The present invention concerns a procedure for adding coordination catalyst in powder form into a pressurized reactor.

The present invention also concerns a means for adding coordination catalyst in powder form into a pressurized reactor.

Copolymerizing of olefins is effected either by gas phase, s.olution or suspension polymerization. In suspension and solution polymeriz¬ ing the fluid, or solvent, is an organic hydrocarbon, such as heptane for instance, in which the catalyst is suspended (solid catalysts) or dissolved and the monomers are dissolved, and the polymer either goes into suspension (suspension polymerizing) or is solved (solution polymerizing). The pressure in the reactor is 5-150 bar, usually

10-30 bar, and the temperature is 0-250 C.

Coordination catalysts, e.g. TiCl- • 1/3 A1C1,, have a high tendency to lose their activity even at minimal oxygen or moisture contents which come into contact with them. In all steps, the handling of the catalyst has to be accomplished in an inert environment, e.g. in a nitrogen atmosphere. Coordination catalysts are either liquids or solid powders. Cocatalysts are always liquids, such as e.g. Et,Al, the continuous supply of which into a reactor is no problem.

The solid catalyst is in the form of a fine powder. The introduc- tion of such powder into a reactor has been dealt with e.g. in the U.S. patents No. 3,849,334, 3,652,527, 3,726,845, 3,780,135 and 3,846,394. In the U.S. patent No. 3,849,334, a Ziegler catalyst system has been placed in solid wax with melting point higher than

30°C.

The powdered catalyst is usually suspended in a separate mixing vessel in a hydrocarbon fluid, e.g. in heptane. The suspension is thereafter fed into the reactor by means of pumping. The problem is

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that the solid matter tends to precipitate and to form occlusions. On the other hand, pumping of a suspension containing solid matter with a dispensing pump is not feasible. In this kind of adding systems one has been compelled to incorporate various line cleaning and flushing systems, as has been disclosed e.g. in the U.S. patent No. 3,726,845.

The object of the present invention is to provide an improvement in the procedure known in the art. The more detailed object of the invention is to present a procedure which enables coordination catalyst in powder form to be added continuously into a pressurized reactor so that the solid matter precipitation problems are elim¬ inated, so that no line cleaning and flushing systems are needed.

The aims of the invention are achieved by a procedure which is mainly characterized in that the coordination catalyst in powder form is suspended in fluid wax, and that the mixture of catalyst and wax is with the aid of an inert fluid pumped into the polymerizing reactor, where the wax is dissolved and the catalyst released.

It is also an aim of the invention to provide a means for continu¬ ously adding coordination catalyst in powder form into a pressurized reactor in which means no line cleaning and flushing systems are needed.

The means of the invention is mainly characterized in that the means comprises a catalyst adding tube connected to the polymerizing reactor, containing coordination catalyst in powder form suspended in fluid wax, and means for pumping an inert fluid into the adding tube and feeding the mixture into the polymerizing reactor.

As taught by the invention, the coordination catalyst in powder form can be suspended in wax which has been diluted with a suitable solvent to be in fluid, viscous form. For solvent, it is advantageous to use a hydrocarbon solvent, preferably the same solvent that is used in the polymerizing reactor, for instance heptane. For wax it is advan¬ tageous to use polyethylene wax. The concentration of polyethylene

wax in the heptane may be 5-20%.

The use of polyethylene wax and heptane is advantageous for the reason that:

(a) The small quantity of wax added in polymerizing polyethylene or its copolymers is "of the right stuff", which is even otherwise produced during polymerization in the reactor.

(b) Polyethylene wax contains no substances which are harmful in view of the catalyst (e.g. polar compounds) and it is therefore inert regarding the polymerization.

(c) The viscosity of the wax is easy to regulate with the aid of the proportion in which it is solved in heptane; the catalyst powder does not precipitate in such a mixture, not even during prolonged (2 weeks) storage, while all the same the mixture is manageable e.g. with injection syringes.

(d) The catalyst admixed to the mixture of polyethylene wax and heptane is not as sensitive to environmental oxygen and moisture as the pure catalyst in powder form because the wax mixture protects the surface of the catalyst particles.

(e) The fluid wax mixture goes into solution in well-agitated heptane (or other hydrocarbon) of about 0-250 C in the reactor so that the solid catalyst particles are released and are ready for the polym¬ erizing process.

(f) The mixture is easy to dispense.

To the wax/heptane mixture, catalyst powder can in general be added 0.5-25 mmol, or about 0.1 - 5 g per 30 ml wax, of which quantity polymer is typically obtained about 1500 kg at the most.

The viscosity of the polyethylene wax and heptane mixture is such that the mixture will not move without trouble on the suction side

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of the dispenser pump. On the other hand the solid matter (= the catalyst) also causes clogging and wear of the pump.

