JPS6364443B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for gas phase polymerization of olefins.

In recent years, gas phase polymerization has been attracting attention as a method for polymerizing olefins. However, conventional gas phase polymerization methods tend to produce block-like polymers and chip-like polymers, and they also tend to produce fine polymers in the circulating gas. There are disadvantages such as easy contamination by coagulation, large amount of gas entrained in the recovered polymer, and high manufacturing cost of the entire system, making it difficult to produce a good-quality olefin polymer economically and stably for a long period of time. It was considered difficult to manufacture.

Conventionally known gas phase polymerization systems for olefins are roughly divided into those using a vertical fluidized bed polymerization apparatus and those using a horizontal stirred bed polymerization apparatus. An example of the former is Japanese Patent Publication No. 47-13962, in which the produced polymer is discharged from the vicinity of the gas distribution plate of the polymerization apparatus. However, in such a method, a large amount of gas components are entrained in the produced polymer, and it is necessary to separate the two. In this case, since the gas component is reduced in pressure together with the polymer, it is essential to increase the pressure again and circulate it, which is extremely uneconomical. In addition, the original circulating gas component passes through a large-diameter, so-called deceleration zone located in the upper part of the polymerization apparatus to reduce its flow rate and precipitate fine polymer powder before being subjected to the circulation process. However, increasing the column diameter of a polymerization apparatus operated under high pressure is not economical from a manufacturing standpoint and also causes the formation of sheet-like polymers. Furthermore, the above method also has drawbacks such as the need for a dedicated level measuring device to control the bed level of the polymer powder in the polymerization apparatus.

On the other hand, an example of using a horizontal stirred bed type polymerization apparatus is JP-A-51-86584, but in the method disclosed therein, the gas component is extracted from the top of the polymerization apparatus separately from the produced polymer. . In such a system, it is unavoidable that fine polymers are mixed into the gas components, so in the above example, an absorption tower is used to remove the polymers. In addition, a method is adopted in which the produced polymer is passed over the outlet weir and put into the collection container, but with this method, chip-like polymer tends to form on the walls of the collection container, making stable operation over a long period of time difficult. Further, in the above method, it is essential to use liquid hydrocarbon to remove the heat of polymerization, and it can be said that it is virtually impossible to put it into practical use without using this. Furthermore, all of the conventionally known horizontal stirred bed polymerization apparatuses have the disadvantage that hot spots are likely to occur, making it difficult to prevent the formation of block polymers, and requiring a large amount of power for stirring.

The present invention improves the drawbacks of conventional gas phase polymerization methods and provides a highly effective gas phase polymerization method that can economically and stably produce olefin polymers of good quality over a long period of time.

That is, the present invention provides an olefin polymerization system in which an olefin gas and a polymerization catalyst are introduced into a gas phase polymerization apparatus to perform gas phase polymerization to obtain a polymer product, and at the same time, a gas component including unreacted olefin gas is circulated to the gas phase polymerization apparatus. In the continuous gas phase polymerization method, a plurality of small chambers each having an upper part opening to the inner surface of the lower portion of the container are provided at the bottom of a hollow cylindrical horizontal container equipped with a stirring blade inside as a gas phase polymerization apparatus, and at least the side wall of the small chambers is provided. Using a gas phase polymerization apparatus having small holes in the part, the raw olefin gas is introduced into the gas phase polymerization apparatus through the small holes, and the entire amount of circulating gas components and the overflow amount of produced polymer are subjected to gas phase polymerization. The present invention relates to a gas phase polymerization method for olefins, which is characterized in that they are extracted together from an apparatus and separated into components and produced polymers using a cyclone.

