DE102012110118A1 - Carrying out mechanical, chemical or thermal process comprises adding reactant or product and catalyst in housing having feed point, through which the product to desired degree of conversion reacts - Google Patents

Abstract

Carrying out mechanical, chemical and/or thermal processes comprises adding a reactant (starting material) and/or product and at least one catalyst in a housing having at least one feed point, through which the product to a desired degree of conversion reacts, where the starting material is mixed prior to entering into the housing with the catalyst. An independent claim is also included for apparatus for carrying out mechanical, chemical and/or thermal processes, comprising a housing with the mixing and cleaning elements on shafts, where the mixing and cleaning elements of the shafts with their rotation around their axes interlinks.

Description

In a method for carrying out mechanical, chemical and / or thermal processes in a starting material or product in a housing which has at least one feed point (feed point), wherein the starting material at least one catalyst is admixed, through which the product to a desired Turnover level reacts.

State of the art

Such devices are performed for example in mixing kneaders. These serve very diverse purposes. First of all mention should be made of evaporation with solvent recovery, which is carried out batchwise or continuously and often under vacuum. As a result, for example, distillation residues and in particular toluene diisocyanates are treated, but also production residues with toxic or high-boiling solvents from chemistry and pharmaceutical production, washing solutions and paint sludge, polymer solutions, elastomer solutions from the solvent, adhesives and sealants.

With the apparatuses is also a continuous or batchwise contact drying, water and / or solvent-moist products, often also under vacuum, performed. The application is intended primarily for pigments, dyes, fine chemicals, additives such as salts, oxides, hydroxides, antioxidants, temperature-sensitive pharmaceutical and vitamin products, active ingredients, polymers, synthetic rubbers, polymer suspensions, latex, hydrogels, waxes, pesticides and residues from the chemical or pharmaceutical production, such as salts, catalysts, slags, waste liquors. These processes are also used in food production, for example in the production and / or treatment of block milk, sugar substitutes, starch derivatives, alginates, for the treatment of industrial sludges, oil sludges, biosludge, paper sludge, paint sludge and generally for the treatment of sticky, crusty viscose products, waste products and cellulose derivatives.

 In a Mischkneter a polycondensation reaction, usually continuously and usually in the melt, take place and is mainly used in the treatment of polyamides, polyesters, polyacetates, polyimides, thermoplastics, elastomers, silicones, urea resins, phenolic resins, detergents and fertilizers. For example, it has application to polymer melts after bulk polymerization to derivatives of methacrylic acid.

It is also possible to carry out a polymerization reaction, likewise usually continuously. This is applied to polyacrylates, hydrogels, polyols, thermoplastic polymers, elastomers, syndiotactic polystyrene and polyacrylamides.

In mixing kneaders, degassing and / or devolatilization may take place. This is applied to polymer melts, after (co) polymerization of monomer (s), after condensation of polyester or polyamide melts, on spinning solutions for synthetic fibers and on polymer or elastomer granules or powder in the solid state.

In general, solid, liquid or multiphase reactions can take place in the mixing kneader. This is especially true for baking reactions, in the treatment of hydrofluoric acid, stearates, cyanides, polyphosphates, cyanuric acids, cellulose derivatives, esters, ethers, polyacetal resins, sulphanilic acids, copper phthalocyanines, starch derivatives, ammonium polyphosphates, sulfonates, pesticides and fertilizers.

Furthermore, reactions may take place solid / gaseous (e.g., carboxylation) or liquid / gaseous. This is used in the treatment of acetates, acids, Kolbe-Schmitt reactions, e.g. BON, Na salicylates, parahydroxibenzoates and pharmaceuticals.

Reactions liquid / liquid occur in neutralization reactions and transesterification reactions.

Dissolving and / or degassing in such mixing kneaders takes place in spinning solutions for synthetic fibers, polyamides, polyesters and celluloses.

A so-called Flushing takes place in the treatment or production of pigments.

Solid state post-condensation occurs in the preparation or treatment of polyesters, polycarbonates and polyamides, continuous mulling, e.g. in the treatment of fibers, e.g. Cellulose fibers with solvents, a melt crystallization or from solutions in the treatment of salts, fine chemicals, polyols, alcoholates, compounding, mixing (continuous and / or batchwise) in polymer blends, silicone compositions, sealants, fly ash, coagulating (in particular continuous) in the treatment of polymer suspensions.

