DE102016015199A1 - Solvent and method for dissolving at least two plastics from a solid within a suspension - Google Patents

Abstract

The invention relates to a solvent (L) for dissolving at least two plastics (K1, K2) located in and / or on a solid (F) within a suspension (S), in particular waste suspension. According to the invention this is designed so that its solvent effect on the plastics (K1, K2) is temperature-dependent. As a result, a first plastic (K1) is detachable at a first dissolution temperature (T1) of the solvent (L) and a second plastic (K2) at a second dissolution temperature (T2) of the solvent (L). The invention also relates to a method for dissolving at least two plastics (K1, K2) in and / or on a solid (F) within a suspension (S), such as waste suspension, by means of a solvent (L). According to the invention, the suspension (16) is heated in several stages to different dissolution temperatures (T1, T2), wherein in a first stage at a first dissolution temperature (T1) a first plastic (K1) is released and in a second stage at a second Dissolve temperature (T2) a second plastic (K2) is released. Furthermore, the invention relates to a use of the solvent (L) in a waste separation plant (1) and a method for assembling a solvent (L).

Description

Field of the invention

The invention relates to a solvent for dissolving at least two plastics in and / or on a solid within a suspension, in particular waste suspension, with the features in the preamble of claim 1. Furthermore, the invention relates to a method for releasing at least two in and / or at one Solids contained plastics within a suspension, such as waste suspension, with a solvent according to the features of claim 2.

Technological background

In the industrialized nations in particular, national and cross-border trade in goods requires an increasingly sustainable raw materials industry. In order to keep the amount of waste ultimately to be disposed of as low as possible, goods and goods supplied to the commodity cycle should therefore be increasingly recycled at the end of their life cycle. This requires an at least rough pre-sorting in order to be able to supply the actually recyclable fractions to a suitable recycling process.

Already established options, such as the direct disposal of recyclable materials at established collection points (recycling centers), are supplemented, for example, in Germany by household-related collection and disposal of domestic pre-sorted waste (waste separation). The basis for this is the so-called "dual system", in which special components - such as those made of paper and / or plastic - recorded separately by the consumer and separated from the rest of the waste are made available to the municipal waste company for collection. This can be done, for example, through specially set up for outdoor containers or provided by the individual household bags.

On the one hand, the at least roughly sorted waste on the other hand contrasts with the targeted separation and processing of the valuable substances contained therein. In particular, such parts represent particular challenges, which have one or more compounds of different materials. Usually, the waste to be recycled is supplied to a first coarse fragmentation in order to allow the simplest possible handling and in particular effective processing in waste separation plants. Based on the type of waste, the shredder granules then present surface and / or on the other hand spatial structures, so that between so-called 2D (area) and corresponding 3D materials (spatial) is distinguished.

Using the example of sales packaging, the waste to be processed can be, for example, foil bags or beverage cartons, the latter of which are generally also known by the generic name "Tetra Pak®". Such packages have a multi-layer composite construction, which comprise, for example, individual layers of paper and / or aluminum and plastic. Due to their essentially flat form as shredder granules, such packages are considered 2D materials. In contrast, for example, recyclable devices such as computer keyboards and screens or automotive parts such as panels and dashboards already due to their still existing after mechanical crushing volume of the 3D materials belonging.

Regardless of the type of waste to be processed, at the end of the process the separation and recovery of the recyclable constituents from material compounds that are as low in contaminants as possible or as separate as possible is necessary in order to reuse them in terms of material recycling. In the prior art, methods are known which are based on the heating of composites containing waste. As a result, in particular the thermoplastic materials contained therein are separable from the other components by these melted and the remaining impurities contained in the plastic melt are screened out by suitable filter means. The plastics are often monolayer or multilayer films of polyamide (PA) and / or polyethylene (PE) and / or polypropylene (PP).

