WO2009068920A1

WO2009068920A1 - Mixing device for mixing two liquids and process for the continuous preparation of organic mono-, di- or polyisocyanates

Info

Publication number: WO2009068920A1
Application number: PCT/HU2008/000041
Authority: WO
Inventors: József RÉTI; Tibor Klement; Zoltán KOZÁR; Tamás PURZSA; Miklós BODNÁR
Original assignee: BorsodChem Zrt
Current assignee: BorsodChem Zrt
Priority date: 2007-11-30
Filing date: 2008-04-29
Publication date: 2009-06-04
Anticipated expiration: 2010-05-30
Also published as: HU0700771D0; HUP0700771A2

Abstract

A device for mixing two liquids containing fast reacting components, particularly mono-, di- or polyamine and phosgene or solutions thereof, the device comprising an inner flow path (1) for a first liquid and an outer flow path (9) for a second liquid, said flow paths (1, 9) are coaxially disposed and interconnected by at least one through opening formed on a wall portion of the inner flow path (1), and the downstream end (6) of the inner flow path (1) is closed, and said through opening is a nozzle (N) provided on the wall of the inner flow path (1) between the closed downstream end (6) and the upstream end (3) thereof. The invention also discloses a process for continuous preparation of an organic mono-, di, or polyisocyanate achieved by the device according to the invention.

Description

MIXING DEVICE FOR MIXING TWO LIQUIDS AND PROCESS FOR THE

CONTINUOUS PREPARATION OF ORGANIC MONO-, DI- OR

POLYISOCYANATES

This invention relates to a rapid mixing device for mixing two liquids containing fast reacting components, particularly mono-, di- or polyamine and phosgene or solutions thereof, the device comprising an inner flow path for a first liquid and an outer flow path for a second liquid, said first and second flow path each having an upstream end and a downstream end, said flow paths are coaxially disposed and interconnected by at least one nozzle formed on a wall portion of the inner flow path, and further comprising means for fluidly connecting said flow paths to a source of said first and second liquid, respectively, and means for building in and sealing the device in a bore provided on a wall of a reactor vessel, and further relates to a reactor adapted to perform a fast chemical reaction of industrial scale by mixing liquids, particularly a mono-, di- or polyamine and phosgene reaction to produce mono-, di- or polyisocyanates, respectively, said reactor having an inner containment receiving mixed liquid components to proceed subsequent reactions, and said containment is defined by reactor walls and means for discharging reaction products and having agitating means thereinside, and at least one bore arranged on the reactor wall. The invention also discloses a process for the continuous preparation of an organic mono-, di- or polyisocyanate by mixing two liquids containing fast reacting components, particularly mono-, di- or polyamine and phosgene or solutions thereof, comprising the steps of introducing a first component such as mono-, di- or polyamine corresponding to the mono-, di- or polyisocyanate into an upstream end of a first flow path to flow towards the downstream end thereof, and introducing a second component such as phosgene into an upstream end of a second flow path disposed concentrically to the first flow path, to flow towards the downstream end thereof, and pressurizing the first component to flow out from the first flow path through at least one nozzle connecting the first and second flow paths, into the second flow path.

The manufacture of organic mono-, di-, or polyisocyanates from the corresponding primary amines and phosgene is well known. Depending on the nature of the amines, the reaction is carried out either in the gas phase or the liquid phase, either batchwise or by means of a continuous process (W.Siefken, Liebigs Ann. 562, 75 (1949); H.Ulrich, "Chemistry and Technology of Isocyanates", John Wiley & Sons, Chichester, England, 1996; Ullmann's Encyclopedia of Industrial Chemistry, 7^th Edition, Volume Al 4, John Wiley & Sons, New York, 2003).

Organic isocyanates are now produced on a large industrial scale, usually in continuous liquid phase processes, where even small improvements in process efficiencies have significant economic importance.

The conventional processes suffer from numerous disadvantages. The most frequently described processes are two-stage processes, where amine, usually dissolved in an organic solvent, and a stoichiometric excess of phosgene, sometimes also dissolved in an organic solvent, are mixed in a first "cold" stage to ensure efficient reaction and minimization of by-products which affect both yield and quality. Intermediate amine hydrochlorides and carbamoyl chlorides are formed, and the reaction mixture is then fed to a second "hot" stage where the amine hydrochlorides are converted to carbamoyl chlorides and the carbamoyl chlorides are dissociated into isocyanate and hydrogen chloride. Optionally additional phosgene is added in this second stage. An early example of this type of process is described in US patent 2,680,127. Although the term "cold phosgenation" is often used for the first step, the temperature may be as high as 90 deg C (US 2,908,703). It is generally taught that the second stage is operated above the decomposition temperature of the carbamoyl chlorides, usually in the range 85 to 200 deg C, depending upon the type of isocyanate being produced. US patent 3,781,320 teaches that the preferred temperature range for aromatic isocyanates such as toluene diisocyanate is 102-130 deg C, whereas for aliphatic isocyanates such as 4,4'-bis(diisocyantocyclohexyl)-methane a temperature range of 150-175 deg C is preferred. Higher temperatures can be used but are not required.

These two-stage processes generally suffer from the disadvantage that a significant amount of solids are formed in the first stage, giving viscous fluids which makes rapid mixing difficult and the solids form blockages in the first reactor or transfer piping to the second reactor. One patent (US 4,422,976) attempts to overcome partially this disadvantage by operating the first stage in a temperature and pressure regime where 30-70% of the intermediate carbamoyl chloride is dissociated to isocyanate.

Single stage processes are also described in the prior art, for example US 2,683,160; US 2,822,373; US 3,287,387. In single stage processes, the reactor or reaction system in which the amine, phosgene and reaction mixture are mixed together is operated at a temperature above the decomposition temperature of the carbamoyl chlorides.

