EP2054217A1

EP2054217A1 - Device and method for processing thermosetting plastics

Info

Publication number: EP2054217A1
Application number: EP07787710A
Authority: EP
Inventors: Rainer Zimmet; Josef Renkl; Ernst Berchtenbreiter
Original assignee: KraussMaffei Technologies GmbH
Current assignee: KraussMaffei Technologies GmbH
Priority date: 2006-08-16
Filing date: 2007-07-19
Publication date: 2009-05-06
Also published as: EP2213444A2; CN101484299A; DE102006038197A1; WO2008019922A1; EP2213444A3

Abstract

The present invention relates to a method for processing thermosetting plastics, particularly thermosetting polyurethane, as well as a device for performing such a method. The device comprises an extruder device (10) having a cylinder, in which an extruder screw is received in a rotating manner, wherein the cylinder has at least one inlet opening (12, 14, 16) and one outlet opening (18), and that at least one inlet opening (12) of the cylinder is provided for filling the plastic material into the cylinder, as well as a tool (22), into which, or by means of which the material discharged by the extruder device can be guided in or through. According to the invention the device is characterized in that at least one inlet opening (12, 14, 16) is configured for the feeding of at least one cross-linked or reactive component of a thermosetting plastic.

Description

Apparatus and method for processing thermosets

The present invention relates to an apparatus and a method for processing thermosets according to the preambles of claims 1 and 16, respectively.

Duroplast is generally understood to mean thermally irreversible (covalently) crosslinking macromolecules having an amorphous structure and a high crosslinking density. A thermo-elastic softening is different depending on the level of intermolecular forces and crosslinking density. In very close networking, it is without practical significance. In particular, thermosets change from the hard state to the region of thermal decomposition with increasing temperature, without softening so much that reshaping would be possible. In principle, thermosets are insoluble, but depending on the network more or less swellable in suitable media. A subset of the thermosets forms the thermoset Pulyurethan.

Crosslinking and reactive systems in which two different components (component A and component B) are brought together, which bring about the crosslinking or reaction, are also understood to mean thermosetting and reactive systems for the present invention. In addition to polyol and isocyanate, phenolic resin, polyester resin, epoxy resin, melamine resin or reactive components such as peroxide can be mentioned as material components for the processing. The one or the other component may also be present in solid form.

For example, in the processing of thermosetting polyurethane two reactive starting components, namely a polyol component and an isocyanate component are mixed together, which mixed together give a reaction mixture. This reaction mixture is introduced after mixing in a mold of a mold and reacts there chemically. This process is often referred to as a foaming process, which is to distinguish between a compact polyurethane and a foamed polyurethane. The reaction process is irreversible and thus unlike the processing of thermoplastics irreversible. Once reacted with each other polyol and isocyanate components can not be separated again, at least mechanically, so that recycling into a new polyurethane processing per se is not possible. It is only possible to finely chop the corresponding products (eg, mill them) and add them as blending products to other components.

Usually, the mixing of the polyol and isocyanate components in a mixing head, in which the two components are supplied via nozzles of a mixing chamber and mixed there with each other.

At the outlet of the mixing or a settling chamber, the reaction mixture thus prepared can then be discharged into the cavity of a mold. A distinction is made between the introduction into an open and a closed mold. When introduced into an open mold, the cavity is initially opened upon introduction of the reactive mixture and the reaction mixture is applied to a cavity surface. After the introduction or application of the reactive mixture, the cavity is closed, possibly the tool is heated to accelerate the reaction and carried out the curing.

When introduced into a closed mold, the cavity is already closed before the reaction mixture is filled to the level corresponding to the product, and it is filled into a cavity space which is at least substantially closed to the outside environment.

A special type of polyurethane processing is characterized in that Fülloder or fibrous materials for changing the physical properties, in particular the mechanical properties, the components are supplied. In this case, for example, short fibers in the range of up to 0.2 mm of a component may be added before this component is brought together with the other reactive component. It is also known to produce a reaction mixture with long fibers, in which first the reaction mixture itself is prepared from the polyol and the isocyanate component in a mixing chamber and the cut long fiber is then introduced into the reaction mixture at the outlet of the mixing chamber. This process is known to the Applicant for example under the trademark "LFI-PUR". The problem with the use of fillers, in particular of long fibers, however, is the currently exclusive possibility of introduction into an open mold. When introducing into a closed mold there is a risk of clogging of the nozzles and components by means of the fillers.

In contrast to the processing of thermosets, an extruder device is usually used in a wide variety of embodiments in the processing of thermoplastic material. In particular, the extruder device, in which at least one screw in a cylinder is rotatably (and possibly also axially displaceable) is added, the introduction of shearing energy in the starting material, which - possibly together with an external energy input for melting the usually in granular, powder or chipform present starting material leads.

