CH703947B1 - Homo- or copolymerization of monomers including thermoplastics and elastomers, comprises providing monomer in emulsion or suspension in reactor, adding monomer, catalyst, additive and/or inhibitor and removing reacted product - Google Patents

Abstract

Homo- or copolymerization of monomers including thermoplastics and elastomers, comprises providing at least one monomer in an emulsion or suspension in a reactor in the presence of at least one catalyst, additive and/or inhibitor, adding monomer, catalyst, additive and/or inhibitor, which is the reaction mixture, continuously into at least one vertical reactor (1) and removing the reacted product continuously from at least one vertical reactor. An independent claim is also included for a device for carrying out the above mentioned method, where reactor is a vertical reactor, which is arranged parallel to at least one agitator shaft along a vertical axis.

Description

The invention relates to a process for the homo- or copolymerization of products such as thermoplastics and elastomers, preferably of at least one monomer in an emulsion or suspension in a reactor and in the presence of at least one catalyst, additive and / or inhibitor, and a Device for this.

State of the art

A considerable part of polymerization reactions are carried out commercially as "slurry or solution process" in one or more series-connected continuously operated stirred tank reactors, so-called "CSTR" = continuous stirred tank reactors. These stirred tank reactors have the task to distribute the monomers, the catalysts and initiators as homogeneously as possible in a solvent under well-defined process conditions, such as temperature and pressure, so that the reaction proceeds in a controlled manner, a uniform product quality with the desired molecular weight and also controls the heat of reaction becomes.

The problem of these stirred tank reactors is that only products with a low apparent viscosity can be processed. As the concentration of the polymer in the solvent increases, the apparent viscosity of the reaction mass increases such that the stirrer can not finally generate sufficient convective flow. The consequence of this is an inhomogeneous distribution of the monomers. This leads to lump formation, poor molar mass distribution, caking, local overheating up to the uncontrollable reaction sequence of the entire reactor contents.

Another problem of stirred tank reactors is the formation of foam in individual products, which can lead to blockages in the steam take-offs.

In conventional stirred tank reactors a plug flow is not or insufficiently feasible. Theoretically, this can be produced by several series-connected, continuously operated stirred tank reactors. In practice, however, this comes in terms of number of stages, reactor size and required peripherals to economic limits.

The process risks mentioned now lead to that in stirred tank reactors with a large excess of solvent up to about 90% of the reaction mass, in bulk polymerizations, however, only conversions of less than 50% can be achieved.

task

The object of the present invention is to find a method and a corresponding device which make it possible to carry out slow (co-) polymerization reactions (residence time up to several hours).

Solution of the task

To achieve the object that monomer, catalyst, additives and / or inhibitor (reaction mixture) are added continuously to a vertical reactor and the reacted product is withdrawn continuously from the vertical reactor.

According to the invention, the vertical reactor is completely filled. This means that there is an intense, dead space-free, radial mixing in the entire product-filled volume space, and this also with pseudoplastic product behavior.

The vertical reactor is preferably divided into individual storage spaces. That is, the reaction mixture is stowed in these reservoirs and intensively treated and mixed. The reaction mixture is moved tangentially, radially and / or helically. For this purpose, corresponding mixing bars and discs are provided on a hollow shaft, which move in the storage spaces. Discs and mixing bars are arranged on corresponding stirrer shafts. The mixing intensity should be adjustable independently of the throughput on the speed of the stirring shaft.

The reactor inner walls can be provided with internals (harassment), in which engage the mixing bars during operation such that arise in one revolution of the hollow shaft one or more narrowing columns with trailing edges.

The heater for generating the required reaction temperature in the reactor may be housed in the hollow shaft and / or in the housing and e.g. by an indirect flow with heated to the desired temperature heat transfer medium, e.g. Thermal oil, done. The inflow of the heat carrier into the hollow shaft takes place in a preferred embodiment substantially tangentially. The heating jacket of the reactor is divided in a preferred embodiment into several areas.

All, both the dynamic and the static mixing and kneading elements are self-cleaning, edge-going and avoid by their arrangement and design dead, unmixed zones. In this case, the geometry of the stirrer shafts can be designed differently with writing and ingots over the reactor height. This allows different products to be taken into account. The particle size and mixing is optimized based on the product properties.

The heatable or coolable stirring shaft with its discs and mixing bars rotates concentrically in a cylindrical housing which is chambered at the same axial distances as the shaft by static discs. These static storage rings form the above-mentioned storage chambers.

