JPH0559927B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing a propylene block copolymer. Specifically, the present invention relates to an improved polymerization method for propylene block copolymers, in which propylene alone or a small amount of ethylene and propylene are continuously copolymerized, and ethylene and propylene are copolymerized batchwise.

BACKGROUND OF THE INVENTION Methods for producing propylene block copolymers for the purpose of improving the impact resistance of polypropylene, particularly at low temperatures, are well known and many methods have been proposed. (Tokuko Showa 44-
20621, Japanese Patent Publication No. 49-24593, etc.) On the other hand, as a polymerization method that allows multi-stage copolymerization of ethylene and propylene with different reaction ratios using a relatively small number of polymerization vessels, a block polymerization method that combines a continuous polymerization method and a batch polymerization method has been proposed. The present inventors have previously proposed a method for producing a copolymer. (For example, JP-A-57-
145114, JP 57-145115, JP 57-149319,
JP-A-57-149320) Problems to be Solved by the Invention The method that combines the continuous polymerization method and the batch polymerization method described above makes it possible to produce block copolymers of many qualities using a polymerization machine with a small number of polymerization tanks in series. However, in actual industrial production, the amount of slurry charged to the batch polymerization tank and the amount of slurry There was a problem that the concentration was not constant and delicate quality control was difficult.

The inventors of the present invention have conducted intensive studies on methods for solving the above problems, and have found that the above problems can be solved by carrying out specific control during batch polymerization, and have completed the present invention.

An object of the present invention is to provide a method for producing a propylene block copolymer of constant quality with good controllability.

Means for Solving the Problems That is, the present invention first copolymerizes propylene alone or a small amount of ethylene and propylene (first stage polymerization), and then copolymerizes ethylene and propylene (second stage polymerization) to produce ethylene. When producing a block copolymer, in a method in which the first stage polymerization is carried out continuously and the second stage polymerization is carried out batchwise using a polymerization machine in which two or more polymerization tanks are connected, the slurry is transferred to the polymerization tank in which the second stage polymerization is carried out. Addition of the organoaluminum compound to the polymerization tank in which the post-polymerization is carried out so that the amount of polymer in the post-stage polymerization calculated from the calorific value is a constant ratio to the amount of polymer transferred according to the amount of polymer calculated from the amount of liquid transferred. The present invention relates to a method for producing a propylene block copolymer, which is characterized by controlling the amount and/or reaction time.

In the present invention, the first stage polymerization is carried out using propylene alone or at a reaction ratio of ethylene/propylene of 6/94 or less by weight. In order to maintain a good balance between rigidity and impact resistance of the obtained block copolymer, the ratio of the first stage polymerization to the second stage polymerization is preferably 60 to 95:40 to 5 wt. The conditions for the first stage polymerization are the well-known general propylene polymerization temperature and polymerization pressure, which is normal temperature to 90°C and normal pressure to 50 kg/cm ² G. Polymerization can be carried out by adding a molecular weight regulator such as hydrogen if necessary. You can also.

In the present invention, the pre-polymerization is preferably carried out in two or more polymerization tanks in order to maintain good physical properties of the resulting polypropylene, particularly its fisheye and falling ball impact resistance.

Examples of polymerization methods to which the method of the present invention is applied include solution polymerization using an inert medium, bulk polymerization in which an inert medium is not substantially present, and gas phase polymerization. The first stage polymerization is a bulk polymerization method, and the second stage polymerization is a bulk polymerization method or a gas phase polymerization method.

In the present invention, the reaction ratio of ethylene and propylene is 15/85 to 95/5wt in order to maintain good physical properties, especially impact resistance, of the resulting polypropylene in the post-polymerization.
It is a ratio. It is also possible to copolymerize a small amount of other olefins, butene-1, hexene-1, etc. in the first-stage polymerization or the second-stage polymerization to improve gloss, transparency, and elongation at break.

The catalyst used for polymerization in the present invention is not particularly limited as long as it has a highly stereoregular catalyst system for the polypropylene obtained as is clear from the structure of the invention, and titanium trichloride and organic aluminum modified by various methods can be used. Catalysts made of compounds, catalysts obtained by supporting titanium halides such as titanium trichloride or titanium tetrachloride, or alkoxy titanium on carriers such as magnesium halides, and catalysts made of organoaluminum compounds are exemplified as general examples. can.

