DE2411180A1 - CONTINUOUS BLOCK POLYMERIZATION PROCESS OF POLYALKYLAROMATIC POLYMERIZES - Google Patents

Description

St. Louis, Missouri / USA

Continuous block polymerisation process of polyalkenyl aromatic polymers

Those skilled in the art of styrene polymerization have long recognized that polystyrene and similar alkenyl aromatic polymers having a substantially narrow molecular weight distribution for many applications, and are particularly advantageous for injection molding applications. The professional world has also various high volume, commercial molded products which require a relatively broad molecular weight distribution; sometimes has they further modify their viscosities at the mold temperatures by using internal plasticizers, mold release

(O8rl2-O25O A & W) -2-

Telegrams: BERGSTAPFPATENT Munich Banks: Bayerische Vereinsbank Munich 453100 TELEX: 05 24 560 BERG d Hypo-Bank Munich 389 2623 Post check Munich 653 43 -808

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medium and the like. Both types of these polystyrene products for molding applications have enjoyed great popularity and good prices. In the past, practice has gone over to separating these very different products batchwise reactions or in the case of the polymers with a relatively broad molecular weight distribution produced in a separate continuous bulk polymerization process. So far, however, there was still no continuous block polymerization process, which is carried out with the same procedure and with the same Equipment both polystyrene with a narrow molecular weight distribution and polystyrene with essentially different properties of relatively broad molecular weight distribution. Surprisingly, however, a method was found after which one polystyrenes from a uniform by a continuous block polymerization process Can produce medium molecular weight distribution and also polystyrenes with a relatively broad Molecular weight distribution. Such a continuous bulk polymerization process can according to the same procedure and with the same equipment be performed. The polystyrenes of different average molecular weight and physical Properties and the production rates thereof are determined by the fact that special reaction

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conditions and flow rates are selected and maintained in the process. The new continuous bulk polymerization process of the present invention therefore brings about a remarkable flexibility and enables many types of polyalkenyl aromatic polymers of different physical properties to be prepared without changes in the process equipment and process control and piping system are required. Furthermore, this new block polymerization process brings with it a similar flexibility with regard to the production capacity of polyalkenyl aromatic polymers, which can be quickly adapted to the market requirements for the various polymers. The significant economy which is realized in this way in the design, construction and process management for such polyalkenyl aromatic polymers makes the present process particularly advantageous for industrial use. . . The present invention is directed to an improved continuous bulk polymerization process for the preparation of polyalkenyl aromatic polymers. These polymers are produced with molecular weights in the range from about 20,000 to 100,000 Staudinger and have a dispersion index in the range from about 2.0 to A ₁₀ .

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The procedure involves the practical implementation of several stages at the same time, namely the following: a) The supply of a monomer mixture, which at least a monoalkenyl aromatic compound of the formula

C = CH ₀
Ar

comprises, in which Ar is a phenyl or halophenyl radical and X is a hydrogen atom or an alkyl radical means less than 3 carbon atoms in a first continuously stirred reaction zone; b) Maintaining the reaction conditions in the first continuously stirred reaction zone, which leads to 10 to 100% of their volume with a liquid phase mixture of the monomer mixture and its polymer is filled to a polymer with a molecular weight of 20,000 to 100,000 Staudinger and a solids concentration of the polymer obtain from 10 - 60%;

c) Drawing off a liquid mixture of the polyalkenyl aromatic Polymer and the unreacted alkenyl aromatic monomer mixture from the first continuously stirred reaction zone;

d) The feeding of the withdrawn polymer and monomer mixture into a second reaction zone, the second reaction zone being continuously stirred The reaction zone is that of the variable filling

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added polymer and monomer mixture is adapted in the liquid phase;

e) Maintaining the reaction conditions in the second Reaction zone to a polymer with a molecular weight of 20,000 to 100,000 Staudinger to obtain an increased solids concentration of the polymer of about 40-90% if the second Reaction zone to about 15-75% by volume with liquid phase mixture of the monomer mixture and polymer is filled and the remaining volume of the zone is filled by vapor phase monomer mixture;

f) The feeding of the monomer mixture into the first reaction zone at a rate equal to the overall rate at which the monomer polymerizes and removed from the first reaction zone;

g) The removal of the liquid phase from the second reaction zone at a rate sufficient to around the vapor and liquid phase monomer mixture therein and maintain the volume of liquid and approximate the total rate at which all additions of liquid, including the mixture of polymer and monomer, are fed into the second reaction zone.

