PROCESS FOR PRODUCING A PROPYLENE COPOLYMER

Abstract

Process for the production of a polypropylene random copolymer (PP), the process comprising the steps of polymerising in a first reactor (R1) propylene and a comonomer (C1a) selected from a C.sub.4 to C.sub.8 -olefin in the presence of a first metallocene catalyst (MC1) yielding a first polypropylene copolymer (PP1), wherein the ratio of the feed of the comonomer (C1a) to the feed of propylene is in the range of 1 to 100 mol/kmol and the MFR.sub.2 of the first polypropylene copolymer (PP1) is in the range of 0.01 to 100 g/10 min; transferring the first polypropylene copolymer (PP1) to a second reactor (R2); polymerising in the second reactor (R2) and in the presence of said first polypropylene (PP1), propylene, a comonomer (C1b) selected from a C.sub.4 to C.sub.8 -olefin, and a second metallocene catalyst (MC2) yielding a second polypropylene copolymer (PP2), wherein the ratio of the feed of the comonomer (C1b) to the feed of propylene is in the range of 40 to 150 mol/kmol and the MFR.sub.2 of the second polypropylene copolymer (PP2) is in the range of 0.01 to 100 g/10 min; withdrawing the polypropylene random copolymer (PP) comprising the first polypropylene copolymer (PP1) and the second polypropylene copolymer (PP2) from the second reactor (R2); wherein the first metallocene catalyst (MC1) and/or the second metallocene catalyst (MC2) is a metallocene catalyst (MC) comprising a metallocene complex, and wherein the metallocene catalyst (MC) comprises a support comprising silica.

Claims

1. Process for the production of a polypropylene random copolymer (PP), the process comprising the steps of a) polymerising in a first reactor (R1) propylene and a comonomer (C1a) selected from a C.sub.4 to C.sub.8 -olefin in the presence of a first metallocene catalyst (MC1) yielding a first polypropylene copolymer (PP1), wherein the ratio of the feed of the comonomer (C1a) to the feed of propylene is in the range of 1 to 100 mol/kmol and the MFR.sub.2 of the first polypropylene copolymer (PP1) is in the range of 0.01 to 100 g/10 min. b) transferring the first polypropylene copolymer (PP1) to a second reactor (R2), c) polymerising in the second reactor (R2) and in the presence of said first polypropylene (PP1), propylene, a comonomer (C1b) selected from a C.sub.4 to C.sub.3 -olefin, and a second metallocene catalyst (MC2) yielding a second polypropylene copolymer (PP2), wherein the ratio of the feed of the comonomer (C1b) to the feed of propylene is in the range of 40 to 150 mol/kmol and the MFR.sub.2 of the second polypropylene copolymer (PP2) is in the range of 0.01 to 100 g/10 min, d) withdrawing the polypropylene random copolymer (PP) comprising the first polypropylene copolymer (PP1) and the second polypropylene copolymer (PP2) from the second reactor (R2), wherein the first metallocene catalyst (MC1) and/or the second metallocene catalyst (MC2) is a metallocene catalyst (MC) comprising a metallocene complex, wherein the metallocene catalyst (MC) comprises a support comprising silica, and wherein the support has a D50 of between 10 and 80 m.

