Propylene homopolymers

Abstract

A propylene homopolymer, optionally containing up to 1.0% by weight of ethylene derived units, characterized in that: two melting points are present-the higher melting point ranges from 155 DEG C to 170 DEG C; -the fraction soluble in xylene at 25 DEG C is comprised between 6.0 wt% and 2.0 wt%; -an isotactic quintuple (mmmm%) in the range of from 96.5 mol% to 90.0 mol%; -an intrinsic viscosity (IV), measured in tetrahydronaphthalene at 135 DEG C, in the range of 5.5 dl / g to 12.0 dl / g; -the melt strength is higher than 0.70 N.

Description

Technical Field

[0001] The present disclosure relates to polypropylene homopolymers having high molecular weight and high melt strength. Background Art

[0002] Propylene homopolymer is widely used in injection molding, extrusion, casting and biaxial stretching due to its adjustable structure. However, the common polypropylene molecular chain is a linear structure, which is different from amorphous polymers, such as polystyrene PS, which has a region similar to rubber elasticity in a wide temperature range. Therefore, polypropylene cannot be thermoformed in a wide temperature range. At the same time, the softening point of polypropylene is close to its melting point. When the temperature is higher than the melting point, the melt strength and melt viscosity of polypropylene will drop rapidly, resulting in the following problems: uneven product wall thickness during thermoforming, curling and shrinkage during extrusion, coating and rolling, and foam collapse during extrusion foaming. Therefore, the application of polypropylene in thermoforming, foaming and blow molding is limited. Therefore, the development of polypropylene with high melt strength has always been an interesting issue. Therefore, it is necessary to develop a propylene homopolymer for blends to improve the melt strength of more traditional propylene polymers. Summary of the invention

[0003] The present disclosure relates to a propylene homopolymer optionally containing up to 1.0 wt% of ethylene derived units characterized by:

[0004] - the presence of two melting points in the DSC thermogram measured according to ISO 11357-3 at a heating and cooling rate of 20°C / min;

[0005] - the higher melting point range is 155°C to 170°C measured according to ISO 11357-3 at a heating and cooling rate of 20°C / min;

[0006] - the fraction soluble in xylene at 25° C., measured according to ISO 16 152-2005, is comprised between 6.0% and 2.0% by weight;

[0007] - As reported in the Examples section using C 13 The isotactic pentad mmmm% measured by NMR ranged from 96.5 mol% to 90.0 mol%;

[0008] - an intrinsic viscosity (IV) ranging from 5.5 dl / g to 12.0 dl / g measured in tetralin at 135°C;

[0009] - According to ISO 16790-2005, at 250°C, applied at 6 mm / s 2 The melt strength measured by the acceleration is higher than 0.070N. DETAILED DESCRIPTION

[0010] The present disclosure relates to a propylene homopolymer optionally containing up to 1.0 wt% ethylene, preferably up to 0.6 wt% ethylene derived units characterized by:

[0011] - the presence of two melting points in the DSC thermogram measured according to ISO 11357-3 at a heating and cooling rate of 20°C / min; preferably the lower melting point ranges from 135°C to 150°C;

[0012] - the higher melting point ranges from 155°C to 170°C, measured according to ISO 11357-3 at a heating and cooling rate of 20°C / min; preferably from 157°C to 168°C;

[0013] - the fraction soluble in xylene at 25° C., measured according to ISO 16 152-2005, is comprised between 6.0% and 2.0% by weight; preferably comprised between 5.0% and 2.5% by weight; more preferably comprised between 4.0% and 2.8% by weight;

[0014] - As reported in the Examples section using C 13 The isotactic pentad (mmmm%) measured by NMR ranges from 96.5 mol% to 90.0 mol%; preferably from 96.0 mol% to 93.0 mol%; more preferably from 95.5 mol% to 93.5 mol%;

[0015] - an intrinsic viscosity (IV) measured in tetralin at 135°C in the range of 5.5 dl / g to 12.0 dl / g; preferably 7.0 dl / g to 11.0 dl / g; more preferably 8.0 dl / g to 10.0 dl / g;

[0016] - According to ISO 16790-2005, at 250°C, applied at 6 mm / s 2 The melt strength measured by the acceleration is higher than 0.070N; preferably higher than 0.080N; more preferably higher than 0.090N.

[0017] Preferably, the propylene homopolymers of the present disclosure are not nucleated.

[0018] Preferably, the homopolymers of the present disclosure have a melt strength value below 0.30N.

[0019] Preferably, the polydispersity index PI of the homopolymers of the present disclosure, measured according to ISO 6721-10, is comprised between 4.5 and 7.5; more preferably between 5.0 and 7.2; more preferably between 5.5 and 6.5.

