JP2011057721A - Method for producing polyolefin, apparatus for producing the same, and polymerization device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a polyolefin, by which a desired polyolefin can easily be produced. <P>SOLUTION: A necessary amount of an olefin, a solvent, a catalyst, hydrogen gas, and the third component are supplied to a vaporization latent heat-removing style polymerization tank 210A of polymerization means 210, and then subjected to a solution polymerization. While the hydrogen concentration in a gas phase space in the polymerization tank 210A is kept at a constant value or while the feed flow rate of the hydrogen is kept at a constant value, the gas phase components of the polymerization tank 210A are cooled with the vaporization latent heat of a monomer and circulated to control the temperature of the polymerization solution in such a state as giving the intrinsic viscosity of the polyolefin having a desired molecular weight. The polymerization solution is subjected to the removal of evaporation components and then granulated in a pellet-like state. Thus, the polyolefin having a molecular weight giving a desired intrinsic viscosity can be produced by the simple control for adjusting the temperature, and a metallocene-based compound catalyst having high temperature dependency can be used to improve the production yield in the good response of the intrinsic viscosity on adjustment. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a polyolefin production method for producing a polyolefin using a catalyst, a production apparatus therefor, and a polymerization apparatus.

As a method for producing a polyolefin, a method is known in which an olefin is polymerized in the presence of hydrogen using a Ziegler catalyst or a Philips catalyst (see, for example, Patent Document 1).
The method described in Patent Document 1 includes the supply amount of olefin, hydrogen, catalyst and promoter in the olefin polymerization zone, the olefin concentration in the gas phase, the hydrogen concentration and pressure, and the temperature and liquid level in the liquid phase. Is detected. Also, the melt flow index of the polyolefin product flowing out from the polymerization zone is measured. Then, the MFR of the polyolefin instantaneously generated in the polymerization zone is estimated by a predetermined calculation using the detected value and the actually measured value, and the transition of the MFR value in the future is predicted. After that, based on the comparison between the predicted value and the target value, the target value of the hydrogen / olefin molar ratio in the gas phase, the polymerization temperature, and the concentration of the catalyst / cocatalyst in the liquid phase is calculated, and based on the target value. Thus, a configuration is adopted in which the supply amount of the olefin raw material, hydrogen, catalyst, and the like and the polymerization temperature are adjusted.

Japanese Patent Laid-Open No. 5-140229

However, in the configuration in which the supply amount of raw materials and hydrogen as described in Patent Document 1 is adjusted according to the target value, since the control is performed by a plurality of adjustment factors, the control is complicated and the configuration can be controlled more easily. Is desired.
In view of the above, an object of the present invention is to provide a polyolefin production method, a production apparatus thereof, and a polymerization apparatus that can easily produce a desired polyolefin.

  The method for producing a polyolefin described in the present invention is a method for producing a polyolefin by producing a polyolefin by solution polymerization of an olefin in a polymerization tank using a solvent and a catalyst, and the gas phase in the polymerization tank at the time of the solution polymerization The hydrogen concentration in the space is constant at a predetermined value or the hydrogen feed flow rate is constant, and the molecular weight of the polyolefin to be produced is controlled by adjusting the temperature of the polymerization solution for solution polymerization.

And in this invention, it is preferable to set it as the structure which uses the evaporative latent heat removal system which cools the gaseous-phase part in the said polymerization tank by external circulation, and controls the temperature of the polymerization solution in the said polymerization tank.
In the present invention, the catalyst preferably has a high temperature dependency.
In the present invention, the catalyst is preferably a metallocene compound.
Furthermore, in the present invention, as the catalyst, (A) a transition metal compound, (B) a solid organoboron compound that forms an ion pair with the transition metal compound, (C) an organoaluminum compound, and (D) an α-olefin. It is preferable to use a structure in which one or two or more compounds selected from internal olefins and polyenes are contacted.
Moreover, in this invention, it is preferable to set it as the structure which recognizes the molecular weight of the said polyolefin manufactured based on the value of the intrinsic viscosity of the said polymerization solution.
And in this invention, it is preferable to set it as the structure which manufactures the intrinsic viscosity of the said polymerization solution at 0.5 dL / g or more and 15.0 dL / g or less.
In the present invention, the polyolefin preferably has an isotactic pentad fraction of 20 mol% to 60 mol%.
Furthermore, in the present invention, it is preferable that the polyolefin is a low molecular weight low regularity polypropylene.
In the present invention, the pressure during the solution polymerization is preferably 0.5 MPa or more and 3 MPa or less.

  The polyolefin production apparatus according to the present invention includes a solution polymerization means having a polymerization tank for solution polymerization of olefins using a solvent and a catalyst, and a predetermined hydrogen concentration in a gas phase space in the polymerization tank of the solution polymerization means. And a control means for adjusting the temperature of the polymerization solution to be solution-polymerized by the solution polymerization means while maintaining a constant value or a constant hydrogen feed flow rate.

  The polymerization apparatus according to the present invention includes a polyolefin production apparatus according to the present invention, a volatile component removal means for removing a volatile component from a polymerization solution solution-polymerized by the polyolefin production apparatus, and a volatile component removal means for volatilization. And a granulating means for granulating the polymerization solution from which the components have been removed.

