BR112019004401B1 - PROCESS FOR PRODUCING A RECYCLED POLYOLEFINE - Google Patents

Abstract

The present invention relates to a process for the production of polyolefin recyclates and particularly HDPE recyclates, in which mixed-color waste materials containing polyolefins are subjected to a low temperature wash, a high temperature wash in an alkaline medium , flake classification and high temperature treatment to remove migrating materials in a predetermined sequence. Through the described process, recycled polyolefin can be obtained with essentially improved purity compared to recycled materials available on the market, which can be used for the production of new product packaging for consumption. Furthermore, unpleasant odors associated with known polyolefin recyclates due to the decomposition products of migration materials formed during the extrusion process are largely avoided.

Description

[001] The present invention relates to an improved process for the production of polyolefin recyclates and particularly HDPE and PP recyclates.

BACKGROUND OF THE INVENTION

[002] Polyolefins are robust, flexible plastic materials, which present, due to their simple processing capacity and chemical nature, numerous applications and represent, with a portion of around 45%, the largest individual group of consumer plastics in Europe.

[003] The largest field of application for polyolefin plastics is packaging. The predominant presence of plastic packaging keeps them in the focus of environmental debates. If there is no adequate collection, sorting and recycling infrastructure, plastic packaging can become a problem, as the debate on marine pollution shows. The EU Packaging Directives, as well as relevant national legislation, have initiated the development of such infrastructures, across Europe, at different levels, over the last 25 years. In Germany, these are yellow bag/yellow collector type collection systems and the concepts associated with this, as well as sorting and recycling systems. The long-term sustainability of these infrastructures and their extension to other countries largely depends on the demand for recycled plastics - which improves when the quality of the recycled materials on offer also improves.

[004] With PET packaging, this is already possible in the so-called closed circuit, with plastic packaging being used to make packaging again, in the next cycle of use. In polyolefins the problem arises that the polyolefins are processed into mixed colors from standard recycling processes, which are also found in the recycled material. The final products thus produced therefore have different shades of gray depending on the composition of the starting material. Since the recycling processes available to date also leave residual impurities in polyolefin plastics, typical recycling odors develop in the processed products that impede end-user-friendly applications. As a result, today's polyolefin plastics are predominantly associated with more end-user open-loop applications, meaning recycled materials are no longer packaging, but durable plastic products processed from the industry. of construction.

[005] For reuse of polyolefin plastics, foreign substances are particularly problematic, which are absorbed during the primary use of polyolefins in small quantities. Thus, a polyethylene shampoo bottle can absorb non-polar ingredients, such as shampoo perfumes, that cannot be removed by simply washing them with water. If such recycled polyolefin is exposed to high thermal loads, as is the case, for example, in extrusion processes, then these migration substances decompose, which constitutes an essential source of the typical recycling odor.

[006] Furthermore, it is particularly problematic in polyolefin packaging materials, which, in contrast to, for example, PET beverage packaging, do not appear as a relatively uniform output material color. This leads to products with different shades of gray, as mentioned above, using the usual classification methods to this day.

[007] An exception is formed by special collection systems for unitary packaging, for example in the form of milk bottles, which, like other beverage containers, can be collected separately from UK supermarkets. Most polyolefin packaging, which often contains not only different colored polyolefin packaging but also a significant proportion of other plastics and foreign substances such as metals, wood or paper, is separated, however, only by material type (e.g. example, "PE") and, as explained above, granulated generally after crushing and washing with cold water and brought to a level of release in consumer applications, which is, in most cases, well below the price of the new material.

[008] The long-term trend of rising commodity prices, as well as the pressure felt in the consumer goods industry to accommodate a growing demand for sustainably produced products, has created a need for processes with which to process waste of polyolefin packaging, especially from household products, for reuse in final consumer packaging. For this purpose, the process must provide a recycled product that is as pure as possible, which can be fed to a new extrusion, without generating an unpleasant odor by-product. Furthermore, it must be possible to carry out the process simply, even with large production volumes and low costs, in order to obtain a competitive product on the market. The present invention addresses this need.

SUMMARY OF THE INVENTION

[009] In general, the present invention discloses processes for producing recycled polyolefin from waste materials containing mixed color polyolefin. In particular, the disclosed process can separate polyolefin from contaminating components, which have been inserted into the polyolefin as a result of migration processes, the process can also separate, however, contaminating components that adhere to the polyolefin on the surface or that exist in the mixture with the polyolefins.

[010] In particular, the present invention relates to a process for producing a recycled polyolefin from waste materials containing mixed color polyolefin suitable for the production of consumer products, which comprises the following steps: (i) treating a mixed color polyolefin waste material fraction with water without adding thermal energy, (ii) treating the polyolefin waste material fraction consisting of (i) in the context of a wash with an alkaline medium at a temperature of at least minus 60 °C, (iii) classify the flakes of the polyolefin waste material fraction obtained in (ii) by obtaining one or more polyolefin waste material fractions of pure color, in which there is, respectively, a polyolefin in concentrated form, whereby steps (ii) and (iii) can also be carried out in reverse sequence, (iv) treating fractions of pure colored polyolefin waste material obtained in the above steps at a temperature in the range of 50 to 155 °C, preferably , for an interval of at least 60 minutes.

