Polypropylene composition

Abstract

The present invention is directed to a polypropylene composition (C) comprising abase polymer being a first polypropylene (PP1) and a second polypropylene (PP2). The present invention is further directed to a film and a fiber comprising said polypropylene composition (C).

Claims

1. A polypropylene composition (C), comprising i) 80.0 to 99.5 wt.-%, based on the overall weight of the polypropylene composition (C), of a first polypropylene (PP1), and ii) 0.5 to 20.0 wt.-%, based on the overall weight of the polypropylene composition (C), of a second polypropylene (PP2) which is a propylene homopolymer different from the first polypropylene (PP1) and has a melting temperature Tm of 130° C. or less, wherein said first polypropylene (PP1) fulfils in-equation (I)
C7(PP1)−C6(PP1)≤1.5   (I) wherein C7(PP1) is the amount of heptane solubles [in wt.-%] within the first polypropylene (PP1) and C6(PP1) is the amount of hexane solubles [in wt.-%] within the first polypropylene (PP1), and wherein the polypropylene composition (C) fulfils in-equation (II)
1.5<[C7(C)−C6(C)]≤5.0   (II) wherein C7(C) is the amount of heptane solubles [in wt.-%] within the polypropylene composition (C) and C6(C) is the amount of hexane solubles [in wt. %] within polypropylene composition (C).

2. The polypropylene composition (C) according to claim 1, having a comonomer content in the range of 0.0 to 5.0 mol-%.

3. The polypropylene composition (C) according to claim 1, wherein the first polypropylene (PP1) is a propylene homopolymer (H-PP1) or a random propylene copolymer (R-PP1).

4. The polypropylene composition (C) according to claim 1, having a xylene soluble content (XCS) below 10.0 wt.-%.

5. The polypropylene composition (C) according to claim 1, wherein the second polypropylene (PP2) has a molecular weight distribution Mw/Mn in the range of 1.0 to 4.0.

6. The polypropylene composition (C) according to claim 1, wherein the second polypropylene (PP2) has a weight average molecular weight Mw in the range of 20 to 300 kg/mol.

7. The polypropylene composition (C) according to claim 1, wherein the second polypropylene (PP2) has a density below 895 kg/m.sup.3.

8. The polypropylene composition (C) according to claim 1, wherein the second polypropylene (PP2) has a melting temperature Tm in the range of 50 to 125° C.

9. The polypropylene composition (C) according to claim 1, not comprising (a) further polymeric material different to the first polypropylene (PP1) and the second polypropylene (PP2) in an amount exceeding 5.0 wt.-%, based on the overall weight of the polypropylene composition (C).

10. An article comprising the polypropylene composition (C) according to claim 1.

11. The article according to claim 10, wherein said article is a film.

12. The article according to claim 11, wherein said film is a biaxially oriented film (BOPP).

13. The article according to claim 10, wherein said article is a fiber.

14. The article according to claim 13, wherein said fiber is a melt spun fiber or a spunbonded fiber.

Description

EXAMPLES

(1) 1. Measuring Methods

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

(3) Quantification of Microstructure by NMR Spectroscopy

(4) 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 optimized 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 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 optimized tip angle, 1 s recycle delay and a hi-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.

(5) 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).

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

(7) 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.

(8) 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).

(9) 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.

(10) 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)

(11) 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.

(12) 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).

(13) 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

(14) 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

(15) 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

(16) 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:

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

(23) 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.

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

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

(26) 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.

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

(28) 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

(29) 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 μL 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.

(30) DSC analysis, melting temperature (T.sub.m) and heat of fusion (H.sub.f), crystallization temperature (T.sub.c) and heat of crystallization (H.sub.c): measured with a TA Instrument Q200 differential scanning calorimetry (DSC) on 5 to 7 mg samples. DSC is run according to ISO 3146/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. Crystallization temperature (T.sub.c) and heat of crystallization (H.sub.c) are determined from the cooling step, while melting temperature (T.sub.m) and heat of fusion (H.sub.f) are determined from the second heating step.

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

(32) The xylene solubles (XCS, wt.-%): Content of xylene cold solubles (XCS) is determined at 25° C. according ISO 16152; first edition; 2005-07-01. The part which remains insoluble is the xylene cold insoluble (XCI) fraction.

(33) The amount of heptane solubles (C7) [in wt.-%] was determined via Soxhlet extraction. Around 1 g of a powdered test portion is carefully dried and weighed out exactly. The powdered test portion is extracted in a Soxhlet-apparatus with 150 ml n-heptane (p.a. quality) during 24 h. As thimble a standard 603 cellulose extraction thimble is used. To avoid that polymer powder will leave the extraction thimble it is closed on the top with another half cut thimble. The weight of the glass extractor including the polymer after extraction is weighed out after reaching constant weight. The mass of residue of the test portion in the glass extractor is determined in the following way:
C7 solubles (%))=((m2−mt))/m1×100

(34) with:

(35) m1=original sample weight

(36) m2=weight of the glass extractor with polymer after extraction

(37) mt=weight of the glass extractor.