Preferably, the static discs also carry counter bars, in which the mixing bars engage the writing or on the stirring shaft so that between the static and rotating discs quasi ideal mixed reaction chambers result successively from top to bottom or from bottom to bottom flows through the top.

Between the rotating disks and the inner wall of the housing and also between the static storage rings and the shaft ring gaps arise, which are so dimensioned that on the one hand, the total pressure loss for the pumping of the reaction mixture through the product-filled storage chambers is not too high and on the other the backmixing through the annular gaps remains low.

According to the invention, large self-cleaning or self-cleaned heat transfer surfaces should be present in the vertical reactors. These allow accurate temperature control even in highly exothermic processes, which is important for temperature-sensitive products and for suppressing unwanted side reactions. It is provided on the one hand, that the housing of the vertical reactor is double-walled, so that in him a heat exchange medium can be performed. Likewise, the stirring shaft should have an axial cavity; if necessary, other elements such as disks or bars or even the storage rings with cavities can be provided for guiding a heat exchange medium. These large, self-cleaning heat exchanger surfaces allow accurate temperature control even in highly exothermic processes, which in turn is important for temperature-sensitive products and suppression of unwanted side reactions. It is desired to have a high ratio of heat exchanger surfaces to reactor volume. It should also be possible to divide in height the vertical reactor in different heating zones to impose exact temperature profiles.

The vertical reactor is preferably made of several parts which are welded together. For example, it can consist of two half-shells. The design of two half-shells also allows disassembly for cleaning and maintenance purposes.

The stirring shaft itself is stored on one or both sides and driven accordingly. The shaft seal is made by a double mechanical seal with a labyrinth pre-seal.

The vertical reactor is preceded by at least one metering device for the addition of the individual component. The dosing devices are adapted to the properties of the components to be delivered. The material flows are matched by a measuring and control system with respect to the mass ratios to each other and with respect to the total mass to the required residence time in the reactor. One or more streams may be preheated. If necessary, the waste heat of the reactor can be used for this purpose.

As a result of the embodiment according to the invention, a pronounced plug flow with a narrow residence time distribution is obtained in the vertical reactor. It ensures a good, radial mixing of the reaction mixture over the entire reaction time and dead spaces in the reaction space avoided. There is a continuous self-cleaning of the wetted surfaces. It is a slow reaction despite high sales while maintaining quality and foaming largely avoided. The resulting heat of reaction and dissipated or mechanical mixing energy can be dissipated very easily by means of the large specific heat exchanger surfaces.

The mixing intensity is independent of the throughput on the speed of the stirring shaft adjustable. The vertical reactor offers a large usable volume and a very narrow residence time distribution at product viscosities up to 10 3 Pas, typical average residence times ranging from a few minutes to several hours (Bo number up to 60). Operation is possible under vacuum and under pressure. In particular, the pressure in the vertical reactor is regulated by means of an inerting agent or a control valve to a specific value.

The ability to combine long residence times in continuous operation with large self-cleaning heat exchanger surfaces and to optimize the mixing intensity regardless of throughput, makes the vertical reactor particularly suitable for polymerization reactions (suspension (co) polymerization, emulsion polymerization, free-radical polymerization etc.) in the viscosity range 10 <-> <2> to 10 <3> Pas.

Other processes in which this vertical reactor can be used are continuous mixing, heating (cooling), reacting liquids, e.g. Neutralization reactions, esterification reactions, hydrolysis / saponification reactions, suspension polymerizations Dissolution reactions with the aim of re-dissolving polymers, resins, etc. by reverse reaction in the monomers, Solid / liquid reactions wherein the solid is in finely dispersed / suspended form. Cooling of oil / fat masses from liquid to doughy state, Multi-stage reactions in the liquid / viscous range, especially those with strong heat of reaction.

For example, should only be mentioned the preparation of prepolymer for epoxy resin (diglycidyl ether of bisphenol A), prepolymer for polyimide (pyromellitic dianhydride (PMDA) + - diamine), polymerization of polydimethylsiloxane (Decamethylcyclopentasiloxan) and free radical polymerization of acrylic monomers.

It should be noted that no free gaseous reactants may be involved.

figure description

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawing; this shows in <Tb> FIG. 1 is a block diagram of a device according to the invention for the homo- or copolymerization of products in two reactors; <Tb> FIG. 2 <sep> a longitudinal section through a vertical reactor according to the invention shown in block diagram form; <Tb> FIG. 3 shows an enlarged detail of the longitudinal section of the vertical reactor according to FIG. 2.

