JPH0322405B2 - - Google Patents

Description

Detailed Description of the Invention The present invention comprises a polymerization step in which an olefin is polymerized in a liquid olefin of the same type to obtain a polyolefin, and then a copolymerization step in which the polyolefin is copolymerized with another olefin to obtain a block copolymer. This invention relates to a novel method for producing block copolymers in which the following steps are carried out continuously.

The method for producing the block copolymer basically consists of continuously extracting the polyolefin obtained in the polymerization process in the form of a slurry, vaporizing the liquid olefin from the slurry, and separating the solid polyolefin.
This is supplied to a copolymerization step and copolymerized with other olefins to obtain a block copolymer. Conventionally, as a method for separating solid polyolefin from a polyolefin slurry obtained in a polymerization process, a method has generally been adopted in which the slurry is supplied to a flash tank maintained at atmospheric pressure and the liquid polyolefin is vaporized. however,
It is virtually impossible to feed the solid polyolefin separated by the above method to the copolymerization process under pressure, so it is usually made into a slurry with an inert solvent, etc., and then the pressure is increased to carry out the copolymerization. was supplied to the process. Therefore, not only does the process become complicated, but also when the copolymerization is carried out in a gas phase, it is difficult to fluidize the copolymerization, making it difficult to carry out the copolymerization. Further, the above method requires a large-scale compressor and the like to recover the vaporized olefin, which is very disadvantageous from an industrial perspective. On the other hand, as a method for solving the problem in recovering the vaporized olefin, a method has been proposed in which heated water or steam is supplied to the flashing tank to maintain the pressure of the flashing tank at a high level while vaporizing the liquid olefin. . According to the above method, the vaporized olefin can be easily liquefied and recovered by cooling with water, but since the liquefied olefin contains water, dehydration treatment is required, which is industrially disadvantageous. Furthermore, when trying to feed the polyolefin separated by the above method to a copolymerization process, it is virtually impossible to produce a block copolymer because the polymerization catalyst is inactivated by the water present. Become.

In the present invention, research has been carried out to solve various problems in the method for producing the block copolymer.
As a result, the polyolefin slurry that is continuously extracted from the polymerization process is heated under pressure to vaporize the liquid olefin contained therein and separate the solid polyolefin, which is then copolymerized while maintaining the pressurized state. It was discovered that by supplying the solid polyolefin to the copolymerization process, the vaporized olefin can be easily recovered by water cooling, and the solid polyolefin can also be supplied to the copolymerization process without turning it into a slurry. It was completed.

In the present invention, a polymerization step of polymerizing an olefin in a liquid olefin of the same type to obtain a polyolefin is followed by a copolymerization step of copolymerizing the polyolefin with another olefin to obtain a block copolymer. The polyolefin obtained in the polymerization process is taken out in a slurry state, the liquid olefin is vaporized from the slurry under pressure to separate the solid polyolefin, and the solid polyolefin is subjected to the copolymerization process while maintaining the pressurized state. A method for producing a block copolymer is provided.

The present invention will be explained in detail below.

In the present invention, propylene, butene-1, etc. are generally used as the olefin. Among the above olefins, in the polymerization step of the present invention, olefins that are easily liquefied during polymerization are preferably used. For example, propylene or mixtures of propylene with small amounts of other olefins such as ethylene are suitable.
The olefin polymerization catalyst used in the present invention is not particularly limited and any ordinary polymerization catalyst may be used, but generally an organometallic catalyst containing titanium trichloride, an organoaluminum compound, and a third component added as necessary is used. A so-called solvent-free polymerization method is employed in which the olefin itself is used as a solvent in the presence of the catalyst. In addition, the polymerization conditions are not particularly limited and may be selected as necessary as long as the olefin remains liquid, but generally, for example, 50 to 80
C. and 22 to 40 kg/cm ² -G is suitable for polymerization. Of course, the olefin may contain a small amount of an inert hydrocarbon such as propane. The polyolefin obtained by the above-mentioned solvent-free polymerization method exists in a slurry state in the reaction tank of the polymerization process because unreacted liquid olefin exists. In the present invention, as will be described later, the polyolefin in the slurry state is used as the slurry, or if necessary, the slurry concentration is concentrated using a liquid cyclone or the like, and then the liquid olefin in the slurry is vaporized. The latter, that is, the use of a concentrated slurry, is often preferred because it can reduce the heat source necessary for vaporizing the liquid olefin, which will be described later.

