Polypropylene composition with excellent surface appearance

Abstract

The present invention is directed to a polypropylene composition (C) comprising a heterophasic propylene copolymer (HECO1) having an intrinsic viscosity (IV) of the xylene soluble fraction (XCS) above 3.5 dl/g, an inorganic filler (F) and a nucleating agent (NU) being a dicarboxylic acid and/or a salt thereof. Further, the present invention is directed to the use of said polypropylene composition (C) for the production of a foamed article as well as a foamed article comprising said polypropylene composition (C). The present invention is also directed to the use of a nucleating agent (NU) being dicarboxylic acid and/or a salt thereof for the reduction of tigerskin of a polypropylene composition.

Claims

1. A foamed article comprising a polypropylene composition (C), wherein the polypropylene composition (C) comprises: a) 15.0 to 35.0 wt. % of a heterophasic propylene copolymer HECO1 having an intrinsic viscosity (IV) of the xylene soluble fraction (XCS) above 3.5 dl/g, wherein the xylene soluble fraction (XCS) is determined at 25° C. according to ISO 16152, said heterophasic propylene copolymer HECO1 comprising: i) a matrix being a propylene polymer M1 and ii) an elastomeric propylene copolymer E1 being dispersed in said matrix, b) 5.0 to 30.0 wt. % of an inorganic filler (F), c) 0.001 to 2.0 wt. % of a nucleating agent (NU) being a dicarboxylic acid and/or a salt thereof, and further comprising 38.0 to 45.0 wt. % of a heterophasic propylene copolymer HECO2 having an intrinsic viscosity (IV) of the xylene soluble fraction (XCS) in the range of 1.0 to 3.3 dl/g, wherein the xylene soluble fraction (XCS) is determined at 25° C. according to ISO 16152, said heterophasic propylene copolymer HECO2 comprising: i) a matrix being a propylene polymer M2 and ii) an elastomeric propylene copolymer E2 being dispersed in said matrix.

2. The foamed article according to claim 1, wherein the heterophasic propylene copolymer HECO1 has a comonomer content of the xylene soluble fraction (XCS) below 40.0 mol %, wherein the xylene soluble fraction (XCS) is determined at 25° C. according to ISO 16152.

3. The foamed article according to claim 1, wherein the heterophasic propylene copolymer HECO2 has a comonomer content of the xylene soluble fraction (XCS) equal or above 40.0 mol %, wherein the xylene soluble fraction (XCS) is determined at 25° C. according to ISO 16152.

4. The foamed article according to claim 1, further comprising a high density polyethylene (HDPE) and/or a plastomer (PL) being a copolymer of ethylene and a C.sub.4 to C.sub.8 α-olefin.

5. The foamed article according to claim 4, wherein the plastomer (PL) is a copolymer of ethylene and 1-octene.

6. The foamed article according to claim 1, wherein the heterophasic propylene copolymer HECO1 has: i) a melt flow rate MFR.sub.2 (230° C.) determined according to ISO 1133 in the range of 1.0 to 20.0 g/10 min, and/or ii) a comonomer content in the range of 5.0 to 30.0 mol %, and/or iii) a xylene soluble fraction (XCS) in the range of 15.0 to 40.0 wt. %, wherein the xylene soluble fraction (XCS) is determined at 25° C. according to ISO 16152.

7. The foamed article according claim 1, wherein the heterophasic propylene copolymer HECO2 has: i) a melt flow rate MFR.sub.2 (230° C.) determined according to ISO 1133 in the range of 50 to 120 g/10 min, and/or ii) a comonomer content in the range of 4.0 to 30.0 mol %, and/or iii) a xylene soluble fraction (XCS) in the range of 8.0 to 35.0 wt. %, wherein the xylene soluble fraction (XCS) is determined at 25° C. according to ISO 16152.

8. The foamed article according to claim 1, wherein the propylene polymer M1 is a propylene homopolymer.

9. The foamed article according to claim 1, wherein the elastomeric propylene copolymer E1 is a copolymer of propylene and ethylene.

10. The foamed article according to claim 1, having a melt flow rate MFR.sub.2 (230° C.) determined according to ISO 1133 in the range of 10.0 to 40.0 g/10 min.

11. The foamed article according to claim 1, wherein the inorganic filler (F) is talc and/or wollastonite.

12. The foamed article according to claim 1, wherein the nucleating agent (NU) is 1,2-cyclohexane dicarboxylic acid and/or a salt thereof.