Purely thermally operating recycling processes are already reaching their limits with regard to a preferably selective separation of, for example, multilayer composite construction of different plastics. This is mainly due to the sometimes close melting points of individual plastics. Since the present local temperatures are difficult to control during treatment, especially in large-scale plants, it can not be ruled out that the separated plastic is composed of two or more different types of plastic.

Alternative methods for separating and dissolving plastics therefore rely on the use of solvents:

From the DE 43 43 784 A1 For this purpose, a device and a method is known which the Use of a solvent in the form of formic acid suggests. The solvent is intended to selectively remove waste polyamide (PA) from it. For this purpose, the waste is transferred to a movable screening drum, which is arranged rotatably in a container filled with the solvent. Within the screen drum arranged strips act mechanically on the waste in order to achieve an improved separation of individual components. The container is connected to a line system, so that the solvent can be circulated by means of a pump. The separation of the remaining components is carried out by filters, decanters or centrifuges, wherein the dissolved polyamide (PA) is precipitated by a suitable precipitant such as water. The subsequent separation of the consisting of the formic acid and the precipitant filtrate is finally carried out by distillation, adsorptive or by crystallization. The polyamide powder thus obtained can then be dried and reprocessed, for example, into technical fibers or regrind.

The procedure of DE 43 43 784 A1 is characterized in particular by moderate temperatures of 0 ° to 60 ° C, resulting in processing under normal atmospheric pressure conditions (without pressure) results. It is specifically aimed at the separation of polyamide (PA).

The DE 10 2005 026 451 A1 describes a process for recycling plastics, which also uses a solvent. The process is used for the recycling of any plastics, in particular plastics from electronic scrap processing and shredder light fractions. The plastics to be recycled contain at least two polystyrene (PS) based polymers, copolymers or blends thereof, which are mixed with the solvent for this purpose. The amount of solvent is kept as low as possible in order to avoid large volumes of solvent. After the plastics have gone into solution, they are subsequently precipitated by adding a suitable precipitant, so that then - due to the small amount of solvent - gel-like precipitate can be separated from the other components of the plastic.

The disclosed method provides for dissolving the plastics under mild temperatures, which are preferably below 100 ° C. Only the subsequent precipitation of the dissolved polymers in the solvent is carried out at temperatures up to 170 ° C, preferably at temperatures up to 100 ° C and more preferably in the temperature range from room temperature (20 ° C) to 50 ° C. By choosing different precipitating agents, the previously dissolved plastics can be selectively precipitated.

With the previously known methods and devices carrying out the standing in particular of the environmental protection recycling of valuable materials is feasible. Solvents used here have the advantage over pure heating that the respective plastic components can be dissolved out as completely as possible from the waste to be treated. However, centrifugal separators with centrifuges are sometimes not always suitable for separating all solids from the viscous melts then present. This applies in particular to those solids having a lower density than the respective emulsion or solution, such as cork, for example. In addition, such systems require a sometimes long period of time to heat the plastic to be separated to its softening temperature. It can not be ruled out that the waste contains further constituents with a plastic material to be dissolved below or at the same softening temperature, so that targeted separation of quasi-pure plastic or, for example, pure polyethylene (PE) or polyamide (PA) is difficult or even impossible. Due to the impurities and / or plastic mixtures contained then far more measures are necessary to ensure adequate separation of the substances to be recycled.

The advantageous use of solvents offers the possibility of separating and dissolving one or more plastics simultaneously. In the latter case, the selective recovery of the respective target plastic from the dissolved plastics requires a targeted after-treatment of the solution, which is based on the use of different precipitants. In addition to the dependent on the number of dissolved plastics provision and disposal of different precipitants require such methods also an increased amount of time to remove in particular the precipitant used for the respective target plastic and substitute for another quasi.

Against this background, the currently known solvents and methods for carrying out the large-scale recycling of waste containing different plastics therefore continue to offer room for improvement.

Summary of the invention

On this basis, the invention is based on the object, a solvent as indicated above and a method for dissolving at least two in and / or on a solid plastics within a suspension, in particular for large-scale use in a waste separation plant, with a solvent to further develop it so that the selective extraction of plastics can be carried out more economically and ecologically.

