JP2764073B2 - Method for producing propylene block copolymer - Google Patents

Description

The present invention relates to a method for producing a propylene block copolymer. More specifically, the present invention relates to an improved method in which a countercurrent washing tower is provided between a polymerization tank for substantially polymerizing propylene alone and a polymerization tank for copolymerizing ethylene and propylene.

[Conventional technology]

In order to improve the impact resistance of isotactic polypropylene, especially at low temperatures, it is widely practiced to first conduct propylene homopolymerization and then polymerize ethylene and propylene. Various attempts have been made to improve the balance between stiffness and rigidity.

In general, the balance between impact resistance and rigidity is determined by the ratio of the portion that polymerizes substantially with propylene alone and the portion that copolymerizes ethylene and propylene, but the impact resistance is further affected by the molecular weight of the copolymerized portion. However, the reaction ratio of the copolymer affects the rigidity. Therefore, depending on the required physical properties, it is necessary to change the reaction ratio and the molecular weight of the copolymerized portion by performing multi-stage polymerization. To this end, the present inventors have already taken advantage of the bulk polymerization method,
Moreover, as a method for producing a block copolymer having an excellent balance between impact resistance and rigidity, a method combining continuous polymerization and batch polymerization has been proposed (for example, JP-A-58-11519 and JP-A-58-11519).
-11520 etc.).

[Problems to be solved by the invention]

A block copolymer having excellent physical properties can be obtained by combining continuous polymerization and batch polymerization.However, this method slightly uses a large amount of organoaluminum and the like, and does not have a good basic unit of catalyst such as organoaluminum, or after polymerization. There is a problem that the catalyst residue in the polymer increases if the method of simply evaporating and removing the unreacted monomer is removed, and if a reaction having a large reaction ratio of ethylene is performed at a later stage in batch polymerization, ethylene is recovered. There were problems such as restrictions on reuse.

[Means for solving the problem]

Means for Solving the Problems The present inventors have solved the above-mentioned problems and intensively studied a method for efficiently producing a block copolymer having excellent physical properties, and completed the present invention.

That is, the present invention uses a stereoregular catalyst, first polymerizes substantially propylene alone using a polymerization tank in which two or more reaction tanks are connected, and then converts ethylene and propylene into 15
In the method for producing a block copolymer of propylene by polymerizing at a ratio of / 85 to 95/5, the polymerization is a bulk polymerization method using propylene itself as a medium, and the first substantially homopolymerization of propylene is 2 The reaction is performed using a polymerization tank in which more than one reaction tanks are connected in series, and the obtained slurry is introduced into a countercurrent washing tower, countercurrently washed with propylene, and the washing liquid taken out from the upper part of the countercurrent washing tower is substantially removed. Introduced into the reaction vessel for the polymerization of propylene alone, the washing slurry taken out from the lower part of the countercurrent washing tower was further introduced into the subsequent polymerization vessel, and ethylene and propylene were added in the latter polymerization vessel at 15/85 to 95/95. A process for producing a block copolymer of propylene, characterized in that the polymerization is carried out at a ratio of 5.

The stereoregularity catalyst used in the present invention is not particularly limited, and various known catalyst systems can be employed. In general, a transition metal catalyst, a catalyst comprising organoaluminum and, if necessary, a stereoregularity improver can be used. For example, a titanium halide is preferably used as the transition metal catalyst. For example, titanium trichloride obtained by reducing titanium tetrachloride with metallic aluminum, hydrogen or organic aluminum, or those obtained by modifying them with an electron donating compound and organic aluminum A catalyst system comprising a compound and, if necessary, a stereoregularity improver such as an oxygen-containing organic compound, or a carrier such as a magnesium halide, or those obtained by treating them with an electron-donating compound, by supporting a titanium halide. A catalyst system comprising a transition metal catalyst and a stereoregularity improver such as an organic aluminum compound and, if necessary, an oxygen-containing organic compound is exemplified. For example, various examples are described in the following documents.

Ziegler-Natta Catalysts and Polymerization by Jo
hn Boor Jr. (Academic Press), Journal of Macromore
cular Sience-Reviews in Macromolecular Chemistry a
nd Physics, C24 (3) 355-385 (1984), C25 (1) 57
8-597 (1985)).