It is necessary to vaporize the liquid olefin in the slurry by heating the slurry under pressure. The liquid olefin may be vaporized by connecting a flash tank to the reaction tank of the polymerization step.
(The following explanation is based on the case where liquid olefin is vaporized using a flash tank.) Generally, the pressure in the flash tank is maintained to be lower than the pressure state in the reaction tank, and the unreacted It is preferable to easily vaporize the liquid olefin by reducing pressure and supplying heat.
Of course, if necessary, a pump may be provided in front of the flashing tank to pressurize the supplied slurry and maintain the pressure in the flashing tank higher than that in the reaction tank. The pressure and temperature of the flashing tank are preferably selected to such a level that the olefin vaporized in the flashing tank can be easily liquefied by cooling with cooling water, for example, cooling water at 5 to 50°C. More specifically, these conditions are preferably maintained at a temperature of 30 to 100°C and a pressure of 2 to 20 kg/cm ² -G. In order to adjust the pressure in the flash tank, it is preferable to provide a pressure regulating valve after the condenser for condensing the olefin vaporized in the flash tank. Further, the temperature of the flash tank may be controlled by any method that does not inactivate the catalyst contained in the polyolefin. For example, a method of heating a part of the olefin vaporized in the flashing tank and circulating it to the flashing tank is preferable because of its good thermal efficiency. Other methods include a method of providing a heat exchanger in the flashing tank and a method of heating the slurry before supplying it to the flashing tank. Through such an operation, in the flash tank, all unreacted liquid olefin is vaporized without deactivating the catalyst in the solid polyolefin, so that the solid polyolefin containing no liquid olefin can be easily separated. . The heating temperature of the olefin is not particularly limited, and may be appropriately determined depending on the amount of slurry to be flashed, the set temperature of the flashing tank, etc. Generally 50-150
°C is preferred.

In the above method, it is desirable that the olefin vaporized in the flashing tank is then washed with liquid olefin. This washing removes the mist containing fine particles of polymer and organic metals as catalyst components, which are carried along with the olefin vaporized in the flashing tank. Removal of these particulate polymers and mist is of great industrial advantage in the sense of preventing recovery of olefin gas, scale formation in the refining process, or damage to sliding parts of rotating equipment. As mentioned above, the olefin gas vaporized in the flashing tank is washed with liquid olefin as necessary, then partially heated and circulated to the flashing tank, and the remaining olefin gas is heated using a cooling device such as a heat exchanger. For example, it is liquefied and recovered by heat exchange with cooling water at room temperature. Therefore,
Unlike the case where liquid olefin is vaporized under normal pressure, the method of the present invention eliminates the need for a compressor or the like in the olefin gas recovery process, thereby significantly reducing equipment costs and operating costs.

On the other hand, when olefin gas vaporized and taken out in a flushing tank is washed with liquid olefin,
The liquid olefin after washing contains a finely divided polymer and an active catalyst as described above. Therefore, by circulating this washing liquid as it is to the polymerization tank, the amount of expensive organometallic catalyst used can be reduced, contributing to a reduction in manufacturing costs.

The polyolefin separated from the slurry by vaporizing the liquid olefin is obtained in solid form. In the present invention, the solid polyolefin is fed to the copolymerization step while being kept under pressure. Therefore, when the pressure in the flash tank is higher than the pressure in the reaction tank in the copolymerization step,
The pressure difference can be used as a driving force to supply the reaction tank, and if the pressure difference is small or non-existent, it can be easily supplied using a simple supply device such as a screw feeder or rotary leaf feeder. It has advantages such as being able to In particular, by adjusting the degree of pressurization so as to sequentially reduce the pressure in the polymerization step, flashing tank, and copolymerization step throughout the entire process of the present invention, it is possible to extremely easily transport the polyolefin continuously.

In the present invention, the polymerization method in the copolymerization step is not particularly limited, but as described above, a gas phase polymerization method is preferably employed because it can supply a solid polyolefin containing no liquid olefin to the copolymerization step.

For the above-mentioned gas phase polymerization method, known conditions may be employed without particular limitations. Copolymerization is usually carried out at 30 to 100°C and at 1 to 50 Kg/cm ² -G such that the polymerization ratio of the subsequent α-olefin block portion to the total polymer is 3 to 50 wt%, preferably 10 to 30 wt%. .
When using an ethylene-propylene mixed gas, which is a more preferred embodiment, the gas composition generally has an ethylene content of 20 to 90 mol%, preferably 40 to 90 mol%.
It is 80mol%. In the copolymerization process of the present invention, solid polyolefin containing substantially no liquid olefin is supplied from the flash tank, so the amount of olefin entrained is extremely small.
Therefore, it becomes extremely easy to control the composition of other olefins to be copolymerized in this step.

