DE3511711A1 - Reprocessing high-quality plastics from wastes and reject workpieces - Google Patents

Abstract

In the production of sheet-shaped information media with high storage density, as are used in particular for optically readable information media for image and sound signals, because of the high requirements for the dimensional stability and the processing quality, high-quality plastics must be used. As is found in practice, a large proportion of the raw starting material used leads to wastes and reject workpieces, substantially increasing the production costs. It is proposed to reprocess these wastes and reject workpieces into reusable starting raw material in situ, by subjecting the wastes and the delaminated reject workpieces, which have been ground into granules, together with a predetermined proportion of higher molecular weight granules of plastic of the same structure to a coextrusion in which the plastic, having a loss in viscosity, from the wastes and reject workpieces is just compensated so that the plastic obtained in this manner can be fed back to the production process as a starting raw material. <IMAGE>

Description

Polygram GmbH My reference

Glockengießerwall 3 VPA 85 P 5 2 0 3 DE

D-2000 Hamburg 1

Reconditioning of high quality plastics from waste and rejects

Technical area

The invention relates to a method for reprocessing of starting raw material in the form of high-quality plastics, for example polycarbonate, from waste and scrap work in connection with the production of disk-shaped information carriers with high storage density, for example CD.

Underlying state of the art

In the production of disc-shaped information carriers with a high storage density, such as those used optically Readable video disks and digital audio disks (CD) must represent with a view to the high requirements high-quality plastics are processed to ensure the dimensional stability of such panels. Like practice, in CD manufacture, for example, shows the scrap rate of such information disks very high in particular due to the inevitable errors occurring in the information microstructure, see above that the proportion of plastic waste caused by the process and the reject workpieces made from the plastic approx. 50% of the starting raw material used matters.

Disclosure of the invention
35

The invention is based on the object of a Jae 1 May / 14.03.85

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To show the possibility of reprocessing the waste and scrap workpieces that arise during the mentioned panel production in the sense of a recovery of the starting raw material.
5

This task is based on a method of initially mentioned type according to the invention by the features specified in claim 1 solved.

The invention is based on the essential knowledge that in the manufacture of the information discs in the Processing of the plastic melt in the injection molding or transfer molding process, a reduction in molecular weight and so that a lowering of the melt viscosity takes place. Including the waste generated during the manufacturing process the decoated reject workpieces can therefore not even after their cleaning, drying and granulation in turn be introduced into the manufacturing process as the starting raw material, because the art- Substance material does not have the physical properties to be required for the starting raw material. By the inventive coextrusion of the scrap waste granulate together with a decrease in viscosity of the Rejected waste granulate compared to the required starting raw material compensating proportion of a correspondingly higher molecular weight plastic same molecular weight Structure, the waste reject granules can be processed in an extremely advantageous manner so that it can be directly fed back into the manufacturing process as the starting raw material.

Advantageous embodiments of the extrusion device for the preparation of the waste granules are specified in claims 2 and 3. 35

For stripping the scrap workpieces basically two possibilities, namely a chemical one

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Process in which the layers to be removed are in suitable Solvents or a process in which the layers under the action of a liquid and / or a particle beam or an abrasive medium or tool are mechanically removed.

The method that carries out the stripping by chemical means is set out in claim 4 and expedient refinements of these are specified in claims 5 to 7.

A method which carries out the stripping by mechanical means is specified in claim 8. Appropriate refinements of this last-mentioned method are described in claims 9 to 13.

Brief description of the drawings

In the drawing, the figures used to explain the invention in more detail mean

Fig. 1 shows the schematic representation of the method for stripping the scrap workpieces chemical route,

Fig. 2 shows the schematic representation of the method for stripping the reject workpieces by mechanical means Ablation,

3 shows the schematic representation of a device for coextrusion for the reprocessing of Waste scrap granulate for a raw material that complies with the specification.

Best way to carry out the invention

The schematic representation of the process for decoating reject workpieces by chemical means

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according to Fig. 1 shows a container 1 for receiving solvents and cleaning liquids, in which a vertical axis 2a a basket 2 is rotatably arranged. The basket 2 has a hexagonal cross section and has side walls designed as sieves with a mesh size of preferably 50 χ 50 mm. He is inside him provided with baffles 3 in the form of baffles and rod-like approaches, via a la des in the stand base Container 1 provided drive motor 4, the basket 2 can be set in rotation. Above the container is a filling funnel 5 is arranged, via which the scrap workpieces to be stripped are filled into the basket 2 can. The basket 2 itself has a closable lid 6 on the top, which is only used when filling or Drain is opened.

