JPS6326761B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to solution polymerization, in particular, to polymerization of various polymerizable monomers such as The present invention relates to an improvement in a type of polymerization method for polymerizing olefins, and more particularly to a polymerization method that allows easy control of the density and average molecular weight of the produced olefin polymer. In the present invention, the term "polymerization" may be used to include copolymerization, and similarly, the term "polymer" may be used to include copolymers. The above-mentioned type of polymerization method is known as one type in which a polymer is produced by polymerizing various polymerizable monomers. For example, taking the polymerization of olefins as an example, inert hydrocarbons and/or olefins to be polymerized are used as a medium that forms a liquid phase under reaction conditions, and the olefin polymers formed are dissolved in the liquid medium. A method of polymerizing olefins under such conditions is known. This method is particularly suitable for producing medium- and low-density grade ethylene copolymers, which are difficult to carry out slurry polymerization. When carrying out this type of solution polymerization,
In order to obtain a polymer with good homogeneity, it is generally preferable to carry out the polymerization under conditions in a non-two-phase separation region that exhibits a uniform liquid phase between the upper cloud point and the lower cloud point. It is common to carry out polymerization. However, when attempting to produce high molecular weight polymers by these types of solution polymerization techniques, the solution viscosity of the polymerization system increases, making it difficult to remove the polymerization heat, pump the product, and process the polymerization system. Stirring and mixing cannot be performed smoothly. For this reason, it is forced to operate in a state where the polymer concentration is diluted, and as a result, there are problems with disadvantages such as a decrease in production capacity per unit volume of the polymerization vessel and an increase in polymer separation cost. The present inventors conducted research in order to develop an improvement method that avoids the above-mentioned disadvantages in solution polymerization. As a result, solution polymerizations of the type described above are carried out under conditions in the two-phase separation region above the upper cloud point, where polymerization uniformity would be expected to be lost, but with the exception that both phases are in a well-dispersed state of mixing. By carrying out the polymerization under sufficient stirring conditions, it is possible to create a dispersion-mixed state such as a droplet dispersion system with a higher concentration of polymer in a liquid phase with a lower concentration of polymer. This is presumed to be due to the formation of a reaction system, but it was discovered that an improvement could be achieved in which the above-mentioned troubles could be conveniently overcome without impairing the uniformity of polymerization, and
It has already been proposed in Publication No. 58-7402. This method is
To significantly increase the solution viscosity of a polymerization system by leading the produced polymerization liquid to a separation zone, separating the phases, collecting a polymer-concentrated liquid phase, and recycling and reusing the polymer-diluted liquid phase in a polymerization tank. without pumping the product,
It was a rational process for producing polymers because the stirring and mixing of the polymerization system and the removal of polymerization heat could be carried out smoothly. The present inventors conducted studies with the aim of further improving the above-mentioned polymerization process and developing a more rational process, and found that the polymerization system inside the polymerization tank is in the two-phase separation region above the upper cloud point. When performing polymerization in a polymerization process consisting of a polymerization tank in which both phases are dispersed and stirred, the polymer dilute solution obtained by separating the polymerization product liquid into two liquid phases contains low molecular weight polymers, especially low molecular weight polymers. During the production of polyolefins by polymerizing olefins, low-density, low-molecular-weight polymers are selectively dissolved, so a part of the polymer dilute liquid phase is recycled and reused in the polymerization system, and the remaining part is By removing it from the polymerization system, the density and molecular weight distribution of the resulting polymer can be easily adjusted;
Alternatively, the inventors have discovered that when the densities of the produced polymers are the same, a high-quality polymer can be obtained because the low-density, low-molecular-weight polymer has been removed, and the present invention has been achieved. To summarize the invention, the present invention provides a process for polymerizing olefin monomers in a medium that is in a liquid phase under reaction conditions, and under conditions such that the olefin polymer formed is soluble in the medium. i) The polymerization is carried out in a polymerization system in which the interior of the polymerization tank is in a two-phase separation region condition above the upper cloud point, and both phases are dispersed and mixed, (ii) the polymerization product liquid in the polymerization tank is (iii) collecting the olefin polymer concentrated liquid phase; and collecting the olefin polymer concentrated liquid phase; and (iv) recycling 40 to 95% by weight (A) of the dilute olefin polymer liquid phase to the polymerization tank, and reusing 60 to 5% by weight of the dilute olefin polymer liquid phase. %(B) is extracted from the polymerization system, and the olefin polymer dilute liquid phase (B) is extracted from the polymerization system.