The catalyst tube to be used in the means of the invention has no moving parts which could be damaged by solid particles. The cata¬ lyst charge may be prepared in a nitrogen chamber and transported in a sealed catalyst tube to the site. The catalyst addition rate can be controlled by regulating the heptane pumping rate at the dispensing pump. When two catalyst adding tubes are mounted in parallel, it is possible for instance with the aid of three-way valves to operate with one adding tube while the other is being filled, whereby in the means of the invention completely continuous operation is achieved. Continuous operation may also be arranged in other ways, which will be become apparent later on.

The invention is described in detail referring to an advantageous embodiment of the invention, presented in the figures of the at¬ tached drawing, to which however the invention is not intended to be exclusively confined.

Fig. 1 presents an advantageous embodiment of the design of the procedure of the invention, in schematic elevational view.

Fig. 2 presents an advantageous embodiment of the catalyst adding tube used in the means of Fig. 1, in elevational view.

Fig. 3 shows another advantagous embodiment of the design used in the procedure of the invention; in schematic elevational view.

In the embodiment depicted Fig. 1, the means applied in the proce¬ dure of the invention in general is indicated by reference numeral 10. With the means 10, a coordination catalyst in powder form is continuously added into a pressurized reactor 11. In this embodi¬ ment, the means 10 comprises a catalyst adding tube 12, a dispens- ing pump 16, a heptane supply tank 17, and a feed line 15 for pumping heptane to one end of the catalyst adding tube 12 with the aid of a dispensing pump 16. The catalyst adding tube 12 is by the

other end naturally connected to the reactor 11 by a line 14. The catalyst adding tube 12 contains coordination catalyst in powder form suspended in wax, e.g. in polyethylene wax, 13. The catalyst adding tube 12 is provided on both ends with spherical valves 24 and 25. Instead of the spherical valve 25, also a three-way valve may of course be used. The catalyst adding tube 12 is connected by a clamp connector 26 to the feed line 15 and, similarly, by a clamp connector 27 to the line 14 leading to the reactor 11. The dried and nitrogenated heptane in the heptane supply tank 17 has been indicated with reference numeral 18. The arrow 19 indicates the inflow of nitrogen, respectively, arrow 20 the outflow of nitrogen. In the feed line 15 have been included: a pressure gauge 21, a safety valve 22, and a valve 23 located in the feed line 15 before the clamp connector 26.

In Fig. 2 is shown the more detailed construction of the catalyst adding tube 12, on an enlarged scale. The shell of the adding tube 12 is advantageously of stainless steel, and at one end of the shell is provided a spherical valve 24 and at the other a three-way valve 25. The inflow of nitrogen to the adding tube 12 is indicated by reference numeral 28.

In the procedure of the invention, the solid catalyst powder mixed in the wax is loaded, in a nitrogen chamber, into a catalyst tube 12 as in Fig. 2, whereupon the valves 24 and 25 on the ends of the catalyst tube 12 are closed. Thereafter, the catalyst keeps intact within the tube 12, and the catalyst tube 12 is ready to be-mounted on the polymerizing reactor 11. The wax 13 containing the catalyst is pressed from the catalyst tube 12 into the reactor 11 by pumping dried and nitrogenated heptane 18, under high pressure, in at one end of the catalyst tube 12 through the feed line 15 by means of a dispensing pump 16. In the reactor 11, the wax is dissolved, and the catalyst is set free, and the solid catalyst particles are ready for the polymerizing process. The rate at which catalyst is added into the reactor 11 is controllable by regulating the pumping rate of the heptane 18 in the dispensing pump 16.

In an advantageous_ embodiment of the invention, between the lines 15 and 14 are installed two or more catalyst adding tubes 12 using three-way valves, whereby when one of the catalyst adding tubes 12 is being used to other catalyst adding tube 12 can be taken off to be filled, and hereby completely continuous operation is achieved.

The continuous operation feature is also implementable with the aid of the construction depicted in Fig. 3. In this, the operation is the same in principle in the catalyst introduction step as in the construction applying two catalyst adding tubes, described in the foregoing. The difference is that when the catalyst adding tube has been emptied it can be filled by shifting the three-way valves 24a, 25 and drawing the mixture of catalyst and wax, 13, from the storing tank 29 with the aid of vacuum by the pipe line 30 into the cata- lyst adding tube. In this construction there is no need to detach the catalyst tubes for the duration of. filling, and the filling need not be carried out in a nitrogen chamber.

In the embodiment of Fig. 3, the vacuum line has been indicated with reference numeral 32 and the vacuum pump with reference numeral 31. In the vacuum line 32 have been inserted an intermediate tank 33, a sight glass 34 and a valve means 35.

Filling may also be accomplished with the aid of pressure, in which case no vacuum pump 31 and no vacuum line 32 is needed at all.

In the foregoing, merely a few advantageous embodiments of the invention have been presented, and it is obvious to a-person skilled in the art that.numerous modifications thereof are feasible within the scope of the inventive idea stated in the claims below.