In the present invention, the gas phase polymerization apparatus is a hollow cylindrical horizontal container having a plurality of small chambers each having a plurality of small chambers at least in the side wall portion for supplying gas components including the raw material olefin gas to the polymerization system, the upper part of which constitutes the polymerization system. The essence is to use a horizontal fluidized stirred bed type polymerization apparatus installed so as to open on the lower inner surface of the polymerization apparatus. The main body of this device has a hollow cylindrical horizontal structure, and the length ratio to the vertical cross-sectional diameter inside the hollow cylinder is
Usually 0.5-10, particularly 1-5 is preferred. Further, this device may be provided with a chamber such as a vertical cylindrical body in the upper part, if necessary. In this case, the ratio of the cross-sectional diameter of the upper vertical cylinder to the internal cross-sectional diameter of the horizontal hollow cylinder of the main body is usually preferably 0.6 to 1.0. The stirring device used has a drive shaft at the center in the longitudinal direction of a horizontal hollow cylinder and one or more stirring blades. Stirring blades include paddle type, inclined paddle type,
There are spiral types, blades equipped with scrapers for scraping the inner walls of the polymerization apparatus, etc. Usually, a plurality of stirring blades are provided, but the distance between the inner wall of the polymerization apparatus and the tip of the stirring blade is 3.
Particularly favorable results are obtained when the thickness is about 10 mm.

A small chamber equipped with a small hole for supplying the raw material olefin gas is usually arranged through the small hole into a raw material olefin supply chamber that is arranged at regular intervals in the lower part of the hollow cylindrical horizontal container and covers the entire container. There is. The part where the small chamber is provided is a curved part centered on the lowest part of the cylindrical body. The angle from the center of the cylinder is
Preferably, the chamber is provided on a curved surface corresponding to an angle of 30° to 180°, in particular 60° to 120°. The diameter of the small hole is 2 to 6.
Approximately mm is preferable. The small holes may be oriented diagonally, or the bubble cap may be placed in reverse. The shape of the chamber can be arbitrary, such as cylindrical, but the diameter of the opening is usually preferably about 8 to 35 mm, and the depth is about 8 mm.
~25mm is preferable. Further, the small chamber may be formed into a long groove and installed so as to cross or longitudinally cross the lower part of the cylindrical body, as shown in FIG. The diameter of the opening in this case refers to the diameter of the transverse opening of the groove. The number of olefin gas supply holes provided in a small chamber varies depending on the size, shape, etc. of the small chamber, but in the case of a small chamber as shown in FIGS. 3 and 4, it is usually preferable to have about 2 to 8 holes.

The distance between the small chambers is preferably approximately 50 to 300 mm. By providing such a small chamber at the bottom of the cylinder, the gas is uniformly dispersed within the polymerization system, and it is also easy to obtain an appropriate opening ratio, which reduces pressure loss and gas circulation energy. be able to. Furthermore, even when the device is stationary, the produced polymer powder does not fall, and the stirring efficiency is further improved.

The catalyst is usually supplied as a slurry of saturated hydrocarbons or as a solid. At this time, the promoter may be added at the same time or may be supplied separately. It is also preferable to supply hydrogen or nitrogen gas to prevent clogging of the catalyst inlet.

The essence of the present invention is to use such a gas phase polymerization apparatus, discharge the gas components and discharge the produced polymer at the same time using the same discharge port, supply these to a cyclone, and separate the two by the cyclone. shall be.

A common outlet for gas components and produced polymer is usually provided above the center of the polymerization apparatus. Specifically, the level of the polymer powder changes depending on the type of stirring blade in the polymerization equipment and its rotation speed, so after determining the optimal stirring condition, the height of the discharge port is adjusted according to the level of the polymer powder. It can be decided. Usually, the outlet is preferably provided on the side of the polymerization apparatus on the side where the polymer is lifted by stirring, at a height in the range of 1/3 to 1 radius of the polymerization apparatus upward from the horizontal center plane of the polymerization apparatus.

A mixture of the total amount of circulating gas leaving the polymerization device and the overflow amount of produced polymer is supplied to the cyclone, and the gas flow rate in the piping from the polymerization device to the cyclone is 5 m/sec to 30 m/sec. ,
Desirable for preventing polymer from adhering to walls.

