Fiber reinforced polypropylene compositions

Abstract

The present invention is directed to granules comprising a fiber reinforced composition (C), said composition comprising a propylene polymer (PP), an elastomeric ethylene copolymer (E) and short fibers (SF). Further, the present invention is directed to an article comprising said fiber reinforced composition (C).

Claims

1. Granules comprising a fiber reinforced composition (C), comprising: i) 20.0 to 70.0 wt. % of a propylene polymer (PP) having a melt flow rate MFR.sub.2 (230° C., 2.16 kg) determined according to ISO 1133 in the range of 50 to 150 g/10 min, ii) 2.0 to 12.0 wt. % of an elastomeric ethylene copolymer (E) being a copolymer of ethylene and a C.sub.4-C.sub.10 α-olefin, iii) 0.1 to 5.0 wt. % of an adhesion promoter (AP), and iv) 10.0 to 70.0 wt. % of short glass fibers (SF) having an average length of 1.0 to 10.0 mm, based on the overall weight of the fiber reinforced composition (C), and wherein said fiber reinforced composition (C) fulfils in-equation (I) $\begin{array}{cc}\frac{w\left(PP\right)}{w\left(E\right)}>2.0,& \left(I\right)\end{array}$ wherein w(PP) is the weight fraction [in wt. %] of the propylene polymer (PP), based on the overall weight of the polypropylene composition (C), and w(E) is the weight fraction [in wt. %] of the elastomeric ethylene copolymer (E), based on the overall weight of the fiber reinforced composition (C), and wherein the polypropylene composition (C) has a tensile modulus determined according to ISO 527 of at least 8000 MPa.

2. The granules according to claim 1, wherein the fiber reinforced composition (C) fulfils in-equation (II): $\begin{array}{cc}\frac{w\left(SF\right)}{w\left(E\right)}>3.3,& \left(\mathrm{II}\right)\end{array}$ wherein w(SF) is the weight fraction [in wt. %] of the short glass fibers (SF), based on the overall weight of the polypropylene composition (C), and w(E) is the weight fraction [in wt.-%] of the elastomeric ethylene copolymer (E), based on the overall weight of the fiber reinforced composition (C).

3. The granules according to claim 1, wherein the fiber reinforced composition (C) has a melt flow rate MFR.sub.2 (230° C., 2.16 kg) determined according to ISO 1133 below 100.0 g/10 min.

4. The granules according to claim 1, wherein the adhesion promoter (AP) is a polar modified polypropylene (PM-PP) being a propylene homo- or copolymer grafted with maleic anhydride having a melt flow rate MFR (190° C., 2.16 kg) determined according to ISO 1133 of at least 50.0 g/10 min.

5. The granules according to claim 1, wherein the elastomeric ethylene copolymer (E) has a melt flow rate MFR (190° C., 2.16 kg) determined according to ISO 1133 of at least 25.0g/10 min.

6. The granules according to claim 1, wherein the elastomeric ethylene copolymer (E) has one or more of: a) a comonomer content of 2.0 to 25.0 mol %, and b) a density below 0.900 g/cm.sup.3.

7. The granules according to claim 1, wherein the elastomeric ethylene copolymer (E) is a copolymer of ethylene and 1-octene.

8. The granules according to claim 1, wherein the propylene polymer (PP) is a propylene homopolymer.

9. The granules according to claim 1, wherein the propylene polymer (PP) is at least bimodal.

10. The granules according to claim 1, wherein the propylene polymer (PP) comprises: i) 10.0 to 35.0 wt. % of a first propylene polymer (PP1), ii) 30.0 to 70.0 wt. % of a second propylene polymer (PP2), and iii) 10.0 to 35.0 wt. % of a third propylene polymer (PP3), based on the overall weight of the propylene polymer (PP), wherein said first propylene polymer (PP1), said second propylene polymer (PP2) and said third propylene polymer (PP3) have different melt flow rates MFR.sub.2 (230° C., 2.16 kg) determined according to ISO 1133.

11. The granules according to claim 1, wherein the short glass fibers (SF) have an average diameter of 8 to 20 μm.

12. The granules according to claim 1, comprising at least 80.0 wt. % of the fiber reinforced polypropylene composition (C), based on the overall weight of the granules.

13. The granules according to claim 1, wherein the polypropylene composition (C) has a tensile modulus determined according to ISO 527 of at least 10 000 MPa.

14. An article comprising the fiber reinforced polypropylene composition (C) according to claim 1.

Description

EXAMPLES

(1) 1. Measuring Methods

(2) MFR.sub.2 (230° C.) is measured according to ISO 1133 (230° C., 2.16 kg load).

