JPH06814B2 - Method of removing heat of polymerization in slurry polymerization of polyolefin - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for removing heat of polymerization in a slurry polymerization method of polyolefin, and more specifically, a so-called slurry cooler for circulating the produced polymer slurry into a polymerization process through a cooling device. Method for removing polymerization heat.

Conventional technology and technical problems to be solved As a polymerization heat removal method in the slurry polymerization method of polyolefin, a large heat exchanger in which a latent heat of vaporization of a volatile solvent such as hexane is circulated by circulating gas in the polymerization vessel is installed. A so-called gas circulation system for removing the gas is known. Since the removal of the heat of polymerization by this method utilizes the removal of latent heat of vaporization, the circulation pipe itself becomes long and thick (for example, 10
0m, 16 inches φ), the heat exchanger itself becomes large, and further, a hexane condenser and a blower are required, and it is necessary to provide a space of about 40% above the polymerization unit, resulting in a large equipment cost. Have On the other hand, since a large volume of gas is circulated, a large blower is required, and the running cost becomes high.

As another method, a so-called slurry cooler system in which a polymer slurry produced by polymerization is cooled by a heat exchanger and circulated in the polymerization vessel is disclosed in JP-A-57-151602. According to this method, a blower or a coagulation container is not necessary, the heat exchanger itself may be small, and the circulation pipe itself can be short and have a small diameter. The advantage that the can be liquid-filled is achieved. However, this slurry cooler system has a fatal defect that the polymer adheres to the circulation pipe due to slurry sedimentation or the like to cause clogging of the pipe.

OBJECT AND STRUCTURE OF THE INVENTION That is, an object of the present invention is to provide a method for removing polymerization heat in which the above-mentioned drawbacks are eliminated in a slurry cooler system.

Another object of the present invention is to remove the heat of polymerization capable of increasing the polymerization amount per unit volume of the polymerization vessel in the slurry polymerization method of polyolefin, which can reduce the construction cost of the polymerization apparatus and simplify the operation. There is a way to provide.

According to the present invention, the olefin monomer to be polymerized is subjected to predetermined conditions in a solvent in the presence of a catalyst comprising a transition metal catalyst component of a titanium or vanadium compound and an organometallic compound of a Group I to III metal of the periodic table. In a liquid circulation type slurry polymerization method of polyolefin in which at least a part of the produced polymer slurry is circulated through a cooling device during the polymerization process, the yield of the polyolefin per 1 mmol of the catalyst as the catalyst is
1000 g or more of high activity catalyst was used in an amount such that the catalyst concentration in the solvent was 0.25 mmo / 1 or less in terms of titanium or vanadium atoms, and the average linear velocity of the polymer slurry during the circulation process was 5 m / sec. A method for removing polymerization heat in a slurry polymerization method for a polyolefin, which is characterized by the above, is provided.

BEST MODE FOR CARRYING OUT THE INVENTION In FIG. 1 for explaining the method for removing heat of polymerization of the present invention, polymerization is carried out by supplying an olefin monomer to be polymerized through a pipe 1 and a solvent and a catalyst through a pipe 2 into a polymerization vessel 3.

It is preferable that the polymerization vessel 3 is of a tank type and that a jacket 4 is provided for convenience of heating and cooling.

As the olefin monomer to be polymerized, one or a combination of two or more 1-olefins such as ethylene, propylene, 1-butene and 4-methylpentene is used.
When supplying the olefin monomer, it is also possible to supply H ₂ gas together in order to adjust the degree of polymerization of the produced polymer.

As the solvent, hydrocarbon oils such as hexane, heptane, octane and decane are usually used.

In the present invention, a highly active catalyst is used as a catalyst in the solvent
It is used in an amount of 0.25 mmol / or less, preferably 0.005 to 0.05 mmol /. That is, when a highly active catalyst is used and the amount used is extremely small in the above range, when the polymer slurry produced is circulated and cooled under predetermined conditions, a clogging trouble in the piping for circulation is caused. Can be effectively prevented. Such a highly active catalyst has a polymer yield of 1000 g or more per 1 mmol of the catalyst, and in the method of the present invention, a transition metal catalyst of a titanium or vanadium compound having the above-mentioned activity. Any catalyst can be used as long as it is a catalyst composed of an organic metal compound of a group I or III metal of the periodic table.

Such a high activity catalyst is not necessarily limited to this, but for example, a halide of a Group II metal of the Periodic Table coordinated with an electron donor described in JP-A No. 50-32270. A transition metal catalyst component obtained by reacting a reaction product of an organometallic compound or hydride of a metal of group I to group III of the periodic table with a transition metal compound selected from the group consisting of titanium compounds and vanadium compounds; A catalyst composed of an organometallic compound or hydride of a metal of group I to group III of the periodic table, a solid titanium catalyst component containing magnesium, titanium, halogen and an electron donor as essential components and a group I or group of the periodic table A catalyst comprising a Group III metal organic compound catalyst component (JP-A-56-811) or a solid product obtained by contacting a hydrocarbon solution of a magnesium compound with a liquid titanium compound. Or a hydrocarbon solution of a magnesium compound and a titanium compound is formed, solid product formation is performed in the presence of an electron donor, and the solid product is formed during or after the formation of the solid product. Solid titanium catalyst component [A as magnesium, titanium, halogen and polycarboxylic acid ester and / or polyhydric hydroxy compound ester essential component obtained by supporting polyhydric carboxylic acid ester and / or polyhydric hydroxy compound on the product [A ], Organometallic compound catalyst component [B] of group I to group III metal of the periodic table and Si
Examples of the catalyst include catalysts formed from an organosilicon compound catalyst component [C] having a —O—C or Si—N—C bond (Japanese Patent Laid-Open No. 58-83006).