  According to the present invention, the molecular weight of the polyolefin is controlled by adjusting the temperature of the polymerization solution while keeping the hydrogen concentration in the gas phase space in the polymerization tank constant during solution polymerization, or keeping the hydrogen feed flow rate constant. A polyolefin having a desired molecular weight can be obtained by simple control of adjusting the temperature.

It is a block diagram showing a schematic structure of an olefin polymerization device of one embodiment concerning the present invention. It is a block diagram which shows schematic structure of the superposition | polymerization means periphery in this embodiment. It is a graph which shows the relationship between the vapor pressure of the polymerization solution in this embodiment, temperature, and a density | concentration.

The olefin polymerization apparatus according to the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram showing a schematic configuration of an olefin polymerization apparatus.

[Configuration of olefin polymerization equipment]
In FIG. 1, 100 is an olefin polymerization apparatus, and this polymerization apparatus 100 is an apparatus for producing a polyolefin by homopolymerizing various olefins or copolymerizing different olefins.
Here, as the olefin, various olefins such as methylene, ethylene, propylene and butylene can be targeted. In particular, the present invention is suitable when producing a low molecular weight low regularity polypropylene.

In particular, the polymerization apparatus 100 is suitable for polymerization of a polymer having a weight average molecular weight (Mw) of 2 or more and 400,000 or less, preferably 4 or more and 100,000 or less.
That is, when producing a low molecular weight, it is necessary to increase the polymerization temperature. If the polymerization temperature is high, the catalytic activity may decrease, and the production efficiency may decrease. On the other hand, in the case of producing a high molecular weight, since the viscosity of the polymer becomes high, there is a concern about poor extraction from the polymerization tank for carrying out the polymerization reaction to be polymerized, so the concentration of the polymer is increased in order to avoid the defective extraction. This is because it is necessary and production efficiency may be reduced.

Furthermore, when the number average molecular weight is Mn, Mw / Mn is preferably 1.8 or more and 4 or less, more preferably 3 or less, and even more preferably 2.4 or less.
That is, when Mw / Mn is larger than 4, the molecular weight distribution is widened and the low molecular weight components are increased, so that the product surface may be so-called bleed and sticky.

And as polyolefin to manufacture, in DSC measurement, melting | fusing point (Tm (degreeC)) is not shown, or when showing Tm, Tm and fusion | melting endothermic quantity (DELTA) H (J / g) show the following relational expression (1). What satisfies is preferable.
(Relational formula 1)
ΔH ≧ 6 × (Tm−140) (1)
That is, in particular, when a low molecular weight low regularity polypropylene is produced using a catalyst described later, those having a melting point of 50 ° C. or higher and 110 ° C. or lower, preferably 60 ° C. or higher and 80 ° C. or lower are suitable.

Further, the intrinsic viscosity of the polymerization solution is 0.5 dL / g or more and 15.0 dL / g or less, preferably 0.3 dL / g or more and 1.2 dL / g or less, more preferably 0.4 dL / g or more and 0.95 dL / g. The following molecular weight is preferred.
When producing a polymer having an intrinsic viscosity of less than 0.5 dL / g, it is necessary to increase the polymerization temperature. By raising the polymerization temperature, there is a possibility that the catalyst activity is lowered and the production efficiency is lowered. On the other hand, in the case of producing a polymer having an intrinsic viscosity greater than 15.0 dL / g, the viscosity of the polymer becomes high, and thus there is a risk of poor extraction from the polymerization tank in which the polymerization reaction is carried out. For this reason, it is necessary to reduce the concentration of the polymer in the polymerization solution in order to avoid a defective blowing of the polymer, which may reduce the production efficiency. For these reasons, the limiting viscosity is set to the predetermined range described above.

Further, as the polyolefin to be produced, the isotactic pentad fraction is 20 mol% or more and 60 mol% or less, preferably 40 mol% or more and 55 mol% or less, more preferably 44 mol% or more and 51 mol% or less. Is particularly suitable for the production of low molecular weight, low order polypropylene.
When the isotactic pentad fraction is less than 20 mol%, the obtained polyolefin becomes sticky, and there is a possibility that particles are reattached during granulation in a subsequent process and productivity is lowered. On the other hand, if the isotactic pentad fraction is greater than 60 mol%, the catalyst performance will not be exceeded and production may not be possible.

Here, the measurement of the isotactic pentad fraction used as an index of stereoregularity is as follows. This was carried out in accordance with the ¹³ C-NMR method (Macromolecules, 6925, 1973) disclosed by Zambelli. Specifically, first, 220 mg of the i-PP sample was collected in a 10 mm diameter NMR sample tube, and 2.5 ml of a 1,2,4-trichlorobenzene / heavy benzene mixed solution (90/10 vol%) was added, and uniform at 140 ° C. After the mixture was dissolved, ¹³ C-NMR spectrum was measured using JNM-EX400 (trade name: manufactured by JEOL Ltd.). ^{The 13} C-NMR spectrum measurement conditions are shown below.
・ Pulse width: 7.5μs / 45 degrees ・ Observation frequency range: 25,000Hz
-Pulse repetition time: 4 seconds-Measurement temperature: 130 ° C
・ Total number of times: 10,000

