EP0776245A1

EP0776245A1 - Process for the production of substantially homogenous mixtures

Info

Publication number: EP0776245A1
Application number: EP95930423A
Authority: EP
Inventors: Mathias Pauls
Original assignee: Rathor AG
Current assignee: Rathor AG
Priority date: 1994-07-28
Filing date: 1995-07-28
Publication date: 1997-06-04
Also published as: AU3164695A; DE59504999D1; WO1996003204A1; WO1996003230A1; CA2196088A1; AU7496194A; CA2196177A1; WO1996003231A1; AU3381595A

Abstract

In the proposed process for producing substantially homogenous mixtures of substances capable of reacting with one another, the substances in question are fed separately into a cold zone (2) and cooled to a point at which they are solid and non-reactive; they are then conveyed in finely divided form to a mixing zone (6) where they are mixed together, the temperature in the mixing zone (6) being maintained at a level below the softening temperature of the mixture contained therein.

Description

description

Process for the production of essentially homogeneous mixtures

The invention relates to a method for producing essentially homogeneous mixtures of reactive substances.

Chemical process engineering knows numerous methods of mixing substances which are reactive with one another in such a way that they react with one another in a desired manner. The large number of methods reflects the problem of producing mixtures. It is therefore common practice to work in diluting solvents which simultaneously serve to supply or dissipate energy, with all reaction components being dissolved in the solvent or the reaction partners being gradually combined, for example dropwise. Other mixing techniques include bringing together two feed streams in a reaction chamber, gradually dissolving or reacting a first component in a reaction medium containing one or more further components, or controlling reactions by adding catalysts. Mechanical or other stirring tools are often used to achieve thorough mixing of the reaction medium required for the reaction. Nevertheless, the production of a mixture of reactive substances that is as homogeneous as possible and optimal for the respective purpose remains problematic, in particular because the chemical reactions already start during the mixing process, that is to say before an optimal mixing of the components is produced. This works often depend on the yield and purity of the products and thus lead to increased costs for the products, be it because of the low yield, complex cleaning processes or high outlay on equipment for producing the mixtures.

In many cases, work is also carried out to optimize chemical reactions in large amounts of solvent in order to influence the mixing behavior of the reaction partners and thus the course of the reaction via the dilution effect. Large amounts of solvent require complex work-up processes, apart from the fact that the amounts of solvent not only have to be provided, but also have to be handled, separated, cleaned / reprocessed or removed.

Particularly when reacting highly reactive substances, undesired secondary reactions can occur if the reaction partners are not distributed homogeneously. However, such a distribution is problematic when one substance has to be mixed into a second one, as is often done in the laboratory with the aid of dropping funnels. Where the added substance gets into the reaction medium, a high concentration is currently being formed, which can no longer be broken down quickly enough in the case of rapid reactions with conventional mixing and agitators in order to avoid a selective reaction with subsequent reactions.

The same applies to the manufacture and further processing of plastics if there are several reaction partners. Selective focal points of the reaction can lead to selectively changed reaction conditions and thus influence the nature, structure or distribution of the products. This also applies, for example, to catalyzed reactions if the Catalyst is not distributed homogeneously. Such inhomogeneities also occur, for example, in the curing of polyurethane foams, for example if moisture-curing foams harden from the outside inwards with the onset of air humidity, in the case of two-component foams the second component is only incompletely mixed with the first component and therefore only locally reacted or, in the work-up of prepolymer residues, reactions on the one hand take place with water introduced, and on the other hand with an added agent. Since the reactions proceed according to the availability of the reactive substances, there are inhomogeneities with regard to the products as well as problems with the implementation of the reprocessing processes, in particular also because incomplete due to the simultaneous presence of emptied except for a small residue emptied or unusable cans of prepolymers of different quality, different amounts of hardeners and, in the case of cans that have become moist, also different amounts of water are introduced into the process. This also results in a batch-dependent quality of the products.

There is therefore a need for a mixing process with which it is possible to mix chemical substances which are reactive with one another in a substantially homogeneous manner, without a reaction occurring before the mixing process has ended.