The process according to the invention is carried out in practice using a monomer mixture which has at least 90% by weight styrene and the remainder OC-methylstyrene

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includes. The process according to the invention is also preferably practiced in such a way that the liquid phase in the first reaction zone consists of 35-50% by weight of polystyrene and the second reaction zone consists of 45-85% by weight of polystyrene and that the remainder is up to about 100% by weight. -% of which is the styrene monomer. The products which are produced according to the invention have a dispersion index (M _w / M _n ) in the range from 2.2 to 3.5 and the molecular weight is 40,000 to 68,000 Staudinger. The present invention can be better understood from the accompanying drawings, in which: Figure 1 is a front view, partly in section, of the

preferred continuously stirred first reactor for use in the present invention;
Figure 2 is a vertical cross-section along line 2-2

in Fig. 1 represents;
Fig. 3 is a horizontal cross-section along the line 3-3

in Fig. 1 represents;
Figure 4 is a horizontal cross-section taken along line 4-4 in Figure 1;

FIG. 5 is a schematic drawing of the entire device, in which two variable precipitation reactors are drawn which are suitable for the practical implementation of the method according to the invention and is an embodiment of the device which is suitable for carrying out the present

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driving, and

Figure 6 is a schematic drawing of a preferred control method of two variable fill reactors as used in the present invention will.

The process of the present invention involves the use of two variable, stirred reactors of the filler type for the polymerization of alkenyl aromatic monomers, such as styrene, for various polymer molecular weight distributions and an equally wide range of manufacturing speeds through correct Adjustment of the polymerization conditions and the flow rates as between the first and second reaction zones represented by reactors I and II in Fig. 5. The first reaction zone is represented by reactor I and can be a continuously stirred one Reactor vessel of any type adapted to variable filling operations from as low as 10 to as high as 100% by volume of it for the production of polyalkenyl aromatic polymers with high molecular weight and up to 60% solids concentration. This continuously stirred reactor vessels can be either horizontal or vertical and can be devices for final control of temperature by any desired means including control by cooling jacket, internal cooling coils, or by pulling off of vaporized monomers and their subsequent

A 0 9 Ώ '- 7 / Π 8 9 1

the condensation and recycling of the condensed monomer into the reaction zone.

It is readily apparent to a person skilled in the art that the first reaction zone can, if necessary, be several continuously stirred, series-connected reactor vessels exist can, with the conversion of the polymer to about 10 to 30% solids in the first of such reactors concentration is made and in the second, where, for example, the solids concentration to about 25 up to 60% increases.

It is also clear that if necessary, such first reaction zone comprise more than one continuously stirred reactor vessel connected in parallel can to use several relatively small reactors to the capacity of the second reaction zone as well as a single large reactor for this purpose.

A type of continuously stirred reactor that has been found to be very suitable for carrying out the process is of the general type illustrated in FIG. Here is a reactor vessel with inner Cooling coils are provided, which are sufficient to heat the polymerization to remove that is not done by increasing the temperature of the continuously fed monomer mixture was taken to maintain a predetermined desired temperature for polymerization therein. Such a continuously stirred reactor vessel is equipped with at least one and usually several blades

U 0 9 S r: 7/0 8 9 1

- Q -

Stirrers are provided, which are fed by an external power source, such as the motor, .der denoted by the symbol M. is. At least one of the stirrers is located so that stirring of the liquid contained in the reactor takes place while this is working with the minimum filling, i.e. at 10 vol.% filling. Such a continuous agitated reactor vessel can, if necessary, be provided with additional means for improved work efficiency and safety, such as additional Series of internal cooling coils adapted to effectively prevent any runaway polymerizations if the normal occupancy has to be extended for various reasons, and with an external one Jacket for additional cooling or heating of the contents of the reactor.

In Fig. 1, the reactor of the present invention, indicated generally by the numeral 10, illustrated. Inside the reactor 10 is the reaction chamber 11, which is oriented vertically and is generally cylindrical in shape defined by the cylindrical housing 12 and bottom and head end closures 13 is defined, all made of soft iron or the like. Made. Located next to the top of the reactor 10 a monomer inlet line 4 with the aid of which suitable styrene monomer mixtures enter the reaction chamber can be initiated. In the center of the bottom wall 13 of the reactor is the corresponding polymer

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product outlet line 9 through which the polymer - typically in a high percentage solution of unpolymerized monomers - from the reaction chamber is deducted.

