Method and device for producing polyurethane components

Abstract

The invention relates to a method for producing polyurethane components, wherein, before entering a mixing chamber (3), an additional component (5) is added to a first chemical component (1), and wherein the chemical component (1) is passed through a nozzle element (6) which is arranged in front of or on the mixing chamber (3) and has a first flow path (7) for the chemical component (1), wherein the first flow path (7) for the chemical component (1) has a constriction (8), wherein the additional component (5) is supplied to the nozzle element (6) and is guided through the nozzle element (6) along a second flow path (9). In order to introduce an additional material into the polyol stream such that it can be mixed in and conveyed to the mixer with optimum conveyance with the lowest possible shear loading, according to the invention: a gas (G) is supplied into a container (10) for the additional component (5) and / or into a flow path (11) for the additional component (5), which flow path extends from the container (10) to the nozzle element (6); and means (12) for discharging the gas (G) are arranged in or on the nozzle element (6), and the gas (G) is discharged from the nozzle element (6) via the means (12). The invention also relates to a device for carrying out the method.

Description

[0001] Method and device for the production of

[0002] Polyurethane components

[0003] The invention relates to a method for producing polyurethane components, in which at least two different chemical components, including at least one polyol component and one isocyanate component, are individually metered and then fed to the mixing chamber of a mixing head, in which they are mixed to form a polyurethane reactive mixture and then discharged from the mixing chamber, in particular into an open or closed mold, wherein a further component, in particular a filler, is added to at least one of the chemical components before entering the mixing chamber of the chemical component, wherein the further component is in liquid or solid form, in particular as a powdery, granular or lumpy mixture, and wherein the chemical component to which the further component is added is passed through a nozzle element,which is arranged in front of or on the mixing chamber and which has a first flow path for the chemical component, wherein the first flow path for the chemical component has a constriction, wherein the further component is fed to the nozzle element and guided along a second flow path through the nozzle element. Furthermore, the invention relates to a device for carrying out such a method.

[0004] Known mixing devices for polyurethane high-pressure mixing – without the additional addition of special components – are designed so that the at least two reactive components meet in a mixing chamber with high flow energy in the form of pulse energy, thus mixing them together. In high-pressure mixing, there are generally no additional mixing elements for further mixing of the reaction mixture, so mixing occurs exclusively through the flow energy contained in the reactive components. In practice, the countercurrent injection process has become established.

[0005] Mixing primarily takes place in a mixing chamber that is mechanically cleaned by a plunger. Groove-controlled mixing heads feature return grooves in the control piston, through which the components circulate separately from the inlet opening through the grooves in the circulation position without mixing. In the metering position, the plunger is moved accordingly, forming a mixing chamber in the area of ​​the inlet openings and mixing the reactive components.

[0006] As an alternative, nozzle-controlled mixing heads are known, which are designed without such circulation grooves. Component control is achieved by controlled nozzles arranged in the inlet openings.

[0007] The task of the nozzles is to generate the required flow energy and convert the pressure energy into flow energy. Narrow flow cross-sections are required in the nozzle to create the required orifice effect.

[0008] Due to the properties required of the produced components, it is sometimes necessary to add various additives to the reaction mixture. These additives can be in liquid, solid, lumpy, or powdered form.

[0009] Liquid additional components include, for example, activators, additives, and colors. The liquid components are usually only added to the reaction mixture in small quantities. They are either mixed into the polyol component in a batch or dosed directly into the mixing chamber. When added directly into the mixing chamber, the problem often arises that the pulse generated by the very small dosage does not generate enough momentum to be adequately mixed during countercurrent injection. Processing as a polyol batch has the disadvantage that the sometimes corrosive properties of the additional component cause problems with the service life of the system and sometimes require special components for conditioning and conveying. If colors are to be processed in batches, multiple rinsing processes are often necessary when changing the color, which makes rapid color changes difficult.

[0010] Solid fillers are usually in lumpy, short-fiber, or powdered form. These are often abrasive and cause significant wear on conveying equipment and piping systems. Furthermore, some fillers, such as expandable graphite, are particularly shear-sensitive, creating further challenges in handling and mixing into the reaction mixture.

[0011] A method of the aforementioned generic type is known from DE 33 35 787 A1. A similar solution is disclosed in DE 10 2010 031 958 A1.