This object is achieved with a method of the type mentioned in the introduction, in which the substances are introduced separately into a cold zone and cooled to such an extent that they are in a solid and unreactive state, and then introduced into the mixing zone in a finely divided state and there are mixed with one another, the temperature in the mixing zone is kept below the softening temperature of the mixture obtained therein.

The mixtures produced in the process according to the invention are stable only at the respective low temperatures, so that when the temperature rises, a reaction occurs when a minimum temperature necessary to start the reaction is exceeded. As a rule, it can be assumed that a slow reaction starts when one of the reactive substances reaches the melting temperature. It is therefore important that the substances are kept individually and in a mixture below the respective softening temperature.

The method according to the invention serves to mix at least two components together; however, more than two components can also be mixed with one another. One of the components can also be a catalyst. Furthermore, it is possible to add additives, which are to be contained in products made from them, as well as solvents which may be important for the course of the reaction, for example for temperature control, in the production of these mixtures. As a rule, at least one of the reactive substances is a liquid or is in solution under normal conditions or at the reaction temperature.

The mixtures obtained according to the invention can be further processed immediately by bringing them to a temperature which is conducive to the reaction or by introducing them into a reaction medium, or they can be stored or transported in a cooled state. It is also conceivable to pack such reactive mixtures appropriately or to bring them into a form suitable for an intended use and to store them in a cooled state. store so that they can only be removed from a cool box and used there for their use in another location. This can be done, for example, in a chemical laboratory or company, but also by a craftsman who, for example, brings a reactive mixture to produce a foam to a desired location and lets it foam there by the action of temperature. A further possible application would be, for example, a mixture of reactive substances which remain unchanged next to one another at low temperature, but which cause a color reaction when the temperature rises, for example above 0 ° C., so that such a mixture serves as an indicator substance for the uninterrupted functionality of cooling units can be used.

The process according to the invention is preferably carried out at a temperature which is below −80 ° C. It is particularly expedient to carry out the process at the temperature of liquid nitrogen. It is then expedient to work in the absence of oxygen, but this may also be necessary at higher temperatures and oxygen-sensitive substances.

The substances which are reactive with one another are generally liquid substances or at least one liquid substance which can serve as a solvent for one or more substances. In this respect, it is important to bring this liquid substance into a solid form that prevents the ability to react, which happens in the cold zone. Naturally, substances in solution can also be used, in particular when the solvent is required for the subsequent reaction.

In order to convert the reactive substances used into the finely divided ones required for the mixture Any size reduction process can be used to bring the shape into shape. Spray processes are particularly preferred in which the liquid substance or the substance is atomized in solution while cooling, so that a finely divided powder is obtained. Another preferred possibility is the pulverization of the reactive substance, initially solidified in a coarse form, in a mill, hammer mill or the like. Furthermore, it is possible to obtain the substance in powder form by means of a spray drying process, the powder possibly being first cooled to the low temperature required for the mixing process.

The mixing zone used according to the invention is expediently a spray tower. For example, a first substance in the form of a finely divided powder can be introduced into this spray tower from above and a second or further reactive substances can be injected while cooling and solidifying. In order to ensure the low temperature required in the spray tower in accordance with the method, it may be necessary to inject liquid or gaseous nitrogen for temperature control, the injection of cold gaseous nitrogen in the lower region of the spray tower and the outlet at the upper end being preferred in order to achieve a swirling effect .

The method according to the invention is particularly suitable for use in the preparation of packs which contain reactive residues. Packaging that contains isocyanate-containing prepolymers for polyurethane foams should be mentioned here in particular. The process according to the invention is therefore further described in the context of a reprocessing process for cartridges which contain prepolymers containing isocyanate groups for polyurethane foams. Residue-containing packaging, such as occurs in large quantities, for example in the form of completely or partially emptied cartridges, is increasingly becoming a disposal problem. A deposit on landfills is prohibited for reasons of environmental protection, since the residues contained therein can get into the atmosphere, into the ground or into the groundwater and can cause considerable damage there. The same applies to the combustion, which is often only incomplete, in particular in the case of chemical-technical products, and generates large amounts of pollutants which, if at all, can only be bound by expensive measures. Insofar as incineration leads to a sharp reduction in the volume of waste, it does not necessarily eliminate the environmental impact.

