JPS6185424A - Production of block copolymer of propylene - Google Patents

Abstract

PURPOSE:To produce the titled copolymer having stable quality, by carrying out the bulk-polymerization of propylene, etc. continuously at a constant slurry concentration, and copolymerizing with ethylene controlling the rate of polymerization according to the amount of the slurry supplied to the batch polymerization reactor. CONSTITUTION:A block copolymer of propylene is produced by (1) carrying out the homopolymerization of propylene or the copolymerization of propylene and a small amount of other alpha-olefin by the bulk-polymerization process using propylene as a liquid medium (the continuous polymerization step), and (2) carrying out the batchwise copolymerization with ethylene and propylene (the batch polymerization step). In the above process, the polymerization in the continuous polymerization step is carried out keeping the concentration of the slurry at a specific level, and the rate of polymerization in the batchwise polymerization step is controlled in a manner to give a definite ratio of the batchwise polymerization according to the amount of slurry supplied to the batchwise polymerizer.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a process for producing block copolymers of propylene. Specifically, the present invention relates to an operating method for producing a propylene pro-copolymer by combining a continuous polymerization section and a batch polymerization section using a bulk polymerization method.

BACKGROUND ART A bulk polymerization method using propylene itself as a medium has been known for a long time. However, in order to produce a block copolymer using propylene itself as a medium, it is difficult to perform polymerization at a desired reaction ratio because the polymerization pressure is determined by the monomer ratio and polymerization temperature.

For example, when block copolymerizing a propylene homopolymerization part with an ethylene and propylene copolymerization part, in order to continuously perform polymerization with a high ethylene/propylene ratio in the latter stage, the pressure in the latter stage polymerization tank must be high at a constant temperature. There is a problem in that it is difficult to transfer the slurry, and therefore, if the polymerization temperature is lowered, it becomes difficult to remove the polymerization heat.This problem can be solved by combining continuous polymerization and batch polymerization. is known (Japanese Unexamined Patent Publication No. 57-145
11/11 JP-A-57-145115, JP-A-57-1
49319, JP-A-57-149320, JP-A-58-
11519, JP-A-58-11520, etc.).

Problems to be Solved by the Invention The method that combines the continuous polymerization section and the batch polymerization section described above has high productivity per volume of polymerization tank, and the copolymerization carried out in the batch polymerization section is performed at a different reaction ratio of ethylene/propylene. Although this is an excellent method that allows the steps to be taken freely, there is a problem in that even if the amount of polymerization in the batch polymerization section is constant, the quality may vary.

As a result of intensive studies on methods for solving the above problems, the inventors of the present invention found that the above-mentioned variations in quality were due to variations in the slurry concentration of the slurry received in the polymerization tank that performs the batch polymerization section. The present invention was completed by discovering that a high quality block copolymer can be obtained.

OBJECTS OF THE INVENTION The object of the present invention is to provide an operating method for obtaining block copolymers of stable quality when producing block copolymers by combining a connected polymerization section and a batch polymerization section using a bulk polymerization method.

A means for solving the problem, that is, the present invention, is a bulk polymerization method using propylene itself as a liquid medium, in which propylene is first continuously copolymerized alone or with a small amount of other α-olefins (in the continuous polymerization section). ) Next, in the method of producing a block copolymer of propylene by performing copolymerization of ethylene and propylene batchwise (batch polymerization section), the polymerization in the first continuous polymerization section is operated so that the slurry concentration is constant, and then This method for producing a propylene block copolymer is characterized in that the amount of polymerization in a batch polymerization section is controlled so that the ratio of batch polymerization is constant according to the amount of slurry received in a polymerization tank for polymerization.

In the present invention, the polymerization of propylene in the continuous polymerization section refers to propylene homopolymerization or copolymerization of propylene with other α-olefins such as ethylene, butene-1, hexene-1, etc. to the extent that the rigidity of the resulting block copolymer is not significantly reduced. Up to 4% by weight and preferably 2% by weight of other α-olefins which also exhibit polymerization
It also includes making polypropylene containing up to.

In the present invention, the copolymerization of ethylene and propylene in the batch polymerization section means that the reaction ratio of ethylene/propylene is from 20/80 to
9515 weight ratio copolymerization, and also includes replacing a part of ethylene with other α-olefins such as butene-1 and hexene-1. The above reaction ratio is 20780
If it is smaller than 9515 or larger than 9515, the impact resistance of the propylene block copolymer will be insufficient, which is not preferable.

Also, for the same reason, the proportion of the portion in which polymerization is carried out at a reaction ratio of ethylene/propylene of 20/80 to 9515 weight percent in the batch polymerization section is 3% by weight or more, preferably 5 to 4% by weight.
If the content is outside this range, the impact resistance and rigidity will be unbalanced, which is not preferable.

The catalyst used for polymerization in the present invention is not particularly limited, and any known catalyst can be used.

That is, it is a catalyst system consisting of a reduction metal compound and an organometallic compound (and, if necessary, a stereoregularity improver such as an oxygen-containing organic compound), which is normally used to produce highly stereoregular polypropylene. A halide or its support on a carrier such as magnesium halide, silica, alumina, etc. can be used as the reduction metal compound, and organoaluminium, organomagnesium, etc. can be used as the organometallic compound.

What is important in the present invention is to operate the polymerization in the continuous polymerization section so that the slurry concentration is constant. The batch polymerization section is operated so that the ratio of the batch polymerization section to the continuous polymerization section is constant depending on the amount of slurry received.