[0012] For conveying powdery fillers, DE 27 50 938 A1 proposes the use of the internal pressure of a gas-filled filler container. This represents a particularly gentle conveying option, as no pumps or other dynamic conveying devices are required. The gas pressure can be used as a targeted conveying pressure via a control system, thus allowing the desired flow rate to be adjusted. Since solid fillers are prone to flow problems, such as pitting and bridging, it is necessary to keep the bulk material flowing.

[0013] Fluidizing bulk materials by means of air aeration is well known in silo technology. The aforementioned DE 27 50 938 A1 applies this approach to polyurethane processing. A porous cone in the filler container creates a fine air distribution, keeping the bulk material flowable. The mixing process in the mixing chamber is not described.

[0014] Various methods are known for adding solid fillers, such as chalk, expandable graphite or similar materials, to the reaction mixture:

[0015] First, the filler can be added to one of the main components. Furthermore, the filler can be added to the reaction mixture within the discharge system after high-pressure mixing.

[0016] Finally, the filler can be added via a separate feed into the mixing chamber.

[0017] When the filler is added to one of the reaction components, the filler is injected into the mixing chamber together with the main component, meaning the fillers must be pumped together with the main component under high pressure via a metering pump. A disadvantage here is that fluids filled with fillers tend to segregate and form deposits in the pipes. Abrasive fillers often lead to increased wear on surfaces subject to high mechanical and fluidic stress, for example, inside nozzles, metering pumps, and valves. Sensitive fillers can be damaged to an unacceptable degree by processing under high pressure.

[0018] The processing of expandable graphite, in particular, presents significant challenges for machine technology. Expandable graphite is used as a flame retardant in polyurethane processing. The mode of action, advantages, and problems associated with the processing of shear-sensitive fillers such as expandable graphite are explained, for example, in EP 3 892 432 A2.

[0019] One problem with processing expanded graphite is that the expanded graphite particles can be destroyed when exposed to mechanical stress, particularly shear forces in pumps or nozzles. This impairs their flame-retardant properties; on the other hand, the acid released negatively impacts the chemistry of the foaming process.

[0020] It is therefore problematic if expandable graphite, as is common with other fillers, is mixed as a filler-polyol mixture in a container, where it must be kept in suspension by means of a stirrer and additionally pumped in a circuit to prevent expandable graphite from settling in the pipes.

[0021] A method for reducing the circulation time of the expandable graphite-polyol mixture under high pressure is described in the aforementioned EP 3 892 432 A2.

[0022] Addition downstream of the mixing chamber is proposed, for example, in EP 0 037 523 A1, DE 27 50 938 A1, and DE 10 2009 011 900 B3, but this disadvantageously leads to insufficient mixing. In these previously known solutions, the additional component is added to the reaction mixture. No additional mixing device is present in these cases; this procedure is not feasible with self-cleaning mixing heads.

[0023] DE 42 16 943 A1 describes a process in which the filler is fed directly into the mixing chamber. However, the arrangement described here exhibits insufficient mixing for many applications. Tests have shown that the pulse energy is usually insufficient to adequately mix the additional component into the reaction mixture. Similar solutions are disclosed in AT 519 978 A4, DE 25 44 559 A1, DE 690 15 821 T2, DE 10 2010 018 946 A1, DE 10 2011 002 881 A1, FR 1 496 800 A, and US 2012 / 0178895 A1.

[0024] In light of the problems described above, the object of the present invention is to provide a generic method and a corresponding device with which both liquid and solid, lumpy or powdery additives can be introduced into a reaction mixture, which is mixed using the countercurrent injection process, in such a way that the additive is mixed in as well as possible. Particular attention should be paid to ensuring that filler particles can be mixed in as gently as possible and with low shear stress, and that liquid additives can be mixed in in small quantities and with low pre-pressures. Furthermore, an essential requirement of the task is to convey the additive as well as possible from its storage container to its mixing into one of the chemical components from which the reaction mixture is produced.

[0025] The solution to this problem by the invention is characterized in that a gas is fed into a container for the further component and / or into a flow path for the further component, which extends from the container to the nozzle element, and that means for discharging the gas are arranged in or on the nozzle element and the gas is discharged from the nozzle element via the means.