The gist of the invention is a method for polymerizing olefin monomers, which is characterized in that a low molecular weight, low density olefin polymer contained in the olefin monomer is removed. The above objects and many other objects and advantages of the present invention will become more apparent from the following description. Although the method of the present invention can be advantageously applied to the polymerization of any various monomers that can be solution polymerized and exhibit an upper cloud point, the polymerization method of the present invention will be explained in more detail below using the polymerization of olefins as an example. do. When carrying out the polymerization method of the present invention, various transition metal-containing catalysts, such as those conventionally proposed for medium-low pressure methods, can be used. As such a catalyst, for example, a transition metal-containing catalyst formed from a transition metal compound catalyst component and an organometallic compound catalyst component of a metal from Group 1 to Group 3 of the periodic table can be used. The transition metal compound catalyst component is a compound of a transition metal such as titanium, vanadium, chromium, zirconium, etc., and may be liquid or solid under the conditions of use. These do not need to be a single compound, and may be supported on other compounds or mixed. Furthermore, it may be a complex compound or composite compound with other compounds. The preferred component is a highly active transition metal compound catalyst component that can produce olefin polymer of 5000 g or more, especially 8000 g or more per mmol of transition metal, and a typical example thereof is a highly active transition metal compound catalyst component that can produce olefin polymer of 5000 g or more, especially 8000 g or more per mmol of transition metal. An example may be an activated titanium catalyst component. for example,
A solid titanium catalyst component containing titanium, magnesium, and halogen as essential components, containing amorphous magnesium halide, and having a specific surface area of preferably about 40 m 2 /g or more, particularly preferably about 40 m ² /g or more. 80 to about 800 m ² /g can be exemplified. It may also contain electron donors such as organic acid esters, silicate esters, acid halides, acid anhydrides, ketones, acid amides, tertiary amines, phosphoric esters, phosphites, ethers, and the like. This titanium catalyst component is, for example,
It contains about 0.5 to about 10% by weight of titanium, especially about 1 to about 8% by weight, and the titanium/magnesium (atomic ratio) is about 1/2 to about 1/100, especially about 1/3 to about 1/50, Halogen/titanium (atomic ratio) from about 4 to about 100, especially from about 6 to about 80,
electron donor/titanium (molar ratio) from 0 to about 10;
Particularly preferred is one in the range of 0 to about 6. Alternatively, as such a titanium catalyst component,
An example of a titanium catalyst component is a combination of a magnesium compound dissolved in a hydrocarbon solvent and a liquid titanium compound in the presence of an electron donor such as an alcohol. The organometallic compound catalyst component is an organometallic compound having a bond between a metal of Group 1 to 3 of the periodic law and carbon, and examples thereof include organic compounds of alkali metals and organometallic compounds of alkaline earth metals. , organic aluminum compounds, etc.