The solution to this problem consists according to the invention in a solvent having the features of claim 1 and in a method for dissolving at least two in and / or on a solid plastics located within a suspension, such as waste suspension, with a solvent according to the features of claim 2. Further details, features and advantages of the objects of the invention will become apparent from the respective dependent claims.

The basis for this is the prior application of a suspension by initially plastic-containing solid, such as waste, at least one solvent is supplied. This can be done for example in suitable basins or containers. The at least one solvent is adjusted so that at least one plastic is separated from the solid by the plastic is at least partially in solution within the solvent.

The invention is based on a formulation for the solvent, wherein the solvent effect of which depends on the achievement of a dissolution temperature. In other words, the solvent is adjusted in such a way that its intended properties achieve their dissolving effect on the plastic only when they reach and / or in the region of a dissolving temperature of the solvent. This means that only then its solvent effect is activated or highest. According to the invention, the solvent is adjusted so that its solvent effect on different plastics is dependent on the particular release temperature achieved. In other words, the solvent according to the invention has a temperature dependence with respect to its properties in the foreground here. This is chosen so that a first plastic at a first dissolution temperature of the solvent or the suspension is solvable while releasing a further second plastic at a different from the first dissolution temperature second dissolving temperature of the solvent or the suspension is feasible.

According to this, the invention is directed to the selective dissolution of various plastics located in or on a solid, it being possible to use one and the same solvent. In this case, the remaining solids in the suspension after dissolution of the first plastic, for example, the still undissolved second plastic and / or another solid include, such as a metal or paper. The resulting advantage is the use of only a single solvent to selectively dissolve different plastics. Since the effect of the solvent on different plastics insofar depends only on the respective set release temperature, now a purely temperature-dependent selective extraction of plastics using one and the same solvent is possible.

Due to the omission of a necessary replacement of solvent otherwise acting only on a particular plastic or acting on several plastics simultaneously acting solvent results in total a very economic and ecological feasibility of a particular large-scale use for the recycling of plastics. In addition to the elimination of the exchange or the possible addition of further additives to change the effect on different plastics in solvents known in the prior art, only a change in the temperature or dissolving temperature of the solvent is necessary according to the invention to selectively dissolve at least two or more plastics , As a result, the purity of the so extractable plastics can be increased again.

A possible solvent according to the invention may for example comprise a mixture of alkanes, isooctane or cycloalkanes, such as methylcyclohexane. For example, the use of decalin is also conceivable instead of isooctane. The particular choice of ingredients is to be determined by those skilled in the art, which will choose depending on the or to be dissolved plastics, a suitable solvent or a suitable composition of solvents. For example, cycloalkanes are particularly advantageously suitable for dissolving polyethylene (PE).

A preferred goal here is to set the lowest possible boiling temperature for the solvent, resulting in an economical operation and easy detachment of the dissolved plastic from the solvent. The boiling temperature may preferably be, for example, in a range from 100.degree. C. to 140.degree. C., which can be set appropriately by the choice of a suitable solvent or in the form of a blend of two or more solvents. In principle, it is considered to be particularly advantageous if, from a range of suitable solvents, the one which has the lowest boiling temperature is selected.

Of course, the dissolution temperature of the solvent is chosen so that it is below a value for the melt of the respective plastic in order to reliably prevent any destruction of the polymers of the plastics. At the same time, the boiling temperature of the solvent can be set as low as possible, for example, it can be from 80 ° C to below 120 ° C.

Furthermore, the invention is directed to a process which serves to dissolve in and / or on a solid plastics within a suspension, such as waste suspension, with a solvent. With particular preference, the solvent to be used in this case may be the solvent according to the invention indicated above, so that the statements on this also apply correspondingly to the process according to the invention. In the present case, the method according to the invention assumes that a suspension containing the solid together with plastics in combination with the solvent is applied beforehand by converting the plastics or the solid containing the plastics into the solvent. Here at least one of the plastics within the solvent goes into solution, the solvent and the plastic dissolved therein together forming a polymer solution.