The isotactic pentad fraction is a total of nine types of bond patterns of five propylene molecules (“mmmm”, “mmmr”, “rmrr”, “mmrr”, “rmrr + mrmm”, “rmrm”, “rrrr”, “Mrrr” and “mrrm”) are defined as relative ratios of the peak area corresponding to “mmmm” with respect to the area of all nine peaks observed as ¹³ C-NMR spectra corresponding to each of Specifically, it was calculated by the following equation (2). Here, when there was an overlap between the two peaks, a perpendicular line was drawn vertically from the valley of the two peaks to the base line to divide both peaks (vertical division method).
Isotactic pentad fraction (mol%)
= {A (mmmm) / A (total)} × 100 (2)
Here, A (mmmm) is the area of the mmmm peak, and A (total) means the sum of the nine peak areas.
In addition, when there is an overlap between two peaks, in addition to the above vertical division method, there is also known a method of performing waveform separation using each peak as an aggregate of Lorentz-type peaks. Analysis software (ALICE 2 from JEOL Ltd.) is also known. ) May be used.

The polymerization apparatus 100 includes a polymerization facility 200 and a control device 300 as a control unit that controls the operation of the polymerization facility 200.
The polymerization facility 200 is a plant facility that produces a polyolefin by polymerizing an olefin (solution polymerization) using a solvent. The polymerization facility 200 includes a polymerization means 210, a devolatilization means 220 as a volatile component removal device for the polymerization solution, and a granulation means 230.

The polymerization means 210 is a device for performing a polymerization reaction, and includes a polymerization tank 210A as shown in FIG. For this polymerization tank 210A, for example, a latent heat of vaporization heat removal method is preferably used. This latent heat removal method uses, for example, the latent heat of vaporization of the monomer and is economically superior because it can secure a large amount of heat removal per one heat removal system. Further, the latent heat of vaporization heat removal method is preferable because it can be efficiently and satisfactorily cooled even when the viscosity of the polymerization solution in the polymerization tank 210A increases due to polymerization.
If the production volume is relatively small enough to cool the whole, the jacket heat removal method for cooling from the outside of the polymerization tank 210A that can reduce the size of the polymerization tank 210A, or when the viscosity of the polymerization solution is not high May be an external circulation method in which the polymerization solution is circulated and cooled, or in the case of using a catalyst system whose molecular weight does not greatly depend on the polymerization temperature, a raw material sensible heat removal method in which the raw material or solvent is cooled and supplied in advance may be used. .
The polymerization means 210 is connected to a raw material supply means 211 for supplying propylene, which is a raw material olefin, to the polymerization tank 210A. The polymerization means 210 is connected to a solvent supply means 212 for supplying, for example, n-heptane to the polymerization tank 210A in the case of solution polymerization of a solvent such as propylene. Further, a catalyst supply means 213 for supplying a catalyst is connected to the polymerization means 210. The polymerization means 210 is connected to a hydrogen gas supply means 214 that supplies hydrogen gas (H ₂ ) that activates the catalyst and starts propylene polymerization. Further, the polymerization means 210 is connected to a third component supply means 215 for supplying a cocatalyst and a third component.

In the polymerization tank 210A, for example, when polymerizing low molecular weight, low order polypropylene, the pressure during solution polymerization is preferably 0.5 MPa or more and 3 MPa or less.
That is, if the pressure is increased, the concentration of the polymer in the polymerization solution increases and the production efficiency is improved. However, at a pressure higher than 3 MPa, the concentration of the polymer in the polymerization solution hardly increases and improvement in production efficiency cannot be expected, and there is a possibility that inconveniences such as increase in equipment size and increase in energy consumption due to increased pressure may occur. On the other hand, when the pressure is lower than 0.5 MPa, stereoregularity does not appear and the intended polymer cannot be obtained.

The polymerization temperature in the polymerization vessel 210A is preferably set to 60 ° C. or higher and 100 ° C. or lower.
That is, the temperature range is suitable for controlling the molecular weight based on the activity of the catalyst when polymerizing low molecular weight and low-order polypropylene.

Furthermore, the residence time of the polymerization solution in the polymerization vessel 210A is preferably set to 0.5 hours or more and 2 hours or less.
By setting the residence time long, the catalyst can be used effectively, but if the residence time is too long, the size of the polymerization tank 210A increases, which may cause inconveniences such as an increase in equipment size and equipment cost. is there. For this reason, it is preferable to set to the residence time mentioned above, especially when polymerizing a low molecular weight low regularity polypropylene.

The concentration of the polymer in the polymerization solution in the polymerization tank 210A is preferably set to 20% by mass or more and 40% by mass or less.
By increasing the polymer concentration, the solvent can be reduced and the production cost can be reduced. On the other hand, if the polymer concentration is too high, the mixing property in the polymerization tank 210A may be deteriorated and the product properties may be deteriorated. There is. For this reason, when polymerizing a low molecular weight low regularity polypropylene, it is preferable to set the polymer concentration described above.

