DE4414750C2 - Method and device for cleaning viscous plastic melts - Google Patents

Description

The invention relates to a method for cleaning ver unclean, possibly also paper-containing, more viscous Plastic melting and a device according to the preamble of claim 10.

When recycling packaging waste the collected packaging in a condition that its Reprocessing for a new production use impossible without prior sorting and cleaning makes. In particular, the collected plastics are cases for immediate recycling by anorga African impurities, e.g. B. silicate substances as in for example earth, dirt, sand or metallic materials such as for example metal chips or aluminum foil, and by organic contaminants, e.g. B. textiles, paper scraps, Cellulose, too dirty.

In appropriately designed sorting systems the collected packaging waste is pre-sorted by hand and that appear suitable according to criteria such as size or type the plastic waste is then sorted out by hand. However, this from sorted plastic waste still needs of adhering organic and inorganic impurities cleaning before the plastic waste can be recycled.

The cleaning process for cleaning plastic waste of adhering organic and inorganic impurities inclinations can be broken down into at least two steps will.  

First, the plastic waste is crushed and washed afterwards. If necessary, they are different which plastics are separated as far as possible. Then the resulting still wet art dried shredded fabric.

In the second step, the washed and dried Plastic chips are plasticized in an extruder. The resulting plasticized plastic mass must however, before processing into new plastic products by means of suitable separation or filter devices to be cleaned further.

From DE-GM 17 60 883 is a centrifuge for separation of suspensions with a speci fish lighter solid known. The centrifuge is there from a conical solid drum with inlet, Sedimentation room and subsequent drying room as well a cylindrical one, just the one on the liquid floating solid layer penetrating discharge slug. The discharge screw is attached to the course of the Adjusted drying room. With the help of the discharge screw who the cleaned solids, which are on the inner Surface of the air expelled by centrifugal force Collect the liquid from the sedimentation area into the dry held space. This procedure is to cope with the re treatment of packaging waste problems not suitable.

From DE 91 06 688 U1 is a device for back extraction of raw materials from with underbody protection coated masking stencils as recyclable materials known due to the investment in plant and operating costs. These The device described has a comminution for this Setup with knife shafts and casing-side in the measurement rings of the scraper engaging knife shafts, one  fixed to the shredding device material conveyor and a subordinate to the solid material conveyor Sieve screw centrifuge. The use of a sieve screw centrifuge has ver dirty viscous plastic melts the disadvantage that Particles smaller in size than those of the sieve holes, cannot be held back. Another, nachge orderly filtering device is inevitable. In addition, at this process, the gelled PVC using solvents diluted what the environmental impact of this process is detrimental. The one described in DE 91 06 688 U1 Separation of solid substances from a viscous mass a continuous centrifugation process can be considered a general my state of the art are classified and contains no information on the solution of the reprocessing problems arising from packaging waste.

For cleaning a plasticized plastic mass of the impurities in it are in usually filter devices in use, as they do in the processing of freshly-made plastics be set. Even fresh factory-made plastic granules sometimes holds foreign matter particles. Such foreign matter particles can be used when processing the fresh from the factory Plastic granules for malfunctions or for quality impairment tion or lead to committee parts.

There are different ways of catching such foreign substances Filter devices become known. For example with the help of a sieve arranged in the melt stream is not yet fluidized plastic granules or Foreign matter particles are filtered out. It sits down the strainer over time due to the stuck in it Foreign particles too, so that it is either replaced or e.g. B. must be cleaned by reversing the flow. In a other filter device continuously pass through fende sieves for use.  

Filter devices similar to those used in processing processing of brand new plastic granules facilities are also used for cleaning the Plastic melting from plasticized plastic waste, from appropriately pre-sorted and washed art waste was obtained, used. It did however, showed that the degree of contamination of the plastic melt, usually with at least 5% dirt content lies in the recycling mass, is too high, so that the filter clog too quickly. That is why it has already been tried Sieves in such filter devices through lamella packets to replace, on the inlet side of the impurities should then be removed mechanically to become. However, these plate packs are also for unsuitable for continuous operation. Especially the silicate ones Impurities are both for the slats and for the Scraper on the inlet side, which is used for mechanical ent distance of the deposited impurities is necessary hard. The lamellae or the scraper can be mecha African abrasion can be destroyed.

The known filter devices also have the disadvantage that they only up to silicate impurities can filter out to a certain degree from that Size of the silicate contaminants depends. Furthermore ren are these known filter devices also for this reason not suitable for cleaning plastics because of art Substantial waste of paper or paper Cardboard are contaminated. In particular there is packaging usually made of plastic, cardboard or paper is combined or connected. For example, exist so-called composite packaging, such as. B. the known TetraPak container for liquid food from one Combination of plastic with printed cardboard and part wise with aluminum foil.  

