POLYPROPYLENE COMPOSITION WITH GOOD SEALING PROPERTIES

FIELD OF THE INVENTION

[0001] The present disclosure relates to a polypropylene composition comprising a copolymer of propylene with 1 -hexene, a propylene-ethylene-hexene terpolymer and a copolymer of propylene with ethylene, the composition being blended with polybutene and particularly suited for preparing films, in particular biaxially oriented polypropylene (BOPP) and cast films having low seal initiation temperature (SIT), high crystallization temperature and reduced fish-eye count.

BACKGROUND OF THE INVENTION

[0002] Copolymer of propylene and 1 -hexene are already known in the art. For example W02006/002778 describes a copolymer of propylene and 1 -hexene having from 0.2 wt.% to 5 wt.% of 1 -hexene derived units. This copolymer has a monomodal molecular weight distribution is used for pipes systems.

[0003] WO2017/097579 relates to a composition comprising a copolymer of propylene with

1 -hexene and a copolymer of propylene and ethylene particularly suited for preparing films, in particular biaxially oriented polypropylene films (BOPP) and cast films having a low seal initiation temperature (SIT) and high transparency. The seal initiation temperature is still not satisfactory and can be lowered.

[0004] WO2018/202396 relates to a propylene polymer composition comprising: from 35 wt.% to 65 wt.% of a propylene 1 -hexene copolymer containing from 10.2 to 13% by weight, of 1 -hexene derived units and from 35 wt.% to 65 wt.% of a propylene ethylene copolymer containing from 1.5 wt.% to 6.5 wt.% of ethylene derived units. Even if the exemplified composition shows low SIT, the xylene soluble content is high.

[0005] Films containing blends of polypropylene and polubutene-1 in the external sealing layers are known in the art. [0006] The patent application W02004/048424 discloses a multilayer film having low sealing initiation temperature wherein the sealing layer comprises a polybutene- 1 containing 2.1 mol.% of ethylene in combination with a propylene-butene-ethylene terpolymer.

[0007] In WO2012/031953 the use of butene-1 homo or copolymers to lower the seal initiation temperature of sealing layers containing propylene copolymers with hexene- 1 is disclosed. The films also have a reduced number of fish eyes.

[0008] The applicant found that it is possible to produce films or sheets having a low seal initiation temperature (SIT), high crystallization temperature, good optical properties and low fish eyes count by using a polypropylene composition comprising a propylene 1 -hexene copolymer, a propylene 1 -hexene ethylene terpolymer and a propylene ethylene copolymer as component (A) and polybutene as component (B).

SUMMARY OF THE INVENTION

[0009] The present disclosure provides a polypropylene composition (I) comprising:

[0010] (A) at least 90.0% by weight of a propylene polymer comprising (based on the weight of (a)+(b)+(c), the weight being 100%):

[0011] (a) from 20% to 44% by weight of a propylene-hexene copolymer comprising from

5.0% to 8.3 % by weight of hexene derived units, based on the weight of component (a), and having a Melt Flow Rate (MFR(a)), measured according to ISO 1133-1 :2011 (230°C/2.16 kg), ranging from 3.5 to 8.5 g/10 min;

[0012] (b) from 25% to 45% by weight of a propylene-hexene-ethylene terpolymer comprising from 7.2% to 12.0% by weight of hexene derived units and from 0.5% to 2.5% by weight of ethylene derived units, wherein the Melt Flow Rate (MFR(a+b)) of components a) + b), measured according to ISO 1133-1:2011 (230°C/2.16 kg), ranges from 3.5 to 8.5 g/10 min; and

[0013] (c) from 25% to 50% by weight of a propylene-ethylene copolymer comprising from

3.5% to 8.7% by weight of ethylene derived units,

[0014] wherein the Melt Flow Rate of components (a)+(b)+(c), measured according to ISO 1133-1:2011, (230°C/2.16 kg) ranges from 3.5 to 12.0 g/10 min, and

[0015] wherein the propylene polymer (A) has: [0016] (i) a xylene soluble content at 25°C ranging from 13.0% to 25.0% by weight, based on the weight of (a)+(b)+(c); and

[0017] (ii) a melting point ranging from 122°C to 132°C; and

[0018] (B) up to and including 10.0% by weight of a polybutene selected from butene homopolymers, butene copolymers with up to and including 5.0% by weight, based on the weight of component (B), of units deriving from ethylene and/or propylene, and mixtures thereof,

[0019] wherein the amounts of (A) and (B) are based on the total weight of (A)+(B), the total weight being 100%.

