Conversion of polyurethane in conical reactor

Abstract

The invention relates to a continuous process for converting a plastic material comprising polyurethane, comprising the following steps: providing a reaction mixture wherein the reaction mixture comprises-a plastic material, which is in solid form and comprises polyurethane, and further-an aqueous medium, optionally comprising a reaction additive, the mass ratio of water and polyurethane in the aqueous medium does not exceed 0.6 to 1, a filling opening formed by a pressure lock for conveying the reaction mixture to the reactor by means of a first screw conveyor arranged in the first line, said filling opening tapering with respect to the conveying direction at least in one end region, at a pressure of more than 1 bar to 60 bar and a temperature of 180 DEG C to 270 DEG C, the reaction mixture is conveyed to an end region of the reactor by means of a reactor screw conveyor arranged in the reactor vessel, in which end region the reaction mixture subjected to pressure and heat treatment is transferred through a discharge opening designed as a pressure lock into a second line, the reaction mixture subjected to pressure and heat treatment is conveyed by means of a second screw conveyor arranged in a second line, in which an evaporation zone having a temperature higher than the general temperature in the reactor is provided, in which the gaseous components are removed by means of at least one degassing point, and in or after the evaporation zone, in which the gaseous components are removed by means of at least one degassing point. The reaction mixture that has undergone pressure and heat treatment and is free of gaseous components is recovered.

Description

Technical Field

[0001] The invention relates to a method for converting a plastic material comprising polyurethane and to a corresponding device. Background Art

[0002] Polyurethanes are widely used in industrial or domestic products due to their many adjustable properties. Examples of such products are foams, paints, adhesives, potting compounds, hoses, seals, floor coverings, mattresses, automotive parts, sports equipment parts, shoe parts, etc.

[0003] Therefore, a large proportion of polyurethane waste is generated when the corresponding products are damaged or reach the end of their service life.

[0004] Therefore, in the past, attempts have been made to recycle polyurethane. For example, European Patent 01976719B1 describes a method for hydrolyzing polyurethane resin by contacting it with water only at elevated temperature. Summary of the invention

[0005] It is an object of the present invention to provide an improved method.

[0006] The invention derives from the features of the independent claim. Advantageous further developments and implementations are the subject matter of the dependent claims.

[0007] In the context of the present invention, plastic materials are understood to mean materials including plastics, ranging from pure plastics to mixtures containing plastics. The term "plastic" is used in the usual sense and refers to synthetically produced materials, such as materials produced as part of an organic synthesis, such as polymers produced by polymerization, polyaddition and / or polycondensation from one or more different monomers. Plastics can be divided into thermosetting plastics, thermoplastics, elastomers and thermoplastic elastomers according to the usual classification. Well-known examples of plastics are polyethylene, polycarbonate, polyacrylic acid, polymethacrylic acid, polyacrylamide, polystyrene, acrylonitrile-butadiene rubber, styrene-butadiene rubber, chloroprene rubber, butadiene rubber and ethylene-propylene-diene rubber, as well as polyurethanes, wherein in a particular embodiment, the plastic material comprises only hydrolyzable plastics as plastics, for example, polyesters, polyamides and / or polycarbonates in addition to polyurethanes. Natural rubbers previously used for technical tasks, for example in the context of mattress production or chemical processing, such as vulcanized natural rubber, are also considered to be plastics within the scope of the present invention, but lignin, i.e. wood, is not. Depending on their originally intended use, plastics may contain other substances, such as plasticizers, biocides, antioxidants, stabilizers, such as UV stabilizers), flame retardants, dyes or residues of polymerization initiators. Plastics also include those plastics which are not petroleum-based starting products, but are produced from renewable raw materials as part of a sustainability and renewability concept, or as part of a chemical synthesis, or as part of a biotechnological or microbiological process using appropriately designed enzymes or production organisms. The mixtures containing plastics mentioned at the beginning can be mixtures of pure plastics or also mixtures which also contain one or more non-plastics, such as metals, ceramics or glasses. Preferably, the plastics in such mixtures which also contain non-plastics represent the relatively largest proportion by mass or volume, such as at least 67%, at least 75%, at least 80%, at least 90%, at least 95%, at least 98% or at least 99%. Preferably, no non-plastics are present in the plastic material, whereby methods for reducing these non-plastics are known to the person skilled in the art and include, for example, manual removal of non-plastics, magnetic removal of magnetic metals or metal alloys, or separation of plastics and optionally other materials of similar density due to density differences between materials of different densities, for example by air sieving or shaking or vibrating devices. Among the plastic materials, polyurethane accounts for the largest mass proportion, preferably greater than 60%, for example at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90% or at least 95%, and thus represents the main major component. For example, discarded polyurethane mattresses usually contain corresponding small amounts of polyethylene or polypropylene, which usually come from the covering material.