Particular problems arise when the residues contained in the packaging themselves are reactive and possibly also toxic products, as is the case, for example, with isocyanate-containing prepolymers for polyurethane foams. The same also applies to other reactive plastic products, for example self-curing or curable mixtures for coatings, adhesive mixtures, etc.

In many cases, polyurethane foams are brought out of cartridges which contain a polyurethane prepolymer together with the necessary additives. These cartridges cannot be reused after use. On the other hand, they represent problem waste that is not accessible for normal disposal.

As part of efforts to contain household and commercial waste, measures are increasingly being discussed and prescribed that compel manufacturers to take back packaging of their products after use and to ensure that they are reused or disposed of. Such measures have made it necessary to look for ways of economically treating such waste. In the treatment of withdrawn cartridges for the production of polyurethane foam, there are a number of problems which make economic reprocessing difficult. For example, part of the withdrawn cartridges can be under pressure due to moisture penetration if improperly stored or handled, which makes opening and combustion both a problem. Furthermore, the cartridges have a different filling state, from old cartridges with practically complete prepolymer filling, which can no longer be dispensed due to a blocked valve, to practically completely empty cartridges with only the remainder adhering to the edges from prepolymer in uncrosslinked to crosslinked state.

To date, a number of processes for the treatment of packaging, including aerosol cans for the production of polyurethane foam, have become known. For example, it has been proposed to inject pressure cans into a system under inert gas and to shred them there via a lock system. Furthermore, methods have become known for introducing aerosol cans into a plant, comminuting them there and extracting the contents with suitable solvents. In these processes, both the packaging materials and the ingredients (prepolymer, propellant) are obtained.

These known methods, some of which are quite efficient and are practiced, can be improved with regard to occupational safety, process management and quality of the products. It prepares It is difficult to separate the residues contained in the packaging in a simple manner and to obtain homogeneous products for suitable further use.

With the method according to the invention it is possible to process reactive residues of packaging in a completely harmless manner. The reactive residues, for example in the case of cartridges for the production of polyurethane foam containing prepolymers containing isocyanate, are treated in a manner which is safe from a safety point of view. Freezing the reactive substances or residues does not lead to a reaction-related pressure increase in the process or to undesired reactions between reactive components. At the temperatures prevailing in the process, the presence of water is also harmless. The latter two points are important in the treatment of products containing isocyanate, for example if water is carried into the process due to damaged packaging. At the same time, reactive second components contained in so-called 2-component foams, for example glycols, carboxylic acids or water, can be introduced into the process without problems. In this respect, the method according to the invention is suitable for simultaneously treating both cartridges for 1-component and 2-component foams as well as transition forms between the two and converting the reactive residues into high-quality and homogeneous products.

In the process according to the invention, packaging, for example cartridges, is first introduced into a cold zone and cooled therein to such an extent that the residues reactive therein, including low-boiling solvents therein, solidify. Temperatures of less than -80 ° C to -100 ° C are generally sufficient for this; expediently but is worked in liquid nitrogen as a refrigeration medium. In this case it is important that the process is carried out in the absence of oxygen in order to avoid the condensation of liquid oxygen, which could have a disadvantageous effect in later process steps.

After the desired temperature, generally the temperature of liquid nitrogen, has been reached, the packaging is crushed in the cold state. The temperatures here should expediently be below -80 ° C to - 100 ° C; if necessary, liquid nitrogen or cold gaseous nitrogen must be injected.

