DE1520064A1 - Process for the polymerization of ethylene under high pressure - Google Patents

Description

DR. I. M. MAAS

DR. W. G. PFEIFFER 1520064

PATENT LAWYERS MUNICH 23 UNGERERSiR. 25 - TEL. 333036

Halcon International, Inc. Hew York, N ₃ Y ₀ , V.St ₀ A

Process for the polymerization of ethylene under high pressure

The invention relates to processes for high pressure polymerization of ethylene in an elongated reaction vessel, in which the reaction mixture is placed on the side Pressure changes or so-called flow pulses or Is subjected to power surges in order to ensure long-term continuous operation. The invention relates to a method whereby the time between the individual flow surges is adjusted according to the extent, up to which the flow of the reaction mixture and the dissipation of the heat of reaction through the walls of the

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ReaktionegefäQes were reduced since the preceding current pulse, as eo is determined by MeaBung certain process variables, and in particular a darartiges V _c rfahren, wherein the time of T _e iles a joden cycle, wherein the ^ reaction proceeds under constant conditions, corresponding to a function of the preceding Cycle is set so that if the value of this puncture in the previous cycle is less than the value of the function in the cycle immediately preceding this, the time of the current cycle, in which the reaction proceeds under constant conditions, is shortened, whereby the ejection is shortened the reaction vessel is increased and the quality of the product is improved o Conversely, if the value of the function of the previous cycle is greater. The value of this function is considered to be related to the degree of contamination of the reaction vessel

Bs is known, the Hochdrucopolymerieation of ethylene in an elongate reaction vessel with intermittent D _r uckstößen perform a long-term continuous

to borrow implementation of the method / achieve, wherein the Pressure surges occur at fixed time intervals (USA «patent specification 2 852 501) ο The disadvantage of this method is the low output of the reaction vessels o and in Products do not meet the requirements

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Beschaffenheitο There is therefore in this field of T _e chnik the task process to provide improved quality and at the same time to eteigern the yield per the reaction vessel air production of polyethylene.

In a process for the polymerization of ethylene under high pressure in an elongated reaction vessel wherein the reaction mixture regular D _r uckstößen is subjected at least once in two Hinuten in such a way that, at each pressure pulse to increase the linear velocity of the mixture through the Reaktioncgefäß on at least the If this occurs twice, the object is achieved according to the invention by setting the period of operation of the reaction vessel under constant conditions according to the factor of the degree of contamination since the previous cycle, so that if this factor for the previous cycle is increased by more than a predetermined limit amount (la Btrtiob bie of 0 5 f>%, preferably at least 1 $ dta Wtrte stint · immediate predecessor) is smaller let ale immediate for its predecessor, the time is verkürst to -nächsten Druoketoß and vice versa, and if this factor for both cycles within the predetermined Gren values is the same , the time remains the same in both, whereby this factor corresponds to the integral defined by the following equation:

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(τ _ββ -T) ^b de

v / orin mean

I χ the integral A * a constant

T «reactor temperature falls below during operation constant conditions

T ». Temperature in the reactor

b β a constant (g) a time in seconds

I = time of the start of the rush current O ₂ "= time of the end of the rush current

The rush current is preferably achieved by opening the The outlet side of the reaction vessel against an area lower pressure achieved =

It is particularly favorable when the D _r uckabfall about 5 to 23 $> of ions React print is.

The reaction pressure is preferably at least 100 atmospheres (20,000 psig).

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Preferred React ion temperature s in the range of 200 ⁰ C (400 ⁰ P) to just below the temperature at which an explosive decomposition deo reaction mixtures.

Particularly good results are obtained when using a reaction mixture containing less than 200 T _e ile / million oxygen contained as an initiator or catalyst

The pressure change frequency is preferably in the range from 1/10 to 1/120 see "* ¹ o

According to one embodiment of the method according to the invention becomes the linear velocity corresponding to the factor of the degree of pollution since the previous StrometoS increased so that if this paktor for the previous one Current surge by more than a predetermined limit amount less than the factor for the one immediately preceding it, the increase in speed is increased and vice versa, this factor corresponding to the integral defined by the equation given above ο

This can also reduce the duration of the reactor operation constant conditions according to the factor of the Degree of contamination since the previous power surge so set v / earth that if this paktor for üen

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previous rush current is smaller than the factor for which it is immediate by more than a predetermined limit amount previous! shortens the time to the next electrical surge will, and vice versa.