In a mixing kneader also multifunctional processes can be combined, for example heating, drying, melting, crystallizing, mixing, degassing, reacting - all this continuously or in batches. This produces or treats polymers, elastomers, inorganic products, residues, pharmaceutical products, food products, printing inks.

In mixed kneaders, vacuum sublimation / desublimation may also occur, thereby reducing chemical precursors, e.g. Anthrachinon, metal chlorides, ferrocenes, iodine, organometallic compounds, etc. are purified. Furthermore, pharmaceutical intermediates can be prepared.

Continuous carrier gas desublimation finds e.g. for organic intermediates, e.g. Anthraquinone and fine chemicals instead.

Essentially, a single-shaft and two-shaft mixing kneader are distinguished. A single-shaft mixing kneader is for example from AT 334 328 , of the CH 658 798 A5 or the CH 686 406 A5 known. In this case, an axially extending, occupied with disc elements and rotating about a rotational axis in a rotational direction shaft is arranged in a housing. This causes the transport of the product in the transport direction. Between the disc elements counter elements are fixedly mounted on the housing. The disc elements are arranged in planes perpendicular to the kneader shaft and form between them free sectors, which form with the planes of adjacent disc elements Knüräume.

A multi-shaft mixing and kneading machine is in the CH-A 506 322 described. There are on a shaft radial disc elements and arranged between the discs axially aligned kneading. Between these discs engage from the other wave frame-like shaped mixing and kneading elements. These mixing and kneading elements clean the disks and kneading bars of the first shaft. The kneading bars on both shafts in turn clean the inside of the housing.

A Mischkneter of the above type is for example from the EP 0 517 068 B1 known. With him turn in a mixer housing two axially parallel shafts either in opposite directions or in the same direction. In this case, mixing bars applied to disk elements interact with each other. In addition to the function of mixing, the mixing bars have the task of cleaning product-contacted areas of the mixer housing, the shafts and the disk elements as well as possible and thus avoid unmixed zones.

Furthermore, from the DE 199 40 521 A1 a mixing kneader of the above type is known, in which the support elements form a recess in the region of the kneading bars, so that the kneading bar has the largest possible axial extent. Such a mixing kneader has excellent self-cleaning of all product-contacting surfaces of the housing and the waves, but has the property that the support elements of the kneading bars due to the paths of the kneading bars make recesses necessary, which lead to complicated Tragelementformen.

task

The object of the present invention is to improve the reaction process in the educt or in the product.

Solution of the task

To achieve the object, the educt is mixed with the catalyst before it is introduced into the housing.

The process, which is the subject of this invention, is based on a catalytic reaction, wherein the conversion and thus the necessary size of the reactor or the residence time of a mixture of reactant and product in the reactor of the concentration of catalyst in the mixture of starting material and Product of the reaction depends. The starting material and the product, as well as the catalyst should be well mixed or even better soluble in each other.

These are, above all, processes for the catalytic polymerization or reaction of monomers or other starting materials with increased conversion. It should be a reaction in which there is no or only temporarily to the formation of intermediates. An example which may be mentioned is the polymerization of polylactides (PLA), which is carried out by catalytic ring-opening polymerization of lactides.

Typical of this reaction is that the monomer is thoroughly premixed with the catalyst and then fed to a polymerization reactor. The polymerization reactor is typically continuous, since the end product is viscous and thus poorly flowable. Therefore, horizontal mixing kneaders, screw extruders, stirred tanks or ring reactors with static mixers are used. All these reactor types have in common that during the polymerization, a thorough mixing of the polymer with the catalyst and the monomer must be ensured. Only in this way is it possible to produce high molecular weight PLA. While the reactor types differ with regard to the possibility of achieving high conversion rates, it is common that the reaction rate in a first approximation depends linearly on the catalyst concentration. Unfortunately, the best catalysts are zinc based, which can give rise to toxic degradation products. The concentration of catalyst must therefore be limited, but then increases the reaction time. As a result, unwanted side reactions also have more time to develop, which leads to a deterioration of the product properties. These side reactions can be counteracted by lowering the temperature, but this further slows down the reaction rate.

