FI68630C - FOERFARANDE OCH ANORDNING FOER KONTINUERLIG TILLSAETTNING AV EN PULVERFORMIG KOORDINATIONSKATALYSATOR TILL EN TRYCKSATT REKTOR - Google Patents

Description

68630

Method and apparatus for continuously adding a powdered coordination catalyst to a pressurized reactor For the purpose of adding a powdered coordination catalyst to a pulverulent coordination catalyst in a reactor

The invention relates to a process for adding a powdered coordination catalyst to a pressurized reactor.

The invention also relates to an apparatus for adding a powdered coordination catalyst 5 to a pressurized reactor.

The coordination polymerization of olefins takes place either as a gas phase, solution or suspension polymerization. In suspension and solution polymerization, the medium or solvent is an organic hydrocarbon, such as heptane, in which the catalyst is suspended (solid catalysts) or dissolved, the monomers are soluble, and the polymer is either suspended (suspension polymerization) or soluble (solution polymerization). The reactor pressure is 5-150 bar, usually 10-30 bar and the temperature 0-250 ° C.

15 Coordination catalysts such as TiCl 2. 1/3 AlCl 2 are very sensitive to losing their activity even at low oxygen or moisture contents that come into contact with them. The treatment of the catalyst must take place at all stages in an inert environment, e.g. under a nitrogen atmosphere. Coordination catalysts are either liquids or solid powders. Cocatalysts are always liquids, such as Et 2 Al, whose continuous supply to the reactor is not a problem.

The solid catalyst is in the form of a fine powder. The supply of such powder to the reactor is discussed, for example, in U.S. Patents 3,849,334, 3,652,527, 3,726,845, 3,780,135 and 3,846,394. In U.S. Patent 3,849,334, a Ziegler catalyst system is placed in a solid wax having a melting point above 30 ° C.

The powdered catalyst is generally suspended in a separate mixing vessel in a hydrocarbon medium, e.g. heptane. This suspension is then fed to the reactor by pumping. The problem is that the solid precipitates easily and forms blockages. On the other hand, pumping the solid-containing suspension with the dosing pump does not work. Various line cleaning and rinsing systems have been required for such addition systems, as disclosed, for example, in U.S. Patent 3,726,845.

The object of the invention is to provide an improvement on the currently known methods. It is a more detailed object of the invention to provide a process which allows the continuous addition of a powdered coordination catalyst to a pressurized reactor so that solids precipitation problems are eliminated without the need for various line cleaning and flushing systems.

The objects of the invention are achieved by a process which is mainly characterized in that the powdered coordination catalyst is suspended in a running wax and that the mixture of catalyst and wax is pumped by means of an inert medium into a polymerization reactor in which the wax dissolves and the catalyst is released.

20

It is also an object of the invention to provide an apparatus for continuously adding a powdered coordination catalyst to a pressurized reactor in which the apparatus does not require various line cleaning and flushing systems.

25

The device according to the invention is mainly characterized in that the device comprises a catalyst addition tube connected to the polymerization reactor, containing a powdered coordination catalyst suspended in a running wax, and means for pumping an inert medium into the addition tube and feeding the mixture to the polymerization reactor.

According to the invention, the powdered coordination catalyst can be suspended in a wax diluted with a suitable solvent in a flowable, thick form. As the solvent, it is preferable to use a hydrocarbon solvent, preferably the same solvent as in the polymerization reactor, for example heptane. It is preferred to use polyethylene wax as the wax. The content of polyethylene wax in heptane can be 5-20%.

The use of polyethylene wax and heptane is preferred because: a) The small amount of wax added in the polyterizations of polyethylene or its copolymers is the "real substance" that is otherwise generated in the reactor during polymerization.

b) The polyethylene wax does not contain catalyst-harmful substances (e.g. polar compounds) and is therefore inert to polymerization.

c) The viscosity of the wax is easily controlled by the solution ratio to heptane, the catalyst powder does not precipitate in such a mixture for a long time (15 weeks), but the mixture can still be treated, for example, by means of syringes.

d) A catalyst mixed with a mixture of polyethylene wax and heptane is not as sensitive to ambient oxygen and moisture as a pure powdered catalyst, as the wax mixture protects the surface of the catalyst particles.

e) The liquid wax mixture dissolves in the well-stirred heptane (or other hydrocarbon) at a temperature of about 0 to 250 ° C in the reactor so that the solid catalyst particles are released and ready for polymerization.

f) The mixture is easy to dispense.

Catalyst powder can generally be added to the wax / heptane mixture, generally from 0.5 to 25 mmol, i.e. from about 0.1 to 5 g per 30 ml of wax, from which amount of polymer is typically obtained up to about 1500 kg.

The viscosity of the mixture of polyethylene wax and heptane is such that the mixture does not pass properly on the suction side of the dosing pump. On the other hand, solids (= catalyst) also cause the pump to clog and wear.

4,68630

The catalyst tube used in the device according to the invention has no moving parts which could be damaged by solid particles. The catalyst charge can be pre-prepared in a nitrogen cabinet and transported in a closed catalyst tube to the site of use. The rate of catalyst addition-5 can be controlled by adjusting the pumping rate of heptane in the dosing pump. When two catalyst addition pipes are connected in parallel, a second addition pipe can be used, for example by means of three-way valves, while the second addition pipe is being filled, as a result of which complete continuous operation is achieved in the device according to the invention. Continuity can also be achieved in other ways, as will be seen below.

