EP4677026A1

EP4677026A1 - Polymer composition comprising propylene ethylene random copolymer

Info

Publication number: EP4677026A1
Application number: EP24707545.0A
Authority: EP
Inventors: Michele Grazzi; Marco Ciarafoni; Alberto Nardin; Davide TARTARI; Eleonora Ciaccia
Original assignee: Basell Poliolefine Italia SRL
Current assignee: Basell Poliolefine Italia SRL
Priority date: 2023-03-07
Filing date: 2024-02-29
Publication date: 2026-01-14
Also published as: WO2024184190A1

Abstract

A polymer composition comprising: A) from 70 wt% to 95 wt% of a random propylene ethylene copolymer having: i) xylene soluble fraction at 25°C ranging from 10 wt% to 16 wt%; ii) melt flow rate, MFR, measured according to ISO 1133 at 230 °C with a load of 2.16 kg, ranging from 1.0 g/10 min to 12.0 g/10 min; iii) an ethylene derived units content, measured by ¹³C NMR, ranging from 3.2 wt% and 7.8 wt%; iv) the crystallization temperature measured by DSC, ranges from 82°C to 105°C; v) the C¹³ NMR sequences PEP ranging from 4.0mol% to 5.8mol%; B) from 5.0 wt% to 30.0 wt% of a copolymer of 1-butene and ethylene

Description

TITLE

POLYMER COMPOSITION COMPRISING PROPYLENE ETHYLENE RANDOM COPOLYMER

FIELD OF THE INVENTION

[0001] The present disclosure relates to a polymer compositions comprising a propylene ethylene random copolymer fit for producing films in particular blown and cast films having improved features in particular a reduced number of gels.

BACKGROUND OF THE INVENTION

[0006] Such kind of polypropylene compositions is widely used for making films in the packaging field, especially in the food packaging field, but also for the packaging non food products and for the production of non-packaging items.

[0007] Packaging examples are the primary packaging of hygienic items, textile articles, magazines, mailing films, secondary collation packaging, shrink packaging films and sleeves, stretch packaging films and sleeves, form-fill-seal packaging films for portioning various types of articles such as bags, pouches or sachets, vacuum formed blisters.

[0008] Examples of form-fill-seal applications are the packaging of peat and turf, chemicals, plastic resins, mineral products, food products, small size solid articles.

[0009] The above applications and, in general, all the applications involving use of plastic films for packaging are included in the general definition of “flexible plastic packaging”.

[0010] Non packaging items are for example synthetic clothing articles or medical and surgical films, films which are formed into flexible conveying pipes, membranes for isolation and protection in soil, building and construction applications, films which are laminated with non-woven membranes.

[0011] An important feature of this kind of films is the sealing initiation temperature that it is preferred to be very low, without losing other features of the films such as hot tack.

WO 2011/036077 relates to heat-sealable polyolefin films comprising an heterophasic propylene copolymer and a butene- 1 (co)polymer having a content of butene- 1 derived units of 75 wt% or more and a flexural modulus (MEF) of 70 MPa or less.

[0012] WO201 8/211107 relates to a polyolefin composition comprising a random copolymer of propylene and a polymer of 1 -butene wherein preferably the 1 -butene polymer is a 1 -butene copolymer having a 1 -butene derived units content lower than 50 wt%.

WO 20110/064131 relates to a polyolefin composition comprising from 70 to 95 wt% of a copolymer of propylene and from 5 to 30 wt% of a butene copolymer having a flexural modulus of 60 MPa or less.

[0013] The applicant found that it is possible to improve the properties of films by using a composition comprising a propylene ethylene random copolymer and a 1 -butene copolymer having particular features.