[011] If the fact mentioned above is specified, that steps (ii) and (iii) can also be carried out in reverse sequence, then it must be understood here that, in this case, treatment with water (i), in the which no thermal energy is added, a flake classification of the fraction of polyolefin waste material, obtained by treatment with water to obtain one or more fractions of pure colored polyolefin waste material, is subsequently associated, in which a treatment of the fraction of residual material in the context of washing with an alkaline medium at a temperature of at least 60°C. The treatment described in (iv) is then associated with this washing.

[012] The fractions of polyolefin waste material to be considered in the process according to the invention as output material may be fractions of polyolefin waste material or mixtures of polyolefins that arise. However, it is preferred if the fraction of residual polyolefin material is a material consisting of a predominant portion, that is, at least 75% by weight, preferably at least 80% by weight, and particularly preferably, at least 90% by weight of polyolefins of the same polymer. The basic polymers include, among others, homopolymers such as polypropylene or polyethylene, but also copolymers of ethylene or propylene with other α-olefin monomers. By polyethylene, the various known modifications should also be seen, such as HDPE, LDPE or LLDPE respectively as independent basic polymers. In the context of the present invention, particularly preferred polyolefins are polypropylenes and modifications of polyethylene, particularly in the form of LDPE and HDPE, preferably in the form of HDPE.

[013] As raw material, fractions of residual material pre-classified according to the components of the main synthetic material, which can be obtained by conventional waste separation equipment, can be used for the process. Such previously classified fractions of residual material can be obtained, for example, in the form of compressed bales as commercial products, and consist, in a predominant portion (about 90 to 95%, referring to the synthetic material portion) of one or more polymers. base of defined plastic material (e.g. PP, HDPE or LDPE).

[014] In the context of the process according to the invention it is also possible to use waste materials collected separately, such as, for example, milk packaging. Since such separately collected waste materials generally have essentially uniform impurities, the process according to the invention cannot fully exercise its advantages in conditioning such waste materials. It is preferred, therefore, if the residual material fraction to be considered in the process according to the invention contains at least polyolefins of different colors. As colored, transparent, white and black polyolefin articles are also considered in the context of the invention. It is particularly preferred if the portion of the residual material fraction, which constitutes the main color of the residual material fraction, is not more than 80% by weight, particularly, not more than 60% by weight, and particularly preferred, is not greater than 40% by weight. Furthermore, it may be preferred if in the process according to the invention the transparent residual material fraction to be considered contains residual white colored polyolefin articles, preferably with a portion of about 10 to 60% by weight of transparent article, about 10 to 60% by weight of white article and about 10 to 60% by weight of colored article remaining, and particularly preferred, with a portion of about 20 to 45% by weight of transparent article, of about 20 to 45% by weight of white article and approximately 20 to 45% by weight of residual color article.

[015] Furthermore, it is preferred if the residual material fraction comprises packaging for different applications (for example, shampoo and long-life products), since such residual material fractions are contaminated with a wider range of impurities, such that the advantages of the process according to the invention become fully efficient.

[016] In the first step (i), which can also be referred to as cold washing, the fraction of residual polyolefin material is washed with water, to remove surface impurities from the polyolefins, for example, in the form of food remains, salts or paper labels. To achieve this, it is not necessary to heat the water or modify it with additives before the washing process. The temperature at which this washing is carried out depends, since no thermal energy is added, on the insertion of mechanical energy and on the external temperature and is often at 30°C or less. Depending on the degree of impurity and the existing impure components, cold washing can be replaced, in isolated cases, however, also by mechanical dry cleaning, for example, in which abrasive components are added and the mixture is moved intensively, posteriorly. By stirring with the polyolefin components, impurities can thus be released from their surfaces. The abrasive components can be separated from the polyolefins again, for example, with the help of a Schwimm/Sink process, in which the polyolefin floats in water due to its density, while the abrasive components sink.

[017] For washing in the context of step (i) it is necessary that the output material is subjected to one or more crushing steps before cold washing. This is particularly significant if the output material contains packaging with hollow spaces, as in this case it is possible to ensure through crushing that the washing water can come into contact with the entire surface of the packaging. The crushing may necessarily be carried out in a crusher, a granulator or similar crushing devices. Grinding can occur either wet (i.e., by adding water or humidity) or dry. Furthermore, crushing can also occur in a process of two or more levels, particularly in a two-level process, with the first level being preferably arranged as a dry process and the second level as a wet process.

[018] The average size of the particles to be adjusted through crushing should be about 20 mm, particularly at most 15 mm, preferably, however, at least 2 mm and particularly at least 4 mm. A particularly favorable particle size is in the range of 5 to 10 mm. Particle size means, here, in this case, the greatest spatial expansion of the respective particle.

