DE2124510A1 - Processing mixed waste plastic - in successively hotter extruder stages with interstage expulsion - Google Patents

Abstract

A method of preparing mixed waste plastics for reuse in the plastics ind. is carried out as follows - the mixed granulate is fed into a first extruder where it is raised to a temp. sufficient to melt the lowest melting type of plastics contained in the mix, this melt then being removed; the remaining mixt. passes to another extruder operating at a higher temp., where the next lowest melting component is melted and again removed, and so on for further stages until an unworkable residue only remains. The prefd. appts. comprises a single shaft extruder constituted by the successive shafts of the successive stages, each shaft being conically widening in the flow direction; at the discharge (downstream) end of each stage, the barrel is perforated, so that the smelt from that stage is squeezed out laterally and removed from the extruder. The final, unworkable residue may be used as a cheap fill material for civil engineering works.

Description

Catching and device for the treatment of mixed accumulations Plastic waste for the purpose of reuse Contains the garbage that accumulates today increasingly plastics of all kinds, e.g. 3. as packaging material, disposable bottles or industrial waste. The proportion of plastics in the total German garbage will currently indicated with a little under 10%. With increased conversion of the beverage industry On disposable plastic bottles, the proportion of plastic in the garbage can easily increase to 20%.

The proportion of PVC in the garbage is currently estimated at 2%. Using for non-returnable bottles made of PVC, an increase to 4 ... 5% is expected.

The elimination of plastic waste brings insurmountable difficulties with himself. A deposit of the plastic waste on heaps or depots is on the Duration not possible because plastic, in contrast to the most common types of waste not rotten or corroded. There are easily biodegradable plastics and there won't be. Can be used for packaging food and beverages Biologically resistant plastics in particular are required. But are plastic parts Thrown on garbage dumps, there is always the risk of unpredictable slipping and sinking of the heaps, since, as I said, plastic does not contain any organic compounds goes into the rest of the garbage or soil.

A plastic waste disposal is therefore generally only through the incineration takes place. Burning, however, brings considerable dangers to the environmental pollution with himself. This is especially true for PVC.

PVC not only burns with difficulty because of its low calorific value, but when it burns it splits off hydrogen chloride, which leads to the corrosion of the Boiler systems leads to a reduction in the service life of the system. This is how E.g. when burning one meter of a commercially available PVC-insulated conductor with a cross section of 1 mm2 1.35 normal liters of hydrochloric acid gas, this from the chimneys The gas escaping from the incineration plant forms at low humidity Hydrochloric acid, which becomes strong when it rains on buildings, on machines or apparatus Corrosion damage. In addition, it can be caused by the burning of PVC Air pollution in humans and animals through inhalation of the oxford fumes causes irritation and possibly injuries to the respiratory system.

A satisfactory, fast, technically perfect and safe, i.e. not a polluting method of disposing of plastic waste not known so far. But it is precisely this that the invention has set itself the task. The respective type of plastic should not only ensure safe and risk-free disposal experienced, but the plastics that arise in each case should be separated into as much as possible reane types can be reused. It should be used in the procedure according to the Invention no unusable remnants remain, which is what has been done so far The problem of plastic waste, which is regarded as insurmountable, would be solved in a simple manner.

Before working according to the method according to the invention; can, the garbage is at least roughly of not made of plastic to clean existing waste, e.g. using a standard metal cutter can be reached. However, the industry also supplies pure plastic waste.

The garbage, which then consists of different types of plastic, then becomes according to the invention added to an extruder known per se and to a first temperature heated, at which the lowest melting plastic melts.

The melt obtained is not yet melted by the rest Granulate separated and discharged from the extruder e.g. with the help of a back pressure.

Then the higher melting, remaining mill residue is in a subsequent operation, namely to heat up until the next higher Melting temperature of another type of plastic has been reached. The then arising Melt is discharged from the extruder in the same way as described.

There are consequently different temperature zones over the length of the extruder provided, the temperature of the individual zones being the melting temperatures of the correspond to the plastics contained in the waste granulate. The zones are staggered so that the temperature of the first zone of the plastic melting at the lowest temperature is equivalent to. The temperature of the following zones increase accordingly Melting temperatures of the plastics contained in the granulate. In the one through the extruder transported plastic granulate is only the plastic in the temperature zones plasticized, the melting temperature of which corresponds to the temperature range.