For this purpose, it is now proposed that the previously applied suspension is heated in several stages to different dissolution temperatures. In this case, multi-stage means that the same solvent is either heated to different temperatures over a particular period of time or that the same solvent is heated in structurally separate regions and thus simultaneously has mutually different temperatures. The central idea in any case is the use of one and the same solvent, of which a quantity is heated in successive stages (multi-stage) or, for example, two quantities at the same time have different temperatures in order to be used in successive stages. It is proposed that in a first stage at a first dissolution temperature, a first plastic is released. Furthermore, a second plastic is then dissolved in a second stage at a second dissolution temperature. The resulting in particular from the temperature-dependent effect of the solvent on the respective plastic advantages have been previously explained in more detail in connection with the presentation of the solvent according to the invention, so that reference is made to avoid repetition at this point to the corresponding statements.

The basic idea of the invention provides that the plastics may preferably be, for example, waste that occurs frequently, typical types. Thus, the first plastic may advantageously be polyethylene (PE), while the second plastic may be polypropylene (PP). Thereafter, the polyethylene (PE) can be dissolved at or in the range of the first dissolution temperature of the solvent used, while the polypropylene (PP) is dissolved at or in the range of the second dissolution temperature. In this way, polyethylene (PE) and polypropylene (PP) are successively dissolved in solution by selecting the appropriate dissolution temperature of the solvent.

In principle, the first dissolution temperature can be below the second dissolution temperature and vice versa. Preferably, the second dissolution temperature is above the first dissolution temperature. For example, the first plastic can be dissolved at a first dissolving temperature of 80 ° C to 110 ° C. In contrast, then the second plastic at a second dissolution temperature of, for example, 120 ° C to 180 ° C can be solved. In any case, the maximum dissolution temperature to be applied is to be aligned with the type of the respective plastic so as not to damage or even destroy its polymers at too high a temperature.

In the context of the invention, it is considered to be particularly advantageous if the respective dissolution temperatures have a sufficient temperature separation from each other. This against the background of a safe, especially large-scale use, which receives enough room for any fluctuations in the respective temperature to be respected and / or achieved. This significantly increases the process reliability. Thus, it is considered advantageous if the temperature difference between the first release temperature and the second release temperature of 10 ° K to 30 ° K. The temperature interval may preferably be from 15 ° K to 25 ° K. Particularly advantageous is a temperature interval of 20 ° K, in particular +/- 2 ° K, considered.

According to a preferred development, two devices containing the solvent can be kept available, for example in the form of suitable containers, trays or housings. In this way, the solvent in a first device may be heated to the first dissolution temperature while being heated to the second dissolution temperature in a second device. This measure is independent of whether it is in each case the same amount of solvent or two separate amounts of one and the same solvent. In other words, the solvent heated to the first dissolution temperature in the first device may, for example, be transferred to the second device to be heated therein to the second dissolving temperature. Alternatively, an amount of solvent present in the two devices may advantageously be used independently of each other These are heated simultaneously to each one of the different dissolution temperatures.

The preparation of two different amounts of different temperature-controlled solvent has the advantage of a continuously practicable method, wherein the suspension first spent in the first device and can be transferred from there into the second device. This allows the first device to be used to accommodate further suspension without the need for alternating heating and cooling of the solvent (when heated within one device from the first dissolution temperature to the second dissolution temperature and vice versa from the second dissolution Temperature to cool back to the first dissolution temperature).

It goes without saying that the property and / or composition of the suspension can be changed between said devices, since virtually all plastics are still present in undissolved form when the first device is reached. During the transfer into the second device, its composition can then essentially be reduced to the remaining solid and solvent-permeated and / or wetted solid (undissolved second plastic or undissolved second plastic and further solid). In the context of the invention, the term suspension is also used in principle for this modified property and / or composition.