There are described both two-stage and single-stage process designs which incorporate recycling of the reaction mixture with amine addition into the recycle stream (US 2,822,373; US 3,465,021; US 3,544,611; US 4,128,569; US 4,581,570; US 5,599,968). These processes have the advantage that when the recycle rate is many times the amine feed rate, the effective stoichiometric excess of phosgene at the mixing point is much larger than the excess as measured by the ratio of the feed streams. However, they have the corresponding disadvantage that the added amine can react with an effectively higher concentration of isocyanate in the recycled reaction mixture, reducing the isocyanate yield and/or reducing the purity of the derived isocyanate.

Many prior art methods attempt to improve the yield in phosgenation processes and/or the quality of the isocyanate by the use of special high-speed mixing devices. Mechanical mixing devices may be used, for example high shear mixers (US 3,321,283; US 3,781,320), single stage pumps, turbomixers and colloid mills (all in US 3,188,337), multiple stage pumps (US 3,947,484), and rotor/stator mixers (US 4,851,571). Static mixers are also described, for example tubular reactors with high turbulence (US 3,226,410), venturi mixers (US 3,507,626; US 5,117,048), annular slot nozzles (French patent no. 2,325,637), extremely fine smooth jet nozzles (US 4,419,295), drive-jet nozzle for recycle stream into reaction chamber (US 4,128,569), and fan jet nozzles (US 4,289,295). Impinging jet mixers are also described, either with a protruding centrebody (WO2004/004878) or without (WO2006/001786).

Many designs have been described for equipment to provide residence time at the hot stage of phosgenation. These include stirred tanks (US 3,287,387, US 4,422,976), vertical tube reactors (US 3,188,337), packed columns (US 3,829,458), perforated plate columns (US 4,851,570), distillation columns (US 3,544,611), or valve tray columns or bubble cap tray columns with relatively high liquid weirs (US 6,576,788). Some designs for hot stage phosgenation incorporate recirculation circuits. These may be external pumped loops (US 3,781,320; US 3,829,458; US 4,128,569), or natural circulation systems either internal or external to the reactor (US 4,581,174). US 3,465,021 and US 5,599,968 operate natural recirculation systems for "cold" stage phosgenation (up to lOOdeg C) but then require further, hot stage, finishing reactors.

Most phosgenation process designs incorporate some means of separation of the gases generated in the hot stage, either integrally with the hot stage reactor (US 3,781,320, US 4,422,976) or in a gas-liquid separator subsequent to the residence time apparatus (US 3,287,387; US 3,829,458)

Aromatic isocyanates, especially MDI and TDI, are now produced on a very large industrial scale. AU of the aforementioned prior art mixing devices have the disadvantage that they are difficult to scale up to the throughput rates necessary for modern world-scale plants. The initial reaction of amine with phosgene is extremely rapid. US3, 321,283 teaches that the half-life of the reaction is of the order of 5-100 milliseconds at 70 degrees C, and the examples suggest that the half-life for TDI is of the order of 10 milliseconds, since yield improvements are demonstrated when the mixing time is reduced from 7 to 4 milliseconds. The consequence of this is that mixing distances, even at high flow rates, are extremely short. Linear distances such as the width of the reactant streams become critical under these conditions. One approach is to use multiple mixing devices, but this has the disadvantage of being mechanically very complex. Some devices use multiple inlet ports for at least one of the reactant streams, for example US5, 117,048 claims an improvement over US3,507,626. However, the number of inlet ports is limited by the mechanical design in prior art processes. Also, the combination of inlet ports of small dimension with the need for high linear velocities, especially in impingement jet mixers, demands very high pressure drops for the pumped reactant streams.

The aim of this invention is to improve efficiency of the phosgenation stage by providing a mixing device and a mixing process adjustable in a very wide range of parameters, i.e. at any particular phosgene to amine ratio of reactant concentrations, the isocyanate yield and/or quality will be improved by means of a device to be designed for the homogeneous and effective mixing of two fluid phases compared to the solutions known in the art; alternatively the concentration of amine in the feed solution may be increased to give higher output at constant yield; or the excess of phosgene used in the process, which is expensive to recycle, may be reduced.

Further objective of the invention is that solids, which are formed during phosgenation stage, do not form blockages in the mixing device or any obstacle in transfer piping to a subsequent reactor without the need of using higher temperature and pressure in the first stage of phosgenation.

To solve above problem the invention provides a device for mixing two liquids containing fast reacting components, particularly mono-, di- or polyamine and phosgene or solutions thereof, the device comprising an inner flow path for a first liquid and an outer flow path for a second liquid, said first and second flow path each having an upstream end and a downstream end, said flow paths are coaxially disposed and interconnected by at least one nozzle formed on a wall portion of the inner flow path, means for fluidly connecting said flow paths to a source of said first and second liquid, respectively, means for building in and sealing the device in a bore provided on a wall of a reactor vessel, the downstream end of the inner flow path is closed, and said nozzle is provided between the closed downstream end and the upstream end thereof.

The inner flow path and the outer flow path are formed as tubes having cylindrical walls forming an annular gap therebetween. Said through opening is formed as a nozzle having mim^'mal and maximal cross sectional areas. Said minimal cross sectional area is formed between the inner and the outer surface of said inner tube.

Said minimal cross sectional area is formed on a surface of said inner tube. The inner wall of the nozzle is radiused. Said nozzle has an elongated shape along the longitudinal axis of the inner tube. Said elongated shape is oblong rounded at least on one side thereof. Several nozzles are circumferentially provided on the inner tube. Nozzles are spaced apart circumferentially by equal angular distances. Nozzles are arranged in at least two circumferential rows.

Subsequent rows of nozzles are spaced at least two nozzle diameters apart, with the nozzles of each subsequent row off-set so as to be midway between nozzles of the adjacent row. The axial distance of a circumferential row of nozzles from the downstream end of the outer tube is between 0 and 5K, preferably between 0 and 3K, and most advantageously D=K the width of the annular gap between the tubes. The downstream end of the inner tube forming the inner flow path is closed by a cap being movable by means of a shaft along the longitudinal axis of the inner tube between an inner position and an outer position, and said nozzles are disposed at least partly between said inner and said outer position of said cap.