The polymer amount calculated from the slurry transfer amount, which is important in the present invention, can be determined as follows. That is, in order to know the amount of polymer, it is essential to know the following two things. That is,
These are the polymer concentration in the slurry and the amount of slurry transferred to the polymerization tank in which the post-stage polymerization is carried out at the beginning of each batch of post-stage polymerization. The former method of determining the slurry concentration is to calculate the amount of polymer produced by the amount of solvent and propylene introduced into the polymerization tank for the first stage polymerization and the amount of polymer produced detected by the heat of polymerization. The slurry concentration can be determined as the value divided by the sum of (the amount of propylene and solvent present in the gas phase may be corrected if necessary).

It is also possible to directly detect the slurry concentration using an orifice or electromagnetic wave transmittance.

In the latter case, the amount of liquid transferred can be easily determined by using a level meter to determine the amount transferred to the polymerization tank for subsequent polymerization, or by transferring the slurry at a constant speed using a pump or the like. It is also possible to know this as the product of the time required for liquid transfer.

By the above method, it is possible to know the amount of polymer present when starting the second-stage polymerization. Next, the second stage polymerization is carried out in the presence of the polymer that has been subjected to the first stage polymerization. The amount of polymerization in the second stage polymerization is given as the value obtained by dividing the calorific value by the calorific value per unit polymer corrected by the reaction ratio of ethylene and propylene. By doing this, it is possible to keep the ratio of first-stage polymerization and second-stage polymerization constant, but in order to maintain this ratio, the following control values are used. That is, the amount of organic aluminum added and the reaction time of the second-stage polymerization.
The relationship between the quantitative ratio of organoaluminium and titanium trichloride and the activity per titanium trichloride catalyst can be found, for example, at Kinetics.
of Ziegler Natta Polymerizatien by T.Keii
(KODANSHA Publishing) Page 23 Fig2.7 As shown in Fig2.22, there is a certain relationship, and it is understood that the activity can be controlled by varying the amount of the organoaluminum compound added. Furthermore, a similar relationship has been found in the case of a catalyst in which titanium tetrachloride is supported on magnesium chloride, for example, as disclosed in JP-A-57-
No. 149319, Figure 3. The amount of polymerization is a value obtained by integrating the activity over time, and it is easily understood that the amount of polymerization in the subsequent stage polymerization can be controlled by controlling the activity and/or reaction time.

Effect By producing a propylene block copolymer by the method of the present invention, it is possible to keep the ratio of the first stage polymerization and the second stage polymerization constant, so that a propylene block copolymer of constant quality can be obtained. It seems possible to manufacture it.

Examples The method of the present invention will be further explained with reference to Examples below.

EXAMPLE A block copolymer was synthesized using the polymerization test described in Example 1 of Japanese Patent Application Laid-Open No. 57-149319, which is an invention of the present inventors, that is, the following method.

) Synthesis of solid catalyst Prepare a vibratory mill equipped with four crushing pots with an internal volume of 4 each containing 9 kg of steel balls with a diameter of 12 mm. 300 g of magnesium chloride in a nitrogen atmosphere in each pot.
60 ml of tetraethoxysilane and 45 ml of α,α,α-trichlorotoluene were added and pulverized for 40 hours. Internal volume
Add 3 kg of the above pulverized material and 20 titanium tetrachloride to a No. 50 autoclave, stir at 80°C for 2 hours, remove the supernatant liquid by decantation, then add 35 kg of n-heptane and stir at 80°C for 15 minutes. After repeating the washing operation seven times to remove the supernatant liquid by post-decantation, an additional 20 g of n-heptane was added to obtain a solid catalyst slurry. When a part of the solid catalyst slurry was sampled, n-heptane was evaporated, and analyzed, it was found that the solid catalyst contained 1.4% by weight of Ti.