Vertically extending deflecting elements 14 are radial Located around the inner wall of the housing 12 and these deflecting elements extend substantially over the Total length of the side wall of the reactor chamber 11. Deflection elements 14 are used to guide the outer row of cooling coils 15, which is also substantially perpendicular to the entire length of the side wall of the reaction chamber 11 extend, support. The Umlenkelemente 14 also serve to the inner row of cooling tubes 16 to support d-ie extending vertically upwards from the bottom wall 13 of the reaction chamber only within of the lower part of the reaction chamber. Rotatable in the central vertical axis of the reactor 10, there is a steel shaft 17 driven by a motor 18 located at the top of the reactor 10 is located at the motor point 19, which is intended for this. The rotating shaft 17 carries several horizontally oriented disks 20 to which a plurality of flat cutting elements 21 are bound with the aid of the Heat transfer and the heat circulation within the reaction chamber 11 is accomplished.

The exact configuration of the temperature control and stirring means located in and around the reaction chamber 11

is best with reference to Figures 2, 3 and 409837/0891

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4 of the drawings. In Fig. 2, for example the configuration of the row of cooling coils can be seen much more clearly. The outer row of cooling coils 15 is made up of several individual coils that extend around the entire periphery the reaction chamber 11 extend formed. Each line, which begin at the cooling inlet line 24 and continue their way to the outlet cooling line 25. Both cooling lines 24 and 25 go through the bottom wall 13 and are connected to the source of cooling liquid such as water Using a flange 26 and 27 connected. Although not easy to see, each of the cooling coils is 15 slightly from the inlet line 24 against the

there

Outlet line 25 inclined to allow better drying properties.

Referring to Figures 2 and 4, it can be seen that the inner row of cooling coils 16 are constructed quite similarly is like the outer row of cooling coils in the sense that the row is composed of several vertically divided independent Coiled tubing is constructed which originate and terminate at a coolant inlet header 28 and a coolant outlet header. The inner row of cooling coils 16 is also supported by the deflecting elements 14. The inner row of cooling coils is the primary source of heat dissipation in the reaction chamber 11 and is therefore carried out in the reactor 10 during the polymerization process is carried out continuously. Independent of Λ098: 7/089 1

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the special content level in the reactor can be an efficient and concentrated heat dissipation can be accomplished by the inner serpentine row 16, which is only in the Bottom part of the reaction chamber 11 is located on the basis of the reactor content flow diagram, found as a result a special design of the stirring elements according to the invention. It is specifically necessary that this series of cooling coils 16 extending upward to a level of the lowest disc 20 which is the cutting members 21 wears. The outer row of cooling coils 15 is inside the reaction chamber 11 only for safety reasons provided, should it become necessary due to drainage difficulties or the like, read the content quickly of the reactor 10 to cool and to slow down the polymerization reaction that takes place therein. This series of cooling coils is consequently normally not in use. All cooling coils described here are preferably made of stainless steel in order to reduce the effects of corrosion to hold, although tubes made from soft iron will do the same for most applications are good.

In Fig. 2 it can also be seen that the outer surface of the housing 12 of the reactor 10 with a Hexßiquid jacket 34 is provided, which allows the circulation of a heated liquid around the entire periphery from at least the side walls and preferably

U 0 9 Γ> Γ ⁿ I 0 8 9 1

also enables the bottom wall 13 in the event that it should become necessary to cease the polymerization process stop, but at the same time the reactor content 10 is maintained under liquid conditions and the same before to keep from becoming hard.

In Fig. 2, the structure of the central shaft 17 is clearly illustrated and the stirring elements, the discs 20 and blades 21 carried by the shaft. Each disc 20 is a solid integral Disc made of metal or the like. As it is better in cross section in Figures 3 and 4 of the drawings see is. Each disc 20 is connected to the shaft 17 with means which are intended to be perpendicular adjust each disc a certain distance in any direction in order to accommodate them adjust for more or fewer disc links along the shaft. This adjustment factor can, for example can be provided by making a series of subdivided recesses along the shaft 17 in which a given disc 20 can be suitably wedged. The flat cutting elements 21 are fastened in the corresponding recesses around the periphery of the discs 20 and in such Aus

so
Savings ensure that they are radially outward from

the central shaft 17 extend.

On the lowest disc 20 are the flat cutting elements 21 attached to the panes so that they lower

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. fairly oriented in terms of their flat surfaces will. On the other hand, for each of the disks 20 except for the lowest disk, the cutting elements 21 attached at an angle to the plane defined by the disc 2O. This angle is preferably about 45 °. Therefore, when the shaft 17 is rotated by the motor 18, the oblique adjustments serve of the cutting edges 21 on the uppermost disks 20 to a downwardly directed cross-sectional reduction within to create the bulk of the reactants within the reactor.