[0008] The plastic material used in the method comprises polyurethane and optionally one or more hydrolyzable plastics selected from polyester, polyamide or polycarbonate, or consists of polyurethane and optionally polyester, polyamide or polycarbonate and / or a mixture thereof. According to a particular embodiment, the plastic material consists of polyurethane or a polyurethane mixture, or consists of polyurethane and polyester or a polyester mixture, such as polyethylene terephthalate or a mixture of polyethylene terephthalate, or consists of a polyurethane / polyolefin composite material, wherein the proportion of polyurethane in the composite material is preferably at least 50% by mass. Polyurethane accounts for the largest mass proportion of hydrolyzable plastics, preferably greater than 60%, such as at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90% or at least 95%, and therefore represents the main main component. For example, the plastic material is a mattress or waste generated during the production of a mattress, and the raw materials thereof contain polyurethane as a hydrolyzable component. The polyurethane may be in particular in the form of a foam, a particular advantage of the process being that a high volume of starting material (i.e., a foam that can be compressed to some extent but always tends to occupy a large volume and therefore requires a first line and reaction vessel of appropriate size) is reacted in the presence of a relatively small volume of reaction medium, resulting in a significantly smaller volume after appropriate pressure and heat treatment. In essence, a large mass of solid (i.e., foam) is converted into a more easily handled form, with a significantly higher liquid content and a smaller volume, thereby solving a major problem in the polyurethane waste and recycling industry.

[0009] One aspect of the present invention relates to a continuous method for converting a plastic material comprising at least one hydrolyzable plastic, comprising the following steps: providing a reaction mixture, wherein the reaction mixture comprises a plastic material, which is present in solid form and comprises polyurethane and also comprises an aqueous medium, wherein the mass ratio of water to polyurethane in the aqueous medium in the reaction mixture does not exceed 0.6 to 1; conveying the reaction mixture further to a filling opening by a first screw conveyor arranged in a first pipeline, the filling opening being designed as a pressure lock of the reactor, the filling opening being tapered at least in one end region relative to the conveying direction; at a pressure of greater than 1 bar to 60 bar and 180° C. to 270° C., the reaction mixture is further conveyed to the end region of the reactor by a reactor screw conveyor arranged in the reactor, the reaction mixture subjected to pressure and heat treatment in the end region of the reactor is further transferred to a second pipeline through a removal opening designed as a pressure lock, the reaction mixture subjected to pressure and heat treatment is further conveyed by a second screw conveyor arranged in the second pipeline, a heating zone having a temperature higher than the temperature prevailing in the reactor is further provided in the second pipeline, gaseous components in the evaporation zone are further removed by at least one degassing point, and a reaction mixture subjected to pressure and heat treatment in or after the evaporation zone and free of gaseous components is obtained. The reaction mixture may be partially or completely free of gaseous components.

[0010] The aqueous medium comprises or consists of water and may optionally contain reaction additives.

[0011] The liquid phase and the contained solids can optionally be separated from the obtained pressure and heat treated reaction mixture, for example by centrifugation or filtration, and the obtained solids can optionally be dried.

[0012] The mass ratio between the water in the aqueous medium and the polyurethane in the plastic material is no more than 0.6 to 1, in particular no more than 0.5 to 1, for example 0.45 to 1, so that the polyurethane is present in a significant excess relative to the mass ratio. Larger amounts of aqueous medium are possible, but surprisingly it has been found that good conversions can be achieved with a specific mass ratio. Thus, the plastic material does not need to be suspended in a viscous aqueous medium, but only needs to be wetted with it. With the goal of a resource-saving circular economy, reducing water consumption is a significant advantage.

[0013] At the beginning of the method, the reaction mixture is conveyed to the filling opening of the reactor by a first screw conveyor, which is designed as a pressure lock. An example of such a pressure lock is the well-known double lock. Other examples are screw conveyors that convey the material while compacting it, or even screw conveyors with return elements that cause local compaction of the conveyed material, which in turn represent a pressure barrier and therefore act as a pressure lock. The volume of the reactor can range, for example, from liters to the cubic meter range to a large range of volumes of several tens of cubic meters or more.

[0014] After passing through the pressure lock, the polyurethane contained in the plastic material, which is initially present in solid form, and any other hydrolyzable plastics present therein, are converted into the liquid phase, since the hydrolyzable plastics contained therein, in the presence of an aqueous medium, optionally containing reaction additives, are gradually converted into the liquid phase due to the temperature and pressure conditions prevailing in the reactor. Due to the low water content, the volume of the reaction mixture is mainly due to the plastic material, which gradually decreases during transport to the discharge opening. Thus, it is possible to use a reactor which is tapered at least in one end region, which advantageously requires less heating power and less space with the tapering and the associated reduction in the volume of the reaction mixture.