SUMMARY OF THE INVENTION

[0014] Thus, an object of the present disclosure is a polymer composition comprising:

[0015] A) from 70 wt% to 95 wt% of a random propylene ethylene copolymer having: i) xylene soluble fraction at 25°C ranging from 10 wt% to 16 wt%; ii) melt flow rate, MFR, measured according to ISO 1133 at 230 °C with a load of 2.16 kg, ranging from 1.0 g/10 min to 12.0 g/10 min; iii) an ethylene derived units content, measured by ¹³C NMR, ranging from 3.2 wt% and 7.8 wt%; iv) the crystallization temperature measured by DSC, ranges from 82°C to 105°C; v) the C¹³ NMR sequences PEP ranging from 4.0mol% to 5.8mol%;

[0016] B) from 5.0 wt% to 30.0 wt% of a copolymer of 1-butene and ethylene containing from 3.0 wt% to 4.2 wt% of ethylene derived units; said copolymer of 1-butene and ethylene having:

[0017] - a Melt Flow Rate: measured according to ISO 1133-2011 -(190 °C, 2.16 Kg) ranging from 1.0 to 5.5 g/10 min;

[0018] Flexural modulus measured according to ISO 178 2010 ranging from 80 MPa to 250 MPa;

[0019] The melting temperature measured according to ISO 11357-2013 ranging from 83 °C and 108 °C, form I; [0020] the sum of the amounts of A) and B) being 100 wt%.

DETAILED DESCRIPTION OF THE INVENTION

[0021] Thus, an object of the present disclosure is a polymer composition comprising:

[0022] A) from 70.0 wt% to 95.0 wt%; preferably from 72.0 wt% to 93.0 wt%; more preferably from 74.0 wt% to 87.0 wt% of a random propylene ethylene copolymer having: i) xylene soluble fraction at 25°C ranging from 10 wt% to 16 wt%; preferably from 11 wt% to 15 wt%; more preferably from 11.5 wt% to 14.5 wt; ii) melt flow rate, MFR, measured according to ISO 1133 at 230 °C with a load of 2.16 kg, ranging from 1.0 g/10 min to 12.0 g/10 min; preferably from 3.0 g/10 min to 11.0 g/10 min more preferably from 4.5 g/10 min to 11.0 g/10 min; iii) an ethylene derived units content, measured by ¹³C NMR, ranging from3.2 wt% to 7.8 wt%;preferably from 3.5 wt% to 7.3 wt%; more preferably from 4.0 wt% to 6.8 wt%; iv) the crystallization temperature measured by DSC, ranges from 82°C to 105°C;preferably from 84°C to 100°C; from 85°C to 99°C; v) the C¹³ NMR sequences PEP ranging from 4.0mol% to 5.8mol%; preferably from 4.2mol% to 5.7mol%; more preferably 4.5mol% to 5.5mol%

[0023] B) from 5.0 wt% to 30.0 wt%; preferably from 7.0 wt% to 28.0 wt%; more preferably from 13.0 wt% to 26 wt% of a copolymer of 1 -butene and ethylene containing from 3.0 wt% to 4.2 wt% preferably from 3.2 wt% to 4.0 wt%; more preferably from 3.3 wt% to 3.9 wt% of ethylene derived units; said copolymer of 1 -butene and ethylene having:

[0024] - a Melt Flow Rate: measured according to ISO 1133-2011 -(190 °C, 2.16 Kg) ranging from 1.0 to 5.5 g/10 min; preferably from 2.1 to 4.8 g/10 min; more preferably from 2.4 to 4.1 g/10 min;

[0025] Flexural modulus measured according to ISO 178 - 2010 ranging from 50 MPa to 250 MPa; preferably ranging from 80 MPa to 210 MPa; more preferably ranging from 92 MPa, to 174 MPa;

[0026] The melting temperature measured according to Iso 11357-2013 ranging from 83°C and 108 °C, preferably ranging from 84°C and 103 °C; more preferably ranging from 88°C and 100 °C, form I; the sum of the amounts of A) and B) being 100 wt%. [0027] The term "copolymer" as used in the present patent application refers to polymers containing only two comonomers such as propylene and ethylene or 1 -butene and ethylene or propylene and 1 -butene.

