JPS6264808A - Process and apparatus for producing polyolefin - Google Patents

Abstract

PURPOSE:To obtain continuously and stably a polyolefin having a specified MW distribution, by estimating the amount of a polyolefin fed from the first polymerization zone to the second polymerization zone and determining polymerization conditions in the second polymerization zone on the basis of the estimated value in polymerizing an olefin by two-stage polymerization. CONSTITUTION:The amount of an olefin fed, that of a solvent fed, the olefin concentration and pressure in a vapor phase and the temperature and liquid level in a liquid phase in the first polymerization zone are detected, and the amount of a polyolefin fed from the first polymerization zone to the second polymerization zone is estimated by processing these data with a computer. The amounts of an olefin and hydrogen fed to the second polymerization zone are calculated by the processing of these estimated values and the sets determined for a polyolefin having the desired MW distribution. By the control output produced from the computer processing of the calculated values, the amounts of an olefin and hydrogen fed to the second polymerization zone and the amount of a vapor phase purged in the second polymerization are controlled.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for producing polyolefins.

More specifically, in the polymerization of olefins in the reaction medium in the presence of hydrogen using Ziegler-based catalysts and Phillips-based catalysts in one stage polymerization zone, each polymerization zone is operated under stable conditions. The present invention relates to a method for producing a polyolefin having a specific molecular weight distribution.

[Prior art]

Conventionally, polyolefins have been molded by various molding methods and used for a wide variety of purposes. Depending on the molding method and application, polyolefins having various molecular weight distributions and, in some cases, composition distributions are desired. Generally, the type of polymerization catalyst is used to adjust the molecular weight distribution.

Methods of changing the composition, amount, etc., and varying the polymerization conditions are known. In this case, since there is a limit to controlling the molecular weight distribution etc. with a method of performing polymerization in only one polymerization zone, it is possible to set up two or more polymerization zones and produce polymers with different molecular weights in each polymerization zone. A method of controlling the molecular weight distribution of a five-polymer composition sound body has been adopted.

In this method, an olefin is usually polymerized in the second polymerization zone in the presence of hydrogen under conditions of a high hydrogen/olefin molar ratio to produce a polyolefin with a small molecular weight, which is then further polymerized in a second polymerization zone. In the zone, polymerization is performed under conditions of a low hydrogen/O-refine molar ratio to produce a polyolefin with a high molecular weight.

The molecular weight distribution, etc. of the entire polyolefin composition is controlled.

To produce polyolefins on an industrial scale by the above method, a predetermined amount of catalyst, a predetermined amount of olefin, a predetermined amount of hydrogen, and a solvent are fed into two polymerization zones maintained at a predetermined temperature. The system is operated under conditions such that a predetermined amount of polyolefin having a predetermined specification, that is, a predetermined molecular weight distribution, is continuously produced.

However, as mentioned above, even if continuous polymerization is carried out under conditions where each supply amount is kept constant, it is difficult to maintain a constant state in the polymerization zone, and it is difficult to maintain a constant production amount of polyolefin of a predetermined specification. However, the olefin concentration in the polymerization zone changes due to minute changes in the catalyst, decreases in activity, etc. For example, if the activity of the catalyst decreases, the olefin concentration in the zone increases, and the ratio of the concentration of hydrogen, which is a molecular weight regulator, to olefin decreases.
The molecular weight of the polyolefin produced increases. There are many such minute disturbances for which the reasons are not clear, and they cause changes in the olefin concentration in the polymerization zone, and the molecular weight of the polyolefin produced.

As a method to solve the above-mentioned problems in the conventional method, when producing polyolefin by polymerizing olefin in the coexistence of hydrogen, the detected A method of inputting a signal amount into a computer and operating the supply valves for catalyst, hydrogen, solvent, and olefin to a polymerization reactor based on the control calculation output of the computer according to changes in the signal amount (JP-A-Shoj? -/Ag
No. 90'1] has been proposed.

[Problem that the invention seeks to solve]

The above method is effective when producing a polyolefin having a predetermined molecular weight at a constant production rate. However, when polymerizing in one N zone under different reaction conditions to produce polyolefins with different specific molecular weights at specific production ratios, to produce polyolefins with a specific molecular weight distribution, Although it is possible to control the molecular weight of each polyolefin, it is difficult to control the production ratio within a specific range. In particular, when the first polymerization zone is in an unsteady state, for example, when the polymerization reaction is started, when the polymerization reaction is stopped, when a disturbance occurs, or when the polymerization reaction conditions are changed, the conditions in the polymerization zone are changed. In response to changes in the conditions of the second polymerization zone,
In addition, it is not possible to respond and follow accurately, and the above-mentioned production ratio of the polyolefin obtained fluctuates, resulting in fluctuations in the quality of the product, resulting in a substandard product, or from an industrial perspective, interfering with safe operation. However, there are problems such as trespassing, and it is not completely satisfactory.

