JPS6365081B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing an α-olefin polymer and an apparatus therefor. Polyethylene, polypropylene, polybutene
1. α-olefin polymers and copolymers such as poly-4-methylpentene-1, ethylene-propylene copolymer, ethylene-butene-1 copolymer, and ethylene-octene-1 copolymer are polymerized by coordination polymerization. It is produced industrially by polymerizing α-olefins or mixtures of α-olefins in a hydrocarbon solvent using a catalyst. Such coordination polymerization catalysts used include transition metal compounds and organometallic compounds as major constituents. As the transition metal compound, for example, a transition metal halide of Group 1, such as titanium halide, vanadium halide, vanadium oxyhalide, etc., is used. As the organometallic compound, an organoaluminum compound such as an alkyl aluminum or an alkyl aluminum chloride, or an organoaluminum-magnesium complex such as an alkyl aluminum-magnesium complex or an alkyl alkoxy aluminum-magnesium complex is used. The manufacturing process includes solution polymerization, which is carried out at a temperature at which the produced polymer dissolves in a hydrocarbon solvent, and a solution polymerization method, in which the produced polymer is not substantially dissolved in the hydrocarbon solvent, and the polymer is present in the form of solid particles. A slurry polymerization method that is carried out at temperatures such as In any of the above processes, the biggest problem is how to remove the large amount of polymerization heat generated during polymerization. Especially ethylene
It has a heat of polymerization of 800 to 900 Kcal/Kg, which is the largest value among α-olefins, making it particularly difficult to remove the heat of polymerization. The most common polymerization apparatus used in solution polymerization and slurry polymerization is a stirred tank polymerization apparatus. It is used. However, when the capacity of the polymerization reactor is increased, the heat transfer area of the jacket and coil does not increase compared to the capacity of the polymerization reactor, so the amount of heat removed from these external sources becomes extremely insufficient. For this reason, it is difficult to remove heat from large industrial polymerization vessels, and the production volume per unit volume of the polymerization vessel cannot be increased. Various methods have been proposed to solve this problem. Another polymerization apparatus for the slurry polymerization method is an annular reactor with a smooth curved part and no internal obstructions, as shown in Japanese Patent Publication No. 37-10087, Japanese Patent Publication No. 39-5784, and U.S. Patent No. 3,257,963. Are known. Since a tube with a large surface area per unit volume is used in the reactor, the heat removal ability is superior to the above-mentioned stirred tank polymerization reactor. Another problem with the process is the scale that develops within the reactor. In slurry polymerization, if there is insufficient mixing in the reactor, the polymerization temperature locally increases, causing polymer particles to fuse and adhere to the reactor wall, or in polymerization systems with a gas phase. When a solid polymer is formed in a reaction zone that does not come into contact with the solvent, the molten polymer often adheres to the walls of the reactor due to insufficient heat conduction. Once such scale occurs, it tends to grow, and the polymerization vessel will eventually become clogged with scale. In the solution polymerization method, when a cooling medium lower than the dissolution temperature of the polymer in the solvent is passed through the jacket or coil of the reactor, the polymer often solidifies, adheres, and grows on the surface of the jacket or coil. If the polymer adheres, heat conduction through the jacket or coil becomes insufficient, which not only hinders control of polymerization temperature but also adversely affects the uniformity of the resulting polymer. Furthermore, if the monomer or solvent is supplied at a temperature far lower than the melting temperature of the polymer, problems often arise in that the polymer solidifies and precipitates at the supply port, resulting in clogging. The present inventors have discovered that the heat of polymerization can be efficiently removed, the production volume per unit volume of the reactor is extremely large compared to conventional known reactors, and α-olefin polymers can be produced without the generation of scale. As a result of intensive research into methods and devices for this purpose, the present invention has been achieved. That is, the present invention provides a method for continuously polymerizing at least one α-olefin monomer in a tubular annular reactor in the presence of a coordination polymerization catalyst and a hydrocarbon solvent. A method for producing an α-olefin polymer, characterized in that the flow of the mixture is subdivided into a large number of independent flows and cooled during circulation in the reactor, and the present invention also provides a method for producing an α-olefin polymer. - A polymerization apparatus having a tubular annular reactor in which an olefin monomer is continuously polymerized in the presence of a polymerization catalyst and a solvent and the reaction mixture is circulated within the reactor, wherein the reactor is a multi-tubular thermal reactor. A tubular cyclic reaction apparatus for polymerizing α-olefin monomers, comprising an exchanger and a tube, at least a portion of which is smoothly curved, connecting an inlet and an outlet of the heat exchanger. be. At least one α-olefin monomer used in the present invention includes, for example, ethylene, propylene, butene-1, pentene-1, hexene-1, 4-methylpentene-1, heptene-1,