The second reaction zone comprises a continuously stirred reaction zone adapted for variable loading of at least 15-75% of the total volume thereof and for the production of polyalkenylaromatic Polymer blends of high molecular weight is designed to contain very high viscous liquids of about 40% up to 90% by weight solids concentration in a mixture of high polymers and alkenyl aromatic monomers. This second reaction zone can also have different reactors Types include. Such reactors can be either horizontal or vertical and have double blades moving boiler, partially divided boiler, include, in which polymers of higher molecular weight from Inlet to outlet part thereof, or reactors with one or more powered stirrers include that to mix the very homogeneous

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highly viscous liquid mixture of the polymer and monomers are designed in it. However, all continuously stirred reactors must be adapted to the very tight control for temperature and / or pressure, the production of the desired homopolymers and To enable copolymers of relatively narrow molecular weight distribution.

One type of the second reaction zone is represented by reactor II in FIG. 5 and these are those horizontally continuously stirred reactors whose internal temperature and / or pressure are very easily obtained by the means of stripping from the vapor phase of alkenyl aromatic monomers that are above the liquid phase is present, is checked. Such a type of control by increasing or decreasing the evaporation of the vapor phase has been found to provide very precise and responsible control of the polymerization temperature or pressure in a continuously stirred reaction zone for the production of high molecular weight polymers in a viscous liquid mixture with monomers . A very preferred type of the second reaction zone is represented by reactor II and consists in the fact that the type of a horizontal, continuously stirred reactor, the homogeneous isothermal mixing of the supplied liquid polymer and monomer phase with any filling of 15-90% by volume, in U.S. Patents 3,747,899, 3,751,010, 3,752,447. U 0 9 ? ■ ": 7 / Π 8 9 1.

In practicing the present improved continuous Bulk polymerization process can realize the greatest flexibility and range of polymer types are, in the production by suitable choice of the polymerization reaction conditions in the first and second reaction zones can be obtained when operating continuously at the same time. Fig. 5 illustrates the operation of the first and second reaction zones of the present invention and the manner in which like such an operation into a total polyalkenyl aromatic Polymer production line is installed. When carrying out a monomer mixture that polyalkenyl aromatic monomers as described above, and preferably styrene monomer, to the reactor I passed and the temperature of it rises from

to 180 ° C to obtain thermal polymerization.

The pressure in reactor I can vary from 1.05 to 10.55 kg / cm or even more. It is preferred to use the reactor

I at 1.41 to 5.27 kg / cm and more preferably at 2.46 to

2
3.52 kg / cm to work.

The latter pressure transitions of the liquid mixture of the polymer and monomer to further reaction process zones can be reached without the need for a pump, as long as the pressure in reactor II exceeds the pressure exceeds in reactor II and the transition lines. These are therefore the most desirable means for Implementation of the first reaction zone. After the initial filling of the reactor I to the desired

Λ 0 9: ■■■: · / o 8 9 1

- 17 -

te predetermined level and polymerizing the fed monomer to approximate it to the desired solids content, the volume of the added monomer mixture is then adjusted to a value around such a predetermined value Maintain liquid level in reactor I. The liquid mixture of the polymer and monomers will then withdrawn from reactor I to the predetermined level of such a liquid mixture in the first Maintain reaction zone. Polymerization conditions are continuously maintained in reactor I to a polymer of selected molecular weight and selected degree of conversion or weight percent solids of the To obtain polymers in such a liquid mixture. The first reaction zone can operate that a liquid mixture having a polymer concentration or percent solids content of 10 to 60% by weight is obtained and such a polymer can have an average molecular weight of 20,000 to 100,000 Staudinger exhibit. The level of filling of the reactor I can vary from 10 to 100% or it can be completely filled and can be controlled by any desired means, such as level control and associated Valve in the transition line of reactor I as shown in FIG.

Any desired means of controlling the temperature within reactor I can be used. It it is preferred that the temperature be controlled by circulating a cooling liquid such as cooling water,

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through internal cooling coils in those reactors so equipped, such as reactors of the type of Fig. 1. The entry of relatively cool monomer mixture is used to serve the greater proportion of the liberated heat of polymerization to be removed and the internal cooling coils to _f to the .restlichen to remove in order to adjust the temperature of the liquid mixture to a predetermined value, and so to obtain a polymer of the desired degree of conversion and average molecular weight.

As the polymer concentration advances, the rate of polymerization is decreased and so is the possibility damage due to "runaway" reactions is significantly reduced. Generally will preferably, in the first reaction zone, a solids content of 35 to 50% by weight of a polymer of relative high average molecular weight of about 50,000 to 1,000,000 Staudinger and a relatively narrow molecular weight distribution. The residence time in the first reaction zone can vary from about 1 to 10 hours.