The plasticized or melted plastic material is now laterally excreted from the non-plasticized material due to, for example, the jam. In an embodiment of the invention, the dynamic pressure can thereby be achieved or increased be that in each case a melting zone is followed by a cooling zone. The temperature the cooling zone should be set so that it is at least 30 ... 5000 below the Temperature of the melting zone in front of it. The one melted in each temperature zone Plastic can be removed from the extruder in any way. Advantageous it is, the respective melted plastic type, as a result of a jam from which not plasticizable material to be discharged laterally opposite the extruder working direction, to a pure granulate containing only one type in a manner known per se to be processed .. A jam immediately at the end of each temperature zone can also be achieved in that the unmelted granules in the following Work stage is transported more slowly than in the previous one.

Depending on the composition of the processed garbage it cannot be avoided that a certain non-plasticizable residue in the extruder remains. However, this remainder can also, as the invention further provides, can be used to advantage. To do this, this mixture is possibly with additional metal stiffeners or the like, pressed and discontinuous ejected. Such bodies can then be used with advantage for the sub-construction of roads, Dikes for filling cavities, e.g. in mines and especially in polder, Dike construction can be used.

In the ground state, the remainder that can no longer be reused is also suitable as an additive for synthetic cement.

The one required to carry out the process, shown chemically Device with still further inventive features is based on a. Embodiment are described in more detail. It should be noted that all described in the test and technical features shown in the drawing alone and also in combination have inventive importance.

The device consists essentially of a cylindrical housing 1, in which a worm shaft 2 is rotatably supported and by means of a motor 3 is driven. The screw has a conically widening cross-section Core on. At one end of the housing 1, a funnel 4 is provided, through the. the plastic waste prepared to granulate is entered into the device will.

A heating device 5 is arranged around the cylindrical housing 1, which heats the granules conveyed by the screw 3, which through the heating device 5 The temperature to be reached in the housing 1 depends on the composition of the waste away. In any case, the first section of the garbage processing device is the To reach temperature at which essentially only the plastic contained in the garbage with the lowest melting point initially plasticizes and melts through the during During the transport by means of the screw, the pressure in the granulate will gradually increase the molten plastic through the perforated wall 6 of the housing 1 in a the housing 1 annularly surrounding receiving container 7 pressed. Of course the melt will also be able to flow out automatically.

The jam of the material in the housing can be achieved in two ways. For this purpose, the core 8 of the screw 2 can be conical in cross section in the working direction expand so that the treatment room in the direction of the end of the respective treatment zone narrowed. Also, with the help of a cooling device 9, which is behind each zone is arranged and the unmelted granulate cools down by about 20 ... 30% Congestion in the previous treatment room can be achieved because of the renewed hardening of the remaining granulate the further transport of the material. to the next treatment chamber is made more difficult. The residual waste will therefore be located in the area of the cooling device 9 damming up.

Another measure to achieve a traffic jam is the control of the granulate transport in the subsequent treatment room. At least it should Further transport takes place at a lower speed than in the previous section. For this purpose, either the incline of the worm threads is flatter or if it is done separately The following worm drive is designed to be slower in terms of its number of revolutions.

The melt passing through the screen-shaped wall 6 is controlled by a smaller one by means of a motor at a constant temperature 10 driven screw 11, which serves only as a transport device, detected and pressed into a storage head 12. In front of the storage head 12, an exchangeable Sieve 13 are located to remove any impurities from the melt to free. From the reservoir 12, the melt then passes through a nozzle in which it formed into strands and finally back to the now pure granules is crushed. The device required for this is designated as a whole by 14.

The granules not removed from the garbage in the first treatment stage is detected by a further screw 3 after passing through the cooling zone 9. This snail has a smaller thread pitch for slower transport of the remaining granulate on.

This causes a jam in the area of the cooling device 9, which acts back on the material contained in the previous unitb Nonetheless approximately the same amount is transported per screw revolution.