Includes octene-1, decene-1, etc. The α-olefin polymer of the present invention is a polymer obtained by polymerizing at least one of these α-olefin monomers. In addition, as a modifier, 1,4-hexadiene, 1,7-octadiene, ethylidenenorbornene, bicyclo-(2,2,1)-2,5-
It is also within the scope of the present invention to copolymerize a diene such as heptadiene, 1,4-butadiene, etc. with a small amount of α-olefin. As the coordination polymerization catalyst used in the present invention, all known catalysts suitable for the polymerization of the respective α-olefins can be used. For example, for the copolymerization of ethylene or ethylene with an α-olefin having 3 to 18 carbon atoms, a so-called Ziegler catalyst consisting of a combination of a transition metal compound of Group 1 and an organometallic compound of Group 1, silica, alumina, etc. Alternatively, high-activity catalysts that do not require catalyst removal, such as chromium oxide catalysts with silica/alumina as carriers, are being developed in recent years, such as the catalysts described in JP-A-53-40696 and JP-A-56-28206. 120～
An organic magnesium that shows high activity even at high temperatures of 350℃.
Catalysts synthesized from inorganic halides, titanium compounds and vanadium compounds can also be suitably used. In addition, for the copolymerization of polypropylene or polypropylene and ethylene, the so-called Natsuta catalyst, which combines titanium trichloride and an organoaluminum compound, is used, as described in U.S. Pat. Highly active catalysts that do not require extensive catalyst removal and provide high II PP can also be suitably used. Other α-olefins can also be polymerized using the same Ziegler-Natsuta catalyst as above. Hydrocarbon solvents that can be used in the present invention include chain saturated hydrocarbons such as butane, isobutane, pentane, hexane, heptane, octane, isooctane, dodecane, and undecane, alicyclic carbonated hydrocarbons such as cyclopentane, methylcyclopentane, and cyclohexane It is one kind or a mixture of one or more kinds of aromatic hydrocarbons such as hydrogen, benzene, and toluene. Also,
It is also possible to use α-olefins such as propylene, butene-1, hexene-1, octene-1, 4-methylpentene-1, etc. as hydrocarbon solvents in the present invention. Next, the present invention will be explained based on the drawings. A reactor and a method for controlling the reactor for producing an α-olefin polymer by a solution polymerization method carried out at a temperature at which the produced polymer dissolves in a hydrocarbon solvent are shown in FIGS. 1 and 2, respectively. The reactor shown in Fig. 1 has a shell-and-tube heat exchanger 1, a straight pipe section 2 with a jacket, an L-shaped short pipe 3, and a straight pipe section with different inner diameters for connecting the shell-and-shell heat exchanger. This is a tubular annular reactor (hereinafter referred to as an annular reactor) consisting of a tube 4. A large number of thin single tubes 5 are arranged in the shell-and-tube heat exchanger 1, and the circumference of the tubes is filled with a cooling medium. Solvent and α from supply port 7
- Olefin, further a catalyst and a solvent from the supply port 8,
Further, hydrogen and the like as a molecular weight regulator are continuously supplied to the annular reactor at a constant rate from the supply port 7 as required. The interior of the annular reactor is filled with a polymerization solution, and the polymerization pressure is controlled so as to create a liquid-sealed state with substantially no gas phase. Propeller 1 of circulation axial flow pump 6
1, the feedstock and polymerization solution are intensively mixed and transported upwards into the shell-and-tube heat exchanger 1. The polymerization solution entering the shell-and-tube heat exchanger 1 is dispersed, passes through the capillary tubes 5 in the heat exchanger, and then joins again and circulates in the annular reactor. Further, a portion of the polymerization solution is continuously extracted from the discharge port 12. The discharge rate is controlled by a control valve (not shown) at the end of the outlet so that the pressure within the reactor remains constant. Most of the polymerization heat generated is transferred to the shell-and-tube heat exchanger 1.