Support means are arranged between the inner tube and the outer tube, and each support means is fixed to one of said tubes. A rim of the downstream end of the outer tube is radiused. The inner tube is movable relative to the outer tube along its longitudinal axis.

A reactor adapted to perform a fast chemical reaction of industrial scale by mixing liquids, particularly a mono- or polyamine and phosgene reaction to produce mono- or polyisocyanates, respectively, said reactor having an inner containment receiving mixed liquid components to proceed subsequent reactions, and said containment is defined by reactor walls and means for discharging reaction products and having agitating means thereinside, and at least one bore arranged on the reactor wall, a mixing device according to the invention is placed and sealed in said bore.

The reactor vessel is provided with means for discharging from and reentering reaction products into the vessel, and a point of reentry is arranged close beside the mixing device. The reactor vessel has at least two bores receiving a mixing device are formed on the reactor wall, and a mixing device is arranged in each bore.

It is also provided a process for the continuous preparation of an organic monoisocyanate or polyisocyanate by mixing two liquids containing fast reacting components, particularly mono- or polyamine and phosgene or solutions thereof, comprising the steps of introducing a first component such as monoamine or polyamine corresponding to the monoisocyanate or polyisocyanate into an upstream end of a first flow path to flow towards the downstream end thereof, and introducing a second component such as phosgene into an upstream end of a second flow path disposed concentrically to the first flow path, to flow towards the downstream end thereof, and pressurizing the first component to flow out from the first flow path through at least one nozzle connecting the first and second flow paths, into the second flow path, providing said nozzle between the downstream end and the upstream end of said flow paths, closing the downstream end of the first flow path, and flowing the first component out through said nozzle radially outwardly from the first flow path to the second flow path.

Said first component flowing in the concentrically inner first flow path and the second component flowing in the outer second flow path both flow paths are formed as tubes having cylindrical walls forming an annular gap therebetween.

Said first component is pumped out from the first flow path through at least one nozzle having minimal and maximal cross sectional areas and an elongated shape along a section of the longitudinal axis of the inner tube.

Component is pumped through the nozzle at a velocity of 5 to 50 m/s, preferably 10 to 40 m/s and more preferably 30 m/s. Component is preferably pumped through several nozzles circumferentially provided on the inner tube.

A length of the nozzle along a section of the axis is changed while component being pumped out.

A relative velocity of the components is at least 2 and preferably 4 or more with the component flowing in the outer flow path.

The velocity of the component in the inner tube is 1 to 10 m/s, preferably 3 to 7 m/s, and more preferably 5 m/s.

The inner tube is moved relative to the outer tube along its longitudinal axis.

The closed downstream end of the first flow path is moved outwards beyond the downstream end of the second flow path and at least a nozzle at least partly is operating beyond the downstream end of the second flow path, and closing or opening at least partly at least one nozzle.

Closing or opening at least partly at least one nozzle is achieved by moving a cap closing said downstream end of the inner tube along the longitudinal axis of the inner tube between an inner position and an outer position of the edge thereof in such a way, that said nozzle are disposed at least partly between said inner and said outer position of said edge of the cap.

In this way the present invention overcomes the limitations of the prior art mixing devices and processes by providing a mixing device with a multiplicity of very small nozzles having preferably non circular shape for one of the reactant streams, while at the same time reducing the required pressure drop by novel design of the jet nozzles. The design of the disposition of the mixing nozzles makes use of the very high reaction rates, and hence short reaction distances, to provide an array of "mini-reactors" which are essentially mutually independent in a single device, and a special streaming profile substantially different from the prior art solutions is formed. The second reactant stream is preferably, but not necessarily, added via a pipe, which is substantially concentric with the pipe having the multiplicity of nozzles. This way the streams of the two reactants form a streaming cone - or a section of a cone surface in the case of each nozzle - having a half cone angle Θ, and react freely streaming and mixing along this surface into a large space of a reactor, dissimilarly from the prior art solutions. The present invention also provides a process for the continuous preparation of organic isocyanates through the reaction of organic amines with phosgene, optionally in the presence of organic solvents, incorporating the said mixer device into a variety of reactor configurations. In this process the first reactant stream consisting of amine, optionally dissolved in organic solvent, is pumped through the specially shaped nozzles, while phosgene, optionally dissolved in organic solvent, enters through the substantially concentric outer pipe. The mixer of the present invention can be connected directly to many of the phosgenation process designs, either into a recirculation loop or into a reactor vessel, and will show numerous advantages.

The invention will be discussed in details according to the attached drawings. In the drawings:

Fig 1. is a first embodiment of the mixing device according to the invention,

Fig 2.-2a is a cross sectional view of a preferred embodiment of a nozzle,

Fig 3.-4 is cross sectional views of nozzles with special geometry,

Fig 5. is a cross sectional view of the tubes taken across a row of nozzles

Fig 6. is a cross sectional view of the tubes with support means,

Fig 7. is a cross sectional view of the downstream end of the inner tube forming the inner flow path closed by a cap,

Fig 8. is a cross sectional view of the downstream end of the inner tube forming the inner flow path closed by a cap and with support means,

Fig 9. is a cross sectional view of the downstream end of the outer tube a rim of which is radiused inwardly,

Fig 10.-11 is a cross sectional view of the movable the inner tube,

Fig 12. is a cross sectional view of the reactor according to the invention,

Fig 13. is a cross sectional view of the downstream end of the mixing device in operation performing the process according to the invention, where a 'micro reaction chamber' is formed, and in Fig 14. the exiting geometry of the component B exiting nozzle is shown.

