METHOD FOR PRODUCING A FOAMED POLYMER COMPOSITE BOARD FROM MIXED PLASTIC WASTE

Abstract

In a method for producing a polymer composite board from plastic waste, in which the plastic waste is processed in an extruder in a melt-kneading step to form a melt, the melt is introduced into an injector and injected under pressure into a cavity of a closed mold by the injector, in order to form a board. The melt is formed from a free-flowing agglomerate and a blowing agent. The free-flowing agglomerate is produced from unsorted, mixed plastic waste, and the melt is introduced into the closed mold via an injection nozzle along an end side of the cavity, in which mold the melt is foamed and cooled to form a foamed core layer of the polymer composite board.

Claims

1-14. (canceled)

15. A process for the production of a polymer composite board from plastic waste, the process comprising: processing the plastic waste into a melt by a melt-kneading step in an extruder; introducing the melt into an injector; injecting under pressure from the injector into a cavity of a closed mold in order to form a board, wherein the melt is formed from a granulated agglomerate and a blowing agent, wherein the granulated agglomerate is produced from unsorted mixed plastic waste, and wherein the melt is introduced into the closed mold via an injection nozzle along an end/edge side of the cavity, in which mold the melt foams and cools to form a foamed core layer of the polymer composite board.

16. The process as claimed in claim 15, wherein prior to injecting the melt, a prefabricated upper cover layer and a prefabricated lower cover layer is placed in the cavity of the mold.

17. The process as claimed in claim 16, wherein the mold has an upper mold shell and a lower mold shell which together form the cavity, and the upper cover layer is sucked onto the inner wall of the upper mold shell by means of a partial vacuum and the lower cover layer is sucked onto the inner wall of the lower mold shell by means of a partial vacuum.

18. The process as claimed in claim 15, wherein the injection nozzle is a wide slot nozzle, and the melt is injected via the wide slot nozzle, which extends over the entire end/edge side of the cavity, into the cavity of the mold.

19. The process as claimed in claim 18, wherein the wide slot nozzle has a row of nozzle openings which are evenly spaced with respect to each other, through which the melt is injected into the cavity of the mold.

20. The process as claimed in claim 19, wherein the wide slot nozzle has a closing device which comprises a shaft with through openings for the respective nozzle openings.

21. The process as claimed in claim 15, wherein the melt is injected at a low pressure of 15 to 30 bar.

22. The process as claimed in claim 15, wherein the unsorted mixed plastic waste is melt-kneaded in the extruder at a temperature of 200 C. to 250 C. until a melt is formed and the closed mold into which the melt is injected is tempered at a low temperature of less than 60 C.

23. A device for the production of a polymer composite board in accordance with the process as claimed claim 15, the device comprising an extruder, an injector, an injection nozzle and a closed mold with a board-shaped cavity, wherein the injection nozzle is constructed and disposed in a manner such that the melt can be injected into the cavity along an entire end/edge side of the cavity.

24. The device as claimed in claim 23, wherein the mold has cooling channels in order to cool the mold to a temperature of less than 60 C.

25. The device as claimed in claim 23, wherein the injection nozzle is disposed so as to be movable with respect to the mold.

26. The device as claimed in claim 23, wherein the injection nozzle is a wide slot nozzle.

27. The device as claimed in claim 26, wherein the wide slot nozzle has a row of nozzle openings which are uniformly spaced with respect to each other.

28. The device as claimed in claim 23, wherein the mold has an upper mold shell and a lower mold shell the inner walls of which having holes which are uniformly distributed over the surface, which are connected to a pump which produces a partial vacuum.

29. A polymer composite board produced from mixed plastic waste, comprising a core layer produced and foamed from unsorted mixed plastic waste, the core layer having been injected between an upper cover layer and a lower cover layer, wherein the core layer is blowhole-free and has a degree of foaming of at least 20%, with cell dimensions of less than 3 mm.

30. The polymer composite board as claimed in claim 29, wherein the core layer has a degree of foaming of 60% to 80%, with cell dimensions with a diameter of 0.5 mm to 2 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The invention will now be described in more detail with the aid of exemplary embodiments and with reference to the drawing(s), in which:

[0035] FIGS. 1A and 1B show (a) a diagrammatic view (FIG. 1A), and (b) a photograph (FIG. 1B) of a polymer composite board with a core layer produced from mixed plastic waste;

[0036] FIG. 2 shows a perspective view of a device for the production of a polymer composite board in accordance with FIGS. 1A and 1B;

[0037] FIG. 3 shows a side view of the device of FIG. 2 with the mold in the closed state;

[0038] FIG. 4 shows a side view of the device of FIG. 2 with the mold in the open state;

[0039] FIG. 5 shows a perspective view of the press of FIG. 2 in the open state;

[0040] FIG. 6 shows a perspective view of a nozzle of the device of FIG. 2.

DETAILED DESCRIPTION

[0041] FIGS. 1A and 1B show a section through a polymer composite board 10 which has been produced in accordance with the process described above. FIG. 1A shows a diagrammatic view and FIG. 1B shows a photograph of the polymer composite board 10. The polymer composite board 10 has an upper cover layer 11 and a lower cover layer 13. A foamed core layer 12 has been injected between the two cover layers 11, 13.

