FILLED POLYPROPYLENE (PP) COMPOSITIONS WITH IMPROVED THERMO-MECHANICAL PROPERTIES

Abstract

The present application relates to a polypropylene (PP) composition comprising a) 50.0 to 95.0 wt.-%, based on the total weight of the polypropylene (PP) composition, of a polypropylene (PP) homopolymer being polymerized in the presence of a single-site catalyst and b) 5.0 to 50.0 wt.-%, based on the total weight of the polypropylene (PP) composition, of a mineral filler, to an article comprising the polypropylene (PP) composition as well as the use of the polypropylene (PP) composition for improving the thermo-mechanical properties.

Claims

1. Polypropylene (PP) composition comprising a) 50.0 to 95.0 wt.-%, based on the total weight of the polypropylene (PP) composition, of a polypropylene (PP) homopolymer being polymerized in the presence of a single-site catalyst and having i) a melt flow rate MFR.sub.2 (230 C.) measured according to ISO 1133 in the range of 1 to 200 g/10 min, and ii) a melting temperature (T.sub.m) measured by differential scanning calorimetry (DSC) of 153 C., and b) 5.0 to 50.0 wt.-%, based on the total weight of the polypropylene (PP) composition, of a mineral filler.

2. The polypropylene (PP) composition according to claim 1, wherein the polypropylene (PP) homopolymer is unimodal and/or has a molecular weight distribution Mw/Mn measured according to ISO 16014 in the range of 1.5 to 4.5, preferably in the range from 2.0 to 4.0, and more preferably in the range from 2.5 to 4.0.

3. The polypropylene (PP) composition according to claim 1 or 2, wherein the polypropylene (PP) homopolymer has a) a melt flow rate MFR.sub.2 (230 C.) measured according to ISO 1133 in the range of 2 to 100 g/10 min, preferably from 2.2 to 50 g/10 min, and/or b) a melting temperature (T.sub.m) measured by differential scanning calorimetry (DSC) in the range from 153 to 165 C., preferably in the range from 153 to 163 C., and/or c) a heat deflection temperature HDT B measured in accordance with ISO 75 at a load of 0.46 MPa of at least 90 C., preferably in the range from 90 to 100 C.

4. The polypropylene (PP) composition according to any one of the preceding claims, wherein the polypropylene (PP) homopolymer has a) a xylene cold soluble fraction (XCS) determined at 23 C. according ISO 16152 of equal or below 2.0 wt.-%, and/or b) a weight average molecular weight (Mw) measured according to ISO 16014 in the range from 80 to 500 kg/mol, and/or c) an isotactic triad fraction (mm) determined from .sup.13C-NMR spectroscopy of at least 98.0%, and/or d) a content of <2,1> erythro regiodefects as determined from .sup.13C-NMR spectroscopy in the range from 0.10 to 1.00 mol.-%.

5. The polypropylene (PP) composition according to any one of the preceding claims, wherein the polypropylene (PP) homopolymer has a flexural modulus measured according to ISO 178 of at least 1300 MPa, preferably in the range from 1300 to 2200 MPa.

6. The polypropylene (PP) composition according to any one of the preceding claims, wherein the mineral filler is an anisotropic mineral filler, preferably a mineral filler selected from the group comprising talc, wollastonite, mica, montmorillonite, magnesium sulfate, magnesium hydroxide, halloysite and mixtures thereof.

7. The polypropylene (PP) composition according to any one of the preceding claims, wherein the mineral filler has a particle size d.sub.50 in the range from 0.1 to 10 m, preferably in the range from 0.2 to 6.0 m, more preferably in the range from 0.3 to 4.0 m.

8. The polypropylene (PP) composition according to any one of the preceding claims, wherein the polypropylene (PP) composition further comprises a nucleating agent in an amount in the range from 0.002 to 1.5 wt.-%, based on the total weight of the polypropylene (PP) composition.

9. The polypropylene (PP) composition according to claim 8, wherein the nucleating agent is a -nucleating agent, preferably a phosphate-based -nucleating agent.

