DD294426A5 - RUHRKESSELREAKTOR FOR THE PRODUCTION HIGH VISCOSER POLYMERER - Google Patents

Abstract

The invention relates to a stirred tank reactor for carrying out polymerization reactions in highly viscous reaction media and at high reaction rates. Through the use of a coolable plug-in tube in a hollow cylinder stirrer equipped on both sides with the inventive arrangement of the inlet opening and the mixing elements between the passage openings on the yoke, the mixing and homogeneity of the reaction mass as well as the heat removal are improved. The polymerization is safely controlled; polymers of high uniformity are produced {reactor; polymerization; Waermeabfuhr; Styrene-acrylonitrile copolymer; Molecular weight distribution; Hollow cylinder; spigot; Einlaszoeffnung; Mixing elements; Durchtrittsoeffnung}

Description

For this 2 pages drawings Field of application of the invention

The invention relates to a stirred tank reactor for the preparation of highly viscous polymers of unsaturated monomers, optionally in the presence of elastomers and auxiliaries, by bulk or solution polymerization.

Characteristic of the known state of the art It is known that in the preparation of polymers according to the bulk polymerization technology without or under Use of low solvent at high conversions due to the greatly increasing viscosity of the reaction mixture Difficulties in the mixing, the promotion, the heat dissipation and the rapid interference of the

occur generally low-viscosity feedstocks that complicate the mastery of the process. To solve this

Problems are e.g. Stirred tank reactors with coolable plug-in tube and continuous heat exchangers in the annulus

between stirrer and reactor wall in which the stirrer blades with guide tube are used as mixing devices (US 3679 651, GB 1238943, GB1404163). Although these reactors allow high turnover in terms of heat technology, they can not avoid the formation of stagnant areas, especially in the recirculation spaces between the reactor jacket and guide tube.

Specialty reactors with one or more screws become more and more extruder-like with increasing product viscosity

thus more expensive (DD 57700, DE-AS 1719321, DE-OS 2160410, US 3953002, EP 0202826, EP 0222599, EP 0160570, EP 0189507, EP 0274668).

Although these reactors ensure good mixing of the low-viscosity starting materials into the highly viscous ones Reaction mass, however, have only a limited reaction volume and are due to the lack of backmixing for

Numerous polymers for reasons of quality only partially suitable.

Also known is a method for mixing the starting materials in the reaction mass and to improve the Heat removal, in which the starting materials and condensed monomer vapors with a portion of the reaction product outside

of the stirred tank reactor are homogenized in a static or dynamic mixer and the resulting mixture is fed to the reactor (DE OS 2343871). The disadvantage here is that an additional melt pump along with piping and mixing devices for the removal and re-feeding of a portion of the reaction product are needed and that the Siedekühlung especially at Monomergemlschen to a deterioration in product quality due to the different

Composition of reaction mass and gas space leads. DD144064 describes a reactor equipped with a reversible helical stirrer and central return flow channel

(Hollow shaft) is equipped. US Pat. No. 4,007,016 likewise describes a reactor with a central return flow channel, in which case there are additional helical static mixers in the return flow channel. Both reactors have with the

Return flow channels poorly mixed areas. EP 0202706 describes a stirred tank reactor for continuous bulk polymerizations with a plug-in tube, which has a Schneckenband- and a propeller stirrer for the circulatory and Mischpolymerisationen with Einsteckrohr, the one Worm conveyor · and a propeller stirrer for the circulation and Mischprozesso has- This reactor is for continuous Polymerization processes with high reaction rate, high heat generation and short residence times

larger, unstirred volume fractions and the associated disadvantages in heat dissipation through the wall, the risk of formation of precipitates in these areas and a non-homogeneous reaction mass not or only very limited suitable.

For the same reasons unsuitable for rapid polymerization in highly viscous reaction mixtures are stirred reactors mounted on the shaft stirrer arms, which have in the vicinity of the reactor attached to these arms stirring elements (DE 3332069) or for circulation with a correspondingly complicated stirrer configuration still have a separate propeller stirrer (DD 230157 ).

The reactor described in DD 24603Γ is basically suitable for the preparation of polymers in highly viscous reaction mixtures at high reaction rates, but still has shortcomings with respect to a sufficiently rapid mixing of the low-viscosity starting mixture into the highly viscous reaction mass.