For example, alkyllithium, aleem sodium, alkylmagnesium, arylmagnesium, alkylmagnesium halide, arylmagnesium halide, alkylmagnesium hydride, trialkylaluminum, alkylaluminum halide, alkylaluminum hydride, alkylaluminum alkoxide, alkyllithium aluminum, and mixtures thereof. For example, In addition to the above two components, for the purpose of adjusting stereoregularity, molecular weight, molecular weight distribution, etc., hydrogen, halogenated hydrocarbons, electron donor catalyst components such as organic acid esters, silicate esters, carboxylic acid halides,
Carboxylic acid amides, tertiary amines, acid anhydrides, ethers, ketones, aldehydes, etc. may also be used. This electron donor component may be used in the form of a complex compound (or addition compound) formed in advance with the organometallic compound catalyst component during polymerization, or may be used in the form of a complex compound (or addition compound) formed in advance with the organometallic compound catalyst component. It may also be used in the form of a complex (or addition compound) with other compounds. Examples of olefins used in polymerization include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene,
1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 3-methyl-1-butene, 3-methyl-1-pentene, 4-methyl-1
-pentene, 4,4-dimethyl-1-pentene,
Butadiene, 1-isoprene, 1,4-hexadiene, dicyclopentadiene, 5-ethylidene-
Examples include 2-norbornene and 1,7-octadiene. These can be used alone or
A mixture of two or more types may be used. In particular, the present invention provides homopolymers of ethylene or
Suitable for producing resinous ethylene copolymers containing 90 mol% or more. The polymerization of olefins is carried out under conditions such that the olefin polymer formed is dissolved in a medium that is in a liquid phase under the reaction conditions. Examples of the medium used as a polymerization solvent include inert hydrocarbons and/or olefins used in polymerization. Examples of inert hydrocarbons include aliphatic hydrocarbons such as propane, butane, pentane, hexane, heptane, octane, nonane, decane, dodecane, and kerosene; for example, cyclopentane,
Examples include alicyclic hydrocarbons such as methylcyclopentane, cyclohexane, and methylcyclohexane; aromatic hydrocarbons such as benzene, toluene, and xylene; or a mixture of two or more of these components. . In the method of the present invention, polymerization is carried out in a multistage polymerization tank that satisfies the conditions that the polymer formed forms two liquid phases and is dissolved and dispersed in a medium that forms a liquid phase under reaction conditions. At this time, the polymerization system inside each polymerization tank is in a two-phase separation region above the upper cloud point, and both phases are in a dispersed and stirred mixed state. The resulting polymer solution produced in each polymerization tank is then led to a separation zone where it is separated into two liquid phases consisting of a polymer-rich liquid phase and a polymer-dilute liquid phase. It is recycled and the polymer concentrated liquid phase is collected. At that time, a part of the polymer dilute liquid phase, specifically in the range of 20 to 98% by weight, preferably 40 to 95% by weight, is recycled to the polymerization tank, and the remaining polymer dilute liquid phase, specifically An amount in the range of 80 to 2%, preferably 60 to 5% by weight of the total polymer dilute liquid phase is removed from the polymerization system. By treating the polymer dilute liquid phase removed from the polymerization system using a conventional method such as flash distillation, the medium is recovered, and the recovered medium is recycled and reused in the polymerization system of the polymerization tank, and can also be recycled to the polymerization system in the polymerization tank. The low molecular weight polymer recovered as a polymer is removed from the polymerization system. In the case of polyolefin polymerization, low density, low molecular weight polymers are removed. In the method of the present invention, monomers, catalysts, and media are supplied individually or as a mixture of two or more to the polymerization tank constituting the process, and polymerized under the conditions described below. In the method of the present invention, details of the polymerization process and conditions for the polymerization reaction are as follows. The temperature of polymerization is selected in such a range that phase separation above the upper cloud point is observed. The upper cloud point is
Although it depends on the type and mutual ratio of liquid phase components in the polymerization system, experimentally, the transmitted light is measured,
It can be easily determined as the temperature at which the transmitted light intensity rapidly attenuates. At temperatures between the lower and upper cloud points, the polymer dissolves in a homogeneous liquid phase, but at temperatures above the upper cloud point, a concentrated solution phase of the polymer and a dilute polymer phase occur. Phase separates into solution phase. In general, the higher the temperature, the higher the concentration of the polymer in the concentrated solution phase, and conversely, the lower the concentration of the polymer in the dilute solution phase. The two-phase separation region can vary depending on not only the temperature but also the type of polymer in which monomers are formed, the amount ratio, the type of solvent, the pressure of the reaction system, and other conditions, so it depends on these implementation conditions. Therefore, by using the above-mentioned transmitted light measurement method, the conditions of the two-phase separation region above the upper cloud point can be easily determined in advance experimentally. From the point of view of polymerization operations, the higher the polymer concentration in the concentrated solution phase and the higher the average molecular weight of the polymer, the more viscous it becomes, so the stirring power required to uniformly disperse the concentrated solution phase in the dilute solution phase also increases. However, it also tends to adhere to the stirring blades and polymerization walls.