The inlet port 7 for different solution liquids is via a switching valve 8 with the respective Outlet valve 9 connected to three solvent containers. of which the solvent container 10 is an etchant for Removal of the metal layer, e.g. sodium hydroxide solution (NL), the solvent container 11 methanol solution (ML) and the Solvent container 12 contains hydrochloric acid (SS). The drain nozzle 13 in the area of the stand base la des Container 1 is also provided with an outlet valve 9 and has behind this outlet valve 9 a Pump P, which pumps out the contents via a drain line AL when the container is emptied.

Furthermore, the schematic representation according to FIG. 1 has a water inlet line ZL-W on the top, which also connected via an outlet valve 9 to two spray nozzles 14 projecting into the container 1 from above are.

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At the beginning of a stripping process, 5 reject workpieces are placed in the opened via the hopper Basket 2 filled, then the lid 6 closed and the container over the filler neck 7, the Switching valve 8 and the outlet valve 9 of the solvent container 11 are filled with methanol. Then the Basket 2 set in a rotary motion by the drive 4, the baffles provided in the interior of the basket Filled reject workpieces are kept constantly in motion. After the methanol this way has acted on the scrap workpieces for a predetermined time, the drive 4 is stopped and that Methanol is pumped out by the pump P via the outlet connection 13 and the outlet valve 9. Then the repeat the same process. The third step is water purification, during which the outlet valve 9 the water supply line ZL-W is opened.

The methanol solution is used to remove the usually lacquer layer present on such scrap workpieces. The generally under this layer of varnish The existing metal layer in the form of a reflective layer is now removed by adding an etchant, e.g. caustic soda brought about from the solvent container 10 into the container 1. As with the exposure to the methanol solution the basket 2 is set in a rotary motion even during the exposure time to the sodium hydroxide solution. After pumping of the etchant from the container 1 is diluted hydrochloric acid via the solvent container 12 into the container 1 let in to neutralize the etchant residues. After the hydrochloric acid has also been pumped out again the now decoated scrap workpieces are thoroughly rinsed with water from the water supply line ZL-W. The rinsing process is intensified by the spray nozzles 14.

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The scrap workpieces that have been decoated and cleaned are then fed into a funnel 15 in a · Conveyor belt drying section 16 supplied. The scrap workpieces are on the conveyor belt 17 by a Heating zone 18 passed through, which has a radiant heater 19 on both sides of the conveyor belt 17.

The alternative mechanical stripping process shown in FIG. 2 for the reject workpieces has four workstations I, II, III and IV arranged one behind the other, through which the workstations to be processed Reject workpieces are guided on a transport path 20.

On the input side of the first work station I is a reject workpieces receiving Collecting container 21 which acts as a separator with the beginning of the transport path 20 via a Conveyor 22 is connected. The conveyor 22 promotes the reject workpieces to be processed one after the other on the Transport path 20, where they are then in the first work station I from above, for example a high pressure fluid and / or Particle beam are exposed. The high pressure liquid and / or particle jet can either a high pressure water jet, a high pressure water jet with abrasive material, for example sand or Glass balls, or a sandblast. The exposure time of the high pressure liquid and / or particle jet is dimensioned so that the undesired layers on the surface facing the high pressure jet the scrap workpieces are completely eliminated. Then in the transition of the transport route 20 from the exit of the first workstation I to the second workstation II through a specified here Vertical offset H turned the scrap workpieces. In the

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Second work station II becomes the second side of the scrap workpieces in the same way as in work station I freed from any unwanted layers that may be present here. Then takes place in the third workstation III a thorough water purification. In the fourth and last workstation IV The scrap workpieces from which the coating has been removed are then transported by a device on the upper and lower side of the transport path 20 provided radiant heater 19 dried. .

In a variant of the device described above instead of the high pressure liquid and / or particle jet, an abrasive tool, for example used a roller or brush.

The stripped, cleaned, dried and removed either by the method according to FIG. 1 or FIG Ground reject workpieces are now together with the likewise cleaned and ground waste supplied to the device for coextrusion shown schematically in FIG. 3.

First, the waste granules are placed in the hopper 23. It then runs through again a dryer 24 and is then fed via the metering chute 25 to the feed hopper 26 on the inlet side of a Single screw extruder 27 supplied. At the same time, this funnel 26 is via a further metering device 28 with filling funnel 29, a predetermined proportion of a higher molecular weight granulate made of plastic The same structure is added to the drop in viscosity of the waste granules during the coextrusion that is now to be carried out to compensate, i.e. to obtain a plastic over this coextrusion process, which has the physical properties of the original raw material.