[Means for solving problems]

The present inventors have solved the drawbacks of the above-mentioned conventional method for producing polyolefins by two-stage polymerization of olefins, and have solved the problem of producing polyolefins with a specific molecular weight distribution, which contains polyolefins of different specific molecular weights in specific production ratios. As a result of intensive research and study in order to provide a method for continuously and stably producing polyolefin having The amount of polyolefin to be supplied from the first polymerization zone to the second polymerization zone is predicted, and based on the predicted value and a target value determined corresponding to the production of polyolefin having a predetermined molecular weight distribution, The above problem is solved by calculating the olefin supply amount and furthermore the hydrogen supply amount and adjusting the olefin supply amount in the second polymerization zone, furthermore the hydrogen supply amount or gas phase purge amount based on the calculated value. They discovered what they could do and completed the present invention.

The gist of the invention is to polymerize olefins in the presence of a catalyst, a solvent, and hydrogen in a λ-stage polymerization zone, that is, in one of the polymerization zones, under conditions of a high hydrogen/olefin molar ratio in the gas phase. to produce a predetermined amount of low molecular weight polyolefin, and then in the other polymerization zone, polymerize under conditions of a low hydrogen/olefin molar ratio in the gas phase to produce a predetermined amount of high molecular weight polyolefin. Molecular weight distribution! The amount of olefin and solvent supplied in the first polymerization zone; the olefin concentration and pressure in the gas phase; and the temperature and liquid level height in the liquid phase are detected and their The data signal 7 is input to a computer, and the amount of polyolefin to be supplied from the first polymerization zone to the second polymerization zone is estimated by calculation using the data, and the amount of polyolefin that is supplied from the first polymerization zone to the second polymerization zone is calculated to correspond to the estimated value and the polyolefin having a predetermined molecular weight distribution. The amount of olefin to be supplied to the second polymerization zone and furthermore the amount of hydrogen to be supplied to the second polymerization zone are calculated from the target value determined by the calculation process, and the operation is carried out based on the calculated values. The method of producing a polyolefin is characterized in that a polyolefin having a predetermined molecular weight distribution is produced by adjusting the amount of olefin supplied to the olefin, furthermore the amount of hydrogen supplied, or the gas phase barge pressure.

In addition, the gist of the second invention is that olefins are polymerized in one stage in the presence of a catalyst, a solvent, and hydrogen, that is, in either one of the polymerization zones, under conditions where the molar ratio of hydrogen to olefin in the gas phase is high. In the other polymerization zone, polymerization is performed under conditions of low hydrogen/olefin molarization in the gas phase to produce a predetermined amount of polyolefin in the polymer tray. A single polymerization reaction control device for producing a polyolefin having a predetermined molecular weight distribution, the following means (CL) to (f) provided for the seventh polymerization zone, (aJ olefin supply itY detection Means to do (1)
J Means for detecting the solvent supply lid (c) Means for detecting the hydrogen concentration and/or olefin concentration in the gas phase ((LJ Means for detecting pressure (e) Means for detecting temperature (f) Liquid level height Means for detecting the amount of polyolefin supplied from the seventh polymerization zone to the second polymerization zone is estimated by arithmetic processing using the data 7 obtained from the means of (a) to (fJ) above, and the amount of polyolefin supplied from the seventh polymerization zone to the second polymerization zone is a calculation means (means [g)) for calculating the amount of olefin supplied to the second polymerization zone and also the amount of hydrogen supplied from the target value determined corresponding to the polyolefin of the molecular weight distribution'&[[g]]; In order to adjust the olefin supply amount and hydrogen supply amount to the second polymerization zone calculated by the means, the following (h) ~
(Means for k and l (h) Means for adjusting the amount of olefin supplied (1) Means for adjusting the amount of hydrogen supplied l Means for measuring the hydrogen concentration and/or olefin concentration in the gas phase (k) In the gas phase The present invention relates to a polymerization reaction control apparatus for producing a polyolefin having a predetermined molecular weight distribution, which is capable of partially purging a gas out of the system, and has means for adjusting its fi:.

Hereinafter, the present invention will be explained in more detail.