The accompanying drawings of a preferred embodiment of the invention and the following B _e ispiele illustrate the invention without limiting it. Parts and percentages are based on weight, unless otherwise stated *

example 1

As shown in the accompanying drawing, a mixture of ethylene and initiator is passed through line 11 into preheating zone 12 and then into reaction zone 10a of elongated drilling reactor 10. In the reaction zone 10a, the same conditions are maintained in a known manner that considerable polymerization of the ethylene took place. The polymer formed and unconverted ethylene can, if desired, be further cooled in the cooling zone 12 and then through the pressure relief valve 14 the line 16 discharged \ - «r & an. The ec-alcfcion mixture from the line 16 is provided. further processed in a known way "

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A voltmeter 24 is provided at the Realcto inlet to measure the pressure in the reactor. The pressure signal is passed on from the voltmeter via line 25 to the pressure measuring and control unit 36, which then acts in a corresponding manner on the control valve 14 for the reactor pressure. , reaction and Kühlzono provided and D _r uckwasser of different temperatures flowing through the dumbbell through the lines 30, 31 '32, 33, 34 and 35' to cause the respective required heating or cooling "

While the polymerization takes place in the reactor tube 10, accumulations of polymers form, from which swan « changes in throughput, the heat transfers from the reactor and the Quality dee products result.

Oemäfl a preferred embodiment form of the invention A temperature measuring device 18, for example, allows control of this polyaerane collection. an immediately responding thermocouple is provided in the critical section of the reactor, where the reactor temperature is above 204 * 0 (400 ° P), and above the line or lines 19 to the temperature controller and, via line 21, to the computer or calculator 22 connected, which is connected to the timer 26 via the line 23

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The timer is in turn connected via the line _x mlt to the switch 28 and actuates this S _c holder, which determines whether the valve .14 at the reactor outlet is controlled by the pressure regulator 36 or the controller 38 for the valve division. Further measuring devices 18a, etc. can also be provided, which then analog circuits, controllers and computers etc. (not shown) on v / iron "

The computer 22 is designed to calculate the time integral of the reactor temperatures for the past time during the pressure drop, as defined by the equation given above. The result is an indication of the degree of contamination of the reaction tube. In dependence on the result computer and timer set the time interval between the measured pressure drop and the next pressure drop, the calculated integral of the temperature is more than a predetermined Grenebetrng greater via the line 23, a "case than the previously measured, then the interval is to correspondingly reduced to the next D _r uckeendung. A smaller value for the integral of the temperature over time during the pressure change indicates a greater degree of reactor deposits and vice versa

The predetermined limit amount, which can range from 0 to 5 $> the value of the integral, is in this example 2 # ₀

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With the above-described operation, an in A much greater degree of trouble-free production is achieved than by the known method, whereby the pressure change takes place according to a predetermined or fixed cycle. When carrying out the process according to the invention generally those given in U.S. Patent 2,852,501 Polymerization conditions of the temperature des

■ ·

Pressure and the catalysts or initiators used can be used "Depending on the desired product but also other initiator systems and modifiers

to be used »

In a series of tests, normal continuous operation without changes in pressure over time results in a low output and the frequent occurrence of "continuous", cUh "practically uncontrollable decomposition reactions improved quality of the product and somewhat higher yields. Some of the experiments give a product of poor quality. The reaction pressure is at 1540 kg / cm ² (22,000 psi) and the pressure change is wide open the exhaust valve up to a pressure drop to about 1225 kg / cm (17 500 pei) obtained is then closed daa V _e ntil and allows the D _r uck

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come back to the reaction address (in about 1 to 15 seconds), after which this is maintained for 55 seconds and then the cycle is repeated by opening the outlet valve. The reaction temperature is about 285 ⁰ C (545 ° F) »1 · αβ Beschickungsgemiseh contains etv / a 20 parts / million oxygen as an initiator and the residence time is about 1 to 2 minutes,

According to the modification of the above-described procedure according to the invention, the length of time until a pressure change is set in accordance with the integral of the temperature in the reactor according to the above equation ₉ so that if this integral for one cycle is greater than the predetermined limit value by more than daa for the immediately preceding cycle, the time until the next pressure drop is extended and vice versa. If the integrals within the predetermined limit values are equal, then the times of approximately equal length "The lengthening or shortening of each cycle during which the operation is continuous and D _r uckaenkungaperiode comprises, is the period are about 5 $ of the D _For the cycle in seconds »Daa integral is calculated with the computer connected to a timer 26 which controls the outlet valve U via the selector switch 28, the pressure regulator and the valve position regulator 38» In this way, a high quality product is regularly e aalten and the

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Yield is compared to an average of about 5 to 8 # that of the previously known methods increased, resulting in shorter ones Shutdowns that are required to clean the system.

