DE102008063232A1 - Producing a processable plastic material from waste mixture of plastics, comprises presorting the waste mixture of plastics, cleaning and then crushing to flakes and/or gravels, and feeding the crushed product to a treatment - Google Patents

Abstract

The method comprises presorting the waste mixture of plastics, cleaning and then crushing to flakes and/or gravels, and feeding the crushed product to a treatment. The polyolefinic plastic is sorted off from the waste mixture of plastics and the crushed polyolefinic plastic waste mixture is crushed and/or compressed to gravels, pellets, flakes, small pieces or agglomerate particles to a basis raw material, where the pellets or agglomerate particles are completely or partially melted. The polyolefinic plastic waste is separated into soft plastic and hard plastic. The method comprises presorting the waste mixture of plastics, cleaning and then crushing to flakes and/or gravels, and feeding the crushed product to a treatment. The polyolefinic plastic is sorted off from the waste mixture of plastics and the crushed polyolefinic plastic waste mixture is crushed and/or compressed to gravels, pellets, flakes, small pieces or agglomerate particles to a basis raw material, where the pellets or agglomerate particles are completely or partially melted. The polyolefinic plastic waste is separated into soft plastic and hard plastic and the fractions are incorporated into a mixer in a predetermined ratio. A predetermined quantity of basis raw material is jointly and homogenously mixed with a predetermined quantity of high-grade sorted, type-determined plastic or a mixture of high-grade sorted, type-determined plastic, aggregates, filling materials and/or reinforcement materials. The mixed material that is present in a flowable state is subsequently fed for its use. The material from the mixer is granulated to a compound in an extruder, and is spreaded to a double-band unit for the production of plate material. The crushed soft plastic is compressed to pellets and/or agglomerates, where the plastic particles are only partially melted in the pellets and/or the agglomerate particles. The hard plastic is crushed to gravel. The type-determined plastic is pure plastic, and is high-grade sorted waste plastic or mixture of high-grade sorted waste plastics. The material is dryly incorporated in the extruder. A single-stage mixing process takes place and an agglomerate or aggregate is produced by adding a cold-adhering binder to the material in the mixer present in gravel-, pellet- or powder form, where the material is heated, so that the low-temperature molten plastic forms no clumps and the low-temperature molten additive is already provided by melting for binding the further components. A two-stage mixing process is carried out, where clumps are formed in a first stage by low-temperature molten plastic and the clumps are homogeneously crushed in a cooling mixer in a second stage with respect to the grain size. The process-optimized additive and pigments, UV-protector and/or compatibilizer are supplied as microgranules or in powder form in the mixing process. The reinforcement material is introduced in the form of fibers in the mixing process. The reaction agent is introduced in the form of a liquid in the mixing process. The power consumption of the extruder is measured and is used as regulating parameter for the dosage of aggregate.

Description

The The invention relates to a process for producing a processable and property-specific plastic material from waste plastic according to claim 1.

The Reuse of trash Plastics is of increasing importance. The problem is, out the different types of plastic, with different Shares in the waste plastic occur (inhomogeneous waste streams) recovery enabled To produce plastic material of consistent quality, because the shares the different types of plastic are not known, especially since they constantly change.

For the preparation pre-sorted plastic waste There are different technologies. The invention is limited here on the use of NIR technology or density detection in one Waste stream for the positive identification of polyolefin plastic waste, the is called Plastic waste the grades polyethylene, polypropylene and derivatives. It is known, with the help of car washes the plastic waste to clean and shred. There are also so-called sorting centrifuges become known to plastic waste in cleaned or unpurified Separate shape according to density. Finally, it has become known by crushing of plastic agglomerate in the milling process and by appropriate cleaning processes waste plastics a Processing. With a sufficient degree of comminution, the agglomerated grinding can be carried out Plastic can be dispensed with. Finally, it is also known pulp, which proves to be extremely disturbing in the further processing, from the crushed Remove waste plastic.