Trouble can be prevented by modifying the shape of the stirring blade. On the other hand, from the viewpoint of separation operations, the larger the density difference between the two phases, the better the separation efficiency, which facilitates the operations required for post-processing operations and reduces costs. The actual polymerization temperature should be determined by taking into consideration various factors such as the advantages and disadvantages of such operations, as well as changes in catalyst activity due to temperature and equipment costs associated with increases and decreases in operating pressure. It is preferred to select a temperature between about 200° C. above the upper cloud point and in particular about 10° C. above the upper cloud point and about 150° C. above. Further, when using a titanium catalyst component highly activated by a magnesium compound as described above, it is preferable to carry out the polymerization at a temperature range of about 100 to about 300°C, particularly about 120 to about 250°C. The concentration of the olefin polymer varies depending on the molecular weight of the olefin polymer, but is adjusted to a range of about 10 to about 1000 g/, more preferably about 50 to about 200 g/in the combined state of both liquid phases. It is industrially advantageous to do so. The polymerization pressure is preferably in the range of, for example, atmospheric pressure to about 150 kg/cm ² , particularly about 2 to about 70 kg/cm ² . Hydrogen optionally used in the polymerization is preferably used in an amount of, for example, about 0.0001 to about 20 mol, particularly about 0.001 to about 10 mol, per 1 mol of olefin. When using a transition metal compound catalyst component, an organometallic compound catalyst component, an electron donor catalyst component, etc. as described above, the transition metal compound catalyst component is approximately
0.0005 to about 1 mmol, especially about 0.001 to about 0.5 mmol, of the organometallic compound catalyst component,
The metal/transition metal (atomic ratio) is about 1 to about
2000, particularly preferably from about 1 to about 500. Further, the electron donor catalyst component is preferably used in a proportion of 0 to about 1 mol, particularly 0 to about 0.5 mol, per 1 mol of the organometallic compound catalyst component. In the method of the present invention, in addition to carrying out the polymerization under conditions in the two-phase separation region above the upper cloud point, the polymerization is carried out in a state where both phases are dispersed and mixed so that the concentrated phase of the polymer is well dispersed in the dilute phase. The stirring conditions are as follows. If the stirring is insufficient, a dilute phase clearly appears in the upper phase portion, which impairs the uniformity of polymerization, which is not preferable. Therefore, stirring conditions are adopted such that such a separated phase does not appear. By performing polymerization in a well-dispersed state in this way, the polymerization rate is lower than when performing homogeneous phase solution polymerization at the same polymer concentration.
It is possible to carry out polymerization in a state where the viscosity is actually low, and even when producing a high molecular weight polymer, the polymerization can be carried out under relatively high concentration conditions. Advantageously, the olefin polymerization is carried out continuously. For example, it is possible to adopt a method in which the required raw materials are continuously supplied to the polymerization vessel, while the polymerization product liquid is continuously extracted so that the volume of the polymerization vessel is constant. At this time, the operating conditions may be such that a gas phase portion exists, or the operating conditions may be such that a discharge-filling type operation is performed. The extracted polymer solution is introduced into a separation zone and is separated into a polymer-concentrated liquid phase in the lower phase and a dilute polymer liquid phase in the upper phase. Phase separation can be easily performed by omitting stirring as in a polymerization vessel, and
It may be heated if necessary. Of course, the separation band is
It is necessary to be under phase separation region conditions above the upper cloud point, and therefore it is advantageous to maintain conditions such as temperature, pressure, etc. similar to those of the polymerization vessel, for example. It is not necessary to completely separate the phases; for example, the two phases may be separated in a state in which a part of the concentrated phase and the dilute phase are mixed together. Part or all of the polymer diluted liquid phase in the upper phase is recycled and reused in the polymerization reaction. At this time, if the material is cooled in advance before being introduced into the polymerization zone, the heat of polymerization can be effectively removed. In other words, compared to cooling the polymerization product liquid itself, the phase-separated polymer thinner phase has a lower viscosity, so the heat exchange effect in the cooler is higher, so it is less efficient in terms of thermal energy and industrial efficiency. This is extremely advantageous for practical implementation. Furthermore, since a highly concentrated polymer solution can be obtained by simply performing phase separation, operations required for polymer separation can be facilitated and separation costs