DE102014004222A1 - Method for carrying out mechanical, chemical and / or thermal processes - Google Patents

Abstract

In a method for the continuous implementation of mechanical, chemical and / or thermal processes in a product, which in a housing (1) with mixing / kneading / cleaning or transport elements (6) on at least one shaft (4, 5 ) and is transported via these elements (6) from an inlet (2) to a discharge (10), the discharge (10) in the transport direction (x) to the housing (1) connect and a variable or changeable setting of Cross-section of the housing (1) in the region of the transition between the housing (1) and discharge (10) are performed, according to DE 10 2013 100 182.3. The polymerization is started by addition of additives or initiators, which are mixed into the product before metering into the housing (1). The product passes through a viscous phase in the housing (1) to the solid phase before discharge.

Description

The invention relates to a method for carrying out mechanical, chemical and / or thermal processes in a product according to the preamble of claim 1.

State of the art

Such devices are also referred to as mixing kneader. They 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 can take place solid / gaseous (for example carboxylation) or liquid / gaseous. This is used in the treatment of acetates, acids, Kolbe-Schmitt reactions, eg. B. BON, Na salicylates, Parahydroxibenzoaten and pharmaceutical products.

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.

A solid state postcondensation takes place in the preparation or treatment of polyester, polycarbonates and polyamides, a continuous Anmaischen z. As in the treatment of fibers, for. As cellulose fibers with solvents, crystallization from the melt or from solutions in the treatment of salts, fine chemicals, polyols, alcoholates, a compounding, mixing (continuous and / or batchwise) in the case of polymer mixtures, silicone compositions, sealants, fly ash, coagulation (in particular continuously) 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 and / or treats polymers, elastomers, inorganic products, residues, pharmaceutical products, food products, printing inks.

In Mischknetern can also take place vacuum sublimation / desublimation, whereby chemical precursors, eg. As anthraquinone, metal chlorides, ferrocenes, iodine, organometallic compounds, etc. are purified. Furthermore, pharmaceutical intermediates can be prepared.

A continuous carrier gas desublimation z. B. in organic intermediates, eg. As 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.

These known two-shaft mixing kneaders have the disadvantage that they have a weak point due to the eight-shaped housing cross section in the region of the connection of the two shaft housing. In this area, the processing of tough products and / or processes that take place under pressure, high voltages that can be controlled only by complex design measures.

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. Particularly in the case of strongly compacting, hardening and crusting products, the randomness of the mixing bars leads to high local mechanical loads on the mixing bars and the shafts. These force peaks occur in particular when engaging the mixing bars in those zones where the product can escape badly, especially at high filling level and especially if the degree of filling increases uncontrollably to 100%. Such zones are z. B. given where the disk elements are placed on the shaft.

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. On the one hand, this results in a complex manufacturing process and, secondly, in the case of mechanical stress local stress peaks on the shaft and the supporting elements, especially if the degree of filling increases to 100%. These stress peaks, which occur mainly in the sharp-edged recesses and thickness changes, especially in the area where the support elements are welded onto the shaft core, are triggers for cracks in the shaft and the support elements due to material fatigue.

task

The object of the present invention is to better control the degree of filling of the product between inlet and outlet.

Solution of the task

To achieve the object, the features of the characterizing part of claim 1.

The present invention is preferably used in twin-shaft machines. However, it is also covered by the concept of the invention that the invention finds use in single-shaft or multi-shaft machine applications. The filling itself can be controlled by weighing cells, the present invention relates primarily to the control of the degree of filling.

Provided for this purpose is a baffle plate, which narrows or widens a free cross-section of the housing or a passage depending on the requirements of the product. In this way, the residence time and above all the degree of filling and thus also the throughput of the product can be changed by the housing, whereby of course the processing of the product is also influenced in this context (eg granulometry).

For example, in the polymerization, a monomer is charged in the mixing kneader and processed. The input can be made in a liquid state of aggregation. During processing, the product becomes viscous due to evaporation of solvent or the like, and eventually may even be granulated. It can happen that the viscous or pasty phase moves ever further towards the weir and then it can also lead to a blockage of the passage. By adjusting the weir or the passage, the spatial arrangement of this pasty phase can be determined and limited in the mixing kneader. This also serves the safety of the operation of the mixing kneader. Especially with sticky formulations, this adjustable weir has proven to be extremely valuable. Here are also much less crosslinkers necessary.

Preferably, this position-variable baffle plate is located in the region between the housing and the transition to the discharge, however, the invention is also intended to encompass a different positioning in the housing.

In a preferred embodiment, the baffle plate is still to be assigned a fixed weir, wherein the baffle plate can be guided along this weir. Of course, the weir itself already narrows the housing cross-section, but still leaves a passage for the product open. This passage can then be changed in its cross section through the variable position baffle plate.