From the above explanations it is clear that both organic contaminants such as B. textile fibers, paper, Cardboard, cellulose and food residues as well as inorganic cal impurities z. B. silicate substances as in for example dirt, earth, lime, fillers or sand, or metallic materials such as aluminum foil or metal chips known filter devices are not satisfactory the plastic waste can be removed so that this be recycled in a way that conserves resources can.

It is also known that using the filters partly cleaned plastic waste contaminated by other substances such as paints or varnishes are, so that they too only for reprocessing are conditionally suitable. This is because some art dyed fabrics or printed plastic products are. As a result of the coloring, such plastics contain low-boiling substances that can be reprocessed processing as part of recycling in the form of gas bubbles annoying.

It is therefore often advisable to prepare plastic waste reprocessing in addition to the removal of Verunreini to degas. The removal of low-boiling Substances or volatile components made of plastic melt by degassing usually happens in one separate process step. There are also systems for this known, such as screw kneader, by the plastic producing industry can be used. in the Melt state of the plastics is in a degassing housing with degassing dome by evacuating a pressure drop generated. This causes that in the degassing zone Low boilers or volatile components in art Molten material intensifies forming gas bubbles in the direction of the pressure gradient and migrate to the melt surface burst open, from where they can then be suctioned off.  

With the previously explained Filter devices is a degassing of the plastic melt ze, which was obtained from the plastic waste, currently not possible.

The object of the invention is therefore a method of to create with the plastic melt that from appropriately processed Plastic waste was obtained, of which there are the impurities, including where appropriate Paper or the like can be exempted in a rational manner can.

This task is solved by the Features of claim 1.

Surprisingly, it has been shown that the specific lighter impurities with a lower bulk density,  such as shredded paper or cardboard, and the heavier impurities, such as silicate dirt or metal chips, in one Process step by centrifuging out the verun cleaned plastic melt can be separated. This finding contradicts the experience of the expert, that both components, i.e. impurities with less Density and heavy impurities are not at the same time can be centrifuged out of a plastic melt.

So far, the skilled person considered that contaminated, viscous se plastic melting only with the help of, for example Sieve in appropriately trained filter devices are clean, and that taking into account the diff the dirt particles in the plastic melt as well as in view of the enormous toughness of the hochvis free plastic melt, the use of the centrifugation ver insufficient cleaning of contaminated art expected to melt. With the usual Processing temperatures is the viscosity of the Plastic melts around 1 million to 1 billion, so about 10⁶ to 10⁹ times larger than that of water.

Another reason for hindrance, already shown, is the bulk density of the impurities, which differ considerably riert. For example, the density of polyolefi around 0.9 g / cm³, the density of silicate dirt particles around 1.9 g / cm³, the density of paper around 0.7 g / cm³. Therefore, centrifuging appears Paper or cardboard excluded from a plastic melt sen. In fact, the plastic melt seems despite their high viscosity below that of the centrifuge gas forces generated considerable pressure between to penetrate the fibers of paper or the like so that Instead of the bulk density, the material density increases Wear comes in the case of cellulose at around 1.4 g / cm³ lies.  

All solid impurities are also under different bulk densities due to the centrifugal force in the Plastic melt in the direction of the Zen line of action centrifugal force driven radially outwards. There they can eliminated impurities either continue immediately radial using the existing centrifugal force be removed or by an appropriate design the centrifuge can turn the centrifugal force into a radial and an axial component will split, so that the eliminated impurities using the axial Force component can be separated, so that inside cleaned plastic melt back remains.

By removing the impurities together can the cleaning method according to the invention if possible be kept simple since the secluded Verunreini not occur in different areas and therefore not ent with the help of several laxative procedures must be removed. A discharge device for the abge separated contaminants can be kept simple and thus helps to reduce the costs of the procedure. This also reduces the number of items to be regulated Process sizes.

On the elaborate and expensive washing of the whole Melted plastic waste can be obtained from plastic chips may be waived. This has the advantage that a further reduction in the cost of cleaning the Plastic waste is achievable and water consumption can be significantly reduced. In addition, the Dispensing with the washing process, an elaborate clarification of the otherwise there is no waste water. A drying of the Plastic chips before their pastification is at Ver no washing required.  