[0026] The nozzle element preferably has a chamber into which the gas-infused further component is introduced. The means for discharging the gas are arranged on the chamber, and the gas is discharged via these means. The gas is preferably supplied at an overpressure (compared to ambient pressure).

[0027] The second flow path preferably ends in the region of the constriction so that the further component can be mixed with the chemical component, wherein the flow rate of the chemical component to which the further component is added is increased by the constriction and thus a local negative pressure is generated in the chemical component and wherein the further component is fed in the region of the local negative pressure of the chemical component.

[0028] The constriction in the first flow path of the chemical component can be designed as an annular gap, and the additional component can be fed concentrically in the flow direction of the components behind the annular gap. In particular, it can be provided that the additional component is fed behind the annular gap in the direction of an axis of the nozzle element.

[0029] The chemical component is preferably accelerated to a speed of at least 20 m / s after flowing through the constriction.

[0030] The chemical components are mixed in the mixing chamber, preferably by countercurrent injection. They are preferably injected into the mixing chamber via nozzles.

[0031] The other component is preferably expanded graphite.

[0032] The nozzle element is preferably arranged near the mixing chamber. The device for producing polyurethane components comprises at least one metering pump for metering a chemical component in the form of a polyol component, at least one metering pump for metering a chemical component in the form of an isocyanate component, a mixing head with a mixing chamber for mixing the polyol component and the isocyanate component, and at least one container for storing a further component, in particular expandable graphite. A nozzle element is arranged in front of or on the mixing chamber, which is designed to mix the further component with at least one of the chemical components. The nozzle element has a first flow path for the chemical component, which has a constriction, and a second flow path for the further component. According to the invention,that the second flow path for the further component ends in the region of the constriction, that gas supply means are arranged for supplying gas into the container for the further component and / or into a flow path for the further component extending from the container to the nozzle element, and that means for discharging the gas are arranged on the nozzle element.

[0033] The nozzle element preferably has a chamber into which the further component mixed with gas can be introduced, wherein the means for discharging the gas are arranged on the chamber.

[0034] The means for discharging the gas are preferably designed such that they are permeable to gas, but impermeable to solid or liquid components of the other component. In particular, it is contemplated that the means for discharging the gas have small openings and / or gaps with a diameter or clear width of less than 0.5 mm, preferably less than 0.25 mm. For this purpose, porous materials, for example, can also be used, through which the gas can escape from the chamber, but which are impermeable to solid particles.

[0035] An adjustable throttle for adjusting the gas flow rate can be arranged in a line that is fluidly connected to the gas discharge means. This throttle can also be arranged directly on the gas discharge means, if necessary.

[0036] The constriction in the first flow path of the chemical component is preferably designed as an annular gap, with the second flow path for the additional component ending behind the annular gap in the flow direction of the components. In particular, it is provided that the second flow path for the additional component extends at least partially in the direction of an axis of the nozzle element.

[0037] The second flow path for the further component is preferably formed, at least in sections, by a cylindrical opening at which a piston-like, axially displaceable slide is arranged, which is designed to enter the opening in order to close it.

[0038] The nozzle element preferably comprises a nozzle housing and a nozzle needle that is axially displaceable relative to the nozzle housing, wherein the constriction, in particular the annular gap, is formed between one axial end of the nozzle needle and the nozzle housing. Means are preferably arranged to influence the position of the nozzle needle relative to the nozzle housing, wherein the means can be designed in particular as electrical, hydraulic, or pneumatic control and / or regulating means. It is also possible for spring means to be arranged to generate a pressing force of the one axial end of the nozzle needle against the nozzle housing, wherein the spring means are preferably designed as a mechanical spring or a pneumatic spring.

[0039] By adding a gas (especially, but not necessarily, air; carbon dioxide, for example, can also be used), optimal conveyance of the other component, especially the expandable graphite, from its reservoir to the nozzle element and through the latter can be ensured. Its flowability can thus be easily ensured.

[0040] Generally, a highly soluble gas (such as carbon dioxide) is used to flood the other component. The gas pressure can also be used to regulate the discharge rate from the nozzle element.

[0041] The introduction of a pressurized gas can also be provided to flow through the region of the second flow path and thus keep the other component flowable. For this purpose, corresponding gas inlet and outlet openings can be provided between the axial end regions of the second flow path to conduct gas through the second flow path.