And it is preferable to set the hydrogen partial pressure in the polymerization tank 210A to 1 kPa or more and 100 kPa or less.
If the hydrogen partial pressure is too high, the polymerization pressure increases, and as described above, there is a possibility of causing problems such as an increase in the size of the equipment. Therefore, it is preferable to keep the hydrogen partial pressure as low as possible. Is used, the catalytic activity is reduced if the hydrogen partial pressure is too low. For these reasons, it is preferable to set the hydrogen partial pressure within the above-described range.

  Here, as the catalyst, various catalysts used for olefin polymerization can be used. In particular, a metallocene-based catalyst having high temperature dependency, specifically (A) a transition metal compound, (B) a solid organoboron compound that forms an ion pair with the transition metal compound, and (C) an organoaluminum compound, (D) a catalyst obtained by contacting one or more compounds selected from α-olefins, internal olefins, and polyenes (the catalyst described in Japanese Patent Application No. 2007-514550), or (A) a transition metal compound (B) A catalyst obtained by contacting a solid organoboron compound that forms an ion pair with a transition metal compound and (C) an organoaluminum compound is preferable because a polyolefin can be obtained with high efficiency and stability. For example, (1,2'-dimethylsilylene) (2,1'dimethylsilylene) -bis (3-trimethylsilylmethylindenyl) zirconium dichloride can be suitably used.

The devolatilization unit 220 is an apparatus that is connected to the polymerization unit 210 and removes volatile components from the polymerization solution flowing out from the polymerization tank 210A of the polymerization unit 210. The devolatilization means 220 includes a demonomer tank 221 and a solvent removal tank shown in FIG.
The demonomer tank 221 is connected to the polymerization tank 210A, and the polymerization solution is flowed into it. Connected to the demonomer tank 221 is a volatile component gas recovery means 222 for recovering unreacted raw material propylene that is volatilized from the polymerization solution and a volatile component that is a solvent.
Volatile component gas recovery means 222 includes a decompression device that decompresses the inside of the demonomer tank 221, a recovery device that collects volatile components from the gas phase sucked by the decompression device, and a volatile component recovered by the recovery device. And a refining device for refining each component.
The demonomer tank 221 is configured to remove volatile components until the concentration of the polymer in the polymerization solution is 90% by mass or more, preferably 95% by mass or more. That is, the amount of the volatile component remaining in the product is determined by the vapor-liquid equilibrium state between the polyolefin and the volatile component determined by the temperature and pressure conditions in the tank in which the volatile component is separated and removed. And when the density | concentration of the polymer in a polymerization solution is low, the ratio in which temperature falls by the latent heat of vaporization of the volatile component in the solvent removal tank in the latter stage becomes large. For this reason, the desired vapor-liquid equilibrium cannot be obtained in the solvent removal tank, and it is necessary to separately supplement the amount of heat for the temperature decrease due to latent heat of evaporation, and it becomes difficult to sufficiently evaporate and separate the volatile components. Volatile components are separated and removed in advance so that the concentration of the polymer is 90% by mass or more.
The condition for separating and removing the polymer at a concentration of 90% by mass or more depends on the temperature and pressure, which are conditions for vapor-liquid equilibrium between the polyolefin and the volatile component, as described above. In the case where the volatile component gas recovery means 222 has a pressure reducing capability of 0.02 MPa in the demonomer tank 221, the temperature of the polymerization solution is 188 ° C. or higher (inflow of the polymerization solution in the demonomer tank 221). The temperature at the time is set to about 200 to 220 ° C.
The demonomer tank 221 preferably has a multi-stage structure in which not only one tank but also, for example, unreacted monomer is separated and removed in the former stage, and most of the solvent is separated and removed in the latter stage. That is, the volatile component gas recovery means 222, the tank, and the like can be further downsized, and the volatile component after the recovery can be easily purified.

The desolvation tank is connected to the demonomer tank 221 via a polymerization solution inflow path, and a polymerization solution from which a certain amount of volatile components has been removed in the demonomer tank 221 is flowed. This desolvation tank is provided with a decompression device (not shown) that depressurizes the internal decompression space into which the polymerization solution is introduced, and the desolvation tank is constructed in a depressurization resistant structure. This decompression device and the solvent removal tank constitute the decompression means of the present invention. This decompression device is preferably used in common with the decompression device of the volatile component gas recovery means 222 to simplify the plant equipment.
The decompression device is preferably configured to be able to fully vacuum the inside of the solvent removal tank at 0.5 kPa or less (4 torr or less). That is, the amount of the remaining volatile component needs to be 200 ppm by mass or less, preferably 100 ppm by mass or less, in order to prevent the deterioration of the product quality due to the odor of the volatile component. Thus, based on the vapor-liquid equilibrium value between the polyolefin and the volatile component, when the temperature is set to 230 ° C., which is a temperature condition at which the polyolefin does not change, it is set to 0.5 kPa or less (4 torr or less).