10. The polypropylene (PP) composition according to any one of the preceding claims, wherein the polypropylene (PP) composition has a) a melt flow rate MFR.sub.2 (230 C., 2.16 kg) measured according to ISO 1133 in the range from 0.5 to 175 g/10 min, more preferably in the range from 1.0 to 90 g/10 min, like in the range from 2.0 to 45 g/10 min, and/or b) a melting temperature (T.sub.m) measured by differential scanning calorimetry (DSC) in the range from 154 to 165 C., preferably in the range from 155 to 163 C., and/or c) a crystallization temperature (T.sub.c) measured by differential scanning calorimetry (DSC) in the range from 120 to 135 C., preferably in the range from 122 to 132 C., and/or d) a flexural modulus measured according to ISO 178 in the range from 2700 to 6500 MPa, preferably in the range from 2750 to 6000 MPa, and/or e) a heat deflection temperature (HDT) measured according to ISO 75 A at a load of 1.8 MPa in the range of 76 to 95 C., more preferably in the range from 77 to 92 C.

11. The polypropylene (PP) composition according to any one of the preceding claims, wherein the polypropylene (PP) composition has a ratio of melting temperature (T.sub.m) measured by differential scanning calorimetry (DSC) to heat deflection temperature (HDT) measured according to ISO 75 A [Tm/HDT] of 2.0.

12. Article comprising the polypropylene (PP) composition according to any one of the preceding claims.

13. The article according to claim 12, wherein the article is an automotive interior article.

14. Use of a polypropylene (PP) composition as defined in any one of claims 1 to 11 for improving the thermo-mechanical properties, wherein the improvement is achieved if the polypropylene (PP) composition has a ratio of melting temperature (T.sub.m) measured by differential scanning calorimetry (DSC) to heat deflection temperature (HDT) measured according to ISO 75 A [Tm/HDT] of 2.0.

Description

EXAMPLES

1. Definitions/Measuring Methods

[0234] The following definitions of terms and determination methods apply for the above general description of the invention as well as to the below examples unless otherwise defined.

[0235] Melting temperature Tm was measured according to ISO 11357-3.

[0236] MFR.sub.2 (230 C.) was measured according to ISO 1133 (230 C., 2.16 kg load).

[0237] MFR.sub.2 (190 C.) was measured according to ISO 1133 (190 C., 2.16 kg load).

[0238] The xylene cold solubles (XCS, wt.-%) were determined at 25 C. according to ISO 16152; first edition; 2005-07-01.

[0239] Intrinsic viscosity is measured according to DIN ISO 1628/1, October 1999 (in Decalin at 135 C.).

Quantification of Microstructure by NMR Spectroscopy

[0240] Quantitative nuclear-magnetic resonance (NMR) spectroscopy was used to quantify the comonomer content of the polymers. Quantitative .sup.13C {.sup.1H} NMR spectra were recorded in the solution-state using a Bruker Advance III 400 NMR spectrometer operating at 400.15 and 100.62 MHz for .sup.1H and .sup.13C respectively. All spectra were recorded using a .sup.13C optimised 10 mm extended temperature probehead at 125 C. using nitrogen gas for all pneumatics. Approximately 200 mg of material was dissolved in 3 ml of 1,2-tetrachloroethane-d.sub.2 (TCE-d.sub.2) along with chromium-(III)-acetylacetonate (Cr(acac).sub.3) resulting in a 65 mM solution of relaxation agent in solvent (Singh, G., Kothari, A., Gupta, V., Polymer Testing 28 5 (2009), 475). To ensure a homogenous solution, after initial sample preparation in a heat block, the NMR tube was further heated in a rotatary oven for at least 1 hour. Upon insertion into the magnet the tube was spun at 10 Hz. This setup was chosen primarily for the high resolution and quantitatively needed for accurate ethylene content quantification. Standard single-pulse excitation was employed without NOE, using an optimised tip angle, 1 s recycle delay and a bi-level WALTZ16 decoupling scheme (Zhou, Z., Kuemmerle, R., Qiu, X., Redwine, D., Cong, R., Taha, A., Baugh, D. Winniford, B., J. Mag. Reson. 187 (2007) 225; Busico, V., Carbonniere, P., Cipullo, R., Pellecchia, R., Severn, J., Talarico, G., Macromol. Rapid Commun. 2007, 28, 1128). A total of 6144 (6 k) transients were acquired per spectra.

