JPS62138505A - Multi-chamber continuous polymerization method - Google Patents

Abstract

PURPOSE:To avoid overload of a valve and stably carry out the operation of a polymerizer over a long period without causing trouble, by controlling the transfer rate of a slurry by a variable opening valve attached to a specific part of a polymerizer. CONSTITUTION:An alpha-olefin (e.g. propylene, butene-1, etc.) is continuously polymerized by bulk-polymerization using the alpha-olefin itself as a medium with a polymerizer composed of reactors 1, 2, 3 furnished with circulation line of slurry. Two or more reactors are connected with each other by a liquid transfer line branched from the circulation line. In the above process, variable opening valves 1-3, 1-4, 2-3, 2-4, 3-3, 3-4 are attached to the transfer line and to a returning part of the circulation line to the reactor. The transfer amount of the slurry is controlled by the operation of the valves from the start of the polymerization reaction until the polymerization condition in each reactor reaches a desired condition (by setting the ratio of period of the state of opened valve 1-3 and closed valve 1-4 to the period of the state of closed valve 1-3 and opened valve 1-4). When the polymerization condition of each reactor reaches the prescribed state, the transfer rate of the slurry is controlled by controlling the opening of the valves.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a bulk polymerization method using α-olefin itself as a medium. Specifically, the present invention relates to a method for continuous polymerization of α-olefins using a polymerization machine in which two or more reaction vessels each having a slurry circulation line are connected.

[Conventional technology]

It has been known for a long time that α-olefins are polymerized by bulk polymerization using the α-olefin itself as a liquid medium. In addition, in order to obtain many brands of polymer,
Alternatively, since it is difficult to remove the polymerization heat in a large reactor, it is also known to carry out the polymerization reaction using a reactor in which two or more polymerization tanks are connected. However, when polymerizing α-olefins using the bulk polymerization method, the pressure at the back of reaction 1 is determined by the temperature, and hydrogen is introduced in order to control the molecule m of the polypropylene obtained. When increasing the amount of hydrogen in the step, it is difficult to make the slurry overnight unless the polymerization temperature is lowered in the latter stage. Therefore, for example, JP-A-53-25585 discloses lowering the polymerization temperature in a later polymerization tank. A method of pumping slurry using a slurry pump is also well known.

[Problem that the invention seeks to solve]

However, the method of creating a pressure difference using a temperature difference and transferring the liquid has the problem that the polymerization temperature decreases in the later tanks, which reduces desolvation activity and makes it difficult to remove heat, and there is no flexibility in determining the polymerization temperature. . In addition, in the latter method, although it is not necessary to lower the polymerization temperature significantly, a large reverse pressure will cause the slurry IJ -,
There is a problem that the load on the 7 pump increases and, in some cases, it may close. Furthermore, since the amount of liquid transferred depends on the difference between the increased pressure and the pressure in the next reaction tank, in order to control the slurry transfer i1, the slurry circulation line/l-equipment transfers the slurry by opening and closing the valve. One option is to drain the valve, but valves, especially those for high pressure, often leak if they are opened and closed for long periods of time, which is not only dangerous, but also expensive to replace.

[Means for Solving the Problems] As a result of intensive study on methods for solving the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by a specific method, and have completed the present invention. That is, the present invention uses a polymer fitting to connect a reaction tank equipped with a slurry circulation line with a liquid transfer line taken out from a circulation line of 241" or more.
In a method of continuously polymerizing α-olefin / olefin by bulk polymerization using olefin itself as a medium, a valve with a variable opening degree is provided in the return section of the circulation line to the reaction tank and in the liquid transfer line,
From the start of the polymerization reaction until the polymerization conditions at each end reach the desired conditions, the amount of slurry transferred and the opening/closing of valves are controlled.
After the polymerization conditions in the tank reach the desired conditions, turn the valve valve 4.
A multi-function device characterized by controlling the amount of slurry transferred at a
'3 continuous polymerization method.

In the present invention, the α-olefin refers to propylene, butene-1, hexene-1, and mixtures thereof or mixtures thereof with ethylene.

In the present invention, any known catalyst can be used to polymerize the α-olefin, and there are no particular limitations. A catalyst system consisting of a transition metal compound and an organometallic compound is used, and specifically, a titanium halide is used. Alternatively, those supported on a carrier such as magnesium halide, silica, or alumina are used as transition metal compounds, and are preferably used as organometallic compounds such as organoaluminum and organomagnesium.

Embodiments of the present invention will be explained in detail using the drawings.

reaction! An α-olefin is polymerized by a bulk polymerization method using a polymerization machine consisting of three tanks in which units 1, 2, and 3 are connected. Reaction tank 3
The slurry from ff3-4t%I is sent to a slurry post-treatment step. Each 1 is a liquid level gauge 1-1.2-1.3-
The liquid level height is detected by the controller 1-5.2-5°3-5 according to the signal.
-3.2-4° 3-3.3-4 six valves are operated to control the liquid level to be constant.

What is most important to the present invention is that the liquid level is controlled by opening and closing the six valves only until the six tanks are stabilized under the desired conditions, and after the conditions are stable, it is controlled by the valve opening of the six valves; II
It is to be treated. For this purpose, it is preferable that the shape of the box be one that allows the slurry to be transferred steadily up and down at a specific valve opening, such as a V&R valve, and a valve that can be opened as needed. It is also possible to prevent clogging of the slurry by flushing α-olefin or an inert solvent at the slurry, or by controlling the liquid level for short periods at specific time intervals by opening and closing six valves.