[0020] Preferably, the tensile modulus of the homopolymers of the present disclosure ranges from 2100 MPa to 1100 MPa; preferably from 1800 MPa to 1200 MPa.

[0021] Preferably, the homopolymers of the present disclosure exhibit a Charpy impact test at 23°C in the range of 4.0 kJ / m2 to 11.0 kJ / m2; preferably 5.5 kJ / m2 to 9.0 kJ / m2.

[0022] If present, ethylene derived units were measured using 13C-NMR as reported in the Examples section.

[0023] The polypropylene homopolymer disclosed in the present invention is characterized by high melt strength and high molecular weight. Therefore, the homopolymer disclosed in the present invention can be blended with other polymers with lower melt strength to improve the melt strength of the latter, so that the obtained blend can be used to produce foam products, biaxially oriented films, thermoformed products and blow molded products.

[0024] Propylene homopolymer disclosed herein can be prepared by the following process, which includes polymerization of propylene and ethylene (optionally) in the presence of a Ziegler-Natta catalyst. An essential component of the catalyst is a solid catalyst component, which includes a titanium compound having at least one titanium-halogen bond and an electron donor compound, both of which are supported on a magnesium halide in an active form. Another essential component (cocatalyst) is an organoaluminum compound, such as an alkyl aluminum compound. An external donor is optionally added.

[0025] Catalysts having the above characteristics are well known in the patent literature; particularly advantageous are the catalysts described in US Pat. No. 4,399,054 and European Patent No. 45977. Other examples can be found in US Pat. No. 4,472,524.

[0026] The solid catalyst component used in the catalyst comprises as an electron donor (internal donor) a compound selected from the group consisting of ethers, ketones, lactones, compounds containing N, P and / or S atoms, and esters of mono- and dicarboxylic acids.

[0027] Particularly suitable electron donor compounds are esters of phthalic acid and 1,3-diethers of the following formula:

[0028]

[0029] wherein RI and RII are identical or different and are C1-C18 alkyl, C3-C18 cycloalkyl or C7-C18 aryl radicals; RIII and RIV are identical or different and are C1-C4 alkyl radicals; or is a 1,3-diether, wherein the carbon atom at position 2 belongs to a cyclic or polycyclic structure consisting of 5, 6 or 7 carbon atoms or 5-n or 6-n' carbon atoms and n nitrogen atoms and n' heteroatoms selected from the group consisting of N, O, S and Si, respectively, wherein n is 1 or 2 and n' is 1, 2 or 3, said structure containing two or three degrees of unsaturation (cyclic polycyclic structure); alkyl radicals) and optionally condensed with other cyclic structures, or substituted by one or more substituents selected from the group consisting of: straight or branched alkyl radicals, cycloalkyl radicals, aryl, aralkyl, alkaryl radicals and halogens, or condensed with other cyclic structures and substituted by one or more of the above substituents, one or more of which may also be bonded to the condensed cyclic structure; a condensed cyclic structure of one or more of the above alkyl, cycloalkyl, aryl, aralkyl or alkaryl radicals and optionally containing one or more heteroatoms as substituents of carbon atoms or hydrogen atoms or both.

[0030] Ethers of this type are described in published European Patent Applications 361,493 and 728,769.

[0031] Representative examples of the diethers are 2-methyl-2-isopropyl-1,3-dimethoxypropane, 2,2-diisobutyl-1,3-dimethoxypropane, 2-isopropyl-2-cyclopentyl-1,3-dimethoxypropane, 2-isopropyl-2-isopentyl-1,3-dimethoxypropane, 9,9-bis(methoxymethyl)fluorene.

[0032] Other suitable electron donor compounds are phthalic acid esters, such as diisobutyl phthalate, dioctyl phthalate, diphenyl phthalate and benzyl butyl phthalate.

[0033] The preparation of the above-mentioned catalyst components is performed according to various methods.

[0034] For example, MgCl2.nROH adduct (especially in the form of spherical particles) (where n is generally from 1 to 3 and ROH is ethanol, butanol or isobutanol) is reacted with an excess of TiCl4 containing an electron donor compound. The reaction temperature is generally 80° C. to 120° C. The solid is then separated and reacted once more with TiCl4 in the presence or absence of an electron donor compound, after which it is separated and washed with an aliquot of a hydrocarbon until all chloride ions are gone.

[0035] In the solid catalyst component, the titanium compound, denoted Ti, is generally present in an amount of 0.5 to 10% by weight. The amount of electron donor compound remaining fixed on the solid catalyst component is generally 5 to 20 mol% relative to the magnesium dihalide.