Detailed description of the invention

Figure 1. depicts a first embodiment of the device according to the invention for mixing two liquids containing fast reacting components, particularly mono-, di or polyamines and phosgene or solutions thereof. The device comprising an inner flow path 1 for a first liquid and an outer flow path 9 for a second liquid. Each flow path 1, 9 have an upstream end 3, 4 and a downstream end 5, 6. Said flow paths 1, 9 are coaxially disposed and interconnected by at least one, but preferably several through nozzle(s) N formed on a wall portion of the inner flow path 1. In a preferred embodiment of this invention, the mixing device consisting of two substantially concentric tubes 7, 8 has flange-joint with sealing that fixes the device with the flanges of a receiving bore of a reactor vessel. The device is provided with means for fluidly connecting said flow paths to sources (not shown in the drawing and well known to those skilled in the art) of said first and second liquid, respectively. Also means for building in and sealing the device in a bore 16 provided on a wall 14 of a reactor vessel 13 is arranged. In this preferred embodiment the inner flow path 1 and the outer flow path 9 are formed as concentric tubes 7, 8 having cylindrical walls 7a, 8a forming an annular gap 9a therebetween. Therefore, the first liquid can flow in the inner tube 1 and the second liquid can flow in said gap 9a between the tubes 7, 8 from the upstream ends 3, 4 towards the downstream ends 5, 6 of the tubes 7, 8, respectively. It is shown in the drawing, that the downstream end 6 of the inner flow path is closed such a way, that the first liquid flowing inside the first flow path 1 could leave the latter through nozzles N only, which are formed on the wall 7a of the inner flow path 1. In the Figure 2 and 2a through nozzles N can be seen, which are formed as nozzles N having minimal and maximal cross sectional areas.

Said minimal cross sectional area is formed between the inner and the outer surfaces 7a, 7b of said inner tube 7, spaced apart of these surfaces 7a, 7b, and the inner wall of the nozzle is radiused. In this preferred embodiment said minimum cross sectional area is situated close to the inner surface of the inner tube 7, and a radius Rl is in the range of 0 to 3 mm, preferably 0,5 to 2mm, more preferably 1mm is shaped toward the inner surface 7b, and a radius R4 is in the range of 3 to 7 mm, preferably 3,5 to 4,5 mm, more preferably 4 mm, is shaped toward the outer surface 7a. These nozzles N of the inner tube 7 have a special shape. The two radiuses Rl, R4 ensure that the component B gets into the gap 9a through a narrow i.e. 0,7 mm aperture, which is self- cleaning due to the high velocity of the component B. Solid deposits, cannot build up on a small surface like this.

Therefore, the maximal cross sectional area of the nozzle N is on the outer surface 7a of the inner tube 7. In an alternative embodiment said minimal cross sectional area may be formed i.e. on the inner surface 7a of said inner tube 7 or anywhere, i.e. midway between these surfaces 7a, 7b, the latter is shown in Fig. 3. However, in the preferred embodiment of the invention the position of the minimal cross sectional area, and therefore the inner shape of the nozzle N is similar to that is shown in Fig. 2., since we have found, that this kind of mixing nozzle N makes use of the very high reaction rates, and hence short reaction distances, to provide an array of mini-reactors which are essentially mutually independent in a single mixing device in one hand, as well as to avoid clogging formed by solid reaction products in the nozzle N, in other hand, that is the nozzle N will have a self-cleaning feature.

Advantageously, instead of being circular, the nozzle N has an elongated geometry along the longitudinal axis 11 of the inner tube 7, as it can be seen in the Figure 2a., and this elongated geometry is oblong with semicircular ends.

Possible shapes of nozzles N of the inner tube 7 have a special geometry shown in Figs 2,3 and 4, and are preferably defined by the following values: W is in the range of 4 to 10mm, preferably 5 to 7mm, more preferably 5.5 mm, X is in the range of 3 to 10 mm, preferably 5 to 8 mm, more preferably 7.5 mm, Y is in the range of 1 to 6 mm, preferably 2 to 5 mm, more preferably 4.0 mm. As it mentioned above the overall geometry is oblong with semicircular ends and preferably contains no right angles. The length direction of the nozzle N is substantially parallel with the direction of the axis 11 of the concentric tubes 7, 8, and X is always greater than Y.

Figure 5. is a cross sectional view of the tubes 7, 8 taken across a row of nozzles N provided circumferentially on the inner tube 7. In a preferred embodiment said nozzles N are spaced apart circumferentially by equal angular distances. In a preferred embodiment the nozzles N are arranged in at least two circumferential rows. In this case the subsequent row or rows of nozzles N are spaced at least two nozzle N diameters apart, with the nozzles N of each subsequent row off-set so as to be midway between nozzles N of the adjacent row. The nozzles N are preferably spaced a minimum of two diameters Y apart. A larger number of nozzles N can be accommodated by increasing the diameter of the inner and outer tubes 7, 8, or by adding further rows of nozzles N downstream from the first row. In the latter case each row must be at least twice the diameter Y apart from the other, with the nozzles N in each row offset so as to be midway between the nozzles N of the previous row. The nozzles N comprised in this invention are designed and machined such that the stream of a first liquid containing the key reactant being converted to the desired product mixes very rapidly with the second stream of liquid at the lay side of the constriction in each nozzle N, in such way that locally a "micro reactor" is created. It appears that this configuration affords substantial avoidance of contact between the primary reactant and the contents of the bulk reaction vessel or recirculation pipe into which the combined streams exit. As a consequence of the foregoing, avoidance of unwanted side- and by-reactions and concomitant formation of unwanted by-products is substantially suppressed. The specially shaped nozzles N also provide a self-cleaning operation mode. To those skilled in the art it is known that conventionally highly intricate machinery is required when attempting to achieve a similar objective.