The comminution is expediently carried out in a hammer mill which works against a sieve. As a result, a shaking and flexing effect is achieved which, in addition to the comminution to a desired grain size, brings about a separation of the different materials: metal, paper, plastic and ingredients. It has surprisingly been found that the packaging materials - metal, paper and plastic - can be separated extraordinarily well from the ingredients - reactive substances and solvents / additives - the ingredients being obtained as a fine powder.

In a subsequent separation stage, the shredded packaging is separated into at least two fractions, one of which contains the reactive residues, including the propellant gas, in a solid state. A screen is expediently provided in this separation stage, expediently a vibrating screen through which the fine constituents, predominantly reactive residues and solvents, fall. Metal parts are separated using magnetic methods, larger plastic parts and scraps of paper are screened off on the vibrating screen. The frozen ingredients from reactive substances and solvents pass from the separation zone into a mixing zone, into which an agent reactive with the residues is simultaneously introduced as a further reactive substance. Also in this mixing zone prevail temperatures of less than -80 ° C to - 100 ^C C to the frozen state of the introduced Ma¬ terialien and to ensure the injected reakti¬ capabilities in an agent immediately Stigen to a fine powder to verfe¬. The result of this is that a uniform mixture of ingredients in powder form and reactive agent is formed, but which cannot react due to the prevailing temperature conditions. The temperatures in the mixing zone are in any case below the melting point of the residues and the reactive agent as well as the mixture.

A spray tower is expediently used as the mixing zone, into which the frozen ingredients fall from above. The reactive agent is sprayed into this powder stream from side nozzles, expediently together with cold gaseous nitrogen, in order to ensure the required low temperatures. Pre-cooling of the reactive agent is advisable, but the sprayability must remain guaranteed.

It may be expedient to inject the reactive agent together with a catalyst which promotes the reaction with the reactive residues of the packaging. In the case of isocyanate-containing prepolymers, however, this is generally not necessary if the isocyanate-containing mixtures already contain such catalysts. The cold powdery mixture of ingredients and reactive agent and optionally catalyst is then passed into a reaction zone which, for example, consists of a conveyor belt which moves continuously under the mixing zone. The powder collected here is then brought to a temperature sufficient for the reaction to react. The solvents contained evaporate on this occasion and are condensed out at a suitable point, which is the case when nitrogen is used as the refrigerant is not a problem. In order to give the reaction product the desired shape, the conveyor belt can have lateral boundaries. To separate the reaction product from the conveyor belt, it is possible to provide release agents, for example suitable coatings or release paper. The heating in the reaction zone is expediently carried out using microwaves, which bring about a rapid, direct heating of the powder material from the inside, so that there is uniform degassing and heating.

Following the reaction zone, further processing and treatment zones can be provided, and finally a lock for discharging the fully reacted material.

As already mentioned, the method according to the invention is particularly suitable for preparing residue-containing polyurethane foam cartridges. In this case, the reactive agent is in particular a compound containing hydroxyl groups, for example water, ethylene glycol, propylene glycol, glycerol, oligomers and mixtures thereof and derivatives thereof. Ethylene glycol, water and polyether alcohols are preferred, and in any case at least two reactive hydrogen atoms should be present. Polycarboxylic acids can also be used. Among the polyether alcohols the so-called Jeffamine (trademark) are particularly suitable.

In the preparation of packaging for the production of polyurethane foams, it is advisable to convert the isocyanate-containing prepolymers into foam materials that can be used for insulation and insulation purposes, for example. Thus, with the method according to the invention, insulating boards can be produced continuously, the propellant gases contained in the powder produced in the mixing zone promoting foam formation. However, it is also readily possible to produce films or to admix additives, for example cellulose-containing materials, and then to compress these mixtures during or after the reaction to give composite materials. However, it is preferred to produce granules from reacted material, which is later processed.