can be reduced. When the main part of the separated upper phase polymer dilute liquid phase is recycled and reused in the polymerization reaction, when the method of the present invention is carried out in a single polymerization tank, it must be recycled and reused to the polymerization tank. However, when carrying out the process using a plurality of polymerization tanks, it is not necessarily necessary to circulate and reuse the polymerization product liquid to the same tank from which it was taken out, but it can also be circulated and reused to other polymerization tanks. After removing inert hydrocarbons and dissolved olefins from the concentrated phase of the polymer obtained from the final stage polymerization tank by appropriately employing various operations such as heating, flashing, and vacuum suction, can be supplied to produce polymer pellets. According to the present invention, high-quality polymerization and polymer separation can be performed labor-savingly and economically with omitted operations and equipment. Next, examples will be shown. Example 1 <Catalyst Preparation> 10 mol of commercially available anhydrous magnesium chloride was suspended in dehydrated and purified hexane 50 in a nitrogen stream, 60 mol of ethanol was added dropwise over 1 hour with stirring, and the mixture was reacted for 1 hour at room temperature. . 28 mol of diethylaluminum chloride was added dropwise to this at room temperature, and 1
Stir for hours. Subsequently, 75 mol of titanium tetrachloride was added, and the system was heated to 80° C. and the reaction was carried out with stirring for 3 hours. The generated solid portion was separated by decantation, washed repeatedly with purified hexane, and then made into a hexane suspension. The concentration of titanium was determined by titration. <Polymerization> Using continuous polymerization reactor A with a diameter of 50 cmφ and a volume of 200 as shown in Figure 1, a dehydrated and purified solvent (n-hexane containing 15 vol% of methylcyclopentane) was added to diethyl aluminum chloride from tube 3 at 75/hr.
10 mmol/hr, converting the supported catalyst into Ti,
0.8 mmol/hr was continuously supplied through tube 4, and in the polymerization vessel, ethylene was simultaneously supplied at a rate of 16 kg/hr, 4-methyl-1-pentene 7.3 kg/hr, and hydrogen 25/hr through tubes 1 and 2, respectively. Continuous supply, polymerization temperature 180℃,
Polymerization was carried out under conditions of a total pressure of 30 Kg/cm ² -G and a residence time of 30 minutes. In polymerization reactor A, the product liquid containing the ethylene copolymer produced is continuously discharged through pipe 5 at a rate of 120% solvent/hr, at a temperature of 180°C and a pressure of 30kg/hr.
cm ² -G was supplied to two-phase separator B as it was. The product liquid containing the ethylene copolymer supplied to the two-phase separator B is separated into phases, and the concentrated phase containing most of the ethylene copolymer is transferred from the bottom to the pipe 7 at a rate of 60/hr of solvent.
through heater G and hopper C through heater G.
The solvent is evaporated and the ethylene copolymer is separated.
Obtained at a rate of 16.2Kg/hr. The obtained ethylene copolymer has an MI of 2.2 g/10 min and a density of 0.9275 g/cm ²
It was hot. On the other hand, the dilute liquid phase obtained in the two-phase separator B is extracted from the upper part of the separator B through a pipe 6 at a rate of 60/hr of solvent, and is passed through a cooler J to an extent that the dissolved ethylene copolymer does not precipitate. After cooling to , 50% of the dilute liquid phase was recycled directly to polymerization reactor A. Drum D evaporates and separates the remaining 50% of the dilute liquid phase into solvent and ethylene copolymer.
0, and after condensing in condenser I, polymerization reactor A
was recycled. Pipe 1 from the bottom of drum D
1, a low molecular weight ethylene copolymer was extracted. Solvents containing ethylene copolymer were sampled from pipes 5, 6, and 7 using sampling containers, and the ethylene copolymer concentration in each was measured.
Tube 6 is 6g ethylene copolymer/-solvent, tube 7 is
270g ethylene copolymer/-solvent. or,
Analysis of the ethylene copolymer contained in the dilute liquid phase in tube 6 revealed that the average molecular weight was approximately 5000 and the density was
It had a low molecular weight and low density of 0.910 g/cm ³ . By evaporating 50% of the dilute liquid phase and recycling it to the polymerization reactor, it was possible to remove approximately 1.5% of the low molecular weight ethylene copolymer based on the total ethylene copolymer produced. Figure 2 shows the MI of ethylene copolymer and the concentration of ethylene copolymer in the dilute liquid phase at that time, and Figure 3 shows the MI of ethylene copolymer and the concentration of ethylene copolymer in the dilute liquid phase at that time. The average molecular weight results of the coalescence are shown. Comparative Example 1 Comparative Example 1 is a comparative example in which 100% of the polymer dilute liquid phase was directly recycled to the polymerization reactor. <Catalyst adjustment> Same as Example 1. <Polymerization> Using continuous polymerization reactor A with a diameter of 50 cmφ and a volume of 200 as shown in Figure 1, a dehydrated and purified solvent (n-hexane containing 15 vol% of methylcyclopentane) was added to diethyl aluminum chloride from tube 3 at 75/hr.
