JPS6138926B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a polypropylene block copolymer having excellent properties such as impact resistance and rigidity. More specifically, the present invention relates to a method for producing a polypropylene block copolymer by multi-stage polymerization using a special method using a stereoregular catalyst. Crystalline polyolefin is a general-purpose resin with excellent properties such as excellent rigidity, heat resistance, and lightweight molded products, but it has the disadvantage of being brittle at low temperatures, so it is not suitable for applications that require impact resistance at low temperatures. is difficult to use. Many studies have been conducted on methods to improve this drawback, and one of the most industrially useful methods is the block copolymerization of propylene and other olefins, especially ethylene.
Tokuko Sho 38-14834, Tokuko Sho 39-1836, Tokko Sho 39-
15535, etc. In addition, even more rigidity,
Japanese Patent Publication No. 44-20621, Japanese Patent Publication No. 49-24593, etc. proposed methods to improve the drawbacks of low transparency and whitening of deformed parts when deformed by impact or folding, and the resulting block copolymers is very good. To continuously produce a block copolymer as described above, a plurality of independent polymerization tanks are usually connected in series, and propylene (or propylene and a small amount of ethylene or butene-1), a catalyst, and a polymerization medium are mixed. In the first half of the series polymerization tank, the propylene homopolymer (or random copolymer of propylene and a small amount of ethylene or butene 1), which forms the main part of the total polymer, is quantitatively and continuously charged into the polymerization tank in the first stage. A method is used in which a slurry having polymerization activity is continuously fed into a subsequent polymerization tank, where a monomer mixture of ethylene and/or butene 1 or propylene is charged to form a predetermined block copolymer. However, in the above method, although it is possible to make the polymerization amount per solid catalyst particle and the reaction ratio of each monomer the same as that of batch polymerization as a statistical average value, it is difficult to continuously operate a tank reactor. Due to the unavoidable particle shortcut phenomenon, the amount of polymer produced per individual catalyst particle and the reaction ratio of each monomer will have a wide distribution. Although the direct cause of the above phenomenon is not clear, the physical properties of the obtained block copolymer are significantly reduced, and in particular, the low-temperature impact temperature is significantly reduced. Furthermore, when the molecular weight of the polymer polymerized in each polymerization tank is greatly changed, or when the reaction ratio of each monomer is greatly changed, not only the physical properties described above may deteriorate, but also the surface of the molded product may become rough. When molded into a film, what is generally referred to as spots or spots occur, which not only impairs the appearance but also deteriorates other physical properties and greatly reduces the commercial value. The present inventors have studied various methods for solving the above-mentioned disadvantages of the continuous polymerization method, and have found a method of solving the above-mentioned disadvantages without losing the advantages of the continuous polymerization method by performing special operations. Heading The invention has been completed. The object of the present invention is to relate to a method for producing a propylene block copolymer with an excellent balance of physical properties by multi-stage polymerization using two or more polymerization tanks. That is, the present invention involves the continuous production of a propylene block copolymer by multi-stage polymerization using two or more polymerization tanks using a stereoregular catalyst.
By intermittently charging the solid catalyst component of the stereoregular catalyst only into the first tank and intermittently discharging the polypropylene slurry from the first tank to the second tank, it is possible to Polypropylene characterized in that 5 to 50% of the total amount of polypropylene produced is polymerized during a time period when no solid catalyst component is charged to the first tank and no polypropylene slurry is discharged to the second tank. This is a method for producing a block copolymer. The present invention relates to a catalytic polymerization method using an inert solvent as a medium;
It is applicable to a bulk polymerization method using propylene itself as a medium and a gas phase polymerization method substantially free of a liquid medium. The medium used in the solvent polymerization method is one that is inert to ordinary olefin polymerization catalysts, and specifically, butane, pentane, hexane, heptane,
Nonane, decane, cyclohexane, benzene, toluene, xylene, etc. or a mixture thereof can be used. There are no particular restrictions on the stereoregular catalyst as long as it is a catalyst system used for the stereoregular polymerization of polypropylene. A catalyst system is used in which a solid catalyst component is magnesium, aluminum, manganese, etc. supported on chloride, etc., and an organic metal compound such as aluminum, zinc, magnesium, etc. is combined with the solid catalyst component, and furthermore, a suitable organic compound is used. For example, it is also possible to add esters, ethers, amines, amides, phosphoric esters, silicate esters, etc. as stereoregularity improvers. The monomer used in the method of the present invention is mainly propylene, and as a comonomer, ethylene or butene 1, and even a small amount of
