JPS58113208A - Continuous vapor phase polymerization of olefin - Google Patents

Abstract

PURPOSE:To obtain an uniform olefin polymer in stable condition, by carrying out an agitation, in a vapor phase polymerizer, so that the upper end of the agitating blade is imbedded in the fluidized bed zone, and detecting a pressure difference between said zone and the upper space to maintain the height of the above zone constant. CONSTITUTION:An olefin is preliminarily polymerized in a prepolymerizer 1 followed by continuously feeding the resultant intermediate product to a vapor phase polymerizer equipped with an agitator 4. While agitating the fluidized bed zone 3 so that the upper end of the agitating blade is imbedded in said zone 3, a pressure difference between said zone 3 and the space 2 above the zone 3 is detected through the pressure-detecting element 20 in the space 2 and the other element 21 set at a site within said zone 3 and higher than said upper end of the agitating blade. The olefin polymer produced is drawn through the pipe 19 according to the pressure difference value so that the height of said zone 3 is maintained to a nearly constant level, thus obtaining the objective polymer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for gas phase polymerization of olefins. More specifically, the present invention relates to a method for continuous gas phase polymerization of olefins, which allows continuous and stable operation for a long period of time, and therefore enables the production of olefin polymers of constant quality.

In particular, in the present invention, in a gas phase polymerization tank equipped with a stirrer,
In a gas phase polymerization method for olefins in which gas phase polymerization is carried out continuously while forming a fluidized bed layer under stirring conditions, (1) the upper end of the height of one stirring blade of the stirrer forms a fluidized bed layer; (11) Pressure within the fluidized bed area provided in the fluidized bed area and at a position exceeding the upper end of the stirring blade height. a detection end;
A pressure detection end in the upper space area provided in the upper space area above the fluidized bed area detects the differential pressure between the two areas, and according to the detected pressure difference, the pressure in the upper space area is increased. The present invention relates to a process for the continuous gas phase polymerization of olefins, characterized in that the olefin polymer is withdrawn from the zone so that the height is maintained substantially constant.

Continuous gas phase polymerization of olefins while forming a fluidized bed by blowing gaseous olefin into a layer of olefin polymer particles containing a catalyst in a gas phase polymerization tank equipped with an agitator. is publicly known.

At this time, in order to prevent entrainment of fine olefin polymer particles and catalyst particles, the gas flow rate is reduced.
Alternatively, attempts to obtain a good mixing state by stirring the fluidized bed by mechanical stirring are also known. However, despite these attempts, it is difficult to make the mixing state uniform in the fluidized bed layer, resulting in the formation of olefin polymer lumps that clog the gas inlet and olefin polymer outlet. This often makes long-term operation impossible. In addition, when performing such gas phase polymerization continuously, it is important to extract the olefin polymer while maintaining the height of the fluidized bed zone as constant as possible to obtain a homogeneous polymer and to ensure stable operation. It is necessary for

To this end, it is conceivable to measure the height of the fluidized bed zone and adjust the opening and closing of the polymer discharge valve to keep it constant. Based on this idea, the present inventors
As a method of measuring the height of the fluidized bed zone, two pressure detection ends are installed in the gas phase polymerization tank, one above the fluidized bed zone and the other in the upper space area above the fluidized bed zone. We tried a method of determining the height of the fluidized bed section by installing it at the top or within the fluidized bed section and measuring the differential pressure between the two.

As a result, when the other pressure detection end is provided at the upper end of the fluidized bed area, when the upper end of the fluidized bed area reaches the pressure detection end, a pressure difference with the upper space area is generated. This is detected, and the polymer discharge valve is opened to withdraw the polymer in response to the detected differential pressure, and in response to this withdrawal, the height of the fluidized bed section is lowered to detect the other pressure. When the level is lower than the end, there is no pressure difference with the upper space area, so it is necessary to adopt a control system that detects this and closes the polymer discharge valve. The disadvantage of this method is that it is not operationally possible to control the height of the fluidized bed zone to make fine adjustments, and the height of the fluidized bed zone fluctuates considerably, making stable operation difficult. I found out something.