At the beginning of the process, both reactor I and II are filled to the desired level with monomer, brought to the desired polymerization temperature and the polymerization is carried out with stirring, until the desired degree of conversion is achieved, i.e. until the liquid mixture of the monomer and

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Polymer the desired percent solids concentration achieved. Following the establishment of the standing Polymerization conditions are the continuous withdrawal of liquid mixture of polymers and monomers initiated from reactor I with the help of Pur.pen of the gear type or other type or .vor preferably with the help of Pressure maintained in the first zone as described above. This liquid mixture of monomers and polymer is then transferred and fed into the second reaction zone as through reactor I in FIG. 5 shown. This second reaction zone operates at a temperature of 130 to 180 ° C and at the same or lower than. the first reaction zone.

. The alkenyl aromatic monomer mixture in the form additional polymer therein is further polymerized to a higher percent solids content. The same or preferably a slightly higher temperature is selected and maintained in the second reaction zone, to obtain the desired further polymerization. The residence time in the second reaction zone can vary from about 1/4 hour to 5 hours. This second reaction zone can take the form of a variable Assume different filling of a continuously stirred reactor, with either a fixed Temperature and / or a fixed pressure can be maintained as discussed further below will. The second reaction zone, which is about 15-'75% by volume with a liquid mixture of monomer and polymer

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^; - 2o-

can be filled, (the remaining volume of it is filled by evaporated monomer) can work to prepare a liquid mixture of high molecular weight polymer and monomer, the Degree of conversion to polymer or to solids content will vary from about 40-90% solids weight% can.

The temperature and pressure conditions and also the addition of further amounts of monomer to the second reaction zone can be adjusted to produce a mixture of polymers a relatively lower average molecular weight than the polymer in the first reaction zone, for example a polymer with an average molecular weight of about 20,000 to 55,000 Staudinger. on the other hand the conditions in the first reaction zone can be maintained to produce a mixture of polymers in the higher average molecular weight range, i.e. about 55,000 to 100,000 Staudinger, as in is generally produced in the first reaction zone. The flexibility brings with it the ability to create a to obtain a wide range of polymerization of different mean molecular weight distribution and at different degree of filling of the first and second reaction zone.

When working in the first reaction zone, it is preferred to use a continuously stirred reactor, that by taking off evaporated monomer mixture

is controlled above the liquid level, which is 409837 / Q891 - 21 -

maintained at temperature and / or pressure to control in such a second reaction zone. This vent stream of vaporized monomers is in a condenser, as shown, is collected in a container and can either be transferred to the first reaction zone or recycled to the second reaction zone, depending on the one to be produced selected in the process Polymer. In some cases, especially when a polymer of relatively high molecular weight and a relatively narrow molecular weight distribution is desired, it is preferred that the fume hood and the condensed monomer stream is returned to the first reaction zone as shown in FIG. One Such recycling of the monomer in the circuit serves to generally produce high molecular weight polymers to be obtained with shorter residence times in the first reaction zone.

As pointed out above, the preferred first reac- ' tion zone used in the present process reactor type a reactor that is used to control the temperature and / or the pressure is adjusted with the aid of withdrawal and recirculation or reflux of part of the vapor phase of the monomer over the liquid phase mixture of the monomer and polymer in the reactor. .Such a reactor can operate in a somewhat lower pressure range than the reactor that comprises the first reaction zone described above includes. In one such by vapor phase

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controlled reactor, the pressure maintained can fluctuate from bottom to top, ie up to equilibrium ■ boiling point of the specific mixture of monomers and polymers contained therein. In the example of the polymers, obtained in the present invention, the pressure can vary from 0.35 to 1.41. if one works under such an equilibrium pressure, the liquid present in the second reaction zone becomes by evaporation of the monomer in such a liquid phase expands to at least about 5% at least about 10% above the volume of the liquid phase in a substantially unexpanded form, i.e. at a pressure slightly above such an equilibrium pressure at the same temperature. Various means of control for the vaporized monomer stream withdrawal from the second reaction zone can be used. If the Pressure control to a given value in the reactor is desired, such a control can be obtained by sensing the pressure in the vapor phase inside the reactor and a signal generated thereby is used to control a pressure controller modified by a signal, whose signal comes from a "set point" generator is generated, which operates at a predetermined value and thereby controls the pressure that is in the Monomer vapor phase over the condensed liquid in the monomer return tank with the aid of a pressurized controlled valve in the drain line from the

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upper part of the container is retained. If it is desired to keep the temperature in such a reactor at a predetermined value, the temperature in the liquid phase in the reactor is sensed, converted into a signal that is used for control a temperature controller is used, which is also modified by a predetermined "set point" signal and the signal obtained is used to control a control valve in the cooling water line, which is connected to connected to the cooler.

