Process for the Polymerization of Olefins in Solution Comprising Deactivating the Polymerization Catalyst by Heat

Abstract

The present invention relates to a polymerization process, comprising: a) supplying a feed containing ethylene and at least one alpha-olefin having 3 to 12 carbon atoms in a hydrocarbon solvent to a polymerization reactor, b) contacting the feed of step a) in the reactor with a catalyst to form a reaction mixture containing an ethylene-alpha-olefin co-polymer, c) withdrawing the reaction mixture from the polymerization reactor as a reactor outlet stream which comprises the ethylene-alpha-olefin co-polymer, unreacted monomer and comonomer, catalyst, and hydrocarbon solvent, d) heating the reactor outlet stream to a temperature which is at least 5° C. higher than the temperature of the reaction mixture at the outlet of the reactor for a time period of between 1 and 250 seconds in order to de-activate the polymerization catalyst, and e) separating hydrocarbon solvent, monomer and comonomer from the reactor outlet stream and recycling it back to the polymerization reactor without further purification steps.

Claims

1. A polymerization process, comprising: a) supplying a feed containing ethylene and at least one alpha-olefin having 3 to 12 carbon atoms in a hydrocarbon solvent to a polymerization reactor, b) contacting the feed of step a) in the reactor with a catalyst to form a reaction mixture containing an ethylene-alpha-olefin co-polymer, c) withdrawing the reaction mixture from the polymerization reactor as a reactor outlet stream which comprises the ethylene-alpha-olefin co-polymer, unreacted monomer and comonomer, catalyst, and hydrocarbon solvent, d) heating the reactor outlet stream to a temperature which is at least 5° C. higher than the temperature of the reaction mixture at the outlet of the reactor for a time period of between 1 and 250 seconds in order to de-activate the polymerization catalyst, and e) separating hydrocarbon solvent, monomer and comonomer from the reactor outlet stream and recycling it back to the polymerization reactor without further purification steps.

2. The process according to claim 1 wherein the reactor outlet stream is heated to a temperature which is at least 10° C. higher than the temperature of the reaction mixture at the outlet of the reactor.

3. The process according to claim 2 wherein the reactor outlet stream is heated to a temperature which is at least 15° C. higher than the temperature of the reaction mixture at the outlet of the reactor.

4. The process according to claim 1 wherein the reactor outlet stream is heated to the prescribed temperature for a time period of between 10 and 200 seconds.

5. The process according to claim 1 wherein the reactor outlet stream is heated for a time period t (min) to a temperature which is at least x (° C.) higher than the temperature in the solution reactor complying with the relation:
t*x>0.05.

6. The process according to claim 1 wherein no catalyst de-activation agent is added to the reactor outlet stream before entering the separation stage e).

7. The process according to claim 1 wherein the reactor outlet stream between leaving the reactor and entering the separation stage e) apart from being heated in step d) is not subjected to any further treatment steps.

8. The process according to claim 1 wherein the reactor outlet stream is heated to a temperature of at least 180° C.

9. The process according to claim 1 wherein after heat treatment of the reactor outlet stream no more than 10 wt. % of the catalyst is in an active state.

10. The process according to claim 1 wherein the polymerization catalyst is a metallocene catalyst.

11. The process according to claim 10 wherein the metallocene catalyst comprises a hafnocene catalyst.

12. The process according to claim 11 wherein the hafnocene catalyst comprises a hafnocene catalyst complex, comprising a cyclopentadienyl (Cp) ligand, a fluorenyl (Flu) ligand and a covalent bridge connecting the two ligands.

13. The process according to claim 1, wherein the polymerization reaction is performed at a temperature of between 100° C. to 250° C.

14. The process according to claim 1, wherein the polymerization reaction is performed at a pressure of between 50 to 300 bar.

15. Use of heat applied to the outlet stream of a polymerization reactor in which ethylene monomer and at least one alpha-olefin comonomer having 3 to 12 carbon atoms are copolymerized in solution for de-activating the polymerization catalyst.

Description

[0059] In the following the present invention will be illustrated by examples and by referring to the following FIGURES which show:

[0060] FIG. 1: Time vs. polymerization temperature 130° C. to 190° C. for catalyst 1.