The rest is removed by the cooling medium in the single-tube jacket 9. In Fig. 1, only four thin single tubes 5 are shown in the shell-and-tube heat exchanger 1, but this is to simplify the diagram, and in reality there are many. A single tube is accommodated. The inner diameter of the single tube 5 is preferably 1/4 inch to 3 inches. If it is less than 1/4 inch, the pressure loss will be large and the power of the pump will be large.
Moreover, if it exceeds 3 inches, the heat transfer area per unit volume of the tube is small, and there is a drawback that the volume of the heat exchanger becomes too large to ensure the required heat transfer area. There is no particular restriction on the length of the single tube 5, but an appropriate length should be selected based on the relationship between the pressure loss in the single tube 5, the pressure loss throughout the annular reactor, and the performance of the pump 6, especially the circulating flow rate and the pump head. Ru. Although two supply ports 7 and 8 are shown in FIG. 1, the supply ports are not necessarily limited to two locations, and the supply ports may be provided at several locations on the suction port side of the pump 6. When carrying out a polymerization reaction using the apparatus shown in Figure 1,
The polymerization temperature is the temperature at which the produced polymer dissolves in the hydrocarbon solvent, and the temperature depends on the type of hydrocarbon solvent, but for example, ethylene polymer or ethylene-α-olefin copolymer containing 80% by weight or more of ethylene. 110℃ or higher for coalescence, preferably 130℃
to 350℃, and for polybutene-1 polymer
The temperature is preferably 50°C or higher, and 100°C or higher for ethylene-propylene ternary copolymer rubber containing approximately equal amounts of ethylene and propylene and a diene such as ethylidenenorbornene as a third component. In addition, the polymerization pressure depends on the type of monomer used, the concentration of monomer in the polymerization solution, the type of solvent, and the polymerization temperature, but the inside of the annular reactor is maintained in a liquid-sealed state with virtually no gas phase. In order to achieve this, it is preferable to operate at a pressure that is at least 3 kg/cm ² higher than the vapor-liquid equilibrium pressure of the polymerization solution. In particular, when producing an ethylene polymer or an ethylene-α-olefin copolymer containing 80% by weight or more of ethylene, it is preferable to operate at a pressure that is at least 5 kg/cm ² higher than the vapor-liquid equilibrium pressure. Polymerization at a pressure higher than the vapor-liquid equilibrium pressure promotes the dissolution or dispersion of the gaseous monomer in the hydrocarbon solvent,
Favorable conditions are provided for carrying out a homogeneous and rapid polymerization reaction. In addition, the viscosity of the polymerization solution is determined by the shear rate
2000cp or less at 500sec ^-1 , preferably 1000cp
It is as follows. If the viscosity exceeds 2000 cp, the heat transfer efficiency of the shell-and-tube heat exchanger will decrease, the pressure loss of the annular reactor will increase, and it will be difficult to dissolve or disperse the gaseous monomer in the hydrocarbon solvent. Various disadvantages arise, such as the inability of the catalyst to exhibit its inherent activity due to monomer diffusion rate limitation. The circulation flow rate of the annular reactor is at least 10 times the total feed flow rate of catalyst, solvent, and monomer. If the circulation flow rate is less than 10 times the supply flow rate, the heat transfer effect of the shell-and-tube heat exchanger will be reduced, and the features of the present invention will not be exhibited, and the composition of the polymerization solution will be affected along the passage of the annular reactor. There is a temperature gradient, making it difficult to obtain a uniform polymer. Although FIG. 1 uses a propeller-type axial flow pump 6 to mix and circulate the polymer solution, it is within the scope of the present invention to provide other types of power.