[0028] Preferably in the random propylene ethylene copolymer (A) of the present disclosure only one melting point is present at the DSC thermogram measured according to ISO 11357-3, at scanning rate of 20C/min.

[0029] Preferably in the random propylene ethylene copolymer (A) of the present disclosure, the relative content of isolated to block ethylene sequences 1(E) is higher than 60. 1 ; preferably higher than 65.0; more preferably higher than 68.0; even more preferably higher than 70.1;

[0030] wherein 1(E) is calculated with the following relation

[0031] I(E)= (PEP/[EEE+PEE+PEP])xl00;

Wherein 1(E) is the relative content of isolated to block ethylene sequences (%); PEP is the mol fraction of propylene/ethylene sequences in the sample; PEE is the mol fraction of propylene/ethylene sequences in the sample; EEE is the mol fraction of propylene/ethylene sequences in the sample and wherein all sequence concentrations being based on a statistical triad analysis of ¹³C-NMR data.

[0032] Preferably in the random propylene ethylene copolymer (A) of the present disclosure, the melting point, Tm and the ethylene content wt% C2, fulfills the following relation:

[0033] Tm<-5.8C2+167.0;

[0034] Preferably the relation is:

[0035] Tm<-5.8C2+166.2;

[0036] The 1(E) is the relative content of isolated to block ethylene sequences (%) and is an indication of the randomness of the polymer. For the present disclosure the term “random” is referred to a propylene ethylene copolymer having (IE) higher than 65.0 %.

[0037] Preferably in the random propylene ethylene copolymer (A) the 2, 1 insertion are not detectable at the ¹³C NMR spectra acquired on a Bruker AV-600 spectrometer equipped with cryoprobe, operating at 160.91 MHz as described in the examples.

[0038] The random propylene ethylene copolymer (A) does not contain propylene homopolymer fraction. [0039] Random Propylene ethylene copolymer (A) is preferably obtained with a process being carried out in a reactor having two interconnected polymerization zones, a riser and a downcomer, wherein the growing polymer particles:

(a) flow through the first of said polymerization zones, the riser, under fast fluidization conditions in the presence of propylene and of ethylene;

(b) leave the riser and enter the second of said polymerization zones, the downcomer, through which they flow downward in a densified form in the presence of propylene and of ethylene, wherein the concentration of ethylene in the downcomer is higher than in the riser;

(c) leave the downcomer and are reintroduced into the riser, thus establishing a circulation of polymer between the riser and the downcomer.

[0040] In the first polymerization zone (riser), fast fluidization conditions are established by feeding a gas mixture comprising one or more alpha-olefins at a velocity higher than the transport velocity of the polymer particles. The velocity of said gas mixture is generally comprised between 0.5 and 15 m/s, preferably between 0.8 and 5 m/s. The terms “transport velocity” and “fast fluidization conditions” are well known in the art; for a definition thereof, see, for example, "D. Geldart, Gas Fluidisation Technology, page 155 et seq., J. Wiley & Sons Ltd., 1986".

[0041] In the second polymerization zone (downcomer), the polymer particles flow under the action of gravity in a densified form, so that high values of density of the solid (mass of polymer per volume of reactor) are achieved, said density of solid approaching the bulk density of the polymer. Throughout the present description a "densified form" of the polymer implies that the ratio between the mass of polymer particles and the reactor volume is higher than 80% of the "poured bulk density" of the obtained polymer. The "poured bulk density" of a polymer is a parameter well known to the person skilled in the art. In view of the above, it is clear that in the downcomer the polymer flows downward in a plug flow and only small quantities of gas are entrained with the polymer particles.