As for the operation method to keep the slurry concentration constant, in the bulk polymerization method, unlike solvent polymerization, polymerization is carried out under a constant pressure, and a simple method of calculating from the amount of solvent introduced and the amount of propylene introduced cannot be adopted. It is possible to detect with high accuracy, thereby knowing the amount of polypropylene produced in the continuous polymerization section, and by calculating the ratio of the amount of propylene charged to the continuous polymerization section, it is possible to know the slurry concentration. By varying the input, the slurry concentration can be kept constant.

The amount of slurry received in a polymerization tank for batch polymerization can be easily determined by providing a pressure level meter in the polymerization tank for batch polymerization. Since the continuous polymerization section is operated so that the slurry concentration is constant, the amount of slurry detected by the level meter is proportional to the amount of polypropylene in the slurry. Therefore, by controlling the amount of polymerization in the batch polymerization section so that the ratio of batch polymerization is constant according to the amount of slurry received, polypropylene made in the continuous polymerization section or a small amount of copolymer of ethylene and propylene can be used. It becomes possible to keep the proportion of the ethylene and propylene copolymer constant in the batch polymerization section.

The amount of polymerization in the batch polymerization section can be determined by the calorific value in the same way as in the continuous polymerization section, but it can also be calculated by the amount of ethylene (or ethylene and propylene) required to maintain a constant pressure at a constant temperature. It is possible.

When the amount of polymerization in the batch polymerization section, detected by the calorific value or the amount of ethylene charged, reaches the desired value, the propylene block copolymer is discharged from the batch polymerization section (a deactivator is added as necessary). later).

The amount of polymerization in the batch polymerization section is controlled by the amount of an activator added to the polymerization tank in which the batch polymerization is carried out, specifically, the above-mentioned organometallic compounds, preferably organoaluminiums such as trialkyl aluminum and dialkyl aluminum. It can be controlled by the polymerization time in a batch polymerization section.

Effect The reason why the method of the present invention is effective in producing a propylene block copolymer of constant quality is that in propylene polymerization on an industrial scale, it is due to variations in activity among catalysts, etc. The production amount of polypropylene may fluctuate, and the physical properties of the propylene block copolymer include copolymerization of propylene alone or a portion copolymerized with a small amount of other α-olefins and ethylene and propylene. The ratio varies greatly depending on the ratio between the continuous polymerization part and the batch polymerization part, and even if materials with different proportions are mixed to achieve the desired ratio, the physical properties will be inferior. It can be assumed that by keeping constant, a block copolymer with excellent physical properties can be obtained.

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

Examples and Comparative Examples (1) Synthesis of Catalyst Components A vibratory mill equipped with two crushing bots each having an internal volume of 11 and containing 2.2 mm steel balls with a diameter of 12+n is prepared.

4 ml of magnesium chloride 20y-tetraexisilane and 3 ml of α5α5α-trichlorotoluene were added to each pot in a nitrogen atmosphere and pulverized for 40 hours. 10 similar operations
A total of 20 batches of co-pulverized products were obtained. The resulting conjugate materials (approximately 25 f each) were placed in 1 g round-bottomed flasks, each with a capacity of 300 m7! After stirring with titanium tetrachloride at 80°C for 2 hours, let stand and remove the supernatant, then add 500m7 of n-hebutane, stir at 30°C for 5 minutes, leave to separate, and wash to remove the supernatant. After repeating 7 times, further n-
500 mJ of hebutane was added to form a solid catalyst slurry.

(11) JP-A-57-149320 Example 111)
A block copolymer was produced by the method described in the polymerization section. However, after the polymerization stabilized, the polymerization reaction was carried out using the solid catalyst component prepared above, changing each catalyst batch every 5 hours, and the resulting block copolymer was mixed and granulated every 10 hours. The physical properties were measured.

In the example, the slurry concentration of polypropylene was increased to 40W 10% (polymer/
Continuous polymerization is carried out in polymerization tanks A and B to maintain the same level of ethylene (propylene), and a predetermined amount of ethylene is charged to the batch polymerization section according to the amount of slurry received in the batch polymerization section (while keeping the pressure constant). Polymerizations were carried out from 1 to 20 hours by varying the polymerization time (the ethylene was charged to maintain the temperature) and by varying the amount of triethylaluminum charged from 21 to 30 hours. On the other hand, in the comparative example, polymerization was carried out without changing the amount charged into the polymerization tank or the polymerization time at all, polymerization was carried out for 30 hours, and the physical properties of the block copolymers taken out every 10 hours were measured.The results are shown in the table. show. It is clear that the comparative example has inferior rigidity and impact resistance even though the ethylene content is not significantly different from that of the example.

Effect: By carrying out the method of the present invention, a block copolymer with excellent physical properties can be stably obtained, which is extremely valuable industrially.

Claims (1)

[Claims] 1. In a bulk polymerization method using propylene itself as a liquid medium, propylene alone or a small amount of other α-olefins are first copolymerized continuously (continuous polymerization part), and then ethylene and propylene are copolymerized. In a method for producing a propylene block copolymer by performing copolymerization batchwise (batch polymerization section), the polymerization in the first continuous polymerization section is operated so that the slurry concentration is constant, and batch polymerization is carried out. A method for producing a propylene block copolymer, comprising controlling the amount of polymerization in a batch polymerization section so that the ratio of batch polymerization is constant according to the amount of slurry received in a tank. 2. The method according to claim 1, wherein the amount of polymerization in the batch polymerization section is controlled by the amount of activator charged into the batch polymerization section. 3. The method according to claim 1, wherein the amount of polymerization in the batch polymerization section is controlled by the polymerization time in the batch polymerization section.