Since liquids, preferably phosgene and amine of different temperature are to be introduced into the mixing device, the inner tube 7 and outer tube 8 will have different thermal expansions in operating conditions, causing possible fatigue break down of the seams fixing the structure of the mixing device. We have found that special support means, as shown in Figure L, 5 and 6, namely spacing-and-sliding plates P are suitable for supporting the inner tube 7 relative to the outer one 8 in such a way, that at least two plates P are evenly distributed and e.g. welded on the inner periphery of the outer tube 8 in room temperature while abutting the outer periphery of the inner tube 7. These kind of support means arranged between the inner tube 7 and the outer tube 8 will fix the position of the tubes 7, 8 when their temperatures reach the operating levels, since the component A, preferably phosgene, flows at a temperature of -16 °C in the outer gap 9a, and component B, preferably amine, flows at 80 °C in the inner tube 7.

In a most preferred embodiment shown in Fig. 7., 8. said downstream end 6 of the inner tube forming the inner flow path 1 is closed by a cap C being movable by means of a shaft S along the longitudinal axis 11 of the inner tube 7 between an inner position and an outer position such a way, that at least a group of said nozzles N are always disposed at least partly between said inner and said outer position of the upstream edge E of said cap C. In this way the size X of the nozzles will become adjustable. If the cap C movable by the shaft S is in its inner position the nozzles N are covered at least partly by the cap C and in the outer position of the cap C the nozzles are open in a greater extent or fully. The cap C may be guided in a similar way as the tubes, i.e. by means of sliding spacers arranged between the shaft S and the inner tube 7, or an outer support as depicted in Figure 8. In this embodiment a further self-cleaning feature will be obtained, since an occurring clogging may easily be removed from the nozzle N by moving the cap C.

A rim R of the downstream end 5 of the outer tube 8 is radiused inwardly and therefore it operates as an annular nozzle, as it can be seen in the Figure 9. Component A, preferably phosgene or its solution flows out from the outer gap 9a in the form of a flow cone, and component B exiting the nozzles N of the inner tube 7 will blown away by the liquid flowing by high velocity in this cone, resulted in a homogeneous mixing of the components.

In a further preferred embodiment of the device according to the invention the inner tube 7 is movable relative to the outer tube 8 along its longitudinal axis 11 in order to let the optimal distance between the nozzles N and the rim R of the outer tube 8 be experimentally adjusted, as it can be seen in Fig 10.- 11. In a preferred embodiment, the positioning of the nozzles N is such that the distance D between the a row of nozzles N downstream from the exit of the outer tube 8 is approximately equal to K, the width of the annular gap 9a, that is the axial distance of a circumferential row of nozzles N from the end of the outer tube is equal to the width of the annular gap between the tubes 7, 8. However, the axial distance of a circumferential row of nozzles from the downstream end of the outer tube in an optional embodiment may be between 0 and 5K, preferably between 0 and 3 K, the width of the annular gap between the tubes. Due to the movable inner tube 7 the distance D is freely adjustable in both directions, depending on the process parameters, like flow rates of the components A, B and diameter of the tubes 7, 8 etc.

A further objective of the present invention is to provide a reactor 13 adapted to perform a fast chemical reaction of industrial scale by mixing liquids, particularly a mono-, di- or polyamine and phosgene reaction to produce mono-, di- or polyisocyanates, respectively. The reactor shown in Figure 12. has an inner containment receiving mixed liquid components to precede subsequent reactions. Said containment is defined by reactor walls 14 and means for discharging reaction products. Agitating means 15 are arranged inside the reactor and at least one bore 16 is arranged on the reactor wall 14. A mixing device according to the invention is placed and sealed in said bore 16. In a preferred embodiment two or more mixing devices are mounted in bores 16 formed in the reactor wall 14.

The reactor vessel is provided with means for discharging from and reentering reaction products into the vessel, and in an embodiment the point(s) of reentry is/are arranged close beside the mixing device(s).

It has surprisingly been found that the apparatus of this invention facilitates processes wherein chemicals react very rapidly such that they can be carried out with low pressure drops and higher concentrations, can provide high product yield with very short residence times in the actual mixing zones of this apparatus, and can avoid blockages and solid deposits in these mixing zones, while permitting the use of conventional pumps.

The aim of this invention is achieved also by a continuous method of rapid mixing of liquids, especially fast reacting chemicals, and more especially amines and phosgene or preferably solutions thereof to make organic isocyanates.

The process according to the invention for the continuous preparation of an organic mono-, di- or polyisocyanate by mixing two liquids containing fast reacting components, particularly mono-, di- or polyamine and phosgene or solutions thereof, comprises the steps of: introducing a first component such as mono-, di- or polyamine corresponding to the mono-, di or polyisocyanate into an upstream end 3 of a first flow path 1 to flow towards the downstream end thereof 6, and introducing a second component such as phosgene into an upstream end 4 of a second flow path 9 disposed concentrically to the first flow path 1, to flow towards the downstream end 5 thereof, then pressurizing the first component to flow out from the first flow path 1 through at least one nozzle N interconnecting the first and second flow paths 1, 9, into the second flow path 9, and providing said nozzle N between the downstream ends 5, 6 and the upstream ends 3, 4 of said flow paths 1, 9, closing the downstream end 6 of the first flow path 1, and pumping the first component out through said nozzle N radially outwards from the first flow path 1.