Control of the liquid level by opening and closing the six valves is performed as follows.Reaction tank 1 will be described as an example. The slurry extracted from the reaction tank 1 is pressurized by the pump 1-2, and when the valve 1-4 is closed, the valve 1-3 is opened and is circulated back to the reaction tank 1. At this time, valve 1-3 is closed and the slurry is transferred to reaction tank 2. By determining the time ratio between when valve 1-3 is open and when valve 1-4 is open, the approximate amount of slurry transferred from reaction tank 1 to reaction tank 2 is determined (in detail, the amount of slurry transferred from reaction tank 1 to reaction tank 2 is determined) and the pressure drop difference on the reaction tank 2 side is added). When valve 1-4 is open, valve 1-3 is closed, so there is no risk of backflow.Since the slurry pressurized by slurry pump 1-2 is transferred to reaction tank 2, there is no risk of backflow. Liquid transfer is possible even under pressure. By opening and closing the valve in small steps, even if the differential pressure between reaction tank 1 and reaction tank 2 is large, a large amount of slurry will not be transferred at once, and various changes will be made when starting polymerization or changing conditions. The liquid level can be well controlled even if the pressure fluctuates. each·
After iU has stabilized to a desired condition, the slurry movement 'f'J, M is controlled by the valve opening degree of the valve. At this time, it is preferable to set a limit value for the valve opening degree of each valve (especially on the closer side) and to prevent the valve opening degree from changing beyond that limit value, because the solid particles in the slug IJ- This is because if the valve is opened only once, the slurry will be filtered and spread out. Therefore, when it becomes necessary to change the valve opening degree beyond the limit value of 1b, the valve opening is automatically controlled to switch to a]lI a by opening and closing the valve, +Il device 1-5.2-5.3 -5t
- It is preferable to set this in advance. Note that the broken line indicates the connection state of the control system.

An example of ml closing of the square and opening of the valve 1fJll + wholesale will be described below.

When controlling by opening and closing the tank, the liquid level is detected by a liquid level gauge and compared with the preset liquid level, and if the liquid level is lower than the set value, the slurry control valve 1-3 is activated. Shorten the opening time by a certain amount of time. If the liquid level is higher than the previous measurement level even after the valve 1-3 has been activated a certain number of times, the valve 1-4
+i'] v.

Extend for a certain amount of time. Next, after a certain number of times, the level is compared with the previous measurement level, and if it is lower, it is further compared with a set value, and the opening time 'fti of the cell is recorded.

After the conditions at each end are approximately stabilized, the control section v method sets upper and lower limits for the valve openings of the six valves (upper limits are not necessarily required). Then, each valve is adjusted to a predetermined volume according to various pressures, pump discharge pressures, and pump discharge ends. Next, various liquid levels are detected and compared with the set value, and if the level is higher than the set value, the slurry transfer is 0. Increase the opening degree of the 5th part of the side square by a certain value. In the same way as for a certain period of time, compare the known height of the tL surface with the set value, and if the liquid level is better, reduce the valve opening of the slurry return valve 11111 by a certain value. The set liquid level is compared with the detected liquid level at regular intervals, and the valve opening degree is controlled based on the value.

[Effect]

By carrying out the method of the present invention, it becomes possible to avoid excessive load on the valve, so that stable operation for a long period of time becomes possible.

〔Example〕

When the control method of the present invention was applied to a plant for bulk polymerization of all-polypropylene, no problems occurred even after 3,000 hours of continuous operation. 5 times, but no fins were observed from the valve. When dispersion was performed by opening and closing one-way valves (6 valves were opened and closed repeatedly at a rate of 2.5 minutes/1 time), approximately 1100
At one time, one tank leaked, so operation was suspended.

〔Effect of the invention〕

By carrying out the method of the present invention, it is possible to carry out extremely stable operation for a long period of time without troubles such as damage to valves, which is extremely valuable industrially.

[Brief explanation of drawings]

FIG. 1 is a flow diagram showing a part of the plant flow for carrying out the entire method of the present invention. 1.2.3...Polymerization tank, 1-2.2-2.3-2...
・Slurry pump, 1-1, 2-1, 3-1...Liquid level gauge, 1-311-412-312-413-3゜3-4
...Valve, 1-5.2-5.3-5...Controller.

Claims (2)

[Claims] (1) α-olefin is continuously produced using a bulk polymerization method using α-olefin itself as a medium, using two or more reaction vessels equipped with a slurry circulation line and a polymerization machine connected by a liquid transfer line taken out from the circulation line. In the method of polymerizing the slurry continuously, valves with variable opening degrees are installed in the return section of the circulation line to the reaction tank and in the liquid transfer line, and the slurry is The slurry transfer amount is controlled by opening and closing the valves, and after the polymerization conditions in each tank reach the desired conditions, the slurry transfer amount is controlled by the valve opening degree. Polymerization method. (2) The method according to claim 1, in which the amount of slurry in each tank is used as the control value for the amount of slurry transferred.