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On the output side of the single screw extruder is a melt filtration device with a screen changing device provided with a sieve mesh size of 0.06 mm and any remaining contamination residues holding back.

The material extruded in this way is passed over the strand head 31, which has, for example, a 90 ° deflection angle and has a larger number of bores, for example 3 mm in diameter, passed into a water bath 32.

Then the processed plastic, which is due to its own heat in connection with the water bath largely self-drying, ground in a mill 33 to give granules of the desired grain size.

Commercial usability

The method according to the invention can be used with advantage in production facilities for the production of disk-shaped, optically readable information carriers with high storage density, such as video disks, optical data storage devices and CDs are used because it is suitable for the high Accumulation of plastic material in the form of waste and scrap workpieces immediately for its reuse to be processed as starting raw material for the manufacturing process.

13 claims

3 figures
30th

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Claims (13)

> ζ VPA 85 P 5 2 O 3 DE claims 1. Process for the recycling of starting raw material in the form of high-quality plastics, for example Polycarbonate, made from scrap and scrap pieces in connection with the manufacture of sheet-like products Information carriers of high storage density, for example CD, characterized in that that the scrap workpieces, which may have been freed from applied layers, together with the waste after cleaning and drying in granulated form (scrap waste granulate) together with one of the Decrease in viscosity of the scrap waste granulate compared to the starting raw material compensating proportion of a correspondingly higher molecular weight plastic of the same structure in granulated form via a melt filtration device (30) having extruder with exit-side strand head (31) into a water bath (32) are passed and that the so reprocessed plastic material with a given viscosity after Renewed granulation and drying are also available to the manufacturing process as starting raw material is provided. 2. The method according to claim 1, characterized that the melt filtration device (30) of the extruder (27) has a screen changing device having. 3. The method according to claim 1 or 2, characterized in that the proportion of the higher molecular plastic of the same structure is 1 to 15 percent by weight of the scrap waste granulate. 4. The method according to any one of the preceding claims, -X- VPA 85 P 5 2 O 3 DE characterized in that the scrap workpieces for decoating initially in a two-stage methanol bath with subsequent water cleaning of any paint layers that may be present are freed and then a further multi-stage wet process to remove metal layers are subjected, in which the reject workpieces first an etchant, then a neutralizing agent exposed and finally rinsed several times with water and that the decoated reject workpieces after they have dried by crushing, they can be transferred to ground material. 5. The method according to claim 4, characterized in that that the reject workpieces for carrying out the wet processes in a polygonal one Cross-section, for example hexagonal cross-section, having basket (2) made of stainless material be inserted with side walls designed as sieves, which are provided with baffles (3) inside and is arranged rotatably about its longitudinal axis in a container (1) receiving the processing fluids. 6. The method according to claim 4 and 5, characterized in that the designed as sieves Side walls of the basket (2) have a mesh size of 50 χ 50 mm. 7. The method according to claim 5 or 6, characterized in that the basket (2) can be closed is executed. 8. The method according to any one of claims 1 to 3, characterized in that the d Reject workpieces via a separator acting -A * VPA 85 P 5 2 O 3 DE same conveyor line (22) one after the other leading through several work stations (I, II, III, IV) Transport path (20) are supplied, of which the first two work stations (I, II) of the stripping the reject work pieces by mechanical means, the third work station (III) the water purification of the stripped Reject workpieces and the fourth and last work station (IV) are used to dry them, that also the mechanical processing of the scrap workpieces on the transport path in the first and second work station takes place in each case from above and that the scrap workpieces when transferring from the first workstation to the second workstation with regard to their Rest on the transport route can be turned. 9. The method according to claim 8, characterized that the turning of the scrap workpieces via a height offset (H) of the transport route (20) brought about in the transition area between the first and the second work station (I, II) will. 10. The method according to claim 8 or 9, characterized in that the stripping of the Reject workpieces are made by high pressure water jets. 11. The method according to claim 8 or 9, characterized in that the stripping of the Rejected workpieces by high-pressure water jets, where an abrasive material, for example sand or glass balls, is attached. 12. The method according to claim 8 or 9, characterized in that the stripping -} <- VPA 85 P 5 2 O 3 DE the scrap workpieces are carried out by a preferably dry sandblast. 13. The method according to claim 8 or 9, characterized in that the decoating of the scrap workpieces is carried out by abrasive mechanical devices, for example rollers and / or brushes.