Purely for the purposes of the method according to the invention known and commercially available instruments are used, the use of a high-speed calculator, e.g. an electronic analog computer is preferred.

According to a preferred Aiisführungsform the pressure through a stress »βsC 24 and associated therewith amplifier giMBsen which supplies a (Reich current signal of up to 10 volts, that a D _r piece of up to 3300 atmospheres (50,000 corresponds psig · The differens between the signal of the voltmeter and the set pressure (for example, set to a potentiometer) is algebraically aufgtgeben to an amplifier and the resulting signal is conducted away through the conduit 29 below a series of amplifiers 14 control the outlet valve to maintain the desired pressure. An ordinary three-stage regulator can be used to control the reaction pressure during the continuous part of the cycle.Both the amplifiers and the three-stage regulator are located in the pressure regulator 36ο

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«12

While dee _Τ Θ ϋε of the cycle, wherein the piece falls D _r; the temperature signal from one or more thermocouples (18, 18a UBWo), which are located in the reaction zone, where the temperature is at least 204- * C (4C-O ⁰ F), continued to one or more integrators, each of which the Zeitintegrel the reaction temperature t during this period according to the above equation eiv · reckoned the output of integrator joden (all in the computer 22 are included) reaches the timer for the automatic adjustment de3 time interval until the next D _r uckßenkung. During this part of the cycle of D _r piece until su 15 / "dec ReaktionBdruck3 reduced by a previously unidentified extent s.3 _o, thus a corresponding reduction in temperature is accompanied. This pressure reduction is achieved by the control of the valve 14 through the Ventiletellungsreglor 58 ₀

The desired time interval for the continuous part operation for the following cycle is determined by the voltage output of another integrator in the timer determined according to the signal received from computer 22 through line 23. At the beginning of this part of the In operation, another integrator, which is also contained in the timer 26, measures the actually executed Time of this part, when that voltage signal of the elapsed

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Tent equal to the voltage signal for the desired period of time is what is measured by a comparator contained in the timer 26, a brief pulse for the decrease in pressure is fed to the selector switch 28 via the line 27.

The momentary pulse operates the selector switch 26 in such a way that it closes appropriate Beiais. As a result, the valve 14 is controlled by the valve position controller 38. In the same way, a signal is passed through the line 27a to the computer 22, as a result of which each integrator in the computer 22 starts calculating the time integral of the reactor temperature in accordance with that given above. Grip starts until the reactor pressure has dropped to a predetermined value. If the signal determined by the integral during this period is smaller than the value obtained in the same way in the previous cycle by more than the previously specified amount, then a signal is passed on through the line 23 to the timer 26 as a result of the fact that the Duration of continuous operation of the following cycle is reduced. If this signal is greater, then this duration is extended in the same way in the next cycle. The percentage increase or decrease in the cycle time can be adjusted using the appropriate potentiometer, e.g. ₀ in a range of up to £ 20,

909846 / 10SI

Preferably less than 10 i »of the previous continuous operating time. Precautions have been taken to keep the acidity of the cycles within predetermined maximum and minimum «limits.

When the reactor pressure is decreased by a predetermined value, Z ₀ B ₀ 5 to 15 # of the pressure during the continuous operation, the comparator 40 gives a signal through the line 41b to the selector switch 28 and another signal through the line 41a to the Computer 22 next. After receiving the signal from the comparator, the selector switch opens appropriate circuits in such a way that the

Valve 14 by controlling the pressure regulator 36 and by resetting each of the various measuring devices to the predetermined output value for the beginning of a new continuous operation. In appropriate Catfish hurt on the signal from the comparator via the Line 41a to count every integrator in the computer, so that he can calculate the time integral of the reactor temperature during the following pressure reduction period in the starting position is brought after the integral has been stored in a suitable memory device in the integrator. This stored signal is transferred to the Compared to the integral signal that must be calculated for the following operating cycle ο

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You can carry out the method according to the invention with other control devices can be combined, e.g. controlling the maximum reactor pressure and start-up and Shutting down the operation, which can be done manually or if necessary caused by a corresponding computer modification can be. Ea can be used as an alternative to the one in the patent. », ... <. (Patent application S 80 886 IYd / 39o) described method can be applied.