In addition, the polymerization solution inflow path includes a delivery pump (not shown) for sending the polymerization solution in the demonomer tank 221 to the solvent removal tank, a heat exchange means as a heating means, and a solvent removal tank on the downstream side of the heat exchange means. A pressure adjusting valve as a pressurizing means is provided on the side.
The heat exchange means, for example, heats the polymerization solution by utilizing heat exchange with the polymerization means 210 of the latent heat of vaporization heat removal method, that is, heat removed during the polymerization reaction. Specifically, when propylene is homopolymerized, it may be heated to about 230 ° C to 250 ° C. That is, the polymer may be heated to a high temperature at which a vapor pressure that does not change the quality and can sufficiently foam the volatile component at the time of decompression at a later stage is obtained. Specifically, since the amount of remaining volatile components is determined by the vapor-liquid equilibrium between the polyolefin and the volatile components depending on the conditions of temperature and pressure, it is necessary to increase the degree of vacuum in the processing tank as the temperature decreases. . For this reason, it is necessary to set a high degree of vacuum that is difficult to set industrially if the temperature is lower than 230 ° C., and if heated higher than 250 ° C., the polymer is decomposed to lower the molecular weight or the color. This is because the polymer may be deteriorated such as.
The pressure adjustment valve adjusts the pressure so that the polymerization solution flowing through the polymerization solution inflow passage flows at a pressure that does not foam when heated by the heat exchange means. That is, since the vapor pressure varies depending on the composition of the polymerization solution, the pressure at which the polymerization solution does not foam may be set according to the vapor pressure, and foaming can be prevented by adjusting the pressure higher than the vapor pressure.

Moreover, the dome part is provided in the upper part which the polymerization solution inflow path of a solvent removal tank connects. A porous member is provided on the bottom surface of the dome that faces the decompression space. The porous member has a disk shape and is formed with a plurality of flow paths having an axial direction along the thickness direction.
For example, when the viscosity of the polymerization solution is about the same as that of polypropylene obtained by homopolymerizing propylene as a polymer, the flow path may be formed with a diameter of 2 mm to 15 mm, preferably 3 mm to 7 mm. This is because when the diameter of the flow path is smaller than 2 mm, it is difficult for the polymerization solution to flow, pressure loss increases, and it becomes difficult to improve the production efficiency. On the other hand, when the diameter of the flow path is larger than 15 mm, when the volatile component is foamed in the polymerization solution flowing through the flow path, the foaming does not reach the outer surface side of the polymerization solution, and the foam does not break and enters the polymerization solution. This is because there is a possibility of melting again. That is, in order to efficiently break the bubbles, it is necessary to increase the surface area of the polymerization solution. However, if the diameter of the flow path is larger than 15 mm, it is difficult to obtain the bubble breaking effect due to the increase of the surface area.
Furthermore, the pitch of the flow path is preferably 7 mm or more and 16 mm or less. When the pitch of the flow path becomes narrower than 7 mm, in the case of a polymer solution having a relatively high viscosity, the bubbles are closely attached to the adjacent bubbles before the bubbles swell and break like a balloon at the downstream end of the flow path. There is a risk that bubbles cannot be broken. Furthermore, it is necessary to increase the thickness of the porous member so that the strength does not decrease, which may cause inconveniences such as an increase in the size of the device and an increase in the cost of the porous member. On the other hand, when the pitch of the flow path is larger than 16 mm, the surface area of the polymerization solution when passing through the porous member decreases, and there is a possibility that bubbles cannot be broken sufficiently. Furthermore, it is necessary to provide a plurality of flow paths so that the surface area of the polymerization solution does not decrease, and the diameter of the porous member increases, which may cause inconveniences such as an increase in the size of the apparatus and an increase in the cost of the porous member. Therefore, the pitch of the flow path is designed to be 7 mm or more and 16 mm or less.
The ratio of the hole diameter of the channel to the pitch dimension of the channel, that is, the relationship (D / L) between the channel diameter (D) and the pitch (L) is 0.4 or less, particularly in the case of propylene homopolymerization. 2.3 is preferable. Here, if the value of L is too small with respect to D, it is difficult to obtain an effect of dispersing the polymer by adhering to the polymer solution flowing through the adjacent flow path. This is because the member becomes large, the equipment becomes large, and the equipment cost may increase. That is, the porous member is not limited to the purpose of merely breaking bubbles but is also intended to disperse the polymer.
The bottom of the solvent removal tank is provided with a transfer pump for sending the polymerization solution from which volatile components are highly removed to the granulating means 230 in the next step, and an outflow path is connected.

The granulating means 230 includes a cooler (not shown), a granulator, a cooling tank, a dehydrating means, and the like.
The cooler cools the polymerization solution transferred from the solvent removal tank to a temperature having a certain degree of viscosity that enables granulation.
The granulator allows the polymer cooled by the cooler to flow out of the mold nozzle and spray water, and then cut into pellets with a rotary cutting blade spaced from the outlet of the mold nozzle by a predetermined gap. .
A cooling tank fully cools the pellet-shaped polymer granulated with the granulator, stirring with the water sprayed at the time of granulation. That is, since the cooling tank is not completely solidified at the time of granulation, in order to prevent inconvenience that the pellets adhere to each other after granulation, the cooling tank is sufficiently cooled to a temperature at which the pellets do not adhere to each other while stirring. A coalescence is produced. As the water used for cooling, when the polyolefin to be produced has a relatively low melting point such as low molecular weight and low order polypropylene, a mixture of emulsion type silicone oil should be used to prevent so-called blocking. Is preferred.
The dehydrating means removes water adhering to the pellets after granulation. As a method for removing the moisture, various methods such as centrifugation and air drying can be used.
The produced pellet-shaped olefin polymer is appropriately stored in a storage hopper or the like.
Note that a plurality of granulation means 230 may be provided in parallel in order to accommodate a wide range of pellet production.

