b:<NUM>,<NUM>-b']-dithiophene)}zirconium dimethyl.

Examples of alumoxanes are methylalumoxane (MAO), tetra-(isobutyl)alumoxane (TIBAO), tetra-(<NUM>,<NUM>,<NUM>-trimethyl-pentyl)alumoxane (TIOAO), tetra-(<NUM>,<NUM>-dimethylbutyl)alumoxane (TDMBAO) and tetra-(<NUM>,<NUM>,<NUM>-trimethylbutyl)alumoxane (TTMBAO).

Examples of compounds able to form an alkylmetallocene cation are compounds of formula D+E-, wherein D+ is a Brønsted 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.

Examples organo aluminum compound are trimethylaluminum (TMA), triisobutylaluminium (TIBA), tris(<NUM>,<NUM>,<NUM>-trimethyl-pentyl)aluminum (TIOA), tris(<NUM>,<NUM>-dimethylbutyl)aluminium (TDMBA) and tris(<NUM>,<NUM>,<NUM>-trimethylbutyl)aluminum (TTMBA).

Examples of the said catalyst system and of polymerization processes employing such catalyst system can be found in <CIT> and <CIT>.

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.

The hydrocarbon solvent can be either aromatic (such as toluene) or aliphatic (such as propane, hexane, heptane, isobutane, cyclohexane and <NUM>,<NUM>,<NUM>-trimethylpentane, isododecane).

Preferably, the polymerization process is carried out by using liquid butene-<NUM> as polymerization medium. The polymerization temperature can be from <NUM> to <NUM>, in particular between <NUM> and <NUM>, for example from <NUM> to <NUM>.

The concentration of hydrogen in the liquid phase during the polymerization reaction (molar ppm H<NUM>/ butene-<NUM> monomer) is generally from <NUM> ppm to <NUM> ppm, in particular from <NUM> ppm to <NUM> ppm.

When the present butene-<NUM> polymer comprises the previously said two components B1) and B2), these can be prepared separately and then blended together in the molten state by using known polymer processing apparatuses, such as mono- and twin screw extruders.

However, the present butene-<NUM> polymer comprising said components can be prepared directly in polymerization.

The polymerization process thus comprises in this case at least two sequential stages, carried out in two or more reactors connected in series, wherein components B1) 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.

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

Specific examples of butene-<NUM> polymers B) having MIE of equal to or higher than <NUM>/<NUM>. are disclosed in <CIT>, <CIT>, <CIT>, <CIT> and <CIT>.

The present polymer composition can be prepared by melting and blending the components, and the blending is effected in a blending apparatus at temperatures generally of from <NUM> to <NUM>, preferably from <NUM> to <NUM>, more preferably from <NUM> to <NUM>. Any known apparatus and technology can be used for this purpose.

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.

The present polymer 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.

During the preparation of the polymer composition, besides the components A) and B) and other optional polymer components, it is possible to introduce additives commonly employed in the art, such as stabilizing agents (against heat, light, U. ), plasticizers, antiacids, antistatic and water repellant agents, pigments.

As previously mentioned, the present polymer composition has high values of impact resistance.

In particular it preferably has at least one of the following:.

said Charpy values being measured according to ISO <NUM>/1eA, <NUM> hours after molding.

The present polymer composition has also relatively low flexural modulus values, which are preferably lower than the flexural modulus of component A), translating into an improved flexibility.

In particular the present polymer composition has preferably a flexural modulus of from <NUM> to <NUM> MPa, more preferably from <NUM> to <NUM> MPa, measured according to norm ISO <NUM>:<NUM>, <NUM> hours after molding.

The present polymer composition can be processed on conventional injection molding machines. The finish on the articles obtained is homogeneous and can be improved further by increasing the rate of injection or raising the mold temperature.

Due to the high melt flowability, it can also be used for preparing extruded articles, in particular for cable covering by extrusion.

Thus the present disclosure also provides an injection molded or extruded article comprising the present polymer composition.

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.

The following analytical methods are used to characterize the polymer compositions. MIF, MIE and MIP.

Determined according to norm ISO <NUM>-<NUM>:<NUM> at <NUM> with the specified load.

Measured according to ISO <NUM>-<NUM>:<NUM> at <NUM>.

Measured at <NUM> 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 <NUM>%.

The selected spindle/chamber combination was SC4-<NUM> / SC4-13R/RP.

During the test, the sample was subjected to a stepwise rotation increase until a torque value of around <NUM>% was reached and maintained. Rotation started at <NUM> RPM then increased stepwise by <NUM> RPM every <NUM> seconds.

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

The comonomer content was determined by means of IR in accordance with ASTM D <NUM><NUM>, using an FT-IR spectrometer Tensor <NUM> from Bruker.

Comonomer contents were determined via FT-IR.

The spectrum of a pressed film of the polymer was recorded in absorbance vs. wavenumbers (cm-<NUM>). The following measurements were used to calculate the ethylene content:.