[019] The particle size distribution may vary. Ideally, however, at least 80% (± 10%) of the particle should have a particle size within the specified area.

[020] Furthermore, it may be significant to subject the output material, prior to treatment in step (i), to a physical removal step to release contaminating components. For example, metal or glass components can be removed from the output material, which can be extracted from the output material with the aid of magnets, or the higher specific gravity of the impurity is exploited. Since polyolefins are lighter than glass or metals, the output material can be transported, for example, with the aid of a conveyor through a column, which is metered in such a way that the impurities fall into the column, while the Lighter polyolefin components are transported out through the column. In the same way, it is possible to charge the material flow from below with a gas flow, whereby the lighter components are moved upwards. Since heavier components suffer less fluctuation, they can be separated from lighter components by means of such a device. Finally, a Schwimm/Sink process can be used to remove components with a higher specific weight, in which it is exploited that polyolefins are lighter than water. In the context of such a process, polyolefin components are therefore obtained with a floating fraction on water, while components such as glass and metals sink in water and can be separated as sediments.

[021] For the separation specified above of components with a higher specific weight, it is necessary that these be associated with crushing of the output material, since, through this, there is a uniform output material. Furthermore, prior crushing has the advantage that impurities that are present before crushing in the cavities of the polyolefin output material can also be removed.

[022] It may still be appropriate for the output material to be separated before crushing by color and/or polymer, and in particular a rough distribution into transparent, white and colored (residual) components and by type may be carried out. of polymer. By “gross” color separation it is understood that the output materials must be separated according to their main color, with mixed color consumer products being assigned those color fractions that correspond to their main color. Similarly, by “gross” classification of polymers, it is a separation according to the main polymer. Therefore, HDPE bottles usually have PP closures; in this case, these bottles are attributed to HDPE polymers.

[023] To avoid accumulations of washing water contaminated with impurities, it is important to drain as mechanically as possible the fraction of residual polyolefin material obtained in step (i), before it is subjected to the following steps of the process.

[024] In the second step (ii), which is also called hot washing, the residual polyolefin material fraction is treated at elevated temperature with a water-soluble alkaline solution. In this step, on the one hand, the residues of glue adhered or labels printed on the output material are dissolved and removed, and, on the other hand, residual contaminations are removed, which, in the context of cold washing, could not be removed. separated from the output material. The term “printed labels” refers, for example, to inks that are printed directly on packaging, such as beverage or shampoo bottles. For example, non-alcoholic beverage bottles are often printed with epoxy-based inks. Furthermore, acrylate- or ethylene-co-vinyl alcohol-based polymer coatings (e.g. EVOH film) can be removed by alkaline treatment.

[025] Step (ii) is necessarily carried out at a temperature of at least 60 °C, particularly at least 70 °C and preferably in the range of 80 to 90 °C, more preferably, of 80 to 85 °C. Alternatively or in addition to this, it is preferred for step (ii) if, by alkaline means, it is a bleach, particularly an aqueous sodium or potassium bleach and, preferably, an aqueous sodium bleach. The concentration of sodium bleach in relation to sodium hydroxide should not exceed 10% by weight, as this generally places higher demands on the devices in which step (ii) is carried out. Since it has been proven that most impurities can be removed even at low sodium hydroxide contents, a concentration range of 0.5 to 5% by weight for sodium hydroxide solution can be specified as preferred. A particularly preferred concentration range is 1 to 3% by weight.

[026] After step (ii) and before the subsequent step (iii) it is important to dry the residual material fraction, so known drying methods can be used. Examples of suitable drying devices are fluidized bed dryer, circulating air dryer or adsorption dryer. Before drying, it may be appropriate if the residual polyolefin material fraction derived from step (ii) is washed with water, to remove as completely as possible the alkaline medium used in step (ii). This is particularly true when the alkaline medium contains inorganic components, which can be removed in the following process steps only with great effort, again from the polyolefin waste material fraction. As drying occurs with the evaporation or evaporation of water from the alkaline aqueous solution, it is also appropriate to subject the fraction of residual material, before drying, to mechanical drainage, to minimize as much as possible the permanence and accumulation of components dissolved in water.

[027] After the drying mentioned above, it may also be significant if the residual polyolefin material fraction is subjected to an air separation step, in which label residues can be separated. Air separation is particularly suitable for the waste material fraction containing printed or highly polluted labels or synthetic material films. Since they are very fine compared to particles of synthetic material packaging, they can be separated from the main constituents of the waste material fraction by means of air separation.

[028] In step (iii) of the process according to the invention, the residual polyolefin material fraction is subjected to flake classification, with the material being separated, firstly, by color. Thus, in the context of flake classification, particularly particle mixtures can be separated into colorless/transparent particles, white particles and particles with remaining color. In addition, however, further separation of the colored particles by color is also possible.