It is also possible to use α-olefins with C ₄ or more. There is no particular restriction on the reaction ratio of each of the above monomers in each step of the method of the present invention, but the purpose of the present invention is to produce a propylene block copolymer with an excellent balance of physical properties such as rigidity and impact resistance. In order to achieve this, in the first step, propylene alone or a small amount of ethylene or a copolymer of butene-1 and propylene is produced, and then the reaction ratio of (ethylene and/or butene-1)/propylene is 15/85 to 15/85. It is preferable to carry out polymerization at a weight ratio of 95/5. Depending on the desired physical property balance, the first stage reaction may be further divided into two stages: polymerization of propylene alone, then polymerization of a small amount of ethylene or butene. It is also possible to carry out polymerization of 1 and propylene, or copolymerization can be carried out by further dividing the polymerization into several stages in which the reaction ratio of (ethylene and/or butene 1)/propylene is 15/85 to 95/5 by weight. It is also possible to do this. For example, in the second stage, the reaction ratio of (ethylene and/or butene 1)/propylene is
It is possible to perform polymerization at a weight ratio of 15/85 to 50/50, and further perform polymerization at a reaction ratio of 40/60 to 80/20 in the third stage. The ratio of polymerization amount at each of the above reaction ratios can also be changed according to the required physical properties, but generally the reaction ratio of propylene alone or (ethylene and/or butene 1)/propylene is 4/
It is preferable that the amount of polymerization at a weight ratio of 96 or less is 30 to 80% by weight. The method of the present invention has major features in the method of charging the stereoregular catalyst and the method of transferring the slurry between the polymerization tanks. That is, among the stereoregular catalysts, the solid catalyst component is intermittently charged only to the first tank of a polymerization tank in which two or more polymerization tanks are connected, and the slurry is not discharged from the first tank to the second tank. This should not be carried out while the solid catalyst is being charged into the first tank and until the amount of polymerization per catalyst in the first tank reaches 5 to 50% of the total polymerization amount. There are no particular restrictions on the specific method for the above, as long as the above conditions are met; for example, the first tank is charged with a solid catalyst at regular intervals, and the process from the time the solid catalyst is charged until the slurry is discharged. The polymerization amount per catalyst is between 5 and 5 of the total polymerization amount.
% or more, then a predetermined amount of slurry is discharged into the second tank, usually an amount corresponding to the amount that will be polymerized while the solid catalyst is not charged, and after the discharge is finished, the next solid catalyst is poured into the second tank. Charge into one tank. The liquid cocatalyst can be charged intermittently or continuously. Polymerization in the second tank and above is usually preferably carried out continuously, but depending on the desired physical properties, it is also possible to carry out batch polymerization. The above method can be carried out by varying the amount of slurry retained in the first tank and the second tank; however, in the first tank, the slurry is kept at a constant amount by adding a polymerization catalyst during discharge; It is also possible to maintain a substantially constant slurry amount by not charging the polymerization catalyst during the period from charging the solid catalyst to discharging the slurry. It is an essential condition for carrying out the method of the present invention that the amount of polymerization per catalyst is set to 5 to 50% of the total amount of polymerization between the charging of the solid catalyst and the discharge of the slurry. If the amount is less than 5%, the obtained polymer will not have any particular effect on physical properties as compared to a conventional polymerization method. If it exceeds 50%, the continuous polymerization method will hardly be as effective as the complete batch polymerization method. Particularly preferably, it is set to 10% to 30%. There are no particular restrictions on the polymerization temperature and pressure in each of the above steps, and room temperature to 100°C, preferably 40°C
~90°C, pressure is normal pressure ~50Kg/ ^cm2 . By carrying out the method of the present invention, a propylene block copolymer with an excellent balance of physical properties can be efficiently produced and is of great industrial value. EXAMPLES The present invention will be explained in more detail with reference to examples below, but the present invention is not limited thereto. In the examples and comparative examples, melt flow index (hereinafter abbreviated as MI) is based on ASTM-D1238 Bending rigidity ASTM-D747-63 Izot (with notch) ASTM-D256-56 Dupont JIS-K-6718 MI was measured at 230°C under a load of 2.16 kg, bending rigidity was measured at 20°C, and Izotsu and Dupont were measured at 20°C and -10°C, respectively. In addition, Fuishui creates 0.1mm T-die film (width 10cm) and sells it ^per 100cm2.
Measure the number of fisheyes of 200μ or more, A:
0 to 10 pieces, B: 11 to 50 pieces, C: 51 to 100 pieces, D:
Evaluation was made on a four-level scale of 101 or more. In addition, the intrinsic viscosity number (hereinafter abbreviated as η) was measured using a tetralin solution at 135°C. Also, isotactic index (hereinafter referred to as II)
) was calculated as (boiling n-heptane extraction residual polymer/total polymer). Example 1 Titanium trichloride (TGy-
30) as a solid catalyst component and diethylaluminum chloride as a co-catalyst using the apparatus shown in Figure 1, under the conditions shown in Table 1, polymerization was carried out using n-heptane as a polymerization catalyst. I went there. The catalyst consisting of the above solid catalyst component and diethylaluminium chloride was placed in an autoclave A.
The slurry is charged once every 30 minutes, and polymerization is carried out without discharging the slurry from autoclave A to B for 20 minutes after charging the above catalyst.