The plastic melt is continuously through Zen centrifugation freed of impurities, so allowed this is advantageous for an uninterrupted cleaning process. The method of centrifuging can thus advantageously be used the coarse process, which also runs continuously Pre-sorting, washing and other processes steps to obtain a plastic melt from art waste, can be arranged directly, so that no interim Storage of the plastic prepared for cleaning melt is necessary. In addition, there is the possibility speed, behind the process step of cleaning the verun cleaned plastic melt with the help of continuous Centrifugation process, the cleaned plastic melt directly the further procedural steps of a reprocessing processing, which usually also takes place continuously, feed. Overall, this can significantly energy be saved since the plastic waste only once Melt needs to be warmed and repeated warming the plastic melt, which is the result of a discount necessary intermediate storage possible chilled, can advantageously be omitted.

According to claim 2, the zen during centrifugation centrifugal acceleration more than 50 times the earth's acceleration. So the accelerating force on the Contamination in the plastic melt so large that these due to the high viscosity of the plastic melt large retention forces of the plastic melt can overcome and the impurities radially after move outside through the plastic melt.

Is according to claim 3 when centrifuging the Zen centrifugal acceleration at least 500 times the earth's acceleration, preferably at least 1000 times that Acceleration due to gravity is enough for the centrifuge achieved gas force out to melt the plastic into the intermediate to let spaces of paper or cardboard fibers penetrate. Consequently  can replace the bulk density of paper or cardboard respective material density come into play, so that also Contaminants such as paper or cardboard radially outwards through the plastic melt can be separated. The higher the centrifugal acceleration, the greater the centrifugal force, which the plastic melt into the fiber interstices from drives even firmer materials, such as heavy Cardboards whose bulk density is still lower than that of Plastic melt, so that these heavy cardboards are removed can be separated.

The plastic melt can at the same time according to claim 4 be degassed. With the advantageous summary the process steps cleaning and degassing in a ver driving step during centrifugation can add che devices for performing the step degassing largely eliminated. This also helps reduce the cost of the procedure. In addition, the Degassing the plastic melt occurring gases, at sucked off, for example, using a pressure gradient. On the one hand, this advantageously achieves that gases or low-boiling substances through the adjacent sub pressure significantly faster gas bubbles in the plastic train melt. As a result of these gas bubbles Vacuum easier to the surface of the plastic melt get where they burst and the low boiling sub punch in the form of gases that are then extracted can be. On the other hand, it is guaranteed that all gases generated during centrifuging cleaning the plastic melt will definitely be sucked out what the passive security of the procedure increases if below the resulting gases are flammable or toxic gases should.

Because the viscosity of the plastic melt from the tempe depends on the temperature of the plastic melt and depending on the processing  temperature can fluctuate by up to a factor of 1000 the plastic melt according to claim 5 during the centri fugierens added or withdrawn heat. Doing so will partially achieved that a desired viscosity of the Plastic melt can be adhered to at any time.

With the help of a conveyor according to claim 6 the impurities separated from the plastic melt Advantages along the inner wall of the centrifuge preferably against the direction of flow of the Vermrei Additions liberated melt towards Verunreini be removed. Doing so pushes the conveyor, which is preferably a belt screw is, the contaminants are continuously ahead. There the band auger preferably in the radial direction Width, which is about an expected layer corresponds to the thickness of the separated impurities, however, none radially inside in the center of the slug has continuous surfaces, but z. B. only the forehead sides of webs or similar devices for connecting that the helix of the belt screw with the drive axis can the cleaned plastic melt inside for free Flow plastic discharge device.

If the ribbon screw according to claim 7 with a clot angular velocity difference to the centrifuge in the rotated in the same direction, can advantageously be inevitable bare signs of abrasion and wear caused by the sili cat or metallic impurities in art melt away, be reduced to a minimum, since only due to the small angular velocity difference very low frictional forces between the slug and the excreted impurities or between the Zen trifuge and the impurities occur. Is further this enables a very high speed of the centrifuge causes a correspondingly large centrifugal acceleration,  thus also impurities such as paper or cardboard radially can be separated outwards.

According to claim 8, the contaminated plastic melt when they are subjected to a shear stress subject. This allows the viscosity of the highly viscous Plastic melt are advantageously significantly reduced, which improves the removal of impurities can be.

According to claim 9, the cleaned and degassed Plastic melt fed to a processing plant will. The still warm plasticized plastic melt can directly to new plastic granulate, for example or processed into finished plastic products the, with no interruptions and no inter Storage of the plastic melt with unnecessary cooling and energy-consuming reheating of the plastic melt is required.