[0241] Quantitative .sup.13C {.sup.1H} NMR spectra were processed, integrated and relevant quantitative properties determined from the integrals using proprietary computer programs. All chemical shifts were indirectly referenced to the central methylene group of the ethylene block (EEE) at 30.00 ppm using the chemical shift of the solvent. This approach allowed comparable referencing even when this structural unit was not present. Characteristic signals corresponding to the incorporation of ethylene were observed Cheng, H. N., Macromolecules 17 (1984), 1950).

[0242] With characteristic signals corresponding to 2,1 erythro regio defects observed (as described in L. Resconi, L. Cavallo, A. Fait, F. Piemontesi, Chem. Rev. 2000, 100 (4), 1253, in Cheng, H. N., Macromolecules 1984, 17, 1950, and in W-J. Wang and S. Zhu, Macromolecules 2000, 33 1157) the correction for the influence of the regio defects on determined properties was required. Characteristic signals corresponding to other types of regio defects were not observed.

[0243] The comonomer fraction was quantified using the method of Wang et. al. (Wang, W-J., Zhu, S., Macromolecules 33 (2000), 1157) through integration of multiple signals across the whole spectral region in the .sup.13C {.sup.1H} spectra. This method was chosen for its robust nature and ability to account for the presence of regio-defects when needed. Integral regions were slightly adjusted to increase applicability across the whole range of encountered comonomer contents.

[0244] For systems where only isolated ethylene in PPEPP sequences was observed the method of Wang et. al. was modified to reduce the influence of non-zero integrals of sites that are known to not be present. This approach reduced the overestimation of ethylene content for such systems and was achieved by reduction of the number of sites used to determine the absolute ethylene content to:

E=0.5(S+S+S+0.5(S+S))

Through the use of this set of sites the corresponding integral equation becomes:

E=0.5(I.sub.H+I.sub.G+0.5(I.sub.C+I.sub.D))

using the same notation used in the article of Wang et. al. (Wang, W-J., Zhu, S., Macromolecules 33 (2000), 1157). Equations used for absolute propylene content were not modified.

[0245] The mole percent comonomer incorporation was calculated from the mole fraction:

E [mol %]=100*fE

[0246] The weight percent comonomer incorporation was calculated from the mole fraction:

E [wt %]=100*(fE*28.06)/((fE*28.06)+((1fE)*42.08))

[0247] The comonomer sequence distribution at the triad level was determined using the analysis method of Kakugo et al. (Kakugo, M., Naito, Y., Mizunuma, K., Miyatake, T. Macromolecules 15 (1982) 1150). This method was chosen for its robust nature and integration regions slightly adjusted to increase applicability to a wider range of comonomer contents.

[0248] Flexural Modulus was determined in 3-point-bending according to ISO 178 on injection molded specimens of 80104 mm prepared in accordance with ISO 294-1:1996.

[0249] DSC analysis, melting temperature (T.sub.m), crystallization temperature (T.sub.e), heat of fusion (H.sub.m) and heat of crystallization (H.sub.e): measured with a TA Instrument Q2000 differential scanning calorimetry (DSC) on 5 to 7 mg samples. DSC is running according to ISO 11357/part 3/method C.sub.2 in a heat/cool/heat cycle with a scan rate of 10 C./min in the temperature range of 30 to +225 C. Crystallization temperature (T.sub.c) and heat of crystallization (H.sub.e) are determined from the cooling step, while melting temperature (T.sub.m) and heat of fusion (H.sub.m) are determined from the second heating step.

[0250] Heat Deflection Temperature A (HDT A) was determined according to ISO 75 A with a load of 1.8 MPa using 80104 mm.sup.3 test bars injection molded in line with EN ISO 1873-2.

[0251] Heat deflection temperature B (HDT B) was determined according to ISO 75 B at 0.45 MPa using 80104 mm.sup.3 test bars injection molded in line with EN ISO 1873-2.