[0020] The polypropylene composition (I) of the present disclosure is endowed with good thermal, sealing and optical properties. Accordingly, the polypropylene composition (I) is suitable for producing films or sheets.

[0021] Accordingly, a further object of the present disclosure is a film or sheet comprising the polypropylene composition (I).

[0022] While multiple embodiments are disclosed, still other embodiments will become apparent to those skilled in the art from the following detailed description. As will be apparent, certain embodiments, as disclosed herein, are capable of modifications in various obvious aspects, all without departing from the spirit and scope of the claims as presented herein. Accordingly, the following detailed description is to be regarded as illustrative in nature and not restrictive.

DETAILED DESCRIPTION OF THE INVENTION

[0023] In the context of the present disclosure;

[0024] - the percentages are expressed by weight, unless otherwise specified;

[0025] - the total weight of a polymer composition sums up to 100%, unless otherwise specified;

[0026] - the term “comprising” referred to a polymer, a plastic material, a polymer composition, mixture or blend, should be construed to mean “comprising or consisting essentially of’;

[0027] - the term “consisting essentially of’ means that, in addition to those components which are mandatory, other components may also be present in the material, provided that the essential characteristics of the material are not materially affected by their presence. Examples of components that, when present in customary amounts, do not materially affect the characteristics of a polymer or of a polyolefin composition, mixture or blend are catalyst residues, antistatic agents, processing aids, melt stabilizers, light stabilizers, antioxidants and antiacids;

[0028] - the term “copolymer” is referred to a polymer deriving from the intentional polymerization of two different comonomers, i.e. the term “copolymer” does not include terpolymers;

[0029] - the term “terpolymer” is referred to a polymer deriving from the intentional polymerization of three different comonomers;

[0030] - the term “hexene” refers to hexene- 1. The term “butene” refers to butene- 1 and the term “polybutene” refers to polymers of butene- 1;

[0031] - a “film” is thin layer of material having thickness equal to or lower than 2000 pm;

[0032] - a “sheet” is a layer of material more than 2000 pm thick;

[0033] - the term “skin layer” is referred to an outermost layer of a multilayer film;

[0034] - the term “base layer” is referred to the innermost layer of a multilayer film.

[0035] The present disclosure provides a polypropylene composition (I) comprising:

[0036] - at least 90.0% by weight, preferably from 90.0% to 99.5% by weight, more preferably from 93.0% to 99.0% by weight, still more preferably from 95.0% to 98.0% by weight, of the propylene polymer (A), and

[0037] - up to and including 10.0% by weight, preferably from 0.5% to 10.0% by weight, more preferably from 1.0% to 7.0% by weight, still more preferably from 2.0% to 5.0% by weight, of the poly butene (B),

[0038] wherein the amounts of (A) and (B) are based on the total weight of (A)+(B), the total being 100%.

[0039] In the following the individual components of the polypropylene composition (I) are defined in more detail. The individual components may be comprised in the polypropylene composition (I) in any combination.

[0040] The propylene polymer (A) comprises (based on the weight of (a)+(b)+(c), the weight being 100%):

[0041] (a) from 20% to 44% by weight, preferably from 27% to 40% by weight, more preferably from 29% to 35% by weight, based on the weight of the component (a), of a propylene- hexene copolymer comprising from 5.0% to 8.3% by weight, preferably from 6.3% to 7.8% by weight, more preferably from 6.5% to 7.4% by weight, of hexene derived units, based on the weight of component (a), and having a Melt Flow Rate (MFR(a)), measured according to ISO 1133-1 :2011 (230°C/2.16 kg), ranging from 3.5 to 8.5 g/10 min, preferably from 4.4 to 8.0 g/10 min, more preferably from 5.0 to 7.0 g/10 min;