In terms of device technology, the task Features of claim 10 solved.

Accordingly, an inventive device for Clean art contaminated with paper if necessary a separation unit melts, which is about an art material feed device, a plastic melt discharge direction and has a pollution removal device, wherein the separation unit has a solid bowl centrifuge. This has the great advantage that there are no constantly constipating Strainers have to be used which have to be cleaned continuously are, as is the case with known filter devices is. This allows the maintenance of a front according to the invention Direction for cleaning may be blurred with paper plastic melt can be drastically simplified, whereby the costly replacement of the screens ent ent can fall.  

Furthermore, the wear and tear can be contaminated with the plastic melt in direct contact due to the sanding force of the silicate or metallic contamination from use a centrifuge can be significantly reduced since there are none standing surfaces hinder the plastic melt flow and generate frictional forces that cause wear gene.

With the help of a belt screw, the excreted Contaminants according to claim 11 advantageously independent on the direction of flow of the cleaned plastic melt ze along the inner wall of the centrifuge to avoid contamination guide device are promoted. The centrifu Galkraft completely as a cleaning radially directed force can be used without splitting into one additional axial component would be required because the axia le force to remove the excreted impurities gene is applied by the slug.

If the relative speed between the Belt screw and the centrifuge kept low, it is advantageously possible, the resulting small groove phenomena due to the frictional forces between the Band auger and the separated impurities or between the centrifuge and the separated verunreini to keep small. A slow promotion of the out various impurities continue to ensure that no backmixing with the cleaned plastic melt can occur. The adjustability of the angular speed keits-difference according to claim 12 allows the rotation speed of the belt screw regardless of the rotation speed of the centrifuge for the respective degree Impurities and the respective composition of the Contamination and the consistency of the plastic melt ze to adjust.  

According to claim 13 is for applying a shear force a shear element on the inflowing plastic melt provided, for example, via a gap-forming, stationary or slower rotating, towards the centrifuge inner wall geometrically similar counter surface. By the up applying a shear force to the contaminated plastic melt between two differently due to shear Fast moving surfaces can affect the viscosity of the plastic melt can be advantageously reduced. This improves that subsequent separation of the impurities.

According to claim 14, the distance of the shear element be adjusted to the inner wall of the centrifuge. That’s it possible to control the shear force over the gap distance lieren. The shear force acting on the plastic melt can be increased or decreased as needed.

According to claim 15, a gas extraction device opens into the inside of the centrifuge. By evaporation of low gases and other boiling substances through the cleaning of the plastic melt Gases can thus advantageously from the interior of the Zentri be sucked off.

According to claim 16, the plastic melt film flows into a ring-shaped pocket in which the secluded Advantageously collect and concentrate contaminants first can before they emerge through an annular gap can. The centrifuge is preferably overcri table speed can be driven. This means that the centri join at a speed above the resonance speed rotates, which largely prevents unavoidable unrest can be minimized as these are over critical Speed of increasing rotational speed decrease again men.  

The annular pocket is essentially according to claim 17 lichen by an upper edge, a lower edge and formed a gap. This allows a relatively simple one and inexpensive construction of the annular pocket, in whose radial outer area is the deposited Ver Accumulate contaminants in front of the gap during the mess plastic melt in the radially inner area over the collected contaminants can flow away.

According to claim 18, the gap of the annular pocket in an open position and a final position on leadership bar, which makes it possible to open the gap only when the ring-shaped pocket with separated contaminants conditions is largely filled, so that on the one hand un wished losses of carried out cleaned To prevent plastic melt and on the other hand a Kon center the separated impurities in the ring shaped bag.

Is the gap of the annular pocket according to claim 19 trained by at least one elastic hollow chamber profile det can advantageously open and close the gap due to an increase or decrease in pressure in the hollow chamber profile. This offers an advantageously simple Possibility of self-regulation of opening and closing of the gap because of a certain closing pressure in the cavity a minimum back pressure of accumulated impurities must oppose such that they then flow away can.

The subclaims 20 to 25 have advantageous further Formations of the device according to the invention for content.

The Erfin is followed by some Exemplary embodiments explained with reference to the drawing.  

It shows:

Fig. 1 shows a first embodiment of an inventive device for cleaning viscous plastic melts in axial section;

Fig. 2 shows an exemplary plant from the plastifi cation of the contaminated plastic waste in an extruder to a pulsation-free conveyance of the cleaned melt to a reprocessing plant;

Fig. 3 shows a detail "A" of Figure 1 in an enlarged view.

FIG. 4 shows the detail "A" of Figure 1 in an enlarged representation, but with changes of a second embodiment.

