Thermoplastic polyolefins with high flowability and excellent surface quality produced by a multistage process

Abstract

Reactor grade thermoplastic polyolefins with high flowability and excellent surface quality comprising (A) 40-90 wt % of a propylene homo- or copolymer matrix with an MFR in accordance with ISO 1 133 (230 C., 2.16 kg load) of 200 g/10 min and (B) 2-30 wt % of an elastomeric ethylene-propylene copolymer having an intrinsic viscosity IV (according to ISO 1628 with decalin as solvent) of 2.8 dl/g and an ethylene content of >50 to 80 wt % and (C) 8-30 wt % of an elastomeric ethylene-propylene copolymer having an intrinsic viscosity IV (according to ISO 1628 with decalin as solvent) of 3.0-6.5 dl/g and an propylene content of 50 to 80 wt %, the reactor grade thermoplastic polyolefins being obtainable by a multistage polymerization process with at least 3 polymerization steps in the presence of a catalyst system comprising (i) a Ziegler-Natta procatalyst which contains a trans-esterification product of a lower alcohol and a phthalic ester and (ii) an organometallic cocatalyst and (iii) external donor represented by formula (I) Si(OCH.sub.2CH.sub.3).sub.3(NR.sup.1R.sup.2) wherein R.sup.1 and R.sup.2 can be the same or different a represent a hydrocarbon group having 1 to 12 carbon atoms, as well as the use of these reactor grade thermoplastic polyolefins and molded articles produced from them.

Claims

1. A catalyst system, comprising: (i) a Ziegler-Natta procatalyst which contains a trans-esterification product of a lower alcohol and a phthalic acid ester and (ii) an organometallic cocatalyst and (iii) external donor represented by the formula
Si(OCH.sub.2CH.sub.3).sub.3(NR.sub.xR.sub.y) wherein R.sup.x and R.sup.y can be the same or different a represent a hydrocarbon group having 1 to 12 carbon atoms, suitable for producing a reactor grade thermoplastic polyolefin in a multistage process with at least 3 polymerization steps, said reactor grade thermoplastic polyolefin having an MFR (230 C.) of greater than 30 g/10 min and comprising (A) 40-90 wt % of a propylene homo- or copolymer matrix with an MFR.sub.2 in accordance with ISO 1133 (230 C., 2.16 kg load) of 200 g/10 min and (B) 2-30 wt % of an elastomeric ethylene-propylene copolymer having an intrinsic viscosity IV (according to ISO 1628 with decalin as solvent) of 2.8 dl/g and an ethylene content of in the range of 50 to 75 wt % and (C) 15-27 wt % of an elastomeric ethylene-propylene copolymer having an intrinsic viscosity IV (according to ISO 1628 with decalin as solvent) of 3.0-6.5 dl/g and a propylene content of 50 to 80 wt %.

2. The catalyst system according to claim 1, wherein the Ziegler-Natta procatalyst (i) has been prepared by a) reacting a spray crystallized or emulsion solidified adduct of MgCl.sub.2 and a C.sub.1 to C.sub.2 alcohol with TiCl.sub.4 b) reacting the product of stage a) with a dialkylphthalate of formula (I) ##STR00003## wherein R.sub.1 and R.sub.2 are independently at least a C.sub.5 alkyl under conditions where a transesterification between said C.sub.1 to C.sub.2 alcohol and said dialkylphthalate of formula (I) takes place to form an internal donor c) washing the product of stage b) and d) optionally reacting the product of step c) with TiCl.sub.4.

3. The catalyst system according to claim 2, wherein the dialkylphthalate of formula (I) is dioctylphthalate and that the C.sub.1 to C.sub.2 alcohol is ethanol.

4. The catalyst system according to claim 1, wherein the organometallic cocatalyst (ii) is selected from the group consisting of trialkylaluminium, dialkyl aluminium chloride and alkyl aluminium sesquichloride.

5. The catalyst system according to claim 4, wherein the organometallic cocatalyst (ii) is triethylaluminium.

6. The catalyst system according to claim 1, wherein the external donor (iii) is diethylaminotriethoxysilane.

7. The catalyst system of claim 1, further comprising the reaction grade thermoplastic polyolefin produced by the catalyst system and said at least 3 polymerization steps.

8. The catalyst system of claim 2, further comprising the reaction grade thermoplastic polyolefin produced by the catalyst system and said at least 3 polymerization steps.

9. The catalyst system of claim 3, further comprising the reaction grade thermoplastic polyolefin produced by the catalyst system and said at least 3 polymerization steps.