Polymerization is usually carried out at a temperature of 60 to 95 ° C., preferably 70 to 90 ° C., a pressure of 1 to 10 Kgf / cm ² , preferably 1.5 to
9.0 kgf / cm ² , and retention time of the reactant in the system is 0.2 to 4
The time is generally 0.5 to 3.0 hours.

The polymer slurry thus formed is circulated to the polymerization vessel 3 via the pump 5. An important feature of the present invention is that the circulating polymer slurry is cooled by the slurry cooler 6 and the average linear velocity of the polymer slurry in the circulating path is 5 m / sec or more, particularly 6 m / sec or more.

That is, when the average linear velocity of this polymer slurry is lower than the above range, it is at most 2 to 3 as shown in an example described later.
The piping for circulation will be totally blocked in about a day. On the other hand, when the linear velocity of the polymer slurry is set to 6 m / sec or more according to the present invention, the problem of pipe clogging does not occur even when continuous operation is performed for a long period of time.

Further, in the present invention, the retention time of the polymer slurry in the circulation path is usually preferably 60 seconds or less.
This is because if the length of the circulation pipe is increased and the retention time is increased, the slurry may be deposited in the pipe and the polymer may adhere to the inner wall of the pipe to cause a clogging trouble.

According to the present invention, the temperature on the inlet side of the slurry cooler 6 of the circulating slurry is usually about 80 ° C., the temperature on the outlet side is about 70 ° C., and the heat of polymerization is effectively removed.

In addition, a part of the produced polymer slurry is transferred to the next process through the pipe 7, and is made into a product through an overoperation such as centrifugation, drying, extrusion and the like.

EFFECTS OF THE INVENTION In the present invention, as described above, the heat of polymerization can be removed by the slurry cooler system without causing the trouble of pipe clogging, and moreover, a large volume of gas is circulated and cooled as in the gas circulation system. Since it does not require a blower and a large capacity heat exchanger to operate, it has a remarkable advantage of saving power.

In addition, the length and diameter of the pipe itself can be reduced, the entire device can be downsized, and the facility cost can be significantly reduced.

Further, according to the present invention, since the heat of polymerization is removed by a slurry circulation system, the polymerization vessel 3 can be of a liquid-filled type having no space in the upper portion, and the polymer production amount per unit volume of the polymerization vessel can be increased. The significant advantage of being able to do is achieved.

Example 1 A polyethylene slurry was produced by removing the heat of polymerization by the slurry cooler method shown in FIG.

The specifications of the equipment used are as follows.

Polymerizer 3 35m ³ Jacket 4 30m ² Slurry cooler 6 160m ² Circulating pump 5 910m ³ / h, 85KW Observing the blocked state of the pipes when the linear velocities of the catalyst and circulating slurry were changed in this polyethylene slurry production example. The results are shown in Table 1.

Example 2 A polyethylene slurry was produced under the same conditions as in Experiment No. 5 of Example 1 using the gas recycle cooling system as shown in FIG. 2, and the reactor volume and power consumption of the polymerization vessel were compared. . The results are shown in Table 2.

The specifications of the main equipment used in the apparatus shown in FIG. 2 are as follows.

Polymerizer 10 60 m ³ Jiyaketsuto area 52m ² over head condenser 12 520m ² circulation pump 15 100m0 ³ / H, 30KW blower 14 7000m ³ / H, 260KW

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a slurry cooler system of the present invention, and FIG. 2 is a diagram showing a conventional gas circulation type cooling system. 3 is a polymerization vessel, 4 is a jacket, 5 is a circulation pump, 6 is a slurry cooler, 10 is a polymerization vessel, 11 is a jacket, 12
Is an overhead condenser, 13 is a gas-liquid separator,
14 is a blower and 15 is a pump.

Claims (1)

[Claims] 1. An olefin monomer to be polymerized, in the presence of a catalyst composed of a transition metal catalyst component of a titanium or vanadium compound and an organometallic compound of a metal of group I to group III of the periodic table, in a solvent under predetermined conditions. In a liquid circulation slurry polymerization method of polyolefin in which at least a part of the polymer slurry produced by the polymerization is circulated in a polymerization step through a cooling device, the yield of the polyolefin per 1 mmol of the catalyst as the catalyst is
1000 g or more of a highly active catalyst is used in an amount such that the catalyst concentration in the solvent becomes 0.25 mmol / or less in terms of titanium or vanadium atom, and the average linear velocity of the polymer slurry in the circulation step is 5 m / sec or more. A method for removing polymerization heat in a slurry polymerization method of polyolefin, characterized by: