DE19934259A1 - Process for the selective separation of predefinable substances from mixtures - Google Patents

Abstract

The invention concerns a method for selectively separating predetermined materials contained in mixtures of materials, in particular mixtures formed by waste and containing other materials with characteristics similar to said predetermined materials. The method is characterised in that the mixtures of materials are subjected, according to a known operation, to at least a process of automatic separation by density, the materials whereof the mass density is within a first range of values being separated from those within a second range of values. Before or while they are being treated, the predetermined materials are enriched with at least an additive providing them a with mass density within the first range of values. Said method enables simple and economical separation for example of high value or biodegradable synthetic materials contained in waste mixtures, such that they can be subsequently treated in accordance with prescribed rules or upgraded during removal.

Description

The invention relates to a method for selective separation of predeterminable substances Mixtures of substances that arise during waste production. The entire area is under waste production from waste or old goods collection to Understand waste recovery or recycling.

There is a great need in this field of application of processes that promote the recycling or recycling of Waste materials, especially high-quality art enable fabrics. A high quality material Recycling plastic waste sets the stage Obtaining sufficient varieties or species Plastic fractions from the waste ahead. This particularly fails in the case of heterogeneous waste mixes that the plastics sort their own are missing due to which the separation with cost-effective process engineering fractionation or Sorting procedures could be carried out. Costs intensive, specialized in individual plastics Separation processes are not economical sensible.

Among the well-known automatic separation processes that Working inexpensively includes separation procedures according to density differences. The fractionation after the specific (mass) density is subject to sufficiently large differences in density between the separating fractions ahead. Usually under  the densities of plastics differ in the However, relevant mixtures present in the waste are not sufficient to be sufficient by means of density separation win single or pure plastic fractions to be able to.

In the case of pure plastic fractions, the in the plastics contained in their fraction Base thermoplastics should be chemically identical. For varieties pure plastic fractions are those in the fraction contained plastics with regard to their base thermal plastically chemically and physically-structurally identical and also uniformly additive.

Another inexpensive separation process, the works automatically, the separation is after magnetic properties. The fractionation after magnetic properties inevitably sets magnetic properties of the mixture components to be separated in advance, but at No plastics.

Plastics are therefore primarily used sorted by hand or separated by means of air classifiers. It density separation processes are also used, the however with only slight differences in density between fail the plastics or only inferior, not enough pure or species-specific fractions deliver. The windsifting process separates large plastic parts from those with small specific surface. This procedure is therefore only able to sort by plastic types or types separate, where the surface criterion with the Variety or species criterion matches. This is  for example with large packaging films, which are often made from LDPE and LLDPE. Manual sorting is complex and only for large-scale plastics can be used economically.

The German Packaging Ordinance (VerpackV) provides that sales packaging and catering Tableware can be recycled to a fixed percentage have to. The industrial, largely manual sorting the plastic packaging is under pressure this packaging regulation in Germany article based. This implies the separate recording of certain Packaging and catering waste fractions ahead. The Packaging waste is here in "large hollow body "," foils "and" mixed plastics "separately. However, "large hollow bodies" and "foils" are neither species-specific still single-fraction fractions.

A small proportion of the hollow body and film fractions are subjected to density separation and each is separated into a light (density <1.0 g / cm ³ ) and a heavy fraction (density << 1.0 g / cm ³ ) ( When using salt solutions instead of pure water, the separation step is shifted to higher densities). The light fraction contains a mixture consisting essentially of 30-50% PP, 50-70% PE and, depending on the selectivity of the separation process, parts of PS. This PE-PP mixture can, however, only be recycled with additional expensive compatibilizers, ie processed thermoplastic. Despite the separation of the heavy plastics, the mixed polyolefins result in low-quality regranulates, which can only be marketed with low proceeds, sometimes even with additional payment. The heavy fraction, consisting of PET, PVC, PC, PA and parts of PS, is usually thermally treated or deposited.

Unless the mixed plastic fraction directly is eliminated, it is processed into an agglomerate works. This will predominantly (approx. 94%) raw material and only to a very small extent (approx. 6%) inferior material recycling. The ecologically and economically sensible use of these Products is because of their low material quality extremely limited.

Also one that is currently being tested and primarily on the mixed plastic fraction centrifugal separation method to be used, the so-called KAKTUS process, works with regard to Plastic separation based on density sub divorced. It separates primarily, as already mentioned above, Polyolefins of non-polyolefins. In addition, that will PVC from the heavy fraction electrostatically removed divorced. The rest contains PET, PA, PC etc. and can be used raw or energetically become.

The electrostatic separation process Separation is based on the different charging of plastics in an electrical field. The charged particles are in free fall by a electrical high-voltage field in a so-called Free fall separator to the corresponding electrodes distracted and separated from each other in this way. This method can be used among other things Separation of PE from a PE / PP mixture, from a PC  a PC / PMMA mixture and around filled PP from Separate PP / ABS / PVC blends.

The material recycling of PP / PE mixtures is strong due to the material incompatibility limited or with additional costs connected. It would be technically possible to use PE with a to separate electrostatic separation processes from PP, however, this method is in view of the relatively low-value end products too expensive, to be put to wide use.

Also the one contained in the heavy fraction high quality PET cannot be material are recycled, but is thermally treated or deposited.

So far, there is no procedural sorting criterion for biodegradable materials or plastics (BAW). Biodegradable materials or plastics contained in packaging waste have densities between 1.1 g / cm ³ and 1.4 g / cm ³ . In the article-related sorting explained above, the BAW remain primarily in the mixed plastic fraction. In the case of fractionation of the mixed plastics by means of density separation, the BAW mostly end up in the heavy fraction. Thus, they are recycled in terms of raw materials or energy or simply disposed of, but are not subjected to material recycling or their intended biological recycling.

In particular, BAW can use the previously known Process not inexpensive from mixed catering  waste that, in addition to disposable tableware, also packaging, Leftovers, printed matter, hygiene articles etc. contain, procedurally separated and their proper disposal.

For the future is - according to a voluntary Voluntary commitment by car manufacturers - planned, Recycle 95% of the end-of-life vehicle. This means that for the shredder light in this area fraction from conventional plastics a higher Recovery rate than before, especially for the recycling, must be achieved. Due to the high degree of mixing, this can Plastic waste fraction currently only energetically or can be used as raw materials. An inexpensive selective separation and thus a material Recycling one in the shredder light fraction contained higher-quality engineering plastic with the known methods of the prior art however not possible.

In summary, occurs with the previously used Prior art methods raised the problem that they are not an economical separation of varietal or at least species-pure plastic materials Mixtures of substances, such as those used in packaging waste or automobile disposal, enable. Such plastics in mixtures can therefore no high-quality material or another material-specific recycling more be made accessible.  

The present invention is therefore based on the object based on a method for the selective separation of specify specifiable substances from waste mixtures with the - depending on the objective - different substances simple and inexpensive way out of the fabric mixtures can be recovered so that they then processed as intended or can be disposed of.

In particular, the inventive method make sure one or more certain plastics individually or as a class of substances inexpensive from a mixture of materials can be separated to this plastic / this Plastic class z. B. then a specific one To be able to supply recovery. This affects above all Cases in which a proper separation from other plastics due to the lack pronounced material properties of this plastic / this class of plastics that cost separation technology can be used cheaply, was not possible.

Furthermore, the inventive method should cost-effective separation of biodegradable materials or plastics (BAW) from waste mixtures lichen.

The object is achieved with the method according to claim 1 solved. Advantageous configurations or applications the method are the subject of further claims.

A method is used to solve the problem proposed, in which the substance mixtures at least one go through automatic separation process that substances with a first property of fabrics with a  second property separates. Such separation processes, such as density separation processes or magnetic separation processes are from the prior art Technique known, in which case the first and second property different material dense or different magnetic properties the substances (e.g. ferromagnetic - not ferromag represent). The predeterminable, d. H. the ones from Substances to be separated are fiction according to before or during processing with a Enriched with additive, which is one for these substances the decisive factor is the separation process used produces substances similar to those to be separated do not have in the mixture. That way you can the substances to be separated by the used Separation processes can be separated from similar substances. The additives must therefore be used on the Separation process and the respective separation task be true. For this, the mixture of substances and Analyzes properties of the substances involved appropriate separation process determined, and the required type and amount of additives that the Desired separation with the selected separation process enable.

Although in particular in the following examples on separation processes based on the principle of density separation and the magnetic separation is dealt with there these can currently work very inexpensively with the method according to the invention also others Separation processes that differ, for example dielectric properties of the materials can use as long as those for separation  relevant properties in the to be separated Substances by enrichment with appropriate fill substances can be influenced.

A preferred application of the invention The process relates to the separation of certain or specifiable plastics from mixtures of substances. Under the The term plastics is used in the present Description also plastic-like materials understood that biodegradable or not are biodegradable based on synthetic or based on native polymers, and the thermoplastic are processable.

A suitable Additi of the intended for later separation Base thermoplastics with an additive - or a mixture of additives - carried out, the specifically significantly heavier than the base thermoplastic and / or is ferromagnetic. The aggregate is the base thermoplastic in the molten state added. This creates a dense one modified and / or ferromagnetic granules of the Base thermoplastics. This granulate then stands for Manufacture special items that are available later selectively separated from waste mixtures should be. The separation takes place with a suitable, known from the prior art Separation process.

The granules can also advantageously Manufacture of items that are used improved in terms of haptic properties should be, as will be explained later.  

Preferably, an additive is used finely divided mineral, especially also metallic, metal oxide or salt-like, Filler used. If necessary, will improve the miscibility of aggregate and base thermoplastic continues to be an auxiliary or auxiliary mixed substance. This can also be a second Be thermoplastic.

The amount of the base thermoplastic per mass unit admixed aggregate is fiction according dimensioned so that the plastic or from it molded objects or by crushing manufactured fragments with inexpensive separation proceed as known from the prior art are, from objects from originally density-like Plastics can be separated. Which includes in particular separation processes which are carried in carrier media such as for example water, aqueous solutions, air or Carrier gases, after gravity or centrifugal principle in the presence or absence of others fluid dynamics effects that the separation after the Favor or complicate density, or after Principle of magnetic deposition, such as wise overbelt magnet separator, work.

Examples of suitable fillers are dolomite (MgCa (CO ₃ ) ₂ ) with a density of 2.8-2.9 g / cm ³ , calcium carbonate (CaCO ₃ ) with a density of 2.7-2.9 g / cm ³ , Barium sulfate (BaSO ₄ ) with a density of 4.0-4.9 g / cm ³ or ferromagnetic iron powder (Fe) with a density of 7.8-7.9 g / cm ³ .

It is known from other areas, mineral Incorporate fillers into polymers, for example to the mechanical properties or the color of the Targeting plastic or around the material to "stretch", d. H. reduce material costs. In addition, the barrier properties of Polymers against vapors and permeate gases increasing mineral fill level. this concerns however, only specific application-related properties of the polymers.

In the present process, the plastic however, mineral fillers for the purpose of selective separability from mixtures, in particular Waste mixes, added to it for example to confer ferromagnetic properties and / or to increase its material density. Nor is it known such fillers to improve haptic, d. H. appealing to the sense of touch shafts of the plastic or the manufactured therefrom To incorporate the object.

The present process enables the varieties pure separation of certain or predetermined art substances from waste mixtures using density separators drive, e.g. B. floating-sink method, or magnetic Separation processes, e.g. B. with an overband magnet Separator. The method according to the invention thus bears contribute to the recovery required by law quotas, e.g. B. for the shredder light fraction, sales packaging or catering dishes, in particular for material recycling, cheaper in the future  and optionally meet the specified size to be able to.

Surprisingly, the accumulation of Plastics with fillers to increase density or conferring ferromagnetic properties also an improvement in the haptic properties of the objects made from these plastics. Disposable tableware made from a modifi according to the invention graced plastic is made, is heavier and thus more secure in the hand. In addition, the material grippy and the object made of it slides not so easy to get out of hand.

With the present procedure, the procedure technical separation of biodegradable Plastics or plastics-like materials (BAW) from non-degradable plastics to simple and Cost effective way to be achieved by the former processing according to the invention with the additive be enriched.