The method according to the invention can be used, in particular, in the course of working up unpressurized polyurethane foam cartridges which are emptied at the place of use with the aid of a suitable gun and are then returned to the manufacturer for reprocessing. These cartridges, which are used for both 1K and 2K foams, are pressureless during storage and generally contain no blowing or foaming agents. If an improvement in the foaming behavior is necessary and this improvement cannot be achieved by using water as the second component, low-boiling solvents may be present, for example pentane which is liquid at normal temperature and nitrogen at the temperature of liquid are solid, but evaporate below the reaction temperatures of the prepolymer with the second component and cause a blowing effect. The use of the method according to the invention for aerosol It is also possible to produce polyurethane foam if effective propellant gas separation is ensured in the later reaction. Thus, the method can in principle be applied to the processing of packs which, in addition to reactive substances, also contain blowing agents and, if appropriate as a function of the temperature, achieve a driving and / or foaming effect.

The method according to the invention is explained in more detail by the accompanying figures. Of these shows

Fig. 1 shows schematically a plant for the processing of packaging;

FIG. 2 shows the entrance area of the system according to FIG. 1;

3 shows the conveying, crushing and sorting part of the system according to FIG. 1; and

4 shows the mixing and reaction zone of the plant according to FIG. 1.

The illustration shown in FIG. 1 of a treatment plant for cartridges with reactive residues has an entrance lock 1, to which the cartridges 13 to be treated are fed. The entrance lock is preferably designed as a cellular wheel blow-through lock, in the chambers 12 of which the cartridges 13 drop in from above via a feed funnel 14 (FIG. 2). By rotating the cellular wheel 1, the cartridges enter the lower region of the lock and are laterally ejected from the line 15 with the aid of gaseous nitrogen GAN. In order to make this possible, the cellular wheel rotates in a gas-tight container which is open at the top and which in its lower region is pressurized from one side Gaseous nitrogen GAN can be applied so that the cartridge 13 located therein can be ejected into a guide system 21 on the opposite side. The nitrogen supply via line 15 is preferably ensured with gaseous nitrogen from the cooling bath 2. It is understood that the speed of rotation of the cellular wheel 1 and the pressure surges from the nitrogen line 15 for ejecting the cartridges from the cellular wheel are coordinated with one another. For this purpose, the cellular wheel has a measuring sensor marked with M.

The cartridges pass from the cell wheel via a guide 21 into the cold bath 2, which is filled with liquid nitrogen. The guide 21 expediently consists of an elongated basket construction which is open on all sides and which enables the unhindered entry of liquid nitrogen and the exit of gaseous nitrogen.

The cartridges 13 are cooled to the bath temperature on their way through the cooling bath 2, which is fed with fresh liquid nitrogen LIN via line 24 depending on the level and has a measuring sensor LIC for level control. The cage structure of the guide 21 ensures free access of the cooling medium and the rapid removal of the gaseous nitrogen generated. Gaseous nitrogen is withdrawn from the bath area via line 16 with the aid of a fan 17. The length of the guide 21 and the transport speed are set in such a way that the cartridges 13 are cooled to a sufficiently low temperature of at least -80 ° C. to -100 ° C. even when the remaining filling is completely full.

The cartridges 13 are transported in the guide 21 with the aid of the transport device 23, which moderately consists of a circular conveyor belt 25 with projecting forks 26 which engage from above in the guide 21 and push the cartridges 13 guided in front of it. Transport rollers 27 ensure precise guidance of the transport forks 26. The forks 26 are arranged on the conveyor belt 25 at intervals which are matched to the size of the cartridges 13 to be transported. A measuring station M is used to monitor the transport speed and to coordinate it with the feed speed of the cartridges 13.

After passing through the cooling bath 2, the cartridges 13 pass from the guide 21 into the conveying device 3 (FIG. 3) in the form of a revolving conveyor belt 31 which has transport segments matched to the size of the cartridges 13. The conveying device 3 is preferably designed as a steep conveyor which receives the cartridges 13 in the segments formed by transport forks 33 arranged at regular intervals and delivers them overhead into the comminution device 4. The conveyor belt is guided over rollers 32 provided with a measuring station M for monitoring and controlling the conveying speed.