[0015] The method is carried out at a pressure in the range of greater than 1 bar to 60 bar, i.e. at an overpressure, based on 1 bar atmospheric pressure, for example 5 to 50 bar, 10 to 40 bar or 20 to 30 bar, for example about 10, 15, 20, 25, 30, 35, 40, 45, 50, 55 or 60 bar. The temperature during the method is in the range of 180°C to 270°C, for example 180°C to 250°C, for example 190°C to 245°C, 200°C to 240°C, 210°C to 235°C, or 215°C to 230°C, for example 185, 190, 200, 210, 215, 220, 225, 230, 235, 240 or 250°C. Preferably, a target temperature and a target pressure are specified, but it will be appreciated by those skilled in the art that during the implementation of the method, the actual values ​​may deviate from the target values ​​or fluctuate around the target values ​​and may be controlled or adjusted accordingly if necessary. Temperature and pressure can be actively regulated. According to a special development, only the temperature is actively regulated, and the pressure is passively regulated as the equilibrium pressure based on the current temperature of the aqueous reaction mixture in the predetermined reaction volume. The conveying speed from the filling opening to the removal opening can be adjusted according to the reduction of the solid content achieved, for example, if the optional sample removal shows that the solid content in the reaction mixture subjected to pressure and heat treatment is too high, the conveying speed will be reduced. The non-limiting example of the duration of pressure and heat treatment is, for example, 1 to 8 hours, for example, 1.5 to 6 hours, for example, 2 to 4 hours, for example, 1, 2, 3, 4, 5, 6, 7 or 8 hours, ± 0 to 59 minutes. For example, the duration of pressure and heat treatment is 45 to 250 minutes, particularly 45 to 240 minutes. However, it is clear to those skilled in the art that in order to adapt to a specific reaction process, the time can be adjusted accordingly, for example, if the reaction occurs very quickly, the time can be less than 1 hour, or if the reaction occurs very slowly, it is necessary to be greater than 8 hours. The process is carried out continuously, and the degree of reaction is determined by sampling from the reactor if necessary, and the time is adjusted accordingly. The reaction is carried out in the absence of air. It can take place in particular under anaerobic conditions. Suitable measures for producing anaerobic conditions are known to the person skilled in the art, for example by expelling oxygen from the aqueous reaction mixture by heating, by generating steam and / or by flushing with an inert gas such as nitrogen.

[0016] The taper of the reactor in the conveying direction can be continuous, so that the cross section between the filling opening and the removal opening is constantly reduced, such as linearly reduced. As another option, it can be specified that the cross section of the reactor after the filling opening is initially kept constant. This takes into account the fact that the conversion must first begin after the reaction mixture is introduced into the reactor, and therefore a smaller reduction in the solid volume in the filling opening is expected. Then, the cross section of the reactor can be reduced at a distance from the filling opening. In fact, it is surprisingly found that even with a small proportion of aqueous medium, solids begin to be converted into liquids after a short conveyance in the reactor, and this is accompanied by a reduction in the solid volume. Therefore, it can be specified, for example, that the first 5% to 20% of the reactor length, such as 10% to 15% of the length, has a constant cross section, and the rest has a taper, such as a linear taper. According to one embodiment, the conveying direction in the reactor follows gravity.

[0017] After the reactor, the reaction mixture of pressure and heat treatment is transferred to the second pipeline by a discharge port designed as a pressure lock. At this time, compared with the reaction mixture initially used, the reaction mixture has a significantly lower solid volume fraction and may not have solids. On the contrary, the reaction mixture of pressure and heat treatment is a liquid or a liquid with solids. An object of the method is to reduce the volume of solids used, which is composed of plastic materials in solid form and possible other solids. For example, based on the volume of solids used, it is possible to reduce up to 95%, up to 90%, or 4% to 50%, for example 5% to 30%, for example 7% to 25% or 10% to 15%. Especially for foams, a high reduction can be achieved.

[0018] Another optional purpose of the method is to further use the product obtained in the reaction process. In order to provide a more uniform reaction mixture through pressure and heat treatment, a vaporization zone with a temperature higher than the prevailing temperature in the reactor is provided in the second pipeline. Therefore, the vaporization zone is suitable for removing components with a boiling point higher than the prevailing temperature in the reactor but lower than the prevailing temperature in the vaporization zone. This is accomplished by one or more degassing points, in which the gaseous components with the corresponding boiling point are removed. If desired, known cold traps, vacuum traps and / or valves or control devices for maintaining a pressure gradient can be used at the degassing point.

[0019] The removed gaseous components can be used separately. The pressure- and heat-treated reaction mixture, now free of gaseous components having a boiling point above the temperature prevailing in the reactor, is recovered in or after the evaporation zone.

[0020] For improved performance, the plastic material is preferably used in a comminuted state, especially if it comprises plastics that do not expand in water. Standard comminution methods can be used here, for example the plastic material can be cut, torn, flaked, shredded, granulated, ground or pulverized, if necessary after previously reducing the temperature to increase brittleness. A non-limiting example of the size of the plastic particles used is about 0.5 cm 3 Up to 10cm 3 (0.5ml to 10ml), for example about 1cm 3 Up to 5cm 3 , in particular for porous plastic materials or plastic materials with a large surface area, or plastic particles having a diameter of at most about 10.5, 2, 1, 0.5, 0.1, 0.05 or 0.01 mm measured at the largest point.

[0021] According to one embodiment, the temperature in the evaporation zone is greater than or equal to the boiling point of the nitrogen-containing components and lower than the boiling point of the high-boiling components. Such nitrogen-containing components are present in particular when the plastic material contains nitrogen-containing plastics, i.e. in the case of polyurethanes. The nitrogen-containing components are usually diamines or degradation products or reaction products thereof. By removing these nitrogen-containing components, on the one hand, they can be used alone and, on the other hand, a more homogeneous reaction mixture subjected to pressure and heat treatment can be provided. In particular, a reaction mixture with few or no nitrogen-containing components is more suitable for any subsequent processing steps, such as pyrolysis.

[0022] In one embodiment, the temperature of the evaporation zone is set at 265°C to 300°C, in particular 265°C to 280°C, for example 270°C to 280°C. In these temperature ranges, it has been determined that a significant proportion of nitrogen-containing components can be advantageously partially or completely removed from the reaction mixture after pressure and heat treatment through at least one degassing point. In particular, it has been determined that at a temperature of 265°C to 280°C in the evaporation zone, diaminotoluene can be removed from the reaction mixture in gaseous form through the degassing point. It is also advantageous that the remaining reaction mixture after pressure and heat treatment, which is partially or completely free of nitrogen-containing components in this way, contains components that boil at higher temperatures. Without wishing to be bound by theory, it is assumed that the polyurethane present in the reaction mixture initially used is a polyol and its degradation products and / or conversion products.

[0023] In one embodiment, a dehydration zone is arranged in the second pipeline upstream of the evaporation zone, wherein the temperature is above the boiling point of water and below the boiling point of the nitrogen-containing components. Thus, gaseous water vapor can be removed by one or more water vapor removal points in the dehydration zone, thereby reducing the water content of the pressurized and heat-treated reaction mixture. This makes it possible to provide a pressurized and heat-treated reaction mixture that is also partially or completely dehydrated and therefore advantageously also in a more easily handled solid form. If desired, cooling traps, vacuum traps and / or valves or controls for maintaining a pressure gradient can be used at the water vapor removal points.

[0024] The pressure in the second pipeline can correspond to the pressure in the reactor or can be atmospheric pressure. In the former case, another pressure lock can be provided at the end of the second pipeline to convert to atmospheric pressure. In the latter case, the pressure is reduced to atmospheric pressure through the discharge port of the reactor, which is designed as a pressure lock. Another option is to use one or more additional pressure locks between the discharge port, which is itself designed as a pressure lock, and the end of the second pipeline to gradually reduce the pressure.

[0025] According to one embodiment, in the second line, in which atmospheric pressure prevails, the temperature prevailing in the second line corresponds at least to the boiling point of water at the corresponding atmospheric pressure. This advantageously enables the water content to be reduced when a dehydration zone having at least one degassing point is provided. In a further development, the temperature in the dehydration zone is below the boiling point of the nitrogen-containing components, wherein the dehydration zone is followed by an evaporation zone at a temperature above the boiling point of the nitrogen-containing components, and wherein the nitrogen-containing components can be removed from the pressure- and heat-treated and partially or completely freed from water reaction mixture by one or more corresponding degassing points in the evaporation zone.

[0026] According to one embodiment, in the reaction mixture supplied to the first pipeline, the volume ratio between solids and aqueous medium is 100:1 to 5:1, such as 75:1 to 10:1, 30:1 to 20:1, such as 25:1. In this regard, it is clear that the aqueous medium in which the plastic material is suspended as a solid (and possibly other solids) does not dominate, but the main volume fraction consists of plastic material, which is only wetted by the much smaller volume of aqueous medium. For example, it can be provided that 0.05 to 0.2 volume fractions of aqueous medium are provided per volume fraction of polyurethane foam or per volume fraction of solids. Therefore, at the beginning of the reaction, only plastic material wetted by the aqueous medium, i.e., essentially solids wetted by the reaction medium, is present in the reaction mixture, whereby when the transport is carried out in the transport direction, the reaction converts the solid with a high capacity requirement into a liquid phase with a lower capacity requirement.

[0027] According to a particular embodiment, the ratio of the cross-sectional area of ​​the reactor before tapering to the cross-sectional area at maximum tapering may be 10: 1, in particular 5: 1, in particular 2: 1. This advantageously takes into account the desired reduction in solid volume.

[0028] According to one embodiment, the obtained reaction mixture after pressure and heat treatment is introduced directly or indirectly into a pyrolysis device for pyrolysis. The principle of pyrolysis itself is known and is based on the thermochemical conversion of substances in the absence of external oxygen, usually in a temperature range of 150°C to 800°C. In the context of the method described herein, the maximum temperature prevailing in the reactor or in the downstream second pipeline is preferably used as the lower limit of the temperature range, such as a temperature range of 265°C to 800°C. For example, this is a temperature range of 265°C to 500°C or 300°C to 500°C. Another example of a temperature range is a range of 700°C to 800°C, in particular 750°C to 800°C, which is advantageously suitable for decomposing calcium carbonate present in the plastic material into calcium oxide and carbon dioxide, thereby providing pyrolysis coke with little or no calcium carbonate as a pyrolysis product. Pyrolysis treatment is superior to using the resulting reaction medium after pressure and heat treatment. Assuming that it mainly contains polyols and possible conversion products, additional purification or separation steps are required to ensure that its quality is sufficient for further use. On the other hand, pyrolysis can advantageously yield monomers of polyols, which are believed to have higher mass purity than polyols.

[0029] According to a preferred embodiment, the reaction mixture after pressure and heat treatment introduced directly or indirectly into the pyrolysis device is a reaction mixture in which the gaseous components with boiling points lower than the prevailing temperature of the evaporation zone have been partially or completely removed in advance. In particular, according to the embodiments described herein, such a reaction mixture with a lower proportion of nitrogen-containing components or without such components can be fed to pyrolysis. This makes it possible to provide pyrolysis products, which can be further used advantageously. In particular, liquid, gaseous and solid pyrolysis products can be obtained during the pyrolysis process. As for liquid products, these are pyrolysis oils, which in turn can be sent to chemical cracking, however, wherein a high proportion of nitrogen-containing components will be destructive. The pyrolysis gas obtained can be used for power generation, whereby a low proportion of nitrogen-containing components reduces the problem of forming nitrogen oxides. Solid pyrolysis products are a kind of pyrolysis coke, which can be used for a variety of purposes, such as as a substitute for carbon black or as petroleum coke that can also be used for power generation, so low nitrogen content or no nitrogen components are also advantageous here.