As the cyclone, a well-known type of cyclone is used as appropriate. Preferably, the structure is as simple as possible.
For example, those having the basic structure described in Chemical Engineering Handbook, page 1233 (published by Maruzen, 1979) can be used as appropriate. The inner surface of the cyclone must be smoothed by buffing. A receiver for the produced polymer is provided at the bottom of the cyclone. It is preferable that this receiver be small. It is also preferred that the receiver be externally cooled to prevent the polymer from melting therein. The produced polymer may be withdrawn from the system by any appropriate method, such as intermittent withdrawal by intermittent opening and closing of a ball valve or continuous withdrawal using a ball valve type control valve.

The gas flow velocity at the inlet of the cyclone is 5m/sec to 30m/
sec, especially preferably maintained at 10 m/sec to 25 m/sec.

Two or more cyclones may be installed in one polymerization apparatus.

The present invention will be explained below with reference to the drawings.

FIG. 1 is a schematic process diagram showing an example of olefin polymerization according to the present invention. A raw material olefin gas 4 is supplied via the gas supply chamber 5 to a horizontal polymerization apparatus 3 equipped with a stirring blade 1 and a small chamber 2 for supplying raw material olefin gas, and a catalyst 6 and, if necessary, hydrogen 7 and a cooling liquid are also supplied. . The raw material olefin gas is
Ethylene, propylene, butene-1, hexene-
α-olefins usually having 12 or less carbon atoms, such as 1,4-methylpentene-1, are used alone or in a mixture of two or more. Furthermore, dienes such as butadiene, 1,4-hexadiene, and ethylidene norbornene can be further added to these olefins for copolymerization.

The temperature of the polymerization reaction tank is 0 to 125℃, especially 20 to 100℃
is preferred. Pressure is normal pressure ~ 70Kg/cm ² G, especially 2 ~
60Kg/cm ² G is preferred. The rotation speed of the stirring device is 10~
500 rpm, especially 20-300 rpm is preferred. The circulating gas linear velocity in the polymerization equipment is 0.5 to 25 cm/cm based on the cross-sectional area.
sec, especially 1 to 10 cm/sec is preferred. As the catalyst, a known Ziegler type, Phillips type, or standard type catalyst, which is usually used in the production of polyolefins, is used.

The entire amount of circulating gas and the overflow amount of produced polymer are supplied to a cyclone 9 via a pipe 8, and the produced polymer is separated into a receiver 10 and then a ball valve 1.
It is intermittently extracted from the system by the intermittent opening and closing of 1 and 12. The gas components separated by the cyclone are supplied to the cooler 13 to liquefy the cooling liquid, and the separated cooling liquid is sent to the receiving tank 14 and the cooling liquid pump 1.
5 and then circulated to the polymerization apparatus. The gas components are circulated to the polymerization apparatus by a gas circulation blower 16.

FIG. 2 is a schematic sectional view showing an example of the polymerization apparatus used in the present invention, where a is a longitudinal section and b is a line 1'--
1' cross section is shown. The numbers in the figure are the same as in FIG. 1, and 17 and 17' are piping for guiding the raw material olefin gas to the olefin gas supply chamber 5. Third
4 and 5 are schematic diagrams showing an example of a small chamber having an olefin gas supply hole.

In the method of the present invention, when a cyclone is used to separate the mixture of the total amount of produced polymer to be obtained and the total amount of circulating gas, both can be separated extremely efficiently and no powder will adhere to the wall surface. do not have. When intermittent opening and closing of a ball valve is used to extract the produced polymer, the pressure fluctuations that occur at that time also have the effect of preventing powder adhesion more effectively.