10 mmol/hr, converting the above supported catalyst into titanium.
0.8 mmol/hr was continuously supplied from tube 4, and at the same time in the polymerization vessel, ethylene 16 kg/hr, 4-methyl-1-pentene 7.3 kg/hr, and hydrogen 25 kg/hr were continuously supplied from tubes 1 and 2, respectively. Supply, polymerization temperature 180℃,
Polymerization was carried out under conditions of a total pressure of 30 Kg/cm ² -G and a residence time of 30 minutes. The product liquid containing the ethylene copolymer purified in the polymerization reactor A was continuously discharged through the tube 5 at a rate of 120% solvent/hr, at a temperature of 180°C and a pressure of 30Kg/cm ² -.
G was supplied to the two-phase separator B as it was. The product liquid containing the ethylene copolymer supplied to the two-phase separator B is phase-separated, and the concentrated liquid phase containing most of the ethylene copolymer is discharged from the bottom through the pipe 7 at a rate of 60% solvent/hr, and is then transferred to the heater. The solvent is evaporated and separated in hopper C through G, and the ethylene copolymer is
Obtained at a rate of 16.2Kg/hr. The obtained ethylene copolymer had an MI of 2.3 g/min and a density of 0.9270 g/cm ³ . On the other hand, the dilute liquid phase obtained in two-phase separator B is extracted from the upper part of separator B through pipe 6 at a rate of 60/hr of solvent, passed through cooler F, and after cooling, 100% of the dilute liquid phase is directly extracted. It was then recycled to polymerization reactor A. Sampling the solvent containing the ethylene copolymer from pipes 5, 6, and 7 in sampling containers,
When the concentration of each ethylene copolymer was measured,
Tube 5 is 138g ethylene copolymer/-solvent, tube 6
is 6g ethylene copolymer/-solvent, tube 7 is 270
g ethylene copolymer/-solvent. Films with a thickness of 30 μm were prepared from the ethylene copolymers obtained in Example 1 and Comparative Example 1, respectively.
When compared, the strength and optical properties are almost the same, but the method of Example 1 yields an ethylene copolymer with improved blocking properties, and the low-density, low-molecular-weight ethylene copolymer is removed. I understand. Table 1 shows the data. 【table】

[Brief explanation of the drawing]

FIG. 1 shows an example of an apparatus for carrying out the polymerization method of the present invention. A: Polymerization reactor, B: Separator,
C: hopper, D: evaporation drum, E: drum,
F: Heater, G: Heater, H: Condenser, FIG. 2 shows the relationship between the MI of the ethylene copolymer in the concentrated liquid phase and the concentration of the ethylene copolymer in the dilute liquid phase in Examples. FIG. 3 shows the relationship between the MI of the ethylene copolymer in the concentrated liquid phase and the average molecular weight of the ethylene copolymer in the dilute liquid phase in Examples.

Claims (1)

[Scope of Claims] 1. A method of polymerizing an olefin monomer in a medium that forms a liquid phase under reaction conditions under conditions such that the olefin polymer to be formed is dissolved in the medium, comprising: (i) the polymerization; (ii) conduct the polymerization product liquid in the polymerization tank to a separation zone; (iii) collecting the olefin polymer concentrated liquid phase and extracting the olefin polymer from the olefin polymer concentrated liquid phase; and (iv) 40 to 95% by weight (A) of the dilute olefin polymer liquid phase is recycled and reused in the polymerization tank, and 60 to 5% by weight (B) of the dilute olefin polymer liquid phase is separated. is extracted from the polymerization system, and the olefin polymer dilute liquid phase (B) is extracted from the polymerization system.
A method for polymerizing an olefin monomer, comprising: removing a low molecular weight, low density olefin polymer contained in the olefin monomer.