According to FIG. 1, homo- or copolymerization of products according to the invention takes place in two successive vertical reactors 1.1 and 1.2. The vertical reactors 1.1 and 1.2 are connected to each other by a connecting line 2.

In the vertical reactor 1.1, a monomer from a memory 4 is introduced via a feed line 3. Likewise, an addition of an additive via the feed line 5 and - slightly offset in height - also takes place a feed line 6 of initiators or catalysts.

In the vertical reactor 1 polymerization takes place, wherein the corresponding reacted product is passed through the connecting line 2 in the vertical reactor 1.2. There may, for example, a copolymerization or grafting take place by the vertical reactor 1.2 charged with a different monomer and / or operated at different reaction conditions and / or the molecular weight distribution is influenced in the polymer. The corresponding product, i. The polymer is discharged via a discharge line 7 in a transport container 8.

According to FIGS. 2 and 3, each vertical reactor 1.1 or 1.2 has a cylindrical housing 9, which is double-walled. It consists of an inner wall 10 and an outer wall 11, which form an annular space 12 between them. This annular space 12 can be filled via a lockable supply line 13 with a heat exchanger medium.

In the housing 9 is a stirring shaft 14, which is also hollow. In the stirring shaft 14, a heat exchange medium can be filled via a supply line 15 and a corresponding valve 16. This heat exchange medium is then withdrawn via a discharge line 17.

Incidentally, the agitator shaft is rotated by a gear 18 and a corresponding motor 19. The motor 19 is associated with a controller 20.

At the stirrer shaft 14 are spaced from each other discs 21 whose outer periphery is at least partially occupied by mixing bars 22. The disks 21 and the mixing bars 22 rotate in storage spaces 23, which are formed by spaced-apart storage rings 24. Of these accumulation rings 24 hooks 25 can protrude near the agitator shaft 14 on both sides, which cooperate with the mixing bars 22 or are in engagement with the mixable bars 22.

The operation of the present invention is as follows:

A monomer is pumped from the memory 4 via a motor-driven pump 26 in the upper region of the vertical reactor 1.1 / 1.2 in this. Also, the upper portion of the vertical reactor 1.1 / 1.2 is supplied with a catalyst from a reservoir 27 via a motor-driven pump 28.

In the following storage space 23, an additive from a reservoir 30 is added to the reaction mixture via a further motor-driven pump 29.

This reaction mixture now migrates from storage space to storage space down along the agitator shaft 14, where it, as can be seen in particular in Fig. 3, must pass through the annular gaps 31 in a subsequent storage space, there intense, as indicated by the arrows, in the process, the outer circumference of the disk 21 between it and the inner wall 10 of the housing 9 must also be overcome, an intensive tangential and also radial mixing of the reaction mixture taking place through the mixing bars 22. These mixing bars 22 are then cleaned in cooperation with the hooks 25, although the mixing bars 22 also perform internal cleaning of the housing inner wall 10. Over the entire length of the vertical reactor 1.1 / 1.2 there is a temperature control 32.1 to 32.3.

In the last mixing chamber, the reaction mixture is supplied via a motor-driven pump 32 from a memory 33 at least one inhibitor.

The resulting from the reaction in the vertical reactor 1.1 / 1.2 polymer is discharged with the assistance of a corresponding pressure system 34 through the discharge line 7.

LIST OF REFERENCE NUMBERS

[0041] <Tb> 1 <sep> vertical reactor <Tb> 2 <sep> Connection line <Tb> 3 <sep> lead <Tb> 4 <sep> Memory <tb> 5 <sep> supply line additive <tb> 6 <sep> Supply Catalyst <Tb> 7 <sep> discharge <Tb> 8 <sep> Transport containers <Tb> 9 <sep> Housing <Tb> 10 <sep> inner wall <Tb> 11 <sep> outer wall <Tb> 12 <sep> annulus <Tb> 13 <sep> lead <Tb> 14 <sep> agitator <Tb> 15 <sep> lead <Tb> 16 <sep> Valve <Tb> 17 <sep> derivation <Tb> 18 <sep> Gear <Tb> 19 <sep> Engine <Tb> 20 <sep> Control <Tb> 21 <sep> Discs <Tb> 22 <sep> mixing bars <Tb> 23 <sep> storage <Tb> 24 <sep> storage ring <Tb> 25 <sep> Hook <Tb> 26 <sep> pump <Tb> 27 <sep> Memory <Tb> 28 <sep> pump <Tb> 29 <sep> pump <tb> 30 <sep> memory (additive) <Tb> 31 <sep> annular gaps <Tb> 32 <sep> pump <Tb> 33 <sep> Memory <Tb> 34 <sep> Printing System