[0042] The gas is preferably introduced into the additional component directly in the container for the additional component. Combined with the gas being discharged from the chamber near the nozzle, this creates a gas flow from the container to the nozzle. This has the advantage that the solid filler can be easily conveyed into the mixing chamber via the nozzle. The amount of filler introduced into one of the chemical components, particularly the polyol, can be adjusted by adjusting the selected gas pressure in the additional component and within the nozzle.

[0043] The continuous overflow of gas ensures that the filler remains fluid within the piping system.

[0044] The amount of gas flowing out can be regulated via an adjustable throttle in order to use as little gas as possible for overflow.

[0045] The gas outlet opening at the nozzle is designed in such a way that gas can escape, but the filler remains within the dosing line and cannot escape to the outside.

[0046] Solid fillers can thus be conveyed into the mixing chamber more effectively via the internal pressure of the gas-filled filler container. The means for discharging the gas (overflow opening) in the area of ​​the nozzle ensure that lumpy, granular, or powdery fillers are kept flowable and that no leakage of the solid fillers occurs. The overflow opening can be designed as a valve, a bore, or an orifice plate. Furthermore, the use of a porous material, a sieve, a perforated plate, or a filter is also possible. Finally, a combination of the aforementioned elements is also possible. This allows gas to escape from the chamber, but no solid component can escape.According to the proposed concept, a liquid, lumpy, or powdery additive component is preferably concentrically mixed into at least one of the two reaction components using a nozzle element in the form of a multi-component nozzle. The nozzle element is arranged in the area of ​​the line of a main component immediately before entering the mixing chamber, and the additive component is only injected into the mixing chamber during the mixing process with the main component. In combination with the gas addition to optimize the delivery of the additive component, this results in the possibility of significantly improved processing of polyurethane, to which expandable graphite must be added.

[0047] Mixing is preferably carried out in such a way that the additional component is guided within one of the two countercurrents and meets at the same point as the high-pressure component.

[0048] The concentric addition causes an acceleration of the additional component and thus increases its impulse force.

[0049] Separation of polyol and isocyanate as well as the additional component occurs until shortly before the mixing chamber.

[0050] The additional component is therefore preferably introduced concentrically within the main component stream. It is preferably not introduced at high pressure.

[0051] The inlet opening for the additive component into the mixing chamber can be closed by a plunger (see the axially movable slide valve mentioned above). This allows the production of a reaction mixture with or without the additive component. Furthermore, the plunger prevents the additive component from leaking into the reaction components or from clogging the additive component with the reaction mixture. In recirculation mode (using recirculation grooves), the slide valve closes the opening. In shot mode, it can be opened or closed as required, depending on whether the additive is to be introduced into the mixing chamber during this shot or not.

[0052] In addition, active vibration generators (means for generating vibration) can lead to an improvement in flow behavior.

[0053] The nozzle element is preferably designed with a drilled nozzle needle through which the additional component is guided into the mixing chamber. The nozzle needle has an annular throttle gap. The throttle gap converts the pressure energy of the reaction components into flow energy and thus into mixing energy. The throttle gap can be adjusted either as a function of the travel distance or as a function of the component pressure upstream of the nozzle. Mechanical and gas springs are preferred as pressure-dependent adjustment elements.

[0054] The position of the nozzle needle allows the amount of component flow to be adjusted depending on the distance and / or pressure, as this allows the size of the annular gap to be specifically changed. This can be done either manually or via a control or closed-loop control system.

[0055] The proposed solution allows for particularly gentle processing of fillers. They do not need to be mixed into one of the two main components beforehand. Thus, particularly shear-sensitive solid fillers are not subjected to the otherwise required pumps and nozzles.

[0056] Abrasive or corrosive additives can be conveyed to the mixing chamber in a separate dosing line and have no negative impact on the longevity of the production plant.

[0057] Problems with deposits and segregation of solid particles in a liquid main component can be prevented with the proposed solution.

[0058] By mixing the additional component into the main component stream with high pulse energy, the additional component is entrained and therefore does not need to be conveyed with high energy itself until it enters the mixing chamber.

[0059] An embodiment of the invention is shown in the drawings.