For example, the propeller may be replaced with an impeller-shaped pump (Uzumaki pump). FIG. 2 shows a method for controlling pressure and temperature and a method for circulating a cooling medium when performing solution polymerization using the annular reactor shown in FIG. The feedstocks, such as catalyst, monomer, solvent, etc., are partially heated in a heat exchanger 13 before entering the annular reactor. The pressure in the annular reactor is detected by the PIC 14 and controlled by the opening degree of the control valve 15 at the outlet of the polymerization solution. Hot water as a cooling medium is supplied from a circulation hot water tank 16 to the multi-tubular heat exchanger 5 and the jacket 9 at a constant rate using a pump 17. A portion of the hot water leaving the annular reactor enters heat exchanger 13 to heat the feedstock. The polymerization temperature is controlled by the temperature of the feed material, and the feed temperature is controlled by the heat exchanger 13.
controlled by the amount of hot water supplied to the That is, the polymerization temperature is detected by the TIC 18, and if the detected polymerization temperature is lower than the set temperature, the valve 19
On the other hand, if the detected polymerization temperature is higher than the set temperature, the opening degree of the valve 19 is decreased and the flow rate of hot water is decreased. The hot water line coming out of the valve 19 and the hot water in the bypass line 20 are combined and sent to the circulation hot water tank 1.
Return to 6. The excess heat of the returned hot water is recovered as steam in the circulating hot water tank 16.
That is, the PIC 21 and the control valve 22 are used to keep the pressure and temperature of the circulating hot water tank constant. After the steam is used, it is returned to the tank as condensed hot water. As described above, when the reactor of the present invention is used in a solution polymerization process, (1) a high polymer production rate per unit volume of the reactor can be obtained, (2) a high polymer concentration is possible, and therefore, , it is possible to reduce the amount of hydrocarbon solvent used, (3) and the polymerization temperature can be lowered.
At temperatures above 100℃, the heat removed by the shell-and-tube heat exchanger can be used to heat the feedstock and generate steam, making it an extremely energy-saving process and of great industrial significance. big. The annular reactor of FIG. 1 can also be used in slurry polymerization processes in which polymerization occurs at temperatures such that the resulting polymer is not substantially soluble in the hydrocarbon solvent and is present in the form of solid particles. In the case of the slurry polymerization method, it is also possible to attach the discharge port 10 to the bottom of the annular reactor in front of the supply port 7, and to draw out the polymer slurry after concentrating it. When carrying out a slurry polymerization reaction in the apparatus shown in Figure 1, the polymerization temperature is such that the resulting polymer does not dissolve in the hydrocarbon solvent and exists in the form of solid particles, and the Depending on the type of hydrogen solvent, for example, ethylene polymer or ethylene-α-olefin copolymer containing 80% by weight or more of ethylene has a temperature of 110°C or less, polypropylene polymer or propylene-ethylene containing 70% by weight or more of propylene. For polymers, the temperature is below 90°C, preferably below 80°C, poly 4-methylpentene-1
The temperature is preferably 100°C or less. Although the polymerization pressure depends on the type of monomer used, the monomer concentration in the polymerization solution, the type of solvent, and the polymerization temperature, the inside of the annular reactor is maintained in a liquid-sealed state with virtually no gas phase. For this reason, it is preferable to operate at a hydraulic pressure that is at least 2 Kg/cm ² higher than the vapor-liquid equilibrium pressure of the polymerization solution. To prevent the formation of scale within the annular reactor, the polymerization solution must be maintained in a turbulent state at all locations within the annular reactor. The turbulent flow state in the present invention is a region where the Reynolds number is 2300 or more. Reynolds number (Re) is Re=
Defined by density x flow rate x diameter/viscosity. More preferably, the mixture is performed under conditions such that the Reynolds number is 10,000 or more. By carrying out slurry polymerization of α-olefin monomer using the annular reactor of the present invention, the production amount per unit volume of the reactor can be significantly improved.