Preferred examples of the stereoregularity improver or the electron donating compound include oxygen-containing compounds such as ethers, esters, orthoesters, and alkoxysilicon compounds, and nitrogen-containing compounds such as amines and amides. Further, alcohol, aldehyde, water and the like can be used.

Examples of the organoaluminum compound include trialkylaluminum, dialkylaluminum halide, alkylaluminum sesquihalide, and alkylaluminum dihalide.Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, and a hexyl group. Examples of the halide include chlorine, bromine and iodine.

In the present invention, first, propylene homopolymerization is substantially carried out by a bulk polymerization method in a polymerization machine having two or more reaction tanks connected to each other. Here, substantially propylene alone means, in the case of complete homopolymerization or copolymerization with other olefins such as ethylene, butene, and hexene, copolymerization is usually performed so that the rigidity of the final polymer is sufficient. Means that the polymerization is carried out so that the olefin content is 6 wt% or less. The polymerization is usually carried out at normal temperature to 100 ° C., and the pressure is such that the polymerization medium is kept in a liquid state at the temperature. This substantially homopolymerization of propylene is usually 95% based on the whole polymer.
When the content exceeds 95% by weight, the improvement in impact resistance is insufficient, and when the content is less than 40% by weight, the rigidity inherent to polypropylene decreases, which is not preferable.

In the present invention, the polymerization slurry is then introduced into a countercurrent washing tower and washed with propylene. The washed slurry is introduced into a polymerization tank for performing the next copolymerization of ethylene and propylene. The countercurrent washing method is not particularly limited, and various known methods and devices can be employed (for example, JP-A-51-143091, JP-A-51-139886, and JP-A-58210908).
etc). As the temperature during washing, it is convenient that the temperature of the slurry taken out from the lower part of the countercurrent washing tower is equal to or lower than the temperature at which batch polymerization is performed. The washing liquid extracted from the upper part of the countercurrent washing tower is introduced into the distillation tower,
Although propylene can be recovered, it is preferable to use a catalyst that gives sufficient stereoregularity to return the propylene to the polymerization zone where homopolymerization of propylene is substantially performed. In this manner, energy for recovering propylene, an organometallic compound dissolved in propylene, or an electron donating compound can be effectively used. Further, it is also possible to increase the linear velocity of the washing liquid so that the transition metal catalyst particles that have not reacted much are extracted from the upper part of the countercurrent washing tower together with the washing liquid and returned to the continuous polymerization zone.

In the present invention, the polymerization of ethylene and propylene can be carried out batchwise or continuously using one or more reaction vessels. In the case of batch polymerization, in the batch polymerization tank, after receiving the slurry, copolymerization with ethylene is performed with or without the addition of an organometallic compound or, if necessary, an electron-donating compound. In order to continuously and continuously receive the slurry subjected to countercurrent washing during the batch polymerization, preferably, the polymerization tank for performing the batch polymerization is connected to the polymerization tank for performing the continuous polymerization in two or more tanks in parallel, During the polymerization in one tank, the slurry is received in another polymerization tank.

The polymerization in the batch polymerization tank is carried out at a reaction ratio of ethylene and propylene of 15/85 to 95/5, and a part of ethylene can be changed to another olefin such as butene, pentene and hexene. If the reaction ratio is out of this range, the effect of improving impact resistance is insufficient. Of course, the copolymerization reaction ratio,
Alternatively, the reaction can be performed in multiple stages by changing the molecular weight, or the reaction ratio can be changed in multiple stages by changing the type of the electron donor to be introduced.

The polymerization temperature of the batch polymerization section is 0 ° C to 80 ° C, preferably 30 to 80 ° C.
The reaction is performed at 70 ° C., and the pressure is determined by ethylene and the like introduced to maintain the reaction ratio.

