DE2308698A1 - Recovering extruded tubing waste - by collecting, shredding and mixing with fresh granulate - Google Patents

Abstract

Extruded film tubing is laid flat, and the edges cut off and passed by rollers to the inlets of an earthed suction tube which deposits them in a shredder. The obtd. flakes pass to a cyclone and then to a screw in a horizontal tube, where they are joined by fresh granulate from the main feed. The materials are mixed in further passage along the tube and at its end they finally fall to the feed end of the extruder. The system maintains uniform material and prevents sepn.

Description

Annex to the entry from February 16, 1973 Pat / 12.239 / vB-Hx.

Device for recycling plastic waste.

The invention relates to a device for recycling during the extrusion process accruing plastic waste, in particular edge strips, into the extruder, whereby the plastic waste is forcibly detected by mechanical means after it has been generated transported to a shredded mill, shredded and then connected to a mixing and conveying device are supplied. In the manufacture of plastic films falls when starting the units and then when cutting the foils before they being wound into rolls generates a significant amount of waste. To the use to enable this waste and thus the film production to be more economical various proposals have already been made. This is how it is, for example known to process this waste into regrind and then return it to the extruder to feed. This type of work-up is very low and therefore only for Profitable companies that produce large quantities of polishing in a single execution. Under Execution is to be understood that both the same color additives as well Sunscreens, lubricants, etc.

clogs. If this is not the case, the different types of regenerated material are mixed Starting products and it is no longer possible to produce an end product with constant Values.

To avoid these difficulties # it has already been suggested that the trimmed edge is fed back directly into the feed hopper of the extruder in the form of strips. However, considerable difficulties arise here, in particular because it is involved what is required is that the cut edge strips run at the same speed must be deducted with which they arise and at this speed as well must be pulled into the feed hopper of the extruder.

Another suggestion is therefore to chop the edge strips and by means of a screw the shredded edge strips into the extruder screw to be brought in directly.

A disadvantage of this method has been found to be the fact that a very uneven film is produced, since there is practically no mixing of the fed Schnitzel with the granulate in the extruder screw erfo. It surrendered There are surfaces in the extruded film that are practically made of pure regrind exist and thus physically have completely different values than those surrounding them Surfaces made from pure new granulate.

Another suggestion builds on these failures, according to which the edge strips continuously peeled off, chopped and then with it Granules mixed are blown into the feed hopper of an extruder. Amazingly Here too the fact arises that, although a careful mix between Granules and chips occurred, the extruded film was uneven. That is due to fluctuations in the conveyance of the extruder, which in turn results from segregation of the granulate cuttings in the extruder funnel results.

The invention is therefore based on the object of the extruder screw to supply the material, i.e. the granulate mixture, in such a way that a constant Mixture between granules and schnitzel is guaranteed and no de-ionization rehr can occur.

According to the invention, this object is achieved by a method for Recycling of plastic waste produced during the extrusion process, in particular Edge trim, in the extruder, with the plastic waste through after its accumulation mechanical means detected, forcibly transported into a pulp mill, shredded iind are fed to a mixing and conveying device with solid granules the characteristic feature that by means of a screw schnitzel and fresh granules mixed and the homogeneous mixture is fed directly to the extruder without pressure.

This method according to the invention ensures that the extruder screw is supplied with a homogeneous plastic material which, during extrusion, only leads to a likewise homogeneous material with the same physical properties. In all previous systems, no comogenic material was fed to the extruder screw. So it happened The segregation of the chip granulate mixture in the feed hopper of the extruder, because due to the different bulk density the granulate was drawn into the screw of the extruder more easily, while the chips built up into nests and bridges and only then reached the extruder as a larger accumulation. Since considerable amounts of air were drawn into the extruder during this process, there was pumping and thus an uneven demand, ie fluctuations in the thickness of the extruded film. Because, according to the invention, the homogeneous mixture is fed directly to the extruder screw, segregation can no longer take place, and the homogeneity of the material is thus maintained.

Another important point is that the supply of the homogeneous Mixture takes place without pressure. According to an older proposal, a plug screw is used into the extruder that already over the filling line with granules was charged, shredded waste in shredded form. The pumping of the extruder this is avoided, but there is no mixing of the waste material possible with the newly introduced granulate. Rather, the stream of chips leads to a Formation of streaks, which differ physically from the new granulate Has values. It is therefore of the utmost importance for the method according to the invention that that a fresh granulate waste mixture is supplied as a completely homogeneous mixture and is introduced into the extruder without pressure.