[029] Suitably, the flake classification is arranged in such a way that residual material components that do not correspond to the main material of the residual material fraction entered into the flake classification can also be removed. If the residual material fraction contains, for example, HDPE as the main component, then, in a corresponding flake classification, residual portions of polypropylenes or other synthetic polyolefin materials can be removed, but also existing residues of other synthetic materials or of non-synthetic materials. Furthermore, it is possible, particularly for the gain of transparent or white particles, to separate printed or highly polluted particles from them, to thus avoid unwanted discolorations in further processing of the particles.

[030] The device used for flake classification is preferably a sensor-assisted separation system. Sensor-assisted separation systems may consist of a conveyor belt for material individualization and contact, a detector or several detectors, which are arranged below or above the conveyor belt or in the material disposal area, and a bar of nozzles with which the material component to be classified as positive is distributed. Alternatively, the material can be distributed through vibrating chutes in steep slide channels, at the ends of which the particles are released in free fall into the detectors.

[031] The classification of particles, particularly for the separation of particles of different materials, occurs appropriately through the use of NIR (Near Infrared) detectors. To separate particles with different colors, conventional color cameras can also be used. For colored fractions, it may also be useful to use a post-classification step that ensures compliance with a defined color spectrum. In this case, the color composition is initially only measured by a detection unit in standard operation and compared against a color standard, without the particle being distributed. Only when the color composition deviates from a color standard by a given tolerance range is it classified into which particles of the respective excess color are discarded.

[032] Devices suitable for flake sorting are operated, for example, by the company Bühler GmbH under the trade name SORTEX or by the company Steinert Global under the trade name UniSort.

[033] As specified above, mixed color output products can be incorporated into the process according to the invention that have a homogeneous color distribution. Thus, a mixed color output product, which has, for example, 20 to 45% by weight transparent components, 20 to 45% by weight white components, and 20 to 45% by weight remaining color components, can be subjected to flake classification. Since conventional color sorters are optimized in a separation for relatively smaller, discolored portions (e.g. << 5%) from a feed stream, with such color sorters, a unit of color required for a product quality acceptable cannot be easily achieved.

[034] In the context of the experiments underlying this patent application, it was surprisingly determined that it is possible to ensure high color unity when using intensely mixed color output materials through the sequence of several color classifiers. If the output material therefore contains essential portions (20% by weight or more, relative to the total weight of the polymer to be separated from the output material) in components, which do not correspond to the main color of the output material (e.g. , 20% by weight of remaining color and 80% by weight of white particles), the use of two color sorters connected in sequence is suitable for raising the color unit of the product obtained by the first color sorter to a significant measure. If the output material contains significant portions (i.e. 10% by weight or more, relative to the total weight of the target polymer to be separated into the output material) of white, transparent and colored components, then it is preferred, in addition, if, in the context of flake classification, in a first step, white and transparent components are separated from the remaining color components and subsequently, in a second step, the white components from the transparent ones.

[035] A problem with current color classifiers is that their harmonization depends on the desired components remaining in the product, while unwanted components are selectively extracted from the mixture. Technically, color sorters do not allow adjustment in such a way that a product with high yield and high purity (> 95%) is obtained in one or more color sorters connected in sequence. A measure determined by overclassification, i.e. an incorrect output of desired components with undesired components, cannot be technically avoided.

[036] A particularly favorable separation result in the sense of a product with better color quality (i.e., a portion of incorrect particles preferably of about 2% or less and particularly of about 1% or less) and high yield can be achieved according to the invention via a unit of three color sorters, in which the first color sorter separates a desired color component (e.g. white/clear) from an undesired color component (e.g. remaining color). Due to the inevitable incorrect separation in conventional color sorters, the fractions of desired and undesired color components obtained from these color sorters still obtain significant residual portions in desired or undesired color components. The fraction with predominantly desired color components is therefore fed to a second color classifier, which subsequently separates the product obtained from the first color classifier, and there, further elevates the portion of the desired color component . Finally, a third color classifier is provided in the unit, to which the fraction with predominantly unwanted color components is fed from the first color classifier and into which the portion of unwanted color components is even higher. .

[037] The enriched unwanted color component obtained in the color classifier can subsequently be suitably fed to another unit, as described above, in which, from this, another color component (for example, red/ yellow) is separated according to the same scheme. The separated fractions obtained in the third and second color classifier in turn respectively contain even more significant portions in desired color fractions and are therefore fed again to the first color classifier as output material. The unwanted color components enriched in the second color sorter, if the color component contains more colors (e.g. white/transparent), are suitably fed to another unit, as described previously, in which another color component is color (e.g. transparent) is separated from it.

[038] The output material to be separated is a mixture of more than three components of different colors, for example, a mixture of white/discolored/red/yellow/green/blue components, such that the separation preferably comprises at least two units, described as mentioned above, wherein in the first unit, a color pair, e.g. white/bleached, is separated from remaining color components and in the second unit, the color pair is separated into individual colored components. The separation of a color pair into a first unit (instead of just the material of just one color) has the advantage that in mixtures distributed approximately equally in relation to color, the quantity of particles to be separated and the particles to be left in the mixture is similar, which allows for better quantity management in the total composition.