Example 2

Xthylenbeschiokungsgfts (about 5450 kg per hour, 12,000 lbs / hr.) With a spit clay about 1540 atü (22,000 peig) and a temperature of 26 ° G (80 *?) With an oxygen content (O.) of 20 parts / million is inserted into the Vorheiezone wherein the temperature mat 177 * 0 (350 *?) is increased.

Si · Setting the instruments is as follows Torgenonaeni

1 · S «r timer 26 is set to a cycle duration of 55 seconds set and the time of observation is the elapsed time thereafter 10 seconds. In this way the timer 26 actuates the selector switch 28 via the Line 27 .so that the pressure regulator 36 with the engine is connected in the valve unit for adjusting the valve H (via line 29). At this time

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Therefore, the valve H is under the control of the pressure regulator 36 t which adjusts the position of the valve in such a way that that the pressure at the voltmeter 24 is kept at 1540 atmospheres.

2, The computerized measurement controller 22 has registered a value of 58 000 during the previous Vorherr D _r ucksenkung (ties also happens to be its value in a previous throughput where the reactor was clean) ο

3ο The temperature measuring controller 20 shows a temperature Ton 282 ⁰ C (540 ⁰ P).

4. The valve position regulator 38 is set to an opening of 70 1> and is not in the circuit at this point in time since the timer keeps the selector switch in the open position.

5. The comparator 40 is set to and is at 1330 atm (19,000 pslg) as well not in the circuit. Its function is to determine the actual reactor pressure from the measuring device is transmitted via line 25 and line 25a, to compare with its set pressure. When the comparator is put into operation and these two If the pressures are equal, an electrical signal is passed on to the controller 22 through the line 41a

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When the timer reaches the end of the 55 second time, the following happens:

a) The timer 26 actuates the selector switch 28 so that the valve position controller 38 is connected to the motor of the valve H via the line 29. The valve now goes into the 70 % open position. At the same time, the timer 26 is reset to 0. In addition, the timer 26 starts the computer 22 at the same time.

b) Using comparator 40, compares the actual reactor pressure transmitted to it by voltmeter 24, with its pressure set point (1330 atü). If those both values (both of which are forwarded as electrical voltages that are appropriately amplified) are the same, then the comparator actuates the selector switch 28 (via line 41b), so that the motor for: the valve H, in turn, is controlled by the pressure regulator 36 and at the same time the comparator die Calculation of controller 22 aborts via line 41a «,

c) The three-stage pressure regulator 36 now takes over its again Function whereby the reactor pressure is increased to its set value (1540 atU). At the same time the Computer 22 performs the calculation and compares the result

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with the control point (the stored tent temperature integral for the previous cycle). If the calculated integral is less than the control point set on the computer 22, beyond the predetermined limit, the computer will reset the time in the timer so that the next cycle by a percentage of the previous cycle, that on the timer 26 was set, is shortened, and / or the computer resets the pressure control point on the comparator 40 via the line 23a, so that the control pressure of the comparator 40 is reduced o If the calculated integral is greater than the control point by more than the predetermined limit amount, then the computer the timer 26 in the V / eiae one that the next cycle wirdo extended If the correction of the computer is unsuccessful, then the subsequent cycles are too short (less than 30 seconds) ₀ at this point, the alarm device 43 actuated (by a signal from the line 42), whereupon the operating personnel shut down the plant and the reactor with a solution ittel, ZoB. Xylene cleans.

This procedure leads to improved results which are analogous to those obtained according to Example 1 »

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Example 3 Preferably "more than a computer-controlled Hegler."

the same type as the computer 22 provided «Each of these

has its own unit 20 and its own thermocouple (18a etc.) at different points in the reactor. As long as it is known that the reactor is clean, various corresponding values are set as control elements on each computer-controlled controller, but with each computer while the pressure drop does its own calculation.

Each computer is designed so that the calculated value generates a high voltage signal when the time cycle of 26 is to be shortened and a low voltage signal when the time cycle of 26 is to be lengthened. The voltage at the output of each computer is then introduced into a high-voltage transformer (Swartouta Underide and Overide Adapter »Type A5A aind suitable for this).