Another idea of the invention relates to the fact that the waves not only pull through the housing itself, but also a subsequent discharge, wherein on the shaft in the region of the discharge additional transport element, which may optionally edit the product again, are provided. In a preferred embodiment, transport elements may be provided which push the product down into the discharge and / or elements which return the product. As a result, a blockage in the discharge is avoided with certainty.

Another idea of the present invention relates to the fact that the shaft itself is divided into at least two tempering zones, which are acted upon by a tempering medium. In this case, the temperature control can be tempered differently, so that in one area rather a heating of the product and in another area is rather a cooling of the product.

It is further provided that the discharge is assigned a separate vapor withdrawal. This has the advantage that the product in the discharge itself is still surrounded by vapors, which causes quasi a lubrication of the product, so that adhesion to the walls of the discharge is avoided.

The absence of any dome / neck between inlet and outlet allows the possibility of driving the machine with a controlled high degree of filling. This is especially important in order to reduce possible clumps. This driving style is "lump free process".

The method and the device according to the invention should be used above all for the production of so-called superabsorbers. Superabsorbents are polymers that are many times their own weight can absorb liquid. In the present case, they are to be prepared especially and preferably from acrylic acid and sodium acrylate by homo- and copolymerization, in which case water is additionally present in the product introduced into the device. After the polymerization, as a rule, drying, milling, sifting, surface coating and subsequent sagging occur.

According to one embodiment of the present invention, a homo- and / or copolymerization of polymers of monomers is carried out in the housing, which lead to gel-like products, wherein the polymer matrix allows a division of the polymer under the action of shear and thus behave the resulting particles as a bed ,

Examples include polymers of the monomers acrylic acid, sodium acrylate, acrylamides, polyvinyl alcohols and biodegradable substances such as cellulose, cellulose derivatives, polysaccharides and polyasparagine. These and other examples are familiar to those skilled in the reference Buchholz (Edition 1998).

The polymerization begins with the introduction of the monomer into preferably a mixing kneader of the abovementioned type. This mixing kneader should preferably have a length / diameter ratio of 1-6. It is preferably a two-shaft mixing kneader with a horizontal housing and a speed ratio of the waves of 1: 1. Thanks to axially offset mixing / kneading / cleaning and transport elements (short kneading elements) on the shafts, the housing is cleaned to 100%. The shafts and the housing and preferably also disc elements as parts of the kneading elements on the shafts should be tempered.

Before being introduced into the mixing kneader, additives, in particular initiators, which start the polymerization process, are added. In the kneader, the product passes through a viscous phase and then goes into a solid phase. This is preferably done after 50% and in particular after 50-80% of the process space length in the housing.

In a mixing kneader, it should be emphasized above all that a continuous product space from the entry to the discharge is present, but also, in contrast to an extruder, a continuous gas space. This means that the housing space above the product-filled space between entry and discharge for receiving evaporation components, in particular of solvents, is open. In the present case, a degree of filling is set in particular to 40-100%. In the latter, however, no free gas space would be available, which occurs in rare cases.

Due to the heat input by the contact with the heated surfaces, but also by the heat input due to the mechanical shear between the product and the moving kneading elements within the housing of the mixing kneader, a strong heating of the product that should be controlled so that the product is not damaged , This is done mainly by evaporative cooling, which can be done to a certain extent, a pre-drying.

According to the present invention, there is an obstacle towards the end of the housing, in particular a baffle plate. In the area in front of the baffle plate, the polymer produced from the product during the process is comminuted and in particular granulated. This is preferably done already at a transition of the viscous phase in the solid phase, when the polymer becomes gel-like. Advantageously, the above-mentioned kneading elements and in particular kneading bars arranged thereon have an angle at which the gel is cut. As a result, the granulation is much easier and improved.

The arrangement of the baffle plate should be designed so that the polymer particles are evenly distributed and large agglomerates are crushed to fine particles. In this case, the dewatering mechanism in front of the baffle plate is such that, due to the hydrostatic height, which is present in the bed before the baffle plate and running through the fixed bed kneading bar and their interaction, the particle agglomerates are divided and by the type of fragmentation undersize is avoided , In this case, the particle size distribution can be adjusted by a variation of the rotational speed of the waves. Also, adjustment is made by the selected height of the baffle plate in the housing.

The baffle plate is adjustable so that is preferably discharged in the area of engagement of kneading elements of both waves.

The granulated polymer is conveyed through the baffle plate and then passes into a preferably vertical discharge chute and to the following units for the treatment of the product. there should be attached after the baffle plate on the shaft cleaning members that prevent a closure of the discharge.