The process according to the invention can perfectly be performed by means of the new mixing device according to the invention. Figure 13. shows the downstream end 5, 6 of the mixing device in operation, where a 'micro reaction chamber' is formed at the streaming out area of the components A, B. First component B is flowing in the concentrically inner first flow path 1 and the second component A is flowing in the outer second flow path 9. Flow paths 1 , 9 are both formed as tubes 7, 8 with cylindrical wall surfaces 7a, 8a and there is an annular gap 9a therebetween. Component B is exiting the first flow path 1 , that is it exits the inner tube 7 through nozzles N into the stream of the component A. This way the streams of the two reactant form a streaming cone - or a section of a cone surface in the case of each nozzle N - having a half cone angle Θ, and react freely streaming and mixing along this surface into a large space of a reactor 13. As it can be seen in the Figure 13. the angle of entry of stream of component B at the nozzle N relative to the direction of stream of component A is 90°, then this angle becomes smaller as the stream of component B being carried away by the stream of component A. In this way an outstreaming cone is formed with said half angle Θ to the axis 11. The components A, B are mixing homogeneously in the envelope of the cone providing very short mixing distances, even at high flow rates with a necessary excess of component A. Exiting geometry of the component B exiting nozzle N is shown in Fig. 14. Component B is pumped through the nozzle N at a velocity of 5 to 50 m/s, preferably 10 to 40 m/s and more preferably 30 m/s. At this latter velocity, the pressure drop across the nozzles N is approximately 1,7 MPa, permitting the use of conventional pumps for component B. It is experimentally stated and shown in the drawing, that the cross section Cb of the stream of component B is turned by 90° relative to the cross section Cn of the nozzle N almost readily after the time of exit, providing a greater surface in front of the component A, and it begins spreading perpendicularly to the axis 11. This spreading of component B exiting adjacent nozzles N creates a surface, which is blown to get the shape of said cone by the stream of component A. Component B is pumped through several nozzles N a row of which, that can be seen in the drawing, is provided circumferentially on the inner tube 7. A relative velocity of the components A, B is at least 2 and preferably 4 or more with the component A flowing in the outer flow path 9. To ensure rapid mixing there must be a relative velocity of at least 2 with the outer stream, and preferably 4 or more. In this embodiment the outer stream component A is pumped in the gap 9a of the mixer device, and the velocity of this stream is 1 to 10 m/s, preferably 3 to 7 m/s, and more preferably 5 m/s. Because of the low pressure containment of the reactor into which the reaction products are taken, no backstream of the reaction products is observed towards the micro reaction site shown in the Figure 13.

In a preferred embodiment of the process according to the invention a length of the nozzle N along a section X of the axis 11 is changed before or even during performing the process, that is while mixing device is in operation, since the downstream end 6 of the inner tube 7 forming the inner flow path 1 is closed by a cap C, which is movable along the longitudinal axis 11 of the inner tube 7 between an inner position and an outer position of the edge E of the cap C in such a way, that said nozzles N are disposed at least partly between said inner and said outer position of the edge E of the cap C. Therefore, the nozzles may be covered partly or wholly by the cap C. In this way the relative volume flow rate of the components is adjustable even during operation without the need of changing the volume flow rate of the component A.

In a further preferred embodiment of the process according to the invention the axial distance D between the nozzles N and the radiused downstream end 5 of the outer flow path 9 may be altered, since the inner tube 7 is movable relative to the outer tube 8 along its longitudinal axis 11 as above discussed. In this way the operational features of the 'micro reaction chamber' can easily be converted. For example, if the closed downstream end 6 of the first flow path 1 is moved outwards beyond the downstream end 5 of the second flow path 9, a nozzle N - or a row or rows of nozzles N - will be at least partly operating beyond the downstream end 5 of the second flow path 9, as it can be seen in Fig. 10, and therefore, the half angle Θ of the outstreaming cone becomes greater, that is the farther the nozzles beyond the end 5 the greater the half angle Θ of the outstreaming cone. Fig. 11 shows a retracted position of the inner tube 7, where said angle Θ of the outstreaming cone is minimal. However, the latter position also has advantages namely the components A, B form a premixture having a high flow rate before exiting the gap (9a) and spreading in said cone.

The process according to the invention is quite generally applicable to the manufacture of organic isocyanates, which can be obtained by reacting amines with a solution of phosgene in suitable organic solvents at elevated temperatures, followed by distillative work-up of the resulting reaction mixture. For example, monoisocyanates, diisocyanates and/or polyisocyanates can be manufactured from the corresponding organic monoamines, diamines and polyamines. Suitable organic monoamino compounds have the formula R-NH₂, where R is an unsubstituted or substituted monofunctional aliphatic, cycloaliphatic or, preferably, aromatic radical having 1 to 20, preferably 6 to 12, carbon atoms. Examples are aliphatic monoamines, e.g., methylamine, ethylamine, butylamine, octylamine and stearylamine, cycloaliphatic monoamines, e.g., cyclohexylamine, and especially aromatic monoamines, e.g., aniline, toluidines, naphthylamines, chloroanilines and anisidines.

Preferably, however, the diisocyanates and polyisocyanates, which are of importance for the industrial manufacture of polyurethanes, are manufactured from the corresponding diamines and polyamines by the new process. Suitable diamino compounds have the formula H₂ N~R'~NH₂, where R¹ is a difunctional aliphatic or cycloaliphatic radical having 2 to 18, preferably 4 to 12 carbon atoms or, preferably, is a functional aromatic radical which consists of one or more aromatic rings having from 6 to 18 carbon atoms directly linked to one another or linked via divalent bridge members, e.g., ~O~, -SO₂ — , -CH₂ — and -C(CHa)₂- . The diamino compounds and/or polyamino compounds may be used individually or as mixture.

Said aliphatic, cycloaliphatic, or, preferably, aromatic diamino compounds are, for example: 1,4-diaminobutane, 1 ,6-diaminohexane, 1,10-diaminodecane, 1,12- diaminododecane, 1,4- or 1,3-diaminocyclohexane, 4,4'-diaminodicyclohexyl, 4,4'-, 2,4'-, 2,2'-diaminodicyclohexylmethane, 3 ,3 '-dimethyl-4,4'-diaminodicyclohexyl- methane, 4,4'-diaminodiphenyl-, 1,4- or 1,3-diphenylenediamine, 1,5- or 1,8- naphthylenediamine, 2,4- or 2,6-toluenediamine, and 2,2'-, 2,4'- or 4,4'- diaminodiphenylmethane.

Examples of suitable polyamines are tri(p-aminophenyl)methane, 2,4,6-triamino- toluene and condensation products, which are obtained from substituted or unsubstituted aniline derivatives and aldehydes or ketones in the presence of acids, e.g., polyphenyl- polymethylene-polyamines.