[0042] The recycle gas stream is generally withdrawn from a gas/solid separator placed downstream the riser, cooled by passage through an external heat exchanger and then recycled to the bottom of the riser. Of course, the recycle gas stream comprises, besides the gaseous monomers, also the inert polymerization components, such as propane, and chain transfer agents, such as hydrogen. Moreover, the composition of the barrier stream deriving from condensation and/or distillation of the gas recycle stream may be suitably adjusted by feeding liquid make-up monomers and propane before its introduction into the upper part of downcomer.

The operating parameters of temperature and pressure are those that are usual in gas-phase catalytic polymerization processes. For example, in both riser and downcomer the temperature is generally comprised between 60°C and 120°C, while the pressure can range from 5 to 40 bar.

[0043] The process for preparing the propylene ethylene copolymer of the present disclosure is 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 co-catalyst and optionally an external electron-donor compound.

[0044] Suitable catalysts systems are described in the European patents EP45977, EP361494, EP728769, EP 1272533 and in the international patent application W000163261.

[0045] 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.

[0046] 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 Ra⁵Rb⁶Si(OR⁷)_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; R⁵, R⁶, and R⁷, 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.

[0047] Component B) is known in the art it is a 1 -butene ethylene copolymer commercially available, such as Koattro DP 8310M sold by LyondellBasell.

[0048] The polymer composition of the present disclosure can be prepared by mechanically blending component A) and component B) in accordance with processes well known in the art.

[0049] The polymer composition of the present disclosure can be advantageously used for the preparation of films, in particular cast and blow films.

[0050] Thus a further object of the present disclosure is a film comprising the polymer composition of the present disclosure in particular a further object of the present disclosure is a cast film or a blow film comprising the polymer composition of the present disclosure.

[0051] The polymer composition of the present disclosure can further contain additives used in the art.

[0052] The polymer composition of the present disclosure can be advantageously used as sealing layer in a multilayer film, it allows to seal the film at lower temperature.

The polymer composition of the present invention has a very low seal initiation temperature (SIT). The seal initiation temperature, measured as reported in the examples, fulfils the following relation (III):

SIT<SIT(A)+3.00* (-0.20* (CB * CB))+(0.43 * CB) (III)

Wherein SIT(A) is the value of the seal initiation temperature of component (A) alone; CB is the amount (wt%) of component B.

Preferably relation III is

SIT<SIT(A)+ 1.5 * (-0.20* (CB* CB))+(0.43 * CB) (III)

More preferably relation III is

SIT<SIT(A)+0.50*(-0.20*(CB*CB))+(0.43*CB) (III) The film obtained with the composition of the present disclosure show a reduced number of gels with respect to component (A) alone.

[0053] Preferably the polymer composition of the present disclosure consists essentially of components A) and B) as above described.

[0054] Wherein the term “consists essentially of’ means that specific further components can be present, namely those not materially affecting the essential characteristics of the compound or composition. In particular no further polymers in particular polyolefins are present in the composition.

[0055] The following examples are given to illustrate, not to limit, the present disclosure:

EXAMPLES

Xylene-soluble (XS) Fraction at 25 °C

[0056] Xylene Solubles at 25°C have been determined according to ISO 16 152; with solution volume of 250 ml, precipitation at 25°C for 20 minutes, 10 of which with the solution in agitation (magnetic stirrer), and drying at 70°C.

DSC method for melting temperature and crystallization temperature

[0057] Melting point has been measured according to ISO 11357-3, at scanning rate of 20C/min both in cooling and heating, on a sample of weight between 5 and 7 mg., under inert N2 flow. Instrument calibration made with indium

Melt Flow Rate (MFR)

[0058] Measured according to ISO 1133 at 230 °C with a load of 2.16 kg, unless otherwise specified.

Ethylene content in the copolymers

[0059] ¹³ C NMR spectra were acquired on a Bruker AV-600 spectrometer equipped with cry oprobe, operating at 160.91 MHz in the Fourier transform mode at 120 °C.