[0042] The core layer 12 is produced from mixed plastic waste, which is mixed as a granulated agglomerate with a blowing agent and is injected between the cover layers as a melt. In this way, the plastic mass can foam up uniformly, whereupon a fine and uniform pore distribution is obtained. Thus, the core layer contains a homogeneous structure in which the original various different plastic parts of different plastics cannot or can barely be distinguished from each other with the naked eye.

[0043] Glass fibre waste or carbon fibre waste, for example from industrial waste, shredded rotor blades or old boats, inter alia, may be used for the cover layer of the polymer composite board. This may be embedded as a powder fraction in a thermoplastic matrix, for example produced from polyethylene (PE), polypropylene (PP), polystyrene (PS) or acrylonitrile-butadiene-styrene (ABS). Waste of this type comes into recycling firms and cannot readily be upgraded. It is therefore incinerated. As an alternative to glass fibre waste, recycled nonwoven materials, for example from composite waste (glass fibres, natural fibres, artificial fibres and carbon fibres), and electrodynamically fragmented thermoplastic composite fragments may also be considered.

[0044] FIG. 2 shows a perspective view of a device for the production of a polymer composite board in accordance with FIGS. 1A and 1B. The device comprises a press 60 in which a closed mold 40 is disposed, i.e. in the closed form, the mold 40 forms a cavity 41 for the injection of a melt (in contrast to an open mold, into which all of the ingredients are introduced before closing). Furthermore, the device comprises an extruder 20 for the preparation of the melt and an injector 30 for injecting the desired quantity of the melt into the cavity 41 through an injection nozzle 50.

[0045] FIG. 3 shows a side view of the device of FIG. 2 with the mold 40 in the closed state. The mold 40 comprises an upper mold shell 42 and a lower mold shell 43 which together form the cavity 41. The cavity 41 has an opening along an end/edge side, to which the injection nozzle 50 is connected for injection of the melt. The mold 40 furthermore comprises an upper retaining plate 44 for the upper mold shell 42 and a lower retaining plate 45 for the lower mold shell 43. Heating/cooling channels are provided in the two retaining plates 44, 45 in order to bring the mold shells 42, 43 to the desired process temperature or to keep them at the desired process temperature. Furthermore, the two retaining plates 44, 45 are respectively connected to a suction device the suction openings 46 of which (see FIG. 5) are respectively disposed in the upper mold shell 42 or the lower mold shell 43. The respective cover layers 11, 13 of the polymer composite board can be held by suction and retained in the correct position.

[0046] FIG. 4 shows a side view of the device of FIG. 2 with the mold in the open state. In the open state, the press 60 and the injection molding device (extruder 20, injector 30, injection nozzle 50) can be moved away from each other in order to prevent the transfer of heat from the hot injection nozzle 50 to the cold mold 40.

[0047] FIG. 5 shows a perspective view of the press of FIG. 2 in the open state. Here, the suction openings 46 in the lower mold shell 43 can be seen. Suction openings of this type are also present in the upper mold shell 42. The mold shells each have side walls 47 which delimit the cavity 41. In the embodiment shown, the upper side walls 47 are higher than the lower walls. These also serve to position the cover layers 11, 13 correctly.

[0048] FIG. 6 shows a perspective view of the injection nozzle 50. The injection nozzle 50 is a wide slot nozzle which extends over the entire end/edge side of the cavity 41 or the mold 40 in order to inject the melt over the entire end/edge side of the cavity 41. In the embodiment shown, the injection nozzle 50 has a plurality of regularly spaced nozzle openings 51. Preferably, they are circular and their diameter increases from the centre to the respective sides. In this way, the melt can be injected with a uniform flow front, so that the flow front all reaches the end of the cavity 41 at the same time over the entire opposite end/edge side. Furthermore, the injection nozzle 50 may have a closing device 52, which in the embodiment shown has a shaft with a plurality of through openings for the respective nozzle openings 51. The nozzle openings can be closed or opened by turning the shaft.

[0049] The device shown in FIGS. 2 to 6 may be used for the process for the production of a polymer composite board 10 from mixed plastic waste described above. Here, an agglomerate of mixed plastic waste is mixed with a blowing agent and processed in the extruder 20 into a melt. A quantity used for a polymer composite board passes from the extruder 20 into the injector 30 and is then injected through the injection nozzle 50 into the cavity 41 to mold the polymer composite board.

[0050] Before the injection procedure, the cover layers 11, 13 are placed in the open cavity 41 and sucked onto the two mold shells 42, 43. The melt is then injected into the closed mold, in which it foams up and bonds with the cover layers. The foamed core layer 12 of the polymer composite board 10 is formed in this manner. In the mold 40, the core layer 12 cools down and the mold 40 can be opened in order to unmold the polymer composite board 10. Preferably, the lower suction here is switched off first in order to retain the polymer composite board 10 on the upper mold shell 42. A suitable tool can be driven between the mold shells 42, 43, the upper suction can be switched off and the finished polymer composite board 10 can therefore easily be removed from the press 60.

LIST OF REFERENCE NUMERALS

[0051] 10 polymer composite board [0052] 11 upper cover layer [0053] 12 foamed core layer [0054] 13 lower cover layer [0055] 14 end/edge side of cavity [0056] 20 extruder [0057] 30 injector [0058] 40 closed mold [0059] 41 cavity [0060] 42 upper mold shell [0061] 43 lower mold shell [0062] 44 upper retaining plate [0063] 45 lower retaining plate [0064] 46 suction openings [0065] 47 side wall [0066] 50 injection nozzle [0067] 51 nozzle openings [0068] 60 press