Soft and flexible polyolefin composition

Abstract

A polyolefin composition comprising: A) from 50 to 90% by weight of a copolymer of butene-1 with ethylene having a copolymerized ethylene content of up to 18% by mole and no melting peak detectable at the DSC at the second heating scan; B) from 10 to 50% by weight of a propylene copolymer having a melting temperature Tm, measured by DSC at the second heating scan, of from 130°C to 165°C and a crystallization temperature Tc, measured by DSC after the first heating scan, of 100°C or higher; wherein the amounts of A) and B) are referred to the total weight of A) + B).

Description

Basell Poliolefine Italia S.r.l. FE7777-WO-01SOFT AND FLEXIBLE POLYOLEFIN COMPOSITIONFIELD OF THE INVENTION

[0001] The present disclosure relates to a flexible and thermoplastic polyolefin composition having high flexibility and low values of shore hardness in combination with good tensile and optical properties.BACKGROUND OF THE INVENTION

[0002] Polyolefin compositions having high flexibility while maintaining a good thermoplastic behavior are disclosed in the art. They have been used in many application fields, due to the valued properties which are typical of polyolefins (such as chemical inertia, mechanical properties and nontoxicity).

[0003] They generally comprise crystalline and amorphous portions, in various relative amounts.

[0004] Such crystalline and amorphous portions can be present in the same polymer chain, and / or in distinct phases.

[0005] Depending upon the chemical composition of such portions, their relative amounts and the way in which they are combined in the polyolefin composition, different sets of properties are obtained.

[0006] However it is always difficult to achieve a good balance of flexibility, softness, optical properties, in particular a low haze, and thermoplastic behavior.

[0007] An example of flexible and thermoplastic composition is provided in PCT Publication No. WO2016 / 096281, wherein low values of flexural modulus and Shore hardness are obtained by combining a butene- 1 copolymer and a crystalline copolymer of propylene.

[0008] It has now been found that by combining selected butene- 1 polymers with propylene polymers having specific thermal properties, it is possible to obtain a flexible polyolefin composition having an excellent and unusual set of properties.

[0009] Such properties make it possible to use the compositions for preparing laminar articles, like films and sheets, specially for encapsulation of photovoltaic cells.SUMMARY OF THE INVENTION

[0010] Thus the present disclosure provides a polyolefin composition comprising:A) from 50% to 90% by weight, preferably from 55% to 90% by weight, more preferably from 60% to 85% by weight, of a copolymer of butene- 1 with ethylene having a copolymerizedBasell Poliolefine Italia S.r.l. FE7777-WO-01 ethylene content of up to 18% by mole and no melting peak detectable at the DSC at the second heating scan;B) from 10% to 50% by weight, preferably from 10% to 45% by weight, more preferably from 15% to 40% by weight, of a propylene copolymer having a melting temperature Tm, measured by DSC at the second heating scan, of from 130°C to 165°C, preferably from 131 to 165°C, more preferably from 131 to 160°C, and a crystallization temperature Tc, measured by DSC after the first heating scan, of 100°C or higher, preferably of 105°C or higher, more preferably of 108°C or higher, the preferred upper limit being in all cases of 115°C; wherein the amounts of A) and B) are referred to the total weight of A) + B) and all the DSC scans are carried out with a heating or cooling rate of 10°C per minute.DETAILED DESCRIPTION OF THE INVENTION

[0011] The present polyolefin composition as provided herein has a melting temperature Tm which is equal to or close to the melting temperature Tmthe propylene copolymer component B), namely a Tm from 130°C to 165°C, preferably from 131 to 165°C, more preferably from 131 to 160°C.

[0012] The crystallization temperature Tcof the present polyolefin composition is preferably of 75°C or higher, preferably of 85°C or higher, more preferably of 90°C or higher, the preferred upper limit being in all cases of 105°C.

[0013] Generally one or more melting peaks and a single crystallization peak are detected in the DSC scan of the propylene copolymer B) and in the DSC scan of the polyolefin composition, carried out in the said temperature range and under the said measurement conditions.

[0014] Should more than one peak be detected, the temperature of the most intense melting peak and crystallization peak in the said temperature ranges is to be taken as the Tmand Tcvalue respectively for both the propylene copolymer B) and the polyolefin composition comprising A) and B).

[0015] The corresponding AHm(melting enthalpy) is preferably given by the area of the melting peak or the total area of melting peaks (if more than one) in the DSC temperature range from 130° to 160°C.

[0016] The corresponding AHC(crystallization enthalpy) is preferably given by the area of the crystallization peak or the total area of crystallization peaks (if more than one) in the DSC temperature range of 75°C or higher.Basell Poliolefine Italia S.r.l. FE7777-WO-01

[0017] Preferably, both the present polyolefin composition and the propylene copolymer B) have a melting enthalpy AHm, measured by DSC at the second heating scan, of from 7 to 65 J / g, more preferably from 8 to 55 J / g.