[0060] 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 an internal reference at 29.9 ppm. The samples were dissolved in 1 , 1 ,2,2-tetrachloroethane- d2 at 120 °C with a 8 % wt/v concentration. Each spectrum was acquired with a 90° pulse, and 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.

[0061] 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

[0062] The molar percentage of ethylene content was evaluated using the following equation: [0063] E% mol = 100 * [PEP+PEE+EEE], The weight percentage of ethylene content was evaluated using the following equation:

100 * E% mol * MWE

E% wt. = E% mol * MWE + P% mol * MWP

[0064] where P% mol is the molar percentage of propylene content, while MWE and MWP are the molecular weights of ethylene and propylene, respectively.

[0065] The content of isolated to block ethylene sequences 1(E) is calculated with the following relation:

[0066] I(E)= (PEP/[EEE+PEE+PEP])xl00;

[0067] The product of reactivity ratio rlr2 was calculated according to Carman (C.J. Carman,

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

[0068] 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). Determination of the regioinvertions: determined by means of C¹³-NMR according to the methodology described by J.C. Randall in "Polymer sequence determination Carbon 13 NMR method", Academic Press 1977. The content of regioinvertions is calculated on the basis of the relative concentration of S_ap + Spp methylene sequences.

Ethylene content in a 1-butene ethylene copolymer

[0069] The content of comonomers was determined by infrared spectroscopy by collecting the IR spectrum of the sample vs. an air background with a Fourier Transform Infrared spectrometer (FTIR). The instrument data acquisition parameters were:

■ purge time: 30 seconds minimum

■ collect time: 3 minutes minimum

■ apodization: Happ-Genzel

■ resolution: 2 cm’¹.

[0070] Sample Preparation - Using a hydraulic press, a thick sheet was obtained by compression molding about g 1 of sample between two aluminum foils. A small portion was cut from this sheet to mold a film. The film thickness was set in order to have a maximum absorbance of the CH2 absorption band recorded at -720 cm’¹ of 1.3 a.u. (% Transmittance > 5%). Molding conditions were 180±10°C (356°F) and pressure was around 10 kg/cm² (142.2 PSI) for about one minute. The pressure was then released, the sample removed from the press and cooled to room temperature. The spectrum of pressed film sample was recorded in absorbance vs. wavenumbers (cm’¹). The following measurements were used to calculate ethylene (C2) and 1-butene (C4) contents: a) Area (At) of the combination absorption bands between 4482 and 3950 cm’¹ which is used for spectrometric normalization of film thickness. b) Area (Ac2) of the absorption band due to methylenic sequences (CH2 rocking vibration) in the range 660 to 790 cm’¹ after a proper digital subtraction of an isotactic polypropylene (IPP) and a C2C4 references spectrum. c) The factor of subtraction (FCRc4) between the spectrum of the polymer sample and the C2C4 reference spectrum The reference spectrum is obtained by digital subtraction of a linear polyethylene from a C2C4 copolymer, in order to extract the C4 band (ethyl group at -771 cm-1). [0071] The ratio Ac2 / At is calibrated by analyzing ethylene- 1 -butene standard copolymers of known compositions, determined by NMR spectroscopy. In order to calculate the ethylene (C2) and 1 -butene (C4) content, calibration curves were obtained by using samples of known amount of ethylene and 1 -butene detected by ¹³C-NMR.

[0072] Calibration for ethylene - A calibration curve was obtained by plotting Ac2/At versus ethylene molar percent (%C2m), and the coefficient ac2, bc2 and cc2 then calculated from a “linear regression”.

[0073] Calibration for 1 -butene - A calibration curve was obtained by plotting FCRc At versus butane molar percent (%C4m) and the coefficients ac4, bc4 and Cc4 then calculated from a “linear regression”.

[0074] The spectra of the unknown samples are recorded and then (At), (Ac2) and (FCRc4) of the unknown sample are calculated.

