JPS61179208A - Polymerization of propylene - Google Patents

Abstract

PURPOSE:To make it possible to produce PP having a consistent quality at a constant production rate, by regulating the amount of addition of an organoaluminum compound according to a detected production rate of PP in polymerizing propylene by using a transition metal/organoaluminum compound catalyst. CONSTITUTION:In a process for polymerizing propylene by using a catalyst system comprising a transition metal catalyst and an organoaluminum compound (e.g., a catalyst system comprising a catalyst formed by allowing a magnesium halide to support a titanium halide and a dialkylaluminum halide/ trialkylaluminum halide) and detecting the production rate of PP based on the quantity of the heat of reaction, the production rate of PP is fixed by varying the amount of addition of the organoaluminum compound in the catalyst according to the detected production rate of PP. Thus, it is possible to produce PP of a consistent quality at a constant production rate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for polymerizing propylene. More specifically, the present invention relates to a method for producing polypropylene of a constant quality with a constant production amount.

[Conventional technology]

A method for producing polypropylene by polymerizing propylene using a Ziegler-Natsuta catalyst is well known, and polypropylene is already produced industrially on a scale of several hundred tons per day. In the production of polypropylene on an industrial scale, it is desirable to produce polypropylene of constant quality at a constant production rate, and it is difficult to remove the polymerization heat with a large reactor, so two tanks are usually used. It is produced continuously using a reactor in which the above polymerization tanks are connected.

Many types of Ziegler-Natsuta catalysts are known for use in the production of polypropylene, and many types are also used in the actual industrial production of polypropylene. However, the performance of the catalyst varies considerably depending on the lot, so simply charging a fixed amount of catalyst into the reactor will cause the production volume to fluctuate. Therefore, it is necessary to vary the amount of catalyst charged to keep the production volume constant. will be held.

[Problem that the invention seeks to solve]

However, in the second method, the production amount per catalyst varies depending on the catalyst performance, so the catalyst residue remaining in the polypropylene obtained varies, making it impossible to obtain a constant quality product.Furthermore, it is expensive and requires a long manufacturing process. There was a problem in that the amount of transition metal catalyst used varied due to the relatively complicated charging equipment.

In addition, as mentioned above, it is difficult to remove heat in a large reactor, and the polymerization is performed in a multi-vessel reaction system in which polymerization tanks are connected, and the heat removal capacity of each type is limited, so the amount of polymerization of each type must be adjusted individually. If this is not controlled, there is a problem that the entire reaction system will be determined by the polymerization tank with the lowest heat removal capacity.

An object of the present invention is to provide a method for producing polypropylene of constant quality and with a constant production amount.

[Means for solving problems]

As a result of intensive studies on methods for solving the above problems, the inventors of the present invention discovered that the above problems could be solved by controlling the production of polypropylene using a specific method, and completed the present invention.

That is, the present invention is a method of polymerizing propylene using a catalyst consisting of a transition metal catalyst and an organoaluminum while detecting the production amount of polypropylene based on the calorific value, in which the amount of the organoaluminum added is changed according to the detected production amount of polypropylene. The present invention relates to a method for polymerizing propylene, which is characterized by controlling the production amount to a constant value.

What is important in constituting the present invention is that in the production of transition metal catalysts on an actual industrial scale, the performance of the transition metal catalysts obtained is not constant even if produced by a certain prescribed method. In the production of polypropylene on an industrial scale, the production volume varies even when using the same catalyst due to various uncertain factors. It is based on the discovery that scales that vary greatly in activity and that in continuous polymerization their amounts can be expressed in terms of various retention volumes. Another reason is that even if the ratio of organoaluminium/transition metal catalyst is varied over a fairly wide range, changes in stereoregularity and molecular weight distribution, which greatly affect the physical properties of the resulting polypropylene, are negligible.

Catalyst systems that achieve the above characteristics with a wide range of organoaluminum/transition metal catalyst ratios include catalysts consisting of titanium trichloride catalysts modified with ether and dialkyl aluminum halides, and titanium halide supported on magnesium halide. Catalysts consisting of a transition metal catalyst and organoaluminum are mentioned, among which are catalysts consisting of a transition metal catalyst in which titanium halide is supported on magnesium halide and an organoaluminium. In particular, as a catalyst system in which the quantitative ratio of organoaluminium/transition metal catalyst can be changed over a wide range that can almost absorb the usual fluctuations in activity between lots, a transition metal catalyst with titanium halide supported on magnesium halide is used. 'A A catalyst system that uses a catalyst system consisting of an oxygen-containing compound-dialkyl aluminum halide-trialkylaluminum and varies the quantitative ratio of the trialkylaluminum and the transition metal catalyst is exemplified.

