JPS6181418A - Production of propylene block copolymer - Google Patents

Abstract

PURPOSE:To obtain the titled copolymer having small variability of quality, by calculating and controlling an amount of an organoaluminum compound and a reaction time in such a way that an amount of polymerization at the latter stage becomes constant when ethylene is copolymerized with propylene. CONSTITUTION:Ethylene/propylene in a weight ratio of preferably 6/&h94 are polymerized at the first stage. The slurry is transported to a polymerization tank to carry out the latter stage polymerization, an amount of the polymer is obtained from the amount of the slurry transported and the polymer concentration, an amount of an organoaluminum added and a reaction time are controlled in such a way that an amount of polymerization (value obtained by dividing heat released value by heat release value per unit polymer corrected by reaction ratio of ethylene to propylene) is constant in the first stage polymerization and the latter stage polymerization, to give the aimed copolymer having the reaction ratio of ethylene to propylene of preferably 15/85-96/5 (weight ratio).

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 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 block copolymers of propylene for the purpose of improving the impact resistance of polypropylene, particularly at low temperatures, are well known and many methods have been proposed. (Tokuko Sho 44-20621, Sho 49-24
593, etc.) On the other hand, as a polymerization method that allows multi-stage copolymerization with different reaction ratios of ethylene and propylene using a relatively small number of polymerization vessels, a block copolymer is produced by combining continuous polymerization method and batch polymerization method. A method was previously proposed by the present inventors. ((!/IJEha JP11/f,'J
7-I y5114, JP-A-57-145115. Japanese Patent Publication No. 57-149319. Japanese Patent Publication No. 57-149320
) Problems to be Solved by the Invention The method of combining the continuous polymerization method and the batch polymerization method described above is an excellent method that allows production of 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 into the batch polymerization tank and the slurry concentration are not constant due to differences in performance between lots of catalysts or variations in the quality of raw materials. There was a problem that quality control was difficult.

The present inventors have conducted intensive studies on methods for solving the above-mentioned problems, and have found that the above-mentioned 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.

A means for solving the problem, that is, the present invention, is to first copolymerize propylene alone or a small amount of ethylene and propylene (first stage polymerization), and then copolymerize ethylene and propylene (second stage polymerization) to form a block of propylene. When producing a 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 types of polymerization tanks are connected, the slurry is transferred to the polymerization tank where the second stage polymerization is carried out. The amount of polymerization in the post-stage polymerization calculated from the calorific value according to the amount of polymer calculated from the liquid volume.The amount of organoaluminum compound added to the polymerization tank in which post-stage polymerization is performed so that the amount of polymer transferred is a constant ratio. The present invention relates to a method for producing a propylene block copolymer characterized by controlling the reaction time and/or the 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 resulting block copolymer, the ratio of the first stage polymerization to the second stage polymerization is preferably 60-95:40-5 wt.

The conditions for the first-stage polymerization are the well-known general propylene polymerization temperature and polymerization pressure, which is room temperature to 90°C and normal pressure to 50°C, and can be carried out using Noah G. Polymerization can be carried out by adding a molecular weight regulator such as hydrogen as necessary. You can also.

In the present invention, the first stage polymerization is preferably carried out in two or more types of polymerization tanks in order to maintain good physical properties of the resulting polypropylene, particularly fish-eye 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 in the post-polymerization is 15/85 to 9515 Wt in order to maintain good physical properties, particularly impact resistance, of the polypropylene obtained. In addition, small amounts of other olefins such as butene-1, hexene-1, etc. are copolymerized in the first stage polymerization or the second stage polymerization, resulting in gloss, transparency,
It is also possible to improve the elongation at break.

The catalyst used for polymerization in the present invention is not particularly limited as long as it is a long-lasting polypropylene catalyst with high stereoregularity, as is clear from the structure of the invention, and titanium trichloride and organic aluminum modified by various methods can be used. Common examples include a catalyst made of a compound, a catalyst obtained by supporting a titanium halide or alkoxy titanium such as titanium trichloride or titanium tetrachloride on a carrier such as 710 magnesium saponide, and a catalyst made of an organoaluminum compound. 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, the polymer concentration in the slurry,
and the slough IJ-ft transferred to the polymerization tank in which the post-stage polymerization is carried out at the beginning of each batch of the post-stage polymerization. The former method of determining the slurry concentration is to calculate the amount of polymer produced by calculating the sum of the amount of solvent and propylene introduced into the polymerization tank that performs the first stage polymerization, and the amount of polymer produced as detected by the heat of polymerization. (The amount of propylene and solvent present in the gas phase may be corrected if necessary) to determine the slurry concentration.

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 determined by using a level meter to determine the amount transferred to the polymerization tank for subsequent polymerization, or by using a pump or the like to transfer the slurry at a constant speed. Therefore, it is also possible to understand it as a bond with the time required.

By the above method, it is possible to know which polymers are 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.

For example, the relationship between the ht ratio of organic aluminum panom and titanium trichloride and the activity per titanium trichloride catalyst can be found in Kinetics.
of Ziegler Natta Polymeri
zatien by T, Keii (KODANSH
As shown in Fig. 2.7, Fig. 2.22, page 23, 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 exists even in the case of a catalyst in which titanium tetrachloride is supported on manesium chloride, as shown in FIG. 3 of JP-A-57-149319, for example. The amount of polymerization is the value obtained by integrating the activity over time,
It is easily understood that the amount of polymerization in the post-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 it is possible to produce a propylene block copolymer of constant quality. It seems possible.

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

Example In this example, the polymerization test shown in Example 1 of JP-A-57-149319, which is an invention of the present inventors, was carried out using The amount of polymer produced from the calorific value calculated from the amount of heat removed and the slurry concentration calculated from the amount of heat removed are continuously determined, the amount of slurry transferred is constant, and the amount of polymerization in each autoclave C, C2 is calculated as the amount of heat removed. Polymerization was performed while changing the amount of triethylaluminum and ram charged into C7C2 so that the amount of polymerization was 13.6% based on the calorific value calculated from the polypropylene transferred, and propylene was added once every hour. The block copolymer was sampled and changes in eye knot impact at 20'C were tracked.

In the comparative example, polymerization was carried out without changing the amounts of triethylaluminum charged to C and C2. In the Examples, the relationship between the amount of 1-ethylaluminum 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 example, the value of the eye-knot impact strength changes, but in the example, it remains 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 drawings show changes over time in the slurry concentration of Example (A) and Comparative Example (B) and the Izod impact strength of the obtained copolymers.

Claims (1)

[Claims] 1) When producing a block copolymer of propylene 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), two or more types of propylene are used. 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 polymerization tanks, the calorific value is calculated according to the amount of polymer calculated from the amount of slurry transferred to the polymerization tank that performs the second stage polymerization. The amount of the organoaluminum compound added to the polymerization tank in which the post-polymerization is carried out and/or the reaction time are controlled so that the polymerization amount of the post-polymerization calculated by the method is a constant ratio to the amount of transferred polymer. A method for producing a propylene block copolymer.