Figure 5 shows a section through the ring pocket of a third embodiment with only one hollow chamber profile.

Figure 6 shows a section through the ring pocket of a fourth embodiment with two hollow chamber profiles.

Fig. 7 shows a cross section through a fifth exporting approximate shape of a centrifuge according to the invention with a band screw;

FIG. 8 shows a detail "A" from FIG. 7 in an enlarged representation; and

Fig. 9 is a schematically simplified cross section through a sixth embodiment of a cylindrical centrifuge according to the invention with a belt screw.

In the embodiment shown in Fig. 1, a rotating conical centrifuge 1 are on a lower base of a Kegelman means 2 of the conical centrifuge 1 an annular pocket 4 , which has the shape of a lying V with a blunted open end 6 and two flanks 8 and 10th The width of the open gap-shaped end 6 can be adjusted by an adjustable ring 12 or the gap can be opened or closed by the ring 12 . The flanks 8 and 10 of the ring-shaped pocket 4 are connected to one another by webs 14 distributed over the circumference, which are curved forward or backward, for example, in the shape of a centrifugal pump.

The cone-shaped centrifuge 1 , the cone jacket 2 and the annular pocket 4 can be driven, for example, with a motor, not shown, optionally with the interposition of a gear, preferably at a critical speed. In bearings 16 , the conical centrifuge 1 is rotatable about its vertical axis of rotation and horizontally immovable.

A shear element 18 of similar geometry, preferably a cone 18, is arranged in the tip of the cone shell 2 or the inner wall of the centrifuge at an adjustable distance from the cone shell 2 . The cone 18 has a through hole in the middle and is arranged on a plastic melt feed device 20 , preferably on a plastic melt feed tube 20 , through which contaminated plastic melt 202 is fed to the centrifuge 1 .

The lower flank 10 of the annular pocket 4 has an overflow edge 22 towards the centrifuge center axis. From there, the overflowing, cleaned and, if necessary, degassed plastic melt is collected by a collecting container 24 , which is arranged below the annular pocket 4 . A plastic melt discharge device 26 is arranged on the collecting container 24 , for example a collecting pipe 26 , through which the cleaned plastic melt 206 can flow off. A suction device 28 , for example a suction pipe 28 , opens through the collecting container 24 into the conical centrifuge 1 . The end of the suction pipe 28 is covered, for example, by a hood 30 which is arranged on the suction pipe 28 . Through the suction pipe 28 gases 208 flow to a vacuum pump, not shown in this illustration.

The contaminants 204 flowing out of the gap 6 are guided away by a contaminant removal device which is formed, for example, by ring caps 32 , 34 and a collecting trough 36 .

A heat source 38 is arranged at a distance from the conical centrifuge 1 , which can be arranged around the conical centrifuge 1 , for example in the form of an electric heating element or a liquid-filled heating coil. Furthermore, 12 cooling or heating elements 50 are arranged at a distance from the annular pocket 4 and the adjustable ring 12 , for example in the form of cooling or Heizroh ren, through which a cooling or heating medium can flow.

In order to facilitate understanding, the following Course of the description of the figures same reference numerals for used identical or corresponding items.

In Fig. 2 an advantageous embodiment of an overall system for cleaning contaminated plastic melt and their further processing is shown. The plastic waste collected is plasticized in an extruder 62 . The plasticized plastic melt 202 is then conveyed into the centrifuge 1 by the extruder 62 .

The cleaned and possibly degassed plastic melt 206 flows from the collecting container 24 through the plastic discharge device 26 to a gear pump 64 which, for example in a preferred embodiment, can also meter highly viscous plastic melts from a system under negative pressure when the pump is completely full and deliver it without pulsation. The cleaned plastic melt 206 is conveyed by the gear pump 64 to a further processing system, not shown. A vacuum pump 66 sucks the released gases 208 out of the centrifuge 1 . With the help of a motor 60 , the centrifuge 1 can be rotated.

Fig. 3 shows a section "A" of Fig. 1 in an enlarged view. The V-shaped annular pocket 4 is formed by the upper flank 8 and the lower flank 10 and ends in the width-adjustable gap 6 . The width is adjusted by the adjustable ring 12 . From the gap 6 radially outward, the ring covers 32, 34 are arranged, wherein the annular hood 32 is disposed further from the center of the centrifuge 1 away than the annular dome 34th Both ring caps 32 , 34 together form an annular drain channel for the contaminants 204 flowing out of the gap 6 . The heating or cooling coil 50 serves to temper the annular gap 6 . On the lower flank 10 , an annular nose 40 is arranged, the joint for low-friction sealing of the conical Zentri fugge 1 against the environment in an annular groove 42 into which, for example, a liquid boiling at room temperature such as a fluid plastic 52 such as. B. silicone oil is filled as a sealing medium.