In the present invention, propylene polymerization is carried out by any of the following methods: a solvent polymerization method using an inert liquid medium, a bulk polymerization method using liquid propylene itself as a medium, and a gas phase polymerization method substantially free of a liquid medium. Moreover, the polymerization of propylene includes not only propylene alone but also copolymerization with ethylene, butene-1, hexene, etc.

In the present invention, the relationship between the amount of organoaluminium charged and the activity per transition metal catalyst needs to be determined in advance, and is preferably determined by a continuous polymerization method similar to that used in an actual polymerization apparatus.

What is important in the present invention is to continuously know the production amount of polypropylene by detecting the calorific value. Transition metal catalysts are produced in batches because the performance of the resulting catalyst is good and the production equipment and various compounds used in the production can be recovered using simple equipment. Therefore, if the polymerization reaction is carried out with a fixed amount of catalyst charged in the performance of the catalyst produced in each batch, the production amount of polypropylene will change, and after this change is detected in the amount of polypropylene obtained, the organoaluminium charging amount will change. Changing the amount will result in large fluctuations in the production amount of polypropylene. Therefore, the amount of transition metal catalyst per serving is large. The effect of the present invention is significant when the polymerization system is used for a long time and the residence time of the polymerization system is long.

FIG. 1 shows the relationship between the amount of polypropylene produced and the stereoregularity and molecular weight distribution of the polypropylene obtained when the amount of organoaluminum charged was varied in the three-bath continuous polymerization method.

(The catalyst shown in the example was used, and only the relationship between triethylaluminum and transition metal catalyst was changed.From this, by changing the quantitative ratio of organoaluminum and transition metal catalyst within the range shown in the upper part of Figure 1, It can be seen that it is possible to change the activity by ~3 times (without changing the molecular weight distribution and stereoregularity). Therefore, it is possible to control the production amount by varying within specific upper and lower limits. In addition, it is understood that even in multi-vessel continuous polymerization, it is possible to maintain the same activity by changing the above ratio (the various catalyst activities are reduced by the deactivation phenomenon of the catalyst itself, (indicates that it is possible to operate under conditions that do not deteriorate in the polymerization tank).

The production amount of polypropylene in each polymerization tank is calculated by detecting various calorific values. In other words, the true amount of heat generated is detected by correcting the amount of heat added to the polymerization tank and the amount of heat removed in order to maintain each type at a constant temperature by the amount of heat released, which is determined by the equipment and environment. The production amount of polypropylene is obtained by dividing the amount of heat generated by the amount of heat released when propylene is polymerized or the amount of heat released when propylene and another olefin are copolymerized.

The above operation detects the production amount of polypropylene at a certain moment, but if it is a continuous polymerization method and each type is operated at a certain residence time, simply compare the desired production amount with the production amount at a certain moment. For example, it is not preferable to vary the amount of organic aluminum charged based on the relationship shown in FIG. Particularly when the residence time of each type is long, if the charging amount is changed as described above, the desired production amount will further deviate over time. Therefore, the amount of organic aluminum to be charged is determined as follows. The retention amount of each type of organic aluminum when the production amount is detected based on the amount of organic aluminum charged to each type is calculated by integrating. Since each type is a complete mixing tank, this integral can be calculated by simple calculation based on the amount of organic aluminum charged to each type over time, the amount of other polymerization solvents, propylene, and polypropylene charged, and the amount discharged. .

For continuous control, it is best to perform this calculation online at all times on a computer, including the loading and unloading amounts of each component. Furthermore, if necessary, the consumption rate of organic aluminum can also be taken into consideration in the above calculation.

From the thus determined production amount and the organic aluminum retention amount, the required organic aluminum retention amount (target organic aluminum amount) to achieve the desired production amount is determined.

Next, the amount of organic aluminum to be charged is set so as to reach the target amount of organic aluminum. For example, the amount of t-aluminum charged per unit time to reach the target value is multiplied by a specific coefficient or formula, and the organic aluminum is charged per unit time, and after a certain period of time, the target amount of organic aluminum is reached. It can be a fixed amount of organoaluminium charged per unit time. For example, Fig. 2 shows the passage of time (to-
t, ), the organoaluminium charging rate, and the organic aluminum retention amount.