However, the use of an extruder device in connection with the processing of the above-mentioned thermosets, in particular of thermoset polyurethane has hitherto been neither known nor desired. This is also because at a stop of the extruder device networking (curing) of the reaction mixture was to be feared in the extruder, which could have led to the inoperability of the entire system.

To be solved is the problem of processing thermosets according to the above-mentioned understanding, in which two reactive or crosslinking components are mixed together, in particular of thermosetting polyurethane, together with fillers (eg long fibers) and additives and in particular the introduction of such a reactive mixture in a closed tool without malfunctions.

This object is achieved in terms of apparatus by the features mentioned in claim 1 and the features mentioned in claim 16 procedurally.

An idea of the present invention is to be seen in that for the processing of such thermosets, in particular thermoset polyurethane a Extruder device comprising at least one extruder screw and an extruder barrel is used. At least one of the components necessary for later crosslinking, in particular the reactive component of the thermosetting plastic, is supplied to the extruder device via a filling opening. Fillers of any type or additives of any composition and form can be admixed via the same or further filling openings, whereby the production of a homogeneously mixable material component or of a corresponding reaction mixture can be carried out by rotation of the at least one extruder screw in the extruder barrel.

Based on this basic principle, there are a large number of modifications and implementation possibilities for producing the later crosslinking or reacting mixture itself. For example, the isocyanate and also polyol components-either already mixed or still to be mixed-can be supplied to the extruder device via the same feed opening , Alternatively, the two reactive components can also be supplied via different filling openings of the extruder device. Again alternatively, it is also possible to supply only one reactive component to the extruder device and to add the second reactive component to the material flow only after the extruder device via a separate mixing device.

With the device according to the invention, all imaginable materials, such as fillers (chalk, lime, wood, recycled material, glass fibers, natural fibers, etc.) and also additives can be admixed without there being any obstruction problems. Moreover, in this way pressures can be built up, which allow an introduction into a closed tool.

Depending on the embodiment, the material is conveyed via the extruder device discontinuously or continuously from the filling area or from the filling openings in the direction of the extruder exit and discharged there. Depending on the viscosity situation, operating mode and desired pressures, it is possible to supply the material mixture with the interposition of a storage device and / or an injection device to a molding tool, similar to an injection molding tool. The supply can - as in the injection molding - by a tool half or in a Parting line done. Of course, it is also possible to use as a tool a profile tool, through which the material is passed (for example, flat nozzle, profile tool, round die, etc.) and as it is known from the extruder technology to use.

As with the operation of a normal extruder device, it is advantageous to design the extruder barrel temperature-controlled. However, the tempering range differs considerably during processing compared to the processing of thermoplastic material. Thus, it is necessary in the present case possibly even to cool the process unit or the processing temperature below 75 ° C, especially below 60 ⁰ C, preferably below 50 ⁰ C to adjust. At these temperatures, the reaction process of the reactive components is slowed down so that curing during the process time is not to be feared.

Alternatively to the use of an injection device, it is also possible to provide a gear pump between the extruder device and a tool to build up a desired pressure.

As a special material which can be fed to the extruder, water or another foaming material is to be mentioned. By supplying water, for example, to a polyurethane mixture, a foaming process can be started during the crosslinking or reaction in the mold, which leads to a foamed product (compared to a compact product).

Particularly advantageous is the use of a co-rotating twin-screw extruder for the extruder, since not only a high throughput but also a good mixing can be achieved. Depending on whether the extruder device is operated continuously or cyclically, the metered addition of the reactive components to the extruder device can be carried out, for example, volumetrically or gravimetrically.

It should be mentioned that the tool should also be tempered. Thus, depending on the starting materials, the reaction process in particular be accelerated at temperatures above 60 ⁰ C or from 75 ° C in a significant manner. If the temperature in the tool before, held over a substantial period of the injection process or during the injection process of the reaction mixture below such a material-dependent temperature threshold, so there is no significant Ausreagieren the material mixture. If the temperature is then raised above the initialization temperature of, for example, 75 ° C., a relatively rapid reaction takes place, with which very short reaction times and thus removal and cycle times can be realized. Of particular interest is the use of a highly dynamic temperature control (heating and / or cooling).