Object of the invention

The object of the invention is to improve the conditions in the preparation of polymers of monomers of different reactivity by mass or Lösungspolymerisationstechnologie so that even at high polymerization rates, the polymerization is reliably controlled and molecularly uniform copolymers are obtained with desired properties.

Explanation of the essence of the invention

The invention is based on the object, a stirred tank reactor for the continuous production of polymers, consisting of temperature-controllable reactor jacket, fixed Einsteckrohr and a centrally symmetrically arranged rotor, which consists of a rotor shaft, a yoke and a stirrer cylinder is open at the top and bottom, in the axial direction of the rotor shaft extends from the bottom of the reactor to the reactor cover, and in the annular space between the stirrer cylinder and the plug has Rührerwendeln and the inlet openings on the reactor cover, reactor bottom, rotor shaft and / or plug-in tube and outlet openings has to be designed so that even at viscosities of the reaction mass to 1000 Pas and small average residence times the low-viscosity starting materials are mixed very quickly in the highly viscous reaction mass, an improved mixing and isotherm of the reaction mass, a safe dissipation of the heat of reaction and a precipitation-free operation gewä are guaranteed.

This object is achieved in that are preferably arranged on the yoke between the passage openings on and / or under the yoke mixing elements, wherein the mixing elements are preferably webs and / or helical and the yoke is designed as a displacement body.

Through the use of multiple inlet and outlet ports in conjunction with the trained as a displacer yoke and additional mixing elements, a specific arrangement of inlet ports and mixing elements and the overall configuration of the reactor is achieved that even at high reaction rates, short residence times and thus high throughput in the reactor constantly a largely homogeneous and isothermal reaction mass is present. Stratification and channeling of low-viscosity feed mixture components or large temperature gradients with the consequence of deterioration in molecular uniformity and the risk of formation of local precipitates in the reactor are avoided. The cooling capacity of the cold feed, the feed mixture, which is important for the heat balance of such reactors, is utilized to a greater extent without components being heated directly on the hot reactor wall or causing the production of polymers having altered molecular weights.

embodiment

The invention will be explained in more detail below

 In the accompanying drawing show

Fig. 1: Side view stirred tank reactor

Fig. 2: Top view of the rotor in the stirred tank reactor

1 shows a temperature-controllable stirred-tank reactor with a rotor consisting of rotor shaft 1, yoke 2 and stirring cylinder with inner and outer spirals 3.

FIG. 2 shows the plan view of the rotor in the stirred tank reactor with the mixing elements 4 and the passage openings 5. As shown, the mixing elements may have different shapes.

Due to the special arrangement of the mixing elements 4 precipitates are virmieden on the reactor cover and a local and rapid mixing of the feed mixture achieved in the reaction mass. Likewise, an additional promotion of the product flow can thus be achieved.

Claims (4)

1. Rührkesselreaktor for continuous or semi-continuous production of polymers of unsaturated monomers of different reactivities, optionally in the presence of elastomers and auxiliaries by the mass polymerization at high reaction rates, high toughness and short average residence times of the reaction mass in the reactor, consisting of temperature-controllable reactor jacket, fixed Einsteckrohrund a Centrally symmetrically arranged rotor, which consists of a rotor shaft, a yoke with Druchtrittsöffnungen and a stirrer cylinder is open at the top and bottom, extending in the axial direction of the rotor shaft from the Rodenboden to the reactor lid, and in the annular space between the stirrer cylinder and the reactor jacket and in the annular space between the Rührerzylinder and the plug-in tube has Rührerwendeln and the inlet openings on the reactor cover, reactor bottom, rotor shaft and / or plug-in tube and outlet openings, characterized characterized in that mixing elements are arranged on the yoke between the passage openings on and / or under the yoke. 2. stirred tank reactor according to claim 1, characterized in that the yoke is formed in the form of a displacement body. 3. stirred tank reactor according to claim 1 and 2, characterized in that the mixing elements webs and or spirals. 4. Rührkesselreaktor according to claim 1,2 and 3, characterized in that the mixing elements, based on the direction of the circulation flow, are arranged after or the respective inlet openings.