13. The foamed article according to claim 1, further comprising: v) 2.0 to 10.0 wt. % of a high density polyethylene (HDPE), and vi) 5.0 to 15.0 wt. % of a plastomer (PL) being a copolymer of ethylene and a C.sub.4 to C.sub.8 α-olefin, based on the overall polypropylene composition (C).

14. The foamed article according to claim 1, wherein the propylene polymer M2 is a propylene homopolymer.

15. The foamed article according to claim 1, wherein the elastomeric propylene copolymer E2 is a copolymer of propylene and ethylene.

16. The foamed article according to claim 1, wherein the polypropylene composition has a melt flow rate MFR.sub.2 (230° C.) determined according to ISO 1133 in the range of 14.0 to 28.0 g/10 min.

17. The foamed article according to claim 1, wherein the polypropylene composition (C) comprises: a) 22.0 to 27.0 wt. % of the heterophasic propylene copolymer HECO1 having an intrinsic viscosity (IV) of the xylene soluble fraction (XCS) above 3.5 dl/g, wherein the xylene soluble fraction (XCS) is determined at 25° C. according to ISO 16152, said heterophasic propylene copolymer HECO1 comprising: i) the matrix being a propylene polymer M1 and ii) the elastomeric propylene copolymer E1 being dispersed in said matrix, b) 12.0 to 16.0 wt. % of the inorganic filler (F), c) 0.05 to 1.0 wt. % of the nucleating agent (NU) being a dicarboxylic acid and/or a salt thereof, further comprising 38.0 to 45.0 wt. % of the heterophasic propylene copolymer HECO2 having an intrinsic viscosity (IV) of the xylene soluble fraction (XCS) in the range of 1.0 to 3.3 dl/g, wherein the xylene soluble fraction (XCS) is determined at 25° C. according to ISO 16152, said heterophasic propylene copolymer HECO2 comprising: i) the matrix being a propylene polymer M2 and ii) the elastomeric propylene copolymer E2 being dispersed in said matrix, 4.0 to 6.0 wt. % of a high density polyethylene (HDPE), and 7.0 to 10.0 wt. % of a plastomer (PL) being a copolymer of ethylene and a C.sub.4 to C.sub.8 α-olefin, based on the overall polypropylene composition (C).

18. The foamed article according to claim 17, wherein: said heterophasic propylene copolymer HECO1 comprises i) the matrix being a propylene homopolymer M1 and ii) the elastomeric copolymer of propylene and ethylene E1 being dispersed in said matrix, said inorganic filler (F) is talc, said nucleating agent (NU) is selected from the group consisting of 1,2-cyclohexane dicarboxylic acid, 1,3-cyclohexane dicarboxylic acid, 1,4-cyclohexane dicarboxylic acid, 1,1-cyclobutane dicarboxylic acid, 1,2-cyclopentane dicarboxylic acid and/or salts thereof, said heterophasic propylene copolymer HECO2 comprises i) the matrix being a propylene homopolymer M2 and ii) the elastomeric copolymer of propylene and ethylene E2 being dispersed in said matrix, and said plastomer (PL) is a copolymer of ethylene and a 1-octene.

Description

(1) A schematic setup is given in figure 1.

(2) 2. Image Analysis:

(3) The specimen is floodlit from one side and the upwards reflected portion of the light is deflected via two mirrors to a CCD-sensor. The such created grey value image is analyzed in lines. From the recorded deviations of grey values the mean square error average (MSEaverage) or mean square error maximum (MSEmax) values are calculated allowing a quantification of surface quality/homogeneity, i.e. the higher the MSE value the more pronounced is the surface defect. MSEaverage and MSEmax values are not comparable. Generally, for one and the same material, the tendency to flow marks increases when the injection speed is increased.

(4) The MSEaverage values were collected on compact injection-moulded plaques 440×148×2.8 mm produced with grain G1. The plaques were injection-moulded with different filling times of 1.5, 3 and 6 sec respectively.

(5) Further Conditions:

(6) Melt temperature: 240° C.

(7) Mould temperature 30° C.

(8) Dynamic pressure: 10 bar hydraulic

(9) The MSEmax values were collected on compact and foamed injection-moulded plaques 210×148×2 mm produced with a one-point gating system and a grain marked here as G2, which differs from G1. The plaques were injection-moulded with filling time of 0.8 s. Hydrocerol ITP 825 from Clariant, with a decomposition temperature of 200° C. was used as a chemical blowing agent. The blowing agent was added during the conversion step in a form of a masterbatch, which contains 40% of active substance defined as a citric acid [www.clariant.com].

(10) Cell structure of the foamed parts was determined by light microscopy from a cross-section of the foamed injection-molded plate.