Examples of the catalyst used in the present invention include Ziegler catalysts and Phillips catalysts, with Ziegler catalysts being particularly preferred.

As a solvent, aliphatic hydrocarbons such as hexane and heptane,
Inert hydrocarbon solvents such as aromatic hydrocarbons such as benzene, toluene, and xylene, and alicyclic hydrocarbons such as cyclohexane and methylcyclohexane are used. Olefins include ethylene, propylene, butene-1, hexene-
α-olefins such as olefins of 10 methylbentene/fatty olefins may be mentioned, and these olefins may be used alone or in mixtures of these olefins. A mixture of these and other olefins is used. In the present invention, the polymerization reaction Y of olefin I is carried out in two stages, that is, in the presence of the reaction mixture obtained by polymerization in the first polymerization zone, the second
Further polymerization is carried out in the polymerization zone. First, in some of the first and second polymerization zones, under conditions where the hydrogen/olefin molar ratio in the gas phase is high, for example, the hydrogen/olefin molar ratio is 1 or more, preferably /~30. The reaction temperature is in the range of: to.

℃, preferably in the range of go-iso ℃, and the reaction pressure is under pressure, preferably 0. ! rkg/c! T gauge~10
Oyu, olefin under conditions in the 4-gauge range? A polyolefin produced by homopolymerization or copolymerization and having a low molecular weight, for example, an average molecular weight of 10,000 or less? A predetermined amount 1, for example 30 to 70% by weight of the total amount of polyolefin finally produced, is produced.

Next, in the other polymerization zone, under conditions where the hydrogen/olefin molar ratio in the gas phase is low, for example, the hydrogen/olefin molar ratio is less than 1, preferably in the range 5
The anti-stone temperature is preferably 20A7-00℃! ;0-/k
Olefins are homopolymerized or copolymerized at a temperature of 0°C under an increased reaction pressure, preferably in a range of Q,S Yuichi gauge to lθOkVd gauge to produce polyolefins with a high molecular weight, for example, an average molecular weight of 100,000 or more. A predetermined amount, for example, 70 to 70% of the total amount of all polyolefins to be finally produced.
30 wt % is produced to produce a polyolefin having a predetermined molecular weight distribution.

If necessary between the first and second polymerization zones described above,
A flash facility or a degassing tank can be provided to purge most of the dissolved hydrogen in the polyolefin-containing liquid extracted from the imo zone of the system.

An example of the method of the present invention will be explained in more detail below with reference to the drawings.

FIG. 1 shows a block diagram of seven examples of polyolefin production processes that illustrate embodiments of the method of the present invention.

In Figure 7, the polymerization reactor includes a hydrogen supply line,
Olefin supply line 3, solvent supply line, catalyst supply line! are connected, hydrogen, olefin, solvent,
Catalysts and the like are continuously supplied in a predetermined amount depending on the molecular weight of the polyolefin to be produced. Inside the polymerization reactor, a liquid phase part /a and a gas phase part /b are formed by the above-mentioned feed, and the olefin is polymerized while being stirred by a stirrer IC. The produced polyolefin is continuously extracted from the polyolefin extraction line 6 and supplied to the polymerization reactor λ0. The above hydrogen supply line, olefin supply line 3, and solvent supply line are equipped with supply valves a, Ja, 41a for regulating the respective supplies i', and flow rate detectors for detecting the respective supplies iY -°C, jl), 4tt. )
are provided respectively, and the flow rate detector-1]5. ?
A data signal regarding the flow rate from b, 4 (b) is input to the computer, and a control signal from the computer, which will be described later, is used to control the catalyst supply pump ta to change the olefin concentration and hydrogen concentration so as to produce a polyolefin of a predetermined molecular weight. The stroke and the opening degree of the hydrogen supply valve 2a are controlled.

The liquid level height of the liquid phase part /a is detected by the liquid level height detector/co and input into the computer.

ff! A sampling line 7 is provided in the gas phase part /b of the reaction vessel l, and the gas in the gas phase part /1 is led to an analyzer j, for example, a gas chromatography device, through an on-off valve, and The hydrogen concentration and/or olefin concentration is measured by the analyzer t. A data signal based on the hydrogen concentration and/or olefin a degree measured by the analyzer is input to the computer 30. Further, the pressure in the gas phase portion /b is detected by the pressure detector. The above data signals input to the computer are processed in accordance with a preset program within the computer, and calculations are made of water fraction partial pressure, olefin partial pressure, hydrogen/olefin molar ratio, etc. in the gas phase (1). The value is calculated, and the deviation is calculated by comparing and calculating each calculated value with each target value set in advance to produce a polyolefin with a predetermined molecular weight, and the control signal based on the deviation is used. For example, by operating the hydrogen supply valves J&Y to adjust the hydrogen concentration in the gas phase section 1b, or by operating the catalyst supply pump Ia to adjust the catalyst supply amount, the gas phase section /b can be adjusted. The hydrogen concentration and olefin concentration are controlled such that the hydrogen/olefin molar ratio in the gas phase is adjusted to a predetermined value of 7 to produce a polyolefin having a predetermined molecular ikw.