[0075] The ethylene content (% molar fraction C2m) of the sample was calculated as follows:

[0076] The 1 -butene content (% molar fraction C4m) of the sample was calculated as follows: ac4, bc4, cc4 ac2, bc2, cc2 are the coefficients of the two calibrations.

Changes from mol% to wt% are calculated by using molecular weights.

Seal Initiation Temperature (SIT)

Preparation of the BOPP film specimens

[0077] Some films with a thickness of 50 pm are prepared by extruding each test composition in a 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 do 210-250 °C. Each resulting film is superimposed on a 1000 pm thick film of a propylene homopolymer having a xylene insoluble fraction of 97 wt% and a MFR L of 2 g/10 min. The superimposed films are bonded to each other in a Carver press at 200°C under a 9000 kg load, which is maintained for 5 minutes. The resulting laminates are stretched longitudinally and transversally, i.e. biaxially, by a factor 7 with a Karo 4 Brueckener film stretcher at 160°C, thus obtaining a 20 pm thick film (18 pm homopolymer+2 pm test).

Determination of the SIT

[0078] 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.

[0079] The test is than repeated by changing the temperature as follows:

• If seal strength <1.5 N then increase the temperature

• If seal strength >1.5 N then decrease the temperature

• 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.

• 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.

The gels count test

[0080] The gels count test has been carried out on a cast film Collin Extrusion line diameter with a 25 mm single screw with the following features:

Single screw L/D 25

Temperature profile

Cylinders 200 (close to the hopper) -> 230°C (at the end of the extruder, before the inlet to the die) Die 240°C

Die width 150 mm

Chill roll 30°C

Film speed 3.0 m/min

Film thickness 50 micron

Inspected area 1 m2

CS FS5 gel count unit on a 4 cm wide stripe

[0081] Component A

Preparation of the Ziegler-Natta solid catalyst component

[0082] The Ziegler-Natta catalyst was prepared according to Example 5, lines 48-55, of the European Patent EP728769B 1.

Preparation of the catalyst system - Precontact

[0083] Before introducing it into the polymerization reactors, the solid catalyst component described above is contacted with aluminum-triethyl (TEAL) and with the dicyclopentyldimethoxysilane (D donor) under the conditions reported in Table 1.

Prepolymerization

[0084] The catalyst system is then subject to prepolymerization treatment at 20°C by maintaining it in suspension in liquid propylene for a residence time of 9 minutes before introducing it into the polymerization reactor.

Polymerization

[0085] The polymerization was carried out in gas-phase polymerization reactor comprising two interconnected polymerization zones, a riser and a downcomer, as described in European Patent EP782587. Hydrogen was used as molecular weight regulator. The polymer particles exiting from the polymerization step were subjected to a steam treatment to remove the unreacted monomers and dried under a nitrogen flow.

[0086] The main precontact, prepolymerization and polymerization conditions and the quantities of monomers and hydrogen fed to the polymerization reactor are reported in Table 1. Table 1

H2=hydrogen; C2- = ethylene, C3-= propylene

[0087] The features of the polymers obtained according to the above process are reported in Table 2.

Table 2

Nd=not detectable

[0088] Component B is a commercial product sold by Lyondelbasell under the tradename Koattro DP 8310M.

[0089] The features of component B are reported on table 3.

Table 3

[0090] Various amount of component B) have been blended with components A). A cast has been produced by the compositions. The seal initiation temperature has been measured. Table 3 reports the SIT for each sample. The cast film thickness was 50 micron. Table 4

* comparative

[0091] The number of Gel the obtained films are measured and the results are reported on table 5

Table 5

Table 5 cont.