[0030] According to a particularly preferred embodiment, the pressure- and heat-treated reaction mixture introduced directly or indirectly into the pyrolysis unit has a low water content or is free of water, since it passes through a dehydration zone, in which the water content is reduced before passing through the evaporation zone.

[0031] According to one embodiment, the reaction additive optionally included in the aqueous medium is selected from nitric acid, carboxylic acid, urea and / or biomaterial.Good conversion can be achieved with nitric acid.However, if a reaction mixture with a low ratio of nitrogen-containing components is required, other reaction additives are preferred because nitric acid provides additional nitrogen.In general, inorganic acids such as hydrochloric acid or phosphoric acid, or inorganic bases such as sodium hydroxide are less preferred because chlorine, phosphorus and sodium components will be present in the reaction medium under pressure and heat treatment and may have a disadvantageous effect in the case of downstream pyrolysis or subsequent use of the pyrolysis product obtained. Alternative reaction additives that can achieve good conversions are carboxylic acids, for example, in particular linear saturated monocarboxylic acids, such as formic acid, acetic acid, propionic acid, butyric acid or valeric acid, hexanoic acid, heptanoic acid; dicarboxylic acids, such as oxalic acid (oxalic acid), malonic acid (malonic acid), succinic acid (succinic acid), glutaric acid (glutaric acid), adipic acid (adipic acid), malic acid (2-hydroxysuccinic acid), tartaric acid (2,3-dihydroxysuccinic acid); and tricarboxylic acids, such as 3-carboxy-2-oxo-glutaric acid (acid oxalyl succinic acid), propane-1,2,3-tricarboxylic acid, citric acid (2-hydroxypropane-1,2,3-tricarboxylic acid) and isocitric acid (1-hydroxypropane-1,2,3-tricarboxylic acid). Another reaction additive is urea. Based on the total mass of the aqueous medium, the proportion of urea in the aqueous medium is, for example, 1 to 45 mass percent, in particular 1 to 20 mass percent, for example 1 to 10 mass percent, for example 1 to 7 mass percent, for example 1.5 to 5 mass percent, 1.5 to 4 mass percent, 2 to 4 mass percent, 2.5 to 3.5 mass percent or 3 mass percent. Other ranges or examples of other concentrations are 5 to 10 mass percent, 1 mass percent, 5 mass percent, 7.5 mass percent and 10 mass percent. From the relationship between the amount of urea and the degree of polyurethane degradation, a range of 1 to 10 mass percent is preferred, for example 2.5 to 10 mass percent, 2 to 7.5 mass percent, for example 3 to 5 mass percent.

[0032] According to a particular embodiment, the aqueous medium contains 2.5 to 10 mass percent urea, and the duration of the pressure and heat treatment is preferably 45 to 250 minutes, in particular 45 to 240 minutes. The ratio between the urea-containing aqueous medium and the polyurethane-containing plastic material can be, for example, 0.2 ml / g to 5 ml / g, in particular 0.4 ml / g to 5 ml / g.

[0033] The reaction additive can also be a biomaterial. In the context of the present invention, biomaterial is understood to refer to plant, animal or microbial material, such as complete plant or plant parts, such as wood, leaves, stems, roots or seeds, such as garden waste or grass clippings. The biomaterial is preferably a plant material. According to a specific embodiment, the biomaterial is wood, particularly chopped wood, such as in the form of sawdust, wood chips or crushed wood. It has been found that for plant material, such as wood, after suitable dehydration in the dehydration zone, a free-flowing solid can be obtained, which is, for example, very suitable for transportation by a screw conveyor. Subsequent use, such as conveying and introducing a pyrolysis device, therefore becomes quite easy. Therefore, the presence of plant material in the reaction mixture has led to significant improvements. The mass ratio of plastic material to biomaterial (particularly plant material) can be, for example, 3:1 to 1.5:1, such as 2:1. In particular, at a mass proportion of one third or more based on the total mass of plastic material and biomaterial, for example 33 to 50 mass percent, in particular 33 to 45 mass percent, for example 34 to 40 mass percent, a very free-flowing solid is obtained in the pressure- and heat-treated reaction medium after passing through the dewatering zone.

[0034] The aforementioned reaction additives may be used alone or in any combination of two or more thereof.

[0035] An example of a mixing ratio of plastic material to an aqueous medium containing a reactive additive is to wet 2 to 25 liters of plastic material with at least 0.08 to 1 liter of aqueous medium. The aqueous medium may contain 3 to 50 mass percent, in particular 4 to 40 mass percent, for example 4 to 20 mass percent of nitric acid, carboxylic acid, dicarboxylic acid, tricarboxylic acid and / or urea. In the case of adding a biomaterial, it may be provided that the plastic material accounts for 55 volume percent to 95 volume percent, in particular 67 volume percent to 95 volume percent, and the biomaterial correspondingly accounts for 5 volume percent to 45 volume percent, in particular 5 volume percent to 33 volume percent. The biomaterial may be mixed with the plastic material and then the aqueous medium may be added, or first mixed with the aqueous medium and then mixed with the plastic material, or all three components may be mixed simultaneously.