The invention will be explained in detail with reference to a preferred embodiment of the invention shown in the figures of the accompanying drawings, to which, however, the invention is not intended to be exclusively limited.

15

Figure 1 shows a schematic side view of a preferred embodiment of the device solution used in the method according to the invention.

Figure 2 shows a side view of a preferred embodiment of the catalyst 20 addition tube used in the apparatus of Figure 1.

Figure 3 shows a schematic side view of another preferred embodiment of the device solution used in the method according to the invention.

In the embodiment of Figure 1, the apparatus used in the process of the invention is generally designated 10. The powder 10 is continuously added to the pressurized reactor 11. In this embodiment, the apparatus 10 includes a catalyst addition tube 12, a dosing pump 16, a heptane feed 16 to the other end of the catalyst addition tube 12. The catalyst addition pipe 12 is naturally connected at one end down the line 14 to the reactor 11. The catalyst addition pipe 12 contains a powdered coordination catalyst 13 suspended in a wax, such as polyethylene wax 13. The catalyst addition pipe 12 is also three-way valve. The catalyst addition pipe 5 68630 ki 12 is connected by a press connector 26 to the supply line 15 and by a press connector 27 to the line IA leading to the reactor 11, respectively. The dried and nitrogenated heptane in the heptane feed tank 17 is denoted by reference numeral 18. Arrow 19 denotes the inflow of nitrogen and arrow 5 denotes the outflow of nitrogen. A pressure gauge 21, a safety valve 22 and a valve 23 are located in the supply line 15, which is located in the supply line 15 before the press connection 26.

Figure 2 shows a more detailed structure of the catalyst addition tube 12 on a larger scale. The jacket of the addition pipe 12 is preferably stainless steel and has a ball valve 24 at one end of the jacket and a three-way valve 25 at the other end. The inflow of nitrogen into the addition pipe 12 is indicated by reference numeral 28.

In the process of the invention, the wax-mixed solid catalyst powder is charged in a nitrogen cabinet to the catalyst tube 12 of Figure 2, after which the valves 24 and 25 at the ends of the catalyst tube 12 are closed. Thereafter, the catalyst remains inside the tube 12 and the catalyst tube 12 can be ready to be attached to the polymerization reactor 11. The catalyst-containing wax 13 is compressed from the catalyst tube 12 to the reactor 11 by pumping the catalyst tube 12 to the other end of the In reactor 11, the wax dissolves and the catalyst is released and the solid catalyst particles are ready for polymerization. The rate of catalyst addition to the reactor 11 can be controlled by adjusting the pumping rate of heptane 18 in the metering pump 16.

In a preferred embodiment of the invention, two or more catalyst addition pipes 12 are connected between the lines 15 and 14, e.g. by means of three-way valves, whereby when the second catalyst addition pipe 12 is used the second catalyst addition pipe 12 can be filled to fill,

Continuous operation is also achieved with the structure according to Figure 3. In it, the operation in the catalyst feed stage 35 is basically the same as in the structure using the two catalyst addition tubes described above. The difference is that when the catalyst pipe is emptied, it can be filled by changing the position of the three-way valves 24a, 25 and suction the catalyst and wax mixture 13 from the storage tank 29 by vacuum down the line 30 to the catalyst addition pipe 12. In this construction tar-5 joke to make a nitrogen cabinet.

In the embodiment according to Figure 3, the vacuum line is indicated by reference numeral 32 and the vacuum pump by reference numeral 31. An intermediate vessel 33, a sight glass 34 and a valve device 35 are placed in the vacuum line 32.

Filling can also be effected by means of pressure, in which case a vacuum pump 31 and a vacuum line 32 are not required at all.

Only some preferred embodiments of the invention have been described above and it will be apparent to those skilled in the art that numerous modifications may be made to them within the scope of the inventive idea set out in the appended claims.

Claims (8)

A process for adding a powdery coordination catalyst to a pressurized polymerization reactor, wherein the powdery coordination catalyst is suspended in a liquid wax, characterized in that the mixture of catalyst and wax is placed in a separate catalyst additional tube (12). , from which the mixture is pumped by means of an inert medium to the polymerization reactor (11) where the wax is dissolved and the catalyst is released. 10 Process according to claim 1, characterized in that the rate of addition of the wax suspended coordination catalyst (13) to the reactor (11) is controlled by changing the pumping rate of the inert medium. 15 3. A process according to claim 1 or 2, characterized in that a dried and nitrated heptane (18) is used as the inert medium and which waxes a polyethylene wax. 4. Device for adding a powder coordination catalyst 20 to a pressurized polymerization reactor, characterized in that the device (10) includes a catalyst addition tube (12) connected to the liquid wax suspended powder coordination catalyst coordination catalyst (11). of the inert medium to the addition tube (12) and to feed the mixture into the polymerization reactor (11). 5. Device according to claim 4, characterized in that the catalyst addition tube (12) is provided with valve means (24,25) at both ends thereof. 30 Device according to claim 4 or 5, characterized in that the device (10) includes means for filling the additive tube (12) by means of suction or pressure. 35