[0042] (b) from 25% to 45% by weight, preferably from 35% to 40% by weight, more preferably from 36% to 39% by weight of a propylene- hexene-ethylene terpolymer comprising from 7.2% to 12.0% by weight, preferably from 7.5% to 9.5% by weight, more preferably from 8.2% to 9.1% by weight, of hexene derived units and from 0.5% to 2.5% by weight, preferably from 0.7% to 2.2% by weight, more preferably from 0.8% to 2.0% by weight of ethylene derived units, wherein the Melt Flow Rate of components a) + b) (MFR(a+b)), measured according to ISO 1133-1 :2011 (230°C/2.16 kg), ranging from 3.5 to 8.5 g/10 min, preferably from 4.4 to 8.0 g/10 min, more preferably from 5.0 to 7.0 g/10 min and the amounts of hexene and ethylene are based on the weight of (b); and

[0043] (c) from 25% to 50% by weight, preferably from 27% to 40 % by weight, more preferably from 29% to 35% by weight, of a propylene-ethylene copolymer comprising from 3.5% to 8.7% by weight, preferably from 4.5% to 8.4% by weight, of ethylene derived units, based on the weight of (c), wherein the Melt Flow Rate of components (a)+(b)+(c), measured according to ISO 1133-1:2011, (230°C/2.16 kg) ranges from 3.5 to 12.0 g/10 min, preferably from 4.4 to 8.0 g/10 min, more preferably ranging from 5.0 to 8.5 g/10 min,

[0044] and wherein the propylene polymer (A) has:

[0045] (i) xylene soluble content at 25°C ranging from 13.0% to 25.0% by weight, preferably from 14.0% to 23.0% by weight, more preferably from 15.0% to 20.0% by weight; and

[0046] (ii) melting point ranging from 122°C to 132°C, preferably from 125°C to 131°C, more preferably from 126°C to 130°C.

[0047] Preferably, the propylene polymer (A) is a reactor blend of components (a), (b) and (c). The process for preparing the propylene polymer (A) is preferably carried out in presence of a highly stereospecific heterogeneous Ziegler-Natta catalyst. The Ziegler-Natta catalysts suitable for producing the propylene ethylene copolymer of the disclosure comprise a solid catalyst component comprising at least one titanium compound having at least one titanium-halogen bond and at least an electron-donor compound (internal donor), both supported on magnesium chloride. The Ziegler-Natta catalysts systems further comprise an organo-aluminum compound as essential cocatalyst and optionally an external electron-donor compound.

[0048] Suitable catalysts systems are described in the European patents EP45977, EP361494, EP728769, EP 1272533 and in the international patent application W000163261.

[0049] The organo-aluminum compound is preferably an alkyl-Al selected from the trialkyl aluminum compounds such as for example triethylaluminum, triisobutylaluminum, tri-n- butylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum. It is also possible to use mixtures of trialkylaluminum's with alkylaluminum halides, alkylaluminum hydrides or alkylaluminum sesqui chlorides such as AlEt2Cl and AhEtsCh.

[0050] Preferred external electron-donor compounds include silicon compounds, ethers, esters such as ethyl 4-ethoxybenzoate, amines, heterocyclic compounds and particularly 2, 2,6,6- tetramethyl piperidine, ketones and the 1,3 -di ethers. Another class of preferred external donor compounds is that of silicon compounds of formula Ra ⁵ Rb ⁶ Si(OR ⁷ ) _c where a and b are integer from 0 to 2, c is an integer from 1 to 3 and the sum (a+b+c) is 4; R ⁵ , R ⁶ , and R ⁷ , are alkyl, cycloalkyl or aryl radicals with 1-18 carbon atoms optionally containing heteroatoms. Particularly preferred are methylcyclohexyldimethoxysilane, diphenyldimethoxysilane, methyl-t-butyldimethoxysilane, di cyclopentyldimethoxysilane, 2-ethylpiperidinyl-2-t-butyldimethoxysilane and 1,1,1 ,trifluoropropyl-2-ethylpiperidinyl-dimethoxysilane and 1,1,1 ,trifluoropropyl-metil- dimethoxysilane. The external electron donor compound is used in such an amount to give a molar ratio between the organo-aluminum compound and said electron donor compound of from 0.1 to 500; preferably from 1 to 100; more preferably from 2 to 50.