Table 1 shows a list as an example more biodegradable and non-biodegradable thermoplastics and their densities in Dependence on the degree of filling with dolomite as filler.

This table clearly shows how when enriching biodegradable substances with a suitable amount of a filler such as dolomite Density of substances can be brought into an area can, the separation of non-biodegradable  Plastics by means of an automatic Density separation process allows.

Especially in the packaging area and related Applications such as B. there is a catering area great market potential for BAW. Be foreseeable biodegradable and non-degradable materials side by side especially in packaging waste as well in mixed waste from catering and fast food Companies etc. occur. These can be done with the Method according to the invention for the purpose of their material specific recycling inexpensively from each other be separated.

Furthermore, the present method enables Cost-effective separation of processes Plastic or a class of plastics a mixture.

A source of such mixtures are e.g. B. the according to the sorting criteria for Plastic fractions arising from packaging waste, but also components of the shredder light fraction automotive recycling or housing and component Plastics from electronic scrap.  

Table 1

The proposed enrichment of the specifiable substances with additives to increase density or generation of ferromagnetism also causes one Improving the haptic properties of the processed plastics. Dishes from one Modified plastic according to the invention is in Comparison to dishes from the corresponding unfilled plastic better in the hand. Through the modification according to the invention also changes the Surface micro roughness, so that adhesion and Increase sliding friction coefficient. The material conveys a pleasant dry feeling when touched Sensation, is more grippy and slides accordingly not as easy to get out of hand as conventional ones Plastic dishes. The modification according to the invention The plastics therefore increase their grip and thus ensures an advantageous safer and more pleasant to use objects made therefrom.

Just everyday items are often made from plastics. Disposable tableware is here due to the constant Efforts to save material are particularly thin-walled molded. Disposable tableware is therefore often not very stable and lies easily in the Hand. The consumer must therefore always be careful Handling. To make matters worse, the plastic-based disposable tableware through a very smooth and therefore, especially in the case of damp Hands, slippery surface. This one haptic disadvantages can by the invention Modification of the plastics can be counteracted.  

The procedure for the invention The procedure is based on execution examples again illustrated.

First, let's look at five problem positions the implementation of the procedure in use a device for density separation are shown. The groups mentioned relate to those in the Introduction to the described sorting process the state of the art.

Selective separation using density separation requires under practical, equipment and costs economic aspects a difference in density between the fractions to be separated, the 10% in the case centrifugal separation (case a) or 20% in the case of Float-sink separation (case b) is not essential should fall below. The ones shown below Examples of practical separation tasks are included therefore see a difference in density from a) at least 10% and b) at least 20%.

Separation task 1

A heavy BAW should be separated from the heavy fraction consisting of PET, PC and PVC. According to case a) the density of the BAW has to be increased to 1.57 g / cm ³ , according to case b) to 1.72 g / cm ³ . This should be done with dolomite as a filler.

Table 2 gives the required degree of filling of the BAW with Dolomit to solve this separation task.  

Table 2

Separation task 2

A heavy BAW should be separated from the light fraction consisting of PE, PP and PS. According to case a) the density of the BAW has to be increased to 1.19 g / cm ³ , according to case b) to 1.30 g / cm ³ . This should be done with dolomite as a filler.

Table 3 gives the required degree of filling of the BAW with Dolomit to solve this separation task.  

Table 3

Separation task 3

Heavy PP or heavy PS should be separated from the light fraction consisting of PE, PP and PS. According to case a) the density of the heavy plastic has to be increased to 1.19 g / cm ³ , according to case b) to 1.30 g / cm ³ . This should be done with dolomite as a filler.

The required degree of filling of the BAW with Dolomite is shown in Table 4.

Table 4

Separation task 4

Heavy PET should be separated from the heavy fraction consisting of PET, PC and PVC. According to case a) the density of the heavy plastic has to be increased to 1.57 g / cm ³ , according to case b) to 1.72 g / cm ³ . This should be done with iron powder as a filler.

Table 5 gives the required degree of filling for this with iron powder.