2. The process according to claim 1, wherein the first metallocene catalyst (MC1) and/or the second metallocene catalyst (MC2) comprises a complex of formula (I): ##STR00006## wherein each X independently is a sigma-donor ligand, L is a divalent bridge selected from R.sub.2C, R.sub.2CCR.sub.2, R.sub.2Si, R.sub.2SiSiR.sub.2, R.sub.2Ge, wherein each R is independently a hydrogen atom or a C.sub.1-C.sub.20-hydrocarbyl group optionally containing one or more heteroatoms from groups 14-16 of the periodic table or fluorine atoms, or optionally two R groups taken together can form a ring, each R.sup.1 are independently the same or can be different and are hydrogen, a linear or branched C.sub.1-C.sub.6-alkyl group, a C.sub.7-20-arylalkyl, C.sub.7-20-alkylaryl group or C.sub.6-20-aryl group or an OY group, wherein Y is a C.sub.1-10-hydrocarbyl group, and optionally two adjacent R.sup.1 groups can be part of a ring including the phenyl carbons to which they are bonded, each R.sup.2 independently are the same or can be different and are a CH.sub.2R.sup.8 group, with R.sup.8 being H or linear or b ranched C.sub.1-6-alkyl group, C.sub.3-8-cycloalkyl group, C.sub.6-10-aryl group, R.sup.3 is a linear or branched C.sub.1-C.sub.6-alkyl group, C.sub.7-20-arylalkyl, C.sub.7-20-alkylaryl group or C.sub.6-C.sub.20-aryl group, R.sup.4 is a C(R.sup.9).sub.3 group, with R.sup.9 being a linear or branched C.sub.1-C.sub.6-alkyl group, R.sup.5 is hydrogen or an aliphatic C.sub.1-C.sub.20-hydrocarbyl group optionally containing one or more heteroatoms from groups 14-16 of the periodic table; R.sup.6 is hydrogen or an aliphatic C.sub.1-C.sub.20-hydrocarbyl group optionally containing one or more heteroatoms from groups 14-16 of the periodic table; or R.sup.5 and R.sup.6 can be taken together to form a 5 membered saturated carbon ring which is optionally substituted by n groups R.sup.10, n being from 0 to 4; each R.sup.10 is same or different and may be a C.sub.1-C.sub.20-hydrocarbyl group, or a C.sub.1-C.sub.20-hydrocarbyl group optionally containing one or more heteroatoms belonging to groups 14-16 of the periodic table; R.sup.7 is H or a linear or branched C.sub.1-C.sub.6-alkyl group or an aryl or heteroaryl group having 6 to 20 carbon atoms optionally substituted by one to three groups R.sup.1, each R.sup.11 are independently the same or can be different and are hydrogen, a linear or branched C.sub.1-C.sub.6-alkyl group, a C.sub.7-20-arylalkyl, C.sub.7-20-alkylaryl group or C.sub.6-20-aryl group or an OY group, wherein Y is a C.sub.1-10-hydrocarbyl group.

3. The process according to claim 1, wherein the support has an average particle size of from 15 to 80 m and preferably 18 to 50 m.

4. The process according to claim 1 wherein the support has an average pore size of from 10 to 100 nm.

5. The process according to claim 1, wherein the comonomer (C1a) and/or the comonomer (C1b) are/is selected from the group consisting of C.sub.4 and C.sub.6 -olefins, preferably are/is 1-butene.

6. The process according to claim 1, wherein the comonomer (C1a) and the comonomer (C1b) are identical.

7. The process according to claim 6, wherein the polypropylene random copolymer (PP) is a terpolymer and wherein step a) is carried out in the presence of a second comonomer (C2) selected from the group consisting of ethylene and C.sub.4 to C.sub.8 -olefins, wherein the second comonomer (C2) is different from the comonomer (C1a/C1b), wherein the ratio of the feed of the second comonomer (C2) to the feed of propylene is in the range of 5 to 60 mol/kmol, and step c) is carried out in the presence of the second comonomer (C2), wherein the ratio of the feed of the second comonomer (C2) to the feed of propylene is in the range of 50 to 150 mol/kmol.

8. The process according to claim 7, wherein the second comonomer (C2) is ethylene.

9. The process according to claim 1, wherein step a) is carried out as a slurry-phase polymerisation step and/or the first reactor (RK1) is a loop reactor.

10. The process according to claim 1, wherein in step a) the ratio of the feed of the comonomer (C.sub.1a) to the feed of propylene is in the range of 30 to 50 mol/kmol, preferably 35 to 45 mol/kmol.