The method of the present invention can be operated stably and continuously for a long period of time without producing block polymers or chip polymers, and there is no mixing of fine polymers into the circulating gas, which are entrained in the separated produced polymers. This has the advantage that the amount of gas used is small and the level of the polymer bed in the polymerization apparatus can be kept constant.

Example 1 A 40 horizontal fluidized stirred bed polymerization reactor as shown in FIG. 2 was used, and 14 small chambers as shown in FIG. 3 were installed below it. The chambers have a diameter of 12 mm and a depth of 27 mm, and there are four holes of 3 mm diameter on the side of each chamber.
They are matched one by one.

Gas was circulated through the horizontal fluidized stirred bed polymerization reactor, cyclone, cooler, blower, and flow regulator loop as shown in FIG. The temperature of the reactor was controlled by running hot water through the jacket. The cyclone used has a diameter of 78 mm and a total length of 243 mm.
It is.

1 kg of anhydrous magnesium chloride, 50 g of 1,2-dichloroethane, and 170 g of titanium tetrachloride were ball milled at room temperature in a nitrogen atmosphere for 16 hours to support the titanium compound on the carrier. 1g of solid material obtained
Contains 35mg of titanium per serving.

The above solid material was placed in a reactor containing 9.3 kg of dry polyethylene powder and adjusted to 80°C.
500ml/hr of catalyst slurry in which 300mg and 5mmol of triethylaluminum are dispersed in 1 part hexane.
hydrogen, and ethylene and butene-1 while adjusting the hydrogen/ethylene (molar ratio) in the gas phase to 0.28 and the butene-1/ethylene (mole ratio) to 0.31. A mixture of these was supplied from lines 7 and 4, respectively, and the gas in the system was circulated at 24 m ³ /hr using a blower. A paddle type stirring blade is attached to the reaction tank.
The polymerization was carried out at a total pressure of 8 kg/cm ² ·G while stirring at 50 rpm.

The polymer was extracted as appropriate during the polymerization, and the polymerization was terminated due to normal termination after 121 hours.

After the polymerization was completed, 310 kg of white polyethylene (excluding the polyethylene initially added to the reaction tank) was obtained, the melt index of the polymer was 1.5, the density was 0.9185, and the bulk density was 0.29.

Next, when the reaction tank was opened and inspected, no polymer adhesion was observed inside the tank.

[Brief explanation of drawings]

FIG. 1 is a schematic process diagram showing an example of polymerization of olefin according to the present invention, and FIG. 2 is a schematic sectional view showing an example of a polymerization apparatus used in the present invention, where a is a longitudinal section and b is a line 1. '-1' cross section is shown. Third
The figure is a schematic diagram showing an example of a small chamber having an olefin gas supply hole, where a is a longitudinal section and b is a line 2'--
2' cross section is shown. FIGS. 4 and 5 are schematic diagrams showing other examples of small chambers having olefin gas supply holes.

Claims (1)

[Scope of Claims] 1. Introducing olefin gas and a polymerization catalyst into a gas phase polymerization apparatus to perform gas phase polymerization to obtain a produced polymer, and at the same time circulating gas components including unreacted olefin gas to the gas phase polymerization apparatus. In a continuous gas phase polymerization method for olefins, a plurality of small chambers are provided at the bottom of a hollow cylindrical horizontal container equipped with a stirring blade inside as a gas phase polymerization device, the upper part of which opens into the inner surface of the bottom of the container. Using a gas phase polymerization apparatus having small holes at least in the side wall, the raw olefin gas is introduced into the gas phase polymerization apparatus through the small holes, and the total amount of circulating gas components and the overflow amount of produced polymer are A method for the gas phase polymerization of olefins, which is characterized in that they are extracted together from a phase polymerization apparatus and separated into a gas component and a produced polymer using a cyclone. 2. The method according to claim 1, wherein the entire amount of the circulating gas component and the overflow polymer are extracted together from an outlet provided at the top of the gas phase polymerization apparatus and supplied to the cyclone.