A preferred method of controlling the second reaction zone, like reactor II, is illustrated in Figure 6 of the drawing. As illustrated, it is changeable controlled variable the temperature in reactor II. The control system shown includes the sensing of the Temperature and uses a signal so generated to control a temperature controller running through a signal is modified by a "set point" generator through a predetermined temperature valve. The signal obtained, which is modified by a signal generated by sensing the pressure in the vapor phase of the reactor is used,

to control a pressure controller that has a pressure valve in the drain line from the condensed, controlled returned monomer tank. By such an adjustment of the pressure above the condensed Monomers in the container becomes the temperature in the reactor

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II precisely and quickly controlled to a predetermined desired value. As shown in Fig. 6, the liquid Level in the condensed monomer tank used, in order to reduce the return speed of the liquid contents of the container in reactor I with the aid of the valve check. Such a reverse speed is controlled by the liquid level in the container, which is determined by the speed of the withdrawal of the evaporated Monomers in the reactor II, which is controlled as outlined above, is controlled. Using the present process to an overall process polyalkenylaromatic High molecular weight polymer is shown in FIG. The high molecular weight polymer and the monomer mixture comprising the liquid phase in reactor II and a solids content of about 40 to about 90% by weight is withdrawn therefrom by suitable means such as a gear pump and to a devolatilization zone or zones.

In Fig. 5, two devolatilization zones are shown operating at the same or different reduced pressures or can work in a vacuum. The method of the present invention can, however, by using work in a single or several devolatilization zones if necessary. In the case of the procedure mentioned the vaporized alkenyl aromatic monomers and lower oligomers therefrom from the first devolatilization zone removed, condensed and made into a container

40 9 £: ■■ · '/ 089 1 - 25 -

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directed. From the container, a stream of the condensed monomers and oligomers to reactor II, as shown, be returned or - if preferred - to reactor I. The monomers and oligomers in the second devolatilization zone, which are also evaporated in the second devolatilization zone, generally at slightly lower pressures than the first works are withdrawn, condensed and sent to a container. A stream of condensed monomers and oligomers can also be fed to reactor I from this container or II as shown. The oligomers in one of the two evaporation zones can be vaporized from the vaporized monomer prior to its condensation and separately to the reaction zone be returned or cleaned by the process.

It is generally found to be advantageous in the manufacture of certain of the desired polymers been to add certain high-boiling organic compounds to the polymers produced and the addition takes place preferably during the polymerization. These additives are internal lubricants, such as mineral oil or other heavy oil and mold release agents such as fatty acids, fatty acid esters and waxes. These additions can are expediently placed in one of the two reaction zones, but are preferably in the reactor II, as in Fig. 5 shown, with the help of metering pumps

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guided. Adding such additions to reactor II facilitates the change in the polymer product mix, without closing or cleaning the reactor I. In any case, it is necessary for economic reasons, recover the relatively high-boiling additives and return them to the process. Such additives are generally condensed into a reaction zone together with the oligomers in a stream of the. Monomers recycled if such monomers oligomers from the vaporized monomers or optionally with the concentrated condensed and recycled monomer streams have been. In the present process, it is preferred that the oligomers and additives be concentrated are in a stream of concentrated monomers, rich in oligomers and additives and that one such Stream is recycled to the second reaction zone, while a separate stream of condensed monomer essentially free of oligomers and additives to the initial reaction zone from the devolatilization zone or zones is returned.

If one works in the manner described above, the correct control brings a first reaction zone and a second reaction zone comprising both reactors of variable charge type with one another extremely useful advantage of the possibility of using polymers of special physical properties and Molecular weight distribution over a range of capacities

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from 35 to 100% of the design capacity for the individual manufacturing facilitation described. This flexibility in usable capacity is very much desired in order to give a ready-made answer to the changes in market requirements for the total polymers or to the market shares for various polymers which are produced with such ease of manufacture. The following examples illustrate the invention. All parts are parts by weight, unless otherwise stated. Unless otherwise stated, all molecular weights are Staudinger values.
example 1

A vertical stirred reactor vessel, which is connected to a cooling water jacket for cooling, was filled to 46% of its volume with styrene monomer and brought to a polymerization temperature of about 140.degree. The polymerization was started with stirring and continued until the solids content of the liquid contents reached about 40 percent solids. A continuous flow of 20 parts per hour of styrene monomer, including 12.5 parts per hour of condensed styrene monomer, recycled from the second reactor was established in the first reactor. The temperature of the polymerizing liquid in the first reactor was maintained _au f approximately 140 ⁰ C by circulating cooling water through the reactor jacket. A continuous withdrawal of the liquid polymer and monomer mixture was

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set to maintain the initial level in reactor I.