The heating device 5 'now heats up the remaining granules a temperature corresponding to the next higher melting plastic, so that this Plastic that has become liquid and affects a different type of plastic through the perforated Wall 6 'flows out of the extruder. About the granulating device 14 'is then the melt is also processed into pure plastic granules.

As the number of melting and cooling zones built into the extruder corresponds to the types of plastic contained in the waste granulate, the repeats described processes until all thermoplastics with melting temperatures up to about 50,000 are eliminated.

The plastic material that has not been plasticized after the last melting zone, including all dirt residues in it that were not sorted out beforehand could be at the end of 15 of the extruder with the power of Screw 3 through a nozzle into one. Jam head pressed and accumulated there. To When a certain volume is reached, the material is pressed into a mold and then cooled down. The resulting pressed body can be because of its indefinable Do not use the composition as reclaimed plastic. For this compact result However, the following possible uses: They can be used for the substructure of roads, dikes, for filling cavities such as mines for polder construction and also for synthetic cement.

Claims (17)

Claims A 1; Process for processing mixed plastic waste for renewed economic recovery in the plastics industry through the following process steps: a) made of different types of plastic, as desired mixed, küll delivered as ground granulate is put into a well-known extruder given and heated to a first, such temperature, at which the lowest melting point Type of plastic melts, b) the melt is removed from the still hard one e.g. by back pressure Rubbish residue separated and discarded, c) then the higher melting, remaining one is Rubbish remainder in a subsequent operation, heated to a higher level, up to one Melting temperature of the next melting type of plastic, temperature of the next melting one Type of plastic, d) then the melt of this different type of plastic is used again separated by e.g. pressure from the still hard garbage residue and excreted, e) further similar treatment stages, until one of them does not remain Processable residues can follow. 2. The method according to claim 1, characterized in that each heating zone a cooling zone is connected immediately afterwards. 3. The method according to claim 2 ,. characterized in that 0 that the temperature the cooling zone each about 30 .F. 50 C below the previous melting zone temperature is held. 4. The method according to claim 1, characterized in that in the extruder as many melting zones and, if applicable, subsequent cooling zones are included, how many types of plastic are present in the granulate. 5. The method according to claim 1, characterized in that the remaining Granulate is transported more slowly after each melting zone than in the previous one. 6. The method according to claim 1, characterized in that the molten Type of plastic, for example, as a result of a jam from the unplasticized Material discharged laterally opposite the extruder working direction and to a one pure plastic; art contained granules further processed in a known manner will. 7. The method according to claim 1, characterized in that the not The remainder of the plastic waste that can be recycled is compressed and discontinuous by means of a damming head is ejected. 8. Use of the pressed body according to claim 7 in the substructure of roads, Dykes, for filling cavities in e.g. mines, in polder and dyke construction and or in the ground state in synthetic cement. 9. Device for performing the method according to one or more the existing claims with a known extruder, which consists of an in a heated cylinder rotatably mounted, driven screw consists, thereby characterized in that several such extruders (1, 2; 1 ', 2' ....) directly behind one another are connected and in the area of the lower end of each extruder unit one Opening (6, 6 ') is provided for discharging melt. 10. The device according to claim 9, characterized in that the respective Cylinder (1, 11) at the lower end at least partially as a sieve-shaped tube (6, 6 ') is trained. 11. The device according to claim 9, characterized in that the screw (2 11; 2 ', 11') has a core (8, 8 ') which widens conically in cross section. 12. The device according to claim 9, characterized in "that the Outflow opening (6, 6 ') is connected to a granulating device (14, 14'), 13. Apparatus according to claim 9 and 12, characterized in that the with the Outflow opening (6; 6 ') provided section annularly of a receptacle (7, 7 '), which the melted plastic type to the granulating device (14, 14 ') leads. 14. Apparatus according to claim 13, characterized in that between the receiving container (7, 7 ') and the granulating device (14t 14') another Screw (11, 11 ') is provided for the transport of the melt. 15. The device according to claim 9, characterized in that behind a cooling device (9, 9 ') is provided at the outlet of each extruder unit. 16. Device according to one or more of the preceding claims, characterized in that the screw of all extruder units as a single one Wave with. a central drive (3) is provided. 17. The device according to claim 15, characterized in that the The pitch of each screw (2, 2 ') following in the working direction is flatter is.