11. The process according to claim 3, wherein in step a) the ratio of the feed of the second comonomer (C2) to the feed of propylene is in the range of 10 to 20 mol/kmol, preferably 13 to 18 mol/kmol.

12. The process according to claim 1, wherein step c) is carried out as a gas-phase polymerisation step and/or the second reactor (RK2) is a gas-phase reactor, preferably step c) is carried out as a fluidized bed gas-phase polymerisation step and/or the second rector (2) is fluidized bed gas-phase reactor.

13. The process according to claim 1, wherein in step c) the ratio of the feed of the comonomer (C1b) to the feed of propylene is in the range of 40 to 60 mol/kmol, preferably 45 to 50 mol/kmol.

14. The process according to claim 7, wherein in step c) the ratio of the feed of the second comonomer (C2) to the feed of propylene is in the range of 90 to 130 mol/kmol, preferably 105 to 115 mol/kmol.

15. The process according to claim 1, wherein the polypropylene random copolymer (PP) has a combined residual content of the comonomer (C1a) and the comonomer (C1b) of lower than 6.5 ppm, preferably lower than 5 ppm, and most preferably lower than 4 ppm.

Description

EXAMPLES

[0218] The following examples were carried out in a Borstar pilot plant, comprising a reactor sequence consisting of a prepolymerisation reactor, a loop reactor and a gas phase reactor (GPR1). Process and properties are given in table 1.

[0219] The pelletization of the powder of the base polymers is done in a twin screw extruder with a screw diameter of 18 mm at a melt temperature of 240 C. and a throughput of 7 kg/h.