According to a preferred embodiment of the invention, this method carried out with a device in which a mixing and conveying device Schneeke, which has a progressive slope, is used, the screw is flanged to the extruder via an intermediate piece. The intermediate piece is where dimensioned so that between the niche and conveyor screw and the extruder screw one pressure can build up, on the other hand also a separation of the in the Snail generated homogeneous material is avoided.

According to a particularly advantageous embodiment of the invention, has the screw core diameter is smaller from the area of the granulate dosing opening Diameter than at the cossette entry opening, with the change in the diameter of the diameter corresponding enlargement of the screw conveying volume of the amount to be fed Granulate corresponds.

When the edge section is used, the ratio changes from extruded film to the cut edge width essentially not. It there is thus a constant amount of waste in the range from 5 to 10%, with these percentages are dependent on the width of the film being used.

The narrower the film web} the greater the percentage of waste. The design of the mixing and conveyor screw is based on these percentages, The bulk weight of the shredded edge strips must also be taken into account like the fact that nXlr has a certain relationship to granules and chips results in a fully pourable mixture that does not tend to separate. At a Chip size of 3 mm 2, this granulate-chip mixture has a ratio from a. lo: 1, i.e. 1 kg of schnitzel per lo kg of granulate. It is possible with it yourself a high proportion of waste, i.e. wide wall strips with a narrow usable width, the result in a waste rate of 9%, can still be recycled. One adjusted to this relationship The screw has a relatively large core diameter in the entry area of the chips which is maintained until shortly before the granulate dosing opening. Of this At the moment it is removed and thus enables the addition of further material.

The ratio of the two core diameters to one another corresponds to this Ratio of the desired dosage of fresh granulate to schnitzel, i.e. it is the space that is automatically filled by the trickling granules by reducing the core diameter of the screw. For better Mixing of the granules may make sense if the Granulate is added in two stages, each of which is followed by a mixing section. This is of particular interest when a relatively yerine percentage sn decreases, e.h. Edge trimmed and an analogous percentage of fresh granulate is fed. In this case, the first reduction in the screw core diameter is completed after the first mixing section, a further reduction in the screw core diameter on, which is also followed by a mixing section. Also in this reduction of the screw core diameter, granules are added.

According to a further advantageous embodiment of the invention the screw speed of the mixing and dosing screw is variable. The lowest speed range the screw is aiif the minimum, the upper to the maximum flow rate of the Extruder turned off. The control range is expediently in the ratio 1: BeisDiel: The mixing and conveyor screw is made of the material according to DIN 1.4541. The conveying capacity for chips: 40 kp / hour, corresponding to 400 dm3 / hour.

Granulate dosing from nozzle 1: 180 kp / hour. corresponding to 334 dm3 / hour

Granulate metering from nozzle 2: 100 kp / hour. corresponding to 185 dm3 / hour

Total screw length approx. 1300 mm, thread diameter 150 mm, arrangement / horizontal, design: as a pipe trough, last outlet as a trough trough, screw spiral stored on the fly in the trough.

Screw speed 8 to 40 revolutions / min., Drive power: 1 HP.

When the extruder and the mixing and conveyor screw are fully utilized a blown film of 50 μ was run.

The diameter of the tube bladder was about 1.50 m.

Edge strips of 120 mm are cut on both sides, whereby there were two individual foils with a width of approx. 2.18 m. The film obtained was completely homogeneous and had neither thickenings nor streaks, just like that physical properties in different areas of the film tube were identical to each other.

The invention is described below as an example with reference to FIGS. 1 and 2 described: 1 schematically shows the structure of a tubular film extrusion system with the edge strip return according to the invention.

FIG. 2 is a partial representation of the extruder shown in FIG on a larger scale.

The extruder 1 is equipped with an extruder screw @ with which the supplied material is pressed to the extruder head 3 and nar, h Allstritt as the tube 4 forms the ring nozzles. The tube 4 is pulled off vertically upwards and put together to form a flat hose 6 by means of a hose laying device 5 and drawn off over the guide rollers 7. The flat hose 6 is then Trimmed at the edge, i.e. the knife 8 swiveled into the path of the flat hose 6 and cut an edge strip 9 on both sides from the flat tube 6, so that two individual film webs lo arise from the flat tube 6. The margins 9 are grasped by pairs of rollers 11 in the immediate vicinity of the knife 8 and introduced into each funnel 12 of the suction pipe 13. The suction pipe 13 is kept under negative pressure by means of a fan 14 and a Ventiiridüse 15; she consists made of seamlessly drawn tube, which is grounded to prevent electrical charging is. Through these measures, a jam of the film, that is to say a jam Aer, is peeled off Edge strips 9 within the suction pipe 13 avoided.