On the other hand, if the other pressure detection end is installed in the fluidized bed area, the detection end will be affected by the agitator depending on the installation position, and the pressure will not be detected accurately. It has been found that it is difficult to constantly adjust the layer zone height. Furthermore, it has been found that there is a problem in that the detection end is likely to become clogged, even making measurement impossible. There is no risk of this if the measurement is carried out in an area where the agitation is insufficient in the fluidized bed area, but if agitation conditions that cause such a state are adopted, the formation of a uniform fluidized bed state will be inhibited. However, it was found that stable polymerization did not occur and there was a problem of formation of bulk polymers.

However, as a result of further investigation, the above (1) and (I)
By adopting the method of detecting the differential pressure described above under conditions that satisfy I), it is possible to control the height of the fluidized bed area to be almost constant, and to maintain a good mixing state in the fluidized bed area. It was discovered that stable polymerization was possible, and troubles such as the formation of bulk polymers and the adhesion of polymers to walls could be prevented. It is therefore an object of the present invention to provide an improved continuous gas phase polymerization process for olefins.

In the olefin polymerization of the present invention, in a steady state, a catalyst is continuously supplied under stirring conditions to a fluidized bed section consisting of an olefin polymer and a catalyst, and a gaseous olefin is transferred to the lower part of the fluidized bed section. The fluid state is maintained and polymerization is carried out by blowing into the solution. The inside of the fluidized bed zone is stirred by a stirrer, preferably an anchor type stirrer, thereby making it possible to obtain a good mixing state also in the lateral direction.

The lower end (bottom) of the fluidized bed zone is preferably a perforated plate to aid in uniform dispersion of the gaseous olefin and to prevent falling of polymer particles, etc. Hydrogen can be used for molecular weight control purposes and may be fed from the lower end of the fluidized bed section with the gaseous olefin or directly into the fluidized bed section.

The fluidized bed section of the polymerization reactor preferably has a truncated conical or cylindrical shape. The stirrer used in the present invention, preferably a squid type stirrer, has a truncated conical shape,
The bottom of a fluidized bed shaped like a cylinder (usually made of a perforated plate)
It has a structure in which the stirring blade rotates close to the side wall surface, and extends from the rotating shaft along the bottom surface of the fluidized bed area to the vicinity of the side wall section, and then further rises along the side wall section. Usually, it has a structure with a plurality of stirring blades that extend from one side to the other. The heights of the plurality of stirring blades do not necessarily have to be the same. The Ikari type stirrer may also be provided with auxiliary stirring blades or may have other modified designs as long as it has the basic structure as described above.

During the polymerization of olefins, the height of the fluidized bed zone is
The height of the stirring blade of the stirrer to the upper end is preferably 1
．． The olefin weight is maintained at 0.02 to 1.4 times, more preferably 1.02 to 1.2 times, and preferably so that the height of the fluidized bed area does not vary as much as possible and is maintained approximately constant. It is preferable to extract the coalescence continuously or intermittently. The height to the upper end of the stirring blade of the stirrer is the distance from the bottom of the fluidized bed zone to the upper end of the stirring blade, and when the stirrer has multiple stirring blades and their heights are different, is based on the highest standard.

In the present invention, the stirring blade of the stirrer is thus operated so as to be buried within the fluidized bed zone.

If a part of the upper part of the stirring blade is exposed from the fluidized bed zone and extends into the head space area, the olefin polymer will adhere or form agglomerates in that part, which will impede stable operation. Also,
If the height of the fluidized bed zone is maintained higher than the above-mentioned preferred range, mixing of the entire system of the fluidized bed zone may become insufficient and there is a risk of wall adhesion, etc., so it is recommended to appropriately select the height within the above-mentioned preferred range. . By using an agitation type stirrer and adjusting the height of the fluidized bed zone to an appropriate position, preferably within the above range, it is possible to prevent the polymer from adhering to the wall or clumping, and to achieve stable operation. be able to.

Furthermore, such a configuration also makes it possible to accurately measure the height of the fluidized bed zone using the differential pressure method, so that the detected difference can be adjusted to keep the zone height approximately constant. Automatic control is possible by instructing the olefin polymer extraction valve to open and close depending on the pressure.