Preferable organic amines are: 1 ,6-hexamethylenediamine, mixtures of 1,6- hexamethylene, 2-methyl-l,5-pentamethylene, and 2-ethyl-l,4-butylenediamine, 3- aminomethyl-3,5,5-trimethylcyclohexylamine, 2,4'-, 4,4'-, 2,2'-diaminodiphenyl- methane, or mixtures of at least two of the cited isomers, 2,4- and 2,6-toluenediamine or their mixtures, polyphenyl-polymethylene-polyamines or mixtures of diaminodiphenylmethanes and polyphenyl-polymethylenepolyamines. The process according to the invention is particularly suitable for the manufacture of aromatic diisocyanates and/or polyisocyanates from the corresponding amines and is therefore preferentially used for this purpose.

Liquid phosgene was used as the other initial component A. The liquid phosgene can be reacted as such or when diluted with a solvent suitable for phosgenation, for example, monochlorobenzene, dichlorobenzene, xylene, toluene, etc.

Suitable inert organic solvents are compounds in which the amines and the phosgene are at least partially soluble.

Chlorinated aromatic hydrocarbons, e.g., chlorobenzene, o-dichlorobenzene, p- dichlorobenzene, trichlorobenzenes, the corresponding chloro-toluenes and xylenes, chloroethylbenzene, monochlorodiphenyl, .alpha.- and .beta.-naphthyl chloride, alkyl benzoates, and dialkyl phthalates, e.g., diethyl isophthalate, toluene and xylenes have proved particularly suitable. The solvents may be used individually or as mixtures. Advantageously, the solvent used has a lower boiling point than the isocyanate to be manufactured, so that the solvent can readily be separated from the isocyanate by distillation. The amount of solvent is advantageously such that the reaction mixture has an isocyanate content of from 2 to 40 percent by weight, preferably from 10 to 30 percent by weight, based on the total weight of the reaction mixture.

The amines may be used undiluted or as solutions in organic solvents as component B. In particular, amine solutions with an amine content of from 5 to 50 percent by weight, preferably from 15 to 35 percent by weight, based on the total weight of the solution, are used.

In the process performed according to the invention, phosgene can be used in the form of a 20 to 80 % by weight, preferably from 40 to 60% by weight solution in inert solvent. The equivalent ratio of phosgene to amine is generally at least 1.5, and may be up to 20. The ratio is preferably in the range of 2 to 8.

In a preferred embodiment of the process according to the invention, the operating pressure in the phosgenation reactor into which the mixer exits is in the range of 1 to 10 bar gauge, preferably 3 to 7 bar gauge, and more preferably 5 bar gauge. The preferred temperature range in the reactor is 50 to 150 deg C, preferably 70 to 130 deg C, and more preferably 80 to 90 deg C.

The reaction mixtures, which have been prepared in the mixing device, which is essential to this invention, may subsequently be introduced into conventional reactors such as stirrer tanks or towers to provide residence time to complete the reaction. In the case of phosgenation of amines to produce mono- di-, or polyisocyanate end product, the temperature of this finishing process is from 100 to 200 deg C, preferably 110 to 160 deg C, and more preferably 120 to 150deg C. Subsequent processing stages include removal of excess phosgene, removal of solvent, and further purification of the isocyanate product by conventional means.

Due to the features described above the device and process according to the invention have many advantages over prior art solutions. The component A effusing through the gap 9a with high velocity blows along component B exiting perpendicularly the nozzles N, and form a homogeneous mixture. The technology of phosgenation with improved efficiency provided by the new mixing device ad process can be exploited in a number of economically advantageous ways. The phosgenation stage might be adjusted through a very wide range of parameters, i.e. at any particular phosgene to amine ratio of reactant concentrations, the isocyanate yield and/or quality will be improved; alternatively the concentration of amine in the feed solution may be increased to give higher output at constant yield; or the excess of phosgene used in the process, which is expensive to recycle, may be reduced. Of course, any combination of these alternatives may be chosen to give the most advantageous outcome. Further advantage of the device and process of the invention is that solids which are formed during phosgenation stage can not form, blockages due to the unique shape of the nozzles N and also the cap C movable over the nozzles N, since these solids break and leave the nozzles in small particles and form no obstacles in transfer piping to a subsequent reactor without the need of operating the first stage of phosgenation in a higher temperature and pressure regime where 30-70% of the intermediate carbamoyl chloride would be dissociated to isocyanate, but at higher costs of production.

Claims

1. A device for mixing two liquids containing fast reacting components, particularly mono-, di- or polyamine and phosgene or solutions thereof, the device comprising: an inner flow path (1) for a first liquid and an outer flow path (9) for a second liquid, said first and second flow path (1, 9) each having an upstream end

(3, 4) and a downstream (5, 6) end, said flow paths (1 , 9) are coaxially disposed and interconnected by at least one through opening formed on a wall portion of the inner flow path (1), means for fluidly connecting the upstream ends (3, 4) of said flow paths (1, 9) to a source of said first and second liquid, respectively, means for building in and sealing the device in a bore (16) provided on a wall (14) of a reactor (13) vessel, characterised in that the downstream end (6) of the inner flow path (1) is closed, and said through opening is a nozzle (N) provided on the wall of the inner flow path (1) between the closed downstream end (6) and the upstream end (3) thereof.

2. A device according to claim 1., characterised in that the inner flow path (1) and the outer flow path (9) are defined by tubes (7, 8) having cylindrical walls forming an annular gap (9a) therebetween.

3. A device according to claim 2., characterised in that said nozzle (N) is provided by minimal and maximal cross sectional areas.

4. A device according to claim 3., characterised in that said minimal cross sectional area is formed between the inner and the outer surfaces (7a, 7b) of said inner tube (7).

5. A device according to claim 3., characterised in that said minimal cross sectional area is formed on a surface (7a, 7b) of said inner tube (7).