) Polymerization reaction 300 and 300 autoclaves (A, B) are connected in series, and two 200 autoclaves (C1,
C2) A propylene block copolymer was produced using an apparatus in which 300 autoclaves D were connected in series to autoclaves C1 and C2. In a separately prepared 50 autoclave that was sufficiently dried and purged with nitrogen, 30 n-heptane, 50 g of the above solid catalyst, and diethylaluminum chloride were added.
240 ml and 140 ml of methyl p-toluate were added and stirred at 25°C. This mixture is used as a catalyst slurry mixture. Polymerization was carried out using the above-mentioned polymerization apparatus which had been thoroughly dried, purged with nitrogen gas, and further purged with propylene gas. Autoclaves A and B were charged with 60 kg of propylene, and the above catalyst slurry mixture was added as a solid catalyst at 1 g/h and triethylaluminum at 1.5 kg/h.
ml/h, propylene is charged to autoclave A at 30 kg/h. Triethyl aluminum was added to autoclave B at a rate of 3.0 ml/h, and polypropylene slurry was added to autoclave A at a rate of 30 kg/h.
The hydrogen concentration in the gas phase of autoclaves A and B was checked while continuously charging the polypropylene slurry from autoclave B at a rate of 30 kg/h.
Hydrogen was charged to maintain the concentration at 6.5 Vol%, and polymerization was carried out at 75°C. After 6 hours had passed from the start of polymerization and the polymerization was stable, the slurry being continuously extracted from the lower part of autoclave B and methyl p-toluate were simultaneously charged into autoclave C1 at a rate of 1.4 ml/30 min, and the slurry was kept in C1 for 30 minutes. After acceptance into
The destination of the slurry and methyl p-toluate from autoclave B was changed to autoclave C2. In C1, as soon as the slurry is received, 5 kg of liquid propylene is injected while purging the gas phase, and at the same time the internal temperature is brought to 50°C, the hydrogen concentration is increased.
It was set to 0.3vol%. The activity during this period was reduced to about 1/5 by charging methyl p-toluate. Furthermore, ethylene and hydrogen are charged to increase the hydrogen concentration in the gas phase.
0.55 vol%, the ethylene concentration was set to 35.0 mol%, and 3.0 ml of triethylaluminum was injected at once to increase the activity by about 2.5 times. Polymerization was carried out at 50°C for 9 minutes while maintaining the above hydrogen and ethylene concentrations, and then ethylene was added. Polymerization was carried out for 2.0 minutes at a hydrogen concentration of 0.50 vol% and an ethylene concentration of 40.0 mol%. Then p
- After charging 2 ml of methyl toluate, 10 kg of liquid propylene and 50 ml of isopropanol are added.
The mixture was pumped into autoclave D for 7 minutes.
The inside of autoclave C1 is cleaned with liquid propylene, and the washed propylene is also transferred to autoclave D.
I sent it to Autoclave C1 was prepared to receive the next slurry at approximately 3 kg/cm ² gauge. Meanwhile, isopropanol was charged into autoclave D at a rate of 1 ml/h, and the slurry was transferred from the lower part of autoclave D to flash tank E, and further passed through hopper F and taken out as powder. The discharge from autoclave D is continuous at a rate of approximately 40 kg/h, and then the autoclave
Approximately 10 kg of slurry remained in autoclave D when receiving slurry from C2. Autoclave C2 received the slurry from autoclave B and methyl p-toluate for 30 minutes, and then copolymerized in the same manner as in C1. The obtained block copolymer was dried at 60° C. and 100 mmHg for 10 hours, granulated with commonly added additives, and the following physical properties were measured.

Izot (with notch) ASTM D256-56 Measured at 20°C. However, in the example, the amount of polymer produced from the amount of propylene charged into autoclaves A and B, the amount of heat generated from the amount of heat removed, and the slurry concentration calculated from the amount of slurry transferred were continuously determined. is constant, and the amount of polymerization in each autoclave C ₁ and C ₂ is determined from the calorific value calculated from the amount of heat removed _. The propylene block copolymer was polymerized while changing the charging amount to ₂ , and the propylene block copolymer was sampled once every hour to track changes in the Izod impact value at 20°C.

In the comparative example, polymerization was carried out without changing the amount of triethylaluminum charged into C ₁ C ₂ . In the Examples, the relationship between the amount of triethylaluminum added and the activity was determined each time, and the amount of triethylaluminum to be added to the next batch polymerization was corrected.

The results are shown in the drawing. In the comparative examples, the Izod impact strength values vary, but in the examples, they remain almost constant.

Effects By carrying out the method of the present invention, it is possible to produce a propylene block copolymer of constant quality, which is industrially valuable.

[Brief explanation of the drawing]

The drawing shows autoclave C of Example (A) and Comparative Example (B).
Fig. 1 shows the changes over time in the amount of triethylaluminum charged into C2, the slurry concentration, and the Izod impact strength of the obtained copolymer.

Claims (1)

[Claims] 1. When producing a propylene block copolymer by first copolymerizing propylene alone or a small amount of ethylene and propylene (first stage polymerization), and then copolymerizing ethylene and propylene (second stage polymerization),
In a method in which the first-stage polymerization is carried out continuously and the second-stage polymerization is carried out batchwise using a polymerization machine that connects two or more polymerization tanks, the amount of polymer calculated from the amount of slurry transferred to the polymerization tank that performs the second-stage polymerization is Controlling the amount and/or reaction time of the organoaluminum compound added to the polymerization tank in which the post-polymerization is performed so that the amount of polymerization in the post-polymerization calculated from the calorific value is a constant ratio to the amount of transferred polymer. A method for producing a propylene block copolymer characterized by: