JPH0128051B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing polypropylene by slurry polymerization. More specifically, when propylene is slurry polymerized in an inert hydrocarbon or liquefied propylene, most of the inert hydrocarbon or liquefied propylene used as a polymerization solvent is recycled directly to the polymerization process without any purification treatment. It is about using. Conventionally, polypropylene manufacturing methods, both continuous and batchwise, generally consist of a polymerization step, a polymer purification step, a dry granulation step, and a solvent purification step. After the polymerization solvent is used in the polymerization process, it becomes contaminated with alcohol, water, decomposition products, etc. during the polymer purification process, so unless the polymerization contaminants are removed through the solvent purification process, the polymerization process cannot proceed. It could not be recycled. Furthermore, it is known that the cost of solvent refining accounts for a high proportion of the cost of producing polypropylene. In recent years, with the rise in energy costs, reducing the manufacturing cost of polypropylene has become a serious issue. As a cost reduction method for the solvent refining process, Japanese Patent Application Laid-Open No. 49-83784 discloses a method for removing solvent-insoluble polymers from the slurry without purifying the separated solvent after the polymerization is completed and before the catalyst decomposition operation. , a method is disclosed in which a desired amount is recycled as it is, a newly purified solvent and a new catalyst are added thereto, and polymerization is carried out again. Similarly, in JP-A-50-79589, after carrying out homopolymerization or copolymerization of propylene in liquid phase propylene, the extracted polymer slurry is brought into countercurrent contact with liquid phase propylene, and liquid phase propylene containing an active catalyst is produced. A method for recycling and reusing the polymer in the polymerization process is disclosed. However, these methods have the drawback that the production ratio of a polymer soluble in the polymerization solvent (hereinafter simply referred to as soluble polymer) increases as the polymerization solvent is recycled and reused. As a result of intensive study on these points, the present inventors have discovered a method that can achieve the same level of soluble polymer production ratio even when the polymerization solvent is recycled and reused as in the conventional case where the polymerization solvent is not reused. The invention has been achieved. That is, an object of the present invention is that when propylene is homopolymerized or copolymerized using a catalyst system consisting of a titanium-containing composition and an organoaluminum, even if the solvent used for polymerization is recycled and unpurified, soluble polymers are not produced. Another object of the present invention is to provide a method for producing polypropylene in which the production ratio of coalescence does not increase, and another object is to provide a process in which the polymerization solvent after the polymerization is used in an unpurified state by complete circulation. The method for producing polypropylene of the present invention involves homopolymerizing or copolymerizing propylene using a titanium-containing composition and an organic aluminum catalyst system, and converting the slurry after polymerization into a polymerization solvent-insoluble polymer (hereinafter simply referred to as In a method for producing polypropylene by recycling part or all of the solvent obtained by separating an insoluble polymer (insoluble polymer) into the polymerization process without purification and reusing it, a titanium-containing composition and an organic aluminum are used as a catalyst system. 0.1 per gram of titanium-containing composition on a catalyst consisting of
The present invention is characterized in that a system is used which is subjected to a polymerization pretreatment to form a propylene polymer having a weight of at least 100 g. The titanium-containing composition used in the present invention includes (1)
Titanium tetrachloride is reduced with metal aluminum, excess titanium tetrachloride is removed, and then pulverized and activated. (2) A reaction product of 1 above and an electron donor. (3) A reaction product of titanium tetrachloride, an organic ether compound, and an organic aluminum compound. (4) A product obtained by reacting a reaction product of titanium tetrachloride and an organoaluminum compound with an organic ether, followed by treatment with titanium tetrachloride. (5) A reaction product of a chlorine-containing magnesium compound with an electron donor and titanium tetrachloride. etc. can be mentioned. The organoaluminum compound used in the present invention has the general formula AlR _3-o Cl _o (where R has 1 to 8 carbon atoms).
alkyl groups, n = 0 to 1),
Preferred examples include triethylaluminum, diethylaluminum chloride, triisobutylaluminum, diisobutylaluminum chloride, and mixtures thereof. Further, in addition to the above-mentioned components, a third component such as various compounds containing N, O, P, or Si, or an unsaturated hydrocarbon compound may be added. The catalyst system in the method for producing polypropylene of the present invention refers to a catalyst consisting of a titanium-containing composition and an organoaluminium, and a catalyst comprising a titanium-containing composition and an organic aluminum.
This is a system that is subjected to a polymerization pretreatment to form 0.1 g or more of propylene polymer. More specifically, a titanium-containing composition and an organic aluminum are mixed with an inert hydrocarbon to prepare a catalyst liquid, then the liquid is maintained at a temperature of 10 to 80°C, and hydrogen and propylene are supplied. 1g of titanium-containing composition
This refers to a system in which 0.1 g or more of propylene polymer is formed per unit. The formation of propylene polymer in the catalyst system of the present invention (hereinafter, the polymer formed here may be referred to as prepolymer) is in the range of 0.1 to 500 g, preferably 0.5 to 300 g, per 1 g of titanium-containing composition. It is preferable to control it within the range of , more preferably within the range of 1 to 100. If it is less than 0.1, the present invention will not be effective. On the other hand, if it exceeds 500, the effect of the present invention will be in an equilibrium state, and the catalyst polymerization pretreatment equipment will become large, which is not practical. The prepolymerization conditions for the catalyst of the present invention, that is, the conditions for forming the propylene (pre)polymer, are as follows:
Range of 10-80℃, preferably 30-60℃, time 1
Ranges from minutes to 24 hours. If the temperature is less than 10°C, it is not practical, and if it exceeds 80°C, the APP production rate in the polymerization of the present invention increases, which is not preferred. Further, it can be carried out in the presence or absence of hydrogen, which is a molecular weight regulator. Pre-polymerization treatment of catalyst,
That is, the propylene used to form the prepolymer contains 0.5 mol% of α-olefin containing ethylene.
The following propylenes are used, but it is preferable to use propylene alone. If the amount of α-olefin containing ethylene exceeds 0.5 mol %, the bulk density of the insoluble polymer produced in the polymerization of the present invention, that is, polypropylene, will be undesirably low. Although the rate of formation of propylene polymer (prepolymer) in the prepolymerization treatment of the catalyst of the present invention is not critical, it is preferably lower;
Alternatively, it can be carried out continuously in the gas phase or liquid phase. When carried out in the gas phase, it is carried out in gaseous propylene, and when carried out in the liquid phase, it is carried out using an inert hydrocarbon such as pentane, hexane, heptane, etc., or liquefied propylene. In either case, it is necessary to perform purification to remove propylene polymerization inhibitors before use. Polymerization in the production method of the present invention is carried out using the catalyst system described above and an unpurified polymerization solvent separated from the post-polymerization slurry described below. The temperature is normal temperature to 100°C, preferably 30°C to 80°C.
A polymerization pressure of normal pressure to 50 kg/cm ² G is suitable. By carrying out the polymerization in the presence of hydrogen, the molecular weight can be adjusted to a desired value without impairing the crystallinity of the polymer. The polymerization of the present invention can be applied to the production of propylene homopolymers, random copolymers or block copolymers of propylene and ethylene and/or alpha-olefins other than propylene. The slurry obtained after polymerization is optionally degassed to separate the insoluble polymer and polymerization solvent from the slurry. Examples of this separation device include a centrifuge, a vertical countercurrent extraction column, and a hydrocyclone. The polymerization solvent separated from the slurry contains a soluble polymer, a propylene oligomer, a third component constituting a polymerization catalyst, a small amount of an insoluble polymer, and others. A part or all of the separated polymerization solvent is recycled to the polymerization process and reused as a polymerization solvent, depending on the quality of the polypropylene produced. On the other hand, the insoluble polymer separated from the slurry can be immediately neutralized and made into a product, or it can be purified by adding a polymerization solvent, a purifying solvent such as alcohol, and made into a product. A process in which the polymerization solvent separated from the slurry after polymerization is completely recycled and used in an unpurified state according to the production method of the present invention will be explained with reference to FIGS. 1 and 2.
The present invention is not limited to these. FIG. 1 shows the case where the polymerization process uses an inert hydrocarbon such as hexane or heptane as the polymerization solvent. Into a storage tank 7 equipped with a stirrer, an inert hydrocarbon such as normal hexane or normal heptane is introduced into pipe 1 , an organoaluminum compound such as diethylaluminum cloide is introduced into pipe 2 , a titanium-containing composition is introduced into pipe 3 , and a third component is introduced from pipe 4 . supply. While stirring the storage tank 7 and keeping it at a predetermined temperature, a desired amount of propylene is charged from the pipe 5 and, if necessary, hydrogen is charged from the pipe 6 to form a propylene prepolymer to obtain a catalyst system. This operation can be carried out batchwise or continuously. The catalyst system is charged by a pump 8 to a polymerization vessel 9 having an agitator and the ability to remove heat of the polymerization reaction. A hydrogen pipe 10 is connected to the polymerization vessel 9 .
Replenishment solvent is connected to pipe 11 , propylene is connected to pipe 12 ,
And if necessary, ethylene or α-olefin other than propylene is supplied from a pipe 13 for producing a random copolymer. The residence time in the polymerization vessel 9 is 1 to 8 hours. Polymerization vessel 9
Control the slurry concentration within 50% by weight or less. When producing block copolymers in a continuous manner, it is necessary to arrange two or more polymerization vessels 9 in series and to control the hydrogen concentration and monomer composition of each polymerization vessel. Soluble polymers, inert polymers,
The slurry after polymerization containing a catalyst, an inert hydrocarbon, propylene, etc. is transferred from the polymerization vessel 9 to a flash drum 15 by a control valve 14 .
will be extracted. Unreacted propylene separated in flash drum 15 is circulated to polymerizer 9 via heat exchanger 16 . The slurry from which unreacted propylene has been separated is transferred to a centrifuge 1 by a pump 40 .
7 and is separated into a wet cake of insoluble polymer containing a small amount of solvent and a solvent containing the catalyst and soluble polymer. The solvent containing the catalyst and soluble polymer is circulated to the polymerization vessel 9 via a pipe 18 by a pump 19 . A part of it can be removed from the piping 20 to the outside of the system, if necessary. On the other hand, the wet cake is brought into contact with heated nitrogen gas and flash dried in a pipe 21 , and an insoluble polymer is obtained as a polypropylene powder in a cyclone 22 . on the other hand,
The nitrogen gas containing the solvent is introduced into the scrubber 24 via the pipe 23 and comes into countercurrent contact with the cooled solvent in the heat exchanger 25 . The solvent is returned to the polymerization vessel 9 . Since active catalyst remains in the polypropylene powder separated from the cyclone 22, the polypropylene powder is stabilized by being treated with a stabilizer such as epoxide, alcohol, water, etc. introduced from a pipe 27 in a stabilization tank 26 . . The polypropylene powder extracted from the stabilization tank 26 contains a small amount of stabilization and its reaction product, or a small amount of solvent, and is therefore sent to the fluidized fluidized dryer 28 . The sufficiently dried polypropylene powder is obtained from the pipe 29 as a final product. The heated nitrogen gas for fluidization in the fluidized dryer 28 is purified in a scrubber 30 and heated in a heat exchanger 31 before being used. A neutralizing agent such as caustic soda aqueous solution is charged from the pipe 32 .
The gas coming out of the fluidized fluidized dryer 28 is neutralized and nitrogen gas is circulated. FIG. 2 shows the case where liquefied propylene is used as the polymerization solvent. Into a storage tank 7 equipped with a stirrer, an inert hydrocarbon, such as normal hexane or normal heptane, is supplied from pipe 1 , an organoaluminum compound, such as diethylaluminum chloride, from pipe 2 , and a titanium-containing composition from pipe 3 . The third component is supplied from piping 4 as required. While stirring and maintaining the temperature at a predetermined temperature, propylene is fed from pipe 5 and a desired amount of hydrogen is charged from pipe 6 as required to form a propylene prepolymer, thereby obtaining a catalyst system. This operation can be carried out batchwise or continuously. The catalyst system is charged by a pump 8 to a polymerization vessel 9 having a stirrer and a polymerization reaction heat removal capability. Polymerization vessel 9 has piping 1
Hydrogen is supplied from 0 for molecular weight control, liquefied propylene for replenishment is supplied from a pipe 12, and ethylene or/and α-olefin other than propylene is supplied from a pipe 13 for producing a random copolymer as required. The residence time in the polymerization vessel 9 is 1 to 8 hours. The slurry concentration in the polymerization vessel 9 is controlled to 65% by weight or less. When producing a block copolymer continuously, it is necessary to arrange two or more polymerization vessels 9 in series and to control the hydrogen concentration and monomer composition of each polymerization vessel. The polymerization slurry is discharged from the polymerization vessel 9 to a hydrocyclone 33 by a control valve 14 . At the same time, purified liquefied propylene is introduced into the liquid cyclone 33 from the pipe 34 , and a liquefied propylene stream containing most of the organoaluminum compound and soluble polymer is obtained from the upper part, and a polypropylene stream containing a small amount of liquefied propylene is obtained from the lower part. The liquefied propylene stream from the top is returned to the polymerizer 9 by a pump 35 . A portion of it can be extracted from the pipe 36 . On the other hand, the polypropylene stream containing a small amount of liquefied propylene from the bottom is heated in the heat exchanger 37 ,
It is dried and introduced into the cyclone 38 . The propylene gas separated by the cyclone is compressed and liquefied by a compressor 39 and returned to the polymerizer 9 . On the other hand, the polypropylene powder dried in the cyclone 38 is stabilized as shown in FIG. 1 and becomes a product. The effect of the present invention is that even if the solvent separated from the slurry is recycled and reused without purification after polymerization of propylene, the production ratio of amorphous polypropylene does not increase. Therefore, the present invention can provide a complete circulation process for the polymerization solvent, reducing the burden of refining the solvent and making it possible to significantly reduce the cost of producing polypropylene. Furthermore, since the polymerization solvent can be completely circulated without being purified, there is an advantage that the amount of the organoaluminum compound, which is a component of the polymerization catalyst, can be reduced. The manufacturing method of the present invention will be explained below using Examples, Comparative Examples, and Reference Examples. Here, the reference example is a production example using a purified solvent. The values shown in Examples, Comparative Examples, and Reference Examples represent the following. Formation of prepolymer in prepolymerization treatment of catalyst:
- (preliminary) polymer formation amount (g) per 1 g of titanium-containing composition (hereinafter sometimes referred to as composition)
was expressed as (g/g-composition). The value was obtained in another identical experiment. Production amount: - Production amount (g) of polymer insoluble in the polymerization solvent. Yield: - Yield (g) of insoluble polymer (minus prepolymer) per gram of titanium-containing composition. Soluble polymer production rate (hereinafter referred to as APP production rate): - In the case of polymerization using an inert hydrocarbon such as hexane, the percentage of the total polymer produced (soluble polymer + insoluble polymer) that is soluble in the inert hydrocarbon after polymerization In the case of polymerization in liquefied propylene, extract the hexane-soluble polymer using normal hexane in a Kumagawa extractor under reflux for 6 hours, and calculate the ratio of the hexane-soluble polymer. I asked for it. The soluble polymer contained in the reused solvent was subtracted from the soluble polymer in the APP production rate calculation. MFI: - Based on flow index (g/10 minutes) according to ASTM-D1238-70. Bulk Density: - Density of an insoluble polymer powder. Flexural modulus: -According to ASTM D-790-70. Tensile strength: -According to ASTM D-638-68. Hardness: According to -ASTMD-785-65. Preparation of titanium-containing composition (a) used in the following examples. Reactor with a stirrer of capacity 15 (rotation speed
200rpm), maintain a nitrogen atmosphere inside, add 2.7% of normal hexane and 0.69% of titanium tetrachloride,
Cooled to 0°C. Next, hexane 3.4 and diethyl aluminum chloride (hereinafter abbreviated as DEAC)
0.78 was added over 4 hours at 0°C. Thereafter, the mixture was stirred for 1 hour, and further stirred at 65°C for 1 hour to carry out the reaction, and then cooled to room temperature and allowed to stand still.
Separate the upper liquid phase and dissolve the solid in the sediment layer with hexane.
Washed twice. Next, the solid was reacted with 9.8 g of hexane and 1.3 g of diisoamyl ether by stirring at 35° C. for 100 minutes. After the reaction, the supernatant liquid was separated and the second precipitate obtained was washed with hexane. To the second precipitate, 3.9 g of hexane and 1.0 g of titanium tetrachloride were added over 60 minutes, and the mixture was heated at 65°C for 20 minutes.
After stirring for a period of time and allowing the mixture to stand still, the supernatant liquid was removed, and the resulting third precipitate was washed with hexane and dried under reduced pressure to obtain 1 kg of a titanium-containing composition. Reference example 1 (1) Catalyst system Purified normal hexane (hereinafter n-
After preparing a catalyst mixture with 0.8 g of hexane, 0.20 g of DEAC, and 0.123 g of the titanium-containing composition (a),
Propylene was press-fitted and stirred at a temperature of 50℃.
A total pressure of 1.0 Kg/cm ² G and a reaction time of 30 minutes were used to form a composition of 7.2 g/g of propylene polymer (prepolymer). (2) Polymerization To the above catalyst system, add 2.2 g of purified n-hexane, 0.48 g of DEAC, and 780 Nml of hydrogen as a polymerization solvent,
After raising the temperature to 70°C, propylene was pressurized and polymerization of propylene was carried out at a temperature of 80°C, a total pressure of 8 kg/cm ² G, and a reaction time of 4 hours. Table 1 shows polymerization conditions and polymerization results.
It was shown to. Examples 1 to 3 (1) In the same manner as in Reference Example 1, a catalyst system was prepared by forming a prepolymer under similar conditions as shown in Table 1. (2) The conditions shown in Table 1 were carried out in the same manner as in Reference Example 1, except that hexane, which had been obtained by removing the insoluble polymer from the slurry after polymerization in the previous example, was reused as the polymerization solvent in the above catalyst system. Polymerization of propylene was carried out. The conditions and results are shown in Table 1. Comparative Example 1 (1) In the same manner as in Example 1, a catalyst system was prepared by simply preparing a catalyst mixture as shown in Table 1 without performing any treatment to form a prepolymer. (2) After preparing the above catalyst system, the table was prepared in the same manner as in Example 1, except that hexane, which had been separated from the slurry after polymerization in Example 3 by removing the insoluble polymer, was reused as the polymerization solvent. Polymerization of propylene was carried out under the conditions of 1. The conditions and results are shown in Table 1. Example 4 (1) A prepolymer 0.5 g/g composition was formed under the same conditions as in Example 1, except that the hydrogen amount and propylene supply conditions were different. system. (2) Example 1 as shown in Table 1, except that hexane, which was separated by removing the insoluble polymer from the slurry after polymerization of Comparative Example 1, was reused as the polymerization solvent in the above catalyst system. Polymerization of propylene was carried out in the same manner. The conditions and results are shown in Table 1. Table 1 shows that when reusing hexane as a polymerization solvent after removing the insoluble polymer from the slurry after polymerization,
By forming a prepolymer in the catalyst system
This indicates that the increase in APP production rate is prevented. [Table] [Table] [Table] Reference Example 2 (1) The catalyst was not treated to form a prepolymer. (2) Purified n-hexane 3.0, DEAC 0.68 g,
Add 0.122 g of titanium-containing composition (a), stir, add 800 Nml of hydrogen, raise the temperature to 70°C, add propylene, and polymerize propylene at a temperature of 80°C, a total pressure of 8 kg/cm ² G, and a reaction time of 4 hours. I did it. The polymerization conditions and results are shown in Table 2. Comparative Examples 2 to 3 (1) In the same manner as in Example 1, only the catalyst mixture as shown in Table 2 was prepared, but no treatment to form a prepolymer was performed. (2) After preparing the above catalyst mixture, as shown in Table 2, the same procedure as in Example 1 was performed, except that hexane, which was separated from the slurry after polymerization in the previous example by removing the insoluble polymer, was reused as the polymerization solvent. Polymerization of propylene was carried out under the conditions shown in Table 2. The results are shown in Table 2. Table 2 shows that when the solvent after polymerization is used again as a polymerization solvent without purification, the yield of insoluble polymer (polypropylene) per gram of titanium-containing composition remains the same, but the production rate of soluble polymer remains the same. (APP production rate) increases significantly. This shows that it has not been practical to reuse the solvent after polymerization without purifying it. [Table] [Table] Reference Example 3 (1) In the same manner as in Example 1, a treatment was carried out to form a prepolymer composition of 7.2 g/g under the conditions shown in Table 3 to obtain a catalyst system. (2) Using the above catalyst system, propylene was polymerized in the same manner as in Reference Example 1. The conditions and results are shown in Table 3. Comparative Example 4 (1) A catalyst mixture similar to that in Example 1 was prepared, and the propylene supply conditions were changed to produce a prepolymer formation of 0.05 g/g, which is outside the scope of the present invention. A catalyst system was created. (2) Polymerization of propylene was carried out in the same manner as in Example 1 under similar conditions, except that hexane from which the insoluble polymer was removed from the slurry after polymerization in Reference Example 3 was reused as the polymerization solvent in the above catalyst system. Ivy. The conditions and results are shown in Table 1. Table 3 shows that even if the catalyst is treated to form a prepolymer, the APP production rate will significantly increase, which is undesirable, if the catalyst deviates from the scope of the present invention. Reference Example 4 (1) In the same manner as Reference Example 3, Example 1, etc., Table 3
A catalyst system was prepared by forming a prepolymer (9.1 g/g) under the following conditions. (2) In the above catalyst system, except that ethylene is mixed with propylene, the temperature is 60℃, and the amount of hydrogen is 870NL,
An ethylene-propylene random copolymer (ethylene content: 2.4% by weight) was obtained in the same manner as in Reference Example 1. The conditions and results are shown in Table 3. Example 5 (1) Table 3 was prepared in the same manner as Reference Example 4, Example 1, etc.
A catalyst system was prepared by forming a prepolymer composition of 3.1 g/g under the following conditions. (2) A random copolymer of propylene and ethylene (ethylene content 2.6% by weight). Table 3 shows the conditions and results.
Shown below. As is clear from Table 3, the method of the present invention also applies to random copolymerization of propylene and ethylene.
It can be seen that the APP generation rate does not increase. [Table] [Table] Reference Example 5 (1) 20 ml of purified n-hexane, 0.278 g of DEAC,
After mixing 0.048 g of titanium-containing composition (a) to prepare a catalyst mixture, the temperature was raised to 60°C, and propylene gas was pressurized until the total pressure was 10 kg/cm ² G.
The treatment was carried out to form a composition of 9.2 g prepolymer/g for 1 min, resulting in a catalyst system. (2) Charge 1600 g of purified liquefied propylene into a nitrogen-substituted polymerization reactor with a 5-capacity stirrer, add 98 Nml of hydrogen, add 0.274 g of DEAC and the above catalyst system, and incubate propylene at a temperature of 70°C for 3 hours. Polymerization was carried out. Table 4 shows the conditions and results. Examples 6 to 8, Comparative Example 5 (1) A prepolymer was formed in the same manner as in Reference Example 5 under the conditions shown in Table 4. (In Comparative Example 5, only the catalyst mixture was prepared and no treatment was performed.) (2) Instead of the liquefied propylene in Reference Example 5-(2), purified liquefied propylene as shown in Table 4 was used in the previous experiment (comparison). ) Reference Example 5 except that the mixture of the liquefied propylene phase after polymerization was used and DEAC was not added.
- Polymerization was carried out in the same manner as in (2) (only in Comparative Example 5, only the catalyst mixture was used as the catalyst system). Table 4 shows the conditions and results. As is clear from Table 4, when the catalyst is treated to form a prepolymer as in the present invention, the APP extraction rate, that is, the APP production rate does not increase, but when the treatment is not carried out (Comparative Example 5), the APP generation rate is significantly reduced. To increase. [Table] [Table] *5 Reference example 6 using the liquefied propylene phase after polymerization in the previous example (1) The catalyst was not treated to form a prepolymer. (2) Charge 1600 g of purified liquefied propylene into a nitrogen-substituted polymerization vessel with an internal volume of 5 and a stirrer.
DEAC 0.552g, titanium-containing composition (a) 0.050g,
960 Nml of hydrogen was added, and bulk polymerization of propylene was carried out at a temperature of 70°C and a time of 180 minutes. The results are shown in Table 5. Comparative Examples 6, 7 (1) Purified n-hexane 20ml, DEAC 0.281g, in a reactor with a nitrogen purged internal volume of 100ml and a stirrer.