[0060] Fig. 1 shows schematically an apparatus for producing a molded part from polyurethane, in which a high-pressure mixing head is used, into which polyol and isocyanate as well as a further component in the form of expandable graphite are injected by means of component nozzles,

[0061] Fig. 2 shows the section through a nozzle element which is arranged on or in the mixing head, wherein the working position of the nozzle element is sketched, in which the further component in the form of expandable graphite is supplied to the polyol, and Fig. 3 shows the nozzle element in the representation according to Figure 2, wherein the position of the nozzle element is now sketched, in which both the supply of the chemical component and the supply of the further component are blocked.

[0062] Figure 1 shows an apparatus for producing a molded part (not shown) from polyurethane. In this case, the reactive mixture is poured into a mold (not shown).

[0063] A container for polyol 1 and a container for isocyanate 2 can be seen. Each container is connected via a line to a metering pump 14 and 15, respectively. The metering pumps 14, 15 then convey the respective component to a mixing head 4, which has a mixing chamber 3. Both the polyol 1 and the isocyanate 2 are injected into the mixing chamber 3 via a nozzle element 6 and a nozzle (not shown) at high pressure, where they are mixed, creating the reactive mixture.

[0064] The mixing head 4 has an axially movable control slide and recirculation grooves to circulate the components. The relevant technology is only of marginal interest here and is well known in the state of the art.

[0065] A container 10 is also provided for a further component 5 in the form of expandable graphite. The aim is to mix the further component 5 into the polyol 1 as evenly distributed as possible without subjecting it to strong stresses, particularly in the form of shear. Furthermore, smooth conveying of the further component must be ensured. This is achieved by the special nozzle element 6, which in the exemplary embodiment is arranged directly next to the mixing chamber 3.

[0066] Figures 2 and 3 show the nozzle element 6 in more detail. Figure 2 shows a position of the nozzle element open for the additional component 5, while Figure 3 shows both the supply for the chemical component 1 and the additional component 5 blocked. The components of the nozzle element 6 correspond to one another, so that only a few reference numbers mentioned in Figure 2 are also entered in Figure 3.

[0067] The nozzle element 6 has a nozzle housing 21. A nozzle needle 22 is arranged in the nozzle housing 21 so as to be displaceable in the direction of an axis a. The nozzle housing 21 has a feed 24 for the additional component 5. A feed 23 for the polyol 1 is provided in the nozzle housing 21. Furthermore, an outlet 25 for the mixture consisting of the polyol 1 and the additional component 5 is provided in the nozzle housing 21.

[0068] In the present case, the nozzle element 6 is arranged directly upstream of the mixing chamber 3 and via this the further component 5 is mixed into the polyol 1 (additively or alternatively also into the isocyanate 2). The nozzle element 6 has a first flow path 7 for the polyol 1, wherein the first flow path 7 has a constriction 8 in the form of an annular gap. Furthermore, the further component 5 is fed to the nozzle element 6, wherein it is guided along a second flow path 9 in the nozzle element 6. The second flow path 9 ends in the region of the constriction 8. The flow paths 7 and 9 are illustrated in Figure 2 by dotted lines. The size of the annular gap 8 can be adjusted by the appropriate position of the nozzle needle 22 relative to the nozzle housing 21. An adjustment device 27 is provided for this purpose.

[0069] By adjusting the size of the annular gap 8 accordingly, the polyol 1 is accelerated accordingly, so that the static pressure in the material is reduced. The second flow path 9 opens in the area of ​​reduced pressure, so that when the further component 5 is added, this is optimally mixed into the polyol 1. As can be seen from Figure 2, the annular gap 8 and the end of the second flow path 9 are arranged concentrically to the axis a. In the preferred embodiment, the further component 5 is guided radially inward and the polyol 1 radially outward, and both components are combined behind the annular gap 8 in the conveying direction and thus optimally mixed with one another.

[0070] Whether and how much material of the further component 5 is added to the polyol 1 can be influenced by an axially displaceable slide 20 with a drive 26, whereby the slide 20 can enter a cylindrical opening 19 in the nozzle needle 22 (this happens in the illustration according to Figure 3).

[0071] In the second flow path 9 for the further component 5, a chamber 13 is formed which is provided with means for discharging a gas G.