[039] If the remaining color components also contain more colors, for example, red/yellow/green/blue components, then another unit is appropriately needed, in which another color pair , for example, of red/yellow components are separated from the remaining color components (e.g. green/blue). In mixtures with white/bleached/red/yellow/green/blue components, a separation of 1 white/bleached, 2 red/yellow and 3 green/blue components in that sequence is particularly preferred. Furthermore, for each color pair thus obtained, respectively, another unit of three color types, as described above, is preferably preferred, in which the color pairs are separated into individual color components.

[040] The described units of color classifiers and arrangements of several of these units offer, unlike the separation processes available to date, the advantage that equally distributed mixtures can be separated into several defined products with high purities. In a distribution with color classifiers connected in sequences only in a linear fashion, on the contrary, either the yield loss or the number of separation steps required would be very large, which would seriously undermine the cost efficiency of the separation.

[041] It is possible, in addition to the mentioned color classifier units, to include other individual color classifiers in the sequence of the polyolefin waste material fraction. Such color classifiers can be used, for example, to further reduce incorrect color components in the pure color fractions that have been cleaned, in order to improve product quality.

[042] Following flake classification in step (iii), the polyolefin residual material fractions obtained in step (iv), as described above, are subjected to treatment at a temperature in the range of 50 to 155 °C, This treatment must be carried out adequately for an interval of at least 60 minutes. Through this treatment, pollutants, migration products or contaminants that have diffused into the outermost layer of the container, contained in the polyolefin waste material fractions, must be separated as much as possible.

[043] The process parameters are directed according to the inertia and the chemical and physical properties of the corresponding polymer. Therefore, it should be noted that the treatment temperature is possibly higher than the glass transition temperature, however, it is lower than the melting temperature of the synthetic material to be treated. This ensures, on the one hand, that the molecule chains present an enriched mobility, to be able to release migrating substances, and, on the other hand, that they do not melt or soften, which would lead to the individual particles clumping together.

[044] As suitable temperature ranges for the most commonly used polyolefins HDPE, LDPE and polypropylenes, the following ranges can be specified:

[045] HDPE: 50 to 130 °C, preferably 90 to 122 °C, even more preferably 110 to 115 °C

[046] LDPE: 50 to 110 °C, preferably 75 to 105 °C

[047] Polypropylene: 50 to 155 °C, preferably 100 to 150 °C

[048] Through timing, it is ensured that a minimum purification of the material occurs. The timing is guided by different criteria, such as the diffusion speed of the migration products in the corresponding polymer and the softening and melting temperature. As specified previously, the timing for possible complete removal of migration products is about at least 60 minutes. Preferably, the timing is at least about 120 minutes, however, a timing should not exceed about 600 minutes, since in polyolefins, at timings greater than 600 minutes, no further enhanced removal of migrating substances is generally seen. As a particularly suitable timing in the context of the invention, an interval of about 180 to 360 minutes and particularly of 180 to 240 minutes can be specified.

[049] The separation of migrating substances in the context of step (iv) can be positively influenced by the creation of a vacuum. The creation of a vacuum is coupled, furthermore, with the advantages that migrating substances can be removed by the vacuum of the device, in which heat treatment takes place, and that synthetic materials, at elevated temperatures, are not exposed to any atmosphere. containing oxygen, in which oxidative damage to synthetic materials may occur. If the heat treatment is carried out under vacuum, then a pressure of ≤ 15000 Pa, preferably ≤ 5000 Pa, particularly ≤ 2000 Pa and even more preferably between 10 and 200 Pa must be set.

[050] Since oxidative damage can also be suppressed, in which the heat treatment is carried out in an inert gas, the treatment in step (iv) can also be carried out in an inert gas atmosphere. The term “inert gas atmosphere” should not in this case necessarily be understood as inert gas within the entire device. On the contrary, it is sufficient when inert gas exists in the area of the device directly surrounding the heated particles. As inert gases, particularly nitrogen and argon are considered, of which, however, nitrogen is preferred, for reasons of cost.

[051] For heat treatment, suitable devices are used, for example, from the company Erema (AT) under the trade name VACUREMA.

[052] Between steps (iii) and (iv), the residual material fraction obtained by step (iii) is fed to an extrusion device for the purpose of producing a polyolefin granulate. This can be arranged in such a way that the particles obtained by step (iii) are only plastically molded into a granulate, however, it is possible that, during extrusion, additives are fed, for example, in the form of dyes or pigments. In conjunction, for example with polypropylenes, common additives such as peroxides or talc can also be fed during extrusion for compatibility purposes. Since, in the extrusion of polypropylenes, in which such additives have been included, odorous substances result, which can be perceived as unpleasant by the consumer, it is, in this case, advantageous if the extrusion is carried out in step (iv), since in this case, the odor substances formed can be at least partially removed again. This means that unpleasant odors can be reduced even compared to new polypropylene products composed of talc.