[0036] If the plastic material and / or the hydrolysable plastic contained therein is a compressible plastic, in particular a foam, the stated volume refers to the uncompressed plastic.

[0037] According to one embodiment, one or more pressure barriers are arranged in the first line and / or the second line. When a pressure gradient is generated, these devices are advantageously used to prevent the reaction mixture from being transported in a direction opposite to the desired transport direction.

[0038] According to one embodiment and with respect to the conveying direction, a reactor screw conveyor in a reactor can extend only over a portion of the reactor, for example over a portion in which a high proportion of solids is still present in the reactor vessel.

[0039] According to a further embodiment, the reactor conveyor screw extends with a corresponding taper into the conical end region of the reactor, thereby advantageously ensuring that the reaction medium is conveyed over the entire conveying path to the removal opening.

[0040] The feed rate of the reactor feed screw is controllable. This advantageously opens the possibility of influencing the residence time of the reaction mixture in the reactor. For example, in the event of a lower conversion rate than initially assumed, the delivery rate can be reduced to achieve a longer residence time and thus a higher conversion rate. In the event of a faster conversion than initially assumed, the delivery rate can be increased and therefore the throughput of the reactor can be increased.

[0041] According to one embodiment, water obtained by removing solids from the reaction mixture obtained, which has been subjected to pressure and heat treatment and does not contain gaseous components, and / or water obtained from gaseous water extracted by means of a steam extraction point, is added to the reaction mixture to be provided, optionally after the addition of a reaction additive. Thus, a circulation process is advantageously carried out, in which the water of the aqueous medium which has been used is at least partially returned to the continuous process, thereby reducing the consumption of resources.

[0042] Another aspect of the invention relates to an apparatus for carrying out the method described herein. The apparatus comprises a first line, wherein the first line is provided with a first screw conveyor, the first line leads to a reactor via a filling opening designed as a pressure lock, the reactor screw conveyor is arranged in a reactor, the reactor is tapered at least in one end region, and leads to a second line via a removal opening designed as a pressure lock, wherein the second line is provided with a second screw conveyor, an evaporation zone is provided in the second line, wherein the evaporation zone can be assigned a higher temperature than in the reactor, and the second line has a degassing point in the evaporation zone, through which gaseous components can be removed from the second line. Thus, such an apparatus is suitable for conveying a reaction mixture as described herein, i.e. a reaction mixture containing a plastic material in solid form containing polyurethane and also containing an aqueous medium, optionally containing a reaction additive, with which the plastic material is moistened, the reaction mixture being conveyed via the first screw conveyor of the first line to the filling opening of the reactor, the filling opening being designed as a pressure lock, the reactor being tapered at least in one end region. After entering the reactor through the filling opening, the reaction mixture is exposed to the pressure and temperature conditions prevailing there and is converted and can be transferred to the second line through a removal opening designed as a pressure lock in the end region of the reactor. By means of a second screw conveyor arranged in the second line, the pressure- and heat-treated reaction mixture can be conveyed to an evaporation zone, where gaseous components can be removed via at least one degassing point. Thus, the rare gaseous components in the pressure- and heat-treated reaction mixture can be removed after further transport in the second line, for example for a pyrolysis treatment, or can, for example, be fed directly into a pyrolysis device, which optionally represents an extension of the device described herein.

[0043] In another embodiment of the device, a dehydration zone is arranged in the second line upstream of the evaporation zone, wherein the temperature is above the boiling point of water and below the boiling point of the nitrogen-containing components, and wherein gaseous water can be removed by means of a steam extraction point. After the steam is removed, the reaction mixture remaining in the second line, which has been subjected to pressure and heat treatment and contains little or no water, is then partially or completely freed from the remaining gaseous components, preferably gaseous nitrogen-containing components, in the evaporation zone. The remaining reaction mixture, which has been subjected to pressure and heat treatment, contains little or no water, and contains little or no other gaseous components, can then be removed in turn and, for example, fed directly or indirectly to the pyrolysis.

[0044] Reference is made to implicit disclosures of apparatus relating to the method and vice versa. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Further advantages, features and details emerge from the following description, in which - if necessary - at least one embodiment is described in detail with reference to the drawings. Identical, similar and / or functionally identical parts are provided with the same reference numerals.

[0046] show:

[0047] Figure 1 : Schematic cross-sectional view of a reactor with an evaporation zone,

[0048] Figure 2 : Schematic diagram of a reactor with an evaporation zone and a dehydration zone.

[0049] The illustrations in the figures are schematic, not necessarily to scale and only show essential components. DETAILED DESCRIPTION

[0050] Example

[0051] Example 1: Preparation of reaction mixture

[0052] In a pilot test, a polyurethane foam mixture was extracted from a mattress that had reached the end of its life cycle as the plastic material. The mattress, which had a density of about 40 kg per cubic meter, was shredded, and the resulting material was a mixture of standard ether foam, HR foam and viscoelastic foam. 400 g of the resulting material was placed in a 10 L bucket, thereby filling the bucket to about 85%.

[0053] To the chopped material were added 100 g of fine sawdust and 100 g of chopped wood chips as biomaterial, assuming a density of about 700 kg per cubic meter. The plastic material was mixed with the biomaterial, after which the barrel was still about 85% full.