[0252] Number average molecular weight (M.sub.n) and weight average molecular weight (M.sub.w) were determined by Gel Permeation Chromatography (GPC) according to ISO 16014-4:2003 and ASTM D 6474-99. A PolymerChar GPC instrument, equipped with infrared (IR) detector was used with 3 Olexis and 1 Olexis Guard columns from Polymer Laboratories and 1,2,4-trichlorobenzene (TCB, stabilized with 250 mg/L 2,6-Di tert butyl-4-methyl-phenol) as solvent at 160 C. and at a constant flow rate of 1 mL/min. 200 L of sample solution were injected per analysis. The column set was calibrated using universal calibration (according to ISO 16014-2:2003) with at least 15 narrow MWD polystyrene (PS) standards in the range of 0.5 kg/mol to 11 500 kg/mol. Mark Houwink constants for PS, PE and PP used are as described per ASTM D 6474-99. All samples were prepared by dissolving 5.0-9.0 mg of polymer in 8 mL (at 160 C.) of stabilized TCB (same as mobile phase) for 2.5 hours for PP or 3 hours for PE at max. 160 C. under continuous gentle shaking in the autosampler of the GPC instrument.

[0253] Particle size d.sub.50 and top cut d.sub.95 were calculated from the particle size distribution [mass percent] as determined by gravitational liquid sedimentation according to ISO 13317-3 (Sedigraph).

2. Examples

[0254] All the chemicals and chemical reactions were handled under an inert gas atmosphere using Schlenk and glovebox techniques, with oven-dried glassware, syringes, needles or cannulas.

[0255] MAO was purchased from Albermarle and used as a 30 wt-% solution in toluene. Perfluoroalkylethyl acrylate ester mixture (CAS number 65605-70-1) was purchased from the Cytonix corporation, dried over activated molecular sieves (2 times) and degassed by argon bubbling prior to use.

[0256] Hexadecafluoro-1,3-dimethylcyclohexane (PFC) (CAS number 335-27-3) was obtained from commercial sources and dried over activated molecular sieves (2 times) and degassed by argon bubbling prior to use.

[0257] Triethylaluminum was purchased from Aldrich and used as a 1 M solution in n-hexane. Hydrogen is provided by Air Liquide and purified before use. Propylene is provided by Borealis and purified before use.

[0258] Complex:

[0259] As metallocene complex was used the racemic anti-dimethylsilanediyl[2-methyl-4-(4-tert-butylphenyl)-inden-1-yl] [2-methyl-4-(4-tert-butylphenyl)-5-methoxy-6-tert-butyl-inden-1-yl]zirconium dichloride (MC1) according to the following formula

##STR00011##

[0260] Synthesis of racemic anti-dimethylsilanediyl[2-methyl-4-(4-tert-butylphenyl)-inden-1-yl] [2-methyl-4-(4-tert-butylphenyl)-5-methoxy-6-tert-butyl-inden-1-yl]zirconium dichloride can be found in WO2013/007650.

Catalyst Preparation:

[0261] Inside the glovebox, 54 L of dry and degassed mixture of perfluoroalkylethyl acrylate ester (used as surfactant) were mixed with 2 mL of MAO in a septum bottle and left to react overnight. The following day, 44.50 mg of metallocene MC1 (0.051 mmol, 1 equivalent) were dissolved with 4 mL of the MAO solution in another septum bottle and left to stir inside the glovebox.

[0262] After 60 minutes, 1 mL of the surfactant solution and the 4 mL of the MAO-metallocene solution were successively added into a 50 mL emulsification glass reactor containing 40 mL of PFC at 10 C. and equipped with an overhead stirrer (stirring speed=600 rpm). Total amount of MAO is 5 mL (450 equivalents). A red emulsion formed immediately and stirred during 15 minutes at 10 C./600 rpm. Then the emulsion was transferred via a 2/4 teflon tube to 100 mL of hot PFC at 90 C., and stirred at 600 rpm until the transfer is completed, then the speed was reduced to 300 rpm. After 15 minutes stirring, the oil bath was removed and the stirrer turned off. The catalyst was left to settle up on top of the PFC and after 35 minutes the solvent was siphoned off. The remaining catalyst was dried during 2 hours at 50 C. over an argon flow. 1,0 g of a red solid catalyst was obtained.