In the present invention, as another embodiment, the copolymerization can be carried out continuously. In this case, the copolymerization is preferably carried out by connecting two or more reaction vessels in view of the physical properties of the obtained polymer. The polymerization in each tank of the copolymerization section is the same as the conditions performed in the above batch polymerization, but in a later stage, if an attempt is made to increase the reaction ratio between ethylene and propylene, an electron donor is added in the latter stage and the ethylene and propylene are added. It is preferable to make the reaction ratio of propylene higher than that of ethylene, because it is difficult to transfer the slurry to a higher pressure reactor, and it is difficult to remove the heat of reaction when lowering the polymerization temperature and lowering the polymerization pressure. This is because the productivity per volume of the reaction tank is reduced. The electron donating compound that can be used to change the reaction ratio of ethylene and propylene varies depending on what transition metal catalyst is used, but is usually used as an electron donating compound that can be used to perform a reaction from ethylene. As the carboxylic acid ester, a carboxylic acid ester, a dicarboxylic acid diester, a phosphoric acid ester, an alkylamine, and the like can be used, and an alkoxysilane or the like can be used to carry out a reaction from propylene. When an electron-donating compound different from the electron-donating compound used in the polymerization of propylene alone is used, it is preferable to strictly wash in a countercurrent washing cylinder. Further, when changing the reaction ratio in the copolymerization section, it is more preferable to use the electron donating compound only in the latter stage without using the electron donating compound in the first stage of the copolymerization section, because the reaction is likely to be performed by mixing and using the electron donating compound. This is because the effect of changing the ratio becomes smaller.

There is no particular limitation on the molecular weight of the polymer in the substantial homopolymerization part of propylene and the copolymerization part of ethylene and propylene, but the intrinsic viscosity measured at 135 ° C. tetralin solution is about 0.5 to 3 in the continuous polymerization part, and the batch polymerization part. The melt flow index (hereinafter abbreviated as MI) of the copolymer as measured at 230 ° C. with a load of 2.3 kg is 0.1.
Generally, it is set to about 100.

Examples are described below to further explain. In Examples and Comparative Examples, melt flow index ASTM D1238 (230 ° C) Flexural rigidity ASTM D747-63 (23 ° C) Izod (with notch) Impact strength kg · cm / cm ASTM D25
6-56 (23 ℃, -10 ℃) Dupont impact strength kg ・ cm / 1/2 ″ φ JIS K6718 (23 ℃,
MI was measured at a load of 2.16 kg. The intrinsic viscosity is
At 135 ° C in tetralin solution, the isotactic index (hereinafter abbreviated as II) is determined by boiling using a Soxhlet extractor.
-Extracted with heptane for 6 hours and calculated as the extraction residue.

Example 1 Synthesis of Transition Metal Catalyst A vibration mill equipped with four 4 l crushing pots containing 9 kg of steel balls having a diameter of 12 mm and having a capacity of 4 l is prepared. 300g of magnesium chloride in each pot in a nitrogen atmosphere, tetraethoxysilane
45 ml and 60 ml of α, α, α-trichlorotoluene were added and pulverized for 40 hours.

300 g of the above co-ground product is placed in a 5 l flask and titanium tetrachloride
1.5 l of toluene and 1.5 l of toluene were added, and the mixture was stirred at 80 ° C. for 30 minutes, and then allowed to stand still to remove the supernatant twice. Then, the solid content was washed with 4 l of n-heptane. Repeated times.

The obtained transition metal catalyst contained 1.9% by weight of titanium.

Polymerization Reaction Polymerization was carried out using a polymerization apparatus shown in FIG. The continuous polymerization was carried out using a polymerization apparatus in which two 300-liter autoclaves were connected. 1 g of the above catalyst in autoclave A
/ h, diethyl aluminum chloride 4.8 ml / h, methyl toluate 2.8 ml / h, mixed and introduced.From another nozzle,
1.5 ml / h of triethylaluminum, 30 kg / h of propylene
Introduced in h. The slurry was withdrawn at a rate of 30 kg / h from the autoclave A and introduced into the autoclave B, and at the same time, triethylaluminum was charged at a rate of 3.0 ml / h. The internal temperature of each autoclave is maintained at 75 ° C, and the hydrogen concentration in the gas phase is 6.
It was 5 mol%. The slurry from the autoclave B was introduced at 30 kg / h into the upper part of a countercurrent washing tower with a lower part having an inner diameter of 10 cm and a length of 10 m, an upper part having an inner diameter of 30 cm and a length of 2 m. More washing propylene 40Kg / h
With 30 parts of the polypropylene slurry washed from the bottom
Extracted at Kg / h. 30 kg of washed propylene extracted from the upper part was returned to the autoclave A, and the remainder was taken out of the system. Therefore, after returning the propylene to the autoclave A, the insertion of the other propylene was stopped, and the charged amount of triethylaluminum was reduced so that the activities became substantially the same. On the other hand, the slurry extracted from the lower part is alternately received in autoclaves C1 and C2 every 30 minutes, ethylene and hydrogen are introduced after the completion of the reception, the temperature is raised to 45 ° C, 3.0 ml of triethylaluminum is charged, and the mixture is heated at 50 ° C. Gas-phase hydrogen concentration 0.6 mol%,
Polymerization was carried out at an ethylene concentration of 35 mol% for 15 minutes. Then, the slurry was purged into a flash tank to remove unreacted monomers to obtain a block copolymer of propylene at 12 kg / h. The obtained copolymer was granulated by a conventional method, and the physical properties were evaluated as a 1 mm injection sheet. The results are shown in Table 1.