[0018] Preferably, propylene copolymer B) has a crystallization enthalpy AHC, measured by DSC after the first heating scan, of from -30 to -90 J / g, more preferably from -40 to -85 J / g.

[0019] Preferred values of crystallization enthalpy AHC, measured by DSC after the first heating scan, for the present polyolefin composition, are from -10 to -30 J / g, preferably from -15 to -28 J / g.

[0020] The present polyolefin composition maintains a thermoplastic behavior due to the presence of a crystalline fraction, as revealed by the said melting enthalpy values.

[0021] The polyolefin composition as provided herein has low values of tensile elastic modulus, preferably equal to or lower than 100 MPa, more preferably equal to or lower than 60 MPa in particular from 100 or from 60 to 10 MPa.

[0022] Preferred values of MIE for the present polyolefin composition are from 0.1 to 5 g / 10 min., where MIE is the melt flow index at 190°C with a load of 2.16 kg, determined according to ISO 1133-1 2012-03.

[0023] Preferred Shore A values for the present polyolefin composition are of lower than 90, particularly equal to or lower than 88, the lower limit being preferably of 70.

[0024] The Shore D values are equal to or or lower than 25, preferably equal to or lower than 20, in particular from 25 to 5 or from 20 to 5.

[0025] Preferred Haze values for the present polyolefin composition are of 35% or lower, more preferably of 30% or lower, the preferred lower limit being in all cases of 15%.

[0026] The butene-1 copolymer A) just after it has been melted and cooled does not show a melting peak at the second heating scan, however it is crystallizable, i.e. after about 10 days that it has been melted the polymer shows a measurable melting point and a melting enthalpy measured by DSC. In other words the butene-1 copolymer shows no melting temperature attributable to polybutene-1 crystallinity (Tmll) DSC, measured after cancelling the thermal history of the sample, according to the DSC method described herein below in the experimental part.

[0027] Moreover, the butene-1 copolymer A) can have at least one of the following additional features:- MIE of from 0.5 to 3 g / 10 min.;- a lower limit of the copolymerized ethylene content of 12% by mole;- a Shore A value equal to or lower than 80, more preferably equal to or lower than 70, in particular from 80 to 40 or from 70 to 40;Basell Poliolefine Italia S.r.l. FE7777-WO-01- a Shore D value equal to or lower than 20, in particular from 20 to 5, more preferably lower than 20, in particular from lower than 20 to 5;- a Mw / Mn value, where Mw is the weight average molar mass and Mn is the number average molar mass, both measured by GPC, equal to or lower than 3, in particular from 3 to 1.5.- a tension set of less than 30% at 100% of deformation at 23°C (ISO 2285), more preferably equal to or less than 20%, wherein the lower limit is of 5;- a percentage of butene-1 units in form of isotactic pentads (mmmm%) greater than 80%, preferably equal to or greater than 85%, even more preferably equal to or greater than 90%, wherein the upper limit is 99%;- tensile stress at break, measured according to ISO 527, of from 3 MPa to 20 MPa, more preferably from 4 MPa to 13 MPa;- tensile elongation at break, measured according to ISO 527, of from 550% to 1000%; more preferably from 700% to 1000%;- intrinsic viscosity (I V.) equal to or higher than 1 dl / g; more preferably equal to or higher than 1.5 dl / g, wherein the upper limit is of 3 dl / g;- crystallinity of less than 30% measured via X-ray, more preferably of less than 20%;- density of 0.895 g / cm3or less, more preferably of 0.875 g / cm3or less; wherein the lower limit is of 0.86 g / cm3;- content of xylene insoluble fraction at 0°C of less than 15% by weight, wherein the lower limit is of 0%.

[0028] The butene-1 copolymer A) 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.

[0029] Preferably the stereorigid metallocene compound belongs to the following formula (I):wherein:Basell Poliolefine Italia S.r.l. FE7777-WO-01M 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-C20-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, C7-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-C20-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 R5and R6, and / or R8and R9can 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 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-alkyl radicals; more preferably R3is a methyl, or ethyl radical; and R4is a methyl, ethyl or isopropyl radical.

[0030] Preferably the compounds of formula (I) have formula (la):(la)Wherein:M, X, R1, R2, R5, R6, R8and R9have been described above;Basell Poliolefine Italia S.r.l. FE7777-WO-01R3is 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.

[0031] Specific examples of metallocene compounds are dimethylsilanediyl{(l-(2,4,7- trimethylindenyl)-7-(2,5-dimethyl-cyclopenta[l,2-b:4,3-b’]-dithiophene)}Zirconium di chloride and dimethylsilanediyl{(l-(2,4,7-trimethylindenyl)-7-(2,5-dimethyl-cyclopenta[l,2-b:4,3-b’]- dithiophene) (Zirconium dimethyl.

[0032] 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).

[0033] 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.