Against this background, it is considered particularly advantageous if the respective material (solid) or the combination of good (solid) and at least some solvent after the at least partial release of the first plastic from the first device is transferred to the second device, within the then the second plastic is at least partially dissolved.

According to a preferred further development of the method according to the invention, it is proposed that the suspension can be heated to at least one of the possible dissolution temperatures within a gas-tight system. The gas-tight design of the system also makes it possible to overheat the solvent to a dissolution temperature above its boiling point without evaporating it within a short time. The resulting in particular from the possible overheating of the solvent to a dissolution temperature above its boiling temperature resulting advantages are in a high reactivity of the solvent, which leads to a very fast dissolution of the plastic. At the same time a more complete subsequent dissolution of the plastic from the polymer solution can be realized, whereby the yield of plastic to be recycled is correspondingly increased. The advantages according to the invention are based, in particular, on the increase in pressure resulting from the quasi-superheatability of the solvent within the closed, gas-tight system.

Furthermore, it can be manipulated within the closed, gas-tight system existing internal pressure. Such a manipulation can manifest itself in particular in an increase of the internal pressure. In addition to the possible use of a compressor connected to the system in a suitable manner, such an increase in the internal pressure can already take place solely from the heating to be carried out anyway or even overheating of the solvent. In contrast, a reduction of the internal pressure can be based solely on a corresponding cooling of the solvent and / or the relaxation of the system. In particular, the increase in the internal pressure improves the properties of the solvent such that a faster dissolution of the plastic and an increase in the yield of dissolved plastic are feasible. The standing at the end of the process detachment of the plastic can then be improved by the flashing (relaxation of the system after overheating) of the solvent in an advantageous manner.

In principle, the detachment of the respective plastic from the polymer solution can take place by evaporating the solvent and / or dissolved plastic-containing solvent (polymer solution). Alternatively or in addition to this, the solvent and / or dissolved plastic-containing solvent can be replaced after its overheating by the gas-tight system is at least partially relaxed (flashing) after its overheating. In this case, in particular, a high dissolution temperature of the solvent can advantageously be noticed. Due to the dissolution temperature, which is preferably close to the boiling temperature, a relaxation of the system causes a very rapid to sudden evaporation of the solvent, wherein the respective plastic previously dissolved therein is peeled off and thus remains. This results in a very economical since fast operation. It goes without saying that the solvent then in the gaseous state is recondensed in a suitable manner in order to achieve its recovery and preferential reuse in the sense of a continuous cycle.

A further development envisages the use of a centrifuge as part of the gastight system. In this case, the centrifuge the improved separation and / or release of the respective Plastic from a good or centrifuged material contained at least one further solid serve. For this purpose, it is proposed that the suspension is centrifuged so that a uniform and in a short time taking place separation of the going plastic in the remaining solids is made possible. The structure required for this purpose provides that the centrifuge comprises a correspondingly gas-tight designed housing, within which a centrifugal material receiving, preferably hollow cylindrical, rotating insert is arranged rotatably. In this way, the suspension, if necessary under pressure, centrifuged by the rotating rotating insert, while this is enclosed gas-tight by the housing.

The invention is based on the finding that the gas-tight construction of the centrifuge enables safe handling even with at least one easily or even highly flammable solvent, since inflammation of any solvent vapors is precluded by the quasi-encapsulated centrifuging of the suspension. As a result, the advantageous use of solvents for dissolving plastic can now be reliably combined with the advantageous centrifuging out of the other solids or solids. In addition, the gas-tight design of the system offers the possibility of overheating the solvent close to or even above its boiling point. Thus, the plastic to be separated in each case go into solution within a very short time, while the other solids are removed due to their inertia by means of centrifuging controlled by the solvent containing the dissolved plastic. The consistency of the solvent or the dissolved polymer solution containing polymer can be adjusted, for example, so that it has the lowest possible viscosity. In this way, unlike its separation by pure heating, the dissolved plastic can be separated from it without any appreciable resistance by the remainder of the centrifuging material.