[053] In the context of extrusion, the material can also be degassed by applying a vacuum and freed from substances in the polyolefin melt. Hereby, it should be noted, however, that such degassing cannot replace the heat treatment in step (iv), because the degassing had to be carried out in a time interval, which does not allow for any economical operation of the extrusion device. .

[054] If the residual material fraction obtained by step (iii) is fed to an extrusion, then the extrusion device is appropriately arranged directly before the device for heat treatment, in step (iv), since that the material was heated in place. Since the heat treatment is also carried out at a high temperature, less energy is therefore required in such an arrangement than when the material is initially cooled after extrusion, and then needs to be heated again during the treatment. heat at a predicted temperature. To prevent energy loss through the transport steps between the extrusion and the treatment container, certain measures can be taken, such as, for example, transport mechanisms, insulation, additional vacuum in the passage area, etc.

[055] In individual cases, it is also possible to perform, initially after steps (iii) and (iv), an extrusion for a granulate. This has, however, the advantage that the residual material fraction, before granulation, generally still contains small particles, such as film fibers, which can be extracted in a heat treatment using a vacuum. In carrying out the process in such a way, it would therefore be essential to install filters, which would also need to be cleaned at relatively short intervals. Furthermore, the polyolefin particle presents, before processing into a granulate, a relatively large volume, which limits extraction through the heat treatment device.

[056] Another disadvantage of extrusion after step (iv) is that through the thermal load of the material, during extrusion, new substances can be generated, which lead to an unpleasant odor in the product. Such substances may be reduced in an extrusion prior to step (iv) by step (iv); in an extrusion after step (iv) this, in turn, is not possible.

[057] In fact, it must be assumed that processing a granulate before heat treatment adversely affects the properties of the product and the required heat treatment time. Therefore, on the one hand, during the extrusion of the migration substances, decomposition products can result that can be removed from the granulate again, but only in a bad way; on the other hand, there are migration substances generally on the surface of the particles and must therefore be slightly removed by heat treatment, such as migration substances, which are distributed following extrusion in the granulate particles. Surprisingly, it was determined, however, that these effects have only minimal impacts on the product and are overcompensated through the advantages of a heat-treated granulate. Furthermore, due to its more compact structure, a granulate cools less quickly than the polymer material before granulation, so that in a direct feed of the granulate into the heat treatment in step (iv) less energy is required in total to granulation and heat treatment perform the reverse of the process.

[058] In the context of the present invention, the underlying investigations have demonstrated that it is of less essential importance for the quality of the products that steps (ii) and (iii) are carried out before step (iv) and a granulation step, provided that included, is found after flake classification. Furthermore, it is essential to the process that hot washing is performed before heat treatment.

[059] As previously specified, the present invention also refers to a process in which steps (ii) and (iii) are carried out in reverse sequence. In this case, for example, flake classification (iii) can be performed before hot washing (ii), hot washing (ii) before granulation and granulation before heat treatment (iv). Likewise, the present invention relates, in this embodiment, to a process, in which flake classification (iii) is carried out before hot washing (ii), hot washing (ii) before heat treatment (iv) and heat treatment (iv) before granulation. This last process, in comparison to the previous process, is associated, however, with the same disadvantages, which were previously described for a process execution with heat treatment (iv) before granulation. For preferred embodiments of hot washing, flake classification, heat treatment and granulation the embodiments mentioned above are valid.

[060] Regarding the sequence of individual reaction steps, in one embodiment, hot washing (step ii), flake classification (step iii), granulation and heat treatment (step iv) are preferred.

[061] Without the applicant being able to rely on a certain theory for this purpose, it is suggested that the residual polyolefin material from consumer products presents impurities, for example, in the form of prints, which are dissolved in the context of washing hot, initially, of polyolefin particles. Likewise, it is possible for polyolefin waste labels to contain other polyolefins, for example polypropylenes, which are dissolved in the context of hot washing of the main product. Even if these labels are essentially removed from the pretreated material by an air classifier, small portions of label residue may remain on the material. If this material is subsequently subjected directly to treatment, the residue may re-adhere, particularly when the label material has a softening point or a glass temperature that is below or in the range of the temperature at which they are used. treated the residual polyolefin substances in step (iv). Such adhesions could be difficult to identify in a subsequent flake classification, which would have the consequence that the product obtained would be more contaminated than in a procedure with the sequence of hot washing (step ii), flake classification (step iii ) and heat treatment (step iv).

[062] In another embodiment, an execution of the process with the sequence of flake classification (step iii), hot washing (step ii), granulation and heat treatment (step iv) is preferred. This embodiment is particularly associated with advantages when there are consumers only for a part of the products (for example, white or non-residual or transparent colored products). Since hot washing is associated with a relatively high energy cost, it may therefore be significant to reduce the amount of material to be purified by hot washing by flake classification, to continue purifying only that material by hot washing to which there is a relevant market.