[0034] Examples organo aluminum compound are trimethylaluminum (IMA), triisobutylaluminium (TIB AL), tris(2,4,4-trimethyl-pentyl)aluminum (TIOA), tris(2,3- dimethylbutyl)aluminium (TDMBA) and tris(2,3,3-trimethylbutyl)aluminum (TTMBA).

[0035] Examples of the said catalyst system and of polymerization processes employing such catalyst system can be found in W02004099269 and W02009000637.

[0036] In general, the polymerization process for the preparation of the butene- 1 copolymer A) can be carried out according to known techniques, for example slurry polymerization using as diluent a liquid inert hydrocarbon, or solution polymerization using for example the liquid butene- 1 as a reaction medium. Moreover, it may also be possible to carry out the polymerization process in the gas-phase, operating in one or more fluidized bed or mechanically agitated reactors. The polymerization carried out in the liquid butene- 1 as a reaction medium is preferred.

[0037] As a general rule, the polymerization temperature is generally of from -100°C to 200°C, preferably from 20°C to 120°C, more preferably from 40°C to 90°C, most preferably from 50°C to 80°C.

[0038] The polymerization pressure is generally comprised between 0.5 and 100 bar.The polymerization can be carried out in one or more reactors that can work under same or different reaction conditions such as concentration of molecular weight regulator, comonomer concentration, temperature, pressure etc.Basell Poliolefine Italia S.r.l. FE7777-WO-01

[0039] The propylene copolymer B) is a semicrystalline polymer, as demonstrated by the said melting and crystallization temperature values, and has a stereoregularity of isotactic type.

[0040] It has preferably a solubility in xylene at room temperature (about 25°C) equal to or lower than 25% by weight, the lower limit being of 0.5% by weight.

[0041] Moreover it has preferably MIL values of from 0.5 to 9 g / 10 min, more preferably from 1 to 8 g / 10 min., where MIL is the melt flow index at 230°C with a load of 2.16 kg, determined according to ISO 1133-1 2012-03.

[0042] Preferably the propylene copolymer B) is selected from copolymers of propylene with one or more comonomers selected from ethylene and C4-C10 alpha-olefins, and combinations of said copolymers.

[0043] From the above definition it is evident that the term "copolymer" includes polymers containing more than one kind of comonomers.

[0044] Preferred amounts of comonomers in the propylene copolymer B) are of from 1 to 15% by weight, in particular from 2 to 10% by weight, referred to the weight of the concerned copolymer.

[0045] The said C4-C10 alpha-olefins are selected from olefins having formula CH2=CHR wherein R is an alkyl radical, linear or branched, or an aryl radical, having from 2 to 8 carbon atoms.

[0046] Specific examples of C4-C10 alpha-olefins are butene-1, pentene-1, 4-methylpentene-l, hexene- 1 and octene- 1.

[0047] The preferred comonomers in the propylene copolymer B) are ethylene, butene-1 and hexene- 1.

[0048] The propylene copolymer B) can be prepared by using a Ziegler-Natta catalyst or a metallocene-based catalyst system in the polymerization process.

[0049] 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.

[0050] 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.

[0051] Preferred organometallic compounds are the aluminum alkyl compounds.

[0052] Thus preferred Ziegler-Natta catalysts are those comprising the product of reaction of:Basell Poliolefine Italia S.r.l. FE7777-WO-011) a solid catalyst component comprising a Ti compound 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).

[0053] 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.

[0054] 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.

[0055] Particularly suited among the said electron-donor compounds are phthalic acid esters, preferably diisobutyl phthalate, and succinic acid esters.

[0056] Other electron-donors particularly suited are the 1,3-diethers, as illustrated in published European patent applications EP-A-361 493 and 728769.

[0057] As cocatalysts (2), one preferably uses the trialkyl aluminum compounds, such as Al- triethyl, Al-triisobutyl and Al-tri-n-butyl.

[0058] 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 alkylic benzoates), heterocyclic compounds (such as the 2,2,6,6-tetramethylpiperidine and the 2,6- diisopropylpiperidine), and in particular silicon compounds containing at least one Si-OR bond (where R is a hydrocarbon radical).

[0059] Examples of the said silicon compounds are those of formula R1aR2bSi(OR3)c, where a and b are integer numbers from 0 to 2, c is an integer from 1 to 3 and the sum (a+b+c) is 4; R1, R2and R3are alkyl, cycloalkyl or aryl radicals with 1-18 carbon atoms optionally containing heteroatoms.

[0060] Useful examples of silicon compounds are (tert-butyl)2Si(OCH3)2, (cyclohexyl)(m ethyl) Si (OCEE (phenyl)2Si(OCH3)2 and (cyclopentyl)2Si(OCH3)2.

[0061] The previously said 1,3- diethers are also suitable to be used as external donors. In the case that the internal donor is one of the said 1,3-diethers, the external donor can be omitted.

[0062] The said 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.

[0063] 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.Basell Poliolefine Italia S.r.l. FE7777-WO-01

[0064] Preferred examples of metallocene-based catalyst systems are disclosed in US20060020096 and W098040419.