The gas-tight design of the centrifuge and / or the entire system also allows the particularly advantageous heating of the polymer solution and in particular of the solvent to near, at or even above its boiling point, which - in addition to a sometimes so possible increase its reactivity - especially the subsequent Removal of the dissolved plastic from the polymer solution advantageously facilitated.

Due to the gas tightness of the invention resulting from the system and in particular the closed housing of the centrifuge can now be carried out despite high safety requirements, a large-scale use of solvent, which allows a high throughput of Zentrifugiergut. Compared with operated in some cases high temperatures centrifuges also results in the advantage of a very economical and low-maintenance operation.

According to a particularly preferred further measure, the proportion of oxygen within the housing can be at least partially reduced. This can be done in an advantageous manner by the introduction of inert gas, as a result of which the oxygen contained within the housing is displaced to a corresponding extent. This allows a high degree of safety for the operation of the centrifuge, since the propagating within the housing solvent vapors can not achieve an inflammatory state lack of sufficient oxygen content. In addition, by introducing inert gas into the gas-tight system, its internal pressure can be raised to or above the vapor pressure of the solvent, so that even when the boiling temperature of the solvent is exceeded, evaporation thereof is reliably prevented.

According to a further development of the method, solids separated from the centrifuging material can be transferred into a gas-tight container connected to the housing. Said transfer of solids can be carried out continuously or temporarily. Thanks to the gas-tight exchange of the centrifuged solids from the centrifuge out in said container, the safety is increased again, since any contact with atmospheric oxygen is completely avoided.

In order to facilitate the further treatment of the centrifuged solids, an advantageous measure provides for the addition of a suitable agent in order to resuspend the solids transferred into the gas-tight container within it. The agent used may be water (H ₂ O) in a particularly preferred manner. Any remaining solvent and / or dissolved plastic containing solvent is thereby diluted to an uncritical level, so that a safe further treatment is also guaranteed in subsequent open and thus non-gas-tight executable processes. Alternatively or in addition to water, at least one further solvent can also be used here.

In the context of the present invention, it is considered to be extremely advantageous if the solvent according to the invention is used in a gas-tight centrifuge, in particular within a gas-tight system of a waste separation plant. Herein it can be operated in a particularly preferred manner according to the measures of the inventive method to at least two in and / or to dissolve dissimilar plastics present on a solid within a suspension, such as waste suspension.

Furthermore, the invention is directed to a method for assembling a solvent composed as a blend of two or more solvents, which is provided for dissolving at least two plastics in and / or on a solid. The solvent to be compiled in this way may preferably be the solvent according to the invention which was explained in more detail above. For this purpose, it is proposed that from the groups of solvents to be mixed together, the solvent having the lowest boiling temperature is added. This results in the advantage of the lowest possible and thus economic heating of the solvent in order to heat it to above its boiling point within a gas-tight system. This is advantageous insofar as the dissolved plastic can be easily removed from the solvent by the subsequent flashing of the polymer solution and within a very short time with only little effort.

list of figures

• 1 schematically shows an embodiment of the inventive method with the solvent according to the invention.

Detailed description of embodiments

1 shows a schematic structure of a waste separation plant 1 for carrying out the method according to the invention. The at least in relevant areas designed as a gas-tight system waste separation plant 1 comprises an initially arranged first release station 2 which is used for the preparation of waste for the subsequent separation of substances therein. For this purpose, in the present case is solid F with at least two plastics contained therein or therein K1 . K2 having waste in the solvents L containing first dissolution station 2 transferred. The first release station 2 For example, it may include one or more containers and / or basins not shown here in detail, which at least partially contain solvents L are filled.