• – Das Material muss homogenisiert sein. Darunter ist zu verstehen, dass eine intensive Durchmischung der verschiedenen Kunststoffarten und sonstigen Stoffe erfolgen muss. Wichtiges Ziel der Homogenisierung ist die Erzeugung von wieder verwendbaren Kunststoffen mit verlässlichen Eigenschaften in einem definierten Eigenschaftsfenster.
• – Damit das verarbeitbare Kunststoffmaterial mit marktüblichen Maschinen zur Kunststoffverarbeitung verwendet werden kann, muss es zuvor thermomechanisch zu einem Granulat umgeformt sein. Dieser Umformprozess muss stabil ablaufen, d. h., bei stabilen Prozesstemperaturen. Eine stabilisierte Schmelze soll keine Schmelzabrisse aufweisen und als Ergebnis soll ein sauberes, glattes und porenfreies Granulat erzielbar sein. Besonders wichtig hierbei ist, dass eine sogenannte Schmelzefiltration nicht übermäßig beansprucht wird. Ansonsten führt dies zu einer Kapazitätsminderung und Ausbeuteverlust.
• – Das bei dem thermomechanischen Umformprozess erzielte Granulat muss so beschaffen sein, dass es mit den üblichen Kunststoffverarbeitungsmaschinen verarbeitet werden kann. Es dürfen daher kaum Störstoffe enthalten sein, die zum Verstopfen von Düsen oder Kanälen führen. Das Material darf sich nicht zersetzen. Es darf keine Entmischung geben, und Ausgasungen müssen sich in Grenzen halten, zumindest dürfen die Ausgasungen nicht zum Aufschäumen des Materials führen. Es muss außerdem eine definierte Verarbeitungsviskosität (Melting Flow Rate – MFR) eingestellt werden.
• – Schließlich kann es bei der Weiterverarbeitung des verarbeitungsfähigen Kunststoffmaterials zu einer Geruchsbelästigung kommen, die aufgrund einer schlechten Reinigung der abfallstämmigen Kunststoffe entsteht. Ein besonderes Problem besteht hier mit an Kunststoff anhaftenden Zellstoffen, beispielsweise von Aufklebern und Etiketten.

So that plastic grinding material made of waste plastic can be used as a new raw material in the plastics processing industry, the following conditions must be met:

• - The material must be homogenized. By this is meant that an intensive mixing of the different types of plastic and other substances must be made. An important goal of the homogenization is the production of reusable plastics with reliable properties in a defined property window.
• - So that the processable plastic material can be used with commercially available machinery for plastics processing, it must first be thermomechanically converted into a granulate. This forming process must be stable, ie at stable process temperatures. A stabilized melt should have no melt fractures and as a result, a clean, smooth and pore-free granules should be achievable. Particularly important here is that so-called melt filtration is not overstressed. Otherwise, this leads to a reduction in capacity and yield loss.
• - The granules obtained in the thermomechanical forming process must be such that they can be processed by the usual plastics processing machines. It must therefore be contained hardly any impurities that lead to the clogging of nozzles or channels. The material must not decompose. There must be no segregation, and outgassing must be kept within limits, at least the outgassing must not lead to the foaming of the material. In addition, a defined Melting Flow Rate (MFR) must be set.
• - Finally, it may come in the processing of the workable plastic material to an odor, which arises due to poor cleaning of waste plastics. A particular problem here is with plastic adhering pulps, such as labels and labels.

As initially explained at least partially, occur in the production of polyolefin plastic materials, in particular plastic granules of waste plastics different Problems on. The most important representatives of polyolefins, which occur in the proportion of plastic waste, are polyethylene (PE-LD and PE-HD) and polypropylene (PP). The ratio of Polyethylene to polypropylene varies more or less strongly and determines therefore the processing and use characteristics of the processable Material. This makes it difficult to maintain a constant level over a longer period of time quality to achieve. In the production of processable plastic material Additives are added, which are mostly in powder form. The addition of powdery additives in the extruder together with z. B. in flake form existing plastic prepared problems. at thermomechanical transformation into granules can be the pulp in the plastic material lead to Wasserdampfausgasungen, causing a porous one Granules are formed. Pulp leads also, as already mentioned, to odor problems in the further processing of granules. Finally, can it to capacity losses in the extruder come when PET or aluminum contain impurities in the input material is.