(3) MFR.sub.2 (190° C.) is measured according to ISO 1133 (190° C., 2.16 kg load).

(4) The melt flow rate MFR.sub.2 (230° C.) of the propylene polymer (PP) is calculated according to equation (I)
log MFR(PP)=w(PP1).Math.log MFR(PP1)w(PP2).Math.log MFR(PP2)+w(PP3).Math.log MFR(PP3)  (I),

(5) Wherein w(PP1) is the weight fraction of the first propylene polymer (PP1) w(PP2) is the weight fraction of the second propylene polymer (PP2) w(PP3) is the weight fraction of the third propylene polymer (PP3) MFR(PP1) is the melt flow rate MFR.sub.2 (230° C., 2.16 kg) in g/10 min of the first propylene polymer (PP1) MFR(PP2) is the melt flow rate MFR.sub.2 (230° C., 2.16 kg) in g/10 min of the second propylene polymer (PP2), MFR(PP3) is the melt flow rate MFR.sub.2 (230° C., 2.16 kg) in g/10 min of the third propylene polymer (PP3), and MFR(PP) is the melt flow rate MFR.sub.2 (230° C., 2.16 kg) in g/10 min of the propylene polymer (PP)
Quantification of Microstructure by NMR Spectroscopy

(6) Quantitative nuclear-magnetic resonance (NMR) spectroscopy was used to quantify the comonomer content and comonomer sequence distribution 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(cac).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. 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).

(7) For polypropylene homopolymers all chemical shifts are internally referenced to the methyl isotactic pentad (mmmm) at 21.85 ppm.

(8) Characteristic signals corresponding to regio defects (Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253; Wang, W-J., Zhu, S., Macromolecules 33 (2000), 1157; Cheng, H. N., Macromolecules 17 (1984), 1950) or comonomer were observed.

(9) The tacticity distribution was quantified through integration of the methyl region between 23.6-19.7 ppm correcting for any sites not related to the stereo sequences of interest (Busico, V., Cipullo, R., Prog. Polym. Sci. 26 (2001) 443; Busico, V., Cipullo, R., Monaco, G., Vacatello, M., Segre, A. L., Macromoleucles 30 (1997) 6251).

(10) Specifically the influence of regio defects and comonomer on the quantification of the tacticity distribution was corrected for by subtraction of representative regio defect and comonomer integrals from the specific integral regions of the stereo sequences.

(11) The isotacticity was determined at the pentad level and reported as the percentage of isotactic pentad (mmmm) sequences with respect to all pentad sequences:
[mmmm]%=100*(mmmm/sum of all pentads)

(12) The presence of 2,1 erythro regio defects was indicated by the presence of the two methyl sites at 17.7 and 17.2 ppm and confirmed by other characteristic sites.

(13) Characteristic signals corresponding to other types of regio defects were not observed (Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253).

(14) The amount of 2,1 erythro regio defects was quantified using the average integral of the two characteristic methyl sites at 17.7 and 17.2 ppm:
P.sub.21e=(I.sub.e6+I.sub.e8)/2

(15) The amount of 1,2 primary inserted propene was quantified based on the methyl region with correction undertaken for sites included in this region not related to primary insertion and for primary insertion sites excluded from this region:
P.sub.12=I.sub.CH3+P.sub.12e

(16) The total amount of propene was quantified as the sum of primary inserted propene and all other present regio defects:
P.sub.total=P.sub.12+P.sub.21e
The mole percent of 2,1 erythro regio defects was quantified with respect to all propene:
[21e] mol %=100*(P.sub.21e/P.sub.total)

(17) For copolymers characteristic signals corresponding to the incorporation of ethylene were observed (Cheng, H. N., Macromolecules 17 (1984), 1950).

(18) With regio defects also observed (Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem. Rev. 2000, 100, 1253; Wang, W-J., Zhu, S., Macromolecules 33 (2000), 1157; Cheng, H. N., Macromolecules 17 (1984), 1950) correction for the influence of such defects on the comonomer content was required.

(19) 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.

(20) 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(Sββ+Sβγ+Sβδ+0.5(Sαβ+Sαγ))

(21) 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))

(22) 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.

(23) The mole percent comonomer incorporation was calculated from the mole fraction:
E[mol %]=100*fE

(24) The weight percent comonomer incorporation was calculated from the mole fraction:
E[wt %]=100*(fE*28.06)/((fE*28.06)+((1−fE)*42.08))

(25) 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.