MEASUREMENT AND SIMULATION METHODS

Melt Flow Rate and Flow Rate Ratio

[0061] The melt flow rate (MFR) is determined according to ISO 1133 and is indicated in g/10 min. The MFR is determined at 190° C. for polyethylene and at a loading of 2.16 kg (MFR.sub.2), 5.00 kg (MFR.sub.5), 10.00 kg (MFR.sub.10) or 21.6 kg (MFR.sub.21).

[0062] The quantity FRR (flow rate ratio) is an indication of molecular weight distribution and denotes the ratio of flow rates at different loadings. Thus, for example, FRR.sub.21/10 denotes the value of MFR.sub.21/MFR.sub.10.

Density

[0063] Density of the polymer is measured according to ISO 1183-1 method A using compression moulded samples. It is indicated in kg/m.sup.3.

Amount of Active Catalyst Leaving the Reactor

[0064] The amount of catalyst leaving the reactor in an active state is determined by modelling of the reaction as can routinely done by the skilled person.

Catalyst Productivity

[0065] The productivity of the catalyst was determined as the amount of polymer produced divided by the amount of metal in the catalyst (in g-PO/mg-Hf).

Chemicals

[0066] Complex-1: [(Phenyl)(3-buten-1-yl)methylene(cyclopentadienyl)(2,7-di-tert-butylfluoren-9-yl) hafnium dimethyl was prepared as described in the patent application WO2018178152A1(C-2)

[0067] Complex-2: (Phenyl)(cyclohexyl)methylene(cyclopentadienyl)(2,7-di-tert-butylfluoren-9-yl)hafnium dimethyl was prepared as described in the patent application WO2018108918A1(IC)

[0068] Cocatalyst: N,N-Dimethylanilinium Tetrakis(pentafluorophenyl)borate (AB) (CAS 118612-00-3) was purchased from Boulder.

[0069] 1-octene as co-monomer (99%, Sigma Aldrich) was dried over molecular sieves and degassed with nitrogen before use. Heptane and decane (99.9%, Sigma Aldrich) were dried under molecular sieves and degassed with nitrogen before use.

Examples

[0070] The effect of temperature on the catalyst activity (catalyst activity vs temperature) was investigated with two hafnocene catalysts, catalyst 1 and 2 using complex 1 and 2, respectively, as described above. The catalysts were used in ethylene copolymerization using decane, C.sub.10, as the polymerization solvent and 1-octene, C.sub.8, as comonomer.

Polymerization Procedure

[0071] Activation Procedure

[0072] Complex and borate are dissolved separately in toluene, then the borate solution is transferred and premixed with the complex solution (ratio AB/Complex=1.25 Molar ratio) for 45 seconds and their mixture is injected immediately in the reactor.

[0073] Typical Polymerization Procedure:

[0074] The vessels were loaded inside a glovebox utilizing a 3-axis liquid handling robot. A pre-weighed glass vial with stirring paddles was sealed and purged with nitrogen. A volume of about 4.1 mL of corresponding solvent (decane) was filled in each PPR reactor. Then, adequate amount of triethyl aluminium (TEA) as scavenger was added, along with precise volume of octene as co-monomer at room temperature. The ethylene pressure was set to 10 bar to check any leaks. Then, the temperature and pressure had been increased to the set value (e.g. T=190° C. and 24 bar) and once the steady state was reached, the corresponding volume of pre-activated catalyst (0.9 mL) as a solution in toluene had been injected in the reactor to start the polymerization under mechanical stirring. The run was quenched with CO.sub.2 after the set amount of ethylene uptake had been reached (5 min as a maximum run time). The glass vials had been dried by vacuum centrifuge and weighed.

[0075] Productivity has been calculated as follows:

[00001]$\mathrm{Productivity}\left(g\mathrm{polymer}\mathrm{per}\mathrm{mg}\mathrm{hafnocene}\right)=\frac{\mathrm{Yield}\left(g\right)}{\mathrm{Hafnocene}\mathrm{Amount}\left(\mathrm{mg}\right)}$

[0076] The results are displayed in FIG. 1, which illustrates the time (Sec) vs temperature, with the conditions: pre-contact time=45 sec, AB/Complex1=1.25 molar ratio, P=24 bar, and C.sub.8/C.sub.10=25 wt %.

[0077] It was recorded when the polymerization activity of catalyst 1 is below 5 and below 10% of the maximum activity observed as a function of the temperature. Therefore, at high temperatures >210° C. catalyst 1 can be considered completely deactivated. The same applies for catalyst 2 which is not shown in FIG. 1.