In addition, even if the hydrogen supply amount to the polymerization reactor is stopped due to changes in the polymerization reaction conditions, etc., and it is still difficult to adjust the hydrogen concentration in the gas phase, the gas phase of the polymerization reactor is ), a gas phase purge valve (not shown) is installed, and the opening degree of the degassing valve is adjusted to purge part of the gas in the gas phase out of the system, thereby adjusting the hydrogen gas concentration in the gas phase. You can also.

It is well known that this is an extremely important element in producing polyolefins by such a continuous method.

There are various possible causes for changes in the polymerization reaction temperature, gas phase pressure, etc., but they are collectively referred to as disturbances.

Examples of disturbances include changes in the amount of catalyst poison components (e.g., water) in the raw olefin, changes in catalyst concentration, changes in catalyst activity when changing catalyst lots, changes in catalyst activity due to changes in co-catalyst,
There are other disturbances that are certain to occur this year.

It is known that when the above-mentioned disturbance occurs, the polymerization reaction temperature, which is the main polymerization condition, changes sensitively, but the polymerization reaction pressure changes with a considerable delay in time compared to the change in the polymerization reaction temperature. In addition, subtle changes in the polymerization reaction temperature become changes in the cooling water temperature without delay and are detected in an enlarged form [however, the sign of the temperature change is opposite], which is better than directly detecting changes in the polymerization reaction temperature. It is convenient to indirectly detect the cooling water temperature change by a cooling water temperature detector //b.

Therefore, when there is a disturbance, the polymerization reaction temperature is detected by the temperature detector io, the deviation is determined from the comparison pressure between the detected value and the preset reaction temperature target value, and the deviation signal is used to cool the polymerization reaction temperature. When the water supply valve //EL is opened and closed, the amount of cooling water supplied from the cooling water supply line // is adjusted, and the temperature of the cooling water entering the cooling jacket changes. //1), predicts the timing and amount of change in gas phase pressure from the timing and amount of change in temperature, and changes polymerization conditions, such as the amount of catalyst supplied, so as to cancel out the predicted pressure change [ Tokukai Showa 3g-///gor
By adopting the above-mentioned disturbances, it is possible to respond quickly and accurately to fluctuations in the polymerization reaction temperature and pressure, and to minimize the fluctuations (refer to No. 1). It is possible to reduce fluctuations in the molecular weight of

By operating as described above, the polymerization reactor/Y can be stably operated under predetermined polymerization conditions, thereby making it possible to continuously produce a polyolefin having a specific molecular weight.

The polyolefin produced in the polymerization reactor 1 is continuously extracted from the polyolefin extraction line 6 and is supplied to the polymerization reactor -0. If the polymerization reaction is carried out in polymerization reactor 1 under conditions of a high hydrogen/olefin molar ratio, and then in the polymerization reactor - ○ under conditions of a low hydrogen/olefin molar ratio, the reaction may be carried out as necessary. vessel l and the reactor-
During this period, it is desirable to install a flash tank or degassing tank to purge most of the dissolved hydrogen in the reaction mixture. In the polymerization reactor 20, a polymerization reaction is carried out under polymerization reaction conditions different from those in the polymerization reactor 1, and a polyolefin having a specific molecular weight is produced at a specific production ratio to produce a polyolefin having a specific molecular weight distribution. .

In the present invention, the polyolefin i# to be supplied from the polymerization reactor L to the polymerization reactor 20 is estimated by calculation processing using the prediction model described later from data such as the amount of olefin and solvent supplied in the polymerization reactor L. , Calculate the amount of olefin supplied to the polymerization reactor and furthermore the amount of hydrogen supplied to the polymerization reactor by calculation processing from the estimated value and the target value determined corresponding to the production of polyolefin having a predetermined molecular weight distribution. By controlling the amount of olefin supplied to the polymerization reactor θ based on the amount of hydrogen supplied or the amount of gas phase purge, the polyolefin of a specific molecular weight to be produced in the reactor 〇 and the specific molecular weight to be produced in the reactor I The production ratio of polyolefin with a molecular weight of

Hereinafter, the second polymerization reaction will be performed using prediction model 71/ from parameters such as the amount of olefin and solvent supplied in the first polymerization reactor.
Prediction of the amount of polyolefin to be supplied to the polymerization reactor will be explained in detail.