As the control device 300, for example, a computer is used to control the operating conditions of the polymerization equipment 200. Specifically, the supply amount of the raw material from the raw material supply means 211, the supply amount of the solvent from the solvent supply means 212, the supply amount of the catalyst from the catalyst supply means 213, the supply amount of hydrogen gas from the hydrogen gas supply means 214 The amount of the third component supplied from the third component supply means 215, the temperature of the polymerization solution by circulating the gas phase in the polymerization tank 210A, the pressure at which the devolatilization means 220 depressurizes, the heat exchange means The heating temperature, the pressure applied by the pressure adjusting valve, the flow rate control by driving control of the transfer pump, the cooling temperature in the granulating means 230, the rotational speed of the rotary cutting blade, and the like are controlled.
Here, the computer is not limited to a single personal computer, but a configuration in which a plurality of computers are combined in a network form, a circuit such as a CPU (Central Processing Unit) or a microcomputer, or a plurality of electronic components. It also includes a substrate.
Further, the control device 300 sets the volatile component content in the polymer solution after the decompression process to 200 mass ppm or less based on the concentration of the polyolefin, the temperature of the polymer solution, the vapor pressure of the polymer solution, and the time length of the decompression process. The preset conditions, that is, the pressure applied by the pressure adjusting valve, the temperature heated by the heat exchange means, the pressure reduced by the pressure reducing means, and the flow rate of the polymerization solution are controlled.
That is, as shown in FIG. 3, since there is a predetermined relationship between the vapor pressure and temperature of the volatile component at the concentration of the aggregate of the polymerization solution, the pressure is reduced based on the characteristics of the vapor pressure based on the composition of the polymerization solution. The pressure, the temperature heated by the heat exchanging means, the flow rate with respect to the size of the demonomer tank 221 and the solvent removal tank, which are the length of time for the decompression process, are set, and the polymerization equipment 200 is controlled according to the set numerical values.

[Production of olefin polymer]
The control device 300 recognizes the necessary amount of raw materials based on the production plan data acquired in advance, and supplies the raw material supply means 211, the solvent supply means 212, the catalyst supply means 213, the hydrogen gas supply means 214, and the third component supply means 215. Are controlled to supply necessary amounts of raw material, solvent, catalyst, hydrogen gas, and third component to the polymerization vessel 210A of the polymerization means 210.
Then, the control device 300 circulates the gas phase component in the polymerization tank 210A while appropriately cooling it with a cooler (not shown) to control the temperature of the polymerization solution in the polymerization tank 210A to advance the polymerization reaction. During this polymerization reaction, the control device 300 adjusts the temperature of the polymerization solution by keeping the hydrogen concentration in the gas phase space in the polymerization vessel 210A constant at a predetermined value or by keeping the hydrogen feed flow rate constant. The intrinsic viscosity is controlled so as to be a value corresponding to the desired molecular weight of the polyolefin.

Thereafter, the controller 300 transfers the polymerization solution in the polymerization tank 210A to the demonomer tank 221 of the devolatilization means 220, and the volatile component gas recovery means 222, which is separately driven and controlled, removes the volatile components from the polymerization solution. Remove. As operation control of the volatile component gas recovery means 222, the volatile component gas recovery means 222 is retained in the demonomer tank 221 decompressed to a predetermined pressure until the concentration of the polymer in the polymerization solution becomes 90% by mass or more. That is, based on the relationship between the vapor pressure and temperature of the volatile component in the concentration of the aggregate of the polymerization solution, the pressure and flow rate for reducing the pressure are controlled.
Then, the controller 300 causes the polymerization solution in which the volatile components have been removed so that the concentration of the polymer in the polymerization solution is 90% by mass or more in the demonomer tank 221 flows into the solvent removal tank via the polymerization solution inflow path. When this polymerization solution flows through the polymerization solution inflow passage, the pressure is adjusted to a predetermined pressure, that is, a pressure at which foaming does not occur during heating, by the pressure adjustment valve in the polymerization solution inflow passage controlled by the control device 300. Further, the polymerization solution is heated by heat exchange to a predetermined temperature by the heat exchange means controlled by the control device 300. Then, the polymer solution heated in the pressurized state flows through the pressure regulating valve, and immediately flows into the dome portion of the solvent removal tank whose pressure is reduced to a predetermined pressure by the control device 300.
The foamed polymerization solution is in a state where a large number of bubbles are mixed without breaking. And the polymerization solution in which this bubble mixes distribute | circulates the several flow path of a porous member. During this distribution, the polymerization solution further foams and the bubble diameter increases, and bubbles mixed in the polymerization solution appear on the outer surface of the polymerization solution serving as the inner surface of the flow path, and the bubbles break. That is, when the polymerization solution flows through the plurality of flow paths, the surface area is increased. As a result, bubbles mixed in the inside appear on the outer surface of the polymerization solution and break the bubbles. The volatile components separated by the bubble breaking are recovered by the volatile component gas recovery means 222 from the upper part of the solvent removal tank so as not to be dissolved again in the polymerization solution.