Its industrial significance is extremely large. The features of the annular reactor of the present invention are more clearly exhibited when the scale of the reactor is increased, both in the solution polymerization method and in the slurry polymerization method. This is because, in the reactor of the present invention, the heat transfer area can be increased by increasing the reactor volume by increasing the number and length of the tubes without changing the inner diameter of the single tube in the tubular heat exchanger. It is possible to increase it proportionately. On the other hand, in a normal ring reactor, the reactor volume is proportional to the cube of the inner diameter of the tube, and the heat transfer area is proportional to the square of the inner diameter of the tube, so if you try to scale up, the heat transfer area will increase. This is because it becomes relatively small and it becomes increasingly difficult to remove heat. Examples of the present invention are shown below, but the present invention is not limited in any way by these examples. Example 1 Catalyst, ethylene, butene-1, cyclohexane and hydrogen were fed into a ring reactor of the type shown in Figure 1 and polymerization was carried out. The annular reactor used had a volume of 126 straight pipes and an L-shaped pipe with an inner diameter of 6 inches.
The inner diameter of the propeller part is 6 inches, and the inner diameter of the shell-and-tube heat exchanger is 16 cm. The shell-and-tube heat exchanger contains 20 single tubes with an inner diameter of 1 inch and a length of 2 meters, and its heat transfer area is 3.1 m ²
It is. For comparison, similar polymerization was carried out using an annular reactor of the same volume, without a shell-and-tube heat exchanger, consisting of straight tubes and L-shaped tubes with an inner diameter of 6 inches, and a propeller part with an inner diameter of 6 inches. I went. The operation results are shown in Table 1.

【table】

【table】

[Table] As is clear from Table 1, in Comparative Example 1 without a shell-and-tube heat exchanger, the production rate was 23Kg/hr, whereas in the cyclic reactor of the present invention, the production rate was 34Kg/hr, about 1.5 times higher. /
hr production rate was achieved. Furthermore, in the method of the present invention, the polymer concentration is 15% by weight.
Since the concentration is 1.5 times higher than that of 10% by weight in the comparative example, the amount of solvent per unit weight of polymer is 1.6 times higher.
It also has the advantage of reducing solvent purification costs. In addition, using the hot water circulation system shown in Figure 2, the feedstock is heated using hot water that passes through the annular reactor.
It was heated from 40℃ to 130℃, and then steam was generated in a hot water circulation tank. 160℃, 5Kg/ ^cm2
Approximately 7.7Kg/hr of G steam was generated. This corresponds to 0.22 kg of steam per kg of polymer produced.
This steam has sufficient pressure to be used for purposes such as refining solvents, so it has great advantages.
On the other hand, from the hot water of Comparative Example 1, a sufficient amount of heat required for heating the feedstock could not be obtained. In addition, in Example 1, the raw material supply temperature was set at 130°C and the hot water temperature was set at 160°C, which were higher than the solidification temperature of the produced polymer, so no scale was formed at all even during two months of long-term continuous operation. . Example 2 A catalyst, ethylene, and n-hexane were fed into a ring reactor of the type shown in FIG. 1, and polymerization was carried out. However, a leg-shaped outlet was attached to the bottom of the reactor in front of the outlet. The annular reactor used had a volume of 126
, the inner diameter of the straight tube and L-shaped tube is 6 inches, the inner diameter of the propeller part is 6 inches, and the inner diameter of the shell-and-tube heat exchanger is 16 cm. A shell-and-tube heat exchanger has a single tube with an inner diameter of 1 inch and a length of 2 meters.
It accommodates 20 tubes, and its heat transfer area is ^3.1m2 . For comparison, an inner diameter of 6 without a shell-and-tube heat exchanger
A similar polymerization was carried out using an annular reactor of the same volume, consisting of an inch-inch straight tube and an L-shaped tube, with a propeller section having an inner diameter of 6 inches. The polymer slurry concentration in both annular reactors was maintained at 25%, and the discharged polymerization solution allowed the polymer to settle in the legs, and a slurry with a slurry concentration of about 45% by weight was extracted. The operation results are shown in Table 2.