Example 2 Synthesis of transition metal catalyst B 7 l of kerosene, 100 g of magnesium chloride and 370 g of 2-ethylhexanol were added to an autoclave having an internal volume of 20 l.
The mixture was stirred at 100 ° C. for 24 hours to completely dissolve. 23 g of phthalic anhydride was added thereto, and the mixture was stirred, and then gradually added dropwise to 40 l of titanium tetrachloride kept at -10 ° C in a 100 l autoclave with stirring. Thereafter, the temperature was slowly raised, and when the temperature reached 100 ° C., 56 ml of diisobutyl phthalate was added and the mixture was treated for 1 hour. Next, the supernatant was removed, 20 l of titanium tetrachloride was further added, and the mixture was stirred at 100 ° C. Finally, the solid content was washed 10 times with n-heptane to obtain a transition metal catalyst.

The transition metal catalyst B contained 2.8% by weight of titanium and 7.2% by weight of diisobutyl phthalate.

Pretreatment of propylene was performed using the transition metal catalyst B obtained by the above reaction. In a 5 l flask containing 3 l of heptane, 50 g of the above transition metal catalyst B and 10 ml of diethylaluminum chloride were charged, and 150 g of propylene were introduced. After stirring at 20 ° C. for 2 hours, the mixture was allowed to stand, the supernatant was removed, and the solid content was washed with 3 l of heptane to obtain a transition metal catalyst slurry.

Polymerization reaction Same as Example 1 except that the above transition metal catalyst was introduced into autoclave A at a rate of 0.3 g / h as a transition metal catalyst component, triethylaluminum at 2 ml / h, and diphenyldiethoxysilane at 0.3 ml / h. did. In addition, during batch polymerization, 2 ml of triethylaluminum and 0.2 ml of diphenyldiethoxysilane were added and the polymerization time was set to 18 minutes.
A block copolymer was obtained at about 11 kg / h. The measurement results of the physical properties of the obtained copolymer are shown in Table 1.

Comparative Example 1 Continuous polymerization was carried out in the same manner as in Example 1, and then the slurry was put into a polymerization tank for batch polymerization without washing,
The ethylene gas phase concentration and hydrogen concentration were the same as in Example 1. However, since the polymerization reaction proceeds even during the receiving of the slurry, the amount of triethylaluminum introduced was 1 ml, and the polymerization time was changed to 7 minutes so that the ethylene content was the same as in Example 1. The physical properties of the obtained polymer are shown in Table 1.

Comparative Example 2 Continuous polymerization was performed in the same manner as in Example 1, and batch polymerization was performed as in Comparative Example 1, without washing the slurry. By adding 16 minutes to the polymerization time without adding triethylaluminum and diphenyldiethoxysilane to the batch polymerization section, substantially the same ethylene content was obtained. The physical properties of the obtained polymer are shown in Table 1.

Example 3 In the continuous polymerization, after making the gas phase hydrogen concentration 10.5 mol% and extracting the slurry from the countercurrent washing tower, the slurry was received in autoclaves C1 and C2. In the received copolymerization tank, ethylene and hydrogen were charged. Triethyl aluminum 3.0ml, 1,2
-50 ml charged with 1.2 ml of ethyl cyclohexyldicarboxylate
15 ° C when the gaseous phase hydrogen concentration is 4 mol%
A block copolymer was obtained in the same manner as in Example 2 except that polymerization was performed for minutes. The physical properties of the obtained polymer are shown in Table 1.
Similar physical properties can be obtained under conditions where the ethylene concentration is lower than that in Example 1.