[0051] The polymerization process, which can be continuous or batch, is preferably carried out following known techniques of operating in gas phase, or in liquid phase, optionally in the presence of inert diluent, or by mixed liquid-gas techniques.

[0052] It is preferable to carry out the polymerization in gas phase in three reactors, wherein each component is prepared in a different reactor. More preferably, in the first two reactors components (a) and (b) are respectively obtained component (c) is obtained in the third and last reactor. [0053] Polymerization reaction time, pressure and temperature are not critical, however it is preferred if the polymerization temperature ranges from 20°C to 100°C. The polymerization pressure is atmospheric or, preferably, higher.

[0054] The regulation of the molecular weight of the components (a), (b) and (c) is carried out by using known molecular weight regulators, hydrogen in particular.

[0055] Preferably, the component (B) is a butene-ethylene copolymer. More preferably, the component (B) is a butene-ethylene copolymer having at least one of, preferably all, the following properties:

[0056] - content of units deriving from ethylene ranging from 1.0% to 4.5% by weight, preferably from 1.5% to 4.5% by weight, more preferably from 2.0% to 4.0% by weight, still more preferably from 2.5% to 3.5% by weight, based on the weight of (B); and/or

[0057] - melting temperature Tm(I) of the form I, measured by DSC according to the method

ISO 11357-3:2018, lower than 100°C, preferably ranging from 80° to lower than 100°C, more preferably from 90° to 97°C; and/or

[0058] - melt flow rate measured according to ISO 1133-1:2011 (190°C/2.16 kg) ranging from

1.0 to 6.0 g/10 min., preferably from 2.0 to 5.0 g/10 min, still more preferably from 3.0 to 4.5 g/10 min; and/or

[0059] - flexural modulus measured according to ISO 178:2010 equal to or higher than 80

MPa, preferably ranging from 80 to 250 MPa, more preferably from 100 to 210 MPa.

[0060] In a preferred embodiment, in addition to one or more of the properties above, the butene-ethylene copolymer (B) has molecular weight distribution Mw/Mn ranging from 4.0 to 9.0, preferably from 4.0 to 8.0, more preferably more preferably from 4.0 to 7.0, still more preferably from more than 4.5 to less than 6.0.

[0061] In some embodiments, the polybutene (B) is obtained using a metallocene-based catalyst system.

[0062] In a preferred embodiment, the polybutene (B) is obtained by polymerizing the relevant monomers in the presence of a Ziegler-Natta catalyst system as described above.

[0063] The polymerization process 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 as a reaction medium. It is also possible to carry out the polymerization process in the gas-phase, operating in one or more fluidized or mechanically agitated bed reactors. The solution polymerization carried out using liquid butene as a reaction medium is highly preferred.

[0064] The polymerization is generally carried out at temperature of from 20° to 120°C, preferably of from 40° to 90°C. 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.

[0065] A suitable catalyst system and polymerization process to obtain the polybutene (B) is disclosed in the patent document W02004/048424A1.

[0066] The poly butene (B) is also commercially available, e.g. with the trade name Toppyl marketed by LyondellBasell.

[0067] In one embodiment, the polypropylene composition (I) comprises up to and including 5.0% by weight, more preferably from 0.01% to 5.0% by weight, of at least one additive (C) selected from the group consisting of nucleating agents, antistatic agents, anti-oxidants, light stabilizers, slipping agents, anti-acids, melt stabilizers, and combinations thereof, the amount of additive being based on the total weight of the polypropylene compositions (I) comprising the additive, the total weight being 100%.

[0068] In one embodiment, the polyolefin composition (I) consists of the component (A), the component (B) and optionally an additive (C) as described above.

[0069] The polyolefin composition (I) is obtained by mixing the components (A), (B) and optionally (C) in a conventional melt mixing apparatus, e.g. a twin screw extruder, operated under conventional conditions.