A predetermined amount (Table 5) of the titanium-containing composition (a) was added and a catalyst mixture was prepared without any treatment to form a prepolymer. (2) Instead of the liquefied propylene in Reference Example 6-(2), as shown in Table 5, purified liquefied propylene and the previous example (Reference Example 6 in the case of Comparative Example 6, Comparative Example 6 in the case of Comparative Example 7) were used. Polymerization of propylene was carried out in the same manner as in Reference Example 6 under the conditions shown in Table 5, except that the mixture of the liquefied propylene phase after the polymerization reaction was used and DEAC was not added. The results are shown in Table 5. [Table] [Table] Preparation of titanium-containing composition (b) used in the following examples. 12.16 g of anhydrous Mg(OH) ₂ and 27.84 g of anhydrous AlCl ₃ are ground in a ball mill at 200° C. for 24 hours. Furthermore, 13.3 ml of ethyl benzoate and 6.6 ml of silicon tetrachloride are added, and the grinding is continued for 48 hours. 40 g of the thus obtained pulverized product and 250 ml of titanium tetrachloride are reacted at 80° C. for 3 hours in a reactor equipped with a stirrer. The product was washed five times with 300 ml of purified n-hexane and dried to obtain 42 g of titanium-containing composition (b). Reference Example 7 (1) The catalyst was not treated to form a prepolymer. (2) Purified n-hexane 2.5 mmol, triethylaluminum 5 mmol, methyl paratoluate (methyl paratoluate) 0.5 mmol, titanium-containing composition (b) 64 mg, methyl paratoluate in a nitrogen-substituted polymerization vessel with an internal volume of 5 and a stirrer. Eight
Add 0.37 mmol in order. Add 600Nml of hydrogen,
Polymerization of propylene was carried out under the conditions of 70° C., 8 kg/cm ² and 2 hours. The yield was 6530 g/g of composition, and the APP production rate was 3.4%. Example 9 (1) Purified n-hexane 1.0, triethylaluminum 3.0 mmol, methyl paratoluate 0.3 mmol, titanium-containing composition (b) 59 mg, methyl paratoluate were placed in a nitrogen-substituted polymerization vessel with an internal volume of 5 and equipped with a stirrer. Add 0.2 mmol of ate in order to prepare a catalyst mixture, then 30℃, total pressure 1.0Kg/cm ² 10
The treatment was carried out under conditions of 156 g/g of prepolymer to form a composition of 156 g/g. This system was designated as a catalyst system. (2) Add 1.3 of the hexane phase obtained after the polymerization in Reference Example 7-(2) to the above catalyst system, add 600Nml of hydrogen, and polymerize propylene at 70℃, 8Kg/cm ² G, and for 2 hours. Summer. The yield was 6580 g/g of composition, and the APP production rate was 3.6%. Comparative Example 8 (1) Only the catalyst mixture was prepared in the same manner as in Example 9, and no treatment for forming a prepolymer was performed. (2) The same procedure as in Example 9 was carried out, except that hexane phase 1.3 obtained after carrying out the same polymerization as in Reference Example 7-(2) was used as the catalyst solution. The yield is
6475g/g composition, APP production rate was 7.8%. Example 10 Propylene homopolymerization was carried out using the continuous apparatus shown in FIG. From pipe 1 to storage tank 7 with a capacity of 100 and equipped with a stirrer,
Purified n-hexane 30 kg/hr, diethylaluminium chloride 180 g/hr from pipe 2 , and titanium-containing composition (a) 91 g/hr from pipe 3 were supplied, and the prepolymer was heated to 7 g/g at a temperature of 50°C with stirring. - In order to form a composition, propylene was supplied from piping 5 , and hydrogen was supplied from piping 6 so that the gas phase hydrogen concentration in storage tank 7 with a stirrer was 4.0% by volume to continuously create a catalyst system. A polymerization vessel 9 with a capacity of ^30M3 is supplied with a pump 8 .