(11) Maximum force at break was determined on plaques with dimensions 148×148×2 mm during instrumented falling weight impact testing according to ISO 6603-2. The test was performed at room temperature with a lubricated tup with a diameter of 20 mm and impact velocity of 10 mm/s. The maximum force at break was determined as the maximum peak at the force-deformation curve collected during the test.

(12) Compression test was performed on 10×10×2 mm plaques at room temperature according to ISO 604: 2002. The tests were carried out on a Zwick Z010U machine with a test speed of 0.87 mm/min at room temperature. The compressive stress was determined at 1 mm deformation. Thus, the compressive stress is defined as the force at break at 1 mm deformation divided by the specimen area at the beginning of the experiment.

(13) Puncture energy is determined in the instrumented falling weight test according to ISO 6603-2 using injection moulded plaques of 60×60×1 mm and a test speed of 2.2 m/s, clamped, lubricated striker with 20 mm diameter. The reported puncture energy results from an integral of the failure energy curve measured at (60×60×2 mm).

(14) Compressive stress at break was determined on 10×10×3 mm plaques at room temperature according to ISO 604: 2002. The tests were carried out on a Zwick Z010U machine with a test speed of 5 0.87 mm/min at room temperature. The compressive stress was determined at 1 mm deformation. Thus, the compressive stress is defined as the force at break at 1 mm deformation divided by the specimen area at the beginning of the experiment.

2. Examples

Preparation of the Catalyst for HECO1a and HECO2a

(15) First, 0.1 mol of MgCl2×3 EtOH was suspended under inert conditions in 250 ml of decane in a reactor at atmospheric pressure. The solution was cooled to the temperature of −15° C. 5 and 300 ml of cold TiCl.sub.4 was added while maintaining the temperature at said level. Then, the temperature of the slurry was increased slowly to 20° C. At this temperature, 0.02 mol of dioctylphthalate (DOP) was added to the slurry. After the addition of the phthalate, the temperature was raised to 135° C. during 90 minutes and the slurry was allowed to stand for 60 minutes. Then, another 300 ml of TiCl.sub.4 was added and the temperature was kept at 135° C. 10 for 120 minutes. After this, the catalyst was filtered from the liquid and washed six times with 300 ml heptane at 80° C. Then, the solid catalyst component was filtered and dried. Catalyst and its preparation concept is described in general e.g. in patent publications EP 491566, EP 591224 and EP 586390.

(16) The catalyst was further modified (VCH modification of the catalyst). 15 35 ml of mineral oil (Paraffinum Liquidum PL68) was added to a 125 ml stainless steel reactor followed by 0.82 g of triethyl aluminum (TEAL) and 0.33 g of dicyclopentyl dimethoxy silane (donor D) under inert conditions at room temperature. After 10 minutes 5.0 g of the catalyst prepared above (Ti content 1.4 wt.-%) was added and after additionally 20 minutes 5.0 g of vinylcyclohexane (VCH) was added. The temperature was increased to 20 60° C. during 30 minutes and was kept there for 20 hours. Finally, the temperature was decreased to 20° C. and the concentration of unreacted VCH in the oil/catalyst mixture was analysed and was found to be 200 ppm weight

Preparation of the Catalyst for HECO1b

(17) The catalyst for the preparation of HECO1b was prepared analogously to the preparation of the catalyst for HECO1a and HECO2a except that diethylaminotriethoxysilane (donor U) was used instead of dicyclopentyl dimethoxy silane.

Preparation of the Catalyst for HECO2b

(18) The catalyst for the preparation of HECO2b is the commercial catalyst ZN180M by Lyondell Basell used along with dicyclopentyl dimethoxy silane (donor D) as donor.

(19) The aluminum to donor ratio, the aluminum to titanium ratio and the polymerization conditions are indicated in table 1.