Claims (25)

1. A process for the homo- or copolymerization of monomers, such as thermoplastics and elastomers, preferably of at least one monomer in an emulsion or suspension in a reactor (1.1, 1.2) and in the presence of at least one catalyst, additive and / or inhibitor, characterized in that monomer, catalyst, additive and / or inhibitor, ie the reaction mixture, continuously at least one vertical reactor (1.1, 1.2) are added and the reacted product is withdrawn continuously from the at least one vertical reactor (1.1, 1.2). 2. The method according to claim 1, characterized in that the reaction mixture in individual vertical zones (23) of the at least one vertical reactor (1.1, 1.2) is jammed. 3. The method according to claim 1 or 2, characterized in that the reaction mixture in the at least one vertical reactor (1.1, 1.2) is moved tangentially, radially and / or helically and thereby mixed. 4. The method according to any one of claims 1 to 3, characterized in that the catalyst, additive and / or inhibitor distributed over the height of the at least one vertical reactor (1.1, 1.2) and / or at different heights of the at least one vertical reactor (1.1, 1.2) be introduced into these. 5. The method according to any one of claims 1 to 4, characterized in that a heat generated in the reaction is removed via heat exchanger surfaces. 6. The method according to any one of claims 1 to 5, characterized in that a pressure and / or a temperature in at least one vertical reactor (1.1, 1.2) is regulated to a predetermined value. 7. The method according to any one of claims 1 to 6, characterized in that at least one of the vertical reactors (1.1, 1.2) is always completely filled with the reaction mixture or the reacting or the reacted product. 8. The method according to any one of claims 1 to 7, characterized in that in particular for the production of copolymers a plurality of vertical reactors (1.1, 1.2) are connected in series. 9. The method according to claim 8, characterized in that the series-connected vertical reactors (1.1, 1.2) are charged with different monomers and / or operated under different reaction conditions. 10. The method according to any one of claims 1 to 9, characterized in that one or more streams of products of the reaction mixture are preheated. 11. The method according to claim 10, characterized in that for heating of one or more streams of products of the reaction mixture, a waste heat of at least one vertical reactor (1.1, 1.2) is used. 12. An apparatus for carrying out a method according to any one of claims 1 to 11, characterized in that the reactor is at least one vertical reactor (1.1, 1.2), in which at least one stirring shaft (14) along a vertical axis or arranged parallel thereto. 13. The apparatus according to claim 12, characterized in that the stirring shaft (14) has cavities for filling with a heat exchange medium. 14. The apparatus of claim 12 or 13, characterized in that the stirring shaft (14) with horizontally arranged discs (21) or disk segments is occupied. 15. Device according to one of claims 12 to 14, characterized in that the stirring shaft (14) are associated with mixing bars (22). 16. The device according to claim 15, characterized in that mixing bars (22) and / or discs (21) or disc segments over the height of the at least one vertical reactor (1.1, 1.2) are designed differently. 17. Device according to one of claims 12 to 16, characterized in that the at least one vertical reactor (1.1, 1.2) has a cylindrical housing (9). 18. The apparatus according to claim 17, characterized in that the cylindrical housing (9) is double-walled. 19. The apparatus according to claim 18, characterized in that the cylindrical housing (9) has cavities (12) for receiving a heat exchange medium. 20. Device according to one of claims 17 to 19, characterized in that protrude from an inner wall (10) of the housing (9) to the shaft (14) towards stagnation rings (24), which with the shaft (14) has an annular gap (31). form for the reaction mixture or the product. 21. The apparatus according to claim 20, characterized in that protrude from the storage rings (24) near the shaft (14) hooks (25) which cooperate with the mixing bars (22). 22. Device according to one of claims 17 to 21, characterized in that the cylindrical housing (9) is formed from at least two shells. 23. Device according to one of claims 12 to 22, characterized in that at different heights of at least one vertical reactor (1.1, 1.2) are provided for at least one catalyst inlet, an additive and / or an initiator. 24. Device according to one of claims 12 to 23, characterized in that a plurality of vertical reactors (1.1, 1.2) connected in series and connected to each other. 25. Device according to one of claims 12 to 24, characterized in that the at least one vertical reactor (1.1, 1.2) is associated with at least one metering device.