[0036] Titanium compounds which can be used for the preparation of the solid catalyst component are titanium halides and halogen alcoholates. Titanium tetrachloride is the preferred compound.

[0037] The above reactions form magnesium halides in active form. Other reactions are known in the literature which, starting from magnesium compounds other than halides, such as magnesium carboxylates, form magnesium halides in active form.

[0038] Al-alkyl compounds used as co-catalysts include Al-trialkyls such as Al-triethyl, Al-triisobutyl, Al-tri-n-butyl and linear or cyclic Al-alkyl compounds containing two or more Al atoms bonded to each other via O or N atoms or SO4 or SO3 groups.

[0039] The Al-alkyl compound is generally used in such an amount that the Al / Ti ratio is 1 to 1000.

[0040] Electron donor compounds that can be used as external donors include aromatic acid esters, such as alkyl benzoates, and in particular silicon compounds containing at least one Si-OR bond, wherein R is a hydrocarbon radical.

[0041] Examples of silicon compounds are (tert-butyl)2Si(OCH3)2, (cyclohexyl)(methyl)Si(OCH3)2, (cyclopentyl)2Si(OCH3)2 and (phenyl)2Si(OCH3)2 and (1,1,2-trimethylpropyl)Si(OCH3)3.

[0042] 1,3-Diethers of the abovementioned formula can also be used advantageously. If the internal donor is one of these diethers, the external donor can be omitted.

[0043] In particular, component A) is preferably prepared by using a catalyst containing a phthalate as internal donor and (cyclopentyl)2Si(OCH3)2 as external donor, or the 1,3-diether as internal donor, even though many other combinations of the aforementioned catalyst components may allow obtaining the composition according to the invention.

[0044] The polymerization is usually carried out at a temperature of from 20°C to 120°C, preferably from 40°C to 80°C. When the polymerization is carried out in the gas phase, the operating pressure is usually between 0.5MPa and 5MPa, preferably between 1MPa and 4MPa. In bulk polymerization, the operating pressure is usually 1MPa to 8MPa, preferably 1.5MPa to 5MPa. Hydrogen is usually used as a molecular weight regulator. The polymerization can be carried out in the gas phase, slurry or solution. In one or more reactors. Preferably, the polymerization is carried out in two slurry reactors operated in series.

[0045] The propylene homopolymers of the present disclosure, optionally containing up to 1.0 wt.% of ethylene-derived units, can be used to obtain fibers, films, molded articles and foamed articles.

[0046] The following examples are given to illustrate but not to limit the present disclosure.

[0047] Example

[0048] Characterization

[0049] Insoluble and soluble fractions in xylene at 25°C

[0050] The xylene soluble fraction was measured according to ISO 16 152-2005; the solution volume was 250 ml, sedimentation was carried out for 20 minutes at 25°C, of ​​which 10 minutes the solution was stirred (magnetic stirrer), and drying was carried out at 70°C.

[0051] Melt flow rate (MFR)

[0052] Unless otherwise stated, measurements were made according to ISO 1133 at 230°C and a load of 21.6 kg.

[0053] Polydispersity Index (PI)

[0054] According to ISO 6721-10, a few grams of molten homopolymer are dynamically tested in a rate sweep at a temperature of 200°C with a parallel plate rheometer. G' (storage modulus) and G" (loss modulus) are measured as a function of frequency. From the rate sweep data, PI is defined by PI = 105 / Gc, where Gc is the crossover modulus as the modulus value at G' = G".

[0055] Melting temperature was determined by differential scanning calorimetry (DSC).

[0056] The melting point (Tm) of the polymers was measured by differential scanning calorimetry (DSC) at a measurement rate of 20°C / min on a PerkinElmer DSC-1 calorimeter that had been previously calibrated to the melting point of indium and complies with ISO 11357-1, 2009 and ISO 11357-3, 2011. The sample weight in each DSC crucible was maintained at 6.0 mg ± 0.5 mg.

[0057] To obtain the melting point, the weighed sample was sealed into an aluminum pan and heated to 200°C at a rate of 20°C / min. The sample was kept at 200°C for 2 minutes to allow all crystallites to melt completely, and then cooled to 5°C at a rate of 20°C / min. After standing at 5°C for 2 minutes, the sample was heated to 200°C for a second time at a rate of 20°C / min. In this second heating run, the peak temperature (Tp,m) was taken as the melting temperature.

[0058] Homopolymers and propylene / ethylene copolymers 13 C NMR

[0059] 13 C NMR spectra were obtained on a Bruker Av-600 spectrometer equipped with a cryoprobe, operating at 160.91 MHz in Fourier transform mode at 120 °C.