The inventive method improves the mentioned limitations by the catalyst is mixed with a partial amount of the educt and then fed to the polymerization reactor. Since the catalyst concentration is higher, the reaction rate is correspondingly faster. The largely thoroughly reacted product is mixed with a further subset of starting material. The reaction rate will now be slower. This process is repeated until the total amount of starting material has been mixed in and reacted through. The concentration of catalyst is therefore identical to the case where the starting material was completely mixed in advance with catalyst, but the reaction was initially faster.

When this idea of the process is transferred to a continuous process, the benefits become truly visible. The continuous process always uses the completely available reactor volume. However, since the required residence time of the first feed point is shorter, the distance to the second feed point can be reduced. The same applies to the following feed sites. As an example, mention that the reaction is first order and linearly dependent on the catalyst concentration. Then the required residence time will triple when the amount of catalyst is reduced by a factor of three. However, if the feed is distributed over three identical feed points, an increase of the required residence time by only 35% (instead of 200%) results at a distance of 25% between feed point 1 and 2, and of 25% between feed point 2 and 3.

If the continuous process is partially remixed over the length, a further advantage of the method according to the invention results from the fact that the back-mixed area around each individual feed point can be set separately with regard to the degree of conversion and the temperature level. Many reactions are exothermic and therefore require accurate temperature control. In the back-mixed process, the temperature level is set when starting the process and then kept on the energy balance. If there is only one feed point, only one temperature level can be adjusted. The portion of the reactor downstream, which is not adequately remixed with the area of the feed, gets its feed with starting material and product from the preceding remixed apparatus part and is therefore not independently regulated. At several feed points, the degree of conversion and the temperature level over the entire reactor space can be adjusted by controlling the other feed points in terms of time and quantity. For this purpose, separate protection is sought after.

Partially back-mixed reactors are e.g. large-volume, horizontal kneaders, the mixing in the wave direction is hindered by appropriate installations on the shaft or the housing. These apparatuses have a good radial and tangential mixing action. The product flow and thus the orientation of the backmixing is therefore realized in the wave direction.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• AT 334328 [0016]
• CH 658798 A5 [0016]
• CH 686406 A5 [0016]
• CH 506322 A [0017]
• EP 0517068 B1 [0018]
• DE 19940521 A1 [0019]

Claims (10)

A process for carrying out mechanical, chemical and / or thermal processes in a starting material or product in a housing which has at least one feed point (feed point), wherein the reactant at least one catalyst is admixed, through which the product reacts to a desired degree of conversion , characterized in that the educt is mixed with the catalyst before entering the housing. A process for carrying out mechanical, chemical and / or thermal processes in a starting material or product in a housing which has at least one feed point (feed point), wherein the reactant at least one catalyst is admixed, through which the product reacts to a desired degree of conversion , characterized in that the educt at a plurality of feed points in time and / or quantitatively different is entered into the housing. A method according to claim 1 or 2, characterized in that the amount of starting material with catalyst is divided into partial quantities and added in a batch process staggered in time to the reactor. A method according to claim 1 or 2, characterized in that the amount of educt with catalyst in a continuous process is spatially separated via separate feed sites added to the reactor. A method according to claim 4, characterized in that in the continuous process between the feed points, the back-mixing is hindered or prevented. Method according to at least one of the preceding claims, characterized in that the amount of catalyst is entered completely or for the most part together with the first input into the reactor amount of the starting material or in the continuous process in the direction of product flow in the first-placed feed point. Method according to at least one of the preceding claims, characterized in that it is a polymerization reaction. A method according to claim 7, characterized in that it is a ring-opening polymerization. Method according to at least one of the preceding claims, characterized in that an initiator is added to start the reaction. Device for carrying out mechanical, chemical and / or thermal processes in a housing ( 3 ) with mixing and cleaning elements ( 5 ) on waves ( 1 . 2 ), whereby the mixing and cleaning elements ( 5 ) of the waves ( 1 . 2 ) intermesh with their rotation about their axes,