10. The catalyst system of claim 4, further comprising the reaction grade thermoplastic polyolefin produced by the catalyst system and said at least 3 polymerization steps.

11. The catalyst system of claim 5, further comprising the reaction grade thermoplastic polyolefin produced by the catalyst system and said at least 3 polymerization steps.

12. The catalyst system of claim 6, further comprising the reaction grade thermoplastic polyolefin produced by the catalyst system and said at least 3 polymerization steps.

Description

EXAMPLES

(1) Methods:

(2) Melt Flow Rate

(3) Unless otherwise specified, the melt flow rate is measured as the MFR in accordance with ISO 1133 (230 C., 2.16 kg load) for polypropylene and is indicated in g/10 min. The MFR is an indication of the flowability, and hence the processability, of the polymer. The higher the melt flow rate, the lower the viscosity of the polymer.

(4) Comonomer content was measured with Fourier transform infrared spectroscopy (FTIR) calibrated with .sup.13C-NMR. When measuring the ethylene content in polypropylene, a thin film of the sample (thickness about 250 mm) was prepared by hot-pressing. The area of CH.sub.2 absorption peak (800-650 cm.sup.1) was measured with Perkin Elmer FTIR 1600 spectrometer. The method was calibrated by ethylene content data measured by .sup.13C-NMR.

(5) Flexural modulus was measured according to ISO 178 by using injection molded test specimens as described in EN ISO 1873-2 (80104 mm)

(6) Xylene Solubles

(7) The xylene soluble fraction (XS) as defined and described in the present invention was determined as follows: 2.0 g of the polymer are dissolved in 250 ml p-xylene at 135 C. under agitation. After 30 minutes, the solution was allowed to cool for 15 minutes at ambient temperature and then allowed to settle for 30 minutes at 250.5 C. The solution was filtered with filter paper into two 100 ml flasks. The solution from the first 100 ml vessel was evaporated in nitrogen flow and the residue dried under vacuum at 90 C. until constant weight is reached. The xylene soluble fraction (percent) can then be determined as follows:
XS%=(100m.sub.1X v.sub.0)/(m.sub.0v.sub.1),
wherein m.sub.0 designates the initial polymer amount (grams), m.sub.1 defines the weight of residue (grams), v.sub.0 defines the initial volume of solvent taken (250 milliliters) and v.sub.1 defines the volume of the aliquot taken for determination (analysed sample; 100 milliliters).

(8) The intrinsic viscosity (IV) value increases with the molecular weight of a polymer. The IV values were measured according to DIN EN ISO 1628-1 in Decalin at 135 C.

(9) The tensile modulus was measured according to ISO 572-3 at 1 mm/min and 23 C. Test specimens as described in EN ISO 1873-2 (80104 mm) were used.

(10) Charpy, notches impact strength (NIS), was measured according to ISO 179/1 eA at +23 C., 0 C. and at 20 C. by using injection molded test specimens as described in EN ISO 1873-2 (80104 mm)

(11) Shrinkage was measured according to an internal standard using 150802 mm injection molded plaques. Measurements were performed after injection and conditioning at room temperature for at least 96 h in the flow direction and perpendicular to the flow direction. Following conditions were used for injection molding: injection time: 3 s, melt temperature: 240 C., mold temperature: 50 C., hold pressure: from 73 to 23 bars in 10 steps, hold time: 10 s, cooling time: 20 s.

(12) The fines were determined by sieving the polymer powder according to ASTM D1921-06. The screen set consisted of screens having openings of 4,000 mm; 2,800 mm; 2,000 mm; 1,400 mm; 1,000 mm; 0,500 mm; 0,180 mm; 0,106 mm and 0,053 mm.

(13) The powder passing the 0,180 mm screen was considered as fines.

(14) Zinc oxide was used as antistat.

Example 1: Preparation of Base Resin According to the Invention

(15) The base resin was produced in a plant having a prepolymerization reactor, a loop reactor and two fluid bed gas-reactors connected in series. The catalyst used in the polymerization was prepared according to WO 92/19653 with DOP as dialkylphthalat of the formula (I) and ethanol as alcohol, the cocatalyst was Triethylaluminium (TEA) and as an external donor (D) diethylamino triethoxy silane was used.

(16) After a first pre-polymerisation step the catalyst system was fed to the slurry reactor, where the polymerisation of the polypropylene homopolymer matrix phase was performed. The slurry phase loop reactor was then followed by a first gas phase reactor in series, in which a first elastomeric rubber disperse phase was produced by copolymerisation of propylene with ethylene comonomer. The polymerisation temperature in the slurry phase loop reactor was 62 C., whereas the temperature in the first gas phase reactor was 80 C. After transfer to a second gas phase reactor the second ethylene/propylene copolymer was produced. The operating temperature in the second gas phase reactor was 80 C.