First, in order to produce a polyolefin having a predetermined molecular weight distribution, the molecular weight C melt index of the polyolefin produced in the first reactor and the target value l of the production amount ratio L are determined by the following formula (1). decide.

'log M ay=(/-'νm)logM11+W
Hlog M1 proverb ”” (1) M in formula aV
+Average melt index target value MI1 of the polyolefin produced: Target melt index value Ml of the polyolefin produced in the seventh reactor: Target melt index value WH of the polyolefin produced in the first reactor; Target value of production amount ratio of polyolefin Here, the melt index is a measure of the molecular weight of polyolefin, and is determined by the ratio of hydrogen gas concentration to olefin concentration.

M = f (hydrogen/olefin concentration ratio)...f: M = determinant function In the first reactor, as described above, a predetermined olefin supply amount and ( Hydrogen/olefin concentration ratio]
operated under the following conditions. If the first reactor is regarded as a complete mixing tank, the following material balance equation is established.

G in the formula: g phase weight subscript Fp: Polyolefin supply amount 1: First reactor.

,,,state quantity 11Fs of Noo v Hui @ degree
: Solvent supply amount G1 ``'vl''l'l In the formula, Vt! 'f
Fi phase capacity V,: f, (Hl) tl: liquid density ρp/: polyolefin density ρday 1-= f(11) pH/; solvent density fI
=solvent density determining function tl; reaction temperature]! 'p/:' FO/-80/ To/niolefin supply amount 80/-f8 (t1+Pl η inno 80
1: Amount of olefin dissolved in the solvent f3; function P for determining the amount of olefin dissolved, olefin: olefin partial pressure (total pressure x olefin concentration) - to 3- Numerically calculated from each state quantity using equation (2) above. By calculating the amount of polyolefin supplied to the first reactor, an estimated value [Ol(Fp/-4-It's/J)] can be obtained.

h. If a degassing tank is installed between the 7th reactor and the 1st reactor, use equation (3) below as the material balance equation for the degassing tank, and calculate numerically sequentially from each state quantity. By calculating the estimated amount of polyolefin fed to the first reactor [:011("p/10'p2+Fs/-1-Fa
Cough] is obtained.

aa Goose G11 “King-=Fpco+01 (Fp/ +1’θ/)0
2 (Fl)/+Fp+Fa/+Fs+
・・・・・・(3) Subscript 2: State amount of degassing tank The amount of olefin supplied to the first reactor is the estimated value above! It is calculated using the following formula.

From equation (4), in equation 24, WH: target value of the production amount ratio of polyolefin produced in the first reactor [from equation (1)] R2: amount C of polyolefin supplied to the first reactor, estimated value above].

F3: Target value of olefin supply amount in the second reactor [
From Equation (1)] Furthermore, the amount of hydrogen supplied to the fourth reactor is calculated from the amount of olefin supplied and the target value of the hydrogen/olefin concentration ratio determined in accordance with the production of polyolefin of a predetermined molecular weight. That is, it has been known that there is a functional relationship as shown in the following equation between the molecular weight of the polyolefin produced and the polymerization reaction conditions, particularly the hydrogen/olefin concentration ratio in the gas phase.

MI, = f ((hydrogen/olefin concentration ratio...)
・・・・・・(M step 3 in G6 formula: Approximate melt index value f of polyolefin produced in the second reactor: Melt index determination function From the above equation (6), the polyolefin produced in the second reactor The concentration ratio of hydrogen/olefin in the gas phase is calculated from the target value of the melt index of , and the amount of hydrogen supplied is calculated from this concentration ratio. If the concentration ratio cannot achieve the target value, the amount of gas Y in the gas phase to be partially purged may be calculated.

Hereinafter, a method for controlling the amount of olefin and hydrogen supplied to the second polymerization reactor using the above prediction model will be described in detail.