[0060] At 29.9ppm S ββ The peak of carbon (according to the nomenclature of "Monomer sequence distribution in ethylene-propylene rubber measured by 13C NMR. 3. Use of reaction probability models" CJ Carman, RA Harrington and CE Wilkes, Macromolecules, 1977, 10, 536) was used as an internal reference. The sample was dissolved in 1,1,2,2-tetrachloroethane-d2 at 8% wt / v concentration at 120°C. Each spectrum was collected with a 90° pulse, with a delay of 15 seconds between the pulse and CPD to remove 1H-13C coupling. 512 transients were stored in 32K data points using a spectral window of 9000 Hz.

[0061] Evaluation of spectral assignments, triplet distribution, and composition was performed according to Kakugo ("Carbon-13 NMR determination of monomer sequence distribution in ethylene-propylene copolymers prepared with δ-titanium trichloride-diethylaluminum chloride" M. Kakugo, Y. Naito, K. Mizunuma, and T. Miyatake, Macromolecules, 1982, 15, 1150) using the following equation:

[0062] PPP=100T ββ / S PPE=100T βδ / S EPE=100T δδ / S

[0063] PEP=100s ββ / S PEE=100S βδ / S EEE=100(0.25S γδ +0.5S δδ ) / S

[0064] S=T ββ +T βδ +T δδ +S ββ +S βδ +0.25S γδ +0.5S δδ

[0065] The mole percentage of ethylene content was estimated using the following equation:

[0066] E mol% = 100*[PEP+PEE+EEE]

[0067] The weight percent ethylene content was estimated using the following equation:

[0068]

[0069] Where P mol% is the molar percentage of propylene content, and MW E and MW P are the molecular weights of ethylene and propylene respectively.

[0070] The product of the reactivity ratios r1r2 is calculated according to Carman (CJ Carman, RA Harrington and CE Wilkes, Macromolecules, 1977; 10, 536):

[0071]

[0072] The stereoregularity of the propylene sequence is determined by PPP mmT ββ (28.90ppm to 29.65ppm) and total T ββ The ratio of (29.80 ppm to 28.37 ppm) was calculated as the mm content.

[0073] Intrinsic viscosity

[0074] The sample is dissolved in tetralin at 135°C and poured into a capillary viscometer. The viscometer tube (Ubbelohde type) is surrounded by a cylindrical glass jacket; this setup allows temperature control with a circulating thermostatic liquid. The descent of the meniscus is timed by a photoelectric device. The passage of the meniscus in front of the upper lamp starts a counter with a quartz crystal oscillator. When the meniscus passes the lower lamp, the counter stops and the outflow time is recorded: Assuming that the flow time of the pure solvent is known under the same experimental conditions (same viscometer and same temperature), it can be converted into an intrinsic viscosity value by the Huggins equation. A single polymer solution was used to determine [IV].

[0075] Melt Strength

[0076] Melt strength is measured according to ISO 16790-2005 by a traction melt strength tester produced by Geottfert Werkstoff Pruefmaschinen, Germany. The system measures the tensile properties of polymer melts by stretching a vertical melt beam at a constant stretching speed or linear or exponential acceleration. The traction system measures the force required to stretch the melt beam and calculates the tensile stress, stretch ratio, apparent stretch rate and viscosity. The polymer is melted and plasticized by a capillary rheometer and then extruded from a hole die with a diameter of 1 mm, a length of 30 mm and an inlet angle of 180°. The test was carried out at 250°C. The distance from the capillary outlet to the center of the sensor pulley is 150 mm. At each temperature test, a force equal to 6 mm / s was applied. 2 The filament is stretched with an acceleration of 1.5° and its tension is measured by an angle sensor. In addition to the entire curve, the stretch ratio (dimensionless value) and the force (cN) value are recorded as the final result. The value of the melt strength is the maximum force value of the curve.

[0077] Charpy impact test

[0078] Charpy impact test on compression specimens according to ISO 179-1eA, e ISO 1873-2

[0079] Tensile modulus

[0080] Tensile modulus measurements on compression samples according to ISO 527-2 and ISO 1873-2

[0081] Example 1 - Preparation of Homopolymer

[0082] Steps for preparing the solid catalyst component

[0083] The solid catalyst used in the following examples was prepared according to Example 10 of International Patent Application WO 00 / 63261. Triethylaluminium (TEAL) was used as cocatalyst and dicyclopentyldimethoxysilane as external donor in the weight ratios shown in Table 1.