It should be noted that the solid F from at least two different plastics K1 . K2 and another solid F , such as metal and / or paper, but also only from two different plastics K1 . K2 can assemble. In the latter case, the plastic is then within the scope of the invention K1 . K2 as a solid F which is not or not yet within the solvent L has gone into solution.

By way of example, it is assumed in the present case of a composition of the waste from a mixture containing 50% by mass of polyethylene (PE) and another 40% by mass of polypropylene (PP) and 10% by mass of solid F includes, for example, any fillers and / or impurities. The mixture becomes inside the dissolution station 2 in two parts with nine parts of solvent L in the form of methylcyclohexane (MCH) to a suspension S (Waste suspension) mixed.

The suspension so applied S remains within the first release station for a sufficient period of time 2 with its temperature at a first release temperature T1 of the solvent K (MCH) increased from 100 ° C and / or at least the first dissolution station 2 at a first dissolution temperature T1 can be operated. Because the first dissolution temperature T1 of the solvent L above its boiling temperature ST of 99 ° C ( T1 > ST ), it would lead to undesirable evaporation of the solvent L come. To prevent this, the system can be the waste separation plant 1 preferably with one above the atmospheric pressure or the vapor pressure of the solvent L lying internal pressure to be operated. For this purpose, an inerting device not shown in detail can be provided, via which - to increase the internal pressure and for the at least partial displacement of oxygen from the system - then an inert gas is passed into the entire gas-tight system.

During this period, the first plastic to be dissolved goes K1 (PE) at least partially, preferably completely, within its first dissolution temperature T1 having solvent L in solution during the non-dissolving solid F (in the form of the non-dissolving second plastic K2 and / or the further solid F ) within one from the solvent L and the dissolved first plastic K1 forming polymer solution remains.

Then we add the previously applied suspension S in a separation station 3 transferred, which includes a gas-tight centrifuge not shown in detail. The suspension passes S over an enema 4 in said centrifuge of the separation station 3, within which the solid F together with or in the form of the non-dissolving second plastic K2 from the suspension S is centrifuged out.

The from the separation station 3 remaining polymer solution is forwarded to a solvent separation, not shown here in detail, which the detachment of the first plastic K1 (PP) from the solvent L out serves. This can be done in a particularly preferred manner by the "flashing" of the polymer solution. In doing so, the system becomes local relaxed within the solvent removal by abruptly lowering the increased internal pressure. Because that's above its boiling temperature ST lying first dissolution temperature T1 heated solvents L abruptly in the polymer solution to its boiling point ST Cools, this goes quickly into the vapor state, so that a very fast detachment of the first plastic K1 out of the polymer solution is possible. As a result, the thus-recovered first plastic remains K1 (PE) free of solvent L ,

The evaporated solvent L is condensed in a manner not shown within the system and discharged via a drain from the solvent removal out.

The solid obtained during centrifugation F (in the form of the undissolved second plastic K2 or in combination with further solid F ) will have a suitable outlet 5 the centrifuge of the separation station 3 out of this into a second release station 6 forwarded. In this is the solid F or second dissolved plastic K2 again within the solvent L resuspended, with the solvent L doing so on one with a temperature difference .DELTA.T above the first dissolution temperature T1 lying second dissolution temperature T2 of 125 ° C is heated. The suspension so applied S indicates a mixture of five parts solid F and forty parts solvent L in the form of methylcyclohexane (MCH). By at the second dissolution temperature T2 in solution going second plastic K2 This results in a 10 M% polymer solution with polypropylene (PP).

The suspension S from the second release station 6 is fed in a manner not shown further to another separation station to the remaining solid F from the polymer solution of solvent L and dissolved in the second plastic K2 To separate (PP), for example, by centrifuging. This polymer solution is also forwarded to a solvent separation, not shown here in detail, which is the detachment of the second plastic K2 (PP) from the solvent L out serves. This can also be done in a particularly preferred manner by the "flashing" of the polymer solution. As a result, the thus-recovered second plastic remains K2 (PP) free of solvents L ,

The solid recovered from the previous measures F is finally a solid treatment 7 passed, wherein the solvent L in a suitable manner from the solid F separated and via an effluent from the solids treatment 7 is discharged out. The solid treatment 7 may, for example, have a built-in or downstream lock over which ultimately the solid F free of any residual solvent L can be removed.