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

A hydraulic press with platens heatable to <NUM> (Carver or equivalent) was used.

A calibration straight line is obtained by plotting %(BEB + BEE)wt vs. FCRC2/At. The slope Gr and the intercept Ir are calculated from a linear regression.

A calibration straight line is obtained by plotting %(EEE)wt vs. AC2,block/At. The slope GH and the intercept IH are calculated from a linear regression.

Using a hydraulic press, a thick sheet was obtained by pressing about g <NUM> 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 <NUM>-<NUM>.

The pressing temperature was <NUM> ± <NUM>.

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.

The instrument data acquisition parameters were as follows:.

Calculate the concentration by weight of the BEE + BEB sequences of ethylene units: <MAT>.

Calculate 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: <MAT>.

Calculate the total amount of ethylene percent by weight:<MAT>.

Thermal properties (melting temperatures and enthalpies).

Determined by Differential Scanning Calorimetry (D S C. ) on a Perkin Elmer DSC-<NUM> instrument, as hereinafter described.

<NUM>C NMR spectra were acquired on a Bruker AV-<NUM> spectrometer equipped with cryo-probe, operating at <NUM> in the Fourier transform mode at <NUM>.

The peak of the Tβδ carbon (nomenclature according to <NPL>)) was used as internal reference at <NUM> ppm. The samples were dissolved in <NUM>,<NUM>,<NUM>,<NUM>-tetrachloroethane-d2 at <NUM> with a <NUM> % wt/v concentration. Each spectrum was acquired with a <NUM>° pulse, <NUM> seconds of delay between pulses and CPD to remove <NUM>H-<NUM>C coupling. About <NUM> transients were stored in <NUM> data points using a spectral window of <NUM>.

The assignments of the spectra, the evaluation of triad distribution and the composition were made according to Kakugo [<NPL>)] and Randall [<NPL>)] using the following: <MAT> <MAT> <MAT> <MAT> <MAT> <MAT>.

To a first approximation, the mmmm was calculated using 2B2 carbons as follows:.

Measured by way of Gel Permeation Chromatography (GPC) in <NUM>,<NUM>,<NUM>-trichlorobenzene (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 <NUM> × <NUM> and their particle size was <NUM> µm. The mobile phase flow rate was kept at <NUM>/min. All the measurements were carried out at <NUM>. Solution concentrations were <NUM>/mL (at <NUM>) and <NUM>/L of <NUM>,<NUM>-diterbuthyl-p-chresole were added to prevent degradation. For GPC calculation, a universal calibration curve was obtained using <NUM> polystyrene (PS) standard samples supplied by PolymerChar (peak molecular weights ranging from <NUM> to <NUM>). 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 <NUM> (Waters). The Mark-Houwink relationship was used to determine the molecular weight distribution and the relevant average molecular weights: the K values were KPS = <NUM> × <NUM>-<NUM> dL/g and KPB = <NUM> × <NUM>-<NUM> dL/g for PS and polybutene (PB) respectively, while the Mark-Houwink exponents α = <NUM> for PS and α = <NUM> for PB were used.

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: <MAT> where KEB is the constant of the copolymer, KPE (<NUM> × <NUM>-<NUM>, dL/g) and KPB (<NUM> × <NUM>-<NUM> 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 = <NUM>. The Mark-Houwink exponents α = <NUM> 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 <NUM> in terms of molecular weight equivalent. Fractions below <NUM> were investigated via GC.

The X-ray crystallinity was measured with an X-ray Diffraction Powder Diffractometer (XDPD) that uses the Cu-Kα1 radiation with fixed slits and able to collect spectra between diffraction angle 2Θ = <NUM>° and 2Θ = <NUM>° with step of <NUM>° every <NUM> seconds.

The samples were diskettes of about <NUM>-<NUM> of thickness and <NUM>-<NUM> of diameter made by compression moulding. The diskettes were aged at room temperature (<NUM>) for <NUM> hours.

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 2Θ = <NUM>° to 2Θ = <NUM>° with steps of <NUM>° by using counting time of <NUM> seconds, and at the end the final spectrum was collected.

Defining Ta as the total area between the spectrum profile and the baseline expressed in counts/sec·2Θ and Aa as the total amorphous area expressed in counts/sec·2Θ, Ca is total crystalline area expressed in counts/sec·2Θ.

The spectrum or diffraction pattern was analyzed in the following steps:.

Molded specimens of <NUM> by <NUM> by <NUM> were fixed to the DMTA machine for tensile stress. The frequency of the tension and relies of the sample was fixed at <NUM>. The DMTA translates the elastic response of the specimen starting from -<NUM> to <NUM>. 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'/E" = tan (δ) vs temperature. The glass transition temperature Tg was assumed to be the temperature at the maximum of the curve E'/E" = tan (δ) vs temperature.