[0072] Reference is made to Figure 1, which shows that the container 10 for the additional component 5 is fluidically connected to gas supply means 16. A gas under pressure (higher than ambient pressure) is introduced into the container 10 via the gas supply means 16. The gas G flows through the additional component 5 and thus supports the conveyance of the component 5 from the container 10 via a flow path 11 to the nozzle element 6.

[0073] In Figure 2, the path taken by gas G when component 5 loaded with gas G enters nozzle element 6 via inlet 24 is indicated by dot-dash lines. The mixture of gas G and component 5 enters chamber 13, to which means 12 for discharging gas G are attached. Accordingly, gas G escapes from chamber 13 in the direction schematically indicated by an arrow.

[0074] For example, by using a component with a very small gap (a few tenths of a millimeter in size) or by using porous material, it can be ensured that the gas G can escape from the chamber 13, but the component 5 (in particular the expandable graphite in solid form) is retained in the chamber 13 and is further conveyed.

[0075] In Figure 1 it is shown schematically that in the line 17, via which the gas G is discharged from the chamber 13, a throttle 18 can be arranged, with which the volume flow of the escaping gas G can be adjusted.

[0076] The gas G keeps the additional component 5 in a readily pumpable condition, so that precise dosing of the additional component 5 is particularly easy. List of reference symbols:

[0077] 1 chemical component (polyol)

[0078] 2 chemical component (isocyanate)

[0079] 3 Mixing chamber

[0080] 4 Mixing head

[0081] 5 additional components (filler, expandable graphite)

[0082] 6 nozzle element

[0083] 7 first flow path

[0084] 8 Constriction (annular gap)

[0085] 9 second flow path

[0086] 10 containers for the additional component

[0087] 11 Flow path for the further component

[0088] 12 Means of gas removal

[0089] 13 Chamber in the nozzle element

[0090] 14 Dosing pump for polyol

[0091] 15 Dosing pump for isocyanate

[0092] 16 Gas supply means

[0093] 17 Management

[0094] 18 Throttle

[0095] 19 cylindrical opening

[0096] 20 axially movable slide

[0097] 21 Nozzle housing

[0098] 22 jet needle

[0099] 23 Feed chemical component (polyol)

[0100] 24 Supply of further component 25 Outlet for mixing chemical component with further component

[0101] 26 Drive for slide 27 Adjustment device for constriction (annular gap)

[0102] G Gas a Axis of the nozzle element

Claims

TI Patent claims:

1. A method for producing polyurethane components, in which at least two different chemical components (1, 2), including at least one polyol component and one isocyanate component, are individually metered and then fed to the mixing chamber (3) of a mixing head (4), in which they are mixed to form a polyurethane reactive mixture and then discharged from the mixing chamber (3), in particular into an open or closed mold, wherein a further component (5) is added to at least one of the chemical components (1) before the chemical component (1) enters the mixing chamber (3), wherein the further component (5) is in liquid or solid form, and wherein the chemical component (1), to which the further component (5) is added, is passed through a nozzle element (6) which is arranged upstream of or on the mixing chamber (3) and which has a first flow path (7) for the chemical component (1),wherein the first flow path (7) for the chemical component (1) has a constriction (8), wherein the further component (5) is fed to the nozzle element (6) and is guided along a second flow path (9) through the nozzle element (6), characterized in that that a gas (G) is fed into a container (10) for the further component (5) and / or into a flow path (11) for the further component (5), which extends from the container (10) to the nozzle element (6), and that means (12) for discharging the gas (G) are arranged in or on the nozzle element (6) and the gas (G) is discharged from the nozzle element (6) via the means (12).

2. Method according to claim 1, characterized in that the nozzle element (6) has a chamber (13) into which the further component (5) mixed with gas (G) is introduced, wherein the means (12) for discharging the gas (G) are arranged on the chamber (13) and the gas (G) is discharged via these means.

3. Method according to claim 1 or 2, characterized in that the gas (G) is supplied under excess pressure.

4. Method according to one of claims 1 to 3, characterized in that the second flow path (9) ends in the region of the constriction (8) so that the further component (5) can be mixed with the chemical component (1), wherein the flow rate of the chemical component (1) to which the further component (5) is added is increased by the constriction (8) and thus a local negative pressure is generated in the chemical component (1), and wherein the further component (5) is fed to the chemical component (1) in the region of the local negative pressure.