Fig. 4 shows the section "A" of Fig. 1 in a modified embodiment. In this embodiment, the lower flank 10 of the annular pocket 4 has a separating device which is formed, for example, by an annular slot 70 and an overflow edge 72 . Through the annular slot 70 flows a portion of the cleaned plastic melt while on the angled overflow edge 72, a further part of the gerei-adjusted molten plastic material flows, which has a lower density than those that can flow through the annular slot 70th

Fig. 5 shows the annular pocket 4 and part of the cone shell 2 of another exemplary embodiment. The annular pocket 4 is formed by the two flanks 8 and 10 , which together form an outwardly open, truncated V lying. At the radially outer end of the flank 8 there is a hollow chamber profile 88 made of, for example, an elastic material that is resistant to approximately 200 ° C., such as rubber, PUR or silicone rubber, with a support 84 . The hollow chamber profile 88 forms with a counterpart 92 , which is protected with a material 94, for example, resilient up to about 200 ° C., an annular gap with flanges which are connected to the flanks 8 , 10 of the annular pocket 4 .

Fig. 6 shows the annular pocket 4 and part of the cone shell 2 of another exemplary embodiment. At the radially outer ends of the flanks 8 and 10 , hollow chamber profiles 88 , 90 are made of, for example, elastic material up to approximately 200 ° C., such as rubber, PUR or silicone rubber, each with a support 84 , 86 . With their supports 84 , 86, the hollow chamber profiles 88 , 90 form an annular gap with flanges which are connected to the flanks 8 , 10 of the annular pocket 4 .

FIG. 7 shows a further exemplary embodiment of a conical centrifuge 1 in axial section with a belt screw 110 . The centrifuge 1 has a cone shell region 109 , the cone angle of which is steeper than that of a cone shell region 109 a. The band auger 110 is arranged in the conical jacket region 109 . The band 131 of the worm 110 is connected to a drive shaft 112 by webs 111 . The drive of the drive shaft 112 can take place, for example, with the aid of a pulley 113 . The drive shaft 112 has a longitudinal channel 114 in its center in the direction of its longitudinal axis with an outlet 115 through which the contaminated plastic melt 202 can reach the interior of the centrifuge 1 , for example under pressure. The outlet 115 is in this exemplary embodiment above the lower end of the band screw 110th The contaminated plastic melt 202 is continuously fed to the centrifuge 1, for example via the rotatably sealed connecting device 132, to the longitudinal channel 114 .

As a result of the continuous supply of the contaminated plastic melt 202 , a plastic melt film forms on the centrifuge wall 109 . The impurities in the plastic melt are pressed radially outward against the centrifuge wall 109 by the centrifugal force. From there, the separated impurities are conveyed to a passage 116 against the flow direction of the plastic melt film by means of the rotating belt screw 110 . Through a throttle 117 and / or a conveyor screw 118 , the amount of impurities discharged can be regulated. Via a disk 119 arranged on the drive shaft, the separated contaminants 204 enter a collecting device 120 and from there via a dirt removal device (not shown in more detail) to a collecting container.

The passage 116 is followed by an outlet pipe 121 for the separated contaminants 204 , which carries the cone jacket 109 and is rotatably mounted in the bearings 122 , 123 about its axis of rotation. The centrifuge 1 can thus be driven, for example, via a pulley 124 which is arranged on the outlet pipe 121 . The drive shaft 112 of the belt screw 110 is rotatably supported in the bearings 125 , 126 about its axis of rotation, which are located above and below the centrifuge 1 .

In order to accelerate the degassing of the plastic melt, the resulting gas 208 can be sucked out of the interior of the centrifuge 1 via a pipe 128 with the aid of a negative pressure. A cover 129 of the centrifuge 1 is connected to a collecting vessel 127 . A seal 130 is located between the collecting vessel 127 and the conical jacket 109 a. The seal 130 prevents pressure equalization between the interior of the centrifuge 1 and the surroundings. By means of a discharge device 210 , cleaned and possibly degassed plastic melt 206 accumulated in the collecting vessel 127 can be fed to a reprocessing system (not shown in any more detail).