From known upstream sorting and cleaning processes, the product is a comminuted Ab obtained from plastic, which consists mainly of flakes. These flakes have a low bulk density, so their direct feed into an extruder for granulation is very difficult or nearly impossible. Therefore, it has already become known to compress the flakes into agglomerate particles and then to crush them, in particular to grind. However, the flakes are not homogeneous in their proportions of PE and PP, unless there is a costly separation of the plastic types by a specific NIR separation or other physical processes that use the different density of the polyolefins as separation criterion. However, all these separation methods are only small capacity possible and economically expensive.

It This also creates difficulties in adding additives, that unequal particle sizes mixed Need to become. The additives are usually present as powder or granules, while the Flakes have a significantly different surface volume ratio.

At Plastic flakes obtained from waste plastic streams Pulp residues always stick in the upstream Processes are not complete can be separated. In a regranulation in an extruder, as they usually carried out when the cell-bound water evaporates on heating in the extruder and must over Vacuum degassing be extracted. But this is not completely possible, and the granules foam as soon as it leaves the extruder head, as the water vapor at atmospheric Pressure expands. this leads to to quality losses on the granules. By heating and evaporating the water from the pulp arises around the pulp fibers a kind of steam jacket. This Prevents the pulp from completely entering the plastic matrix is involved. Through the resulting channels, moisture from the Ambient air after cooling again absorbed by the pulp fibers, so that in the Granulate forms a compensatory moisture, which for the continuing Process extremely disturbing is. This moisture then provides under the high pressures in an injection molding machine for overheated Steam. This in turn leads to a depolymerization of the plastic chains and the pulps and extremely unpleasant odor by the decomposition products.

Of the Invention is based on the object, a process for the preparation a workable plastic material from waste plastic, which is suitable for granulation in a Extruder or other use continuously specified Properties, e.g. B. has a predetermined processing and / or product quality.

These The object is solved by the features of claim 1.

at the method according to the invention is sorted from the waste plastic a polyolefin plastic waste. The crushed polyolefin mixed plastic waste becomes dependent on its texture to semolina, Pellets, stuffy material, flakes or Agglomeratteilchen to a Basic raw material crushed or compacted, the pellets or Agglomerate particles may be completely or partially melted through. Flakes or Fibers are tangled together and partially connected by fusion. When melt through let the individual parts of the agglomerate particle or the pellet no longer identify. A given amount of basic raw material is combined with a predetermined amount of pure plastic or a mixture of single-grade plastics, aggregates and / or fillers and / or reinforcing materials homogeneously mixed. The preferably free-flowing, homogeneously mixed material will follow fed to its use. An authoritative Use is the feed in an extruder for the production of a granulated compounds. An alternative embodiment of the invention sees the application of the material from the mixer on a double belt plant for the production of plate material. The plate material is either plastic plates or plastic plates with a fiber reinforcement organic or inorganic fibers.

The properties, quality and / or processability of the reclaimed plastic material are highly dependent on the ratio of polyethylene and polypropylene and thus correlated with the proportions of soft plastic (predominantly PE-LD) and hard plastic (predominantly PE-HD and PP). Since a pre-sorting of waste plastic for these types of plastic very expensive or hardly possible and on the other hand, their ratio varies more or less over time, it is not possible without special precautions to achieve desired properties in a sufficient consistency. In the invention, it was recognized that this problem is solved in that the comminuted waste plastic shredded sorted plastic or a mixture of varietal plastics known properties is mixed in a more or less large proportion. The unmixed plastic can either be pure plastic or single-grade waste plastic or mixtures thereof. A prerequisite in the invention is that at least one property of the plastic or plastics is known. A preferred mixture of pure plastics contains polyamide and polyethylene. The introduction of the type-determining plastic - in this case, a defined mixture of PE and PA has the consequence that specific properties of the material mixture are enhanced by targeted selection. Using a type-specific single-grade plastic, the quality, property and processability of the mixture can be kept constant within more or less narrow limits. Is z. B. strives that the workable plastic material should have the properties of polyethylene in conjunction with high impact resistance, a mixture of polyethylene and polyamide is added as the type-determining plastic. If, on the other hand, the property of polypropylene is sought in conjunction with high rigidity, polypropylene and polyamide can be used as the type-determining plastic. The tolerance in the properties and the quality of workable material naturally depends on the ratio of waste plastic and sorted plastic. As a type-determining plastic bifunctional polymers or bifunctional polymer blends can be used. The type-determining plastic used depends, as described above, on the desired properties of the compound to be produced.

