JPS5940841B2 - Polymerization method of α-olefin - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for polymerizing alpha-olefins.

More specifically, the present invention relates to improving slurry transfer between polymerization vessels when α-olefin is continuously bulk polymerized in a plurality of polymerization vessels connected in series through slurry transport pipes.
When α-olefin is continuously bulk polymerized in multiple polymerization vessels connected in series with slurry transport pipes,
A pump is usually used to transport the slurry in the polymerization vessel.

However, in this case, the pump is not only expensive because it is of high pressure, but also tends to clog, resulting in accidents. In order to improve this drawback, the special public
587, a polymerization reactor is filled with α-olefin liquid and the slurry is transferred by the difference in pressure inside the polymerization reactor before and after the polymerization reactor, and the mechanical pressure change and temperature of the pump that pressurizes the α-olefin into the polymerization reactor are determined. α is kept at a higher temperature than the polymerization vessel in order to buffer sudden changes such as expansion of the liquid due to rise in α.
- A method has been proposed for connecting an olefin vapor-liquid balancer to a polymerization vessel.

However, this method still has the following problems. That is, 1
If the pressure in the polymerization reactor increases from time to time, there may be a backflow of slurry to the vapor-liquid balancer. If there is a temporary backflow of slurry, there will be a time when the flow rate of slurry in the slurry transfer pipe connecting the polymerization vessels becomes zero.

Powder tends to settle from the slurry around this area. The powder is active, so after it settles, it thickens and sticks to each other,
Eventually, the slurry transfer pipe becomes blocked. If the slurry transfer pipe is blocked, not only will it be impossible to operate the polymerization vessel, but the polymerization vessel may explode, which is dangerous. In addition, since the polymerization vessel is filled with slurry, there is a risk that the slurry may enter the seal portion of the stirrer. On the other hand, there is a transfer method using a head difference, but in this method, when the polymerization temperature in the latter stage becomes high, the slurry flows back into the former stage, causing the above-mentioned problem. In addition, in this case, the polymerization temperature must be lowered the later the stage, and such restrictions on the polymerization temperature limit the flexibility of controlling the quality of the resulting polymer, such as stereoregularity and molecular weight distribution. become. In addition, in the conventional method of polymerizing α-olefin monomers under gas-liquid equilibrium, once the polymerization temperature is determined, the polymerization pressure is automatically determined, which may limit the quality of the polymer or reduce the polymerization cost. It had the disadvantage of being expensive.

An object of the present invention is to provide a polymerization method that does not use a pump for slurry transfer, prevents slurry from flowing back into the slurry transfer pipe connecting polymerization vessels, and allows separate control of polymerization temperature and polymerization pressure. .

The present invention provides a method for continuously bulk polymerizing α-olefin in a plurality of polymerization vessels arranged in series, in which a pressurized inert low-boiling gas is supplied to at least the polymerization vessels other than the last polymerization vessel. The gist of this method is to increase the pressure inside the vessel in the earlier stage polymerizer, and to transfer the slurry from the earlier stage polymerizer to the latter stage polymerizer using the pressure difference between the adjacent front and rear polymerizers.

N2 can be suitably used as the inert low boiling point gas used in the present invention. According to the present invention, the solubility of N2 in liquefied α-olefin is determined by
It is a small amount of 5% or less based on the volume of . For example 30
Bulk polymerization of propylene, which occurs around k9/(71), can be carried out at 1% or less. Therefore, separation of N2 and α-olefin in the later stage is also easy. H2 is used as an inert gas other than N2. However, in that case, since H2 is used to adjust the molecular weight of the polymer, it is not preferable to use H2 as an inert gas in the present invention considering the quality of the polymer. In particular, copolymerization of propylene, butene-1, 4-methylbenzene-1, hemocene-1, or these α-olefins or copolymerization of these with ethylene can be mentioned, but the present invention is particularly concerned with the polymerization of propylene or the copolymerization of propylene with propylene as the main component. This method is suitable for copolymerization.

In addition, propylene is homopolymerized in the first stage polymerization vessel,
It is then used to produce a copolymer of propylene and ethylene by introducing ethylene into the second stage polymerization vessel. In the α-olefin polymerization reaction according to the present invention, the pressure in the polymerization vessel must be sufficient to keep the monomer in a liquid state at the reaction temperature, and is preferably 20 to 50 kg/CILG.

The pressure difference between the polymerization vessels must be about 0.5-3k9/C7ll, preferably about 11<g/d.

When the pressure difference becomes lower than 0.5k9/~, the slurry transfer pipe becomes easily clogged. Additionally, if the pressure difference exceeds 3k9/d, due to the problem of pressure resistance of the polymerization vessel, the wall thickness of the body of the polymerization vessel becomes thicker in the earlier stages of the polymerization vessel, making it difficult to remove polymerization heat and increasing the manufacturing cost of the polymerization vessel. , which is not desirable. In propylene polymerization according to the method of the invention, each polymerization vessel is preferably maintained at a temperature of 50 to 80°C.

According to the present invention, the polymerization temperature of each polymerization vessel can be operated at a high temperature in the former polymerization vessel and at a low temperature in the latter polymerization vessel. In the polymerization reaction of the present invention, it is preferable to polymerize the α-olefin monomer without a solvent in a liquid phase, but if desired, a solvent with a relatively low vapor pressure relative to the α-olefin may be present in the reaction system. Polymerization reactions can also be carried out.

Since various catalyst systems can be used for the polymerization of α-olefins, the present invention is not limited to the polymerization reaction with α-olefins using a particular catalyst system, such as the Ziegler type catalyst shown in the Examples.