[0065] The polymerization process, which can be continuous or batch, is carried out in the presence of said catalysts following known techniques and operating in liquid phase, in the presence or not of inert diluent, or in gas phase, or by mixed liquid-gas techniques.

[0066] Polymerization reaction time, pressure and temperature are not critical, however it is best if the temperature is from 20 to 150°C. The pressure can be atmospheric or higher.

[0067] The regulation of the molecular weight, resulting into the said MFR values, is carried out by using hydrogen or other known regulators.

[0068] In particular, the propylene copolymer B) can be produced by a polymerization process carried out in a gas-phase polymerization reactor comprising at least two interconnected polymerization zones.

[0069] The process according to the preferred polymerisation process is illustrated in EP application 782 587.

[0070] In detail, the process is carried out in a first and in a second interconnected polymerization zones into which propylene and the comonomers are fed in the presence of a 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.

[0071] 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 polymerisation zones and by the head loss introduced into the system.

[0072] 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.

[0073] 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 conventionalBasell Poliolefine Italia S.r.l. FE7777-WO-01 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.

[0074] The control of the polymer circulation between the two polymerisation 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.

[0075] The operating parameters, such as the temperature, are those that are usual in olefin polymerisation process, for example between 50 to 120 °C.

[0076] The process can be carried out under operating pressures of between 0.5 and 10 MPa, preferably between 1.5 to 6 MPa.

[0077] 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.

[0078] The various catalysts are fed up to the riser at any point of the said riser. However, they 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.

[0079] The propylene copolymer B) is generally blended with a nucleating agent, to achieve the said Tcof at least 100°C.

[0080] With the term “nucleating agent” it is intended any additive which is able to regulate and control crystallinity of propylene polymers.

[0081] Suitable nucleating agents include phosphate ester salts as well as the acetals of sorbitols and xylitols.

[0082] Specific examples of phosphate ester salts include aluminum-hydroxy-bis[2,2’- methylene-bis(4,6-di-t-butylphenyl)phosphate]; 2,2'-methylenebis(2,4-di-tert- butylphenyl)phosphate lithium salt and 2,2'-methylene-bis(4,6-ditertbutylphenyl)phosphate sodium or lithium salt. Examples of commercially available phosphate ester salts for use as nucleating agents include ADK stabilizer NA-71 and ADK Stabilizer NA-21, both available from Amfine Chemical Corp.

[0083] Specific examples of acetals of sorbitols include dibenzylidenesorbitol or its Ci-Cs- alkyl-substituted derivatives such as methyldibenzylidenesorbitol, ethyldibenzylidenesorbitol or dimethyldibenzylidenesorbitol. Examples of suitable commercially available sorbitol-acetal nucleating agents are those designated as Millad 3940 and Millad 3988, both available from Milliken Chemical.Basell Poliolefine Italia S.r.l. FE7777-WO-01

[0084] Other nucleating agents different from sorbitols and phosphate ester salts are, for example, N,N',N"-tris-isopentyl-l,3,5-benzene-tricarboxoamide, bicyclo[2.2.1]heptane-2,3- dicarboxylic acid disodium or calcium salt (1R,2R,3R,4S) or the commercial nucleating agent NJ Star PCI.

[0085] Combinations of any of the above may also be employed.

[0086] The nucleating agent may be added to the propylene copolymer B) by known methods, such as by melt blending the nucleating agent and the propylene copolymer B) under shear condition in a conventional extruder. Said nucleating agent can be added in the pure state or in form of concentrate in a suited carrier, in particular in a polyolefin, like a propylene homopolymer or copolymer.

[0087] Preferably, the propylene copolymer B) is blended with up to 2500 ppm, more preferably from 100 to 2000 ppm by weight, of at least one nucleating agent. Such amounts are referred to the total weight of B) and the nucleating agent.

[0088] The present polyolefin composition can also contain additives commonly employed in the art, such as antioxidants, light stabilizers, heat stabilizers, colorants and fillers.

[0089] It can also contain additional polyolefins, in particular crystalline ethylene homopolymers and copolymers of ethylene with propylene and / or a C4-C10 a-olefin, such as HDPE, LLDPE or LDPE, or crystalline propylene homopolymers and copolymers of propylene with ethylene and / or a C4-C10 a-olefin.

[0090] Other additional polyolefins than can be present are elastomeric copolymers, like copolymers of ethylene with propylene and / or higher alpha-olefins, like in particular butene- 1, hexene- 1 or octene- 1. Such copolymer materials are commonly known as EPR or EPDM copolymers.

[0091] Preferred amounts of said additional polyolefins are from 1 to 15% by weight, more preferably from 3 to 10% by weight with respect to the total weight of the polyolefin composition.

[0092] The polyolefin composition may be manufactured by mixing the components together, extruding the mixture, and pelletizing the resulting composition using known techniques and apparatus.