[063] The process, according to the invention, can be carried out in batch form or partially in batch form in which all or part of steps (i) to (iv) with individual charges of residual polyolefin substances. As this is associated with greater technical effort and longer downtimes of individual device components, it is preferred, however, if steps (i) to (iv) are performed continuously.

[064] Another aspect of the present invention relates to a recycled polyolefin obtained according to the process described above. Preferably, this recycled material is recycled LDPE, HPDE or polypropylene.

BRIEF DESCRIPTION OF THE DRAWINGS

[065] Figure 1 depicts a unit 1 of three color classifiers 2, 3 and 4. The polyolefin waste material fraction is fed into the unit by feed 5. In the first color classifier 2 the polyolefin waste material fraction is separated into a desired color fraction 6 (e.g. white/transparent) and an unwanted color fraction 7 (e.g. residual color). The desired color fraction 6 is subsequently fed to the second color classifier 3, in which residual portions of the unwanted color fraction 9 are separated from the mixture and another desired color fraction 8 is generated. The unwanted color fraction 7 obtained in the first color classifier is fed to the third color classifier 4, in which residual portions of this desired color fraction 11 are generated by obtaining a purified fraction in unwanted color fraction 10 from the mixture 7 The portions of desired color fraction 11 and unwanted color fractions 9 are subsequently fed back into the first color classifier 2.

[066] Figure 2 describes a construction with two units connected in sequence 1 and 12, and in the first unit 1 with three color classifiers 2A, 3A and 4A, a color pair (for example white/transparent) is separated from the mixture of polyolefin waste material fraction. The color pair obtained from the first unit is then fed by feed 8 into the second unit 12 in which the color pair is separated into individual components (i.e. white on one side and transparent on the other). In this case, the color pair, analogously to the first unit 1, passes through three color classifiers 2B, 3B and 4B. The individual very pure color components of color pair 13 (e.g. transparent) and 14 (e.g. white) are obtained as a product. The purified residual fraction 10A obtained in the third color classifier 4A of the first unit 1 is fed to another color classifier unit 15, and there it is purified again, and this unit is formed analogous to units 1 and 12.

Example:

[067] Separation of a mixture of polyolefin waste material with a portion of white/transparent flakes and remaining colors of 34%, 34% or 32%.

[068] The specified mixture is fed to a first unit 1 of three color classifiers 2A, 3A and 4A. In the first color classifier, remaining color flakes are separated from the mixture in such a way that a purified fraction of white/clear flakes 6A is obtained with a white/clear/remaining color distribution of about 47.5%/47.5 %/5%. Separate mixture 7A consists of white/clear/colored remaining flakes with a distribution of about 20%/20% and 60%. The purified white/clear fraction 6A is fed to the second color classifier 3A in which the fraction is purified again. In this case, a pure fraction 8 is obtained with a distribution of about 49.5%/49.5%/1% in remaining white/transparent/colored flakes. The additional fraction obtained by the second purification 9A has a distribution of about 40%/40%/20% remaining white/clear/color flakes, and is fed back to the first color classifier 2A. The separated mixture 7A from the first color classifier 2A is conducted in the third color classifier 4A and there they are separated into a fraction of flakes predominantly of residual color 10A (distribution white/transparent/remaining color 2.5%/2.5% /95%) and a fraction 11A, in which transparent and white flakes are enriched (distribution white/transparent/remaining color 32.5%/32.5%/35%). This enriched fraction 11A is fed back, in the same way, into the first color classifier 2A.

[069] The mixture 8 of transparent/white flakes obtained in the first unit is fed to a second separation unit 12 with three color classifiers 2B, 3B and 4B. In the first color classifier 2B, the white flakes are separated from the transparent ones, obtaining a 6B fraction enriched in relation to the transparent flakes (distribution white/transparent/remaining color 6%/93%/1%) and a 7B fraction enriched in compared to whites (white/transparent/remaining color distribution 66%/33%/1%). The fraction enriched in relation to the transparent flakes 6B is further purified in the second color classifier 3B by obtaining a mixture 13 of white/transparent/flakes with a remaining color of 6%/93.5%/0.4% and a fraction residual 9B with a remaining white/clear/color distribution of 6%/88%/6%.

[070] The fraction 7B enriched in relation to white flakes is fed to a third color classifier 4B, in which a white color fraction 14 is created with a distribution of 95%/3.5%/1.5% flakes white/transparent/remaining color and a residual fraction 11B with a distribution of 39%/60.5%/0.5% white/transparent/remaining color flakes. The residual fractions 9B and 11B from the second and third color classifiers 3B and 4B are fed back into the first color classifier 2B of the second unit. If necessary, another color sorter can also be connected to the color sorter 4B to reduce, for example, the portion of color flakes remaining in the white color fraction below 1%.