According to ISO <NUM>/1eA at <NUM>, <NUM> and -<NUM>, measured <NUM> hours after molding.

According to norm ISO <NUM>:<NUM>, measured <NUM> hours after molding.

The spiral flow test was carried out on a Ripress FL <NUM> HES apparatus equipped with a spiral mold having spiral thickness of <NUM>.

The tested polymer was injected into the cavity of the spiral mold through a <NUM> die, under the following conditions:.

The spiral length is the length of the solid polymer spiral extracted from the spiral mold after cooling.

The higher the spiral length, the easier the polymer is to process under the injection molding process conditions.

The hereinafter described materials were used.

High density polyethylene having density of <NUM>/cm<NUM>, MIP of <NUM>/<NUM>. , MIF of <NUM>/<NUM>. and MIE of <NUM>/<NUM>. , sold by Basell with trademark Hostalen GD <NUM> LS.

Two different polymers were used, namely butene-<NUM> polymer B)-I and butene-<NUM> polymer B)-II.

Under nitrogen atmosphere, <NUM> of a <NUM>/L solution of triisobutylaluminium (TIBA) in isododecane and <NUM> of <NUM>% wt/wt solution of methylalumoxane (MAO) in toluene were loaded in a <NUM> jacketed glass reactor, stirred by means of an anchor stirrer, and allowed to react at room temperature for about <NUM> hour under stirring.

After this time, <NUM> of metallocene dimethylsilyl{(<NUM>,<NUM>,<NUM>-trimethyl-l-indenyl)-<NUM>-(<NUM>,<NUM>-dimethyl-cyclopenta[l,<NUM>-b:<NUM>,<NUM>-b']-dithiophene)} zirconium dichloride, prepared according to Example <NUM> of <CIT>, was added and dissolved under stirring for about <NUM> minutes.

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

The composition of the solution resulted to be:.

The polymerization was carried out in two stirred reactors operated in series, in which liquid butene-<NUM> constituted the liquid medium. The catalyst solution described above was fed in both reactors. The polymerization conditions are reported in Table <NUM>. The butene-<NUM>/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 <NUM>.

Using the same catalytic solution and the same polymerization equipment as used for the preparation of the butene-<NUM> polymer B)-I, the polymerization was carried out in the said two stirred reactors operated in series, in which liquid butene-<NUM> 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 <NUM>. The residence time in each reactor was in a range of <NUM>÷<NUM>. The concentration of hydrogen during polymerization was <NUM> ppm mol H<NUM>/(C<NUM>-) bulk, where C<NUM>- = butene-<NUM>. The comonomer was fed to the reactors in an amount of C<NUM>-/C<NUM>- <NUM>%wt. The ethylene comonomer was almost immediately copolymerized (C<NUM>- "stoichiometric" feed to the reactor). The catalyst yield (mileage) was of <NUM>/g metallocene active component. The butene-<NUM> copolymer was recovered as melt from the solution and cut in pellets. The copolymer was further characterized and the data are reported in Table <NUM>.

Fischer-Tropsch wax, having Drop melting point (measured according to ASTM D <NUM>) of <NUM>, Penetration at <NUM> (measured according to ASTM D <NUM>) of <NUM> and Brookfield viscosity at <NUM> (measured according to method Sasol Wax <NUM>) of <NUM> cP, sold by Sasol with trademark EnHance FG.

The said butene-<NUM> polymers B)-I and B)-II were blended with the ethylene polymer A) in the amounts reported in the following Table <NUM>, wherein also the final properties of the resulting polymer compositions are reported.

In the following Table <NUM>, Comparative Example <NUM> reports the properties of the ethylene polymer A) in pure state.

In Comparative Examples <NUM> - <NUM>, the previously described Fischer-Tropsch wax was blended with the ethylene polymer A) in the amounts reported in Table <NUM>, wherein also the final properties of the resulting polymer compositions are reported.

The amounts reported in Tables <NUM> and <NUM> are expressed in weight percent with respect to the total weight of the polymer composition.

The compositions of Examples <NUM>-<NUM> and Comparative Examples <NUM> - <NUM> were prepared by dry-mixing off-line the components and feeding them in the hopper of the injection molding equipment for the spiral flow test.

The melt blending step thus occurred in the said injection molding equipment.

Claim 1:
A polymer composition comprising:
A) from <NUM>% to <NUM>% by weight of an ethylene polymer having MIP of equal to or higher than <NUM>/<NUM>., where MIP is the melt flow index at <NUM> with a load of <NUM>, determined according to ISO <NUM>-<NUM>:<NUM>;
B) from <NUM>% to <NUM>% by weight of a butene-<NUM> polymer having MIE of equal to or higher than <NUM>/<NUM>., where MIE is the melt flow index at <NUM> with a load of <NUM>, determined according to ISO <NUM>-<NUM>:<NUM>;
wherein the amounts of A) and B) are referred to the total weight of A) + B).