Due to the nature of the particles formed in the kneader with a homogeneous particle distribution, a convective downstream drying with significantly reduced, up to 10%, sometimes up to 20-30%, less drying performance.

Also due to the nature of the particles produced in the kneader with a homogeneous particle distribution results in the drying downstream grinding and sighting significantly less undersize, based on the amount of acrylic acid used, namely less than 10% to less than 5% less undersize.

Also due to the nature of the particles formed in the kneader with a homogeneous particle distribution, they can be wetted in an effective manner. Again, a subsequent drying can be done with less drying power.

Overall, due to the nature of the particles formed in the kneader with a homogeneous particle distribution, a product of significantly higher quality is produced.

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

1 a schematically illustrated side view of an inventive device for performing mechanical, chemical and / or thermal processes;

2 a cross section through the device according to 1 along line II-II;

3 to 5 schematic representations of other possibilities of the inventive cross-sectional constriction of the housing of a mixing kneader.

A device P according to the invention for carrying out mechanical, chemical and / or thermal processes has a housing 1 on which an inlet 2 for a product to be treated. The housing 1 can be designed to be heated, for which special housing shells 3 are provided with spaces not shown in detail, in which a heating medium is performed.

The case itself is of two shafts 4 . 5 crossed, on which mixing and cleaning element or transport element 6 are located. The wave 4 / 5 extends in the transport direction x. In a preferred embodiment, the shaft is 4 / 5 designed to be heated, wherein two tempering zones are formed, which pass through a wall 7 in the wave 4 / 5 are separated. In this way it is possible from both sides of the shaft 4 a tempering medium 8th respectively. 9 to introduce into the wave.

To the case 1 closes a discharge 10 on, the z. B. a cooling jacket 11 can be assigned. The wave 4 extends through this discharge 10 and is there occupied with other transport elements, with elements 6.1 and 6.2 are provided, different from the elements 6 differ. The element 6.1 is with a transport bar 12.1 provided, which in contrast to a transport bar 12 of the elements 6 not employed. That means that this transport bar 12.1 or the element 6.1 suitable for pushing the product down into the discharge.

A transport bar 12.2 of the element 6.2 on the other hand is opposite to the transport bar 12 of the elements 6 adjusted so that it causes a transport direction for the product, which is opposite to the transport direction x of the transport bar 12 is aligned. The transport bars 12.2 are considered as reclaiming kneading bars to relieve the end plate.

In the lower part of the discharge 10 there is still a vapor withdrawal 13 for the purpose of extracting vapors and / or nitrogen.

On the discharge 10 is a heated / coolable sight glass 14 placed. The sight glass 14 , designed as a nozzle, is an option to trim 13 to condense the vapors back (reflux) or to remove the vapors and / or the nitrogen.

At the transition between housing 1 and discharge 10 is on the one hand a fixed weir 15 provided, on the other hand a in 1 dashed baffle plate shown 16 intended. In 2 is apparent that the fixed weir 15 closes a large part of a housing cross-section. Only in the upper area is a passage 17 kept open for the product. But also the cross section of the passage 17 can additionally through the baffle plate 16 can be reduced, in the illustrated embodiment of the weir 15 is guided. It is guided by lateral guide rollers 18.1 and 18.2 and by a bolt 19 in a long hole 20 in the baffle plate 16 intervenes. Well recognizable is that at least a part 21 the contour of the baffle plate 16 the contour of the housing 1 is adjusted.

On the side of the housing is also an entry twin screw (EDS) 22 indicated with N ₂ purge. This is mainly used to enter fines / powder.

The operation of the present invention is as follows:
Any product in which mechanical, chemical and / or thermal processes are to be carried out in the device P is introduced into the inlet 2 entered. It then enters the area of the elements 6 with the transport bars 12 which detect the product and transport it further in the transport direction x. During transport, the product is kneaded, sheared, etc. and possibly simultaneously with initiators, solvents, catalysts, etc. added.

In the area of the first zone of the wave in front of the wall 7 The product can not only by the heat medium in the housing shell 3 but also be heated by the heat medium in the shaft additionally. In the second region of the shaft then takes place, as desired, a cooling of the product, including a less tempered medium or cooling medium in the shaft 4 and contributes there in the second temperature zone.

As a result of the weir 15 the product builds up so that a very intensive mixing and kneading action can be carried out in this area before the product is discharged 10 arrives. The free passage 17 is optimized according to the requirements of the product in which the baffle plate 16 more or less this free passage 17 reduced or increased.