The present invention will be explained in more detail below with reference to various embodiments and with reference to the accompanying drawings. The drawings show in

1 shows a schematic side view of a first embodiment of a processing device according to the invention for thermosetting polyurethane, wherein both reactive starting components are supplied via the same filling opening,

FIG. 2 shows a schematic side view of a second embodiment of a processing device according to the invention, wherein the two reactive components are supplied via two different filling openings,

FIG. 3 shows a schematic side view of a third embodiment of a processing device according to the invention, wherein a reactive component is fed to the extruder device via a filling opening and a further reactive component,

Figure 4 is a schematic side view of a fourth embodiment of a processing device according to the invention, wherein additionally a memory device is provided and Figure 5 is a schematic side view of a fifth embodiment of a processing device according to the invention, wherein in addition to the memory device nor an injection device is provided.

FIG. 1 shows, in a highly simplified, schematic manner, a first embodiment of the present invention, which comprises an extruder device 10 as a central element. The extruder device (short of the extruder) 10 is presently configured as a co-rotating twin-screw extruder with two extruder screws (not shown) and an extruder barrel surrounding the two extruder screws. The extruder device 10 comprises a plurality of filling openings 12, 14 and 16, via which materials, as described later, can be supplied to the various process zones.

The two extruder screws are rotationally driven via a drive device 11, wherein this drive device comprises a rotary drive, for example in the form of an electric motor, and a transmission.

At the downstream end of the extruder, the material processed in the extruder device 10 is delivered via an outlet 18 to an injection line 20, which connects the extruder 10 to an injection mold 22, which in the present case is also shown only schematically. Of course, the extruder device can also be docked directly to the tool or designed dockable.

Since such extruder devices and corresponding tools and the associated flow connections and ancillary units from the thermoplastic processing are well known, most components need not be discussed in detail in the present invention. In particular, the supply of the reactive components to the extruder device should be different, which must be based on the rather low viscosity of a liquid. In this regard, the extruder device in the filling (in the case of thermoplastic material feed area) or in the formation of a connection for a supply device can be configured accordingly. The worm should also be designed for processing the reactive components, whereby it should be taken into account that as little as possible of shearing energy is to be introduced into the reaction mixture. In the embodiment shown in Figure 1, the two reactive material components, namely the isocyanate and the polyol component, together (reference numeral 24) of the filling opening 12 is supplied. The two components are taken from different containers, conveyed via normal feed pumps and mixed together just before the filling opening or added separately to the filling opening.

Downstream of the fill port 12, other materials such as fillers (e.g., long glass fibers) and additives (e.g., catalysts) are supplied via the further fill ports 14 and 16.

The screws provided in the extruder device 10 are designed for a good mixing of the reactive components and supplied materials, so that at the extruder outlet 18 a homogeneous reaction mixture with the fillers leaves the extruder 10.

This reactive material mixture is then fed to the closed mold of the mold 22 via a parting line, where it cures after being fed to a finished product.

According to the structural design according to FIG. 1, cyclic or discontinuous operation of the extruder device 10 preferably makes sense, since the reaction mixture can only be filled into the cavity of the tool 22 when the tool is empty and closed. After the tool has been completely filled, the delivery should be stopped so that the product can cure in the tool before it is removed and a new cycle can be started. Theoretically, it is also possible to let the extruding device 10 continue to rotate when the supply of substances is switched off, if this does not damage the reaction mixture or the substances contained therein.

Due to the use of an extruder device for the introduction of a filler and long fibers can be used easily without clogging or clog any nozzles. Even with a suitable mode of operation, it is not necessary to fear hardening of the polyurethane mate neck in the extruder device itself. During the processing, the extruder device 10 should be tempered, in particular cooled, so that it proceeds process technology in a temperature range of for example below 60 ⁰ C, in which the reaction of the reaction mixture is very slow going on.

If the extruder operation is interrupted in the medium or long term, the supply of one of the reactive components to the filling opening can be stopped so that no reaction mixture is left in the extruder apparatus itself. Thus, even with a stop of several hours or several days, the material contained in the extruder device does not harden, so that no fixing of the extruder screws in the extruder device has to be feared. Alternatively or additionally, the extruder device can be rinsed with an additional flushing agent during a longer stop so that it is free of all the reactants.

The embodiment in FIG. 2 differs from that in FIG. 1 in that the two reactive components are no longer supplied via one and the same filling opening but via two different filling openings, namely the filling opening 12 and the filling opening Polyol component 24 'supplied via the filling opening 12 and the isocyanate component via the filling opening 26. Otherwise, the process device can be operated in the same way. Only the tool differs in the present case, wherein in Figure 1, a vertical tool in Figure 2, a horizontal tool 22 'is used. Also, in contrast to the embodiment of FIG. 1, the addition into the tool 22 'takes place through a tool half. However, this has no significance for the present invention.