That is, it is possible to measure the height of the fluidized bed by measuring the differential pressure between the fluidized bed area and the upper space area. However, the pressure sensing end in the fluidized bed zone is generally prone to clogging and is also easily affected by the agitator. However, as mentioned above, the height of the fluidized bed zone is preferably maintained at about 1.02 to 1.4 times the height of the stirring blade to the upper end, and in the fluidized bed zone and By installing the pressure detection end in the fluidized bed area at a position exceeding the upper end of the stirring blade height, there will be no clogging, no leakage, and no influence from the stirrer, so accurate measurements can be made over a long period of time. becomes. As a result, the fluidized bed area pressure detection end and the upper space area pressure detection end detect the pressure difference between the two areas, and the height of the fluidized bed area is approximately adjusted according to the detected pressure difference. It is possible to draw out the olefin polymer in a constant manner, and continuous operation for long periods of time can be carried out automatically. The pressure detection end on the fluidized bed side is preferably located at a height of 1.05 to 1.15 times the height of the stirring blade to the upper end.

In the present invention, another pressure detection end is provided slightly above the pressure detection end in the fluidized bed zone, and the pressure difference between this end and the pressure detection end at the upper part of the fluidized bed is measured, and the height of the fluidized bed zone is measured. You may adopt the aspect which controls an upper limit by this differential pressure in combination with the above-mentioned control.

Olefin polymerization in the present invention includes not only homopolymerization of olefins, but also copolymerization of olefins, copolymerization of olefins and dienes, and the like. Examples of olefins include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, and 1-decene. In particular, it is suitable for producing a crystalline polymer mainly composed of ethylene or propylene, and containing, for example, 90 mol% or more of these monomers.

As the polymerization catalyst, various catalyst systems such as Ziegler type catalyst and Phillips type catalyst can be used. For example, compounds such as titanium, vanadium, chromium, zirconium, etc. can be used as catalyst components. In particular, it is preferable to use a titanium catalyst component supported on a magnesium compound and an organic aluminum compound catalyst component because the catalyst activity is high. These catalyst systems are already widely known. In the polymerization, hydrogen, electron donors, halogen compounds, and other various additives can be used for the purpose of controlling molecular weight, molecular weight distribution, stereoregularity, and the like. These catalyst components and additives can be supplied to any location in the polymerization vessel. In the polymerization, easily volatile inert hydrogen can also be present for the purpose of heat removal. These serve the purpose of heat removal by being vaporized in the polymerization vessel.

The polymerization temperature of the olefin varies depending on the type of olefin, but generally a temperature range of about 30°C to about 90°C is adopted. Further, the reaction pressure may be any pressure as long as it is lower than the pressure at which the olefin is liquefied, and is, for example, about 2 to about 30 kq/ax2.G.

The olefin is transported from the lower part of the fluidized bed section at a linear velocity of 1 to 607/sea, particularly about 3 to about 4037/sea.
It is preferable to blow it so that it becomes c. In order to remove the heat of polymerization, a liquid olefin may be supplied to the polymerization vessel. When a liquid olefin is supplied, it is preferably supplied above the fluidized bed.

The olefin polymer is withdrawn continuously or intermittently from the side of the fluidized bed section to maintain a constant fluidized bed height.

Adopting such a method to carry out continuous polymerization for a long period of time -
I can do it.

One embodiment of the invention is shown in FIG. After the olefin is prepolymerized in the prepolymerization tank 1 using a titanium catalyst component supported on a magnesium compound and an organoaluminum compound component, it is continuously supplied to the fluidized bed zone 3 of the gas phase polymerization tank via a pipe 11. . Additional organoaluminum compound is fed via line 12 to the fluidized bed section 3 of the gas phase polymerization vessel.

The fluidized bed zone 3, which is the reaction bed of the gas phase polymerization tank, is stirred by an agitation type stirrer 4. For gaseous olefin, condenser 6
The material that is not condensed is fed to the lower part of the polymerization tank through the pipe 16 or through the new pipe 14, and enters the fluidized bed layer section 3 through the perforated plate 5, fluidizing the reaction bed and starting the polymerization. use. Hydrogen used for molecular weight adjustment is g1
5 and supplied to the polymerization tank. Unreacted olefin discharged from the polymerization tank passes through a pipe 16 and is condensed in a condenser 6, passes through a drum 7 through a pipe 17, and is sprayed from a spraying section 18 onto the reaction bed.

The height of the fluidized bed section 3 is determined by the low pressure side line 20 having a detection end in the upper space section 2 and the high pressure side line 20 having a detection end at a position within the fluidized bed section 3 and beyond the upper end of the stirring blade. The differential pressure in the line 21 is measured with a level meter 23, and the polymer is extracted from the pipe 19 by instructing the opening and closing of the level control valve 24 while keeping the height h2 of the fluidized bed section constant. Pipe 22 to prevent clogging of high pressure side line 21
It is better to keep the purge gas flowing.