LIST OF NUMERICAL REFERENCES

[071] 1 first color type unit

[072] 2, 2A, 2B first color sorter

[073] 3, 3A, 3B according to color classifier

[074] 4, 4A, 4B third color sorter

[075] 5 feed fraction of polyolefin waste material to the first unit of the color sorter

[076] 6, 6A, 6B desired color fraction enriched in the first color classifier

[077] 7, 7A, 7B unwanted color fraction enriched in the first color classifier

[078] 8 desired color fraction purified in the first unit of the color sorter

[079] 9, 9A, 9B unwanted color fraction enriched in the second color classifier

[080] 10, 10A, unwanted color fraction enriched in the third color classifier

[081] 11, 11A, 11B desired color fraction enriched in the third color classifier

[082] 12 second color type unit

[083] 13 individual components of 8 pure color

[084] 14 individual pure color components of 8

[085] 15 third color type unit

Claims (13)

1. PROCESS FOR PRODUCING A RECYCLED POLYOLEFINE, suitable for the production of consumer products, from waste materials containing polyolefin of mixed color, characterized by comprising the following steps: (i) treating a fraction of waste material of mixed color polyolefin with water, without adding thermal energy, (ii) treating the fraction of residual polyolefin material obtained in (i) by washing with an alkaline medium at a temperature of at least 60 °C, (iii) classify the flakes of the polyolefin waste material fraction obtained in (ii) by obtaining one or more polyolefin waste material fractions of pure color, in which there is, respectively, a polyolefin in concentrated form, in which steps (ii) and (iii) can also be carried out in reverse sequence, (iv) treat one or several fractions of pure colored polyolefin waste material obtained in the above steps at a temperature in the range of 50 to 155 °C, preferably for a range of at least least 60 minutes, wherein in the flak classification of step (iii), the polyolefin waste material fraction is subjected to a separation using a unit (1) comprising three color classifiers, in which the polyolefin waste material fraction is added to a first color classifier (2), in which a desired color component (6) is separated from an undesired color component (7), the desired color components (6) contained in the first color classifier being added to a second color classifier (3), in which the product obtained from the first color classifier is further classified, and the portion of desired color components is further increased, and the unwanted components obtained in the first color classifier are added to a third color classifier (4), in which the portion of the unwanted color component is further increased and the fractions separated in the second and third color classifiers (9, 11) are added again to the first color classifier as output material, wherein the waste fraction to be brought into the method comprises transparent, white and colored waste polyolefin articles with a proportion of 20 to 45% by weight of transparent articles, 20 to 45% by weight of white articles and 20 to 45% by weight of residual colored articles. 2. PROCESS, according to claim 1, characterized by the single or several fractions of pure colored polyolefin residual material for the production of a polyolefin granulate between steps (iii) and (iv) or after step (iv) , preferably between steps (iii) and (iv), are added to an extrusion device. 3. PROCESS, according to claim 1, characterized by classifying flakes in step (iii) considering several units of three color classifiers, in accordance with the specifications of claim 1. 4. PROCESS, according to any one of claims 1 or 3, characterized in that the polyolefin waste material fraction comprises more than three colors and, in units (1, optionally 15) comprises three color classifiers (2, 3, 4) , respective color pairs are separated from the polyolefin waste material fraction, the color pairs being respectively separated in a later unit (12) into the corresponding color components. 5. PROCESS, according to any one of claims 1 to 4, characterized in that the polyolefin is polyethylene or polypropylene, preferably high density polyethylene. 6. PROCESS according to any one of claims 1 to 5, characterized in that the treatment of the polyolefin residual material fraction occurs in step (ii) at a temperature of at least 70 °C, preferably in the range of 80 to 90 °C . 7. PROCESS, according to any one of claims 1 to 6, characterized in that the alkaline medium in step (ii) is an aqueous sodium hydroxide solution with a concentration of less than 10% by weight, preferably a concentration in the range of 0.5 to 5% by weight and, particularly, a concentration in the range of 1 to 3% by weight. 8. PROCESS, according to any one of claims 1 to 7, characterized in that, in the context of classifying flakes in step (iii), particles that do not consist of polyolefin and particles that present color deviations in relation to the number are separated. predominant number of particles in the polyolefin waste material fraction. 9. PROCESS according to any one of claims 1 to 8, characterized in that the treatment according to step (iv) is applied at a reduced pressure of < 150 mbar, preferably < 50 mbar, particularly < 20 mbar and, in a even more preferred, between 0.1 and 2 mbar. 10. PROCESS, according to any one of claims 1 to 9, characterized in that the treatment according to step (iv) is carried out in an inert gas atmosphere, preferably in a nitrogen atmosphere. 11. PROCESS, according to any one of claims 1 to 10, characterized in that the treatment according to step (iv) is carried out for an interval of 120 to 300 minutes and, preferably, of 180 to 240 minutes. 12. PROCESS, according to any one of claims 1 to 11, characterized in that waste materials containing polyolefin, before step (i), are subjected to pre-classification according to color. 13. PROCESS, according to any one of claims 1 to 12, characterized in that the fraction of residual polyolefin material obtained in step (ii) is subjected to subsequent drying and treatment in an air classifier.