In Fig. 8, a section "A" of Fig. 7 is shown enlarged. The band worm 110 is cut and shows the band 131 and a section of the cone shell 109 on the inside of which the band 131 of the band worm 110 passes. The pitch of the belt screw 110 is generally constant, but can also advantageously be carried out progressively.

FIG. 9 shows a schematically simplified cross section of a further exemplary embodiment of a cylindrical centrifuge 1 with a belt screw 110 similar to the centrifuge 1 shown in FIG. 7. It is clear that the centrifuge 1 can in principle be oriented anywhere in space to carry out the centrifugation process. For constructional reasons or for the purpose of easier handling, the centrifuge 1 can be oriented, for example, vertically, as shown in FIG. 1 or in FIG. 7, or horizontally in space. In order to facilitate understanding, the same reference symbols are used for identical or corresponding objects. The centrifuge jacket 2 can be rotated horizontally and axially immovably with the aid of bearings 220 , 222 and can be driven, for example, via a pulley 228 . The belt screw 110 is arranged, for example, on webs 111 on a partially hollow shaft 232 . The partially hollow shaft 232 is supported by bearings 224 , 226 horizontally rotatable and axially immovable and, for example, driven by a further pulley 230 with the same rotation as the centrifuge jacket 2 . The plastic melt feed device 20 feeds the contaminated plastic melt 202 to the centrifuge 1 , for example under pressure. With the aid of a shear element and not shown in detail a geome symmetrical similarly shaped counter-surface is not shown in the course of feeding a shearing force can be exercised on the plastic melt 202. The belt screw 110 conveys the impurities separated by the centrifugal forces to the outside along the centrifuge jacket 2 to an impurity supply removal device 236 , through which the separated impurities 204 can be conveyed out of the centrifuge 1 . In this embodiment, the band 131 of the band worm 110 is connected to the shaft 232 via webs 111 . The cleaned and possibly degassed plastic melt 206 flows along the shaft 232 past the webs 111 via an overflow edge 234 , which is arranged radially inward at the end of the cylinder jacket 2 in the area of the plastic melt discharge, through the plastic melt discharge device 238 to a further processing system, not shown. This Wei processing system can for example be a blown film plant or a plant for the production of plastic granules. The direction of conveyance of the cleaned plastic melt 206 or the separated impurities 204 can also be reversed, for example. Further, for example, a Separierungsvor direction, not shown, can be used to separate melt components of different weights. The gas evacuation device 28 can be used to extract gas 208, for example, by means of negative pressure.

attempt

To demonstrate the simultaneous separation of Sand and shredded paper from a model liquid were meh More experiments carried out.

A continuous centrifuge was found for the experiments with a drum shell diameter of 250 mm and a screw length of 300 mm with 13 gears Use.

The model liquid was made using the centrifuge fed to a piston pump. The model fluid itself consisted of a polyglycol that was just pumpable. The polyglycol P41 / 12000, type GUS-040670 is manufactured by BASF plant in Gendorf.

To simulate the contamination was considered dirt Enrich the polyglycol with 5% by weight fine sand an average size less than 0.1 mm and 1 Weight% shredded paper with an average Cutlet size of approx. 10 × 20 mm added.

The speed of the centrifuge jacket was during the Try 3260 rpm. The resulting centrifugal acceleration is approximately 900 times that of Earth acceleration. The speed of the belt screw within the Centrifuge jacket was 3263 1 / min. This results in a differential speed of 3 1 / min.

Through the contamination removal device of the centri The separated paper came out and fisted  Mix with the sand particles through glycol residues as spit fabric made of.

In another experiment, one was collected Plastic waste obtained by extruding plastifi adorned plastic melt in additional impurities Form of earth or dirt added. This contaminated Plastic melt was working discontinuously fed to the centrifuge and then centrifuged. The elimination of impurities could Centrifugation can also be confirmed.

Claims (25)