Advantageously, the recovered solvent L circulated and via appropriate return lines back to the release stations 2 . 6 be supplied.

LIST OF REFERENCE NUMBERS

1

Waste separation plant

2

first release station

3

separating station

4

enema

5

outlet

6

second dissolution station

7

Solid Treatment

F

solid fuel

K1

first plastic

K2

second plastic

L

solvent

S

suspension

T1

first dissolution temperature

T2

second dissolution temperature

ST

Boiling temperature

.DELTA.T

temperature distance

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 4343784 A1 [0009, 0010]
• DE 102005026451 A1 [0011]

Claims (13)

Solvent for dissolving at least two plastics (K1, K2) in and / or on a solid (F) within a suspension (S), in particular waste suspension, characterized by a temperature dependence of the dissolving action of the solvent (L) on the plastics (K1, K2), wherein the first plastic (K1) at a first dissolution temperature (T1) of the solvent (L) and the second plastic (K2) at a second dissolution temperature (T2) of the solvent (L) is releasable. Method for dissolving at least two plastics (K1, K2) in and / or on a solid (F) within a suspension (S), such as waste suspension, with a solvent (L), in particular Claim 1 , characterized in that the suspension (S) is multi-stage heated to different dissolution temperatures (T1, T2), wherein in a first stage at a first dissolution temperature (T1) of the first plastic (K1) is dissolved and in a second stage at a second release temperature (T2) of the second plastic (K2) is released. Method according to Claim 2 , characterized in that as the first plastic (K1) polyethylene (PE) and as a second plastic (K2) polypropylene (PP) is dissolved. Method according to Claim 2 or 3 , characterized in that the first plastic (K1) is dissolved at a first dissolution temperature (T1) of 80 ° C to 110 ° C and the second plastic (K2) at a second dissolution temperature (T2) of 120 ° C. is dissolved to 180 ° C. Method according to one of Claims 2 to 4 , characterized in that the first release temperature (T1) and the second release temperature (T2) are set at a temperature interval (ΔT) of 20 ° K from each other. Method according to one of Claims 2 to 5 characterized by the provision of two devices containing the solvent (L), in which the solvent (L) is heated in a first device to the first dissolution temperature (T1) and the solvent (L) in a second device to the second solution Temperature (T2) is heated. Method according to Claim 6 , characterized in that the suspension (S) after the at least partial release of the first plastic (K1) is transferred from the first device into the second device to at least partially release the second plastic (K2). Method according to one of Claims 2 to 7 , characterized in that the suspension (S) within a gas-tight system to at least one of the dissolution temperatures (T1, T2) is heated. Method according to Claim 7 , characterized in that an internal pressure of the gas-tight system manipulated by a compressor and / or a change in temperature, in particular increased, is. Method according to Claim 7 or 8th , characterized in that the gas-tight system comprises a centrifuge having a gas-tight housing, wherein the suspension (S) is centrifuged within the gas-tight housing of the centrifuge. Method according to one of Claims 7 to 9 , characterized in that a proportion of oxygen within the gas-tight system is at least partially displaced by introducing inert gas. Use of a solvent (L) after Claim 1 in a gas-tight centrifuge comprehensive gas-tight system, such as from a waste separation plant (1), in particular for a method for dissolving at least two in and / or on a solid (F) located plastics (K1, K2) within a suspension (S ), such as waste suspension, according to one of Claims 2 to 10 , Process for the preparation of a solvent (L) composed as a mixture of two or more solvents, in particular according to Claim 1 for dissolving at least two plastics (K1, K2) in and / or on a solid (F) within a suspension (S), such as waste suspension, wherein the respective lowest boiling temperature (ST ) is added.

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