Example 1 Preparation of titanium catalyst component> Commercially available anhydrous magnesium chloride 30 g 1 ethyl benzoate 7
．． 5mA' and methylpolysiloxane (viscosity 2Qc,
a, (25° C.)) were brought into contact for 40 hours using a vibrating ball mill in a nitrogen atmosphere. Obtained solid treated product 20
g was suspended in 2000 ml of TIC14 and contacted at 80° C. for 2 hours with stirring. After the reaction was completed, the supernatant was washed with purified hexane by decantation. This operation was repeated until no chlorine was detected in the supernatant hexane. The obtained titanium catalyst component contains titanium i,
It contained 9 wt% and 65 wt% chlorine. By repeating the above operation several times, the following polymerization was carried out.

Prepolymerization treatment> The titanium catalyst component was added to 1.5n+mol/in hexane.
l, triethyl aluminum (hereinafter abbreviated as TEA) 6m
mol//, p-) Methyl ruylate (hereinafter abbreviated as MPT) 2 mmol/A! The amount of propylene added was twice the weight of the titanium catalyst component.

Gas Phase Polymerization of Polypropylene> Using the catalyst prepolymerized as described above, polymerization was carried out according to the flow diagram shown in FIG.

The inner diameter of the gas phase polymerization tank is 500 mm, and the height (hl) of the stirring blade of the Ikari type stirrer 4 to the upper end is 45 mm from the perforated plate 5.
3 mm, and the high pressure side line 21 is made of SUS with an inner diameter of 2 mm, and the pressure detection end in the fluidized bed zone is set at 200 rpm with a zero-point stirrer inserted 150 mm from the inner wall of the polymerization tank and 30 mm from the upper end of the stirring blade. While rotating, the prepolymerized titanium catalyst component i mmol/h
r (titanium atom equivalent), TEA 50 mmol/hr,
5M P T 12 mm o l/hr % propylene gas (including circulating gas) in the polymerization tank 40117
45k of propylene liquid at a speed of s e c
Spraying from spraying s18 at a rate of g/hr, polymerization temperature 70
Continuous polymerization of propylene was carried out under the conditions of 9/4 G and 18° C. polymerization pressure. Further, the polymer was extracted from the pipe 19 at a rate of 10 kg/hr according to the instructions of the level meter so that the height h2) of the fluidized bed zone was 490 mm above the perforated plate.

In order to prevent clogging of the high pressure side line, propylene gas was supplied from the pipe 22 at a rate of 100 Nl/hr.

Polypropylene having an MI of 9.1 and an n-heptane insoluble content of 93.5% by weight could be produced stably for a long period of time.

Comparative Example When the detection end of the high-pressure side line 21 was set at the height of the stirring blade and 440 mm below the top end of the stirrer, it was difficult to detect the level and it was not possible to detect an increase or decrease in the level.

[Brief explanation of the drawing]

FIG. 1 of the accompanying drawings is an illustrative apparatus diagram illustrating one embodiment of carrying out the method of the present invention. Applicant Mitsui Petrochemical Industries Co., Ltd. Agent Heikichi Odashima (1 other person) Figure 1

Claims (1)

[Scope of Claims] (1) A method for gas phase polymerization of olefins, in which gas phase polymerization is carried out continuously while forming a fluidized bed layer under stirring conditions in a gas phase polymerization tank equipped with an agitator. (1) Performing gas phase polymerization while stirring the fluidized bed zone with the upper end of the stirring blade of the stirrer buried in the fluidized bed zone; (11) In the fluidized bed zone. In addition, a pressure detection end in the fluidized bed section provided at a position exceeding the upper end of the height of the stirring blade, and a pressure detection end in the upper space section provided in the upper space section above the fluidized bed bed section, Detects the differential pressure between areas,
A method for the continuous gas phase polymerization of olefins, characterized by: extracting the olefin polymer from the fluidized bed bed zone so that the height of the zone is maintained substantially constant according to the detected differential pressure. (2) The method according to claim 1, wherein the height of the fluidized bed zone is within a range of 1.02 to 1.4 times the height of the stirring blade to the upper end. (5) The method according to claim 1 or 2, wherein the gas flow rate in the fluidized bed layer is 1 to 6017 seconds.