(26) Number Average Molecular Weight (M.sub.n), Weight Average Molecular Weight (M.sub.w) and Molecular Weight Distribution (MWD)

(27) Molecular weight averages (Mw, Mn), and the molecular weight distribution (MWD), i.e. the Mw/Mn (wherein Mn is the number average molecular weight and Mw is the weight average molecular weight), 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 lx 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. 200μï. 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.

(28) DSC analysis, melting temperature (T.sub.m) and heat of fusion (H.sub.f), crystallization temperature (T.sub.c) and melt enthalpy (Hm): measured with a TA Instrument Q200 differential scanning calorimetry (DSC) on 5 to 7 mg samples. DSC is run according to ISO 11357/part 3/method C2 in a heat/cool/heat cycle with a scan rate of 10° C./min in the temperature range of −30 to +225° C. The crystallization temperature (T.sub.c) is determined from the cooling step, while melting temperature (T.sub.m) and melting enthalpy (H.sub.m) are determined from the second heating step. The crystallinity is calculated from the melting enthalpy by assuming an Hm-value of 209 J/g for a fully crystalline polypropylene (see Brandrup, J., Immergut, E. H., Eds. Polymer Handbook, 3rd ed. Wiley, New York, 1989; Chapter 3).

(29) The glass transition temperature Tg is determined by dynamic mechanical analysis according to ISO 6721-7. The measurements are done in torsion mode on compression moulded samples (40×10×1 mm.sup.3) between −100° C. and +150° C. with a heating rate of 2° C./min and a frequency of 1 Hz.

(30) Comonomer content in elastomer (E) was measured in a known manner based on Fourier transform infrared spectroscopy (FTIR) calibrated with .sup.13C-NMR, using Nicolet Magna 550 IR spectrometer together with Nicolet Omnic FTIR software. Films having a thickness of about 250 μm were compression molded from the samples. Similar films were made from calibration samples having a known content of the comonomer. The comonomer content was determined from the spectrum from the wave number range of from 1430 to 1100 cm.sup.−1. The absorbance is measured as the height of the peak by selecting the so-called short or long base line or both. The short base line is drawn in about 1410-1320 cm.sup.−1 through the minimum points and the long base line about between 1410 and 1220 cm.sup.−1. Calibrations need to be done specifically for each base line type. Also, the comonomer content of the unknown sample needs to be within the range of the comonomer contents of the calibration samples.

(31) Ash content is measured according to ISO 3451-1 (1997) standard.

(32) Density is measured according to ISO 1183-187. Sample preparation is done by compression moulding in accordance with ISO 1872-2:2007.

(33) Charpy notched and unnotched impact strength is determined according to ISO 179-1/1 eA and ISO 179-1/1 eU at 23° C. by using injection moulded test specimens as described in ISO 19069-2 (80×10×4 mm).

(34) Tensile properties were determined on injection molded dogbone specimens prepared in accordance with ISO 19069-2. Tensile modulus was determined according to ISO 527-1A at 1 mm/min. and 23° C. To determine stress at yield and strain at yield, a speed of 50 mm/min. was used.

(35) Instrumented failing weight test: Puncture energy, maximum force and puncture deflection was determined in the instrumented falling weight test according to ISO 6603-2 using injection moulded plaques of 60×60×3 mm in accordance with ISO 19069-2 and a test speed of 4.4 m/s. The reported puncture energy results from an integral of the failure energy curve measured at +23° C. and −30° C.

(36) Average fiber diameter is determined according to ISO 1888:2006(E), Method B, microscope magnification of 1000.

2. Examples

(37) The following inventive examples IE1 to IE5 and comparative examples CE1 and CE2 were prepared by compounding on a co-rotating twin-screw extruder (ZSK 40 from Coperion) with an ID ratio of 43. The following process parameters were used: throughput of 100 kg/h screw speed of 100-150 rpm barrel temperatures of 220-250° C. increasing from the feeding zone and decreasing again towards the die plate die plate with 4 mm diameter holes and 3 strands

(38) The polymer and the additives different from the short fibers were fed to the extruder and melt-kneaded in the 2.sup.nd barrel. A first kneading zone for mixing the polymer and the additives is located between the 3.sup.rd and 5.sup.th barrel. The short fibers were added in the 6.sup.th barrel using a side feeder. A second kneading zone for glass fiber dispersion is located between the 7.sup.th and 12.sup.th barrel.

(39) The composition and properties are summarized in Table 1.