[0093] The present disclosure also provides final articles made of or comprising the said polyolefin composition, in particular, as previously said, laminar articles.

[0094] The expression “laminar articles”, as used herein, includes films, generally having a thickness of less than 100 pm, in particular from less than 100 pm to 15 pm or from 90 pm to 15 pm, and sheets or foils, generally having a thickness of at least 100 pm, in particular from 100 pm to 1000 pm.Basell Poliolefine Italia S.r.l. FE7777-WO-01

[0095] Due to its flexibility and softness, the present polyolefin composition is specially suited for encapsulation of photovoltaic cells, as previously mentioned.

[0096] Hence the present disclosure also provides an encapsulated photovoltaic cell which is obtained by using a photovoltaic encapsulating material comprising the present polyolefin composition.

[0097] In general, all the said articles can be prepared with equipment and processes well known in the art, like extrusion, blow molding and injection molding.

[0098] In particular, the said films can be prepared by extrusion-blowing, extrusion-casting or extrusion-bioriented stretching, while the said sheets and foils can be prepared by extrusioncalendering.

[0099] The encapsulation of photovoltaic cells is generally obtained by laying the said films, sheets or foils on the photovoltaic cells with the application of heat and pressure.EXAMPLES

[0100] The practice and advantages of the 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 in any manner whatsoever.

[0101] The following analytical methods are used to characterize the polymer compositions.

[0102] Thermal properties (melting temperatures, crystallization temperatures and enthalpies)

[0103] Determined by Differential Scanning Calorimetry (DSC) on a Perkin Elmer DSC-7 instrument.The melting and crystallization temperatures of the butene- 1 copolymer A) were determined according to the following method:- Tmll (measured in second heating scan): a weighted sample (5-10 mg) obtained from the polymerization was sealed into aluminum 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, when present is taken as the melting temperature of the polybutene- 1 (PB) crystalline form II (Tmil) and the area as global melting enthalpy (AHmll).The butene- 1 copolymer component A) of the polyolefin composition of the invention does not have a TmII peak.Basell Poliolefine Italia S.r.l. FE7777-WO-01- In order to determine the Tml, the sample was melted, 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 at 200°C with a scanning speed corresponding to 10°C / min. In this heating run, the first peak temperature coming from the lower temperature side in the thermogram was taken as the melting temperature (Tml).The melting and crystallization temperatures Tmand Tcof the propylene copolymer component B) and of the overall composition comprising the polymer components A) and B) were measured at the second heating scan, as regards Tm, and at the cooling scan after the first heating scan, as regards Tc, under the same conditions as above reported for the determination of Tmll of the butene- 1 copolymer component A).The areas of the melting and crystallization peaks are taken as the melting enthalpy AHmand the crystallization enthalpy AHCrespectively.

[0104] MIE

[0105] Determined according to norm ISO 1133-1 2012-03 with a load of 2.16 kg at 190 °C.

[0106] MIL

[0107] Determined according to norm ISO 1133-1 2012-03 with a load of 2.16 kg at 230 °C.

[0108] Tensile elastic modulus

[0109] According to norm ISO 527-3:2018.

[0110] Shore A and D

[0111] According to norm ISO 868:2003.

[0112] Tensile stress and elongation at yield and at break

[0113] According to norm ISO 527-3:2018.

[0114] Intrinsic viscosity

[0115] Determined according to norm ASTM D 2857 in tetrahydronaphthalene at 135 °C.

[0116] Density

[0117] Determined according to ISO 1183-1 :2012 at 23°C, immersion method.

[0118] Comonomer contents

[0119] Determined by IR spectroscopy or by NMR.

[0120] Particularly for the butene-1 copolymers the amount of comonomer is calculated from13C-NMR spectra of the copolymers. Measurements were performed on a polymer solution (8-12 wt%) in dideuterated 1, 1,2,2-tetrachloro-ethane at 120 °C. The13C NMR spectra were acquired on a Bruker AV-600 spectrometer operating at 150.91 MHz in the Fourier transform mode at 120 °C using a 90° pulse, 15 seconds of delay between pulses and CPD (WALTZ 16) to remove H-13CBasell Poliolefine Italia S.r.l. FE7777-WO-01 coupling. About 1500 transients were stored in 32K data points using a spectral window of 60 ppm (0-60 ppm).