[0054] The aqueous medium used was 150 ml of the liquid phase of a pressure- and heat-treated reaction medium from a previous experiment, to which plant material had been added as a reaction additive and which assumed a pH value of 4 during the reaction. This aqueous medium was mixed with the mixture of plastic material and biomaterial, thereby moistening it. The volume of the reaction mixture obtained in this way, i.e. the mixture of chopped mattress material and biomaterial moistened with the reaction medium, was about 8.6 liters.

[0055] Example 2: Loading the Reactor

[0056] A Büchi reactor pressure vessel was used as the reactor, which had a volume of 10 liters and was designed for a maximum pressure of 60 bar, whereby the prepared reaction mixture was placed in a stainless steel inner barrel (liner), which was then placed in the Büchi reactor pressure vessel. The Büchi reactor pressure vessel was then sealed with a lid.

[0057] Example 3: Implementation of transformation

[0058] The purpose of this experiment is to determine the reduction in the solids fraction caused by the reaction. The reactor is first heated to a jacket temperature of 260° C., which is reached after about 6 to 10 minutes, then maintained at 260° C. for 1 hour, and then at 240° C. for 2 hours, during which time an equilibrium pressure is established in the reactor. The pressure vessel is then actively and rapidly cooled to ambient temperature.

[0059] Example 4: Determination of Remaining Solid Volume

[0060] After the reaction was complete, the liquid phase of the reaction medium, which had been subjected to pressure and heat treatment, was discharged to determine the volume of the remaining solid. The remaining solid no longer had any recognizable original components; instead, it was a brown-black substance, the volume of which was determined to be 1.2 liters. Thus, as a result of the reaction, the volume of the solid had been reduced to about 14% of the initial volume.

[0061] In other tests using urea solution as a reaction additive, complete liquefaction was determined. Therefore, a solid volume reduction of 90-95% ± 5% is feasible.

[0062] Embodiment 5:

[0063] In another experiment, 500 g of chopped mattress material was added to a Büchi reactor pressure vessel along with 150 mm water containing 40 g of citric acid and 50 g of 96% acetic acid. The mattress material used consisted mainly of polyurethane foam and some polyethylene and polypropylene.

[0064] The reaction mixture was heated to 260°C at equilibrium pressure for 60 minutes and then at 250°C for 120 minutes.

[0065] After the reaction mixture thus subjected to pressure and heat is cooled, the solid particles of polyethylene / polypropylene float on the liquid phase due to their lower density and can be easily separated mechanically.

[0066] After separation of the liquid phase of the reaction mixture subjected to pressure and heat treatment, a black material remains, which is dried, resulting in a volume reduction of about 95% compared to the volume of the plastic material initially used.

[0067] Figure 1A schematic diagram of a reactor 16 is shown. A reaction mixture is filled into a first pipeline 10 via a feed hopper (not further specified), the reaction mixture comprising a plastic material in solid form and comprising at least one polyurethane and an aqueous medium, optionally comprising a reaction additive. In the pipeline 10, the reaction mixture is conveyed to a filling opening 14 of a reactor 16 designed as a pressure lock by a first screw conveyor 12 and introduced into the reactor 16 via the filling opening. The pressure in the reactor 16 is ≥1 bar to 60 bar at a temperature of 180° C. to 270° C. The reaction mixture is conveyed in the direction of the end region of the reactor 16 by a reactor screw conveyor 18 arranged in the reactor 16. The conversion of the polyurethane and any other hydrolyzable plastic contained in the plastic material of the reactor 16 reduces the volume fraction of solids in the reaction mixture, which is why the reactor 16 can be tapered towards the end region. The reaction mixture is introduced into a second pipeline 22 via a discharge opening 20 of the reactor 16 designed as a pressure lock and conveyed by a second screw conveyor 24 located therein. In the second pipeline 22 there is an evaporation zone 26, in which the temperature is higher than the prevailing temperature in the reactor 16. At this temperature, the gaseous components can be removed from the second pipeline 22 via the degassing point 28, so that the reaction mixture, which is correspondingly low in gaseous components and has been subjected to pressure and heat treatment, is conveyed in the second pipeline 22 downstream of the discharge port and can be recycled. Details such as motors for driving the first screw conveyor 12, the second screw conveyor 24 or the reactor screw conveyor 18, or heating means for heating the reactor 16 or the evaporation zone 26 are not shown.

[0068] Figure 2 Another schematic diagram of the reactor 16 is shown, which corresponds to Figure 1 , but additionally has a dehydration zone 30 in the second line 22. The dehydration zone 30 is located upstream of the evaporation zone 26 with respect to the conveying direction of the reaction mixture to be conveyed. The dehydration zone 30 is designed to exhibit a temperature which is higher than the temperature prevailing in the reactor 16 but lower than the temperature prevailing in the subsequent evaporation zone 26. The temperature prevailing in the dehydration zone 30 is selected so that water evaporates under corresponding pressure and temperature conditions.

[0069] The embodiments mentioned here and / or their respective elements can be freely combined with each other. Although the present invention has been described and explained in more detail by preferred embodiments, the present invention is not limited to the disclosed examples, and those skilled in the art can derive other variations from these examples without departing from the scope of protection of the present invention. It is therefore obvious that there are a large number of possible changes. It is also clear that the embodiments mentioned in the form of examples actually only represent embodiments and should not be interpreted as limitations on the scope of protection of the present invention, application possibilities or configurations in any case. On the contrary, the description above and the description of the accompanying drawings enable those skilled in the art to specifically implement the exemplary embodiments, so that those skilled in the art can make various changes in the case of understanding the disclosed inventive concept, for example, about the function or setting of the various elements mentioned in the exemplary embodiments, without departing from the scope of protection defined by the claims and their legal equivalents, such as further explanations in the specification.