6. A device according to any claims of 1.- 5., characterised in that the inner wall (10) of the nozzle (N) is radiused.

7. A device according to claim 6., characterised in that said nozzle (N) has an elongated shape along a section (X) of longitudinal axis (11) of the inner tube (7), and a width (Y) measured perpendicularly to that section (X), and said section (X) is grater than said width (Y).

8. A device according to claim 7., characterised in that said elongated shape is oblong rounded at least on one side thereof.

9. A device according to any of claims 1.-8., characterised in that several nozzles (N) are circumferentially provided on the inner tube (7).

10. A device according to claim 9., characterised in that said nozzles (N) are spaced apart circumferentially by equal angular distances.

11. A device according to claim 10., characterised in that said nozzles (N) are arranged in at least two circumferential rows.

12. A device according to claim 11., characterised in that subsequent rows (12) of nozzles (N) are spaced at least two nozzle (N) width (Y) apart, with the nozzles (N) of each subsequent row (12) off-set so as to be midway between nozzles (N) of the adjacent row (12).

13. A device according to claim 11 or 12., characterised in that the axial distance (D) of a circumferential row (12) of nozzles (N) from the downstream end (5) of the outer tube (8) is between 0 and 5K, preferably between 0 and 3K, and most advantageously D=K the width (K) of the annular gap (9a) between the tubes (7, 8).

14. A device according to claim 13, characterised in that said downstream end (6) of the inner tube (7) forming the inner flow path (1) is closed by a cap (C) being movable by means of a shaft (S) along the longitudinal axis (11) of the inner tube (7) between an inner position and an outer position of the edge (E) thereof, and said nozzles (N) are disposed at least partly between said inner and said outer position of said cap (C) edge (E).

15. A device according to claim 14., characterised in that support means P are arranged between the inner tube (7) and the outer tube (8), and each support means P is fixed to one of said tubes (7, 8).

16. A device according to any of claims 15., characterised in that a rim (R) of the downstream end (5) of the outer tube (8) is radiused.

17. A device according to claim 16, characterised in that the inner tube (7) is movable relative to the outer tube (8) along its longitudinal axis (11).

18. A reactor adapted to perform a fast chemical reaction of industrial scale by mixing liquids, particularly a mono-, di-, or polyamine and phosgene to produce mono- di-, or polyisocyanates, respectively, said reactor (13) having an inner containment receiving mixed liquid components to proceed subsequent reactions, and said containment is defined by reactor walls (14) and means for discharging reaction products and having agitating means (15) thereinside, and at least one bore (16) arranged on the reactor wall (14), characterised in that a mixing device according to any of claims 1.-17. is arranged and sealed in said bore (16).

19. A reactor according to claim 18., characterised in that it is provided with means for discharging from and reentering reaction products back into the reactor (13), and a point of reentry is arranged close beside the bore (16).

20. A reactor according to claim 19., characterised in that at least two bores (16) receiving a mixing device are formed on the reactor wall (14), and a mixing device is arranged in each bore (16).

21. A process for the continuous preparation of an organic mono-, di, or polyisocyanate by mixing two liquids containing fast reacting components, particularly mono-, di, or polyamine and phosgene or solutions thereof, comprising the steps of: i) introducing a first component (B) such as mono-, di, or polyamine corresponding to the mono-, di, or polyisocyanate into an upstream end (3) of a first flow path (1) to flow towards the downstream end (6) thereof, and ii) introducing a second component (A) such as phosgene into an upstream end (4) of a second flow path (9) disposed concentrically to the first flow path (1), to flow towards the downstream end (5) thereof, and iii) pressurizing the first component (B) to flow out from the first flow path (1) through at least one nozzle (N) provided on the wall of the first flow path (1), characterised in that iv) providing said nozzle (N) between the downstream end (6) and the upstream end (3) of said first flow path (1), v) keeping closed the downstream end (6) of the first flow path (1), and vi) pumping the first component (B) out through said nozzle (N) radially outwards from the first flow path (1).

22. The process according to the Claim 21., characterised in that that first component (B) flowing in the concentrically inner first flow path (1) and the second component (A) flowing in the outer second flow path (9) both formed as tubes (7, 8) having cylindrical walls (7b, 8a) forming an annular gap (9a) therebetween.

23. A process according to claim 22., characterised in that said first component (B) is pumped out from the first flow path (1) through at least one nozzle (N) having minimal and maximal cross sectional areas and an elongated shape along a section (X) of the longitudinal axis (11) of the inner tube (7).

24. A process according to claim 23., characterised in that component (B) is pumped through the nozzle (N) at a velocity of 5 to 50 m/s, preferably 10 to 40 m/s and more preferably 30 m/s.

25. A process according to claim 24., characterised in that component (B) is pumped through several nozzles (N) circumferentially provided on the inner tube (7).

26. A process according to claim 25., characterised in that a length of the nozzle (N) along a section (X) of the axis (11) is changed while component (B) being pumped out.

27. A process according to claim 26., characterised in that a relative velocity of the components (A, B) is at least 2 and preferably 4 or more with the component (A) flowing in the outer flow path (9).

28. A process according to claim 27., characterised in that the velocity of the component (A) is 1 to 10 m/s, preferably 3 to 7 m/s, and more preferably 5 m/s.

29. A process according to claim 28., characterised in that the inner tube (7) is moved relative to the outer tube (8) along its longitudinal axis (11).

30. A process according to claim 29., characterised in that the closed downstream end (6) of the first flow path (1) is moved outwards beyond the downstream end (5) of the second flow path (9) and at least a nozzle at least partly is operating beyond the downstream end (5) of the second flow path (9).

31. A process according to claim 30., characterised in that closing or opening at least partly at least one nozzle (N).

32. A process according to claim 30., characterised in that closing or opening at least partly at least one nozzle (N) by moving a cap (C) closing said downstream end (6) of the inner tube (7), along the longitudinal axis (11) of the inner tube (7) between an inner position and an outer position of the edge (E) thereof in such a way, that said nozzle (N) are disposed at least partly between said inner and said outer position of said edge (E) of the cap (C).