Around z. B. a desired Need to produce compound the two main grain components, namely waste plastic and type-specific plastic mixed according to recipe requirement are still being added aggregates, additives and reinforcing agents be mixed. Preferably, a reactant may also be added become.

generally known a distinction is made between soft plastic and hard plastic. It is therefore advantageous according to an embodiment of the invention, when the polyolefine plastic waste into the fractions soft plastic and hard plastic separated and the fractions in a given relationship be entered in the mixer. In a further embodiment the invention, the crushed soft plastic into pellets and / or Agglomerate particles compacted, wherein the plastic particles in the Pellets or Agglomeratteilchen only partially melted become. In the hard plastic fraction are in a further embodiment of the Invention preferably pellets and / or Agglomeratteilchen provided the plastic particles in the pellets or agglomerate particles only partially melted are. Furthermore, in one embodiment the invention in hard plastic also used to semolina crushed particles become. It is important that within the political groups one possible same grain size is present, to the desired Homogenization to achieve and avoid a segregation effect.

Under Aggregates are commonly used Understood substances, which are mainly the rigidity of plastics to adjust. It can but also exceptionally basic materials, eg. B. the impact resistance modifying additives, such. B. TPE be metered targeted. Additives are process-optimizing substances, such as stabilizers, Dispersing aids and flow improvers. Additives also include pigments, UV protection and compatibilizers understood, which contribute to the optimization of use. Under reinforcements become common Organic or inorganic fibers understood that are mixed. Reactants make sure that the different polyolefin plastics at least one similar molecular building block or ramifications have.

It is naturally problematic Substances that are added only in small amounts (eg <1%) evenly with the rest To mix substances. A dosage to make at an extruder plant, is difficult. Therefore, it is known in practice, in advance so-called masterbatches in which the aggregates, additives, pigments etc. in an easily dosed Granule form to be transferred. These Granules consist of a carrier plastic, the premix before filling of the extruder into a so-called cold blend. The disadvantage of this dosage form is that it is almost impossible to Change recipe in a timely manner. Furthermore is the production of masterbatches complicated.

at the invention, the plastic material before the loading of a Granulator extruder homogenized. Agglomerate Formations of Powder and semolina materials be dissolved, to the desired homogenization to reach. This concerns above all the aggregates, Color pigments, but also fibers. In addition, the Substances are introduced dry into the extruder, to disruptive outgassing to reduce, because the outgassing of water vapor can above all then to an insoluble one Become problem if aggregates or organic fibers too much fibrilär or crystalline water. This bound water can barely over one of the usual Vacuum degassing of extruders are evacuated and thus remains as a foaming agent in the melt. To be entered in the extruder Material must also be eligible. This in turn affects the aggregates, additives and reinforcing materials.

In the invention, an inhomogeneous regenerate is used as the basic raw material. This Regenerat be is made of a mixture of polyolefin plastics and is z. B. as semolina or in anpelletierter or anagglomerated form. The latter means that the plastic particles in the pellets or Agglomeratteilchen are only partially melted. Flakes can also be processed, and it may be necessary to make the bulk density of the flakes finer by milling. From the origin of such a Regenerat hard plastic (blow molded parts, thermoformed parts or injection molded parts) or has foil origin. As already stated, such a regenerate is blended in a defined ratio with type-determining plastic or a plastic mixture together with additives, it may be preheated for this purpose. Alternatively, the metered addition takes place at room temperature. The addition of the type-determining plastic takes place in order to produce a property tendency in a defined direction. The adjustment and targeted production of processing and service properties (flow improvement, stiffness, impact resistance, releasability, etc.) and the support of the type-determining plastic is carried out with the help of aggregates, fillers and / or reinforcing materials. A metering is preferably carried out via a multiple metering device in the mixer used. Powder and fibrous materials are predried by friction heat and can be impregnated or rendered hydrophobic by the addition of waxes or low molecular weight polyolefins.