[0070] Reference Symbols List

[0071] 10 First pipeline

[0072] 12. First Screw Conveyor

[0073] 14 Filling opening

[0074] 16 Reactor

[0075] 18 Reactor screw conveyor

[0076] 20 Remove the opening

[0077] 22 Second pipeline

[0078] 24 Second screw conveyor

[0079] 26 Evaporation Zone

[0080] 28 Degassing point

[0081] 30 Dehydration Zone

[0082] 32 Steam extraction point.

Claims

1. A continuous process for converting a plastic material comprising polyurethane, comprising the following steps: Providing a reaction mixture, wherein the reaction mixture comprises - a plastic material which is in solid form and comprises polyurethane, and further - aqueous medium, wherein, in the reaction mixture, the mass ratio of water to polyurethane in the aqueous medium is no more than 0.6 to 1, The reaction mixture is conveyed by a first screw conveyor arranged in a first pipeline to a filling opening formed by a pressure lock of the reactor, the filling opening being tapered at least in one end region with respect to the conveying direction, The reaction mixture is conveyed to the end region of the reactor by a reactor screw conveyor arranged in the reactor vessel at a pressure of greater than 1 bar to 60 bar and a temperature of 180° C. to 270° C., In the end region of the reactor, the pressure- and heat-treated reaction mixture is transferred via a discharge port designed as a pressure lock into a second line, The pressure- and heat-treated reaction mixture is conveyed by a second screw conveyor disposed in the second pipeline, providing in said second line an evaporation zone at a temperature higher than the temperature prevailing in the reactor, In the evaporation zone, gaseous components are removed by at least one degassing point and in or after the evaporation zone, the pressure- and heat-treated reaction mixture freed from gaseous components is recovered.

2. The method according to claim 1, characterized in that The temperature of the evaporation zone is greater than or equal to the boiling point of the nitrogen-containing component and lower than the boiling point of the high-boiling component.

3. The method according to any one of the preceding claims, characterized in that The temperature in the evaporation zone is 265°C to 300°C.

4. The method according to any one of the preceding claims, characterized in that A dehydration zone is provided in the second pipeline upstream of the evaporation zone, wherein the temperature is higher than the boiling point of water and lower than the boiling point of the nitrogen-containing component, and gaseous water therein can be removed through a water vapor removal point.

5. The method according to any one of the preceding claims, characterized in that Atmospheric pressure prevails in the second line and the temperature corresponds at least to the boiling point of water at atmospheric pressure.

6. The method according to any one of the preceding claims, characterized in that The volume ratio between the solid and the aqueous medium is 100:1 to 5:

1.

7. The method according to any one of the preceding claims, characterized in that The ratio of the cross-sectional area of ​​the reactor vessel before tapering to the cross-sectional area at maximum tapering is 10:1, in particular 5:1, in particular 2:

1.

8. The method according to any one of the preceding claims, characterized in that The obtained reaction mixture, which has been subjected to pressure and heat treatment and optionally freed of gaseous components having a boiling temperature below the temperature prevailing in the evaporation zone, is introduced directly or indirectly into a pyrolysis device to be subjected to pyrolysis.

9. The method according to any one of the preceding claims, characterized in that The aqueous medium contains a reaction additive selected from nitric acid, a carboxylic acid, a dicarboxylic acid (especially adipic acid), a tricarboxylic acid (especially citric acid), and / or urea and / or a biomaterial.

10. The method according to claim 9, characterized in that The reaction additive is plant material.

11. The method according to any one of the preceding claims, characterized in that One or more pressure barriers are arranged in the first pipeline and / or the second pipeline.

12. The method according to any one of the preceding claims, characterized in that The reactor screw conveyor extends with a corresponding taper into the conical end region of the reactor vessel.

13. The method according to any one of the preceding claims, characterized in that - water obtained after removal of solids from the reaction mixture obtained after pressure and heat treatment and from the gaseous components, and / or - water obtained from gaseous water extracted through steam extraction points, Optionally after the addition of the reaction additives, it is added to the reaction mixture to be provided.

14. A device for carrying out the method according to any one of claims 1 to 13, comprising a first pipeline (10), wherein the first pipeline is provided with a first screw conveyor (12), the first pipeline leading to a reactor (16) via a filling opening (14) designed as a pressure lock, wherein: A reactor screw conveyor (18) is arranged in the reactor (16), wherein the reactor (16) is conical at least in one end region and opens into a second line (22) via a removal opening (20) designed as a pressure lock, wherein the second line (22) is provided with a second screw conveyor (24), an evaporation zone (26) is arranged in the second line (22), wherein a higher temperature can be set in the evaporation zone (26) than in the reactor (16), and the second line (22) has a degassing point (28) in the evaporation zone (26), via which gaseous components can be removed from the second line (22).

15. The device according to claim 14, characterized in that A dehydration zone (30) is provided in the second pipeline (22) upstream of the evaporation zone (26), wherein the temperature is above the boiling point of water and below the boiling point of the nitrogen-containing components and gaseous water can be removed through a water vapor removal point (32).

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