Transparent thin wall packaging material with improved stiffness and flowability

Abstract

Heterophasic polypropylene resin having an MFR (2.16 kg, 230 C.) of more than 27 g/10 min, determined according ISO 1133 comprising a propylene homo- or copolymer matrix (A) and an ethylene-propylene rubber phase (B) dispersed within the matrix, wherein the heterophasic polypropylene resin has a fraction insoluble in p-xylene at 25 C. (XCU) in an amount of 75 to 85 wt.-% with a weight average molecular weight of 110 to 190 kg/mol measured by GPC analysis according to ISO 16014-1, and 4, the fraction insoluble in p-xylene at 25 C. (XCU) containing monomer units derived from ethylene in an amount of 12.0 to 21.0 wt.-% and a fraction soluble in p-xylene at 25 C. (XCS) in an amount of 15 to 25 wt.-% having an intrinsic viscosity of 1.4 to 2.0 dl/g, determined according to DIN EN ISO 1628-1 and -3 and being composed of propylene monomer units in an amount of 40 wt.-% or more, and having a glass transition temperature Tg as measured by DSC according to ISO 6721-7 at a compression molded sample consisting of the XCS fraction in the range of 60 to 50 C.

Claims

1. Heterophasic polypropylene resin having an MFR (2.16 kg, 230 C.) of more than 27 g/10 min, determined according to ISO 1133 comprising a propylene homo- or copolymer matrix (A) and an ethylene-propylene rubber phase (B) dispersed within the matrix, wherein the heterophasic polypropylene resin has a fraction insoluble in p-xylene at 25 C. (XCU) in an amount of 75 to 85 wt.-% with a weight average molecular weight of 110 to 190 kg/mol measured by GPC analysis according to ISO 16014-1, and 4, the fraction insoluble in p-xylene at 25 C. (XCU) containing monomer units derived from ethylene in an amount of 12.0 to 21.0 wt.-% and a fraction soluble in p-xylene at 25 C. (XCS) in an amount of 15 to 25 wt.-% having an intrinsic viscosity of 1.4 to 2.0 dl/g, determined according to DIN EN ISO 1628-1 and -3 and being composed of propylene monomer units in an amount of 40 wt.-% or more, and having a glass transition temperature Tg as measured by DSC according to ISO 6721-7 at a compression moulded sample consisting of the XCS fraction in the range of 60 to 50 C.

2. Heterophasic polypropylene resin according to claim 1, wherein the XCU fraction has a weight average molecular weight Mw of 125 to 175 kg/mol, measured by GPC according to ISO 16014-1, and 4.

3. Heterophasic polypropylene resin according to claim 1, wherein the XCU fraction is present in an amount of 76 to 84 wt.-% of the heterophasic polypropylene resin.

4. Heterophasic polypropylene resin according to claim 1, wherein the XCS fraction has an average molecular weight M.sub.w of 110 to 190 kg/mol, measured by GPC according to ISO 16014-1, and 4.

5. Heterophasic polypropylene resin according to claim 1, wherein the haze of the resin is lower than 50% measured on 1 mm injection moulded plaques.

6. Heterophasic polypropylene resin according to claim 1, wherein the haze of the resin is lower than 25% measured on 0.5 mm injection moulded plaques.

7. Heterophasic polypropylene resin according to claim 1, wherein the resin has a Charpy notched impact strength according to ISO 179/1 eA at 23 C. of at least 6.5 kJ/m.sup.2.

8. Heterophasic polypropylene resin according to claim 1, wherein the resin has a Charpy notched impact strength according to ISO 179/1 eA at 20 C. of at least 1.6 kJ/m.sup.2.

9. Heterophasic polypropylene resin according to claim 1, wherein the resin has a puncture energy at 23 C. of at least 16 J, determined according to ISO 6603-2.

10. Heterophasic polypropylene resin according to claim 1, wherein the resin has a puncture energy at 20 C. of at least 20 J, determined according to ISO 6603-2.

11. Heterophasic polypropylene resin according to claim 1, wherein the tensile modulus measured according to ISO 527-2 on injection moulded specimens of type 1B(F3/4) prepared in accordance with EN ISO 1873-2 is 1100 MPa or higher.

12. Heterophasic polypropylene resin according to claim 1 being produced in the presence of a Ziegler-Natta catalyst system comprising an external donor with an AI/donor ratio of 2 to 8.