1596 kg of n-hexane is reused after the polymerization reaction containing the catalyst in the storage tank 7 and the soluble polymer is supplied with hydrogen from pipe 10 , propylene from pipe 12 , and catalyst from pipe 18 so that the gas phase hydrogen concentration is 2.5% by volume. hr,
and n-hexane 570 removed by scrubber 24
Kg/hr was supplied. Polymerization was carried out at a total pressure of 20 kg/cm ² G and a temperature of 70°C. A polymerization slurry containing a soluble polymer, an insoluble polymer, a catalyst, n-hexane, propylene, etc. was discharged from the polymerization vessel 9 to a flash drum 15 via a control valve 14 . Unreacted propylene separated in the flash drum 15 is circulated to the polymerization vessel 9 via a heat exchanger 16 . The polypropylene slurry from which unreacted propylene has been separated is introduced into a centrifuge 17 by a pump 16 . In this centrifuge 17 , a wet cake of insoluble polymer (polypropylene) (1000 Kg/hr) and n-hexane [600 Kg/hr (including 9 Kg/hr of soluble polymer)], and a wet cake of n-hexane [1596 Kg/hr]
(including 23.9Kg/hr of soluble polymer)]. The former wet cake is contacted with heated nitrogen gas,
Air flow drying was carried out in a pipe 21 , and the dried polypropylene powder was separated in a cyclone 22 . The latter is piping 18
The polymer is circulated via the pump 19 to the polymerization vessel 9 and reused as a polymerization solvent. Nitrogen gas containing n-hexane from the cyclone 22 is introduced into the scrubber 24 , and 570 kg/h of n-hexane is returned to the polymerization vessel 9 and reused for polymerization. The polypropylene powder containing 30 kg/h of n-hexane separated from the cyclone 22 was introduced into the stabilization tank 26 . The polypropylene powder introduced into the stabilization tank 26 is stabilized at 90° C. by introducing 265 g/hr of propylene oxide vapor from the pipe 27. The stabilized polypropylene powder was introduced into a fluidized fluidized dryer 28 , and trace amounts of volatile components were removed at a temperature of 100°C. 1000Kg/hr of polypropylene powder containing 500ppm of n-hexane from pipe 29
was gotten. The polypropylene was mixed with a stabilizer and evaluated for physical properties by injection molding. The results are shown in Table 6. Comparative example 9 DEAC 180g/without using storage tank 7 with stirrer
hr, that 95 g/hr of titanium-containing composition (a) was directly supplied to the main polymerization vessel 9 , and that the gas phase hydrogen concentration in the polymerization vessel 9 was
The operation was carried out under the same conditions as in Example 10 except that it was set to 2.0%. The physical properties of the produced polypropylene were evaluated in the same manner by injection molding. The results are shown in Table 6. Comparative example 10 DEAC 0.60Kg/without using storage tank 7 with agitator
hr, titanium-containing composition (a) 92g/hr was directly supplied to the polymerization vessel 9 , purified n-hexane 2166Kg/hr
Example 10 except that hr was supplied from the pipe 11 , and the reused n-hexane containing the catalyst-soluble polymer in the pipe 18 and the n-hexane removed by the scrubber 24 were not returned to the polymerization vessel 9 . It was operated under the same conditions. The physical properties of the produced polypropylene were evaluated in the same manner by injection molding. The results are shown in Table 6. 【table】

[Brief explanation of drawings]

Figures 1 and 2 show a continuous propylene polymerization process in which the polymerization solvent is completely circulated. is a centrifuge, 22 and 38 are cyclones, 26 is a stabilization tank,
28 is a fluidized dryer, and 30 is a scrubber. FIG. 3 is a flow sheet explaining the present invention.

Claims (1)

[Claims] 1 Homopolymerization or copolymerization of propylene using a catalyst system consisting of a titanium-containing composition and organoaluminum, and removing a solvent-insoluble polymer from the polymerization slurry and purifying a part or the entire amount of the separated solvent. In a method for producing polypropylene by recycling and reusing the titanium-containing composition in the polymerization process, 0.1 g per 1 g of the titanium-containing composition is added to a catalyst consisting of a titanium-containing composition and an organoaluminium.
A method for producing polypropylene, characterized by using a catalyst system subjected to a polymerization pretreatment to form the above propylene polymer.