[0121] Diad distribution is calculated from13C NMR spectra using the following relations:• PP = 100 Ii / S• PB = 100 I2 / 2• BB = 100 (I3- Ii9) / S• PE = 100 (Is + Ie) / 2• BE =100 (I9 + Iio) / 2• EE = 100 (0.5(115 + I6+ ho) + 0.25 (II4)) / 2• Where 2 = Ii+ I2 + I3 - 119 + Is + le + 19 + I10 + 0.5(hs + h + I10) + 0.25 (I14)• The molar content is obtained from diads using the following relations:• P (m%)= PP + 0.5 (PE+PB)• B (m%)= BB + 0.5 (BE+PB)• E (m%)= EE + 0.5 (PE+BE)Ii, I2, 13, h, h, I9, h, ho, I14, 115, 119 are integrals of the peaks in the13C NMR spectrum (peak of EEE sequence at 29.9 ppm as reference). The assignments of these peaks are made according to J.C. Randal, Macromol. Chem Phys., C29, 201 (1989), M. Kakugo, Y. Naito, K. Mizunuma and T. Miyatake, Macromolecules, 15, 1150, (1982), and H.N. Cheng, Journal of Polymer Science, Polymer Physics Edition, 21, 57 (1983). They are collected in Table A (nomenclature according to C.J. Carman, R.A. Harrington and C.E. Wilkes, Macromolecules, 10, 536 (1977)).Basell Poliolefine Italia S.r.l. FE7777-WO-01Table A.

[0122] For the propylene copolymers the comonomer content is 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 are: purge time: 30 seconds minimum; collect time: 3 minutes minimum; apodization: Happ-Genzel; resolution: 2 cm'1.

[0123] Sample Preparation

[0124] Using a hydraulic press, a thick sheet is 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 is cut from this sheet to mold a film. Recommended film thickness ranges between 0.02-:0.05 cm (8 - 20 mils).

[0125] Pressing temperature is 180±10°C (356°F) and about 10 kg / cm2(142.2 PSI) pressure for about one minute. Then the pressure is released and the sample is removed from the press and cooled the to room temperature.Basell Poliolefine Italia S.r.l. FE7777-WO-01

[0126] The spectrum of a pressed film of the polymer is recorded in absorbance vs. wavenumbers (cm'1). The following measurements are used to calculate ethylene and butene- 1 content:Area (At) of the combination absorption bands between 4482 and 3950 cm1which is used for spectrometric normalization of film thickness.If ethylene is present, Area (AC2) of the absorption band between 750-700 cm'1after two proper consecutive spectroscopic subtractions of an isotactic non additivated polypropylene spectrum and then, if butene-1 is present, of a reference spectrum of a butene- 1 -propylene random copolymer in the range 800-690 cm'1.If butene-1 is present, 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 is present, of a reference spectrum of an ethyl ene-propylene random copolymer in the range 800-690 cm'1.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.

[0127] Mw / Mn determination by GPC

[0128] The determination of the means Mn and Mw, and Mw / Mn derived therefrom was carried out using a Waters GPCV 2000 apparatus, which was equipped with a column set of four PLgel Olexis mixed-gel (Polymer Laboratories) and an IR4 infrared detector (PolymerChar). The dimensions of the columns were 300 x 7.5 mm and their particle size 13 / m. The mobile phase used was 1-2-4-tri chlorobenzene (TCB) and its flow rate was kept at 1.0 ml / min. All the measurements were carried out at 150°C. Solution concentrations were 0.1 g / dl in TCB and 0.1 g / 1 of 2,6-diterbuthyl- / ?-chresole were added to prevent degradation. For GPC calculation, a universal calibration curve was obtained using 10 polystyrene (PS) standard samples supplied by Polymer Laboratories (peak molecular weights ranging from 580 to 8500000). A third order polynomial fit was used for interpolate the experimental data and obtain the relevant calibration curve. Data acquisition and processing was done using Empower (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 10'4dL / g and KPB = 1.78 X 10'4dL / g for PS and PB respectively, while the Mark-Houwink exponents a = 0.706 for PS and a = 0.725 for PB were used.

[0129] For butene-1 / ethylene copolymers, as far as the data evaluation is concerned, it is assumed that the composition is constant in the whole range of molecular weight and the K value of the Mark-Houwink relationship is calculated using a linear combination as reported below:Basell Poliolefine Italia S.r.l. FE7777-WO-01

[0130] 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 and polybutene, XE and XB are the ethylene and the butene-1 weight% content. The Mark-Houwink exponents a = 0.725 is used for all the butene- 1 / ethylene copolymers independently of their composition.

[0131] Fractions soluble and insoluble in xylene at 0°C (XS-0°C)

[0132] 2.5 g of the polymer sample are dissolved in 250 ml of xylene at 135°C under agitation.After 30 minutes the solution is 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 is allowed to settle for 1 hour in the water and ice bath. The precipitate is filtered with filter paper. During the filtering, the flask is 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 is 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 are evaporated in nitrogen flow, and the residue dried under vacuum at 80° C until constant weight is 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:XI%0°C=100-XS%0°C.

[0133] Fractions soluble and insoluble in xylene at 25 °C (XS-25°C)

[0134] 2.5 g of polymer are dissolved in 250 ml of xylene at 135° C under agitation. After 20 minutes the solution is allowed to cool to 25° C, still under agitation, and then allowed to settle for 30 minutes. The precipitate is filtered with filter paper, the solution evaporated in nitrogen flow, and the residue dried under vacuum at 80° C until constant weight is reached. Thus, one calculates the percent by weight of polymer soluble (Xylene Solubles - XS) and insoluble at room temperature (25° C).