[0084] polymerization

[0085] The polymerization operation is carried out in a series of two reactors in a continuous mode, which are equipped with means for transferring the product from one reactor to the one immediately adjacent thereto. Both reactors are liquid phase loop reactors. Propylene is the main solvent and hydrogen is used as molecular weight regulator. The gas phase is continuously analyzed by gas chromatography.

[0086] At the end of the run, the powder was discharged and dried under a stream of nitrogen. The main polymerization conditions and the properties of the polymers are reported in Tables 1 and 2.

[0087] Table 1 - Polymerization conditions

[0088]

[0089]

[0090] The characteristics of the polymers of Example 1 and Comparative Example 2 are reported in Table 2

[0091] Table 2

[0092] Example 1 Comparative Example MFR g / 10min 1.1 46 IV dl / g 9.4 3.4 XS wt% 3.2 4.6 mmmm mol% 94.8 92.8 Polydispersity index, PI 6.0 4.4 Tensile modulus MPa 1400 1460 Charpy impact test at 23°C <![CDATA[kJ / m 2 ]]> 6.9 5.3 Melt Strength N 0.110 0.030 Tm 1 ℃ 164 157 Tm 2 ℃ 148

[0093] Comparative Example 2 was HP556E, a propylene homopolymer sold by LyondellBasell.

Claims

1. A propylene homopolymer optionally containing up to 1.0 wt.% ethylene derived units, wherein the ethylene derived units are characterized by: - the presence of two melting points in the DSC thermogram measured according to ISO 11357-3 at a heating and cooling rate of 20°C / min; - the higher melting point range is 155°C to 170°C measured according to ISO 11357-3 at a heating and cooling rate of 20°C / min; - the fraction soluble in xylene at 25° C., measured according to ISO 16 152-2005, is comprised between 6.0% and 2.0% by weight; - as reported in the Examples section of the specification using C 13 The isotactic pentad mmmm% measured by NMR ranged from 96.5 mol% to 90.0 mol%; - an intrinsic viscosity (IV) ranging from 5.5 dl / g to 12.0 dl / g measured in tetralin at 135°C; - According to ISO 16790-2005, at 250°C, applied at 6 mm / s 2 The melt strength measured by the acceleration is higher than 0.070N.

2. The propylene homopolymer according to claim 1, wherein there are two melting points in the DSC thermogram measured according to ISO 11357-3 at a heating and cooling rate of 20°C / min; and the lower melting point ranges from 135°C to 150°C.

3. The propylene homopolymer according to claim 1 or 2, wherein the higher melting point ranges from 157°C to 168°C measured according to ISO 11357-3 at a heating and cooling rate of 20°C / min.

4. Propylene homopolymer according to any of claims 1 to 3, wherein the fraction soluble in xylene at 25°C measured according to ISO 16 152-2005 is comprised between 5.0 wt.-% and 2.5 wt.-%.

5. Propylene homopolymer according to any of claims 1 to 4, wherein the fraction soluble in xylene at 25°C measured according to ISO 16 152-2005 is comprised between 4.0 wt.-% and 2.8 wt.-%.

6. The propylene homopolymer according to any one of claims 1 to 5, wherein C 13 The isotactic pentad mmmm% measured by NMR ranged from 96.0 mol% to 93.0 mol%.

7. The propylene homopolymer according to any one of claims 1 to 6, wherein C 13 The isotactic pentad mmmm% measured by NMR ranged from 95.5 mol% to 93.5 mol%.

8. The propylene homopolymer according to any one of claims 1 to 7, wherein the intrinsic viscosity (IV) measured in tetralin at 135°C is in the range of 7.0 dl / g to 11.0 dl / g.

9. The propylene homopolymer according to any one of claims 1 to 8, wherein the intrinsic viscosity (IV) measured in tetralin at 135°C is in the range of 8.0 to 10.0 dl / g.

10. The propylene homopolymer according to any one of claims 1 to 9, wherein a speed of 6 mm / s at 250°C is applied according to ISO 16790-2005. 2 The melt strength measured by the acceleration is higher than 0.080N.

11. The propylene homopolymer according to any one of claims 1 to 10, wherein the propylene homopolymer has a strength of 6 mm / s at 250°C according to ISO 16790-2005. 2 The melt strength measured by the acceleration is higher than 0.090N.

12. Propylene homopolymer according to any one of claims 1 to 11, wherein the polydispersity index PI of the homopolymer measured according to ISO 6721-10 is comprised between 4.5 and 7.

5.

13. The propylene homopolymer according to any one of claims 1 to 12 is not nucleated.

14. Fibers, films, molded articles or foamed articles comprising the propylene homopolymer according to claims 1 to 13.

15. Foamed article comprising the propylene homopolymer according to claims 1 to 13.

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