A second reactor II from the right side continuously agitated type provided with homogeneous and isothermal mixing of the type described in U.S. Patent No. 3,751,010, 52% of its volume was filled with styrene monomer. The content was brought to a temperature of 180 ° C and the polymerization continued with stirring until the liquid Phase reached a solids content of about 70%. When steady-state conditions were reached in both reactors, the inflow of styrene monomer and the withdrawal of liquid mixture from the first reactor established. The first reactor became a continuous one Mixed monomer and polymer stream of 40.3% polymer solids with an average Molecular weight of 61,800 Staudinger subtracted and a dispersion index of 2.1.

This stream was continuously passed to the second reactor. The temperature in the second reactor was maintained at approximately 180 ^° C. by removing approximately 12.5 parts per hour of the vaporized monomer which was condensed and returned to the first reactor via a container. A second polystyrene polymare with an average molecular weight of 30,400 Staudinger was thus produced in the second reactor. From the second reactor, a liquid mixture of polymers and unreacted monomers was

409837/0891 - 29-

speed of 187.5 parts per hour of 76% solids content carried out, the average polymer molecular weight was approximately 48,000 Staudinger and of a broad molecular weight distribution was as recognized by a dispersion index of 2.8. This polymer and monomer mixture was placed in a devolatilization zone and the devolatilized polymer melt was processed into sticks and tabletted. The polystyrene obtained was suitable for molding purposes in which a polymer having a broad molecular weight distribution was used.

Example 2

The same vertical stirred reactor vessel, which was filled to 42% of its volume, was brought to a stationary state as described in Example 1. The same horizontal, stirred, homogeneous and isothermal reactor, which was filled to 51% of its volume, was brought to a stationary state at 150 ° C., as described in Example 1. When steady-state was reached, a continuous flow of 200 parts per hour of styrene was allowed into the first reactor including 31.7 parts per hour of condensed styrene monomer which was returned from the second reactor. The first reactor was maintained at approximately 140 ° C by circulating cooling water through the reactor jacket. The first reactor became

U 0 9?. - ^; ■ I 0 8 9 1

sufficient ilencre withdrawn to maintain the level therein of a liquid stream of monomer and polymer at 35.3% solids, the polystyrene having an average molecular weight of 61,800 Staudinger and a dispersion index of 2.11. This stream was fed to the second reactor. The second reactor was maintained at approximately 150 ⁰ C, by 31.7 parts per hour of monomer vapor were removed therefrom which was condensed and returned to the first reactor via a container. In this way, an additional polystyrene polymer with an average molecular weight of 53,600 Staudinger and a relatively narrow molecular weight distribution was produced in the second reactor. 168.3 parts per hour were withdrawn from the second reactor, an amount to maintain the same liquid level in such a reactor, of a mixture of so / ohl polymers and unreacted monomers at 69% solids. The polystyrene had an average molecular weight of 58,600 Staudinger and a dispersion index of 2.26. This mixture was devolatilized in a devolatilization zone, rods and tabletted as in Example 1. Polystyrene was found to be useful for injection molding at high speeds in the same manner as other low dispersion index polystyrenes.

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Example 3

The procedure of Example 2 was repeated using a monomargin mixture of 90% by weight styrene and 10% by weight o (.- methylstyrene. The mixture of polymers and unreacted monomers withdrawn from the second reactor will have a solids content of about 65-70% found, and contained the copolymer with an average molecular weight of 50,000 to 65,000 Staudinger and a dispersion index of 2.2 to 2.5. This polystyrene copolymer is equally suitable for molding purposes as a polystyrene of similar molecular weight and dispersion index.

Example 4

The procedure of Example 2 is repeated using a monomer mixture of 95% by weight of styrene and 5 wt% monochlorostyrene. The mixture of polymers and unreacted monomers withdrawn from the second reactor will have a solids content of about 66-72% and contains a copolymer with an average molecular weight of 50,000 up to 65,000 Staudinger and a dispersion index of 2.2 to 2.5. This polystyrene copolymer is in equally suitable for molding purposes as a polystyrene of similar molecular weight and dispersion index.