Table 5

Separation task 5

Heavy PP should be separated from the light fraction consisting of PP, PE and PS. According to case a) the density of the heavy plastic has to be increased to 1.19 g / cm ³ , according to case b) to 1.30 g / cm ³ . This should be done with barium sulfate as a filler.

Table 6 gives the required degree of filling Barium sulfate to solve this separation task.  

Table 6

For all five separation tasks, the Filler proportion depending on that later used separation processes and the properties of the involved substances selected. The admixture takes place before or during the processing of the fabrics.

The following is another problem position the implementation of the Ver driving when using a device for magnetic Separation shown.

Selective separation using a magnetic separator requires filling the plastic with a ferromagnetic filler, the degree of filling below practical, technical equipment and cost management aspects must be optimized.

Separation task 6

PE doped with a ferromagnetic substance is said to consist of the light fraction consisting of PP, PE and PS, can be separated using a magnetic separator. To PE is added with iron powder.  

Table 7 shows that in a given Magnetic field specimen from a greater distance attracted by the magnet, the greater their share is ferromagnetic iron powder. The mass and therefore the size (volume) of the specimen plays a role apparently a subordinate role.

Table 7

The inventive method using the Material modification according to the invention therefore enables basically the following separation processes.

A density increase using a suitable additive or additive mixture and / or the "incorporation" of one Ferromagnetic material allows them at BAW selective separation of non-degradable waste components and their biological utilization. For high-priced biodegradable plastics, such as B. Polylactic acid (PLA), the present invention also the possibility of high quality material Open up utilization of a BAW.  

The material modification according to the invention leaves also use conventional or novel, non-biodegradable plastics from one Mixture of originally density-like mixture constituents, in the case of doping with a ferromagnetic aggregate regardless of the resulting density, using known methods technical separation process as technically sufficient separate fraction. Usually it will the mixtures are wastes from which a component sorted for the purpose of one if possible high quality, especially material or biological recycling to be separated, like this is shown in the previous examples.

The targeted use of modes according to the invention plastic, both biodegradable and also not biodegradable, is especially for such Suitable applications for which a closed substance cycle (production of the primary product; recycling and preparation of the primary product; specific recovery of the obtained as high as possible Secondary raw material) should be installed, such as for example with the old car and electronic scrap recycling, recycling packaging waste, catering catering waste, etc.

By incorporating fillers in addition, e.g. B. for applications in the catering sector, an improvement in haptics. That from these Catering tableware made of plastics is in the Compared to the unfilled plastic heavier and therefore  safe in the hand. Preliminary examinations for compounding availability of polylactic acid (PLA) with dolomite further shown that this material gets a pleasant dry grip. This sensation is based on the change in the surface micro roughness and thus an increase in the adhesion and Coefficient of sliding friction. This will make it slip counteracted the object.

Claims (8)

1. A process for the selective separation of predeterminable substances from mixtures of substances that arise during waste production and contain other substances with similar properties to the predeterminable substances,
in which the substance mixtures go through at least one automatic separation process which separates substances with a first property from substances with a second property, the further substances having the second property, characterized in that
that the predefinable substances are enriched with one or more additives before or during their processing, which give the predeterminable substances modified in this way the first property. 2. The method according to claim 1, characterized, that the mixtures of substances a magnetic Separation processes are subjected, one or several additives are used that are ferromagnetic. 3. The method according to claim 1, characterized, that the mixtures of substances a density separation process be subjected to one or more  Additives are used that are specific Increase the weight of the specified substances. 4. The method according to any one of claims 1 to 3, characterized, that as an additive a mineral substance, in particular a metallic, metal oxide or salt-like additive is used. 5. The method according to claim 4, characterized, that as an additive dolomite, calcium carbonate, Barium sulfate, iron powder or barium ferrite is used. 6. The method according to any one of claims 1 to 5, characterized, that the specifiable substances are thermoplastics, the enrichment with the additive (s) by admixture while the Thermoplastics are in the molten state. 7. Application of the method according to one of the claims 1 to 6 for the separation of valuable materials Fabrics. 8. Application of the method according to one of the claims 1 to 6 for the separation of biodegradable Fabrics.