[0070] The polypropylene composition (I) is endowed with good thermal and sealing properties, so that the composition can be advantageously used for the production of films or sheets. A relatively high melting point results in an improved processability of the composition when used to produce films or sheets. A low SIT value renders the film or sheet suitable for use in sealing applications. The polyolefin composition (I) also results in a film or sheet having low fish eyes count. [0071] Advantageously, the ATm-SIT (difference between Tm of the polypropylene composition (I) and SIT measured on a BOPP film) is broad, thereby allowing good processability of films.

[0072] Preferably, the SIT measured on BOPP film ranges from 70°C to 85°C, more preferably from 72°C to 83°C.

[0073] In a preferred embodiment, the ATm-SIT value measured on a BOPP film, ranges from 40.0°C to 60.0°C, preferably from 45.0°C to 55°C, wherein the Tm of the polypropylene composition (I) and the SIT on a BOPP film are measured as illustrated below.

[0074] In one further aspect, the present disclosure refers to a film or sheet comprising or consisting of the polypropylene composition (I) as described in any one of the embodiments above. [0075] The film or sheet is single-layer or multilayer, preferably is a multilayer film or sheet wherein the polypropylene composition (I) is comprised in at least one skin layer, more preferably in both skin layers.

[0076] The features describing the subject matter of the present disclosure are not inextricably linked to each other. Hence, preferred ranges of one feature may be combined with more or less preferred ranges of a different feature, independently from their level of preference.

EXAMPLES

[0077] The following examples are given to illustrate the present invention without limiting purpose.

[0078] CHARACTERIZATION METHODS : the following methods are used to determine the properties indicated in the description, claims and examples.

[0079] Melt Flow Rate: Determined according to the method ISO 1133-1:2011 (230°C/2.16 kg for the propylene polymers and 190°C/2.16kg for polybutene).

[0080] Solubility in xylene at 25°C for propylene polymers: 2.5 g of polymer sample and 250 ml of xylene are introduced in a glass flask equipped with a refrigerator and a magnetic stirrer. The temperature is raised in 30 minutes up to 135°C. The obtained clear solution is kept under reflux and stirring for further 30 minutes. The solution is cooled in two stages. In the first stage, the temperature is lowered to 100°C in air for 10 to 15 minute under stirring. In the second stage, the flask is transferred to a thermostatically controlled water bath at 25°C for 30 minutes. The temperature is lowered to 25°C without stirring during the first 20 minutes and maintained at 25°C with stirring for the last 10 minutes. The formed solid is filtered on quick filtering paper (eg. Whatman filtering paper grade 4 or 541). 100 ml of the filtered solution (SI) is poured in a previously weighed aluminum container, which is heated to 140°C on a heating plate under nitrogen flow, to remove the solvent by evaporation. The container is then kept on an oven at 80°C under vacuum until constant weight is reached. The amount of polymer soluble in xylene at 25°C is then calculated. XS(I) and XSA values are experimentally determined. The fraction of component (B) soluble in xylene at 25°C (XSB) can be calculated from the formula:

XS = W(A)X(XSA) + W(B)X(XSB) wherein W(A) and W(B) are the relative amounts of components (A) and (B), respectively, and W(A)+ W(B)=1.

[0081] Hexene content of propylene-hexene copolymers by NMR: ¹³ C NMR spectra are acquired on an AV-600 spectrometer operating at 150.91 MHz in the Fourier transform mode at 120 °C. The peak of the propylene CH was used as internal reference at 28.83. The ¹³ C NMR spectrum is acquired using the following parameters:

[0082] The total amount of 1 -hexene as molar percent is calculated from diad using the following relations:

[P] = PP + 0.5PH

[H] = HH + 0.5PH [0083] Assignments of the ¹³ C NMR spectrum of propylene/1 -hexene copolymers was calculated according to the following table:

[0084] Ethylene content of propylene-ethylene copolymers by NMR: ¹³ C NMR spectra were acquired on a Bruker AV-600 spectrometer equipped with cryoprobe, operating at 160.91 MHz in the Fourier transform mode at 120°C. The peak of the S00 carbon (nomenclature according to “Monomer Sequence Distribution in Ethylene-Propylene Rubber Measured by 13C NMR. 3. Use of Reaction Probability Mode”, C. J. Carman, R. A. Harrington and C. E. Wilkes, Macromolecules, 1977, 10, 536) was used as internal reference at 29.9 ppm. The samples were dissolved in l,l,2,2-tetrachloroethane-d2 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 1H-13C coupling. 512 transients were stored in 32K data points using a spectral window of 9000 Hz. The assignments of the spectra, the evaluation of triad distribution and the composition were made according to Kakugo (“Carbon- 13 NMR determination of monomer sequence distribution in ethylene-propylene copolymers prepared with 5-titanium trichloride- diethylaluminum chloride”