Example 4 At the time of batch polymerization, 1.2 ml of di (2-ethylhexyl) phosphate was added instead of ethyl 1,2-cyclohexyldicarboxylate, and the ethylene concentration in the gas phase was 25 mol%, and the ethylene content was the same as in Example 3. The procedure was carried out in the same manner as in Example 3 except that the polymerization time was changed to 18 minutes to obtain a block copolymer at 13 kg / h. At this time, the phosphoric acid di (2
-Ethylhexyl) to titanium was 20 in molar ratio, and the total pressure in the autoclave was 32 kg / cm ² . The results are shown in Table 1.

Example 5 At the time of batch polymerization, 0.96 ml of triethyl phosphate was added instead of ethyl 1,2-cyclohexyldicarboxylate.
The procedure was carried out in the same manner as in Example 3 except that the ethylene concentration in the gas phase was 25 mol% and the polymerization time was changed to 18 minutes so that the ethylene content was equivalent to that in Example 3. Was obtained. At this time, the molar ratio of phosphoric acid triethyl ester to titanium was 30, and the total pressure of the autoclave was 32 kg / cm ² . The results are shown in Table 1.

Example 6 In Example 2, the polymerization tanks C1 and C2 for copolymerization were connected in series to a countercurrent washing tower to perform continuous polymerization. C1 in the copolymerization tank was charged with 0.2 ml / h of slurry and triethylaluminum from the lower part of the countercurrent washing tower, and 10 kg / h of propylene. % Polymerized at 50 ° C. Next, the slurry was withdrawn at 40 kg / h into the next copolymerization tank C2, and 1.2 ml / h of triethylaluminum and 0.3 ml / h of cyclohexyldicarboxylic acid were added. %, Polymerized at 50 ° C. Since the ethylene concentration of C2 was lower than that of the copolymerization tank C1, the pressure was ² kg / cm ² and the slurry could be transferred. According to the analysis, the reaction ratios of the copolymers obtained in the copolymerization tanks C1 and C2 were both 55/45. The physical properties of the obtained polymer are shown in Table 1.

[Effects of the Invention] By carrying out the method of the present invention, a polymer having extremely excellent physical properties can be efficiently provided, which is extremely valuable industrially.

[Brief description of the drawings]

FIG. 1 shows an example of a flow suitable for carrying out the method of the present invention. Autoclaves A and B are polymerization tanks for performing continuous polymerization, and D indicates a countercurrent washing tower. Autoclave 1 and C2 are polymerization tanks for performing batch polymerization, and E is a cyclone.

 ──────────────────────────────────────────────────続 き Continuation of the front page Examiner Yumiko Isshiki (56) References JP-A-58-69215 (JP, A) JP-A-58-49716 (JP, A)

Claims (3)

(57) [Claims] (1) using a stereoregular catalyst, using a polymerization tank in which two or more reaction tanks are connected to each other, first polymerizing substantially propylene alone;
In the method of producing a block copolymer of propylene by polymerizing at a ratio of 5/5, the polymerization is a bulk polymerization method using propylene itself as a medium, and the initial substantially homopolymerization of propylene is performed in two or more tanks. The reaction is carried out using a polymerization tank in which the reaction tanks are connected in series, and the obtained slurry is introduced into a countercurrent washing tower, countercurrently washed with propylene, and the washing liquid taken out from the upper part of the countercurrent washing tower is substantially made of propylene alone. Introduced into the reaction tank for polymerization, the washing slurry taken out from the lower part of the countercurrent washing tower is further introduced into a subsequent polymerization tank, and ethylene and propylene are mixed in the latter polymerization tank at a ratio of 15/85 to 95/5. A process for producing a block copolymer of propylene, characterized in that the polymerization is carried out in the following manner. 2. The method for producing a block copolymer of propylene according to claim 1, wherein the subsequent polymerization tank is two or more polymerization tanks connected in parallel to the countercurrent washing tower. For producing a propylene block copolymer. 3. The process for producing a block copolymer of propylene according to claim 1, wherein an electron-donating compound and / or an organometallic compound is added to a subsequent polymerization tank. Manufacturing method of coalescence.