(40) TABLE-US-00001 TABLE 1 Composition and properties of the inventive and comparative examples CE1 CE2 IE1 IE2 IE3 IE4 IE5 PP1 [wt.-%] 10.0 6.7 8.9 9.4 8.9 8.3 7.8 PP2 [wt.-%] 25.0 16.6 22.2 23.7 22.2 20.9 19.4 PP3 [wt.-%] 10.0 6.7 8.9 9.4 8.9 8.3 7.8 E [wt.-%] - 15.0 5.0 2.5 5.0 7.5 10.0 SF [wt.-%] 50.0 50.0 50.0 50.0 50.0 50.0 50.0 AP [wt.-%] 2.0 2.0 2.0 2.0 2.0 2.0 2.0 Pigment [wt.-%] 1.0 1.0 1.0 1.0 1.0 1.0 1.0 AD [wt.-%] 2.0 2.0 2.0 2.0 2.0 2.0 2.0 Ash content [wt.-%] 49.9 50.9 49.1 49.4 49.8 49.6 49.8 MFR [g/10 min] 2.81 4.04 3.04 2.14 2.45 2.33 2.29 Tensile Modulus [MPa] 13016 10097 12275 12608 12210 11820 11350 Tensile Strength [MPa] 147.27 97.84 141.60 154.94 145.19 137.17 127.06 Tensile Strain at [%] 2.16 2.41 2.32 2.29 2.46 2.62 2.70 Tensile Strength Tensile Stress at [MPa] 147.27 97.70 141.38 154.94 145.14 136.92 126.77 Break Tensile Strain at [%] 2.16 2.44 2.33 2.29 2.45 2.57 2.60 Break Charpy notched [kJ/m.sup.2] 12.72 16.81 16.86 12.59 14.10 13.56 14.37 impact strength (23° C.) Charpy [kJ/m.sup.2] 62.58 55.41 63.16 60.37 63.38 61.55 60.01 unnotched impact strength (23° C.) Maximum Force [N] 1789 1681 1955 2102 2072 2186 2039 Deflection at [mm] 4.91 5.71 6.17 4.79 4.73 5.42 5.04 Maximum Force [J] 5.58 6.39 8.02 6.23 6.15 7.57 6.43 Energy to Maximum Force [mm] 5.76 7.70 7.35 5.62 6.02 6.49 6.53 Puncture Deflection [J] 6.78 9.10 9.91 7.67 8.40 9.60 8.91 Puncture Energy PH1 is the conmmerical high flow propylene homopolymer HL504FB of Borealis AG having a melt flow rate MFR.sub.2 (230° C.) of 450 g/10 min and a glass transition temperature Tg of +0° C. PP2 is the comimerical propylene homopolymer HJ2UB of Borealis AG having a melt flow rate MFR.sub.2 (230° C.) of 75 g/10 min, a density of 905 kg/m.sup.3 and a glass transition temperature Tg of +2° C. PP3 is the commercial propylene homopolymer HF955MO of Borealis AG having a melt flow rate MFR.sub.2 (230° C.) of 20 g/10 min, a density of 908 kg/m.sup.3 and a glass transition temperature Tg of +4° C. The propylene homopolymer HF955MO is α-nucleated with polyvinyl cyclohexane (polyVCH). E is the commercial ethylene-octene copolymer Queo8230 by Borealis having a density of 0.882 g/cm.sup.3, a melt flow rate MFR.sub.2 (190° C.) of 30.0 g/10 min and an 1-octene content of 7.5 mol-%. SF is the commercial product ECS 03 T-480H of Nippon Electric Glass Co., Ltd. having a filament diameter of 10.5 μm and a strand length of 3 mm. AP is the adhesion promoter SCONA TPPP 9012 GA by Scona being a polypropylene functionalized with maleic anhydride having a maleic anhydride content of 1.4 wt.-% and a MFR (190° C.) above 50 g/10 min. Pigment is a masterbatch comprising 1 wt.-% Remafin Schwarz P-AP (MP 99-BLACK 7-PP-30) by Clariant. AD is a composition comprising 1 part by weight of tris (2,4-di-t-butylphenyl) phosphite (Kinox-68-G by HPL Additives) and 2 parts by weight of pentaerythrityl-tetrakis(3-(3′,5′-di-tert. butyl-4-hydroxyphenyl)-propionate (Irganox 1010FF by BASF)

(41) As can be gathered from Table 1, the composition according to comparative example CE2 containing 15.0 wt.-% of the elastomeric compound is featured by a high puncture energy and, therefore, excellent impact properties, but the tensile modulus decreases significantly compared to CE1 which contains the same amount of fibers, but no elastomeric compound. The compositions according to inventive examples IE1 to IE5 containing 2.5 to 10.0 wt.-% of the elastomeric compound also show high puncture energies, but the tensile modulus remains on a high level. Thus, a good balance between stiffness and impact behavior is achieved.