DD282583A7 - METHOD FOR FAELLING AND WORKING ON CHLORINE ROLLING SOLUTIONS - Google Patents

Abstract

Method for treating and working up chlorinated rubber from its solutions in chlorination-resistant solvents, such that the chlorinated rubber solution before being washed with water from post-dehydration heating, which is heated with the bungs of the degassing stage, at a pressure of at least 0.2 MPa is above the vapor pressure of the solvent, mixed and in a Faellbehaelter in which a pressure of 0.02 MPa to 0.12 MPa prevails is relaxed, the dispersion anschlieszend mechanically Entwaessert, redispersed with hot water, treated in a degassing with steam and dried after mechanical dehydration, the separated water being recycled to the redispersion. If appropriate, the mechanically dehydrated chlorinated rubber is mechanically comminuted before redispersion to a particle size of less than 50 mm and subsequently further treated according to the invention.

Description

Field of application of the invention

The invention relates to a process for the precipitation and workup of chlorinated rubber, prepared from natural and / or synthetic rubber, from solutions in chlorination-resistant solvents having a polymer content of between 5% by volume and 30% by weight, in which the dried polymer has a very high content low residual solvent content is required.

Characteristic of the known solutions

To obtain chlorinated polymers with a low residual solution content, a number of processes are known in which the polymers precipitated in Wrisser or alcohol are further treated with alcohol and the residual solvent is removed by extraction. Although the polymers thus treated have a low residual solvent content, all of these processes have the decisive disadvantage that the solvent and precipitant are present. Extraction must be separated again, which is possible only with a considerable expenditure on equipment and energy.

According to CA-PS 688081 is described to add steam to the polymer solution to bring the partially coagulated mixture in a precipitation vessel, there above the boiling temperature of the solution to precipitate by means of and to cut the precipitated polymer by rotating internals. In a further 'container then the precipitated and comminuted polymer is further treated with steam.

The disadvantages of this method are that when steam is introduced into the solution, partial coagulation of the chlorinated polymer occurs and blockages may occur there, comminution of the precipitated polymer at the point of highest gas loading is very ineffective and the rotating one employed Parts are prone to failure.

In addition, the steam in the second stage is not used effectively.

According to DE-AS 1570094, it is described to mix the polymer solution with water and atomize it via a two-fluid nozzle with steam as blowing agent into a rofziell designed folding container. This method, in addition to the need for special equipment, has the disadvantage of high steam consumption. The reason for this is the inefficient use of steam for introducing the heat into the system.

In addition, to achieve low residual solvent contents, a large driving force (solvent phase difference difference in the polymer phase and in the vapor phase) is required for the diffusion-controlled mass transfer of the residual solvent from the polymer to the gas phase. To achieve this, all of the evaporated solvent must be diluted with water vapor.

Goal db: invention

The aim of the invention is the precipitation and workup of chlorinated rubber solutions with reduced technical and technological complexity and a residual solvent content below 1 wt .-%.

Explanation of the subject of the invention The technical task

The invention has for its object to develop a process for the precipitation and workup of chlorinated rubber solutions having a solids content of 5Ma .-% to 30Ma .-%, which meets the above requirements.

Features of the invention

The object is achieved according to the invention by mixing the chlorinated rubber solution of water, the temperature of which is 7O ⁰ C and 105 ³ C, at a pressure which is at least 0.2 MPa above the solvent ^{1 of} the solvent, and immediately thereafter in o on precipitation vessel, which has a pressure of 0.02 MPa bi> i MPa, is expanded, the chlorinated rubber dispersion discharged from the precipitation vessel and mechanically dehydrated to a residual moisture content of less than 90Ma .-%, the separated water with vapors of the following degassing to the Temperature of 7O ⁰ C to 105 ⁰ C and used again to prepare the dispersion of C hlorkautschuklösung and water, the dehydrated chlorinated rubber is re-dispersed with water having a temperature higher than 80 ° C, wherein the solids content between 10Ma .-% and 20Ma .-%, the chlorinated rubber dispersion is then in a En'gasungsopparatur, which is used as a column apparatus with Kreuzgegenstromböden and / or r treated with a steam cascade of continuous Rührkdsseln having a number of vessels of at least two at a temperature between 95 ⁰ C and 105 ⁰ C and a residence time of 10min to 60 min and the dispersion wii d, wherein the water phase having a temperature greater than 80 ° C in the circuit again to redisperse the precipitated and dehydrated chlorinated rubber used and the vapors from the degassing used to heat the water necessary for the precipitation of the chlorinated rubber solution and the dehydrated chlorinated rubber is dried with a residual solvent content less than 1 Ma .-% in a known manner. Another feature of the invention is that the precipitated chlorinated rubber is mechanically dehydrated in a known manner and is mechanically comminuted to particle sizes smaller than 50μηΊιη known manner and then further treated according to the invention.