(17) The split between loop, 1.sup.st GPR and 2.sup.nd GPR was: 70.5%:17.0%:12.5%

(18) Reaction Conditions:

(19) 1) Prepolymerization

(20) TABLE-US-00001 T [ C.] 20 TEA/D [g/g] 3 TEA/C.sub.3 [g/kg] 0.20

(21) 2) Loop

(22) TABLE-US-00002 Reactor-T [ C.] 62 Pressure [bar] 34 MFR [g/10 min] 253 H.sub.2 [ppm] 8800 C.sub.2 [wt %] 0.0 XS [wt %] 2.5

(23) 3) 1.sup.st Gas Phase Reactor

(24) TABLE-US-00003 Reactor-T [ C.] 80 Pressure [bar] 12 C.sub.2 [wt %] 8.0 H.sub.2/C.sub.2[mol/mol] 0.022 C.sub.2/C.sub.2 + C.sub.3 [mol %/mol %] 0.270 C.sub.3/EPR [wt %] 59.5 IV/XS [dl/g] 3.64 MFR [g/10 min] 77 XS [wt %] 17.8

(25) 4) 2.sup.nd Gas Phase Reactor

(26) TABLE-US-00004 Reactor-T [ C.] 80 Pressure [bar] 12 C.sub.2 [wt %] 20.3 H.sub.2/C.sub.2[mol/mol] 0.28 C.sub.2/C.sub.2 + C.sub.3 [mol %/mol %] 0.670 C.sub.3/EPR [wt %] 48.5 IV/XS [dl/g] 2.81 MFR [g/10 min] 38.0 XS [wt %] 23.2

(27) Values for C.sub.3/EPR, IV/XS, MFR and XS of the 2.sup.nd Gas phase reactor product are total values for the final RTPO.

(28) Since the IV of the EPR produced in the 2.sup.nd Gas phase reactor (IV/XS.sub.(EPR 2nd GPR)) can not be measured directly it has been calculated using the following formula:
IV/XS.sub.(EPR 2nd GPR)=[(IV.sub.totalw.sub.total)(IV.sub.(EPR 1st GPR)w.sub.1st GPR)]w.sub.2nd GPR
Where:

(29) IV.sub.total is the IV of the fraction soluble in xylene of the final composition

(30) W.sub.total=100% EPR [the sum of polymer splits for the 1.sup.st and the 2.sup.nd gas phase reactor (17%+12.5%=29.5%) represents the total of EPR (100% EPR) produced]

(31) IV.sub.(EPR 1st GPR) is the IV of the fraction soluble in xylene produced in the 1.sup.st gas phase reactor

(32) W.sub.1st GPR is the percentage of ERR produced in the 1.sup.st gas phase reactor based on 100% EPR [(17%.sub.polymer split for 1stGPR100%.sub.EPR total)/29.5%.sub.sum of polymer splits for 1st and 2nd GPR]

(33) W.sub.2nd GPR is the percentage of EPR produced in the 2.sup.nd gas phase reactor based on 100% EPR [(12.5%.sub.polymer split for 2ndGPR100%.sub.EPR total)/29.5%.sub.sum of polymer splits for 1st and 2nd GPR]

(34) The IV of the fraction soluble in xylene produced in the 2.sup.nd gas phase reactor was therefore 1.68 dl/g

(35) The C.sub.3-amount of the EPR produced in the 2.sup.nd Gas phase reactor (C.sub.3/EPR.sub.EPR 2nd GPR)) has been calculated accordingly using the following formula:
C.sub.3/EPR.sub.(EPR 2nd GPR)=[(C.sub.3/EPR.sub.totalw.sub.total)(C.sub.3/EPR.sub.(EPR 1st GPR)w.sub.1st GPR)]/w.sub.2nd GPR
Where:

(36) C.sub.3/EPR.sub.total is the C.sub.3-amount of the ERR of the final composition

(37) W.sub.total=100% EPR [the sum of polymer splits for the 1.sup.st and the 2.sup.nd gas phase reactor (17%+12.5%=29.5%) represents the total of EPR (100% EPR) produced]

(38) C.sub.3/EPR.sub.(EPR 1st GPR) is the C.sub.3-amount of the EPR produced in the 1.sup.st gas phase reactor

(39) W.sub.1st GPR is the percentage of EPR produced in the 1.sup.st gas phase reactor based on 100% EPR [(17%.sub.polymer split for 1st GPR100%.sub.EPR total)/29.5%.sub.sum of polymer splits for 1st and 2nd GPR]

(40) W.sub.2nd GPR is the percentage of EPR produced in the 2.sup.nd gas phase reactor based on 100% EPR [(12.5%.sub.polymer split for 2nd GPR100%.sub.EPR total)/29.5%.sub.sum of polymer splits for 1st and 2nd GPR]

(41) The C.sub.3-amount of the EPR produced in the 2.sup.nd gas phase reactor was therefore 33.54 wt %

(42) This value complies with datas evaluated by using so-called master curves.