M. Kakugo, Y. Naito, K. Mizunuma and T. Miyatake, Macromolecules, 1982, 15, 1150) using the following equations:

PPP = 100 Tpp/S PPE = 1OO TP5/S EPE = 100 T55/S

PEP = 100 SPP/S PEE= 100 SP5/S EEE = 100 (0.25 SyS+0.5 S55)/S

S = TPP + TP5 + T55 + SPP + SP5 + 0.25 Sy5 + 0.5 S55

[0085] The molar percentage of ethylene content was evaluated using the following equation:

E% mol = 100 * [PEP+PEE+EEE]

[0086] The weight percentage of ethylene content was evaluated using the following equation:

100 * E% mol * MWE

E% wt. = >

E% mol * MWE + P% mol * MWp

[0087] where P% mol is the molar percentage of propylene content, while MWE and MWp are the molecular weights of ethylene and propylene, respectively.

[0088] The product of reactivity ratio rm was calculated according to Carman (C. J. Carman,

R.A. Harrington and C.E. Wilkes, Macromolecules, 1977; 10, 536) as:

[0089] The tacticity of Propylene sequences was calculated as mm content from the ratio of the PPP mmTpp (28.90-29.65 ppm) and the whole Tpp (29.80-28.37 ppm).

[0090] Hexene and ethylene content of propylene-hexene-ethylene terpolymers: ¹³ C NMR spectra are acquired on an AV-600 spectrometer operating at 150.91 MHz in the Fourier transform mode at 120 °C. The peak of the propylene CH was used as internal reference at 28.83. The ¹³ C

NMR spectrum is acquired using the following parameters:

Spectral width (SW): 60 ppm

Spectrum centre (01): 30 ppm

Decoupling sequence: WALTZ 65_64pl Pulse program (1): ZGPG

Pulse Length (Pl) (2): for 90°

Total number of points (TD): 32K

Relaxation Delay (2): 15 s

Number of transients (3): 1500

[0091] The total amount of 1 -hexene and ethylene as molar percent is calculated from diad using the following relations:

[P] = PP + 0.5PH + 0.5PE [H] = HH + 0.5PH

[E] = EE+ 0.5PE

[0092] Assignments of the ¹³ C NMR spectrum of propylene/l-hexene/ethylene copolymers have been calculated according to the following table:

[0093] Comonomer content of polybutene: 13C NMR spectra are acquired on a Bruker AV- 600 spectrometer equipped with cryoprobe, operating in the Fourier transform mode at 120°C. The samples are dissolved in l,l,2,2-tetrachloroethane-d2 at 120°C with a 8 % wt/v concentration. Each spectrum is acquired with a 90° pulse, and 15 seconds of delay between pulses and CPD to remove 1H-13C coupling. The spectrometer is operated at 160.91 MHz. The peak of the S55 carbon (nomenclature according to “Monomer Sequence Distribution in Ethylene-Propylene Rubber Measured by 13C NMR. 3. Use of Reaction Probability Mode” C. J. Carman, R. A. Harrington and C. E. Wilkes, Macromolecules, 1977, 10, 536) is used as an internal reference at 29.9 ppm. 512 transients are stored in 32K data points using a spectral window of 9000 Hz.

[0094] 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 BBE = 100 Tp ₅ /S EBE = 100 P ₅₅ /S

BEB = 100 Spp/S BEE = 100 S _a5 /S EEE = 100(0.25 S ₅ + 0.5 S ₅₅ )/S

S = Tpp + Tpg + Poo + Spp + Sa5 + 0.25 Soo + 0.5 S55

[0095] The total amount of 1 -butene and ethylene as molar percent is calculated from triad using the following relations:

[E] = EEE+BEE+BEB

[B] = BBB+BBE+EBE

[0096] The weight percentage of ethylene content (E% wt) is calculated using the following equation: wherein

[B] mol = the molar percentage of 1 -butene content; MWE = molecular weights of ethylene

MWB = molecular weight of 1 -butene.