【table】

【table】

[Table] The feed amount of the catalyst [A] component in Table 2 is the number of moles of the titanium compound in the [A] component, and the amount of the catalyst [B]
The amount of component supplied was expressed in moles of triisobutylaluminum. Note that the catalyst [A] component was supplied as suspended in a solvent. As is clear from Table 2, in Example 2, 126
49Kg/hr of polymer can be produced using a ring reactor of
To maintain the temperature at ℃, only 25Kg/hr of polymer could be produced. Therefore, the annular reactor of the present invention has approximately twice the production capacity with the same reactor volume, and has extremely great industrial significance. As can be seen from the Lenoyles number, the inside of the annular reactor was in a sufficiently turbulent state, and no scale was generated at all even during two months of continuous operation. Example 3 Using the same apparatus as in Example 1, butene-1 was polymerized. The operation results are shown in Table 3. Table 3 Conditions for the annular reactor (1) With shell-and-tube heat exchanger (2) Volume of the annular reactor 126 (3) Volume of the shell-and-tube heat exchanger in the volume of the annular reactor 20 (4) Heat transfer area 5.1 m ² (5) Polymerization temperature 85℃ (6) Polymerization pressure 40Kg/cm ² (7) Temperature of heat transfer liquid (hot water) Inlet 75℃ Outlet 81℃ (8) Butene-1 supplied to the annular reactor 58Kg /hr Cyclohexane 153Kg/hr Catalyst (Note 1) [A] component 2.0mmol/hr [B] component 3.6mmol/hr (9) Temperature when feed material is supplied to the annular reactor 30℃ (Note 1) The catalyst is a patent The [A] component of Example 1 of No. 127888/1988 was replaced with AlEt ₃ as the [B] component. (10) Average residence time of polymerization solution 20 minutes (11) Circulating flow rate 1600/min Circulating flow rate 150 cm/sec (12) Multi-tube heat exchanger straight pipe 5 Flow rate and flow rate per tube 80/min 270 cm/sec ( 13) Discharge amount, composition, and characteristics of polymerization solution at outlet 12 Butene-1 18Kg/hr Cyclohexane 153Kg/hr Polymer 38Kg/hr 209Kg/hr Butene-1 conversion rate 68% Polymer concentration 17% by weight (14) Properties of coalescence Melt index (Note 2) 0.57g/10min Density (Note 3) 0.915g/ml

[Brief explanation of drawings]

FIG. 1 is a front view of the tubular annular reactor of the present invention, and FIG. 2 shows the pressure during use of the device of the present invention.
FIG. 2 is an explanatory diagram showing a temperature control method and a cooling medium circulation method. 1... Multi-tube heat exchanger, 2... Straight pipe section with jacket, 3... L-shaped short pipe, 4... Connecting pipe, 5...
...Thin single pipe, 6...Axial flow pump for circulation, 7,8...
... Supply port, 9 ... Jacket, 10 ... Discharge port,
11...propeller, 12...exhaust port.

Claims (1)

[Scope of Claims] 1. A method of continuously polymerizing at least one α-olefin monomer in a tubular ring reactor in the presence of a coordination polymerization catalyst and a hydrocarbon solvent, comprising:
A method for producing an α-olefin polymer, characterized in that the flow of the reaction mixture in the reactor is subdivided into a number of independent streams and cooled during circulation within the reactor. 2 A solution polymerization method in which polymerization is performed at a temperature at which the resulting polymer dissolves in a hydrocarbon solvent, and the viscosity of the polymer solution is
2000 centipoise or less, and the circulating flow rate of the polymer solution is at least 10 times the total feed flow rate of catalyst, solvent and monomer. 3. A slurry polymerization method in which polymerization is carried out at a temperature at which the produced polymer does not substantially dissolve in a hydrocarbon solvent and exists in the form of solid particles, and a patent claim in which a slurry solution of the produced polymer is circulated in the reactor in a turbulent state. The manufacturing method according to item 1. 4. The manufacturing method according to claims 1 to 3, wherein the at least one α-olefin monomer is ethylene alone or a mixture of ethylene and at least one α-olefin having 3 to 18 carbon atoms. . 5. The production method according to claim 2, wherein hot water of 100°C or higher is used as a cooling medium for the tubular annular reactor, and a part of the polymerization heat is recovered as steam. 6 In a polymerization apparatus having a tubular ring reactor in which an α-olefin monomer is continuously polymerized in the presence of a polymerization catalyst and a solvent and the reaction mixture is circulated within the reactor, the reactor is a multi-tubular reactor. A tubular cyclic reaction for polymerizing an α-olefin monomer, comprising a heat exchanger and a tube at least partially curved smoothly connecting an inlet and an outlet of the heat exchanger. Device.