(38) The amount of hexane solubles (C6) [in wt.-%] was determined via Soxhlet extraction. Around 1 g of a powdered test portion is carefully dried and weighed out exactly. The powdered test portion is extracted in a Soxhlet-apparatus with 150 ml n-hexane (p.a. quality) during 24 h. As thimble a standard 603 cellulose extraction thimble is used. To avoid that polymer powder will leave the extraction thimble it is closed on the top with another half cut thimble. The weight of the glass extractor including the polymer after extraction is weighed out after reaching constant weight. The mass of residue of the test portion in the glass extractor is determined in the following way:
C6 solubles (%))=((m2−mt))/m1×100

(39) with:

(40) m1=original sample weight

(41) m2=weight of the glass extractor with polymer after extraction

(42) mt=weight of the glass extractor.

(43) Tensile modulus of the first polypropylene (PP1) was measured according to ISO 527-3 (cross head speed=1 mm/min; test speed 50 mm/min at 23° C.) using BOPP film (Stretching ratio of MD 5 and TD 7) with thickness of 20 μm. The measurement is done after 96 h conditioning time of the specimen.

(44) Tensile modulus of the second polypropylene (PP2) was measured according to ISO 527 on injection-molded specimens.

(45) B-Viscosity was determined according to ASTM D 3236 at 190° C.

(46) B. Examples

(47) 1. The First Polypropylene (PP1):

(48) The following commercial polypropylene material was used as the first polypropylene (PP1): PP1a is the commercial polypropylene HC401BF by Borouge having a melt flow rate MFR.sub.2 of 3.2 g/10 min, a melting temperature, Tm, of 162° C. and a density of 905 kg/m.sup.3, and a tensile modulus (MD) of 2100 MPa when using 20 μm film samples.

(49) 2. The Second Polypropylene (PP2)

(50) The following commercial polypropylene materials were used as the second polypropylene (PP2):

(51) PP2a is the commercial polypropylene L-MODU S400 by Idemitsu.

(52) PP2b is the commercial polypropylene L-MODU S600 by Idemitsu.

(53) PP2c is the commercial polypropylene L-MODU S901 by Idemitsu.

(54) The properties of the second polypropylene (PP2) materials are summarized in Table 1.

(55) TABLE-US-00001 TABLE 1 Properties of the second polypropylene (PP2) sample PP2a PP2b PP2c MFR [g/10 min] 2000 350 50 Tm [° C.] 79 82 83 B-viscosity [mPa .Math. s] 8,500 50,000 360,000 Density [kg/m.sup.3] 870 870 870 Tensile modulus [MPa] 90 90 90 M.sub.w [kg/mol] 45 75 130 MWD [Mw/Mn] 2 2 2

(56) Commercial reference is the commercial polypropylene HC402BF by Borouge suitable for stretching and having a melt flow rate MFR.sub.2 of 3.2 g/10 min, a melting temperature Tm of 161° C., a density of 904 kg/m.sup.3, a tensile modulus (MD) of 1900 MPa when using 20 μm film samples.

(57) 2. Preparation of the Polypropylene Composition (C)

(58) The polypropylene compositions (C) were compounded on a ZSK18 twin screw extruder line at a screw speed pf 250 rpm, a SEI of 0.254 kwh/kg and a temperature profile of about 200° C.

(59) The properties of the comparative and inventive compositions are summarized in Table 2.

(60) TABLE-US-00002 TABLE 2 Composition and properties of the Commercial reference, comparative and inventive examples Ref CE1 IE1 IE2 IE3 Commercial reference [wt.-%] 100 PP1a [wt.-%] 100 95 95 95 PP2a [wt.-%] 5 PP2b [wt.-%] 5 PP2c [wt.-%] 5 C7 solubles [wt.-%] 3.69 1.77 4.05 3.52 3.26 C6 solubles [wt.-%] 1.92 0.55 1.47 1.32 0.93 C7-C6 solubles [wt.-%] 1.77 1.22 2.58 2.20 2.33 XCS [wt.-%] 4.0 1.1 3.7 3.0 3.0

(61) As mentioned earlier, the value of C7-C6 as claimed indicates the stretchability and spinning performance of a polymer composition.

(62) Accordingly, to evaluate the stretchability of films obtained from the inventive and comparative compositions, biaxially oriented films (BOPP films) are prepared from the compositions CE1 (PP1a alone) and IE1 to IE3 as follows using an conventional industrial full-scale BOPP film line:

(63) The starting films of 800 μm of Ref, CE1 and IE1 to IE3 are stretched on at a stretching (draw) ratio of about 5 in machine direction (MD) and a stretching (draw) ratio of 8 in transversal direction (TD) at 10 mm/sec.

(64) The 800 μm film based on CE1 (PP1 alone) ca of be stretched to obtain a final film thickness of 20 μm.

(65) The 800 μm films based on IE1, IE2 and IE3 fulfilling the claimed relationship between heptane and hexane solubles can easily be stretched under the above mentioned conditions to obtain a final film thickness of 20 μm.