[0135] 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 polypropylene polymers.

[0136] Determination of isotactic pentads content

[0137] 50 mg of each sample were dissolved in 0.5 ml of C2D2CI4.

[0138] The13C NMR spectra were acquired on a Bruker DPX-400 (100.61 Mhz, 90° pulse, 12s delay between pulses). About 3000 transients were stored for each spectrum; the mmmm pentad peak (27.73 ppm) was used as reference.Basell Poliolefine Italia S.r.l. FE7777-WO-01

[0139] The microstructure analysis was carried out as described in literature (Macromolecules 1991, 24, 2334-2340, by Asakura T. et Al. . and Polymer, 1994, 35, 339, by Chujo R. et Al.).

[0140] The percentage value of pentad tacticity (mmmm%) for butene- 1 copolymers is the percentage of stereoregular pentads (isotactic pentad) as calculated from the relevant pentad signals (peak areas) in the NMR region of branched methylene carbons (around 27.73 ppm assigned to the BBBBB isotactic sequence), with due consideration of the superposition between stereoirregular pentads and of those signals, falling in the same region, due to the comonomer.

[0141] Determination of X-ray crystallinity

[0142] The X-ray crystallinity was measured with an X-ray Diffraction Powder Diffractometer using the Cu-Kal radiation with fixed slits and collecting spectra between diffraction angle 20 = 5° and 20 = 35° with step of 0.1° every 6 seconds.

[0143] Measurements were performed on compression molded specimens in the form of disks of about 1.5-2.5 mm of thickness and 2.5-4.0 cm of diameter. These specimens are obtained in a compression molding press at a temperature of 200°C ± 5°C without any appreciable applied pressure for 10 minutes, then applying a pressure of about 10Kg / cm2for about few second and repeating this last operation for 3 times.

[0144] The diffraction pattern was used to derive all the components necessary for the degree of crystallinity by defining a suitable linear baseline for the whole spectrum and calculating the total area (Ta), expressed in counts / sec20, between the spectrum profile and the baseline. Then a suitable amorphous profile was defined, along the whole spectrum, that separate, according to the two phase model, the amorphous regions from the crystalline ones. Thus it is possible to calculate the amorphous area (Aa), expressed in counts / sec20, as the area between the amorphous profile and the baseline; and the crystalline area (Ca), expressed in counts / sec20, as Ca = Ta- Aa The degree of crystallinity of the sample was then calculated according to the formula:%Cr = lOO x Ca / Ta

[0145] Example 1

[0146] Materials used in the examplesPB-1 : butene- 1 / ethylene copolymer containing 16% by moles of copolymerized ethylene and having a density of 0.870 g / cm3, MIE of 1.3 g / 10 min. and Shore A of 60, produced according to the process described in W02009000637 and in-line blended with a copolymer of propylene with ethylene, added in amount of 10% by weight with respect to the total weight of the butene-l / ethylene copolymer and the propyl ene / ethylene copolymer.Such propylene copolymer composition has MFRL of 1.8 g / 10 min., copolymerized ethylene content of 3% by weight, Tmof 142.3 °C, and Tcof 95.7°C;Basell Poliolefine Italia S.r.l. FE7777-WO-01PP: copolymer of propylene with ethylene, containing 5% by weight of ethylene, having Tmof 142.8°C AHmof 48.5 J / g, Tc of 111°C AHCof -69 J / g, MIL of about 2 g / 10 min., XS-25°C of 10% by weight, nucleated with 750 ppm of a phosphate ester salt;

[0147] Due to the reduced content of propylene polymer, no crystallization peak is detected in the DSC analysis of the above described PB-1.

[0148] The said materials are melt-blended in a co-rotating twin screw extruder Coperion ZSK40SC, with screw diameter of 40 mm and screw length / diameter ratio of 43: 1, under the following conditions:- extrusion temperature of 180-200°C;- screw rotation speed of 220 rpm;- production rate of 60 kg / hour.The properties of the so obtained final composition is reported in Table 1.Basell Poliolefine Italia S.r.l. FE7777-WO-01Table 1Note: * weight % with respect to the total weight of A) + B); MD = Machine Direction; TD = Transverse Direction.

Claims

Basell Poliolefine Italia S.r.l. FE7777-WO-01CLAIMSWhat is claimed is:

1. A polyolefin composition comprising:A) from 50% to 90% by weight, preferably from 55% to 90% by weight, more preferably from 60% to 85% by weight, of a copolymer of butene- 1 with ethylene having a copolymerized ethylene content of up to 18% by mole and no melting peak detectable at the DSC at the second heating scan;B) from 10% to 50% by weight, preferably from 10% to 45% by weight, more preferably from 15% to 40% by weight, of a propylene copolymer having a melting temperature Tm, measured by DSC at the second heating scan, of from 130°C to 165°C, preferably from 131 to 165°C, more preferably from 131 to 160°C, and a crystallization temperature Tc, measured by DSC after the first heating scan, of 100°C or higher, preferably of 105°C or higher, more preferably of 108°C or higher, the preferred upper limit being in all cases of 115°C; wherein the amounts of A) and B) are referred to the total weight of A) + B) and all the DSC scans are carried out with a heating or cooling rate of 10°C per minute.