Hereinafter, typical embodiments of the present invention will be described in detail with reference to the accompanying drawings, but the present invention is not limited to these accompanying drawings. The olefin is supplied to the polymerization tank 1 through a pipe 4 and the catalyst components are supplied through pipes 2 and 3, respectively, and the olefin is polymerized under conditions where the olefin remains in a liquid state (polymerization step). A slurry of polymerized polyolefin is extracted from a pipe 5 and supplied to a flash tank 10 via a concentrator 9 if necessary. The concentrator 9
The unreacted liquid olefin separated is pumped to pump 1.
1 from the pipe 6 to the polymerization tank 1. The flush tank 10 is maintained at a predetermined pressure by a pressure regulating valve 23. This pressure is appropriately set depending on the type of olefin used, the temperature of the cooling water, the pressure of the next stage polymerization tank, etc. Further, it is preferable to provide the flash tank with a stirrer or to blow heated olefin gas from the lower part of the flash tank to bring the polyolefin into a fluid state.
The solid polyolefin separated by vaporizing the unreacted olefin is supplied from the flash tank to the gas phase polymerization tank 25 through a valve 15 using a pressure difference. In the gas phase polymerization tank 25, copolymerization is carried out while the solid polyolefin is fluidized by circulating the raw olefin mixed gas using the pressurizer 26 to produce a block copolymer (copolymerization step).
In addition, 27, 28 and 29 are olefin and hydrogen, respectively. On the other hand, the olefin gas vaporized in the flushing tank passes through the pipe 13 and is washed by contacting with the liquid olefin supplied from the pipe 16 in, for example, a wet washing device 14 . As the wet cleaning device 14, a commonly used wet dust collector can be suitably used. For example, spray towers, cyclones, scrubbers, ventilators, etc. may be used alone or in combination. The liquid olefin after washing is separated from the gaseous olefin in a tank 17,
It is preferable to circulate it to the polymerization tank 1 using the pump 18. On the other hand, a part of the washed olefin gas may be sent to the heat exchanger 12 by the pressurizer 19, heated, and then supplied to the flashing tank 10. The remainder of the olefin gas is liquefied in a condenser 20, and the liquefied olefin is separated in a separation tank 22, and a pump 21 supplies part of it to the wet cleaning device 14 via a pipe 16, and the rest to the polymerization tank 1. It is sufficient to use it in circulation and to transfer it to the recovery process through the pipe 24.

EXAMPLES In order to explain the present invention more specifically, the present invention will be described below with reference to Examples, but the present invention is not limited to these Examples.

Example 1 A block copolymer was produced according to the process shown in FIG. 1 of the attached drawings. As a polymerization catalyst, brown titanium trichloride obtained by reducing titanium tetrachloride from diethylaluminum monochloride in an inert solvent was treated with about an equimolar amount of diisoamyl ether at room temperature, and then the brown titanium trichloride was further treated with about an equimolar amount of diisoamyl ether at room temperature. titanium trichloride obtained by chemical treatment with a hexane solution of 1.5 times the mole of titanium tetrachloride at 65°C (the polymerization activity of this titanium trichloride is 3,300 g・polymer/g・TiCl ₃ /1 hour, and Total co-weight is 11,200g・polymer/g・
It was _TiCl3 . ) and diethylaluminum monochloride were used. First, in polymerization tank 1 of 300,
Polymerization of propylene was carried out in liquid propylene monomer in the presence of the above catalyst. Polymerization was carried out at a temperature of 60° C. and a pressure of 26 kg/cm ² -G, and during the polymerization, the gas phase hydrogen concentration in the tank was adjusted to 3 mol %. The above titanium trichloride (8 mmol/Hr) was supplied as a heptane suspension through piping 2, and diethylaluminum monochloride (50 mmol/Hr) as a heptane solution was supplied through piping 3. In addition, the amount of liquid propylene monomer supplied from pipe 4 was adjusted to maintain a constant liquid level in the polymerization tank.