TABLE-US-00001 TABLE 1 Example CE1 CE2 CE3 CE4 IE1 IE2 IE3 Catalyst ZNC1 ZNC1 SSC1 SSC1 SSC2 SSC2 SSC2 Prepolymerisation reactor Temp. [ C.] 20 20 20 20 20 20 20 Press. [kPa] 5298 5105 5258 4973 4919 4973 5090 Catalyst feed [g/h] 1.1 1.3 0.7 0.7 5.2 3.7 3.5 Donor/C3 [g/t] 50 50 TEAL/C3 [g/t] 160.0 160.0 H2 [g/h] 0.98 0.98 0.10 0.10 0.12 0.12 0.12 C3 [kg/h] 66.5 65.0 67.0 65.0 65.0 65.0 65.0 Loop reactor Temp. [ C.] 65 60 70.0 69.9 70 70 65 Press. [kPa] 5203 5082 5138 4864 4835 4840 5209 C3 feed [kg/h] 147.0 131.1 174.4 174.5 187.7 189.0 179.6 C4 feed [kg/h] 25 39.5 5.9 6.5 9.8 10 13.7 C2 feed [kg/h] 0.0 0.5 2.1 1.9 0.0 2.2 2.2 Feed H2/C3 ratio [mol/kmol] 1.1 1.0 0.1 0.1 0.06 0.09 0.1 Feed C2/C3 ratio [mol/kmol] 0 6.0 17.8 16.1 0 17.06 18.5 Feed C4/C3 ratio [mol/kmol] 120 225 30.3 25.4 39.20 39.61 57.2 Residence time [h] 0.42 0.4 0.5 0.5 0.45 0.46 0.3 Production rate [kg/h] 37.0 27.9 37.6 32.5 31.4 36.6 31.6 Solid Concentration [wt-%] 24.4 31.7 33.9 30.6 21.0 23.9 13.9 Split [wt-%] 58 51 47 41 45 40 61 MFR.sub.2 [g/10 min] 5.3 5.2 56.0 59.7 4.7 3.8 3.7 C2 [wt-%] 0.0 0.4 1.0 0.9 0.0 1.0 0.6 C4 [wt-%] 4.5 7.5 5.5 5.5 5.5 5.2 4.8 XS % 3.3 5.0 1.2 1.1 0.9 1.2 1 Gas phase reactor Temp. [ C.] 80 75 75 75 80 80 80 Press. [kPa] 1800 1850 2480 2441 2500 2524 2400 H2/C3 ratio [mol/kmol] 13.2 25.9 1.5 1.5 1.3 2.6 1.6 C2/C3 ratio [mol/kmol] 0.0 10.0 121 121 0 109 79.1 C4/C3 ratio [mol/kmol] 83.7 197.5 59 61 43 47 50.5 C4 feed [kg/h] 16.1 43.0 9.0 12.0 2.5 2.8 18.5 Residence time [h] 1.4 1.3 1.7 1.7 2 2 2 Split [wt-%] 42 49 53 59 55 60 39 MFR.sub.2 [g/10 min] 6.3 5.5 3.6 3.0 4.9 6.0 6.7 C2 [wt-%] 0 1.1 1.2 1.2 0 1.2 1 C4 [wt-%] 5.8 8.8 5.3 6.0 4.8 6.0 6.1 XS % 3.1 9.0 9.4 10.0 0.6 12.0 1.6 Total reactor Production rate [kg/h] 63.3 55.0 79 78 74.0 92.0 52 C4 feed 41.1 82.5 14.9 18.5 12.3 12.8 13.6 C4 conversion % 9.2 5.9 27.6 34.4 28.3 43.8 23.3 Catalyst productivity [kg PP/g cat] 55 42 118 112 14 25 15 Final polymer, powder MFR.sub.2 [g/10 min] 5.8 5.0 2.6 2.23 4.6 6.3 5.95 C2 [wt-%] 0.0 1.2 1.1 1.2 0.0 1.1 1 C4 [wt-%] 6.0 8.8 5.2 8.1 4.7 6.1 6.1 XS % 3.2 8.8 17.3 14.6 0.7 12.4 1.1 Bulk Density [kg/m.sup.3] 439 438 435 418 497 447 495 APS [mm] 1.23 1.17 2.2 2.1 0.9 1.3 0.82 PSD < 0.106 mm 0.25 0.02 0.0 0.0 0.0 0.0 0.07 PSD > 0.106 mm 0.42 0.2 0.1 0.5 0.1 0.1 0.14 PSD > 0.250 mm 0.15 1.9 0.2 0.5 0.5 0.2 0.32 PSD > 0.355 mm 25.53 32.92 2.9 6.0 59.6 28.1 73.55 PSD > 0.850 mm 72.21 64.72 47.8 48.6 39.4 67.7 25.79 PSD > 2.0 mm 1.44 0.24 43.0 37.3 0.5 3.7 0.13 PSD > 4.0 mm 0.00 0 5.9 7.2 0.0 0.3 0 Final polymer, pellet MFR.sub.2 [g/10 min] 5.6 4.9 1.94 2.03 4.4 6.7 5.6 Tc [ C.] 110.7 94.5 92.5 91.2 108.6 93.2 92.3 Tm [ C.] 152.8 133.0 130.8 130.2 142.8 130.2 129 Residual C4 [ppm] 14 7 542 802 6 4 4

[0220] From the examples it can be seen that the process using Ziegler Natta catalysts, i.e. comparative examples CE1 and CE2, have very low total comonomer conversions. Therefore, the process of the present invention is more efficient both in terms of energy and material consumption.

[0221] Furthermore, it can be seen that non-silica-supported metallocene catalysts known from the prior art as used in comparative examples CE3 and CE4, while achieving similar comonomer conversion rates, exhibit very high residual comonomer in the produced polymer, resulting in high amounts of volatiles in the product. Furthermore, it can also be seen that such catalysts produce powder having particle distributions conferring to higher particle sizes, thereby causing higher C.sub.4 residual content in the product.

[0222] Finally, from the inventive examples IE1-IE3 it can be seen that the present invention works well for both type of copolymers, i.e. bipolymers and terpolymers. The C4 conversion is high and the C4 residuals in the product are low.