applications

I.Beispiel

A chlorinated rubber solution containing 20% by mass of solid in carbon tetrachloride is fed continuously at a mass flow rate of 100 kg / h of the precipitation stage. Immediately before the introduction into the precipitation stage 800 kg / h of water at a temperature of 9O ⁰ C i ι the solution is fed, wherein the pressure at the mixing point is 1.2 MPa and then sprayed in the precipitation vessel; is, in which a pressure of 0.02 MPa prevails. The tetrachloromethane-containing vapors and the aqueous chlorinated rubber dispersion are withdrawn at separate points from the precipitation apparatus, wherein the vapors are completely condensed and the dispersion is dewatered via an inclined screen to 80% residual moisture. The separated water is heated with the vapors from the degassing to 9O ⁰ C and returned to the predispersion of the chlorinated rubber solution. In a stirred tank, the solid with 100 ⁰ C hot water from the mechanical separation after degassing in a dispersion having a solids content of about 14Ma .-% is transferred. The amount of water returned for this purpose is 45 kg / h. The degassing stage consists of two series-connected stirred tanks, which are operated at a temperature of 100 ⁰ C. 60 kg / h and 40 kg / h steam are introduced into the first boiler. The vapors leaving the boilers are combined and used to heat the water from the mechanical drainage after precipitation. The residence time of the solid in the cascade is 30 minutes. After leaving the cascade, the dispersion is dewatered through a slant and the separated water is recycled to the redispersion of the solid after the first dewatering step. The thus-treated solid has a residual solvent content of 0.4 mass%.

2nd example

As in Example 1, precipitated chlorinated rubber is ground in a mill to a particle size of less than 40 μm and after-treated under the same conditions as in Example 1. The thus worked up chlorinated rubber has a residual solvent content of 0.1% by mass.

Claims (2)

1. A process for the precipitation and processing of natural rubber and / or synthetic rubber chlorinated rubber from solutions in chlorination-resistant solvents having a polymer content between 5% by mass and 30% by mass with the addition of water and the use of steam to separate off the solvent, characterized that the chlorinated rubber solution a) is mixed with water at temperatures between 70 ⁰ C and 105 ⁰ C and at a pressure which is at least 0.2 MPa above the vapor pressure of the solvent, and this mixture in a precipitation vessel with a pressure of 0.02 MPa to 0 , 12 MPa is relaxed, b) the chlorinated rubber dispersion is drained from the precipitation vessel mechanically to a residual moisture less than 90mA .-%, wherein the off -> might water, brought back to the temperature of 70 ⁰ C to 105 ⁰ C with the vapors of the sus Entgasungsstu'e is used again to prepare the dispersion of chlorinated rubber solution and water, c) the dewatered chlorinated rubber 80 ⁰ C is redispersed with water having a temperature higher, wherein the solids content of the dispersion between 10mA .-% and 20Ma is .-%, d) the chlorinated rubber dispersion according to the Redispe ^r Government in a ^ r degassing apparatus, which is designed as a column apparatus with a cross-counter-flow trays and / or a cascade of continuous stirred tanks with a Kassel number of at least two, at a temperature between 95 ° C and 105 ⁰ C and a Time from 10 min to 60 min with steam in a ratio of 0.1 to 0.8 to disperse ·> η is treated. 2. The method according to claim 1, characterized ^ indicates that the redispersed with water higher 80 ⁰ C chlorinated rubber is mechanically comminuted to line size less than 50 μιη.