Pre-Activation Procedure:

[0263] The catalyst as prepared above (MC1-Cat) was pre-polymerised according to the following procedure Off-line pre-polymerisation experiments were done in a 125 mL pressure reactor equipped with gas-feeding lines and an overhead stirrer. Dry and degassed perfluoro-1,3-dimethylcyclohexane (PFC)(15 ml) and the desired amount of the catalyst MC1-Cat (604.6 mg) to be pre-polymerised were loaded into the reactor inside a glove box and the reactor was sealed. The reactor was then taken out from the glove box and placed inside a water cooled bath kept at 25 C. The overhead stirrer and the feeding lines were then connected. The experiment was started by opening the propylene feed into the reactor and setting the stirrer speed at 450 rpm. The propylene feed was left open and the monomer consumption was compensated by keeping the total pressure in the reactor constant (about 5 barg). The experiment was continued for the polymerisation time (17.5 min) sufficient to provide the desired degree of polymerisation (DP). The reactor was then taken back inside the glove box before opening and the content was poured into a glass vessel. PFC was evaporated until a constant weight was obtained to yield 2.90 g of the pre-polymerised catalyst. The degree of polymerisation (DP) was determined gravimetrically and/or by analysis of the ash and/or aluminium content of the catalyst. Pre-polymerization degree is 3.8 g(PP)/g(cat).

[0264] Prepolymerised MC1-Cat is marked as PMC1-Cat.

[0265] The catalyst used and its composition is listed in table 1:

TABLE-US-00001 TABLE 1 used catalyst Catalyst type DP MC1 g/g wt.-% PMC1-Cat 3.8 0.65

[0266] The homopolymers H-PP5, H-PP6 and H-PP7 were polymerized in a 20 L bench scale reactor at 75 C. in bulk slurry phase.

[0267] The following comparative examples CE1 to CE6 as well as inventive examples IE1 to IE4 were prepared by mixing the corresponding propylene homopolymer with talc, and, if present, with the nucleating agent and additives, as outlined in tables 2 and 3, and compounding the mixtures on a co-rotating twin-screw extruder TSE16TC with an L/D ratio of 30:1 and D of 16 mm.

TABLE-US-00002 TABLE 2 Overview of the composition for comparative examples CE1 to CE6 CE1 CE2 CE3 CE4 CE5 CE6 H-PP1 [wt.-%] 74.55 H-PP2 [wt.-%] 74.55 H-PP3 [wt.-%] 74.55 H-PP4 [wt.-%] 74.75 99.75 H-PP5 [wt.-%] 99.75 Talc [wt.-%] 25 25 25 25 NA [wt.-%] 0.2 0.2 0.2 Additives [wt.-%] 0.25 0.25 0.25 0.25 0.25 0.25

TABLE-US-00003 TABLE 3 Overview of the composition for inventive examples IE1 to IE4 IE1 IE2 IE3 IE4 H-PP6 [wt.-%] 74.55 H-PP7 [wt.-%] 74.55 H-PP5 [wt.-%] 89.75 59.75 Talc [wt.-%] 25 25 10 40 NA [wt.-%] 0.2 0.2 Additives [wt.-%] 0.25 0.25 0.25 0.25 [0268] H-PP1 is the commercial unimodal propylene homopolymer B-Powder-10 of Borealis AG having a melt flow rate MFR.sub.2 (230 C.) of about 0.3 g/10 min, a Tm of 162 C., a Mw of 1010 kg/mol and Mw/Mn of 5.1, prepared in the presence of a Ziegler-Natta catalyst. [0269] H-PP2 is the commercial unimodal propylene homopolymer HC001A-B1 of Borealis AG having a melt flow rate MFR.sub.2 (230 C.) of about 2 g/10 min, a Tm of 160 C., a Mw of 605 kg/mol and Mw/Mn of 4.5, prepared in the presence of a Ziegler-Natta catalyst. [0270] H-PP3 is an unimodal propylene homopolymer having a melt flow rate MFR.sub.2 (230 C.) of about 0.6 g/10 min, a Tm of 151 C., a Mw of 307 kg/mol and Mw/Mn of 2.9, prepared in the presence of a single-site catalyst. [0271] H-PP4 is a propylene homopolymer of Borealis AG having a melt flow rate MFR.sub.2 (230 C.) of about 20 g/10 min, a Tm of 165 C., a Mw of 180 kg/mol and Mw/Mn of 4.7, prepared in the presence of a Ziegler-Natta catalyst. [0272] H-PP5 is an unimodal propylene homopolymer having a melt flow rate MFR.sub.2 (230 C.) of about 32 g/10 min, a Tm of 158 C., a Mw of 159 kg/mol and Mw/Mn of 3.3, prepared in the presence of a single-site catalyst. [0273] H-PP6 is an unimodal propylene homopolymer having a melt flow rate MFR.sub.2 (230 C.) of about 2.8 g/10 min, a Tm of 153 C., a Mw of 274 kg/mol and Mw/Mn of 3.6, prepared in the presence of a single-site catalyst. [0274] H-PP7 is an unimodal propylene homopolymer having a melt flow rate MFR.sub.2 (230 C.) of about 3.5 g/10 min, a Tm of 157 C., a Mw of 230 kg/mol and Mw/Mn of 3.5, prepared in the presence of a single-site catalyst. [0275] NA is the commercial nucleating agent aluminium-hydroxy-bis[2,2-methylene-bis(4,6-di-t-butylphenyl)phosphate], NA-21, of Adeka Corporation. [0276] Talc is the commercial product Jetfine 3CA of Imerys Talc Austria having an average particle size (d.sub.50) of 1.2 m. [0277] Additives include 0.2 wt.-% of Irganox B225 (1:1-blend of Irganox 1010 (Pentaerythrityltetrakis(3-(3,5-di-tert.butyl-4-hydroxytoluyl)-propionate and tris (2,4-di-t-butylphenyl) phosphate) phosphite) of BASF AG, Germany) and 0.05 wt.-% calcium stearate.