at the method according to the invention may be a one-step premix or a two-stage. In the single-stage premix, the plastic particles, the in semolina, pellet or powdered Form are agglomerated by adding a cold tacky binder or compacted into a heap. Alternatively to the addition of a binder The temperature in the heating mixer can be increased so much that additives like For example, melt wax and thus can bind other additives. The Temperature can also be increased so far be that low-temperature melting plastics such as. Melt PE-LD and incorporate the additives. The difficulty this is to make the process stable in a temperature window drive so that the material does not clump together. Depending on the used Plastic types, it is hardly possible Temperatures greater than 100 ° C to reach. In two-stage premixing can also flakes or lumpy Material present. Here, first in the first stage, a Melt agglomeration and then in the second stage a Korngrößenhomogenisierung in a cooling mixer. The material is heated in a heating mixer, so less in the extruder Energy must be applied. The temperature in the heating mixer is higher than 100 ° C, with it the moisture bound in the pulp evaporates. essential to the invention is therefore that the addition of all components initially in a the extruder upstream mixing device he follows. The extruder is only used for thermo-mechanical forming and granulation. In the extruder no further addition of additives takes place etc..

aid the invention is z. B. a compound of waste plastics obtained, namely plastic granules with defined processing and service characteristics at a constant Quality. at of the invention also the melt viscosity control by adjusting the recipe during the process. Serves as a controlled variable z. B. the power consumption of the extruder.

In the capacity the for the implementation There are no restrictions on the plant to be used in the process for example due to difficulties in conveying and metering to the extruder. As always a premixed material of the same bulk density entered into the extruder is, there are no set-up times at a recipe changeover.

As already mentioned, the peculiarity of the invention is that of an inhomogeneous one Base mixture of waste plastic is a type-determining plastic and reactive substances added which determined the mixture of the different plastics Give basic properties which are then and fillers supports become. A purified, inherently homogeneous plastic stream is through Mix with a purified or pure plastic in itself homogeneous Plastic stream (type-determining plastic) so homogenized that within a property window, a defined new type of plastic results. Although this may be from the point of view of distribution the plastic varieties are still considered inhomogeneous, but not when it comes to a desired one Product feature goes, such as B. the impact resistance. About suitable additives is the processing feature set by the product feature independently is. With additives, the processing property is pronounced the existing inhomogeneity balances. Thus, a mixture can be obtained which behaves as "low viscosity" polyethylene, though they z. B. consists of 50% polypropylene.

One Another advantage of the invention is that friction peaks in the catchment area of the extruder and decomposition of the pulp fibers be avoided. In the invention, specifically stable plastic molecules are produced, which have a certain property.

following Two method examples are shown schematically using a Annex explained.

1 shows the implementation of the method according to the invention in a single-stage mixing process.

2 shows the implementation of the method according to the invention in a two-stage mixing process.

At the plant after 1 is located in a silo hard plastic and in another silo plastic flakes from pre-sorted plastic waste. As already mentioned, the plastic waste is previously cleaned and comminuted, for example, films to flakes. Hard plastic is broken up and crushed accordingly. Another type of silo contains type-specific plastic. This is pure plastic, which is either pure plastic or is also obtained from waste plastic. Alternatively, a mixture of pure plastics can be present. For better handling and compaction, the plastic flakes are suitably compacted. They are z. B. agglomerated or pelleted, preferably only on and not melted through. In other reservoirs are additives. In appropriate proportions, the individual plastic components and additives are placed in a heating mixer. In these, a binder is given, whereby the individual components adhere to each other. The resulting particles are fed into an extruder, which generates by thermal deformation granules, which are fed to further processing.