Thereafter, the product enters the discharge 10 and gets there from the elements 6 . 6.1 and 6.2 in the lower part of the discharge 10 pressed, so that there is no blockage. For this purpose, the discharge is preferably internally coated with PTFE, so that the product hardly adheres. Also, the only taking place in the exhaust vapor take-off ensures better lubrication.

In the 3 to 5 Further possibilities of changing the housing cross section can be seen. For one thing 3 to that the idea of the invention applies not only for two-shaft kneader but of course for single-shaft kneader. Of course, should several waves be provided as two, the concept of the invention also applies to these mixing kneaders.

According to 3 is by the arrow 23 indicated that a weir 15.1 also around the wave 4 / 5 can be adjusted around. Furthermore, in this case, for example, a baffle plate 16.1 to the left of the wave 4 / 5 arranged. Of course, this can also be above the wave 4 / 5 to be ordered. The possibilities shown are only examples.

According to 4 is another embodiment of a fixed weir 15.2 indicated, which partly also the waves 4 respectively. 5 embraces. Behind or in front of the weir can be preferred around the waves 4 / 5 rotatably arranged semicircular baffles 16.2 respectively. 16.3 be provided. These are indicated by dashed lines.

According to 5 is again a fixed weir 15.2 provided, the remaining free spaces of the housing can in its cross section through various sword-like baffle plates 16.4 to 16.6 to be changed.

The absence of any dome / spigot between inlet and outlet provides the opportunity to drive a controlled high level of fill. This is especially interesting to crush possible lumps. This driving style is also referred to as "lump free process". LIST OF REFERENCE NUMBERS 1 casing 2 inlet 3 housing jacket 4 wave 5 wave 6 element 7 wall 8th tempering 9 tempering 10 discharge 11 cooling jacket 12 transport bars 13 vapor draw 14 Sight glass / Neck 15 weir 16 baffle plate 17 passage 18 leadership 19 bolt 20 Long hole 21 part of 16 22 Entry twin screw 23 arrow P contraption x transport 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 [0019]
• DE 19940521 A1 [0020]

Claims (15)

Method for the continuous performance of mechanical, chemical and / or thermal processes in a product that is housed in a housing ( 1 ) with mixing / kneading / cleaning or transport elements ( 6 ) on at least one wave ( 4 . 5 ) and via these elements ( 6 ) from an inlet ( 2 ) to a discharge ( 10 ), the discharge ( 10 ) in the transport direction (x) to the housing ( 1 ) and a variable or changeable setting of the cross section of the housing ( 1 ) in the area of the transition between housings ( 1 ) and discharge ( 10 ) is carried out according to DE 10 2013 100 182.3, characterized in that the polymerization by addition of additives or initiators, which before metering into the housing ( 1 ) is mixed into the product, is started and the product in the housing ( 1 ) passes through a viscous phase to the solid phase before discharge. Method according to claim 1, characterized in that in the housing ( 1 ) a homo- and / or copolymerization of polymers is carried out from monomers, being obtained as products gel-like products to solids, wherein a polymer matrix is such that it allows under the action of shearing a division of the polymer, and thus thereby Behave particles formed as a bed. A method according to claim 1 or 2, characterized in that the product after 50%, preferably 50-80% of the process space length converted into the solid phase and optionally granulated. Method according to claim 3, characterized in that in the region of the discharge ( 10 ) the granulated polymer via a baffle plate ( 16 - 16.6 ) and then in the discharge ( 10 ) to be led A method according to claim 3 or 4, characterized in that the polymer is uniformly distributed and large agglomerates are comminuted to finer particles. Method according to at least one of claims 3-5, characterized in that a particle size and / or its distribution during granulation is adjusted by a change in the rotational speed. Method according to at least one of the preceding claims, characterized in that a particle size and / or its distribution by a change in the height of the dust plate in the housing ( 1 ) is / are set. Method according to at least one of the preceding claims, characterized in that the granulated product is dried after the discharge. A method according to claim 8, characterized in that the product is ground after drying. A method according to claim 8 or 9, characterized in that the granulated product is rewetted before drying. Method according to at least one of the preceding claims, characterized in that vapors from the discharge ( 10 ) subtracted from. Device for carrying out the method according to at least one of the preceding claims, characterized in that in the housing ( 1 ) a the cross-section of the housing variable baffle plate ( 16 - 16.6 ) is provided. Apparatus according to claim 12, characterized in that the baffle plate ( 16 - 16.6 ) at the transition of housing ( 1 ) and discharge ( 10 ) is arranged. Apparatus according to claim 12 or 13, characterized in that a height of the baffle plate in the housing ( 1 ) between 20-99%, preferably between 80 and 95% of the height of the housing ( 1 ) is adjustable. Device according to at least one of claims 12-14, characterized in that the housing ( 1 ) has a length / diameter ratio of 1-6.

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