(20) TABLE-US-00001 TABLE 1 Preparation of HECO1a, HECO1b, HECO2a and HECO2b HECO1a HECO1b HECO2a HECO2b Prepolymerization TEAL/Ti [mol/mol] 200 205 200 220 TEAL/donor [mol/mol] 10 10 5.01 10 Temperature [° C.] 30 30 30 30 res. time [h] 0.26 0.09 0.17 0.08 Loop Temperature [° C.] 76 72 80 75 Split [%] 35 29 34 52 H2/C3 ratio [mol/kmol] 25 21 7 22 C2/C3 ratio [mol/kmol] 0 0 0 0 MFR.sub.2 [g/10 min] 160 120 162 160 XCS [wt.-%] 2.1 2.2 2.0 2.0 C2 content [mol-%] 0 0 0 0 GPR 1 Temperature [° C.] 80 85 95 80 Pressure [kPa] 2400 2500 1500 2200 Split [%] 40 36 45 34 H2/C3 ratio [mol/kmol] 45 204 84 175 C2/C3 ratio [mol/kmol] 0 0 0 0 MFR.sub.2 [g/10 min] 55 120 159 160 XCS [wt.-%] 2.0 2.0 2.9 13.0 IV (XCS) [dl/g] nd nd nd nd C2 (XCS) [mol-%] nd nd nd nd C2 content [mol-%] 0 0 0 0 GPR 2 Temperature [° C.] 67 75 85 80 Pressure [kPa] 2100 2000 1400 2190 Split [%] 15 22 21 14 C2/C3 ratio [mol/kmol] 242 701 600 550 H2/C2 ratio [mol/kmol] 23 85 170 250 MFR.sub.2 [g/10 min] 20 40 66 95 XCS [wt.-%] 18 18 20 15 IV (XCS) [dl/g] nd nd 2.9 2.3 C2 (XCS) [mol-%] nd 10.8 53 20 C2 content [mol-%] 10 18 11 GPR 3 Temperature [° C.] 67 85 Pressure bar 1500 1400 Split [%] 10 13 C2/C3 ratio [mol/kmol] 250 699 H2/C2 ratio [mol/kmol] 22 129 MFR.sub.2 [g/10 min] 5 24 XCS [wt.-%] 25 29 IV (XCS) [dl/g] 6.3 3.2 C2 (XCS) [mol-%] 25.7 56 C2 content [mol-%] 11.2 20 C2 ethylene H2/C3 ratio hydrogen/propylene ratio C2/C3 ratio ethylene/propylene ratio H2/C2 ratio hydrogen/ethylene ratio GPR 1/2/3 1st/2nd/3rd gas phase reactor Loop Loop reactor

(21) A Borstar PP pilot plant comprised of a stirred-tank prepolymerization reactor, a liquid-bulk loop reactor, and one, two or three gas phase reactors (GPR1 to GPR3) were used for the main polymerization. The resulting polymer powders were compounded in a co-rotating twin-screw extruder Coperion ZSK 57 at 220° C. with 0.2 wt.-% of Irganox B225 (1:1-blend of Irganox 1010 (Pentaerythrityl-tetrakis(3-(3′,5′-di-tert.butyl-4-hydroxytoluyl)-propionate and tris (2,4-di-t-5 butylphenyl) phosphate) phosphite) of BASF AG, Germany) and 0.05 wt.-% calcium stearate.

Preparation of the Composition (C)

Inventive Examples 1 and 2

(22) HECO1a, HECO2a, HECO2b, PL and HDPE were melt blended on a co-rotating twin screw extruder in amounts as indicated in Table 2 with 0.1 wt.-% of Songnox 1010FF (Pentaerythrityl-tetrakis(3-(3′,5′-di-tert. butyl-4-hydroxyphenyl)), 0.07 wt.-% Kinox-68 G (Tris (2,4-di-t-butylphenyl) phosphite) from HPL Additives, 0.16 wt % hindered amine light stabilizers which were mixed in a 1:1 blend based on Sabostab UV119 (1,3,5-Triazine-2,4,6-triamine) and Hilite 77(G)(Bis-(2,2,6,6-tetramethyl-4-piperidyl)-sebacate), 0.1 wt % 1,2-cyclohexane dicarboxylic acid and Ca-salt from Miliken and 0.1 wt % Erucamide (13-docosenamide) and 1.47 wt.-% of the polypropylene homopolymer HC001A-B1. The polymer melt mixture was discharged and pelletized.

Comparative Examples 1 and 2

(23) HECO1a and HECO2a and optionally PL and HDPE were melt blended on a co-rotating twin screw extruder in amounts as indicated in Table 2 with 0.1 wt.-% of Songnox 1010FF (Pentaerythrityl-tetrakis(3-(3′,5′-di-tert. butyl-4-hydroxyphenyl)), 0.07 wt.-% Kinox-68 G (Tris (2,4-di-t-butylphenyl) phosphite) from HPL Additives, 0.16 wt % hindered amine light stabilizers which were mixed in a 1:1 blend based on Sabostab UV119 (1,3,5-Triazine-2,4,6-triamine) and Hilite 77(G)(Bis-(2,2,6,6-tetramethyl-4-piperidyl)-sebacate), 0.1 wt % NA11UH (Sodium 2,2′-methylene bis-(4,6-di-tert. butylphenyl) phosphate) and 0.1 wt % Erucamide (13-docosenamide) and 1.47 wt.-% of the polypropylene homopolymer HC001A-B 1. The polymer melt mixture was discharged and pelletized.