[0278] The mechanical characteristics of the inventive examples IE1 to IE4 and of comparative examples CE1 to CE6 are indicated in table 4 below.

TABLE-US-00004 TABLE 4 Characteristics of the prepared polypropylene (PP) compositions CE1 CE2 CE3 CE4 CE5 CE6 IE1 IE2 IE3 IE4 polypropylene (PP) homopolymer HDT B [ C.] 90 89 86 85 85 92 90 95 92 92 XCS [wt.-%] 2.4 2.5 0.6 2.7 2.7 0.5 0.3 0.4 0.5 0.5 Isotactic triad fraction [%] 97.5 95.2 99.6 97.8 97.8 99.7 99.4 99.6 99.7 99.7 <2.1> defects [%] nd nd 0.89 nd nd 0.34 0.73 0.45 0.34 0.34 Flexural modulus [MPa] 1550 1420 1213 1367 1367 1468 1522 1601 1468 1468 polypropylene (PP) composition MFR.sub.2 [g/10 min] 0.3 2.44 0.6 22 33 32 2.5 3.3 28 22 Tc [ C.] 128 128 123 nd 118 114 124 127 123 126 Tm1 [ C.] 166 166 152 nd 165 158 156 160 156 157 Tm2 [ C.] nd nd 139 nd nd nd 143 nd nd nd Hm1 [J/g] 69 77 68 nd 102 99 71 75 89 42 Hm2 [J/g] nd nd 1.3 nd nd nd 2 nd nd nd HDT A [ C.] 76 74 77 nd 50 55 80 81 77 90 HDT B [ C.] 127 128 127 130 85 92 132 133 125 142 HDT B (limit) [ C.] 131 131 131 131 80 80 131 131 113 129 Tm/HDT A 2.2 2.2 2.1 nd 3.3 2.9 2.0 2.0 2.0 1.7 Flexural modulus [MPa] 4125 3898 3723 3056 1367 1468 4017 4112 2850 5978

[0279] It can be gathered from the data set out in table 4 that the stiffness of the polypropylene (PP) composition is low if the melting temperature of the polypropylene (PP) homopolymer being polymerized in the presence of a single-site catalyst is low (see CE3). If the melting temperature of the polypropylene (PP) homopolymer is 153 C., then the stiffness of the polypropylene (PP) composition is similar to that of a composition comprising a polypropylene (PP) homopolymer being polymerized in the presence of a Ziegler-Natta catalyst. In particular, it can be gathered that a polypropylene (PP) composition comprising a polypropylene (PP) homopolymer being polymerized in the presence of a single-site catalyst and having a melting temperature of 153 C. is advantageous over the same polypropylene (PP) composition comprising a polypropylene (PP) homopolymer being polymerized in the presence of a single-site catalyst but having a melting temperature of <153 C. or a polypropylene (PP) homopolymer being polymerized in the presence of a Ziegler-Natta catalyst.