The slurry of polymerized propylene polymer was drawn out by opening the valve 5 once every 15 minutes using a timer so that the average residence time was 3 hours. At this time, the slurry concentration in the polymerization tank was approximately 50 wt%. While extracting slurry from the polymerization tank, valves 5 and 6 are opened and valves 7 and 8 are closed. While extraction is stopped, valves 5 and 6 are closed, valves 7 and 8 are opened, and liquid propylene is removed. The monomer was automatically supplied from valve 7, and the following steps were operated continuously. The slurry extracted from the polymerization tank was concentrated in a liquid cyclone 9 and introduced into a flash tank 10. Further, the liquid propylene monomer separated by the liquid cyclone 9 and a small amount of the polymer and catalyst components accompanying it were circulated to the polymerization tank 1 through a pump 11 at a rate of 15/hr. The flash tank 10 was stirred by a ribbon stirrer, and heated propylene gas heated to about 100° C. by a heat exchanger 12 was supplied to the flash tank 10. The pressure inside the flash tank was maintained at 15.5 Kg/cm ² -G with a pressure regulating valve 23, and maintained at 40° C. by adjusting the amount of heated propylene supplied. The liquid propylene monomer in the slurry introduced into the flash tank is heated and vaporized by the heated propylene gas to form gaseous propylene monomer, which is then passed through the pipe 13 together with the heated propylene gas to the ventilate. Approximately 4 kg of solid polypropylene substantially free of liquid propylene monomer was extracted from the valve 15 once every 15 minutes to the scrubber 14 and transferred to the next stage gas phase polymerization tank 25 using a pressure difference. Liquid propylene monomer was injected from the pipe 16 into the ventilate scrubber 14 at a rate of 10/hr to remove mist such as particulate polymer and catalyst components accompanying the introduced propylene gas. The liquid propylene monomer containing the removed mist was circulated to the polymerization tank 1 by a pump 18. A portion of the gaseous propylene monomer from which the mist was removed by the ventilate scrubber 14 was sent to the heat exchanger 12 by the pressurizer 19 and heated, and then supplied to the flash tank. When the remaining propylene gas was cooled by passing cooling water at 18° C. into the condenser 20, most of it was liquefied. The liquefied propylene monomer was supplied to the ventilate scrubber 14 at a rate of 10/hr by the pump 21, and the remainder was circulated to the polymerization tank 1 (however, if the liquid level in the polymerization tank 1 was high, it was supplied from the valve 24). (I pulled it out of the system.)
The temperature of the separation tank 22 was 35°C, and the pressure was 15Kg/cm ² -G. The gas that was not liquefied in the condenser 20 was transferred to a recovery process by a pressure regulating valve 23. The condenser 2
The amount of liquid propylene monomer liquefied at 0 is approximately 18
/Hr, and the amount of gas transferred from the pressure regulating valve 22 to the recovery process is approximately 200N/Hr;
10 mol% was hydrogen gas. On the other hand, in the gas phase polymerization tank 25, the polymer is stirred with a ribbon stirrer,
Furthermore, by circulating a mixed gas of propylene, ethylene, and hydrogen with the pressurizer 26, the gas phase polymerization tank 2
The polymer in 5 was allowed to flow. The gas phase polymerization tank 25 has a pressure of 15 Kg/cm ² -G, and the concentrations of propylene, ethylene, and hydrogen in the gas in the polymerization tank are each 40 in molar ratio.
Propylene, ethylene, and hydrogen were supplied from pipes 27, 28, and 29, respectively, so that the amount of the reactor was 59,1. The temperature inside the polymerization tank was controlled at 60° C. by cooling the circulating gas with a heat exchanger 30. Polymerization tank 25
The polymer inside was extracted from the valve 31 once every 15 minutes and sent to the next polymer purification step. The obtained polymer had an ethylene content of 3.5 wt% and an MFI of 4.5 g/
It was hot in 10 minutes.

[Brief explanation of drawings]

The accompanying drawings are flow sheets for explaining embodiments of the invention. 1: Polymerization tank, 9: Concentrator, 10: Flush tank, 12: Heat exchanger, 14: Wet cleaning device, 1
7: Gas-liquid separation device, 19: Pressurizer, 20: Condenser, 22: Separator, 23: Pressure regulating valve, 25: Gas phase reaction tank, 26: Pressurizer.

Claims (1)

[Claims] 1. Next to the polymerization step of polymerizing an olefin in a liquid olefin of the same type to obtain a polyolefin,
When carrying out the copolymerization step of copolymerizing the polyolefin with another olefin to obtain a block copolymer, the polyolefin obtained in the polymerization step is taken out in the form of a slurry, and the slurry is converted into a liquid olefin under pressure. 1. A method for producing a block copolymer, which comprises separating a solid polyolefin by vaporizing it, and supplying the solid polyolefin to a copolymerization step while maintaining a pressurized state. 2. The method according to claim 1, wherein at least a portion of the vaporized olefin is heated and used as a heat source when separating the solid polyolefin. 2. The method according to claim 1, wherein the solid polyolefin separated from the slurry is supplied to the copolymerization step using a pressure difference between the solid polyolefin and the copolymerization step. 3. Method 4 according to claim 1, wherein the solid polyolefin separated from the slurry is co-supplied to the copolymerization step by utilizing a pressure difference between the solid polyolefin and the copolymerization step.
The method according to claim 1, wherein the copolymerization step is carried out by gas phase polymerization. 5. The method according to claim 1, wherein the olefin is propylene and the other olefin to be copolymerized is ethylene. 6 The pressure in the polymerization process is 22 to 40 Kg/cm ² -G, and the temperature is
The method according to claim 1, wherein the temperature is 50 to 80°C. 7. The method according to claim 1, wherein the solid polyolefin is separated at a pressure of 2 to 20 kg/cm ² -G and a temperature of 30 to 100°C. 8. The method according to claim 1, wherein the copolymerization step is carried out at a pressure lower than that used to separate the solid polyolefin.