This high voltage selector locks out an ifl spring voltage signal from any of the computers for as long as from any one another computer comes a high voltage signal, so that one Signal that leads to a shortening of the cycle time is preferably forwarded. So that leads the signal that eventually passes through the high voltage selector switch that - - Correction of the tent generator 26 and / or aes control point aea Komparatvore 40, as explained in Example 2, from ..

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The predetermined Grenebetrag is within an operations from O to 5 # of values dee integral in dependence on the respectively desired Ä'nderungsgeschv / indigkeit selected which in turn can be derived from the experience with the overall system · Is the Vert O f, "then causes if there is very little difference between the relevant integrals, the cycle duration is adjusted. If, on the other hand, the predetermined value is higher, e.g. £ 2, the cycle duration will only be changed when the difference between the integrals is at least 2 $> (dee er et en integrals) let ο the same applies to every other value of the ranges mentioned * here it possible to use less sensitive instruments and trotedem get a reliable operation jeu. A value in the range of £ 1 to £ 5 is appropriate.

BAD ORIGINAL 0 9 8 4 6/1055

Claims (1)

Claims 1. A process for the polymerization of ethylene under high pressure in an elongated reaction vessel, wherein the reaction mixture is subjected to regular pulses of current at least once every 2 hours in such a way that with each pulse an increase in the linear velocity of the mixture through the reaction vessel to at least twice takes place, 'characterized in that the duration of the reactor operation under constant conditions is set according to the factor of the degree of contamination since the previous shock, so that if this factor for the previous shock by more than a predetermined limit (in the range of 0 to 5 # the value of its immediate predecessor) less i * t than that for its immediate predecessor, the time to the closest collision is shortened and vice versa, and if these factors are the same within the predetermined limit values, the time remains the same, this factor being the duroh defined the following equation Integral corresponds to: BAD 909846 / 1Ö6S in which significant I β is the integral A ■ a constant Reactor temperature during dea operations under lihblibd Bdi p constant conditions T «temperature in the reactor b * a constant η * time in seconds ₁ m Time of the start of the StromstoQea ^H 2 β time of the end of the current impulse a 2. The method according to claim 1, characterized in that the current surge is obtained by opening the outside of the reactor wide against an area of lower pressures and working at a predetermined amount of less than 1 fl . 3. The method according to Anepruoh 2, characterized in that a pressure drop of 5 to 25 pounds dea reaction adruoka is used. 4 »The method according to claim 3, characterized in that one a reaction address of at least UOO atü (20 0OO pal «} applies. BATH 909846 / $ 105 5. The method according to claim 4 »characterized in that an Eeaktiottetemperatur in the range of 200 ⁰ C (400 ⁰ F) ble course applies before the temperature, the Heaktionsgenisch explosive serset. 6 · Method according to claim 5 * in that one less than every 200 parts / million oxygen used as an initiator in the reaction mixture. 7 · The method according to claim 6, daduroh known that one a shock frequency of 1/10 to 1/120 see * "applies and. ■ works with a predetermined amount of 2 # * 8. Modification of the method according to claim 1, daduroh marked that one can increase the linear speed of the factor of the degree of contamination since the previous stream, so that if this factor for the previous shock by more than a predetermined amount (in the range from 0 to 5 % of the value set of the immediate predecessor) is less effective than that for its immediate predecessor, the The increase in speed is increased and vice versa, and if the two factors are equal within the predetermined limit values, no change is made, this factor corresponding to the integral defined by the following equation 9098A6 / 106I where mean: I ■ the integral A «a constant Reactor temperature during operation »under li p constant conditions T · temperature in the reactor b * a constant * Tent in seconds j ■ Tent dea Beginning of the current surge W j * tent at the end of the power surge 9. The method according to Anapruoh 8, characterized by the fact that the days of reactor operation are set under constant conditions according to the degree of contamination as of the previous reaction, so that if this factor is more than a predetermined one for the previous shock Amount (in the range from 0 to 5 i> the value of its unnatural larger predecessor) smaller int ala of the for an immediate IT failure, the tent is shortened until the next collision and vice versa and if the two factors are the same within the predetermined limit values, the duration dea Reactor operation8 is not changed under constant conditions, _A ^. BATH ORIGINAL 909846 / 10SI