Then, the polymer, which is a polymerization solution in which the volatile components are sufficiently separated by the devolatilizing means 220, for example, the remaining volatile components are separated to 200 ppm or less, is transferred to the granulating means 230 through the outflow path with a transfer pump. The
In this granulating means 230, the polymer transferred by the cooler controlled by the control device 300 is cooled and granulated into pellets by the granulator. The pelletized polymer after granulation is immediately cooled and solidified sufficiently in a cooling bath so as not to adhere to each other, and a pellet-shaped olefin polymer is produced.
The cooled and solidified polymer is appropriately removed after moisture, and then transferred to a storage hopper or the like and appropriately stored.

[Effects of Embodiment]
According to the above-described embodiment, the molecular weight of the polyolefin is controlled by adjusting the temperature of the polymerization solution while keeping the hydrogen concentration in the gas phase space in the polymerization tank 210A at the time of solution polymerization constant or keeping the hydrogen feed flow rate constant. Therefore, it can be manufactured with simple control of adjusting the temperature.
For example, by using a catalyst having high temperature dependence, the response time for controlling to a desired molecular weight can be shortened. Further, temperature control can be easily performed by using a latent heat of vaporization heat removal method that can cool the polymerization solution sufficiently efficiently even with a certain amount of production. As described above, according to the present invention, in which the hydrogen concentration in the gas phase space in the polymerization vessel 210A is constant or the temperature during the polymerization reaction is adjusted with the hydrogen feed flow rate constant, the conventional hydrogen supply amount is adjusted. Thus, in the configuration in which the hydrogen partial pressure is controlled, the yield can be improved and the production can be efficiently performed without causing the disadvantage that the response time becomes long and the off-spec product increases.

In this embodiment, the temperature of the polymerization solution is adjusted by an evaporation latent heat removal method.
For this reason, since the polymerization reaction tends to stagnate, hydrogen is supplied to maintain the activity of the polymerization reaction, and even in the configuration of the polymerization tank 210A in which the volume of the gas phase is relatively large, It is relatively quick and easy to adjust to the desired temperature. Therefore, it can be satisfactorily prepared in a polymerization solution having a polar viscosity that gives a desired molecular weight of polyolefin.

In this embodiment, a catalyst having a high temperature dependency, particularly a metallocene compound, is used.
Therefore, the polymerization can be controlled with good response according to the temperature control of the polymerization solution, and the desired polyolefin can be efficiently produced by reducing the number of off-spec products.
As the metallocene-based compound catalyst, in particular, (A) a transition metal compound, (B) a solid organic boron compound that forms an ion pair with the transition metal compound, (C) an organoaluminum compound, and (D) α- One or two or more compounds selected from olefins, internal olefins, and polyenes, or (A) transition metal compounds and (B) solid organoboron compounds that form ion pairs with transition metal compounds And (C) those which are brought into contact with the organoaluminum compound have a particularly high temperature dependency, and therefore, polyolefins having a desired molecular weight can be produced particularly according to temperature control.

In the present embodiment, the molecular weight of the polyolefin to be produced is recognized based on the intrinsic viscosity value of the polymerization solution.
For this reason, since the temperature of the assembly solution can be easily adjusted based on the properties of the polymerization solution, a polyolefin having a desired molecular weight can be produced with a high yield.

And it is suitable for manufacture of a low molecular weight low regularity polypropylene.
Low molecular weight low regularity polypropylene foams and breaks the solvent in the polymer in a short time, so it is easy to reach the amount of solvent in the polymer in parallel while the polymer is devolatilized in the solvent removal tank. It is suitable because it can be easily devolatilized and the size of the apparatus can be easily reduced.

[Modification of Embodiment]
The aspect described above shows one aspect of the present invention, and the present invention is not limited to the above-described embodiment, and is within a range in which the object and effect of the present invention can be achieved. Needless to say, modifications and improvements are included in the content of the present invention. In addition, the specific structure and shape when implementing the present invention can be applied to other structures and shapes as long as the objects and effects of the present invention can be achieved.

That is, the configuration in which the operation condition of the polymerization equipment 200 is controlled by the control device 300 to automatically operate the polymerization device 100 is illustrated, but the configuration is not limited thereto. For example, it is good also as a structure set as the manual driving | operation which sets and sets driving | running conditions manually manually.
Further, the production is not limited to the continuous type, and may be a batch type.
Moreover, although it controlled based on Formula 1 mentioned above as conditions at the time of controlling with the control apparatus 300, it is not restricted to the conditions of Formula 1 as control conditions.

And as an olefin, various olefins, such as ethylene, propylene, butylene, can be made into object.
Furthermore, the polyolefin to be produced is not limited to a homopolymer such as polyethylene or polypropylene, but can also be applied to the case of producing a copolymer of ethylene and propylene.