According to the present invention, since no pump is used to transport slurry, the problem of clogging of the pump with slurry does not occur, and the polymerization temperature in each polymerization vessel can be set arbitrarily (unlike the conventional method that does not use a pump to transport slurry). (There were restrictions on the temperature setting of each polymerization vessel), and it also has the advantage of acting as a buffer against a sudden increase in the internal pressure of the polymerization vessel.

Furthermore, if the pressure in the downstream polymerization vessel suddenly rises temporarily, according to the present invention, the differential pressure control valve is immediately activated to increase the pressure in the upstream polymerization vessel to the set pressure difference. Slurry transport between polymerization vessels does not stop even temporarily, and sedimentation of the slurry can be prevented, allowing long-term stable operation. The present invention will be explained below with reference to the drawings.

A first stage polymerization vessel 1 having an agitator 16 and a cooling jacket 26 is provided with a pipe 5 for liquefied α-olefin and a pipe 6 for a catalyst.
, H2 for molecular weight adjustment is continuously supplied from the pipe 7 and mixed with stirring.

The heat of polymerization is removed by cooling jacket 26. The contents of the polymerization vessel 1 are transferred to the second stage polymerization vessel 2 through the slurry transfer pipe 13 . From pipe 8, catalyst and H2 are supplied as desired.
, α-olefin is supplied. At this time, the pressure difference between polymerization vessel 1 and polymerization vessel 2 is detected via pipes 23 and 24, respectively, and the differential pressure control valve 21 is activated so that the pressure of polymerization vessel 1 is higher than the pressure of polymerization vessel 2 by the set pressure difference. Activate, pipe 19
Introduce more inert gas. The third-stage polymerizer 3 is not necessarily provided in parallel, and three or more polymerizers may be installed in series if desired. Piping 25 has the same meaning as 23 and 24. Reference numeral 22 indicates a differential pressure regulating valve, and 17 and 18 indicate control means for the differential pressure regulating valves 21 and 22.

The contents of the polymerization vessel that have completed a predetermined polymerization reaction pass through the control pipe 10 from the pipe 15 and are flashed into the flash chamber 4, gaseous olefin is recovered from the pipe 12, and α-olefin polymer is extracted from the pipe 11. and then transferred to a post-processing step. Although not shown, the contents of the polymerization vessel from the pipe 15 may be transferred to a catalytic decomposer or a polymer washer in which α-olefin can be liquefied.

Examples are shown below. Example In a small continuous device in which three 5M3 polymerization vessels 1, 2, and 3 are arranged in series and connected to a flash chamber 4 as shown in the drawing, titanium trichloride 449/H is supplied to the polymerization vessel 1 from a pipe 6.
, diethylaluminum chloride 3309/H. ．． n
- Continuously supplying hexane 6.61/H1 H2 from pipe 7 and propylene chloride 13201<9/H from pipe 5,
Bulk polymerization of propylene was carried out.

The pressure inside the polymerization vessel 1 was set to 33 kg/CTiiG. Cooling water was flowed through the jacket 31 to maintain the temperature inside the polymerization vessel 1 at 68°C. The contents of the polymerization vessel 1 were supplied to the polymerization vessel 2 through a slurry transfer pipe 13. The pressure of polymerization vessel 2 was maintained at 321<9/(71G, and the temperature was 68°C. H2 was supplied from pipe 8. The contents of polymerization vessel 2 were supplied from pipe 14 to polymerization vessel 3. Polymerization vessel 3 The pressure is 31k
9/CTilG, the temperature was maintained at 68°C. Piping a to H
2 was supplied. The contents of the polymerization vessel 3 passed through the pipe 15 and were flushed from the control valve 10 into the flash chamber. Propylene gas 6601<g/H was discharged from the pipe 12, and polyprene powder 660k9/H was discharged from the pipe 11.
Under steady state conditions, the pressure differences between polymerization vessels 2 and 3 and stacks 1 and 2 were adjusted by operating differential pressure control valves 22 and 21, respectively, and allowing N2 gas to flow in from pipes 20 and 19, respectively. After reaching a steady state, continuous operation was carried out for 30 days.
Pipes 13, 14, and 15 were never clogged, and very stable operation was possible.

[Brief explanation of drawings]

The figure is a schematic diagram showing an example of the process for producing an α-olefin polymer according to the present invention. As shown in the figure, 1, 2, and 3 are polymerization vessels: 4 is a flashing chamber:
5, 6, 7, 8, 9 are pipes that supply raw materials, etc.; 10 is a control valve; 13, 14 are slurry transport pipes:
21, 22 are differential pressure regulating valves: 17, 18 are differential pressure regulating valves 21
, 22 are control means: 23, 24, 25 are pressure detection pipes; 26 is a cooling jacket.

Claims (1)

[Claims] 1. In a method of continuously bulk polymerizing α-olefin in a plurality of polymerization vessels connected in series, pressurized N_2 gas is supplied to at least the polymerization vessels other than the last stage polymerization vessel. By doing this, the pressure inside the reactor is increased as the polymerization reactor is located in the earlier stage, and the pressure difference between the adjacent polymerization reactors is 0.5 to 3 kg/c.
The polymerization method described above is characterized in that the slurry is transferred from the first stage polymerization vessel to the second stage polymerization vessel while adjusting the slurry so that the slurry becomes m^2. 2 In claim 1, the internal pressure of the polymerization vessel is set to 20
A method of polymerizing at ~50 kg/cm^2. 3. The method according to claim 1 or 2, wherein the α-olefin polymerization is a propylene polymerization or a copolymerization having propylene as a main component. 4 In claim 1, 2 or 3, the polymerization temperature is 5
A method in which the temperature is 0 to 80°C.