2. The polyolefin composition of claim 1, wherein both the polyolefin composition and the propylene copolymer B) have a melting enthalpy AHm, measured by DSC at the second heating scan, of from 7 to 65 J / g, preferably from 8 to 55 J / g.

3. The polyolefin composition of claim 1 or 2, wherein the propylene copolymer B) has a crystallization enthalpy AHC, measured by DSC after the first heating scan, of from -30 to -90 J / g, more preferably from -40 to -85 J / g.

4. The polyolefin composition of claim 1 or 2, having a crystallization enthalpy AHC, measured by DSC after the first heating scan, of from -10 to -30 J / g, preferably from -15 to -28 J / g.

5. The polyolefin composition of claim 1 or 2, having tensile elastic modulus equal to or lower than 100 MPa, preferably equal to or lower than 60 MPa in particular from 100 or from 60 to 10 MPa.Basell Poliolefine Italia S.r.l. FE7777-WO-016. The polyolefin composition of claim 1 or 2, having Shore A values of lower than 90, particularly equal to or lower than 88, the lower limit being preferably of 70.

7. The polyolefin composition of claim 1 or 2, having Shore D values equal to or or lower than 25, preferably equal to or lower than 20, in particular from 25 to 5 or from 20 to 5.

8. The polyolefin composition of claim 1 or 2, having Haze values of 35% or lower, preferably of 30% or lower, the preferred lower limit being in all cases of 15%.

9. The polyolefin composition of claim 1 or 2, wherein the butene- 1 copolymer component A) has Shore A value equal to or lower than 80.

10. The polyolefin composition of claim 1 or 2, wherein the butene- 1 copolymer component A) has at least one of the following additional features:- MIE, of from 0.5 to 3 g / 10 min., where MIE is the melt flow index at 190°C with a load of 2.16 kg, determined according to ISO 1133-1 2012-03;- a lower limit of the copolymerized ethylene content of 12% by mole;- a Shore A value equal to or lower than 80, in particular from 80 to 40;- a Shore D value equal to or lower than 20, in particular from 20 to 5;- a Mw / Mn value, where Mw is the weight average molar mass and Mn is the number average molar mass, both measured by GPC, equal to or lower than 3, in particular from 3 to 1.5;- a tension set of less than 30% at 100% of deformation at 23°C (ISO 2285), more preferably equal to or less than 20%;- a percentage of butene- 1 units in form of isotactic pentads (mmmm%) greater than 80%, preferably equal to or greater than 85%, even more preferably equal to or greater than 90%;- tensile stress at break, measured according to ISO 527, of from 3 MPa to 20 MPa, more preferably from 4 MPa to 13 MPa;- tensile elongation at break, measured according to ISO 527, of from 550% to 1000%; more preferably from 700% to 1000%;Basell Poliolefine Italia S.r.l. FE7777-WO-01- intrinsic viscosity (I V.) equal to or higher than Idl / g; more preferably equal to or higher than 1.5 dl / g, wherein the upper limit is of 3 dl / g;- crystallinity of less than 30% measured via X-ray, more preferably of less than 20%;- density of 0.895 g / cm3or less, more preferably of 0.875 g / cm3or less;- content of xylene insoluble fraction at 0°C of less than 15% by weight.

11. The polyolefin composition of claim 1 or 2, wherein the propylene copolymer B) is selected from copolymers of propylene with one or more comonomers selected from ethylene and C4-C10 alpha-olefins, and combinations of said copolymers.

12. The polyolefin composition of claim 1 or 2, wherein the propylene copolymer B) is blended with a nucleating agent, preferably in amounts up to 2500 ppm, more preferably from 100 to 2000 ppm by weight, with respect to the total weight of B) and the nucleating agent.

13. The polyolefin composition of claim 11, wherein the nucleating agent is selected from phosphate ester salts and the acetals of sorbitols and xylitols.

14. The polyolefin composition of claim 1 or 2, wherein the propylene copolymer B) has MIL values of from 0.5 to 9 g / 10 min, preferably from 1 to 8 g / 10 min., where MIL is the melt flow index at 230°C with a load of 2.16 kg, determined according to ISO 1133-1 2012-03.

15. A formed article comprising the polyolefin composition of any of claims 1 to 14.

16. Formed article according to claim 15, in form of a laminar article, in particular film, sheet or foil.

17. An encapsulated photovoltaic cell which is obtained by using a photovoltaic encapsulating material comprising the polyolefin composition of any of claims 1 to 14.

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