13. A method for obtaining a heterophasic polypropylene resin having an MFR (2.16 kg, 230 C.) of more than 27 g/10 min, determined according to ISO 1133, by a quadruple stage reactor process, the method comprising: operating a first loop reactor under conditions to produce a propylene homo- or copolymer (A) being composed of propylene monomer units in an amount of at least 95 wt.-%, and an MFR (2.16 kg, 230 C.) of more than 60 g/10 min, and a xylene solubility of 3.0 wt. % or less, feeding the obtained product from the bulk reactor to a first gas phase reactor the first gas phase reactor being operated at a temperature of 65 to 75 C., a pressure of 1900 to 2300 kPa, and a H2/C3 ratio of 10 to 16 mol/kmol, a C2/C3 ratio of 1100 to 1500 mol/kmol feeding the obtained product from the first gas phase reactor to a second gas phase reactor, the second gas phase reactor being operated at a temperature of 10 C. when compared with the first gas phase reactor, at a pressure of 1800 to 2300 kPa, a C2/C3 ratio of 1600 to 2000 mol/kmol, a H2/C2 ratio mol/kmol of 400 to 500 mol/kmol feeding the obtained product from the second gas phase reactor to a third gas phase reactor, the third gas phase reactor being operated at a temperature of 5 C. to 15 C. higher than the temperature in the first gas phase reactor, at a pressure of 2300 to 2700 kPa, a C2/C3 ratio of 300 to 420 mol/kmol, a H2/C2 ratio of 375 to 450 mol/kmol optionally subjecting the product from the third gas phase reactor to a degassing step, and compounding the product obtained from the third gas phase reactor or the degassed product in an amount of 70.5 to 84.5 wt.-% with respect to the final heterophasic polypropylene resin with an ethylene homo- or copolymer having a density measured according to ISO 1183 of less than 930 kg/m.sup.3 in an amount of 15 to 24.5 wt.-% with respect to the final heterophasic polypropylene resin in the presence of stabilisers in an amount of 0.5 to 5.0 wt with respect to the final heterophasic polypropylene resin; wherein the final heterophasic polypropylene resin has a fraction insoluble in p-xylene at 25 C. (XCU) in an amount of 75 to 85 wt.-% with a weight average molecular weight of 110 to 190 kg/mol measured by GPC analysis according to ISO 16014-1, and 4, the fraction insoluble in p-xylene at 25 C. (XCU) containing monomer units derived from ethylene in an amount of 12.0 to 21.0 wt.-% and a fraction soluble in p-xylene at 25 C. (XCS) in an amount of 15 to 25 wt.-% having an intrinsic viscosity of 1.4 to 2.0 dl/g, determined according to DIN EN ISO 1628-1 and -3 and being composed of propylene monomer units in an amount of 40 wt.-% or more, and having a glass transition temperature Tg as measured by DSC according to ISO 6721-7 at a compression moulded sample consisting of the XCS fraction in the range of 60 to 50 C.

14. The method of claim 13, wherein the heterophasic polypropylene resin is produced in the presence of a Ziegler-Natta catalyst system comprising an external donor with an AI/donor ratio of 2 to 8.

15. Heterophasic polypropylene composition consisting of the heterophasic polypropylene resin according to claim 1 and at least one nucleating agent in an in an amount of 0.1 to 5 wt.-% with respect to the weight of the total heterophasic polypropylene composition, and/or at least one additive in an amount of up to 1 wt.-% with respect to the heterophasic polypropylene composition, and/or at least one impact modifier in an amount of up to 10 wt.-% with respect to the heterophasic polypropylene composition.

16. Heterophasic polypropylene composition consisting of the heterophasic polypropylene resin produced by the method of claim 13 and at least one nucleating agent in an in an amount of 0.1 to 5 wt.-% with respect to the weight of the total heterophasic polypropylene composition, and/or at least one additive in an amount of up to 1 wt.-% with respect to the heterophasic polypropylene composition, and/or at least one impact modifier in an amount of up to 10 wt.-% with respect to the heterophasic polypropylene composition.

17. Article comprising the heterophasic polypropylene resin according to claim 1.

18. Article comprising the heterophasic polypropylene resin produced by the method of claim 13.

19. Article comprising the heterophasic polypropylene composition according to claim 15.

20. Article comprising the heterophasic polypropylene composition according to claim 16.

Description

EXAMPLES

(1) A polymer has been produced in four reactors connected in series. The properties of the products obtained from the individual reactors are given in Tables 1. In said Example the first fraction has been produced in a loop reactor, fractions two to four have been produced in gas phase reactors.

(2) The properties of the products obtained from the individual reactors naturally are not measured on homogenized material but on reactor samples (spot samples). The properties of the final resin are measured on homogenized material, the MFR.sub.2 on pellets made thereof.