(43) Such master curves were generated by determining the C.sub.3-amount of an EPR produced in the first gas phase reactor of the above described reactor set up using the same catalyst system as described above but different C.sub.2/C.sub.2+C.sub.3 ratios, leading to corresponding C.sub.3-amounts in the EPR. From these master curves an art skilled person can determine the C.sub.3-amount of the EPR produced in the 2.sup.nd gas phase reactor using a special C.sub.2/C.sub.2+C.sub.3 ratio.

Example 2

(44) In order to show the advantageousness of the catalyst system used according to inventive Example 1 in comparison to the catalyst system used according to EP 1 600 480 (ZN104 (commercially available from LyondellBasell), triethylaluminium as cocatalyst and dicyclopentyldimethoxysilane as external donor) regarding fines produced during production of the polypropylene matrix, several polypropylene matrices with different MFR were produced in the above described plant set up and the amount of fines produced in the loop reactor were determined by sieving the polymer powder obtained from the loop reactor. The powder passing a 0.180 mm screen was considered as fines.

(45) TABLE-US-00005 TABLE 1 wt % of fines MFR.sub.PP-matrix Cat. of [g/10 min] ZN104/DCDMS Example 1/DEATES 50 2.5 wt % 0.9 wt % 100 5.4 wt % 1.2 wt % 250 n.a. 1.4 wt % DCDMS . . . dicyclopentyl dimethoxy silane DEATES . . . diethylamino triethoxy silane n.a . . . not applicable

(46) With the combination of ZN104/DCDMS it was not possible to produce a polypropylene matrix with an MFR of above 100 g/10 min, especially of 250 g/10 min due to the high amount of fines produced, which block the reactor.

Example 3: Testing of the Base Resin

(47) The base resin (RTPO) was initially obtained in powder form.

(48) The resin together with 10 wt % Tital15 (talc from Ankerport) and 0.1% NA11 as well as 10 wt % of EG8200 (elastomer Engage8200 from DuPont Dow Elastomers) were pelletized by feeding the blend to a Prism 24 twin-screw extruder (Prism Ltd., Staffordshire, UK). The polymer was extruded through a strand die, cooled and chopped to form pellets.

(49) TABLE-US-00006 TABLE 2 Properties of compounded RTPO MFR 230 C./2, 16 kg [g/10] 29.2 Flexural Modulus [MPa] 1281 Tensile Modulus [MPa] 1229 Impact - Charpy NIS(23 C.) [kJ/m.sup.2] 17.5 Impact - Charpy NIS(0 C.) [kJ/m.sup.2] 8.2 Impact - Charpy NIS(20 C.) [kJ/m.sup.2] 5.5 Shrinkage longitudinal [%] 0.58 Shrinkage lateral [%] 0.9
Surface Quality (Tigerskin)

(50) Plaques of a dimension of 2101893 mm.sup.3, grained with VW grain K50, were produced under following conditions:

(51) Melt temperature: 240 C.

(52) Mold temperature: 30 C.

(53) Dynamic pressure: 10 bar hydraulic

(54) The filmgate over the whole width had a thickness of 1.4 mm.

(55) With the above mentioned conditions 5 plaques with different injection speed were produced. The test series were done with following screw advance velocities:

(56) 10, 20, 42, 60, 75 mm/sec, where the screw diameter was 50 mm and different injection times of 8, 4, 2, 1.5 and 1 sec.

(57) The produced plaques are judged visually by a tester in terms of tigerskin.

(58) The tigerskin level was assessed by a number between 1 (no flow mark excellent) and 5 (a large area of flow marks, insufficient) according to FIG. 3.

(59) TABLE-US-00007 TABLE 3 Tigerskin level: Injection time [sec] 1 1.5 2 4 8 1 1 1 1 1

(60) Result: With the RTPO of the present invention no flow marks could be seen, independently of the test conditions; the surface quality was in each case excellent.