[For production]

The present invention is based on the fact that the yield of polypropylene per transition metal catalyst can be controlled without changing the physical properties of polypropylene by changing the quantitative ratio of organoaluminum and transition metal catalyst within a specific range. The method of the present invention is based on the discovery that organoaluminum is relatively easily removed as a catalyst residue, and the adverse effect on physical properties is smaller than that of transition metal catalysts. It is estimated that polypropylene of constant quality can be produced in quantity.

〔Example〕

The present invention will be explained below with reference to Examples.

Example: A transition metal catalyst consisting of titanium tetrachloride supported on magnesium chloride (produced according to Example 1 of JP-A No. 55-102606). 100 g per 10 tons, using a 40° plate and an internal volume of 500.
A reactor in which three autoclaves of 1 are connected together (a reactor with the structure shown in Fig. 3, 2 tanks and a catalyst depletion reactor 1 without a reflux condenser)
Propylene was polymerized using a bulk polymerization method using propylene itself as a medium using a knee-angle device consisting of a tank. After deactivating the catalyst, the obtained polymer was washed with propylene in a countercurrent washing tower, and unreacted propylene was removed by evaporation to obtain polypropylene powder. As a catalyst, transition metal catalyst 1 is used only in the first tank.
0(l) Methyl Ruyate 200m/.

A mixture of diethylaluminum chloride 425d was charged as a transition metal catalyst at a rate of 49/h, and the polymer slurry in the first tank was continuously transferred to the second tank at 5'+, -2nd tank.
The liquid is transferred from the tank to the third tank and deactivated. 1st
The second tank contains the amount of heat removed by the reflux condenser (specifically, calculated from the amount and temperature of the condensed liquid, the number of people entering the condenser, and the amount and temperature of the gas exiting the condenser) and the amount of heat removed by the salmon, The amount of polymerization was calculated by correcting the amount of cooling water supplied to the reactor and the temperature of the reactor by the amount of heat released, and triethylaluminum was charged so that the value remained constant. As a result, as shown in Figure 4, a certain amount of polypropylene production (40
kg/h ± 0.5 kg/h) and constant quality polypropylene (boiling n-heptane extraction residual rate (6h extraction) 96.8 ±
0.2%, /6°4±0.2)N was obtained.

〔Effect of the invention〕

By carrying out the method of the present invention, it is possible to produce polypropylene of stable quality at a constant production rate, which is of industrial value.

[Brief explanation of drawings]

Figure 1 shows the amount ratio of organoaluminium/M transfer metal catalyst and the production amount of polypropylene per unit time per transition metal catalyst,
This figure shows the relationship between the molecular weight distribution and stereoregularity of the polypropylene obtained. FIG. 2 is a graph showing changes in the amount of organic aluminum retained when the charging rate of organic aluminum was changed. Figure 3 shows an example of an apparatus for carrying out the polymerization of the present invention, in which 1 is a reaction tank, 2 is a reflux condenser, 3 is a blower, 14 is a pump for charging the transition metal catalyst mixed slurry, and F-1 is a pump for charging the transition metal catalyst mixed slurry. Condensate flow meter and thermometer, F-2 is charging cooling water flow meter and thermometer, F-3 is discharge cooling water thermometer, F-4 is charging propylene flow meter, F-5 is Charge organoaluminum flow meter,? -6 is a flow meter for discharged slurry. FIG. 4 is a graph showing the relationship between the elapsed time in Examples, the amount of triethylaluminum charged, the amount of polypropylene produced (instantaneous value) calculated from the calorific value, and the amount of polypropylene produced.

Claims (1)

[Claims] 1) In a method of polymerizing propylene while detecting the production amount of polypropylene based on the calorific value using a catalyst consisting of a transition metal catalyst and an organoaluminium, the amount of addition of organoaluminum is determined based on the production amount of polypropylene detected. A propylene polymerization method characterized by controlling the production amount to a constant value by changing the amount of the propylene. 2) Production of polypropylene according to the detected production amount of propylene, the retention amount of organic aluminum calculated from the amount of organic aluminum charged to the reaction tank, and a predetermined relational expression between organic aluminum and the production amount of polypropylene. The method according to claim 1, wherein the amount of organoaluminum charged is determined so that the amount is constant.