DD294428A5 - 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. By using a coolable insert tube in a hollow cylinder stirrer equipped on both sides with conveying elements with the arrangement according to the invention and attachment of the stirrers, the thorough 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; Ruehrerwendeln; Mixing; Homogeneity}

Description

Field of application of the invention

The invention relates to a stirred tank reactor for producing highly viscous polymers of unsaturated monomers, optionally in the presence of elastomers and auxiliaries jffen, 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 M'issepolymerisations- technology without or using low solvent at high conversions Due to the sharp increase in viscosity of the reaction mixture difficulties in mixing, promotion, heat dissipation and rapid interference of the In general, lower-viscosity starting materials occur, which complicate the mastery of the process. To solve these problems z. B. stirred tank reactors with coolable Einsteckrohr and tube bundle heat exchanger in the annulus between the stirrer and reactor wall proposed in which the stirrer screws are used with guide tube as mixing elements (US 3679561, GB 123894% GB 1404163). Although these reactors allow high turnover in terms of heat technology, they can not avoid the formation of stagnant areas, in particular in the recirculation spaces between the reactor jacket and the guide tube.

Speziaireaktoren with one or more screws are always extruder-like and thus more expensive with increasing product viscosity (DD 67700, DE-AS 1719321, DE-OS 2160410, US 3953002, EP 0202826, EP 0222599, EP 0160570, EP 0189507, EP 0274668).

Although these reactors ensure a good mixing of the low-viscosity starting materials in the highly viscous reaction mass, but 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 process for mixing the starting materials in the reaction mass and to improve heat dissipation, in which the starting materials and condensed monomer vapors are homogenized with a portion of the reaction product outside of the stirred tank reactor 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 reintroduction of a portion of the reaction product are needed and that the Siedekühlung especially in monomer mixtures leads to a deterioration in product quality because of the different composition of reaction mass and gas space.

In DD 144064 a reactor is described which is equipped with a reversible helical stirrer and central return flow channel (hollow shaft). US Pat. No. 4,007,016 likewise describes a reactor with a central return flow channel, with additional helical static mixers being located in the return flow channel. Both reactors have poorly mixed areas with the return passages.

EP 0202706 describes a stirred tank reactor for continuous bulk polymerizations with a plug-in tube which has a screw conveyor and a propeller stirrer for the circulation and mixing processes. This reactor is for continuous polymerization with high reaction rate, high heat and short residence times due to 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 picht homogeneous reaction mass or only very limited.

For the same reasons unsuitable for rapid polymerization processes in highly viscous reaction mixtures are stirred reactors with We¬a attached 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 (OD 230157 ).

The reactor described in DD 246038 is fundamentally 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 reactivities by the bulk 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 insert tube and a centrally symmetrically arranged rotor, which consists of a rotor shaft, a yoke and a Rohrerzylinder is open at the top and bottom, in the axial direction of Rotor shaft extends from the reactor bottom to the reactor cover, and in the annular space between the stirrer cylinder and the reactor jacket and in the annulus between the stirrer cylinder and the Einsteckrohr Rührerwendoln and the inlet openings on reactor cover, reactor bottom, rotor shaft and / or plug-in tube and outlet openings has to make so that even at viscosities of the reaction mass to 1000 Pas and small mean residence times the low-viscosity starting materials are particularly fast mixed into the highly viscous reaction mass, improved mixing and isothermia of the reaction mass, a safe Able tion of the heat of reaction and a precipitation-free operation are guaranteed. This object is achieved in that are arranged on the circumference of the stirrer cylinder side by side 2 to 10 Rührerwendeln, these Rührerwendeln are in their angle of rise up to 10 "from each other, over the length of the Rührerzylinders preferably 3 zones of Rührerwendeln are arranged so that the average rise angle of Rührerwendeln in the individual zones to each other preferably the same and the stirrer coil of each successive zones are preferably offset by the angle Pi / 2 divided by the Rührerwendelzahl and the Rührerwendeln are attached to the stirrer cylinder such that between Rührerwendeln and Rührerzylinder a distance of not more than 2 Due to the specific helical design in the annular spaces between the stirrer cylinder and the reactor jacket and between the stirrer cylinder and insert tube and the overall configuration of the reactor is achieved that even at high reaction rates iten, short residence times and thus high throughput in the reactor constantly present a largely homogeneous and isothermal reaction mass. 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 of 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 with altered molecular weights.

Aueführungibeleplel

The invention will be explained in more detail below

 In the accompanying drawing show

Fig. 1: Side view of the stirred tank reactor Fig. 2: Side view of the rotor

1 shows a temperature-controllable stirred-tank reactor with a rotor consisting of rotor shaft 1, yoke 2, stirring cylinder 3 and inner and outer spirals 4, 5.

2, the rotor with the outer coils 5 is shown. There are 3 zones of filaments different in their mean increase. Furthermore, different rises of the helical pieces within a zone can be seen. The special arrangement of the helical pieces an intensive local mixing of the mixture components is achieved.

Claims (2)

Rührkesselreaktor for continuous or semi-continuous production of polymers of unsaturated monomers of different reactivities, optionally in the presence of elastomers and adjuvants by Massepolymeristionstechnologie at high reaction rates, high toughness and short mean residence times of the reaction mass in the reactor, consisting of temperature-controllable reactor jacket, fixed insert tube and a centrally symmetric arranged rotor, which consists of a rotor shaft, a yoke and a stirrer cylinder, open at the top and bottom, extending in the axial direction of the rotor shaft from the reactor bottom to the reactor top, and in the annular space between the stirrer cylinder and the reactor shell and in the annular space between the stirrer cylinder and the Einsteckrohr has stirrer coils and the inlet openings on the reactor cover, reactor bottom, rotor shaft and / or plug-in tube and outlet openings, characterized in that on the circumference of Rüh Rzylinders are arranged side by side 2 to 10 Rührnwendeln, these Rührwendeln are different in their angle of rise up to 10 ° from each other over the length of the Rührzylinders zones of Rühret are arranged so that the average rise angle of the Rührerwendeln in the individual zones equal to each other and the Rührerwendeln each successive zones are offset by the angle Pi / 2 divided by the Rührerwendelzahl and the Rührerwendelzahl are offset and the Rührerwendeln are attached to the stirrer cylinder such that between Rührerwendeln and Rührerzylinder a distance of a maximum 2 millimeters is present. For this 2 pages drawings