A further embodiment is shown in FIG. 3, wherein this embodiment differs in that the extruder device 10 is supplied with only a single reactive component, in the present case the polyol component 24 '. The further reactive component, in this case the isocyanate component 30, is only after the exit of the extruder device 10 via a separate mixing element 28th added and added to the mixture. This mixing device may for example be a static mixer. Although in such a device, the reaction mixture is not produced well mixed even in the extruder device. However, fillers can be homogeneously mixed into a reactive component. In addition, upon restarting after a prolonged stop, the entire contents of the extruder need not be removed, this is required if both reactive components are supplied through one and the same fill port and the supply of a component is stopped before the device is shut down.

FIG. 4 illustrates a further embodiment of the present invention in a schematic manner, whereby according to FIG. 1 the two reactive components are again supplied via the filling opening 12. However, a storage device 40 is now inserted between the extruder device 10 and the injection mold 22, and connected to the line 20. The storage device 40 comprises a reciprocating storage piston 42, which defines a correspondingly large storage volume 44 depending on the movement.

With such a construction, the extruder device 10 can be operated continuously despite the discontinuous operation of the injection molding tool 22. Of course, this is a shut-off between the storage device 40 and the injection molding device 22 provide, which is not shown here. For the period in which no material is to be demanded in the mold, there is an intermediate storage of the material continuously produced in the extruder device 10 in the storage volume 44. If the reaction mixture is then injected into the cavity, then a simultaneous delivery from the extruder device 10 and the memory 40 via the injection line 20 into the cavity of the injection mold.

A last embodiment is shown in FIG. 5, whereby this embodiment differs from the embodiment in FIG. 4 in that now a separate injection device for generating a high injection pressure is shown between the storage device 40 and the tool 22 '. This injection device comprises a guided in a cylinder injection piston 52, by means of a drive device, not shown, corresponding to the arrow 56th can be acted upon with a certain pressure in Einspritzhchtung. Depending on the position of the injection piston, an injection volume 54 is defined. In this method, the polyurethane mixture is buffered via the storage device 40 and fed discontinuously to the injector 50. The injector 50 is adapted to introduce the reactive polyurethane mixture with a correspondingly high pressure in the injection mold. In this case, the injection device 50 should be formed as possible without dead spaces in which the polyurethane mixture can settle and react. Rather, the injector should have a substantially vanishing piston 52 has a substantially vanishing storage space 54. Of course, corresponding valves and shut-off units would have to be provided again in this embodiment, which, depending on the operation of the system, prevent backflow of the material either into the extruder device 10, the storage device 40, etc. These devices are known in the art because the device described above is generally used for processing thermoplastic material.

Overall, the device is suitable for processing added with fillers and / or additives polyurethane, especially if you set a mixing or shear temperature of not more than 75 ° C. In this case, pressures of up to 60 bar can be ensured with the extruder alone. As already mentioned, foaming of the polyurethane in the injection mold can be achieved by the supply of water to the extruder device 10. In this respect, you can adjust by switching on or off the water supply, whether foamed or not.

Also, the present construction is suitable for realizing a high throughput, for this purpose, the extruder device only has to be rotated faster. Overall, it is conceivable that you can cover almost all applications in the polyurethane sector with only two extruder sizes.

The addition of filler or additives by composition and form is almost unlimited possible; Thus, a previously ground PUR recyclate can be used as an additive. Of course, it is also possible to use a per se known extrusion tool instead of an injection molding tool, through which the reaction mixture is pushed through continuously at the extruder outlet. As such extruder tool, for example, offer a profile tool, a slot die, a pipe nozzle, etc. on.

A particular embodiment is characterized in that the tool, in particular the injection mold is highly dynamically tempered. The advantage of such a tool is clear when you know that the reaction time can be shortened by leaps and bounds when (depending on the material) exceeds a certain temperature, for example 75 ° C. This makes it possible to carry out processes in which the mixture formation of the reactive mixture takes place in the region below such an activation temperature at which the reaction mixture is also introduced into the mold. Only after the introduction of the reaction mixture into the tool, the temperature is increased abruptly above the aforementioned temperature value, so that the reacting takes place immediately and suddenly. So it is possible to shorten the heating time by means of the very new application of a heating of the tool by means of an electrically heatable ceramic material to a few seconds. Such an electrically heatable ceramic material can be heated for example within 5 to 10 seconds from a temperature of 70 ⁰ C to 125 ⁰ C. In this way, today's usual cycle times of more than 1 minute could be reduced down to the range of a few seconds, which would lead to a considerable increase in productivity.