Drain the slurry into autoclave B for 10 minutes. Therefore, the discharge of slurry from autoclave A to B takes 1/3 of the total time, and the average retention time of slurry in autoclave A (calculated as the average amount of slurry retained in the polymerization tank/the amount of slurry discharged per hour) ) was 2.1 hours. The slurry was continuously withdrawn from autoclave B at a constant rate, and the average residence time in autoclave B was 1.5 hours. The slurry from autoclave B is charged to autoclave C;
Then, the gas phase was extracted from the system and adjusted to the desired hydrogen concentration. The average residence time in autoclave C is
It was 0.47. The slurry continuously extracted from autoclave C was charged into autoclave D, and copolymerization of ethylene and propylene was carried out under the conditions shown in Table 1. The average residence time in autoclave D was 0.93 hours, and the reaction ratio of ethylene and propylene determined from mass balance was 42/58 wt. Autoclave E continuously received the slurry from autoclave D, and copolymerized ethylene and propylene under the conditions shown in Table 1. The average residence time in autoclave E was 1.5 hours, and the reaction ratio of ethylene and propylene determined from mass balance was 45/65 wt. Next, the catalyst was deactivated with methanol in autoclave E, and the slurry was washed in continuous washing tower G, and then filtered and dried by a known method to obtain a product powder. The product powder was granulated with known additives and its physical properties were measured. The results are shown in Table 3. Table 2 also shows the material balance of the above polymerization. According to the material balance, the amount of polymerization in autoclave A while the slurry was not being discharged was about 37% of the total amount of polymerization. Comparative Example 1 Continuous charging of catalyst to autoclave A,
Example 1 except that the slurry was transferred continuously from autoclave A to autoclave B.
Polymerization was carried out in the same manner. The detailed conditions are shown in Tables 1 and 2, and the physical properties of the obtained copolymer are shown in Table 3. The film has many edges and also has poor impact resistance. Comparative Example 2 The catalyst was charged into autoclave A once every 30 minutes, and the slurry was not discharged from autoclave A to B for 2.5 minutes after the catalyst was charged. Autoclave B for the next 27.5 minutes
Example 1 except that the slurry was continuously discharged.
It was polymerized in the same way. The detailed conditions are shown in Tables 1 and 2, and the physical properties of the obtained copolymer are shown in Table 3. Almost no improvement was observed compared to Comparative Example 1. The amount of polymerization in autoclave A when the slurry was not discharged was about 4.7% of the total amount of polymerization, as determined from the mass balance. Example 2 The method of charging the catalyst into autoclave A and discharging the slurry from autoclave A to B were the same as in Example 1, and as shown in Table 1, the ethylene and propylene in the gas phase in autoclave D and E were By changing the concentration, the reaction of ethylene and propylene in autoclave D and E was 53/47 and 73/, respectively.
Polymerization was carried out by changing the ratio to 27wt. The detailed polymerization conditions are shown in Tables 1 and 2, and the physical properties of the copolymer are shown in Table 3. Comparative Example 3 Polymerization was carried out in the same manner as in Example 2, except that the catalyst was continuously charged into autoclave A, and the slurry was also continuously discharged from autoclave A to B. The detailed polymerization method is shown in Tables 1 and 2, and the physical properties of the obtained copolymer are shown in Table 3. Example 3 Catalyst was charged to autoclave A once every 30 minutes, and autoclave A was charged for 26 minutes after charging the catalyst.
After charging the catalyst without discharging the slurry from to B.
Polymerization was carried out in the same manner as in Example 2, except that the slurry was discharged from autoclave A into autoclave B for 4 minutes after 26 minutes. Detailed polymerization conditions first
Table 2 shows the physical properties of the obtained copolymer, and Table 3 shows the physical properties of the obtained copolymer. Furthermore, the amount of polymerization in autoclave A when the slurry was not discharged, calculated from the material balance, was about 40% of the total polymerization amount, which was 30% in Example 2.
larger, and the resulting copolymer has even fewer fissures.

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【table】 [Brief explanation of the drawing]

FIG. 1 is a flow sheet of one embodiment of the present invention. In the figure: A, B, C, D, E, F are autoclaves, and G is a continuous washing tower.

Claims (1)

[Scope of Claims] 1. A method for continuously producing a propylene block copolymer by multi-stage polymerization using two or more polymerization tanks using a stereoregular catalyst. By intermittently charging the solid catalyst component only into the first tank and intermittently discharging the polypropylene slurry from the first tank to the second tank, the amount of polypropylene per solid catalyst component can be increased. Polypropylene polymerization characterized in that 5 to 50% of the total production amount is polymerized during a time period when no solid catalyst component is charged into the first tank and when the polypropylene slurry is not discharged into the second tank. Method for producing block copolymer. 2. The manufacturing method according to claim 1, wherein the polypropylene block copolymer is a block copolymer of propylene and ethylene and/or butene-1. 3 Polypropylene block copolymer is polymerized in the first stage with propylene alone or with a reaction ratio of (ethylene and/or butene 1)/propylene of 6/94 or less by weight, and then in the second and subsequent tanks (ethylene and/or the reaction ratio of butene 1)/propylene is
2. The manufacturing method according to claim 1, comprising at least one step of polymerizing at a weight ratio of 15/85 to 95/5.