(3) The catalyst used in the polymerization processes was the commercial BCF20P catalyst (1.9 wt.-% Ti-Ziegler-Natta-catalyst as described in EP 591 224) of Borealis with triethyl-aluminium (TEA) as co-catalyst and dicyclo pentyl dimethoxy silane as donor.

(4) The AI/donor D ratio was 5 mol/mol.

(5) TABLE-US-00001 TABLE 1 Base polymer Loop reactor MFR.sub.2/g/10 min/dl/g 70 Xylene solubles/wt.-% 1.4 Ethylene content/wt.-% Amount of polymer made in loop/wt.-% 41.5 Gas phase reactor GPR.sub.1 calculated MFR.sub.2 g/10 min for the product obtained 80 in GPR1* Amount of polymer made in GPR1/wt.-% 41.5 Xylene solubles/wt.-% made in GPR1 3.8 Ethylene content/wt.-% of material made in GPR1 2.2 Xylene solubles (total)/wt.-% 2.6 MFR.sub.2 total/g/10 min 75 Ethylene content total/wt.-% 1.1 Gas phase reactor GPR.sub.2 MFR.sub.2/g/10 min 51 xylene soluble (total)/wt.-% 13.7 ethylene content of the XCS produced in GPR2/wt.-% 65 Intrinsic viscosity XS/dl/g 1.4 Amount of polymer made in GPR2/wt.-% 10.5 Gas phase reactor GPR3 MFR.sub.2/g/10 min 43 Xylene solubles total/wt.-% 20.1 Amount of polymer made in GPR3/wt.-% 6.5 ethylene content of the XCS produced in GPR3/wt.-% 20 Intrinsic viscosity XS.sub.total/dl/g 1.7 Ethylene content of XCS total after GPR3/wt.-% 49 *The MFR is measured after each reactor. That means that MFR of Reactor 1 as well as the total MFR are measured values. The values of reactor 2 is formally calculated according to: $\mathrm{MFR}\left(\mathrm{PP}2\right)={10}^{\left[\frac{\log \left(\mathrm{MFR}\left(R2\right)\right)-w\left(\mathrm{PP}1\right)\log \left(\mathrm{MFR}\left(\mathrm{PP}1\right)\right)}{w\left(\mathrm{PP}2\right)}\right]}$wherein w(PP1) is the weight fraction of the first polypropylene fraction (PP1), i.e. the product of the first reactor (R1), w(PP2) is the weight fraction of the second polypropylene fraction (PP2), i.e. of the polymer produced in the second reactor (R2), MFR(PP1) is the melt flow rate MFR.sub.2 (230 C.) [in g/10 min] measured according ISO 1133 of the first polypropylene fraction (PP1), i.e. of the product of the first reactor (R1), MFR(R2) is the melt flow rate MFR.sub.2 (230 C.) [in g/10 min] measured according ISO 1133 of thr product obtained in the second reactor (R2), i.e. the mixture of the first polypropylene fraction (PP1) and the second polypropylene fraction (PP2), MFR(PP2) is the calculated melt flow rate MFR.sub.2 (230 C.) [in g/10 min] of the second polypropylene fraction (PP2).

(6) TABLE-US-00002 TABLE 2 shows the polymerization conditions. Process conditions for the preparation of the base polymer Al/Donor [mol/mol] 5 T(R1) [ C.] 70 p(R1) [kPa] 5300 H2/C3 ratio 13 [mol/kmol] in R1 Gpr1 T(R2) [ C.] 70 p(R2) [kPa] 2100 H2/C3 ratio 13 [mol/kmol] in R2 C2-feed in R2 [kg/h] 44 in R2 C2/C3 ratio 1270 [mol/kmol] in R2 Gpr2 T(R3) [ C.] 70 p(R3) [kPa] 2100 C2-feed in R2 [kg/h] 54 in R3 H2/C2 ratio 570 [mol/kmol] in R3 C2/C3 ratio 1780 [mol/kmol] in R3 Gpr3 T(R4) [ C.] 80 p(R4) [kPa] 2460 C2-feed in R2 [kg/h] 18 in R4 H2/C2 ratio 450 [mol/kmol] in R4 C2/C3 ratio 360 [mol/kmol] in R4

(7) All examples were compounded on a co-rotating twin-screw extruder (Thermo-Prism TSE24) of 24 mm screw diameter and a length to diameter ratio of 48 with a high-intensity mixing screw and a temperature profile at 180-220 C. with a throughput of 10 kg/h and a screw speed of 50 rpm.