In FIG. 1, the polyolefin produced in the polymerization reactor 1 is supplied from the extraction line 6 to the polymerization reactor 0 via a degassing tube (not shown) if necessary. An olefin supply line λ/, a hydrogen supply line 1 and a solvent supply line 3 are connected to the reactor, and olefin, water bath medium, etc. are continuously supplied in a predetermined amount according to the molecular weight of the polyolefin to be produced. has been done. Inside the reactor 50, a liquid phase part -○a and a gas phase part 20b are formed from the above-mentioned feed, and the polymerization of olefin is carried out while being stirred by the stirrer -○○.

Man-made polyolefin is a polyolefin extraction line! are continuously extracted from. The above-mentioned olefin, hydrogen, and solvent supply lines are equipped with supply valves ko/a, ko, 2a, and λ3a for adjusting their respective supply amounts, and flow rate detectors ko/1), λ3a for detecting their respective supply amounts. Co., Ltd. b and Co. 3b are provided. The liquid level height detector 5t is in the liquid phase section.
It was established in 2011.

As mentioned above, in the polymerization reactor 1, input signals regarding the supply amount of olefin and solvent, the pressure and component composition of the gas phase (concentration of olefin and hydrogen if necessary), the temperature and liquid level of the liquid phase, etc. is the above prediction model (2) that is pre-programmed in the computer.
An estimated value of the amount of polyolefin (produced) to be supplied to the first polymerization reactor or the second polymerization reactor is calculated based on the formula or formula (3), and the amount of polyolefin (produced) is calculated. The estimated value of !, the target value of the polyolefin produced in the polymerization reactor 2, 20, that is, the production amount ratio of the polyolefin to the specific molecular weight produced in each polymerization reactor ((4) and W in equation (5)
Based on the target value of the H value, the amount of olefin supplied to the polymerization reactor - is calculated by calculation based on the above formula (5), and the amount of hydrogen supplied is further calculated based on the target value of the hydrogen/olefin molar ratio. The opening degree of each of the olefin supply valve λ/a and the hydrogen supply valve Cocoa is adjusted by a control signal from the computer that correlates with the calculated olefin and hydrogen supply amounts based on the above calculation results.

In addition, a sampling line roller is provided in the gas phase section 20b of the polymerization reactor -0, and the gas in the gas phase section Ob is guided to the analyzer λ7, for example, by gas chromatography, through the on-off valve roller a. , the analyzer core measures hydrogen concentration and olefin concentration. Signals based on the hydrogen concentration 28 and olefin concentration measured by the analyzer are sent to the computer 30.
is input. Also, the gas phase part job is detected by the pressure detector.
pressure is detected. Polymerization conditions for producing a polyolefin of a predetermined molecular weight, such as target values such as hydrogen concentration, olefin concentration, hydrogen/olefin molar ratio, etc., are programmed in advance in the computer, and calculations are performed according to changes in the signal amount. The processing is performed, and the opening degree of the hydrogen supply valve, 2 core a or gas phase barge valve λ/i1a is manipulated by a control signal from the computer correlated to each supply amount based on the calculation result, and the gas phase part, The hydrogen concentration in 20b is adjusted to maintain the hydrogen/olefin molar ratio within a predetermined range, resulting in a predetermined molecular weight distribution! A polyolefin having the following properties is produced. The gas phase purge valve Koda a is installed in the degassing line Koro of the gas phase part Ko Ob, and the hydrogen supply valve 2.2e
Even if L is fully closed, and the hydrogen concentration in the gas phase θb cannot be adjusted, a part of the gas in the gas phase is purged out of the system to adjust the hydrogen concentration in the gas phase. It is used.

In addition, when the reaction is performed in the first polymerization reactor under conditions where the molar ratio of hydrogen/olefin in the gas phase is high, and then in the second polymerization reactor under conditions where the molar ratio of hydrogen/olefin in the gas phase is low. In this case, the amount of dissolved hydrogen dissolved in the polyolefin-containing liquid supplied from the extraction line 6 of the first polymerization reactor to the second polymerization reactor is large, and the hydrogen concentration in the second polymerization reactor is low. Adjustment is often not easy.

Therefore, when conducting one reaction using the method described above, a degassing tank is installed between the first polymerization reactor and the second polymerization reactor, and the degassing tank is used to remove the gas from the first polymerization reactor. After purging a part of the dissolved hydrogen dissolved in the extracted polyolefin-containing solution to the outside of the system, the polyolefin-containing solution is supplied to a second polymerization reactor to adjust the hydrogen concentration. is desirable.

In the present invention, when polyolefin is produced by the above-mentioned control chain, especially when the seventh polymerization reactor is in an unsteady state as described above, it is important to avoid fluctuations in that state! It is possible to quickly and accurately respond to and follow changes in the conditions of the second polymerization reactor.