1. Process for cleaning contaminated, if necessary also paper-containing, viscous plastic melts, at which the contaminated plastic melt in a full jacket centrifuge a continuous centrifuge is subjected to the process, the impurities, possibly different bulk densities, through which Centrifugal force in the plastic melt layer in Direction of the line of action of the centrifugal force radially driven outwards, abge from the plastic melt divorced and discharged separately. 2. The method according to claim 1, characterized in that centrifugal acceleration more when centrifuging than 50 times the acceleration due to gravity. 3. The method according to claim 1 or 2, characterized net that the centrifugal acceleration more than 500 times the acceleration due to gravity preferably more than 1000 times the acceleration due to gravity is. 4. The method according to any one of claims 1 to 3, characterized ge indicates that the plastic melt during the Centrifuging is degassed, and that when degassing the gases escaping from the plastic melt are sucked off the. 5. The method according to any one of claims 1 to 4, characterized ge indicates that the plastic melt during the Centrifuging heat is supplied or withdrawn. 6. The method according to any one of claims 1 to 5, characterized ge indicates that the deposited impurities using a conveyor, preferably one  Belt screw, along the inner wall of the centrifuge, in front preferably against the flow direction of the cleaned Plastic melt, are transported away. 7. The method according to claim 6, characterized in that the band auger with a low angular velocity difference to the centrifuge is rotated. 8. The method according to any one of claims 1 to 7, characterized ge indicates that the plastic melt in the course of their Feeding is subjected to a shear stress. 9. The method according to any one of claims 1 to 8, characterized ge indicates that the cleaned and, if necessary degassed plastic melt under pressure increase one Processing system is fed. 10. Apparatus for cleaning, possibly contaminated with paper, viscous plastic melts ( 202 ) with a separating unit, which has at least one plastic melt feed device ( 20 , 112 ), a discharge device ( 26 , 127 , 238 ) for the cleaned plastic melt and has a contamination removal device ( 4 , 36 , 120 , 236 ), characterized in that the separating unit has a full-jacket centrifuge ( 1 ). 11. The device according to claim 10, characterized in that in the centrifuge ( 1 ) is a band screw ( 110 ) is arranged, which the ge by the centrifugal forces against the centrifuge inner wall ( 200 ) pressed impurities preferably against the flow direction of the cleaned plastic melt ( 206 ) to the pollution removal device ( 4 , 36 , 120 , 236 ) promotes. 12. The apparatus according to claim 11, characterized in that the relative speed between the centrifuge gene jacket ( 2 , 109 , 109 a) and the belt screw ( 110 ) is adjustable to different values. 13. The device according to one of claims 10 to 12, characterized in that in the region of the plastic melt feed ( 20 ) into the centrifuge ( 1 ) concentrically to the Zen trifuge inner wall ( 2 , 200 ) a shear element ( 18 ) is easily seen. 14. The apparatus according to claim 13, characterized in that the distance of the shear element ( 18 ) to the centrifuge inner wall ( 2 , 200 ) is adjustable. 15. Device according to one of claims 10 to 14, characterized in that in the interior of the centrifuge ( 1 ) opens a gas extraction device ( 28 ). 16. The device according to one of claims 10 to 15, characterized in that the centrifuge ( 1 ) is conical, and at its base an annular, radially outwardly directed pocket ( 4 ) for receiving the separated impurities ( 204 ) , which can preferably be driven at supercritical speed. 17. The apparatus according to claim 16, characterized in that the annular pocket ( 4 ) via an upper flank ( 8 ), a lower flank ( 10 ), and a gap ( 6. 10 ) formed at the radially outer end of the two flanks ( 8 , 10 ) ) has. 18. The apparatus according to claim 17, characterized in that the gap ( 6 ) can be transferred into an open position and from a closed position. 19. The apparatus of claim 17 or 18, characterized in that the gap ( 6 ) is formed by at least one ela-elastic hollow chamber profile ( 84 , 86 ). 20. Device according to one of claims 17 to 19, characterized in that the upper and lower flanks ( 8 , 10 ) of the annular pocket ( 4 ) by circularly pumping mig forward or reverse curved webs ( 14 ) are connected to each other. 21. Device according to one of claims 17 to 20, characterized in that the annular pocket ( 4 ) in cross section has the shape of a lying truncated "V". 22. Device according to one of claims 16 to 21, characterized in that the cone-shaped centrifuge ( 1 ) with its tip points upwards, below the ro-based base of the centrifuge ( 1 ), a collecting container ( 24 ) for receiving the cleaned and optionally degassed plastic melt ( 206 ) is arranged. 23. The device according to one of claims 16 to 22, characterized in that for the removal of the separated Ver impurities ( 204 ) at least one adjoining the gap ( 6 ) annular channel ( 32 , 34 ) is provided, which leads to at least one collecting channel ( 36 ) leads. 24. Device according to one of claims 16 to 23, characterized in that the conical centrifuge ( 1 ) for sealing has a circumferential nose ( 40 ) which projects into an annular groove ( 42 ), in which as a sealing medium preferably one at room temperature low boiling liquid, for example a fluid plastic ( 52 ) is filled. 25. Device according to one of claims 10 to 24, characterized in that a pump, in particular a gear pump ( 64 ) is provided for supplying the cleaned and optionally degassed plastic melt ( 206 ) to a further processing system.