[0097] Molecular weight distribution Mw/Mn: 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 (Polymer Char). The dimensions of the columns were 300 x 7.5 mm and their particle size 13 pm. The mobile phase used was 1 -2-4-trichlorobenzene (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-p-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 interpolating the experimental data and obtaining 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 10-4 dL/g and KPB = 1.78 x 10-4 dL/g for PS and PB respectively, while the Mark-Houwink exponents a = 0.706 for PS and a = 0.725 for PB were used. 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 weights and the K value of the Mark-Houwink relationship is calculated using a linear combination as reported below:

^EB ~ ^X E^PE + ^X p pB where KEB is the constant of the copolymer, KPE (4.06 x I O ⁴ , dL/g) and KPB (1.78 x 10 ⁴ dl/g) are the constants of polyethylene and poly butene and xE and xB are the ethylene and the butene- 1 weight% content. The Mark-Houwink exponent a = 0.725 is used for all the butene- 1 /ethylene copolymers independently of their composition.

[0098] Melting temperature: measured according to the method ISO 11357-3:2018. Polypropylene and polypropylene compositions: scanning rate of 20°C/min in cooling and heating, on a sample weighting 5-7 mg, under nitrogen flow. Instrument calibration made with Indium. Polybutene: to determine the melting temperature of the polybutene crystalline form I (Tm(I)), 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 Tm(I).

[0099] Flexural Modulus: determined according to the method ISO 178:2010 on injection molded test specimens (80 x 10 x 4 mm) obtained according to the method ISO 1873-2:2007 for propylene polymers or on compression molded specimens for butene polymers. Specimens of butene copolymers were conditioned for 10 days at 23 °C before testing.

[0100] Preparation of BOPP film test specimens. Films with thickness of 50 pm are prepared by extruding each test composition in a single screw Collin extruder (length/diameter ratio of screw 1:25) at a film drawing speed of 7 m/min and a melt temperature of 210-250°C. Each film is superimposed on a 1000pm thick film of a propylene homopolymer having a xylene insoluble fraction of 97 wt.% and a MFR (ISO1133-1 :2011, 230°C/2.16kg) of 2.0 g/10 min. The superimposed films are bonded to each other in a plat press at 200°C under a 35 kg x cm ² load, which is maintained for 5 minutes. The resulting laminates are simultaneously stretched longitudinally and transversally, i.e. biaxially, by a factor 7 with a Karo 4 Brueckener film stretcher at 160°C, thus obtaining a 20pm thick BOPP film (18pm homopolymer + 2pm test composition).

[0101] Sealing Initiation Temperature on BOPP films: Film Strips, 6 cm wide and 35 cm length are cut from the center of the BOPP film he film was superimposed with a BOPP film made of PP homopolymer. The superimposed specimens are sealed along one of the 2 cm sides with a Brugger Feinmechanik Sealer, model HSG-ETK 745. Sealing time is 5 seconds at a pressure of 0.14 MPa (20 psi). The starting sealing temperature is from about 10 °C less than the melting temperature of the test composition. The sealed strip is cut in 6 specimens 15 mm wide long enough to be claimed in the tensile tester grips. The seal strength is tested and load cell capacity 100 N, cross speed 100 mm/min and grip distance 50 mm. The results is expressed as the average of maximum seal strength (N). from are left to cool and then their unsealed ends are attached to an Instron machine where they are tested at a traction speed of 50 mm/min.

[0102] The test is than repeated by changing the temperature as follows:

[0103] If seal strength <1.5 N then increase the temperature

[0104] If seal strength >1.5 N then decrease the temperature [0105] Temperature variation must be adjusted stepwise, if seal strength is close to target select steps of 1°C if the strength is far from target select steps of 2°C.

[0106] The target seal strength (SIT) is defined as the lowest temperature at which a seal strength higher or equal to 1.5 N is achieved.