* comparative

From table 5 it is clear that there is reduction of gel numbers when the composition of the present invention is used vs component A) alone

Claims

CLAIMS What is claimed is:

1. A polymer composition comprising:

A) from 70 wt% to 95 wt% of a random propylene ethylene copolymer having: i) xylene soluble fraction at 25°C ranging from 10 wt% to 16 wt%; ii) melt flow rate, MFR, measured according to ISO 1133 at 230 °C with a load of 2.16 kg, ranging from 1.0 g/10 min to 12.0 g/10 min; iii) an ethylene derived units content, measured by ¹³C NMR, ranging from 3.2 wt% and 7.8 wt%; iv) the crystallization temperature measured by DSC, ranges from 82°C to 105°C; v) the C¹³ NMR sequences PEP ranging from 4.0mol% to 5.8mol%;

B) from 5.0 wt% to 30.0 wt% of a copolymer of 1 -butene and ethylene containing from 3.0 wt% to 4.2 wt% of ethylene derived units; said copolymer of 1 -butene and ethylene having: a Melt Flow Rate: measured according to ISO 1133-2011 -(190 °C, 2.16 Kg) ranging from 1.0 to 5.5 g/10 min; flexural modulus measured according to ISO 178 ranging from 80 MPa to 250 MPa; the melting temperature measured according to Iso 11357-2013 ranging from 83°C and 108 °C, form I; the sum of the amounts of A) and B) being 100 wt%.

2. The polymer composition according to claim 1 wherein one melting point is present at the DSC thermogram measured according to ISO 11357-3, at scanning rate of 20°C/min.

3. The polymer composition according to claims 1 or 2 wherein in component A): the ethylene derived units content measured by ¹³C NMR ranges 3.5 wt% to 7.3 wt%.

4. The polymer composition according to anyone of claims 1-3 wherein the 1 -butene ethylene copolymer component B) contains from 3.2 wt% to 4.0 wt% of ethylene derived units.

5. The polymer composition according to anyone of claims 1-4 wherein in component B) the Melt Flow Rate: measured according to ISO 1133-2011 -(190 °C, 2.16 Kg) ranges from 2.1 to 4.8 g/10 min.

6. The polymer composition according to anyone of claims 1-5 wherein component A ranges from 72.0 wt% to 93.0 wt%; and component B) ranges from 7.0 wt% to 28.0 wt%.

7. The polymer composition according to anyone of claims 1-6 wherein in component A) the crystallization temperature measured by DSC, ranges from 84°C to 100°C.

8. The polymer composition according to anyone of claims 1-7 wherein in component A) the relative content of isolated to block ethylene sequences 1(E) is higher than 60.1 ; wherein 1(E) is calculated with the following relation

I(E)= (PEP/[EEE+PEE+PEP])xlOO; wherein 1(E) is the relative content of isolated to block ethylene sequences (%); PEP is the mol fraction of propylene/ethylene sequences in the sample; PEE is the mol fraction of propylene/ethylene sequences in the sample; EEE is the mol fraction of propylene/ethylene sequences in the sample and wherein all sequence concentrations being based on a statistical triad analysis of ¹³C-NMR data.

9. The polymer composition according to anyone of claims 1-8 wherein in component A) Tm and the ethylene content wt% C2, fulfills the following relation:

Tm<-5.8C2+167.0.

10. The polymer composition according to anyone of claims 1-3 wherein the 1 -butene ethylene copolymer component B) contains from 3.3 wt% to 3.9 wt% of ethylene derived units.

11. The polymer composition according to anyone of claims 1-10 wherein component B) has the melting temperature measured according to Iso 11357-2013 ranging from 84°C and 103 °C, form I.

12. The polymer composition according to anyone of claims 1-11 wherein component B) has flexural modulus measured according to ISO 178 - 2010 ranging from 80 MPa to 210 MPa.

13. The polymer composition according to anyone of claims 1-10 wherein component A)) has the C¹³ NMR sequences PEP ranging from 4.2mol% to 5.7mol%.

14. A film comprising the the polymer composition of claims 1-13.

15. A cast or BOPP film according to claim 14 comprising the the polymer composition of claims 1-13.