5. Method according to one of claims 1 to 4, characterized in that the constriction (8) in the first flow path (7) is designed as an annular gap and the further component (5) is fed concentrically in the flow direction of the components behind the annular gap (8).

6. Method according to claim 5, characterized in that the further component (5) is fed in the direction of an axis (a) of the nozzle element (6) behind the annular gap (8).

7. Method according to one of claims 1 to 6, characterized in that the chemical component (1) is accelerated to a speed of at least 20 m / s after flowing through the constriction (8).

8. Method according to one of claims 1 to 7, characterized in that the chemical components (1, 2) are mixed in the mixing chamber (3) by means of countercurrent injection.

9. Method according to one of claims 1 to 8, characterized in that the chemical components (1, 2) are injected into the mixing chamber (3) by means of nozzles.

10. Process according to one of claims 1 to 9, characterized in that the further component (6) is expandable graphite.

11. A device for producing polyurethane components, in particular for carrying out the method according to one of claims 1 to 10, comprising at least one metering pump (14) for metering a chemical component in the form of a polyol component (1), at least one metering pump (15) for metering a chemical component in the form of an isocyanate component (2), a mixing head (4) with a mixing chamber (3) for mixing the polyol component (1) and the isocyanate component (2), at least one container (10) for storing a further component (5), wherein a nozzle element (6) is arranged in front of or on the mixing chamber (3), which nozzle element is designed to mix the further component (5) with at least one of the chemical components (1), wherein the nozzle element (6) has a first flow path (7) for the chemical component (1), which has a constriction (8), and a second flow path (9) for the further component (5), characterized in that that the second flow path (9) for the further component (5) ends in the region of the constriction (8), that gas supply means (16) are arranged for supplying gas (G) into the container (10) for the further component (5) and / or into a flow path (11) for the further component (5) which extends from the container (10) to the nozzle element (6), and that means (12) for discharging the gas (G) are arranged on the nozzle element (6).

12. Device according to claim 11, characterized in that the nozzle element (6) has a chamber (13) into which the further component (5) mixed with gas (G) can be introduced, wherein the means (12) for discharging the gas (G) are arranged on the chamber (13).

13. Device according to claim 11 or 12, characterized in that the means (12) for discharging the gas (G) are designed such that they are permeable to gas (G) but impermeable to solid or liquid components of the further component (5).

14. Device according to claim 13, characterized in that the means (12) for discharging the gas (G) have openings and / or gaps with small dimensions, the diameter or clear width of which is less than 0.5 mm, preferably less than 0.25 mm.

15. Device according to one of claims 11 to 13, characterized in that an adjustable throttle (18) for adjusting the volume flow of gas (G) is arranged in a line (17) which is in fluid communication with the means (12) for discharging the gas (G).

16. Device according to one of claims 11 to 15, characterized in that the constriction (8) in the first flow path (7) of the chemical component (1) is designed as an annular gap and the second flow path (9) for the further component (5) ends behind the annular gap in the flow direction of the components.

17. Device according to claim 16, characterized in that the second flow path (9) for the further component (5) extends at least in sections in the direction of an axis (a) of the nozzle element (6).

18. Device according to one of claims 11 to 17, characterized in that the second flow path (9) for the further component (5) is formed at least in sections by a cylindrical opening (19) on which a piston-like, axially displaceable slide (20) is arranged, which is designed to enter the opening (19) in order to close it.

19. Device according to one of claims 11 to 18, characterized in that the nozzle element (6) has a nozzle housing (21) and a nozzle needle (22) which is axially displaceable relative to the nozzle housing (21), wherein the constriction (8) can be formed between one axial end of the nozzle needle (22) and the nozzle housing (21).

20. Device according to claim 19, characterized in that means are arranged to influence the position of the nozzle needle (22) relative to the nozzle housing (21), wherein the means are designed in particular as electrical, hydraulic or pneumatic control and / or regulating means, or that spring means are arranged to generate a pressing force of the one axial end of the nozzle needle (22) against the nozzle housing (21), wherein the spring means are preferably designed as a mechanical spring or as a pneumatic spring.

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