Comparative Example 3

(24) HECO1b, HECO2b, PL and HDPE were melt blended on a co-rotating twin screw extruder in amounts as indicated in Table 2 with 0.1 wt.-% of Songnox 1010FF (Pentaerythrityl-tetrakis(3-(3′,5′-di-tert. butyl-4-hydroxyphenyl)), 0.07 wt.-% Kinox-68 G (Tris (2,4-di-t-butylphenyl) phosphite) from HPL Additives, 0.16 wt % hindered amine light stabilizers which were mixed in a 1:1 blend based on Sabostab UV119 (1,3,5-Triazine-2,4,6-triamine) and Hilite 77(G)(Bis-(2,2,6,6-tetramethyl-4-piperidyl)-sebacate), 0.1 wt % 1,2-cyclohexane dicarboxylic acid and Ca-salt from Miliken and 0.1 wt % Erucamide (13-docosenamide) and 1.47 wt.-% of the polypropylene homopolymer HC001A-B1. The polymer melt mixture was discharged and pelletized.

(25) TABLE-US-00002 TABLE 2 Properties of comparative and inventive examples collected on 2 mm compact and chemically injection-moulded foamed plates. IE1 IE2 CE1 CE2 CE3 HECO1a [wt.-%] 26.50 26.50 26.50 25.50 HECO1b [wt.-%] 26.5 HECO2a [wt.-%] 38.11 42.50 56.50 HECO2b [wt.-%] 38.11 37.62 PL [wt.-%] 8.00 8.00 8.00 8.00 HDPE1 [wt.-%] 5.00 5.00 5.00 HDPE2 [wt.-%] 5.00 Talc1 [wt.-%] 14.50 Talc2 [wt.-%] 14.50 14.50 14.50 14.50 Nu1 [wt.-%] 0.10 0.10 Nu2 [wt.-%] 0.10 0.10 0.10 Pigments [wt.-%] 5.89 5.89 1.50 1.50 6.38 Additives [wt.-%] 1.90 1.90 1.90 1.90 1.90 Properties of compact parts, 2 mm thick MFR [g/10 min] 18 16 20 27 32 IPT, Energy to max [J] 21 22 nd nd 21 Flexural Modulus [MPa] 2030 2007 1886 2505 2072 CLTE (−30/80° C.) [—] 87 92 nd nd nd Charpy impact strength, +23° C. [kJ/m.sup.2] 15 19 14 6 10 Compressive stress at break [MPa] 84 92 69 85 78 MSEaverage, 1.5 s, G3 [—] 25 40 45 nd 25 Density [g/cm.sup.3] 1.03 1.03 1.04 1.04 1.04 Properties of foamed parts, 3 mm thick Cell size [μm] 50 50 60 60 70 CLTE (−30/80° C.) [—] 95 102 nd nd nd Compressive stress at break [MPa] 56 35 30 55 33 MSEmax, 0.8 s, G2 [—] nd nd 43 43 nd MSEmax, 1.5 s, G3 [—] 40 40 50 nd 120 Density [g/cm.sup.3] 0.85 0.85 0.89 0.89 0.89 PL is the commercial ethylene-octene copolymer Queo8230 of Borealis having a density of 0.880 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 7.0 mol-%. HDPE1 is the commercial high density polyethylene MB7541 of Borealis HDPE2 is the commercial high density polyethylene MG9601 of Borealis Talc1 is the commercial Talc Jetfine 3CA of Luzenac Talc2 is the commercial Talc HAR T84 of Luzenac Nu1 is Sodium 2,2′-methylene bis-(4,6-di-tert. butylphenyl) phosphate Nu2 is 1,2-cyclohexane dicarboxylic acid and Ca-salt from Miliken Pigments is a masterbatch of 70 wt.-% of linear density polyethylene (LDPE) and 30 wt.-% carbon black, with MFR (190° C./21.6 kg) of 15 g/10 min. Additives is a masterbatch of Songnox 1010FF (Pentaerythrityl-tetrakis(3-(3′,5′-di-tert. butyl-4-hydroxyphenyl)), Kinox-68 G (Tris (2,4-di-t-butylphenyl)phosphite) from HPL Additives, hindered amine light stabilizers which were mixed in a 1:1 blend based on Sabostab UV119 (1,3,5-Triazine-2,4,6-triamine) and Hilite 77(G)(Bis-(2,2,6,6-tetramethyl-4-piperidyl)-sebacate), and Erucamide (13-docosenamide) and the polypropylene homopolymer HC001A-B1as outlined above.