The comminution device 4 consists of a shredder or preferably a hammer mill 41. The hammer mill 41 preferably works against a sieve in order to ensure a certain grain size of the comminuted material. At the same time, the sieve 42 has a flexing effect, which has a positive effect on the separation of the ingredients, which are embrittled by the cold, from the container material. It goes without saying that, in order to maintain the required low temperatures of -80 ° C. to -100 ° C., refrigerant, preferably liquid nitrogen LIN, can be added via line 43 if the temperature control TK permissible temperature rise reports. The working speed is checked and controlled via the measuring sensor M. Gaseous nitrogen is discharged via line 44 and recycled or blown off via a valve 45.

From the comminution 4, the comminuted material arrives in the sorting device 5. This initially consists of a vibrating screen 51, on which the coarse and the fine parts are separated. Large parts are mainly the comminuted materials of the container, which are shaken off on the inclined sieve 51 and are discharged from the process via a lock, not shown.

Powdery ingredients and fine particles of the container pass through the vibrating screen 51 to a first magnetic separator 52, which separates the remaining iron and aluminum components from plastic particles and ingredients. Magnetic components are first separated on the first magnetic separator 52 and placed on a first conveyor belt 53, which also receives the metal and plastic parts shaken off the sieve 51. A second conveyor belt 54 receives plastics, ingredients and non-magnetic metal parts, which are separated into metallic and non-metallic components via a second magnetic separator 55 coupled to the conveyor belt. The metallic components get on the first conveyor belt 53, the non-metallic components are fed directly into the spray tower 6. Cold gaseous nitrogen can be supplied via line 56 when the temperature control TIC reports an impermissible temperature increase. Measuring sensors M check the working speed of all moving parts of the separation system 5. If the cartridges are made entirely of non-metallic 04 PCΪ7EP95 / 03010

18th

If there are materials, the magnetic separator can of course be dispensed with.

It goes without saying that a temperature of at most -80.degree. C. to -100.degree. C. is ensured in the comminution system as well as in the sorting device by appropriate feed lines for refrigerants, preferably nitrogen in gaseous or liquid form.

The powdery ingredients and plastic parts which reach the spray tower 6 (FIG. 4) and which have a temperature of at most -80.degree. C. to -100.degree. C., so that solvents contained therein are also present in a solid state with the reaction medium sprayed in via the feed line 61 in the upper region of the spray tower 6 and optionally catalyst. The reaction medium, preferably ethylene glycol, is in the liquid state in the storage tank 62, the catalyst in the storage tank 63. Dosing stations are assigned to the tanks.

Reaction medium from the container 62 and catalyst from the container 63 are injected via the line 61 into the spray tower 6 in a metered ratio to the reactive ingredients, it being possible for a pre-cooling section to be provided in the course of the supply line 61 in order to bring the materials to an acceptable temperature cool (above the melting point). The spray material is solidified upon entry into or within the spray tower, even at the temperatures of less than -80 ° C. to -100 ° C. To maintain the temperature in the spray tower, it is therefore expedient to introduce additional cooling medium, for example liquid nitrogen LIN via line 64 or gaseous nitrogen via line 65 when the temperature control TIC signals a need. It is expedient to inject the cooling medium in the lower areas of the spray tower in order to Spray tower 6 ascending cold nitrogen to ensure an additional swirling and mixing of reactive compound, catalyst and reactive dose content.

The mixture of reactive cartridge contents, reactive compound and catalyst in powder form reaches the reaction space 7 from the spray tower 6. A reaction belt 71 is arranged inside the reaction space 7, which takes up the falling material from the spray tower 6 and into the actual reaction zone 72 leads where the reaction is induced by heat. For this purpose, heating elements 73 are arranged above the conveyor belt 71, which use microwaves or infrared rays to heat the reaction material on the conveyor belt 71 to a temperature sufficient for the reaction, for example about room temperature or above.

In order for the reaction material 74, e.g. H. To prevent the mixture of reactive cartridge content, reactive compound and catalyst on the conveyor belt 71, it may be expedient to cover the conveyor belt with a separating film 75, which is unwound from a roll 76a and wound onto a second roll 76b becomes. The release film can be used several times if necessary.