For example, when starting a polymerization reaction, the amount of solvent supplied, the temperature in the liquid phase, the pressure in the gas phase, and the hydrogen/olefin molar ratio are adjusted to predetermined values in the first polymerization reactor. , the supply of olefin and catalyst is started, and while the reaction temperature is maintained at a predetermined value, the supply amount of olefin and catalyst is gradually increased to a predetermined value, and the supply amount of olefin and solvent, temperature of the liquid phase, and liquid level are increased. Input signals [to the computer] concerning the height, the pressure of the gas phase, the concentration of olefins and hydrogen cause the amount of polyolefin to be fed into the second polymerization reactor to be calculated in the computer based on the above-mentioned predictive model. A predicted value is calculated, and the olefin supply amount is calculated from the predicted value based on the above formula (5). Furthermore, the hydrogen supply amount is determined based on the target value of the hydrogen/olefin molar ratio, and based on the above calculation result. The amount of olefin and hydrogen supplied is controlled by a control signal from a computer that correlates with the amount of olefin and hydrogen supplied, and the amount of the supplied amount is supplied to the second polymerization reactor while producing polyolefin χ having a predetermined molecular weight distribution. The amount of polyolefin C produced is gradually increased to a predetermined amount.

Further, when the polymerization reaction Y is to be stopped, the supply i of the catalyst is stopped and maintained in the first polymerization reactor l, and is gradually reduced, according to the input signal to the C computer regarding the above-mentioned data.

The above polymerization reaction! As in the case of starting, the predicted value of polyolefin, olefin and hydrogen supply amount to be supplied to the second polymerization reactor-〇 is calculated, and the computer calculates the predicted value of polyolefin and the supply amount of olefin and hydrogen based on the calculation results. The supply amount of olefin and hydrogen is controlled by the control signal of , and a polyolefin having a predetermined molecular weight distribution is produced, and the supply amount is gradually decreased in proportion to the polyolefin (produced) i' supplied to the second reactor. The polymerization reaction is stopped.

〔Example〕

Figure 2 shows the operating method at the start of the λ-stage polymerization reaction, that is, the change in the amount of ethylene supplied to the polymerization reactor.
Progress of polymerization reactor t.

That is, B is when the ethylene supply amount is controlled by the method of the present invention, 0 is when the ethylene supply amount is larger than B, and D is when the ethylene supply amount is controlled by the method of the present invention.
The figures show cases where the amount of ethylene supplied is smaller than that of the previous example. Figure 3 shows the melt index (M
This shows the transition of F.

In addition, Fig. 4 shows the operating method when the polymerization reaction is stopped, that is, the change in the amount of ethylene supplied to the polymerization reactor, and A' is the change in the amount of ethylene supplied to the first polymerization reactor. ′
is the transition of the second polymerization reactor, that is, B' is the transition of the second polymerization reactor, that is, when the ethylene supply i1 is controlled by the method of the present invention, 0' is B
When the amount of ethylene supplied is greater than B', 1)' is shown as t when the amount of ethylene supplied is less than B'. FIG. S shows the transition of the melt index of the polyethylene produced in each of the above cases B' to D.

〔Effect of the invention〕

According to the present invention, in producing a polyolefin containing a specific molecule-m'va by step polymerization of an olefin,
Changes in the state of the first polymerization zone, such as when starting, stopping, or changing reaction conditions, can be quickly and accurately responded to changes in the conditions of the second polymerization zone. Therefore, it is possible to extremely stably produce polyolefins having a predetermined molecular basin distribution, and it is possible to save labor through automation. In addition, from an industrial perspective, it greatly contributes to safe operation and operation.

[Brief explanation of drawings]