[0107] RAW MATERIALS

[0108] Irganox 1010: Pentaerythritol tetrakis (3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate) marketed by BASF.

[0109] Irgafos 168: tris(2,4-di-tert. -butylphenyl) phosphite marketed by BASF.

[0110] PB1(B): a copolymer of butene- 1 with ethylene, containing 3.5% by weight of ethylene and having a Tm(I) of 94°C, a molecular weight distribution Mw/Mn of 5.6, a melt flow rate of 3.1 g/lO min. (ISO 1133-1:2011, 190°C/2.16 kg), a flexural modulus (ISO 178:2010) of l20 MPa. The butene- 1 copolymer was obtained by sequential polymerization in two reactors, using butene- 1 as liquid medium and a Ziegler-Natta catalyst system according to the Example 11 of the patent W02004/048424, with the following polymerization conditions of the first reactor: temperature of 75°C and hydrogen/butene feed ratio of 1000 ppmV. After 2.5 hours the polymerization content of the first reactor was transferred into the second reactor where the copolymerization continued under the same conditions with the only difference that the ethylene feed was discontinued. The polymerization was stopped after 2 hours.

[0111] PB2(B): a copolymer of butene- 1 with ethylene, containing 3.5% by weight of ethylene and having a Tm(I) of 65°C, a molecular weight distribution Mw/Mn of 2.2, a melt flow rate of 3.3 g/lO min. (ISO 1133-1:2011, 190°C/2.16 kg), a flexural modulus (ISO 178:2010) of l30 MPa. [0112] Propylene polymer (A)

[0113] Procedure for the preparation of the spherical adduct: microspheroidal MgCh PC2H5OH adduct was prepared according to the method described in Comparative Example 5 of W098/44009, with the difference that BiCh in a powder form and in an amount of 3 mol% with respect to the magnesium is added before the feeding of the oil.

[0114] Procedure for the preparation of the solid catalyst component: the solid catalyst component was prepared according to Example 1 of EP728769 with the following differences: [0115] - the second and third titanations were carried out at 110°C (instead of 120°C); and [0116] - MgCh 3 C2H5OH in the form of spherical solid particles with a maximum diameter less than or equal to 65 microns (instead of 50 microns) is used.

[0117] Catalyst system and prepolymerization treatment: before introducing it into the polymerization reactor, the solid catalyst component described above is contacted at 15°C for about 6 minutes with aluminum triethyl (TEAL) and dicyclopentyl dimethoxy silane (DCPMS) as external donor.

[0118] The catalyst system is then subjected to prepolymerization by maintaining it in suspension in liquid propylene at 20°C for about 20 minutes before introducing it into the polymerization reactor.

[0119] Polymerization: into a first gas phase polymerization reactor a propylene-hexene copolymer (component (a)) is produced by feeding in a continuous and constant flow the prepolymerized catalyst system, hydrogen, propylene and 1 -hexene in the gas state. The propylene copolymer produced in the first reactor is discharged in a continuous flow and is introduced, in a continuous flow, into a second gas phase polymerization reactor, together with quantitatively constant flows of hydrogen, hexene, ethylene and propylene in the gas state. The propylene terpolymer produced in the second reactor is discharged in a continuous flow and, after having been purged of unreacted monomers, is introduced, in a continuous flow, into a third gas phase polymerization reactor, together with quantitatively constant flows of hydrogen, hexene and propylene in the gas state. The polymerization conditions are reported in table 1.

Table 1 [0120] The polymer obtained from the polymerization run was additivated with 0.05 wt.% of Irganox 1010, 0.1 wt.% of Irgafos 168, 0.05% of calcium stearate, wherein the amounts of the additives are based on the total weight of the polymer including the additives, and pelletized. Table 2 illustrates the features of the propylene polymer.

Table 2

[0121] Examples E1-E3

[0122] The propylene polymer (A) and the polybutene (B) were melt blended in the proportions illustrated in Table 3 in a twin screw extruder (Werner 58, model WP ZSK-58) at a rotation speed of 220 rpm and with an extruder output of 220kg/hour.

[0123] The thermal and sealing properties of the polypropylene composition are illustrated in Table 3. The polypropylene composition also showed a significantly low fish eye count on cast films.

Table 3