(8) The composition of the comparative examples as well as of the inventive examples is shown in table 3.

(9) TABLE-US-00003 TABLE 3 Composition of comparative and inventive examples Component/wt.-% CE2 CE3 IE1 IE2 Base polymer 81.8 81.8 82.8 82.8 Millad 3998 0.2 0.2 0.2 0.2 CA9150 17 15 VS5580 18 15 Engage 8411 3 Engage 8400 2

(10) Millad 3988 (supplied by Milliken Inc.) is 1,3:2,4 Bis(3,4-dimethylbenzylidene)sorbitol, CAS-No. 135861-56-2.

(11) CA9150 is a low density ethylene homopolymer having an MFR2 (190 C., 2.16 kg) of 15 g/10 min and a density of 915 kg/m3 and is commercially available from Borealis.

(12) VS5580 is a high density ethylene homopolymer having an MFR2 (190 C., 2.16 kg) of 0.95 g/10 min and a density of 958 kg/m3 and is commercially available from Borealis.

(13) Engage 8411 is an ethylene-octene copolymer having a density of 880 kg/m3 and an MFR2 (190 C., 2.16 kg) of 18 g/10 min, and is commercially available from Dow Chemical.

(14) Engage 8400 is an ethylene-octene copolymer having a density of 870 kg/m3 and an MFR2 (190 C., 2.16 kg) of 30 g/10 min, and is commercially available from Dow.

(15) Comparative example 1 is an impact-modified polypropylene random copolymer having an MFR2 (230 C., 2.16 kg) of 25 g/10 min, and is commercially available from Borealis under the trade name Borpact SG930MO.

(16) Contrary to all the comparative examples, the inventive examples show increased flowability, see table 4. Although the stiffness impact balance achievable by using the HDPE or a combination of HDPE and plastomer is impressing it leads to a significant increase of the haze values and thus the material is not transparent any more. By using the LDPE or a combination of LDPE and plastomer, the haze values and the flowability could be kept on a high level. Also the impact-stiffness balance of these materials is outperforming that of the actual commercial benchmark SG930MO.

(17) TABLE-US-00004 TABLE 4 Properties of comparative and inventive examples CE1 CE2 CE3 IE1 IE2 MFR2/g/10 min 25 24 26 35 35 Tensile Modulus/MPa 1003 1210 1161 1117 1171 Tensile Stress at Yield/MPa 22 25 24 23 23 Tensile Strain at Yield/% 13 10 11 11 10 Tensile Strength/MPa 22 25 24 23 23 Strain at Tensile Strength/% 13 10 11 11 10 Stress at Break/MPa 13 11 6 11 6 Tensile Strain at Break/% 396 135 233 426 302 Charpy/kJ/m2, 23 C. 7.6 8.0 9.2 8.2 8.1 Charpy/kJ/m2, 20 C. 2 2.2 3.0 2.2 3.3 Transparency (60 * 60 * 1 mm)/% 83 72 73 82 82 Haze (60 * 60 * 1 mm)/% 41 96 94 45 43 Clarity (60 * 60 * 1 mm)/% 96 45 54 94 94 Transparency (60 * 60 * 0.5 mm)/% 89 81 82 89 89 Haze (60 * 60 * 0.5 mm)/% 19 72 67 20 20 Clarity (60 * 60 * 0.5 mm)/% 98 72 70 96 96 Puncture Energy/J, 23 C. 24 25 24 23 23 Puncture Energy/J, 20 C. 7 22 19 29 27

(18) TABLE-US-00005 TABLE 5 provides details as to molecular weight, Tg, Mw/Mn and C2 content of the total composition and the XCS and XCU fraction. Total MFR/ C2 total/ composition g/min XCS/wt.-% wt.-% IE1 35 17.3 29.3 IE2 35 19.4 30.4 CE2 24 17 34 CE3 26 20 32.1 CE1 25 14.9 27.2 C2 XCS content Mn/ Mw/ fraction Tg/ C. wt.-% kg/mol Kg/mol Mw/Mn IE1 54 44.74 27 150 5.5 IE2 54 49.1 31 147 4.7 CE2 55 45.2 36 157 4.3 CE3 55 51.4 37 146 4 C2 XCU content Mn/ Mw/ fraction IV/dl/g wt.-% kg/mol Kg/mol Mw/Mn IE1 1.7 18.7 31 148 4.8 IE2 1.7 18.1 31 147 4.9 CE2 24.4 32 147 4.9 CE3 21.7 31 147 4.8