Figure 1 is a block A diagram of an example of a polyolefin production process showing an embodiment of the method of the present invention by manpower, and Figure 2 shows the amount of ethylene supplied to the polymerization reactor at the start of the λ-stage polymerization reaction. An example of the transition is a graph showing changes over time. Figure 3 is a graph showing changes in the melt index of polyethylene produced at the start of the reaction. Figure 3 is a graph showing changes in the amount of ethylene supplied to the polymerization reactor when the polymerization reaction is stopped. Figure S is a graph showing an example of static time, and Figure S is a graph showing changes in the melt index of polyethylene produced at the time of termination of the reaction. In FIG. 1, l is the first polymerization reactor, /a is the liquid phase part,
lb is the gas phase part, 10 is the stirrer, /d is the cooling jacket,
ko is the hydrogen supply line, 3 is the olefin supply line, da is the solvent supply line 5.2a, Ja, 4Za are the respective supply valves, lb, 31), llb are the respective flow rate detectors,
S is a catalyst supply line, 5a is a catalyst supply pump, 6 is a polyolefin extraction line, 7 is a sampling line, 7a
is a sampling line opening/closing valve, g is an analyzer, 9 is a pressure detector, 10 is a temperature detector, /l is a cooling water supply line,
/la is the cooling water supply valve, llb is the cooling water temperature detector, /
2 is liquid level height detector, -〇 is i, 2/combination reactor, λOa
is a liquid phase part, θb is a gas phase part, -〇〇 is a stirrer, 21 is an olefin supply line, 5.22 is a hydrogen supply line, KO is a solvent supply line, KO/a% KOKO a. 3a are the respective supply valves, ko/b, and λkob. 3b is each flow rate detector, Koku is the degassing line,
Ko (Za is the gas phase purge valve, Ko3 is the polyolefin extraction line, -≦ is the sampling line, -1B- is the sampling line opening/closing valve, Ko is the analyzer, Ko is the liquid level height detector%, 29 is 3/ represents a pressure sensor, 3/ represents a temperature sensor, and 3θ represents a computer.

Claims (2)

[Claims] (1) In the presence of catalyst, solvent and hydrogen, olefin is
Stage polymerization zones, that is, one of the polymerization zones, is polymerized under conditions of a high hydrogen/olefin molar ratio in the gas phase to produce a predetermined amount of low molecular weight polyolefin, and then in the other polymerization zone, the gas phase is polymerized to produce a predetermined amount of low molecular weight polyolefin. In producing a polyolefin having a predetermined molecular weight distribution by polymerizing under conditions of a low molar ratio of hydrogen/olefin in the phase to produce a predetermined amount of high molecular weight polyolefin, supplying an olefin and a solvent in a first polymerization zone. Detect the olefin concentration and pressure in the gas phase, as well as the temperature and liquid level in the liquid phase, input these data signals to a computer, and use the data to calculate the first Estimating the amount of polyolefin to be supplied from the polymerization zone to the second polymerization zone, and calculating the amount of polyolefin to be supplied to the second polymerization zone from the estimated value and a target value determined corresponding to a polyolefin having a predetermined molecular weight distribution. The olefin supply amount and furthermore the hydrogen supply amount are calculated, and the olefin supply amount to the second polymerization zone, the hydrogen supply amount or the gas phase purge amount are determined by the calculation control output of the computer performed based on the calculated values. 1. A method for producing a polyolefin, which comprises adjusting the molecular weight distribution to produce a polyolefin having a predetermined molecular weight distribution. (2) In the presence of catalyst, solvent and hydrogen, olefin is
Stage polymerization zones, i.e., in one of the polymerization zones, polymerization is performed under conditions with a high molar ratio of hydrogen to olefin in the gas phase to produce a predetermined amount of low molecular weight polyolefin, and then in the other polymerization zone, the gas phase is polymerized to produce a predetermined amount of low molecular weight polyolefin. A polymerization reaction control device for producing a polyolefin having a predetermined molecular weight distribution by polymerizing under conditions of a low hydrogen/olefin molar ratio to produce a predetermined amount of high molecular weight polyolefin, the first polymerization The following means (a) to (f) provided for the zone: (a) means for detecting the amount of olefin supplied; (b) means for detecting the amount of solvent supplied; (c) hydrogen concentration in the gas phase. and/or means for detecting olefin concentration (d) means for detecting pressure (e) means for detecting temperature (f) means for detecting liquid level The amount of polyolefin to be supplied from the first polymerization zone to the second polymerization zone is estimated through calculation processing using the data, and a target value is determined corresponding to the estimated value and the polyolefin having a predetermined molecular weight distribution. Calculating means (means (g)) for calculating the amount of olefin to be supplied to the second polymerization zone as well as the amount of hydrogen to be supplied to the second polymerization zone by arithmetic processing, the olefin supply to the second polymerization zone calculated by the means (g) In order to adjust each according to the amount and hydrogen supply amount, the following (h) ~
(k) Means (h) Means for adjusting the amount of olefin supplied (i) Means for adjusting the amount of hydrogen supplied (j) Means for measuring the hydrogen concentration and/or olefin concentration in the gas phase (k) Gas phase A polymerization reaction control device for producing a polyolefin having a predetermined molecular weight distribution, comprising means for purging a part of the gas out of the system and adjusting the amount thereof.