Overall, with the present invention, a problem-free processing of the above-mentioned thermosets is possible, in which two mutually crosslinking or reacting components are mixed and to which also materials such as polyester with a hardener, silicone rubber with silane added and in particular also consisting of isocyanate and polyol polyurethane counting. LIST OF REFERENCE NUMBERS

extruder means

driving means

First filling device

Second filling device

Third filling device

extruder outlet

Injection pipe, 22 'tool

Polyol and isocyanate components' polyol component

isocyanate

mixing element

isocyanate

memory device

accumulator piston

storage volume

Injector

Injection piston

Injection volume

Injection direction / injection pressure

Claims

claims

1. An apparatus for processing thermosets, in particular thermosetting polyurethane, wherein two components causing a crosslinking or reaction are mixed together, comprising an extruder with a cylinder in which an extruder screw is rotatably received, wherein the cylinder has at least one filling opening and an outlet opening, and at least one filling opening of the cylinder for filling of plastic material is provided in the cylinder, and a tool in or through which the discharged material from the extruder device or is feasible. characterized in that

- Provided at least one filling opening for supplying at least one reactive or a crosslinking component of a thermoset, and

- The extruder screw are designed for processing this reactive or crosslinking component.

2. Apparatus according to claim 1, characterized in that one or more filling openings are formed for supplying at least two mutually crosslinking or reacting components of a thermoset, wherein the at least two components via separate or via a common filling opening to the interior of the cylinder can be fed.

3. Apparatus according to claim 1 or 2, characterized in that in terms of flow after the outlet opening of the cylinder, a device for supplying a crosslinking or reactive component of a thermoset is provided.

4. Device according to one of the preceding claims, characterized in that additional materials, such as fillers or additives, can be supplied via one or more filling openings.

5. Device according to one of the preceding claims, characterized in that the cylinder is designed to be tempered.

6. Apparatus according to claim 5, characterized in that a processing temperature in the cylinder of less than 75 ⁰ C, preferably less than 60 ⁰ C, in particular less than 50 ⁰ C is adjustable

7. Device according to one of the preceding claims, characterized in that in terms of flow after the extruder, a storage device for at least temporarily caching recording of the discharged material from the extruder is formed.

8. Device according to one of the preceding claims, characterized in that a gear pump is arranged between the extruder device and the tool.

9. Device according to one of the preceding claims, characterized in that an injection device is arranged between the extruder device and the tool.

10. Device according to one of the preceding claims, characterized in that an inlet opening is formed as a connection for a water supply.

11. Device according to one of the preceding claims, characterized in that a co-rotating twin-screw extruder is used as the extruder device.

12. Device according to one of the preceding claims, characterized in that at least one filling opening is associated with a metering device with which a volumetric or gravimetric dosing of the crosslinking or reactive component is made possible.

13. Device according to one of the preceding claims, characterized in that the tool for initiating the reaction process is temperature controlled.

14. The apparatus according to claim 13, characterized in that the tool to a temperature of 60 ⁰ C to 100 ⁰ C is temperature controlled.

15. The apparatus of claim 13 or 14, characterized in that the temperature of the tool is component-specific adjustable.

16. A process for producing a thermoset product, in particular a polyurethane product comprising the steps of

Feeding at least one crosslinking or reactive component of the thermoset to an extruder device,

- Producing a crosslinking or reactive mixture by supplying a further reactive component either to the extruder device or after the exit of the material from the extruder device

- And introduction or implementation of the reactive mixture in or by a tool.

17. The method according to claims 16, characterized in that the extruder device further materials, such as fillers or additives are supplied, which are mixed by the operation of the extruder device with the at least one crosslinking or reactive component.

18. The method according to any one of claims 16 or 17, characterized in that the extruder device is heated and / or cooled.

19. The method according to claim 18, characterized in that the temperature is controlled to a temperature below 75 ⁰ C, in particular below 60 ⁰ C, preferably below 50 ⁰ C.

20. The method according to any one of claims 16 to 19, characterized in that the extruder device water is supplied.

21. The method according to any one of claims 16 to 20, characterized in that by means of a gear pump or an injection device following the extruder device, the discharge material is brought to a predetermined pressure level

22. The method according to any one of claims 16 to 21, characterized in that at least one crosslinking or reactive component of the extruder device is added gravimetrically or volumetically.

23. The method according to any one of claims 16 to 22, characterized in that a temperature-controlled injection molding tool with at least one cavity is used as the tool and the temperature of the cavity wall of the tool is raised after the injection process to a temperature value which initializes the crosslinking or reaction process.

24. The method according to claim 23, characterized that a temperature in the range of 60 ° C to 100 ° C is selected.