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Claims (10)

Claims 1. Continuous block polymerization process for the production of poly alkenylaroinati see polymers with a molecular weight of 20,000 to 100,000 Staudinger and a dispersion index of 2.0 to 4.0, characterized by the stages of continuous (A) feeding in a monomer mixture containing at least a monoalkenyl aromatic compound of the formula C = CH " ι 2 ν Ar in which Ar is a phenyl or halophenyl radical and X is a hydrogen atom or an alkyl radical with less as 3 carbon atoms consists, to a first continuously stirred reaction zone; (B) maintaining the reaction conditions in first continuously stirred reaction zone, 10 to 100% of its volume with the liquid phase mixture of the monomer mixture and its polymers is filled to a polymer with a molecular weight of 20,000 to 100,000 Staudinger and a To obtain solids concentration of the polymer of 10 to 60%, (C) drawing off a liquid mixture of the polyalke £ 098 ~ ^7/089 1 nylaromatic polymer and unreacted alkeny! aromatic monomer mixture from the first continuously stirred reaction zone; (D) feeding the withdrawn polymer and monomer mixture into a second reaction zone, the second reaction zone being continuously stirred Reaction zone, which is a variable filling with the fed polymer and monomer mixture in liquid phase is adjusted; (E) maintaining the reaction conditions in the second reaction zone to produce a polymer with a Molecular weight from 20,000 to 100,000 Staudinger and an increased solids concentration of the polymer from about 40-90% when the second reaction zone is about 15-75% of its volume with the liquid phase mixture of the monomer mixture and the polymer is filled and the remaining volume of the zone is filled by the vapor phase monomer mixture will; (F) feeding the monomer mixture to the first Reaction zone at a rate approximately approximating the total rate at which the monomer is polymerized and withdrawn from the first reaction zone, and (G) removing the liquid phase from the second reaction zone at a rate sufficient to the vapor phase of the monomer mixture therein - 34- A 0 9 B -. '/ 0 8 9 1 maintain and approximate the overall speed, with which all liquid additions are fed into the second reaction zone. 2. The method according to claim 1, characterized in that that the second reaction zone is a continuously stirred reaction zone in which the internal temperature or pressure is controlled by removing vapor phase therefrom. 3. The method according to claim 1, characterized in, that the vaporized monomer mixture in the second reaction zone from the vapor phase is removed at a rate sufficient to maintain a predetermined temperature of about 130 to 180 ° C in the second reaction zone and that the vaporized monomer mixture condenses to a liquid v / ird and the liquid monomer is recycled to the polymerization reaction zone. 4. The method according to claim 3, characterized in that that the condensed liquid monomer is recycled into the first reaction zone. 5. The method according to claim 1, characterized in that the reaction conditions in - 35 - U 0 9 S Γ5 "/ 0891 the first reaction zone has a temperature of about 130 to 180 ° C and a pressure of 3.15 to 10.55 kg / cm include. 6. The method according to claim l _f, characterized in that the reaction conditions in the second reaction zone are temperatures in the range from 130 to 180 ° C and pressures in the range from 1.05 to 10.55 kg / cm. 7. The method according to claim 1, characterized in that that the? ionomer mixture is styrene or a monomer mixture of at least about 90% by weight Is styrene and up to about 10% by weight o ^ -methylstyrene. 8. Apparatus designed for use in the continuous bulk polymerization of alkenyl aromatic Monomers is suitable and which comprises a vertically arranged, usually cylindrical chamber, which of a Housing is formed which is provided with terminal closures and via monomer inlet means in the vicinity its upper end and via polymer outlet means in the Near its lower end, characterized in that the chamber has several cooling devices comprises that one of the cooling devices cool at least the lower part of the chamber that a rotatable element along the vertical axis of the - 36 - 409837/0891 Chamber is located, which has a central shaft with several integral, circular, horizontally oriented
Includes disc elements that are divided into vertically
Circumstances are along the lines that each of the
Disc elements around its periphery in subdivided
Interstices with several radially extending
flat cutting elements is connected that the cutting element of the lowest disc element is perpendicular
is oriented with regard to its flat surfaces and that all cutting elements of the remaining disc elements with their flat surfaces at an angle in
Are oriented with regard to the plane of the horizontal disc elements and that drive means are provided,
to make them rotate. 9. Apparatus according to claim 8, characterized in that the coolant comprises a first set of a plurality of cooling coils which extend around the
extend the entire periphery of the chamber and the in
vertically subdivided proportions are located next to the total vertical length of the inner wall of the chamber housing and which are supported by deflection elements,
and a second set of multiple cooling coils,
which extend around the entire periphery of the channels and which are located radially inward from the first set of cooling coils and extend perpendicularly from the bottom of the chamber to a point at least above the level of the low- - 37- U 0 9 ° · '· ' ■ I 0 8 9 1 Most disk elements extend. 10. The device according to claim 8, characterized in that that a total of three disc elements are provided and that the upper two of the disc elements with their flat surfaces in one 45 ° angle with respect to the plane of the horizontal disc elements are oriented. 409837 / G891