Further, as the devolatilization means 220, a two-stage configuration of the devolatilization tank 221 and the solvent removal tank is illustrated, but it may be a single-stage configuration or a multi-stage configuration of three or more stages.
In particular, since a structure that does not foam when heated by a heat exchange means while applying pressure is preferable, it is preferable that the concentration of the polymer is, for example, 90% by mass or more when applying pressure and heating. Therefore, a volatile component can be separated and removed efficiently and easily by using a multi-stage configuration. Note that the devolatilization tank 221 may not remove the volatile component until the polymer concentration is 90 mass% or more. That is, pressure may be applied so as not to foam during heating.
And as a pressurization means, not only a pressure control valve but the structure which pressurizes variously, such as press-fitting in a container using a pump etc. and pressurizing a polymerization solution, for example can be utilized.
Similarly, the heating configuration is not limited to the heat exchanging means, and various heating methods such as heating the outside of the container storing the polymerization solution with a heater or the like can be used. It is preferable that the heat exchange using the heat generated in the polymerization means 210 can effectively use energy and can be efficiently manufactured.

Further, in the configuration in which propylene is homopolymerized, for example, when the pressure to be reduced in the solvent removal tank can be highly reduced to 0.5 kPa or less, it is not necessary to heat to 230 to 250 ° C. by the heat exchange means.
Furthermore, the pressure to be reduced is not limited to 0.5 kPa or less.

And as a porous member, it is not restricted to D / L <= 0.4, Any thing is applicable if a bubble-breaking and a dispersion effect are acquired.
Further, as the porous member, for example, a porous member such as a pumice or the like in which the flow path is not linear but bent or branched, or a mesh member may be used.

  In addition, the specific structure and procedure for carrying out the present invention may be changed to other configurations as long as the object of the present invention can be achieved.

  The present invention relates to an apparatus for removing a volatile component from a polymerization solution for removing a volatile component from a polymerization solution when a polyolefin is produced by homopolymerization or copolymerization of an olefin using a solvent, and further a polymerization equipped with this volatile component removal apparatus Available for equipment.

DESCRIPTION OF SYMBOLS 100 ... Polymerization apparatus 210 ... Polymerization means 210A ... Polymerization tank 220 ... Volatilization means as a volatile component removal apparatus 300 ... Control apparatus as control means

Claims (12)

A method for producing a polyolefin, wherein a polyolefin is produced by solution polymerization of an olefin in a polymerization tank using a solvent and a catalyst,
The hydrogen concentration in the gas phase space in the polymerization tank during the solution polymerization is made constant at a predetermined value, or the hydrogen feed flow rate is made constant, and the temperature of the polymerization solution for solution polymerization is adjusted to produce the solution. A method for producing a polyolefin, comprising controlling the molecular weight of the polyolefin. A method for producing a polyolefin according to claim 1,
A method for producing polyolefin, characterized by using a latent heat of vaporization heat removal method in which a gas phase in the polymerization tank is cooled by external circulation to control the temperature of the polymerization solution in the polymerization tank. A method for producing the polyolefin according to claim 1 or 2,
A method for producing a polyolefin, wherein the catalyst has a high temperature dependency. A method for producing a polyolefin according to claim 3,
The method for producing a polyolefin, wherein the catalyst is a metallocene compound. A method for producing a polyolefin according to claim 3 or 4, wherein
Examples of the catalyst include (A) a transition metal compound, (B) a solid organoboron compound that forms an ion pair with the transition metal compound, (C) an organoaluminum compound, (D) an α-olefin, an internal olefin, and a polyene. A method for producing a polyolefin, comprising using one or two or more selected compounds in contact with each other. A method for producing a polyolefin according to any one of claims 1 to 5,
A method for producing a polyolefin, comprising recognizing a molecular weight of the polyolefin to be produced based on a value of an intrinsic viscosity of the polymerization solution. A method for producing a polyolefin according to claim 6,
A method for producing a polyolefin, wherein the polymerization solution is produced with an intrinsic viscosity of 0.5 dL / g or more and 15.0 dL / g or less. A method for producing a polyolefin according to any one of claims 1 to 7,
The polyolefin is characterized in that the isotactic pentad fraction is 20 mol% or more and 60 mol% or less. A method for producing a polyolefin according to any one of claims 1 to 8,
The polyolefin is a low molecular weight, low regularity polypropylene. A method for producing a polyolefin according to any one of claims 1 to 9,
The method for producing a polyolefin, wherein the pressure during the solution polymerization is 0.5 MPa or more and 3 MPa or less. A solution polymerization means comprising a polymerization tank for solution polymerization of olefin using a solvent and a catalyst;
Control means for adjusting the temperature of the polymerization solution to be polymerized by the solution polymerization means while keeping the hydrogen concentration in the gas phase space in the polymerization tank of the solution polymerization means constant at a predetermined value or keeping the hydrogen feed flow rate constant When,
An apparatus for producing polyolefin, comprising: An apparatus for producing the polyolefin according to claim 11,
Volatile component removing means for removing volatile components from the polymerization solution solution polymerized by the polyolefin production apparatus,
A granulating means for granulating the polymerization solution from which the volatile components have been removed by the volatile component removing means;
A polymerization apparatus characterized by comprising:

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