The plant after 2 is different from the after 1 First of all by the fact that both a heating and a cooling mixer are used, in which the individual components are registered in the manner described above. At low-temperature melting plastics, such as PE-LD films are formed in the heating mixer into lumps, which are already mixed in relatively homogeneous. The lumps are smashed into small lumps in the cooling mixer. Subsequently, the particulate material is fed either to an extruder or Doppelbandkalandern. Double belt calenders can either be operated without pressure to produce thin panels for vacuum forming or double belt calenders operated with high pressing force to produce thicker panels or panels. At the plant after 2 A compaction of the flakes can also be omitted. They can be entered directly into the heating-cooling mixer. Example of a recipe: Folienkompaktat 39.0% by weight Hard plastics 19.6% by weight bifunctional polymer blend 13.1% by weight wax 2.5% by weight CaCO ₃ 25.0% by weight Additive flow improver 0.5% by weight Additive dispersing aid 0.3% by weight

Claims (21)

Process for the preparation of a workable plastic material from waste mixed plastic, presorted in the waste mixed plastic, cleaned and crushed into flakes and / or semolina and the minced good fed to a processing is characterized by the following features: - from mixed waste plastic polyolefin plastic is sorted out, - the shredded polyolefins Mixed plastic waste becomes dependent from its constitution to semolina, pellets, flakes, small ones pieces or agglomerate particles comminuted to a base raw material or compacted, wherein the pellets or Agglomeratteilchen whole or partially melted down, - a predetermined amount Basic raw material is sorted together with a predetermined quantity, type-defining plastic or a mixture of unmixed, type-determining plastics, aggregates and / or fillers and / or reinforcing materials homogeneously mixed and - the in free-flowing Condition present mixed material is subsequently his Use supplied. Method according to claim 1, characterized in that that the material from the mixer in an extruder to a compound is granulated. A method according to claim 1, characterized in that the material from the mixer to a dop Pelbandanlage for the production of plate material is scattered. Method according to one of claims 1-3, characterized that the polyolefine plastic waste into the fractions soft plastic and Hartkunst fabric is separated and the fractions in a given relationship be entered in the mixer. Method according to claim 4, characterized in that that the crushed soft plastic into pellets and / or agglomerate is compacted, with the plastic particles in the pellets or Agglomerate particles are only partially melted. Method according to one of claims 1-4, characterized that the crushed hard plastic into pellets and / or agglomerate is compacted, wherein the plastic particles in the pellets and / or Agglomerate particles are only partially melted. Method according to one of claims 1-4, characterized that the crushed hard plastic is crushed into semolina. Method according to one of claims 1-7, characterized that pure plastic is used as the type-determining plastic. Method according to one of claims 1-7, characterized as a type-determining plastic sorted waste plastic or a mixture of varietal waste plastics used becomes. Method according to one of claims 1-9, characterized that as a type-determining plastic is a bifunctional polymer or bifunctional polymer blend, in particular a mixture of Polyethylene or polypropylene and polyamide is used. Method according to Claims 1 and 2, characterized that the material is introduced dry into the extruder. Method according to one of Claims 1-10, characterized that a one-step mixing process takes place and by adding a cold-tacky binder for semolina, pellet or powder present material in the mixer produces an agglomerate or heap becomes. Method according to one of Claims 1-10, characterized that a one-step mixing process takes place and the material only warmed up is that the low-temperature melting plastics still no Forming lumps, with low-temperature melting additives already by melting for Connect the other components. Method according to one of Claims 1-10, characterized that a one-step mixing process takes place and the material only warmed up is that the low-temperature melting plastics still no Forming lumps, adding additives and other added components into the melted surface of the material. Method according to one of Claims 1-11, characterized that a two-stage mixing process is performed, wherein in a first Stage one by low temperature melting plastic lumps be formed and in a second stage in a cooling mixer the lumps crushed and homogenized in grain size be in a cooling mixer he follows. Method according to one of claims 1-13, characterized that aggregates as micro-granules or in powder form in the Mixing process can be entered. Method according to claim 14, characterized in that that process-optimizing additives as micro-granules or in powder form be entered in the mixing process. Method according to one of claims 1-15. characterized, that pigments, UV protection and / or Compatibilizer as microgranules or in powder form in the mixing process. Method according to one of claims 1-16, characterized that reinforcing materials be introduced in the form of fibers in the mixing process. Method according to one of claims 1-17, characterized that reactant in the form of a liquid in the mixing process is introduced. Method according to Claims 1 and 2, characterized that measured the power consumption of the extruder and as a controlled variable for the dosage the aggregate is used.