After passing the Venturi nozzle 15, the edge strips 9 enter the Schnitzelwerk 16, where they are cut into leaf-shaped scales 21. The Schnitzelwerk 16 can be designed so that the rotation of the Knife 8 a vacuum can be generated in the suction pipe 14, so that I the Use of a fan 14 and the Venturi nozzle 15 is unnecessary. Via the blowpipe 17 The edge strips 9, which have been processed into flakes 91, leave the chipping mill 16 and enter the cyclone 18. The cyclone 18 has a double air separator equipped so that the air both through the upper nozzle 19 as well as can escape through the transfer funnel pQ, which is shown as a cross Scales 21 fall into the screw conveyor 22, which is stored in a tubular trough 29 is. The screw conveyor 22 has a relatively large core diameter in this area in order to be able to promote a certain amount of the scales 21. Through the granulate dosing opening 24, which via the metering tube 25 with the metering flap 26, the screw conveyor 22 with the granulate hopper 27 connects, lies in the area of the tubular trough 29, in which the screw conveyor 22 has a reduced core diameter. the Reducing this diameter corresponds to the desired addition of granules i.e. the free space w created by the thinning of the screw conveyor core rd automatically filled with granulate, which is via the dosing tube 25 with the dosing flap 26 flows into the granulate metering opening 24. Through the revolutions of the screw conveyor 22 there is a dissolution of the scales 21 with the granulate. Another Addition of granules when the screw conveyor core diameter is reduced again can be done directly under the granulate funnel 27, if only a very narrow one Edge strip 9 is separated from the flat tube 6. In this case, how shown, the slide 28, which is located below the granulate hopper 27, pulled out and supplemented in the now designed as a U-shaped trough 23 trough the granulate content.

The overhung screw conveyor 22 ends in the intermediate piece 30, which connects the filling opening of the extruder 1 with the metering device.

List of terms.

1 extruder 2 extruder head 3 extruder head 4 hose 5 hose laying device 6 flat hose 7 guide rollers 8 knives 9 edge strips lo film webs 11 roller pair 12 Funnel 13 Suction pipe 14 Blower 15 Venturi nozzle 16 Schnitzelwerk 17 Blow pipe 18 cyclone 19 upper nozzle 20 transfer funnel 21 scales 22 screw conveyor 23 tubular Trough 24 Granulate dosing opening 2-5 Dosing tube 26 Dosing flap 27 Granulate filling line 28 Slider @@ 29 U-shaped recess 30 Intermediate piece

Claims (6)

Claims. 1. Process for recycling from the extrusion process Plastic waste, especially edge strips in the extruder, with the plastic waste captured by mechanical means close to their occurrence, compulsorily in a pulp mill transported, chopped and with fresh granulate a mixing and conveying device are fed. characterized in that a screw conveyor (22) Scales (21) and fresh granulate mixed and the homogeneous mixture immediately is fed to the extruder (1) without pressure. 2. Device for recycling of the extrusion process Plastic waste, especially edge strips; n the extruder, with the plastic waste after their occurrence seized by mechanical means, forcibly in a pulp mill transported, chopped and with solid granulate of a mixing and conveying device are supplied, characterized in that a mixing and conveying device Conveyor screw (22) is used, which has a progressive pitch and is flanged to the extruder (1) via an intermediate piece (30). 3. Apparatus according to claim 2, characterized in that the screw conveyor (22) is introduced into a tubular trough (23) which is located in the entry area of the Shed (21) Iznd of the granulate is designed as a U-shaped trough (29). 4. Device according to one of claims 2 and 3, characterized in that that the schnitzel entry opening is at the beginning of the screw and at least one granulate metering opening (24) downstream of it. 5. Device according to one of claims 2 to 4, characterized in that that the screw core diameter from the area of the granulate metering opening (24) from one has a smaller diameter than at the schnitzel entry opening, the Change in diameter corresponding enlargement of the screw delivery volume Corresponds to the amount of granules to be fed. 6. Device according to one of claims 2 to 5, characterized in that that the screw speed is variable.