The reaction material reacts on the conveyor belt 71 to the respectively desired product. At the same time, solvents and adsorptively bound nitrogen of the refrigerant still contained in the mixture from the spray tower are released and sucked off via line 77 and fed to a separation (not shown) and solvent extraction. In the presence or formation of a foaming agent, such as pentane or CO 2, the exit from the reaction material 74 causes a partial foaming tion of the reaction mixture, which is not undesirable for certain purposes.

At the end of the conveyor belt 71 there is a scraper 78 with which the reacted reaction material is detached from the conveyor belt or the separating film and discharged from the process via the product lock 8 and discharged via a conveyor belt 81. Nitrogen lines 81 and 82 regulate the shielding gas supply in the lock area, nitrogen being expediently used as the shielding gas, but this need not be cooled. Further nitrogen lines 83 and 84 in the area of the entry and exit of the separating film 75 prevent oxygen from entering the system in this area. The use of cooling nitrogen is not necessary here either.

It is understood that the method according to the invention is carried out in a cold and was insulated plant. In particular, the entry of oxygen must also be prevented here in order to prevent the condensation of liquid oxygen into the cold bath 2. It is advantageous for the gas supply that the entire process is carried out into the spray tower 6 at temperatures at which loose and foaming agents are present in a solid state. This allows them to be withdrawn centrally via the suction line 77 in the reaction space 7 and fed to the extraction. The fully reacted / hardened polyurethane material, which emerges from the process from the product lock 8, can be used as granules for any further use. For example, the use for insulating materials and in composite materials comes into question.

Claims

claims

1. A process for the production of substantially homogeneous mixtures of reactive substances, characterized gekenn¬ characterized in that the substances are introduced separately from each other in a cold zone and cooled to the extent that they are in solid and unreactive state, and then in a finely divided state in a mixing zone introduced and mixed there, the temperature in the mixing zone being kept below the softening temperature of the mixture thus obtained.

2. The method according to claim 1, characterized in that it is carried out at a temperature <-80 "C.

3. The method according to claim 2, characterized in that it is carried out at the temperature of liquid nitrogen with exclusion of oxygen.

4. The method according to any one of claims 1 to 3, characterized ge indicates that at least one of the substances is present as a liquid.

5. The method according to any one of claims 1 to 4, characterized ge indicates that at least one of the substances is dissolved in egg nem solvent.

6. The method according to claim 4 or 5, characterized gekennzeich¬ net that at least one of the substances is cooled under spraying and solidified.

7. The method according to any one of the preceding claims, characterized in that at least one of the substances zen is mechanically pulverized at a temperature <-80 ° C.

8. The method according to any one of the preceding claims, characterized in that the mixing zone is a spray tower.

9. The method according to claim 8, characterized in that one of the reactive substances is injected into the spray tower while cooling and solidifying, one or more further substances passing through the spray tower in a finely divided state.

10. The method according to claim 8 or 9, characterized gekennzeich¬ net that gaseous or liquid cold nitrogen for temperature control in the spray tower is preferably injected in its lower region.

11. The method according to any one of the preceding claims, characterized in that the mixing zone is followed by a reaction zone in which the substantially homogeneous mixture of substances which are reactive with one another is brought to a temperature sufficient for the reaction and allowed to react.

12. The method according to any one of the preceding claims, characterized in that it is applied to the treatment of reactive residues contained in packaging.

13. The method according to claim 12, characterized in that the reactive residues are prepolymers containing isocyanate groups for the production of polyurethane foam.

14. The method according to claim 13, characterized in that the prepolymers containing isocyanate groups are mixed with a compound containing hydroxyl groups.

15. The method according to claim 14, characterized in that the hydroxy-containing compound is water, ethylene glycol or a polyether alcohol.

16. The method according to any one of claims 12 to 15, characterized in that additives are added in the mixing and / or reaction zone.

17. The method according to any one of claims 12 to 16, characterized in that the reaction zone is heated with microwaves.